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Editorial: Mechanisms of action of small molecules on CFTR mutants and the impact on cystic fibrosis pathogenesis
No full textThe investigational Cystic Fibrosis drug Trimethylangelicin directly modulates CFTR by stabilizing the first membrane-spanning domain.
Full text linkCystic Fibrosis (CF) is caused by mutations in the Cystic Fibrosis Transmembrane Conductance Regulator
(CFTR) gene. The most common mutation, deletion of phenylalanine 508 (F508del), disrupts tertiary
assembly, causing protein misprocessing and loss of CFTR function in epithelial tissues. Lumacaftor
(VX-809) is a Class 1 corrector molecule shown to partially rescue misprocessing of F508del and together
with the potentiator of channel activity: ivacaftor (VX-770) has been approved for treatment of CF
patients homozygous for the F508del mutation. The specificity of these modulators for CFTR is thought
to be conferred through direct binding. Trimethylangelicin (TMA) is a distinct small molecule modulator,
previously shown to exhibit both corrector and potentiator activities. We were prompted to determine if
TMA also mediates these activities by direct binding. Interestingly, we found that like VX-770, TMA was
effective in enhancing anion efflux mediated by purified WT-CFTR reconstituted in phospholipid liposomes.
Furthermore, like VX-809, TMA was effective in stabilizing the functional expression of CFTR lacking
the regulatory ‘‘R” domain or second nucleotide-binding domain (NBD2). The smallest domain that
was stabilized by TMA binding was the first membrane-spanning domain (MSD1) as previously observed
for VX-809. Together, our findings support the claim that TMA binds directly to CFTR, and despite its distinct
chemical structure, shares similar mechanisms as VX-770 and VX-809 to potentiate and stabilize
CFTR, respectively
Editorial: Mechanisms of Novel Drugs and Gene Modifiers in the Treatment of Cystic Fibrosis
Full text linkThe era of CFTR modulators: improvements made and remaining challenges
Full text linkThe entry into the clinic of CFTR modulators such as TRIKAFTA has significantly improved life for ∼90% CF patients carrying one or two F508del mutations but challenges remain for rare CFTR mutations and the management of lung infections @SaraOcana1 https://bit.ly/3aRafQF
Olive Leaf Extract (OLE) as a Novel Antioxidant That Ameliorates the Inflammatory Response in Cystic Fibrosis
No full textThe deletion of phenylalanine at position 508 (F508del) produces a misfolded CFTR protein that is retained in the ER and degraded. The lack of normal CFTR channel activity is associated with chronic infection and inflammation which are the primary causes of declining lung function in Cystic Fibrosis (CF) patients. Moreover, LPS-dependent oxidative stress downregulates CFTR function in airway epithelial cells. Olive leaf extract (OLE) is used in traditional medicine for its effects, including anti-oxidant and anti-inflammatory ones. We found that OLE decreased the intracellular ROS levels in a dose-response manner in CFBE cells. Moreover, OLE attenuates the inflammatory response to LPS or IL-1 beta/TNF alpha stimulation, mimicking the infection and inflammatory status of CF patients, in CFBE and primary nasal epithelial (HNE) cells. Furthermore, we demonstrated that OLE restored the LPS-mediated decrease of Trikfafta (TM)-dependent F508del-CFTR function in CFBE and HNE cultures. These findings provide strong evidence of OLE to prevent redox imbalance and inflammation that can cause chronic lung damage by enhancing the antioxidant activity and attenuating inflammation in CF airway epithelial cells. Additionally, OLE might be used in combination with CFTR modulators therapy to improve their efficacy in CF patients
Insulin-Like Growth Factor Binding Protein (IGFBP-6) as a Novel Regulator of Inflammatory Response in Cystic Fibrosis Airway Cells
Full text linkCystic Fibrosis (CF) patients are prone to contracting bacterial lung infections with opportunistic pathogens, especially Pseudomonas aeruginosa. Prolonged P. aeruginosa infections have been linked to chronic inflammation in the CF lung, whose hallmarks are increased levels of cytokines (i.e., TNF-α, IL-1β, IL-6) and neutrophil attraction by chemokines, like IL-8. Recently, insulin-like growth factor binding protein 6 (IGFBP-6) has been shown to play a putative role in the immune system and was found at higher levels in the sera and synovial tissue of rheumatoid arthritis patients. Moreover, it has been demonstrated that IGFBP-6 has chemoattractant properties towards cells of the innate (neutrophils, monocytes) and adaptive (T cells) immunity. However, it is not known whether IGFBP-6 expression is dysregulated in airway epithelial cells under infection/inflammatory conditions. Therefore, we first measured the basal IGFBP-6 mRNA and protein levels in bronchial epithelial cells lines (Wt and F508del-CFTR CFBE), finding they both are upregulated in F508del-CFTR CFBE cells. Interestingly, LPS and IL-1β+TNFα treatments increased the IGFBP-6 mRNA level, that was reduced after treatment with an anti-inflammatory (Dimethyl Fumarate) in CFBE cell line and in patient-derived nasal epithelial cultures. Lastly, we demonstrated that IGFBP-6 reduced the level of pro-inflammatory cytokines in both CFBE and primary nasal epithelial cells, without affecting rescued CFTR expression and function. The addition of a neutralizing antibody to IGFBP-6 increased pro-inflammatory cytokines expression under challenge with LPS. Together, these data suggest that IGFBP-6 may play a direct role in the CF-associated inflammation
Advances in Preclinical In Vitro Models for the Translation of Precision Medicine for Cystic Fibrosis
