Search Results (75)

The Apolipoprotein L1 (APOL1) innate immunity gene product represents the sole member of the APOL gene family in humans capable of secretion into circulation, thereby mediating the trypanolysis of T. brucei brucei. Gain-of-function variants of the APOL1 gene originated and spread among human population groups to extend APOL1’s protective capacity to include also serum-resistant subspecies, such as T. brucei gambiense (S342G known as APOL1-G1) and T. brucei rhodesiense (N388_Y389del known as APOL1-G2). The biochemical pathways underlying the lytic activity of these evolutionary favored mutations against bloodstream trypanosomes have been elucidated with remarkable precision. However, the intricate molecular mechanisms by which such variants confer an increased susceptibility to renal cellular injury and consequent kidney disease remain incompletely defined. In the absence of a consistent mechanistic explanation for differential kidney injury, we propose pursuing three interrelated avenues of investigation informed by prior epidemiological and mechanistic evidence linking them to APOL1’s cytotoxicity: (1) Molecular evolution of APOL1 haplotypes in human populations, (2) APOL1 splicing and consequent splice isoforms, (3) Interaction of APOL1 with other APOL gene family members, prioritizing APOL3. In the current study, we use reanalysis of population genetics datasets to resolve the haplotype contexts of all protein-altering APOL1 variants, uncovering previously unrecognized variant–haplotype couplings. We further characterize distinct cellular physiological properties among APOL1 splice isoforms, stressing the importance of isoform vB and what can be learned from isoform vC. Finally, a native interaction, and its interface, between APOL1 and APOL3 is reported, and shown to be differentially modulated by G1 and G2. We contend that continuing studies integrating these three interrelated domains will substantially advance mechanistic insights into APOL1 variant-driven renal injury, and leverage the findings to provide a more cohesive framework to guide future research. Full article

Background: Human African trypanosomiasis (HAT), caused by Trypanosoma brucei, is a neglected tropical disease with limited treatments, highlighting the pressing need for new drugs. Cell division cycle-2-related kinase 12 (CRK12), a pivotal protein involved in the cell cycle regulation of T. brucei, has emerged as a promising therapeutic target for HAT, yet effective CRK12 inhibitors remain lacking. Methods: An integrated strategy combining computational modeling, virtual screening, molecular dynamics (MD) simulations, and experimental validation was adopted to discover potential inhibitors against CRK12. By using the predicted and refined 3D structure of CRK12 from AlphaFold2 and MD simulation, over 1.5 million compounds were screened based on multiple-scale molecular docking, and 26 compounds were selected for evaluation of biological activity based on anti-T. brucei bioassays. Dose–response curves were generated for the most potent inhibitors, and the interaction mechanism between the top four compounds and CRK12 was explored by MD simulations and MM/GBSA binding free energy analysis. Results: Of the 26 compounds, six compounds demonstrated sub-micromolar to low-micromolar IC₅₀ values (0.85–3.50 µM). The top four hits, F733-0072, F733-0407, L368-0556, and L439-0038, exhibited IC₅₀ values of 1.11, 1.97, 0.85, and 1.66 µM, respectively. Binding free energy and energy decomposition analyses identified ILE335, VAL343, PHE430, ALA433, and LEU482 as hotspot residues for compound binding. Hydrogen bonding analysis demonstrated that these compounds can form stable hydrogen bonds with the hinge residue ALA433, ensuring their stable binding within the active site. Conclusions: This study establishes a robust and cost-effective pipeline for CRK12 inhibitor discovery, identifying several novel inhibitors demonstrating promising anti-HAT activity. The newly discovered scaffolds exhibit structural diversity distinct from known CRK12 inhibitors, providing valuable lead compounds for anti-trypanosomal drug development. Full article

