Association of temperament with oral health behaviour and caries status in Thai preschool children.

BACKGROUND: Temperament associated with oral health behaviour and early childhood caries (ECC) in preschoolers remains inconclusive. AIM: This cross-sectional study investigated the association of temperament with oral health behaviour and ECC status. DESIGN: A total of 421 Thai preschoolers were recruited from elementary schools in Chonburi Province, Thailand. Their caregivers assessed three temperament dimensions (surgency, negative affectivity and effortful control) using the Thai version of the Children's Behaviour Questionnaire Very Short Form and reported oral health behaviours (brushing cooperation and cariogenic snack frequency). Three calibrated dentists assessed ECC status using the modified WHO dmft/dmfs (decayed, missing and filled teeth/surface) index that included noncavitated and cavitated carious lesions. RESULTS: Multiple regression analysis, after adjusting for child's and caregiver's characteristics, revealed that children with high negative affectivity or low effortful control were more likely to have uncooperative brushing behaviour. The temperament scores of children who consumed cariogenic snacks daily and those who did not were comparable. Children with low surgency, high negative affectivity or low effortful control were more likely to have high dmfs scores. CONCLUSION: Negative affectivity and effortful control were associated with brushing behaviour. Temperament was not associated with the frequency of cariogenic snack consumption. All temperamental dimensions, however, were associated with ECC.

Long-term effects of prenatal stress on the development of prefrontal cortex in the adolescent offspring.

Exposure to stress during pregnancy consequently prompts long-lasting effects on fetal brain development and predisposes the offspring to mental illnesses in later life. Adolescence is a vulnerable period of prefrontal cortex (PFC) development and coincident with the onset of neuropsychiatric symptoms. The medial PFC (mPFC) is the brain area that plays a significant role in emotional processing, and stress alters the function of this brain area leading to emotional disorders. Microglia not only play a role in neuroinflammatory responses but also play a crucial role in brain development, especially during synaptic development and pruning. Previous studies have revealed the long-term effects of prenatal stress (PS) on microglia activation and neuroinflammation in the hippocampus of the offspring. However, there is still a need to investigate how PS alters the mPFC development during adolescence. This study examines the effects of maternal stress during the last week of gestation on microglia activation and neuroimmune response in the mPFC of adolescent offspring. Morphological study demonstrated that PS increased the density of activated microglia in the prelimbic region of the mPFC of adolescent offspring. Besides, PS significantly increased the levels of microglia marker (Iba1), interleukin-6 (IL-6), and brain-derived neurotrophic factor (BDNF) in the mPFC of the adolescent offspring. In conclusion, PS-induced microglia activation and neuroinflammation in the mPFC might increase the risk for neuropsychiatric disorders in the offspring in later years.

Altered Development of Prefrontal GABAergic Functions and Anxiety-like Behavior in Adolescent Offspring Induced by Prenatal Stress.

Maternal stress can afflict fetal brain development, putting the offspring at risk of cognitive deficits, including anxiety. The prefrontal cortex (PFC), a protracted maturing region, is notably affected by prenatal stress (PS). However, it remains unclear how PS interferes with the maturation of the GABAergic system, considering its functional adjustment in the PFC during adolescence. The present study thus investigated the long-lasting consequences of PS on the prefrontal GABAergic functions of adolescent offspring. Pregnant Sprague-Dawley rats were divided into controls and the PS group, which underwent restraint stress during the last week of gestation. Male pups from postnatal days (PND) 40-42 were submitted to the elevated plus maze (EPM) test. Proteins essentially involved in GABAergic signaling were then examined in PFC tissues, including the K+-Cl- cotransporter (KCC2), Na+-K+-Cl- cotransporter (NKCC1), α1 and α5 subunits of GABA type A receptors (GABAA receptors), and parvalbumin (PV), along with cAMP response element-binding protein phosphorylation (pCREB), which reacts in the plasticity regulation of PV-positive interneurons. The results revealed that the higher anxiety-like behavior of PS adolescent rats concurred with the significant decreases of the KCC2 and α1 subunits, with PV- and pCREB-lowered levels. The findings suggested that PS disrupts the continuance of PFC maturity by reducing the essential elements of GABAergic functions. These changes likely underlie the anxiety emerging in adolescence, possibly progressing to mental disorders.

Maternal stress induced autophagy dysfunction and immune activation in the hippocampus of adolescence rat pups.

