STAT-1 signaling in human lung fibroblasts is induced by vanadium pentoxide through an IFN-beta autocrine loop

Metabolic alterations and mitochondrial dysfunction in human airway BEAS-2B cells exposed to vanadium pentoxide

Vanadium pentoxide (V+5) is a hazardous material that has drawn considerable attention due to its wide use in industrial sectors and increased release into environment from human activities. It poses potential adverse effects on animals and human health, with pronounced impact on lung physiology and functions. In this study, we investigated the metabolic response of human bronchial epithelial BEAS-2B cells to low-level V+5 exposure (0.01, 0.1, and 1 ppm) using liquid chromatography-high resolution mass spectrometry (LC-HRMS). Exposure to V+5 caused extensive changes to cellular metabolism in BEAS-2B cells, including TCA cycle, glycolysis, fatty acids, amino acids, amino sugars, nucleotide sugar, sialic acid, vitamin D3, and drug metabolism, without causing cell death. Altered mitochondrial structure and function were observed with as low as 0.01 ppm (0.2 μM) V+5 exposure. In addition, decreased level of E-cadherin, the prototypical epithelial marker of epithelial-mesenchymal transition (EMT), was observed following V+5 treatment, supporting potential toxicity of V+5 at low levels. Taken together, the present study shows that V+5 has adverse effects on mitochondria and the metabolome which may result in EMT activation in the absence of cell death. Furthermore, results suggest that high-resolution metabolomics could serve as a powerful tool to investigate metal toxicity at levels which do not cause cell death.

Low-dose vanadium pentoxide perturbed lung metabolism associated with inflammation and fibrosis signaling in male animal and in vitro models

Vanadium is available as a dietary supplement and also is known to be toxic if inhaled, yet little information is available concerning the effects of vanadium on mammalian metabolism when concentrations found in food and water. Vanadium pentoxide (V+5) is representative of the most common dietary and environmental exposures, and prior research shows that low-dose V+5 exposure causes oxidative stress measured by glutathione oxidation and protein S-glutathionylation. We examined the metabolic impact of V+5 at relevant dietary and environmental doses (0.01, 0.1, and 1 ppm for 24 h) in human lung fibroblasts (HLFs) and male C57BL/6J mice (0.02, 0.2, and 2 ppm in drinking water for 7 mo). Untargeted metabolomics using liquid chromatography-high-resolution mass spectrometry (LC-HRMS) showed that V+5 induced significant metabolic perturbations in both HLF cells and mouse lungs. We noted 30% of the significantly altered pathways in HLF cells, including pyrimidines and aminosugars, fatty acids, mitochondrial and redox pathways, showed similar dose-dependent patterns in mouse lung tissues. Alterations in lipid metabolism included leukotrienes and prostaglandins involved in inflammatory signaling, which have been associated with the pathogenesis of idiopathic pulmonary fibrosis (IPF) and other disease processes. Elevated hydroxyproline levels and excessive collagen deposition were also present in lungs from V+5-treated mice. Taken together, these results show that oxidative stress from environmental V+5, ingested at low levels, could alter metabolism to contribute to common human lung diseases.NEW & NOTEWORTHY We used relevant dietary and environmental doses of Vanadium pentoxide (V+5) to examine its metabolic impact in vitro and in vivo. Using liquid chromatography-high-resolution mass spectrometry (LC-HRMS), we found significant metabolic perturbations, with similar dose-dependent patterns observed in human lung fibroblasts and male mouse lungs. Alterations in lipid metabolism included inflammatory signaling, elevated hydroxyproline levels, and excessive collagen deposition were present in V+5-treated lungs. Our findings suggest that low levels of V+5 could trigger pulmonary fibrotic signaling.

Gene Expression in Bronchial Epithelial Cell Responses to Vanadium Exposure

Vanadium exposure has the adverse effect on lung function in human, whereas the detailed mechanisms of vanadium exposure-induced pulmonary toxicity are limited. Hence, the present study aimed to investigate the hub genes and signaling pathways related to sodium metavanadate (SMV)-induced pulmonary toxicity. The transcript expression profile GSE36684 downloaded from Gene Expression Omnibus contained eight human bronchial epithelial cell (HBEC) samples including five SMV-treated and three control HBEC samples. Totally 455 differentially expressed genes (DEGs) were screened, especially 201 and 254 genes were up- and down-regulated in the HBECs treated with SMV. Gene ontology analysis suggested that the DEGs were mainly involved in signal transduction, the response to drug, cell proliferation, adhesion, and migration. Pathway analysis demonstrated that the DEGs were primarily participated in NF-κB, Wnt, MAPK, and PI3K-Akt signaling pathways. Moreover, the hub genes, including ITGA5, ITGB3, ITGA2, LAMC2, MMP2, and ITGA4, might contribute to SMV-induced pulmonary toxicity. Our study improves the understanding of the molecular mechanisms by which SMV induced the pulmonary toxicity.

