Protective effects of flavonoids from Coreopsis tinctoria Nutt. on experimental acute pancreatitis via Nrf-2/ARE-mediated antioxidant pathways

Abstract

Ethnopharmacological relevance: Oxidative stress is a prominent feature of clinical acute pancreatitis (AP). Coreopsis tinctoria has been used traditionally to treat pancreas disorders like diabetes mellitus in China and Portugal and its flavonoid-rich fraction contain the main phytochemicals that have antioxidant and anti-inflammatory activities.

Aim of the study: To investigate the effects of flavonoids isolated from C. tinctoria on experimental AP and explore the potential mechanism.

Materials and methods: LC-MS based online technique was used to analyse and isolate targeted flavonoids from C. tinctoria. Freshly isolated mouse pancreatic acinar cells were treated with taurocholic acid sodium salt hydrate (NaT, 5 mM) with or without flavonoids. Fluorescence microscopy and a plate reader were used to determine necrotic cell death pathway activation (propidium iodide), reactive oxygen species (ROS) production (H2-DCFDA) and ATP depletion (luminescence) where appropriate. AP was induced by 7 repeated intraperitoneal caerulein injections (50 μg/kg) at hourly interval in mice or retrograde infusion of taurolithocholic acid 3-sulfate disodium salt (TLCS; 5 mM, 50 μL) into the pancreatic duct in mice or infusion of NaT (3.5%, 1 mL/kg) in rats. A flavonoid was intraperitoneally administered at 0, 4, and 8 h after the first caerulein injection or post-operation. Disease severity, oxidative stress and antioxidant markers were determined.

Results: Total flavonoids extract and flavonoids 1-6 (C1-C6) exhibited different capacities in reducing necrotic cell death pathway activation with 0.5 mM C1, (2 R,3 R)-taxifolin 7-O-β-D-glucopyranoside, having the best effect. C1 also significantly reduced NaT-induced ROS production and ATP depletion. C1 at 12.5 mg/kg and 8.7 mg/kg (equivalent to 12.5 mg/kg for mice) significantly reduced histopathological, biochemical and immunological parameters in the caerulein-, TLCS- and NaT-induced AP models, respectively. C1 administration increased pancreatic nuclear factor erythroid 2-related factor 2 (Nrf2) and Nrf2-medicated haeme oxygenase-1 expression and elevated pancreatic antioxidant enzymes superoxide dismutase and glutathione peroxidase levels.

Conclusions: Flavonoid C1 from C. tinctoria was protective in experimental AP and this effect may at least in part be attributed to its antioxidant effects by activation of Nrf2-mediated pathways. These results suggest the potential utilisation of C. tinctoria to treat AP.

Keywords: (2R,3R)-taxifolin 7-O-β-D-glucopyranoside; (2S)-eriodictyol 7-O-β-D-glucopyranoside; (2S)-flavanocorepsin; (2S)-flavanomarein; Acute pancreatitis; Antioxidant enzymes; Coreopsis tinctoria; Flavonoids; Marein; Maritimein; Nrf2; Oxidative stress.