Alterations in intracellular reactive oxygen species generation and redox potential modulate mast cell function
The administration of mercuric chloride (HgCI2), gold compounds, or Dpenicillamine to Brown Norway (BN) rats causes a T helper (Th)2 cellassociated autoimmune syndrome characterized by the production of a number of autoantibodies, marked elevation of serum IgE concentration, and tissue injury in the form of a vasculitis and arthritis. We have recently shown that the same compounds in v i m sensitize BN rat peritoneal mast cells for IgE-triggered mediator release and interleukin-4 mRNA production. We wished to test the hypothesis that these agents influence mast cell function via an effect on intracellular reactive oxygen species (ROS) production/redox balance. Mast cells were obtained from BN rats by peritoneal washout. Incubation with HgC12, gold compounds or D-penicillamine (the latter only in the presence of copper ions) led to the intracellular production of ROS as shown by the oxidative production of the fluorescent compound 2' ,7'-dichlorofluorescein. Mast cells were more sensitive than splenocytes to this effect. Direct oxidative stress (exposure to H202) produced a similar sensitization for mediator release to that caused by HgC12. Inhibition of ROS formation by desferrioxamine or catalase diminished the enhancement of IgE-mediated serotonin release caused by HgC12, as did replenishment of intracellular glutathione. 2-Mercaptoethanol exacerbated the toxicity of HgC12, perhaps due to the formation of a lipophilic complex that enhanced HgC12 uptake. Blocking of glutathione synthesis increased the toxicity of HgCI2, but also abolished any sensitizing effect on mediator release. These results support three main predictions of our hypothesis: (1) the compounds known to influence mast cell function all lead to the generation of ROS within the mast cell; (2) direct oxidative stress causes sensitization for mediator release by the mast cell; and (3) modulation of ROS production/redox balance within the mast cell modulates the effects of these compounds on mast cell function. The balance of oxidative/antioxidative influences may play an important role in the modulation of mast cell function, particularly in the context of chemically induced autoimmunity.