Progression Of Silicosis Research Articles

IL33-mediated NPM1 promotes fibroblast-to-myofibroblast transition via ERK/AP-1 signaling in silica-induced pulmonary fibrosis.

Silicosis is a global occupational pulmonary disease due to the accumulation of silica dust in the lung. Lacking effective clinical drugs makes the treatment of this disease quite challenging in clinics largely because the pathogenic mechanisms remain obscure. Interleukin 33 (IL33), a pleiotropic cytokine, could promote wound healing and tissue repair via the receptor ST2. However, the mechanisms governing the involvement of IL33 in silicosis progression remain to be further explored. Here, we demonstrated that the IL33 levels in the lung sections were significantly overexpressed after bleomycin and silica treatment. Chromatin immunoprecipitation assay, knockdown, and reverse experiments were performed in lung fibroblasts to prove gene interaction following exogenous IL33 treatment or cocultured with silica-treated lung epithelial cells. Mechanistically, we illustrated that silica-stimulated lung epithelial cells secreted IL33 and further promoted the activation, proliferation, and migration of pulmonary fibroblasts by activating the ERK/AP-1/NPM1 signaling pathway in vitro. And more, treatment with NPM1 siRNA-loaded liposomes markedly protected mice from silica-induced pulmonary fibrosis in vivo. In conclusion, the involvement of NPM1 in the progression of silicosis is regulated by the IL33/ERK/AP-1 signaling axis, which is the potential therapeutic target candidate in developing novel antifibrotic strategies for pulmonary fibrosis.

Bioinformatics analysis reveals lipid metabolism may play an important role in the SiO2-stimulated rat model

Silicosis is a progressive and irreversible common occupational disease caused by long-term inhalation of a large amount of free silica dust. Its pathogenesis is complex, and the existing prevention and treatment methods can not effectively improve silicosis injury. To uncover potential differential genes in silicosis, SiO2-stimulated rats and their control original transcriptomic data sets GSE49144, GSE32147 and GSE30178 were downloaded for further bioinformatics analysis. We used R packages to extract and standardize transcriptome profiles, then screened differential genes, and enriched GO and KEGG pathways through clusterProfiler packages. In addition, we investigated the role of lipid metabolism in the progression of silicosis by qRT-PCR validation and transfection with si-CD36. A total of 426 differential genes were identified in this study. Based on GO and KEGG enrichment analysis, it was found that lipid and atherosclerosis were significantly enriched. qRT-PCR was used to detect the relative expression level of differential genes in this signaling pathway of silicosis rat models. mRNA levels of Abcg1, Il1b, Sod2, Cyba, Cd14, Cxcl2, Ccl3, Cxcl1, Ccl2 and CD36 increased, mRNA levels of Ccl5, Cybb and Il18 decreased. In addition, at the cellular level, SiO2-stimulated lead to lipid metabolism disorder in NR8383, and silencing CD36 inhibited SiO2-induced lipid metabolism disorder. These results indicate that lipid metabolism plays an important role in the progression of silicosis, and the genes and pathways reported in this study may provide new ideas for the pathogenesis of silicosis.

449 Progression of silica-induced pulmonary fibrosis is arrested after selective ablation of Col1a1+ fibroblasts

OBJECTIVES/GOALS: Silicosis is a highly fatal progressive fibrotic disease of the lungs characterized by accumulation and persistence of fibroblasts that excessively deposit Collagen1a1. We sought to eliminate Collagen1a1-expressing fibroblasts through a targeted genetic ablation strategy and hypothesized that this would arrest the progression of Silicosis. METHODS/STUDY POPULATION: Silicosis was induced with a single intratracheal (i.t.) instillation of silica particles ( RESULTS/ANTICIPATED RESULTS: Targeted ablation of Col1a1+ fibroblast in established Silicosis resulted in a decrease in: 1) Col1a1+ fibroblasts by flow cytometry and within fibrotic nodules by immunofluorescent staining, 2) total lung collagen content by histology and hydroxyproline assay, 3) tissue-associated disease by microCT and an increase in arterial oxygen saturation by pulse oximetry. Cessation of targeted Col1a1+ fibroblast ablation resulted in a rebound effect in Silicosis disease progression. Following ablation, Col1a1+ fibroblasts expanded by proliferation (Ki67+) and total lung collagen levels returned to pre-ablation levels. DISCUSSION/SIGNIFICANCE: Silicosis is a often fatal disease with no FDA approved therapies. These results suggest that targeted loss of Col1a1+ fibroblasts in Silicosis is sufficient to arrest disease progression. Thus, it is essential to understand how targeted loss of pro-fibrotic fibroblasts can alter disease progression as a tool to develop novel therapeutic strategies.

