Trypanosoma cruzi epimastigotes store cholesteryl esters in lipid droplets after cholesterol endocytosis

Protocols for Extraction of miRNA from Extracellular Vesicles of Lyophilized Human Saliva Samples

Extracellular vesicles (EVs) are emerging as crucial biomarkers in molecular diagnostics, providing early detection of disease progression. Although ultracentrifugation remains the gold standard for vesicle isolation from biofluids, it has limitations in scalability and accessibility. This study presents lyophilization as an innovative method for preserving EVs and isolating microRNAs from saliva, utilizing its proven ability to maintain biological activity and prevent unwanted chemical reactions. We assessed five different sample preparation protocols combined with a dual-purification strategy. Structural and molecular integrity analyses revealed that lyophilized samples retained essential EV characteristics, including CD63/CD9 membrane localization. QELS analysis and electron microscopy confirmed distinct vesicle populations in both ultracentrifuged (30-50 nm and 320-360 nm) and lyophilized samples (50-70 nm and 360-380 nm). Importantly, lyophilized samples exhibited higher total RNA concentrations (p < 0.0001) while preserving key microRNA signatures (miR-16, miR-21, miR-33a, and miR-146b) with high fidelity. The efficacy of lyophilization is linked to its ability to systematically reduce solvent content through sublimation while maintaining vesicle integrity and molecular cargo. This method offers a practical, scalable alternative for EV isolation with significant implications for biomarker-based diagnostics.

Lipid Metabolism in Insect Vectors of Diseases

According to the World Health Organization vector-borne diseases account for more than 17% of all infectious diseases, causing more than 700,000 deaths annually. Vectors are organisms that are able to transmit infectious pathogens between humans, or from animals to humans. Many of these vectors are hematophagous insects, which ingest the pathogen from an infected host during a blood meal, and later transmit it into a new host. Malaria, dengue, African trypanosomiasis, yellow fever, leishmaniasis, Chagas disease, and many others are examples of diseases transmitted by insects.Both the diet and the infection with pathogens trigger changes in many metabolic pathways, including lipid metabolism, compared to other insects. Blood contains mostly proteins and is very poor in lipids and carbohydrates. Thus, hematophagous insects attempt to efficiently digest and absorb diet lipids and also rely on a large de novo lipid biosynthesis based on utilization of proteins and carbohydrates as carbon source. Blood meal triggers essential physiological processes as molting, excretion, and oogenesis; therefore, lipid metabolism and utilization of lipid storage should be finely synchronized and regulated regarding that, in order to provide the necessary energy source for these events. Also, pathogens have evolved mechanisms to hijack essential lipids from the insect host by interfering in the biosynthesis, catabolism, and transport of lipids, which pose challenges to reproduction, survival, fitness, and other insect traits.In this chapter, we have tried to collect and highlight the current knowledge and recent discoveries on the metabolism of lipids in insect vectors of diseases related to the hematophagous diet and pathogen infection.

A CTL - Lys immune function maintains insect metamorphosis by preventing gut bacterial dysbiosis and limiting opportunistic infections

BACKGROUND

Gut bacteria are beneficial to the host, many of which must be passed on to host offspring. During metamorphosis, the midgut of holometabolous insects undergoes histolysis and remodeling, and thus risks losing gut bacteria. Strategies employed by holometabolous insects to minimize this risk are obscure. How gut bacteria affect host insects after entering the hemocoel and causing opportunistic infections remains largely elusive.

RESULTS

We used holometabolous Helicoverpa armigera as a model and found low Lactobacillus load, high level of a C-type lectin (CTL) gene CD209 antigen-like protein 2 (CD209) and its downstream lysozyme 1 (Lys1) in the midgut of the wandering stage. CD209 or Lys1 depletion increased the load of midgut Lactobacillus, which further translocate to the hemocoel. In particular, CD209 or Lys1 depletion, injection of Lactobacillus plantarum, or translocation of midgut L. plantarum into the hemocoel suppressed 20-hydroxyecdysone (20E) signaling and delayed pupariation. Injection of L. plantarum decreased triacylglycerol and cholesterol storage, which may result in insufficient energy and 20E available for pupariation. Further, Lysine-type peptidoglycan, the major component of gram-positive bacterial cell wall, contributed to delayed pupariation and decreased levels of triacylglycerols, cholesterols, and 20E, in both H. armigera and Drosophila melanogaster.

