Nitazoxanide stimulates autophagy and inhibits mTORC1 signaling and intracellular proliferation of Mycobacterium tuberculosis. PLoS Pathog. 2012;8:e1002691. [PMID: 22589723 DOI: 10.1371/journal.ppat.1002691]

Glycogen synthase kinase 3 inhibition controls Mycobacterium tuberculosis infection

Compounds targeting host control of infectious diseases provide an attractive alternative to antimicrobials. A phenotypic screen of a kinase library identified compounds targeting glycogen synthase kinase 3 as potent inhibitors of Mycobacterium tuberculosis (Mtb) intracellular growth in the human THP-1 cell line and primary human monocytes-derived macrophages (hMDM). CRISPR knockouts and siRNA silencing showed that GSK3 isoforms are needed for the growth of Mtb and that a selected compound, P-4423632 targets GSK3β. GSK3 inhibition was associated with macrophage apoptosis governed by the Mtb secreted protein tyrosine phosphatase A (PtpA). Phospho-proteome analysis of macrophages response to infection revealed a wide array of host signaling and apoptosis pathways controlled by GSK3 and targeted by P-4423632. P-4423632 was additionally found to be active against other intracellular pathogens. Our findings strengthen the notion that targeting host signaling to promote the infected cell's innate antimicrobial capacity is a feasible and attractive host-directed therapy approach.

Tristetraprolin mediates immune evasion of mycobacterial infection in macrophages

Immune evasion of Mycobacterium tuberculosis (Mtb) facilitates intracellular bacterial growth. The mechanisms of immune evasion, however, are still not fully understood. In this study, we reveal that tristetraprolin (TTP), one of the best characterized RNA-binding proteins controlling the stability of targeted mRNAs, mediates innate immune evasion of mycobacteria. We found that TTP knockout mice displayed reduced bacterial burden in the early stage after Mtb aerosol challenge. Macrophages deficient in TTP also showed an inhibition in intracellular mycobacterial growth. Live mycobacteria induced TTP protein expression in macrophages, which was blocked by the mTOR inhibitor rapamycin. Rapamycin and AZD8055 specifically blocked 4EBP1 phosphorylation in infected macrophages and suppressed intracellular BCG growth. Rapamycin promoted TTP protein degradation through the ubiquitination pathway, whereas the proteasome inhibitor MG-132 blocked rapamycin function and thus stabilized TTP protein. TTP induction suppressed the expression of iNOS/TNF-α/IL-12/IL-23, and weakened protective immune responses in macrophages, whereas rapamycin enhanced the bactericidal effects through TTP inhibition. Moreover, blocking TTP binding increased the expression of TNF-α and iNOS and suppressed intracellular mycobacterial growth. Overall, our study reveals a novel role for RNA-binding protein TTP in Mtb immune evasion mechanisms and provides a potential target for host-directed therapy against tuberculosis (TB).

Divergent responses of human intestinal organoid monolayers using commercial in vitro cytotoxicity assays

In vitro models, such as primary cells and continuous cell lines routinely used for evaluating drug candidates, have limitations in their translational relevance to human diseases. Organotypic cultures are increasingly being used to assess therapeutics for various cancers and infectious diseases. Monitoring drug cytotoxicity in cell cultures is crucial in drug development, and several commercially available kits for cytotoxicity assessment offer distinct advantages and limitations. Given the complexity of organoid cultures, including donor-driven variability, we investigated drug-treated, tissue stem cell-derived human intestinal organoid responses with commonly used cell cytotoxicity assay kits. Using seven different compounds, we compared the cytotoxicity assay performance of two different leaky membrane-based and two metabolism-based assays. Significant variability was seen in reported viability outcomes across assays and organoid lines. High baseline activity of lactate dehydrogenase (LDH) in four human intestinal organoid lines required modification of the standard LDH assay protocol. Additionally, the LDH assay reported unique resilience to damage in a genetically-modified line contrasting results compared to other assays. This study highlights factors that can impact the measurement of cell cytotoxicity in intestinal organoid models, which are emerging as valuable new tools for research and pre-clinical drug testing and suggest the need for using multiple assay types to ensure reliable cytotoxicity assessment.

Host Cell Death and Modulation of Immune Response against Mycobacterium tuberculosis Infection

Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis (TB), a prevalent infectious disease affecting populations worldwide. A classic trait of TB pathology is the formation of granulomas, which wall off the pathogen, via the innate and adaptive immune systems. Some key players involved include tumor necrosis factor-alpha (TNF-α), foamy macrophages, type I interferons (IFNs), and reactive oxygen species, which may also show overlap with cell death pathways. Additionally, host cell death is a primary method for combating and controlling Mtb within the body, a process which is influenced by both host and bacterial factors. These cell death modalities have distinct molecular mechanisms and pathways. Programmed cell death (PCD), encompassing apoptosis and autophagy, typically confers a protective response against Mtb by containing the bacteria within dead macrophages, facilitating their phagocytosis by uninfected or neighboring cells, whereas necrotic cell death benefits the pathogen, leading to the release of bacteria extracellularly. Apoptosis is triggered via intrinsic and extrinsic caspase-dependent pathways as well as caspase-independent pathways. Necrosis is induced via various pathways, including necroptosis, pyroptosis, and ferroptosis. Given the pivotal role of host cell death pathways in host defense against Mtb, therapeutic agents targeting cell death signaling have been investigated for TB treatment. This review provides an overview of the diverse mechanisms underlying Mtb-induced host cell death, examining their implications for host immunity. Furthermore, it discusses the potential of targeting host cell death pathways as therapeutic and preventive strategies against Mtb infection.

Targeting Mycobacterium tuberculosis pH-driven adaptation

Mycobacterium tuberculosis (Mtb) senses and adapts to host environmental cues as part of its pathogenesis. One important cue sensed by Mtb is the acidic pH of its host niche - the macrophage. Acidic pH induces widespread transcriptional and metabolic remodelling in Mtb. These adaptations to acidic pH can lead Mtb to slow its growth and promote pathogenesis and antibiotic tolerance. Mutants defective in pH-dependent adaptations exhibit reduced virulence in macrophages and animal infection models, suggesting that chemically targeting these pH-dependent pathways may have therapeutic potential. In this review, we discuss mechanisms by which Mtb regulates its growth and metabolism at acidic pH. Additionally, we consider the therapeutic potential of disrupting pH-driven adaptations in Mtb and review the growing class of compounds that exhibit pH-dependent activity or target pathways important for adaptation to acidic pH.

The antimicrobial activity of innate host-directed therapies: A systematic review

Intracellular human pathogens are the deadliest infectious diseases and are difficult to treat effectively due to their protection inside the host cell and the development of antimicrobial resistance (AMR). An emerging approach to combat these intracellular pathogens is host-directed therapies (HDT), which harness the innate immunity of host cells. HDT rely on small molecules to promote host protection mechanisms that ultimately lead to pathogen clearance. These therapies are hypothesized to: (1) possess indirect yet broad, cross-species antimicrobial activity, (2) effectively target drug-resistant pathogens, (3) carry a reduced susceptibility to the development of AMR and (4) have synergistic action with conventional antimicrobials. As the field of HDT expands, this systematic review was conducted to collect a compendium of HDT and their characteristics, such as the host mechanisms affected, the pathogen inhibited, the concentrations investigated and the magnitude of pathogen inhibition. The evidential support for the main four HDT hypotheses was assessed and concluded that HDT demonstrate robust cross-species activity, are active against AMR pathogens, clinical isolates and laboratory-adapted pathogens. However, limited information exists to support the notion that HDT are synergistic with canonical antimicrobials and are less predisposed to AMR development.

Natural products in anti-tuberculosis host-directed therapy

Given that the disease progression of tuberculosis (TB) is primarily related to the host's immune status, it has been gradually realized that chemotherapy that targets the bacteria may never, on its own, wholly eradicate Mycobacterium tuberculosis, the causative agent of TB. The concept of host-directed therapy (HDT) with immune adjuvants has emerged. HDT could potentially interfere with infection and colonization by the pathogens, enhance the protective immune responses of hosts, suppress the overwhelming inflammatory responses, and help to attain a state of homeostasis that favors treatment efficacy. However, the HDT drugs currently being assessed in combination with anti-TB chemotherapy still face the dilemmas arising from side effects and high costs. Natural products are well suited to compensate for these shortcomings by having gentle modulatory effects on the host immune responses with less immunopathological damage at a lower cost. In this review, we first summarize the profiles of anti-TB immunology and the characteristics of HDT. Then, we focus on the rationale and challenges of developing and implementing natural products-based HDT. A succinct report of the medications currently being evaluated in clinical trials and preclinical studies is provided. This review aims to promote target-based screening and accelerate novel TB drug discovery.

