Tag: long covid pathophysiology

Neuroinflammation in post-acute sequelae of COVID-19 (PASC) as assessed by [11C]PBR28 PET correlates with vascular disease measures

Abstract:

The COVID-19 pandemic caused by SARS-CoV-2 has triggered a consequential public health crisis of post-acute sequelae of COVID-19 (PASC), sometimes referred to as long COVID. The mechanisms of the heterogeneous persistent symptoms and signs that comprise PASC are under investigation, and several studies have pointed to the central nervous and vascular systems as being potential sites of dysfunction.

In the current study, we recruited individuals with PASC with diverse symptoms, and examined the relationship between neuroinflammation and circulating markers of vascular dysfunction. We used [11C]PBR28 PET neuroimaging, a marker of neuroinflammation, to compare 12 PASC individuals versus 43 normative healthy controls.

We found significantly increased neuroinflammation in PASC versus controls across a wide swath of brain regions including midcingulate and anterior cingulate cortex, corpus callosum, thalamus, basal ganglia, and at the boundaries of ventricles. We also collected and analyzed peripheral blood plasma from the PASC individuals and found significant positive correlations between neuroinflammation and several circulating analytes related to vascular dysfunction.

These results suggest that an interaction between neuroinflammation and vascular health may contribute to common symptoms of PASC.

Source: Michael B VanElzakker, Hannah F Bues, Ludovica Brusaferri, Minhae Kim, Deena Saadi, Eva-Maria Ratai, Darin D Dougherty, Marco L Loggia. Neuroinflammation in post-acute sequelae of COVID-19 (PASC) as assessed by [11C]PBR28 PET correlates with vascular disease measures. bioRxiv 2023.10.19.563117; doi: https://doi.org/10.1101/2023.10.19.563117 https://www.biorxiv.org/content/10.1101/2023.10.19.563117v1 (Full text available as PDF file)

From ‘mental fog’ to post-acute COVID-19 syndrome’s executive function alteration: Implications for clinical approach

Abstract:

A common symptom of the neuropsychiatric Post-Acute COVID-19 syndrome (neuro-PACS) is the so called ‘brain fog’. Patients describe the brain fog as problems with attention, memory and mental fatigue. Brain fog is experienced by 9-55% of people for months after having contracted SARS-CoV-2 virus. Several theories have been proposed to explain PACS’s brain fog, including a neuroinflammatory hypothesis, but the hypothesis remains to be proven. Here, we examined inflammatory and immunological blood profile in a cohort of patients with PACS to investigate the association between executive functions and blood inflammatory markers.

Executive function was assessed by the Trail Making Test (TMT) Part A and Part B, as well as the Barkley Deficits in Executive Functioning Scale (BDEFS), in 71 patients (36 men), average age of 40 years (range: 15-82, SD: 15.7). Impairment in executive functioning (BDEFS scores and TMT B scores) correlated with increased levels of Interleukin-6 (IL-6), fibrinogen and ferritin. Moreover, elevated levels of Il-6, fibrinogen, ferritin, tumor necrosis factor-alpha and C-reactive protein have been observed in PACS.

These findings demonstrate that PACS is characterized by the presence of an immuno-inflammatory process, which is associated with diminished executive functioning. Here, we argue in favour of a shift from the non-descriptive definition of ‘mental fog’ to a characterization of a subtype of PACS, associated with alteration in executive functioning. Implication for clinical settings and prevention are discussed.

Source: Pallanti S, Di Ponzio M, Gavazzi G, Gasic G, Besteher B, Heller C, Kikinis R, Makris N, Kikinis Z. From ‘mental fog’ to post-acute COVID-19 syndrome’s executive function alteration: Implications for clinical approach. J Psychiatr Res. 2023 Sep 30;167:10-15. doi: 10.1016/j.jpsychires.2023.09.017. Epub ahead of print. PMID: 37804756. https://pubmed.ncbi.nlm.nih.gov/37804756/

Serotonin reduction in post-acute sequelae of viral infection

Highlights:

  • Long COVID is associated with reduced circulating serotonin levels
  • Serotonin depletion is driven by viral RNA-induced type I interferons (IFNs)
  • IFNs reduce serotonin through diminished tryptophan uptake and hypercoagulability
  • Peripheral serotonin deficiency impairs cognition via reduced vagal signaling

Summary:

