Efficacy and safety of methylene blue in the treatment of malaria: a systematic review

N,N'-bridged heterocyclic bis-iminium salts as potent antimalarial agents against multi-resistant Plasmodium falciparum

The emergence of Plasmodium resistance to past and newly introduced antimalarial drugs reinforces the need for new antimalarial agents with innovative mechanisms of action. In this regard, the search for new redox-cycling compounds might offer an interesting approach to treat malaria since P. falciparum is sensitive to oxidative stress. Based on our experience in the design of powerful organic reducers, we undertook here the synthesis and evaluation of different families of N-heterocyclic iminium salts that could provide more selective redox-cycling candidates against the K1 multi-resistant Plasmodium falciparum strain (PfK1). Bis-aminopyridinium salts emerged as the most promising candidates, exhibiting nanomolar antiplasmodial activity comparable to that of methylene blue. The biological study also underlined the positive impact on the in vitro activity of electron-donating groups and bis-salt forms, likely due to simultaneous bivalent interactions with the target. Our investigations revealed differences in the mechanism of action according to the heterocycle nature, highlighting an original mechanism for bis-aminopyridinium derivatives, different from that of chloroquine.

Imaging malaria parasites across scales and time

The idea that disease is caused at the cellular level is so fundamental to us that we might forget the critical role microscopy played in generating and developing this insight. Visually identifying diseased or infected cells lays the foundation for any effort to curb human pathology. Since the discovery of the Plasmodium-infected red blood cells, which cause malaria, microscopy has undergone an impressive development now literally resolving individual molecules. This review explores the expansive field of light microscopy, focusing on its application to malaria research. Imaging technologies have transformed our understanding of biological systems, yet navigating the complex and ever-growing landscape of techniques can be daunting. This review offers a guide for researchers, especially those working on malaria, by providing historical context as well as practical advice on selecting the right imaging approach. The review advocates an integrated methodology that prioritises the research question while considering key factors like sample preparation, fluorophore choice, imaging modality, and data analysis. In addition to presenting seminal studies and innovative applications of microscopy, the review highlights a broad range of topics, from traditional techniques like white light microscopy to advanced methods such as superresolution microscopy and time-lapse imaging. It addresses the emerging challenges of microscopy, including phototoxicity and trade-offs in resolution and speed, and offers insights into future technologies that might impact malaria research. This review offers a mix of historical perspective, technological progress, and practical guidance that appeal to novice and advanced microscopists alike. It aims to inspire malaria researchers to explore imaging techniques that could enrich their studies, thus advancing the field through enhanced visual exploration of the parasite across scales and time.

Yeast encapsulation of photosensitive insecticides increases toxicity against mosquito larvae while protecting microorganisms

An important defense against the deadly diseases that mosquitoes transmit is the application of insecticides that reduce mosquito populations. Unfortunately, the evolution and subsequent spread of insecticide resistance has decreased their efficacy. Therefore, new mosquito control strategies are needed. One class of larvicides, known as photosensitive insecticides, or PSIs, kills larvae via light-activated oxidative damage. PSIs are promising larvicides because of their high larvicidal efficacy, rapid photodegradation, inexpensive cost, and mechanism that is dissimilar to other insecticide classes. We explored a novel delivery strategy for increasing both the larvicidal efficiency and environmental biocompatibility of PSIs, known as yeast encapsulation. Using the PSIs, curcumin and methylene blue, we measured the survival of Anopheles gambiae larvae and Escherichia coli following exposure to either non-encapsulated or yeast-encapsulated PSIs and a photoperiod. Yeast encapsulation increased the phototoxicity of both curcumin and methylene blue against mosquito larvae, likely by increasing ingestion. Furthermore, yeast encapsulation protected E. coli from the phototoxicity of yeast-encapsulated curcumin, but not yeast-encapsulated methylene blue. Yeast encapsulation increases the larvicidal efficacy of a PSI while also increasing biocompatibility. Therefore, yeast encapsulation of PSIs is a promising insecticide delivery strategy for mosquito control.

Carbon Dots in Photodynamic/Photothermal Antimicrobial Therapy

Antimicrobial resistance (AMR) presents an escalating global challenge as conventional antibiotic treatments become less effective. In response, photodynamic therapy (PDT) and photothermal therapy (PTT) have emerged as promising alternatives. While rooted in ancient practices, these methods have evolved with modern innovations, particularly through the integration of lasers, refining their efficacy. PDT harnesses photosensitizers to generate reactive oxygen species (ROS), which are detrimental to microbial cells, whereas PTT relies on heat to induce cellular damage. The key to their effectiveness lies in the utilization of photosensitizers, especially when integrated into nano- or micron-scale supports, which amplify ROS production and enhance antimicrobial activity. Over the last decade, carbon dots (CDs) have emerged as a highly promising nanomaterial, attracting increasing attention owing to their distinctive properties and versatile applications, including PDT and PTT. They can not only function as photosensitizers, but also synergistically combine with other photosensitizers to enhance overall efficacy. This review explores the recent advancements in CDs, underscoring their significance and potential in reshaping advanced antimicrobial therapeutics.

Transmission-Blocking Strategies for Malaria Eradication: Recent Advances in Small-Molecule Drug Development

Malaria drug research and development efforts have resurged in the last decade following the decelerating rate of mortality and malaria cases in endemic regions. The inefficiency of malaria interventions is largely driven by the spreading resistance of the Plasmodium falciparum parasite to current drug regimens and that of the malaria vector, the Anopheles mosquito, to insecticides. In response to the new eradication agenda, drugs that act by breaking the malaria transmission cycle (transmission-blocking drugs), which has been recognized as an important and additional target for intervention, are being developed. These drugs take advantage of the susceptibility of Plasmodium during population bottlenecks before transmission (gametocytes) and in the mosquito vector (gametes, zygotes, ookinetes, oocysts, sporozoites). To date, compounds targeting stage V gametocytes predominate in the chemical library of transmission-blocking drugs, and some of them have entered clinical trials. The targeting of Plasmodium mosquito stages has recently renewed interest in the development of innovative malaria control tools, which hold promise for the application of compounds effective at these stages. In this review, we highlight the major achievements and provide an update on the research of transmission-blocking drugs, with a particular focus on their chemical scaffolds, antiplasmodial activity, and transmission-blocking potential.

Antimicrobial Activity of Methylene Blue Associated with Photodynamic Therapy: In Vitro Study in Multi-Species Oral Biofilm

The control of infectious diseases caused by biofilms is a continuing challenge for researchers due to the complexity of their microbial structures and therapeutic implications. Photodynamic therapy as an adjunctive anti-infective treatment has been described as a possible valid approach but has not been tested in polymicrobial biofilm models. This study evaluated the effect of photodynamic therapy in vitro with methylene blue (MB) 0.01% and red LEDs (λ = 660 nm, power density ≈ 330 mW/cm2, 2 mm distance from culture) on the metabolic activity and composition of a multispecies subgingival biofilm. Test Groups LED and MB + LED showed a more significant reduction in metabolic activity than the non-LED application group (~50 and 55%, respectively). Groups LED and MB equally affected (more than 80%) the total bacterial count in biofilms. No differences were noted in the bacterial biofilm composition between the groups. In vitro LED alone or the MB + LED combination reduced the metabolic activity of bacteria in polymicrobial biofilms and the total subgingival biofilm count.

