Immunoglobulin binding protein gene and protein expression in femur tissue of fluorosis rats / 中国地方病学杂志

ABSTRACT

Objective To observe the protein and gene expression of immunoglobulin binding protein (BiP) in the femur of fluoride-treated rats, and preliminarily study the possible role of endoplasmic reticulum stress in the pathogenesis of skeletal fluorosis. Methods Sixty Wistar rats were divided into 4 groups according to body weight, n =15. The control and low-calcium groups were fed with normal diet(0.79％ calcium) and low-calcium diet(0.063％ calcium), respectively, and both drank tap water(fluoride concentrations ＜ 1 mg/L). High-fluoride and coexpesure to low-calcium groups were fed with conventional feed (0.79％ calcium) and low-calcium diet (0.063％ calcium), respectively, and both drank tap water containing sodium fluoride (sodium fluoride concentration of 221 mg/L). During experimental period, rats were measured body weight once a week with a stand diet and water available ad libitum. The experiment lasted for 12 weeks. The immunohistochemical and reverse transcription polymerase chain reaction(RT-PCR) techniques were used to detect the protein and gene expression of BiP in the femur of fluoride-treated rats and control subjects. Results The bone mineral contents of high fluoride, lowcalcium and coexposure groups[(0.131 ± 0019), (0.097 ± 0.011 ), (0.083 ± 0.007)g/cm] were lower than those of the control group[(0.159 ± 0.029)g/cm, all P ＜ 0.05]; the bone mineral density of low calcium and coexpesure to fluoride group[(0.243 ± 0.018), (0.223 ± 0.022)g/cm2] was lower than that of the control group[(0.296 ± 0.046)g/cm2, all P ＜ 0.05]. The immunohistochemical staining showed that the anti-BiP antibody positive osteoblasts were significantly increased in the low calcium diet and coexposure to fluoride groups than that in the control, and coexposure to fluoride elevated the positive cells than that in only low calcium diet group. The mRNA expression of osteopontin(OPN) and osteocalcin(OCN) in coexposure to fluoride with low-calcium group(1.36 ± 0.20, 1.31 ±0.11 ) was higher than that of the control groups (0.82 ± 0.16, 0.85 ± 0.15, all P ＜ 0.05) ; moreover, OPN expression significantly increased in this group than that of the only high fluoride group (0.97 ± 0.29, P ＜ 0.05). The mRNA expression of BiP in the low calcium and coposure to fluoride group (1.38 ± 0.24,1.35 ± 0.12) was significantly higher than that of the control group ( 1.14 ± 0.06, all P ＜ 0.05 ). Conclusions Higher fluoride or coexposure to low calcium diet stimulates the gene and protein expression in rat femur BiP, indicating that varying degrees of endoplasmic reticulum stress is likely involved in the pathogenesis of rat skeletal fluorosis.