Oxidative stress and antioxidant therapy in cystic fibrosis

Dual role of Nrf2 signaling in hepatocellular carcinoma: promoting development, immune evasion, and therapeutic challenges

Hepatocellular carcinoma (HCC) is the predominant form of liver cancer and ranks as the third leading cause of cancer-related mortality globally. The liver performs a wide range of tasks and is the primary organ responsible for metabolizing harmful substances and foreign compounds. Oxidative stress has a crucial role in growth and improvement of hepatocellular carcinoma (HCC). Nuclear factor erythroid 2 (1)-related factor 2 (Nrf2) is an element that regulates transcription located in the cytoplasm. It controls the balance of redox reactions by stimulating the expression of many genes that depend on antioxidant response elements. Nrf2 has contrasting functions in the normal, healthy liver and HCC. In the normal liver, Nrf2 provides advantageous benefits, while in HCC it promotes harmful effects that support the growth and survival of HCC. Continuous activation of Nrf2 has been detected in HCC and promotes its advancement and aggressiveness. In addition, Activation of Nrf2 may lead to immune evasion, weakening the immune cells' ability to attack tumors and thereby promoting tumor development. Furthermore, chemoresistance in HCC, which is considered a form of stress response to chemotherapy medications, significantly impedes the effectiveness of HCC treatment. Stress management is typically accomplished by activating specific signal pathways and chemical variables. One important element in the creation of chemoresistance in HCC is nuclear factor-E2-related factor 2 (Nrf2). Nrf2 is a transcription factor that regulates the activation and production of a group of genes that encode proteins responsible for protecting cells from damage. This occurs through the Nrf2/ARE pathway, which is a crucial mechanism for combating oxidative stress within cells.

Beyond insulin: Unraveling the complex interplay of ER stress, oxidative damage, and CFTR modulation in CFRD

CF-related diabetes (CFRD) is a prevalent comorbidity in people with Cystic Fibrosis (CF), significantly impacting morbidity and mortality rates. This review article critically evaluates the current understanding of CFRD molecular mechanisms, including the role of CFTR protein, oxidative stress, unfolded protein response (UPR) and intracellular communication. CFRD manifests from a complex interplay between exocrine pancreatic damage and intrinsic endocrine dysfunction, further complicated by the deleterious effects of misfolded CFTR protein on insulin secretion and action. Studies indicate that ER stress and subsequent UPR activation play critical roles in both exocrine and endocrine pancreatic cell dysfunction, contributing to β-cell loss and insulin insufficiency. Additionally, oxidative stress and altered calcium flux, exacerbated by CFTR dysfunction, impair β-cell survival and function, highlighting the significance of antioxidant pathways in CFRD pathogenesis. Emerging evidence underscores the importance of exosomal microRNAs (miRNAs) in mediating inflammatory and stress responses, offering novel insights into CFRD's molecular landscape. Despite insulin therapy remaining the cornerstone of CFRD management, the variability in response to CFTR modulators underscores the need for personalized treatment approaches. The review advocates for further research into non-CFTR therapeutic targets, emphasizing the need to address the multifaceted pathophysiology of CFRD. Understanding the intricate mechanisms underlying CFRD will pave the way for innovative treatments, moving beyond insulin therapy to target the disease's root causes and improve the quality of life for individuals with CF.

Crosstalk between ROS-inflammatory gene expression axis in the progression of lung disorders

A significant number of deaths and disabilities worldwide are brought on by inflammatory lung diseases. Many inflammatory lung disorders, including chronic respiratory emphysema, resistant asthma, resistance to steroids, and coronavirus-infected lung infections, have severe variants for which there are no viable treatments; as a result, new treatment alternatives are needed. Here, we emphasize how oxidative imbalance contributes to the emergence of provocative lung problems that are challenging to treat. Endogenic antioxidant systems are not enough to avert free radical-mediated damage due to the induced overproduction of ROS. Pro-inflammatory mediators are then produced due to intracellular signaling events, which can harm the tissue and worsen the inflammatory response. Overproduction of ROS causes oxidative stress, which causes lung damage and various disease conditions. Invasive microorganisms or hazardous substances that are inhaled repeatedly can cause an excessive amount of ROS to be produced. By starting signal transduction pathways, increased ROS generation during inflammation may cause recurrent DNA damage and apoptosis and activate proto-oncogenes. This review provides information about new targets for conducting research in related domains or target factors to prevent, control, or treat such inflammatory oxidative stress-induced inflammatory lung disorders.

Metabolic specialization drives reduced pathogenicity in Pseudomonas aeruginosa isolates from cystic fibrosis patients

Metabolism provides the foundation for all cellular functions. During persistent infections, in adapted pathogenic bacteria metabolism functions radically differently compared with more naïve strains. Whether this is simply a necessary accommodation to the persistence phenotype or if metabolism plays a direct role in achieving persistence in the host is still unclear. Here, we characterize a convergent shift in metabolic function(s) linked with the persistence phenotype during Pseudomonas aeruginosa colonization in the airways of people with cystic fibrosis. We show that clinically relevant mutations in the key metabolic enzyme, pyruvate dehydrogenase, lead to a host-specialized metabolism together with a lower virulence and immune response recruitment. These changes in infection phenotype are mediated by impaired type III secretion system activity and by secretion of the antioxidant metabolite, pyruvate, respectively. Our results show how metabolic adaptations directly impinge on persistence and pathogenicity in this organism.

Pulmonary Vascular Dysfunctions in Cystic Fibrosis

Cystic fibrosis (CF) is an inherited disorder caused by a deleterious mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Given that the CFTR protein is a chloride channel expressed on a variety of cells throughout the human body, mutations in this gene impact several organs, particularly the lungs. For this very reason, research regarding CF disease and CFTR function has historically focused on the lung airway epithelium. Nevertheless, it was discovered more than two decades ago that CFTR is also expressed and functional on endothelial cells. Despite the great strides that have been made in understanding the role of CFTR in the airway epithelium, the role of CFTR in the endothelium remains unclear. Considering that the airway epithelium and endothelium work in tandem to allow gas exchange, it becomes very crucial to understand how a defective CFTR protein can impact the pulmonary vasculature and overall lung function. Fortunately, more recent research has been dedicated to elucidating the role of CFTR in the endothelium. As a result, several vascular dysfunctions associated with CF disease have come to light. Here, we summarize the current knowledge on pulmonary vascular dysfunctions in CF and discuss applicable therapies.

Pseudomonas aeruginosa transcriptome analysis of metal restriction in ex vivo cystic fibrosis sputum

Chronic Pseudomonas aeruginosa lung infections are a feature of cystic fibrosis (CF) that many patients experience even with the advent of highly effective modulator therapies. Identifying factors that impact P. aeruginosa in the CF lung could yield novel strategies to eradicate infection or otherwise improve outcomes. To complement published P. aeruginosa studies using laboratory models or RNA isolated from sputum, we analyzed transcripts of strain PAO1 after incubation in sputum from different CF donors prior to RNA extraction. We compared PAO1 gene expression in this "spike-in" sputum model to that for P. aeruginosa grown in synthetic cystic fibrosis sputum medium to determine key genes, which are among the most differentially expressed or most highly expressed. Using the key genes, gene sets with correlated expression were determined using the gene expression analysis tool eADAGE. Gene sets were used to analyze the activity of specific pathways in P. aeruginosa grown in sputum from different individuals. Gene sets that we found to be more active in sputum showed similar activation in published data that included P. aeruginosa RNA isolated from sputum relative to corresponding in vitro reference cultures. In the ex vivo samples, P. aeruginosa had increased levels of genes related to zinc and iron acquisition which were suppressed by metal amendment of sputum. We also found a significant correlation between expression of the H1-type VI secretion system and CFTR corrector use by the sputum donor. An ex vivo sputum model or synthetic sputum medium formulation that imposes metal restriction may enhance future CF-related studies.IMPORTANCEIdentifying the gene expression programs used by Pseudomonas aeruginosa to colonize the lungs of people with cystic fibrosis (CF) will illuminate new therapeutic strategies. To capture these transcriptional programs, we cultured the common P. aeruginosa laboratory strain PAO1 in expectorated sputum from CF patient donors. Through bioinformatic analysis, we defined sets of genes that are more transcriptionally active in real CF sputum compared to a synthetic cystic fibrosis sputum medium. Many of the most differentially active gene sets contained genes related to metal acquisition, suggesting that these gene sets play an active role in scavenging for metals in the CF lung environment which may be inadequately represented in some models. Future studies of P. aeruginosa transcript abundance in CF may benefit from the use of an expectorated sputum model or media supplemented with factors that induce metal restriction.

