Diisocyanates are a common cause of occupational asthma, but risk factors are not well defined. A case-control study was conducted to investigate whether genetic variants of antioxidant defense genes, glutathione S-transferases (GSTM1, GSTT1, GSTM3, GSTP1), manganese superoxide dismutase (SOD2), and microsomal epoxide hydrolase (EPHX1) are associated with increased susceptibility to diisocyanate-induced asthma (DA). The main study population consisted of 353 Caucasian French-Canadians from among a larger sample of 410 diisocyanate-exposed workers in three groups: workers with specific inhalation challenge (SIC) confirmed DA (DA+, n = 95); symptomatic diisocyanate workers with a negative SIC (DA−, n = 116); and asymptomatic exposed workers (AW, n = 142). Genotyping was performed on genomic DNA, using a 5′-nuclease PCR assay. The SOD2 rs4880, GSTP1 rs1695, and EPHX1 rs2740171 variants were significantly associated with DA in both univariate and multivariate analyses. In the first logistic regression model comparing DA+ and DA− groups, SOD2 rs4880, GSTM1 (null), GSTP1 rs762803, and EPHX1 rs2854450 variants were associated with DA (p = 0.004, p = 0.047, p = 0.021, p <0.001, respectively). Genotype combinations GSTT1*GSTP1 rs762803, GSTM1*EPHX1 rs2854450, EPHX1 rs2740168*EPHX1 rs1051741, and GSTP1 rs762803*EPHX1 rs2740168 were also associated with DA in this model (p = 0.027, p = 0.002, p = 0.045, p = 0.044, respectively). The GSTP1 rs1695 and EPHX1 rs1051741 and rs2740171 variants showed an association with DA in the second model comparing DA+ and AW groups (p = 0.040, p = 0.019, p = 0.002, respectively). The GSTM3 rs110913*EPHX1 rs1051741 genotype combination was also associated with DA under this model (p = 0.042). The results suggest that variations in SOD2, GST, and EPHX1 genes and their interactions contribute to DA susceptibility.
diisocyanates; occupational asthma; antioxidant; genetics; single-nucleotide polymorphism.
To estimate the prevalence, types and sociodemographic and biobehavioral correlates of antinuclear antibodies (ANA) in the United States (U.S.).
Cross-sectional analysis of 4,754 individuals from the National Health and Nutrition Examination Survey (NHANES) 1999–2004. ANA by indirect immunofluorescence, including cellular staining patterns and specific autoantibody reactivities by immunoprecipitation in those with ANA.
ANA prevalence in the U.S. population ages 12 years and older was 13.8% (95% CI, 12.2% to 15.5%). ANA increased with age (P = 0.01) and were more prevalent among females than males (17.8% vs. 9.6%, P < 0.001), with the female to male ratio peaking at 40–49 years of age. ANA prevalence was modestly higher in African Americans than whites (adjusted prevalence odds ratio [POR], 1.30; 95% CI, 1.00 to 1.70). Remarkably, ANA were less common in overweight and obese (adjusted POR, 0.74; 95% CI, 0.59 to 0.94) individuals than persons of normal weight. No significant associations were seen with education, family income, alcohol use, smoking history, serum levels of cotinine or C-reactive protein. In ANA-positive individuals, nuclear patterns were seen in 84.6%, cytoplasmic patterns in 21.8%, and nucleolar patterns in 6.1%, and the most common specific autoantibodies were anti-Ro (3.9%) and anti-Su (2.4%).
These findings suggest that over 32 million persons in the U.S. have ANA and the prevalence is higher among females, older individuals, African Americans and those with normal weight. These data will serve as a useful baseline for future investigations of predictors and changes in ANA prevalence over time.
