Myelin basic protein in CSF (cerebrospinal fluid). Neurochemistry - Ashmarin I.P. In white matter

6. MYELIN PROTEINS

The protein composition of myelin is peculiar, but much simpler than in neurons and glial cells.

Myelin contains a large proportion of cationic protein - CBM. It is a relatively small polypeptide with Mg = 16–18 kD. CBM contains a significant proportion of diamino acids, and at the same time, about half of its constituent amino acids are non-polar. This provides, on the one hand, close contact with the hydrophobic components of myelin lipids, and, on the other hand, determines its ability to form ionic bonds with acidic lipid groups.

The so-called Folch proteolipid proteins, which make up most of the rest of the myelin proteins, are characterized by an unusually high hydrophobicity. In turn, the main of these proteins is lipophilin, in which 2/3 of the constituent amino acids are non-polar. Of interest is a certain selectivity of contacts between lipophilin and lipids, for example, the displacement of cholesterol from its environment. It is believed that this is due to the peculiarities of the secondary structure of lipophilin.

The proportion of the so-called Wolfgram protein is also quite large - an acidic proteolipid, quite rich in dicarboxylic amino acid residues, and, at the same time, containing about half of non-polar amino acid residues.

Finally, from several dozen other myelin proteins, we note a myelin-associated glycoprotein located on the extracellular surface of membranes; it is also found in pre-myelination oligodendrocytes and in the myelin of the peripheral nervous system. In the human CNS, it is represented by three polypeptide chains with M g = 92, 107, 113 kD, and in the peripheral nervous system, by one protein with M g = 107 kD. MAG belongs to glycoproteins with a relatively low content of carbohydrate residues - about 30% of the mass of the molecule, but contains a set of carbohydrates characteristic of glycoproteins: N-acetylglucosamine, N-acetylneuraminic acid, fucose, mannose and galactose. The protein part of the molecule is characterized by a high content of glutamic and aslaric acids.

The functions of the Wolfgram protein and MAG are unknown, except for general considerations about their participation in the organization of the structure of the myelin sheaths.

7. NEUROSPECIFIC GLIA PROTEINS

The S-100 protein is found in both neurons and glial cells, and its share in the latter is high - about 85%.

In 1967, a neurospecific a 2 -glycoprotein with a molecular weight of 45 kD was isolated from the a 2 -globulins of the brain. In the human brain, it appears at the 16th week of embryonic development. Its carbohydrate components include glucosamine, mannose, glucose, galactose, galactosamine, and N-acetylneuraminic acid. and 2-glycoprotein is localized only in astrocytes, but is absent in neurons, oligodendrocytes and endothelial cells. Therefore, it can be considered as one of the specific markers of astrocytes.

Another protein is again characteristic only of glial cells. It was isolated from areas of the human brain rich in fibrous astrocytes, and subsequently - in much larger quantities - from the brain of patients with multiple sclerosis. This substance was named glial fibrillar acidic protein. It is specific only to the CNS, and it is not found in the PNS. Its content in the white matter of the brain exceeds that in the gray matter. In the ontogeny of mice, the maximum content of GFA is observed between the 10th and 14th days of postnatal development; coincides in time with the period of myelination and the peak of differentiation of astrocytes. The molecular weight of the protein is 40–54 kD. The glial localization of this protein also allows it to be used as a "marker" protein for these cells.

The functions of a 2 -glycoprotein and GFA protein are unknown.

As for microglial proteins, one should keep in mind the participation of these cells in the construction of myelin. Many of the myelin proteins are found in microglia.

Glia also contains many receptor and enzymatic proteins involved in the synthesis of second messengers, precursors of neurotransmitters, and other regulatory compounds that can be classified as neurospecific.

8. INTENSITY OF PROTEIN METABOLISM IN DIFFERENT SECTIONS OF THE NERVOUS SYSTEM

The modern concept of the dynamic state of proteins in the nervous tissue was established thanks to the use of isotopes by A.V. Palladin, D. Richter, A. Laita and other researchers. Starting from the late 1950s and during the 1960s, various precursors of their biosynthesis labeled with C, H, S were used in the study of protein metabolism. It was shown that proteins and amino acids in the brain of an adult animal metabolize, in general, more intensely than in other organs and tissues.

For example, in experiments in vivo using uniformly labeled C-1-6-glucose as a precursor, it turned out that, according to the intensity of amino acid formation due to glucose, a number of organs can be arranged in the following order:

brain > blood > liver > spleen and lungs > muscle.

A similar picture was observed when using other labeled precursors. It has been shown that the carbon skeleton of amino acids, especially monoaminodicarboxylic acids and, above all, glutamate, is intensively synthesized from C-acetate in the brain; from monoaminomonocarboxylic acids, glycine, alanine, serine, etc. are quite intensively formed. It should be noted that glutamate occupies a special place in the metabolism of amino acids. In vitro experiments using labeled glutamate showed that if only one glutamic acid is added to the reaction medium of the brain homogenate, then it can be a source of formation of 90–95% of amino acids.

Numerous studies have been carried out to study the differences in the intensity of metabolism of total and individual proteins using labeled precursors. In vivo experiments using C-glutamate showed that it is incorporated 4–7 times more intensively into gray matter proteins than white matter. In all cases, the intensity of the exchange of total proteins of the gray matter of the cerebral hemispheres and cerebellum was significantly higher than that of the white matter of the same parts of the brain, no matter what precursor was used in the study. At the same time, the difference in the intensity of metabolism of total gray matter proteins compared with white matter proteins takes place not only in the norm, but, as a rule, also in various functional states of the body.

