Papel de receptores Toll-like tipo 4 e polimorfismos ASP299GLY e THR399ILE na patogênese da mucosite intestinal induzida pelo quimioterápico irinotecano

Abstract

Colorectal cancer (CRC) is a disease with high incidence and mortality. Irinotecan is an anticancer drug used as first and second-line therapy for CRC. Conversely, irinotecan-associated side effects include intestinal mucositis and severe diarrhea, which affect approximately 20-40% of patients undergoing chemotherapy, reducing patients’ quality of life. The pathophysiology of mucositis is not completely known, the reason why no specific treatment is available. Then, the investigation of the underlying pathophysiological mechanisms can provide new disease biomarkers and/or novel therapeutic strategies. Previous studies report the involvement of the Toll-like receptor 4 (TLR4) in the regulation of intestinal homeostasis. However, the role of TLR4 in the pathogenesis of intestinal mucositis is still to be investigated. Objective: To evaluate the role of TLR4 and its receptor polymorphisms in the pathogenesis of experimental and clinical intestinal mucositis. Methods: C57BL/6 (WT, 20-25g) or TLR4 knockout mice (TLR4-/-) were injected with saline (5 ml/kg, i.p.) or irinotecan (45 mg/kg, i.p.) once daily/4 days for induction of intestinal mucositis. Animals were daily weighted and, on the seventh day post first dose of chemotherapy, diarrhea severity was assessed. The animals were killed and an ileum sample was harvested for myeloperoxidase assay and histopathological and morphometric analysis. In a clinical approach, the impact of TLR4 polymorphisms on mucositis development was verified through a genotyping cohort study in CRC patients. The study consisted on the analysis of single nucleotide polymorphisms (SNP) Asp299Gly (rs 4986790) and Thr399Ile (rs 4986791) for TLR4 in patients with CRC who underwent irinotecan-based chemotherapy. Data were analyzed with ANOVA / Bonferroni test or Kruskal Wallis / Dunn test. For genotyping, analyzes were performed through the Hardy-Weiberg equilibrium and logistic regression. Results: Irinotecan injection caused a significant body weight loss and increased diarrhea associated with neutrophil infiltration in the intestine, morphometric changes and destruction of the villi and crypts architecture in TLR4-/- mice versus WT animals, which showed no signs of intestinal injury. In addition, the genotyping study indicated that the Asp299Gly polymorphism was associated with the homozygous wild-type A/A genotype and with a decreased risk of CRC. However, there was no association of Asp299Gly or Thr399Ile polymorphism with diarrhea, abdominal pain and nausea. Conclusion: TLR4 is essential for the maintenance of intestinal homeostasis and to protect from irinotecan-related intestinal damage.