Systemic metabolic derangement, pulmonary effects, and insulin insufficiency following subchronic ozone exposure in rats.

Acute ozone exposure induces a classical stress response with elevated circulating stress hormones along with changes in glucose, protein and lipid metabolism in rats, with similar alterations in ozone-exposed humans. These stress-mediated changes over time have been linked to insulin resistance. We hypothesized that acute ozone-induced stress response and metabolic impairment would persist during subchronic episodic exposure and induce peripheral insulin resistance. Male Wistar Kyoto rats were exposed to air or 0.25ppm or 1.00ppm ozone, 5h/day, 3 consecutive days/week (wk) for 13wks. Pulmonary, metabolic, insulin signaling and stress endpoints were determined immediately after 13wk or following a 1wk recovery period (13wk+1wk recovery). We show that episodic ozone exposure is associated with persistent pulmonary injury and inflammation, fasting hyperglycemia, glucose intolerance, as well as, elevated circulating adrenaline and cholesterol when measured at 13wk, however, these responses were largely reversible following a 1wk recovery. Moreover, the increases noted acutely after ozone exposure in non-esterified fatty acids and branched chain amino acid levels were not apparent following a subchronic exposure. Neither peripheral or tissue specific insulin resistance nor increased hepatic gluconeogenesis were present after subchronic ozone exposure. Instead, long-term ozone exposure lowered circulating insulin and severely impaired glucose-stimulated beta-cell insulin secretion. Thus, our findings in young-adult rats provide potential insights into epidemiological studies that show a positive association between ozone exposures and type 1 diabetes. Ozone-induced beta-cell dysfunction may secondarily contribute to other tissue-specific metabolic alterations following chronic exposure due to impaired regulation of glucose, lipid, and protein metabolism.

Inhaled ozone (O3)-induces changes in serum metabolomic and liver transcriptomic profiles in rats.

Air pollution has been linked to increased incidence of diabetes. Recently, we showed that ozone (O3) induces glucose intolerance, and increases serum leptin and epinephrine in Brown Norway rats. In this study, we hypothesized that O3 exposure will cause systemic changes in metabolic homeostasis and that serum metabolomic and liver transcriptomic profiling will provide mechanistic insights. In the first experiment, male Wistar Kyoto (WKY) rats were exposed to filtered air (FA) or O3 at 0.25, 0.50, or 1.0ppm, 6h/day for two days to establish concentration-related effects on glucose tolerance and lung injury. In a second experiment, rats were exposed to FA or 1.0ppm O3, 6h/day for either one or two consecutive days, and systemic metabolic responses were determined immediately after or 18h post-exposure. O3 increased serum glucose and leptin on day 1. Glucose intolerance persisted through two days of exposure but reversed 18h-post second exposure. O3 increased circulating metabolites of glycolysis, long-chain free fatty acids, branched-chain amino acids and cholesterol, while 1,5-anhydroglucitol, bile acids and metabolites of TCA cycle were decreased, indicating impaired glycemic control, proteolysis and lipolysis. Liver gene expression increased for markers of glycolysis, TCA cycle and gluconeogenesis, and decreased for markers of steroid and fat biosynthesis. Genes involved in apoptosis and mitochondrial function were also impacted by O3. In conclusion, short-term O3 exposure induces global metabolic derangement involving glucose, lipid, and amino acid metabolism, typical of a stress-response. It remains to be examined if these alterations contribute to insulin resistance upon chronic exposure.

Soy biodiesel emissions have reduced inflammatory effects compared to diesel emissions in healthy and allergic mice.

Toxicity of exhaust from combustion of petroleum diesel (B0), soy-based biodiesel (B100), or a 20% biodiesel/80% petrodiesel mix (B20) was compared in healthy and house dust mite (HDM)-allergic mice. Fuel emissions were diluted to target fine particulate matter (PM(2.5)) concentrations of 50, 150, or 500 µg/m(3). Studies in healthy mice showed greater levels of neutrophils and MIP-2 in bronchoalveolar lavage (BAL) fluid 2 h after a single 4-h exposure to B0 compared with mice exposed to B20 or B100. No consistent differences in BAL cells and biochemistry, or hematological parameters, were observed after 5 d or 4 weeks of exposure to any of the emissions. Air-exposed HDM-allergic mice had significantly increased responsiveness to methacholine aerosol challenge compared with non-allergic mice. Exposure to any of the emissions for 4 weeks did not further increase responsiveness in either non-allergic or HDM-allergic mice, and few parameters of allergic inflammation in BAL fluid were altered. Lung and nasal pathology were not significantly different among B0-, B20-, or B100-exposed groups. In HDM-allergic mice, exposure to B0, but not B20 or B100, significantly increased resting peribronchiolar lymph node cell proliferation and production of T(H)2 cytokines (IL-4, IL-5, and IL-13) and IL-17 in comparison with air-exposed allergic mice. These results suggest that diesel exhaust at a relatively high concentration (500 µg/m(3)) can induce inflammation acutely in healthy mice and exacerbate some components of allergic responses, while comparable concentrations of B20 or B100 soy biodiesel fuels did not elicit responses different from those caused by air exposure alone.

