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MiRNA-31 Improves Cognition and Abolishes Amyloid-β Pathology by Targeting APP and BACE1 in an Animal Model of Alzheimer's Disease.

ABSTRACT: Alzheimer's disease (AD) is the most common form of dementia worldwide, characterized by progressive memory impairment, behavioral changes, and, ultimately, loss of consciousness and death. Recently, microRNA (miRNA) dysfunction has been associated with increased production and impaired clearance of amyloid-β (Aβ) peptides, whose accumulation is one of the most well-known pathophysiological markers of this disease. In this study, we identified several miRNAs capable of targeting key proteins of the amyloidogenic pathway. The expression of one of these miRNAs, miR-31, previously found to be decreased in AD patients, was able to simultaneously reduce the levels of APP and Bace1 mRNA in the hippocampus of 17-month-old AD triple-transgenic (3xTg-AD) female mice, leading to a significant improvement of memory deficits and a reduction in anxiety and cognitive inflexibility. In addition, lentiviral-mediated miR-31 expression significantly ameliorated AD neuropathology in this model, drastically reducing Aβ deposition in both the hippocampus and subiculum. Furthermore, the increase of miR-31 levels was enough to reduce the accumulation of glutamate vesicles in the hippocampus to levels found in non-transgenic age-matched animals. Overall, our results suggest that miR-31-mediated modulation of APP and BACE1 can become a therapeutic option in the treatment of AD.

SUBMITTER: Barros-Viegas AT

PROVIDER: S-EPMC7031139 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Backgroundβ-site amyloid precursor protein cleaving enzyme 1 (BACE1) is the rate-limiting enzyme in the production of amyloid beta (Aβ), the toxic peptide that accumulates in the brains of Alzheimer's disease (AD) patients. Our previous studies have shown that the clathrin adaptor Golgi-localized γ-ear-containing ARF binding protein 3 (GGA3) plays a key role in the trafficking of BACE1 to lysosomes, where it is normally degraded. GGA3 depletion results in BACE1 stabilization both in vitro and in vivo. Moreover, levels of GGA3 are reduced and inversely related to BACE1 levels in post-mortem brains of AD patients.MethodIn order to assess the effect of GGA3 deletion on AD-like phenotypes, we crossed GGA3 -/- mice with 5XFAD mice. BACE1-mediated processing of APP and the cell adhesion molecule L1 like protein (CHL1) was measured as well as levels of Aβ42 and amyloid burden.ResultsIn 5XFAD mice, we found that hippocampal and cortical levels of GGA3 decreased while BACE1 levels increased with age, similar to what is observed in human AD brains. GGA3 deletion prevented age-dependent elevation of BACE1 in GGA3KO;5XFAD mice. We also found that GGA3 deletion resulted in increased hippocampal levels of Aβ42 and amyloid burden in 5XFAD mice at 12 months of age. While levels of BACE1 did not change with age and gender in GGAKO;5XFAD mice, amyloid precursor protein (APP) levels increased with age and were higher in female mice. Moreover, elevation of APP was associated with a decreased BACE1-mediated processing of CHL1 not only in 12 months old 5XFAD mice but also in human brains from subjects affected by Down syndrome, most likely due to substrate competition.ConclusionThis study demonstrates that GGA3 depletion is a leading candidate mechanism underlying elevation of BACE1 in AD. Furthermore, our findings suggest that BACE1 inhibition could exacerbate mechanism-based side effects in conditions associated with APP elevation (e.g. Down syndrome) owing to impairment of BACE1-mediated processing of CHL1. Therefore, therapeutic approaches aimed to restore GGA3 function and to prevent the down stream effects of its depletion (e.g. BACE1 elevation) represent an attractive alternative to BACE inhibition for the prevention/treatment of AD.

Project description:Background: ABCA1 has recently been identified as a novel genetic risk factor for Alzheimer’s disease. The major known role of ABCA1 in the brain is to transfer lipids onto lipid poor APOE. Given that APOEε4 is the strongest genetic risk factor for developing late onset Alzheimer’s disease, this recent finding implicates the cholesterol homeostatic pathway in the onset/progression of Alzheimer’s disease. microRNAs (miRs) are small RNA species that negatively regulate expression of their target genes. ABCA1 is regulated by miR-33, and loss of this miR significantly increases protein levels of ABCA1 and increases the lipidation of APOE. However, it is unknown if loss of miR-33 and subsequent increase in ABCA1 protein levels ameliorates amyloid pathology. Methods: We generated miR-33+/+;APP/PS1 and miR-33-/-;APP/PS1 mice to determine changes in amyloid-beta (Aβ) peptides and amyloid plaque formation utilizing biochemical and histological analyses. In addition to amyloid pathology, we assessed if deletion of miR-33 altered the activation of glial cells in the brains of these mice. We utilized in vitro methods to determine if miR-33 alters the phagocytosis of Aβ aggregates. We utilized RNA-sequencing and mass spectrometry to identify the transcriptome and proteome regulation by miR-33 in the context of amyloid pathology. Results: Deletion of miR-33 dramatically reduces insoluble Aβ peptide levels and the deposition of amyloid plaques in APP/PS1 mice. In addition, we identified that astrocyte and microglial activation is markedly decreased in miR-33-/-;APP/PS1 mice through histological analyses. Intriguingly, we show that loss of miR-33 results in amyloid plaques that are more compact, potentially implicating enhanced microglial phagocytosis. We confirm in vitro that loss of miR-33 significantly increases microglial phagocytosis of Aβ aggregates. Our multi-omics analyses reveal that deletion of miR-33 regulates immune response in the context of amyloid pathology. Interestingly, we identified that WNT/Beta-catenin signaling is significantly upregulated in miR-33-/-;APP/PS1 mice. Conclusion: We confirm that the deletion of miR-33 increases APOE lipidation and significantly reduces amyloid pathology as well as glial activation in APP/PS1 mice. Our results agree with previous work identifying APOE lipidation as an important modulator of amyloid pathology. We show, for the first time, that loss of miR-33 increases the phagocytosis of Aβ by microglia. In total, we identify miR-33 as a promising target for the amelioration of amyloid pathology.

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MiRNA-31 Improves Cognition and Abolishes Amyloid-β Pathology by Targeting APP and BACE1 in an Animal Model of Alzheimer's Disease.

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