title: Oxidative stress mediated Ca(2+) release manifests endoplasmic reticulum stress leading to unfolded protein response in UV-B irradiated human skin cells.
abstract: BACKGROUND
  Exposure of skin to ultraviolet (UV) radiation, an environmental stressor induces number of adverse biological effects (photodamage), including cancer. The damage induced by UV-irradiation in skin cells is initiated by the photochemical generation of reactive oxygen species (ROS) and induction of endoplasmic reticulum (ER) stress and consequent activation of unfolded protein response (UPR).
  
  
  OBJECTIVE
  To decipher cellular and molecular events responsible for UV-B mediated ER stress and UPR activation in skin cells.
  
  
  METHODS
  The study was performed on human skin fibroblast (Hs68) and keratinocyte (HaCaT) cells exposed to UV-B radiations in lab conditions. Different parameters of UVB induced cellular and molecular changes were analyzed using Western-blotting, microscopic studies and flow cytometry.
  
  
  RESULTS
  Our results depicted that UV-B induces an immediate ROS generation that resulted in emptying of ER Ca(2+) stores inducing ER stress and activation of PERK-peIF2α-CHOP pathway. Quenching ROS generation by anti-oxidants prevented Ca(2+) release and subsequent induction of ER stress and UPR activation. UV-B irradiation induced PERK dependent G2/M phase cell cycle arrest in Hs68 and G1/S phase cell cycle arrest in HaCaT. Also our study reflects that UV-B exposure leads to loss of mitochondrial membrane potential, activation of apoptotic cascade as evident by AnnexinV/PI staining, decreased expression of Bcl-2 and increased cleavage of PARP-1 protein.
  
  
  CONCLUSIONS
  UV-B induced Ca(2+) deficit within ER lumen was mediated by immediate ROS generation. Insufficient Ca(2+) concentration within ER lumen developed ER stress leading to UPR activation. These changes were reversed by use of anti-oxidants which quench ROS.
authors.affiliation: PK-PD and Toxicology Division, CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu Tawi, Jammu and Kashmir, India.
authors.forename: Mufti R
authors.initials: MR
authors.lastname: Farrukh
authors.affiliation: PK-PD and Toxicology Division, CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu Tawi, Jammu and Kashmir, India; Academy of Scientific and Innovative Research (AcSIR), New Delhi, India.
authors.forename: Ul A
authors.initials: UA
authors.lastname: Nissar
authors.affiliation: PK-PD and Toxicology Division, CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu Tawi, Jammu and Kashmir, India.
authors.forename: Quadri
authors.initials: Q
authors.lastname: Afnan
authors.affiliation: PK-PD and Toxicology Division, CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu Tawi, Jammu and Kashmir, India.
authors.forename: Rather A
authors.initials: RA
authors.lastname: Rafiq
authors.affiliation: PK-PD and Toxicology Division, CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu Tawi, Jammu and Kashmir, India; Academy of Scientific and Innovative Research (AcSIR), New Delhi, India.
authors.forename: Love
authors.initials: L
authors.lastname: Sharma
authors.affiliation: Department of Biochemistry, University of Kashmir, Srinagar, Jammu and Kashmir, India.
authors.forename: Shajrul
authors.initials: S
authors.lastname: Amin
authors.affiliation: PK-PD and Toxicology Division, CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu Tawi, Jammu and Kashmir, India.
authors.forename: Peerzada
authors.initials: P
authors.lastname: Kaiser
authors.affiliation: Cancer Pharmacology Division, CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu Tawi, Jammu and Kashmir, India.
authors.forename: Parduman R
authors.initials: PR
authors.lastname: Sharma
authors.affiliation: PK-PD and Toxicology Division, CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu Tawi, Jammu and Kashmir, India; Academy of Scientific and Innovative Research (AcSIR), New Delhi, India. Electronic address: stabdullah@iiim.ac.in.
authors.forename: Sheikh A
authors.initials: SA
authors.lastname: Tasduq
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000528:radiation effects; D020013:Calcium Signaling / Q000187:drug effects / Q000528:radiation effects*; D059447:Cell Cycle Checkpoints / Q000528:radiation effects; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects / Q000528:radiation effects*; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*; D053078:Membrane Potential, Mitochondrial / Q000528:radiation effects; D018384:Oxidative Stress / Q000187:drug effects / Q000528:radiation effects*; D010766:Phosphorylation; D017382:Reactive Oxygen Species / Q000378:metabolism; D051742:Transcription Factor CHOP / Q000378:metabolism; D014466:Ultraviolet Rays; D056811:Unfolded Protein Response / Q000187:drug effects / Q000528:radiation effects*; D019892:eIF-2 Kinase / Q000378:metabolism
chemical_list: D000975:Antioxidants; C497249:DDIT3 protein, human; D015852:Eukaryotic Initiation Factor-2; D017382:Reactive Oxygen Species; D051742:Transcription Factor CHOP; C460640:EIF2AK3 protein, human; D019892:eIF-2 Kinase
keywords: Endoplasmic reticulum stress; Intracellular calcium; Oxidative stress; Skin; Ultraviolet-B; Unfolded protein response