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Activation of AMP-activated protein kinase inhibits oxidized LDL-triggered endoplasmic reticulum stress in vivo.

Dong Y, Zhang M, Wang S, Liang B, Zhao Z, Liu C, Wu M, Choi HC, Lyons TJ, Zou MH - Diabetes (2010)

Bottom Line: Exposure of BAECs to clinically relevant concentrations of HOG-LDL induced prolonged ER stress and reduced SERCA activity but increased SERCA oxidation.Likewise, AMPK activation by pharmacological (5'-aminoimidazole-4-carboxymide-1-beta-d-ribofuranoside, metformin, and statin) or genetic means (adenoviral overexpression of constitutively active AMPK mutants) significantly mitigated ER stress and SERCA oxidation and improved the endothelium-dependent relaxation in isolated mouse aortae.We conclude that HOG-LDL, via enhanced SERCA oxidation, causes aberrant ER stress, endothelial dysfunction, and atherosclerosis in vivo, all of which are inhibited by AMPK activation.

View Article: PubMed Central - PubMed

Affiliation: ection of Endocrinology and Diabetes, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA.

ABSTRACT

Objective: The oxidation of LDLs is considered a key step in the development of atherosclerosis. How LDL oxidation contributes to atherosclerosis remains poorly defined. Here we report that oxidized and glycated LDL (HOG-LDL) causes aberrant endoplasmic reticulum (ER) stress and that the AMP-activated protein kinase (AMPK) suppressed HOG-LDL-triggered ER stress in vivo.

Research design and methods: ER stress markers, sarcoplasmic/endoplasmic reticulum Ca(2+) ATPase (SERCA) activity and oxidation, and AMPK activity were monitored in cultured bovine aortic endothelial cells (BAECs) exposed to HOG-LDL or in isolated aortae from mice fed an atherogenic diet.

Results: Exposure of BAECs to clinically relevant concentrations of HOG-LDL induced prolonged ER stress and reduced SERCA activity but increased SERCA oxidation. Chronic administration of Tempol (a potent antioxidant) attenuated both SERCA oxidation and aberrant ER stress in mice fed a high-fat diet in vivo. Likewise, AMPK activation by pharmacological (5'-aminoimidazole-4-carboxymide-1-beta-d-ribofuranoside, metformin, and statin) or genetic means (adenoviral overexpression of constitutively active AMPK mutants) significantly mitigated ER stress and SERCA oxidation and improved the endothelium-dependent relaxation in isolated mouse aortae. Finally, Tempol administration markedly attenuated impaired endothelium-dependent vasorelaxation, SERCA oxidation, ER stress, and atherosclerosis in ApoE(-/-) and ApoE(-/-)/AMPKalpha2(-/-) fed a high-fat diet.

Conclusion: We conclude that HOG-LDL, via enhanced SERCA oxidation, causes aberrant ER stress, endothelial dysfunction, and atherosclerosis in vivo, all of which are inhibited by AMPK activation.

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Genetic activation or inhibition of AMPK alters HOG-LDL–induced ER stress in ex vivo aortae. A: Aortic rings were cut (∼3-mm length) and pretreated with 2 mmol/l metformin or 50 μmol/l simvastatin for 30 min, followed by addition of 100 μg/ml HOG-LDL or N-LDL (latter as control), with or without metformin or statin for up to 6 h. *P < 0.05 metformin or statin vs. controls; #P < 0.05 controls vs. metformin plus HOG-LDL or statin plus HOG-LDL. B and C: ER stress markers were detected from set (A); n ≥ 4 in each treatment. *P < 0.01 HOG-LDL vs. N-LDL; #P < 0.01 HOG-LDL+metformin or HOG-LDL+statin vs. HOG-LDL alone. D: HOG-LDL impaired aortic relaxation, which can be restored by metformin or statin. n = 4 in each group. *P < 0.05 HOG-LDL vs. N-LDL or HOG-LDL+metformin or HOG-LDL+statin.
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Figure 6: Genetic activation or inhibition of AMPK alters HOG-LDL–induced ER stress in ex vivo aortae. A: Aortic rings were cut (∼3-mm length) and pretreated with 2 mmol/l metformin or 50 μmol/l simvastatin for 30 min, followed by addition of 100 μg/ml HOG-LDL or N-LDL (latter as control), with or without metformin or statin for up to 6 h. *P < 0.05 metformin or statin vs. controls; #P < 0.05 controls vs. metformin plus HOG-LDL or statin plus HOG-LDL. B and C: ER stress markers were detected from set (A); n ≥ 4 in each treatment. *P < 0.01 HOG-LDL vs. N-LDL; #P < 0.01 HOG-LDL+metformin or HOG-LDL+statin vs. HOG-LDL alone. D: HOG-LDL impaired aortic relaxation, which can be restored by metformin or statin. n = 4 in each group. *P < 0.05 HOG-LDL vs. N-LDL or HOG-LDL+metformin or HOG-LDL+statin.

Mentions: To further test the role of AMPK in response to HOG-LDL–induced ER stress and consequent vascular dysfunction, we assayed the effects of metformin and statins, two clinically used AMPK activators, in isolated aortas ex vivo. Metformin or simvastatin was added 30 min prior to HOG-LDL exposure. As shown in Fig. 6A, both metformin and statin treatment activated AMPK when aortic rings were incubated with or without HOG-LDL. HOG-LDL induced ER stress, as indicated by stress markers p-PERK and p-eIF2α (Fig. 6B). Pretreatment of isolated aortae with metformin or statins ablated the effects of HOG-LDL on ER stress (Fig. 6B and C).


