Suppression of oxidant-induced glutathione synthesis by erythromycin in human bronchial epithelial cells

Erythromycin attenuates oxidative stress-induced cellular senescence via the PI3K-mTOR signaling pathway in chronic obstructive pulmonary disease

Background and Purpose: Chronic obstructive pulmonary disease (COPD) is proposed to hasten lung aging. Erythromycin protects against oxidative stress and inflammatory responses. However, the potential anti-senescence effect of erythromycin remains disclosed. In the present study, we investigated whether erythromycin influenced oxidative stress-induced cellular senescence and investigated its related mechanisms. Methods: A cigarrete smoke (CS) -induced emphysema mouse model and a H₂O₂-induced premature senescence model in human bronchial epithelial cell line (BEAS-2B) were established. Senescence-related markers (P53, P21 and SA-β-Gal activity), and levels of oxidative stress biomarkers (MDA, SOD and ROS) were measured. Additionally, cells were pretreated with rapamycin (mTOR inhibitor) or erythromycin, and the expression levels of components of the PI3K-mTOR signaling pathway were measured in BEAS-2B cells. Results: Exposed to H₂O₂, increased SA-β-gal activity was observed in BEAS-2B cells suggesting premature senescence. Erythromycin inhibited the expression of P53 and P21 in the CS-induced emphysema mouse model. MDA levels significantly increased and SOD levels decreased in the CS-exposed mice and H₂O₂-induced BEAS-2B cells. Rapamycin and erythromycin significantly suppressed the expression of P53 and P21. Additionally, rapamycin and erythromycin inhibited the PI3K-mTOR signaling pathway. Conclusion: Our findings suggest that erythromycin ameliorates oxidative stress-induced cellular senescence via the PI3K-mTOR signaling pathway. Hence, we establish a theoretical foundation for the clinical application of erythromycin for COPD prevention and treatment.

Continuous Production of Human Epidermal Growth Factor Using Escherichia coli Biofilm

Increasing demand for recombinant proteins necessitates efficient protein production processes. In this study, a continuous process for human epidermal growth factor (hEGF) secretion by Escherichia coli was developed by taking advantage of biofilm formation. Genes bcsB, fimH, and csgAcsgB that have proved to facilitate biofilm formation and some genes moaE, yceA, ychJ, and gshB potentially involved in biofilm formation were examined for their effects on hEGF secretion as well as biofilm formation. Finally, biofilm-based fermentation processes were established, which demonstrated the feasibility of continuous production of hEGF with improved efficiency. The best result was obtained from ychJ-disruption that showed a 28% increase in hEGF secretion over the BL21(DE3) wild strain, from 24 to 32 mg/L. Overexpression of bcsB also showed great potential in continuous immobilized fermentation. Overall, the biofilm engineering here represents an effective strategy to improve hEGF production and can be adapted to produce more recombinant proteins in future.

Idiopathic pulmonary fibrosis and diabetes mellitus: a meta-analysis and systematic review

Background

Idiopathic pulmonary fibrosis (IPF) is a chronic diffuse interstitial lung disease, of which the etiology has been poorly understood. Several studies have focused on the relationship between IPF and diabetes mellitus (DM) in the past years but have failed to reach a consensus. This meta-analysis aimed to examine the association between diabetes to IPF.

Methods

We accumulated studies investigating the association between DM and IPF from databases including Medline, Cochrane Library, Embase, Web of Science, and China National Knowledge Infrastructure. RevMan 5.3 and the Newcastle–Ottawa Scale (NOS) were utilized to analyze the data and assess the quality of the included studies. The value of odds ratio (OR) with 95% confidence interval (CI) was used as the measure to estimate the risk of DM in IPF. Heterogeneity was assessed by I² statistics. We also performed subgroup analysis, meta-regression, and Egger’s test for bias analysis.

