Trypsin inhibitors inhibit induction by interferon-gamma of HLA-DR antigen expression on human skin cells.

Serine protease inhibitors with a specificity for trypsin inhibit interferon-gamma (INF-gamma)-induced HLA-DR expression on a hybrid human epidermal cell line (H12), dermal fibroblasts, and primary keratinocytes. Protease inhibitors with a specificity for chymotrypsin or papain fail to inhibit IFN-gamma. The inhibitory effect of the trypsin inhibitors is similar to that of glucocorticoids in that it is a transient event, fading with length of exposure to IFN-gamma, and is reversed by the addition of dibutyryl cyclic AMP (dbcAMP) and phospholipase C(PLC) from Clostridium perfringens. In H12 cells, dbcAMP and PLC enhance the IFN-gamma induction of HLA-DR, but do not induce in the absence of INF-gamma. Evidence suggests that the protease inhibitors, as well as dbcAMP and PLC, may modulate HLA-DR expression at a post-translational site as well as during IFN-gamma signal transduction. These results suggest that trypsin-like protease activity may be required for cellular HLA-DR antigen expression following exposure to IFN-gamma.

Human plasma extrinsic pathway inhibitor activity: I. Standardization of assay and evaluation of physiologic variables.

An assay was standardized to measure extrinsic pathway inhibitor (EPI) activity in human plasma. Variables that could potentially influence its measurement were systematically examined. The coefficient of variation of the assay was 6.3% for the same sample assayed on different days. The linear regression line for a plot of observed v expected values of mixtures of plasmas with different EPI levels was Y = 1.01X - 2.7%. Single samples from 21 healthy adults under 60 years of age varied between 74% and 159% of a pooled reference plasma. The plasma level of a given individual (eight subjects) did not vary on repeat sampling over weeks to months. EPI activity was significantly lower in plasma from umbilical cord blood (64.3% +/- 12.7%, n = 16) than in plasma from adults. Mean EPI activity in adults greater than or equal to 60 years of age was slightly but significantly higher (112% +/- 16.8%, n = 23) than in adults less than 60 years of age (97.2% +/- 19.0%, n = 21). EPI levels in the third trimester of pregnancy were slightly higher than in nonpregnant women. Plasma EPI levels fell slightly after surgical procedures that caused fibrinogen levels to rise, which suggests that EPI is not an acute phase reactant. Administration of 1-desamino-8-d-arginine vasopressin (DDAVP) did not alter plasma EPI levels. In two patients subjected to plasmapheresis and volume replacement with albumin and isotonic saline, plasma EPI levels returned to one-half of the levels before pheresis within about one day.

Amyloid beta protein precursor is a mitogen.

The form of the secreted amyloid beta-protein precursor which contains the protease inhibitor sequence is mitogenic for Swiss 3T3 cells, while the precursor molecule lacking the protease inhibitor domain is not. A ten-fold stimulation of DNA synthesis occurs at 8 x 10(-9) M protein.

Tissue distribution of antileukoprotease and lysozyme in humans.

We studied the distribution of the proteinase inhibitor antileukoprotease (ALP) and lysozyme (LSZ) in normal human tissues by use of an immunohistochemical technique. ALP could be demonstrated in a variety of healthy tissues, generated by secretory cells in lacrimal, respiratory, proximal digestive, and genital glands, but not in the urinary tract, endocrine glands, or the hematological system. In lung, part of the non-ciliated cell population in membranous bronchiolar epithelium, as well as in respiratory bronchioles, stained positively for the inhibitor. The distribution of ALP and LSZ was parallel in most but not all of the tissues examined. The distribution of ALP around most of the external orifices of the human body is discussed in relation to its possible local physiological role in defense against inflammatory reactions. The widespread parallel distribution of LSZ, a bacteriolytic agent, suggests a complementary role to ALP in local defense.

Inhibition and complexation of activated protein C by two major inhibitors in plasma.

