Aspartic peptidases of human pathogenic trypanosomatids: perspectives and trends for chemotherapy

Inhibition of the NOTCH and mTOR pathways by nelfinavir as a novel treatment for T cell acute lymphoblastic leukemia

T cell acute lymphoblastic leukemia (T‑ALL), a neoplasm derived from T cell lineage‑committed lymphoblasts, is characterized by genetic alterations that result in activation of oncogenic transcription factors and the NOTCH1 pathway activation. The NOTCH is a transmembrane receptor protein activated by γ‑secretase. γ‑secretase inhibitors (GSIs) are a NOTCH‑targeted therapy for T‑ALL. However, their clinical application has not been successful due to adverse events (primarily gastrointestinal toxicity), limited efficacy, and drug resistance caused by several mechanisms, including activation of the AKT/mTOR pathway. Nelfinavir is an human immunodeficiency virus 1 aspartic protease inhibitor and has been repurposed as an anticancer drug. It acts by inducing endoplasmic reticulum (ER) stress and inhibiting the AKT/mTOR pathway. Thus, it was hypothesized that nelfinavir might inhibit the NOTCH pathway via γ‑secretase inhibition and blockade of aspartic protease presenilin, which would make nelfinavir effective against NOTCH‑associated T‑ALL. The present study assessed the efficacy of nelfinavir against T‑ALL cells and investigated mechanisms of action in vitro and in preclinical treatment studies using a SCL‑LMO1 transgenic mouse model. Nelfinavir blocks presenilin 1 processing and inhibits γ‑secretase activity as well as the NOTCH1 pathway, thus suppressing T‑ALL cell viability. Additionally, microarray analysis of nelfinavir‑treated T‑ALL cells showed that nelfinavir upregulated mRNA levels of CHAC1 (glutathione‑specific γ‑glutamylcyclotransferase 1, a negative regulator of NOTCH) and sestrin 2 (SESN2; a negative regulator of mTOR). As both factors are upregulated by ER stress, this confirmed that nelfinavir induced ER stress in T‑ALL cells. Moreover, nelfinavir suppressed NOTCH1 mRNA expression in microarray analyses. These findings suggest that nelfinavir inhibited the NOTCH1 pathway by downregulating NOTCH1 mRNA expression, upregulating CHAC1 and suppressing γ‑secretase via presenilin 1 inhibition and the mTOR pathway by upregulating SESN2 via ER stress induction. Further, nelfinavir exhibited therapeutic efficacy against T‑ALL in an SCL‑LMO1 transgenic mouse model. Collectively, these findings highlight the potential of nelfinavir as a novel therapeutic candidate for treatment of patients with T‑ALL.

Influence of grape consumption on the human microbiome

Over the years, a substantial body of information has accumulated suggesting dietary consumption of grapes may have a positive influence on human health. Here, we investigate the potential of grapes to modulate the human microbiome. Microbiome composition as well as urinary and plasma metabolites were sequentially assessed in 29 healthy free-living male (age 24-55 years) and female subjects (age 29-53 years) following two-weeks of a restricted diet (Day 15), two-weeks of a restricted diet with grape consumption (equivalent to three servings per day) (Day 30), and four-weeks of restricted diet without grape consumption (Day 60). Based on alpha-diversity indices, grape consumption did not alter the overall composition of the microbial community, other than with the female subset based on the Chao index. Similarly, based on beta-diversity analyses, the diversity of species was not significantly altered at the three time points of the study. However, following 2 weeks of grape consumption, taxonomic abundance was altered (e.g., decreased Holdemania spp. and increased Streptococcus thermophiles), as were various enzyme levels and KEGG pathways. Further, taxonomic, enzyme and pathway shifts were observed 30 days following the termination of grape consumption, some of which returned to baseline and some of which suggest a delayed effect of grape consumption. Metabolomic analyses supported the functional significance of these alterations wherein, for example, 2'-deoxyribonic acid, glutaconic acid, and 3-hydroxyphenylacetic acid were elevated following grape consumption and returned to baseline following the washout period. Inter-individual variation was observed and exemplified by analysis of a subgroup of the study population showing unique patterns of taxonomic distribution over the study period. The biological ramifications of these dynamics remain to be defined. However, while it seems clear that grape consumption does not perturb the eubiotic state of the microbiome with normal, healthy human subjects, it is likely that shifts in the intricate interactive networks that result from grape consumption have physiological significance of relevance to grape action.