Antinuclear antibodies; epidemiology; NHANES
Prevalence of fungal sensitization and atopy was lower among farmers than the US population. Fungal sensitization was related to growing specific agricultural commodities.
fungal sensitization; atopy; agriculture; farmers; specific and total IgE
Toxicology and careers in toxicology, as well as many other scientific disciplines, are undergoing rapid and dramatic changes as new discoveries, technologies, and hazards advance at a blinding rate. There are new and ever increasing demands on toxicologists to keep pace with expanding global economies, highly fluid policy debates, and increasingly complex global threats to public health. These demands must be met with new paradigms for multidisciplinary, technologically complex, and collaborative approaches that require advanced and continuing education in toxicology and associated disciplines. This requires paradigm shifts in educational programs that support recruitment, development, and training of the modern toxicologist, as well as continued education and retraining of the midcareer professional to keep pace and sustain careers in industry, government, and academia. The Society of Toxicology convened the Toxicology Educational Summit to discuss the state of toxicology education and to strategically address educational needs and the sustained advancement of toxicology as a profession. The Summit focused on core issues of: building for the future of toxicology through educational programs; defining education and training needs; developing the “Total Toxicologist”; continued training and retraining toxicologists to sustain their careers; and, finally, supporting toxicology education and professional development. This report summarizes the outcomes of the Summit, presents examples of successful programs that advance toxicology education, and concludes with strategies that will insure the future of toxicology through advanced educational initiatives.
In addition to the effector T-cells subsets, T-cells can also differentiate into cells that play a suppressive or regulatory role in adaptive immune responses. The cell types currently identified as regulatory T-cells (Tregs) include natural or thymic-derived Tregs, T-cells which express Foxp3+CD25+CD4+ and can suppress immune responses to autoreactive T-cells, as well as inducible Tregs, that are generated from naïve T-cells in the periphery after interaction with antigens presented by dendritic cells. Inducible Tregs include TH3 cells, Tr1 cells, and Foxp3+-inducible Tregs. Tregs have been shown to be critical in the maintenance of immune responses and T-cell homeostasis. These cells play an important role in suppressing responses to self-antigens and in controlling inappropriate responses to non-self-antigens, such as commensal bacteria or food in the gut. For example, depletion of CD4+CD25+ Tregs from mice resulted in the development of multi-organ autoimmune diseases. CD4+CD25+ Tregs and/or IL-10-producing Tr1 cells are capable of suppressing or attenuating TH2 responses to allergens. Moreover, adoptive transfer of CD4+CD25+ Tregs from healthy to diseased animals resulted in the prevention or cure of certain autoimmune diseases, and was able to induce transplantation tolerance. Clinical improvement seen after allergen immunotherapy for allergic diseases such as rhinitis and asthma is associated with the induction of IL-10- and TGFβ-producing Tr1 cells as well as FoxP3-expressing IL-10 T-cells, with resulting suppression of the TH2 cytokine milieu. Activation, expansion, or suppression of CD4+CD25+ Tregs
in vivo by xenobiotics, including drugs, may therefore represent a relevant mechanism underlying immunotoxicity, including immunosuppression, allergic asthma, and autoimmune diseases.
Regulatory T-cells; immunosuppression; allergy; autoimmunity
Benzene is an established leukemogen and hematotoxin in humans. However, the finding that benzene is a multiple-site carcinogen in rodents raises the possibility that other tissues could be susceptible to benzene-induced carcinogenicity, especially since a significant excess of squamous cell carcinomas and papillomas arise from epidermal and oral keratinocytes in benzene-exposed rats. Since inflammation and sustained hyperplasia are two integral components in carcinogenesis, the elaboration of proinflammatory cytokines and growth factors by keratinocytes might provide a mechanistic link between tumor initiation and promotion in benzene-induced cancers. We observed that the principal benzene metabolites, represented by hydroquinone, 1,4-benzoquinone, phenol, 1,2,4-benzenetriol, and catechol, significantly alters the production of transforming growth factor of (TGF)-α and interleukin (IL)-8 in human epidermal keratinocyte cultures. These cytokines represent the primary growth promoting factor and neutrophil chemotactant in the skin, respectively. Cytokine secretion correlated with the known redox potential of individual benzene metabolites and antioxidants, including dimethyl sulfoxide, 1,1,3,3-tetramethylthiourea, and N-acetylcysteine, attenuated the response. Binary combinations of selected benzene metabolites synergized in the induction of IL-8, while benzene, by itself, induced about a three-fold increase in IL-8 production. Taken together, our studies suggest that benzene and many of its phase I metabolites induce inflammatory cytokines and growth factors and this occurs through direct covalent binding or the generation of reactive oxygen species by autooxidation and reduction. The elaboration of proinflammatory cytokines and growth factors by keratinocytes in response to benzene and its principal metabolites may participate in benzene-induced skin carcinogenesis.
