The antipsychotic thioridazine shows promising therapeutic activity in a mouse model of multidrug-resistant tuberculosis

In Vitro and In Vivo Antileishmanial Activity of Thioridazine

INTRODUCTION

Leishmaniasis is a neglected disease with high prevalence and incidence in tropical and subtropical areas. Existing drugs are limited due to cost, toxicity, declining efficacy and unavailability in endemic places. Drug repurposing has established as an efficient way for the discovery of drugs for a variety of diseases.

PURPOSE

The objective of the present work was testing the antileishmanial activity of thioridazine, an antipsychotic agent with demonstrated effect against other intracellular pathogens.

METHODS

The cytotoxicity for mouse peritoneal macrophages as well as the activity against Leishmania amazonensis, Leishmania mexicana and Leishmania major promastigotes and intracellular amastigotes, as well as in a mouse model of cutaneous leishmaniasis, were assessed.

RESULTS

Thioridazine inhibited the in vitro proliferation of promastigotes (50% inhibitory concentration-IC50-values in the range of 0.73 µM to 3.8 µM against L. amazonensis, L. mexicana and L. major) and intracellular amastigotes (IC50 values of 1.27 µM to 4.4 µM for the same species). In contrast, in mouse peritoneal macrophages, the 50% cytotoxic concentration was 24.0 ± 1.89 µM. Thioridazine inhibited the growth of cutaneous lesions and reduced the number of parasites in the infected tissue of mice. The dose of thioridazine that inhibited lesion development by 50% compared to controls was 23.3 ± 3.1 mg/kg and in terms of parasite load, it was 11.1 ± 0.97 mg/kg.

CONCLUSIONS

Thioridazine was effective against the promastigote and intracellular amastigote stages of three Leishmania species and in a mouse model of cutaneous leishmaniasis, supporting the potential repurposing of this drug as an antileishmanial agent.

Elucidating the function of hypothetical PE_PGRS45 protein of Mycobacterium tuberculosis as an oxido-reductase: a potential target for drug repurposing for the treatment of tuberculosis

Mycobacterium tuberculosis (Mtb) encodes a total of 67 PE_PGRS proteins and definite functions of many of them are still unknown. This study reports PE_PGRS45 (Rv2615c) protein from Mtb as NADPH dependent oxido-reductase having substrate specificity for fatty acyl Coenzyme A. Computational studies predicted PE_PGRS45 to be an integral membrane protein of Mtb. Expression of PE_PGRS45 in non-pathogenic Mycobacterium smegmatis, which does not possess PE_PGRS genes, confirmed its membrane localization. This protein was observed to have NADPH binding motif. Experimental validation confirmed its NADPH dependent oxido-reductase activity (Km value = 34.85 ± 9.478 μM, Vmax = 96.77 ± 7.184 nmol/min/mg of protein). Therefore, its potential to be targeted by first line anti-tubercular drug Isoniazid (INH) was investigated. INH was predicted to bind within the active site of PE_PGRS45 protein and experiments validated its inhibitory effect on the oxido-reductase activity of PE_PGRS45 with IC50/Ki values of 5.66 μM. Mtb is resistant to first line drugs including INH. Therefore, to address the problem of drug resistant TB, docking and Molecular Dynamics (MD) simulation studies between PE_PGRS45 and three drugs (Entacapone, Tolcapone and Verapamil) which are being used in Parkinson's and hypertension treatment were performed. PE_PGRS45 bound the three drugs with similar or better affinity in comparison to INH. Additionally, INH and these drugs bound within the same active site of PE_PGRS45. This study discovered Mtb's PE_PGRS45 protein to have an oxido-reductase activity and could be targeted by drugs that can be repurposed for TB treatment. Furthermore, in-vitro and in-vivo validation will aid in drug-resistant TB treatment. HIGHLIGHTSIn-silico and in-vitro studies of hypothetical protein PE_PGRS45 (Rv2615c) of Mycobacterium tuberculosis (Mtb) reveals it to be an integral membrane proteinPE_PGRS45 protein has substrate specificity for fatty acyl Coenzyme A (fatty acyl CoA) and possess NADPH dependent oxido-reductase activityDocking and simulation studies revealed that first line anti-tubercular drug Isoniazid (INH) and other drugs with anti-TB property have strong affinity for PE_PGRS45 proteinOxido-reductase activity of PE_PGRS45 protein is inhibited by INHPE_PGRS45 protein could be targeted by drugs that can be repurposed for TB treatmentCommunicated by Ramaswamy H. Sarma.

Potential Repurposed Drug Candidates for Tuberculosis Treatment: Progress and Update of Drugs Identified in Over a Decade

The devastating impact of Tuberculosis (TB) has been a menace to mankind for decades. The World Health Organization (WHO) End TB Strategy aims to reduce TB mortality up to 95% and 90% of overall TB cases worldwide, by 2035. This incessant urge will be achieved with a breakthrough in either a new TB vaccine or novel drugs with higher efficacy. However, the development of novel drugs is a laborious process involving a timeline of almost 20-30 years with huge expenditure; on the other hand, repurposing previously approved drugs is a viable technique for overcoming current bottlenecks in the identification of new anti-TB agents. The present comprehensive review discusses the progress of almost all the repurposed drugs that have been identified to the present day (∼100) and are in the development or clinical testing phase against TB. We have also emphasized the efficacy of repurposed drugs in combination with already available frontline anti-TB medications along with the scope of future investigations. This study would provide the researchers a detailed overview of nearly all identified anti-TB repurposed drugs and may assist them in selecting the lead compounds for further in vivo/clinical research.

Something Old, Something New: Ion Channel Blockers as Potential Anti-Tuberculosis Agents

Tuberculosis (TB) remains a challenging global health concern and claims more than a million lives every year. We lack an effective vaccine and understanding of what constitutes protective immunity against TB to inform rational vaccine design. Moreover, treatment of TB requires prolonged use of multi-drug regimens and is complicated by problems of compliance and drug resistance. While most Mycobacterium tuberculosis (Mtb) bacilli are quickly killed by the drugs, the prolonged course of treatment is required to clear persistent drug-tolerant subpopulations. Mtb’s differential sensitivity to drugs is, at least in part, determined by the interaction between the bacilli and different host macrophage populations. Therefore, to design better treatment regimens for TB, we need to understand and modulate the heterogeneity and divergent responses that Mtb bacilli exhibit within macrophages. However, developing drugs de-novo is a long and expensive process. An alternative approach to expedite the development of new TB treatments is to repurpose existing drugs that were developed for other therapeutic purposes if they also possess anti-tuberculosis activity. There is growing interest in the use of immune modulators to supplement current anti-TB drugs by enhancing the host’s antimycobacterial responses. Ion channel blocking agents are among the most promising of the host-directed therapeutics. Some ion channel blockers also interfere with the activity of mycobacterial efflux pumps. In this review, we discuss some of the ion channel blockers that have shown promise as potential anti-TB agents.

