Polymorphisms in the glutathione pathway modulate cystic fibrosis severity: a cross-sectional study

Unveiling thiol biomarkers: Glutathione and cysteamine

The physiological and clinical importance of Glutathione and Cysteamine is emphasized by their participation in a range of conditions, such as diabetes, cancer, renal failure, Parkinson's disease, and hypothyroidism. This necessitates the requirement for accessible, expedited, and cost-efficient testing that can facilitate clinical diagnosis and treatment options. This article examines numerous techniques used to detect both glutathione and cysteamine. The discussed methods include electroanalytical techniques such as voltammetry and amperometry, which are examined for their sensitivity and ability to provide real-time analysis. Furthermore, this study investigates the accuracy of gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC) in measuring the concentrations of glutathione and cysteamine. Additionally, the potential of new nanotechnology-based methods, such as plasmonic nanoparticles and quantum dots, to improve the sensitivity of detecting glutathione and cysteamine is emphasized.

Inflammation in the COVID-19 airway is due to inhibition of CFTR signaling by the SARS-CoV-2 spike protein

SARS-CoV-2-contributes to sickness and death in COVID-19 patients partly by inducing a hyper-proinflammatory immune response in the host airway. This hyper-proinflammatory state involves activation of signaling by NFκB, and unexpectedly, ENaC, the epithelial sodium channel. Post-infection inflammation may also contribute to "Long COVID"/PASC. Enhanced signaling by NFκB and ENaC also marks the airway of patients suffering from cystic fibrosis, a life-limiting proinflammatory genetic disease due to inactivating mutations in the CFTR gene. We therefore hypothesized that inflammation in the COVID-19 airway might similarly be due to inhibition of CFTR signaling by SARS-CoV-2 spike protein, and therefore activation of both NFκB and ENaC signaling. We used western blot and electrophysiological techniques, and an organoid model of normal airway epithelia, differentiated on an air-liquid-interface (ALI). We found that CFTR protein expression and CFTR cAMP-activated chloride channel activity were lost when the model epithelium was exposed to SARS-CoV-2 spike proteins. As hypothesized, the absence of CFTR led to activation of both TNFα/NFκB signaling and α and γ ENaC. We had previously shown that the cardiac glycoside drugs digoxin, digitoxin and ouabain blocked interaction of spike protein and ACE2. Consistently, addition of 30 nM concentrations of the cardiac glycoside drugs, prevented loss of both CFTR protein and CFTR channel activity. ACE2 and CFTR were found to co-immunoprecipitate in both basal cells and differentiated epithelia. Thus spike-dependent CFTR loss might involve ACE2 as a bridge between Spike and CFTR. In addition, spike exposure to the epithelia resulted in failure of endosomal recycling to return CFTR to the plasma membrane. Thus, failure of CFTR recovery from endosomal recycling might be a mechanism for spike-dependent loss of CFTR. Finally, we found that authentic SARS-CoV-2 virus infection induced loss of CFTR protein, which was rescued by the cardiac glycoside drugs digitoxin and ouabain. Based on experiments with this organoid model of small airway epithelia, and comparisons with 16HBE14o- and other cell types expressing normal CFTR, we predict that inflammation in the COVID-19 airway may be mediated by inhibition of CFTR signaling by the SARS-CoV-2 spike protein, thus inducing a cystic fibrosis-like clinical phenotype. To our knowledge this is the first time COVID-19 airway inflammation has been experimentally traced in normal subjects to a contribution from SARS-CoV-2 spike-dependent inhibition of CFTR signaling.

Beyond Mendelian Inheritance: Genetic Buffering and Phenotype Variability

Understanding the way genes work amongst individuals and across generations to shape form and function is a common theme for many genetic studies. The recent advances in genetics, genome engineering and DNA sequencing reinforced the notion that genes are not the only players that determine a phenotype. Due to physiological or pathological fluctuations in gene expression, even genetically identical cells can behave and manifest different phenotypes under the same conditions. Here, we discuss mechanisms that can influence or even disrupt the axis between genotype and phenotype; the role of modifier genes, the general concept of genetic redundancy, genetic compensation, the recently described transcriptional adaptation, environmental stressors, and phenotypic plasticity. We furthermore highlight the usage of induced pluripotent stem cells (iPSCs), the generation of isogenic lines through genome engineering, and sequencing technologies can help extract new genetic and epigenetic mechanisms from what is hitherto considered 'noise'.

