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1.
Free Radic Biol Med ; 115: 421-435, 2018 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-29248721

RESUMO

In this study, we report the ability of a set of eight 3-phenylcoumarin derivatives bearing 6,7- or 5,7-dihydroxyl groups, free or acetylated, bound to the benzopyrone moiety, to modulate the effector functions of human neutrophils. In general, (i) 6,7-disubstituted compounds (5, 6, 19, 20) downmodulated the Fcγ receptor-mediated neutrophil oxidative metabolism more strongly than 5,7-disubstituted compounds (21, 22, 23, 24), and (ii) hydroxylated compounds (5, 19, 21, 23) downmodulated this neutrophil function more effectively than their acetylated counterparts (6, 20, 22, 24, respectively). Compounds 5 (6,7-dihydroxy-3-[3',4'-methylenedioxyphenyl]-coumarin) and 19 (6,7-dihydroxy-3-[3',4'-dihydroxyphenyl]-coumarin) effectively downmodulated the neutrophil oxidative metabolism elicited via Fcγ and/or complement receptors. Compound 5 also downmodulated the immune complex-stimulated phagocytosis, degranulation of elastase, and production and release of neutrophil extracellular traps, as well as the human neutrophil chemotaxis towards n-formyl-methionyl-leucyl-phenylalanine, without altering the expression level of formyl peptide receptor type 1. Both compounds 5 and 19 did not impair the neutrophil capacity to recognize and kill Candida albicans. Docking calculations revealed that compounds 5 and 19 directly interacted with three catalytic residues - Gln-91, His-95, and Arg-239 - inside the myeloperoxidase active site. Together, these findings indicate that (i) inhibition of reactive oxygen species generation and degranulation of elastase are closely associated with downmodulation of release of neutrophil extracellular traps; and (ii) compound 5 can be a prototype for the development of novel immunomodulating drugs to treat immune complex-mediated inflammatory diseases.


Assuntos
Anti-Inflamatórios/farmacologia , Cumarínicos/farmacologia , Armadilhas Extracelulares/metabolismo , Neutrófilos/fisiologia , Elastase Pancreática/metabolismo , Receptores de Complemento/metabolismo , Receptores de IgG/metabolismo , Anti-Inflamatórios/química , Células Cultivadas , Cumarínicos/química , Humanos , Imunomodulação , Oxirredução , Estresse Oxidativo/efeitos dos fármacos , Peroxidase/metabolismo , Fagocitose , Espécies Reativas de Oxigênio/metabolismo
2.
J Phys Condens Matter ; 29(50): 504002, 2017 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-29125472

RESUMO

Biological membranes are continuously remodeled in the cell by specific membrane-shaping machineries to form, for example, tubes and vesicles. We examine fundamental mechanisms involved in the vesiculation processes induced by a cluster of envelope (E) and membrane (M) proteins of the dengue virus (DENV) using molecular dynamics simulations and a coarse-grained model. We show that an arrangement of three E-M heterotetramers (EM3) works as a bending unit and an ordered cluster of five such units generates a closed vesicle, reminiscent of the virus budding process. In silico mutagenesis of two charged residues of the anchor helices of the envelope proteins of DENV shows that Arg-471 and Arg-60 are fundamental to produce bending stress on the membrane. The fine-tuning between the size of the EM3 unit and its specific bending action suggests this protein unit is an important factor in determining the viral particle size.


Assuntos
Membrana Celular/química , Vírus da Dengue/química , Simulação de Dinâmica Molecular , Proteínas do Envelope Viral/química , Estrutura Secundária de Proteína
3.
J Pharm Pharmacol ; 69(12): 1829-1845, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28994118

RESUMO

OBJECTIVES: To examine whether the hydroalcoholic extract from Baccharis dracunculifolia leaves (BdE) modulates the human neutrophil oxidative metabolism, degranulation, phagocytosis and microbial killing capacity. METHODS: In-vitro assays based on chemiluminescence, spectrophotometry, flow cytometry and polarimetry were used, as well as docking calculations. KEY FINDINGS: At concentrations that effectively suppressed the neutrophil oxidative metabolism elicited by soluble and particulate stimuli (<10 µg/ml), without clear signs of cytotoxicity, BdE (1) inhibited NADPH oxidase and myeloperoxidase activity; (2) scavenged H2 O2 and HOCl; (3) weakly inhibited phagocytosis; and (4) did not affect neutrophil degranulation and microbial killing capacity, the expression levels of TLR2, TLR4, FcγRIIa, FcγRIIIb and CR3 and the activity of elastase and lysozyme. Caffeic acid, one of the major B. dracunculifolia secondary metabolites, did not inhibit phagocytosis but interfered in the myeloperoxidase-H2 O2 -HOCl system by scavenging H2 O2 and HOCl, and interacting with the catalytic residues His-95, Arg-239 and Gln-91. CONCLUSIONS: BdE selectively modulates the effector functions of human neutrophils, inhibits the activity of key enzymes and scavenges physiological oxidant species. Caffeic acid contributes to lower the levels of oxidant species. Our findings help to unravel the mechanisms by which these natural products exert immunomodulatory action towards neutrophils.


