Limits...
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.

Show MeSH

Related in: MedlinePlus

AMPK activation by AICAR suppresses HOG-LDL–induced ER stress and protects SERCA activity. BAECs were treated with HOG-LDL, with or without AICAR preincubation (1 mmol/l, 30 min). A: AICAR increases AMPK phosphorylation at Thr172 in BAECs. n = 3. *P < 0.05 HOG-LDL-3 h vs. 0 h control; #P < 0.01 AICAR+HOG-LDL vs. HOG-LDL alone at times indicated. B: AICAR suppresses the rise of intracellular [Ca2+]i in BAECs at 6 h. n = 3. *P < 0.05 HOG-LDL vs. control or N-LDL; #P < 0.05 HOG-LDL+AICAR vs. HOG-LDL alone. C: AICAR suppresses HOG-LDL–induced ER stress in BAECs. n = 4. D: AICAR pretreatment inhibited NADPH oxidase activation by blocking p47 translocation. n = 3. *P < 0.05 HOG-LDL vs. N-LDL in cytosol and membrane portion; # and † indicate P < 0.05 AICAR pretreatment completely blocked p47 translocation by HOG-LDL in cytosol and membrane, respectively. E: AICAR protects SERCA activity under HOG-LDL treatment. n = 4. *P < 0.05 AICAR treatment vs. N-LDL or control samples; #P < 0.05 HOG-LDL vs. N-LDL or control; †P < 0.05 AICAR+HOG-LDL vs. HOG-LDL alone. F: Ratiometric measurement of intracellular Ca2+. BAECs were treated with 100 μg/ml N-LDL, 100 μg/ml HOG-LDL, and AICAR (pretreated for 30 min)+HOG-LDL for 6 h. Ratiometric measurement of intracellular Ca2+ was done as described in the “Research Design and Methods” section. The small arrows indicate the timing for cytosolic Ca2+ return to its homeostasis. n = 6.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2874699&req=5

Figure 4: AMPK activation by AICAR suppresses HOG-LDL–induced ER stress and protects SERCA activity. BAECs were treated with HOG-LDL, with or without AICAR preincubation (1 mmol/l, 30 min). A: AICAR increases AMPK phosphorylation at Thr172 in BAECs. n = 3. *P < 0.05 HOG-LDL-3 h vs. 0 h control; #P < 0.01 AICAR+HOG-LDL vs. HOG-LDL alone at times indicated. B: AICAR suppresses the rise of intracellular [Ca2+]i in BAECs at 6 h. n = 3. *P < 0.05 HOG-LDL vs. control or N-LDL; #P < 0.05 HOG-LDL+AICAR vs. HOG-LDL alone. C: AICAR suppresses HOG-LDL–induced ER stress in BAECs. n = 4. D: AICAR pretreatment inhibited NADPH oxidase activation by blocking p47 translocation. n = 3. *P < 0.05 HOG-LDL vs. N-LDL in cytosol and membrane portion; # and † indicate P < 0.05 AICAR pretreatment completely blocked p47 translocation by HOG-LDL in cytosol and membrane, respectively. E: AICAR protects SERCA activity under HOG-LDL treatment. n = 4. *P < 0.05 AICAR treatment vs. N-LDL or control samples; #P < 0.05 HOG-LDL vs. N-LDL or control; †P < 0.05 AICAR+HOG-LDL vs. HOG-LDL alone. F: Ratiometric measurement of intracellular Ca2+. BAECs were treated with 100 μg/ml N-LDL, 100 μg/ml HOG-LDL, and AICAR (pretreated for 30 min)+HOG-LDL for 6 h. Ratiometric measurement of intracellular Ca2+ was done as described in the “Research Design and Methods” section. The small arrows indicate the timing for cytosolic Ca2+ return to its homeostasis. n = 6.

Mentions: We had reported that AMPK activation by AICAR reduces oxidative stress in diabetes (35). It was therefore interesting to investigate whether AMPK activation alleviated SERCA oxidation and consequent ER stress caused by HOG-LDL. Short exposure (<3 h) of BAECs to HOG-LDL (100 μg/ml) markedly increased the detection of AMPK phosphorylation at Thr172 (Fig. 4A), an index for AMPK activation. AICAR significantly enhanced AMPK Thr172 phosphorylation caused by HOG-LDL alone (Fig. 4A).