Trypanosomes are parasitic protozoa that cause severe diseases in humans and animals. The most important species of Trypanosmes include Trypanosoma evansi and Trypanosoma brucei gambiense. The most well-known human diseases are sleeping sickness in Africa and Chagas disease in South America. The most identified animal diseases include Nagana in the African tsetse fly belt and Surra in South Asia, North Africa, and the Middle East. Surra is caused by Trypanosoma evansi. Diminazene resistance is an emerging threat caused by T. evansi infecting animals. The underlying mechanism of diminazene resistance is poorly understood. Trypanosoma brucei gambiense causes African sleeping sickness. The development of diminazene resistance in Trypanosoma brucei gambiense is associated with the alterations in the corresponding P2 adenosine transporter-1 (AT-1) gene. In the present study, by extrapolating the findings from Trypanosoma brucei gambiense, we analyzed genetic diversity in the P2 adenosine transporter-1 gene (AT-1) from T. evansi to explore a potential link between the presence of mutations in this locus and diminazene treatment in ruminants. We examined T. evansi-infected blood samples collected from goats, sheep, camels, buffalo, and cattle in seven known endemic regions of the Punjab province of Pakistan. Heterozygosity (H_e) indices indicated a high level of genetic diversity between seven T. evansi field isolates that had resistance-type mutations at codons 178E/S, 239Y/A/E, and 286S/H/I/D/T of the P2 adenosine transporter-1 (AT-1) locus. A low level of genetic diversity was observed in 19 T. evansi field isolates with susceptible-type mutations at codons A178, G181, D239, and N286 of the P2 adenosine transporter-1 (AT-1) locus. Our results on T. evansi warrant further functional studies to explore the relationship between diminazene resistance and the mutations in AT-1. Full article

Salinomycin and its derivatives display promising anti-proliferating activity against bloodstream forms of Trypanosoma brucei. The mechanism of trypanocidal action of these compounds is due to their ionophoretic activity inducing an influx of sodium cations followed by osmotic water uptake, leading to massive swelling of bloodstream-form trypanosomes. Generally, higher trypanocidal activities of salinomycin derivatives are associated with higher cell swelling activities. Although ironomycin (C20-propargylamine derivative of salinomycin) and salinomycin showed identical cell swelling activities, ironomycin was 6 times more trypanocidal than salinomycin, and the 50% growth inhibition (GI₅₀) values were 0.034 μM and 0.20 μM, respectively. However, when bloodstream-form trypanosomes were incubated with ironomycin in the presence of vitamin E and ammonium ferric citrate, the trypanocidal activity of the compound was reduced to that of salinomycin (GI₅₀ = 0.21 μM vs. GI₅₀ = 0.20 μM). In addition, vitamin E was found to decrease the trypanocidal activity of ironomycin much more than ammonium ferric citrate (GI₅₀ = 0.18 μM vs. GI₅₀ = 0.042 μM). Moreover, ironomycin caused a reduction in the uptake of the iron-carrier protein transferrin mediated by a downregulation of the transferrin receptor and led to the accumulation and sequestering of iron(II) in the parasite’s lysosome, triggering an increase production of reactive oxygen species (ROS). These results suggest that the increased trypanocidal activity of ironomycin can be mainly attributed to an increased ROS production and, to a lesser extent, an impairment in iron uptake. Full article

Apolipoprotein-L1 (APOL1) is a membrane-interacting protein induced by inflammation, which confers human resistance to infection by African trypanosomes. APOL1 kills Trypanosoma brucei through induction of apoptotic-like parasite death, but two T. brucei clones acquired resistance to APOL1, allowing them to cause sleeping sickness. An APOL1 C-terminal sequence alteration, such as occurs in natural West African variants G1 and G2, restored human resistance to these clones. However, APOL1 unfolding induced by G1 or G2 mutations enhances protein hydrophobicity, resulting in kidney podocyte dysfunctions affecting renal filtration. The mechanism involved in these dysfunctions is debated. The ability of APOL1 to generate ion pores in trypanosome intracellular membranes or in synthetic membranes was provided as an explanation. However, transmembrane insertion of APOL1 strictly depends on acidic conditions, and podocyte cytopathology mainly results from secreted APOL1 activity on the plasma membrane, which occurs under non-acidic conditions. In this review, I argue that besides inactivation of APOL3 functions in membrane dynamics (fission and fusion), APOL1 variants induce inflammation-linked podocyte toxicity not through pore formation, but through plasma membrane disturbance resulting from increased interaction with cholesterol, which enhances cation channels activity. A natural mutation in the membrane-interacting domain (N264K) abrogates variant APOL1 toxicity at the expense of slightly increased sensitivity to trypanosomes, further illustrating the continuous mutual adaptation between host and parasite. Full article

