Inhibition of Tyrosinase by 4H-Chromene Analogues: Synthesis, Kinetic Studies and Computational Analysis

Inhibition of mushroom tyrosinase was observed with synthetic dihydropyrano[3,2-b]chromenediones. Among them, DHPC04 displayed the most potent tyrosinase inhibitory activity with a Ki value of 4μM, comparable to the reference standard inhibitor kojic acid. A kinetic study suggested that these synthetic heterocyclic compounds behave as competitive inhibitors for the L-DOPA binding site of the enzyme. Furthermore, molecular modeling provided important insight into the mechanism of binding interactions with the tyrosinase copper active site

Alterações hematológicas, bioquímicas e histopatológicas no modelo de malária aviária Gallus gallus por Plasmodium gallinaceum: papel do óxido nítrico

Malária é uma das doenças infecciosas de maior causa de morte no mundo. Modelos experimentais são necessários para melhor compreensão de mecanismos envolvidos na patogênese de doenças e desenvolvimento de novos tratamentos. Galinhas infectadas com Plasmodium gallinaceum fornecem bom modelo de malária devido a proximidade filogenética com o Plasmodium de humano assim como aspectos clínicos comuns, como a malária cerebral. O presente estudo objetivou investigar a participação do óxido nítrico no desenvolvimento da malária aviária, através do tratamento ou não com aminoguanidina (AG - inibidor da enzima Óxido Nítrico Sintase) in vivo de galinhas infectadas experimentalmente com P. gallinaceum. Foi verificado sobrevida, hematologia clássica, bioquímica sérica e patologia nos animais no percurso da infecção. Observou-se maior sobrevida nos animais tratados com AG, apesar de parasitemias mais elevadas. Houve ainda diminuição nos parâmetros hematológicos e aumento no Volume Corpuscular Médio de hemácias, indicando resposta medular para anemia. Linfopenia e trombocitopenia foram detectadas em animais infectados, com menor proporção nos animais tratados. Monócitos, linfócitos e heterófilos apresentaram aumento de tamanho e alterações que indicam ativação. Trombócitos também aumentaram de tamanho durante a infecção e apresentaram morfologia atípica. Os animais tratados mostraram lesões mais brandas nas secções histopatológicas de cérebro, fígado e baço, além de produção diminuída de NO, mesmo em alta parasitemia, em relação aos animais não tratados. Esses resultados confirmam a participação do mediador químico óxido nítrico na patogênese da malária no modelo experimental aviário.ABSTRACT: Malaria causes major losses to human populations in the world. Experimental models are needed for a better understanding of the pathological mechanisms of the diseases and the development of new treatments. Chickens infected with Plasmodium gallinaceum constitute an adequate malaria model due to the phylogenetic proximity of this parasite to human Plasmodium as well as similarities in disease manifestation, as cerebral malaria. The aim of the present study was to investigate the role of nitric oxide in avian malaria development in chickens experimentally infected with P. gallinaceum, treated or not with aminoguanidine (AG - nitric oxide synthase inhibitor). Survival, classical hematology, serum biochemistry and pathology was assayed during the development of the disease. The greatest survival was observed in animals treated with AG that also presented higher parasitemia. Decrease in hematological parameters and Mean Corspucular Volume of erythrocytes increase was showed, indicating bone marrow response to anemia. Lymphopenia and thrombocytopenia were detected in infected animals, but not at the same proportion in treated animals. Monocytes, lymphocytes and heterophils showed an increase in size and changes that indicated activation. Thrombocytes were also higher with the infection and with atypical morphology. Treated animals showed fewer lesions in histological sections of brain, liver and spleen, and NO production decreased, principally during high parasitemia, compared to untreated animals. These results characterize the participation of the chemistry mediator nitric oxide in the pathogenesis of malaria in the avian model