The secreted FolAsp aspartic protease facilitates the virulence of Fusarium oxysporum f. sp. lycopersici

Pathogens utilize secretory effectors to manipulate plant defense. Fusarium oxysporum f. sp. lycopersici (Fol) is the causal agent of Fusarium wilt disease in tomatoes. We previously identified 32 secreted effector candidates by LC-MS analysis. In this study, we functionally identified one of the secreted proteins, FolAsp, which belongs to the aspartic proteases (Asp) family. The FolAsp was upregulated with host root specifically induction. Its N-terminal 1-19 amino acids performed the secretion activity in the yeast system, which supported its secretion in Fol. Phenotypically, the growth and conidia production of the FolAsp deletion mutants were not changed; however, the mutants displayed significantly reduced virulence to the host tomato. Further study revealed the FolAsp was localized at the apoplast and inhibited INF1-induced cell death in planta. Meanwhile, FolAsp could inhibit flg22-mediated ROS burst. Furthermore, FolAsp displayed protease activity on host protein, and overexpression of FolAsp in Fol enhanced pathogen virulence. These results considerably extend our understanding of pathogens utilizing secreted protease to inhibit plant defense and promote its virulence, which provides potential applications for tomato improvement against disease as the new drug target.

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.

Phospholipid Analogues as Chemotherapeutic Agents Against Trypanosomatids

BACKGROUND

Neglected tropical diseases (NTDs) represent a serious problem in a number of countries around the world and especially in Africa and South America, affecting mostly the poor population which has limited access to the healthcare system. The drugs currently used for the treatment of NTDs are dated many decades ago and consequently, present in some cases very low efficacy, high toxicity and development of drug resistance. In the search for more efficient chemotherapeutic agents for NTDs, a large number of different compound classes have been synthesized and tested. Among them, ether phospholipids, with their prominent member miltefosine, are considered one of the most promising.

OBJECTIVE

This review summarizes the literature concerning the development of antiparasitic phospholipid derivatives, describing the efforts towards more efficient and less toxic analogues while providing an overview of the mechanism of action of this compound class against trypanosomatids.

CONCLUSION

Phospholipid analogues are already known for their antiprotozoal activity. Several studies have been conducted in order to synthesize novel derivatives with the aim to improve current treatments such as miltefosine, with promising results. Photolabeling and fluorescent alkyl phospholipid analogues have contributed to the clarification of the mode of action of this drug family.

Molecular and evolutionary basis for survival, its failure, and virulence factors of the zoonotic nematode Anisakis pegreffii

Parasitism is a highly successful life strategy and a driving force in genetic diversity that has evolved many times over. Accidental infections of non-targeted hosts represent an opportunity for lateral host switches and parasite niche expansion. However, if directed toward organisms that are phylogenetically distant from parasite's natural host, such as humans, it may present a dead-end environment where the parasite fails to mature or is even killed by host immunity. One example are nematodes of Anisakidae family, genus Anisakis, that through evolution have lost the ability to propagate in terrestrial hosts, but can survive for a limited time in humans causing anisakiasis. To scrutinize versatility of Anisakis to infect an evolutionary-distant host, we performed transcriptomic profiling of larvae successfully migrating through the rat, a representative model of accidental human infection and compared it to that of larvae infecting an evolutionary-familiar, paratenic host (fish). In a homeothermic accidental host Anisakis upregulated ribosome-related genes, cell division, cuticle constituents, oxidative phosphorylation, in an unsuccessful attempt to molt to the next stage. In contrast, in the paratenic poikilothermic host where metabolic pathways were moderately upregulated or silenced, larvae prepared for dormancy by triggering autophagy and longevity pathways. Identified differences and the modelling of handful of shared transcripts, provide the first insights into evolution of larval nematode virulence, warranting their further investigation as potential drug therapy targets.

