Histone deacetylases inhibitors as new potential drugs against Leishmania braziliensis, the main causative agent of new world tegumentary leishmaniasis

Metalloenzyme Inhibitors against Zoonotic Infections: Focus on Leishmania and Schistosoma

The term "zoonosis" denotes diseases transmissible among vertebrate animals and humans. These diseases constitute a significant public health challenge, comprising 61% of human pathogens and causing an estimated 2.7 million deaths annually. Zoonoses not only affect human health but also impact animal welfare and economic stability, particularly in low- and middle-income nations. Leishmaniasis and schistosomiasis are two important neglected tropical diseases with a high prevalence in tropical and subtropical areas, imposing significant burdens on affected regions. Schistosomiasis, particularly rampant in sub-Saharan Africa, lacks alternative treatments to praziquantel, prompting concerns regarding parasite resistance. Similarly, leishmaniasis poses challenges with unsatisfactory treatments, urging the development of novel therapeutic strategies. Effective prevention demands a One Health approach, integrating diverse disciplines to enhance diagnostics and develop safer drugs. Metalloenzymes, involved in parasite biology and critical in different biological pathways, emerged in the last few years as useful drug targets for the treatment of human diseases. Herein we have reviewed recent reports on the discovery of inhibitors of metalloenzymes associated with zoonotic diseases like histone deacetylases (HDACs), carbonic anhydrase (CA), arginase, and heme-dependent enzymes.

Exploring host epigenetic enzymes as targeted therapies for visceral leishmaniasis: in silico design and in vitro efficacy of KDM6B and ASH1L inhibitors

In order to combat various infectious diseases, the utilization of host-directed therapies as an alternative to chemotherapy has gained a lot of attention in the recent past, since it bypasses the existing limitations of conventional therapies. The use of host epigenetic enzymes like histone lysine methyltransferases and lysine demethylases as potential drug targets has successfully been employed for controlling various inflammatory diseases like rheumatoid arthritis and acute leukemia. In our earlier study, we have already shown that the functional knockdown of KDM6B and ASH1L in the experimental model of visceral leishmaniasis has resulted in a significant reduction of organ parasite burden. Herein, we performed a high throughput virtual screening against KDM6B and ASH1L using > 53,000 compounds that were obtained from the Maybridge library and PubChem Database, followed by molecular docking to evaluate their docking score/Glide Gscore. Based on their docking scores, the selected inhibitors were later assessed for their in vitro anti-leishmanial efficacy. Out of all inhibitors designed against KDM6B and ASH1L, HTS09796, GSK-J4 and AS-99 particularly showed promising in vitro activity with IC50 < 5 µM against both extracellular promastigote and intracellular amastigote forms of L. donovani. In vitro drug interaction studies of these inhibitors further demonstrated their synergistic interaction with amphotericin-B and miltefosine. However, GSK-J4 makes an exception by displaying an in different mode of interaction with miltefosine. Collectively, our in silico and in vitro studies acted as a platform to identify the applicability of these inhibitors targeted against KDM6B and ASH1L for anti-leishmanial therapy.

Drug Discovery for Cutaneous Leishmaniasis: A Review of Developments in the Past 15 Years

Leishmaniasis is a group of vector-borne, parasitic diseases caused by over 20 species of the protozoan Leishmania spp. The three major disease classifications, cutaneous, visceral, and mucocutaneous, have a range of clinical manifestations from self-healing skin lesions to hepatosplenomegaly and mucosal membrane damage to fatality. As a neglected tropical disease, leishmaniasis represents a major international health challenge, with nearly 350 million people living at risk of infection a year. The current chemotherapeutics used to treat leishmaniasis have harsh side effects, prolonged and costly treatment regimens, as well as emerging drug resistance, and are predominantly used for the treatment of visceral leishmaniasis. There is an undeniable need for the identification and development of novel chemotherapeutics targeting cutaneous leishmaniasis (CL), largely ignored by concerted drug development efforts. CL is mostly non-lethal and the most common presentation of this disease, with nearly 1 million new cases reported annually. Recognizing this unaddressed need, substantial yet fragmented progress in early drug discovery efforts for CL has occurred in the past 15 years and was outlined in this review. However, further work needs to be carried out to advance early discovery candidates towards the clinic. Importantly, there is a paucity of investment in the translation and development of therapies for CL, limiting the emergence of viable solutions to deal with this serious and complex international health problem.