Assuntos
Baccharis/química , Fatores Imunológicos/farmacologia , Neutrófilos/efeitos dos fármacos , Extratos Vegetais/farmacologia , Adulto , Ácidos Cafeicos/isolamento & purificação , Ácidos Cafeicos/farmacologia , Citometria de Fluxo , Sequestradores de Radicais Livres/isolamento & purificação , Sequestradores de Radicais Livres/farmacologia , Humanos , Fatores Imunológicos/isolamento & purificação , Luminescência , Neutrófilos/metabolismo , Fagocitose/efeitos dos fármacos , Folhas de Planta , Espectrofotometria
4.
PLoS One ; 9(11): e112351, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25383618

RESUMO

The Flaviviridae family includes several virus pathogens associated with human diseases worldwide. Within this family, Dengue virus is the most serious threat to public health, especially in tropical and sub-tropical regions of the world. Currently, there are no vaccines or specific antiviral drugs against Dengue virus or against most of the viruses of this family. Therefore, the development of vaccines and the discovery of therapeutic compounds against the medically most important flaviviruses remain a global public health priority. We previously showed that phospholipase A2 isolated from the venom of Crotalus durissus terrificus was able to inhibit Dengue virus and Yellow fever virus infection in Vero cells. Here, we present evidence that phospholipase A2 has a direct effect on Dengue virus particles, inducing a partial exposure of genomic RNA, which strongly suggests inhibition via the cleavage of glycerophospholipids at the virus lipid bilayer envelope. This cleavage might induce a disruption of the lipid bilayer that causes a destabilization of the E proteins on the virus surface, resulting in inactivation. We show by computational analysis that phospholipase A2 might gain access to the Dengue virus lipid bilayer through the pores found on each of the twenty 3-fold vertices of the E protein shell on the virus surface. In addition, phospholipase A2 is able to inactivate other enveloped viruses, highlighting its potential as a natural product lead for developing broad-spectrum antiviral drugs.


Assuntos
Antivirais/farmacologia , Venenos de Crotalídeos/enzimologia , Crotalus , Vírus da Dengue/efeitos dos fármacos , Vírus da Dengue/fisiologia , Fosfolipases A2/farmacologia , Inativação de Vírus/efeitos dos fármacos , Animais , Antivirais/isolamento & purificação , Antivirais/metabolismo , Chlorocebus aethiops , Bicamadas Lipídicas/metabolismo , Fosfolipases A2/isolamento & purificação , Fosfolipases A2/metabolismo , Células Vero , Vírion/efeitos dos fármacos , Vírion/fisiologia
5.
J Biol Inorg Chem ; 19(7): 1113-20, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24944024

RESUMO

Changes in the concentration of different ions modulate several cellular processes, such as Ca(2+) and Zn(2+) in inflammation. Upon activation of immune system effector cells, the intracellular Ca(2+) concentration rises propagating the activation signal, leading to degranulation and generation of reactive oxygen species, which increases the Zn(2+) intracellular concentration as a consequence of the cellular antioxidant machinery. In this context, S100A12 is of special interest because it is a pro-inflammatory protein expressed in neutrophils whose structure and function are modulated by both Ca(2+) and Zn(2+). The current hypothesis about its mechanism of action was built based on biochemical and crystallographic data. However, there are missing connections between molecular structure and the way in which many events are concatenated at the triggering and along the inflammatory process. In this work we use molecular dynamics simulations to describe how variations in Zn(2+) and Ca(2+) concentrations modulate the structural dynamics of the calcium-free S100A12 dimer and monomer, which was not considered a part of the mechanism of action before. Our results suggest that (i) Zn(2+) have a determinant role in the dimerization step, as well as in the unbinding of the Na(+) complexed to the N-terminal EF-hand; (ii) the N-terminal EF-hand domain is the first to bind Ca(2+), and not the C-terminal, as usually accepted; and that (iii) Ca(2+) modulates the structural dynamics of H-III.