Type I photodynamic antimicrobial therapy: Principles, progress, and future perspectives

The emergence of drug-resistant bacteria has significantly diminished the efficacy of existing antibiotics in the treatment of bacterial infections. Consequently, the need for finding a strategy capable of effectively combating bacterial infections has become increasingly urgent. Photodynamic therapy (PDT) is considered one of the most promising emerging antibacterial strategies due to its non-invasiveness, low adverse effect, and the fact that it does not lead to the development of drug resistance. However, bacteria at the infection sites often exist in the form of biofilm instead of the planktonic form, resulting in a hypoxic microenvironment. This phenomenon compromises the treatment outcome of oxygen-dependent type-II PDT. Compared to type-II PDT, type-I PDT is not constrained by the oxygen concentration in the infected tissues. Therefore, in the treatment of bacterial infections, type-I PDT exhibits significant advantages over type-II PDT. In this review, we first introduce the fundamental principles of type-I PDT in details, including its physicochemical properties and how it generates reactive oxygen species (ROS). Next, we explore several specific antimicrobial mechanisms utilized by type-I PDT and summarize the recent applications of type-I PDT in antimicrobial treatment. Finally, the limitations and future development directions of type-I photosensitizers are discussed. STATEMENT OF SIGNIFICANCE: The misuse and overuse of antibiotics have accelerated the development of bacterial resistance. To achieve the effective eradication of resistant bacteria, pathfinders have devised various treatment strategies. Among these strategies, type I photodynamic therapy has garnered considerable attention owing to its non-oxygen dependence. The utilization of non-oxygen-dependent photodynamic therapy not only enables the effective elimination of drug-resistant bacteria but also facilitates the successful eradication of hypoxic biofilms, which exhibits promising prospects for treating biofilm-associated infections. Based on the current research status, we anticipate that the novel type I photodynamic therapy agent can surmount the biofilm barrier, enabling efficient treatment of hypoxic biofilm infections.

Interaction of Methylene Blue with Severe Acute Respiratory Syndrome Coronavirus 2 Envelope Revealed by Molecular Modeling

Methylene blue has multiple antiviral properties against Severe Acute Respiratory Syndrome-related Coronavirus 2 (SARS-CoV-2). The ability of methylene blue to inhibit different stages of the virus life cycle, both in light-independent and photodynamic processes, is used in clinical practice. At the same time, the molecular aspects of the interactions of methylene blue with molecular components of coronaviruses are not fully understood. Here, we use Brownian dynamics to identify methylene blue binding sites on the SARS-CoV-2 envelope. The local lipid and protein composition of the coronavirus envelope plays a crucial role in the binding of this cationic dye. Viral structures targeted by methylene blue include the S and E proteins and negatively charged lipids. We compare the obtained results with known experimental data on the antiviral effects of methylene blue to elucidate the molecular basis of its activity against coronaviruses.

Exploring Methylene Blue and Its Derivatives in Alzheimer's Treatment: A Comprehensive Review of Randomized Control Trials

Methylene blue (MB) and its compounds are investigated for their potential benefits in the management of Alzheimer's disease (AD). AD is a widely seen neuropathological disorder characterized by the gradual decline of cognitive abilities, ultimately leading to the development of severe dementia. It is anticipated that there will be a significant increase in the prevalence of AD due to the aging population. Histopathologically, AD is distinguished by the presence of intracellular tangles of neurofibrillary tissues (NFTs) and extracellular amyloid plaques within the brain. MB is a thiophenazine dye with FDA approval for treating several illnesses. Its ease in crossing the blood-brain barrier and potential therapeutic use in central nervous system diseases have increased interest in its application for treating AD. The literature review includes randomized clinical trials investigating MB's potential benefits in treating AD. The findings of the studies indicate that the administration of MB has demonstrated enhancements in cognitive function, reductions in the accumulation of plaques containing beta-amyloid, improvements in memory and cognitive function in animal subjects, and possesses antioxidant properties that can mitigate oxidative stress and inflammation within the brain. This review evaluates the modern and latest research on the application of MB for treating AD.

Rejuvenating old fluorophores with new chemistry

The field of organic chemistry began with 19th century scientists identifying and then expanding upon synthetic dye molecules for textiles. In the 20th century, dye chemistry continued with the aim of developing photographic sensitizers and laser dyes. Now, in the 21st century, the rapid evolution of biological imaging techniques provides a new driving force for dye chemistry. Of the extant collection of synthetic fluorescent dyes for biological imaging, two classes reign supreme: rhodamines and cyanines. Here, we provide an overview of recent examples where modern chemistry is used to build these old-but-venerable classes of optically responsive molecules. These new synthetic methods access new fluorophores, which then enable sophisticated imaging experiments leading to new biological insights.

Recent developments in antimalarial drug discovery

Although malaria remains a big burden to many countries that it threatens their socio-economic stability, particularly in the countries where malaria is endemic, there have been great efforts to eradicate this disease with both successes and failures. For example, there has been a great improvement in malaria prevention and treatment methods with a net reduction in infection and mortality rates. However, the disease remains a global threat in terms of the number of people affected because it is one of the infectious diseases that has the highest prevalence rate, especially in Africa where the deadly Plasmodium falciparum is still widely spread. Methods to fight malaria are being diversified, including the use of mosquito nets, the target candidate profiles (TCPs) and target product profiles (TPPs) of medicine for malarial venture (MMV) strategy, the search for newer and potent drugs that could reverse chloroquine resistance, and the use of adjuvants such as rosiglitazone and sevuparin. Although these adjuvants have no antiplasmodial activity, they can help to alleviate the effects which result from plasmodium invasion such as cytoadherence. The list of new antimalarial drugs under development is long, including the out of ordinary new drugs MMV048, CDRI-97/78 and INE963 from South Africa, India and Novartis, respectively.

Production of non-activated biochar based on Biden pilosa and its application in removing methylene blue from aqueous solutions

Biden pilosa (BP) is a type of weed commonly found in Thailand that needs to be removed from agricultural areas for protecting main crops. This research proposed a method to reduce BP by using BP as a feedstock for biochar production. Non-activated BP biochar from fresh BP was produced in pilot scale using a drum kiln with a heat-transferring duct at a pyrolysis temperature of 550 °C at a slow heating rate. The physical properties of the non-activated BP biochar were investigated using scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, and a surface area analyzer. A batch experiment was used to study the adsorption behavior of methylene blue (MB) on BP biochar. The microstructure study of the BP biochar indicated that it has a cell structure similar to that of BP, which shows the non-destructive nature of the proposed technique for BP production. Six dominant peaks at 3283, 2915, 1559, 1403, 1116, and 863/839 cm^⁻1 were observed in the FTIR spectrum. The BP biochar exhibited a surface area of 5.21 m²/g and a pore size of 8 nm. The adsorption of MB on the BP biochar followed the Langmuir adsorption isotherm and pseudo-second-order kinetics. The Langmuir-based maximum adsorption capacity of MB on the BP biochar was 200 mg/g at 303 K.

Insight into the Crosstalk between Photodynamic Therapy and Immunotherapy in Breast Cancer

Breast cancer (BC) is the world's second most frequent malignancy and the leading cause of mortality among women. All in situ or invasive breast cancer derives from terminal tubulobular units; when the tumor is present only in the ducts or lobules in situ, it is called ductal carcinoma in situ (DCIS)/lobular carcinoma in situ (LCIS). The biggest risk factors are age, mutations in breast cancer genes 1 or 2 (BRCA1 or BRCA2), and dense breast tissue. Current treatments are associated with various side effects, recurrence, and poor quality of life. The critical role of the immune system in breast cancer progression/regression should always be considered. Several immunotherapy techniques for BC have been studied, including tumor-targeted antibodies (bispecific antibodies), adoptive T cell therapy, vaccinations, and immune checkpoint inhibition with anti-PD-1 antibodies. In the last decade, significant breakthroughs have been made in breast cancer immunotherapy. This advancement was principally prompted by cancer cells' escape of immune regulation and the tumor's subsequent resistance to traditional therapy. Photodynamic therapy (PDT) has shown potential as a cancer treatment. It is less intrusive, more focused, and less damaging to normal cells and tissues. It entails the employment of a photosensitizer (PS) and a specific wavelength of light to create reactive oxygen species. Recently, an increasing number of studies have shown that PDT combined with immunotherapy improves the effect of tumor drugs and reduces tumor immune escape, improving the prognosis of breast cancer patients. Therefore, we objectively evaluate strategies for their limitations and benefits, which are critical to improving outcomes for breast cancer patients. In conclusion, we offer many avenues for further study on tailored immunotherapy, such as oxygen-enhanced PDT and nanoparticles.

