Structure of the Ebola virus polymerase complex.

Filoviruses, including Ebola virus, pose an increasing threat to the public health. Although two therapeutic monoclonal antibodies have been approved to treat the Ebola virus disease1,2, there are no approved broadly reactive drugs to control diverse filovirus infection. Filovirus has a large polymerase (L) protein and the cofactor viral protein 35 (VP35), which constitute the basic functional unit responsible for virus genome RNA synthesis3. Owing to its conservation, the L-VP35 polymerase complex is a promising target for broadly reactive antiviral drugs. Here we determined the structure of Ebola virus L protein in complex with tetrameric VP35 using cryo-electron microscopy (state 1). Structural analysis revealed that Ebola virus L possesses a filovirus-specific insertion element that is essential for RNA synthesis, and that VP35 interacts extensively with the N-terminal region of L by three protomers of the VP35 tetramer. Notably, we captured the complex structure in a second conformation with the unambiguous priming loop and supporting helix away from polymerase active site (state 2). Moreover, we demonstrated that the century-old drug suramin could inhibit the activity of the Ebola virus polymerase in an enzymatic assay. The structure of the L-VP35-suramin complex reveals that suramin can bind at the highly conserved NTP entry channel to prevent substrates from entering the active site. These findings reveal the mechanism of Ebola virus replication and may guide the development of more powerful anti-filovirus drugs.

First comprehensive untargeted metabolomics study of suramin-treated Trypanosoma brucei: an integrated data analysis workflow from multifactor data modelling to functional analysis.

INTRODUCTION: Human African trypanosomiasis, commonly known as sleeping sickness, is a vector-borne parasitic disease prevalent in sub-Saharan Africa and transmitted by the tsetse fly. Suramin, a medication with a long history of clinical use, has demonstrated varied modes of action against Trypanosoma brucei. This study employs a comprehensive workflow to investigate the metabolic effects of suramin on T. brucei, utilizing a multimodal metabolomics approach. OBJECTIVES: The primary aim of this study is to comprehensively analyze the metabolic impact of suramin on T. brucei using a combined liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance spectroscopy (NMR) approach. Statistical analyses, encompassing multivariate analysis and pathway enrichment analysis, are applied to elucidate significant variations and metabolic changes resulting from suramin treatment. METHODS: A detailed methodology involving the integration of high-resolution data from LC-MS and NMR techniques is presented. The study conducts a thorough analysis of metabolite profiles in both suramin-treated and control T. brucei brucei samples. Statistical techniques, including ANOVA-simultaneous component analysis (ASCA), principal component analysis (PCA), ANOVA 2 analysis, and bootstrap tests, are employed to discern the effects of suramin treatment on the metabolomics outcomes. RESULTS: Our investigation reveals substantial differences in metabolic profiles between the control and suramin-treated groups. ASCA and PCA analysis confirm distinct separation between these groups in both MS-negative and NMR analyses. Furthermore, ANOVA 2 analysis and bootstrap tests confirmed the significance of treatment, time, and interaction effects on the metabolomics outcomes. Functional analysis of the data from LC-MS highlighted the impact of treatment on amino-acid, and amino-sugar and nucleotide-sugar metabolism, while time effects were observed on carbon intermediary metabolism (notably glycolysis and di- and tricarboxylic acids of the succinate production pathway and tricarboxylic acid (TCA) cycle). CONCLUSION: Through the integration of LC-MS and NMR techniques coupled with advanced statistical analyses, this study identifies distinctive metabolic signatures and pathways associated with suramin treatment in T. brucei. These findings contribute to a deeper understanding of the pharmacological impact of suramin and have the potential to inform the development of more efficacious therapeutic strategies against African trypanosomiasis.

Suramin analogues protect cartilage against osteoarthritic breakdown by increasing levels of tissue inhibitor of metalloproteinases 3 (TIMP-3) in the tissue.

