Immunotoxicity of N-butylbenzenesulfonamide: impacts on immune function in adult mice and developmentally exposed rats.

N-butylbenzenesulfonamide (NBBS) is a high-production volume plasticizer that is an emerging contaminant of concern for environmental and human health. To understand the risks and health effects of exposure to NBBS, studies were conducted in adult-exposed mice and developmentally exposed rats to evaluate the potential for NBBS to modulate the immune system. Beginning between 8 and 9 weeks of age, dosed feed containing NBBS at concentrations of 0, 313, 625, 1250, 2500, and 5000 ppm was continuously provided to B6C3F1/N female mice for 28 days. Dosed feed was also continuously provided to time-mated Harlan Sprague Dawley (Sprague Dawley SD) rats at concentrations of 0-, 250-, 500-, and 1000-ppm NBBS from gestation day 6 to postnatal day 28 and in F1 rats until 11-14 weeks of age. Functional assessments of innate, humoral, and cell-mediated immunity were conducted in adult female mice and F1 rats following exposure to NBBS. In female mice, NBBS treatment suppressed the antibody-forming cell (AFC) response to SRBC with small increases in T-cell responses and natural killer (NK)-cell activity. In developmentally exposed rats, NBBS treatment-related immune effects were sex dependent. A positive trend in NK-cell activity occurred in male F1 rats while a negative trend occurred in female F1 rats. The AFC response to SRBC was decreased in female F1 rats but not in male F1 rats. These data provide evidence that oral exposure to NBBS has the potential to produce immunomodulatory effects on both innate and adaptive immune responses, and these effects appear to have some dependence on species, sex, and period of exposure (developmental vs adult).

Evaluation of immunotoxicity of sodium metavanadate following drinking water exposure in female B6C3F1/N mice in a 28-day study.

Sodium metavanadate (NaVO3 ) is a pentavalent vanadium compound used in the metal industry and dietary supplements; human exposure occurs through inhalation of fumes and dust and ingestion of NaVO3 -containing products. The objective of this study was to assess the potential immunotoxicity of NaVO3 . Female B6C3F1/N mice were exposed to 0-500 ppm NaVO3 in drinking water for 28 days and evaluated for effects on immune cell populations and innate, cellular-mediated, and humoral-mediated immunity. There was a decreasing trend in body weight (BW) and BW gain in NaVO3 exposed mice, with a decrease (p ≤ 0.05) in BW gain at ≥250 ppm, relative to control. Conversely, increasing trends in spleen weights and an increase (p ≤ 0.05) in the spleen:BW ratio at ≥250 ppm NaVO3 were observed. NaVO3 exposure altered antibody production against sheep red blood cells (SRBC). Antibody forming cells (AFC)/106 spleen cells exhibited a decreasing trend, with a decrease (p ≤ 0.05) at 500 ppm NaVO3 , concurrent with an increase in percent B cells. NaVO3 had no effect on the serum anti-SRBC IgM antibody titers or anti-keyhole limpet hemocyanin antibody production. Exposure to NaVO3 decreased the percentage of natural killer cells at all dose levels (p ≤ 0.05), with no effect on the lytic activity. NaVO3 altered T-cell populations at 500 ppm but had no effect on T-cell proliferative responses or the lytic activity of cytotoxic T cells. Collectively, these data indicate that NaVO3 exposure can adversely affect the immune system by inducing alterations in humoral-mediated immunity, specifically the AFC response, with no effect on cell-mediated or innate immunity.

Evaluation of skin sensitization induced by four ionic liquids.

Ionic liquids (ILs) are synthetic solvents used as replacements for volatile organic solvents. Human exposure occurs through dermal or oral routes. In rodents, several ILs were reported to induce dermal toxicity, irritation, and sensitization. Due to the potential for occupational exposure, and industrial use as nonvolatile solvents, 1-ethyl-3-methylimidazolium chloride (EMIM, 6.25% to 50% v/v), 1-butyl-3-methylimidazolium chloride (BMIM, 3.12% to 12.5% v/v), 1-butyl-1-methylpyrrolidinium chloride (BMPY, 0.825% to 6.25% v/v), and N-butylpyridinium chloride (NBuPY, 0.825% to 12.5% v/v) were nominated to the National Toxicology Program and evaluated for skin sensitization. The test compound was applied to the ears of female BALB/c mice daily for 3 days in a primary irritancy (IRR)/local lymph node assay (LLNA). Sensitization was assessed in vitro in the direct peptide reactivity assay (DPRA), KeratinoSens™ assay, and human cell line activation test (h-CLAT). In the LLNA, the butylated ILs, BMIM, and BMPY were more potent than NBuPY (butylated) or EMIM (ethylated), which was neither an irritant nor a sensitizer. NBuPY induced skin irritation in vivo at ≥3.12% (p ≤ 0.01), and sensitization in vitro in the KeratinoSens™ assay and h-CLAT, but was negative for sensitization in vivo and in the DPRA. Although SI3 was not achieved, dermal treatment with 12.5% BMIM or 6.25% BMPY increased (p ≤ 0.01) lymph node cell proliferation in the LLNA. In vitro, BMIM was positive for sensitization in the h-CLAT, and BMPY was positive in the h-CLAT and KeratinoSens™ assay; both were negative in the DPRA. Integrated data analyses, weighted toward in vivo data, suggested that BMIM and BMPY may induce weak to mild sensitization.

Application of Defined Approaches to Assess Skin Sensitization Potency of Isothiazolinone Compounds.

Introduction: Isothiazolinones (ITs) are widely used as antimicrobial preservatives in cosmetics and as additives for preservation of consumer and industrial products to control bacteria, fungi, and algae. Although they are effective biocides, they have the potential to produce skin irritation and sensitization, which poses a human health hazard. In this project, we evaluated nonanimal defined approaches (DAs) for skin sensitization that can provide point-of-departure estimates for use in quantitative risk assessment for ITs. Materials and Methods: The skin sensitization potential of six ITs was evaluated using three internationally harmonized nonanimal test methods: the direct peptide reactivity assay, KeratinoSens™, and the human cell line activation test. Results from these test methods were then applied to two versions of the Shiseido Artificial Neural Network DA. Results: Sensitization hazard or potency predictions were compared with those of the in vivo murine local lymph node assay (LLNA). The nonanimal methods produced skin sensitization hazard and potency classifications concordant with those of the LLNA. EC3 values (the estimated concentration needed to produce a stimulation index of three, the threshold positive response) generated by the DAs had less variability than LLNA EC3 values, and confidence limits from the DAs overlapped those of the LLNA EC3 for most substances. Conclusion: The application of in silico models to in chemico and in vitro skin sensitization data is a promising data integration procedure for DAs to support hazard and potency classification and quantitative risk assessment.

Immunotoxicity studies of sulfolane following developmental exposure in Hsd:Sprague Dawley SD rats and adult exposure in B6C3F1/N mice.

Sulfolane is a solvent used in the petrochemical industry and a groundwater contaminant in areas near refineries. The current studies were conducted to assess the impact of oral exposure to sulfolane on the immune system using two models: (1) a perinatal drinking water exposure to 0, 30, 100, 300, or 1000 mg/L from gestation day (GD) 6 until ∼13 weeks-of-age in Harlan Sprague Dawley rats; and, (2) a 90-day gavage exposure of adult female B6C3F1/N mice to 0, 1, 10, 30, 100, or 300 mg/kg/day. Immune parameters evaluated included measurement of antibody production against sheep red blood cells (SRBC) and keyhole limpet hemocyanin (KLH), ex vivo measurements of natural killer (NK) cell activity, cytotoxic T-cell (CTL) activity, and T-cell proliferation, as well as measures of splenic immune cell populations, hematological parameters, and histopathology of immune tissues. A decrease in ex vivo NK cell activity was observed in cells from female - but not male - F1 rats following developmental exposure. In adult female mice, splenic NK cell number was lower than the vehicle controls at doses ≥ 100 mg/kg; however, ex vivo NK cell activity was not affected by sulfolane treatment. In female mice, a decrease in the number of large unstained cells at doses ≥ 30 mg/kg was observed. In F1 rats, effects on white blood cells (WBC) were limited to a decreasing trend in leukocytes in females; no effects were observed in males. Under the conditions of this study, a no-observed-effect level (NOEL) of 3 mg/kg/day was identified based on reduced NK cell activity in female F1 rats. Overall, these findings suggest that oral exposure to sulfolane in rodents had minimal effects on the immune system.

Host Resistance Assays.

The goal of immunotoxicity testing is to obtain data useful for immunotoxicity safety assessment. Guidance in the performance of immunotoxicity safety evaluations is provided in documents from the US EPA for chemicals and the ICH S8 document for pharmaceuticals. The ICH S8 document outlines a tiered approach that includes (1) standard toxicity studies with associated hematology, immune system organ weights, and histopathology data; (2) functional assays, such as cytotoxic T lymphocyte (CTL) assays, natural killer (NK) cell assays, respiratory burst, phagocytosis, and T-cell-dependent antibody response (TDAR) assays; and (3) host resistance assays. Host resistance assays are considered the gold standard in immunotoxicity testing and provide a critical overview of the extent to which innate, adaptive, and homeostatic regulatory immune functions are integrated to protect the host. Both comprehensive and targeted host resistance assays are available, each with distinct advantages. This chapter serves to provide a general overview of the various assays that may be used, as well as a summary of procedures.

Evaluation of 4-methylcyclohexanemethanol (MCHM) in a combined irritancy and Local Lymph Node Assay (LLNA) in mice.

4-Methylcyclohexanemethanol (MCHM) is a flotation reagent used in fine coal beneficiation. On January 9, 2014, crude MCHM, a mixture containing predominantly MCHM, was inadvertently released into the Elk River, a municipal water source that serves about 300,000 people in the Charleston, WV area, resulting in temporary contamination of 15 percent of the state's tap water and causing significant dermal exposure. The current studies were undertaken to determine whether crude MCHM or MCHM has the potential to produce dermal irritancy and/or sensitization. BALB/c female mice were treated daily for 3 consecutive days by direct epicutaneous application of 25 µL of various concentrations of crude MCHM or MCHM to the dorsum of each ear. A mouse ear-swelling test was used to determine irritancy potential and was undertaken in combination with the standardized Local Lymph Node Assay (LLNA) to determine skin sensitizing potential. MCHM was found to produce skin irritation at concentrations above 20% and did not produce sensitization. Crude MCHM also produced irritation, although weaker, and in addition was found to be a weak to moderate skin sensitizer. The results are discussed in terms of potential human health hazard.

Association of MHC region SNPs with irritant susceptibility in healthcare workers.

Irritant contact dermatitis is the most common work-related skin disease, especially affecting workers in "wet-work" occupations. This study was conducted to investigate the association between single nucleotide polymorphisms (SNPs) within the major histocompatibility complex (MHC) and skin irritant response in a group of healthcare workers. 585 volunteer healthcare workers were genotyped for MHC SNPs and patch tested with three different irritants: sodium lauryl sulfate (SLS), sodium hydroxide (NaOH) and benzalkonium chloride (BKC). Genotyping was performed using Illumina Goldengate MHC panels. A number of SNPs within the MHC Class I (OR2B3, TRIM31, TRIM10, TRIM40 and IER3), Class II (HLA-DPA1, HLA-DPB1) and Class III (C2) genes were associated (p < 0.001) with skin response to tested irritants in different genetic models. Linkage disequilibrium patterns and functional annotations identified two SNPs in the TRIM40 (rs1573298) and HLA-DPB1 (rs9277554) genes, with a potential impact on gene regulation. In addition, SNPs in PSMB9 (rs10046277 and ITPR3 (rs499384) were associated with hand dermatitis. The results are of interest as they demonstrate that genetic variations in inflammation-related genes within the MHC can influence chemical-induced skin irritation and may explain the connection between inflamed skin and propensity to subsequent allergic contact sensitization.

