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UVA irradiation promotes ROS-mediated formation of the common deletion in mitochondrial DNA

ABSTRACT: Ultraviolet (UV) radiation from the sun causes adverse skin changes such as premature aging. UV-induced mitochondrial DNA (mtDNA) alterations, including deletions, contribute to photoaging and cellular dysfunction. The most frequent mtDNA rearrangement is the common deletion (CD), characterized by the loss of nearly one-third of the genome (4,977 bp). Although UV radiation exposure leads to CD formation, the molecular mechanisms initiating UV-induced CD remain poorly defined. In this study, we show that increasing UV doses increase CD levels in human skin fibroblasts. UVA exposure increased cellular reactive oxygen species (ROS) and mtDNA oxidation. Antioxidant preconditioning prevented UVA-induced CD accumulation, indicating a ROS-dependent mechanism. Conversely, UVB exposure induced cyclobutane pyrimidine dimers (CPDs) without affecting ROS, suggesting a ROS-independent pathway. Using a 3D full-thickness human skin model, we confirmed UVA-dependent CD formation in both epidermis and dermis. RNA-Seq analysis of UVA-exposed fibroblasts revealed upregulation of mitochondrial DNA replication genes and downregulation of mtDNA repair genes. Taken together, our findings provide insight into how UVA and UVB differ in their detrimental effects on mtDNA, with UVA impacting mtDNA maintenance and transcription via a ROS-dependent mechanism.

ORGANISM(S): Homo sapiens

PROVIDER: GSE302943 | GEO | 2025/11/30

REPOSITORIES: GEO

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Project description:Ultraviolet (UV) wavebands in sunlight are immunomodulatory. About half the amount of UVA within a minimum erythemal dose of sunlight is systemically immunosuppressive, while higher doses protect from UVB immunosuppression in mice. We have previously shown that these responses to UVA are genetically restricted as they occur in C57BL/6 but not Balb/c mice. We used gene set enrichment analysis of microarray data and real-time RT-PCR confirmation to determine the molecular mechanisms associated with UVA immunomodulation. We found up-regulation of mRNA for the alternative complement pathway. The core-enriched genes complement component 3, properdin and complement factor B were all activated by the immunosuppressive dose of UVA only in UVA-responsive C57BL/6 but not unresponsive BALB/c mice. This therefore matched the genetic restriction and dose responsiveness of UVA immunosuppression. The immune-protective higher UVA dose prevented UVB from down regulating chemokine receptor 7 and IL-12B, and decreased IL-10, supporting previous identification of IL-12 and IL-10 in high dose UVA protection from UVB immunosuppression. Our study has identified activation of the alternative complement pathway as a trigger of UVA-induced systemic immunosuppression and suggests that this pathway is likely to be an important sensor of UVA-induced damage to the skin. 24 hours after UVA, UVB and ssUV irradiation, a 1 cm2 uniform section of skin was excised from the dorsal surface of irradiated and control mice. Total RNA was then extracted from the whole skin using TRIzol reagent (Gibco Invitrogen Life Technologies, Carlsbad, CA, USA) according to the manufacturerâ??s instructions, purified, DNase treated and reverse transcribed into cDNA. For the microarray study a direct incorporation of Cyanine 3-dCTP and Cyanine 5-dCTP fluorescent dyes (Perkin Elmer Life Sciences, Inc. Boston, MA, USA) was used for cDNA synthesis. For each UV dose, a reference design was used to compare an unirradiated control against an irradiated sample. Microarray experiments used compugen 22k mouse oligonucleotide microarray slides (The Clive and Vera Ramaciotti Centre for Gene Function Analysis, Sydney Australia (http://www.ramaciotti.unsw.edu.au). Lower and higher UVA doses were used. C57BL/6 mice were irradiated with lower UVA, higher UVA, UVB, or ssUV; Balb/C mice were irradiated with lower or higher UVA. Experiments were replicated 6 times for each UV dose. A fluorescent dye swap was done for each alternate hybridisation to reduce systematic dye bias of incorporated fluorescent dyes.

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UVA irradiation promotes ROS-mediated formation of the common deletion in mitochondrial DNA

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