Eicosanoid release is increased by membrane destabilization and CFTR inhibition in Calu-3 cells

Dysregulation of the Arachidonic Acid Pathway in Cystic Fibrosis: Implications for Chronic Inflammation and Disease Progression

Cystic fibrosis (CF) is the most common fatal genetic disease among Caucasian people, with over 2000 mutations in the CFTR gene. Although highly effective modulators have been developed to rescue the mutant CFTR protein, unresolved inflammation and persistent infections still threaten the lives of patients. While the central role of arachidonic acid (AA) and its metabolites in the inflammatory response is widely recognized, less is known about their impact on immunomodulation and metabolic implications in CF. To this end, here we provided a comprehensive analysis of the AA metabolism in CF. In this context, CFTR dysfunction appeared to complexly disrupt normal lipid processing, worsening the chronic airway inflammation, and compromising the immune responses to bacterial infections. As such, potential strategies targeting AA and its inflammatory mediators are being investigated as a promising approach to balance the inflammatory response while mitigating disease progression. Thus, a deeper understanding of the AA pathway dysfunction in CF may open innovative avenues for designing more effective therapeutic interventions.

The role of ANXA1 in the tumor microenvironment

Annexin A1 (ANXA1) is widely expressed in a variety of body tissues and cells and is also involved in tumor development through multiple pathways. The invasion, metastasis, and immune escape of tumor cells depend on the interaction between tumor cells and their surrounding environment. Research shows that ANXA1 can act on a variety of cells in the tumor microenvironment (TME), and subsequently affect the proliferation, invasion and metastasis of tumors. This article describes the role of ANXA1 in the various components of the tumor microenvironment and its mechanism of action, as well as the existing clinical treatment measures related to ANXA1. These findings provide insight for the further design of strategies targeting ANXA1 for the diagnosis and treatment of malignant tumors.

Elevated Prostaglandin E2 Synthesis Is Associated with Clinical and Radiological Disease Severity in Cystic Fibrosis

Background: Previous studies found high but very variable levels of tetranor-PGEM and PGDM (urine metabolites of prostaglandin (PG) E2 and PGD2, respectively) in persons with cystic fibrosis (pwCF). This study aims to assess the role of cyclooxygenase COX-1 and COX-2 genetic polymorphisms in PG production and of PG metabolites as potential markers of symptoms' severity and imaging findings. Methods: A total of 30 healthy subjects and 103 pwCF were included in this study. Clinical and radiological CF severity was evaluated using clinical scoring methods and chest computed tomography (CT), respectively. Urine metabolites were measured using liquid chromatography/tandem mass spectrometry. Variants in the COX-1 gene (PTGS1 639 C>A, PTGS1 762+14delA and COX-2 gene: PTGS2-899G>C (-765G>C) and PTGS2 (8473T>C) were also analyzed. Results: PGE-M and PGD-M urine concentrations were significantly higher in pwCF than in controls. There were also statistically significant differences between clinically mild and moderate disease and severe disease. Patients with bronchiectasis and/or air trapping had higher PGE-M levels than patients without these complications. The four polymorphisms did not associate with clinical severity, air trapping, bronchiectasis, or urinary PG levels. Conclusions: These results suggest that urinary PG level testing can be used as a biomarker of CF severity. COX genetic polymorphisms are not involved in the variability of PG production.

Recent Advances in Molecular and Cellular Functions of S100A10

S100A10 (p11, annexin II light chain, calpactin light chain) is a multifunctional protein with a wide range of physiological activity. S100A10 is unique among the S100 family members of proteins since it does not bind to Ca2+, despite its sequence and structural similarity. This review focuses on studies highlighting the structure, regulation, and binding partners of S100A10. The binding partners of S100A10 were collated and summarized.

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.

Abnormal n-6 fatty acid metabolism in cystic fibrosis contributes to pulmonary symptoms

Cystic fibrosis (CF) is a recessively inherited fatal disease that is the subject of extensive research and ongoing development of therapeutics targeting the defective protein, cystic fibrosis transmembrane conductance regulator (CFTR). Despite progress, the link between CFTR and clinical symptoms is incomplete. The severe CF phenotypes are associated with a deficiency of linoleic acid, which is the precursor of arachidonic acid. The release of arachidonic acid from membranes via phospholipase A₂ is the rate-limiting step for eicosanoid synthesis and is increased in CF, which contributes to the observed inflammation. A potential deficiency of docosahexaenoic acid may lead to decreased levels of specialized pro-resolving mediators. This pathophysiology may contribute to an early and sterile inflammation, mucus production, and to bacterial colonization, which further increases inflammation and potentiates the clinical symptoms. Advances in lipid technology will assist in elucidating the role of lipid metabolism in CF, and stimulate therapeutic modulations of inflammation.

