Tag: review

Animal Models for Neuroinflammation and Potential Treatment Methods

Abstract:

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating chronic disease of unknown etiology and without effective treatment options. The onset of ME/CFS is often associated with neuroinflammation following bacterial or viral infection.

A positron emission tomography imaging study revealed that the degree of neuroinflammation was correlated with the severity of several symptoms in patients with ME/CFS. In animal studies, lipopolysaccharide- and polyinosinic-polycytidylic acid-induced models are thought to mimic the pathological features of ME/CFS and provoke neuroinflammation, characterized by increased levels of proinflammatory cytokines and activation of microglia.

In this review, we described the anti-inflammatory effects of three compounds on neuroinflammatory responses utilizing animal models. The findings of the included studies suggest that anti-inflammatory substances may be used as effective therapies to ameliorate disease symptoms in patients with ME/CFS.

Source: Tamura Y, Yamato M, Kataoka Y. Animal Models for Neuroinflammation and Potential Treatment Methods. Front Neurol. 2022 Jun 27;13:890217. doi: 10.3389/fneur.2022.890217. PMID: 35832182; PMCID: PMC9271866. https://pubmed.ncbi.nlm.nih.gov/35832182/  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9271866/ (Full study)

Could the kynurenine pathway be the key missing piece of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) complex puzzle?

Abstract:

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a complex and debilitating disease with a substantial social and economic impact on individuals and their community. Despite its importance and deteriorating impact, progresses in diagnosis and treatment of ME/CFS is limited. This is due to the unclear pathophysiology of the disease and consequently lack of prognostic biomarkers.

To investigate pathophysiology of ME/CFS, several potential pathologic hallmarks have been investigated; however, these studies have failed to report a consistent result. These failures in introducing the underlying reason for ME/CFS have stimulated considering other possible contributing mechanisms such as tryptophan (TRP) metabolism and in particular kynurenine pathway (KP).

KP plays a central role in cellular energy production through the production of nicotinamide adenine dinucleotide (NADH). In addition, this pathway has been shown to mediate immune response and neuroinflammation through its metabolites. This review, we will discuss the pathology and management of ME/CFS and provide evidence pertaining KP abnormalities and symptoms that are classic characteristics of ME/CFS. Targeting the KP regulation may provide innovative approaches to the management of ME/CFS.

Source: Kavyani B, Lidbury BA, Schloeffel R, Fisher PR, Missailidis D, Annesley SJ, Dehhaghi M, Heng B, Guillemin GJ. Could the kynurenine pathway be the key missing piece of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) complex puzzle? Cell Mol Life Sci. 2022 Jul 11;79(8):412. doi: 10.1007/s00018-022-04380-5. PMID: 35821534. https://link.springer.com/article/10.1007/s00018-022-04380-5  (Full text)

Post-infectious disease syndrome

Abstract:

Many post-infectious syndromes have been recognized in the last 50 years, some following viral infections and others closely related to bacterial disease. The occurrence of prolonged fatigue following an apparent viral illness of varying severity is also well documented. The lack of a recognizable precipitating cause and the tendency for epidemic fatigue to occur among hospital staff led many to believe that the illness may be psychogenic in origin. However, there is serological evidence that some cases may follow enterovirus infections or occasionally delayed convalescence from infectious mononucleosis. Much interesting work is currently in progress relating fatigue to persisting immunological abnormalities, and the development of molecular immunology makes this a most exciting field of research. This paper reviews the evidence for and against a definitive post-viral fatigue syndrome and examines the results of research carried out in the last 50 years.

Source: Bannister BA. Post-infectious disease syndrome. Postgrad Med J. 1988 Jul;64(753):559-67. doi: 10.1136/pgmj.64.753.559. PMID: 3074289; PMCID: PMC2428896.  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2428896/ (Full text)

Inflammation From Peripheral Organs to the Brain: How Does Systemic Inflammation Cause Neuroinflammation?

Abstract:

As inflammation in the brain contributes to several neurological and psychiatric diseases, the cause of neuroinflammation is being widely studied. The causes of neuroinflammation can be roughly divided into the following domains: viral infection, autoimmune disease, inflammation from peripheral organs, mental stress, metabolic disorders, and lifestyle. In particular, the effects of neuroinflammation caused by inflammation of peripheral organs have yet unclear mechanisms.

Many diseases, such as gastrointestinal inflammation, chronic obstructive pulmonary disease, rheumatoid arthritis, dermatitis, chronic fatigue syndrome, or myalgic encephalomyelitis (CFS/ME), trigger neuroinflammation through several pathways. The mechanisms of action for peripheral inflammation-induced neuroinflammation include disruption of the blood-brain barrier, activation of glial cells associated with systemic immune activation, and effects on autonomic nerves via the organ-brain axis. In this review, we consider previous studies on the relationship between systemic inflammation and neuroinflammation, focusing on the brain regions susceptible to inflammation.

