Carbon nanotubes and crystalline silica stimulate robust ROS production, inflammasome activation, and IL-1β secretion in macrophages to induce myofibroblast transformation

A Network Toxicology Approach for Mechanistic Modelling of Nanomaterial Hazard and Adverse Outcomes

Hazard assessment is the first step in evaluating the potential adverse effects of chemicals. Traditionally, toxicological assessment has focused on the exposure, overlooking the impact of the exposed system on the observed toxicity. However, systems toxicology emphasizes how system properties significantly contribute to the observed response. Hence, systems theory states that interactions store more information than individual elements, leading to the adoption of network based models to represent complex systems in many fields of life sciences. Here, they develop a network-based approach to characterize toxicological responses in the context of a biological system, inferring biological system specific networks. They directly link molecular alterations to the adverse outcome pathway (AOP) framework, establishing direct connections between omics data and toxicologically relevant phenotypic events. They apply this framework to a dataset including 31 engineered nanomaterials with different physicochemical properties in two different in vitro and one in vivo models and demonstrate how the biological system is the driving force of the observed response. This work highlights the potential of network-based methods to significantly improve their understanding of toxicological mechanisms from a systems biology perspective and provides relevant considerations and future data-driven approaches for the hazard assessment of nanomaterials and other advanced materials.

Role of NLRP3 inflammasome in nanoparticle adjuvant-mediated immune response

The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) inflammasome is pivotal in orchestrating the immune response induced by nanoparticle adjuvants. Understanding the intricate mechanisms underlying the activation of NLRP3 inflammasome by these adjuvants is crucial for deciphering their immunomodulatory properties. This review explores the involvement of the NLRP3 inflammasome in mediating immune responses triggered by nanoparticle adjuvants. It delves into the signaling pathways and cellular mechanisms involved in NLRP3 activation, highlighting its significance in modulating the efficacy and safety of nanoparticle-based adjuvants. A comprehensive grasp of the interplay between NLRP3 inflammasome and nanoparticle adjuvants holds promise for optimizing vaccine design and advancing immunotherapeutic strategies.

Curcumin coating: a novel solution to mitigate inherent carbon nanotube toxicity

Multi-walled Carbon Nanotubes (MWCNTs) are inert structures with high aspect ratios that are widely used as vehicles for targeted drug delivery in cancer and many other diseases. They are largely non-toxic in nature however, when cells are exposed to these nanotubes for prolonged durations or at high concentrations, they show certain adverse effects. These include cytotoxicity, inflammation, generation of oxidative stress, and genotoxicity among others. To combat such adverse effects, various moieties can be attached to the surface of these nanotubes. Curcumin is a known anti-inflammatory, antioxidant and cytoprotective compound derived from a medicinal plant called Curcuma longa. In this study, we have synthesized and characterized Curcumin coated-lysine functionalized MWCNTs and further evaluated the cytoprotective, anti-inflammatory, antioxidant and antiapoptotic effect of Curcumin coating on the surface of MWCNTs. The results show a significant decrease in the level of inflammatory molecules like IL-6, IL-8, IL-1β, TNFα and NFκB in cells exposed to Curcumin-coated MWCNTs as compared to the uncoated ones at both transcript and protein levels. Further, compared to the uncoated samples, there is a reduction in ROS production and upregulation of antioxidant enzyme-Catalase in the cells treated with Curcumin-coated MWCNTs. Curcumin coating also helped in recovery of mitochondrial membrane potential in the cells exposed to MWCNTs. Lastly, cells exposed to Curcumin-coated MWCNTs showed reduced cell death as compared to the ones exposed to uncoated MWCNTs. Our findings suggest that coating of Curcumin on the surface of MWCNTs reduces its ability to cause inflammation, oxidative stress, and cell death.

Effects of Nanomaterials on Synthesis and Degradation of the Extracellular Matrix

Extracellular matrix (ECM) remodeling is accompanied by the continuous synthesis and degradation of the ECM components. This dynamic process plays an important role in guiding cell adhesion, migration, proliferation, and differentiation, as well as in tissue development, body repair, and maintenance of homeostasis. Nanomaterials, due to their photoelectric and catalytic properties and special structure, have garnered much attention in biomedical fields for use in processes such as tissue engineering and disease treatment. Nanomaterials can reshape the cell microenvironment by changing the synthesis and degradation of ECM-related proteins, thereby indirectly changing the behavior of the surrounding cells. This review focuses on the regulatory role of nanomaterials in the process of cell synthesis of different ECM-related proteins and extracellular protease. We discuss influencing factors and possible related mechanisms of nanomaterials in ECM remodeling, which may provide different insights into the design and development of nanomaterials for the treatment of ECM disorder-related diseases.

Silica-induced macrophage pyroptosis propels pulmonary fibrosis through coordinated activation of relaxin and osteoclast differentiation signaling to reprogram fibroblasts

Silica nanoparticle (SiNP) exposure induces severe pulmonary inflammation and fibrosis, but the pathogenesis remains unclear, and effective therapies are currently lacking. To explore the mechanism underlying SiNPs-induced pulmonary fibrosis, we constructed in vivo silica exposure animal models and in vitro models of silica-induced macrophage pyroptosis and fibroblast transdifferentiation. We found that SiNP exposure elicits upregulation of pulmonary proteins associated with pyroptosis, including NLRP3, ASC, IL-1β, and GSDMD, while the immunofluorescence staining co-localized NLRP3 and GSDMD with macrophage-specific biomarker F4/80 in silica-exposed lung tissues. However, the NLRP3 inhibitor MCC950 and classical anti-fibrosis drug pirfenidone (PFD) were found to be able to alleviate silica-induced collagen deposition in the lungs. In in vitro studies, we exposed the fibroblast to a conditioned medium from silica-induced pyroptotic macrophages and found enhanced expression of α-SMA, suggesting increased transdifferentiation of fibroblast to myofibroblast. In line with in vivo studies, the combined treatment of MCC950 and PFD was demonstrated to inhibit the expression of α-SMA and attenuate fibroblast transdifferentiation. Mechanistically, we adopted high throughput RNA sequencing on fibroblast with different treatments and found activated signaling of relaxin and osteoclast differentiation pathways, where the expression of the dysregulated genes in these two pathways was examined and found to be consistently altered both in vitro and in vivo. Collectively, our study demonstrates that SiNP exposure induces macrophage pyroptosis, which subsequently causes fibroblast transdifferentiation to myofibroblasts, in which the relaxin and osteoclast differentiation signaling pathways play crucial roles. These findings may provide valuable references for developing new therapies for pulmonary fibrosis.