Anthelmintic nitazoxanide protects against experimental pulmonary fibrosis

BACKGROUND AND PURPOSE

Nitazoxanide is a therapeutic anthelmintic drug. Our previous studies found that nitazoxanide and its metabolite tizoxanide activated adenosine 5'-monophosphate-activated protein kinase (AMPK) and inhibited signal transducer and activator of transcription 3 (STAT3) signals. As AMPK activation and/or STAT3 inhibition are targets for treating pulmonary fibrosis, we hypothesized that nitazoxanide would be effective in experimental pulmonary fibrosis.

EXPERIMENTAL APPROACH

The mitochondrial oxygen consumption rate of cells was measured by using the high-resolution respirometry system Oxygraph-2K. The mitochondrial membrane potential of cells was evaluated by tetramethyl rhodamine methyl ester (TMRM) staining. The target protein levels were measured by using western blotting. The mice pulmonary fibrosis model was established through intratracheal instillation of bleomycin. The examination of the lung tissues changes were carried out using haematoxylin and eosin (H&E), and Masson staining.

KEY RESULTS

Nitazoxanide and tizoxanide activated AMPK and inhibited STAT3 signalling in human lung fibroblast cells (MRC-5 cells). Nitazoxanide and tizoxanide inhibited transforming growth factor-β1 (TGF-β1)-induced proliferation and migration of MRC-5 cells, collagen-I and α-smooth muscle cell actin (α-SMA) expression, and collagen-I secretion from MRC-5 cells. Nitazoxanide and tizoxanide inhibited epithelial-mesenchymal transition (EMT) and inhibited TGF-β1-induced Smad2/3 activation in mouse lung epithelial cells (MLE-12 cells). Oral administration of nitazoxanide reduced the bleomycin-induced mice pulmonary fibrosis and, in the established bleomycin-induced mice, pulmonary fibrosis. Delayed nitazoxanide treatment attenuated the fibrosis progression.

CONCLUSIONS AND IMPLICATIONS

Nitazoxanide improves the bleomycin-induced pulmonary fibrosis in mice, suggesting a potential application of nitazoxanide for pulmonary fibrosis treatment in the clinic.

The pipeline for drugs for control and elimination of neglected tropical diseases: 2. Oral anti-infective drugs and drug combinations for off-label use

In its 'Road map for neglected tropical diseases 2021-2030', the World Health Organization outlined its targets for control and elimination of neglected tropical diseases (NTDs) and research needed to achieve them. For many NTDs, this includes research for new treatment options for case management and/or preventive chemotherapy. Our review of small-molecule anti-infective drugs recently approved by a stringent regulatory authority (SRA) or in at least Phase 2 clinical development for regulatory approval showed that this pipeline cannot deliver all new treatments needed. WHO guidelines and country policies show that drugs may be recommended for control and elimination for NTDs for which they are not SRA approved (i.e. for 'off-label' use) if efficacy and safety data for the relevant NTD are considered sufficient by WHO and country authorities. Here, we are providing an overview of clinical research in the past 10 years evaluating the anti-infective efficacy of oral small-molecule drugs for NTD(s) for which they are neither SRA approved, nor included in current WHO strategies nor, considering the research sponsors, likely to be registered with a SRA for that NTD, if found to be effective and safe. No such research has been done for yaws, guinea worm, Trypanosoma brucei gambiense human African trypanosomiasis (HAT), rabies, trachoma, visceral leishmaniasis, mycetoma, T. b. rhodesiense HAT, echinococcosis, taeniasis/cysticercosis or scabies. Oral drugs evaluated include sparfloxacin and acedapsone for leprosy; rifampicin, rifapentin and moxifloxacin for onchocerciasis; imatinib and levamisole for loiasis; itraconazole, fluconazole, ketoconazole, posaconazole, ravuconazole and disulfiram for Chagas disease, doxycycline and rifampicin for lymphatic filariasis; arterolane, piperaquine, artesunate, artemether, lumefantrine and mefloquine for schistosomiasis; ivermectin, tribendimidine, pyrantel, oxantel and nitazoxanide for soil-transmitted helminths including strongyloidiasis; chloroquine, ivermectin, balapiravir, ribavirin, celgosivir, UV-4B, ivermectin and doxycycline for dengue; streptomycin, amoxicillin, clavulanate for Buruli ulcer; fluconazole and isavuconazonium for mycoses; clarithromycin and dapsone for cutaneous leishmaniasis; and tribendimidine, albendazole, mebendazole and nitazoxanide for foodborne trematodiasis. Additional paths to identification of new treatment options are needed. One promising path is exploitation of the worldwide experience with 'off-label' treatment of diseases with insufficient treatment options as pursued by the 'CURE ID' initiative.

Mycobacterium tuberculosis: Pathogenesis and therapeutic targets

Tuberculosis (TB) remains a significant public health concern in the 21st century, especially due to drug resistance, coinfection with diseases like immunodeficiency syndrome (AIDS) and coronavirus disease 2019, and the lengthy and costly treatment protocols. In this review, we summarize the pathogenesis of TB infection, therapeutic targets, and corresponding modulators, including first-line medications, current clinical trial drugs and molecules in preclinical assessment. Understanding the mechanisms of Mycobacterium tuberculosis (Mtb) infection and important biological targets can lead to innovative treatments. While most antitubercular agents target pathogen-related processes, host-directed therapy (HDT) modalities addressing immune defense, survival mechanisms, and immunopathology also hold promise. Mtb's adaptation to the human host involves manipulating host cellular mechanisms, and HDT aims to disrupt this manipulation to enhance treatment effectiveness. Our review provides valuable insights for future anti-TB drug development efforts.

Tizoxanide as a novel theraputic candidate for osteoarthritis

Osteoarthritis (OA) is a frequently seen degenerative joint disease in the elderly. Its pathogenesis is highly related to the local inflammatory reaction and autophagy. Tizoxanide (Tiz), the main active metabolite of nitazoxanide, has proved its anti-inflammatory properties in several diseases. However, the exact role of Tiz in OA remains to explore. In this study, we investigated the anti-arthritic effects and the underlying molecular mechanisms of Tiz on rat OA. The results showed that Tiz could attenuate the IL-1β-induced inflammatory disorders, cartilage matrix damage and autophagy reduction in rat chondrocytes. Moreover, employment of autophagy inhibitor 3-methyladenine (3-MA) could antagonize the protective effects of Tiz in IL-1β-treated rat chondrocytes. Additionally, Tiz also inhibited the IL-1β-induced PI3K/AKT/mTOR and P38/JNK phosphorylation in chondrocytes. In vivo, intra-articular injection of Tiz could significantly alleviate the progression of cartilage damage in rat OA model. Briefly, our study demonstrated the therapeutic potential of Tiz in OA, suggesting that Tiz administration might serve as a promising strategy in OA therapy.

The FDA-approved drug nitazoxanide is a potent inhibitor of human seasonal coronaviruses acting at postentry level: effect on the viral spike glycoprotein

Coronaviridae is recognized as one of the most rapidly evolving virus family as a consequence of the high genomic nucleotide substitution rates and recombination. The family comprises a large number of enveloped, positive-sense single-stranded RNA viruses, causing an array of diseases of varying severity in animals and humans. To date, seven human coronaviruses (HCoV) have been identified, namely HCoV-229E, HCoV-NL63, HCoV-OC43 and HCoV-HKU1, which are globally circulating in the human population (seasonal HCoV, sHCoV), and the highly pathogenic SARS-CoV, MERS-CoV and SARS-CoV-2. Seasonal HCoV are estimated to contribute to 15-30% of common cold cases in humans; although diseases are generally self-limiting, sHCoV can sometimes cause severe lower respiratory infections and life-threatening diseases in a subset of patients. No specific treatment is presently available for sHCoV infections. Herein we show that the anti-infective drug nitazoxanide has a potent antiviral activity against three human endemic coronaviruses, the Alpha-coronaviruses HCoV-229E and HCoV-NL63, and the Beta-coronavirus HCoV-OC43 in cell culture with IC50 ranging between 0.05 and 0.15 μg/mL and high selectivity indexes. We found that nitazoxanide does not affect HCoV adsorption, entry or uncoating, but acts at postentry level and interferes with the spike glycoprotein maturation, hampering its terminal glycosylation at an endoglycosidase H-sensitive stage. Altogether the results indicate that nitazoxanide, due to its broad-spectrum anti-coronavirus activity, may represent a readily available useful tool in the treatment of seasonal coronavirus infections.