Tuberculosis: An Overview of the Immunogenic Response, Disease Progression, and Medicinal Chemistry Efforts in the Last Decade toward the Development of Potential Drugs for Extensively Drug-Resistant Tuberculosis Strains

Tuberculosis (TB) is a slow growing, potentially debilitating disease that has plagued humanity for centuries and has claimed numerous lives across the globe. Concerted efforts by researchers have culminated in the development of various strategies to combat this malady. This review aims to raise awareness of the rapidly increasing incidences of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis, highlighting the significant modifications that were introduced in the TB treatment regimen over the past decade. A description of the role of pathogen-host immune mechanisms together with strategies for prevention of the disease is discussed. The struggle to develop novel drug therapies has continued in an effort to reduce the treatment duration, improve patient compliance and outcomes, and circumvent TB resistance mechanisms. Herein, we give an overview of the extensive medicinal chemistry efforts made during the past decade toward the discovery of new chemotypes, which are potentially active against TB-resistant strains.

The Cholinergic System Contributes to the Immunopathological Progression of Experimental Pulmonary Tuberculosis

The cholinergic system is present in both bacteria and mammals and regulates inflammation during bacterial respiratory infections through neuronal and non-neuronal production of acetylcholine (ACh) and its receptors. However, the presence of this system during the immunopathogenesis of pulmonary tuberculosis (TB) in vivo and in its causative agent Mycobacterium tuberculosis (Mtb) has not been studied. Therefore, we used an experimental model of progressive pulmonary TB in BALB/c mice to quantify pulmonary ACh using high-performance liquid chromatography during the course of the disease. In addition, we performed immunohistochemistry in lung tissue to determine the cellular expression of cholinergic system components, and then administered nicotinic receptor (nAChR) antagonists to validate their effect on lung bacterial burden, inflammation, and pro-inflammatory cytokines. Finally, we subjected Mtb cultures to colorimetric analysis to reveal the production of ACh and the effect of ACh and nAChR antagonists on Mtb growth. Our results show high concentrations of ACh and expression of its synthesizing enzyme choline acetyltransferase (ChAT) during early infection in lung epithelial cells and macrophages. During late progressive TB, lung ACh upregulation was even higher and coincided with ChAT and α7 nAChR subunit expression in immune cells. Moreover, the administration of nAChR antagonists increased pro-inflammatory cytokines, reduced bacillary loads and synergized with antibiotic therapy in multidrug resistant TB. Finally, in vitro studies revealed that the bacteria is capable of producing nanomolar concentrations of ACh in liquid culture. In addition, the administration of ACh and nicotinic antagonists to Mtb cultures induced or inhibited bacterial proliferation, respectively. These results suggest that Mtb possesses a cholinergic system and upregulates the lung non-neuronal cholinergic system, particularly during late progressive TB. The upregulation of the cholinergic system during infection could aid both bacterial growth and immunomodulation within the lung to favor disease progression. Furthermore, the therapeutic efficacy of modulating this system suggests that it could be a target for treating the disease.

The Comparative Effect of Nisin and Thioridazine as Potential Anticancer Agents on Hepatocellular Carcinoma

BACKGROUND

Hepatocellular carcinoma is a major health problem worldwide especially in Egypt. It accounts for the fifth common cancer and the second cause of death among different cancers. This study investigated the efficacy and molecular mechanism of Nisin and/or Thioridazine as anticancer treatment on human liver cancer HepG2 cell line.

METHODS

Nisin and Thioridazine were applied for 24 h on human liver cancer cell line (HepG2). 3-(4, 5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was done to assess the cytotoxicity of Nisin and Thioridazine. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) was used for the assessment of PI3K, AKT, SIRT-1, and NRF2 expression in the treated cell line. The protein level of reactive oxygen species (ROS) and vascular endothelial growth factor (VEGF) was measured in the collected media by ELISA technique. Western blot analysis was done for, tAKT, pAKT, tPI3K, and pPI3K.

RESULTS

Cell proliferation results showed that compared with the untreated cancer, Nisin and/or Thioridazine treated groups had decreased cell proliferation (p value< 0.0001). Nisin and/or Thioridazine decreased PI3K/AKT mRNA and protein expression in hepatocellular carcinoma cells (HCC). Also Nisin and/or Thioridazine decreased anti-oxidative SIRT1/NRF2 mRNA expression. ROS level highly increased with Nisin and/or Thioridazine treatment in contrast to VEGF protein level which was highly decreased.

CONCLUSION

These results introduce Nisin and Thioridazine as new therapeutic lines in HCC.

Thioridazine Is an Efflux Pump Inhibitor in Mycobacterium avium Complex but of Limited Clinical Relevance

Treatment of Mycobacterium avium complex pulmonary disease (MAC-PD) is challenging partly due to high efflux pump expression. Thioridazine might block these efflux pumps. We explore the efficacy of thioridazine against M. avium isolates using MICs, time-kill combination assays, ex vivo macrophage infection assays, and efflux assays. Thioridazine is bactericidal against M. avium, inhibits intracellular growth at 2× MIC, and blocks ethidium bromide efflux. However, its toxicity and low plasma concentrations make it unlikely to add efficacy to MAC-PD therapy.

In Vitro Efficacies, ADME, and Pharmacokinetic Properties of Phenoxazine Derivatives Active against Mycobacterium tuberculosis

Mycobacterium tuberculosis, the causative agent of tuberculosis, remains a leading infectious killer globally, demanding the urgent development of faster-acting drugs with novel mechanisms of action. Riminophenazines such as clofazimine are clinically efficacious against both drug-susceptible and drug-resistant strains of M. tuberculosis We determined the in vitro anti-M. tuberculosis activities, absorption, distribution, metabolism, and excretion properties, and in vivo mouse pharmacokinetics of a series of structurally related phenoxazines. One of these, PhX1, displayed promising drug-like properties and potent in vitro efficacy, supporting its further investigation in an M. tuberculosis-infected animal model.

The interplay between depression and tuberculosis

Depression is a major mental health condition and is expected be the most debilitating and widespread health disorder by 2030. Tuberculosis (TB) is also a leading cause of morbidity and mortality worldwide and interestingly, is a common comorbidity of depression. As such, much attention has been paid to the association between these 2 pathologies. Based on clinical reports, the association between TB and depression seems to be bidirectional, with a substantial overlap in symptoms between the 2 conditions. TB infection or reactivation may precipitate depression, likely as a consequence of the host's inflammatory response and/or dysregulation of the hypothalamic-pituitary-adrenal axis. Nevertheless, few studies have considered whether patients with depression are at a higher risk for TB. In this review, we discuss the hypotheses on the association between depression and TB, highlighting the immuno-inflammatory response and lipid metabolism as potential mechanisms. Improving our understanding of the interplay between these 2 disorders should help guide TB clinical care and prevention both in patients with comorbid depression and in the general population.

