Abstract
Autophagy is a life-sustaining process by which cytoplasmic constituents are segregated in double-lipid bilayer membrane vesicles and undergo degradation into lysosomes. In recent studies, the basal autophagy is an indispensable process mediating proper vascular function in the body. Moreover, autophagy activated by many stress-related stimuli in the arterial wall protects endothelial cells and smooth muscle cells against cell death and the progression of vascular disease including atherosclerosis. Autophagy is protective to atherosclerosis during early stage but becomes dysfunctional in advanced atherosclerotic lesions. Following this finding, the need is emphasized which pharmacological development with compounds that activate the protective effects of autophagy in the vascular disease. Autophagy stimulated by oral or vascular delivery of rapamycin or derivatives effectively suppressed the atherosclerotic plaque growth and plaque destabilization. In this review, the recent finding is summarized on the role of autophagy in atherosclerosis and find out whether the activation or rescue of autophagy could provide a breakthrough in the treatment of atherosclerosis.
Figures and Tables
![]() | Fig. 1The different types of autophagy. (A) Aggrephagy, (B) Mitophagy, (C) Lipophagy, (D) Xenophagy, (E) Schematic overview of the autophagic pathway. |
![]() | Fig. 2Potential role of autophagy in atherosclerosis. (A) Oxidative stress induced by the production of reactive oxygen species or the oxidized lipids is abundant in advanced atherosclerotic plaques. In the case of mild oxidative stress, activated autophagy promotes the removal of damaged organelles (eg, depolarized mitochondria) and contributes to cellular recovery, (B) Severe oxidative stress makes excessive cellular damage. Autophagy is not sufficient for the removal of that. Depolarized mitochondria release apoptosis inducer such as cytochrome c. Lysosome membrane damage results in cytosolic leakage of hydrolases, which could cause substantial cytosolic damage followed by apoptosis. Moreover, formation of ceroid that cannot be degraded by lysosomal hydrolases lead to preferential allocation of lysosomal enzymes to ceroid-loaded lysosomes at the expense of active autolysosomes which, in turn, would lead to the autophagy inhibition followed by apoptosis. |
References
3. Stolz A, Ernst A, Dikic I. Cargo recognition and trafficking in selective autophagy. Nat Cell Biol. 2014; 16:495–501.


4. Martinet W, De Meyer GR. Autophagy in atherosclerosis: a cell survival and death phenomenon with therapeutic potential. Circ Res. 2009; 104:304–317.
5. Rubinsztein DC, Codogno P, Levine B. Autophagy modulation as a potential therapeutic target for diverse diseases. Nat Rev Drug Discov. 2012; 11:709–730.


6. Sridhar S, Botbol Y, Macian F, Cuervo AM. Autophagy and disease: always two sides to a problem. J Pathol. 2012; 226:255–273.


7. Choi AM, Ryter SW, Levine B. Autophagy in human health and disease. N Engl J Med. 2013; 368:651–662.


9. Tsukamoto S, Kuma A, Murakami M, Kishi C, Yamamoto A, Mizushima N. Autophagy is essential for preimplantation development of mouse embryos. Science. 2008; 321:117–120.


10. Nair S, Ren J. Autophagy and cardiovascular aging: lesson learned from rapamycin. Cell Cycle. 2012; 11:2092–2099.
11. Ezaki J, Matsumoto N, Takeda-Ezaki M, Komatsu M, Takahashi K, Hiraoka Y, et al. Liver autophagy contributes to the maintenance of blood glucose and amino acid levels. Autophagy. 2011; 7:727–736.


12. Torisu T, Torisu K, Lee IH, Liu J, Malide D, Combs CA, et al. Autophagy regulates endothelial cell processing, maturation and secretion of von Willebrand factor. Nat Med. 2013; 19:1281–1287.


13. Singh R, Kaushik S, Wang Y, Xiang Y, Novak I, Komatsu M, et al. Autophagy regulates lipid metabolism. Nature. 2009; 458:1131–1135.


