Novel Lung Targeting Cell Penetrating Peptides as Vectors for Delivery of Therapeutics

Cell penetrating peptides are unique, 5-30 amino acid long peptides that are able to breach cell membrane barriers and carry cargoes intracellularly in a functional form. Our prior work identified a synthetic, non-naturally occurring 12-amino acid long peptide that we termed cardiac targeting peptide (CTP: APWHLSSQYSRT) due to its ability to transduce cardiomyocytes in vivo. Studies looking into its mechanism of transduction identified two lung targeting peptides (LTPs), S7A (APWHLSAQYSRT) and R11A (APWHLSSQYSAT). These peptides robustly transduced human bronchial epithelial cell lines in vitro and mouse lung tissue in vivo. This uptake occurred independently of clathrin mediated endocytosis. Biodistribution studies of R11A showed peak uptake at 15 minutes with uptake in liver but not kidneys, indicating primarily a hepatobiliary mode of excretion. Cyclic version of both peptides was ~100-fold more efficient in permeating cells than their linear counterparts. As proof of principle, we conjugated anti-spike and anti-envelope SARS-CoV-2 siRNAs to cyclized R11A and demonstrate anti-viral efficacy in vitro. Our work presented here identifies two novel lung-specific cell penetrating peptides that could potentially deliver myriad therapeutic cargoes to lung tissue.

Co-Translational Folding of the First Transmembrane Domain of ABC-Transporter CFTR is Supported by Assembly with the First Cytosolic Domain

ABC transporters transport a wealth of molecules across membranes and consist of transmembrane and cytosolic domains. Their activity cycle involves a tightly regulated and concerted domain choreography. Regulation is driven by the cytosolic domains and function by the transmembrane domains. Folding of these polytopic multidomain proteins to their functional state is a challenge for cells, which is mitigated by co-translational and sequential events. We here reveal the first stages of co-translational domain folding and assembly of CFTR, the ABC transporter defective in the most abundant rare inherited disease cystic fibrosis. We have combined biosynthetic radiolabeling with protease-susceptibility assays and domain-specific antibodies. The most N-terminal domain, TMD1 (transmembrane domain 1), folds both its hydrophobic and soluble helices during translation: the transmembrane helices pack tightly and the cytosolic N- and C-termini assemble with the first cytosolic helical loop ICL1, leaving only ICL2 exposed. This N-C-ICL1 assembly is strengthened by two independent events: (i) assembly of ICL1 with the N-terminal subdomain of the next domain, cytosolic NBD1 (nucleotide-binding domain 1); and (ii) in the presence of corrector drug VX-809, which rescues cell-surface expression of a range of disease-causing CFTR mutants. Both lead to increased shielding of the CFTR N-terminus, and their additivity implies different modes of action. Early assembly of NBD1 and TMD1 is essential for CFTR folding and positions both domains for the required assembly with TMD2. Altogether, we have gained insights into this first, nucleating, VX-809-enhanced domain-assembly event during and immediately after CFTR translation, involving structures conserved in type-I ABC exporters.

Capturing the Direct Binding of CFTR Correctors to CFTR by Using Click Chemistry

Cystic fibrosis (CF) is a lethal genetic disease caused by the loss or dysfunction of the CF transmembrane conductance regulator (CFTR) channel. F508del is the most prevalent mutation of the CFTR gene and encodes a protein defective in folding and processing. VX-809 has been reported to facilitate the folding and trafficking of F508del-CFTR and augment its channel function. The mechanism of action of VX-809 has been poorly understood. In this study, we sought to answer a fundamental question underlying the mechanism of VX-809: does it bind CFTR directly in order to exert its action? We synthesized two VX-809 derivatives, ALK-809 and SUL-809, that possess an alkyne group and retain the rescue capacity of VX-809. By using Cu(I) -catalyzed click chemistry, we provide evidence that the VX-809 derivatives bind CFTR directly in vitro and in cells. Our findings will contribute to the elucidation of the mechanism of action of CFTR correctors and the design of more potent therapeutics to combat CF.

