title: MLK3 is a novel target of dehydroglyasperin D for the reduction in UVB-induced COX-2 expression in vitro and in vivo.
abstract: Dehydroglyasperin D (DHGA-D), a compound present in licorice, has been found to exhibit anti-obesity, antioxidant and anti-aldose reductase effects. However, the direct molecular mechanism and molecular targets of DHGA-D during skin inflammation remain unknown. In the present study, we investigated the effect of DHGA-D on inflammation and its mechanism of action on UVB-induced skin inflammation in HaCaT human keratinocytes and SKH-1 hairless mice. DHGA-D treatment strongly suppressed UVB-induced COX-2 expression, PGE2 generation and AP-1 transactivity in HaCaT cells without affecting cell viability. DHGA-D also inhibited phosphorylation of the mitogen-activated protein kinase kinase (MKK) 3/6/p38, MAPK/Elk-1, MKK4/c-Jun N-terminal kinase (JNK) 1/2/c-Jun/mitogen, and stress-activated protein kinase (MSK), whereas phosphorylation of the mixed-lineage kinase (MLK) 3 remained unaffected. Kinase and co-precipitation assays with DHGA-D Sepharose 4B beads showed that DHGA-D significantly suppressed MLK3 activity through direct binding to MLK3. Knockdown of MLK3 suppressed COX-2 expression as well as phosphorylation of MKK4/p38 and MKK3/6/JNK1/2 in HaCaT cells. Furthermore, Western blot assay and immunohistochemistry results showed that DHGA-D pre-treatment significantly inhibits UVB-induced COX-2 expression in vivo. Taken together, these results indicate that DHGA-D may be a promising anti-inflammatory agent that mediates suppression of both COX-2 expression and the MLK3 signalling pathway through direct binding and inhibition of MLK3.
authors.affiliation: WCU Biomodulation Major, Department of Agricultural Biotechnology and Center for Food and Bioconvergence, Seoul National University, Seoul, Korea; Division of Metabolism and Functionality Research, Korea Food Research Institute, Seongnam, Korea.
authors.forename: Sung Keun
authors.initials: SK
authors.lastname: Jung
authors.forename: Su Jeong
authors.initials: SJ
authors.lastname: Ha
authors.forename: Yeong A
authors.initials: YA
authors.lastname: Kim
authors.forename: Jihoon
authors.initials: J
authors.lastname: Lee
authors.forename: Tae-Gyu
authors.initials: TG
authors.lastname: Lim
authors.forename: Yun Tai
authors.initials: YT
authors.lastname: Kim
authors.forename: Nam Hyouck
authors.initials: NH
authors.lastname: Lee
authors.forename: Jun Seong
authors.initials: JS
authors.lastname: Park
authors.forename: Myeong-Hun
authors.initials: MH
authors.lastname: Yeom
authors.forename: Hyong Joo
authors.initials: HJ
authors.lastname: Lee
authors.forename: Ki Won
authors.initials: KW
authors.lastname: Lee
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D015232:Dinoprostone / Q000096:biosynthesis; D005260:Female; D005419:Flavonoids / Q000737:chemistry / Q000494:pharmacology*; D055785:Gene Knockdown Techniques; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000201:enzymology / Q000528:radiation effects; D048371:MAP Kinase Kinase 3 / Q000378:metabolism; D048669:MAP Kinase Kinase 6 / Q000378:metabolism; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000528:radiation effects; D008812:Mice, Hairless; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D011485:Protein Binding / Q000187:drug effects / Q000528:radiation effects; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014466:Ultraviolet Rays; D000097767:Mitogen-Activated Protein Kinase Kinase Kinase 11
chemical_list: D051546:Cyclooxygenase 2; D015232:Dinoprostone; D005419:Flavonoids; D048371:MAP Kinase Kinase 3; D048669:MAP Kinase Kinase 6; D020930:MAP Kinase Kinase Kinases; D018808:Transcription Factor AP-1; D000097767:Mitogen-Activated Protein Kinase Kinase Kinase 11; C551630:dehydroglyasperin D
keywords: cyclooxygenase-2; dehydroglyasperin D; inflammation; licorice; mixed-lineage kinase 3