Role of ATP-dependent K channels in the effects of erythropoietin in renal ischaemia injury.

BACKGROUND & OBJECTIVES: Erythropoietin (EPO) has cytoprotective and anti-apoptotic effects in pathological conditions, including hypoxia and ischaemia-reperfusion injury. One of the targets to protect against injury is ATP-dependent potassium (KATP ) channels. These channels could be involved in EPO induced ischaemic preconditoning like a protective effect. We evaluated the cell cytoprotective effects of EPO in relation to KATP channel activation in the renal tubular cell culture model under hypoxic/normoxic conditions.

METHODS

Dose and time dependent effects of EPO, KATP channel blocker glibenclamide and KATP channel opener diazoxide on cellular proliferation were evaluated by colorimetric assay MTT [3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide] under normoxic and hypoxic conditions in human renal proximal tubular cell line (CRL-2830). Evaluation of the dose and time dependent effects of EPO, glibenclamide and diazoxide on apoptosis was done by caspase-3 activity levels. Hypoxia inducible factor-1 alpha (HIF-1 α) mRNA levels were measured by semi-quantative reverse transcription polymerase chain reaction (RT)-PCR. Kir 6.1 protein expresion was evalutaed by Western blot.

RESULTS

Glibenclamide treatment decreased the number of living cells in a time and dose dependent manner, whereas EPO and diazoxide treatments increased. Glibenclamide (100 μM) treatment significantly blocked the anti-apoptotic effects of EPO (10 IU/ml) under both normoxic and hypoxic conditions. EPO (10 IU/ml) and diazoxide (100 μM) treatments significantly increased (p <0.01) whereas glibenclamide decreased ( p<0.05) HIF-1 α mRNA expression. Glibenclamide significantly ( p<0.01) decreased EPO induced HIF-1 α mRNA expression when compared with the EPO alone group.

INTERPRETATION & CONCLUSIONS: Our results showed that the cell proliferative, cytoprotective and anti-apoptotic effects of EPO were associated with KATP channels in the renal tubular cell culture model under hypoxic/normal conditions.