In vitro assessment for cytotoxicity screening of new antimalarial candidates

Abstract In antimalarial research there are no standard procedures to determine the toxicity of a drug candidate. Among the alternatives available, in vitro cytotoxicity assays are the most widely used to predict toxic effects of future therapeutic products. They have the advantage over the in vivo assays, in that they offer the possibility to restrain the number of experimental variables. The objective of the present study was to compare in vitro cytotoxic methods by testing various compounds currently used to treat malaria against different cell lines. Neutral red (NR) uptake and methylthiazoletetrazolium (MTT) colorimetric in vitro assays were used to determine preliminary toxicity of commercially available antimalarial drugs against tumor and non-tumor cells lines. Toxicity through brine shrimp lethality bioassay and hemolytic activity were also evaluated. Significant differences were observed in the tests measured by NR uptake. The tumor cell lines TOV-21G and HepG2 and non-tumor WI-26VA4 cells showed relatively uniform toxicity results, with TOV-21G being the most sensitive cell tested, presenting the lowest concentration to cause death to 50% of viable cells (CC50) values. The results of this study support the use of TOV-21G, HepG2 and WI-26VA4 cells lines as the choice for cytotoxicity tests to evaluate potential bioactive compounds.

COVID-19 pandemic: multilevel dental technical guidelines based on new scientific evidence

ABSTRACT The COVID-19 pandemic imposed restrictive measures on dentistry in different regions of the world, ranging from stoppage of care to only permission for urgent and emergency dental services. Thus, new biosafety guidelines for resuming activities, whether in single dental offices, large clinics or dental education activities, are urgently required. In this sense, herein, guidelines that incorporate common points of the main protocols found in the literature for the resumption of dental activities at their different levels, whether in the scope of care or education, are presented. Furthermore, we present the incorporation of measures that allow an increase in the level of biosafety, such as the control of the dental team, the inclusion in the history of conjunctivitis as a possible alert for COVID-19, and the use of the pulse oximeter to assess the risk of silent hypoxemia, which may indicate a complication of COVID-19. In addition, new perspectives for directing research and innovation for biosafety in dentistry are discussed.

In vitro and in silico assessment of new beta amino ketones with antiplasmodial activity

ABSTRACT Background: Based on the current need for new drugs against malaria, our study evaluated eight beta amino ketones in silico and in vitro for potential antimalarial activity. Methods: Using the Brazilian Malaria Molecular Targets (BraMMT) and OCTOPUS® software programs, the pattern of interactions of beta-amino ketones was described against different proteins of P. falciparum and screened to evaluate their physicochemical properties. The in vitro antiplasmodial activities of the compounds were evaluated using a SYBR Green-based assay. In parallel, in vitro cytotoxic data were obtained using the MTT assay. Results: Among the eight compounds, compound 1 was the most active and selective against P. falciparum (IC50 = 0.98 µM; SI > 60). Six targets were identified in BraMMT that interact with compounds exhibiting a stronger binding energy than the crystallographic ligand: P. falciparum triophosphate phosphoglycolate complex (1LYX), P. falciparum reductase (2OK8), PfPK7 (2PML), P. falciparum glutaredoxin (4N0Z), PfATP6, and PfHT. Conclusions: The physicochemical properties of compound 1 were compatible with the set of criteria established by the Lipinski rule and demonstrated its potential as a drug prototype for antiplasmodial activity.

COVID-19 Vaccines: Bioethical Consideration / Vacunas contra la covid-19: consideración bioética / Vacinas contra a covid-19: consideração bioética

Abstract The COVID-19 pandemic produced immeasurable impacts on the economy, education, and socialization, besides the loss of mi llions of lives. Thus, there has been an accelerated development of an unprecedented number of COVID-19 vaccine candidates to control the pandemic. The World Health Organization's emergency use authorization of COVID-19 vaccines still in clinical trial allowed immunizing the population. This paper presents a perspective of the bioethical precepts of autonomy, non-maleficence, beneficence, and justice in the emergency use of COVID-19 vaccines. Furthermore, it emphasizes the importance of surveillance at all stages of vaccine development to detect adverse effects and ensure compliance with bioethical precepts.

