Nitrosoglutathione improves blood perfusion and flap survival by suppressing iNOS but protecting eNOS expression in the flap vessels after ischemia/reperfusion injury.
BACKGROUND
The effects of nitric oxide (NO) on the microcirculation and free tissue survival remain controversial. With the use of a rat inferior epigastric artery flap as an ischemia/reperfusion injury (I/R) model, we investigated whether exogenous NO donation regulates endogenous NO synthase (NOS) expression in the flap vessels and promotes flap survival.


METHODS
Thirty minutes before flap reperfusion, normal saline (1 ml), nitrosoglutathione (GSNO 0.2, 0.6, 3 mg/kg), or N(G)-nitro-L-arginine-methyl ester (L-NAME, 450 mg/kg), was injected intravenously into 20 rats. Total plasma NOx (NO(2)-/NO(3)-) was measured to reflect NO production. Immunohistochemical staining was investigated for the endothelin-1 (ET-1) and NOS isoforms expression on the flap vessels. NOS isoforms expression was evaluated by Western blot. Laser-Doppler flowmetry monitored flap perfusion. Survival areas were assessed by gross examination at 7 days postoperatively.


RESULTS
Flap ischemia at 12 hours followed by reperfusion resulted in endothelial cell damage, as demonstrated by induction of iNOS and ET-1 expression in the flap vessels. An optimal dose of nitrosoglutathione (0.6 mg GSNO/kg) significantly increased plasma NOx levels (P=.027) and improved flap perfusion by laser Doppler measurement (P=.014), and increased the flap viability area (P<.001). Additionally, it selectively suppressed iNOS induction, but enhanced eNOS expression and decreased ET-1 deposition in the flap vessels. In contrast, an NOS inhibitor, N(G)-nitro-L-arginine methyl ester, inhibited both iNOS and eNOS expression in the flap vessels, decreased endogenous NOx production, and compromised flap viability.


CONCLUSIONS
This study indicates that intravenous administration of exogenous GSNO can appropriately donate NO to suppress iNOS induction and enhance eNOS expression in pedicle vessels, resulting in better blood perfusion and a higher flap survival after I/R injury.
Kuo
Yur-Ren
YR
Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital at Kaohsiung and Chang Gung University, 123 TaPei Road, Niao-Sung Hsiang, Kaohsiung 833, Taiwan.
Wang
Feng-Sheng
FS
Jeng
Seng-Feng
SF
Lutz
Barbara S
BS
Huang
Hui-Chen
HC
Yang
Kuender D
KD
D000818:Animals; D019332:Endothelin-1 / Q000096:biosynthesis; D005978:Glutathione / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006085:Graft Survival / Q000187:drug effects*; D008297:Male; D008833:Microcirculation / Q000187:drug effects*; D023421:Models, Animal; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D009574:Nitro Compounds / Q000494:pharmacology*; D051381:Rats; D011917:Rats, Inbred Lew; D015427:Reperfusion Injury / Q000503:physiopathology*; D013524:Surgical Flaps / Q000098:blood supply*
D019332:Endothelin-1; D020030:Nitric Oxide Donors; D009574:Nitro Compounds; C116027:S-nitroglutathione; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat; D005978:Glutathione