Novel S-Nitrosothiols Have Potential Therapeutic Uses for Cystic Fibrosis

Abstract

Cystic fibrosis (CF) is a multisystem disease associated with mutations in the gene that encodes the CF transmembrane conductance regulatory (CFTR) protein. The majority of wild-type CFTR and virtually all mutant ΔF508 CFTR are degraded before reaching the cell surface. Certain agents and conditions that increase expression and maturation of CFTR enable the protein to function at the cell surface. We and several research groups have reported that S-nitrosoglutathione (GSNO), a class of endogenous S-nitrosothiols, increases the maturation and function of CFTR in human airway epithelial cells. S-nitrosothiols (SNOs) are endogenous molecules with several cell signaling effects and potential relevance to human lung disease. SNOs are normally present in the human airway and have beneficial effects on lung function. Biochemical evidence suggests that SNOs act on post-translational protein modifications through mechanisms involving S-nitrosylation reactions. S-nitrosylation reactions are increasingly recognized to represent metabolically regulated cell signaling processes. Airway epithelial S-nitrosylation signaling disorders have been observed in a range of diseases, including CF. SNO levels are low in CF patients and normal physiological concentrations are effective in increasing CFTR maturation. The mechanisms by which SNOs improve CFTR expression appear to be novel. However, the precise mechanisms by which SNOs exert their beneficial effects are poorly understood. In the near future, we expect to identify the novel mechanisms by which SNO augments CFTR maturation. This information will be critical for optimizing the design and dosing of SNOs that might be used as CFTR corrector therapies in clinical trials.

The role of S-nitrosoglutathione reductase (GSNOR) in human disease and therapy

“…Two of these, N6022 (3-(5-(4-(1H-imidazol-1-yl) phenyl)-1-(4-carbamoyl-2-methylphenyl)-1H-pyrrol-2-yl) propionic acid) and N91115 from Nivalis Pharmaceuticals show promise as potentially safe and effective GSNOR inhibitors that have undergone clinical trial for both the treatment of mild asthma (clinicaltrials.gov - NCT01316315), and cystic fibrosis in individuals who are heterozygous for the cystic fibrosis transmembrane conductance regulator (CFTR) gating mutation CFTRΔF508+ (clinicaltrials.gov – N6022: NCT01746784; N91115: NCT02724527). Endogenous GSNO levels are low in the airways of cystic fibrosis patients (Grasemann et al, 1999) and GSNOR inhibition is an appealing alternative to the direct administration to of GSNO (Snyder et al, 2002; Zaman et al, 2013, 2001). N6022 is well tolerated with minimal side effects, even at high concentrations, in both animals (Blonder et al, 2014; Colagiovanni et al, 2012) and humans (clinicaltrials.gov – NCT01147406, NCT01746784).…”

Modifying disease in cystic fibrosis

“…A phase 2 dose escalation study of VX-661 monotherapy (doses 10, 30, 100, 150 mg) and in combination with ivacaftor (150 mg twice daily) has been completed in 128 homozygous F508del adult patients [37]. In airway cell culture models, S-nitrosothiols increase CFTR function and potentially affect airway inflammation [39,40]. N6022 targets an alternate corrector pathway thought to stimulate maturation of the CFTR protein by regulation of cell metabolism.…”

S-nitrosothiols increases cystic fibrosis transmembrane regulator expression and maturation in the cell surface

“…The butyrate class of compounds such as 4-phenylbutyrate, efficiently correct F508del CFTR processing, transport, and function in vitro [8]. Current literature suggests that other correctors were shown to be relatively specific for rescuing F508del CFTR [12]. For example, Corr-4, Corr2b, VX-809 and VX-532 promote maturation of F508del CFTR.…”

“…For example, Corr-4, Corr2b, VX-809 and VX-532 promote maturation of F508del CFTR. In addition, multiple molecular chaperones assist in the productive folding of wild-type and mutant forms of CFTR, including heat shock protein 70 (Hsp70) and 90 (Hsp90), heat shock cognate 70 (Hsc70), cysteine string protein (Csp), and Hsp70/Hsp90 organizing protein (Hop) [12,13]. …”