title: Leishmania donovani isolates with antimony-resistant but not -sensitive phenotype inhibit sodium antimony gluconate-induced dendritic cell activation.
abstract: The inability of sodium antimony gluconate (SAG)-unresponsive kala-azar patients to clear Leishmania donovani (LD) infection despite SAG therapy is partly due to an ill-defined immune-dysfunction. Since dendritic cells (DCs) typically initiate anti-leishmanial immunity, a role for DCs in aberrant LD clearance was investigated. Accordingly, regulation of SAG-induced activation of murine DCs following infection with LD isolates exhibiting two distinct phenotypes such as antimony-resistant (Sb(R)LD) and antimony-sensitive (Sb(S)LD) was compared in vitro. Unlike Sb(S)LD, infection of DCs with Sb(R)LD induced more IL-10 production and inhibited SAG-induced secretion of proinflammatory cytokines, up-regulation of co-stimulatory molecules and leishmanicidal effects. Sb(R)LD inhibited these effects of SAG by blocking activation of PI3K/AKT and NF-kappaB pathways. In contrast, Sb(S)LD failed to block activation of SAG (20 microg/ml)-induced PI3K/AKT pathway; which continued to stimulate NF-kappaB signaling, induce leishmanicidal effects and promote DC activation. Notably, prolonged incubation of DCs with Sb(S)LD also inhibited SAG (20 microg/ml)-induced activation of PI3K/AKT and NF-kappaB pathways and leishmanicidal effects, which was restored by increasing the dose of SAG to 40 microg/ml. In contrast, Sb(R)LD inhibited these SAG-induced events regardless of duration of DC exposure to Sb(R)LD or dose of SAG. Interestingly, the inhibitory effects of isogenic Sb(S)LD expressing ATP-binding cassette (ABC) transporter MRPA on SAG-induced leishmanicidal effects mimicked that of Sb(R)LD to some extent, although antimony resistance in clinical LD isolates is known to be multifactorial. Furthermore, NF-kappaB was found to transcriptionally regulate expression of murine gammaglutamylcysteine synthetase heavy-chain (mgammaGCS(hc)) gene, presumably an important regulator of antimony resistance. Importantly, Sb(R)LD but not Sb(S)LD blocked SAG-induced mgammaGCS expression in DCs by preventing NF-kappaB binding to the mgammaGCS(hc) promoter. Our findings demonstrate that Sb(R)LD but not Sb(S)LD prevents SAG-induced DC activation by suppressing a PI3K-dependent NF-kappaB pathway and provide the evidence for differential host-pathogen interaction mediated by Sb(R)LD and Sb(S)LD.
authors.affiliation: Division of Infectious Diseases and Immunology, Indian Institute of Chemical Biology, Council of Scientific and Industrial Research, Kolkata, India.
authors.forename: Arun Kumar
authors.initials: AK
authors.lastname: Haldar
authors.forename: Vinod
authors.initials: V
authors.lastname: Yadav
authors.forename: Eshu
authors.initials: E
authors.lastname: Singhal
authors.forename: Kamlesh Kumar
authors.initials: KK
authors.lastname: Bisht
authors.forename: Alpana
authors.initials: A
authors.lastname: Singh
authors.forename: Suniti
authors.initials: S
authors.lastname: Bhaumik
authors.forename: Rajatava
authors.initials: R
authors.lastname: Basu
authors.forename: Pradip
authors.initials: P
authors.lastname: Sen
authors.forename: Syamal
authors.initials: S
authors.lastname: Roy
mesh_terms: D000818:Animals; D000967:Antimony Sodium Gluconate / Q000494:pharmacology*; D000981:Antiprotozoal Agents / Q000494:pharmacology*; D006224:Cricetinae; D003713:Dendritic Cells / Q000187:drug effects / Q000378:metabolism / Q000469:parasitology; D004351:Drug Resistance; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism; D006790:Host-Parasite Interactions / Q000187:drug effects; D016753:Interleukin-10 / Q000378:metabolism; D007893:Leishmania donovani / Q000187:drug effects* / Q000254:growth & development; D007898:Leishmaniasis, Visceral / Q000188:drug therapy / Q000276:immunology / Q000469:parasitology; D008297:Male; D008647:Mesocricetus; D051379:Mice; D008807:Mice, Inbred BALB C; D016328:NF-kappa B / Q000378:metabolism; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000276:immunology
chemical_list: D000981:Antiprotozoal Agents; D016328:NF-kappa B; D016753:Interleukin-10; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D005721:Glutamate-Cysteine Ligase; D000967:Antimony Sodium Gluconate