bims-inflin 2024-12-22 papers

FASEB J. 2024 Dec 13. 38(24): e70235

Time-of-day control of mitochondria regulates NLRP3 inflammasome activation in macrophages.

James R O'Siorain, Shannon L Cox, Cloé Payet, Frances K Nally, Yan He, Tabea T Drewinksi, Oran D Kennedy, Jennifer K Dowling, Mark Mellett, James O Early, Annie M Curtis.

Macrophages are innate immune cells that orchestrate the process of inflammation, which varies across time of day. This ensures appropriate biological timing of the immune response with the external environment. The NLRP3 inflammasome mediates IL-1-family cytokine release via pyroptosis. Mitochondria play a multifaceted role regulating NLRP3 inflammasome activity. Mitochondria exhibit distinct metabolic changes across time of day, which are influenced by clock genes. However, whether the macrophage clock regulates the NLRP3 inflammasome via mitochondrial control remains unclear. We find heightened mitochondrial membrane potential (Δψm) and enhanced NLRP3 inflammasome activation from peritoneal exudate cells (PECs) isolated at circadian time (CT) 12 compared to CT 0. In vitro time-of-day synchronization of bone-marrow derived macrophages (BMDMs) induced time-dependent differences in NLRP3 inflammasome activation. Myeloid-specific Bmal1-deletion enhanced NLRP3 inflammasome activity in PECs at CT0 and in unsynchronized BMDMs compared to controls. Pharmacologically disrupting Δψm in synchronized cells reduced NLRP3 inflammasome activation to comparable levels, and the same occurred with Bmal1-deletion. These results further demonstrate circadian clock timing of the NLRP3 inflammasome, which is dependent on mitochondrial function and driven through the circadian gene Bmal1.

Keywords: NLRP3 inflammasome; circadian rhythms; macrophages; mitochondria; pyroptosis

DOI: https://doi.org/10.1096/fj.202400508RR

PLoS Pathog. 2024 Dec 17. 20(12): e1012805

Zinc homeostasis regulates caspase activity and inflammasome activation.

Xiao Gong, Weidi Gu, Shuo Fu, Gonglu Zou, Zhengfan Jiang.

Inflammasome activation drives pyroptotic cell death and the release of inflammatory cytokines, and many diseases involve its overactivation. Zinc is essential for all organisms as a trace element, but its functions in innate immunity remain undefined. Here, we reported that Zn2+ inhibits caspase-1 to hinder inflammasome activation. We first identified the zinc exporter solute carrier family 30 member 1 (SLC30A1) as an inflammasome regulator, using a genome-wide CRISPR-Cas9-mediated screen. SLC30A1 deficiency suppressed multiple inflammasomes by increasing intracellular levels of Zn2+, which bound and inhibited caspase-1 at its active site residues H237, C244 and C285. Mutation of these residues almost completely blocked zinc binding. Similarly, Zn2+ also inhibited caspase-4/5/11-mediated noncanonical inflammasome activation. Importantly, zinc supplementation significantly relieved cecal ligation and puncture (CLP)-induced sepsis, Imiquimod (IMQ)-induced psoriasis and Alzheimer's disease. Thus, zinc might be used to treat inflammasome-related diseases as a broad-spectrum inflammasome inhibitor.

DOI: https://doi.org/10.1371/journal.ppat.1012805

Proc Natl Acad Sci U S A. 2024 Dec 24. 121(52): e2406776121

Single-cell atlas of Leishmania development in sandflies reveals the heterogeneity of transmitted parasites and their role in infection.

Carolina M C Catta-Preta, Kashinath Ghosh, David L Sacks, Tiago R Ferreira.

Sandfly vectors transmit Leishmania through egestion of parasites into the host skin. The transmissible dose is shaped by Leishmania development in the sandfly gut, described as a sequential differentiation of promastigote morphotypes. Apart from isolated mammal-infective metacyclic promastigotes, little is known about the transcriptional programs and molecular markers for other stages coinhabiting the midgut in mature infections and cotransmitted by the sandfly bite. Here, we elucidate the single-cell transcriptomic complexity of Leishmania major colonizing its natural vector Phlebotomus duboscqi at early and late infection, providing markers for three transmissible stages. Contrary to prevailing models, our analyses indicate a nonlinear developmental progression, with bifurcation into either replicating early metacyclics or attached and detached haptomonads. We demonstrate that haptomonads constitute a key component of the transmitted inoculum and, along with nondividing late metacyclics, are infectious to and exacerbate the pathology in mice. Our single-cell analysis and validated markers will facilitate further studies on the Leishmania life cycle and its implications for vector-to-host transmission dynamics.

Keywords: Leishmania; infection; sand fly; single-cell RNA-seq; transmission

DOI: https://doi.org/10.1073/pnas.2406776121

Cell Rep. 2024 Dec 12. pii: S2211-1247(24)01431-1. [Epub ahead of print]43(12): 115080

SARS-CoV-2 3CLpro (main protease) regulates caspase activation of gasdermin-D/E pores leading to secretion and extracellular activity of 3CLpro.

Peter M Grin, Kaushal Baid, Hugo C R de Jesus, Nedim Kozarac, Peter A Bell, Steven Z Jiang, Reinhild Kappelhoff, Georgina S Butler, Nathan G F Leborgne, Christina Pan, Isabel Pablos, Yoan Machado, John C Vederas, Hugh Kim, Charaf Benarafa, Arinjay Banerjee, Christopher M Overall.

