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Regulation of hypoxia inducible factor-1α expression by the alteration of redox status in HepG2 cells.

Jin WS, Kong ZL, Shen ZF, Jin YZ, Zhang WK, Chen GF - J. Exp. Clin. Cancer Res. (2011)

Bottom Line: To further confirm the effect of intracellular redox status on HIF-1α expression, N-acetylcysteine (NAC) was added to culture cells for 8 h before the hypoxia treatment.The results showed that BSO pretreatment down-regulated HIF-1α and the effect was concentration-dependent, on the other hand, the increases of intracellular GSH contents by NAC could partly elevate the levels of HIF-1α expression.The levels of P-Gp (MDR-1) and EPO were concomitant with the trend of HIF-1α expression.

View Article: PubMed Central - HTML - PubMed

Affiliation: Teaching & Research Section of Nuclear Medicine, An-hui Medical University, Hefei, China. wensenjn@139.com

ABSTRACT
Hypoxia inducible factor-1 (HIF-1) has been considered as a critical transcriptional factor in response to hypoxia. It can increase P-glycoprotein (P-Gp) thus generating the resistant effect to chemotherapy. At present, the mechanism regulating HIF-1α is still not fully clear in hypoxic tumor cells. Intracellular redox status is closely correlated with hypoxic micro-environment, so we investigate whether alterations in the cellular redox status lead to the changes of HIF-1α expression. HepG2 cells were exposed to Buthionine sulphoximine (BSO) for 12 h prior to hypoxia treatment. The level of HIF-1α expression was measured by Western blot and immunocytochemistry assays. Reduce glutathione (GSH) concentrations in hypoxic cells were determined using glutathione reductase/5,5'-dithiobis-(2-nitrob-enzoic acid) (DTNB) recycling assay. To further confirm the effect of intracellular redox status on HIF-1α expression, N-acetylcysteine (NAC) was added to culture cells for 8 h before the hypoxia treatment. The levels of multidrug resistance gene-1 (MDR-1) and erythropoietin (EPO) mRNA targeted by HIF-1α in hypoxic cells were further determined with RT-PCR, and then the expression of P-Gp protein was observed by Western blotting. The results showed that BSO pretreatment down-regulated HIF-1α and the effect was concentration-dependent, on the other hand, the increases of intracellular GSH contents by NAC could partly elevate the levels of HIF-1α expression. The levels of P-Gp (MDR-1) and EPO were concomitant with the trend of HIF-1α expression. Therefore, our data indicate that the changes of redox status in hypoxic cells may regulate HIF-1α expression and provide valuable information on tumor chemotherapy.

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Toxicity of BSO on HepG2 cells. Under normoxic or hypoxic condition, HepG2 cells were treated with different concentration of BSO for 12 h before subjected to the MTT assay. The viability was calculated by subtracting the background absorbance and divided by the control absorbance. Both normoxia and hypoxia, the results showed that there was not significance in the decrease of cells viability until the concentration of BSO was at 400 μM. The change of cells viability, under normoxia or hypoxia, was displayed in Diagram A and Diagram B respectively.
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Figure 1: Toxicity of BSO on HepG2 cells. Under normoxic or hypoxic condition, HepG2 cells were treated with different concentration of BSO for 12 h before subjected to the MTT assay. The viability was calculated by subtracting the background absorbance and divided by the control absorbance. Both normoxia and hypoxia, the results showed that there was not significance in the decrease of cells viability until the concentration of BSO was at 400 μM. The change of cells viability, under normoxia or hypoxia, was displayed in Diagram A and Diagram B respectively.

Mentions: In order to select the appropriate concentration of BSO for the study, a 12 h dose-response study was conducted by exposing cells to different concentrations of BSO. Cell viability was measured by the MTT assay. The results showed that there was not significant decrease in viability over a 12 h exposure to BSO concentration ranging from 12.5 to 200 μM (Figure 1). In subsequent studies, the concentrations of BSO used were set at 50, 100, 200 μM.