14. Ichimura Y, Komatsu M. Pathophysiological role of autophagy: lesson from autophagy-deficient mouse models. Exp Anim. 2011; 60:329–345.


15. Lavandero S, Troncoso R, Rothermel BA, Martinet W, Sadoshima J, Hill JA. Cardiovascular autophagy: concepts, controversies, and perspectives. Autophagy. 2013; 9:1455–1466.
17. Liu Y, Shoji-Kawata S, Sumpter RM Jr, Wei Y, Ginet V, Zhang L, et al. Autosis is a Na+,K+-ATPase-regulated form of cell death triggered by autophagy-inducing peptides, starvation, and hypoxia-ischemia. Proc Natl Acad Sci U S A. 2013; 110:20364–20371.


19. Martinet W, Schrijvers DM, Timmermans JP, Bult H, De Meyer GR. Immunohistochemical analysis of macroautophagy: recommendations and limitations. Autophagy. 2013; 9:386–402.
20. Martinet W, Timmermans JP, De Meyer GR. Methods to assess autophagy in situ--transmission electron microscopy versus immunohistochemistry. Methods Enzymol. 2014; 543:89–114.


22. Hansson GK. Inflammation, atherosclerosis, and coronary artery disease. N Engl J Med. 2005; 352:1685–1695.


23. Kannel WB, D’Agostino RB, Sullivan L, Wilson PW. Concept and usefulness of cardiovascular risk profiles. Am Heart J. 2004; 148:16–26.


24. Wang JC, Bennett M. Aging and atherosclerosis: mechanisms, functional consequences, and potential therapeutics for cellular senescence. Circ Res. 2012; 111:245–259.
25. Waxman S, Ishibashi F, Muller JE. Detection and treatment of vulnerable plaques and vulnerable patients: novel approaches to prevention of coronary events. Circulation. 2006; 114:2390–2411.


26. Schrijvers DM, De Meyer GR, Martinet W. Autophagy in atherosclerosis: a potential drug target for plaque stabilization. Arterioscler Thromb Vasc Biol. 2011; 31:2787–2791.
27. Martinet W, De Meyer I, Verheye S, Schrijvers DM, Timmermans JP, De Meyer GR. Drug-induced macrophage autophagy in atherosclerosis: for better or worse? Basic Res Cardiol. 2013; 108:321.


28. Martinet W, De Loof H, De Meyer GR. mTOR inhibition: a promising strategy for stabilization of atherosclerotic plaques. Atherosclerosis. 2014; 233:601–607.


29. Levine B, Yuan J. Autophagy in cell death: an innocent convict. J Clin Invest. 2005; 115:2679–2688.


30. Kiffin R, Bandyopadhyay U, Cuervo AM. Oxidative stress and autophagy. Antioxid Redox Signal. 2006; 8:152–162.


31. Martinet W, Schrijvers DM, Timmermans JP, Bult H. Interactions between cell death induced by statins and 7-ketocholesterol in rabbit aorta smooth muscle cells. Br J Pharmacol. 2008; 154:1236–1246.


32. Pan M, Maitin V, Parathath S, Andreo U, Lin SX, St Germain C, et al. Presecretory oxidation, aggregation, and autophagic destruction of apoprotein-B: a pathway for late-stage quality control. Proc Natl Acad Sci U S A. 2008; 105:5862–5867.


33. Fisher EA, Pan M, Chen X, Wu X, Wang H, Jamil H, et al. The triple threat to nascent apolipoprotein B. Evidence for multiple, distinct degradative pathways. J Biol Chem. 2001; 276:27855–27863.
34. Sparks JD, Phung TL, Bolognino M, Sparks CE. Insulin-mediated inhibition of apolipoprotein B secretion requires an intracellular trafficking event and phosphatidylinositol 3-kinase activation: studies with brefeldin A and wortmannin in primary cultures of rat hepatocytes. Biochem J. 1996; 313:567–574.


