Yongyi Bi

Inhibition of DNA-dependent protein kinase catalytic subunit by small molecule inhibitor NU7026 sensitizes human leukemic K562 cells to benzene metabolite-induced apoptosis

SummaryBenzene is an established leukotoxin and leukemogen in humans. We have previously reported that exposure of workers to benzene and to benzene metabolite hydroquinone in cultured cells induced DNA-dependent protein kinase catalytic subunit (DNA-PKcs) to mediate the cellular response to DNA double strand break (DSB) caused by DNA-damaging metabolites. In this study, we used a new, small molecule, a selective inhibitor of DNA-PKcs, 2-(morpholin-4-yl)-benzo[h]chomen-4-one (NU7026), as a probe to analyze the molecular events and pathways in hydroquinone-induced DNA DSB repair and apoptosis. Inhibition of DNA-PKcs by NU7026 markedly potentiated the apoptotic and growth inhibitory effects of hydroquinone in proerythroid leukemic K562 cells in a dose-dependent manner. Treatment with NU7026 did not alter the production of reactive oxygen species and oxidative stress by hydroquinone but repressed the protein level of DNA-PKcs and blocked the induction of the kinase mRNA and protein expression by hydroquinone. Moreover, hydroquinone increased the phosphorylation of Akt to activate Akt, whereas co-treatment with NU7026 prevented the activation of Akt by hydroquinone. Lastly, hydroquinone and NU7026 exhibited synergistic effects on promoting apoptosis by increasing the protein levels of pro-apoptotic proteins Bax and caspase-3 but decreasing the protein expression of anti-apoptotic protein Bcl-2. Taken together, the findings reveal a central role of DNA-PKcs in hydroquinone-induced hematotoxicity in which it coordinates DNA DSB repair, cell cycle progression, and apoptosis to regulate the response to hydroquinone-induced DNA damage.Benzene is an established leukotoxin and leukemogen in humans. We have previously reported that exposure of workers to benzene and to benzene metabolite hydroquinone in cultured cells induced DNA-dependent protein kinase catalytic subunit (DNA-PKcs) to mediate the cellular response to DNA double strand break (DSB) caused by DNA-damaging metabolites. In this study, we used a new, small molecule, a selective inhibitor of DNA-PKcs, 2-(morpholin-4-yl)-benzo[h]chomen-4-one (NU7026), as a probe to analyze the molecular events and pathways in hydroquinone-induced DNA DSB repair and apoptosis. Inhibition of DNA-PKcs by NU7026 markedly potentiated the apoptotic and growth inhibitory effects of hydroquinone in proerythroid leukemic K562 cells in a dose-dependent manner. Treatment with NU7026 did not alter the production of reactive oxygen species and oxidative stress by hydroquinone but repressed the protein level of DNA-PKcs and blocked the induction of the kinase mRNA and protein expression by hydroquinone. Moreover, hydroquinone increased the phosphorylation of Akt to activate Akt, whereas co-treatment with NU7026 prevented the activation of Akt by hydroquinone. Lastly, hydroquinone and NU7026 exhibited synergistic effects on promoting apoptosis by increasing the protein levels of pro-apoptotic proteins Bax and caspase-3 but decreasing the protein expression of anti-apoptotic protein Bcl-2. Taken together, the findings reveal a central role of DNA-PKcs in hydroquinone-induced hematotoxicity in which it coordinates DNA DSB repair, cell cycle progression, and apoptosis to regulate the response to hydroquinone-induced DNA damage.

Cross-sectional study of cardiovascular effects of carbon disulfide among Chinese workers of a viscose factory