Maternal stress (MS) has long-term effects on fetal brain development and consequently increases the risk of neuropsychiatric diseases in the offspring, however, the mechanism that links between early life stress and subsequent neuropsychiatric diseases is still not clear. It is well known that both neuroinflammation and autophagy dysfunction contributes to the pathology of psychiatric disorders. We hypothesized that MS might alter autophagy function and activate the neuroimmune response in the pup's brain. To test this hypothesis, we investigated the effects of MS on the expression of the autophagy biomarker and neuroimmune response in the hippocampus of rat pups. Results revealed that MS-induced a long-term decrease of LC3B-II throughout the postnatal periods, together with an increase of IL-6 and IL-10 in the hippocampus of rat pups during adolescence. These changes lasted at least until adulthood. Results from the In vitro studies showed that a partially toxic dose of corticosterone (CORT) induced a significant decrease of LC3B-II, together with an increase of IL-6 and IL-10, in the SH-SY5Y cells. Moreover, suppression of autophagy by mycophenolic acid (MPA) leads to an increased IL-6 and IL-10 expression in the CORT-treated SH-SY5Y cells. Findings suggested that CORT decreased autophagy dysfunction could activate neuroimmune response in the SH-SY5Y cells. Results from this study provides initial evidence for the relationship between stress hormone, autophagy dysfunction, and neuroimmune activation, which may be the linking mechanism between early-life stress and subsequent neuropsychiatric disorders.

Microglia enhances proliferation of neural progenitor cells in an in vitro model of hypoxic-ischemic injury.

Microglial cells are the primary immune cells in the central nervous system. In the mature brain, microglia perform functions that include eliminating pathogens and clearing dead/dying cells and cellular debris through phagocytosis. In the immature brain, microglia perform functions that include synapse development and the regulation of cell production through extensive contact with and phagocytosis of neural progenitor cells (NPCs). However, the functional role of microglia in the proliferation and differentiation of NPCs under hypoxic-ischemic (HI) injury is not clear. Here, we tested the hypothesis that microglia enhance NPCs proliferation following HI insult. Primary NPCs cultures were divided into four treatment groups: 1) normoxic NPCs (NN); 2) normoxic NPCs cocultured with microglia (NN+M); 3) hypoxic NPCs (HN); and 4) hypoxic NPCs cocultured with microglia (HN+M). Hypoxic-ischemic injury was induced by pretreatment of the cell cultures with 100 µM deferoxamine mesylate (DFO). NPCs treated with 100 µM DFO (HN groups) for 24 hours had significantly increased expression of hypoxia-inducible factor 1 alpha (HIF-1α), a marker of hypoxic cells. Cell number, protein expression, mitosis, and cell cycle phase were examined, and the data were compared between the four groups. We found that the number of cells expressing the NPCs marker Sox2 increased significantly in the HN+M group and that the number of PH3-positive cells increased in the HN+M group; flow cytometry analysis showed a significant increase in the percentage of cells in the G2/M phase in the HN+M group. In summary, these results support the concept that microglia enhance the survival of NPCs under HI injury by increasing NPCs proliferation, survival, and differentiation. These results further suggest that microglia may induce neuroprotective effects after hypoxic injury that can be explored to develop novel therapeutic strategies for the treatment of HI injury in the immature brain.

Effects of social and nonsocial reward on executive function in preschoolers.

INTRODUCTION: Executive function, a set of higher order cognitive skills underlying goal-directed behaviors, develops rapidly during preschool years. Reward increases executive function engagement in adolescents and adults. However, there is still a scarcity of data on how reward affects executive function in young children. The present study examines whether different incentive types contribute differently to executive function performance and neural activity in children. METHODS: Twenty-five preschoolers of 5-6 years old were provided an incentive Go/No-go task, comparing social, nonsocial, and nonreward conditions. Activations in the prefrontal regions during the tasks were measured using functional near-infrared spectroscopy. RESULTS: The results revealed that social reward enhanced right prefrontal activations in young children. In contrast to adult literature, younger children did not show any significant differences in executive function performance across conditions. CONCLUSION: This study expands our understanding of motivation and EF engagement in preschoolers. Specifically, social reward enhanced prefrontal activations in young children. The implications and recommendations for future research are discussed.

Delayed cortical maturation at the centrotemporal brain regions in patients with benign childhood epilepsy with centrotemporal spikes (BCECTS).