Results

Nine case–control studies with 5096 IPF patients and 19,095 control subjects were included in the present meta-analysis, which indicated a positive correlation between DM and IPF (OR 1.65, 95% CI 1.30–2.10; P < 0.0001). Meta-regression and subgroup analysis negated the influence of covariates like cigarette smoking, age and gender, but the heterogeneity existed and could not be fully explained.

Conclusion

IPF and DM may be associated, but the causal relationship remains indeterminate till now. Further rigorously designed studies are required to confirm the present findings and investigate the possible mechanisms behind the effect of DM on IPF.

The Precursor to Glutathione (GSH), γ-Glutamylcysteine (GGC), Can Ameliorate Oxidative Damage and Neuroinflammation Induced by Aβ40 Oligomers in Human Astrocytes

Glutathione (GSH) is one of the most abundant thiol antioxidants in cells. Many chronic and age-related diseases are associated with a decline in cellular GSH levels or impairment in the catalytic activity of the GSH biosynthetic enzyme glutamate cysteine ligase (GCL). γ-glutamylcysteine (GGC), a precursor to glutathione (GSH), can replenish depleted GSH levels under oxidative stress conditions, by circumventing the regulation of GSH biosynthesis and providing the limiting substrate. Soluble amyloid-β (Aβ) oligomers have been shown to induce oxidative stress, synaptic dysfunction and memory deficits which have been reported in Alzheimer’s disease (AD). Calcium ions, which are increased with age and in AD, have been previously reported to enhance the formation of Aβ₄₀ oligomers, which have been casually associated with the pathogenesis of the underlying neurodegenerative condition. In this study, we examined the potential beneficial effects of GGC against exogenous Aβ₄₀ oligomers on biomarkers of apoptosis and cell death, oxidative stress, and neuroinflammation, in human astrocytes. Treatment with Aβ₄₀ oligomers significantly reduced the cell viability and apoptosis of astrocyte brain cultures and increased oxidative modifications of DNA, lipids, and protein, enhanced pro-inflammatory cytokine release and increased the activity of the proteolytic matrix metalloproteinase enzyme, matric metalloproteinase (MMP)-2 and reduced the activity of MMP-9 after 24 h. Co-treatment of Aβ₄₀ oligomers with GGC at 200 μM increased the activity of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) and led to significant increases in the levels of the total antioxidant capacity (TAC) and GSH and reduced the GSSG/GSH ratio. GGC also upregulated the level of the anti-inflammatory cytokine IL-10 and reduced the levels of the pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) and attenuated the changes in metalloproteinase activity in oligomeric Aβ₄₀-treated astrocytes. Our data provides renewed insight on the beneficial effects of increased GSH levels by GGC in human astrocytes, and identifies yet another potential therapeutic strategy to attenuate the cytotoxic effects of Aβ oligomers in AD.

Biological activity of Echinops spinosus on inhibition of paracetamol-induced renal inflammation

This study was designed to evaluate the possible mechanisms through which Echinops spinosus (ES) extract demonstrates nephroprotective effect on the paracetamol acetominophen (N-acetyl-p-aminophenol (APAP)) induced nephrotoxicity in rats. Twenty-four Swiss albino rats were divided into four groups (six rats each). The placebo group was orally administered sterile saline, the APAP group received APAP (200 mg·kg–1·day–1 i.p.) daily, the ES group was given ES extract orally (250 mg/kg), and the APAP + ES group received APAP as for the APAP group and administrated the ES extract as for the ES group. Pretreatment of methyl alcohol extract of ES reduced the protein expression of inflammatory parameters including cyclooxygenase-2 and nuclear factor κB in the kidney. It also reduced the mRNA gene expression of tumor necrosis factor-α and interleukin-1β. The ES extract compensated for deficits in the total antioxidant activity, suppressed lipid peroxidation, and amended the APAP-induced histopathological kidney alterations. Moreover, ES treatment restored the elevated levels of urea nitrogen in the blood and creatinine in the serum by APAP. The ES extract attenuated the APAP-induced elevations in renal nitric oxide levels. We clarified that the ES extract has the potential to defend the kidney from APAP-induced inflammation, and the protection mechanism might be through decreasing oxidative stress and regulating the inflammatory signaling pathway through modulating key signaling inflammatory biomarkers.

