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Recent evidence suggests that neutrophil recruitment may initiate cell apoptosis in ischemic tissues. We have recently shown that enterocyte apoptosis is increased following intestinal ischemia-reperfusion (IR) injury. The purpose of the present study was to examine the effect of hyperoxia on E-selectin expression, neutrophil recruitment and enterocyte apoptosis following intestinal IR in a rat. Male Sprague-Dawley rats were divided into three experimental groups: (1) sham rats underwent laparotomy without vascular occlusion and were ventilated with air (Sham) (2) IR rats underwent occlusion of both the superior mesenteric artery and portal vein for 30 min and were ventilated with air (IR), and (3) IR-O2 rats underwent IR and were ventilated with 100% started 10 min before reperfusion and continued for 6 h (IR-O2). Intestinal structural changes were determined 24 h following IR. Immunohistochemistry for E-selectin (using E-selectin cleaved concentrated polyclonal antibody) was performed to identify E-selectin immunoreactivity localized to the endothelium of venules. The recruitment of neutrophils was calculated per 100 venules. Immunohistochemistry for Caspase-3 was performed for identification of apoptotic cells. Non-parametric one-way ANOVA test was used for statistical analysis with p less than 0.05 considered statistically significant. A significant increase in E-selectin expression in the jejunum (6.1 +/- 2.2 vs. 2.5 +/- 1.0 E-selectin positive vessels/100 vessels, p < 0.05) and ileum (12.1 +/- 2.7 vs. 3.3 +/- 1.2 E-selectin positive vessels/100 vessels, p < 0.05) and a concomitant increase in neutrophil recruitment in the ileum (5.5 +/- 1.6 vs. 1.3 +/- 0.6 adhered PMN's per 100 venules) were observed in IR rats compared to sham animals and were accompanied by increased cell apoptosis (p < 0.05). Treatment with 100% oxygen resulted in a significant attenuation in E-selectin expression in the ileum (2.7 +/- 1.1 vs. 12.1 +/- 2.7 E-selectin positive vessels/100 vessels, p < 0.05), and neutrophil recruitment in the jejunum (2.5 +/- 1.4 vs. 7.7 +/- 1.9 adhered PMN's per 100 venules, p < 0.05) and ileum (1.5 +/- 0.7 vs. 5.5 +/- 1.6 adhered PMN's per 100 venules, p < 0.05) compared to IR animals, and was accompanied by decreased cell apoptosis (p < 0.05). Hyperoxia inhibits enterocyte apoptosis following intestinal ischemia-reperfusion. Down-regulation of E-selectin expression with subsequent decrease in neutrophil recruitment may be responsible for this effect.

Recent evidence suggests that neutrophil recruitment may initiate germ cell apoptosis in the ischemic testis. The purpose of the present study was to examine the relationship between germ cell apoptosis and neutrophil recruitment in the contralateral testis following testicular ischemia-reperfusion (IR) injury in a rat. Adult male Sprague-Dawley rats were divided randomly into two experimental groups: Group A: Sham operated animals; Group B: IR rats underwent 90 min of unilateral testicular ischemia following by 96 h of reperfusion. The rats were sacrificed and testes were harvested. Johnsen's criteria and the number of germinal cell layers were measured to categorize the spermatogenesis. TUNEL assay was used to determine germ cell apoptosis in both the ischemic and contralateral testis. The recruitment of neutrophils was calculated per 100 venules. Expression of E-selectin was determined using immunohistochemical analysis. Statistical analysis was performed using Student's t test, with P less than 0.05 considered statistically significant. Germ cell apoptosis in both the ischemic and the contralateral testis increased significantly after IR. E-selectin expression was significantly greater in ischemic testis from IR rats compared to sham animals. The small increase in E-selectin expression and the concomitant increase in neutrophil recruitment in the contralateral testis of the IR rats (vs. sham animals) were not statistically significant. In conclusion, testicular ischemia causes an increase in germ cell apoptosis in the contralateral testis. Mechanisms other than neutrophil recruitment apparently initiate this process. [ABSTRACT FROM AUTHOR]