Diseases rarely, if ever, occur in isolation. Instead, most represent part of a more complex web or “pattern” of conditions that are connected via underlying biological mechanisms and processes, emerge across a lifetime, and have been identified with the aid of large medical databases.
We have described how an understanding of patterns of disease may be used to develop new strategies for reducing the prevalence and risk of major immune-based illnesses and diseases influenced by environmental stimuli.
Examples of recently defined patterns of diseases that begin in childhood include not only metabolic syndrome, with its characteristics of inflammatory dysregulation, but also allergic, autoimmune, recurrent infection, and other inflammatory patterns of disease. The recent identification of major immune-based disease patterns beginning in childhood suggests that the immune system may play an even more important role in determining health status and health care needs across a lifetime than was previously understood.
Focusing on patterns of disease, as opposed to individual conditions, offers two important venues for environmental health risk reduction. First, prevention of developmental immunotoxicity and pediatric immune dysfunction can be used to act against multiple diseases. Second, pattern-based treatment of entryway diseases can be tailored with the aim of disrupting the entire disease pattern and reducing the risk of later-life illnesses connected to underlying immune dysfunction. Disease-pattern–based evaluation, prevention, and treatment will require a change from the current approach for both immune safety testing and pediatric disease management.
asthma; developmental immunotoxicity; health risks; immune dysfunction; inflammation; intervention; metabolic syndrome; patterns of disease; prevention; safety testing
We previously demonstrated that cyclooxygenase (COX)-1 deficiency results in greater morbidity and inflammation, whereas COX-2 deficiency leads to reduced morbidity, inflammation and mortality in influenza infected mice.
We investigated the effects of COX-1 and COX-2 inhibitors in influenza A viral infection. Mice were given a COX-1 inhibitor (SC-560), a COX-2 inhibitor (celecoxib) or no inhibitor beginning 2 weeks prior to influenza A viral infection (200 PFU) and throughout the course of the experiment. Body weight and temperature were measured daily as indicators of morbidity. Animals were sacrificed on days 1 and 4 post-infection and bronchoalveolar lavage (BAL) fluid was collected or daily mortality was recorded up to 2 weeks post-infection. Treatment with SC-560 significantly increased mortality and was associated with profound hypothermia and greater weight loss compared to celecoxib or control groups. On day 4 of infection, BAL fluid cells were modestly elevated in celecoxib treated mice compared to SC-560 or control groups. Viral titres were similar between treatment groups. Levels of TNF-α and G-CSF were significantly attenuated in the SC-560 and celecoxib groups versus control and IL-6 levels were significantly lower in BAL fluid of celecoxib treated mice versus control and versus the SC-560 group. The chemokine KC was significantly lower in SC-560 group versus control.
Treatment with a COX-1 inhibitor during influenza A viral infection is detrimental to the host whereas inhibition of COX-2 does not significantly modulate disease severity. COX-1 plays a critical role in controlling the thermoregulatory response to influenza A viral infection in mice.
Arsenic is a carcinogen with transplacental activity that can affect human skin stem cell population dynamics in vitro by blocking exit into differentiation pathways. Keratinocyte stem cells (KSC) are probably a key target in skin carcinogenesis. Thus, we tested the effects of fetal arsenic exposure in Tg.AC mice, a strain sensitive to skin carcinogenesis via activation of the v-Ha-ras transgene likely in KSCs. After fetal arsenic treatment, offspring received topical 12-O-tetradecanoyl phorbol-13-acetate (TPA) through adulthood. Arsenic alone had no effect, whereas TPA alone induced papillomas and squamous cell carcinomas (SCC). However, fetal arsenic treatment before TPA increased SCC multiplicity 3-fold more than TPA alone, and these SCCs were much more aggressive (invasive, etc.). Tumor v-Ha-ras levels were 3-fold higher with arsenic plus TPA than TPA alone, and v-Ha-ras was over expressed early on in arsenic-treated fetal skin. CD34, considered a marker for both KSCs and skin cancer stem cells, and Rac1, a key gene stimulating KSC self-renewal, were greatly increased in tumors produced by arsenic plus TPA exposure versus TPA alone, and both were elevated in arsenic-treated fetal skin. Greatly increased numbers of CD34-positive probable cancer stem cells and marked over expression of RAC1 protein occurred in tumors induced by arsenic plus TPA compared with TPA alone. Thus, fetal arsenic exposure, although by itself oncogenically inactive in skin, facilitated cancer response in association with distorted skin tumor stem cell signaling and population dynamics, implicating stem cells as a target of arsenic in the fetal basis of skin cancer in adulthood.
