The Effect of Hypothermia on Lung Inducible Nitric Oxide Synthase Gene Expression in Intestinal Ischemia-Reperfusion Injury

ABSTRACT

PURPOSE: Although hypothermia has been used in many clinical situations, such as post cardiopulmonary resuscitation, stroke, traumatic brain injury, septic shock, and hemorrhagic shock, the mechanism by which it works has not been clearly elucidated. We aimed to evaluate the effect of hypothermia on the plasma nitric oxide (NO) concentration, lung iNOS expression, and histologic changes in intestinal ischemia-reperfusion (IR). METHOD: Male Sprague-Dawley rats were randomly divided into the hypothermia group (HT, n=8, 27~30 degrees C) and the normothermia group (NT, n=8, 36~37 degrees C). They underwent 30 min of intestinal ischemia by clamping the superior mesenteric artery, which was followed by 1.5 h of reperfusion. They were then sacrificed. The acute lung injury (ALI) score, the plasma NO concentration, and lung iNOS gene expression were measured. RESULTS: Compared with the HT group, the NT group showed severe infiltrations of inflammatrory cells, alveolar hemorrhages, and interstitial hypertrophies in lung tissues. There were significant differences in the ALI scores between the NT and the HT groups (8.7 +/- 1.5/HPF in NT vs 5.8 +/- 1.2/HPF in HT, p=0.008). Although the plasma NO concentration was slightly lower in the HT group, there was no significant difference between the two groups (0.80 +/- 0.24 micromol/L in NT vs 0.75 +/- 0.30 micromol/L in HT, p=0.917). Lung iNOS gene expression was stronger in the NT group than in the HT group. The band density of the expression of iNOS in lung tissues was significantly increased in the NT group compared to the HT group (5.54 +/- 2.75 in NT vs 0.08 +/- 0.52 in HT, p=0.002). CONCLUSIONS: This study showed that hypothermia in intestinal IR reduces inflammatory responses, ALI scores, and iNOS gene expression in lung tissues. There was no significant effect of hypothermia on the plasma NO concentration.