Recent Strategic Advances in CFTR Drug Discovery: An Overview

Cystic fibrosis transmembrane conductance regulator (CFTR)-rescuing drugs have already transformed cystic fibrosis (CF) from a fatal disease to a treatable chronic condition. However, new-generation drugs able to bind CFTR with higher specificity/affinity and to exert stronger therapeutic benefits and fewer side effects are still awaited. Computational methods and biosensors have become indispensable tools in the process of drug discovery for many important human pathologies. Instead, they have been used only piecemeal in CF so far, calling for their appropriate integration with well-tried CF biochemical and cell-based models to speed up the discovery of new CFTR-rescuing drugs. This review will give an overview of the available structures and computational models of CFTR and of the biosensors, biochemical and cell-based assays already used in CF-oriented studies. It will also give the reader some insights about how to integrate these tools as to improve the efficiency of the drug discovery process targeted to CFTR.

Annexin A2 expression and partners during epithelial cell differentiation

The members of the annexin family of calcium- and phospholipid-binding proteins participate in different cellular processes. Annexin A2 binds to S100A10, forming a functional heterotetrameric protein that has been involved in many cellular functions, such as exocytosis, endocytosis, cell junction formation, and actin cytoskeleton dynamics. Herein, we studied annexin A2 cellular movements and looked for its partners during epithelial cell differentiation. By using immunofluorescence, mass spectrometry (MS), and western blot analyses after S100A10 affinity column separation, we identified several annexin A2–S100A10 partner candidates. The association of putative annexin A2–S100A10 partner candidates obtained by MS after column affinity was validated by immunofluorescence and sucrose density gradient separation. The results show that three proteins are clearly associated with annexin A2: E-cadherin, actin, and caveolin 1. Overall, the data show that annexin A2 can associate with molecular complexes containing actin, caveolin 1, and flotillin 2 before epithelial differentiation and with complexes containing E-cadherin, actin, and caveolin 1, but not flotillin 2 after cell differentiation. The results indicate that actin, caveolin 1, and E-cadherin are the principal protein partners of annexin A2 in epithelial cells and that the serine phosphorylation of the N-terminal domain does not play an essential role during epithelial cell differentiation.

Specialized Pro-Resolving Lipid Mediators in Cystic Fibrosis

In cystic fibrosis (CF), impaired airway surface hydration (ASL) and mucociliary clearance that promote chronic bacterial colonization, persistent inflammation, and progressive structural damage to the airway wall architecture are typically explained by ion transport abnormalities related to the mutation of the gene coding for the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) channel. However, the progressive and unrelenting inflammation of the CF airway begins early in life, becomes persistent, and is excessive relative to the bacterial burden. Intrinsic abnormalities of the inflammatory response in cystic fibrosis have been suggested but the mechanisms involved remain poorly understood. This review aims to give an overview of the recent advances in the understanding of the defective resolution of inflammation in CF including the abnormal production of specialized pro-resolving lipid mediators (lipoxin and resolvin) and their impact on the pathogenesis of the CF airway disease.

Role of IRE1α/XBP-1 in Cystic Fibrosis Airway Inflammation

Cystic fibrosis (CF) pulmonary disease is characterized by chronic airway infection and inflammation. The infectious and inflamed CF airway environment impacts on the innate defense of airway epithelia and airway macrophages. The CF airway milieu induces an adaptation in these cells characterized by increased basal inflammation and a robust inflammatory response to inflammatory mediators. Recent studies have indicated that these responses depend on activation of the unfolded protein response (UPR). This review discusses the contribution of airway epithelia and airway macrophages to CF airway inflammatory responses and specifically highlights the functional importance of the UPR pathway mediated by IRE1/XBP-1 in these processes. These findings suggest that targeting the IRE1/XBP-1 UPR pathway may be a therapeutic strategy for CF airway disease.