The activity of methylene blue against asexual and sexual stages of Plasmodium vivax

Methylene blue (MB) is an alternative for combating drug-resistant malaria parasites. Its transmission-blocking potential has been demonstrated in vivo in murine models, in vitro, and in clinical trials. MB shows high efficacy against Plasmodium vivax asexual stages; however, its efficacy in sexual stages is unknown. In this study, we evaluated the potential of MB against asexual and sexual forms of P. vivax isolated from the blood of patients residing in the Brazilian Amazon. An ex vivo schizont maturation assay, zygote to ookinete transformation assay, direct membrane feed assay (DMFA), and standard membrane feed assay (SMFA) using P. vivax gametocytes with MB exposure were performed. A cytotoxicity assay was also performed on freshly collected peripheral blood mononuclear cells (PBMCs) and the hepatocyte carcinoma cell line HepG2. MB inhibited the P. vivax schizont maturation and demonstrated an IC₅₀ lower than that of chloroquine (control drug). In the sexual forms, the MB demonstrated a high level of inhibition in the transformation of the zygotes into ookinetes. In the DMFA, MB did not considerably affect the infection rate and showed low inhibition, but it demonstrated a slight decrease in the infection intensity in all tested concentrations. In contrast, in the SMFA, MB was able to completely block the transmission at the highest concentration (20 µM). MB demonstrated low cytotoxicity to fresh PBMCs but demonstrated higher cytotoxicity to the hepatocyte carcinoma cell line HepG2. These results show that MB may be a potential drug for vivax malaria treatment.

Generation of singlet oxygen by porphyrin and phthalocyanine derivatives regarding the oxygen level

Background. The principle of photodynamic effect is based on the combined action of photosensitiser, molecular oxygen and light, which produce various reactive oxygen species and are associated with significant cellular damage. Singlet oxygen is one of the most serious representatives, which is characterised by powerful oxidising properties. Moreover, concomitant hyperbaric oxygen treatment can support these effects. Therefore, the subject of our study was to compare the yields of singlet oxygen for four different photosensitizers in dependency on the oxygen concentration. Material and methods. Four different photosensitizers 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate), tetramethylthionine chloride, 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin zinc(II) and zinc phthalocyanine disulfonate were investigated to determine the yield of singlet oxygen in PBS by Singlet Oxygen Sensor Green reagent under different partial pressures of oxygen (0.4 and 36 mg/l). Results. There were no noticeable shifts in the excitation and emission fluorescence spectra regarding the oxygen concentration. Concerning the same molar concentration of photosensitizers the production of singlet oxygen was highest for 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin zinc(II), where the rate of the fluorescence change was more than 3 times higher than that obtained for 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate). On the other hand, zinc phthalocyanine disulfonate showed the lowest yield in singlet oxygen production. Conclusions. Singlet oxygen production, within the range of oxygen concentrations achievable in tissues under normoxia or hyperoxia, does not depend on these concentrations. However, the singlet oxygen generation is significantly influenced by the type of photosensitizer, with the highest yield belonging to 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin zinc(II).

Rapid and Specific Action of Methylene Blue against Plasmodium Transmission Stages

Methylene blue (MB) is the oldest synthetic anti-infective. Its high potency against asexual and sexual stages of malaria parasites is well documented. This study aimed to investigate possible additional activities of MB in interfering with parasite transmission and determine target stages in Anopheles vectors and humans. MB's transmission-blocking activity was first evaluated by an ex vivo direct membrane feeding assay (DMFA) using Plasmodium falciparum field isolates. To investigate anti-mosquito stage activity, Plasmodium berghei-infected Anopheles stephensi mosquitoes were fed a second blood meal on mice that had been treated with methylene blue, 3, 6- and 15-days after the initial infectious blood meal. Anti-sporozoite and liver stage activities were evaluated in vitro and in vivo via sporozoite invasion and liver stage development assays, respectively. MB exhibited a robust inhibition of P. falciparum transmission in An. gambiae, even when added shortly before the DMFA but only a moderate effect against P. berghei oocyst development. Exposure of mature P. berghei and P. falciparum sporozoites to MB blocked hepatocyte invasion, yet P. berghei liver stage development was unaffected by MB. Our results indicate previously underappreciated rapid specific activities of methylene blue against Plasmodium transmission stages, preventing the establishment of both mosquito midgut and liver infections as the first essential steps in both hosts.

Necroptosis activation is associated with greater methylene blue-photodynamic therapy-induced cytotoxicity in human pancreatic ductal adenocarcinoma cells

Pancreatic ductal adenocarcinomas (PDAC) are the fourth leading cause of death due to neoplasms. In view of the urgent need of effective treatments for PDAC, photodynamic therapy (PDT) appears as a promising alternative. However, its efficacy against PDAC and the mechanisms involved in cell death induction remain unclear. In this study, we set out to evaluate PDT's cytotoxicity using methylene blue (MB) as a photosensitizer (PS) (MB-PDT) and to evaluate the contribution of necroptosis in its effect in human PDAC cells. Our results demonstrated that MB-PDT induced significant death of different human PDAC models presenting two different susceptibility profiles. This effect was independent of MB uptake or its subcellular localization. We found that the ability of triggering necroptosis was determinant to increase the treatment efficiency. Analysis of single cell RNA-seq data from normal and neoplastic human pancreatic tissues showed that specific necroptosis proteins RIPK1, RIPK3 and MLKL presented significant higher expression levels in cells displaying a transformed phenotype providing further support to the use of approaches that activate necroptosis, like MB-PDT, as useful adjunct to surgery of PDAC to tackle the problem of microscopic residual disease as well as to minimize the chance of local and metastatic recurrence.

Chemical Control of Mosquitoes and the Pesticide Treadmill: A Case for Photosensitive Insecticides as Larvicides

Insecticides reduce the spread of mosquito-borne disease. Over the past century, mosquito control has mostly relied on neurotoxic chemicals-such as pyrethroids, neonicotinoids, chlorinated hydrocarbons, carbamates and organophosphates-that target adults. However, their persistent use has selected for insecticide resistance. This has led to the application of progressively higher amounts of insecticides-known as the pesticide treadmill-and negative consequences for ecosystems. Comparatively less attention has been paid to larvae, even though larval death eliminates a mosquito's potential to transmit disease and reproduce. Larvae have been targeted by source reduction, biological control, growth regulators and neurotoxins, but hurdles remain. Here, we review methods of mosquito control and argue that photoactive molecules that target larvae-called photosensitive insecticides or PSIs-are an environmentally friendly addition to our mosquitocidal arsenal. PSIs are ingested by larvae and produce reactive oxygen species (ROS) when activated by light. ROS then damage macromolecules resulting in larval death. PSIs are degraded by light, eliminating environmental accumulation. Moreover, PSIs only harm small translucent organisms, and their broad mechanism of action that relies on oxidative damage means that resistance is less likely to evolve. Therefore, PSIs are a promising alternative for controlling mosquitoes in an environmentally sustainable manner.

