Yue Ba

COL1A2 gene polymorphisms (Pvu II and Rsa I), serum calciotropic hormone levels, and dental fluorosis

OBJECTIVES To investigate the relationship between dental fluorosis, polymorphisms in the COL1A2 gene, and serum calciotropic hormone levels. METHODS We conducted a case-control study among children between 8 and 12 years of age with (n = 75) and without (n = 165) dental fluorosis in two counties in Henan Province, China. The PvuII and RsaI polymorphisms in the COL1A2 gene were genotyped using the PCR-RFLP procedure. Calcitonin and osteocalcin levels in the serum were measured using radioimmunassays. RESULTS Children carrying the homozygous genotype PP of COL1A2 PvuII had a significantly increased risk of dental fluorosis (OR =4.85, 95% CI: 1.22-19.32) compared to children carrying the homozygous genotype pp in an endemic fluorosis village (EFV). However, the risk (OR = 1.07, 95% CI: 0.45-2.52) was not elevated when the control population was recruited from a non-endemic fluorosis village. Additionally, fluoride levels in urine and osteocalcin levels in serum were found to be significantly lower in controls from non-endemic villages compared to cases. However, the differences in fluoride and osteocalcin levels were not observed when cases were compared to a control population from endemic fluorosis villages. CONCLUSIONS This study provides the first evidence of an association between polymorphisms in the COL1A2 gene with dental fluorosis in high fluoride exposed populations. Future studies are needed to confirm the association.

Association of Dental Fluorosis with Polymorphisms of Estrogen Receptor Gene in Chinese Children

Dental fluorosis (DF) is one of the important performances of endemic fluorosis. Some studies indicated that estrogen receptor (ESR) gene polymorphisms were associated with bone metabolism-related diseases. Therefore, it is possible that the variation in ESR genotypes will be associated with DF status. A case–control study was conducted among children aged 8–12 years with (n = 75) or without (n = 165) DF in China to investigate the relationship between ESR gene polymorphisms and DF. Gene polymorphisms were genotyped using the PCR-RFLP procedure. Children carrying R allele of ER RsaI had significantly increased risk of DF (Odds ratio (OR) = 1.821; 95% confidence interval (CI), 1.013–3.274) compared to children carrying r allele of ER RsaI in endemic fluorosis villages. For children with high-loaded fluoride status, carrying X allele of ESRα XbaI had a significantly decreased risk of DF (OR = 0.542; 95% CI, 0.314–0.936) compared to carrying x allele. This study provides the first evidence of an association between polymorphisms in the ESR gene with DF in high-fluoride-exposed populations. Further studies are needed to confirm the association.

Effect of oxidative stress on fluoride-induced apoptosis in primary cultured Sertoli cells of rats

This study examined the effect of oxidative stress on the apoptosis of Sertoli cells induced by sodium fluoride (NaF). Cell viability, reactive oxygen species, malondialdehyde content, superoxide dismutase activity, mitochondrial membrane potential, and apoptosis were measured after the rat Sertoli cells were exposed to various concentrations of (0, 6, 12, and 24 μg/ml) sodium fluoride in the presence and absence of 2 mM N-acetylcysteine (NAC) for 24 h. The present study showed that decrease in cell viability and excessive oxidative stress were observed in NaF-treated cells. The treatment with NAC restored the decreased cell viability and excessive oxidative stress. Moreover, fluoride exposure decreased mitochondrial membrane potential and increased apoptosis in Sertoli cells. NAC was also found to suppress a loss of mitochondrial membrane potential and the percentage of apoptosis in NaF-treated Sertoli cells. This study proved that oxidative stress probably play a major role in NaF-induced apoptosis of Sertoli cells.

The association between osteocalcin gene polymorphism and dental fluorosis among children exposed to fluoride in People's Republic of China.

Excessive fluoride intake has been shown to affect dentin and cementum mineralization throughout life. Some studies indicated that a HindIII polymorphism, of osteocalcin (OC) gene, was associated with bone metabolism-related diseases. Therefore, it is possible that the variation in OC genotypes will be associated with dental fluorosis (DF) status and/or serum caciotropic hormone level. A case-control study was conducted among children aged 8-12 years in Henan Province, PR China to investigate the association between dental fluorosis, serum calciotropic hormone level, and polymorphisms in the OC gene. HindIII polymorphism in OC gene was genotyped using the PCR-RFLP procedure. OC and calcitonin (CT) level in serum was detected using radioimmunoassay. No significant difference was observed for OC HindIII genotypes among the cases with dental fluorosis, the controls from endemic fluorosis area (EFA) and the controls from non-endemic fluorosis area (NEFA). A significant negative correlation was observed between serum calcium and OC level. No significant relationship was found between OC HindIII polymorphisms and the level of OC and CT. In conclusion, OC HindIII polymorphisms may not be a useful genetic marker for differential risk of dental fluorosis among children in PR China.

