Cardiac-specific blockade of NF-kappaB in cardiac pathophysiology: differences between acute and chronic stimuli in vivo.
The role of NF-kappaB in cardiac physiology and pathophysiology has been difficult to delineate due to the inability to specifically block NF-kappaB signaling in the heart. Cardiac-specific transgenic models have recently been developed that repress NF-kappaB activation by preventing phosphorylation at specific serine residues of the inhibitory kappaB (IkappaB) protein isoform IkappaBalpha. However, these models are unable to completely block NF-kappaB because of a second signaling pathway that regulates NF-kappaB function via Tyr42 phosphorylation of IkappaBalpha. We report the development of transgenic (3M) mouse lines that express the mutant IkappaBalpha(S32A,S36A,Y42F) in a cardiac-specific manner. NF-kappaB activation in cardiomyopathic TNF-1.6 mice is completely blocked by the 3M transgene but only partially blocked (70-80%) by the previously described double-mutant 2M [IkappaBalpha(S32A,S36A)] transgene, which demonstrates the action of two proximal pathways for NF-kappaB activation in TNF-alpha-induced cardiomyopathy. In contrast, after acute stimuli including administration of TNF-alpha and ischemia-reperfusion (I/R), NF-kappaB activation is blocked in both 2M and 3M transgenic mice. This result suggests that phosphorylation of the regulatory Ser32 and Ser36 predominantly mediates NF-kappaB activation in these situations. We show that infarct size after I/R is reduced by 70% in 3M transgenic mice, which conclusively demonstrates that NF-kappaB is involved in I/R injury. In summary, we have engineered novel transgenic mice that allow us to distinguish two major proximal pathways for NF-kappaB activation. Our results demonstrate that the serine and tyrosine phosphorylation pathways are differentially activated during different pathophysiological processes (cardiomyopathy and I/R injury) and that NF-kappaB contributes to infarct development after I/R.
Brown
Maria
M
Dept. of Pharmacology and Cell Biophysics, 231 Albert Sabin Way, ML0575, Univ. of Cincinnati, Cincinnati, OH 45267-0575, USA.
McGuinness
Michael
M
Wright
Terry
T
Ren
Xiaoping
X
Wang
Yang
Y
Boivin
Gregory P
GP
Hahn
Harvey
H
Feldman
Arthur M
AM
Jones
W Keith
WK
D000818:Animals; D015139:Blotting, Southern; D015153:Blotting, Western; D009202:Cardiomyopathies / Q000378:metabolism* / Q000503:physiopathology; D016207:Cytokines / Q000494:pharmacology; D004452:Echocardiography; D006321:Heart / Q000503:physiopathology; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D009203:Myocardial Infarction / Q000209:etiology / Q000473:pathology; D015428:Myocardial Reperfusion Injury / Q000150:complications / Q000378:metabolism* / Q000503:physiopathology; D009206:Myocardium / Q000378:metabolism*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism
D016207:Cytokines; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606205:Nfkbia protein, mouse; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha