B. Jean Meade

Immunotoxicity of perfluorooctanoic acid and perfluorooctane sulfonate and the role of peroxisome proliferator-activated receptor alpha.

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are environmentally widespread and persistent chemicals with multiple toxicities reported in experimental animals and humans. These compounds can trigger biological activity by activating the alpha isotype of peroxisome proliferator-activated receptors (PPARs), ligand-activated transcription factors that regulate gene expression; however, some biological effects may occur independently of the receptor. Activation of the peroxisome proliferator-activated receptor alpha (PPARα) modulates lipid and glucose homeostasis, cell proliferation and differentiation, and inflammation. Reported immunomodulation in experimental animals exposed to PFOA and PFOS has included altered inflammatory responses, production of cytokines and other proteins, reduced lymphoid organ weights, and altered antibody synthesis. Mounting experimental animal evidence suggests PPARα independence of some immune effects. This evidence originates primarily from studies with PPARα knockout models exposed to PFOA that demonstrate hepatic peroxisome proliferation, reduced lymphoid organ weights, and altered antibody synthesis. As human PPARα expression is significantly less than that of rodents, potential PPARα independence indicates that future research must explore mechanisms of action of these compounds, including PPARα -dependent and -independent pathways. This multiauthored review contains brief descriptions of current and recently published work exploring immunomodulation by PFOA and PFOS, as well as a short overview of other PPARα ligands of therapeutic and environmental interest.

Comparison of mouse strains using the local lymph node assay

The local lymph node assay (LLNA), as recommended by the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM), only allows for the use of CBA mice. The objective of these studies was to begin to assess the response of chemical sensitizers in the LLNA across six strains of female mice (C57BL/6, SJL/J, BALB/c, B6C3F1, DBA/2 and CBA). The moderate sensitizer alpha-hexylcinnamaldehyde (HCA) was chosen as the test chemical, while toluene diisocyanate (TDI) and 2,4-dinitrofluorobenzene (DNFB) were evaluated at single concentrations as positive controls. Draining lymph node cell proliferation following acetone exposure varied across strains. SJL mice had a significantly higher degree of proliferation with 2111 d.p.m./2 nodes. The remaining five strains demonstrated responses which ranged from 345 to 887 dpm/2 nodes. DBA/2, B6C3F1, BALB/c and CBA mice had essentially equal levels of lymph node proliferation following exposure to the three chemicals. While C57BL/6 mice gave similar results as CBA mice following DNFB and HCA administration, the LLNA response to TDI was considerably lower. SJL mice provided low stimulation indexes (SI) values for all three chemicals evaluated. Regardless of the level of LLNA response, all six mouse strains identified the sensitization potential of HCA, TDI or DNFB. Based on these studies, DBA/2, B6C3F1 and BALB/c mice are good choices for continued evaluation as additional mouse strains for use in the LLNA.

Octamethylcyclotetrasiloxane exhibits estrogenic activity in mice via ERα

Octamethylcyclotetrasiloxane (D4) is a low molecular weight cyclic silicone used in the synthesis of larger silicone polymers and in the formulation of a variety of personal care products. The effects of oral D4 exposure in mice on serum estradiol levels, uterine wet weight, and uterine peroxidase activity were investigated. Additionally, in vitro estrogen receptor binding activity was evaluated. Serum estradiol levels decreased in a dose-dependent manner after exposure to 100 mg/kg to 1000 mg/kg D4. Studies with adrenalectomized animals demonstrated that the decreased serum estradiol levels were not due to elevated serum corticosterone levels. Uterine wet weights in ovariectomized mice were significantly increased in a dose-dependent manner by exposure to 250-1000 mg of D4/kg, but not by exposure to other silicone compounds tested (hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, decamethyltetrasiloxane, and octaphenylcyclotetrasiloxane). Uterine peroxidase activity, a marker for estrogenic activity, was also significantly increased in D4-exposed mice, but not in mice exposed to the other siloxanes. Pretreating mice with the estrogen receptor antagonist ICI 182,780 completely blocked the D4-induced increase in uterine weight, and ovariectomized estrogen receptor-alpha knockout mice showed no increases in uterine weights when orally exposed to D4 or estradiol. In an in vitro estrogen receptor binding assay, D4 showed significant competition with (3)H-estradiol for binding to estrogen receptor-alpha, but not estrogen receptor-beta. The data presented here indicate that D4 has weak estrogenic activity, and that these effects are mediated through estrogen receptor-alpha.