Genetic Basis of Irritant Susceptibility in Health Care Workers.

OBJECTIVE: The aim of this study was to investigate the association of single nucleotide polymorphisms (SNPs) within genes involved in inflammation, skin barrier integrity, signaling/pattern recognition, and antioxidant defense with irritant susceptibility in a group of health care workers. METHODS: The 536 volunteer subjects were genotyped for selected SNPs and patch tested with three model irritants: sodium lauryl sulfate (SLS), sodium hydroxide (NaOH), and benzalkonium chloride (BKC). Genotyping was performed on genomic DNA using Illumina Goldengate custom panels. RESULTS: The ACACB (rs2268387, rs16934132, rs2284685), NTRK2 (rs10868231), NTRK3 (rs1347424), IL22 (rs1179251), PLAU (rs2227564), EGFR (rs6593202), and FGF2 (rs308439) SNPs showed an association with skin response to tested irritants in different genetic models (all at P < 0.001). Functional annotations identified two SNPs in PLAU (rs2227564) and ACACB (rs2284685) genes with a potential impact on gene regulation. In addition, EGF (rs10029654), EGFR (rs12718939), CXCL12 (rs197452), and VCAM1 (rs3917018) genes showed an association with hand dermatitis (P < 0.005). CONCLUSIONS: The results demonstrate that genetic variations in genes related to inflammation and skin homeostasis can influence responses to irritants and may explain inter-individual variation in the development of subsequent contact dermatitis.

Associating Changes in the Immune System with Clinical Diseases for Interpretation in Risk Assessment.

This overview is an update of the unit originally published in 2004. While the basic tenets of immunotoxicity have not changed in the past 10 years, several publications have explored the application of immunotoxicological data to the risk assessment process. Therefore, the goal of this unit is still to highlight relationships between xenobiotic-induced immunosuppression and risk of clinical diseases progression. In immunotoxicology, this may require development of models to equate moderate changes in markers of immune functions to potential changes in incidence or severity of infectious diseases. For most xenobiotics, exposure levels and disease incidence data are rarely available, and safe exposure levels must be estimated based on observations from experimental models or human biomarker studies. Thus, it is important to establish a scientifically sound framework that allows accurate and quantitative interpretation of experimental or biomarker data in the risk assessment process.

Genetic variants in TNFα, TGFB1, PTGS1 and PTGS2 genes are associated with diisocyanate-induced asthma.

Diisocyanates are the most common cause of occupational asthma, but risk factors are not well defined. A case-control study was conducted to investigate whether genetic variants in inflammatory response genes (TNFα, IL1α, IL1ß, IL1RN, IL10, TGFB1, ADAM33, ALOX-5, PTGS1, PTGS2 and NAG-1/GDF15) are associated with increased susceptibility to diisocyanate asthma (DA). These genes were selected based on their role in asthmatic inflammatory processes and previously reported associations with asthma phenotypes. The main study population consisted of 237 Caucasian French Canadians from among a larger sample of 280 diisocyanate-exposed workers in two groups: workers with specific inhalation challenge (SIC) confirmed DA (DA(+), n = 95) and asymptomatic exposed workers (AW, n = 142). Genotyping was performed on genomic DNA, using a 5' nuclease PCR assay. After adjusting for potentially confounding variables of age, smoking status and duration of exposure, the PTGS1 rs5788 and TGFB1 rs1800469 single nucleotide polymorphisms (SNP) showed a protective effect under a dominant model (OR = 0.38; 95% CI = 0.17, 0.89 and OR = 0.38; 95% CI = 0.18, 0.74, respectively) while the TNFα rs1800629 SNP was associated with an increased risk of DA (OR = 2.08; 95% CI = 1.03, 4.17). Additionally, the PTGS2 rs20417 variant showed an association with increased risk of DA in a recessive genetic model (OR = 6.40; 95% CI = 1.06, 38.75). These results suggest that genetic variations in TNFα, TGFB1, PTGS1 and PTGS2 genes contribute to DA susceptibility.