Potential mechanisms of some selected heavy metals in the induction of inflammation and autoimmunity

Inflammation is a physiological event that protects tissues from infection and injury. Chronic inflammation causes immune cell over activation and sustained release of inflammatory cytokines and chemokines cause pathologic conditions including autoimmune diseases. Heavy metals exposure affects innate and adaptive immune systems through triggering inflammatory responses. It seems that extended inflammatory responses could accelerate heavy metal-induced autoimmunity. In the present review we discuss the exposure route and toxicity of Cadmium (Cd), Lead (Pb), Mercury (Hg), Vanadium (V) and Platinum (Pt) and their effects on inflammatory responses by innate and adaptive immune system and autoimmunity.

VAOS, a novel vanadyl complexes of alginate saccharides, inducing apoptosis via activation of AKT-dependent ROS production in NSCLC

Previous studies have confirmed that protein tyrosine phosphatase 1B (PTP1B) can promote tumour progression in non-small cell lung cancer (NSCLC). Vanadyl alginate oligosaccharides (VAOS) is a new coordination compounds that possesses a good PTP1B inhibitory activity. However, the potent anticancer efficacy of VAOS in human NSCLC requires further study. In this study, VAOS exhibited effective inhibitory effects in NSCLC both in cultured cells and in a xenograft mouse model. VAOS was further identified to induce NSCLC cell apoptosis through activating protein kinase B (AKT) to elevate intracellular reactive oxygen species (ROS) levels by increasing in oxygen consumption and impairing the ROS-scavenging system. Neither silencing of PTP1B by siRNA nor transient overexpression of PTP1B had an effect on the AKT phosphorylation triggered by VAOS, indicating that PTP1B inhibition was not involved in VAOS-induced apoptosis. Through phosphorus colorimetric assay, we demonstrated that VAOS notably inhibited phosphatase and tensin homologue deleted on chromosome 10 (PTEN) dephosphorylation activity, another member of the protein tyrosine phosphatases (PTPases)-upstream factor of AKT. Interestingly, PTEN knockdown sensitized cells to VAOS, whereas ectopic expression of PTEN markedly rescued VAOS-mediated lethality. In vivo, VAOS treatment markedly reduced PTEN activity and tumour cell burden with low systemic toxicity. Thus, our data not only provided a new therapeutic drug candidate for NSCLC, but presented new understanding into the pharmacological research of VAOS.

Activation of the interferon type I response rather than autophagy contributes to myogenesis inhibition in congenital DM1 myoblasts

Congenital myotonic dystrophy type 1 (CDM1) is characterized by severe symptoms that affect patients from birth, with 40% mortality in the neonatal period and impaired skeletal muscle development. In this paper, we examined the relationship between autophagy and abnormal myogenic differentiation of CDM1 myoblasts. We investigated these pathological features at both ultrastructural and molecular levels, utilizing two CDM1 foetal myoblasts, CDM13 and CDM15, with 1800 and 3200 repeats, respectively. The congenital nature of these CDM1 myoblasts was confirmed by the high methylation level at the DMPK locus. Our results indicated that abnormal autophagy was independent of myogenic differentiation, as CDM13 myoblasts differentiated as well as control myoblasts but underwent autophagy like CDM15, displaying impaired differentiation. miRNA expression profiles revealed that CDM15 myoblasts failed to upregulate the complex network of myo-miRNAs under MYOD and MEF2A control, while this network was upregulated in CDM13 myoblasts. Interestingly, the abnormal differentiation of CDM15 myoblasts was associated with cellular stress accompanied by the induction of the interferon type 1 pathway (innate immune response). Indeed, inhibition of the interferon (IFN) type I pathway restores myogenic differentiation of CDM15 myoblasts, suggesting that the inappropriate activation of the innate immune response might contribute to impaired myogenic differentiation and severe muscle symptoms observed in some CDM1 patients. These findings open up the possibility of new therapeutic approaches to treat CDM1.

