Lipid Droplet Formation, Their Localization and Dynamics during Leishmania major Macrophage Infection

Abstract

Leishmania, the causative agent of vector-borne diseases, known as leishmaniases, is an obligate intracellular parasite within mammalian hosts. The outcome of infection depends largely on the activation status of macrophages, the first line of mammalian defense and the major target cells for parasite replication. Understanding the strategies developed by the parasite to circumvent macrophage defense mechanisms and to survive within those cells help defining novel therapeutic approaches for leishmaniasis. We previously showed the formation of lipid droplets (LDs) in L. major infected macrophages. Here, we provide novel insights on the origin of the formed LDs by determining their cellular distribution and to what extent these high-energy sources are directed to the proximity of Leishmania parasites. We show that the ability of L. major to trigger macrophage LD accumulation is independent of parasite viability and uptake and can also be observed in non-infected cells through paracrine stimuli suggesting that LD formation is from cellular origin. The accumulation of LDs is demonstrated using confocal microscopy and live-cell imagin in parasite-free cytoplasmic region of the host cell, but also promptly recruited to the proximity of Leishmania parasites. Indeed LDs are observed inside parasitophorous vacuole and in parasite cytoplasm suggesting that Leishmania parasites besides producing their own LDs, may take advantage of these high energy sources. Otherwise, these LDs may help cells defending against parasitic infection. These metabolic changes, rising as common features during the last years, occur in host cells infected by a large number of pathogens and seem to play an important role in pathogenesis. Understanding how Leishmania parasites and different pathogens exploit this LD accumulation will help us define the common mechanism used by these different pathogens to manipulate and/or take advantage of this high-energy source.

Lopinavir, an HIV-1 peptidase inhibitor, induces alteration on the lipid metabolism ofLeishmania amazonensispromastigotes

“…In microorganisms such as fungi, microalgae and bacteria, the accumulation of these LB seems to be induced specifically in response to some stress. The structure and morphology of LB have been described in mammalian cells, especially in adipocytes, and consist of a monolayer of phospholipids, amphipathic glycolipids and/or steroids that surround a hydrophobic core of neutral lipids, mainly TG and esters of sterols (Murphy, 2001 ; Farese and Walther, 2009 ; d'Avila et al , 2012 ; Rabhi et al , 2016 ; Roingeard and Melo, 2017 ). Lipid metabolism has been demonstrated as an important pathway modulated by protozoan parasites in host cells.…”

“…Several studies with Toxoplamasma gondii , Plasmodium spp. and L. amazonensis have documented that these pathogens are able to induce accumulation of lipids, such as TG, DG, CHOE, CHO and/or phospholipids (Coppens et al , 2000 ; Das et al , 2016 ; Rabhi et al , 2016 ; Toledo et al , 2016 ). Our results suggest that the content of LB observed in the treatment with lopinavir in L. amazonensis promastigotes can be composed of CHOE, because the sterol analysis demonstrated an increase of both LB and CHOE in a concentration-dependent manner.…”

Mitochondria Restrict Growth of the Intracellular Parasite Toxoplasma gondii by Limiting Its Uptake of Fatty Acids

“…Toxoplasma proliferates within a membrane-bound vacuole and scavenges host FAs (Caffaro and Boothroyd, 2011;Charron and Sibley, 2002). Because FAs are largely stored in LDs as triglycerides and LDs traffic to the vacuoles where Toxoplasma and several intracellular pathogens grow (Cocchiaro et al, 2008;Mota et al, 2014;Nolan et al, 2017;Rabhi et al, 2016), we speculated that Toxoplasma acquires FAs from host LDs. LDs are dynamically remodeled when FAs are required for energy conversion or biosynthesis of complex molecules (Walther and Farese, 2012).…”

“…Intact host LDs have been visualized in Chlamydia and Leishmania vacuoles during infection (Cocchiaro et al, 2008;Rabhi et al, 2016), and Toxoplasma internalizes host LDs into the parasite vacuole following supplementation of infected cells with exogenous FAs (Nolan et al, 2017). However, host LDs that were labeled with FL C 12 were not evident in the Toxoplasma vacuole at early, middle, or late stages of infection ( Figure 1F), suggesting that LD catabolism preceded host FA acquisition by Toxoplasma.…”

Organoboron Schiff bases as cell‐staining fluorescent probes: Synthesis, Chemio‐photophysical characterization, DFT, and X‐ray structures

“…Based on the above mentioned, it is important to design and synthesize new fluorescent cytoplasm markers with suitable photophysical properties and photostability, low cytotoxicity, solubility in polar solvents to be used in the modern cell biology in vitro and in vivo . Nowadays, the Boron dipyrromethanes (BODIPYs) are the most widely fluorescence organic compounds studied due to the vast range of biochemical and medical applications and probably in the second place the Boron diketonates (BODIKEs) where both show selective cytoplasm staining in vitro (Figure a) . However, in the last decade, the Boron Schiff bases (BOSCHIBAs, Figure a) have gained attention due to easy and green synthesis, non‐linear optical and linear optical properties, sensitive for solar cells .…”