Article ; Online: SARS-COV-2 viroporins activate the NLRP3-inflammasome by the mitochondrial permeability transition pore.
2023 Volume 14, Page(s) 1064293
Abstract: Background: Compared to healthy controls, severe COVID19 patients display increased levels of activated NLRP3-inflammasome (NLRP3-I) and interleukin (IL)-1β. SARS-CoV-2 encodes viroporin proteins E and Orf3a(2-E+2-3a) with homologs to SARS-CoV-1, 1-E+1- ... ...
| Abstract | Background: Compared to healthy controls, severe COVID19 patients display increased levels of activated NLRP3-inflammasome (NLRP3-I) and interleukin (IL)-1β. SARS-CoV-2 encodes viroporin proteins E and Orf3a(2-E+2-3a) with homologs to SARS-CoV-1, 1-E+1-3a, which elevate NLRP3-I activation; by an unknown mechanism. Thus, we investigated how 2-E+2-3a activates the NLRP3-I to better understand the pathophysiology of severe COVID-19. Methods: We generated a polycistronic expression-vector co-expressing 2-E+2-3a from a single transcript. To elucidate how 2-E+2-3a activates the NLRP3-I, we reconstituted the NLRP3-I in 293T cells and used THP1-derived macrophages to monitor the secretion of mature IL-1β. Mitochondrial physiology was assessed using fluorescent microscopy and plate reader assays, and the release of mitochondrial DNA (mtDNA) was detected from cytosolic-enriched fractions using Real-Time PCR. Results: Expression of 2-E+2-3a in 293T cells increased cytosolic Ca++ and elevated mitochondrial Ca++, taken up through the MCUi11-sensitive mitochondrial calcium uniporter. Increased mitochondrial Ca++ stimulated NADH, mitochondrial reactive oxygen species (mROS) production and the release of mtDNA into the cytosol. Expression of 2-E+2-3a in NLRP3-I reconstituted 293T cells and THP1-derived macrophages displayed increased secretion of IL-1β. Increasing mitochondrial antioxidant defenses via treatment with MnTBAP or genetic expression of mCAT abolished 2-E+2-3a elevation of mROS, cytosolic mtDNA levels, and secretion of NLRP3-activated-IL-1β. The 2-E+2-3a-induced release of mtDNA and the secretion of NLRP3-activated-IL-1β were absent in cells lacking mtDNA and blocked in cells treated with the mitochondrial-permeability-pore(mtPTP)-specific inhibitor NIM811. Conclusion: Our findings revealed that mROS activates the release of mitochondrial DNA via the NIM811-sensitive mitochondrial-permeability-pore(mtPTP), activating the inflammasome. Hence, interventions targeting mROS and the mtPTP may mitigate the severity of COVID-19 cytokine storms. |
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| MeSH term(s) | Humans ; Inflammasomes/genetics ; Inflammasomes/metabolism ; NLR Family, Pyrin Domain-Containing 3 Protein/genetics ; NLR Family, Pyrin Domain-Containing 3 Protein/metabolism ; Viroporin Proteins ; SARS-CoV-2/genetics ; Mitochondrial Permeability Transition Pore ; COVID-19 ; DNA, Mitochondrial/metabolism |
| Chemical Substances | Inflammasomes ; NLR Family, Pyrin Domain-Containing 3 Protein ; Viroporin Proteins ; Mitochondrial Permeability Transition Pore ; DNA, Mitochondrial |
| Language | English |
| Publishing date | 2023-02-20 |
| Publishing country | Switzerland |
| Document type | Journal Article ; Research Support, U.S. Gov't, Non-P.H.S. |
| ZDB-ID | 2606827-8 |
| ISSN | 1664-3224 ; 1664-3224 |
| ISSN (online) | 1664-3224 |
| ISSN | 1664-3224 |
| DOI | 10.3389/fimmu.2023.1064293 |
| Database | MEDical Literature Analysis and Retrieval System OnLINE |
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