N-Acetyltransferase 2 Genotypes Are Associated With Diisocyanate-Induced Asthma.

OBJECTIVE: To investigate whether genetic variants of N-acetyltransferase (NAT) genes are associated with diisocyanate asthma (DA). METHODS: The study population consisted of 354 diisocyanate-exposed workers. Genotyping was performed using a 5'-nuclease polymerase chain reaction assay. RESULTS: The NAT2 rs2410556 and NAT2 rs4271002 variants were significantly associated with DA in the univariate analysis. In the first logistic regression model comparing DA+ and asymptomatic worker groups, the rs2410556 (P = 0.004) and rs4271002 (P < 0.001) single nucleotide polymorphisms and the genotype combination, NAT2 rs4271002*NAT1 rs11777998, showed associations with DA risk (P = 0.014). In the second model comparing DA+ and DA- groups, NAT2 rs4271002 variant and the combined genotype, NAT1 rs8190845*NAT2 rs13277605, were significantly associated with DA risk (P = 0.022, P = 0.036, respectively). CONCLUSIONS: These findings suggest that variations in the NAT2 gene and their interactions contribute to DA susceptibility.

Genetic variants in the major histocompatibility complex class I and class II genes are associated with diisocyanate-induced Asthma.

OBJECTIVE: To investigate the association between single nucleotide polymorphisms (SNPs) located across the major histocompatibility complex and susceptibility to diisocyanate-induced asthma (DA). METHODS: The study population consisted of 140 diisocyanate-exposed workers. Genotyping was performed using the Illumina GoldenGate major histocompatibility complex panels. RESULTS: The HLA-E rs1573294 and HLA-DPB1 rs928976 SNPs were associated with an increased risk of DA under dominant (odds ratio [OR], 6.27; 95% confidence interval [CI], 2.37 to 16.6; OR, 2.79, 95% CI, 0.99 to 7.81, respectively) and recessive genetic models (OR, 6.27, 95% CI, 1.63 to 24.13; OR, 10.10, 95% CI, 3.16 to 32.33, respectively). The HLA-B rs1811197, HLA-DOA rs3128935, and HLA-DQA2 rs7773955 SNPs conferred an increased risk of DA in a dominant model (OR, 7.64, 95% CI, 2.25 to 26.00; OR, 19.69, 95% CI, 2.89 to 135.25; OR, 8.43, 95% CI, 3.03 to 23.48, respectively). CONCLUSION: These results suggest that genetic variations within HLA genes play a role in DA risk.

Influenza vaccine response in adults exposed to perfluorooctanoate and perfluorooctanesulfonate.

Supported by several epidemiological studies and a large number of animal studies, certain polyfluorinated alkyl acids are believed to be immunotoxic, affecting particularly humoral immunity. Our aim was to investigate the relationship between the antibody response following vaccination with an inactivated trivalent influenza vaccine and circulating levels of perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS). The study population consisted of 411 adults living in the mid-Ohio region of Ohio and West Virginia where public drinking water had been inadvertently contaminated with PFOA. They participated in a larger cross-sectional study in 2005/2006 and were followed up in 2010, by which time serum levels of PFOA had been substantially reduced but were still well above those found in the general population. Hemagglutination inhibition tests were conducted on serum samples collected preinfluenza vaccination and 21 ± 3 days postvaccination in 2010. Serum samples were also analyzed for PFOA and PFOS concentrations (median: 31.5 and 9.2 ng/ml, respectively). Questionnaires were conducted regarding the occurrence and frequency of recent (during the last 12 months) respiratory infections. Our findings indicated that elevated PFOA serum concentrations are associated with reduced antibody titer rise, particularly to A/H3N2 influenza virus, and an increased risk of not attaining the antibody threshold considered to offer long-term protection. Although the direct relationship between weakened antibody response and clinical risk of influenza is not clear, we did not find evidence for an association between self-reported colds or influenza and PFOA levels nor between PFOS serum concentrations and any of the endpoints examined.

