Microarray Profile of Long Noncoding RNA and Messenger RNA Expression in a Model of Alzheimer's Disease

Epigenetics of Alzheimer’s Disease: Past, Present and Future

Alzheimer’s disease (AD) exemplifies a looming epidemic lacking effective treatment and manifests with the accumulation of neurofibrillary tangles, amyloid-β plaques, neuroinflammation, behavioral changes, and acute cognitive impairments. It is a complex, multifactorial disorder that arises from the intricate interaction between environment and genetic factors, restrained via epigenetic machinery. Though the research progress has improved the understanding of clinical manifestations and disease advancement, the causal mechanism of detrimental consequences remains undefined. Despite the substantial improvement in recent diagnostic modalities, it is challenging to distinguish AD from other forms of dementia. Accurate diagnosis is a major glitch in AD as it banks on the symptoms and clinical criteria. Several studies are underway in exploring novel and reliable biomarkers for AD. In this direction, epigenetic alterations have transpired as key modulators in AD pathogenesis with the impeding inferences for the management of this neurological disorder. The present chapter aims to discuss the significance of epigenetic modifications reported in the pathophysiology of AD such as DNA methylation, hydroxy-methylation, methylation of mtDNA, histone modifications, and noncoding RNAs. Additionally, the chapter also describes the possible therapeutic avenues that target epigenetic modifications in AD.

Plasma long non-coding RNAs ASMTL-AS1, AP001363.1, AC005730.3 and AL133415.1 as a potential biomarker for Alzheimer's disease

BACKGROUND

Long non-coding RNAs (lncRNAs) play critical role in the pathogenesis of neurodegenerative diseases. Human plasma contains lncRNAs that are present in the blood, and their disease-specific profile has been considered a potential biomarker in some diseases.

METHODS

This study reports screening of the plasma levels of lncRNAs between Alzheimer disease(AD) (n = 45) and matched healthy controls (n = 45). The plasma samples of 5 AD patients and 5 matched healthy controls were randomly selected for expression levels of lncRNAs using the TruSeq RNA Sample Prep Kit (Illumina). The receiver operating characteristic (ROC) curve and area under the curve (AUC) were used to study the potential of lncRNAs as biomarkers.

RESULTS

The differential expression profiles of plasma showed that 514 lncRNAs were upregulated, whereas 499 lncRNAs were downregulated.We found that the lncRNAs AL133415.1, AC020916.1, ENST00000654948, ASMTL-AS, AC005730.3, and AP001363.1 levels in the plasma of the AD patients were significantly lower compared to the control group (p1 = 0.0006, p2 < 0.001, p3 < 0.001, p4 = 0.039, p5 = 0.006, p6 < 0.001, respectively). ROC curve analysis revealed that the AUC of AL133415.1 was 0.635 (95% CI]: 0.507-0.763, p = 0.036), the AUC of ASMTL-AS1 was 0.658 (95% CI: 0.513-0.785, p = 0.015), the AUC of AC005730.3 was 0.627 (95%CI: 0.498-0.756, p = 0.049), and the AUC of AP001363.1 was 0.708 (95%CI: 0.595-0.822, p = 0.001).

CONCLUSION

This study indicated that the plasma levels of the lncRNAs ASMTL-AS1, AP001363.1, AC005730.3, and AL133415.1 might be considered potential biomarkers for AD in the Chinese Population.

Circadian rhythm sleep disorders and time-of-day-dependent memory deficiency in Presenilin1/2 conditional knockout mice with long noncoding RNA expression profiling changes

