Dual roles of MC proteases in the regulation of inflammatory processes. MC proteases may affect inflammation at different levels, either by promoting inflammatory processes (A) or by offering protection (B). (A) Proinflammatory activities include (1) activating cleavages of proinflammatory cytokines/chemokines, (2) degradation of endothelial cell-cell contacts, (3) activation of extracellular matrix (ECM)–degrading enzymes, (4) recruitment of eosinophils/neutrophils, and (5) effects on gene expression (eg, via cleavage of protease-activated receptor 2). (B) Protective activities include (1) degradation of proinflammatory cytokines/chemokines, (2) degradation of toxic peptides, and (3) suppression of smooth muscle cell expansion.