Chromium metabolism characteristics of coexpression of ChrA and ChrT gene

OBJECTIVE

Serratia sp. S2 is a wild strain with chromium resistance and reduction ability. Chromium(VI) metabolic-protein-coding gene ChrA and ChrT were cloned from Serratia sp. S2, and ligated with prokaryotic expression vectors pET-28a (+) and transformed into E. coli BL21 to construct ChrA, ChrT and ChrAT engineered bacteria. By studying the characteristics of Cr(VI) metabolism in engineered bacteria, the function and mechanism of the sole expression and coexpression of ChrA and ChrT genes were studied.

METHODS

Using Serratia sp. S2 genome as template, ChrA and ChrT genes were amplified by PCR, and prokaryotic expression vectors was ligated to form the recombinant plasmid pET-28a (+)-ChrA, pET-28a (+)-ChrT and pET-28a (+)-ChrAT, and transformed into E. coli BL21 to construct ChrA, ChrT, ChrAT engineered bacteria. The growth curve, tolerance, and reduction of Cr(VI), the distribution of intracellular and extracellular Cr, activity of chromium reductase and intracellular oxidative stress in engineered bacteria were measured to explore the metabolic characteristics of Cr(VI) in ChrA, ChrT, ChrAT engineered bacteria.

RESULTS

ChrA, ChrT and ChrAT engineered bacteria were successfully constructed by gene recombination technology. The tolerance to Cr(VI) was Serratia sp. S2 > ChrAT ≈ ChrA > ChrT > Control (P < 0.05), and the reduction ability to Cr(VI) was Serratia sp. S2 > ChrAT ≈ ChrT > ChrA (P < 0.05). The chromium distribution experiments confirmed that Cr(VI) and Cr(III) were the main valence states. Effect of electron donors on chromium reductase activity was NADPH > NADH > non-NAD(P)H (P < 0.05). The activity of chromium reductase increased significantly with NAD(P)H (P < 0.05). The Glutathione and NPSH (Non-protein Sulfhydryl) levels of ChrA, ChrAT engineered bacteria increased significantly (P < 0.05) under the condition of Cr(VI), but there was no significant difference in the indexes of ChrT engineered bacteria (P > 0.05).

CONCLUSION

ChrAT engineered bacteria possesses resistance and reduction abilities of Cr(VI). ChrA protein endows the strain with the ability to resist Cr(VI). ChrT protein reduces Cr(VI) to Cr(III) by using NAD(P)H as electronic donor. The reduction process promotes the production of GSH, GSSG and NPSH to maintain the intracellular reduction state, which further improves the Cr(VI) tolerance and reduction ability of ChrAT engineered bacteria.

The Role of Specialized Pro-Resolving Mediators in Cystic Fibrosis Airways Disease

Cystic Fibrosis (CF) is a recessive genetic disease due to mutations of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene encoding the CFTR chloride channel. The ion transport abnormalities related to CFTR mutation generate a dehydrated airway surface liquid (ASL) layer, which is responsible for an altered mucociliary clearance, favors infections and persistent inflammation that lead to progressive lung destruction and respiratory failure. The inflammatory response is normally followed by an active resolution phase to return to tissue homeostasis, which involves specialized pro-resolving mediators (SPMs). SPMs promote resolution of inflammation, clearance of microbes, tissue regeneration and reduce pain, but do not evoke unwanted immunosuppression. The airways of CF patients showed a decreased production of SPMs even in the absence of pathogens. SPMs levels in the airway correlated with CF patients' lung function. The prognosis for CF has greatly improved but there remains a critical need for more effective treatments that prevent excessive inflammation, lung damage, and declining pulmonary function for all CF patients. This review aims to highlight the recent understanding of CF airway inflammation and the possible impact of SPMs on functions that are altered in CF airways.

Circulating biomarkers of antioxidant status and oxidative stress in people with cystic fibrosis: A systematic review and meta-analysis

Introduction

Oxidative stress may play an important role in the pathophysiology of cystic fibrosis (CF). This review aimed to quantify CF-related redox imbalances.

Methods

Systematic searches of the Medline, CINAHL, CENTRAL and PsycINFO databases were conducted. Mean content of blood biomarkers from people with clinically-stable CF and non-CF controls were used to calculate the standardized mean difference (SMD) and 95% confidence intervals (95% CI).

