The 2022 world health organization reevaluation of human and mammalian toxic equivalency factors for polychlorinated dioxins, dibenzofurans and biphenyls

In October 2022, the World Health Organization (WHO) convened an expert panel in Lisbon, Portugal in which the 2005 WHO TEFs for chlorinated dioxin-like compounds were reevaluated. In contrast to earlier panels that employed expert judgement and consensus-based assignment of TEF values, the present effort employed an update to the 2006 REP database, a consensus-based weighting scheme, a Bayesian dose response modeling and meta-analysis to derive "Best-Estimate" TEFs. The updated database contains almost double the number of datasets from the earlier version and includes metadata that informs the weighting scheme. The Bayesian analysis of this dataset results in an unbiased quantitative assessment of the congener-specific potencies with uncertainty estimates. The "Best-Estimate" TEF derived from the model was used to assign 2022 WHO-TEFs for almost all congeners and these values were not rounded to half-logs as was done previously. The exception was for the mono-ortho PCBs, for which the panel agreed to retain their 2005 WHO-TEFs due to limited and heterogenous data available for these compounds. Applying these new TEFs to a limited set of dioxin-like chemical concentrations measured in human milk and seafood indicates that the total toxic equivalents will tend to be lower than when using the 2005 TEFs.

Clinical application of endoscopic soft palate augmentation in the treatment of velopharyngeal insufficiency

Velopharyngeal structure augmentation with the injection of autologous fat tissue into the nasal mucosa of the soft palate has been reported previously. However, as the injection points in the velopharyngeal space cannot be observed directly, these injections may be difficult to perform accurately. This report describes a new endoscope-assisted approach in which the materials for velopharyngeal structure augmentation are administered while observing the injection points directly, also enabling adjustment of the amount of material injected. A case series of five patients aged 8-16 years who underwent endoscopic soft palate augmentation under general anaesthesia is reported. Autologous fat tissue was injected into the nasal mucosa of the soft palate using a needle-type device of an endoscope, and the effects of the treatment were evaluated. The injections were performed successfully, and the velopharyngeal function was improved. This new technique of endoscopy-assisted augmentation was useful for the treatment of velopharyngeal insufficiency.

Gestational arsenic exposure induces anxiety-like behaviors in F1 female mice by dysregulation of neurological and immunological markers

BACKGROUND

Arsenic is a harmful heavy metal and a well-known developmental neurotoxicant. Previously, we have reported that gestational arsenic exposure resulted in impaired social behaviors in F1 and F2 male mice. However, little is known about the developmental arsenic exposure on anxiety-like behavior. This study aimed to detect the effect of gestational arsenic exposure on anxiety-like behavior and related gene expressions in 74-week-old F1 female mice.

METHOD

Pregnant C3H/HeN mice (F0) were given drinking water containing 85 ppm sodium arsenite (NaAsO₂) from gestational day 8 to 18. The control mice were given tap water only. At 74-week-old, open field test was performed, then anxiety and apoptosis-related factors were determined by real_time RT_PCR and immunohistochemical analyses.

RESULTS

The arsenite-exposed F1 female mice showed decreased center entry and center time in open field test. In addition, the number of grooming and fecal pallet was significantly increased in the arsenite-exposed F1 female mice compared to the control. Downregulation of brain-derived neurotrophic factor (BDNF), serotonin receptor (5HT1A) and upregulation of nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB), interleukin 1 β (IL-1β), cyclooxygenase 2 (COX2), caspase-3, Bcl2-associated X protein (Bax) were detected in the prefrontal cortex in the arsenite-exposed F1 female mice. Microglial marker ionized calcium-binding adapter molecule 1 (Iba1)-positive cells were increased in the arsenite-exposed F1 female mice. Moreover, a significantly increased plasma corticosterone level was observed in the arsenic-exposed F1 female mice.

CONCLUSIONS

This study suggested that gestational arsenic exposure induced anxiety-like behavior accompanied with dysregulation of neurological and immunological markers, neuroinflammatory responses, neuronal apoptosis, and decreased neurogenesis in the prefrontal cortex of F1 female mice.

Inorganic arsenic exposure-induced premature senescence and senescence-associated secretory phenotype (SASP) in human hepatic stellate cells

Exposure to inorganic arsenic has been known to induce cancers in various organs, however, the underlying mechanisms remain unclear. Premature senescence refers to the irreversible growth arrest induced by stress stimuli. The senescence-associated secretory phenotype (SASP), particularly in fibroblasts, has been shown to promote cancer development. In this study, we examined whether arsenite exposure causes premature senescence and induction of SASP in liver fibroblasts using the human hepatic stellate cell line, LX-2. Exposure of LX-2 cells to 5 or 7.5 μM of sodium arsenite for 144 h induced the features of senescence in the cells, including morphological changes, growth inhibition, increased senescence-associated β-galactosidase activity, increased P21 gene expression, and decreased LAMINB1 gene expression. The mRNA expressions of SASP factors, such as MMP1, MMP3, IL-8, IL-1β, and CXCL1, were also highly upregulated. The wound healing assay revealed that the conditioned medium from LX-2 cells with arsenite-induced senescence increased the migration activity of cells of the human hepatoma cell line, Huh-7. Gene expression data of liver cancer samples from the Human Protein Atlas showed that high expression levels of the SASP factors that were upregulated in the cells with arsenite-induced senescence were strongly associated with a poor prognosis. In addition, the cellular levels of γ-H2AX, a DNA double-strand break marker, were increased by arsenite exposure, suggesting that DNA damage could contribute to premature senescence induction. These results show that arsenite exposure induces premature senescence in hepatic stellate cells and suggest that the SASP factors from the senescent cells promote hepatic carcinogenesis.

Potential differences in chitin synthesis ability cause different sensitivities to diflubenzuron among three strains of Daphnia magna

Ecotoxicity testing of crustaceans using Daphnia magna has been implemented in the chemical management systems of various countries. While the chemical sensitivity of D. magna varies depending on genetically different clonal lineages, the strain used in ecotoxicity tests, including the acute immobilization test (OECD TG202), has not been specified. We hypothesized that comprehensive gene expression profiles could provide useful information on phenotypic differences among strains, including chemical sensitivity. To test this hypothesis, we performed mRNA sequencing on three different strains (NIES, England, and Clone 5) of D. magna under culture conditions. The resulting expression profile of the NIES strain was clearly different compared to the profiles of the other two strains. Gene ontology (GO) enrichment analysis suggested that chitin metabolism was significantly enriched in the NIES strain compared to that in the England strain. Consistent with the GO analysis, evidence of high levels of chitin metabolism in the NIES strain were observed across multiple levels of biological organization, such as expression of chitin synthase genes, chitin content, and chitinase activity, which suggested that the different strains would exhibit different sensitivities to chemicals used to inhibit chitin synthesis. We found that among all strains, the NIES strain was more tolerant to diflubenzuron, a chitin synthesis inhibitor, with a 14-fold difference in the 48 h-EC₅₀ value for the acute immobilization test compared to the England strain. The present study demonstrates that the differences among strains in chitin metabolism may lead to sensitivity difference to diflubenzuron, and serves as a case study of the usefulness of comprehensive gene expression profiles in finding sensitivity differences.

