Novel mechanistic insight on the neuroprotective effect of berberine: The role of PPARδ for antioxidant action.

Cerebral ischemic stroke ranks the second leading cause of death and the third leading cause of disability in lifetime all around the world, urgently necessitating effective therapeutic interventions. Reactive oxygen species (ROS) have been implicated in stroke pathogenesis and peroxisome proliferator-activated receptors (PPARs) are prominent targets for ROS management. Although recent research has shown antioxidant effect of berberine (BBR), little is known regarding its effect upon ROS-PPARs signaling in stroke. The aim of this study is to explore whether BBR could target on ROS-PPARs pathway to ameliorate middle cerebral artery occlusion (MCAO)-induced stroke. Herein, we report that BBR is able to scavenge ROS in oxidation-damaged C17.2 neural stem cells and stroked mice. PPARδ, rather than PPARα or PPARγ, is involved in the anti-ROS effect of BBR, as evidenced by the siRNA transfection and specific antagonist treatment data. Further, we have found BBR could upregulate NF-E2 related factor-1/2 (NRF1/2) and NAD(P)H:quinone oxidoreductase 1 (NQO1) following a PPARδ-dependent manner. Mechanistic study has revealed that BBR acts as a potent ligand (Kd = 290 ± 92 nM) to activate PPARδ and initiates the transcriptional regulation functions, thus promoting the expression of PPARδ, NRF1, NRF2 and NQO1. Collectively, our results indicate that BBR confers neuroprotective effects by activating PPARδ to scavenge ROS, providing a novel mechanistic insight for the antioxidant action of BBR.

Berberine Protects C17.2 Neural Stem Cells From Oxidative Damage Followed by Inducing Neuronal Differentiation.

Neurodegeneration is the loss of structure and/or function of neurons. Oxidative stress has been suggested as one of the common etiology in most of the neurodegenerative diseases. Previous studies have demonstrated the beneficial effects of berberine in various neurodegenerative and neuropsychiatric disorders. In this study, we hypothesized that berberine could protect C17.2 neural stem cells (NSCs) from 2,2'-Azobis(2-amidinopropane) dihydrochloride (AAPH)-induced oxidative damage then promote neuronal differentiation. AAPH was used to induce oxidative damage. After the damage, berberine protected C17.2 cells were kept cultured for another week in differentiation medium with/without berberine. Changes in cell morphology were detected by microscopy and cell viability was determined by MTT assay. Real-time PCR and western blot analysis were performed to confirm the associated pathways. Berberine was able to protect C17.2 NSCs from the oxidative damage. It lowered the cellular reactive oxygen species (ROS) level in C17.2 cells via Nuclear Factor Erythroid 2-Related Factor 1/2 (NRF1/2) - NAD(P)H Quinone Dehydrogenase 1 (NQO-1) - Heme Oxygenase 1 (HO-1) pathway. It also down-regulated the apoptotic factors-Caspase 3 and Bcl2 Associated X (Bax) and upregulated the anti-apoptotic factor-Bcl2 to reduce cell apoptosis. Besides, berberine increased C17.2 cell viability via up-regulating Extracellular-signal-Related Kinase (ERK) and phosphor-Extracellular-signal-Related Kinase (pERK) expression. Then, berberine promoted C17.2 cell to differentiate into neurons and the differentiation mechanism involved the activation of WNT/ß-catenin pathway as well as the upregulation of expression levels of pro-neural factors Achaete-Scute Complex-Like 1 (ASCL1), Neurogenin 1 (NeuroG1), Neuronal Differentiation 2 (NeuroD2) and Doublecortin (DCX). In conclusion, berberine protected C17.2 NSCs from oxidative damage then induced them to differentiate into neurons.