Particulate matter phagocytosis induces tissue factor in differentiating macrophages

Autophagy alleviates hippocampal neuroinflammation by inhibiting the NLRP3 inflammasome in a juvenile rat model exposed particulate matter

Ambient fine particulate matter (PM) is a global public and environmental problem. PM is closely associated with several neurological diseases, which typically involve neuroinflammation. We investigated the impact of PM exposure on neuroinflammation using both in vivo (in a juvenile rat model with PM exposure concentrations of 1, 2, and 10 mg/kg for 28 days) and in vitro (in BV-2 and HT-22 cell models with PM concentrations of 50-200 μg/ml for 24 h). We observed that PM exposure induced the activation of the NLRP3 inflammasome, leading to the production of IL-1β and IL-18 in the rat hippocampus and BV-2 cells. Furthermore, inhibition of the NLRP3 inflammasome with MCC950 effectively reduced neuroinflammation and ameliorated hippocampal damage. In addition, autophagy activation was observed in the hippocampus of PM-exposed rats, and the promotion of autophagy by rapamycin (Rapa) effectively attenuated the NLRP3-mediated neuroinflammation induced by PM exposure. However, autophagic flow was blocked in BV-2 cells exposed to PM, and Rapa failed to ameliorate NLRP3 inflammasome activation. We found that autophagy was activated in HT-22 cells exposed to PM and that treatment with Rapa reduced the release of reactive oxygen species (ROS) and malondialdehyde (MDA), as well as cell apoptosis. In a subsequent coculture model of BV-2 and HT-22 cells, we observed the activation of the NLRP3 inflammasome in BV-2 cells when the HT-22 cells were exposed to PM, and this activation was alleviated when PM-exposed HT-22 cells were pretreated with Rapa. Overall, our study revealed that PM exposure triggered hippocampal neuroinflammation by activating the NLRP3 inflammasome. Notably, autophagy mitigated NLRP3 inflammasome activation, potentially by reducing neuronal ROS and apoptosis. This research emphasized the importance of reducing PM exposure and provided valuable insight into its neurotoxicity.

Crosstalk between septic shock and venous thromboembolism: a bioinformatics and immunoassay analysis

Background

Herein, we applied bioinformatics methods to analyze the crosstalk between septic shock (SS) and venous thromboembolism (VTE), focusing on the correlation with immune infiltrating cells.

Methods

Expression data were obtained from the Gene Expression Omnibus (GEO) database, including blood samples from SS patients (datasets GSE64457, GSE95233, and GSE57065) and VTE patients (GSE19151). We used the R package "limma" for differential expression analysis (p value<0.05,∣logFC∣≥1). Venn plots were generated to identify intersected differential genes between SS and VTE and conducted Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) Enrichment analysis. The protein-protein interaction (PPI) network of intersected genes was constructed by Cytoscape software. The xCell analysis identified immune cells with significant changes in VTE and SS and correlated them with significant molecular pathways of crosstalk. Finally, we validated the mRNA expression of crosstalk genes by qPCR, while Matrix Metalloprotein-9 (MMP-9) protein levels were assessed through Western blotting (WB) and Immunohistochemistry (IHC) in human umbilical vein endothelial cells (HUVECs) and mice.

Results

In the present study, we conducted a comparison between 88 patients with septic shock and 55 control subjects. Additionally, we compared 70 patients with venous thromboembolism to 63 control subjects. Twelve intersected genes and their corresponding three important molecular pathways were obtained: Metabolic, Estrogen, and FOXO signaling pathways. The resulting PPI network has 194 nodes and 388 edges. The immune microenvironment analysis of the two diseases showed that the infiltration levels of M2 macrophages and Class-switched memory B cells were correlated with the enrichment scores of metabolic, estrogen, and FOXO signaling pathways. Finally, qPCR confirmed that the expression of MMP9, S100A12, ARG1, SLPI, and ANXA3 mRNA in the SS with VTE group was significantly elevated. WB and IHC experiments revealed that MMP9 protein was significantly elevated in the experimental group.

