Synergistic Activity between Statins and Bisphosphonates against Acute Experimental Toxoplasmosis

Comprehensive Insights into the Development of Antitoxoplasmosis Drugs: Current Advances, Obstacles, and Future Perspectives

Current therapies for toxoplasmosis rely on a few drugs, most of which have severe side effects, and seeking ideal therapies for different types of toxoplasmosis is a long-term and challenging mission. Research and development (R&D) of novel drugs against Toxoplasma gondii (T. gondii) has focused on two main directions, the structural modification of lead compounds and natural products. Here we summarize the recent advances in the development of anti-T. gondii drugs from these two perspectives and provide comprehensive insights, reflecting on the advantages and selected molecules in each field. This review also focuses on the current obstacles to the development of novel anti-T. gondii agents, proposes comprehensive solutions, and facilitates future development.

Lipophilic bisphosphonates reduced cyst burden and ameliorated hyperactivity of mice chronically infected with Toxoplasma gondii

The current treatments for toxoplasmosis are only active against fast-growing tachyzoites, present in acute infections, with little effect on slow-growing bradyzoites within tissue cysts, present in latent chronic infections. The mitochondrion of Toxoplasma gondii is essential for its survival, and one of the major anti-parasitic drugs, atovaquone, inhibits the mitochondrial electron transport chain at the coenzyme Q:cytochrome c oxidoreductase site. Coenzyme Q (also known as ubiquinone [UQ]) consists of a quinone head and a lipophilic, isoprenoid tail that anchors UQ to membranes. The synthesis of the isoprenoid unit is essential for cell growth and is inhibited by lipophilic bisphosphonates, which inhibit the parasite growth. In this work, we investigated the effect of lipophilic bisphosphonates on the chronic stages of T. gondii. We discovered that three lipophilic bisphosphonates (BPH-1218, BPH-1236, and BPH-1238), effective for the acute infection, were also effective in controlling the development of chronic stages. We showed effectiveness by testing them against in vitro cysts and in vivo derived tissue cysts and, most importantly, these compounds reduced the cyst burden in the brains of chronically infected mice. We monitored the activity of infected mice non-invasively and continuously with a novel device termed the CageDot. A decrease in activity accompanied the acute phase, but mice recovered to normal activity and showed signs of hyperactivity when the chronic infection was established. Moreover, treatment with atovaquone or BPH-1218 ameliorated the hyperactivity observed during the chronic infection.IMPORTANCETreatment for toxoplasmosis is challenged by a lack of effective drugs to eradicate the chronic stages. Most of the drugs currently used are poorly distributed to the central nervous system, and they trigger allergic reactions in a large number of patients. There is a compelling need for safe and effective treatments for toxoplasmosis. Bisphosphonates (BPs) are analogs of inorganic pyrophosphate and are used for the treatment of bone disorders. BPs target the isoprenoid pathway and are effective against several experimental parasitic infections. Some lipophilic BPs can specifically inhibit the mitochondrial activity of Toxoplasma gondii by interfering with the mechanism by which ubiquinone is inserted into the inner mitochondrial membrane. In this work, we present the effect of three lipophilic BPs against T. gondii chronic stages. We also present a new strategy for the monitoring of animal activity during disease and treatment that is non-invasive and continuous.

Evaluation of the efficacy of Chitosan nanoparticles based on Rosuvastatin in the treatment of acute toxoplasmosis: An In vitro and In vivo study

