Inhaled high molecular weight hyaluronan ameliorates respiratory failure in acute COPD exacerbation: a pilot study.

BACKGROUND: Acute exacerbations of chronic obstructive pulmonary disease (AECOPD) carry significant morbidity and mortality. AECOPD treatment remains limited. High molecular weight hyaluronan (HMW-HA) is a glycosaminoglycan sugar, which is a physiological constituent of the lung extracellular matrix and has notable anti-inflammatory and hydrating properties. RESEARCH QUESTION: We hypothesized that inhaled HMW-HA will improve outcomes in AECOPD. METHODS: We conducted a single center, randomized, placebo-controlled, double-blind study to investigate the effect of inhaled HMW-HA in patients with severe AECOPD necessitating non-invasive positive-pressure ventilation (NIPPV). Primary endpoint was time until liberation from NIPPV. RESULTS: Out of 44 screened patients, 41 were included in the study (21 for placebo and 20 for HMW-HA). Patients treated with HMW-HA had significantly shorter duration of NIPPV. HMW-HA treated patients also had lower measured peak airway pressures on the ventilator and lower systemic inflammation markers after liberation from NIPPV. In vitro testing showed that HMW-HA significantly improved mucociliary transport in air-liquid interface cultures of primary bronchial cells from COPD patients and healthy primary cells exposed to cigarette smoke extract. INTERPRETATION: Inhaled HMW-HA shortens the duration of respiratory failure and need for non-invasive ventilation in patients with AECOPD. Beneficial effects of HMW-HA on mucociliary clearance and inflammation may account for some of the effects (NCT02674880, www.clinicaltrials.gov ).

Multiwalled carbon nanotubes induce altered morphology and loss of barrier function in human bronchial epithelium at noncytotoxic doses.

Multiwalled carbon nanotubes (MWCNTs) have seen increasing application in consumer products over the past decade, resulting in an increasing risk of human exposure. While numerous toxicological studies have been performed using acute high doses of various carbonaceous nanomaterials, the effects of longer-term, low doses of MWCNTs remain relatively unexplored. This study examined bronchoscopy-derived healthy human bronchial epithelial cells exposed in submerged culture to noncytotoxic doses of MWCNTs over 7 days. Under these conditions, doses as low as 3 µg/mL caused altered cell morphology, superficially resembling fibroblasts. Electrical impedance of the epithelial monolayer was greatly reduced following MWCNT exposure. However, Western blot and polymerase chain reaction showed no elevated expression of the fibroblast markers, vimentin, α-smooth muscle actin, or fibronectin, indicating that a mechanism other than epithelial-mesenchymal transition may be responsible for the changes. Phalloidin and tubulin immunostaining showed disruption of the cytoskeleton, and confocal imaging showed a reduction of the tight junction proteins, zona occludens 1 and occludin. We propose that MWCNTs interfere with the cytoskeleton of the lung epithelium, which can result in a harmful reduction in barrier function over time, even at noncytotoxic doses.

Inflammasome activation in airway epithelial cells after multi-walled carbon nanotube exposure mediates a profibrotic response in lung fibroblasts.

BACKGROUND: In vivo studies have demonstrated the ability of multi-walled carbon nanotubes (MWCNT) to induce airway remodeling, a key feature of chronic respiratory diseases like asthma and chronic obstructive pulmonary disease. However, the mechanism leading to remodeling is poorly understood. Particularly, there is limited insight about the role of airway epithelial injury in these changes. OBJECTIVES: We investigated the mechanism of MWCNT-induced primary human bronchial epithelial (HBE) cell injury and its contribution in inducing a profibrotic response. METHODS: Primary HBE cells were exposed to thoroughly characterized MWCNTs (1.5-24 µg/mL equivalent to 0.37-6.0 µg/cm2) and MRC-5 human lung fibroblasts were exposed to 1:4 diluted conditioned medium from these cells. Flow cytometry, ELISA, immunostainings/immunoblots and PCR analyses were employed to study cellular mechanisms. RESULTS: MWCNT induced NLRP3 inflammasome dependent pyroptosis in HBE cells in a time- and dose-dependent manner. Cell death and cytokine production were significantly reduced by antioxidants, siRNA to NLRP3, a caspase-1 inhibitor (z-WEHD-FMK) or a cathepsin B inhibitor (CA-074Me). Conditioned medium from MWCNT-treated HBE cells induced significant increase in mRNA expression of pro-fibrotic markers (TIMP-1, Tenascin-C, Procollagen 1, and Osteopontin) in human lung fibroblasts, without a concomitant change in expression of TGF-beta. Induction of pro-fibrotic markers was significantly reduced when IL-1ß, IL-18 and IL-8 neutralizing antibodies were added to the conditioned medium or when conditioned medium from NLRP3 siRNA transfected HBE cells was used. CONCLUSIONS: Taken together these results demonstrate induction of a NLRP3 inflammasome dependent but TGF-beta independent pro-fibrotic response after MWCNT exposure.

