CD40 signaling is impaired in L. major-infected macrophages and is rescued by a p38MAPK activator establishing a host-protective memory T cell response.
Leishmania, a protozoan parasite, lives and multiplies as amastigote within macrophages. It is proposed that the macrophage expressed CD40 interacts with CD40 ligand on T cells to induce IFN-gamma, a Th1-type cytokine that restricts the amastigote growth. Here, we demonstrate that CD40 cross-linking early after infection resulted in inducible nitric oxide synthetase type-2 (iNOS2) induction and iNOS2-dependent amastigote elimination. Although CD40 expression remained unaltered on L. major-infected macrophages, delay in the treatment of macrophages or of mice with anti-CD40 antibody resulted in significant reduction in iNOS2 expression and leishmanicidal function suggesting impaired CD40 signaling in Leishmania infection. The inhibition of CD40-induced iNOS2 expression by SB203580, a p38-mitogen activated protein kinase (p38MAPK)-specific inhibitor, and the reversal of the inhibition by anisomycin, a p38MAPK activator, suggested a crucial role of p38MAPK in CD40 signaling. Indeed, the CD40-induced p38MAPK phosphorylation, iNOS2 expression and anti-leishmanial function were impaired in Leishmania-infected macrophages but were restored by anisomycin. Anisomycin's effects were reversed by SB203580 emphasizing the role of p38MAPK in CD40-induced iNOS2-dependent leishmanicidal function. Anisomycin administration in L. major-infected BALB/c mice resulted in significant reduction in the parasite load and established a host-protective Th1-type memory response. Also implicated in these findings is a scientific rationale to define novel anti-parasite drug targets and to bypass the problem of drug resistance.
Awasthi
Amit
A
National Centre for Cell Science, Ganeshkhind, Pune 411007, India.
Mathur
Ramkumar
R
Khan
Aslam
A
Joshi
Bimba N
BN
Jain
Nitya
N
Sawant
Sangeeta
S
Boppana
Ramanamurthy
R
Mitra
Debashis
D
Saha
Bhaskar
B
D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D019013:CD40 Antigens / Q000276:immunology / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation; D007093:Imidazoles / Q000494:pharmacology; D018320:Leishmania major / Q000276:immunology* / Q000502:physiology; D016773:Leishmaniasis, Cutaneous / Q000276:immunology / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000378:metabolism* / Q000469:parasitology*; D051379:Mice; D008807:Mice, Inbred BALB C; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology*; D018417:Th1 Cells / Q000276:immunology* / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
D019013:CD40 Antigens; D004791:Enzyme Inhibitors; D007093:Imidazoles; D011500:Protein Synthesis Inhibitors; D011725:Pyridines; D000841:Anisomycin; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580