Meroterpenoids from Gongolaria abies-marina against Kinetoplastids: In Vitro Activity and Programmed Cell Death Study

Leishmaniasis and Chagas disease affect millions of people worldwide. The available treatments against these parasitic diseases are limited and display multiple undesired effects. The brown alga belonging to the genus Gongolaria has been previously reported as a source of compounds with different biological activities. In a recent study from our group, Gongolaria abies-marine was proven to present antiamebic activity. Hence, this brown alga could be a promising source of interesting molecules for the development of new antiprotozoal drugs. In this study, four meroterpenoids were isolated and purified from a dichloromethane/ethyl acetate crude extract through a bioguided fractionation process targeting kinetoplastids. Moreover, the in vitro activity and toxicity were evaluated, and the induction of programmed cell death was checked in the most active and less toxic compounds, namely gongolarone B (2), 6Z-1'-methoxyamentadione (3) and 1'-methoxyamentadione (4). These meroterpenoids triggered mitochondrial malfunction, oxidative stress, chromatin condensation and alterations of the tubulin network. Furthermore, a transmission electron microscopy (TEM) image analysis showed that meroterpenoids (2-4) induced the formation of autophagy vacuoles and ER and Golgi complex disorganization. The obtained results demonstrated that the mechanisms of action at the cellular level of these compounds were able to induce autophagy as well as an apoptosis-like process in the treated parasites.

In vitro evaluation of Resveratrol as a potential pre-exposure prophylactic drug against Trypanosoma cruzi infection

Chagas' disease or American trypanosomiasis, caused by Trypanosoma cruzi infection, is an endemic disease in Latin America, which has spread worldwide in the past years. The drugs presently used for treatment have shown limited efficacy due to the appearance of resistant parasites and severe side effects. Some of the most recent studies on anti-parasitic drugs have been focused on protein acetylation, a reversible reaction modulated by Acetyl Transferases (KATs) and Deacetylases (KDACs). We have previously reported the anti-parasite activity of resveratrol (RSV), an activator of KDACs type III (or sirtuins), and showed that this drug can reduce the growth of T. cruzi epimastigotes and the infectivity of trypomastigotes. Since RSV is now widely used in humans due to its beneficial effects as an antioxidant, it has become an attractive candidate as a repurposing drug. In this context, the aim of the present study was to evaluate the ability of this drug to protect three different types of host cells from parasite infection. RSV treatment before parasite infection reduced the percentage of infected cells by 50-70% depending on the cell type. Although the mammalian cell lines tested showed different sensitivity to RSV, apoptosis was not significantly affected, showing that RSV was able to protect cells from infection without the activation of this process. Since autophagy has been described as a key process in parasite invasion, we also monitored this process on host cells pretreated with RSV. The results showed that, at the concentrations and incubation times tested, autophagy was not induced in any of the cell types evaluated. Our results show a partial protective effect of RSV in vitro, which justifies extending studies to an in vivo model to elucidate the mechanism by which this effect occurs.

The repositioned drugs disulfiram/diethyldithiocarbamate combined to benznidazole: Searching for Chagas disease selective therapy, preventing toxicity and drug resistance

Chagas disease (CD) affects at least 6 million people in 21 South American countries besides several thousand in other nations all over the world. It is estimated that at least 14,000 people die every year of CD. Since vaccines are not available, chemotherapy remains of pivotal relevance. About 30% of the treated patients cannot complete the therapy because of severe adverse reactions. Thus, the search for novel drugs is required. Here we tested the benznidazole (BZ) combination with the repositioned drug disulfiram (DSF) and its derivative diethyldithiocarbamate (DETC) upon Trypanosoma cruzi in vitro and in vivo. DETC-BZ combination was synergistic diminishing epimastigote proliferation and enhancing selective indexes up to over 10-fold. DETC was effective upon amastigotes of the BZ- partially resistant Y and the BZ-resistant Colombiana strains. The combination reduced proliferation even using low concentrations (e.g., 2.5 µM). Scanning electron microscopy revealed membrane discontinuities and cell body volume reduction. Transmission electron microscopy revealed remarkable enlargement of endoplasmic reticulum cisternae besides, dilated mitochondria with decreased electron density and disorganized kinetoplast DNA. At advanced stages, the cytoplasm vacuolation apparently impaired compartmentation. The fluorescent probe H2-DCFDA indicates the increased production of reactive oxygen species associated with enhanced lipid peroxidation in parasites incubated with DETC. The biochemical measurement indicates the downmodulation of thiol expression. DETC inhibited superoxide dismutase activity on parasites was more pronounced than in infected mice. In order to approach the DETC effects on intracellular infection, peritoneal macrophages were infected with Colombiana trypomastigotes. DETC addition diminished parasite numbers and the DETC-BZ combination was effective, despite the low concentrations used. In the murine infection, the combination significantly enhanced animal survival, decreasing parasitemia over BZ. Histopathology revealed that low doses of BZ-treated animals presented myocardial amastigote, not observed in combination-treated animals. The picrosirius collagen staining showed reduced myocardial fibrosis. Aminotransferase de aspartate, Aminotransferase de alanine, Creatine kinase, and urea plasma levels demonstrated that the combination was non-toxic. As DSF and DETC can reduce the toxicity of other drugs and resistance phenotypes, such a combination may be safe and effective.

