DESCRIPTION (provided by applicant): Morbidity and mortality of severely burned patients still remain unacceptably high. Recent evidence indicates that hypermetabolism, a hallmark of severely burned patients, is a major contributor to these detrimental outcomes. Despite the widely recognized importance and complexity of the post-burn hypermetabolic response, the underlying mechanisms by which a thermal injury induces and sustains hypermetabolism for years after the injury are not well defined. Over the previous funding period, we identified that the endoplasmic reticulum (ER) stress response is profoundly affected by a severe burn. We further investigated the role of ER stress during the post-burn response and found that ER stress is associated with substantial metabolic alterations including insulin resistance (IR), lipolysis, cell death, inflammatory responses, and ultimately organ dysfunction. Our novel preliminary data indicate that augmenting ER stress greatly increases post-burn mortality. Thus, we hypothesize that the ER stress response is one of the central mediators of post-burn morbidity and mortality. As such, we aim to test the mechanistic basis by which the ER stress response is activated and leads to significantly greater morbidity. Specifically, the goal of this competitive renewal is to investigate the precise molecular mechanisms by which ER stress leads to increased morbidity and mortality. Based on extensive preliminary data we propose to determine the effects of augmented ER stress on mitochondrial function, calcium signaling via IP3R activity, and mTOR signaling at mitochondria-associated ER membranes (Aim 1). In Aim 2 we propose to test the novel hypothesis that unfolded proteins that accumulate during ER stress are Danger Associated Molecular Pattern (DAMP) molecules. Aim 3 will focus on our recent discovery that burn-induced ER stress causes profound activation of the hepatic NLRP3 inflammasome. We will test the hypothesis that released DAMPs, including ER stress-induced protein aggregates, can activate the NLRP3 inflammasome in the liver to stimulate IL-ß production and systemic inflammation contributing to post-burn multi-organ dysfunction. This project is highly innovative in that to-date the cellular and molecular mechanisms underlying the post-burn hypermetabolic response have not been identified and despite improved clinical care, the detrimental sequelae of this response leads to substantial morbidity and mortality after burn. The relevance of this project is that we will explore novel mechanisms that can lead to the development of new treatment avenues for burn patients or other patients in a hypermetabolic state.