MIP From Legionella pneumophila Influences the Phagocytosis and Chemotaxis of RAW264.7 Macrophages by Regulating the lncRNA GAS5/miR-21/SOCS6 Axis

Silencing of lncRNA Gm26917 Attenuates Alveolar Macrophage-mediated Inflammatory Response in LPS-induced Acute Lung Injury Via Inhibiting NKRF Ubiquitination

The inflammatory response mediated by alveolar macrophages plays a crucial role in the development of acute lung injury. Numerous studies have reported that lncRNAs are highly expressed in acute lung injury in mouse models and cell lines, and acute lung injury (ALI) can be effectively alleviated by targeting these lncRNAs. The aim of this study was to explore the mechanism by LncRNA Gm26917 regulates the inflammatory response in alveolar macrophages during acute lung injury mouse model. We initially observed a significant upregulation of Gm26917 expression in both ALI conditions and in MH-S cells treated with LPS. Furthermore, the silencing of Gm26917 via lentivirus-mediated methods conferred protection against LPS-induced ALI. Additionally, siRNA-mediated knockdown of Gm26917 attenuated LPS-induced inflammatory responses and modulated the function of alveolar macrophages. Subsequent mechanistic studies revealed that Gm26917 interacts with NKRF, and its knockdown suppressed NKRF ubiquitination, thereby enhancing NKRF binding to p50 and subsequently inhibiting the NF-κB signaling pathway. In conclusion, our findings demonstrate that silencing Gm26917 can mitigate LPS-induced ALI by modulating the NF-κB signaling pathway in alveolar macrophages through interactions with NKRF.

Development of Polymerase Chain Reaction-High-Resolution Melt Assay for Waterborne Pathogens Legionella pneumophila, Vibrio parahaemolyticus, and Camplobacter jejuni

Legionella pneumophila is the waterborne pathogen primarily responsible for causing both Pontiac Fever and Legionnaire's Disease in humans. L. pneumophila is transmitted via aerosolized water droplets. The purpose of this study was to design and test primers to allow for rapid polymerase chain reaction (PCR) melt detection and identification of this infectious agent in cases of clinical or emergency response detection. New PCR primers were designed for this species of bacteria; the primer set was purchased from IDT and the target bacterial DNA was purchased from ATCC. The L. pneumophila primers targeted the macrophage infectivity potentiator gene (mip), which inhibits macrophage phagocytosis. The primers were tested for specificity, repeatability, and sensitivity using PCR-high-resolution melt (HRM) assays. The primer set was found to be specific to the designated bacteria and did not amplify the other twenty-one species from the panel. The L. pneumophila assay was able to be multiplexed. The duplex assay consists of primers for L. pneumophila and Vibrio parahaemolyticus, which are both waterborne pathogens. The triplex assay consists of primers for L. pneumophila, V. parahaemolyticus, and Campylobacter jejuni. The unique melting temperature for the L. pneumophila primer assay is 82.84 ± 0.19 °C, the C. jejuni assay is 78.10 ± 0.58 °C, and the V. parahaemolyticus assay is 86.74 ± 0.65 °C.

Xinfeng Capsule Inhibits Pyroptosis and Ameliorates Myocardial Injury in Rats with Adjuvant Arthritis via the GAS5/miR-21/TLR4 Axis

Purpose

This study probed the mechanism of action of Xinfeng Capsule (XFC) in myocardial injury in rats with adjuvant arthritis (AA) via the growth arrest-specific transcript 5 (GAS5)/microRNA-21 (miR-21)/Toll-like receptor 4 (TLR4) axis.

Methods

Rats were injected with Freund's complete adjuvant to establish a rat model of AA. Then, some modeled rats were given normal saline or drugs only, and some modeled rats were injected with adeno-associated viruses or necrosulfonamide (NSA; a pyroptosis inhibitor) before drug administration. Toe swelling and arthritis index (AI) were calculated. Pathological and morphological changes in synovial and myocardial tissues were analyzed with hematoxylin-eosin staining, and pyroptotic vesicles and the ultrastructural changes of myocardial tissues were observed with transmission electron microscopy. The serum levels of interleukin (IL)-1β, IL-18, IL-6, and tumor necrosis factor (TNF)-α were detected, and lactate dehydrogenase (LDH) release was measured in myocardial tissues, accompanied by the examination of GAS5, miR-21, TLR4, nuclear factor-kB (NF-κB) p65, nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), Caspase-1, and Gasdermin D (GSDMD) expression in myocardial tissues.

Results

After AA modeling, rats presented with significantly increased toe swelling and AI scores, synovial and myocardial tissue damage, elevated pyroptotic vesicles, and markedly enhanced serum levels of IL-1β, IL-18, IL-6, and TNF-α, accompanied by significantly diminished GAS5 expression, substantially augmented miR-21, TLR4, NF-κB p65, NLRP3, Caspase-1, and GSDMD expression, greatly increased LDH release in myocardial tissues. XFC treatment significantly declined toe swelling, AI scores, synovial and myocardial tissue damage, and the serum levels of IL-1β, IL-18, IL-6, and TNF-α in AA rats. Additionally, XFC treatment markedly elevated GAS5 expression and substantially lowered LDH release and miR-21, TLR4, NF-κB p65, NLRP3, Caspase-1, and GSDMD expression in myocardial tissues of AA rats. Moreover, the above effects of XFC in AA rats were further promoted by GAS5 overexpression or NSA treatment.

