The problems due to allergic diseases are currently a highlighted topic due to the increase of people who are showing symptoms and suffering the consequences of rapid changes in the habits of our society. Despite various therapies offered, allergic patients still suffer side effects from the use of anti-allergic drugs. Thus, the search for new alternatives that can alleviate the allergic symptoms becomes relevant. Natural substances have been the subject of intense research due to the pharmacological properties in the treatment of several diseases, including allergic ones. In this context, this work was focused on Vimang extract and its major component, the mangiferin (Mgf), which has shown several biological activities. Given that the biological activity of an extract can be enhanced by the synergism between its components, the synergistic effect of compounds isolated from Vimang such as mangiferin, quercetin, catechin, gallic acid and benzoic acid was evaluated. These components were combined and the mixtures tested for their ability to inhibit mast cell degranulation. The Vimang, quercetin and mangiferin inhibit mast cell degranulation while catechin, gallic acid and benzoic acid are not active and for that reason they were not included in the determination of the isobologram adopted in the synergism study. The isobologram of additivity shows synergism for the concentration of mangiferin equal to 5, 10, 20 and 40 μM and quercetin equal 0.2, 1 and 1.6 μM, and shows antagonism for mangiferin 80 μM and quercetin 0.4 and 0.8 μM. The low solubility of flavonoids in physiological medium led to the study of the interaction of Mgf with liposomes of L-α-dimyristoyl-phosphatidylcholine (DMPC) for application in biological assays. The interaction of Mgf with DMPC liposomes as well as the liposomal stability was evaluated considering the effects of pH, ionic strength and cholesterol presence. The pH influences the incorporation efficiency (IE) of mangiferin, which is higher in acidic pHs. In solutions of acidic or physiological pH, the liposome size increases in the presence of Mgf, which reinforces the hypothesis of interaction of Mgf with the lipid bilayer. The increased ionic strength in the absence of Mgf decreases the stability of the liposome. In the absence of salt, Mgf favors the formation of aggregates and decreases the stability of the liposomes. When in presence of salt, Mgf prevents the aggregation and stabilizes the liposomal aggregates. The IE of mangiferin in DMPC prepared by the ethanol injection method, at physiological pH, were around 13%. The attempt to optimize the IE was performed by the addition of cholesterol in different proportions lipid:cholesterol. An increase from 13% to 17% was observed for the proportion of DMPC:cholesterol (9:1). Free mangiferin inhibits mast cells degranulation in a dose-dependent manner, but the presence of liposomes prepared by the ethanol injection method does not significantly change this profile. The IE of mangiferin in liposomes of DMPC:cholesterol (9:1), prepared by ...
RESUMOObjetivo: Avaliar o efeito do dinitrato de isossorbida (DNI) sobre a hiperalgesia corneana e a infiltração de neutrófilos em um modelo experimental de ceratite superficial induzida pelo lipopolissacarídeo (LPS). Métodos: A hiperalgesia foi estudada através da indução de uma ceratite inflamatória em ratos (n = 60), pela exposição da córnea ao LPS (LPS +). Após a exposição, os olhos foram tratados durante quatro dias, com as soluções tópicas: DNI (200 mg, 65 mg e 20 mg), prednisolona 1% (PRED) ou Veículo. Olhos controles foram expostos apenas à solução salina (LPS -). Para avaliar a dor ocular, contouse o número de piscadas em 40 segundos, após instilação de uma gota de capsaicina 0,01 mM. A análise histopatológica foi realizada para avaliação da infiltração neutrofílica. Resultados: Foram observadas áreas esbranquiçadas no estroma corneano dos olhos com a ceratite induzida pelo LPS, entre os dias 3 e 15 dias. Esses olhos (LPS +) apresentaram um número significativamente maior de piscadas que os LPS -(P = 0,019) à estimulação química. O tratamento tópico com o DNI reduziu o número de piscadas observadas (P = 0,010). Da mesma forma, olhos expostos ao LPS e tratados com DNI demonstraram redução significativa na infiltração neutrofílica (P = 0,0031). Conclusão: Baixas doses de DNI reduziram a hiperalgesia corneana e a infiltração neutrofílica nesse modelo de ceratite. Dessa forma, doadores de óxido nítrico, como o DNI, poderão ser úteis no futuro ao tratamento clínico de diversas condições dolorosas da superfície ocular.Descritores: Dinitrato de isossorbida/uso terapêutico; Hiperalgesia/induzido quimicamente; Lipopolissacarídeos/ efeitos adversos ABSTRACT Purpose: To analyze effects of isosorbide dinitrate (DNI) on corneal hyperalgesia and neutrophil infiltration in an experimental model of superficial keratitis induced by lipopolysaccharide (LPS). Methods: Hyperalgesia was studied through the induction of inflammatory keratitis in rats (n=60), by corneal exposure to LPS. Following exposure, the inflamed eye was treated for four days, with one of the following solutions: topical DNI (200 µg, 65 µg and 20 µg), prednisolone 1% (PRED), and vehicle. Saline-exposed eyes (LPS -) underwent the same protocol. To evaluate ocular pain, the number of blinks in 40 seconds was counted, after one drop of 0.01 µM capsaicin. Histopathological analysis was performed with evaluation of neutrophil infiltration. Results: White clouding areas were observed in the corneal stroma of eyes with LPS-induced keratitis, between day 3 and day 15. Eyes exposed to LPS had a significantly higher number of blinks than LPS -(P=0.019). Topical treatment of LPS-induced keratitis eyes with DNI reduced capsaicin-induced blinks (P=0.010). Similarly, eyes exposed to LPS and treated with DNI also displayed reduced neutrophil infiltration (P=0.0031). Conclusion: Low doses of topical NO donors, like DNI, reduce corneal hyperalgesia and neutrophil infiltration in this keratitis model. NO donors may be useful in the clinical treatment of painful condition...
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