Non-antibiotic adjunctive therapy: A promising approach to fight tuberculosis

Tuberculosis (TB) is currently a clinical and public health problem. There is a concern about the emergence and development of multidrug-resistant (MDR-TB) and extensively drug-resistant (XDR-TB) species. Additionally, the lack of effective vaccines is another limitation to control the related infections. To overcome these problems various approaches have been pursued such as finding novel drug candidates with a new mechanism of action or repurposing conventional antibiotics. However, these strategies are still far from clinical application. Hence, the use of adjunctive therapy has been suggested for TB. In this paper, we review non-antibiotic adjunctive treatment options for TB. Natural products, vitamins, micronutrients, and trace elementals, as well as non-antibiotic drugs, are examples of agents which have been used as adjunctive therapies. The use of these adjunctive therapies has been shown to improve disease outcomes and reduce the adverse effects of antibiotic drugs. Employing these agents, either alone or in combination with antibiotics, might be considered as a promising approach to control TB infections and achieve better clinical outcomes. However, supportive evidence from randomized controlled trials is still scant and merits further investigations.

A Protein Complex from Human Milk Enhances the Activity of Antibiotics and Drugs against Mycobacterium tuberculosis

Mycobacterium tuberculosis, the causative agent of human tuberculosis (TB), has surpassed HIV/AIDS as the leading cause of death from a single infectious agent. The increasing occurrence of drug-resistant strains has become a major challenge for health care systems and, in some cases, has rendered TB untreatable. However, the development of new TB drugs has been plagued with high failure rates and costs. Alternative strategies to increase the efficacy of current TB treatment regimens include host-directed therapies or agents that make M. tuberculosis more susceptible to existing TB drugs. In this study, we show that HAMLET, an α-lactalbumin-oleic acid complex derived from human milk, has bactericidal activity against M. tuberculosis HAMLET consists of a micellar oleic acid core surrounded by a shell of partially denatured α-lactalbumin molecules and unloads oleic acid into cells upon contact with lipid membranes. At sublethal concentrations, HAMLET potentiated a remarkably broad array of TB drugs and antibiotics against M. tuberculosis For example, the minimal inhibitory concentrations of rifampin, bedaquiline, delamanid, and clarithromycin were decreased by 8- to 16-fold. HAMLET also killed M. tuberculosis and enhanced the efficacy of TB drugs inside macrophages, a natural habitat of M. tuberculosis Previous studies showed that HAMLET is stable after oral delivery in mice and nontoxic in humans and that it is possible to package hydrophobic compounds in the oleic acid core of HAMLET to increase their solubility and metabolic stability. The potential of HAMLET and other liprotides as drug delivery and sensitization agents in TB chemotherapy is discussed here.

Gene module analysis of juvenile myelomonocytic leukemia and screening of anticancer drugs

Juvenile myelomonocytic leukemia (JMML) is a rare but severe primary hemopoietic system tumor of childhood, most frequent in children 4 years and younger. There are currently no specific anticancer therapies targeting JMML, and the underlying gene expression changes have not been revealed. To define molecular targets and possible biomarkers for early diagnosis, optimal treatment, and prognosis, we conducted microarray data analysis using the Gene Expression Omnibus, and constructed protein‑protein interaction networks of all differentially expressed genes. Modular bioinformatics analysis revealed four core functional modules for JMML. We analyzed the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway functions associated with these modules. Using the CMap database, nine potential anticancer drugs were identified that modulate expression levels of many JMML‑associated genes. In addition, we identified possible miRNAs and transcription factors regulating these differentially expressed genes. This study defines a new research strategy for developing JMML‑targeted chemotherapies.

Challenging the Drug-Likeness Dogma for New Drug Discovery in Tuberculosis

The emergence of multi- and extensively drug resistant tuberculosis worldwide poses a great threat to human health and highlight the need to discover and develop new, effective and inexpensive antituberculosis agents. High-throughput screening assays against well-validated drug targets and structure based drug design have been employed to discover new lead compounds. However, the great majority fail to demonstrate any antimycobacterial activity when tested against Mycobacterium tuberculosis in whole-cell screening assays. This is mainly due to some of the intrinsic properties of the bacilli, such as the extremely low permeability of its cell wall, slow growth, drug resistance, drug tolerance, and persistence. In this sense, understanding the pathways involved in M. tuberculosis drug tolerance, persistence, and pathogenesis, may reveal new approaches for drug development. Moreover, the need for compounds presenting a novel mode of action is of utmost importance due to the emergence of resistance not only to the currently used antituberculosis agents, but also to those in the pipeline. Cheminformatics studies have shown that drugs endowed with antituberculosis activity have the peculiarity of being more lipophilic than many other antibacterials, likely because this leads to improved cell penetration through the extremely waxy mycobacterial cell wall. Moreover, the interaction of the lipophilic moiety with the membrane alters its stability and functional integrity due to the disruption of the proton motive force, resulting in cell death. When a ligand-based medicinal chemistry campaign is ongoing, it is always difficult to predict whether a chemical modification or a functional group would be suitable for improving the activity. Nevertheless, in the “instruction manual” of medicinal chemists, certain functional groups or certain physicochemical characteristics (i.e., high lipophilicity) are considered red flags to look out for in order to safeguard drug-likeness and avoid attritions in the drug discovery process. In this review, we describe how antituberculosis compounds challenge established rules such as the Lipinski's “rule of five” and how medicinal chemistry for antituberculosis compounds must be thought beyond such dogmatic schemes.

Addressing the tuberculosis-depression syndemic to end the tuberculosis epidemic

Tuberculosis (TB) and depression act synergistically via social, behavioral, and biological mechanisms to magnify the burden of disease. Clinical depression is a common, under-recognized, yet treatable condition that, if comorbid with TB, is associated with increased morbidity, mortality, community TB transmission, and drug resistance. Depression may increase risk of TB reactivation, contribute to disease progression, and/or inhibit the physiological response to anti-tuberculosis treatment because of poverty, undernutrition, immunosuppression, and/or negative coping behaviors, including substance abuse. Tuberculous infection and/or disease reactivation may precipitate depression as a result of the inflammatory response and/or dysregulation of the hypothalamic-pituitary-adrenal axis. Clinical depression may also be triggered by TB-related stigma, exacerbating other underlying social vulnerabilities, and/or may be attributed to the side effects of anti-tuberculosis treatment. Depression may negatively impact health behaviors such as diet, health care seeking, medication adherence, and/or treatment completion, posing a significant challenge for global TB elimination. As several of the core symptoms of TB and depression overlap, depression often goes unrecognized in individuals with active TB, or is dismissed as a normative reaction to situational stress. We used evidence to reframe TB and depression comorbidity as the 'TB-depression syndemic', and identified critical research gaps to further elucidate the underlying mechanisms. The World Health Organization's Global End TB Strategy calls for integrated patient-centered care and prevention linked to social protection and innovative research. It will require multidisciplinary approaches that consider conditions such as TB and depression together, rather than as separate problems and diseases, to end the global TB epidemic.