35. Pan M, Cederbaum AI, Zhang YL, Ginsberg HN, Williams KJ, Fisher EA. Lipid peroxidation and oxidant stress regulate hepatic apolipoprotein B degradation and VLDL production. J Clin Invest. 2004; 113:1277–1287.


36. von Schacky C. The role of omega-3 fatty acids in cardiovascular disease. Curr Atheroscler Rep. 2003; 5:139–145.


37. Mitchinson MJ. Insoluble lipids in human atherosclerotic plaques. Atherosclerosis. 1982; 45:11–15.


38. Kurz T, Terman A, Brunk UT. Autophagy, ageing and apoptosis: the role of oxidative stress and lysosomal iron. Arch Biochem Biophys. 2007; 462:220–230.


39. Brunk UT, Jones CB, Sohal RS. A novel hypothesis of lipofuscinogenesis and cellular aging based on interactions between oxidative stress and autophagocytosis. Mutat Res. 1992; 275:395–403.


40. Lee FY, Lee TS, Pan CC, Huang AL, Chau LY. Colocalization of iron and ceroid in human atherosclerotic lesions. Atherosclerosis. 1998; 138:281–288.


41. Yuan XM, Li W, Brunk UT, Dalen H, Chang YH, Sevanian A. Lysosomal destabilization during macrophage damage induced by cholesterol oxidation products. Free Radic Biol Med. 2000; 28:208–218.


42. Debnath J, Baehrecke EH, Kroemer G. Does autophagy contribute to cell death? Autophagy. 2005; 1:66–74.


44. Porter NA. Chemistry of lipid peroxidation. Methods Enzymol. 1984; 105:273–282.
45. Hill BG, Haberzettl P, Ahmed Y, Srivastava S, Bhatnagar A. Unsaturated lipid peroxidation-derived aldehydes activate autophagy in vascular smooth-muscle cells. Biochem J. 2008; 410:525–534.


46. Bardag-Gorce F, Li J, French BA, French SW. The effect of ethanol-induced CYP2E1 on proteasome activity: the role of 4-hydroxynonenal. Exp Mol Pathol. 2005; 78:109–115.


47. Nowicki M, Zabirnyk O, Duerrschmidt N, Borlak J, Spanel-Borowski K. No upregulation of lectin-like oxidized low-density lipoprotein receptor-1 in serumdeprived EA.hy926 endothelial cells under oxLDL exposure, but increase in autophagy. Eur J Cell Biol. 2007; 86:605–616.


48. Martinet W, De Bie M, Schrijvers DM, De Meyer GR, Herman AG, Kockx MM. 7-ketocholesterol induces protein ubiquitination, myelin figure formation, and light chain 3 processing in vascular smooth muscle cells. Arterioscler Thromb Vasc Biol. 2004; 24:2296–2301.


49. Martinet W, Schrijvers DM, De Meyer GR, Thielemans J, Knaapen MW, Herman AG, et al. Gene expression profiling of apoptosis-related genes in human atherosclerosis: upregulation of death-associated protein kinase. Arterioscler Thromb Vasc Biol. 2002; 22:2023–2029.


50. Inbal B, Bialik S, Sabanay I, Shani G, Kimchi A. DAP kinase and DRP-1 mediate membrane blebbing and the formation of autophagic vesicles during programmed cell death. J Cell Biol. 2002; 157:455–468.


51. Jin Y, Gallagher PJ. Antisense depletion of deathassociated protein kinase promotes apoptosis. J Biol Chem. 2003; 278:51587–51593.


52. Zhou J, Lhoták S, Hilditch BA, Austin RC. Activation of the unfolded protein response occurs at all stages of atherosclerotic lesion development in apolipoprotein E-deficient mice. Circulation. 2005; 111:1814–1821.


53. Tabas I. Apoptosis and plaque destabilization in atherosclerosis: the role of macrophage apoptosis induced by cholesterol. Cell Death Differ. 2004; 11:Suppl 1. S12–S16.


54. Yorimitsu T, Nair U, Yang Z, Klionsky DJ. Endoplasmic reticulum stress triggers autophagy. J Biol Chem. 2006; 281:30299–30304.


