Activation of GPR81 by lactate inhibits oscillatory shear stress‐induced endothelial inflammation by activating the expression of KLF2

Abstract

Atherosclerosis is a common and deadly cardiovascular disease with extremely high prevalence. Areas of the vasculature exposed to oscillatory shear stress (OSS) or disturbed blood flow are particularly prone to the development of atherosclerotic lesions. In part, various mechanosensitive receptors on the surface of endothelial cells play a role in regulating the ability of the vasculature to cope with variations in blood flow patterns. However, the exact mechanisms behind flow-mediated endothelial responses remain poorly understood. Along with the development of highly specific receptor agonists, the class of G coupled-protein receptors has been receiving increasing attention as potential therapeutic targets. G coupled-protein receptor 81 (GPR81), also known as hydroxycarboxylic acid receptor 1 (HCA 1 ), is activated by lactate, its endogenous ligand. In the present study, we show for the first time that expression of GPR81 is significantly downregulated in response to OSS in endothelial cells and that activation of GPR81 using physiologically relevant doses of lactate can rescue OSS-induced reduced GPR81 expression. Importantly, our findings demonstrate that activation of GPR81 can exert valuable atheroprotective effects in endothelial cells exposed to OSS by reducing oxidative stress and significantly downregulating the expression of inflammatory cytokines including interleukin (IL)-6, IL-8, monocyte chemoattractant protein (MCP)-1, and high mobility group box 1 (HMGB1). We also show that activation of GPR81 can potentially prevent the attachment of monocytes to the endothelium by suppressing OSS-induced secretion of vascular cellular adhesion molecule (VCAM)-1 and endothelial-selectin (E-selectin). Finally, we show that activation of GPR81 can rescue OSS-induced reduced expression of the key atheroprotective transcription factor Kruppel-like factor 2 (KLF2), which is mediated through the extracellularregulated kinase 5 (ERK5) pathway. These findings demonstrate a potential Abbreviations: ECL, electrochemiluminescence; E-selectin, endothelial-selectin; ELISA, Enzyme-linked immunosorbent assay; ERK5, extracellularregulated kinase 5; FBS, fetal bovine serum; GPR81, G coupled-protein receptor 81; GPCRs, G protein-coupled receptors; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; HMGB1, high mobility group box 1; HSS, high shear stress; HUVECs, human umbilical vascular endothelial cells; HCA 1 , hydroxycarboxylic acid receptor 1; IL-6, interleukin; KLF2, Kruppel-like factor 2; MAPK, mitogen-activated protein kinase; MCP-1, monocyte chemoattractant protein; OSS, oscillatory shear stress; PAK1, p21-activated kinase 1; PVDF, polyvinylidene fluoride; ROS, reactive oxygen species; RT-PCR, reverse transcription PCR; SDS-PAGE, sodium dodecyl sulfate-polyacrylamide gel electrophoresis; VCAM-1, vascular cellular adhesion molecule.

Longitudinal shear stress response in human endothelial cells to atheroprone and atheroprotective conditions

“…Some of the pathways such as oxidative stress and inflammation are overall up-regulated by OS vs. PS, i.e., most genes in these pathways are up-regulated. Some of these findings are in agreement with other previous results on HUVECs, e.g., Sun et al (38) have shown that OS increased gene and protein expressions for VCAM1 and SELE and levels of mitochondrial ROS, and Hsu et al (39) have reported similar findings. Gene expressions of VCAM1, ICAM1, and MCP1 have been shown to increase in OS vs. PS in HAECs [Brooks et al (40)] and HUVECs [Fan et al (41)].…”

Endothelin-1 Mediates the Systemic and Renal Hemodynamic Effects of GPR81 Activation

“…16 Single-cell RNA sequencing detected GPR81 in cerebral and lung vascular smooth muscle cells. 18 GPR81 has been identified in cultured human umbilical vein endothelial cells, 19 but we suggest this is not a major expression site, finding discernable levels in only 1 of 4 isolated renal endothelial cell samples and no in situ endothelial GPR91 mRNA expression in large arteries. Similarly, GPR81 does not co-localize with endothelial cell markers in the cerebral vasculature.…”

Lactic acid in macrophage polarization: The significant role in inflammation and cancer

“…It was also found that activation of GPR81 reduced the expression of Kruppel-like factor-2 (KLF2), a key atherosclerotic protective transcription factor induced by OSS. These findings suggested that GPR81 had a potential protective effect on atherosclerosis and targeting GPR81 may inhibit OSS-induced endothelial inflammation and dysfunction [99]. In 2020, KunYang discovered a new mechanism, found that lactic acid inhibited the activation of YAP and NF-κB during inflammation through GPR81-mediated signal transduction, and inhibited the pro-inflammatory response of macrophages stimulated by LPS [89].…”