Gene Profiling of Normal Human Bronchial Epithelial Cells in Response to Asbestos and Benzo(a)pyrene diol epoxide (BPDE)

Crystalline silica-exposed human lung epithelial cells presented enhanced anchorage-independent growth with upregulated expression of BRD4 and EZH2 in autocrine and paracrine manners

Crystalline silica-induced inflammation possibly facilitates carcinogenesis. Here, we investigated its effect on lung epithelium damage. We prepared conditioned media of immortalized human bronchial epithelial cell lines (hereinafter bronchial cell lines) NL20, BEAS-2B, and 16HBE14o- pre-exposed to crystalline silica (autocrine crystalline silica conditioned medium), a phorbol myristate acetate-differentiated THP-1 macrophage line, and VA13 fibroblast line pre-exposed to crystalline silica (paracrine crystalline silica conditioned medium). As cigarette smoking imposes a combined effect on crystalline silica-induced carcinogenesis, a conditioned medium was also prepared using the tobacco carcinogen benzo[a]pyrene diol epoxide. Crystalline silica-exposed and growth-suppressed bronchial cell lines exhibited enhanced anchorage-independent growth in autocrine crystalline silica and benzo[a]pyrene diol epoxide conditioned medium compared with that in unexposed control conditioned medium. Crystalline silica-exposed nonadherent bronchial cell lines in autocrine crystalline silica and benzo[a]pyrene diol epoxide conditioned medium showed increased expression of cyclin A2, cdc2, and c-Myc, and of epigenetic regulators and enhancers, BRD4 and EZH2. Paracrine crystalline silica and benzo[a]pyrene diol epoxide conditioned medium also accelerated the growth of crystalline silica-exposed nonadherent bronchial cell lines. Culture supernatants of nonadherent NL20 and BEAS-2B in crystalline silica and benzo[a]pyrene diol epoxide conditioned medium had higher EGF concentrations, whereas those of nonadherent 16HBE14o- had higher TNF-α levels. Recombinant human EGF and TNF-α promoted anchorage-independent growth in all lines. Treatment with EGF and TNF-α neutralizing antibodies inhibited cell growth in crystalline silica conditioned medium. Recombinant human TNF-α induced BRD4 and EZH2 expression in nonadherent 16HBE14o-. The expression of γH2AX occasionally increased despite PARP1 upregulation in crystalline silica-exposed nonadherent lines with crystalline silica and benzo[a]pyrene diol epoxide conditioned medium. Collectively, crystalline silica- and benzo[a]pyrene diol epoxide-induced inflammatory microenvironments comprising upregulated EGF or TNF-α expression may promote crystalline silica-damaged nonadherent bronchial cell proliferation and oncogenic protein expression despite occasional γH2AX upregulation. Thus, carcinogenesis may be cooperatively aggravated by crystalline silica-induced inflammation and genotoxicity.

The Potential Importance of CXCL1 in the Physiological State and in Noncancer Diseases of the Cardiovascular System, Respiratory System and Skin

In this paper, we present a literature review of the role of CXC motif chemokine ligand 1 (CXCL1) in physiology, and in selected major non-cancer diseases of the cardiovascular system, respiratory system and skin. CXCL1, a cytokine belonging to the CXC sub-family of chemokines with CXC motif chemokine receptor 2 (CXCR2) as its main receptor, causes the migration and infiltration of neutrophils to the sites of high expression. This implicates CXCL1 in many adverse conditions associated with inflammation and the accumulation of neutrophils. The aim of this study was to describe the significance of CXCL1 in selected diseases of the cardiovascular system (atherosclerosis, atrial fibrillation, chronic ischemic heart disease, hypertension, sepsis including sepsis-associated encephalopathy and sepsis-associated acute kidney injury), the respiratory system (asthma, chronic obstructive pulmonary disease (COPD), chronic rhinosinusitis, coronavirus disease 2019 (COVID-19), influenza, lung transplantation and ischemic-reperfusion injury and tuberculosis) and the skin (wound healing, psoriasis, sunburn and xeroderma pigmentosum). Additionally, the significance of CXCL1 is described in vascular physiology, such as the effects of CXCL1 on angiogenesis and arteriogenesis.