Conclusion

XFC alleviated myocardial injury in AA rats by regulating the GAS5/miR-21/TLR4 axis and inhibiting pyroptosis and pro-inflammatory cytokine secretion.

A Structural Proteome Screen Identifies Protein Mimicry in Host-Microbe Systems

Host-microbe systems are evolutionary niches that produce coevolved biological interactions and are a key component of global health. However, these systems have historically been a difficult field of biological research due to their experimental intractability. Impactful advances in global health will be obtained by leveraging in silico screens to identify genes involved in mediating interspecific interactions. These predictions will progress our understanding of these systems and lay the groundwork for future in vitro and in vivo experiments and bioengineering projects. A driver of host-manipulation and intracellular survival utilized by host-associated microbes is molecular mimicry, a critical mechanism that can occur at any level from DNA to protein structures. We applied protein structure prediction and alignment tools to explore host-associated bacterial structural proteomes for examples of protein structure mimicry. By leveraging the Legionella pneumophila proteome and its many known structural mimics, we developed and validated a screen that can be applied to virtually any host-microbe system to uncover signals of protein mimicry. These mimics represent candidate proteins that mediate host interactions in microbial proteomes. We successfully applied this screen to other microbes with demonstrated effects on global health, Helicobacter pylori and Wolbachia , identifying protein mimic candidates in each proteome. We discuss the roles these candidates may play in important Wolbachia -induced phenotypes and show that Wobachia infection can partially rescue the loss of one of these factors. This work demonstrates how a genome-wide screen for candidates of host-manipulation and intracellular survival offers an opportunity to identify functionally important genes in host-microbe systems.

Low pH modulates lipopolysaccharide-induced tumor necrosis factor-alpha expression and macropinocytotic activity in RAW264.7 cells

Inflammation triggers various types of diseases that need to be addressed. Macrophages play important roles in the inflammatory responses. As atherosclerosis progresses, macrophages transform into foam cells. Extracellular acidification is observed at and around bacterial infection and atherosclerotic sites. However, the effects of acidification on the inflammatory response of macrophages and the progression of atherosclerosis have not been fully understood. This study investigates the impact of extracellular acidification on lipopolysaccharide-induced tumor necrosis factor-alpha (TNF-α) expression and macropinocytotic activity in RAW264.7 cells. TNF-α expression is measured by real-time polymerase chain reaction (relative value to glyceraldehyde-3-phosphate dehydrogenase expression). Macropinocytotic activity is measured by neutral red uptake (absorbance at 540 nm). Results show that TNF-α expression increased with decreasing extracellular pH in both un-foamed and foamed cells. Macropinocytotic activity was upregulated at pH 6.8 in un-foamed cells, but downregulated in foamed cells stimulated at low pH. Proton-sensing G protein-coupled receptors (GPCRs) were involved in the expression of TNF-α and in the macropinocytotic activity of foamed cells. In conclusion, this study reveals that extracellular acidification differently affect various inflammatory responses such as LPS-induced TNF-α expression and macropinocytotic activity of RAW264.7 cells and different proton-sensing GPCRs are involved in the different inflammatory responses.

Role of Legionella pneumophila outer membrane vesicles in host-pathogen interaction

Legionella pneumophila is an opportunistic intracellular pathogen that inhabits artificial water systems and can be transmitted to human hosts by contaminated aerosols. Upon inhalation, it colonizes and grows inside the alveolar macrophages and causes Legionnaires' disease. To effectively control and manage Legionnaires' disease, a deep understanding of the host-pathogen interaction is crucial. Bacterial extracellular vesicles, particularly outer membrane vesicles (OMVs) have emerged as mediators of intercellular communication between bacteria and host cells. These OMVs carry a diverse cargo, including proteins, toxins, virulence factors, and nucleic acids. OMVs play a pivotal role in disease pathogenesis by helping bacteria in colonization, delivering virulence factors into host cells, and modulating host immune responses. This review highlights the role of OMVs in the context of host-pathogen interaction shedding light on the pathogenesis of L. pneumophila. Understanding the functions of OMVs and their cargo provides valuable insights into potential therapeutic targets and interventions for combating Legionnaires' disease.

Legionella pneumophila: The Journey from the Environment to the Blood

An outbreak of a potentially fatal form of pneumonia in 1976 and in the annual convention of the American Legion was the first time that Legionella spp. was identified. Thereafter, the term Legionnaires’ disease (LD) was established. The infection in humans is transmitted by the inhalation of aerosols that contain the microorganisms that belong to the Legionellaceae family and the genus Legionella. The genus Legionella contains genetically heterogeneous species and serogroups. The Legionella pneumophila serogroup 1 (Lp1) is the most often detected strain in outbreaks of LD. The pathogenesis of LD infection initiates with the attachment of the bacterial cells to the host cells, and subsequent intracellular replication. Following invasion, Legionella spp. activates its virulence mechanisms: generation of specific compartments of Legionella-containing vacuole (LCV), and expression of genes that encode a type IV secretion system (T4SS) for the translocation of proteins. The ability of L. pneumophila to transmigrate across the lung’s epithelium barrier leads to bacteremia, spread, and invasion of many organs with subsequent manifestations, complications, and septic shock. The clinical manifestations of LD depend on the bacterial load in the aerosol, the virulence factors, and the immune status of the patient. The infection has two distinct forms: the non- pneumatic form or Pontiac fever, which is a milder febrile flu-like illness, and LD, a more severe form, which includes pneumonia. In addition, the extrapulmonary involvement of LD can include heart, brain, abdomen, and joints.