CONCLUSIONS

A mechanism by which (Lactobacillus-induced) opportunistic infections delay insect metamorphosis was found, namely by disturbing the homeostasis of lipid metabolism and reducing 20E production. Moreover, the immune function of CTL - Lys was characterized for insect metamorphosis by maintaining gut homeostasis and limiting the opportunistic infections.

Fatty acid elongases 1-3 have distinct roles in mitochondrial function, growth, and lipid homeostasis in Trypanosoma cruzi

Trypanosomatids are a diverse group of uniflagellate protozoan parasites that include globally relevant pathogens such as Trypanosoma cruzi, the causative agent of Chagas disease. Trypanosomes lack the fatty acid synthase system typically used for de novo fatty acid (FA) synthesis in other eukaryotes. Instead, these microbes have evolved a modular FA elongase (ELO) system comprised of individual ELO enzymes (ELO1-4) that can operate processively to generate long chain- and very long chain-FAs. The importance of ELO's for maintaining lipid homeostasis in trypanosomatids is currently unclear, given their ability to take up and utilize exogenous FAs for lipid synthesis. To assess ELO function in T. cruzi, we generated individual KO lines, Δelo1, Δelo2, and Δelo3, in which the genes encoding ELO1-3 were functionally disrupted in the parasite insect stage (epimastigote). Using unbiased lipidomic and metabolomic analyses, in combination with metabolic tracing and biochemical approaches, we demonstrate that ELO2 and ELO3 are required for global lipid homeostasis, whereas ELO1 is dispensable for this function. Instead, ELO1 activity is needed to sustain mitochondrial activity and normal growth in T. cruzi epimastigotes. The cross-talk between microsomal ELO1 and the mitochondrion is a novel finding that, we propose, merits further examination of the trypanosomatid ELO pathway as critical for central metabolism.

Dual Functional Full-Color Carbon Dot-Based Organelle Biosensor Array for Visualization of Lipid Droplet Subgroups with Varying Lipid Composition in Living Cells

In situ visualization of lipid composition diversity in lipid droplets (LDs) is essential for decoding lipid metabolism and function. However, effective probes for simultaneously localizing and reflecting the lipid composition of LDs are currently lacking. Here, we synthesized full-color bifunctional carbon dots (CDs) that can target LDs as well as respond to the nuance in internal lipid compositions with highly sensitive fluorescence signals, due to lipophilicity and surface state luminescence. Combined with microscopic imaging, uniform manifold approximation and projection, and sensor array concept, the capacity of cells to produce and maintain LD subgroups with varying lipid composition was clarified. Moreover, in oxidative stress cells, LDs with characteristic lipid compositions were deployed around mitochondria, and the proportion of LD subgroups changed, which gradually disappeared when treated with oxidative stress therapeutics. The CDs demonstrate great potential for in situ investigation of the LD subgroups and metabolic regulations.

FABP4-mediated lipid droplet formation in Streptococcus uberis-infected macrophages supports host defence

Foamy macrophages containing prominent cytoplasmic lipid droplets (LDs) are found in a variety of infectious diseases. However, their role in Streptococcus uberis-induced mastitis is unknown. Herein, we report that S. uberis infection enhances the fatty acid synthesis pathway in macrophages, resulting in a sharp increase in LD levels, accompanied by a significantly enhanced inflammatory response. This process is mediated by the involvement of fatty acid binding protein 4 (FABP4), a subtype of the fatty acid-binding protein family that plays critical roles in metabolism and inflammation. In addition, FABP4 siRNA inhibitor cell models showed that the deposition of LDs decreased, and the mRNA expression of Tnf, Il1b and Il6 was significantly downregulated after gene silencing. As a result, the bacterial load in macrophages increased. Taken together, these data demonstrate that macrophage LD formation is a host-driven component of the immune response to S. uberis. FABP4 contributes to promoting inflammation via LDs, which should be considered a new target for drug development to treat infections.

