Involvement of Nrf2 Activation and NF-kB Pathway Inhibition in the Antioxidant and Anti-Inflammatory Effects of Hesperetin in Activated BV-2 Microglial Cells

Alzheimer's disease is a progressive neurodegenerative disorder leading to cognitive decline and memory loss. The incidence of this disease continues to increase due to the limited number of novel therapeutics that prevent or slow down its progression. Flavonoids have been investigated for their potential effects on cellular damage triggered by excessive reactive oxygen species (ROS) and neuroinflammatory conditions. This study investigated the effect of the flavonoid hesperetin on LPS-activated murine BV-2 microglial cells. Results show that hesperetin reduced nitric oxide levels and increased catalase, glutathione, and superoxide dismutase levels, suggesting its potential to reduce neuroinflammation and oxidative stress. Moreover, RT-PCR arrays showed that hesperetin modulated multiple genes that regulate oxidative stress. Hesperetin downregulated the mRNA expression of ERCC6, NOS2, and NCF1 and upregulated HMOX1 and GCLC. RT-PCR results showed that hesperetin-induced Nrf2 mRNA and protein expression in LPS-activated BV-2 microglial cells is involved in the transcription of several antioxidant genes, suggesting that hesperetin's antioxidant effects may be exerted via the Keap1/Nrf2 signaling pathway. Furthermore, the data demonstrated that hesperetin reduced the gene expression of PD-L1, which is upregulated as an individual ages and during chronic inflammatory processes, and inhibited the expression of genes associated with NF-kB signaling activation, which is overactivated during chronic inflammation. It was concluded from this investigation that hesperetin may have therapeutic potential to prevent or slow down the progression of neurodegenerative diseases, such as Alzheimer's disease, by reducing chronic oxidative stress and modulating neuroinflammation.