Therapeutic potential of MCC950, a specific inhibitor of NLRP3 inflammasome in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex autoimmune disorder with a pathogenesis that remains incompletely understood, resulting in limited treatment options. MCC950, a highly specific NLRP3 inflammasome inhibitor, effectively suppresses the activation of NLRP3, thus reducing the production of caspase-1, the pro-inflammatory cytokines IL-1β and IL-18. This review highlights the pivotal role of NLRP3 inflammasome activation pathways in the pathogenesis of SLE and discusses the potential therapeutic application of MCC950 in SLE. Notably, it comprehensively elucidates the mechanism of MCC950 targeting the NLRP3 pathway in SLE treatment, outlining its potential role in regulating autophagy and necroptosis. The insights gained contribute to a deeper understanding of the value of MCC950 in SLE therapy, serving as a robust foundation for further research and potential clinical applications.

Molecular Activation of NLRP3 Inflammasome by Particles and Crystals: A Continuing Challenge of Immunology and Toxicology

Particles and crystals constitute a unique class of toxic agents that humans are constantly exposed to both endogenously and from the environment. Deposition of particulates in the body is associated with a range of diseases and toxicity. The mechanism by which particulates cause disease remains poorly understood due to the lack of mechanistic insights into particle-biological interactions. Recent research has revealed that many particles and crystals activate the NLRP3 inflammasome, an intracellular pattern-recognition receptor. Activated NLRP3 forms a supramolecular complex with an adaptor protein to activate caspase 1, which in turn activates IL-1β and IL-18 to instigate inflammation. Genetic ablation and pharmacological inhibition of the NLRP3 inflammasome dampen inflammatory responses to particulates. Nonetheless, how particulates activate NLRP3 remains a challenging question. From this perspective, we discuss our current understanding of and progress on revealing the function and mode of action of the NLRP3 inflammasome in mediating adaptive and pathologic responses to particulates in health and disease.

Environmental pollutants induce NLRP3 inflammasome activation and pyroptosis: Roles and mechanisms in various diseases

Environmental pollution is changing with economic development. Most environmental pollutants are characterized by stable chemical properties, strong migration, potential toxicity, and multiple exposure routes. Harmful substances are discharged excessively, and large quantities of unknown new compounds are emerging, being transmitted and amplifying in the food chain. The increasingly severe problems of environmental pollution have forced people to re-examine the relationship between environmental pollution and health. Pyroptosis and activation of the NLRP3 inflammasome are critical in maintaining the immune balance and regulating the inflammatory process. Numerous diseases caused by environmental pollutants are closely related to NLRP3 inflammasome activation and pyroptosis. We intend to systematically explain the steps and important events that are common in life but easily overlooked by which environmental pollutants activate the NLRP3 inflammasome and pyroptosis pathways. This comprehensive review also discusses the interaction network between environmental pollutants, the NLRP3 inflammasome, pyroptosis, and diseases. Thus, research progress on the impact of decreasing oxidative stress levels to inhibit the NLRP3 inflammasome and pyroptosis, thereby repairing homeostasis and reshaping health, is systematically examined. This review aims to deepen the understanding of the impact of environmental pollutants on life and health and provide a theoretical basis and potential programs for the development of corresponding treatment strategies.

Crystalline silica-induced proinflammatory eicosanoid storm in novel alveolar macrophage model quelled by docosahexaenoic acid supplementation

Introduction

Phagocytosis of inhaled crystalline silica (cSiO2) particles by tissue-resident alveolar macrophages (AMs) initiates generation of proinflammatory eicosanoids derived from the ω-6 polyunsaturated fatty acid (PUFA) arachidonic acid (ARA) that contribute to chronic inflammatory disease in the lung. While supplementation with the ω-3 PUFA docosahexaenoic acid (DHA) may influence injurious cSiO2-triggered oxylipin responses, in vitro investigation of this hypothesis in physiologically relevant AMs is challenging due to their short-lived nature and low recovery numbers from mouse lungs. To overcome these challenges, we employed fetal liver-derived alveolar-like macrophages (FLAMs), a self-renewing surrogate that is phenotypically representative of primary lung AMs, to discern how DHA influences cSiO2-induced eicosanoids.

Methods

We first compared how delivery of 25 µM DHA as ethanolic suspensions or as bovine serum albumin (BSA) complexes to C57BL/6 FLAMs impacts phospholipid fatty acid content. We subsequently treated FLAMs with 25 µM ethanolic DHA or ethanol vehicle (VEH) for 24 h, with or without LPS priming for 2 h, and with or without cSiO2 for 1.5 or 4 h and then measured oxylipin production by LC-MS lipidomics targeting for 156 oxylipins. Results were further related to concurrent proinflammatory cytokine production and cell death induction.

Results

DHA delivery as ethanolic suspensions or BSA complexes were similarly effective at increasing ω-3 PUFA content of phospholipids while decreasing the ω-6 PUFA arachidonic acid (ARA) and the ω-9 monounsaturated fatty acid oleic acid. cSiO2 time-dependently elicited myriad ARA-derived eicosanoids consisting of prostaglandins, leukotrienes, thromboxanes, and hydroxyeicosatetraenoic acids in unprimed and LPS-primed FLAMs. This cSiO2-induced eicosanoid storm was dramatically suppressed in DHA-supplemented FLAMs which instead produced potentially pro-resolving DHA-derived docosanoids. cSiO2 elicited marked IL-1α, IL-1β, and TNF-α release after 1.5 and 4 h of cSiO2 exposure in LPS-primed FLAMs which was significantly inhibited by DHA. DHA did not affect cSiO2-triggered death induction in unprimed FLAMs but modestly enhanced it in LPS-primed FLAMs.

Discussion

FLAMs are amenable to lipidome modulation by DHA which suppresses cSiO2-triggered production of ARA-derived eicosanoids and proinflammatory cytokines. FLAMs are a potential in vitro alternative to primary AMs for investigating interventions against early toxicant-triggered inflammation in the lung.

