Project Summary Chronic, low-grade inflammation (inflammaging) is a hallmark of aging and is one of the ‘seven pillars of aging. Inflammaging is a highly significant risk factor for both morbidity and mortality in the elderly people and in a variety of age-related diseases. Various tissues such as adipose tissue, muscle, brain, and liver have been proposed to play a role in inflammaging, yet the pathway(s) responsible for inflammaging in a tissue or how inflammaging in one tissue can impact other tissues is not known. In the current proposal, we will focus on liver inflammaging. Liver macrophages are the major source of inflammation in the liver and they play a critical role in the pathogenesis of age-related liver diseases, such as NASH. Damage-associated molecular patterns (DAMPs, e.g., HMGB1) are major activators of macrophages and levels of DAMPs increase with age. Necroptosis is a programmed cell death pathway that play a major role in inflammation through the generation of DAMPs. In this proposal we will test the effect of hepatocyte-specific necroptosis on liver inflammation because of the following reasons: (1) Our data show that necroptosis and inflammation increase with age in the liver (and in hepatocytes) of wild type mice that is correlated with chronic liver disease (NASH). Inhibiting necroptosis using necroptosis inhibitor, necrostatin-1s, reduced liver inflammation and NASH. (2) Our data show that necroptosis can affect cell senescence, a pathway associated with aging and inflammation: i.e. inhibiting necroptosis reduced markers of cell senescence in the livers of old mice. (3) There are data showing that inflammation associated with chronic liver disease can cause detrimental effects in other tissues such as brain and skeletal muscle, two key tissues associated with healthspan. Our preliminary studies show that over-expression of MLKL in hepatocytes increases expression of proinflammatory cytokines in the liver and brain of young mice. The central hypothesis of the supplement is that inducing necroptosis in one cell type will affect other cell types in that tissue increasing inflammation in that tissue and will also have cell non-autonomous effects on other tissues. The hypothesis will be tested using a novel knockin mouse model that will allow us to induce necroptosis specifically in hepatocytes by conditionally overexpressing Mlkl, a key gene in necroptosis. Aim 1. To determine the effects of hepatocyte necroptosis on liver; Aim 2. To determine the effect of hepatocyte necroptosis on the secretome; Aim 3. To determine the non-autonomous effects of hepatocyte necroptosis on other tissues.