Extracellular HMGB1 regulates multi-walled carbon nanotube-induced inflammation in vivo

Integrative applications of network pharmacology and molecular docking: An herbal formula ameliorates H9c2 cells injury through pyroptosis

Background

QiShen YiQi pills (QSYQ) is a Traditional Chinese Medicine (TCM) formula, which has a significant effect on the treatment of patients with myocardial infarction (MI) in clinical practice. However, the molecular mechanism of QSYQ regulation pyroptosis after MI is still not fully known. Hence, this study was designed to reveal the mechanism of the active ingredient in QSYQ.

Methods

Integrated approach of network pharmacology and molecular docking, were conducted to screen active components and corresponding common target genes of QSYQ in intervening pyroptosis after MI. Subsequently, STRING and Cytoscape were applied to construct a PPI network, and obtain candidate active compounds. Molecular docking was performed to verify the binding ability of candidate components to pyroptosis proteins and oxygen-glucose deprivation (OGD) induced cardiomyocytes injuries were applied to explore the protective effect and mechanism of the candidate drug.

Results

Two drug-likeness compounds were preliminarily selected, and the binding capacity between Ginsenoside Rh2 (Rh2) and key target High Mobility Group Box 1 (HMGB1)was validated in the form of hydrogen bonding. 2 μM Rh2 prevented OGD-induced H9c2 death and reduced IL-18 and IL-1β levels, possibly by decreasing the activation of the NLRP3 inflammasome, inhibiting the expression of p12-caspase1, and attenuating the level of pyroptosis executive protein GSDMD-N.

Conclusions

We propose that Rh2 of QSYQ can protect myocardial cells partially by ameliorating pyroptosis, which seems to have a new insight regarding the therapeutic potential for MI.

Ginsenoside Rh2 Inhibits NLRP3 Inflammasome Activation and Improves Exosomes to Alleviate Hypoxia-Induced Myocardial Injury

The inflammatory microenvironment after acute myocardial infarction (MI) is a key limiting factor in the clinical application of stem cell transplantation and paracrine exosome therapy. Qishen Yiqi Pills contain a saponin ingredient called Ginsenoside Rh2 (Rh2) which exhibits a certain therapeutic effect on MI. However, the mechanism by which Rh2 alleviates the inflammatory microenvironment and improves the therapeutic efficiency of exosomes remains enigmatic. Here, we found that Rh2 attenuated the adverse effect of oxygen-glucose deprivation (OGD)-induced cellular injury, an in vitro pathological model of MI. Confocal microscopy revealed that DiI-labeled BMSCs-derived exosomes exhibited an increased homing ability of cardiomyocytes, which, in turn, inhibited the nuclear translocation of NF-κB p65 and NLRP3 inflammasome activation, thereby alleviating the inflammatory microenvironment and further facilitating the homing of exosomes to cardiomyocytes by forming a feed-forward enhancement loop. Additionally, we found that Rh2 could regulate the HMGB1/NF-κB signaling pathway to improve the OGD environment of cardiomyocytes, increasing the efficiency of the feed-forward loop. In conclusion, we found that Rh2 can improve the inflammatory microenvironment by enhancing the protection of exosomes against myocardial injury, providing new insights into the indirect modification of exosomes by Rh2 in MI treatment.

Multi-walled carbon nanotubes trigger lysosome-dependent cell death (pyroptosis) in macrophages but not in neutrophils

Carbon nanotubes (CNTs) have been extensively investigated, and several studies have shown that multi-walled CNTs can trigger inflammation and fibrosis in animal models. However, while neutrophils are involved in inflammation, most in vitro studies have addressed macrophages. Here we explored the impact of three MWCNTs with varying morphology (i.e. long and rigid versus short and/or tangled) on primary human macrophages and macrophage-differentiated THP-1 cells versus primary human neutrophils and neutrophil-differentiated HL-60 cells. We found that long and rigid MWCNTs triggered caspase-dependent cell death in macrophages, accompanied by NLRP3 inflammasome activation and gasdermin D (GSDMD)-mediated release of pro-inflammatory IL-1β. The release of IL-1β was suppressed by disulfiram, an FDA-approved drug known to act as an inhibitor of membrane pore formation by GSDMD. Evidence of autophagic cell death was noted in macrophages exposed to higher concentrations of the long and rigid MWCNTs. Furthermore, lysosomal damage with cytosolic release of cathepsin B was observed in macrophages exposed to the latter MWCNTs. On the other hand, there was little evidence of uptake of MWCNTs in neutrophils and the cells failed to undergo MWCNT-triggered cell death. Our studies have demonstrated that long and rigid MWCNTs trigger pyroptosis in human macrophages.

Dietary Docosahexaenoic Acid as a Potential Treatment for Semi-acute and Chronic Particle-Induced Pulmonary Inflammation in Balb/c Mice

Acute and chronic inflammation are vital contributing factors to pulmonary diseases which can be triggered by exposure to occupational and man-made particles; however, there are no established treatments. One potential treatment shown to have anti-inflammatory capabilities is the dietary supplement docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid found in fish oil. DHA's anti-inflammatory mechanisms are unclear for particle-induced inflammation; therefore, this study evaluated DHA as a prophylactic treatment for semi-acute and chronic particle-induced inflammation in vivo. Balb/c mice were fed a control or 1% DHA diet and exposed to dispersion media, an inflammatory multi-walled carbon nanotube (MWCNT), or crystalline silica (SiO₂) either once (semi-acute) or once a week for 4 weeks (chronic). The hypothesis was that DHA will decrease pulmonary inflammatory markers in response to particle-induced inflammation. Results indicated that DHA had a trending anti-inflammatory effect in mice exposed to MWCNT. There was a general decrease in inflammatory signals within the lung lavage fluid and upregulation of M2c macrophage gene expression in the spleen tissue. In contrast, mice exposed to SiO₂ while on the DHA diet significantly increased most inflammatory markers. However, DHA stabilized the phagolysosomal membrane upon prolonged treatment. This indicated that DHA treatment may depend upon certain inflammatory particle exposures as well as the length of the exposure.

Value of HMGB1 expression for assessing gastric cancer severity: a systematic meta-analysis

OBJECTIVE

To evaluate the clinical value of high mobility group box-1 (HMGB1) expression levels in patients with gastric cancer.