Advances in the Use of N-Acetylcysteine in Chronic Respiratory Diseases

N-acetylcysteine (NAC) is widely used because of its mucolytic effects, taking part in the therapeutic protocols of cystic fibrosis. NAC is also administered as an antidote in acetaminophen (paracetamol) overdosing. Thanks to its wide antioxidative and anti-inflammatory effects, NAC may also be of benefit in other chronic inflammatory and fibrotizing respiratory diseases, such as chronic obstructive pulmonary disease, bronchial asthma, idiopathic lung fibrosis, or lung silicosis. In addition, NAC exerts low toxicity and rare adverse effects even in combination with other treatments, and it is cheap and easily accessible. This article brings a review of information on the mechanisms of inflammation and oxidative stress in selected chronic respiratory diseases and discusses the use of NAC in these disorders.

Mechanistic insights into severe pulmonary inflammation caused by silica stimulation: The role of macrophage pyroptosis

Respirable silica dust is a common hazard faced by occupational workers and prolonged exposure to this dust can lead to pulmonary inflammation, fibrosis and, in severe cases, silicosis. However, the underlying mechanism by which silica exposure causes these physical disorders is not yet understood. In this study, we aimed to shed light on this mechanism by establishing in vitro and in vivo silica exposure models from the perspective of macrophages. Our results showed that compared to the control group, silica exposure resulted in an upregulation of the pulmonary expression of P2X7 and Pannexin-1, but this effect was suppressed by treatment with MCC950, a specific inhibitor of NLRP3. Our in vitro studies showed that silica exposure induced mitochondrial depolarization in macrophages, which led to a reduction of intracellular ATP and an influx of Ca²⁺. Furthermore, we found that creating an extracellular high potassium environment by adding KCl to the macrophage medium inhibited the expression of pyroptotic biomarkers and pro-inflammatory cytokines such as NLRP3 and IL-1β. Treatment with BBG, a P2X7 antagonist, also effectively inhibited the expression of P2X7, NLRP3, and IL-1β. On the other hand, treatment with FCF, a Pannexin-1 inhibitor, suppressed the expression of Pannexin-1 but had no effect on the expression of pyroptotic biomarkers such as P2X7, NLRP3, and IL-1β. In conclusion, our findings suggest that silica exposure triggers the opening of P2X7 ion channels, resulting in intracellular K⁺ efflux, extracellular Ca²⁺ influx, and the assembly of the NLRP3 inflammasome, ultimately leading to macrophage pyroptosis and pulmonary inflammation.

Multi-walled carbon nanotubes induce arachidonate 5-lipoxygenase expression and enhance the polarization and function of M1 macrophages in vitro

Fibrogenic carbon nanotubes (CNTs) induce the polarization of M1 and M2 macrophages in mouse lungs. Polarization of the macrophages regulates the production of proinflammatory and pro-resolving lipid mediators (LMs) to mediate acute inflammation and its resolution in a time-dependent manner. Here we examined the molecular mechanism by which multi-walled CNTs (MWCNTs, Mitsui-7) induce M1 polarization in vitro. Treatment of murine macrophages (J774A.1) with Mitsui-7 MWCNTs increased the expression of Alox5 mRNA and protein in a concentration- and time-dependent manner. The MWCNTs induced the expression of CD68 and that induction persisted for up to 3 days post-exposure. The expression and activity of inducible nitric oxide synthase, an intracellular marker of M1, were increased by MWCNTs. Consistent with M1 polarization, the MWCNTs induced the production and secretion of proinflammatory cytokines tumor necrosis factor-α and interleukin-1β, and proinflammatory LMs leukotriene B4 (LTB4) and prostaglandin E2 (PGE2). The cell-free media from MWCNT-polarized macrophages induced the migration of neutrophilic cells (differentiated from HL-60), which was blocked by Acebilustat, a specific leukotriene A4 hydrolase inhibitor, or LY239111, an LTB4 receptor antagonist, but not NS-398, a cyclooxygenase 2 inhibitor, revealing LTB4 as a major mediator of neutrophil chemotaxis from MWCNT-polarized macrophages. Knockdown of Alox5 using specific small hairpin-RNA suppressed MWCNT-induced M1 polarization, LTB4 secretion, and migration of neutrophils. Taken together, these findings demonstrate the polarization of M1 macrophages by Mitsui-7 MWCNTs in vitro and that induction of Alox5 is an important mechanism by which the MWCNTs promote proinflammatory responses by boosting M1 polarization and production of proinflammatory LMs.

Role of mitochondrial stress and the NLRP3 inflammasome in lung diseases

BACKGROUND

As an organelle essential for intracellular energy supply, mitochondria are involved in intracellular metabolism and inflammation, and cell death. The interaction of mitochondria with the NLRP3 inflammasome in the development of lung diseases has been extensively studied. However, the exact mechanism by which mitochondria mediate the activation of the NLRP3 inflammasome and trigger lung disease is still unclear.

METHODS

The literatures related to mitochondrial stress, NLRP3 inflammasome and lung diseases were searched in PubMed.

RESULTS

This review aims to provide new insights into the recently discovered mitochondrial regulation of the NLRP3 inflammasome in lung diseases. It also describes the crucial roles of mitochondrial autophagy, long noncoding RNA, micro RNA, altered mitochondrial membrane potential, cell membrane receptors, and ion channels in mitochondrial stress and regulation of the NLRP3 inflammasome, in addition to the reduction of mitochondrial stress by nuclear factor erythroid 2-related factor 2 (Nrf2). The effective components of potential drugs for the treatment of lung diseases under this mechanism are also summarized.

CONCLUSION

This review provides a resource for the discovery of new therapeutic mechanisms and suggests ideas for the development of new therapeutic drugs, thus promoting the rapid treatment of lung diseases.

