Tag: neuroinflammation

Broken Connections: The Evidence for Neuroglial Failure in ME/CFS

Abstract:

In spite of decades of research, the pathobiology of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is still poorly understood. Several pathomechanisms have been identified, yet, it remains unclear how they are related and which of them may be upstream or downstream.

In this paper, we present a theoretical strategy that may help clarify the causal chain of pathophysiological events in ME/CFS. We propose to focus on the common final histological pathway of ME/CFS and suggest to ask: Which cellular compartment may explain the pathological processes and clinical manifestations observed in ME/CFS? Any functional unit consistently identified through this search may then be a plausible candidate for further exploration.

For this “histological” approach we have compiled a list of 22 undisputed clinical and pathophysiological features of ME/CFS that need to be plausibly and most directly explained by the dysfunctional cellular unit in question. For each feature we have searched the literature for pathophysiological explanations and analyzed if they may point to the same functional cellular unit. Through this search we have identified the CNS neuroglia – microglia and astroglia – as the one functional unit in the human body which may best explain all and any of the clinical and pathological features, dysfunctions and observations described for ME/CFS.

While this points to neuroinflammation as the central hub in ME/CFS, it also points to a novel understanding of the neuroimmune basis of ME/CFS. After all, the neuroglial cells are now understood as the functional matrix of the human brain connectome which operates beyond and above specific brain centers, receptor units or neurotransmitter systems and integrates innate immune functions with CNS regulatory functions pertaining to autonomous regulation, cellular metabolism and the stress response.

Source: Renz-Polster, H. (2021, August 3). Broken Connections: The Evidence for Neuroglial Failure in ME/CFS. https://doi.org/10.31219/osf.io/ef3n4 https://osf.io/ef3n4/ (Full text)

Molecular Mechanisms of Neuroinflammation in ME/CFS and Long COVID to Sustain Disease and Promote Relapses

Abstract:

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a disease now well-documented as having arisen commonly from a viral infection, but also from other external stressors, like exposure to agricultural chemicals, other types of infection, surgery, or other severe stress events. Research has shown these events produce a systemic molecular inflammatory response and chronic immune activation and dysregulation. What has been more difficult to establish is the hierarchy of the physiological responses that give rise to the myriad of symptoms that ME/CFS patients experience, and why they do not resolve and are generally life-long.

The severity of the symptoms frequently fluctuates through relapse recovery periods, with brain-centered symptoms of neuroinflammation, loss of homeostatic control, “brain fog” affecting cognitive ability, lack of refreshing sleep, and poor response to even small stresses. How these brain effects develop with ME/CFS from the initiating external effector, whether virus or other cause, is poorly understood and that is what our paper aims to address.

We propose the hypothesis that following the initial stressor event, the subsequent systemic pathology moves to the brain via neurovascular pathways or through a dysfunctional blood-brain barrier (BBB), resulting in chronic neuroinflammation and leading to a sustained illness with chronic relapse recovery cycles. Signaling through recognized pathways from the brain back to body physiology is likely part of the process by which the illness cycle in the peripheral system is sustained and why healing does not occur. By contrast, Long COVID (Post-COVID-19 condition) is a very recent ME/CFS-like illness arising from the single pandemic virus, SARS-CoV-2.

We believe the ME/CFS-like ongoing effects of Long COVID are arising by very similar mechanisms involving neuroinflammation, but likely with some unique signaling, resulting from the pathology of the initial SARS-CoV-2 infection. The fact that there are very similar symptoms in both ongoing diseases, despite the diversity in the nature of the initial stressors, supports the concept of a similar dysfunctional CNS component common to both.