Toxoplasma gondii (T.gondii) is an obligate intracellular protozoan that infects warm-blooded animals and has a global distribution. Acute toxoplasmosis is commonly reported in patients with acquired/congenital toxoplasmosis and immune deficiency. New methods are needed to prevent the sideffects of classical treatment. In this study, Rosuvastatin loaded chitosan nanoparticle (CH-NP-ROS) were synthesized and zeta potential and size were determined, and an MTT assay was performed to evaluate the cell toxicity on Macrophage cells (MQ) and anti-Toxoplasma activity using Trypan-blue staining by different concentrations of Rosuvastatin (ROS), and Rosuvastatin loaded chitosan nanoparticle (CH-NP-ROS). The cell viability assay demonstrated that CH-NP-ROS had lower cell toxicity (<15 %) compared to ROS (<30 %). Statistical analysis showed that CH-NP-ROS significantly killed 98.950 ± 1.344; P < 0.05) of Toxoplasma gondii tachyzoites. In vivo results of perituneal fluid showed that CH-NP significantly reduced the parasite load in the CH-NP-ROS group, compared to that in negative control group (P < 0.001). Growth inhibition rates of tachyzoites in mice receiving free ROS and CH-NP-ROS (injection and oral form) were found to be 166.125 + 4.066, 118.750 + 4.596 and 124.875 + 2.652, respectively, compared to mice in Sulfadiazine/Pyrimethamine treated group (positive control). In the infected untreated mice (control +), the mean tachyzoite counts per oil immersion field in the spleen was 8.25 respectively. The mean survival time in all the groups treated with ROS and CH-NP-ROS was longer than that in the negative control group Therefore, nanoformulation is a promising approach for the delivery and is safe for using therapeutic effects in acute toxoplasmosis.

Anti-Toxoplasma gondii effects of XYP1-derived peptides and regulatory mechanisms of XYP1

BACKGROUND

Toxoplasmosis, caused by Toxoplasma gondii , poses serious health issues for humans and animals. Individuals with impaired immune systems are more susceptible to severe toxoplasmosis. Pregnant women infected by T. gondii can face the possibility of birth defects and miscarriages. While pyrimethamine and sulfadiazine are commonly used drugs in clinical practice, concerns over their side effects and resistance are on the rise. A spider peptide XYP1 isolated from Lycosa coelestis had potent anti-T. gondii effects, but it had a high synthesis cost and strong cytotoxicity.

METHODS

This study intended to modify XYP1 for producing derived peptides via amino acid truncation and substitution. The anti-T. gondii effect was evaluated by trypan blue staining assay and killing experiment of RH strain tachyzoites. The CCK8 and hemolysis assays were used to compare their safeties. The morphological changes of T. gondii were observed by scanning electron microscope and transmission electron microscope. In addition, the mechanism of XYP1 against T. gondii through RNA-sequencing was further explored.

RESULTS

In vivo and in vitro experiments revealed that XYP1-18 and XYP1-18-1 had excellent anti-T. gondii activity with lower cytotoxicity and hemolysis activity than XYP1. XYP1, XYP1-18, and XYP1-18-1 were able to disrupt the surface membrane integrity of T. gondii tachyzoites, forming pores and causing the disruption of organelles. Furthermore, RNA-sequencing analysis indicated that XYP1 could stimulate the host immune response to effectively eliminate T. gondii and lessen the host's inflammatory reaction.

CONCLUSIONS

XYP1-18 had lower cytotoxicity and hemolysis activity than XYP1, as well as significantly extending the survival time of the mice. XYP1 played a role in host inflammation and immune responses, revealing its potential mechanism. Our research provided valuable insights into the development and application of peptide-based drugs, offering novel strategies and directions for treating toxoplasmosis.

An updated review of chemical compounds with anti-Toxoplasma gondii activity

The opportunistic apicomplexan parasite Toxoplasma gondii is the etiologic agent for toxoplasmosis, which can infect a widespread range of hosts, particularly humans and warm-blooded animals. The present chemotherapy to treat or prevent toxoplasmosis is deficient and is based on diverse drugs such as atovaquone, trimethoprim, spiramycine, which are effective in acute toxoplasmosis. Therefore, a safe chemotherapy is required for toxoplasmosis considering that its responsible agent, T. gondii, provokes severe illness and death in pregnant women and immunodeficient patients. A certain disadvantage of the available treatments is the lack of effectiveness against the tissue cyst of the parasite. A safe chemotherapy to combat toxoplasmosis should be based on the metabolic differences between the parasite and the mammalian host. This article covers different relevant molecular targets to combat this disease including the isoprenoid pathway (farnesyl diphosphate synthase, squalene synthase), dihydrofolate reductase, calcium-dependent protein kinases, histone deacetylase, mitochondrial electron transport chain, etc.

