Enhanced Vascular PI3K/Akt-NOX Signaling Underlies the Peripheral NMDAR-mediated Pressor Response in Conscious Rats

Abstract

The molecular mechanisms for peripheral N-Methyl-D-Aspartate receptor (NMDAR)-mediated vascular oxidative stress and pressor response are not known. We conducted integrative (in vivo) and ex vivo biochemical studies to test the hypothesis that ROS-dependent calcium influx, triggered by activation of vascular kinases, underlies the NMDAR-mediated pressor response. Pharmacological inhibition of PI3K/Akt (Wortmannin; 15 μg/kg), PKC (Chelerythrine; 5 mg/kg, i.v.), Ca2+ influx (nifedipine; 0.35 or 0.75 mg/kg) or NOX (apocynin; 5 mg/kg) attenuated the peripheral NMDAR-mediated pressor response in conscious male Sprague-Dawley rats. NMDAR activation enhanced the phosphorylation of Akt, ERK1, JNK and p38 (Western blot) and NADPH oxidase (NOX) activity in vascular tissues collected during the pressor response caused by NMDA infusion (180 μg/kg/min, 30 min). Further, ex vivo studies showed that wortmannin, chelerythrine or apocynin abrogated the NMDAR-mediated vascular NO and ROS generation and NOX activation in the vasculature. These findings implicate vascular PI3K/Akt-PKC signaling in the peripheral NMDAR-mediated increases in vascular NO and NOX activation (ROS), which ultimately lead to calcium influx and pressor response in conscious rats.

Ethanol attenuates peripheral NMDAR-mediated vascular oxidative stress and pressor response

“…5), consistent with our recent findings in the same tissue (McGee & Abdel-Rahman, 2012, 2014) and in other tissues (Gunasekar et al, 1995). In agreement with reported findings (Krenz & Korthuis, 2012; Yogi et al, 2010), ethanol produced modest, but significant increases in ROS, at least partly, via its oxidative metabolites, acetaldehyde and acetate (Deng & Deitrich, 2007; Seitz & Stickel, 2007).…”

N-Methyl-D-Aspartate Receptor Signaling and Function in Cardiovascular Tissues

“…The latter conclusion gains credence from recent findings that the Ca 2+ entry blocker nifedipine caused dose-dependent attenuation of the pressor response caused by peripheral NMDAR activation in conscious rats. 59 …”

“…42, 53, 59,57 Despite the widespread distribution of the different NOX isoforms in cardiovascular tissues, 84 the possible contribution of NOX to peripheral NMDAR-mediated ROS and its functional relevance remained unknown until very recently. Data generated in our laboratory showed that pretreatment with the nonspecific NOX inhibitor, apocynin, attenuated the ROS production in vasculature, and pressor response caused by peripheral NMDAR activation.…”

“…Data generated in our laboratory showed that pretreatment with the nonspecific NOX inhibitor, apocynin, attenuated the ROS production in vasculature, and pressor response caused by peripheral NMDAR activation. 59 Nevertheless, the exact NOS isoform(s) implicated in this phenomenon remain(s) to be elucidated.…”

“…In vivo and biochemical findings have shown that the PI3K inhibitor, wortmannin significantly attenuated the pressor response, and the associated increases in NO, ROS and NOX activity caused by peripheral NMDAR activation. 59 …”