Repositioning of HIV Aspartyl Peptidase Inhibitors for Combating the Neglected Human Pathogen Trypanosoma cruzi

Chagas disease, caused by the flagellate parasite Trypanosoma cruzi, is a wellknown neglected tropical disease. This parasitic illness affects 6-7 million people and can lead to severe myocarditis and/or complications of the digestive tract. The changes in its epidemiology facilitate co-infection with the Human Immunodeficiency Virus (HIV), making even more difficult the diagnosis and prognosis. The parasitic infection is reactivated in T. cruzi/HIV co-infection, with the appearance of unusual manifestations in the chronic phase and the exacerbation of classical clinical signs. The therapeutic arsenal to treat Chagas disease, in all its clinical forms, is restricted basically to two drugs, benznidazole and nifurtimox. Both drugs are extremely toxic and the therapeutic efficacy is still unclear, making the clinical treatment a huge issue to be solved. Therefore, it seems obvious the necessity of new tangible approaches to combat this illness. In this sense, the repositioning of approved drugs appears as an interesting and viable strategy. The discovery of Human Immunodeficiency Virus Aspartyl Peptidase Inhibitors (HIV-PIs) represented a milestone in the treatment of Acquired Immune Deficiency Syndrome (AIDS) and, concomitantly, a marked reduction in both the incidence and prevalence of important bacterial, fungal and parasitic co-infections was clearly observed. Taking all these findings into consideration, the present review summarizes the promising and beneficial data concerning the effects of HIV-PIs on all the evolutionary forms of T. cruzi and in important steps of the parasite's life cycle, which highlight their possible application as alternative drugs to treat Chagas disease.

Unraveling oxidative stress response in the cestode parasite Echinococcus granulosus

Cystic hydatid disease (CHD) is a worldwide neglected zoonotic disease caused by Echinococcus granulosus. The parasite is well adapted to its host by producing protective molecules that modulate host immune response. An unexplored issue associated with the parasite's persistence in its host is how the organism can survive the oxidative stress resulting from parasite endogenous metabolism and host defenses. Here, we used hydrogen peroxide (H₂O₂) to induce oxidative stress in E. granulosus protoescoleces (PSCs) to identify molecular pathways and antioxidant responses during H₂O₂ exposure. Using proteomics, we identified 550 unique proteins; including 474 in H₂O₂-exposed PSCs (H-PSCs) samples and 515 in non-exposed PSCs (C-PSCs) samples. Larger amounts of antioxidant proteins, including GSTs and novel carbonyl detoxifying enzymes, such as aldo-keto reductase and carbonyl reductase, were detected after H₂O₂ exposure. Increased concentrations of caspase-3 and cathepsin-D proteases and components of the 26S proteasome were also detected in H-PSCs. Reduction of lamin-B and other caspase-substrate, such as filamin, in H-PSCs suggested that molecular events related to early apoptosis were also induced. We present data that describe proteins expressed in response to oxidative stress in a metazoan parasite, including novel antioxidant enzymes and targets with potential application to treatment and prevention of CHD.

