Pathological Proteolysis Research Articles

Перспективы применения протеомного анализа в офтальмологии

This paper reviews the perspectives of proteomic analysis of tear and aqueous humor to determine biomarkers for the differential diagnosis of eye disorders. The methodology of sample collection and the advantages and disadvantages of the available methods are discussed in detail. The results of proteomic mapping of tear and aqueous humor in dry eye disease, keratoconus, glaucoma, cataract, age-related macular degeneration, and diabetic retinopathy are described. The association between the levels of identified proteins and their role in triggering pathological processes, e.g., oxidative stress with autophagy (and, as a result, tissue dystrophy), initiation of inflammation, and impairment of metabolic processes at the molecular level with activation of pathological proteolysis (that ultimately lead to cellular and tissue changes with the development of the above-mentioned diseases) are of particular importance. This paper also emphasizes the practical relevance of using proteomics to study the pathogenesis of eye diseases, which implies determining the association between genotype and phenotype of a patient in clinical practice with further treatment personalization. Proteomics also provides an early noninvasive diagnosis of socially significant eye diseases. KEYWORDS: proteomic analysis, tear, aqueous humor, mass spectrometry, eye disorders. FOR CITATION: Krylova A.A., Zakharchuk A.V., Krivosheina O.I., Pekov S.I., Popov I.A. Perspectives of proteomic analysis in ophthalmology. Russian Journal of Clinical Ophthalmology. 2023;23(4):213–218 (in Russ.). DOI: 10.32364/2311-7729-2023-23-4-7.

Inhibition of Human Cathepsins B and L by Caffeic Acid and Its Derivatives.

Caffeic acid (CA) and its derivatives caffeic acid phenethyl ester (CAPE) and chlorogenic acid (CGA) are phenolic compounds of plant origin with a wide range of biological activities. Here, we identify and characterize their inhibitory properties against human cathepsins B and L, potent, ubiquitously expressed cysteine peptidases involved in protein turnover and homeostasis, as well as pathological conditions, such as cancer. We show that CAPE and CGA inhibit both peptidases, while CA shows a preference for cathepsin B, resulting in the strongest inhibition among these combinations. All compounds are linear (complete) inhibitors acting via mixed or catalytic mechanisms. Cathepsin B is more strongly inhibited at pH 7.4 than at 5.5, and CA inhibits its endopeptidase activity preferentially over its peptidyl-dipeptidase activity. Altogether, the results identify the CA scaffold as a promising candidate for the development of cathepsin B inhibitors, specifically targeting its endopeptidase activity associated with pathological proteolysis of extracellular substrates.

Proteolytic cleavage of Podocin by Matriptase exacerbates podocyte injury

Podocyte injury is a critical step toward the progression of renal disease and is often associated with a loss of slit diaphragm proteins, including Podocin. Although there is a possibility that the extracellular domain of these slit diaphragm proteins can be a target for a pathological proteolysis, the precise mechanism driving the phenomenon remains unknown. Here we show that Matriptase, a membrane-anchored protein, was activated at podocytes in CKD patients and mice, whereas Matriptase inhibitors slowed the progression of mouse kidney disease. The mechanism could be accounted for by an imbalance favoring Matriptase over its cognate inhibitor, hepatocyte growth factor activator inhibitor type 1 (HAI-1), because conditional depletion of HAI-1 in podocytes accelerated podocyte injury in mouse model. Matriptase was capable of cleaving Podocin, but such a reaction was blocked by either HAI-1 or dominant-negative Matriptase. Furthermore, the N terminus of Podocin, as a consequence of Matriptase cleavage of Podocin, translocated to nucleoli, suggesting that the N terminus of Podocin might be involved in the process of podocyte injury. Given these observations, we propose that the proteolytic cleavage of Podocin by Matriptase could potentially cause podocyte injury and that targeting Matriptase could be a novel therapeutic strategy for CKD patients.

