Acute stress modulates the irritant component of sensitizers in allergic contact dermatitis: implications for exposure assessment.

Exposure of skin to noxious environmental stimuli can cause allergic contact dermatitis (ACD), which is a major health risk. Epidemiological studies have determined that 40% of workers report that their jobs are very, or extremely, stressful, and the number of chemicals to which workers are exposed increases each year. We hypothesized that combined exposure to a workplace stressor and a sensitizing chemical would alter the time course and magnitude of the skin immune response. We assessed the mixed exposure of chemical and restraint stress using three potent skin sensitizers, 2,4 dinitrofluorbenzene (DNFB), dicyclohexylcarbodiimide (DCC), and oxazolone, (OXA) on the ear swelling response in stress-susceptible BALB/c mice. Quantitative analyses showed that the dose-response relationship for each chemical followed a cubic trend. Although stress did not alter the shape of the curve, application of restraint stress on day 1 or on day 6 diminished the ear swelling response to 0.1% DNFB. However, if the concentration of the challenge dose was increased to a more irritating concentration, 0.25% DNFB, ear swelling was enhanced. Restraint stress applied on day 6 also increased ear swelling in response to the highly irritating sensitizer DCC, but not to the low-irritancy chemical OXA. These data support the hypothesis that dose-response relationships exist for sensitization with chemical and that restraint stress modulation of the ear swelling response is both chemical specific and dependent on the irritancy potential of the chemical.

Assessment of glycosylation-dependent cell adhesion molecule 1 as a correlate of allergen-stimulated lymph node activation.

Early changes in gene expression have been identified by cDNA microarray technology. Analysis of draining auricular lymph node tissue sampled at 48 h following exposure to the potent contact allergen 2,4-dinitrofluorobenzene (DNFB) provided examples of up- and down-regulated genes, including onzin and guanylate binding protein 2, and glycosylation-dependent cell adhesion molecule 1 (GlyCAM-1), respectively. Allergen-induced changes in these three genes were confirmed in dose-response and kinetic analyses using Northern blotting and/or reverse transcription-polymerase chain reaction techniques. The results confirmed that these genes are robust and relatively sensitive markers of early changes provoked in the lymph node by contact allergen. Upon further investigation, it was found that altered expression of the adhesion molecule GlyCAM-1 was not restricted to treatment with DNFB. Topical sensitization of mice to a chemically unrelated contact allergen, oxazolone, was also associated with a decrease in the expression of mRNA for GlyCAM-1. Supplementary experiments revealed that changes in expression of this gene are independent of the stimulation by chemical allergens of proliferative responses by draining lymph node cells. Taken together these data indicate that the expression of GlyCAM-1 is down-regulated rapidly following epicutaneous treatment of mice with chemical allergens, but that this reduction is associated primarily with changes in lymph node cell number, or some other aspect of lymph node activation, rather than proliferation.

Assessment of preferential Th1 or Th2 induction by low-molecular-weight compounds using a reverse transcription-polymerase chain reaction method: comparison of two mouse strains, C57BL/6 and BALB/c.

The aim of this study was to examine whether the RT-PCR method for various Th1/Th2 cytokines is appropriate for determination of response to allergens using C57BL/6 and Balb/c mice, which are known to preferentially demonstrate Th1 and Th2 responses, respectively. To this end, both strains of mice were sensitized by skin painting with the contact allergen dinitrochlorobenzene (DNCB) or the respiratory allergen trimellitic anhydride (TMA). We used the sensitizing protocol adopted by Kimber and coworkers (Toxicology 103, 63-73, 1995). At various time points after the last application, the levels of mRNA expression for Th1-type cytokines IFN-gamma, IL-18, and IL-12p40, as well as receptor IL-18R, and the Th2-type cytokine IL-4 and the receptor ST2L, in lymph nodes were measured. The results suggest that differential expression of IL-12p40 and IL-4 mRNA after 24 h allows clear discrimination between DNCB and TMA in C57BL/6 mice, more obviously than in Balb/c mice. Furthermore, to examine this method, C57BL/6 mice were exposed to OXA, DNFB, and TNCB (Th1-predominant allergens) or PA, TDI, and MDI (Th2-predominant allergens). Elevation of IL-12p40 expression was significant with the Th1 inducers, while the level of IL-4 was higher with Th2-predominant allergens. The results of the present study demonstrate, for the first time, that differential expression of IL-12p40 and IL-4 in C57BL/6 mice may be useful as a parameter for assessing influence of contact and respiratory allergens.