Uptake of silica and carbon nanotubes by human macrophages/monocytes induces activation of fibroblasts in vitro -- potential implication for pathogenesis of inflammation and fibrotic diseases

Lung decellularized matrix-derived 3D spheroids: Exploring silicosis through the impact of the Nrf2/Bax pathway on myofibroblast dynamics

Silicosis is an occupational respiratory disease caused by long-term inhalation of high concentrations of free silica particles. Studies suggest that oxidative stress is a crucial initiator of silicosis fibrosis, and previous studies have linked the antioxidative stress transcription factor known as Nrf2 to fibrosis antagonism. Myofibroblasts play a pivotal role in tissue damage repair due to oxidative stress. Unlike physiological repair, myofibroblasts in fibrosis exhibit an apoptosis-resistant phenotype, continuously synthesising and secreting significant amounts of collagen and other extracellular matrices, which could be a direct cause of silicosis fibrosis. However, the relationship and mechanism of action between oxidative stress and myofibroblast apoptosis resistance remain unclear. In this study, a new 3D cell culture model using mice lung decellularised matrix particles and fibroblasts was developed, simulating the changes in myofibroblasts during the development of silicotic nodules. Western Blot results indicate that silica stimulation leads to increased collagen deposition and decreased apoptosis-related protein Bax and oxidative stress-related protein Nrf2 in the 3D spheroid model. Immunofluorescence experiments reveal co-localisation in their expression. In Nrf2 overexpressing spheroids, Bax exhibits significant upregulation. In the Nrf2 knockout spheroids, Bax is also significantly downregulated; after intervention with Bax inhibitors, a significant downregulation of Bax-induced apoptosis was also detected in the Nrf2-overexpressed spheroids. In contrast, Bax-induced apoptosis showed a significant upregulation trend in Nrf2-overexpressed spheroids after intervention with Bax agonists. The results demonstrate that the spheroid model can mimic the development process of silicotic nodules, and silica stimulation leads to an apoptosis-resistant phenotype in myofibroblasts in the model, acting through the Nrf2/Bax pathway. This research establishes a new methodology for silicosis study, identifies therapeutic targets for silicosis, and opens new avenues for studying the mechanisms of silicosis fibrosis.

Antiproliferative and Antitumour Effect of Nongenotoxic Silver Nanoparticles on Melanoma Models

During the last 3 decades, there has been a slow advance to obtain new treatments for malignant melanoma that improve patient survival. In this work, we present a systematic study focused on the antiproliferative and antitumour effect of AgNPs. These nanoparticles are fully characterized, are coated with polyvinylpyrrolidone (PVP), and have an average size of 35 ± 15 nm and a metallic silver content of 1.2% wt. Main changes on cell viability, induction of apoptosis and necrosis, and ROS generation were found on B16-F10 cells after six hours of exposure to AgNPs (IC50 = 4.2 μg/mL) or Cisplatin (IC50 = 2.0 μg/mL). Despite the similar response for both AgNPs and Cisplatin on antiproliferative potency (cellular viability of 53.95 ± 1.88 and 53.62 ± 1.04) and ROS production (20.27 ± 1.09% and 19.50 ± 0.35%), significantly different cell death pathways were triggered. While AgNPs induce only apoptosis (45.98 ± 1.88%), Cisplatin induces apoptosis and necrosis at the same rate (22.31 ± 1.72% and 24.07 ± 1.10%, respectively). In addition to their antiproliferative activity, in vivo experiments showed that treatments of 3, 6, and 12 mg/kg of AgNPs elicit a survival rate almost 4 times higher (P < 0.05) compared with the survival rate obtained with Cisplatin (2 mg/kg). Furthermore, the survivor mice treated with AgNPs do not show genotoxic damage determined by micronuclei frequency quantification on peripheral blood cells. These results exhibit the remarkable antitumour activity of a nongenotoxic AgNP formulation and constitute the first advance toward the application of these AgNPs for melanoma treatment, which could considerably reduce adverse effects provoked by currently applied chemotherapeutics.

Identification of an Association of TNFAIP3 Polymorphisms With Matrix Metalloproteinase Expression in Fibroblasts in an Integrative Study of Systemic Sclerosis-Associated Genetic and Environmental Factors

OBJECTIVE

Systemic sclerosis (SSc) is a fibrotic disease attributed to both genetic susceptibility and environmental factors. This study was undertaken to investigate the associations between SSc-associated genetic variants and the expression of extracellular matrix (ECM) genes in human fibroblasts stimulated with silica particles in time-course and dose-response experiments.

