Inhibition of human type IV collagenase by a highly conserved peptide sequence derived from its prosegment

Tissue inhibitors of metalloproteinases are proteolytic targets of matrix metalloproteinase 9

Extracellular proteolysis and turnover are core processes of tissue homeostasis. The predominant matrix-degrading enzymes are members of the Matrix Metalloproteinase (MMP) family. MMPs extensively degrade core matrix components in addition to processing a range of other factors in the extracellular, plasma membrane, and intracellular compartments. The proteolytic activity of MMPs is modulated by the Tissue Inhibitors of Metalloproteinases (TIMPs), a family of four multi-functional matrisome proteins with extensively characterized MMP inhibitory functions. Thus, a well-regulated balance between MMP activity and TIMP levels has been described as critical for healthy tissue homeostasis, and this balance can be chronically disturbed in pathological processes. The relationship between MMPs and TIMPs is complex and lacks the constraints of a typical enzyme-inhibitor relationship due to secondary interactions between various MMPs (specifically gelatinases) and TIMP family members. We illustrate a new complexity in this system by describing how MMP9 can cleave members of the TIMP family when in molar excess. Proteolytic processing of TIMPs can generate functionally altered peptides with potentially novel attributes. We demonstrate here that all TIMPs are cleaved at their C-terminal tails by a molar excess of MMP9. This processing removes the N-glycosylation site for TIMP3 and prevents the TIMP2 interaction with latent proMMP2, a prerequisite for cell surface MMP14-mediated activation of proMMP2. TIMP2/4 are further cleaved producing ∼14 kDa N-terminal proteins linked to a smaller C-terminal domain through residual disulfide bridges. These cleaved TIMP2/4 complexes show perturbed MMP inhibitory activity, illustrating that MMP9 may bear a particularly prominent influence upon the TIMP:MMP balance in tissues.

Bioengineering of an elastase inhibitor from Caesalpinia echinata (Brazil wood) seeds

Protease inhibitors have been widely used in several therapeutic applications such as in the treatment of bleeding disorders, hypertension, cancer and pulmonary diseases. In a previous work, we demonstrated that a Kunitz-type serine protease inhibitor isolated from the seeds of Caesalpinia echinata (CeEI) exhibits pharmacological potential in lung inflammatory diseases in which neutrophil elastase plays a crucial role. However, an important challenge in the use of natural products is to ensure a commercially viable production. In this work, we report the cloning, expression and purification of two recombinant CeEI isoinhibitors with 700 base pairs encoding two proteins with 181 amino acid residues (rCeEI-4 and rCeEI-5). After the expression, each yielding 22 mg/L of active protein, both isoinhibitors presented a molecular mass of about 23.0 kDa, evaluated by SDS-PAGE. The inhibition constants for human neutrophil elastase (HNE) were 0.67 nM (rCeEI-4) and 0.57 nM (rCeEI-5), i.e., similar to the native inhibitor (1.90 nM). Furthermore, rCeEI-4 was used as a template to design smaller functional peptides flanking the inhibitor reactive site: rCeEI-36, delimited between the amino acid residues N³⁶ and S⁸⁸ containing a disulfide bond in the reactive-site loop, and rCeEI-46, delimited between S⁴⁶ and L⁷⁵ without the disulfide bond. The yields were 18 mg/L (rCeEI-36) and 12 mg/L (rCeEI-46). Both peptides inhibit HNE in the nanomolar range (K_i 0.30 ± 0.01 and 8.80 ± 0.23, respectively). Considering their size and the inhibitory efficiency, these peptides may be considered in strategies for the development of drugs targeting pulmonary disorders where elastase is involved.

