Hypoxia-inducible factor-1alpha is a critical mediator of hypoxia induced apoptosis in cardiac H9c2 and kidney epithelial HK-2 cells

Abstract

Abstract Background Hypoxia inducible factor-1 (HIF-1) is a transcription factor that functions to maintain cellular homeostasis in response to hypoxia. There is evidence that HIF-1 can also trigger apoptosis, possibly when cellular responses are inadequate to meet energy demands under hypoxic conditions. Methods Cardiac derived H9c2 and renal tubular epithelial HK-2 cells expressing either the wild type oxygen regulated subunit of HIF-1 (pcDNA3-Hif-1α) or a dominant negative version that lacked both DNA binding and transactivation domains (pcDNA3-DN-Hif-1α), were maintained in culture and exposed to hypoxia. An RNA interference approach was also employed to selectively knockdown expression of Hif-1α. Apoptosis was analyzed in both H9c2 and HK-2 cells by Hoechst and TUNEL staining, caspase 3 activity assays and activation of pro-apoptotic Bcl2 family member Bax. Results Overexpression of pcDNA3-DN-Hif-1α led to a significant reduction in hypoxia -induced apoptosis (17 ± 2%, P Conclusion These data demonstrate that HIF-1α is an important component of the apoptotic signaling machinery in the two cell types.