Reactive oxygen species and senescence modulatory effects of rice bran extract on 4T1 and NIH-3T3 cells co-treatment with doxorubicin

Objective:
To determine the effect of rice bran extract (RBE) in combination with doxorubicin on 4T1 triple-negative breast cancer cells and NIH-3T3 cells.

Methods:
RBE was obtained by maceration with n-hexane. The phytochemical profile of RBE was observed using highperformance liquid chromatography. Cytotoxic effect of RBE was evaluated through MTT assay. In addition, flow cytometry was used for cell cycle and apoptosis analysis. Cellular senescence was observed using SA-β-Gal assay and intracellular reactive oxygen species (ROS) levels were evaluated using DCFDA staining. The pro-oxidant property of RBE was also evaluated through 1-chloro- 2,4-dinitrobenzene spectrophotometry and molecular docking.

Results:
RBE was obtained with a yield of 18.42% w/w and contained tocotrienols as the major compound. RBE exerted no cytotoxic effect on 4T1 and NIH-3T3 cells. However, RBE in combination with doxorubicin decreased 4T1 cell viability synergistically (combination index<0.9) and induced apoptosis and senescence on 4T1 cells. RBE significantly decreased senescence in doxorubicin-treated NIH-3T3 cells. Additionally, RBE did not increase ROS levels in doxorubicin-treated 4T1 cells. Meanwhile, the combination of RBE and doxorubicin reduced ROS levels in NIH-3T3 cells. RBE significantly reduced glutathione-S-transferase activity and alpha-tocotrienol interacted with glutathione-S- transferase in the glutathione binding site.

Conclusions:
Rice bran may be used as a co-chemotherapeutic agent to improve the therapeutic effectiveness of doxorubicin while protecting against the cellular senescence effects of doxorubicin on healthy cells.