mTOR signaling promotes foam cell formation and inhibits foam cell egress through suppressing the SIRT1 signaling pathway

Zheng,Haixiang; Fu,Yucai; Huang,Yusheng; Zheng,Xinde; Yu,Wei; Wang,Wei

doi:10.3892/mmr.2017.7032

mTOR signaling promotes foam cell formation and inhibits foam cell egress through suppressing the SIRT1 signaling pathway

Authors:
- Haixiang Zheng
- Yucai Fu
- Yusheng Huang
- Xinde Zheng
- Wei Yu
- Wei Wang
View Affiliations

Affiliations: Department of Cardiology, The Second Affiliated Hospital of Shantou University Medical College, Shantou, Guangdong 515041, P.R. China, Laboratory of Cell Senescence, Shantou University Medical College, Shantou, Guangdong 515041, P.R. China
Published online on: July 18, 2017 https://doi.org/10.3892/mmr.2017.7032
Pages: 3315-3323
Copyright: © Zheng et al. This is an open access article distributed under the terms of Creative Commons Attribution License.

Metrics: Total Views: 0 (Spandidos Publications: | PMC Statistics: )

Metrics: Total PDF Downloads: 0 (Spandidos Publications: | PMC Statistics: )

Cited By (CrossRef): 0 citations Loading Articles...

Abstract

Atherosclerosis (AS) is a chronic immuno‑inflammatory disease accompanied by dyslipidemia. The authors previously demonstrated that sirtuin 1 (SIRT1) may prevent atherogenesis through influencing the liver X receptor/C‑C chemokine receptor type 7/nuclear factor‑κB (LXR‑CCR7/NF‑κB) signaling pathway. Previous studies have suggested a role for mammalian target of rapamycin (mTOR) signaling in the pathogenesis of cardiovascular diseases. The present study investigated the potential association between mTOR signaling and SIRT1‑LXR‑CCR7/NF‑κB signaling (SIRT1 signaling) in AS pathogenesis. To induce foam cell formation, U937 cells were differentiated into macrophages by exposure to phorbol 12‑myristate 13‑acetate (PMA) for 24 h, followed by treatment with palmitate and oxidized low density lipoprotein for a further 24 h. Oil red O staining revealed a large accumulation of lipid droplets present in foam cells. Western blot analysis demonstrated increased protein levels of phosphorylated (p)‑mTOR and its downstream factor p‑ribosomal protein S6 kinase (p70S6K). Reverse transcription‑quantitative polymerase chain reaction and western blot analyses additionally revealed decreased expression of SIRT1, LXRα and CCR7 and increased expression of NF‑κB and its downstream factor tumor necrosis factor‑α (TNF‑α) in an atherogenetic condition induced by lysophosphatidic acid (LPA). In addition, abundant lipid droplets accumulated in U937‑LPA‑treated foam cells. Rapamycin, an mTOR inhibitor, suppressed the expression and activity of mTOR and p70S6K, however enhanced expression of SIRT1, LXRα, and CCR7. Conversely, rapamycin deceased TNF‑α and NF‑κB activity, the latter of which was further confirmed by immunofluorescence analysis demonstrating increased levels of NF‑κB present in the cytoplasm compared with the nucleus. The findings of the present study suggest that mTOR signaling promotes foam cell formation and inhibits foam cell egress via suppression of SIRT1 signaling.

