Silicosis

Efficacy and safety of a novel short course rifapentine and isoniazid regimen for the preventive treatment of tuberculosis in Chinese silicosis patients: a pilot study (SCRIPT-TB)

BACKGROUND

Tuberculosis preventive treatment (TPT) is essential for the end TB Strategy, but shorter and better tolerated regimens are needed to boost its coverage and acceptance.

METHODS

Silicosis patients aged 18 to 65 years received a novel 1H3P3 regimen (400 mg isoniazid and 450 mg rifapentine, thrice-weekly for 4 weeks) under direct observation and were actively followed up for 3 years. The safety and efficacy were compared to the 3-month, once-weekly isoniazid/rifapentine (3HP) group and observation group from our previous trials.

RESULTS

A total of 279 eligible participants were enrolled, and 238 participants provided informed consent. All eligible participants had a median age of 56 years (IQR 52-60), 163 (68.5%) participants had a Bacillus Calmette-Guerin vaccine scar, and 74 (31.1%) participants were QuantiFERON-TB Gold In-Tube positive. There were 88 adverse events from 66 (27.7%) participants and only one (0.4%) participant had a Grade 3 adverse event. The completion rate was 92.0% (219/238). Six (2.5%) participants were diagnosed with active TB, five of which were bacterial confirmed cases. The cumulative active TB rate was 1.67 cases per 100 person-years. Compared to the previous study, the 1H3P3 regimen significantly reduced the 3-year cumulative active TB rate than the observation group (HR = 0.26, Log-rank P = 0.02) and was comparable with the 3HP group (HR = 0.74, Log-rank P = 0.69), while significantly reducing adverse events.

CONCLUSION

The 1H3P3 TPT regimen was both safe and effective among silicosis patients. Further work is necessary to test the regimen in other high-risk populations.Trial registration: ClinicalTrials.gov identifier: NCT06022146 and NCT03900858.

Exploring the efficacy and constraints of platinum nanoparticles as adjuvant therapy in silicosis management

Silicosis represents a formidable occupational lung pathology precipitated by the pulmonary assimilation of respirable crystalline silica particulates. This condition engenders a cascade of cellular oxidative stress via the activation of bioavailable silica, culminating in the generation of reactive oxygen species (ROS). Such oxidative mechanisms lead to irrevocable pulmonary impairment. Contemporary scholarly examinations have underscored the substantial antioxidative efficacy of platinum nanoparticles (PtNPs), postulating their utility as an adjunct therapeutic modality in silicosis management. The physicochemical interaction between PtNPs and silica demonstrates a propensity for adsorption, thereby facilitating the amelioration and subsequent pulmonary clearance of silica aggregates. In addition to their detoxifying attributes, PtNPs exhibit pronounced anti-inflammatory and antioxidative activities, which can neutralize ROS and inhibit macrophage-mediated inflammatory processes. Such attributes are instrumental in attenuating inflammatory responses and forestalling subsequent lung tissue damage. This discourse delineates the interplay between ROS and PtNPs, the pathogenesis of silicosis and its progression to pulmonary fibrosis, and critically evaluates the potential adjunct role of PtNPs in the therapeutic landscape of silicosis, alongside a contemplation of the inherent limitations associated with PtNPs application in this context.

Global scenario of silica-associated diseases: A review on emerging pathophysiology of silicosis and potential therapeutic regimes

Silicosis is an occupational fibrotic lung disease caused by exposure to respirable crystalline silica dust particles produced during industrial activities. Other crystalline silica-induced pulmonary disorders include a predisposition to mycobacterial infections, obstructive airway diseases, idiopathic pulmonary fibrosis, and lung cancer. This review paper discusses the burden of silicosis and associated co-morbidities in developed as well as developing countries globally using the published data of various government agencies, related organizations, and epidemiological findings. Moreover, it sheds light on diverse mechanisms of silicosis, outlining molecular events and peculiar alterations in lung parenchyma leading to this occupational lung disease. Evaluation of pathophysiological mechanisms could aid in the identification of novel target molecules and treatments; to date, there is no curative treatment for silicosis. In recent periods, a lot of attention has been focused on the development and fabrication of suitable nanocarriers for improved and sustained drug delivery in the pulmonary system. Nanoparticle-based therapeutic modality has been evaluated in in-vitro and ex-vivo silicosis models for prolongation of drug activity and improved therapeutic outcomes. The preclinical findings open the doors to clinical trials for operational and regenerative nanoformulations, which eventually create a positive change in medical practice. The following review summarizes various therapeutic approaches available and in the pipe line for silicosis and also stresses the preventive practices for effectively combating this occupational hazard.

Innate immune checkpoint SIRPα/CD47 blockade ameliorates silica-induced pulmonary fibrosis by modulating macrophage immunity

Silicosis is a fibrotic disease caused by prolonged inhalation of silica particles. Signal regulatory protein alpha (SIRPα) and its ligand CD47, key innate immune checkpoints mediating inhibition of phagocytosis, have been reported to regulate organ fibrosis. However, the role of SIRPα/CD47 in silicosis remains unexplored. In this study, a silicosis mouse model was constructed and revealed a significant upregulation of SIRPα and CD47 expression in lung tissue with disease progression. In addition, the expression patterns of SIRPα and CD47 in various silicosis effector cells exhibit distinct cell specificity. Using RRx-001 to block SIRPα/CD47 signaling in mice, we observed a marked reduction in lung injury, decreased collagen deposition, and improved pulmonary function. Mechanistically, blocking SIRPα/CD47 affected T cell activation, macrophage polarization and the expression of pro-inflammatory and pro-fibrotic factors. In vitro, we found that inhibiting SIRPα/CD47 countered the silica-induced suppression of macrophage phagocytosis and induced macrophage polarization towards the M1 phenotype. Additionally, levels of soluble SIRPα and CD47 in the peripheral blood of silicosis patients were significantly higher than those in healthy controls. In summary, this study demonstrates that SIRPα/CD47-mediated immunomodulatory signaling is the driving factor for the progression of silicosis, and this pathway might serve as a therapeutic target for silicosis treatment.

Interstitial Lung Diseases and Lung Cancer: A Review on Similarities, Common Pathogenesis and Therapeutic Approach

Interstitial lung disease (ILD) prevalence and survival are increasing due to improvement in scientific research together with clinical complications typical of advanced disease. Lung cancer (LC) is described as a possible event occurring in lung parenchyma in the context of fibrotic abnormalities that worsen patients' prognosis. This growth of malignant cells on a fibrotic background has also been called scar-cinoma. For this reason, not only an early diagnosis but also personalized decisions on the best treatment approach should be considered for each patient in a multidisciplinary discussion, since in some cases chemotherapy or surgery could be detrimental for patients with pulmonary fibrosis. LC and lung fibrosis may share common pathogenetic mechanisms like an altered healing process in response to repeated tissue damage from environmental exposure in genetically susceptible individuals. Smoking history and air pollution together with mutations in telomere and surfactant protein genes lead to the production of cytokines and nitro derivatives in the microenvironment that facilitate the carcinomatous transformation during fibrogenesis. The evolution of LC therapy and the implementation of immunotherapy acting on targetable immune checkpoints have raised interest in evaluating ILD-LC actionable mutations. The main pathogenetic mechanisms, clinical presentations and treatment implications are presented in this review.

Exploring agglomeration of respirable silica and other particles in coal mine dust

A better understanding of respirable dust particle characteristics is needed to advance exposure monitoring and prevent health effects. In coal mines and other occupational environments, understanding respirable silica is especially important. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) enables particle-level dust analysis, but interpretation of data can be challenging when samples include agglomerated particles (i.e., particulates consisting of multiple independent particles attached together). On the other hand, a failure to recognize agglomerates or account for them in analysis risks oversimplification in exposure assessment. This research explores possible effects of agglomerates on respirable coal mine dust classification by SEM-EDX, with a specific focus on silica. Analysis was conducted both on respirable samples (collected with a typical apparatus including a cyclone size selector) and on respirable-sized particulates identified in passive samples. Results demonstrate that silica is often contained in respirable-sized agglomerates, though the typical respirable sampling apparatus appears to break up some of those agglomerates. For agglomerates that do persist, they may influence SEM-EDX results-possibly increasing apparent size distributions and/or "hiding" some of their constituents, including silica.