Vanadate oxidative and apoptotic effects are mediated by the MAPK-Nrf2 pathway in layer oviduct magnum epithelial cells

Vanadium is a metal of high physiological, environmental and industrial importance. However, vanadium-induced oxidative stress can reduce the egg quality of poultry, and be potentially harmful to humans, and the underlying mechanism is not clear. In this study, we investigated the underlying relationship between the oxidant-sensitive mitogen-activated protein kinase (MAPK) signaling pathway and vanadium-induced oxidative stress in oviduct magnum epithelial (OME) cells. Cultured OME cells were treated with 100 μmol L^-1 vanadium and/or MAPK inhibitors [P38 MAPK inhibitor, SB203580; extracellular regulated protein kinase 1 and 2 (ERK1/2) inhibitor, U0126; c-JUN N-terminal kinases (JNK) inhibitor, SP600125]. Cell viability, apoptosis, and generation of reactive oxygen species (ROS) were assessed using flow cytometry. The expression of oxidative stress-related genes and their proteins was measured by reverse transcription-polymerase chain reaction and western blotting. Vanadium treatment reduced cell viability, whereas pretreated OME cells with SB203580 and U0126 prevented the reducing effect of vanadium on cell viability (P < 0.05). Likewise, MAPK inhibitors effectively suppressed vanadium-induced apoptosis and ROS generation (P < 0.05). In the OME cells treated with vanadium, SB203580 (P < 0.05) and SP600125 (P = 0.08) increased catalase activity by 89.3% and 55.3%; SB203580 and U0126 increased (P < 0.05) glutathione peroxidase activity by 44.9% and 51.1%, respectively. Incubation of OME cells with MAPK inhibitors also prevents malondialdehyde concentration increase and lactic dehydrogenase activity decrease in response to vanadium (P < 0.05). Vanadium downregulated P38, ERK1/2, JNK, Nrf2, sMaf, GCLC, NQO1 and HO-1 mRNA expression (P < 0.05). In contrast, inhibition of JNK with SP600125 upregulated P38, ERK1/2, JNK, Nrf2, GCLC and HO-1 mRNA expression (P < 0.05); inhibition of P38 with SB203580 upregulated JNK, NQO1 and HO-1 mRNA expression (P < 0.05); and inhibition of ERK1/2 with U0126 upregulated ERK1/2, GCLC and HO-1 mRNA expression (P < 0.05). Moreover, phosphorylation of P38, ERK1/2, JNK, and Nrf2 proteins was enhanced by V incubation; however, SP600125 blocked the phosphorylation of these proteins, whereas SB203580 blocked the phosphorylation of P38 and Nrf2. These results indicate that vanadium inducing oxidative stress in OME cells might be, at least, associated with the phosphorylation of the P38MAPK/JNK-Nrf2 pathway, which reduces the expression of phase II detoxifying enzymes.

CXCL8 and CXCL11 chemokine secretion in dermal fibroblasts is differentially modulated by vanadium pentoxide

An increase in skin rashes or atopic dermatitis has been observed in individuals working with vanadium. However, to the best of our knowledge no in vivo or in vitro studies have evaluated the effect of exposure to vanadium in dermal fibroblasts. Cells viability and proliferation were assessed by WST‑1 assay, cells were treated with increasing concentrations of V2O5 (1, 10 and 100 nM). CXCL8 and CXCL11 concentrations were measured in the supernatants using an ELISA assay. V2O5 was not observed as having a significant effect on dermal fibroblast's viability and proliferation. However, it was revealed that V2O5 was able to induce the secretion of CXCL8 and CXCL11 chemokines into dermal fibroblasts. V2O5 synergistically increased the effect of interferon (IFN)γ on CXCL11 secretion. In addition, V2O5 synergistically increased the effect of the tumor necrosis factor α on CXCL8 secretion and abolished the inhibitory effect of IFNγ. V2O5 induction of CXCL8 and CXCL11 chemokines may lead to the appearance and perpetuation of an inflammatory reaction into the dermal tissue. Further studies are required to evaluate dermal integrity and manifestations in subjects occupationally exposed, or living in polluted areas.

Differential modulation by vanadium pentoxide of the secretion of CXCL8 and CXCL11 chemokines in thyroid cells

Recently it has been hypothesized that vanadium serves a carcinogenic role in the thyroid. However, to date, no in vivo or in vitro studies have evaluated thyroid disruption in humans and/or animals following exposure to vanadium. The present study evaluated the effect of vanadium pentoxide (V2O5) on cell viability and proliferation, and chemokine (C‑X‑C motif) ligand (CXCL)8 and CXCL11 secretion in normal thyrocytes. The results demonstrated that V2O5 had no effect on thyroid follicular cell viability and proliferation. However, V2O5 was able to induce the secretion of CXCL8 and CXCL11 chemokines from thyrocytes. Notably, V2O5 synergistically increased the effect of the interferon (IFN)‑γ on CXCL11 secretion. In addition, V2O5 synergistically increased the effect of tumor necrosis factor‑α on CXCL8 secretion, and abolished the inhibitory effect of IFN‑γ. Overall this induction of CXCL8 and CXCL11 secretion may lead to the induction and perpetuation of an inflammatory reaction in the thyroid. Further studies are now required to evaluate thyroid function and nodule development in subjects who are occupationally exposed, or living in polluted areas.

