ASC and NLRP3 maintain innate immune homeostasis in the airway through an inflammasome-independent mechanism

Mass spectrometry-based proteomic exploration of diverse murine macrophage cellular models

Immortalised cell lines that mimic their primary cell counterparts are fundamental to research, particularly when large cell numbers are required. Here, we report that immortalisation of bone marrow-derived macrophages (iBMDMs) using the J2 virus resulted in the loss of a protein of interest, MSR1, in WT cells by an unknown mechanism. This led us to perform an in-depth mass spectrometry-based proteomic characterisation of common murine macrophage cell lines (J774A.1, RAW264.7, and BMA3.1A7), in comparison with the iBMDMs, as well as primary BMDMs from both C57BL/6 and BALB/c mice. This analysis revealed striking differences in protein profiles associated with macrophage polarisation, phagocytosis, pathogen recognition, and interferon signalling. Among the cell lines, J774A.1 cells were the most similar to the gold standard primary BMDM model, whereas BMA3.1A7 cells were the least similar because of the reduction in abundance of several key proteins related closely to macrophage function. This comprehensive proteomic dataset offers valuable insights into the use and suitability of macrophage cell lines for cell signalling and inflammation research.

Arsenic Exposure Induces Neuro-immune Toxicity in the Cerebral Cortex and the Hippocampus via Neuroglia and NLRP3 Inflammasome Activation in C57BL/6 Mice

This study aimed to examine the immuntoxic effects of arsenic in the nervous system. Our results showed that arsenic increased corticocerebral and hippocampal weights (p < 0.05). Morris water maze tests revealed that arsenic significantly increased the time spent in latency to platform on the fourth day in 50 mg/L arsenic exposure and the fifth day in 25 and 50 mg/L arsenic exposure, as well as reduced the path length in target quadrant, time spent in target quadrant, and crossing times of the platform (p < 0.05). Hematoxylin-eosin staining showed that the vacuolated degeneration and pyknosis was found in the cerebral cortex and hippocampus of arsenic-treated mice. The mRNA levels of corticocerebral and hippocampal brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) were decreased in the 50 mg/L arsenic-treated group (p < 0.05). In addition, immunofluorescence staining showed that 25 and 50 mg/L arsenic all increased the expression of CD11b and glial fibrillary acidic protein (GFAP) in the cerebral cortex and hippocampus (p < 0.05). Arsenic markedly raised antigen-presenting molecule MHCII and CD40 mRNA levels in the cerebral cortex and hippocampus and upregulated the cell chemokine receptor 5 (CCR5) and CCR7 mRNA levels in the cerebral cortex at the 50 mg/L arsenic group, and increased the CCR7 mRNA levels in the hippocampus at the 25 and 50 mg/L arsenic groups (p < 0.05). Arsenic activated the nucleotide-binding domain-like receptor protein-3 (NLRP3) inflammasome, and enhanced its upstream promoter NF-κB protein level and downstream regulators IL-18 mRNA levels. Collectively, these results provide new evidences for the neuro-immune toxicity of arsenic.

Traditional approaches and recent tools for studying inflammasome activity

Inflammasomes play a major role in the immune response to infection, development of autoimmune disease, and control of cancer. Western blots were originally used in the early 2000s to characterize inflammasome activation. Since then, a panoply of techniques has been developed to characterize and visualize inflammasome activation in cells, tissues, and animals. This review article describes the most common techniques used by researchers in the inflammasome field and proposes that cell-specific characterization of inflammasome activation in tissues or animals may soon be commonly reported.

Synergistic effect of Toll-like receptor 2 ligands and alendronate on proinflammatory cytokine production in mouse macrophage-like RAW-ASC cells is accompanied by upregulation of MyD88 expression

OBJECTIVES

Toll-like receptors (TLRs) recognize whole cells or components of microorganisms. Alendronate (ALN) is an anti-bone-resorptive drug that has inflammatory side effects. The aim in this study was to examine whether ALN augments TLR2 ligand-induced proinflammatory cytokine production using mouse macrophage-like RAW264.7 cells transfected with murine apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) gene (hereafter, referred to as "RAW-ASC cells").

