A Pilot Study of the Effect of Gentamicin on Nasal Potential Difference Measurements in Cystic Fibrosis Patients Carrying Stop Mutations

Abstract

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene containing a premature termination signal are expected to produce little or no CFTR chloride channels. It has been shown in vitro, that aminoglycoside antibiotics can increase the frequency of erroneous insertion of nonsense codons hence permitting the translation of CFTR alleles carrying missense mutations to continue reading to the end of the gene. This led to the appearance of functional CFTR channels at the apical plasma membrane. The aim of this research was to determine if topical application of gentamicin to the nasal epithelium of patients with cystic fibrosis (CF) carrying stop mutations can express, in vivo, functional CFTR channels. Nine CF patients carrying stop mutations (mean age 23 +/- 11 yr, range 12 to 46 yr) received gentamicin drops (0.3%, 3 mg/ml) three times daily intranasally for a total of 14 d. Nasal potential difference (PD) was measured before and after the treatment. Before gentamicin application all the patients had abnormal nasal PD typical of CF. After gentamicin treatment, significant repolarization of the nasal epithelium representing chloride transport was increased from -1 +/- 1 mV to -10 +/- 11 mV (p < 0. 001). In conclusion, gentamicin may influence the underlying chloride transport abnormality in patients with CF carrying stop mutations.

Effect of Readthrough Treatment in Fibroblasts of Patients Affected by Lysosomal Diseases Caused by Premature Termination Codons

“…In our study, we focused on nonsense or frameshift mutations leading to PTC resulting in an almost complete absence of particular key proteins involved in lysosomal function and cell homeostasis maintenance. Preclinical studies with gentamicin or PTC124 had succeeded by enhancing stop codon readthrough and were able to be used as therapeutic agents for genetic diseases [9][10][11][12][13][14][15][16][17][18][36][37][38][39][40][41][42]. PTC124 has been successfully extended into clinical trials [18,43], although preliminary results are not clear for Duchenne muscular dystrophy [44].…”

“…Glutamine is preferably inserted at nonsense UAG or UAA codons, whereas UGA miscode to tryptophan [36][37][38]. Taking into account these rules, the predicted amino acid changes were analyzed, using an in silico approach, for each patient (Polyphen-2 and SIFT analyses).…”

Premature stop codons involved in muscular dystrophies show a broad spectrum of readthrough efficiencies in response to gentamicin treatment

“…These results thus strongly suggest that only a subset of DMD and CMD patients carrying stop mutations would potentially benefit of a gentamicin treatment aiming at suppressing premature termination codons. They may also explain the failure or relative difficulty to obtain significant improvement of symptoms in clinical trials already reported, [34][35][36] since the patients included in these trials were not chosen on the criteria of the response of their mutation. Similarly, Gentamicin and muscular dystrophies L Bidou et al our efforts to correct the albino phenotype associated with the platinum (Typ cÀp ) coat color mutation by local or systemic treatment with gentamicin at several stages during embryogenesis, in pups and in adults failed (data not shown).…”

Uptake of Gentamicin by Bullfrog Saccular Hair Cells in vitro

“…However, other studies have reported neither the presence nor absence of gentamicin in the nucleus (Hashino et al 1997;Sundin et al 1997;Girton et al 2002). Nonetheless, a subset of cystic fibrosis patients can be partially rehabilitated through gentamicin therapy, which causes bypassing of the premature stop codon in the cystic fibrosis (CF) mutation, allowing functional transcription of the CF transmembrane protein (Howard et al 1996;Bedwell et al 1997;Wilschanski et al 2000;Clancy et al 2001;Du et al 2002;Zsembery et al 2002). This suggests that gentamicin can enter the nucleus.…”