Induction of Th1 chemokine secretion in dermal fibroblasts by vanadium pentoxide

Vanadium is a soft, silvery‑grey metal with a number of different oxidation states. The most common commercial form of vanadium is vanadium pentoxide (V2O5). All vanadium compounds are considered toxic. An increase in skin rashes has been observed in certain vanadium workers, including the development of atopic dermatitis. However, to the best of our knowledge, no prior in vivo or in vitro studies have evaluated the effect of vanadium exposure in human dermal fibroblasts. The present study evaluated the effect of V2O5 on proliferation and chemokine secretion in dermal fibroblasts. The results revealed that V2O5 had no significant effect on the viability or proliferation of fibroblasts, however it was able to induce the secretion of T‑helper (Th)1 chemokines from dermal fibroblasts, synergistically increasing the effect of important Th1 cytokines, including interferon‑γ and tumor necrosis factor‑α. Through these processes, V2O5 may lead to the induction and perpetuation of an inflammatory reaction in dermal tissue. The induction and perpetuation of inflammation in the dermis and the variety of involved candidate genes may be at the base of V2O5‑induced effects following occupational and environmental exposures. Further studies are necessary to evaluate dermal integrity and manifestations in subjects who are occupationally exposed, or living in polluted areas.

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.

Genetic susceptibility to interstitial pulmonary fibrosis in mice induced by vanadium pentoxide (V2O5)

Interstitial lung diseases (ILDs) are characterized by injury, inflammation, and scarring of alveoli, leading to impaired function. The etiology of idiopathic forms of ILD is not understood, making them particularly difficult to study due to the lack of appropriate animal models. Consequently, few effective therapies have emerged. We developed an inbred mouse model of ILD using vanadium pentoxide (V2O5), the most common form of a transition metal found in cigarette smoke, fuel ash, mineral ores, and steel alloys. Pulmonary responses to V2O5, including dose-dependent increases in lung permeability, inflammation, collagen content, and dysfunction, were significantly greater in DBA/2J mice compared to C57BL/6J mice. Inflammatory and fibrotic responses persisted for 4 mo in DBA/2J mice, while limited responses in C57BL/6J mice resolved. We investigated the genetic basis for differential responses through genetic mapping of V2O5-induced lung collagen content in BXD recombinant inbred (RI) strains and identified significant linkage on chromosome 4 with candidate genes that associate with V2O5-induced collagen content across the RI strains. Results suggest that V2O5 may induce pulmonary fibrosis through mechanisms distinct from those in other models of pulmonary fibrosis. These findings should further advance our understanding of mechanisms involved in ILD and thereby aid in identification of new therapeutic targets.

Regulation and activity of secretory leukoprotease inhibitor (SLPI) is altered in smokers

A hallmark of cigarette smoking is a shift in the protease/antiprotease balance, in favor of protease activity. However, it has recently been shown that smokers have increased expression of a key antiprotease, secretory leukoprotease inhibitor (SLPI), yet the mechanisms involved in SLPI transcriptional regulation and functional activity of SLPI remain unclear. We examined SLPI mRNA and protein secretion in differentiated nasal epithelial cells (NECs) and nasal lavage fluid (NLF) from nonsmokers and smokers and demonstrated that SLPI expression is increased in NECs and NLF from smokers. Transcriptional regulation of SLPI expression was confirmed using SLPI promoter reporter assays followed by chromatin immunoprecipitation. The role of STAT1 in regulating SLPI expression was further elucidated using WT and stat1(-/-) mice. Our data demonstrate that STAT1 regulates SLPI transcription in epithelial cells and slpi protein in the lungs of mice. Additionally, we reveal that NECs from smokers have increased STAT1 mRNA/protein expression. Finally, we demonstrate that SLPI contained in the nasal mucosa of smokers is proteolytically cleaved but retains functional activity against neutrophil elastase. These results demonstrate that smoking enhances expression of SLPI in NECs in vitro and in vivo, and that this response is regulated by STAT1. In addition, despite posttranslational cleavage of SLPI, antiprotease activity against neutrophil elastase is enhanced in smokers. Together, our findings show that SLPI regulation and activity is altered in the nasal mucosa of smokers, which could have broad implications in the context of respiratory inflammation and infection.