Results

Forty-nine studies were eligible for this review including a total of 1792 people with CF and 1675 controls. Meta-analysis revealed that protein carbonyls (SMD: 1.13, 95% CI: 0.48 to 1.77), total F₂-isoprostane 8-iso-prostaglandin F_2α (SMD: 0.64, 95% CI: 0.23 to 1.05) and malondialdehyde (SMD: 1.34, 95% CI: 0.30 to 2.39) were significantly higher, and vitamins A (SMD: −0.66, 95% CI -1.14 to −0.17) and E (SMD: −0.74, 95% CI: −1.28 to −0.20), β-carotene (SMD: −1.80, 95% CI: −2.92 to −0.67), lutein (SMD: −1.52, 95% CI: −1.83 to −1.20) and albumin (SMD: −0.98, 95% CI: −1.68 to −0.27) were significantly lower in the plasma or serum of people with CF versus controls.

Conclusions

This systematic review and meta-analysis found good evidence for reduced antioxidant capacity and elevated oxidative stress in people with clinically-stable CF.

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Blood biomarkers of oxidative stress were elevated in stable CF vs non-CF controls.

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Lipid peroxidation was positively correlated with age and immune cell count in CF.

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Antioxidants vitamins A & E, β-carotene, lutein and albumin were lower in stable CF.

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Antioxidants were positively correlated with body mass index and lung function in CF.

Gene modifiers of cystic fibrosis lung disease: A systematic review

BACKGROUND

Lung disease is the major source of morbidity and mortality in cystic fibrosis (CF), with large variability in severity between patients. Although accurate prediction of lung disease severity would be extremely useful, no robust methods exist. Twin and sibling studies have highlighted the importance of non-cystic fibrosis transmembrane conductance regulator (CFTR) genes in determining lung disease severity but how these impact on the severity in CF remains unclear.

METHODS

A systematic review was undertaken to answer the question "In patients with CF which non-CFTR genes modify the severity of lung disease?" The method for this systematic review was based upon the "Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)" statement, with a narrative synthesis of results planned.

RESULTS

A total of 1168 articles were screened for inclusion, with 275 articles undergoing detailed assessment for inclusion. One hundred and forty articles were included. Early studies focused on candidate genes, whereas more recent studies utilized genome-wide approaches and also examined epigenetic mechanisms, gene expression, and therapeutic response.

DISCUSSION

A large body of evidence regarding non-CFTR gene modifiers of lung disease severity has been generated, examining a wide array of genes. Limitations to existing studies include heterogeneity in outcome measures used, limited replication, and relative lack of clinical impact. Future work examining non-CFTR gene modifiers will have to overcome these limitations if gene modifiers are to have a meaningful role in the care of patients with CF.

Oxidative stress and abnormal bioactive lipids in early cystic fibrosis lung disease

BACKGROUND

Clinical data indicate that airway inflammation in children with cystic fibrosis (CF) arises early, is associated with structural lung damage, and predicts progression. In bronchoalveolar lavage fluid (BALF) from CFTR mutant mice, several aspects of lipid metabolism are abnormal that contributes to lung disease. We aimed to determine whether lipid pathway dysregulation is also observed in BALF from children with CF, to identify biomarkers of early lung disease and potential therapeutic targets.

METHODS

A comprehensive panel of lipids that included Sphingolipids, oxylipins, isoprostanes and lysolipids, all bioactive lipid species known to be involved in inflammation and tissue remodeling, were measured in BALF from children with CF (1-6 years, N = 33) and age-matched non-CF patients with unexplained inflammatory disease (N = 16) by HPLC-MS/MS. Lipid data were correlated with chest CT scores and BALF inflammation biomarkers.

RESULTS

The ratio of long chain to very long chain ceramide species (LCC/VLCC) and lysolipid levels were enhanced in CF compared to non-CF patients, despite comparable neutrophil counts and bacterial load. In CF patients both LCC/VLCC and lysolipid levels correlated with inflammation and chest CT scores. The ceramide precursors Sphingosine, Sphinganine, Sphingomyelin, correlated with inflammation, whilst the oxidative stress marker isoprostane correlated with inflammation and chest CT scores. No correlation between lipids and current bacterial infection in CF (N = 5) was observed.

CONCLUSIONS

Several lipid biomarkers of early CF lung disease were identified, which point toward potential disease monitoring and therapeutic approaches that can be used to complement CFTR modulators.