SiO2 particles induce pulmonary fibrosis by modulating NLRP3 through the ROS/Keap1/Nrf2 signaling pathway in rats

Recent studies have shown that the activation of the ROS-dependent NLRP3 inflammasome plays a key role in the pathogenesis of silicosis; however, the mechanism by which SiO2-induced ROS activates NLRP3 remains unclear. In this study, rats were intratracheally instilled with a SiO2 suspension once and then received daily intravenous injections of NAC (at doses of 20, 40, and 80 mg/kg, respectively) to inhibit SiO2-induced ROS. Rats that were intratracheally instilled with a SiO2 suspension once served as silicosis models, while those that were intratracheally instilled with PBS once served as controls. After 40 days, lung samples were taken for pathological observation, and the BALF was collected to measure ROS levels. The mRNA and protein expression levels of Keap1/Nrf2 signaling indicators (Keap1, Nrf2) and NLRP3 inflammasome indicators (NLRP3, GSDMD) were detected. The results showed that the Keap1/Nrf2 signaling pathway and the NLRP3 were activated in the silicosis rat lungs, accompanied by an increase in ROS levels. When ROS was inhibited, the Keap1/Nrf2 signaling pathway, the NLRP3, and the degree of pulmonary fibrosis were all suppressed in a dose-dependent manner. Therefore, we conclude that SiO2 particles induce pulmonary fibrosis in rats by modulating the NLRP3 inflammasome via the ROS/Keap1/Nrf2 signaling pathway.

Early diagnosis and survival outcomes in silicosis: a retrospective cohort study of 11,809 patients in Guangdong Province, China (1956-2020)

Introduction

Silicosis, a progressive occupational lung disease caused by silica dust exposure, remains a global public health challenge due to limited therapeutic options. Early diagnosis is hypothesized to improve survival outcomes, yet evidence linking diagnostic stage to mortality remains scarce. This study aimed to evaluate the association between early diagnosis and survival in silicosis patients and assess the impact of delayed diagnosis on mortality.

Methods

A retrospective cohort study analyzed 11,809 silicosis patients diagnosed between 1956 and 2020 in Guangdong Province, China. Data were extracted from occupational disease registries, multi-sectoral databases, and provincial monitoring systems. Exclusion criteria included ambiguous diagnosis dates, pre-adolescent exposure, and missing variables. Cox proportional hazards models adjusted for covariates (sex, age, region, industry, exposure duration) were used to assess mortality risks across stages I-III. Survival curves, temporal trends, and subgroup analyses were performed.

Results

Most patients (77.8%) were diagnosed at stage I, with median survival times declining sharply across stages: 27 years (stage I), 20 years (stage II), and 11 years (stage III) (p < 0.001). Adjusted mortality risks increased progressively: stage II (HR = 1.42, 95%, CI: 1.33-1.51) and stage III (HR = 2.42, 95%, CI: 2.17-2.70)compared to stage I. Temporal analysis revealed peak diagnoses in 1963 and the early 1980s, stabilizing post-2006. Subgroup analyses confirmed staging as an independent prognostic factor across industries and exposure durations (p < 0.001).

Discussion

This study demonstrates that early diagnosis significantly prolongs survival in silicosis patients, with advanced stages correlating with exponentially higher mortality. The findings underscore the urgent need for systematic early screening, such as high-resolution CT, and stricter occupational health policies to reduce silica exposure. Despite limitations, including unmeasured confounders like smoking status, this research provides critical evidence to inform global strategies for mitigating silicosis through timely detection and workplace safety reforms.

Fermented Cordyceps Powder alleviates silica-induced inflammation and fibrosis by inhibiting M1 macrophage polarization via the HMGB1-TLR4-NF-κB pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Cordyceps sinensis is a valuable Chinese medicine that has the effects of tonifying the lungs and kidneys, regulating the immune system, etc. Fermented Cordyceps Powder (FCP) is the fermentation product of Cordyceps sinensis mycelium, which has similar composition and effects to natural Cordyceps sinensis. FCP has been used as an adjunctive treatment of silicosis, however, the complete comprehension of these molecular mechanisms remains elusive.

AIM OF THE STUDY

To study the molecular immunological mechanism by which FCP alleviate inflammation and fibrosis in silicosis based on macrophage polarization and High Mobility Group Box protein 1 (HMGB1)-Toll-like receptor 4 (TLR4)-Nuclear factor kappaB (NF-κB) pathway through in vivo and in vitro experiments.

MATERIALS AND METHODS

A rat model of silicosis and a co-culture cell model (NR8383 and RFL-6) exposed to silica were established and then intervened with different levels of FCP and FCP-containing serum, respectively, to explore the impacts of FCP on silica-induced inflammation and fibrosis and macrophage polarization at different time points. Upon the application of glycyrrhizic acid (GZA) to suppress HMGB1, an extensive analysis was undertaken to elucidate the impact of HMGB1-TLR4-NF-κB axis on the macrophages polarization.

RESULTS

FCP reduced M1, M2 macrophage polarization, and the HMGB1 expression in the lung of silicosis rats. Suppression of HMGB1 led to a pronounced reduction in the polarization of M1 macrophages, whereas it exerted no significant influence on the polarization of M2 macrophages. FCP-containing serum reduced silica-induced inflammation and fibrosis in the co-culture cell system. FCP-containing serum also reduced M1 macrophage polarization and inhibited stimulation of the HMGB1-TLR4-NF-κB signaling axis in NR8383 cells.

CONCLUSIONS

Reduction of M1, M2 macrophage polarization is an important mechanism by which FCP attenuates inflammation and fibrosis in silicosis, in which reduction of M1 macrophage polarization may be achieved by suppression of the HMGB1-TLR4-NF-κB signaling axis.

Proteomics and Metabolomics Analyses Reveal a Dynamic Landscape of Coal Workers' Pneumoconiosis: An Insight into Disease Progression

Coal worker's pneumoconiosis (CWP) is characterized by chronic inflammation and pulmonary fibrosis. The key factor contributing to the incurability of CWP is the unclear pathogenesis. This study explored the characteristic changes in proteomics and metabolomics of early and advanced CWP patients through proteomics and metabolomics techniques. Proteomics identified proteins that change with the progression of CWP, with significant enrichment in the TGF-β signaling pathway and autoimmune disease pathways. Metabolomics revealed the metabolic characteristics of CWP at different stages. These metabolites mainly include changes in amino acid metabolism, unsaturated fatty acid synthesis, and related metabolites. Integrated analysis found that ABC transporters are a shared pathway among the three groups, and ABCD2 is involved in the ABC transporter pathway. In the subsequent independent sample verification analysis, consistent with proteomics experiments, compared to the CM group, FMOD expression level was upregulated in the NIC group. TFR expression level was consistently downregulated in both the IC and NIC groups. Additionally, ABCD2 increased in the IC group but decreased in the NIC group. In summary, this study revealed the metabolic characteristics of CWP at different stages. These findings may provide valuable insights for the early prediction, diagnosis, and treatment of CWP.

Integrated network pharmacological analysis and multi-omics techniques to reveal the mechanism of polydatin in the treatment of silicosis via gut-lung axis

Silicosis is a pulmonary disease characterized by inflammation and progressive fibrosis. Previous studies have shown that polydatin (PD) has potential biological activity in key signaling pathways regulating inflammation and apoptosis. To investigate the effect of PD on rats with silicosis, this study used network pharmacology and molecular docking methods to determine the target of PD treatment for silicosis. The therapeutic effect of PD on silicosis was confirmed by measuring the lung injury score, hydroxyproline content, and mRNA expression levels of key targets. In addition, metagenomic sequencing and gas chromatography-mass spectrometry were used to determine the gut microbiota composition and targeted metabolomics analysis, respectively. The results showed that PD could inhibit the expression of inflammation-related indexes and apoptosis-related indexes at protein and mRNA levels. PD also regulates the diversity of the intestinal flora and the content of short-chain fatty acids. In conclusion, the current data suggest that PD has a protective effect against silica-induced lung injury and plays a protective role in regulating intestinal flora diversity and short-chain fatty acid levels through the gut-lung axis.

What rationale for treatment of occupational interstitial lung diseases with the drugs approved for idiopathic pulmonary fibrosis?

PURPOSE OF REVIEW

To critically discuss the rationale for the use of drugs approved for idiopathic pulmonary fibrosis (IPF) to treat occupational interstitial lung diseases (OILDs).