No full textThe development of preclinical in vitro models has provided significant progress to the studies of cystic fibrosis (CF), a frequently fatal monogenic disease caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR) protein. Numerous cell lines were generated over the last 30 years and they have been instrumental not only in enhancing the understanding of CF pathological mechanisms but also in developing therapies targeting the underlying defects in CFTR mutations with further validation in patient-derived samples. Furthermore, recent advances toward precision medicine in CF have been made possible by optimizing protocols and establishing novel assays using human bronchial, nasal and rectal tissues, and by progressing from two-dimensional monocultures to more complex three-dimensional culture platforms. These models also enable to potentially predict clinical efficacy and responsiveness to CFTR modulator therapies at an individual level. In parallel, advanced systems, such as induced pluripotent stem cells and organ-on-a-chip, continue to be developed in order to more closely recapitulate human physiology for disease modeling and drug testing. In this review, we have highlighted novel and optimized cell models that are being used in CF research to develop novel CFTR-directed therapies (or alternative therapeutic interventions) and to expand the usage of existing modulator drugs to common and rare CF-causing mutations
Correctors of the major cystic fibrosis mutant interact through membrane-spanning domainsS
Full text linkThe most common cystic fibrosis causing mutation is deletion of phenylalanine at position 508 (F508del), a mutation that leads to protein misassembly with defective processing. Small molecule corrector compounds: VX-809 or Corr-4a (C4) partially restores processing of the major mutant. These two prototypical corrector compounds cause an additive effect on F508del/cystic fibrosis transmembrane conductance regulator (CFTR) processing, and hence were proposed to act through distinct mechanisms: VX-809 stabilizing the first membrane-spanning domain (MSD) 1, and C4 acting on the second half of the molecule [consisting of MSD2 and/or nucleotide binding domain (NBD) 2]. We confirmed the effect of VX-809 in enhancing the stability of MSD1 and showed that it also allosterically modulates MSD2 when coexpressed with MSD1. We showed for the first time that C4 stabilizes the second half of the CFTR protein through its action on MSD2. Given the allosteric effect of VX-809 on MSD2, we were prompted to test the hypothesis that the two correctors interact in the full-length mutant protein. We did see evidence supporting their interaction in the full-length F508del-CFTR protein bearing secondary mutations targeting domain:domain interfaces. Disruption of the MSD1:F508del-NBD1 interaction (R170G) prevented correction by both compounds, pointing to the importance of this interface in processing. On the other hand, stabilization of the MSD2: F508del-NBD1 interface (by introducing R1070W) led to a synergistic effect of the compound combination on the total abundance of both the immature and mature forms of the protein. Together, these findings suggest that the two correctors interact in stabilizing the complex of MSDs in F508del-CFTR
IL-17 family members exert an autocrine pro-inflammatory loop in CF respiratory epithelial cells ex vivo
No full textBackground: Lungs of people with Cystic Fibrosis (pwCF) are characterized by chronic inflammation and infection with P. aeruginosa. High levels of IL-17 A and F have been observed in sputum of pwCF and the interleukin-17(IL-17) family (A-to-F) has been suggested to play a key role in CF pulmonary disease. Methods: We measured mRNA levels of IL-17 receptors (IL-17R) by RT-qPCR in CF bronchial epithelial (CFBE) cultured cells upon infection with P. aeruginosa PAO1 strain or clinical exoproducts (EXO) isolated from pwCF. We measured IL-17 mRNA expression by RT-qPCR and the release of cytokines by ELISA and Bioplex from CF primary nasal epithelial (HNE) cultured cells. Results: Infection of CFBE cells with PAO1 or EXO isolated from 15 pwCF significantly increased mRNA expression of all IL-17R, except IL-17RD. Infection of HNE cells with EXO isolated from the correspondent donor significantly increased the mRNA levels of all the IL-17 cytokines and receptors, except for IL-17D and IL-17RD, and the release of the cytokines IL-17 A, IL-17B, IL-17C, IL-17E and IL-17F. HNE exposed to IL-17 A and F were induced to release pro-inflammatory cytokines (IL-1β, IL-6, TNF-α), neutrophil chemokines (IL-8, G-CSF) and cytokines known to be involved in chloride and bicarbonate secretion, together with mucin upregulation (IL-4, IL-13). Conclusion: These results highlight a wider expression of IL-17 family member in respiratory epithelial cells, which can play a role as an autocrine inflammatory amplification loop in CF airways. These in-vitro studies using patient-derived cultures underline the relevant role of IL-17 family members in CF pulmonary immune response
A protocol for identifying the binding sites of small molecules on the cystic fibrosis transmembrane conductance regulator (CFTR) protein
Full text linkWe describe a protocol to identify the binding site(s) for a drug called ivacaftor that potentiates the CFTR chloride channel. We use photoaffinity probes-based on the structure of ivacaftor-to covalently modify the CFTR protein at the region that constitutes the drug binding site(s). We define the methods for photo-labeling CFTR, its membrane extraction, and enzymatic digestion using trypsin. We then describe the experimental methods to identify the modified peptides by using mass spectrometry. For complete details on the use and execution of this protocol, please refer to Laselva et al. (2021)
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