Expression And Functional Responses To Proteinase Activated Receptors On Human Monocytes And T Cells

Serine proteases, such as thrombin, trypsin, tryptase and elastase, serve as a modulators of immune response in inflammation via regulating the hemostatic and fibrinolytic balance, degrading neuropeptides involved in neurogenic inflamma and modulating complement system. Recent studies elucidated the ability of these serine proteinases to regulate cell function via proteinase activated receptors(PARs) that belongs to a new subfamily of G-protein coupled receptor. To date, four PARs have been identified and cloned: PAR-1, PAR-2, PAR-3 and PAR-4. Thrombin is capable of activating PAR-1, PAR-3 and PAR-4, trypsin can activate PAR-1, PAR-2 and PAR-4, and tryptase and elastase is an activator of PAR-2. Monocytes and T cells is important effector cellsin immune response and inflammation. However, little is known of the expression and function of PARs on human monocytes and T cells.In the present study, expression of PARs in protein and mRNA levels on highly purified human monocytes and T cell were analyzed by flow cytometry and RT-PCR, respectively. We challenged monocytes and T cells from human peripheral blood with serine proteinases and agonist peptides of PARs, and measured the levels of interleukin (IL)-6, IL-1β and IL-12 in culture supernatants of monocytes and IL-6 and IL-13 in culture supernatants of T cells by ELISA.FACS analysis showed that monocytes express PAR-1, PAR-3, PAR-4, but not PAR-2. An agarose gel electrophoresis revealed that monocytes express PAR-1 and PAR-3, but not PAR-2 and PAR-4 mRNAs. Thrombin, trypsin, tryptase and elastase provoked a dose dependent release of IL-6 from monocytes following 16 h incubation period. Thrombin inhibitor hirudin, trypsin and tryptase inhibitor leupeptin and elastase inhibitor MSACK was able to inhibit thrombin, trypsin and tryptase and elastase induced secretion of IL-6 from monocytes, respectively. SFLLR-NH₂ (a specific PAR-1 agonist peptide), GYPGQV-NH-2 (an agonist peptide of PAR-4) stimulated increase in IL-6 secretion from monocytes following 16 h...