Acute kidney injury (AKI) is a severe, rapid-onset disease characterized by a rapid loss in renal function leading to substantial morbidity and mortality. Frequent causes of AKI include ischemia/reperfusion (I/R) injury and acute drug or toxicant exposure. Despite attempts to develop new therapeutic strategies to treat AKI, few have been successful, and mortality has remained unchanged for several decades. Therefore, novel targets must be examined for the development of useful therapies for AKI. It has been shown that renal proximal tubule cells exhibit severe mitochondrial dysfunction and depletion of mitochondrial proteins following toxicant exposure or I/R injury. Mitochondrial dysfunction leads to oxidative stress and persistent energy depletion, which exacerbates injury and impairs energy-dependent repair, leading to end organ damage and failure in a variety of tissues. Our laboratory has demonstrated that injured renal proximal tubules can recover if they are induced to generate new mitochondria through mitochondrial biogenesis (MB). In addition, our laboratory has identified several compounds capable of inducing MB in vitro and in in vivo models of AKI. Among these compounds are several b2 adrenergic receptor (b2AR) agonists; however, not all b2AR agonists were found to induce MB. The capacity of these compounds to induce MB biogenesis did not correlate with affinity, but did correlate with the capacity of these compounds to increase levels of cGMP. In turn, cGMP has been shown to induce MB by increasing the activity of peroxisome proliferator-activated receptor gamma coactivator-1a (PGC1a), the master regulator of MB. We hypothesize that biogenic b2AR agonists stimulate MB and promote recovery of renal function by inducing a specific receptor conformation that leads to the production of cGMP. This hypothesis will be addressed through the following Specific Aims.
Aim 1 will determine the effects of mitochondrial biogenic agonists-induced effects on the b2AR that lead to a biogenic conformation. Site-directed mutagenesis and immunoblot analysis will identify b2AR phosphorylation sites required for the induction of MB.
Aim 2 will elucidate the role of Gas- and Gai-dependent signaling pathways in the generation of cGMP and the induction of MB. Pharmacologic inhibitors and siRNA will identify the relevant signaling pathways for the induction of MB. Non-MB b2AR agonists will be used as controls.
Aim 3 will determine the b2AR signaling pathways found in Aims 1 and 2 in the recovery of renal function following I/R injury using b2AR KO mice and pharmacological inhibitors. These results will further support the approach of using drugs that induce MB to accelerate recovery of renal function after AKI.
Acute kidney injury (AKI) affects a large number of people and currently has few effective treatments. This project seeks to elucidate the mechanisms of beta-2 adrenergic receptor signaling that lead to recovery from AKI, with hope that it will lead to the identification and development of novel therapies for AKI.
| Cameron, Robert B; Beeson, Craig C; Schnellmann, Rick G (2017) Structural and pharmacological basis for the induction of mitochondrial biogenesis by formoterol but not clenbuterol. Sci Rep 7:10578 |
| Cameron, Robert B; Beeson, Craig C; Schnellmann, Rick G (2016) Development of Therapeutics That Induce Mitochondrial Biogenesis for the Treatment of Acute and Chronic Degenerative Diseases. J Med Chem 59:10411-10434 |
| Leonard, Anthony P; Cameron, Robert B; Speiser, Jaime L et al. (2015) Quantitative analysis of mitochondrial morphology and membrane potential in living cells using high-content imaging, machine learning, and morphological binning. Biochim Biophys Acta 1853:348-60 |