SiO2 dust induces inflammation and pulmonary fibrosis in rat lungs through activation of ASMase/Ceramide pathway.

The role of ASMase/Ceramide signaling pathway in the development of silicosis needs to be verified by in vivo experiments. We investigated the role of the ASMase/Ceramide signaling pathway in the progression of silicosis and the effect of desipramine (DMI)(1mg/mL) on the development of silicosis, by establishing a silica(1mL, 50mg/mL) dust-contaminated rat silicosis model and administering the ASMase inhibitor, DMI, to the dust-contaminated rats. The results showed that levels of IL-1β and IL-6 were increased in the lung tissues of the rats in the dust-contaminated group at the initial stage after dusting, the inflammatory cell aggregation in the lung tissue was increased. With time progression, the hydroxyproline content in the lung tissue increased, and α-SMA, collagen I and vimentin substantially increased, suggesting that silicosis were formed in the lung tissue of the rats 28 days after SiO2 dust treatment. Moreover, the levels of ASMase, ceramide and S1P were increased in the lung tissue of rats. The expression of β-catenin, fibronectin and caspase-3 protein was increased, and E-cadherin protein expression was decreased in the lung tissue of the rats in the late stage of dust contamination. The ASMase and ceramide in the lung tissues of the rats in the DMI intervention group were reduced, as were the lung tissue inflammation levels, collagen expression, and lung fibrosis. These results suggest that SiO2 dust may activate the ASMase/ceramide signaling pathway in rat lung tissue, promoting pulmonary fibrosis. DMI inhibited these activation, attenuated apoptosis and blocked epithelial-mesenchymal transition and halted silica dust-induced silicofibrosis.

AAV9-HGF cooperating with TGF-beta/Smad inhibitor attenuates silicosis fibrosis via inhibiting ferroptosis

Silicosis is a devastating interstitial lung disease characterized by silicon nodules and diffuse pulmonary fibrosis. To date, inefficient therapy is still a challenge of this disease due to its complicated pathogenesis. Hepatocyte growth factor (HGF) which is highly expressed in hepatocyte with anti-fibrotic and anti-apoptotic function was downregulated in silicosis. In addition, the upregulation of transforming growth factor-beta (TGF-β), another pathological molecular was observed to aggravate the severity and accelerate the progression of silicosis. Here AAV expressed HGF with targeting pulmonary capillaries and SB431542, the inhibitor of TGF-β signal pathway, were simultaneously adopted to synergistically reduce silicosis fibrosis. In vivo result demonstrated that the cooperation of HGF with SB431542 showed strong anti-fibrosis effects on the silicosis mice via tracheal administration of silica, compared to the separate treatment. The high efficacy was mainly achieved by remarkably by reducing ferroptosis of lung tissue. In our point, the combination of AAV9-HGF with SB431542 provide an alternative to relieve silicosis fibrosis from the perspective of targeting pulmonary capillaries.

Epidemiological Characteristics and Drug Resistance of Microbial Pathogens of Patients With Silicosis Combined With Pulmonary Infection