Assuntos
Cálcio/metabolismo , Motivos EF Hand , Proteínas S100/química , Proteínas S100/metabolismo , Sódio/metabolismo , Zinco/metabolismo , Sítios de Ligação , Humanos , Simulação de Dinâmica Molecular , Concentração Osmolar , Conformação Proteica , Multimerização Proteica , Proteína S100A12
6.
Biochim Biophys Acta ; 1844(2): 384-8, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24513313

RESUMO

Super secondary structures of proteins have been systematically searched and classified, but not enough attention has been devoted to such large edifices beyond the basic identification of secondary structures. The objective of the present study is to show that the association of secondary structures that share some of their backbone residues is a commonplace in globular proteins, and that such deeper fusion of secondary structures, namely extended secondary structures (ESSs), helps stabilize the original secondary structures and the resulting tertiary structures. For statistical purposes, a set of 163 proteins from the protein databank was randomly selected and a few specific cases are structurally analyzed and characterized in more detail. The results point that about 30%of the residues from each protein, on average, participate in ESS. Alternatively, for the specific cases considered,our results were based on the secondary structures produced after extensive Molecular Dynamics simulation of a protein­aqueous solvent system. Based on the very small width of the time distribution of the root mean squared deviations, between the ESS taken along the simulation and the ESS from the mean structure of the protein, for each ESS, we conclude that the ESSs significantly increase the conformational stability by forming very stable aggregates.The ubiquity and specificity of the ESS suggest that the role they play in the structure of proteins, including the domains formation, deserves to be thoroughly investigated.


Assuntos
Estrutura Secundária de Proteína , Proteínas/química , Animais , Biologia Computacional , Histidina/fisiologia , Humanos , Modelos Moleculares , Multimerização Proteica , Estrutura Terciária de Proteína , Proteínas/metabolismo , Análise de Sequência de Proteína
7.
J Comput Aided Mol Des ; 26(12): 1311-25, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-23160852

RESUMO

The Dengue has become a global public health threat, with over 100 million infections annually; to date there is no specific vaccine or any antiviral drug. The structures of the envelope (E) proteins of the four known serotype of the dengue virus (DENV) are already known, but there are insufficient molecular details of their structural behavior in solution in the distinct environmental conditions in which the DENVs are submitted, from the digestive tract of the mosquito up to its replication inside the host cell. Such detailed knowledge becomes important because of the multifunctional character of the E protein: it mediates the early events in cell entry, via receptor endocytosis and, as a class II protein, participates determinately in the process of membrane fusion. The proposed infection mechanism asserts that once in the endosome, at low pH, the E homodimers dissociate and insert into the endosomal lipid membrane, after an extensive conformational change, mainly on the relative arrangement of its three domains. In this work we employ all-atom explicit solvent Molecular Dynamics simulations to specify the thermodynamic conditions in that the E proteins are induced to experience extensive structural changes, such as during the process of reducing pH. We study the structural behavior of the E protein monomer at acid pH solution of distinct ionic strength. Extensive simulations are carried out with all the histidine residues in its full protonated form at four distinct ionic strengths. The results are analyzed in detail from structural and energetic perspectives, and the virtual protein movements are described by means of the principal component analyses. As the main result, we found that at acid pH and physiological ionic strength, the E protein suffers a major structural change; for lower or higher ionic strengths, the crystal structure is essentially maintained along of all extensive simulations. On the other hand, at basic pH, when all histidine residues are in the unprotonated form, the protein structure is very stable for ionic strengths ranging from 0 to 225 mM. Therefore, our findings support the hypothesis that the histidines constitute the hot points that induce configurational changes of E protein in acid pH, and give extra motivation to the development of new ideas for antivirus compound design.


Assuntos
Vírus da Dengue/química , Dengue/metabolismo , Fusão de Membrana/fisiologia , Simulação de Dinâmica Molecular , Proteínas do Envelope Viral/química , Ligação de Hidrogênio , Concentração Osmolar , Conformação Proteica , Termodinâmica
8.
Biophys J ; 87(3): 1567-77, 2004 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-15345537

RESUMO

A new and efficient Monte Carlo algorithm for sampling protein configurations in the continuous space is presented; the efficiency of this algorithm, named Local Moves for Proteins (LMProt), was compared to other alternative algorithms. For this purpose, we used an intrachain interaction energy function that is proportional to the root mean square deviation (rmsd) with respect to alpha-carbons from native structures of real proteins. For phantom chains, the LMProt method is approximately 10(4) and 20 times faster than the algorithms Thrashing (no local moves) and Sevenfold Way (local moves), respectively. Additionally, the LMProt was tested for real chains (excluded-volume all-atoms model); proteins 5NLL (138 residues) and 1BFF (129 residues) were used to determine the folding success xi as a function of the number eta of residues involved in the chain movements, and as a function of the maximum amplitude of atomic displacement delta r(max). Our results indicate that multiple local moves associated with relative chain flexibility, controlled by appropriate adjustments for eta and delta r(max), are essential for configurational search efficiency.


Assuntos
Conformação Proteica , Proteínas/química , Algoritmos , Modelos Estatísticos , Método de Monte Carlo , Distribuição Normal , Software
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