TY - JOUR
T1 - Interactive effects of ultraviolet-B radiation and pesticide exposure on DNA photo-adduct accumulation and expression of DNA damage and repair genes in Xenopus laevis embryos
AU - Yu, Shuangying
AU - Tang, Song
AU - Mayer, Gregory D.
AU - Cobb, George P.
AU - Maul, Jonathan D.
N1 - Funding Information:
S. Yu received support from a Sigma Xi Grant-In-Aid of Research . The authors would like to thank Mike Wages for his assistance with breeding frogs. Appendix A
Publisher Copyright:
© 2014 Elsevier B.V.
PY - 2015/2/1
Y1 - 2015/2/1
N2 - Pesticide use and ultraviolet-B (UVB) radiation have both been suggested to adversely affect amphibians; however, little is known about their interactive effects. One potential adverse interaction could involve pesticide-induced dysregulation of DNA repair pathways, resulting in greater numbers of DNA photo-adducts from UVB exposure. In the present study, we investigated the interactive effects of UVB radiation and two common pesticides (endosulfan and α-cypermethrin) on induction of DNA photo-adducts and expression of DNA damage and repair related genes in African clawed frog ( Xenopus laevis) embryos. We examined 13 genes that are, collectively, involved in stress defense, cell cycle arrest, nucleotide excision repair (NER), base excision repair, mismatch repair, DNA repair regulation, and apoptosis. We exposed X. laevis embryos to 0, 25, and 50. μg/L endosulfan or 0, 2.5, and 5.0. μg/L α-cypermethrin for 96. h, with environmentally relevant exposures of UVB radiation during the last 7. h of the 96. h exposure. We measured the amount of cyclobutane pyrimidine dimers (CPDs) and mRNA abundance of the 13 genes among treatments including control, pesticide only, UVB only, and UVB and pesticide co-exposures. Each of the co-exposure scenarios resulted in elevated CPD levels compared to UVB exposure alone, suggesting an inhibitory effect of endosulfan and α-cypermethrin on CPD repair. This is attributed to results indicating that α-cypermethrin and endosulfan reduced mRNA abundance of XPA and HR23B, respectively, to levels that may affect the initial recognition of DNA lesions. In contrast, both pesticides increased transcript abundance of CSA and MUTL. In addition, mRNA abundance of HSP70 and GADD45α were increased by endosulfan and mRNA abundance of XPG was increased by α-cypermethrin. XPC, HR23B, XPG, and GADD45α exhibited elevated mRNA concentrations whereas there was a reduction in MUTL transcript concentrations in UVB-alone treatments. It appeared that even though expression of XPC and CSA were induced by exposure to UVB or pesticides, XPA was the limiting factor in the NER pathway. Our results suggest that pesticides may increase the accumulation of UVB-induced DNA photo-adducts and one likely mechanism is the alteration of critical NER gene expression. The present study provides important implications for evaluating the combined risks of pesticide usage and potentially increasing UVB radiation in aquatic ecosystems.
AB - Pesticide use and ultraviolet-B (UVB) radiation have both been suggested to adversely affect amphibians; however, little is known about their interactive effects. One potential adverse interaction could involve pesticide-induced dysregulation of DNA repair pathways, resulting in greater numbers of DNA photo-adducts from UVB exposure. In the present study, we investigated the interactive effects of UVB radiation and two common pesticides (endosulfan and α-cypermethrin) on induction of DNA photo-adducts and expression of DNA damage and repair related genes in African clawed frog ( Xenopus laevis) embryos. We examined 13 genes that are, collectively, involved in stress defense, cell cycle arrest, nucleotide excision repair (NER), base excision repair, mismatch repair, DNA repair regulation, and apoptosis. We exposed X. laevis embryos to 0, 25, and 50. μg/L endosulfan or 0, 2.5, and 5.0. μg/L α-cypermethrin for 96. h, with environmentally relevant exposures of UVB radiation during the last 7. h of the 96. h exposure. We measured the amount of cyclobutane pyrimidine dimers (CPDs) and mRNA abundance of the 13 genes among treatments including control, pesticide only, UVB only, and UVB and pesticide co-exposures. Each of the co-exposure scenarios resulted in elevated CPD levels compared to UVB exposure alone, suggesting an inhibitory effect of endosulfan and α-cypermethrin on CPD repair. This is attributed to results indicating that α-cypermethrin and endosulfan reduced mRNA abundance of XPA and HR23B, respectively, to levels that may affect the initial recognition of DNA lesions. In contrast, both pesticides increased transcript abundance of CSA and MUTL. In addition, mRNA abundance of HSP70 and GADD45α were increased by endosulfan and mRNA abundance of XPG was increased by α-cypermethrin. XPC, HR23B, XPG, and GADD45α exhibited elevated mRNA concentrations whereas there was a reduction in MUTL transcript concentrations in UVB-alone treatments. It appeared that even though expression of XPC and CSA were induced by exposure to UVB or pesticides, XPA was the limiting factor in the NER pathway. Our results suggest that pesticides may increase the accumulation of UVB-induced DNA photo-adducts and one likely mechanism is the alteration of critical NER gene expression. The present study provides important implications for evaluating the combined risks of pesticide usage and potentially increasing UVB radiation in aquatic ecosystems.
KW - Amphibians
KW - Climate change
KW - HR23B
KW - Insecticides
KW - XPA
UR - http://www.scopus.com/inward/record.url?scp=84920718979&partnerID=8YFLogxK
U2 - 10.1016/j.aquatox.2014.12.004
DO - 10.1016/j.aquatox.2014.12.004
M3 - Article
C2 - 25569846
AN - SCOPUS:84920718979
VL - 159
SP - 256
EP - 266
JO - Aquatic Toxicology
JF - Aquatic Toxicology
SN - 0166-445X
ER -