Thyroid effects of endocrine disrupting chemicals

In recent years, many studies of thyroid-disrupting effects of environmental chemicals have been published. Of special concern is the exposure of pregnant women and infants, as thyroid disruption of the developing organism may have deleterious effects on neurological outcome. Chemicals may exert thyroid effects through a variety of mechanisms of action, and some animal experiments and in vitro studies have focused on elucidating the mode of action of specific chemical compounds. Long-term human studies on effects of environmental chemicals on thyroid related outcomes such as growth and development are still lacking. The human exposure scenario with life long exposure to a vast mixture of chemicals in low doses and the large physiological variation in thyroid hormone levels between individuals render human studies very difficult. However, there is now reasonably firm evidence that PCBs have thyroid-disrupting effects, and there is emerging evidence that also phthalates, bisphenol A, brominated flame retardants and perfluorinated chemicals may have thyroid disrupting properties.     

Diet-induced obesity in mice causes changes in immune responses and bone loss manifested by bacterial challenge

Obesity has been suggested to be associated with an increased susceptibility to bacterial infection. However, few studies have examined the effect of obesity on the immune response to bacterial infections. In the present study, we investigated the effect of obesity on innate immune responses to Porphyromonas gingivalis infection, an infection strongly associated with periodontitis. Mice with diet-induced obesity (DIO) and lean control C57BL/6 mice were infected orally or systemically with P. gingivalis, and periodontal pathology and systemic immune responses were examined postinfection. After oral infection with P. gingivalis, mice with DIO had a significantly higher level of alveolar bone loss than the lean controls. Oral microbial sampling disclosed higher levels of P. gingivalis in mice with DIO vs. lean mice during and after infection. Furthermore, animals with DIO exposed to oral infection or systemic inoculation of live P. gingivalis developed a blunted inflammatory response with reduced expression of TNF-alpha, IL-6, and serum amyloid A (SAA) at all time points compared with lean mice. Finally, peritoneal macrophages harvested from mice with DIO and exposed to P. gingivalis exhibited reduced levels of proinflammatory cytokines compared with lean mice and when exposed to P. gingivalis LPS treatment had a significantly reduced recruitment of NF-kappaB to both TNF-alpha and IL-10 promoters 30 min after exposure. These data indicate that obesity interferes with the ability of the immune system to appropriately respond to P. gingivalis infection and suggest that this immune dysregulation participates in the increased alveolar bone loss after bacterial infection observed in mice with DIO.     

Cuticular hydrocarbon analysis of an awake behaving fly using direct analysis in real-time time-of-flight mass spectrometry

In mammals and insects, pheromones strongly influence social behaviors such as aggression and mate recognition. In Drosophila melanogaster, pheromones in the form of cuticular hydrocarbons play prominent roles in courtship. GC/MS is the primary analytical tool currently used to study Drosophila cuticular hydrocarbons. Although GC/MS is highly reproducible and sensitive, it requires that the fly be placed in a lethal solution of organic solvent, thereby impeding further behavioral studies. We present a technique for the analysis of hydrocarbons and other surface molecules from live animals by using direct analysis in real-time (DART) MS. Cuticular hydrocarbons were sampled from the surface of a restrained, awake behaving fly by using several brief, carefully controlled depressions of the abdomen with a small steel probe. DART mass spectral analysis of the probe detected ions with mass-to-charge ratio (m/z) of the protonated molecule corresponding to many of the previously identified unsaturated hydrocarbons. Six additional cuticular hydrocarbons also were identified. Consistent with previous GC/MS studies, male and female differences in chemical composition were evident. Spatial differences in the expression profile also were observed on males. Sampling from an individual female first as a virgin and then 45 and 90 min after successful copulation showed that mass signals likely to correspond to cis-vaccenyl acetate, tricosene, and pentacosene increased in relative intensity after courtship. This method provides near-instantaneous analysis of an individual animal's chemical profile in parallel with behavioral studies and could be extended to other models of pheromone-mediated behavior.     