A Novel Approach of Combining Methylene Blue Photodynamic Inactivation, Photobiomodulation and Oral Ingested Methylene Blue in COVID-19 Management: A Pilot Clinical Study with 12-Month Follow-Up

Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 virus was first recognized in late 2019 and remains a significant threat. We therefore assessed the use of local methylene blue photodynamic viral inactivation (MB-PDI) in the oral and nasal cavities, in combination with the systemic anti-viral, anti-inflammatory and antioxidant actions of orally ingested methylene blue (MB) and photobiomodulation (PBM) for COVID-19 disease. The proposed protocol leverages the separate and combined effects of MB and 660nm red light emitted diode (LED) to comprehensively address the pathophysiological sequelae of COVID-19. A total of eight pilot subjects with COVID-19 disease were treated in the Bahamas over the period June 2021-August 2021, using a remote care program that was developed for this purpose. Although not a pre-requisite for inclusion, none of the subjects had received any COVID-19 vaccination prior to commencing the study. Clinical outcome assessment tools included serial cycle threshold measurements as a surrogate estimate of viral load; serial online questionnaires to document symptom response and adverse effects; and a one-year follow-up survey to assess long-term outcomes. All subjects received MB-PDI to target the main sites of viral entry in the nose and mouth. This was the central component of the treatment protocol with the addition of orally ingested MB and/or PBM based on clinical requirements. The mucosal surfaces were irradiated with 660 nm LED in a continuous emission mode at energy density of 49 J/cm2 for PDI and 4.9 J/cm2 for PBM. Although our pilot subjects had significant co-morbidities, extremely high viral loads and moderately severe symptoms during the Delta phase of the pandemic, the response to treatment was highly encouraging. Rapid reductions in viral loads were observed and negative PCR tests were documented within a median of 4 days. These laboratory findings occurred in parallel with significant clinical improvement, mostly within 12-24 h of commencing the treatment protocol. There were no significant adverse effects and none of the subjects who completed the protocol required in-patient hospitalization. The outcomes were similarly encouraging at one-year follow-up with virtual absence of "long COVID" symptoms or of COVID-19 re-infection. Our results indicate that the protocols may be a safe and promising approach to challenging COVID-19 disease. Moreover, due its broad spectrum of activity, this approach has the potential to address the prevailing and future COVID-19 variants and other infections transmitted via the upper respiratory tract. Extensive studies with a large cohort are warranted to validate our results.

Microtubule-affinity regulating kinase 4: A potential drug target for cancer therapy

The human genome encodes more than 500 protein kinases that work by transferring the γ-phosphate group from ATP to serine, threonine, or tyrosine (Ser/Thr/Tyr) residues. Various kinases are associated with the onset of cancer and its further progression. The recent advancements in developing small-molecule kinase inhibitors to treat different cancer types have shown noticeable results in clinical therapies. Microtubule-affinity regulating kinase 4 (MARK-4) is a Ser/Thr protein kinase that relates structurally to AMPK/Snf1 subfamily of the CaMK kinases. The protein kinase modulates major signalling pathways such as NF-κB, mTOR and the Hippo-signalling pathway. MARK4 is associated with various cancer types due to its important role in regulating microtubule dynamics and subsequent cell division. Aberrant expression of MARK4 is linked with several pathologies such as cancer, Alzheimer's disease, obesity, etc. This review provides detailed information on structural aspects of MARK4 and its role in various signalling pathways related to cancer. Several therapeutic molecules were designed to inhibit the MARK4 activity from controlling associated diseases. The review further highlights kinase-targeted drug discovery and development in oncology and cancer therapies. Finally, we summarize the latest findings regarding the role of MARK4 in cancer, diabetes, and neurodegenerative disease path to provide a solid rationale for future investigation and therapeutic intervention.

Adsorption to the Surface of Hemozoin Crystals: Structure-Based Design and Synthesis of Amino-Phenoxazine β-Hematin Inhibitors

In silico adsorption of eight antimalarials that inhibit β-hematin (synthetic hemozoin) formation identified a primary binding site on the (001) face, which accommodates inhibitors via formation of predominantly π-π interactions. A good correlation (r2 =0.64, P=0.017) between adsorption energies and the logarithm of β-hematin inhibitory activity was found for this face. Of 53 monocyclic, bicyclic and tricyclic scaffolds, the latter yielded the most favorable adsorption energies. Five new amino-phenoxazine compounds were pursued as β-hematin inhibitors based on adsorption behaviour. The 2-substituted phenoxazines show good to moderate β-hematin inhibitory activity (<100 μM) and Plasmodium falciparum blood stage activity against the 3D7 strain. N1 ,N1 -diethyl-N4 -(10H-phenoxazin-2-yl)pentane-1,4-diamine (P2a) is the most promising hit with IC50 values of 4.7±0.6 and 0.64±0.05 μM, respectively. Adsorption energies are predictive of β-hematin inhibitory activity, and thus the in silico approach is a beneficial tool for structure-based development of new non-quinoline inhibitors.

Review on Methylene Blue: Its Properties, Uses, Toxicity and Photodegradation

The unavailability of clean drinking water is one of the significant health issues in modern times. Industrial dyes are one of the dominant chemicals that make water unfit for drinking. Among these dyes, methylene blue (MB) is toxic, carcinogenic, and non-biodegradable and can cause a severe threat to human health and environmental safety. It is usually released in natural water sources, which becomes a health threat to human beings and living organisms. Hence, there is a need to develop an environmentally friendly, efficient technology for removing MB from wastewater. Photodegradation is an advanced oxidation process widely used for MB removal. It has the advantages of complete mineralization of dye into simple and nontoxic species with the potential to decrease the processing cost. This review provides a tutorial basis for the readers working in the dye degradation research area. We not only covered the basic principles of the process but also provided a wide range of previously published work on advanced photocatalytic systems (single-component and multi-component photocatalysts). Our study has focused on critical parameters that can affect the photodegradation rate of MB, such as photocatalyst type and loading, irradiation reaction time, pH of reaction media, initial concentration of dye, radical scavengers and oxidising agents. The photodegradation mechanism, reaction pathways, intermediate products, and final products of MB are also summarized. An overview of the future perspectives to utilize MB at an industrial scale is also provided. This paper identifies strategies for the development of effective MB photodegradation systems.

An update on pharmacogenetic factors influencing the metabolism and toxicity of artemisinin-based combination therapy in the treatment of malaria

INTRODUCTION

Artemisinin-based combination therapies (ACTs) are recommended first-line antimalarials for uncomplicated Plasmodium falciparum malaria. Pharmacokinetic/pharmacodynamic variation associated with ACT drugs and their effect is documented. It is accepted to an extent that inter-individual variation is genetically driven, and should be explored for optimized antimalarial use.

AREAS COVERED

We provide an update on the pharmacogenetics of ACT antimalarial disposition. Beyond presently used antimalarials, we also refer to information available for the most notable next-generation drugs under development. The bibliographic approach was based on multiple Boolean searches on PubMed covering all recent publications since our previous review.

EXPERT OPINION

The last 10 years have witnessed an increase in our knowledge of ACT pharmacogenetics, including the first clear examples of its contribution as an exacerbating factor for drug-drug interactions. This knowledge gap is still large and is likely to widen as a new wave of antimalarial drug is looming, with few studies addressing their pharmacogenetics. Clinically useful pharmacogenetic markers are still not available, in particular, from an individual precision medicine perspective. A better understanding of the genetic makeup of target populations can be valuable for aiding decisions on mass drug administration implementation concerning region-specific antimalarial drug and dosage options.

Revisiting the grammar of Tau aggregation and pathology formation: how new insights from brain pathology are shaping how we study and target Tauopathies

Converging evidence continues to point towards Tau aggregation and pathology formation as central events in the pathogenesis of Alzheimer's disease and other Tauopathies. Despite significant advances in understanding the morphological and structural properties of Tau fibrils, many fundamental questions remain about what causes Tau to aggregate in the first place. The exact roles of cofactors, Tau post-translational modifications, and Tau interactome in regulating Tau aggregation, pathology formation, and toxicity remain unknown. Recent studies have put the spotlight on the wide gap between the complexity of Tau structures, aggregation, and pathology formation in the brain and the simplicity of experimental approaches used for modeling these processes in research laboratories. Embracing and deconstructing this complexity is an essential first step to understanding the role of Tau in health and disease. To help deconstruct this complexity and understand its implication for the development of effective Tau targeting diagnostics and therapies, we firstly review how our understanding of Tau aggregation and pathology formation has evolved over the past few decades. Secondly, we present an analysis of new findings and insights from recent studies illustrating the biochemical, structural, and functional heterogeneity of Tau aggregates. Thirdly, we discuss the importance of adopting new experimental approaches that embrace the complexity of Tau aggregation and pathology as an important first step towards developing mechanism- and structure-based therapies that account for the pathological and clinical heterogeneity of Alzheimer's disease and Tauopathies. We believe that this is essential to develop effective diagnostics and therapies to treat these devastating diseases.