This study compared pathological findings from a neonatal rat model of sudden death with those from 40 sudden infant death syndrome (SIDS) infants collected at autopsy. In the rat model, influenza A virus was administered intranasally on postnatal day 10, and on day 12 a sublethal, intraperitoneal dose of Escherichia coli endotoxin; mortality was 80%. Tissue samples from the animals and infants were fixed in formaldehyde, embedded in paraffin, and sections stained with hematoxylin and eosin. Tissues from the SIDS specimens were additionally cultured for bacteria and viruses; post-mortem blood samples were evaluated for signs of inflammation. All sections were examined by a pediatric forensic pathologist familiar with SIDS pathology. Comparisons between the rat model and the human SIDS cases revealed that both exhibited gross and microscopic pathology related to organ shock, possibly associated with the presence of endotoxin. Uncompensated shock appeared to be a likely factor that caused death in both infants and rat pups. Response to a shock-inducing event might have played an important role in the events leading to death. The similarities between the neonatal rats and the human cases indicate that further research with the model might elucidate additional aspects of SIDS pathology.
Endotoxin; organ shock; sudden infant death syndrome; SIDS; thymic involution
Inorganic arsenic (iAs) is a well-established carcinogen and human exposure has been associated with a variety of cancers including those of skin, lung, and bladder. High expression of transforming growth factor alpha (TGF-α) has associated with local relapses in early stages of urinary bladder cancer. iAs exposures are at least in part determined by the rate of formation and composition of iAs metabolites (MAsIII, MAsV, DMAsIII, DMAsV). This study examines the relationship between TGF-α concentration in exfoliated bladder urothelial cells (BUC) separated from urine and urinary arsenic species in 72 resident women (18-51 years old) from areas exposed to different concentrations of iAs in drinking water (2-378 ppb) in central Mexico. Urinary arsenic species, including trivalent methylated metabolites were measured by hydride generation atomic absorption spectrometry method. The concentration of TGF-α in BUC was measured using an ELISA assay. Results show a statistically significant positive correlation between TGF-α concentration in BUC and each of the six arsenic species present in urine. The multivariate linear regression analyses show that the increment of TGF-α levels in BUC was importantly associated with the presence of arsenic species after adjusting by age, and presence of urinary infection. People from areas with high arsenic exposure had a significantly higher TGF-α concentration in BUC than people from areas of low arsenic exposure (128.8 vs. 64.4 pg/mg protein; p<0.05). Notably, exfoliated cells isolated from individuals with skin lesions contained significantly greater amount of TGF-α than cells from individuals without skin lesions: 157.7 vs. 64.9 pg/mg protein (p=0.003). These results suggest that TGF-α in exfoliated BUC may serve as a susceptibility marker of adverse health effects on epithelial tissue in arsenic-endemic areas.
Transforming growth factor alpha; Susceptibility marker; Bladder urothelial cells; Arsenic; Trivalent arsenic; Urine metabolites; Arsenic-skin lesions; Hyperkeratosis; Hypo-hyperpigmentation
Assessing adverse effects from environmental chemical exposure is integral to public health policies. Toxicology assays identifying early biological changes from chemical exposure are increasing our ability to evaluate links between early biological disturbances and subsequent overt downstream effects. A workshop was held to consider how the resulting data inform consideration of an “adverse effect” in the context of hazard identification and risk assessment.
Our objective here is to review what is known about the relationships between chemical exposure, early biological effects (upstream events), and later overt effects (downstream events) through three case studies (thyroid hormone disruption, antiandrogen effects, immune system disruption) and to consider how to evaluate hazard and risk when early biological effect data are available.