Role of metalloproteinases and their inhibitors in intervertebral disc degeneration: research progress

Intervertebral disc degeneration(IVDD)is characterized by the excessive degradation of extracellular matrix(ECM),which underlies many spine-related disorders.Matrix metalloproteinases(MMPs)and a disintegrin metalloproteinases with thrombospondin motifs(ADAMTSs)are believed to be the major proteolytic enzymes responsible for ECM degradation.This review summarizes the current literatures on gene expression and regulation of MMPs,ADAMTSs,and tissue inhibitors of metalloproteinases(TIMPs)in IVDD.Reports have showen that specific MMPs(MMP-1,-2,-3,-7,-8,-10,and-13)and ADAMTS(ADAMTS-1,-4,and-15)are upregulated in human degenerated intervertebral discs.Tissue inhibitor of metalloproteinase-3is downregulated and TIMP-1 is upregulated in human degenerated intervertebral discs relative to nondegenerated intervertebral discs.Regulation of the MMP and ADAMTS expression is affected by many factors including mechanical,inflammatory,oxidative stress,and so on.Genetic predisposition also plays an important role in expression of MMP-1,-2,-3,and-9.Upregulation of MMP and ADAMTS expression is implicated in ECM destruction,which can lead to the development of IVDD.Future IVDD therapeutics may target specific MMPs and ADAMTSs which is essential in the pathological proteolysis of ECM.

Calpain Protease Causes Hypoxia-Induced Proteolysis in Cultured Human Retina

Purpose/Aim: Calpain proteases are known to be involved in retinal cell death in animal models. The purpose of the present study was to test for calpain activation in human retinas cultured under hypoxic conditions.Materials and Methods: Calpain activation was detected by immunoblotting for calpain substrates in human and monkey retinas cultured in gas generating pouches to reduce oxygen.Results: Hypoxia caused activation of calpains as measured by accumulation of the calpain-specific 145 kDa α-spectrin breakdown product. Opsin-1 (photoreceptor marker) and vimentin (Müller cell marker) were degraded. Calpain inhibitor SNJ-1945 ameliorated these changes. Results were similar to comparative data from cultured monkey retinas.Conclusions: In cultured human retina, hypoxia caused activation of calpain and subsequent proteolysis of critical substrates. The efficacy of SNJ-1945 in ameliorating these changes indicated that it might be useful to test as a drug for protecting against pathologic proteolysis of photoreceptor and Müller cells.

The C Terminus of Cardiac Troponin I Stabilizes the Ca 2+ -Activated State of Tropomyosin on Actin Filaments

Ca(2+) control of troponin-tropomyosin position on actin regulates cardiac muscle contraction. The inhibitory subunit of troponin, cardiac troponin (cTn)I is primarily responsible for maintaining a tropomyosin conformation that prevents crossbridge cycling. Despite extensive characterization of cTnI, the precise role of its C-terminal domain (residues 193 to 210) is unclear. Mutations within this region are associated with restrictive cardiomyopathy, and C-terminal deletion of cTnI, in some species, has been associated with myocardial stunning. We sought to investigate the effect of a cTnI deletion-removal of 17 amino acids from the C terminus- on the structure of troponin-regulated tropomyosin bound to actin. A truncated form of human cTnI (cTnI(1-192)) was expressed and reconstituted with troponin C and troponin T to form a mutant troponin. Using electron microscopy and 3D image reconstruction, we show that the mutant troponin perturbs the positional equilibrium dynamics of tropomyosin in the presence of Ca(2+). Specifically, it biases tropomyosin position toward an "enhanced C-state" that exposes more of the myosin-binding site on actin than found with wild-type troponin. In addition to its well-established role of promoting the so-called "blocked-state" or "B-state," cTnI participates in proper stabilization of tropomyosin in the "Ca(2+)-activated state" or "C-state." The last 17 amino acids perform this stabilizing role. The data are consistent with a "fly-casting" model in which the mobile C terminus of cTnI ensures proper conformational switching of troponin-tropomyosin. Loss of actin-sensing function within this domain, by pathological proteolysis or cardiomyopathic mutation, may be sufficient to perturb tropomyosin conformation.