The Effect of UW Solution and Its Components on the Collagenase Digestion of Human and Porcine Pancreas

University of Wisconsin (UW) solution is used extensively as a cold storage solution during the procurement and transport of the pancreas prior to islet isolation. However, it has been observed that UW inhibits the collagenase digestion phase of human but not porcine islet isolation, resulting in poor islet yields and islets of poor viability. The aim of this study was, therefore, to confirm this species difference and to determine which components of UW are responsible for the inhibition in the human. In the initial experiment, blocks of human and porcine pancreas (n = 7) were incubated in test tubes containing collagenase at a concentration of 4 mg/mL at 37°C dissolved in 4 mL of either Hanks' solution or UW. Every 5 min the tubes were manually shaken and the degree of tissue dissociation scored on a scale of + and +++. Our results confirm the inhibition of collagenase digestion in the human but not the pig. Using the same methodology, we then investigated the components of UW that were causing the observed inhibition in the human pancreas (n = 7). This time the collagenase was dissolved in individual or combinations of UW components. Using Hank's as a control, the results were then expressed as a median ratio. The components found to be most inhibitory were magnesium, the Na+/K+ ratio, hydroxyethyl starch (HES), and adenosine. Allopurinol in combination with either lactobionate or glutathione was markedly inhibitory (i.e., median ratio 1.8 and 1.9, respectively). The most inhibitory solution tested was a combination of the three components raffinose, glutathione, and lactobionate (median ratio 2.1). This combination was almost as inhibitory as UW itself (median ratio 2.7). These findings are essential for the development of effective cold-storage solutions for the human pancreas that do not inhibit the subsequent collagenase digestion phase of islet isolation.

TIMP-2 gene methylation in cervical precursor and invasive lesions

OBJECTIVE

To analyze the presence of HPV-DNA and TIMP-2 gene methylation in cervical precursor and invasive lesions, as well as to study the associations among the latter, the presence of HPV-DNA, and the clinical evolution of such lesions.

METHODS

Cross-sectional study that includes 49 biopsy or brush smear samples from women with a normal cervix, LSIL, HSIL, microinvasive carcinoma and invasive carcinoma. The presence of HPV-DNA and specific methylation was analyzed using PCR. Thirty-eight biopsy samples for HSIL, microinvasive carcinoma and frank invasive carcinoma as well as 11 brush smear samples for LSIL and normal cervices were analyzed.

RESULTS

TIMP-2 gene methylation was detected in 86.8% (33/38) of the samples from the group with lesions and 50% (4/8) of the normal samples (p=0.03). HPV-DNA was detected in 81.6% (31/38) of the samples from the group with lesions and 25% (2/8) of the normal samples (p=0.003). HPV-DNA was more frequent in the methylated samples (50%), and the group with methylation had a higher risk of unfavorable evolution than the group without methylation; however, such observations were not statistically significant (p=0.19).

CONCLUSION

TIMP-2 gene methylation and the presence of HPV-DNA were characteristic of the group with cervical lesions. Methylation was not associated with the presence of HPV-DNA or an unfavorable clinical evolution.

A novel mechanism of latency in matrix metalloproteinases

The matrix metalloproteinases (MMPs) are a family of secreted soluble or membrane-anchored multimodular peptidases regularly found in several paralogous copies in animals and plants, where they have multiple functions. The minimal consensus domain architecture comprises a signal peptide, a 60-90-residue globular prodomain with a conserved sequence motif including a cysteine engaged in "cysteine-switch" or "Velcro" mediated latency, and a catalytic domain. Karilysin, from the human periodontopathogen Tannerella forsythia, is the only bacterial MMP to have been characterized biochemically to date. It shares with eukaryotic forms the catalytic domain but none of the flanking domains. Instead of the consensus MMP prodomain, it features a 14-residue propeptide, the shortest reported for a metallopeptidase, which lacks cysteines. Here we determined the structure of a prokarilysin fragment encompassing the propeptide and the catalytic domain, and found that the former runs across the cleft in the opposite direction to a bound substrate and inhibits the latter through an "aspartate-switch" mechanism. This finding is reminiscent of latency maintenance in the otherwise unrelated astacin and fragilysin metallopeptidase families. In addition, in vivo and biochemical assays showed that the propeptide contributes to protein folding and stability. Our analysis of prokarilysin reveals a novel mechanism of latency and activation in MMPs. Finally, our findings support the view that the karilysin catalytic domain was co-opted by competent bacteria through horizontal gene transfer from a eukaryotic source, and later evolved in a specific bacterial environment.

