BackgroundDeposition of aggregated amyloid beta (Aβ) protein is hallmark of Alzheimer’s disease, leading to dysfunction and apoptosis of neurons. The isoflavone phytoestrogen compound genistein (Gen) exerts a significant protective effect against Aβ25–35 induced neurotoxicity and mitochondrial damage in rat pheochromocytoma (PC12) cells. However, the mechanisms underlying Gen’s rescue remain elusive. Therefore we endeavored to research further the molecular mechanisms underlying Gen’s inhibition of Aβ25–35 induced apoptosis of neurons.ResultsWe found that Gen dramatically suppressed the activation by Aβ25–35 of p-c-Jun N-terminal kinase (p-JNK), and also inhibited the JNK-dependent decreased of Bcl-w and increased of Bim. Furthermore, Gen significantly reduced the cytoplasmic concentrations of cytochrome c and Smac protein as well as caspase-3 activity. Additionally, pretreatment with JNK inhibitor SP600125 effectively suppressed Aβ25–35 induced PC12 cell cytotoxicity.ConclusionTaken together, the results suggested that Gen protects PC12 cells from Aβ25–35 induced neurotoxicity by interfering with p-JNK activation, thus attenuating the JNK-dependent apoptosis through the mitochondrial pathway. These findings constitute novel insights into the pathway for Aβ25–35 toxicity, and the neuroprotective action of Gen.Electronic supplementary materialThe online version of this article (doi:10.1186/s12868-016-0329-9) contains supplementary material, which is available to authorized users.

The β-amyloid protein (Aβ) is considered to be the key factor for inducing Alzheimer's disease (AD). In recent years, the neuroprotective effects of genistein have drawn increasing attention. However, the molecular mechanisms of GEN (genistein) against Aβ are unclear. In the present study, we investigated the inhibitory effects of GEN on Aβ25-35-induced apoptosis in cultured PC12 cells and the related signaling pathway. Our data show that GEN significantly inhibited Aβ25-35-induced apoptosis of PC12 cells. GEN suppressed Aβ25-35-induced JNK activation and the JNK-dependent upregulation of Fas/FasL at the mRNA and protein levels induced by Aβ25-35 were significantly decreased by GEN. Additionally, GEN inhibited mRNA expression and activity of caspase-3 and caspase-8 induced by Aβ25-35. Together, these findings showed that Aβ-induced apoptosis of PC12 cells proceeds through the Fas/FasL pathway. The JNK signaling plays a critical role in regulating the anti-apoptotic effects of genistein. Thus, our results suggest that genistein can inhibit Aβ-induced apoptosis of PC12 cells through blockage of the JNK activation and subsequent suppression of the JNK-dependent Fas/FasL pathway.