bims-inflin 2024-03-10 papers

on Inflammasome and infection

Issue of 2024‒03‒10
two papers selected by
Juliane Cristina Ribeiro Fernandes, Faculdade de Medicina de Ribeirão Preto

METTL3-deficiency m6A-dependently degrades MALAT1 to suppress NLRP3-mediated pyroptotic cell death and inflammation in Mycobacterium tuberculosis (H37Ra strain)-infected mouse macrophages.
SARS-CoV-2 virus-like particle variants alpha and delta mimic the native viruses in their differential inflammasome activating potential.

Tuberculosis (Edinb). 2024 Mar 04. pii: S1472-9792(24)00028-3. [Epub ahead of print]146 102502

METTL3-deficiency m6A-dependently degrades MALAT1 to suppress NLRP3-mediated pyroptotic cell death and inflammation in Mycobacterium tuberculosis (H37Ra strain)-infected mouse macrophages.

Limei Han, Nueramina Tieliwaerdi, Xin Li.

  Mycobacterium tuberculosis (Mtb)-infected macrophages aggravated the development of pulmonary tuberculosis, but its detailed molecular mechanisms are still largely unknown. Here, the mouse primary peritoneal macrophages were infected with the attenuated strain of Mtb H37Ra, and we firstly verified that targeting a novel METTL3/N6-Methyladenosine (m6A)/LncRNA MALAT1/miR-125b/TLR4 axis was effective to suppress pyroptotic cell death in the Mtb-infected macrophages. Specifically, through performing Real-Time qPCR and Western Blot analysis, we validated that METTL3, LncRNA MALAT1 and TLR4 were elevated, whereas miR-125b and the anti-oxidant agents (Nrf2 and HO-1) were downregulated in Mtb-infected mouse macrophages. In addition, functional experiments confirmed that both ROS scavenger NAC and METTL3-ablation downregulated NLRP3, GSDMD-C, cleaved Caspase-1 and ASC to restrain pyroptotic cell death and decreased the expression levels of IL-1β, IL-18, IL-6 and TNF-α to restrain inflammatory cytokines expression in Mtb-infected macrophages. Next, METTL3-ablation induced m6A-demethylation and instability in LncRNA MALAT1, and low-expressed LncRNA MALAT1 caused TLR4 downregulation through sponging miR-125b, resulting in the inactivation of NLRP3 inflammasome. Finally, silencing of METTL3-induced protective effects in Mtb-infected macrophages were all abrogated by overexpressing LncRNA MALAT1 and downregulating miR-125b. Thus, we concluded that targeting METTL3-mediated m6A modifications suppressed Mtb-induced pyroptotic cell death in mouse macrophages, and the downstream LncRNA MALAT1/miR-125b/TLR4 axis played critical role in this process.

Keywords:  Cellular inflammation; METTL3; Mycobacterium tuberculosis; NLRP3 inflammasome; Pulmonary tuberculosis; m6A modifications

DOI:  https://doi.org/10.1016/j.tube.2024.102502
Antiviral Res. 2024 Mar 05. pii: S0166-3542(24)00065-2. [Epub ahead of print]224 105857

SARS-CoV-2 virus-like particle variants alpha and delta mimic the native viruses in their differential inflammasome activating potential.

Magdalena Bandyszewska, Magdalena Ambrożek-Latecka, Grażyna Hoser, Małgorzata Grzanka, Franziska Hornung, Stefanie Deinhardt-Emmer, Tomasz Skirecki.

  The emerging SARS-CoV-2 variants are evolving to evade human immunity and differ in their pathogenicity. While evasion of the variants from adaptive immunity is widely investigated, there is a paucity of knowledge about their interactions with innate immunity. Inflammasome assembly is one of the most potent mechanisms of the early innate response to viruses, but when it is inappropriate, it can perpetuate tissue damage. In this study, we focused on the capacity of SARS-CoV-2 Alpha and Delta variants to activate the NLRP3 inflammasome. We compared the macrophage activation, particularly the inflammasome formation, using Alpha- and Delta-spike virus-like particles (VLPs). We found that VLPs of both variants activated the inflammasome even without a priming step. Delta-spike VLPs had a significantly stronger effect on triggering pyroptosis and inflammasome assembly in THP-1 macrophages than did Alfa-spike VLPs. Cells treated with Delta VLPs showed greater cleavage of caspase-1 and IL-1β release. Furthermore, Delta VLPs induced stronger cytokine secretion from macrophages and caused essential impairment of mitochondrial respiration in comparison to Alpha VLPs. Additionally, infection of primary human monocyte-derived macrophages with the SARS-CoV-2 variants confirmed the observations in VLPs. Collectively, we revealed that SARS-CoV-2 Delta had a greater impact on the inflammasome activation, cell death and mitochondrial respiration in macrophages than did the Alpha variant. Importantly, the differential response to the SARS-CoV-2 variants can influence the efficacy of therapies targeting the host's innate immunity.

Keywords:  COVID-19; Caspase-1; Innate immunity; Macrophages; Pyroptosis

DOI:  https://doi.org/10.1016/j.antiviral.2024.105857