RECENT FINDINGS

Although IPF and OILDs share several clinical, radiological and probably pathogenetic features, currently, OILDs do not have a standard of care. In recent years, our knowledge and understanding of ILDs has improved substantially. Recently, the progressive pulmonary fibrosis (PPF) phenotype, which refers to non-IPF fibrotic ILDs that progress despite appropriate treatment, has been defined. OILDs may also be progressive. Nintedanib, initially approved for treatment of IPF, is also approved in patients with PPF. On the other hand, pirfenidone is approved in IPF but not in PPF, due to the lack of robust evidence of efficacy in this patient subset.

SUMMARY

OILDs are a large and highly heterogeneous group of conditions without a proper standard of care. Nintedanib may slow functional decline and disease progression in progressive OILDs, and new clinical trials are ongoing.

GDF15 activates human fibroblast MRC5 cells via miR-338/STAT1 in silicosis

Growth differentiation factor 15 (GDF-15) has been implicated in multiple biological functions. However, the role of GDF15 in silicosis remains unclear. In this study, the serum level of GDF-15 was investigated in 46 patients with silicosis by ELISA and results showed it was higher than that of control patients. The effects of exogenous GDF15 on mRNA and miRNA expression profiles of MRC5 cells were analyzed by RNA sequencing. GDF15 activated human embryonic lung fibroblast MRC5 cells with upregulation of col1a and α-SMA. GDF15 reduced miR-338 expression and increased STAT1 expression in MRC5 cells. The results of the luciferase reporter assay and bioinformatics analysis indicated that STAT1 was a direct target of miR-338. miR-338 mimics down-regulated col1a and α-SMA expression induced by GDF15 with STAT1 overexpression, whereas miR-338 inhibitor up-regulated col1a and α-SMA expression induced by GDF15 with STAT1 knockdown. Those results indicated GDF15 activated MRC5 cells through the miR-338/STAT1 pathway and GDF-15 may play an important role in silicosis.

Association between interleukin gene polymorphisms and the risk of pneumoconiosis: a systematic review and meta-analysis

Numerous studies have demonstrated that interleukin (IL) plays an essential role in the development of chronic inflammatory diseases, especially in pneumoconiosis. The association between various IL gene polymorphisms and pneumoconiosis susceptibility has been investigated extensively, but the results remain controversial. A literature search was conducted using PubMed, EMBASE, Web of Science, Cochrane Library, China National Knowledge Infrastructure (CNKI), and Wanfang database to obtain relevant studies before 22 January 2025. Subsequently, odds ratios (ORs) with 95% confidence intervals (CIs) were used to evaluate the strength of correlations. A sensitivity analysis was performed to evaluate the robustness and reliability of the included studies. Overall, there was a significant association between IL-1RA +2018 and IL-6 -634 with the risk of pneumoconiosis. The IL-1RA +2018 variant was positively associated with an increased risk of pneumoconiosis among both Asians and Caucasians. In contrast, the IL-6 -634 genotype was associated with a lower risk of pneumoconiosis among Asians. Additionally, the IL-1RA +2018 genotype was significantly linked to a predisposition to coal workers' pneumoconiosis (CWP) and silicosis. The IL-6 -634 mutant significantly decreased silicosis and CWP risk. Additional large-scale replication studies are needed to elucidate the precise role of various IL SNPs in the etiology of pneumoconiosis.

Serum Proteomic Markers in Patients with Systemic Sclerosis in Relation to Silica Exposure

Background: Systemic sclerosis (SSc) is a multisystem autoimmune disease characterised by fibrosis, vasculopathy, and immune dysfunction. Silica exposure has been associated with a more aggressive phenotype of the disease, including diffuse cutaneous involvement and interstitial lung disease. This study aims to identify proteomic differences between SSc patients exposed to silica and those not exposed to silica. Methods: An observational study of 32 SSc patients (11 silica-exposed and 21 non-exposed) was performed, with occupational history and quantitative proteomic analysis using SWATH-MS mass spectrometry. Differentially expressed proteins were analysed, and functional pathway enrichment was performed. Results: Eight proteins showed significant differences between groups, all with reduced levels in silica-exposed patients: adiponectin, immunoglobulins (IGLV3-19, IGLV2-18), complement C2, alpha-2-macroglobulin, vitronectin, cytoplasmic actin 2, and pigment epithelium-derived factor. Alterations in pathways related to fibrinolysis, complement activation, and inflammation were highlighted, suggesting that silica exposure may influence the pathogenesis of SSc and worsen its clinical course. Conclusions: This study supports the hypothesis that silica exposure is not only a triggering factor for SSc, but is also modulating its progression through inflammatory, procoagulant, and fibrotic pathways. The identification of proteomic biomarkers could contribute to the phenotypic classification of patients and the development of personalised therapies. Future studies should expand the cohort and further investigate the functional mechanisms of these proteins in SSc.

Long-term exposure to low-level crystalline silica and risk assessment of silicosis: a cohort study

BACKGROUND

High-level exposure to crystalline silica dust is the key factor in silicosis. Long-term exposure to low-level silica dust, for example, lower than that in occupational exposure limits, still needs to be studied for their risk of silicosis.

METHODS

A total of 30 697 workers were included from a cohort in China. Low-level silica dust exposure was defined as those having a lifetime mean silica dust concentration equal to or under permissible exposure limits, including 0.05 mg/m3, 0.10 mg/m3 and 0.35 mg/m3. Cumulative respirable silica dust exposure (CDE) for individual workers was assessed by linking a job-exposure matrix to personal work history.

RESULTS

Among those with average exposure level equal to or lower than 0.05 mg/m3, compared with the lowest quartile CDE (Q1), the HRs of silicosis were 1.32 (95% CI 0.82 to 2.10) for Q2, 1.87 (95% CI 1.22 to 2.88) for Q3 and 2.00 (95% CI 1.30 to 3.09) for Q4. Among those exposed to 0.10 mg/m3 or less exposure level, compared with Q1, the HRs were 2.52 (95% CI 1.88 to 3.38) for Q2, 4.08 (95% CI 3.09 to 5.39) for Q3 and 4.02 (95% CI 3.04 to 5.32) for Q4. Among those exposed to 0.35 mg/m3 or less exposure level, compared with Q1, the HRs were 2.80 (95% CI 2.38 to 3.28) for Q2, 5.76 (95% CI 4.93 to 6.73) for Q3 and 7.14 (95% CI 6.07 to 8.40) for Q4, respectively. Stratified analysis showed that the results and trends did not change with facilities and smoking status.

CONCLUSION

Long-term exposure to low-level silica dust is still associated with a higher risk of silicosis. Control measurements and personal protective equipment should be emphasised to protect the health of workers.

BI 1015550 Improves Silica-Induced Silicosis and LPS-Induced Acute Lung Injury in Mice

Silicosis is an interstitial lung disease (ILD) caused by prolonged inhalation of silica particles. Acute lung injury (ALI) is a critical clinical syndrome involving bilateral lung infiltration and acute hypoxic respiratory failure. However, there is currently no effective treatment for these two diseases. Previous research has established that cyclic adenosine monophosphate (cAMP) is pivotal in the pathogenesis of silicosis and acute lung injury. Phosphodiesterase 4 (PDE4) is a hydrolase enzyme of cAMP, and BI 1015550, as an inhibitor of PDE4B, is expected to be a candidate drug for treating both. BI 1015550 has shown certain anti-inflammatory and anti-fibrotic properties in systemic sclerosis-associated interstitial lung disease (SSc-ILD) and idiopathic pulmonary fibrosis (IPF), but there is a lack of research on silicosis and acute lung injury. In this research, we successfully synthesized BI 1015550 autonomously and demonstrated that it could significantly improve lung fibrosis and inflammation in a silica-induced silicosis mouse model. Furthermore, we found that BI 1015550 could also alleviate lung inflammation in a Lipopolysaccharide (LPS)-induced acute lung injury mouse model. The mechanism of action may involve the regulation of cAMP-related signaling pathways.