Osteoarthritis is a chronic degenerative joint disease affecting millions of people worldwide, with no disease-modifying drugs currently available to treat the disease. Tissue inhibitor of metalloproteinases 3 (TIMP-3) is a potential therapeutic target in osteoarthritis because of its ability to inhibit the catabolic metalloproteinases that drive joint damage by degrading the cartilage extracellular matrix. We previously found that suramin inhibits cartilage degradation through its ability to block endocytosis and intracellular degradation of TIMP-3 by low-density lipoprotein receptor-related protein 1 (LRP1), and analysis of commercially available suramin analogues indicated the importance of the 1,3,5-trisulfonic acid substitutions on the terminal naphthalene rings for this activity. Here we describe synthesis and structure-activity relationship analysis of additional suramin analogues using ex vivo models of TIMP-3 trafficking and cartilage degradation. This showed that 1,3,6-trisulfonic acid substitution of the terminal naphthalene rings was also effective, and that the protective activity of suramin analogues depended on the presence of a rigid phenyl-containing central region, with para/para substitution of these phenyl rings being most favourable. Truncated analogues lost protective activity. The physicochemical characteristics of suramin and its analogues indicate that approaches such as intra-articular injection would be required to develop them for therapeutic use.

100 years since the publication of the suramin formula.

Suramin was the first drug developed using the approach of medicinal chemistry by the German Bayer company in the 1910s for the treatment of human African sleeping sickness caused by the two subspecies Trypanosoma brucei gambiense and Trypanosoma brucei rhodesienese. However, the drug was politically instrumentalized by the German government in the 1920s in an attempt to regain possession of its former African colonies lost after the First World War. For this reason, the formula of suramin was kept secret for more than 10 years. Eventually, the French pharmacist Ernest Fourneau uncovered the chemical structure of suramin by reverse engineering and published the formula of the drug in 1924. During the Nazi period, suramin became the subject of colonial revisionism, and the development of the drug was portrayed in books and films to promote national socialist propaganda. Ever since its discovery, suramin has also been tested for bioactivity against numerous other infections and diseases. However, sleeping sickness caused by Trypanosoma brucei rhodesiense is the only human disease for which treatment with suramin is currently approved.

Effects of Suramin on Polycystic Kidney Disease in a Mouse Model of Polycystin-1 Deficiency.

The aberrant activation of the purinergic signaling pathway has been shown to promote cyst growth and fluid secretion in autosomal dominant polycystic kidney disease (ADPKD). Suramin is an anti-parasitic drug that has strong anti-purinergic properties. Whether suramin could have a therapeutic effect on ADPKD has not been fully investigated. We examined the effect of suramin on cyst progression in a Pkd1 microRNAs transgenic mouse model that presented stable Pkd1 knockdown and moderate disease progression. The Pkd1-deficient mice were treated with suramin (60 mg/kg) by intraperitoneal injection twice a week from postnatal days 35 to 90. Kidney-to-body weight ratios, cyst indices, and blood urea nitrogen (BUN) levels were measured. Cell proliferation and macrophage infiltration were determined by immunohistochemistry. The suramin-treated group had significantly lower renal cyst densities, cell proliferation, and macrophage infiltration compared with saline-treated controls. Suramin significantly inhibited ERK phosphorylation and the expression of Il1b, Il6, Nlrp3, Tgfb, Fn1, P2rx7, and P2ry2 mRNAs in the kidneys. However, BUN levels remained high despite the reduction in cyst growth. Furthermore, plasma cystatin C and neutrophil gelatinase-associated lipocalin (NGAL) levels were significantly higher in the suramin-treated group compared with the control group. Periodic acid-Schiff staining revealed degenerative changes and epithelial cell vacuolation in the non-cystic renal tubules, which indicated phospholipidosis following suramin treatment. These results suggest that suramin may reduce renal cyst growth and inflammation, but the associated tubular cell injuries could limit its therapeutic potential. Other purinergic receptor antagonists with less nephrotoxicity may deserve further investigation for the treatment of ADPKD.

