GABA_BReceptors Expressed in Human Aortic Endothelial Cells Mediate Intracellular Calcium Concentration Regulation and Endothelial Nitric Oxide Synthase Translocation

Abstract

GABAB receptors regulate the intracellular Ca2+ concentration ([Ca2+]i) in a number of cells (e.g., retina, airway epithelium and smooth muscle), but whether they are expressed in vascular endothelial cells and similarly regulate the [Ca2+]i is not known. The purpose of this study was to investigate the expression of GABAB receptors, a subclass of receptors to the inhibitory neurotransmitter γ-aminobutyric acid (GABA), in cultured human aortic endothelial cells (HAECs), and to explore if altering receptor activation modified [Ca2+]i and endothelial nitric oxide synthase (eNOS) translocation. Real-time PCR, western blots and immunofluorescence were used to determine the expression of GABAB1 and GABAB2 in cultured HAECs. The effects of GABAB receptors on [Ca2+]i in cultured HAECs were demonstrated using fluo-3. The influence of GABAB receptors on eNOS translocation was assessed by immunocytochemistry. Both GABAB1 and GABAB2 mRNA and protein were expressed in cultured HAECs, and the GABAB1 and GABAB2 proteins were colocated in the cell membrane and cytoplasm. One hundred μM baclofen caused a transient increase of [Ca2+]i and eNOS translocation in cultured HAECs, and the effects were attenuated by pretreatment with the selective GABAB receptor antagonists CGP46381 and CGP55845. GABAB receptors are expressed in HAECs and regulate the [Ca2+]i and eNOS translocation. Cultures of HAECs may be a useful in vitro model for the study of GABAB receptors and vascular biology.

Gamma-aminobutyric acid-salt attenuated high cholesterol/high salt diet induced hypertension in mice

“…In resting ECs, eNOS is primarily placed at cell membranes and in cytoplasm, and translocate close to the nucleus by agonists [ 45 , 46 ]. eNOS translocation leads to increase level of [Ca 2+ ]i in ECs [ 47 ]. It has been shown GABA B receptors which expressed in cultured human arterial ECs regulate the translocations of eNOS and level of [Ca 2+ ]i [ 47 ].…”

“…eNOS translocation leads to increase level of [Ca 2+ ]i in ECs [ 47 ]. It has been shown GABA B receptors which expressed in cultured human arterial ECs regulate the translocations of eNOS and level of [Ca 2+ ]i [ 47 ]. Furthermore, another study showed baclofen, agonist GABA B receptor, induced vasodilation of 50% of rat retina vessels, and that this vasodilation is inhibited by 2-hydroxysaclofen, the GABA B receptor antagonist [ 48 ].…”

Quantitative pharmacokinetic–pharmacodynamic modelling of baclofen‐mediated cardiovascular effects using BP and heart rate in rats

“…Peripheral GABA B receptors directly induce vasodepression in the retina and in the pulmonary vascular bed (Kaye et al ., ; Hinds et al ., ). The mechanism underpinning these effects may be related to changes in calcium handling and/or nitric oxide production as evidenced by studies using cell culture systems (Wang et al ., ). Additionally, GABA B receptors are associated with renal‐induced elevations in BP (Donato et al ., ) tubular fibrosis and atrophy as well as attenuation of renal nerve‐induced noradrenaline release (Erdö, ; Fujimura et al ., ; Sasaki et al ., ).…”

A Buttery Taste to Vascular Biology

“…Two recent studies suggest that cultured endothelial and smooth muscle cells express GABA B receptors. 9,10 However, whether intact vessels also contain these receptors to a functional significant amount is unclear.…”

“…11 Homogenates of human aortic endothelial cells and human umbilical vein endothelial cells converted radiolabeled [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]glutamate into [1-14 C]GABA, and incubation of living human umbilical vein endothelial cells with [1-14 C]glutamate resulted in the release of [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]GABA into the culture medium. Inhibition of GABA transaminase, which degrades GABA and, thus, limits the half-life of this amino acid, increased its release by ≈18%, whereas inhibition or siRNAmediated knockdown of GABA producing GADs decreased GABA release by ≈50%.…”