Peripheral blood granulocyte activity following contact sensitization of rats with dinitrochlorobenzene

Low-level laser reduces the production of TNF-α, IFN-γ, and IL-10 induced by OVA

Delayed, or type IV, hypersensitivity reactions are a useful model to study the effects of new substances on the immune system. In this study, the experimental model of the delayed type hypersensitivity (DTH) reaction to ovalbumin (OVA) was used to evaluate the immunomodulating effects of low-level laser therapy (LLLT), which is used as an adjuvant therapy in medicine, dentistry, and physical therapy because of its potential anti-inflammatory and analgesic effects observed in several studies. The effects of LLLT (λ 780 nm, 0.06 W/cm(2) of radiation, and fluency of 3.8 J/cm(2)) in reaction to ovalbumin in Balb/C mice were examined after the induction phase of the hypersensitivity reaction. The animals treated with azathioprine (AZA), the animals that received a vehicle instead of ovalbumin, and those not immunized served as controls (n = 6 for each group). Footpad thickness measurements and hematoxylin-eosin histopathological exams were performed. Proliferation tests were also performed (spontaneous, in the presence of concanavalin A and ovalbumin) to determine the production in mononuclear cells cultures of tumor necrosis factor-alpha (TNF-α), INF-γ, and IL-10. In the group of animals irradiated with lasers and in the group treated with AZA, footpad thickness measurements were significantly reduced in comparison to the control group (p < 0.05). This reduction was accompanied by a very significant reduction in the density of the inflammatory infiltrate and by a significant reduction in the levels of TNF-α, INF-γ, and IL-10. LLLT radiation was shown to have an immunomodulating effect on DTH to OVA in Balb/C mice.

Inflammatory and immune mechanisms in contact hypersensitivity (CHS) in rats

Contact hypersensitivity (CHS) is a T-cell-mediated skin inflammatory reaction to cutaneous exposure to small sensitizing chemicals, haptens. Majority of CHS studies were conducted in mice and there is paucity of data in other experimental animals. In this review, after a brief survey of murine CHS, hitherto known characteristics of CHS in rats were presented including inflammatory and immune mechanisms of both sensitization and elicitation phases. Survey of literature of rat CHS is presented, with our data concerning the importance of genetic background both in the induction and in the expression of reaction to dinitrochlorobenzene. The knowledge of CHS in rats, preferred animal in immunopharmacological studies, might help development of immunomodulatory intervention in contact allergy.

Systemic immunomodulatory effects of topical dinitrochlorobenzene (DNCB) in rats. Activity of peripheral blood polymorphonuclear cells

Topical application of dinitrochlorobenzene (DNCB) is employed in the immunotherapy of skin diseases. Activation of T-cell mediated immune responses (Th1/type1) is the supposed mechanism of the clinical effect of DNCB, but there are no data concerning innate/inflammatory mechanisms. In this study, the effect of repeated topical DNCB application on peripheral blood polymorphonuclear (PMN) leukocytes has been examined in two rat strains which differ in the propensity to mount Th1/type1 or Th2/type2 responses. The dynamics of changes in PMN numbers and effector activities (respiratory burst, nitric oxide production and myeloperoxidase content), as well as in adhesion and TNF-α production following the rat skin sensitization with low (0.4%) and high (4%) DNCB doses were measured. Both priming and activation of PMNs were observed following skin sensitization with DNCB, with dose-dependent as well as time-dependent differences in some PMN activities. Obtained data might be relevant for understanding the immune mechanisms of topical DNCB therapy.

Percutaneous toxicity of dinitrochlorobenzene (DNCB) in rats

Contact hypersensitivity reaction (CHS) is a T-cell-mediated skin inflammatory reaction to cutaneous exposure to small sensitizing chemicals, haptens. While the significance of local inflammatory skin response to the hapten application in CHS induction and expression is known, there is paucity of data concerning systemic inflammation in CHS. In this study, changes in cellular (peripheral blood granulocytes) and humoral (plasma tumor necrosis factor (TNF)-α levels) components of inflammation during sensitization of rats with two consecutive applications of dinitrochlorobenzene (DNCB) were examined. The impact of sensitization on these parameters was determined by employing low (0.4%) and high (4%) hapten doses and by examining the dynamics (i.e. one and three days following the last application of DNCB) of these changes. Dose-dependent increase in relative numbers and priming (for respiratory burst and adhesion) effect of skin sensitization with DNCB on peripheral blood neutrophils in rats were noted. No changes in circulating TNF-α levels were observed following the sensitization. The increase in lung myeloperoxidase content and histologically evident presence of neutrophils was observed in lungs of the sensitized rats. The changes in granulocyte priming for adhesion might have accounted for the observed increase in lung neutrophil content in the sensitized rats.

