Cross-talk between CFTR and sphingolipids in cystic fibrosis.

Cystic fibrosis (CF) is the most common inherited, life-limiting disorder in Caucasian populations. It is caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR), which lead to an impairment of protein expression and/or function. CFTR is a chloride/bicarbonate channel expressed at the apical surface of epithelial cells of different organs. Nowadays, more than 2100 CFTR genetic variants have been described, but not all of them cause CF. However, around 80-85% of the patients worldwide are characterized by the presence, at least in one allele, of the mutation F508del. CFTR mutations cause aberrant hydration and secretion of mucus in hollow organs. In the lungs, this condition favors bacterial colonization, allowing the development of chronic infections that lead to the onset of the CF lung disease, which is the main cause of death in patients. In recent years, evidence has reported that CFTR loss of function is responsible for alterations in a particular class of bioactive lipids, called sphingolipids (SL). SL are ubiquitously present in eukaryotic cells and are mainly asymmetrically located within the external leaflet of the plasma membrane, where they organize specific platforms capable of segregating a selected number of proteins. CFTR is associated with these platforms that are fundamental for its functioning. Considering the importance of SL in CFTR homeostasis, we attempt here to provide a critical overview of the literature to determine the role of these lipids in channel stability and activity, and whether their modulation in CF could be a target for new therapeutic approaches.

SARS-CoV-2 viral entry and replication is impaired in Cystic Fibrosis airways due to ACE2 downregulation.

As an inherited disorder characterized by severe pulmonary disease, cystic fibrosis could be considered a comorbidity for coronavirus disease 2019. Instead, current clinical evidence seems to be heading in the opposite direction. To clarify whether host factors expressed by the Cystic Fibrosis epithelia may influence coronavirus disease 2019 progression, here we describe the expression of SARS-CoV-2 receptors in primary airway epithelial cells. We show that angiotensin converting enzyme 2 (ACE2) expression and localization are regulated by Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) channel. Consistently, our results indicate that dysfunctional CFTR channels alter susceptibility to SARS-CoV-2 infection, resulting in reduced viral entry and replication in Cystic Fibrosis cells. Depending on the pattern of ACE2 expression, the SARS-CoV-2 spike (S) protein induced high levels of Interleukin 6 in healthy donor-derived primary airway epithelial cells, but a very weak response in primary Cystic Fibrosis cells. Collectively, these data support that Cystic Fibrosis condition may be at least partially protecting from SARS-CoV-2 infection.

ß-sitosterol ameliorates inflammation and Pseudomonas aeruginosa lung infection in a mouse model.

We previously demonstrated that ß-sitosterol (BSS) inhibits the expression of the chemokine IL-8 in CF bronchial epithelial cells exposed to P. aeruginosa. In the mouse model of lung chronic infection, herein shown, BSS significantly reduced leukocyte recruitment in the bronchoalveolar lavage fluid and decreased bacteria recovered in the airways. Treatment with BSS decreased the expression of key cytokines involved in immune response, mainly neutrophil chemotaxis, in the lung homogenate. This anti-inflammatory activity is accompanied by a beneficial protecting activity against infection and improvement of health status. Our data suggest that BSS has the potential to become a new drug to target the excessive neutrophil recruitment in lungs chronically infected by P. aeruginosa and encourage future investigations on mechanism of protection driven by BSS.

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.

Improved Trimethylangelicin Analogs for Cystic Fibrosis: Design, Synthesis and Preliminary Screening.

A small library of new angelicin derivatives was designed and synthesized with the aim of bypassing the side effects of trimethylangelicin (TMA), a promising agent for the treatment of cystic fibrosis. To prevent photoreactions with DNA, hindered substituents were inserted at the 4 and/or 6 positions. Unlike the parent TMA, none of the new derivatives exhibited significant cytotoxicity or mutagenic effects. Among the synthesized compounds, the 4-phenylderivative 12 and the 6-phenylderivative 25 exerted a promising F508del CFTR rescue ability. On these compounds, preliminary in vivo pharmacokinetic (PK) studies were carried out, evidencing a favorable PK profile per se or after incorporation into lipid formulations. Therefore, the selected compounds are good candidates for future extensive investigation to evaluate and develop novel CFTR correctors based on the angelicin structure.

miRNAs in Serum Exosomes for Differential Diagnosis of Brain Metastases.