METHODS

Articles published from January 2000 to August 2022 were searched using PubMed, Google Scholar and Science Direct, Springer, Wiley and NIH to evaluate the clinicopathological significance of HMGB1 expression in gastric cancer.

RESULTS

A total of 156 publications were selected, of which six studies, comprising 846 patients, met the criteria for inclusion in this study. Forest plots of clinicopathological characteristics indicated that HMGB1 expression was not associated with age (odds ratio (OR) = 1.07, 95% confidence interval (CI): 0.89-1.28), sex (OR = 0.90, 95% CI: 0.81-1.00), TNM (OR = 1.39, 95% CI: 0.82-2.37), N stage (OR = 1.42, 95% CI: 0.97-2.07), or tumor differentiation (OR = 0.96, 95% CI: 0.71-1.29), but was highly correlated with pT stage (OR = 1.56, 95% CI: 1.17-2.07). Funnel plots showed no significant publication bias in the included studies in terms of age, sex, TNM, pT stage, N stage, or tumor differentiation.

CONCLUSION

HMGB1 expression was significantly correlated with tumor pT stage, but not with age, sex, TNM stage, tumor N stage, tumor differentiation, or lymphatic metastasis in patients with GC.

Therapeutic treatment of dietary docosahexaenoic acid for particle-induced pulmonary inflammation in Balb/c mice

OBJECTIVE AND DESIGN

The omega-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) has been reported to suppress inflammation. Pulmonary inflammation can be directly linked to exposure of various occupational and man-made particles leading to pulmonary diseases. Therapeutic treatments are lacking for particle-induced pulmonary inflammation. These studies evaluated DHA as a therapeutic treatment for semi-acute and chronic particle-induced pulmonary inflammation.

METHODS

Balb/c mice were oropharyngeal instilled with hydrophobic multi-walled carbon nanotube (MWCNT) or hydrophilic crystalline silica (SiO2) either as one instillation (semi-acute) or once a week for 4 weeks (chronic). One week later, the mice were placed on either a control or 1% DHA-containing diet for 3 weeks (semi-acute) or 12 weeks (chronic). Mice were assessed for inflammatory signaling within the lung lavage fluid, impact on phagolysosomal membrane permeability, shifts of macrophage phenotype gene expression (M1, M2a, M2b, and M2c), and pulmonary histopathology.

RESULTS

DHA increased pulmonary inflammatory markers and lung pathology when mice were exposed to SiO2. There were trending decreases of inflammatory markers for MWCNT-exposed mice with DHA treatment, however, mostly not statistically significant.

CONCLUSION

The anti-inflammatory benefits of DHA treatment depend upon the type of inflammatory particle, magnitude of inflammation, and duration of treatment.

Docosahexaenoic acid impacts macrophage phenotype subsets and phagolysosomal membrane permeability with particle exposure

Inhalation of particles results in pulmonary inflammation; however, treatments are currently lacking. Docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid shown to exhibit anti-inflammatory capabilities. The impact of DHA on particle-induced inflammation is unclear; therefore, the aim of this study was to examine the hypothesis that DHA downregulates macrophage inflammatory responses by altering phagolysosomal membrane permeability (LMP) and shifting macrophage phenotype. Isolated Balb/c alveolar macrophages (AM) were polarized into M1, M2a, M2b, or M2c phenotypes in vitro, treated with DHA, and exposed to a multi-walled carbon nanotube (MWNCT) or crystalline silica (SiO₂). Results showed minimal cytotoxicity, robust effects for silica particle uptake, and LMP differences between phenotypes. Docosahexaenoic acid prevented these effects to the greatest extent in M2c phenotype. To determine if DHA affected inflammation similarly in vivo, Balb/c mice were placed on a control or 1% DHA diet for 3 weeks, instilled with the same particles, and assessed 24 hr following instillation. Data demonstrated that in contrast to in vitro findings, DHA increased pulmonary inflammation and LMP. These results suggest that pulmonary responses in vivo may not necessarily be predicted from single-cell responses in vitro.

Ozone exposure promotes pyroptosis in rat lungs via the TLR2/4-NF-κB-NLRP3 signaling pathway

OBJECTIVE

Ozone has become a major air pollutant in recent years, which leading to a variety of lung diseases. This study aimed to explore the mechanisms of pyroptosis and related signaling pathways in ozone-induced lung injury.

METHODS

We exposed 120 Wistar rats to ozone, 20 in each group (half male and half female). Ozone exposure concentrations were 0, 0.12, 0.5, 1.0, 2.0 and 4.0 ppm for 6 h. At the same time, we isolated and cultured type I alveolar epithelial cells, then intervened with high mobility group box 1 protein (HMGB1), hyaluronic acid (HA) and Toll-like receptors 2/4 (TLR2/4) inhibitor. In animal experiments, histopathological experiments, TUNEL, ELISA and biochemical indicators were performed. RT-qPCR and western blot experiments assay were used to detect the expression changes of key factors in relevant signal pathways in vivo and in vitro.

RESULTS

After acute ozone exposure, the levels of lung cell injury indicators in bronchoalveolar lavage fluid (BALF), as well as the levels of inflammatory factors in BALF, blood, and lung tissue were significantly increased. Male rats were more sensitive to ozone exposure. Low-concentration ozone exposure caused mild interstitial inflammation in rat lung tissue. Severe inflammation and pulmonary edema appeared with increases in concentration. ELISA results in BALF showed that HMGB1 and HA expressions increased gradually with the increase of ozone exposure concentration. RT-qPCR and Western blot showed that when ozone concentrations increased above 0.5 ppm, the expression of nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing 3 (NLRP3), cleaved caspase-1, and N-gasdermin D (N-GSDMD) in the lung tissue increased significantly, suggesting that ozone exposure induces pyroptosis. At the same time, it was found that ozone exposure activated the nuclear factor kappa B (NF-κB) signal pathway, and increased the mRNA expressions of Toll-like receptors TLR2/4. The results of cell experiments showed that after the addition of HMGB1 and HA, the expression of NF-κB and pyroptosis related indexes increased in type I alveolar epithelial cells, while the corresponding expression decreased after the addition of TLR2/4 inhibitors.

CONCLUSION

Ozone exposure causes lung injury in a dose- and gender-dependent manner, and is more severe in males. When injured, the levels of HMGB1 and HA in BALF increased, which interact with TLR 2/4 to activate the downstream NF-κB signaling pathway. Further activating the NLRP3 inflammasome complex and regulating the ozone-induced pyroptosis.

