IRE1α-XBP1 Activation Elicited by Viral Singled Stranded RNA via TLR8 May Modulate Lung Cytokine Induction in SARS-CoV-2 Pneumonia
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Abstract
Initial symptoms of COVID-19 infection depend on viral replication, while hyperinflammation is a hallmark of critical illness and may drive severe pneumonia and death. Among the mechanisms potentially involved in the hyperinflammatory state, we focused on the unfolded protein response, because the IRE1α-XBP1 branch can be activated as result of the endoplasmic reticulum stress produced by the overwhelming synthesis of viral components and synergizes with Toll-like receptor signaling to induce cytokine expression. Viral RNA may trigger the IRE1α-XBP1 branch via TLR7/8 activation and like TLR2 and TLR4 may underpin cytokine expression trough XBP1 splicing ( sXBP1 ). The expression of IL1B , IL6 , and TNF mRNA in bronchoalveolar aspirates (BAAs) were higher in COVID-19 patients under mechanical ventilation and intubation who showed sXBP1 . The scrutiny of monocytic/macrophagic markers during active infection showed a reduction of those involved in antigen presentation and survival, as well as the IFN stimulated gene MX1 . These changes reverted after infection tests turned negative. In contrast, the expression of the mRNA of the serine protease TMPRSS2 involved in S protein priming showed a high expression during active infection. TLR8 mRNA showed an overwhelming expression as compared to TLR7 mRNA, which suggests the presence of monocyte-derived dendritic cells (MDDCs). In vitro experiments in MDDCs activated with ssRNA40, a positive-sense, single-stranded RNA (+ssRNA) like SARS-CoV-2 RNA, induced sXBP1 and the expression of IL-1β, IL-6, and TNF α at mRNA and protein levels. These responses were blunted by the IRE1α ribonuclease inhibitor MKC8866. Given the analogies between the results observed in BAAs and the effects induced by +ssRNA in MDDCs, IRE1α ribonuclease inhibition might be a druggable target in severe COVID-19 disease.
Author summary
COVID-19 pandemics put an unprecedented pressure on health systems. The need of new therapies urged research on the mechanisms triggered by the interaction of SARS-CoV-2 virus with host cells and the ensuing pathophysiology driving pneumonia and multiorgan failure. Hyperinflammation soon appeared as a mechanism involved in mortality that could even proceed after viral infection comes to an end. Hyperinflammation is supported by an inappropriate production of cytokines, and this explains the use of the term cytokine storm to refer to this phase of the disease. Given that insight into the molecular mechanisms driving cytokine storm should focus on the interaction of viral components with immune cells, experiments addressing the effect of viral components on its cognate receptors were carried out. It was observed that viral RNA induces a cytokine pattern like the one observed in bronchoalveolar aspirates of COVID-19 patients with critical disease. Overall, the study revealed that both cell organelle overload and receptors involved in the recognition of viral RNA may team up to induce proinflammatory cytokines. This mechanism can be exploited to develop new treatments for COVID-19 disease.
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SciScore for 10.1101/2022.01.26.22269752: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics IRB: The clinical part of the study was approved by the Ethics Committee of Area de Salud Valladolid Este (ref.
Consent: The study was approved by the Bioethical Committee of the Spanish Council of Research (CSIC) and the written informed consent of all healthy donors was obtained at Centro de Hemoterapia y Hemodonación de Castilla y León Biobank.Sex as a biological variable not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Table 2: Resources
Software and Algorithms Sentences Resources MDDCs were incubated under different conditions and then fixed, stained with Proteostat® dye and used for the assay of fluorescence in a Gallios flow cytometer at 488 nm in the … SciScore for 10.1101/2022.01.26.22269752: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Ethics IRB: The clinical part of the study was approved by the Ethics Committee of Area de Salud Valladolid Este (ref.
Consent: The study was approved by the Bioethical Committee of the Spanish Council of Research (CSIC) and the written informed consent of all healthy donors was obtained at Centro de Hemoterapia y Hemodonación de Castilla y León Biobank.Sex as a biological variable not detected. Randomization not detected. Blinding not detected. Power Analysis not detected. Table 2: Resources
Software and Algorithms Sentences Resources MDDCs were incubated under different conditions and then fixed, stained with Proteostat® dye and used for the assay of fluorescence in a Gallios flow cytometer at 488 nm in the FL3 channel using the Kaluza software version 1.1 for quantitative analysis (Beckman Coulter Life Sciences) Kaluzasuggested: (Kaluza, RRID:SCR_016182)Quantification and Statistical Analysis: Data are represented as the mean ± SEM and were analyzed with the Prism 9.0 statistical program. Prismsuggested: (PRISM, RRID:SCR_005375)Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
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Results from scite Reference Check: We found no unreliable references.
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