Conclusion

Metabolic, estrogen, and FOXO pathways play important roles in both SS and VTE and are related to the immune cell microenvironment of M2 macrophages and Class-switched memory B cells. MMP9 shows promise as a biomarker for diagnosing sepsis with venous thrombosis and a potential molecular target for treating this patient population.

Citrus junos Tanaka Peel Extract and Its Bioactive Naringin Reduce Fine Dust-Induced Respiratory Injury Markers in BALB/c Male Mice

Particulate matter (PM) 10 refers to fine dust with a diameter of less than 10 µm and induces apoptosis and inflammatory responses through oxidative stress. Citrus junos Tanaka is a citrus fruit and contains bioactive flavonoids including naringin. In the present study, we aimed to identify the preventive effect of Citrus junos Tanaka peel extract (CPE) against PM10-induced lung injury. As a proof of concept, NCI-H460 cells were treated with CPE (800 μg/mL, 12 h) in conjunction with PM10 to examine intracellular antioxidative capacity in the pulmonary system. In an in vivo model, male BALB/c mice (n = 8/group) were randomly assigned into five groups: NEG (saline-treated), POS (PM10 only), NAR (PM10 + naringin, 100 mg/kg), CPL (PM10 + CPE low, 100 mg/kg), and CPH (PM10 + CPE high, 400 mg/kg). Intervention groups received dietary supplementations for 7 days followed by PM10 exposure (100 mg/kg, intranasal instillation). Compared to the NEG, the CPE decreased to 22% of the ROS generation and significantly increased cell viability in vitro. The histological assessments confirmed that pulmonary damages were alleviated in the PM10 + CPL group compared to the POS. Pro-inflammatory cytokines and NF-κB/apoptosis signaling-related markers were decreased in the PM10 + CPL group compared to the POS. These results indicated that CPE showed promising efficacy in preventing pulmonary injuries in vivo. Such protection can be explained by the anti-oxidative capacity of CPE, likely due to its bioactives, including naringin (7.74 mg/g CPE). Follow-up human intervention, as well as population-level studies, will further shed light on the preventive efficacy of CPE against pulmonary damage in humans.

Metabolic Response of RAW 264.7 Macrophages to Exposure to Crude Particulate Matter and a Reduced Content of Organic Matter

Exposure to air pollution from various airborne particulate matter (PM) is regarded as a potential health risk. Airborne PM penetrates the lungs, where it is taken up by macrophages, what results in macrophage activation and can potentially lead to negative consequences for the organism. In the present study, we assessed the effects of direct exposure of RAW 264.7 macrophages to crude PM (NIST1648a) and to a reduced content of organic matter (LAp120) for up to 72 h on selected parameters of metabolic activity. These included cell viability and apoptosis, metabolic activity and cell number, ROS synthesis, nitric oxide (NO) release, and oxidative burst. The results indicated that both NIST1648a and LAp120 negatively influenced the parameters of cell viability and metabolic activity due to increased ROS synthesis. The negative effect of PM was concentration-dependent; i.e., it was the most pronounced for the highest concentration applied. The impact of PM also depended on the time of exposure, so at respective time points, PM induced different effects. There were also differences in the impact of NIST1648a and LAp120 on almost all parameters tested. The negative effect of LAp120 was more pronounced, what appeared to be associated with an increased content of metals.

Emerging role of mitochondria in airborne particulate matter-induced immunotoxicity

The immune system is one of the primary targets of airborne particulate matter. Recent evidence suggests that mitochondria lie at the center of particulate matter-induced immunotoxicity. Particulate matter can directly interact with mitochondrial components (proteins, lipids, and nucleic acids) and impairs the vital mitochondrial processes including redox mechanisms, fusion-fission, autophagy, and metabolic pathways. These disturbances impede different mitochondrial functions including ATP production, which acts as an important platform to regulate immunity and inflammatory responses. Moreover, the mitochondrial DNA released into the cytosol or in the extracellular milieu acts as a danger-associated molecular pattern and triggers the signaling pathways, involving cGAS-STING, TLR9, and NLRP3. In the present review, we discuss the emerging role of mitochondria in airborne particulate matter-induced immunotoxicity and its myriad biological consequences in health and disease.

