Abstract
Obesity is associated with increased leptin production which may contribute to cardiac hypertrophy. However, the mechanism of leptin-induced cardiac hypertrophy remains incompletely understood. The Rho family (RhoA, Rac1, and Cdc42) and mammalian target of rapamycin (mTOR) have recently emerged as important regulators of cell growth. We therefore explored the roles and interrelationships of phosphatidylinositol 3-kinase (PI3K), mTOR, and the Rho family in the regulation of actin polymerization and leptin-induced hypertrophy in cultured neonatal rat ventricular myocytes. Five minutes treatment with leptin (3.1 nM) resulted in activation of RhoA and Rac1 (by 330 and 160%, respectively, P < 0.05) which was significantly attenuated by AG-490 (50 μM) and LY294002 (10 μM), specific inhibitors of JAK2 and PI3K, respectively. However, Cdc42 activity was unaffected by leptin. The hypertrophic effect of leptin was associated with an increase in phosphorylation of p70S6K, the major target of mTOR, by 110% (P < 0.05). The specific mTOR inhibitor rapamycin (10 nM) attenuated leptin-induced RhoA and Rac1 activation. Furthermore, the leptin-induced decrease in the G/F-actin ratio, a measure of actin polymerization, was blunted by rapamycin. Leptin produced activation of the transcriptional factor GATA4 which was attenuated by the RhoA inhibitor C3, the p38 MAPK inhibitor SB203580 (10 μM) as well as rapamycin. Our results demonstrate a critical role for PI3K/mTOR/p70S6K in leptin-induced RhoA activation resulting in cardiomyocyte hypertrophy associated with GATA4 stimulation.
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References
Karmazyn M, Purdham DM, Rajapurohitam V, Zeidan A (2007) Leptin as a cardiac hypertrophic factor: a potential target for therapeutics. Trends Cardiovasc Med 17:206–211
Purdham DM, Zou MX, Rajapurohitam V, Karmazyn M (2004) Rat heart is a site of leptin production and action. Am J Physiol Heart Circ Physiol 287:H2877–H2884
Zeidan A, Purdham DM, Rajapurohitam V, Javadov S, Chakrabarti S, Karmazyn M (2005) Leptin induces vascular smooth muscle cell hypertrophy through angiotensin II- and endothelin-1-dependent mechanisms and mediates stretch-induced hypertrophy. J Pharmacol Exp Ther 315:1075–1084
Lollmann B, Gruninger S, Stricker-Krongrad A, Chiesi M (1997) Detection and quantification of the leptin receptor splice variants Ob-Ra, b, and, e in different mouse tissues. Biochem Biophys Res Commun 238:648–652
Rajapurohitam V, Gan XT, Kirshenbaum LA, Karmazyn M (2003) The obesity-associated peptide leptin induces hypertrophy in neonatal rat ventricular myocytes. Circ Res 93:277–279
Rajapurohitam V, Javadov S, Purdham DM, Kirshenbaum LA, Karmazyn M (2006) An autocrine role for leptin in mediating the cardiomyocyte hypertrophic effects of angiotensin II and endothelin-1. J Mol Cell Cardiol 41:265–274
Wold LE, Relling DP, Duan J, Norby FL, Ren J (2002) Abrogated leptin-induced cardiac contractile response in ventricular myocytes under spontaneous hypertension: role of Jak/STAT pathway. Hypertension 39:69–74
Zeidan A, Javadov S, Karmazyn M (2006) Essential role of Rho/ROCK-dependent processes and actin dynamics in mediating leptin-induced hypertrophy in rat neonatal ventricular myocytes. Cardiovasc Res 72:101–111
Shin HJ, Oh J, Kang SM, Lee JH, Shin MJ, Hwang KC, Jang Y, Chung JH (2005) Leptin induces hypertrophy via p38 mitogen-activated protein kinase in rat vascular smooth muscle cells. Biochem Biophys Res Commun 329:18–24