Resumen La pandemia de la covid-19 ha tenido impactos inconmensurables en la economía, la educación y la socialización, además de la pérdida de millones de vidas. Por lo tanto, se ha acelerado el desarrollo de un número sin precedentes de candidatos a vacunas contra la covid-19 para controlar la pandemia. A su vez, la autorización para su uso de emergencia por parte de la Organización Mundial de la Salud permitió el inicio de la inmunización de la población a través de vacunas que aún se encuentran en ensayos clínicos. Aquí presentamos una perspectiva de los preceptos bioéticos de autonomía, no maleficencia, beneficencia y justicia en el contexto del uso de emergencia de vacunas contra la covid-19. Además, se enfatiza la importancia de la vigilancia en todas las etapas del desarrollo de la vacuna con el fin de detectar efectos adversos y asegurar el cumplimiento de los preceptos bioéticos.

Resumo A pandemia ocasionada pela covid-19, além da perda de milhões de vidas, vem trazendo consequências incomensuráveis para a economia, a educação e a socialização. Portanto, vem sendo acelerado o desenvolvimento de um número sem precedentes de candidatos a vacinas contra a covid-19 para controlar a pandemia. Por sua vez, a autorização para seu uso emergencial por parte da Organização Mundial da Saúde permitiu o início da imunização da população por meio de vacinas que ainda se encontram em ensaios clínicos. Aqui, apresentamos uma perspectiva dos princípios bioéticos de autonomia, não maleficencia, beneficência e justiça no contexto do uso emergencial de vacinas contra covid-19. Além disso, é enfatizada a importância da vigilância em todas as etapas do desenvolvimento da vacinação a fim de detectar efeitos adversos e assegurar o cumprimento dos princípios bioéticos.

Use of wide-field optical fluorescence for visualization of oral biofilm in a patient with peri-implant mucositis: a new approach / Uso da fluorescência óptica de campo amplo para visualização de biofilme oral em paciente com mucosite peri-implantar: uma nova abordagem

ABSTRACT Peri-implant diseases, caused by bacteria from biofilm related to dental implants, are one of the main causes of late loss of implants. In this sense, peri-implant diseases are divided into peri-implant mucositis, when it affects only the soft tissues, and peri-implantitis, when there is a bone involvement, which can lead to the failure of dental implant therapy. Thus, biofilm removal is essential for peri-implant health, allowing long-term success in implant therapy. To improve the visualization of oral biofilm, which is usually transparent or colorless, disclosing agents have been routinely used. However, disclosing agents have allergenic potential and can cause staining extrinsically in restorative and prosthetic materials, leading to aesthetic impairment. Thus, the use of fluorescence has been studied as an alternative for visualization of oral biofilm. Therefore, this report describes the use of wide-field optical fluorescence for visualization of oral biofilm associated with implants and teeth, in a routine appointment and follow-up of a partially edentulous patient with peri-implant mucositis. In addition, this report showed wide-field optical fluorescence can be used in a clinical routine of care of patients with dental implants. In this sense, wide-field optical fluorescence allowed easy and immediate visualization of the mature oral biofilm for its adequate removal, evaluation of the quality of restoration to sealing of screw access-hole of implant and identification of cariogenic lesions, without risk of allergic reactions or staining of prostheses and restorations.

