ABSTRACT
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.
ABSTRACT
Objective To know the effects of laver intake on arsenic species in urine of people, and investigate the characteristics of arsenic metabolism. Methods The urine samples were collected from 24 subjects who had laver available on markets, arsenic species in urine samples were detected with hydride generation atomic fluorescence spectroscopy. Results There was a significant increase of urinary iAs seventy-two hours after laver intake except one and forty-eight hours, increase of MMA seventy-two hours after laver intake except one and twelve hours, and increase of DMA from the first hour to the 72nd hour in male group. There was a significant increase in the urinary iAs seventy-two hours after laver intake except three, five and forty-eight hours, increase of MMA seventy-two hours after laver intake except five and twelve hours, increase of DMA from one to seventy-two hours after laver intake in female group. Conclusion The urinary concentration of DMA is significantly higher in female group compared with male group after laver intake in the same weight and urinary DMA increases in the beginning, after that decreases gradually.