Antioxidant therapy against TGF-β/SMAD pathway involved in organ fibrosis

Fibrosis refers to excessive build-up of scar tissue and extracellular matrix components in different organs. In recent years, it has been revealed that different cytokines and chemokines, especially Transforming growth factor beta (TGF-β) is involved in the pathogenesis of fibrosis. It has been shown that TGF-β is upregulated in fibrotic tissues, and contributes to fibrosis by mediating pathways that are related to matrix preservation and fibroblasts differentiation. There is no doubt that antioxidants protect against different inflammatory conditions by reversing the effects of nitrogen, oxygen and sulfur-based reactive elements. Oxidative stress has a direct impact on chronic inflammation, and as results, prolonged inflammation ultimately results in fibrosis. Different types of antioxidants, in the forms of vitamins, natural compounds or synthetic ones, have been proven to be beneficial in the protection against fibrotic conditions both in vitro and in vivo. In this study, we reviewed the role of different compounds with antioxidant activity in induction or inhibition of TGF-β/SMAD signalling pathway, with regard to different fibrotic conditions such as gastro-intestinal fibrosis, cardiac fibrosis, pulmonary fibrosis, skin fibrosis, renal fibrosis and also some rare cases of fibrosis, both in animal models and cell lines.

Secondary Metabolites for the Reduction of Oxidative Stress

Oxidative stress is a condition that occurs when there is an imbalance between the production of reactive oxygen species (ROS) and the body's ability to neutralize them [...].

Biomarkers of nitrosative stress in exhaled breath condensate and serum among patients with cystic fibrosis

PURPOSE

The measurement of biomarkers in exhaled breath condensate (EBC) offers a non-invasive way to assess airway disease and can be easily done in a clinical setting among patients with cystic fibrosis (CF). The role of oxidative and nitrosative stress in the complex pathophysiology of CF is widely accepted and biomarkers of oxidative and nitrosative stress can be measured in the serum and EBC. To our knowledge, this is the first study to assess markers of nitrosative stress in EBC and serum, collected simultaneously from the CF patients.

PATIENTS AND METHODS

Paired EBC and serum samples were collected from 36 stable patients with CF and 14 healthy controls. Markers of nitrosative stress ‒ 3-nitrotyrosine and nitrate/nitrite were measured in the EBC and serum using an enzyme-linked immunosorbent assay.

RESULTS

We found no differences in 3-nitrotyrosine and nitrate/nitrite in the EBC of patients with CF as compared to healthy controls (125.37 ​± ​3.29 vs. 126.24 ​± ​2.21 ​nmol/L, p ​= ​0.218; 12.66 ​± ​7.23 vs. 8.79 ​± ​4.83 ​μmol/L, p ​= ​0.133, respectively). Furthermore, 3-nitrotyrosine and nitrate/nitrite were significantly higher in the serum of patients with CF as compared to the healthy controls (0.13 ​± ​0.02 vs. 0.11 ​± ​0.01 ​nmol/mg protein, p ​= ​0.003; 70.78 ​± ​22.55 vs. 53.08 ​± ​8.5 ​μmol/L, p ​= ​0.009, respectively). No correlations were found between the markers determined in the EBC and serum.

CONCLUSIONS

The results of the EBC nitrosative stress biomarkers should be interpreted with caution, especially in patients with stable disease, as the EBC values may be independent on levels of circulating markers that are elevated in the serum of patients with stable CF.

Analysis of Pseudomonas aeruginosa transcription in an ex vivo cystic fibrosis sputum model identifies metal restriction as a gene expression stimulus

Chronic Pseudomonas aeruginosa lung infections are a distinctive feature of cystic fibrosis (CF) pathology, that challenge adults with CF even with the advent of highly effective modulator therapies. Characterizing P. aeruginosa transcription in the CF lung and identifying factors that drive gene expression could yield novel strategies to eradicate infection or otherwise improve outcomes. To complement published P. aeruginosa gene expression studies in laboratory culture models designed to model the CF lung environment, we employed an ex vivo sputum model in which laboratory strain PAO1 was incubated in sputum from different CF donors. As part of the analysis, we compared PAO1 gene expression in this "spike-in" sputum model to that for P. aeruginosa grown in artificial sputum medium (ASM). Analyses focused on genes that were differentially expressed between sputum and ASM and genes that were most highly expressed in sputum. We present a new approach that used sets of genes with correlated expression, identified by the gene expression analysis tool eADAGE, to analyze the differential activity of pathways in P. aeruginosa grown in CF sputum from different individuals. A key characteristic of P. aeruginosa grown in expectorated CF sputum was related to zinc and iron acquisition, but this signal varied by donor sputum. In addition, a significant correlation between P. aeruginosa expression of the H1-type VI secretion system and corrector use by the sputum donor was observed. These methods may be broadly useful in looking for variable signals across clinical samples.

Control of mitochondrial functions by Pseudomonas aeruginosa in cystic fibrosis

Cystic fibrosis (CF) is a genetic disease characterized by mutations of cystic fibrosis transmembrane conductance regulator (CFTR) gene, which lead to a dysfunctional chloride and bicarbonate channel. Abnormal mucus viscosity, persistent infections and hyperinflammation that preferentially affect the airways, referred to the pathogenesis of CF lung disease. It has largely demonstrated that Pseudomonas aeruginosa (P. aeruginosa) represents the most important pathogen that affect CF patients, leading to worsen inflammation by stimulating pro-inflammatory mediators release and tissue destruction. The conversion to mucoid phenotype and formation of biofilms, together with the increased frequency of mutations, are only few changes that characterize the P. aeruginosa's evolution during CF lung chronic infection. Recently, mitochondria received increasing attention due to their involvement in inflammatory-related diseases, including in CF. Alteration of mitochondrial homeostasis is sufficient to stimulate immune response. Exogenous or endogenous stimuli that perturb mitochondrial activity are used by cells, which, through the mitochondrial stress, potentiate immunity programs. Studies show the relationship between mitochondria and CF, supporting the idea that mitochondrial dysfunction endorses the exacerbation of inflammatory responses in CF lung. In particular, evidences suggest that mitochondria in CF airway cells are more susceptible to P. aeruginosa infection, with consequent detrimental effects that lead to amplify the inflammatory signals. This review discusses the evolution of P. aeruginosa in relationship with the pathogenesis of CF, a fundamental step to establish chronic infection in CF lung disease. Specifically, we focus on the role of P. aeruginosa in the exacerbation of inflammatory response, by triggering mitochondria in CF.

Revisiting Host-Pathogen Interactions in Cystic Fibrosis Lungs in the Era of CFTR Modulators

Cystic fibrosis transmembrane conductance regulator (CFTR) modulators, a new series of therapeutics that correct and potentiate some classes of mutations of the CFTR, have provided a great therapeutic advantage to people with cystic fibrosis (pwCF). The main hindrances of the present CFTR modulators are related to their limitations in reducing chronic lung bacterial infection and inflammation, the main causes of pulmonary tissue damage and progressive respiratory insufficiency, particularly in adults with CF. Here, the most debated issues of the pulmonary bacterial infection and inflammatory processes in pwCF are revisited. Special attention is given to the mechanisms favoring the bacterial infection of pwCF, the progressive adaptation of Pseudomonas aeruginosa and its interplay with Staphylococcus aureus, the cross-talk among bacteria, the bronchial epithelial cells and the phagocytes of the host immune defenses. The most recent findings of the effect of CFTR modulators on bacterial infection and the inflammatory process are also presented to provide critical hints towards the identification of relevant therapeutic targets to overcome the respiratory pathology of pwCF.

Distribution of OGTT-Related Variables in Patients with Cystic Fibrosis from Puberty to Adulthood: An Italian Multicenter Study

Background: Insulin secretion and glucose tolerance is annually assessed in patients with cystic fibrosis (PwCF) through oral glucose tolerance tests (OGTTs) as a screening measure for cystic fibrosis-related diabetes. We aimed to describe the distribution and provide reference quartiles of OGTT-related variables in the Italian cystic fibrosis population. Methods: Cross-sectional study of PwCF receiving care in three Italian cystic fibrosis centers of excellence, from 2016 to 2020. We performed a modified 2-h OGTT protocol (1.75 g/kg, maximum 75 g), sampling at baseline and at 30-min intervals, analyzing plasma glucose, serum insulin, and C-peptide. The modified OGTT allowed for the modeling of β cell function. For all variables, multivariable quantile regression was performed to estimate the median, the 25th, and 75th percentiles, with age, sex, and pancreatic insufficiency as predictors. Results: We have quantified the deterioration of glucose tolerance and insulin secretion with age according to sex and pancreatic insufficiency, highlighting a deviation from linearity both for patients <10 years and >35 years of age. Conclusions: References of OGTT variables for PwCF provide a necessary tool to not only identify patients at risk for CFRD or other cystic fibrosis-related complications, but also to evaluate the effects of promising pharmacological therapies.