Studies were also carried out to study differences in the intensity of incorporation of labeled precursors into total proteins of the central and peripheral nervous systems. It turned out that despite significant differences in the composition, metabolism, and functional activity of various parts of the CNS and PNS, as well as the complexity and heterogeneity of the proteins that make up them, the total CNS proteins of adult animals are updated much more intensively than the total PNS proteins.

A lot of research is devoted to the metabolism of proteins in various parts of the brain. For example, when studying the distribution of radioactivity in the brain after the administration of C-glutamate, it turned out that the gray matter of the cerebral hemispheres accounts for 67.5 radioactivity, the cerebellum - 16.4, the medulla oblongata - 4.4, and the share of other parts of the brain - about 11.7. In experiments in vivo, when various precursors, namely C-glutamate, C-1-6-glucose, C-2-acetate, were administered to adult animals, it turned out that, according to the intensity of label incorporation into total proteins, different parts of the nervous system are arranged in the following sequence: gray matter of the cerebral hemispheres and cerebellum > thalamus > optic tubercle > middle and diencephalon > Varolii pons > medulla oblongata > white matter of the cerebral hemispheres and cerebellum > spinal cord > sciatic nerve > myelin.

There were also studies devoted to the study of the intensity of protein metabolism in various parts of the CNS using the autoradiographic method. A similar picture was obtained: the most intense inclusion of the label took place in the proteins of the gray matter of the cerebral hemispheres and cerebellum, the slowest in the spinal cord, and even more slowly in the proteins of the sciatic nerve. As for the subcortical formations, the intensity of their protein metabolism was average between the rate of renewal of the proteins of the gray and white matter of the cerebral hemispheres and the cerebellum. Less significant differences are observed between individual subcortical formations than between the metabolic activity of white and gray matter.

The total proteins of different areas of the cerebral cortex, frontal, temporal, parietal, and occipital, were also studied. According to Welsh and VAPalladin, the proteins of the sensory area of ​​the cortex have a higher renewal rate, and the proteins of the temporal lobe of the cerebral cortex have a lower one. The same authors showed that higher protein renewal is characteristic of phylogenetically younger and functionally more active structural formations of the brain.

Against the backdrop of the generally highly renewable brain proteins, a few rather inert proteins deserve special mention. These include the histones of the neurons of the neocortex, the cationic proteins of the chromatin of these cells. In an adult organism, neocortical neurons do not multiply. Accordingly, the rate of histone renewal is very low. The average time for the renewal of half of the molecules of some histone fractions is measured in tens of days.

There are no absolutely inert proteins in the brain, and individual proteins and protein complexes of neurons undergo continuous restructuring associated with their participation in the functional activity of neurons and neuroglia. In addition to the synthesis and breakdown of whole protein molecules, changes occur in their structure, which occur, in particular, during amination and deamination of brain proteins. They should be considered as a partial renewal of individual fragments of the protein molecule.

1. In the nervous tissue, neurospecific proteins characteristic only of it were found. Chemically, they can be acidic or basic, simple or complex, and are often glycoproteins or phosphoproteins. Many neurospecific proteins have a subunit structure. The number of discovered neurospecific proteins has already exceeded 200 and is growing rapidly.

2. Neurospecific proteins directly or indirectly participate in the implementation of all functions of the nervous system - the generation and conduction of a nerve impulse, the processes of processing and storing information, synaptic transmission, cell recognition, reception, etc.

3. According to localization in the tissue of the nervous system, exclusively or predominantly neuronal and glial neurospecific proteins are distinguished. According to subcellular localization, they can be cytopyasmatic, nuclear or membrane-bound. Of particular importance are neurospecific proteins localized in the membranes of synaptic formations.

4. Many acidic potassium-binding neurospecific proteins are involved in ion transport processes. It is assumed that, in particular, they play a significant role in the formation of memory.

5. A special group of neurospecific proteins are contractile proteins of the nervous tissue, which provide orientation and mobility of cytostructural formations, active transport of a number of neuron components and participate in neurotransmitter processes in synapses.

6. The group of neurospecific proteins associated with humoral regulation carried out by the brain includes some glycoproteins of the hypothalamus, as well as neurophysins and similar proteins that are carriers of peptide regulators.

7. A variety of neurospecific glycoproteins are involved in the formation of myelin, in the processes of cell adhesion, neuroreception and mutual recognition of neurons in ontogenesis and regeneration.

8. A number of neurospecific proteins are brain isoenzymes of known enzymes, such as enolase, aldolase, creatine kinase, etc.

9. Many neurospecific proteins are very actively metabolized in the brain of animals, and the intensity of metabolism is different in different parts of the brain and depends on the functional state of the nervous system. On the whole, brain proteins significantly exceed the proteins of other tissues and organs in terms of the intensity of renewal.