Sulfite-mediated oxidation of myeloperoxidase to a free radical: immuno-spin trapping detection in human neutrophils.

Previous studies focused on catalyzed oxidation of (bi)sulfite, leading to the formation of the reactive sulfur trioxide ((•)SO3(-)), peroxymonosulfate ((-)O3SOO(•)), and sulfate (SO4(•-)) anion radicals, which can damage target proteins and oxidize them to protein radicals. It is known that these very reactive sulfur- and oxygen-centered radicals can be formed by oxidation of (bi)sulfite by peroxidases. Myeloperoxidase (MPO), an abundant heme protein secreted from activated neutrophils that play a central role in host defense mechanisms, allergic reactions, and asthma, is a likely candidate for initiating the respiratory damage caused by sulfur dioxide. The objective of this study was to examine the oxidative damage caused by (bi)sulfite-derived free radicals in human neutrophils through formation of protein radicals. We used immuno-spin trapping and confocal microscopy to study the protein oxidations driven by sulfite-derived radicals. We found that the presence of sulfite can cause MPO-catalyzed oxidation of MPO to a protein radical in phorbol 12-myristate 13-acetate-activated human neutrophils. We trapped the MPO-derived radicals in situ using the nitrone spin trap 5,5-dimethyl-1-pyrroline N-oxide and detected them immunologically as nitrone adducts in cells. Our present study demonstrates that myeloperoxidase initiates (bi)sulfite oxidation leading to MPO radical damage, possibly leading to (bi)sulfite-exacerbated allergic reactions.

Cerium dioxide nanoparticles induce apoptosis and autophagy in human peripheral blood monocytes.

Cerium dioxide nanoparticles (CeO(2) NPs) have diversified industrial uses, and novel therapeutic applications are actively being pursued. There is a lack of mechanistic data concerning the effects of CeO(2) NPs on primary human cells. We aimed at characterizing the cytotoxic effects of CeO(2) NPs in human peripheral blood monocytes. CeO(2) NPs and their suspensions were thoroughly characterized, including using transmission electron microscopy (TEM), dynamic light scattering, and zeta potential analysis. Blood from healthy human volunteers was drawn through phlebotomy, and CD14+ cells were isolated. Cells were exposed to CeO(2) NPs (0.5-10 µg/mL) for 20 or 40 h, and mechanisms of cell injury were studied. TEM revealed that CeO(2) NPs are internalized by monocytes and are found either in vesicles or free in the cytoplasm. CeO(2) NP exposure leads to decrease in cell viability, and treated cells exhibit characteristic hallmarks of apoptosis (activation of Bax, loss of mitochondrial membrane potential, DNA fragmentation). CeO(2) NP toxicity is caused by mitochondrial damage and overexpression of apoptosis inducing factor, but is not due to caspase activation or reactive oxygen species production. Moreover, CeO(2) NP exposure leads to autophagy, which is further increased after pharmacological inhibition of tumor suppressor protein p53. Inhibition of autophagy partially reverses cell death by CeO(2) NPs. It is concluded that CeO(2) NPs are toxic to primary human monocytes at relatively low doses.

Cerium dioxide nanoparticles do not modulate the lipopolysaccharide-induced inflammatory response in human monocytes.

