Cardioprotection afforded by inducible nitric oxide synthase gene therapy is mediated by cyclooxygenase-2 via a nuclear factor-kappaB dependent pathway.

Abstract

BACKGROUND:

Gene therapy with inducible nitric oxide synthase (iNOS) markedly reduces myocardial infarct size; this effect is associated with cyclooxygenase-2 (COX-2) upregulation and is ablated by COX-2 inhibitors. However, pharmacological inhibitors are limited by relative lack of specificity; furthermore, the mechanism whereby iNOS gene therapy upregulates COX-2 remains unknown. Accordingly, we used genetically engineered mice to test the hypothesis that the cardioprotection afforded by iNOS gene transfer is mediated by COX-2 upregulation via a nuclear factor (NF)-kappaB-dependent pathway.

METHODS AND RESULTS:

Mice received an intramyocardial injection of Av3/LacZ (LacZ group) or Av3/iNOS (iNOS group); 3 days later, myocardial infarction was produced by a 30-minute coronary occlusion followed by 4 hours of reperfusion. Among Av3/LacZ-treated mice, infarct size was similar in COX-2(-/-) and wild-type groups. iNOS gene transfer (confirmed by iNOS immunoblotting and activity assays) markedly reduced infarct size in wild-type mice but failed to do so in COX-2(-/-) mice. In transgenic mice with cardiac-specific expression of a dominant-negative mutant of IkappaB alpha (IkappaB alpha(S32A,S36A)), the upregulation of phosphorylated IkappaB alpha, activation of NF-kappaB, and cardiac COX-2 protein expression 3 days after iNOS gene therapy were abrogated, which was associated with the abolishment of the cardioprotective effects afforded by iNOS gene therapy.

CONCLUSIONS:

These data provide strong genetic evidence that COX-2 is an obligatory downstream effector of iNOS-dependent cardioprotection and that NF-kappaB is a critical link between iNOS and COX-2. Thus, iNOS imparts its protective effects, at least in part, by recruiting NF-kappaB, leading to COX-2 upregulation. However, COX-2 does not play an important cardioprotective role under basal conditions (when iNOS is not upregulated).

• Authors: Qianhong Li, Yiru Guo, Wei Tan, Qinghui Ou, Wen-Jian Wu, Diana Sturza, Buddhadeb Dawn, Greg Hunt, Chuanjue Cui, Roberto Bolli
• Journal: Circulation (Circulation) Vol. 116 Issue 14 Pg. 1577-84 (Oct 02 2007) ISSN: 1524-4539 [Electronic] United States
• PMID: 17785622 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• I-kappa B Proteins
• NF-kappa B
• Nfkbia protein, mouse
• RNA, Messenger
• NF-KappaB Inhibitor alpha
• Nitric Oxide Synthase Type II
• Nos2 protein, mouse
• Ptgs2 protein, mouse
• Cyclooxygenase 2

Topics

• Adenoviridae (genetics)
• Animals
• Cyclooxygenase 2 (genetics, metabolism)
• Disease Models, Animal
• Gene Expression Regulation, Enzymologic
• Genetic Therapy (methods)
• Heart Rate
• I-kappa B Proteins (metabolism)
• Lac Operon
• Mice
• Mice, Inbred Strains
• Mice, Transgenic
• Myocardial Infarction (metabolism, pathology, therapy)
• Myocardium (enzymology, pathology)
• NF-KappaB Inhibitor alpha
• NF-kappa B (metabolism)
• Nitric Oxide Synthase Type II (genetics, metabolism)
• Phosphorylation
• RNA, Messenger (metabolism)