METHODS

RAW-ASC cells were pretreated with or without ALN and then incubated with or without TLR2 ligands. The levels of secreted mouse IL-1α, IL-1β, IL-6, and tumor necrosis factor-α (TNF-α) in culture supernatants and the activation of activator protein-1 (AP-1) or nuclear factor-κB (NF-κB) were measured using enzyme-linked immunosorbent assay (ELISA). The expressions of myeloid differentiation factor 88 (MyD88), caspase-11, nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3), ASC, NF-κB p65, and actin were analyzed via Western blotting. TLR2 expression was analyzed using flow cytometry.

RESULTS

ALN substantially upregulated the Pam3CSK4-induced release of IL-1α, IL-1β, IL-6, and TNF-α and MyD88 expression in RAW-ASC cells. ST-2825, a MyD88 inhibitor, inhibited the ALN-augmented release of these cytokines. Pretreatment with ALN augmented Pam3CSK4-induced NF-κB activation in RAW-ASC cells and upregulated AP-1 activation. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) S protein and ALN synergically upregulated the release of IL-1α, IL-1β, IL-6 and TNF-α in RAW-ASC cells.

CONCLUSIONS

Our findings suggest that ALN augments TLR2 ligand-induced proinflammatory cytokine production via the upregulation of MyD88 expression, and this augmentation is accompanied by the activation of NF-κB and AP-1 in RAW-ASC cells.

A novel mechanism for regulating lung immune homeostasis: Zukamu granules alleviated acute lung injury in mice by inhibiting NLRP3 inflammasome activation and regulating Th17/Treg cytokine balance

ETHNOPHARMACOLOGICAL RELEVANCE

Acute lung injury (ALI) is a severely acute lung inflammation with high morbidity and mortality. Zukamu granules (ZKMG) is one of the Uygur patent drugs commonly used in clinic, which is included in the National Essential Drugs List (2018 edition). Clinical studies have shown that ZKMG has a significant effect on acute upper respiratory tract infection, and has better anti-inflammatory and antipyretic effects. However, the immunomodulatory mechanism of ZKMG on ALI is still not clear.

AIM OF THE STUDY

The aim of this study is to investigate the lung protective effect and immunomodulatory mechanism of ZKMG on lipopolysaccharide (LPS) -induced ALI mice, and to provide an important basis for the treatment strategy and theoretical basis of ALI.

MATERIALS AND METHODS

First, network pharmacology was used to predict the potential signaling pathways and biological processes of ZKMG related to immunology. Molecular docking technique was used to predict the possibility between the core components of ZKMG acting on NLRP3 protein. In addition, protein levels of F4/80 in lung tissues were assessed by Immunohistochemistry (IHC). The contents of IL-1β, IL-18, IL-17A and IL-10 in the lung tissue and serum, MPO in the lung tissue were detected by enzyme-linked immunosorbent assay (ELISA). Real-time quantitative PCR analysis (RT-qPCR) was used to detect NLRP3 mRNA in lung tissue. Protein levels of NLRP3, Caspase-1, Cleaved caspase-1 p20, ASC, and GSDMD were detected by Western blot (WB).

RESULTS

The results of network pharmacology showed that the immune pathways of ZKMG were mainly Th17 signaling pathway, IL-17 signaling pathway, NOD-like receptor signaling pathway, etc. Molecular docking results showed that the core components of ZKMG had good binding ability to NLRP3 protein. The verification experiments showed that ZKMG can reduce the degree of lung injury, and reduce the level of inflammatory infiltration of neutrophils and macrophages by reducing the content of MPO and F4/80. In addition, ZKMG can reduce NLRP3 mRNA, inhibit the expression of NLRP3/Caspase-1/GSDMD and other related pathway proteins, and reduce inflammatory factors such as IL-1β and IL-18. It can also reduce the content of pro-inflammatory cytokine IL-17A, increase the content of anti-inflammatory cytokine IL-10 in lung tissue.

