Abstract

Degradation of the extracellular matrix occurs under physiological and pathological conditions, thought to be principally mediated by a family of neutral proteolytic enzymes termed the matrix metalloproteinases (MMPs). The present study was initiated to determine whether mast cells have the ability to produce these proteases in diseased and normal human tissue. Immunohistochemistry and in situ hybridization was performed to localize interstitial collagenase protein and mRNA transcripts in diseased human tissue. The human mast cell line HMC-1 was cultured under serum free conditions, stimulated with phorbol mystrate acetate (PMA) and supernatants analyzed by Western blotting and zymography to determine the profile of secreted MMPs. The dog mast cell line BR, known to secrete gelatinolytic enzymes, was used in parallel studies. Total RNA was extracted and analyzed by RT-PCR for the expression of tissue inhibitors of MMP (TIMPs). Collagenase-1 protein and mRNA were expressed by tryptase and chymase positive human mast cells in all tissue analyzed. This proteinase wa also detected in the cytoplasm and conditioned media of HMC-1 cells. PMA induced gelatinolytic activity in both mast cell lines examined. TIMP-1 immunoreactivity was detected and TIMP-1, and-2 (but not TIMP-3) mRNA transcripts were amplified from HMC-1 cells. This is the first demonstration of the expression of collagenase-1 by human mast cells in both inflamed and normal tissues, and by a human mast cell line. MMPs secreted by these cells could contribute to the extensive matrix lysis characteristic of diseases such as rheumatoid arthritis and inflammatory ocular disorders. Alternatively collagenase-1 production by mast cells may play a critical role in cell invasion and migration into sites of inflammation.

Highlights

  • Recent studies have focused on the potential importance of mast cells in a variety of inflammatory disorders affecting the integrity of the connective tissue matrix such as rheumatoid arthritis (RA) (Godfrey et al, 1984) and asthma (Galli, 1993)

  • Mast cells were identified based on the specificity of two monoclonal antibodies directed against tryptase and chymase, which are proteases stored in mast cells granules

  • The localization of interstitial collagenase to mast cells has particular significance, as this enzyme denatures interstitial collagen type-I, II, and III, matrix proteins frequently encountered by mast cells as they migrate ttirough the connective tissue

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Summary

Introduction

Recent studies have focused on the potential importance of mast cells in a variety of inflammatory disorders affecting the integrity of the connective tissue matrix such as rheumatoid arthritis (RA) (Godfrey et al, 1984) and asthma (Galli, 1993). Mast cells have been shown to play a key role in initiating inflammatory responses, via their release of pro-inflammatory mediators such as cytokines (Gordon and Galli, 1990), growth factors (Powers et al, 1997), chemokines (Wang et al, 1998; Moller et al, 1993), histamine and proteases (McNeil, 1996). Proteases such as tryptase and chymase serve as specific markers for mast cells (Schwartz, 1994). The membrane-associated MMPs (MT-MMPs) can activate other MMPs and degrade some fibrillar collagens

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