Associations of TNF-α -308 G>A and TNF-β 252 A>G with Physical Function and BNP-Rugao Longevity and Ageing Study

OBJECTIVES

To explore the associations of TNF-α -308 G>A (rs1800629) and TNF-β 252 A>G (rs909253) with physical function and plasma B-type natriuretic peptide (BNP).

METHODS

Data of 1747 community-dwelling elders from the ageing arm of the Rugao Longevity and Ageing Study was used. Physical function was measured by handgrip strength, Timed Up and Go (TUG) test and 5-meter walking test (5MWT).

RESULTS

AA genotype of the TNF-α -308 G>A was associated with higher mean time of TUG test and 5MWT (multivariable adjusted β=5.75 and 5.70, respectively, p<0.05), compared with GG genotype. For the TNF-β 252 A>G polymorphism, GG genotype was associated with higher mean time of TUG test and 5MWT (multivariable adjusted β=1.55 and 0.83, respectively, p<0.05) and lower handgrip strength (multivariable adjusted β=-0.69, p<0.05), compared with AA genotype. Further, GG was associated with greater odds of low handgrip strength (OR=1.47, 95% CI=1.06-2.04), low speed of TUG test (OR=1.87, 95% CI=1.20-2.01) and elevated BNP (OR=1.30, 95% CI=1.08-1.84). GG also interacted with elevated BNP to be associated with greater odds of low handgrip strength and 5MWT.

CONCLUSIONS

TNF-β 252 A>G was associated with physical function measurements, plasma BNP level, and odds of elevated BNP in an elderly population. TNF-β 252 A>G also interacted with elevated BNP to be associated with greater odds of physical function measurements.

Cathepsin S controls adipocytic and osteoblastic differentiation, bone turnover, and bone microarchitecture

Cathepsin S is a cysteine protease that controls adipocyte differentiation and has been implicated in vascular and metabolic complications of obesity. Considering the inverse relation of osteoblasts and adipocytes and their mutual precursor cell, we hypothesized that cathepsin S may also affect osteoblast differentiation and bone remodeling. Thus, the fat and bone phenotypes of young (3 months old) and aged (12 or 18 months old) cathepsin S knock-out (KO) and wild-type (WT) mice were determined. Cathepsin S KO mice had a normal body weight at both ages investigated, even though the amount of subscapular and gonadal fat pads was reduced by 20%. Further, cathepsin S deficiency impaired adipocyte formation (-38%, p<0.001), which was accompanied by a lower expression of adipocyte-related genes and a reduction in serum leptin, IL-6 and CCL2 (p<0.001). Micro-CT analysis revealed an unchanged trabecular bone volume fraction and density, while tissue mineral density was significantly lower in cathepsin S KO mice at both ages. Aged KO mice further had a lower cortical bone mass (-2.3%, p<0.05). At the microarchitectural level, cathepsin S KO mice had thinner trabeculae (-8.3%), but a better connected trabecular network (+24%). Serum levels of the bone formation marker type 1 procollagen amino-terminal-propeptide and osteocalcin were both 2-3-fold higher in cathepsin S KO mice as was the mineralized surface. Consistently, osteogenic differentiation was increased 2-fold along with an increased expression of osteoblast-specific genes. Interestingly, serum levels of C-terminal telopeptide of type I collagen were also higher (+43%) in cathepsin S KO mice as were histological osteoclast parameters and ex vivo osteoclast differentiation. Thus, cathepsin S deficiency alters the balance between adipocyte and osteoblast differentiation, increases bone turnover, and changes bone microarchitecture. Therefore, bone and fat metabolisms should be monitored when using cathepsin S inhibitors clinically.

Immunomodulation of vascular diseases: atherosclerosis and autoimmunity

The autoimmune disease atherosclerosis contributes to several vascular complications. Besides vascular cells, inflammatory cells occur prominently in atherosclerotic lesions; lymphocytes play a detrimental role in the initiation and progression of this common vascular disease. Recent discoveries have led to the identification of several important lymphocyte types within the atherosclerotic lesions. However, peripheral lymphocytes and those in the lymphoid organs both figure critically in the regulation of atherosclerotic lesion growth. Although the concept of atherosclerosis as an autoimmune disease is well known, the ways in which autoantigens and autoantibodies contribute to atherogenesis in human or even in animal models remains largely unknown. For example, autoantigen immunisation can either promote or attenuate atherogenesis in animals, depending on the antigen types and the routes and carriers of immunisation. This article summarises recent findings regarding lesion inflammatory cell types, autoantigens and autoantibody isotypes that can affect the initiation and progression of atherosclerosis from both human and animal studies.

Leukocyte cathepsin S is a potent regulator of both cell and matrix turnover in advanced atherosclerosis

OBJECTIVE

A dysbalance of proteases and their inhibitors is instrumental in remodeling of atherosclerotic plaques. One of the proteases implicated in matrix degradation is cathepsin-S (CatS). To address its role in advanced lesion composition, we generated chimeric LDLr(-/-) mice deficient in leukocyte CatS by transplantation with CatS(-/-)xLDLr(-/-) or with LDLr(-/-) bone marrow and administered a high-fat diet.

METHODS AND RESULTS

No difference in aortic root lesion size could be detected between CatS(+/+) and CatS(-/-) chimeras. However, leukocyte CatS deficiency markedly changed plaque morphology and led to a dramatic reduction in necrotic core area by 77% and an abundance of large foam cells. Plaques of CatS(-/-) chimeras contained 17% more macrophages, 62% less SMCs, and 33% less intimal collagen. The latter two could be explained by a reduced number of elastic lamina fractures. Moreover, macrophage apoptosis was reduced by 60% with CatS deficiency. In vitro, CatS was found to be involved in cholesterol metabolism and in macrophage apoptosis in a collagen and fibronectin matrix.

CONCLUSIONS

Leukocyte CatS deficiency results in considerably altered plaque morphology, with smaller necrotic cores, reduced apoptosis, and decreased SMC content and collagen deposition and may thus be critical in plaque stability.

Cathepsin L function in insect moulting: molecular cloning and functional analysis in cotton bollworm, Helicoverpa armigera

Moulting is an essential process of insect development but little is known about cysteine proteases in the process. Here, we detail a proteolytic activity profile from fifth larval instar to new pupae of the lepidopteran Helicoverpa armigera. At fifth to sixth instar moulting, the activities were significantly higher than those in non-moulting stages, and were inhibited by the cysteine protease inhibitor, 2S, 3S-trans-epoxysuccinyl-L-leucylamido-3-methylbutane ethyl ester (E-64), or by the cathepsin L-selective inhibitor CLIK148. Further, a 1513 bp cathepsin L cDNA (Har-CL) was isolated from the H. armigera larval cuticle and epidermis layer. Har-CL gene expression, which is correlated closely with ecdysone, was higher during larval moulting. Injection of E-64 or CLIK148 resulted in delayed fifth to sixth instar moulting, suggesting an essential role for cathepsin L in larval moulting.

