Radioprotective effect on HepG2 cells of low concentrations of cobalt chloride: induction of hypoxia-inducible factor-1 alpha and clearance of reactive oxygen species.
It has been found that low doses of certain toxicants might generate a protective response to cellular damage. Previous data have shown that elevated doses of cobalt (Co) induce injury to cells and organisms or result in radiological combined toxicity. Whether low doses of Co generate a protective effect or not, however, remains controversial. In this study, we investigated the effect and mechanism of action of low dose cobalt chloride (CoCl2, 100 μM) on the viability of irradiated cells. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay was used to observe the radio-sensitivity of HepG2 cells under different pretreatments. The alteration of intracellular DNA damage was further measured using micronucleus (MN) assay. Levels of hypoxia inducible factor-1α (HIF-1α) expression and its target gene, EPO, were monitored by western blot and reverse transcription polymerase chain reaction (RT-PCR), respectively, and intracellular reactive oxygen species (ROS) content was determined by 2',7'-dichlorofluorescein diacetate (DCFH-DA) probe staining. Our results show that low dose CoCl2does not influence HepG2 cell viability, but induces the expression of HIF-1α, followed by increased radio-resistance. Additionally, cells treated with HIF-1α siRNA retained a partial refractory response to irradiation concomitant with a marked reduction in intracellular ROS. The change of MN further indicated that the reduction of DNA damage was confirmed with the alteration of ROS. Our results demonstrate that low dose CoCl2may protect cells against irradiative harm by two mechanisms, namely HIF-1α expression and ROS clearance.
Teaching & Research Section of Nuclear Medicine, An-hui Medical University, 81 Mei-Shan Road, Hefei, China.
Wensen
W
Jin
Juan
J
Wang
Shiguo
S
Xu
Linlin
L
Xiao
Guangfu
G
Chen
Wukui
W
Zhang
Jun
J
Li
D002470:Cell Survival / Q000187:drug effects* / Q000502:physiology*; D003035:Cobalt / Q000008:administration & dosage*; D004249:DNA Damage / Q000187:drug effects / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D056945:Hep G2 Cells; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D008657:Metabolic Clearance Rate / Q000187:drug effects / Q000502:physiology; D011836:Radiation Tolerance / Q000187:drug effects / Q000502:physiology*; D011837:Radiation-Protective Agents / Q000008:administration & dosage; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D011837:Radiation-Protective Agents; D017382:Reactive Oxygen Species; D003035:Cobalt; C018021:cobaltous chloride