Macrophage MerTK Promotes Liver Fibrosis in Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH) is emerging as a leading cause of chronic liver disease. However, therapeutic options are limited by incomplete understanding of the mechanisms of NASH fibrosis, which is mediated by activation of hepatic stellate cells (HSCs). In humans, human genetic studies have shown that hypomorphic variations in MERTK, encoding the macrophage c-mer tyrosine kinase (MerTK) receptor, provide protection against liver fibrosis, but the mechanisms remain unknown. We now show that holo- or myeloid-specific Mertk targeting in NASH mice decreases liver fibrosis, congruent with the human genetic data. Furthermore, ADAM metallopeptidase domain 17 (ADAM17)-mediated MerTK cleavage in liver macrophages decreases during steatosis to NASH transition, and mice with a cleavage-resistant MerTK mutant have increased NASH fibrosis. Macrophage MerTK promotes an ERK-TGFβ1 pathway that activates HSCs and induces liver fibrosis. These data provide insights into the role of liver macrophages in NASH fibrosis and provide a plausible mechanism underlying MERTK as a genetic risk factor for NASH fibrosis.

Exposure to Ambient Air Particles Increases the Risk of Mental Disorder: Findings from a Natural Experiment in Beijing

Epidemiology studies indicated that air pollution has been associated with adverse neurological effects in human. Moreover, the secretion of glucocorticoid (GC) affects the mood regulation, and the negative feedback of hippocampal glucocorticoid receptors (GR) inhibits the GC secretion. Meanwhile, the over secretion of GC can interfere the immune system and induce neurotoxicity. In the present study, the human test showed that the secretion of the cortisol in plasma was elevated after exposure in heavy air pollution. In the mouse model, we found that breathing the highly polluted air resulted in the negative responses of the mood-related behavioral tests and morphology of hippocampus, as well as the over secretion of GC in plasma, down regulation of GR, and up-regulation of cytokine and chemokine in the hippocampus. When considering the interrelated trends between the hippocampal GR, inflammatory factors, and plasmatic GC, we speculated that PM_2.5 exposure could lead to the increased secretion of GC in plasma by decreasing the expression of GR in hippocampus, which activated the inflammation response, and finally induced neurotoxicity, suggesting that PM_2.5 exposure negatively affects mood regulation. When combined with the results of the human test, it indicated that exposure to ambient air particles increased the risk of mental disorder.

Inflammation in induced sputum after aluminium oxide exposure: an experimental chamber study

INTRODUCTION

Workers in aluminium production are exposed to a complex mixture of particles and gases potentially harmful to the airways, among them aluminium oxide (Al2O3). With the use of an exposure chamber, we aimed to examine the effects of short-term controlled exposure to Al2O3 on lung function and inflammatory markers in healthy volunteers.

METHODS

15 men (age 19-31) were exposed in random order to clean air or Al2O3 particles (3.8-4.0 mg/m(3)) for 2 h including 30 min exercise (stationary bike, 75 W). The permissible exposure level (PEL) for Al2O3 by Occupational Safety and Health Administration, USA, is 5 mg/m(3) time weighted average (TWA). Sham and particle exposures were separated by at least 2 weeks. Spirometry was carried out, and induced sputum and blood samples were collected 48 h before and 4 and 24 h after exposure.

RESULTS

Levels of sputum neutrophils (mean (±SEM)) was increased 24 h post-Al2O3 vs pre-Al2O3 exposure (43% (4) vs 31% (4), p=0.01) and the protein level of interleukin (IL)-8 had a 4.8 (0.9)-fold change increase 24 h after exposure (p<0.01). Following Al2O3 exposure, gene signatures in sputum were significantly increased related to several pathways.

CONCLUSIONS

The present study suggests that controlled exposure to Al2O3 particles at levels below PEL (TWA) induces airway inflammation in healthy humans marked by elevated neutrophils and elevated IL-8. In addition, increased expression of genes associated with several biological processes was observed in sputum. Interestingly, inhaled Al2O3-induced effects were localised to the airways and not systemic.