Statin and aspirin use in parasitic infections as a potential therapeutic strategy: A narrative review

Infections, including zoonoses, constitute a threat to human health due to the spread of resistant pathogens. These diseases generate an inflammatory response controlled by a resolving mechanism involving specialized membrane lipid-derived molecules called lipoxins, resolvins, maresins, and protectins. The production of some of these molecules can be triggered by aspirin or statins. Thus, it is proposed that modulation of the host response could be a useful therapeutic strategy, contributing to the management of resistance to antiparasitic agents or preventing drift to chronic, host-damaging courses. Therefore, the present work presents the state of the art on the use of statins or aspirin for the experimental management of parasitic infections such as Chagas disease, leishmaniasis, toxoplasmosis or malaria. The methodology used was a narrative review covering original articles from the last seven years, 38 of which met the inclusion criteria. Based on the publications consulted, modulation of the resolution of inflammation using statins may be feasible as an adjuvant in the therapy of parasitic diseases. However, there was no strong experimental evidence on the use of aspirin; therefore, further studies are needed to evaluate its role inflammation resolution process in infectious diseases.

The Heptaprenyl Diphosphate Synthase (Coq1) Is the Target of a Lipophilic Bisphosphonate That Protects Mice against Toxoplasma gondii Infection

Prenyldiphosphate synthases catalyze the reaction of allylic diphosphates with one or more isopentenyl diphosphate molecules to form compounds such as farnesyl diphosphate, used in, e.g., sterol biosynthesis and protein prenylation, as well as longer "polyprenyl" diphosphates, used in ubiquinone and menaquinone biosynthesis. Quinones play an essential role in electron transport and are associated with the inner mitochondrial membrane due to the presence of the polyprenyl group. In this work, we investigated the synthesis of the polyprenyl diphosphate that alkylates the ubiquinone ring precursor in Toxoplasma gondii, an opportunistic pathogen that causes serious disease in immunocompromised patients and the unborn fetus. The enzyme that catalyzes this early step of the ubiquinone synthesis is Coq1 (TgCoq1), and we show that it produces the C35 species heptaprenyl diphosphate. TgCoq1 localizes to the mitochondrion and is essential for in vitro T. gondii growth. We demonstrate that the growth defect of a T. gondii TgCoq1 mutant is rescued by complementation with a homologous TgCoq1 gene or with a (C45) solanesyl diphosphate synthase from Trypanosoma cruzi (TcSPPS). We find that a lipophilic bisphosphonate (BPH-1218) inhibits T. gondii growth at low-nanomolar concentrations, while overexpression of the TgCoq1 enzyme dramatically reduced growth inhibition by the bisphosphonate. Both the severe growth defect of the mutant and the inhibition by BPH-1218 were rescued by supplementation with a long-chain (C30) ubiquinone (UQ6). Importantly, BPH-1218 also protected mice against a lethal T. gondii infection. TgCoq1 thus represents a potential drug target that could be exploited for improved chemotherapy of toxoplasmosis. IMPORTANCE Millions of people are infected with Toxoplasma gondii, and the available treatment for toxoplasmosis is not ideal. Most of the drugs currently used are only effective for the acute infection, and treatment can trigger serious side effects requiring changes in the therapeutic approach. There is, therefore, a compelling need for safe and effective treatments for toxoplasmosis. In this work, we characterize an enzyme of the mitochondrion of T. gondii that can be inhibited by an isoprenoid pathway inhibitor. We present evidence that demonstrates that inhibition of the enzyme is linked to parasite death. In addition, the inhibitor can protect mice against a lethal dose of T. gondii. Our results thus reveal a promising chemotherapeutic target for the development of new medicines for toxoplasmosis.