Sodium fluoride induces apoptosis through reactive oxygen species-mediated endoplasmic reticulum stress pathway in Sertoli cells

Excessive fluoride exposure is known to contribute to reproductive system dysfunction, ultimately leading to pathological damage and apoptosis in cells. Although both oxidative and endoplasmic reticulum (ER) stresses have been implicated in fluorosis, the signaling pathways and their roles in sodium fluoride (NaF)-induced apoptosis of Sertoli cells have been sparsely described. In this study, oxidative damage, ER stress, and apoptosis were analyzed after Sertoli cells were treated with varying doses of NaF for 24hr. Moreover, the antioxidant N-acetylcysteine (NAC) and pro-apoptotic transcription factor CHOP knockdown were used to clarify the precise interplay between reactive oxygen species (ROS), ER stress and their roles in NaF-induced apoptosis in Sertoli cells. The present study indicated that NaF significantly decreased cell viability and induced apoptosis in Sertoli cells. In addition, NaF exposure facilitated the accumulation of ROS and increased nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) in Sertoli cells. Treatment with NAC caused remarkable recovery from these NaF-induced responses. Meanwhile, excessive NaF triggered ER stress as evidenced by up-regulated glucose-regulated protein 78 kDa (GRP78), PKR-like ER kinase (PERK), phosphorylation of eukaryotic translation initiation factor 2α (p-eIF2α) and CCAAT/enhancer-binding protein-homologous protein (CHOP), without affecting total eukaryotic translation initiation factor 2α (eIF2α). NAC effectively blocked the activation of ER stress, suggesting that NaF-induced ROS is an early event that triggers ER stress. Taken together, the results demonstrate that the ROS-mediated ER stress pathway is the crucial mechanistic event involved in NaF-induced apoptosis of Sertoli cells.

The relationship of PTH Bst BI polymorphism, calciotropic hormone levels, and dental fluorosis of children in China.

The aim of this study was to explore the association of parathyroid hormone (PTH) gene Bst BI polymorphism, calciotropic hormone levels, and dental fluorosis of children. A case–control study was conducted in two counties (Kaifeng and Tongxu) in Henan Province, China in 2005–2006. Two hundred and twenty-five children were recruited and divided into three groups including dental fluorosis group (DFG), non-dental fluorosis group (NDFG) from high fluoride areas, and control group (CG). Urine fluoride content was determined using fluoride ion selective electrode; PTH Bst BI were genotyped using PCR–RFLP; osteocalcin (OC) and calcitonin (CT) levels in serum were detected using radioimmunoassay. Genotype distributions were BB 85.3% (58/68), Bb 14.7% (10/68) for DFG; BB 77.6% (52/67), Bb 22.4% (15/67) for NDFG; and BB 73.3% (66/90), Bb 27.7% (24/90) for CG. No significant difference of Bst BI genotypes was observed among three groups (P > 0.05). Serum OC and urine fluoride of children were both significantly higher in DFG and NDFG than in CG (P < 0.05, respectively), while a similar situation was not observed between DFG and NDFG in high fluoride areas (P > 0.05). Serum OC level of children with BB genotype was significantly higher compared to those with Bb genotype in high fluoride areas (P < 0.05). However, no significant difference of serum CT or calcium (Ca) was observed. In conclusion, there is no correlation between dental fluorosis and PTH Bst BI polymorphism. Serum OC might be a more sensitive biomarker for detecting early stages of dental fluorosis, and further studies are needed.

Fluoride Exposure, Follicle Stimulating Hormone Receptor Gene Polymorphism and Hypothalamus-pituitary-ovarian Axis Hormones in Chinese Women.

The effects of fluoride exposure on the functions of reproductive and endocrine systems have attracted widespread attention in academic circle nowadays. However, it is unclear whether the gene-environment interaction may modify the secretion and activity of hypothalamus-pituitary- ovarian (HPO) axis hormones. Thus, the aim of this study was to explore the influence of fluoride exposure and follicle stimulating hormone receptor (FSHR) gene polymorphism on reproductive hormones in Chinese women. A cross sectional study was conducted in seven villages of Henan Province, China during 2010-2011. A total of 679 women aged 18-48 years were recruited through cluster sampling and divided into three groups, i.e. endemic fluorosis group (EFG), defluoridation project group (DFPG), and control group (CG) based on the local fluoride concentration in drinking water. The serum levels of gonadotropin releasing hormone (GnRH), follicle stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E2) were determined respectively and the FSHR polymorphism was detected by real time PCR assay. The results provided the preliminary evidence indicating the gene-environment interaction on HPO axis hormones in women.

