Cyclooxygenase-2 inhibition improves vascular endothelial dysfunction in a rat model of endotoxic shock: role of inducible nitric-oxide synthase and oxidative stress.
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 N(G)-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 A(2) (TxA(2)) 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 TxA(2) 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.
Virdis
Agostino
A
Department of Internal Medicine, University of Pisa, Via Roma, 67, 56100 Pisa, Italy. a_virdis@yahoo.com
Colucci
Rocchina
R
Fornai
Matteo
M
Blandizzi
Corrado
C
Duranti
Emiliano
E
Pinto
Stefania
S
Bernardini
Nunzia
N
Segnani
Cristina
C
Antonioli
Luca
L
Taddei
Stefano
S
Salvetti
Antonio
A
Del Tacca
Mario
M
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000627:therapeutic use*; D016207:Cytokines / Q000097:blood; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D008297:Male; D019001:Nitric Oxide Synthase / Q000502:physiology*; D052247:Nitric Oxide Synthase Type II; D009638:Norepinephrine / Q000494:pharmacology; D018384:Oxidative Stress; D011451:Prostaglandin-Endoperoxide Synthases / Q000032:analysis; D011720:Pyrazoles / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012772:Shock, Septic / Q000188:drug therapy* / Q000503:physiopathology; D013482:Superoxide Dismutase / Q000494:pharmacology; D014655:Vascular Resistance / Q000187:drug effects; D014661:Vasoconstriction / Q000187:drug effects; D019323:omega-N-Methylarginine / Q000494:pharmacology
D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D016207:Cytokines; D011720:Pyrazoles; C115461:SC 560; D019323:omega-N-Methylarginine; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; D013482:Superoxide Dismutase; D000109:Acetylcholine; D001205:Ascorbic Acid; D009638:Norepinephrine