Overview and recent advances in electrochemical sensing of glutathione - A review

The present paper is aimed at providing an overview of the recent advances in the electrochemical sensing of glutathione (GSH), an important electrochemically and biologically active molecule, for the period 2012-2018. Herein, the analytical performances of newly developed electrochemical methods, procedures and protocols for GSH sensing are comprehensively and critically discussed with respect to the type of method, electrodes used (new electrode modifications, advanced materials and formats), sample matrices, and basic validation parameters obtained (limit of detection, linear dynamic range, precision, selectivity/evaluation of interferences). This paper considers electrochemical methods used alone as well as the hyphenated methods with electrochemical detection (ECD), such as HPLC-ECD or CE-ECD. The practical applicability of the platforms developed for GSH detection and quantification is mostly focused on pharmaceutical and biomedical analysis. The most significant electrochemical approaches for GSH detection in multicomponent analyte samples and multicomponent matrices and for real-time in vivo GSH analysis are highlighted. The great variability in the electrochemical techniques, electrode approaches, and obtainable performance parameters, discussed in this review, brought new insights not only on current GSH and glutathione disulfide (GSSG) determinations, but, along with this, on the advances in electrochemical analysis from a more general point of view.

Disease-modifying genetic factors in cystic fibrosis

PURPOSE OF REVIEW

To compile data from the past 10 years regarding the role of modifying genes in cystic fibrosis (CF).

RECENT FINDINGS

CF is a model disease for understanding of the action of modifying genes. Although it is a monogenic (CFTR) autosomal recessive disease, CF presents with wide phenotypic variability. In CF, variability occurs with different intensity among patients by each organ, being organ-specific, resulting from the mutual interaction of environmental and genetic factors, including CFTR mutations and various other genes, most of which are associated with inflammatory processes. In individuals, using precision medicine, gene modification studies have revealed individualized responses to drugs depending on particular CFTR mutations and modifying genes, most of which are alternative ion channels.

SUMMARY

Studies of modifying genes in CF allow: understanding of clinical variability among patients with the same CFTR genotype; evaluation of precision medicine; understanding of environmental and genetic effects at the organ level; understanding the involvement of genetic variants in inflammatory responses; improvements in genetic counseling; understanding the involvement of genetic variants in inflammatory responses in lung diseases, such as asthma; and understanding the individuality of the person with the disease.

How many copies of GSTM1 and GSTT1 are associated with head and neck cancer risk?

Purpose: GSTM1 and GSTT1 present a polymorphism that can drive complete gene deletions. The current methodology can powerfully determine GSTM1 and GSTT1 copy number variations (CNVs), which may clarify the real contribution of each gene copies to the cellular detoxification process and tumour risk. However, only analysing the presence/absence of these genes yielded controversial results for several disorders, including cancer. Because head and neck cancer (HNC) is becoming a serious global health problem, this study determined the CNVs of GSTM1 and GSTT1 in an HNC case-control population and investigated the possible association between gene copy numbers and tumour risk. Methods: CNV was evaluated by (Ct) 2^-ΔΔCt qPCR methodology in 619 HNC patients and 448 patients with no tumour diagnosis. Results: The genes copy number range was 0-3. The CNV of GSTM1 and GSTT1 frequencies were similar between the cases and control. Thus, none copy of GSTM1 and GSTT1 were associated with HNC risk. Notwithstanding, one copy of both genes had higher frequencies among individuals who carried GSTM1 and GSTT1. Conclusions: One copy number of GSTM1 and GSTT1 presented a higher frequency among carrier genes, but the CNV of GSTM1 and GSTT1 was not associated with HNC risk.

Induced pluripotent stem cells for treating cystic fibrosis: State of the science

Induced pluripotent stem cells (iPSCs) are a recently developed technology in which fully differentiated cells such as fibroblasts from individual CF patients can be repaired with [wildtype] CFTR, and reprogrammed to differentiate into fully differentiated cells characteristic of the proximal and distal airways. Here, we review properties of different epithelial cells in the airway, and the in vitro genetic roadmap which iPSCs follow as they are step-wise differentiated into either basal stem cells, for the proximal airway, or into Type II Alveolar cells for the distal airways. The central theme is that iPSC-derived basal stem cells, are penultimately dependent on NOTCH signaling for differentiation into club cells, goblet cells, ciliated cells, and neuroendocrine cells. Furthermore, given the proper matrix, these cellular progenies are also able to self-assemble into a fully functional pseudostratified squamous proximal airway epithelium. By contrast, club cells are reserve stem cells which are able to either differentiate into goblet or ciliated cells, but also to de-differentiate into basal stem cells. Variant club cells, located at the transition between airway and alveoli, may also be responsible for differentiation into Type II Alveolar cells, which then differentiate into Type I Alveolar cells for gas exchange in the distal airway. Using gene editing, the mutant CFTR gene in iPSCs from CF patients can be repaired, and fully functional epithelial cells can thus be generated through directed differentiation. However, there is a limitation in that the lung has other CFTR-dependent cells besides epithelial cells. Another limitation is that there are CFTR-dependent cells in other organs which would continue to contribute to CF disease. Furthermore, there are also bystander or modifier genes which affect disease outcome, not only in the lung, but specifically in other CF-affected organs. Finally, we discuss future personalized applications of the iPSC technology, many of which have already survived the "proof-of-principle" test. These include (i) patient-derived iPSCs used as a "lung-on-a-chip" tool for personalized drug discovery; (ii) replacement of mutant lung cells by wildtype lung cells in the living lung; and (iii) development of bio-artificial lungs. It is hoped that this review will give the reader a roadmap through the most complicated of the obstacles, and foster a guardedly optimistic view of how some of the remaining obstacles might one day be overcome.