Profiles of urine and blood metabolomics in autism spectrum disorders.

Early diagnosis and treatment for autism spectrum disorder (ASD) pose challenges. The current diagnostic approach for ASD is mainly clinical assessment of patient behaviors. Biomarkers-based identification of ASD would be useful for pediatricians. Currently, there is no specific treatment for ASD, and evidence for the efficacy of alternative treatments remains inconclusive. The prevalence of ASD is increasing, and it is becoming more urgent to find the pathogenesis of such disorder. Metabolomic studies have been used to deeply investigate the alteration of metabolic pathways, including those associated with ASD. Metabolomics is a promising tool for identifying potential biomarkers and possible pathogenesis of ASD. This review comprehensively summarizes and discusses the abnormal metabolic pathways in ASD children, as indicated by evidence from metabolomic studies in urine and blood. In addition, the targeted interventions that could correct the metabolomic profiles relating to the improvement of autistic behaviors in affected animals and humans have been included. The results revealed that the possible underlying pathophysiology of ASD were alterations of amino acids, reactive oxidative stress, neurotransmitters, and microbiota-gut-brain axis. The potential common pathways shared by animal and human studies related to the improvement of ASD symptoms after pharmacological interventions were mammalian-microbial co-metabolite, purine metabolism, and fatty acid oxidation. The content of this review may contribute to novel biomarkers for the early diagnosis of ASD and possible therapeutic paradigms.

100 Years of Suramin.

Suramin is 100 years old and is still being used to treat the first stage of acute human sleeping sickness, caused by Trypanosoma bruceirhodesiense Suramin is a multifunctional molecule with a wide array of potential applications, from parasitic and viral diseases to cancer, snakebite, and autism. Suramin is also an enigmatic molecule: What are its targets? How does it get into cells in the first place? Here, we provide an overview of the many different candidate targets of suramin and discuss its modes of action and routes of cellular uptake. We reason that, once the polypharmacology of suramin is understood at the molecular level, new, more specific, and less toxic molecules can be identified for the numerous potential applications of suramin.

Suramin Inhibits Osteoarthritic Cartilage Degradation by Increasing Extracellular Levels of Chondroprotective Tissue Inhibitor of Metalloproteinases 3.

Osteoarthritis is a common degenerative joint disease for which no disease-modifying drugs are currently available. Attempts to treat the disease with small molecule inhibitors of the metalloproteinases that degrade the cartilage matrix have been hampered by a lack of specificity. We aimed to inhibit cartilage degradation by augmenting levels of the endogenous metalloproteinase inhibitor, tissue inhibitor of metalloproteinases (TIMP)-3, through blocking its interaction with the endocytic scavenger receptor, low-density lipoprotein receptor-related protein 1 (LRP1). We discovered that suramin (C51H40N6O23S6) bound to TIMP-3 with a KD value of 1.9 ± 0.2 nM and inhibited its endocytosis via LRP1, thus increasing extracellular levels of TIMP-3 and inhibiting cartilage degradation by the TIMP-3 target enzyme, adamalysin-like metalloproteinase with thrombospondin motifs 5. NF279 (8,8'-[carbonylbis(imino-4,1-phenylenecarbonylimino-4,1-phenylenecarbonylimino)]bis-1,3,5-naphthalenetrisulfonic acid hexasodium salt), a structural analog of suramin, has an increased affinity for TIMP-3 and increased ability to inhibit TIMP-3 endocytosis and protect cartilage. Suramin is thus a promising scaffold for the development of novel therapeutics to increase TIMP-3 levels and inhibit cartilage degradation in osteoarthritis.

LbL Assembly of Albumin on Nitric Oxide-Releasing Silica Nanoparticles Using Suramin, a Polyanion Drug, as an Interlayer Linker.

