Effect of inhibition of glutathione synthesis on the immunogenicity of captopril and captoprilprotein conjugates in the mouse

Abstract

The effect of glutathione (GSH) depletion on the immunogenicity of captopril (CP) and d-penicillamine (PA) was investigated in C57 mouse. Depletion of GSH was by dl-buthionine sulfoximine (BSO), a potent and specific inhibitor of GSH synthesis, injected on the days of immunization of the drug/drug-protein conjugates. Chronic BSO pretreatment for 5 consecutive days, before and including the 4-day immunization period, caused tissue GSH depletion (liver 60%, kidney 71%, lung 14%, spleen 14% and whole blood 36%) in C57 mouse. After chronic administration of CP (270 μmol/kg, i.p. or i.m.) or CP-HSA (200 μg, i.p. or i.m.), IgG antibody response to CP-derived antigen was detected by an enzyme-linked immunosorbent assay (ELISA). The IgG antibody recognised CP-OVA but not OVA, and was inhibited by CP in other protein conjugated form, thus confirming its specificity to CP. Depletion of GSH by BSO caused an increase in the CP-specific IgG antibody titre when CP/CP-HSA was immunized through i.p. (with or without Freund's Complete Adjuvant) but not i.m. administration. In contrast, chronic administration of PA (270 μmol kg , i.p.) or PA-HSA (200μg, i.p.), with or without BSO pre-treatment, did not lead to detectable PA-specific IgG antibody. The results again illustrate the difference in the intrinsic immunogenicity between CP and PA, in that depletion of GSH increased the humoral (Blymphocyte) anti-CP responses but not anti-PA responses under the experimental conditions. These findings suggest that GSH status, apart from its effects on the disposition of CP/CP-protein conjugates, should be considered as an important determinant of both the immunological and toxicological response to CP.