Efflux Activity Differentially Modulates the Levels of Isoniazid and Rifampicin Resistance among Multidrug Resistant and Monoresistant Mycobacterium tuberculosis Strains

With the growing body of knowledge on the contribution of efflux activity to Mycobacterium tuberculosis drug resistance, increased attention has been given to the use of efflux inhibitors as adjuvants of tuberculosis therapy. Here, we investigated how efflux activity modulates the levels of efflux between monoresistant and multi- and extensively drug resistant (M/XDR) M. tuberculosis clinical isolates. The strains were characterized by antibiotic susceptibility testing in the presence/absence of efflux inhibitors, molecular typing, and genetic analysis of drug-resistance-associated genes. Efflux activity was quantified by real-time fluorometry. The results demonstrated that all the M. tuberculosis clinical strains, susceptible or resistant, presented a faster, rapid, and non-specific efflux-mediated short-term response to drugs. The synergism assays demonstrated that the efflux inhibitors were more effective in reducing the resistance levels in the M/XDR strains than in the monoresistant strains. This indicated that M/XDR strains presented a more prolonged response to drugs mediated by efflux compared to the monoresistant strains, but both maintain it as a long-term stress response. This work shows that efflux activity modulates the levels of drug resistance between monoresistant and M/XDR M. tuberculosis clinical strains, allowing the bacteria to survive in the presence of noxious compounds.

Bioenergetics of Mycobacterium: An Emerging Landscape for Drug Discovery

Mycobacterium tuberculosis (Mtb) exhibits remarkable metabolic flexibility that enables it to survive a plethora of host environments during its life cycle. With the advent of bedaquiline for treatment of multidrug-resistant tuberculosis, oxidative phosphorylation has been validated as an important target and a vulnerable component of mycobacterial metabolism. Exploiting the dependence of Mtb on oxidative phosphorylation for energy production, several components of this pathway have been targeted for the development of new antimycobacterial agents. This includes targeting NADH dehydrogenase by phenothiazine derivatives, menaquinone biosynthesis by DG70 and other compounds, terminal oxidase by imidazopyridine amides and ATP synthase by diarylquinolines. Importantly, oxidative phosphorylation also plays a critical role in the survival of persisters. Thus, inhibitors of oxidative phosphorylation can synergize with frontline TB drugs to shorten the course of treatment. In this review, we discuss the oxidative phosphorylation pathway and development of its inhibitors in detail.

Rifamycin action on RNA polymerase in antibiotic-tolerant Mycobacterium tuberculosis results in differentially detectable populations

Mycobacterium tuberculosis (Mtb) encounters stresses during the pathogenesis and treatment of tuberculosis (TB) that can suppress replication of the bacteria and render them phenotypically tolerant to most available drugs. Where studied, the majority of Mtb in the sputum of most untreated subjects with active TB have been found to be nonreplicating by the criterion that they do not grow as colony-forming units (cfus) when plated on agar. However, these cells are viable because they grow when diluted in liquid media. A method for generating such "differentially detectable" (DD) Mtb in vitro would aid studies of the biology and drug susceptibility of this population, but lack of independent confirmation of reported methods has contributed to skepticism about their existence. Here, we identified confounding artifacts that, when avoided, allowed development of a reliable method of producing cultures of ≥90% DD Mtb in starved cells. We then characterized several drugs according to whether they contribute to the generation of DD Mtb or kill them. Of the agents tested, rifamycins led to DD Mtb generation, an effect lacking in a rifampin-resistant strain with a mutation in rpoB, which encodes the canonical rifampin target, the β subunit of RNA polymerase. In contrast, thioridazine did not generate DD Mtb from starved cells but killed those generated by rifampin.

Type-II NADH Dehydrogenase (NDH-2): a promising therapeutic target for antitubercular and antibacterial drug discovery

INTRODUCTION

Tuberculosis (TB) is highly dangerous due to the development of resistance to first-line drugs. Moreover, Mycobacterium tuberculosis (Mtb) has also developed resistance to newly approved antitubercular drug bedaquiline. This necessitates the search for drugs acting on newer molecular targets. The energy metabolism of mycobacteria is the prime focus for the discovery of novel antitubercular drugs. Targeting type-2 NADH dehydrogenase (NDH-2) involved in the production of respiratory ATP could, therefore, be effective in treating the disease. Areas covered: This review describes the energetics of mycobacteria and the role of NDH-2 in ATP synthesis. Special attention has been given for genetic and chemical validations of NDH-2 as a molecular target. The reported kinetics and crystal structures of NDH-2 have been given in detail for better understanding of the enzyme. Expert opinion: NDH-2 is an essential enzyme for ATP synthesis and has a potential role in dormancy and persistence of Mtb. The human counterpart lacks this enzyme and hence NDH-2 inhibitors could have more clinical importance. Phenothiazines are potent inhibitor of NDH-2 and are effective against both drug-susceptible and drug-resistant Mtb. Thus, it is highly desirable to optimize phenothiazine class of compounds for the development of next generation anti-TB drugs.

Thioridazine enhances sensitivity to carboplatin in human head and neck cancer cells through downregulation of c-FLIP and Mcl-1 expression

Carboplatin is a less toxic analog of cisplatin, but carboplatin also has side effects, including bone marrow suppression. Therefore, to improve the capacity of the anticancer activity of carboplatin, we investigated whether combined treatment with carboplatin and thioridazine, which has antipsychotic and anticancer activities, has a synergistic effect on apoptosis. Combined treatment with carboplatin and thioridazine markedly induced caspase-mediated apoptosis in head and neck squamous cell carcinoma (AMC-HN4) cells. Combined treatment with carboplatin and thioridazine induced downregulation of Mcl-1 and c-FLIP expression. Ectopic expression of Mcl-1 and c-FLIP inhibited carboplatin plus thioridazine-induced apoptosis. We found that augmentation of proteasome activity had a critical role in downregulation of Mcl-1 and c-FLIP expression at the post-translational level in carboplatin plus thioridazine-treated cells. Furthermore, carboplatin plus thioridazine induced upregulation of the expression of proteasome subunit alpha 5 (PSMA5) through mitochondrial reactive oxygen species (ROS)-dependent nuclear factor E2-related factor 2 (Nrf2) activation. In addition, combined treatment with carboplatin and thioridazine markedly induced apoptosis in human breast carcinoma (MDA-MB231) and glioma (U87MG) cells, but not in human normal mesangial cells and normal human umbilical vein cells (EA.hy926). Collectively, our study demonstrates that combined treatment with carboplatin and thioridazine induces apoptosis through proteasomal degradation of Mcl-1 and c-FLIP by upregulation of Nrf2-dependent PSMA5 expression.

Thioridazine has potent antitumor effects on lung cancer stem-like cells

Thioridazine (TDZ), originally an anti-psychotic drug, suppresses several types of cancer and has specificity for leukemia stem cells. The present study was performed to assess its effect on lung cancer stem-like cells, as its effect remains unknown. TDZ was utilized to treat lung cancer stem-like cells (A549 sphere cells) and its cytotoxic effect and mechanism were evaluated in vitro and in vivo. TDZ elicited cytotoxicity in A549 sphere cells and inhibited their proliferation in a dose-dependent pattern. A549 sphere cells treated with TDZ showed nuclear fragmentation, increased G0/G1 phase distribution, positive Annexin V staining, and a change in the expression of caspase family and cell cycle-associated proteins. These results suggest the induction of caspase-dependent apoptosis and cell cycle arrest. In addition, TDZ treatment resulted in significant inhibitory effect on mice xenografts established by A549 sphere cells. TDZ repressed growth of lung cancer stem-like cells in vitro and in vivo, indicating its potential application in targeting lung cancer stem-like cells.