RAMN, 1996. - 470 p.
ISBN 5-900760-02-2
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3.6 MYELIN PROTEINS
The protein composition of myelin is peculiar, but much simpler than in neurons and glial cells.
Myelin has a high proportion of cationic protein - CBM (about 30 percent). It is a relatively small polypeptide with Mg = 16-18 kD. CBM contains a significant proportion of diamino acids (about 20 percent) and at the same time, about half of its constituent amino acids are non-polar. This provides, on the one hand, close contact with the hydrophobic components of myelin lipids, and, on the other hand, determines its ability to form ionic bonds with acidic lipid groups. The functions of the CBM will be considered in more detail in the chapter on lipids in connection with a general analysis of the structure of myelin membranes.
The so-called Folch proteolipid proteins, which make up most of the rest of the myelin proteins, are characterized by an unusually high hydrophobicity. In turn, the main of these proteins is lipophilin (Mg = 28 kDa), in which 2/3 of the constituent amino acids are non-polar. Of interest is a certain selectivity of contacts between lipophilin and lipids, for example, the displacement of cholesterol from its environment. It is believed that this is due to the peculiarities of the secondary structure of lipophilin. Its role in the formation of myelin sheaths is discussed in more detail in the chapter on lipids.
The share of the so-called Wolf-gram protein (about 15% of proteins) is also quite large - an acidic proteolipid, quite rich in dicarboxylic amino acid residues, and, at the same time, containing about half of non-polar amino acid residues.
Finally, from several dozen other myelin proteins, we note myelin-associated glycoprotein (MAG) located on the extracellular surface of membranes; it is also found in pre-myelination oligodendrocytes and in the myelin of the peripheral nervous system. In the human CNS, it is represented by three polypeptide chains with Mg = 92, 107, 113 kD, and in the peripheral nervous system - by one protein with Mg = 107 kD. MAG belongs to glycoproteins with a relatively low content of carbohydrate residues - about 30% by weight of the molecule, but contains a set of carbohydrates characteristic of glycoproteins: N-acetylglucosamine, N-acetylneuraminic acid, fucose, mannose and galactose. The protein part of the molecule is characterized by a high content of glutamine and
90
aspartic acids.
The functions of the Wolfgram protein and MAG are unknown, except for general considerations about their participation in the organization of the structure of the myelin sheaths.
3.7 NEUROSPECIFIC GLIA PROTEINS
The S-100 protein described in detail in Section 3.1 is found in both neurons and glial cells, and its share in the latter is high, about 85%.
In 1967, a neurospecific a2-glycoprotein with a molecular weight of 45 kD was isolated from brain a2-globulins. In the human brain, it appears at the 16th week of embryonic development. Its carbohydrate components include glucosamine, mannose, glucose, galactose, galactosamine, and N-acetylneuraminic acid. α2-glycoprotein is localized only in asgrocytes, but is absent in neurons, oligodendrocytes, and endothelial cells. Therefore, it can be considered as one of the specific markers of astrocytes.
Another protein is again characteristic only of glial cells. It was isolated from areas of the human brain rich in fibrous astrocytes, and later - in much larger quantities - from the brain of patients with multiple sclerosis (fibral gliosis). This substance has been named glial fibrillar acidic protein (GFA). It is specific only to the CNS, and it is not found in the PNS. Its content in the white matter of the brain exceeds that in the gray matter. In the ontogeny of mice, the maximum content of GFA is observed between the 10th and 14th days of postnatal development, i.e., it coincides in time with the period of myelination and the peak of astrocyte differentiation. The molecular weight of the protein is 40-54 kD. The glial localization of this protein also allows it to be used as a “marker” protein for these cells.
The functions of a2-glycoprotein and GFA protein are unknown.
As for microglial proteins, one should keep in mind the participation of these cells in the construction of myelin. Many of the myelin proteins. described in the previous section are found in microglia.
Glia also contains many receptor and enzymatic proteins involved in the synthesis of second messengers, precursors of neurotransmitters, and other regulatory compounds that can be classified as neurospecific. Some of them are described in the following chapters.
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3.8 INTENSITY OF PROTEIN METABOLISM IN DIFFERENT SECTIONS OF THE NERVOUS SYSTEM
The modern idea of ​​the dynamic state of proteins in the nervous tissue was established thanks to the use of isotopes by A.V. Palladin, D. Richter, A. Laita and other researchers. Starting from the end of the 1950s and during the 1960s, various precursors of their biosynthesis (amino acids, glucose, acetate, and others) labeled with 14C, 3H, 35S were used in the study of protein metabolism. It was shown that proteins and amino acids in the brain of an adult animal are metabolized, in general, more intensively than in other organs and tissues.

All lipids found in the rat brain are also present in myelin, i.e., there are no lipids localized exclusively in non-myelin structures (with the exception of the specific mitochondrial lipid diphosphatidylglycerol). The reverse is also true - there are no myelin lipids that are not found in other subcellular fractions of the brain.

Cerebroside is the most typical component of myelin. With the exception of the very early period of development of the organism, the concentration of cerebroside in the brain is directly proportional to the amount of myelin in it. Only 1/5 of the total galactolipid content in myelin occurs in the sulfated form. Cerebrosides and sulfatides play an important role in maintaining myelin stability.

Myelin is also characterized by high levels of its major lipids, cholesterol, total galactolipids, and ethanolamine-containing plasmalogen. It has been established that up to 70% of brain cholesterol is located in myelin. Since up to half of the white matter of the brain may be composed of myelin, it is clear that the brain contains the highest amount of cholesterol compared to other organs. The high concentration of cholesterol in the brain, especially in myelin, is determined by the main function of neuronal tissue - to generate and conduct nerve impulses. The high content of cholesterol in myelin and the peculiarity of its structure lead to a decrease in ion leakage through the neuron membrane (due to its high resistance).

Phosphatidylcholine is also an essential constituent of myelin, although sphingomyelin is present in relatively minor amounts.

The lipid composition of both the gray matter and the white matter of the brain is distinctly different from that of myelin. The composition of myelin in the brain of all studied mammalian species is almost the same; there are only minor differences (eg, rat myelin has less sphingomyelin than bovine or human myelin). There are some variations depending on the localization of myelin, for example, myelin isolated from the spinal cord has a higher lipid-to-protein ratio than myelin from the brain.