To investigate the epidemiological characteristics of patients with silicosis combined with pulmonary infection in recent years, to study the distribution and the drug susceptibility of fungal and bacterial pathogens in their sputum samples, and to provide references for the prevention and treatment of silicosis and the appropriate drug use. The clinical data and drug sensitivity test results of patients with silicosis combined with pulmonary infection diagnosed at the Department of Occupational Diseases, West China Fourth Hospital, Sichuan University were retrospectively analyzed. A total of 318 patients with silicosis combined with pulmonary infection who received treatment between January 2017 and December 2020 were enrolled. All the patients had positive microorganism test results. All participants were male. Their median age at the time of onset was 51.00 years and the median time of exposure to silica dust at work was 12.40 years. They worked mostly in construction, non-ferrous metal mining, and coal mining. The main types of work they did were pneumatic drilling, coal digging, and mining. The positive detection rates for the first, second and third phases of silicosis were 27.54%, 28.32%, and 32.97%, respectively. A total of 341 strains of fungal and bacterial pathogens were isolated, of which, 54.1% were fungi, including 114 strains (35.8%) of Candida albicans, and 53.1% were bacteria, including 168 strains (52.8%) of gram-negative bacteria, most of which being Klebsiella pneumoniae (30.2%). There was only 1 strain (0.3%) of gram-positive bacteria, namely Staphylococcus hemolyticus. Gram-negative bacilli were most resistant to ampicillin and highly sensitive to penicillin G and ofloxacin. Among patients with silicosis combined with pulmonary infection, the incidence of pulmonary infection increases along with the progress of silicosis. Microorganism analysis reveals high detection rates for fungi and the bacteria detected are predominantly gram-negative bacteria. The overall prospect for drug resistance rate was not optimistic.

Exosomal miR-125a-5p regulates T lymphocyte subsets to promote silica-induced pulmonary fibrosis by targeting TRAF6

Silicosis caused by long-term inhalation of crystalline silica during occupational activities seriously threatens the health of occupational populations. Imbalances in T helper 1(Th1), Th2, Th17, and regulatory T cells (Tregs) promote the development of pulmonary silicosis. Exosomes and their contents, especially microRNAs (miRNAs), represent a new type of intercellular signal transmission mediator related to various diseases including pulmonary fibrosis. However, whether exosomal miRNAs can affect the progression of silicosis by regulating T cell differentiation remains to be determined. To test this hypothesis, we established a miR-125a-5p antagomir mouse model and examined changes in miR-125a-5p levels and T cell subtypes. We found that miR-125a-5p levels were increased in lung tissues and serum exosomes in the silica group at 7 days and 28 days. Downregulation of miR-125a-5p attenuated α-smooth muscle actin (α-SMA), collagen I, fibronectin, p-p65, and p-inhibitor of nuclear factor kappa B (NF-κB) kinase (IKK) protein expression, while tumor necrosis factor receptor-associated factor 6 (TRAF6) and p-inhibitor of κBα (IKBα) expression were increased. MiR-125a-5p anta-miR treatment contributes to the maintenance of Th1/Th2 balance during the progression of pulmonary fibrosis. Our findings indicated that knockdown miR-125a-5p could regulate T lymphocyte subsets and significantly reduce pulmonary fibrosis by targeting TRAF6.

The emerging role of epigenetic regulation in the progression of silicosis.

Silicosis is one of the most severe occupational diseases worldwide and is characterized by silicon nodules and diffuse pulmonary fibrosis. However, specific treatments for silicosis are still lacking at present. Therefore, elucidating the pathogenesis of silicosis plays a significant guiding role for its treatment and prevention. The occurrence and development of silicosis are accompanied by many regulatory mechanisms, including epigenetic regulation. The main epigenetic regulatory mechanisms of silicosis include DNA methylation, non-coding RNA (ncRNA), and histone modifications. In recent years, the expression and regulation of genes related to silicosis have been explored at epigenetic level to reveal its pathogenesis further, and the identification of aberrant epigenetic markers provides new biomarkers for prediction and diagnosis of silicosis. Here, we summarize the studies on the role of epigenetic changes in the pathogenesis of silicosis to give some clues for finding specific therapeutic targets for silicosis.

C-X-C-Chemokine-Receptor-Type-4 Inhibitor AMD3100 Attenuates Pulmonary Inflammation and Fibrosis in Silicotic Mice.

