Interrogating stress-relieving neural circuits to alleviate cardiovascular disease

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Project Summary Stressful life events are linked to the etiology of cardiovascular disease (CVD), which is the leading cause of death in the U.S. The mechanisms by which stress causes pathophysiology contributing to CVD are poorly understood and effective therapeutics that relieve stress and improve cardiovascular health are lacking. A premise of this proposal is that exploration of the neural circuits controlling the perception of stress may provide insight towards mechanisms underlying CVD and interventions aimed at its reversal. Causally-linking patterns of neural activity to stress and the development of CVD in humans is challenging. However, preclinical studies using laboratory mice that implement modern neuroscience and genetic technologies to excite or inhibit specific neural circuits make causally-linking neural activity and indices of stress responsiveness achievable. Using genetically-modified mice, we revealed that the activity of neurons that express genes encoding particular angiotensin receptor subtypes is coupled to cardiovascular, neuroendocrine and behavioral responses to stress. Specifically, we discovered that neurons expressing the angiotensin type-2 (AT2R) and Mas receptor (MasR) densely populate cortical and limbic brain regions controlling the perception of psychological stress and that excitation of these neurons decreases blood pressure, heart rate, circulating levels of corticosterone and anxiety- like behavior. In the periphery, we discovered that the nodose ganglion is densely populated by neurons expressing the angiotensin type 1a receptor (AT1R). These neurons function as primary baroreceptor afferents and excitation of these neurons lowers blood pressure, heart rate and energy expenditure. Collectively, these observations have led to the overall hypothesis that excitation of particular neuronal populations that express the AT1R, AT2R or MasR alters the perception of stress to protect against CVD. Experiments will use the Cre-LoxP system in mice with a cadre of modern neuroscience techniques and classical systems physiology to confirm or refute this hypothesis. Initial experiments utilize Cre-diver mice with virally-mediated gene transfer and in vivo optogenetics to determine whether the excitation or inhibition of neurons that express AT1R, AT2R, or MasR attenuates or exacerbates stress responding. Subsequent experiments use a model of stress-induced pathophysiology to evaluate how the structure and function of neurons that express the AT1R, AT2R or MasR is altered by disease. The final experiments attempt to alleviate stress-induced pathophysiology with optogenetic, genetic or pharmacological manipulations that alter the excitability of neurons that express the AT1R, AT2R or MasR. We anticipate that the proposed research will reveal, at a detailed and mechanistic level, neural circuits that provide stress relief, thereby guiding development of novel therapeutics for CVD.