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)

AMPK activation by AICAR suppresses HOG-LDL–induced ER stress and protects SERCA activity. BAECs were treated with HOG-LDL, with or without AICAR preincubation (1 mmol/l, 30 min). A: AICAR increases AMPK phosphorylation at Thr172 in BAECs. n = 3. *P < 0.05 HOG-LDL-3 h vs. 0 h control; #P < 0.01 AICAR+HOG-LDL vs. HOG-LDL alone at times indicated. B: AICAR suppresses the rise of intracellular [Ca2+]i in BAECs at 6 h. n = 3. *P < 0.05 HOG-LDL vs. control or N-LDL; #P < 0.05 HOG-LDL+AICAR vs. HOG-LDL alone. C: AICAR suppresses HOG-LDL–induced ER stress in BAECs. n = 4. D: AICAR pretreatment inhibited NADPH oxidase activation by blocking p47 translocation. n = 3. *P < 0.05 HOG-LDL vs. N-LDL in cytosol and membrane portion; # and † indicate P < 0.05 AICAR pretreatment completely blocked p47 translocation by HOG-LDL in cytosol and membrane, respectively. E: AICAR protects SERCA activity under HOG-LDL treatment. n = 4. *P < 0.05 AICAR treatment vs. N-LDL or control samples; #P < 0.05 HOG-LDL vs. N-LDL or control; †P < 0.05 AICAR+HOG-LDL vs. HOG-LDL alone. F: Ratiometric measurement of intracellular Ca2+. BAECs were treated with 100 μg/ml N-LDL, 100 μg/ml HOG-LDL, and AICAR (pretreated for 30 min)+HOG-LDL for 6 h. Ratiometric measurement of intracellular Ca2+ was done as described in the “Research Design and Methods” section. The small arrows indicate the timing for cytosolic Ca2+ return to its homeostasis. n = 6.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2874699&req=5

Figure 4: AMPK activation by AICAR suppresses HOG-LDL–induced ER stress and protects SERCA activity. BAECs were treated with HOG-LDL, with or without AICAR preincubation (1 mmol/l, 30 min). A: AICAR increases AMPK phosphorylation at Thr172 in BAECs. n = 3. *P < 0.05 HOG-LDL-3 h vs. 0 h control; #P < 0.01 AICAR+HOG-LDL vs. HOG-LDL alone at times indicated. B: AICAR suppresses the rise of intracellular [Ca2+]i in BAECs at 6 h. n = 3. *P < 0.05 HOG-LDL vs. control or N-LDL; #P < 0.05 HOG-LDL+AICAR vs. HOG-LDL alone. C: AICAR suppresses HOG-LDL–induced ER stress in BAECs. n = 4. D: AICAR pretreatment inhibited NADPH oxidase activation by blocking p47 translocation. n = 3. *P < 0.05 HOG-LDL vs. N-LDL in cytosol and membrane portion; # and † indicate P < 0.05 AICAR pretreatment completely blocked p47 translocation by HOG-LDL in cytosol and membrane, respectively. E: AICAR protects SERCA activity under HOG-LDL treatment. n = 4. *P < 0.05 AICAR treatment vs. N-LDL or control samples; #P < 0.05 HOG-LDL vs. N-LDL or control; †P < 0.05 AICAR+HOG-LDL vs. HOG-LDL alone. F: Ratiometric measurement of intracellular Ca2+. BAECs were treated with 100 μg/ml N-LDL, 100 μg/ml HOG-LDL, and AICAR (pretreated for 30 min)+HOG-LDL for 6 h. Ratiometric measurement of intracellular Ca2+ was done as described in the “Research Design and Methods” section. The small arrows indicate the timing for cytosolic Ca2+ return to its homeostasis. n = 6.
Mentions: We had reported that AMPK activation by AICAR reduces oxidative stress in diabetes (35). It was therefore interesting to investigate whether AMPK activation alleviated SERCA oxidation and consequent ER stress caused by HOG-LDL. Short exposure (<3 h) of BAECs to HOG-LDL (100 μg/ml) markedly increased the detection of AMPK phosphorylation at Thr172 (Fig. 4A), an index for AMPK activation. AICAR significantly enhanced AMPK Thr172 phosphorylation caused by HOG-LDL alone (Fig. 4A).

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