Chronic Inflammation, Immune Response, and Infection in Abdominal Aortic Aneurysms

Abdominal aortic aneurysms (AAA) are associated with atherosclerosis, transmural degenerative processes, neovascularization, decrease in content of vascular smooth muscle cells, and a chronic infiltration, mainly located in the outer aortic wall. The chronic infiltration consists mainly of macrophages, lymphocytes, and plasma cells. The dominant cells are Th2 restricted CD3+ lymphocytes expressing interleukine 4, 5, 8, and 10, and tumor necrosis factor-alpha for regulation of the local immune response. They also produce interferon-gamma and CD40 ligand to stimulate surrounding cells to produce matrix metalloproteases and cysteine proteases for aortic matrix remodeling. The lymphocyte activation may be mediated by microorganisms as well as autoantigens generated from vascular structural proteins, perhaps through molecular mimicry. As in autoimmune diseases, the risk of AAA is increased by certain genotypes concerning human leucocyte antigen class II. These types are also associated with increased aneurysmal inflammation indicating a genetic susceptibility to aortic inflammation. Chlamydia pneumoniae is often detected in AAA but the validity of the methods can be questioned, and two small antibiotic trials have been disappointing. However, serum antibodies against C. pneumoniae have been associated with AAA growth and cross-react with AAA wall proteins. Thus, immune responses mediated by microorganisms and autoantigens may play a pivotal role in AAA pathogenesis.

Relationships between activators and inhibitors of plasminogen, and the progression of small abdominal aortic aneurysms

OBJECTIVE

plasmin is a common activator of the known proteolytic systems involved in the aneurysmal degradation, and is reported to be associated with the expansion of abdominal aortic aneurysms (AAA). The aim of this study was to study the activating pathways of plasminogen as predictors of the progression of AAA.

MATERIALS AND METHODS

one hundred and twelve of 122 male patients with a small AAA (def.: +3cm) were interviewed, examined, had blood samples taken at diagnosis, and scanned annually for 1-5 years (mean 3.5 years), and referred for surgery if the AAA exceeded 5cm in diameter.A random sample of 70 of the 112 cases had plasma levels of urokinase-like-plasminogen activator (uPA), tissue-type-plasminogen activator (tPA), plasminogen-activator-inhibitor-1 (PAI-1), macrophage inhibiting factor (MIF), tumour-growth-factor-beta1 (TGF-beta1), homocysteine, and serum levels of IgA-antibodies against Chlamydia pneumoniae (IgA-CP) and Cotinine (a nicotine metabolite) measured. Spearmans correlation analysis was used for statistics.

RESULTS

the annual expansion rate correlated positively with tPA, IgA-CP and S-Cotinine; r =0.37 (p=0.002), 0.29 (p=0.006) and 0.24 (p=0.038), while PAI1, uPA, TGF-beta1, homocysteine, and MIF did not. S-Cotinine did also correlate positively with tPA, r=0.24 (p=0.049).

CONCLUSION

the aortic matrix degradation in AAA may be partly caused by an activation of plasminogen by tPA, but apparently not by uPA, which usually dominates matrix degradation. Smoking seems to be a factor for this pathway, while the pathways of IgA-CP and MIF, a new marker of aneurysmal progression, seem different. The latter observations suggest that other proteolytic pathways are involved in the aortic wall degradation in AAA.

Deficiency of the cysteine protease cathepsin S impairs microvessel growth

During angiogenesis, microvascular endothelial cells (ECs) secrete proteinases that permit penetration of the vascular basement membrane as well as the interstitial extracellular matrix. This study tested the hypothesis that cathepsin S (Cat S) contributes to angiogenesis. Treatment of cultured ECs with inflammatory cytokines or angiogenic factors stimulated the expression of Cat S, whereas inhibition of Cat S activity reduced microtubule formation by impairing cell invasion. ECs from Cat S-deficient mice showed reduced collagenolytic activity and impaired invasion of collagens type I and IV. Cat S-deficient mice displayed defective microvessel development during wound repair. This abnormal angiogenesis occurred despite normal vascular endothelial growth factor and basic fibroblast growth factor levels, implying an essential role for extracellular matrix degradation by Cat S during microvessel formation. These results demonstrate a novel function of endothelium-derived Cat S in angiogenesis.

Regulation of CD1 function and NK1.1(+) T cell selection and maturation by cathepsin S

NK1.1(+) T cells develop and function through interactions with cell surface CD1 complexes. In I-A(b) mice lacking the invariant chain (Ii) processing enzyme, cathepsin S, NK1.1(+) T cell selection and function are impaired. In vitro, thymic dendritic cells (DCs) from cathepsin S(-/-) mice exhibit defective presentation of the CD1-restricted antigen, alpha-galactosylceramide (alpha-GalCer). CD1 dysfunction is secondary to defective trafficking of CD1, which colocalizes with Ii fragments and accumulates within endocytic compartments of cathepsin S(-/-) DCs. I-A(k), cathepsin S(-/-) mice do not accumulate class II-associated Ii fragments and accordingly do not display CD1 abnormalities. Thus, function of CD1 is critically linked to processing of Ii, revealing MHC class II haplotype and cathepsin S activity as regulators of NK T cells.

[Role of hydrogen peroxide in promoting proliferation and transformation of rat liver oval cell line WB-F344]

OBJECTIVE

To study the role of hydrogen peroxide (H2O2) in promoting proliferation and transformation of rat liver oval cell line WB-F344.

METHODS

Culturing WB-F344 cells were stimulated directly by H2O2. The effect of H2O2 in promoting proliferation of WB cells was investigated by using MTT colorimetric analysis and 3H-TdR incorporation liquid scintillation counter. The normal WB cells and the WB cells initiated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were both promoted by stimulating continuously with H2O2 of low concentration (800 nmol/L). The transformation effect was tested by morphologic observation, karyotype analysis, and anchorage-independent growth assay.

RESULTS

Proliferation of WB cells was induced obviously by H2O2 of low concentration for only one time. The normal WB cells and the WB cells initiated with MNNG were transformed by action with H2O2 of low concentration continuously for 28 days and typical morphologic characters of transformed cells were observed. In karyotype analysis the cells chromosome number changed and the frequency of structure aberration raised dramatically. Otherwise the transformed cells could form clone on self-solid culture medium.

CONCLUSIONS

The biological effects of H2O2 were related to the low dose concentration in promoting proliferation and transformation of liver oval cells indicating its important role in hepatocarcinogenesis. Therefore antioxidants should be able to provide a new clue in prevention and cure of hepatoma.

Expression of cathepsins B and S in the progression of prostate carcinoma

Cathepsins B and S (CatB, CatS) are lysosomal cysteine proteases which, among other functions, appear to play a role in cancer progression in different tumor models due to their matrix-degrading properties. To investigate their possible involvement in the development of prostate carcinoma, we immunohistochemically analyzed CatB and CatS in 38 primary human prostatic adenocarcinomas, as well as concomitant high-grade prostatic intra-epithelial neoplasia, nodular hyperplasia and normal tissue. CatB expression was observed in 28 (74%) and CatS in 32 (84%) carcinomas, being concomitant in 24 cases (63%). High-grade intra-epithelial neoplasia expressed CatB in 20/23 cases (87%), and a similar result was obtained for CatS, with expression of both coinciding in 18 cases (78%). In non-neoplastic tissue, strong expression of both proteases was observed in macrophages, inflamed glands and transitional metaplasia, whereas atrophic glands and basal cells of normal glands displayed intense CatB positivity. We conclude that CatB and CatS are often expressed together in neoplastic prostatic cells from pre-invasive to invasive and clinically detectable stages, suggesting a putative role in local invasion, though other functions cannot be ruled out.