Alzheimer's disease (AD) patients exhibit sleep and circadian disturbances prior to the onset of cognitive decline, and these disruptions worsen with disease severity. However, the molecular mechanisms behind sleep and circadian disruptions in AD patients are poorly understood. In this study, we investigated sleep pattern and circadian rhythms in Presenilin-1/2 conditional knockout (DKO) mice. Assessment of EEG and EMG recordings showed that DKO mice displayed increased NREM sleep time but not REM sleep during the dark phase compared to WT mice at the age of two months; at the age of six months, the DKO mice showed increased wakefulness periods and decreased total time spent in both NREM and REM sleep. WT exhibited time-of-day dependent modulation of contextual and cued memory. Compared with WT mice, 4-month-old DKO mice exhibited the deficiency regardless trained and tested in the same light/night phase or not. Particularly interesting was that DKO showed circadian modulation deficiency when trained in the resting period but not in the active period. Long noncoding RNAs (lncRNAs) are typically defined as transcripts longer than 200 nucleotides, and they have rhythmic expression in mammals. To date no study has investigated rhythmic lncRNA expression in Alzheimer's disease. We applied RNA-seq technology to profile hippocampus expression of lncRNAs in DKO mice during the light (/resting) and dark (/active) phases and performed gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses of the cis lncRNA targets. Expression alteration of lncRNAs associated with immune response and metallodipeptidase activity may contribute to the circadian disruptions of DKO mice. Especially we identified some LncRNAs which expression change oppositely between day and light in DKO mice compared to WT mice and are worthy to be studied further. Our results exhibited the circadian rhythm sleep disorders and a noteworthy time-of-day-dependent memory deficiency in AD model mice and provide a useful resource for studying the expression and function of lncRNAs during circadian disruptions in Alzheimer's disease.

Construction of lncRNA-ceRNA networks to reveal the potential role of Lfng/Notch1 signaling pathway in Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) develops through a complex pathological process, in which many genes play a synergistic or antagonistic role. LncRNAs represent a kind of non-coding RNA, which can regulate gene expression at the epigenetic, transcriptional and post-transcriptional levels. Multiple lncRNAs have been found to have important regulatory functions in AD. Thus, their expression patterns, targets and functions should be explored as therapeutic targets.

METHODS

We used deep RNA-seq analysis to detect the dysregulated lncRNAs in the hippocampus of APP/PS1 mice. We performed Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses to predict the biological roles and potential signaling pathways of dysregulated lncRNAs. Finally, we constructed lncRNA-miRNA-mRNA and lncRNA-mRNA co-expression networks to reveal the potential regulator roles in AD pathogenesis.

RESULTS

Our findings revealed 110 significantly dysregulated lncRNAs. GO and KEGG annotations showed the dysregulated lncRNAs to be closely related to the functions of axon and protein digestion and absorption. The lncRNA-mRNA network showed that 19 lncRNAs regulated App, Prnp, Fgf10 and Il33, while 5 lncRNAs regulated Lfng via the lncRNA-miR-3102-3p-Lfng axis. Furthermore, we preliminarily demonstrated the important regulatory role of the Lfng/Notch1 signaling pathway through lncRNA-ceRNA networks in AD.

CONCLUSION

We revealed the important regulatory roles of dysregulated lncRNAs in the etiopathogenesis of AD through lncRNA expression profiling. Our results showed that the mechanism involves the regulation of the Lfng/Notch1 signaling pathway.

Assessing spermatozoal small ribonucleic acids and their relationship to blastocyst development in idiopathic infertile males

Clinical testing strategies for diagnosing male factor infertility are limited. A deeper analysis of spermatozoa-derived factors could potentially diagnose some cases of 'unexplained infertility'. Spermatozoa carry a rich and dynamic profile of small RNAs, which have demonstrated potential developmental importance and association with fertility status. We used next-generation sequencing to correlate sperm small RNA profiles of normozoospermic males (n = 54) with differing blastocyst development rates, when using young donor oocytes. While ribosomal RNAs accounted for the highest number of sequencing reads, transfer RNA fragments of tRNA^Gly/GCC and tRNA^Val-CAC were the most abundant sequences across all sperm samples. A total of 324 small RNAs were differentially expressed between samples with high (n = 18) and low (n = 14) blastocyst rates (p-adj < 0.05). Ninety three miRNAs were differentially expressed between these groups (p-adj < 0.05). Differentially expressed transfer RNA fragments included: 5'-tRF-Asp-GTC; 5'-tRF-Phe-GAA; and 3'-tRF-Ser-GCA. Differentially expressed miRNAs included: let-7f-2-5p; miR-4755-3p; and miR-92a-3p. This study provides the foundation on which to validate a clinical panel of fertility-related sperm small RNAs, as well as to pursue potential mechanisms through which they alter blastocyst development.