Comparative study of MMP-2 (matrix metalloproteinase 2) immune expression in normal uterine cervix, intraepithelial neoplasias, and squamous cells cervical carcinoma

OBJECTIVE

This study was undertaken to evaluate the levels of matrix metalloproteinase 2 (MMP-2) in the precursors lesions and in the invasive cervical carcinoma and to quantify the immune reactive expression of MMP-2, using MMP-2 immunohistochemistry, in intraepithelial cervical neoplasias and in the invading cervical carcinoma.

STUDY DESIGN

We evaluated 60 samples of cervical tissues using immunohistochemistry for MMP-2 in 5 distinct groups. The groups were divided in control, cervical intraepithelial neoplasia I (CIN I), CIN II, CIN III, and cervical invading carcinoma.

RESULTS

MMP-2 expression was found gradually increased according to the degree of cervical intraepithelial neoplasia and cervical carcinoma. (Control<CIN I<CIN II<CIN III<Carcinoma)

CONCLUSION

Our results suggest that the expression of MMP-2 can distinguish CIN I, II, and III grades and the invading carcinoma.

Activation of matrix metalloproteinase-2 by overexpression of manganese superoxide dismutase in human breast cancer MCF-7 cells involves reactive oxygen species

Matrix metalloproteinases (MMPs) participate in cell migration and remodeling processes by affecting the extracellular matrix. MMP-2 is thought to be involved in cancer cell invasiveness. It has been proposed that the activity of MMP-2 can be modulated by intracellular reactive oxygen species (ROS)/reactive nitrogen species. We hypothesized that manganese superoxide dismutase (MnSOD) could mediate MMP-2 activity by changing the intracellular ROS level and that nitric oxide ((.)NO) may be involved in this process. Human breast cancer MCF-7 cells were stably transfected with plasmids containing MnSOD cDNA. A 2-30-fold increase of MnSOD protein and activity was observed in four clones. Our data demonstrated that overexpression of MnSOD stimulated the activation of MMP-2 with a corresponding elevation of ROS. A decrease in ROS by ebselen, a glutathione peroxidase mimetic, or by transduction of adenovirus containing human catalase or glutathione peroxidase cDNA abolished the effect of MnSOD on MMP-2 activation. Treatment of MCF-7 cells with antimycin A or rotenone increased intracellular ROS production and MMP-2 activation simultaneously. Our data also showed a suppression of endothelial nitric-oxide synthase expression that was accompanied by decreased (.)NO production in MnSOD-overexpressing cells. However, the changes in endothelial nitric-oxide synthase and (.)NO did not correlate with the MnSOD activity. Corresponding changes of MMP-2 activity after the addition of a NOS inhibitor (N(G)-amino-l-arginine) or a (.)NO donor ((Z)-1-[(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate) to the cells suggested the possibility that (.)NO may be involved in the MnSOD-mediated MMP-2 activation pathway. These results indicate that MnSOD induces MMP-2 activity by regulation of intracellular ROS and imply that signaling pathways involving (.)NO may also be involved in the MnSOD mediation of MMP-2 activity.

AAC-11 overexpression induces invasion and protects cervical cancer cells from apoptosis