Biochemistry and Nanomechanical Properties of Human Colon Cells upon Simvastatin, Lovastatin, and Mevastatin Supplementations: Raman Imaging and AFM Studies

One of the most important areas of medical science is oncology, which is responsible for both the diagnostics and treatment of cancer diseases. Over the years, there has been an intensive development of cancer diagnostics and treatment. This paper shows the comparison of normal (CCD-18Co) and cancerous (CaCo-2) cell lines of the human gastrointestinal tract on the basis of nanomechanical and biochemical properties to obtain information on cancer biomarkers useful in oncological diagnostics. The research techniques used were Raman spectroscopy and imaging and atomic force microscopy (AFM). In addition, the studies also included the effect of the statin compounds—mevastatin, lovastatin, and simvastatin—and their influence on biochemical and nanomechanical changes of cell properties using Raman imaging and AFM techniques. The cytotoxicity of statins was determined using XTT tests.

Inhibition of Toxoplasma gondii Growth by Dihydroquinine and Its Mechanisms of Action

Toxoplasma gondii is a zoonotic parasite that infects the brain of humans and causes cerebral toxoplasmosis. The recommended drugs for the treatment or prophylaxis of toxoplasmosis are pyrimethamine (PY) and sulfadiazine (SZ), which have serious side effects. Other drugs available for toxoplasmosis are poorly tolerated. Dihydroquinine (DHQ) is a compound closely related to quinine-based drugs that have been shown to inhibit Plasmodium falciparum and Plasmodium berghei in addition to its anti-arrhythmia properties. However, little is known about the effect of DHQ in T. gondii growth and its mechanism of action in vitro. In this study, we report the anti-Toxoplasma and anti-invasion properties of DHQ. DHQ significantly inhibited T. gondii tachyzoite growth with IC50s values of 0.63, 0.67, and 0.00137 µM at 24, 48, and 72 h, respectively. Under similar conditions, SZ and PY, considered as the gold standard drugs for the treatment of toxoplasmosis, had IC50s values of 1.29, 1.55, and 0.95 and 3.19, 3.52, and 2.42 µM, respectively. The rapid dose-dependent inhibition of T. gondii tachyzoites by DHQ compared to the standard drugs (SZ and PY) indicates that DHQ has high selective parasiticidal effects against tachyzoite proliferation. Remarkably, DHQ had an excellent selectivity index (SI) of 149- and 357-fold compared to 24- and 143-fold for PY and SZ, respectively, using fibroblast cells. In addition, DHQ disrupted T. gondii tachyzoite mitochondrial membrane potential and adenosine triphosphate (ATP) production and elicited high reactive oxygen species (ROS) generation. Taking all these findings together, DHQ promises to be an effective and safe lead for the treatment of toxoplasmosis.

In Vivo Efficacy of SQ109 against Leishmania donovani, Trypanosoma spp. and Toxoplasma gondii and In Vitro Activity of SQ109 Metabolites

SQ109 is an anti-tubercular drug candidate that has completed Phase IIb/III clinical trials for tuberculosis and has also been shown to exhibit potent in vitro efficacy against protozoan parasites including Leishmania and Trypanosoma cruzi spp. However, its in vivo efficacy against protozoa has not been reported. Here, we evaluated the activity of SQ109 in mouse models of Leishmania, Trypanosoma spp. as well as Toxoplasma infection. In the T. cruzi mouse model, 80% of SQ109-treated mice survived at 40 days post-infection. Even though SQ109 did not cure all mice, these results are of interest since they provide a basis for future testing of combination therapies with the azole posaconazole, which acts synergistically with SQ109 in vitro. We also found that SQ109 inhibited the growth of Toxoplasma gondii in vitro with an IC50 of 1.82 µM and there was an 80% survival in mice treated with SQ109, whereas all untreated animals died 10 days post-infection. Results with Trypanosoma brucei and Leishmania donovani infected mice were not promising with only moderate efficacy. Since SQ109 is known to be extensively metabolized in animals, we investigated the activity in vitro of SQ109 metabolites. Among 16 metabolites, six mono-oxygenated forms were found active across the tested protozoan parasites, and there was a ~6× average decrease in activity of the metabolites as compared to SQ109 which is smaller than the ~25× found with mycobacteria.