Latex allergy: past and present

Although latex products have been in use for over a century, allergic responses to latex proteins have only been recognized as a serious health problem for the past 15 years. Latex allergy particularly affects two groups, health care workers (HCW) and children with spina bifida (SB). This manuscript provides a brief history of latex allergy, and a review of the following: the manufacturing process for dipped latex products, the 11 latex allergens that have been characterized and received allergen designations by the International Union of Immunological Societies, the methods used in exposure assessment, the epidemiology and clinical management of latex allergy, and the use of animal models in investigating mechanisms underlying latex allergy.

Exposure to Triclosan Augments the Allergic Response to Ovalbumin in a Mouse Model of Asthma

During the last decade, there has been a remarkable and unexplained increase in the prevalence of asthma. These studies were conducted to investigate the role of dermal exposure to triclosan, an endocrine-disrupting compound, on the hypersensitivity response to ovalbumin (OVA) in a murine model of asthma. Triclosan has had widespread use in the general population as an antibacterial and antifungal agent and is commonly found in consumer products such as soaps, deodorants, toothpastes, shaving creams, mouthwashes, and cleaning supplies. For these studies, BALB/c mice were exposed dermally to concentrations of triclosan ranging from 0.75 to 3% (0.375-1.5mg/mouse/day) for 28 consecutive days. Concordantly, mice were ip injected with OVA (0.9 µg) and aluminum hydroxide (0.5mg) on days 1 and 10 and challenged with OVA (125 µg) by pharyngeal aspiration on days 19 and 27. Compared with the animals exposed to OVA alone, increased spleen weights, OVA-specific IgE, interleukin-13 cytokine levels, and numbers of lung eosinophils were demonstrated when mice were coexposed to OVA and triclosan. Statistically significant increases in OVA-specific and nonspecific airway hyperreactivity were observed for all triclosan coexposed groups compared with the vehicle and OVA controls. In these studies, exposure to triclosan alone was not demonstrated to be allergenic; however, coexposure with a known allergen resulted in enhancement of the hypersensitivity response to that allergen, suggesting that triclosan exposure may augment the allergic responses to other environmental allergens.

Toxicological analysis of limonene reaction products using an in vitro exposure system.

Epidemiological investigations suggest a link between exposure to indoor air chemicals and adverse health effects. Consumer products contain reactive chemicals which can form secondary pollutants which may contribute to these effects. The reaction of limonene and ozone is a well characterized example of this type of indoor air chemistry. The studies described here characterize an in vitro model using an epithelial cell line (A549) or differentiated epithelial tissue (MucilAir™). The model is used to investigate adverse effects following exposure to combinations of limonene and ozone. In A549 cells, exposure to both the parent compounds and reaction products resulted in alterations in inflammatory cytokine production. A one hour exposure to limonene+ozone resulted in decreased proliferation when compared to cells exposed to limonene alone. Repeated dose exposures of limonene or limonene+ozone were conducted on MucilAir™ tissue. No change in proliferation was observed but increases in cytokine production were observed for both the parent compounds and reaction products. Factors such as exposure duration, chemical concentration, and sampling time point were identified to influence result outcome. These findings suggest that exposure to reaction products may produce more severe effects compared to the parent compound.

Latex Sensitization by Dermal Exposure Can Lead to Airway Hyperreactivity

Background: Using non-powdered, low-protein natural rubber latex (NRL) gloves has been shown to reduce the elicitation of respiratory symptoms in latex-allergic individuals; however, the role of dermal exposure in the induction of sensitization is not completely understood. Objective: These studies were conducted to (1) determine levels of NRL protein in gloves currently in use and (2) evaluate, using a murine model, the potential for dermal exposure to induce NRL sensitization and subsequent airway hyperreactivity upon respiratory challenge. Methods: Total extractable protein and NRL allergen levels were evaluated from 38 glove samples using the Lowry and CAP inhibition assays, respectively. BALB/c mice were dermally exposed to non-ammoniated latex (NAL, 6.25–25 µg) 5 days/week for 13 weeks and monitored weekly/biweekly for IgE levels. Airway hyperreactivity was determined following respiratory challenge with methacholine (MCH) or NAL proteins on days 60 and 93, respectively. Results: Glove total protein and NRL allergen levels ranged from below the limit of detection to 946 µg/g and from 0.002 to 112 µg/g, respectively. Mice demonstrated dose-dependent increases in total serum IgE levels by day 58 with increased airway hyperreactivity observed upon respiratory challenge with MCH (day 60) or NAL proteins (day 93). Conclusions: These studies investigated the continued use of gloves with high levels of total extractable protein and NRL allergen. The potential for dermal exposure to induce NRL-specific IgE and airway hyperreactivity upon respiratory challenge suggests there should be continued concern regarding the induction of sensitization in individuals using non-powdered latex gloves.