Leishmanicidal therapy targeted to parasite proteases

Leishmaniasis is considered a serious public health problem and the current available therapy has several disadvantages, which makes the search for new therapeutic targets and alternative treatments extremely necessary. In this context, this review focuses on the importance of parasite proteases as target drugs against Leishmania parasites, as a chemotherapy approach. Initially, we discuss about the current scenario for the treatment of leishmaniasis, highlighting the main drugs used and the problems related to their use. Subsequently, we describe the inhibitors of major proteases of Leishmania already discovered, such as Compound s9 (aziridine-2,3-dicarboxylate), Compound 1c (benzophenone derivative), Au2Phen (gold complex), AubipyC (gold complex), MDL 28170 (dipeptidyl aldehyde), K11777, Hirudin, diazo-acetyl norleucine methyl ester, Nelfinavir, Saquinavir, Nelfinavir, Saquinavir, Indinavir, Saquinavir, GNF5343 (azabenzoxazole), GNF6702 (azabenzoxazole), Benzamidine and TPCK. Next, we discuss the importance of the protease gene to parasite survival and the aspects of the validation of proteases as target drugs, with emphasis on gene disruption. Then, we describe novel important strategies that can be used to support the research of new antiparasitic drugs, such as molecular modeling and nanotechnology, whose main targets are parasitic proteases. And finally, we discuss possible perspectives to improve drug development. Based on all findings, proteases could be considered potential targets against leishmaniasis.

Structure of ScpC, a virulence protease from Streptococcus pyogenes, reveals the functional domains and maturation mechanism

Group A Streptococcus (GAS; Streptococcus pyogenes) causes a wide range of infections, including pharyngitis, impetigo, and necrotizing fasciitis, and results in over half a million deaths annually. GAS ScpC (SpyCEP), a 180-kDa surface-exposed, subtilisin-like serine protease, acts as an essential virulence factor that helps S. pyogenes evade the innate immune response by cleaving and inactivating C-X-C chemokines. ScpC is thus a key candidate for the development of a vaccine against GAS and other pathogenic streptococcal species. Here, we report the crystal structures of full-length ScpC wild-type, the inactive mutant, and the ScpC–AEBSF inhibitor complex. We show ScpC to be a multi-domain, modular protein consisting of nine structural domains, of which the first five constitute the PR + A region required for catalytic activity. The four unique C-terminal domains of this protein are similar to collagen-binding and pilin proteins, suggesting an additional role for ScpC as an adhesin that might mediate the attachment of S. pyogenes to various host tissues. The Cat domain of ScpC is similar to subtilisin-like proteases with significant difference to dictate its specificity toward C-X-C chemokines. We further show that ScpC does not undergo structural rearrangement upon maturation. In the ScpC–inhibitor complex, the bound inhibitor breaks the hydrogen bond between active-site residues, which is essential for catalysis. Guided by our structure, we designed various epitopes and raised antibodies capable of neutralizing ScpC activity. Collectively, our results demonstrate the structure, maturation process, inhibition, and substrate recognition of GAS ScpC, and reveal the presence of functional domains at the C-terminal region.

Lopinavir, an HIV-1 peptidase inhibitor, induces alteration on the lipid metabolism of Leishmania amazonensis promastigotes

The anti-leishmania effects of HIV peptidase inhibitors (PIs) have been widely reported; however, the biochemical target and mode of action are still a matter of controversy in Leishmania parasites. Considering the possibility that HIV-PIs induce lipid accumulation in Leishmania amazonensis, we analysed the effects of lopinavir on the lipid metabolism of L. amazonensis promastigotes. To this end, parasites were treated with lopinavir at different concentrations and analysed by fluorescence microscopy and spectrofluorimetry, using a fluorescent lipophilic marker. Then, the cellular ultrastructure of treated and control parasites was analysed by transmission electron microscopy (TEM), and the lipid composition was investigated by thin-layer chromatography (TLC). Finally, the sterol content was assayed by gas chromatography-mass spectrometry (GC/MS). TEM analysis revealed an increased number of lipid inclusions in lopinavir-treated cells, which was accompanied by an increase in the lipophilic content, in a dose-dependent manner. TLC and GC-MS analysis revealed a marked increase of cholesterol-esters and cholesterol. In conclusion, lopinavir-induced lipid accumulation and affected lipid composition in L. amazonensis in a concentration-response manner. These data contribute to a better understanding of the possible mechanisms of action of this HIV-PI in L. amazonensis promastigotes. The concerted action of lopinavir on this and other cellular processes, such as the direct inhibition of an aspartyl peptidase, may be responsible for the arrested development of the parasite.