The endoplasmic reticulum of trypanosomatids: An unrevealed road for chemotherapy

The endoplasmic reticulum (ER) of higher eukaryotic cells forms an intricate membranous network that serves as the main processing facility for folding and assembling of secreted and membrane proteins. The ER is a highly dynamic organelle that interacts with other intracellular structures, as well as endosymbiotic pathogenic and non-pathogenic microorganisms. A strict ER quality control (ERQC) must work to ensure that proteins entering the ER are folded and processed correctly. Unfolded or misfolded proteins are usually identified, selected, and addressed to Endoplasmic Reticulum-Associated Degradation (ERAD) complex. Conversely, when there is a large demand for secreted proteins or ER imbalance, the accumulation of unfolded or misfolded proteins activates the Unfold Protein Response (UPR) to restore the ER homeostasis or, in the case of persistent ER stress, induces the cell death. Pathogenic trypanosomatids, such as Trypanosoma cruzi, Trypanosoma brucei and Leishmania spp are the etiological agents of important neglected diseases. These protozoans have a complex life cycle alternating between vertebrate and invertebrate hosts. The ER of trypanosomatids, like those found in higher eukaryotes, is also specialized for secretion, and depends on the ERAD and non-canonical UPR to deal with the ER stress. Here, we reviewed the basic aspects of ER biology, organization, and quality control in trypanosomatids. We also focused on the unusual way by which T. cruzi, T. brucei, and Leishmania spp. respond to ER stress, emphasizing how these parasites' ER-unrevealed roads might be an attractive target for chemotherapy.

Biogenesis and Breakdown of Lipid Droplets in Pathological Conditions

Lipid droplets (LD) have long been considered as mere fat drops; however, LD have lately been revealed to be ubiquitous, dynamic and to be present in diverse organelles in which they have a wide range of key functions. Although incompletely understood, the biogenesis of eukaryotic LD initiates with the synthesis of neutral lipids (NL) by enzymes located in the endoplasmic reticulum (ER). The accumulation of NL leads to their segregation into nanometric nuclei which then grow into lenses between the ER leaflets as they are further filled with NL. The lipid composition and interfacial tensions of both ER and the lenses modulate their shape which, together with specific ER proteins, determine the proneness of LD to bud from the ER toward the cytoplasm. The most important function of LD is the buffering of energy. But far beyond this, LD are actively integrated into physiological processes, such as lipid metabolism, control of protein homeostasis, sequestration of toxic lipid metabolic intermediates, protection from stress, and proliferation of tumours. Besides, LD may serve as platforms for pathogen replication and defense. To accomplish these functions, from biogenesis to breakdown, eukaryotic LD have developed mechanisms to travel within the cytoplasm and to establish contact with other organelles. When nutrient deprivation occurs, LD undergo breakdown (lipolysis), which begins with the LD-associated members of the perilipins family PLIN2 and PLIN3 chaperone-mediated autophagy degradation (CMA), a specific type of autophagy that selectively degrades a subset of cytosolic proteins in lysosomes. Indeed, PLINs CMA degradation is a prerequisite for further true lipolysis, which occurs via cytosolic lipases or by lysosome luminal lipases when autophagosomes engulf portions of LD and target them to lysosomes. LD play a crucial role in several pathophysiological processes. Increased accumulation of LD in non-adipose cells is commonly observed in numerous infectious diseases caused by intracellular pathogens including viral, bacterial, and parasite infections, and is gradually recognized as a prominent characteristic in a variety of cancers. This review discusses current evidence related to the modulation of LD biogenesis and breakdown caused by intracellular pathogens and cancer.

Trypanosoma cruzi Affects Rhodnius prolixus Lipid Metabolism During Acute Infection