CONCLUSION

ZKMG can reduce the degree of lung tissue injury in ALI by inhibiting NLRP3/Caspase-1/GSDMD signaling pathway and restoring the IL-17A/IL-10 cytokine balance, and its protective mechanism may be related to the regulation of lung immune homeostasis. It will provide a new strategy for studying the regulation of lung immune homeostasis.

Mechanistic insights into targeting caspase-3 activation and alveolar macrophage pyroptosis by Ephedra and bitter almond compounds for treating pediatric pneumonia via network pharmacology and bioinformatics

This study investigates the molecular mechanism of Ma Huang-Ku Xing Ren, a traditional Chinese medicine formula, in treating pediatric pneumonia. The focus is on the regulation of caspase-3 activation and reduction of alveolar macrophage necrosis through network pharmacology and bioinformatics analyses of Ephedra and bitter almond components. Active compounds and targets from ephedrine and bitter almond were obtained using TCMSP, TCMID, and GeneCards databases, identifying pediatric pneumonia-related genes. A protein-protein interaction (PPI) network was constructed, and core targets were screened. GO and KEGG pathway enrichment analyses identified relevant genes and pathways. An acute pneumonia mouse model was created using the lipopolysaccharide (LPS) inhalation method, with caspase-3 overexpression induced by a lentivirus. The mice were treated with Ephedra and bitter almond through gastric lavage. Lung tissue damage, inflammatory markers (IL-18 and IL-1β), and cell death-related gene activation were assessed through H&E staining, ELISA, western blot, flow cytometry, and immunofluorescence. The study identified 128 active compounds and 121 gene targets from Ephedra and bitter almond. The PPI network revealed 13 core proteins, and pathway analysis indicated involvement in inflammation, apoptosis, and cell necrosis, particularly the caspase-3 pathway. In vivo results showed that Ephedra and bitter almond treatment significantly mitigated LPS-induced lung injury in mice, reducing lung injury scores and inflammatory marker levels. It also decreased caspase-3 activity and cell death in alveolar macrophages. In conclusion, the active ingredients of Ma Huang-Ku Xing Ren, particularly targeting caspase-3, may effectively treat pediatric pneumonia by reducing apoptosis in alveolar macrophages, as demonstrated by both network pharmacology, bioinformatics analyses, and experimental data.

Cryptotanshinone Inhibits Bladder Cancer Cell Malignant Progression in a Lipopolysaccharide-Induced Inflammatory Microenvironment through NLRP3 Inhibition

Background

Bladder cancer (BC) is one of the most common malignancies of the urogenital system. This study assessed the nucleotide-binding oligomerization domain and leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) in BC as well as the effects of cryptotanshinone on changes in BC malignant behaviors and NLRP3 expression under a lipopolysaccharide (LPS)-induced inflammatory microenvironment.

Methods

BC tissue specimens from 62 patients were collected for immunohistochemical detection of NLRP3 protein. BC and normal urothelial cell lines were cultured for the detection of NLRP3 mRNA and protein. Then, BC cells were pretreated with LPS to mimic the inflammatory tumor microenvironment. Next, these cells were incubated with a low or high dose of cryptotanshinone to assess its effects on tumor cell malignant behaviors as well as transfected with NLRP3 cDNA to confirm the role of NLRP3 in BC cells in vitro.

