Innate Immune Memory in Macrophages

Caspase-1 is critical for mice in the defense against Streptococcus equi subsp. zooepidemicus infection by promoting macrophage phagocytosis

Streptococcus equi subsp. zooepidemicus (SEZ) is an important pathogen which is responsible for a wide range of diseases in various species. Macrophages are professional phagocytes that can engulf microorganisms and trigger responses leading to microbial death. Caspase-1 is considered as a proinflammatory factor that mediates antibacterial response to protect hosts from bacteria. Here, we revealed a novel role of Caspase-1 in mice against SEZ. Through both in vitro and in vivo infection assays, we demonstrated that the maturation and secretion of the cytokine IL-1β are critically dependent on Caspase-1 activation. The Caspase-1 deficient mice displayed attenuation of bactericidal activity against SEZ, mainly by decreasing the accumulation of macrophage. In addition to the recruitment of macrophages, deficiency of Caspase-1 also impaired the phagocytosis of SEZ by macrophages. Our study demonstrated that Caspase-1 is critical for mice to defense against SEZ depending on the recruitment and phagocytosis of macrophage.

Autologous precision-cut lung slice co-culture models for studying macrophage-driven fibrosis

Precision-cut lung slices (PCLS) are commonly used as an ex vivo model to study lung fibrosis; however, traditional models lack immune cell infiltration, including the recruitment of monocytes and macrophages, which are critical for inflammation and fibrosis. To address this limitation, we developed novel autologous PCLS-immune co-culture models that better replicate the processes of inflammation, repair, and immune cell recruitment associated with fibrosis. Fibrotic responses to nicotine, cigarette smoke extract (CSE), and a fibrosis-inducing cocktail (FC) were first evaluated in PCLS containing only tissue-resident macrophages, with upregulation of α-SMA-expressing fibroblasts confirmed by immunofluorescence and Western blotting, and collagen deposition quantified using Sirius Red staining. To study macrophage recruitment, we employed an indirect co-culture model using transwells to approximate blood vessel function. Chemotactic studies revealed increased migration of autologous bone marrow-derived macrophages (BMDMs) toward and infiltration into CSE-injured PCLS. In a direct co-culture model simulating the repair phase of fibrosis, PCLS exposed to CSE and FC showed further increased collagen deposition in the presence of autologous BMDMs, but not heterologous ones. These findings suggest that our novel PCLS-immune co-culture models provide a platform for studying macrophage involvement in fibrosis and offer potential for developing macrophage-targeted therapeutic strategies in pulmonary fibrosis.

The Role of Innate Priming in Modifying Tumor-associated Macrophage Phenotype

Tumor-associated macrophages (TAMs) are innate immune cells that exert far reaching influence over the tumor microenvironment (TME). Depending on cues within the local environment, TAMs may promote tumor angiogenesis, cancer cell invasion and immunosuppression, or, alternatively, inhibit tumor progression via neoantigen presentation, tumoricidal reactive oxygen species generation and pro-inflammatory cytokine secretion. Therefore, TAMs have a pivotal role in determining tumor progression and response to therapy. TAM phenotypes are driven by cytokines and physical cues produced by tumor cells, adipocytes, fibroblasts, pericytes, immune cells, and other cells within the TME. Research has shown that TAMs can be primed by environmental stimuli, adding another layer of complexity to the environmental context that determines TAM phenotype. Innate priming is a functional consequence of metabolic and epigenetic reprogramming of innate cells by a primary stimulant, resulting in altered cellular response to future secondary stimulation. Innate priming offers a novel target for development of cancer immunotherapy and improved prognosis of disease, but also raises the risk of exacerbating existing inflammatory pathologies. This review will discuss the mechanisms underlying innate priming including metabolic and epigenetic modification, its relevance to TAMs and tumor progression, and possible clinical implications for cancer treatment.