BACKGROUND: Cerium dioxide (CeO(2)) nanoparticles have potential therapeutic applications and are widely used for industrial purposes. However, the effects of these nanoparticles on primary human cells are largely unknown. The ability of nanoparticles to exacerbate pre-existing inflammatory disorders is not well documented for engineered nanoparticles, and is certainly lacking for CeO(2) nanoparticles. We investigated the inflammation-modulating effects of CeO(2) nanoparticles at noncytotoxic concentrations in human peripheral blood monocytes. METHODS: CD14(+) cells were isolated from peripheral blood samples of human volunteers. Cells were exposed to either 0.5 or 1 µg/mL of CeO(2) nanoparticles over a period of 24 or 48 hours with or without lipopolysaccharide (10 ng/mL) prestimulation. Modulation of the inflammatory response was studied by measuring secreted tumor necrosis factor-alpha, interleukin-1beta, macrophage chemotactic protein-1, interferon-gamma, and interferon gamma-induced protein 10. RESULTS: CeO(2) nanoparticle suspensions were thoroughly characterized using dynamic light scattering analysis (194 nm hydrodynamic diameter), zeta potential analysis (-14 mV), and transmission electron microscopy (irregular-shaped particles). Transmission electron microscopy of CD14(+) cells exposed to CeO(2) nanoparticles revealed that these nanoparticles were efficiently internalized by monocytes and were found either in vesicles or free in the cytoplasm. However, no significant differences in secreted cytokine profiles were observed between CeO(2) nanoparticle-treated cells and control cells at noncytotoxic doses. No significant effects of CeO(2) nanoparticle exposure subsequent to lipopolysaccharide priming was observed on cytokine secretion. Moreover, no significant difference in lipopolysaccharide-induced cytokine production was observed after exposure to CeO(2) nanoparticles followed by lipopolysaccharide exposure. CONCLUSION: CeO(2) nanoparticles at noncytotoxic concentrations neither modulate pre-existing inflammation nor prime for subsequent exposure to lipopolysaccharides in human monocytes from healthy subjects.

Formation of reactive sulfite-derived free radicals by the activation of human neutrophils: an ESR study.

The objective of this study was to determine the effect of (bi)sulfite (hydrated sulfur dioxide) on human neutrophils and the ability of these immune cells to produce reactive free radicals due to (bi)sulfite oxidation. Myeloperoxidase (MPO) is an abundant heme protein in neutrophils that catalyzes the formation of cytotoxic oxidants implicated in asthma and inflammatory disorders. In this study sulfite ((•)SO(3)(-)) and sulfate (SO(4)(•-)) anion radicals are characterized with the ESR spin-trapping technique using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) in the reaction of (bi)sulfite oxidation by human MPO and human neutrophils via sulfite radical chain reaction chemistry. After treatment with (bi)sulfite, phorbol 12-myristate 13-acetate-stimulated neutrophils produced DMPO-sulfite anion radical, -superoxide, and -hydroxyl radical adducts. The last adduct probably resulted, in part, from the conversion of DMPO-sulfate to DMPO-hydroxyl radical adduct via a nucleophilic substitution reaction of the radical adduct. This anion radical (SO(4)(•-)) is highly reactive and, presumably, can oxidize target proteins to protein radicals, thereby initiating protein oxidation. Therefore, we propose that the potential toxicity of (bi)sulfite during pulmonary inflammation or lung-associated diseases such as asthma may be related to free radical formation.

Androgen receptor-mediated apoptosis is regulated by photoactivatable androgen receptor ligands.

We have studied nonsteroidal ligands of the human androgen receptor (hAR) and have shown elsewhere that when photoactivated by visible light they collide with O2 to yield singlet oxygens (1O2) in vitro. Here we report cell killing after brief light activation (405 nm) of 1,2,3,4-tetrahydro-2,2-dimethyl-6-(trifluoromethyl)-8-pyridono[5,6-g]quinoline (TDPQ) in human prostate tumor cells. TDPQ/AR complexes were required for the death response because AR-positive LNCaP cells were killed, whereas AR-negative PC-3 cells were resistant. Excess dihydrotestosterone (DHT) blocked the TDPQ effect when the two were added together; irradiation of cells containing DHT alone had no effect. When LNCaP AR expression was suppressed using small interfering oligonucleotides targeting AR, photocytotoxicity was diminished. Conversely, stable transfection of hAR into PC-3 cells made the cells photosensitive to TDPQ. Similar results were obtained using a structural isomer of TDPQ, and also the synthetic steroidal AR ligand R1881. Cell death occurred via apoptosis as demonstrated by annexin V immunostaining, nuclear condensation, and caspase inhibition. Death involved oxidative stress, because it was prevented by addition of the antioxidant ascorbic acid during photoactivation. Detection of elevated levels of 8-hydroxy-2'-deoxyguanosine in nuclei of irradiated cells indicated oxidative DNA damage. Apoptosis spread into adjacent nonirradiated cells by direct cell-cell contacts, indicative of a bystander effect. Other photoactivatable ligands are described, implying a general method for ablation of cells bearing specific nuclear hormone receptors.