The mitochondrial uncoupling effects of nitazoxanide enhances cellular autophagy and promotes the clearance of α-synuclein: Potential role of AMPK-JNK pathway

Upregulation and aggregation of the pre-synaptic protein, α-synuclein plays a key role in Parkinson's disease (PD) and mitochondrial dysfunction was surmised to be an upstream event in the disease pathogenesis. Emerging reports identified the role of nitazoxanide (NTZ), an anti-helminth drug, in enhancing mitochondrial oxygen consumption rate (OCR) and autophagy. In the present study, we have examined the mitochondrial effects of NTZ in mediating cellular autophagy and subsequent clearance of both endogenous and pre-formed aggregates of α-synuclein in cellular model of PD. Our results demonstrate that the mitochondrial uncoupling effects of NTZ results in the activation of AMPK and JNK, which in-turn leads to the enhancement of cellular autophagy. Also,1-methyl-4-phenylpyridinium (MPP⁺) mediated decrease in autophagic flux with a concomitant increase in the α-synuclein levels were ameliorated in cells treated with NTZ. However, in cells lacking functional mitochondria (ρ0 cells), NTZ did not mitigate MPP⁺ mediated alterations in the autophagic clearance of α-synuclein, indicating that the mitochondrial effects of NTZ play a crucial role in the clearance of α-synuclein by autophagy. Also, the ability of AMPK inhibitor, compound C, in abrogating NTZ mediated enhancement in the autophagic flux and α-synuclein clearance highlight the pivotal role of AMPK in NTZ mediated autophagy. Further, NTZ per se enhanced the clearance of preformed α-synuclein aggregates that were exogenously added to the cells. Overall, the results of our present study suggest that NTZ activates macroautophagy in cells due to its uncoupling effects on mitochondrial respiration via activation of AMPK-JNK pathway resulting in the clearance of both endogenous and pre-formed α-synuclein aggregates. As NTZ happens to possess good bioavailability and safety profile, considering this drug for PD based on its mitochondrial uncoupling and autophagy enhancing properties for mitigating mitochondrial reactive oxygen species (ROS) and α-synuclein toxicity appears to be a promising therapeutic option.

The immune response in tubercular uveitis and its implications for treatment: From anti-tubercular treatment to host-directed therapies

Tubercular uveitis (TB-uveitis) remains a conundrum in the uveitis field, which is mainly related to the diverse clinical phenotypes of TB-uveitis. Moreover, it remains difficult to differentiate whether Mycobacterium tuberculosis (Mtb) is present in the ocular tissues, elicits a heightened immune response without Mtb invasion in ocular tissues, or even induces an anti-retinal autoimmune response. Gaps in the immuno-pathological knowledge of TB-uveitis likely delay timely diagnosis and appropriate management. In the last decade, the immunopathophysiology of TB-uveitis and its clinical management, including experts' consensus to treat or not to treat certain conditions with anti-tubercular treatment (ATT), have been extensively investigated. In the meantime, research on TB treatment, in general, is shifting more toward host-directed therapies (HDT). Given the complexities of the host-Mtb interaction, enhancement of the host immune response is expected to boost the effectiveness of ATT and help overcome the rising burden of drug-resistant Mtb strains in the population. This review will summarize the current knowledge on the immunopathophysiology of TB-uveitis and recent advances in treatment modalities and outcomes of TB-uveitis, capturing results gathered from high- and low-burden TB countries with ATT as the mainstay of treatment. Moreover, we outline the recent progress of HDT development in the pulmonary TB field and discuss the possibility of its applicability to TB-uveitis. The concept of HDT might help direct future development of efficacious therapy for TB-uveitis, although more in-depth research on the immunoregulation of this disease is still necessary.

Targeting mycobacterial membranes and membrane proteins: Progress and limitations

Among the various bacterial infections, tuberculosis continues to hold center stage. Its causative agent, Mycobacterium tuberculosis, possesses robust defense mechanisms against most front-line antibiotic drugs and host responses due to their complex cell membranes with unique lipid molecules. It is now well-established that bacteria change their membrane composition to optimize their environment to survive and elude drug action. Thus targeting membrane or membrane components is a promising avenue for exploiting the chemical space focussed on developing novel membrane-centric anti-bacterial small molecules. These approaches are more effective, non-toxic, and can attenuate resistance phenotype. We present the relevance of targeting the mycobacterial membrane as a practical therapeutic approach. The review highlights the direct and indirect targeting of membrane structure and function. Direct membrane targeting agents cause perturbation in the membrane potential and can cause leakage of the cytoplasmic contents. In contrast, indirect membrane targeting agents disrupt the function of membrane-associated proteins involved in cell wall biosynthesis or energy production. We discuss the chronological chemical improvements in various scaffolds targeting specific membrane-associated protein targets, their clinical evaluation, and up-to-date account of their ''mechanisms of action, potency, selectivity'' and limitations. The sources of anti-TB drugs/inhibitors discussed in this work have emerged from target-based identification, cell-based phenotypic screening, drug repurposing, and natural products. We believe this review will inspire the exploration of uncharted chemical space for informing the development of new scaffolds that can inhibit novel mycobacterial membrane targets.

Repurposing nitazoxanide as a novel anti-atherosclerotic drug based on mitochondrial uncoupling mechanisms

BACKGROUND AND PURPOSE

The anthelmintic drug nitazoxanide has a mitochondrial uncoupling effect. Mitochondrial uncouplers have been proven to inhibit smooth muscle cell proliferation and migration, inhibit NLRP3 inflammasome activation of macrophages and improve dyslipidaemia. Therefore, we aimed to demonstrate that nitazoxanide would protect against atherosclerosis.

EXPERIMENTAL APPROACH

The mitochondrial oxygen consumption of cells was measured by using the high-resolution respirometry system, Oxygraph-2K. The proliferation and migration of A10 cells were measured by using Edu immunofluorescence staining, wound-induced migration and the Boyden chamber assay. Protein levels were measured by using the western blot technique. ApoE (-/-) mice were fed with a Western diet to establish an atherosclerotic model in vivo.

KEY RESULTS

The in vitro experiments showed that nitazoxanide and tizoxanide had a mitochondrial uncoupling effect and activated cellular AMPK. Nitazoxanide and tizoxanide inhibited serum- and PDGF-induced proliferation and migration of A10 cells. Nitazoxanide and tizoxanide inhibited NLRP3 inflammasome activation in RAW264.7 macrophages, the mechanism by which involved the AMPK/IκBα/NF-κB pathway. Nitazoxanide and tizoxanide also induced autophagy in A10 cells and RAW264.7 macrophages. The in vivo experiments demonstrated that oral administration of nitazoxanide reduced the increase in serum IL-1β and IL-6 levels and suppressed atherosclerosis in Western diet-fed ApoE (-/-) mice.

CONCLUSION AND IMPLICATIONS

Nitazoxanide inhibits the formation of atherosclerotic plaques in ApoE (-/-) mice fed on a Western diet. In view of nitazoxanide being an antiprotozoal drug already approved by the FDA, we propose it as a novel anti-atherosclerotic drug with clinical translational potential.

Nitazoxanide and COVID-19: A review

Coronavirus disease 2019 (COVID-19) is a current global illness triggered by severe acute respiratory coronavirus 2 (SARS-CoV-2) leading to acute viral pneumonia, acute lung injury (ALI), acute respiratory distress syndrome (ARDS), and cytokine storm in severe cases. In the COVID-19 era, different unexpected old drugs are repurposed to find out effective and cheap therapies against SARS-CoV-2. One of these elected drugs is nitazoxanide (NTZ) which is an anti-parasitic drug with potent antiviral activity. It is effectively used in the treatment of protozoa and various types of helminths in addition to various viral infections. Thus, we aimed to elucidate the probable effect of NTZ on SARS-CoV-2 infections. Findings of the present study illustrated that NTZ can reduce SARS-CoV-2-induced inflammatory reactions through activation of interferon (IFN), restoration of innate immunity, inhibition of the release of pro-inflammatory cytokines, suppression of the mammalian target of rapamycin (mTOR), and induction of autophagic cell death. Moreover, it can inhibit the induction of oxidative stress which causes cytokine storm and is associated with ALI, ARDS, and multi-organ damage (MOD). This study concluded that NTZ has important anti-inflammatory and immunological properties that may mitigate SARS-CoV-2 infection-induced inflammatory disorders. Despite broad-spectrum antiviral properties of NTZ, the direct anti-SARS-CoV-2 effect was not evident and documented in recent studies. Then, in silico and in vitro studies in addition to clinical trials and prospective studies are needed to confirm the beneficial impact of NTZ on the pathogenesis of SARS-CoV-2 infection.

Different modalities of host cell death and their impact on Mycobacterium tuberculosis infection

Mycobacterium tuberculosis (Mtb) is the pathogen that causes tuberculosis (TB), a leading infectious disease of humans worldwide. One of the main histopathological hallmarks of TB is the formation of granulomas comprised of elaborately organized aggregates of immune cells containing the pathogen. Dissemination of Mtb from infected cells in the granulomas due to host and mycobacterial factors induces multiple cell death modalities in infected cells. Based on molecular mechanism, morphological characteristics, and signal dependency, there are two main categories of cell death: programmed and nonprogrammed. Programmed cell death (PCD), such as apoptosis and autophagy, is associated with a protective response to Mtb by keeping the bacteria encased within dead macrophages that can be readily phagocytosed by arriving in uninfected or neighboring cells. In contrast, non-PCD necrotic cell death favors the pathogen, resulting in bacterial release into the extracellular environment. Multiple types of cell death in the PCD category, including pyroptosis, necroptosis, ferroptosis, ETosis, parthanatos, and PANoptosis, may be involved in Mtb infection. Since PCD pathways are essential for host immunity to Mtb, therapeutic compounds targeting cell death signaling pathways have been experimentally tested for TB treatment. This review summarizes different modalities of Mtb-mediated host cell deaths, the molecular mechanisms underpinning host cell death during Mtb infection, and its potential implications for host immunity. In addition, targeting host cell death pathways as potential therapeutic and preventive approaches against Mtb infection is also discussed.

