Hypoxia-inducible factor-1α regulates the expression of L-type voltage-dependent Ca2+ channels in PC12 cells under hypoxia

Hypoxia is an important factor in regulation of cell behavior both under physiological and pathological conditions. The mechanisms of hypoxia-induced cell death have not been completely elucidated yet. It is well known that Ca2+ is critically related to cell survival. Hypoxia-inducible factor-1 alpha (HIF-1 alpha) is a core regulatory factor during hypoxia, and L-type voltage-dependent Ca2+ channels (L-VDCCs) have been reported to play a critical role in cell survival. This study was conducted to explore the relationship between L-VDCC expression and HIF-1 alpha regulation in PC12 cells under hypoxia. PC12 cells were treated at 20 or 3 % O-2 to observe its proliferation and the intracellular calcium concentration. Then, we detected the protein expression of HIF-1 alpha and L-VDCCs subtypes, Ca(v)1.2 and Ca(v)1.3. At last, to verify the relationship between HIF-1 alpha and Ca(v)1.2 and Ca(v)1.3, we got the expression of Ca(v)1.2 and Ca(v)1.3 with Western blot and luciferase report gene assays after PC12 cells were treated by echinomycin, which is an HIF-1 alpha inhibitor. Compared with 20 % O-2 (normoxia), 3 % O-2 (hypoxia) inhibited cell proliferation, increased the intracellular calcium concentration, and induced protein expression of HIF-1 alpha. The protein expression of two L-VDCCs subtypes expressed in the nervous system, Ca(v)1.2 and Ca(v)1.3, was upregulated by hypoxia and reduced dose dependently by treatment with echinomycin, a HIF-1 alpha inhibitor. Luciferase report gene assays showed that the expression of Ca(v)1.2 and Ca(v)1.3 genes was augmented under 3 % O-2. However, echinomycin only slightly and dose dependently decreased expression of the Ca(v)1.2 gene, but not that of the Ca(v)1.3 gene. These data indicated that Ca(v)1.2 might be regulated by HIF-1 alpha as one of its downstream target genes and involved in regulation of PC12 cells death under hypoxia.