14 In livers of MCD diet–fed mice, impaired MAVS function and decreased mitochondrial association was associated with significantly reduced IRF3 phosphorylation after poly(I:C) stimulation (Fig. 4E). These data suggest that decreased association of MAVS with mitochondria at baseline may impair downstream signaling in steatohepatitis. Mitochondrial dysfunction plays a role in the pathogenesis of NASH18 and upon mitochondrial damage, its content leaks into the cytosol, triggering diverse signaling pathways, including apoptosis.19 Thus, we hypothesized that decreased

association of MAVS with mitochondria may be linked to mitochondrial damage in NASH. Indeed, mitochondrial damage was indicated by relocation of cytochrome JQ1 ic50 c from the mitochondria to the cytoplasm (Fig. 5A), and by enrichment of the mitochondria with β-actin (Fig. selleck chemical 5B) in livers of MCD compared with MCS diet–fed mice. We further identified evidence for increased cellular damage pathways in steatohepatitis

as indicated by caspase 8 (Fig. 5C) and caspase 1 (Fig. 5D) activation. Relevant to our observation of decreased MAVS in steatohepatitis, both caspase 8 and caspase 1 were shown to cleave MAVS from the mirochondria.20-22 Mitochondrial damage in NASH has been linked to excessive levels of reactive oxygen species (ROS).18 Indeed, we detected significantly increased liver TBARS levels revealing ROS-induced lipid peroxidation at baseline and after poly(I:C) stimulation in steatohepatitis (Fig.

5E). These results indicate that ROS and lipid peroxidation occur in NASH, and their production is exacerbated in response to dsRNA stimulation. Liver damage, indicated by steatosis and elevated ALT, is a hallmark of steatohepatitis. Here we found that a poly(I:C) challenge significantly increased liver injury in MCD diet–fed mice as indicated by tissue hemorrhage, hepatocyte degeneration (Fig. 6A), and significantly increased serum ALT levels compared with MCS control mice (Fig. 6B). Because dsRNA-induced activation of RIG-I and Mda5 leads to type I IFN induction as well as activation of NFκB and production of proinflammatory cytokines,14 we sought to evaluate whether the increased liver damage was aminophylline the consequence of enhanced proinflammatory cytokine production in steatohepatitis. At baseline, MCD diet–fed mice showed increased serum (Fig. 6C) and liver mRNA levels (Fig. 6D) of tumor necrosis factor α (TNFα), interleukin (IL)-6, and IL-1β compared with MCS control mice. Whereas poly(I:C) challenge increased TNFα, IL-6, and IL-1β production both in control mice and in MCD diet–fed groups (Fig. 6C,D), the extent of proinflammatory cytokine protein (Fig. 6C) and mRNA (Fig. 6D) induction was significantly lower in mice fed an MCD diet compared with mice fed an MCS diet.