Injury of cortical neurons is caused by the advanced glycation end products-mediated pathway

Advanced glycation end products lead to cell apoptosis, and cause cell death by increasing endoplasmic reticulum stress. Advanced glycation end products alone may also directly cause damage to tissues and cells, but the precise mechanism remains unknown. This study used primary cultures of rat cerebral cortex neurons, and treated cells with different concentrations of glycation end products （50, 100, 200, 400 mg/L）, and with an antibody for the receptor of advanced glycation end products before and after treatment with advanced glycation end products. The results showed that with increasing concentrations of glycation end products, free radical content increased in neurons, and the number of apoptotic cells increased in a dose-dependent manner. Before and after treatment of advanced glycation end products, the addition of the antibody against advanced glycation end-products markedly reduced hydroxyl free radicals, malondialdehyde levels, and inhibited cell apoptosis. This result indicated that the antibody for receptor of advanced glycation end-products in neurons from the rat cerebral cortex can reduce glycation end product-induced oxidative stress damage by suppressing glycation end product receptors. Overall, our study confirms that the advanced glycation end products-advanced glycation end products receptor pathway may be the main signaling pathway leading to neuronal damage.

Effect of Aβ protein on inhibiting proliferation and promoting apoptosis of retinal pigment epithelial cells

AIM： To identify the effect and regulatory mechanism of amyloid β （Aβ） protein on retinal pigment epithelial （RPE） cells in cell proliferation and apoptosis, and clarify Aβ role in the pathogenesis of age-related macular degeneration （AMD）. METHODS： The model of Aβ25-35 protein cytotoxicity in RPE cell was successfully established to investigate the effect of Aβ protein on RPE cells in vitro. Based on Aβ protein, the specific inhibitors （HY-50682 or BAY11-7082） or activating agent （lipopolysaccharide） was used to analyze the regulatory mechanism of Aβ protein to RPE cells on cell proliferation and apoptosis by flow cytometry, real-time polymerase chain reaction, Western blotting, enzyme-linked immunosorbent assay and dual-luciferase reporter gene assay. RESULTS： The number of RPE cells, treated with Aβ25-35 from 0.3 to 60 μmol/L, significantly reduce （P〈0.01）, and had the dose-dependent effect. Aβ protein 60 μmol/L inhibits the G1/S phase transition （P〈0.01） and down-regulated cyclin E mRNA level （P〈0.01）. Similarly, Aβ25-35 induced a significant increase of cell apoptosis, accompanied by the significantly higher level of activated caspase 3 protein. Furthermore, nuclear factor-kappaB （NF-κB） activity and hosphorylated Iκ-Ba level would significantly lower in treated RPE cells. Using specific inhibitors or activating agent based on the Aβ, the cell numbers, NF-κB activity, phosphorylated Iκ-Ba level, receptor for advanced glycation endproducts （RAGE） gene expression levels, cyclin E mRNA level and activated caspase 3 level had accordingly changed by different methods, confirming that RAGE/NF-κB signaling pathway involved in the regulation of Aβ protein on RPE cell apoptosis and proliferation. CONCLUSION： Aβ protein inhibits cell proliferation and activates apoptosis via inactivation of the RAGE/NF-κB signaling pathway in RPE cell.