ALTERATIONS IN INTRACELLULAR REACTIVE OXYGEN SPECIES GENERATION AND REDOX POTENTIAL MODULATE MAST-CELL FUNCTION

The administration of mercuric chloride (HgCl2), gold compounds, or D- penicillamine to Brown Norway (BN) rats causes a T helper (Th)2 cell-a ssociated autoimmune syndrome characterized by the production of a num ber of autoantibodies, marked elevation of serum IgE concentration, an d tissue injury in the form of a vasculitis and arthritis. We have rec ently shown that the same compounds in vitro sensitize BN rat peritone al mast cells for IgE-triggered mediator release and interleukin-4 mRN A production. We wished to test the hypothesis that these agents influ ence 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 HgCl2, gold compounds or D-penicillamine (the latter only in the presence of copper ions) le d to the intracellular production of ROS as shown by the oxidative pro duction of the fluorescent compound 2',7'-dichlorofluorescein. Mast ce lls were more sensitive than splenocytes to this effect. Direct oxidat ive stress (exposure to H2O2) produced a similar sensitization for med iator release to that caused by HgCl2. Inhibition of ROS formation by desferrioxamine or catalase diminished the enhancement of IgE-mediated serotonin release caused by HgCl2, as did replenishment of intracellu lar glutathione. 2-Mercaptoethanol exacerbated the toxicity of HgCl2, perhaps due to the formation of a lipophilic complex that enhanced HgC l2 uptake. Blocking of glutathione synthesis increased the toxicity of HgCl2, but also abolished any sensitizing effect on mediator release. These results support three main predictions of our hypothesis: (1) t he compounds known to influence mast cell function all lead to the gen eration of ROS within the mast cell; (2) direct oxidative stress cause s sensitization for mediator release by the mast cell; and (3) modulat ion of ROS production/redox balance within the mast cell modulates the effects of these compounds on mast cell function. The balance of oxid ative/antioxidative influences may play an important role in the modul ation of mast cell function, particularly in the context of chemically induced autoimmunity.