Reducing endoplasmic reticulum stress through a macrophage lipid chaperone alleviates atherosclerosis

  • An Erratum to this article was published on 01 February 2010

Abstract

Macrophages show endoplasmic reticulum (ER) stress when exposed to lipotoxic signals associated with atherosclerosis, although the pathophysiological importance and the underlying mechanisms of this phenomenon remain unknown. Here we show that mitigation of ER stress with a chemical chaperone results in marked protection against lipotoxic death in macrophages and prevents macrophage fatty acid–binding protein-4 (aP2) expression. Using genetic and chemical models, we show that aP2 is the predominant regulator of lipid-induced macrophage ER stress. The absence of lipid chaperones incites an increase in the production of phospholipids rich in monounsaturated fatty acids and bioactive lipids that render macrophages resistant to lipid-induced ER stress. Furthermore, the impact of aP2 on macrophage lipid metabolism and the ER stress response is mediated by upregulation of key lipogenic enzymes by the liver X receptor. Our results demonstrate the central role for lipid chaperones in regulating ER homeostasis in macrophages in atherosclerosis and show that ER responses can be modified, genetically or chemically, to protect the organism against the deleterious effects of hyperlipidemia.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Figure 1: PBA treatment protects against macrophage ER stress and reduces vascular disease progression.
Figure 2: Requirement for aP2 in lipid-induced ER stress and apoptosis.
Figure 3: aP2 deficiency protects from hypercholesteremia-induced macrophage ER stress and apoptosis in atherosclerotic lesions.
Figure 4: Regulation of macrophage lipid composition by aP2.
Figure 5: A central role for SCD and C16:1n7 in aP2 mediated lipotoxic signaling.
Figure 6: Linking toxic lipids to ER stress and atherosclerosis through aP2–LXR-α crosstalk.

Change history

  • 04 February 2010

    In the version of this article initially published, the official symbol for the gene encoding the aP2 protein was misidentified as Tcfap2a (the gene symbol for the transcription factor AP-2). The correct gene symbol is Fabp4. In no instances anywhere in the study was AP-2 examined. Additionally, Supplementary Figure 2a should also have been cited where Figure 2c was cited. The errors have been corrected in the HTML and PDF versions of the article.

References

  1. 1

    Hotamisligil, G.S. Inflammation and metabolic disorders. Nature 444, 860–867 (2006).

  2. 2

    Gregor, M.F. & Hotamisligil, G.S. Thematic review series: Adipocyte Biology. Adipocyte stress: the endoplasmic reticulum and metabolic disease. J. Lipid Res. 48, 1905–1914 (2007).

  3. 3

    Feng, B. et al. The endoplasmic reticulum is the site of cholesterol-induced cytotoxicity in macrophages. Nat. Cell Biol. 5, 781–792 (2003).

  4. 4

    Tabas, I. Consequences and therapeutic implications of macrophage apoptosis in atherosclerosis: the importance of lesion stage and phagocytic efficiency. Arterioscler. Thromb. Vasc. Biol. 25, 2255–2264 (2005).

  5. 5

    Ozcan, U. et al. Endoplasmic reticulum stress links obesity, insulin action and type 2 diabetes. Science 306, 457–461 (2004).

  6. 6

    Ozawa, K. et al. The endoplasmic reticulum chaperone improves insulin resistance in type 2 diabetes. Diabetes 54, 657–663 (2005).

  7. 7

    Ozcan, U. et al. Chemical chaperones reduce ER stress and restore glucose homeostasis in a mouse model of type 2 diabetes. Science 313, 1137–1140 (2006).

  8. 8

    Myoishi, M. et al. Increased endoplasmic reticulum stress in atherosclerotic plaques associated with acute coronary syndrome. Circulation 116, 1226–1233 (2007).

  9. 9

    Ron, D. & Walter, P. Signal integration in the endoplasmic reticulum unfolded protein response. Nat. Rev. Mol. Cell Biol. 8, 519–529 (2007).