Effects of maternal exposure to arsenic on social behavior and related gene expression in F2 male mice

Background

Arsenic is a developmental neurotoxicant. It means that its neurotoxic effect could occur in offspring by maternal arsenic exposure. Our previous study showed that developmental arsenic exposure impaired social behavior and serotonergic system in C3H adult male mice. These effects might affect the next generation with no direct exposure to arsenic. This study aimed to detect the social behavior and related gene expression changes in F2 male mice born to gestationally arsenite-exposed F1 mice.

Methods

Pregnant C3H/HeN mice (F0) were given free access to tap water (control mice) or tap water containing 85 ppm sodium arsenite from days 8 to 18 of gestation. Arsenite was not given to F1 or F2 mice. The F2 mice were generated by mating among control F1 males and females, and arsenite-F1 males and females at the age of 10 weeks. At 41 weeks and 74 weeks of age respectively, F2 males were used for the assessment of social behavior by a three-chamber social behavior apparatus. Histological features of the prefrontal cortex were studied by ordinary light microscope. Social behavior-related gene expressions were determined in the prefrontal cortex by real time RT-PCR method.

Results

The arsenite-F2 male mice showed significantly poor sociability and social novelty preference in both 41-week-old group and 74-week-old group. There was no significant histological difference between the control mice and the arsenite-F2 mice. Regarding gene expression, serotonin receptor 5B (5-HT 5B) mRNA expression was significantly decreased (p < 0.05) in the arsenite-F2 male mice compared to the control F2 male mice in both groups. Brain-derived neurotrophic factor (BDNF) and dopamine receptor D1a (Drd1a) gene expressions were significantly decreased (p < 0.05) only in the arsenite-F2 male mice of the 74-week-old group. Heme oxygenase-1 (HO-1) gene expression was significantly increased (p < 0.001) in the arsenite-F2 male mice of both groups, but plasma 8-hydroxy-2′-deoxyguanosine (8-OHdG) and cyclooxygenase-2 (COX-2) gene expression were not significantly different. Interleukin-1β (IL-1β) mRNA expression was significantly increased only in 41-week-old arsenite-F2 mice.

Conclusions

These findings suggest that maternal arsenic exposure affects social behavior in F2 male mice via serotonergic system in the prefrontal cortex. In this study, COX-2 were not increased although oxidative stress marker (HO-1) was increased significantly in arsnite-F2 male mice.

Gestational arsenic exposure induces site-specific DNA hypomethylation in active retrotransposon subfamilies in offspring sperm in mice

Background

Environmental impacts on a fetus can disrupt germ cell development leading to epimutations in mature germ cells. Paternal inheritance of adverse health effects through sperm epigenomes, including DNA methylomes, has been recognized in human and animal studies. However, the impacts of gestational exposure to a variety of environmental factors on the germ cell epigenomes are not fully investigated. Arsenic, a naturally occurring contaminant, is one of the most concerning environmental chemicals, that is causing serious health problems, including an increase in cancer, in highly contaminated areas worldwide. We previously showed that gestational arsenic exposure of pregnant C3H mice paternally induces hepatic tumor increase in the second generation (F2). In the present study, we have investigated the F1 sperm DNA methylomes genome-widely by one-base resolution analysis using a reduced representation bisulfite sequencing (RRBS) method.

Results

We have clarified that gestational arsenic exposure increases hypomethylated cytosines in all the chromosomes and they are significantly overrepresented in the retrotransposon LINEs and LTRs, predominantly in the intergenic regions. Closer analyses of detailed annotated DNA sequences showed that hypomethylated cytosines are especially accumulated in the promoter regions of the active full-length L1MdA subfamily in LINEs, and 5′LTRs of the active IAPE subfamily in LTRs. This is the first report that has identified the specific positions of methylomes altered in the retrotransposon elements by environmental exposure, by genome-wide methylome analysis.

Conclusion

Lowered DNA methylation potentially enhances L1MdA retrotransposition and cryptic promoter activity of 5′LTR for coding genes and non-coding RNAs. The present study has illuminated the environmental impacts on sperm DNA methylome establishment that can lead to augmented retrotransposon activities in germ cells and can cause harmful effects in the following generation.

Gestational arsenic exposure and paternal intergenerational epigenetic inheritance

A growing body of evidence has shown that gestational exposure to environmental factors such as imbalanced diet, environmental chemicals, and stress can lead to late-onset health effects in offspring and that some of these effects are heritable by the next generation and subsequent generations. Furthermore, altered epigenetic modifications in DNA methylation, histone modifications and small RNAs in a single sperm genome have been shown to transmit disease phenotypes acquired from the environment to later generations. Recently, our group found that gestational exposure of F0 pregnant dams to an inorganic arsenic, sodium arsenite, increases the incidence of hepatic tumors in male F2 mice, and the effects are paternally transmitted to the F2. Here, we first overview the epigenetic changes involved in paternal intergenerational and transgenerational inheritance caused by exposure to environmental factors. Then, we discuss our recent studies regarding paternal inheritance of the tumor-augmenting effects in F2 mice by gestational arsenite exposure, in which we investigated alterations of DNA methylation status in F2 tumors and causative F1 sperm. We also discuss the possible targets of the F2 effects. Finally, we discuss future perspectives on the studies that are needed to fully understand the health effects of arsenic exposure.

Identification by TCGA database search of five genes that are aberrantly expressed and involved in hepatocellular carcinoma potentially via DNA methylation changes

BACKGROUND

Various treatments for hepatocellular carcinoma (HCC) are utilized in clinical practice; however, the prognosis is still poor on account of high recurrence rates. DNA methylation levels of CpG islands around promoters (promoter CpGis) inversely regulate gene expression and closely involved in carcinogenesis. As a new strategy, several chemicals globally inhibiting DNA methylation have been developed aiming at reducing DNA methylation levels and maintaining the expression of tumor suppressor genes. On the other hand, since these drugs nonspecifically modify DNA methylation, they can cause serious adverse effects. In order to ameliorate the methods by targeting specific CpGs, information of cancer-related genes that are regulated by DNA methylation is required.

METHODS

We searched candidate genes whose expressions were regulated by DNA methylation of promoter CpGi and which are involved in HCC cases. To do so, we first identified genes whose expression were changed in HCC by comparing gene expressions of 371 HCC tissues and 41 non-tumor tissues using the Cancer Genome Atlas (TCGA) database. The genes were further selected for poor prognosis by log-rank test of Kaplan-Meier plot and for cancer relevance by Pubmed search. Expression profiles of upregulated genes in HCC tissues were assessed by Gene Ontology (GO) analysis. Finally, using DNA methylation data of TCGA database, we selected genes whose promoter DNA methylation levels were inversely correlated with gene expression.

RESULTS

We found 115 genes which were significantly up- or downregulated in HCC tissues and were associated with poor prognosis and cancer relevance. The upregulated genes were significantly enriched in cell division, cell cycle, and cell proliferation. Among the upregulated genes in HCC, we identified hypomethylation of CpGis around promoters of FANCB, KIF15, KIF4A, ERCC6L, and UBE2C. In addition, TCGA data showed that the tumor suppressor gene P16 is unexpectedly overexpressed in many types of cancers.