Preformed protein corona of nanoparticles can be utilized as a promising formulation strategy for improving nano drug delivery. Nitric oxide (NO) is a labile molecule with extensive therapeutic implications. In this study, we test whether preformation of protein coatings can enhance the performance of NO-delivering nanoparticles. S-Nitroso (SNO) silica nanoparticles (SNO-SiNPs) were prepared using a nanoprecipitation method. For the first time, bovine serum albumin (BSA) was used to coat NO-releasing nanoparticles, facilitated by a polyanionic drug, suramin, under a layer-by-layer (LbL) scheme. Bare and coated nanoparticles were characterized by zeta-potential, size, and spectroscopic measurements. We demonstrate that albumin/suramin-surface coassembly has advantages in preventing particle aggregation during lyophilization, controlling NO release and exerting an enhanced anticancer effect.

Inhibition of G protein-coupled P2Y2 receptor induced analgesia in a rat model of trigeminal neuropathic pain.

BACKGROUNDS: ATP and P2X receptors play important roles in the modulation of trigeminal neuropathic pain, while the role of G protein-coupled P2Y2 receptors and the underlying mechanisms are less clear. The threshold and frequency of action potentials, fast inactivating transient K+ channels (IA) are important regulators of membrane excitability in sensory neurons because of its vital role in the control of the spike onset. In this study, pain behavior tests, QT-RT-PCR, immunohistochemical staining, and patch-clamp recording, were used to investigate the role of P2Y2 receptors in pain behaviour. RESULTS: In control rats: 1) UTP, an agonist of P2Y2/P2Y4 receptors, caused a significant decrease in the mean threshold intensities for evoking action potentials and a striking increase in the mean number of spikes evoked by TG neurons. 2) UTP significantly inhibited IA and the expression of Kv1.4, Kv3.4 and Kv4.2 subunits in TG neurons, which could be reversed by the P2 receptor antagonist suramin and the ERK antagonist U0126. In ION-CCI (chronic constriction injury of infraorbital nerve) rats: 1) mRNA levels of Kv1.4, Kv3.4 and Kv4.2 subunits were significantly decreased, while the protein level of phosphorylated ERK was significantly increased. 2) When blocking P2Y2 receptors by suramin or injection of P2Y2R antisense oligodeoxynucleotides both led to a time- and dose-dependent reverse of allodynia in ION-CCI rats. 3) Injection of P2Y2 receptor antisense oligodeoxynucleotides induced a pronounced decrease in phosphorylated ERK expression and a significant increase in Kv1.4, Kv3.4 and Kv4.2 subunit expression in trigeminal ganglia. CONCLUSIONS: Our data suggest that inhibition of P2Y2 receptors leads to down-regulation of ERK-mediated phosphorylation and increase of the expression of I(A)-related Kv channels in trigeminal ganglion neurons, which might contribute to the clinical treatment of trigeminal neuropathic pain.

Structure of severe fever with thrombocytopenia syndrome virus nucleocapsid protein in complex with suramin reveals therapeutic potential.

Severe fever with thrombocytopenia syndrome is an emerging infectious disease caused by a novel bunyavirus (SFTSV). Lack of vaccines and inadequate therapeutic treatments have made the spread of the virus a global concern. Viral nucleocapsid protein (N) is essential for its transcription and replication. Here, we present the crystal structures of N from SFTSV and its homologs from Buenaventura (BUE) and Granada (GRA) viruses. The structures reveal that phleboviral N folds into a compact core domain and an extended N-terminal arm that mediates oligomerization, such as tetramer, pentamer, and hexamer of N assemblies. Structural superimposition indicates that phleboviral N adopts a conserved architecture and uses a similar RNA encapsidation strategy as that of RVFV-N. The RNA binding cavity runs along the inner edge of the ring-like assembly. A triple mutant of SFTSV-N, R64D/K67D/K74D, almost lost its ability to bind RNA in vitro, is deficient in its ability to transcribe and replicate. Structural studies of the mutant reveal that both alterations in quaternary assembly and the charge distribution contribute to the loss of RNA binding. In the screening of inhibitors Suramin was identified to bind phleboviral N specifically. The complex crystal structure of SFTSV-N with Suramin was refined to a 2.30-Å resolution. Suramin was found sitting in the putative RNA binding cavity of SFTSV-N. The inhibitory effect of Suramin on SFTSV replication was confirmed in Vero cells. Therefore, a common Suramin-based therapeutic approach targeting SFTSV-N and its homologs could be developed for containing phleboviral outbreaks.