Potential Health Effects Associated with Dermal Exposure to Occupational Chemicals

There are a large number of workers in the United States, spanning a variety of occupational industries and sectors, who are potentially exposed to chemicals that can be absorbed through the skin. Occupational skin exposures can result in numerous diseases that can adversely affect an individuals health and capacity to perform at work. In general, there are three types of chemical-skin interactions of concern: direct skin effects, immune-mediated skin effects, and systemic effects. While hundreds of chemicals (metals, epoxy and acrylic resins, rubber additives, and chemical intermediates) present in virtually every industry have been identified to cause direct and immune-mediated effects such as contact dermatitis or urticaria, less is known about the number and types of chemicals contributing to systemic effects. In an attempt to raise awareness, skin notation assignments communicate the potential for dermal absorption; however, there is a need for standardization among agencies to communicate an accurate description of occupational hazards. Studies have suggested that exposure to complex mixtures, excessive hand washing, use of hand sanitizers, high frequency of wet work, and environmental or other factors may enhance penetration and stimulate other biological responses altering the outcomes of dermal chemical exposure. Understanding the hazards of dermal exposure is essential for the proper implementation of protective measures to ensure worker safety and health.

Evaluation of the hypersensitivity potential of alternative butter flavorings.

Concern has been raised over the association of diacetyl with lung disease clinically resembling bronchiolitis obliterans in food manufacturing workers. This has resulted in the need for identification of alternative chemicals to be used in the manufacturing process. Structurally similar chemicals, 2,3-pentanedione, 2,3-hexanedione, 3,4-hexanedione and 2,3-heptanedione, used as constituents of synthetic flavoring agents have been suggested as potential alternatives for diacetyl, however, immunotoxicity data on these chemicals are limited. The present study evaluated the dermal irritation and sensitization potential of diacetyl alternatives using a murine model. None of the chemicals were identified as dermal irritants when tested at concentrations up to 50%. Similar to diacetyl (EC3=17.9%), concentration-dependent increases in lymphocyte proliferation were observed following exposure to all four chemicals, with calculated EC3 values of 15.4% (2,3-pentanedione), 18.2% (2,3-hexanedione), 15.5% (3,4-hexanedione) and 14.1% (2,3-heptanedione). No biologically significant elevations in local or total serum IgE were identified after exposure to 25-50% concentrations of these chemicals. These results demonstrate the potential for development of hypersensitivity responses to these proposed alternative butter flavorings and raise concern about the use of structurally similar replacement chemicals. Additionally, a contaminant with strong sensitization potential was found in varying concentrations in diacetyl obtained from different producers.

Analysis of gene expression induced by irritant and sensitizing chemicals using oligonucleotide arrays

Chemical-induced allergy continues to be an important occupational health problem. Despite decades of investigation, the molecular mechanisms underlying chemical-induced hypersensitivity and irritancy remain unclear because of the complex interplay between properties of different chemicals and the immune system. In this study, gene expression induced by toluene diisocyanate (TDI, a primarily IgE-inducing sensitizer), oxazolone (OXA, a cell-mediated hypersensitivity inducing sensitizer), or nonanoic acid (NA, a non-sensitizing irritant) was investigated using gene arrays. Female BALB/c mice were dermally exposed on the ears once daily for 4 consecutive days. On day 5, the lymph nodes draining the exposure sites were collected and used for RNA extraction and subsequent hybridization to Affymetrix Mu6500 oligonucleotide arrays. Of the 6519 genes on the arrays, there were 44, 13, and 51 genes in the TDI-, OXA-, and NA-exposed samples, respectively, that displayed a minimum of twofold change in expression level relative to the vehicle control. There were 32, 19, and 19 genes that were differentially expressed (with a minimum of twofold change) between TDI and OXA, TDI and NA, OXA and NA, respectively. The differentially expressed genes include immune response-related genes, transcriptional factors, signal transducing molecules, and Expressed Sequence Tags. Based on the gene array results, candidate genes were further evaluated using RT-PCR. There was only about 47% concordance between the gene array and RT-PCR results.