Involvement of testicular growth factors in fetal Leydig cell aggregation after exposure to phthalate in utero

Exposures to di-(2-ethylhexyl) phthalate (DEHP) have been shown to be associated with decreased adult testosterone (T) levels and increased Leydig cell numbers. As yet, little is known about DEHP effects in utero on fetal Leydig cells (FLC). The present study investigated effects of DEHP on FLC function. Pregnant Long-Evans female rats received vehicle (corn oil) or DEHP at 10, 100, or 750 mg/kg by oral gavage from gestational day (GD)2-20. At GD21, T production, FLC numbers and distribution, and testicular gene expression were examined. The percentage of FLC clusters containing 6-30 cells increased in all treatment groups, with 29 +/- 2% in control vs. 37 +/- 3, 35 +/- 3, and 56 +/- 4% in rats receiving 10, 100, and 750 mg/kg DEHP, respectively. In contrast, FLC numbers were 33% and 39% lower than control after exposures to 100 and 750 mg/kg DEHP, respectively. At these doses, mRNA levels of leukemia inhibitory factor (LIF) increased. LIF was found to induce cell aggregation in FLCs in vitro, consistent with the hypothesis that DEHP induced FLC aggregation. Testicular T levels were doubled by the 10 mg/kg dose and halved at 750 mg/kg. The mRNA levels of IGF-1 and c-Kit ligand (KITL) were induced by 10 mg/kg DEHP. These results, taken together, indicate that fetal exposures to DEHP have effects on FLC number, distribution, and most importantly, steroidogenic capacity and suggest that abnormal expressions of IGF1, KITL, and LIF genes may contribute to the reproductive toxicity of phthalates.     

Helicobacter pylori-related chronic gastritis as a risk factor for colonic neoplasms

To summarize the current views and insights on associations between Helicobacter pylori(H. pylori)-related chronic gastritis and colorectal neoplasm, we reviewed recent studies to clarify whether H. pylori infection/H. pylori-related chronic gastritis is associated with an elevated risk of colorectal neoplasm. Recent studies based on large databases with careful control for confounding variables have clearly demonstrated an increased risk of colorectal neoplasm associated with H. pylori infection. The correlation between H. pylori-related chronic atrophic gastritis(CAG) and colorectal neoplasm has only been examined in a limited number of studies. A recent large study using a national histopathological database, and our study based on the stage of H. pylori-related chronic gastritis as determined by serum levels of H. pylori antibody titer and pepsinogen, indicatedthat H. pylori-related CAG confers an increased risk of colorectal neoplasm, and more extensive atrophic gastritis will probably be associated with even higher risk of neoplasm. In addition, our study suggested that the activity of H. pylori-related chronic gastritis is correlated with colorectal neoplasm risk. H. pylori-related chronic gastritis could be involved in an increased risk of colorectal neoplasm that appears to be enhanced by the progression of gastric atrophy and the presence of active inflammation.     

Association of Fusobacterium nucleatum with immunity and molecular alterations in colorectal cancer

The human intestinal microbiome plays a major role in human health and diseases, including colorectal cancer. Colorectal carcinogenesis represents a heterogeneous process with a differing set of somatic molecular alterations, influenced by diet, environmental and microbial exposures, and host immunity. Fusobacterium species are part of the human oral and intestinal microbiota. Metagenomic analyses have shown an enrichment of Fusobacterium nucleatum(F. nucleatum) in colorectal carcinoma tissue. Using 511 colorectal carcinomas from Japanese patients, we assessed the presence of F. nucleatum. Our results showed that the frequency of F. nucleatum positivity in the Japanese colorectal cancer was 8.6%(44/511), which was lower than that in United States cohort studies(13%). Similar to the United States studies, F. nucleatum positivityin Japanese colorectal cancers was significantly associated with microsatellite instability(MSI)-high status. Regarding the immune response in colorectal cancer, high levels of infiltrating T-cell subsets(i.e., CD3+, CD8+, CD45RO+, and FOXP3+ cells) have been associated with better patient prognosis. There is also evidence to indicate that molecular features of colorectal cancer, especially MSI, influence T-cell-mediated adaptive immunity. Concerning the association between the gut microbiome and immunity, F. nucleatum has been shown to expand myeloid-derived immune cells, which inhibit T-cell proliferation and induce T-cell apoptosis in colorectal cancer. This finding indicates that F. nucleatum possesses immunosuppressive activities by inhibiting human T-cell responses. Certain micro RNAs are induced during the macrophage inflammatory response and have the ability to regulate host-cell responses to pathogens. Micro RNA-21 increases the levels of IL-10 and prostaglandin E2, which suppress antitumor T-cell-mediated adaptive immunity through the inhibition of the antigen-presenting capacities of dendritic cells and T-cell proliferation in colorectal cancer cells. Thus, emerging evidence may provide insights for strategies to target microbiota, immune cells and tumor molecular alterations for colorectal cancer prevention and treatment. Further investigation is needed to clarify the association of Fusobacterium with T-cells and micro RNA expressions in colorectal cancer.     