Update on Innate and Adaptive Immunity in Cystic Fibrosis

Cystic fibrosis (CF) pathophysiology is hallmarked by excessive inflammation and the inability to resolve lung infections, contributing to morbidity and eventually mortality. Paradoxically, despite a robust inflammatory response, CF lungs fail to clear bacteria and are susceptible to chronic infections. Impaired mucociliary transport plays a critical role in chronic infection but the immune mechanisms contributing to the adaptation of bacteria to the lung microenvironment is not clear. CFTR modulator therapy has advanced CF life expectancy opening up the need to understand changes in immunity as CF patients age. Here, we have summarized the current understanding of immune dysregulation in CF.

New TMA (4,6,4'-Trimethyl angelicin) Analogues as Anti-Inflammatory Agents in the Treatment of Cystic Fibrosis Lung Disease

A series of new-generation TMA (4,6,4'-trimethyl angelicin) analogues was projected and synthetized in order to ameliorate anti-inflammatory activity, with reduced or absent toxicity. Since the NF-κB transcription factor (TF) plays a critical role in the expression of IL-8 (Interluekin 8), a typical marker of lung inflammation in Cystic Fibrosis (CF), the use of agents able to interfere with the NF-κB pathway represents an interesting therapeutic strategy. Through preliminary EMSA experiments, we identified several new TMA derivatives able to inhibit the NF-κB/DNA complex. The selected active molecules were then analyzed to evaluate the anti-inflammatory effect using both Pseudomonas aeruginosa (PAO1) infection and TNF-alpha stimulus on the CF IB3-1 cell line. It was demonstrated that mainly two TMA analogues, GY971a mesylate salt (6-p-minophenyl-4,4'-dimethyl-angelicin) and GY964 (4-phenyl-6,4'-dimethyl-angelicin), were able to decrease the IL-8 gene expression. At the same time, these molecules were found to have no pro-apoptotic, mutagenic and phototoxic effects, facilitating our decision to test the efficacy in vivo by using a mouse model of acute P. aeruginosa lung infection. The anti-inflammatory effect of GY971a was confirmed in vivo; this derivative was able to deeply decrease the total number of inflammatory cells, the neutrophil count and the cytokine/chemokine profile in the P. aeruginosa acute infection model, without evident toxicity. Considering all the obtained and reported in vitro and in vivo pre-clinical results, GY971a seems to have interesting anti-inflammatory effects, modulating the NF-κB pathway, as well as the starting lead compound TMA, but without side effects.

Glutathione: A Samsonian life-sustaining small molecule that protects against oxidative stress, ageing and damaging inflammation

Many local and systemic diseases especially diseases that are leading causes of death globally like chronic obstructive pulmonary disease, atherosclerosis with ischemic heart disease and stroke, cancer and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing coronavirus disease 19 (COVID-19), involve both, (1) oxidative stress with excessive production of reactive oxygen species (ROS) that lower glutathione (GSH) levels, and (2) inflammation. The GSH tripeptide (γ- L-glutamyl-L-cysteinyl-glycine), the most abundant water-soluble non-protein thiol in the cell (1-10 mM) is fundamental for life by (a) sustaining the adequate redox cell signaling needed to maintain physiologic levels of oxidative stress fundamental to control life processes, and (b) limiting excessive oxidative stress that causes cell and tissue damage. GSH activity is facilitated by activation of the Kelch-like ECH-associated protein 1 (Keap1)-Nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) redox regulator pathway, releasing Nrf2 that regulates expression of genes controlling antioxidant, inflammatory and immune system responses. GSH exists in the thiol-reduced (>98% of total GSH) and disulfide-oxidized (GSSG) forms, and the concentrations of GSH and GSSG and their molar ratio are indicators of the functionality of the cell. GSH depletion may play a central role in inflammatory diseases and COVID-19 pathophysiology, host immune response and disease severity and mortality. Therapies enhancing GSH could become a cornerstone to reduce severity and fatal outcomes of inflammatory diseases and COVID-19 and increasing GSH levels may prevent and subdue these diseases. The life value of GSH makes for a paramount research field in biology and medicine and may be key against systemic inflammation and SARS-CoV-2 infection and COVID-19 disease. In this review, we emphasize on (1) GSH depletion as a fundamental risk factor for diseases like chronic obstructive pulmonary disease and atherosclerosis (ischemic heart disease and stroke), (2) importance of oxidative stress and antioxidants in SARS-CoV-2 infection and COVID-19 disease, (3) significance of GSH to counteract persistent damaging inflammation, inflammaging and early (premature) inflammaging associated with cell and tissue damage caused by excessive oxidative stress and lack of adequate antioxidant defenses in younger individuals, and (4) new therapies that include antioxidant defenses restoration.

Identification of Exhaled Metabolites in Children with Cystic Fibrosis

The early detection of inflammation and infection is important to prevent irreversible lung damage in cystic fibrosis. Novel and non-invasive monitoring tools would be of high benefit for the quality of life of patients. Our group previously detected over 100 exhaled mass-to-charge (m/z) features, using on-line secondary electrospray ionization high-resolution mass spectrometry (SESI-HRMS), which distinguish children with cystic fibrosis from healthy controls. The aim of this study was to annotate as many m/z features as possible with putative chemical structures. Compound identification was performed by applying a rigorous workflow, which included the analysis of on-line MS2 spectra and a literature comparison. A total of 49 discriminatory exhaled compounds were putatively identified. A group of compounds including glycolic acid, glyceric acid and xanthine were elevated in the cystic fibrosis group. A large group of acylcarnitines and aldehydes were found to be decreased in cystic fibrosis. The proposed compound identification workflow was used to identify signatures of volatile organic compounds that discriminate children with cystic fibrosis from healthy controls, which is the first step for future non-invasive and personalized applications.

α-Tocopherol Pharmacokinetics in Adults with Cystic Fibrosis: Benefits of Supplemental Vitamin C Administration

BACKGROUND

Numerous abnormalities in cystic fibrosis (CF) could influence tocopherol absorption, transportation, storage, metabolism and excretion. We hypothesized that the oxidative distress due to inflammation in CF increases vitamin E utilization, which could be positively influenced by supplemental vitamin C administration.

METHODS

Immediately before and after receiving vitamin C (500 mg) twice daily for 3.5 weeks, adult CF patients (n = 6) with moderately advanced respiratory tract (RT) disease consumed a standardized breakfast with 30% fat and a capsule containing 50 mg each hexadeuterium (d₆)-α- and dideuterium (d₂)-γ-tocopheryl acetates. Blood samples were taken frequently up to 72 h; plasma tocopherol pharmacokinetics were determined. During both trials, d₆-α- and d₂-γ-tocopherols were similarly absorbed and reached similar maximal plasma concentrations ~18-20 h. As predicted, during vitamin C supplementation, the rates of plasma d₆-α-tocopherol decline were significantly slower.

CONCLUSIONS

The vitamin C-induced decrease in the plasma disappearance rate of α-tocopherol suggests that vitamin C recycled α-tocopherol, thereby augmenting its concentrations. We conclude that some attention should be paid to plasma ascorbic acid concentrations in CF patients, particularly to those individuals with more advanced RT inflammatory disease and including those with severe exacerbations.

The NHE3 Inhibitor Tenapanor Prevents Intestinal Obstructions in CFTR-Deleted Mice

Mutations in the CFTR chloride channel result in intestinal obstructive episodes in cystic fibrosis (CF) patients and in CF animal models. In this study, we explored the possibility of reducing the frequency of obstructive episodes in cftr^−/− mice through the oral application of a gut-selective NHE3 inhibitor tenapanor and searched for the underlying mechanisms involved. Sex- and age-matched cftr^+/+ and cftr^−/− mice were orally gavaged twice daily with 30 mg kg⁻¹ tenapanor or vehicle for a period of 21 days. Body weight and stool water content was assessed daily and gastrointestinal transit time (GTT) once weekly. The mice were sacrificed when an intestinal obstruction was suspected or after 21 days, and stool and tissues were collected for further analysis. Twenty-one day tenapanor application resulted in a significant increase in stool water content and stool alkalinity and a significant decrease in GTT in cftr^+/+ and cftr^−/− mice. Tenapanor significantly reduced obstructive episodes to 8% compared to 46% in vehicle-treated cftr^−/− mice and prevented mucosal inflammation. A decrease in cryptal hyperproliferation, mucus accumulation, and mucosal mast cell number was also observed in tenapanor- compared to vehicle-treated, unobstructed cftr^−/− mice. Overall, oral tenapanor application prevented obstructive episodes in CFTR-deficient mice and was safe in cftr^+/+ and cftr^−/− mice. These results suggest that tenapanor may be a safe and affordable adjunctive therapy in cystic fibrosis patients to alleviate constipation and prevent recurrent DIOS.