Source: Sun Y, Koyama Y, Shimada S. Inflammation From Peripheral Organs to the Brain: How Does Systemic Inflammation Cause Neuroinflammation? Front Aging Neurosci. 2022 Jun 16;14:903455. doi: 10.3389/fnagi.2022.903455. PMID: 35783147; PMCID: PMC9244793. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9244793/ (Full text)

Neurological Sequelae of COVID-19

Abstract:

Background: Though primarily a pulmonary disease, Coronavirus disease 2019 (COVID-19) caused by the SARS-CoV-2 virus can generate devastating disease states that affect multiple organ systems including the central nervous system (CNS). The various neurological disorders associated with COVID-19 range in severity from mild symptoms such as headache, or myalgias to more severe symptoms such as stroke, psychosis, and anosmia. While some of the COVID-19 associated neurological complications are mild and reversible, a significant number of patients suffer from stroke. Studies have shown that COVID-19 infection triggers a wave of inflammatory cytokines that induce endothelial cell dysfunction and generate coagulopathy that increases the risk of stroke or thromboses. Inflammation of the endothelium following infection may also destabilize atherosclerotic plaque and induce thrombotic stroke. Although uncommon, there have also been reports of hemorrhagic stroke associated with COVID-19.

The proposed mechanisms include a blood pressure increase caused by infection leading to a reduction in angiotensin converting enzyme-2 (ACE-2) levels that results in an imbalance of the renin-angiotensin system ultimately manifesting inflammation and vasoconstriction. Coagulopathy, as demonstrated by elevated prothrombin time (PT), has also been posited as a factor contributing to hemorrhagics stroke in patients with COVID-19. Other neurological conditions associated with COVID-19 include encephalopathy, anosmia, encephalitis, psychosis, brain fog, headache, depression, and anxiety. Though there are several hypotheses reported in the literature, a unifying pathophysiological mechanism of many of these disorders remains unclear. Pulmonary dysfunction leading to poor oxygenation of the brain may explain encephalopathy and other disorders in COVID-19 patients. Alternatively, a direct invasion of the CNS by the virus or breach of the blood-brain barrier by the systemic cytokines released during infection may be responsible for these conditions. Notwithstanding, the relationship between the inflammatory cytokine levels and conditions such as depression and anxiety is contradictory and perhaps the social isolation during the pandemic may in part be a contributing factor to some of the reported CNS disorders.

Objective: In this article, we review the current literature pertaining to some of the most significant and common neurological disorders such as ischemic and hemorrhagic stroke, encephalopathy, encephalitis, brain fog, Long COVID, headache, Guillain-Barre syndrome, depression, anxiety, and sleep disorders in the setting of COVID-19. We summarize some of the most relevant literature to provide a better understanding of the mechanistic details regarding these disorders in order to help physicians monitor and treat patients for significant COVID-19 associated neurologic impairments.

Methods: A literature review was carried out by the authors using PubMed with the search terms “COVID-19” and “Neurology”, “Neurological Manifestations”, “Neuropsychiatric Manifestations”, “Stroke”, “Encephalopathy”, “Headache”, “Guillain-Barre syndrome”, “Depression”, “Anxiety”, “Encephalitis”, “Seizure”, “Spasm”, and “ICUAW”. Another search was carried out for “Long-COVID” and “Post-Acute COVID-19” and “Neurological Manifestations” or “Neuropsychiatric Manifestations”. Articles such as case reports, case series, and cohort studies were included as references. No language restrictions were enforced. In the case of anxiety and depression, attempts were made to focus mainly on articles describing these conditions in infected patients.

Results: A total of 112 articles were reviewed. The incidence, clinical outcomes, and pathophysiology of selected neurological disorders are discussed below. Given the recent advent of this disease, the incidence of certain neurologic sequelae was not always available. Putative mechanisms for each condition in the setting of COVID-19 are outlined.

Source: Ahmad SJ, Feigen CM, Vazquez JP, Kobets AJ, Altschul DJ. Neurological Sequelae of COVID-19. J Integr Neurosci. 2022 Apr 6;21(3):77. doi: 10.31083/j.jin2103077. PMID: 35633158. https://www.imrpress.com/journal/JIN/21/3/10.31083/j.jin2103077/htm (Full text)

The Role of Kynurenine Pathway and NAD + Metabolism in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Abstract:

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a serious, complex, and highly debilitating long-term illness. People with ME/CFS are typically unable to carry out their routine activities. Key hallmarks of the disease are neurological and gastrointestinal impairments accompanied by pervasive malaise that is exacerbated after physical and/or mental activity. Currently, there is no validated cure of biomarker signature for this illness. Impaired tryptophan (TRYP) metabolism is thought to play significant role in the pathobiology of ME/CFS.