Methylene Blue-Based Nano and Microparticles: Fabrication and Applications in Photodynamic Therapy

Methylene blue (MB) has been used in the textile industry since it was first extracted by the German chemist Heinrich Caro. Its pharmacological properties have also been applied toward the treatment of certain diseases such as methemoglobinemia, ifosfamide-induced encephalopathy, and thyroid conditions requiring surgery. Recently, the utilization of MB as a safe photosensitizer in photodynamic therapy (PDT) has received attention. Recent findings demonstrate that photoactivated MB exhibits not only anticancer activity but also antibacterial activity both in vitro and in vivo. However, due to the hydrophilic nature of MB, it is difficult to create MB-embedded nano- or microparticles capable of increasing the clinical efficacy of the PDT. This review aims to summarize fabrication techniques for MB-embedded nano and microparticles and to provide both in vitro and in vivo examples of MB-mediated PDT, thereby offering a future perspective on improving this promising clinical treatment modality. We also address examples of MB-mediated PDT in both cancer and infection treatments. Both in-vitro and in-vivo studies are summarized here to document recent trends in utilizing MB as an effective photosensitizer in PDT. Lastly, we discuss how developing efficient MB-carrying nano- and microparticle platforms would be able to increase the benefits of PDT.

The Use of High Surface Area Mesoporous-Activated Carbon from Longan Seed Biomass for Increasing Capacity and Kinetics of Methylene Blue Adsorption from Aqueous Solution

Microporous- and mesoporous-activated carbons were produced from longan seed biomass through physical activation with CO2 under the same activation conditions of time and temperature. The specially prepared mesoporous carbon showed the maximum porous properties with the specific surface area of 1773 m2/g and mesopore volume of 0.474 cm3/g which accounts for 44.1% of the total pore volume. These activated carbons were utilized as porous adsorbents for the removal of methylene blue (MB) from an aqueous solution and their effectiveness was evaluated for both the adsorption kinetics and capacity. The adsorption kinetic data of MB were analyzed by the pseudo-first-order model, the pseudo-second-order model, and the pore-diffusion model equations. It was found that the adsorption kinetic behavior for all carbons tested was best described by the pseudo-second-order model. The effective pore diffusivity (De) derived from the pore-diffusion model had the values of 4.657 × 10-7-6.014 × 10-7 cm2/s and 4.668 × 10-7-19.920 × 10-7 cm2/s for the microporous- and mesoporous-activated carbons, respectively. Three well-known adsorption models, namely the Langmuir, Freundlich and Redlich-Peterson equations were tested with the experimental MB adsorption isotherms, and the results showed that the Redlich-Peterson model provided the overall best fitting of the isotherm data. In addition, the maximum capacity for MB adsorption of 1000 mg/g was achieved with the mesoporous carbon having the largest surface area and pore volume. The initial pH of MB solution had virtually no effect on the adsorption capacity and removal efficiency of the methylene blue dye. Increasing temperature over the range from 35 to 55 °C increased the adsorption of methylene blue, presumably caused by the increase in the diffusion rate of methylene blue to the adsorption sites that could promote the interaction frequency between the adsorbent surface and the adsorbate molecules. Overall, the high surface area mesoporous carbon was superior to the microporous carbon in view of the adsorption kinetics and capacity, when both carbons were used for the removal of MB from an aqueous solution.

Antiprotozoal agents: How have they changed over a decade?

Neglected tropical diseases are a diverse group of communicable diseases that are endemic in low- or low-to-middle-income countries located in tropical and subtropical zones. The number and availability of drugs for treating these diseases are low, the administration route is inconvenient in some cases, and most of them have safety, efficacy, or adverse/toxic reaction issues. The need for developing new drugs to deal with these issues is clear, but one of the most drastic consequences of this negligence is the lack of interest in the research and development of new therapeutic options among major pharmaceutical companies. Positive changes have been achieved over the last few years, although the overall situation remains alarming. After more than one decade since the original work reviewing antiprotozoal agents came to light, now it is time to question ourselves: How has the scenario for the treatment of protozoal diseases such as malaria, leishmaniasis, human African trypanosomiasis, and American trypanosomiasis changed? This review covers the last decade in terms of the drugs currently available for the treatment of these diseases as well as the clinical candidates being currently investigated.

Glutathione reductase: A cytoplasmic antioxidant enzyme and a potential target for phenothiazinium dyes in Neospora caninum

Neospora caninum causes heavy losses related to abortions in bovine cattle. This parasite developed a complex defense redox system, composed of enzymes as glutathione reductase (GR). Methylene blue (MB) impairs the activity of recombinant form of Plasmodium GR and inhibits the parasite proliferation in vivo and in vitro. Likewise, MB and its derivatives inhibits Neospora caninum proliferation, however, whether the MB mechanism of action is correlated to GR function remains unclear. Therefore, here, N. caninum GR (NcGR) was characterized and its potential inhibitors were determined. NcGR was found in the tachyzoite cytosol and has a similar structure and sequence compared to its homologs. We verified the in vitro activity of rNcGR (875 nM) following NADPH absorbance at 340 nM (100 mM KH2PO4, pH 7.5, 1 mM EDTA, ionic strength: 600 mM, 25 °C). rNcGR exhibited a Michaelian behavior (Km(GSSG):0.10 ± 0.02 mM; kcat(GSSG):0.076 ± 0.003 s-1; Km(NADPH):0.006 ± 0.001 mM; kcat(NADPH): 0.080 ± 0.003 s-1). The IC50 of MB,1,9-dimethyl methylene blue, new methylene blue, and toluidine blue O on rNcGR activity were 2.1 ± 0.2 μM, 11 ± 2 μM, 0.7 ± 0.1 μM, and 0.9 ± 0.2 μM, respectively. Our results suggest the importance of NcGR in N. caninum biology and antioxidant mechanisms. Moreover, data presented here strongly suggest that NcGR is an important target of phenothiazinium dyes in N. caninum proliferation inhibition.

Repurposing methylene blue in the management of COVID-19: Mechanistic aspects and clinical investigations

The severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) is the most recent coronaviruses, which has infected humans, and caused the disease COVID-19. The World Health Organization has declared COVID-19 as a pandemic in March 2020. The SARS-CoV-2 enters human hosts majorly via the respiratory tract, affecting the lungs first. In few critical cases, the infection progresses to failure of the respiratory system known as acute respiratory distress syndrome acute respiratory distress syndrome may be further associated with multi-organ failure and vasoplegic shock. Currently, the treatment of COVID-19 involves use of antiviral and anti-cytokine drugs. However, both the drugs have low efficacy because they cannot inhibit the production of free radicals and cytokines at the same time. Recently, some researchers have reported the use of methylene blue (MB) in COVID-19 management. MB has been used since a long time as a therapeutic agent, and has been approved by the US FDA for the treatment of other diseases. The additional advantage of MB is its low cost. MB is a safe drug when used in the dose of < 2 mg/kg. In this review, the applicability of MB in COVID-19 and its mechanistic aspects have been explored and compiled. The clinical studies have been explained in great detail. Thus, the potential of MB in the management of COVID-19 has been examined.

Antimalarial drug discovery: from quinine to the most recent promising clinical drug candidates

Malaria is a tropical threatening disease caused by Plasmodium parasites, resulting in 409,000 deaths in 2019. The delay of mortality and morbidity has been compounded by the widespread of drug resistant parasites from Southeast Asia since two decades. The emergence of artemisinin-resistant Plasmodium in Africa, where most cases are accounted, highlights the urgent need for new medicines. In this effort, the World Health Organization and Medicines for Malaria Venture joined to define clear goals for novel therapies and characterized the target candidate profile. This ongoing search for new treatments is based on imperative labor in medicinal chemistry which is summarized here with particular attention to hit-to-lead optimizations, key properties, and modes of action of these novel antimalarial drugs. This review, after presenting the current antimalarial chemotherapy, from quinine to the latest marketed drugs, focuses in particular on recent advances of the most promising antimalarial candidates in clinical and preclinical phases.