To determine the major physiologic inhibitors of activated protein C (APC), plasma was incubated with APC or with Protac C and subjected to immunoblotting. APC:inhibitor complexes gave two major bands reacting with antiprotein C antibodies when immunoblotted on nondenaturing gels, and additional minor bands that varied between serum and plasma. Formation of one of the two major bands of APC:inhibitor complex, but not the other, was stimulated by heparin and only this band reacted with antibodies to the previously described APC inhibitor that is here designated PCI-1. Plasma immunodepleted of PCI-1 formed complexes with APC as visualized with antiprotein C but not anti-PCI-1 antibodies, and exhibited heparin-independent inhibition of APC activity, providing evidence for the existence of a second major physiologic APC inhibitor, PCI-2. Formation of APC:PCI-2 complexes in PCI-1-depleted plasma paralleled inhibition of APC amidolytic activity. PCI-2 was separated from PCI-1 and partially purified using column chromatography. PCI-2 formed inactive complexes of approximately 110,000 molecular weight (mol wt) with APC suggesting PCI-2 has an approximate mol wt of 50,000. Thus, inhibition of APC in plasma involves two major distinct 50,000 mol wt inhibitors, the heparin-dependent PCI-1 and the heparin-independent PCI-2.

Proteinases and their inhibitors in cells and tissues.

A large body of evidence has been assembled to indicate the substantial importance of proteolytic processes in various physiological functions. It has recently become clear too that endo-acting peptide bond hydrolases provisionally characterized and classified at present as serine, cysteine, aspartic and metallo together with unknown catalytic mechanism proteinases sometimes act in cascades. They are controlled by natural proteinase inhibitors present in cells and body fluids. In the first part of the present monograph the author was concerned to present an overview on the morphological and physiological approach to localization, surveying reaction principles and methods suitable for visualization of proteolytic enzymes and their natural and synthetic inhibitors. In the second part the roles played by proteinases have been summarized from the point of view of cell biology. The selection of earlier and recent data reviewed on the involvement of proteolysis in the behavior of individual cells reveals that enzymes, whether they be exogeneous or intrinsic, can be effective and sensitive modulators of cellular growth and morphology. There exists a close correlation between malignant growth and degradation of cells. It appears likely that as yet unknown or at least so far inadequately characterized factors that influence the survival or the death of cells may turn out to be proteinases. The causal role of extracellular proteolysis in cancer cell metastases, in stopping cancer cell growth and in cytolysis remains for further investigated. Ovulation, fertilization and implantation are basic biological functions in which proteolytic enzymes play a key role. The emergence of new approaches in reproductive biology and a growing factual basis will inevitably necessitate a reevaluation of present knowledge of proteolytic processes involved. The molecular aspects of intracellular protein catabolism have been discussed in terms of the inhibition of lysosomal and/or non-lysosomal protein breakdown. Peptide and protein hormone biosynthesis and inactivation are still at the centre of interest in cell biology, and a number of proteinases have been implicated in both processes. A number of conjectures partly based on the author's own work have been discussed which suggest the possibility of the involvement of proteolysis in exocytosis and endocytosis. The author's optimistic conclusion is that through the common action of biochemists, cell biologists, cytochemists, and pharmacologists the mystery of cellular proteolysis is beginning to be solved.

The organization of the human-plasminogen-activator-inhibitor-1 gene. Implications on the evolution of the serine-protease inhibitor family.