Susceptibility of signal transducer and activator of transcription-1-deficient mice to pulmonary fibrogenesis.

The signal transducer and activator of transcription (Stat)-1 mediates growth arrest and apoptosis. We postulated that lung fibrosis characterized by excessive proliferation of lung fibroblasts would be enhanced in Stat1-deficient (Stat1-/-) mice. Two weeks after bleomycin aspiration (3 U/kg), Stat1-/- mice exhibited a more severe fibroproliferative response and significantly elevated total lung collagen compared to wild-type mice. Growth factors [epidermal growth factor (EGF) or platelet-derived growth factor (PDGF)] enhanced [3H]thymidine uptake in lung fibroblasts isolated from Stat1-/- mice compared to wild-type mice. Interferon (IFN)-gamma, which signals growth arrest via Stat1, inhibited EGF- or PDGF-stimulated mitogenesis in wild-type fibroblasts but enhanced [3H]thymidine uptake in Stat1-/- fibroblasts. Moreover, IFN-gamma treatment in the absence of growth factors induced a concentration-dependent increase in [3H]thymidine uptake in Stat1-/- but not wild-type fibroblasts. Mitogen-activated protein kinase (ERK-1/2) phosphorylation in response to PDGF or EGF did not differ among Stat1-/- and wild-type fibroblasts. However, Stat3 phosphorylation induced by PDGF, EGF, or IFN-gamma increased twofold in Stat1-/- fibroblasts compared to wild-type fibroblasts. Our findings indicate that Stat1-/- mice are more susceptible to bleomycin-induced lung fibrosis than wild-type mice due to 1) enhanced fibroblast proliferation in response to growth factors (EGF and PDGF), 2) stimulation of fibroblast growth by a Stat1-independent IFN-gamma signaling pathway, and 3) increased activation of Stat3.

ErbB2 activity is required for airway epithelial repair following neutrophil elastase exposure.

In cystic fibrosis and chronic bronchitis, airways are chronically injured by exposure to neutrophil elastase (NE). We sought to identify factors required for epithelial repair following NE exposure. Normal human bronchial epithelial cells were treated with NE (50 nM, 22 h) or control vehicle. Following NE treatment, we found a marked and sustained decrease in epithelial proliferation as detected by Ki67 immunostaining. 3H-thymidine incorporation was also initially depressed but increased over 72 h in NE-treated cells, which suggests that DNA synthesis constitutes an early repair process following NE exposure. We hypothesized that ErbB2 receptor tyrosine kinase, a regulator of cancer cell proliferation, was required for epithelial DNA synthesis following NE exposure. Immediately following NE treatment, by flow cytometry analysis, we found a decrease in ErbB2 surface expression. Protein levels of the full-length 185 kD ErbB2 receptor significantly decreased following NE treatment and smaller ErbB2-positive bands, ranging in size from 23 to 40 kD, appeared, which suggests that NE caused ErbB2 degradation. By real-time RT-PCR analysis, we found no change in ErbB2 mRNA expression following NE treatment, which suggests that changes in ErbB2 protein levels were regulated at the post-translational level. Following NE treatment, full-length 185 kD ErbB2 levels increased to pretreatment levels, correlating with the increase in thymidine incorporation during the same time period. Importantly, inhibition of ErbB2 activity with AG825 (5 microM) or Herceptin (3.1 microM), an ErbB2-neutralizing antibody, blocked thymidine incorporation only in NE-treated cells. These results suggest ErbB2 is a critical factor for epithelial recovery following NE exposure.

IL-13 and IL-1beta promote lung fibroblast growth through coordinated up-regulation of PDGF-AA and PDGF-Ralpha.

