Anti-inflammatory and anti-arthritic effects of new synthetic 3-(4-hydroxyphenyl)-4-(4-thiomethoxyphenyl)-1H-pyrrole-2,5-dione

We previously reported that 3-(4-hydroxyphenyl)-4-(4-thiomethoxyphenyl)-1H- pyrrole-2,5-dione (1, HMP) has a strong inhibitory effect on prostaglandin E ₂ (PGE ₂) production. In this study, the anti-inflammatory and anti-arthritic effects of HMP were evaluated on LPS-induced RAW 264.7 macrophages and rats with carrageenan-induced paw edema and adjuvant-induced arthritis (AIA). The attenuation of PGE ₂ production by HMP was found to be caused by the inhibition of cyclooxygenase-2 (COX-2) activity, but not COX-1 activity. However, HMP did not affect COX-2 at the protein or mRNA levels, whereas it suppressed the releases and expressions of inflammatory cytokines, such as, interleukin-1β (IL-1β) and IL-6 in LPS-induced macrophages. Furthermore, HMP suppressed LPS-induced nitric oxide (NO) production by down regulating the protein and mRNA expressions of inducible nitric oxide synthase (iNOS). In rats with carrageenan-injected acute inflammation, oral administration of HMP (25 or 50 mg/kg, po) reduced paw swelling, and PGE ₂ release and myeloperoxidase (MPO) activity in tissue. Furthermore, HMP (25 or 50 mg/kg, po) significantly reduced paw swelling, arthritic indices and plasma PGE ₂ concentrations in rat with AIA. These results show that HMP reduces swelling in a model acute inflammation and inhibits arthritic responses in a model of chronic inflammation via the inhibition of PGE ₂ production. These results suggest that HMP is a potential therapeutic agent for the treatment of arthritis and associated disorders.