The transcription factor early growth-response factor 1 modulates tumor necrosis factor-alpha, immunoglobulin E, and airway responsiveness in mice

Early growth-response factor 1 (Egr-1) is a sequence-specific transcription factor that plays a regulatory role in the expression of many genes important in inflammation, cell growth, apoptosis, and the pathogenesis of disease. In vitro studies suggest that Egr-1 is capable of regulating the expression of tumor necrosis factor-alpha (TNF-alpha) and other genes involved in airway inflammation and reactivity following allergen stimulation. On the basis of these data, we hypothesized that in the absence of Egr-1, the TNF-alpha response and subsequent downstream inflammatory events that usually follow allergen challenge would be diminished. To test our hypothesis Egr-1 knock-out (KO) mice were examined in an ovalbumin (OVA)-induced model of airway inflammation and reactivity, and compared with identically treated wild-type (WT) control mice. In response to OVA sensitization and airway challenge, KO mice had diminished TNF-alpha mRNA and protein in the lungs and mast cells compared with WT mice. Interestingly, the KO mice had elevated IgE levels at baseline and after allergen challenge compared with WT mice. Furthermore, the airways of KO mice were hyporesponsive to methacholine challenge at baseline and after allergen challenge. These data indicate that Egr-1 modulates TNF-alpha, IgE, and airway responsiveness in mice.

Expression of cathepsins B and S in the progression of prostate carcinoma

Cathepsins B and S (CatB, CatS) are lysosomal cysteine proteases which, among other functions, appear to play a role in cancer progression in different tumor models due to their matrix-degrading properties. To investigate their possible involvement in the development of prostate carcinoma, we immunohistochemically analyzed CatB and CatS in 38 primary human prostatic adenocarcinomas, as well as concomitant high-grade prostatic intra-epithelial neoplasia, nodular hyperplasia and normal tissue. CatB expression was observed in 28 (74%) and CatS in 32 (84%) carcinomas, being concomitant in 24 cases (63%). High-grade intra-epithelial neoplasia expressed CatB in 20/23 cases (87%), and a similar result was obtained for CatS, with expression of both coinciding in 18 cases (78%). In non-neoplastic tissue, strong expression of both proteases was observed in macrophages, inflamed glands and transitional metaplasia, whereas atrophic glands and basal cells of normal glands displayed intense CatB positivity. We conclude that CatB and CatS are often expressed together in neoplastic prostatic cells from pre-invasive to invasive and clinically detectable stages, suggesting a putative role in local invasion, though other functions cannot be ruled out.

Identification of the increased expression of monocyte chemoattractant protein-1, cathepsin S, UPIX-1, and other genes in dystrophin-deficient mouse muscles by suppression subtractive hybridization

The lack of dystrophin results in muscular dystrophy characterized by degeneration, inflammation, and partial regeneration of skeletal muscles. The fate of these muscles may be determined by the extent of adaptation to the defect and the efficiency of regeneration that is affected by inflammatory cells. We have used suppression subtractive hybridization and quantitative Northern blot analysis to identify differentially expressed genes. Increased expression of murine monocyte chemoattractant protein-1 (JE/MCP-1), cathepsin S, UPIX-1, nmb, cathepsin B, and lysozyme M mRNAs were identified in 2-month-old mdx mouse leg muscles. UPIX-1 is a novel gene. Although it was not expressed in control muscles, it was expressed in control brain, heart, and spleen. JE/MCP-1 and cathepsin S proteins in mdx muscles, as well as JE/MCP-1 protein in the serum of mdx mice were also detected. JE/MCP-1 may be responsible for attraction of inflammatory cells, and cathepsin S, a potent elastolytic protease, may contribute to the remodeling of the extracellular matrix that is required for the migration of these cells to the injured muscles.

Pathologic gene expression in Gaucher disease: up-regulation of cysteine proteinases including osteoclastic cathepsin K

Deficiency of lysosomal acid beta-glucosidase induces glycolipid storage in the macrophages of Gaucher disease but the pathways of multisystem tissue injury and destruction are unknown. To investigate the cognate molecular pathology of this inflammatory disorder, genes that were differentially expressed in spleen samples from a patient with Gaucher disease (Gaucher spleen) were isolated. Of 64 complementary DNA (cDNA) fragments sequenced from an enriched Gaucher cDNA library, 5 encode lysosomal proteins (cathepsins B, K, and S, alpha-fucosidase, and acid lipase), 10 encode other known proteins, and 2 represent novel sequences from human macrophage cell lines. Transcript abundance of the cathepsins, novel genes, pulmonary and activation-regulated chemokine (PARC), and NMB, a putative tumor suppressor gene, was greatly increased. Immunoblotting showed increased mature forms of all 3 cathepsins found in samples of Gaucher spleens. Immunofluorescence microscopy showed strong cathepsin B and K reactions in sinusoidal endothelium and Gaucher cells. The respective means, plus or minus SD, of cathepsin B, K, and S activities were 183 +/- 35, 97 +/- 39, and 91 +/- 45 nmol/min/mg protein in 4 Gaucher spleens, and 26 +/- 4, 10.5 +/- 2, and 4.0 +/- 2.1 nmol/min/mg protein in 3 control spleens. Plasma cathepsin B, K, and S activities were also elevated in Gaucher disease plasma (P <.001), but compared with control plasma samples, neither cathepsin B nor K activities were significantly elevated in 8 patients with nonglycosphingolipid lysosomal storage diseases or in 9 patients with other glycosphingolipidoses, which suggests disease specificity. All 3 cathepsin activities were increased 2-fold to 3-fold in Gaucher sera compared with control sera. In all 6 patients treated by enzyme replacement for 16-22 months, serum cathepsin activities decreased significantly (P <.01). Longitudinal studies confirmed the progressive reduction of proteinase activities during imiglucerase therapy but in 3 Gaucher patients with mild disease not so treated, serum cathepsin activities remained constant or increased during follow-up. Enhanced expression of cysteine proteinases may promote tissue destruction. Moreover, the first identification of aberrant cathepsin K expression in hematopoietic tissue other than osteoclasts implicates this protease in the breakdown of the matrix that characterizes lytic bone lesions in Gaucher disease. (Blood. 2000;96:1969-1978)

Identification of the increased expression of monocyte chemoattractant protein-1, cathepsin S, UPIX-1, and other genes in dystrophin-deficient mouse muscles by suppression subtractive hybridization

The lack of dystrophin results in muscular dystrophy characterized by degeneration, inflammation, and partial regeneration of skeletal muscles. The fate of these muscles may be determined by the extent of adaptation to the defect and the efficiency of regeneration that is affected by inflammatory cells. We have used suppression subtractive hybridization and quantitative Northern blot analysis to identify differentially expressed genes. Increased expression of murine monocyte chemoattractant protein-1 (JE/MCP-1), cathepsin S, UPIX-1, nmb, cathepsin B, and lysozyme M mRNAs were identified in 2-month-old mdx mouse leg muscles. UPIX-1 is a novel gene. Although it was not expressed in control muscles, it was expressed in control brain, heart, and spleen. JE/MCP-1 and cathepsin S proteins in mdx muscles, as well as JE/MCP-1 protein in the serum of mdx mice were also detected. JE/MCP-1 may be responsible for attraction of inflammatory cells, and cathepsin S, a potent elastolytic protease, may contribute to the remodeling of the extracellular matrix that is required for the migration of these cells to the injured muscles.