Peribronchiolar fibrosis is a prominent feature of airway remodeling in asthma and involves fibroblast growth and collagen deposition. Interleukin-13 (IL-13), a T-helper 2 cytokine, is a key mediator of airway remodeling in asthma, yet the mechanism through which IL-13 promotes fibroblast growth has not been investigated. In this study, we show that IL-13 stimulates the mitogenesis of mouse, rat, and human lung fibroblasts through release of a soluble mitogen that we identified as PDGF-AA. The IL-13-induced growth of human lung fibroblasts was attenuated by an anti-PDGF-AA neutralizing antibody, and IL-13 stimulated human lung fibroblasts to secrete PDGF-AA. Fibroblasts derived from mouse embryos possessing the lethal Patch mutation, which lack the PDGF-Ralpha, showed no mitogenic response to IL-13. However, Patch cells did exhibit IL-13-induced STAT-6 phosphorylation. Stable transfection of the PDGF-Ralpha into Patch cells restored the growth response to PDGF-AA and IL-13. Through the use of lung fibroblasts from STAT-6-deficient mice, we showed that IL-13-induced PDGF-AA release is STAT-6 dependent, but PDGF-AA-induced growth is STAT-6 independent. Finally, we showed that IL-1beta enhanced IL-13-induced mitogenesis of rat lung fibroblasts through up-regulation of the PDGF-Ralpha. Our findings indicate that IL-13 acts in synergy with IL-1beta to stimulate growth by coordinately up-regulating PDGF-AA and the PDGF-Ralpha, respectively.

Vanadium-induced STAT-1 activation in lung myofibroblasts requires H2O2 and P38 MAP kinase.

Vanadium compounds present in air pollution particulate matter activate signal transduction pathways in pulmonary cell types leading to pathological outcomes including aberrant cell proliferation, apoptosis, and cytokine expression. Vanadium has been proposed to activate transcription factors via the generation of hydrogen peroxide (H2O2). We investigated the mechanisms through which vanadium pentoxide (V2O5), the major form of vanadium released from the industrial burning of fuel oil, activated the signal transducer and activator of transcription (STAT)-1. V2O5-induced STAT-1 activation was blocked by catalase and N-acetyl-L-cysteine (NAC), suggesting vanadium-induced generation of H2O2. Surprisingly, however, V2O5 did not increase H2O2 levels released by rat lung myofibroblasts into cell culture supernatants. Instead, these quiescent myofibroblasts spontaneously released micromolar concentrations of H2O2, and the addition of V2O5 reduced H2O2 levels in cell culture supernatants within minutes. V2O5 suppressed H2O2 for as long as 24 h. Differences in the temporal activation of STAT-1 and p38 MAPK were observed following V2O5 or H2O2 treatment, and STAT-1 activation by V2O5 or H2O2 was attenuated by an inhibitor of the EGF receptor tyrosine kinase (AG1478) or p38 MAPK (SB203580). The phosphorylation of p38 MAPK by V2O5 was inhibited by NAC and catalase, yet the EGF receptor inhibitor AG1478 had no effect on V2O5-induced p38 MAPK activation. Collectively, our findings support the novel hypothesis that H2O2 spontaneously generated by myofibroblasts fuels vanadium-induced activation of STAT-1. Moreover, p38 MAPK and EGF receptor activation are required for V2O5-induced STAT-1 activation.

Vanadium-induced HB-EGF expression in human lung fibroblasts is oxidant dependent and requires MAP kinases.

