Inhibitors of Nucleotide Excision Repair Decrease UVB-Induced Mutagenesis-An In Vitro Study.

Eszter Fidrus,Éva Remenyik,Gabriella Emri,György Paragh,Eszter Anna Janka,Csaba Hegedűs

doi:10.3390/ijms22041638

Eszter Fidrus, Éva Remenyik + Show 4 more

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https://doi.org/10.3390/ijms22041638

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Abstract

The high incidence of skin cancers in the Caucasian population is primarily due to the accumulation of DNA damage in epidermal cells induced by chronic ultraviolet B (UVB) exposure. UVB-induced DNA photolesions, including cyclobutane–pyrimidine dimers (CPDs), promote mutations in skin cancer driver genes. In humans, CPDs are repaired by nucleotide excision repair (NER). Several commonly used and investigational medications negatively influence NER in experimental systems. Despite these molecules’ ability to decrease NER activity in vitro, the role of these drugs in enhancing skin cancer risk is unclear. In this study, we investigated four molecules (veliparib, resveratrol, spironolactone, and arsenic trioxide) with well-known NER-inhibitory potential in vitro, using UVB-irradiated CHO epithelial and HaCaT immortalized keratinocyte cell lines. Relative CPD levels, hypoxanthine phosphoribosyltransferase gene mutation frequency, cell viability, cell cycle progression, and protein expression were assessed. All four molecules significantly elevated CPD levels in the genome 24 h after UVB irradiation. However, veliparib, spironolactone, and arsenic trioxide reduced the mutagenic potential of UVB, while resveratrol did not alter UVB-induced mutation formation. UVB-induced apoptosis was enhanced by spironolactone and arsenic-trioxide treatment, while veliparib caused significantly prolonged cell cycle arrest and increased autophagy. Spironolactone also enhanced the phosphorylation level of mammalian target of rapamycin (mTOR), while arsenic trioxide modified UVB-driven mitochondrial fission. Resveratrol induced only mild changes in the cellular UVB response. Our results show that chemically inhibited NER does not result in increased mutagenic effects. Furthermore, the UVB-induced mutagenic potential can be paradoxically mitigated by NER-inhibitor molecules. We identified molecular changes in the cellular UVB response after NER-inhibitor treatment, which may compensate for the mitigated DNA repair. Our findings show that metabolic cellular response pathways are essential to consider in evaluating the skin cancer risk–modifying effects of pharmacological compounds.

Highlights

The incidence of melanoma [1,2,3,4] and nonmelanoma skin cancers [4,5] is increasing in lighter skin types and is attributed to enhanced exposure of the skin to ultravioletB (UVB) [6,7,8]
To verify the nucleotide excision repair (NER)-inhibitory effect of veliparib, resveratrol, arsenic trioxide, and spironolactone, CHO cells were pretreated with the chemicals and irradiated with 20 mJ/cm2 UVB
We evaluated the kinetics of cyclobutane–pyrimidine dimers (CPDs) removal after UVB irradiation, and we found that most of the UV-induced lesions (~60%) are eliminated from the DNA in the first 24 h [51]

Summary

Introduction

The incidence of melanoma [1,2,3,4] and nonmelanoma skin cancers [4,5] is increasing in lighter skin types and is attributed to enhanced exposure of the skin to ultravioletB (UVB) [6,7,8]. UVB radiation induces DNA damage in epidermal cells [9]. The most common UVB-induced DNA changes are pyrimidine–pyrimidone photoproducts (6-4PPs) and cyclobutane–pyrimidine dimers (CPDs) [9,10]. These photolesions disrupt DNA structure by forming stable bonds between two adjacent pyrimidine bases [10,11]. CPDs form up to five times more frequently after UVB radiation than 6-4PPs [12,13], and CPDs are the leading cause of UV-signature mutations, specific markers for UV-induced DNA damage [11]. Wei et al showed that CPDs show different accumulation throughout the genome, as enrichment of UV-signature mutations on specific genetic locations (mutational hotspots) can be detected [14,15]

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