Methylmercury inhibits prolactin release in a cell line of pituitary origin

Heavy metals, such as methylmercury, are key environmental pollutants that easily reach human beings by bioaccumulation through the food chain. Several reports have demonstrated that endocrine organs, and especially the pituitary gland, are potential targets for mercury accumulation; however, the effects on the regulation of hormonal release are unclear. It has been suggested that serum prolactin could represent a biomarker of heavy metal exposure. The aim of this study was to evaluate the effect of methylmercury on prolactin release and the role of the nitrergic system using prolactin secretory cells (the mammosomatotroph cell line, GH3B6). Exposure to methylmercury (0-100 μM) was cytotoxic in a time- and concentration-dependent manner, with an LC50 higher than described for cells of neuronal origin, suggesting GH3B6 cells have a relative resistance. Methylmercury (at exposures as low as 1 μM for 2 h) also decreased prolactin release. Interestingly, inhibition of nitric oxide synthase by N-nitro-L-arginine completely prevented the decrease in prolactin release without acute neurotoxic effects of methylmercury. These data indicate that the decrease in prolactin production occurs via activation of the nitrergic system and is an early effect of methylmercury in cells of pituitary origin.MAUÉS, L. A. L. Dr. Docente da Universidade Federal do Pará, Campus Universitário de AltamiraMACCHI, B. de M. Dr. Docente da Universidade Federal do Pará, Instituto de Ciências BiológicasCRESPO LÓPEZ, M. E. Dr. Docente da Universidade Federal do Pará, Insituto de Ciências Biológica

Fatty Acid Amides Synthesized from Andiroba Oil (Carapa guianensis Aublet.) Exhibit Anticonvulsant Action with Modulation on GABA-A Receptor in Mice: A Putative Therapeutic Option

Epilepsy is a chronic neurological disease characterized by excessive neuronal activity leading to seizure; about 30% of affected patients suffer from the refractory and pharmacoresistant form of the disease. The anticonvulsant drugs currently used for seizure control are associated with adverse reactions, making it important to search for more effective drugs with fewer adverse reactions. There is increasing evidence that endocannabinoids can pharmacologically modulate action against seizure and antiepileptic disorders. Therefore, the objective of this study is to investigate the anticonvulsant effects of fatty acid amides (FAAs) in a pentylenetetrazole (PTZ)-induced seizure model in mice. FAAs (FAA1 and FAA2) are obtained from Carapa guianensis oil by biocatalysis and are characterized by Fourier Transform Infrared Analysis (FT-IR) and Gas Chromatography-Mass Spectrometry (GC-MS). Only FAA1 is effective in controlling the increased latency time of the first myoclonic jerk and in significantly decreasing the total duration of tonic-clonic seizures relative to the pentylenetetrazol model. Also, electrocortical alterations produced by pentylenetetrazol are reduced when treated by FAA1 that subsequently decreased wave amplitude and energy in Beta rhythm. The anticonvulsant effects of FAA1 are reversed by flumazenil, a benzodiazepine antagonist on Gamma-Aminobutyric Acid-A (GABA-A) receptors, indicating a mode of action via the benzodiazepine site of these receptors. To conclude, the FAA obtained from C. guianensis oil is promising against PTZ-induced seizures

Revisiting Astrocytic Roles in Methylmercury Intoxication

Intoxication by heavy metals such as methylmercury (MeHg) is recognized as a global health problem, with strong implications in central nervous system pathologies. Most of these neuropathological conditions involve vascular, neurotransmitter recycling, and oxidative balance disruption leading to accelerated decline in fine balance, and learning, memory, and visual processes as main outcomes. Besides neurons, astrocytes are involved in virtually all the brain processes and perform important roles in neurological response following injuries. Due to astrocytes’ strategic functions in brain homeostasis, these cells became the subject of several studies on MeHg intoxication. The most heterogenous glial cells, astrocytes, are composed of plenty of receptors and transporters to dialogue with neurons and other cells and to monitor extracellular environment responding tightly through fluctuation of cytosolic ions. The overall toxicity of MeHg might be determined on the basis of the balance between MeHg-mediated injury to neurons and protective responses from astrocytes. Although the role of neurons in MeHg intoxication is relatively well-established, the role of the astrocytes is only beginning to be understood. In this review, we update the information on astroglial modulation of the MeHg-induced neurotoxicity, providing remarks on their protective and deleterious roles and insights for future studies.This research was funded by Conselho Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq, grant numbers 27724/2018–2 and 307564/2017–7), Ministerio de Ciencia e Innovación (MCINN, grant number PID2019-106285RB-C22) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES, grant numbers 88887.200500/2018–00)

Morphine Protects against Methylmercury Intoxication: A Role for Opioid Receptors in Oxidative Stress?