Ruthenium(II) Polypyridyl Complexes for Antimicrobial Photodynamic Therapy: Prospects for Application in Cystic Fibrosis Lung Airways

Antimicrobial photodynamic therapy (aPDT) depends on a variety of parameters notably related to the photosensitizers used, the pathogens to target and the environment to operate. In a previous study using a series of Ruthenium(II) polypyridyl ([Ru(II)]) complexes, we reported the importance of the chemical structure on both their photo-physical/physico-chemical properties and their efficacy for aPDT. By employing standard in vitro conditions, effective [Ru(II)]-mediated aPDT was demonstrated against planktonic cultures of Pseudomonas aeruginosa and Staphylococcus aureus strains notably isolated from the airways of Cystic Fibrosis (CF) patients. CF lung disease is characterized with many pathophysiological disorders that can compromise the effectiveness of antimicrobials. Taking this into account, the present study is an extension of our previous work, with the aim of further investigating [Ru(II)]-mediated aPDT under in vitro experimental settings approaching the conditions of infected airways in CF patients. Thus, we herein studied the isolated influence of a series of parameters (including increased osmotic strength, acidic pH, lower oxygen availability, artificial sputum medium and biofilm formation) on the properties of two selected [Ru(II)] complexes. Furthermore, these compounds were used to evaluate the possibility to photoinactivate P. aeruginosa while preserving an underlying epithelium of human bronchial epithelial cells. Altogether, our results provide substantial evidence for the relevance of [Ru(II)]-based aPDT in CF lung airways. Besides optimized nano-complexes, this study also highlights the various needs for translating such a challenging perspective into clinical practice.

How Aging and Oxidative Stress Influence the Cytopathic and Inflammatory Effects of SARS-CoV-2 Infection: The Role of Cellular Glutathione and Cysteine Metabolism

SARS-CoV-2 infection can cause a severe respiratory distress syndrome with inflammatory and thrombotic complications, the severity of which increases with patients’ age and presence of comorbidity. The reasons for an age-dependent increase in the risk of severe COVID-19 could be many. These include defects in the homeostatic processes that control the cellular redox and its pivotal role in sustaining the immuno-inflammatory response to the host and the protection against oxidative stress and tissue degeneration. Pathogens may take advantage of such age-dependent abnormalities. Alterations of the thiol redox balance in the lung tissue and lining fluids may influence the risk of infection, and the host capability to respond to pathogens and to avoid severe complications. SARS-CoV-2, likewise other viruses, such as HIV, influenza, and HSV, benefits in its replication cycle of pro-oxidant conditions that the same viral infection seems to induce in the host cell with mechanisms that remain poorly understood. We recently demonstrated that the pro-oxidant effects of SARS-CoV-2 infection are associated with changes in the cellular metabolism and transmembrane fluxes of Cys and GSH. These appear to be the consequence of an increased use of Cys in viral protein synthesis and to ER stress pathway activation that interfere with transcription factors, as Nrf2 and NFkB, important to coordinate the metabolism of GSH with other aspects of the stress response and with the pro-inflammatory effects of this virus in the host cell. This narrative review article describes these cellular and molecular aspects of SARS-CoV-2 infection, and the role that antivirals and cytoprotective agents such as N-acetyl cysteine may have to limit the cytopathic effects of this virus and to recover tissue homeostasis after infection.

Overview of CF lung pathophysiology

Defects of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) protein affect the homeostasis of chloride, bicarbonate, sodium, and water in the airway surface liquid, influencing the mucus composition and viscosity, which induces a severe condition of infection and inflammation along the whole life of CF patients. The introduction of CFTR modulators, novel drugs directly intervening to rescue the function of CFTR protein, opens a new era of experimental research. The review summarizes the most recent advancements to understand the characteristics of the infective and inflammatory pathology of CF lungs.

Proteostasis Regulators in Cystic Fibrosis: Current Development and Future Perspectives

In cystic fibrosis (CF), the deletion of phenylalanine 508 (F508del) in the CF transmembrane conductance regulator (CFTR) leads to misfolding and premature degradation of the mutant protein. These defects can be targeted with pharmacological agents named potentiators and correctors. During the past years, several efforts have been devoted to develop and approve new effective molecules. However, their clinical use remains limited, as they fail to fully restore F508del-CFTR biological function. Indeed, the search for CFTR correctors with different and additive mechanisms has recently increased. Among them, drugs that modulate the CFTR proteostasis environment are particularly attractive to enhance therapy effectiveness further. This Perspective focuses on reviewing the recent progress in discovering CFTR proteostasis regulators, mainly describing the design, chemical structure, and structure-activity relationships. The opportunities, challenges, and future directions in this emerging and promising field of research are discussed, as well.

Roscovitine Worsens Mycobacterium abscessus Infection by Reducing DUOX2-mediated Neutrophil Response

Persistent neutrophilic inflammation associated with chronic pulmonary infection causes progressive lung injury and, eventually, death in individuals with cystic fibrosis (CF), a genetic disease caused by biallelic mutations in the CF transmembrane conductance regulator (CFTR) gene. Therefore, we examined whether roscovitine, a cyclin-dependent kinase inhibitor that (in other conditions) reduces inflammation while promoting host defense, might provide a beneficial effect in the context of CF. Herein, using CFTR-depleted zebrafish larvae as an innovative vertebrate model of CF immunopathophysiology, combined with murine and human approaches, we sought to determine the effects of roscovitine on innate immune responses to tissue injury and pathogens in the CF condition. We show that roscovitine exerts antiinflammatory and proresolution effects in neutrophilic inflammation induced by infection or tail amputation in zebrafish. Roscovitine reduces overactive epithelial reactive oxygen species (ROS)-mediated neutrophil trafficking by reducing DUOX2/NADPH-oxidase activity and accelerates inflammation resolution by inducing neutrophil apoptosis and reverse migration. It is important to note that, although roscovitine efficiently enhances intracellular bacterial killing of Mycobacterium abscessus in human CF macrophages ex vivo, we found that treatment with roscovitine results in worse infection in mouse and zebrafish models. By interfering with DUOX2/NADPH oxidase-dependent ROS production, roscovitine reduces the number of neutrophils at infection sites and, consequently, compromises granuloma formation and maintenance, favoring extracellular multiplication of M. abscessus and more severe infection. Our findings bring important new understanding of the immune-targeted action of roscovitine and have significant therapeutic implications for safely targeting inflammation in CF.

Increased susceptibility of cystic fibrosis airway epithelial cells to ferroptosis

BACKGROUND

Defective chloride transport in airway epithelial cells (AECs) and the associated lung disease are the main causes of morbidity and early mortality in cystic fibrosis (CF). Abnormal airway iron homeostasis and the presence of lipid peroxidation products, indicative of oxidative stress, are features of CF lung disease.

RESULTS

Here, we report that CF AECs (IB3-1) are susceptible to ferroptosis, a type of cell death associated with iron accumulation and lipid peroxidation. Compared to isogenic CFTR corrected cells (C38), the IB3-1 cells showed increased susceptibility to cell death upon exposure to iron in the form of ferric ammonium citrate (FAC) and the ferroptosis inducer, erastin. This phenotype was accompanied by accumulation of intracellular ferrous iron and lipid peroxides and the extracellular release of malondialdehyde, all indicative of redox stress, and increased levels of lactate dehydrogenase in the culture supernatant, indicating enhanced cell injury. The ferric iron chelator deferoxamine (DFO) and the lipophilic antioxidant ferrostatin-1 inhibited FAC and erastin induced ferroptosis in IB3-1 cells. Glutathione peroxidase 4 (GPX4) expression was decreased in IB3-1 cells treated with FAC and erastin, but was unchanged in C38 AECs. Necroptosis appeared to be involved in the enhanced susceptibility of IB3-1 AECs to ferroptosis, as evidenced by partial cell death rescue with necroptosis inhibitors and enhanced mixed lineage kinase domain-like (MLKL) localisation to the plasma membrane.

CONCLUSION

These studies suggest that the increased susceptibility of CF AECs to ferroptosis is linked to abnormal intracellular ferrous iron accumulation and reduced antioxidant defences. In addition, the process of ferroptotic cell death in CF AECs does not appear to be a single entity and for the first time we describe necroptosis as a potential contributory factor. Iron chelation and antioxidant treatments may be promising therapeutic interventions in cystic fibrosis.