Circulating miRNAs are increasingly studied and proposed as tumor markers with the aim of investigating their role in monitoring the response to therapy as well as the natural evolution of primary or secondary brain tumors. This study aimed to evaluate the modulation of the expression of three miRNAs, miR-21, miR-222 and miR-124-3p, in the serum exosomes of patients with high-grade gliomas (HGGs) and brain metastases (BMs) to verify their usefulness in the differential diagnosis of brain masses; then, it focused on their variations following the surgical and/or radiosurgical treatment of the BMs. A total of 105 patients with BMs from primary lung or breast cancer, or melanoma underwent neurosurgery or radiosurgery treatment, and 91 patients with HGGs were enrolled, along with 30 healthy controls. A significant increase in miR-21 expression in serum exosomes was observed in both HGGs and BMs compared with healthy controls; on the other hand, miR-124-3p was significantly decreased in BMs, and it was increased in HGGs. After the surgical or radiosurgical treatment of patients with BMs, a significant reduction in miR-21 was noted with both types of treatments. This study identified a signature of exosomal miRNAs that could be useful as a noninvasive complementary analysis both in the differential diagnosis of BMs from glial tumors and in providing information on tumor evolution over time.

A Peptide-Nucleic Acid Targeting miR-335-5p Enhances Expression of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Gene with the Possible Involvement of the CFTR Scaffolding Protein NHERF1.

(1) Background: Up-regulation of the Cystic Fibrosis Transmembrane Conductance Regulator gene (CFTR) might be of great relevance for the development of therapeutic protocols for cystic fibrosis (CF). MicroRNAs are deeply involved in the regulation of CFTR and scaffolding proteins (such as NHERF1, NHERF2 and Ezrin). (2) Methods: Content of miRNAs and mRNAs was analyzed by RT-qPCR, while the CFTR and NHERF1 production was analyzed by Western blotting. (3) Results: The results here described show that the CFTR scaffolding protein NHERF1 can be up-regulated in bronchial epithelial Calu-3 cells by a peptide-nucleic acid (PNA) targeting miR-335-5p, predicted to bind to the 3'-UTR sequence of the NHERF1 mRNA. Treatment of Calu-3 cells with this PNA (R8-PNA-a335) causes also up-regulation of CFTR. (4) Conclusions: We propose miR-335-5p targeting as a strategy to increase CFTR. While the efficiency of PNA-based targeting of miR-335-5p should be verified as a therapeutic strategy in CF caused by stop-codon mutation of the CFTR gene, this approach might give appreciable results in CF cells carrying other mutations impairing the processing or stability of CFTR protein, supporting its application in personalized therapy for precision medicine.

Treatment of human airway epithelial Calu-3 cells with a peptide-nucleic acid (PNA) targeting the microRNA miR-101-3p is associated with increased expression of the cystic fibrosis Transmembrane Conductance Regulator () gene.

Since the identification of microRNAs (miRNAs) involved in the regulation of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene, miRNAs known to down-regulate the expression of the CFTR and associated proteins have been investigated as potential therapeutic targets. Here we show that miR-101-3p, targeting the 3'-UTR sequence of the CFTR mRNA, can be selectively inhibited by a peptide nucleic acid (PNA) carrying a full complementary sequence. With respect to clinical relevance of microRNA targeting, it is expected that reduction in concentration of miRNAs (the anti-miRNA approach) could be associated with increasing amounts of target mRNAs. Consistently to this hypothesis, we report that PNA-mediated inhibition of miR-101-3p was accompanied by CFTR up-regulation. Next Generation Sequencing (NGS) was performed in order to verify the effects of the anti-miR-101-3p PNA on the Calu-3 miRNome. Upon inhibition of miR-101-3p we observed a fold change (FC) expression <2 of the majority of miRNAs (403/479, 84.13%), whereas we identified a list of dysregulated miRNAs, suggesting that specific miRNA inhibition (in our case miR-101-3p) might be accompanied by alteration of expression of other miRNAs, some of them known to be involved in Cystic Fibrosis (CF), such as miR-155-5p and miR-125b-5p.

Sphingolipids and plasma membrane hydrolases in human primary bronchial cells during differentiation and their altered patterns in cystic fibrosis.