2,6-Diaryl-4H-tetrahydro-thiopyran-4-ones and corresponding sulfoxide and sulfone derivatives were designed to lower the major toxicity of their parent anti-kinetoplatidal diarylideneacetones through a prodrug effect. Novel diastereoselective methodologies were developed and generalized from diarylideneacetones and 2,6-diaryl-4H-tetrahydro-thiopyran-4-ones to allow the introduction of a wide substitution profile and to prepare the related S-oxides. The in vitro biological activity and selectivity of diarylideneacetones, 2,6-diaryl-4H-tetrahydro-thiopyran-4-ones, and their S-sulfoxide and sulfone metabolites were evaluated against Trypanosoma brucei brucei, Trypanosoma cruzi, and various Leishmania species in comparison with their cytotoxicity against human fibroblasts hMRC-5. The data revealed that the sulfides, sulfoxides, and sulfones, in which the Michael acceptor sites are temporarily masked, are less toxic against mammal cells while the anti-trypanosomal potency was maintained against T. b. brucei, T. cruzi, L. infantum, and L. donovani, thus confirming the validity of the prodrug strategy. The mechanism of action is proposed to be due to the involvement of diarylideneacetones in cascades of redox reactions involving the trypanothione system. After Michael addition of the dithiol to the double bonds, resulting in an elongated polymer, the latter—upon S-oxidation, followed by syn-eliminations—fragments, under continuous release of reactive oxygen species and sulfenic/sulfonic species, causing the death of the trypanosomal parasites in the micromolar or submicromolar range with high selectivity indexes. Full article

Although located at the chromosome end, telomeres are an essential chromosome component that helps maintain genome integrity and chromosome stability from protozoa to mammals. The role of telomere proteins in chromosome end protection is conserved, where they suppress various DNA damage response machineries and block nucleolytic degradation of the natural chromosome ends, although the detailed underlying mechanisms are not identical. In addition, the specialized telomere structure exerts a repressive epigenetic effect on expression of genes located at subtelomeres in a number of eukaryotic organisms. This so-called telomeric silencing also affects virulence of a number of microbial pathogens that undergo antigenic variation/phenotypic switching. Telomere proteins, particularly the RAP1 homologs, have been shown to be a key player for telomeric silencing. RAP1 homologs also suppress the expression of Telomere Repeat-containing RNA (TERRA), which is linked to their roles in telomere stability maintenance. The functions of RAP1s in suppressing telomere recombination are largely conserved from kinetoplastids to mammals. However, the underlying mechanisms of RAP1-mediated telomeric silencing have many species-specific features. In this review, I will focus on Trypanosoma brucei RAP1’s functions in suppressing telomeric/subtelomeric DNA recombination and in the regulation of monoallelic expression of subtelomere-located major surface antigen genes. Common and unique mechanisms will be compared among RAP1 homologs, and their implications will be discussed. Full article

Glucose metabolism is critical for the African trypanosome, Trypanosoma brucei, serving as the lone source of ATP production for the bloodstream form (BSF) parasite in the glucose-rich environment of the host blood. Recently, phosphonate inhibitors of human enolase (ENO), the enzyme responsible for the interconversion of 2-phosphoglycerate (2-PG) to phosphoenolpyruvate (PEP) in glycolysis or PEP to 2-PG in gluconeogenesis, have been developed for the treatment of glioblastoma multiforme (GBM). Here, we have tested these agents against T. brucei ENO (TbENO) and found the compounds to be potent enzyme inhibitors and trypanocides. For example, (1-hydroxy-2-oxopyrrolidin-3-yl) phosphonic acid (deoxy-SF2312) was a potent enzyme inhibitor (IC₅₀ value of 0.60 ± 0.23 µM), while a six-membered ring-bearing phosphonate, (1-hydroxy-2-oxopiperidin-3-yl) phosphonic acid (HEX), was less potent (IC₅₀ value of 2.1 ± 1.1 µM). An analog with a larger seven-membered ring, (1-hydroxy-2-oxoazepan-3-yl) phosphonic acid (HEPTA), was not active. Molecular docking simulations revealed that deoxy-SF2312 and HEX had binding affinities of −6.8 and −7.5 kcal/mol, respectively, while the larger HEPTA did not bind as well, with a binding of affinity of −4.8 kcal/mol. None of these compounds were toxic to BSF parasites; however, modification of enzyme-active phosphonates through the addition of pivaloyloxymethyl (POM) groups improved activity against T. brucei, with POM-modified (1,5-dihydroxy-2-oxopyrrolidin-3-yl) phosphonic acid (POMSF) and POMHEX having EC₅₀ values of 0.45 ± 0.10 and 0.61 ± 0.08 µM, respectively. These findings suggest that HEX is a promising lead against T. brucei and that further development of prodrug HEX analogs is warranted. Full article

