Pinocembrin protects against beta-amyloid-induced toxicity in neurons through inhibiting receptor for advanced glycation end products (RAGE)-independent signaling pathways and regulating mitochondrion-mediated apoptosis

Background

It is known that amyloid-beta peptide (Abeta) play a pivotal role in the pathogenesis of Alzheimer's disease (AD). Interaction between Abeta and the receptor for advanced glycation end products (RAGE) has been implicated in neuronal degeneration associated with this disease. Pinocembrin, a flavonoid abundant in propolis, has been reported to possess numerous biological activities beneficial to health. Our previous studies have demonstrated that pinocembrin have neuroprotective effects on ischemic and vascular dementia animal models. It has been approved by the State Food and Drug Administration of China for clinical use in stroke patients. Against this background, we investigate the effects of pinocembrin on the cognitive function and neuronal protection against Abeta-induced toxicity and explored its potential mechanism.

Methods

Mice received an intracerebroventricular fusion of Abeta25-35. Pinocembrin was administrated orally of 20 mg/kg/day and 40 mg/kg/day for 8 days. The behavioral performance, cerebral cortex neuropil ultrastructure, neuronal degeneration and RAGE expression were detected. Further, a RAGE-overexpressing cell model and an AD cell model were applied for investigating the mechanisms of pinocembrin. The mechanisms underlying the efficacy of pinocembrin were conducted on target action, mitochondrial function and potential signal transduction using fluorescence-based multiparametric technologies on a high-content analysis platform.

Results 

Our results showed that oral administration of pinocembrin improved cognitive function, preserved ultrastructural neuropils and decreased neurodegeneration of cerebral cortex in Abeta25-35-treated mice. Pinocembrin did not provide sufficient effect on inhibiting Abeta1-42 production and scavenging intracellular ROS. However, pinocembrin significantly inhibited the upregulation of RAGE transcripts and protein expression both in vivo and in vitro, and then, markedly depressed the activation of p38MAPK-MK2-HSP27 and SAPK/JNK-c-Jun pathways and the downstream NF-kappaB inflammatory response subsequent to Abeta-RAGE interaction. In addition, pinocembrin significantly alleviated mitochondrial dysfunction through improving mitochondrial membrane potential and inhibiting mitochondrial oxidative stress, and regulated mitochondrion-mediated apoptosis by restoration of bcl-2 and cytochrome c and inactivation of caspase-3 and caspase-9.

Conclusions

Pinocembrin showed cognitive improvement and neuronal protection in AD models. The mechanisms of the compound were illustrated on RAGE-dependent transduction inhibition and mitochondrion protection. It appears to be a promising candidate for the prevention and therapy of AD.