Results

High NLRP3 expression was associated with larger tumor diameters (>2 cm), muscle invasion, and metastasis. The levels of NLRP3 mRNA and protein were greater in BC cells than in normal urothelial cells. LPS pretreatment significantly promoted NLRP3 and inflammatory cytokine expression in BC cells, and induced cell viability, migration, and invasion. However, cryptotanshinone was able to reduce the LPS-induced increase of NLRP3 and inflammatory cytokine expression as well as the BC cell malignant progression. NLRP3 overexpression using NLRP3 cDNA further promoted BC cell malignant progression after LPS stimulation and reversed cryptotanshinone-reduced LPS-induced BC cell malignant behaviors.

Conclusion

NLRP3 might possess oncogenic activity in BC, and the antitumor activity of cryptotanshinone in BC in vitro might be related to its inhibition of NLRP3 expression.

[Dynamics of expression of NOD-like receptors of periodontal tissue cells in patients with aggressive periodontitis]

THE AIM OF THE STUDY

To study the expression of NOD receptors of immunotropic periodontal tissue cells in patients with aggressive periodontitis before and after complex treatment.

MATERIALS AND METHODS

15 patients aged 22 to 36 years with aggressive periodontitis were examined before and 21 days after the start of complex treatment. 15 patients with fibroids of the oral mucosa without signs of inflammation served as controls. Samples of the gingival mucosa after surgical treatment were sent to a routine histological and immunohistochemical (IHC) method with polyclonal rabbit antibodies. The expression of pro- and anti-inflammatory receptors was studied: NOD receptors - NLRP3 and NLRP12 as the most significant. The criterion for evaluating the expression of NLRP12 and NLRP3 receptors was the staining of nuclei and cytoplasm of cells of the multilayer squamous epithelium and cytoplasm of inflammatory infiltrate cells in the own plate of the mucous membrane. The intensity of staining was assessed as: no staining (0), weak staining (1+), medium (2+) and intense (3+).

RESULTS

In the control group of patients diagnosed with fibroma without signs of inflammation in the oral mucosa, expression of NOD receptors was not observed. The maximum expression of NOD receptors was detected during exacerbation of the aggressive form of periodontitis in the nuclei and cytoplasm of stratified squamous epithelial cells and in the lamina propria of the gingival mucosa in the cells of the inflammatory infiltrate. After complex treatment of patients with an aggressive form of periodontitis, there is a significant (p<0.05) decrease in the expression of NLRP12 receptors in the cells of the inflammatory infiltrate, which inhibit the inflammatory response in periodontal tissues.

CONCLUSION

The expression of NMDA receptors in the multilayer squamous epithelium characterizes the activity of the inflammatory process in the oral mucosa and can be recommended for use in evaluating the effectiveness of the treatment of an aggressive form of periodontitis.

Diagnostic and Prognostic Value of Serum Omentin-1 in Sepsis: A Prospective Study in Critically Ill Patients

Background and Objectives: Omentin-1, also known as intelectin-1, is a novel adipokine with anti-inflammatory activities implicated in inflammatory diseases and sepsis. We aimed to explore serum omentin-1 and its kinetics in critically ill patients early in sepsis and its association with severity and prognosis. Materials and Methods: Serum omentin-1 was determined in 102 critically ill patients with sepsis during the first 48 h from sepsis onset and 1 week later, and in 102 age- and gender-matched healthy controls. The outcome of sepsis at 28 days after enrollment was recorded. Results: Serum omentin-1 at enrollment was significantly higher in patients compared to controls (763.3 ± 249.3 vs. 451.7 ± 122.3 μg/L, p < 0.001) and it further increased 1 week after (950.6 ± 215.5 vs. 763.3 ± 249.3 μg/L, p < 0.001). Patients with septic shock (n = 42) had higher omentin-1 compared to those with sepsis (n = 60) at enrollment (877.9 ± 241.2 vs. 683.1 ± 223.7 μg/L, p < 0.001) and 1 week after (1020.4 ± 224.7 vs. 901.7 ± 196.3 μg/L, p = 0.007). Furthermore, nonsurvivors (n = 30) had higher omentin-1 at sepsis onset (952.1 ± 248.2 vs. 684.6 ± 204.7 μg/L, p < 0.001) and 1 week after (1051.8 ± 242 vs. 908.4 ± 189.8 μg/L, p < 0.01). Patients with sepsis and survivors presented higher kinetics than those with septic shock and nonsurvivors (Δ(omentin-1)% 39.8 ± 35.9% vs. 20.2 ± 23.3%, p = 0.01, and 39.4 ± 34.3% vs. 13.3 ± 18.1%, p < 0.001, respectively). Higher omentin-1 at sepsis onset and 1 week after was an independent predictor of 28-day mortality (HR 2.26, 95% C.I. 1.21-4.19, p = 0.01 and HR: 2.15, 95% C.I. 1.43-3.22, p < 0.001, respectively). Finally, omentin-1 was significantly correlated with the severity scores, the white blood cells, coagulation biomarkers, and CRP, but not procalcitonin and other inflammatory biomarkers. Conclusions: Serum omentin-1 is increased in sepsis, while higher levels and lower kinetics during the first week of sepsis are associated with the severity and 28-day mortality of sepsis. Omentin-1 may be a promising biomarker of sepsis. However, more studies are needed to explore its role in sepsis.

