AGE-Rich Bread Crust Extract Boosts Oxidative Stress Interception via Stimulation of the NRF2 Pathway

Background: Advanced glycation end products (AGEs) result from a non-enzymatic reaction of proteins with reactive carbohydrates. Heat-processed food like bread contains high amounts of AGEs. The activation of the NF-κB signaling pathway by bread crust extract (BCE) is well understood. However, it is largely unknown whether NRF2, the master regulator of oxidative stress resistance in mammalian cells, is affected by BCE. We have investigated the molecular mechanisms by which BCE induces antioxidant gene expression in cellular models.

Method: We developed a cell culture model to elucidate the effect of bread crust extracts on NRF2 activation in an endothelial reporter cell line (NRF2-mCherry). Nuclear translocation of NRF2 in these cells results in elevated mCherry expression, which was analyzed by flow cytometry. Furthermore, NRF2 pathway activation was confirmed by microarray analyses, qRT-PCR measurements, and Western blot analyses.

Results: Our data showed that soluble extracts from bread crust are capable of stimulating the NRF2 signaling pathway. Furthermore, NRF2 pathway activation was confirmed by microarray and reporter-cell analyses. QRT-PCR measurements and Western blot analyses indicated an induction of antioxidative genes like HMOX1, GCLM, and NQO1 upon BCE treatment. Moreover, BCE pretreated cells had a survival advantage compared with control cells when exposed to oxidative stress. BCE induces phosphorylation of AKT and ERK kinase in EA.hy926 cells.

Conclusion: Our findings indicate that BCE activates NRF2-dependent antioxidant gene expression thus provoking a protection mechanism against oxidative stress-mediated tissue injury. Hence, BCE can be considered as functional food with antioxidative and cardioprotective potential.

Publication History

Article published online:
03 February 2022