Mitogen-activated Protein Kinases and Mitogen-activated Protein Kinase Phosphatases Mediate the Inhibitory Effects of All-trans Retinoic Acid on the Hypertrophic Growth of Cardiomyocytes

Ants Palm-Leis,Ugra S. Singh,Jing Pan,Greg D. Olsovsky,Bradley S. Herbelin,Kenneth M. Baker

doi:10.1074/jbc.m407383200

Ants Palm-Leis, Ugra S. Singh + Show 4 more

Open Access

https://doi.org/10.1074/jbc.m407383200

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Abstract

All-trans retinoic acid (RA) has been implicated in mediation of cardiac growth inhibition in neonatal cardiomyocytes. However, the associated signaling mechanisms remain unclear. Utilizing neonatal cardiomyocytes, we demonstrated that RA suppressed the hypertrophic features induced by cyclic stretch or angiotensin II (Ang II). Cyclic stretch- or Ang II-induced activation of extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAP kinase) was dose- and time-dependently inhibited by RA. Significant inhibition was observed by 5 microm RA, from 8 to 24 h of pretreatment. This inhibitory effect was not mediated at the level of mitogen-activated protein kinase kinases (MKKs), because RA had no effect on stretch- or Ang II-induced phosphorylation of MEK1/2, MKK4, and MKK3/6. However, the phosphatase inhibitor vanadate reversed the inhibitory effect of RA on MAP kinases and protein synthesis. RA up-regulated the expression level of MAP kinase phosphatase-1 (MKP-1) and MKP-2, and the time course was correlated with the inhibitory effect of RA on activation of MAP kinases. Overexpression of wild-type MKP-1 inhibited the phosphorylation of JNK and p38 in cardiomyocytes. These data indicated that MKPs were involved in the inhibitory effect of RA on MAP kinases. Using specific RAR and RXR antagonists, we demonstrated that both RARs and RXRs were involved in regulating stretch- or Ang II-induced activation of MAP kinases. Our findings provide the first evidence that the anti-hypertrophic effect of RA is mediated by up-regulation of MKPs and inhibition of MAP kinase signaling pathways.

Highlights

Retinoid is a generic term for synthetic and natural vitamin A-related compounds, of which all-trans retinoic acid (RA)1 is a biologically active prototype
We provide the first evidence that RA inhibits the activation of MAP kinases induced by cyclic stretch or angiotensin II (Ang II), by regulating the expression of MAP kinase phosphatase-1 (MKP-1) and MKP-2 in cardiomyocytes
We demonstrated that cyclic stretch- or Ang II-induced cardiac hypertrophic features, including increased total protein content, protein synthesis, cell size, and myofibrillar reorganization were significantly inhibited by RA pretreatment, suggesting that retinoid-mediated signaling pathways have an important role in regulating cyclic stretchor Ang II-induced cardiomyocyte growth

Summary

RA Inhibits Cardiac Hypertrophy through MAP Kinase Pathways

Factors, cytokines, and mechanical stretch) induced cardiac hypertrophy, in vitro and in vivo [25,26,27,28,29,30]. Up-regulation of MKP-1 and inhibition of JNK phosphorylation is involved in the antiapoptotic effect of RA on H2O2-exposed mesangial cells [38] These observations clearly suggest a potential link between retinoids and MAP kinase signaling, the mechanisms involved, in hypertrophic cardiomyocytes, have not been elucidated. Our results show that RA had inhibitory effects on the activation of MAP kinases induced by cyclic stretch or Ang II, and that the up-regulation of MKPs by RA was involved. These results identify a mechanism whereby RA regulates expression of MKPs and inhibition of MAP kinases, which play an important role in the anti-hypertrophic effects of RA

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION

Baker and Jing Pan