Tetrahydrobiopterin prevents platelet-activating factor-induced intestinal hypoperfusion and necrosis: Role of neuronal nitric oxide synthase.
OBJECTIVE
We reported previously that neuronal nitric oxide synthase (nNOS) is the predominant NOS in rat small intestine and is down-regulated by platelet-activating factor (PAF). The severity of the bowel injury induced by PAF is inversely related to its suppressing effect on nNOS. Here, we investigated whether intestinal perfusion is regulated by nNOS and whether tetrahydrobiopterin, a co-factor and stabilizer of nNOS, reverses PAF-induced intestinal hypoperfusion and injury.


METHODS
Animal laboratory.


METHODS
We first examined nNOS regulation of splanchnic blood flow by measuring the perfusion of the heart, lung, ileum, and kidney in rats after a nNOS inhibitor. We then examined the protective effect of tetrahydrobiopterin on PAF-induced bowel injury, mesenteric hypoperfusion, and systemic inflammation.


METHODS
Adult male Sprague-Dawley rats.


METHODS
In part 1 of the experiment, rats were given 7-nitroindazole (a specific nNOS inhibitor, 50 mg.kg.day). In part 2 of the experiment, rats were treated with tetrahydrobiopterin (20 mg/kg) 5 mins before and 30 mins after PAF challenge (2.2 microg/kg, intravenously)


METHODS
Perfusion of the heart, lung, ileum, and kidney was measured at 1 and 4 days after 7-nitroindazole, using fluorescent microspheres. Intestinal injury and inflammation (myeloperoxidase content), blood perfusion, calcium dependent-NOS activity, and systemic inflammation (hypotension and hematocrit increase) were assessed 1 hr after PAF with and without tetrahydrobiopterin treatment.


RESULTS
In part 1 of the experiment, 7-nitroindazole induced a long-lasting reduction of blood perfusion and inducible NOS expression selectively in the ileum but not in nonsplanchnic organs such as heart, lungs, and kidneys. In part 2, tetrahydrobiopterin protected against PAF-induced intestinal necrosis, hypoperfusion, neutrophil influx, and NOS suppression. It also reversed hypotension and hemoconcentration. Sepiapterin (2 mg/kg, stable tetrahydrobiopterin precursor) also attenuated PAF-induced intestinal injury.


CONCLUSIONS
We conclude that nNOS selectively regulates intestinal perfusion. Tetrahydrobiopterin prevents PAF-induced intestinal injury, probably by stabilizing nNOS and maintaining intestinal perfusion.
Qu
Xiao-Wu
XW
Department of Pathology, Children's Memorial Hospital, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA.
Thaete
Larry G
LG
Rozenfeld
Ranna A
RA
Zhu
Yaqin
Y
De Plaen
Isabelle G
IG
Caplan
Michael S
MS
Hsueh
Wei
W
D000818:Animals; D000975:Antioxidants / Q000627:therapeutic use*; D001708:Biopterins / Q000031:analogs & derivatives* / Q000627:therapeutic use*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007191:Indazoles / Q000494:pharmacology; D007410:Intestinal Diseases / Q000209:etiology / Q000517:prevention & control*; D008297:Male; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000502:physiology*; D052248:Nitric Oxide Synthase Type I; D010972:Platelet Activating Factor / Q000037:antagonists & inhibitors* / Q000633:toxicity; D011622:Pterins / Q000627:therapeutic use; D051381:Rats; D017207:Rats, Sprague-Dawley; D013152:Splanchnic Circulation / Q000187:drug effects
D000975:Antioxidants; D004791:Enzyme Inhibitors; D007191:Indazoles; D009419:Nerve Tissue Proteins; D010972:Platelet Activating Factor; D011622:Pterins; D001708:Biopterins; C016727:sepiapterin; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; C003402:sapropterin; C080122:7-nitroindazole