Exploring aerosol-specific calibration and performance of three direct-reading photometers

Laser photometers provide real-time data on airborne aerosols. They are a valuable tool for assessing task exposures, as well as process and environmental changes. However, their performance compared to the validated National Institute of Occupational Health and Safety (NIOSH) method Particulates Not Otherwise Regulated, Respirable 0600 gravitational method is uncertain. NIOSH has established a criterion for sampling and analytical methods to be within 25% of the 'true' concentration. Manufacturers and research scientists cite the importance of using an aerosol-specific calibration factor to improve instrument correlation with the gravimetric method. Field data from three photometers are presented to illustrate instrument performance variability and evaluate single and averaged aerosol-specific calibration factors. Respirable particulate and respirable crystalline silica (RCS) were simultaneously measured ten times in an operating rock crushing facility using the NIOSH methods 0600 and 7500 Silica, Crystalline, by XRD (filter redeposition) and three factory calibrated photometers. Ten aerosol-specific calibration factors were calculated for each photometer and used to determine single and averaged aerosol-specific calibration factors. Single and averaged aerosol-specific calibration factors were mathematically applied to "correct" the factory calibrated instrument measurements. Performance was evaluated using absolute relative error. With the factory calibration, the average absolute relative error for each instrument exceeded 25%. A single-event aerosol-specific calibration factor reduced the average absolute relative error for all instruments, bringing it below 25% for one of the three photometers. A 3-run average aerosol-specific calibration factor reduced the average absolute relative error below 25% for all instruments. Further averaging of calibration factor provided no significant advantage. The 95th percentile of absolute error fell below 25% for one of the tested instruments when applying both a single and averaged calibration factor but remained above 25% for the other two instruments. Field testing of the single-run, three-run average and ten-run average calibration factors revealed that the absolute relative error exceeded 25% in at least one of the three CF-field tests for each instrument. The average absolute relative error in estimates of RCS varied from 7 to 38%.

Silica-induced ferroptosis activates retinoic acid signaling in dendritic cells to drive inflammation and fibrosis in silicosis

Silicosis, a chronic lung disease caused by inhalation of silica (SiO2) particles from environmental contamination or industrial exposure, is characterized by persistent inflammation and fibrosis. This study elucidates a novel mechanism where SiO2 exposure triggers ferroptosis, a lipid peroxidation-dependent form of cell death, in dendritic cells (DCs), thereby activating retinoic acid (RA) signaling. The RA response amplifies inflammatory pathways, including cGAS-STING-IFN-I and IL-1β signaling, exacerbating lung inflammation and fibrosis. The study uses murine models to demonstrate that ferroptosis inhibitors, such as ferrostatin-1, mitigate SiO2-induced inflammation and collagen deposition. Furthermore, systemic administration of the synthetic retinoid AM80 reduces pulmonary damage by modulating immune cell distribution and promoting lymphocyte homing. These findings reveal the interplay between ferroptosis and RA signaling as a pivotal driver of silicosis pathology and suggest therapeutic avenues targeting ferroptosis and RA modulation for disease management.

Combined therapy with pirfenidone and nintedanib counteracts fibrotic silicosis in mice

BACKGROUND AND PURPOSE

Pneumoconiosis, especially silicosis, is a prevalent occupational disease with substantial global economic implications and lacks a definitive cure. Both pneumoconiosis and idiopathic pulmonary fibrosis (IPF) are interstitial lung diseases, which share many common physiological characteristics. Because pirfenidone and nintedanib are approved to treat IPF, their potential efficacy as antifibrotic agents in advanced silicosis deserves further exploration. Thus, we aimed to evaluate the individual and combined effects of pirfenidone and nintedanib in treating advanced silicosis mice and elucidate the underlying mechanisms of their therapeutic actions via multiomics.

EXPERIMENTAL APPROACH

We administered monotherapy or combined therapy of pirfenidone and nintedanib, with low and high doses, in silicosis established after 6 weeks and evaluated lung function, inflammatory responses and fibrotic status. Additionally, we employed transcriptomic and metabolomic analyses to uncover the mechanisms underlying different therapeutic strategies.

KEY RESULTS

Both pirfenidone and nintedanib were effective in treating advanced silicosis, with superior outcomes observed in combination therapy. Transcriptomic and metabolomic analyses revealed that pirfenidone and nintedanib primarily exerted their therapeutic effects by modulating immune responses, signalling cascades and metabolic processes involving lipids, nucleotides and carbohydrates. Furthermore, we experimentally validated both monotherapy and combined therapy yielded therapeutic benefits through two common signalling pathways: steroid biosynthesis and purine metabolism.

CONCLUSION AND IMPLICATIONS

In conclusion, pirfenidone and nintedanib, either individually or in combination, demonstrate substantial potential in advanced silicosis. Furthermore, combined therapy outperformed monotherapy, even at low doses. These therapeutic benefits are attributed to their influence on diverse signalling pathways and metabolic processes.

Metabolic landscape of human alveolar type II epithelial cells undergoing epithelial-mesenchymal transition induced directly by silica exposure

Epithelial-mesenchymal transition (EMT) plays an irreplaceable role in the development of silicosis. However, molecular mechanisms of EMT induced by silica exposure still remain to be addressed. Herein, metabolic profiles of human alveolar type II epithelial cells (A549 cells) exposed directly to silica were characterized using non-targeted metabolomic approaches. A total of 84 differential metabolites (DMs) were identified in silica-treated A549 cells undergoing EMT, which were mainly enriched in metabolisms of amino acids (e.g., glutamate, alanine, aspartate), purine metabolism, glycolysis, etc. The number of DMs identified in the A549 cells obviously increased with the elevated exposure concentration of silica. Remarkably, glutamine catabolism was significantly promoted in the silica-treated A549 cells, and the levels of related metabolites (e.g., succinate) and enzymes (e.g., α-ketoglutarate (α-KG) dehydrogenase) were substantially up-regulated, with a preference to α-KG pathway. Supplementation of glutamine into the cell culture could substantially enhance the expression levels of both EMT-related markers and Snail (zinc finger transcription factor). Our results suggest that the EMT of human alveolar epithelial cells directly induced by silica can be essential to the development of silicosis.

Mechanisms and Therapeutic Potential of Myofibroblast Transformation in Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive, irreversible, and fatal disease with an increasing incidence and limited therapeutic options. It is characterized by the formation and deposition of excess extracellular matrix proteins resulting in the gradual replacement of normal lung architecture by fibrous tissue. The cellular and molecular mechanism of IPF has not been fully understood. A hallmark in IPF is pulmonary fibroblast to myofibroblast transformation (FMT). During excessive lung repair upon exposure to harmful stimuli, lung fibroblasts transform into myofibroblasts under stimulation of cytokines, chemokines, and vesicles from various cells. These mediators interact with lung fibroblasts, initiating multiple signaling cascades, such as TGFβ1, MAPK, Wnt/β-catenin, NF-κB, AMPK, endoplasmic reticulum stress, and autophagy, contributing to lung FMT. Furthermore, single-cell transcriptomic analysis has revealed significant heterogeneity among lung myofibroblasts, which arise from various cell types and are adapted to the altered microenvironment during pathological lung repair. This review provides an overview of recent research on the origins of lung myofibroblasts and the molecular pathways driving their formation, with a focus on the interactions between lung fibroblasts and epithelial cells, endothelial cells, and macrophages in the context of lung fibrosis. Based on these molecular insights, targeting the lung FMT could offer promising avenues for the treatment of IPF.

NLRP3 inflammasome in health and disease (Review)

Activation of inflammasomes is the activation of inflammation‑related caspase mediated by the assembly signal of multi‑protein complex and the maturity of inflammatory factors, such as IL‑1β and IL‑18. Among them, the Nod‑like receptor family pyrin domain containing 3 (NLRP3) inflammasome is the most thoroughly studied type of inflammatory corpuscle at present, which is involved in the occurrence and development of numerous human diseases. Therefore, targeting the NLRP3 inflammasome has become the focus of drug development for related diseases. In this paper, the research progress of the NLRP3 inflammasome in recent years is summarized, including the activation and regulation of NLRP3 and its association with diseases. A deep understanding of the regulatory mechanism of NLRP3 will be helpful to the discovery of new drug targets and the development of therapeutic drugs.

