OxLDL-dependent activation of arginase II is dependent on the LOX-1 receptor and downstream RhoA signaling

Abstract

Aims 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. Methods and 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−/− 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.

Oxidized LDL signals through Rho-GTPase to induce endothelial cell stiffening and promote capillary formation

“…1D). OxLDL-induced RhoA activation is dose-dependent, increasing significantly between 10 and 100 g/ml oxLDL, a typical range used in earlier in vitro studies (4,19,23,24,26), at a peak exposure time of 15 min (Fig. 1B, E).…”

“…It is also generally believed that the level of oxLDL within the vascular wall, particularly within an atherosclerotic plaque, might be significantly higher than circulating oxLDL, but further studies are required to provide the quantitative analysis. Similarly to previous studies from our laboratory and from other investigators (19,23,24,26), we use a range of 10-100 g/ml oxLDL, which has been shown to cause endothelial stiffening (3,4). Importantly, our earlier studies showed that diet-induced dyslipidemia in a porcine model What are the functional implications of oxLDL-induced endothelial stiffening?…”

“…Previous studies suggested that lectin-like Lox1 is the principal oxLDL receptor in ECs (36). It was also shown that downregulation of Lox1 inhibits activation of RhoA in ECs (23,24). On the other hand, CD36 was shown to be critical for oxLDL-induced regulation of macrophage migration and polarity (27,37).…”

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“…The formation of pores in the endothelium and hyperpermeability in the lungs (as occurs in severe pneumonia) can increase intracellular calcium concentration, activating protein kinase C (PKCα), which activates RhoA/ROCK to elevate ARG expression [67]. Similarly, the atherogenic stimulus oxLDL acts via the RhoA effectors ROCK and mDia1 to activate L-arginine catabolism by augmenting ARG levels [50]. Microgravity conditions activate the p38 MAPK (mitogenactivated protein kinase)-C/EBPβ pathway [68].…”

Pulmonary Hypertension Is a Probable NO/ONOO−Cycle Disease: A Review

“…Jin et al [174] showed that various free radicals and reactive oxygen species increased RhoA/Rho-kinase signaling. Ryoo et al [175] showed that oxidative stress, acting through oxidized LDL, stimulated RhoA signaling.…”