Abstract 1518: Gene expression profiling reveals acidosis/GPR4-induced inflammatory responses in vascular endothelial cells

Due to deficient blood perfusion, hypoxia, and glycolytic metabolism, acidic tissue microenvironments commonly exist in solid tumors, inflammation, and many other pathological conditions. However, the molecular mechanisms by which cells respond to acidic microenvironments are not well understood. GPR4 has recently been identified as a novel proton-sensing receptor expressed in endothelial cells, cancer cells, and other cell types. GPR4 is activated by acidic extracellular pH but has lower activation at the physiological pH 7.4 and minimal activation at more alkaline pH. To delineate the function and signaling pathways of GPR4 in endothelial cells under acidic conditions, we performed gene expression microarray analyses. Primary human umbilical vein endothelial cells (HUVEC) that express endogenous GPR4 were stably transduced with the MSCV-IRES-GFP control vector (designated as HUVEC/Vector cells) or the MSCV-GPR4-IRES-GFP construct (designated as HUVEC/GPR4 cells). HUVEC/Vector and HUVEC/GPR4 cells were treated with pH 6.4 (400 nM H+) for 5 hours to activate GPR4 or with pH 8.4 (4 nM H+) as a negative control. RNAs were isolated, labeled, and hybridized with the Agilent Whole Genome Microarray Chip to compare gene expression. The results demonstrated that the acidic pH treatment of HUVEC/Vector cells stimulated the expression of a number of inflammatory genes, which represent a predominant signature in the microarray dataset. The induction of most of the acid-responsive inflammatory genes were further enhanced by GPR4 overexpression in HUVEC/GPR4 cells at pH 6.4, suggesting these genes are responsive to varying levels of GPR4 signaling. The inflammatory genes with substantial up-regulation by acidosis/GPR4 include chemokines, cytokines, adhesion molecules, genes involved in the TNFα and NF-κB pathways, prostaglandin-endoperoxidase synthase, and EGR transcription factors. The up-regulation of the genes at pH 6.4, compared to pH 7.4 and pH 8.4, was further confirmed by real-time RT-PCR. Taken together, our results show that activation of GPR4 by acidosis stimulates the expression of a wide range of inflammatory genes in endothelial cells. Since the inflammatory response of endothelial cells is important for blood vessels to interact with immune cells and tumor cells in the microenvironment, the acidosis/GPR4 signaling may play a role in the processes such as tumor immunity and metastasis.Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1518. doi:10.1158/1538-7445.AM2011-1518

Duke Scholars

Author Jen-Tsan Ashley Chi Molecular Genetics and Microbiology