Simple modifications of the serpin reactive site loop convert SCCA2 into a cysteine proteinase inhibitor: a critical role for the P3' proline in facilitating RSL cleavage

The human squamous cell carcinoma antigens (SCCA) 1 and 2 are members of the serpin family that are 92% identical in their amino acid sequence. Despite this similarity, they inhibit distinct classes of proteinases. SCCA1 neutralizes the papain-like cysteine proteinases, cathepsins (cat) S, L, and K; and SCCA2 inhibits the chymotrypsin-like serine proteinases, catG and human mast cell chymase. SCCA2 also can inhibit catS, as well as other papain-like cysteine proteinases, albeit at a rate 50-fold less than that of SCCA1. Analysis of the mechanism of inhibition by SCCA1 revealed that the reactive site loop (RSL) is important for cysteine proteinase inhibition. The inhibition of catS by a mutant SCCA2 containing the RSL of SCCA1 is comparable to that of wild-type SCCA1. This finding suggested that there were no motifs outside and only eight residues within the RSL that were directing catS-specific inhibition. The purpose of this study was to determine which of these residues might account for the marked difference in the ability of SCCA1 and SCCA2 to inhibit papain-like cysteine proteinases. SCCA2 molecules containing different RSL mutations showed that no single amino acid substitution could convert SCCA2 into a more potent cysteine proteinase inhibitor. Rather, different combinations of mutations led to incremental increases in catS inhibitory activity with residues in four positions (P1, P3', P4', and P11') accounting for 80% of the difference in activity between SCCA1 and SCCA2. Interestingly, the RSL cleavage site differed between wild-type SCCA2 and this mutant. Moreover, these data established the importance of a Pro residue in the P3' position for efficient inhibition of catS by both wild-type SCCA1 and mutated SCCA2. Molecular modeling studies suggested that this residue might facilitate positioning of the RSL within the active site of the cysteine proteinase.

Early endosomal maturation of MHC class II molecules independently of cysteine proteases and H-2DM

Major histocompatibility complex (MHC) class II molecules bind and present to CD4(+) T cells peptides derived from endocytosed antigens. Class II molecules associate in the endoplasmic reticulum with invariant chain (Ii), which (i) mediates the delivery of the class II-Ii complexes into the endocytic compartments where the antigenic peptides are generated; and (ii) blocks the peptide-binding site of the class II molecules until they reach their destination. Once there, Ii must be removed to allow peptide binding. The bulk of Ii-class II complexes reach late endocytic compartments where Ii is eliminated in a reaction in which the cysteine protease cathepsin S and the accessory molecule H-2DM play an essential role. Here, we here show that Ii is also eliminated in early endosomal compartments without the intervention of cysteine proteases or H-2DM. The Ii-free class II molecules generated by this alternative mechanism first bind high molecular weight polypeptides and then mature into peptide-loaded complexes.

Proteases involved in MHC class II antigen presentation

Major histocompatibility complex class II antigen presentation requires the participation of lysosomal proteases in two convergent processes. First, the antigens endocytosed by the antigen-presenting cells must be broken down into antigenic peptides. Second, class II molecules are synthesized with their peptide-binding site blocked by invariant chain (Ii), and they acquire the capacity to bind antigens only after Ii has been degraded in the compartments where peptides reside. The study of genetically modified mice deficient in single lysosomal proteases has allowed us to determine their role in these processes. Cathepsins (Cat) B and D, previously considered major players in MHC class II antigen presentation, are dispensable for degradation of Ii and for generation of several antigenic determinants. By contrast, Cat S plays an essential role in removal of Ii in B cells and dendritic cells, whereas Cat L apparently does so in thymic epithelial cells. Accordingly, the absence of Cat S and L have major consequences for the onset of humoral immune responses and for T-cell selection, respectively. It is likely that other as yet uncharacterized lysosomal enzymes also play a role in Ii degradation and in generation of antigenic determinants. Experiments involving drugs that interfere with protein traffic suggest that more than one mechanism for Ii removal, probably involving different proteases, can co-exist in the same antigen-presenting cell. These findings may allow the development of protease inhibitors with possible therapeutic applications.

Cystatin C deficiency in human atherosclerosis and aortic aneurysms

The pathogenesis of atherosclerosis and abdominal aortic aneurysm involves breakdown of the elastic laminae. Elastolytic cysteine proteases, including cathepsins S and K, are overexpressed at sites of arterial elastin damage, but whether endogenous local inhibitors counterbalance these proteases is unknown. We show here that, whereas cystatin C is normally expressed in vascular wall smooth muscle cells (SMCs), this cysteine protease inhibitor is severely reduced in both atherosclerotic and aneurysmal aortic lesions. Furthermore, increased abdominal aortic diameter among 122 patients screened by ultrasonography correlated inversely with serum cystatin C levels. In vitro, cytokine-stimulated vascular SMCs secrete cathepsins, whose elastolytic activity could be blocked when cystatin C secretion was induced by treatment with TGF-beta(1). The findings highlight a potentially important role for imbalance between cysteine proteases and cystatin C in arterial wall remodeling and establish that cystatin C deficiency occurs in vascular disease.

Pro-inflammatory cytokines induce expression of matrix-metabolizing enzymes in human cervical smooth muscle cells

The process of cervical ripening has been likened to an inflammatory reaction associated with the catabolism of cervical extracellular matrix by enzymes released from infiltrating leukocytes. We hypothesized that smooth muscle cells in the cervix also participate in this process and that pro-inflammatory cytokines act on cervical smooth muscle cells (CSMC) to provoke the expression of matrix-degrading enzymes. We treated primary cultures of human CSMC with tumor necrosis factor-alpha (TNF-alpha) and examined expression of the elastinolytic enzyme, cathepsin S, the collagen metabolizing matrix metalloproteinases (MMP)-1, -3, -9, and the tissue inhibitor of metalloproteinase (TIMP)-1 and -2. A time course analysis revealed that 10 ng/ml of TNF-alpha induced cathepsin S, MMP-1, -3, and -9 mRNA expression with the maximal response observed after 24-48 hours. TNF-alpha induced cathepsin S, MMP-1, -3, and -9 mRNA expression in a dose-dependent manner: the maximal effect was observed at a concentration of 10 ng/ml, with appreciable increases observed at concentrations of 0.1 to 1.0 ng/ml. In contrast, TIMP-1 and -2 mRNAs were not significantly increased by TNF-alpha treatment. Interleukin-1beta produced a pattern of gene expression in the CSMC similar to that observed following TNF-alpha treatment. Western blot analysis and zymography confirmed the induction of proMMP-1, -3, and -9 in response to TNF-alpha, but MMP-2 immunoreactivity and zymographic activity were unaffected. TNF-alpha increased secretion of procathepsin S, but did not affect TIMP-1 and reduced TIMP-2 production. We conclude that CSMC are targets of pro-inflammatory cytokines, which induce a repertoire of enzymes capable of degrading the cervical extracellular matrix. The induction of these enzymes may facilitate the normal ripening of the cervix at term and participate in the premature cervical changes associated with preterm labor.