Synergistic effects of sulfur dioxide and polycyclic aromatic hydrocarbons on pulmonary pro-fibrosis via mir-30c-1-3p/ transforming growth factor β type II receptor axis

SO₂ and PAHs are well-known pollutants of coal burning and significant contributors to haze episodes. The purpose of the study is to determine whether the combined effects of SO₂ and BaP are synergetic and to investigate the pro-fibrotic influences and possible mechanism from the aspect of microRNAs. In the present study cellular metabolic activity of BEAS-2B was assessed using MTT probe. C57BL/6 mice were exposed to BaP (40 mg/kg b.w.) for 5 days or SO₂ (7 mg/m³) inhalation for 4 weeks alone or together. Lung tissues were processed for histology to assess pulmonary fibrosis. The protein level of pulmonary pro-fibrotic genes (Col1a1, Col3a1, alpha-SMA, fibronectin) and TGFβR2 were analyzed by Western blot and immunofluorescence in vivo and in vitro. Furthermore, we clarified that the microRNA expression of mir-30c-1-3p by real-time RT-PCR. The luciferase reporter assay was used to determine the binding sites of mir-30c-1-3p in the 3'-UTR of TGFβR2. It was confirmed that SO₂ and BaP acted together to produce synergistic effects in cellular metabolic activity. Coexisting of SO₂ and BaP increased the protein expression of pro-fibrotic genes and TGFβR2 and decreased mir-30c-1-3p in vivo and in vitro. Dual-luciferase reporter gene assays showed that TGFβR2 was a validated target of mir-30c-1-3p. All above results demonstrated that mir-30c-1-3p was involved in the synergistic pro-fibrotic effects of SO₂ and BaP in lung via targeting TGFβR2. This work implies the potential risk of pulmonary fibrosis from the co-existence of SO₂ and PAHs and provides new insights into the molecular markers for relevant diseases.

Secondhand Smoke-Prevalent Polycyclic Aromatic Hydrocarbon Binary Mixture-Induced Specific Mitogenic and Pro-inflammatory Cell Signaling Events in Lung Epithelial Cells

Low molecular weight polycyclic aromatic hydrocarbons (LMW PAHs; < 206.3 g/mol) are prevalent and ubiquitous environmental contaminants, presenting a human health concern, and have not been as thoroughly studied as the high MW PAHs. LMW PAHs exert their pulmonary effects, in part, through P38-dependent and -independent mechanisms involving cell-cell communication and the production of pro-inflammatory mediators known to contribute to lung disease. Specifically, we determined the effects of two representative LMW PAHs, 1-methylanthracene (1-MeA) and fluoranthene (Flthn), individually and as a binary PAH mixture on the dysregulation of gap junctional intercellular communication (GJIC) and connexin 43 (Cx43), activation of mitogen activated protein kinases (MAPK), and induction of inflammatory mediators in a mouse non-tumorigenic alveolar type II cell line (C10). Both 1-MeA, Flthn, and the binary PAH mixture of 1-MeA and Flthn dysregulated GJIC in a dose and time-dependent manner, reduced Cx43 protein, and activated the following MAPKs: P38, ERK1/2, and JNK. Inhibition of P38 MAPK prevented PAH-induced dysregulation of GJIC, whereas inhibiting ERK and JNK did not prevent these PAHs from dysregulating GJIC indicating a P38-dependent mechanism. A toxicogenomic approach revealed significant P38-dependent and -independent pathways involved in inflammation, steroid synthesis, metabolism, and oxidative responses. Genes in these pathways were significantly altered by the binary PAH mixture when compared with 1-MeA and Flthn alone suggesting interactive effects. Exposure to the binary PAH mixture induced the production and release of cytokines and metalloproteinases from the C10 cells. Our findings with a binary mixture of PAHs suggest that combinations of LMW PAHs may elicit synergistic or additive inflammatory responses which warrant further investigation and confirmation.

