Our overarching goal is to advance understanding of mitochondrial mechanisms of carbon monoxide (CO) poisoning to develop diagnostics, therapeutics and clinical trials. CO poisoning remains a major cause of death and disability, affecting 50,000 people per year in the United States alone. Patients removed from fires or following exposure to car and home generator exhaust are placed on 100% oxygen and transferred to a facility with a hyperbaric oxygen (HBO) delivery system. Despite the availability of HBO therapy centers in most major cities, inherent delays in access to and initiation of therapy greatly limit efficacy. In fact, even with HBO oxygen therapy a substantial number of surviving patients exhibit permanent neurocognitive impairments. This highlights an urgent need for alternative therapy. In the present proposal, we propose to study novel antidotal therapies for CO poisoning, based on our ex vivo findings that the use of a succinate prodrug relieves partial CIV inhibition caused by CO poisoning. Another existing gap is the lack of effective biomarkers to gauge severity, prognosis, and response to treatment. While a carboxyhemoglobin level is readily available at most institutions, its use is limited only to confirm exposure with no predictive value. The three main objectives our proposal seeks to address are: (1) limited mechanistic understanding of the key role the mitochondria has in CO poisoning; (2) limitations of current biomarkers to gauge severity of disease and treatment response; (3) lack of treatment strategies that target mitochondrial dysfunction to mitigate long-term neurologic and cardiac disability. This project will define the mitochondrial pathways involved in CO poisoning using blood cells compared against brain and cardiac tissue in a porcine model of CO poisoning, furthering the mechanistic understanding of CO poisoning. Another important feature of this proposal is the evaluation of a new treatment strategy involving a mitochondrial prodrug with the potential to shift existing treatment paradigm. To achieve these objectives, a large animal trial in a porcine model of CO poisoning is proposed with the following aims: Aim 1 • To establish the mitochondrial mechanisms that contribute to the neurologic and cardiac injury that occur in CO poisoning and assess blood cell mitochondrial function as a potential liquid biomarker. Aim 2 • Randomized, blinded pre-clinical intervention trial in porcine models of CO poisoning to compare an engineered succinate prodrug to standard therapy of hyperbaric oxygen (HBO).