Irinotecan-Induced Gastrointestinal Dysfunction and Pain Are Mediated by Common TLR4-Dependent Mechanisms

Abstract

Strong epidemiological data indicate that chemotherapy-induced gut toxicity and pain occur in parallel, indicating common underlying mechanisms. We have recently outlined evidence suggesting that TLR4 signaling may contribute to both side effects. We therefore aimed to determine if genetic deletion of TLR4 improves chemotherapy-induced gut toxicity and pain. Forty-two female wild-type (WT) and 42 Tlr4 null (−/−) BALB/c mice weighing between 18 and 25 g (10–13 weeks) received a single 270 mg/kg (i.p.) dose of irinotecan hydrochloride or vehicle control and were killed at 6, 24, 48, 72, and 96 hours. Bacterial sequencing was conducted on cecal samples of control animals to determine the gut microbiome profile. Gut toxicity was assessed using validated clinical and histopathologic markers, permeability assays, and inflammatory markers. Chemotherapy-induced pain was assessed using the validated rodent facial grimace criteria, as well as immunologic markers of glial activation in the lumbar spinal cord. TLR4 deletion attenuated irinotecan-induced gut toxicity, with improvements in weight loss (P = 0.0003) and diarrhea (P < 0.0001). Crypt apoptosis was significantly decreased in BALB/c-Tlr4−/−billy mice (P < 0.0001), correlating with lower mucosal injury scores (P < 0.005). Intestinal permeability to FITC-dextran (4 kDa) and LPS translocation was greater in WT mice than in BALB/c-Tlr4−/−billy (P = 0.01 and P < 0.0001, respectively). GFAP staining in the lumbar spinal cord, indicative of astrocytic activation, was increased at 6 and 72 hours in WT mice compared with BALB/c-Tlr4−/−billy mice (P = 0.008, P = 0.01). These data indicate that TLR4 is uniquely positioned to mediate irinotecan-induced gut toxicity and pain, highlighting the possibility of a targetable gut/CNS axis for improved toxicity outcomes. Mol Cancer Ther; 15(6); 1376–86. ©2016 AACR.

Gut microbiota is critical for the induction of chemotherapy-induced pain

“…Since LPS is a ligand of Toll-like receptor 4 (TLR4) 11 , we compared the development of mechanical hyperalgesia following oxaliplatin treatment in TLR4 knockout (TLR4 −/− ) mice and littermate heterozygous (TLR4 +/− ) mice. Oxaliplatin-induced mechanical hyperalgesia was substantially less severe in TLR4 −/− mice than in their littermate TLR4 +/− counterparts during the entire observation period (Fig 3b), which is in agreement with previous findings on other models of CIPN 12–14 . Taken together, these results suggest that gut microbiota influences the development of mechanical hyperalgesia following oxaliplatin therapy through a LPS-TLR4 pathway.…”

Gut microbiota modulation of chemotherapy efficacy and toxicity

“…Conversely, knockout of Tlr4 in mice is associated with improvement in symptoms of toxicity from irinotecan (CPT-11, a topoisomerase I poison), despite modestly elevated levels of Proteobacteria, which express β-glucuronidases and, therefore, might increase reactivation of SN-38 (the active metabolite of irinotecan) 37 .…”

Selective MMP Inhibition, Using AZD3342, to Reduce Gastrointestinal Toxicity and Enhance Chemoefficacy in a Rat Model

“…A total tissue injury score was generated using a validated grading system based on the occurrences of eight histological criteria in the jejunum, and six criteria in the colon [19, 20]. These criteria were villous fusion and villous atrophy (jejunum only), disruption of brush border and surface enterocytes, crypt loss/architectural disruption, disruption of crypts cells, infiltration of polymorphonuclear cells and lymphocytes, dilation of lymphatics and capillaries, and edema.…”