Effect of IFN-α on KC and LIX expression: role of STAT1 and its effect on neutrophil recruitment to the spleen after lipopolysaccharide stimulation

The spleen is a crucial lymphoid organ. It is involved in the recruitment of various immunocytes to their correct locations using specific chemokines, but little is known concerning the role of type-I interferon (IFN) in the regulation of chemokines. In this study, we first used protein microarrays to assess the expression of keratinocyte-derived chemokine (KC) and lipopolysaccharide-induced CXC chemokine (LIX) in murine spleens. Both expressions were smoothly enhanced by IFN-α pretreatment after LPS injection. Then, we focused on the IFN-α regulation of KC, LIX, and their target cells, neutrophils, using an IFN-α neutralizing antibody and fludarabine (specific signal transducers and activators of transcription 1 - STAT1 inhibitor). Next, LPS was found to attenuate the production of KC and LIX in spleen. Even the elevated production of chemokines caused by exogenous IFN-α was found to be attenuated by fludarabine pretreatment. We later determined that the marginal zone and red pulp are the main sites of KC and LIX production. Last, we determined that the number of neutrophils was slightly increased by IFN-α treatment and diminished by IFN-α neutralization or fludarabine treatment. Further, the elevated neutrophils due to exogenous IFN-α were partially reversed by fludarabine pretreatment. In this way, these results indicate that IFN-α facilitates KC and LIX expression in mouse spleens after an LPS challenge. This effect was found to be mainly dependent upon the activation of STAT1, it may be involved in the recruitment of neutrophils to the spleen for the clearance of pathogens.

PAR-1 contributes to the innate immune response during viral infection

Coagulation is a host defense system that limits the spread of pathogens. Coagulation proteases, such as thrombin, also activate cells by cleaving PARs. In this study, we analyzed the role of PAR-1 in coxsackievirus B3-induced (CVB3-induced) myocarditis and influenza A infection. CVB3-infected Par1(-/-) mice expressed reduced levels of IFN-β and CXCL10 during the early phase of infection compared with Par1(+/+) mice that resulted in higher viral loads and cardiac injury at day 8 after infection. Inhibition of either tissue factor or thrombin in WT mice also significantly increased CVB3 levels in the heart and cardiac injury compared with controls. BM transplantation experiments demonstrated that PAR-1 in nonhematopoietic cells protected mice from CVB3 infection. Transgenic mice overexpressing PAR-1 in cardiomyocytes had reduced CVB3-induced myocarditis. We found that cooperative signaling between PAR-1 and TLR3 in mouse cardiac fibroblasts enhanced activation of p38 and induction of IFN-β and CXCL10 expression. Par1(-/-) mice also had decreased CXCL10 expression and increased viral levels in the lung after influenza A infection compared with Par1(+/+) mice. Our results indicate that the tissue factor/thrombin/PAR-1 pathway enhances IFN-β expression and contributes to the innate immune response during single-stranded RNA viral infection.

Thrombin-induced CCN2 expression in human lung fibroblasts requires the c-Src/JAK2/STAT3 pathway

Thrombin might activate c-Src to induce JAK2 activation, which causes STAT3 activation, inducing CCN2 expression in human lung fibroblasts.

Thrombin is a multifunctional serine protease and an important fibrotic mediator that induces CCN2 expression. We previously showed that thrombin induces CCN2 expression via an ASK1-dependent JNK/AP-1 pathway in human lung fibroblasts. In this study, we further investigated the roles of c-Src, JAK2, and STAT3 in thrombin-induced CCN2 expression. Thrombin-induced CCN2 expression and CCN2-Luc activity were attenuated by a JAK inhibitor (AG490) and JAK2DN, STAT3DN, and the STAT decoy ODN. Moreover, transfection of cells with a CCN2-mtSTAT-Luc construct inhibited thrombin-induced CCN2-Luc activity. Treatment of cells with thrombin caused JAK2 phosphorylation at Tyr1007/1008 and STAT3 phosphorylation at Tyr705 in time-dependent manners. Thrombin-induced STAT3 phosphorylation was inhibited by AG490 and JAK2DN. Thrombin-induced STAT3 binding to the CCN2 promoter was analyzed by a DNA-binding affinity pull-down assay. In addition, thrombin-induced CCN2 expression and CCN2-Luc activity were inhibited by c-SrcDN and PP2 (an Src inhibitor). Transfection of cells with c-SrcDN also inhibited thrombin-induced JAK2 and STAT3 phosphorylation. Taken together, these results indicate that thrombin might activate c-Src to induce JAK2 activation, which in turn, causes STAT3 activation, and finally induces CCN2 expression in human lung fibroblasts.

