Kaempferol stimulation of autophagy regulates the ferroptosis under the oxidative stress as mediated with AMP-activated protein kinase

Recent studies have highlighted the positive effects of Kaempferol (KP), including its anti-inflammatory and antioxidant properties. However, its impact on oxidative damage induced by heavy metals and pro-inflammatory mediators, such as arachidonic acid (AA), has not yet been identified. Our objective was to specifically evaluate liver damage due to AA + iron-induced oxidative stress, both in vitro and in vivo. In HepG2 cells, KP activated the AMP-activated protein kinase (AMPK), suggesting a hepatoprotective effect through AMPK inhibition, as assessed by immunoblot and FACS analysis (EC50 = 10 μM). KP also stimulated autophagy, a degradation process that eliminates aged, damaged, and unnecessary components, via mTOR inhibition and ULK1 phosphorylation. This activation was further validated by the upregulation of autophagy-related genes (ATG5) and Beclin-1, along with the conversion of LC3BI to LC3BII. Ferroptosis, a non-apoptotic type of cell death characterized by oxidative stress from the production of reactive oxygen species (ROS) and excessive iron accumulation, was linked to the activation of autophagy, as confirmed through the protein expression of deferoxamine (DFO) and ferrostatin-1 (Fer-1), the representative ferroptosis inhibitors (positive controls). In mice, oral administration of KP demonstrated protective effects against CCl4-induced hepatotoxicity. In conclusion, KP provides hepatoprotective effects against oxidative stress induced by AA + iron treatment in vitro and CCl4 treatment in vivo.