BackgroundSilicosis is a severe pulmonary disease caused by inhaling dust containing crystalline silica. The progression of silicosis to pulmonary fibrosis is usually unavoidable. Recent studies have revealed positivity for the overexpression of C-X-C chemokine receptor type 4 (CXCR4) in pulmonary fibrosis and shown that the CXCR4 inhibitor AMD3100 attenuated pulmonary fibrosis after bleomycin challenge and paraquat exposure. However, it is unclear whether AMD3100 reduces crystalline silica-induced pulmonary fibrosis.MethodsC57BL/6 male mice were instilled intranasally with a single dose of crystalline silica (12 mg/60 μL) to establish an acute silicosis mouse model. Twelve hours later, the mice were injected intraperitoneally with 5 mg/kg AMD3100 or control solution. Then, the mice were weighed daily and sacrificed on day 7, 14, or 28 to collect lung tissue and peripheral blood. Western blotting was also applied to determine the level of CXCR4, while different histological techniques were used to assess pulmonary inflammation and fibrosis. In addition, the level of B cells in peripheral blood was measured by flow cytometry.ResultsCXCR4 and its ligand CXCL12 were upregulated in the lung tissues of crystalline silica-exposed mice. Blocking CXCR4 with AMD3100 suppressed the upregulation of CXCR4/CXCL12, reduced the severity of lung injury, and prevented weight loss. It also inhibited neutrophil infiltration at inflammatory sites and neutrophil extracellular trap formation, as well as reduced B-lymphocyte aggregates in the lung. Additionally, it decreased the recruitment of circulating fibrocytes (CD45+collagen I+CXCR4+) to the lung and the deposition of collagen I and α-smooth muscle actin in lung tissue. AMD3100 also increased the level of B cells in peripheral blood, preventing circulating B cells from migrating to the injured lungs.ConclusionBlocking CXCR4 with AMD3100 delays pulmonary inflammation and fibrosis in a silicosis mouse model, suggesting the potential of AMD3100 as a drug for treating silicosis.

Identification of key pathways and genes in the progression of silicosis based on WGCNA

Silicosis, induced by inhaling silica particles in workplaces, is one of the most common occupational diseases. The prognosis of silicosis and its consequent fibrosis is extremely poor due to limited treatment modalities and lack of understanding of the disease mechanisms. In this study, a Wistar rat model for silicosis fibrosis was established by intratracheal instillation of silica (0, 50, 100 and 200 mg/mL, 1 mL) with the evidence of Hematoxylin and Eosin (HE) and Masson staining and the expressions of inflammatory and fibrotic proteins of rats’ lung tissues. RNA of lung tissues of rats exposed to 200 mg/mL silica particles and normal saline for 14 d and 28 d was extracted and sequenced to detect differentially expressed genes (DEGs) and to identify silicosis fibrosis-associated modules and hub genes by Weighted gene co-expression network analysis (WGCNA). Predictions of gene functions and signaling pathways were conducted using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. In this study, it has been demonstrated the promising role of the Hippo signaling pathway in silicosis fibrosis, which will be conducive to elucidating the specific mechanism of pulmonary fibrosis induced by silica and to determining molecular initiating event (MIE) and adverse outcome pathway (AOP) of silicosis fibrosis.

Glycyrrhizic Acid Attenuates Pulmonary Fibrosis of Silicosis by Inhibiting the Interaction between HMGB1 and BRG1 through PI3K/Akt/mTOR Pathway.

Purpose: High mobility group protein 1 (HMGB1) is a highly conserved DNA-binding nuclear protein that participates in the occurrence and development of silicosis. HMGB1 binds to its specific receptor and activates phosphatidylinositol 3-kinase (PI3K)/protein kinase B, (PKB; Akt)/mammalian target of rapamycin (mTOR) pathway. Brahma-related genes 1 (BRG1; SMARCA4) is the core subunit of SWI/SNF. HMGB1 activates the Akt pathway through BRG1 to promote the proliferation of prostate cancer. Glycyrrhizic acid is a new pharmacological inhibitor of HMGB1, which may inhibit the occurrence and development of silicosis. We speculate that glycyrrhizic acid inhibits the interaction between HMGB1 and BRG1 through the PI3K/Akt/mTOR pathway to affect the progression of silicosis. Methods: We carried out an in vitro study and stimulated A549 with TGF-β1 to establish an epithelial–mesenchymal transition (EMT) model, knocked down the HMGB1 and BRG1 genes in cells, observed the expression of EMT markers, and detected the interaction between HMGB1 and BRG1 by co-immunoprecipitation. In vivo, we injected glycyrrhizic acid into the mouse silicosis model to inhibit the expression of HMGB1. Results: Both HMGB1 and BRG1 were highly expressed in the process of EMT. After knocking down HMGB1 and BRG1, the process of EMT was inhibited through the PI3K/Akt/mTOR pathway, and their expressions were influenced by each other. HMGB1 and BRG1 interact with each other in A549 cells. HMGB1 and BRG1 are also highly expressed in the mouse silicosis model, and glycyrrhizic acid can inhibit the expression of HMGB1/BRG1 through the PI3K/Akt/mTOR pathway. Conclusion: Glycyrrhizic acid can inhibit the interaction between HMGB1 and BRG1 through the PI3K/Akt/mTOR pathway to affect the progression of silicosis.

