title: Downregulation of Rad51 participates in OTA-induced DNA double-strand breaks in GES-1 cells in vitro.
abstract: Ochratoxin A (OTA), a mycotoxin produced by ubiquitous Aspergilli, is carcinogenic, teratogenic, and nephrotoxic in both humans and animals. Our previous study found that OTA induced DNA double-strand breaks (DSBs) and resulted in G2 phase arrest in human gastric epithelium immortalized (GES-1) cells. DSBs can cause genomic instability, mutations, and neoplastic transformations, and improper repair of DSBs may lead to the development of cancer. Rad51 is a key protein in the homologous recombination (HR) pathway of DSBs repair. The roles of Rad51 in the repair of DNA damage vary in response to different types of cytotoxic agents. The effect of OTA on Rad51 expression and its putative role in the OTA-induced DSBs in GES-1 cells are still not clear enough. The aim of the current study is to elucidate the role of Rad51 in OTA-induced DSBs in GES-1 cells. The results showed that OTA treatment decreased Rad51 expression in a dose- and time-dependent manner. Specific downregulation of Rad51 by siRNA induced DSBs and G2 phase arrest. Rad51 overexpression by transfection with a Rad51-expressing plasmid partly rescued the DSBs and G2 phase arrest in OTA-treated cells. The findings indicate that downregulation of Rad51 contributes to OTA-induced DNA damage in GES-1 cells. Knockdown of p53 with siRNA for 48h effectively reversed the downregulation of Rad51, and decreased the OTA-induced DSBs in GES-1 cells. In addition, the downregulation of Rad51 induced by OTA could be significantly attenuated with specific ERK inhibitor PD98059 or specific p38 MAPK inhibitor SB203580 pre-treatment in GES-1 cells. Thus, the results suggest that downregulation of Rad51 participates in OTA-induced DNA double-strand breaks in GES-1 cells in vitro. And p53, ERK and p38 signaling pathways are all involved in the process.
authors: Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China.
authors: Hongguang
authors: H
authors: Lian
authors: Department of Pathology, The Second Hospital, Hebei Medical University, Shijiazhuang, China.
authors: Jinfeng
authors: J
authors: Cui
authors: Department of Pathology, The Second Hospital, Hebei Medical University, Shijiazhuang, China.
authors: Yuan
authors: Y
authors: Wang
authors: Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China.
authors: Jing
authors: J
authors: Liu
authors: Department of Pathology, The Second Hospital, Hebei Medical University, Shijiazhuang, China.
authors: Juan
authors: J
authors: Wang
authors: Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China.
authors: Haitao
authors: H
authors: Shen
authors: Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China.
authors: Lingxiao
authors: L
authors: Xing
authors: Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China.
authors: Junling
authors: J
authors: Wang
authors: Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China.
authors: Xia
authors: X
authors: Yan
authors: Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China. Electronic address: zhangxianghong2008@163.com.
authors: Xianghong
authors: X
authors: Zhang
mesh_terms: D002460:Cell Line; D053903:DNA Breaks, Double-Stranded; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects; D005753:Gastric Mucosa / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D006801:Humans; D009793:Ochratoxins / Q000633:toxicity*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034622:RNA Interference; D051135:Rad51 Recombinase / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D009793:Ochratoxins; D047428:Protein Kinase Inhibitors; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C025589:ochratoxin A; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C495153:RAD51 protein, human; D051135:Rad51 Recombinase
keywords: Cell cycle arrest; DNA double-strand breaks; Homologous recombination repair pathway; Human gastric epithelium immortalized cell; Ochratoxin A; Rad51