The immunosuppressive activity of artemisinin-type drugs towards inflammatory and autoimmune diseases

The sesquiterpene lactone artemisinin from Artemisia annua L. is well established for malaria therapy, but its bioactivity spectrum is much broader. In this review, we give a comprehensive and timely overview of the literature regarding the immunosuppressive activity of artemisinin-type compounds toward inflammatory and autoimmune diseases. Numerous receptor-coupled signaling pathways are inhibited by artemisinins, including the receptors for interleukin-1 (IL-1), tumor necrosis factor-α (TNF-α), β3-integrin, or RANKL, toll-like receptors and growth factor receptors. Among the receptor-coupled signal transducers are extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K), AKT serine/threonine kinase (AKT), mitogen-activated protein kinase (MAPK)/extracellular signal regulated kinase (ERK) kinase (MEK), phospholipase C γ1 (PLCγ), and others. All these receptors and signal transduction molecules are known to contribute to the inhibition of the transcription factor nuclear factor κ B (NF-κB). Artemisinins may inhibit NF-κB by silencing these upstream pathways and/or by direct binding to NF-κB. Numerous NF-κB-regulated downstream genes are downregulated by artemisinin and its derivatives, for example, cytokines, chemokines, and immune receptors, which regulate immune cell differentiation, apoptosis genes, proliferation-regulating genes, signal transducers, and genes involved in antioxidant stress response. In addition to the prominent role of NF-κB, other transcription factors are also inhibited by artemisinins (mammalian target of rapamycin [mTOR], activating protein 1 [AP1]/FBJ murine osteosarcoma viral oncogene homologue [FOS]/JUN oncogenic transcription factor [JUN]), hypoxia-induced factor 1α (HIF-1α), nuclear factor of activated T cells c1 (NF-ATC1), Signal transducers and activators of transcription (STAT), NF E2-related factor-2 (NRF-2), retinoic-acid-receptor-related orphan nuclear receptor γ (ROR-γt), and forkhead box P-3 (FOXP-3). Many in vivo experiments in disease-relevant animal models demonstrate therapeutic efficacy of artemisinin-type drugs against rheumatic diseases (rheumatoid arthritis, osteoarthritis, lupus erythematosus, arthrosis, and gout), lung diseases (asthma, acute lung injury, and pulmonary fibrosis), neurological diseases (autoimmune encephalitis, Alzheimer's disease, and myasthenia gravis), skin diseases (dermatitis, rosacea, and psoriasis), inflammatory bowel disease, and other inflammatory and autoimmune diseases. Randomized clinical trials should be conducted in the future to translate the plethora of preclinical results into clinical practice.

Methylene Blue has a potent antiviral activity against SARS-CoV-2 and H1N1 influenza virus in the absence of UV-activation in vitro

Methylene blue is an FDA (Food and Drug Administration) and EMA (European Medicines Agency) approved drug with an excellent safety profile. It displays broad-spectrum virucidal activity in the presence of UV light and has been shown to be effective in inactivating various viruses in blood products prior to transfusions. In addition, its use has been validated for methemoglobinemia and malaria treatment. In this study, we first evaluated the virucidal activity of methylene blue against influenza virus H1N1 upon different incubation times and in the presence or absence of light activation, and then against SARS-CoV-2. We further assessed the therapeutic activity of methylene blue by administering it to cells previously infected with SARS-CoV-2. Finally, we examined the effect of co-administration of the drug together with immune serum. Our findings reveal that methylene blue displays virucidal preventive or therapeutic activity against influenza virus H1N1 and SARS-CoV-2 at low micromolar concentrations and in the absence of UV-activation. We also confirm that MB antiviral activity is based on several mechanisms of action as the extent of genomic RNA degradation is higher in presence of light and after long exposure. Our work supports the interest of testing methylene blue in clinical studies to confirm a preventive and/or therapeutic efficacy against both influenza virus H1N1 and SARS-CoV-2 infections.

Baseline and multinormal distribution of ex vivo susceptibilities of Plasmodium falciparum to methylene blue in Africa, 2013-18

BACKGROUND

Plasmodium falciparum resistance to most antimalarial compounds has emerged in Southeast Asia and spread to Africa. In this context, the development of new antimalarial drugs is urgent.

OBJECTIVES

To determine the baseline in vitro activity of methylene blue (Proveblue®) on African isolates and to determine whether parasites have different phenotypes of susceptibility to methylene blue.

METHODS

Ex vivo susceptibility to methylene blue was measured for 609 P. falciparum isolates of patients hospitalized in France for malaria imported from Africa. A Bayesian statistical analysis was designed to describe the distribution of median effective concentration (EC50) estimates.

RESULTS

The EC50 ranged from 0.16 to 87.2 nM with a geometric mean of 7.17 nM (95% CI = 6.21-8.13). The 609 EC50 values were categorized into four components: A (mean = 2.5 nM; 95% CI = 2.28-2.72), B (mean = 7.44 nM; 95% CI = 7.07-7.81), C (mean = 16.29 nM; 95% CI = 15.40-17.18) and D (mean = 38.49 nM; 95% CI = 34.14-42.84). The threshold value for in vitro reduced susceptibility to methylene blue was estimated at 35 nM using the geometric mean of EC50 plus 2 SDs of the 609 isolates. This cut-off also corresponds to the lower limit of the 95% CI of the methylene blue EC50 of component D. Thirty-five isolates (5.7%) displayed EC50 values above this threshold.

CONCLUSIONS

Methylene blue exerts a promising efficacy against P. falciparum and is a potential partner for triple combinations.

Nrf2/ARE Activators Improve Memory in Aged Mice via Maintaining of Mitochondrial Quality Control of Brain and the Modulation of Gut Microbiome

Aging is one of the most serious factors for central nervous dysfunctions, which lead to cognitive impairment. New highly effective drugs are required to slow the development of cognitive dysfunction. This research studied the effect of dimethyl fumarate (DMF), methylene blue (MB), and resveratrol (RSV) on the cognitive functions of 15-month-old mice and their relationship to the maintenance of mitochondrial quality control in the brain and the bacterial composition of the gut microbiome. We have shown that studied compounds enhance mitochondrial biogenesis, mitophagy, and antioxidant defense in the hippocampus of 15-month-old mice via Nrf2/ARE pathway activation, which reduces the degree of oxidative damage to mtDNA. It is manifested in the improvement of short-term and long-term memory. We have also shown that memory improvement correlates with levels of Roseburia, Oscillibacter, ChristensenellaceaeR-7, Negativibacillus, and Faecalibaculum genera of bacteria. At the same time, long-term treatment by MB induced a decrease in gut microbiome diversity, but the other markers of dysbiosis were not observed. Thus, Nrf2/ARE activators have an impact on mitochondrial quality control and are associated with a positive change in the composition of the gut microbiome, which together lead to an improvement in memory in aged mice.

Expanding the ZIFs Repertoire for Biological Applications with the Targeted Synthesis of ZIF-20 Nanoparticles

Owing to their facile synthesis, tailorable porosity, diverse compositions, and low toxicity, zeolitic imidazolate framework (ZIF) nanoparticles (NPs) have emerged as attractive platforms for a variety of biologically relevant applications. To date, a small subset of ZIFs representing only two topologies and very few linker chemistries have been studied in this realm. We seek to expand the bio-design space for ZIF NPs through the targeted synthesis of a hierarchically complex ZIF based on two types of cages, ZIF-20, with lta topology. This study demonstrates the rapid synthesis and size tunability of ZIF-20 particles across the micro and nanoregimes via microwave heating and the use of a modulating agent. To evaluate the utility of ZIF particles for biological applications, we examine their stability in biologically relevant media and demonstrate biocompatibility with A549 human epithelial cells. Further, the ability to encapsulate and release methylene blue, a therapeutic and bioimaging agent, is validated. Importantly, ZIF-20 NPs display a unique behavior relative to previously studied ZIFs based on their specific structural and chemical features. This finding highlights the need to expand the design space across the broader ZIFs family, to exploit a wider range of relevant properties for biological applications and beyond.