Asymmetric peptidomimetics containing L-tartaric acid core inhibit the aspartyl peptidase activity and growth of Leishmania amazonensis promastigotes

Aspartyl-type peptidases are promising chemotherapeutic targets in protozoan parasites. In the present work, we identified an aspartyl peptidase activity from the soluble extract of Leishmania amazonensis promastigotes, which cleaved the fluorogenic peptide 7-methoxycoumarin-4-acetyl-Gly-Lys-Pro-Ile-Leu-Phe-Phe-Arg-Leu-Lys(DNP)-D-Arg-amide (cathepsin D substrate) under acidic pH conditions at 37°C, showing a KM of 0.58 μM and Vmax of 129.87 fluorescence arbitrary units/s mg protein. The leishmanial aspartyl peptidase activity was blocked by pepstatin A (IC50 = 6.8 μM) and diazo-acetyl-norleucinemetilester (IC50 = 10.2 μM), two classical aspartyl peptidase inhibitors. Subsequently, the effects of 6 asymmetric peptidomimetics, containing L-tartaric acid core, were tested on both aspartyl peptidase and growth of L. amazonensis promastigotes. The peptidomimetics named 88, 154 and 158 promoted a reduction of 50% on the leishmanial aspartyl peptidase activity at concentrations ranging from 40 to 85 μM, whereas the peptidomimetic 157 was by far the most effective, presenting IC50 of 0.04 μM. Furthermore, the peptidomimetics 157 and 154 reduced the parasite proliferation in a dose-dependent manner, displaying IC50 values of 33.7 and 44.5 μM, respectively. Collectively, the peptidomimetic 157 was the most efficient compound able to arrest both aspartyl peptidase activity and leishmanial proliferation, which raises excellent perspectives regarding its use against this human pathogenic protozoan.

Identification of Tight-Binding Plasmepsin II and Falcipain 2 Inhibitors in Aqueous Extracts of Marine Invertebrates by the Combination of Enzymatic and Interaction-Based Assays

Natural products from marine origin constitute a very promising and underexplored source of interesting compounds for modern biotechnological and pharmaceutical industries. However, their evaluation is quite challenging and requires specifically designed assays to reliably identify the compounds of interest in a highly heterogeneous and interfering context. In the present study, we describe a general strategy for the confident identification of tight-binding protease inhibitors in the aqueous extracts of 62 Cuban marine invertebrates, using Plasmodium falciparum hemoglobinases Plasmepsin II and Falcipain 2 as model enzymes. To this end, we first developed a screening strategy that combined enzymatic with interaction-based assays and then validated screening conditions using five reference extracts. Interferences were evaluated and minimized. The results from the massive screening of such extracts, the validation of several hits by a variety of interaction-based assays and the purification and functional characterization of PhPI, a multifunctional and reversible tight-binding inhibitor for Plasmepsin II and Falcipain 2 from the gorgonian Plexaura homomalla, are presented.

Nelfinavir and lopinavir impair Trypanosoma cruzi trypomastigote infection in mammalian host cells and show anti-amastigote activity

There is an urgent need to implement new strategies and to search for new chemotherapeutic targets to combat Chagas' disease. In this context, repositioning of clinically approved drugs appears as a viable tool to combat this and several other neglected pathologies. An example is the use of aspartic peptidase inhibitors (PIs) currently applied in human immunodeficiency virus (HIV) treatment against different infectious agents. Therefore, the main objective of this work was to verify the effects of the HIV-PIs nelfinavir and lopinavir against Trypanosoma cruzi using in vitro models of infection. Cytotoxicity assays with LLC-MK₂ epithelial cells and RAW macrophages allowed an evaluation of the effects of HIV-PIs on the interaction between trypomastigotes and these cells as well as the survival of intracellular amastigotes. Pre-treatment of trypomastigotes with nelfinavir and lopinavir inhibited the association index with LLC-MK₂ cells and RAW macrophages in a dose- and time-dependent manner. In addition, nelfinavir and lopinavir also significantly reduced the number of intracellular amastigotes in both mammalian cell lineages, particularly when administered in daily doses. Both compounds had no effect on nitric oxide production in infected RAW macrophages. These results open the possibility for the use of HIV-PIs as a tangible alternative in the treatment of Chagas' disease. However, the main mechanism of action of nelfinavir and lopinavir has yet to be elucidated, and more studies using in vivo models must be conducted.