The interaction between Rhodnius prolixus and Trypanosoma cruzi has huge medical importance because it responds to the transmission of Chagas disease, a neglected tropical disease that affects about eight million people worldwide. It is known that trypanosomatid pathogens depend on active lipid endocytosis from the insect host to meet growth and differentiation requirements. However, until now, knowledge on how the parasite affects the lipid physiology of individual insect organs was largely unknown. Herein, the biochemical and molecular dynamics of the triatomine R. prolixus lipid metabolism in response to T. cruzi acute infection were investigated. A qRT-PCR approach was used to determine the expression profile of 12 protein-coding genes involved in R. prolixus lipid physiology. In addition, microscopic and biochemical assays revealed the lipid droplet profile and the levels of the different identified lipid classes. Finally, spectrometry analyses were used to determine fatty acid and sterol composition and their modulation towards the infection. T. cruzi infection downregulated the transcript levels of protein-coding genes for lipid biosynthetic and degrading pathways in individual triatomine organs. On the other hand, upregulation of lipid receptor transcripts indicates an attempt to capture more lipids from hemolymphatic lipoproteins. Consequently, several lipid classes (such as monoacylglycerol, diacylglycerol, triacylglycerol, cholesteryl ester, phosphatidylcholine, and phosphatidylethanolamine) were involved in the response to the parasite challenge, although modulating only the insect fat body. T. cruzi never leaves the insect gut and yet it modulates non-infected tissues, suggesting that the association between the parasite and the vector organs is reached by cell signaling molecules. This hypothesis raises several intriguing issues to inspire future studies in the parasite-vector interaction field.

Lipid and fatty acid metabolism in trypanosomatids

Trypanosomiases and leishmaniases are neglected tropical diseases that have been spreading to previously non-affected areas in recent years. Identification of new chemotherapeutics is needed as there are no vaccines and the currently available treatment options are highly toxic and often ineffective. The causative agents for these diseases are the protozoan parasites of the Trypanosomatidae family, and they alternate between invertebrate and vertebrate hosts during their life cycles. Hence, these parasites must be able to adapt to different environments and compete with their hosts for several essential compounds, such as amino acids, vitamins, ions, carbohydrates, and lipids. Among these nutrients, lipids and fatty acids (FAs) are essential for parasite survival. Trypanosomatids require massive amounts of FAs, and they can either synthesize FAs de novo or scavenge them from the host. Moreover, FAs are the major energy source during specific life cycle stages of T. brucei, T. cruzi, and Leishmania. Therefore, considering the distinctive features of FAs metabolism in trypanosomatids, these pathways could be exploited for the development of novel antiparasitic drugs. In this review, we highlight specific aspects of lipid and FA metabolism in the protozoan parasites T. brucei, T. cruzi, and Leishmania spp., as well as the pathways that have been explored for the development of new chemotherapies.

The role of lipid droplets in microbial pathogenesis

The nonpolar lipids present in cells are mainly triacylglycerols and steryl esters. When cells are provided with an abundance of nutrients, these storage lipids accumulate. As large quantities of nonpolar lipids cannot be integrated into membranes, they are isolated from the cytosolic environment in lipid droplets. As specialized, inducible cytoplasmic organelles, lipid droplets have functions beyond the regulation of lipid metabolism, in cell signalling and activation, membrane trafficking and control of inflammatory mediator synthesis and secretion. Pathogens, including fungi, viruses, parasites, or intracellular bacteria can induce and may benefit from lipid droplets in infected cells. Here we review biogenesis of lipid droplets as well as the role of lipid droplets in the pathogenesis of selected viruses, bacteria, protists and yeasts.

Lopinavir and Nelfinavir Induce the Accumulation of Crystalloid Lipid Inclusions within the Reservosomes of Trypanosoma cruzi and Inhibit Both Aspartyl-Type Peptidase and Cruzipain Activities Detected in These Crucial Organelles

Several research groups have explored the repositioning of human immunodeficiency virus aspartyl peptidase inhibitors (HIV-PIs) on opportunistic infections caused by bacteria, fungi and protozoa. In Trypanosoma cruzi, HIV-PIs have a high impact on parasite viability, and one of the main alterations promoted by this treatment is the imbalance in the parasite’s lipid metabolism. However, the reasons behind this phenomenon are unknown. In the present work, we observed by transmission electron microscopy (TEM) that the treatment of T. cruzi epimastigotes with the HIV-PIs lopinavir and nelfinavir induced a huge accumulation of crystalloid-shaped lipids within the reservosomes, most of them deforming these key organelles. As previously reported, those structures are characteristic of lipid inclusions formed mostly of cholesterol and cholesterol-esters. The fractionation of nontreated epimastigotes generated two distinct fractions enriched in reservosomes: one mostly composed of lipid inclusion-containing reservosomes (Fraction B1) and one where lipid inclusions were much less abundant (Fraction B2). Interestingly, the extract of Fraction B2 presented enzymatic activity related to aspartyl-type peptidases 3.5 times higher than that found in the extract obtained from Fraction B1. The cleavage of cathepsin D substrate by this class of peptidases was strongly impaired by pepstatin A, a prototypical aspartyl PI, and the HIV-PIs lopinavir and nelfinavir. In addition, both HIV-PIs also inhibited (to a lesser extent) the cruzipain activity present in reservosomes. Finally, our work provides new evidence concerning the presence and supposed participation of aspartyl peptidases in T. cruzi, even as it adds new information about the mechanisms behind the alterations promoted by lopinavir and nelfinavir in the protozoan.