Applying Finite Mixture Models to Quantify Respirable Dust Mass in Coal and Metal-Nonmetal Mines Using Fourier Transform Infrared Spectroscopy

Respirable dust mass is a prevalent occupational health hazard to the mining workforce. Mineral matrices observed in the mine environment are complex, time varying, and heterogeneous. This poses a challenge to assessing dust exposure using Fourier transform infrared (FT-IR) spectrometry as calibrations for constituent dust species (e.g., crystalline silica) have historically been trained using homogeneous standards or simple mixtures therein. Investigations have considered direct-on-filter analysis, which collects FT-IR spectra directly from sampling filters for calibration, as an alternative. Direct-on-filter analysis using a partial least squares (PLS) method has gained particular interest recently due to the potential to rapidly quantify multiple species from a single filter at the mine site. By design, heterogeneity, and its presumed impact on method accuracy, cannot be addressed in the laboratory when using a direct-on-filter approach motivating the need for more advanced calibration approaches. When heterogeneity is present, mixture of experts (MoE) finite mixture models offer a promising and novel alternative to PLS direct-on-filter analysis as MoE incorporates cluster discovery, regression, and outlier identification into model fitting. Three MoE models of increasing complexity were tasked with determining respirable dust mass in 243 field samples from thirteen active coal, limestone, sandstone, and silver mines. All MoE models, including those using only "expert" spectroscopic predictors or a combination of expert and categorical "gate" variables (e.g., mine type), significantly outperform PLS in terms of accuracy (α = 0.05). Decomposing bias by mine type shows that accuracy generally improves across all types considered when MoE models are not overfitted. The MoE method's effectiveness was linked to its ability to endogenously classify outliers as well as possibly to the use of an additional cluster model for mass predictions. Overall, MoE methods appear as a capable and novel tool to addressing problems of heterogeneity for direct-on-filter quantitative analysis.

Elevating VAPB-PTPIP51 integration repairs damaged mitochondria-associated endoplasmic reticulum membranes and inhibits lung fibroblasts activation

Long-term silica exposure to silica dust leads to irreversible pulmonary fibrosis, during which lung fibroblast activation plays an essential role. Mitochondria-associated endoplasmic reticulum membranes (MAMs) is a structural interface for communication between the outer mitochondrial membrane and the endoplasmic reticulum. VAPB-PTPIP51 is a key complex on MAMs. However, the role of VAPB-PTPIP51-linked MAMs in lung fibroblast activation remains under investigation. In this study, we observed mitochondrial damage and endoplasmic reticulum stress in a SiO2-induced lung fibrosis model using C57BL/6J mice. In the model of TGF-β1-induced mouse lung fibroblast (MLG) activation, interventions with Dioscin and TUDCA reduced mitochondrial damage and alleviated endoplasmic reticulum stress by repairing damaged MAMs. Additionally, TUDCA may restore the MAMs structure by enhancing the interaction between VAPB and PTPIP51. Our findings indicate that MAMs may play a crucial role in linking mitochondrial damage and endoplasmic reticulum stress, suggesting their potential involvement in fibroblast activation.

Exosomal miRNA reprogramming in pyroptotic macrophage drives silica-induced fibroblast-to-myofibroblast transition and pulmonary fibrosis

Silicosis is an occupational lung disease characterized by progressive pulmonary fibrosis, threatening millions of occupational workers worldwide due to a lack of effective treatments. To unveil mechanisms underlying silica-induced pulmonary fibrosis, we established in vitro and in vivo silicosis models, then employed scRNA-sequencing to profile the cellular landscape of lung tissues followed by characterization of macrophage pyroptosis and exosome therefrom in driving fibroblast-to-myofibroblast-transdifferentiation. Using hyperspectral imaging and artificial intelligence-powered pathological recognition, we found that silica nanoparticle (SiNP) triggered progressive lung fibrosis in vivo, and scRNA-seq implicated interstitial macrophage as pivotal regulators for fibroblast transdifferentiation. Mechanistically, SiNPs were demonstrated to induce macrophage pyroptosis and liberate exosomes, which upregulated pro-fibrotic markers and promoted myofibroblast transition. Subsequent high-throughput miR-sequencing revealed distinct exosomal miRNA signatures that modulated TGF-β signaling and induced fibroblast transdifferentiation. Lastly, we administered these exosomes into silicotic mice and found exacerbated inflammatory infiltration and pulmonary fibrosis. In conclusion, SiNPs exposure caused the remodeling of exosomal miRNAs by inducing interstitial macrophage pyroptosis, and exosomes derived from pyroptotic macrophage fuel fibroblast transdifferentiation by creating a pro-fibrotic microenvironment and promoting silicotic fibrosis. These findings provide critical insights into the pathogenesis of silicosis and the formulation of emerging therapeutic strategies.

Hyperacute silicosis after bronchoscopy-induced melanoptysis in a lung transplant patient. A first report in literature

Silicosis, a fibrotic lung disease caused by crystalline silica inhalation, presents unique challenges in lung transplantation. This case reports an unprecedented complication in a lung transplant recipient with chronic silicosis. A man in his 60s, post left single-lung transplantation for silica-induced pneumoconiosis, developed acute respiratory deterioration following routine bronchoscopy. Melanoptysis, followed by imaging showing extensive inflammatory involvement in the transplanted lung, required intubation and prone positioning. This case highlights the potential for residual silicotic material to trigger acute post-transplant complications. It underscores the importance of comprehensive pretransplant evaluation of occupational exposures and heightened awareness of silica-related complications in post-transplant care. The report emphasizes gaps in understanding long-term outcomes and optimal management strategies for lung transplant recipients with silicosis.

PD-L1 upregulation in activated fibroblasts promotes silica particle-induced pulmonary fibrosis

Silicosis is a severe interstitial lung disease resulting from prolonged exposure to silica dust in working environment, characterized by inflammation and fibrosis. This condition is closely associated with immune dysregulation, although the precise regulatory mechanisms remain elusive. Immune checkpoints (ICs) comprise receptor-ligand pairs crucial for immune cell activation and coordination of immune responses. Among these, PD-1 and its ligand PD-L1 have garnered significant attention in tumor research and have recently been implicated in the regulation of fibrotic diseases. Nonetheless, their involvement in silicosis remains unexplored. In this study, we observed a global upregulation of PD-1 and PD-L1 expression concomitant with the progression of silicosis, exhibiting cell specificity. Targeting PD-1/PD-L1 signaling mitigated silicosis in mice by modulating T cell homeostasis, macrophage polarization, and activation of fibrotic effector cells. Notably, PD-L1 expression on activated fibroblasts emerged as a pivotal driver of silicosis progression. Mechanistically, elevated PD-L1 levels in fibroblast activation fostered a positive feedback loop by binding to p-Smad2/3 and p-STAT3 proteins, thereby facilitating their nuclear translocation and augmenting protein stability, ultimately promoting fibroblast transdifferentiation. Consistently, knockdown of PD-L1 in lung fibroblasts significantly ameliorated silicosis in mice. In summary, PD-1/PD-L1 signaling mediates critical profibrotic signals during the progression of silicosis.

Pulmonary and systemic effects of inhaled crystalline silica in the HOCl-induced mouse model of systemic sclerosis: An experimental model of Erasmus syndrome

Occupational exposure to crystalline silica is etiologically linked to an increased incidence of systemic sclerosis (SSc), also called Erasmus syndrome. The underlying mechanisms of silica-related SSc are still poorly understood. We demonstrated that early and repeated silica exposure contribute to the severity of SSc symptoms in the hypochloric acid (HOCl)-induced SSc mouse model. Analyses of lung samples from silica-exposed HOCl mice revealed a slightly aggravation of fibrosis and an exacerbation of inflammation, notably an additionally overexpression of NLRP3 inflammasome genes and a recruitment of classical monocytes, macrophages, dendritic cells and neutrophils. Silica exposure showed systemic effects in SSc mouse model with an elevated circulating classical monocyte counts and an overexpression of inflammatory genes in the skin. Silica-exposed SSc patients also had more severe skin disease than unexposed patients. Overall, we provide new insights on immune cell populations and related pathways in early pathogenic mechanisms contributing to HOCl-induced and silica-related SSc.