Sofosbuvir/ledipasvir in combination or nitazoxanide alone are safe and efficient treatments for COVID-19 infection: A randomized controlled trial for repurposing antivirals

BACKGROUND AND STUDY AIMS

Currently, there is no therapy approved for COVID-19. We evaluated the efficacy and safety of sofosbuvir/ledipasvir and nitazoxanide for the treatment of patients with COVID-19 infection.

PATIENTS AND METHODS

A multicenter, open-label randomized controlled trial included one hundred and ninety patients with non-severe COVID-19 infection. Patients were randomized into three groups. All groups received standard care treatment (SCT). In addition, group 1 received sofosbuvir/ledipasvir, and group 2 received nitazoxanide. Follow-up by reverse-transcriptase polymerase chain reaction (RT-PCR) was done at intervals of 5, 8, 11, and 14 days. The primary endpoint was viral clearance.

RESULTS

Viral clearance was significantly higher in the sofosbuvir/ledipasvir and nitazoxanide groups compared to the SCT group in all follow-up intervals (p < 0.001). In the sofosbuvir/ledipasvir arm, 36.9% showed early viral clearance by day 5. By day 14, 83.1% of the sofosbuvir/ledipasvir group, 39.7% of the nitazoxanide group, and 19.4% of the SCT group tested negative for SARS-CoV-2. Sofosbuvir/ledipasvir and nitazoxanide treatment were the only significant factors in Cox regression of negative RT-PCR with the highest OR (17.88, 95% CI: 6.66-47.98 and 2.59, 95% CI: 1.11-6.07, respectively). No mortality or serious adverse events were recorded.

CONCLUSION

The addition of sofosbuvir/ledipasvir or nitazoxanide to the SCT results in an early and high viral clearance rate in mild and moderate patients with COVID-19. These drugs represent a safe and affordable treatment for COVID-19.

Nitazoxanide potentiates linezolid against linezolid-resistant Staphylococcus aureus in vitro and in vivo

BACKGROUND

Antimicrobial resistance is a growing menace, claiming millions of lives all over the world. In this context, drug repurposing is one approach gaining interest as a suitable alternative to conventional drug discovery and development.

METHODS

Whole-cell assays were used to screen FDA-approved drugs to identify novel antimicrobial agents active against bacterial pathogens. Following identification of nitazoxanide, its various characteristics, such as antimicrobial activity against MDR isolates, time-kill kinetics, ability to synergize with approved drugs, antibiofilm activity and ability to generate resistance in Staphylococcus aureus, were determined, followed by determination of its in vivo potential against MDR S. aureus.

RESULTS

Nitazoxanide demonstrated a potent in vitro antistaphylococcal profile, including equipotent activity against clinical drug-resistant S. aureus and Enterococcus spp. Nitazoxanide exhibited concentration-dependent killing, significantly eradicated preformed S. aureus biofilm and S. aureus did not generate resistance to it. Nitazoxanide strongly synergized with linezolid both in vitro and in vivo against linezolid-susceptible and -resistant S. aureus, displaying superior activity to untreated control and drug-alone treatment groups.

CONCLUSIONS

Nitazoxanide can be utilized in combination with linezolid against infections caused by linezolid-resistant S. aureus as it exhibits strong synergism in vitro and in vivo.

Anthelmintics nitazoxanide protects against experimental hyperlipidemia and hepatic steatosis in hamsters and mice

Lipid metabolism disorders contribute to hyperlipidemia and hepatic steatosis. It is ideal to develop drugs simultaneous improving both hyperlipidemia and hepatic steatosis. Nitazoxanide is an FDA-approved oral antiprotozoal drug with excellent pharmacokinetic and safety profile. We found that nitazoxanide and its metabolite tizoxanide induced mild mitochondrial uncoupling and subsequently activated AMPK in HepG2 cells. Gavage administration of nitazoxanide inhibited high-fat diet (HFD)-induced increases of liver weight, blood and liver lipids, and ameliorated HFD-induced renal lipid accumulation in hamsters. Nitazoxanide significantly improved HFD-induced histopathologic changes of hamster livers. In the hamsters with pre-existing hyperlipidemia and hepatic steatosis, nitazoxanide also showed therapeutic effect. Gavage administration of nitazoxanide improved HFD-induced hepatic steatosis in C57BL/6J mice and western diet (WD)-induced hepatic steatosis in Apoe -/- mice. The present study suggests that repurposing nitazoxanide as a drug for hyperlipidemia and hepatic steatosis treatment is promising.

Shedding Light on Autophagy During Human Tuberculosis. A Long Way to Go

Immunity against Mycobacterium tuberculosis (Mtb) is highly complex, and the outcome of the infection depends on the role of several immune mediators with particular temporal dynamics on the host microenvironment. Autophagy is a central homeostatic mechanism that plays a role on immunity against intracellular pathogens, including Mtb. Enhanced autophagy in macrophages mediates elimination of intracellular Mtb through lytic and antimicrobial properties only found in autolysosomes. Additionally, it has been demonstrated that standard anti-tuberculosis chemotherapy depends on host autophagy to coordinate successful antimicrobial responses to mycobacteria. Notably, autophagy constitutes an anti-inflammatory mechanism that protects against endomembrane damage triggered by several endogenous components or infectious agents and precludes excessive inflammation. It has also been reported that autophagy can be modulated by cytokines and other immunological signals. Most of the studies on autophagy as a defense mechanism against Mycobacterium have been performed using murine models or human cell lines. However, very limited information exists about the autophagic response in cells from tuberculosis patients. Herein, we review studies that face the autophagy process in tuberculosis patients as a component of the immune response of the human host against an intracellular microorganism such as Mtb. Interestingly, these findings might contribute to recognize new targets for the development of novel therapeutic tools to combat Mtb. Actually, either as a potential successful vaccine or a complementary immunotherapy, efforts are needed to further elucidate the role of autophagy during the immune response of the human host, which will allow to achieve protective and therapeutic benefits in human tuberculosis.

PI3K/AKT/p53 pathway inhibits infectious spleen and kidney necrosis virus infection by regulating autophagy and immune responses

The PI3K/AKT/p53 signaling pathway is activated by various types of cellular stimuli or pathogenic infection, and then regulates fundamental cellular functions to combat these stimulations. Here, we studied the meaningful roles of PI3K/AKT/p53 in regulating cellular machine such as autophagy, immune responses, as well as antiviral activity in Chinese perch brain (CPB) cells infected by infectious spleen and kidney necrosis virus (ISKNV), which is an agent caused devastating losses in mandarin fish (Siniperca chuatsi) industry. We found that ISKNV infection induced up-regulation of host PI3K/AKT/p53 axis, but inhibited autophagy in CPB cells. Interestingly, activation of PI3K/AKT/p53 axis factors trough agonists or overexpression dramatically decreased host autophagy level, inhibited ISKNV replication, and elevated the expression of immune-related genes in CPB cells. In contrast, suppression of PI3K/AKT/p53 pathway by inhibitors or small interfering RNA (siRNA)-mediated gene silence increased the autophagy and ISKNV replication, but down-regulated immune responses in CPB cells. All these results indicate that PI3K/AKT/p53 pathway plays an important role in anti-ISKNV infection and can be used as a new target for controlling ISKNV disease.

Nitazoxanide, an Antiprotozoal Drug, Reduces Bone Loss in Ovariectomized Mice by Inhibition of RANKL-Induced Osteoclastogenesis

Nitazoxanide (NTZ) is an FDA-approved anti-parasitic drug with broad-spectrum anti-infective, anti-inflammatory, and antineoplastic potential. However, its regulatory effects on osteoclastogenesis and the underlying mechanisms remain unclear. The present study found that NTZ potently inhibited osteoclast formation at the early stage of receptor activator of NF-κB ligand-induced osteoclastogenesis in a concentration-dependent manner at a non-growth inhibitory concentration. NTZ suppressed actin ring formation and decreased osteoclast marker gene expression, including TRAP, MMP9, and cathepsin K. NTZ significantly impaired the bone resorption activity of osteoclasts. In vivo, ovariectomized mice were treated with 50, 100 and 200 mg/kg/d NTZ for 3 months. NTZ (100 mg/kg/d) administration markedly reduced ovariectomy-induced bone loss by suppressing osteoclast activity. Mechanistically, osteoclastogenesis blockade elicited by NTZ resulted from inhibition of STAT3 phosphorylation, and reduction of the Ca2+ fluorescence intensity and NFATc1 expression. NTZ weakened the binding between STAT3 and the NFATc1 promoter region. Furthermore, enforced NFATc1 expression partly rescued the impaired osteoclast differentiation in NTZ-treated RAW264.7 cells. In summary, NTZ could inhibit osteoclastogenesis and bone loss through modulation of the receptor activator of NF-κB ligand-induced STAT3-NFATc1 signaling pathway, which might be a potential alternative treatment regimen against bone destruction-related diseases including osteoporosis.