Basic Biology of Trypanosoma cruzi

The present review addresses basic aspects of the biology of the pathogenic protozoa Trypanosoma cruzi and some comparative information of Trypanosoma brucei. Like eukaryotic cells, their cellular organization is similar to that of mammalian hosts. However, these parasites present structural particularities. That is why the following topics are emphasized in this paper: developmental stages of the life cycle in the vertebrate and invertebrate hosts; the cytoskeleton of the protozoa, especially the sub-pellicular microtubules; the flagellum and its attachment to the protozoan body through specialized junctions; the kinetoplast-mitochondrion complex, including its structural organization and DNA replication; glycosome and its role in the metabolism of the cell; acidocalcisome, describing its morphology, biochemistry, and functional role; cytostome and the endocytic pathway; the organization of the endoplasmic reticulum and Golgi complex; the nucleus, describing its structural organization during interphase and division; and the process of interaction of the parasite with host cells. The unique characteristics of these structures also make them interesting chemotherapeutic targets. Therefore, further understanding of cell biology aspects contributes to the development of drugs for chemotherapy.

Fatty acid oxidation participates in resistance to nutrient-depleted environments in the insect stages of Trypanosoma cruzi

Trypanosoma cruzi, the parasite causing Chagas disease, is a digenetic flagellated protist that infects mammals (including humans) and reduviid insect vectors. Therefore, T. cruzi must colonize different niches in order to complete its life cycle in both hosts. This fact determines the need of adaptations to face challenging environmental cues. The primary environmental challenge, particularly in the insect stages, is poor nutrient availability. In this regard, it is well known that T. cruzi has a flexible metabolism able to rapidly switch from carbohydrates (mainly glucose) to amino acids (mostly proline) consumption. Also established has been the capability of T. cruzi to use glucose and amino acids to support the differentiation process occurring in the insect, from replicative non-infective epimastigotes to non-replicative infective metacyclic trypomastigotes. However, little is known about the possibilities of using externally available and internally stored fatty acids as resources to survive in nutrient-poor environments, and to sustain metacyclogenesis. In this study, we revisit the metabolic fate of fatty acid breakdown in T. cruzi. Herein, we show that during parasite proliferation, the glucose concentration in the medium can regulate the fatty acid metabolism. At the stationary phase, the parasites fully oxidize fatty acids. [U-14C]-palmitate can be taken up from the medium, leading to CO2 production. Additionally, we show that electrons are fed directly to oxidative phosphorylation, and acetyl-CoA is supplied to the tricarboxylic acid (TCA) cycle, which can be used to feed anabolic pathways such as the de novo biosynthesis of fatty acids. Finally, we show as well that the inhibition of fatty acids mobilization into the mitochondrion diminishes the survival to severe starvation, and impairs metacyclogenesis.

Lipid droplets of protozoan parasites: survival and pathogenicity

Lipid droplets (LDs; lipid bodies) are intracellular sites of lipid storage and metabolism present in all cell types. Eukaryotic LDs are involved in eicosanoid production during several inflammatory conditions, including infection by protozoan parasites. In parasites, LDs play a role in the acquisition of cholesterol and other neutral lipids from the host. The number of LDs increases during parasite differentiation, and the biogenesis of these organelles use specific signaling pathways involving protein kinases. In addition, LDs are important in cellular protection against lipotoxicity. Recently, these organelles have been implicated in eicosanoid and specialised lipid metabolism. In this article, we revise the main functions of protozoan parasite LDs and discuss future directions in the comprehension of these organelles in the context of pathogen virulence.