View Figures

View References

1	Yusuf S, Reddy S, Ounpuu S and Anand S: Global burden of cardiovascular diseases: Part I: General considerations, the epidemiologic transition, risk factors, and impact of urbanization. Circulation. 104:2746–2753. 2001. View Article : Google Scholar : PubMed/NCBI
2	Go AS, Mozaffarian D, Roger VL, Benjamin EJ, Berry JD, Blaha MJ, Dai S, Ford ES, Fox CS, Franco S, et al: Heart disease and stroke statistics-2014 update: A report from the American Heart Association. Circulation. 129:e28–e292. 2014. View Article : Google Scholar : PubMed/NCBI
3	Falk E: Pathogenesis of atherosclerosis. J Am Coll Cardiol. 47:(8 Suppl). C7–C12. 2006. View Article : Google Scholar : PubMed/NCBI
4	Cruzado JM: Nonimmunosuppressive effects of mammalian target of rapamycin inhibitors. Transplant Rev (Orlando). 22:73–81. 2008. View Article : Google Scholar : PubMed/NCBI
5	Yang Z and Ming XF: mTOR signalling: The molecular interface connecting metabolic stress, aging and cardiovascular diseases. Obes Rev. 13:(Suppl 2). S58–S68. 2012. View Article : Google Scholar
6	Yang Q and Guan KL: Expanding mTOR signaling. Cell Res. 17:666–681. 2007. View Article : Google Scholar : PubMed/NCBI
7	Sciarretta S, Volpe M and Sadoshima J: Mammalian target of rapamycin signaling in cardiac physiology and disease. Circ Res. 114:549–564. 2014. View Article : Google Scholar : PubMed/NCBI
8	Martinet W, De Loof H and De Meyer GR: mTOR inhibition: A promising strategy for stabilization of atherosclerotic plaques. Atherosclerosis. 233:601–607. 2014. View Article : Google Scholar : PubMed/NCBI
9	Johnson SC, Rabinovitch PS and Kaeberlein M: mTOR is a key modulator of ageing and age-related disease. Nature. 493:338–345. 2013. View Article : Google Scholar : PubMed/NCBI
10	Mueller MA, Beutner F, Teupser D, Ceglarek U and Thiery J: Prevention of atherosclerosis by the mTOR inhibitor everolimus in LDLR^−/− mice despite severe hypercholesterolemia. Atherosclerosis. 198:39–48. 2008. View Article : Google Scholar : PubMed/NCBI
11	Chen WQ, Zhong L, Zhang L, Ji XP, Zhang M, Zhao YX, Zhang C and Zhang Y: Oral rapamycin attenuates inflammation and enhances stability of atherosclerotic plaques in rabbits independent of serum lipid levels. Br J Pharmacol. 156:941–951. 2009. View Article : Google Scholar : PubMed/NCBI
12	Ma KL, Ruan XZ, Powis SH, Moorhead JF and Varghese Z: Anti-atherosclerotic effects of sirolimus on human vascular smooth muscle cells. Am J Physiol Heart Circ Physiol. 292:H2721–H2728. 2007. View Article : Google Scholar : PubMed/NCBI
13	Mathis AS, Jin S, Friedman GS, Peng F, Carl SM and Knipp GT: The pharmacodynamic effects of sirolimus and sirolimus-calcineurin inhibitor combinations on macrophage scavenger and nuclear hormone receptors. J Pharm Sci. 96:209–222. 2007. View Article : Google Scholar : PubMed/NCBI
14	Yu M, Kang X, Xue H and Yin H: Toll-like receptor 4 is up-regulated by mTOR activation during THP-1 macrophage foam cells formation. Acta Biochim Biophys Sin (Shanghai). 43:940–947. 2011. View Article : Google Scholar : PubMed/NCBI
15	Thomson AW, Turnquist HR and Raimondi G: Immunoregulatory functions of mTOR inhibition. Nat Rev Immunol. 9:324–337. 2009. View Article : Google Scholar : PubMed/NCBI
16	Sordi V, Bianchi G, Buracchi C, Mercalli A, Marchesi F, D'Amico G, Yang CH, Luini W, Vecchi A, Mantovani A, et al: Differential effects of immunosuppressive drugs on chemokine receptor CCR7 in human monocyte-derived dendritic cells: Selective upregulation by rapamycin. Transplantation. 82:826–834. 2006. View Article : Google Scholar : PubMed/NCBI
17	Trogan E, Feig JE, Dogan S, Rothblat GH, Angeli V, Tacke F, Randolph GJ and Fisher EA: Gene expression changes in foam cells and the role of chemokine receptor CCR7 during atherosclerosis regression in ApoE-deficient mice. Proc Natl Acad Sci USA. 103:3781–3786. 2006. View Article : Google Scholar : PubMed/NCBI
18	Feig JE, Pineda-Torra I, Sanson M, Bradley MN, Vengrenyuk Y, Bogunovic D, Gautier EL, Rubinstein D, Hong C, Liu J, et al: LXR promotes the maximal egress of monocyte-derived cells from mouse aortic plaques during atherosclerosis regression. J Clin Invest. 120:4415–4424. 2010. View Article : Google Scholar : PubMed/NCBI
19	Baker RG, Hayden MS and Ghosh S: NF-κB, inflammation, and metabolic disease. Cell Metab. 13:11–22. 2011. View Article : Google Scholar : PubMed/NCBI