Endemic fluorosis in Henan province, China: ERα gene polymorphisms and reproductive hormones among women

BACKGROUND AND OBJECTIVES The aim of this study was to explore the influence of fluoride exposure and ERα gene polymorphisms on reproductive hormone concentrations of women in accordance with endemic fluorosis residence. METHODS AND STUDY DESIGN A cross sectional study was conducted in Tongxu county, Henan Province, China. A total of 679 women were recruited using cluster sampling and each subject provided fasting blood and an associated urine sample. We measured the concentrations of serum gonadotropin releasing hormone (GnRH), follicle-stimulating hormone, luteinizing hormone, and estradiol and urinary fluoride. RESULTS In the defluoridation project group (DFPG), serum GnRH was lower in women carrying C/C genotype compared to in those carrying C/T and T/T genotypes of ERα gene rs3798577 (p<0.05). In the endemic fluorosis group (EFG), serum GnRH was lower in women carrying Pp genotype compared to in those carrying PP and pp genotypes of ERα PvuII (p<0.05). Serum GnRH in women from EFG who carried Pp, pp, Xx and xx genotypes in ERα gene PvuII and XbaI was lower than in those in the control group (CG) who carried same genotypes (p<0.05). Furthermore, serum GnRH in women from EFG was significantly lower than in those in CG, regardless of whether the women were carrying C/C, C/T or T/T genotypes of ERα rs3798577 (p<0.05). Serum estradiol concentrations in EFG were significantly lower than in CG when the women were carrying the Pp, Xx and T/T genotypes in ERα gene (p<0.05). CONCLUSION Interaction of ERα gene and fluoride exposure may influence womens serum reproductive hormone concentrations.

Gene-environment interaction: Does fluoride influence the reproductive hormones in male farmers modified by ERα gene polymorphisms?

The occurrence of endemic fluorosis is derived from high fluoride levels in drinking water and industrial fumes or dust. Reproductive disruption is also a major harm caused by fluoride exposure besides dental and skeletal lesions. However, few studies focus on the mechanism of fluoride exposure on male reproductive function, especially the possible interaction of fluoride exposure and gene polymorphism on male reproductive hormones. Therefore, we conducted a cross-sectional study in rural areas of Henan province in China to explore the interaction between the estrogen receptor alpha (ERα) gene and fluoride exposure on reproductive hormone levels in male farmers living in the endemic fluorosis villages. The results showed that fluoride exposure significantly increased the serum level of estradiol in the hypothalamic-pituitary-testicular (HPT) axis in male farmers. Moreover, the observations indicated that fluoride exposure and genetic markers had an interaction on serum concentration of follicle-stimulating hormone and estradiol, and the interaction among different loci of the ERα gene could impact the serum testosterone level. Findings in the present work suggest that chronic fluoride exposure in drinking water could modulate the levels of reproductive hormones in males living in endemic fluorosis areas, and the interaction between fluoride exposure and ERα polymorphisms might affect the serum levels of hormones in the HPT axis in male farmers.

Do Environmental Fluoride Exposure and ESRα Genetic Variation Modulate Methylation Modification on Bone Changes in Chinese Farmers

Although increasing evidence suggests that estrogen receptor α (ESRα) genetic variation could modify bone damage caused by environmental fluoride exposure, little is known about epigenetic mechanisms in relation to bone changes. A case-control study was conducted among farmers aged 18-55 years in Henan Province, China. X-ray was used to detect bone changes. Methylation status was determined by methylation-specific PCR. Genotypes were identified by Taqman probe and real-time PCR. In this study, we found that methylation status in the promoter region of the ESRα gene was lower in bone change cases than that in controls, which was only observed in male farmers after stratification by gender. Furthermore, methylation level was negatively associated with the urinary fluoride concentration in male farmers. No significant association was found between the distribution of ESRα rs2941740 genotypes and the risk of bone changes. Multivariate logistic regression analysis showed that after adjusting for age and gender, increased serum calcium and methylation status were protective factors for bone changes. No interaction effect was observed between fluoride exposure and ESRα rs2941740 polymorphism on bone changes. In conclusion, the current work suggests that bone changes are associated with methylation status, which might be modulated by fluoride exposure in male farmers. Methylation status and bone changes were not modified by ESRα gene rs2941740 polymorphism in the promoter region.