Lysosomal cysteine proteases are mediators of cell death in macrophages following exposure to amorphous silica nanoparticles

Unveiling research hotspots: a bibliometric study on macrophages in musculoskeletal diseases

Research on the role of macrophages in musculoskeletal (MSK) diseases has significantly increased in recent years. However, a thorough evaluation of the developmental trajectory of this field, including the contributions of prominent authors and primary research themes, remains insufficient. Furthermore, the identification of emerging research hotspots requires more detailed exploration. This study collated articles and reviews addressing "macrophages in MSK diseases" published between 2004 and 2023, with all data extracted from the Web of Science database. The collected data were analyzed using a variety of bibliometric and visualization tools, such as VOSviewer, CiteSpace, GraphPad Prism, and R packages. Results indicate that China and the United States are the leading contributors in this research domain. Among the many academic institutions involved, Shanghai Jiao Tong University and the University of California stand out as the most productive. The journal "Frontiers in Immunology" had the highest publication output on this topic. The five most frequently explored research domains include Immunology, Rheumatology, Pharmacology and Pharmacy, Cell Biology, and Biochemistry and Molecular Biology. These results offer a comprehensive overview of the current state of research in this field and provide meaningful insights for guiding future studies.

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.

Advances in the study of silica nanoparticles in lung diseases

Silicon dioxide nanoparticles (SiNPs) are one of the major forms of silicon dioxide and are composed of the most-abundant compounds on earth. Based on their excellent properties, SiNPs are widely used in food production, synthetic processes, medical diagnostics, drug delivery, and other fields. The mass production and wide application of SiNPs increases the risk of human exposure to SiNPs. In the workplace and environment, SiNPs mainly enter the human body through the respiratory tract and reach the lungs; therefore, the lungs are the most important and most toxicologically affected target organ of SiNPs. An increasing number of studies have shown that SiNP exposure can cause severe lung toxicity. However, studies on the toxicity of SiNPs in ex vivo and in vivo settings are still in the exploratory phase. The molecular mechanisms underlying the lung toxicity of SiNPs are varied and not yet fully understood. As a result, this review summarizes the possible mechanisms of SiNP-induced lung toxicity, such as oxidative stress, endoplasmic reticulum stress, mitochondrial damage, and cell death. Moreover, this study provides a summary of the progression of diseases caused by SiNPs, thereby establishing a theoretical basis for future studies on the mechanisms of SiNP-induced lung toxicity.

Assessing regulated cell death modalities as an efficient tool for in vitro nanotoxicity screening: a review

Nanomedicine is a fast-growing field of nanotechnology. One of the major obstacles for a wider use of nanomaterials for medical application is the lack of standardized toxicity screening protocols for assessing the safety of newly synthesized nanomaterials. In this review, we focus on less frequently studied nanomaterials-induced regulated cell death (RCD) modalities, including eryptosis, necroptosis, pyroptosis, and ferroptosis, as a tool for in vitro nanomaterials safety evaluation. We summarize the latest insights into the mechanisms that mediate these RCDs in response to nanomaterials exposure. Comprehensive data from reviewed studies suggest that ROS (reactive oxygen species) overproduction and ROS-mediated pathways play a central role in nanomaterials-induced RCDs activation. On the other hand, studies also suggest that individual properties of nanomaterials, including size, shape, or surface charge, could determine specific toxicity pathways with consequent RCD induction as well. We anticipate that the evaluation of RCDs can become one of the mechanism-based screening methods in nanotoxicology. In addition to the toxicity assessment, evaluation of necroptosis-, pyroptosis-, and ferroptosis-promoting capacity of nanomaterials could simultaneously provide useful information for specific medical applications as could be their anti-tumor potential. Moreover, a detailed understanding of molecular mechanisms driving nanomaterials-mediated induction of immunogenic RCDs will substantially aid novel anti-tumor nanodrugs development.

Characterization of Cathepsin B in Mediating Silica Nanoparticle-Induced Macrophage Pyroptosis via an NLRP3-Dependent Manner

Introduction

Silica nanoparticles (SiNPs) are one of the most widely used inorganic nanomaterials, and exposure to SiNP has been demonstrated to induce pulmonary inflammation, primarily promoted by the NLRP3-mediated macrophage pyroptosis. However, mechanisms underlying the activation of NLRP3 signaling are complex, and whether cathepsin B (CTSB), an enzyme released by the ruptured lysosome, could trigger NLRP3 assembly is controversial.

Methods

To further characterize the role of CTSB in silica-induced pyroptosis, we conducted this study by establishing SiNP exposure models in vitro. The morphological features of SiNPs were exhibited by the SEM and TEM, and the effects of SiNPs’ internalization on macrophages were examined by the TEM and immunofluorescent staining. Moreover, Western blot was performed to detect the expression of proteins related to pyroptosis and CTSB after blocking the expression of NLRP3 and CTSB.

Results

We found that SiNPs internalization caused the rupture of macrophage membrane and promoted the aging of cells with increased intracellular vacuoles. Also, the expression of NLRP3, ASC, Caspase-1, GSDMD, Pro-IL-1β, IL-1β, and CTSB increased under the stimulation of SiNP, which could be suppressed by additional treatment with MCC950, an NLRP3-specific inhibitor. Besides, we found SiNP joint treatment with leupeptin, a CTSB inhibitor, could inhibit the expression of CTSB, but it had no effect on the expression of NLRP3, ASC, and Caspase-1, and the process of macrophage pyroptosis was also not affected.

Conclusion

SiNP exposure induces rupture of macrophages and the release of lysosomal CTSB, but CTSB fails to specifically act on the NLRP3 inflammasome to induce pyroptosis which is causally linked to lung inflammation and fibrosis.