SARS-CoV-2 Spike protein alters microglial purinergic signaling

Abstract

Despite long-term sequelae of COVID-19 are emerging as a substantial public health concern, the mechanism underlying these processes still unclear. Evidence demonstrates that SARS-CoV-2 Spike protein can reach different brain regions, irrespective of viral brain replication resulting in activation of pattern recognition receptors (PRRs) and neuroinflammation. Considering that microglia dysfunction, which is regulated by a whole array of purinergic receptors, may be a central event in COVID-19 neuropathology, we investigated the impact of SARS-CoV-2 Spike protein on microglial purinergic signaling. Here, we demonstrate that cultured microglial cells (BV2 line) exposed to Spike protein induce ATP secretion and upregulation of P2Y6, P2Y12, NTPDase2 and NTPDase3 transcripts. Also, immunocytochemistry analysis shows that spike protein increases the expression of P2X7, P2Y1, P2Y6, and P2Y12 in BV2 cells. Additional, hippocampal tissue of Spike infused animals (6,5ug/site, i.c.v.) presents increased mRNA levels of P2X7, P2Y1, P2Y6, P2Y12, NTPDase1, and NTPDase2. Immunohistochemistry experiments confirmed high expression of the P2X7 receptor in microglial cells in CA3/DG hippocampal regions after spike infusion. These findings suggest that SARS-CoV-2 Spike protein modulates microglial purinergic signaling and opens new avenues for investigating the potential of purinergic receptors to mitigate COVID-19 consequences.

Self-DNA driven inflammation in COVID-19 and after mRNA-based vaccination: lessons for non-COVID-19 pathologies

“…Others discovered that S1 and S2 proteins administered intraperitoneally triggered enhanced concentrations of IL-6, IL-1β, and TNFα (16 hr post treatment) in WT mice but not in mice lacking TLR2, which indicates a role of TLR2, rather than TLR4 ( 279 ). In addition, CoV-2 S induced an enhanced release of ATP and IL-1β from human lung epithelial cells ( 249 ) and cultured microglial cells (BV2 line) and in the latter, it also induced the expression of the purinergic eATP receptor P2X7 ( 343 ).…”

Role of Microglia, Decreased Neurogenesis and Oligodendrocyte Depletion in Long COVID-Mediated Brain Impairments

“…The P2Y6 receptor stimulates phagocytosis after brain injury, which can lead to viable neuronal loss and memory impairment. Similarly, P2Y12 is associated with increased inducible nitric oxide synthase (iNOS) levels and inflammatory cytokines like IL-1β and TNF-α [ 41 ]. Furthermore, microgliosis has persisted even after viral clearance, contributing to cortical proteinopathies [ 42 ].…”

Intrinsic factors behind long‐COVID: II. SARS‐CoV‐2, extracellular vesicles, and neurological disorders

“…The alteration in the purinergic pathway occurs mainly after the induction of ATP secretion by the SARS-CoV-2 spike, leading to microglia activation, stimulation of the secretion of pro-inflammatory cytokines, and induction of neuroinflammation. 138 ATP activates the P2 receptors, particularly P2X4 and P2X7, microglial function modulators, resulting in the stimulation of free radicals and oxidative stress production in microglia. This stimulation is followed by inflammation and a chronic stress effect.…”

“…Alteration in purinergic signaling leading to neuroinflammation and neurodegeneration have been found to be related to long neurological conditions such as dementia and other neurodegenerative symptoms. 138 The main role of the P2Y6 receptor is to stimulate the removal of dead cell debris by inducing phagocytosis after CNS injury. 157 In the overexpression of microglia after SARS-CoV-2 infection and brain injury, the P2Y6 receptor can nonspecifically affect viable neuronal cells, leading to neurodegeneration and memory loss.…”

“…157 In the overexpression of microglia after SARS-CoV-2 infection and brain injury, the P2Y6 receptor can nonspecifically affect viable neuronal cells, leading to neurodegeneration and memory loss. 138 The exosomes carry miRNAs and regulatory proteins that have the potential to enhance the generation of antiinflammatory cytokines or prevent M2 macrophages from transitioning into an M1 pro-inflammatory activation state. Exosomes are facilitated the polarization of microglia into M1/M2 phenotypes by suppressing miR-130b-3p and enhancing the expression of PPARγ.…”