Tripartite motif-containing 32 regulated by miR-6236-p5 inhibited silica-induced apoptosis of alveolar macrophages

Apoptosis of alveolar macrophages (AMs) induced by silica is one of the crucial driving factors of silicosis inflammation and fibrosis. However, the mechanism of silica-induced AMs apoptosis remains unclear. In this study, transcriptome sequencing identified 11 differentially expressed (DE)-mRNAs enriched in the regulation of apoptotic signaling pathways in AMs treated with 250 μg/mL silica for 24 h, of which tripartite motif-containing 32 (Trim32) was the most significant and down-regulated. The decreased Trim32 promoted AMs apoptosis, while Trim32 overexpression inhibited the apoptosis of AMs induced by silica at 250 μg/mL for 24 h. MiR-6236-p5 was then identified by MiRNA sequencing as the most significant DE-miRNA potentially regulating Trim32 expression, and the interaction between miR-6236-p5 and Trim32 3'-UTR was confirmed by dual luciferase reporter gene assay. Treated with 100 nM miR-6236-p5 inhibitor increased the expression of Trim32 and inhibited the apoptosis of AMs induced by silica at 250 μg/mL for 24 h, while miR-6236-p5 mimic promoted the apoptosis of silica-induced AMs. In conclusion, this study identified Trim32 regulated by miR-6236-p5 played an important role in silica-induced AMs apoptosis based on RNA sequencing, which provided a novel clue for exploring the mechanism of silica-induced AMs apoptosis.

miR-207 Suppresses the Progression of SiO2-Induced Pulmonary Fibrosis by Targeting Smad3 to Regulate the TGF-β1/Smad3 Signaling Pathway in C57BL/6 Mice

Silicosis is a worldwide occupational disease characterized by irreversible pulmonary fibrosis. Recent studies have showed that microRNAs (miRNAs) may play a crucial role in silicosis progression by modulating fibrosis-related gene express. In this study, we selected miR-207 as our research subject because we found that miR-207 can be match with Smad3 using bioinformatic techniques, which might silence the key fibrosis-related TGF-β1/Smad3 signal pathway. In this study, the mice were given silica suspension (20 µg/µL, 80 µL) via nostril once a day for 16 days to establish silicosis models, and then were transfected with miR-207 mimic or inhibitor. The mice which were given phosphate-buffered saline (PBS) (80 µL) via nostril were used as control. All mice were killed on Day 45 after the first exposure to dust, after which their lungs were removed for pathological observation and to measure the hydroxyproline content. Then, real-time polymerase chain reaction and Western blot analysis were applied to detect the relative expression levels of TGF-β1/Smad3 signaling pathway indicators (TGF-β1, TGF-βR, and Smad3), and myofibroblast transformation indicators (α-SMA and Fn). Results showed that the lung pathological images of silicosis model group mice showed significant fibrosis, and TGF-β1, TGF-βR, Smad3, α-SMA, and Fn were all highly upregulated compared with the control group mice. Intervention with miR-207 mimics significantly inhibited pulmonary fibrosis in silicosis mice by downregulation of TGF-β1/Smad3 and inhibiting of myofibroblast formation. Whereas these phenomena were not observed in silicosis mice treated with miR-207 inhibitor. The results demonstrated that miR-207 can block the progression of SiO2-induced pulmonary fibrosis by targeting the TGF-β/Smad3 signaling pathway.

The degree of cross-linking of polyacrylic acid affects the fibrogenicity in rat lungs

Polyacrylic acid (PAA) with different concentrations of cross-linker was instilled into the trachea of rats to examine the effect of PAA crosslink density on lung disorders. Methods: F344 rats were intratracheally exposed to low and high doses of PAA with cross-linker concentrations of 0.1, 1.0, and 5.0% (CL0.1%, CL1.0%, and CL5.0%, respectively). Rats were sacrificed at 3 days, 1 week, 1 month, 3 months, and 6 months after exposure. PAA with different cross-linker concentrations caused an increase in neutrophil influx, cytokine-induced neutrophils, and chemotactic factor (CINC) in bronchoalveolar lavage fluid (BALF) from 3 days to 1 week after instillation. Lactate dehydrogenase (LDH) activity in BALF and heme oxygenase-1 (HO-1) release in lung tissue were higher in the CL0.1% exposure group during the acute phase. Lung histopathological findings also showed that severe fibrotic changes induced by CL0.1% were greater than those observed in CL1.0% and CL5.0% exposure during the observation period. CL0.1% was associated with more severe lung fibrosis, and a decrease in lung fibrosis was observed with increasing cross-linker concentrations, suggesting that the cross-link density of PAA is a physicochemical feature that affects lung disorders.

Development of a multi-laboratory integrated predictive model for silicosis utilizing machine learning: a retrospective case-control study

Objective

Due to the high global prevalence of silicosis and the ongoing challenges in its diagnosis, this pilot study aims to screen biomarkers from routine blood parameters and develop a multi-biomarker model for its early detection.

Methods

A case-control study was conducted to screen biomarkers for the diagnosis of silicosis using LASSO regression, SVM and RF. A sample of 612 subjects (half cases and half controls) were randomly divided into training and test groups in a 2:1 ratio. Logistic regression analysis and receiver operating characteristic (ROC) curves were used to construct a multiple biomarker-based model for the diagnosis of silicosis, which was applied to both the training and the testing datasets.

Results

The training cohort revealed significant statistical differences (P < 0.05) in multiple hematologic parameters between silicosis patients and healthy individuals. Based on machine learning, eight silicosis biomarkers were screened and identified from routine blood cell, biochemical and coagulation parameters. D-dimer (DD), Albumin/Globulin (A/G), lactate dehydrogenase (LDH) and white blood cells (WBC) were selected for constructing the logistic regression model for silicosis diagnostics. This model had a satisfactory performance in the training cohort with an area under the ROC curve (AUC) of 0.982, a diagnostic sensitivity of 95.4%, and a specificity of 92.2%. In addition, the model had a prediction accuracy of 0.936 with an AUC of 0.979 in the independent test cohort. Moreover, the diagnostic accuracies of the logistic model in silicosis stages 1, 2, and 3 were 88.0, 95.4, and 94.3% with an AUC of 0.968, 0.983, and 0.990 for silicosis, respectively.

Conclusion

A diagnostic model based on DD, A/G, LDH and WBC is successfully proposed for silicosis diagnostics. It is cheap, sensitive, specific, and preliminarily offers a potential strategy for the large-scale screening of silicosis.

Silica-exposed patients with silicosis show shorter telomeres than do unexposed individuals: a pilot study in a population in southeastern Brazil

OBJECTIVE

Silicosis is a pneumoconiosis characterized by fibrosis of the lung parenchyma caused by the inhalation of silica particles. Silica dust inhalation is associated with inflammation and induction of oxidative stress in the lungs. This oxidative stress affects telomeres, which are short tandem DNA repeats that cap the end of linear chromosomes. We aimed to determine whether telomere length (TL) correlates with silicosis or severity of silicosis in silica-exposed workers in Brazil.

METHODS

We included 200 men in southeastern Brazil: 100 with silicosis and 100 who had not been exposed to silica. We extracted DNA from buccal cells and assessed TL by multiplex quantitative polymerase chain reaction.

RESULTS

The median TL was significantly shorter in the patients with silicosis than in the unexposed controls (p < 0.0001), although it did not differ between the patients with simple silicosis and those with complicated silicosis (p = 0.961). We also found that, in patients with silicosis, TL was influenced by smoking (p = 0.034) and by a history of personal protective equipment use in the workplace (p = 0.002).

CONCLUSIONS

Silica exposure appears to have an impact on TL, which was found to be shorter in patients with silicosis than in unexposed controls. Further studies are needed in order to confirm the impact that oxidative stress caused by silica inhalation has on telomeres.

Stat3 Induces IL-10 and SR-A/CD204 Expression in Silica Nanoparticle-Triggered Pulmonary Fibrosis through Transactivation

Inhalation of silica dust in the workplace has been addressed as a serious occupational pulmonary disease subsequently leading to inflammation and fibrosis. Enhanced expression of IL-10 significantly contributes to the disease etiology, along with an elevated Th2-type paradigm. Previously, we showed that the exaggerated Th2-type response was also associated with consistent upregulation of Stat3 in mouse airways stimulated with silica microparticles. However, a precise understanding of silicosis in light of the IL-10/Stat3 immune axis is required. We, therefore, aimed to determine the regulatory role of IL-10 in nanosized silica (nSiO2)-induced pulmonary fibrosis in association with Stat3. Herein, we report that amorphous nSiO2 could induce pulmonary fibrosis with consistent and concomitant upregulation of IL-10, Stat3, and SR-A/CD204. Following exogenous administration of siStat3 and rIL-10, the study further confirmed that Stat3 mediates the regulation of IL-10 and SR-A/CD204 and that IL-10 could regulate its own expression in an autoregulatory loop. The ChIP assay highlighted the localization of Stat3 over two putative binding sites in the IL-10 promoter region, which subsequently resulted in the overexpression of SR-A/CD204. Conclusively, Stat3-mediated transregulation of IL-10 through an autoregulatory loop in silicosis could offer novel molecular targets for therapeutic interventions.