Vanadium pentoxide (V(2)O(5)) is a transition metal derived from the burning of petrochemicals that causes airway fibrosis and remodeling. Vanadium compounds activate many intracellular signaling pathways via the generation of hydrogen peroxide (H(2)O(2)) or other reactive oxygen species. In this study, we investigated the regulation of heparin-binding epidermal growth factor-like growth factor (HB-EGF) in human lung fibroblasts after V(2)O(5) treatment. V(2)O(5)-induced HB-EGF mRNA expression was abolished by N-acetyl-l-cysteine, suggesting an oxidant-mediated effect. Exogenous H(2)O(2) (>10 microM) mimicked the effect of V(2)O(5) in upregulating HB-EGF expression. Fibroblasts spontaneously released low levels of H(2)O(2) (1-2 microM), and the addition of V(2)O(5) depleted the endogenous H(2)O(2) pool within minutes. V(2)O(5) caused a subsequent increase of H(2)O(2) into the culture medium at 12 h. However, the burst of V(2)O(5)-induced H(2)O(2) occurred after V(2)O(5)-induced HB-EGF mRNA expression at 3 h, indicating that the V(2)O(5)-stimulated H(2)O(2) burst did not mediate HB-EGF expression. Either V(2)O(5) or H(2)O(2) activated ERK-1/2 and p38 MAP kinase. Inhibitors of the ERK-1/2 pathway (PD-98059) or p38 MAP kinase (SB-203580) significantly reduced either V(2)O(5)- or H(2)O(2)-induced HB-EGF expression. These data indicate that vanadium upregulates HB-EGF via ERK and p38 MAP kinases. The induction of HB-EGF is not related to a burst of H(2)O(2) in V(2)O(5) treated cells, yet the action of V(2)O(5) in upregulating HB-EGF is oxidant dependent and could be due to the reaction of V(2)O(5) with endogenous H(2)O(2).

p38 mitogen-activated protein kinase regulates growth factor-induced mitogenesis of rat pulmonary myofibroblasts.

Myofibroblast proliferation is a central feature of pulmonary fibrogenesis. Several growth factors, including platelet-derived growth factor (PDGF) and epidermal growth factor (EGF), stimulate myofibroblast growth by activating extracellular signal regulated kinases 1 and 2 (ERK1/2). In this report, we demonstrate that PDGF-BB and EGF also activate the p38 mitogen-activated protein (MAP) kinase. Inhibition of p38 activity with the pyridinylimidazole compound SB203580 enhanced both PDGF-BB and EGF-stimulated DNA synthesis in rat lung myofibroblasts. ERK1/2 phosphorylation in response to either PDGF-BB or EGF treatment was significantly increased by pretreatment of cells with SB203580. We also demonstrated that ERK1/2-induced phosphorylation of PHAS-1 substrate was enhanced by inhibition of p38 MAP kinase with SB203580. However, SB203580 did not significantly increase growth factor-induced activation of MEK, the upstream kinase that phosphorylates ERK1/2. p38 MAP kinase was co-immunoprecipitated with ERK-1/2 following growth factor stimulation. Collectively, these data demonstrate that p38 MAP kinase activation negatively regulates PDGF- and EGF-mediated growth responses by directly interacting with ERK1/2 and suppressing its phosphorylation.

Susceptibility of cyclooxygenase-2-deficient mice to pulmonary fibrogenesis.

The cyclooxygenase (COX)-2 enzyme has been implicated as an important mediator of pulmonary fibrosis. In this study, the lung fibrotic responses were investigated in COX-1 or COX-2-deficient (-/-) mice following vanadium pentoxide (V(2)O(5)) exposure. Lung histology was normal in saline-instilled wild-type and COX-deficient mice. COX-2(-/-), but not COX-1(-/-) or wild-type mice, exhibited severe inflammatory responses by 3 days following V(2)O(5) exposure and developed pulmonary fibrosis 2 weeks post-V(2)O(5) exposure. Western blot analysis and immunohistochemistry showed that COX-1 protein was present in type 2 epithelial cells, bronchial epithelial cells, and airway smooth muscle cells of saline or V(2)O(5)-exposed wild-type and COX-2(-/-) mice. COX-2 protein was present in Clara cells of wild-type and COX-1(-/-) terminal bronchioles and was strongly induced 24 hours after V(2)O(5) exposure. Prostaglandin (PG) E(2) levels in the bronchoalveolar lavage (BAL) fluid from wild-type and COX-1(-/-) mice were significantly up-regulated by V(2)O(5) exposure within 24 hours, whereas PGE(2) was not up-regulated in COX-2(-/-) BAL fluid. Tumor necrosis factor-alpha was elevated in the BAL fluid from all genotypes after V(2)O(5) exposure, but was significantly and chronically elevated in the BAL fluid from COX-2(-/-) mice above wild-type or COX-1(-/-) mice. These findings indicate that the COX-2 enzyme is protective against pulmonary fibrogenesis, and we suggest that COX-2 generation of PGE(2) is an important factor in resolving inflammation.