Source: Tate W, Walker M, Sweetman E, Helliwell A, Peppercorn K, Edgar C, Blair A, Chatterjee A. Molecular Mechanisms of Neuroinflammation in ME/CFS and Long COVID to Sustain Disease and Promote Relapses. Front Neurol. 2022 May 25;13:877772. doi: 10.3389/fneur.2022.877772. PMID: 35693009; PMCID: PMC9174654.  https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9174654/ (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)

Neuropathology and virus in brain of SARS-CoV-2 infected non-human primates

Abstract:

Neurological manifestations are a significant complication of coronavirus disease (COVID-19), but underlying mechanisms aren’t well understood. The development of animal models that recapitulate the neuropathological findings of autopsied brain tissue from patients who died from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection are critical for elucidating the neuropathogenesis of infection and disease.

Here, we show neuroinflammation, microhemorrhages, brain hypoxia, and neuropathology that is consistent with hypoxic-ischemic injury in SARS-CoV-2 infected non-human primates (NHPs), including evidence of neuron degeneration and apoptosis. Importantly, this is seen among infected animals that do not develop severe respiratory disease, which may provide insight into neurological symptoms associated with “long COVID”. Sparse virus is detected in brain endothelial cells but does not associate with the severity of central nervous system (CNS) injury.

We anticipate our findings will advance our current understanding of the neuropathogenesis of SARS-CoV-2 infection and demonstrate SARS-CoV-2 infected NHPs are a highly relevant animal model for investigating COVID-19 neuropathogenesis among human subjects.

Source: Rutkai I, Mayer MG, Hellmers LM, Ning B, Huang Z, Monjure CJ, Coyne C, Silvestri R, Golden N, Hensley K, Chandler K, Lehmicke G, Bix GJ, Maness NJ, Russell-Lodrigue K, Hu TY, Roy CJ, Blair RV, Bohm R, Doyle-Meyers LA, Rappaport J, Fischer T. Neuropathology and virus in brain of SARS-CoV-2 infected non-human primates. Nat Commun. 2022 Apr 1;13(1):1745. doi: 10.1038/s41467-022-29440-z. PMID: 35365631. https://www.nature.com/articles/s41467-022-29440-z (Full text)

Clinical characteristics with inflammation profiling of long-covid and association with one-year recovery following hospitalisation in the UK: a prospective observational study.

Summary:

Background: There are currently no effective pharmacological or non-pharmacological interventions for Long-COVID. To identify potential therapeutic targets, we focussed on previously described four recovery clusters five months after hospital discharge, their underlying inflammatory profiles and relationship with clinical outcomes at one year.

Methods: PHOSP-COVID is a prospective longitudinal cohort study, recruiting adults hospitalised with COVID-19 across the UK. Recovery was assessed using patient reported outcomes measures (PROMs), physical performance, and organ function at five-months and one-year after hospital discharge. Hierarchical logistic regression modelling was performed for patient-perceived recovery at one-year. Cluster analysis was performed using clustering large applications (CLARA) k-medoids approach using clinical outcomes at five-months. Inflammatory protein profiling from plasma at the five-month visit was performed.

Findings: 2320 participants have been assessed at five months after discharge and 807 participants have completed both five-month and one-year visits. Of these, 35·6% were female, mean age 58·7 (SD 12·5) years, and 27·8% received invasive mechanical ventilation (IMV). The proportion of patients reporting full recovery was unchanged between five months 501/1965 (25·5%) and one year 232/804 (28·9%). Factors associated with being less likely to report full recovery at one year were: female sex OR 0·68 (95% CI 0·46-0·99), obesity OR 0·50 (95%CI 0·34-0·74) and IMV OR 0·42 (95%CI 0·23-0·76).

Cluster analysis (n=1636) corroborated the previously reported four clusters: ‘very severe’, ‘severe’, ‘moderate/cognitive’, ‘mild’ relating to the severity of physical, mental health and cognitive impairments at five months in a larger sample. There was elevation of inflammatory mediators of tissue damage and repair in both the ‘very severe’ and the ‘moderate/cognitive’ clusters compared to the ‘mild’ cluster including interleukin-6 which was elevated in both comparisons. Overall, there was a substantial deficit in median (IQR) EQ5D-5L utility index from pre-COVID (retrospective assessment) 0·88 (0·74-1·00), five months 0·74 (0·60-0·88) to one year: 0·74 (0·59-0·88), with minimal improvements across all outcome measures at one-year after discharge in the whole cohort and within each of the four clusters.

