AMPA-Type Glutamate Receptors Associated With Vascular Smooth Muscle Cell Subpopulations in Atherosclerosis and Vascular Injury.

Alessandro L Gallina,Ljubica Matic,Thomas Quertermous,Anton Gisterå,Vladimir S Shavva,Stephen G Malin,Robert C Wirka,Anton Razuvaev,Glykeria Karadimou,Mariette Lengquist,Gabrielle Paulsson-Berne,Laura Tarnawski,Peder S Olofsson,April S Caravaca,Urszula Rykaczewska,Mohamad Youness

doi:10.3389/fcvm.2021.655869

Abstract

Objectives and Aims: Vascular smooth muscle cells (VSMCs) are key constituents of both normal arteries and atherosclerotic plaques. They have an ability to adapt to changes in the local environment by undergoing phenotypic modulation. An improved understanding of the mechanisms that regulate VSMC phenotypic changes may provide insights that suggest new therapeutic targets in treatment of cardiovascular disease (CVD). The amino-acid glutamate has been associated with CVD risk and VSMCs metabolism in experimental models, and glutamate receptors regulate VSMC biology and promote pulmonary vascular remodeling. However, glutamate-signaling in human atherosclerosis has not been explored.Methods and Results: We identified glutamate receptors and glutamate metabolism-related enzymes in VSMCs from human atherosclerotic lesions, as determined by single cell RNA sequencing and microarray analysis. Expression of the receptor subunits glutamate receptor, ionotropic, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic (AMPA)-type subunit 1 (GRIA1) and 2 (GRIA2) was restricted to cells of mesenchymal origin, primarily VSMCs, as confirmed by immunostaining. In a rat model of arterial injury and repair, changes of GRIA1 and GRIA2 mRNA level were most pronounced at time points associated with VSMC proliferation, migration, and phenotypic modulation. In vitro, human carotid artery SMCs expressed GRIA1, and selective AMPA-type receptor blocking inhibited expression of typical contractile markers and promoted pathways associated with VSMC phenotypic modulation. In our biobank of human carotid endarterectomies, low expression of AMPA-type receptor subunits was associated with higher content of inflammatory cells and a higher frequency of adverse clinical events such as stroke.Conclusion: AMPA-type glutamate receptors are expressed in VSMCs and are associated with phenotypic modulation. Patients suffering from adverse clinical events showed significantly lower mRNA level of GRIA1 and GRIA2 in their atherosclerotic lesions compared to asymptomatic patients. These results warrant further mapping of neurotransmitter signaling in the pathogenesis of human atherosclerosis.

Highlights

Cardiovascular disease (CVD) accompanied by chronic inflammation causes disability, suffering, and death, and in 2017, accounted for 45% of deaths in Europe [1]
To investigate the presence of mediators associated with glutamate signaling and metabolism (Figure 1A) in human atherosclerotic plaques, we queried the microarray data from our Biobank of Carotid Endarterectomies (BiKE) [19, 20] for mRNA expression of enzymes associated with glutamate turnover and components of ionotropic glutamate receptors of NMDA, amino3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), KA- and delta-type
Among the highly expressed genes, there was no significant difference in NMDA- and delta-type receptor transcript levels between non-atherosclerotic arteries and carotid plaques with the exception of Glutamate receptor, ionotropic, Nmethyl D-aspartate 1 (GRIN1), which was more abundant in non-atherosclerotic biopsies than in atherosclerotic lesions (Figures 1B,C, Supplementary Table 1)

Summary

Introduction

Cardiovascular disease (CVD) accompanied by chronic inflammation causes disability, suffering, and death, and in 2017, accounted for 45% of deaths in Europe [1]. Available treatments fail to completely prevent atherosclerosis development, which is a major cause of cardiovascular events and death. Vascular smooth muscle cells (VSMCs) are a key constituent of normal arteries and participate in the structural and functional changes in arteries that underlie atheroprogression. They have intrinsic plasticity and an ability to phenotypically modulate [2,3,4]. VSMCs are abundantly present in the fibrous cap that often demarcates advanced atherosclerotic plaques [3]. While VSMC proliferation commonly appears to support vascular repair in atherosclerosis, specific VSMC phenotypes may instead promote inflammation and plaque vulnerability [2, 3]. Improved understanding of plaque VSMC phenotype and its regulation in atherosclerosis is important [2]

Objectives

Methods

Results

Discussion

Conclusion