SARS-CoV-2 Spike Glycoprotein S1 Induces Neuroinflammation in BV-2 Microglia

Abstract

In addition to respiratory complications produced by SARS‐CoV‐2, accumulating evidence suggests that some neurological symptoms are associated with the disease caused by this coronavirus. In this study, we investigated the effects of the SARS‐CoV‐2 spike protein S1 stimulation on neuroinflammation in BV-2 microglia. Analyses of culture supernatants revealed an increase in the production of TNF-α, IL-6, IL-1β and iNOS/NO. S1 also increased protein levels of phospho-p65 and phospho-IκBα, as well as enhanced DNA binding and transcriptional activity of NF-κB. These effects of the protein were blocked in the presence of BAY11-7082 (1 µM). Exposure of S1 to BV-2 microglia also increased the protein levels of NLRP3 inflammasome and enhanced caspase-1 activity. Increased protein levels of p38 MAPK was observed in BV-2 microglia stimulated with the spike protein S1 (100 ng/ml), an action that was reduced in the presence of SKF 86,002 (1 µM). Results of immunofluorescence microscopy showed an increase in TLR4 protein expression in S1-stimulated BV-2 microglia. Furthermore, pharmacological inhibition with TAK 242 (1 µM) and transfection with TLR4 small interfering RNA resulted in significant reduction in TNF-α and IL-6 production in S1-stimulated BV-2 microglia. These results have provided the first evidence demonstrating S1-induced neuroinflammation in BV-2 microglia. We propose that induction of neuroinflammation by this protein in the microglia is mediated through activation of NF-κB and p38 MAPK, possibly as a result of TLR4 activation. These results contribute to our understanding of some of the mechanisms involved in CNS pathologies of SARS-CoV-2.

A Peek into Pandora’s Box: COVID-19 and Neurodegeneration

“…Exaggerated systemic- and neuroinflammation may alter the course of or precipitate neuropathology in neurodegenerative diseases [ 166 , 167 ]. Based on their previous studies and others, Heneka et al have proposed that SARS-CoV-2 infection results in NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome activation which, in turn, produces impaired clearance and pathological accumulation of neurodegeneration-associated peptides such as amyloid β (Aβ) and tau [ 163 , 168 , 169 , 170 ]. Using 3D human brain organoids, Ramani et al showed that SARS-CoV-2 preferably targets neurons, causing mislocalization of tau from axons to soma, tau hyperphosphorylation, and, ultimately, neuronal death [ 171 ].…”

Potential benefits of ginseng against COVID-19 by targeting inflammasomes

“…Although the respiratory system is the primary target of SARS-CoV-2 infection, many COVID-19 patients exert mind and severe neurological manifestations [ 40 , 41 ], which indicates the potential for neurotropism and neuropathogenesis by SARS-CoV-2 through inducing neuroinflammation, and some studies reported the regulatory role of SARS-CoV-2 in NLRP3 inflammasome activated neuroinflammation. An in vitro study demonstrated that SARS-CoV-2 spike protein induces neuroinflammation by activating the NLRP3 inflammasome and NLRP3 inflammasome-activated inflammatory signaling pathways in BV2 microglial cells [ 42 ]. A case study of deceased COVID-19 patients also reported that SARS-CoV-2 nucleocapsid protein was co-localized with ACE2 and NLRP3 inflammasome in the cerebral cortical tissue-resident macrophages of deceased COVID-19 patients [ 43 ], which strongly suggests the involvement of NLRP3 inflammasome in SARS-CoV-2 cerebral pathogenicity.…”

“… Types Roles Activators/inhibitors Models Ref. NLRP3 Activation SARS-CoV-2 spike protein Caco-2 [ 24 ] SARS-CoV-2 viroporin HEK293 & A549 [ 25 ] SARS-CoV-2 single-stranded RNA Macrophages [ 26 ] SARS-CoV-2 envelope protein BMDMs [ 27 ] SARS-CoV-2 nucleocapsid protein BMDMs & THP-1 [ 28 ] SARS-CoV-2 spike protein PBMCs [ 30 ] SARS-CoV-2 spike protein HSPCs & EPCs [ 31 ] SARS-CoV-2 spike protein HSPCs & EPCs [ 34 ] SARS-CoV-2 NSP6 Lung epithelial cells of COVID-19 patients [ 35 ] SARS-CoV-2 Blood cells of COVID-19 patients [ 37 ] SARS-CoV-2 Circulating monocytes of COVID-19 patients [ 38 ] SARS-CoV-2 Circulating monocytes of COVID-19 patients [ 39 ] SARS-CoV-2 spike protein BV-2 [ 42 ] SARS-CoV-2 Cerebral cortical tissues of COVID-19 patients [ 43 ] SARS-CoV-2 Aged COVID-19 patients [ 46 ] Inhibition SARS-CoV-2 NSP1 and NSP13 HEK293 & THP-1 [ 29 ] …”

Therapeutic Targeting of Innate Immune Receptors Against SARS-CoV-2 Infection

“…Due to ACE2 upregulation mediated by TLR-4, SARS-CoV-2 is able to infect more heart and lung cells ( Heads, 2020 ; Aboudounya et al, 2021 ; Han et al, 2021 ; Manik et al, 2022 ). TAK-242, an anti-inflammatory molecule which inhibits TLR4 mediated signaling, was found to reduce the level of TNF-α and IL-6 in BV-2 mouse microglial cell line ( Olajide et al, 2022 ).…”