Does the GH–IGF axis play a role in cancer pathogenesis?

Recent case-controlled studies have found increases in the serum levels of insulin-like growth factor-I (IGF-I) in subjects who had, or who eventually developed, prostate or premenopausal breast cancers. Since growth hormone (GH) increases IGF-I levels, concern has been raised regarding its potential role as a cancer initiation factor. The epidemiological studies, which indicate an association between serum IGF-I levels and cancer risk, have not established causality. In fact, several alternative explanations for the elevated serum IGF-I levels in cancer patients may be proposed based on human and animal models. First, an effect of IGF-I causing symptomatic benign tissue hyperplasia may result in an ascertainment bias leading to an initiation of procedures resulting in the diagnosis of asymptomatic cancers. Second, elevated serum IGF-I in cancer patients may originate within the tumor (as suggested by some animal studies). Thirdly, serum IGF-I may actually be a surrogate marker of tissue IGF-I levels or of nutritional factors, which are not under GH control and may be involved in cancer initiation. The role of GH in cancer initiation is further negated by the fact that in acromegaly, the incidence of cancer, other than possibly colonic neoplasia does not appear to be significantly increased. Furthermore, GH transgenic mice, with high IGF-I levels, do not develop breast, prostate, or colonic malignancies. It is known that IGFBP-3 can inhibit IGF action on cancer cells in vitro and also can induce apoptosis via an IGF-independent mechanism. Importantly, in addition to increasing IGF-I levels, GH also increases the serum levels of IGFBP-3 and serum IGFBP-3 levels have been shown to be negatively correlated with the risk of cancer in the above mentioned epidemiological studies and in a similar study on colon cancer. These studies suggest that cancer risk is increased in individuals in whom both high IGF-I levels and low IGFBP-3 levels are present. In subjects treated with GH, IGF-I and IGFBP-3 levels both rise together and are not within the elevated cancer-risk range, based on published studies. Long-term studies are needed to assess the potential risks, including the long-term cancer risk associated with GH therapy. These should take into account several factors, including the duration of exposure, the risk magnitude associated with the degree of serum IGF-I elevation, and the adjusted risk based on a concomitant increase in IGFBP-3 levels. Since GH treated patients often have sub-normal IGF-I serum levels, which normalize on therapy, one might predict that their cancer risk on GH therapy should not increase above the normal population. Until further research in the area dictates otherwise, on-going cancer surveillance and routine monitoring of serum IGF-I and IGFBP-3 levels in GH-recipients should be the standard of care. At present, the data that are available do not warrant a change in our current management of approved indications for GH therapy.     

PON2 and ATP2B2 gene polymorphisms with noise-induced hearing loss

Background

Noise-induced hearing loss (NIHL) is a complex disease induced by a combination of genetic and environmental factors. Paraoxonase2 (PON2) gene involved in the regulation of reactive oxygen species, and affecting the vulnerability of cochlea to NIHL, and ATPase, calcium-transporting, plasma membrane 2 (ATP2B2) gene which encodes plasma membrane calcium-transporting ATPase isoform 2 (PMCA2) are the candidate genes relating to the attack of NIHL. In this study, we investigated whether ATP2B2 and PON2 polymorphisms were associated with NIHL in Chinese of Han nationality population.

