Pulsatile versus oscillatory shear stress regulates NADPH oxidase subunit expression: implication for native LDL oxidation.
Shear stress regulates endothelial nitric oxide and superoxide (O2-*) production, implicating the role of NADPH oxidase activity. It is unknown whether shear stress regulates the sources of reactive species production, consequent low-density lipoprotein (LDL) modification, and initiation of inflammatory events. Bovine aortic endothelial cells (BAECs) in the presence of 50 microg/mL of native LDL were exposed to (1) pulsatile flow with a mean shear stress (tau(ave)) of 25 dyne/cm2 and (2) oscillating flow at tau(ave) of 0. After 4 hours, aliquots of culture medium were collected for high-performance liquid chromatography analyses of electronegative LDL species, described as LDL- and LDL2-. In response to oscillatory shear stress, gp91phox mRNA expression was upregulated by 2.9+/-0.3-fold, and its homologue, Nox4, by 3.9+/-0.9-fold (P<0.05, n=4), with a corresponding increase in O2-* production rate. The proportion of LDL- and LDL2- relative to static conditions increased by 67+/-17% and 30+/-7%, respectively, with the concomitant upregulation of monocyte chemoattractant protein-1 expression and increase in monocyte/BAEC binding (P<0.05, n=5). In contrast, pulsatile flow downregulated both gp91phox and Nox4 mRNA expression (by 1.8+/-0.2-fold and 3.0+/-0.12-fold, respectively), with an accompanying reduction in O2-* production, reduction in the extent of LDL modification (51+/-12% for LDL- and 30+/-7% for LDL2-), and monocyte/BAEC binding. The flow-dependent LDL oxidation is determined in part by the NADPH oxidase activity. The formation of modified LDL via O2-* production may also affect the regulation of monocyte chemoattractant protein-1 expression and monocyte/BAEC binding.
Department of Biomedical Engineering and Division of Cardiovascular Medicine, University of Southern California, Los Angeles, Calif, USA.
Juliana
J
Hwang
Michael H
MH
Ing
Adler
A
Salazar
Bernard
B
Lassègue
Kathy
K
Griendling
Mohamad
M
Navab
Alex
A
Sevanian
Tzung K
TK
Hsiai
D000818:Animals; D002417:Cattle; D002448:Cell Adhesion; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism; D003847:Deoxyglucose / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004996:Ethidium / Q000031:analogs & derivatives* / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D008077:Lipoproteins, LDL / Q000378:metabolism; D009000:Monocytes / Q000166:cytology; D019255:NADPH Oxidases / Q000235:genetics* / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D010084:Oxidation-Reduction; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D011673:Pulsatile Flow; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013314:Stress, Mechanical; D013481:Superoxides / Q000378:metabolism
D018932:Chemokine CCL2; D008077:Lipoproteins, LDL; D021122:Protein Subunits; D012333:RNA, Messenger; C067883:dihydroethidium; D013481:Superoxides; D003847:Deoxyglucose; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D019255:NADPH Oxidases; D004996:Ethidium