Inhibition of proinflammatory tumor necrosis factor-α-induced inducible nitric-oxide synthase by xanthine-based 7-[2-[4-(2-chlorobenzene)piperazinyl]ethyl]-1,3-dimethylxanthine (KMUP-1) and 7-[2-[4-(4-nitrobenzene)piperazinyl]ethyl]-1,3-dimethylxanthine (KMUP-3) in rat trachea:: The involvement of soluble guanylate cyclase and protein kinase G

In the study of anti-proinflammation by 7-[2-[4-(2-chlorobenzene) piperazinyl] ethyl]-1,3-dimethylxanthine (KMUP-1) and 7[2-[4-(4-nitrobenzene) piperazinyl] ethyl]-1,3-dimethylxanthine (KMUP-3), exposure of rat tracheal smooth muscle cells (TSMCs) to tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine, increased the expression of inducible nitric-oxide synthase (iNOS) and NO production and decreased the expression of soluble guanylate cyclase alpha(1) (sGC alpha(1)), soluble guanylate cyclase beta(1) (sGC beta(1)), protein kinase G (PKG), and the release of cGMP in TSMCs. The cell-permeable cGMP analog 8-Br-cGMP, xanthine-based KMUP-1 and KMUP-3, and the phosphodiesterase 5 inhibitor zaprinast all inhibited TNF-alpha-induced increases of iNOS expression and NO levels and reversed TNF-alpha-induced decreases of sGC alpha(1), sGC beta(1), and PKG expression. These results imply that cGMP enhancers could have anti-proinflammatory potential in TSMCs. TNF-alpha also increased protein kinase A (PKA) expression and cAMP levels, cyclooxygenase-2 (COX-2) expression, and activated productions of prostaglandin (PG) E-2 and 6-keto-PGF(1)alpha (stable PGI(2) metabolite). Dexamethasone and N-[2-(cyclohexyloxyl)-4-nitrophenyl]methane sulfonamide (NS-398; a selective COX-2 inhibitor) attenuated TNF-alpha-induced expression of COX-2 and activated productions PGE(2) and PGI(2). However, KMUP-1 and KMUP-3 did not affect COX-2 activities and did not further enhance cAMP levels in the presence of TNF-alpha. It is suggested that TNF-alpha-induced increases of PKA expression and cAMP levels are mediated by releasing PGE(2) and PGI(2), the activation products of COX-2. In conclusion, xanthine-based KMUP-1 and KMUP-3 inhibit TNF-alpha-induced expression of iNOS in TSMCs, involving the sGC/cGMP/PKG expression pathway but without the involvement of COX-2.