Interaction among variants in the SLC gene family (SLC6A14, SLC26A9, SLC11A1, and SLC9A3) and CFTR mutations with clinical markers of cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) is due to dysfunction of the CFTR channel and function of this channel is, in turn, affected by modifier genes that can impact the clinical phenotype. In this context, we analyzed the interaction among rs3788766*SLC6A14, rs7512462*SLC26A9, rs17235416*SLC11A1, and rs17563161*SLC9A3 variants, CFTR mutations and 40 CF severity markers by the Multifactor Dimensionality Reduction (MDR) model.

METHODS

A total of 164 patients with CF were included in the study. The variants in the modifier genes were identified by real-time PCR and the genotype of the CFTR gene in the diagnostic routine. Analysis of interaction between variants, CFTR mutations groupings and demographic, clinical and laboratory data were performed by the MDR.

RESULTS

There were interaction between the rs3788766, rs7512462, rs17235416, and rs17563161 variants, and CFTR mutations with pancreatic insufficiency (PI), onset of digestive symptoms, and presence of mucoid Pseudomonas aeruginosa. Regarding PI, the interaction was observed for CFTR*rs17563161 (P-value = 0.015). Also, for onset of digestive symptoms the interaction was observed for CFTR*rs3788766*rs7512462*rs17235416*rs17563161 (P-value = 0.036). Considering the presence of mucoid P. aeruginosa, the interaction occurred for CFTR*rs3788766*rs7512462*rs17563161 (P-value = 0.035).

CONCLUSION

Interaction between variants in the SLC family genes and the grouping for CFTR mutations were associated with PI, onset of digestive symptoms and mucoid P. aeruginosa, being important to determine one of the factors that may cause the diversity among the patients with CF.

The EGFR-ADAM17 Axis in Chronic Obstructive Pulmonary Disease and Cystic Fibrosis Lung Pathology

Chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF) share molecular mechanisms that cause the pathological symptoms they have in common. Here, we review evidence suggesting that hyperactivity of the EGFR/ADAM17 axis plays a role in the development of chronic lung disease in both CF and COPD. The ubiquitous transmembrane protease A disintegrin and metalloprotease 17 (ADAM17) forms a functional unit with the EGF receptor (EGFR), in a feedback loop interaction labeled the ADAM17/EGFR axis. In airway epithelial cells, ADAM17 sheds multiple soluble signaling proteins by proteolysis, including EGFR ligands such as amphiregulin (AREG), and proinflammatory mediators such as the interleukin 6 coreceptor (IL-6R). This activity can be enhanced by injury, toxins, and receptor-mediated external triggers. In addition to intracellular kinases, the extracellular glutathione-dependent redox potential controls ADAM17 shedding. Thus, the epithelial ADAM17/EGFR axis serves as a receptor of incoming luminal stress signals, relaying these to neighboring and underlying cells, which plays an important role in the resolution of lung injury and inflammation. We review evidence that congenital CFTR deficiency in CF and reduced CFTR activity in chronic COPD may cause enhanced ADAM17/EGFR signaling through a defect in glutathione secretion. In future studies, these complex interactions and the options for pharmaceutical interventions will be further investigated.

Pancreatic Insufficiency in Cystic Fibrosis: Influence of Inflammatory Response Genes

OBJECTIVE

Pancreatic insufficiency (PI) in cystic fibrosis (CF) patients is a crucial clinical marker for severity and disease progression. In our study, 125 modifier genes and their SNPs were associated between CF patients with PI or pancreatic sufficiency.