To identify the genes involved in cervical carcinogenesis, we applied the mRNA differential display (DD) method to analyze normal cervical tissue, cervical cancer, metastatic lymph node, and cervical cancer cell line. We cloned a 491-bp cDNA fragment, CC231, which was present in metastatic tissue and cervical cancer cell line, but absent in normal cervical and cervical cancer tissues. The 491 bp cDNA fragment has 98% homology to the previously published sequence, AAC-11 (antiapoptosis clone 11). The levels of AAC-11 mRNA expressions in nine normal cervical and nine primary cervical cancer tissues were low. Its expression was higher in three metastatic tissues and five cervical cancer cell lines (HeLa, CaSki, SiHa, CUMC-3, and CUMC-6). Invasion of matrigel and adhesion to laminin by AAC-11 transfected CUMC-6 cells were increased by approximately 2-fold and 4-fold, respectively. Northern blot analysis showed that matrix metalloproteinase (MMP)-2 and membrane type 1 MMP (MT1-MMP) genes were found to be expressed in high levels in AAC-11-transfected cancer cells. But MMP-2 and MT1-MMP were not expressed in cells transfected with vector alone or wild-type cells. AAC-11-transfected cells expressed an elevated level of MMP-2 protein as assessed by immunoblotting. On the contrary, tissue inhibitor of MMP (TIMP-2) expression was detectable in cells transfected with vector alone or wild-type cells, respectively. Its expression was undetectable in AAC-11 transfected cells. In cervical cancer cells transfected with AAC-11, the expression of beta-catenin was up-regulated. These suggest that overexpressions of MMP-2 and MT1-MMP, loss of TIMP-2 expression, and up-regulation of beta-catenin by AAC-11 transfection may contribute to the development of cervical cancer invasion. AAC-11 gene transfection increased cervical cancer cell colonization. The effect of AAC-11 on cultured cervical cancer cells was associated with antiapoptotic process. Approximately 50% of the AAC-11 transfected cells in serum-free medium died after 2 weeks, compared to 1 week for vector alone or wild-type cells. These results suggest that AAC-11 may serve as a candidate metastasis-related and apoptosis-inhibiting gene in human cervical cancer.

Matrix metalloproteinase inhibition. From the Jurassic to the third millennium

A brief historical introduction to the matrix metalloproteinase (MMP) field, which began in 1962, is followed by an overview of the inhibition of these proteases by natural inhibitors such as alpha 2 macroglobulin and the TIMPs (tissue inhibitors of metalloproteinases) and by synthetic inhibitors, which are largely chelating agents. The latter include thiol, alkylcarbonyl, phosponamidate and hydroxamate compounds, as well as the tetracyclines. A review of the most recent progress concludes with prognostications as to where the field may be going next.

A zinc chelator inhibiting gelatinases exerts potent in vitro anti-invasive effects

Matrix metalloproteinases are zinc metalloenzymes involved in remodelling of the extracellular matrix. We compared the anti-invasive properties of a zinc ejector matrix metalloproteinase inhibitor with those of reference compounds (hydroxamic acid-based BB-94 and Ro-31-9790) which form inactive ternary complexes with the enzymes and the catalytic zinc. We show that the compound undecadenedioic acid bis-[[2-(3 H-imidazol-4-yl)-ethyl]-amide] (S 30372) is active against gelatinases, chelates zinc and exhibits enzymatic features compatible with the potential to extract zinc from gelatinases. We then used five invasive cell lines in the Matrigel invasion chamber assay (NIH-3T3 fibroblasts, Lewis lung carcinoma cells, EJ138 and J82 bladder carcinoma and HT1080 fibrosarcoma cells). With the exception of J82 cells which were unaffected by the three inhibitors, all remaining cells were substantially more sensitive to S 30372 in terms of maximal inhibition of invasion attained. This suggests that matrix metalloproteinase inhibitors with zinc chelating/ejecting properties may be more efficient in preventing tumor progression.

Selection of a histidine-containing inhibitor of gelatinases through deconvolution of combinatorial tetrapeptide libraries

A fully automated peptide synthesizer was used to generate tetrapeptide sublibraries from 24 natural and nonnatural amino acids, from which new inhibitors of gelatinases (matrix metalloproteinases MMP-2 and MMP-9) were selected as potential anticancer drugs. MMP-2 and MMP-9 from mouse Balbc/3T3 fibroblasts conditioned media were assayed in their linear range response by zymography to quantify inhibition at each step of the tetrapeptide library deconvolution. The histidine-epsilon-amino caproic acid-beta-alanine-histidine (His-epsilon Ahx-beta Ala-His) sequence was found to yield optimal inhibition of both MMP-2 and MMP-9. Inhibition by selected tetrapeptides was also evaluated with two other techniques, a native type IV collagen degradation assay and a fluorogenic enzymatic assay, confirming the tetrapeptide potency. The His-epsilon Ahx-beta Ala-His tetrapeptide also inhibited purified human MMP-2 and MMP-9 and the corresponding enzymes present in conditioned media from human tumour cells. Finally, the length of the spacer between the two terminal histidines was found to be crucial to the inhibitory potential. This approach may thus be considered as a-successful strategy to yield specific peptide or pseudopeptide inhibitors, although their potency remains moderate, since it was measured before any chemical optimization was undertaken.