Role of the caspase-8/RIPK3 axis in Alzheimer's disease pathogenesis and Aβ-induced NLRP3 inflammasome activation

The molecular mediators of cell death and inflammation in Alzheimer's disease (AD) have yet to be fully elucidated. Caspase-8 is a critical regulator of several cell death and inflammatory pathways; however, its role in AD pathogenesis has not yet been examined in detail. In the absence of caspase-8, mice are embryonic lethal due to excessive receptor interacting protein kinase 3-dependent (RIPK3-dependent) necroptosis. Compound RIPK3 and caspase-8 mutants rescue embryonic lethality, which we leveraged to examine the roles of these pathways in an amyloid β-mediated (Aβ-mediated) mouse model of AD. We found that combined deletion of caspase-8 and RIPK3, but not RIPK3 alone, led to diminished Aβ deposition and microgliosis in the mouse model of AD carrying human presenilin 1 and amyloid precursor protein with 5 familial AD mutations (5xFAD). Despite its well-known role in cell death, caspase-8 did not appear to affect cell loss in the 5xFAD model. In contrast, we found that caspase-8 was a critical regulator of Aβ-driven inflammasome gene expression and IL-1β release. Interestingly, loss of RIPK3 had only a modest effect on disease progression, suggesting that inhibition of necroptosis or RIPK3-mediated cytokine pathways is not critical during midstages of Aβ amyloidosis. These findings suggest that therapeutics targeting caspase-8 may represent a novel strategy to limit Aβ amyloidosis and neuroinflammation in AD.

ROS antagonizes the protection of Parkin-mediated mitophagy against aluminum-induced liver inflammatory injury in mice

Aluminum (Al) is a food pollutant that has extensive deleterious effects on the liver. Our previous research proposed that E3 ubiquitin ligase PARK2 knockout (Parkin^-/-) could aggravate Al-induced liver damage by inhibiting mitophagy, during which the reactive oxygen species (ROS) content increases. Inhibition of mitophagy can activate inflammasome. But the link between Parkin-mediated mitophagy and liver inflammatory injury caused by Al, and the role of ROS in it remain unclear. In this study, we applied Al, Parkin^-/- and N-acetyl-L-cysteine (NAC) to act on C57BL/6N mice to investigate them. We found that Al could induce liver inflammatory injury and Parkin^-/- could aggravate it. Meanwhile, inhibition of ROS alleviated oxidative stress, mitochondrial damage, mitophagy and inflammatory injury caused by Al in Parkin^-/- mice liver. These results indicated that ROS antagonized the protection of Parkin-mediated mitophagy against Al-induced liver inflammatory damage in mice.

