title: The ethyl acetate fraction of Sargassum muticum attenuates ultraviolet B radiation-induced apoptotic cell death via regulation of MAPK- and caspase-dependent signaling pathways in human HaCaT keratinocytes.
abstract: BACKGROUND
  Our previous work demonstrated that an ethyl acetate extract derived from Sargassum muticum (Yendo) Fenshol (SME) protected human HaCaT keratinocytes against ultraviolet B (UVB)-induced oxidative stress by increasing antioxidant activity in the cells, thereby inhibiting apoptosis.
  
  
  OBJECTIVE
  The aim of the current study was to further elucidate the anti-apoptotic mechanism of SME against UVB-induced cell damage.
  
  
  METHODS
  The expression levels of several apoptotic-associated and mitogen-activated kinase (MAPK) signaling proteins were determined by western blot analysis of UVB-irradiated HaCaT cells with or without prior SME treatment. In addition, the loss of mitochondrial membrane potential (Δψm) was detected using flow cytometry or confocal microscopy and the mitochondria membrane-permeate dye, JC-1. Apoptosis was assessed by quantifying DNA fragmentation and apoptotic body formation. Furthermore, cell viability was evaluated using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay.
  
  
  RESULTS
  SME absorbed electromagnetic radiation in the UVB range (280-320 nm) of the UV/visible light spectrum. SME also increased Bcl-2 and Mcl-1 expression in UVB-irradiated cells and decreased the Bax expression. Moreover, SME inhibited the UVB-induced disruption of mitochondrial membrane potential and prevented UVB-mediated increases in activated caspase-9 and caspase-3 (an apoptotic initiator and executor, respectively) levels. Notably, treatment with a pan-caspase inhibitor enhanced the anti-apoptotic effects of SME in UVB-irradiated cells. Finally, SME reduced the UVB-mediated phosphorylation of p38 MAPK and JNK, and prevented the UVB-mediated dephosphorylation of Erk1/2 and Akt.
  
  
  CONCLUSIONS
  The present results indicate that SME safeguards HaCaT keratinocytes from UVB-mediated apoptosis by inhibiting a caspase-dependent signaling pathway.
authors.affiliation: School of Medicine, Jeju National University , Jeju , Republic of Korea .
authors.forename: Mei Jing
authors.initials: MJ
authors.lastname: Piao
authors.forename: Ki Cheon
authors.initials: KC
authors.lastname: Kim
authors.forename: Jian
authors.initials: J
authors.lastname: Zheng
authors.forename: Cheng Wen
authors.initials: CW
authors.lastname: Yao
authors.forename: Ji Won
authors.initials: JW
authors.lastname: Cha
authors.forename: Sun Jin
authors.initials: SJ
authors.lastname: Boo
authors.forename: Weon Jong
authors.initials: WJ
authors.lastname: Yoon
authors.forename: Hee Kyoung
authors.initials: HK
authors.lastname: Kang
authors.forename: Eun Sook
authors.initials: ES
authors.lastname: Yoo
authors.forename: Young Sang
authors.initials: YS
authors.lastname: Koh
authors.forename: Mi Hee
authors.initials: MH
authors.lastname: Ko
authors.forename: Nam Ho
authors.initials: NH
authors.lastname: Lee
authors.forename: Jin Won
authors.initials: JW
authors.lastname: Hyun
mesh_terms: D000085:Acetates / Q000737:chemistry; D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D053938:DNA Fragmentation / Q000187:drug effects / Q000528:radiation effects; D005434:Flow Cytometry; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D020935:MAP Kinase Signaling System / Q000187:drug effects; D018613:Microscopy, Confocal; D010766:Phosphorylation / Q000187:drug effects; D010936:Plant Extracts / Q000494:pharmacology*; D044647:Sargassum / Q000737:chemistry*; D015398:Signal Transduction / Q000187:drug effects; D014466:Ultraviolet Rays / Q000009:adverse effects
chemical_list: D000085:Acetates; D010936:Plant Extracts; C007650:ethyl acetate; D053148:Caspase 3; D053453:Caspase 9
keywords: Apoptosis; caspase; mitochondrial membrane potential; mitogen-activated protein kinase