Methods

We performed a case-control study between six single nucleotide polymorphisms (SNPs) (rs1719571, rs3209637 and rs4327369 within ATP2B2, rs12026, rs7785846 and rs12704796 within PON2) and NIHL in 454 subjects. All the SNPs were genotypes, using the TaqMan MGB probe assay. Odds ratios (ORs) were calculated with 95% confidence intervals (95% CIs) with logistic regression analysis to test the level of association for SNPs.

Results

In our study, 221 subjects with hearing loss and 233 subjects without hearing loss were recruited. The frequencies of the CG and CG + GG genotype of rs12026 (PON2) conferred risk factors for NIHL with adjusted OR values of 2.62 (95% CI, 1.69–4.06) and 2.48 (95% CI, 1.63–3.78), respectively. This kind of significance was also found at locus rs7785846, where genotypes CT and CT + TT were the risk types, with adjusted ORs of 2.52 (95% CI, 1.62–3.93) and 2.35 (95% CI, 1.54–3.58), respectively. We performed stratified analysis per noise exposure level, when it came to rs7785846 and rs12026 in the >92 dB(A) noise exposure group, the subjects who carried heterozygote were of significantly (P<0.01) higher susceptibility to NIHL than homozygote carriers. By contrast, no significantly higher risk was found for any rs12704796 genotypes or any genotypes in ATP2B2 (P>0.05), which may suggest that these SNPs did not have significant effects on noise susceptibility across noise exposure.

Conclusions

Our research suggested that PON2 might play a role in the etiology of NIHL in Chinese of Han nationality population.     

Demonstration of functional neuronal beta3-adrenoceptors within the enteric nervous system

BACKGROUND & AIMS: Although the beta(3)-adrenoceptor (AR) has been suggested to be involved in regulation of gut motility and visceral algesia, the precise mechanisms have been unknown. beta(3)-AR has been postulated to have a nonneuronal expression, being initially characterized in adipocytes and subsequently in the smooth muscle. We aimed to investigate the expression of beta(3)-AR in human enteric nervous system and its role in motility and visceral algesia. METHODS: The expression of beta(3)-AR in human colon myenteric and submucosal plexus was investigated using immunohistochemistry. The effects of a beta(3)-AR agonist on nerve-evoked and carbachol-induced contractions as well as somatostatin release were investigated in strips of human colon. The effect of an agonist on diarrhea and visceral pain was investigated in vivo in rat models. RESULTS: beta(3)-AR is expressed in cholinergic neurons in the myenteric plexus and submucosal plexus of human colon. Activation of beta(3)-AR causes the release of somatostatin from human isolated colon. In a rat model of visceral pain, beta(3)-AR agonist elicits somatostatin-dependent visceral analgesia. beta(3)-AR agonists inhibit cholinergically mediated muscle contraction of the human colon, as well as chemically induced diarrhea in vivo in a rat model. CONCLUSIONS: This is the first demonstration of expression of beta(3)-AR in the enteric nervous system. Activation of these receptors results in inhibition of cholinergic contractions and enhanced release of somatostatin, which may lead to visceral analgesia and inhibition of diarrhea. Therefore, beta(3)-AR could be a novel therapeutic target for functional gastrointestinal disorders.     

