Thiol Antioxidants Block the Activation of Antigen-Presenting Cells by Contact Sensitizers

Abstract

Strong contact sensitizers are able to induce signal transduction mechanisms such as tyrosine phosphorylation and activation of MAP kinases in antigen-presenting cells. We studied the capacity of different antioxidants (ascorbic acid, alpha-tocopherol, pyrrolidine dithiocarbamate, N-acetylcysteine, and glutathione) to block the increase in tyrosine phosphorylation in human monocytes seen after stimulation with strong contact sensitizers. Human peripheral blood mononuclear cells were stimulated with 5-chloro-2-methylisothiazolinone plus 2-methylisothiazolinone in the presence or absence of these antioxidants. The total amount of membrane-associated phosphotyrosine in CD14+ cells was quantified using flow cytometric techniques. Complete inhibition of tyrosine phosphorylation was noticed when cells were stimulated in the presence of N-acetylcysteine or glutathione. Using N-acetylcysteine as inhibitor similar results were obtained for cells stimulated with formaldehyde, thimerosal methyldibromoglutaronitrile, diphenylcyclopropenone, p-phenylenediamine, toluene-2,5-diamine, and 2,4-dinitrofluorobenzene. By use of a trinitrophenyl-specific monoclonal antibody it was shown that N-acetylcysteine as well as cysteine prevents the binding of 2,4,6-trinitrochlorobenzene to proteins in monocytes and monocyte-derived mature dendritic cells. Furthermore, the capacity of N-acetylcysteine to block the activation of p38 and ERK1/2 MAP kinases by 2,4,6-trinitrochlorobenzene was demonstrated. The radical scavengers ascorbic acid and alpha-tocopherol as well as the nuclear factor kappaB inhibitor pyrrolidine dithiocarbamate failed to prevent the increase in tyrosine phosphorylation. Our data present evidence that reactive oxygen species as well as transcription factor nuclear factor kappaB seem to be unimportant for the induction of tyrosine phosphorylation by contact sensitizers. On the other hand, protection of thiol groups using compounds with free sulfhydryl groups is very effective to block this process. This finding may have implications for prevention of occupational sensitization to strong contact allergens.

Signal transduction profile of chemical sensitisers in dendritic cells: An endpoint to be included in a cell-based in vitro alternative approach to hazard identification?

“…The results showed that p38 phosphorylation in DC may be useful for the identification of potential skin contact sensitisers. The activation of p38 MAPK and ERK1/2 was also induced by the sensitiser TNCB in DC (Bruchhausen et al, 2003) and MAPKs activation by contact sensitisers was later confirmed (Aiba et al, 2003). The authors stimulated human monocyte-derived dendritic cells with nickel and DNCB and observed that DNCB-induced p38 MAPK and JNK1/2 phosphorylation, whereas nickel-induced p38 MAPK, JNK1/2 and ERK1/2 phosphorylation.…”

Sulfamethoxazole and Its Metabolite Nitroso Sulfamethoxazole Stimulate Dendritic Cell Costimulatory Signaling

“…Since then, many studies have identified signals, which can generally be divided into pathogen-associated patterns, such as LPS (49,50) and CpG oligodeoxynucleotides (51,52), and indicators of cell toxicity (27), such as uric acid release (28) or thiol depletion (30,33,53). The effect of these signaling pathways is to switch a T cell response to a specific Ag from tolerance to full activation.…”

“…It is known that dendritic cell maturation signals can also be provided by necrotic cell death through the release of intracellular molecules into the extracellular matrix (27,28), apoptotic cell death (29), or the induction of oxidative stress (30,31). Indeed, studies with contact sensitizers have demonstrated that small protein-reactive compounds can induce dendritic cell maturation (30,32,33) at concentrations associated with significant cell death (34).…”

“…Indeed, studies with contact sensitizers have demonstrated that small protein-reactive compounds can induce dendritic cell maturation (30,32,33) at concentrations associated with significant cell death (34). It is interesting to note, therefore, that lymphocytes from hypersensitive patients are more susceptible to cell death in response to reactive drug metabolites than control cells (35)(36)(37)(38).…”

Danger, intracellular signaling, and the orchestration of dendritic cell function in skin sensitization

“…Importantly, many in vitro studies have revealed that ROS production is induced by contact allergens (Bruchhausen et al, 2003;Mehrotra et al, 2005;Martin et al, 2011). In human monocytes, the inhibition of ROS production, as achieved by administration of the NADPH oxidase inhibitor diphenyleneiodonium (DPI), inhibits ATP-mediated inflammasome activation (Hewinson et al, 2008).…”