CONCLUSIONS

We identified five candidate genes whose expressions were regulated by DNA methylation of promoter CpGi and associate with cancer cases and poor prognosis in HCC. Modification of site-specific DNA methylation of these genes enables a different approach for HCC treatment with higher selectivity and lower adverse effects.

Association between chronic arsenic exposure and the characteristic features of asthma

Widespread contamination of arsenic (As) has become a global public health concern. Exposure to As causes respiratory complications. Asthma, a major respiratory complication, is increasing worldwide. However, the effect of chronic As exposure on the risk of asthma remains to be clarified. This study aims to examine the associations between As exposure (water, hair and nail As) and the risk of asthma among 842 individuals exposed to a wide range of As concentrations through drinking water in Bangladesh. Subjects' As exposure levels were measured with ICP-MS. Lung function was examined by a handheld spirometer. Characteristic features of asthma were evaluated by bronchodilator-mediated reversibility in airway obstruction and asthma-like symptoms through a structured questionnaire. Total serum immunoglobulin E (sIgE) levels were measured by immunoassay. As exposure metrics showed inverse associations with lung function measures (FEV1, FEV6, and FEV1/FEV6 ratio) and positive associations with the risks of airway obstruction (AO), reversible airway obstruction (RAO), and asthma-like symptoms. The majority of AO patients (70 of 97) were RAO with one or more characteristic symptoms of asthma. Intriguingly, subjects' As exposure levels showed positive associations with total sIgE levels. Total sIgE in RAO patients was significantly (p < 0.001) higher than that in the control group. Thus the results revealed that chronic As exposure was associated with the risk of the characteristic features of asthma. Additionally the association between As exposure and subjects' total sIgE levels and an elevated level of total sIgE in RAO group suggested that As exposure-related asthma might be allergic in nature.

Influence of Olfactory Function on Appetite and Nutritional Status in the Elderly Requiring Nursing Care

OBJECTIVE

To investigate olfactory function in elderly subjects requiring nursing care to clarify its association with appetite and nutritional status.

SETTING

Facility for the elderly requiring nursing care.

PARTICIPANTS

The subjects were 158 elderly people requiring nursing care and 37 elderly people not requiring nursing care.

MEASUREMENTS

Experiment I: Olfactory function and factors (cognitive function, appetite, and nutritional status) that may be associated with it were compared between the elderly subjects requiring nursing care and those not requiring nursing care using covariance analysis in consideration of age. For evaluation, the OSIT-J was used for olfactory function, the HDS-R for cognitive function, the CNAQ for appetite, and BMI for nutritional status. Experiment II: The subjects were the same elderly subjects requiring nursing care in Experiment I, and food intake was surveyed in addition to the OSIT-J, HDS-R, CNAQ, and BMI. A univariate linear regression analysis was performed with OSIT-J as the response variable, and age, HDS-R, CNAQ, BMI, and food intake as the explanatory variables.

RESULTS

Experiment I: On covariance analysis, the OSIT-J score was significantly lower for the elderly subjects requiring nursing care than for those not requiring nursing care (p<0.01). The mean score was 8 or lower in both groups, demonstrating lower olfactory function in both groups. Regarding factors that may be associated with olfactory function, a significant difference was noted in the HDS-R (p<0.01), confirming significantly lower cognitive function in the elderly subjects requiring nursing care. No significant difference was noted in the CNAQ or BMI. Experiment II: On a univariate linear regression analysis, an association with the OSIT-J was noted for age and HDS-R. Age was inversely correlated and the HDS-R was positively correlated. Factors associated with lower olfactory function in the elderly subjects requiring nursing were age and cognitive function, whereas appetite, nutritional status, and food intake were not associated.

CONCLUSION

Olfactory function in elderly subjects requiring nursing care was poorer than that in those not requiring nursing care, suggesting that aging and cognitive decline are associated with lower olfactory function. In addition, no association of lower olfactory function with appetite, nutritional status, or food intake was noted in the elderly subjects requiring nursing care.

Oral exposure to lead for Japanese children and pregnant women, estimated using duplicate food portions and house dust analyses

BACKGROUND

Lead is a toxic metal abundant in the environment. Consumption of food contaminated at low levels of lead, especially by small children and pregnant women, raises a health concern.

METHODS

Duplicated food portions and drinking water were collected over 3 days from 88 children and 87 pregnant women in Shimotsuke, Tochigi, Japan. Participants were recruited in this study between January 2014 and October 2015. Dust was also collected from their homes. Lead concentrations were measured and consequent oral lead exposure levels were estimated for this population at high risk to environmental toxicants. Lead concentrations of peripheral and cord blood, taken from children and pregnant women, and were also analyzed.

RESULTS

Lead concentrations in food, drinking water, and house dust were low in general. Oral lead exposure to lead was higher for children (Mean ± SEM; 5.21 ± 0.30 μg/kg BW/week) than in pregnant women (1.47 ± 0.13 μg/kg BW/week). Food and house dust were main sources of lead contamination, but the contribution of house dust widely varied. Means ± SEM of peripheral and cord blood lead concentrations were 0.69 ± 0.04 μg/dL and 0.54 ± 0.05 μg/dL, respectively for pregnant women and 1.30 ± 0.07 μg/dL (peripheral only) in children. We detect no correlation between smoking situations and blood lead concentration in pregnant women.

CONCLUSION

We conclude that oral lead exposure levels for Japanese children and pregnant women were generally low, with higher concentrations and exposure for children than for pregnant women. More efforts are necessary to clarify the sources of lead contamination and reduce lead exposure of the population at high risk even in Japan.

DNA methylation changes involved in the tumor increase in F2 males born to gestationally arsenite-exposed F1 male mice

Multigenerational adverse effects from the environment such as nutrition and chemicals are among important concerns in environmental health issues. Previously, we have found that arsenite exposure of only F0 females during their pregnancy increases hepatic tumors in the F2 males in C3H mice. In the current study, we investigated the association of DNA methylation with the hepatic tumor increase in the F2 males of the arsenite group. Reduced-representation bisulfite sequencing analysis newly identified that DNA methylation levels of regions around the transcriptional start sites of Tmem54 and Cd74 were decreased and the expression of these genes were significantly increased in the hepatic tumors of F2 males of the arsenite group. The associations between DNA methylation in these regions and gene expression changes were confirmed by treatment of murine hepatoma cell lines and hepatic stellate cell line with 5-aza-2'-deoxycytidine. Overexpression of Cd74 in Hepa1c1c7 cells increased Trib3 expression and suppressed the expression of tumor suppressor genes Id3 and Atoh8. Human database analysis using the Cancer Genome Atlas indicated that TMEM54, CD74, and TRIB3 were significantly increased and that ATOH8 was decreased in hepatocellular carcinoma. The data also showed that high expression of TMEM54 and TRIB3 and low expression of ATOH8 were associated with poor survival. These results suggested that an increase in Tmem54 and Cd74 expression via DNA methylation reduction was involved in the tumor increase in the F2 male offspring by gestational arsenite exposure of F0 females. This study also suggested that genes downstream of Cd74 were involved in tumorigenesis.

