Time‐course Expression of DNA Repair‐related Genes in Hepatocytes of Zebrafish (Danio rerio) After UV‐B Exposure

Abstract

The objective of this study was to evaluate the time-course effects of UV-B exposure on expression of genes involved in the DNA repair system of zebrafish (Danio rerio) hepatocytes, a highly competent species in terms of damage repair induced by UV radiation. For gene expression analysis (RT-PCR), cells were exposed to 23.3 mJ cm )2 UV-B, which was the dose that affected viable cell number (reduction of 30% when compared with the control group) and produced no visual alteration on cell morphology. The early response observed (6 h) showed induction in the expression of the CDKI gene (cyclin-dependent kinase inhibitor) and genes related to DNA damage repair (mainly XPC and DDB2), while the late response observed (24 h) was more related to up-regulation of p53 and genes involved in cell cycle arrest (gadd45a, cyclinG1). In all times analyzed, the antiapoptotic gene Bcl-2 was down-regulated. Another interesting result observed was the up-regulation of the Apex-1 gene after UV-B exposure, which could indicate the induction of oxidative lesions in the DNA molecule. In conclusion, these results demonstrate an activation of the DNA repair system in hepatocytes of zebrafish exposed to UV-B radiation, mainly involving the participation of p53.

Zebrafish Have a Competent p53-Dependent Nucleotide Excision Repair Pathway to Resolve Ultraviolet B–Induced DNA Damage in the Skin

“…We find that the expression DDB2 increased in UV exposed wild type and p53 mutant embryos, with a greater increase in wild type embryos. In contrast, KU80 involved in nonhomologous end joining (NHEJ) pathway (Bladen et al , 2005) did not change after UV treatment, consistent with the finding in zebrafish hepatocytes indicating that NHEJ is not the main mechanism of DNA repair in zebrafish after UVB irradiation (Sandrini et al, 2009). Light induced apoptosis can also cause an increase in expression of the pro-apoptotic caspase3 gene that correlates with Caspase 3 activity (Wu et a l., 2002).…”

“…DNA repair appears to vary at specific stages in development, with 12hpf embryos showing the greatest sensitivity to UVA and UVB treatment (Dong et al, 2007). In cultured zebrafish hepatocytes, the early response to UVB irradiation involves DNA repair genes such as XPC and DDB2, and the late response includes up-regulation of p53 and cell cycle arrest (Sandrini et al , 2009). In this study, we describe a methodology for treating larval and young adult zebrafish with UV.…”

UVA and UVB Penetration in the Water Column of a South West Atlantic Warm Temperate Estuary and its Effects on Cells and Fish Larvae

“…The results with the highest UVB radiation (0.075 J cm −2 ) were indicative of phototoxicity, since it reduced cell proliferation significantly. Corroborating our results, Sandrini et al (2009) showed that irradiation of zebrafish hepatocytes with UVB (0.07 J cm −2 ) reduced the number of viable cells. Only the lowest dose (0.01 J cm −2 ) was unable to significantly reduce viable cell numbers.…”

Simulation study of natural UV-B radiation on Catla catla and its impact on physiology, oxidative stress, Hsp 70 and DNA fragmentation

“…Prolonged exposure of fish to UV-B radiation often results in DNA damage that can pose a significant threat to its survival [14,15]. If DNA damage is not repaired, cells undergo complex enzymatic reactions expends high energy that might lead to apoptosis, necrosis or other forms of cell death [16]. The alterations most frequently induced are cyclobutane pyrimidine dimers (CPDs) and pyrimidine pyrimodone photoproducts [17,18,1].…”