| Nuclear factor erythroid 2-related factor 2 (Nrf2) has a pivotal role in promoting chemoresistance by regulation of antioxidants
and detoxification enzymes. Trigonelline is one of the major alkaloids in raw coffee which has been recently introduced
as potent inhibitor of Nrf2. This study investigated the role of trigonelline and trigonelline loaded micelles in Nrf2
inhibition to break down oxaliplatin resistance in colon cancer cells. The PCL-PEG-PCL and PLA-PCL-PEG-PCL-PLA
copolymers and trigonelline loaded micelles were prepared and characterized for fourier transforms infrared (FTIR), hydrogen
nuclear magnetic resonance (1H-NMR), carbon nuclear magnetic resonance (13C-NMR) spectroscopy, particle size,
zeta potential, scanning electron microscopy (SEM) and entrapment efficiency. Cell viability and apoptosis were evaluated
by using MTT and flow cytometry assays, respectively. Nrf2, MRP1, NQO1, HO-1, Bax, and Bcl2 gene expressions were
examined by qRT-PCR. Our results revealed that micelles had spherical shapes with narrow sizes and zeta potential indexes
of − 9.06 ± 6.94 mV for trigonelline loaded 3Block and − 7.47 ± 6.08 mV for trigonelline loaded 5Block micelles. After Nrf2
inhibition by trigonelline, antioxidant response element (ARE) related gene expressions were decreased (p < 0.05) with a
significantly higher impact by trigonelline loaded micelles (p < 0.05). Trigonelline loaded micelles also strongly decreased
IC50 value of oxaliplatin in resistant colon cancer cells (p < 0.05). Furthermore, trigonelline loaded 5Block micelle increased
oxaliplatin-induced apoptosis in a Nrf2/ARE dependent manner. Altogether, the current study suggests that delivery of
trigonelline loaded micelles as potent Nrf2 inhibitors can be considered as a promising strategy to overcome oxaliplatin
resistance in colon cancer patients. |