Immunogenicity and protective efficacy of recombinant chimeric antigens based on surface proteins of Toxoplasma gondii

Introduction

Toxoplasmosis is caused by the opportunistic, cosmopolitan protozoan Toxoplasma gondii is one of the most common parasitoses in the world. This parasite can pose a threat to people with immunodeficiency but also to the fetus, since the invasion can lead to miscarriages. Moreover, this parasite can contribute to economic losses in livestock farming. These problems lead to the implementation of new, safe solutions for the development of effective toxoplasmosis immunoprophylaxis.

Methods

In this work, newly produced recombinant trivalent chimeric proteins of T. gondii, based on SAG1-SAG2 recombinant chimeric antigen that differ in one terminal antigenic component, were tested in terms of their ability to induce an effective post-vaccination response. Antigens were tested in vitro to assess their ability to elicit APC cells response and further mice of the C3H/HeOuJ strain were immunized using those antigens, to evaluate their immunogenicity and immunoprotective effect in vivo. Two weeks after the last dose mice were either sacrificed to assess selected parameters of the immune response or infected with T. gondii DX strain to determine the degree of protection one month later.

Results

The results of serological tests revealed a high level of serum IgG antibodies specific for the native T. gondii TLA antigens. TLA-stimulated splenocytes produced cytokines that are important in inhibiting protozoal invasion. Additionally, CD3+ CD4+ and CD3+ CD8+ T cell subpopulations of splenocytes were analysed by flow cytometry. One month after experimental infection mice were sacrificed, and their brains were isolated to count T. gondii tissue cyst. Immunization of mice with recombinant trivalent chimeric proteins of T. gondii resulted in reduction of tissue cyst burden rates reaching even 74%.

Discussion

The obtained results demonstrate strong immunogenicity of the studied proteins and will allow to select candidates for further research aimed at increasing the immunoprotective properties of experimental vaccines against toxoplasmosis based on T. gondii chimeric antigens.

Targeting Macrophages in Organ Transplantation: A Step Toward Personalized Medicine

Organ transplantation remains the most optimal strategy for patients with end-stage organ failure. However, prevailing methods of immunosuppression are marred by adverse side effects, and allograft rejection remains common. It is imperative to identify and comprehensively characterize the cell types involved in allograft rejection, and develop therapies with greater specificity. There is increasing recognition that processes mediating allograft rejection are the result of interactions between innate and adaptive immune cells. Macrophages are heterogeneous innate immune cells with diverse functions that contribute to ischemia-reperfusion injury, acute rejection, and chronic rejection. Macrophages are inflammatory cells capable of innate allorecognition that strengthen their responses to secondary exposures over time via "trained immunity." However, macrophages also adopt immunoregulatory phenotypes and may promote allograft tolerance. In this review, we discuss the roles of macrophages in rejection and tolerance, and detail how macrophage plasticity and polarization influence transplantation outcomes. A comprehensive understanding of macrophages in transplant will guide future personalized approaches to therapies aimed at facilitating tolerance or mitigating the rejection process.

miRNA‑mRNA network contributes to HBV‑related hepatocellular carcinoma via immune infiltration induced by GRB2

Chronic hepatitis B virus (HBV) infection is a critical causative factor in the tumorigenesis and progression of hepatocellular carcinoma (HCC). MicroRNAs (miRNAs) serve a critical role in the process of viral infection. However, there has been insufficient evaluation of HBV-associated miRNA-mRNA regulatory networks in HCC. The differential expression levels of miRNAs were compared in HBV-associated HCC tumor and normal tissues using the Gene Expression Omnibus database. The present study evaluated potential target genes of differentially expressed miRNAs using protein-protein interaction network, hub gene, Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, gene set enrichment and immune infiltration analysis. A total of five miRNAs and seven target genes were identified in the HBV-associated miRNA-mRNA network. miRNA-93 could positively regulate the growth factor receptor bound protein 2 (GRB2) gene, while there was a positive correlation between GRB2 and cancer immune infiltrate function in Tumor Immune Estimation Resource. Collectively, the present study investigated the miRNA-mRNA regulatory network in HCC with HBV infection and showed that miRNA-93 positively regulated immune infiltration-related GRB2. Restoring GRB2 may be a candidate strategy for the treatment of HBV-related HCC.

