SARS-CoV-2 amyloid, is COVID-19-exacerbated dementia an amyloid disorder in the making?

Amyloidogenesis of SARS-CoV-2 delta plus and omicron variants receptor-binding domain (RBD): impact of SUMO fusion tag

PURPOSE

The RBD of SARS-CoV-2 mediates viral entry into host cells by binding to the host receptor ACE2. SARS-CoV-2 infection is linked to various health issues resembling amyloid-related problems, persuading us to investigate the amyloidogenicity of the SARS-CoV-2 spike RBD.

METHODS

The FoldAmyloid program was used to assess the amyloidogenic propensities in the RBD of Delta Plus and RBD of the Omicron variant, with and without the SUMO tag. After the expression of RBDs, purification, and dialysis steps were performed, subsequently the ThT assay, FTIR, and TEM were employed to check the RBD ability to form fibrils.

RESULTS

The ThT assay, TEM, and FTIR revealed the ability of RBD to self-assemble into β-sheet-rich aggregates (48.4% β-sheet content). Additionally, the presence of the SUMO tag reduced the formation of RBD amyloid-like fibrils. The amyloidogenic potential of Omicron RBD was higher than Delta Plus, according to both in silico and experimental analyses.

CONCLUSIONS

The SARS-CoV-2 RBD can assemble itself by forming aggregates containing amyloid-like fibrils and the presence of a SUMO tag can significantly decrease the formation of RBD amyloid-like fibrils. In silico analysis suggested that variation in the ThT fluorescence intensity of amyloid accumulations in the two SARS-CoV-2 strains arises from specific mutations in their RBD regions.

Plasmalogens Improve Lymphatic Clearance of Amyloid Beta from Mouse Brain and Cognitive Functions

Amyloid beta (Aβ) is a neuronal metabolic product that plays an important role in maintaining brain homeostasis. Normally, intensive brain Aβ formation is accompanied by its effective lymphatic removal. However, the excessive accumulation of brain Aβ is observed with age and during the development of Alzheimer's disease (AD) leading to cognitive impairment and memory deficits. There is emerging evidence that plasmalogens (Pls), as one of the key brain lipids, may be beneficial for AD and cognitive aging. Here, we studied the effects of Pls on cognitive functions and the lymphatic clearance of Aβ from the brain of AD mice and mice of different ages. The results showed that Pls effectively reduce brain Aβ levels and facilitate learning in aged but not old mice. In AD mice, Pls improve the lymphatic clearance of Aβ that is accompanied by an increase in general motor activity and an improvement of the emotional status and learning ability. Thus, these findings suggest that Pls could be a promising candidate for the alternative or concomitant therapy of AD and age-related brain diseases to enhance the lymphatic clearance of Aβ from the brain and cognitive functions.

Parallel electrophysiological abnormalities due to COVID-19 infection and to Alzheimer's disease and related dementia

Many coronavirus disease 2019 (COVID-19) positive individuals exhibit abnormal electroencephalographic (EEG) activity reflecting "brain fog" and mild cognitive impairments even months after the acute phase of infection. Resting-state EEG abnormalities include EEG slowing (reduced alpha rhythm; increased slow waves) and epileptiform activity. An expert panel conducted a systematic review to present compelling evidence that cognitive deficits due to COVID-19 and to Alzheimer's disease and related dementia (ADRD) are driven by overlapping pathologies and neurophysiological abnormalities. EEG abnormalities seen in COVID-19 patients resemble those observed in early stages of neurodegenerative diseases, particularly ADRD. It is proposed that similar EEG abnormalities in Long COVID and ADRD are due to parallel neuroinflammation, astrocyte reactivity, hypoxia, and neurovascular injury. These neurophysiological abnormalities underpinning cognitive decline in COVID-19 can be detected by routine EEG exams. Future research will explore the value of EEG monitoring of COVID-19 patients for predicting long-term outcomes and monitoring efficacy of therapeutic interventions. HIGHLIGHTS: Abnormal intrinsic electrophysiological brain activity, such as slowing of EEG, reduced alpha wave, and epileptiform are characteristic findings in COVID-19 patients. EEG abnormalities have the potential as neural biomarkers to identify neurological complications at the early stage of the disease, to assist clinical assessment, and to assess cognitive decline risk in Long COVID patients. Similar slowing of intrinsic brain activity to that of COVID-19 patients is typically seen in patients with mild cognitive impairments, ADRD. Evidence presented supports the idea that cognitive deficits in Long COVID and ADRD are driven by overlapping neurophysiological abnormalities resulting, at least in part, from neuroinflammatory mechanisms and astrocyte reactivity. Identifying common biological mechanisms in Long COVID-19 and ADRD can highlight critical pathologies underlying brain disorders and cognitive decline. It elucidates research questions regarding cognitive EEG and mild cognitive impairment in Long COVID that have not yet been adequately investigated.