Curcumin (CUR) is known for its wide folkloric effects on various infections; however, its solubility status has remained a hindrance to its bioavailability in the host. This study evaluated the comparative effects of CUR and CUR-nanoparticle in vitro on T. congolense, T. b. brucei, and T. evansi. Additionally, CUR and CUR-nanoparticle anti-Trypanosoma efficacy were assessed in vivo against T. congolense. All the CUR-nanoparticles were two folds more effective on the T. congolense as compared to CUR in vitro, with recorded efficacy of 3.67 ± 0.31; 7.61 ± 1.22; and 6.40 ± 3.07 μM, while the CUR-nanoparticles efficacy was 1.56 ± 0.50; 28.16 ± 9.43 and 13.12 ± 0.13 μM on T. congolense, T. b. brucei, and T. evansi, respectively. Both CUR and CUR-nanoparticles displayed moderate efficacy orally. The efficacy of CUR and CUR-nanoparticles in vivo was influenced by solubility, presence of food, and treatment period. CUR-treated mice were not cured of the infection; however, the survival rate of the orally treated mice was significantly prolonged as compared with intraperitoneal-treated mice. CUR-nanoparticles resulted in significant suppression of parasitemia even though relapsed was observed. In conclusion, CUR and CUR-nanoparticles possess moderate efficacy orally on the trypanosomes as compared to the intraperitoneal treatment. Full article

Human African trypanosomiasis is a neglected tropical disease caused by the extracellular protozoan parasite Trypanosoma brucei, and targeted for eradication by 2030. The COVID-19 pandemic contributed to the lengthening of the proposed time frame for eliminating human African trypanosomiasis as control programs were interrupted. Armed with extensive antigenic variation and the depletion of the B cell population during an infectious cycle, attempts to develop a vaccine have remained unachievable. With the absence of a vaccine, control of the disease has relied heavily on intensive screening measures and the use of drugs. The chemotherapeutics previously available for disease management were plagued by issues such as toxicity, resistance, and difficulty in administration. The approval of the latest and first oral drug, fexinidazole, is a major chemotherapeutic achievement for the treatment of human African trypanosomiasis in the past few decades. Timely and accurate diagnosis is essential for effective treatment, while poor compliance and resistance remain outstanding challenges. Drug discovery is on-going, and herein we review the recent advances in anti-trypanosomal drug discovery, including novel potential drug targets. The numerous challenges associated with disease eradication will also be addressed. Full article

Human African Trypanosomiasis (HAT) is still endemic in the Republic of Congo. Although the incidence of cases has significantly decreased over years, the disease still persists in some active foci. Factors contributing to the maintenance of the disease such as the existence of an animal reservoir or population knowledge are still not well known. It is in this context that a study focusing on the knowledge and practices of the population with regard to HAT as well as on the prevalence of trypanosomes infecting animals was undertaken in three active HAT foci in the Republic of Congo. The study was performed using field surveys conducted from November 2019 to June 2021. Domestic animal blood was examined by microscopy and PCR to detect the presence of trypanosomes. A structured questionnaire was administered to the population to assess their knowledge and practices concerning HAT in these endemic foci. More than half of the animals examined were found to be infected with trypanosomes (51.22%). The main trypanosome species infecting animals were Trypanosoma congolense savannah (67.2%) and Trypanosoma brucei (s.l.) (32.8%). No trypanosomes infecting humans were detected. Concerning household surveys, more than half of the respondents (52.9%) were fully aware of the mode of transmission and symptoms of the disease. The majority of people preferred to wear clothes covering the whole body and to use locally made soap as repellents to protect themselves from tsetse fly bites. This study suggests frequent circulation of animal trypanosomes in domestic animals and the use of personal measures to protect against tsetse fly bites. Updating information on the HAT animal reservoir and population knowledge alongside regular monitoring of the tsetse fly populations and the use of traps to control tsetse flies are crucial to drive efforts towards the elimination of gHAT in the Republic of Congo. Full article

Flaviviridae infections, such as those caused by hepatitis C (HCV) and dengue viruses (DENVs), represent global health risks. Infected people are in danger of developing chronic liver failure or hemorrhagic fever, both of which can be fatal if not treated. The tropical parasites Trypanosoma brucei and Trypanosoma cruzi cause enormous socioeconomic burdens in Sub-Saharan Africa and Latin America. Anti-HCV chemotherapy has severe adverse effects and is expensive, whereas dengue has no clinically authorized treatment. Antiparasitic medicines are often toxic and difficult to administer, and treatment failures are widely reported. There is an urgent need for new chemotherapies. Based on our previous research, we have undertaken structural modification of lead compound V with the goal of producing derivatives with both antiviral and trypanocidal activity. The novel spirocarbocyclic-substituted hydantoin analogs were designed, synthesized, and tested for antiviral activity against three HCV genotypes (1b, 3a, 4a), DENV, yellow fever virus (YFV), and two trypanosome species (T. brucei, T. cruzi). The optimization was successful and led to compounds with significant antiviral and trypanocidal activity and exceptional selectivity. Several modifications were made to further investigate the structure–activity relationships (SARs) and confirm the critical role of lipophilicity and conformational degrees of freedom. Full article

