TY - JOUR T1 - Cyclooxygenase-2 Inhibition Improves Vascular Endothelial Dysfunction in a Rat Model of Endotoxic Shock: Role of Inducible Nitric-Oxide Synthase and Oxidative Stress JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 945 LP - 953 DO - 10.1124/jpet.104.077644 VL - 312 IS - 3 AU - Agostino Virdis AU - Rocchina Colucci AU - Matteo Fornai AU - Corrado Blandizzi AU - Emiliano Duranti AU - Stefania Pinto AU - Nunzia Bernardini AU - Cristina Segnani AU - Luca Antonioli AU - Stefano Taddei AU - Antonio Salvetti AU - Mario Del Tacca Y1 - 2005/03/01 UR - http://jpet.aspetjournals.org/content/312/3/945.abstract N2 - We investigated whether cyclooxygenase (COX) isoforms (COX-1 and COX-2) and decreased NO availability contribute to endothelial dysfunction in endotoxemic rats. The involvement of reactive oxygen species (ROS) was also evaluated. Rats were injected with Salmonella-derived lipopolysaccharide or saline. After 6 h, endothelial function of mesenteric resistance arteries was evaluated. In controls, acetylcholine (ACh)-induced relaxation was inhibited by the nitric-oxide synthase inhibitor NG-monomethyl-l-arginine (l-NMMA) and unaffected by 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl)-phenyl-2(5H)-furanone (DFU) (COX-2 inhibitor). In lipopolysaccharide (LPS)-treated rats, the response to ACh was blunted compared with controls, less sensitive to l-NMMA, and enhanced by DFU. COX-2 blockade also improved the inhibitory effect of l-NMMA on cholinergic relaxation. SC-560 [5-(4-clorophenyl)-1-(4-metoxyphenyl)-3-trifluoromethylpirazole] (COX-1 inhibitor) did not modify the response to ACh in both groups. LPS-induced endothelial dysfunction was unaffected by the thromboxane A2 (TxA2) receptor antagonist SQ-29548 (7-[3-[[2-[(phenylamino)carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1] hept-2-yl]-[1S(1alpha,2alpha(Z),3alpha,4alpha)]-5-heptenoic acid). In vivo inducible nitric-oxide synthase (iNOS) inhibition by S-methylisothiourea partly attenuated LPS-induced endothelial dysfunction. The antioxidants ascorbic acid and superoxide dismutase normalized endothelium-dependent relaxation and restored the inhibitory action of l-NMMA on ACh. Responses to sodium nitroprusside were similar in both groups. In LPS-treated rats, reverse transcription-polymerase chain reaction showed a marked increase in mesenteric iNOS and COX-2 expressions, whereas endothelial nitric-oxide synthase and COX-1 were unchanged. LPS-induced COX-2 overexpression was reduced but not abrogated by S-methylisothiourea. LPS-induced COX-2 up-regulation was also documented by immunohistochemistry. In conclusion, mesenteric resistance vessels from endotoxemic rats show impaired endothelial function due to reduced NO availability, a condition that is partly ascribable to an iNOS-dependent enhanced COX-2 expression, whereas TxA2 does not seem to be involved. Oxidative stress is the main mechanism responsible for reduced NO availability, and COX-2 might act as a source of ROS. The American Society for Pharmacology and Experimental Therapeutics ER -