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

Abstract

Reactive oxygen species (ROS) are generated in the vascular wall upon stimulation by pro-inflammatory cytokines and are important mediators of diverse cellular responses that occur as a result of vascular injury. Member of the NADPH oxidase (NOX) family of proteins have been identified in vascular smooth muscle cells (VSM) as important sources of ROS. In this study, we tested the hypothesis that NOX4 is a proximal mediator of IL-1β-dependent activation of PKCδ and increases IL-1β stimulated c-Jun kinase (JNK) signaling in primary rat aortic VSM cells. We found that stimulation of VSM cells with IL-1β increased PKCδ activity and intracellular ROS generation. SiRNA silencing of NOX4 but not NOX1 ablated the IL-1β-dependent increase in ROS production. Pharmacological inhibition of PKCδ activity as well as siRNA depletion of PKCδ or NOX4 blocked the IL-1β-dependent activation of JNK. Further studies showed that the IL-1β-dependent upregulation of iNOS expression was inhibited through JNK inhibition and NOX4 silencing. Taken together, these results indicate that IL-1β-dependent activation of PKCδ is modulated by NOX4-derived ROS. Our study positions PKCδ as an important redox sensitive mediator of IL-1β-dependent signaling and downstream activation of inflammatory mediators in VSM cells.

Loss of angiotensin II receptor expression in dopamine neurons in Parkinson’s disease correlates with pathological progression and is accompanied by increases in Nox4- and 8-OH guanosine-related nucleic acid oxidation and caspase-3 activation

“…An example of the deleterious role of Nox4 in the brain comes from studies of ischemic stroke, where Nox4 is a major source of oxidative stress, a finding supported by the observations that pharmacological as well as genetic inhibition of Nox4 in a mouse model of stroke prevents oxidative stress and neurodegeneration [ 36 ]. In addition to its role in oxidation, Nox4 promotes inflammation as reported by Ginnan and colleagues in smooth muscle cells where Nox4 is required for interleukin 1β-mediated activation of protein kinase C and of c-jun N-terminal kinase [ 37 ].…”

The role of oxidative stress during inflammatory processes

“…ROS produced by NOXs regulate multiple cellular (e.g., differentiation, proliferation, and migration) and physiological (e.g., vascular tone, oxygen sensing) processes (Drummond et al, 2011;Segal et al, 2012). Excess ROS production and oxidative stress occurs when overactivation of NOX occurs in response to stimuli as diverse as hyperglycemia, angiotensin II, growth factors, hormones (Schramm et al, 2012), and most significantly inflammatory cytokines such as interleukin (IL)-1β (Ginnan et al, 2013) and TNFα (Frey et al, 2002). In addition, activated neutrophils and macrophages produce large amounts of ROS through the activation of NOX2 during the so-called oxidative burst, which is essential for eliminating invading pathogens but which may also become a significant pathway of tissue injury under sterile inflammatory conditions associated with the activation of phagoyctes (Segal et al, 2012).…”

A Potential Link Between Oxidative Stress and Endothelial-to-Mesenchymal Transition in Systemic Sclerosis

“…Cytokines can also modulate ROS generation by influencing the cellular concentrations of NOX at both RNA and protein levels, as well as by improving both stability and NOX translocation to the cell membrane by stimulating the phosphorylation of NOX complex's components ( 42 ). For instance, in rat aortic smooth muscle cells, production of ROS by IL-1β is mediated by NOX4 ( 43 ). Although IL1-β induces its expression ( 44 ), NOX1 does not appear to be involved in IL1-β-induced ROS production ( 43 ).…”