TNFα receptor 1 causes endocytosis‐dependent NF‐κB and ‐ independent JNK activation in vascular smooth muscle cells

Abstract

Tumor necrosis factor‐α (TNFα), a pro‐inflammatory cytokine can cause either vascular smooth muscle cell (VSMC) apoptosis (JNK‐dependent) or proliferation (NF‐κB‐dependent). We hypothesized that TNFα receptor 1 (TNFR1) endocytosis balances these two pathways. We quantified NF‐κB activation and MAPK (JNK, p38, ERK1/2) phosphorylation by TNFα in the presence of siRNA targeting TNFR1 or 2 in cultured murine mesenteric VSMC. Both NF‐κB activation (Fig. 1, n=3–4) and JNK phosphorylation are TNFR1‐dependent, and NF‐κB activation is potentiated by JNK inhibition (SP600125, 3μM). Impairing endocytosis (Dynasore, 15μM) reduced NF‐κB activation by TNFα (1.5‐fold, n=5) and prevented this effect of SP600125 (2.2‐fold, n=4). TNFα also caused phosphorylation of p38 and ERK1/2. JNK and ERK1/2 phosphorylation were TNFR1‐dependent while p38 activation was altered by both TNFR1 and 2 siRNA. Thus, TNFR1 activates both NF‐κB and JNK activation and JNK modulates endocytosis‐dependent NF‐κB activation in VSMC.