Each case study presents data on the toxicity pathways linking early biological perturbations with downstream overt effects. Case studies also emphasize several factors that can influence risk of overt disease as a result from early biological perturbations, including background chemical exposures, underlying individual biological processes, and disease susceptibility. Certain effects resulting from exposure during periods of sensitivity may be irreversible. A chemical can act through multiple modes of action, resulting in similar or different overt effects.
For certain classes of early perturbations, sufficient information on the disease process is known, so hazard and quantitative risk assessment can proceed using information on upstream biological perturbations. Upstream data will support improved approaches for considering developmental stage, background exposures, disease status, and other factors important to assessing hazard and risk for the whole population.
adverse health effects; androgen antagonists; hazard identification; immunotoxicants; risk assessment; science policy; thyroid hormone; toxicologic assessments
Accumulating evidence suggests that gender impacts the incidence, susceptibility and severity of several lung diseases. Gender also influences lung development and physiology. Data from both human and animal studies suggests that sex hormones may contribute to disease pathogenesis or serve as protective factors, depending on the disease involved. In this review, the influence of gender and sex hormones on lung development and pathology will be discussed, with specific emphasis on pulmonary fibrosis, asthma and cancer.
Evaluation of xenobiotic-induced changes in gene expression as a method to identify and classify potential toxicants is being pursued by industry and regulatory agencies worldwide. A workshop was held at the Research Triangle Park campus of the Environmental Protection Agency to discuss the current state of the science of “immunotoxicogenomics”, and to explore the potential role of genomics techniques for immunotoxicity testing. The genesis of the workshop was the current lack of widely accepted triggering criteria for Tier 1 immunotoxicity testing in the context of routine toxicity testing data, the realization that traditional screening methods would require an inordinate number of animals and are inadequate to handle the number of chemicals that may need to be screened (e.g., high production volume compounds) and the absence of an organized effort to address the state of the science of toxicogenomics in the identification of immunotoxic compounds. The major focus of the meeting was on the theoretical and practical utility of genomics techniques to 1) replace or supplement current immunotoxicity screening procedures, 2) provide insight into potential modes or mechanisms of action, and 3) provide data suitable for immunotoxicity hazard identification or risk assessment. The latter goal is of considerable interest to a variety of stakeholders as a means to reduce animal use and to decrease the cost of conducting and interpreting standard toxicity tests. A number of data gaps were identified that included a lack of dose response and kinetic data for known immunotoxic compounds and a general lack of data correlating genomic alterations to functional changes observed in vivo. Participants concluded that a genomics approach to screen chemicals for immunotoxic potential or to generate data useful to risk assessors holds promise, but that routine use of these methods is years in the future. However, recent progress in molecular immunology has made mode and mechanism of action studies much more practical. Furthermore, a variety of published immunotoxicity studies suggest that microarray analysis is already a practical means to explore pathway-level changes that lead to altered immune function. To help move the science of immunotoxicogenomics forward, a partnership of industry, academia and government was suggested to address data gaps, validation, quality assurance, and protocol development.
The objective of this study was to determine if the immune responses could be differentially modulated by the phytoestrogen genistein (GEN) in mice from the first and second litters, and if the effects were persistent or reversible. B6C3F1 mice were exposed to a control or GEN-containing diet at 25, 250 and 1250 μg/g for the first litters, and 500 μg/g for the second litters from day 0 of gestation to PND22, and through feed after weaning. At PND42, an increase in the anti-CD3 antibody-stimulated splenic T cell proliferation and the percentages of T cells was observed in mice from the first litters at 250 and 1250 μg/g GEN but not from the second litters. At PND84, the activity of IL-2-treated NK cells was significantly increased by GEN in mice from the second litters but not from the first litters. The activity of cytotoxic T cells (CTLs) was also significantly increased by GEN in male mice from the second litters. However, the increases in the CTL activity were not significant when the male mice were shifted from GEN-containing food to control food at PND22. Additionally, the increases in T-cell activities in female mice from the first litters and male mice from the second litters were associated with a decrease in the percentage of CD4+CD25+ T regulatory cells. Overall, the results demonstrated that GEN could enhance the immune responses in mice from the first and second litters; however, the effects varied depending on the exposure duration, gender, and litter order.
genistein; developmental exposure; immune stimulation and litter order; CTLs, cytotoxic T cells; DES, diethylstilbestrol; ER, estrogen receptors; E:T, effector:target ratio; F1M = F1 males; F1F = F1 females; FITC, fluorescein isothiocyanate; GD, gestation day; GEN, genistein; mAb, monoclonal antibody; NCTR, the National Center for Toxicological Research; PND, postnatal day; PE, phycoerythrin
Rationale: Airway hyperresponsiveness is a critical feature of asthma. Substantial epidemiologic evidence supports a role for female sex hormones in modulating lung function and airway hyperresponsiveness in humans.