Plasminogen activator inhibitor-1 is locked in active conformation and polymerizes upon binding ligands neutralizing its activity

Plasminogen activator inhibitor-1 (PAI-1), a member of the serpin super-family, forms a covalent complex with its target proteinases, such as tissue and urokinase plasminogen activators. Thus, PAI-1 controls the physiological and pathological proteolysis. An abnormal expression of PAI-1 has been observed in different diseases, which can be treated by returning the proteolysis back to normal physiological levels. It has been reported that some PAI-1 inhibitors neutralize its activity by accelerating the conversion of PAI-1 into a latent form. We have found small organic chemicals that also neutralize PAI-1 activity, but by a different mechanism. Using the NBD fluorescent probe [N,N'-dimethyl-N-(acetyl)-N'-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)] incorporated into the reactive center loop (RCL) of PAI-1, we measured the kinetics of conversion from an active to a latent form. Unexpectedly, we found that some inhibitors of PAI-1 arrest this serpin in its active form instead of increasing the speed of conversion. Using docking calculations, we located two possible binding sites for these chemicals. The sites are in proximity of the P1/P1' amino acids of the RCL of PAI-1. Binding in this area can inactivate PAI-1 and additionally create a steric obstacle on the RCL making insertion of this loop between the A3 and A5 strands more difficult; hence abolishing a necessary step in the conversion of this protein into the latent form. Additionally, PAI-1 inhibitors link the RCL of one PAI-1 molecule with the strand 3C and strand 4C or helix A and strand 1B regions of the other PAI-1 molecule aiding polymerization or stabilizing the junction of the two. The polymerization of PAI-1 reduces PAI-1 activity by encapsulating the critical RCL fragment inside the formed PAI-1/PAI-1 polymers.

Cystatin C is highly expressed in the human male reproductive system.

Cystatin C displays the strongest inhibitory activity of all cystatins toward lysosomal cysteine proteases in general and has a widespread distribution in human tissues and body fluids, including seminal plasma. The aim of this study was to investigate the distribution of cystatin C in the male reproductive system. Immunohistochemistry revealed a widespread distribution of cystatin C in normal tissues from the testis, epididymis, vas deferens, seminal vesicle, and prostate gland. Immunoreactive cystatin C was localized in basal and secretory epithelial cells, but also in neuroendocrine cells in the prostate, identified by immunostaining for chromogranin A. On adjacent tissue sections, we demonstrated local production of cystatin C utilizing nonradioactive in situ hybridization with a 201-base-long digoxigenin-labeled antisense RNA probe specific for the cystatin C transcript. Staining patterns obtained by immunohistochemistry and in situ hybridization correlated well. Enzyme-linked immunosorbent assay for quantitative analysis of cystatin C demonstrated that cystatin C was present at high concentrations in tissue homogenates from all locations investigated, compared to liver, muscle, spleen, and other general tissues. Western blotting of tissue homogenates revealed a predominant 15-kd cystatin C immunoreactive component in accordance with previous findings in other organs. Quantitative real-time polymerase chain reaction analysis to determine messenger RNA levels in whole tissue extracts showed that the cystatin C gene is highly expressed in the seminal vesicles and the prostate gland, indicating that the major amount of cystatin C in the male reproductive organs and seminal plasma is produced by cells in these 2 tissues. It is concluded that cystatin C is highly expressed and widely distributed throughout the male genital tract, suggesting that cystatin C is an important regulator for normal and pathological proteolysis in the male reproductive system.

Cathepsin B expression and down-regulation by gene silencing and antisense DNA in human chondrocytes.

Cathepsin B, a marker of the dedifferentiated chondrocyte phenotype, contributes to cartilage destruction in osteoarthritis and pathological proteolysis in rheumatoid arthritis and cancer. In search of possible means for neutralizing the action of this enzyme, we compared its expression, biosynthesis and distribution in articular chondrocytes and two lines of immortalized human chondrocytes. Native articular chondrocytes in primary culture and the polyclonal T/C-28a2 chondrocyte cell line were similar with respect to the number of endosomes and lysosomes, the distribution of three alternatively spliced cathepsin B mRNA forms, and the cathepsin B activity. In contrast, the clonal C-28/I2 cell line contained four times higher levels of intracellular cathepsin B activity, slightly higher numbers of endosomes and lysosomes, and uniform distribution of all three cathepsin B transcripts and thus resembled subcultured chondrocytes at an early stage of dedifferentiation. Transfection of T/C-28a2 chondrocytes with double-stranded cathepsin B mRNA resulted in inhibition of cathepsin B biosynthesis by up to 70% due to RNA interference, and single-stranded antisense DNAs of various sizes decreased cathepsin B biosynthesis by up to 78%. An antisense oligonucleotide designed to hybridize to the end of cathepsin B's exons 1 and the beginning of exon 3 was successful in specifically inhibiting the mRNA splice variant lacking exon 2. These results indicate that cathepsin B expression and activity may be targeted for gene silencing by RNA interference and antisense DNA in chondrocytes. Furthermore, the differential expression and distribution of cathepsin B and presence of the necessary molecular apparatus for gene silencing in the immortalized human chondrocyte cell lines indicate that they may serve as a useful model for studying the function of relevant enzymes in cartilage pathologies.