Signaling Pathways Implicated in Carbon Nanotube-Induced Lung Inflammation

Inflammation is a tissue response to a variety of harmful stimuli, such as pathogens, irritants, and injuries, and can eliminate insults and limit tissue damage. However, dysregulated inflammation is recognized as a cause of many human diseases, exemplified by organ fibrosis and cancer. In this regard, inflammation-promoted fibrosis is commonly observed in human lung diseases, such as idiopathic pulmonary fibrosis and pneumoconiosis. Carbon nanotubes (CNTs) are a type of nanomaterials with unique properties and various industrial and commercial applications. On the other hand, certain forms of CNTs are potent inducers of inflammation and fibrosis in animal lungs. Notably, acute inflammation is a remarkable phenotype elicited by CNTs in the lung during the early acute phase post-exposure; whereas a type 2 immune response is evidently activated and dominates during the late acute and chronic phases, leading to type 2 inflammation and lung fibrosis. Numerous studies demonstrate that these immune responses involve distinct immune cells, various pathologic factors, and specific functions and play crucial roles in the initiation and progression of inflammation and fibrosis in the lung exposed to CNTs. Thus, the mechanistic understanding of the immune responses activated by CNTs has drawn great attention in recent years. This article reviews the major findings on the cell signaling pathways that are activated in immune cells and exert functions in promoting immune responses in CNT-exposed lungs, which would provide new insights into the understanding of CNT-induced lung inflammation and inflammation-driven fibrosis, the application of CNT-induced lung inflammation and fibrosis as a new disease model, and the potential of targeting immune cells as a therapeutic strategy for relevant human lung diseases.

Role of inflammation in the malignant transformation of pleural mesothelial cells induced by multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) are one of the most widely used types of novel nano-fiber materials. The aim of this study was to establish an experimental system based on actual exposure dosage and environments and explore the roles and mechanisms of inflammation in the malignant transformation of pleural mesothelial cells induced by MWCNTs after low doses and long-term exposure. Here, we established an in vitro system by co-culturing macrophages and mesothelial cells and exposing these cells to high aspect ratio MWCNTs (0.1 μg/mL) for three months. Results indicated that IL-1β, secreted by macrophages stimulated by MWCNTs, may significantly enhance the release of inflammatory cytokines, such as IL-8, TNF-α, and IL-6, from mesothelial cells. Results obtained from proliferation, migration, invasion, colony formation, and chromosomal aberration studies indicated that MWCNTs may promote malignant transformation of mesothelial cells after long-term and low-dose exposure via inflammation. Furthermore, the obtained results demonstrated that the NF-κB/IL-6/STAT3 pathway was active in the malignant transformation of Met 5A cells, induced by MWCNTs, and played an important role in the process. In conclusion, our results showed that the NF-κB (p65)/IL-6/STAT3 molecular pathway, which was mediated by inflammation, played an important role in the malignant transformation of pleural mesothelial cells induced by MWCNTs. These findings also provide novel ideas and references for the treatment of mesothelioma and offers options for the occupational safety of nanomaterial practitioners.

Nanomaterials and Innate Immunity: A Perspective of the Current Status in Nanosafety

Human exposure to engineered nanomaterials (ENMs) is inevitable due to the plethora of applications for which they are being manufactured and integrated within. ENMs demonstrate plentiful advantages in terms of industrial approaches as well as from a consumer perspective. However, despite such positives, doubts remain over the human health implications of ENM exposure. In light of the increased research focus upon the potential effects of ENM exposure to human health in recent decades, questions still remain regarding the safety of these highly advanced, precision-tuned physical entities. The risk of short-term, high-dose exposure to humans is considered relatively low, although this has formed the direction of the hazard-assessment community since the turn of the 21st century. However, the possibility of humans being exposed repeatedly over a long period of time to a low-dose of ENMs of varying physicochemical characteristics is of significant concern, and thus, industry, government, academic, and consumer agencies are only now beginning to consider this. Notably, when considering the human health implications of such low-dose, long-term, repeated exposure scenarios, the impact of ENMs upon the human immune system is of primary importance. However, there remains a real need to understand the impact of ENMs upon the human immune system, especially the innate immune system, at all stages of life, given exposure to nanosized particles begins before birth, that is, of the fetus. Therefore, the purpose of this perspective is to summarize what is currently known regarding ENM exposure of different components of the innate immune system and identify knowledge gaps that should be addressed if we are to fully deduce the impact of ENM exposure on innate immune function.

Microenvironmental Alterations in Carbon Nanotube-Induced Lung Inflammation and Fibrosis

Carbon nanotube (CNT)-induced pulmonary inflammation and fibrosis have been intensively observed and characterized in numerous animal studies in the past decade. Remarkably, CNT-induced fibrotic lesions highly resemble some human fibrotic lung diseases, such as IPF and pneumoconiosis, regarding disease development and pathological features. This notion leads to a serious concern over the health impact of CNTs in exposed human populations, considering the rapidly expanding production of CNT materials for diverse industrial and commercial applications, and meanwhile provides the rationale for exploring CNT-induced pathologic effects in the lung. Accumulating mechanistic understanding of CNT lung pathology at the systemic, cellular, and molecular levels has demonstrated the potential of using CNT-exposed animals as a new disease model for the studies on inflammation, fibrosis, and the interactions between these two disease states. Tissue microenvironment plays critical roles in maintaining homeostasis and physiological functions of organ systems. When aberrant microenvironment forms under intrinsic or extrinsic stimulation, tissue abnormality, organ dysfunction, and pathological outcomes are induced, resulting in disease development. In this article, the cellular and molecular alterations that are induced in tissue microenvironment and implicated in the initiation and progression of inflammation and fibrosis in CNT-exposed lungs, including effector cells, soluble mediators, and functional events exemplified by cell differentiation and extracellular matrix (ECM) modification, are summarized and discussed. This analysis would provide new insights into the mechanistic understanding of lung inflammation and fibrosis induced by CNTs, as well as the development of CNT-exposed animals as a new model for human lung diseases.

