title: Erp29 Attenuates Cigarette Smoke Extract-Induced Endoplasmic Reticulum Stress and Mitigates Tight Junction Damage in Retinal Pigment Epithelial Cells.
abstract: OBJECTIVE
  Endoplasmic reticulum protein 29 (ERp29) is a novel chaperone that was recently found decreased in human retinas with AMD. Herein, we examined the effect of ERp29 on cigarette smoke-induced RPE apoptosis and tight junction disruption.
  
  
  METHODS
  Cultured human RPE (HRPE) cells (ARPE-19) or mouse RPE eyecup explants were exposed to cigarette smoke extract (CSE) for short (up to 24 hours) or long (up to 3 weeks) periods. Expression of ERp29 was up- and downregulated by adenovirus and siRNA, respectively. Endoplasmic reticulum stress markers, apoptosis, and cell death, the expression and distribution of tight junction protein ZO-1, transepithelial electrical resistance (TEER), and F-actin expression were examined.
  
  
  RESULTS
  Endoplasmic reticulum protein 29 was significantly increased by short-term exposure to CSE in ARPE-19 cells or eyecup explants but was reduced after 3-week exposure. Overexpression of ERp29 increased the levels of GRP78, p58(IPK), and Nrf-2, while reducing p-eIF2α and C/EBP homologous protein (CHOP), and protected RPE cells from CSE-induced apoptosis. In contrast, knockdown of ERp29 decreased the levels of p58(IPK) and Nrf2, but increased p-eIF2α and CHOP and exacerbated CSE-triggered cell death. In addition, overexpression of ERp29 attenuated CSE-induced reduction in ZO-1 and enhanced the RPE barrier function, as measured by TEER. Knockdown of ERp29 decreased the level of ZO-1 protein. These effects were associated with changes in the expression of cytoskeleton F-actin.
  
  
  CONCLUSIONS
  Endoplasmic reticulum protein 29 attenuates CSE-induced ER stress and enhances cell viability and barrier integrity of RPE cells, and therefore may act as a protective mechanism for RPE survival and activity.
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China 2Departments of Ophthalmology and Biochemistry, Ross Eye Institute, University at Buffalo, State University of New York, Buffalo, New York, United.
authors.forename: Chuangxin
authors.initials: C
authors.lastname: Huang
authors.affiliation: Departments of Ophthalmology and Biochemistry, Ross Eye Institute, University at Buffalo, State University of New York, Buffalo, New York, United States 3SUNY Eye Institute, State University of New York, Buffalo, New York, United States 4Department of Med.
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Wang
authors.affiliation: Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States.
authors.forename: Guangjun
authors.initials: G
authors.lastname: Jing
authors.affiliation: Departments of Ophthalmology and Biochemistry, Ross Eye Institute, University at Buffalo, State University of New York, Buffalo, New York, United States 3SUNY Eye Institute, State University of New York, Buffalo, New York, United States.
authors.forename: Junhua
authors.initials: J
authors.lastname: Li
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Chenjin
authors.initials: C
authors.lastname: Jin
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Yu
authors.affiliation: Departments of Ophthalmology and Biochemistry, Ross Eye Institute, University at Buffalo, State University of New York, Buffalo, New York, United States.
authors.forename: Marek W
authors.initials: MW
authors.lastname: Falkowski
authors.affiliation: Departments of Ophthalmology and Biochemistry, Ross Eye Institute, University at Buffalo, State University of New York, Buffalo, New York, United States 3SUNY Eye Institute, State University of New York, Buffalo, New York, United States.
authors.forename: Sarah X
authors.initials: SX
authors.lastname: Zhang
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects / Q000235:genetics*; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D012313:RNA / Q000235:genetics; D055213:Retinal Pigment Epithelium / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012907:Smoking / Q000009:adverse effects*; D019108:Tight Junctions / Q000378:metabolism*
chemical_list: C491738:ERP29 protein, human; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D012313:RNA