Sarcopenia, the depletion of muscle mass, an independent predictor of respiratory complications after oncological esophagectomy

Surgery for esophageal carcinoma is known to be associated with high morbidity. Recent studies have reported a correlation of nutritional and inflammatory parameters with postoperative course. This study aims to clarify the risk factors for operative morbidity after resection of esophageal carcinoma. Consecutive patients who underwent esophagectomy for esophageal squamous cell carcinoma at our institute were included (n = 102; 89 males and 13 females; mean age: 67.3 years). Clinicopathological characteristics, presence or absence of sarcopenia, and modified Glasgow prognostic score were assessed, and their correlation with postoperative complications was investigated using univariate and multivariate analyses. Sarcopenia was defined using a combination of muscle mass area and body mass index. Of the included 102 patients, 45 (44.1%) exhibited sarcopenia (sarcopenia group), while 57 (55.9%) did not (non-sarcopenia group). No significant difference was observed between the groups regarding surgical procedures and tumor stage; furthermore, there was no mortality. Twenty-six patients developed respiratory complications (including 20 cases of pneumonia). On univariate analysis, sarcopenia, modified Glasgow prognostic score, and American Society of Anesthesiologists physical status were found to be significantly associated with the development of postoperative respiratory complications. On multivariate analysis, sarcopenia was found to be an independent risk factor for postoperative respiratory complications after esophagectomy. We believe that identifying patients at risk and providing preoperative nutritional support as well as physical therapy aimed at strengthening of body muscles may help reduce the incidence of postoperative respiratory complications in such patients.

Effects of Developmental Arsenic Exposure on the Social Behavior and Related Gene Expression in C3H Adult Male Mice

Arsenic is carcinogenic and teratogenic. In addition, it is also a developmental neurotoxicant. Little is known however about the effect of arsenic exposure during brain development on social behavior. This study aimed to detect the effect of developmental arsenic exposure on social behavior and related gene expression in C3H adult male mice. Pregnant C3H mice were exposed to sodium arsenite (NaAsO₂, 85 ppm in the drinking water) from gestational day (GD) 8 to 18. The F1 generation male pups from different mothers were taken and social behavior tasks were examined. Social behavioral-related gene expression in the prefrontal cortex was determined by the real-time RT-PCR method. The mice with developmental arsenic exposure showed poor sociability and poor social novelty preference. Glutamate receptor expression (NMDA and AMPA receptor subunits) showed no significant difference, but gene expressions of serotonin receptor 5B (5-HT 5B) and brain-derived neurotrophic factor (BDNF) were significantly decreased (p < 0.05) in the arsenic-exposed group compared to control group. The heme oxygenase-1 (HO-1) and cyclooxygenase-2 (COX-2) gene expressions were not significantly different. Our findings indicate that developmental arsenic exposure might affect social behavior by modulating serotonin receptors and reducing BDNF. Some oxidative stress markers and inflammatory markers were not affected.

Epigenetics as a mechanism linking developmental exposures to long-term toxicity

A variety of experimental and epidemiological studies lend support to the Developmental Origin of Health and Disease (DOHaD) concept. Yet, the actual mechanisms accounting for mid- and long-term effects of early-life exposures remain unclear. Epigenetic alterations such as changes in DNA methylation, histone modifications and the expression of certain RNAs have been suggested as possible mediators of long-term health effects of environmental stressors. This report captures discussions and conclusions debated during the last Prenatal Programming and Toxicity meeting held in Japan. Its first aim is to propose a number of criteria that are critical to support the primary contribution of epigenetics in DOHaD and intergenerational transmission of environmental stressors effects. The main criteria are the full characterization of the stressors, the actual window of exposure, the target tissue and function, the specificity of the epigenetic changes and the biological plausibility of the linkage between those changes and health outcomes. The second aim is to discuss long-term effects of a number of stressors such as smoking, air pollution and endocrine disruptors in order to identify the arguments supporting the involvement of an epigenetic mechanism. Based on the developed criteria, missing evidence and suggestions for future research will be identified. The third aim is to critically analyze the evidence supporting the involvement of epigenetic mechanisms in intergenerational and transgenerational effects of environmental exposure and to particularly discuss the role of placenta and sperm. While the article is not a systematic review and is not meant to be exhaustive, it critically assesses the contribution of epigenetics in the long-term effects of environmental exposures as well as provides insight for future research.

The DNA methylation profile of liver tumors in C3H mice and identification of differentially methylated regions involved in the regulation of tumorigenic genes

Background

C3H mice have been frequently used in cancer studies as animal models of spontaneous liver tumors and chemically induced hepatocellular carcinoma (HCC). Epigenetic modifications, including DNA methylation, are among pivotal control mechanisms of gene expression leading to carcinogenesis. Although information on somatic mutations in liver tumors of C3H mice is available, epigenetic aspects are yet to be clarified.

Methods

We performed next generation sequencing-based analysis of DNA methylation and microarray analysis of gene expression to explore genes regulated by DNA methylation in spontaneous liver tumors of C3H mice. Overlaying these data, we selected cancer-related genes whose expressions are inversely correlated with DNA methylation levels in the associated differentially methylated regions (DMRs) located around transcription start sites (TSSs) (promoter DMRs). We further assessed mutuality of the selected genes for expression and DNA methylation in human HCC using the Cancer Genome Atlas (TCGA) database.

Results

We obtained data on genome-wide DNA methylation profiles in the normal and tumor livers of C3H mice. We identified promoter DMRs of genes which are reported to be related to cancer and whose expressions are inversely correlated with the DNA methylation, including Mst1r, Slpi and Extl1. The association between DNA methylation and gene expression was confirmed using a DNA methylation inhibitor 5-aza-2′-deoxycytidine (5-aza-dC) in Hepa1c1c7 cells and Hepa1-6 cells. Overexpression of Mst1r in Hepa1c1c7 cells illuminated a novel downstream pathway via IL-33 upregulation. Database search indicated that gene expressions of Mst1r and Slpi are upregulated and the TSS upstream regions are hypomethylated also in human HCC. These results suggest that DMRs, including those of Mst1r and Slpi, are involved in liver tumorigenesis in C3H mice, and also possibly in human HCC.

Conclusions

Our study clarified genome wide DNA methylation landscape of C3H mice. The data provide useful information for further epigenetic studies of mice models of HCC. The present study particularly proposed novel DNA methylation-regulated pathways for Mst1r and Slpi, which may be applied not only to mouse HCC but also to human HCC.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4221-0) contains supplementary material, which is available to authorized users.

Chronic exposure to arsenic, LINE-1 hypomethylation, and blood pressure: a cross-sectional study in Bangladesh

BACKGROUND

Chronic exposure to arsenic is associated with cancer and hypertension. Growing evidence suggests that altered methylation in long interspersed nuclear element-1 (LINE-1) is involved in many types of disorders, including cardiovascular disease. Here we evaluated the association between arsenic exposure and LINE-1 methylation levels, especially in relation to blood pressure (BP).

METHODS

A total of 236 subjects (175 from arsenic-endemic areas and 61 from a non-endemic area) in rural Bangladesh were recruited. The subjects' arsenic exposure levels (i.e., drinking water, hair and nail arsenic concentrations) were measured by inductively coupled plasma mass spectroscopy. The subjects' LINE-1 methylation levels were determined by pyrosequencing.