Chemotherapeutics for Toxoplasma gondii: Molecular Biotargets, Binding Modes, and Structure-Activity Relationship Investigations

Toxoplasmosis, an infectious zoonotic disease caused by the apicomplexan parasite Toxoplasma gondii (T. gondii), is a major worldwide health problem. However, there are currently no effective options (chemotherapeutic drugs or prophylactic vaccines) for treating chronic latent toxoplasmosis infection. Accordingly, seeking more effective and safer chemotherapeutics for combating this disease remains a long-term and challenging objective. In this paper, we summarize possible molecular biotargets, with an emphasis on those that are druggable and promising, including, without limitation, calcium-dependent protein kinase 1, bifunctional thymidylate synthase-dihydrofolate reductase, and farnesyl diphosphate synthase. Meanwhile, as important components of medicinal chemistry, the binding modes and structure-activity relationship profiles of the corresponding inhibitors were also illuminated. We anticipate that this information will be helpful for further identification of more effective chemotherapeutic interventions to prevent and treat zoonotic infections caused by T. gondii.

Anti-Toxoplasma gondii Effects of a Novel Spider Peptide XYP1 In Vitro and In Vivo

Toxoplasmosis, caused by an obligate intracellular parasite Toxoplasma gondii, is one of the most prevalent zoonoses worldwide. Treatments for this disease by traditional drugs have shown numerous side effects, thus effective alternative anti-Toxoplasma strategies or drugs are urgently needed. In this study, a novel spider peptide, XYP1, was identified from the cDNA library of the venom gland of the spider Lycosa coelestis. Our results showed that XYP1 has potent anti-Toxoplasma activity in vitro and in vivo. Specifically, treatment with XYP1 significantly inhibited the viability, invasion and proliferation of tachyzoites with low cytotoxicity (IC₅₀ = 38.79 μΜ) on human host cells, and increased the survival rate of mice acutely infected with T. gondii. Next, scanning electron microscopy, transmission electron microscopy and RNA sequencing were employed to further explore the functional mechanism of XYP1, and the results indicated that XYP1 causes membrane perforation, swelling and disruption of tachyzoites, which could be closely associated with differential expression of several membrane-associated proteins including HSP29. In conclusion, XYP1 may be a promising new drug candidate for the treatment of toxoplasmosis.

Rosuvastatin revert memory impairment and anxiogenic-like effect in mice infected with the chronic ME-49 strain of Toxoplasma gondii

The aim of this study was to investigate the effect of rosuvastatin treatment on memory impairment, and anxiogenic-like effects in mice chronically infected with Toxoplasma gondii. For this, Balb/c mice were infected orally with chronic ME-49 strain of Toxoplasma gondii. Oral treatment with rosuvastatin (40mg/kg/day) started on the 51^st day post-infection and was performed daily for 21 days. After completion of treatment, anxiety-like effects and locomotion were investigated in the open field (OF) test, whereas novel object recognition (NOR) test was used for evaluation of short- and long-term memory. At the end of the experiments, the brain was collected for Toxoplasma gondii DNA quantification and histopathological analysis. Infection with ME-49 strain decreased the time spent in the center of OF, indicating an anxiogenic effect, without affecting total and peripheral locomotion. Rosuvastatin treatment inhibited the change in the center time. Besides, pharmacological treatment increased total and central locomotion in both non-infected and infected animals. Infection also impaired both short- and long-term memory in the NOR test, and these effects were reverted by rosuvastatin treatment. In addition to effects in behavioral changes, rosuvastatin also reduced parasite load in the brain and attenuated signs of brain inflammation such as perivascular cuffs, inflammatory cell infiltration and tissue damage. These findings indicate for the first time the efficacy of rosuvastatin in treatment of memory impairment and anxiogenic effect evoked by infection with Toxoplasma gondii. These effects might be mediated by reduced cyst load, which in turn decrease inflammation and damage in the brain.