Thioridazine: A Non-Antibiotic Drug Highly Effective, in Combination with First Line Anti-Tuberculosis Drugs, against Any Form of Antibiotic Resistance of Mycobacterium tuberculosis Due to Its Multi-Mechanisms of Action

This review presents the evidence that supports the use of thioridazine (TZ) for the therapy of a pulmonary tuberculosis infection regardless of its antibiotic resistance status. The evidence consists of in vitro and ex vivo assays that demonstrate the activity of TZ against all encountered Mycobacterium tuberculosis (Mtb) regardless of its antibiotic resistance phenotype, as well as in vivo as a therapy for mice infected with multi-drug resistant strains of Mtb, or for human subjects infected with extensively drug resistant (XDR) Mtb. The mechanisms of action by which TZ brings about successful therapeutic outcomes are presented in detail.

Inhibition of Bacterial RNase P RNA by Phenothiazine Derivatives

There is a need to identify novel scaffolds and targets to develop new antibiotics. Methylene blue is a phenothiazine derivative, and it has been shown to possess anti-malarial and anti-trypanosomal activities. Here, we show that different phenothiazine derivatives and pyronine G inhibited the activities of three structurally different bacterial RNase P RNAs (RPRs), including that from Mycobacterium tuberculosis, with Ki values in the lower μM range. Interestingly, three antipsychotic phenothiazines (chlorpromazine, thioridazine, and trifluoperazine), which are known to have antibacterial activities, also inhibited the activity of bacterial RPRs, albeit with higher Ki values than methylene blue. Phenothiazines also affected lead(II)-induced cleavage of bacterial RPR and inhibited yeast tRNA(Phe), indicating binding of these drugs to functionally important regions. Collectively, our findings provide the first experimental data showing that long, noncoding RNAs could be targeted by different phenothiazine derivatives.

In vitro evaluation of novel inhalable dry powders consisting of thioridazine and rifapentine for rapid tuberculosis treatment

Thioridazine is an orally administered antipsychotic drug with potential for treatment of drug-resistant tuberculosis (TB). However, drug-induced adverse cardiac effects have been reported when thioridazine was used at an efficacious oral dose of 200mg/day to treat TB. Pulmonary delivery of thioridazine could be a rational approach to reduce dose-related side effects while enabling high drug concentrations at the primary site of infection. The present study compares in vitro aerosol performance, storage stability, and in vitro antimicrobial activity and cytotoxicity of two inhalable powders composed of thioridazine and a first-line anti-TB drug, rifapentine. Formulation 1 is a combination of amorphous thioridazine and crystalline rifapentine, while Formulation 2 consisted of both drugs as amorphous forms. Both thioridazine-rifapentine formulations were found suitable for inhalation with a total fine particle fraction (<5μm) of 68-76%. The two powders had similar MIC90 to rifapentine alone, being 0.000625μg/mL and 0.005μg/ml against Mycobacterium tuberculosis H37Ra and M. tuberculosis H37Rv, respectively. In contrast, thioridazine alone had a MIC90 of 12.5μg/mL and 500μg/mL, against M. tuberculosis H37Ra and M. tuberculosis H37Rv, respectively, demonstrating no synergistic anti-TB activity. However, thioridazine and rifapentine in a ratio of 1:3 enhanced the killing of M. tuberculosis H37Ra within the human monocyte-derived macrophages (THP-1) compared to the single drug treatments. Both powders showed an acceptable half maximal inhibitory concentration (IC50) of 31.25μg/mL on both THP-1 and human lung epithelial (A549) cells. However, Formulation 1 showed greater chemical stability than Formulation 2 after three months of storage under low humidity (vacuum) at 20±3°C. In conclusion, we have demonstrated a novel inhalable powder consisted of amorphous thioridazine and crystalline rifapentine (Formulation 1) with a good aerosol performance, potent anti-TB activity and storage stability, which deserves further in vivo investigations.

Thioridazine Alters the Cell-Envelope Permeability of Mycobacterium tuberculosis

The increasing occurrence of multidrug resistant tuberculosis exerts a major burden on treatment of this infectious disease. Thioridazine, previously used as a neuroleptic, is active against extensively drug resistant tuberculosis when added to other second- and third-line antibiotics. By quantitatively studying the proteome of thioridazine-treated Mycobacterium tuberculosis, we discovered the differential abundance of several proteins that are involved in the maintenance of the cell-envelope permeability barrier. By assessing the accumulation of fluorescent dyes in mycobacterial cells over time, we demonstrate that long-term drug exposure of M. tuberculosis indeed increased the cell-envelope permeability. The results of the current study demonstrate that thioridazine induced an increase in cell-envelope permeability and thereby the enhanced uptake of compounds. These results serve as a novel explanation to the previously reported synergistic effects between thioridazine and other antituberculosis drugs. This new insight in the working mechanism of this antituberculosis compound could open novel perspectives of future drug-administration regimens in combinational therapy.

Modulating antibiotic activity towards respiratory bacterial pathogens by co-medications: a multi-target approach

Non-antibiotic drugs can modulate bacterial physiology and/or antibiotic activity, opening perspectives for innovative therapeutic strategies. Focusing on respiratory pathogens and considering in vitro, in vivo, and clinical data, here we examine the effect of these drugs on the expression of resistance mechanisms, biofilm formation, and intracellular survival, as well as their influence on the activity of antibiotics on bacteria. Beyond the description of the effects observed, we also comment on concentrations that are active and discuss the mechanisms of drug-drug or drug-target interactions. This discussion should be helpful in defining useful targets for adjuvant therapy and establishing the corresponding pharmacophores for further drug fine-tuning.

Repurposing-a ray of hope in tackling extensively drug resistance in tuberculosis

Tuberculosis (TB) remains a serious concern more than two decades on from when the World Health Organization declared it a global health emergency. The alarming rise of antibiotic resistance in Mycobacterium tuberculosis, the etiological agent of TB, has made it exceedingly difficult to control the disease with the existing portfolio of anti-TB chemotherapy. The development of effective drugs with novel mechanism(s) of action is thus of paramount importance to tackle drug resistance. The development of novel chemical entities requires more than 10 years of research, requiring high-risk investment to become commercially available. Repurposing pre-existing drugs offers a solution to circumvent this mammoth investment in time and funds. In this context, several drugs with known safety and toxicity profiles have been evaluated against the TB pathogen and found to be efficacious against its different physiological states. As the endogenous targets of these drugs in the TB bacillus are most likely to be novel, there is minimal chance of cross-resistance with front-line anti-TB drugs. Also, reports that some of these drugs may potentially have multiple targets means that the possibility of the development of resistance against them is minimal. Thus repurposing existing molecules offers immense promise to tackle extensively drug-resistant TB infections.

