Secretory transport of irinotecan metabolite SN-38 across isolated intestinal tissue

Opioid-induced microbial dysbiosis disrupts irinotecan (CPT-11) metabolism and increases gastrointestinal toxicity in a murine model

BACKGROUND AND PURPOSE

Opioids are commonly used for the management of cancer-associated pain and chemotherapy-induced diarrhoea. The chemotherapeutic irinotecan (CPT-11) causes severe gastrointestinal (GI) toxicity due to deconjugation of inactive metabolite SN-38 glucuronide (SN-38G) by bacterial β-glucuronidases to the active 7-ethyl-10-hydroxycamptothecin (SN-38). Opioids are known to cause gut microbial dysbiosis, this study evaluated whether CPT-11 anti-tumour efficacy and GI toxicity are exacerbated by opioid co-administration.

EXPERIMENTAL APPROACH

Eight-week-old C57BL/6 male mice were co-administration with CPT-11 ± opioid. 16S rRNA sequencing was used for gut microbiome analysis. LC-MS analyses of plasma and intestinal extracts were performed to investigate the pharmacokinetic profile of CPT-11. Histological analysis and quantitative real-time polymerase chain reaction were used to determine the severity of intestinal tissue damage. Human liver microsome In vitro assay was performed to confirm the effects of opioids on CPT-11 metabolism.

KEY RESULTS

Gut microbiome analysis showed that morphine treatment induced enrichment of β-glucuronidase-producing bacteria in the intestines of CPT-11-treated mice, resulting in SN-38 accumulation and exacerbation of GI toxicity in the small intestine. Oral administration of both antibiotics and glucuronidase inhibitor protected mice against GI toxicity induced with CPT-11 and morphine co-administration, implicating a microbiome-dependent mechanism. Additionally, morphine and loperamide decreased the plasma concentration of SN-38 and compromised CPT-11 anti-tumour efficacy, this seemed to be microbiome independent.

CONCLUSION AND IMPLICATIONS

Gut microbiota play a significant role in opioid and chemotherapeutic agent drug-drug interactions. Inhibition of gut microbial glucuronidase may also prevent adverse GI effects of CPT-11 in patients on opioids.

Effect of genistein, a natural soy isoflavone, on the pharmacokinetics and intestinal toxicity of irinotecan hydrochloride in rats

Objectives

The effect of genistein, a natural soy isoflavone, on pharmacokinetics and intestinal toxicity, or late-onset diarrhoea, of irinotecan hydrochloride (CPT-11) was examined in rats.

Methods

Probenecid, a typical inhibitor of multidrug resistance-associated protein (MRP) 2, was also employed for comparison with genistein. Plasma concentration, biliary excretion and intestinal secretion of CPT-11, 7-ethyl-10-hydroxycamptothecin (SN-38) and SN-38 glucuronide (SN-38G) were determined in untreated, genistein-treated and probenecid-treated rats. CPT-11 was administered repeatedly by intravenous injection (60 mg/kg/day for 4 days), and the effects of genistein and probenecid on CPT-11-induced intestinal toxicity were evaluated by measuring body weight, induction of diarrhoea, and alkaline phosphatase (ALP) activity in the intestinal mucosal membranes.

Key findings

Genistein, as well as probenecid, significantly suppressed the MRP2-mediated biliary and intestinal secretion of CPT-11 and its metabolites and increased their plasma concentrations. Multiple administration of CPT-11 reduced body weight and ALP activity, and induced watery diarrhoea. Genistein, as well as probenecid, significantly suppressed the loss in body weight and the reduced mucosal ALP activity in the ileum, and ameliorated the symptoms of diarrhoea induced by CPT-11.

Conclusions

Intravenous genistein was effective in ameliorating CPT-11-induced late-onset diarrhoea, by suppressing MRP2-mediated biliary excretion of CPT-11 and its metabolites.

Intestinal tract injury by drugs: Importance of metabolite delivery by yellow bile road

Drug secretion into bile is typically considered a safe route of clearance. However, biliary delivery of some drugs or their reactive metabolites to the intestinal tract evokes adverse consequences due to direct toxic actions or indirect disruption of intestinal homeostasis. Biliary concentration of the chemotherapy agent 5-fluorodeoxyuridine (FUDR) and other compounds is associated with bile duct damage while enterohepatic cycling of antibiotics contributes to the disruptions of gut flora that produce diarrhea. The goal of this review is to describe key evidence that biliary delivery is an important factor in the intestinal injury caused by representative drugs. Emphasis will be given to 3 widely used drugs whose reactive metabolites are plausible causes of small intestinal injury, namely the nonsteroidal anti-inflammatory drug (NSAID) diclofenac, the immunosuppressant mycophenolic acid (MPA), and the chemotherapy agent irinotecan. Capsule endoscopy and other sensitive diagnostic techniques have documented a previously unappreciated, high prevalence of small intestinal injury among NSAID users. Clinical use of MPA and irinotecan is frequently associated such severe intestinal injury that dosage must be reduced. Observations from clinical and experimental studies have defined key events in the pathogenesis of these drugs, including roles for multidrug resistance-associated protein 2 (MRP2) and other transporters in biliary secretion and adduction of enterocyte proteins by reactive acyl glucuronide metabolites as a likely mechanism for intestinal injury. New strategies for minimizing the adverse intestinal consequences of irinotecan chemotherapy illustrate how basic information about key events in the biliary secretion of drugs and the nature of their proximate toxicants can lead to safer protocols for drugs.