RESULTS

The average LINE-1 methylation levels of the subjects living in the arsenic-endemic areas were significantly (p < 0.01) lower than those of the subjects living in the non-endemic area. In a sex-stratified analysis, the arsenic exposure levels in female but not male subjects showed a significant inverse association with LINE-1 methylation levels before (water arsenic: p < 0.01, hair arsenic: p < 0.05, nail arsenic: p < 0.001) and after (water arsenic: p < 0.01, hair arsenic: p < 0.05, nail arsenic: p < 0.001) adjustment for age, body mass index and smoking. Analyses examining interactions among arsenic levels, BP and LINE-1 methylation showed that arsenic-related elevated levels of BP were associated with LINE-1 hypomethylation.

CONCLUSIONS

Our findings demonstrated that chronic exposure to arsenic was inversely associated with LINE-1 methylation levels in blood leukocyte DNA and this was more pronounced in females than males; in addition, the decreased levels of LINE-1 methylation might be involved in the arsenic-induced elevation of BP.

Tumor-augmenting effects of gestational arsenic exposure on F1 and F2 in mice

The consequences of early-life exposure to chemicals in the environment are emerging concerns. Chronic exposure to naturally occurring inorganic arsenic has been known to cause various adverse health effects, including cancers, in humans. On the other hand, animal studies by Dr. M. Waalkes’ group reported that arsenite exposure of pregnant F0 females, only from gestational day 8 to 18, increased hepatic tumors in the F1 (arsenite-F1) males of C3H mice, whose males tend to develop spontaneous hepatic tumors later in life. Since this mice model illuminated novel unidentified consequences of arsenic exposure, we wished to further investigate the background mechanisms. In the same experimental model, we identified a variety of factors that were affected by gestational arsenic exposure, including epigenetic and genetic changes, as possible constituents of multiple steps of late-onset hepatic tumor augmentation in arsenite-F1 males. Furthermore, our study discovered that the F2 males born to arsenite-F1 males developed hepatic tumors at a significantly higher rate than the control F2 males. The results imply that the tumor augmenting effect is inherited by arsenite-F2 males through the sperm of arsenite-F1. In this article, we summarized our studies on the consequences of gestational arsenite exposure in F1 and F2 mice to discuss novel aspects of biological effects of gestational arsenic exposure.

[Biological effects of arsenic and diseases: The mechanisms involved in arsenic-induced carcinogenesis]

Chronic arsenic exposure is associated with many diseases, including cancers. Our study using in vivo assay in gpt-delta transgenic mice showed that arsenic particularly induces G : C to T : A transversions, a mutation type induced through oxidative-stress-induced 8-OHdG formation. Gestational arsenic exposure of C3H mice was reported to increase hepatic tumor incidence. We showed that gestational arsenic exposure increased hepatic tumors having activated oncogene Ha-ras by C to A mutation. We also showed that DNA methylation status of Fosb region is implicated in tumor augmentation by gestational arsenic exposure. We further showed that long-term arsenic exposure induces premature senescence. Recent studies reported that senescence is involved in not only tumor suppression, but also tumorgenesis. All these effects of arsenic might be involved in arsenic-induced carcinogenesis.

In utero and Lactational Exposure to Acetamiprid Induces Abnormalities in Socio-Sexual and Anxiety-Related Behaviors of Male Mice

Neonicotinoids, a widely used group of pesticides designed to selectively bind to insect nicotinic acetylcholine receptors, were considered relatively safe for mammalian species. However, they have been found to activate vertebrate nicotinic acetylcholine receptors and could be toxic to the mammalian brain. In the present study, we evaluated the developmental neurotoxicity of acetamiprid (ACE), one of the most widely used neonicotinoids, in C57BL/6J mice whose mothers were administered ACE via gavage at doses of either 0 mg/kg (control group), 1.0 mg/kg (low-dose group), or 10.0 mg/kg (high-dose group) from gestational day 6 to lactation day 21. The results of a battery of behavior tests for socio-sexual and anxiety-related behaviors, the numbers of vasopressin-immunoreactive cells in the paraventricular nucleus of the hypothalamus, and testosterone levels were used as endpoints. In addition, behavioral flexibility in mice was assessed in a group-housed environment using the IntelliCage, a fully automated mouse behavioral analysis system. In adult male mice exposed to ACE at both low and high doses, a significant reduction of anxiety level was found in the light-dark transition test. Males in the low-dose group also showed a significant increase in sexual and aggressive behaviors. In contrast, neither the anxiety levels nor the sexual behaviors of females were altered. No reductions in the testosterone level, the number of vasopressin-immunoreactive cells, or behavioral flexibility were detected in either sex. These results suggest the possibility that in utero and lactational ACE exposure interferes with the development of the neural circuits required for executing socio-sexual and anxiety-related behaviors in male mice specifically.

Prenatal Exposure to Arsenic Impairs Behavioral Flexibility and Cortical Structure in Mice

Exposure to arsenic from well water in developing countries is suspected to cause developmental neurotoxicity. Although, it has been demonstrated that exposure to sodium arsenite (NaAsO₂) suppresses neurite outgrowth of cortical neurons in vitro, it is largely unknown how developmental exposure to NaAsO₂ impairs higher brain function and affects cortical histology. Here, we investigated the effect of prenatal NaAsO₂ exposure on the behavior of mice in adulthood, and evaluated histological changes in the prelimbic cortex (PrL), which is a part of the medial prefrontal cortex that is critically involved in cognition. Drinking water with or without NaAsO₂ (85 ppm) was provided to pregnant C3H mice from gestational days 8 to 18, and offspring of both sexes were subjected to cognitive behavioral analyses at 60 weeks of age. The brains of female offspring were subsequently harvested and used for morphometrical analyses. We found that both male and female mice prenatally exposed to NaAsO₂ displayed an impaired adaptation to repetitive reversal tasks. In morphometrical analyses of Nissl- or Golgi-stained tissue sections, we found that NaAsO₂ exposure was associated with a significant increase in the number of pyramidal neurons in layers V and VI of the PrL, but not other layers of the PrL. More strikingly, prenatal NaAsO₂ exposure was associated with a significant decrease in neurite length but not dendrite spine density in all layers of the PrL. Taken together, our results indicate that prenatal exposure to NaAsO₂ leads to behavioral inflexibility in adulthood and cortical disarrangement in the PrL might contribute to this behavioral impairment.

Exposure assessment of lead from food and airborne dusts and biomonitoring in pregnant mothers, their fetus and siblings in Karachi, Pakistan and Shimotsuke, Japan

AIM

Exposure assessment of lead (Pb) and Arsenic (As) from food, water, and house dust intake were assessed among pregnant women, their children and fetuses in Pakistan and Japan, as well as their body burden of the metals in their blood.

METHOD

Fifty families which included a pregnant woman, a fetus and the 1-3-year-old siblings were recruited in Karachi and Khairpur in Pakistan, and Shimotsuke and Asahikawa in Japan, respectively. Their dietary exposure to Pb and As was measured in 3-day food duplicates and drinking water by ICP-MP. Pb in house dust and respirable dust was evaluated with an energy dispersive X-ray fluorescence spectrometry. Non-radioactive isotope Pb profiles of blood specimens will be compared with those of the exposure origins, such as food duplicates, respirable house dust, the soils nearby, and gasoline.