  10. 10

    Hotamisligil, G.S. & Erbay, E. Nutrient sensing and inflammation in metabolic diseases. Nat. Rev. Immunol. 8, 923–934 (2008).

  11. 11

    Sriburi, R., Jackowski, S., Mori, K. & Brewer, J.W. XBP1: a link between the unfolded protein response, lipid biosynthesis, and biogenesis of the endoplasmic reticulum. J. Cell Biol. 167, 35–41 (2004).

  12. 12

    Brookheart, R.T., Michel, C.I. & Schaffer, J.E. As a matter of fat. Cell Metab. 10, 9–12 (2009).

  13. 13

    Ferré, P. & Foufelle, F. SREBP-1c transcription factor and lipid homeostasis: clinical perspective. Horm. Res. 68, 72–82 (2007).

  14. 14

    Oyadomari, S., Harding, H.P., Zhang, Y., Oyadomari, M. & Ron, D. Dephosphorylation of translation initiation factor 2α enhances glucose tolerance and attenuates hepatosteatosis in mice. Cell Metab. 7, 520–532 (2008).

  15. 15

    Rutkowski, D.T. et al. UPR pathways combine to prevent hepatic steatosis caused by ER stress–mediated suppression of transcriptional master regulators. Dev. Cell 15, 829–840 (2008).

  16. 16

    Ramanadham, S. et al. Apoptosis of insulin-secreting cells induced by endoplasmic reticulum stress is amplified by overexpression of group VIA calcium–independent phospholipase A2 (iPLA2 β) and suppressed by inhibition of iPLA2 β. Biochemistry 43, 918–930 (2004).

  17. 17

    Tessitore, A. et al. GM1-ganglioside–mediated activation of the unfolded protein response causes neuronal death in a neurodegenerative gangliosidosis. Mol. Cell 15, 753–766 (2004).

  18. 18

    Furuhashi, M. & Hotamisligil, G.S. Fatty acid–binding proteins: role in metabolic diseases and potential as drug targets. Nat. Rev. Drug Discov. 7, 489–503 (2008).

  19. 19

    Shum, B.O. et al. The adipocyte fatty acid–binding protein aP2 is required in allergic airway inflammation. J. Clin. Invest. 116, 2183–2192 (2006).

  20. 20

    Hotamisligil, G.S. et al. Uncoupling of obesity from insulin resistance through a targeted mutation in aP2, the adipocyte fatty acid binding protein. Science 274, 1377–1379 (1996).

  21. 21

    Uysal, K.T., Scheja, L., Wiesbrock, S.M., Bonner-Weir, S. & Hotamisligil, G.S. Improved glucose and lipid metabolism in genetically obese mice lacking aP2. Endocrinology 141, 3388–3396 (2000).

  22. 22

    Makowski, L. et al. Lack of macrophage fatty-acid–binding protein aP2 protects mice deficient in apolipoprotein E against atherosclerosis. Nat. Med. 7, 699–705 (2001).

  23. 23

    Cao, H. et al. Regulation of metabolic responses by adipocyte/macrophage fatty acid–binding proteins in leptin-deficient mice. Diabetes 55, 1915–1922 (2006).

  24. 24

    Ozcan, U. et al. Loss of the tuberous sclerosis complex tumor suppressors triggers the unfolded protein response to regulate insulin signaling and apoptosis. Mol. Cell 29, 541–551 (2008).

  25. 25

    Borradaile, N.M. et al. Disruption of endoplasmic reticulum structure and integrity in lipotoxic cell death. J. Lipid Res. 47, 2726–2737 (2006).

  26. 26

    Lai, E., Bikopoulos, G., Wheeler, M.B., Rozakis-Adcock, M. & Volchuk, A. Differential activation of ER stress and apoptosis in response to chronically elevated free fatty acids in pancreatic beta-cells. Am. J. Physiol. Endocrinol. Metab. 294, E540–E550 (2008).

  27. 27

    Schaffer, J.E. Lipotoxicity: when tissues overeat. Curr. Opin. Lipidol. 14, 281–287 (2003).

