Lymphatic Regulation of Skin Electrolyte Metabolism and Blood Pressure

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DESCRIPTION (provided by applicant): Primary essential hypertension is the major cardiovascular disease risk factor. Dietary salt intake is a putative driving force of blood pressure elevation; however, the mechanisms of this effect remain unclear. The central nervous system, heart and blood vessels, and kidney are primary participants and the kidney is the putative grand regulator of salt disposition and blood pressure. The overall goal of this work is t address whether or not local regulation of skin electrolyte metabolism is important for blood pressure control. Clinical evidence from pilot studies in humans and preliminary experimental data accumulated in our laboratory, support this hypothesis. Our data point to macrophage-derived vascular endothelial growth factor C (VEGF-C) as a crucial factor controlling skin electrolyte homeostasis. VEGF-C promotes interstitial electrolyte clearance through the cutaneous lymph capillary network. Macrophages induce hyperplasia of subcutaneous lymph capillaries after sensing local Na+ or Cl- overload in the interstitium. The sensing function is accomplished by binding of the transcription factor tonicity-enhancer binding protein (TonEBP) to the promoter region of the VEGF-C gene. The cells exert their regulatory function by increasing VEGF-C expression and secretion. Blockade of this VEGF-C response from macrophages leads to skin electrolyte accumulation and arterial hypertension. We propose a comprehensive program to characterize the importance of TonEBP for macrophage-driven lymphatic regulation of skin electrolyte homeostasis in vivo (Aim 1). We will address whether or not disruption of subcutaneous lymph capillaries by selective VEGF-C depletion in the skin will lead to specific changes in skin electrolyte composition and increase blood pressure systemically (Aim 2). Finally, we will test whether macrophage-derived VEGF-C exerts its blood pressure-lowering effect via receptor binding to blood vessels, or by binding to cutaneous lymph vessels (Aim 3).