Objective To study the effects of chronic exposure to inorganic arsenic (iAs) in drinking water on bone mineral density (BMD) in mice and its underlying mechanisms.Methods Five-month-old female C57BL/6 mice were randomly divided into sham groups and ovarectomy (OVX) groups (n =19 mice each group),which were further randomly assigned into control group (distilled water) and iAs exposure groups [5 mg/L and 20 mg/L,inorganic arsenite (iAsⅢ):inorganic arsenate (iAsv) =1 ∶ 1].Following 3 months of exposure to iAs,BMD of the mice were determined by the dual energy X-ray detector.RAW 264.7 cell line and bone marrow hematopoietic stem cells (BMHSC) primarily isolated from C57BL/6 mice were used to study the in vitro effects of iAs on osteoclast differentiation and underlying mechanisms.During differentiation induced by receptor activator of nuclear factor-κ B ligand (RANKL,50 μg/L) and macrophage colony-stimulating factor (M-CSF,30 μg/L),RAW 264.7 cell line were treated with 0.00,0.25,0.50,0.75,1.00,1.50 μmol/L iAsⅢ,while BMHSC with 0.0,0.2,0.4,0.6,0.8,1.0 μmol/L iAsⅢ for 6 days.Based on the effect of iAsⅢ on the differentiation of RAW cells,RAW 264.7 cell line were treated by 0.6 μmol/L iAsⅢ combined with 0,5,10 mmol/L of N-acetyl-cysteine (NAC).Tartrate resistant acid phosphatase (TRAP)-positive red-colored cells with 3 or more nuclei were considered mature osteoclast.Results The femoral BMD of the mice [(80.04 ± 4.06) mg/cm2] that had been exposed to 20 mg/L of iAs for 3 months was substantially decreased compared to that of sham control mice [(84.44 ± 4.40) mg/cm2].As expected,the BMD of the OVX group [(76.36 ± 3.36) mg/cm2] was significant decreased compared to that of the sham control group (P ＜ 0.05).However,the BMD among the OVX groups showed no significant difference [5 mg/L:(77.74 ± 4.91) mg/cm2;20 mg/L:(75.56 ± 3.71) mg/cm2,P ＞ 0.05].In vitro studies,the iAsⅢ evidently affected the osteoclast differentiation in a concentration-dependent fashion.Low concentrations of iAs Ⅲ exposure significantly augmented osteoclast differentiation in the two cell models while high concentrations showed inhibitory effect.In RAW 264.7 cells,the number of osteoclasts in different groups was significantly different (F =1 522,P ＜ 0.05),in the 0.50 μmol/L iAs Ⅲ group the number of osteoclasts reached the peak.In the BMHSC,the nmnber of osteoclasts in different groups was also significantly different (F =1 781,P ＜ 0.05),in the 0.6 μmol/L iAsⅢ group the number of osteoclasts reached the peak.NAC pretreatment significantly abolished low-level iAsⅢ(0.6 μmol/L)-induced augmentation of osteoclast differentiation in a concentration-dependent fashion (0 mmol/L:109.33 ± 3.06;5 mmol/L:56.00 ± 2.65;10 mmol/L:22.67 ± 0.58,F =1 940,P ＜ 0.05).Conclusions The inhibitory effect of iAs on bone metabolism is dependent on the availability of ovary function,suggesting that iAs may interfere with estrogen metabolism and/or function to disturb bone metabolism.Oxidative stress induced by iAs exposure stimulates osteoclast differentiation,and the increased osteoclast differentiation may be involved in the reduction of BMD caused by chronic iAs exposure.These preliminary findings suggest that antioxidant intervention may be an effective approach to prevent osteoporosis induced by chronic iAs exposure.

BackgroundDue to the COVID-19 pandemic， both teenagers' studies and personal life are critically affected， which has resulted in a variety of mental health problems. In this regard， scholars at home and abroad have carried out a large number of research concerning adolescent mental health， of which there still exists a lack of systematic combing and review. ObjectiveTo understand the status and development trend of research on adolescent mental health during the COVID-19 pandemic at home and abroad， and to grasp the current research hotspots and trends in this field， so as to provide references for relevant research and practice in the post-epidemic era. MethodsOn October 30， 2022， we searched through China Knowledge Network Infrastructure （CNKI） and Web of Science database， and the publishing time of articles to be retrieved was limited between December 1， 2019 and October 30， 2022. Excel and CiteSpace were used to perform visual analysis on these articles in terms of number， author， institution， country and keywords of the articles. ResultsA total of 7 608 articles were included. At home and abroad， the number of papers related to adolescent mental health generally increased at first and then decreased under the pandemic situation. Compared with foreign countries， the connection and cooperation among domestic scholars and institutions was not close enough. The top three countries in the number of English literature published were the United States， Britain and China， and those in intermediary center were Tunis， Cameroon and Anguilla. The parent-child relationship and mental health of teenagers during were much concerned by scholars both at home and abroad. With the passage of time， researchers at home and abroad had shifted their focus from only negative factors to positive factors. ConclusionChinese scholars or institutions need to strengthen more domestic and international exchanges and cooperation. Scholars from different countries can carry out cross-cultural study on research topics of common concern， and continue to explore the positive psychological changes of teenagers in the post-epidemic era.［Funded by National Social Science Foundation 2020 Education Youth Project of 13th Five-Year Plan （number， CHA200259）］