Aggrecanases and cartilage matrix degradation

The loss of extracellular matrix macromolecules from the cartilage results in serious impairment of joint function. Metalloproteinases called 'aggrecanases' that cleave the Glu(373)–Ala(374 )bond of the aggrecan core protein play a key role in the early stages of cartilage destruction in rheumatoid arthritis and in osteoarthritis. Three members of the ADAMTS family of proteinases, ADAMTS-1, ADAMTS-4 and ADAMTS-5, have been identified as aggrecanases. Matrix metalloproteinases, which are also found in arthritic joints, cleave aggrecans, but at a distinct site from the aggrecanases (i.e. Asn(341)–Phe(342)). The present review discuss the enzymatic properties of the three known aggrecanases, the regulation of their activities, and their role in cartilage matrix breakdown during the development of arthritis in relation to the action of matrix metalloproteinases

Engineering of tissue inhibitor of metalloproteinases mutants as potential therapeutics

Matrix metalloproteinases (MMPs) play a central role in many biological processes such as development, morphogenesis and wound healing, but their unbalanced activities are implicated in numerous disease processes such as arthritis, cancer metastasis, atherosclerosis, nephritis and fibrosis. One of the key mechanisms to control MMP activities is inhibition by endogenous inhibitors called tissue inhibitors of metalloproteinases (TIMPs). This review highlights the structures and inhibition mechanism of TIMPs, the biological activities of TIMPs, the unique properties of TIMP-3, and the altered specificity towards MMPs achieved by mutagenesis. A potential therapeutic use of TIMP variants is discussed

Identification of a novel 82 kDa proMMP-9 species associated with the surface of leukaemic cells

MMP-9 (matrix metalloproteinase 9) plays a critical role in tumour progression. Although the biochemical properties of the secreted form of proMMP-9 are well characterized, little is known about the function and activity of cell surface-associated proMMP-9. We purified a novel 82 kDa species of proMMP-9 from the plasma membrane of THP-1 leukaemic cells, which has substantial differences from the secreted 94 kDa proMMP-9. The 82 kDa form was not detected in the medium even upon stimulation with a phorbol ester. It is truncated by nine amino acid residues at its N-terminus, lacks O-linked oligosaccharides present in the 94 kDa proMMP-9, but retains N-linked carbohydrates. Incubation of 94 kDa proMMP-9 with MMP-3 generated the well-known 82 kDa active form, but the 82 kDa proMMP-9was converted into an active species of 35 kDa, which was also produced by autocatalytic processing in the absence of activating enzymes. The activated 35 kDa MMP-9 efficiently degraded gelatins, native collagen type IV and fibronectin. The enzyme was less sensitive to TIMP-1 (tissue inhibitor of metalloproteinase 1) inhibition with IC50 values of 82 nM compared with 1 nMfor the 82 kDa active MMP-9. The synthetic MMP inhibitor GM6001 blocked the activity of both enzymes, with similar IC50 values below 1 nM. The 82 kDa proMMP-9 is also produced in HL-60 and NB4 leukaemic cell lines as well as ex vivo leukaemic blast cells. It is, however, absent from neutrophils and mononuclear cells isolated from peripheral blood of healthy individuals. Thus, the 82 kDa proMMP-9 expressed on the surface of malignant cells may escape inhibition by natural TIMP-1, thereby facilitating cellular invasion in vivo

Stimulation of angiogenesis through cathepsin B inactivation of the tissue inhibitors of matrix metalloproteinases

AbstractThe tissue inhibitors of matrix metalloproteinases (MMPs), TIMP-1 and TIMP-2, are also angiogenesis inhibitors. Cathepsin B and MMPs are found at sites of neovascularization in pathologies such as cancer and osteoarthritis. Treatment of TIMP-1, TIMP-2, and of a mixture of both inhibitors from human articular chondrocytes with cathepsin B resulted in their fragmentation, whereby they lost their MMP-inhibitory and anti-angiogenic activities. Our data suggest that, besides directly participating in tissue destruction, cathepsin B can be harmful for two further reasons: it raises the activity of the MMPs also in the absence of mechanisms up-regulating these enzymes, and it stimulates angiogenesis. This is a prerequisite for blood vessel invasion in a variety of pathological situations of which cancer and osteoarthritis are prominent examples

Development of a monoclonal anti-ADAMTS-5 antibody that specifically blocks the interaction with LRP1

The potent aggrecanase ADAMTS-5 is constitutively secreted by chondrocytes, but it is rapidly endocytosed in normal cartilage via the cell surface endocytic receptor LRP1. Therefore it is difficult to detect the total ADAMTS-5 activity produced. In this study, we isolated a monoclonal anti-ADAMTS-5 antibody 1B7 that blocks LRP1-mediated internalization without affecting the aggrecanolytic activity. Addition of 1B7 to cultured human chondrocytes revealed the full aggrecanolytic activity of ADAMTS-5 generated by the cells. 1B7 is a useful tool to estimate the ADAMTS-5 activity and to identify its potential roles in the tissues

Tumor necrosis factor α (TNFα) induces pro-matrix metalloproteinase 9 production in human uterine cervical fibroblasts but interleukin 1 α antagonizes the inductive effect of TNFα

AbstractWe have examined the regulation of precursor of matrix metalloproteinase 9 (proMMP-9)/progelatinase B production by tumor necrosis factor α (TNFα) and interleukin 1α (IL-1α) using human uterine cervical fibroblasts. TNFα, but not IL-1α, induces the production of proMMP-9 in the cervical cells. IL-1α, however, suppresses the TNFα-induced proMMP-9 production. 12-O-tetradecanoylphorbol 13-acetate (TPA) also stimulates the cervical cells to produce proMMP-9, and IL-1α synergistically enhances its production. TNFα-induced proMMP-9 production is not mediated by protein kinase C (PKC), whereas the effect of IL-1α is through PKC. By contrast, proMMP-3/prostromelysin 1 is up-regulated by TNFα or TPA in the presence of IL-1α, whose modulation is PKC-dependent. The suppressive effect of IL-1α on the TNFα-induced proMMP-9 production is a new biological effect of IL-1 on MMP production

N-Cadherin cleavage during activated hepatic stellate cell apoptosis is inhibited by tissue inhibitor of metalloproteinase-1. [In supplement: 11th International Symposium on the Cells of the Hepatic Sinusoid and their Relation to Other Cells]

Apoptosis of hepatic stellate cells (HSC) has previously been shown to occur during spontaneous resolution of experimental liver fibrosis. TIMP-1 has also been shown to have a key role because of its ability to inhibit apoptosis of HSC via matrix metalloproteinase (MMP) inhibition. This has led to further study of novel substrates for MMPs that might impact on HSC survival. N-Cadherin is known to mediate cell-cell contacts in fibroblasts. In this study we demonstrate that N-Cadherin is expressed by activated rat HSC. Furthermore, during apoptosis of HSC, the N-Cadherin is cleaved into smaller fragments. Apoptosis of HSC may be inhibited by TIMP-1. This is associated with reduced fragmentation of N-Cadherin. N-Cadherin may have an important role in supporting HSC survival while N-Cadherin cleavage may play a part in promoting HSC apoptosis in recovery from liver fibrosis