Using Immunotoxicity Information to Improve Cancer Risk Assessment for Polycyclic Aromatic Hydrocarbon Mixtures

Estimating cancer risk from environmental mixtures containing polycyclic aromatic hydrocarbons (PAHs) is challenging. Ideally, each mixture would undergo toxicity testing to derive a cancer slope factor (CSF) for use in site-specific cancer risk assessments. However, this whole mixture approach is extremely costly in terms of finances, time, and animal usage. Alternatively, if an untested mixture is “sufficiently similar” to a well-characterized mixture with a CSF, the “surrogate” CSF can be used in risk assessments. We propose that similarity between 2 mixtures could be established using an in vitro battery of genotoxic and nongenotoxic tests. An observed association between carcinogenicity and immunosuppression of PAHs suggests that the addition of immune suppression assays may improve this battery. First, using published studies of benzo[a]pyrene (BaP) and other PAHs, we demonstrated a correlation between the derived immune suppression relative potency factors (RPFs) for 9 PAHs and their respective cancer RPFs, confirming observations published previously. Second, we constructed an integrated knowledge map for immune suppression by BaP based on the available mechanistic information. The map illustrates the mechanistic complexities involved in BaP immunosuppression, suggesting that multiple in vitro tests of immune suppression involving different processes, cell types, and tissues will have greater predictive value for immune suppression in vivo than a single test. Based on these observations, research strategies are recommended to validate a battery of in vitro immune suppression tests that, along with tests for genotoxic and other nongenotoxic modes of cancer action, could be used to establish “sufficient similarity” of 2 mixtures for site-specific cancer risk assessments.

Effect of calcium phosphate particle shape and size on their antibacterial and osteogenic activity in the delivery of antibiotics in vitro

Powders composed of four morphologically different calcium phosphate particles were prepared by precipitation from aqueous solutions: flaky, brick-like, elongated orthogonal, and spherical. The particles were then loaded with either clindamycin phosphate as the antibiotic of choice or fluorescein, a model molecule used to assess the drug release properties. A comparison was carried out of the effect of such antibiotic-releasing materials on: sustained drug release profiles; Staphylococcus aureus growth inhibition; and osteogenic propensities in vitro. Raman spectroscopic analysis indicated the presence of various calcium phosphate phases, including monetite (flaky and elongated orthogonal particles), octacalcium phosphate (brick-shaped particles), and hydroxyapatite (spherical particles). Testing the antibiotic-loaded calcium phosphate powders for bacterial growth inhibition demonstrated satisfying antibacterial properties both in broths and on agar plates. All four calcium-phosphate-fluorescein powders exhibited sustained drug release over 21 days. The calcium phosphate sample with the highest specific surface area and the smallest, spherical particle size was the most effective in both drug loading and release, consequently having the highest antibacterial efficiency. Moreover, the highest cell viability, the largest gene expression upregulation of three different osteogenic markers--osteocalcin, osteopontin, and Runx2--as well as the least disrupted cell cytoskeleton and cell morphologies were also noticed for the calcium phosphate powder composed of the smallest, spherical nanosized particles. Still, all four powders exerted a viable effect on osteoblastic MC3T3-E1 cells in vitro, as evidenced by both morphological assessments on fluorescently stained cells and measurements of their mitochondrial activity. The obtained results suggest that the nanoscale particle size and the corresponding coarseness of the surface of particle conglomerates as the cell attachment points may present a favorable starting point for the development of calcium-phosphate-based osteogenic drug delivery devices.

Molecular basis of asbestos-induced lung disease

Asbestos causes asbestosis and malignancies by molecular mechanisms that are not fully understood. The modes of action underlying asbestosis, lung cancer, and mesothelioma appear to differ depending on the fiber type, lung clearance, and genetics. After reviewing the key pathologic changes following asbestos exposure, we examine recently identified pathogenic pathways, with a focus on oxidative stress. Alveolar epithelial cell apoptosis, which is an important early event in asbestosis, is mediated by mitochondria- and p53-regulated death pathways and may be modulated by the endoplasmic reticulum. We review mitochondrial DNA (mtDNA)-damage and -repair mechanisms, focusing on 8-oxoguanine DNA glycosylase, as well as cross talk between reactive oxygen species production, mtDNA damage, p53, OGG1, and mitochondrial aconitase. These new insights into the molecular basis of asbestos-induced lung diseases may foster the development of novel therapeutic targets for managing degenerative diseases (e.g., asbestosis and idiopathic pulmonary fibrosis), tumors, and aging, for which effective management is lacking.