METHODS

We prospectively evaluated 214 CF patients admitted at 1 hospital for a 2-year period. The PI status was associated with clinical variables and SNPs related with inflammatory response considering CFTR mutations. Open Array technique was used to perform the SNPs identification.

RESULTS

For PI risk, after correction by multiple test, in CF patients and 2 CFTR mutations class I, II, and/or III, there were 6 SNPs with positive association (P < 0.005). The odds ratio amplitude was 0.087 (95% confidence interval [CI], 0.004-0.544) for rs9870255*CG (CTNNB1 gene) to 11.06 (95% CI, 1.746-252.3) for rs729302*AA (IRF5 gene). For all CF patients at the same time, 9 SNPs showed positive association. The odds ratio amplitude was 0.144 (95% CI, 0.028-0.602) for rs2348071*AA (PSMA3 gene) to 5.809 (95% CI, 1.536-37.54) for rs11702779*AA (RUNX1 gene). In our data, we observed the interaction between CFTR mutations, rs9870255*CTNNB1, rs9378805*IRF4, and rs7664617*KCNIP4 to PI status.

CONCLUSIONS

Multiple SNPs in inflammatory response genes showed association with PI considering the CFTR mutations screening.

Variants in the interleukin 8 gene and the response to inhaled bronchodilators in cystic fibrosis

OBJECTIVE

Interleukin 8 protein promotes inflammatory responses, even in airways. The presence of interleukin 8 gene variants causes altered inflammatory responses and possibly varied responses to inhaled bronchodilators. Thus, this study analyzed the interleukin 8 variants (rs4073, rs2227306, and rs2227307) and their association with the response to inhaled bronchodilators in cystic fibrosis patients.

METHODS

Analysis of interleukin 8 gene variants was performed by restriction fragment length polymorphism of polymerase chain reaction. The association between spirometry markers and the response to inhaled bronchodilators was evaluated by Mann-Whitney and Kruskal-Wallis tests. The analysis included all cystic fibrosis patients, and subsequently patients with two mutations in the cystic fibrosis transmembrane conductance regulator gene belonging to classes I to III.

RESULTS

This study included 186 cystic fibrosis patients. There was no association of the rs2227307 variant with the response to inhaled bronchodilators. The rs2227306 variant was associated with FEF_50% in the dominant group and in the group with two identified mutations in the cystic fibrosis transmembrane conductance regulator gene. The rs4073 variant was associated with spirometry markers in four genetic models: co-dominant (FEF_25-75% and FEF_75%), dominant (FEV₁, FEF_50%, FEF_75%, and FEF_25-75%), recessive (FEF_75% and FEF_25-75%), and over-dominant (FEV₁/FVC).

CONCLUSIONS

This study highlighted the importance of the rs4073 variant of the interleukin 8 gene, regarding response to inhaled bronchodilators, and of the assessment of mutations in the cystic fibrosis transmembrane conductance regulator gene.

Increased Expression of Plasma-Induced ABCC1 mRNA in Cystic Fibrosis

The ABCC1 gene is structurally and functionally related to the cystic fibrosis transmembrane conductance regulator gene (CFTR). Upregulation of ABCC1 is thought to improve lung function in patients with cystic fibrosis (CF); the mechanism underlying this effect is unknown. We analyzed the ABCC1 promoter single nucleotide polymorphism (SNP rs504348), plasma-induced ABCC1 mRNA expression levels, and ABCC1 methylation status and their correlation with clinical variables among CF subjects with differing CFTR mutations. We assigned 93 CF subjects into disease severity groups and genotyped SNP rs504348. For 23 CF subjects and 7 healthy controls, donor peripheral blood mononuclear cells (PBMCs) stimulated with plasma underwent gene expression analysis via qRT-PCR. ABCC1 promoter methylation was analyzed in the same 23 CF subjects. No significant correlation was observed between rs504348 genotypes and CF disease severity, but pancreatic insufficient CF subjects showed increased colonization with any form of Pseudomonas aeruginosa (OR = 3.125, 95% CI: 1.192-8.190) and mucoid P. aeruginosa (OR = 5.075, 95% CI: 1.307-28.620) compared to the pancreatic sufficient group. A significantly higher expression of ABCC1 mRNA was induced by CF plasma compared to healthy control plasma (p < 0.001). CF subjects with rs504348 (CC/CG) also had higher mRNA expression compared to those with the ancestral GG genotype (p < 0.005). ABCC1 promoter was completely unmethylated; therefore, we did not detect any association between methylation and CF disease severity. In silico predictions suggested that histone modifications are crucial for regulating ABCC1 expression in PBMCs. Our results suggest that ABCC1 expression has a role in CFTR activity thereby increasing our understanding of the molecular underpinnings of the clinical heterogeneity in CF.

