Rapamycin Inhibits the mTOR/p70S6K Pathway and Attenuates Cardiac Fibrosis in Adriamycin-induced Dilated Cardiomyopathy

Abstract

Background The objective of the present study was to investigate whether mTOR is involved in cardiac fibrosis evident in dilated cardiomyopathy, and whether rapamycin provides therapeutic potential for cardiac fibrosis.

Methods Forty-five rats were divided into three groups. Fifteen rats in the Adriamycin group underwent 8 weeks of Adriamycin treatment (2.5 mg/kg, twice per week; i.v.) to induce cardiac fibrosis and dilated cardiomyopathy. Fifteen rats in the rapamycin group received rapamycin (2 mg/kg, per day, orally) and i.v. Adriamycin simultaneously for 8 weeks. Fifteen untreated rats served as controls. Cardiac morphology and function were quantified using echocardiography. mTOR and p70S6K1 mRNA expression were assessed using reverse transcription-PCR.

Results Collagen volume fraction (CVF) was significantly elevated in the adriamycin group (3.36 ± 0.75) compared with controls (1.51 ± 0.31), whereas mTOR and p70S6K mRNA expression were significantly increased in the adriamycin group (0.68 ± 0.03 and 0.69 ± 0.03) compared with controls (0.38 ± 0.03 and 0.34 ± 0.02). The Adriamycin group was associated with cardiac dilation and decreased contractile function. The rapamycin group showed significantly decreased CVF (1.87 ± 0.45), accompanied with a significant decrease in mTOR and p70S6K mRNA expression (0.42 ± 0.05 and 0.45 ± 0.04) relative to the Adriamycin group. In addition, treatment with rapamycin recovered impairments in cardiac morphology and function.

Conclusion The mTOR/p70S6K pathway plays an important role in adriamycin-induced cardiac fibrosis resulting from dilated cardiomyopathy. Rapamycin is a potential therapeutic treatment that can be used to attenuate cardiac fibrosis and improve cardiac function.