A novel circRNA-SNP may increase susceptibility to silicosis

In this study, we aimed to reveal the association between circRNA-related single nucleotide polymorphisms (SNPs) with the susceptibility of silicosis. To achieve this goal, a silicosis-related GWAS was constructed to select the candidate SNPs, and circBase database was utilized to select the promising SNPs which may locate on circRNAs. In addition, the eQTL analysis between the SNPs and located genes was performed to select the candidate SNPs. Finally, the association between candidate SNPs with the susceptibility of silicosis was validated. As a result, we firstly selected 10,922 SNPs with P < 1 × 10−3 through the silicosis-related GWAS. Among which, 1,752 SNPs were identified that may locate on 2,660 circRNAs. After the MAF evaluation and the sequences checking, we obtained 94 SNPs and related 105 circRNAs. EQTL analysis indicated that 7 circRNA-SNPs might regulate the expression of located genes. Subsequently, a strong association was found between variant A of rs17115143 and silicosis risk in the validation stage (OR= 1.68, P = 0.032). Combination of the GWAS data and Taqman genotyping data also revealed a strong association between rs17115143 and silicosis risk in both dominant and additive models (dom: OR= 1.96, P = 3.98 × 10−4; add: OR= 1.40, P = 3.06 × 10−4). In conclusion, the variant A allele of circRNA-SNP rs17115143 could be a risk factor in the progression of silicosis. And related 6 circRNAs may function as novel biomarkers for the diagnostic of silicosis. Further researches to explore the biological mechanisms of rs17115143 related 6 circRNAs in the regulation of silicosis are warranted.

The regulatory effect of pulmonary lymphatic drainage on silicosis fibrosis

Silicosis is a fibrotic disease caused by long-term inhalation of SiO2 particles that currently has no effective treatment. Earlier studies have suggested that pulmonary lymphatic vessels play a key role in the transport of silica but have not address the long-term effects of altered pulmonary lymphatic drainage on silicosis. Here, we investigated the impact of impaired pulmonary lymphatic drainage on silicosis. In the past, lymphatic drainage disorders were established mainly through the use of VEGF inhibitors. For the first time, we established a model of pulmonary lymphatic drainage disorder by ligating the thoracic duct in rats. Impaired pulmonary lymphatic drainage was found to aggravate inflammation and oxidative damage in silicosis rats and accelerate silicosis progression. Next, we investigated the effect of pulmonary lymphatic drainage on silicosis. We have demonstrated the effect of sodium tanshinone IIA sulfonate(STS) on lymphangiogenesis, which revealed that STS promotes lymphangiogenesis and can delay inflammation, oxidative damage, and fibrosis progression in silicosis rats by promoting the pulmonary lymphatic drainage response, and this effect is mediated by the VEGFR-3/PI3K/AKT signaling pathway. These findings suggest that pulmonary lymphogenesis plays an important role in silicosis pathogenesis, and targeted intervention in pulmonary lymphangiogenesis may be a potential strategy for treating of silicosis in the future.

Gefitinib and fostamatinib target EGFR and SYK to attenuate silicosis: a multi-omics study with drug exploration

Silicosis is the most prevalent and fatal occupational disease with no effective therapeutics, and currently used drugs cannot reverse the disease progress. Worse still, there are still challenges to be addressed to fully decipher the intricated pathogenesis. Thus, specifying the essential mechanisms and targets in silicosis progression then exploring anti-silicosis pharmacuticals are desperately needed. In this work, multi-omics atlas was constructed to depict the pivotal abnormalities of silicosis and develop targeted agents. By utilizing an unbiased and time-resolved analysis of the transcriptome, proteome and phosphoproteome of a silicosis mouse model, we have verified the significant differences in transcript, protein, kinase activity and signaling pathway level during silicosis progression, in which the importance of essential biological processes such as macrophage activation, chemotaxis, immune cell recruitment and chronic inflammation were emphasized. Notably, the phosphorylation of EGFR (p-EGFR) and SYK (p-SYK) were identified as potential therapeutic targets in the progression of silicosis. To inhibit and validate these targets, we tested fostamatinib (targeting SYK) and Gefitinib (targeting EGFR), and both drugs effectively ameliorated pulmonary dysfunction and inhibited the progression of inflammation and fibrosis. Overall, our drug discovery with multi-omics approach provides novel and viable therapeutic strategies for the treatment of silicosis.

