Analysis of the Function of Bitter Taste Receptors TAS2R in Extraoral Tissues in Mice

• Published in: Annals of nutrition and metabolism 2019-01, Vol.75, p.297
• Main Authors: Komai, Michio, Oizumi, Yuka, Yamaki, Michiko, Shirakawa, Hitoshi
• Format: Article
• Language: English
• Subjects: Animal tissues; Bitter taste; Calcium (intracellular); Calcium ions; Cytokines; G protein-coupled receptors; Gene expression; Inflammation; Intestine; Intracellular; Kidneys; Leydig cells; Ligands; Lipopolysaccharides; Liver; Lungs; Macrophages; Microglia; MicroRNAs; mRNA; Nutrition; Organs; Quinine; Receptor mechanisms; Receptors; Rodents; Signal transduction; Small intestine; Taste; Taste receptors; Tongue
• ISSN: 0250-6807; 1421-9697
• DOI: 10.1159/000501751

Background/Aims: TAS2Rs are members of GPCR family and encoded by distinct 25 and 35 genes in human (TAS2Rs) and mice (Tas2rs), respectively.Therefore, Tas2rs have been thought to exhibit distinct functions within the respective tissues in which they are expressed. Methods: We comprehensively measured mRNA levels of all 35 mouse T2Rs in several organs and cultured cells, and compared their expression levels.Total RNA isolated from tissues of the tongue, liver, small intestine, kidney, lung, stomach, testis, brain of C57BL/6NCrSlc mouse (8 to 12 weeks old, male, female) and cell line of mouse microglia (MG6), macrophages (RAW264.7) and Leydig cells (I-10).The levels of mRNA of 35 mTas2r were determined by qRT-PCR to determine whether the mTas2r signaling pathway was functional in RAW264.7 cells, so we detected the change of intracellular Ca2+ after the treatment of quinine-HCl. RAW264.7 cells were treated with the media containing lipopolysaccharide (LPS) and quinine-HCl.The mRNA levels of inflammatory cytokine were determined using qRT-PCR. Results: The present investigation revealed that the level of mTas2r103 expression in the testis was tended to be higher than in the tongue; and that of mTas2r 126 in the lung, and mTas2r 137 in the liver were tended to be higher than other organs.It was also shown that mTas2rs were expressed in peripheral macrophages and RAW264.7 cells. Furthermore, quinine-HCl, a ligand of mTas2rs, induced an increase in intracellular Ca²+ in RAW264.7 cells, suggesting the possibility that the bitter taste receptors might have functions in this cell line, and this was actually proven that quinine-HCl suppressed LPS-induced inflammatory cytokines expression.