Nonalcoholic fatty liver disease (NAFLD) is a global epidemic, progresses to nonalcoholic steatohepatitis (NASH) and fibrosis, and results in the development of hepatocellular carcinoma and increased cardiovascular mortality. NAFLD affects greater than 30% of the general US adult population, and disturbingly, prevalence rates appear to be greater in the military and veteran population. Unfortunately, no pharmacological therapies are available yet to treat NASH and fibrosis, necessitating the identification of novel targets and approaches. We have recently reported that hepatic eNOS is reduced in human patients with increasing NASH severity, and in vivo deletion of eNOS in hepatocytes exacerbated hepatic steatosis and NASH susceptibility. Here we present novel preliminary data demonstrating that eNOS deletion in hepatocytes upregulates the lipogenic transcription factor sterol regulatory element binding protein 1c (SREBP1c) and the DNL regulatory proteins acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS). In addition, both hepatocyte-specific eNOS overexpression suppressed markers of DNL, concurrent with decreased histological steatosis and inflammation. These results clearly show in hepatocytes that eNOS depletion is deleterious for liver disease. In contrast, we have recently made the novel preliminary observation that silencing eNOS specifically in Kupffer cells (KCs) in vitro and in vivo dramatically suppressed KC pro-inflammatory activation status and reduced short-term western diet induced NASH. Similarly, silencing eNOS in hepatic stellate cells (HSCs) in vitro reduced HSC fibrogenic activation. Whereas overexpressing eNOS in KCs and HSCs increased pro- inflammatory cytokine expression and increased HSC activation. Collectively, these data indicate that there is an apparent dichotomy in eNOS function in hepatocytes vs. nonparenchymal cells. Therefore, we hypothesize that hepatocyte-specific eNOS deletion transcriptionally upregulates DNL and SREBP1c and drives NAFLD (Aim 1), while KC- and HSC- specific eNOS deletion attenuates NASH and fibrosis (Aim 2). We will mechanistically interrogate both of these aims using gain-of-function and loss-of-function studies in vivo and in vitro to target eNOS in hepatocytes, KCs and HSCs. These studies will establish the cell type specific importance of eNOS and provide valuable insight into reducing the incidence of NAFLD and NASH in our Veteran population.