RESULTS

Judging from the data collected and analyzed so far, contribution from dietary intake is highly correlated to higher body burden of Pb among Pakistani mothers. Additional data analyses will reveal the status of Pb and As body burden in Pakistani mothers, fetuses and their siblings, and causal sources of high body burden is delineated by Pb isotope profile analysis of different sources of Pb exposure.

[Exploration of Epigenetic Changes and DNA Methylation Markers Associated with Liver Tumors Induced by Inorganic Arsenite Exposure in Mice]

Naturally occurring inorganic arsenic is known to increase the risk of cancers of the skin and several other organs, including the urinary bladder, lung, and liver. Epidemiological studies have also indicated that gestational arsenic exposure is associated with increased incidences of cancers in several organs, including the bladder and liver, in adulthood. Previous studies have shown that epigenetic changes are involved in arsenic-induced carcinogenesis. Among epigenetic changes, DNA methylation changes that are specific to arsenic-induced tumors would be useful for distinguishing such tumors from tumors induced by other factors and for clarifying arsenic carcinogenesis. It has been reported that gestational arsenic exposure of C3H mice, whose males tend to spontaneously develop liver tumors, increases the incidence of tumors in the male offspring. Using the same experimental protocol, we found a number of regions where the DNA methylation status was altered in the liver tumors compared with the normal liver tissues by the methylated DNA immunoprecipitation (MeDIP)-CpG island microarray method. Among such regions, we demonstrated using real-time methylation-specific PCR and bisulfite sequencing that a gene body region of the oncogene Fosb underwent alteration in DNA methylation following gestational arsenic exposure. We also showed that the Fosb expression level significantly increased following gestational arsenic exposure. These findings suggest that the DNA methylation status of the Fosb region is implicated in tumor augmentation and can also be utilized for characterizing tumors induced by gestational arsenic exposure.

Augmenting effects of gestational arsenite exposure of C3H mice on the hepatic tumors of the F₂ male offspring via the F₁ male offspring

Gestational exposure can affect the F2 generation through exposure of F1 germline cells. Previous studies reported that arsenite exposure of only F0 females during their pregnancy increases hepatic tumors in the F1 males in C3H mice, whose males are predisposed spontaneously to develop hepatic tumors later in life. The present study addressed the effects of gestational arsenite exposure on tumorigenesis of the F2 males in C3H mice. Expression analysis of several genes in the normal livers at 53 and 80 weeks of age clearly showed significant changes in the F2 males obtained by crossing gestational arsenite-exposed F1 (arsenite-F1) males and females compared to the control F2 males. Some of the changes were shown to occur in a late-onset manner. Then the tumor incidence was assessed at 75-82 weeks of age in the F2 males obtained by reciprocal crossing between the control and arsenite-F1 males and females. The results demonstrated that the F2 males born to arsenite-F1 males developed tumors at a significantly higher rate than the F2 males born to the control F1 males, irrespective of exposure of F1 females. Gene expressions of hepatocellular carcinoma markers β-catenin (CTNNB1) and interleukin-1 receptor antagonist in the tumors were significantly upregulated in the F2 males born to arsenite-F1 males compared to those born to the control F1 males. These results show that arsenite exposure of only F0 pregnant mice causes late-onset changes and augments tumors in the livers of the F2 males by affecting the F1 male offspring.

Endoscopic evaluation of food bolus formation and its relationship with the number of chewing cycles

It is known that solid food is transported to the pharynx actively in parallel to it being crushed by chewing and mixed with saliva in the oral cavity. Therefore, food bolus formation should be considered to take place from the oral cavity to the pharynx. In previous studies, the chewed food was evaluated after the food had been removed from the oral cavity. However, it has been pointed out that spitting food out of the oral cavity interferes with natural food bolus formation. Therefore, we observed food boluses immediately before swallowing using an endoscope to establish a method to evaluate the food bolus-forming function, and simultaneously performed endoscopic evaluation of food bolus formation and its relationship with the number of chewing cycles. The subject was inserted the endoscope nasally and instructed to eat two coloured samples of boiled rice simultaneously in two ingestion conditions ('as usual' and 'chewing well'). The condition of the food bolus was graded into three categories for each item of grinding, mixing and aggregation and scored 2, 1 and 0. The score of aggregation was high under both ingestion conditions. The scores of grinding and mixing tended to be higher in subjects with a high number of chewing cycles, and the score of aggregation was high regardless of the number of chewing cycles. It was suggested that food has to be aggregated, even though the number of chewing cycles is low and the food is not ground or mixed for a food bolus to reach the swallowing threshold.

The effect of a methyl-deficient diet on the global DNA methylation and the DNA methylation regulatory pathways

Methyl-deficient diets are known to induce various liver disorders, in which DNA methylation changes are implicated. Recent studies have clarified the existence of the active DNA demethylation pathways that start with oxidization of 5-methylcytosine (5meC) to 5-hydroxymethylcytosine by ten-eleven translocation (Tet) enzymes, followed by the action of base-excision-repair pathways. Here, we investigated the effects of a methionine-choline-deficient (MCD) diet on the hepatic DNA methylation of mice by precisely quantifying 5meC using a liquid chromatography-electrospray ionization-mass spectrometry and by investigating the regulatory pathways, including DNA demethylation. Although feeding the MCD diet for 1 week induced hepatic steatosis and lower level of the methyl donor S-adenosylmethionine, it did not cause a significant reduction in the 5meC content. On the other hand, the MCD diet significantly upregulated the gene expression of the Tet enzymes, Tet2 and Tet3, and the base-excision-repair enzymes, thymine DNA glycosylase and apurinic/apyrimidinic-endonuclease 1. At the same time, the gene expression of DNA methyltransferase 1 and a, was also significantly increased by the MCD diet. These results suggest that the DNA methylation level is precisely regulated even when dietary methyl donors are restricted. Methyl-deficient diets are well known to induce oxidative stress and the oxidative-stress-induced DNA damage, 8-hydroxy-2'-deoxyguanosine (8OHdG), is reported to inhibit DNA methylation. In this study, we also clarified that the increase in 8OHdG number per DNA by the MCD diet is approximately 10 000 times smaller than the reduction in 5meC number, suggesting the contribution of 8OHdG formation to DNA methylation would not be significant.

