Targeted inhibition of p38 MAPK promotes hypertrophic cardiomyopathy through upregulation of calcineurin-NFAT signaling
Julian C. Braz, … , Timothy E. Hewett, Jeffery D. Molkentin
Julian C. Braz, … , Timothy E. Hewett, Jeffery D. Molkentin
Published May 15, 2003
Citation Information: J Clin Invest. 2003;111(10):1475-1486. https://doi.org/10.1172/JCI17295.
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Article Cardiology

Targeted inhibition of p38 MAPK promotes hypertrophic cardiomyopathy through upregulation of calcineurin-NFAT signaling

Abstract

The MAPKs are important transducers of growth and stress stimuli in virtually all eukaryotic cell types. In the mammalian heart, MAPK signaling pathways have been hypothesized to regulate myocyte growth in response to developmental signals or physiologic and pathologic stimuli. Here we generated cardiac-specific transgenic mice expressing dominant-negative mutants of p38α, MKK3, or MKK6. Remarkably, attenuation of cardiac p38 activity produced a progressive growth response and myopathy in the heart that correlated with the degree of enzymatic inhibition. Moreover, dominant-negative p38α, MKK3, and MKK6 transgenic mice each showed enhanced cardiac hypertrophy following aortic banding, Ang II infusion, isoproterenol infusion, or phenylephrine infusion for 14 days. A mechanism underlying this enhanced-growth profile was suggested by the observation that dominant-negative p38α directly augmented nuclear factor of activated T cells (NFAT) transcriptional activity and its nuclear translocation. In vivo, NFAT-dependent luciferase reporter transgenic mice showed enhanced activation in the presence of the dominant-negative p38α transgene before and after the onset of cardiac hypertrophy. More significantly, genetic disruption of the calcineurin Aβ gene rescued hypertrophic cardiomyopathy and depressed functional capacity observed in p38-inhibited mice. Collectively, these observations indicate that reduced p38 signaling in the heart promotes myocyte growth through a mechanism involving enhanced calcineurin-NFAT signaling.

Authors

Julian C. Braz, Orlando F. Bueno, Qiangrong Liang, Benjamin J. Wilkins, Yan-Shan Dai, Stephanie Parsons, Joseph Braunwart, Betty J. Glascock, Raisa Klevitsky, Thomas F. Kimball, Timothy E. Hewett, Jeffery D. Molkentin

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Generation of cardiac-specific transgenic mice expressing dominant-negat...
Generation of cardiac-specific transgenic mice expressing dominant-negative mutants of p38α, MKK3, and MKK6. (a) Western blot analysis with Ab’s against p38α, p38β, MKK3, and MKK6 from nontransgenic (NTG) and transgenic (TG) hearts regulated by the α-MHC promoter (b) Western blot analysis of p38 phosphorylation in the hearts of nontransgenic (wild-type littermates) or dnMKK3 and dnMKK6 transgenic mice injected for 30 min with either PBS or PE (10 mg/kg). To verify specificity, phospho–ERK-1/2 (phos-ERK-1/2) and phospho-JNK (phos-JNK) were also assayed. The asterisks show the reduced phosphorylation of p38 at baseline (PBS) and in response to PE stimulation. (c) p38 immune kinase assay from PBS- and PE-injected nontransgenic mice or dnp38α, dnMKK3, and dnMKK6 mice. Thirty minutes after stimulation, the hearts were removed and phosphorylation of MBP was monitored by immune kinase assay with p38-specific Ab. Three independent p38 immune kinase assays showed increased activity in NTG hearts and dnMKK6 hearts. Veh, vehicle. (d) Western blot analysis of MAPKAPK2 phosphorylation (phos-MKAPK2), a direct p38 target, in the hearts of nontransgenic (wild-type littermates) or each of the dominant-negative transgenic mice after PE stimulation (10 mg/kg). All three dominant-negative strategies significantly reduced p38 kinase activity in c and d (#P < 0.05 versus NTG vehicle injected; †P < 0.05 versus NTG PE-injected).