  28. 28

    Tuncman, G. et al. A genetic variant at the fatty acid–binding protein aP2 locus reduces the risk for hypertriglyceridemia, type 2 diabetes and cardiovascular disease. Proc. Natl. Acad. Sci. USA 103, 6970–6975 (2006).

  29. 29

    Furuhashi, M. et al. Treatment of diabetes and atherosclerosis by inhibiting fatty-acid–binding protein aP2. Nature 447, 959–965 (2007).

  30. 30

    Sha, R.S., Kane, C.D., Xu, Z., Banaszak, L.J. & Bernlohr, D.A. Modulation of ligand binding affinity of the adipocyte lipid-binding protein by selective mutation. Analysis in vitro and in situ. J. Biol. Chem. 268, 7885–7892 (1993).

  31. 31

    Makowski, L., Brittingham, K.C., Reynolds, J.M., Suttles, J. & Hotamisligil, G.S. The fatty acid-binding protein, aP2, coordinates macrophage cholesterol trafficking and inflammatory activity. Macrophage expression of aP2 impacts peroxisome proliferator-activated receptor γ and IκB kinase activities. J. Biol. Chem. 280, 12888–12895 (2005).

  32. 32

    Enoch, H.G., Catala, A. & Strittmatter, P. Mechanism of rat liver microsomal stearyl-CoA desaturase. Studies of the substrate specificity, enzyme-substrate interactions, and the function of lipid. J. Biol. Chem. 251, 5095–5103 (1976).

  33. 33

    Heinemann, F.S. & Ozols, J. Stearoyl-CoA desaturase, a short-lived protein of endoplasmic reticulum with multiple control mechanisms. Prostaglandins Leukot. Essent. Fatty Acids 68, 123–133 (2003).

  34. 34

    Cao, H. et al. Identification of a lipokine, a lipid hormone linking adipose tissue to systemic metabolism. Cell 134, 933–944 (2008).

  35. 35

    Joseph, S.B. et al. Direct and indirect mechanisms for regulation of fatty acid synthase gene expression by liver X receptors. J. Biol. Chem. 277, 11019–11025 (2002).

  36. 36

    Chu, K., Miyazaki, M., Man, W.C. & Ntambi, J.M. Stearoyl-coenzyme A desaturase 1 deficiency protects against hypertriglyceridemia and increases plasma high-density lipoprotein cholesterol induced by liver X receptor activation. Mol. Cell. Biol. 26, 6786–6798 (2006).

  37. 37

    Venkateswaran, A. et al. Human white/murine ABC8 mRNA levels are highly induced in lipid-loaded macrophages. A transcriptional role for specific oxysterols. J. Biol. Chem. 275, 14700–14707 (2000).

  38. 38

    Repa, J.J. et al. Regulation of absorption and ABC1-mediated efflux of cholesterol by RXR heterodimers. Science 289, 1524–1529 (2000).

  39. 39

    Joseph, S.B. et al. LXR-dependent gene expression is important for macrophage survival and the innate immune response. Cell 119, 299–309 (2004).

  40. 40

    Peet, D.J. et al. Cholesterol and bile acid metabolism are impaired in mice lacking the nuclear oxysterol receptor LXR alpha. Cell 93, 693–704 (1998).

  41. 41

    Aqel, N.M., Ball, R.Y., Waldmann, H. & Mitchinson, M.J. Monocytic origin of foam cells in human atherosclerotic plaques. Atherosclerosis 53, 265–271 (1984).

  42. 42

    Han, S. et al. Macrophage insulin receptor deficiency increases ER stress-induced apoptosis and necrotic core formation in advanced atherosclerotic lesions. Cell Metab. 3, 257–266 (2006).

  43. 43

    Boord, J.B. et al. Adipocyte fatty acid–binding protein, aP2, alters late atherosclerotic lesion formation in severe hypercholesterolemia. Arterioscler. Thromb. Vasc. Biol. 22, 1686–1691 (2002).