Glutamine metabolism modulates azole susceptibility in Trypanosoma cruzi amastigotes

The mechanisms underlying resistance of the Chagas disease parasite, Trypanosoma cruzi, to current therapies are not well understood, including the role of metabolic heterogeneity. We found that limiting exogenous glutamine protects actively dividing amastigotes from ergosterol biosynthesis inhibitors (azoles), independent of parasite growth rate. The antiparasitic properties of azoles are derived from inhibition of lanosterol 14α-demethylase (CYP51) in the endogenous sterol synthesis pathway. We find that carbons from ¹³C-glutamine feed into amastigote sterols and into metabolic intermediates that accumulate upon CYP51 inhibition. Incorporation of ¹³C-glutamine into endogenously synthesized sterols is increased with BPTES treatment, an inhibitor of host glutamine metabolism that sensitizes amastigotes to azoles. Similarly, amastigotes are re-sensitized to azoles following addition of metabolites upstream of CYP51, raising the possibility that flux through the sterol synthesis pathway is a determinant of sensitivity to azoles and highlighting the potential role for metabolic heterogeneity in recalcitrant T. cruzi infection.

Lipid hijacking: a unifying theme in vector-borne diseases

Vector-borne illnesses comprise a significant portion of human maladies, representing 17% of global infections. Transmission of vector-borne pathogens to mammals primarily occurs by hematophagous arthropods. It is speculated that blood may provide a unique environment that aids in the replication and pathogenesis of these microbes. Lipids and their derivatives are one component enriched in blood and are essential for microbial survival. For instance, the malarial parasite Plasmodium falciparum and the Lyme disease spirochete Borrelia burgdorferi, among others, have been shown to scavenge and manipulate host lipids for structural support, metabolism, replication, immune evasion, and disease severity. In this Review, we will explore the importance of lipid hijacking for the growth and persistence of these microbes in both mammalian hosts and arthropod vectors.

Trypanocidal Mechanism of Action and in silico Studies of p-Coumaric Acid Derivatives

Trypanosoma species are responsible for chronic and systemic infections in millions of people around the world, compromising life quality, and family and government budgets. This group of diseases is classified as neglected and causes thousands of deaths each year. In the present study, the trypanocidal effect of a set of 12 ester derivatives of the p-coumaric acid was tested. Of the test derivatives, pentyl p-coumarate (7) (5.16 ± 1.28 μM; 61.63 ± 28.59 μM) presented the best respective trypanocidal activities against both epimastigote and trypomastigote forms. Flow cytometry analysis revealed an increase in the percentage of 7-AAD labeled cells, an increase in reactive oxygen species, and a loss of mitochondrial membrane potential; indicating cell death by necrosis. This mechanism was confirmed by scanning electron microscopy, noting the loss of cellular integrity. Molecular docking data indicated that of the chemical compounds tested, compound 7 potentially acts through two mechanisms of action, whether by links with aldo-keto reductases (AKR) or by comprising cruzain (CZ) which is one of the key Trypanosoma cruzi development enzymes. The results indicate that for both enzymes, van der Waals interactions between ligand and receptors favor binding and hydrophobic interactions with the phenolic and aliphatic parts of the ligand. The study demonstrates that p-coumarate derivatives are promising molecules for developing new prototypes with antiprotozoal activity.

Rab18: new insights into the function of an essential protein

Rab18 is one of the small number of conserved Rab proteins which have been traced to the last eukaryotic common ancestor. It is found in organisms ranging from humans to trypanosomes, and localizes to multiple organelles, including most notably endoplasmic reticulum and lipid droplets. In humans, absence of Rab18 leads to a severe illness known as Warburg-Micro syndrome. Despite this evidence that Rab18 is essential, its role in cells remains mysterious. However, recent studies identifying effectors and interactors of Rab18, are now shedding light on its mechanism of action, suggesting functions related to organelle tethering and to autophagy. In this review, we examine the variety of roles proposed for Rab18 with a focus on new evidence giving insights into the molecular mechanisms it utilizes. Based on this summary of our current understanding, we identify priority areas for further research.