Role of the route of leukotrienes in an experimental model of oral mucositis induced by 5-fluorouracil

4-Experimental Surgery Role of the route of leukotrienes in an experimental model of oral mucositis induced by 5-fluorouracil1 Viviane Carvalho da SilvaI, Renata Ferreira de Carvalho LeitãoII, Gerly Anne de Castro BritoII, Conceição da Silva MartinsII, Gildenio Estevam FreireIII, Karoline Saboia AragãoIV, Carlos Wagner de Souza WanderleyV, Marcos Rabelo de FreitasVI Fellow PhD degree, Postgraduate Program in Medical and Surgical Sciences, Department of Surgery, School of Medicine, Universidade Federal do Ceará (UFCE), Fortaleza-CE, Brazil. Conception and design of the study, acquisition and interpretation of data, statistics analysis, manuscript preparation, final approval. II PhD, Postgraduate Program in Morphofunctional Sciences, Department of Morphology, School of Medicine, UFCE, Fortaleza-CE, Brazil. Acquisition and interpretation of data, histopathological examinations, manuscript preparation. III Fellow Master degree, Postgraduate Program in Morphofunctional Sciences, Department of Morphology, School of Medicine, UFCE, Fortaleza-CE, Brazil. Acquisition and interpretation of data, manuscript preparation. IV PhD, Laboratory of Inflammation and Cancer Pharmacology (LAFICA), UFCE, Fortaleza-CE, Brazil. Conception and design of the study, acquisition and interpretation of data, manuscript preparation. V Fellow PhD degree, LAFICA, UFCE, Fortaleza-CE, Brazil. Acquisition and interpretation of data, manuscript preparation. VI PhD, Postgraduate Program in Medical and Surgical Sciences, Department of Surgery, Faculty of Medicine, UFCE, Fortaleza-CE, Brazil. Conception and design of the study, interpretation of data, manuscript preparation, final approval. I Abstract Purpose: To investigate the participation of cysteinyl leukotrienes in the pathophysiology of oral mucositis. Methods: Oral mucositis was induced in hamsters using 5-fluorouracil (5-FU; 60 and 40 mg/ kg; i.p., on days 1 and 2, respectively, and with excoriations in jugal mucosa on day 4). Montelukast (10, 20, or 40 mg/kg/d; gavage), MK886 (3 mg/kg/d, i.p.), or saline or celecoxib (7.5 mg/kg/d; i.p.) was administered 1 h prior to 5-FU and daily, until the fourth (MK886) or tenth day, when the animals were euthanized and their jugal mucosa was collected for macroscopic, histopathological, and immunohistochemical evaluation. Results: Neither montelukast nor MK-886 prevented the oral mucositis induced by 5-FU, as observed by histopathological evaluation. In addition, we did not find significant differences in the expression of inducible nitric oxide synthase-2, cyclooxygenase-2, or interleukin (IL)-1β between the experimental and control groups. However, we did observe a significant decrease in tumor necrosis factor (TNF)-α expression for all doses of montelukast; we also observed a significant decrease in IL-10 with 40 mg/kg/d and MK 886. Conclusions: Cysteinyl leukotrienes do not play an important role in experimental oral mucositis induced by 5-FU. There is a modulating action specifically on TNF-α. Key words: Leukotrienes. Arachidonate 5-Lipoxygenase. Stomatitis. Fluorouracil. Cricetinae. DOI: http://dx.doi.org/10.1590/s0102-865020170090000004 712 Acta Cir. Bras. 2017;32(9):712-725 Acta Cir Bras. 2017;32(9):712-725 ■■ Role of the route of leukotrienes in an experimental model of oral mucositis induced by 5-fluorouracil Silva VC et al. Introduction leukotrienes receptor) and MK-886 (5-LOX inhibitor), while evaluating inflammatory parameters such as cytokines. Oral mucositis (OM) is an important, dose-limiting side effect observed in patients undergoing radiotherapy (RT) and chemotherapy (CT)1,2. Proinflammatory cytokines are released in response to reactive oxygen species produced by CT-damaged cells; the pathogenesis of OM, however, is yet to be fully elucidated3. Cyclooxygenase (COX)-2 and 5-lipoxygenase (5-LOX) are key enzymes involved in the metabolism of arachidonic acid (AA); these enzymes lead to the formation of fatty acids known as eicosanoids4. The COX pathway helps mediate the inflammatory response; many chemotherapeutic drugs can directly activate this pathway at several sites, including the oral mucosa4. Despite the well-known relationship of the COX pathway with chemotherapy-induced OM4,5, we could not find any study investigating the role of leukotrienes (AA metabolites) in OM caused by antineoplastic agents. It has been proposed that the inhibition of one arm of the AA cascade may result in amplification of another arm, with potentially undesirable effects; for example, inhibition of the COX-2 pathway may lead to activation of 5-LOX and increased production of leukotrienes such as LTD46. Studies have identified leukotrienes as mediators in the inflammatory processes of the gastric and intestinal mucosa7-10. It is known that oral and gastrointestinal mucositis present similarities in their pathophysiology. Therefore, elucidating the pathophysiological mechanisms by which leukotrienes participate in inflammatory processes of the oral mucosa may lead to methods of prevention and control. The present study was performed to investigate the participation of cysteinyl leukotrienes (cysLT) in 5-FU induced OM pathophysiology, using montelukast (MTK), (blocker of the cysteinyl ■■ Methods All procedures involving animals were approved by Universidade Federal do Ceará, Committee on ethical treatment of research animals (protocol 0033/2012). Surgical procedures and animal treatments were conducted in accordance with the Guidelines for Institutional Animal Care, and were approved by our local ethics committee for experimental use on the animals. Eighty-four adult male golden hamsters weighing 100–150g were housed in temperature-controlled rooms and received water and food ad libitum. Drugs 5-FU (25 mg/mL; Fluoro-acil®, Roche, Rio de Janeiro, Brazil); MTK (Singulair®, Merck Sharp and Dohme, Hoddesdon, HRT, United Kingdom); MK 886 (MK-886 sodium salt hydrate- (M2692 SIGMA) >98% (HPLC) -Synonym: 3-[3-tert-Butylthio-1-(4chlorobenzyl)-5-isopropyl-1H-indol-2-yl]-2,2dimethylpropionic acid, sodium salt hydrate); celecoxib (Celebra®, capsules com 200 mg, Pfizer, São Paulo, Brazil); tribromoethanol 2,5% (25 mg/mL). Induction of experimental OM OM was induced using two intraperitoneal (i.p.) administrations of 5-FU on days 1 and 2 of the experiment (60 and 40 mg/ kg, respectively), according to an experimental OM model previously described11,12. On day 4, under anesthesia with 2.5% tribromoethanol (250 mg/kg, i.p.), the cheek pouch mucosa was irritated by superficial scratching, to potentiate OM. We performed this step by dragging the 713 Role of the route of leukotrienes in an experimental model of oral mucositis induced by 5-fluorouracil Silva VC et al. tip of an 18-gauge needle twice, in a linear manner, across the everted cheek pouch. The animals were killed on day 10 after the initial injection of 5-FU, under anesthesia with 2.5% tribromoethanol (250 mg/kg, i.p.). There were at least 5 animals in e (...truncated)