Removal and killing of multispecies endodontic biofilms by N-acetylcysteine

Removal of bacterial biofilm from the root canal system is essential for the management of endodontic disease. Here we evaluated the antibacterial effect of N-acetylcysteine (NAC), a potent antioxidant and mucolytic agent, against mature multispecies endodontic biofilms consisting of Actinomyces naeslundii, Lactobacillus salivarius, Streptococcus mutans and Enterococcus faecalis on sterile human dentin blocks. The biofilms were exposed to NAC (25, 50 and 100 mg/mL), saturated calcium hydroxide or 2% chlorhexidine solution for 7 days, then examined by scanning electron microscopy. The biofilm viability was measured by viable cell counts and ATP-bioluminescence assay. NAC showed greater efficacy in biofilm cell removal and killing than the other root canal medicaments. Furthermore, 100 mg/mL NAC disrupted the mature multispecies endodontic biofilms completely. These results demonstrate the potential use of NAC in root canal treatment.(AU)

OTIMIZAÇÃO DO PERFIL DE SEGURANÇA DA NIMESULIDA ATRAVÉS DA ASSOCIAÇÃO COM HEPATOPROTETOR

Autor: Amanda Godoi Elias Orientador: Luciana Grazziotin Rossato Grando Passo Fundo, 30 de Setembro de 2019 Os antiinflamatórios juntamente com os antibióticos são as causas mais frequentes de lesões hepáticas induzidas por drogas. A nimesulida é um potente antiinflamatório, muito utilizado por ter seus efeitos rápidos e duradouros, porém é um medicamento que tem alto risco de hepatotoxicidade. Diante deste contexto, o objetivo deste trabalho foi avaliar os efeitos de hepatoprotetores sobre os mecanismos hepatotóxicos induzidos pela nimesulida visando propor uma formulação mais segura. Inicialmente, fizemos um estudo in vitro através do modelo de cultura celular HepG2 para testar três possíveis hepatoprotetores: N-acetilcisteína, o Ginkgo biloba e a L-carnitina. Neste estudo constatamos que tanto N-acetelcisteína como o Gingko biloba tem bom potencial para antagonizar a citotoxicidade induzida pela nimesulida. Diante disso, selecionamos a N-acetilcisteína devido ao seu potencial antioxidante e maior experiência clínica em seu uso como antídoto de intoxicações hepatotóxicas. O estudo in vivo foi realizado utilizando 24 ratos Wistar machos como modelo animal. Os animais foram divididos em 4 grupos (6 animais por grupo): Controle que receberam solução salina; nimesulida 100mg/kg/dia de nimesulida; nimesulida e N-acetilcisteína 100mg/kg/dia de cada e Nacetilcisteína 100mg/kg/dia de N-acetilcisteína. Os tratamentos foram administrados por via oral (gavagem), durante o estudo dois animais do grupo que recebeu somente nimesulida morreram, após apresentar um emagrecimento progressivo. Com relação ao peso relativo dos animais, os que receberam nimesulida somente, apresentaram um menor ganho de peso com relação aos controles (p<0.0001) e a associação de nimesulida com N-acetilcisteína apresentou um ganho de peso significativamente maior quando comparado ao grupo que recebeu somente a nimesulida (p<0.05). Nas análises de histopatologia dos fígados, o grupo que recebeu somente nimesulida apresentou muitas lesões de degeneração e necrose, enquanto que no grupo que recebeu associação de nimesulida e N-acetilcisteína essas lesões foram de menor intensidade. Não houve alterações significativas em nenhum dos grupos com relação aos biomarcadores sanguíneos de lesão hepática e nem ocorrência de stress oxidativo nos fígados. Neste trabalho, pela primeira vez os efeitos da N-acetilcisteína como hepatoprotetor na lesão hepática induzida pela nimesulida foi demonstrado. Apesar dos excelentes resultados deste hepatoprotetor como antídoto em outras intoxicações, há uma proteção parcial na associação da nimesulida com Nacetilcisteína.

Author: Amanda Godoi Elias Advisor: Luciana Grazziotin Rossato Grando Passo Fundo, 30 de Setembro de 2019 Anti-inflamatory drugs, together with antibiotics, are the most relevant cause of druginduced hepatotoxicity. Nimesulide is a potent anti-inflammatory, which presents rapid and last-longing effects and also a high risk of hepatotoxicity. Thus, the aim of this work was to enhance nimesulide safety profile through the association with an hepatoprotector. First, we performed an in vitro study using HepG2 cell line model to test 3 possible hepatoprotectors: Nacetylcisteine, Gingko biloba, and L-carnitine. N-acetylcysteine and G. biloba show promisor results, then we selected N-acetylcysteine due to its board antioxidant effect and clinical experience as an antidote of hepatotoxicity. In vivo study was performed using 24 male Wistar rats, divided in 4 groups (6 animals/group): Control (receiving saline solution), Nimesulide 100mg/kg/day, Nimesulide 100mg/kg/day + N-acetylcysteine 100mg/kg/day, and Nacetylcysteyne 100mg/kg/day alone. Treatments were given through gavage, daily, for 15 days. During the study, 2 rats treated with nimesulide died after present a progressive weight-loss. Animals treated with nimesulide alone present lower body weight gain compared to control (p<0.0001and the association of nimesulide and N-acetylcysteine group presents higher body weight gain compared to nimesulide alone (p<0.05). Liver histology revealed hepatic lesions with degeneration and necrosis in animals receiving nimesulide. Rats treated with the association of nimesulide+N-acetylcysteine present hepatic lesions less pronounced. Liver, heart and spleen of animals treated with nimesulide show higher relative mass when compared to control. This change is reverted by the association with nimesulide only in hearts. It was not observed significant differences between groups in biochemical biomarkers or oxidative stress parameters. To the best our knowledge, we show for the first time the protection elicited by Nacetylcysteine against nimesulide-induced hepatotoxicity. Despite excellent effects of Nacetylcysteine used as antidote in other drug-induced hepatotoxicity, the protection obtained here is only partial.

Farnesol in combination with N-acetylcysteine against Staphylococcus epidermidis planktonic and biofilm cells

Staphylococcus epidermidis is the most frequent cause of nosocomial sepsis and catheter-related infections, in which biofilm formation is considered to be the main virulence mechanism. In biofilm environment, microbes exhibit enhanced resistance to antimicrobial agents. This fact boosted the search of possible alternatives to antibiotics. Farnesol and N-acetylcysteine (NAC) are non-antibiotic drugs that have demonstrated antibacterial properties. In this study, the effect of farnesol and NAC isolated or in combination (farnesol+NAC) was evaluated. NAC at 10 × MIC caused a total cell death in planktonic cells. On the other hand, S. epidermidis biofilms exhibited 4 log reduction in viable cell number after a 24h treatment with NAC at the former concentration. Our results demonstrated that there was a higher CFU log reduction of S. epidermidis planktonic cells when farnesol was combined with NAC at 1 × MIC relatively to each agent alone. However, these results were not relevant because NAC alone at 10 × MIC was always the condition which gave the best results, having a very high killing effect on planktonic cells and a significant bactericidal effect on biofilm cells. This study demonstrated that no synergy was observed between farnesol and NAC. However, the pronounced antibacterial effect of NAC against S. epidermidis, on both lifestyles, indicates the use of NAC as a potential therapeutic agent in alternative to antibiotics.