title: Baicalin Protects Keratinocytes from Toll-like Receptor-4 Mediated DNA Damage and Inflammation Following Ultraviolet Irradiation.
abstract: UVB radiation contributes to both direct and indirect damage to the skin including the generation of free radicals and reactive oxygen species (ROS), inflammatory responses, immunosuppression and gene mutations, which can ultimately lead to photocarcinogenesis. A plant-derived flavonoid, baicalin, has been shown to have antioxidant, anti-inflammatory and free radical scavenging activities. Previous studies from our laboratory have shown that in murine skin, Toll-like receptor-4 (TLR4) enhanced both UVB-induced DNA damage and inflammation. The aim of this study was to investigate the efficacy of baicalin against TLR4-mediated processes in the murine keratinocyte PAM 212 cell line. Our results demonstrate that treating keratinocytes with baicalin both before and after UV radiation (100 mJ cm(-2) ) significantly inhibited the level of intracellular ROS and decreased cyclobutane pyrimidine dimers and 8-Oxo-2'-deoxyguanosine (8-oxo-dG)-markers of DNA damage. Furthermore, cells treated with baicalin demonstrated an inhibition of TLR4 and its downstream signaling molecules, MyD88, TRIF, TRAF6 and IRAK4. TLR4 pathway inhibition resulted in NF-κB inactivation and down-regulation of iNOS and COX-2 protein expression. Taken together, baicalin treatment effectively protected keratinocytes from UVB-induced inflammatory damage through TLR pathway modulation.
authors.affiliation: Department of Dermatology and Skin Diseases Research Center, University of Alabama at Birmingham, Birmingham, AL.|Department of Dermatology, The First Affiliated Hospital of Soochow University, Suzhou, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Min
authors.affiliation: Department of Dermatology and Skin Diseases Research Center, University of Alabama at Birmingham, Birmingham, AL.
authors.forename: Israr
authors.initials: I
authors.lastname: Ahmad
authors.affiliation: Department of Dermatology and Skin Diseases Research Center, University of Alabama at Birmingham, Birmingham, AL.
authors.forename: Michelle E
authors.initials: ME
authors.lastname: Chang
authors.affiliation: Department of Dermatology and Skin Diseases Research Center, University of Alabama at Birmingham, Birmingham, AL.
authors.forename: Erin M
authors.initials: EM
authors.lastname: Burns
authors.affiliation: Department of Dermatology, The First Affiliated Hospital of Soochow University, Suzhou, China.
authors.forename: Qihong
authors.initials: Q
authors.lastname: Qian
authors.affiliation: Department of Dermatology and Skin Diseases Research Center, University of Alabama at Birmingham, Birmingham, AL.
authors.forename: Nabiha
authors.initials: N
authors.lastname: Yusuf
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D002478:Cells, Cultured; D004249:DNA Damage / Q000187:drug effects*; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects*; D017382:Reactive Oxygen Species; D051197:Toll-Like Receptor 4; D014466:Ultraviolet Rays
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D005419:Flavonoids; D017382:Reactive Oxygen Species; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; C038044:baicalin