Immunotoxicity of epicutaneously applied anticoagulant rodenticide warfarin: evaluation by contact hypersensitivity to DNCB in rats

The immunotoxicity of epicutaneously administered anticoagulant rodenticide warfarin (WF) was examined in this work by using experimental contact hypersensitivity (CHS) reaction to hapten dinitrochlorobenzene (DNCB). WF (0.05 and 0.5 mg/kg) administration 24 h before the induction of CHS does not change expression of CHS evaluated by ear swelling assay. Regional draining lymph node response during sensitization phase was characterized by decreased cellularity but increased spontaneous and IL-2 stimulated proliferation of draining lymph node cells (DLC). No changes in IL-2 production and in numbers of CD25(+) cells were noted and even decreased proliferative index (ratio of IL-2 stimulated to unstimulated DLC proliferation) was detected. Increase in granulocyte activity (MTT reduction and adhesion to plastic) was noted following application of WF solely with further increase following subsequent application of DNCB, when granulocyte activation (NBT reduction) was noted also. Access of WF into general circulation might be responsible for observed changes, what was supported by ex vivo changes in DLC and granulocyte functions assessed before initiation of sensitization and by in vitro effect of exogenous WF as well. Differential effects of WF on lymphocytes and granulocytes noted in this study highlight the need for simultaneous testing of both cell type activity what might constitute a more integrated approach in immunotoxicity studies.

Production of TNF-alpha by skin explants of dinitrochlorobenzene-challenged ears in rats: a model for the evaluation of contact hypersensitivity

BACKGROUND

Contact hypersensitivity (CHS) is a local inflammatory response of the skin following challenge of hapten-sensitized animals. It is the consequence of cell infiltration of derm and the release of inflammation mediators, among which Tumor necrosis factor-alpha (TNF-alpha) is one of the most important factors. The intensity of the inflammation could be quantified by ear swelling which is the classical manifestation of the reaction. This study was testing the working hypothesis that levels of TNF-alpha in skin organ culture medium should correlate with the intensity of CHS reaction measured in vivo by ear swelling assay, and with the density of dermal infiltrate in ear skin samples. In order to test the working hypothesis, the intensity of inflammatory reaction following challenge was evaluated by classical measurements of ear swelling, by the determination of TNF-alpha levels in culture fluids of ear skin following epicutaneous application of dinitrochlorobenzene (DNCB) into the ears of sensitized animals.

METHODS

Animal model of CHS reaction to DNCB in Albino Oxford rats was used as described. Ear swelling was quantified in percentage terms as the difference in thickness between the challenged and nontreated ears of the same animal. Dermal infiltrate density in histopathologically analyzed samples of ear skin was evaluated by computer-assisted image analysis. Ear skin samples were cultured in standard medium for 24 h, and TNF-alpha concentration in the conditioned medium was subsequently determined with ELISA test.

RESULTS

Dose-dependent increase in the density of the dermal infiltrate and in TNF-alpha in CM were noted following the application of 0.65%, 1.3% and 2.6% of DNCB to the ears of previously sensitized rats. The correlation between ear swelling and the levels of TNF-alpha (r = 0.933, p < 0.001) in CM, and between ear swelling and dermal infiltrate density (r = 0.916, p < 0.001) was found. Correlation was also found between the density of the dermal infiltrate and the levels of TNF-alpha (r = 0.865, p < 0.001).

CONCLUSION

Presented data suggested that skin-organ culture system and the quantification of inflammatory mediators might be used for the evaluation of contact hypersensitivity reaction and its intensity.