Genetic susceptibility for dental fluorosis: a metabolic and proteomic study with different strains of mice

Dental fluorosis occurs during tooth formation when excessive doses of fluoride (F) are ingested. The mechanisms that underlie the pathogenesis of dental fluorosis are not known so far. The influence of genetic factors has been considered in individual susceptibility/resistance to develop fluorosis. Two inbred mice strains (A/J and 129P3/J) have been reported to have different susceptibilities to dental fluorosis. They were used in the present study to determine if the susceptibility to dental fluorosis can be explained by alterations in F metabolism and to evaluate if there is difference in the profile of protein expression in kidney and urine of these animals. For this, a metabolic study was conducted with 18 A/J (susceptible) and 18 129P3/J (resistant) weanling mice. Each strain was divided into 3 groups, with differed according to the F concentration given in the drinking water (0, 10 and 50 ppm F). Since a pilot study showed that the A/J mice drank a higher volume of water when compared with the 129P3/J, the F concentration in the water given to the A/J mice was weekly adjusted in order to provide similar F intakes for both strains. The mice were housed in metabolic cages (n=2/cage) for 7 weeks, with free access to water and low-F diet (0.95 ppm). F intake and excretion were calculated, as well as plasma, femur and kidney F levels. The degree of dental fluorosis was assessed using QLF and clinical examination. Renal and urinary proteome profiles were examined using 2D-PAGE and coomassie brilliant blue staining. Data were tested for significant differences by 2-way repeated-measures ANOVA (p<0.05). The gels images and statistical differences (ANOVA, p <0.05) were analyzed by the Image Master Platinum 7.0 software. Significantly higher QLF scores were observed for the A/J mice submitted to 50 ppm F. The total F intake did not significantly differ between the strains. The total F excretion was significantly higher for the A/J mice, due to the higher urinary F excretion. The two strains did not differ in respect to F absorption, but the 129P3/J mice retained significantly higher amounts of F, which was consistent with their higher femur F levels. Plasma F levels, however, did not significantly differ between the strains. For kidney, quantitative intensity analysis detected, between strains A/J and 129P3/J, 122, 126 e 134 spots differentially expressed in the control group, in the group receiving low and high F concentrations, respectively. For urine, 84 spots differentially expressed were detected for control group, 68 for the group receiving low F concentration and 66 for the group receiving high F concentration. Data showed that intrinsic differences occur in the metabolism of F and profile of protein expression between these strains and that these profiles can be altered in the presence of F. (AU)