Overcoming the Prokaryote/Eukaryote Barrier in Tuberculosis Treatment: A Prospect for the Repurposing and Use of Antiparasitic Drugs

Antimicrobial resistance, the so-called silent pandemic, is pushing industry and academia to find novel antimicrobial agents with new mechanisms of action in order to be active against susceptible and drug-resistant microorganisms. In the case of tuberculosis, the need of novel anti-tuberculosis drugs is specially challenging because of the intricate biology of its causative agent, Mycobacterium tuberculosis. The repurposing of medicines has arisen in recent years as a fast, low-cost, and efficient strategy to identify novel biomedical applications for already approved drugs. This review is focused on anti-parasitic drugs that have additionally demonstrated certain levels of anti-tuberculosis activity; along with this, natural products with a dual activity against parasites and against M. tuberculosis are discussed. A few clinical trials have tested antiparasitic drugs in tuberculosis patients, and have revealed effective dose and toxicity issues, which is consistent with the natural differences between tuberculosis and parasitic infections. However, through medicinal chemistry approaches, derivatives of drugs with anti-parasitic activity have become successful drugs for use in tuberculosis therapy. In summary, even when the repurposing of anti-parasitic drugs for tuberculosis treatment does not seem to be an easy job, it deserves attention as a potential contributor to fuel the anti-tuberculosis drug pipeline.

Clionamines stimulate autophagy, inhibit Mycobacterium tuberculosis survival in macrophages, and target Pik1

The pathogen Mycobacterium tuberculosis (Mtb) evades the innate immune system by interfering with autophagy and phagosomal maturation in macrophages, and, as a result, small molecule stimulation of autophagy represents a host-directed therapeutics (HDTs) approach for treatment of tuberculosis (TB). Here we show the marine natural product clionamines activate autophagy and inhibit Mtb survival in macrophages. A yeast chemical-genetics approach identified Pik1 as target protein of the clionamines. Biotinylated clionamine B pulled down Pik1 from yeast cell lysates and a clionamine analog inhibited phosphatidyl 4-phosphate (PI4P) production in yeast Golgi membranes. Chemical-genetic profiles of clionamines and cationic amphiphilic drugs (CADs) are closely related, linking the clionamine mode of action to co-localization with PI4P in a vesicular compartment. Small interfering RNA (siRNA) knockdown of PI4KB, a human homolog of Pik1, inhibited the survival of Mtb in macrophages, identifying PI4KB as an unexploited molecular target for efforts to develop HDT drugs for treatment of TB.

Nitazoxanide impairs mitophagy flux through ROS-mediated mitophagy initiation and lysosomal dysfunction in bladder cancer

Bladder cancer is one of the most common malignancy in the urinary tract with high recurrence and drug resistance in clinics. Alternative treatments from existing drugs might be a promising strategy. Nitazoxanide (NTZ), an FDA-approved antiprotozoal drug, has got increasingly noticed because of its favorable safety profile and antitumor potential, yet the effects in bladder cancer and underlying mechanisms remain poorly understood. Herein, we find that NTZ induces mitochondrial damage and mitophagy initiation through PINK1-generated phospho-ubiquitin(pS65-Ub) and autophagy receptor-mediated pathway even in the absence of Atg5/Beclin1. Meanwhile, NTZ inhibits lysosomal degradation activity, leading to mitophagy flux impairment at late stage. Mitochondrial reactive oxygen species (ROS) production is critical in this process, as eliminating ROS with N-acetylcysteine (NAC) efficiently inhibits PINK1 signaling-mediated mitophagy initiation and alleviates lysosomal dysfunction. Co-treatment with NTZ and autophagy inhibitor Chloroquine (CQ) to aggravate mitophagy flux impairment promotes NTZ-induced apoptosis, while alleviation of mitophagy flux impairment with ROS scavenger reduces cell death. Moreover, we also discover a similar signaling response in the 3D bladder tumor spheroid after NTZ exposure. In vivo study reveals a significant inhibition of orthotopic bladder tumors with no obvious systemic toxicity. Together, our results uncover the anti-tumor activities of NTZ with the involvement of ROS-mediated mitophagy modulation at different stages and demonstrate it as a potential drug candidate for fighting against bladder tumors.

Repositioning rafoxanide to treat Gram-negative bacilli infections

OBJECTIVES

Repurposing drugs provides a new approach to the fight against MDR Gram-negative bacilli (MDR-GNB). Rafoxanide, a veterinary antihelminthic drug, has shown antibacterial activity in vitro against Gram-positive bacteria. We aimed to analyse the in vitro and in vivo efficacy of rafoxanide in combination with colistin against colistin-susceptible (Col-S) and colistin-resistant (Col-R) GNB.

METHODS

A collection of Col-S and Col-R Acinetobacter baumannii, Pseudomonas aeruginosa and Klebsiella pneumoniae were used. Chequerboard and time-kill curve analyses were performed to determine the synergy between rafoxanide and colistin. Changes in membrane structure and permeability were analysed using transmission electron microscopy and fluorescence assays. A murine peritoneal sepsis model using Col-R strains of these pathogens was performed to study the efficacy of rafoxanide (10 mg/kg/24 h, IV), colistimethate sodium (CMS) (20 mg/kg/8 h, intraperitoneally) and rafoxanide (10 mg/kg/24 h, IV) plus CMS (20 mg/kg/8 h, intraperitoneally) for 72 h.

RESULTS

Rafoxanide showed MICs ≥256 mg/L for all Col-S and Col-R strains. Chequerboard and time-kill curve analyses showed that rafoxanide (1 mg/L) is more synergistic with colistin against Col-R than Col-S strains. Col-R, but not Col-S, strains treated with rafoxanide demonstrated higher membrane permeabilization. Transmission electron microscopy visualization confirmed that Col-R strains suffer morphological changes. In the murine peritoneal sepsis model with Col-R strains, rafoxanide plus CMS, compared with CMS alone, increased mouse survival to 53.8% and 73.3%, and reduced bacterial loads in tissues and blood between 2.34 and 4.99 log10 cfu/g or mL, respectively.

CONCLUSIONS

Rafoxanide repurposing, as monotherapy and in combination with CMS, may address the urgent need for new treatments for infections caused by MDR-GNB.

Autophagy Induction as a Host-Directed Therapeutic Strategy against Mycobacterium tuberculosis Infection

Tuberculosis (TB), a bacterialinfectious disease caused by Mycobacterium tuberculosis (M.tb), which causes significant mortality in humans worldwide. Current treatment regimen involve the administration of multiple antibiotics over the course of several months that contributes to patient non-compliance leading to relapse and the development of drug-resistant M.tb (MDR and XDR) strains. Together, these facts highlight the need for the development of shorter TB treatment regimens. Host-directed therapy (HDT) is a new and emerging concept that aims to augment host immune response using drugs/compounds with or without adjunct antibiotics against M.tb infection. Autophagy is a natural catabolic mechanism of the cell that involves delivering the cytosolic constituents to the lysosomes for degradation and recycling the components; thereby maintaining the cellular and energy homoeostasis of a cell. However, over the past decade, an improved understanding of the role of autophagy in immunity has led to autophagy activation by using drugs or agents. This autophagy manipulation may represent a promising host-directed therapeutic strategy for human TB. However, current clinical knowledge on implementing autophagy activation by drugs or agents, as a stand-alone HDT or as an adjunct with antibiotics to treat human TB is insufficient. In recent years, many reports on high-throughput drug screening and measurement of autophagic flux by fluorescence, high-content microscopy, flow cytometry, microplate reader and immunoblotting have been published for the discovery of drugs that modulate autophagy. In this review, we discuss the commonly used chemical screening approaches in mammalian cells for the discovery of autophagy activating drugs against M.tbinfection. We also summarize the various autophagy-activating agents, both pre-clinical candidates and compounds approved for advanced clinical investigation during mycobacterial infection. Finally, we discuss the opportunities and challenges in using autophagy activation as HDT strategy to improve TB outcome and shorten treatment regimen.