Low concentrations of clarithromycin upregulate cellular antioxidant enzymes and phosphorylation of extracellular signal-regulated kinase in human small airway epithelial cells

BACKGROUND

It is well known that low-dose, long-term macrolide therapy is effective against chronic inflammatory airway diseases. Oxidative stress is considered to be a key pathogenesis factor in those diseases. However, the mechanism of action of low-dose, long-term macrolide therapy remains unclear. We have reported that clarithromycin (CAM), which is a representative macrolide antibiotic, could inhibit hydrogen peroxide (H2O2)-induced reduction of the glutathione (GSH)/glutathione disulfide (GSSG) ratio in human small airway epithelial cells (SAECs), via the maintenance of GSH levels through an effect on γ-glutamylcysteine synthetase (γ-GCS) expression. In this study, we examined the influence of CAM against H2O2-induced activities of cellular antioxidant enzymes and phosphorylated extracellular signal regulatory kinase (p-ERK) using SAECs, the main cells involved in chronic airway inflammatory diseases.

METHODS

SAECs were pretreated with CAM (1, 5, and 10 μM) for 72 h, and subsequently exposed to H2O2 (100 μM) for 0.5-2 h. Levels of GSH and GSSG, and activities of glutathione peroxidase (GPx)-1, glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT), heme oxygenase (HO)-1 and p-ERK were assayed. mRNA expressions of GPx-1 and HO-1 were measured using the real-time reverse transcription polymerase chain reaction (RT-PCR). Tukey's multiple comparison test was used for analysis of statistical significance.

RESULTS

Pretreatment with low-dose (1 and 5 μM) CAM for 72 h inhibited H2O2-induced reductions of GPx-1, GR, SOD, CAT and HO-1 activities, and mRNA expressions of GPx-1 and HO-1, and improved the GSH/GSSG ratio. However, these alterations were not observed after pretreatment with high-dose (10 μM) CAM, which suppressed phosphorylation of cell proliferation-associated ERK to cause a significant (p < 0.01) decrease in cell viability.

CONCLUSIONS

CAM is efficacious against deterioration of cellular antioxidant enzyme activity caused by oxidative stress under low-dose, long-term treatment conditions. On the other hand, pretreatment with high-dose CAM suppressed phosphorylation of cell proliferation-associated ERK and decreased cell viability. The present study may provide additional evidence as to why low-dose, long-term administration of macrolides is effective for treating chronic inflammatory airway diseases.

Long-term treatment of clarithromycin at a low concentration improves hydrogen peroxide-induced oxidant/antioxidant imbalance in human small airway epithelial cells by increasing Nrf2 mRNA expression

Background

Clarithromycin (CAM), a representative macrolide antibiotic, has been used widely at low doses for long-term therapy of chronic inflammatory airway diseases. Anti-inflammatory effects of macrolide antibiotics were first discovered in clinical practice. Although oxidative stress is known as a key pathogenesis factor in chronic airway inflammatory diseases, the mechanism of action of low-dose, long-term CAM therapy remains unclear. We aimed to examine the cytoprotective action of CAM against hydrogen peroxide (H₂O₂)-induced cell dysfunction, focusing on CAM dose and treatment duration, and using human small airway epithelial cells (SAECs), the main cells involved in chronic airway inflammatory diseases.

Methods

SAECs were pretreated with CAM (1, 5 or 10 μM) for 24, 48 or 72 h, and were subsequently exposed to H₂O₂ for 0.5–4 h. Levels of interleukin (IL)-8, glutathione (GSH) and glutathione disulfide (GSSG), and the activities of nuclear factor (NF)-κB and γ-glutamylcysteine synthetase (γ-GCS) were assayed using specific methods. IL-8 mRNA and NF erythroid 2-related factor 2 (Nrf2) mRNA expression were measured using real-time reverse transcription polymerase chain reaction (RT-PCR). Tukey’s multiple comparison test was used for analysis of statistical significance.

