c-Jun N-terminal kinase attenuates TNFα signaling by reducing Nox1-dependent endosomal ROS production in vascular smooth muscle cells

Tumor necrosis factor-alpha (INF alpha), a proinflammatory cytokine, causes vascular smooth muscle cell (VSMC) proliferation and migration and promotes inflammatory vascular lesions. Nuclear factor-kappa B (NF-kappa B) activation by TNF alpha requires endosomal superoxide production by Nox1. In endothelial cells, TNFa stimulates c-Jun N-terminal kinase (INK), which inhibits NF-kappa B signaling. The mechanism by which JNK negatively regulates TNF alpha-induced NF-kappa B activation has not been defined. We hypothesized that JNK modulates NF-kappa B activation in VSMC, and does so via a Nox1-dependent mechanism. TNF alpha-induced NF-kappa B activation was TNFR1- and endocytosis-dependent. Inhibition of endocytosis with dominant-negative dynamin (DynK44A) potentiated TNF alpha-induced JNK activation, but decreased ERK activation, while p38 kinase phosphorylation was not altered. DynK44A attenuated intracellular, endosomal superoxide production in wild-type (WT) VSMC, but not in NADPH oxidase 1 (Nox1) knockout (KO) cells siRNA targeting JNK1 or JNK2 potentiated, while a JNK activator (anisomycin) inhibited, TNF alpha-induced NF-kappa B activation in WT, but not in Nox1 KO cells. TNF alpha-stimulated superoxide generation was enhanced by JNK1 inhibition in WT, but not in Nox1 KO VSMC. These data suggest that JNK suppresses the inflammatory response to TNF alpha by reducing Nox1-dependent endosomal ROS production. JNK and endosomal superoxide may represent novel targets for pharmacologic modulation of TNF alpha signaling and vascular inflammation. (C) 2015 Elsevier Inc. All rights reserved.