Post-acute sequelae of COVID-19 (PASC, “Long COVID”) pose a significant global health challenge. The pathophysiology is unknown, and no effective treatments have been found to date. Several hypotheses have been formulated to explain the etiology of PASC, including viral persistence, chronic inflammation, hypercoagulability, and autonomic dysfunction. Here, we propose a mechanism that links all four hypotheses in a single pathway and provides actionable insights for therapeutic interventions. We find that PASC are associated with serotonin reduction.
Viral infection and type I interferon-driven inflammation reduce serotonin through three mechanisms: diminished intestinal absorption of the serotonin precursor tryptophan; platelet hyperactivation and thrombocytopenia, which impacts serotonin storage; and enhanced MAO-mediated serotonin turnover. Peripheral serotonin reduction, in turn, impedes the activity of the vagus nerve and thereby impairs hippocampal responses and memory. These findings provide a possible explanation for neurocognitive symptoms associated with viral persistence in Long COVID, which may extend to other post-viral syndromes.
Source: Wong et al., Serotonin reduction in post-acute sequelae of viral infection, Cell (2023), https://doi.org/
10.1016/j.cell.2023.09.013 https://www.cell.com/cell/fulltext/S0092-8674(23)01034-6 (Full text)

Accelerating discovery: A novel flow cytometric method for detecting fibrin(ogen) amyloid microclots using long COVID as a model

Abstract:

Long COVID has become a significant global health and economic burden, yet there are currently no established methods or diagnostic tools to identify which patients might benefit from specific treatments. One of the major pathophysiological factors contributing to Long COVID is the presence of hypercoagulability; this results in insoluble amyloid microclots that are resistant to fibrinolysis. Our previous research using fluorescence microscopy has demonstrated a significant amyloid microclot load in Long COVID patients. However, this approach lacked the elements of statistical robustness, objectivity, and rapid throughput.

In the current study, we have used imaging flow cytometry for the first time to show a significantly increased concentration and size of these microclots. We identified notable variations in size and fluorescence between microclots in Long COVID and those of controls even using a 20× objective. By combining cell imaging and the high-event-rate and full-sample analysis nature of a conventional flow cytometer, imaging flow cytometry can eliminate erroneous results and increase accuracy in gating and analysis beyond what pure quantitative measurements from conventional flow cytometry can provide.

Although imaging flow cytometry was used in our study, our results suggest that the signals indicating the presence of microclots should be easily detectable using a conventional flow cytometer. Flow cytometry is a more widely available technique than fluorescence microscopy and has been used in pathology laboratories for decades, rendering it a potentially more suitable and accessible method for detecting microclots in individuals suffering from Long COVID or conditions with similar pathology, such as myalgic encephalomyelitis.

Source: Turner S, Laubscher GJ, Khan MA, Kell DB, Pretorius E. Accelerating discovery: A novel flow cytometric method for detecting fibrin(ogen) amyloid microclots using long COVID as a model. Heliyon. 2023 Aug 29;9(9):e19605. doi: 10.1016/j.heliyon.2023.e19605. PMID: 37809592; PMCID: PMC10558872. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10558872/ (Full text)

What Role Does Microthrombosis Play in Long COVID?

Abstract:

Soon after the outbreak of coronavirus disease 2019 (COVID-19), unexplained sustained fatigue, cognitive disturbance, and muscle ache/weakness were reported in patients who had recovered from acute COVID-19 infection. This abnormal condition has been recognized as “long COVID (postacute sequelae of COVID-19 [PASC])” with a prevalence estimated to be from 10 to 20% of convalescent patients. Although the pathophysiology of PASC has been studied, the exact mechanism remains obscure.

Microclots in circulation can represent one of the possible causes of PASC. Although hypercoagulability and thrombosis are critical mechanisms of acute COVID-19, recent studies have reported that thromboinflammation continues in some patients, even after the virus has cleared. Viral spike proteins and RNA can be detected months after patients have recovered, findings that may be responsible for persistent thromboinflammation and the development of microclots. Despite this theory, long-term results of anticoagulation, antiplatelet therapy, and vascular endothelial protection are inconsistent, and could not always show beneficial treatment effects.

In summary, PASC reflects a heterogeneous condition, and microclots cannot explain all the presenting symptoms. After clarification of the pathomechanisms of each symptom, a symptom- or biomarker-based stratified approach should be considered for future studies.

Source: Iba T, Connors JM, Levy JH. What Role Does Microthrombosis Play in Long COVID? Semin Thromb Hemost. 2023 Sep 25. doi: 10.1055/s-0043-1774795. Epub ahead of print. PMID: 37748518. https://pubmed.ncbi.nlm.nih.gov/37748518/

Immune cell proteomes of Long COVID patients have functional changes similar to those in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Abstract:

Of those infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), ~ 10% develop the chronic post-viral debilitating condition, Long COVID (LC). Although LC is a heterogeneous condition, about half of cases have a typical post-viral fatigue condition with onset and symptoms that are very similar to Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). A key question is whether these conditions are closely related.