METHODS

A total of 200 fibroblast strains were examined for ECM gene expression after stimulation with silica particles. The fibroblasts were genetically profiled using Immunochip assays and then subjected to whole-genome genotype imputation. Associations of genotypes and gene expression were first analyzed in a Caucasian cohort and then validated in a meta-analysis combining the results from Caucasian, African American, and Hispanic subjects. A linear mixed model for longitudinal data analysis was used to identify genetic variants associated with the expression of ECM genes, and the associations were validated by using a haplotype-based longitudinal association test on regions that included the loci identified.

RESULTS

The single-nucleotide polymorphism rs58905141 in TNFAIP3 was consistently associated with time-course and/or dose-response expression of MMP3 and MMP1 in the fibroblasts stimulated with silica particles in both the analysis of Caucasian subjects only and the meta-analysis. Results of the haplotype-based analysis validated the association signals.

CONCLUSION

Our findings indicate that a genetic variant of TNFAIP3 is strongly associated with the silica-induced profibrotic response of fibroblasts. In silico functional analysis based on the ENCODE database revealed that rs58905141 might affect the binding activities of the transcription factors for TNFAIP3. This is the first genome-wide study of interactions between genetic and environmental factors in a complex SSc fibroblast model.

Effect of Clinoptilolite and Sepiolite Nanoclays on Human and Parasitic Highly Phagocytic Cells

Nanoclays have potential applications in biomedicine raising the need to evaluate their toxicity in in vitro models as a first approach to its biocompatibility. In this study, in vitro toxicity of clinoptilolite and sepiolite nanoclays (NC) was analyzed in highly phagocytic cultures of amoebas and human and mice macrophages. While amebic viability was significantly affected only by sepiolite NC at concentrations higher than 0.1 mg/mL, the effect on macrophage cultures was dependent on the origin of the cells. Macrophages derived from human peripheral blood monocytes were less affected in viability (25% decrease at 48 h), followed by the RAW 264.7 cell line (40%), and finally, macrophages derived from mice bone marrow monocytes (98%). Moreover, the cell line and mice macrophages die mainly by necrosis, whereas human macrophages exhibit increased apoptosis. Cytokine expression analysis in media of sepiolite NC treated cultures showed a proinflammatory profile (INFγ, IL-1α, IL-8, and IL-6), in contrast with clinoptilolite NC that induced lees cytokines with concomitant production of IL-10. The results show that sepiolite NC is more toxic to amoebas and macrophages than clinoptilolite NC, mostly in a time and dose-dependent manner. However, the effect of sepiolite NC was comparable with talc powder suggesting that both NC have low cytotoxicity in vitro.

A secretomics analysis reveals major differences in the macrophage responses towards different types of carbon nanotubes

Certain types of carbon nanotubes (CNT) can evoke inflammation, fibrosis and mesothelioma in vivo, raising concerns about their potential health effects. It has been recently postulated that NLRP3 inflammasome activation is important in the CNT-induced toxicity. However, more comprehensive studies of the protein secretion induced by CNT can provide new information about their possible pathogenic mechanisms. Here, we studied protein secretion from human macrophages with a proteomic approach in an unbiased way. Human monocyte-derived macrophages (MDM) were exposed to tangled or rigid, long multi-walled CNT (MWCNT) or crocidolite asbestos for 6 h. The growth media was concentrated and secreted proteins were analyzed using 2D-DIGE and DeCyder software. Subsequently, significantly up- or down-regulated protein spots were in-gel digested and identified with an LC-MS/MS approach. Bioinformatics analysis was performed to reveal the different patterns of protein secretion induced by these materials. The results show that both long rigid MWCNT and asbestos elicited ample and highly similar protein secretion. In contrast, exposure to long tangled MWCNT induced weaker protein secretion with a more distinct profile. Secretion of lysosomal proteins followed the exposure to all materials, suggesting lysosomal damage. However, only long rigid MWCNT was associated with apoptosis. This analysis suggests that the CNT toxicity in human MDM is mediated via vigorous secretion of inflammation-related proteins and apoptosis. This study provides new insights into the mechanisms of toxicity of high aspect ratio nanomaterials and indicates that not all types of CNT are as hazardous as asbestos fibers.

