Phosphorylation of Nox1 Regulates Association With NoxA1 Activation Domain

Rationale: Activation of Nox1 initiates redox-dependent signaling events crucial in the pathogenesis of vascular disease. Selective targeting of Nox1 is an attractive potential therapy, but requires a better understanding of the molecular modifications controlling its activation.

Objective: To determine whether posttranslational modifications of Nox1 regulate its activity in vascular cells. Methods and Results: We first found evidence that Nox1 is phosphorylated in multiple models of vascular disease. Next, studies using mass spectroscopy and a pharmacological inhibitor demonstrated that protein kinase C-beta1 mediates phosphorylation of Nox1 in response to tumor necrosis factor-α. siRNA-mediated silencing of protein kinase C-beta1 abolished tumor necrosis factor-α–mediated reactive oxygen species production and vascular smooth muscle cell migration. Site-directed mutagenesis and isothermal titration calorimetry indicated that protein kinase C-beta1 phosphorylates Nox1 at threonine 429. Moreover, Nox1 threonine 429 phosphorylation facilitated the association of Nox1 with the NoxA1 activation domain and was necessary for NADPH oxidase complex assembly, reactive oxygen species production, and vascular smooth muscle cell migration.

Conclusions: We conclude that protein kinase C-beta1 phosphorylation of threonine 429 regulates activation of Nox1 NADPH oxidase.

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Opportunity nox: the future of NADPH oxidases as therapeutic targets in cardiovascular disease

Over 40 years ago, NADPH (nicotinamide adenine dinucleotide phosphate) oxidase 2 (Nox2) was discovered in phagocytes and found to be essential in innate immunity. More than 20 years passed before additional Nox isoforms were discovered; and since then, studies have revealed that several of these isoforms (Nox1, Nox2, Nox4, and Nox5) are found in human cardiac and vascular cells and contribute to the pathogenesis of cardiovascular diseases (CVDs). Recently, major efforts have focused on identifying inhibitors capable of ameliorating Nox-mediated CVD. In this review, we briefly discuss the role of each Nox isoform in CVD, identify steps in Nox signaling that will serve as potential targets for the design of therapeutics, and highlight innovative strategies likely to yield effective Nox inhibitors within the next decade.

Smooth Muscle Cell-targeted RNA Aptamer Inhibits Neointimal Formation

Inhibition of vascular smooth muscle cell (VSMC) proliferation by drug eluting stents has markedly reduced intimal hyperplasia and subsequent in-stent restenosis. However, the effects of antiproliferative drugs on endothelial cells (EC) contribute to delayed re-endothelialization and late stent thrombosis. Cell-targeted therapies to inhibit VSMC remodeling while maintaining EC health are necessary to allow vascular healing while preventing restenosis. We describe an RNA aptamer (Apt 14) that functions as a smart drug by preferentially targeting VSMCs as compared to ECs and other myocytes. Furthermore, Apt 14 inhibits phosphatidylinositol 3-kinase/protein kinase-B (PI3K/Akt) and VSMC migration in response to multiple agonists by a mechanism that involves inhibition of platelet-derived growth factor receptor (PDGFR)-β phosphorylation. In a murine model of carotid injury, treatment of vessels with Apt 14 reduces neointimal formation to levels similar to those observed with paclitaxel. Importantly, we confirm that Apt 14 cross-reacts with rodent and human VSMCs, exhibits a half-life of ~300 hours in human serum, and does not elicit immune activation of human peripheral blood mononuclear cells. We describe a VSMC-targeted RNA aptamer that blocks cell migration and inhibits intimal formation. These findings provide the foundation for the translation of cell-targeted RNA therapeutics to vascular disease.

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