Recombinant Human Erythropoietin Pretreatment Attenuates Acute Renal Tubular Injury Against Ischemia-Reperfusion by Restoring Transient Receptor Potential Channel-6 Expression and Function in Collecting Ducts

Objective: Acute renal tubular injury is a serious complication in the postoperative period, which is associated with high mortality and increased ICU stay. We aimed to demonstrate the protective effect of rhEPO against acute tubular injury induced by ischemia-reperfusion and to explore the mechanism of canonical transient receptor potential channel-6. Design: Randomized laboratory animal study. Settings: Animal research laboratory. Interventions: Male Sprague-Dawley rats were randomly divided into three groups: the sham group, the control group, and the rhEPO group. Experimental acute tubular injury was established in rats by bilateral renal arterial occlusion for 30 minutes followed by reperfusion. Measurements and Main Results: Blood samples were obtained for cystatin-C and neutrophil gelatinase-associated lipocalin measurements by enzyme-linked immunosorbance assays. Seventy-two hours after reperfusion, urine samples were collected for osmolality and fractional excretion of sodium (%) assays on a chemistry analyzer. Kidneys were harvested at 24, 48, and 72 hours after reperfusion. Transient receptor potential channel-6, aquaporin-2, and Na, K-ATPase expression in collecting ducts were studied by immunofluorescence and Western blot. Coimmunoprecipitations were also performed to identify the possible signalplex relation between transient receptor potential channel-6 and aquaporin-2 or Na, K-ATPase channels. RhEPO pretreatment significantly inhibited serum cystatin-C (2 hr: 453 +/- 64 mu g/L vs 337 +/- 28 mu g/L, p < 0.01), serum neutrophil gelatinase-associated lipocalin (72 hr: 1,175 +/- 107 ng/L vs 1,737 +/- 402 ng/L, p < 0.05), and urinary fractional excretion of sodium (%) increase (0.9 +/- 0.1 vs 2.2 +/- 0.8, p < 0.05) and alleviated the decrease of urinary osmolality (1,293 +/- 101 mosmol/kg H2O vs 767 +/- 91 mosmol/kg H2O, p < 0.05) induced by ischemia-reperfusion injury. Meanwhile, recombinant human erythropoietin greatly improved the ischemia-reperfusion-induced attenuation of transient receptor potential channel-6 expression (48 hr: 42% +/- 2% vs 67% +/- 2% and 72 hr: 55% +/- 2% vs 66% +/- 2%), as well as aquaporin-2 and Na, K-ATPase expression in collecting ducts. Transient receptor potential channel-6 functionally interacted with Na, K-ATPase but not aquaporin-2. Conclusions: Recombinant human erythropoietin pretreatment at the dose of 5,000 IU/kg potently prevented ischemia-reperfusion-induced acute tubular injury, which might be partly attributed to the restoring the effect of transient receptor potential channel-6 expression and collecting duct function.