RESUMO Doenças peri-implantares, causadas por bactérias de biofilme relacionadas a implantes dentários, são uma das principais causas de perda tardia de implantes. Nesse sentido, as doenças peri-implantares são divididas em mucosite peri-implantar, quando afeta apenas tecidos moles, e peri-implantite, quando há comprometimento ósseo, o que pode levar ao fracasso da terapia com implantes dentários. Assim, a remoção do biofilme é essencial para a saúde peri-implantar, permitindo sucesso a longo prazo na terapia com implantes. A fim de melhorar a visualização do biofilme oral, que geralmente é transparente ou incolor, agentes reveladores têm sido rotineiramente utilizados. No entanto, esses agentes têm potencial alergênico e podem causar manchas extrinsecamente em materiais restauradores e protéticos, levando a prejuízo estético. Assim, o uso da fluorescência tem sido estudado como alternativa para visualização do biofilme oral. Este relato descreve o uso da fluorescência óptica de campo amplo para visualização do biofilme oral associado a implantes e dentes em uma consulta de acompanhamento de rotina de uma paciente parcialmente edêntula com mucosite peri-implantar. Além disso, este relato evidenciou que a fluorescência óptica de campo amplo pode ser utilizada dentro da rotina clínica de atendimento de pacientes com implantes dentários. Nesse sentido, a fluorescência óptica de campo amplo permitiu a visualização fácil e imediata do biofilme oral maduro para sua remoção adequada, a avaliação da qualidade da restauração do selamento do orifício de acesso do parafuso do implante e a identificação de lesões cariogênicas, sem risco de reações alérgicas ou manchamento de próteses e restaurações.

Dehydrobufotenin extracted from the Amazonian toad Rhinella marina (Anura: Bufonidae) as a prototype molecule for the development of antiplasmodial drugs

he resistance against antimalarial drugs represents a global challenge in the fight and control of malaria. The Brazilian biodiversity can be an important tool for research and development of new medicinal products. In this context, toxinology is a multidisciplinary approach on the development of new drugs, including the isolation, purification, and evaluation of the pharmacological activities of natural toxins. The present study aimed to evaluate the cytotoxicity, as well as the antimalarial activity in silico and in vitro of four compounds isolated from Rhinella marina venom as potential oral drug prototypes. Methods: Four compounds were challenged against 35 target proteins from P. falciparum and screened to evaluate their physicochemical properties using docking assay in Brazilian Malaria Molecular Targets (BraMMT) software and in silico assay in OCTOPUS® software. The in vitro antimalarial activity of the compounds against the 3D7 Plasmodium falciparum clones were assessed using the SYBR Green I based assay (IC50). For the cytotoxic tests, the LD50 was determined in human pulmonary fibroblast cell line using the [3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) assay. Results: All compounds presented a ligand-receptor interaction with ten Plasmodium falciparum-related protein targets, as well as antimalarial activity against chloroquine resistant strain (IC50 = 3.44 µM to 19.11 µM). Three of them (dehydrobufotenine, marinobufagin, and bufalin) showed adequate conditions for oral drug prototypes, with satisfactory prediction of absorption, permeability, and absence of toxicity. In the cell viability assay, only dehydrobufotenin was selective for the parasite. Conclusions: Dehydrobufotenin revealed to be a potential oral drug prototype presenting adequate antimalarial activity and absence of cytotoxicity, therefore should be subjected to further studies.(AU)

In vitro and in vivo antimalarial activity of the volatile oil of Cyperus articulatus (Cyperaceae)

Malaria is a disease of global tropical distribution, being endemic in more than 90 countries and responsible for about 212 million cases worldwide in 2016. To date, the strategies used to eradicate this disease have been ineffective, without specific preventive measures such as vaccines. Currently, the existing therapeutic arsenal is limited and has become ineffective against the expansion of artemisinin-resistant Plasmodium, demonstrating the need for studies that would allow the development of new compounds against this disease. In this context, we studied the volatile oil obtained from rhizomes of Cyperus articulatus (VOCA), a plant species commonly found in the Amazon region and popularly used as a therapeutic alternative for the treatment of malaria, in order to confirm its potential as an antimalarial agent by in vitro and in vivo assays. We cultured Plasmodium falciparum W2 (chloroquine-resistant) and 3D7 (chloroquine-sensitive) strains in erythrocytes and exposed them to VOCA at different concentrations in 96-well microplates. In vivo antimalarial activity was tested in BALB/c mice inoculated with approximately 106 erythrocytes infected with Plasmodium berghei. VOCA showed a high antimalarial potential against the two P. falciparum strains, with IC50 = 1.21 µg mL-1 for W2 and 2.30 µg mL-1 for 3D7. VOCA also significantly reduced the parasitemia and anemia induced by P. berghei in mice. Our results confirmed the antimalarial potential of the volatile oil of Cyperus articulatus. (AU)

