Autonomic control of kidney function

PROJECT SUMMARY: Discrete populations of neurons in the hypothalamus (including the paraventricular hypothalamus (PVH) and medulla (rostroventral lateral medulla, RVLM) of the brain densely innervate the spinal cord, and regulate renal sympathetic nerve activity (SNA). Via these neurons, the brain regulates salt balance, renin release and both renal plasma flow (RPF) and glomerular filtration rate (GFR) in health, and they may play a significant role in chronic hypertension and, in the setting of sudden stress (acute kidney injury). Many brain neurons regulating kidney function project from PVH and RVLM to the T8 - T12 intermediolateral column (IML) region in the spinal cord, synapsing on most of the preganglionic sympathetic fibers which in turn drive renal sympathetic nerve activity (renal SNA). Some PVH neurons which regulate renal function project to RVLM. Because each of these brain regions has many neuron subpopulations which regulate a wide array of somatic functions, we must apply new approaches and tools to identify and characterize those neuron subpopulations which participate in controlling renal function. To achieve this goal this multi-PI R01 proposal brings together a strong group of neuroscientists and renal physiologists to apply these approaches and tools. At BIDMC we have been using RNASeq and NucSeq methods to develop expression atlases of PVH and RVLM neuron subpopulations. At Pittsburgh we have been determining which PVH and RVLM neurons connect polysynaptically to the kidney using pseudorabiesvirus (PRV) injections into the kidney. The proposed studies will identify PVH and RVLM neuron subpopulations which drive renal SNA and regulate renal function. For PVH (Aim 1a) we will identify neuron subpopulations which project to T8 – T12 and RVLM using AAVretro injections into T8 – T12 and RVLM to label nuclei of neuron subpopulations which project to these regions, followed by FACS sorting and NucSeq. These newly identify subpopulations will be validated to polysynaptically innervate the kidney using a kidney injection of the transsynaptic tracer pseudorabies virus and in situ hybridization. In Aim 1b, we will optogenetically stimulate these subpopulations of PVH neurons projecting to T8 – T12 or to RVLM and determine the impact on renal SNA, renin secretion, Na+/electrolyte balance, renal plasma flow (RPF), glomerular filtration rate (GFR), and arterial blood pressure (ABP). Aim 2a will construct an RNASeq atlas for RVLM using NucSeq and validate that these subpopulations innervate the kidney using pseudorabies virus and in situ hybridization. Aim 2b will determine the effect of optogenetic stimulation of bulbospinal C1 and non-C1 RVLM neurons on various aspects of renal function. These studies will identify novel subpopulations of neurons in these critical brain regions that control renal function, which neurons connect to them and likely regulate their activity, and how their activity is altered in disease states. The proposed studies will open the way for a detailed understanding of how the brain controls renal function in health and disease.