MMP13 inhibition rescues cognitive decline in Alzheimer transgenic mice via BACE1 regulation.

MMP13 (matrix metallopeptidase 13) plays a key role in bone metabolism and cancer development, but has no known functions in Alzheimer's disease. In this study, we used high-throughput small molecule screening in SH-SY5Y cells that stably expressed a luciferase reporter gene driven by the BACE1 (ß-site amyloid precursor protein cleaving enzyme 1) promoter, which included a portion of the 5' untranslated region (5'UTR). We identified that CL82198, a selective inhibitor of MMP13, decreased BACE1 protein levels in cultured neuronal cells. This effect was dependent on PI3K (phosphatidylinositide 3-kinase) signalling, and was unrelated to BACE1 gene transcription and protein degradation. Further, we found that eukaryotic translation initiation factor 4B (eIF4B) played a key role, as the mutation of eIF4B at serine 422 (S422R) or deletion of the BACE1 5'UTR attenuated MMP13-mediated BACE1 regulation. In APPswe/PS1E9 mice, an animal model of Alzheimer's disease, hippocampal Mmp13 knockdown or intraperitoneal CL82198 administration reduced BACE1 protein levels and the related amyloid-ß precursor protein processing, amyloid-ß load and eIF4B phosphorylation, whereas spatial and associative learning and memory performances were improved. Collectively, MMP13 inhibition/CL82198 treatment exhibited therapeutic potential for Alzheimer's disease, via the translational regulation of BACE1.

The effect of NR4A1 on APP metabolism and tau phosphorylation.

Alzheimer's disease (AD) is characterized by senile plaques (SP) composed of ß-amyloid protein (Aß) and neurofibrillary tangles (NFTs) composed of intracellular hyperphosphorylated tau. Recently, nuclear receptor subfamily 4 group A member 1 (NR4A1) was implicated in synaptic plasticity, long-term memory formation, suggesting that it may play a role in the pathophysiology of AD. Here, we showed that the expression of NR4A1 was significantly increased in the hippocampus of APP/PS1 transgenic mice. In addition, NR4A1 overexpression in HT22 cells up-regulated APP and BACE1 levels, down-regulated ADAM10 expression, and promoted amyloidogenesis as indicated by decreased α-CTF levels and elevated ß-CTF levels. Furthermore, a raised level of phospho-tau (p-tau, S396) was accompanied by p-GSK3ß (S9) expression reducing, but total tau, p-tau (S262 and T231), CDK5 and ERK remained unchanged in NR4A1-overexpressing cells. Collectively, our results suggest that NR4A1 promotes the amyloidogenic processing of APP by regulating ADAM10 and BACE1 expression in HT22 cells; as well as NR4A1 accelerates tau hyperphosphorylation by GSK3ß signal. Therefore, NR4A1 may play an important role in the pathogenesis of AD.

Increased expression of Myc-interacting zinc finger protein 1 in APP/PS1 mice.

Myc-interacting zinc-finger protein 1 (Miz1) is a member of the poxvirus and zinc-finger domain/zinc finger transcription factor family. Its transcription activation and repression functions in the nucleus are well elucidated; however its cytoplasmic inflammation function is poorly understood and may be associated with the pathogenesis of Alzheimer's disease (AD). The aim of the present study was to investigate the association between AD and Miz1 expression. In the present study, the expression and distribution of Miz1 in wild-type (WT) and amyloid precursor protein/presenelin-1 (AD) mice was studied using reverse transcription-quantitative polymerase chain reaction, western blot analysis, and immunohistochemical and immunofluorescence staining. The results indicated that Miz1 was significantly upregulated in the cortex of AD mice (P<0.05). Double immunofluorescence labeling revealed that Miz1 protein was predominantly expressed in neurons and astrocytes, as evidenced by co-localization with the dendritic markers microtubule associated protein 2 and glial fibrillary acidic protein, respectively. The results of the present study suggest that the expression of Miz1 in the brain tissue of AD mice may serve an important role in AD pathogenesis.

Histone deacetylase inhibitor apicidin increases expression of the α-secretase ADAM10 through transcription factor USF1-mediated mechanisms.

ADAM10 (a disintegrin and metalloproteinase domain-containing protein 10) is the α-secretase that is involved in APP (ß-amyloid precursor protein) processing. Enhancement of the nonamyloidogenic APP pathway by ADAM10 provides therapeutic potential for Alzheimer's disease (AD). By using high-throughput screening that targeted ADAM10, we determined that apicidin-an inhibitor of HDACs (histone deacetylases)-significantly increased mRNA and protein levels of ADAM10 in SH-SY5Y cells. A luciferase assay revealed that the nucleotides -444 to -300 in the ADAM10 promoter were sufficient to mediate this effect. In addition, knockdown of USF1 (upstream transcription factor 1) and HDAC2/3 prevented apicidin regulation of ADAM10. Moreover, USF1 acetylation was increased by apicidin, which enhanced the association of USF1 with HDAC2/3 and with the ADAM10 promoter. We further found that apicidin did not affect the phosphorylation of ERK or USF1; however, ERK inhibitor U0126 blocked the effect of apicidin on ADAM10. Finally, apicidin increased the level of α-site C-terminal fragment from APP and reduced the production of ß-amyloid peptide 1-42. Collectively, our study provides evidence that ADAM10 expression can be regulated by HDAC2/3 inhibitor apicidin via USF1-dependent mechanisms in which ERK signaling plays an important role. Thus, HDAC regulation of ADAM10 might shed new light on the understanding of AD pathology.-Hu, X.-T., Zhu, B.-L., Zhao, L.-G., Wang, J.-W., Liu, L., Lai, Y.-J., He, L., Deng, X.-J., Chen, G.-J. Histone deacetylase inhibitor apicidin increases expression of the α-secretase ADAM10 through transcription factor USF1-mediated mechanisms.