Interpretation: The sequelae of a hospital admission with COVID-19 remain substantial one year after discharge across a range of health domains with the minority in our cohort feeling fully recovered. Patient perceived health-related quality of life remains reduced at one year compared to pre-hospital admission. Systematic inflammation and obesity are potential treatable traits that warrant further investigation in clinical trials.

Source: Rachael A Evans, Olivia C Leavy, Matthew Richardson, Omer Elneima, Hamish J C McAuley, Aarti Shikotra, Amisha Singapuri, Marco Sereno et al. Clinical characteristics with inflammation profiling of long-covid and association with one-year recovery following hospitalisation in the UK: a prospective observational study. medRxiv 2021.12.13.21267471; doi: https://doi.org/10.1101/2021.12.13.21267471 https://www.medrxiv.org/content/10.1101/2021.12.13.21267471v1.full-text (Full Text)

Covid-19: Long covid symptoms among hospital inpatients show little improvement after a year, data suggest

People admitted to hospital with covid-19 who reported “long covid” symptoms five months after discharge had made only limited improvement after a full year, preliminary data from the PHOSP-COVID study show.

Researchers said that their results, released as a preprint on 16 December,1 showed that patients who experienced the most severe symptoms also had raised levels of substances associated with whole body inflammation and tissue damage and repair, suggesting autoimmune involvement.

The study, led by the National Institute for Health Research (NIHR) Leicester Biomedical Research Centre, is following up 2230 adults admitted to hospital with covid-19. At five months after discharge only 2.5 in 10 people felt fully recovered.2 This was largely unchanged after 12 months, at less than 3 in 10 patients, in the 807 people assessed so far.

Chris Brightling, professor of respiratory medicine at the University of Leicester and chief investigator for the study, said, “People who were hospitalised and went on to develop long covid are not getting substantially better a year after they were discharged from hospital.

“Many patients in our study had not fully recovered at five months, and most of these reported little positive change in their health condition at one year.”

Rachael Evans, associate professor at the University of Leicester and respiratory consultant at Leicester’s Hospitals, who is the paper’s lead author, said, “Healthcare professionals will need to proactively continue assessing their patients for some time to come in order to identify their ongoing healthcare needs and provide support.

“We urgently need healthcare packages and medicines that target the potentially treatable traits of long covid to help people feel better and get back to their normal lives. Without these, long covid has the potential to become highly prevalent as a new long term condition.”

Ongoing inflammatory process

The most common long covid symptoms reported by patients were fatigue, muscle pain, physically slowing down, poor sleep, and breathlessness, and patients said that their health related quality of life remained substantially worse one year after hospital discharge than before they had the SARS-CoV-2 infection.

A cluster analysis on the five month data revealed four distinct groups of patients based on the severity of symptoms they experienced: in 39% symptoms were considered mild, in 30% severe, in 20% very severe, and in 11% they were moderate or primarily affected cognition.

Blood samples taken at five months were analysed for around 300 substances linked to inflammation and immunity. These showed that patients in the “very severe” group had higher levels of substances associated with whole body inflammation, tissue damage, and tissue repair, while those reporting poor cognition appeared to have higher levels of substances linked to “brain fog,” suggesting possible neuro-inflammation.

Brightling said that the results suggested “an ongoing inflammatory process” and that other studies had indicated an increase in autoimmunity in some cases against specific organs such as heart or skeletal muscle. “We’re working very closely with immunologists to try to unpick that and see whether autoimmunity may be one of the key drivers [of long covid],” he said.