Histone Deacetylase (HDAC) Inhibitors for the Treatment of Schistosomiasis

Schistosomiasis is a major neglected parasitic disease that affects more than 240 million people worldwide and for which the control strategy consists of mass treatment with the only available drug, praziquantel. Schistosomes display morphologically distinct stages during their life cycle and the transformations between stages are controlled by epigenetic mechanisms. The targeting of epigenetic actors might therefore represent the parasites’ Achilles’ heel. Specifically, histone deacetylases have been recently characterized as drug targets for the treatment of schistosomiasis. This review focuses on the recent development of inhibitors for schistosome histone deacetylases. In particular, advances in the development of inhibitors of Schistosoma mansoni histone deacetylase 8 have indicated that targeting this enzyme is a promising approach for the treatment of this infection.

Combining histone deacetylase inhibitors (HDACis) with other therapies for cancer therapy

Histone deacetylases (HDACs) play an important role in regulating the expression of genes involved in tumorigenesis and tumor maintenance, and hence they have been considered as key targets in cancer therapy. As a novel category of antitumor agents, histone deacetylase inhibitors (HDACis) can induce cell cycle arrest, apoptosis, and differentiation in cancer cells, ultimately combating cancer. Although in the United States, the use of HDACis for the treatment of certain cancers has been approved, the therapeutic efficacy of HDACis as a single therapeutic agent in solid tumorshas been unsatisfactory and drug resistance may yet occur. To enhance therapeutic efficacy and limit drug resistance, numerous combination therapies involving HDACis in synergy with other antitumor therapies have been studied. In this review, we describe the classification of HDACs. Moreover, we summarize the antitumor mechanism of the HDACis for targeting key cellular processes of cancers (cell cycle, apoptosis, angiogenesis, DNA repair, and immune response). In addition, we outline the major developments of other antitumor therapies in combination with HDACis, including chemotherapy, radiotherapy, phototherapy, targeted therapy, and immunotherapy. Finally, we discuss the current state and challenges of HDACis-drugs combinations in future clinical studies, with the aim of optimizing the antitumor effect of such combinations.

Annatto Oil Loaded Nanostructured Lipid Carriers: A Potential New Treatment for Cutaneous Leishmaniasis

Annatto (Bixa orellana L.) is extensively used as food pigment worldwide. Recently, several studies have found it to have healing and antioxidant properties, as well as effective action against leishmaniasis. Therefore, the purpose of this study was to incorporate the oil obtained from annatto seeds into a nanostructured lipid carrier (NLC) and evaluate its physicochemical properties and biological activity against Leishmania major. Nanoparticles were prepared by the fusion-emulsification and ultrasonication method, with the components Synperonic™ PE (PL) as the surfactant, cetyl palmitate (CP) or myristyl myristate (MM) as solid lipids, annatto oil (AO) (2% and 4%, w/w) as liquid lipid and active ingredient, and ultra-pure water. Physicochemical and biological characterizations were carried out to describe the NLCs, including particle size, polydispersity index (PDI), and zeta potential (ZP) by dynamic light scattering (DLS), encapsulation efficiency (EE%), thermal behavior, X-ray diffraction (XRD), transmission electron microscopy (TEM), Electron Paramagnetic Resonance (EPR), cytotoxicity on BALB/c 3T3 fibroblasts and immortalized human keratinocyte cells, and anti-leishmaniasis activity in vitro. Nanoparticles presented an average diameter of ~200 nm (confirmed by TEM results), a PDI of less than 0.30, ZP between -12.6 and -31.2 mV, and more than 50% of AO encapsulated in NLCs. Thermal analyses demonstrated that the systems were stable at high temperatures with a decrease in crystalline structure due to the presence of AOs (confirmed by XRD). In vitro, the anti-leishmania test displayed good activity in encapsulating AO against L. major. The results indicate that the oily fraction of Bixa orellana L. in NLC systems should be evaluated as a potential therapeutic agent against leishmaniasis.