A brain derived peptide preparation reduces the translation dependent loss of a cytoskeletal protein in primary cultured chicken neurons.

Neuronal cytoskeletal proteins like the microtubule associated protein 2 (MAP2) are objected to pathological proteolysis in case of Alzheimer's disease and brain ischemia. The neurotrophic peptidergic drug Cerebrolysin (EBEWE Arzneimittel, Austria, Europe) is produced by a standardized enzymatic break-down of lipid free porcine brain proteins. Cerebolysin protected MAP2 in primary neuronal cultures after a brief histotoxic hypoxia and in a rat model of acute brain ischemia. Furthermore the drug was shown to inhibit the proteases mu- and m-calpain dose dependently in several cell free protease activity assays. The question if the higher MAP2 levels are due to an alleviation of proteolysis, to a higher synthesis rate or both is addressed in the current investigation: Monitoring the MAP2 content of primary neuronal cell cultures over a period of eight days revealed MAP2 to reach a peak level on day six in vitro followed by a degradation phase. In other experiments the protein synthesis of Cerebrolysin treated and untreated cells was blocked with cycloheximide at that moment when all cells exhibited the same MAP2 content. After the following MAP2 degradation phase--i.e. after eight days in vitro--the MAP2 contents were determined by western blotting. Cerebrolysin treated cells contained more MAP2 than untreated controls proving that the drug protects MAP2 independently from de novo synthesis, although further work is in progress to investigate if the drug supplementary boosts this effect by increasing MAP2 synthesis.

Studies of a Second Family With the Quebec Platelet Disorder: Evidence That the Degradation of the α-Granule Membrane and Its Soluble Contents Are Not Secondary to a Defect in Targeting Proteins to α-Granules

AbstractWe recently described a Quebec family with an autosomal dominant bleeding disorder characterized by mildly reduced-low normal platelet counts, an epinephrine aggregation defect, multimerin deficiency, and proteolytic degradation of several, soluble α-granular proteins. Similar clinical features led us to investigate a second family with an unexplained, autosomal dominant bleeding disorder. The affected individuals had reduced to normal platelet counts, absent platelet aggregation with epinephrine, and multimerin deficiency. Their platelet α-granular proteins factor V, thrombospondin, von Willebrand factor, fibrinogen, fibronectin, osteonectin, and P-selectin were proteolyzed and comigrated with the degradation products found in patients from the other family. However, their platelet albumin, IgG, external membrane glycoproteins, CD63 (a lysosomal and dense granular protein), calpain, and plasma von Willebrand factor were normal, indicating restriction in the proteins proteolyzed. Electron microscopy studies indicated preserved α-granular ultrastructure, despite degradation of soluble and membrane α-granular proteins. Immunoelectron microscopy studies of the patients' platelets indicated that fibrinogen, von Willebrand factor, P-selectin, multimerin, and factor V were within α-granules, with normal to reduced labeling for these proteins. Pathologic proteolysis of α-granular contents, rather than a defect in targeting proteins to α-granules, may be the cause of the protein degradation in the Quebec platelet disorder.

Solution structure of the catalytic domain of human stromelysin complexed with a hydrophobic inhibitor.