Mediastinal tuberculosis in Bradford, United Kingdom: the role of mediastinoscopy

OBJECTIVE

To evaluate patients with mediastinal tuberculosis (MT), their demographic profiles, symptoms, radiological features and the role of mediastinoscopy.

METHODS

This retrospective study conducted at Bradford Teaching Hospitals, Bradford, United Kingdom, looked at the case notes of 160 (13%) patients with MT out of a cohort of 1252 notifications of tuberculosis (TB) cases from 1995 to 2004, analysing the demographic data, diagnostic findings, computed tomography (CT) scans and outcomes. Interventions included bronchoscopy, lymph node biopsy and mediastinoscopy.

RESULTS

Patient age ranged from 1 to 75 years; the majority were females and from minority ethnic groups. Contact history was positive in 76% of cases. Cough was the most common symptom (50%); however, asymptomatic patients were also common (45%). Heaf test was positive in 99%. Right paratracheal lymphadenopathy was common on chest X-ray and chest CT scan. Mediastinoscopy was performed in only 37 patients with definitive diagnosis.

CONCLUSION

MT should be suspected in adult asymptomatic immigrants presenting with mediastinal adenopathy and a strongly positive Heaf test. Trial of anti-tuberculosis treatment should be initiated and response should guide further management. Mediastinoscopy is required in only a minority of patients.

Combined bicarbonate conductance-impairing variants in CFTR and SPINK1 variants are associated with chronic pancreatitis in patients without cystic fibrosis

BACKGROUND & AIMS

Idiopathic chronic pancreatitis (ICP) is a complex inflammatory disorder associated with multiple genetic and environmental factors. In individuals without cystic fibrosis (CF), variants of CFTR that inhibit bicarbonate conductance but maintain chloride conductance might selectively impair secretion of pancreatic juice, leading to trypsin activation and pancreatitis. We investigated whether sequence variants in the gene encoding the pancreatic secretory trypsin inhibitor SPINK1 further increase the risk of pancreatitis in these patients.

METHODS

We screened patients and controls for variants in SPINK1 associated with risk of chronic pancreatitis and in all 27 exons of CFTR. The final study group included 53 patients with sporadic ICP, 27 probands with familial ICP, 150 unrelated controls, 375 additional controls for limited genotyping. CFTR wild-type and p.R75Q were cloned and expressed in HEK293 cells, and relative conductances of HCO(3)(-) and Cl(-) were measured.

RESULTS

SPINK1 variants were identified in 36% of subjects and 3% of controls (odds ratio [OR], 18.1). One variant of CFTR not associated with CF, p.R75Q, was found in 16% of subjects and 5.3% of controls (OR, 3.4). Coinheritance of CFTR p.R75Q and SPINK1 variants occurred in 8.75% of patients and 0.38% of controls (OR, 25.1). Patch-clamp recordings of cells that expressed CFTR p.R75Q showed normal chloride currents but significantly reduced bicarbonate currents (P = .0001).

CONCLUSIONS

The CFTR variant p.R75Q causes a selective defect in bicarbonate conductance and increases risk of pancreatitis. Coinheritance of p.R75Q or CF causing CFTR variants with SPINK1 variants significantly increases the risk of ICP.

Absorptive clearance of DTPA as an aerosol-based biomarker in the cystic fibrosis airway

Biomarkers providing in vivo quantification of the basic elements of cystic fibrosis (CF) lung disease are needed. A study was performed to determine whether the absorption of a small radiolabelled hydrophilic molecule (Indium-111 (In-)DTPA) would be increased in CF airways. DTPA clearance has been used previously to assess epithelial permeability and may also be useful for quantifying liquid absorption. The absorptive clearance rate of DTPA was quantified in 10 CF and 11 control subjects using a novel aerosol technique. Subjects inhaled an aerosol containing nonabsorbable technetium-99m sulfur colloid (Tc-SC) particles and In-DTPA. Tc-SC clearance from the lung is exclusively mucociliary, while In-DTPA is cleared by both absorption and mucociliary clearance. The difference between the In-DTPA and Tc-SC clearance rates estimates In-DTPA absorption. Tc-SC (mucociliary) clearance was similar in central and peripheral zones in CF and non-CF lungs. Total In-DTPA clearance was increased in both zones in CF lungs. The absorptive component of In-DTPA clearance was increased in the airway-dominated central lung zones in CF (42% x h( -1) versus 32% x h(-1), p = 0.03). The absorption of In-DTPA is increased in the CF airway. Further study is needed to understand the relative roles of fluid absorption, inflammation and other mechanisms potentially affecting epithelial permeability and DTPA absorption.