Enhancement of in vitro activity of tuberculosis drugs by addition of thioridazine is not reflected by improved in vivo therapeutic efficacy

OBJECTIVES

Assessment of the activity of thioridazine towards Mycobacterium tuberculosis (Mtb), in vitro and in vivo as a single drug and in combination with tuberculosis (TB) drugs.

METHODS

The in vitro activity of thioridazine as single drug or in combination with TB drugs was assessed in terms of MIC and by use of the time-kill kinetics assay. Various Mtb strains among which the Beijing genotype strain BE-1585 were included. In vivo, mice with TB induced by BE-1585 were treated with a TB drug regimen with thioridazine during 13 weeks. Therapeutic efficacy was assessed by the change in mycobacterial load in the lung, spleen and liver during treatment and 13 weeks post-treatment.

RESULTS

In vitro, thioridazine showed a concentration-dependent and time-dependent bactericidal activity towards both actively-replicating and slowly-replicating Mtb. Thioridazine at high concentrations could enhance the activity of isoniazid and rifampicin, and in case of isoniazid resulted in elimination of mycobacteria and prevention of isoniazid-resistant mutants. Thioridazine had no added value in combination with moxifloxacin or amikacin. In mice with TB, thioridazine was poorly tolerated, limiting the maximum tolerated dose (MTD). The addition of thioridazine at the MTD to an isoniazid-rifampicin-pyrazinamide regimen for 13 weeks did not result in enhanced therapeutic efficacy.

CONCLUSIONS

Thioridazine is bactericidal towards Mtb in vitro, irrespective the mycobacterial growth rate and results in enhanced activity of the standard regimen. The in vitro activity of thioridazine in potentiating isoniazid and rifampicin is not reflected by improved therapeutic efficacy in a murine TB-model.

Thioridazine for treatment of tuberculosis: promises and pitfalls

The articles by De Knegt et al. and Singh et al. in a recent issue of this Journal address one of the current debates regarding the potential role of thioridazine in the treatment of tuberculosis. This commentary presents a summary of the available evidence, and, emphasizing the need for further research, asks the question: "How far can we go in repurposing thioridazine?"

Imipramine exploits histone deacetylase 11 to increase the IL-12/IL-10 ratio in macrophages infected with antimony-resistant Leishmania donovani and clears organ parasites in experimental infection

The efflux of antimony through multidrug resistance protein (MDR)-1 is the key factor in the failure of metalloid treatment in kala-azar patients infected with antimony-resistant Leishmania donovani (Sb(R)LD). Previously we showed that MDR-1 upregulation in Sb(R)LD infection is IL-10-dependent. Imipramine, a drug in use for the treatment of depression and nocturnal enuresis in children, inhibits IL-10 production from Sb(R)LD-infected macrophages (Sb(R)LD-Mϕs) and favors accumulation of surrogates of antimonials. It inhibits IL-10-driven nuclear translocation of c-Fos/c-Jun, critical for enhanced MDR-1 expression. The drug upregulates histone deacetylase 11, which inhibits acetylation of IL-10 promoter, leading to a decrease in IL-10 production from Sb(R)LD-Mϕs. It abrogates Sb(R)LD-mediated p50/c-Rel binding to IL-10 promoter and preferentially recruits p65/RelB to IL-12 p35 and p40 promoters, causing a decrease in IL-10 and overproduction of IL-12 in Sb(R)LD-Mϕs. Histone deacetylase 11 per se does not influence IL-12 promoter activity. Instead, a imipramine-mediated decreased IL-10 level allows optimal IL-12 production in Sb(R)LD-Mϕs. Furthermore, exogenous rIL-12 inhibits intracellular Sb(R)LD replication, which can be mimicked by the presence of Ab to IL-10. This observation indicated that reciprocity exists between IL-10 and IL-12 and that imipramine tips the balance toward an increased IL-12/IL-10 ratio in Sb(R)LD-Mϕs. Oral treatment of infected BALB/c mice with imipramine in combination with sodium stibogluconate cleared organ Sb(R)LD parasites and caused an expansion of the antileishmanial T cell repertoire where sodium stibogluconate alone had no effect. Our study deciphers a detailed molecular mechanism of imipramine-mediated regulation of IL-10/IL-12 reciprocity and its impact on Sb(R)LD clearance from infected hosts.

Sterilizing activity of thioridazine in combination with the first-line regimen against acute murine tuberculosis

We recently reported that in lung tissue, thioridazine accumulates at high concentrations relative to serum levels, displaying modest synergy with isoniazid and reducing the emergence of isoniazid-resistant mutants in mouse lungs. In this study, we sought to investigate the sterilizing activity of human-equivalent doses of thioridazine when given in combination with the "Denver regimen" against acute murine tuberculosis. We found a trend toward a positive impact of thioridazine on the bacterial clearance and lowering relapse rates of the combined standard TB chemotherapy.

Reduced emergence of isoniazid resistance with concurrent use of thioridazine against acute murine tuberculosis

The repurposing of existing drugs is being pursued as a means by which to accelerate the development of novel regimens for the treatment of drug-susceptible and drug-resistant tuberculosis (TB). In the current study, we assessed the activity of the antipsychotic drug thioridazine (TRZ) in combination with the standard regimen in a well-validated murine TB model. Single-dose and steady-state pharmacokinetic studies were performed in BALB/c mice to establish human-equivalent doses of TRZ. To determine the bactericidal activity of TRZ against TB in BALB/c mice, three separate studies were performed, including a dose-ranging study of TRZ monotherapy and efficacy studies of human-equivalent doses of TRZ with and without isoniazid (INH) or rifampin (RIF). Therapeutic efficacy was assessed by the change in mycobacterial load in the lung. The human-equivalent dose of thioridazine was determined to be 25 mg/kg of body weight, which was well tolerated in mice. TRZ was found to accumulate at high concentrations in lung tissue relative to serum levels. We observed modest synergy during coadministration of TRZ with INH, and the addition of TRZ reduced the emergence of INH-resistant mutants in mouse lungs. In conclusion, this study further illustrates the opportunity to reevaluate the contribution of TRZ to the sterilizing activity of combination regimens to prevent the emergence of drug-resistant M. tuberculosis.