The function of P2X3 receptor and NK1 receptor antagonists on cyclophosphamide-induced cystitis in rats.

PURPOSE: The purpose of the study is to explore the function of P2X3 and NK1 receptors antagonists on cyclophosphamide (CYP)-induced cystitis in rats. METHODS: Sixty female Sprague-Dawley (SD) rats were randomly divided into three groups. The rats in the control group were intraperitoneally (i.p.) injected with 0.9% saline (4 ml/kg); the rats in the model group were i.p. injected with CYP (150 mg/kg); and the rats in the intervention group were i.p. injected with CYP with subsequently perfusion of bladder with P2X3 and NK1 receptors' antagonists, Suramin and GR 82334. Spontaneous pain behaviors following the administration of CYP were observed. Urodynamic parameters, bladder pressure-volume curve, maximum voiding pressure (MVP), and maximum cystometric capacity (MCC), were recorded. Pathological changes in bladder tissue were observed. Immunofluorescence was used to detect the expression of P2X3 and NK1 receptors in bladder. RESULTS: Cyclophosphamide treatment increased the spontaneous pain behaviors scores. The incidence of bladder instability during urine storage period of model group was significantly higher than intervention group (χ(2) = 7.619, P = 0.007) and control group (χ(2) = 13.755, P = 0.000). MCC in the model group was lower than the control and intervention groups (P < 0.01). Histological changes evident in model and intervention groups rats' bladder included edema, vasodilation, and infiltration of inflammatory cells. In model group, the expression of P2X3 receptor increased in urothelium and suburothelium, and NK1 receptor increased in suburothelium, while the expression of them in intervention group was lower. CONCLUSIONS: In CYP-induced cystitis, the expression of P2X3 and NK1 receptors increased in urothelium and/or suburothelium. Perfusion of bladder with P2X3 and NK1 receptors antagonists ameliorated the bladder function.

Non-invasive quantification of anti-angiogenic therapy by contrast-enhanced MRI in experimental pancreatic cancer.

BACKGROUND: Currently, early changes of tumor vasculature after angiogenesis inhibition can only be evaluated by histopathology, a method not suitable in a clinical setting. PURPOSE: To quantify effects of different angiogenesis inhibitors on the microvasculature of orthotopically implanted pancreatic cancers by contrast-enhanced magnetic resonance imaging (MRI) in order to establish a non-invasive technique for monitoring antiangiogenic cancer treatment. MATERIAL AND METHODS: DSL-6A/C1 pancreatic cancers were implanted in the pancreas of 109 Lewis rats. Three weeks later, antiangiogenic treatment was initiated by administration of Bevacizumab (n = 38) or Suramin (n = 27) while the control group (n = 44) remained untreated. Dynamic MRI was performed 24 h, 1 week, and 4 weeks after treatment initiation. Fractional tumor plasma volume (fPV, %) and vascular permeability (K(PS), mL/min/100 cc) were calculated based on the MRI data by using a pharmacokinetic model. RESULTS: Twenty-four hours after the initial dose, a significant decline in K(PS) was observed in the Bevacizumab group compared to the control and Suramin group (0.002 ± 0.008; 0.057 ± 0.046 and 0.064 ± 0.062 (mean ± SD); P < 0.05). At 1 week, fPV was significantly smaller in Bevacizumab and Suramin treated tumors compared to control tumors (6.25 ± 2.74, 7.47 ± 3.44, and 15.10 ± 9.97, respectively; P < 0.05). Differences in tumor volumes were first observed after 4 weeks of treatment with significantly larger control tumors (4380.3 ± 1590.6 vs. 869.6 ± 717.2 and 1676.5 ± 2524.1 mm(3); P < 0.05). CONCLUSION: Dynamic MRI can quantify antiangiogenic effects on tumor microvasculature before changes in tumor volumes are detectable. Thus, this technique is a reasonable addition to morphological MRI and may be applied as an alternative to histopathology.