Benign childhood epilepsy with centrotemporal spikes (BCECTS) is an epilepsy syndrome commonly found in child and adolescent. Although the prognosis is mostly favorable as long as the seizure is well controlled. However, they are often suffering from the cognitive and behavioral problems which might be the consequences of the initial insults. It is still not clear whether the initial epileptiform discharges has long term impact on the resting-state brain activities at later ages. This study investigated the resting-state brain activities in BCECTS patients with clinical seizure remission stage (n = 16; 11 males) and compared with the non-epileptic, age-matched control subjects. Quantitative electroencephalography (qEEG) revealed a significantly higher absolute power of the theta and alpha waves in BCECTS patients with clinical seizure remission as compared with the non-epileptic control subjects. Interestingly, the differences were observed mainly over the centrotemporal electrodes which are the common sites of the initial epileptiform discharges. The differences were more significant in patients with bilateral epileptiform discharges than those with the unilateral epileptic activities. Typically, the brain wave power continuously decreases with increasing ages. Therefore, higher absolute powers of the brain waves indicate more delayed in cortical maturation compared with the non-epileptic control group. These findings indicated that BCECTS patients have delay cortical maturation at the centrotemporal brain regions even at the clinical seizure remission phase.

Fetal exposure to high levels of maternal glucocorticoids alters reelin signaling in the prefrontal cortex of rat pups.

Maternal stress (MS) is associated with various neuropsychiatric disorders and cognitive impairment in the offspring. However, it is unclear how early life stress alters the pup's brain development and how it contributes to the pathology of neuropsychiatric disorders later in life. Reelin is a large extracellular matrix glycoprotein that plays essential roles in early brain development such as neural migration, synaptic development, and maturation. Dysregulation of reelin and its signaling proteins is associated with the emergence of neuropsychiatric disorders in adulthood. This study examined the effect of repeated maternal Carbenoxolone (CBX) injection during late gestation on reelin signaling in the prefrontal cortex (PFC) of rat pups. CBX is a selective 11ß-HSD2 enzyme inhibitor that promotes the direct transfer of maternal corticosteroids (CORT) to the fetus. Therefore, treatment with CBX can mimic the animal model of early life exposure to high levels of maternal stress hormone. In this study, pregnant rats were injected daily with either saline or CBX during gestation day (GD) 14-21, and the levels of reelin and its signaling proteins were examined in the PFC of rat pups at different postnatal age from P0-P21. The main result of this study is the repeated maternal CBX injections during GD14-21 acutely increase reln mRNA and protein expression in the PFC of rat pups at birth (P0) and follow by a significant decrease during P7-P14. The treatment also causes long term decreases in the amount of VLDLR and Dab1 which are the downstream signaling proteins for the reelin pathway, at least until P21. Our results indicated that fetal exposure to high levels of maternal CORT interferes with reelin signaling which might have profound effects on cortical development associated with neuropsychiatric disorders later in life.

Clinical and molecular correlates in fragile X premutation females.

The prevalence of the fragile X premutation (55-200 CGG repeats) among the general population is relatively high, but there remains a lack of clear understanding of the links between molecular biomarkers and clinical outcomes. In this study we investigated the correlations between molecular measures (CGG repeat size, FMR1 mRNA, FMRP expression levels, and methylation status at the promoter region and in FREE2 site) and clinical phenotypes (anxiety, obsessive compulsive symptoms, depression and executive function deficits) in 36 adult premutation female carriers and compared to 24 normal control subjects. Premutation carriers reported higher levels of obsessive compulsive symptoms, depression, and anxiety, but demonstrated no significant deficits in global cognitive functions or executive function compared to the control group. Increased age in carriers was significantly associated with increased anxiety levels. As expected, FMR1 mRNA expression was significantly correlated with CGG repeat number. However, no significant correlations were observed between molecular (including epigenetic) measures and clinical phenotypes in this sample. Our study, albeit limited by the sample size, establishes the complexity of the mechanisms that link the FMR1 locus to the clinical phenotypes commonly observed in female carriers suggesting that other factors, including environment or additional genetic changes, may have an impact on the clinical phenotypes. However, it continues to emphasize the need for assessment and treatment of psychiatric problems in female premutation carriers.

Size and methylation mosaicism in males with Fragile X syndrome.