Antipsychotic agent thioridazine sensitizes renal carcinoma Caki cells to TRAIL-induced apoptosis through reactive oxygen species-mediated inhibition of Akt signaling and downregulation of Mcl-1 and c-FLIP(L)

Thioridazine has been known as an antipsychotic agent, but it also has anticancer activity. However, the effect of thioridazine on tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) sensitization has not yet been studied. Here, we investigated the ability of thioridazine to sensitize TRAIL-mediated apoptosis. Combined treatment with thioridazine and TRAIL markedly induced apoptosis in various human carcinoma cells, including renal carcinoma (Caki, ACHN, and A498), breast carcinoma (MDA-MB231), and glioma (U251MG) cells, but not in normal mouse kidney cells (TMCK-1) and human normal mesangial cells. We found that thioridazine downregulated c-FLIP(L) and Mcl-1 expression at the post-translational level via an increase in proteasome activity. The overexpression of c-FLIP(L) and Mcl-1 overcame thioridazine plus TRAIL-induced apoptosis. We further observed that thioridazine inhibited the Akt signaling pathway. In contrast, although other phosphatidylinositol-3-kinase/Akt inhibitors (LY294002 and wortmannin) sensitized TRAIL-mediated apoptosis, c-FLIP(L) and Mcl-1 expressions were not altered. Furthermore, thioridazine increased the production of reactive oxygen species (ROS) in Caki cells, and ROS scavengers (N-acetylcysteine, glutathione ethyl ester, and trolox) inhibited thioridazine plus TRAIL-induced apoptosis, as well as Akt inhibition and the downregulation of c-FLIP(L) and Mcl-1. Collectively, our study demonstrates that thioridazine enhances TRAIL-mediated apoptosis via the ROS-mediated inhibition of Akt signaling and the downregulation of c-FLIP(L) and Mcl-1 at the post-translational level.

A review of the interplay between tuberculosis and mental health

AIMS

Tuberculosis and mental illness share common risk factors including homelessness, HIV positive serology, alcohol/substance abuse and migrant status leading to frequent comorbidity. We sought to generate a comprehensive literature review that examines the complex relationship between tuberculosis and mental illness.

METHODS

A literature search was conducted in MedLine, Ovid and Psychinfo, with further examination of the references of these articles. In total 316 articles were identified. It was not possible to conduct a formal meta-analysis due to the absence of randomised controlled data.

RESULTS

Rates of mental illness of up to 70% have been identified in tuberculosis patients. Medications used in the treatment of common mental illnesses, such as depression, may have significant interactions with anti-tuberculosis agents, especially isoniazid and increasingly linezolid. Many medications used in the treatment of tuberculosis can have significant adverse psychiatric effects and some medications such as rifampicin may reduce the effective doses of anti-psychotics y their enzyme induction actions. Treatment with agents such as cycloserine has been associated with depression, and there have been reported cases of psychosis with most anti-tuberculous agents. Mental illness and substance abuse may also affect compliance with treatment, with attendant public health concerns.

CONCLUSIONS

As a result of the common co-morbidity of mental illness and tuberculosis, it is probable that physicians will encounter previously undiagnosed mental illness among patients with tuberculosis. Similarly, psychiatrists are likely to meet tuberculosis among their patients. It is important that both psychiatrists and physicians are aware of the potential for interactions between the drugs used to treat tuberculosis and psychiatric conditions.

Antitubercular specific activity of ibuprofen and the other 2-arylpropanoic acids using the HT-SPOTi whole-cell phenotypic assay

OBJECTIVES

Lead antituberculosis (anti-TB) molecules with novel mechanisms of action are urgently required to fuel the anti-TB drug discovery pipeline. The aim of this study was to validate the use of the high-throughput spot culture growth inhibition (HT-SPOTi) assay for screening libraries of compounds against Mycobacterium tuberculosis and to study the inhibitory effect of ibuprofen (IBP) and the other 2-arylpropanoic acids on the growth inhibition of M tuberculosis and other mycobacterial species.

METHODS

The HT-SPOTi method was validated not only with known drugs but also with a library of 47 confirmed anti-TB active compounds published in the ChEMBL database. Three over-the-counter non-steroidal anti-inflammatory drugs were also included in the screening. The 2-arylpropanoic acids, including IBP, were comprehensively evaluated against phenotypically and physiologically different strains of mycobacteria, and their cytotoxicity was determined against murine RAW264.7 macrophages. Furthermore, a comparative bioinformatic analysis was employed to propose a potential mycobacterial target.

RESULTS

IBP showed antitubercular properties while carprofen was the most potent among the 2-arylpropanoic class. A 3,5-dinitro-IBP derivative was found to be more potent than IBP but equally selective. Other synthetic derivatives of IBP were less active, and the free carboxylic acid of IBP seems to be essential for its anti-TB activity. IBP, carprofen and the 3,5-dinitro-IBP derivative exhibited activity against multidrug-resistant isolates and stationary phase bacilli. On the basis of the human targets of the 2-arylpropanoic analgesics, the protein initiation factor infB (Rv2839c) of M tuberculosis was proposed as a potential molecular target.

CONCLUSIONS

The HT-SPOTi method can be employed reliably and reproducibly to screen the antimicrobial potency of different compounds. IBP demonstrated specific antitubercular activity, while carprofen was the most selective agent among the 2-arylpropanoic class. Activity against stationary phase bacilli and multidrug-resistant isolates permits us to speculate a novel mechanism of antimycobacterial action. Further medicinal chemistry and target elucidation studies could potentially lead to new therapies against TB.

Thioridazine lacks bactericidal activity in an animal model of extracellular tuberculosis

OBJECTIVES

The antipsychotic drug thioridazine is active in the murine model of tuberculosis infection, which is predominantly intracellular in nature. Recent clinical reports suggest that thioridazine may play a role in the treatment of drug-resistant tuberculosis. We studied the tuberculocidal activity of thioridazine in guinea pigs, which develop necrotic lung granulomas histologically resembling their human counterparts.

METHODS

Pharmacokinetic studies were performed in guinea pigs to establish human-equivalent doses of thioridazine. Guinea pigs were aerosol-infected with ∼100 bacilli of Mycobacterium tuberculosis and single-drug treatment was started 4 weeks later with a range of thioridazine doses daily (5 days/week) for up to 4 weeks. Control animals received no treatment or 60 mg/kg isoniazid.

RESULTS

The human-equivalent dose of thioridazine was determined to be 5 mg/kg with saturable absorption noted above 50 mg/kg. At the start of treatment, the lung bacterial burden was ∼6.2 log10 cfu. Although isoniazid reduced bacillary counts more than 10-fold, thioridazine monotherapy showed limited killing over the range of doses tested, reducing lung bacillary counts by 0.3-0.5 log10 following 1 month of treatment. Thioridazine was tolerated up to 40 mg/kg.

CONCLUSIONS

Thioridazine has limited bactericidal activity against extracellular bacilli within necrotic granulomas. Its contribution to the sterilizing activity of combination regimens against drug-susceptible and drug-resistant tuberculosis remains to be determined.