Suramin decreases injury and improves regeneration of ethanol-induced steatotic partial liver grafts.

Steatotic grafts are excluded for use in partial liver transplantation (LT) because of the increased risk of primary nonfunction. This study investigated the effects of suramin, a polysulfonated naphthylurea, on the outcome of steatotic partial LT. Rat livers were harvested after acute ethanol treatment (6 g/kg, intragastric administration), reduced in size to ≈ 1/3, and transplanted. Serum alanine aminotransferase (ALT) and total bilirubin levels as well as hepatic necrosis and apoptosis were significantly higher after transplantation of fatty partial grafts (FPG) than lean partial grafts (LPG). Suramin (5 mg/kg, i.p.) decreased ALT by ≈ 60%, hyperbilirubinemia by 75%, necrosis by 83%, and apoptosis by 70% after FPG transplantation. Hepatic cellular 5-bromo-2'-deoxyuridine (BrdU) incorporation increased to 28% in LPG but was only 2% in FPG at 48 hours, and the mitotic index increased to 7% in LPG but was only 0.2% in FPG, indicating suppressed regeneration in FPG. Suramin increased BrdU incorporation and the mitotic index to 43% and 9%, respectively, in FPG. All FPG recipients died within 5 days. Suramin recovered survival of FPG to 62%. Tumor necrosis factor-α (TNF-α) mRNA was 2.2-fold higher in FPG than in LPG and was associated with activation of caspase-8 and caspase-3 in FPG. Suramin decreased TNF-α and caspase activation in FPG. Transforming growth factor-ß (TGF-ß), phospho-Smad2/3 and p21Cip1 were significantly higher in FPG than in LPG and suramin blocked TGF-ß formation and its down-stream signaling pathway. Taken together, suramin improves the outcome of FPG transplantation, most likely by inhibition of TNF-α and TGF-ß formation.

Duchenne muscular dystrophy fibroblast nodules: a cell-based assay for screening anti-fibrotic agents.

Severe muscle fibrosis is the endpoint of many chronic myopathies. Identification of factors that regulate fibrosis is important for understanding its pathogenesis and for developing anti-fibrotic treatments that prevent muscle destruction. We have developed an in vitro model for screening potential anti-fibrotic agents. The model consists of three-dimensional clusters (nodules) of fibroblasts derived from Duchenne muscular dystrophy (DMD) muscle. The primary fibroblasts spontaneously and quickly form nodules resembling fibrotic foci (cells plus extracellular matrix) when grown on a solid substrate. We tested the anti-fibrotic action of suramin, decorin, and spironolactone (all with established anti-fibrotic activity) on the model. All three agents significantly reduced nodule number, and spironolactone and suramin significantly reduced nodule diameter. Nodule secretion of soluble collagen was also significantly reduced by decorin and spironolactone treatment, whereas suramin had no significant effect. Collagen I and fibronectin protein expression was significantly reduced in the culture medium of control and DMD fibroblasts by spironolactone treatment, but not by decorin and suramin treatment. Finally, in DMD fibroblast monolayers, collagen deposition was significantly reduced by all three agents. Spironolactone significantly reduced collagen I and fibronectin transcript levels, whereas decorin reduced only fibronectin. Our in vitro model of fibrogenesis has thus revealed differing anti-fibrotic effects in the three anti-fibrotic agents tested. It therefore appears as a useful and sensitive system for the testing of anti-fibrotic drugs and could be adapted for the high-throughput screening of new anti-fibrotic molecules.