55. Li J, Ni M, Lee B, Barron E, Hinton DR, Lee AS. The unfolded protein response regulator GRP78/BiP is required for endoplasmic reticulum integrity and stressinduced autophagy in mammalian cells. Cell Death Differ. 2008; 15:1460–1471.


56. Frostegård J, Ulfgren AK, Nyberg P, Hedin U, Swedenborg J, Andersson U, et al. Cytokine expression in advanced human atherosclerotic plaques: dominance of pro-inflammatory (Th1) and macrophage-stimulating cytokines. Atherosclerosis. 1999; 145:33–43.


58. Heymann D. Autophagy: a protective mechanism in response to stress and inflammation. Curr Opin Investig Drugs. 2006; 7:443–450.
59. Jia G, Cheng G, Gangahar DM, Agrawal DK. Insulin-like growth factor-1 and TNF-alpha regulate autophagy through c-jun N-terminal kinase and Akt pathways in human atherosclerotic vascular smooth cells. Immunol Cell Biol. 2006; 84:448–454.


60. Gutierrez MG, Master SS, Singh SB, Taylor GA, Colombo MI, Deretic V. Autophagy is a defense mechanism inhibiting BCG and Mycobacterium tuberculosis survival in infected macrophages. Cell. 2004; 119:753–766.


61. Cromheeke KM, Kockx MM, De Meyer GR, Bosmans JM, Bult H, Beelaerts WJ, et al. Inducible nitric oxide synthase colocalizes with signs of lipid oxidation/peroxidation in human atherosclerotic plaques. Cardiovasc Res. 1999; 43:744–754.


62. Sluimer JC, Gasc JM, van Wanroij JL, Kisters N, Groeneweg M, Sollewijn Gelpke MD, et al. Hypoxia, hypoxia-inducible transcription factor, and macrophages in human atherosclerotic plaques are correlated with intraplaque angiogenesis. J Am Coll Cardiol. 2008; 51:1258–1265.


63. Azad MB, Chen Y, Henson ES, Cizeau J, McMillan-Ward E, Israels SJ, et al. Hypoxia induces autophagic cell death in apoptosis-competent cells through a mechanism involving BNIP3. Autophagy. 2008; 4:195–204.


64. Brunelle JK, Chandel NS. Oxygen deprivation induced cell death: an update. Apoptosis. 2002; 7:475–482.
65. Mizushima N, Yamamoto A, Matsui M, Yoshimori T, Ohsumi Y. In vivo analysis of autophagy in response to nutrient starvation using transgenic mice expressing a fluorescent autophagosome marker. Mol Biol Cell. 2004; 15:1101–1111.


66. Jin S, White E. Role of autophagy in cancer: management of metabolic stress. Autophagy. 2007; 3:28–31.


67. Karantza-Wadsworth V, Patel S, Kravchuk O, Chen G, Mathew R, Jin S, et al. Autophagy mitigates metabolic stress and genome damage in mammary tumorigenesis. Genes Dev. 2007; 21:1621–1635.


68. Kockx MM, De Meyer GR, Muhring J, Jacob W, Bult H, Herman AG. Apoptosis and related proteins in different stages of human atherosclerotic plaques. Circulation. 1998; 97:2307–2315.


69. Kundu M, Thompson CB. Autophagy: basic principles and relevance to disease. Annu Rev Pathol. 2008; 3:427–455.


70. Mizushima N, Levine B, Cuervo AM, Klionsky DJ. Autophagy fights disease through cellular self-digestion. Nature. 2008; 451:1069–1075.


71. Martinet W, Knaapen MW, Kockx MM, De Meyer GR. Autophagy in cardiovascular disease. Trends Mol Med. 2007; 13:482–491.


72. Martinet W, Verheye S, De Meyer GR. Selective depletion of macrophages in atherosclerotic plaques via macrophage-specific initiation of cell death. Trends Cardiovasc Med. 2007; 17:69–75.