The genome ofStrongyloidesspp. gives insights into protein families with a putative role in nematode parasitism

Parasitic nematodes are important and abundant parasites adapted to live a parasitic lifestyle, with these adaptations all aimed at facilitating their survival and reproduction in their hosts. The recently sequenced genomes of fourStrongyloidesspecies, gastrointestinal parasites of humans and other animals, alongside transcriptomic and proteomic analysis of free-living and parasitic stages of their life cycles have revealed a number of protein families with a putative role in their parasitism. Many of these protein families have also been associated with parasitism in other parasitic nematode species, suggesting that these proteins may play a fundamental role in nematode parasitism more generally. Here, we review key protein families that have a putative role inStrongyloides’ parasitism – acetylcholinesterases, astacins, aspartic proteases, prolyl oligopeptidases, proteinase inhibitors (trypsin inhibitors and cystatins), SCP/TAPS and transthyretin-like proteins – and the evidence for their key, yet diverse, roles in the parasitic lifestyle.

Protease Inhibitors as Ad-hoc Antibiotics

Background:

Proteases are important enzymes that can degrade proteins and are found in animals, plants, bacteria, fungi and viruses. The action of proteases can be controlled by Protease Inhibitors (PIs), chemical or proteinaceous in nature that can block the active site of protease. Since the step catalyzed by proteases may play important role in life cycle of microbes, hindering the action of proteases by PIs may act as therapeutic intervention for microbial infection.

Material and Methods:

A thorough study was performed and wide range of literature was surveyed to confirm our results of PIs showing antibacterial activity.

Results:

PIs have shown to be effective drugs against bacterial pathogens, pathogenic viruses- Human Immunodeficiency Virus (HIV), Herpes virus, Hepatitis Virus. PIs have recently been investigated for controlling protozoan parasites. Clinical value of proteases and their inhibitors has been studied inHelicobacter pyloriwhich is the etiologic agent of gastritis.

Conclusion:

This review is intended to highlight the role of PIs in the Battle against Microbial Pathogens.

Parasite Cathepsin D-Like Peptidases and Their Relevance as Therapeutic Targets

Inhibition of aspartic cathepsin D-like peptidases (APDs) has been often discussed as an antiparasite intervention strategy. APDs have been considered as virulence factors of Trypanosoma cruzi and Leishmania spp., and have been demonstrated to have important roles in protein trafficking mechanisms of apicomplexan parasites. APDs also initiate blood digestion as components of multienzyme proteolytic complexes in malaria, platyhelminths, nematodes, and ticks. Increasing DNA and RNA sequencing data indicate that parasites express multiple APD isoenzymes of various functions that can now be specifically evaluated using new functional-genomic and biochemical tools, from which we can further assess the potential of APDs as targets for novel effective intervention strategies against parasitic diseases that still pose an alarming threat to mankind.

Hydroxamic acid derivatives: a promising scaffold for rational compound optimization in Chagas disease

This work describes the antitrypanocidal activity of two hydroxamic acid derivatives containing o-ethoxy (HAD1) and p-ethoxy (HAD2) as substituent in the aromatic ring linked to the isoxazoline ring. HAD1 and HAD2 induced a significant reduction in the number of intracellular parasites and consequently showed activity on the multiplication of the parasite. Treatment of cardiomyocytes and macrophages with the compounds revealed no significant loss in cell viability. Ultrastructural alterations after treatment of cardiomyocytes or macrophages infected by Trypanosoma cruzi with the IC50 value of HAD1 revealed alterations to amastigotes, showing initial damage seen as swelling of the kinetoplast. This gave a good indication of the ability of the drug to permeate through the host cell membrane as well as its selectivity to the parasite target. Both compounds HAD1 and 2 were able to reduce the cysteine peptidases and decrease the activity of metallopeptidases.