Cathepsin S required for normal MHC class II peptide loading and germinal center development

Major histocompatibility complex (MHC) class II molecules acquire antigenic peptides after degradation of the invariant chain (Ii), an MHC class II-associated protein that otherwise blocks peptide binding. Antigen-presenting cells of mice that lack the protease cathepsin S fail to process Ii beyond a 10 kDa fragment, resulting in delayed peptide loading and accumulation of cell surface MHC class II/10 kDa Ii complexes. Although cathepsin S-deficient mice have normal numbers of B and T cells and normal IgE responses, they show markedly impaired antibody class switching to IgG2a and IgG3. These results indicate cathepsin S is a major Ii-processing enzyme in splenocytes and dendritic cells. Its role in humoral immunity critically depends on how antigens access the immune system.

Human cathepsin F. Molecular cloning, functional expression, tissue localization, and enzymatic characterization

A cDNA for a novel human papain-like cysteine protease, designated cathepsin F, has been cloned from a lambdagt10-skeletal muscle cDNA library. The nucleotide sequence encoded a polypeptide of 302 amino acids composed of an 88-residue propeptide and a 214-residue mature protein. Protein sequence comparisons revealed 58% homology with cathepsin W; about 42-43% with cathepsins L, K, S, H, and O; and 38% with cathepsin B. Sequence comparisons of the propeptides indicated that cathepsin F and cathepsin W may form a new cathepsin subgroup. Northern blot analysis showed high expression levels in heart, skeletal muscle, brain, testis, and ovary; moderate levels in prostate, placenta, liver, and colon; and no detectable expression in peripheral leukocytes and thymus. The precursor polypeptide of human recombinant cathepsin F, produced in Pichia pastoris, was processed to its active mature form autocatalytically or by incubation with pepsin. Mature cathepsin F was highly active with comparable specific activities toward synthetic substrates as reported for cathepsin L. The protease had a broad pH optimum between 5.2 and 6.8. Similar to cathepsin L, its pH stability at cytosolic pH (7.2) was short, with a half-life of approximately 2 min. This may suggest a function in an acidic cellular compartment. Transient expression of T7-tagged cathepsin F in COS-7 cells revealed a vesicular distribution of the gene product in the juxtanuclear region of the cells. However, contrary to all known cathepsins, the open reading frame of the cathepsin F cDNA did not encode a signal sequence, thus suggesting that the protease is targeted to the lysosomal compartment via an N-terminal signal peptide-independent lysosomal targeting pathway.

Fc epsilon receptor I on dendritic cells delivers IgE-bound multivalent antigens into a cathepsin S-dependent pathway of MHC class II presentation

In this study, we elucidate the Fc epsilon RI-mediated Ag uptake and presentation mechanisms of dendritic cells (DC). We found that Fc epsilon RI-bound IgE, after polyvalent but not after monovalent ligation, is efficiently internalized into acidic, proteolytic compartments, degraded, and delivered into organelles containing MHC class II, HLA-DM, and lysosomal proteins. To follow the fate of the fragmented ligand, we sought to interfere with invariant chain (Ii) degradation, a process critical for peptide loading of nascent MHC class II molecules. We found DC to express cathepsin (Cat) S, a cysteine protease involved in Ii processing by B cells. Exposure of DC to a specific, active-site inhibitor of Cat S resulted in the loss of anti-Cat S immunoreactivity, led to the appearance of an N-terminal Ii remnant, and decreased the export of newly synthesized MHC class II to the DC surface. Furthermore, inactivation of Cat S as well as blockade of protein neosynthesis by cycloheximide strongly reduced IgE/Fc epsilon RI-mediated Ag presentation by DC. Thus, multimeric ligands of Fc epsilon RI, instead of being delivered into a recycling MHC class H pathway, are channeled efficiently into MIIC (MHC class II compartment)-like organelles of DC, in which Cat S-dependent Ii processing and peptide loading of newly synthesized MHC class II molecules occur. This IgE/Fc epsilon RI-dependent signaling pathway in DC may be a particularly effective route for immunization and a promising target for interfering with the early steps of allergen presentation.

Expression of the elastolytic cathepsins S and K in human atheroma and regulation of their production in smooth muscle cells

Formation of the atherosclerotic intima must involve altered metabolism of the elastin-rich arterial extracellular matrix. Proteases potentially involved in these processes remain unclear. This study examined the expression of the potent elastases cathepsins S and K in human atheroma. Normal arteries contained little or no cathepsin K or S. In contrast, macrophages in atheroma contained abundant immunoreactive cathepsins K and S. Intimal smooth muscle cells (SMC), especially cells appearing to traverse the internal elastic laminae, also contained these enzymes. Extracts of atheromatous tissues had approximately twofold greater elastase-specific activity than extracts of uninvolved arteries, mostly due to cysteine proteases. Cultured human SMC displayed no immunoreactive cathepsins K and S and exhibited little or no elastolytic activity when incubated with insoluble elastin. SMC stimulated with the atheroma-associated cytokines IL-1beta or IFN-gamma secreted active cathepsin S and degraded substantial insoluble elastin (15-20 microg/10(6) cells/24 h). A selective inhibitor of cathepsin S blocked > 80% of this elastolytic activity. The presence of cathepsins K and S at sites of vascular matrix remodeling and the ability of SMC and macrophages to use these enzymes to degrade elastin supports a role for elastolytic cathepsins in vessel wall remodeling and identifies novel therapeutic targets in regulating plaque stability.

Expression of the elastolytic cathepsins S and K in human atheroma and regulation of their production in smooth muscle cells

Formation of the atherosclerotic intima must involve altered metabolism of the elastin-rich arterial extracellular matrix. Proteases potentially involved in these processes remain unclear. This study examined the expression of the potent elastases cathepsins S and K in human atheroma. Normal arteries contained little or no cathepsin K or S. In contrast, macrophages in atheroma contained abundant immunoreactive cathepsins K and S. Intimal smooth muscle cells (SMC), especially cells appearing to traverse the internal elastic laminae, also contained these enzymes. Extracts of atheromatous tissues had approximately twofold greater elastase-specific activity than extracts of uninvolved arteries, mostly due to cysteine proteases. Cultured human SMC displayed no immunoreactive cathepsins K and S and exhibited little or no elastolytic activity when incubated with insoluble elastin. SMC stimulated with the atheroma-associated cytokines IL-1beta or IFN-gamma secreted active cathepsin S and degraded substantial insoluble elastin (15-20 microg/10(6) cells/24 h). A selective inhibitor of cathepsin S blocked > 80% of this elastolytic activity. The presence of cathepsins K and S at sites of vascular matrix remodeling and the ability of SMC and macrophages to use these enzymes to degrade elastin supports a role for elastolytic cathepsins in vessel wall remodeling and identifies novel therapeutic targets in regulating plaque stability.

