A thiol proteinase highly elevated in and around the plaques of multiple sclerosis. Some biochemical parameters of plaque activity and progression

Nuclear Magnetic Resonance Study of Cerebrospinal Fluid From Patients With Multiple Sclerosis

Proton nuclear magnetic resonance (NMR) spectroscopy was used to examine cerebrospinal fluid (CSF) from patients (n = 30) with actively progressive multiple sclerosis (MS). Metabolite concentrations obtained from the spectra were compared to those determined from the spectra of CSF from control patients (n = 27) with benign spinal disorders. No significant difference was found between the 2 groups for most constituents, including lactate, glutamine, citrate, creatine and creatinine, and glucose. Acetate levels were significantly higher in MS patients, while formate levels were significantly lower, than the controls. There were no significant differences in metabolite concentrations in CSF from early and longstanding MS patients. A peak due to an unidentified compound was found at 2.82 ppm in the spectra of CSF from patients with actively progressive MS, but not in the spectra of CSF from the controls. The peak was not found in spectra of CSF from patients with AIDS dementia complex (n = 9) or Parkinson's disease (n = 5), but it did appear in spectra of CSF from 1 patient with Jakob-Creutzfeldt disease (out of 3 examined) and from 1 patient (out of 7) with Guillan-Barré disease. The unidentified compound is volatile and, from the chemical shift of the observed NMR peak, is probably an N-methyl compound. As such, it may be an intermediate in the cholino-glycine cycle, in which an abnormality has been proposed to exist in MS patients.

Biochemistry of demyelination

The myelin sheath, a lipid-rich multilamellar membrane of relative stability, both insulates and enhances conduction in nerve axons. A notable feature of myelin-specific proteins, in particular myelin basic protein, is their susceptibility to proteolytic activity and their encephalitogenicity, which induces inflammatory demyelination in the CNS. The final common pathway of myelin breakdown in vivo is well documented and there is evidence that myelin disruption can be mediated directly by soluble (circulating) factors and for following receptor-driven phagocytosis by macrophages. However the exact mechanism(s) of demyelination in multiple sclerosis is still unresolved, both antigen-specific and--non-specific events having the potential to generate the myelinolytic process.

Increased cathepsin B activity in multiple sclerosis brain

Cathepsin B (CB) activity was measured in aqueous extracts of frozen autopsy specimens of centrum semiovale from three MS patients, five control patients with other neurological diseases, and five normal individuals. Mean activity was significantly increased in the MS tissue compared with controls. The mean activity in MS tissue containing demyelinating lesions was higher than that in normal appearing white matter which was higher than that in normal control specimens but the differences were not statistically significant. The mean CB activity in patients with other neurological diseases was higher than normal control activity and, although the difference was not statistically significant, this observation suggests that increases in CB may not be specific for MS. Immunohistochemical studies of the MS brain tissue analyzed biochemically suggested that monocytes, macrophages and reactive astrocytes are potential sources of increased CB in MS brain.

Biochemical alterations in multiple sclerosis lesions and normal-appearing white matter detected by in vivo 31P and 1H spectroscopic imaging

The goals of the current study were threefold: first, to confirm previous single volume proton (1H) magnetic resonance spectroscopy results of reduced N-acetyl aspartate (NAA, a putative marker of neurons) in multiple sclerosis (MS) white matter lesions using multiple volume 1H magnetic resonance spectroscopic imaging (MRSI); second, to measure the phospholipid metabolites phosphomonoesters and phosphodiesters in such lesions using phosphorus (31P) MRSI; and third, to test the hypothesis that biochemical changes occur in the normal-appearing (on spin echo T2-weighted magnetic resonance images) white matter in patients with MS. Thirteen subjects with clinically definite MS were studied with both 1H and 31P MRSI, and 19 controls were studied with either 1H MRSI, 31P MRSI, or both. MS lesion, MS normal-appearing white matter, and region-matched control spectra from the centrum semiovale were analyzed. The major findings of this study were that in both white matter lesions and normal-appearing white matter in patients with MS, the metabolite ratio NAA/creatine and the total 31P peak integrals were significantly reduced compared with controls. In addition, in MS lesions NAA/choline and phosphodiesters/total 31P were significantly reduced compared with controls, and in MS normal-appearing white matter there was a trend for NAA/choline to be reduced compared with controls. In normal-appearing white matter in patients with MS, total creatine and phosphocreatine were significantly increased compared to controls, as detected with both 1H (total creatine peak integrals) and 31P (phosphocreatine/total 31P) MRSI techniques. These results suggest reduced neuronal density and altered phospholipid metabolites in white matter lesions in patients with MS.(ABSTRACT TRUNCATED AT 250 WORDS)

NPGB-induced inhibition of superoxide anion production by normal Lewis rat macrophages

