Neuroprotective Effects of Baicalein, Wogonin, and Oroxylin A on Amyloid Beta-Induced Toxicity via NF-κB/MAPK Pathway Modulation

Amyloid beta (A beta) peptide, one of the most important pathogenic traits of Alzheimer's disease (AD), invokes a cascade of oxidative damage and eventually leads to neuronal death. In the present study, baicalein, wogonin, and oroxylin A, main active flavones in Scutellaria baicalensis, were evaluated for their neuroprotective effects against A beta(25-35)-stimulated damage. All tested compounds decreased A beta(25-35)-induced ROS generation and cell cycle arrest. In particular, baicalein exhibited the strongest antioxidant activity. In addition, these compounds suppressed apoptosis by attenuating mitochondrial dysfunction such as loss of membrane potential, Ca2+ accumulation and Bax/Bcl-2 ratio. Furthermore, all tested flavones inhibited the expression of iNOS and COX-2, which resulted in suppressing inflammatory cytokines including TNF-alpha, NO, and PGE(2). Noticeably, all compounds exhibited the anti-inflammatory effects through downregulating NF-kappa B/MAPK pathway. Especially, oroxylin A was effective against both p65 and I kappa B alpha, while wogonin and baicalein were suppressed phospho-p65 and phospho-I kappa B alpha, respectively. Taken together, baicalein, wogonin, and oroxylin A can effectively relieve A beta(25-35)-stimulated neuronal apoptosis and inflammation in PC12 cells via downregulating NF-kappa B/MAPK signaling pathway.