Cathepsin S activity regulates antigen presentation and immunity

MHC class II molecules display antigenic peptides on cell surfaces for recognition by CD4(+) T cells. Proteolysis is required in this process both for degradation of invariant chain (Ii) from class II-Ii complexes to allow subsequent binding of peptides, and for generation of the antigenic peptides. The cysteine endoprotease, cathepsin S, mediates Ii degradation in human and mouse antigen-presenting cells. Studies described here examine the functional significance of cathepsin S inhibition on antigen presentation and immunity. Specific inhibition of cathepsin S in A20 cells markedly impaired presentation of an ovalbumin epitope by interfering with class II-peptide binding, not by obstructing generation of the antigen. Administration of a cathepsin S inhibitor to mice in vivo selectively inhibited activity of cathepsin S in splenocytes, resulting in accumulation of a class II-associated Ii breakdown product, attenuation of class II-peptide complex formation, and inhibition of antigen presentation. Mice treated with inhibitor had an attenuated antibody response when immunized with ovalbumin but not the T cell-independent antigen TNP-Ficoll. In a mouse model of pulmonary hypersensitivity, treatment with the inhibitor also abrogated a rise in IgE titers and profoundly blocked eosinophilic infiltration in the lung. Thus, inhibition of cathepsin S in vivo alters Ii processing, antigen presentation, and immunity. These data identify selective inhibition of cysteine proteases as a potential therapeutic strategy for asthma and autoimmune disease processes.

Cross-class inhibition of the cysteine proteinases cathepsins K, L, and S by the serpin squamous cell carcinoma antigen 1: a kinetic analysis

The human squamous cell carcinoma antigens (SCCA) 1 and 2 are tandemly arrayed genes that encode two high-molecular-weight serine proteinase inhibitors (serpins). Although these proteins are 92% identical, differences in their reactive site loops suggest that they inhibit different types of proteinases. Our previous studies show that SCCA2 inhibits chymotrypsin-like serine proteinases [Schick et al. (1997) J. Biol. Chem. 272, 1849-1855]. We now show that, unlike SCCA2, SCCA1 lacks inhibitory activity against any of the more common types of serine proteinases but is a potent cross-class inhibitor of the archetypal lysosomal cysteine proteinases cathepsins K, L, and S. Kinetic analysis revealed that SCCA1 interacted with cathepsins K, L, and S at 1:1 stoichiometry and with second-order rate constants >/= 1 x 10(5) M-1 s-1. These rate constants were comparable to those obtained with the prototypical physiological cysteine proteinase inhibitor, cystatin C. Also relative to cystatin C, SCCA1 was a more potent inhibitor of cathepsin K-mediated elastolytic activity by forming longer lived inhibitor-proteinase complexes. The t1/2 of SCCA1-cathepsin S complexes was >1155 min, whereas that of cystatin C-cathepsin complexes was 55 min. Cleavage between the Gly and Ser residues of the reactive site loop and detection of a stable SCCA1-cathepsin S complex by sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggested that the serpin interacted with the cysteine proteinase in a manner similar to that observed for typical serpin-serine proteinase interactions. These data suggest that, contingent upon their reactive site loop sequences, mammalian serpins, in general, utilize their dynamic tertiary structure to trap proteinases from more than one mechanistic class and that SCCA1, in particular, may be involved in a novel inhibitory pathway aimed at regulating a powerful array of lysosomal cysteine proteinases.

Structure and chromosomal assignment of the human cathepsin K gene

Cathepsin K is a recently identified lysosomal cysteine proteinase that is the major protease responsible for bone resorption and remodeling. Mutations in this gene cause the sclerosing osteochondrodysplasia pycnodysostosis. To assess its evolutionary relatedness to other cysteine proteases and to facilitate mutation identification in patients with pycnodysostosis, a genomic clone, 74e16, containing the cathepsin K gene was isolated from a human PAC library, and the cathepsin K genomic structure was determined. The cathepsin K gene contained eight exons and spanned approximately 9 kb. The transcription initiation site, determined by primer extension analysis, was 169 nucleotides upstream from the translation initiation site. The 5'-flanking region lacked a TATA box but contained two AP1 sites. Comparison of genomic and cDNA sequences suggested that this flanking sequence may be the major promoter in osteoclasts and macrophages. Cathepsin K was mapped to chromosome 1q21 by fluorescence in situ hybridization and found to reside within 150 kb of an evolutionarily related cysteine protease, cathepsin S. These findings expand our understanding of the papain family lysosomal cysteine proteases and should facilitate mutation analysis in pycnodysostosis.

Emerging roles for cysteine proteases in human biology

Cysteine proteases have traditionally been viewed as lysosomal mediators of terminal protein degradation. However, recent findings refute this limited view and suggest a more expanded role for cysteine proteases in human biology. Several newly discovered members of this enzyme class are regulated proteases with limited tissue expression, which implies specific roles in cellular physiology. These roles appear to include apoptosis, MHC class II immune responses, prohormone processing, and extracellular matrix remodeling important to bone development. The ability of macrophages and other cells to mobilize elastolytic cysteine proteases to their surfaces under specialized conditions may also lead to accelerated collagen and elastin degradation at sites of inflammation in diseases such as atherosclerosis and emphysema. The development of inhibitors of specific cysteine proteases promises to provide new drugs for modifying immunity, osteoporosis, and chronic inflammation.

Pycnodysostosis, a lysosomal disease caused by cathepsin K deficiency

Pycnodysostosis, an autosomal recessive osteochondrodysplasia characterized by osteosclerosis and short stature, maps to chromosome 1q21. Cathepsin K, a cysteine protease gene that is highly expressed in osteoclasts, localized to the pycnodysostosis region. Nonsense, missense, and stop codon mutations in the gene encoding cathepsin K were identified in patients. Transient expression of complementary DNA containing the stop codon mutation resulted in messenger RNA but no immunologically detectable protein. Thus, pycnodysostosis results from gene defects in a lysosomal protease with highest expression in osteoclasts. These findings suggest that cathepsin K is a major protease in bone resorption, providing a possible rationale for the treatment of disorders such as osteoporosis and certain forms of arthritis.

[A study on the change of myocardial neuropeptide Y release induced by electric stimulation and myocardial ischemia in guinea pig heart]

Electrical stimulation of the left stellate ganglion in guinea pig heart evoked a calcium-dependent, exocytotic release of neuropeptide Y (NPY). Stimulation after 10 min of global ischemia (S2), compared with control period stimulation (S1), had no significant effect on the NPY release. The release of NPY produced by the same stimulation after 20 min of ischemia was inhibited to certain extent (S2/S1: 0.72, P < 0.05), whereas the inhibition of NPY release disappeared after 5 min of reperfusion (with a S2/S1 of 1.01). Ischemia alone, without electric stimulation, did not apparently induce NPY release, suggesting that electrical stimulation may induce a calcium-dependent, exocytotic release of NPY. It is further suggested that the inhibition of NPY release may be produced by some metabolites and the abolishment of the inhibition after reperfusion may be due to washout of the metabolites.

