Leishmania donovani isolates with antimony-resistant but not -sensitive phenotype inhibit sodium antimony gluconate-induced dendritic cell activation.
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.
Haldar
Arun Kumar
AK
Division of Infectious Diseases and Immunology, Indian Institute of Chemical Biology, Council of Scientific and Industrial Research, Kolkata, India.
Yadav
Vinod
V
Singhal
Eshu
E
Bisht
Kamlesh Kumar
KK
Singh
Alpana
A
Bhaumik
Suniti
S
Basu
Rajatava
R
Sen
Pradip
P
Roy
Syamal
S
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
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