Structure-Activity Study of Nitazoxanide Derivatives as Novel STAT3 Pathway Inhibitors

We identified nitazoxanide (NTZ) as a moderate STAT3 pathway inhibitor through immunoblot analysis and a cell-based IL-6/JAK/STAT3 pathway activation assay. A series of thiazolide derivatives were designed and synthesized to further validate the thiazolide scaffold as STAT3 inhibitors. Eight out of 25 derivatives displayed potencies greater than that of NTZ, and their STAT3 pathway inhibitory activities were found to be significantly correlated with their antiproliferative activities in HeLa cells. Derivatives 15 and 24 were observed to be more potent than the positive control WP1066, which is under phase I clinical trials. Compared with NTZ, 15 also exhibited much improved in vivo pharmacokinetic parameters in rats and efficacies against proliferations in multiple cancer cell lines, indicating a broad-spectrum effect of these thiazolides as antitumor agents targeted on STAT3.

From infection niche to therapeutic target: the intracellular lifestyle of Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) is an obligate human pathogen killing millions of people annually. Treatment for tuberculosis is lengthy and complicated, involving multiple drugs and often resulting in serious side effects and non-compliance. Mtb has developed numerous complex mechanisms enabling it to not only survive but replicate inside professional phagocytes. These mechanisms include, among others, overcoming the phagosome maturation process, inhibiting the acidification of the phagosome and inhibiting apoptosis. Within the past decade, technologies have been developed that enable a more accurate understanding of Mtb physiology within its intracellular niche, paving the way for more clinically relevant drug-development programmes. Here we review the molecular biology of Mtb pathogenesis offering a unique perspective on the use and development of therapies that target Mtb during its intracellular life stage.

5-methoxytryptophan alleviates liver fibrosis by modulating FOXO3a/miR-21/ATG5 signaling pathway mediated autophagy

Liver fibrosis is a critical health issue in the world due to its rapidly increasing prevalence. It is of great demand to develop effective drugs for the treatment of liver fibrosis. 5-methoxytryptophan (5-MTP) has been reported to play an important role in anti-inflammatory, anti-cancer, myocardial-protective effects. However, the anti-fibrotic effect of 5-MTP is never covered in liver. Here, we investigated anti-fibrotic effects of 5-MTP on liver fibrosis and its underlying mechanism. In vitro, 5-MTP treatment could inhibit TGF-β1-induced elevated levels of collagen I, collagen III, fibronectin and α-smooth muscle actin (SMA) by stimulating autophagy process. Mechanically, the expression of FOXO3a was enhanced by 5-MTP and then repressed the level of miR-21, eventually leading to a restoration of autophagy-related gene ATG5. Furthermore, rescue experiments showed 5-MTP could activate autophagy process and suppress the activation of LX-2 cells by regulating FOXO3a/miR-21/ATG5 pathway. Consistently, 5-MTP significantly attenuated CCl4-induced hepatic fibrosis in rat model. In conclusion, our research discovered that 5-MTP effectively alleviated liver fibrosis in vitro and in vivo, which provided new insights into the application of 5-MTP for liver fibrosis.

Transcription Repressor Protein ZBTB25 Associates with HDAC1-Sin3a Complex in Mycobacterium tuberculosis-Infected Macrophages, and Its Inhibition Clears Pathogen by Autophagy

Downregulation of host gene expression is a key strategy employed by intracellular pathogens for their survival in macrophages and subsequent pathogenesis. In a previous study, we have shown that histone deacetylase 1 (HDAC1) levels go up in macrophages infected with Mycobacterium tuberculosis, and it hypoacetylates histone H3 at the promoter of IL-12B gene, leading to its downregulation. We now show that after infection with M. tuberculosis, HDAC1 is phosphorylated, and the levels of phosphorylated HDAC1 (pHDAC1) increase significantly in macrophages. We found that transcriptional repressor protein zinc finger and BTB domain 25 (ZBTB25) and transcriptional corepressor Sin3a associate with the HDAC1 silencing complex, which is recruited to the promoter of IL-12B to downregulate its expression in infected macrophages. Knocking down of ZBTB25 enhanced release of IL-12p40 from infected macrophages. Inhibition of HDAC1 and ZBTB25 promoted colocalization of M. tuberculosis and LC3 (microtubule-associated protein 1A/1B-light chain 3) in autophagosomes. Induction of autophagy resulted in the killing of intracellular M. tuberculosis. Enhanced phosphorylation of JAK2 and STAT4 was observed in macrophages upon treatment with HDAC1 and ZBTB inhibitors, and inhibition of JAK2/STAT4 negated the killing of the intracellular pathogen, suggesting their role in the autophagy-mediated killing of intracellular M. tuberculosis. In view of the emergence of drug resistance in M. tuberculosis, host-directed therapy is an attractive alternative strategy to combat tuberculosis (TB). HDACs have been proposed to be host targets for TB treatment. Our study indicates that ZBTB25, a functional subunit of the HDAC1/Sin3a repressor complex involved in IL-12B suppression, could be an alternative target for host-directed anti-TB therapy.

IMPORTANCE Following infection with M. tuberculosis, levels of HDAC1 go up in macrophages, and it is recruited to the promoter of IL-12B where it hypoacetylates histone H3, leading to the downregulation of the gene. Here, we show that host transcriptional repressor protein ZBTB25 and transcriptional corepressor Sin3a associate with HDAC1 in the silencing complex. Knocking down of ZBTB25 prevented the recruitment of the complex to the promoter and consequently enhanced the gene expression and the release of IL-12p40 from infected macrophages. Pharmacological inhibition of ZBTB25 in infected macrophages resulted in the induction of autophagy and killing of intracellular M. tuberculosis. Drug-resistant TB is a serious challenge to TB control programs all over the world which calls for finding alternative therapeutic methods. Host-directed therapy is gaining significant momentum in treating infectious diseases. We propose that ZBTB25 is a potential target for host-directed treatment of TB.

The Macrophage Response to Mycobacterium tuberculosis and Opportunities for Autophagy Inducing Nanomedicines for Tuberculosis Therapy

The major causative agent of tuberculosis (TB), i.e., Mycobacterium tuberculosis (Mtb), has developed mechanisms to evade host defense responses and persist within host cells for prolonged periods of time. Mtb is also increasingly resistant to existing anti-TB drugs. There is therefore an urgent need to develop new therapeutics for TB and host directed therapies (HDTs) hold potential as effective therapeutics for TB. There is growing interest in the induction of autophagy in Mtb host cells using autophagy inducing compounds (AICs). Nanoparticles (NPs) can enhance the effect of AICs, thus improving stability, enabling cell targeting and providing opportunities for multimodal therapy. In this review, we focus on the macrophage responses to Mtb infection, in particular, the mechanistic aspects of autophagy and the evasion of autophagy by intracellular Mtb. Due to the overlap between the onset of autophagy and apoptosis; we also focus on the relationship between apoptosis and autophagy. We will also review known AICs in the context of Mtb infection. Finally, we discuss the applications of NPs in inducing autophagy with the intention of sharing insights to encourage further research and development of nanomedicine HDTs for TB therapy.

A review on possible mechanistic insights of Nitazoxanide for repurposing in COVID-19

The global pandemic of Coronavirus Disease 2019 (COVID-19) has brought the world to a grinding halt. A major cause of concern is the respiratory distress associated mortality attributed to the cytokine storm. Despite myriad rapidly approved clinical trials with repurposed drugs, and time needed to develop a vaccine, accelerated search for repurposed therapeutics is still ongoing. In this review, we present Nitazoxanide a US-FDA approved antiprotozoal drug, as one such promising candidate. Nitazoxanide which is reported to exert broad-spectrum antiviral activity against various viral infections, revealed good in vitro activity against SARS-CoV-2 in cell culture assays, suggesting potential for repurposing in COVID-19. Furthermore, nitazoxanide displays the potential to boost host innate immune responses and thereby tackle the life-threatening cytokine storm. Possibilities of improving lung, as well as multiple organ damage and providing value addition to COVID-19 patients with comorbidities, are other important facets of the drug. The review juxtaposes the role of nitazoxanide in fighting COVID-19 pathogenesis at multiple levels highlighting the great promise the drug exhibits. The in silico data and in vitro efficacy in cell lines confirms the promise of nitazoxanide. Several approved clinical trials world over further substantiate leveraging nitazoxanide for COVID-19 therapy.

Targeting Autophagy as a Strategy for Developing New Vaccines and Host-Directed Therapeutics Against Mycobacteria

Mycobacterial disease is an immense burden worldwide. This disease group includes tuberculosis, leprosy (Hansen's disease), Buruli Ulcer, and non-tuberculous mycobacterial (NTM) disease. The burden of NTM disease, both pulmonary and ulcerative, is drastically escalating globally, especially in developed countries such as America and Australia. Mycobacteria's ability to inhibit or evade the host immune system has contributed significantly to its continued prevalence. Pre-clinical studies have highlighted promising candidates that enhance endogenous pathways and/or limit destructive host responses. Autophagy is a cell-autonomous host defense mechanism by which intracytoplasmic cargos can be delivered and then destroyed in lysosomes. Previous studies have reported that autophagy-activating agents, small molecules, and autophagy-activating vaccines may be beneficial in restricting intracellular mycobacterial infection, even with multidrug-resistant strains. This review will examine how mycobacteria evade autophagy and discusses how autophagy could be exploited to design novel TB treatment strategies, such as host-directed therapeutics and vaccines, against Mycobacterium tuberculosis and NTMs.

