Effect of hydroquinone on expression of topoisomerase enzyme IIα in human bone marrow mononuclear cells / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the effects of hydroquinone (HQ) on expression of topoisomerase IIα (TOPOIIα) in human bone marrow mononuclear cells, and to explore the role and possible regulatory mechanism of TOPOIIα involved in toxicity of HQ to hematopoietic cells.</p><p><b>METHODS</b>After human bone marrow mononuclear cells were exposed to 50 µmol/L HQ (used the cells which were exposed to sterile distilled water as control); the activity of TOPOII was measured by TOPOII assay kit; the expression levels of TOPOIIα mRNA and protein were detected by RT-PCR technique and Western blotting method respectively; the chromatin immunoprecipitation (ChIP) assay was carried out to study the possible mechanism of TOPOIIα expression changes.</p><p><b>RESULTS</b>(1) The activity of TOPOII was inhibited obviously; the protein and mRNA expression of TOPOIIα were 0.017 ± 0.029 and 0.610 ± 0.128, significantly lower than that in the control with the significant difference (P < 0.01) after treated with HQ for 10 h; (2) The decreased content of TOPOIIα was associated with descended level of histone H4 acetylation than in the control, from 1.198 ± 0.056 to 0.324 ± 0.229, with the significant difference (P < 0.01), without accompanied descended level of histone H3 acetylation, from 1.253 ± 0.045 to 1.177 ± 0.025 (P > 0.05); (3) TOPOIIα mRNA expression decreased gradually after HQ processing, and the chemical modification (histone H4 acetylation) of TOPOIIα promoter happened prior to the mRNA expression.</p><p><b>CONCLUSION</b>HQ could repress the expression of TOPOIIα in human bone marrow mononuclear cells; the change of histone chemical modification plays an important role in the benzene's hematopoietic toxicity.</p>

Apoptosis induced by hydroquinone in bone marrow mononuclear cells in vitro / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To study the effect of hydroquinone on apoptosis of bone marrow mononuclear cells, and to evaluate the toxic effect of benzene on stem cells.</p><p><b>METHODS</b>Cell morphology was observed by HT fluorescent stain method, and DNA fragments were analyzed by agarose gel electrophoresis. Anti-Annexin V FITC plus PI staining for apoptotic and necrotic rate was examined by flow cytometer.</p><p><b>RESULTS</b>After adding different concentrations of hydroquinone to the cells for 6 h culture, the fluorescent intensity of nucleus increased, the color of nucleus became deep and inhomogeneous, and the chromatin was condensed and distributed around the neucleus. DNA ladder was detected in all samples. Cell apoptotic rate in different concentration of hydroquinone groups was significantly higher than that in blank control group (P < 0.05). With the increase of the concentration of hydroquinone, the apoptotic and necrotic rate also increased. The optimal concentration of hydroquinone was 50 micro mol/L. When it was >or= 75 micro mol/L, the necrotic rate increased significantly. Hydroquinone-induced apoptosis was associated with culture time at the concentration of 50 micro mol/L, and the peak apoptotic time was 10 h, then the apoptotic rate decreased and necrotic rate increased.</p><p><b>CONCLUSION</b>Hydroquinone can induce apoptosis of bone marrow mononuclear cells in vitro with dose-effect and time-effect relationship.</p>