Stromelysin, a representative matrix metalloproteinase and target of drug development efforts, plays a prominent role in the pathological proteolysis associated with arthritis and secondarily in that of cancer metastasis and invasion. To provide a structural template to aid the development of therapeutic inhibitors, we have determined a medium-resolution structure of a 20-kDa complex of human stromelysin's catalytic domain with a hydrophobic peptidic inhibitor using multinuclear, multidimensional NMR spectroscopy. This domain of this zinc hydrolase contains a mixed beta-sheet comprising one antiparallel strand and four parallel strands, three helices, and a methionine-containing turn near the catalytic center. The ensemble of 20 structures was calculated using, on average, 8 interresidue NOE restraints per residue for the 166-residue protein fragment complexed with a 4-residue substrate analogue. The mean RMS deviation (RMSD) to the average structure for backbone heavy atoms is 0.91 A and for all heavy atoms is 1.42 A. The structure has good stereochemical properties, including its backbone torsion angles. The beta-sheet and alpha-helices of the catalytic domains of human stromelysin (NMR model) and human fibroblast collagenase (X-ray crystallographic model of Lovejoy B et al., 1994b, Biochemistry 33:8207-8217) superimpose well, having a pairwise RMSD for backbone heavy atoms of 2.28 A when three loop segments are disregarded. The hydroxamate-substituted inhibitor binds across the hydrophobic active site of stromelysin in an extended conformation. The first hydrophobic side chain is deeply buried in the principal S'1 subsite, the second hydrophobic side chain is located on the opposite side of the inhibitor backbone in the hydrophobic S'2 surface subsite, and a third hydrophobic side chain (P'3) lies at the surface.

Cathepsin L inactivates alpha 1-proteinase inhibitor by cleavage in the reactive site region.

The lysosomal cysteine proteinases cathepsin L and cathepsin B were examined for their effect on the neutrophil elastase inhibitory activity of human alpha 1-proteinase inhibitor (alpha 1PI). Human cathepsin L catalytically inactivated human alpha 1PI by cleavage of the bonds Glu354-Ala355 and Met358-Ser359 (the serine proteinase inhibitory site). Cathepsin B did not inactivate alpha 1PI, even when equimolar amounts of enzyme were employed. Cathepsin L is the first human proteinase shown to catalytically inactivate alpha 1PI. These findings, in conjunction with other reports, suggest that alpha 1PI contains a proteolytically sensitive region encompassing residues 350-358. Taken together with the discovery of the elastinolytic activity of cathepsin L (Mason, R. W., Johnson, D. A., Barrett, A. J., and Chapman, H. A. (1986) Biochem. J. 233, 925-927), the present findings emphasize the possible importance of cathepsin L in the pathological proteolysis of elastin and diminish the role that can be attributed to cathepsin B in such processes.

Protease-antiprotease imbalance, hemodynamic and regional blood flow changes in experimental pancreatitis.

Pathologic proteolysis in pancreatitis is an important clue to understand the pathophysiology in pancreatitis. Impairment of pancreatic circulation is also important in the development of severe pancreatitis. In an attempt to study some of the biochemical and circulatory events in experimental pancreatitis in the pig the following experiments were undertaken. Pancreatic and splanchnic blood flow were studied in severe and mild pancreatitis with the microsphere method, together with cardiac output and mean arterial pressure. Kininogen, alpha-2-macroglobulin and alpha-1-proteinase inhibitor were measured in plasma and in peritoneal fluid. In severe pancreatitis consumption of kininogen in the peritoneal cavity was demonstrated together with a final lowering of the plasma protease inhibitors. This was accompanied by a rapid reduction of cardiac output and finally mean arterial blood pressure. Pancreatic blood flow was profoundly diminished in this group. No such changes were found in mild pancreatitis. It is concluded that pancreatic ischemia in pancreatitis is associated with protease-antiprotease imbalance.

A possible role of intestinal mucin in the pathophysiology of intestinal strangulation obstruction. Consequences of tracing a clinical observation.

In intestinal strangulation obstruction, the pathophysiology is created by factors deriving from the host as well as from the intestinal flora. This article has focused upon the importance of one host-derived factor, i.e. intestinal mucin. Based upon a long series of in vitro and in vivo experiments utilizing germfree as well as conventional animals, it is concluded that intestinal mucin plays a major role in triggering a pathological plasma proteolysis, thereby interacting with microbial products (as endotoxin) in creating the whole variety of serious symptoms found in this situation.

Studies on pathological plasma proteolysis in severely burned patients using chromogenic peptide substrate assays: a preliminary report.