Activation of human progelatinase A by collagenase and matrilysin: activation of procollagenase by matrilysin

Proteolytic and nonproteolytic methods were used to investigate the mechanism(s) by which human fibroblast progelatinase A and fibroblast-type procollagenase can be activated. Both collagenase and matrilysin were able to activate progelatinase A, resulting in an amino terminus in gelatinase A of Tyr81. The cleavage occurred distal to Cys73 within the sequence of PRCGNPDVAN80-Y81NFFPRKP. While several nonproteolytic reagents were tested, only the heavy metal Hg(II) and p-chloromercuribenzoate (PCMB) were able to induce activation of progelatinase A and resulted in the conversion of the latent 72-kDa gelatinase A to an active form of about 64.5 kDa. Matrilysin was also able to activate procollagenase and resulted in an amino terminus in collagenase of Phe81. These results suggest that fibroblast-type collagenase and matrilysin may be physiologically relevant activators of progelatinase A; the maintenance of latency and the process of activation for progelatinase A may occur through the cysteine-switch mechanism, and the proteolytic activation of procollagenase by matrilysin resulted in the same amino terminus as produced by stromelysin-1.

TIMP-2 mediates cell surface binding of MMP-2

In order to understand the mechanism for neoplastic cell invasion, we utilized binding studies of TIMP-2, gelatinase A and the TIMP-2/gelatinase A complex to neoplastic cells and correlated these results with their capacity to invade a matrix substrate in a modified Boyden chamber assay. Binding studies were performed on malignant human breast cancer cells and fibrosarcoma cells with rTIMP-2, rGelatinase A, and TIMP-2/gelatinase A complex. Competition studies of the binding characteristics of these proteins indicated that gelatinase A and gelatinase A/TIMP-2 complex bound to the surface of cells via TIMP-2. Furthermore, the localization of either latent or active protease to the surface of MDA-MB-435 breast cancer cells facilitated the invasion of these neoplastic cells through a matrigel barrier. This suggests that in addition to binding this complex, these cells can activate this pro-enzyme-inhibitor complex and use this activity to facilitate cellular invasion. Moreover, their enhanced invasion was suppressed by exogenous additions of rTIMP-2. A working hypothesis and model for the role of gelatinase A/TIMP-2 complex in cellular invasion is presented.

Mechanism of activation of human neutrophil gelatinase B. Discriminating between the role of Ca2+ in activation and catalysis

Gelatinase B is a Zn(2+)- and Ca(2+)-dependent endopeptidase that is secreted from cells as an inactive proenzyme. The enzyme can be activated in vitro by organomercurial compounds and by trypsin. The role of Ca2+ in autoproteolytic processing initiated by 4-aminophenylmercuric acetate and trypsin and in catalytic activity of the activated enzyme was investigated by zymography and by kinetic analysis. Treatment of unglycosylated 57.5-kDa pro-gelatinase B with 4-aminophenylmercuric acetate (1 mM) in the absence of Ca2+ generated a 49-kDa inactive intermediate (E'), whereas a 41.5-kDa active species (E") was generated in the presence of Ca2+ (5 mM). Upon addition of Ca2+ to the reaction mixture of Ca(2+)-depleted E' or E" at 37 degrees C, E' showed a lag period in generation of the product as a function of time, but E" presented an immediate activity. The appearance of enzymatic activity of E' correlated with the generation of the E" species. NH2-terminal sequence analyses showed that E' and E" had the same NH2 termini, i.e. Met-75, suggesting that Ca(2+)-dependent removal of COOH terminus of E' is required for activation of the enzyme. Treatment of pro-gelatinase B with trypsin in the absence of Ca2+, led to degradation of the enzyme. In the presence of Ca2+, trypsin processed the pro-enzyme to a 40-kDa active species. In contrast to E", this active species did not require Ca2+ for activity. The Ca2+ dependence of E" activity was also abolished by treatment of the enzyme with trypsin. NH2-terminal sequence analysis indicated that amino acid residues 75-87 had been removed from the NH2 terminus of E" by trypsin, suggesting that these residues are responsible for the Ca(2+)-dependent activity of the enzyme. Removal of Ca2+ and catalytic Zn2+ inhibited the activities of both E" and trypsin-treated E". In the absence of Ca2+, either Zn2+, Co2+, Mn2+, or Cd2+ was able to restore the activity of trypsin-treated E". None of the divalent cations tested however, was able to stimulate the activity of E" in the absence of Ca2+. These experiments further suggest that binding of Ca2+ to E" or removal of the NH2-terminal residues of the enzyme by trypsin induces a conformational change in the protein and makes the active site of the enzyme accessible to various metal ions rendering the enzyme active.