Nickel nanoparticles enhance platelet-derived growth factor-induced chemokine expression by mesothelial cells via prolonged mitogen-activated protein kinase activation

Pleural diseases (fibrosis and mesothelioma) are a major concern for individuals exposed by inhalation to certain types of particles, metals, and fibers. Increasing attention has focused on the possibility that certain types of engineered nanoparticles (NPs), especially those containing nickel, might also pose a risk for pleural diseases. Platelet-derived growth factor (PDGF) is an important mediator of fibrosis and cancer that has been implicated in the pathogenesis of pleural diseases. In this study, we discovered that PDGF synergistically enhanced nickel NP (NiNP)-induced increases in mRNA and protein levels of the profibrogenic chemokine monocyte chemoattractant protein-1 (MCP-1 or CCL2), and the antifibrogenic IFN-inducible CXC chemokine (CXCL10) in normal rat pleural mesothelial 2 (NRM2) cells in vitro. Carbon black NPs (CBNPs), used as a negative control NP, did not cause a significant increase in CCL2 or CXCL10 in the absence or presence of PDGF. NiNPs prolonged PDGF-induced phosphorylation of the mitogen-activated protein kinase family termed extracellular signal-regulated kinases (ERK)-1 and -2 for up to 24 hours, and NiNPs also synergistically increased PDGF-induced hypoxia-inducible factor (HIF)-1α protein levels in NRM2 cells. Inhibition of ERK-1,2 phosphorylation with the mitogen-activated protein kinase kinase (MEK) inhibitor, PD98059, blocked the synergistic increase in CCL2, CXCL10, and HIF-1α levels induced by PDGF and NiNPs. Moreover, the antioxidant, N-acetyl-L-cysteine (NAC), significantly reduced HIF-1α, ERK-1,2 phosphorylation, and CCL2 protein levels that were synergistically increased by the combination of PDGF and NiNPs. These data indicate that NiNPs enhance the activity of PDGF in regulating chemokine production in NRM2 cells through a mechanism involving reactive oxygen species generation and prolonged activation of ERK-1,2.

Multi-walled carbon nanotubes induce COX-2 and iNOS expression via MAP kinase-dependent and -independent mechanisms in mouse RAW264.7 macrophages

BACKGROUND

Carbon nanotubes (CNTs) are engineered graphene cylinders with numerous applications in engineering, electronics and medicine. However, CNTs cause inflammation and fibrosis in the rodent lung, suggesting a potential human health risk. We hypothesized that multi-walled CNTs (MWCNTs) induce two key inflammatory enzymes in macrophages, cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), through activation of extracellular signal-regulated kinases (ERK1,2).

METHODS

RAW264.7 macrophages were exposed to MWCNTs or carbon black nanoparticles (CBNPs) over a range of doses and time course. Uptake and subcellular localization of MWCNTs was visualized by transmission electron microscopy (TEM). Protein levels of COX-2, iNOS, and ERK1,2 (total ERK and phosphorylated ERK) were measured by Western blot analysis. Prostaglandin-E(2) (PGE(2)) and nitric oxide (NO) levels in cell supernatants were measured by ELISA and Greiss assay, respectively.

RESULTS

MWCNTs, but not CBNPs, induced COX-2 and iNOS in a time- and dose-dependent manner. COX-2 and iNOS induction by MWCNTs correlated with increased PGE(2) and NO production, respectively. MWCNTs caused ERK1,2 activation and inhibition of ERK1,2 (U0126) blocked MWCNT induction of COX-2 and PGE2 production, but did not reduce the induction of iNOS. Inhibition of iNOS (L-NAME) did not affect ERK1,2 activation, nor did L-NAME significantly decrease COX-2 induction by MWCNT. Nickel nanoparticles (NiNPs), which are present in MWCNTs as a residual catalyst, also induced COX-2 via ERK-1,2. However, a comparison of COX-2 induction by MWCNTs containing 4.5 and 1.8% Ni did not show a significant difference in ability to induce COX-2, indicating that characteristics of MWCNTs in addition to Ni content contribute to COX-2 induction.

CONCLUSION

This study identifies COX-2 and subsequent PGE(2) production, along with iNOS induction and NO production, as inflammatory mediators involved in the macrophage response to MWCNTs. Furthermore, our work demonstrates that COX-2 induction by MWCNTs in RAW264.7 macrophages is ERK1,2-dependent, while iNOS induction by MWCNTs is ERK1,2-independent. Our data also suggest contributory physicochemical factors other than residual Ni catalyst play a role in COX-2 induction to MWCNT.