A comprehensive retrospect on the current perspectives and future prospects of pneumoconiosis

Pneumoconiosis is a widespread occupational pulmonary disease caused by inhalation and retention of dust particles in the lungs, is characterized by chronic pulmonary inflammation and progressive fibrosis, potentially leading to respiratory and/or heart failure. Workers exposed to dust, such as coal miners, foundry workers, and construction workers, are at risk of pneumoconiosis. This review synthesizes the international and national classifications, epidemiological characteristics, strategies for prevention, clinical manifestations, diagnosis, pathogenesis, and treatment of pneumoconiosis. Current research on the pathogenesis of pneumoconiosis focuses on the influence of autophagy, apoptosis, and pyroptosis on the progression of the disease. In addition, factors such as lipopolysaccharide and nicotine have been found to play crucial roles in the development of pneumoconiosis. This review provides a comprehensive summary of the most fundamental achievements in the treatment of pneumoconiosis with the purpose of indicating the future direction of its treatment and control. New technologies of integrative omics, artificial intelligence, systemic administration of mesenchymal stromal cells have proved useful in solving the conundrum of pneumoconiosis. These directional studies will provide novel therapeutic targets for the treatment of pneumoconiosis.

Silica-mediated exacerbation of inflammatory arthritis: A novel murine model

Objective

The mucosal origin hypothesis in rheumatoid arthritis (RA) posits that inhalant exposures, such as cigarette smoke and crystalline silica (c-silica), trigger immune responses contributing to disease onset. Despite the established risk posed by these exposures, the mechanistic link between inhalants, lung inflammation, and inflammatory arthritis remains poorly understood, partly from the lack of a suitable experimental model. As c-silica accelerates autoimmune phenotypes in lupus models and is a recognized risk factor for several autoimmune diseases, we investigated whether c-silica exposure could induce RA-like inflammatory arthritis in mice.

Methods

Two arthritis-prone mouse strains, BXD2/TyJ and HLA-DR4 transgenic (DR4-Tg), were exposed to c-silica or PBS via oropharyngeal instillation. Arthritis was evaluated by clinical signs and histopathology. Autoimmunity was further evaluated by serological analysis, including autoantibodies and cytokines and chemokines. Lung pathology was evaluated by histopathology and immunofluorescent staining for lymphocyte and macrophages.

Results

C-silica exposure induced chronic pulmonary silicosis in all mice. In BXD2 mice, this was associated with rapid arthritis development, marked by synovitis, bone erosion, and elevated serum autoantibody levels targeting various antigens, including snRNP and citrullinated protein. Additionally, BXD2 mice exhibited inducible bronchus-associated lymphoid tissue (iBALT) formation and elevated autoantibodies in bronchoalveolar lavage fluid (BALF). Conversely, DR4-Tg mice had no significant arthritis, negligible autoantibody responses, and milder lung inflammation lacking iBALT.

Conclusion

We introduce a novel model of c-silica-mediated inflammatory arthritis, creating a novel platform to unravel the molecular and cellular underpinnings of RA and advance understanding of the mucosal origin hypothesis.

Core-Shell Nanoparticles for Pulmonary Drug Delivery

Nanoscale drug delivery systems have provoked interest for application in various therapies on account of their ability to elevate the intracellular concentration of drugs inside target cells, which leads to an increase in efficacy, a decrease in dose, and dose-associated adverse effects. There are several types of nanoparticles available; however, core-shell nanoparticles outperform bare nanoparticles in terms of their reduced cytotoxicity, high dispersibility and biocompatibility, and improved conjugation with drugs and biomolecules because of better surface characteristics. These nanoparticulate drug delivery systems are used for targeting a number of organs, such as the colon, brain, lung, etc. Pulmonary administration of medicines is a more appealing method as it is a noninvasive route for systemic and locally acting drugs as the pulmonary region has a wide surface area, delicate blood-alveolar barrier, and significant vascularization. A core-shell nano-particulate drug delivery system is more effective in the treatment of various pulmonary disorders. Thus, this review has discussed the potential of several types of core-shell nanoparticles in treating various diseases and synthesis methods of core-shell nanoparticles. The methods for synthesis of core-shell nanoparticles include solid phase reaction, liquid phase reaction, gas phase reaction, mechanical mixing, microwave- assisted synthesis, sono-synthesis, and non-thermal plasma technology. The basic types of core-shell nanoparticles are metallic, magnetic, polymeric, silica, upconversion, and carbon nanomaterial- based core-shell nanoparticles. With this special platform, it is possible to integrate the benefits of both core and shell materials, such as strong serum stability, effective drug loading, adjustable particle size, and immunocompatibility.

[Everything under control?]

A 43-year-old quarry worker, after being exposed to fine quartz dust for 16 years in a German quarry, is on the waiting list for a lung transplant. The inhalation of the fine dust irreversibly damaged his lungs and facilitated the occurrence of fulminant mycobacterial and fungal infections, which have already led to a unilateral pneumonectomy and increasing respiratory failure. Despite regular monitoring by the occupational health and safety board, this dramatic development of silicosis could not be prevented.

Prevalence of pulmonary hypertension in chronic simple silicosis patients and its correlation with smoking history, occupation type, age and duration of silica exposure

Silicosis is a preventable occupational health hazard with the potential for permanent physical disability and increased socio-economic burden. Pulmonary hypertension (PH) secondary to chronic respiratory diseases signifies a poorer prognosis and transthoracic echocardiography (TTE) has proven its usefulness as a screening tool for PH diagnosis. The objectives were to determine PH prevalence in chronic simple silicosis patients through TTE screening and correlate PH prevalence with smoking status, occupation type, age, and duration of silica exposure (DSE). We enrolled 104 patients in the study based on occupational exposure to silica dust and radiologic confirmation of chronic simple silicosis. The study sample was divided into significant smokers (SS group) and insignificant smokers (InS group) based on ≥10 pack years smoking history, and into drillers and dressers based on occupation type. TTE examination was performed to measure resting mean pulmonary artery pressure (mPAP) and the patients were classified into: no PH (mPAP≤20 mm Hg), borderline PH (mPAP>20 and <25 mmHg), and PH (mPAP≥25). PH prevalence was 25% in study subjects (26/104); 29.6% (16/54) among SS group vs. 20% (10/50) among InS group (0.52); and 34.2% (14/41) among drillers vs. 19.1% (12/63) among dressers (p=0.024). Mean age and mean DSE among SS and InS groups were comparatively similar, while they had lower values among dressers against dressers with no statistical significance. Logistic regression analysis established a significant association of PH prevalence with higher age in the study sample, SS group, and drillers group, while a significant association of PH prevalence with longer DSE was only seen in the study sample. PH prevalence was significantly associated (p=0.007) with the SS-driller group when comparing TTE findings with combined smoking and occupation type-based groups. This study has shown PH prevalence in chronic simple silicosis patients at alarming levels, having associations with driller occupation, older age, and longer DSE with varying results among groups and complex interplay with smoking exposure, suggesting the need for large sample-based molecular and genetic studies. Including TTE in the initial work-up of silicosis patients will promote timely intervention and reduce morbidity and mortality with a high benefit-cost ratio.

Myricetin Alleviates Silica-Mediated Lung Fibrosis via PPARγ-PGC-1α Loop and Suppressing Mitochondrial Senescence in Epithelial Cells

OBJECTIVE

Long-term inhalation of silica dust particles leads to lung tissue fibrosis, resulting in impaired gas exchange and increased mortality. Silica inhalation triggers the aging of epithelial cells (AECs), which is a key contributor to the development of pulmonary fibrosis. Myricetin, a flavonoid compound extracted from Myrica genus plants, possesses various biological activities, including antioxidant and immunomodulatory effects. However, the mechanisms underlying myricetin's ability to counter senescence and fibrosis need to be further studied.

EXPERIMENTAL APPROACH

In vivo, the antifibrotic and anti-senescence effects of myricetin were evaluated using a silica-induced pulmonary fibrosis mouse model. To further elucidate the mechanisms by which myricetin counteracts silica-induced senescence, in vitro experiments were conducted using AECs.