Increase in incidence of hepatic tumors caused by oncogenic somatic mutation in mice maternally exposed to inorganic arsenic and the multigenerational and transgenerational effects of inorganic arsenic

Inorganic arsenic is a natural environmental contaminant and known to be a human carcinogen. Although rodent models are pivotal in elucidating the mode of action of arsenic, it has been difficult to verify the carcinogenicity of arsenic in rodents until recently. Waalkes et al. (Toxicol Appl Pharmacol 2003;
186:7-17) reported that maternal exposure to arsenite increases the incidence of hepatic tumors in the male pups of C3H mice in adulthood. This finding indicated that the gestational period is vulnerable to arsenic. Using the same experimental model, we found that maternal arsenite exposure increases the incidence of hepatic tumors caused by a somatic mutation of the C61A Ha-ras gene, which encodes an activated oncogenic Ha-ras protein. The G:C to T:A transversion is attributable to oxidative stress. Our further studies of gpt delta transgenic mice, which enable detection of in vivo mutation, and genome-wide analysis of DNA methylation levels using the methylated DNA immunoprecipitation-CpG island microarray method suggest that oxidative-stress-induced mutation and DNA methylation changes are involved in the tumor augmentation in the pups maternally exposed to arsenic. Our recent study has also suggested that maternal arsenic exposure increases the incidence of hepatic tumors even in the grandchildren (the F2 generation). Consideration should be given to multigenerational and transgenerational effects of maternal exposure in future studies.

The mechanisms underlying sexual differentiation of behavior and physiology in mammals and birds: relative contributions of sex steroids and sex chromosomes

From a classical viewpoint, sex-specific behavior and physiological functions as well as the brain structures of mammals such as rats and mice, have been thought to be influenced by perinatal sex steroids secreted by the gonads. Sex steroids have also been thought to affect the differentiation of the sex-typical behavior of a few members of the avian order Galliformes, including the Japanese quail and chickens, during their development in ovo. However, recent mammalian studies that focused on the artificial shuffling or knockout of the sex-determining gene, Sry, have revealed that sex chromosomal effects may be associated with particular types of sex-linked differences such as aggression levels, social interaction, and autoimmune diseases, independently of sex steroid-mediated effects. In addition, studies on naturally occurring, rare phenomena such as gynandromorphic birds and experimentally constructed chimeras in which the composition of sex chromosomes in the brain differs from that in the other parts of the body, indicated that sex chromosomes play certain direct roles in the sex-specific differentiation of the gonads and the brain. In this article, we review the relative contributions of sex steroids and sex chromosomes in the determination of brain functions related to sexual behavior and reproductive physiology in mammals and birds.

Genome-wide analysis of DNA methylation changes induced by gestational arsenic exposure in liver tumors

Inorganic arsenic is known to be a human carcinogen. Previous studies have reported that DNA methylation changes are involved in arsenic-induced carcinogenesis, therefore, DNA methylation changes that are specific to arsenic-induced tumors would be useful to distinguish tumors induced by arsenic from tumors caused by other factors and to dissect arsenic carcinogenesis. Previous studies have shown that gestational arsenic exposure of C3H mice, which tend to spontaneously develop liver tumors, increases the incidence of tumors in male offspring. In this study we used the same experimental protocol as in those previous studies and searched for DNA regions where methylation status was specifically altered in the liver tumors of arsenic-exposed offspring by using methylated DNA immunoprecipitation-CpG island microarrays. The methylation levels of the DNA regions selected were measured by quantitative methylation-specific PCR and bisulfite sequencing. The results of this study clarified a number of regions where DNA methylation status was altered in the liver tumors in the C3H mice compared to normal liver tissues. Among such regions, we showed that a gene body region of the oncogene Fosb underwent alteration in DNA methylation by gestational arsenic exposure. We also showed that Fosb expression significantly increased corresponding to the DNA methylation level of the gene body in the arsenic-exposed group. These findings suggest that the DNA methylation status can be used to identify tumors increased by gestational arsenic exposure.

Brain-derived neurotrophic factor in VMH as the causal factor for and therapeutic tool to treat visceral adiposity and hyperleptinemia in type 2 diabetic Goto-Kakizaki rats

We previously reported that the type 2 diabetic Goto-Kakizaki (GK) rats at young adult ages (6-12 weeks) exhibited increased visceral fat mass and hyperleptinemia, due to hyperphagia caused primarily by neuropeptide Y (NPY) overexpression in the hypothalamic arcuate nucleus. Later, we found that GK rats continued to exhibit mesenteric fat accumulation and hyperleptinemia at least until 26 weeks of age, while hyperphagia and NPY overexpression ceased at 15 weeks of age. Therefore, we hypothesized that the long-lasting fat accumulation and hyperleptinemia are due to unidentified brain dysfunction other than NPY overexpression. In GK rats aged 26 weeks, glucose transporter-2 (GLUT2) mRNA expression in ventromedial hypothalamus (VMH) was markedly reduced in parallel with significant decreases in brain-derived neurotrophic factor (BDNF) mRNA level and BDNF-expressing cell numbers in the VMH. Pharmacologic inhibition of glucose utilization reduced BDNF mRNA expression in VMH in vivo and in vitro. The results suggested that impaired glucose utilization caused the reduction of BDNF. On the other hand, intracerebroventricular injection of BDNF for 6 days ameliorated hyperleptinemia in a long-lasting manner concurrently with feeding suppression in GK rats. Restricted feeding paired to BDNF-treated rats reduced plasma leptin level only transiently. BDNF treatment also reduced mesenteric fat mass in GK rats. These results reveal a novel action mode of BDNF to long-lastingly counteract visceral adiposity and hyperleptinemia in addition to and independently of its anorexigenic action. These results suggest that visceral fat accumulation and hyperleptinemia are at least partly due to the reduction of BDNF in VMH primarily caused by impaired glucose utilization in GK rats. The BDNF supplementation could provide an effective treatment of visceral obesity, hyperleptinemia and leptin resistance in type 2 diabetes.

Inorganic arsenic exposure induces E2F-dependent G0/G1 arrest via an increase in retinoblastoma family protein p130 in B-cell lymphoma A20 cells

Inorganic arsenic exerts toxic effect on multiple systems including the immune system. We previously showed in a study on mouse thymocytes and B-cell lymphoma A20 cells that arsenite induces cell cycle arrest at G0/G1 by suppressing expression of E2F-target genes. In this study, we furthermore investigated the involvement of retinoblastoma (RB) family proteins in E2F-dependent cell cycle arrest by arsenite. Arsenite exposure of A20 cells was showed to increase the protein level of p130, a RB family member, without changing the mRNA level. Suppression of arsenite-induced p130 by siRNA reduced the G0/G1 phase, indicating that p130 accumulation is responsible for arsenite-induced G0/G1 arrest. The accumulated p130 was shown to increase the p130 complex with E2F4, a transcription-suppressing E2F. Comparison by Western blotting of arsenite-induced p130 and p130 accumulated by a proteasome inhibitor suggested that arsenite-induced p130 is hypophosphorylated and hypoubiquitinated and refractory to proteasome-dependent degradation. We also showed that arsenite increases mRNA and protein of p16(INK4a), an inhibitor of CDK4/6 that phosphorylates p130. Down-regulation of arsenite-induced p16(INK4a) by siRNA suppressed the p130 accumulation. We propose a novel mechanism in which arsenite inhibits phosphorylation/ubiquitin-dependent proteasome degradation of p130 by inducing p16(INK4a) and the accumulated p130 causes cell cycle arrest with E2F4.