Results

Pretreatment with low-dose (1 or 5 μM), long-term (72 h) CAM inhibited H₂O₂-induced IL-8 levels, NF-κB activity, and IL-8 mRNA expression, and improved the GSH/GSSG ratio via the maintenance of γ-GCS expression levels. Similar to its enhancing effect on the GSH/GSSG ratio, pretreatment with low-dose CAM for 72 h significantly increased Nrf2 mRNA expression (p < 0.01 and p < 0.05). In contrast, these alterations were not observed after pretreatment with high-dose (10 μM) or short-term (24 and 48 h) CAM.

Conclusions

CAM is efficacious against cell dysfunction caused by oxidative stress under low-dose, long-term treatment conditions. This effect depended on the suppression of NF-κB activation and improvement of the H₂O₂-induced oxidant/antioxidant imbalance that is achieved by increasing Nrf2 mRNA expression in SAECs. The present study may provide the first evidence of why low-dose, long-term administration of macrolides is effective for treating chronic inflammatory airway diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s40360-017-0119-8) contains supplementary material, which is available to authorized users.

Macrolides: a promising pharmacologic therapy for chronic obstructive pulmonary disease

Chronic inflammation plays a central role in the pathogenesis of chronic obstructive pulmonary disease (COPD). However, there are no effective anti-inflammatory pharmacologic therapies available for COPD so far. Recent evidence suggests that an immunologic mechanism has a role in the pathogenesis of COPD. Macrolides possess anti-inflammatory and immune-modulating effects may be helpful in the treatment of COPD. Several clinical studies have shown that long-term use of macrolides reduces the frequency of COPD exacerbations. However, the subgroups that most effectively respond to long-term treatment of macrolides still need to be determined. The potential adverse events to individuals and the microbial resistance in community populations raises great concern on the long-term use of macrolides. Thus, novel macrolides have anti-inflammatory and immuno-modulating effects, but without antibiotic effects, and are promising as an anti-inflammatory agent for the treatment of COPD. In addition, the combination of macrolides and other anti-inflammatory pharmacologic agents may be a new strategy for the treatment of COPD.

Procaterol but not dexamethasone protects 16HBE cells from H₂O₂-induced oxidative stress

Oxidative stress is an important pathophysiological factor of asthma and chronic obstructive pulmonary disease (COPD). We hypothesized that procaterol and dexamethasone might treat inflammation through inhibiting oxidative stress in vitro. This study evaluated procaterol and dexamethasone in the hydrogen peroxide (H2O2)-induced immortal human bronchial epithelial cell model of oxidative stress and investigated the underlying mechanisms. Results showed that exposure to 125 μM H2O2 for 2 h led to a 50% reduction in the cell viability, significantly increased the percentage of apoptosis, and elevated levels of malondialdehyde and reactive oxygen species. Pretreatment with procaterol (25 - 200 nM) could reduce these effects in a dose-dependent manner. In contrast, pretreatment with dexamethasone (100 nM, 1000 nM) was inefficient. Pretreatment with procaterol plus dexamethasone (100 nM procaterol + 1000 nM dexamethasone) was effective, but the combined effect was not more effective than the sole pretreatment with 100 nM procaterol. The nuclear factor kappa-B (NF-κB) pathway was involved in the pathogenic mechanisms of H2O2. Procaterol may indirectly inhibit H2O2-induced activation of the NF-κB pathway due to its capability of antioxidation. Glucocorticoids may be not recommended to treat asthma or COPD complicated with severe oxidative stress.

Macrolides: from in vitro anti-inflammatory and immunomodulatory properties to clinical practice in respiratory diseases

BACKGROUND

Macrolides have long been recognised to exert immunomodulary and anti-inflammatory actions. They are able to suppress the "cytokine storm" of inflammation and to confer an additional clinical benefit through their immunomodulatory properties.