Human umbilical cord mesenchymal stem cell-derived extracellular vesicles alleviated silica induced lung inflammation and fibrosis in mice via circPWWP2A/miR-223-3p/NLRP3 axis

Silicosis is a progressive inflammatory disease with poorly defined mechanisms and limited therapeutic options. Recent studies found that microRNAs (miRNAs) and circular RNAs (circRNAs) were involved in the development of respiratory diseases; however, the function of non-coding RNAs in silicosis was still needed to be further explored. We found that miR-223-3p was significantly decreased in macrophages and lung tissues of mice after silica treatment, which were consistent with the results of GEO database microarray analysis. Notably, NLRP3 is a target gene downstream of miR-223-3p. And circular RNA PWWP2A (circPWWP2A) was significantly elevated after silica stimulation. To elucidate the role of these RNAs in silica-induced inflammation in macrophages and lung tissues, we investigated the upstream molecular mechanisms of circPWWP2A on the inflammatory response. The inhibitory effect of miR-223-3p on its target NLRP3 was suppressed by circPWWP2A, which led to lung fibrosis. Our study found that circPWWP2A could adsorb miR-223-3p to regulate NLRP3 after silica stimulation in pulmonary fibrosis. And our results revealed that the circPWWP2A-miR-223-3p-NLRP3 axis was potentially instrumental in managing silica-induced inflammation and fibrosis. Previous studies have demonstrated that human umbilical cord mesenchymal stem cell-derived extracellular vesicles (hucMSC-EVs) exhibit anti-inflammatory and anti-fibrotic effects in multiple organs. However, the potential effectiveness of hucMSC-EVs against silicosis or the underlying mechanisms of their biological outcomes remains unclear. Therefore, we used 3D culture technology to extract hucMSC-EVs and observed their effects in macrophages and lung tissues, respectively. According to the EVmiRNA database, miR-223-3p was abundant in MSC-EVs. In addition, hucMSC-EVs may modulate lung function, reduce the secretion of inflammatory factors (NLRP3, IL-1β, IL-18 and cleaved Caspase-1) and attenuate the deposition of fibrosis-related factors (Collagen Ⅰ, Collagen Ⅲ, fibronectin and α-SMA). In vitro results evinced that hucMSC-EVs reduced the inflammatory response of macrophages and restricted the activation and proliferation of fibroblasts. Moreover, our study showed that hucMSCs-EVs acted as a mediator to transfer miR-223-3p to suppress circPWWP2A, thereby alleviating pulmonary fibrosis through the NLRP3 signaling pathway. These data may provide potentially novel strategies for investigating the pathogenesis of silicosis and developing novel treatments for this disease.

Diverse Pathways of Engineered Nanoparticle-Induced NLRP3 Inflammasome Activation

With the rapid development of engineered nanomaterials (ENMs) in biomedical applications, their biocompatibility and cytotoxicity need to be evaluated properly. Recently, it has been demonstrated that inflammasome activation may be a vital contributing factor for the development of biological responses induced by ENMs. Among the inflammasome family, NLRP3 inflammasome has received the most attention because it directly interacts with ENMs to cause the inflammatory effects. However, the pathways that link ENMs to NLRP3 inflammasome have not been thoroughly summarized. Thus, we reviewed recent findings on the role of major ENMs properties in modulating NLRP3 inflammasome activation, both in vitro and in vivo, to provide a better understanding of the underlying mechanisms. In addition, the interactions between ENMs and NLRP3 inflammasome activation are summarized, which may advance our understanding of safer designs of nanomaterials and ENM-induced adverse health effects.

Role of NLRP3 inflammasome in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune rheumatic disease with high mortality, which is featured by inflammation, vascular damage, and aggressive fibrosis. To date, the pathogenesis of SSc remains unclear and effective treatments are still under research. Active NLRP3 recruits downstream proteins such as ASC and caspase-1 and assembles into inflammasome, resulting in excretion of inflammatory cytokines including IL-1β and IL-18, as well as in pyroptosis mediated by gasdermin D. Various studies demonstrated that NLRP3 inflammasome might be involved in the mechanism of tenosynovitis, arthritis, fibrosis, and vascular damage. The pathophysiological changes might be due to the activation of proinflammatory Th2 cells, profibrotic M2 macrophages, B cells, fibroblasts, and endothelial cells. Here, we review the studies focused on NLRP3 inflammasome activation, its association with innate and adaptive immune cells, endothelium injury, and differentiation of fibroblasts in SSc. Furthermore, we summarize the prospect of therapy targeting NLRP3 pathway.

Gene Expression Profiling of Mono- and Co-Culture Models of the Respiratory Tract Exposed to Crystalline Quartz under Submerged and Air-Liquid Interface Conditions

In vitro lung cell models like air-liquid interface (ALI) and 3D cell cultures have advanced greatly in recent years, being especially valuable for testing advanced materials (e.g., nanomaterials, fibrous substances) when considering inhalative exposure. Within this study, we established submerged and ALI cell culture models utilizing A549 cells as mono-cultures and co-cultures with differentiated THP-1 (dTHP-1), as well as mono-cultures of dTHP-1. After ALI and submerged exposures towards α-quartz particles (Min-U-Sil5), with depositions ranging from 15 to 60 µg/cm2, comparison was made with respect to their transcriptional cellular responses employing high-throughput RT-qPCR. A significant dose- and time-dependent induction of genes coding for inflammatory proteins, e.g., IL-1A, IL-1B, IL-6, IL-8, and CCL22, as well as genes associated with oxidative stress response such as SOD2, was observed, even more pronounced in co-cultures. Changes in the expression of similar genes were more pronounced under submerged conditions when compared to ALI exposure in the case of A549 mono-cultures. Hereby, the activation of the NF-κB signaling pathway and the NLRP3 inflammasome seem to play an important role. Regarding genotoxicity, neither DNA strand breaks in ALI cultivated cells nor a transcriptional response to DNA damage were observed. Altogether, the toxicological responses depended considerably on the cell culture model and exposure scenario, relevant to be considered to improve toxicological risk assessment.

Ginsenoside Rb1 Alleviates Bleomycin-Induced Pulmonary Inflammation and Fibrosis by Suppressing Central Nucleotide-Binding Oligomerization-, Leucine-Rich Repeat-, and Pyrin Domains-Containing Protein Three Inflammasome Activation and the NF-κB Pathway

Purpose

Idiopathic pulmonary fibrosis is a chronic and irreversible fibrotic interstitial pneumonia of unknown etiology and therapeutic strategies are limited. Emerging evidence suggests that the continuous activation of the central nucleotide-binding oligomerization-, leucine-rich repeat-, and pyrin domain-containing protein 3 (NLRP3) inflammasome is involved in the pathogenesis of pulmonary fibrosis. Ginsenoside Rb1 (G-Rb1) is the most abundant component in the traditional Chinese herb ginseng and has anti-inflammatory and anti-fibrotic activities. The purpose of this study was to explore whether G-Rb1 exerts anti-inflammatory and anti-fibrotic activities in vivo and in vitro by suppressing the activation of the NLRP3 inflammasome and NF-κB pathway.