Ecopathology of ranaviruses infecting amphibians

Ranaviruses are capable of infecting amphibians from at least 14 families and over 70 individual species. Ranaviruses infect multiple cell types, often culminating in organ necrosis and massive hemorrhaging. Subclinical infections have been documented, although their role in ranavirus persistence and emergence remains unclear. Water is an effective transmission medium for ranaviruses, and survival outside the host may be for significant duration. In aquatic communities, amphibians, reptiles and fish may serve as reservoirs. Controlled studies have shown that susceptibility to ranavirus infection and disease varies among amphibian species and developmental stages, and likely is impacted by host-pathogen coevolution, as well as, exogenous environmental factors. Field studies have demonstrated that the likelihood of epizootics is increased in areas of cattle grazing, where aquatic vegetation is sparse and water quality is poor. Translocation of infected amphibians through commercial trade (e.g., food, fish bait, pet industry) contributes to the spread of ranaviruses. Such introductions may be of particular concern, as several studies report that ranaviruses isolated from ranaculture, aquaculture, and bait facilities have greater virulence (i.e., ability to cause disease) than wild-type isolates. Future investigations should focus on the genetic basis for pathogen virulence and host susceptibility, ecological and anthropogenic mechanisms contributing to emergence, and vaccine development for use in captive populations and species reintroduction programs.     

Testicular dysgenesis syndrome: foetal origin of adult reproductive problems

The evidence for the existence of testicular dysgenesis syndrome (TDS) is presented in this review. Several epidemiological studies have shown that conditions like cryptorchidism, impaired spermatogenesis, hypospadias and testicular cancer can be associated as risk factors for each other. Thus, the risk of testis cancer is significantly increased in men with cryptorchidism and/or infertility. Several recent studies point towards early dysgenesis of the foetal testis as the biological link between these disorders. Dysgenesis has been demonstrated in biopsies of the contralateral testis of men with testis cancer and in infertile men. The histological evidence includes immature seminiferous tubules with undifferentiated Sertoli cells, microliths and Sertoli-cell only tubules. Dysgenetic testes often have an irregular ultrasound pattern, where microliths may also be visible. Our current hypothesis is that maternal exposure to endocrine disrupting chemicals may contribute to the pathogenesis of TDS. Animal experiments have shown that all TDS symptoms, except testicular cancer, can be induced by foetal exposure to anti-androgenic chemicals. However, the cause of TDS in humans remains to be determined.     

Infection by Ascaris lumbricoides and bronchial hyper reactivity: an outstanding association in Venezuelan school children from endemic areas

Asthma and other respiratory diseases have increased in the last years among Venezuelan children from helminthic endemic areas where the infection by Ascaris lumbricoides has been associated to bronchial airway inflammation in parasitized individuals. The aim of this work was to investigate the possible associations between the development of bronchial hyper reactivity and the immune response against A. lumbricoides in urban and rural children. We evaluated 470 school children from rural and urban communities. Pulmonary function tests were performed and >or=20% PC(20) changes were considered as a positive diagnostic of bronchial hyper reactivity. The prevalence and intensity of A. lumbricoides infection was determined by faecal examination. Specific serum IgE levels using a modified ELISA and skin prick tests against A. lumbricoides and the common allergen Dermatophagoides pteronyssinus were done. The number of circulating lymphocyte sub populations was determined by flow cytometry analysis. In rural children, bronchial hyper reactivity was associated with increased specific levels of anti-A. lumbricoides IgE (p<0.0001) and skin test positivity for A. lumbricoides (p<0.0001). The percentage of FEV1 predictive values correlated inversely (p<0.0001) with anti-A. lumbricoides IgE levels. Elevated numbers of circulating CD3+CD4+ and CD20+CD23+ cells were found in rural children with bronchial hyper reactivity compared to their asymptomatic counterparts. They correlated positively with anti-A. lumbricoides IgE levels (p<0.005 and <0.0001, respectively). In contrast, in urban children, bronchial hyper reactivity was associated with elevated anti-D. pteronyssinus IgE levels (p=0. 0089), skin hyper reactivity towards this aero allergen (p=0.003) and to an increase in the number of CD3+CD8+ (p<0.0001). Our results suggest that the IgE response against A. lumbricoides infection may be involved in the development of bronchial hyper reactivity among rural children from endemic areas and also that improved hygienic conditions in the urban environment is associated with increased responses to airborne allergens.     