<div><p>Mercury is an extremely dangerous environmental contaminant responsible for episodes of human intoxication throughout the world. Methylmercury, the most toxic compound of this metal, mainly targets the central nervous system, accumulating preferentially in cells of glial origin and causing oxidative stress. Despite studies demonstrating the current exposure of human populations, the consequences of mercury intoxication and concomitant use of drugs targeting the central nervous system (especially drugs used in long-term treatments, such as analgesics) are completely unknown. Morphine is a major option for pain management; its global consumption more than quadrupled in the last decade. Controversially, morphine has been proposed to function in oxidative stress independent of the activation of the opioid receptors. In this work, a therapeutic concentration of morphine partially protected the cellular viability of cells from a C6 glioma cell line exposed to methylmercury. Morphine treatment also reduced lipid peroxidation and totally prevented increases in nitrite levels in those cells. A mechanistic study revealed no alteration in sulfhydryl groups or direct scavenging at this opioid concentration. Interestingly, the opioid antagonist naloxone completely eliminated the protective effect of morphine against methylmercury intoxication, pointing to opioid receptors as the major contributor to this action. Taken together, the experiments in the current study provide the first demonstration that a therapeutic concentration of morphine is able to reduce methylmercury-induced oxidative damage and cell death by activating the opioid receptors. Thus, these receptors may be a promising pharmacological target for modulating the deleterious effects of mercury intoxication. Although additional studies are necessary, our results support the clinical safety of using this opioid in methylmercury-intoxicated patients, suggesting that normal analgesic doses could confer an additional degree of protection against the cytotoxicity of this xenobiotic.</p></div

Microenvironment of Mycobacterium smegmatis Culture to Induce Cholesterol Consumption Does Cell Wall Remodeling and Enables the Formation of Granuloma-Like Structures

Pathogenic species of mycobacteria are known to use the host cholesterol during lung infection as an alternative source of carbon and energy. Mycobacteria culture in minimal medium (MM) has been used as an in vitro experimental model to study the consumption of exogenous cholesterol. Once in MM, different species of mycobacteria start to consume the cholesterol and initiate transcriptional and metabolic adaptations, upregulating the enzymes of the methylcitrate cycle (MCC) and accumulating a variety of primary metabolites that are known to be important substrates for cell wall biosynthesis. We hypothesized that stressful pressure of cultures in MM is able to induce critical adaptation for the bacteria which win the infection. To identify important modifications in the biosynthesis of the cell wall, we cultured the fast-growing and nonpathogenic Mycobacterium smegmatis in MM supplemented with or without glycerol and/or cholesterol. Different from the culture in complete medium Middlebrook 7H9 broth, the bacteria when cultured in MM decreased growth and changed in the accumulation of cell wall molecules. However, the supplementation of MM with glycerol and/or cholesterol recovered the accumulation of phosphatidylinositol mannosides (PIMs) and other phospholipids but maintained growth deceleration. The biosynthesis of lipomannan (LM) and of lipoarabinomannan (LAM) was significantly modulated after culture in MM, independently of glycerol and/or cholesterol supplementation, where LM size was decreased (LM13-25KDa) and LAM increased (LAM37-100KDa), when compared these molecules after bacteria culture in complete medium (LM17-25KDa and LAM37-50KDa). These changes modified the cell surface hydrophobicity and susceptibility against H2O2. The infection of J774 macrophages with M. smegmatis, after culture in MM, induced the formation of granuloma-like structures, while supplementation with cholesterol induced the highest rate of formation of these structures. Taken together, our results identify critical changes in mycobacterial cell wall molecules after culture in MM that induces cholesterol accumulation, helping the mycobacteria to increase their capacity to form granuloma-like structures

Lipid peroxidation in C6 cells incubated with 1 µM morphine and/or 6 µM methylmercury (MeHg) for 24 h.

<p>Data are reported as mean ± standard deviation (n = 3). *P<0.05 versus control group; #P<0.05 versus control and MeHg groups.</p

Direct scavenging activity of increasing concentrations of morphine against free radicals.

<p>Morphine was incubated with a 1,1diphenyl-2-picrylhydrazyl solution; results are shown as mean ± standard deviation (n = 9). *P<0.01 versus control group. ^#P<0.01 versus all groups.</p

Viability of C6 cells exposed to increasing concentrations of methylmercury (MeHg) for 24 h.

<p>Data are expressed as mean ± standard deviation (n = 4). *P<0.01 versus all groups.</p