Abe Y, Ono K, Kawamura T, Wada H, Kita T, Shimatsu A, Hasegawa K (2007) Leptin induces elongation of cardiac myocytes and causes eccentric left ventricular dilatation with compensation. Am J Physiol Heart Circ Physiol 292:H2387–H2396
Madani S, De Girolamo S, Muñoz DM, Li RK, Sweeney G (2006) Direct effects of leptin on size and extracellular matrix components of human pediatric ventricular myocytes. Cardiovasc Res 69:716–725
Tajmir P, Ceddia RB, Li RK, Coe IR, Sweeney G (2004) Leptin increases cardiomyocyte hyperplasia via extracellular signal-regulated kinase- and phosphatidylinositol 3-kinase-dependent signaling pathways. Endocrinology 145:1550–1555
Xu FP, Chen MS, Wang YZ, Yi Q, Lin SB, Chen AF, Luo JD (2004) Leptin induces hypertrophy via endothelin-1-reactive oxygen species pathway in cultured neonatal rat cardiomyocytes. Circulation 110:1269–1275
Zeidan A, Javadov S, Chakrabarti S, Karmazyn M (2008) Leptin-induced cardiomyocyte hypertrophy involves selective caveolae and RhoA/ROCK-dependent p38 MAPK translocation to nuclei. Cardiovasc Res 77:64–72
Oudit GY, Sun H, Kerfant BG, Crackower MA, Penninger JM, Backx PH (2004) The role of phosphoinositide-3 kinase and PTEN in cardiovascular physiology and disease. J Mol Cell Cardiol 37:449–471
Naga Prasad SV, Esposito G, Mao L, Koch WJ, Rockman HA (2000) Gβγ-dependent phosphoinositide 3-kinase activation in hearts with in vivo pressure overload hypertrophy. J Biol Chem 275:4693–4698
Shioi T, Kang PM, Douglas PS, Hampe J, Yballe CM, Lawitts J, Cantley LC, Izumo S (2000) The conserved phosphoinositide 3-kinase pathway determines heart size in mice. EMBO J 19:2537–2548
Wullschleger S, Loewith R, Hall MN (2006) TOR signaling in growth and metabolism. Cell 124:471–484
McMullen JR, Sherwood MC, Tarnavski O, Zhang L, Dorfman AL, Shioi T, Izumo S (2004) Inhibition of mTOR signaling with rapamycin regresses established cardiac hypertrophy induced by pressure overload. Circulation 109:3050–3055
Villanueva EC, Myers MG Jr (2008) Leptin receptor signaling and the regulation of mammalian physiology. Int J Obes (Lond) 32(Suppl 7):S8–S12
Brown JH, Del Re DP, Sussman MA (2006) The Rac and Rho hall of fame: a decade of hypertrophic signaling hits. Circ Res 98:730–742
Clerk A, Sugden PH (2000) Small guanine nucleotide-binding proteins and myocardial hypertrophy. Circ Res 86:1019–1023
Loirand G, Guerin P, Pacaud P (2006) Rho kinases in cardiovascular physiology and pathophysiology. Circ Res 98:322–334
Rafail S, Ritis K, Schaefer K, Kourtzelis I, Speletas M, Doumas M, Giaglis S, Kambas K, Konstantinides S, Kartalis G (2008) Leptin induces the expression of functional tissue factor in human neutrophils and peripheral blood mononuclear cells through JAK2-dependent mechanisms and TNFalpha involvement. Thromb Res 122:366–375
Tong KM, Shieh DC, Chen CP, Tzeng CY, Wang SP, Huang KC, Chiu YC, Fong YC, Tang CH (2008) Leptin induces IL-8 expression via leptin receptor, IRS-1, PI3K, Akt cascade and promotion of NF-κB/p300 binding in human synovial fibroblasts. Cell Signal 20:1478–1488
Beltowski J (2006) Role of leptin in blood pressure regulation and arterial hypertension. J Hypertens 24:789–801
Nobes CD, Hall A (1995) Rho, Rac, and Cdc42 GTPases regulate the assembly of multimolecular focal complexes associated with actin stress fibers, lamellipodia, and filopodia. Cell 81:53–62
