HIF-1 activation attenuates postischemic myocardial injury: role for heme oxygenase-1 in modulating microvascular chemokine generation

Abstract

The CXC chemokine IL-8, which promotes adhesion, activation, and transmigration of polymorphonuclear neutrophils (PMN), has been associated with production of tissue injury in reperfused myocardium. Hypoxia-inducible factor-1 (HIF-1) is a heterodimeric peptide that is a key regulator of genes such as heme oxygenase (HO)-1 expressed under hypoxic conditions. We hypothesized that HO-1 plays an important role in regulating proinflammatory mediator production under conditions of ischemia-reperfusion. HIF-1 was activated in the human microvascular endothelial cell line (HMEC-1) with the prolyl hydroxylase inhibitor dimethyloxalylglycine (DMOG). DMOG significantly attenuated cytokine-induced IL-8 promoter activity and protein secretion and cytokine-induced PMN migration across human microvascular endothelial cell line HMEC-1 monolayers. In vivo studies in a rabbit model of myocardial ischemia-reperfusion showed that rabbits pretreated with a 20 mg/kg DMOG infusion ( n = 6) 24 h before study exhibited a 21.58 ± 1.76% infarct size compared with 35.25 ± 2.06% in saline-treated ischemia-reperfusion animals ( n = 6, change in reduction = 39%; P < 0.001). In DMOG-pretreated (20 mg/kg) animals, plasma IL-8 levels at 3 h after onset of reperfusion were 405 ± 40 pg/ml vs. 790 ± 40 pg/ml in saline-treated ischemia-reperfusion animals ( P < 0.001). DMOG pretreatment reduced myocardial myeloperoxidase activity, expressed as number of PMN per gram of myocardium, to 1.43 ± 0.59 vs. 4.86 ± 1.1 ( P = 0.012) in saline-treated ischemia-reperfused hearts. Both in vitro and in vivo DMOG-attenuated IL-8 production was associated with robust HO-1 expression. Thus our data show that HIF-1 activation induces substantial HO-1 expression that is associated with attenuated proinflammatory chemokine production by microvascular endothelium in vitro and in vivo.