Lysosomal processing of amyloid precursor protein to A beta peptides: a distinct role for cathepsin S

To investigate the potential contribution of the lysosomal compartment in the processing of amyloid precursor protein (APP) to amyloid beta-peptides (A beta s), we stably overexpressed a series of lysosomal proteases (the cysteine proteases, cathepsins B, L and S, and the aspartic protease, cathepsin D) in a human kidney epithelial cell line (293) transfected to express high levels of beta APP. Preliminary experiments indicated that 293 cells endogenously synthesize cathepsins B, L and D, but not cathepsin S. A beta secretion was assessed by immunoprecipitation and ELISA and found to be increased approximately 2-fold following cathepsin S expression, but to be unchanged (cathepsins B, L) or decreased (cathepsin D) in the other double transfectants. E-64d, an inhibitor of lysosomal cysteine proteases, significantly reduced A beta secretion by the cathepsin S transfectants, but had no effect on cells expressing the other proteases. Radiosequencing of A beta secreted by cathepsin S-expressing cells revealed that a previously unreported variant beginning at Met -1 (relative to the most common A beta N-terminus, Asp -1) accounted for most of the increase in A beta secretion. Immunostaining of human brain sections revealed cathepsin S in cortical neurons and glia in samples of brain from patients with Alzheimer's disease. These results provide evidence in living cells for a pathway in which cathepsin S generates A beta from amyloidogenic fragments of beta APP in the endosomal/lysosomal compartment. This pathway appears to be inducible, distinct from a constitutive pathway used by 293 and other cells to generate A beta, and may be relevant to the pathogenesis of Alzheimer's disease.

Urokinase receptor is a multifunctional protein: influence of receptor occupancy on macrophage gene expression

Binding of urokinase to the glycolipid-anchored urokinase receptor (uPAR) has been implicated in macrophage differentiation. However, no biochemical markers of differentiation have yet been directly linked to uPAR occupancy. As extensive changes in proteolytic profile characterize monocytic differentiation, we have examined the role of uPAR occupancy on protease expression by differentiating phagocytes. Antibodies to either urokinase or to uPAR that prevent receptor binding inhibited induction of cathepsin B in cultured monocytes and both cathepsin B and 92-kD gelatinase mRNA and protein in phorbol diester-stimulated myeloid cells. Mannosamine, an inhibitor of glycolipid anchor assembly, also blocked protease expression. Anti-catalytic urokinase antibodies, excess inactive urokinase, or aprotinin had no effect, indicating that receptor occupancy per se regulated protease expression. Antibodies to the integrins CD11a and CD29 or to the glycolipid-anchored proteins CD14 and CD55 also had no effect. Protease induction was independent of matrix attachment. Antibodies to urokinase or uPAR affected neither the decrease in cathepsin G nor the increase in tumor necrosis factor-alpha in phorbol ester-stimulated cells. These data establish that uPAR is a multifunctional receptor, not only promoting pericellular proteolysis and matrix attachment, but also effecting cysteine- and metallo-protease expression during macrophage differentiation.

The lysosomal cysteine protease, cathepsin S, is increased in Alzheimer's disease and Down syndrome brain. An immunocytochemical study

Expression of cathepsin (cat) S, a lysosomal cysteine protease, has recently been shown to cause an increase in production of amyloid beta-peptides in transfected human cells. In this study, we examined the presence and localization of cat S by immunocytochemistry in 21 control, 24 Alzheimer's disease (AD), and 10 Down syndrome (DS) postmortem brains. An antiserum to a human cat S fusion protein was affinity purified and its specificity confirmed by abolition of immunoreactivity after adsorption with cat S but not cat L fusion protein. A small minority of control cases showed light, focal staining of scattered cortical neurons. Many control cases, as well as most AD and DS cases, showed prominent staining of vascular smooth muscle cells, particularly in leptomeningeal vessels. Both AD and DS brain tissue showed increased immunoreactivity in a subset of neocortical and hippocampal neurons and glia. Cat S immunoreactivity occurred in a granular, cytoplasmic pattern in some neurons or in a more dense staining pattern in certain neurofibrillary tangle-bearing neurons. Cat S-positive neurons were also present in amygdala and basal forebrain in AD brains. A subset of astrocytes were immunoreactive with the cat S antibody in AD and DS but not in control brains. In rare AD cases, cat S immunostaining was observed in astrocytes in the periphery of amyloid-beta-containing plaques. These results suggest that cat S is up-regulated in AD and DS brain. The association of cat S immunoreactivity with tangle-bearing neurons, astrocytes, and rare senile plaques implies a role for altered cat S activity in the pathogenesis of AD.

Molecular cloning of human cathepsin O, a novel endoproteinase and homologue of rabbit OC2

A 1670-bp cDNA coding for a novel human cysteine protease has been isolated from a monocyte-derived macrophage cDNA library. This cDNA predicts a 329-amino acid preprocathepsin with more than 50% identity to both human cathepsin S and cathepsin L and 94% identity to a rabbit cDNA, termed OC2, recently isolated from osteoclasts. Based on its high homology to OC2, we have named the human enzyme cathepsin O. Cathepsin O mRNA was identified as a single approximately 1.7 kb transcript in cultures of 15-day-old monocyte-derived macrophages, but was not expressed in human monocytes or alveolar macrophages. When transfected into COS-7 cells, cathepsin O displayed potent endoprotease activity against fibrinogen at acid pH. This novel endoprotease may play an important role in extracellular matrix degradation.

The role of thiol proteases in tissue injury and remodeling

Human lung macrophages express all four of the known lysosomal thiol proteases: cathepsins B, H, L, and S. These enzymes share a similar size and targeting mechanism for lysosomal accumulation and all have relatively indiscriminate substrate specificity in comparison with such highly selective serine proteases as urokinase or thrombin. These enzymes do have distinctive properties: only cathepsin B has C-terminal dipeptidase activity, only cathepsin H has potent aminopeptidase activity, and only cathepsin L and S are elastolytic. Cathepsin S is unique in that it is stable at neutral pH; indeed, at neutral pH it has elastolytic activity roughly comparable with that of neutrophil elastase. Recent studies of the differential expression of these cathepsins suggest they not only cooperate in terminal degradation of endocytized protein but also have specific functions such as proenzyme activation, antigen processing, and tissue remodeling, especially bone matrix resorption. Lysates of lung macrophages degrade elastin at neutral pH, suggesting that necrosis of macrophages at sites of macrophage accumulation, e.g., caseation necrosis, could contribute to tissue destruction. Tissue destruction and remodeling by thiol proteases expressed by live macrophages, however, is limited by tight compartmentalization of cathepsins to lysosomes. Nonetheless, macrophages accumulate at sites of known injury in cigarette smokers. Because these cells contain potent elastases, and because lysosomal enzyme release and cell surface acidification are regulated events, dysregulation of thiol protease expression in stimulated macrophages may contribute to the injury observed in cigarette smokers with non-alpha-1-protease inhibitor-type emphysema.