ME/CFS is a post-stressor fatigue condition that arises from multiple triggers. To investigate the pathophysiology of LC, a pilot study of patients and healthy controls has used quantitative proteomics to discover changes in peripheral blood mononuclear cell (PBMC) proteins. A principal component analysis separated all Long COVID patients from healthy controls.

Analysis of 3131 proteins identified 162 proteins differentially regulated, of which 37 were related to immune functions, and 21 to mitochondrial functions. Markov cluster analysis identified clusters involved in immune system processes, and two aspects of gene expression-spliceosome and transcription. These results were compared with an earlier dataset of 346 differentially regulated proteins in PBMC’s from ME/CFS patients analysed by the same methodology.

There were overlapping protein clusters and enriched molecular pathways particularly in immune functions, suggesting the two conditions have similar immune pathophysiology as a prominent feature, and mitochondrial functions involved in energy production were affected in both conditions.

Source: Katie Peppercorn, Christina D. Edgar, Torsten Kleffmann, Warren. P Tate. Immune cell proteomes of Long COVID patients have functional changes similar to those in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. Research Square preprint https://doi.org/10.21203/rs.3.rs-3335919/v1 https://www.researchsquare.com/article/rs-3335919/v1 (Full text) https://www.nature.com/articles/s41598-023-49402-9 (Final full text)

Bone marrow alterations in COVID-19 infection: The root of hematological problems

Abstract:

Introduction: The 2019 coronavirus disease (COVID-19) is a respiratory infection caused by the SARS-CoV-2 virus with a significant impact on the hematopoietic system and homeostasis. The effect of the virus on blood cells indicates the involvement of the bone marrow (BM) as the place of production and maturation of these cells by the virus and it reminds the necessity of investigating the effect of the virus on the bone marrow.

Method: To investigate the effects of COVID-19 infection in BM, we reviewed literature from the Google Scholar search engine and PubMed database up to 2022 using the terms “COVID-19; SARS-CoV-2; Bone marrow; Thrombocytopenia; Hemophagocytosis; Pancytopenia and Thrombocytopenia.

Results: Infection with the SARS-CoV-2 virus is accompanied by alterations such as single-line cytopenia, pancytopenia, hemophagocytosis, and BM necrosis. The presence of factors such as cytokine release syndrome, the direct effect of the virus on cells through different receptors, and the side effects of current treatments such as corticosteroids are some of the important mechanisms in the occurrence of these alterations.

Conclusion: To our knowledge, this review is the first study to comprehensively investigate BM alterations caused by SAR-CoV-2 virus infection. The available findings show that the significant impact of this viral infection on blood cells and the clinical consequences resulting from them are deeper than previously thought and it may be rooted in the changes that the virus causes in the BM of patients.

Source: Zeylabi F, Nameh Goshay Fard N, Parsi A, Pezeshki SMS. Bone marrow alterations in COVID-19 infection: The root of hematological problems. Curr Res Transl Med. 2023 Jul 25;71(3):103407. doi: 10.1016/j.retram.2023.103407. Epub ahead of print. PMID: 37544028. https://www.sciencedirect.com/science/article/abs/pii/S2452318623000314 (Full text)

Reactive gliosis and neuroinflammation: prime suspects in the pathophysiology of post-acute neuroCOVID-19 syndrome

Abstract:

Introduction: As the repercussions from the COVID-19 pandemic continue to unfold, an ever-expanding body of evidence suggests that infection also elicits pathophysiological manifestations within the central nervous system (CNS), known as neurological symptoms of post-acute sequelae of COVID infection (NeuroPASC). Although the neurological impairments and repercussions associated with NeuroPASC have been well described in the literature, its etiology remains to be fully characterized.

Objectives: This mini-review explores the current literature that elucidates various mechanisms underlining NeuroPASC, its players, and regulators, leading to persistent neuroinflammation of affected individuals. Specifically, we provide some insights into the various roles played by microglial and astroglial cell reactivity in NeuroPASC and how these cell subsets potentially contribute to neurological impairment in response to the direct or indirect mechanisms of CNS injury.