Genetic variants within the MHC region are associated with immune responsiveness to childhood vaccinations.

The influence of genetic variability within the major histocompatibility complex (MHC) region on variations in immune responses to childhood vaccination was investigated. The study group consisted of 135 healthy infants who had been immunized with hepatitis B (HBV), 7-valent pneumococcal conjugate (PCV7), and diphtheria, tetanus, acellular pertussis (DTaP) vaccines according to standard childhood immunization schedules. Genotype analysis was performed on genomic DNA using Illumina Goldengate MHC panels (Mapping and Exon Centric). At the 1 year post vaccination check-up total, isotypic, and antigen-specific serum antibody levels were measured using multiplex immunoassays. A number of single nucleotide polymorphisms (SNPs) within MHC Class I and II genes were found to be associated with variations in the vaccine specific antibody responses and serum levels of immunoglobulins (IgG, IgM) and IgG isotypes (IgG1, IgG4) (all at p<0.001). Linkage disequilibrium patterns and functional annotations showed that significant SNPs were strongly correlated with other functional regulatory SNPs. These SNPs were found to regulate the expression of a group of genes involved in antigen processing and presentation including HLA-A, HLA-C, HLA-G, HLA-H, HLA-DRA, HLA-DRB1, HLA-DRB5, HLA-DQA1, HLA-DQB1, HLA-DOB, and TAP-2. The results suggest that genetic variations within particular MHC genes can influence immune response to common childhood vaccinations, which in turn may influence vaccine efficacy.

Challenge exposure to isocyanates induces changes in nasal patency in patients reporting work-related respiratory symptoms.

OBJECTIVE: To examine the utility of specific inhalation challenge (SIC) in assessing the nasal congestive response to isocyanate exposure. METHODS: Nine patients complaining of work-related respiratory symptoms underwent SIC with exposure to isocyanate for 4 and 120 minutes on different days. Nasal volume was monitored by acoustic rhinometry and nasal congestion by the visual analogue scale (VAS) for up to 6 hours. RESULTS: The 4-minute isocyanate SIC induced a nonsignificant fall in nasal volume and no increase in the VAS score. The 120-minute isocyanate SIC induced a significant fall in nasal volume at 15, 30, and 60 minutes postchallenge that was associated with a significant increase in the VAS score at 15 and 30 minutes postchallenge. CONCLUSIONS: SIC appears useful to assess changes in nasal patency after exposure to isocyanate. Exposure to isocyanates can induce nasal congestion that can be objectively monitored during SIC.

Winter season, frequent hand washing, and irritant patch test reactions to detergents are associated with hand dermatitis in health care workers.

BACKGROUND: Irritant hand dermatitis (IHD) is common in health care workers. OBJECTIVE: We studied endogenous irritant contact dermatitis threshold by patch testing and exogenous factors such as season and hand washing for their association with IHD in health care workers. METHODS: Irritant patch testing with sodium lauryl sulfate (SLS), sodium hydroxide, and benzalkonium chloride at varying concentrations was measured in 113 health care workers. Examination for hand dermatitis occurred at 1-month intervals for a period of 6 months in the Midwestern United States. RESULTS: Positive patch testing to low-concentration SLS was associated with IHD (P = 0.0310) after adjusting for age, sex, ethnicity, season, history of childhood flexural dermatitis, mean indoor relative humidity, and glove and hand sanitizer usage. Subjects with a positive patch test to SLS were 78% more likely to have occurrence of IHD (incidence rate ratio [IRR] = 1.78; 95% confidence interval [CI], 0.92-3.45). Hand washing frequency (≥10 times a day; IRR = 1.55; 95% CI, 1.01-2.39) and cold season (IRR = 2.76; 95% CI, 1.35-5.65) were associated with IHD. No association was found between history of childhood flexural dermatitis and IHD in this population. CONCLUSIONS: Both genetic and environmental factors are important in the etiology of IHD and should be considered in designing strategies to protect, educate, and treat susceptible individuals.