Carbon Nanomaterials Stimulate HMGB1 Release From Macrophages and Induce Cell Migration and Invasion

Carbon nanomaterials (CNMs) are widely used in industrial and medical sectors. The increasing exposure of CNMs necessitates the studies of their potential environmental and health effects. High-mobility group box-1 (HMGB1) is a nuclear DNA-binding protein, but when released from cells, may cause sustained inflammatory response and promote cell migration and invasion. In this work, we found that 7-day exposure of 2.5 mg/kg/day CNMs, including C60, single-walled carbon nanotubes, and graphene oxides significantly elevated the level of HMGB1 in blood and lung lavage fluids in C57BL/6 mice. Subsequently, cellular effects and underlying mechanism were explored by using Raw264.7. The results showed that noncytotoxic CNMs enhanced HMGB1 intracellular translocation and release via activating P2X7 receptor. Released HMGB1 further activated receptor for advanced glycation endproducts (RAGE) and downstream signaling pathway by upregulating RAGE and Rac1 expression. Simultaneously, CNMs prepared the cells for migration and invasion by modulating MMP2 and TIMP2 gene expression as well as cytoskeleton reorganization. Intriguingly, released HMGB1 from macrophages promoted the migration of nearby lung cancer cell, which can be efficiently inhibited by neutralizing antibodies against HMGB1 and RAGE. Taken together, our work demonstrated that CNMs stimulated HMGB1 release and cell migration/invasion through P2X7R-HMGB1-RAGE pathway. The revealed mechanisms might facilitate a better understanding on the inflammatory property and subsequent cell functional alteration of CNMs.

The variances in cytokine production profiles from non- or activated THP-1, Kupffer cell and human blood derived primary macrophages following exposure to either alcohol or a panel of engineered nanomaterials

The portfolio of cytokines is key to the function of macrophages as sentries of the innate immune system as well as being critical for the transition from innate to adaptive immunity. Cytokine bias is critical in the fate of macrophages into a continuum of inflammatory to anti-inflammatory macrophages. Due to advances in the field of toxicology, increasingly advanced multi-cellular in vitro safety assessment models are being developed in order to allow for a better predication of potential adverse effects in humans with many of these models include a macrophage population. The selection of the correct macrophage cells in these advanced in vitro models is critical for a physiologically relevant and realistic immune response. In this study we investigated cytokine response profile (IL1-β, IL6, IL10 and TNF-α) of activated and non-activated THP-1 (immortalized monocyte-like cell line), primary human Kupffer cells (liver resident macrophages) and human primary peripheral blood mononuclear cells following exposure of a panel of nanomaterials or ethanol. The data demonstrated that the THP-1 cell line are not great cytokine producers. The PBMC appear to be a good in vitro surrogate for circulating/pro-inflammatory macrophages but are not a suitable replacement for Kupffer cells. The findings from this study highlight the necessity for the selection of appropriate macrophages populations to meet the specific physiological requirements of in vitro experiment.

Multi-Walled Carbon Nanotubes Augment Allergic Airway Eosinophilic Inflammation by Promoting Cysteinyl Leukotriene Production

Multi-walled carbon nanotubes (MWCNT) have been reported to promote lung inflammation and fibrosis. The commercial demand for nanoparticle-based materials has expanded rapidly and as demand for nanomaterials grows, so does the urgency of establishing an appreciation of the degree of health risk associated with their increased production and exposure. In this study, we examined whether MWCNT inhalation elicited pulmonary eosinophilic inflammation and influenced the development of allergic airway inflammatory responses. Our data revealed that instillation of FA21 MWCNT into the airways of mice resulted in a rapid increase, within 24 h, in the number of eosinophils present in the lungs. The inflammatory response elicited was also associated with an increase in the level of cysteinyl leukotrienes (cysLTs) present in the bronchoalveolar lavage fluid. CysLTs were implicated in the airway inflammatory response since pharmacological inhibition of their biosynthesis using the 5-lipoxygenase inhibitor Zileuton resulted in a marked reduction in the severity of inflammation observed. Moreover, FA21 MWCNT entering the airways of mice suffering from house dust mite (HDM)-elicited allergic lung inflammation markedly exacerbated the intensity of the airway inflammation. This response was characterized by a pulmonary eosinophilia, lymphocyte infiltration, and raised cysLT levels. The severity of pulmonary inflammation caused by either inhalation of MWCNT alone or in conjunction with HDM allergen correlated with the level of nickel present in the material, since preparations that contained higher levels of nickel (FA21, 5.54% Ni by weight) were extremely effective at eliciting or exacerbating inflammatory or allergic responses while preparations containing lower amounts of nickel (FA04, 2.54% Ni by weight) failed to initiate or exacerbate pulmonary inflammation. In summary, instillation of high nickel MWCNT into the lungs promoted eosinophilic inflammation and caused an intense exacerbation of pre-existing allergic airway inflammation by facilitating cysLT biosynthesis. These findings suggest that exposure to airborne MWCNT is likely to have adverse inflammatory effects in individuals suffering from atopic asthma and, in this context, further investigation of the therapeutic effects of pharmacological agents that block leukotriene synthesis is warranted.

Cytokine Profiling of Primary Human Macrophages Exposed to Endotoxin-Free Graphene Oxide: Size-Independent NLRP3 Inflammasome Activation

Graphene-based materials including graphene oxide (GO) are envisioned for a variety of biomedical applications. However, there are conflicting results concerning the biocompatibility of these materials. Here, a question is raised whether GO with small or large lateral dimensions triggers cytotoxicity and/or cytokine responses in primary human monocyte-derived macrophages. GO sheets produced under sterile conditions by a modified Hummers' method are found to be taken up by macrophages without signs of cytotoxicity. Then, multiplex arrays are used for profiling of proinflammatory and anti-inflammatory responses. Notably, GO suppresses the lipopolysaccharide (LPS)-triggered induction of several chemokines and cytokines, including the anti-inflammatory cytokine, interleukin-10 (IL-10). No production of proinflammatory TNF-α is observed. However, GO elicits caspase-dependent IL-1 β expression, a hallmark of inflammasome activation, in LPS-primed macrophages. Furthermore, GO-triggered IL-1 β production requires NADPH oxidase-generated reactive oxygen species and cellular uptake of GO and is accompanied by cathepsin B release and K+ efflux. Using THP-1 knockdown cells, a role for the inflammasome sensor, NLRP3, the adaptor protein, ASC, and caspase-1 for GO-induced IL-1β secretion is demonstrated. Finally, these studies show that inflammasome activation is independent of the lateral dimensions of the GO sheets. These studies provide novel insights regarding the immunomodulatory properties of endotoxin-free GO.

