The gastroprotective effect of amifostine (ETHYOL®) on ethanol-induced gastric injury in rats: the role of non-protein sulfhydryl groups and afferent sensory nerves

Amifostine (WR-2721) has been widely tested as a cytoprotective agent against a number of aggressors in different organs. Recently, a gastroprotective effect was observed for this drug in a model of indomethacin-induced gastric injury (MOTA et al., 2007). OBJECTIVES: We investigated the effect of amifostine on ethanol-induced gastric injury and the role played by afferent sensory nerves, non-protein sulfhydryl groups, nitric oxide, ATP-sensitive potassium channels and cyclooxygenase-2 in the mechanism. METHODS: Wistar rats were treated with amifostine (22.5, 45, 90 or 180 mg/kg, p.o. or s.c.). Thirty minutes after amifostine administration, the animals were given 100% ethanol (5 ml/kg p.o.). Sixty minutes after ethanol administration the animals were euthanized. Macroscopic and histological studies were carried out and stomach fragments were retrieved and submitted to analysis for non-protein sulfhydryl groups and hemoglobin. Some animals were pretreated with L-NAME (10 mg/kg i.p.), glibenclamide (10 mg/kg p.o.), celecoxib (10 mg/kg p.o.) or saline solution. Thirty minutes after pretreatment the animals were given amifostine (90 mg/kg p.o. or s.c.) and, after another 30 minutes, 100% ethanol (5 ml/kg). The animals were euthanized 60 minutes later. Other rats were desensitized with capsaicin (125 mg/kg s.c.) 10-14 days before amifostine treatment. RESULTS: Amifostine treatment significantly reduced ethanol-induced macroscopic stomach injury at 45, 90 and 180 mg/kg p.o. and at 90 and 180 mg/kg s.c. The histological parameters (edema, hemorrhage and epithelial cell loss) were also reduced (p<0.05) when the animals were treated with amifostine. Animals receiving ethanol only presented reduced GSH levels in the stomach. Amifostine reverted this effect either by stimulating de novo GSH production or by preventing the consumption of GSH. Amifostine-promoted gastroprotection against ethanol-induced stomach injury was reversed by pretreatment with neurotoxic doses of capsaicin, but not by L-NAME, glibenclamide or celecoxib. CONCLUSIONS: Amifostine protects against ethanol-induced gastric injury by increasing GSH levels and stimulating the afferent sensory nerves in the stomach independently of ATP-sensitive potassium channels activation, nitric oxide synthase and cyclooxygenase-2 activity.A amifostina (WR-2721) tem sido largamente estudada como agente citoprotetor em diferentes órgãos e contra os mais diversos agressores do organismo humano. Recentemente, um efeito gastroprotetor deste fármaco foi observado em modelo de lesão gástrica induzida por indometacina (MOTA et al., 2007). OBJETIVOS: Este trabalho investigou o efeito da amifostina na lesão gástrica por etanol e o papel dos neurônios sensoriais aferentes, grupos sulfidrílicos não-protéicos, óxido nítrico, canais de potássio sensíveis ao ATP e ciclooxigenase-2 nesse processo. MÉTODOS: Ratos Wistar foram tratados com amifostina (22,5, 45, 90 ou 180 mg/kg, v.o. ou s.c.). Após 30 minutos, os animais receberam etanol absoluto (5 ml/kg v.o.). Decorridos 60 minutos da administração de etanol, os animais foram sacrificados. Foram realizados estudos macroscópicos e histológicos, bem como dosagem de grupos sulfidrílicos não-protéicos e de hemoglobina em fragmentos de estômago. Outros grupos foram pré-tratados com L-NAME (10 mg/kg i.p.), glibenclamida (10 mg/kg v.o.), celecoxibe (10 mg/kg v.o.) ou salina. Após 30 minutos os ratos receberam amifostina (90 mg/kg v.o. ou s.c.) e depois de mais 30 minutos etanol absoluto (5 ml/kg), com sacrifício ocorrendo 60 minutos depois. Um grupo de animais foi desensibilizado com capsaicina (125 mg/kg s.c.) entre 10 a 14 dias antes do protocolo de tratamento com amifostina. RESULTADOS: A amifostina preveniu de forma significativa o dano macroscópico causado por etanol no estômago nas doses de 45, 90 e 180 mg/kg quando administrada por via oral e 90 e 180 mg/kg quando utilizada por via subcutânea. Os parâmetros histológicos, edema, hemorragia e perda de células epiteliais, também foram reduzidos (p