The ATP Receptors P2X7 and P2X4 Modulate High Glucose and Palmitate-Induced Inflammatory Responses in Endothelial Cells

Abstract

Endothelial cells lining the blood vessels are principal players in vascular inflammatory responses. Dysregulation of endothelial cell function caused by hyperglycemia, dyslipidemia, and hyperinsulinemia often result in impaired vasoregulation, oxidative stress, inflammation, and altered barrier function. Various stressors including high glucose stimulate the release of nucleotides thus initiating signaling via purinergic receptors. However, purinergic modulation of inflammatory responses in endothelial cells caused by high glucose and palmitate remains unclear. In the present study, we investigated whether the effect of high glucose and palmitate is mediated by P2X7 and P2X4 and if they play a role in endothelial cell dysfunction. Transcript and protein levels of inflammatory genes as well as reactive oxygen species production, endothelial-leukocyte adhesion, and cell permeability were investigated in human umbilical vein endothelial cells exposed to high glucose and palmitate. We report high glucose and palmitate to increase levels of extracellular ATP, expression of P2X7 and P2X4, and inflammatory markers. Both P2X7 and P2X4 antagonists inhibited high glucose and palmitate-induced interleukin-6 levels with the former having a significant effect on interleukin-8 and cyclooxygenase-2. The effect of the antagonists was confirmed with siRNA knockdown of the receptors. In addition, P2X7 mediated both high glucose and palmitate-induced increase in reactive oxygen species levels and decrease in endothelial nitric oxide synthase. Blocking P2X7 inhibited high glucose and palmitate-induced expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 as well as leukocyte-endothelial cell adhesion. Interestingly, high glucose and palmitate enhanced endothelial cell permeability that was dependent on both P2X7 and P2X4. Furthermore, antagonizing the P2X7 inhibited high glucose and palmitate-mediated activation of p38-mitogen activated protein kinase. These findings support a novel role for P2X7 and P2X4 coupled to induction of inflammatory molecules in modulating high glucose and palmitate-induced endothelial cell activation and dysfunction.

Müller Cell–Microglia Cross Talk Drives Neuroinflammation in Diabetic Retinopathy

“…Diabetes was found to increase the susceptibility of retinal microvessels to transmembrane pore formation in response to P2X 7 activation, suggesting that extracellular ATP may cause mural cell loss in DR (13). In addition, P2X 7 and P2X 4 receptor antagonists inhibited the induction of endothelial cell inflammation and permeability by high glucose (14). Release of ATP by Müller cells could also contribute to the death of RGC observed in DR, as evidence suggests that the release of ATP by gliotic Müller cells induces RGC apoptosis through P2X 7 activation (15,16).…”

Effect of glucose and palmitate environment on proliferation and migration of PC3‐prostate cancer cells

“…ROS play a major role in NO-related cell activities and can affect NO availability both from production to postproduction scavenging (Pierini and Bryan, 2015). Already, the effects of the association between fatty acids and glucose in culture have been tested by Sathanoori et al (2015) and Souto Padron de Figueiredo et al (2015) reported that these treatments (30 mmol/L glucose, 150 mM palmitate) caused higher production of ROS, NOX2 and decreased the expression of nitric oxide synthase in HUVECs and myotubes, respectively. However, it is already wellknown that these treatments influence the production of ROS and the performance of antioxidant enzymes in endothelial cells, being the one responsible for the cardiovascular alterations of obese and diabetic individuals.…”

“…In this context, studies developed by Piro et al (2012) and Li et al (2015) have shown that chronic exposure of endothelial cells to high concentrations of fatty acids (100 mM) or mice treated with hyperlipidic diet, respectively, induces oxidative stress with high ROS production. Already, the effects of the association between fatty acids and glucose in culture have been tested by Sathanoori et al (2015) and Souto Padron de Figueiredo et al (2015) reported that these treatments (30 mmol/L glucose, 150 mM palmitate) caused higher production of ROS, NOX2 and decreased the expression of nitric oxide synthase in HUVECs and myotubes, respectively. Thus, our data corroborate with the literature and unprecedentedly show the impact of high concentrations of fatty acids and glucose on the oxidative stress of PC3-prostate cancer cells.…”

A Genetic Polymorphism in the Pannexin1 Gene Predisposes for The Development of Endothelial Dysfunction with Increasing BMI

“…Extracellular nucleotides, such as ATP, generally display vasculoprotective properties by regulating vasodilation through nitric oxide production [2,3]. However, ATP has also been shown to participate to the onset of endothelial dysfunction through the activation of P2X4 and P2X7 purinergic receptors [4]. In fact, prolonged exposure of endothelial cells to ATP enhances the expression of chemokines and adhesion molecules by endothelial cells [4,5].…”

“…However, ATP has also been shown to participate to the onset of endothelial dysfunction through the activation of P2X4 and P2X7 purinergic receptors [4]. In fact, prolonged exposure of endothelial cells to ATP enhances the expression of chemokines and adhesion molecules by endothelial cells [4,5]. Pannexin1 (Panx1) channels are newly discovered ATP release channels that are increasingly recognized to critically regulate vascular function [6].…”