An unexpected effect of TNF-α on F508del-CFTR maturation and function

Cystic fibrosis (CF) is a multifactorial disease caused by mutations in the cystic fibrosis transmembrane conductance regulator gene ( CFTR), which encodes a cAMP-dependent Cl (-) channel. The most frequent mutation, F508del, leads to the synthesis of a prematurely degraded, otherwise partially functional protein. CFTR is expressed in many epithelia, with major consequences in the airways of patients with CF, characterized by both fluid transport abnormalities and persistent inflammatory responses. The relationship between the acute phase of inflammation and the expression of wild type (WT) CFTR or F508del-CFTR is poorly understood. The aim of the present study was to investigate this effect. The results show that 10 min exposure to TNF-alpha (0.5-50ng/ml) of F508del-CFTR-transfected HeLa cells and human bronchial cells expressing F508del-CFTR in primary culture (HBE) leads to the maturation of F508del-CFTR and induces CFTR chloride currents. The enhanced CFTR expression and function upon TNFα is sustained, in HBE cells, for at least 24 h. The underlying mechanism of action involves a protein kinase C (PKC) signaling pathway, and occurs through insertion of vesicles containing F508del-CFTR to the plasma membrane, with TNFα behaving as a corrector molecule. In conclusion, a novel and unexpected action of TNFα has been discovered and points to the importance of systematic studies on the roles of inflammatory mediators in the maturation of abnormally folded proteins in general and in the context of CF in particular.

Increased NF-κB Activity and Decreased Wnt/β-Catenin Signaling Mediate Reduced Osteoblast Differentiation and Function in ΔF508 Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Mice

The prevalent human ΔF508 mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) is associated with reduced bone formation and bone loss in mice. The molecular mechanisms by which the ΔF508-CFTR mutation causes alterations in bone formation are poorly known. In this study, we analyzed the osteoblast phenotype in ΔF508-CFTR mice and characterized the signaling mechanisms underlying this phenotype. Ex vivo studies showed that the ΔF508-CFTR mutation negatively impacted the differentiation of bone marrow stromal cells into osteoblasts and the activity of osteoblasts, demonstrating that the ΔF508-CFTR mutation alters both osteoblast differentiation and function. Treatment with a CFTR corrector rescued the abnormal collagen gene expression in ΔF508-CFTR osteoblasts. Mechanistic analysis revealed that NF-κB signaling and transcriptional activity were increased in mutant osteoblasts. Functional studies showed that the activation of NF-κB transcriptional activity in mutant osteoblasts resulted in increased β-catenin phosphorylation, reduced osteoblast β-catenin expression, and altered expression of Wnt/β-catenin target genes. Pharmacological inhibition of NF-κB activity or activation of canonical Wnt signaling rescued Wnt target gene expression and corrected osteoblast differentiation and function in bone marrow stromal cells and osteoblasts from ΔF508-CFTR mice. Overall, the results show that the ΔF508-CFTR mutation impairs osteoblast differentiation and function as a result of overactive NF-κB and reduced Wnt/β-catenin signaling. Moreover, the data indicate that pharmacological inhibition of NF-κB or activation of Wnt/β-catenin signaling can rescue the abnormal osteoblast differentiation and function induced by the prevalent ΔF508-CFTR mutation, suggesting novel therapeutic strategies to correct the osteoblast dysfunctions in cystic fibrosis.

Do annexins participate in lipid messenger mediated intracellular signaling? A question revisited

Annexins are physiologically important proteins that play a role in calcium buffering but also influence membrane structure, participate in Ca²⁺-dependent membrane repair events and in remodelling of the cytoskeleton. Thirty years ago several peptides isolated from lung perfusates, peritoneal leukocytes, neutrophiles and renal cells were proven inhibitory to the activity of phospholipase A₂. Those peptides were found to derive from structurally related proteins: annexins AnxA1 and AnxA2. These findings raised the question whether annexins may participate in regulation of the production of lipid second messengers and, therefore, modulate numerous lipid mediated signaling pathways in the cell. Recent advances in the field of annexins made also with the use of knock-out animal models revealed that these proteins are indeed important constituents of specific signaling pathways. In this review we provide evidence supporting the hypothesis that annexins, as membrane-binding proteins and organizers of the membrane lateral heterogeneity, may participate in lipid mediated signaling pathways by affecting the distribution and activity of lipid metabolizing enzymes (most of the reports point to phospholipase A₂) and of protein kinases regulating activity of these enzymes. Moreover, some experimental data suggest that annexins may directly interact with lipid metabolizing enzymes and, in a calcium-dependent or independent manner, with some of their substrates and products. On the basis of these observations, many investigators suggest that annexins are capable of linking Ca²⁺, redox and lipid signaling to coordinate vital cellular responses to the environmental stimuli.

