Over-expression of human endosulfatase-1 exacerbates cadmium-induced injury to transformed human lung cells in vitro

Selenium alleviates cadmium-induced mitophagy through FUNDC1-mediated mitochondrial quality control pathway in the lungs of sheep

Cadmium (Cd) is a poisonous metal element that causes mitochondrial dysfunction. Selenium (Se) can reduce the damage of Cd to various organs of animals, but the protective mechanism of Se in Cd-induced lung injury has not been fully elucidated. For purpose of further illustrating the specific mechanism of Se alleviated Cd-triggered pulmonary toxicity, 48 sheep were divided into 4 groups, of which the sheep in the treatment group were taken 1 mg/kg body weight (BW) of Cd, 0.34 mg/kg BW of Se, and 0.34 mg Se + 1 mg/kg BW of Cd by intragastric administration for 50 d, respectively. The results indicated that Cd caused inflammatory cell infiltration and alveolar wall thickening, which facilitated mitochondrial vacuolation and formation of mitophagosomes in lung tissues. Simultaneously, Cd treatment impaired the antioxidant capacity of sheep lung tissue. Additionally, Cd treatment down-regulated the expression levels of mitochondrial biogenesis and mitochondrial fusion, but up-regulated the levels of mitochondrial fission and mitophagy mediated by FUNDC1. Moreover, the immunofluorescence co-localization puncta of LC3B/COX IV, LC3B/FUNDC1 were increased after Cd treatment. Nevertheless, co-treatment with Se improved effectively the above variation caused by Cd exposure. In summary, Se could mitigate Cd-generated mitophagy through FUNDC1-mediated mitochondrial quality control pathway in the lungs of sheep.

Epithelial Heparan Sulfate Contributes to Alveolar Barrier Function and Is Shed during Lung Injury

The lung epithelial glycocalyx is a carbohydrate-enriched layer lining the pulmonary epithelial surface. Although epithelial glycocalyx visualization has been reported, its composition and function remain unknown. Using immunofluorescence and mass spectrometry, we identified heparan sulfate (HS) and chondroitin sulfate within the lung epithelial glycocalyx. In vivo selective enzymatic degradation of epithelial HS, but not chondroitin sulfate, increased lung permeability. Using mass spectrometry and gel electrophoresis approaches to determine the fate of epithelial HS during lung injury, we detected shedding of 20 saccharide-long or greater HS into BAL fluid in intratracheal LPS-treated mice. Furthermore, airspace HS in clinical samples from patients with acute respiratory distress syndrome correlated with indices of alveolar permeability, reflecting the clinical relevance of these findings. The length of HS shed during intratracheal LPS-induced injury (≥20 saccharides) suggests cleavage of the proteoglycan anchoring HS to the epithelial surface, rather than cleavage of HS itself. We used pharmacologic and transgenic animal approaches to determine that matrix metalloproteinases partially mediate HS shedding during intratracheal LPS-induced lung injury. Although there was a trend toward decreased alveolar permeability after treatment with the matrix metalloproteinase inhibitor, doxycycline, this did not reach statistical significance. These studies suggest that epithelial HS contributes to the lung epithelial barrier and its degradation is sufficient to increase lung permeability. The partial reduction of HS shedding achieved with doxycycline is not sufficient to rescue epithelial barrier function during intratracheal LPS-induced lung injury; however, whether complete attenuation of HS shedding is sufficient to rescue epithelial barrier function remains unknown.

Crystalline silica alters Sulfatase-1 expression in rat lungs which influences hyper-proliferative and fibrogenic effects in human lung epithelial cells

Lung epithelial cells are the first cell-type to come in contact with hazardous dust materials. Upon deposition, they invoke complex reactions in attempt to eradicate particles from the airways, and repair damage. The cell surface is composed of a heterogeneous network of matrix proteins and proteoglycans, which act as scaffold and control cell-signaling networks. These functions are controlled, in part, by the sulfation patterns of heparin-sulfate proteoglycans (HSPGs), which are enzymatically regulated. Although there is evidence of altered HSPG-sulfation in idiopathic pulmonary fibrosis (IPF), this is not investigated in silicosis. Our previous studies revealed down-regulation of Sulfatase-1 (SULF1) in human bronchial epithelial cells (BECs) by crystalline silica (CS). In this study, CS-induced down-regulation of SULF1, and increases in Sulfated-HSPGs, were determined in human BECs, and in rat lungs. By siRNA and plasmid transfection techniques the effects of SULF1 expression on silica-induced fibrogenic and proliferative gene expression were determined. These studies confirmed down-regulation of SULF1 and subsequent increases in sulfated-HSPGs in vitro. Moreover, short-term exposure of rats to CS resulted in similar changes in vivo. Conversely, effects were reversed after long term CS exposure of rats. SULF1 knockdown, and overexpression alleviated and exacerbated silica-induced decrease in cell viability, respectively. Furthermore, overexpression of SULF1 promoted silica-induced proliferative and fibrogenic gene expression, and collagen production. These findings demonstrate that the HSPG modification enzyme SULF1 and HSPG sulfation are altered by CS in vitro and in vivo. Furthermore, these changes may contribute to CS-induced lung pathogenicity by affecting injury tolerance, hyperproliferation, and fibrotic effects.