The Diguanylate Cyclase YfiN of Pseudomonas aeruginosa Regulates Biofilm Maintenance in Response to Peroxide

Pseudomonas aeruginosa forms surface-attached communities that persist in the face of antimicrobial agents and environmental perturbation. Published work has found extracellular polysaccharide (EPS) production, regulation of motility and induction of stress response pathways as contributing to biofilm tolerance during such insults. However, little is known regarding the mechanism(s) whereby biofilm maintenance is regulated when exposed to such environmental challenges. Here, we provide evidence that the diguanylate cyclase YfiN is important for the regulation of biofilm maintenance when exposed to peroxide. We find that, compared to the wild type (WT), static biofilms of the ΔyfiN mutant exhibit a maintenance defect, which can be further exacerbated by exposure to peroxide (H₂O₂); this defect can be rescued through genetic complementation. Additionally, we found that the ΔyfiN mutant biofilms produce less c-di-GMP than WT, and that H₂O₂ treatment enhanced motility of surface-associated bacteria and increased cell death for the ΔyfiN mutant grown as a biofilm compared to WT biofilms. These data provide evidence that YfiN is required for biofilm maintenance by P. aeruginosa, via c-di-GMP signaling, to limit motility and protect viability in response to peroxide stress. These findings add to the growing recognition that biofilm maintenance by P. aeruginosa is an actively regulated process that is controlled, at least in part, by the wide array of c-di-GMP metabolizing enzymes found in this microbe. Importance We build on previous findings that suggest that P. aeruginosa utilizes c-di-GMP metabolizing enzymes to actively maintain a mature biofilm. Here, we explore how the diguanylate cyclase YfiN contributes to the regulation of biofilm maintenance during peroxide exposure. We find that mature P. aeruginosa biofilms require YfiN to synthesize c-di-GMP, regulate motility and to insure viability during peroxide stress. These findings provide further evidence that the modulation of c-di-GMP in response to environmental signals is an important mechanism by which biofilms are maintained.

The Distribution and Role of the CFTR Protein in the Intracellular Compartments

Cystic fibrosis is a hereditary disease that mainly affects secretory organs in humans. It is caused by mutations in the gene encoding CFTR with the most common phenylalanine deletion at position 508. CFTR is an anion channel mainly conducting Cl⁻ across the apical membranes of many different epithelial cells, the impairment of which causes dysregulation of epithelial fluid secretion and thickening of the mucus. This, in turn, leads to the dysfunction of organs such as the lungs, pancreas, kidney and liver. The CFTR protein is mainly localized in the plasma membrane; however, there is a growing body of evidence that it is also present in the intracellular organelles such as the endosomes, lysosomes, phagosomes and mitochondria. Dysfunction of the CFTR protein affects not only the ion transport across the epithelial tissues, but also has an impact on the proper functioning of the intracellular compartments. The review aims to provide a summary of the present state of knowledge regarding CFTR localization and function in intracellular compartments, the physiological role of this localization and the consequences of protein dysfunction at cellular, epithelial and organ levels. An in-depth understanding of intracellular processes involved in CFTR impairment may reveal novel opportunities in pharmacological agents of cystic fibrosis.

Role of inflammation and oxidative stress in tissue damage associated with cystic fibrosis: CAPE as a future therapeutic strategy

Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, responsible for the synthesis of the CFTR protein, a chloride channel. The gene has approximately 2000 known mutations and all of them affect in some degree the protein function, which makes the pathophysiological manifestations to be multisystemic, mainly affecting the respiratory, gastrointestinal, endocrine, and reproductive tracts. Currently, the treatment of the disease is restricted to controlling symptoms and, more recently, a group of drugs that act directly on the defective protein, known as CFTR modulators, was developed. However, their high cost and difficult access mean that their use is still very restricted. It is important to search for safe and low-cost alternative therapies for CF and, in this context, natural compounds and, mainly, caffeic acid phenethyl ester (CAPE) appear as promising strategies to assist in the treatment of the disease. CAPE is a compound derived from propolis extracts that has antioxidant and anti-inflammatory activities, covering important aspects of the pathophysiology of CF, which points to the possible benefit of its use in the disease treatment. To date, no studies have effectively tested CAPE for CF and, therefore, we intend with this review to elucidate the role of inflammation and oxidative stress for tissue damage seen in CF, associating them with CAPE actions and its pharmacologically active derivatives. In this way, we offer a theoretical basis for conducting preclinical and clinical studies relating the use of this molecule to CF.

SFPQ rescues F508del-CFTR expression and function in cystic fibrosis bronchial epithelial cells

Cystic fibrosis (CF) occurs as a result of mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which lead to misfolding, trafficking defects, and impaired function of the CFTR protein. Splicing factor proline/glutamine-rich (SFPQ) is a multifunctional nuclear RNA-binding protein (RBP) implicated in the regulation of gene expression pathways and intracellular trafficking. Here, we investigated the role of SFPQ in the regulation of the expression and function of F508del-CFTR in CF lung epithelial cells. We find that the expression of SFPQ is reduced in F508del-CFTR CF epithelial cells compared to WT-CFTR control cells. Interestingly, the overexpression of SFPQ in CF cells increases the expression as well as rescues the function of F508del-CFTR. Further, comprehensive transcriptome analyses indicate that SFPQ plays a key role in activating the mutant F508del-CFTR by modulating several cellular signaling pathways. This is the first report on the role of SFPQ in the regulation of expression and function of F508del-CFTR in CF lung disease. Our findings provide new insights into SFPQ-mediated molecular mechanisms and point to possible novel epigenetic therapeutic targets for CF and related pulmonary diseases.

The Glycosylphosphatidylinositol-Anchored Superoxide Dismutase of Scedosporium apiospermum Protects the Conidia from Oxidative Stress

Scedosporium species are common fungal pathogens in patients with cystic fibrosis (CF). To colonize the CF lungs, fungi must cope with the host immune response, especially the reactive oxygen species (ROS) released by phagocytic cells. To this aim, pathogens have developed various antioxidant systems, including superoxide dismutases (SODs) which constitute the first-line protection against oxidative stress. Interestingly, one of the S. apiospermum SOD-encoding genes (SODD gene) exhibits a glycosylphosphatidylinositol (GPI) anchor-binding site and encodes a conidial-specific surface SOD. In this study, a SODDΔ mutant was engineered from a non-homologous end joining-deficient strain (KU70Δ) of S. apiospermum. Compared to its parent strain, the double mutant KU70Δ/SODDΔ exhibited increased susceptibility to various oxidizing agents and triazole antifungals. In addition, the loss of SodD resulted in an increased intracellular killing of the conidia by M1 macrophages derived from human blood monocytes, suggesting the involvement of this superoxide dismutase in the evasion to the host defenses. Nevertheless, one cannot disregard an indirect role of the enzyme in the synthesis or assembly of the cell wall components since transmission electron microscopic analysis revealed a thickening of the inner cell wall layer of the conidia. Further studies are needed to confirm the role of this enzyme in the pathogenesis of Scedosporium infections, including the production of a recombinant protein and study of its protective effect against the infection in a mouse model of scedosporiosis.

The age-dependent decline of the extracellular thiol-disulfide balance and its role in SARS-CoV-2 infection

SARS-CoV-2 (COVID-19) infection can cause a severe respiratory distress syndrome. The risk of severe manifestations and mortality characteristically increase in the elderly and in the presence of non-COVID-19 comorbidity. We and others previously demonstrated that the low molecular weight (LMW) and protein thiol/disulfide ratio declines in human plasma with age and such decline is even more rapid in the case of inflammatory and premature aging diseases, which are also associated with the most severe complications of COVID-19 infection. The same decline with age of the LMW thiol/disulfide ratio observed in plasma appears to occur in the extracellular fluids of the respiratory tract and in association with many pulmonary diseases that characteristically reduce the concentrations and adaptive stress response of the lung glutathione. Early evidence in literature suggests that the thiol to disulfide balance of critical Cys residues of the COVID-19 spike protein and the ACE-2 receptor may influence the risk of infection and the severity of the disease, with a more oxidizing environment producing the worst prognosis. With this hypothesis paper we propose that the age-dependent decline of LMW thiol/disulfide ratio of the extracellular fluids, could play a role in promoting the physical (protein-protein) interaction of CoV-2 and the host cell in the airways. Therefore, this redox-dependent interaction is expected to affect the risk of severe infection in an age-dependent manner. The hypothesis can be verified in experimental models of in vitro CoV-2 infection and at the clinical level in that LMW thiols and protein thiolation can now be investigated with standardized, reliable and versatile laboratory protocols. Presenting the verification strategy of our hypothesis, we also discuss available nutritional and ancillary pharmacological strategies to intervene on the thiol/disulfide ratio of extracellular fluids of subjects at risk of infection and COVID-19 patients.

