Cobalt chloride induces delayed cardiac preconditioning in mice through selective activation of HIF-1alpha and AP-1 and iNOS signaling

Am J Physiol Heart Circ Physiol. 2004 Dec;287(6):H2369-75. doi: 10.1152/ajpheart.00422.2004. Epub 2004 Jul 29.


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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Animals, Outbred Strains
  • Antimutagenic Agents / pharmacology*
  • Cobalt / pharmacology*
  • Coronary Circulation
  • DNA / metabolism
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Ischemic Preconditioning, Myocardial / methods*
  • Male
  • Mice
  • Mice, Inbred ICR
  • Myocardial Reperfusion Injury / drug therapy
  • Myocardial Reperfusion Injury / metabolism
  • Myocardial Reperfusion Injury / mortality
  • Nitric Oxide Synthase / metabolism*
  • Nitric Oxide Synthase Type II
  • Transcription Factor AP-1 / metabolism*
  • Transcription Factors / metabolism*


  • Antimutagenic Agents
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Transcription Factor AP-1
  • Transcription Factors
  • Cobalt
  • DNA
  • Nitric Oxide Synthase
  • Nitric Oxide Synthase Type II
  • Nos2 protein, mouse
  • cobaltous chloride