Suramin attenuates dystrophin-deficient cardiomyopathy in the mdx mouse model of duchenne muscular dystrophy.

INTRODUCTION: The purpose of this study was to determine the effects of suramin, an antifibrotic agent, on cardiac function and remodeling in mdx mice. METHODS: mdx mice (8 months old) received intraperitoneal injections of suramin twice a week for 3 months. Control mdx mice (8 months old) were injected with saline. RESULTS: Suramin improved the electrocardiography profile with the main corrections seen in S- to R-wave ratio, PR interval, and Q amplitude, and a significant decrease in the cardiomyopathy index. Suramin decreased myocardial fibrosis, inflammation, and myonecrosis. CONCLUSIONS: These findings suggest that suramin may be a new adjunctive therapy to help improve cardiomyopathy in DMD.

Susceptibility of Brazilian isolates of Trypanosoma evansi to suramin sodium: test in experimentally infected mice.

This study aimed to evaluate the susceptibility of Brazilian isolates of Trypanosoma evansi to suramin sodium. For this purpose, three isolates of T. evansi (LPV-2005, LPV-2009 and LPV-2010) and seventy mice were used, with the animals divided in 10 groups (A, B, C, D, E, F, G, H, I and J) with seven animals each group. Mice of groups A, B, and C were infected with LPV-2005; Groups D, E and F with LPV-2009 and the groups G, H and I with LPV-2010. The group J was composed by healthy mice or uninfected. The parasitemia was monitored daily through blood smear, and the treatment of all groups was performed three days post-infection (PI), when all mice showed increased parasitemia. Groups A, D and G represented the positives controls, while groups B, E and H received a single dose of suramin sodium at 10 mgkg(-1) intramuscularly. Groups C, F and I were treated with three doses of suramin sodium at 10 mgkg(-1), respecting an interval of 24 h between each dose. Negative blood smears from all animals were obtained 24 h after treatment (AT), status maintained until the end of the experiment (50 days PI). The specific PCR for T. evansi was carried out from blood, showing negative results AT. Therefore, this study showed that a single dose of suramin sodium at 10 mgkg(-1) has the same efficacy of three doses, as recommended by the therapeutic literature. Furthermore, we observed that Brazilian isolates did not show resistance to the drug.

Suramin action in African trypanosomes involves a RuvB-like DNA helicase.

Suramin is one of the oldest drugs in use today. It is still the treatment of choice for the hemolymphatic stage of African sleeping sickness caused by Trypanosoma brucei rhodesiense, and it is also used for surra in camels caused by Trypanosoma evansi. Yet despite one hundred years of use, suramin's mode of action is not fully understood. Suramin is a polypharmacological molecule that inhibits diverse proteins. Here we demonstrate that a DNA helicase of the pontin/ruvB-like 1 family, termed T. brucei RuvBL1, is involved in suramin resistance in African trypanosomes. Bloodstream-form T. b. rhodesiense under long-term selection for suramin resistance acquired a homozygous point mutation, isoleucine-312 to valine, close to the ATP binding site of T. brucei RuvBL1. The introduction of this missense mutation, by reverse genetics, into drug-sensitive trypanosomes significantly decreased their sensitivity to suramin. Intriguingly, the corresponding residue of T. evansi RuvBL1 was found mutated in a suramin-resistant field isolate, in that case to a leucine. RuvBL1 (Tb927.4.1270) is predicted to build a heterohexameric complex with RuvBL2 (Tb927.4.2000). RNAi-mediated silencing of gene expression of either T. brucei RuvBL1 or RuvBL2 caused cell death within 72 h. At 36 h after induction of RNAi, bloodstream-form trypanosomes exhibited a cytokinesis defect resulting in the accumulation of cells with two nuclei and two or more kinetoplasts. Taken together, these data indicate that RuvBL1 DNA helicase is involved in suramin action in African trypanosomes.