Activation of AMP-activated protein kinase inhibits oxidized LDL-triggered endoplasmic reticulum stress in vivo.

Dong Y, Zhang M, Wang S, Liang B, Zhao Z, Liu C, Wu M, Choi HC, Lyons TJ, Zou MH - Diabetes (2010)

Genetic activation or inhibition of AMPK alters HOG-LDL–induced ER stress in ex vivo aortae. A: Aortic rings were cut (∼3-mm length) and pretreated with 2 mmol/l metformin or 50 μmol/l simvastatin for 30 min, followed by addition of 100 μg/ml HOG-LDL or N-LDL (latter as control), with or without metformin or statin for up to 6 h. *P < 0.05 metformin or statin vs. controls; #P < 0.05 controls vs. metformin plus HOG-LDL or statin plus HOG-LDL. B and C: ER stress markers were detected from set (A); n ≥ 4 in each treatment. *P < 0.01 HOG-LDL vs. N-LDL; #P < 0.01 HOG-LDL+metformin or HOG-LDL+statin vs. HOG-LDL alone. D: HOG-LDL impaired aortic relaxation, which can be restored by metformin or statin. n = 4 in each group. *P < 0.05 HOG-LDL vs. N-LDL or HOG-LDL+metformin or HOG-LDL+statin.
© Copyright Policy - creative-commons
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Figure 6: Genetic activation or inhibition of AMPK alters HOG-LDL–induced ER stress in ex vivo aortae. A: Aortic rings were cut (∼3-mm length) and pretreated with 2 mmol/l metformin or 50 μmol/l simvastatin for 30 min, followed by addition of 100 μg/ml HOG-LDL or N-LDL (latter as control), with or without metformin or statin for up to 6 h. *P < 0.05 metformin or statin vs. controls; #P < 0.05 controls vs. metformin plus HOG-LDL or statin plus HOG-LDL. B and C: ER stress markers were detected from set (A); n ≥ 4 in each treatment. *P < 0.01 HOG-LDL vs. N-LDL; #P < 0.01 HOG-LDL+metformin or HOG-LDL+statin vs. HOG-LDL alone. D: HOG-LDL impaired aortic relaxation, which can be restored by metformin or statin. n = 4 in each group. *P < 0.05 HOG-LDL vs. N-LDL or HOG-LDL+metformin or HOG-LDL+statin.
Mentions: To further test the role of AMPK in response to HOG-LDL–induced ER stress and consequent vascular dysfunction, we assayed the effects of metformin and statins, two clinically used AMPK activators, in isolated aortas ex vivo. Metformin or simvastatin was added 30 min prior to HOG-LDL exposure. As shown in Fig. 6A, both metformin and statin treatment activated AMPK when aortic rings were incubated with or without HOG-LDL. HOG-LDL induced ER stress, as indicated by stress markers p-PERK and p-eIF2α (Fig. 6B). Pretreatment of isolated aortae with metformin or statins ablated the effects of HOG-LDL on ER stress (Fig. 6B and C).

Bottom Line: Exposure of BAECs to clinically relevant concentrations of HOG-LDL induced prolonged ER stress and reduced SERCA activity but increased SERCA oxidation.Likewise, AMPK activation by pharmacological (5'-aminoimidazole-4-carboxymide-1-beta-d-ribofuranoside, metformin, and statin) or genetic means (adenoviral overexpression of constitutively active AMPK mutants) significantly mitigated ER stress and SERCA oxidation and improved the endothelium-dependent relaxation in isolated mouse aortae.We conclude that HOG-LDL, via enhanced SERCA oxidation, causes aberrant ER stress, endothelial dysfunction, and atherosclerosis in vivo, all of which are inhibited by AMPK activation.

View Article: PubMed Central - PubMed

Affiliation: ection of Endocrinology and Diabetes, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA.

ABSTRACT

Objective: The oxidation of LDLs is considered a key step in the development of atherosclerosis. How LDL oxidation contributes to atherosclerosis remains poorly defined. Here we report that oxidized and glycated LDL (HOG-LDL) causes aberrant endoplasmic reticulum (ER) stress and that the AMP-activated protein kinase (AMPK) suppressed HOG-LDL-triggered ER stress in vivo.

Research design and methods: ER stress markers, sarcoplasmic/endoplasmic reticulum Ca(2+) ATPase (SERCA) activity and oxidation, and AMPK activity were monitored in cultured bovine aortic endothelial cells (BAECs) exposed to HOG-LDL or in isolated aortae from mice fed an atherogenic diet.

Results: Exposure of BAECs to clinically relevant concentrations of HOG-LDL induced prolonged ER stress and reduced SERCA activity but increased SERCA oxidation. Chronic administration of Tempol (a potent antioxidant) attenuated both SERCA oxidation and aberrant ER stress in mice fed a high-fat diet in vivo. Likewise, AMPK activation by pharmacological (5'-aminoimidazole-4-carboxymide-1-beta-d-ribofuranoside, metformin, and statin) or genetic means (adenoviral overexpression of constitutively active AMPK mutants) significantly mitigated ER stress and SERCA oxidation and improved the endothelium-dependent relaxation in isolated mouse aortae. Finally, Tempol administration markedly attenuated impaired endothelium-dependent vasorelaxation, SERCA oxidation, ER stress, and atherosclerosis in ApoE(-/-) and ApoE(-/-)/AMPKalpha2(-/-) fed a high-fat diet.

Conclusion: We conclude that HOG-LDL, via enhanced SERCA oxidation, causes aberrant ER stress, endothelial dysfunction, and atherosclerosis in vivo, all of which are inhibited by AMPK activation.

Show MeSH
Related in: MedlinePlus