Fibronectin stimulates migration through lipid raft dependent NHE-1 activation in mouse embryonic stem cells: involvement of RhoA, Ca(2+)/CaM, and ERK

BACKGROUND

Extracellular matrix (ECM) components and intracellular pH (pH(i)) may serve as regulators of cell migration in various cell types.

METHODS

The Oris migration assay was used to assess the effect of fibronectin (FN) on cell motility. The Na(+)/H(+) exchanger (NHE)-1 activity was evaluated by measuring pH(i) and [(22)Na(+)] uptake. To examine activated signaling molecules, western blot analysis and immunoprecipitation was performed.

RESULTS

ECM components (FN, laminin, fibrinogen, and collagen type I) increased [(22)Na(+)] uptake, pH(i), and cell migration. In addition, FN-induced increase of cell migration was inhibited by NHE-1 inhibitor amiloride or NHE-1-specific siRNA. FN selectively increased the mRNA and protein expression of NHE-1, but not that of NHE-2 or NHE-3. FN binds integrin β1 and subsequently stimulates caveolin-1 phosphorylation and Ca(2+) influx. Then, NHE-1 is phosphorylated by RhoA and Rho kinases, and Ca(2+)/calmodulin (CaM) signaling elicits complex formation with NHE-1, which is enriched in lipid raft/caveolae microdomains of the plasma membrane. Activation of NHE-1 continuously induces an increase of [(22)Na(+)] uptake and pH(i). Finally, NHE-1-dependent extracellular signal-regulated kinase (ERK) 1/2 phosphorylation enhanced matrix metalloproteinase-2 (MMP-2) and filamentous-actin (F-actin) expression, partially contributing to the regulation of embryonic stem cells (ESCs) migration.

CONCLUSIONS

FN stimulated mESCs migration and proliferation through NHE-1 activation, which were mediated by lipid raft-associated caveolin-1, RhoA/ROCK, and Ca(2+)/CaM signaling pathways.

GENERAL SIGNIFICANCE

The precise role of NHE in the modulation of ECM-related physiological functions such as proliferation and migration remains poorly understood. Thus, this study analyzed the relationship between FN and NHE in regulating the migration of mouse ESCs and their related signaling pathways.

The prostaglandin E₂ type 4 receptor participates in the response to acute oxidant stress in airway epithelial cells

Oxidative stress is implicated in the pathogenesis of many inflammatory pulmonary diseases, including cystic fibrosis (CF). Delineating how oxidative stress stimulates CF transmembrane conductance regulator (CFTR) in airway epithelial cells is useful, both to increase the understanding of airways host defense and suggest therapeutic approaches to reduce the oxidant stress burden in the CF lung. Using the airway epithelial cell line Calu-3, we investigated the hypothesis that hydrogen peroxide (H₂O₂), which stimulates anion efflux through CFTR, does so via the production of prostaglandin E₂ (PGE₂). Using iodide efflux as a biochemical marker of CFTR activity and short circuit current (I(sc)) recordings, we found that the H₂O₂-stimulated efflux was abolished by cyclooxygenase-1 inhibition and potentially also involves microsomal prostaglandin E synthase-1 activity, implicating a role for PGE₂ production. Furthermore, H₂O₂ application resulted in a rapid release of PGE₂ from Calu-3 cells. We additionally hypothesized that the PGE₂ subtype 4 (EP(4)) receptor was involved in mediating this response. In the presence of (4Z)-7-[(rel-1S,2S,5R)-5-((1,1'-biphenyl-4-yl)methoxy)-2-(4-morpholinyl)-3-oxocyclopentyl]-4-heptenoic acid (AH23848) (which blocks the EP₄ receptor), the H₂O₂-stimulated response was abolished. To investigate this finding in a polarized system, we measured the increase in I(sc) induced by H₂O₂ addition in the presence and absence of AH23848. H₂O₂ induced a robust increase in I(sc), which was significantly attenuated in the presence of AH23848, suggesting some role for the EP₄ receptor. In conclusion, with H₂O₂ as a model oxidant stress, stimulation of CFTR seems to involve PGE₂ production and likely EP₄ receptor activation in Calu-3 airway epithelial cells. This mechanism would be compromised in the CF airways.

