[Modern conception of the pathogenesis of neurodegenerative diseases and therapeutic strategy]

[Traumatic brain injury as risk factor of Alzheimer's disease and possibilities of pathogenetic therapy]

The article examines the potential role of brain mechanical damage as a trigger for the development of neurodegenerative changes. Attention is paid to dysfunction of the neurovascular unit, and disruption of the functional and compensatory capabilities of blood flow. The importance of microhemorrhages that occur in the acute period of injury and the formation of first focal and then diffuse neuroinflammation is emphasized. The importance of mitochondrial dysfunction was separately determined as a significant factor in increasing the risk of developing Alzheimer's disease (AD) in patients after traumatic brain injury (TBI). In TBI, there is a decrease in the expression of tight junction (TC) proteins of endothelial cells, such as occludin, claudin, JP, which leads to increased permeability of the blood-brain barrier. TBI, provoking endothelial dysfunction, contributes to the development of metabolic disorders of β-amyloid and tau protein, which in turn leads to worsening vascular damage, resulting in a vicious circle that can ultimately lead to the development of AD and dementia. Age-related changes in cerebral arteries, which impair perivascular transport of interstitial fluid, are currently considered as an important part of the «amyloid cascade», especially against the background of genetically mediated disorders of glial membranes associated with defective aquaporin-4 (encoded by the APOE4). Studies in animal models of TBI have revealed an increase in tau protein immunoreactivity and its phosphorylation, which correlates with the severity of injury. A comprehensive analysis of research results shows that the cascade of reactions triggered by TBI includes all the main elements of the pathogenesis of AD: disorders of energy metabolism, microcirculation and clearance of cerebral metabolic products. This leads to a disruption in the metabolism of amyloid protein and its accumulation in brain tissue with the subsequent development of tauopathy. Cerebrolysin, by modulating the permeability of the blood-brain barrier, blocks the development of neuroinflammation, reduces the accumulation of pathological forms of proteins and may be slow down the progression of neurodegeneration.

[Psychological, psychiatric and neurological aspects of COVID-19]

OBJECTIVE

To analyze neurological, psychological and psychiatric aspects of COVID-19, as well as to study the current state of the problem.

MATERIAL AND METHODS

The study included 103 patients with COVID-19. The main research method was clinical/psychopathological. To study the impact of activities related to the care of patients with COVID-19 in a hospital setting, the medical and psychological state of 197 hospital workers involved in the treatment of patients with COVID-19 was assessed. The level of anxiety distress was assessed with the Psychological Stress Scale (PSM-25), distress indicators corresponded to values of more than 100 points. The severity of anxiety and depressive symptoms was assessed using the Hospital Anxiety and Depression Scale (HADS).

RESULTS

When considering psychopathological disorders in the context of COVID-19, it is necessary to distinguish between two main groups of disorders: mental disorders during the pandemic, and mental disorders directly caused by the causative agent SARS-CoV-2. The analysis of psychological and psychiatric aspects in various periods of the initial stage of COVID-19 showed that each of them was characterized by specific features depending on the nature of the influence of different pathogenic factors. In the structure of nosogenic mental disorders in patients with COVID-19 (103 patients), the following clinical forms were identified: acute reaction to stress (9.7%), anxiety-phobic disorders (41.7%), depressive symptoms (28.1%), hyponosognosic nosogenic reactions (20.5%). At the same time, the majority of the patients had manifestations of somatogenic asthenia (93.2%). A comparative analysis of neurological and psychological/psychiatric aspects of COVID-19 showed that the main mechanisms of the impact of highly contagious coronaviruses, including the SARS-CoV-2, on the central nervous system are: cerebral thrombosis and cerebral thromboembolism, damage to the neurovascular unit, neurodegeneration, including that induced by cytokines, and immune-mediated demyelinating nerve damage.

CONCLUSION

Neurological and psychological/psychiatric aspects of COVID-19 should be taken into account both at the stage of disease treatment and in the post-infection period due to the pronounced neurotropism of SARS-CoV-2 and its effect on the neurovascular unit. Along with helping patients, an important aspect is the preservation of the mental health of medical personnel working in hospitals for infectious diseases, due to special working conditions and a high level of professional stress.

On a New Paradigm of the Development of Neurodegenerative Diseases by the Example of Alzheimer’s Disease and Parkinson’s Disease

The role of neuronal inflammation developing during the formation of amyloid plaques and Lewy bodies is investigated. The influence of various exogenous and endogenous factors on the development of neuroinflammation is established, but the role of various infectious agents in the development of this process is much less studied. Today, the existence of a universal trigger mechanism of the neurodegenerative process is obvious: a specific pathogen of a bacterial or viral nature (including long-term persistent in nervous tissue in a latent state), reactivating, penetrates into certain cerebral structures, where it is influenced by either Aβ or resident macrophages of the central nervous system, which, in turn, are activated and induce the release of proinflammatory cytokines, leading to the development of neuronal inflammation, autophagy and neurodegeneration. The reactivation of latent infection, such as herpes, in APOE4 carriers significantly increases the risk of development of Alzheimer’s disease. Class-II genes of the HLA locus (HLA II) may be related to the progression of neurodegenerative diseases. An increase in iron levels in the glia is induced by inflammation, which leads to neurodegeneration. Disruption of the homeostasis of redox-active metals, iron and copper, is an integral part of the pathogenesis of Alzheimer’s disease and Parkinson’s disease. The developing neuroinflammation leads to intensification of the processes of peroxidation, oxidation of metals and the development of ferroptosis.

Downregulation of microRNA-15b-5p Targeting the Akt3-Mediated GSK-3β/β-Catenin Signaling Pathway Inhibits Cell Apoptosis in Parkinson's Disease

Parkinson's disease (PD) is an incurable progressive disorder resulting from neurodegeneration, and apoptosis is considered a dominant mechanism underlying the process of neurodegeneration. MicroRNAs (miRNAs), which are small and noncoding RNAs involved in many a biological process like apoptosis and regulation of gene expressions, have been found in postmortem brain samples of patients with PD, as well as in vitro and in vivo models of PD. To explore the impact of miR-15b-5p and Akt3 on apoptosis in the progression of PD, the method of quantitative reverse transcription polymerase chain reaction (qRT-PCR) was employed, and the analysis result showed upregulated expression of miR-15b-5p and downregulated expression of Akt3 in the serum of PD patients, MPP+-induced SH-SY5Y cells, and the brain tissues of MPTP-induced mice. Meanwhile, the dual-luciferase reporter assay was used to demonstrate the regulator-target interaction between miR-15b-5p and Akt3; flow cytometry and spectrophotometry revealed that transfection of miR-15b-5p mimic and si-Akt3 increased the rate of apoptosis and caspase-3 activity, whereas transfecting the miR-15b-5p inhibitor and Akt3-overexpression plasmid repressed the rate of apoptosis and caspase-3 activity in the MPP+-induced SH-SY5Y cell model and the MPTP-induced mouse model. Additionally, analysis of western blotting (WB) assays in vivo and in vitro revealed that proapoptosis proteins (Bax, caspase-3, GSK-3β, and β-catenin) showed markedly upregulated expression in the miR-15b-5p inhibitor and si-Akt3-overexpression groups, while the expression of an antiapoptosis gene (i.e., Bcl2) was downregulated. These analysis results indicate that downregulation of miR-15b-5p by targeting the Akt3-mediated GSK-3β/β-catenin signaling pathway would repress cell apoptosis in PD in vivo and in vitro. It is expected that the research findings would help find new therapeutic targets for treatment of PD.