The treatment of Lewis rat peritoneal macrophages with p1-nitrophenyl p-guanidinobenzoate (NPGB) inhibited the superoxide anion production stimulated with phorbol myristate acetate (PMA). The addition of NPGB at the time of maximum superoxide generation was still able to block the superoxide release. It appears from these findings that NPGB may block either the activation process of the membrane bound NAD(P)H oxidase or directly on the active enzyme. Other protease inhibitors such as, epsilon-amino caproic acid (EACA), pepstatin, trans aminomethyl cyclohexane carboxylic acid (AMCA), aprotinin, and leupeptin did not inhibit the superoxide release. The superoxide anion release by the xanthine-xanthine oxidase system was not inhibited by NPGB. This finding indicates that NPGB does not itself react with superoxide. It has been also demonstrated that NPGB is a good reactant toward sulfhydryl group. The relevance of these finding to experimental allergic encephalomyelitis (EAE) is discussed.

Proteolytic enzymes in experimental spinal cord injury

Experimental spinal cord injury was produced in rats by dropping a 10 g weight from 30 cm upon dura-invested exposed spinal cord. Proteolytic activities at neutral (pH 7.6) and acid (pH 5.5 and 3.6) pH were determined in whole homogenate and the cytosolic fraction of the lesion (lumbar) and cervical control segments. The enzyme activity was monitored by SDS-PAGE analysis of the extent of substrate myelin basic protein (MBP) degradation. Activities (neutral and cathepsin B-like) in the sham-operated spinal cord were lower than those of cervical autologous control at 24 h after injury. The increase in neutral proteinase activity was progressive and greater in the lesion than the autologous control. A 61.5% +/- 3.5 loss of MBP was observed at 2 h following injury and increased at 24 h (78.2% +/- 3.4). The loss of MBP coincided with the appearance of several low molecular weight peptides. The cathepsin B-like and cathepsin D activities were also increased in the lesion but to a lesser extent than the neutral proteinase. The neutral proteinase and cathepsin B-like activity were inhibited by leupeptin and not by pepstatin while the converse obtained for cathepsin D activity. The release of neutral proteolytic activity which is nonlysosomal in origin suggests a novel hypothesis for the mechanism of traumatic axon-myelin injury.

Quantitation of the myelin-associated glycoprotein in human nervous tissue from controls and multiple sclerosis patients

Myelin-associated glycoprotein (MAG) was measured by radioimmunoassay in the human CNS and peripheral nervous system (PNS). The level of MAG, expressed as ng/microgram of total protein, was approximately 20-fold higher in whole homogenates of cerebral white matter (4.7 +/- 0.60) than of peripheral nerve (0.12-0.28). MAG concentrations were only slightly higher in the isolated myelin fractions from these tissues: CNS myelin, 5.6 ng/microgram; PNS myelin, 0.37 ng/microgram. The levels of MAG were measured in nine plaques, periplaque regions, and areas of macroscopically normal-appearing white matter (NAWM) from six separate multiple sclerosis brains and compared with the levels of other myelin proteins in the same samples. MAG and other myelin proteins were reduced to very low levels in plaques. The levels of MAG and basic protein (BP) and the activity of 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) in periplaque areas were significantly lower than those in control white matter, and MAG and BP levels were also significantly reduced in NAWM. In a periplaque region and NAWM from the most rapidly progressing case of multiple sclerosis examined, the MAG content was between 30 and 35% of the control level, whereas BP and PLP levels and CNP activity were between 50 and 85% of control values. The reduction of MAG content in periplaque regions from all nine multiple sclerosis plaques examined was significantly greater than the reductions of BP level and CNP activity. In NAWM samples, the mean reduction of MAG content was also greater than the reductions of BP level and CNP activity, but the difference was only statistically significant in comparison to CNP.(ABSTRACT TRUNCATED AT 250 WORDS)

Acidic lipids enhance cathepsin D cleavage of the myelin basic protein

Some acidic lipids including sulfatide and phosphatidylinositol were found to increase greatly the rate of cathepsin D cleavage of the myelin basic protein. Since a similar effect was seen when the substrate was changed to cytochrome C, but not when the enzyme was changed to pepsin, these acidic lipids seem to be acting on cathepsin D rather than on myelin basic protein itself. Even so, chemical modification studies suggest that this phenomenon is only seen when the myelin basic protein is in its native conformation. Succinylation of MBP increases its rate of cleavage by cathepsin D by at least tenfold and, in addition, with this modified and presumably denatured MBP as substrate, activation of cathepsin D is no longer seen with acidic lipids. These findings suggest that the native conformation of MBP is both an important determinant of its rate of cleavage by cathepsin D and is also essential for observing activation of this reaction by acidic lipids. The acidic lipids seem to alter the "extended active site" of cathepsin D in such a way as to enable this enzyme better to utilize the native myelin basic protein as a substrate. Cathepsin D has previously been implicated as the protease responsible for the release into cerebrospinal fluid in multiple sclerosis patients of an encephalitogenic fragment derived from myelin basic protein. It is possible that the elevated levels of cathepsin D and sulfatide that have previously been found associated with multiple sclerosis plaques in vivo act in concert to bring about the rapid cleavage and subsequent loss of the myelin basic protein from these localized regions in the myelin sheath.