Human primary bronchial epithelial cells differentiated in vitro represent a valuable tool to study lung diseases such as cystic fibrosis (CF), an inherited disorder caused by mutations in the gene coding for the Cystic Fibrosis Transmembrane Conductance Regulator. In CF, sphingolipids, a ubiquitous class of bioactive lipids mainly associated with the outer layer of the plasma membrane, seem to play a crucial role in the establishment of the severe lung complications. Nevertheless, no information on the involvement of sphingolipids and their metabolism in the differentiation of primary bronchial epithelial cells are available so far. Here we show that ceramide and globotriaosylceramide increased during cell differentiation, whereas glucosylceramide and gangliosides content decreased. In addition, we found that apical plasma membrane of differentiated bronchial cells is characterized by a higher content of sphingolipids in comparison to the other cell membranes and that activity of sphingolipids catabolic enzymes associated with this membrane results altered with respect to the total cell activities. In particular, the apical membrane of CF cells was characterized by high levels of ceramide and glucosylceramide, known to have proinflammatory activity. On this basis, our data further support the role of sphingolipids in the onset of CF lung pathology.

GM1 as Adjuvant of Innovative Therapies for Cystic Fibrosis Disease.

Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein is expressed at the apical plasma membrane (PM) of different epithelial cells. The most common mutation responsible for the onset of cystic fibrosis (CF), F508del, inhibits the biosynthesis and transport of the protein at PM, and also presents gating and stability defects of the membrane anion channel upon its rescue by the use of correctors and potentiators. This prompted a multiple drug strategy for F508delCFTR aimed simultaneously at its rescue, functional potentiation and PM stabilization. Since ganglioside GM1 is involved in the functional stabilization of transmembrane proteins, we investigated its role as an adjuvant to increase the effectiveness of CFTR modulators. According to our results, we found that GM1 resides in the same PM microenvironment as CFTR. In CF cells, the expression of the mutated channel is accompanied by a decrease in the PM GM1 content. Interestingly, by the exogenous administration of GM1, it becomes a component of the PM, reducing the destabilizing effect of the potentiator VX-770 on rescued CFTR protein expression/function and improving its stabilization. This evidence could represent a starting point for developing innovative therapeutic strategies based on the co-administration of GM1, correctors and potentiators, with the aim of improving F508del CFTR function.

Synthesis and Therapeutic Applications of Iminosugars in Cystic Fibrosis.

Iminosugars are sugar analogues endowed with a high pharmacological potential. The wide range of biological activities exhibited by these glycomimetics associated with their excellent drug profile make them attractive therapeutic candidates for several medical interventions. The ability of iminosugars to act as inhibitors or enhancers of carbohydrate-processing enzymes suggests their potential use as therapeutics for the treatment of cystic fibrosis (CF). Herein we review the most relevant advances in the field, paying attention to both the chemical synthesis of the iminosugars and their biological evaluations, resulting from in vitro and in vivo assays. Starting from the example of the marketed drug NBDNJ (N-butyl deoxynojirimycin), a variety of iminosugars have exhibited the capacity to rescue the trafficking of F508del-CFTR (deletion of F508 residue in the CF transmembrane conductance regulator), either alone or in combination with other correctors. Interesting results have also been obtained when iminosugars were considered as anti-inflammatory agents in CF lung disease. The data herein reported demonstrate that iminosugars hold considerable potential to be applied for both therapeutic purposes.

Peptide Nucleic Acids for MicroRNA Targeting.

The involvement of microRNAs in human pathologies is firmly established. Accordingly, the pharmacological modulation of microRNA activity appears to be a very interesting approach in the development of new types of drugs (miRNA therapeutics). One important research area is the possible development of miRNA therapeutics in the field of rare diseases. In this respect, appealing molecules are based on peptide nucleic acids (PNAs), displaying, in their first description, a pseudo-peptide backbone composed of N-(2-aminoethyl)glycine units, and found to be excellent candidates for antisense and antigene therapies. The aim of the present article is to describe methods for determining the activity of PNAs designed to target microRNAs involved in cystic fibrosis, using as model system miR-145-5p and its target cystic fibrosis transmembrane conductance regulator (CFTR) mRNA. The methods employed to study the effects of PNAs targeting miR-145-5p are presented here by discussing data obtained using as cellular model system the human lung epithelial Calu-3 cell line.

Exploring the effect of chirality on the therapeutic potential of N-alkyl-deoxyiminosugars: anti-inflammatory response to Pseudomonas aeruginosa infections for application in CF lung disease.

