Anthocyanins protect against kainic acid-induced excitotoxicity and apoptosis via ROS-activated AMPK pathway in hippocampal neurons.

INTRODUCTION: Excitotoxicity is an important mechanism involved in neurodegeneration. Kainic acid (KA)-induced excitotoxicity results an unfavorable stress, and we investigated the signaling pathways activated in such conditions. AIMS: Here, we sought to determine the cellular and biochemical benefits of anthocyanins extracted from Korean black bean against KA-induced excitotoxicity and neuronal cell death. METHODS AND
RESULTS: Mouse hippocampal cell line (HT22) and primary prenatal rat hippocampal neurons were treated with KA to induce excitotoxicity. Incubation of the cells with KA alone significantly decreased cell viability, elevated intracellular Ca(2+) level, increased generation of reactive oxygen species (ROS) and loss of mitochondrial membrane potential (Δψ(M)). These events were accompanied by sustained phosphorylation and activation of AMP-activated protein kinase (AMPK). Kainic acid induced upregulation of Bax, decrease in Bcl-2, release of cytochrome-c, and activation of caspase-3 in both cell types. Anthocyanins attenuated KA-induced dysregulation of Ca(2+), ROS accumulation, activation of AMPK, and increase in percentage of apoptotic cells. Pretreatment of the cells with compound C, an inhibitor of AMPK, diminished the KA-induced activation of AMPK and caspase-3. The activation of AMPK through elevation of cellular ROS and Ca(2+) levels is required for KA-induced apoptosis in hippocampal neurons.
CONCLUSIONS: In summary, our data suggest that although anthocyanins have diverse activities, at least part of their beneficial effects against KA-induced hippocampal degeneration can be attributed to their well-recognized antioxidant properties.