title: Inhibitory effect of luteolin on the odorant-induced cAMP level in HEK293 cells expressing the olfactory receptor.
abstract: Luteolin is a flavonoid in many fruits and vegetables. Although luteolin has important biological functions, including antioxidant, anti-inflammatory, antimicrobial, and neuroprotective activities, little is known about the functions of luteolin in the olfactory system. Various odorants can be detected and distinguished by using several molecular processes, including the binding of odorants to odorant receptors, activation of adenylyl cyclase (AC), changes of cyclic adenosine monophosphate (cAMP) and Ca(2+)  levels in olfactory sensory neurons, as well as changes in membrane potentials and the transmission of electric signals to the brain. Because AC-cAMP signal transduction plays a pivotal role in the olfactory system, we evaluated the effects of luteolin on the AC-cAMP pathway that had been stimulated by the odorant eugenol. We demonstrated that eugenol caused an upregulation of the cAMP level and the phosphorylation of phosphokinase A (PKA, a downstream target of cAMP) in human embryonic kidney 293 (HEK293) cells expressing the murine eugenol receptor. This upregulation significantly decreased in the presence of luteolin, suggesting that luteolin inhibited the odorant-induced production of cAMP and affected the downstream phosphorylation of PKA.
authors.affiliation: Division of Metabolism and Functionality Research, Korea Food Research Institute, Baekhyun-Dong, Bundang-Gu, Sungnam, Kyungki-Do, Republic of Korea.
authors.forename: Yeo Cho
authors.initials: YC
authors.lastname: Yoon
authors.forename: Jin-Teak
authors.initials: JT
authors.lastname: Hwang
authors.forename: Mi-Jeong
authors.initials: MJ
authors.lastname: Sung
authors.forename: Shuaiyu
authors.initials: S
authors.lastname: Wang
authors.forename: Davaatseren
authors.initials: D
authors.lastname: Munkhtugs
authors.forename: Mee-Ra
authors.initials: MR
authors.lastname: Rhyu
authors.forename: Jae-Ho
authors.initials: JH
authors.lastname: Park
mesh_terms: D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000819:agonists* / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D015536:Down-Regulation; D005054:Eugenol / Q000494:pharmacology; D015870:Gene Expression; D005822:Genetic Vectors; D057809:HEK293 Cells; D006801:Humans; D047311:Luteolin / Q000494:pharmacology*; D051379:Mice; D009812:Odorants; D010766:Phosphorylation / Q000187:drug effects; D010770:Phosphotransferases / Q000037:antagonists & inhibitors / Q000378:metabolism; D018035:Receptors, Odorant / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D015854:Up-Regulation
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D018035:Receptors, Odorant; D005576:Colforsin; D005054:Eugenol; D000242:Cyclic AMP; D010770:Phosphotransferases; D000262:Adenylyl Cyclases; D047311:Luteolin