Abstract 9053: ASIC3 Knockout Alleviates Exaggerated Blood Pressure Response Induced by P2X3 Activation in Hindlimb Muscle Afferent Nerves of Rats With Experimental Peripheral Artery Disease

Abstract

Background: In peripheral artery disease (PAD), the metaboreceptor and mechanoreceptor in muscle afferent nerves contribute to accentuated sympathetic outflow via a neural reflex. Particularly, lactic acid and ATP produced in exercising muscles respectively stimulate acid sensing ion channel subtype 3 (ASIC3) and purinergic subunit P2X3 receptors in muscle afferent nerves, inducing the reflex sympathetic and arterial blood pressure responses during exercise. Methods: We examined that the P2X3 protein expression in the dorsal root ganglion (DRG) and P2X currents in DRG neurons using western blotting and patch-clamp methods, and the pressor response to P2X3 stimulation using the whole animal preparations. Four groups were included: 1. Wild type (WT) rats; 2. ASIC3 knockout (KO) rats; 3. WT-PAD rats with three days of femoral artery occlusion; 4. KO-PAD rats with three days of femoral artery occlusion. Results: First, P2X3 expression was significantly increased in KO rats compared with that in WT rats (optical density: 6.51±2.20/n=5; P <0.05 vs. WT). However, the levels of P2X3 expression were not significantly increased in KO-PAD rats compared with the KO rats (optical density: 7.99±1.99/n=6; P >0.05 vs. KO) . Second, in WT rats, as 10, 30 and 50 μM of αβ-me ATP (P2X3 agonist) were applied, peak amplitude of both transient and sustained P2X currents was increased by femoral artery occlusion (all P <0.05 WT-PAD vs. WT). Insignificant differences in both transient and sustained P2X currents were found between KO rats and KO-PAD rats (all P >0.05 vs. KO) when αβ-me ATP was applied except of the transient P2X current amplitude at 50 μM of αβ-me ATP. Third, there were insignificant differences in the mean arterial pressure response to 0.0625, 0.125 and 0.25 mM of αβ-me ATP injected into the hindlimb circulation between KO rats and KO-PAD rats (all P >0.05 vs. KO). Conclusions: Compared with WT rats, augmented P2X3-mediated pressor response is blunted by ASIC3 KO in PAD rats and this is accompanied with downregulated P2X3 expression and suppressed activities in P2X3 signaling pathways in muscle afferent neurons.