title: ALDH3A1 Plays a Functional Role in Maintenance of Corneal Epithelial Homeostasis.
abstract: Aldehyde dehydrogenase 1A1 (ALDH1A1) and ALDH3A1 are corneal crystallins. They protect inner ocular tissues from ultraviolet radiation (UVR)-induced oxidative damage through catalytic and non-catalytic mechanisms. Additionally, ALDH3A1 has been postulated to play a regulatory role in the corneal epithelium based on several studies that report an inverse association between ALDH3A1 expression and corneal cell proliferation. The underlying molecular mechanisms and the physiological significance of such association remain poorly understood. In the current study, we established Tet-On human corneal epithelial cell (hTCEpi) lines, which express tetracycline-inducible wild-type (wt) or catalytically-inactive (mu) ALDH3A1. Utilizing this cellular model system, we confirmed that human ALDH3A1 decreases corneal cell proliferation; importantly, this effect appears to be partially mediated by its enzymatic activity. Mechanistically, wt-ALDH3A1, but not mu-ALDH3A1, promotes sequestering of tumor suppressor p53 in the nucleus. In the mouse cornea, however, augmented cell proliferation is noted only in Aldh1a1(-/-)/3a1(-/-) double knockout (DKO) mice, indicating in vivo the anti-proliferation effect of ALDH3A1 can be rescued by the presence of ALDH1A1. Interestingly, the hyper-proliferative epithelium of the DKO corneas display nearly complete loss of p53 expression, implying that p53 may be involved in ALDH3A1/1A1-mediated effect. In hTCEpi cells grown in high calcium concentration, mRNA levels of a panel of corneal differentiation markers were altered by ALDH3A1 expression and modulated by its enzyme activity. In conclusion, we show for the first time that: (i) ALDH3A1 decreases corneal epithelial proliferation through both non-enzymatic and enzymatic properties; (ii) ALDH1A1 contributes to the regulation of corneal cellular proliferation in vivo; and (iii) ALDH3A1 modulates corneal epithelial differentiation. Collectively, our studies indicate a functional role of ALDH3A1 in the maintenance of corneal epithelial homeostasis by simultaneously modulating proliferation and differentiation through both enzymatic and non-enzymatic mechanisms.
authors.affiliation: Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America.
authors.forename: Vindhya
authors.initials: V
authors.lastname: Koppaka
authors.affiliation: Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America.|Department of Environmental Health Sciences, Yale School of Public Health, New Haven, Connecticut, United States of America.
authors.forename: Ying
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Mehta
authors.affiliation: Department of Pathology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America.
authors.forename: David J
authors.initials: DJ
authors.lastname: Orlicky
authors.affiliation: Department of Clinical Pharmacology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America.
authors.forename: David C
authors.initials: DC
authors.lastname: Thompson
authors.affiliation: Department of Ophthalmology, Gavin Herbert Eye Institute, University of California Irvine, Irvine, California, United States of America.
authors.forename: James V
authors.initials: JV
authors.lastname: Jester
authors.affiliation: Department of Environmental Health Sciences, Yale School of Public Health, New Haven, Connecticut, United States of America.
authors.forename: Vasilis
authors.initials: V
authors.lastname: Vasiliou
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000235:genetics / Q000502:physiology*; D000818:Animals; D002384:Catalysis; D002417:Cattle; D002454:Cell Differentiation; D049109:Cell Proliferation; D018076:DNA, Complementary / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology*; D019573:Epithelium, Corneal / Q000378:metabolism*; D057809:HEK293 Cells; D006706:Homeostasis; D006801:Humans; D019394:Ki-67 Antigen / Q000378:metabolism; D016086:Lentivirus / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D010100:Oxygen / Q000737:chemistry; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D000444:Aldehyde Dehydrogenase; D018076:DNA, Complementary; D019394:Ki-67 Antigen; D010100:Oxygen; D016159:Tumor Suppressor Protein p53; C495901:TP53 protein, human; C480021:ALDH3A1 protein, human; C105543:Aldh3a1 protein, mouse