Objectives: To examine the role of estrogen receptors in modulating lung function and airway responsiveness using estrogen receptor–deficient mice.
Methods: Lung function was assessed by a combination of whole-body barometric plethysmography, invasive measurement of airway resistance, and isometric force measurements in isolated bronchial rings. M2 muscarinic receptor expression was assessed by Western blotting, and function was assessed by electrical field stimulation of tracheas in the presence/absence of gallamine. Allergic airway disease was examined after ovalbumin sensitization and exposure.
Measurements and Main Results: Estrogen receptor-α knockout mice exhibit a variety of lung function abnormalities and have enhanced airway responsiveness to inhaled methacholine and serotonin under basal conditions. This is associated with reduced M2 muscarinic receptor expression and function in the lungs. Absence of estrogen receptor-α also leads to increased airway responsiveness without increased inflammation after allergen sensitization and challenge.
Conclusions: These data suggest that estrogen receptor-α is a critical regulator of airway hyperresponsiveness in mice.
lung function; asthma; hyperreactivity; M2 muscarinic receptor; estrogen receptor
Airway hyperresponsiveness is a critical feature of asthma. Substantial epidemiologic evidence supports a role for female sex hormones in modulating lung function and airway hyperresponsiveness in humans.
To examine the role of estrogen receptors in modulating lung function and airway responsiveness using estrogen receptor–deficient mice.
Lung function was assessed by a combination of whole-body barometric plethysmography, invasive measurement of airway resistance, and isometric force measurements in isolated bronchial rings. M2 muscarinic receptor expression was assessed by Western blotting, and function was assessed by electrical field stimulation of tracheas in the presence/absence of gallamine. Allergic airway disease was examined after ovalbumin sensitization and exposure.
Measurements and Main Results
Estrogen receptor-α knockout mice exhibit a variety of lung function abnormalities and have enhanced airway responsiveness to inhaled methacholine and serotonin under basal conditions. This is associated with reduced M2 muscarinic receptor expression and function in the lungs. Absence of estrogen receptor-α also leads to increased airway responsiveness without increased inflammation after allergen sensitization and challenge.
These data suggest that estrogen receptor-α is a critical regulator of airway hyperresponsiveness in mice.
lung function; asthma; hyperreactivity; M2 muscarinic receptor; estrogen receptor
Incorporating the influence of genetic variation in the risk assessment process is often considered, but no generalized approach exists. Many common human diseases such as asthma, cancer, and cardiovascular disease are complex in nature, as they are influenced variably by environmental, physiologic, and genetic factors. The genetic components most responsible for differences in individual disease risk are thought to be DNA variants (polymorphisms) that influence the expression or function of mediators involved in the pathological processes.
The purpose of this study was to estimate the combinatorial contribution of multiple genetic variants to disease risk.
We used a logistic regression model to help estimate the joint contribution that multiple genetic variants would have on disease risk. This model was developed using data collected from molecular epidemiology studies of allergic asthma that examined variants in 16 susceptibility genes.
Based on the product of single gene variant odds ratios, the risk of developing asthma was assigned to genotype profiles, and the frequency of each profile was estimated for the general population. Our model predicts that multiple disease variants broaden the risk distribution, facilitating the identification of susceptible populations. This model also allows for incorporation of exposure information as an independent variable, which will be important for risk variants associated with specific exposures.