Plasminogen activator inhibitor 1 (PAI-1) is a member of the serine protease inhibitor super family (SERPINS) which is thought to play an integral role in the control of plasminogen activation. PAI-1 inhibits both tissue-type plasminogen activator and urokinase-type plasminogen activator and may therefore be implicated in the control of various physiological processes. We have isolated the PAI-1 gene including its 5'-flanking sequence. The gene was characterized by restriction enzyme analysis, Southern blotting and DNA sequencing of all the coding parts as well as the 5'-flanking region. The PAI-1 gene contains nine exons and eight introns distributed over approximately 12.3 kb of DNA. All exon/intron boundaries agree with the 'GT-AG' rule. To characterize the presumptive promoter region, 800 bp of the 5'-flanking region was sequenced and potential binding sites for transacting transcriptional factors were localized. The transcription initiation site was identified by S1 protection experiments and is located 25 base pairs downstream of a TATA consensus sequence. By aligning the gene structure of PAI-1 and four other SERPINS and extrapolating a general tertiary structure to these SERPINS, we find that most introns map between subdomain structures of the proteins. Evidence is presented supporting an intron loss model for the evolution of the SERPIN family.

Human cathepsin B and cysteine proteinase inhibitors (CPIs) in inflammatory and metabolic joint diseases.

Synovial fluid of patients with different inflammatory and metabolic joint diseases contains low-molecular CPIs (stefins and cystatins) and high-molecular CPIs (kininogens). An additional inhibitory fragment with a molecular mass of about 20 kDa, which is a part of the kininogen molecule, has been detected. Cathepsin B and cystatin C were determined by ELISA test in 47 patients with rheumatoid arthritis, seronegative spondylarthritis, osteoarthritis, undifferentiated arthritis and gout. A significantly higher amount of cathepsin B was found in patients with rheumatoid arthritis. The elevation of cathepsin B was accompanied by an increased amount of cystatin C.

Antileukoprotease, its role in the human lung.

The number of antileukoprotease-containing epithelial cells in the bronchioles of 27 surgically removed lungs shows a close positive correlation with inflammation of the small airways (bronchioles) and an inverse correlation with the number of undamaged alveolar walls surrounding the bronchioles. So, more antileukoprotease-producing cells are present when bronchioles and adjacent alveoli are more diseased. These results suggest that antileukoprotease-producing cells constitute part of the inflammatory response in and around bronchioles, serving to minimize local tissue destruction. The increased production of this potent elastase-inhibitor, however, seems insufficient to prevent tissue damage. We investigated in vitro whether antileukoprotease might be inactivated by stimulated polymorphonuclear leukocytes (PMN's). The antitryptic and antielastolytic capacities of antileukoprotease were rapidly destroyed by myeloperoxidase-derived oxidants from stimulated PMN's. It was observed that elastase, released by stimulated PMN's, retains full activity when cell stimulation was performed in the presence of a molar excess of antileukoprotease. These results indicate that inactivation of antileukoprotease by stimulated PMN's might be a factor which plays a role in elastase-mediated destruction of lung tissue.

Possible relationship between the restricted biological function of rat T kininogen (thiostatin) and its behaviour as an acute phase reactant.

Studies on biological properties of rat T kininogen have shown that the role of this peculiar kininogen so far specific to the rat probably differs significantly from that of other low molecular mass kininogens. In particular the kinin precursor function has been either lost or considerably reduced as a result of structural modifications during evolution. The calpain inhibiting function demonstrated for other low and high molecular mass kininogens has also probably disappeared from T kininogen, and since T genes do not allow the synthesis of high molecular mass kininogens [Kitagawa et al. (1987) J. Biol. Chem. 262, 2190-2198], the procoagulant function devoted to the light chain of high molecular mass kininogen has also been lost by T genes products. The only remaining function of rat T kininogen would be therefore that of a lysosomal cysteine proteinase inhibitor which is expressed either by the native molecule or by proteolytic products which appear to be more easily released than vasoactive peptides. Such a specialization for a given function could be related to the behaviour of T kininogen as an acute phase reactant, the dramatic changes in concentration of which could at the same time serve certain functions and be damageable for others.

Effects of fibroblasts and endothelial cells on inactivation of target proteases by protease nexin-1, heparin cofactor II, and C1-inhibitor.