Zoledronate repositioning as a potential trypanocidal drug. Trypanosoma cruzi HPRT an alternative target to be considered

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi and affects 7 million people worldwide. Considering the side effects and drug resistance shown by current treatments, the development of new anti-Chagas therapies is an urgent need. T. cruzi hypoxanthine phosphoribosyltransferase (TcHPRT), the key enzyme of the purine salvage pathway, is essential for the survival of trypanosomatids. Previously, we assessed the inhibitory effect of different bisphosphonates (BPs), HPRT substrate analogues, on the activity of the isolated enzyme. BPs are used as a treatment for bone diseases and growth inhibition studies on T. cruzi have associated BPs action with the farnesyl diphosphate synthase inhibition. Here, we demonstrated significant growth inhibition of epimastigotes in the presence of BPs and a strong correlation with our previous results on the isolated TcHPRT, suggesting this enzyme as a possible and important target for these drugs. We also found that the parasites exhibited a delay at S phase in the presence of zoledronate pointing out enzymes involved in the cell cycle, such as TcHPRT, as intracellular targets. Moreover, we validated that micromolar concentrations of zoledronate are capable to interfere with the progression of cell infection by this parasite. Altogether, our findings allow us to propose the repositioning of zoledronate as a promising candidate against Chagas disease and TcHPRT as a new target for future rational design of antiparasitic drugs.

Two old drugs, NVP-AEW541 and GSK-J4, repurposed against the Toxoplasma gondii RH strain

Background

Toxoplasma gondii is a zoonotic pathogen that causes toxoplasmosis and leads to serious public health problems in developing countries. However, current clinical therapeutic drugs have some disadvantages, such as serious side effects, a long course of treatment and the emergence of drug-resistant strains. The urgent need to identify novel anti-Toxoplasma drugs has initiated the effective strategy of repurposing well-characterized drugs. As a principled screening for the identification of effective compounds against Toxoplasma gondii, in the current study, a collection of 666 compounds were screened for their ability to significantly inhibit Toxoplasma growth.

Methods

The inhibition of parasite growth was determined using a luminescence-based β-galactosidase activity assay. Meanwhile, the effect of compounds on the viability of host cells was measured using CCK8. To assess the inhibition of the selected compounds on discrete steps of the T. gondii lytic cycle, the invasion, intracellular proliferation and egress abilities were evaluated. Finally, a murine infection model of toxoplasmosis was used to monitor the protective efficacy of drugs against acute infection of a highly virulent RH strain.

Results

A total of 68 compounds demonstrated more than 70% parasite growth inhibition. After excluding compounds that impaired host cell viability, we further characterized two compounds, NVP-AEW541 and GSK-J4 HCl, which had IC₅₀ values for parasite growth of 1.17 μM and 2.37 μM, respectively. In addition, both compounds showed low toxicity to the host cell. Furthermore, we demonstrated that NVP-AEW541 inhibits tachyzoite invasion, while GSK-J4 HCl inhibits intracellular tachyzoite proliferation by halting cell cycle progression from G1 to S phase. These findings prompted us to analyse the efficacy of the two compounds in vivo by using established mouse models of acute toxoplasmosis. In addition to prolonging the survival time of mice acutely infected with T. gondii, both compounds had a remarkable ability to reduce the parasite burden of tissues.

Conclusions

Our findings suggest that both NVP-AEW541 and GSK-J4 could be potentially repurposed as candidate drugs against T. gondii infection.

Interaction of apigenin-7-O-glucoside with pyrimethamine against Toxoplasma gondii growth

Apigenin-7-O-glucoside, a flavonoid glucoside known to inhibit cancer cell growth, fungi growth, both intra and extracellular reactive oxygen species generation, causing cell arrest and damage to the plasma membrane, was tested alone or in combination with a dihydrofolate inhibitor (pyrimethamine) against Toxoplasma gondii (T. gondii) growth. The anti-T. gondii activity was carried out using a high throughput antiparasitic drug screening cell-based assay known as 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H tetrazolium, monosodium salt (WST-8) and fluorescence plate reader. The 50% effective concentration inhibition and 95% confidence interval values for individual and combination treatments against T. gondii were 0.80 (0.38-1.29) µg/mL, 1.05 (0.275-2.029) µg/mL, and 0.40 (0-1.06) µg/mL for apigenin-7-O-glucoside, pyrimethamine, and apigenin-7-O-glucoside plus pyrimethamine, respectively. Interestingly, the apigenin-7-O-glucoside plus pyrimethamine combination showed an additive inhibition effect against T. gondii growth in vitro using the fractional inhibitory concentration index method. It was discovered that the apigenin-7-O-glucoside combination with pyrimethamine had a high selectivity index 62.5, which implies 62-fold inhibition activity against the parasite versus human foreskin fibroblast cell cytotoxicity. This new combination hit is novel and will have the potential for future effective, safe, and less costly anti-Toxoplasma drug development, if its in vivo activity shows similar findings.