Mesenchymal cell survival in airway and interstitial pulmonary fibrosis

Fibrotic reactions in the airways of the lung or the pulmonary interstitium are a common pathologic outcome after exposure to a wide variety of toxic agents, including metals, particles or fibers. The survival of mesenchymal cells (fibroblasts and myofibroblasts) is a key factor in determining whether a fibroproliferative response that occurs after toxic injury to the lung will ultimately resolve or progress to a pathologic state. Several polypeptide growth factors, including members of the platelet-derived growth factor (PDGF) family and the epidermal growth factor (EGF) family, are prosurvival factors that stimulate a replicative and migratory mesenchymal cell phenotype during the early stages of lung fibrogenesis. This replicative phenotype can progress to a matrix synthetic phenotype in the presence of transforming growth factor-β1 (TGF-β1). The resolution of a fibrotic response requires growth arrest and apoptosis of mesenchymal cells, whereas progressive chronic fibrosis has been associated with mesenchymal cell resistance to apoptosis. Mesenchymal cell survival or apoptosis is further influenced by cytokines secreted during Th1 inflammation (e.g., IFN-γ) or Th2 inflammation (e.g., IL-13) that modulate the expression of growth factor activity through the STAT family of transcription factors. Understanding the mechanisms that regulate the survival or death of mesenchymal cells is central to ultimately developing therapeutic strategies for lung fibrosis.

Chromium(VI) stimulates Fyn to initiate innate immune gene induction in human airway epithelial cells

Mechanisms for pathogenic metal signaling in airway injury or disease promotion are poorly understood. It is widely believed that one mechanism for pathogenic and possible carcinogenic effects of inhaled chromium (Cr(VI)) is inhibition of inducible gene transactivation. However, we recently reported that Cr(VI) inhibition of Sp1-dependent transactivation required signal transducer and activator of transcription 1 (STAT1)-dependent expression of an inhibitory protein in airway epithelium. Thus, Cr(VI) exposures can induce genes, and we hypothesized that this induction resulted from Cr(VI) signaling through an innate immune-like STAT1-dependent pathway initiated by Fyn. Exposure of human airway epithelial (BEAS-2B) cells to Cr(VI) selectively transactivated the STAT-responsive interferon-stimulated response element (ISRE) and induced ISRE-driven transactivation of interferon regulatory factor 7 (IRF7), without affecting the gamma interferon-activated site (GAS)-driven IRF1 expression. Cr(VI)-induced IRF7 was absent or greatly reduced in cells that lacked STAT1, were treated with the Src family kinase inhibitor, PP2, or lacked Fyn. Expressing Fyn, but not Src, in mouse embryonic fibroblasts cells null for Src, Yes, and Fyn restored Cr(VI)-stimulated STAT1 tyrosine phosphorylation and IRF7 expression. Finally, shRNA knockdown of Fyn in BEAS-2B cells prevented Cr(VI)-activated STAT1 transactivation of IRF7. These data support a novel mechanism through which Cr(VI) stimulates Fyn to initiate interferon-like signaling for STAT1-dependent gene transactivation.

Vanadium pentoxide induces pulmonary inflammation and tumor promotion in a strain-dependent manner

Background

Elevated levels of air pollution are associated with increased risk of lung cancer. Particulate matter (PM) contains transition metals that may potentiate neoplastic development through the induction of oxidative stress and inflammation, a lung cancer risk factor. Vanadium pentoxide (V₂O₅) is a component of PM derived from fuel combustion as well as a source of occupational exposure in humans. In the current investigation we examined the influence of genetic background on susceptibility to V₂O₅-induced inflammation and evaluated whether V₂O₅ functions as a tumor promoter using a 2-stage (initiation-promotion) model of pulmonary neoplasia in mice.

