Prevention of HIF-1 activation and iNOS gene targeting by low-dose cadmium results in loss of myocardial hypoxic preconditioning in the rat.
This study aimed to underline the interaction between hypoxia-inducible factor-1 (HIF-1) and the inducible nitric oxide synthase (iNOS) gene in vivo and their contribution to the delayed myocardial preconditioning induced by acute intermittent hypoxia (IH) in the rat using chromatin immunoprecipitation and pharmacological inhibition by low-dose cadmium. Langendorff-perfused hearts of Wistar rats exposed to normoxia or IH 24 h earlier were submitted to global ischemia and reperfusion. Effects of iNOS inhibition by aminoguanidine (100 microM) before ischemia or of low-dose injection of cadmium chloride (1 mg/kg) before normoxia or IH were tested. Myocardial HIF-1 and iNOS quantification and in vivo chromatin immunoprecipitation of HIF-1 bound to the iNOS gene promoter were performed. IH-induced delayed cardioprotection resulted in an improvement in coronary flow and functional recovery at reperfusion and a decrease in infarct size. Myocardial HIF-1 activity was increased with resulting targeting of the iNOS gene. Aminoguanidine abolished the cardioprotective effects of IH. Cadmium chloride treatment before IH prevented myocardial HIF-1 activation (72.3 +/- 4.0 vs. 42.1 +/- 9.7 arbitrary units after cadmium chloride; P < 0.05), targeting of the iNOS gene, iNOS expression, and preconditioning (infarct size: 15.9 +/- 5.6 vs. 30.1 +/- 5.4% after cadmium chloride; P < 0.05). This study is the first to demonstrate the interaction of HIF-1 with the myocardial iNOS gene in situ after hypoxic preconditioning. Prevention of HIF-1 activation and iNOS gene targeting by a single low dose of cadmium abolished the delayed cardioprotective effects, bringing insight into the cardiovascular consequences of cadmium exposure.
Belaidi
Elise
E
Laboratoire HP2, Hypoxie et Physiopathologies Cardiovasculaire et Respiratoire, Institut National de la Santé et de la Recherche Médicale ERI17, Grenoble, France.
Beguin
Pauline C
PC
Levy
Patrick
P
Ribuot
Christophe
C
Godin-Ribuot
Diane
D
D000818:Animals; D001711:Biotransformation / Q000502:physiology; D015153:Blotting, Western; D019256:Cadmium Chloride / Q000633:toxicity*; D002843:Chromatin / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D006146:Guanidines / Q000494:pharmacology; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors*; D047468:Immunoprecipitation; D019157:Ischemic Preconditioning, Myocardial; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000503:physiopathology; D052247:Nitric Oxide Synthase Type II / Q000235:genetics*; D051381:Rats; D017208:Rats, Wistar
D002843:Chromatin; D006146:Guanidines; C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D052247:Nitric Oxide Synthase Type II; D019256:Cadmium Chloride; C004479:pimagedine