Immunopharmacologic profiles of a thiol protease inhibitor, L-trans-dicyclohexyl epoxysuccinate.

Ep-1, L-trans-Dicyclohexyl epoxysuccinate, is a synthetic and specific inhibitor of thiol proteases. The effects of this inhibitor on some immunological parameters were examined in normal and immunity-impaired mice and rats. In the cultures of splenocytes obtained from the mice treated with Ep-1, it enhanced the lymphocyte blast transformation induced by both suboptimal and optimal concentrations of concanavalin A (Con A) and Lens culinaris (LC). The in vivo administration of Ep-1 caused a depression of the plaque forming cells (PFC) for sheep red blood cell (SRBC) and enhanced the delayed-type hypersensitivity (DTH) for bovine serum albumin (BSA) as well as mixed lymphocytes cultures (MLC). Furthermore, Ep-1 demonstrated a preventive effect on adjuvant arthritic rats. The relevance of immunological regulation and the mode of action of Ep-1 as a thiol protease inhibitor are discussed in these findings.