title: Polypeptide from Chlamys farreri restores endoplasmic reticulum (ER) redox homeostasis, suppresses ER stress, and inhibits ER stress-induced apoptosis in ultraviolet B-irradiated HaCaT cells.
abstract: OBJECTIVE
  To investigate the effects of polypeptide from Chlamys farreri (PCF) on ultraviolet B (UVB)-induced apoptosis in human keratinocyte HaCaT cells.
  
  
  METHODS
  In HaCaT cells at 4 h or 18 h after UVB irradiation, the cell viability was measured by MTT assay. Cellular apoptosis was detected with annexin V-FITC/PI staining by flow cytometry. The expression levels of PDI, Ero-1α, GRP78, and CHOP were assessed by Western blot analysis. Mitochondrial membrane potential (MMP) was measured by fluorescent probe JC-1. Caspase activities were detected with fluorogenic substrates.
  
  
  RESULTS
  PCF alleviated cell viability loss and inhibited apoptosis in HaCaT cells after UVB irradiation. Moreover, PCF increased the expression levels of PDI and Ero-1α, which were related with the ER redox homeostasis. Furthermore, PCF treatment inhibited the expression of GRP78 at 4 h after UVB irradiation, and suppressed CHOP expression at 18 h post-irradiation, indicating that PCF could inhibit UVB-evoked ER stress in the early stage post-irradiation, and suppress the ER stress-induced apoptosis in the late stage. In addition, PCF alleviated UVB-induced MMP loss, and inhibited the activation of caspase-9/-3, in HaCaT cells after UVB irradiation. On the other hand, MMP loss and caspase-9/-3 activation could be partly blocked by the ER stress inhibitor 4-PBA.
  
  
  CONCLUSIONS
  PCF inhibits UVB-induced apoptosis through restoring ER redox homeostasis, suppressing ER stress, and inhibiting ER stress-induced mitochondrial apoptosis in HaCaT cells. These findings provide evidence for the mechanism underlying UVB-induced skin damages, and support the promising role of PCF in treatment of the diseases.
authors.affiliation: Department of Pharmacology, Medical College of Qingdao University Qingdao 266071, Shandong, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Xie
authors.affiliation: Department of Stomatology, Medical College of Qingdao University Qingdao 266003, Shandong, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhong
authors.affiliation: Department of Pharmacology, Medical College of Qingdao University Qingdao 266071, Shandong, China.
authors.forename: Yantao
authors.initials: Y
authors.lastname: Han
authors.affiliation: Department of Pharmacology, Medical College of Qingdao University Qingdao 266071, Shandong, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Gao
authors.affiliation: Department of Pharmacology, Medical College of Qingdao University Qingdao 266071, Shandong, China.
authors.forename: Chunbo
authors.initials: C
authors.lastname: Wang
authors.affiliation: College of Life Sciences, Chongqing Normal University Chongqing 401331, China.
authors.forename: Jianjun
authors.initials: J
authors.lastname: Peng
keywords: HaCaT cells; UVB irradiation; apoptosis; endoplasmic reticulum (ER); mitochondria