Differences in proliferation and invasion by normal, transformed and NF1 Schwann cell cultures are influenced by matrix metalloproteinase expression

Loss of negative growth regulation and high invasive potential are neoplastic traits often associated with abnormal expression of matrix metalloproteinases (MMPs). We previously found MMP-3 (stromelysin/transin) was secreted by quiescent rat Schwann cell cultures and expressed potent antiproliferative activity. In the present study we observed that human Schwann cells and cutaneous neurofibroma Schwann cell cultures secreted abundant MMP-3 and their proliferation was inhibited by autologous and rat Schwann cell conditioned media. Antiproliferative activities were depleted by immunoadsorption with anti-stromelysin antibodies. In contrast, plexiform neurofibroma cultures did not secrete MMP-3 and failed to respond to Schwann cell antiproliferative activities associated with MMP-3. Quiescent Schwann cells constitutively secreted low levels of MMP-2 (gelatinase A) and showed a low invasion potential in filter-based assays of basement membrane invasion. Cyclic AMP elevation, which profoundly influences cell differentiation, increased the invasion potential of rat Schwann cells and caused a corresponding increase in secretion of MMP-2. Schwann cells immortalized by protracted elevation of cAMP, as well as a schwannoma cell line (D6P2T), also rapidly invaded a reconstituted basement membrane and over-expressed MMP-2. Similarly, neurofibroma Schwann cells were highly invasive and secreted up to 10-fold more MMP-2 than normal human Schwann cells. Additionally, only cutaneous neurofibroma Schwann cell cultures secreted MMP-9 (gelatinase B) and MMP-1 (interstitial collagenase) and also invaded native type I collagen barriers. Cultures of normal Schwann cells and plexiform neurofibroma tumor expressed little or no MMP-1 and did not invade type I collagen barriers. These results suggest a role for MMPs in the control of proliferation and invasion by Schwann cells and in the formation of peripheral nerve sheath tumors.

Inhibition of invasion, gelatinase activity, tumor take and metastasis of malignant cells by N-acetylcysteine

The thiol N-acetylcysteine (NAC) is currently considered one of the most promising cancer chemopreventive agents by virtue of its multiple and coordinated mechanisms affecting the process of chemical carcinogenesis. Recent studies have shown that an unpaired cysteine residue in the propeptide plays a key role in inactivation of latent metastasis-associated metalloproteinases: the present study was designed to assess whether NAC could also affect tumor take, invasion and metastasis of malignant cells. As assessed by zymographic analysis, NAC completely inhibited the gelatinolytic activity of type-IV collagenases in the cells tested (gelatinases A and B). Moreover, NAC was efficient in inhibiting the chemotactic and invasive activities of tumor cells of human (A2058 melanoma) and murine origin (K1735 and B16-F10 melanoma cells as well as C87 Lewis lung carcinoma cells) in Boyden-chamber assays, which are predictive of the invasive and metastatic properties. Reduced glutathione (GSH) had a similar, although less effective activity. The number of lung metastases decreased sharply when B16-F10 murine melanoma cells, injected i.v. into nude mice, were pre-treated with NAC and resuspended in medium supplemented with 10 mM NAC. In other experiments NAC was given in drinking water, starting 48-72 hr before subcutaneous inoculation of either B16-F10 cells or of their highly metastatic variant B16-BL6, or intramuscular injection of LLC cells. In all experiments NAC treatment decreased the weight of the locally formed primary tumor and produced a dose-related delay in tumor formation. Spontaneous metastasis formation by B16-F10 and B16-BL6 tumors was slightly yet significantly reduced by oral administration of NAC. However, this was not observed for Lewis lung tumors. These data indicate that NAC affects the process of tumor-cell invasion and metastasis, probably due to inhibition of gelatinases by its sulfhydryl group, with the possible contribution of other mechanisms, including the potent antioxidant activity of this thiol.

