NADPH oxidase 4 is required for interleukin-1β-mediated activation of protein kinase Cδ and downstream activation of c-jun N-terminal kinase signaling in smooth muscle

Reactive oxygen species (ROS) are generated in the vascular wall upon stimulation by proinflammatory cytokines and are important mediators of diverse cellular responses that occur as a result of vascular injury. Members of the NADPH oxidase (NOX) family of proteins have been identified in vascular smooth muscle (VSM) cells as important sources of ROS. In this study, we tested the hypothesis that NOX4 is a proximal mediator of IL-1 beta-dependent activation of PKC delta and increases IL-1 beta-stimulated c-Jun kinase (INK) signaling in primary rat aortic VSM cells. We found that stimulation of VSM cells with IL-1 beta increased PKC delta activity and intracellular ROS generation. SiRNA silencing of NOX4 but not NOX1 ablated the IL-1 beta-dependent increase in ROS production. Pharmacological inhibition of PKC delta activity as well as siRNA depletion of PKC delta or NOX4 blocked the IL-1 beta-dependent activation of JNK. Further studies showed that the IL-1 beta-dependent upregulation of inducible NO synthase expression was inhibited through JNK inhibition and NOX4 silencing. Taken together, these results indicate that IL-1 beta-dependent activation of PKC delta is modulated by NOX4-derived ROS. Our study positions PKC delta as an important redox-sensitive mediator of IL-1 beta-dependent signaling and downstream activation of inflammatory mediators in VSM cells. (C) 2012 Elsevier Inc. All rights reserved.