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Alzheimer's disease (AD) is a progressive neurodegenerative disorder associated with synaptic dysfunction, pathological accumulation of β-amyloid peptide 1-42 (Aβ1-42 ), and neuronal loss. The self-association of Aβ1-42 monomers (Aβ-M) into soluble oligomers seems to be crucial for the development of neurotoxicity. Previous publications have shown that Aβ oligomers and dimers might play key roles in inducing AD. The role of Aβ-M was rarely investigated and still unclear in AD. To understand the effects of Aβ-M on neurons and other cell types in the brain could be the key to understand its function. In our study, we found that Aβ-M expression slowly induced cell apoptosis within 48 hours after transfection, β2 adrenergic receptor (β2AR) interacted with Aβ-M in the pull-down and the yeast two-hybrid assays, and Aβ-M played a major role in inducing phosphorylation of Tau at Ser-214, c-Jun N-terminal kinase (JNK) at Thr-183/Tyr-185, p70 ribosomal protein S6 kinase (p70S6K) at Thr-389. We also discovered that β2AR, G protein-coupled receptor kinase 2 (GRK2), and protein kinase A (PKA) mediated the phosphorylation of Tau and JNK. Aβ-M induced phosphorylation of Tau at Ser-214 through both β2AR-cAMP/PKA-JNK and β2AR-GRK signaling pathways. Mitogen-activated protein kinase kinase (MEK) mediated the phosphorylation of p70S6K induced by Aβ-M.

Keap1 is deemed as a suppressor of Nrf2 in cytoplasm by sequestrating Nrf2 to proteolysis as an adapter of the Cul3-Rbx1 E3 ubiquitin ligase complex. In the study, it was proposed that post-translational modification might affect the interaction between Nrf2 and Keap1, and the profiles of the phosphorylation of amino acid residues of Keap1 and its effects on the binding of Keap1 to Nrf2 was investigated. A mass spectrometry analysis revealed that S53 and S293 were phosphorylated upon an oxidative stress. Using Keap1 proteins with amino acid residues mutated to glutamate to simulate the introduction of a negative charge by phosphorylation, it was found that a potential phosphorylation of S53 affected Keap1-Nrf2 binding in the pull-down assay, and induced nuclear translocation of Nrf2 in the electrophoretic mobility shift assay. Sequence homology analysis showed that S53 was highly conserved. Structural modeling around BTB domain of wild type and S53E-mutant Keap1 showed that the negative charge introduced by S53E mutation generates a salt bridge between E53 and ionized guanidine group of Arg50. Real-time qRT-PCR for transcription levels of antioxidant genes that are modulated by Nrf2 further proved the effects of the potential phosphorylation of S53 under an oxidative stress condition. In summary, S53 is a potential phosphorylation site of Keap1, and the phosphorylation could enhance the antioxidative capacity of cells in response to an oxidative stress.

Troxerutin, a semi-synthetic derivative of the natural bioflavanoid rutin, has been reported to possess many beneficial effects in human bodies, such as vasoprotection, immune support, anti-inflammation and anti-aging. However, the effects of troxerutin on genome-wide transcription in blood cells are still unknown. In order to find out effects of troxerutin on gene transcription, a high-throughput RNA sequencing was employed to analysis differential gene expression in blood cells consisting of leucocytes, erythrocytes and platelets isolated from the mice received subcutaneous injection of troxerutin. Transcriptome analysis demonstrated that the expression of only fifteen genes was significantly changed by the treatment with troxerutin, among which 5 genes were up-regulated and 10 genes were down-regulated. Bioinformatic analysis of the fifteen differentially expressed genes was made by utilizing the Gene Ontology (GO), and the differential expression induced by troxerutin was further evaluated by real-time quantitative PCR (Q-PCR).