Design, synthesis and in vitro trypanocidal and leishmanicidal activities of novel semicarbazone derivatives

Trypanosomatids are protozoan parasites that cause various diseases in human, such as leishmaniasis, Chagas disease and sleeping sickness. The highly syntenic genomes of the trypanosomatid species lead the assumption that they can encode similar proteins, indicating the possibility to design new antitrypanosomatid drugs with dual trypanosomicidal and leishmanicidal activities. In this work a series of compounds (6a-h and 7a-h), containing a semicarbazone scaffold as a peptide mimetic framework, was designed and synthesized. From this series compound 7g (LASSBio-1483) highlighted, showing dual in vitro trypanosomicidal and leishmanicidal activities, with potency similar to the standard drugs nifurtimox and pentamidine. This data, taken together with its good in silico druglikeness profile and its great chemical and plasma stability, make LASSBio-1483 (7g) a new antitrypanosomatid lead-candidate.

The Dialogue of the Host-Parasite Relationship: Leishmania spp. and Trypanosoma cruzi Infection

The intracellular protozoa Leishmania spp. and Trypanosoma cruzi and the causative agents of Leishmaniasis and Chagas disease, respectively, belong to the Trypanosomatidae family. Together, these two neglected tropical diseases affect approximately 25 million people worldwide. Whether the host can control the infection or develops disease depends on the complex interaction between parasite and host. Parasite surface and secreted molecules are involved in triggering specific signaling pathways essential for parasite entry and intracellular survival. The recognition of the parasite antigens by host immune cells generates a specific immune response. Leishmania spp. and T. cruzi have a multifaceted repertoire of strategies to evade or subvert the immune system by interfering with a range of signal transduction pathways in host cells, which causes the inhibition of the protective response and contributes to their persistence in the host. The current therapeutic strategies in leishmaniasis and trypanosomiasis are very limited. Efficacy is variable, toxicity is high, and the emergence of resistance is increasingly common. In this review, we discuss the molecular basis of the host-parasite interaction of Leishmania and Trypanosoma cruzi infection and their mechanisms of subverting the immune response and how this knowledge can be used as a tool for the development of new drugs.

Anti-HIV drugs, lopinavir/ritonavir and atazanavir, modulate innate immune response triggered by Leishmania in macrophages: the role of NF-κB and PPAR-γ

This study evaluated the influence of HIV protease inhibitors lopinavir/ritonavir (LPV/RTV) and atazanavir (ATV) on macrophage functions during their first interaction with Leishmania. Macrophages from BALB/c mice treated for 10days with LPV/RTV and ATV, infected or not in vitro with L. (L.) amazonensis, were used to investigate the effects of these drugs on infection index, leishmanicidal capacity, cytokine production and PPAR-γ and RelB expression. LPV/RTV and ATV treatments significantly increased the infection index and the percentage of Leishmania-infected macrophages compared to untreated infected macrophages. There was no correlated increase in the production of NO and H2O2 leishmanicidal molecules. Promastigotes derived from Leishmania-infected macrophages from LPV/RTV and ATV-treated BALB/c mice had an in vitro growth 45.1% and 56.4% higher in groups treated with LPV/RTV and ATV than with PBS in culture. ATV treatment reduced IL-12p70 and IL-10 secretion in Leishmania-infected macrophages, but had no effect on IL-23 and TNF production. LPV reduced IL-10 and had no effect on IL-12p70, TNF and IL-23 secretion. ATV treatment decreased PPAR-γ expression in Leishmania-infected macrophages compared to untreated infected macrophages. In addition, LPV/RTV, but not ATV, reduced RelB cytoplasm-to-nucleus translocation in Leishmania-infected macrophages. Results showed that LPV/RTV and ATV HIV protease inhibitors were able to modulate innate defense mechanisms against Leishmania via different intracellular pathways. Although HIV protease inhibitors are highly efficient to control the Human Immunodeficiency Virus, these drugs might also influence the course of leishmaniasis in HIV-Leishmania-co-infected individuals.