The composition of myelin also includes polyphosphatidylinositides, of which triphosphoinositide makes up from 4 to 6% of the total myelin phosphorus, and diphosphoinositide - from 1 to 1.5%. The minor components of myelin include at least three cerebroside esters and two glycerol-based lipids; myelin also contains some long-chain alkanes. Mammalian myelin contains 0.1 to 0.3% gangliosides. Myelin contains more monosialoganglioside bM1 compared to what is found in brain membranes. The myelin of many organisms, including humans, contains the unique ganglioside sialosylgalactosylceramide OM4.

Myelin lipids PNS

The myelin lipids of the peripheral and central nervous systems are qualitatively similar, but there are quantitative differences between them. PNS myelin contains less cerebrosides and sulfatides and significantly more sphingomyelin than CNS myelin. It is interesting to note the presence of the ganglioside OMP, which is characteristic of PNS myelin in some organisms. Differences in the composition of myelin lipids of the central and peripheral nervous systems are not as significant as their differences in protein composition.

Myelin proteins in the CNS

The protein composition of CNS myelin is simpler than that of other brain membranes, and is represented mainly by proteolipids and basic proteins, which make up 60-80% of the total. Glycoproteins are present in much smaller amounts. The myelin of the central nervous system contains unique proteins.

The myelin of the human CNS is characterized by the quantitative prevalence of two proteins: the positively charged cationic myelin protein (myelin basic protein, MBP) and myelin proteolipid protein (PLP). These proteins are the main constituents of myelin in the CNS of all mammals.

Myelin proteolipid PLP (proteolipid protein), also known as the Folch protein, has the ability to dissolve in organic solvents. The molecular weight of PLP is approximately 30 kDa (Da - dalton). Its amino acid sequence is extremely conserved, the molecule forms several domains. The PLP molecule comprises three fatty acids, typically palmitic, oleic and stearic, ester-linked to amino acid radicals.

CNS myelin contains slightly smaller amounts of another proteolipid, DM-20, named after its molecular weight (20 kDa). Both DNA analysis and elucidation of the primary structure showed that DM-20 is formed by cleavage of 35 amino acid residues from the PLP protein. During development, DM-20 appears earlier than PLP (in some cases even before the appearance of myelin); suggest that, in addition to its structural role in myelin formation, it may be involved in oligodendrocyte differentiation.

Contrary to the notion that PLP is necessary for the formation of compact multilamellar myelin, the process of myelin formation in PLP/DM-20 knockout mice occurs with only minor deviations. However, these mice have reduced lifespan and impaired general mobility. On the contrary, naturally occurring mutations in PLP, including its increased expression (normal PLP over-expression), have serious functional consequences. It should be noted that significant amounts of PLP and DM-20 proteins are present in the CNS, messenger RNA for PLP is also present in the PNS, and a small amount of the protein is synthesized there, but is not included in myelin.

Myelin cationic protein (MBP) attracts the attention of researchers due to its antigenic nature - when administered to animals, it causes an autoimmune reaction, the so-called experimental allergic encephalomyelitis, which is a model of a severe neurodegenerative disease - multiple sclerosis.

The amino acid sequence of MBP is highly conserved in many organisms. The MBP is located on the cytoplasmic side of the myelin membranes. It has a molecular weight of 18.5 kDa and is devoid of signs of a tertiary structure. This basic protein exhibits microheterogeneity when electrophoresed under alkaline conditions. Most of the mammals studied contained varying amounts of MBR isoforms that shared a significant portion of the amino acid sequence. The molecular weight of MBR mice and rats is 14 kDa. The low molecular weight MBR has the same amino acid sequences at the N- and C-terminal portions of the molecule as the rest of the MBR, but differs by a reduction of about 40 amino acid residues. The ratio of these major proteins changes during development: mature rats and mice have more MBRs with a molecular weight of 14 kDa than MBRs with a molecular weight of 18 kDa. Two other isoforms of MBR, also found in many organisms, have molecular weights of 21.5 and 17 kDa, respectively. They are formed by attaching to the main structure of the polypeptide sequence with a mass of about 3 kDa.

Electrophoretic separation of myelin proteins reveals proteins with a higher molecular weight. Their number depends on the type of organism. For example, mice and rats can contain up to 30% of such proteins of the total. The content of these proteins also changes depending on the age of the animal: the younger it is, the less myelin in its brain, but the more proteins with a higher molecular weight.

The enzyme 2 "3"-cyclic nucleotide 3"-phosphodiesterase (CNP) makes up a few percent of the total content of myelin protein in CNS cells. This is much more than in other cell types. The CNP protein is not the main component of compact myelin, it is concentrated only in certain areas of the myelin sheath associated with the cytoplasm of the oligodendrocyte.The protein is localized in the cytoplasm, but part of it is associated with the cytoskeleton of the membrane - F-actin and tubulin.The biological function of CNP may be to regulate the structure of the cytoskeleton to accelerate the processes of growth and differentiation in oligodendrocytes.

Myelin-associated glycoprotein (MAG) is a quantitatively minor component of purified myelin, has a molecular weight of 100 kDa, is contained in the CNS in a small amount (less than 1% of the total protein). MAG has a single transmembrane domain that separates a highly glycosylated extracellular moiety, composed of five immunoglobulin-like domains, from an intracellular domain. Its overall structure is similar to the neuronal cell adhesion protein (NCAM).