Green Discoloration of Human Postmortem Brains: Etiologies and Mechanisms of Discoloration

ABSTRACT

A variety of gross discolorations of human postmortem brains is occasionally encountered and can have diagnostic implications. We describe 3 cases of green discoloration of the human brain observed on postmortem examination. Two patients who succumbed shortly after administration of methylene blue (MB) showed diffuse green discoloration that was detectable as early as 24 hours and was seen for at least 48 hours after MB administration. Green discoloration was largely in cortical and deep gray matter structures with relative sparing of the white matter. In contrast, a patient with severe hyperbilirubinemia who died after intracerebral hemorrhage showed localized bright green bile stained brain parenchyma in the areas surrounding the hemorrhage. We highlight the distinct patterns of discoloration in different causes of green brain discoloration, including MB, bile staining, and hydrogen sulfide poisoning. Recognition of these patterns by practicing pathologists can be used to differentiate between these etiologies and allow correct interpretation in both the medical and forensic autopsy settings.

Hereditary Spastic Paraplegia and Future Therapeutic Directions: Beneficial Effects of Small Compounds Acting on Cellular Stress

Hereditary spastic paraplegia (HSP) is a group of inherited neurodegenerative conditions that share a characteristic feature of degeneration of the longest axons within the corticospinal tract, which leads to progressive spasticity and weakness of the lower limbs. Mutations of over 70 genes produce defects in various biological pathways: axonal transport, lipid metabolism, endoplasmic reticulum (ER) shaping, mitochondrial function, and endosomal trafficking. HSPs suffer from an adequate therapeutic plan. Currently the treatments foreseen for patients affected by this pathology are physiotherapy, to maintain the outgoing tone, and muscle relaxant therapies for spasticity. Very few clinical studies have been conducted, and it's urgent to implement preclinical animal studies devoted to pharmacological test and screening, to expand the rose of compounds potentially attractive for clinical trials. Small animal models, such as Drosophila melanogaster and zebrafish, have been generated, analyzed, and used as preclinical model for screening of compounds and their effects. In this work, we briefly described the role of HSP-linked proteins in the organization of ER endomembrane system and in the regulation of ER homeostasis and stress as a common pathological mechanism for these HSP forms. We then focused our attention on the pharmacodynamic and pharmacokinetic features of some recently identified molecules with antioxidant property, such as salubrinal, guanabenz, N-acetyl cysteine, methylene blue, rapamycin, and naringenin, and on their potential use in future clinical studies. Expanding the models and the pharmacological screening for HSP disease is necessary to give an opportunity to patients and clinicians to test new molecules.

Targeting Gametocytes of the Malaria Parasite Plasmodium falciparum in a Functional Genomics Era: Next Steps

Mosquito transmission of the deadly malaria parasite Plasmodium falciparum is mediated by mature sexual forms (gametocytes). Circulating in the vertebrate host, relatively few intraerythrocytic gametocytes are picked up during a bloodmeal to continue sexual development in the mosquito vector. Human-to-vector transmission thus represents an infection bottleneck in the parasite's life cycle for therapeutic interventions to prevent malaria. Even though recent progress has been made in the identification of genetic factors linked to gametocytogenesis, a plethora of genes essential for sexual-stage development are yet to be unraveled. In this review, we revisit P. falciparum transmission biology by discussing targetable features of gametocytes and provide a perspective on a forward-genetic approach for identification of novel transmission-blocking candidates in the future.

Liquid-Phase Removal of Methylene Blue as Organic Pollutant by Mesoporous Activated Carbon Prepared from Water Caltrop Husk Using Carbon Dioxide Activation

In this work, a mesoporous activated carbon (AC) was prepared from a unique lignocellulosic biomass (water caltrop husk) in triplicate using a single-step physical activation process at lower temperature (i.e., 750 °C) and longer holding time (i.e., 90 min). Based on the pore properties and adsorption properties for removal of methylene blue (MB) as organic pollutant, the results proved that the resulting AC possesses a mesoporous feature with the Brunauer–Emmett–Teller (BET) surface area of 810.5 m2/g and mesopore volume of about 0.13 cm3/g. Due to its fast adsorption rate and maximal adsorption capacity fitted (126.6 mg/g), the mesoporous carbon material could be used as an excellent adsorbent for liquid-phase removal of MB. In addition, the pseudo-second-order model is well suited for describing the adsorption system between the cationic adsorbate and the resulting AC with oxygen surface groups.

Effect of long-term methylene blue treatment on the composition of mouse gut microbiome and its relationship with the cognitive abilities of mice

In recent years, methylene blue (MB) has attracted considerable interest as a potential drug for the treatment of methemoglobinemia and neurodegenerative diseases. MB is active against microorganisms from various taxonomic groups. However, no studies have yet been conducted on the effect of MB on the intestinal microbiome of model animals. The aim of this work was to study the effect of different concentrations of MB on the mouse gut microbiome and its relationship with the cognitive abilities of mice. We showed that a low MB concentration (15 mg/kg/day) did not cause significant changes in the microbiome composition. The Bacteroidetes/Firmicutes ratio decreased relative to the control on the 2nd and 3rd weeks. A slight decrease in the levels Actinobacteria was detected on the 3rd week of the experiment. Changes in the content of Delta, Gamma, and Epsilonproteobacteria have been also observed. We did not find significant alterations in the composition of intestinal microbiome, which could be an indication of the development of dysbiosis or other gut dysfunction. At the same time, a high concentration of MB (50 mg/kg/day) led to pronounced changes, primarily an increase in the levels of Delta, Gamma and Epsilonproteobacteria. Over 4 weeks of therapy, the treatment with high MB concentration has led to an increase in the median content of Proteobacteria to 7.49% vs. 1.61% in the control group. Finally, we found that MB at a concentration of 15 mg/kg/day improved the cognitive abilities of mice, while negative correlation between the content of Deferribacteres and cognitive parameters was revealed. Our data expand the understanding of the relationship between MB, cognitive abilities, and gut microbiome in respect to the antibacterial properties of MB.

Methylene blue is a potent and broad-spectrum inhibitor against Zika virus in vitro and in vivo

Many flaviviruses including the Dengue virus (DENV), Zika virus (ZIKV), West Nile virus, Yellow Fever virus, and Japanese encephalitis virus are significant human pathogens, unfortunately without any specific therapy. Here, we demonstrate that methylene blue, an FDA-approved drug, is a broad-spectrum and potent antiviral against Zika virus and Dengue virus both in vitro and in vivo. We found that methylene blue can considerably inhibit the interactions between viral protease NS3 and its NS2B co-factor, inhibit viral protease activity, inhibit viral growth, protect 3D mini-brain organoids from ZIKV infection, and reduce viremia in a mouse model. Mechanistic studies confirmed that methylene blue works in both entry and post entry steps, reduces virus production in replicon cells and inhibited production of processed NS3 protein. Overall, we have shown that methylene blue is a potent antiviral for management of flavivirus infections, particularly for Zika virus. As an FDA-approved drug, methylene blue is well-tolerated for human use. Therefore, methylene blue represents a promising and easily developed therapy for management of infections by ZIKV and other flaviviruses.