In the frame of a research program aimed to explore the relationship between chirality of iminosugars and their therapeutic potential, herein we report the synthesis of N-akyl l-deoxyiminosugars and the evaluation of the anti-inflammatory properties of selected candidates for the treatment of Pseudomonas aeruginosa infections in Cystic Fibrosis (CF) lung disease. Target glycomimetics were prepared by the shortest and most convenient approach reported to date, relying on the use of the well-known PS-TPP/I2 reagent system to prepare reactive alkoxyalkyl iodides, acting as key intermediates. Iminosugars ent-1-3 demonstrated to efficiently reduce the inflammatory response induced by P. aeruginosa in CuFi cells, either alone or in synergistic combination with their d-enantiomers, by selectively inhibiting NLGase. Surprisingly, the evaluation in murine models of lung disease showed that the amount of ent-1 required to reduce the recruitment of neutrophils was 40-fold lower than that of the corresponding d-enantiomer. The remarkably low dosage of the l-iminosugar, combined with its inability to act as inhibitor for most glycosidases, is expected to limit the onset of undesired effects, which are typically associated with the administration of its d-counterpart. Biological results herein obtained place ent-1 and congeners among the earliest examples of l-iminosugars acting as anti-inflammatory agents for therapeutic applications in Cystic Fibrosis.

Molecular basis of cystic fibrosis: from bench to bedside.

Cystic fibrosis (CF), is an autosomal recessive disease affecting different organs. The lung disease, characterized by recurrent and chronic bacterial infection and inflammation since infancy, is the main cause of morbidity and precocious mortality of these individuals. The innovative therapies directed to repair the defective CF gene should account for the presence of more than 200 disease-causing mutations of the CF transmembrane conductance regulator (CFTR) gene. The review will recall the different experimental approaches in discovering CFTR protein targeted molecules, such as the high throughput screening on chemical libraries to discover correctors and potentiators of CFTR protein, dual-acting compounds, read-through molecules, splicing defects repairing tools, CFTR "amplifiers".

Molecular Mechanism of Action of Trimethylangelicin Derivatives as CFTR Modulators.

The psoralen-related compound, 4,6,4'-trimethylangelicin (TMA) potentiates the cAMP/PKA-dependent activation of WT-CFTR and rescues F508del-CFTR-dependent chloride secretion in both primary and secondary airway cells homozygous for the F508del mutation. We recently demonstrated that TMA, like lumacaftor (VX-809), stabilizes the first membrane-spanning domain (MSD1) and enhances the interface between NBD1 and ICL4 (MSD2). TMA also demonstrated anti-inflammatory properties, via reduction of IL-8 expression, thus making TMA a promising agent for treatment of cystic fibrosis. Unfortunately, TMA was also found to display potential phototoxicity and mutagenicity, despite the fact that photo-reactivity is absent when the compound is not directly irradiated with UVA light. Due to concerns about these toxic effects, new TMA analogs, characterized by identical or better activity profiles and minimized or reduced side effects, were synthesized by modifying specific structural features on the TMA scaffold, thus generating compounds with no mutagenicity and phototoxicity. Among these compounds, we found TMA analogs which maintained the potentiation activity of CFTR in FRT-YFP-G551D cells. Nanomolar concentrations of these analogs significantly rescued F508del CFTR-dependent chloride efflux in FRT-YFP-F508del, HEK-293 and CF bronchial epithelial cells. We then investigated the ability of TMA analogs to enhance the stable expression of varying CFTR truncation mutants in HEK-293 cells, with the aim of studying the mechanism of their corrector activity. Not surprisingly, MSD1 was the smallest domain stabilized by TMA analogs, as previously observed for TMA. Moreover, we found that TMA analogs were not effective on F508del-CFTR protein which was already stabilized by a second-site mutation at the NBD1-ICL4 interface. Altogether, our findings demonstrate that these TMA analogs mediate correction by modifying MSD1 and indirectly stabilizing the interface between NBD1 and CL4.

Early diagnosis from newborn screening maximises survival in severe cystic fibrosis.