Swallowing frequency in elderly people during daily life

Disuse atrophy of swallowing-related organs due to an excessive decrease in swallowing frequency is suspected to occur in patients with poor oral intake, especially elderly people. However, swallowing frequency in daily life has not previously been examined in the elderly. This study examined swallowing frequency in elderly people and compared these findings to those in a younger population and differences in the degree of activity in daily life. (i) We compared swallowing frequency in 20 elderly people (82·0 ± 8·3 year) and 15 healthy young people (26·5 ± 3·5 year). (ii) 20 elderly people were divided into two groups according to the degree of activity in daily life: a semi-bedridden group and bedridden group; the swallowing frequency was compared between these groups. (i) The swallowing frequency in the elderly people was 2-19 times per hour and the mean was 9·4 ± 4·9, and that in the healthy young people was 16-76 times per hour and the mean was 40·7 ± 19·5. Swallowing frequency in elderly people was significantly lower than that in young healthy people (P < 0·0001). (ii) The swallowing frequency in bedridden group was 2-11 times per hour and the mean was 6·8 ± 3·3, and that in semi-bedridden group was 3-19 times per hour and the mean was 11·9 ± 5·1. Swallowing frequency in bedridden group was significantly lower than that in semi-bedridden group (P < 0·05). These results indicate that in daily life, elderly people tend to swallow less frequently than young people. In addition, swallowing frequency was lower in elderly subjects with a low degree of activity in daily life.

Organic Chemicals Adsorbed onto Diesel Exhaust Particles Directly Alter the Differentiation of Fetal Thymocytes Through Arylhydrocarbon Receptor but Not Oxidative Stress Responses

Diesel exhaust particles (DEP) were reported to have adverse effects on the immune system of laboratory animals and to induce thymic involution, particularly when exposure occurred during the fetal or lactational period. DEP consist of a carbon core to which many organic compounds are adsorbed, including polyaromatic hydrocarbons (PAHs) and their derivatives (e.g., dioxins and quinones). Although it has been suggested that these organic compounds were responsible for mediating the effects of DEP through their regulation of gene expression, the molecular mechanism of action of DEP has not been fully elucidated. In this study, we examined the direct effect of DEP extracts and their constituents on gene expression and phenotype in the fetal thymus. Fetal thymuses from C57BL/6 mice were exposed to DEP extracts for 24 hrs, after which their gene expression was analyzed using an Affymetrix GeneChip system. DEP extracts up-regulated several genes known as arylhydrocarbon receptor (AhR)-target genes, including cytochrome P450 1a1 (Cyp1a1), 1b1 (Cyp1b1), TCDD-inducible poly(ADP-ribose) polymerase (Tiparp), and scinderin (Scin). Similarly, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and benzo[a]pyrene (B[a]P), which are AhR ligands, induced remarkably similar changes in gene expression compared to DEP extracts. In addition, our data showed little contribution of quinones to DEP extracts-induced changes in gene expression in fetal thymus through oxidative stress responses. These changes in gene expression were also confirmed by semi-quantitative RT-PCR. Furthermore, DEP extracts skewed thymic T-cell differentiation in favor of the production of CD8 T-cells, which was also observed when exposed to AhR ligands. Our results suggest that organic compounds adsorbed onto DEP alter thymic gene expression and directly affect thymocyte development by activating the AhR.

Diurnal expression of Dnmt3b mRNA in mouse liver is regulated by feeding and hepatic clockwork

DNA methyltransferase 3B (DNMT3B) is critically involved in de novo DNA methylation and genomic stability, while the regulatory mechanism in liver is largely unknown. We previously reported that diurnal variation occurs in the mRNA expression of Dnmt3b in adult mouse liver. The aim of this study was to determine the mechanism underlying the diurnal expression pattern. The highest level and the lowest level of Dnmt3b mRNA expression were confirmed to occur at dawn and in the afternoon, respectively, and the expression pattern of Dnmt3b closely coincided with that of Bmal1. Since the diurnal pattern of Dnmt3b mRNA expression developed at weaning and scheduled feeding to separate the feeding cycle from the light/dark cycle led to a phase-shift in the expression, it could be assumed that feeding plays a critical role as an entrainment signal. In liver-specific Bmal1 knockout (L-Bmal1 KO) mice, L-Bmal1 deficiency resulted in significantly higher levels of Dnmt3b at all measured time points, and the time when the expression was the lowest in wild-type mice was shifted to earlier. Investigation of global DNA methylation revealed a temporal decrease of 5-methyl-cytosine percentage in the genome of wild-type mice in late afternoon. By contrast, no such decrease in 5-methyl-cytosine percentage was detected in L-Bmal1 KO mice, suggesting that altered Dnmt3b expression affects the DNA methylation state. Taken together, the results suggest that the feeding and hepatic clockwork generated by the clock genes, including Bmal1, regulate the diurnal variation in Dnmt3b mRNA expression and the consequent dynamic changes in global DNA methylation.

Development of a swallowing frequency meter using a laryngeal microphone

Disuse atrophy of swallowing-related organs is suspected when decreased swallowing frequency is seen in the elderly. However, swallowing frequency has not been examined in elderly people during daily life. We developed a swallowing frequency meter containing a laryngeal microphone that does not restrict the subject's ability to perform daily activities. In this study, the utility of the meter was assessed. Experiment 1: The ability of the meter to detect swallowing was examined. The subject was instructed to swallow saliva or foods at a voluntarily pace. During these procedures, swallowing events were simultaneously recorded by the meter, self-enumeration and videofluorography. As a result, all of the swallowing events identified by the meter coincided with the swallowing events identified by self-enumeration and videofluorography. Experiment 2: Swallowing sounds display various patterns both between and within individuals. Therefore, we examined the concordance rate between the number of swallowing events counted by the meter and that counted by self-enumeration in 15 subjects over a longer period than in experiment 1. The concordance rates calculated by two examiners between the meter and self-enumeration were 96·8 ± 4·5% and 98·9 ± 3·3% at rest and 95·2 ± 4·5% and 96·1 ± 4·1% during meals, respectively. Our findings indicate that this meter is useful for measuring the frequency of swallowing during daily situations.

Permanent genetic resources added to Molecular Ecology Resources Database 1 October 2010-30 November 2010

This article documents the addition of 277 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Ascochyta rabiei, Cambarellus chapalanus, Chionodraco hamatus, Coptis omeiensis, Cynoscion nebulosus, Daphnia magna, Gerbillus nigeriae, Isurus oxyrinchus, Lates calcarifer, Metacarcinus magister, Oplegnathus fasciatus, Pachycondyla verenae, Phaethon lepturus, Pimelodus grosskopfii, Rotylenchulus reniformis, Scomberomorus niphonius, Sepia esculenta, Terapon jarbua, Teratosphaeria cryptica and Thunnus obesus. These loci were cross-tested on the following species: Austropotamobius italicus, Cambarellus montezumae, Cambarellus puer, Cambarellus shufeldtii, Cambarellus texanus, Chionodraco myersi, Chionodraco rastrospinosus, Coptis chinensis, Coptis chinensis var. brevisepala, Coptis deltoidea, Coptis teeta, Orconectes virilis, Pacifastacus leniusculus, Pimelodus bochii, Procambarus clarkii, Pseudopimelodus bufonius, Rhamdia quelen, Sepia andreana, Sepiella maindroni, Thunnus alalunga, Thunnus albacares, Thunnus maccoyii, Thunnus orientalis, Thunnus thynnus and Thunnus tonggol.