Source: Ingrid Torjesen. Covid-19: Long covid symptoms among hospital inpatients show little improvement after a year, data suggest. BMJ 2021;375:n3092. Published 15 December 2021. https://www.bmj.com/content/375/bmj.n3092 (Full text)

TLR Antagonism by Sparstolonin B Alters Microbial Signature and Modulates Gastrointestinal and Neuronal Inflammation in Gulf War Illness Preclinical Model

Abstract:

The 1991 Persian Gulf War veterans presented a myriad of symptoms that ranged from chronic pain, fatigue, gastrointestinal disturbances, and cognitive deficits. Currently, no therapeutic regimen exists to treat the plethora of chronic symptoms though newer pharmacological targets such as microbiome have been identified recently. Toll-like receptor 4 (TLR4) antagonism in systemic inflammatory diseases have been tried before with limited success, but strategies with broad-spectrum TLR4 antagonists and their ability to modulate the host-microbiome have been elusive.

Using a mouse model of Gulf War Illness, we show that a nutraceutical, derived from a Chinese herb Sparstolonin B (SsnB) presented a unique microbiome signature with an increased abundance of butyrogenic bacteria. SsnB administration restored a normal tight junction protein profile with an increase in Occludin and a parallel decrease in Claudin 2 and inflammatory mediators high mobility group box 1 (HMGB1), interleukin-1β (IL-1β), and interleukin-6 (IL-6) in the distal intestine. SsnB also decreased neuronal inflammation by decreasing IL-1β and HMGB1, while increasing brain-derived neurotrophic factor (BDNF), with a parallel decrease in astrocyte activation in vitro.

Mechanistically, SsnB inhibited the binding of HMGB1 and myeloid differentiation primary response protein (MyD88) to TLR4 in the intestine, thus attenuating TLR4 downstream signaling. Studies also showed that SsnB was effective in suppressing TLR4-induced nod-like receptor protein 3 (NLRP3) inflammasome activation, a prominent inflammatory disease pathway. SsnB significantly decreased astrocyte activation by decreasing colocalization of glial fibrillary acid protein (GFAP) and S100 calcium-binding protein B (S100B), a crucial event in neuronal inflammation. Inactivation of SsnB by treating the parent molecule by acetate reversed the deactivation of NLRP3 inflammasome and astrocytes in vitro, suggesting that SsnB molecular motifs may be responsible for its anti-inflammatory activity.

Source: Bose D, Mondal A, Saha P, Kimono D, Sarkar S, Seth RK, Janulewicz P, Sullivan K, Horner R, Klimas N, Nagarkatti M, Nagarkatti P, Chatterjee S. TLR Antagonism by Sparstolonin B Alters Microbial Signature and Modulates Gastrointestinal and Neuronal Inflammation in Gulf War Illness Preclinical Model. Brain Sci. 2020 Aug 8;10(8):532. doi: 10.3390/brainsci10080532. PMID: 32784362; PMCID: PMC7463890. https://www.mdpi.com/2076-3425/10/8/532 (Full text)

No Signs of Neuroinflammation in Women With Chronic Fatigue Syndrome or Q Fever Fatigue Syndrome Using the TSPO Ligand [ 11 C]-PK11195

Abstract:

Background and objectives: The pathophysiology of chronic fatigue syndrome (CFS) and Q fever fatigue syndrome (QFS) remains elusive. Recent data suggest a role for neuroinflammation as defined by increased expression of translocator protein (TSPO). In the present study, we investigated whether there are signs of neuroinflammation in female patients with CFS and QFS compared with healthy women, using PET with the TSPO ligand 11C-(R)-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinoline-carbox-amide ([11C]-PK11195).

Methods: The study population consisted of patients with CFS (n = 9), patients with QFS (n = 10), and healthy subjects (HSs) (n = 9). All subjects were women, matched for age (±5 years) and neighborhood, aged between 18 and 59 years, who did not use any medication other than paracetamol or oral contraceptives, and were not vaccinated in the last 6 months. None of the subjects reported substance abuse in the past 3 months or reported signs of underlying psychiatric disease on the Mini-International Neuropsychiatric Interview. All subjects underwent a [11C]-PK11195 PET scan, and the [11C]-PK11195 binding potential (BPND) was calculated.

