Acute kidney injury (AKI) is a major health burden with no FDA-approved drugs for its prevention or treatment. Current barriers to successful treatment of AKI include off-target affects of pharmacological agents, invasive nature of certain therapies, the lack of appropriate animal models of AKI and incomplete understanding of the pathophysiology of AKI. Although we have an immense understanding of the cellular and molecular mechanisms of AKI, an integrative biological understanding of AKI remains a critical gap in our knowledge. Recently, we reported a simple ultrasound (US)-based protocol that reduced tissue and systemic inflammation and prevented ischemia-reperfusion injury (IRI) in mice. This effect was dependent on the spleen and functional ?7 nicotinic acetylcholine receptors (?7nAChRs), consistent with the hypothesis that US activated the splenic cholinergic anti-inflammatory pathway (CAP). Our studies indicate that the protective effect of US depends on an intact spleen, the presence of T cells and bone marrow-derived ?7nAChRs, and splenic innervation. Lastly, US was protective in 3 models of AKI: 1) rodent model of IRI, 2) rodent model of sepsis and 3) pig model of AKI (contrast-IRI). These results suggest that the CAP is important in modulating AKI and that a simple noninvasive, nonpharmacological application of US using parameters within FDA guidelines may protect kidneys from AKI. We propose to test the hypothesis that: 1) splenic nerve innervation of the spleen represents a critical interface in rapid neuro-immune response by the spleen in AKI and 2) a noninvasive use of pulsed US within the FDA guidelines protects kidneys from AKI by activating the splenic CAP. Accordingly we hypothesize that:
Aim 1) pulsed US will attenuate injury in 3 models of AKI (rodent IRI and sepsis and pig AKI), Aim 2) proximal activation of the splenic cholinergic anti-inflammatory pathway (CAP) is causally linked to the protective effect of US in AKI, and Aim 3) cellular mechanisms within the splenic CAP mediate the tissue protective effect of pulsed ultrasound. Our studies will integrate a) a well-characterized mechanism of host response to stress, the CAP, and kidney injury by utilizing state-of-the-art immunological and biomechanical engineering methods including ultrasound and optogenetics, and b) expertise from biomedical engineering, neurophysiology and neuropharmacology to provide necessary tools to better understand a previously unrecognized concept of the neural control of the stress response that contributes to the integrative nature of AKI and will provide c) a potentially important novel and nonpharmacological therapy for AKI. Our studies will define the optimal US characteristics to demonstrate a biomechanical effect to protect kidneys from IRI, define mechanistically the contribution of the CAP to protection from AKI through a unique optogenetic approach to specifically stimulate or silence splenic innervation, and establish the efficacy of US in relevant models of AKI including IRI and septic AKI in mice and AKI in pigs to enable transition to clinical trials in humans. Concepts and therapeutic principles could be pertinent to sepsis, colitis, myocardial ischemia, and arthritis.
Kidney disease, and in particular acute kidney injury (AKI), is a major economic and public health burden in the United States and worldwide with ever increasing rates of hospitalization and unacceptably high mortality (40- 60%) in critically ill patients. Furthermore, AKI may predispose patients to progression to chronic kidney disease and end stage renal disease and ultimately shortened lifespan. The development of effective treatments for AKI is urgently needed and depends on a precise understanding of the molecular, cellular and immunological basis of AKI. The major goal of the current proposal is to further investigate the nonpharmacological, noninvasive, ultrasound-based (US) method that we have shown to protect kidneys from AKI and to examine mechanisms, including modulation of the immune system, that are responsible for this protective effect.
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