Low-dose gamma-irradiation inhibits IL-6 secretion from human lung fibroblasts that promotes bronchial epithelial cell transformation by cigarette-smoke carcinogen

Despite decades of research in defining the health effects of low-dose (<100 mGy) ionizing photon radiation (LDR), the relationship between LDR and human cancer risk remains elusive. Because chemical carcinogens modify the tumor microenvironment, which is critical for cancer development, we investigated the role and mechanism of LDR in modulating the response of stromal cells to chemical carcinogen-induced lung cancer development. Secretion of proinflammatory cytokines such as interleukin-6 (IL-6), CXCL1 and CXCL5 from human lung fibroblasts was induced by cigarette-smoke carcinogen benzo[a]pyrene diol epoxide (BPDE), which was inhibited by a single dose of LDR. The activation of NF-κB, which is important for BPDE-induced IL-6 secretion, was also effectively suppressed by LDR. In addition, conditioned media from BPDE-treated fibroblasts activated STAT3 in the immortalized normal human bronchial epithelial cell line Beas-2B, which was blocked with an IL-6 neutralizing antibody. Conditioned medium from LDR-primed and BPDE-treated fibroblast showed diminished capacity in activating STAT3. Furthermore, IL-6 enhanced BPDE-induced Beas-2B cell transformation in vitro. These results suggest that LDR inhibits cigarette smoke-induced lung carcinogenesis by suppressing secretion of cytokines such as IL-6 from fibroblasts in lung tumor-prone microenvironment.

Differences in gene expression and cytokine production by crystalline vs. amorphous silica in human lung epithelial cells

Background

Exposure to respirable crystalline silica particles, as opposed to amorphous silica, is associated with lung inflammation, pulmonary fibrosis (silicosis), and potentially with lung cancer. We used Affymetrix/GeneSifter microarray analysis to determine whether gene expression profiles differed in a human bronchial epithelial cell line (BEAS 2B) exposed to cristobalite vs. amorphous silica particles at non-toxic and equal surface areas (75 and 150 × 10⁶μm²/cm²). Bio-Plex analysis was also used to determine profiles of secreted cytokines and chemokines in response to both particles. Finally, primary human bronchial epithelial cells (NHBE) were used to comparatively assess silica particle-induced alterations in gene expression.

Results

Microarray analysis at 24 hours in BEAS 2B revealed 333 and 631 significant alterations in gene expression induced by cristobalite at low (75) and high (150 × 10⁶μm²/cm²) amounts, respectively (p < 0.05/cut off ≥ 2.0-fold change). Exposure to amorphous silica micro-particles at high amounts (150 × 10⁶μm²/cm²) induced 108 significant gene changes. Bio-Plex analysis of 27 human cytokines and chemokines revealed 9 secreted mediators (p < 0.05) induced by crystalline silica, but none were induced by amorphous silica. QRT-PCR revealed that cristobalite selectively up-regulated stress-related genes and cytokines (FOS, ATF3, IL6 and IL8) early and over time (2, 4, 8, and 24 h). Patterns of gene expression in NHBE cells were similar overall to BEAS 2B cells. At 75 × 10⁶μm²/cm², there were 339 significant alterations in gene expression induced by cristobalite and 42 by amorphous silica. Comparison of genes in response to cristobalite (75 × 10⁶μm²/cm²) revealed 60 common, significant gene alterations in NHBE and BEAS 2B cells.