Methods

Forty-eight male C57BL/6 mice were randomly divided into four groups (n=12/group) as follows: control, bleomycin (BLM), BLM/G-Rb1, and G-Rb1. A pulmonary fibrosis model was developed via an intratracheal injection of BLM. Six mice from each group were euthanized on days 3 and 21. The degree of pulmonary fibrosis was examined by histological evaluation and assessing α-smooth muscle actin levels. THP-1 cells were differentiated into macrophages, and stimulated by lipopolysaccharide and adenosine triphosphate. Activation of the NLRP3 inflammasome and NF-κB pathway was determined by Western blotting. Interleukin-1 beta and interleukin-18 levels were measured by ELISA. MRC-5 cells were cultured in the conditioned medium of the treated macrophages, after which markers of myofibroblasts were determined by Western blotting.

Results

G-Rb1 ameliorated BLM-induced pulmonary inflammation and fibrosis in mice, and suppressed NLRP3 inflammasome activation and the NF-κB pathway in lung tissues. Moreover, interleukin-1 beta secreted after NLRP3 inflammasome activation in macrophages promoted fibroblast differentiation. G-Rb1 inhibited lipopolysaccharide- and adenosine triphosphate-induced NLRP3 inflammasome activation in macrophages and disturbed the crosstalk between macrophages and fibroblasts.

Conclusion

G-Rb1 ameliorates BLM-induced pulmonary inflammation and fibrosis by suppressing NLRP3 inflammasome activation and the NF-κB pathway. Hence, G-Rb1 is a potential novel therapeutic drug for idiopathic pulmonary fibrosis.

Tricalcium phosphate particles promote pyroptotic death of calvaria osteocytes through the ROS/NLRP3/Caspase-1 signaling axis in amouse osteolysis model

Wear particles-induced inflammatory osteolysis, a major factor of aseptic loosening affects the long-term survival of orthopedic prostheses. Increasing observations have demonstrated that osteocytes, making up over 95% of all the bone cells, is involved in wear particle-induced periprosthetic osteolysis, but its mechanism remains unclear. In the present study, we embedded micro-sized tricalcium phosphate (TCP) particles (30 mg) under the periosteum around the middle suture of the mouse calvaria to establish a calvarial osteolysis model and investigated the biological effects of the particles on calvaria osteocytes in vivo. Results showed that TCP particles induced pyroptosis and activated the NLRP3 inflammasome in calvaria osteocytes, which was confirmed by obvious increases in empty lacunae, protein expressions of speck-like protein containing CARD (ASC), NOD-like receptor protein 3 (NLRP3), cleaved caspase-1 (Casp-1 p20) and cleaved gasdermin D (GSDMD-N), and resulted in elevated ratios of Casp-1 p20/Casp-1 and interleukin (IL)-1β/pro-IL-1β. Simultaneously, TCP particles enhanced serum levels of lactate dehydrogenase (LDH) and IL-1β. Furthermore, the pyroptotic effect was reversed by the Casp-1 inhibitor VX765 or the NLRP3 inhibitor MCC950. In addition, TCP particles increased the levels of intracellular reactive oxygen species (ROS) and malonaldehyde (MDA), whereas decreased the antioxidant enzyme nuclear factor E2-related factor 2 (Nrf2) level, leading to oxidative stress in calvaria osteocytes; the ROS scavenger N-acetylcysteine (NAC) attenuated these effects of pyroptotic death and the NLPR3 activation triggered by TCP particles. Collectively, our data suggested that TCP particles promote pyroptotic death of calvaria osteocytes through the ROS/NLRP3/Caspase-1 signaling axis, contributing to osteoclastogenesis and periprosthetic osteolysis.

Another One Fights the Dust - Targeting the NLRP3 Inflammasome for the Treatment of Silicosis

Silicosis is a multifaceted lung disease, characterised by persistent inflammation and structural remodelling. Despite its poor prognosis, there are no treatments currently available for patients with silicosis. Recent pre-clinical findings in models of lung fibrosis have suggested a major role for the nucleotide binding domain and leucine-rich repeat pyrin domain containing 3 (NLRP3) inflammasome in silica-driven inflammation and fibrosis. This review outlines the beneficial effects of targeting the NLRP3 inflammasome in in vitro cell experiments and in in vivo animal models, whereby inflammation and fibrosis are abrogated following NLRP3 inflammasome inhibition. While preclinical evidence is promising, studies which explore NLRP3 inflammasomes in the clinical setting are warranted. In particular, there is still a need to identify biomarkers which may be helpful for the early detection of silicosis and to fully elucidate mechanisms underlying these beneficial effects to further develop or repurpose existing anti-NLRP3 drugs as novel treatments that limit disease progression.

Role of Pyroptosis in Respiratory Diseases and its Therapeutic Potential

Pyroptosis is an inflammatory type of regulated cell death that is dependent on inflammasome activation and downstream proteases such as caspase-1 or caspase 4/5/11. The main executors are gasdermins, which have an inherent pore-forming function on the membrane and release inflammatory cytokines, such as interleukin (IL)-1β, IL-18 and high mobility group box 1. Emerging evidence demonstrates that pyroptosis is involved in the pathogenesis of various pulmonary diseases. In this review, we mainly discuss the biological mechanisms of pyroptosis, explore the relationship between pyroptosis and respiratory diseases, and discuss emerging therapeutic strategies for respiratory diseases.