Discussion: A better understanding of the mechanisms and biomarkers associated with this maladaptive neuroimmune response will thus provide better diagnostic strategies for NeuroPASC and reveal new potential mechanisms for therapeutic intervention. Altogether, the elucidation of NeuroPASC pathogenesis will improve patient outcomes and mitigate the socioeconomic burden of this syndrome.

Source: Saucier J, Comeau D, Robichaud GA, Chamard-Witkowski L. Reactive gliosis and neuroinflammation: prime suspects in the pathophysiology of post-acute neuroCOVID-19 syndrome. Front Neurol. 2023 Aug 24;14:1221266. doi: 10.3389/fneur.2023.1221266. PMID: 37693763; PMCID: PMC10492094. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10492094/ (Full text)

Long COVID: A Molecular, Cellular and Histopathology Overview

Abstract:

Long COVID has been studied as different sequelae that some individuals can develop after the acute phase of the disease. Persistent symptoms such as dry cough, fatigue, and dyspnea can remain after six months of COVID-19 cure. Others such as lung fibrosis, kidney injury, and thrombotic risk also are observed. Here, a deep review of each human organ and system infected by the virus was performed aiming to show how molecules expression and cell signaling can induce the organism cure or injuries and, subsequently sequelae. The review also suggests the importance of public health surveillance for these cases including a more comprehensive analysis of molecular biology tools that can clarify and assist in the prognosis, treatment, and preventive methods for potentially more serious disorders in post-COVID-19 patients.

Source: da Silva Barros, B. , de Oliveira Cruz, L. , de Sousa, G. , Souza-Silva, G. , de Lima, M. , Oliveira, E. , Silva, A. , Macêdo, L. , Leal, L. , Marcos, B. , Elsztein, C. , Invenção, M. , de Freitas, A. and Moutinho-Melo, C. (2023) Long COVID: A Molecular, Cellular and Histopathology Overview. Journal of Biosciences and Medicines, 11, 90-113. doi: 10.4236/jbm.2023.119009. https://www.scirp.org/journal/paperinformation.aspx?paperid=127523 (Full text)

Structural and functional impairments of skeletal muscle in patients with post-acute sequelae of SARS-CoV-2 infection

Abstract:

Background: Following acute COVID-19, a substantial proportion of patients showed symptoms and sequelae for several months, namely the post-acute sequelae of COVID-19 (PASC) syndrome. Major phenomena are exercise intolerance, muscle weakness and fatigue. We aimed to investigate the physiopathology of exercise intolerance in patients with PASC syndrome by structural and functional analyses of skeletal muscle.

Methods: At least 3 months after infection, non-hospitalized patients with PASC (n=11,ys:54±11; PASC) and patients without long-term symptoms (n=12,ys:49±9; CTRL) visited the laboratory on four non-consecutive days. Spirometry, lung diffusion capacity and quality of life were assessed at rest. Cardiopulmonary incremental exercise test was performed. Oxygen consumption (VO2) kinetics were determined by moderate-intensity exercises. Muscle oxidative capacity (k) was assessed by near-infrared spectroscopy. Histochemical analysis, O2 flux (JO2) by high-resolution respirometry, and quantification of key molecular markers of mitochondrial biogenesis and dynamics were performed in vastus lateralis biopsies.

Results: Pulmonary and cardiac functions were within normal range in all patients. VO2peak was lower in PASC than CTRL (24.7±5.0vs32.9±7.4mL*min-1*kg-1, respectively, P<.05). VO2 kinetics was slower in PASC than CTRL (41±12vs30±9s-1, P<.05). k was lower in PASC than CTRL (1.54±0.49vs2.07±0.51min-1, P<.05). Citrate synthase, PGC1alfa and JO2 for mitochondrial complex II were significantly lower in PASC vs CTRL (all P<.05).

Conclusion: In our cohort of patients with PASC, we showed limited exercise tolerance mainly due to “peripheral” determinants. Substantial reductions were observed for biomarkers of mitochondrial function, content, and biogenesis. PASC syndrome appears to negatively impact skeletal muscle function, although the disease is an heterogenous condition.

Source: Colosio M, Brocca L, Gatti M, Neri M, Crea E, Cadile F, Canepari M, Pellegrino MA, Polla B, Porcelli S, Bottinelli R. Structural and functional impairments of skeletal muscle in patients with post-acute sequelae of SARS-CoV-2 infection. J Appl Physiol (1985). 2023 Sep 7. doi: 10.1152/japplphysiol.00158.2023. Epub ahead of print. PMID: 37675472. https://journals.physiology.org/doi/abs/10.1152/japplphysiol.00158.2023 (Full text available as PDF file)