The present model provided an opportunity to estimate the relative change in risk associated with multiple genetic variants. This will facilitate identification of susceptible populations and help provide a framework to model the genetic contribution in probabilistic risk assessment.
asthma; genetics; polygenic diseases; risk assessment; susceptibility genes
The prevalence of asthma has increased dramatically over the last 25 years in the United States and in other nations as a result of ill-defined changes in living conditions in modern society. On 18 and 19 October 2004 the U.S. Environmental Protection Agency and the National Institute of Environmental Health Sciences sponsored the workshop “Environmental Influences on the Induction and Incidence of Asthma” to review current scientific evidence with respect to factors that may contribute to the induction of asthma. Participants addressed two broad questions: a) What does the science suggest that regulatory and public health agencies could do now to reduce the incidence of asthma? and b) What research is needed to improve our understanding of the factors that contribute to the induction of asthma and our ability to manage this problem? In this article (one of four articles resulting from the workshop), we briefly characterize asthma and its public health and economic impacts, and intervention strategies that have been successfully used to prevent induction of asthma in the workplace. We conclude with the findings of seven working groups that focus on ambient air, indoor pollutants (biologics), occupational exposures, early life stages, older adults, intrinsic susceptibility, and lifestyle. These groups found strong scientific support for public health efforts to limit in utero and postnatal exposure to cigarette smoke. However, with respect to other potential types of interventions, participants noted many scientific questions, which are summarized in this article. Research to address these questions could have a significant public health and economic impact that would be well worth the investment.
air pollution; allergy; asthma economic impact; asthma induction; asthma prevalence; biologics; indoor environment; occupational exposure; public health; susceptibility
Previous research demonstrated that 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment increased the number of skin papillomas in v-Ha-ras transgenic (Tg.AC) mice that had received sodium arsenite [(As(III)] in drinking water, indicating that this model is useful for studying the toxic effects of arsenic in vivo. Because the liver is a known target of arsenic, we examined the pathophysiologic and molecular effects of inorganic and organic arsenical exposure on Tg.AC mouse liver in this study. Tg.AC mice were provided drinking water containing As(III), sodium arsenate [As(V)], monomethylarsonic acid [(MMA(V)], and 1,000 ppm dimethylarsinic acid [DMA(V)] at dosages of 150, 200, 1,500, or 1,000 ppm as arsenic, respectively, for 17 weeks. Control mice received unaltered water. Four weeks after initiation of arsenic treatment, TPA at a dose of 1.25 μg/200 μL acetone was applied twice a week for 2 weeks to the shaved dorsal skin of all mice, including the controls not receiving arsenic. In some cases arsenic exposure reduced body weight gain and caused mortality (including moribundity). Arsenical exposure resulted in a dose-dependent accumulation of arsenic in the liver that was unexpectedly independent of chemical species and produced hepatic global DNA hypomethylation. cDNA microarray and reverse transcriptase–polymerase chain reaction analysis revealed that all arsenicals altered the expression of numerous genes associated with toxicity and cancer. However, organic arsenicals [MMA(V) and DMA(V)] induced a pattern of gene expression dissimilar to that of inorganic arsenicals. In summary, subchronic exposure of Tg.AC mice to inorganic or organic arsenicals resulted in toxic manifestations, hepatic arsenic accumulation, global DNA hypomethylation, and numerous gene expression changes. These effects may play a role in arsenic-induced hepatotoxicity and carcinogenesis and may be of particular toxicologic relevance.
arsenicals (arsenic forms); gene expression; mouse liver; subchronic toxicity; toxicokinetics
Experimental studies in rodents demonstrate evidence of immunosuppressive effects of dietary exposure to DDT [2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane], but human data pertaining to immunomodulating effects of DDT exposure are limited. In this study we examined the association between the persistent organochlorine breakdown product 1,1-dichloro-2,2,bis(p-chlorophenyl)ethylene (p,p′-DDE) and immunologic measures using blood samples in a relatively highly exposed population of farmers in the United States. Levels of serum immunoglobulin A (IgA) and IgG and the prevalence of antinuclear antibodies in relation to plasma p,p′-DDE levels were evaluated in samples from 137 African-American male farmers (30–88 years of age; median, 64 years). Participants were recruited through black churches in four rural counties in eastern North Carolina. Data collection included a telephone interview pertaining to farming practices and health history, and one blood sample was collected from each participant. Linear and logistic regression, adjusting for age, cholesterol, triglycerides, smoking status, and years of any kind of pesticide use, was used to assess the association between immunologic parameters and plasma levels of p,p′-DDE. The median plasma p,p′-DDE concentration was 7.7 μg/L (range, 0.6–77.4 μg/L). There was no association between p,p′-DDE and IgA in any of the models. IgG levels decreased with increasing p,p′-DDE levels, with a statistically significant decrease of approximately 50% in the highest two categories of exposure (≥ 6.0 μg/L) compared with values of < 3.0 μg/L. Sixteen (12%) were positive for antinuclear antibodies. The prevalence of antinuclear antibodies was somewhat elevated in the highest category of p,p′-DDE exposure (odds ratio, 1.9; 95% confidence interval, 0.32–11.3; for ≥ 12.0 μg/L compared with < 3.0 μg/L p,p′-DDE), but this difference was not statistically significant. These analyses provide evidence that p,p′-DDE modulates immune responses in humans.