Interactions of chemical carcinogens and genetic variation in hepatocellular carcinoma

In the etiology of hepatocellular carcinoma (HCC), in addition to hepatitis B virus and hepatitis C virus infections, chemical carcinogens also play important roles. For example, aflatoxin B(1) (AFB(1)) epoxide reacts with guanine in DNA and can lead to genetic changes. In HCC, the tumor suppressor gene p53 codon 249 mutation is associated with AFB(1) exposure and mutations in the K-ras oncogene are related to vinyl chloride exposure. Numerous genetic alterations accumulate during the process of hepatocarcinogenesis. Chemical carcinogen DNA-adduct formation is the basis for these genetic changes and also a molecular marker which reflects exposure level and biological effects. Metabolism of chemical carcinogens, including their activation and detoxification, also plays a key role in chemical hepatocarcinogenesis. Cytochrome p450 enzymes, N-acetyltransferases and glutathione S-transferases are involved in activating and detoxifying chemical carcinogens. These enzymes are polymorphic and genetic variation influences biological response to chemical carcinogens. This genetic variation has been postulated to influence the variability in risk for HCC observed both within and across populations. Ongoing studies seek to fully understand the mechanisms by which genetic variation in response to chemical carcinogens impacts on HCC risk.     

Amphibian metamorphosis as a model for studying endocrine disruption on vertebrate development: Effect of bisphenol A on thyroid hormone action

Thyroid hormone (TH) is essential for proper development in vertebrates. TH deficiency during gestation and early postnatal development produces severe neurological, skeletal, metabolism and growth abnormalities. It is therefore important to consider environmental chemicals that may interfere with TH signaling. Exposure to environmental contaminants that disrupt TH action may underlie the increasing incidence of human developmental disorders worldwide. One contaminant of concern is the xenoestrogen bisphenol A (BPA), a chemical widely used to manufacture polycarbonate plastics and epoxy resins. The difficulty in studying uterus-enclosed mammalian embryos has hampered the analysis on the direct effects of BPA during vertebrate development. As TH action at the cellular level is highly conserved across vertebrate species, amphibian metamorphosis serves as an important TH-dependent in vivo vertebrate model for studying potential contributions of BPA toward human developmental disorders. Using Xenopus laevis as a model, we and others have demonstrated the inhibitory effects of BPA exposure on metamorphosis. Genome-wide gene expression analysis revealed that surprisingly, BPA primarily targets the TH-signaling pathway essential for metamorphosis in Xenopus laevis. Given the importance of the genomic effects of TH during metamorphosis and the conservation in its regulation in higher vertebrates, these observations suggest that the effect of BPA in human embryogenesis is through the inhibition of the TH pathway and warrants further investigation. Our findings further argue for the critical need to use in vivo animal models coupled with systematic molecular analysis to determine the developmental effects of endocrine disrupting compounds.     

Activation of inflammatory mediators and potential role of Ah-receptor ligands in foam cell formation

Epidemiological data and in vivo animal experiments have indicated that exposure to the Ah-receptor (AhR) ligand dioxin and other dioxin-like compounds can lead to cardiovascular toxicity and atherosclerosis. Here, we investigated the effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most potent AhR ligand, on the differentiation of U937 cells into foam cells, which are considered to be early lesions of atherosclerosis. Our findings show that, like oxidized low-density lipoprotein (oxLDL), TCDD promotes the differentiation of U937 macrophages to atherogenic foam cells, verified by lipid accumulation and extensive formation of blebs on the cell surface, which are characteristics of foam cells. Through screening expression patterns of typical genes involved in atherosclerosis and foam cell generation, we could demonstrate that mRNA levels of cyclooxygenase-2, interleukin 1 β, and tumor necrosis factor-α were increased in a time- and dose-dependent manner in U937 macrophages treated with TCDD, like oxLDL, and that these changes accompanied significantly elevated levels of matrix-degrading metalloproteinases (MMP)-1, MMP-3, MMP-12, and MMP-13. Increased levels of MMPs were associated with TCDD-stimulated cell migration of U937 macrophages. These findings clearly indicate that AhR ligands, like TCDD, stimulate differentiation of U937 macrophages into potentially plaque-forming foam cells.