Activation of the NLRP3 inflammasome by RAC1 mediates a new mechanism in diabetic nephropathy

OBJECTIVE

Inflammation is central to the development and progression of diabetic nephropathy (DN). Although the exact mechanisms of inflammation in the kidney have not been well elucidated, pyrin domain containing 3 (NLRP3) inflammasome activation is involved in the onset and progression of DN. Here, we investigated the underlying regulatory mechanisms of hyperglycaemia-induced NLRP3 inflammasome activation in the kidney.

METHODS

HEK293T cells received high glucose, and the cell proliferation and apoptosis were detected. Biochemical indicators in db/db mice were tested by kits, and the morphological changes in the kidney were observed using staining methods and transmission electron microscopy. The interaction of Ras-related C3 botulinum toxin substrate 1 (RAC1) and NLRP3 inflammasome in cells and in mice was assessed by co-immunoprecipitation (Co-IP) and immunofluorescence. Expression of all proteins was examined by western blotting and immunohistochemistry. In additional, the directly combination of RAC1 and NLRP3 was evaluated by GST Pulldown.

RESULTS

High-glucose and hyperglycaemia conditions resulted in Ras-related C3 botulinum toxin substrate 1 (RAC1) and NLRP3 inflammasome interactions in cells and in mice. Additionally, RAC1 promoted NLRP3 inflammasome activation and then induced cell damage, and morphological and functional abnormalities in the kidney. We also observed that RAC1 activates the NLRP3 inflammasome by directly binding to NLRP3.

CONCLUSION

In the present study, we confirmed that RAC1 binding to NLRP3 is sufficient to activate the NLRP3 inflammasome in the kidney and accelerate DN pathological processes. These results elucidate the upstream cellular and molecular mechanisms of NLRP3 inflammasome activation and provide new therapeutic strategies for the treatment of DN.

GABA transporter sustains IL-1β production in macrophages

Accumulating evidence shows that nervous system governs host immune responses; however, how γ-aminobutyric acid (GABA)ergic system shapes the function of innate immune cells is poorly defined. Here, we demonstrate that GABA transporter (GAT2) modulates the macrophage function. GAT2 deficiency lowers the production of interleukin-1β (IL-1β) in proinflammatory macrophages. Mechanistically, GAT2 deficiency boosts the betaine/S-adenosylmethionine (SAM)/hypoxanthine metabolic pathway to inhibit transcription factor KID3 expression through the increased DNA methylation in its promoter region. KID3 regulates oxidative phosphorylation (OXPHOS) via targeting the expression of OXPHOS-related genes and is also critical for NLRP3-ASC-caspase-1 complex formation. Likewise, GAT2 deficiency attenuates macrophage-mediated inflammatory responses in vivo, including lipopolysaccharide-induced sepsis, infection-induced pneumonia, and high-fat diet-induced obesity. Together, we propose that targeting GABAergic system (e.g., GABA transporter) could provide previously unidentified therapeutic opportunities for the macrophage-associated diseases.

Hierarchical cell-type-specific functions of caspase-11 in LPS shock and antibacterial host defense

Caspase-11 sensing of intracellular lipopolysaccharide (LPS) plays critical roles during infections and sepsis. However, the key cell types that sense intracellular LPS and their contributions to the host responses at the organismal level are not completely clear. Here, we show that macrophage/monocyte-specific caspase-11 plays a dominant role in mediating the pathological manifestations of endotoxemia, including gasdermin D (GSDMD) activation, interleukin (IL)-1β, IL-18, and damage-associated molecular pattern (DAMP) release, tissue damage, and death. Surprisingly, caspase-11 expression in CD11c⁺ cells and intestinal epithelial cells (IECs) plays minor detrimental roles in LPS shock. In contrast, caspase-11 expression in neutrophils is dispensable for LPS-induced lethality. Importantly, caspase-11 sensing of intracellular LPS in LyzM⁺ myeloid cells and MRP8⁺ neutrophils, but not CD11c⁺ cells and IECs, is necessary for bacterial clearance and host survival during intracellular bacterial infection. Thus, we reveal hierarchical cell-type-specific roles of caspase-11 that govern the host-protective and host-detrimental functions of the cytosolic LPS surveillance.

