title: Triggering apoptotic death of human epidermal keratinocytes by malic Acid: involvement of endoplasmic reticulum stress- and mitochondria-dependent signaling pathways.
abstract: Malic acid (MA) has been commonly used in cosmetic products, but the safety reports in skin are sparse. To investigate the biological effects of MA in human skin keratinocytes, we investigated the potential cytotoxicity and apoptotic effects of MA in human keratinocyte cell lines (HaCaT). The data showed that MA induced apoptosis based on the observations of DAPI staining, DNA fragmentation, and sub-G1 phase in HaCaT cells and normal human epidermal keratinocytes (NHEKs). Flow cytometric assays also showed that MA increased the production of mitochondrial superoxide (mito-SOX) but decreased the mitochondrial membrane potential. Analysis of bioenergetics function with the XF 24 analyzer Seahorse extracellular flux analyzer demonstrated that oxygen consumption rate (OCR) was significantly decreased whereas extracellular acidification rate (ECAR) was increased in MA-treated keratinocytes. The occurrence of apoptosis was proved by the increased expressions of FasL, Fas, Bax, Bid, caspases-3, -8, -9, cytochrome c, and the declined expressions of Bcl-2, PARP. MA also induced endoplasmic reticulum stress associated protein expression such as GRP78, GADD153, and ATF6α. We demonstrated that MA had anti-proliferative effect in HaCaT cell through the inhibition of cell cycle progression at G0/G1, and the induction of programmed cell death through endoplasmic reticulum stress- and mitochondria-dependent pathways.
authors.affiliation: Institute of Medicine, Chung Shan Medical University, 402 Taichung, Taiwan. missyuping@gmail.com.
authors.forename: Yu-Ping
authors.initials: YP
authors.lastname: Hsiao
authors.affiliation: Institute of Medicine, Chung Shan Medical University, 402 Taichung, Taiwan. hauhauma@yahoo.com.tw.
authors.forename: Wan-Wen
authors.initials: WW
authors.lastname: Lai
authors.affiliation: Department of Biochemistry and Molecular Biology, National Yang-Ming University, 112 Taipei, Taiwan. labboy700110@gmail.com.
authors.forename: Shi-Bei
authors.initials: SB
authors.lastname: Wu
authors.affiliation: Institute of Medicine, Chung Shan Medical University, 402 Taichung, Taiwan. pathology@csmu.edu.tw.
authors.forename: Chung-Hung
authors.initials: CH
authors.lastname: Tsai
authors.affiliation: Department of Dermatology, Buddhist Tzu Chi General Hospital, 907 Hualien, Taiwan. s6160051@yahoo.com.tw.
authors.forename: Sheau-Chung
authors.initials: SC
authors.lastname: Tang
authors.affiliation: School of Biological Science and Biotechnology, China Medical University, 404 Taichung, Taiwan. jgchung@mail.cmu.edu.tw.
authors.forename: Jing-Gung
authors.initials: JG
authors.lastname: Chung
authors.affiliation: Department of Dermatology, Buddhist Tzu Chi General Hospital, 907 Hualien, Taiwan. jh.med.edu@gmail.com.
authors.forename: Jen-Hung
authors.initials: JH
authors.lastname: Yang
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D002460:Cell Line; D004249:DNA Damage; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D000078404:Epidermal Cells; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism; D008293:Malates / Q000633:toxicity*; D008928:Mitochondria / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D008293:Malates; C030298:malic acid; D053148:Caspase 3