Association of clinical severity of cystic fibrosis with variants in the SLC gene family (SLC6A14, SLC26A9, SLC11A1 and SLC9A3)

INTRODUCTION

Cystic fibrosis (CF) manifests with clinical and histopathological variability depending on environmental and genetic factors. Moreover, the genes encoding ion channels[rs3788766(SLC6A14), rs7512462(SLC26A9), rs17235416(SLC11A1) and rs17563161(SLC9A3)] have been insufficiently studied as modifier genes. Then, our objective was associate the variants in the genes of SLC family with 43 CF severity markers.

METHODS

The variants were identified by real-time-PCR in 188 CF patients considering the CFTR genotype. Statistical analyses were performed by parametric and nonparametric tests. The correction by multiple testing was performed by the False Rate Discovery test, alpha=0.05.

RESULTS

Depending on the CFTR mutations, we found association of: (i) rs3788766*CC with mucoid Pseudomonas aeruginosa (OR=0.171; 95%CI=0.029-0.696), non-mucoid P. aeruginosa (OR=0.283; 95%CI=0.094-0.853) and Staphyloccocus aureus (OR=4.443; 95%CI=1.019-40.64), largest FEF_max(p=0.041) and best response to bronchodilator for FEF_50%(p=0.033) and FEV₁/FVC(p=0.044); (ii) rs3788766*CT with early start of pulmonary symptom (OR=3.524; 95%CI=1.229-10.1) and osteoporosis (OR=0.203; 95%CI=0.022-0.883); (iii) rs3788766*TT with lowest body mass index (OR=4.242; 95%CI=1.505-11.95), presence of mucoid P. aeruginosa (OR=3.176; 95%CI=1.29-7.819) and S. aureus (OR=0.116; 95%CI=0.004-0.881), highest Bhalla score (p=0.047) and lowest FEF_max(p=0.028) and FEF_25%(p=0.031) values; (iv) rs7512462*CC with highest Shwachman-Kulczycki score (p=0.019), FVC(p=0.043), FEV₁(p=0.047), FEV₁/FVC(p=0.022), FEF_50%(p=0.038) and FEF_25-75%(p=0.016); (v) rs7512462*CT with lowest values of FVC(p=0.034), FEV₁(p=0.047), FEV₁/FVC(p=0.022), FEF_25%(p=0.012), FEF_50%(p=0.038), FEF_75%(p=0.008), FEF_25-75%(p=0.016) and ERV(p=0.023); (vi) rs7512462*TT with best response to the inhaled bronchodilator for FEV₁(p=0.011), FEF_50%(p=0.019), FEF_75%(p=0.036) and FEF_25-75%(p=0.008); (vii) rs17234516*Normal allele with lowest value of SaO₂ (p=0.010) and S. aureus (OR=3.333; 95%CI=1.085-10.24); (viii) rs17563161*GG with lowest age for onset of digestive symptoms (OR=2.564; 95%CI=1.234-5.33).

CONCLUSIONS

The clinical and laboratory variability of CF were associated with the variants in the genes of SLC family in our sample.

Gclc deficiency in mouse CNS causes mitochondrial damage and neurodegeneration

Gamma glutamyl cysteine ligase (GCL) is the rate-limiting enzyme for intracellular glutathione (GSH) synthesis. The GSH concentration and GCL activity are declining with age in the central nervous system (CNS), and is accompanied by elevated reactive oxygen species (ROS). To study the biological effects of low GSH levels, we disrupted its synthesis both at birth by breeding a Gclc loxP mouse with a thy1-cre mouse (NEGSKO mouse) and at a later age by breeding with a CaMKII-ERT2-Cre (FIGSKO mouse). NEGSKO mice with deficiency of the Gclc in their entire CNS neuronal cells develop at 4 weeks: progressive motor neuron loss, gait problems, muscle denervation and atrophy, paralysis, and have diminished life expectancy. The observed neurodegeneration in Gclc deficiency is of more chronic rather than acute nature as demonstrated by Gclc targeted single-neuron labeling from the inducible Cre-mediated knockout (SLICK) mice. FIGSKO mice with inducible Gclc deficiency in the forebrain at 23 weeks after tamoxifen induction demonstrate profound brain atrophy, elevated astrogliosis and neurodegeneration, particularly in the hippocampus region. FIGSKO mice also develop cognitive abnormalities, i.e. learning impairment and nesting behaviors based on passive avoidance, T-Maze, and nesting behavior tests. Mechanistic studies show that impaired mitochondrial glutathione homeostasis and subsequent mitochondrial dysfunction are responsible for neuronal cell loss. This was confirmed by mitochondrial electron transporter chain activity analysis and transmission electron microscopy that demonstrate remarkable impairment of state 3 respiratory activity, impaired complex IV function, and mitochondrial swollen morphology in the hippocampus and cerebral cortex. These mouse genetic tools of oxidative stress open new insights into potential pharmacological control of apoptotic signaling pathways triggered by mitochondrial dysfunction.

