Leishmania donovani inhibits macrophage apoptosis and pro-inflammatory response through AKT-mediated regulation of β-catenin and FOXO-1.
In order to establish infection, intra-macrophage parasite Leishmania donovani needs to inhibit host defense parameters like inflammatory cytokine production and apoptosis. In the present study, we demonstrate that the parasite achieves both by exploiting a single host regulator AKT for modulating its downstream transcription factors, β-catenin and FOXO-1. L. donovani-infected RAW264.7 and bone marrow-derived macrophages (BMDM) treated with AKT inhibitor or dominant negative AKT constructs showed decreased anti-inflammatory cytokine production and increased host cell apoptosis resulting in reduced parasite survival. Infection-induced activated AKT triggered phosphorylation-mediated deactivation of its downstream target, GSK-3β. Inactivated GSK-3β, in turn, could no longer sequester cytosolic β-catenin, an anti-apoptotic transcriptional regulator, as evidenced from its nuclear translocation during infection. Constitutively active GSK-3β-transfected L. donovani-infected cells mimicked the effects of AKT inhibition and siRNA-mediated silencing of β-catenin led to disruption of mitochondrial potential along with increased caspase-3 activity and IL-12 production leading to decreased parasite survival. In addition to activating anti-apoptotic β-catenin, phospho-AKT inhibits activation of FOXO-1, a pro-apoptotic transcriptional regulator. Nuclear retention of FOXO-1, inhibited during infection, was reversed when infected cells were transfected with dominant negative AKT constructs. Overexpression of FOXO-1 in infected macrophages not only documented increased apoptosis but promoted enhanced TLR4 expression and NF-κB activity along with an increase in IL-1β and decrease in IL-10 secretion. In vivo administration of AKT inhibitor significantly decreased liver and spleen parasite burden and switched cytokine balance in favor of host. In contrast, GSK-3β inhibitor did not result in any significant change in infectivity parameters. Collectively our findings revealed that L. donovani triggered AKT activation to regulate GSK-3β/β-catenin/FOXO-1 axis, thus ensuring inhibition of both host cell apoptosis and immune response essential for its intra-macrophage survival.
Department of Biochemistry, University of Calcutta, Kolkata 700019, India.
Purnima
P
Gupta
Infectious Diseases and Immunology Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700032, India.
Supriya
S
Srivastav
Department of Biochemistry, University of Calcutta, Kolkata 700019, India.
Shriya
S
Saha
Infectious Diseases and Immunology Division, CSIR-Indian Institute of Chemical Biology, Kolkata 700032, India.
Pijush K
PK
Das
Department of Biochemistry, University of Calcutta, Kolkata 700019, India.
Anindita
A
Ukil
D000818:Animals; D017209:Apoptosis; D003600:Cytosol / Q000378:metabolism; D004195:Disease Models, Animal; D004789:Enzyme Activation; D000071161:Forkhead Box Protein O1 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta / Q000378:metabolism; D056747:Immunomodulation; D007249:Inflammation / Q000378:metabolism / Q000473:pathology*; D042541:Intracellular Space / Q000469:parasitology; D007893:Leishmania donovani / Q000502:physiology*; D007898:Leishmaniasis, Visceral / Q000469:parasitology / Q000473:pathology; D008264:Macrophages / Q000469:parasitology* / Q000473:pathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008954:Models, Biological; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D000067996:RAW 264.7 Cells; D015203:Reproducibility of Results; D051176:beta Catenin / Q000378:metabolism*
D000071161:Forkhead Box Protein O1; C467200:Foxo1 protein, mouse; D051176:beta Catenin; D000071679:Glycogen Synthase Kinase 3 beta; D051057:Proto-Oncogene Proteins c-akt
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