MAG is not present in compact, multilamellar myelin, but is found in the periaxonal membranes of oligodendrocytes that form myelin layers. Recall that the periaxonal membrane of the oligodendrocyte is located closest to the plasma membrane of the axon, but nevertheless these two membranes do not merge, but are separated by an extracellular gap. A similar feature of MAG localization, as well as the fact that this protein belongs to the immunoglobulin superfamily, confirms its participation in the processes of adhesion and information transfer (signaling) between the axolemma and myelin-forming oligodendrocytes during myelination. In addition, MAG is one of the CNS white matter components that inhibits the growth of neurites in tissue culture.

Of the other white matter and myelin glycoproteins, the minor myelin-oligodendrocytic glycoprotein (MOG) should be noted. MOG is a transmembrane protein containing a single immunoglobulin-like domain. Unlike MAG, which is located in the inner layers of myelin, MOG is localized in its surface layers, which is why it can participate in the transmission of extracellular information to the oligodendrocyte.

Small amounts of characteristic membrane proteins can be identified by polyacrylamide gel electrophoresis (PAGE) (eg, tubulin). High resolution electrophoresis demonstrates the presence of other minor protein bands; they may be due to the presence of a number of myelin sheath enzymes.

Myelin proteins of the PNS

PNS myelin contains both some unique proteins and several proteins in common with CNS myelin proteins.

P0 is the main PNS myelin protein, has a molecular weight of 30 kDa, and makes up more than half of the PNS myelin proteins. It is interesting to note that although it differs from PLP in amino acid sequence, post-translational modification pathways, and structure, nevertheless, both of these proteins are equally important for the formation of CNS and PNS myelin structure.

The content of MBP in the myelin of the PNS is 5-18% of the total amount of protein, in contrast to the CNS, where its share reaches a third of the total protein. The same four forms of the MBP protein with molecular masses of 21, 18.5, 17, and 14 kDa, respectively, found in CNS myelin, are also present in the PNS. In adult rodents, MBP, at 14 kDa (called "Pr" in the classification of peripheral myelin proteins), is the most significant component of all cationic proteins. In the myelin of the PNS, there is also an MBP with a molecular weight of 18 kDa (in this case it is called the “P1 protein”). It should be noted that the importance of the MBP family of proteins is not as great for the myelin structure of the PNS as it is for the CNS.

Myelin glycoproteins of the PNS

Compact myelin in the PNS contains a 22 kDa glycoprotein called peripheral myelin protein 22 (PMP-22), which accounts for less than 5% of the total protein content. PMP-22 has four transmembrane domains and one glycosylated domain. This protein does not play a significant structural role. However, pmp-22 gene abnormalities are responsible for some human hereditary neuropathologies.

Decades ago, it was believed that myelin forms an inert sheath that performs no biochemical function. However, a large number of enzymes involved in the synthesis and metabolism of myelin components were later found in myelin. A number of enzymes present in myelin are involved in the metabolism of phosphoinositides: phosphatidylinositol kinase, diphosphatidylinositol kinase, the corresponding phosphatases, and diglyceride kinases. These enzymes are of interest due to the high concentration of polyphosphoinositides in myelin and their rapid metabolism. There is evidence of the presence in myelin of muscarinic cholinergic receptors, G proteins, phospholipases C and E, and protein kinase C.

In the myelin of the PNS, Na/K-ATPase was found, which transports monovalent cations, as well as 6"-nucleotidase. The presence of these enzymes suggests that myelin can take an active part in axonal transport.

Determination of the concentration of myelin basic protein in the CSF, used to diagnose, assess the prognosis and control the treatment of multiple sclerosis.

Russian synonyms

MBP in the cerebrospinal fluid, in the CSF.

SynonymsEnglish

Myelin basic protein (MBP), CSF.

Research method

Enzyme immunoassay (ELISA).

Units

ng/mL (nanogram per milliliter).

What biomaterial can be used for research?

How to properly prepare for research?

No preparation required.

General information about the study

Myelin basic protein, MBP is one of the main components of the inner layer of the myelin sheath. During demyelination, MBP and/or its fragments enter the cerebrospinal fluid and, therefore, can be used as a clinical and laboratory marker of myelin destruction for diagnosing, assessing the prognosis, and monitoring the treatment of multiple sclerosis.

It has been shown that an increase in the level of MBP in the cerebrospinal fluid is observed in approximately 80% of cases of exacerbation of multiple sclerosis and only in a few patients in remission of the disease. The increase in the level of MBP correlates with the progression of changes according to MRI and persists for 5-6 weeks after the onset of an exacerbation. During therapy with glucocorticosteroids, the concentration of MBP decreases.

If multiple sclerosis manifests itself only in the form of retrobulbar neuritis, an increase in OBM in the cerebrospinal fluid, as a rule, is not observed. This is probably due to the fact that the focus of demyelination in this case is located at a relatively large distance from the fourth ventricle of the brain. Another feature of MBM is that upon release from myelin, MBM can undergo fragmentation with the formation of many structurally different components, not all of which can be identified using standard test systems. The result of the study in this case does not always correspond to the actual concentration of MBP in the cerebrospinal fluid.

An increase in MBP is observed not only in multiple sclerosis, but also in other diseases of the central nervous system, such as stroke, some encephalopathies and encephalitis. Moreover, since MBP is also found in peripheral nerves, its concentration in the CSF may change in the presence of demyelination of nerve fibers outside the CNS. Thus, MBP is a nonspecific marker of multiple sclerosis.