Mucosal vitiligo in angles of the mouth: clinical and fluorescence aspects

SUMMARY Vitiligo is the most common depigmenting, chronic acquired disease of the skin and mucosa. However, vitiligo of an unclassified type and mucosal subtype affecting only one area of the mucosa is considered quite uncommon. The diagnosis of vitiligo, regardless of its type, is clinical. Nonetheless, a device that allows the visualization of the tissue fluorescence may be useful for confirming the diagnosis. We present the use of wide-field optical fluorescence device for complementary examination and diagnosis of unusual cases of mucosal vitiligo located only in angles of the mouth.

RESUMO O vitiligo é a doença crônica adquirida despigmentante mais comum da pele e/ou da mucosa. Entretanto, o vitiligo do tipo não classificado e subtipo de mucosa afetando apenas uma área da mucosa é considerado bastante incomum. O diagnóstico de vitiligo, independentemente do seu tipo, é clínico. No entanto, o uso de um dispositivo que permite a visualização da fluorescência tecidual pode ser útil para a confirmação do diagnóstico de vitiligo. Apresentamos o uso do dispositivo de exame complementar de fluorescência óptica de campo amplo para o diagnóstico de um caso incomum de vitiligo de mucosa localizado apenas em ângulos da boca.

Hairy tongue: differential diagnosis by use of widefield optical fluorescence

Abstract Hairy tongue is a benign pathology, characterized clinically by hyperkeratinized plaques on the dorsal surface of the tongue, hairlike, whose coloration ranges from unpigment, whitish, yellowish, green, brown to black. Diagnosis is clinical, and, in cases of whitish plaques, it may be difficult to differentiate between oral hairy leukoplakia, potentially malignant leukoplakia or squamous cell carcinoma. Thus, widefield optical fluorescence complementary examination may allow a better visualization of the local hairlike pattern of hyperkeratinization, typical of the hairy tongue, facilitating the diagnosis. In this work, a 57-year-old man was referred to the Dental Specialties Department of the Divinópolis Health Department (MG, Brazil) by a general dental practitioner, aiming a differential diagnosis of possible malignant lesion on the dorsal tongue surface. The complementary examination by wide-field optical fluorescence was performed. For this, it was employed a device with high-power light-emitting diode emitting light centered at a wavelength of (400±10) nm and maximum irradiance of (0.040±0.008) W/cm2 was used for fluorescence visualization. Fluorescence images showed projections of hairlike appearance in tongue dorsal surface with no aspects of malignancy. Hairlike appearance is the principal feature of hairy tongue. In this way, the final diagnosis was established. In conclusion, in this case, the use of widefield optical fluorescence in oral diagnostic routine provided a differential diagnosis, with no need of an incisional biopsy.

Resumo A língua pilosa é uma patologia benigna, caracterizada clinicamente por placas hiperqueratinizadas na face dorsal da língua, semelhante a pelos, cuja coloração varia de despigmentada, esbranquiçada, amarelada, verde, acastanhada a preta. O diagnóstico é clínico, e em casos de placas esbranquiçadas, pode ser difícil diferenciar entre leucoplasia pilosa oral, leucoplasia potencialmente maligna ou carcinoma de células escamosas. Assim, o exame complementar de fluorescência óptica de campo amplo pode permitir uma melhor visualização do padrão local de hiperqueratinização semelhante à pelos, os quais são característicos de língua pilosa, facilitando o diagnóstico. Neste trabalho, um paciente do sexo masculino, 57 anos, foi encaminhado ao Departamento de Odontologia da Secretaria de Saúde de Divinópolis (Minas Gerais) por um clínico geral, visando o diagnóstico de uma possível lesão maligna na face dorsal da língua. O exame complementar por fluorescência óptica de campo amplo foi realizado. Para isso, foi empregado um dispositivo com diodo emissor de luz de alta potência, com luz centrada em um comprimento de onda de (400±10) nm e irradiância máxima de (0,04 ±0,008) W/cm2 para visualização de fluorescência. As imagens de fluorescência mostraram projeções de aparência semelhante à pelos na superfície dorsal da língua, sem aspectos de malignidade. A aparência similar à pelos é a principal característica da língua pilosa. Dessa maneira, o diagnóstico final foi estabelecido. Em conclusão, neste caso, o uso da fluorescência óptica de campo amplo permitiu um diagnóstico diferencial, sem a necessidade de uma biópsia incisional.

