Dopamine Transmission Imbalance in Neuroinflammation: Perspectives on Long-Term COVID-19

Neurological, psychological, psychosocial complications of long-COVID and their management

Since it first appeared, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has had a significant and lasting negative impact on the health and economies of millions of individuals all over the globe. At the level of individual health too, many patients are not recovering fully and experiencing a long-term condition now commonly termed 'long-COVID'. Long-COVID is a collection of symptoms which must last more than 12 weeks following initial COVID infection, and which cannot be adequately explained by alternate diagnoses. The neurological and psychosocial impact of long-COVID is itself now a global health crisis and therefore preventing, diagnosing, and managing these patients is of paramount importance. This review focuses primarily on: neurological functioning deficits; mental health impacts; long-term mood problems; and associated psychosocial issues, among patients suffering from long-COVID with an eye towards the neurological basis of these symptoms. A concise account of the clinical relevance of the neurological and psychosocial impacts of long-COVID, the effects on long-term morbidity, and varied approaches in managing patients with significant chronic neurological symptoms and conditions was extracted from the literature, analysed and reported. A comprehensive account of plausible pathophysiological mechanisms involved in the development of long-COVID, its management, and future research needs have been discussed.

Prevalence and associated risk factors of post COVID fatigue among Parkinson's disease patients during one year follow up

One of the most common post-COVID-19 condition is persistent fatigue, while post-COVID fatigue among Parkinson's disease (PD) patients is less known. This study was aimed to investigate the prevalence and risk factors of post-COVID fatigue in PD patients at 1 month and 12 months after symptom onset. PD patients attending clinic from December 2022 to January 2023 were enrolled consecutively in the study. All participants were assessed demographics, details of COVID-19 infection, clinical characteristics as well as fatigue status with Fatigue Severity Scale (FSS) (cutoff ≥ 36) at 1-month and 12-month after symptom onset. Univariate and multivariate Logistic regression analysis were used to evaluate the risk factors of post-COVID fatigue. Fatigue symptoms were reported by 75.89% of PD patients and associated with decreased physical activity and number of initial symptoms of COVID-19 at 1 month. Meanwhile, 32.99% of PD patients at 12 months reported persistent fatigue. Using of antiviral drugs, decreased physical activity, anxiety status and delayed ON were associated with persistent fatigue at 12 months. Clinically persistent fatigue was pervasive in our study at 12-month after COVID infection. These findings implicate using of antiviral drugs, decreased physical activity, anxiety status and delayed ON were possible predictors of post-COVID persistent fatigue.

Alterations in Striatal Architecture and Biochemical Markers' Levels During Postnatal Development in the Rat Model of an Attention Deficit/Hyperactivity Disorder (ADHD)

Attention deficit/hyperactivity disorder (ADHD) is defined as a neurodevelopmental condition. The precise underlying mechanisms remain incompletely elucidated. A body of research suggests disruptions in both the cellular architecture and neuronal function within the brain regions of individuals with ADHD, coupled with disturbances in the biochemical parameters. This study seeks to evaluate the morphological characteristics with a volume measurement of the striatal regions and a neuron density assessment within the studied areas across different developmental stages in Spontaneously Hypertensive Rats (SHRs) and Wistar Kyoto Rats (WKYs). Furthermore, the investigation aims to scrutinize the levels and activities of specific markers related to immune function, oxidative stress, and metabolism within the striatum of juvenile and maturing SHRs compared to WKYs. The findings reveal that the most pronounced reductions in striatal volume occur during the juvenile stage in SHRs, alongside alterations in neuronal density within these brain regions compared to WKYs. Additionally, SHRs exhibit heightened levels and activities of various markers, including RAC-alpha serine/threonine-protein kinase (AKT-1), glucocorticoid receptor (GCsRβ), malondialdehyde (MDA), sulfhydryl groups (-SH), glucose (G), iron (Fe), lactate dehydrogenase (LDH). alanine transaminase (ALT), and aspartate transaminase (AST). In summary, notable changes in striatal morphology and elevated levels of inflammatory, oxidative, and metabolic markers within the striatum may be linked to the disrupted brain development and maturation observed in ADHD.

Long Neuro-COVID-19: Current Mechanistic Views and Therapeutic Perspectives

Long-lasting COVID-19 (long COVID) diseases constitute a real life-changing burden for many patients around the globe and, overall, can be considered societal and economic issues. They include a variety of symptoms, such as fatigue, loss of smell (anosmia), and neurological-cognitive sequelae, such as memory loss, anxiety, brain fog, acute encephalitis, and stroke, collectively called long neuro-COVID-19 (long neuro-COVID). They also include cardiopulmonary sequelae, such as myocardial infarction, pulmonary damage, fibrosis, gastrointestinal dysregulation, renal failure, and vascular endothelial dysregulation, and the onset of new diabetes, with each symptom usually being treated individually. The main unmet challenge is to understand the mechanisms of the pathophysiologic sequelae, in particular the neurological symptoms. This mini-review presents the main mechanistic hypotheses considered to explain the multiple long neuro-COVID symptoms, namely immune dysregulation and prolonged inflammation, persistent viral reservoirs, vascular and endothelial dysfunction, and the disruption of the neurotransmitter signaling along various paths. We suggest that the nucleoprotein N of SARS-CoV-2 constitutes a "hub" between the virus and the host inflammation, immunity, and neurotransmission.