Previous studies have shown that glycosaminoglycans in the extracellular matrix accelerate the inactivation of target proteases by certain protease inhibitors. It has been suggested that the ability of the matrix of certain cells to accelerate some inhibitors but not others might reflect the site of action of the inhibitors. Previous studies showed that fibroblasts accelerate the inactivation of thrombin by protease nexin-1, an inhibitor that appears to function at the surface of cells in extravascular tissues. The present experiments showed that endothelial cells also accelerate this reaction. The accelerative activity was accounted for by the extracellular matrix and was mostly due to heparan sulfate. Fibroblasts but not endothelial cells accelerated the inactivation of thrombin by heparin cofactor II, an abundant inhibitor in plasma. This is consistent with previous suggestions that heparin cofactor II inactivates thrombin when plasma is exposed to fibroblasts and smooth muscle cells. Neither fibroblasts nor endothelial cells accelerated the inactivation of C1s by plasma C1-inhibitor.

Human cysteine proteinase inhibitors. Isolation, physiological importance, inhibitory mechanism, gene structure and relation to hereditary cerebral hemorrhage.

The isolation and characterization of six human cysteine proteinase inhibitors is reported. Their distribution in human biological fluids is also described and discussed with respect to physiological function. Studies on kininogen and cystatin C with respect to structure-function relationships and, as a result of the cystatin C studies, a general model for the mechanism of cysteine proteinase inhibition by cystatins are presented. The model was used for the construction of synthetic inhibitors which showed good inhibitory properties against papain and the streptococcal cysteine proteinase. Structures of cDNA and gene for normal human cystatin C are accounted for, as well as studies on the cystatin C gene in patients suffering from hereditary cystatin C amyloid angiopathy (HCCAA). As a result of this an RFLP that showed total co-segregation with the disease was found. It was concluded that the disease is caused by a point mutation in the cystatin C structural gene and that the RFLP will be a most useful tool for diagnosis of HCCAA. The production of recombinant cystatin C in E. coli is also reported and its possible use for treatment of HCCAA is discussed.

Anticoagulant potential of endothelial cell membrane components.

In this communication some of the important regulatory mechanisms involving endothelial cell surface associated anticoagulant reactions as well as endothelial cell surface expressed receptors which directly contribute to the inhibition of coagulation are reviewed. In particular, the mechanism of action of protease inhibitors such as antithrombin III, heparin cofactor II, or protease nexin I and their possible interaction with glycosaminoglycan components of the endothelial cells is critically summarized. Thrombin binding to endothelial cells, in particular to thrombomodulin, is believed to be a major event in the induction of anticoagulatory mechanisms such as the protein C/protein S system which warrant a balanced hemostatic system. Additional components such as vascular anticoagulant or extrinsic pathway inhibitor may also contribute to the anticoagulant potential of the vessel wall. Furthermore, the modulation of these membrane-associated anticoagulant reactions by other components such as heparin-binding proteins is discussed.

Regulation of factor XIa activity by platelets and alpha 1-protease inhibitor.

We have studied the complex interrelationships between platelets, Factor XIa, alpha 1-protease inhibitor and Factor IX activation. Platelets were shown to secrete an inhibitor of Factor XIa, and to protect Factor XIa from inactivation in the presence of alpha 1-protease inhibitor and the secreted platelet inhibitor. This protection of Factor XIa did not arise from the binding of Factor XIa to platelets, the presence of high molecular weight kininogen, or the inactivation of alpha 1-protease inhibitor by platelets. The formation of a complex between alpha 1-protease inhibitor and the active-site-containing light chain of Factor XIa was inhibited by activated platelets and by platelet releasates, but not by high molecular weight kininogen. These results support the hypothesis that platelets can regulate Factor XIa-catalyzed Factor IX activation by secreting an inhibitor of Factor XIa that may act primarily outside the platelet microenvironment and by protecting Factor XIa from inhibition, thereby localizing Factor IX activation to the platelet plug.