SARS-CoV-2 3C-like protease (3CLpro or Mpro) cleaves the SARS-CoV-2 polyprotein and >300 intracellular host proteins to enhance viral replication. By lytic cell death following gasdermin (GSDM) pore formation in cell membranes, antiviral pyroptosis decreases 3CLpro expression and viral replication. Unexpectedly, 3CLpro and nucleocapsid proteins undergo unconventional secretion from infected cells via caspase-activated GSDMD/E pores in the absence of cell lysis. Bronchoalveolar lavage fluid of wild-type SARS-CoV-2-infected mice contains 3CLpro, which decreases in Gsdmd-/-Gsdme-/- mice. We identify new 3CLpro cut-sites in GSDMD at LQ29↓30SS, which blocks pore formation by 3CLpro cleavage at LH270↓N lying adjacent to the caspase activation site (NFLTD275↓G). Cleavage inactivation of GSDMD prevents excessive pore formation, thus countering antiviral pyroptosis and increasing 3CLpro secretion. Extracellular 3CLpro retains activity in serum, dampens platelet activation and aggregation, and inactivates antiviral interferon-λ1. Thus, in countering gasdermin pore formation and pyroptosis in SARS-CoV-2 infection, 3CLpro is secreted with extracellular pathological sequelae.

Keywords: COVID-19; CP; Immunology; caspase; gasdermin; infection; interferon; platelet; protease; proteolysis; unconventional protein secretion; virus

DOI: https://doi.org/10.1016/j.celrep.2024.115080

mBio. 2024 Dec 16. e0327424

Inhibition and evasion of neutrophil microbicidal responses by Legionella longbeachae.

Hannah E Hanford, Christopher T D Price, Silvia Uriarte, Yousef Abu Kwaik.

Legionella species evade degradation and proliferate within alveolar macrophages as an essential step for the manifestation of disease. However, most intracellular bacterial pathogens are restricted in neutrophils, which are the first line of innate immune defense against invading pathogens. Bacterial degradation within neutrophils is mediated by the fusion of microbicidal granules to pathogen-containing phagosomes and the generation of reactive oxygen species (ROS) by the phagocyte NADPH oxidase complex. Here, we show that human neutrophils fail to trigger microbicidal processes and, consequently, fail to restrict L. longbeachae. In addition, neutrophils infected with L. longbeachae fail to undergo a robust pro-inflammatory response, such as degranulation and IL-8 production. Here, we identify three strategies employed by L. longbeachae for evading restriction by neutrophils and inhibiting the neutrophil microbicidal response to other bacteria co-inhabiting in the same cell. First, L. longbeachae excludes the cytosolic and membrane-bound subunits of the phagocyte NADPH oxidase complex from its phagosomal membrane independent of the type 4 secretion system (T4SS). Consequently, infected neutrophils fail to generate robust ROS in response to L. longbeachae. Second, L. longbeachae impedes the fusion of azurophilic granules to its phagosome and the phagosomes of bacteria co-inhabiting the same cell through T4SS-independent mechanisms. Third, L. longbeachae protects phagosomes of co-inhabiting bacteria from degradation by ROS through a trans-acting T4SS-dependent mechanism. Collectively, we conclude that L. longbeachae evades restriction by human neutrophils via T4SS-independent mechanisms and utilizes trans-acting T4SS-dependent mechanisms for inhibition of neutrophil ROS generation throughout the cell cytosol.
IMPORTANCE: Legionella longbeachae is commonly found in soil environments where it interacts with a wide variety of protist hosts and microbial competitors. Upon transmission to humans, L. longbeachae invades and replicates within alveolar macrophages, leading to the manifestation of pneumonia. In addition to alveolar macrophages, neutrophils are abundant immune cells acting as the first line of defense against invading pathogens. While most intracellular bacterial species are killed and degraded by neutrophils, we show that L. longbeachae evades degradation. The pathogen impairs the major neutrophils' microbicidal processes, including the fusion of microbicidal granules to the pathogen-containing vacuole. By inhibiting of assembly of the phagocyte NADPH oxidase complex, the pathogen blocks neutrophils from generating microbicide reactive oxygen species. Overall, L. longbeachae employs unique virulence strategies to evade the major microbicidal processes of neutrophils.

Keywords: NADPH oxidase; ROS; azurphilic granules; granules; lysosomes

DOI: https://doi.org/10.1128/mbio.03274-24

Front Immunol. 2024 ;15 1500676

Metabolism: a potential regulator of neutrophil fate.

Zhou Yipeng, Cao Chao, Li Ranran, Pan Tingting, Qu Hongping.

Neutrophils are essential components of the innate immune system that defend against the invading pathogens, such as bacteria, viruses, and fungi, as well as having regulatory roles in various conditions, including tissue repair, cancer immunity, and inflammation modulation. The function of neutrophils is strongly related to their mode of cell death, as different types of cell death involve various cellular and molecular alterations. Apoptosis, a non-inflammatory and programmed type of cell death, is the most common in neutrophils, while other modes of cell death, including NETOsis, necrosis, necroptosis, autophagy, pyroptosis, and ferroptosis, have specific roles in neutrophil function regulation. Immunometabolism refers to energy and substance metabolism in immune cells, and profoundly influences immune cell fate and immune system function. Intercellular and intracellular signal transduction modulate neutrophil metabolism, which can, in turn, alter their activities by influencing various cell signaling pathways. In this review, we compile an extensive body of evidence demonstrating the role of neutrophil metabolism in their various forms of cell death. The review highlights the intricate metabolic characteristics of neutrophils and their interplay with various types of cell death.

Keywords: apoptosis; cell death; cell metabolism; glycolysis; neutrophil

DOI: https://doi.org/10.3389/fimmu.2024.1500676