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Ultraviolet radiation decreases expression and induces aggregation of corneal ALDH3A1
Rizwan Manzer1, Aglaia Pappa, Tia Estey
1Molecular Toxicology and Environmental Health Sciences Program, Department of Pharmaceutical Sciences, University of Colorado Health Sciences Center, Denver, CO 80262, USA.
Abstract:
Substantial reduction in corneal ALDH3A1 enzymatic activity associated with eye pathology was previously reported in C57BL/6J mice subjected to ultraviolet radiation (UVR). The aim of this study was to examine whether UVR diminishes corneal ALDH3A1 expression through modifications at the transcriptional, translational, or post-translational level. Adult C57BL/6J mice were subjected to UVR exposure (302 nm peak wavelength) for various periods of time, and corneal ALDH3A1 mRNA and protein levels were monitored by Northern and Western blot analysis, respectively. In addition, ALDH3A1 enzymatic activity was determined as a measure of post-translational modification. Mice exposed to 0.2 J/cm(2) UVB radiation demonstrated an extensive decrease, approximately 80%, in mRNA and protein levels, as well as enzymatic activity of corneal ALDH3A1. Significant reductions in corneal ALDH3A1 enzymatic activity were detected in mice 96 h after exposure to 0.05 and 0.1 J/cm(2) UVB radiation; no significant changes were observed in mRNA and protein levels. These data suggest that UVB down-regulates corneal ALDH3A1 expression at the transcriptional and/or post-translational level depending on the dose of UVB. Reduction in gene transcription requires UVB doses greater than or equal to 0.2 J/cm(2). In vitro experiments with human corneal epithelial cell lines stably transfected with human ALDH3A1 cDNA, and with purified recombinant human ALDH3A1 protein, indicated that ALDH3A1 undergoes post-translational modifications after UVR exposure. These modifications result in both covalent and non-covalent aggregation of the protein with no detectable precipitation. Such conformational changes may be associated with the function of ALDH3A1 as a chaperone-like molecule in the cornea.
Insights
Ultraviolet radiation (UVR) significantly reduces corneal aldehyde dehydrogenase 3A1 (ALDH3A1) expression and activity in mice. UVR affects gene transcription and protein modification, impacting ALDH3A1
Area of Science:
- Ophthalmology
- Molecular Biology
- Biochemistry
Background:
- Corneal aldehyde dehydrogenase 3A1 (ALDH3A1) enzymatic activity reduction is linked to eye pathology after ultraviolet radiation (UVR) exposure.
- Previous studies indicate UVR's detrimental effects on corneal tissues.
Purpose of the Study:
- To investigate if UVR diminishes corneal ALDH3A1 expression via transcriptional, translational, or post-translational modifications.
- To understand the dose-dependent effects of UVR on ALDH3A1 levels and activity.
Main Methods:
- Adult C57BL/6J mice were exposed to varying doses of UVR (302 nm).
- Corneal ALDH3A1 mRNA and protein levels were assessed using Northern and Western blot analyses.
- Enzymatic activity assays determined post-translational modifications; in vitro studies used human corneal epithelial cells and recombinant ALDH3A1 protein.
Main Results:
- A dose of 0.2 J/cm(2) UVB caused an ~80% decrease in corneal ALDH3A1 mRNA, protein, and enzymatic activity.
- Lower UVB doses (0.05 and 0.1 J/cm(2)) significantly reduced enzymatic activity but not mRNA or protein levels after 96 hours.
- In vitro experiments showed UVR induces ALDH3A1 post-translational modifications, including covalent and non-covalent aggregation.
Conclusions:
- UVB down-regulates corneal ALDH3A1 expression at transcriptional and/or post-translational levels, dependent on the UVR dose.
- Transcriptional reduction requires UVB doses ≥ 0.2 J/cm(2).
- Post-translational modifications, leading to protein aggregation, may alter ALDH3A1's chaperone-like function in the cornea following UVR exposure.