Effects of TgCtwh3 Toxoplasma gondii ROP16 on neuronal apoptosis and β-amyloid production

Abstract

Abstract Background Toxoplasma gondii(T.gondii) has been demonstrated to be a causative agent of Alzheimer's disease (AD). Neuronal apoptosis and β-amyloid (Aβ) aggregation are some of the main pathological features of AD. In recent years, our group found that the main genotype of T.gondii in China is Chinese 1 (ToxoDB#9), and Rhoptry protein16 (ROP16) is an important virulence factor of this type of T.gondii. The effects of ROP16 on hippocampal neurons and β-amyloid have rarely been reported. Methods BALB/c mice were intraperitoneally injected with TgCtwh3 ΔROP16 and TgCtwh3 WT tachyzoites, respectively. Tissues from the hippocampal region of mice were taken one week after infection for pathomorphological analysis, and the expression levels of inflammatory factors, apoptosis-related proteins, as well as proteins and genes related to Aβ formation in the hippocampal region of mice were assessed by Western Blotting and qRT-PCR. In vitro experiments, the mouse hippocampal neuronal cell line HT22 was directly infected with TgCtwh3 ΔROP16 and TgCtwh3 WT tachyzoites, and the expression levels of the relevant proteins were analyzed by Western Blotting and immunofluorescence staining, and apoptosis of the infected HT22 cells was determined by flow cytometry. Results Histopathological changes showed abnormal morphology and reduced number of neurons in hippocampal zone of infected mice. In addition, the expression of pro-apoptotic proteins, pro-inflammatory factors as well as APP and BACE1 increased in control group, TgCtwh3 ΔROP16 group and TgCtwh3 WT group. In vitro experiments showed that the protein blotting results indicated that TgCtwh3 and its virulence factor ROP16 could lead to neuronal apoptosis and Aβ generation through the endoplasmic reticulum stress pathway and NF-κB signaling pathway. And the flow results showed that the apoptosis rate of HT22 cells in the three groups increased step by step. Conclusion TgCtwh3 ROP16 induces neuronal apoptosis, Aβ production and secretion of inflammatory factors.