Kumari et al. reveal hierarchical cell-type-specific roles of caspase-11 that govern the host-protective and host-detrimental functions of the cytosolic LPS surveillance pathway during bacterial infections and sepsis, respectively.

Toxic Shock Syndrome Toxin 1 Induces Immune Response via the Activation of NLRP3 Inflammasome

Staphylococcus aureus is a Gram-positive opportunistic pathogen which causes infections in a variety of vertebrates. Virulence factors are the main pathogenesis of S. aureus as a pathogen, which induce the host’s innate and adaptive immune responses. Toxic shock syndrome toxin 1 (TSST-1) is one of the most important virulence factors of S. aureus. However, the role of nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) in TSST-1-induced innate immune response is still unclear. Here, purified recombinant TSST-1 (rTSST-1) was prepared and used to stimulate mouse peritoneal macrophages. The results showed that under the action of adenosine-triphosphate (ATP), rTSST-1 significantly induced interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) production in mouse macrophages and the production was dose-dependent. In addition, rTSST-1+ATP-stimulated cytokine production in macrophage depends on the activation of toll like receptor 4 (TLR4), but not TLR2 on the cells. Furthermore, the macrophages of NLRP3^−/− mice stimulated with rTSST-1+ATP showed significantly low levels of IL-1β production compared to that of wild-type mice. These results demonstrated that TSST-1 can induce the expression of inflammatory cytokines in macrophages via the activation of the TLR4 and NLRP3 signaling pathways. Our study provides new information about the mechanism of the TSST-1-inducing host’s innate immune responses.

Stem Cell-Derived Exosomes Ameliorate Doxorubicin-Induced Muscle Toxicity through Counteracting Pyroptosis

Doxorubicin (Dox)-induced muscle toxicity (DIMT) is a common occurrence in cancer patients; however, the cause of its development and progression is not established. We tested whether inflammation-triggered cell death, “pyroptosis” plays a role in DIMT. We also examined the potential role of exosomes derived from embryonic stem cells (ES-Exos) in attenuating DIMT. C57BL/6J mice (10 ± 2 wks age) underwent the following treatments: Control (saline), Dox, Dox+ES-Exos, and Dox+MEF-Exos (mouse-embryonic fibroblast-derived exosomes, negative control). Our results demonstrated that Dox significantly reduced muscle function in mice, which was associated with a significant increase in NLRP3 inflammasome and initiation marker TLR4 as compared with controls. Pyroptosis activator, ASC, was significantly increased compared to controls with an upregulation of specific markers (caspase-1, IL-1β, and IL-18). Treatment with ES-Exos but not MEF-Exos showed a significant reduction in inflammasome and pyroptosis along with improved muscle function. Additionally, we detected a significant increase in pro-inflammatory cytokines (TNF-α and IL-6) and inflammatory M1 macrophages in Dox-treated animals. Treatment with ES-Exos decreased M1 macrophages and upregulated anti-inflammatory M2 macrophages. Furthermore, ES-Exos showed a significant reduction in muscular atrophy and fibrosis. In conclusion, these results suggest that DIMT is mediated through inflammation and pyroptosis, which is attenuated following treatment with ES-Exos.

Genetic disruption of the inflammasome adaptor ASC has minimal impact on the pathogenesis of Duchenne muscular dystrophy in mdx mice

AIM

Up-regulation of inflammasome proteins was reported in dystrophin-deficient muscles. However, it remains to be determined whether inflammasome activation plays a role in the pathogenesis of Duchenne muscular dystrophy. This study was therefore set out to investigate whether genetic disruption of the inflammasome pathway impacts the disease progression in mdx mice.

