Cobalt chloride induces delayed cardiac preconditioning in mice through selective activation of HIF-1alpha and AP-1 and iNOS signaling.
Acute systemic hypoxia induces delayed cardioprotection against ischemia (I)-reperfusion (R) injury via inducible nitric oxide synthase (iNOS)-dependent mechanism. Because CoCl2 is known to elicit hypoxia-like responses, we hypothesized that this chemical would mimic the delayed preconditioning effect in the heart. Adult male mice were pretreated with CoCl2 or saline. The hearts were isolated 24 h later and subjected to 20 min of global I and 30 min of R in Langendorff mode. Myocardial infarct size (% of risk area; mean +/- SE, n=6-8/group) was reduced in mice pretreated with 30 mg/kg CoCl2 (16.1 +/- 3.1% vs. 27.6 +/- 3.3% with saline control; P <0.05) without compromising postischemic cardiac function. Higher doses of CoCl2 failed to induce similar protection. Electrophoretic mobility gel shift assay demonstrated significant enhancement in DNA binding activity of hypoxia-inducible factor 1alpha (HIF-1alpha) and activator protein 1 (AP-1) in nuclear extracts from CoCl2-treated hearts. Activation of HIF-1alpha and AP-1 was evident at 30 min and sustained for the next 4 h after CoCl2 injection. In contrast, CoCl2-induced protection was independent of NF-kappaB activation because no DNA binding or p65 translocation was observed in nuclear extracts. Also, CoCl2-induced cardioprotection was preserved in p50 subunit NF-kappaB-knockout (KO) mice (11.1 +/- 3.0% vs. 25.1 +/- 5.0% in saline-treated p50-KO mice; P <0.05). The infarct-limiting effect of CoCl2 was absent in iNOS-KO mice (20.9 +/- 3.0%). We conclude that in vivo administration of CoCl2 preconditions the heart against I/R injury. The delayed protective effect of CoCl2 is achieved through a distinctive signaling mechanism involving HIF-1alpha, AP-1, and iNOS but independent of NF-kappaB activation.
Xi
Lei
L
Division of Cardiology, Box 980281, Virginia Commonwealth Univ., Richmond, VA 23298-0281, USA.
Taher
Mohiuddin
M
Yin
Chang
C
Salloum
Fadi
F
Kukreja
Rakesh C
RC
D000818:Animals; D021461:Animals, Outbred Strains; D016587:Antimutagenic Agents / Q000494:pharmacology*; D003035:Cobalt / Q000494:pharmacology*; D003326:Coronary Circulation; D004247:DNA / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019157:Ischemic Preconditioning, Myocardial / Q000379:methods*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D015428:Myocardial Reperfusion Injury / Q000188:drug therapy / Q000378:metabolism / Q000401:mortality; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*
D016587:Antimutagenic Agents; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D003035:Cobalt; D004247:DNA; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C018021:cobaltous chloride