Role of Phenothiazines and Structurally Similar Compounds of Plant Origin in the Fight against Infections by Drug Resistant Bacteria

Phenothiazines have their primary effects on the plasma membranes of prokaryotes and eukaryotes. Among the components of the prokaryotic plasma membrane affected are efflux pumps, their energy sources and energy providing enzymes, such as ATPase, and genes that regulate and code for the permeability aspect of a bacterium. The response of multidrug and extensively drug resistant tuberculosis to phenothiazines shows an alternative therapy for the treatment of these dreaded diseases, which are claiming more and more lives every year throughout the world. Many phenothiazines have shown synergistic activity with several antibiotics thereby lowering the doses of antibiotics administered to patients suffering from specific bacterial infections. Trimeprazine is synergistic with trimethoprim. Flupenthixol (Fp) has been found to be synergistic with penicillin and chlorpromazine (CPZ); in addition, some antibiotics are also synergistic. Along with the antibacterial action described in this review, many phenothiazines possess plasmid curing activities, which render the bacterial carrier of the plasmid sensitive to antibiotics. Thus, simultaneous applications of a phenothiazine like TZ would not only act as an additional antibacterial agent but also would help to eliminate drug resistant plasmid from the infectious bacterial cells.

Combination approaches to combat multidrug-resistant bacteria

The increasing prevalence of infections caused by multidrug-resistant bacteria is a global health problem that has been exacerbated by the dearth of novel classes of antibiotics entering the clinic over the past 40 years. Herein, we describe recent developments toward combination therapies for the treatment of multidrug-resistant bacterial infections. These efforts include antibiotic-antibiotic combinations, and the development of adjuvants that either directly target resistance mechanisms such as the inhibition of β-lactamase enzymes, or indirectly target resistance by interfering with bacterial signaling pathways such as two-component systems (TCSs). We also discuss screening of libraries of previously approved drugs to identify nonobvious antimicrobial adjuvants.

Antitubercular activity and the subacute toxicity of (-)-Licarin A in BALB/c mice: a neolignan isolated from Aristolochia taliscana

BACKGROUND AND AIMS

Tuberculosis remains a worldwide health problem and requires long-term treatment with several antibiotics; therefore, compliance problems and the emergence of multidrug resistance (MDR) are involved. (-)-Licarin A (LA) was isolated from diverse plants such as Aristolochia taliscana and possesses antimycobacterial, antiinflammatory, trypanocidal, and neuroprotective activities. The aim of the study was to determine the antitubercular and subacute toxicity of LA isolated from A. taliscana in BALB/c mice.

METHODS

The antitubercular activity of LA was tested in a TB murine model inducing disease with M. tuberculosis H37Rv or MDR. Mice were treated with LA (5 mg/kg) for 30 and 60 days; post/treatment, lung bacilli loads and pneumonia percentage were determined. The subacute toxicity of LA (21 days) was evaluated in healthy mice. After treatment, biochemical and hematological parameters were determined and main organs were analyzed histologically.

RESULTS

In animals infected with drug-sensitive or MDR strains, LA produced a significant decrease of pulmonary bacillary burdens at day 30 of treatment, and a significant pneumonia reduction at days 30 and 60 of treatment. Regarding subacute toxicity, LA administration during 21 days showed no abnormalities in main-organ macro- and microarchitecture. Biochemical and hematological parameters analyzed showed no statistical differences between control and treated groups.

CONCLUSIONS

(-)-Licarin A reduces pneumonia of mice infected with both mycobacterium strains. Also, subacute toxicity of LA exhibits no major signs of damage. Biochemical and hematological parameters and histological analyses indicate that LA caused no significant changes at the doses assayed.

Pharmacologic inhibition of MALT1 protease by phenothiazines as a therapeutic approach for the treatment of aggressive ABC-DLBCL

Proteolytic activity of the mucosa-associated lymphoid tissue lymphoma translocation protein-1 (MALT1) paracaspase is required for survival of the activated B cell subtype of diffuse large B cell lymphoma (ABC-DLBCL). We have identified distinct derivatives of medicinal active phenothiazines, namely mepazine, thioridazine, and promazine, as small molecule inhibitors of the MALT1 protease. These phenothiazines selectively inhibit cleavage activity of recombinant and cellular MALT1 by a noncompetitive mechanism. Consequently, the compounds inhibit anti-apoptotic NF-κB signaling and elicit toxic effects selectively on MALT1-dependent ABC-DLBCL cells in vitro and in vivo. Our data provide a conceptual proof for a clinical application of distinct phenothiazines in the treatment of ABC-DLBCL.

Antitubercular pharmacodynamics of phenothiazines

OBJECTIVES

Phenothiazines have been shown to exhibit in vitro and in vivo activity against Mycobacterium tuberculosis (Mtb) and multidrug-resistant Mtb. They are predicted to target the genetically validated respiratory chain component type II NADH:quinone oxidoreductase (Ndh). Using a set of compounds containing the phenothiazine pharmacophore, we have (i) investigated whether chemical validation data support the molecular target and (ii) evaluated pharmacophore tractability for further drug development.

METHODS

Recombinant Mtb Ndh was generated and its functionality confirmed by steady-state kinetics. Pharmacodynamic profiling of the phenothiazines, including antitubercular efficacy in aerobic and O2-limited conditions, time-kill assays and isobole analyses against first-line antituberculars, was performed. Potential mitochondrial toxicity was assessed in a modified HepG2 cell-line assay and against bovine cytochrome bc1.

RESULTS

Steady-state kinetic analyses revealed a substrate preference for coenzyme Q2 and an inability to utilize NADPH. A positive correlation between recombinant Ndh inhibition and kill of aerobically cultured Mtb was observed, whilst enhanced potency was demonstrated in a hypoxic model. Time-kill studies revealed the phenothiazines to be bactericidal whilst isobolograms exposed antagonism with isoniazid, indicative of intracellular NADH/NAD(+) couple perturbation. At therapeutic levels, phenothiazine-mediated toxicity was appreciable; however, specific mitochondrial targeting was excluded.

CONCLUSIONS

Data generated support the hypothesis that Ndh is the molecular target of phenothiazines. The favourable pharmacodynamic properties of the phenothiazines are consistent with a target product profile that includes activity against dormant/persistent bacilli, rapid bactericidal activity and activity against drug-resistant Mtb by a previously unexploited mode of action. These properties warrant further medicinal chemistry to improve potency and safety.

Advances and strategies in discovery of new antibacterials for combating metabolically resting bacteria

Discovery of new antibacterial agents is crucial to counter the challenge of drug-resistant bacterial infections. In this review we discuss the issue of bacterial metabolic resting states, observed for a variety of pathogenic bacteria, which display low susceptibility for most antibacterials. We present examples of how bacterial metabolic states may be controlled, target pathways may be validated and screening on metabolically resting bacteria can be designed. A deeper understanding of bacterial metabolic states may provide valuable input for the design of efficient screening approaches in the discovery of new antibacterial agents.

Why and How the Old Neuroleptic Thioridazine Cures the XDR-TB Patient

This mini-review provides the entire experimental history of the development of the old neuroleptic thioridazine (TZ) for therapy of antibiotic resistant pulmonary tuberculosis infections. TZ is effective when used in combination with antibiotics to which the initial Mycobacterium tuberculosis was resistant. Under proper cardiac evaluation procedures, the use of TZ is safe and does not produce known cardiopathy such as prolongation of QT interval. Because TZ is cheap, it should be considered for therapy of XDR and TDR-Mtb patients in economically disadvantaged countries.