Transcriptomic analysis of CFTR-impaired endothelial cells reveals a pro-inflammatory phenotype

Cystic fibrosis (CF) is a life-threatening disorder characterised by decreased pulmonary mucociliary and pathogen clearance, and an exaggerated inflammatory response leading to progressive lung damage. CF is caused by bi-allelic pathogenic variants of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which encodes a chloride channel. CFTR is expressed in endothelial cells (ECs) and EC dysfunction has been reported in CF patients, but a role for this ion channel in ECs regarding CF disease progression is poorly described.We used an unbiased RNA sequencing approach in complementary models of CFTR silencing and blockade (by the CFTR inhibitor CFTRinh-172) in human ECs to characterise the changes upon CFTR impairment. Key findings were further validated in vitro and in vivo in CFTR-knockout mice and ex vivo in CF patient-derived ECs.Both models of CFTR impairment revealed that EC proliferation, migration and autophagy were downregulated. Remarkably though, defective CFTR function led to EC activation and a persisting pro-inflammatory state of the endothelium with increased leukocyte adhesion. Further validation in CFTR-knockout mice revealed enhanced leukocyte extravasation in lung and liver parenchyma associated with increased levels of EC activation markers. In addition, CF patient-derived ECs displayed increased EC activation markers and leukocyte adhesion, which was partially rescued by the CFTR modulators VX-770 and VX-809.Our integrated analysis thus suggests that ECs are no innocent bystanders in CF pathology, but rather may contribute to the exaggerated inflammatory phenotype, raising the question of whether normalisation of vascular inflammation might be a novel therapeutic strategy to ameliorate the disease severity of CF.

miR-125b/NRF2/HO-1 axis is involved in protection against oxidative stress of cystic fibrosis: A pilot study

In the physiopathology of cystic fibrosis (CF), oxidative stress implications are recognized and widely accepted. The cystic fibrosis transmembrane conductance regulator (CFTR) defects disrupt the intracellular redox balance causing CF pathological hallmarks. Therefore, oxidative stress together with aberrant expression levels of detoxification genes and microRNAs (miRNAs/miRs) may be associated with clinical outcome. Using total RNA extracted from epithelial nasal cells, the present study analyzed the expression levels of oxidative stress genes and one miRNA using quantitative PCR in a representative number of patients with CF compared with in healthy individuals. The present pilot study revealed the existence of an association among CFTR, genes involved in the oxidative stress response and miR-125b. The observed downregulation of CFTR gene expression was accompanied by increased expression levels of Nuclear factor erythroid derived-2 like2 and its targets NAD(P)H:Quinone Oxidoreductase and glutathione S-transferase 1. Moreover, the expression levels of heme oxygenase-1 (HO-1) and miR-125b were positively correlated with a forced expiratory volume in 1 sec (FEV1) >60% in patients with CF with chronic Pseudomonas aeruginosa lung infection (r=0.74; P<0.001 and r=0.57; P<0.001, respectively). The present study revealed the activation of an inducible, but not fully functional, oxidative stress response to protect airway cells against reactive oxygen species-dependent injury in CF disease. Additionally, the correlations of HO-1 and miR-125b expression with an improved FEV1 value suggested that these factors may synergistically protect the airway cells from oxidative stress damage, inflammation and apoptosis. Furthermore, HO-1 and miR-125b may be used as prognostic markers explaining the wide CF phenotypic variability as an additional control level over the CFTR gene mutations.

Copper-Associated Oxidative Stress Contributes to Cellular Inflammatory Responses in Cystic Fibrosis

Cystic fibrosis (CF) is caused by mutations in the gene encoding the CF Transmembrane Conductance Regulator (CFTR), an apical chloride channel. An early inflammation (EI) in the lung of CF patients occurring in the absence of any bacterial infection has been reported. This EI has been proposed to be associated with oxidative stress (OX-S), generated by deregulations of the oxidant/antioxidant status. Recently, we demonstrated that copper (Cu), an essential trace element, mediates OX-S in bronchial cells. However, the role of this element in the development of CF-EI, in association with OX-S, has never been investigated. Using healthy (16HBE14o-; HBE), CF (CFBE14o-; CFBE), and corrected-wild type CFTR CF (CFBE-wt) bronchial cells, we characterized the inflammation and OX-S profiles in relation to the copper status and CFTR expression and function. We demonstrated that CFBE cells exhibited a CFTR-independent intrinsic inflammation. These cells also exhibited an alteration in mitochondria, UPR (Unfolded Protein Response), catalase, Cu/Zn- and Mn-SOD activities, and an increase in the intracellular content of iron, zinc, and Cu. The increase in Cu concentration was associated with OX-S and inflammatory responses. These data identify cellular Cu as a key factor in the generation of CF-associated OX-S and opens new areas of investigation to better understand CF-associated EI.

Oxidative Stress and Endoplasmic Reticulum Stress in Rare Respiratory Diseases

Several studies have shown that some rare respiratory diseases, such as alpha-1 antitrypsin deficiency (AATD), idiopathic pulmonary fibrosis (IPF), cystic fibrosis (CF), and primary ciliary dyskinesia (PCD) present oxidative stress (OS) and endoplasmic reticulum (ER) stress. Their involvement in these pathologies and the use of antioxidants as therapeutic agents to minimize the effects of OS are discussed in this review.

Uncovering the Role of Oxidative Imbalance in the Development and Progression of Bronchial Asthma

Asthma is a chronic inflammatory disease of the airways related to epithelial damage, bronchial hyperresponsiveness to contractile agents, tissue remodeling, and luminal narrowing. Currently, there are many data about the pathophysiology of asthma; however, a new aspect has emerged related to the influence of reactive oxygen and nitrogen species (ROS and RNS) on the origin of this disease. Several studies have shown that an imbalance between the production of ROS and RNS and the antioxidant enzymatic and nonenzymatic systems plays an important role in the pathogenesis of this disease. Considering this aspect, this study is aimed at gathering data from the scientific literature on the role of oxidative distress in the development of inflammatory airway and lung diseases, especially bronchial asthma. For that, articles related to these themes were selected from scientific databases, including human and animal studies. The main findings of this work showed that the respiratory system works as a highly propitious place for the formation of ROS and RNS, especially superoxide anion, hydrogen peroxide, and peroxynitrite, and the epithelial damage is reflected in an important loss of antioxidant defenses that, in turn, culminates in an imbalance and formation of inflammatory and contractile mediators, such as isoprostanes, changes in the activity of protein kinases, and activation of cell proliferation signalling pathways, such as the MAP kinase pathway. Thus, the oxidative imbalance appears as a promising path for future investigations as a therapeutic target for the treatment of asthmatic patients, especially those resistant to currently available therapies.

Cyclic nucleotide phosphodiesterase inhibitors as therapeutic interventions for cystic fibrosis

Cystic Fibrosis (CF) lung disease results from mutations in the CFTR anion channel that reduce anion and fluid secretion by airway epithelia. Impaired secretion compromises airway innate defence mechanisms and leads to bacterial colonization, excessive inflammation and tissue damage; thus, restoration of CFTR function is the goal of many CF therapies. CFTR channels are activated by cyclic nucleotide-dependent protein kinases. The second messengers 3'5'-cAMP and 3'5'-cGMP are hydrolysed by a large family of cyclic nucleotide phosphodiesterases that provide subcellular spatial and temporal control of cyclic nucleotide-dependent signalling. Selective inhibition of these enzymes elevates cyclic nucleotide levels, leading to activation of CFTR and other downstream effectors. Here we examine members of the PDE family that are likely to regulate CFTR-dependent ion and fluid secretion in the airways and discuss other actions of PDE inhibitors that can influence cyclic nucleotide-regulated mucociliary transport, inflammation and bronchodilation. Finally, we review PDE inhibitors and the potential benefits they could provide as CF therapeutics.