African American; autoantibodies; DDE; epidemiology; farmers; IgA; IgG; immunotoxicology
Speakers and participants in the workshop "Assessment of the Allergenic Potential of Genetically Modified Foods" met in breakout groups to discuss a number of issues including needs for future research. These groups agreed that research should progress quickly in the area of hazard identification and that a need exists for more basic research to understand the mechanisms underlying food allergy. A list of research needs was developed.
On the final afternoon of the workshop "Assessment of the Allergenic Potential of Genetically Modified Foods," held 10-12 December 2001 in Chapel Hill, North Carolina, USA, speakers and participants met in breakout groups to discuss specific questions in the areas of use of human clinical data, animal models to assess food allergy, biomarkers of exposure and effect, sensitive populations, dose-response assessment, and postmarket surveillance. Each group addressed general questions regarding allergenicity of genetically modified foods and specific questions for each subject area. This article is a brief summary of the discussions of each of the six breakout groups regarding our current state of knowledge and what information is needed to advance the field.
A workshop cosponsored by the National Institute of Environmental Health Sciences and the National Institute for Occupational Safety and Health was convened in Washington, DC, on 17-18 October 2001 with the goal of developing a consensus document on the most appropriate experimental approaches and assays available to assess developmental immunotoxicity. The work group was composed of scientists from academia, the chemical and pharmaceutical industries, and federal agencies with expertise in developmental immunology, developmental toxicology, immunotoxicology, and risk evaluation. This consensus document presents an overview of the major summations made by the work group. A summary of early work in the field is provided, which includes potential immunotoxic agents, followed by brief discussions of our current understanding of developmental immunology. This report concludes with the work group's consensus of the most appropriate experimental design and tests to screen for potential developmental immunotoxic agents in experimental models, including potential limitations and data gaps.
Arsenic is a carcinogen that poses a significant health risk in humans. Based on evidence that arsenic has differential effects on human, rodent, normal, and transformed cells, these studies addressed the relative merits of using normal human epidermal keratinocytes (NHEK) and immortalized human (HaCaT) and mouse (HEL30) keratinocytes when examining stress-induced gene expression that may contribute to carcinogenesis. We hypothesize that redox-related gene expression is differentially modulated by arsenic in normal versus immortalized keratinocytes. To test the hypothesis, we exposed keratinocytes to sodium arsenite for 4 or 24 hr, at which time serine threonine kinase-25 (stk25) and nicotine adenine dinucleotide phosphate [nad(p)h] quinone oxidoreductase gene expression were measured. The effect of glutathione reduction on arsenite-induced cytotoxicity and gene expression in NHEK also was evaluated by addition of l-buthionine-[S,R]-sulfoximine (BSO) to culture media. Results indicate the term LC(50) for arsenite is approximately 10-15 microM in NHEK and HEL30 keratinocytes and 30 microM in HaCaT keratinocytes. Compared with HaCaT and HEL30 keratinocytes, a nontoxic concentration of arsenite (2.5 microM) increases stk25 and nad(p)h quinone oxidoreductase gene expression in NHEK, an effect partially attenuated by BSO. These data indicate that NHEK and HaCaT/HEL30 keratinocytes have similar sensitivities toward arsenite-induced cytotoxicity but unique gene expression responses. They also suggest that arsenite modulates gene expression in NHEK involved in cellular signaling and other aspects of intermediary metabolism that may contribute to the carcinogenic process.