OBJECTIVE This cross-sectional study investigates the cardiovascular effects among Chinese workers who were occupationally exposed to carbon disulfide (CS2), and evaluates the protective value of the current Chinese Maximum Allowable Concentration (MAC) of CS2 against cardiovascular effects. METHODS The measurements of exposure were performed by personal sampling and gas chromatography. The biological monitoring was performed by HPLC. Three hundred and sixty-seven exposed workers and 125 reference workers (never exposed to CS2,) were included in this study. The exposed workers were divided into 2 sub-groups according to their cumulative exposure indices, the cut-off point being at 100 which means 10 years exposure to the Chinese Maximum Allowable Concentration in the workplace (10 mg/m3). All subjects were examined using a self-administered questionnaire including medical and job history, clinical complaints in the previous three months, and underwent a clinical check-up and a 12 lead electrocardiography (ECG) at rest, coded according to the Minnesota code. Blood pressure (BP) was recorded and blood samples were collected for lipid measurements. RESULTS The personal monitoring showed that the exposures levels (15.47 +/- 2.34 mg/m3) were below the Threshold Limit Value (TLV, 31 mg/m3), and most of the samples analyzed still showed higher values than the Chinese MAC (10 mg/m3). Clinical complaints and abnormal electrocardiograms were not significantly increased in exposed workers. No significant effect of CS2 on blood pressure, cholesterol, HDL and LDL cholesterol or triglycerides was found. Further studies are recommended to elucidate the mechanism of cardiac intoxication after CS2 exposure. CONCLUSION This study showed that Chinese workers exposed to CS2 did not have more clinical complaints, nor more ECG abnormalities than controls and no adverse effects were found in their lipids at an exposure level below the current TLV. The present results indicate that differences of health effects reported worldwide are possibly due to different exposure levels. They also indicate that the current Chinese MAC (10 mg/m3) sufficiently protects workers against negative cardiovascular effects.

Carbon disulfide at a Chinese viscose factory external and internal exposure assessment.

This article presents the results of carbon disulfide exposure measurements in a Chinese viscose rayon factory. The objectives of the study were to identify the external exposure levels at a large factory and to investigate the 2-thiothiazolidine-4-carboxylic acid (TTCA) concentrations in the urine of the subjects who were exposed to carbon disulfide in the working place atmosphere. The metabolism of carbon disulfide in the exposed subjects was also studied in order to demonstrate the best points in time for the internal exposure sampling. The measurement of the amount of personal exposure to carbon disulfide in the air of the workplace was performed by GC-FPD; the presence of TTCA in the workers urine was analyzed by use of a modified HPLC method. The kinetics of TTCA excretion was studied by analyses at different time-points both during and after exposure to carbon disulfide in the subjects. A total of 155 personal samples were obtained. The carbon disulfide concentration in the staple viscose hall was 13.72 +/- 1.12 mg m-3 in terms of the geometric mean +/- geometric standard deviation, and was 20.05 +/- 1.33 mg m-3 in the filament spinning hall. The TTCA values in the subjects who worked in the staple spinning hall were 1.18 +/- 0.43 mg g-1 creatinine and 1.07 +/- 0.38 mg g-1 creatinine for subjects working in the filament spinning hall. The best time for TTCA sampling is at the end of the working shift, the TTCA excretion was stable for a period of 4-12 h after exposure of the subjects to the carbon disulfide. It might be that the Chinese have different anthropometric characteristics; a sampling bias may therefore appear among different races.

Cross-sectional study of the ophthalmological effects of carbon disulfide in Chinese viscose workers

This article presents cross-sectional investigation results of ophthalmological effects for the occupational exposure to carbon disulfide of workers at a large viscose fibre factory in the middle part of China. The total of 271 exposed subjects (191 males, 80 females) and 133 workers (93 males, 40 females) not exposed to any toxic agent in the working environment underwent ophthalmological examination. The self-administered questionnaire collected data on the medical history and ophthalmological complaints during the past three months. The ophthalmologic examination included routine examination for retinal capillary anomalies and and color vision with the FM 100-Hue test method. Nearly all subjects did not use respirators, smocks or aprons, gloves or other personal protective devices during work time. The average personal CS2 exposure level in the present study was 13.7-20.05 mg/m3. The FM 100-Hue test results showed that the total error scores of the exposed group, whether male or female, were higher than that of the control, the discrimination of the green and blue zones was also impaired significantly. A fundus examination showed no retinal capillary anomalies or other serious ophthalmological symptoms that may be related to effects of CS2. In conclusion, color vision was disturbed in workers exposed to CS2, at levels below the present threshold value. Reduced color discrimination may be attributed to long-term carbon disulfide exposure and suggests that health surveillance of workers exposed to carbon disulfide should include the FM 100-Hue Test as a sensitive and easy method.