MAIN METHODS

Mice deficient in both dystrophin and ASC (encoded by Pycard [PYD And CARD Domain Containing]) were generated. The impact of ASC deficiency on muscular dystrophy of mdx mice were assessed by measurements of serum cytokines, Western blot, real-time PCR and histopathological staining.

KEY FINDINGS

The pro-inflammatory cytokines such as TNF-α, IL-6, KC/GRO and IL-10 were markedly increased in the sera of 8-week-old mdx mice compared to WT. Western blotting showed that P2X7, caspase-1, ASC and IL-18 were upregulated. Disruption of ASC and dystrophin expression in the mdx/ASC-/- mice was verified by Western blot analysis. Histopathological analysis did not find significant alterations in the muscular dystrophy phenotype in mdx/ASC-/- mice as compared to mdx mice.

SIGNIFICANCE

Taken together, our results show that disruption of the central adaptor ASC of the inflammasome is insufficient to alleviate muscular dystrophy phenotype in mdx mice.

Neuroinflammation Mediated by NLRP3 Inflammasome After Intracerebral Hemorrhage and Potential Therapeutic Targets

Intracerebral hemorrhage (ICH) is the most fatal subtype of stroke; there is still a lack of effective treatment. Microglia are a major component of the innate immune system, and they respond to acute brain injury by activating and forming classic M1-like (pro-inflammatory) or alternative M2-like (anti-inflammatory) phenotype. The existence of the polarization indicates that the role of microglia in disease's progression and recovery after ICH is still unclear, perhaps involving microglial secretion of anti-inflammatory or pro-inflammatory cytokines and chemokines. The NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome is considered to be the main participant in neuroinflammation. Recent evidence has shown that NLRP3 inflammasome can be activated after ICH, resulting in inflammatory cascade reactions and aggravating brain injury. Furthermore, previous studies have reported that NLRP3 inflammasome is mainly present in microglia, so we speculate that its activation may be strongly associated with microglial polarization. Many scholars have investigated the role of brain injury caused by NLRP3 inflammasome after ICH, but the precise operating mechanisms remain uncertain. This review summarized the activation mechanism of NLRP3 inflammasome after ICH and the possible mechanism of NLRP3 inflammasome promoting neuroinflammation and aggravating nerve injury and discussed the relevant potential therapeutic targets.

Pulmonary Innate Immune Response Determines the Outcome of Inflammation During Pneumonia and Sepsis-Associated Acute Lung Injury

The lung is a primary organ for gas exchange in mammals that represents the largest epithelial surface in direct contact with the external environment. It also serves as a crucial immune organ, which harbors both innate and adaptive immune cells to induce a potent immune response. Due to its direct contact with the outer environment, the lung serves as a primary target organ for many airborne pathogens, toxicants (aerosols), and allergens causing pneumonia, acute respiratory distress syndrome (ARDS), and acute lung injury or inflammation (ALI). The current review describes the immunological mechanisms responsible for bacterial pneumonia and sepsis-induced ALI. It highlights the immunological differences for the severity of bacterial sepsis-induced ALI as compared to the pneumonia-associated ALI. The immune-based differences between the Gram-positive and Gram-negative bacteria-induced pneumonia show different mechanisms to induce ALI. The role of pulmonary epithelial cells (PECs), alveolar macrophages (AMs), innate lymphoid cells (ILCs), and different pattern-recognition receptors (PRRs, including Toll-like receptors (TLRs) and inflammasome proteins) in neutrophil infiltration and ALI induction have been described during pneumonia and sepsis-induced ALI. Also, the resolution of inflammation is frequently observed during ALI associated with pneumonia, whereas sepsis-associated ALI lacks it. Hence, the review mainly describes the different immune mechanisms responsible for pneumonia and sepsis-induced ALI. The differences in immune response depending on the causal pathogen (Gram-positive or Gram-negative bacteria) associated pneumonia or sepsis-induced ALI should be taken in mind specific immune-based therapeutics.