Smoke exposure causes endoplasmic reticulum stress and lipid accumulation in retinal pigment epithelium through oxidative stress and complement activation.
Age-related macular degeneration (AMD) is a complex disease caused by genetic and environmental factors, including genetic variants in complement components and smoking. Smoke exposure leads to oxidative stress, complement activation, endoplasmic reticulum (ER) stress, and lipid dysregulation, which have all been proposed to be associated with AMD pathogenesis. Here we examine the effects of smoke exposure on the retinal pigment epithelium (RPE). Mice were exposed to cigarette smoke or filtered air for 6 months. RPE cells grown as stable monolayers were exposed to 5% cigarette smoke extract (CSE). Effects of smoke were determined by biochemical, molecular, and histological measures. Effects of the alternative pathway (AP) of complement and complement C3a anaphylatoxin receptor signaling were analyzed using knock-out mice or specific inhibitors. ER stress markers were elevated after smoke exposure in RPE of intact mice, which was eliminated in AP-deficient mice. To examine this relationship further, RPE monolayers were exposed to CSE. Short term smoke exposure resulted in production and release of complement C3, the generation of C3a, oxidative stress, complement activation on the cell membrane, and ER stress. Long term exposure to CSE resulted in lipid accumulation, and secretion. All measures were reversed by blocking C3a complement receptor (C3aR), alternative complement pathway signaling, and antioxidant therapy. Taken together, our results provide clear evidence that smoke exposure results in oxidative stress and complement activation via the AP, resulting in ER stress-mediated lipid accumulation, and further suggesting that oxidative stress and complement act synergistically in the pathogenesis of AMD.
From the Departments of Ophthalmology and.
Kannan
K
Kunchithapautham
Microbiology and Immunology, Medical University of South Carolina, Charleston, South Carolina 29425 and.
Carl
C
Atkinson
From the Departments of Ophthalmology and the Research Service, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29401 rohrer@musc.edu.
Bärbel
B
Rohrer
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001559:Benzhydryl Compounds / Q000494:pharmacology; D015153:Blotting, Western; D002478:Cells, Cultured; D003167:Complement Activation / Q000187:drug effects / Q000502:physiology*; D011415:Complement Factor B / Q000235:genetics / Q000378:metabolism; D003170:Complement Pathway, Alternative / Q000187:drug effects / Q000502:physiology; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects / Q000502:physiology*; D016166:Free Radical Scavengers / Q000494:pharmacology; D006360:Heat-Shock Proteins / Q000235:genetics; D006801:Humans; D050356:Lipid Metabolism; D008055:Lipids / Q000032:analysis*; D008268:Macular Degeneration / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009538:Nicotine / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D011951:Receptors, Complement / Q000037:antagonists & inhibitors / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012906:Smoke; D014026:Nicotiana / Q000737:chemistry; D051742:Transcription Factor CHOP / Q000235:genetics
D001559:Benzhydryl Compounds; C497250:Ddit3 protein, mouse; D000091342:Endoplasmic Reticulum Chaperone BiP; D016166:Free Radical Scavengers; D006360:Heat-Shock Proteins; D008055:Lipids; D011951:Receptors, Complement; C431907:SB 290157; D012906:Smoke; C085567:complement C3a receptor; D051742:Transcription Factor CHOP; D009538:Nicotine; D001120:Arginine; D011415:Complement Factor B; D000111:Acetylcysteine
Age-related Macular Degeneration; Complement System; ER Stress; Lipodystrophy; Mitochondria; Oxidative Stress; Smoking; Unfolded Protein Response