The possible role of liver kinase B1 in hydroquinone‐induced toxicity of murine fetal liver and bone marrow hematopoietic stem cells

Epidemiological studies suggest that the increasing incidence of childhood leukemia may be due to maternal exposure to benzene, which is a known human carcinogen; however, the mechanisms involved remain unknown. Liver Kinase B1 (LKB1) acts as a regulator of cellular energy metabolism and functions to regulate hematopoietic stem cell (HSC) homeostasis. We hypothesize that LKB1 contributes to the deregulation of fetal or bone hematopoiesis caused by the benzene metabolite hydroquinone (HQ). To evaluate this hypothesis, we compared the effects of HQ on murine fetal liver hematopoietic stem cells (FL‐HSCs) and bone marrow hematopoietic stem cells (BM‐HSCs). FL‐HSCs and BM‐HSCs were isolated and enriched by a magnetic cell sorting system and exposed to various concentrations of HQ (0, 1.25, 2.5, 5, 10, 20, and 40 μM) for 24 h. We found that the inhibition of differentiation and growth, as well as the apoptosis rate of FL‐HSCs, induced by HQ were consistent with the changes in BM‐HSCs. Furthermore, G1 cell cycle arrest was observed in BM‐HSCs and FL‐HSCs in response to HQ. Importantly, FL‐HSCs were more sensitive than BM‐HSCs after exposure to HQ. The highest induction of LKB1 and adenosine monophosphate‐activated protein kinase (AMPK) was observed with a much lower concentration of HQ in FL‐HSCs than in BM‐HSCs. LKB1 may play a critical role in apoptosis and cell cycle arrest of HQ‐treated HSCs. This research has developed innovative ideas concerning benzene‐induced hematopoietic toxicity or embryotoxicity, which can provide a new experimental evidence for preventing childhood leukemia.

An Integrated Intervention for Increasing Clinical Nurses' Knowledge of HIV/AIDS-Related Occupational Safety.

Background: Approximately 35 new HIV (Human Immunodeficiency Virus, HIV) cases and at least 1000 serious infections are transmitted annually to health care workers. In China, HIV prevalence is increasing and nursing personnel are encountering these individuals more than in the past. Contaminated needle-stick injuries represent a significant occupational burden for nurses. Evidence suggests that nurses in China may not fully understand HIV/AIDS (Acquired immunodeficiency syndrome, AIDS) and HIV-related occupational safety. At this time, universal protection precautions are not strictly implemented in Chinese hospitals. Lack of training may place nurses at risk for occupational exposure to blood-borne pathogens. Objectives: To assess the effectiveness of integrated interventions on nurses’ knowledge improvement about reducing the risk of occupationally acquired HIV infection. Methods: We audited integrated interventions using 300 questionnaires collected from nurses at the Affiliated Hospital of Xiangnan University, a public polyclinic in Hunan Province. The intervention studied was multifaceted and included appropriate and targeted training content for hospital, department and individual levels. After three months of occupational safety integrated interventions, 234 participants who completed the program were assessed. Results: Of the subjects studied, 94.3% (283/300) were injured one or more times by medical sharp instruments or splashed by body fluids in the last year and 95.3% considered their risk of occupational exposure high or very high. After the intervention, awareness of HIV/AIDS-related knowledge improved significantly (χ2 = 86.34, p = 0.00), and correct answers increased from 67.9% to 82.34%. Correct answers regarding risk perception were significantly different between pre-test (54.4%) and post-test (66.6%) (χ2 = 73.2, p = 0.00). When coming into contact with patient body fluids and blood only 24.0% of subjects used gloves regularly. The pre-test knowledge scores on universal precautions were relatively high. Correct answers about universal precautions improved significantly from pre-test (83.71%) to post-test (89.58%; χ2 = 25.00, p = 0.00). After the intervention, nurses’ attitude scores improved significantly from pre-test (3.80 ± 0.79) to post-test (4.06 ± 0.75; t = 3.74, p = 0.00). Conclusions: Integrated educational interventions enhance nurses’ knowledge of risk reduction for occupationally acquired HIV infections and improve the observance of universal precautionary procedures. This enhancement allows nurses to assume a teaching role for prevention and management of HIV/AIDS.