Interplay between endocannabinoids and dopamine in the basal ganglia: implications for pain in Parkinson's disease

Pain is a complex phenomenon, and basal ganglia circuitry integrates many aspects of pain including motor, emotional, autonomic, and cognitive responses. Perturbations in dopamine (DA) signaling are implicated in the pathogenesis of chronic pain due to its involvement in both pain perception and relief. Several lines of evidence support the role of endocannabinoids (eCBs) in the regulation of many electrical and chemical aspects of DAergic neuron function including excitability, synaptic transmission, integration, and plasticity. However, eCBs play an even more intricate and intimate relationship with DA, as indicated by the adaptive changes in the eCB system following DA depletion. Although the precise mechanisms underlying DA control on pain are not fully understood, given the high correlation of eCB and DAergic system, it is conceivable that eCBs may be part of these mechanisms.In this brief survey, we describe the reciprocal regulation of eCB-DA neurotransmission with a particular emphasis on the actions of eCBs on ionic and synaptic signaling in DAergic neurons mediated by CB receptors or independent on them. Furthermore, we analyze the eCB-DA imbalance which characterizes pain condition and report the implications of reduced DA levels for pain in Parkinson's disease. Lastly, we discuss the potential of the eCB-DA system in the development of future therapeutic strategies for the treatment of pain.

Long-COVID-19 autonomic dysfunction: An integrated view in the framework of inflammaging

The recently identified syndrome known as Long COVID (LC) is characterized by a constellation of debilitating conditions that impair both physical and cognitive functions, thus reducing the quality of life and increasing the risk of developing the most common age-related diseases. These conditions are linked to the presence of symptoms of autonomic dysfunction, in association with low cortisol levels, suggestive of reduced hypothalamic-pituitary-adrenal (HPA) axis activity, and with increased pro-inflammatory condition. Alterations of dopamine and serotonin neurotransmitter levels were also recently observed in LC. Interestingly, at least some of the proposed mechanisms of LC development overlap with mechanisms of Autonomic Nervous System (ANS) imbalance, previously detailed in the framework of the aging process. ANS imbalance is characterized by a proinflammatory sympathetic overdrive, and a concomitant decreased anti-inflammatory vagal parasympathetic activity, associated with reduced anti-inflammatory effects of the HPA axis and cholinergic anti-inflammatory pathway (CAP). These neuro-immune-endocrine system imbalanced activities fuel the vicious circle of chronic inflammation, i.e. inflammaging. Here, we refine our original hypothesis that ANS dysfunction fuels inflammaging and propose that biomarkers of ANS imbalance could also be considered biomarkers of inflammaging, recognized as the main risk factor for developing age-related diseases and the sequelae of viral infections, i.e. LC.

The effects of COVID-19 infection on working memory: a systematic review

BACKGROUND

Studies demonstrate that people who have been infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, have experienced cognitive dysfunction, including working memory impairment, executive dysfunction, and decreased concentration. This review aimed to explore the incidence of working memory impairment and possible concomitant symptoms in the acute phase (< 3 months) and chronic phase (> 6 months) of COVID-19.

METHODS

We conducted a systematic review of the following databases for inception: MEDLINE via Pub Med, Cochrane EMBASE, and Web of Science electronic databases. The search strategy was comprised of all the observational studies with COVID-19 patients confirmed by PCR or serology who were infected by SARS-CoV-2 with no previous cognitive impairment. This review protocol was recorded on PROSPERO with registration number CRD 42023413454.

RESULTS

A total of 16 studies from 502 retrieved articles were included. COVID-19 could cause a decline in working memory ability, the results showed that 22.5-55% of the people suffered from working memory impairment in the acute phase (< 3 months) of COVID-19, at 6 months after SARS-CoV2 infection, the impairment of working memory caused by COVID-19 still existed, the prevalence was about 6.2-10%, and 41.1% of the patients had a slight decrease in working memory or a negative change in the boundary value. Moreover, concomitant symptoms could persist for a long time. To some extent, the performance of working memory was affected by age, the time after infection, and the severity of infection (β = -.132, p <.001; β = .098, p <.001; β = .075, p = .003). The mechanism of working memory impairment after infection was mainly focused on the aspects of neuroinflammation and the nerve invasiveness of the virus; at the same time, we also noticed some changes of the brain parenchymal structure.

CONCLUSION

COVID-19 can cause a decline in working memory ability, accompanied by neurological symptoms. However, there is a lack of studies to identify the structural and functional changes in specific brain regions that relate to the impaired working memory.

Olfactory Epithelium Infection by SARS-CoV-2: Possible Neuroinflammatory Consequences of COVID-19

BACKGROUND

The loss of smell is a typical diagnostic symptom of coronavirus disease 2019 (COVID-19). This sensorial deprivation may be expressed as quantitative (anosmia or hyposmia) or qualitative (dysosmia) alterations as a consequence of anatomical disturbances of the nasal epithelium structure. The olfactory system sends direct neuronal connections to brain structures that are involved in emotional processing, including deep temporal nuclei. This anatomical and functional feature may be related to the occurrence of emotional disorders among COVID-19 patients.

SUMMARY

We identify a possible sequence of events, from typical olfactory dysfunction that is associated with COVID-19 and caused by olfactory epithelium damage to disturbances in the quality of life and emotional state of infected patients that is attributable to possible neuroinflammatory processes. Sensorial deprivation causes deleterious actions on mood, negatively affecting quality of life. Olfactory dysfunction that is associated with COVID-19 occurs concurrently with psychological distress, symptoms of anxiety, and depressive disorders and impinges on self-perceived quality of life.

KEY MESSAGES

Changes in mood are certainly associated with multiple factors, including the environment and isolation, but the observation that the virus may penetrate the central nervous system through the olfactory bulb and the connection between the olfactory system and prefrontal and orbitofrontal cortices and the amygdala-hippocampus do not allow one to discard neural factors that are involved in the pathophysiology of emotional symptoms in post-COVID-19 patients. Behavioral symptoms of COVID-19 involve local olfactory actions and the participation of central neuronal systems.