Keywords

rapamycin - mTOR/p70S6K - cardiac fibrosis - dilated cardiomyopathy - adriamycin

• References

• 1 Assomull RG, Prasad SK, Lyne J , et al. Cardiovascular magnetic resonance, fibrosis, and prognosis in dilated cardiomyopathy. J Am Coll Cardiol 2006; 48 (10) 1977-1985
• 2 Agapitos E, Kavantzas N, Nanas J , et al. The myocardial fibrosis in patients with dilated cardiomyopathy. The application of image analysis in the myocardial biopsies. Gen Diagn Pathol 1996; 141 (5–6) 305-311
• 3 Hay N, Sonenberg N. Upstream and downstream of mTOR. Genes Dev 2004; 18 (16) 1926-1945
• 4 Beevers CS, Li F, Liu L, Huang S. Curcumin inhibits the mammalian target of rapamycin-mediated signaling pathways in cancer cells. Int J Cancer 2006; 119 (4) 757-764
• 5 Hartford CM, Ratain MJ. Rapamycin: something old, something new, sometimes borrowed and now renewed. Clin Pharmacol Ther 2007; 82 (4) 381-388
• 6 Winbanks CE, Grimwood L, Gasser A, Darby IA, Hewitson TD, Becker GJ. Role of the phosphatidylinositol 3-kinase and mTOR pathways in the regulation of renal fibroblast function and differentiation. Int J Biochem Cell Biol 2007; 39 (1) 206-219
• 7 Ong CT, Khoo YT, Mukhopadhyay A , et al. mTOR as a potential therapeutic target for treatment of keloids and excessive scars. Exp Dermatol 2007; 16 (5) 394-404
• 8 Gerasimovskaya EV, Tucker DA, Stenmark KR. Activation of phosphatidylinositol 3-kinase, Akt, and mammalian target of rapamycin is necessary for hypoxia-induced pulmonary artery adventitial fibroblast proliferation. J Appl Physiol 2005; 98 (2) 722-731
• 9 Gäbele E, Reif S, Tsukada S , et al. The role of p70S6K in hepatic stellate cell collagen gene expression and cell proliferation. J Biol Chem 2005; 280 (14) 13374-13382
• 10 Saunders RN, Metcalfe MS, Nicholson ML. Rapamycin in transplantation: a review of the evidence. Kidney Int 2001; 59 (1) 3-16
• 11 Wiederrecht GJ, Sabers CJ, Brunn GJ, Martin MM, Dumont FJ, Abraham RT. Mechanism of action of rapamycin: new insights into the regulation of G1-phase progression in eukaryotic cells. Prog Cell Cycle Res 1995; 1: 53-71
• 12 Fruman DA, Wood MA, Gjertson CK, Katz HR, Burakoff SJ, Bierer BE. FK506 binding protein 12 mediates sensitivity to both FK506 and rapamycin in murine mast cells. Eur J Immunol 1995; 25 (2) 563-571
• 13 Thomas G, Hall MN. TOR signalling and control of cell growth. Curr Opin Cell Biol 1997; 9 (6) 782-787
• 14 Sabatini DM, Erdjument-Bromage H, Lui M, Tempst P, Snyder SH. RAFT1: a mammalian protein that binds to FKBP12 in a rapamycin-dependent fashion and is homologous to yeast TORs. Cell 1994; 78 (1) 35-43
• 15 Neef M, Ledermann M, Saegesser H, Schneider V, Reichen J. Low-dose oral rapamycin treatment reduces fibrogenesis, improves liver function, and prolongs survival in rats with established liver cirrhosis. J Hepatol 2006; 45 (6) 786-796
• 16 Zhu J, Wu J, Frizell E , et al. Rapamycin inhibits hepatic stellate cell proliferation in vitro and limits fibrogenesis in an in vivo model of liver fibrosis. Gastroenterology 1999; 117 (5) 1198-1204
• 17 Biecker E, De Gottardi A, Neef M , et al. Long-term treatment of bile duct-ligated rats with rapamycin (sirolimus) significantly attenuates liver fibrosis: analysis of the underlying mechanisms. J Pharmacol Exp Ther 2005; 313 (3) 952-961
• 18 Wu MJ, Wen MC, Chiu YT, Chiou YY, Shu KH, Tang MJ. Rapamycin attenuates unilateral ureteral obstruction-induced renal fibrosis. Kidney Int 2006; 69 (11) 2029-2036
• 19 Liu Y. Rapamycin and chronic kidney disease: beyond the inhibition of inflammation. Kidney Int 2006; 69 (11) 1925-1927
• 20 Korfhagen TR, Le Cras TD, Davidson CR , et al. Rapamycin prevents transforming growth factor-alpha-induced pulmonary fibrosis. Am J Respir Cell Mol Biol 2009; 41 (5) 562-572
• 21 Shioi T, McMullen JR, Tarnavski O , et al. Rapamycin attenuates load-induced cardiac hypertrophy in mice. Circulation 2003; 107 (12) 1664-1670
• 22 McMullen JR, Sherwood MC, Tarnavski O , et al. Inhibition of mTOR signaling with rapamycin regresses established cardiac hypertrophy induced by pressure overload. Circulation 2004; 109 (24) 3050-3055
• 23 Gao XM, Wong G, Wang B , et al. Inhibition of mTOR reduces chronic pressure-overload cardiac hypertrophy and fibrosis. J Hypertens 2006; 24 (8) 1663-1670
• 24 Hou XW, Son J, Wang Y , et al. Granulocyte colony-stimulating factor reduces cardiomyocyte apoptosis and improves cardiac function in adriamycin-induced cardiomyopathy in rats. Cardiovasc Drugs Ther 2006; 20 (2) 85-91
• 25 Christiansen S, Redmann K, Scheld HH , et al. Adriamycin-induced cardiomyopathy in the dog—an appropriate model for research on partial left ventriculectomy?. J Heart Lung Transplant 2002; 21 (7) 783-790
• 26 Woodcock EA, Arnolda L, McGrath BP. Ventricular beta-adrenoceptors in adriamycin-induced cardiomyopathy in the rabbit. J Mol Cell Cardiol 1988; 20 (9) 771-777
• 27 Law BK, Chytil A, Dumont N , et al. Rapamycin potentiates transforming growth factor beta-induced growth arrest in nontransformed, oncogene-transformed, and human cancer cells. Mol Cell Biol 2002; 22 (23) 8184-8198
• 28 Woltman AM, van der Kooij SW, Coffer PJ, Offringa R, Daha MR, van Kooten C. Rapamycin specifically interferes with GM-CSF signaling in human dendritic cells, leading to apoptosis via increased p27KIP1 expression. Blood 2003; 101 (4) 1439-1445