Rosuvastatin reduced brain parasite burden in a chronic toxoplasmosis in vivo model and influenced the neuropathological pattern of ME-49 strain

This study evaluated the effects of rosuvastatin in vivo on toxoplasmosis chronic infection. Thirty-five Swiss mice were orally infected (ME-49 strain). After 50 days, the mice were separated into five groups: GI - non-infected, GII - infected, GIII - infected and treated with pyrimethamine and sulfadiazine (12.5 + 50 mg kg-1 body weight day-1), GIV and GV - infected and treated with rosuvastatin 10 and 40 mg kg-1 body weight day-1, respectively. After 21 days, we collected blood, liver, lungs, femoral biceps and brain were removed for Toxoplasma gondii DNA quantification by qPCR and histopathological analysis. GIV and GV did not present premature death or clinical changes, and the hepatic enzyme levels were lower compared to GI. Toxoplasma gondii DNA was detected mainly in brain and muscle, but the parasite load was significantly lower in GV compared to GII brains (P < 0.05). Histopathological changes were observed in brains, with T. gondii cysts as well as an inflammatory condition, including necrosis areas in GII and GIII. These data confirm active infection with tissue injury. This inflammatory condition was attenuated in the groups treated with rosuvastatin, especially R40 (GV). Our findings demonstrated the in vivo action of rosuvastatin in reducing cerebral parasitic load and indicate that this drug may interfere in chronic toxoplasmosis.

A Metabolic Dependency for Host Isoprenoids in the Obligate Intracellular Pathogen Rickettsia parkeri Underlies a Sensitivity to the Statin Class of Host-Targeted Therapeutics

Obligate intracellular pathogens, which include viruses as well as certain bacteria and eukaryotes, are a subset of infectious microbes that are metabolically dependent on and unable to grow outside an infected host cell because they have lost or lack essential biosynthetic pathways. In this study, we describe a metabolic dependency of the bacterial pathogen Rickettsia parkeri on host isoprenoid molecules that are used in the biosynthesis of downstream products, including cholesterol, steroid hormones, and heme. Bacteria make products from isoprenoids, such as an essential lipid carrier for making the bacterial cell wall. We show that bacterial metabolic dependency can represent a potential Achilles’ heel and that inhibiting host isoprenoid biosynthesis with the FDA-approved statin class of drugs inhibits bacterial growth by interfering with the integrity of the cell wall. This work supports the potential to treat infections by obligate intracellular pathogens through inhibition of host biosynthetic pathways that are susceptible to parasitism.

Gram-negative bacteria in the order Rickettsiales have an obligate intracellular growth requirement, and some species cause human diseases such as typhus and spotted fever. The bacteria have evolved a dependence on essential nutrients and metabolites from the host cell as a consequence of extensive genome reduction. However, it remains largely unknown which nutrients they acquire and whether their metabolic dependency can be exploited therapeutically. Here, we describe a genetic rewiring of bacterial isoprenoid biosynthetic pathways in the Rickettsiales that has resulted from reductive genome evolution. Furthermore, we investigated whether the spotted fever group Rickettsia species Rickettsia parkeri scavenges isoprenoid precursors directly from the host. Using targeted mass spectrometry, we found that infection caused decreases in host isoprenoid products and concomitant increases in bacterial isoprenoid metabolites. Additionally, we report that treatment of infected cells with statins, which inhibit host isoprenoid synthesis, prohibited bacterial growth. We show that growth inhibition correlates with changes in bacterial size and shape that mimic those caused by antibiotics that inhibit peptidoglycan biosynthesis, suggesting that statins lead to an inhibition of cell wall synthesis. Altogether, our results describe a potential Achilles’ heel of obligate intracellular pathogens that can potentially be exploited with host-targeted therapeutics that interfere with metabolic pathways required for bacterial growth.