Predominant VNTR family of strains of Mycobacterium tuberculosis isolated from South Asian patients

SETTING

Despite the low incidence of tuberculosis in the UK, some minority ethnic groups, particularly those originating from South Asia, experience very high incidence rates.

OBJECTIVE

Comparison of the variable number tandem repeat (VNTR) profiles of strains of Mycobacterium tuberculosis circulating in an immigrant community in the UK with those found in the country of ethnic origin.

DESIGN

Isolates of M. tuberculosis were collected from samples obtained from patients attending clinics in Leeds and Bradford, UK and Rawalpindi, Pakistan. Strains were compared using VNTR analysis and mixed-linker PCR.

RESULTS

Comparison of VNTR profiles found that one profile (42235) represented 37% of patient isolates from Rawalpindi and 23% of patient isolates in Leeds and Bradford, where it was associated exclusively with patients with South Asian names. A second profile (02235) represented 15% of patient isolates in Leeds and Bradford, and was also exclusively associated with the South Asian community. These profiles could be subdivided by mixed-linker PCR analysis.

CONCLUSION

The VNTR profile 42235 may represent a family of strains commonly found in communities associated with South Asia.

CFTR drives Na+-nHCO-3 cotransport in pancreatic duct cells: a basis for defective HCO-3 secretion in CF

Pancreatic dysfunction in patients with cystic fibrosis (CF) is felt to result primarily from impairment of ductal HCO-3 secretion. We provide molecular evidence for the expression of NBC-1, an electrogenic Na+-HCO-3 cotransporter (NBC) in cultured human pancreatic duct cells exhibiting physiological features prototypical of CF duct fragments (CFPAC-1 cells) or normal duct fragments [CAPAN-1 cells and CFPAC-1 cells transfected with wild-type CF transmembrane conductance regulator (CFTR)]. We further demonstrate that 1) HCO-3 uptake across the basolateral membranes of pancreatic duct cells is mediated via NBC and 2) cAMP potentiates NBC activity through activation of CFTR-mediated Cl- secretion. We propose that the defect in agonist-stimulated ductal HCO-3 secretion in patients with CF is predominantly due to decreased NBC-driven HCO-3 entry at the basolateral membrane, secondary to the lack of sufficient electrogenic driving force in the absence of functional CFTR.

Cystic fibrosis gene mutation (deltaF508) is associated with an intrinsic abnormality in Ca2+-induced arachidonic acid release by epithelial cells

The mechanism(s) of chronic airway inflammation in cystic fibrosis (CF) remains poorly understood. We studied Ca2+-induced release of arachidonic acid (AA), a precursor of proinflammatory lipid mediators, in epithelial cell lines with the deltaF508 mutation in CF transmembrane conductance regulator (CFTR) gene and in those lacking this mutation or cells in which this mutation was corrected by a functional CFTR gene transfer. We found that: (i) the mutant cells manifested an abnormally high Ca2+-induced AA release as compared to controls, (ii) AA release appeared to be catalyzed by a phospholipase A2 (PLA2) but not by phospholipase C followed by diacylglycerol lipase, and (iii) either correction of the CFTR-mutation or inhibition of PLA2 activity rectified this AA release abnormality. Taken together, our results suggest that CFTR mutation is associated with an intrinsic abnormality in AA release by epithelial cells carrying the deltaF508 mutation and suggest that the mechanism of chronic airway inflammation in CF, at least in part, involves this abnormality. These results also partly explain the effectiveness of high-dose ibuprofen therapy in arresting the progression of destructive lung disease in CF. Furthermore, they raise the possibility that correction of abnormal AA release by inhibiting PLA2 activity may improve the therapeutic benefits of ibuprofen.