Airway Redox Homeostasis and Inflammation Gone Awry: From Molecular Pathogenesis to Emerging Therapeutics in Respiratory Pathology

As aerobic organisms, we are continuously and throughout our lifetime subjected to an oxidizing atmosphere and, most often, to environmental threats. The lung is the internal organ most highly exposed to this milieu. Therefore, it has evolved to confront both oxidative stress induced by reactive oxygen species (ROS) and a variety of pollutants, pathogens, and allergens that promote inflammation and can harm the airways to different degrees. Indeed, an excess of ROS, generated intrinsically or from external sources, can imprint direct damage to key structural cell components (nucleic acids, sugars, lipids, and proteins) and indirectly perturb ROS-mediated signaling in lung epithelia, impairing its homeostasis. These early events complemented with efficient recognition of pathogen- or damage-associated recognition patterns by the airway resident cells alert the immune system, which mounts an inflammatory response to remove the hazards, including collateral dead cells and cellular debris, in an attempt to return to homeostatic conditions. Thus, any major or chronic dysregulation of the redox balance, the air-liquid interface, or defects in epithelial proteins impairing mucociliary clearance or other defense systems may lead to airway damage. Here, we review our understanding of the key role of oxidative stress and inflammation in respiratory pathology, and extensively report current and future trends in antioxidant and anti-inflammatory treatments focusing on the following major acute and chronic lung diseases: acute lung injury/respiratory distress syndrome, asthma, chronic obstructive pulmonary disease, pulmonary fibrosis, and cystic fibrosis.

Oral Glutathione and Growth in Cystic Fibrosis: A Multicenter, Randomized, Placebo-controlled, Double-blind Trial

OBJECTIVES

The nutritional status of children with cystic fibrosis (CF) is associated with mortality and morbidity. Intestinal inflammation may contribute to impaired digestion, absorption, and nutrient utilization in patients with CF and oral glutathione may reduce inflammation, promoting improved nutritional status in patients with CF.

METHODS

The GROW study was a prospective, multicenter, randomized, placebo-controlled, double-blind, phase II clinical trial in pancreatic insufficient patients with CF between the ages of 2 and 10 years. Patients received reduced glutathione or placebo orally daily for 24 weeks. The primary endpoint was the difference in change in weight-for-age z-scores from baseline through week 24 between treatment groups. Secondary endpoints included other anthropometrics, serum, and fecal inflammatory markers in addition to other clinical outcomes.

RESULTS

Fifty-eight participants completed the study. No significant differences were seen between glutathione (n = 30) and placebo (n = 28) groups in the 6-month change in weight-for-age z-score (-0.08; 95% CI: -0.22 to 0.06; P = 0.25); absolute change in weight (kg) (-0.18; 95% CI: -0.55 to 0.20; P = 0.35); or absolute change in BMI kg/m (-0.06; 95% CI: -0.37 to 0.25; P = 0.69). There were no significant differences in other secondary endpoints. Overall, glutathione was safe and well tolerated.

CONCLUSIONS

Oral glutathione supplementation did not impact growth or change serum or fecal inflammatory markers in pancreatic insufficient children with CF when compared with placebo.

Novel Therapy of Bicarbonate, Glutathione, and Ascorbic Acid Improves Cystic Fibrosis Mucus Transport

Defective airway mucus clearance is a defining characteristic of cystic fibrosis lung disease, and improvements to current mucolytic strategies are needed. Novel approaches targeting a range of contributing mechanisms are in various stages of preclinical and clinical development. ARINA-1 is a new nebulized product comprised of ascorbic acid, glutathione, and bicarbonate. Using microoptical coherence tomography, we tested the effect of ARINA-1 on central features of mucociliary clearance in F508del/F508del primary human bronchial epithelial cells to assess its potential as a mucoactive therapy in cystic fibrosis. We found that ARINA-1 significantly augmented mucociliary transport rates, both alone and with CFTR (cystic fibrosis transmembrane conductance regulator) modulator therapy, whereas airway hydration and ciliary beating were largely unchanged compared with PBS vehicle control. Analysis of mucus reflectivity and particle-tracking microrheology indicated that ARINA-1 restores mucus clearance by principally reducing mucus layer viscosity. The combination of bicarbonate and glutathione elicited increases in mucociliary transport rate comparable to those seen with ARINA-1, indicating the importance of this interaction to the impact of ARINA-1 on mucus transport; this effect was not recapitulated with bicarbonate alone or bicarbonate combined with ascorbic acid. Assessment of CFTR chloride transport revealed an increase in CFTR-mediated chloride secretion in response to ARINA-1 in CFBE41o^- cells expressing wild-type CFTR, driven by CFTR activity stimulation by ascorbate. This response was absent in CFBE41o^- F508del cells treated with VX-809 and primary human bronchial epithelial cells, implicating CFTR-independent mechanisms for the effect of ARINA-1 on cystic fibrosis mucus. Together, these studies indicate that ARINA-1 is a novel potential therapy for the treatment of impaired mucus clearance in cystic fibrosis.

Mitochondrial Stress Responses and "Mito-Inflammation" in Cystic Fibrosis

Cystic fibrosis (CF) is a genetic disease associated to mutations in the cystic fibrosis transmembrane conductance regulator gene, which results in the alteration of biological fluid and electrolyte homeostasis. The characteristic pathological manifestation is represented by exaggerated proinflammatory response in lung of CF patients, driven by recurrent infections and worsen by hypersecretion of proinflammatory mediators and progressive tissue destruction. Treating inflammation remains a priority in CF. However, current anti-inflammatory treatments, including non-steroidal agents, are poorly effective and present dramatic side effects in CF patients. Different studies suggest an intimate relationship between mitochondria and CF lung disease, supporting the hypothesis that a decline in mitochondrial function endorses the development of the hyperinflammatory phenotype observed in CF lung. This allowed the implementation of a new concept: the "mito-inflammation," a compartmentalization of inflammatory process, related to the role of mitochondria in engage and sustain the inflammatory responses, resulting a druggable target to counteract the amplification of inflammatory signals in CF. Here, we will offer an overview of the contribution of mitochondria in the pathogenesis of CF lung disease, delving into mitochondrial quality control responses, which concur significantly to exacerbation of CF lung inflammatory responses. Finally, we will discuss the new therapeutic avenues that aim to target the mito-inflammation, an alternative therapeutic advantage for mitochondrial quality control that improves CF patient's inflammatory state.

Comparative Evolutionary Patterns of Burkholderia cenocepacia and B. multivorans During Chronic Co-infection of a Cystic Fibrosis Patient Lung

During chronic respiratory infections of cystic fibrosis (CF) patients, bacteria adaptively evolve in response to the nutritional and immune environment as well as influence other infecting microbes. The present study was designed to gain insights into the genetic mechanisms underlying adaptation and diversification by the two most prevalent pathogenic species of the Burkholderia cepacia complex (Bcc), B. cenocepacia and B. multivorans. Herein, we study the evolution of both of these species during coinfection of a CF patient for 4.4 years using genome sequences of 9 B. multivorans and 11 B. cenocepacia. This co-infection spanned at least 3 years following initial infection by B. multivorans and ultimately ended in the patient's death by cepacia syndrome. Both species acquired several mutations with accumulation rates of 2.08 (B. cenocepacia) and 2.27 (B. multivorans) SNPs/year. Many of the mutated genes are associated with oxidative stress response, transition metal metabolism, defense mechanisms against antibiotics, and other metabolic alterations consistent with the idea that positive selection might be driven by the action of the host immune system, antibiotic therapy and low oxygen and iron concentrations. Two orthologous genes shared by B. cenocepacia and B. multivorans were found to be under strong selection and accumulated mutations associated with lineage diversification. One gene encodes a nucleotide sugar dehydratase involved in lipopolysaccharide O-antigen (OAg) biosynthesis (wbiI). The other gene encodes a putative two-component regulatory sensor kinase protein required to sense and adapt to oxidative- and heavy metal- inducing stresses. This study contributes to understanding of shared and species-specific evolutionary patterns of B. cenocepacia and B. multivorans evolving in the same CF lung environment.

Role of Cystic Fibrosis Bronchial Epithelium in Neutrophil Chemotaxis

A hallmark of cystic fibrosis (CF) chronic respiratory disease is an extensive neutrophil infiltrate in the mucosa filling the bronchial lumen, starting early in life for CF infants. The genetic defect of the CF Transmembrane conductance Regulator (CFTR) ion channel promotes dehydration of the airway surface liquid, alters mucus properties, and decreases mucociliary clearance, favoring the onset of recurrent and, ultimately, chronic bacterial infection. Neutrophil infiltrates are unable to clear bacterial infection and, as an adverse effect, contribute to mucosal tissue damage by releasing proteases and reactive oxygen species. Moreover, the rapid cellular turnover of lumenal neutrophils releases nucleic acids that further alter the mucus viscosity. A prominent role in the recruitment of neutrophil in bronchial mucosa is played by CF bronchial epithelial cells carrying the defective CFTR protein and are exposed to whole bacteria and bacterial products, making pharmacological approaches to regulate the exaggerated neutrophil chemotaxis in CF a relevant therapeutic target. Here we revise: (a) the major receptors, kinases, and transcription factors leading to the expression, and release of neutrophil chemokines in bronchial epithelial cells; (b) the role of intracellular calcium homeostasis and, in particular, the calcium crosstalk between endoplasmic reticulum and mitochondria; (c) the epigenetic regulation of the key chemokines; (d) the role of mutant CFTR protein as a co-regulator of chemokines together with the host-pathogen interactions; and (e) different pharmacological strategies to regulate the expression of chemokines in CF bronchial epithelial cells through novel drug discovery and drug repurposing.

