Differential anti-inflammatory effects of immunosuppressive drugs: Cyclosporin, rapamycin and FK-506 on inducible nitric oxide synthase, nitric oxide, cyclooxygenase-2 and PGE₂ production

Abstract.

Objective and Design: Cyclosporin, FK-506 and rapamycin have similar but distinct modes of interaction with cyclophilins, calcineurins and transcription factors. These immunosuppressive drugs have also been shown to inhibit cytotoxic and inflammatory responses in macrophage. Therefore, we evaluated the mechanism of action of these drugs on iNOS and COX-2 expression by macrophages, the products of which (NO and PGE₂) have cytotoxic and pro-inflammatory activities.¶Materials and Methods: The murine macrophage cell line RAW 264.7 was grown as monolayer cultures. The effects of pharmacologically relevant concentrations of cyclosporin, rapamycin and FK-506 were evaluated in the presence and absence of lipopolysaccharide (LPS) which is a known inducer of iNOS and COX-2. Subsequently the expression of iNOS and COX-2 were analyzed by Western and Northern analysis. The production of NO and PGE₂ were assayed by Greiss and RIA respectively.¶Results: Cyclosporin (1-5 μg/ml) and rapamycin (1.0-10 nM) but not FK-506 (5-10 nM) inhibited both iNOS and COX-2 expression at mRNA level which led to significant inhibition of NO and PGE₂ production.¶Conclusion: These studies characterize differential mechanistic capacity of the immunophilin-binding immunosuppressive drugs (comparable to hydrocortisone) to inhibit both iNOS and COX-2 expression. Inhibition of iNOS and COX-2 mRNA accumulation by cyclosporin and rapamycin seem to be distinct. These studies also highlight potential anti-inflammatory properties of these drugs in addition to their known immunosuppressive activity.¶