Imipramine Exploits Histone Deacetylase 11 To Increase the IL-12/IL-10 Ratio in Macrophages Infected with Antimony-Resistant Leishmania donovani and Clears Organ Parasites in Experimental Infection

The efflux of antimony through multidrug resistance protein (MDR)-1 is the key factor in the failure of metalloid treatment in kalaazar patients infected with antimony-resistant Leishmania donovani ((SbLD)-L-R). Previously we showed that MDR-1 upregulation in (SbLD)-L-R infection is IL-10-dependent. Imipramine, a drug in use for the treatment of depression and nocturnal enuresis in children, inhibits IL-10 production from (SbLD)-L-R-infected macrophages ((SbLD)-L-R-M phi s) and favors accumulation of surrogates of antimonials. It inhibits IL-10-driven nuclear translocation of c-Fos/c-Jun, critical for enhanced MDR-1 expression. The drug upregulates histone deacetylase 11, which inhibits acetylation of IL-10 promoter, leading to a decrease in IL-10 production from (SbLD)-L-R-M phi s. It abrogates (SbLD)-L-R-mediated p50/c-Rel binding to IL-10 promoter and preferentially recruits p65/RelB to IL-12 p35 and p40 promoters, causing a decrease in IL-10 and overproduction of IL-12 in (SbLD)-L-R-M phi s. Histone deacetylase 11 per se does not influence IL-12 promoter activity. Instead, a imipramine-mediated decreased IL-10 level allows optimal IL-12 production in (SbLD)-L-R-M phi s. Furthermore, exogenous rIL-12 inhibits intracellular (SbLD)-L-R replication, which can be mimicked by the presence of Ab to IL-10. This observation indicated that reciprocity exists between IL-10 and IL-12 and that imipramine tips the balance toward an increased IL-12/IL-10 ratio in (SbLD)-L-R-M phi s. Oral treatment of infected BALB/c mice with imipramine in combination with sodium stibogluconate cleared organ (SbLD)-L-R parasites and caused an expansion of the antileishmanial T cell repertoire where sodium stibogluconate alone had no effect. Our study deciphers a detailed molecular mechanism of imipramine-mediated regulation of IL-10/IL-12 reciprocity and its impact on (SbLD)-L-R clearance from infected hosts.