title: Human aldehyde dehydrogenase 3A1 inhibits proliferation and promotes survival of human corneal epithelial cells.
abstract: Aldehyde dehydrogenase 3A1 (ALDH3A1) is a NAD(P)+-dependent enzyme that is highly expressed in mammalian corneal epithelial cells and has been shown to protect against UV- and 4-hydroxynonenal-induced cellular damage, mainly by metabolizing toxic lipid peroxidation aldehydes. Here we report a novel function of ALDH3A1 as a negative cell cycle regulator. We noticed a reduction in ALDH3A1 gene expression in actively proliferating primary human corneal epithelium explant cultures, indicating that ALDH3A1 expression is inversely correlated with replication. To examine this further, a human corneal epithelial cell line (HCE) lacking endogenous ALDH3A1 was stably transfected to express ALDH3A1 at levels similar to those found in vivo. ALDH3A1-transfected cells exhibited an elongated cell cycle, decreased plating efficiency, and reduced DNA synthesis compared with the mock-transfected cells. These effects were associated with reduced cyclin A- and cyclin B-dependent kinase activities and reduced phosphorylation of the retinoblastoma protein (pRb) as well as decreased protein levels of cyclins A, B, and E, the transcription factor E2F1, and the cyclin-dependent kinase inhibitor p21. These observations were further expanded and confirmed on human keratinocyte cells (NCTC-2544) overexpressing ALDH3A1. Consistent with a protective role of an elongated cell cycle, ALDH3A1-transfected cells exhibited increased resistance to the cytotoxic effects of the DNA-damaging agents mitomycin C and Vp-16. Immunohistochemistry and biochemical fractionation revealed that ALDH3A1 is localized both in the nucleus and cytosol of ALDH3A1-transfected cells, implying a possible association between the nuclear localization of the enzyme and its proliferation-suppressive functions. In conclusion, these results suggest that ALDH3A1 may protect corneal epithelial cells against oxidative damage not only through its metabolic function but also by prolonging the cell cycle.
authors.affiliation: Molecular Toxicology and Environmental Health Sciences Program, University Colorado Health Sciences Center, Denver, Colorado 80262, USA.
authors.forename: Aglaia
authors.initials: A
authors.lastname: Pappa
authors.forename: Donald
authors.initials: D
authors.lastname: Brown
authors.forename: Yiannis
authors.initials: Y
authors.lastname: Koutalos
authors.forename: James
authors.initials: J
authors.lastname: DeGregori
authors.forename: Carl
authors.initials: C
authors.lastname: White
authors.forename: Vasilis
authors.initials: V
authors.lastname: Vasiliou
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000378:metabolism / Q000502:physiology*; D000447:Aldehydes / Q000494:pharmacology; D017209:Apoptosis; D015153:Blotting, Western; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D003315:Cornea / Q000166:cytology / Q000378:metabolism; D019925:Cyclin A / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism; D019927:Cyclin E / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D053938:DNA Fragmentation; D004268:DNA-Binding Proteins / Q000378:metabolism; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; D004847:Epithelial Cells / Q000166:cytology*; D005786:Gene Expression Regulation; D006801:Humans; D007150:Immunohistochemistry; D015603:Keratinocytes / Q000166:cytology; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D016685:Mitomycin / Q000494:pharmacology; D018384:Oxidative Stress; D011494:Protein Kinases / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D014466:Ultraviolet Rays
chemical_list: D000447:Aldehydes; D018797:Cell Cycle Proteins; D019925:Cyclin A; D019926:Cyclin B; D019927:Cyclin E; D004268:DNA-Binding Proteins; D050684:E2F Transcription Factors; D050687:E2F1 Transcription Factor; C493753:E2F1 protein, human; D016160:Retinoblastoma Protein; D014157:Transcription Factors; D016685:Mitomycin; D004247:DNA; C480021:ALDH3A1 protein, human; D000444:Aldehyde Dehydrogenase; D011494:Protein Kinases; C102333:histone H1 kinase; D001973:Bromodeoxyuridine; C027576:4-hydroxy-2-nonenal