Plasma membrane wounding and repair in pulmonary diseases

Various pathophysiological conditions such as surfactant dysfunction, mechanical ventilation, inflammation, pathogen products, environmental exposures, and gastric acid aspiration stress lung cells, and the compromise of plasma membranes occurs as a result. The mechanisms necessary for cells to repair plasma membrane defects have been extensively investigated in the last two decades, and some of these key repair mechanisms are also shown to occur following lung cell injury. Because it was theorized that lung wounding and repair are involved in the pathogenesis of acute respiratory distress syndrome (ARDS) and idiopathic pulmonary fibrosis (IPF), in this review, we summarized the experimental evidence of lung cell injury in these two devastating syndromes and discuss relevant genetic, physical, and biological injury mechanisms, as well as mechanisms used by lung cells for cell survival and membrane repair. Finally, we discuss relevant signaling pathways that may be activated by chronic or repeated lung cell injury as an extension of our cell injury and repair focus in this review. We hope that a holistic view of injurious stimuli relevant for ARDS and IPF could lead to updated experimental models. In addition, parallel discussion of membrane repair mechanisms in lung cells and injury-activated signaling pathways would encourage research to bridge gaps in current knowledge. Indeed, deep understanding of lung cell wounding and repair, and discovery of relevant repair moieties for lung cells, should inspire the development of new therapies that are likely preventive and broadly effective for targeting injurious pulmonary diseases.

Heparin and LPS-induced COX-2 expression in airway cells: a link between its anti-inflammatory effects and GAG sulfation

PURPOSE/AIM

Previous studies have indicated that the sulfated polysaccharide heparin has anti-inflammatory effects. However, the mechanistic basis for these effects has not been fully elucidated.

MATERIALS AND METHODS

NCI-H292 (mucoepidermoid) and HBE-1 (normal) human bronchial epithelial cells were treated with LPS alone or in the presence of high-molecular-weight (HMW) fully sulfated heparin or desulfated HMW heparin. Cells were harvested to examine the phosphorylation levels of ERK1/2, p38, and NF-kB p65 and COX-2 protein expression by Western blot and gene expression of both COX-2 and CXCL-8 by TaqMan qRT-PCR.

RESULTS

Heparin is known to exert an influence on receptor-mediated signaling through its ability to both potentiate and inhibit the receptor-ligand interaction, depending upon its concentration. In H292 cells, fully-sulfated HMW heparin significantly reduced LPS-induced gene expression of both COX-2 and CXCL-8 for up to 48 hours, while desulfated heparin had little to no significant suppressive effect on signaling or on COX-2 gene or protein expression. Desulfated heparin, initially ineffective at preventing LPS-induced CXCL8 up-regulation, reduced CXCL8 transcription at 24 hours. In contrast, in normal HBE-1 cells, fully sulfated heparin significantly suppressed only ERK signaling, COX-2 gene expression at 12 hours, and CXCL-8 gene expression at 6 and 12 hours, while desulfated heparin had no significant effects on LPS-stimulated signaling or on gene or protein expression. Sulfation determines heparin's influence and may reflect the moderating role of GAG sulfation in lung injury and health.

CONCLUSIONS

Heparin's anti-inflammatory effects result from its nonspecific suppression of signaling and gene expression and are determined by its sulfation.

In vitro toxicity evaluation of engineered cadmium-coated silica nanoparticles on human pulmonary cells

Cytotoxicity of cadmium-containing silica nanoparticles Cd-SiO2NPs (0.05-100 µg/mL) versus SiO2NPs and CdCl2 was evaluated by an in vitro test battery in A549 by assessing (i) mitochondrial function, (ii) membrane integrity/cell morphology, (iii) cell growth/proliferation, (iv) apoptotic pathway, (v) oxidative stress, after short- (24-48 h) and long-term (10 days) exposure. Both Cd-SiO2NPs and CdCl2 produced dose-dependent cytotoxic effects: (i) MTT-assay: similar cytotoxicity pattern was observed at both 24 and 48 h, with a more Cd-SiO2NPs pronounced effect than CdCl2. Cd-SiO2NPs induced mortality (about 50%) at 1  μ g/mL, CdCl2 at 25  μ g/mL; (ii) calcein-AM/PI staining: decrease in cell viability, noticeable at 25  μ g/mL, enhanced markedly at 50 and 100  μ g/mL, after 24 h. Cd-SiO2NPs induced higher mortality than CdCl2 (25% versus 4%, resp., at 25  μ g/mL) with further exacerbation after 48h; (iii) clonogenic assay: exposure for longer period (10 days) compromised the A549 proliferative capacity at very low dose (0.05  μ g/mL); (iv) a progressive activation of caspase-3 immunolabelling was detected already at 1  μ g/mL; (v) GSH intracellular level was modified by all compounds. In summary, in vitro data demonstrated that both Cd-SiO2NPs and CdCl2 affected all investigated endpoints, more markedly after Cd-SiO2NPs, while SiO2NPs influenced GSH only.