Toxicity of amine-functionalized single-carbon nanotube (NH2 f-SWCNT) to Channel Catfish (Ietalurus Punetaus): Organ pathologies, oxidative stress, inflammation, and apoptosis

The rapid development of carbon nanotubes (CNTs) in the field of fish disease control and prevention raises concerns about the toxicity and safe use in fish. This study was performed to assess the effect on histological changes, oxidative stress related markers in response to various concentrations of amine-functionalized single carbon nanotubes (NH₂ f-SWCNT) (1, 10 and 100 mg kg^-1 fish) in Channel Catfish (Ietalurus Punetaus) for up to 10 days. Moreover, pro-inflammatory cytokine genes and apoptotic genes were analyzed to obtain a better understanding of molecular mechanism of NH₂ f-SWCNT induced toxicity. As a result, intraperitoneal (i.p.) administration of NH₂ f-SWCNT caused dose-dependent and time-dependent injuries in the sampled tissues. In comparison with the control groups, decrease of catalase (CAT) activity and superoxide dismutase (SOD), and increase of malondialdehyde (MDA) and lactin dehydrogenase (LDH) were observed in all treatments. Real-time PCR assay showed inflammatory response with dose-dependent increase of tumor necrosis factor alpha (TNFα) and transient increase of interleukin 1β (IL-1β) in the liver. NH₂ f-SWCNT administration induced increase of p38 as well as caspase-3 in all treatments compared to the control groups, indicating the involvement of p38-MAPK cascade and caspase-3 cascade in liver cell apoptosis. Overall, we conclude that NH₂ f-SWCNT exert effects by direct injury and indirectly oxidative stress, resulting in inflammation and apoptosis, which provides data for understanding of the biological mechanisms underlying the toxicity of CNTs in fish.

Pulmonary delivery of the broad-spectrum matrix metalloproteinase inhibitor marimastat diminishes multiwalled carbon nanotube-induced circulating bioactivity without reducing pulmonary inflammation

BACKGROUND

Multiwalled carbon nanotubes (MWCNT) are an increasingly utilized engineered nanomaterial that pose the potential for significant risk of exposure-related health outcomes. The mechanism(s) underlying MWCNT-induced toxicity to extrapulmonary sites are still being defined. MWCNT-induced serum-borne bioactivity appears to dysregulate systemic endothelial cell function. The serum compositional changes after MWCNT exposure have been identified as a surge of fragmented endogenous peptides, likely derived from matrix metalloproteinase (MMP) activity. In the present study, we utilize a broad-spectrum MMP inhibitor, Marimastat, along with a previously described oropharyngeal aspiration model of MWCNT administration to investigate the role of MMPs in MWCNT-derived serum peptide generation and endothelial bioactivity.

RESULTS

C57BL/6 mice were treated with Marimastat or vehicle by oropharyngeal aspiration 1 h prior to MWCNT treatment. Pulmonary neutrophil infiltration and total bronchoalveolar lavage fluid protein increased independent of MMP blockade. The lung cytokine profile similarly increased following MWCNT exposure for major inflammatory markers (IL-1β, IL-6, and TNF-α), with minimal impact from MMP inhibition. However, serum peptidomic analysis revealed differential peptide compositional profiles, with MMP blockade abrogating MWCNT-derived serum peptide fragments. The serum, in turn, exhibited differential potency in terms of inflammatory bioactivity when incubated with primary murine cerebrovascular endothelial cells. Serum from MWCNT-treated mice led to inflammatory responses in endothelial cells that were significantly blunted with serum from Marimastat-treated mice.

CONCLUSIONS

Thus, MWCNT exposure induced pulmonary inflammation that was largely independent of MMP activity but generated circulating bioactive peptides through predominantly MMP-dependent pathways. This MWCNT-induced lung-derived bioactivity caused pathological consequences of endothelial inflammation and barrier disruption.

Pharmacological Inhibition of the Nod-Like Receptor Family Pyrin Domain Containing 3 Inflammasome with MCC950

Activation of the Nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome drives release of the proinflammatory cytokines interleukin (IL)-1β and IL-18 and induces pyroptosis (lytic cell death). These events drive chronic inflammation, and as such, NLRP3 has been implicated in a large number of human diseases. These range from autoimmune conditions, the simplest of which is NLRP3 gain-of-function mutations leading to an orphan disease, cryopyrin-associated period syndrome, to large disease burden indications, such as atherosclerosis, heart failure, stroke, neurodegeneration, asthma, ulcerative colitis, and arthritis. The potential clinical utility of NLRP3 inhibitors is substantiated by an expanding list of indications in which NLRP3 activation has been shown to play a detrimental role. Studies of pharmacological inhibition of NLRP3 in nonclinical models of disease using MCC950 in combination with human genetics, epigenetics, and analyses of the efficacy of biologic inhibitors of IL-1β, such as anakinra and canakinumab, can help to prioritize clinical trials of NLRP3-directed therapeutics. Although MCC950 shows excellent (nanomolar) potency and high target selectivity, its pharmacokinetic and toxicokinetic properties limited its therapeutic development in the clinic. Several improved, next-generation inhibitors are now in clinical trials. Hence the body of research in a plethora of conditions reviewed herein may inform analysis of the potential translational value of NLRP3 inhibition in diseases with significant unmet medical need. SIGNIFICANCE STATEMENT: The nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is one of the most widely studied and best validated biological targets in innate immunity. Activation of NLRP3 can be inhibited with MCC950, resulting in efficacy in more than 100 nonclinical models of inflammatory diseases. As several next-generation NLRP3 inhibitors are entering proof-of-concept clinical trials in 2020, a review of the pharmacology of MCC950 is timely and significant.

Cathepsin B promotes collagen biosynthesis, which drives bronchiolitis obliterans syndrome

Bronchiolitis obliterans syndrome (BOS) is a major complication after lung transplantation (LTx). BOS is characterised by massive peribronchial fibrosis, leading to air trapping-induced pulmonary dysfunction. Cathepsin B, a lysosomal cysteine protease, has been shown to enforce fibrotic pathways in several diseases. However, the relevance of cathepsin B in BOS progression has not yet been addressed. The aim of the study was to elucidate the function of cathepsin B in BOS pathogenesis.We determined cathepsin B levels in bronchoalveolar lavage fluid (BALF) and lung tissue from healthy donors (HD) and BOS LTx patients. Cathepsin B activity was assessed via a fluorescence resonance energy transfer-based assay and protein expression was determined using Western blotting, ELISA and immunostaining. To investigate the impact of cathepsin B in the pathophysiology of BOS, we used an in vivo orthotopic left LTx mouse model. Mechanistic studies were performed in vitro using macrophage and fibroblast cell lines.We found a significant increase of cathepsin B activity in BALF and lung tissue from BOS patients, as well as in our murine model of lymphocytic bronchiolitis. Moreover, cathepsin B activity was associated with increased biosynthesis of collagen and had a negative effect on lung function. We observed that cathepsin B was mainly expressed in macrophages that infiltrated areas characterised by a massive accumulation of collagen deposition. Mechanistically, macrophage-derived cathepsin B contributed to transforming growth factor-β1-dependent activation of fibroblasts, and its inhibition reversed the phenotype.Infiltrating macrophages release active cathepsin B, thereby promoting fibroblast activation and subsequent collagen deposition, which drive BOS. Cathepsin B represents a promising therapeutic target to prevent the progression of BOS.