Changes in components of the plasma proteolytic enzyme systems were studied in nine patients with severe burns using chromogenic peptide substrate assay technique. All patients were critically ill and five died during a four week observation period. Plasma prekallikrein, plasminogen, prothrombin and platelet values decreases regularly in all patients after the injury. These changes were seen together with a high frequency of increases serum FDP values and presence of soluble fibrin. During critical illness extensive plasma proteolysis occurred, indicated by elevated plasma kallikrein and plasmin activities combined with lowered functional plasma kallikrein inhibition, prekallikrein and plasminogen values. The study confirms that plasma pathological proteolysis occurs in patients with severe burns, and indicates that close monitoring of components of the plasma proteolytic enzyme systems can give information of prognostic and therapeutic value in the severely burned patient.

Proteolytic cleavage and inactivation of alpha 2-plasmin inhibitor and C1 inactivator by human polymorphonuclear leukocyte elastase.

This study has examined the interaction between human leukocyte elastase and alpha 2-plasmin inhibitor, or C1 inactivator, inhibitors of proteases of the complement, kinin, coagulation, and fibrinolytic enzyme systems. Leukocyte elastase, in catalytic concentrations, progressively inactivates the plasmin inhibitory activity of both inhibitors. The C1s binding function of C1 inactivator is also destroyed by leukocyte elastase. The nature of the molecular events underlying the inactivation of these protease inhibitors was examined by acrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Loss of functional activity was accompanied by limited proteolytic cleavage of both inhibitors with the production of several characteristic derivative peptide chains. Leukocyte elastase cleaved alpha 2-plasmin inhibitor at two separate sites and generated lower molecular weight fragments similar to those produced by bovine beta-trypsin. C1 inactivator was hydrolyzed at three different regions on the molecule whereas beta-trypsin cleaved two regions in common with leukocyte elastase. These findings suggest that inactivation of alpha 2-plasmin inhibitor and C1 inactivator by leukocyte elastase released in the inflammatory reaction may potentiate pathological proteolysis. The limited digestion of these inhibitory proteins by leukocyte elastase may prove useful in studies of their primary structure.

Abruptio placentae--treatment with the fibrinolytic inhibitor tranexamic acid.

Abruptio placentae is known to have a bad prognosis for the fetus. Pathologic proteolysis, e.g. a pathologic activation of the coagulation mechanism and/or the fibrinolytic system is known to be a common complication in such cases. Analysis of the coagulation factors and components of the fibronlytic system in the acute stage of 14 cases confirmed the earlier finding of mainly an activation of the fibrinolytic system, which argues for the use of a specific inhibitor. 73 consecutive cases of abruptio placentae were treated with tranexamic acid in the acute stage. 67 of the patients were immediately delivered by cesarean section. The remaining six patients were in early gestational age and were treated for a prolonged period. The perinatal mortality of the entire group was only 8 per cent and the maternal mortality nil. None of the cases were complicated by hemorrhagic diathesis or thromboses. We believe that routine immediate treatment with tranexamic acid can reduce the perinatal mortality in cases of abruptio placentae.

Neutral protease inhibitors from human intervertebral disc and femoral head articular cartilage

Assays of several proteases, incorporating guanidinium chloride extracts of human femoral head cartilage and intervertebral disc, demonstrated that both tissues contain inhibitors of certain serine proteases. Trypsin, chymotrypsin and a granule extract of human polymorphonuclear leukocyte containing elastase and cathepsin G activities, were inhibited by low molecular weight fractions prepared by Sephadex G-75 chromatography. Using a radioassay, it was further shown that these fractions inhibit proteolysis of cartilage proteoglycan. The inhibitor in intervertebral disc is concentrated in the nucleus pulposus, with a decreasing gradient to the periphery of the annulus fibrosus. It is proposed that these inhibitors confer at least partial protection against pathological proteolysis of the proteoglycans in human articular cartilage and nucleus pulposus.

Factor VIII activity and antigen in sick newborns with pathological proteolysis in blood.

Factor VIII clotting activity (VII:C) and factor VIII related antigen (VIII:R:AG) were determined in 12 sick newborn infants with pathological proteolysis in their circulation. A marked discrepancy was noted between VIII:R:AG and VIII:C, the ratio in sick infants being, on average, 2:1, while no discrepancy was seen in healthy newborns. The finding in the sick infants resembled a low grade plasminogen activation, which was studied experimentally. It is concluded that demonstration of a marked discrepancy between VIII:R:AG and VIII:C is a useful indication of pathologic proteolysis in sick newborns.