Rhodesain is the main cysteine protease of Trypanosoma brucei rhodesiense, the parasite causing the acute lethal form of Human African Trypanosomiasis. Starting from the dipeptide nitrile CD24, the further introduction of a fluorine atom in the meta position of the phenyl ring spanning in the P3 site and the switch of the P2 leucine with a phenylalanine led to CD34, a synthetic inhibitor that shows a nanomolar binding affinity towards rhodesain (K_i = 27 nM) and an improved target selectivity with respect to the parent dipeptide nitrile CD24. In the present work, following the Chou and Talalay method, we carried out a combination study of CD34 with curcumin, a nutraceutical obtained from Curcuma longa L. Starting from an affected fraction (f_a) of rhodesain inhibition of 0.5 (i.e., the IC₅₀), we observed an initial moderate synergistic action, which became a synergism for f_a values ranging from 0.6 to 0.7 (i.e., 60–70% inhibition of the trypanosomal protease). Interestingly, at 80–90% inhibition of rhodesain proteolytic activity, we observed a strong synergism, resulting in 100% enzyme inhibition. Overall, in addition to the improved target selectivity of CD34 with respect to CD24, the combination of CD34 + curcumin resulted in an increased synergistic action with respect to CD24 + curcumin, thus suggesting that it is desirable to use CD34 and curcumin in combination. Full article

Trypanosomiasis is a serious disease that affects both humans and animals, causing social and economic losses. Efforts to find new therapeutic approaches are warranted to improve treatment options. Therefore, the purpose of this communication includes the phytochemical screening of a methanolic extract of Garcinia kola nuts and the in vivo evaluation of its biological activity against rats infected with Trypanosoma brucei brucei and treated with 4 different concentrations of the extract (0.01, 0.1, 1, and 10 mg/kg). Treatment with suramin served as a positive control, while the negative control received no drug. Since the general toxicity of the extract could be ruled out, efficacy was evaluated based on physiological changes, such as induction of trypanosome parasitemia, influence on body temperature, and body weight. Survival was assessed during this study. Physical parameters, behavioral characteristics, and various hematological indices were also monitored. Based on the (patho)physiological and behavioral parameters (e.g., no parasitemia, no increase in body temperature, an increase in body weight, no loss of condition, no alopecia, and no gangrene), the efficacy of the extract was evident, which was also confirmed by 100% survival, while in the negative control, all rats died during the observation period. Since overall very similar results were obtained as a result of treatment with the established suramin, the in vivo antitrypanosomal activity of a methanolic extract of G. kola nuts on rats can be demonstrated in this communication. This opens the way, for example, for further development of drug formulations based on this methanolic extract. Full article

Trypanosomiases are a group of tropical diseases that have devastating health and socio-economic effects worldwide. In humans, these diseases are caused by the pathogenic kinetoplastids Trypanosoma brucei, causing African trypanosomiasis or sleeping sickness, and Trypanosoma cruzi, causing American trypanosomiasis or Chagas disease. Currently, these diseases lack effective treatment. This is attributed to the high toxicity and limited trypanocidal activity of registered drugs, as well as resistance development and difficulties in their administration. All this has prompted the search for new compounds that can serve as the basis for the development of treatment of these diseases. Antimicrobial peptides (AMPs) are small peptides synthesized by both prokaryotes and (unicellular and multicellular) eukaryotes, where they fulfill functions related to competition strategy with other organisms and immune defense. These AMPs can bind and induce perturbation in cell membranes, leading to permeation of molecules, alteration of morphology, disruption of cellular homeostasis, and activation of cell death. These peptides have activity against various pathogenic microorganisms, including parasitic protists. Therefore, they are being considered for new therapeutic strategies to treat some parasitic diseases. In this review, we analyze AMPs as therapeutic alternatives for the treatment of trypanosomiases, emphasizing their possible application as possible candidates for the development of future natural anti-trypanosome drugs. Full article