title: Activation of hypoxia-inducible factor-1 via prolyl-4 hydoxylase-2 gene silencing attenuates acute inflammatory responses in postischemic myocardium.
abstract: 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 levels, suggesting that HIF-1 may play an important role in modulating postischemic cardiac inflammation. In the current study, we examined the role of HIF-1 activation in modulating proinflammatory chemokine [macrophage inflammatory protein (MIP)-2, cytokine-induced neutrophil chemoattractant factor (KC), and lipopolysaccharide-induced CXC chemokine (LIX)] and adhesion molecule [intercellular adhesion molecule (ICAM)-1] expression 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 dimethyloxallyl glycine and via small-interfering RNA (siRNA)-mediated prolyl-4 hydroxylase-2 (P4HA2) gene silencing significantly attenuated tumor necrosis factor-alpha-induced chemokine (KC and LIX) and ICAM-1 expression in cardiomyocytes. In vivo, postischemic hearts obtained from animals receiving the P4HA2 siRNA (HIF-1 activation) exhibited significantly reduced CXC chemokine (MIP-2, KC, and LIX), CC chemokine (monocyte chemoattractant protein-1), and ICAM-1 expression when compared with postischemic hearts from either saline I/R controls or postischemic hearts from animals receiving a nontargeting control siRNA (no HIF-1 activation). Diminished chemokine and adhesion molecule expression in HIF-1-activated postischemic hearts was associated with significantly reduced polymorphonuclear leukocyte 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.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Virginia Commonwealth University, PO Box 980050, Richmond, VA 23298-0050, USA.
authors.forename: Ramesh
authors.initials: R
authors.lastname: Natarajan
authors.forename: Fadi N
authors.initials: FN
authors.lastname: Salloum
authors.forename: Bernard J
authors.initials: BJ
authors.lastname: Fisher
authors.forename: Evan D
authors.initials: ED
authors.lastname: Ownby
authors.forename: Rakesh C
authors.initials: RC
authors.lastname: Kukreja
authors.forename: Alpha A
authors.initials: AA
authors.lastname: Fowler
mesh_terms: D000818:Animals; D002460:Cell Line; D054426:Chemokine CXCL2; D054365:Chemokine CXCL5; D018925:Chemokines / Q000378:metabolism; D019743:Chemokines, CXC / Q000378:metabolism; D020868:Gene Silencing; D051547:Heme Oxygenase-1 / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism; D051793:Hypoxia-Inducible Factor 1 / Q000378:metabolism*; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D051379:Mice; D009203:Myocardial Infarction / Q000473:pathology / Q000517:prevention & control; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000517:prevention & control*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D011393:Procollagen-Proline Dioxygenase / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology
chemical_list: D054426:Chemokine CXCL2; D054365:Chemokine CXCL5; D018925:Chemokines; D019743:Chemokines, CXC; C404915:Cxcl2 protein, mouse; C094739:Cxcl5 protein, mouse; D051793:Hypoxia-Inducible Factor 1; D016209:Interleukin-8; D034741:RNA, Small Interfering; D018799:Intercellular Adhesion Molecule-1; D011393:Procollagen-Proline Dioxygenase; D052247:Nitric Oxide Synthase Type II; D051547:Heme Oxygenase-1