Formaldehyde Induces Rho-Associated Kinase Activity to Evoke Airway Hyperresponsiveness

Formaldehyde, a common indoor air pollutant, exacerbates asthma and synergizes with allergen to induce airway hyperresponsiveness (AHR) in animal models. The mechanisms mediating formaldehyde-induced AHR remain poorly understood. We posit that formaldehyde modulates agonist-induced contractile response of human airway smooth muscle (HASM) cells to elicit AHR. HASM cells were exposed to formaldehyde or vehicle and agonist-induced intracellular Ca²⁺ ([Ca²⁺]_i) and myosin light-chain phosphatase (MYPT1) phosphorylation were determined. Air-liquid interface-differentiated human bronchial epithelial (HBE) cells were exposed to formaldehyde or vehicle and cocultured with HASM cells. Agonist-induced [Ca²⁺]_i and MYPT1 phosphorylation were determined in the cocultured HASM cells. Precision-cut human lung slices were exposed to PBS or varying concentrations of formaldehyde, and then carbachol-induced airway narrowing was determined 24 hours after exposure. HASM cells were transfected with nontargeting or nuclear factor erythroid-derived 2, like 2 (Nrf-2)-targeting small interfering RNA and exposed to formaldehyde or vehicle, followed by determination of antioxidant response (quinone oxido-reductase 1 and thioredoxin 1) and basal and agonist-induced MYPT1 phosphorylation. Formaldehyde enhanced the basal Rho-kinase activity and MYPT1 phosphorylation with little effect on agonist-induced [Ca²⁺]_i in HASM cells. Formaldehyde induced Nrf-2-dependent antioxidant response in HASM cells, although the MYPT1 phosphorylation was independent of Nrf-2 induction. Although HBE cells exposed to formaldehyde had little effect on agonist-induced [Ca²⁺]_i or MYPT1 phosphorylation in cocultured HASM cells, formaldehyde enhanced carbachol-induced airway responsiveness in precision-cut human lung slices. In conclusion, formaldehyde induces phosphorylation of the regulatory subunit of MYPT1, independent of formaldehyde-induced Nrf-2 activation in HASM cells. The findings suggest that the Rho kinase-dependent Ca²⁺ sensitization pathway plays a role in formaldehyde-induced AHR.

IL8 gene as modifier of cystic fibrosis: unraveling the factors which influence clinical variability

The severity of cystic fibrosis (CF) is associated with classes of mutations in the CFTR gene (cystic fibrosis transmembrane regulator), physical environment and modifier genes interaction. The IL8 gene (interleukin 8), according to its respective polymorphisms, influences inflammatory responses. This study analyzed IL8 gene polymorphisms (rs4073, rs2227306 and rs2227307), by means of PCR/RFLP, and their association with pulmonary function markers and clinical severity scores in 186 patients with CF, considering the CFTR genotype. There was an association between rs2227307 and precocity of the disease. The severity of lung disease was associated with the following markers: transcutaneous arterial hemoglobin oxygen saturation (SaO2) (regardless of CFTR genotype, for the polymorphisms rs4073, rs2227306 and rs2227307); mucoid Pseudomonas aeruginosa (regardless of CFTR genotype, for the polymorphisms rs2227306 and rs2227307). Pulmonary function markers (SaO2 and spirometric variables) and clinical severity scores were also associated with IL8 gene polymorphisms. This study identified the IL8 gene, represented by rs4073 and rs2227306 polymorphisms, and particularly the rs2227307 polymorphism, as potentiating factors for the degree of variability in the severity of CF, especially in pulmonary clinical manifestation correlated with increased morbidity and mortality.