BACKGROUND: Size and methylation mosaicism are a common phenomenon in Fragile X syndrome (FXS). Here, the authors report a study on twelve fragile X males with atypical mosaicism, seven of whom presented with autism spectrum disorder. METHODS: A combination of Southern Blot and PCR analysis was used for CGG allele sizing and methylation. FMR1 mRNA and FMRP expression were measured by qRT-PCR and by Homogeneous Time Resolved Fluorescence methodology, respectively. RESULTS: DNA analysis showed atypical size- or methylation-mosaicism with both, full mutation and smaller (normal to premutation) alleles, as well as a combination of methylated and unmethylated alleles. Four individuals carried a deletion of the CGG repeat and portions of the flanking regions. The extent of methylation among the participants was reflected in the lower FMR1 mRNA and FMRP expression levels detected in these subjects. CONCLUSION: Decreased gene expression is likely the main contributor to the cognitive impairment observed in these subjects; although the presence of a normal allele did not appear to compensate for the presence of the full mutation, it correlated with better cognitive function in some but not all of the reported cases emphasizing the complexity of the molecular and clinical profile in FXS.

Maternal restraint stress delays maturation of cation-chloride cotransporters and GABAA receptor subunits in the hippocampus of rat pups at puberty.

The GABAergic synapse undergoes structural and functional maturation during early brain development. Maternal stress alters GABAergic synapses in the pup's brain that are associated with the pathophysiology of neuropsychiatric disorders in adults; however, the mechanism for this is still unclear. In this study, we examined the effects of maternal restraint stress on the development of Cation-Chloride Cotransporters (CCCs) and the GABAA receptor α1 and α5 subunits in the hippocampus of rat pups at different postnatal ages. Our results demonstrate that maternal restraint stress induces a transient but significant increase in the level of NKCC1 (Sodium-Potassium Chloride Cotransporter 1) only at P14, followed by a brief, yet significant increase in the level of KCC2 (Potassium-Chloride Cotransporter 2) at P21, which then decreases from P28 until P40. Thus, maternal stress alters NKCC1 and KCC2 ratio in the hippocampus of rat pups, especially during P14 to P28. Maternal restraint stress also caused biphasic changes in the level of GABAA receptor subunits in the pup's hippocampus. GABAA receptor α1 subunit gradually increased at P14 then decreased thereafter. On the contrary, GABAA receptor α5 subunit showed a transient decrease followed by a long-term increase from P21 until P40. Altogether, our study suggested that the maternal restraint stress might delay maturation of the GABAergic system by altering the expression of NKCC1, KCC2 and GABAA receptor α1 and α5 subunits in the hippocampus of rat pups. These changes demonstrate the dysregulation of inhibitory neurotransmission during early life, which may underlie the pathogenesis of psychiatric diseases at adolescence.

Repeated carbenoxolone injections during late pregnancy alter Snk-SPAR and PSD-95 expression in the hippocampus of rat pups.

Homeostasis of circulating cortisol is maintained by the 11ß-HSD2 enzyme which inactivates cortisol into cortisone. It is abundantly expressed in the placenta where it protects the fetus from high levels of maternal glucocorticoids (GCs). Maternal administration of Carbenoxolone (Cbx), a powerful 11ß-HSD2 inhibitor, leads to an increase in fetal cortisol. Previous data showed that intrauterine environment plays a crucial role in determining hippocampal structure and function. Exposure of pregnant rats to high levels of GC leads to low birth weight in offspring and an increased risk of age related memory and cognitive deficits later in life. Glutamate receptors are localized in the postsynaptic density (PSD), where many signaling proteins, cytoskeleton proteins, and ion channels are found. Any change in the number of these molecules can influence the morphology and function of the dendritic spine. We proposed that repeated Cbx injections during late pregnancy may alter the scaffolding proteins of the NMDA receptor in the pup's brain. We investigated the effects of repeated maternal Cbx injections on the scaffolding proteins of NMDA receptor in the hippocampus of rat pups. We showed that injecting pregnant rats with Cbx injections (30mg/kg) during GD 14-21 leads to a significant decrease in SPAR (Spine Associated Rap Guanylate kinase activating protein) (p<0.001) and PSD-95 (p<0.05) but a significant increase in Snk (Serum inducible kinase) (p<0.001) in the pup's hippocampus at P40. In general, Snk is induced by neuronal activity and plays an important role in phosphorylating SPAR. The phosphorylated SPAR is then recognized and degraded by ubiquitin proteasome system (UPS), causing the depletion of SPAR and PSD-95 from the spines. The results suggest that fetal exposure to excessive GC levels may activate the Snk/SPAR pathway and lead to the depletion of SPAR and PSD-95. Since GCs drugs are commonly used in various obstetric and pediatric conditions, it is important to consider the risks and benefits of prenatal GCs exposure in order to prevent neurodevelopmental delay in the offspring.