Abstract 253: Inhibition of Necrosis Attenuates Blood Pressure and Renal Inflammation in Male SHR with no Effect in Females

Abstract

Inflammation plays an important role in the pathogenesis of hypertension, and we recently published that male spontaneously hypertensive rats (SHR) have more pro-hypertensive, pro-inflammatory Th17 cells in their kidneys than females. However, the mechanisms initiating the inflammatory response remain unclear. Damage-associated molecular patterns (DAMPs) are released from dying cells and induce immune system activation. High mobility group box 1 (HMGB1) is a DAMP actively secreted by apoptotic cells in an oxidized form, or passively released by necrotic cells in a reduced form. Reduced HMGB1 has prolonged activity and is more pro-inflammatory. We hypothesized that sex differences in cell death contribute to sex differences in the immune cell profile and hypertension. Renal necrosis and apoptosis were measured by flow cytometry in 12 wk old male and female SHR. Male SHR have greater necrotic cell death (% total renal cells: 5.3±0.8 vs.1.0±0.4; p=0.004; N=6), while female SHR have more apoptosis (% total renal cells: 1.6±0.4 vs.4.0±0.4; p=0.004; N=4-5). Male SHR also had greater reduced HMGB1 in renal cortex compared to females (HMGB1 oxidized/reduced ratio: 1.0±0.1 vs. 1.7±0.1; p=0.002; N=6). We next measured blood pressure by telemetry in male and female SHR treated with vehicle or necrosis inhibitor NecroX-5 (1 mg/kg per day; 2 wks). The renal T cell and macrophage levels were measured by flow cytometry. NecroX-5 treatment in male SHR prevented age-related increases in blood pressure compared to vehicle-treated rats (ΔmmHg/week: 0.8±1.1 vs. 4.2±0.3; p=0.05; N=3). Necrox5 also significantly decreased renal necrosis (% total renal cells: 5.3±0.8 vs. 0.8±0.1; p=0.005; N=3-6), macrophages (% total renal cells: 2.8±0.6 vs. 0.8± 0.1; p=0.04; N=3-4), Th17 cells (% T cells: 4.5±0.3 vs. 2.7±0.3; p=0.009; N=3-4) and the pro-inflammatory cytokine IL-17 (% total renal cells: 10.0±0.4 vs. 5.3±0.7; p=0.002; N=3-4) in male SHR. NecroX-5 had no effect on blood pressure or pro-inflammatory markers in females. We conclude that necrosis is an important contributor in progression of hypertension in male SHR. Sex differences in cell death may contribute to sex differences in blood pressure and the immune profile.