The protective effects of exogenous spermine on renal ischemia-reperfusion injury in rats

Background: To investigate the protective effects of exogenous spermine on renal ischemia-reperfusion injury in rats. Methods: (I) Different doses of spermine were injected into rats to determine the safe dose on the kidneys. Kidney toxicity was assessed by hematoxylin and eosin (HE) staining of kidney tissue and enzyme-linked immunosorbent assay (ELISA) detection of neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule 1 (KIM-1) in the venous blood. (II) A rat model of renal ischemia-reperfusion injury was established. Different doses of spermine were injected into the rats through the tail vein 30 minutes before and 3 days after the establishment of the model. Blood samples and kidney tissues were collected and renal injury was assessed via HE staining of the renal tissue, detection of apoptosis using the TUNEL assay, and detection of NGAL and KIM-1 in blood samples using ELISA. (III) Human HK-2 renal tubular epithelial cells were cultured under hypoxia/reoxygenation conditions. To evaluate the protective effects of spermine, apoptosis was assessed by flow cytometry and TUNEL, assay. The mechanisms underlying the effects of spermine were studied using Western blot analyses. Results: At spermine concentrations below 200 mu M (2 mL/kg body weight), no significant damage to the kidney was observed by I IE staining, and there was no significant difference in NGAL and KIM-1 levels between rats treated with spermine and control rats (P<0.05). At spermine doses below 200 mu M, HE staining showed that the degree of renal ischemia-reperfusion injury was gradually alleviated with increasing doses of spermine. TUNEL assays demonstrated that spermine reduced the apoptosis of renal tissue, and increasing doses of spermine gradually decreased the levels of NGAL and KIM-1 in the blood compared with the control group (P<0.05). Western blot analysis revealed that spermine increased the expression of pro-caspase9, phosphorylated protein kinase B (p-Akt), hypoxia-inducible factor 1 alpha (HIF-1 alpha) cell lymphoma 2 (Bcl-2), and Bcl2 interacting protein 3 (BNIP3), and decreased the expression of cleaved caspase-3, Bax and cytochrome C compared to control cells. Conclusions: Exogenous spermine exerted a protective effect on renal ischemia-reperfusion injury in rats by inhibiting the apoptosis of renal tubular epithelial cells.