ABSTRACT
OBJECTIVE: In surgical aortic repair or cardiac surgery with aorta occlusion, the occurrence of mesenteric ischemia and bowel injury has been associated with higher short-term mortality. The vascular protection of estrogens has been investigated and is mainly mediated by increasing the availability of nitric oxide (NO). Therefore, this study investigated the role of 17ß-estradiol on visceral ischemia-reperfusion (I/R) injury after descending aorta occlusion in male rats. METHODS: Mesenteric ischemia was induced in male Wistar rats by placing a 2F Fogarty arterial embolectomy catheter (Edwards Lifesciences, Irvine, Calif) in the descending aorta, which remained occluded for 15 minutes, followed by reperfusion for up to 2 hours. Rats were divided into four groups: (1) rats that underwent surgical manipulation only (sham, n = 22); (2) rats that underwent I/R injury (n = 22); (3) rats treated with intravenous 17ß-estradiol (280 µg/kg) 30 minutes before I/R (n = 22); (4) or at the beginning of reperfusion (n = 22). Intestinal histopathologic changes were evaluated by histomorphometry. Mesenteric microcirculatory alterations were assessed by laser Doppler flowmetry and intravital microscopy technique. Protein expression of intercellular adhesion molecule-1, P-selectin, endothelial NO synthase (eNOS), and endothelin-1 was evaluated by immunohistochemistry; in addition, eNOS and endothelin-1 gene expressions were quantified by real-time polymerase chain reaction. Serum cytokines were measured by enzyme-linked immunosorbent assay. RESULTS: Relative to the sham group, the I/R group exhibited a highly pronounced loss of intestine mucosal thickness, a reduction in mesenteric blood flow (P = .0203), increased migrated leukocytes (P < .05), and high mortality rate (35%). Treatment with 17ß-estradiol before aorta occlusion preserved intestine mucosal thickness (P = .0437) and mesenteric blood flow (P = .0251), reduced the number of migrated leukocytes (P < .05), and prevented any fatal occurrence. Furthermore, 17ß-estradiol downregulated the expression of intercellular adhesion molecule-1 (P = .0001) and P-selectin (P < .0001) on the endothelium and increased the protein expression of eNOS (P < .0001). The gene expressions of eNOS and endothelin-1 did not differ between the groups. CONCLUSIONS: The prophylactic treatment with 17ß-estradiol showed better overall repercussions and was able to prevent any fatal occurrence, increase eNOS expression, thus preserving mesenteric perfusion and intestinal integrity, and reduce inflammation.