Results

A/J, BALB/cJ (BALB), and C57BL/6J (B6) mice were treated either with the initiator 3-methylcholanthrene (MCA; 10 μg/g; i.p.) or corn oil followed by 5 weekly aspirations of V₂O₅ or PBS and pulmonary tumors were enumerated 20 weeks following MCA treatment. Susceptibility to V₂O₅-induced pulmonary inflammation was assessed in bronchoalveolar lavage fluid (BALF), and chemokines, transcription factor activity, and MAPK signaling were quantified in lung homogenates. We found that treatment of animals with MCA followed by V₂O₅ promoted lung tumors in both A/J (10.3 ± 0.9 tumors/mouse) and BALB (2.2 ± 0.36) mice significantly above that observed with MCA/PBS or V₂O₅ alone (P < 0.05). No tumors were observed in the B6 mice in any of the experimental groups. Mice sensitive to tumor promotion by V₂O₅ were also found to be more susceptible to V₂O₅-induced pulmonary inflammation and hyperpermeability (A/J>BALB>B6). Differential strain responses in inflammation were positively associated with elevated levels of the chemokines KC and MCP-1, higher NFκB and c-Fos binding activity, as well as sustained ERK1/2 activation in lung tissue.

Conclusions

In this study we demonstrate that V₂O₅, an occupational and environmentally relevant metal oxide, functions as an in vivo lung tumor promoter among different inbred strains of mice. Further, we identified a positive relationship between tumor promotion and susceptibility to V₂O₅-induced pulmonary inflammation. These findings suggest that repeated exposures to V₂O₅ containing particles may augment lung carcinogenesis in susceptible individuals through oxidative stress mediated pathways.

SARS-CoV pathogenesis is regulated by a STAT1 dependent but a type I, II and III interferon receptor independent mechanism

Severe acute respiratory syndrome coronavirus (SARS-CoV) infection often caused severe end stage lung disease and organizing phase diffuse alveolar damage, especially in the elderly. The virus-host interactions that governed development of these acute end stage lung diseases and death are unknown. To address this question, we evaluated the role of innate immune signaling in protection from human (Urbani) and a recombinant mouse adapted SARS-CoV, designated rMA15. In contrast to most models of viral pathogenesis, infection of type I, type II or type III interferon knockout mice (129 background) with either Urbani or MA15 viruses resulted in clinical disease outcomes, including transient weight loss, denuding bronchiolitis and alveolar inflammation and recovery, identical to that seen in infection of wildtype mice. This suggests that type I, II and III interferon signaling play minor roles in regulating SARS pathogenesis in mouse models. In contrast, infection of STAT1-/- mice resulted in severe disease, high virus titer, extensive pulmonary lesions and 100% mortality by day 9 and 30 post-infection with rMA15 or Urbani viruses, respectively. Non-lethal in BALB/c mice, Urbani SARS-CoV infection in STAT1-/- mice caused disseminated infection involving the liver, spleen and other tissues after day 9. These findings demonstrated that SARS-CoV pathogenesis is regulated by a STAT1 dependent but type I, II and III interferon receptor independent, mechanism. In contrast to a well documented role in innate immunity, we propose that STAT1 also protects mice via its role as an antagonist of unrestrained cell proliferation.

Respiratory syncytial virus infection reduces lung inflammation and fibrosis in mice exposed to vanadium pentoxide

BACKGROUND

Vanadium pentoxide (V2O5) exposure is a cause of occupational bronchitis and airway fibrosis. Respiratory syncytial virus (RSV) is a ubiquitous pathogen that causes airway inflammation. It is unknown whether individuals with pre-existing respiratory viral infection are susceptible to V2O5-induced bronchitis. We hypothesized that respiratory viral infection will exacerbate vanadium-induced lung fibrosis.

METHODS

In this study we investigated the effect of RSV pre- or post-exposure to V2O5 in male AKR mice. Mice were pre-exposed by intranasal aspiration to RSV or media vehicle prior to intranasal aspiration of V2O5 or saline vehicle at day 1 or day 7. A parallel group of mice were treated first with V2O5 or saline vehicle at day 1 and day 7 then post-exposed to RSV or media vehicle at day 8.

RESULTS

V2O5-induced airway inflammation and fibrosis were decreased by RSV pre- or post-exposure. Real time quantitative RT-PCR showed that V2O5 significantly increased lung mRNAs encoding pro-fibrogenic growth factors (TGF-beta1, CTGF, PDGF-C) and collagen (Col1A2), but also increased mRNAs encoding anti-fibrogenic type I interferons (IFN-alpha, -beta) and IFN-inducible chemokines (CXCL9 and CXCL10). RSV pre- or post-exposure caused a significantly reduced mRNAs of pro-fibrogenic growth factors and collagen, yet reduced RNA levels of anti-fibrogenic interferons and CXC chemokines.

CONCLUSIONS

Collectively these data suggest that RSV infection reduces the severity of V2O5-induced fibrosis by suppressing growth factors and collagen genes. However, RSV suppression of V2O5-induced IFNs and IFN-inducible chemokines suggests that viral infection also suppresses the innate immune response that normally serves to resolve V2O5-induced fibrosis.