Nitrative DNA damage in cultured macrophages exposed to indium oxide

Objectives:

Indium compounds are used in manufacturing displays of mobile phones and televisions. However, these materials cause interstitial pneumonia in exposed workers. Animal experiments demonstrated that indium compounds caused lung cancer. Chronic inflammation is considered to play a role in lung carcinogenesis and fibrosis induced by particulate matters. 8-Nitroguanine (8-nitroG) is a mutagenic DNA lesion formed during inflammation and may participate in carcinogenesis. To clarify the mechanism of carcinogenesis, we examined 8-nitroG formation in indium-exposed cultured cells.

Methods:

We treated RAW 264.7 mouse macrophages with indium oxide (In₂O₃) nanoparticles (primary diameter: 30-50 nm), and performed fluorescent immunocytochemistry to detect 8-nitroG. The extent of 8-nitroG formation was evaluated by quantitative image analysis. We measured the amount of nitric oxide (NO) in the culture supernatant of In₂O₃-treated cells by the Griess method. We also examined the effects of inhibitors of inducible NO synthase (iNOS) and endocytosis on In₂O₃-induced 8-nitroG formation.

Results:

In₂O₃ significantly increased the intensity of 8-nitroG formation in RAW 264.7 cells in a dose-dependent manner. In₂O₃-induced 8-nitroG formation was observed at 2 h and further increased at 4 h, and the amount of NO released from In₂O₃-exposed cells was significantly increased at 2-4 h compared with the control. 8-NitroG formation was suppressed by 1400W (an iNOS inhibitor), methyl-β-cyclodextrin and monodansylcadaverine (inhibitors of caveolae- and clathrin-mediated endocytosis, respectively).

Conclusions:

These results suggest that endocytosis and NO generation participate in indium-induced 8-nitroG formation. NO released from indium-exposed inflammatory cells may induce DNA damage in adjacent lung epithelial cells and contribute to carcinogenesis.

Mechanisms of carbon nanotube-induced pulmonary fibrosis: a physicochemical characteristic perspective

Carbon nanotubes (CNTs) are engineered nanomaterials (ENMs) with numerous beneficial applications. However, they could pose a risk to human health from occupational or consumer exposures. Rodent models demonstrate that exposure to CNTs via inhalation, instillation, or aspiration results in pulmonary fibrosis. The severity of the fibrogenic response is determined by various physicochemical properties of the nanomaterial such as residual metal catalyst content, rigidity, length, aggregation status, or surface charge. CNTs are also increasingly functionalized post-synthesis with organic or inorganic agents to modify or enhance surface properties. The mechanisms of CNT-induced fibrosis involve oxidative stress, innate immune responses of macrophages, cytokine and growth factor production, epithelial cell injury and death, expansion of the pulmonary myofibroblast population, and consequent extracellular matrix accumulation. A comprehensive understanding of how physicochemical properties affect the fibrogenic potential of various types of CNTs should be considered in combination with genetic variability and gain or loss of function of specific genes encoding secreted cytokines, enzymes, or intracellular cell signaling molecules. Here, we cover the current state of the literature on mechanisms of CNT-exposed pulmonary fibrosis in rodent models with a focus on physicochemical characteristics as principal drivers of the mechanisms leading to pulmonary fibrosis. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Respiratory Disease Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.

Length, but Not Reactive Edges, of Cup-stack MWCNT Is Responsible for Toxicity and Acute Lung Inflammation

Multiwalled carbon nanotube (MWCNT) toxicity after inhalation has been associated with size, aspect ratio, rigidity, surface modification, and reactive oxygen species production. In this study, we investigated a series of cup-stacked MWCNT prepared as variants of the Creos 24PS. Mechanical chopping produced a short version (AR10) and graphitization to remove active reaction sites by extreme heat (2,800°C; Creos 24HT) to test the contribution of length and alteration of potential reaction sites to toxicity. The 3 MWCNT variants were tested in vitro in a human macrophage-like cell model and with C57BL/6 alveolar macrophages for dose-dependent toxicity and NLRP3 inflammasome activation. The 24PS and 24HT variants showed significant dose-dependent toxicity and inflammasome activation. In contrast, the AR10 variant showed no toxicity or bioactivity at any concentration tested. The in vivo results reflected those observed in vitro, with the 24PS and 24HT variants resulting in acute inflammation, including elevated polymorphonuclear counts, Interleukin (IL)-18, cathepsin B, and lactate dehydrogenase in isolated lung lavage fluid from mice exposed to 40 µg MWCNT. Taken together, these data indicate that length, but not the absence of proposed reaction sites, on the MWCNT influences particle bioactivity.

Imipramine blocks acute silicosis in a mouse model

BACKGROUND

Inhalation of crystalline silica is associated with pulmonary inflammation and silicosis. Although silicosis remains a prevalent health problem throughout the world, effective treatment choices are limited. Imipramine (IMP) is a FDA approved tricyclic antidepressant drug with lysosomotropic characteristics. The aim of this study was to evaluate the potential for IMP to reduce silicosis and block phagolysosome membrane permeabilization.

METHODS

C57BL/6 alveolar macrophages (AM) exposed to crystalline silica ± IMP in vitro were assessed for IL-1β release, cytotoxicity, particle uptake, lysosomal stability, and acid sphingomyelinase activity. Short term (24 h) in vivo studies in mice instilled with silica (± IMP) evaluated inflammation and cytokine release, in addition to cytokine release from ex vivo cultured AM. Long term (six to ten weeks) in vivo studies in mice instilled with silica (± IMP) evaluated histopathology, lung damage, and hydroxyproline content as an indicator of collagen accumulation.

RESULTS

IMP significantly attenuated silica-induced cytotoxicity and release of mature IL-1β from AM in vitro. IMP treatment in vivo reduced silica-induced inflammation in a short-term model. Furthermore, IMP was effective in blocking silica-induced lung damage and collagen deposition in a long-term model. The mechanism by which IMP reduces inflammation was explored by assessing cellular processes such as particle uptake and acid sphingomyelinase activity.

CONCLUSIONS

Taken together, IMP was anti-inflammatory against silica exposure in vitro and in vivo. The results were consistent with IMP blocking silica-induced phagolysosomal lysis, thereby preventing cell death and IL-1β release. Thus, IMP could be therapeutic for silica-induced inflammation and subsequent disease progression as well as other diseases involving phagolysosomal lysis.