It should be noted that today MBP is an additional marker of multiple sclerosis. Like other CSF markers (oligoclonal immunoglobulins G, IgG index), it is not included in the main algorithm for diagnosing multiple sclerosis.

What is research used for?

• For the diagnosis, evaluation of the prognosis and control of the treatment of multiple sclerosis.

When is the study scheduled?

• In the presence of symptoms of multiple sclerosis: blurred vision (blurred, double vision), weakness, numbness, tingling in the arms and legs, imbalance, increased urination, especially if the symptoms are intermittent and are observed in a young woman;
• when receiving ambiguous results of magnetic resonance imaging of the brain (MRI).

What do the results mean?

Reference values: less than 1 ng/ml.

Positive result:

• multiple sclerosis and other demyelinating diseases of the central nervous system;
• stroke;
• encephalopathy;
• encephalitis.

Negative result:

• norm;
• effective treatment of the disease.

What can influence the result?

• Fragmentation of myelin basic protein when it is released from myelin;
• the presence of comorbidities.

Important Notes

• Myelin basic protein is a non-specific marker for multiple sclerosis and other demyelinating diseases;
• the results of the analyzes should be interpreted taking into account additional clinical, laboratory and instrumental data.

• Diagnosis of multiple sclerosis (isoelectric focusing of oligoclonal IgG in CSF and serum)

Who orders the study?

Neurologist, general practitioner.

Literature

• Giovannoni G. Multiple sclerosis cerebrospinal fluid biomarkers. Dis Markers. 2006;22(4):187-96. review.
• Greene DN, Schmidt RL, Wilson AR, Freedman MS, Grenache DG. Cerebrospinal fluid myelin basic protein is frequently ordered but has little value: a test utilization study. Am J Clin Pathol. 2012 Aug;138(2):262-72.

The concentration of myelin basic protein (MBP) and neuron-specific enolase (NSE) in blood serum was studied in 84 patients with chronic hepatitis (CH) (viral etiology HBV, HCV - 38; alcoholic etiology - 17; autoimmune hepatitis - 11; hepatitis of mixed etiology - 18 ) and 77 liver cirrhosis (LC) (viral etiology HBV, HCV, HBV + HCV - 27; primary biliary cirrhosis - 10, alcoholic etiology - 18; mixed etiology - 22). Control group - 30 practically healthy persons (donors). Serum MBP and NSE concentrations were determined by enzyme-linked immunosorbent assay using commercial test kits 449-5830 DSL MBP and 420-10 Fujirebio NSE. According to the results of the study, in alcoholic liver lesions, both at the stage of chronic hepatitis and the formed cirrhosis, a significant increase in the concentration of blood MBP was observed compared with viral lesions. The concentration of NSE in patients with cirrhosis of the studied etiological groups, in contrast to CG, did not differ significantly.

myelin basic protein

neuron-specific enolase

chronic hepatitis

cirrhosis of the liver

hepatic encephalopathy.

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2. Belopasov V.V. Clinical differentiation of hepatic encephalopathy in patients with liver cirrhosis / V.V. Belopasov, R.I. Mukhamedzyanova, M.K. Andreev, B.N. Levitan // Vyatka Medical Bulletin. - 2002. - No. 1. - S. 46-47.

3. Ivashkin V.T. Liver diseases and hepatic encephalopathy / V.T. Ivashkin, F.I. Komarov, I.O. Ivanikov // Russian Medical Journal. - 2001. - T. 3. - No. 12. - S. 150-155.

4. Levitan B.N. Chronic liver pathology and intestinal microbiocenosis (clinical and pathogenetic aspects) / B.N. Levitan, A.R. Umerova, N.N. Larina. - Astrakhan: AGMA, 2010. - 135 p.

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Chronic hepatitis (CH) and liver cirrhosis (LC) are polyetiological diseases. It is well known that infection with hepatotropic viruses is the main etiological factor leading to the development of CG, and alcohol abuse, in turn, is the second main cause of this pathology.

The course and prognosis of liver diseases is largely determined by the presence and severity of damage to the central nervous system (CNS). Hepatic encephalopathy (PE) is a complex of potentially reversible neuropsychiatric disorders caused by damage to the central nervous system by toxic substances that are not neutralized by a pathologically altered liver, arising primarily as a result of acute or chronic liver failure. Given the extreme aggressiveness of these substances, it can be assumed that under their influence, the destruction of the nervous tissue occurs with the release of its decay products into the liquid media of the body.

A fairly large number of studies have been devoted to the study of the diagnostic and prognostic significance of such markers of neurodestruction as myelin basic protein (MBP) and neuron-specific enolase (NSE) in various pathological conditions of the CNS. At the same time, the issue of their diagnostic value in chronic diffuse liver diseases (CDLD) of various etiologies remains poorly understood. In this regard, the study of MBP and NSE, depending on the etiology of CDPD, is relevant and promising.

Purpose: to study the diagnostic significance of determining the concentration of myelin basic protein and neuron-specific enolase in blood serum, depending on the etiology of CDPD.

Materials and methods. To solve the tasks for the period from 2012 to 2014, 84 patients with chronic hepatitis (viral etiology HBV, HCV - 38; alcoholic etiology - 17; autoimmune hepatitis - 11; mixed etiology - 18) and 77 LC (viral etiology HBV, HCV) were examined. , HBV + HCV - 27; primary biliary cirrhosis - 10, alcoholic etiology - 18; mixed etiology - 22), who were hospitalized in the gastroenterological department of the GBUZ JSC "AMOKB". Among the examined patients with liver pathology, a group of 17 patients was identified, which was not included in the list of patients with chronic hepatitis. This group consisted of patients with acute alcoholic hepatitis (AAH) occurring with symptoms of severe hepatocellular insufficiency. The control group consisted of 30 practically healthy individuals (donors).