Thyroid Malignancy and Cutaneous Lichen Amyloidosis: Key Points Amid RET Pathogenic Variants in Medullary Thyroid Cancer/Multiple Endocrine Neoplasia Type 2 (MEN2)

We aimed to provide an updated narrative review with respect to the RET pathogenic variants and their implications at the clinical and molecular level in the diagnosis of medullary thyroid cancer (MTC)/multiple endocrine neoplasia (MEN) type 2, particularly with respect to the presence of cutaneous lichen amyloidosis (CLA). We searched English-language, in extenso original articles with no timeline nor study design restriction that were published on PubMed. A traditional interplay stands for CLA and MTC in MEN2 (not MEN3) confirmation. While the connection has been reported for more than three decades, there is still a large gap in understanding and addressing it. The majority of patients with MEN2A-CLA have RET pathogenic variants at codon 634; hence, it suggests an involvement of this specific cysteine residue in both disorders (most data agree that one-third of C634-positive subjects have CLA, but the ranges are between 9% and 50%). Females seem more prone to MEN2-CLA than males. Non-C634 germline RET pathogenic variants included (at a low level of statistical evidence) the following: RET V804M mutation in exon 14 for MTC-CLA (CLA at upper back); RET S891A mutation in exon 15 binding OSMR variant G513D (familial MTC and CLA comprising the lower legs to thighs, upper back, shoulders, arms, and forearms); and C611Y (CLA at interscapular region), respectively. Typically, CLA is detected at an early age (from childhood until young adulthood) before the actual MTC identification unless RET screening protocols are already applied. The time frame between CLA diagnosis and the identification of RET pathogenic variants was between 5 and 60 years according to one study. The same RET mutation in one family is not necessarily associated with the same CLA presentation. In MTC/MEN2 subjects, the most affected CLA area was the scapular region of the upper back. Alternatively, another hypothesis highlighted the fact that CLA is secondary to long-term prurit/notalgia paresthetica (NP) in MTC/MEN2. OSMR p. G513D may play a role in modifying the evolutionary processes of CLA in subjects co-harboring RET mutations (further studies are necessary to sustain this aspect). Awareness in CLA-positive patients is essential, including the decision of RET testing in selected cases.

Promising Strategies to Reduce the SARS-CoV-2 Amyloid Deposition in the Brain and Prevent COVID-19-Exacerbated Dementia and Alzheimer's Disease

The COVID-19 pandemic, caused by infection with the SARS-CoV-2 virus, is associated with cognitive impairment and Alzheimer's disease (AD) progression. Once it enters the brain, the SARS-CoV-2 virus stimulates accumulation of amyloids in the brain that are highly toxic to neural cells. These amyloids may trigger neurological symptoms in COVID-19. The meningeal lymphatic vessels (MLVs) play an important role in removal of toxins and mediate viral drainage from the brain. MLVs are considered a promising target to prevent COVID-19-exacerbated dementia. However, there are limited methods for augmentation of MLV function. This review highlights new discoveries in the field of COVID-19-mediated amyloid accumulation in the brain associated with the neurological symptoms and the development of promising strategies to stimulate clearance of amyloids from the brain through lymphatic and other pathways. These strategies are based on innovative methods of treating brain dysfunction induced by COVID-19 infection, including the use of photobiomodulation, plasmalogens, and medicinal herbs, which offer hope for addressing the challenges posed by the SARS-CoV-2 virus.

Exploring the Potential Long-term Impact of SARS-CoV-2 on Protein Misfolding and Amyloid-related Conditions

The long-term impact of the COVID-19 pandemic concerns risk to human health, particularly its potential association with protein misfolding and amyloidosis. This review article explores the causality relationship between SARS-CoV-2 infection, and protein misfolding, leading to amyloid-related conditions. It delves into the mechanisms by which viral proteins may accelerate amyloid formation, exacerbating post-infection complications, including neurological sequelae. Drawing from interdisciplinary research and clinical observations, the potential links between COVID-19, vaccination, and amyloidosis, emphasize the importance of understanding the longterm effect of post-COVID symptoms. This review examines the potential role of COVID-19-related proteins in the formation of amyloid in other related proteins of amyloidosis.