TLR4 and nucleolin influence cell injury, apoptosis and inflammatory factor expression in respiratory syncytial virus‐infected N2a neuronal cells

Abstract

Respiratory syncytial virus (RSV) infection was recently reported to be associated with central nervous system (CNS) symptoms and neurological complications; however, related studies are very limited. Moreover, the molecular mechanism underlying RSV neuropathogenesis is still unclear. Our previous study revealed that toll‐like receptor 4 (TLR4) and nucleolin (C23) could be modulated and that they played a role during RSV infection in mouse neuronal‐2a (N2a) cells. In the present study, the effects of silencing of TLR4 and C23 on RSV propagation and N2a cellular responses were examined by using RNA interference technology. Four N2a cell treatment groups were established, namely, a normal control group, RSV control group, TLR4 siRNA + RSV group, and C23 siRNA + RSV group. Expression changes in NeuN protein and colocalization of C23 and TLR4 with RSV F protein were assessed using confocal microscopy. Changes in TLR4 and C23 mRNA expression, TLR4, C23, TLR3, TLR7, and p‐NF‐κB protein expression, and interleukin (IL)‐8, IL‐6, and tumor necrosis factor (TNF‐α) cytokine secretion was measured using quantitative real‐time reverse‐transcription polymerase chain reaction, Western blot analysis, and enzyme‐linked immunosorbent assay, respectively. RSV titers and the apoptotic status of N2a cells were monitored using plaque formation assays and flow cytometry, respectively. The results indicated that TLR4 and C23 gene knockdown decreased the amount of F protein in RSV‐infected N2a cells, inhibited RSV propagation, attenuated N2a neuronal injury, diminished cell apoptosis levels, downregulated TLR3 and TLR7 protein expression, and reduced inflammatory protein expression. Therefore, TLR4 and C23 knockdown influences cell injury, apoptosis and inflammatory protein expression in RSV‐infected N2a cells.

Overexpression of microRNA-202-3p in bone marrow mesenchymal stem cells improves cerebral ischemia-reperfusion injury by promoting angiogenesis and inhibiting inflammation

“…As TLR4 can aggravate inflammatory damage, many studies are based on directly inhibiting TLR4 expression or related signaling pathways to find suitable drugs to protect against the effects of ischemic stroke [ 34 – 36 ]. There is increasing evidence that down-regulation of TLR4 can significantly inhibit ischemia-induced neuronal apoptosis [ 37 , 38 ]. Besides, TLR4 activation causes the release of IFs such as TNF-a, IL-6, and IL-1β.…”

Coronaviruses: Is Sialic Acid a Gate to the Eye of Cytokine Storm? From the Entry to the Effects

“…In result, the enhanced immune signalling pathways lead to a stage of hyperresponsiveness to PRRs agonists [ 57 ]. It has been shown that respiratory syncytial virus (RSV)-infected airway epithelial cells become hypersensitive to endotoxin by enhancing TLR4 expression with production of IL-8 and tumor necrosis factor α (TNFα) as well as increased mitogen-activated protein (MAP) kinase activity [ 58 ].…”

Nucleolin acts as the receptor for C1QTNF4 and supports C1QTNF4-mediated innate immunity modulation

“…Nucleolin has been identified as part of a multiprotein signaling complex containing annexin A2, calreticulin, and TLR4 on the surface of endothelial cells (34), as well as in complex with heat shock proteins (including HSPA1A), TLR2, and TLR4 on the cell surface of THP-1 cells (35). Further, TLR4 may act as a coreceptor of nucleolin in cellular entry of RSV (36,37). Both nucleolin (18) and TLR4 in conjunction with MD-2 and CD14 (38) have been reported or are known to bind LPS, and engagement of TLR4 can stimulate IL-6 and TNF-α production (39,40).…”