Conclusions

Cristobalite silica, as compared to synthetic amorphous silica particles at equal surface area concentrations, had comparable effects on the viability of human bronchial epithelial cells. However, effects on gene expression, as well as secretion of cytokines and chemokines, drastically differed, as the crystalline silica induced more intense responses. Our studies indicate that toxicological testing of particulates by surveying viability and/or metabolic activity is insufficient to predict their pathogenicity. Moreover, they show that acute responses of the lung epithelium, including up-regulation of genes linked to inflammation, oxidative stress, and proliferation, as well as secretion of inflammatory and proliferative mediators, can be indicative of pathologic potential using either immortalized lines (BEAS 2B) or primary cells (NHBE). Assessment of the degree and magnitude of these responses in vitro are suggested as predictive in determining the pathogenicity of potentially harmful particulates.

Role of mutagenicity in asbestos fiber-induced carcinogenicity and other diseases

The cellular and molecular mechanisms of how asbestos fibers induce cancers and other diseases are not well understood. Both serpentine and amphibole asbestos fibers have been shown to induce oxidative stress, inflammatory responses, cellular toxicity and tissue injuries, genetic changes, and epigenetic alterations in target cells in vitro and tissues in vivo. Most of these mechanisms are believe to be shared by both fiber-induced cancers and noncancerous diseases. This article summarizes the findings from existing literature with a focus on genetic changes, specifically, mutagenicity of asbestos fibers. Thus far, experimental evidence suggesting the involvement of mutagenesis in asbestos carcinogenicity is more convincing than asbestos-induced fibrotic diseases. The potential contributions of mutagenicity to asbestos-induced diseases, with an emphasis on carcinogenicity, are reviewed from five aspects: (1) whether there is a mutagenic mode of action (MOA) in fiber-induced carcinogenesis; (2) mutagenicity/carcinogenicity at low dose; (3) biological activities that contribute to mutagenicity and impact of target tissue/cell type; (4) health endpoints with or without mutagenicity as a key event; and finally, (5) determinant factors of toxicity in mutagenicity. At the end of this review, a consensus statement of what is known, what is believed to be factual but requires confirmation, and existing data gaps, as well as future research needs and directions, is provided.

Benzopyrene and experimental stressors cause compensatory differentiation in placental trophoblast stem cells

Stress causes decreased cell accumulation in early periimplantation embryos and the placental trophoblast stem cells derived from them. Benzopyrene and many other stressors activate stress enzymes that lead to suppressed stem cell accumulation through diminished proliferation and increased apoptosis. Trophoblast stem cells proliferate and a subpopulation of early postimplantation trophoblast cells differentiate to produce the first placental hormones that arise in the implanting conceptus. These hormones mediate antiluteolytic effects that enable the continuation of a successful implantation. The normal determination and differentiation of placental trophoblast stem cells is dependent upon a series of transcription factors. But, these transcription factors can also be modulated by stress through the activity of stress enzymes. This review enumerates and analyzes recent reports on the effects of benzopyrene on placental function in terms of the emerging paradigm that placental differentiation from stem cells can be regulated when insufficient production of stem cells is caused by stress. In addition, we review the other effects caused by benzopyrene throughout placental development.

Benzo[a]pyrene diol epoxide stimulates an inflammatory response in normal human lung fibroblasts through a p53 and JNK mediated pathway

Cellular responses to carcinogens are typically studied in transformed cell lines, which do not reflect the physiological status of normal tissues. To address this question, we have characterized the transcriptional program and cellular responses of human lung WI-38 fibroblasts upon exposure to the ultimate carcinogen benzo[a]pyrene diol epoxide (BPDE). In contrast to observations in cell lines, we find that BPDE treatment induces a strong inflammatory response in these normal fibroblasts. Whole-genome microarrays show induction of numerous inflammatory factors, including genes that encode interleukins (ILs), growth factors and enzymes related to prostaglandin synthesis and signaling. Real-time reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA) revealed a time- and dose-dependent-induced expression and production of cyclooxygenase 2, prostglandin E2 and IL1B, IL6 and IL8. In parallel, cell cycle progression and DNA repair processes were repressed, but DNA damage signaling was increased via p53-Ser15 phosphorylation and induced expression levels of GADD45A, CDKN1A, BTG2 and SESN1. Network analysis suggested that activator protein 1 transcription factors may link the cell cycle response and DNA damage signaling with the inflammatory stress-response in these cells. We confirmed this hypothesis by showing that p53-dependent signaling through c-jun N-terminal kinase (JNK) led to increased cJun-Ser63 phosphorylation and that inhibition of JNK-mediated cJun activation using p53- or JNK-specific inhibitors significantly reduced IL gene expression and subsequent production of IL8. This is the first demonstration that a strong inflammatory response is triggered in normal fibroblasts by BPDE and that this occurs through coordinated regulation with other cellular processes.