Inconsistencies between cytokine profiles, antibody responses, and respiratory hyperresponsiveness following dermal exposure to isocyanates.

Cytokine profiling of local lymph node responses has been proposed as a simple test to identify chemicals, such as low molecular weight diisocyanates, that pose a significant risk of occupational asthma. Previously, we reported cytokine messenger RNA (mRNA) profiles for dinitrochlorobenzene (DNCB) and six isocyanates: toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, isophorone diisocyanate, p-tolyl(mono)isocyanate, and meta-tetramethylene xylene diisocyanate. The present study was conducted to test the hypothesis that relative differences in the cytokine profile are predictive of relative differences in total serum immunoglobulin (Ig) E and respiratory responses to methacholine (Mch) following dermal exposure to the chemicals. After a preliminary experiment to determine an exposure regimen sufficient to achieve responses to Mch following dermal diisocyanate exposure, BALB/c mice received nine dermal exposures over a period of 28 days to one of six isocyanates, DNCB, or vehicle. Mice were then challenged with increasing doses of Mch and responsiveness was assessed using whole-body plethysmography. Serum antibody responses and cytokine mRNA profiles in the draining lymph node were also assessed. In separate experiments, cytokine protein assays were performed after five dermal exposures over a 14-day period. The response pattern for interleukin (IL)-4, IL-10, and IL-13 for the different isocyanates was highly reproducible as determined by RNAse protection assay, reverse transcription-PCR, or cytokine protein levels. However, the relative differences in T-helper cytokine profiles were not predictive of relative differences in either total serum IgE or respiratory responses to Mch following dermal exposure. The data suggest that the cytokine profiling approach needs to be further developed and refined before adoption and that other approaches to hazard identification should be pursued as well. Based on the weight of evidence from all the assays performed, it appears that all six isocyanates tested have some potential to cause respiratory hypersensitivity following dermal exposure.

Ultraviolet radiation downregulates allergy in BALB/c mice.

The immunosuppressive effects of exposure to ultraviolet radiation (UVR) are well known and the underlying mechanisms extensively studied. The suppression of Th1 appears to account for UVR suppression of contact hypersensitivity and delayed-type hypersensitivity responses and increased susceptibility to certain infections and tumor development. The underlying mechanisms suggest Th2-mediated responses associated with immediate-type hypersensitivity and allergic lung disease should be unchanged or possibly enhanced by UVR. The hypothesis that UVR exposure enhances allergic lung disease in BALB/c mice was tested. Effects of UVR on sensitization and elicitation of respiratory hypersensitivity were assessed using a fungal extract, Metarhizium anisopliae (MACA), as the allergen. BALB/c mice were sham or UVR (8 KJ/m(2)) exposed 3d before involuntary aspiration (IA) of MACA or vehicle. The mice received UVR exposures before the first and second of three IAs in the sensitization protocol and 3 d before the fourth IA in the elicitation protocol. Serum and bronchoalveolar lavage fluid (BALF) were harvested before (d 21, sensitization/d 24, elicitation) and at 1 (d 22/d 28), 3 (d 24/d 29), and 7 (d 28/d 35) d following the last IA. UVR exposure prior to sensitization suppressed two hallmarks of allergic disease, immune-mediated inflammation (eosinophil influx) and total immunoglobulin (Ig)E compared to the sham-UVR controls. There were no differences attributable to UVR exposure in previously sensitized mice. These data suggest that UVR exposure prior to sensitization suppresses allergic responses but has no effect on the elicitation of allergic responses in previously sensitized individuals. Consequently, there is no evidence that exposure to UVR enhances the induction or expression of allergic lung disease.