IMPORTANCE Obligate intracellular pathogens, which include viruses as well as certain bacteria and eukaryotes, are a subset of infectious microbes that are metabolically dependent on and unable to grow outside an infected host cell because they have lost or lack essential biosynthetic pathways. In this study, we describe a metabolic dependency of the bacterial pathogen Rickettsia parkeri on host isoprenoid molecules that are used in the biosynthesis of downstream products, including cholesterol, steroid hormones, and heme. Bacteria make products from isoprenoids, such as an essential lipid carrier for making the bacterial cell wall. We show that bacterial metabolic dependency can represent a potential Achilles’ heel and that inhibiting host isoprenoid biosynthesis with the FDA-approved statin class of drugs inhibits bacterial growth by interfering with the integrity of the cell wall. This work supports the potential to treat infections by obligate intracellular pathogens through inhibition of host biosynthetic pathways that are susceptible to parasitism.

Synthesis and biological evaluation of 1-alkylaminomethyl-1,1-bisphosphonic acids against Trypanosoma cruzi and Toxoplasma gondii

As an extension of our project aimed at the search for new chemotherapeutic agents against Chagas disease and toxoplasmosis, several 1,1-bisphosphonates were designed, synthesized and biologically evaluated against Trypanosoma cruzi and Toxoplasma gondii, the etiologic agents of these diseases, respectively. In particular, and based on the antiparasitic activity exhibited by 2-alkylaminoethyl-1,1-bisphosphonates targeting farnesyl diphosphate synthase, a series of linear 2-alkylaminomethyl-1,1-bisphosphonic acids (compounds 21-33), that is, the position of the amino group was one carbon closer to the gem-phosphonate moiety, were evaluated as growth inhibitors against the clinically more relevant dividing form (amastigotes) of T. cruzi. Although all of these compounds resulted to be devoid of antiparasitic activity, these results were valuable for a rigorous SAR study. In addition, unexpectedly, the synthetic designed 2-cycloalkylaminoethyl-1,1-bisphosphonic acids 47-49 were free of antiparasitic activity. Moreover, long chain sulfur-containing 1,1-bisphosphonic acids, such as compounds 54-56, 59, turned out to be nanomolar growth inhibitors of tachyzoites of T. gondii. As many bisphosphonate-containing molecules are FDA-approved drugs for the treatment of bone resorption disorders, their potential nontoxicity makes them good candidates to control American trypanosomiasis and toxoplasmosis.

Farnesyl pyrophosphate synthase is essential for the promastigote and amastigote stages in Leishmania major

Isoprenoid synthesis provides a diverse class of biomolecules including sterols, dolichols, ubiquinones and prenyl groups. The enzyme farnesyl pyrophosphate synthase (FPPS) catalyzes the formation of farnesyl pyrophosphate, a key intermediate for the biosynthesis of all isoprenoids. In Leishmania, FPPS is considered the main target of nitrogen containing bisphosphonates, yet the essentiality of this enzyme remains untested. Using a facilitated knockout approach, we carried out the genetic analysis of FPPS in Leishmania major. Our data indicated that chromosomal null mutants for FPPS could only be generated in presence of an episomally expressed FPPS. Long-term retention of the episome by the chromosomal FPPS-null mutants in culture and in infected BALB/c mice suggests that FPPS is indispensable. In addition, applying negative selection pressure failed to induce the loss of ectopic FPPS in the chromosomal FPPS-null mutants, although it led to significant growth delay in culture and in mice. Together, our findings have confirmed the essentiality of FPPS in both promastigotes and amastigotes in L. major and thus validate its potential as a drug target for the treatment of cutaneous leishmaniasis.