Bioenergetic Inhibitors: Antibiotic Efficacy and Mechanisms of Action in Mycobacterium tuberculosis

Development of novel anti-tuberculosis combination regimens that increase efficacy and reduce treatment timelines will improve patient compliance, limit side-effects, reduce costs, and enhance cure rates. Such advancements would significantly improve the global TB burden and reduce drug resistance acquisition. Bioenergetics has received considerable attention in recent years as a fertile area for anti-tuberculosis drug discovery. Targeting the electron transport chain (ETC) and oxidative phosphorylation machinery promises not only to kill growing cells but also metabolically dormant bacilli that are inherently more drug tolerant. Over the last two decades, a broad array of drugs targeting various ETC components have been developed. Here, we provide a focused review of the current state of art of bioenergetic inhibitors of Mtb with an in-depth analysis of the metabolic and bioenergetic disruptions caused by specific target inhibition as well as their synergistic and antagonistic interactions with other drugs. This foundation is then used to explore the reigning theories on the mechanisms of antibiotic-induced cell death and we discuss how bioenergetic inhibitors in particular fail to be adequately described by these models. These discussions lead us to develop a clear roadmap for new lines of investigation to better understand the mechanisms of action of these drugs with complex mechanisms as well as how to leverage that knowledge for the development of novel, rationally-designed combination therapies to cure TB.

Taming the Autophagy as a Strategy for Treating COVID-19

Currently, an efficient treatment for COVID-19 is still unavailable, and people are continuing to die from complications associated with SARS-CoV-2 infection. Thus, the development of new therapeutic approaches is urgently needed, and one alternative is to target the mechanisms of autophagy. Due to its multifaceted role in physiological processes, many questions remain unanswered about the possible advantages of inhibiting or activating autophagy. Based on a search of the literature in this field, a novel analysis has been made to highlight the relation between the mechanisms of autophagy in antiviral and inflammatory activity in contrast with those of the pathogenesis of COVID-19. The present analysis reveals a remarkable coincidence between the uncontrolled inflammation triggered by SARS-CoV-2 and autophagy defects. Particularly, there is conclusive evidence about the substantial contribution of two concomitant factors to the development of severe COVID-19: a delayed or absent type I and III interferon (IFN-I and IFN-III) response together with robust cytokine and chemokine production. In addition, a negative interplay exists between autophagy and an IFN-I response. According to previous studies, the clinical decision to inhibit or activate autophagy should depend on the underlying context of the pathological timeline of COVID-19. Several treatment options are herein discussed as a guide for future research on this topic.

Interferon-inducer antivirals: Potential candidates to combat COVID-19

Coronavirus disease 2019 (COVID-19) is an infective disease generated by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Given the pandemic urgency and lack of an effective cure for this disease, drug repurposing could open the way for finding a solution. Lots of investigations are ongoing to test the compounds already identified as antivirals. On the other hand, induction of type I interferons are found to play an important role in the generation of immune responses against SARS-CoV-2. Therefore, it was opined that the antivirals capable of triggering the interferons and their signaling pathway, could rationally be beneficial for treating COVID-19. On this basis, using a database of antivirals, called drugvirus, some antiviral agents were derived, followed by searches on their relevance to interferon induction. The examined list included drugs from different categories such as antibiotics, immunosuppressants, anti-cancers, non-steroidal anti-inflammatory drugs (NSAID), calcium channel blocker compounds, and some others. The results as briefed here, could help in finding potential drug candidates for COVID-19 treatment. However, their advantages and risks should be taken into account through precise studies, considering a systemic approach. Even though the adverse effects of some of these drugs may overweight their benefits, considering their mechanisms and structures may give a clue for designing novel drugs in the future. Furthermore, the antiviral effect and IFN-modifying mechanisms possessed by some of these drugs might lead to a synergistic effect against SARS-CoV-2, which deserve to be evaluated in further investigations.

Quantitative proteomic analysis of the tizoxanide effect in vero cells

Nitazoxanide (NTZ) is effective against helminths and numerous microorganisms, including bacteria and viruses. In vivo, NTZ is metabolized into Tizoxanide (TIZ), which is the active circulating metabolite. With the emergence of SARS-Cov-2 as a Pandemic agent, NTZ became one of the molecules already approved for human use to engage clinical trials, due to results in vitro showing that NTZ was highly effective against the SARS-Cov-2, agent of COVID-19. There are currently several ongoing clinical trials mainly in the USA and Brazil involving NTZ due not only to the in vitro results, but also for its long-known safety. Here, we study the response of Vero cells to TIZ treatment and unveil possible mechanisms for its antimicrobial effect, using a label-free proteomic approach (LC/MS/MS) analysis to compare the proteomic profile between untreated- and TIZ-treated cells. Fifteen differentially expressed proteins were observed related to various biological processes, including translation, intracellular trafficking, RNA processing and modification, and signal transduction. The broad antimicrobial range of TIZ points towards its overall effect in lowering cell metabolism and RNA processing and modification. The decreased levels of FASN, HNRNPH and HNRNPK with the treatment appear to be important for antiviral activity.

Treatment Options Available for COVID-19 and an Analysis on Possible Role of Combination of rhACE2, Angiotensin (1-7) and Angiotensin (1-9) as Effective Therapeutic Measure

Corona virus disease (COVID-19), caused by SARS-CoV-2, is rapidly spreading all around the world and is posing a threat to mankind. Since SARS-CoV-2 is a novel virus, little is known about it and no effective drug is available for its treatment. While many drugs are being evaluated, an effective therapeutic measure is still lacking. SARS-CoV-2 like SARS-CoV binds with angiotensin-converting enzyme 2 (ACE2) present on human cells. SARS-CoV has been found to downregulate ACE2 and SARS- CoV-2 infection has been found to be associated with increased level of Angiotensin II. Based on these facts, we presume that SARS-CoV-2 like SARS-CoV downregulates ACE2, and in absence/reduced activity of ACE2, level of angiotensin (1-7) and angiotensin (1-9) is decreased while that of angiotensin II is increased and increased level of angiotensin II has been found to correlate with lung injury and viral load. We presume that restoration of normal functioning of renin-angiotensin system with recombinant human angiotensin-converting enzyme 2 (rhACE2), angiotensin (1-7) and angiotensin (1-9) may be an effective therapeutic measure but studies will be required to test this hypothesis and explore its possible role in treatment of COVID-19.

Chemoprophylactic activity of nitazoxanide in experimental model of mammary gland carcinoma in rats

The current study focuses on the evaluation of the chemoprophylactic activity of nitazoxanide against the mammary gland carcinoma in experimental rats. The experimental protocol involves total 50 female Wistar albino rats of body weight 120-150 g, which were randomly categorized into five groups; Normal control (1% w/v carboxymethyl cellulose, p.o.); Toxic control (N-methyl-N-nitrosourea, MNU, 47 mg/kg i.v.); Standard (MNU, 47 mg/kg i.v. + tamoxifen, 1 mg/kg p.o.); Treatment 1 (MNU, 47 mg/kg i.v. + NTZ low-dose, 25 mg/kg p.o.); and Treatment 2 (MNU, 47 mg/kg, i.v. + NTZ high-dose, 50 mg/kg p.o.). The mammary gland carcinoma was induced by a single tail vein intravenous injection of MNU at a 47 mg/kg dose. Seven days after MNU administration, daily dosing of nitazoxanide and tamoxifen was initiated till 110th day in respective groups. The MNU toxicity was apparent with the altered electrocardiogram and heart rate variability, increased number of alveolar bud count, differentiation score, and upregulated antioxidant parameters. Nitazoxanide treatment restored the histological architecture in rats along with the reduction of alveolar buds and downregulation of oxidative stress markers as well as inflammatory markers. Therefore, nitazoxanide can be utilized as a potential chemoprophylactic agent against mammary gland carcinoma induced by MNU.