Temporal gene expression changes induced by a low concentration of benzo[a]pyrene diol epoxide in a normal human cell line

(+ or -)-anti-Benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE), which causes bulky-adduct DNA damage, is well-characterized as the ultimate carcinogen of benzo[a]pyrene (BaP). In this study, we have employed Affymetrix HG-U133 Plus 2.0 microarray and quantitative real-time RT-PCR methods to investigate a temporal transcriptomic response triggered by a low concentration (0.05 microM) of BPDE at 1, 10, and 22 h after exposure in normal human cells. The differential gene expression profiles at the three time points varied greatly, and generally reflected a cellular responsive process from initiation to progression and to recovery after the BPDE-caused damage. The dynamic regulation of the genes related with cell cycle progression and cell fate exhibited a tendency from inhibition to survival, which was accordant with the cell cycle arrest and cytotoxicity data induced by the low-dose BPDE exposure. In silico comparison of the genomic data revealed that BPDE and ultraviolet induced a panel of common transcriptional responses, which might be related with a series of similar molecular processes elicited by these two DNA-damaging agents. In conclusion, this whole-genome time-course study has identified a dynamically regulated transcriptional signature after low-dose BPDE exposure, which may help to understand the complex mechanisms of mutagenesis and carcinogenesis induced by BPDE.

Utilization of gene profiling and proteomics to determine mineral pathogenicity in a human mesothelial cell line (LP9/TERT-1)

Identifying and understanding the early molecular events that underscore mineral pathogenicity using in vitro screening tests is imperative, especially given the large number of synthetic and natural fibers and particles being introduced into the environment. The purpose of the work described here was to examine the ability of gene profiling (Affymetrix microarrays) to predict the pathogenicity of various materials in a human mesothelial cell line (LP9/TERT-1) exposed to equal surface area concentrations (15 x 10(6) or 75 x 10(6) microm(2)/cm(2)) of crocidolite asbestos, nonfibrous talc, fine titanium dioxide (TiO(2)), or glass beads for 8 or 24 h. Since crocidolite asbestos caused the greatest number of alterations in gene expression, multiplex analysis (Bio-Plex) of proteins released from LP9/TERT-1 cells exposed to crocidolite asbestos was also assessed to reveal if this approach might also be explored in future assays comparing various mineral types. To verify that LP9/TERT-1 cells were more sensitive than other cell types to asbestos, human ovarian epithelial cells (IOSE) were also utilized in microarray studies. Upon assessing changes in gene expression via microarrays, principal component analysis (PCA) of these data was used to identify patterns of differential gene expression. PCA of microarray data confirmed that LP9/TERT-1 cells were more responsive than IOSE cells to crocidolite asbestos or nonfibrous talc, and that crocidolite asbestos elicited greater responses in both cell types when compared to nonfibrous talc, TiO(2), or glass beads. Bio-Plex analysis demonstrated that asbestos caused an increase in interleukin-13 (IL-13), basic fibroblast growth factor (bFGF), granulocyte colony-stimulating factor (G-CSF), and vascular endothelial growth factor (VEGF). These responses were generally dose-dependent (bFGF and G-CSF only) and tumor necrosis factor (TNF)-alpha independent (except for G-CSF). Thus, microarray and Bio-Plex analyses are valuable in determining early molecular responses to fibers/particles and may directly contribute to understanding the etiology of diseases caused by them. The number and magnitude of changes in gene expression or "profiles" of secreted proteins may serve as valuable metrics for determining the potential pathogenicity of various mineral types. Hence, alterations in gene expression and cytokine/chemokine changes induced by crocidolite asbestos in LP9/TERT-1 cells may be indicative of its increased potential to cause mesothelioma in comparison to the other nonfibrous materials examined.