Neutrophil Gelatinase-Associated Lipocalin (NGAL) May Play a Protective Role Against Rats Ischemia/Reperfusion Renal Injury via Inhibiting Tubular Epithelial Cell Apoptosis

We investigated the protective effect and mechanism of neutrophil gelatinase-associated lipocalin (NGAL) on rats ischemia/reperfusion (I/R) renal injury. Eighteen Sprague-Dawley male rats were randomly divided into three groups. Control group (n = 6) suffered left unilateral nephrectomy, I/R + NS (normal saline) (n = 6) and I/R + NGAL (n = 6) group were subjected to 45 min right renal ischemia/24 h reperfusion after left unilateral nephrectomy. Serum creatinine (Scr) and blood urea nitrogen (Bun) were measured on automatic biochemistry analyzer; kidney sections were stained with hematoxylin-eosin; terminal dUTP nick-labeling method was used to examine the apoptosis of tubular epithelial cells; Cleaved caspase-3 and Bax protein expression were detected by immunohistochemistry and Western Blot; real-time polymerase chain reaction was used to detect the expression of Bax mRNA. Rats with NGAL displayed an attenuated renal damage and a decreased number of tubular epithelial cell apoptosis compared to the I/R + NS group (Scr 63.400 +/- 11.908 vs. 121.857 +/- 17.151 mu mol/L, Bun 14.840 +/- 2.868 vs. 28.557 +/- 6.434 mmol/L, apoptosis cell number 7.800 +/- 1.924 vs. 15.400 +/- 3.049/high power field (HPF), p < 0.05), the values were lower in the control group (24.000 +/- 3.829 mu mol/L, 5.814 +/- 1.961 mmol/L, 1.800 +/- 0.837/HPF, p < 0.05) compared to two groups above; NGAL-treated rats showed down-regulated Cleaved caspase-3 protein (0.284 +/- 0.066 vs. 0.409 +/- 0.073, p < 0.05), Bax protein (0.346 +/- 0.055 vs. 0.443 +/- 0.041, p < 0.05), Bax mRNA (1.423 +/- 0.187 vs. 2.550 +/- 0.217, p < 0.05) compared to I/R + NS group, but the values were higher in both of the two groups than those in the control group (Cleaved caspase-3 protein 0.104 +/- 0.029, Bax protein 0.155 +/- 0.027, Bax mRNA 1.000 +/- 0.000, p < 0.05). We supposed that exogenous NGAL can inhibit the activation of caspase-3, reduce the expression of Bax, and thus reduce renal tubular cell apoptosis and protect renal function in I/R injury rats.