Disruption of cytokeratin-8 interaction with F508del-CFTR corrects its functional defect

We have previously reported an increased expression of cytokeratins 8/18 (K8/K18) in cells expressing the F508del mutation of cystic fibrosis transmembrane conductance regulator (CFTR). This is associated with increased colocalization of CFTR and K18 in the vicinity of the endoplasmic reticulum, although this is reversed by treating cells with curcumin, resulting in the rescue of F508del-CFTR. In the present work, we hypothesized that (i) the K8/K18 network may interact physically with CFTR, and that (ii) this interaction may modify CFTR function. CFTR was immunoprecipitated from HeLa cells transfected with either wild-type (WT) CFTR or F508del-CFTR. Precipitates were subjected to 2D-gel electrophoresis and differential spots identified by mass spectrometry. K8 and K18 were found significantly increased in F508del-CFTR precipitates. Using surface plasmon resonance, we demonstrate that K8, but not K18, binds directly and preferentially to the F508del over the WT human NBD1 (nucleotide-binding domain-1). In vivo K8 interaction with F508del-CFTR was confirmed by proximity ligation assay in HeLa cells and in primary cultures of human respiratory epithelial cells. Ablation of K8 expression by siRNA in F508del-expressing HeLa cells led to the recovery of CFTR-dependent iodide efflux. Moreover, F508del-expressing mice topically treated with K8-siRNA showed restored nasal potential difference, equivalent to that of WT mice. These results show that disruption of F508del-CFTR and K8 interaction leads to the correction of the F508del-CFTR processing defect, suggesting a novel potential therapeutic target in CF.

Quantitative differential proteomics of cystic fibrosis cell models by SILAC (stable isotope labelling in cell culture)

Differential proteomics represents an enticing strategy to unmask the proteins involved in CF pathogenesis and to discover potential therapeutic targets and/or markers of disease progression. Quantitative proteomics is possible nowadays owing to the recent progress in protein labelling and/or in label-free approaches, combined to sensitive detection by mass spectrometry (MS). In this chapter, we present one strategy to perform differential quantitative proteomic studies on different cellular compartments of proliferating cell lines expressing wild-type (WT) CFTR and F508del-CFTR using stable isotope labelling in cell culture (SILAC).

Fatty acid composition of serum phospholipids in cystic fibrosis (CF) patients with or without CF related liver disease

BACKGROUND

In cystic fibrosis (CF), changes in fatty acid (FA) composition of serum phospholipids (PL) and cell membranes can account, in part, for the inflammatory state of the disease. The severity of the genotype is known to correlate with the degree of FA changes. Liver diseases, such as cholestasis and cirrhosis are also known to influence FA status. Until now, there is no data on the influence of CF related liver disease (CFRLD) on the FA status of CF patients. The aim of this study was to evaluate, whether the presence of CFRLD influences FA status.

METHODS

A fasting blood sample for the determination of serum vitamin E and PL-FA composition was collected from 79 CF patients with stable pulmonary disease and under good control in our CF centre. Patients with CFRLD (n=13) were compared to CF patients with the same severity of genotype (n=66) but without CFRLD.

RESULTS

The CF patients with CFRLD had lower docosahexaenoic acid (DHA, 22:6n-3) and increased docosatetraenoic acid (22:4n-6). There were no significant differences in the precursors of these FAs.

CONCLUSIONS

DHA concentration in patients with CFRLD is decreased more substantially compared with their genotype controls. The presence of CFRLD should be taken into account in future FA studies in CF patients.

CFTR inhibition provokes an inflammatory response associated with an imbalance of the annexin A1 pathway

Cystic fibrosis (CF), a disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, is characterized by chronic bacterial infections and inflammation in the lung. Having previously shown that deletion of CFTR is associated with lower expression of the endogenous anti-inflammatory protein Annexin A1 (AnxA1), we investigated further this possible functional connection using a validated CFTR inhibitor. Treatment of mice with the CFTR inhibitor-172 (CFTR(172)) augmented the acute peritonitis promoted by zymosan, an effect associated with lower AnxA1 levels in peritoneal cells. Similar results were obtained with another, chemically distinct, CFTR inhibitor. The pro-inflammatory effect of CFTR(172) was lost in AnxA1(-/-), as well as CFTR(-/-) mice. Importantly, administration of hrAnxA1 and its peptido-mimetic to CFTR(-/-) animals or to animals treated with CFTR(172) corrected the exaggerated leukocyte migration seen in these animals. In vitro assays with human Polymorphonuclear leukocyte (PMN) demonstrated that CFTR(172) reduced cell-associated AnxA1 by promoting release of the protein in microparticles. We propose that the reduced impact of the counterregulatory properties of AnxA1 in CF cells contributes to the inflammatory phenotype characteristic of this disease. Thus, these findings provide an important insight into the mechanism underlying the inflammatory disease associated with CFTR inhibition while, at the same time, providing a novel pharmacological target for controlling the inflammatory phenotype of CF.