Using inhibitors of metalloproteinases to treat arthritis. Easier said than done?

Collagenase and stromelysin have a premier role in the irreversible degradation of the extracellular matrix seen in rheumatic disease. It is therefore no surprise that considerable attention has been devoted to developing strategies to reduce their levels in diseased joints. Most efforts have focused on inhibiting the activity of the enzymes, either by increasing the concentration of natural inhibitors such as the TIMPs or by introducing into the joint synthetic compounds that will complex with the enzymes and inactivate them. There have also been studies directed at inhibiting enzyme synthesis. These preclinical studies have been carried out in cell-free and/or cell culture systems and in animal models. Despite promising preclinical data, there have been no stunning successes in the clinical arena. The reasons for this are several. In part, they are rooted in the technical difficulties associated with designing inhibitors of enzyme activity that are of high affinity, and then delivering them to the affected joints while still maintaining specificity and efficacy. The complicated structure of the proteoglycan and collagen that comprise articular cartilage, along with the biochemistry of inflamed synovial tissue, only compound the difficulties. In addition to these technical problems, the lack of fundamental knowledge about the biochemistry and molecular biology of the enzymes has handicapped our efforts. We are just resolving the crystal structure of the metalloproteinases (108) and beginning to understand the mechanisms controlling gene expression (67, 68, 70-72). These advances represent significant achievements in metalloproteinase enzymology and biology and should form the scientific basis for a new generation of effective therapies. For example, knowledge of the active site as derived from the crystal structure of the enzymes may facilitate the development of tightly-binding specific inhibitors which function well in vivo. Similarly, based on our current understanding of mechanisms controlling the regulation of both the TIMP genes and the MMP genes, we are beginning to elucidate how to turn these genes on or off, and hopefully, to modulate disease accordingly. Indeed, although some studies are still at a preclinical level, these possible approaches are becoming a reality (109). Arthritic diseases in general, and rheumatoid arthritis in particular, represent a complicated multifaceted set of clinical disorders. The clinical symptoms and pathologic features result from a cascade of biologic pathways that involve acute and chronic inflammation, the immune response, and metalloproteinase biochemistry.(ABSTRACT TRUNCATED AT 400 WORDS)

Molecular and cellular analysis of basement membrane invasion by human breast cancer cells in Matrigel-based in vitro assays

In vitro analyses of basement membrane invasiveness employing Matrigel (a murine tumor extract rich in basement membrane components) have been performed on human breast cancer model systems. Constitutive invasiveness of different human breast cancer (HBC) cell lines has been examined as well as regulation by steroid hormones, growth factors, and oncogenes. Carcinoma cells exhibiting a mesenchymal-like phenotype (vimentin expression, lack of cell border associated uvomorulin) show dramatically increased motility, invasiveness, and metastatic potential in nude mice. These findings support the hypothesis that epithelial to mesenchymal transition (EMT)-like events may be instrumental in the metastatic progression of human breast cancer. The MCF-7 subline MCF-7ADR appears to have undergone such a transition. The importance of such a transition may be reflected in the emergence of vimentin expression as an indicator of poor prognosis in HBC. Matrix degradation and laminin recognition are highlighted as potential targets for antimetastatic therapy, and analyses of laminin attachment and the matrix metalloproteinase (MMP) family in HBC cell lines are summarized. Matrigel-based assays have proved useful in the study of the molecular mechanisms of basement membrane invasiveness, their regulation in HBC cells, and their potential as targets for antimetastatic therapy.