Polymorphonuclear neutral protease activity in multiple sclerosis and other diseases

Polymorphonuclear neutral protease activity (PMN-NPA) was examined in 87 patients with definite multiple sclerosis (MS) (48 active, 39 inactive), 49 patients with other neurological diseases (OND), 24 patients with immune-mediated non-neurological diseases (INND), and 32 normal subjects. PMN-NPA was found to be significantly increased in active MS compared with inactive MS and compared with each of the control groups. No differences were found between the group of normal subjects and the groups of patients with OND, INND, or inactive MS. Levels of PMN-NPA were significantly higher in the OND group than in inactive MS group. The differences for INND versus normal controls, neurological controls, and patients with inactive MS were not significant. No significant differences have been detected between active and inactive INND. These results suggest that PMN-NPA may be useful in the diagnosis and evaluation of MS.

Proteases of human brain

Growing appreciation of the multiple functions of proteolytic enzymes in intracellular protein degradation and post-translational modification, in the release of biologically active macromolecules and peptides from precursors and in cellular protein regulation and quality control has stimulated interest in proteases in neurobiology and neuropathology. In this article, the proteinases and peptidases thus far studied in the human central nervous system are reviewed with respect to their enzymology, anatomical and cytological distributions and contributions to neurological and psychiatric disease states. Though information concerning brain proteases in man is fragmentary, it suffices to establish the importance of these complex systems for advancing knowledge of human cerebral function in health and disease.

Simultaneous measurement of 2':3' cyclic-nucleotide 3' phosphodiesterase and RNase activities in sera and spinal fluids of multiple sclerosis patients

The enzymes 2':3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) and RNase were simultaneously measured in the sera and CSF of multiple sclerosis (MS) and non-MS patients. No evidence of increased activity for these enzymes could be found regardless of pathology in either fluid source. Discrepancies between the present results and those from two previous studies that reported significant increases in CNPase activity in the CSF of patients with MS were carefully analyzed. It was concluded that the apparent increased CNPase activity correlated with MS in both previous studies was most probably the result of methodological and computational difficulties.

Some immunochemical aspects of HD-brain extracts

Cortical gray matter extracts of patients with Huntington's disease (HD) were investigated for their antigenic properties with serum from both HD patients and normal controls. Both patient and control sera appeared to precipitate two closely migrating proteins of MW 14.4K and 15K, which could be found in normal brain preparations only at much lower concentrations, as precipitation of these proteins could not effectively be inhibited by a concentrated "cold" normal brain extract. It is shown that these molecules are hemoglobin and lysozyme, which to a certain extent bind specifically to the immunoprecipitates. The increase in hemoglobin level, which amounted to about 20% of the total protein concentration, might be explained either as an epiphenomenon to the disease process, in which degeneration of the HD brain leads to a relative increase of the arterial and capillary blood system, or as an artifact due to the preparation of the brain extracts. The lysozomal increase is a feature shared by many degenerative neurological diseases. No measurable humoral reactivity could be demonstrated in patient sera against a presumed mutant HD-specific protein. In addition, using antisera to the viral structural protein p30, no evidence could be found for the involvement of a retrovirus in HD.

Na+- and K+-dependent adenosine triphosphatase changes in multiple sclerosis plaques

Na+- and K+-dependent adenosine triphosphatase [(Na+ + K+)-ATPase] was studied in microdissected samples from sections of histologically active and inactive plaques of multiple sclerosis. In active plaques the enzyme was found to be markedly reduced in activity, whereas in old, chronic plaques ATPase activities were higher than those of unaffected white matter. White matter from control patients and normal-appearing white matter from MS patients did not differ with regard to ATPase activities. The results suggest that reversible changes in the sodium pump mechanism may be involved in the pathophysiology of multiple sclerosis.