TRYP is an important precursor for serotonin and the essential pyridine nucleotide nicotinamide adenine dinucleotide (NAD+). TRYP has been associated with the development of some parts of the brain responsible for behavioural functions. The main catabolic route for TRYP is the kynurenine pathway (KP). The KP produces NAD+ and several neuroactive metabolites with neuroprotective (i.e., kynurenic acid (KYNA)) and neurotoxic (i.e., quinolinic acid (QUIN)) activities. Hyperactivation of the KP, whether compensatory or a driving mechanism of degeneration can limit the availability of NAD+ and exacerbate the symptoms of ME/CFS.

This review discusses the potential association of altered KP metabolism in ME/CFS. The review also evaluates the role of the patient’s gut microbiota on TRYP availability and KP activation. We propose that strategies aimed at raising the levels of NAD+ (e.g., using nicotinamide mononucleotide and nicotinamide riboside) may be a promising intervention to overcome symptoms of fatigue and to improve the quality of life in patients with ME/CFS. Future clinical trials should further assess the potential benefits of NAD+ supplements for reducing some of the clinical features of ME/CFS.

Source: Dehhaghi M, Panahi HKS, Kavyani B, Heng B, Tan V, Braidy N, Guillemin GJ. The Role of Kynurenine Pathway and NAD+ Metabolism in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. Aging Dis. 2022 Jun 1;13(3):698-711. doi: 10.14336/AD.2021.0824. PMID: 35656104; PMCID: PMC9116917. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9116917/ (Full text)

Pathophysiology and mechanism of long COVID: a comprehensive review

Abstract:

Background: After almost 2 years of fighting against SARS-CoV-2 pandemic, the number of patients enduring persistent symptoms long after acute infection is a matter of concern. This set of symptoms was referred to as “long COVID”, and it was defined more recently as “Post COVID-19 condition” by the World health Organization (WHO). Although studies have revealed that long COVID can manifest whatever the severity of inaugural illness, the underlying pathophysiology is still enigmatic.

Aim: To conduct a comprehensive review to address the putative pathophysiology underlying the persisting symptoms of long COVID.

Method: We searched 11 bibliographic databases (Cochrane Library, JBI EBP Database, Medline, Embase, PsycInfo, CINHAL, Ovid Nursing Database, Journals@Ovid, SciLit, EuropePMC, and CoronaCentral). We selected studies that put forward hypotheses on the pathophysiology, as well as those that encompassed long COVID patients in their research investigation.

Results: A total of 98 articles were included in the systematic review, 54 of which exclusively addressed hypotheses on pathophysiology, while 44 involved COVID patients. Studies that included patients displayed heterogeneity with respect to the severity of initial illness, timing of analysis, or presence of a control group. Although long COVID likely results from long-term organ damage due to acute-phase infection, specific mechanisms following the initial illness could contribute to the later symptoms possibly affecting many organs. As such, autonomic nervous system damage could account for many symptoms without clear evidence of organ damage. Immune dysregulation, auto-immunity, endothelial dysfunction, occult viral persistence, as well as coagulation activation are the main underlying pathophysiological mechanisms so far.

Conclusion: Evidence on why persistent symptoms occur is still limited, and available studies are heterogeneous. Apart from long-term organ damage, many hints suggest that specific mechanisms following acute illness could be involved in long COVID symptoms.

KEY MESSAGES:

  • Long-COVID is a multisystem disease that develops regardless of the initial disease severity. Its clinical spectrum comprises a wide range of symptoms.
  • The mechanisms underlying its pathophysiology are still unclear. Although organ damage from the acute infection phase likely accounts for symptoms, specific long-lasting inflammatory mechanisms have been proposed, as well.
  • Existing studies involving Long-COVID patients are highly heterogeneous, as they include patients with various COVID-19 severity levels and different time frame analysis, as well.

Source: Castanares-Zapatero D, Chalon P, Kohn L, Dauvrin M, Detollenaere J, Maertens de Noordhout C, Primus-de Jong C, Cleemput I, Van den Heede K. Pathophysiology and mechanism of long COVID: a comprehensive review. Ann Med. 2022 Dec;54(1):1473-1487. doi: 10.1080/07853890.2022.2076901. PMID: 35594336; PMCID: PMC9132392. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9132392/ (Full text)

Pharmacological significance of MitoQ in ameliorating mitochondria-related diseases

Abstract:

The Mitochondria is a critical sub-cellular organelle that plays an integral part in a normal cellular process. Besides ATP production, the mitochondria participate in various key cellular processes such as cell signaling, epigenetic regulation leading to cell proliferation, migration, apoptosis, differentiation, and autophagy – highlighting their importance to cellular health. However, mitochondrial dysfunction has serious organismal consequences, playing critical roles in the pathophysiology of many diseases, including neurodegenerative disorders, cardiovascular diseases, cancer, pulmonary and liver diseases. In recent years, mitochondrial dysfunction has spurred a surge of interest in developing mitochondria-targeted therapies.

