Carvone Attenuated Irinotecan‐Induced Mucositis and Diarrhea by Enhancing SN‐38 Intestinal Glucuronidation Through Upregulation of Nrf2‐UGT1A1 Axis

Background Irinotecan is a potent antitumor drug widely used to treat various types of cancer especially colorectal carcinoma. However, its therapeutic effectiveness is compromised by severe intestinal mucositis and diarrhea. Irinotecan is a prodrug activated by hepatic and intestinal carboxylesterase to SN‐38, which is the active antitumor metabolite. SN‐38 metabolized by glucuroniadation via hepatic UDP‐glucuronosyltransferase (UGT). The SN‐38 glucuronides (SN‐38G) eliminated mainly through hepatobilliary route into intestine, where it deconjugated to SN‐38 via β‐glucuronidase produced by the intestinal bacterial flora. The re‐formed SN‐38 responsible for mucositis and diarrhea associated with irinotecan therapy. Previous work in our lab proves that Mentha spicata oil improves irinotecan‐induced mucositis. In this study we hypothesized that carvone as the main constituent of the M. spicata oil is responsible for the protective effect against irinotecan‐induced mucositis and diarrhea in mice, with a proposed mechanism of protection by enhance SN‐38 conjugation. Methods Twenty‐four mice were divided into 4 groups each with 6: non treated negative control group, irinotecan treated as a model control group (75mg/Kg 4 days), two treatment groups with carvone 50mg/Kg/dose and 100mg/Kg/dose twice daily (orally for 9 days starting 4 days before irinotecan) plus irinotecan administration. Results results showed that carvone 50mg/kg and 100mg/kg twice daily significantly attenuated mice body weight loss in a dose‐dependent manner compared to model control group. Weight variation percent reported were (‐13.78±1.6%) and (‐9.39±1.56%) vs. (‐23.21±1.65%) respectively. Diarrhea scores also significantly and dose‐dependently reduced by the administration of carvone 50mg/kg and 100mg/kg compared to model control group. Diarrhea score evaluated were (1.00±0.258) and (0.50±0.244) vs. (2.67±0.211), respectively. Serum TNFα level significantly and dose‐dependently decreased in groups of carvone 50mg/kg (2210.48±188.29pg/dL) and carvone 100mg/kg (1362.58±65.88 pg/dL) compared to the model control group (3402.12±321.56 pg/dL). To investigate the mechanism of action behind the observed effect, we proposed that carvone enhances intestinal SN‐38 glucuronidation by overexpression of Nrf2 ‐ UGT1A1 axis. Interestingly, results showed that jejunal UGT1A1 levels significantly and dose‐dependently upregulated in mice received carvone 50mg/kg and 100mg/kg compared to the model control group. Jejunum UGT1A1 level reported were (36.58±8.97 pg/mg) and (82.20±18.14pg/mg) vs. (22.77±3.16 pg/mg) respectively. In the same context, jejunal Nrf2 gene expression significantly and dose‐dependently increased in mice treated with carvone 50mg/kg and carvone 100mg/kg by (7.12±1.04) and (12.79 ±2.4) folds compared to model control animals (3.56±0.78). In conclusion, we showed for the first time that carvone attenuated irinotecan‐induced mucositis and diarrhea in mice by upregulating Nrf2 ‐ UGT1A1 axis resulting in enhanced SN‐38 glucuronidation and thus detoxification.