RESULTS

Our studies revealed that myricetin treatment alleviated silica-induced mortality, improved lung function, and reduced the severity of pulmonary fibrosis in mice. Immunofluorescence analysis suggests its potential in mitigating senescence of AECs. Under laboratory conditions, myricetin intervened in the cellular senescence pathway induced by silica dust by modulating mitochondrial function. It acted through the PPARγ-PGC1α axis, effectively reducing silica-induced mitochondrial oxidative stress in AECs, promoting mitophagy, and maintaining mitochondrial dynamics. However, the efficacy of myricetin was reversed under PPARγ siRNA intervention. Additionally, myricetin exhibited an enhancing effect on PPARγ and autophagy in animal models. Treatment with PPARγ and PGC-1α siRNA elucidated the role of myricetin in promoting the formation of a positive feedback loop between PPARγ and PGC-1α. Additionally, the PPARγ inhibitor GW9662 verified the in vivo effects of myricetin.

CONCLUSIONS

Myricetin activates PPARγ, forming a PPARγ-PGC-1α loop, which promotes mitophagy and maintains mitochondrial dynamics. This alleviates epithelial cell senescence induced by silica exposure, consequently mitigating silica-induced pulmonary fibrosis in mice.

Inhibition of IRF3-STING axis interaction in silicosis using natural compounds: an in-silico study using molecular docking, ADMET, molecular dynamics and MMPBSA approach

Silicosis is a chronic occupational lung disease characterized by persistent inflammation driven by the activation of the cGAS-STING pathway, leading to the downstream activation of IRF3. To develop a natural compound library of COCONUT database for this investigation, Lipinski's rule of five was used and we explored the potential of these compounds to disrupt the IRF3-STING interaction, thereby mitigating the inflammatory response. Molecular docking and molecular dynamics (MD) simulations were employed to assess the binding stability and interaction dynamics of these compounds with IRF3. The stable RMSD values indicate that the protein-ligand complexes maintained structural integrity throughout the simulation period. The compounds also demonstrated drug-like characteristics, a promising safety profile, and formed stable complexes with the target protein. Further, decomposition of binding free energy highlighted the key contributions of IRF3 residues VAL295, ASP308, PRO324, and ARG338 interacting with the selected compounds, potentially inhibiting the IRF3-STING interaction. The origin of the selected compounds was determined using ClassyFire, classifying compound CNP0310627 as a burfenolide and compound CNP0200121 as a psoralen. Both classes are recognized for their anti-inflammatory properties, reinforcing the therapeutic potential of these compounds in reducing inflammation associated with silicosis. Our findings suggest that these compounds could serve as promising candidates for further investigation in the development of anti-inflammatory therapeutic molecules in the cGAS-STING-IRF3 signaling pathway. However, to fully assess the therapeutic potential of these compounds, further in vitro and in vivo studies are required to validate their efficacy and safety in modulating the STING-IRF3 pathway.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-024-00290-5.

The role of the PI3K/AKT/mTOR pathway in mediating PD-L1 upregulation during fibroblast transdifferentiation

Silicosis is a progressive interstitial lung disease characterized by diffuse pulmonary fibrosis. The transdifferentiation of lung fibroblasts into myofibroblasts is a key cellular event driving the progression of silicosis fibrosis. Recent studies have shown that PD-L1 expression is significantly upregulated in activated fibroblasts, and PD-L1 plays a crucial role in mediating fibroblast transdifferentiation. This study aims to elucidate the molecular mechanisms regulating PD-L1 expression in fibroblasts and analyze the functional significance of PD-L1 upregulation in fibroblast activity and silicosis fibrosis. In this research, an in vitro model of TGF-β1-induced NIH-3 T3 fibroblast transdifferentiation was established. Small molecule inhibitors, siRNA, and plasmids were used to interfere with the PI3K/AKT/mTOR signaling pathway and PD-L1 expression. It was found that TGF-β1 stimulation increased PD-L1 expression in fibroblasts, while blocking the PI3K/AKT/mTOR pathway inhibited this upregulation. Knockdown of PD-L1 significantly inhibited fibroblast transdifferentiation and impeded TGF-β1-induced activation of the PI3K/AKT/mTOR pathway, whereas PD-L1 overexpression had the opposite effect. Additionally, PD-L1 protein in fibroblasts undergoes ubiquitin-proteasome-mediated degradation, negatively regulating PD-L1 upregulation. In vivo, adeno-associated virus was used to specifically knockdown PD-L1 in mouse lung fibroblasts, resulting in significantly reduced lung tissue damage and fibrosis in silicosis mice. This effect was associated with the involvement of the PI3K/AKT/mTOR pathway. In summary, PD-L1 expression in fibroblasts is upregulated during transdifferentiation, a process regulated by the PI3K/AKT/mTOR pathway. Upregulated PD-L1 enhances PI3K/AKT/mTOR signaling through positive feedback, sustaining fibroblast activation. Ubiquitin-proteasome-mediated protein degradation may serve as a negative feedback mechanism maintaining PD-L1 homeostasis.

Airborne culprits: A comprehensive review of PM, silica, and TCDD in autoimmune diseases

Autoimmune diseases (ADs) are immunological disorders arising from the breakdown of immune tolerance, influenced by various internal and external factors. Persistent exposure to environmental factors, particularly air pollution, is linked to systemic inflammation, oxidative stress, and apoptosis, which contribute to the development of ADs. This review examines the impact of air pollutants, including particulate matter, silica, and TCDD, by analyzing epidemiological studies, animal models, and in vitro assays. It focuses on how air pollution disrupts the immune system, leading to apoptosis, increased oxidative stress, cytokine production, autoantigen release, autoantibody production, and autoreactivity, which are particularly significant in ADs like rheumatoid arthritis, systemic lupus erythematosus, Sjögren's syndrome, and systemic sclerosis. In essence, this approach aims to provide a profound understanding of how exposure to air pollution can initiate or contribute to ADs, offering potential avenues for more targeted preventive and therapeutic strategies.

New Insights into the Toxic Effects of Different Sizes of Nanosilica Particles in Food on the Mouse Bladder: Involving Epithelial-Mesenchymal Transition

Animals are widely exposed to nanosilica as a food additive. However, the negative effects of such nanosilica particles on animals' bladders are unclear. In the present study, we investigated the impact of MPs-SiO2 on mouse bladder and the underlying mechanisms. Mouse and MBEC cell models exposed to MPs-SiO2 with different particle sizes were established. At the same time, aminoguanidine hydrochloride (RNS inhibitor) and NF-κB activator were used to further explore its mechanism in vitro. We found that MPs-SiO2 of three sizes could induce RNS-induced pyroptosis causing EMT both in vitro and in vivo. After inhibiting RNS, the expression of related proteins in downstream pathways was decreased, and fibrosis was alleviated. The above situation was reversed by the addition of NF-κB activator. Furthermore, our data suggest that 300 nm MPs-SiO2 particles have a greater impact on the bladder than 50 nm particles. This study revealed the potential health risks of MPs-SiO2 and provided new insights into the toxicology of MPs-SiO2.

The risk for ophthalmological conditions in ulcerative colitis: A population-based case-control study. Is silica dust-exposure associated with inflammatory eye disease?

PURPOSE

To study the risk for eye diseases in individuals with Ulcerative Colitis (UC), and to assess whether silica dust-exposure could contribute to the development of inflammatory eye diseases.

METHODS

A case-control study was conducted using a patient register processed by the National Board of Health and Welfare (NBHW) and Statistics Sweden. Cases were diagnosed with UC between 2007 and 2016. Matching was done with two random controls having the same age, sex and county of residence, without a systemic inflammatory disease. Using a job-exposure matrix, cases and controls were assessed for work-related silica dust exposure. The risk for eye disease was estimated by Cox regression analysis with calculation of Hazard Ratio (HR).

RESULTS

A total of 58 989 individuals were included, comprising 19 663 cases and 39 326 controls. The sex distribution was similar. Overall, individuals with UC had an increased risk for eye disease, specified in ICD 10 chapter VII (H00-H59) with HR 1.25 (CI 1.20-1.32). The highest HR on block-level for cases was 1.52 (CI 1.36-1.70), (H15-H22), which includes episcleritis, keratitis and anterior uveitis. The risk for ocular disease was higher in silica dust-exposed than non-exposed with a HR of 1.44 (CI 1.16-1.78) and 1.25 (CI 1.19-1.31), respectively. Among cases, the risk for iridocyclitis (H20) was further elevated by silica dust exposure, with HR of 3.84 (CI 1.64-8.97) in exposed compared to 1.94 (1.57-2.41) in non-exposed.

CONCLUSION

UC is associated with an increased risk for eye diseases, including inflammatory conditions. Our findings highlight that silica dust-exposure may be of importance in the pathogenesis of uveitis.