MitoQ is a selective antioxidant that concentrates in the mitochondria and prevents oxidative damage to the mitochondria. The therapeutic relevance of MitoQ has been studied in various diseased conditions to determine its efficacy in either slowing disease progression or alleviating symptoms. In this review, we discussed mitochondrial dysfunction in selected diseases and the therapeutic benefit of MitoQ in numerous studies.

Source: Lateef Adegboyega Sulaimon, Lukman Olalekan Afolabi, Rahmat Adetutu Adisa, Akinrinade George Ayankojo, Mariam Olanrewaju Afolabi, Abiodun Mohammed Adewolu, Xiaochun Wan. Pharmacological significance of MitoQ in ameliorating mitochondria-related diseases. Advances in Redox Research, 2022 [In Press, Journal pre-proof]  https://www.sciencedirect.com/science/article/pii/S2667137922000091 (Full text)

The Pathobiology of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: The Case for Neuroglial Failure

Abstract:

Although myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) has a specific and distinctive profile of clinical features, the disease remains an enigma because causal explanation of the pathobiological matrix is lacking. Several potential disease mechanisms have been identified, including immune abnormalities, inflammatory activation, mitochondrial alterations, endothelial and muscular disturbances, cardiovascular anomalies, and dysfunction of the peripheral and central nervous systems. Yet, it remains unclear whether and how these pathways may be related and orchestrated.

Here we explore the hypothesis that a common denominator of the pathobiological processes in ME/CFS may be central nervous system dysfunction due to impaired or pathologically reactive neuroglia (astrocytes, microglia and oligodendrocytes). We will test this hypothesis by reviewing, in reference to the current literature, the two most salient and widely accepted features of ME/CFS, and by investigating how these might be linked to dysfunctional neuroglia.

From this review we conclude that the multifaceted pathobiology of ME/CFS may be attributable in a unifying manner to neuroglial dysfunction. Because the two key features – post exertional malaise and decreased cerebral blood flow – are also recognized in a subset of patients with post-acute sequelae COVID, we suggest that our findings may also be pertinent to this entity.

Source: Renz-Polster H, Tremblay ME, Bienzle D, Fischer JE. The Pathobiology of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: The Case for Neuroglial Failure. Front Cell Neurosci. 2022 May 9;16:888232. doi: 10.3389/fncel.2022.888232. PMID: 35614970; PMCID: PMC9124899. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9124899/ (Full text)

Neurological and Psychiatric Symptoms of COVID-19: A Narrative Review

Abstract:

Recently dubbed Long COVID or Long-Haul COVID, those recovering from the initial COVID-19 infection may maintain clinical signs for longer than two or more weeks following the initial onset of the infection. The virus can gain entry into the CNS through axonal transport mediated through the olfactory nerve or hematogenous spread and can also cross the blood–brain barrier to access the temporal lobe and the brainstem. The neurologic and neuropsychiatric symptoms associated with COVID-19 patients are becoming a highly studied area due to the increased frequency of reported cases.
Multiple hospital case series and observational studies have found a headache to be a common symptom among patients who are symptomatic with the SARS-CoV-2 virus. The headache described by many of these patients is similar to new daily persistent headache (NDPH). NDPH potentially develops in response to pro-inflammatory cytokines during a persistent systemic or CNS inflammation, mostly due to the initial infection. The treatments investigated were high-dose steroids, tetracycline derivatives, onabotulinum toxin type A, and long-term multidrug regimens. Among the identified symptoms of post-COVID-19 viral illness, fatigue appears to be the most ubiquitous. High-dose vitamin C is currently a suggested therapy proposed for its antioxidant, anti-inflammatory, and immunomodulatory properties.
The mental health consequences of this diagnosis are being identified among large portions of COVID-19 survivors. Among these consequences, cases of major depressive disorder (MDD) and anxiety are being reported and closely examined. The aim of this narrative review is to highlight the neurological and psychiatric symptoms that have been associated with Long-Haul COVID and their possible treatments.
Source: Edinoff AN, Chappidi M, Alpaugh ES, Turbeville BC, Falgoust EP, Cornett EM, Murnane KS, Kaye AM, Kaye AD. Neurological and Psychiatric Symptoms of COVID-19: A Narrative Review. Psychiatry International. 2022; 3(2):158-168. https://doi.org/10.3390/psychiatryint3020013 https://www.mdpi.com/2673-5318/3/2/13/htm (Full text)