title: Cigarette smoke-related hydroquinone induces filamentous actin reorganization and heat shock protein 27 phosphorylation through p38 and extracellular signal-regulated kinase 1/2 in retinal pigment epithelium: implications for age-related macular degeneration.
abstract: Retinal pigment epithelium (RPE)-derived membranous debris named blebs, may accumulate and contribute to sub-RPE deposit formation, which is the earliest sign of age-related macular degeneration (AMD). Oxidative injury to the RPE might play a significant role in AMD. However, the underlying mechanisms are unknown. We previously reported that hydroquinone (HQ), a major pro-oxidant in cigarette smoke, foodstuff, and atmospheric pollutants, induces actin rearrangement and membrane blebbing in RPE cells as well as sub-RPE deposits in mice. Here, we show for the first time that phosphorylated Heat shock protein 27 (Hsp27), a key regulator of actin filaments dynamics, is up-regulated in RPE from patients with AMD. Also, HQ-induced nonlethal oxidative injury led to Hsp27mRNA up-regulation, dimer formation, and Hsp27 phosphorylation in ARPE-19 cells. Furthermore, we found that a cross talk between p38 and extracellular signal-regulated kinase (ERK) mediates HQ-induced Hsp27 phosphorylation and actin aggregate formation, revealing ERK as a novel upstream mediator of Hsp27 phosphorylation. Finally, we demonstrated that Hsp25, p38, and ERK phosphorylation are increased in aging C57BL/6 mice chronically exposed to HQ, whereas Hsp25 expression is decreased. Our data suggest that phosphorylated Hsp27 might be a key mediator in AMD and HQ-induced oxidative injury to the RPE, which may provide helpful insights into the early cellular events associated with actin reorganization and bleb formation involved in sub-RPE deposits formation relevant to the pathogenesis of AMD.
authors.affiliation: Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Marianne
authors.initials: M
authors.lastname: Pons
authors.forename: Scott W
authors.initials: SW
authors.lastname: Cousins
authors.forename: Karl G
authors.initials: KG
authors.lastname: Csaky
authors.forename: Gary
authors.initials: G
authors.lastname: Striker
authors.forename: Maria E
authors.initials: ME
authors.lastname: Marin-Castaño
mesh_terms: D000199:Actins / Q000378:metabolism*; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005260:Female; D005455:Fluorescent Antibody Technique; D055551:HSP27 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology*; D008268:Macular Degeneration / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D008875:Middle Aged; D010766:Phosphorylation / Q000187:drug effects*; D055213:Retinal Pigment Epithelium / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012907:Smoking; D018709:Statistics, Nonparametric; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D000199:Actins; D055551:HSP27 Heat-Shock Proteins; D006873:Hydroquinones; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C031927:hydroquinone