Nanomaterials and hepatic disease: toxicokinetics, disease types, intrinsic mechanisms, liver susceptibility, and influencing factors

The widespread use of nanomaterials (NMs) has raised concerns that exposure to them may introduce potential risks to the human body and environment. The liver is the main target organ for NMs. Hepatotoxic effects caused by NMs have been observed in recent studies but have not been linked to liver disease, and the intrinsic mechanisms are poorly elucidated. Additionally, NMs exhibit varied toxicokinetics and induce enhanced toxic effects in susceptible livers; however, thus far, this issue has not been thoroughly reviewed. This review provides an overview of the toxicokinetics of NMs. We highlight the possibility that NMs induce hepatic diseases, including nonalcoholic steatohepatitis (NASH), fibrosis, liver cancer, and metabolic disorders, and explore the underlying intrinsic mechanisms. Additionally, NM toxicokinetics and the potential induced risks in the livers of susceptible individuals, including subjects with liver disease, obese individuals, aging individuals and individuals of both sexes, are summarized. To understand how NM type affect their toxicity, the influences of the physicochemical and morphological (PCM) properties of NMs on their toxicokinetics and toxicity are also explored. This review provides guidance for further toxicological studies on NMs and will be important for the further development of NMs for applications in various fields.

An integrated approach to testing and assessment of high aspect ratio nanomaterials and its application for grouping based on a common mesothelioma hazard

Here we describe the development of an Integrated Approach to Testing and Assessment (IATA) to support the grouping of different types (nanoforms; NFs) of High Aspect Ratio Nanomaterials (HARNs), based on their potential to cause mesothelioma. Hazards posed by the inhalation of HARNs are of particular concern as they exhibit physical characteristics similar to pathogenic asbestos fibres. The approach for grouping HARNs presented here is part of a framework to provide guidance and tools to group similar NFs and aims to reduce the need to assess toxicity on a case-by-case basis. The approach to grouping is hypothesis-driven, in which the hypothesis is based on scientific evidence linking critical physicochemical descriptors for NFs to defined fate/toxicokinetic and hazard outcomes. The HARN IATA prompts users to address relevant questions (at decision nodes; DNs) regarding the morphology, biopersistence and inflammatory potential of the HARNs under investigation to provide the necessary evidence to accept or reject the grouping hypothesis. Each DN in the IATA is addressed in a tiered manner, using data from simple in vitro or in silico methods in the lowest tier or from in vivo approaches in the highest tier. For these proposed methods we provide justification for the critical descriptors and thresholds that allow grouping decisions to be made. Application of the IATA allows the user to selectively identify HARNs which may pose a mesothelioma hazard, as demonstrated through a literature-based case study. By promoting the use of alternative, non-rodent approaches such as in silico modelling, in vitro and cell-free tests in the initial tiers, the IATA testing strategy streamlines information gathering at all stages of innovation through to regulatory risk assessment while reducing the ethical, time and economic burden of testing.

Circular RNA circBbs9 promotes PM2.5-induced lung inflammation in mice via NLRP3 inflammasome activation

Fine particulate matter (PM_2.5) is one of the most important components of environmental pollutants, and is associated with pulmonary injury. However, the biological mechanisms of pulmonary damage caused by PM_2.5 are poorly defined, especially the molecular pathways related to inflammation. Following system exposure to PM_2.5 for 3 months in normal mice and in chronic obstructive pulmonary disease (COPD) model mice, it was found that PM_2.5 exposure increased the expression of IL-1β and IL-18 in lung tissues via NLRP3 activation, and these effects were more intense in COPD model mice. Circular RNA (circRNA) sequencing showed that the expression profiles of circRNAs were changed after PM_2.5 exposure, and the positive roles of circBbs9 in inflammation induced by PM_2.5 were verified. The circBbs9 knockdown alleviated PM_2.5-induced inflammation via NLRP3 inflammasome inactivation, as well as IL-1β and IL-18 inhibition in RAW264.7 cells, while overexpression of circBbs9 had the opposite effect. Bioinformatics and luciferase reporter assays showed that circBbs9 bound to microRNA-30e-5p (miR-30e-5p) and co-regulated the expression of Adar, a downstream target gene of miR-30e-5p. Taken together, these results revealed that PM_2.5 induced pulmonary inflammation through NLRP3 inflammasome activation regulated by the circBbs9-miR-30e-5p-Adar pathway. Our findings provide a new target, circBbs9, for the assessment of lung inflammation and COPD exacerbation induced by PM_2.5 exposure.

Cytotoxicity of fractured quartz on THP-1 human macrophages: role of the membranolytic activity of quartz and phagolysosome destabilization

The pathogenicity of quartz involves lysosomal alteration in alveolar macrophages. This event triggers the inflammatory cascade that may lead to quartz-induced silicosis and eventually lung cancer. Experiments with synthetic quartz crystals recently showed that quartz dust is cytotoxic only when the atomic order of the crystal surfaces is upset by fracturing. Cytotoxicity was not observed when quartz had as-grown, unfractured surfaces. These findings raised questions on the potential impact of quartz surfaces on the phagolysosomal membrane upon internalization of the particles by macrophages. To gain insights on the surface-induced cytotoxicity of quartz, as-grown and fractured quartz particles in respirable size differing only in surface properties related to fracturing were prepared and physico-chemically characterized. Synthetic quartz particles were compared to a well-known toxic commercial quartz dust. Membranolysis was assessed on red blood cells, and quartz uptake, cell viability and effects on lysosomes were assessed on human PMA-differentiated THP-1 macrophages, upon exposing cells to increasing concentrations of quartz particles (10–250 µg/ml). All quartz samples were internalized, but only fractured quartz elicited cytotoxicity and phagolysosomal alterations. These effects were blunted when uptake was suppressed by incubating macrophages with particles at 4 °C. Membranolysis, but not cytotoxicity, was quenched when fractured quartz was incubated with cells in protein-supplemented medium. We propose that, upon internalization, the phagolysosome environment rapidly removes serum proteins from the quartz surface, restoring quartz membranolytic activity in the phagolysosomes. Our findings indicate that the cytotoxic activity of fractured quartz is elicited by promoting phagolysosomal membrane alteration.

