Fluoride Alters Gene Expression via Histone H3K27 Acetylation in Ameloblast-like LS8 Cells.

Excessive fluoride ingestion during tooth development can cause dental fluorosis. Previously, we reported that fluoride activates histone acetyltransferase (HAT) to acetylate p53, promoting fluoride toxicity in mouse ameloblast-like LS8 cells. However, the roles of HAT and histone acetylation status in fluoride-mediated gene expression remain unidentified. Here, we demonstrate that fluoride-mediated histone modification causes gene expression alterations in LS8 cells. LS8 cells were treated with or without fluoride followed by ChIP-Seq analysis of H3K27ac. Genes were identified by differential H3K27ac peaks within ±1 kb from transcription start sites. The levels of mRNA of identified genes were assessed using rea-time PCR (qPCR). Fluoride increased H3K27ac peaks associated with Bax, p21, and Mdm2 genes and upregulated their mRNA levels. Fluoride decreased H3K27ac peaks and p53, Bad, and Bcl2 had suppressed transcription. HAT inhibitors (Anacardic acid or MG149) suppressed fluoride-induced mRNA of p21 and Mdm2, while fluoride and the histone deacetylase (HDAC) inhibitor sodium butyrate increased Bad and Bcl2 expression above that of fluoride treatment alone. To our knowledge, this is the first study that demonstrates epigenetic regulation via fluoride treatment via H3 acetylation. Further investigation is required to elucidate epigenetic mechanisms of fluoride toxicity in enamel development.

Microhardness Measurements on Tooth and Alveolar Bone in Rodent Oral Disease Models.

The mechanical property, microhardness, is evaluated in dental enamel, dentin, and bone in oral disease models, including dental fluorosis and periodontitis. Micro-CT (µCT) provides 3D imaging information (volume and mineral density) and scanning electron microscopy (SEM) produces microstructure images (enamel prism and bone lacuna-canalicular). Complementarily to structural analysis by µCT and SEM, microhardness is one of the informative parameters to evaluate how structural changes alter mechanical properties. Despite being a useful parameter, studies on microhardness of alveolar bone in oral diseases are limited. To date, divergent microhardness measurement methods have been reported. Since microhardness values vary depending on the sample preparation (polishing and flat surface) and indentation sites, diverse protocols can cause discrepancies among studies. Standardization of the microhardness protocol is essential for consistent and accurate evaluation in oral disease models. In the present study, we demonstrate a standardized protocol for microhardness analysis in tooth and alveolar bone. Specimens used are as follows: for the dental fluorosis model, incisors were collected from mice treated with/without fluoride-containing water for 6 weeks; for ligature-induced periodontal bone resorption (L-PBR) model, alveolar bones with periodontal bone resorption were collected from mice ligated on the maxillary 2nd molar. At 2 weeks after the ligation, the maxilla was collected. Vickers hardness was analyzed in these specimens according to the standardized protocol. The protocol provides detailed materials and methods for resin embedding, serial polishing, and indentation sites for incisors and alveolar. To the best of our knowledge, this is the first standardized microhardness protocol to evaluate the mechanical properties of tooth and alveolar bone in rodent oral disease models.

Higher IQ in juvenile myoclonic epilepsy: Dodging cognitive obstacles and "masking" impairments.

Executive deficits and impulsiveness are extensively reported in juvenile myoclonic epilepsy (JME). Previous literature suggests that intelligence may mediate these deficits. In this study, we evaluated and compared the performance of adults with JME with high and low intelligence quotient (IQ) and controls on tasks for executive function (EF) and impulsive traits. We investigated the neuropsychological performance of 53 adults with JME and below average IQ (57% women; 26.9 [±7.88] years; mean IQ: 89.8 [±5.1]), 26 adults with JME and average or above average IQ (53.8% women; 28.2 [±9.33] years; mean IQ: 110.7 [±8.3]), 38 controls with below average IQ (55% women; 28.4 [±8.4] years; mean IQ: 90.1 [±5.8]), and 31 controls with average or above average IQ (61.3% women; 32.20 [±11.3] years; mean IQ: 111.6 [±10.5]) with a comprehensive battery of neuropsychological tests that measure executive/attentional function. Impulsive traits were assessed using the Cloninger et al.'s Temperament and Character Inventory (novelty seeking (NS) domain). The group with JME with higher IQ presented worse performance compared with controls with higher IQ on Controlled Oral Word Association (COWA) and Wisconsin Card Sorting Test (WCST) (errors). This group showed worse performance than controls with lower IQ on Stroop Color-Word Test (SCT) 1, Trail Making (TM) A, COWA, and WCST (errors). Patients with lower IQ showed worse performance than controls with higher IQ on Digit Span Forward (DSF), Digit Span Backward (DSB), SCT1, SCT2, SCT3, TM A, COWA, and WCST (errors and failure to maintain set). Patients with lower IQ showed worse performance than controls with lower IQ on DSF, DSB, SCT1, SCT2, SCT3, TM A, TM B, COWA, and WCST (errors and failure to maintain set). Patients from groups with low and high IQ showed higher scores than controls with higher and lower IQ on impulsivity for NS1 and NS2 (except for patients with higher IQ versus controls with lower IQ). Adults with JME and higher IQ show less evidence of EF deficits compared with those with JME and below average IQ, suggesting that a higher degree of intellectual efficiency may act as a compensatory mechanism. However, it does not minimize some aspects of impulsive traits. Patients with JME and higher cognitive reserve may create strategies to dodge their cognitive obstacles. In this context, intelligence may protect and, at the same time, "mask" impairments that could be detected earlier.