Plasma MicroRNAs Are Altered Early and Consistently in a Mouse Model of Tauopathy

Pathogenesis of miR-155 on nonmodifiable and modifiable risk factors in Alzheimer's disease

Alzheimer's disease (AD) is a common age-related neurodegenerative disease in the central nervous system and is the primary cause of dementia. It is clinically characterized by the memory impairment, aphasia, apraxia, agnosia, visuospatial and executive dysfunction, behavioral changes, and so on. Incidence of this disease was bound up with age, genetic factors, cardiovascular and cerebrovascular dysfunction, and other basic diseases, but the exact etiology has not been clarified. MicroRNAs (miRNAs) are small endogenous non-coding RNAs that were involved in the regulation of post-transcriptional gene expression. miRNAs have been extensively studied as noninvasive potential biomarkers for disease due to their relative stability in bodily fluids. In addition, they play a significant role in the physiological and pathological processes of various neurological disorders, including stroke, AD, and Parkinson's disease. MiR-155, as an important pro-inflammatory mediator of neuroinflammation, was reported to participate in the progression of β-amyloid peptide and tau via regulating immunity and inflammation. In this review, we put emphasis on the effects of miR-155 on AD and explore the underlying biological mechanisms which could provide a novel approach for diagnosis and treatment of AD.

Physical Enrichment Triggers Brain Plasticity and Influences Blood Plasma Circulating miRNA in Rainbow Trout (Oncorhynchus mykiss)

Physical enrichment is known to improve living conditions of fish held in farming systems and has been shown to promote behavioral plasticity in captive fish. However, the brain's regulatory-mechanism systems underlying its behavioral effects remain poorly studied. The present study investigated the impact of a three-month exposure to an enriched environment (EE vs. barren environment, BE) on the modulation of brain function in rainbow trout (Oncorhynchus mykiss) juveniles. Using high-throughput RT-qPCR, we assessed mRNA genes related to brain function in several areas of the trout brain. These included markers of cerebral activity and plasticity, neurogenesis, synaptogenesis, or selected neurotransmitters pathways (dopamine, glutamate, GABA, and serotonin). Overall, the fish from EE displayed a series of differentially expressed genes (neurotrophic, neurogenesis, and synaptogenesis markers) essentially localized in the telencephalon, which could underpin the beneficial effects of complexifying the environment on fish brain plasticity. In addition, EE significantly affected blood plasma c-miRNA signatures, as revealed by the upregulation of four c-miRNAs (miR-200b/c-3p, miR-203a-3p, miR-205-1a-5p, miR-218a-5p) in fish blood plasma after 185 days of EE exposure. Overall, we concluded that complexifying the environment through the addition of physical structures that stimulate and encourage fish to explore promotes the trout's brain function in farming conditions.

Promotive role of microRNA‑150 in hippocampal neurons apoptosis in vascular dementia model rats

Cognitive impairment is one of the primary features of vascular dementia (VD). However, the specific mechanism underlying the regulation of cognition function in VD is not completely understood. The present study aimed to explore the effects of microRNA (miR)‑150 on VD. To determine the effects of miR‑150 on cognitive function and hippocampal neurons in VD model rats, rats were subjected to intracerebroventricular injections of miR‑150 antagomiR. The Morris water maze test results demonstrated that spatial learning ability was impaired in VD model rats compared with control rats. Moreover, compared with antagomiR negative control (NC), miR‑150 antagomiR alleviated cognitive impairment and enhanced memory ability in VD model rats. The triphenyltetrazolium chloride, Nissl staining and immunohistochemistry results further demonstrated that miR‑150 knockdown improved the activity of hippocampal neurons in VD model rats compared with the antagomiR NC group. To validate the role of miR‑150 in neurons in vitro, the PC12 cell line was used. The flow cytometry and Hoechst 33342/PI double staining results indicated that miR‑150 overexpression significantly increased cell apoptosis compared with the mimic NC group. Moreover, the dual‑luciferase reporter gene assay results indicated that miR‑150 targeted HOXA1 and negatively regulated HOXA1 expression. Therefore, the present study indicated that miR‑150 knockdown ameliorated VD symptoms by upregulating HOXA1 expression in vivo and in vitro.

MicroRNAs Modulate the Pathogenesis of Alzheimer's Disease: An In Silico Analysis in the Human Brain

MicroRNAs (miRNAs) are small RNAs involved in the post-transcriptional regulation of their target genes, causing a decrease in protein translation from the mRNA. Different miRNAs are found in the nervous system, where they are involved in its physiological functions, but altered miRNAs expression was also reported in neurodegenerative disorders, including Alzheimer's disease (AD). AD is characterized by memory loss, cognitive function abnormalities, and various neuropsychiatric disturbances. AD hallmarks are amyloid β (Aβ) aggregates, called senile plaques, and neurofibrillary tangles (NFTs) formed by hyperphosphorylated Tau protein. In this study, we performed an in silico analysis to evaluate altered patterns of miRNAs expression in the brains of AD patients compared to healthy subjects. We found 12 miRNAs that were differentially expressed in AD compared to healthy individuals. These miRNAs have target genes involved in AD pathogenesis. In particular, some miRNAs influence Aβ production, having as target secretase and amyloid precursor protein (APP). Some miRNAs were reported to be involved in nervous system functions, and their alteration can cause neuronal dysfunction.