20	Takeda-Watanabe A, Kitada M, Kanasaki K and Koya D: SIRT1 inactivation induces inflammation through the dysregulation of autophagy in human THP-1 cells. Biochem Biophys Res Commun. 427:191–196. 2012. View Article : Google Scholar : PubMed/NCBI
21	Zeng HT, Fu YC, Yu W, Lin JM, Zhou L, Liu L and Wang W: SIRT1 prevents atherosclerosis via liver-X-receptor and NF-κB signaling in a U937 cell model. Mol Med Rep. 8:23–28. 2013.PubMed/NCBI
22	Zhang S, Cai G, Fu B, Feng Z, Ding R, Bai X, Liu W, Zhuo L, Sun L, Liu F and Chen X: SIRT1 is required for the effects of rapamycin on high glucose-inducing mesangial cells senescence. Mech Ageing Dev. 133:387–400. 2012. View Article : Google Scholar : PubMed/NCBI
23	Medvedik O, Lamming DW, Kim KD and Sinclair DA: MSN2 and MSN4 link calorie restriction and TOR to sirtuin-mediated lifespan extension in saccharomyces cerevisiae. PLoS Biol. 5:e2612007. View Article : Google Scholar : PubMed/NCBI
24	Ghosh HS, McBurney M and Robbins PD: SIRT1 negatively regulates the mammalian target of rapamycin. PLoS One. 5:e91992010. View Article : Google Scholar : PubMed/NCBI
25	Cui MZ: Lysophosphatidic acid effects on atherosclerosis and thrombosis. Clin Lipidol. 6:413–426. 2011. View Article : Google Scholar : PubMed/NCBI
26	Lamming DW and Sabatini DM: A Central role for mTOR in lipid homeostasis. Cell Metab. 18:465–469. 2013. View Article : Google Scholar : PubMed/NCBI
27	Ma KL, Liu J, Wang CX, Ni J, Zhang Y, Wu Y, Lv LL, Ruan XZ and Liu BC: Activation of mTOR modulates SREBP-2 to induce foam cell formation through increased retinoblastoma protein phosphorylation. Cardiovasc Res. 100:450–460. 2013. View Article : Google Scholar : PubMed/NCBI
28	Fueller M, Wang DA, Tigyi G and Siess W: Activation of human monocytic cells by lysophosphatidic acid and sphingosine-1-phosphate. Cell Signal. 15:367–375. 2003. View Article : Google Scholar : PubMed/NCBI
29	Bot M, Bot I, Lopez-Vales R, van de Lest CH, Saulnier-Blache JS, Helms JB, David S, van Berkel TJ and Biessen EA: Atherosclerotic lesion progression changes lysophosphatidic acid homeostasis to favor its accumulation. Am J Pathol. 176:3073–3084. 2010. View Article : Google Scholar : PubMed/NCBI
30	Ghosh HS, McBurney M and Robbins PD: SIRT1 negatively regulates the mammalian target of rapamycin. PLoS One. 5:e91992010. View Article : Google Scholar : PubMed/NCBI
31	Xu J, Dang Y, Ren YR and Liu JO: Cholesterol trafficking is required for mTOR activation in endothelial cells. Proc Natl Acad Sci USA. 107:4764–4769. 2010. View Article : Google Scholar : PubMed/NCBI
32	Gareus R, Kotsaki E, Xanthoulea S, van der Made I, Gijbels MJ, Kardakaris R, Polykratis A, Kollias G, de Winther MP and Pasparakis M: Endothelial cell-specific NF-κB inhibition protects mice from atherosclerosis. Cell Metab. 8:372–383. 2008. View Article : Google Scholar : PubMed/NCBI
33	Ma KL, Ruan XZ, Powis SH, Chen Y, Moorhead JF and Varghese Z: Inflammatory stress exacerbates lipid accumulation in hepatic cells and fatty livers of apolipoprotein E knockout mice. Hepatology. 48:770–781. 2008. View Article : Google Scholar : PubMed/NCBI
34	Yeung F, Hoberg JE, Ramsey CS, Keller MD, Jones DR, Frye RA and Mayo MW: Modulation of NF-κB-dependent transcription and cell survival by the SIRT1 deacetylase. EMBO J. 23:2369–2380. 2004. View Article : Google Scholar : PubMed/NCBI
35	Salminen A, Kauppinen A, Suuronen T and Kaarniranta K: SIRT1 longevity factor suppresses NF-κB-driven immune responses: Regulation of aging via NF-kappaB acetylation? Bioessays. 30:939–942. 2008. View Article : Google Scholar : PubMed/NCBI
36	Cohen HY, Miller C, Bitterman KJ, Wall NR, Hekking B, Kessler B, Howitz KT, Gorospe M, de Cabo R and Sinclair DA: Calorie restriction promotes mammalian cell survival by inducing the SIRT1 deacetylase. Sci. 305:390–392. 2004. View Article : Google Scholar
37	Blagosklonny MV: Calorie restriction: decelerating mTOR-driven aging from cells to organisms (including humans). Cell Cycle. 9:683–688. 2010. View Article : Google Scholar : PubMed/NCBI
38	Ma L, Dong W, Wang R, Li Y, Xu B, Zhang J, Zhao Z and Wang Y: Effect of caloric restriction on the SIRT1/mTOR signaling pathways in senile mice. Brain Res Bull. 116:67–72. 2015. View Article : Google Scholar : PubMed/NCBI