The role of macrophages in demyelination in experimental allergic neuritis

The role of macrophages and serum factors in demyelination in experimental allergic neuritis (EAN) was examined by a simple in vitro method. Cultivated rabbit peritoneal macrophages, preincubated with serum obtained from rabbit EAN produced by sensitization with bovine spinal nerve roots, could agglutinate and phagocytize purified bovine or rabbit peripheral nerve myelin. Sera from normal animals or from controls given adjuvant alone could not. Adhesion and phagocytosis were inhibited if EAN sera were absorbed with peripheral nerve myelin. Rabbit red blood cells were not phagocytized by macrophages exposed to EAN serum. Concomitant to these observations, three lysosomal acid hydrolases: acid proteinase, acid phosphatase and beta-glucuronidase, were assayed with respect to their topographical and chronological distribution. In the group examined at clinical onset, increases in the specific activities were 1.5-3.0-fold in the spinal roots and 1.0-1.5-fold in the sciatic nerves compared with control. The degree of increase in total activities per whole root or sciatic nerve was much higher for specific activities. The topographical distribution of the increase closely corresponded to the histological distribution of EAN lesions. These observations suggested that the increased lysosomal activity originated from lysosomal-rich infiltrating cells. These observations strongly indicated the significant role of macrophages activated by EAN serum in the demyelination of EAN.

Observations on the effects of protease inhibitors on the suppression of experimental allergic encephalomyelitis

Inhibitors of proteolytic enzymes were tested for their ability to suppress the clinical signs and CNS lesions produced by injection of purified myelin in complete Freund's adjuvant into Lewis rats. Pepstatin or a series of neutral protease inhibitors including aprotinin, soybean trypsin inhibitor, leupeptin, antipain, trans-aminomethyl cyclohexane carboxylic acid (AMCA), epsilon-amino caproic acid (EACA) nitrophenyl guanidino benzoate (NPGB), D- and L-polylysine, or a new commercial protease inhibitor, dipropionyl Rhein (DPR) were injected daily beginning on day 7 after immunization of rats with myelin. Aprotinin and soybean trypsin inhibitor exacerbated the symptoms and lesions of experimental allergic encephalomyelitis (EAE), leupeptin and antipain had no effect, and the plasminogen activators AMCA, EACA, NPGB, as well as poly-L- and poly-D-lysine and DPR suppressed various aspects of EAE. The measurement of acid protease as a biochemical method for quantitation of the degree of cellular infiltration into the CNS is proposed, and the results with the various treatments presented. AMCA and NPGB may exert their effects at the site of entrance of the lymphoid cells into the CNS.

Degradation of basic protein and Wolfgram protein in central nervous system by soluble enzymes of human peripheral polymorphonuclear leucocytes

The present communication describes the ability of soluble enzymes (SE) of peripheral polymorphonuclear leucocytes of control and multiple sclerosis (MS) patients to degrade major myelin proteins of MS and control myelin. MS and control SE degraded in situ both Wolfgram protein (WP) and basic protein (BP) of isolated myelin. No differences were found between the action of control and MS patients SE on myelin. However, significantly less degradation of BP and WP in control myelin compared to that in MS myelin was found. Only 30% of SE samples (both control and MS) degraded significant amounts of proteolipid protein in myelin. It is postulated that SE associated demyelination in MS may be a factor contributing to the demyelinating process.

Annotation. Recent biochemical and immunological observations in multiple sclerosis

As there is evidence of early biochemical and histological changes in the normal-appearing white matter in MS, which appear to be independent of or precede demyelination, the formation of plaques may be incidental to a more primary lesion. The finding of persistently increased levels of IgG in the CSF of patients with MS points to an ongoing immune reaction in the CNS, possible against an infective agent; but virus-specific antibodies account for only a small proportion of IgG in the CSF. Furthermore, in vitro assays of T cell function suggest that there may be a regulator T cell defect in MS. Salk and colleagues (1980) have postulated that MS may be a disorder, attributable to multiple inducing agents, which is potentiated through deregulation of lymphocyte function.

In vitro stimulation of glia cells by a lymphocyte-produced factor

The factors responsible for the activation of astrocytes surrounding inflammatory brain tissues are unknown. The present study was designed to examine the ability of lymphocytes to produce astrocyte stimulating activity in cell culture. Normal rat lymphocytes stimulated with Concanavalin A, or sensitized lymphocytes, challenged with antigen in vitro, activate cultured rat glia cells by a soluble mediator which we have termed glia stimulating factor (GSF). In undifferentiated glioblasts both RNA synthesis, as measured by [5-3H]uridine uptake, and DNA synthesis, as measured by [6-3H]thymidine uptake, were stimulated by the presence of GSF. Preliminary characterisation showed the GSF to be non-dialysable and heat stable at 56 degrees C for 30 min, but not stable at 80 degrees C for 30 min. To study the effect of this factor on differentiated glia cells, brain cell cultures were treated with dibutyryl cyclic AMP (db-cAMP) which induces a morphologic transformation of glioblasts to multipolar cells that have a characteristic astrocytic appearance. After addition of GSF to db-cAMP treated astrocytes only an increase in RNA synthesis was observed. The significance of this in vitro phenomenon, mediated by a glia stimulating factor, to activation of astrocytes and astrocytic gliosis in human brain diseases is discussed.