TLR4 mediates Il-6 production in irinotecan induced mucositis

IntroductionIrinotecan is a first line chemotherapeutic agent for colorectal carcinoma and well known for debilitating diarrhoea caused by mucositis. Tlr4, a pattern recognition receptor, has been implicated in irinotecan -induced mucositis due to its activation of downstream inflammatory pathways and interaction with luminal microbes. Tlr4 deletion has been reported to attenuate mucosal injury in preclinical models of mucositis, hypothesised to occur by blockade of Il-6 production. As such, the current study aimed to determine the relationship between Tlr4 and Il-6 in the context of irinotecan induced mucositis.\n\nMaterials and methodsArchived ileum and colon tissues from BALB/c wild type (WT) and Tlr4 -/-billy (Tlr4 KO) female mice were used throughout the study. Mice had received single dose of irinotecan (i.p. 270 mg/kg) or vehicle and sacrificed at 6 and 72 hours. Il-6 mRNA and protein expression was determined by qPCR and immunofluorescence, respectively. Data was analysed by Kruskal-Wallis test (qPCR delta CT values) and one-way analysis of variance (ANOVA) (immunofluorescence % area stained).\n\nResultsIl-6 protein expression was significantly reduced in Tlr4 KO mice as compared to WT mice at 6 h in ileum and colon. mRNA expression was not significantly different between groups.\n\nConclusionThese findings support the hypothesis that Tlr4 deletion protects from irinotecan-induced mucositis by ameliorating Il-6 production. The effect appears to be post-transcriptionally mediated, although further research is required to determine if it is via a direct or indirect mechanism. In the future, Il-6 may be targeted therapeutically to ameliorate symptoms of mucositis.