Cytosolic phospholipase A2alpha mediates Pseudomonas aeruginosa LPS-induced airway constriction of CFTR -/- mice

Background

Lungs of cystic fibrosis (CF) patients are chronically infected with Pseudomonas aeruginosa. Increased airway constriction has been reported in CF patients but underplaying mechanisms have not been elucidated. Aim: to examine the effect of P. aeruginosa LPS on airway constriction in CF mice and the implication in this process of cytosolic phospholipase A2α (cPLA2α), an enzyme involved in arachidonic acid (AA) release.

Methods

Mice were instilled intra-nasally with LPS. Airway constriction was assessed using barometric plethysmograph. MIP-2, prostaglandin E2 (PGE2), leukotrienes and AA concentrations were measured in BALF using standard kits and gas chromatography.

Results

LPS induced enhanced airway constriction and AA release in BALF of CF compared to littermate mice. This was accompanied by increased levels of PGE2, but not those of leukotrienes. However, airway neutrophil influx and MIP-2 production remained similar in both mouse strains. The cPLA2α inhibitor arachidonyl trifluoro-methyl-ketone (ATK), but not aspirin which inhibit PGE2 synthesis, reduced LPS-induced airway constriction. LPS induced lower airway constriction and PGE2 production in cPLA2α -/- mice compared to corresponding littermates. Neither aspirin nor ATK interfered with LPS-induced airway neutrophil influx or MIP-2 production.

Conclusions

CF mice develop enhanced airway constriction through a cPLA2α-dependent mechanism. Airway inflammation is dissociated from airway constriction in this model. cPLA2α may represent a suitable target for therapeutic intervention in CF. Attenuation of airway constriction by cPLA2α inhibitors may help to ameliorate the clinical status of CF patients.

Cystic fibrosis transmembrane regulator inhibitors CFTR(inh)-172 and GlyH-101 target mitochondrial functions, independently of chloride channel inhibition

Two highly potent and selective cystic fibrosis (CF) transmembrane regulator (CFTR) inhibitors have been identified by high-throughput screening: the thiazolidinone CFTR(inh)-172 [3-[(3-trifluoromethyl)phenyl]-5-[(4-carboxyphenyl)methylene]- 2-thioxo-4-thiazolidinone] and the glycine hydrazide GlyH-101 [N-(2-naphthalenyl)-((3,5-dibromo-2,4-dihydroxyphenyl)methylene)glycine hydrazide]. Inhibition of the CFTR chloride channel by these compounds has been suggested to be of pharmacological interest in the treatment of secretory diarrheas and polycystic kidney disease. In addition, functional inhibition of CFTR by CFTR(inh)-172 has been proposed to be sufficient to mimic the CF inflammatory profile. In the present study, we investigated the effects of the two compounds on reactive oxygen species (ROS) production and mitochondrial membrane potential in several cell lines: the CFTR-deficient human lung epithelial IB3-1 (expressing the heterozygous F508del/W1282X mutation), the isogenic CFTR-corrected C38, and HeLa and A549 as non-CFTR-expressing controls. Both inhibitors were able to induce a rapid increase in ROS levels and depolarize mitochondria in the four cell types, suggesting that these effects are independent of CFTR inhibition. In HeLa cells, these events were associated with a decrease in the rate of oxygen consumption, with GlyH-101 demonstrating a higher potency than CFTR(inh)-172. The impact of CFTR inhibitors on inflammatory parameters was also tested in HeLa cells. CFTR(inh)-172, but not GlyH-101, induced nuclear translocation of nuclear factor-kappaB (NF-kappaB). CFTR(inh)-172 slightly decreased interleukin-8 secretion, whereas GlyH-101 induced a slight increase. These results support the conclusion that CFTR inhibitors may exert nonspecific effects regarding ROS production, mitochondrial failure, and activation of the NF-kappaB signaling pathway, independently of CFTR inhibition.