Polarization of Immune Cells in the Pathologic Response to Inhaled Particulates

Polarization of immune cells is commonly observed in host responses associated with microbial immunity, inflammation, tumorigenesis, and tissue repair and fibrosis. In this process, immune cells adopt distinct programs and perform specialized functions in response to specific signals. Accumulating evidence indicates that inhalation of micro- and nano-sized particulates activates barrier immune programs in the lung in a time- and context-dependent manner, including type 1 and type 2 inflammation, and T helper (Th) 17 cell, regulatory T cell (Treg), innate lymphoid cell (ILC), and myeloid-derived suppressor cell (MDSC) responses, which highlight the polarization of several major immune cell types. These responses facilitate the pulmonary clearance and repair under physiological conditions. When exposure persists and overwhelms the clearance capacity, they foster the chronic progression of inflammation and development of progressive disease conditions, such as fibrosis and cancer. The pulmonary response to insoluble particulates thus represents a distinctive disease process wherein non-infectious, persistent exposures stimulate the polarization of immune cells to orchestrate dynamic inflammatory and immune reactions, leading to pulmonary and pleural chronic inflammation, fibrosis, and malignancy. Despite large variations in particles and their associated disease outcomes, the early response to inhaled particles often follows a common path. The initial reactions entail a barrier immune response dominated by type 1 inflammation that features active phagocytosis by M1 macrophages and recruitment of neutrophils, both of which are fueled by Th1 and proinflammatory cytokines. Acute inflammation is immediately followed by resolution and tissue repair mediated through specialized pro-resolving mediators (SPMs) and type 2 cytokines and cells including M2 macrophages and Th2 lymphocytes. As many particles and fibers cannot be digested by phagocytes, resolution is often extended and incomplete, and type 2 inflammation becomes heightened, which promotes interstitial fibrosis, granuloma formation, and tumorigenesis. Recent studies also reveal the involvement of Th17-, Treg-, ILC-, and MDSC-mediated responses in the pathogenesis caused by inhaled particulates. This review synopsizes the progress in understanding the interplay between inhaled particles and the pulmonary immune functions in disease pathogenesis, with focus on particle-induced polarization of immune cells and its role in the development of chronic inflammation, fibrosis, and cancer in the lung.

Multi-walled carbon nanotubes induce IL-1β secretion by activating hemichannels-mediated ATP release in THP-1 macrophages

Multi-walled carbon nanotubes (MWCNTs) are known to induce pulmonary inflammatory effects through stimulating pro-inflammatory cytokine secretion from alveolar macrophages. Despite extensive studies on MWCNTs' pro-inflammatory reactivity, the understanding of molecular mechanisms involved is still incomplete. In this study, we investigated hemichannel's involvement in MWCNTs-induced macrophage IL-1β release. Our results showed that the unmodified and COOH MWCNTs could induce ATP release and ATP-P2X₇R axis-dependent IL-1β secretion from THP-1 macrophages. By using various inhibitors, we confirmed that the MWCNTs-induced ATP release was primarily through hemichannels. EtBr dye uptake assay detected significant hemichannels opening in MWCNTs exposed THP-1 macrophages. Inhibition of hemichannels by CBX, ⁴³Gap27, or ¹⁰Panx1 pretreatment results in decreased ATP and IL-1β release. The addition of ATP restored the reduced IL-1β secretion level from hemichannel inhibition. We also confirmed with five other types of MWCNTs that the induction of hemichannels by MWCNTs strongly correlates with their capacity to induce IL-1β secretion. Taken together, we conclude that hemichannels-mediated ATP release and subsequent NLRP3 inflammasome activation through P2X₇R may be one mechanism by which MWCNTs induce macrophage IL-1β secretion. Our findings may provide a novel molecular mechanism for MWCNTs induced IL-1β secretion.

Benzene metabolites trigger pyroptosis and contribute to haematotoxicity via TET2 directly regulating the Aim2/Casp1 pathway

Background

Long term low-dose benzene exposure leads to the inhibition of haematopoiesis. However, the underlying mechanisms remained poorly defined, especially mediated by early effector molecules.

Methods

Here, we first found in mRNA microarray that pyroptotic classic genes (Casp1, 4, 5, and IL1β) were up-regulated and represented dose-dependent differential expression in controls, low-dose benzene-exposed and chronic benzene-poisoned workers, and the expression of Casp1 and IL1β were confirmed in low-dose benzene-exposed workers and was accompanied with elevated potent proinflammatory IL1β. In vitro studies showed that benzene metabolites induced AHH-1 cell pyroptosis through activating Aim2/Casp1 pathway with the increased expression of GSDMD. Meanwhile, TET2 overexpression was elevated in vivo and in vitro and it was positively correlated with IL1β. Further, we verified that pyroptosis caused by 1,4-BQ could be ameliorated in vitro by RNAi or pretreatment with Dimethyloxalylglycine (DMOG), the inhibitor of TET2.

Findings

Exposure to benzene can trigger pyroptosis via TET2 directly regulating the Aim2/Casp1 signaling pathway to cause haematotoxicity.

Interpretation

Benzene metabolites induced pyroptotic cell death through activation of the Aim2/Casp1 pathway which can be regulated by Tet2 overexpression. Tet2 may be a potential risk factor and is implicated in the development of benzene-related diseases.

Fund

National Natural Science Foundation of China; the Support Project of High–level Teachers in Beijing Municipal Universities in the Period of 13th Five–year Plan; Beijing Natural Science Foundation Program and Scientific Research Key Program of Beijing Municipal Commission of Education.