Suramin, a drug for the treatment of trypanosomiasis, reduces the prothrombotic and metastatic phenotypes of colorectal cancer cells by inhibiting hepsin.

Recently, our group identified serine-protease hepsin from primary tumor as a biomarker of metastasis and thrombosis in patients with localized colorectal cancer. We described hepsin promotes invasion and thrombin generation of colorectal cancer cells in vitro and in vivo and identified venetoclax as a hepsin inhibitor that suppresses these effects. Now, we aspire to identify additional hepsin inhibitors, aiming to broaden the therapeutic choices for targeted intervention in colorectal cancer. METHODS: We developed a virtual screening based on molecular docking between the hepsin active site and 2000 compounds from DrugBank. The most promising drug was validated in a hepsin activity assay. Subsequently, we measured the hepsin inhibitor effect on colorectal cancer cells with basal or overexpression of hepsin via wound-healing, gelatin matrix invasion, and plasma thrombin generation assays. Finally, a zebrafish model determined whether hepsin inhibition reduced the invasion of colorectal cancer cells overexpressing hepsin. RESULTS: Suramin was the most potent hepsin inhibitor (docking score: -11.9691 Kcal/mol), with an IC50 of 0.66 µM. In Caco-2 cells with basal or overexpression of hepsin, suramin decreased migration and significantly reduced invasion and thrombin generation. Suramin did not reduce the thrombotic phenotype in the hepsin-negative colorectal cancer cells HCT-116 and DLD-1. Finally, suramin significantly reduced the in vivo invasion of Caco-2 cells overexpressing hepsin. CONCLUSION: Suramin is a novel hepsin inhibitor that reduces its protumorigenic and prothrombotic effects in colorectal cancer cells. This suggests the possibility of repurposing suramin and its derivatives to augment the repertoire of molecular targeted therapies against colorectal cancer.

Suramin ameliorates osteoarthritis by acting on the Nrf2/HO-1 and NF-κB signaling pathways in chondrocytes and promoting M2 polarization in macrophages.

Osteoarthritis (OA)-the most prevalent of arthritis diseases-is a complicated pathogenesis caused by cartilage degeneration and synovial inflammation. Suramin has been reported to enhance chondrogenic differentiation. However, the therapeutic effect of suramin on OA-induced cartilage destruction has remained unclear. Suramin is an anti-parasitic drug that has potent anti-purinergic properties. This study investigated the protective effects and underlying mechanisms of suramin on articular cartilage degradation using an in vitro study and mice model with post-traumatic OA. We found that suramin markedly suppressed the IL-1ß increased expression of matrix destruction proteases-such as ADAMT4, ADAMTS5, MMP3, MMP13, and inflammatory mediators-including the iNOS, COX2, TNFα, and IL-1ß; while greatly enhancing the synthesis of cartilage anabolic factors-such as COL2A1, Aggrecan and SOX9 in IL-1ß-induced porcine chondrocytes. In vivo experiments showed that intra-articular injection of suramin ameliorated cartilage degeneration and inhibited synovial inflammation in an anterior cruciate ligament transection (ACLT)-induced OA mouse model. In mechanistic studies, we found that exogenous supplementation of suramin can activate Nrf2, and accordingly inhibit the nuclear factor kappa-light-chain-enhancer of activated B cells (NF- κB) and mitogen-activated protein kinase (MAPK) pathways, thereby alleviating the inflammation and ECM degeneration of chondrocytes stimulated by IL-1ß. In addition, suramin also repolarized M1 macrophages to the M2 phenotype, further reducing the apoptosis of chondrocytes. Collectively, the results of the study suggests that suramin is a potential drugs which could serve as a facilitating drug for the application of OA therapy toward clinical treatment.