Newborn screening (NBS) for cystic fibrosis (CF) has been gradually established in several countries, but scant data are available on its long-term effects on survival. Our objective was to evaluate the long-term effects of CF NBS on survival. 586 patients, diagnosed and followed between 1971 and 2014 at the Verona CF Centre were analysed. Eligibility was confirmed in 342 cases diagnosed by NBS, 101 with meconium ileus and 143 through symptoms (44 out of 143 were NBS false negatives). The primary end-point was the 30-year overall survival in patients diagnosed by NBS. Patients were grouped according to the number of hospitalisations for respiratory or nutritional symptoms in the first 3 years of life: 0 (mild), 1-2 (moderate) and ≥3 (severe). Survival in NBS and symptoms groups was compared. The 30-year survival probability of the NBS group was 80.1% (95% CI 71.4-86.4%); in the symptoms group it was 71.0% (95% CI 62.2-78.2%). The 20-year survival was significantly higher in the NBS versus symptoms group in the severe (85% versus 64%, p=0.007) and moderate (94% versus 86%, p=0.016) groups. An adjusted Cox-model estimation confirmed differences in both the groups. Poor outcome associated with early severe presentation of CF is tempered by NBS.

PLCB3 Loss of Function Reduces Pseudomonas aeruginosa-Dependent IL-8 Release in Cystic Fibrosis.

The lungs of patients with cystic fibrosis (CF) are characterized by an exaggerated inflammation driven by secretion of IL-8 from bronchial epithelial cells and worsened by Pseudomonas aeruginosa infection. To identify novel antiinflammatory molecular targets, we previously performed a genetic study of 135 genes of the immune response, which identified the c.2534C>T (p.S845L) variant of phospholipase C-ß3 (PLCB3) as being significantly associated with mild progression of pulmonary disease. Silencing PLCB3 revealed that it potentiates the Toll-like receptor's inflammatory signaling cascade originating from CF bronchial epithelial cells. In the present study, we investigated the role of the PLCB3-S845L variant together with two synthetic mutants paradigmatic of impaired catalytic activity or lacking functional activation in CF bronchial epithelial cells. In experiments in which cells were exposed to P. aeruginosa, the supernatant of mucopurulent material from the airways of patients with CF or different agonists revealed that PLCB3-S845L has defects of 1) agonist-induced Ca2+ release from endoplasmic reticulum and rise of Ca2+ concentration, 2) activation of conventional protein kinase C isoform ß, and 3) induction of IL-8 release. These results, besides identifying S845L as a loss-of-function variant, strengthen the importance of targeting PLCB3 to mitigate the CF inflammatory response in bronchial epithelial cells without blunting the immune response.

Sphingolipids role in the regulation of inflammatory response: From leukocyte biology to bacterial infection.

Sphingolipids (SLs) are amphiphilic molecules mainly associated with the external leaflet of eukaryotic plasma membrane, and are structural membrane components with key signaling properties. Since the beginning of the last century, a large number of papers described the involvement of these molecules in several aspects of cell physiology and pathology. Several lines of evidence support the critical role of SLs in inflammatory diseases, by acting as anti- or pro-inflammatory mediators. They are involved in control of leukocyte activation and migration, and are recognized as essential players in host response to pathogenic infection. We propose here a critical overview of current knowledge on involvement of different classes of SLs in inflammation, focusing on the role of simple and complex SLs in pathogen-mediated inflammatory response.

A microRNA signature from serum exosomes of patients with glioma as complementary diagnostic biomarker.

Malignant gliomas, the most frequent primary brain tumors, are characterized by a dismal prognosis. Reliable biomarkers complementary to neuroradiology in the differential diagnosis of gliomas and monitoring for post-surgical progression are unmet needs. Altered expression of several microRNAs in tumour tissues from patients with gliomas compared to normal brain tissue have been described, thus supporting the rationale of using microRNA-based biomarkers. Although different circulating microRNAs were proposed in association with gliomas, they have not been introduced into clinical practice so far. Blood samples were collected from patients with high and low grade gliomas, both before and after surgical resection, and the expression of miR-21, miR-222 and miR-124-3p was measured in exosomes isolated from serum. The expression levels of miR-21, miR-222 and miR-124-3p in serum exosomes of patients with high grade gliomas were significantly higher than those of low grade gliomas and healthy controls and were sharply decreased in samples obtained after surgery. The analysis of miR-21, miR-222 and miR-124-3p in serum exosomes of patients affected by gliomas can provide a minimally invasive and innovative tool to help the differential diagnosis of gliomas at their onset in the brain and predict glioma grading and non glial metastases before surgery.