ToxSci Advance Access originally published online on August 9, 2007
Toxicological Sciences 2007 100(1):99-108; doi:10.1093/toxsci/kfm194
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Published by Oxford University Press 2007.
Th2 Cytokines in Skin Draining Lymph Nodes and Serum IgE Do Not Predict Airway Hypersensitivity to Intranasal Isocyanate Exposure in Mice
Experimental Toxicology Division, U.S. EPA, Research Triangle Park, North Carolina
1 To whom correspondence should be addressed. Fax: (919) 541-0026. E-mail: selgrade.maryjane{at}epa.gov.
Received May 9, 2007; accepted July 18, 2007
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Abstract |
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Isocyanate exposure in the workplace has been linked to asthma and allergic rhinitis. Recently, investigators have proposed that Th2 cytokine responses in lymph nodes draining the site of dermal application of chemicals including isocyanates may be used to identify sensitizers that cause asthma-like responses. The purpose of this study was to determine if the cytokine profile induced after dermal sensitization with isocyanates and serum IgE predict immediate (IHS) and methacholine-induced late (LHS) respiratory hypersensitivity responses after intranasal challenge. Dermal application of hexylmethane diisocyanate (HMDI), toluene diisocyanate (TDI), or methylene diisocyanate (MDI) significantly increased interleukin-4 (IL-4), IL-5, and IL-13 secretion in parotid lymph node cells. Isophorone diisocyanate (IPDI) increased IL-4 and IL-13, but not IL-5. Tolyl(mono)isocyanate (TMI), tetramethylene xylene diisocyanate (TMXDI), or the contact sensitizer dinitrochlorobenzene (DNCB), only induced minor increases in some of the Th2 cytokines. HMDI, TDI, MDI, and IPDI elicited greater increases in total serum IgE than DNCB, TMI, and TMXDI. All chemicals except TMXDI caused IHS after intranasal challenge of sensitized female BALB/c mice. Only HMDI-, TMI-, or TMXDI-sensitized and challenged mice had increases in LHS. All chemicals elicited epithelial cytotoxicity indicative of nasal airway irritation. The discordance between dermal cytokine profiles and respiratory responses suggests that dermal responses do not necessarily predict respiratory responses. Serum IgE also was not predictive of the respiratory responses to the isocyanates, suggesting that other unknown mechanisms may be involved.
Key Words: Isocyanates; airway hypersensitivity; Th2 cytokines; serum IgE; skin draining lymph nodes; intranasal instillation; dermal exposure; mice; dinitrochlorobenzene; hazard identification.
Disclaimer: This paper has been reviewed and approved for release by the National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency (U.S. EPA). Approval does neither signify that the contents necessarily reflect the views and policies of the U.S. EPA nor mention of trade names or commercial products constitute endorsement or recommendation for use.