Oral effectiveness of PMIC4, a novel hydroxyethylpiperazine analogue, in Leishmania amazonensis

Pentavalent antimonials have saved the lives of thousands of Leishmania-infected patients more than seventy years but, unfortunately, they are highly toxic and require parenteral delivery. Therefore, the search for safer and orally delivered alternative is a need. This paper describes the antileishmanial properties of PMIC4, a novel hydroxyethylpiperazine analogue. PMIC4 showed potent activity against intracellular amastigotes of Leishmania amazonensis, with IC50 of 1.8 μM and selectivity index higher than 100-fold, calculated in relation to the toxicity on the host cell. Following laboratory animal welfare policies, we analyzed the absorption, distribution, metabolism, excretion and toxicity (ADMET) properties and calculated the Lipinski's rule of five of PMIC4 before proceeding to in vivo tests. PMIC4 satisfied Lipinski's rule of five and presented high probability of human intestinal absorption, suggesting a good chance of druglikeness and oral bioavailability. For in vivo studies, PMIC4 was administered via intralesional injection (3.4 mg/kg/day, three times a week) or orally (34.0 mg/kg/day, five times a week) to L. amazonensis-infected BALB/c mice throughout the 98 day experiments. At the end of the treatment period, serum markers of toxicity were measured. When administered orally, PMIC4 controlled the lesions in L. amazonensis-infected BALB/c mice without altering serological markers of toxicity. These results demonstrate that PMIC4 is a promising molecular scaffold, orally effective against experimental leishmaniasis.

Decoding the anti-Trypanosoma cruzi action of HIV peptidase inhibitors using epimastigotes as a model

Background

Aspartic peptidase inhibitors have shown antimicrobial action against distinct microorganisms. Due to an increase in the occurrence of Chagas' disease/AIDS co-infection, we decided to explore the effects of HIV aspartic peptidase inhibitors (HIV-PIs) on Trypanosoma cruzi, the etiologic agent of Chagas' disease.

Methodology and Principal Findings

HIV-PIs presented an anti-proliferative action on epimastigotes of T. cruzi clone Dm28c, with IC₅₀ values ranging from 0.6 to 14 µM. The most effective inhibitors, ritonavir, lopinavir and nelfinavir, also had an anti-proliferative effect against different phylogenetic T. cruzi strains. The HIV-PIs induced some morphological alterations in clone Dm28c epimastigotes, as reduced cell size and swollen of the cellular body. Transmission electron microscopy revealed that the flagellar membrane, mitochondrion and reservosomes are the main targets of HIV-PIs in T. cruzi epimastigotes. Curiously, an increase in the epimastigote-into-trypomastigote differentiation process of clone Dm28c was observed, with many of these parasites presenting morphological alterations including the detachment of flagellum from the cell body. The pre-treatment with the most effective HIV-PIs drastically reduced the interaction process between epimastigotes and the invertebrate vector Rhodnius prolixus. It was also noted that HIV-PIs induced an increase in the expression of gp63-like and calpain-related molecules, and decreased the cruzipain expression in epimastigotes as judged by flow cytometry and immunoblotting assays. The hydrolysis of a cathepsin D fluorogenic substrate was inhibited by all HIV-PIs in a dose-dependent manner, showing that the aspartic peptidase could be a possible target to these drugs. Additionally, we verified that ritonavir, lopinavir and nelfinavir reduced drastically the viability of clone Dm28c trypomastigotes, causing many morphological damages.

Conclusions and Significance

The results contribute to understand the possible role of aspartic peptidases in T. cruzi physiology, adding new in vitro insights into the possibility of exploiting the use of HIV-PIs in the clinically relevant forms of the parasite.