Abstract
Leishmania donovani (LD), the causative agent of visceral leishmaniasis (VL), extracts membrane cholesterol from macrophages and disrupts lipid rafts, leading to their inability to stimulate T cells. Restoration of membrane cholesterol by liposomal delivery corrects the above defects and offers protection in infected hamsters. To reinforce further the protective role of cholesterol in VL, mice were either provided a high-cholesterol (atherogenic) diet or underwent statin treatment. Subsequent LD infection showed that an atherogenic diet is associated with protection, whereas hypocholesterolemia due to statin treatment confers susceptibility to the infection. This observation was validated in apolipoprotein E knockout mice (AE) mice that displayed intrinsic hypercholesterolemia with hepatic granuloma, production of host-protective cytokines, and expansion of antileishmanial CD8(+)IFN- γ (+) and CD8(+)IFN- γ (+)TNF- α (+) T cells in contrast to the wild-type C57BL/6 (BL/6) mice when infected with LD. Normal macrophages from AE mice (N-AE-MΦ) showed 3-fold higher membrane cholesterol coupled with increased fluorescence anisotropy (FA) compared with wild-type macrophage (N-BL/6-MΦ). Characterization of in vitro LD-infected AE macrophage (LD-AE-MΦ) revealed intact raft architecture and ability to stimulate T cells, which were compromised in LD-BL/6-MΦ. This study clearly indicates that hypercholesterolemia, induced intrinsically or extrinsically, can control the pathogenesis of VL by modulating immune repertoire in favor of the host.
Highlights
ELISA kits for IL-2, IL-4, IL-6, IL-10, IL-12, tumor necrosis factor (TNF)-␣, transforming growth factor (TGF)-, and interferon (IFN)-␥ were purchased from BD Biosciences, while IL-17 and IL-22 were purchased from R and D Systems
Hypocholesterolemia is largely evidenced in visceral leishmaniasis [8, 9]
Further manipulation of serum cholesterol by exogenous means in both wild-type and apolipoprotein E knockout mice (AE) animals showed that cholesterol content has a direct bearing on visceral leishmaniasis (VL) pathogenesis
Summary
Reagents and antibodies RPMI-1640 and M-199 medium, HBSS buffer, sodium bicarbonate,1,6-diphenyl-1,3,5-hexatriene (DPH), Giemsa stain, 2-ME, FITC-conjugated cholera toxin B subunit (CTX-B-FITC), ConA, Ionomycin, PMA, Ovalbumin, RBC lysis buffer, TMB, and hematoxylin and eosin were purchased from Sigma-Aldrich. VECTASHIELD Mounting Medium with DAPI was obtained from Vector Laboratories. ELISA kits for IL-2, IL-4, IL-6, IL-10, IL-12, tumor necrosis factor (TNF)-␣, transforming growth factor (TGF)-, and interferon (IFN)-␥ were purchased from BD Biosciences, while IL-17 and IL-22 were purchased from R and D Systems. FcR blocking reagent, anti-mouse CD3 PE-Cy7, anti-mouse CD4 PerCP, anti-mouse CD8 APC-Cy7, anti-mouse TNF-␣ FITC, and permeabilization and fixation kit were purchased from BD Biosciences. 13.8 [30] was a kind gift from Dr Satyajit Roth (National Institute of Immunology, New Delhi, India). It was maintained in RPMI 1640 medium supplemented with 10% FCS and 2-ME at 37°C with 5% CO2 in a humidified atmosphere
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