Impact of Age and Autoantibody Status on the Gene Expression of Scleroderma Fibroblasts in Response to Silica Stimulation

Environmental factors are believed to play an important role in the pathogenesis of systemic sclerosis (SSc). Silica exposure has been implicated as potentially hazardous in epidemiological studies of SSc. It can activate fibroblasts to express profibrotic genes at certain conditions. The aim of this study is to examine whether the fibroblasts of SSc patients respond to silica particles with specific gene expressions differentially from normal control fibroblasts. The fibroblasts obtained from skin biopsies of 96 SSc patients and 104 controls were examined. Silica particles were used to perturb the cultures of the fibroblasts in time-course and dose-response assays. The transcript levels of COLI A2, COL3A1, MMP1, MMP3, TIMP3 and CTGF genes of the fibroblasts were measured with quantitative RT-PCR. The results showed that the expressions of all six genes in SSc fibroblasts under silica perturbation appeared significantly different from normal control fibroblasts. In age stratified analysis, compared to control fibroblasts, SSc fibroblasts from patients at age 30–40 years and 50–60 years displayed significantly decreased expressions of MMP1 gene in all dosage assays and increased expression of COL3A1 genes started at low dosages perturbation of silica particles, respectively. In autoantibody stratified analysis, specific gene expression patterns were significantly associated with autoantibody-subgroups of fibroblasts. A common feature of SSc fibroblasts was unstable and a wide range of gene expression changes in response to silica perturbation. Our studies may suggest an altered intrinsic dynamic control in SSc fibroblasts. In addition, sensitivity and specificity of SSc fibroblasts to potentially hazardous environmental trigger is age and autoantibody-subgroup-dependent. The fibroblasts of SSc patients at age 30–60 years may be more sensitive to silica perturbation toward a profibrotic gene expression.

Activation of Egr-1 in human lung epithelial cells exposed to silica through MAPKs signaling pathways

The alveolar type II epithelial cell, regarded historically as a key target cell in initial injury by silica, now appears to be important in both defense from lung damage as well as elaboration of chemokines and cytokines. The molecular basis for silica-induced epithelial cell injury is poorly understood. In this study we explored the activation of nuclear factor Egr-1 and related signal pathway. Human II alveolar epithelial line A549 cells were exposed to silica for indicated time to assay the expression and activation of Egr-1 and upstream MAPKs. Immunofluorescence, western-blot techniques, RT-PCR, Electrophoretic mobility shift assay (EMSA), transient transfection assay, kinase inhibitor experiments were performed. It was found that the expression of Egr-1 at mRNA and protein level was significantly increased in A549 cells after administration with silica and the activity of Egr-1 peaked by silica treatment for 60 minutes. Furthermore, phosphorylated-ERK1/2, P38 MAPKs (the upstream kinase of Egr-1) ballooned during 15-30minutes, 30-60minutes respectively after silica exposure in A549 cells. By administration of ERK1/2, P38 inhibitor, the expression and transcription of Egr-1 were both markedly decreased. But PKC inhibitor did not prevent the increase of Egr-1. These results indicated Egr-1 played a critical role in silica-induced pulmonary fibrosis in an ERK1/2, P38 MAPKs-dependent manner, which suggests Egr-1 is an essential regulator in silicosis, and underlines a new molecular mechanism for fibrosis induced by silica.

Mechanical & cell culture properties of elastin-like polypeptide, collagen, bioglass, and carbon nanosphere composites

Collagen, the most commonly used extra-cellular matrix protein for tissue engineering applications, displays poor mechanical properties. Here, we report on the preparation and characterization of novel multi-component composite systems that incorporate a genetically engineered, biocompatible polymer (elastin-like polypeptide, ELP), biodegradable ceramic (45S5 bioglass), carbon nanosphere chains (CNSC), and minimal amount (~25% w/w) of collagen. We hypothesized that incorporation of bioglass and CNSC would improve mechanical properties of the composites. Our results showed that the tensile strength and elastic modulus nearly doubled after addition of the bioglass and CNSC compared to the control ELP-collagen hydrogels. Further, MC3T3-E1 pre-osteoblasts were cultured within the composite hydrogels and a thorough biochemical and morphological characterization was performed. Live/dead assay confirmed high cell viability (>95%) for all hydrogels by day 21 of culture. Alkaline phosphatase (ALP) activity and osteocalcin (OCN) production assessed the pre-osteoblast differentiation. Normalized ALP activity was highest for the cells cultured within ELP-bioglass-collagen hydrogels, while normalized OCN production was equivalent for all hydrogels. Alizarin red staining confirmed the mineral deposition by the cells within all hydrogels. Thus, the multi-component composite hydrogels displayed improved mechanical and cell culture properties and may be suitable scaffold materials for bone tissue engineering.