Abstract
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-α (TNF-α), a proinflammatory cytokine, increased the expression of inducible nitric-oxide synthase (iNOS) and NO production and decreased the expression of soluble guanylate cyclase α1 (sGCα1), soluble guanylate cyclase β1 (sGCβ1), 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-α-induced increases of iNOS expression and NO levels and reversed TNF-α-induced decreases of sGCα1, sGCβ1, and PKG expression. These results imply that cGMP enhancers could have anti-proinflammatory potential in TSMCs. TNF-α also increased protein kinase A (PKA) expression and cAMP levels, cyclooxygenase-2 (COX-2) expression, and activated productions of prostaglandin (PG) E2 and 6-keto-PGF1α (stable PGI2 metabolite). Dexamethasone and N-[2-(cyclohexyloxyl)-4-nitrophenyl]-methane sulfonamide (NS-398; a selective COX-2 inhibitor) attenuated TNF-α-induced expression of COX-2 and activated productions PGE2 and PGI2. However, KMUP-1 and KMUP-3 did not affect COX-2 activities and did not further enhance cAMP levels in the presence of TNF-α. It is suggested that TNF-α-induced increases of PKA expression and cAMP levels are mediated by releasing PGE2 and PGI2, the activation products of COX-2. In conclusion, xanthine-based KMUP-1 and KMUP-3 inhibit TNF-α-induced expression of iNOS in TSMCs, involving the sGC/cGMP/PKG expression pathway but without the involvement of COX-2.
Footnotes
-
This study was supported by grants NSC-94-2320-B-037-002 and NSC-94-2323-B-037-005 to I.-J.C. from the National Science Council, Taiwan.
-
ABBREVIATIONS: TNF-α, tumor necrosis factor-α; TSM, tracheal smooth muscle; COX-2, cyclooxygenase-2; iNOS, inducible nitric-oxide synthase; PDE, phosphodiesterase; PG, prostaglandin; PKA, protein kinase A; PKG, protein kinase G; KMUP-1, 7-[2-[4-(2-chlorobenzene)piperazinyl] ethyl]-1,3-dimethylxanthine; KMUP-3, 7-[2-[4-(4-nitrobenzene)piperazinyl]ethyl]-1,3-dimethylxanthine; sGC, soluble guanylate cyclase; TSMC, tracheal smooth muscle cell; NS-398, N-[2-(cyclohexyloxyl)-4-nitrophenyl]-methane sulfonamide; IL, interleukin; TTBS, Tris-buffered saline/Tween 20; PBS, phosphate-buffered saline; PDEI, phosphodiesterase inhibitor; buffer A, Triton X-100 and bovine serum albumin in phosphate-buffered saline; CPT, chlorophenylthio; YC-1, 3-(5′-hydroxymethyl-2′-furyl)-1-benzylindazole; Bay-41-2272, 5-cyclopropyl-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridin-3-yl]pyrimidin-4-ylamine; Rp-CPT-cAMPs, 8-(4-chlorophenylthio)adenosine-3′,5′-cyclic monophosphorothioate, Rp-isomer; Rp-CPT-cGMPs, 8-(4-chlorophenylthio)guanosine-3′,5′-cyclic monophosphorothioate, Rp-isomer.
- Received March 23, 2006.
- Accepted June 5, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
MolPharm articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|