Results: No statistically significant differences in BPND were found for patients with CFS or patients with QFS compared with HSs. BPND of [11C]-PK11195 correlated with symptom severity scores in patients with QFS, but a negative correlation was found in patients with CFS.

Discussion: In contrast to what was previously reported for CFS, we found no significant difference in BPND of [11C]-PK11195 when comparing patients with CFS or QFS with healthy neighborhood controls. In this small series, we were unable to find signs of neuroinflammation in patients with CFS and QFS.

Source: Raijmakers R, Roerink M, Keijmel S, Joosten L, Netea M, van der Meer J, Knoop H, Klein H, Bleeker-Rovers C, Doorduin J. No Signs of Neuroinflammation in Women With Chronic Fatigue Syndrome or Q Fever Fatigue Syndrome Using the TSPO Ligand [11C]-PK11195. Neurol Neuroimmunol Neuroinflamm. 2021 Nov 23;9(1):e1113. doi: 10.1212/NXI.0000000000001113. PMID: 34815320. https://pubmed.ncbi.nlm.nih.gov/34815320/

Editorial: The Pathogenesis of Long-Term Neuropsychiatric COVID-19 and the Role of Microglia, Mitochondria, and Persistent Neuroinflammation: A Hypothesis

Abstract:

Persistent comorbidities occur in patients who initially recover from acute coronavirus disease 2019 (COVID-19) due to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). ‘Long COVID’ involves the central nervous system (CNS), resulting in neuropsychiatric symptoms and signs, including cognitive impairment or ‘brain fog’ and chronic fatigue syndrome. There are similarities in these persistent complications between SARS-CoV-2 and the Ebola, Zika, and influenza A viruses. Normal CNS neuronal mitochondrial function requires high oxygen levels for oxidative phosphorylation and ATP production. Recent studies have shown that the SARS-CoV-2 virus can hijack mitochondrial function. Persistent changes in cognitive functioning have also been reported with other viral infections. SARS-CoV-2 infection may result in long-term effects on immune processes within the CNS by causing microglial dysfunction. This short opinion aims to discuss the hypothesis that the pathogenesis of long-term neuropsychiatric COVID-19 involves microglia, mitochondria, and persistent neuroinflammation.

Source: Stefano GB, Büttiker P, Weissenberger S, Martin A, Ptacek R, Kream RM. Editorial: The Pathogenesis of Long-Term Neuropsychiatric COVID-19 and the Role of Microglia, Mitochondria, and Persistent Neuroinflammation: A Hypothesis. Med Sci Monit. 2021 May 10;27:e933015. doi: 10.12659/MSM.933015. PMID: 34016942. https://pubmed.ncbi.nlm.nih.gov/34016942/

Long-COVID syndrome-associated brain fog and chemofog: Luteolin to the rescue

Abstract:

COVID-19 leads to severe respiratory problems, but also to long-COVID syndrome associated primarily with cognitive dysfunction and fatigue. Long-COVID syndrome symptoms, especially brain fog, are similar to those experienced by patients undertaking or following chemotherapy for cancer (chemofog or chemobrain), as well in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) or mast cell activation syndrome (MCAS). The pathogenesis of brain fog in these illnesses is presently unknown but may involve neuroinflammation via mast cells stimulated by pathogenic and stress stimuli to release mediators that activate microglia and lead to inflammation in the hypothalamus. These processes could be mitigated by phytosomal formulation (in olive pomace oil) of the natural flavonoid luteolin.

Source: Theoharides TC, Cholevas C, Polyzoidis K, Politis A. Long-COVID syndrome-associated brain fog and chemofog: Luteolin to the rescue. Biofactors. 2021 Apr 12. doi: 10.1002/biof.1726. Epub ahead of print. PMID: 33847020. https://pubmed.ncbi.nlm.nih.gov/33847020/