Hypoxia-inducible factor 1 is required for remote ischemic preconditioning of the heart

Both preclinical and clinical studies suggest that brief cycles of ischemia and reperfusion in the arm or leg may protect the heart against injury following prolonged coronary artery occlusion and reperfusion, a phenomenon known as remote ischemic preconditioning. Recent studies in mice indicate that increased plasma interleukin-10 (IL-10) levels play an important role in remote ischemic preconditioning induced by clamping the femoral artery for 5 min followed by 5 min of reperfusion for a total of three cycles. In this study, we demonstrate that remote ischemic preconditioning increases plasma IL-10 levels and decreases myocardial infarct size in wild-type mice but not in littermates that are heterozygous for a knockout allele at the locus encoding hypoxia-inducible factor (HIF) 1 alpha. Injection of a recombinant adenovirus encoding a constitutively active form of HIF-1 alpha into mouse hind limb muscle was sufficient to increase plasma IL-10 levels and decrease myocardial infarct size. Exposure of C2C12 mouse myocytes to cyclic hypoxia and reoxygenation rapidly increased levels of IL-10 mRNA, which was blocked by administration of the HIF-1 inhibitor acriflavine or by expression of short hairpin RNA targeting HIF-1 alpha or HIF-1 beta. Chromatin immuno-precipitation assays demonstrated that binding of HIF-1 to the II10 gene was induced when myocytes were subjected to cyclic hypoxia and reoxygenation. Taken together, these data indicate that HIF-1 activates II10 gene transcription and is required for remote ischemic preconditioning.