Abstract P216: Cholinergic-mediated Salt-Sensitive Hypertension In A Genetic Model Of Essential Hypertension

Abstract

Inflammation plays a key role in the pathogenesis of hypertension. High dietary sodium intake has been associated with inflammation in patients suffering from high blood pressure & atherosclerosis. Our lab has shown that development of hypertension in a genetic model of human essential hypertension, the Spontaneously Hypertensive Rat (SHR), is dependent on nicotinic acetylcholine receptor (nAChR) mediated renal inflammation, which leads to enhanced expression of the renal sodium-potassium chloride cotransporter (NKCC2). Based on these findings we hypothesized that sodium sensitivity may play a role in the development of cholinergic hypertension. To investigate this hypothesis, we infused young pre-hypertensive SHR and Wistar Kyoto (WKY, normotensive control) rats with either saline or nicotine (15mg/kg/day) and placed them on either low-salt (LSD, 0.01% NaCl) or high-salt (HSD, 4% NaCl) diet for 2 wks. There was no change in systolic blood pressure (SBP) in saline or nicotine infused WKY with either LSD or HSD. Similarly, there was no difference between the SBP of saline infused SHR with either LSD or HSD. Interestingly, nicotine infusion did not change SBP in LSD fed SHR, but did result in ~20% increase in SBP in HSD fed SHR (122.0 ± 0.7 vs. 146.2 ± 0.2mmHg, p= 0.01). HSD alone induced a 2.25-fold increase in renal NKCC2 expression compared to LSD in saline infused SHR (p=0.006). In comparison to saline, nicotine infusion further induced a 58% increase in renal NKCC2 expression in SHR fed HSD (p=0.004). Renal NKCC2 expression did not change in WKY with either diet or nicotine infusion. Nicotine infused SHR on a HSD also manifested a 16% sodium retention compared to saline infused SHR (2.1 ± 0.1 mM/gBW vs. 2.5 ± 0.1 mM/gBW, p = 0.017). Nicotine infused SHR had 1.7 times more renal IL-6 than saline-infused SHR (1442. ± 212 vs 826 ± 103 pg/25mg total protein, p=0.04) and 9 times more renal IL-6 than nicotine-infused WKY controls (1442. ± 212 vs 148. ± 71 pg/25mg total protein, p=0.0041) under HSD conditions. Taken together with our previously published data, we conclude that NKCC2 likely plays a role in cholinergic-mediated renal inflammation and hypertension.