Long Non-Coding RNAs, Extracellular Vesicles and Inflammation in Alzheimer's Disease

Alzheimer's Disease (AD) has currently no effective treatment; however, preventive measures have the potential to reduce AD risk. Thus, accurate and early prediction of risk is an important strategy to alleviate the AD burden. Neuroinflammation is a major factor prompting the onset of the disease. Inflammation exerts its toxic effect via multiple mechanisms. Amongst others, it is affecting gene expression via modulation of non-coding RNAs (ncRNAs), such as miRNAs. Recent evidence supports that inflammation can also affect long non-coding RNA (lncRNA) expression. While the association between miRNAs and inflammation in AD has been studied, the role of lncRNAs in neurodegenerative diseases has been less explored. In this review, we focus on lncRNAs and inflammation in the context of AD. Furthermore, since plasma-isolated extracellular vesicles (EVs) are increasingly recognized as an effective monitoring strategy for brain pathologies, we have focused on the studies reporting dysregulated lncRNAs in EVs isolated from AD patients and controls. The revised literature shows a positive association between pro-inflammatory lncRNAs and AD. However, the reports evaluating lncRNA alterations in EVs isolated from the plasma of patients and controls, although still limited, confirm the value of specific lncRNAs associated with AD as reliable biomarkers. This is an emerging field that will open new avenues to improve risk prediction and patient stratification, and may lead to the discovery of potential novel therapeutic targets for AD.

Nutrigenomic Studies on the Ameliorative Effect of Enzyme-Digested Phycocyanin in Alzheimer's Disease Model Mice

Alzheimer’s disease (AD) is the most common form of dementia, and the cognitive impairments associated with this degenerative disease seriously affect daily life. Nutraceuticals for the prevention or delay of AD are urgently needed. It has been increasingly observed that phycocyanin (PC) exerts neuroprotective effects. AD model mice intracerebroventricularly injected with amyloid beta-peptide 25–35 (Aβ_25–35) at 10 nmol/head displayed significant cognitive impairment in the spontaneous alternation test. Cognitive impairment was significantly ameliorated in mice treated with 750 mg/kg of enzyme-digested (ED) PC by daily oral administration for 22 consecutive days. Application of DNA microarray data on hippocampal gene expression to nutrigenomics studies revealed that oral EDPC counteracted the aberrant expression of 35 genes, including Prnp, Cct4, Vegfd (Figf), Map9 (Mtap9), Pik3cg, Zfand5, Endog, and Hbq1a. These results suggest that oral administration of EDPC ameliorated cognitive impairment in AD model mice by maintaining and/or restoring normal gene expression patterns in the hippocampus.

Long non-coding RNA: An underlying bridge linking neuroinflammation and central nervous system diseases

Central nervous system (CNS) diseases are responsible for a large proportion of morbidity and mortality worldwide. CNS diseases caused by intrinsic and extrinsic stimuli stimulate the resident immune cells including microglia and astrocyte, resulting in neuroinflammation that exacerbates the progression of diseases. Recent evidence reveals the aberrant expression patterns of long non-coding RNAs (lncRNAs) in the damaged tissues following CNS diseases. It was also proposed that lncRNAs possessed immune-modulatory activities by directly or indirectly affecting various effector proteins including transcriptional factor, acetylase, protein kinase, phosphatase, etc. In addition, lncRNAs can form a sophisticated network by interacting with other molecules to regulate the expression or activation of downstream immune response pathways. However, the major roles of lncRNAs in CNS pathophysiologies are still elusive, especially in neuroinflammation. Herein, we tend to review some potential roles of lncRNAs in modulating neuroinflammation based on current evidence in various CNS diseases, in order to provide novel explanations for the initiation and progression of CNS diseases and help to establish therapeutic strategies targeting neuroinflammation.