Graphene and the Immune System: A Romance of Many Dimensions

Graphene-based materials (GBMs) are emerging as attractive materials for biomedical applications. Understanding how these materials are perceived by and interact with the immune system is of fundamental importance. Phagocytosis is a major mechanism deployed by the immune system to remove pathogens, particles, and cellular debris. Here, we discuss recent studies on the interactions of GBMs with different phagocytic cells, including macrophages, neutrophils, and dendritic cells. The importance of assessing GBMs for endotoxin contamination is discussed as this may skew results. We also explore the role of the bio-corona for interactions of GBMs with immune cells. Finally, we highlight recent evidence for direct plasma membrane interactions of GBMs.

Phagolysosome acidification is required for silica and engineered nanoparticle-induced lysosome membrane permeabilization and resultant NLRP3 inflammasome activity

NLRP3 inflammasome activation occurs in response to hazardous particle exposures and is critical for the development of particle-induced lung disease. Mechanisms of Lysosome Membrane Permeabilization (LMP), a central pathway for activation of the NLRP3 inflammasome by inhaled particles, are not fully understood. We demonstrate that the lysosomal vATPases inhibitor Bafilomycin A1 blocked LMP in vitro and ex vivo in primary murine macrophages following exposure to silica, multi-walled carbon nanotubes, and titanium nanobelts. Bafilomycin A1 treatment of particle-exposed macrophages also resulted in decreased active cathepsin L in the cytosol, a surrogate measure for leaked cathepsin B, which was associated with less NLRP3 inflammasome activity. Silica-induced LMP was partially dependent upon lysosomal cathepsins B and L, whereas nanoparticle-induced LMP occurred independent of cathepsin activity. Furthermore, inhibition of lysosomal cathepsin activity with CA-074-Me decreased the release of High Mobility Group Box 1. Together, these data support the notion that lysosome acidification is a prerequisite for particle-induced LMP, and the resultant leak of lysosome cathepsins is a primary regulator of ongoing NLRP3 inflammasome activity and release of HMGB1.

Evaluating the mechanistic evidence and key data gaps in assessing the potential carcinogenicity of carbon nanotubes and nanofibers in humans

In an evaluation of carbon nanotubes (CNTs) for the IARC Monograph 111, the Mechanisms Subgroup was tasked with assessing the strength of evidence on the potential carcinogenicity of CNTs in humans. The mechanistic evidence was considered to be not strong enough to alter the evaluations based on the animal data. In this paper, we provide an extended, in-depth examination of the in vivo and in vitro experimental studies according to current hypotheses on the carcinogenicity of inhaled particles and fibers. We cite additional studies of CNTs that were not available at the time of the IARC meeting in October 2014, and extend our evaluation to include carbon nanofibers (CNFs). Finally, we identify key data gaps and suggest research needs to reduce uncertainty. The focus of this review is on the cancer risk to workers exposed to airborne CNT or CNF during the production and use of these materials. The findings of this review, in general, affirm those of the original evaluation on the inadequate or limited evidence of carcinogenicity for most types of CNTs and CNFs at this time, and possible carcinogenicity of one type of CNT (MWCNT-7). The key evidence gaps to be filled by research include: investigation of possible associations between in vitro and early-stage in vivo events that may be predictive of lung cancer or mesothelioma, and systematic analysis of dose-response relationships across materials, including evaluation of the influence of physico-chemical properties and experimental factors on the observation of nonmalignant and malignant endpoints.

Autophagy deficiency in macrophages enhances NLRP3 inflammasome activity and chronic lung disease following silica exposure

Autophagy is an important metabolic mechanism that can promote cellular survival following injury. The specific contribution of autophagy to silica-induced inflammation and disease is not known. The objective of these studies was to determine the effects of silica exposure on the autophagic pathway in macrophages, as well as the general contribution of autophagy in macrophages to inflammation and disease. Silica exposure enhanced autophagic activity in vitro in Bone Marrow derived Macrophages and in vivo in Alveolar Macrophages isolated from silica-exposed mice. Impairment of autophagy in myeloid cells in vivo using Atg5(fl/fl)LysM-Cre(+) mice resulted in enhanced cytotoxicity and inflammation after silica exposure compared to littermate controls, including elevated IL-18 and the alarmin HMGB1 in the whole lavage fluid. Autophagy deficiency caused some spontaneous inflammation and disease. Greater silica-induced acute inflammation in Atg5(fl/fl)LysM-Cre(+) mice correlated with increased fibrosis and chronic lung disease. These studies demonstrate a critical role for autophagy in suppressing silica-induced cytotoxicity and inflammation in disease development. Furthermore, this data highlights the importance of basal autophagy in macrophages and other myeloid cells in maintaining lung homeostasis.

The complex cascade of cellular events governing inflammasome activation and IL-1β processing in response to inhaled particles

The innate immune system is the first line of defense against inhaled particles. Macrophages serve important roles in particle clearance and inflammatory reactions. Following recognition and internalization by phagocytes, particles are taken up in vesicular phagolysosomes. Intracellular phagosomal leakage, redox unbalance and ionic movements induced by toxic particles result in pro-IL-1β expression, inflammasome complex engagement, caspase-1 activation, pro-IL-1β cleavage, biologically-active IL-1β release and finally inflammatory cell death termed pyroptosis. In this review, we summarize the emerging signals and pathways involved in the expression, maturation and secretion of IL-1β during these responses to particles. We also highlight physicochemical characteristics of particles (size, surface and shape) which determine their capacity to induce inflammasome activation and IL-1β processing.

Multi-walled carbon nanotube induces nitrative DNA damage in human lung epithelial cells via HMGB1-RAGE interaction and Toll-like receptor 9 activation

Background

Carbon nanotube (CNT) is used for various industrial purposes, but exhibits carcinogenic effects in experimental animals. Chronic inflammation in the respiratory system may participate in CNT-induced carcinogenesis. 8-Nitroguanine (8-nitroG) is a mutagenic DNA lesion formed during inflammation. We have previously reported that multi-walled CNT (MWCNT) induced 8-nitroG formation in lung epithelial cells and this process involved endocytosis. To clarify the mechanism of CNT-induced carcinogenesis, we examined the role of Toll-like receptor (TLR) 9, which resides in endosomes and lysosomes, in 8-nitroG formation in human lung epithelial cell lines.