Human cathepsin S: chromosomal localization, gene structure, and tissue distribution

The human lysosomal cysteine proteinases, cathepsins H, L, and B, have been mapped to chromosomes 15, 9, and 8, respectively, and the genomic structures of cathepsins L and B have been determined. We report here the chromosomal localization and partial gene structure for a recently sequenced human cysteine proteinase, cathepsin S. A 20-kilobase pair genomic clone of the human cathepsin S gene was isolated from a human fibroblast genomic library and used to map the human cathepsin S gene to chromosome 1q21 by fluorescence in situ hybridization. This clone contains exons 1 through 5, introns 1 through 4, part of intron 5, and > 7 kilobase pairs of the 5'-flanking sequence. The gene structure of human cathepsin S is similar to that of cathepsin L through the first 5 exons, except that cathepsin S introns are substantially larger. Sequencing of the 5'-flanking region revealed, similar to human cathepsin B, no classical TATA or CAAT box. In contrast to cathepsin B, cathepsin S contains only two SP1 and at least 18 AP1 binding sites that potentially could be involved in regulation of the gene. This 5'-flanking region also contains CA microsatellites. The presence of AP1 sites and CA microsatellites suggest that cathepsin S can be specifically regulated. Results of Northern blotting using probes for human cathepsins B, L, and S are consistent with this hypothesis; only cathepsin S shows a restricted tissue distribution, with highest levels in spleen, heart, and lung. In addition, immunostaining of lung tissue demonstrated detectable cathepsin S only in lung macrophages. The high level of expression in the spleen and in phagocytes suggests that cathepsin S may have a specific function in immunity, perhaps related to antigen processing.

[Platelet neuropeptide Y and its vasoconstriction effect in rat]

Specific radioimmunoassay showed that in rat neuropeptide Y (NPY) immuno-reactivities (IR) in platelets and platelet rich plasma (PRP) were respectively 90 +/- 16 ng/10(7) platelets and 93 +/- 19 ng/ml. Both values were much greater than those in the plasma (1.2 +/- 0.1 ng/ml, P < 0.001) and platelet poor plasma (PPP) (1.7 +/- 0.3 ng/ml, P < 0.001). The NPY-IR in rat platelets eluted at the same position as authentic NPY on reverse phase HPLC. The NPY-IR in the platelets prepared from the PRP aggregated maximally by collagen reduced to 34 +/- 5 ng/10(7) platelets, while the NPY-IR in the PPP prepared from the same PRP increased to 26 +/- 4 ng/ml. PPP 1.6 ml prepared from the aggregated PRP induced contraction of isolated rat caudal arteries with the maximal tension of 380 +/- 80 mg; while the maximal contraction induced by 1.6 ml of the same PPP pretreated with NPY anti-serum was only 190 +/- 40 mg (P < 0.001). Authentic NPY 1 nmol/L did not cause any contraction. The results indicate that rat platelets contain a high concentration of NPY, which can be released during irreversible platelet aggregation. The NPY released can potentiate vasoconstriction responses induced by co-released substances during platelet aggregation.

Molecular cloning and expression of human alveolar macrophage cathepsin S, an elastinolytic cysteine protease

Human alveolar macrophages (HAM) express an elastase activity of acidic pH optimum inhibitable by cysteine protease inhibitors. Recent studies indicate that the only known eukaryotic elastinolytic cysteine protease, cathepsin L, cannot completely account for this activity. In order to search for additional cysteine proteases with elastinolytic activity, low degeneracy oligonucleotide primers based on regions of strong homology among the known cysteine proteases were used to screen reverse-transcribed HAM RNA for cysteine proteases by the polymerase chain reaction. Among the cDNA sequences generated was a 493-base pair product highly homologous to bovine cathepsin S. Screening of a HAM cDNA eukaryotic expression library with this cDNA yielded a 1.7-kilobase full-length cDNA highly homologous to bovine cathepsin S (approximately 85% identical). This cDNA predicts a 331-amino acid preprocathepsin. Expression of this cDNA in COS cells revealed the active enzyme to be a single chain 28-kDa protease, as judged by active site labeling with a novel iodinated analogue of N-(L-3-trans-carboxyoxirane-2-carbonyl)-L-leucylamido-(4-gua nido)butane (E-64). The recombinant enzyme was found to be elastinolytic toward 3H-labeled elastin (bovine ligamentum nuchae) at pH 5.5 but with 25% of this activity retained at pH 7.0. Labeling of HAM with the active site probe revealed these cells express a 28-kDa cysteine protease, and Northern blot analysis revealed the presence of a approximately 1.7-kilobase cathepsin S mRNA. These data establish that human macrophages express at least two cysteine proteases with elastinolytic activity. The relatively broad pH range of human cathepsin S activity suggests this enzyme may contribute to the contact-dependent elastase activity of live human alveolar macrophages.

A serine esterase released by human alveolar macrophages is closely related to liver microsomal carboxylesterases

We identified a 60-kDa diisopropylfluorophosphate-(DFP) reactive protein in human bronchoalveolar lavage fluid, at a yield of 50-100 pmol/lavage. The protein is associated with the cell-free lavage fluid sediment, which consists mainly of surfactant. [3H]DFP labeling is inhibited by heating to 56 degrees C, 2 mM phenylmethylsulfonylfluoride and 1 mM bis(4-nitrophenyl)-phosphate. An identical 60-kDa [3H]DFP-reactive protein is present in the insoluble fraction of alveolar macrophage-conditioned culture medium and in total membrane preparations of alveolar macrophages. The [3H]DFP-labeled protein was purified approximately 30-fold from lavage fluid sediment by size-exclusion (Sephacryl S-200) and ion-exchange (Mono-Q) chromatography. Cyanogen bromide treatment of the partially purified protein produced a major labeled peptide of 14 kDa with an NH2-terminal sequence 90% identical to a region of form 1 rabbit liver microsomal carboxylesterase. Esterase activity in unlabeled starting material, detected using p-nitrophenyl valerate as substrate, copurified with the [3H]DFP-labeled enzyme. Degenerate oligonucleotide primers were designed based on the partial amino acid sequence and on a highly conserved region of known liver carboxylesterase sequences. Polymerase chain reaction using these primers and reverse-transcribed human alveolar macrophage mRNA yielded a 354-base pair product which was then used to screen a human alveolar macrophage cDNA library. A complete esterase sequence was obtained from two incomplete, overlapping clones, and is virtually identical to human liver carboxylesterase partial sequences. Northern blot analysis demonstrated a single approximately 1.7-kilobase transcript in human monocytes and alveolar macrophages, with much higher levels in the latter. These data indicate that human alveolar macrophages both contain and release a serine esterase that is apparently identical to liver microsomal carboxylesterase. Its enzymatic profile suggests it is a major component of alveolar macrophage-nonspecific esterase activity. We hypothesize that it acts as a detoxication enzyme in the lung.