Inhibition of Gas6 promotes crystalline silica-induced inflammatory response of macrophages via blocking autophagy flux.

Inhalation of crystalline silica (CS) can cause silicosis, which is one of the most serious interstitial lung diseases worldwide. Autophagy dysfunction is an essential step in silicosis progression. In this study, we aim to identify the effect of growth arrest-specific protein 6 (Gas6) during autophagy induction and macrophage inflammatory response caused by CS. After RAW 264.7 macrophages exposed to CS, the levels of Gas6 and autophagy markers (p62, Beclin1, and LC3-II/LC3-I) were increased, accompanied with enhanced inflammatory cytokines secretion. Using autophagy activator (rapamycin) repressed, whereas autophagy inhibitor (3-methyladenine) promoted inflammatory cytokines release. Besides, inhibition of Gas6 aggravated CS-induced inflammatory response, and autophagy inhibition facilitated the promoted effect of Gas6 silencing, resulting in elevated expression of inflammatory cytokines. These findings reveal the protective effects of Gas6 and autophagy in macrophages in response to CS exposure, and highlight the autophagy regulated by Gas6 may be a potential prevention target for CS-induced lung inflammatory response.

Risk Factors of Silicosis Progression: A Retrospective Cohort Study in China.

BackgroundSilicosis poses a threat to workers’ health due to the irreversible lung lesions.DesignA retrospective cohort study.MethodsA total of 259 patients [80 worked with artificial stone (AS), 179 with non-artificial stone (non-AS)] with confirmed silicosis were included in this study. Forty-one of AS and 91 of non-AS had approximately 2 years’ follow-up records [lung function tests and high-resolution computer tomography (HRCT)]. Compared with the first records, increased, densified, or newly emerging lesions in lung HRCT images were judged as progression of the disease. Cox proportional hazards models were used to determine the risk factors. Kaplan–Meier survival curve and log-rank test were used to compare prognostic factors for cumulative risk of progression.ResultsIn 132 patients with median follow-up of 24.0 months (IQR, 13.8, 24.9), 66 patients showed progression, in them, 36 (87.8%) were from AS group and 30 (32.9%) from non-AS group. Working experience of AS processing (hazard ratio, 5.671; 95% CI, 3.048–10.550) and complicated silicosis in CT images (hazard ratio, 2.373; 95% CI, 1.379–4.082) were the main risk factors associated with progression. Forced vital capacity decreased after 1-year (241.5 vs. 55.2 mL) and 2-year (328.1 vs. 68.8 mL) follow-up in the two groups (AS vs. non-AS). History of anti-tuberculosis medication, chest oppression and pain, ground-glass opacity, pleural abnormalities, and restrictive pulmonary dysfunction were more frequently found on HRCT images in the AS group than non-AS group. Lung functions (DLCO, %) were lower in the current/former smokers than the non-smokers (P < 0.05) in AS patients.ConclusionPrevention and protection rules are needed to be enforced in the occupation involving AS processing; smoking may be associated with declined lung function in AS patients.

Necroptosis in pulmonary macrophages promotes silica-induced inflammation and interstitial fibrosis in mice

Silicosis is a disease characterized by extensive lung nodules and fibrosis caused by the prolonged inhalation of silica in occupational settings. However, the molecular mechanism of silicosis development is complex and not fully understood. Furthermore, the role of necroptosis, a death receptor-mediated and caspase-independent mode of inflammatory cell death, is not well understood in silicosis. Here, we demonstrate that the necroptotic signaling pathway of macrophages is significantly activated in the lungs of silicosis mouse models. Meanwhile, increased M1 macrophage infiltration and up-regulation of pro-inflammatory cytokines (TNF-α, IL-6) were observed in our silicosis model. Notably, the expression of the pro-fibrotic factor, TGF-β1, and fibrosis biomarkers α-SMA and collagen I were also unregulated; however, these phenomena were recovered by Nec-1, an inhibitor specific for RIP1 kinase-dependent necroptosis. We conclude that macrophage-mediated necroptosis promotes the progression of silicosis by enhancing lung inflammatory responses and fibrogenesis in a mouse model of silicosis. These findings provide new insights for drug discovery and clinical treatment of silicosis.