Antimycobacterial Effects of Everolimus in a Human Granuloma Model

Mycobacterium tuberculosis (M. tb) has been historically and is currently a threat to global public health. First-line antibiotics have been effective but proven to be burdensome as they have many potential adverse side effects. There has been a recent increase in the number of active tuberculosis (TB) cases due to a prevalence of multidrug and extensively drug-resistant strains of M. tb, and an increasing number of highly susceptible people such as those with Type 2 Diabetes (T2DM) and human immunodeficiency virus (HIV) infection. Multidrug-resistant M. tb infection (MDR-TB) is challenging to treat with existing therapeutics, so novel therapeutics and treatment strategies must be developed. Host-Directed Therapy (HDT) has been a potential target mechanism for effective clearance of infection. Host cell autophagy plays an essential role in antibacterial defense. The mammalian target of rapamycin (mTOR) has been negatively correlated with autophagy induction. Everolimus is an mTOR inhibitor that induces autophagy, but with higher water solubility. Therefore, targeting the mTOR pathway has the potential to develop novel and more effective combination drug therapy for TB. This study tested the effect of everolimus, alone and in combination with current first-line antibiotics (isoniazid and pyrazinamide), on the inhibition of M. tb inside in vitro human granulomas. We found that M. tb-infected in vitro granulomas treated with everolimus alone resulted in significantly decreased M. tb burden compared to similar granulomas in the control group. Cells treated with everolimus doses of either 1 nM or 2 nM in conjunction with pyrazinamide (PZA) produced a significant reduction in intracellular M. tb burden. Treatment groups that received everolimus alone in either 1 nM or 2 nM doses experienced a significant reduction in oxidative stress. Additionally, samples treated with 2 nM everolimus alone were observed to have significantly higher levels of autophagy and mTOR inhibition as well. Results from this study indicate that everolimus is efficacious in controlling M. tb infection in the granulomas and has additive effects when combined with the anti-TB drugs, isoniazid and pyrazinamide. This study has shown that everolimus is a promising host-directed therapeutic in the context of in vitro granuloma M. tb infection. Further study is warranted to better characterize these effects.

Formulation of host-targeted therapeutics against bacterial infections

The global burden of bacterial infections is rising due to increasing resistance to the majority of first-line antibiotics, rendering these drugs ineffective against several clinically important pathogens. Limited transport of antibiotics into cells compounds this problem for gram-negative bacteria that exhibit prominent intracellular lifecycles. Furthermore, poor bioavailability of antibiotics in infected tissues necessitates higher doses and longer treatment regimens to treat resistant infections. Although emerging antibiotics can combat these problems, resistance still may develop over time. Expanding knowledge of host-pathogen interactions has inspired research and development of host-directed therapies (HDTs). HDTs target host-cell machinery critical for bacterial pathogenesis to treat bacterial infections alone or as adjunctive treatment with traditional antibiotics. Unlike traditional antibiotics that directly affect bacteria, a majority of HDTs function by boosting the endogenous antimicrobial activity of cells and are consequently less prone to bacterial tolerance induced by selection pressure. Therefore, HDTs can be quite effective against intracellular cytosolic or vacuolar bacteria, which a majority of traditional antibiotics are unable to eradicate. However, in vivo therapeutic efficacy of HDTs is reliant on adequate bioavailability. Particle-based formulations demonstrate the potential to enable targeted drug delivery, enhance cellular uptake, and increase drug concentration in the host cell of HDTs. This review selected HDTs for clinically important pathogens, identifies formulation strategies that can improve their therapeutic efficacy and offers insights toward further development of HDTs for bacterial infections.

C/EBPβ mediates NQO1 and GSTP1 anti-oxidative reductases expression in glioblastoma, promoting brain tumor proliferation

Glioblastoma (GBM) is the most common and most aggressive brain tumor, associated with high levels of reactive oxidative species (ROS) due to metabolic and signaling aberrations. High ROS levels are detrimental to cells, but it remains incompletely understood how cancer cells cope with the adverse effects. Here we show that C/EBPβ, a ROS responsive transcription factor, regulates the transcription of NQO1 and GSTP1, two antioxidative reductases, which neutralize ROS in the GBM and mediates their proliferation. C/EBPβ is upregulated in EGFR overexpressed GBM cells, inversely correlated with the survival rates of brain tumor patients. Interestingly, C/EBPβ binds the promoters of NQO1 and GSTP1 and escalates their expression. Overexpression of C/EBPβ selectively decreases the ROS in EGFR-overexpressed U87MG cells and promotes cell proliferation via upregulating NQO1 and GSTP1; whereas knocking down C/EBPβ elevates the ROS and reduces proliferation by repressing the reductases. Accordingly, C/EBPβ mediates the brain tumor growth in vivo, coupling with NQO1 and GSTP1 expression and ROS levels. Hence, C/EBPβ regulates the expression of antioxidative reductases and balances the ROS, promoting brain tumor proliferation.

Potential anti-TB investigational compounds and drugs with repurposing potential in TB therapy: a conspectus

The latest WHO report estimates about 1.6 million global deaths annually from TB, which is further exacerbated by drug-resistant (DR) TB and comorbidities with diabetes and HIV. Exiguous dosing, incomplete treatment course, and the ability of the tuberculosis bacilli to tolerate and survive current first-line and second-line anti-TB drugs, in either their latent state or active state, has resulted in an increased prevalence of multidrug-resistant (MDR), extensively drug-resistant (XDR), and totally drug-resistant TB (TDR-TB). Although a better understanding of the TB microanatomy, genome, transcriptome, proteome, and metabolome, has resulted in the discovery of a few novel promising anti-TB drug targets and diagnostic biomarkers of late, no new anti-TB drug candidates have been approved for routine therapy in over 50 years, with only bedaquiline, delamanid, and pretomanid recently receiving tentative regulatory approval. Considering this, alternative approaches for identifying possible new anti-TB drug candidates, for effectively eradicating both replicating and non-replicating Mycobacterium tuberculosis, are still urgently required. Subsequently, several antibiotic and non-antibiotic drugs with known treatment indications (TB targeted and non-TB targeted) are now being repurposed and/or derivatized as novel antibiotics for possible use in TB therapy. Insights gathered here reveal that more studies focused on drug-drug interactions between licensed and potential lead anti-TB drug candidates need to be prioritized. This write-up encapsulates the most recent findings regarding investigational compounds with promising anti-TB potential and drugs with repurposing potential in TB therapy.

Early Bactericidal Activity Trial of Nitazoxanide for Pulmonary Tuberculosis

This study was conducted in treatment-naive adults with drug-susceptible pulmonary tuberculosis in Port-au-Prince, Haiti, to assess the safety, bactericidal activity, and pharmacokinetics of nitazoxanide (NTZ). This was a prospective phase II clinical trial in 30 adults with pulmonary tuberculosis. Twenty participants received 1 g of NTZ orally twice daily for 14 days. A control group of 10 participants received standard therapy over 14 days. The primary outcome was the change in time to culture positivity (TTP) in an automated liquid culture system. The most common adverse events seen in the NTZ group were gastrointestinal complaints and headache. The mean change in TTP in sputum over 14 days in the NTZ group was 3.2 h ± 22.6 h and was not statistically significant (P = 0.56). The mean change in TTP in the standard therapy group was significantly increased, at 134 h ± 45.2 h (P < 0.0001). The mean NTZ MIC for Mycobacterium tuberculosis isolates was 12.3 μg/ml; the mean NTZ maximum concentration (C _max) in plasma was 10.2 μg/ml. Negligible NTZ levels were measured in sputum. At the doses used, NTZ did not show bactericidal activity against M. tuberculosis Plasma concentrations of NTZ were below the MIC, and its negligible accumulation in pulmonary sites may explain the lack of bactericidal activity. (This study has been registered at ClinicalTrials.gov under identifier NCT02684240.).

Tizoxanide Inhibits Inflammation in LPS-Activated RAW264.7 Macrophages via the Suppression of NF-κB and MAPK Activation

Tizoxanide is the main active metabolite of nitazoxanide. Nitazoxanide and tizoxanide have a broad-spectrum anti-infective effect, including parasites, bacteria, and virus. In the present study, we investigated the anti-inflammatory effect of tizoxanide on lipopolysaccharide (LPS)-stimulated RAW264.7 cells and revealed underlying molecular mechanisms. The results showed that tizoxanide significantly suppressed production of NO as well as pro-inflammatory cytokines, such as IL-1β, IL-6, and TNF-α in dose-dependent manner. Meanwhile, the levels of gene expression of these cytokines were inhibited significantly by tizoxanide that was discovered using RT-PCR. The increased protein levels of inducible nitric oxide synthase, heme oxygenase-1, and cyclooxygenase-2 by LPS in the cells were also reduced by tizoxanide. Moreover, we found that tizoxanide inhibited the phosphorylation of IKK-α and degradation of IκB by LPS in macrophage cells. The increased protein levels of p65 induced by LPS in the cytoplasm and nucleus were both decreased by tizoxanide, and the nuclear translocation of p65 was also restrained in cell imaging. In addition, tizoxanide considerably also inhibited LPS-activated JNK, p38, and ERK phosphorylation in RAW264.7 cells. Taken together, our results suggested that tizoxanide exerts anti-inflammatory effects, by inhibiting the production of pro-inflammatory cytokines and suppressing of the activation of the NF-κB and the MAPK signaling pathways in LPS-treated macrophage cells.