  44. 44

    Listenberger, L.L. et al. Triglyceride accumulation protects against fatty acid–induced lipotoxicity. Proc. Natl. Acad. Sci. USA 100, 3077–3082 (2003).

  45. 45

    Brown, J.M. et al. Inhibition of stearoyl-coenzyme A desaturase 1 dissociates insulin resistance and obesity from atherosclerosis. Circulation 118, 1467–1475 (2008).

  46. 46

    Rolph, M.S. et al. Regulation of dendritic cell function and T cell priming by the fatty acid–binding protein aP2. J. Immunol. 177, 7794–7801 (2006).

  47. 47

    Erbay, E., Cao, H. & Hotamisligil, G.S. Adipocyte/macrophage fatty acid binding proteins in metabolic syndrome. Curr. Atheroscler. Rep. 9, 222–229 (2007).

  48. 48

    Gregor, M.F. et al. Endoplasmic reticulum stress is reduced in tissues of obese subjects after weight loss. Diabetes 58, 693–700 (2009).

  49. 49

    Joseph, S.B. et al. LXR-dependent gene expression is important for macrophage survival and the innate immune response. Cell 119, 299–309 (2004).

  50. 50

    Furuhashi, M. et al. Treatment of diabetes and atherosclerosis by inhibiting fatty-acid-binding protein aP2. Nature 447, 959–965 (2007).

  51. 51

    Venkateswaran, A. et al. Human white/murine ABC8 mRNA levels are highly induced in lipid-loaded macrophages. A transcriptional role for oxysterols. J. Biol. Chem. 275, 14700–14707 (2000).

  52. 52

    Pan, W. On the use of permutation in and the performance of a class of nonparametric methods to detect differential gene expression. Bioinformatics 19, 1333–1340 (2003).

  53. 53

    Kuehl, R.O . Design of Experiments: Statistical Principles of Research Design and Analysis. 2nd edn., 56–58 (Duxbury Press, Pacific Grove, California, 2000).

Download references

Acknowledgements

This project has been supported by grants from the US National Institutes of Health DK DK52539 (to G.S.H.), HL65405 (to M.F.L. and G.S.H.) and DK59637 (Lipid, Lipoprotein and Atherosclerosis Core of the Vanderbilt Mouse Metabolic Phenotype Center). E.E. is supported by the Ruth Kirschstein National Research Award (F32 HL090258). We are grateful to the members of the Hotamisligil lab, J. Chen and R. Bachman for their scientific input and contributions, to A. Onur for technical assistance, to R. Foote and K. Gilbert for administrative support, to D. Mangelsdorf (University of Texas Southwestern) for TK-LXRE-X3luc reporter and Nr1h3−/− mice, and A. Edgar (Fournier) for the ACAT inhibitor. The pGEX-aP2-LM (R126L, Y128F) plasmid was a generous gift from D. Bernlohr (University of Minnesota).

Author information

E.E. developed the hypothesis, designed and performed the bulk of the experiments, analyzed all data and wrote the manuscript; V.R.B. contributed to the in vivo studies; J.R.M. contributed to the in vitro studies and conducted data analysis, K.N.C. and M.E.S. contributed to the in vitro studies; L.M., M.M.W. and S.M.W. contributed to the analysis of lipidomic data; S.F. and M.F.L. contributed to the analysis of in vivo data and assisted with writing; and G.S.H. developed the hypothesis, designed and analyzed all data, wrote the manuscript and supervised the project and the peer review process.

Correspondence to Gökhan S Hotamisligil.

Ethics declarations

Competing interests

G.S.H. is on the scientific advisory board of Syndexa Pharmaceuticals. M.M.W. and S.M.W. work for Lipomics, an organization for profit.

Supplementary information

Supplementary Text and Figures

Supplementary Figures 1–6 and Supplementary Table 1 (PDF 969 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Erbay, E., Babaev, V., Mayers, J. et al. Reducing endoplasmic reticulum stress through a macrophage lipid chaperone alleviates atherosclerosis. Nat Med 15, 1383–1391 (2009). https://doi.org/10.1038/nm.2067

Download citation

Further reading