Pracyk JB, Tanaka K, Hegland DD, Kim KS, Sethi R, Rovira II, Blazina DR, Lee L, Bruder JT, Kovesdi I, Goldshmidt-Clermont PJ, Irani K, Finkel T (1999) A requirement for the rac1 GTPase in the signal transduction pathway leading to cardiac myocyte hypertrophy. J Clin Invest 102:929–937
Hines WA, Thorburn A (1998) Ras and Rho are required for G#q-induced hypertrophic gene expression in neonatal rat cardiac myocytes. J Mol Cell Cardiol 30:485–494
Sah VP, Minamisawa S, Tam SP, Wu TH, Dorn GW II, Ross J Jr, Chien KR, Brown JH (1999) Cardiac-specific overexpression of RhoA results in sinus and atrioventricular nodal dysfunction and contractile failure. J Clin Invest 103:1627–1634
Sussman MA, Welch S, Walker A, Klevitsky R, Hewett TE, Price RL, Schaefer E, Yager K (2000) Altered focal adhesion regulation correlates with cardiomyopathy in mice expressing constitutively active rac1. J Clin Invest 105:875–886
DeBosch B, Treskov I, Lupu TS, Weinheimer C, Kovacs A, Courtois M, Muslin AJ (2006) Akt1 is required for physiological cardiac growth. Circulation 113:2097–2104
Ha T, Li Y, Gao X, McMullen JR, Shioi T, Izumo S, Kelley JL, Zhao A, Haddad GE, Williams DL, Browder IW, Kao RL, Li C (2005) Attenuation of cardiac hypertrophy by inhibiting both mTOR and NFκB activation in vivo. Free Radic Biol Med 39:1570–1580
Altamirano F, Oyarce C, Silva P, Toyos M, Wilson C, Lavandero S, Uhlén P, Estrada M (2009) Testosterone induces cardiomyocyte hypertrophy through mtorc1 pathway. J Endocrinol 202:299–307
Sandsmark DK, Zhang H, Hegedus B, Pelletier CL, Weber JD, Gutmann DH (2007) Nucleophosmin mediates mammalian target of rapamycin-dependent actin cytoskeleton dynamics and proliferation in neurofibromin-deficient astrocytes. Cancer Res 67:4790–4799
Maekawa M, Ishizaki T, Boku S, Watanabe N, Fujita A, Iwamatsu A, Obinata T, Ohashi K, Mizuno K, Narumiya S (1999) Signaling from Rho to the actin cytoskeleton through protein kinases ROCK and LIM-kinase. Science 285:895–898
Boluyt MO, Zheng JS, Younes A, Long X, O’Neill L, Silverman H, Lakatta EG, Crow MT (1997) Rapamycin inhibits α1-adrenergic receptor-stimulated cardiac myocyte hypertrophy but not activation of hypertrophy-associated genes. Evidence for involvement of p70 S6 kinase. Circ Res 8:176–186
Sadoshima J, Izumo S (1995) Rapamycin selectively inhibits angiotensin II-induced increase in protein synthesis in cardiac myocytes in vitro. Potential role of 70-kD S6 kinase in angiotensin II-induced cardiac hypertrophy. Circ Res 77:1040–1052
Shioi T, McMullen JR, Tarnavski O, Converso K, Sherwood MC, Manning WJ, Izumo S (2003) Rapamycin attenuates load-induced cardiac hypertrophy in mice. Circulation 107:1664–1670
Yanazume T, Hasegawa K, Wada H, Morimoto T, Abe M, Kawamura T, Sasayama S (2002) Rho/ROCK pathway contributes to the activation of extracellular signal-regulated kinase/GATA-4 during myocardial cell hypertrophy. J Biol Chem 277:8618–8625
Akazawa H, Komuro I (2003) Roles of cardiac transcription factors in cardiac hypertrophy. Circ Res 92:1079–1088
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This work was supported by Grant No. MOP 62764 from the Canadian Institutes of Health Research. M. Karmazyn holds a Canada Research Chair in Experimental Cardiology.
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Zeidan, A., Hunter, J.C., Javadov, S. et al. mTOR mediates RhoA-dependent leptin-induced cardiomyocyte hypertrophy. Mol Cell Biochem 352, 99–108 (2011). https://doi.org/10.1007/s11010-011-0744-2
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DOI: https://doi.org/10.1007/s11010-011-0744-2