The studies were carried out on the basis of own observations and data from medical records (clinical history of the disease, outpatient card, conclusions of specialists in paraclinical methods of examination).

Patients were admitted to the clinic in the stage of exacerbation of the underlying disease. The currently accepted classifications were used in making the diagnosis. Clinical diagnosis was established on the basis of patients' complaints, anamnesis, physical data, laboratory and instrumental research methods. In the anamnesis, special attention was paid to surgical interventions, blood transfusions, alcohol and intravenous drug use, long-term use of hepatotoxic drugs, and the presence of hereditary diseases.

Exclusion criteria: concomitant pathology of the central nervous system, treatment with drugs that have a neurotoxic side effect.

Serum MBP and NSE concentrations were determined by enzyme-linked immunosorbent assay using reagent kits of commercial test systems 449-5830 DSL MBP and 420-10 Fujirebio NSE.

Statistical data processing was performed using the Statistica 6.0 software package. Student's parametric test (t) was used to quantify the characteristics of two unrelated groups. Correlation analysis with the calculation of the correlation coefficient (r) was performed using the Spearman test. Differences were considered statistically significant at the achieved significance level p<0,05.

Results and discussion. The concentration of MBP in patients with CG of viral etiology averaged 1.9±0.27 ng/ml, mixed - 2.3±0.3 ng/ml, autoimmune 2.17±0.19 ng/ml, which did not differ significantly from the results obtained in the donor group — 1.9±0.3 ng/ml (p>0.05) (Fig. 1). A more significant increase in the level of MBP was found in patients with chronic hepatitis of alcoholic etiology, amounting to 2.9±0.39 ng/ml, which significantly exceeded the values ​​obtained in the control group, as well as in patients with viral etiology of the disease (p<0,05). Максимальная концентрация ОБМ в сыворотке крови была выявлена в группе больных ОАГ, составив в среднем 5,4±0,17 нг/мл, что достоверно превышало показатели, характерные как для здоровых лиц, так и для больных хроническим гепатитом вирусной, смешанной, аутоиммунной и алкогольной этиологии (р<0,05). В исследуемой группе пациентов ОАГ максимальная концентрация ОБМ в периферической крови наблюдалась в 75% случаев.

The results obtained in the study of the concentration of NSE in patients with CG and OAH were somewhat different (Fig. 2).

The concentration of NSE in patients with chronic hepatitis of viral etiology was 6.9±0.41 ng/ml, mixed - 7.4±0.37 ng/ml, autoimmune - 6.4±0.52 ng/ml. The results obtained are close and did not significantly differ from the values ​​obtained in the control group - 6.49±0.41 ng/ml (p>0.05).

The level of NSE in patients with chronic hepatitis of alcoholic etiology averaged 8.1±0.51 ng/ml, which is significantly higher than in the control group, as well as in patients with autoimmune and chronic hepatitis of viral etiology (p<0,05).

The most significant increase in the concentration of NSE, as well as MBP, was found in patients with OAH, averaging 14.3 ± 0.47 ng / ml, and in 81% of the examined patients, the results obtained significantly exceeded those characteristic for donors, as well as patients with chronic hepatitis of viral, mixed, autoimmune and alcoholic etiology (r<0,05), достигая 25 нг/мл.

Rice. 1. The concentration of MBP in patients with chronic hepatitis, depending on the etiology:

Rice. 2. The concentration of NSE in patients with chronic hepatitis, depending on the etiology:

1 - viral hepatitis (HBV, HCV); 2 - autoimmune hepatitis; 3 - alcoholic hepatitis;

4 - hepatitis of mixed etiology; 5 - control

A high concentration in the peripheral blood of the studied markers of nervous tissue damage, such as MBP and NSE, which we detected in alcoholic liver damage, is probably a manifestation of demyelinating processes, often observed in this pathology. The revealed regularities speak in favor of the fact that the reasons for the development of atrophic changes in the brain and damage to nerve fibers (markers of which are MBP and NSE), which are often found in people who abuse alcohol, are not only the neurotoxic effect of ethanol and its metabolites, but also factors such as as liver dysfunction, malnutrition, as well as a deficiency of B vitamins and nicotinic acid.

As mentioned above, the main etiological factor leading to the occurrence of chronic hepatitis is a hepatotropic viral infection.

The concentrations of MBP and NSE in the blood serum of patients with chronic hepatitis depending on the type of hepatotropic virus (B and C) were close and did not differ significantly from each other, as well as from the indicators obtained in the control (p>0.05). Also, there were no significant differences in the concentrations of the studied markers of destruction of the nervous tissue in CHC patients with genotype 1 and genotype "non-1" (2 and 3a). Consequently, the level in the peripheral blood of the parameters we studied does not depend on the type of viruses.

It is noteworthy that the concentrations of MBP and NSE in patients with CG of viral and CG of mixed etiology (viral + alcoholic) do not differ significantly from each other, as well as from the results obtained in the control (p>0.05). At the same time, it was found that the combination of viral and alcoholic factors has a more significant effect on the state of the studied markers of neurodestruction than only with viral etiology. So, if in patients with mixed etiology, the level of MBP in 42% of cases exceeded the indicators characteristic of healthy individuals, then in chronic viral hepatitis only in 30%. The concentration of NSE, respectively, in 39% of cases exceeded the indicators characteristic of healthy individuals with a mixed etiology of the disease, and only in 31% with a viral one. In our opinion, this indirectly indicates that a high concentration of the studied markers of nerve tissue damage, detected in some patients with chronic hepatitis, is more characteristic in the presence of such an etiological factor as alcohol abuse.