Regulation of hypoxia inducible factor-1α expression by the alteration of redox status in HepG2 cells.

Jin WS, Kong ZL, Shen ZF, Jin YZ, Zhang WK, Chen GF - J. Exp. Clin. Cancer Res. (2011)

Toxicity of BSO on HepG2 cells. Under normoxic or hypoxic condition, HepG2 cells were treated with different concentration of BSO for 12 h before subjected to the MTT assay. The viability was calculated by subtracting the background absorbance and divided by the control absorbance. Both normoxia and hypoxia, the results showed that there was not significance in the decrease of cells viability until the concentration of BSO was at 400 μM. The change of cells viability, under normoxia or hypoxia, was displayed in Diagram A and Diagram B respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3113749&req=5

Figure 1: Toxicity of BSO on HepG2 cells. Under normoxic or hypoxic condition, HepG2 cells were treated with different concentration of BSO for 12 h before subjected to the MTT assay. The viability was calculated by subtracting the background absorbance and divided by the control absorbance. Both normoxia and hypoxia, the results showed that there was not significance in the decrease of cells viability until the concentration of BSO was at 400 μM. The change of cells viability, under normoxia or hypoxia, was displayed in Diagram A and Diagram B respectively.
Mentions: In order to select the appropriate concentration of BSO for the study, a 12 h dose-response study was conducted by exposing cells to different concentrations of BSO. Cell viability was measured by the MTT assay. The results showed that there was not significant decrease in viability over a 12 h exposure to BSO concentration ranging from 12.5 to 200 μM (Figure 1). In subsequent studies, the concentrations of BSO used were set at 50, 100, 200 μM.

Bottom Line: To further confirm the effect of intracellular redox status on HIF-1α expression, N-acetylcysteine (NAC) was added to culture cells for 8 h before the hypoxia treatment.The results showed that BSO pretreatment down-regulated HIF-1α and the effect was concentration-dependent, on the other hand, the increases of intracellular GSH contents by NAC could partly elevate the levels of HIF-1α expression.The levels of P-Gp (MDR-1) and EPO were concomitant with the trend of HIF-1α expression.

View Article: PubMed Central - HTML - PubMed

Affiliation: Teaching & Research Section of Nuclear Medicine, An-hui Medical University, Hefei, China. wensenjn@139.com

ABSTRACT
Hypoxia inducible factor-1 (HIF-1) has been considered as a critical transcriptional factor in response to hypoxia. It can increase P-glycoprotein (P-Gp) thus generating the resistant effect to chemotherapy. At present, the mechanism regulating HIF-1α is still not fully clear in hypoxic tumor cells. Intracellular redox status is closely correlated with hypoxic micro-environment, so we investigate whether alterations in the cellular redox status lead to the changes of HIF-1α expression. HepG2 cells were exposed to Buthionine sulphoximine (BSO) for 12 h prior to hypoxia treatment. The level of HIF-1α expression was measured by Western blot and immunocytochemistry assays. Reduce glutathione (GSH) concentrations in hypoxic cells were determined using glutathione reductase/5,5'-dithiobis-(2-nitrob-enzoic acid) (DTNB) recycling assay. To further confirm the effect of intracellular redox status on HIF-1α expression, N-acetylcysteine (NAC) was added to culture cells for 8 h before the hypoxia treatment. The levels of multidrug resistance gene-1 (MDR-1) and erythropoietin (EPO) mRNA targeted by HIF-1α in hypoxic cells were further determined with RT-PCR, and then the expression of P-Gp protein was observed by Western blotting. The results showed that BSO pretreatment down-regulated HIF-1α and the effect was concentration-dependent, on the other hand, the increases of intracellular GSH contents by NAC could partly elevate the levels of HIF-1α expression. The levels of P-Gp (MDR-1) and EPO were concomitant with the trend of HIF-1α expression. Therefore, our data indicate that the changes of redox status in hypoxic cells may regulate HIF-1α expression and provide valuable information on tumor chemotherapy.

Show MeSH
Related in: MedlinePlus