Methylene blue inhibits replication of SARS-CoV-2 in vitro

In December 2019, a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), causing coronavirus diseases 2019 (COVID-19) emerged in Wuhan, China. Currently there is no antiviral treatment recommended against SARS-CoV-2. Identifying effective antiviral drugs is urgently required. Methylene blue has already demonstrated in vitro antiviral activity in photodynamic therapy as well as antibacterial, antifungal and antiparasitic activities in non-photodynamic assays. In this study. non-photoactivated methylene blue showed in vitro activity at very low micromolar range with an EC₅₀ (median effective concentration) of 0.30 ± 0.03 μM and an EC₉₀ (90% effective concentration) of 0.75 ± 0.21 μM at a multiplicity of infection (MOI) of 0.25 against SARS-CoV-2 (strain IHUMI-3). The EC₅₀ and EC₉₀ values for methylene blue are lower than those obtained for hydroxychloroquine (1.5 μM and 3.0 μM) and azithromycin (20.1 μM and 41.9 μM). The ratios C_max/EC₅₀ and C_max/EC₉₀ in blood for methylene blue were estimated at 10.1 and 4.0, respectively, following oral administration and 33.3 and 13.3 following intravenous administration. Methylene blue EC₅₀ and EC₉₀ values are consistent with concentrations observed in human blood. We propose that methylene blue is a promising drug for treatment of COVID-19. In vivo evaluation in animal experimental models is now required to confirm its antiviral effects on SARS-CoV-2. The potential interest of methylene blue to treat COVID-19 needs to be confirmed by prospective comparative clinical studies.

Effects of Methylene Blue on Ovarian Torsion-Detorsion Injury in a Rat Model

STUDY OBJECTIVES

Methylene blue (MB) is an antioxidant that ameliorates ischemia-reperfusion injury in several tissues. We analyzed the effects of MB as an inhibitor of torsion-detorsion injury in rat ovaries.

METHODS

Rats were randomly divided into 5 groups. Group 1 was the sham group, in which only laparotomy was performed. Group 2 was the torsion group, with 3 hours of ischemia. Group 3 was the torsion + MB group, with 3 hours of ischemia after MB administration. Group 4 was the torsion-detorsion group, with 3 hours of ischemia and reperfusion. Finally, group 5 was the torsion-detorsion + MB group, with 3 hours of ischemia and MB administration before detorsion/reperfusion. Ovary injuries were histopathologically scored. Malondialdehyde (MDA) and total protein levels in ovarian tissues were determined, and long pentraxin-3 (PTX3) levels were measured in ovarian tissue using an enzyme-linked immunosorbent assay.

RESULTS

In comparing group 4 with group 5 and group 2 with 3, histopathological parameters reflecting injury were significantly increased in groups 4 and 2. Group 3 generated increased MDA levels when compared with group 2 (P < .05). However, there was no significant difference between groups 2 and 3 in terms of plasma PTX3 levels. MDA and PTX3 levels decreased in group 5 in comparison with group 4 for MDA (P < .000) and PTX3 levels (P < .01).

CONCLUSIONS

MB alleviated ischemia-reperfusion ovary injury in our experimental model.

[Advances in Identification of Intersegmental Plane during Pulmonary Segmentectomy]

With the popularity of computed tomography (CT) scan in recent years, early stage lung cancer has been discovered in large numbers of patients and pulmonary segmentectomy has been widely used clinically. Identification of the intersegmental plane is one of the key steps in pulmonary segmentectomy, and current methods for identifying the intersegmental plane are numerous and have their own advantages and disadvantages. We will review relevant methods to help the clinical practice.
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Host-parasite interactions in vector-borne protozoan infections

Protists embrace many species, some of which may be either occasional or permanent parasites of vertebrate animals. Between the parasite species, several of medical and veterinary importance are vector-transmitted. The ecology and epidemiology of vector-borne parasitoses, including babesiosis, leishmaniasis and malaria, are particularly complex, as they are influenced by many factors, such as vector reproductive efficiency and geographical spread, vectorial capacity, host immunity, travel and human behaviour and climatic factors. Transmission dynamics are determined by the interactions between pathogen, vector, host and environmental factors and, given their complexity, many different types of mathematical models have been developed to understand them. A good basic knowledge of vector-pathogen relationships and transmission dynamics is thus essential for disease surveillance and control interventions and may help in understanding the spread of epidemics and be useful for public health planning.

A Study of Synergy of Combination of Eosin B with Chloroquine, Artemisinin, and Sulphadoxine-Pyrimethamine on Plasmodium falciparum In Vitro and Plasmodium berghei In Vivo

Methods

Drug assessment was carried out singly or in combination on Plasmodium falciparum in vitro using the candle jar method at three inhibitory concentrations. Percent parasitemia of live cells was obtained by microscopic counting. Peter's suppression test was carried out on mice infected with Plasmodium berghei after 3 administration of the drugs singly and in combination, and parasites were counted by microscopy for 10 days.

Results

Synergy was exhibited by isobolograms of eosin B combined with artesunate and sulphadoxine-pyrimethamine with more than 10 fold reduction of all drugs in vitro. A good combination index was obtained with artesunate at 50% inibitory concentration with 3.4 nM eosin B and 1.7 nM artesunate in contrast to 124 nM eosin B and 7.6 nM artesunate singly. In vivo studies also showed a considerable lowering of the effective dose of eosin B 30 mg/kg: artesunate 3 mg/kg with 200 mg/kg eosin B and 60 mg/kg artesunate separately. Sulphadoxine-pyrimethamine seemed to have the greatest synergistic effect with a combination index of 0.007, but this could be due to it consisting of a combination of three drugs. Eosin B's combination index with chloroquine was fair, and in vivo tests too did not show as much competence as the other two drugs. Conclusion and Interpretation. It can be concluded that eosin B can be used in combination with antimalarial drugs with favorable results.

The photodynamic and direct actions of methylene blue on mitochondrial energy metabolism: A balance of the useful and harmful effects of this photosensitizer

According to the literature, methylene blue (MB) is a photosensitizer (PS) with a high affinity for mitochondria. Therefore, several studies have explored this feature to evaluate its photodynamic effects on the mitochondrial apoptotic pathway under normoxic conditions. We are aware only of limited reports regarding MB's photodynamic effects on mitochondrial energy metabolism, especially under hypoxic conditions. Thus, the purposes of this study were to determine the direct and photodynamic acute effects of MB on the energy metabolism of rat liver mitochondria under hypoxic conditions and its direct acute effects on several parameters linked to energy metabolism in the isolated perfused rat liver. MB presented a high affinity for mitochondria, irrespective of photostimulation or proton gradient formation. Upon photostimulation, MB demonstrated high in vitro oxidizing species generation ability. Consequently, MB damaged the mitochondrial macromolecules, as could be evidenced by the elevated levels of lipid peroxidation and protein carbonyls. In addition to generating a pro-oxidant environment, MB also led to a deficient antioxidant defence system, as indicated by the reduced glutathione (GSH) depletion. Bioenergetically, MB caused uncoupling of oxidative phosphorylation and led to photodynamic inactivation of complex I, complex II, and F₁F_O-ATP synthase complex, thus decreasing mitochondrial ATP generation. Contrary to what is expected for an ideal PS, MB displayed appreciable dark toxicity on mitochondrial energy metabolism. The results indicated that MB acted via at least three mechanisms: direct damage to the inner mitochondrial membrane; uncoupling of oxidative phosphorylation; and inhibition of electron transfer. Confirming the impairment of mitochondrial energy metabolism, MB also strongly inhibited mitochondrial ATP production. In the perfused rat liver, MB stimulated oxygen consumption, decreased the ATP/ADP ratio, inhibited gluconeogenesis and ureogenesis, and stimulated glycogenolysis, glycolysis, and ammoniagenesis, fully corroborating its uncoupling action in intact cells, as well. It can be concluded that even under hypoxic conditions, MB is a PS with potential for photodynamic effect-induced mitochondrial dysfunction. However, MB disrupts the mitochondrial energy metabolism even in the dark, causing energy-linked liver metabolic changes that could be harmful in specific circumstances.