Methods

We performed immunocytochemistry to examine 8-nitroG formation in A549 and HBEpC cells treated with MWCNT with a length of 1-2 μm (CNT-S) or 5-15 μm (CNT-L) and a diameter of 20-40 nm. We examined inhibitory effects of endocytosis inhibitors, small interfering RNA (siRNA) for TLR9, and antibodies against high-mobility group box-1 (HMGB1) and receptor for advanced glycation end-products (RAGE) on 8-nitroG formation. The release of HMGB1 and double-stranded DNA (dsDNA) into the culture supernatant from MWCNT-treated cells was examined by ELISA and fluorometric analysis, respectively. The association of these molecules was examined by double immunofluorescent staining and co-immunoprecipitation.

Results

CNT-L significantly increased 8-nitroG formation at 0.05 μg/ml in A549 cells and its intensity reached a maximum at 1 μg/ml. CNT-L tended to induce stronger cytotoxicity and 8-nitroG formation than CNT-S. Endocytosis inhibitors, TLR9 siRNA and antibodies against HMGB1 and RAGE largely reduced MWCNT-induced 8-nitroG formation. MWCNT increased the release of HMGB1 and dsDNA from A549 cells into culture supernatant. The culture supernatant of MWCNT-exposed cells induced 8-nitroG formation in fresh A549 cells. Double immunofluorescent staining and co-immunoprecipitation showed that TLR9 was associated with HMGB1 and RAGE in lysosomes of MWCNT-treated cells.

Conclusions

MWCNT induces injury or necrosis of lung epithelial cells, which release HMGB1 and DNA into the extracellular space. The HMGB1-DNA complex binds to RAGE on neighboring cells and then CpG DNA is recognized by TLR9 in lysosomes, leading to generation of nitric oxide and 8-nitroG formation. This is the first study demonstrating that TLR9 and related molecules participate in MWCNT-induced genotoxicity and may contribute to carcinogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0127-7) contains supplementary material, which is available to authorized users.

Environmental impact of multi-wall carbon nanotubes in a novel model of exposure: systemic distribution, macrophage accumulation, and amyloid deposition

Carbon nanotubes (CNTs) have been extensively investigated and employed for industrial use because of their peculiar physical properties, which make them ideal for many industrial applications. However, rapid growth of CNT employment raises concerns about the potential risks and toxicities for public health, environment, and workers associated with the manufacture and use of these new materials. Here we investigate the main routes of entry following environmental exposure to multi-wall CNTs (MWCNTs; currently the most widely used in industry). We developed a novel murine model that could represent a surrogate of a workplace exposure to MWCNTs. We traced the localization of MWCNTs and their possible role in inducing an innate immune response, inflammation, macrophage recruitment, and inflammatory conditions. Following environmental exposure of CD1 mice, we observed that MWCNTs rapidly enter and disseminate in the organism, initially accumulating in lungs and brain and later reaching the liver and kidney via the bloodstream. Since recent experimental studies show that CNTs are associated with the aggregation process of proteins associated with neurodegenerative diseases, we investigated whether MWCNTs are able to induce amyloid fibril production and accumulation. Amyloid deposits in spatial association with macrophages and MWCNT aggregates were found in the brain, liver, lungs, and kidneys of exposed animals. Our data suggest that accumulation of MWCNTs in different organs is associated with inflammation and amyloid accumulation. In the brain, where we observed rapid accumulation and amyloid fibril deposition, exposure to MWCNTs might enhance progression of neurodegenerative and other amyloid-related diseases. Our data highlight the conclusion that, in a novel rodent model of exposure, MWCNTs may induce macrophage recruitment, activation, and amyloid deposition, causing potential damage to several organs.

HMGB1 promotes the activation of NLRP3 and caspase-8 inflammasomes via NF-κB pathway in acute glaucoma

Background

Acute glaucoma is a significantly sight-threatening cause of irreversible blindness in the world characterized by a sudden and substantial intraocular pressure (IOP) increase and subsequent retinal ganglion cell (RGC) death. This study aims to explore the role of high-mobility group box 1 (HMGB1) in an acute glaucoma mouse model.

Methods

An acute glaucoma model was induced by a rapid and substantial increase IOP to 70 mmHg for 60 min via anterior chamber punctured and affused with Balance Salt Solution in C57BL/6 mice. Retinal tissue ischemic damage and loss of RGCs were assessed at 6, 24, 48, 72 h after high IOP treatment, and at 48 h, group with or without recombinant high-mobility group box 1 (rHMGB1), the HMGB1 inhibitor, glycyrrhizic acid (GA), and by HE and immunofluorescent staining. The nuclear factor κB (NF-κB) inhibitor, JSH-23, and caspase-8 inhibitor, Z-IETD-fmk, were injected into vitreous. Reverse transcription and semi-quantitative reverse transcription polymerase chain reaction (RT-PCR), western blotting, and immunoprecipitation were performed to evaluate the expression level of nucleotide-binding domain, leucine-rich repeat containing protein 3 (NLRP3), phosphor-NF-κB p65, caspase-8, caspase-1, apoptosis-associated speck-like protein containing a CARD (ASC), and interleukin-1β (IL-1β).

Results

HMGB1 was increased in ischemic retinal tissue during acute glaucoma as early as 6 h after rapid IOP elevation. Exogenous HMGB1 exacerbated retinal ischemic damage, RGC loss, and inhibition of endogenous HMGB1 significantly reduced the severity of disease. HMGB1 significantly induced the elevation of canonical NLRP3, ASC, caspase-1, and non-canonical capase-8-ASC inflammasome and promoted the processing of IL-1β. Furthermore, the effect of HMGB1 on NLRP3 inflammasome activation and IL-1β production was dependent on NF-κB pathway. Thus, HMGB1/caspase-8 pathway promoted the processing of IL-1β via NF-κB pathway.

Conclusion

The findings of this study identified a novel signaling pathway in which HMGB1, in response to acutely elevated intraocular pressure, activated the canonical NLRP3 and non-canonical caspase-8 inflammasomes and production of IL-1β during acute glaucoma development. These results provide new insights to the understanding of the innate response that contributes to pathogenesis of acute glaucoma.