Inhibition of gasdermin D-dependent pyroptosis attenuates the progression of silica-induced pulmonary inflammation and fibrosis

Silicosis is a leading cause of occupational disease-related morbidity and mortality worldwide, but the molecular basis underlying its development remains unclear. An accumulating body of evidence supports gasdermin D (GSDMD)-mediated pyroptosis as a key component in the development of various pulmonary diseases. However, there is little experimental evidence connecting silicosis and GSDMD-driven pyroptosis. In this work, we investigated the role of GSDMD-mediated pyroptosis in silicosis. Single-cell RNA sequencing of healthy and silicosis human and murine lung tissues indicated that GSDMD-induced pyroptosis in macrophages was relevant to silicosis progression. Through microscopy we then observed morphological alterations of pyroptosis in macrophages treated with silica. Measurement of interleukin-1β release, lactic dehydrogenase activity, and real-time propidium iodide staining further revealed that silica induced pyroptosis of macrophages. Additionally, we verified that both canonical (caspase-1-mediated) and non-canonical (caspase-4/5/11-mediated) signaling pathways mediated silica-induced pyroptosis activation, in vivo and in vitro. Notably, Gsdmd knockout mice exhibited dramatically alleviated silicosis phenotypes, which highlighted the pivotal role of pyroptosis in this disease. Taken together, our results demonstrated that macrophages underwent GSDMD-dependent pyroptosis in silicosis and inhibition of this process could serve as a viable clinical strategy for mitigating silicosis.

The Mechanism and Effect of Autophagy, Apoptosis, and Pyroptosis on the Progression of Silicosis.

Silicosis remains one of the most severe pulmonary fibrotic diseases worldwide, caused by chronic exposure to silica dust. In this review, we have proposed that programmed cell death (PCD), including autophagy, apoptosis, and pyroptosis, is closely associated with silicosis progression. Furthermore, some autophagy, apoptosis, or pyroptosis-related signaling pathways or regulatory proteins have also been summarized to contribute greatly to the formation and development of silicosis. In addition, silicosis pathogenesis depends on the crosstalk among these three ways of PCD to a certain extent. In summary, more profound research on these mechanisms and effects may be expected to become promising targets for intervention or therapeutic methods of silicosis in the future.

Alpha-lipoic acid attenuates silica-induced pulmonary fibrosis by improving mitochondrial function via AMPK/PGC1α pathway activation in C57BL/6J mice

Silicosis is characterized by pulmonary interstitial fibrosis that arises as a result of chronic exposure to silica. The few available treatments only delay its progression. As α-lipoic acid (ALA) has been shown to have various beneficial effects, including mitoprotective, antioxidant, and anti-inflammatory effects, we hypothesized that it may exhibit therapeutic effects in pulmonary fibrosis. Therefore, in the present study, we used a murine model of silicosis to investigate whether supplementation with exogenous ALA could attenuate silica-induced pulmonary fibrosis by improving mitochondrial function. ALA was administered to the model mice via continuous intragastric administration for 28 days, and then the antioxidant and mitoprotective effects of ALA were evaluated. The results showed that ALA decreased the production of reactive oxygen species, protected mitochondria from silica-induced dysfunction, and inhibited extracellular matrix deposition. ALA also decreased hyperglycemia and hyperlipidemia. Activation of the mitochondrial AMPK/PGC1α pathway might be responsible for these ALA-mediated anti-fibrotic effects. Exogenous ALA blocked oxidative stress by activating NRF2. Taken together, these findings demonstrate that exogenous ALA effectively prevents the progression of silicosis in a murine model, likely by stimulating mitochondrial biogenesis and endogenous antioxidant responses. Therefore, ALA can potentially delay the progression of silica-induced pulmonary fibrosis.