Renal ischemia reperfusion injury (IRI) is a major source of medical morbidity and mortality, affecting diverse medical scenarios including transplantation, cardiac arrest, cardiopulmonary bypass, trauma, and vascular surgery. Despite the use of preservation solution and minimization of organ ischemia time, early allograft dysfunction occurs in at least 30% of deceased donor transplant recipients and this number is rising with the enhanced use of marginal organ donors. Impaired early graft function impacts long term graft performance and graft loss is a predictor of death. Despite significant efforts, no specific therapies to mitigate ischemic injury have reached clinical use. We have identified that inhibition of histone/protein deacetylases (HDACs), a family of proteins that remove acetyl groups from DNA-associated histone proteins as well as other groups of proteins, is effective in mitigating early renal functional impairment and the development of fibrosis after renal IRI. We have narrowed the specificity of this beneficial effect to the nuclear class I HDACs which tightly regulate broad patterns of gene expression. We have subsequently identified that HDAC2 deletion, even when confined to the kidney itself, conveys major protection from ischemia reperfusion injury. Conversely, deletion of closely homologous HDAC1 leads to impaired renal IRI tolerance. We thus propose to identify the mechanism behind the HDAC2 deletion effect with the intent of translating this benefit to clinically relevant scenarios of renal ischemia such as transplantation and cardiopulmonary bypass. Our proposal uses whole animal, cellular, and molecular approaches to define the role that class I HDACs play in renal ischemia tolerance. We will define remaining unanswered questions such as tissue specificity of effects in cold ischemia transplant models, understand tissue specificity by confining HDAC deletion to renal tubular epithelium, and use innovative hyperpolarized 13C MRI to identify if HDACs are altering in vivo metabolism. We will then use cellular approaches to assess whether inhibiting the deacetylase function of HDAC2 can reproduce the deletion effects, with the possibility of focusing translational targets on deacetylase inhibitors. Lastly, we will utilize molecular approaches to identify the impact that HDAC2 deletion has on nuclear corepressor complex formation, localization, and DNA binding, further highlighting possible mechanisms for future translation. Our studies intend to translate a highly novel finding of a single HDAC knockout drastically improving in vivo renal ischemia tolerance to a clinically approachable process by better understanding how the in vivo effects are achieved. This may have major impact on the development of strategies to minimize renal ischemic damage, which is a major source of cost and comorbidity in our health system.
We will investigate the common medical scenario of kidney injury mediated by temporary interruption or limitation of blood supply to the kidney, focusing on our data that inhibiting a class of genetic regulatory proteins, histone deacetylases (HDACs) ? and particularly HDAC2 ? significantly diminishes this type of kidney injury. We will use a variety of techniques to determine how the elimination of HDAC2 leads to this protection from injury. This work will fill a void by identifying new approaches to protect renal function in patients with a variety of medical conditions, including the optimization of organ function after renal transplantation.
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