An Allergic Lung Microenvironment Suppresses Carbon Nanotube-Induced Inflammasome Activation via STAT6-Dependent Inhibition of Caspase-1

Background

Multi-walled carbon nanotubes (MWCNTs) represent a human health risk as mice exposed by inhalation display pulmonary fibrosis. Production of IL-1β via inflammasome activation is a mechanism of MWCNT-induced acute inflammation and has been implicated in chronic fibrogenesis. Mice sensitized to allergens have elevated T-helper 2 (Th2) cytokines, IL-4 and IL-13, and are susceptible to MWCNT-induced airway fibrosis. We postulated that Th2 cytokines would modulate MWCNT-induced inflammasome activation and IL-1β release in vitro and in vivo during allergic inflammation.

Methods

THP-1 macrophages were primed with LPS, exposed to MWCNTs and/or IL-4 or IL-13 for 24 hours, and analyzed for indicators of inflammasome activation. C57BL6 mice were sensitized to house dust mite (HDM) allergen and MWCNTs were delivered to the lungs by oropharyngeal aspiration. Mice were euthanized 1 or 21 days post-MWCNT exposure and evaluated for lung inflammasome components and allergic inflammatory responses.

Results

Priming of THP-1 macrophages with LPS increased pro-IL-1β and subsequent exposure to MWCNTs induced IL-1β secretion. IL-4 or IL-13 decreased MWCNT-induced IL-1β secretion by THP-1 cells and reduced pro-caspase-1 but not pro-IL-1β. Treatment of THP-1 cells with STAT6 inhibitors, either Leflunomide or JAK I inhibitor, blocked suppression of caspase activity by IL-4 and IL-13. In vivo, MWCNTs alone caused neutrophilic infiltration into the lungs of mice 1 day post-exposure and increased IL-1β in bronchoalveolar lavage fluid (BALF) and pro-caspase-1 immuno-staining in macrophages and airway epithelium. HDM sensitization alone caused eosinophilic inflammation with increased IL-13. MWCNT exposure after HDM sensitization increased total cell numbers in BALF, but decreased numbers of neutrophils and IL-1β in BALF as well as reduced pro-caspase-1 in lung tissue. Despite reduced IL-1β mice exposed to MWCNTs after HDM developed more severe airway fibrosis by 21 days and had increased pro-fibrogenic cytokine mRNAs.

Conclusions

These data indicate that Th2 cytokines suppress MWCNT-induced inflammasome activation via STAT6-dependent down-regulation of pro-caspase-1 and suggest that suppression of inflammasome activation and IL-1β by an allergic lung microenvironment is a mechanism through which MWCNTs exacerbate allergen-induced airway fibrosis.

Elevated HMGB1-related interleukin-6 is associated with dynamic responses of monocytes in patients with active pulmonary tuberculosis

There were limited studies assessing the role of HMGB1 in TB infection. In this prospective study, we aimed to assess the levels of HMGB1 in plasma or sputum from active pulmonary tuberculosis (APTB) patients positive for Mtb culture test, and to evaluate its relationship with inflammatory cytokines and innate immune cells. A total of 36 sputum Mtb culture positive APTB patients and 32 healthy volunteers (HV) were included. Differentiated THP-1 cells were treated for 6, 12 and 24 hrs with BCG at a multiplicity of infection of 10. The absolute values and percentages of white blood cells (WBC), neutrophils, lymphocytes, and monocytes were detected by an automatic blood analyzer. Levels of HMGB1, IL-6, IL-10 and TNF-α in plasma, sputum, or cell culture supernatant were measured by ELISA. The blood levels of HMGB1, IL-6, IL-10 and TNF-α, the absolute values of WBC, monocytes and neutrophils, and the percentage of monocytes were significant higher in APTB patients than those in HV groups (P < 0.05). The sputum levels of HMGB1, IL-10, and TNF-α were also significantly higher in APTB patients than those in HV groups (P < 0.05). Meanwhile, plasma level of HMGB1, IL-6, and IL-10 in APTB patients were positively correlated with those in sputum (P < 0.05), respectively. IL-6 was positively correlated with HMGB1 both in plasma and sputum of APTB patients (P < 0.05). HMGB1 and IL-6 is positively correlated with the absolute number of monocytes in APTB patients (P < 0.05). BCG induced HMGB1, IL-6, IL-10 and TNF-α production effectively in PMA-treated THP-1 cells. HMGB1 may be used as an attractive biomarker for APTB diagnosis and prognosis and may reflect the inflammatory status of monocytes in patients with APTB.

The alarmin IL-1α is a master cytokine in acute lung inflammation induced by silica micro- and nanoparticles

Background

Inflammasome-activated IL-1β plays a major role in lung neutrophilic inflammation induced by inhaled silica. However, the exact mechanisms that contribute to the initial production of precursor IL-1β (pro-IL-1β) are still unclear. Here, we assessed the implication of alarmins (IL-1α, IL-33 and HMGB1) in the lung response to silica particles and found that IL-1α is a master cytokine that regulates IL-1β expression.

Methods

Pro- and mature IL-1β as well as alarmins were assessed by ELISA, Western Blot or qRT-PCR in macrophage cultures and in mouse lung following nano- and micrometric silica exposure. Implication of these immune mediators in the establishment of lung inflammatory responses to silica was investigated in knock-out mice or after antibody blockade by evaluating pulmonary neutrophil counts, CXCR2 expression and degree of histological injury.

Results

We found that the early release of IL-1α and IL-33, but not HMGB1 in alveolar space preceded the lung expression of pro-IL-1β and neutrophilic inflammation in silica-treated mice. In vitro, the production of pro-IL-1β by alveolar macrophages was significantly induced by recombinant IL-1α but not by IL-33. Neutralization or deletion of IL-1α reduced IL-1β production and neutrophil accumulation after silica in mice. Finally, IL-1α released by J774 macrophages after in vitro exposure to a range of micro- and nanoparticles of silica was correlated with the degree of lung inflammation induced in vivo by these particles.

Conclusions

We demonstrated that in response to silica exposure, IL-1α is rapidly released from pre-existing stocks in alveolar macrophages and promotes subsequent lung inflammation through the stimulation of IL-1β production. Moreover, we demonstrated that in vitro IL-1α release from macrophages can be used to predict the acute inflammogenic activity of silica micro- and nanoparticles.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-014-0069-x) contains supplementary material, which is available to authorized users.