title: Overexpressed heat shock protein 70 protects cells against DNA damage caused by ultraviolet C in a dose-dependent manner.
abstract: Heat shock protein 70 (Hsp70) comprises proteins that have been reported to protect cells, tissues, and organisms against damage from a wide variety of stressful stimuli; however, little is known about whether Hsp70 protects against DNA damage. In this study, we investigated the relationship between Hsp70 expression and the levels of ultraviolet C (UVC)-induced DNA damage in A549 cells with normal, inhibited, and overexpressed Hsp70 levels. Hsp70 expression was inhibited by treatment with quercetin or overexpressed by transfection of plasmids harboring the hsp70 gene. The level of DNA damage was assessed by the comet assay. The results showed that the levels of DNA damage (shown as the percentage of comet cells) in A549 cells increased in all cells after exposure to an incident dose of 0, 10, 20, 40, and 80 J/m2 whether Hsp70 was inhibited or overexpressed. This response was dose dependent: a protection against UVC-induced DNA damage in cells with overexpressed Hsp70 was observed at UVC dose 20 J/m2 with a maximum at 40 J/m2 when compared with cells with normal Hsp70 levels and in quercetin-treated cells. This differential protection disappeared at 80 J/m2. These results suggest that overexpressed Hsp70 might play a role in protecting A549 cells from DNA damage caused by UVC irradiation, with a threshold of protection from at UVC irradiation-induced DNA damage by Hsp70. The detailed mechanism how Hsp70 is involved in DNA damage and possible DNA repair warrants further investigation.
authors.affiliation: Institute of Occupational Medicine and The Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Piye
authors.initials: P
authors.lastname: Niu
authors.forename: Lin
authors.initials: L
authors.lastname: Liu
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Gong
authors.forename: Hao
authors.initials: H
authors.lastname: Tan
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Yuan
authors.forename: Youmei
authors.initials: Y
authors.lastname: Feng
authors.forename: Qingyi
authors.initials: Q
authors.lastname: Wei
authors.forename: Robert M
authors.initials: RM
authors.lastname: Tanguay
authors.forename: Tangchun
authors.initials: T
authors.lastname: Wu
mesh_terms: D045744:Cell Line, Tumor; D020552:Comet Assay / Q000379:methods; D004247:DNA / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D004249:DNA Damage; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D010957:Plasmids / Q000235:genetics; D014176:Protein Biosynthesis / Q000187:drug effects; D011794:Quercetin / Q000494:pharmacology; D014466:Ultraviolet Rays
chemical_list: D018840:HSP70 Heat-Shock Proteins; D004247:DNA; D011794:Quercetin