Deletion of cftr Leads to an Excessive Neutrophilic Response and Defective Tissue Repair in a Zebrafish Model of Sterile Inflammation

Inflammation-related progressive lung destruction is the leading causes of premature death in cystic fibrosis (CF), a genetic disorder caused by a defective cystic fibrosis transmembrane conductance regulator (CFTR). However, therapeutic targeting of inflammation has been hampered by a lack of understanding of the links between a dysfunctional CFTR and the deleterious innate immune response in CF. Herein, we used a CFTR-depleted zebrafish larva, as an innovative in vivo vertebrate model, to understand how CFTR dysfunction leads to abnormal inflammatory status in CF. We show that impaired CFTR-mediated inflammation correlates with an exuberant neutrophilic response after injury: CF zebrafish exhibit enhanced and sustained accumulation of neutrophils at wounds. Excessive epithelial oxidative responses drive enhanced neutrophil recruitment towards wounds. Persistence of neutrophils at inflamed sites is associated with impaired reverse migration of neutrophils and reduction in neutrophil apoptosis. As a consequence, the increased number of neutrophils at wound sites causes tissue damage and abnormal tissue repair. Importantly, the molecule Tanshinone IIA successfully accelerates inflammation resolution and improves tissue repair in CF animal. Our findings bring important new understanding of the mechanisms underlying the inflammatory pathology in CF, which could be addressed therapeutically to prevent inflammatory lung damage in CF patients with potential improvements in disease outcomes.

Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) in Human Lung Microvascular Endothelial Cells Controls Oxidative Stress, Reactive Oxygen-Mediated Cell Signaling and Inflammatory Responses

Background

Perturbation of endothelial function in people with cystic fibrosis (CF) has been reported, which may be associated with endothelial cell expression of the cystic fibrosis transmembrane conductance regulator (CFTR). Previous reports indicate that CFTR activity upregulates endothelial barrier function, endothelial nitric oxide synthase (eNOS) expression and NO release, while limiting interleukin-8 (IL-8) release, in human umbilical vein endothelial cells (HUVECs) in cell culture. In view of reported microvascular dysfunction in people with CF we investigated the role of CFTR expression and activity in the regulation of oxidative stress, cell signaling and inflammation in human lung microvascular endothelial cells (HLMVECs) in cell culture.

Methods

HLMVECs were cultured in the absence and presence of the CFTR inhibitor GlyH-101 and CFTR siRNA. CFTR expression was analyzed using qRT-PCR, immunocytochemistry (IHC) and western blot, and function by membrane potential assay. IL-8 expression was analyzed using qRT-PCR and ELISA. Nrf2 expression, and NF-κB and AP-1 activation were determined using IHC and western blot. The role of the epidermal growth factor receptor (EGFR) in CFTR signaling was investigated using the EGFR tyrosine kinase inhibitor AG1478. Oxidative stress was measured as intracellular ROS and hydrogen peroxide (H₂O₂) concentration. VEGF and SOD-2 were measured in culture supernatants by ELISA.

Results

HLMVECs express low levels of CFTR that increase following inhibition of CFTR activity. Inhibition of CFTR, significantly increased intracellular ROS and H₂O₂ levels over 30 min and significantly decreased Nrf2 expression by 70% while increasing SOD-2 expression over 24 h. CFTR siRNA significantly increased constitutive expression of IL-8 by HLMVECs. CFTR inhibition activated the AP-1 pathway and increased IL-8 expression, without effect on NF-κB activity. Conversely, TNF-α activated the NF-κB pathway and increased IL-8 expression. The effects of TNF-α and GlyH-101 on IL-8 expression were additive and inhibited by AG1478. Inhibition of both CFTR and EGFR in HLMVECs significantly increased VEGF expression. The antioxidant N-acetyl cysteine significantly reduced ROS production and the increase in IL-8 and VEGF expression following CFTR inhibition.

Conclusion

Functional endothelial CFTR limits oxidative stress and contributes to the normal anti-inflammatory state of HLMVECs. Therapeutic strategies to restore endothelial CFTR function in CF are warranted.

Metabolic and functional interplay between gut microbiota and fat-soluble vitamins

Gut microbiota is a complex ecosystem seen as an extension of human genome. It represents a major metabolic interface of interaction with food components and xenobiotics in the gastrointestinal (GI) environment. In this context, the advent of modern bacterial genome sequencing technology has enabled the identification of dietary nutrients as key determinants of gut microbial ecosystem able to modulate the host-microbiome symbiotic relationship and its effects on human health. This article provides a literature review on functional and molecular interactions between a specific group of lipids and essential nutrients, e.g., fat-soluble vitamins (FSVs), and the gut microbiota. A two-way relationship appears to emerge from the available literature with important effects on human metabolism, nutrition, GI physiology and immune function. First, FSV directly or indirectly modify the microbial composition involving for example immune system-mediated and/or metabolic mechanisms of bacterial growth or inhibition. Second, the gut microbiota influences at different levels the synthesis, metabolism and transport of FSV including their bioactive metabolites that are either introduced with the diet or released in the gut via entero-hepatic circulation. A better understanding of these interactions, and of their impact on intestinal and metabolic homeostasis, will be pivotal to design new and more efficient strategies of disease prevention and therapy, and personalized nutrition.

Novel Anti-Inflammatory Approaches for Cystic Fibrosis Lung Disease: Identification of Molecular Targets and Design of Innovative Therapies

Cystic fibrosis (CF) is the most common genetic disorder among Caucasians, estimated to affect more than 70,000 people in the world. Severe and persistent bronchial inflammation and chronic bacterial infection, along with airway mucus obstruction, are hallmarks of CF lung disease and participate in its progression. Anti-inflammatory therapies are, therefore, of particular interest for CF lung disease. Furthermore, a better understanding of the molecular mechanisms involved in airway infection and inflammation in CF has led to the development of new therapeutic approaches that are currently under evaluation by clinical trials. These new strategies dedicated to CF inflammation are designed to treat different dysregulated aspects such as oxidative stress, cytokine secretion, and the targeting of dysregulated pathways. In this review, we summarize the current understanding of the cellular and molecular mechanisms that contribute to abnormal lung inflammation in CF, as well as the new anti-inflammatory strategies proposed to CF patients by exploring novel molecular targets and novel drug approaches.

Targeting the Heme Oxygenase 1/Carbon Monoxide Pathway to Resolve Lung Hyper-Inflammation and Restore a Regulated Immune Response in Cystic Fibrosis

In individuals with cystic fibrosis (CF), lung hyper-inflammation starts early in life and is perpetuated by mucus obstruction and persistent bacterial infections. The continuous tissue damage and scarring caused by non-resolving inflammation leads to bronchiectasis and, ultimately, respiratory failure. Macrophages (MΦs) are key regulators of immune response and host defense. We and others have shown that, in CF, MΦs are hyper-inflammatory and exhibit reduced bactericidal activity. Thus, MΦs contribute to the inability of CF lung tissues to control the inflammatory response or restore tissue homeostasis. The non-resolving hyper-inflammation in CF lungs is attributed to an impairment of several signaling pathways associated with resolution of the inflammatory response, including the heme oxygenase-1/carbon monoxide (HO-1/CO) pathway. HO-1 is an enzyme that degrades heme groups, leading to the production of potent antioxidant, anti-inflammatory, and bactericidal mediators, such as biliverdin, bilirubin, and CO. This pathway is fundamental to re-establishing cellular homeostasis in response to various insults, such as oxidative stress and infection. Monocytes/MΦs rely on abundant induction of the HO-1/CO pathway for a controlled immune response and for potent bactericidal activity. Here, we discuss studies showing that blunted HO-1 activation in CF-affected cells contributes to hyper-inflammation and defective host defense against bacteria. We dissect potential cellular mechanisms that may lead to decreased HO-1 induction in CF cells. We review literature suggesting that induction of HO-1 may be beneficial for the treatment of CF lung disease. Finally, we discuss recent studies highlighting how endogenous HO-1 can be induced by administration of controlled doses of CO to reduce lung hyper-inflammation, oxidative stress, bacterial infection, and dysfunctional ion transport, which are all hallmarks of CF lung disease.