OxLDL-dependent activation of arginase II is dependent on the LOX-1 receptor and downstream RhoA signaling.
OBJECTIVE
Arginase II regulates NOS activity by competing for the substrate l-arginine. Oxidized LDL (OxLDL) is a proatherogenic molecule that activates arginase II. We tested the hypotheses that OxLDL-dependent arginase II activation occurs through a specific receptor, and via a Rho GTPase effector mechanism that is inhibited by statins.


RESULTS
Arginase II activation by OxLDL was attenuated following preincubation with the LOX-1 receptor-blocking antibody JTX92. This also prevented the dissociation of arginase II from microtubules. LOX-1(-/-) mice failed to exhibit the increased arginase II activity seen in WT mice fed a high cholesterol diet. Furthermore, endothelium from LOX-1(-/-) mice failed to demonstrate the diet-dependent reduction in NO and increase in ROS that were observed in WT mice. OxLDL induced Rho translocation to the membrane and Rho activation, and these effects were inhibited by pretreatment with JTX92 or statins. Transfection with siRNA for RhoA, or inhibition of ROCK both decreased OxLDL-stimulated arginase II activation. Preincubation with simvastatin or lovastatin blocked OxLDL-induced dissociation of arginase II from microtubules and prevented microtubule depolymerization.


CONCLUSIONS
This study provides a new focus for preventive therapy for atherosclerotic disease by delineating a clearer path from OxLDL through the endothelial cell LOX-1 receptor, RhoA, and ROCK, to the activation of arginase II, downregulation of NO, and vascular dysfunction.
Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins Medical Institutions, Baltimore, MD 21287-4904, United States.
Sungwoo
S
Ryoo
Anil
A
Bhunia
Fumin
F
Chang
Artin
A
Shoukas
Dan E
DE
Berkowitz
Lewis H
LH
Romer
D000818:Animals; D001119:Arginase / Q000378:metabolism*; D050197:Atherosclerosis / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics; D002478:Cells, Cultured; D002791:Cholesterol, Dietary / Q000378:metabolism; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology*; D004789:Enzyme Activation; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008148:Lovastatin / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008870:Microtubules / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D021381:Protein Transport; D034622:RNA Interference; D051127:Scavenger Receptors, Class E / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D019821:Simvastatin / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D014162:Transfection; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
D002791:Cholesterol, Dietary; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D008077:Lipoproteins, LDL; C495137:OLR1 protein, human; C495138:Olr1 protein, mouse; D051127:Scavenger Receptors, Class E; C099252:oxidized low density lipoprotein; D013481:Superoxides; C066737:RHOA protein, human; D009569:Nitric Oxide; D008148:Lovastatin; D019821:Simvastatin; C477631:ARG2 protein, human; D001119:Arginase; D020742:rhoA GTP-Binding Protein