Upregulation of olfactory receptors and neuronal-associated genes highlights complex immune and neuronal dysregulation in [LC], 2025, Shahbaz+

SNT Gatchaman

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Upregulation of olfactory receptors and neuronal-associated genes highlights complex immune and neuronal dysregulation in Long COVID patients
Shahbaz; Rezaeifar; Syed; Redmond; Terveart; Osman; Elahi

A substantial portion of patients infected with SARS-CoV-2 experience prolonged complications, known as Long COVID (LC). A subset of these patients exhibits the most debilitating symptoms, similar to those defined in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS).

We performed bulk RNA sequencing (RNAseq) on the whole blood of LC with ME/CFS, at least 12 months post-onset of the acute disease, and compared them with controls. We found that LC patients had a distinct transcriptional profile compared to controls. Key findings include the upregulation of genes involved in immune dysregulation and neuronal development, such as Fezf2, BRINP2, HOXC12, MEIS2, ZFHX3, and RELN. These genes are linked to neuroinflammatory responses, cognitive impairments, and hematopoietic disturbances, suggesting ongoing neurological and immune disturbances in LC patients.

RELN, encoding the Reelin protein, was notably elevated in LC patients, potentially serving as a biomarker for LC pathogenesis due to its role in inflammation and neuronal function. Immune cell analysis showed altered profiles in LC patients, with increased activated memory CD4+ T cells and neutrophils, and decreased regulatory T cells and NK cells, reflecting immune dysregulation. Changes in cytokine and chemokine expression further underscore the chronic inflammatory state in LC patients. Notably, a unique upregulation of olfactory receptors (ORs) suggest alternative roles for ORs in non-olfactory tissues.

Pathway analysis revealed upregulation in ribosomal RNA processing, amino acid metabolism, protein synthesis, cell proliferation, DNA repair, and mitochondrial pathways, indicating heightened metabolic and immune demands. Conversely, downregulated pathways, such as VEGF signaling and TP53 activity, point to impaired tissue repair and cellular stress responses.

Overall, our study underscores the complex interplay between immune and neuronal dysfunction in LC patients, providing insights into potential diagnostic biomarkers and therapeutic targets. Future research is needed to fully understand the roles and interactions of these genes in LC pathophysiology.

Link | PDF (Brain, Behavior, and Immunity) [Open Access]
 
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Kudos to the authors for not saying ME/CFS = Fatigue.
ME/CFS, is characterized by profound post-exertional malaise, cognitive dysfunction (or brain fog), sleeping disturbance, and unexplained fatigue, can persist for months and possibly years after the acute disease onset

They used CCC, with the DePaul questionnaire as criteria.

The analysis of immune cell subsets demonstrated significant immune cell alterations in LC patients. For instance, we found notable increases in activated memory CD4 + T cells and neutrophils, alongside decreases in Tregs and NK cells. These findings align with our previous reports supporting immune dysregulation in LC patients (Saito, 2024, Saito, 2024)

Given the magnitude of altered genes in LC patients, we performed pathway analysis. We found the upregulation of pathways related to ribosomal RNA processing, amino acid metabolism, and protein synthesis, particularly the rRNA processing, suggesting a state of heightened protein synthesis in LC patients. This may be a response to increased cellular stress and demand for protein production. The activation of the eukaryotic translation initiation, elongation, and termination pathways further indicates a robust cellular response to stress (Pestova and Hellen, 2000, Harding, 2003), possibly involving a response to the tissue repair process, the synthesis of antiviral proteins, or a hijacking of the host's protein synthesis machinery by the virus.

We also observed upregulation of mitochondrial pathways such as electron transport, ATP synthesis, and oxidative phosphorylation. This suggests increased mitochondrial activity or metabolic demand, which aligns with reports of increased energy requirements in chronic conditions (Wallace, 2005).

Interesting study.
 
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