METHODS

A search of electronic journal articles was performed using combinations of the following keywords: macrolides, COPD, asthma, bronchitis, bronchiolitis obliterans, cystic fibrosis, immunomodulation, anti-inflammatory effect, diabetes, side effects and systemic diseases.

RESULTS

Macrolide effects are time- and dose-dependent, and the mechanisms underlying these effects remain incompletely understood. Both in vitro and in vivo studies have provided ample evidence of their immunomodulary and anti-inflammatory actions. Importantly, this class of antibiotics is efficacious with respect to controlling exacerbations of underlying respiratory problems, such as cystic fibrosis, asthma, bronchiectasis, panbrochiolitis and cryptogenic organising pneumonia. Macrolides have also been reported to reduce airway hyper-responsiveness and improve pulmonary function.

CONCLUSION

This review provides an overview on the properties of macrolides (erythromycin, clarithromycin, roxithromycin, azithromycin), their efficacy in various respiratory diseases and their adverse effects.

Genetic variants associated with the risk of chronic obstructive pulmonary disease with and without lung cancer

Chronic obstructive pulmonary disease (COPD) is a strong risk factor for lung cancer. Published studies about variations of genes encoding glutathione metabolism, DNA repair, and inflammatory response pathways in susceptibility to COPD were inconclusive. We evaluated 470 single-nucleotide polymorphisms (SNP) from 56 genes of these three pathways in 620 cases and 893 controls to identify susceptibility markers for COPD risk, using existing resources. We assessed SNP- and gene-level effects adjusting for sex, age, and smoking status. Differential genetic effects on disease risk with and without lung cancer were also assessed; cumulative risk models were established. Twenty-one SNPs were found to be significantly associated with risk of COPD (P < 0.01); gene-based analyses confirmed two genes (GCLC and GSS) and identified three additional genes (GSTO2, ERCC1, and RRM1). Carrying 12 high-risk alleles may increase risk by 2.7-fold; eight SNPs altered COPD risk without lung cancer by 3.1-fold and 4 SNPs altered the risk with lung cancer by 2.3-fold. Our findings indicate that multiple genetic variations in the three selected pathways contribute to COPD risk through GCLC, GSS, GSTO2, ERCC1, and RRM1 genes. Functional studies are needed to elucidate the mechanisms of these genes in the development of COPD, lung cancer, or both.

Environmental toxicity, redox signaling and lung inflammation: the role of glutathione

Glutathione (gamma-glutamyl-cysteinyl-glycine, GSH) is the most abundant intracellular antioxidant thiol and is central to redox defense during oxidative stress. GSH metabolism is tightly regulated and has been implicated in redox signaling and also in protection against environmental oxidant-mediated injury. Changes in the ratio of the reduced and disulfide form (GSH/GSSG) can affect signaling pathways that participate in a broad array of physiological responses from cell proliferation, autophagy and apoptosis to gene expression that involve H(2)O(2) as a second messenger. Oxidative stress due to oxidant/antioxidant imbalance and also due to environmental oxidants is an important component during inflammation and respiratory diseases such as chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, acute respiratory distress syndrome, and asthma. It is known to activate multiple stress kinase pathways and redox-sensitive transcription factors such as Nrf2, NF-kappaB and AP-1, which differentially regulate the genes for pro-inflammatory cytokines as well as the protective antioxidant genes. Understanding the regulatory mechanisms for the induction of antioxidants, such as GSH, versus pro-inflammatory mediators at sites of oxidant-directed injuries may allow for the development of novel therapies which will allow pharmacological manipulation of GSH synthesis during inflammation and oxidative injury. This article features the current knowledge about the role of GSH in redox signaling, GSH biosynthesis and particularly the regulation of transcription factor Nrf2 by GSH and downstream signaling during oxidative stress and inflammation in various pulmonary diseases. We also discussed the current therapeutic clinical trials using GSH and other thiol compounds, such as N-acetyl-l-cysteine, fudosteine, carbocysteine, erdosteine in environment-induced airways disease.