The expression of cyclooxygenases and lipoxygenases in renal ischemia-reperfusion injury

Recent studies of ischemia-reperfusion (I/R) injury have focused on the function of neutrophils as well as the actions of inflammatory cytokines. However, few reports address cyclooxygenases (COXs) and lipoxygenases (LOXs). We researched the expression of COXs (COX-1 and COX-2) and LOXs (5-LOX and 12-LOX) in rat renal I/R injury. The right kidney of male Lewis rats was excised, and the left renal artery and vein clamped for a 90-minute ischemia time. Rats were humanely killed at 0, 1.5, 3, 5, and 12 hours after reperfusion. COX and LOX expressions were studied using immunohistostaining. COX-2 and LOX expressions were observed only on endothelial cells of normal kidney. From 1.5 to 5 hours after reperfusion, COX-2 and LOXs expressions gradually intensified on endothelial cells. COX-2 and LOXs expression were most intense on endothelial cells at 5 hours after reperfusion. Twelve hours after reperfusion, necrosis extended throughout the ischemic kidney and nearly all the tubular epithelial cells were destroyed. Thus, at 12 hours after reperfusion, COX-2 and LOXs expressions on endothelial cells became weaker. However, COX-1 expression was not different at every time after reperfusion. COX-2 and LOXs were expressed in a rat model showing renal I/R injury. Several hours after the maximum of COX-2 and LOXs expressions, the maximal renal I/R injury was observed. These results suggest a relationship between COX-2 and LOXs expressions and renal I/R injury.