Stereo-specific inhibition of sea urchin envelysin (hatching enzyme) by a synthetic autoinhibitor peptide with a cysteine-switch consensus sequence

Inhibition of envelysin, a metalloproteinase which dissolves the fertilization envelope of sea urchin embryo, was studied using a synthetic autoinhibitor peptide. Ac-Pro-Arg-Cys-Gly-Val-Pro-Asp-Val-NH2, with a 'cysteine-switch' consensus sequence. Although its effect is reversible, the hatching of sea urchin embryos was effectively delayed by 0.5 mM of the peptide. When alpha 1-proteinase inhibitor was used as the substrate, envelysin was inhibited by the autoinhibitor and an Ala6 analogue, but not by a D-Cys3 analogue. However, envelysin was weakly inhibited by both D- and L-cysteines to the same extent. Snake venom alpha-protease exhibited cleavage and inhibition behavior similar to envelysin with a little weaker stereo-specificity. The results suggest that the coordination of the autoinhibitor Cys residue with the envelysin active site Zn is established only after the amino acid residues on both sides of the Cys residue get into an appropriate interaction with the catalytic site residues, and that the precise orientation of the cysteine SH group is essential. By contrast, thermolysin was weakly inhibited by the three peptide non-stereo-specifically. Furthermore, thermolysin cleaved the autoinhibitor at the Cys3 Gly4 bond when incubated without substrate.

Peptides based on the conserved predomain sequence of matrix metalloproteinases inhibit human stromelysin and collagenase

Prostromelysin, a member of the family of matrix metalloproteinases, is secreted as a zymogen which is activated after cleavage of the His81-Phe82 bond. The 82 amino acid propeptide that is removed during activation contains 12 amino acids, MRKPRC75GVPDVG, that are highly conserved in all MMPs. We evaluated a series of peptides that span this region for their ability to inhibit stromelysin. The hexapeptide, Ac-RCGVPD, and the pentapeptide, Ac-RCGVP had IC50 values of approx. 10 microM. The tetrapeptide, Ac-RCGV, was somewhat less potent with an IC50 of 60 microM. Smaller peptides, e.g. Ac-RCG, were significantly less potent as inhibitors. Substitutions of Cys75 with Ser resulted in a complete loss of inhibitory activity. The peptides in this series also inhibited human fibroblast collagenase.

Cellular activation of the 72 kDa type IV procollagenase/TIMP-2 complex

Members of the collagenase family of enzymes have been implicated as central mediators of a number of both physiologic and pathologic processes. The 72-kDa type IV collagenase is secreted as a latent proenzyme, complexed with tissue inhibitor of metalloproteinase-2 (TIMP-2). Like other members of the collagenase family, this enzyme complex must be converted to a catalytically active form for proteolytic remodeling of extracellular matrix to occur. In the current study we demonstrate an inducible cell-mediated activation of the 72-kDa type IV procollagenase/TIMP-2 complex. Isolation of the 62 kDa activated enzyme/TIMP-2 complex from conditioned media of concanavalin A treated WI-38 fibroblasts demonstrated that the cell activated species was proteolytically active and amino terminal sequencing gave the sequence YNFF. This is identical to that of the 62 kDa species generated following organomercurial activation of purified 72-kDa type IV procollagenase/TIMP-2 complex. We have also isolated biosynthetically 35S-labeled 72-kDa type IV procollagenase/TIMP-2 complex and used this to further study the cellular activation process. In cell lines tested the activator was retained in the residual cell fraction following lysis in the presence of 0.2% (wt/vol) Brij-35. Inhibitor studies demonstrated that processing and activation of 72-kDa type IV procollagenase/TIMP-2 complex by the residual fraction was inhibited by 5 mM ethylenediaminetetraacetic acid and 0.5 mM 1,10-phenanthroline demonstrating a metal atom dependence. The species responsible for activation could be partially recovered in soluble form with 0.5% (vol/vol) Triton X-100 and 0.25% (wt/vol) CHAPS but was not salt extractable.(ABSTRACT TRUNCATED AT 250 WORDS)