Emerging research suggests that oxidant-driven transcription of key cytokine/chemokine networks within the myocardium plays a crucial role in producing ischemia/reperfusion (I/R) injury. We recently showed that activation of hypoxia inducible factor-1 (HIF-1) attenuated cardiac I/R injury. Diminished injury in these prior studies was associated with significant reductions in circulating interleukin-8 (IL-8) levels, suggesting that HIF-1 may play an important role in modulating post-ischemic cardiac inflammation. In the current study, we examined the role of HIF-1 activation in modulating proinflammatory chemokine (MIP-2, KC, and LIX) and adhesion molecule expression (ICAM-1) in murine cardiomyocytes in vitro (HL-1 cell line) and in intact murine hearts following in vivo I/R injury. Our results show that HIF-1 activation induced both pharmacologically by the prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG) and via siRNA mediated prolyl-4 hydroxylase 2 (P4HA2) gene silencing significantly attenuated TNFa-induced chemokine (KC and LIX) and ICAM-1 expression in cardiomyocytes. In vivo, post-ischemic hearts obtained from animals receiving the P4HA2 siRNA (HIF-1 activation) exhibited significantly reduced CXC chemokine (MIP-2, KC, and LIX), CC chemokine (MCP-1), and ICAM-1 expression when compared to post-ischemic hearts from either saline I/R controls or post-ischemic hearts from animals receiving a non-targeting control siRNA (no HIF-1 activation). Diminished chemokine and adhesion molecule expression in HIF-1 activated post-ischemic hearts was associated with significantly reduced PMN infiltration and myocardial infarct size (>60% reduction P4HA2 siRNA I/R vs Saline I/R, P<0.001, n=6). In conclusion, these results demonstrate for the first time that HIF-1 activation following infusion of siRNA to P4HA2 plays a key role in modulating I/R-associated cardiac inflammatory responses.