Conducted in the general group of patients with CG correlation analysis of the values ​​of MBP and NSE showed the absence of significant relationships between these indicators. At the same time, in the group of patients with alcoholic liver damage, a weak positive correlation was found between the concentrations of MBP and NSE (r=0.45), which, in our opinion, indirectly indicates similar mechanisms leading to an increase in the level of these damage markers. nervous tissue in this pathology.

The revealed patterns make it possible to use the determination of the level of MBP and NSE in the blood serum of patients with chronic hepatitis as an additional marker in the diagnosis of various etiological forms of chronic hepatitis, primarily alcoholic etiology, as well as to identify the presence of demyelinating processes in this pathology.

Given that there are etiological features of the nature of the course of cirrhosis, the rate of progression, the development of complications, a study was made of the concentration of MBP and NSE depending on the etiology of the disease. 27 patients (35%) were diagnosed with cirrhosis of viral etiology, 18 (23%) - alcoholic, 22 (29%) had a history of alcohol abuse and viral hepatitis at the same time (mixed etiology), 10 patients (13%) had diagnosed with primary biliary cirrhosis. The concentrations of MBP and NSE in patients with cirrhosis of viral etiology were 2.3±0.42 and 8.2±0.56 ng/ml, mixed - 2.7±0.34 and 7.8±0.43 ng/ml, biliary 3.2±0.39 and 8.3±0.39 ng/ml, alcoholic 3.4±0.3 and 8.9±044 ng/ml, respectively.

Mean values ​​of NSE concentration in groups of patients with cirrhosis of viral, biliary and alcoholic etiology are significant (p<0,05) превышали показатели в контрольной группе. В то же время отсутствовали достоверные различия концентраций НСЕ в периферической крови в зависимости от этиологии ЦП. Результаты проведённого исследования свидетельствуют, что на стадии ЦП, в отличие от ХГ, концентрация данного маркера нейродеструкции в периферической крови не связана с этиологией заболевания.

Consequently, at the stage of the formed cirrhosis, the causes that cause an increase in the level of NSE in the peripheral blood are somewhat different from those in hepatitis (OAG, CG). Probably, the leading role is played by the neurotoxic effect of endogenous intoxication products circulating in the blood in severe liver dysfunction, and not the direct effect of ethanol and its metabolites.

In addition to the fact that NSE primarily refers to intracellular enzymes of the central nervous system and is considered one of the most specific indicators of its damage, at the same time, there are five molecular forms of NSE isoenzymes found not only in neurons, but also in neuroendocrine cells, skeletal muscles, liver , erythrocytes and platelets, and fluctuations in its general level can be directly related to severe liver dysfunction and the development of various complications characteristic of cirrhosis.

The results obtained in the study of the level of MBP in the peripheral blood of patients with cirrhosis of various etiologies differed somewhat.

Thus, the results of the study indicate that in cirrhosis of biliary (3.2±0.39 ng/ml) and alcoholic (3.4±0.3 ng/ml) etiology, the values ​​of MBP are significantly increased compared to the control group - 1.9 ±0.3 ng/ml and patients with liver cirrhosis of viral etiology - 2.3±0.42 ng/ml (p<0,05). При ЦП вирусной этиологии уровень ОБМ был наиболее низким, сопоставимым с показателями, полученными в контроле (р>0.05). With cirrhosis of mixed etiology (2.7±0.34 ng/ml), its level was slightly higher than with viral cirrhosis, and, accordingly, more than in the control, but no significant differences were found when comparing the results obtained (p>0.05) . Despite a significant difference in blood volume parameters in patients with cirrhosis of alcoholic etiology and PBC compared with the control, we did not reveal a significant difference in the level of the studied protein between these studied groups of patients (p>0.05). The average values ​​of the concentration of MBP in peripheral blood in patients with liver cirrhosis of mixed and alcoholic etiology differed slightly from each other: 2.7±0.34 and 3.4±0.3 ng/ml, respectively, no significant difference was found (p>0 .05). The results obtained are presented in fig. 3 and 4.

Rice. 3. The concentration of NSE in patients with cirrhosis depending on the etiology: 1 - cirrhosis of viral etiology (HBV, HCV); 2 - primary biliary cirrhosis; 3 - cirrhosis of alcoholic etiology; 4 - CP of mixed etiology; 5 - control

Rice. 4. The concentration of MBP in patients with cirrhosis depending on the etiology: 1 - cirrhosis of viral etiology (HBV, HCV); 2 - primary biliary cirrhosis; 3 - cirrhosis of alcoholic etiology; 4 - CP of mixed etiology; 5 - control

Thus, the revealed patterns are similar to the results obtained in patients with CG, in the group of which the maximum concentration of plasma MBP was also observed in the alcoholic etiology of the disease.

Conclusion. With alcoholic liver damage, both at the stage of chronic hepatitis and formed cirrhosis, there is a significant increase in the concentration of blood MBP compared with viral lesions, which confirms our assumption that, in addition to the neurotoxic effect of endogenous intoxication products circulating in the blood in severe liver damage , a significant role in the processes of neurodestruction and demyelination of nerve fibers is played by the direct damaging effect of ethanol and its metabolites.

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