Abstract 647: Toll-like Receptor 4 (TLR4) Activation Impairs the Nitrergic Relaxation Response in Rat Corpus Cavernosum

Abstract

Cardiovascular disease etiology of hypertension and atherosclerosis has been shown to involve pattern-recognition receptor activation, including toll-like receptor 4 (TLR4). Indeed, our lab showed that TLR4 activation was implicated in blood pressure regulation, and its blockade lowered blood pressure in spontaneously hypertensive rats. However, whether TLR4 activation plays a role in erectile dysfunction is not known. Therefore, we hypothesized that TLR4 activation using its ligand, lipopolysaccharide (LPS), would increase reactive oxygen species (ROS) and impair corpus cavernosum (CC) relaxation. To test our hypothesis, rat CC smooth muscle cells were incubated for 15 min with LPS (100 ng/mL) and ROS detected with a fluorescent probe. Treatment with LPS resulted in an increase in ROS, compared to baseline (Fig.1). To investigate vascular reactivity to TLR4 activation, we performed myograph studies on CC isolated from 13-15 week old Sprague-Dawley rats, then incubated 3 hours in DMEM with LPS (+LPS) or vehicle (VEH). Concentration response curves to phenyleprine (PE, 10 -9 -10 -4 M) and to non-adrenergic, non-cholinergic (NANC) stimulation were used to investigate CC reactivity. Contractility to PE did not differ between groups, but +LPS-induced relaxation responses decreased significantly to 20-volt electrical field stimulation compared to VEH (8Hz: 16.3 vs 24.9, p< 0.01 and 16 Hz: 21.2 vs 35.1, p< 0.001). In conclusion, treatment with the TLR4 agonist, LPS, decreased NANC relaxation in the CC. Increased ROS generation may result in scavenging and reducing availability of nitric oxide that could impair relaxation in the CC.