Leishmania donovani inhibits macrophage apoptosis and pro-inflammatory response through AKT-mediated regulation of β-catenin and FOXO-1

Abstract

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. donovaniinfected 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 antiapoptotic 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.

Complement C3a induces axonal hypomyelination in the periventricular white matter through activation of WNT/β‐catenin signal pathway in septic neonatal rats experimentally induced by lipopolysaccharide

“…Therefore, it is speculated that C3a binding to C3aR may activate and phosphorylate AKT, which is associated with the activation of WNT/β-catenin signaling pathway. Similarly, IL-1β binds to and activates the IL-1R, which recruits MyD88, IRAK, TRAF6 and TAK1 to its intracellular domains leading to the activation and phosphorylation of AKT (27,29,53). The phosphorylated AKT interacts with β-catenin/Tcf4, which affects the expression of a multitude of downstream genes.…”

Leishmania donovani Exploits Macrophage Heme Oxygenase-1 To Neutralize Oxidative Burst and TLR Signaling–Dependent Host Defense

“…Infection was allowed to proceed for 4 h, the noninternalized parasites were removed by washing the plates with 13 PBS, and cells were cultured. Determination of intracellular parasite numbers were done by fixing the cells in methanol and then stained with DAPI (29).…”

Leishmania Hijacks Myeloid Cells for Immune Escape

“…Programmed death-1 receptor (PD-1), which mediates T-cell exhaustion, is negatively modulated by L. donovani to avoid macrophage apoptosis ( Roy et al, 2017 ). In addition, L. donovani triggers AKT activation of the anti-apoptotic β-catenin, inhibiting the pro-apoptotic transcriptional regulator FOXO-1 ( Gupta et al, 2016 ). L. donovani also prevents mitochondria-dependent apoptosis by inducing anti-apoptotic protein MCL-1 ( Giri et al, 2016 ).…”