Oxidized LDL upregulates angiotensin II type 1 receptor expression in cultured human coronary artery endothelial cells: the potential role of transcription factor NF-kappaB.
BACKGROUND
We demonstrated earlier that angiotensin II (Ang II), by AT(1) receptor activation, upregulates oxidized LDL (ox-LDL) endothelial receptor LOX-1 gene expression and uptake of ox-LDL in human coronary artery endothelial cells (HCAECs). In this study, we investigated the regulation of Ang II receptors (AT1R and AT2R) by ox-LDL and the role of the redox-sensitive transcription factor NF-kappaB in this process.


RESULTS
HCAECs were incubated with ox-LDL for 24 hours. Ox-LDL (10 to 40 microg protein/mL) upregulated AT1R but not AT2R, mRNA, or protein. Ox-LDL degraded IkappaBalpha in cytoplasm and activated transcription factor NF-kappaB (P65) in HCAEC nuclear extract. Treatment of cells with the antioxidant alpha-tocopherol (10 to 50 micromol/L) attenuated ox-LDL-mediated degradation of IkappaBalpha and activation of NF-kappaB (P65) and inhibited the upregulation of AT1R mRNA and protein. The role of NF-kappaB signal transduction was further examined by use of an NF-kappaB inhibitor, caffeic acid phenethyl ester (CAPE). Pretreatment of cells with CAPE inhibited ox-LDL-mediated degradation of IkappaBalpha and NF-kappaB activation and inhibited ox-LDL-induced upregulation of AT1R expression. Incubation of cells with both ox-LDL and Ang II increased cell injury, measured as cell viability and LDH release, compared with either ox-LDL or Ang II alone. alpha-Tocopherol as well as the specific AT1R blocker CV11974 (candesartan) attenuated the cell-injurious effects of ox-LDL.


CONCLUSIONS
These observations suggest an important role of ox-LDL-mediated AT1R upregulation in cell injury. In this process, NF-kappaB activation seems to play a critical role in signal transduction. These findings provide a basis for the use of antioxidants and AT1R blockers in designing therapy of atherosclerosis.
Li
D
D
Departments of Medicine and Physiology, University of Arkansas and VA Medical Center, Little Rock, USA.
Saldeen
T
T
Romeo
F
F
Mehta
J L
JL
D000804:Angiotensin II / Q000378:metabolism / Q000494:pharmacology; D057911:Angiotensin Receptor Antagonists; D001158:Arteries / Q000166:cytology / Q000378:metabolism; D002109:Caffeic Acids / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D020672:I-kappa B Proteins; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism* / Q000494:pharmacology; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives* / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology; D014810:Vitamin E / Q000378:metabolism / Q000494:pharmacology
D057911:Angiotensin Receptor Antagonists; D002109:Caffeic Acids; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D008077:Lipoproteins, LDL; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; C099252:oxidized low density lipoprotein; D000804:Angiotensin II; D000072000:NF-KappaB Inhibitor alpha; D014810:Vitamin E; D007770:L-Lactate Dehydrogenase; C055494:caffeic acid phenethyl ester; D010626:Phenylethyl Alcohol