Oral squamous papilloma: a view under clinical, fluorescence and histopathological aspects / Papiloma escamoso oral: uma visão sob aspectos clínicos, de fluorescência e histopatológicos

ABSTRACT Oral squamous papilloma is a benign tumor whose pathogenesis has been associated with human papillomavirus infection. Thus, it is noteworthy that human papillomavirus infection is one of the risk factors associated with the development of cervical, anogenital, pharynx, larynx and oral cavity carcinomas. Oral squamous papilloma can affect any region of the oral cavity, and transmission of human papillomavirus can occur by direct contact, sexual intercourse or from mother to child during delivery. The diagnosis is clinical and histopathological, with surgical removal representing the treatment of choice. Recently, widefield optical fluorescence has been used as a complementary examination to the conventional clinical examination in the screening of oral pathological lesions and for the delimitation of surgical margins. We report a case of oral squamous papilloma with its clinical, histopathological features and, in addition, from the perspective of wide field optical fluorescence.

RESUMO O papiloma escamoso oral é um tumor benigno, cuja patogênese tem sido associada à infecção pelo papilomavírus humano. A infecção pelo papilomavírus humano é um dos fatores de risco associado ao desenvolvimento dos carcinomas cervicais, anogenitais, faríngeos, laríngeos e da cavidade oral. O papiloma escamoso oral pode acometer qualquer região da cavidade oral, e a transmissão do papilomavírus humano ocorre por contato direto, relação sexual ou de mãe para filho durante o parto. O diagnóstico é clínico e histopatológico, e a remoção cirúrgica representa o tratamento de escolha. Recentemente, a fluorescência óptica de campo amplo tem sido empregada como exame complementar ao exame clínico convencional, no rastreio de lesões patológicas orais e para delimitação de margens cirúrgicas. Relatamos um caso de papiloma escamoso oral com suas características clínicas e histopatológicas, sob a perspectiva da fluorescência óptica de campo amplo.

Brazilian malaria molecular targets (BraMMT): selected receptors for virtual high-throughput screening experiments

BACKGROUND Owing to increased spending on pharmaceuticals since 2010, discussions about rising costs for the development of new medical technologies have been focused on the pharmaceutical industry. Computational techniques have been developed to reduce costs associated with new drug development. Among these techniques, virtual high-throughput screening (vHTS) can contribute to the drug discovery process by providing tools to search for new drugs with the ability to bind a specific molecular target. OBJECTIVES In this context, Brazilian malaria molecular targets (BraMMT) was generated to execute vHTS experiments on selected molecular targets of Plasmodium falciparum. METHODS In this study, 35 molecular targets of P. falciparum were built and evaluated against known antimalarial compounds. FINDINGS As a result, it could predict the correct molecular target of market drugs, such as artemisinin. In addition, our findings suggested a new pharmacological mechanism for quinine, which includes inhibition of falcipain-II and a potential new antimalarial candidate, clioquinol. MAIN CONCLUSIONS The BraMMT is available to perform vHTS experiments using OCTOPUS or Raccoon software to improve the search for new antimalarial compounds. It can be retrieved from www.drugdiscovery.com.br or download of Supplementary data.