Prolonged Inhibition of the MEK1/2-ERK Signaling Axis Primes Interleukin-1 Beta Expression through Histone 3 Lysine 9 Demethylation in Murine Macrophages

Macrophages undergo different cellular states upon activation that can be hyporesponsive (tolerated) or hyperresponsive (primed or trained) to subsequent stimuli. Epigenetic modifications are known to play key roles in determining these cellular states. However, little is known about the role of signaling pathways that lead to these epigenetic modifications. Here, we examined the effects of various inhibitors targeting key signaling pathways induced by lipopolysaccharide (LPS) on tolerance and priming in murine macrophages. We found that a prolonged inhibition (>18 h) of the mitogen-activated protein kinase (MEK)1/2-extracellular signal-regulated kinase (ERK)1/2 signaling axis reversed tolerance and primed cells in expressing interleukin (IL)-1β and other inflammatory cytokines such as IL-6, tumor necrosis factor (TNF)α, and CXCL10. The ectopic expression of catalytically active and inactive MEK1 mutants suppressed and enhanced IL-1β expression, respectively. A transcriptomic analysis showed that cells primed by the MEK1/2 inhibitor U0126 expressed higher levels of gene sets associated with immune responses and cytokine/chemokine production, but expressed lower levels of genes with cell cycle progression, chromosome organization, and heterochromatin formation than non-primed cells. Of interest, the mRNA expressions of the histone 3 lysine 9 (H3K9) methyltransferase Suv39h1 and the H3K9 methylation reader Cbx5 were substantially suppressed, whereas the H3K9 demethylase Kdm7a was enhanced, suggesting a role of the MEK1/2-ERK signaling axis in H3K9 demethylation. The H3K9 trimethylation levels in the genomic regions of IL-1β, TNFα, and CXCL10 were decreased by U0126. Also, the H3K9 methyltransferase inhibitor BIX01294 mimicked the U0126 training effects and the overexpression of chromobox homolog (CBX)5 prevented the U0126 training effects in both RAW264.7 cells and bone-marrow-derived macrophages. Collectively, these data suggest that the prolonged inhibition of the MEK1/2-ERK signaling axis reverses tolerance and primed macrophages likely through decreasing the H3K9 methylation levels.

Effects of N-acetyl-L-cysteine polysulfides on periodontitis in a mouse model

BACKGROUND

Polysulfides are reported to be involved in various important biological processes. N-acetyl-l-cysteine polysulfide with 2 sulfane sulfur atoms (NAC-S2) regulates diverse toll-like receptor (TLR) signaling pathways. Here, we aimed to determine the role of NAC-S2 in periodontitis and explore the potential mechanism.

METHODS

A periodontitis mouse model was established by ligating the subgingival between the first and second molars in wild-type, TLR4-/- , and Myd88-/- mice.

RESULTS

NAC-S2 did not affect the proportion of macrophages (CD11b+ F4/80+ ) or neutrophils (CD11b+ GR-1+ ) in the bone marrow. Mechanically, lipopolysaccharides (LPS), Zymosan A, or poly I: C induced tumor necrosis factor (TNF), interleukin (IL)-6, and IL-1β expression in bone marrow-derived macrophages (BMDMs) could be inhibited by NAC-S2. On the other hand, NAC-S2 suppressed the phosphorylation levels of IκB-α, p65, and IκB kinase (IKK)-β induced by LPS in BMDMs, while LPS induced phosphorylation of ERK1/2, p38, and transforming growth factor β-activated kinase 1 (TAK1) could not be affected by NAC-S2. In wild-type periodontitis mice, NAC-S2 administration decreased the cemento-enamel-junction-alveolar bone crest (CEJ-ABC) distance and the relative mRNA expression of TNF, IL-6, and IL-1β, while such phenomena could not be observed in TLR4 deficiency or Myd88 deficiency mice.

CONCLUSIONS

All of these results indicate that NAC-S2 ameliorates TLR4/NF-κB pathway mediated inflammation in mouse periodontitis model.