Leucine-rich repeat kinase 2 (LRRK2)-deficient rats exhibit renal tubule injury and perturbations in metabolic and immunological homeostasis.

Genetic evidence links mutations in the LRRK2 gene with an increased risk of Parkinson's disease, for which no neuroprotective or neurorestorative therapies currently exist. While the role of LRRK2 in normal cellular function has yet to be fully described, evidence suggests involvement with immune and kidney functions. A comparative study of LRRK2-deficient and wild type rats investigated the influence that this gene has on the phenotype of these rats. Significant weight gain in the LRRK2 null rats was observed and was accompanied by significant increases in insulin and insulin-like growth factors. Additionally, LRRK2-deficient rats displayed kidney morphological and histopathological alterations in the renal tubule epithelial cells of all animals assessed. These perturbations in renal morphology were accompanied by significant decreases of lipocalin-2, in both the urine and plasma of knockout animals. Significant alterations in the cellular composition of the spleen between LRRK2 knockout and wild type animals were identified by immunophenotyping and were associated with subtle differences in response to dual infection with rat-adapted influenza virus (RAIV) and Streptococcus pneumoniae. Ontological pathway analysis of LRRK2 across metabolic and kidney processes and pathological categories suggested that the thioredoxin network may play a role in perturbing these organ systems. The phenotype of the LRRK2 null rat is suggestive of a complex biology influencing metabolism, immune function and kidney homeostasis. These data need to be extended to better understand the role of the kinase domain or other biological functions of the gene to better inform the development of pharmacological inhibitors.

CTNNA3 (α-catenin) gene variants are associated with diisocyanate asthma: a replication study in a Caucasian worker population.

Recently, a genome-wide association study (GWAS) conducted in Korean subjects identified four CTNNA3 (alpha-T catenin) single nucleotide polymorphisms (SNPs) (rs10762058, rs7088181, rs1786929, and rs4378283) associated with diisocyanate-induced occupational asthma (DA). The CTNNA3 gene codes for a cadherin involved in formation of stretch-resistant cell-cell adhesions. We conducted a candidate gene association study to replicate these findings in Caucasian workers. Genotyping was performed on DNA using a 5' nuclease PCR assay collected from 410 diisocyanate-exposed and predominantly Canadian workers including 132 workers with DA confirmed by a specific inhalation challenge (DA+); 131 symptomatic workers in whom DA was excluded by a negative challenge (DA-); and 147 hexamethylene diisocyanate-exposed asymptomatic workers (AWs). As in the Korean study, highly linked CTNNA3 rs7088181 and rs10762058 SNPs (but not rs4378283 and rs1786929) were significantly associated with DA+ when compared with AWs but not in comparison with DA- workers (p ≤ 0.05). After adjusting for potentially confounding variables of age, smoking status, and duration of exposure, minor allele homozygotes of rs7088181 and rs10762058 SNPs were at increased risk for DA compared with AWs (OR = 9.05 [95% CI: 1.69, 48.54] and OR = 6.82 [95% CI: 1.65, 28.24], respectively). In conclusion, we replicated results from the only reported GWAS study of DA demonstrating an association between two closely linked CTNNA3 gene SNPs and DA. These findings lend further support to the clinical relevance of these genotypes in predicting susceptibility to DA and the potential importance of catenins in the disease process.

Genetic variants in antioxidant genes are associated with diisocyanate-induced asthma.

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.