Successful application of virtual screening and molecular dynamics simulations against antimalarial molecular targets

The main challenge in the control of malaria has been the emergence of drug-resistant parasites. The presence of drug-resistant Plasmodium sp. has raised the need for new antimalarial drugs. Molecular modelling techniques have been used as tools to develop new drugs. In this study, we employed virtual screening of a pyrazol derivative (Tx001) against four malaria targets: plasmepsin-IV, plasmepsin-II, falcipain-II, and PfATP6. The receiver operating characteristic curves and area under the curve (AUC) were established for each molecular target. The AUC values obtained for plasmepsin-IV, plasmepsin-II, and falcipain-II were 0.64, 0.92, and 0.94, respectively. All docking simulations were carried out using AutoDock Vina software. The ligand Tx001 exhibited a better interaction with PfATP6 than with the reference compound (-12.2 versus -6.8 Kcal/mol). The Tx001-PfATP6 complex was submitted to molecular dynamics simulations in vacuum implemented on an NAMD program. The ligand Tx001 docked at the same binding site as thapsigargin, which is a natural inhibitor of PfATP6. Compound TX001 was evaluated in vitro with a P. falciparum strain (W2) and a human cell line (WI-26VA4). Tx001 was discovered to be active against P. falciparum (IC50 = 8.2 µM) and inactive against WI-26VA4 (IC50 > 200 µM). Further ligand optimisation cycles generated new prospects for docking and biological assays.

Structure-based drug design studies of the interactions of ent-kaurane diterpenes derived from Wedelia paludosa with the Plasmodium falciparum sarco/endoplasmic reticulum Ca2+-ATPase PfATP6

Malaria is responsible for more deaths around the world than any other parasitic disease. Due to the emergence of strains that are resistant to the current chemotherapeutic antimalarial arsenal, the search for new antimalarial drugs remains urgent though hampered by a lack of knowledge regarding the molecular mechanisms of artemisinin resistance. Semisynthetic compounds derived from diterpenes from the medicinal plant Wedelia paludosa were tested in silico against the Plasmodium falciparum Ca2+-ATPase, PfATP6. This protein was constructed by comparative modelling using the three-dimensional structure of a homologous protein, 1IWO, as a scaffold. Compound 21 showed the best docking scores, indicating a better interaction with PfATP6 than that of thapsigargin, the natural inhibitor. Inhibition of PfATP6 by diterpene compounds could promote a change in calcium homeostasis, leading to parasite death. These data suggest PfATP6 as a potential target for the antimalarial ent-kaurane diterpenes.

Quimioterapia antimalárica experimental e mecanismos de ação de antimaláricos envolvendo íons cálcio e prótons / Experimental chemotherapy and antimalarial mechanisms of action of antimalarial drugs involving calcium ions and protons

Limitações atuais do arsenal terapêutico na malária humana exigem a busca de novos medicamentos. Além da grande importância econômica e social da malária e da resistência do P. falciparum a cloroquina e outros derivados quinolínicos, as associações medicamentosas compostas por artemisinina e seus derivados apresentam custos de produção elevados, dificultando seu emprego em regiões em desenvolvimento, especialmente no continente africano. Nesse trabalho testamos a atividade antimalárica de: (i) associações dos antimaláricos artesunato (AS) e mefloquina (MQ) com ciprofloxacina, uma fluoroquinolona sintética empregada contra infecções bacterianas; (ii) moléculas obtidas por síntese química, como anti-retrovrais, endoperóxidos, e uma nova molécula híbrida denominada MEFAS e (iii) extratos e compostos purificados de plantas medicinais como falsas quinas e Holostylis reniformis, utilizadas popularmente no tratamento de quadros febris e dispepsias. Os testes esquizonticidas foram feitos em cultivos contínuos de P. falciparum avaliando-se o crescimento das fases intraeritrocitárias através de duas metodologias (teste tradicional ou o ensaio de incorporação de hipoxantina tritiada); e utilizando camundongos inoculados com P. berghei. Estabelecemos ainda um protocolo com sondas fluorescentes que permitiu trabalhar com trofozoítos de P. falciparum viáveis em eritrócitos infectados e acompanhar, em tempo real, ações de potenciais antimaláricos sobre a homeostasia iônica dos parasitos, identificando possíveis alvos intracelulares dos mesmos.