Restoration of CFTR function in patients with cystic fibrosis carrying the F508del-CFTR mutation

Restoration of BECN1/Beclin 1-dependent autophagy and depletion of SQSTM1/p62 by genetic manipulation or autophagy-stimulatory proteostasis regulators, such as cystamine, have positive effects on mouse models of human cystic fibrosis (CF). These measures rescue the functional expression of the most frequent pathogenic CFTR mutant, F508del, at the respiratory epithelial surface and reduce lung inflammation in CftrF508del homozygous mice. Cysteamine, the reduced form of cystamine, is an FDA-approved drug. Here, we report that oral treatment with cysteamine greatly reduces the mortality rate and improves the phenotype of newborn mice bearing the F508del-CFTR mutation. Cysteamine was also able to increase the plasma membrane expression of the F508del-CFTR protein in nasal epithelial cells from F508del homozygous CF patients, and these effects persisted for 24 h after cysteamine withdrawal. Importantly, this cysteamine effect after washout was further sustained by the sequential administration of epigallocatechin gallate (EGCG), a green tea flavonoid, both in vivo, in mice, and in vitro, in primary epithelial cells from CF patients. In a pilot clinical trial involving 10 F508del-CFTR homozygous CF patients, the combination of cysteamine and EGCG restored BECN1, reduced SQSTM1 levels and improved CFTR function from nasal epithelial cells in vivo, correlating with a decrease of chloride concentrations in sweat, as well as with a reduction of the abundance of TNF/TNF-alpha (tumor necrosis factor) and CXCL8 (chemokine [C-X-C motif] ligand 8) transcripts in nasal brushing and TNF and CXCL8 protein levels in the sputum. Altogether, these results suggest that optimal schedules of cysteamine plus EGCG might be used for the treatment of CF caused by the F508del-CFTR mutation.

通过遗传操作或促自噬的蛋白稳态调节剂（如胱胺（cystamine））恢复BECN1/Beclin 1依赖性自噬并耗竭SQSTM1/p62，对人类囊性纤维化（cystic fibrosis, CF）小鼠模型具有积极作用。此类手段可挽救呼吸道上皮表面最常见的致病性囊性纤维化跨膜传导调节因子（cystic fibrosis transmembrane conductance regulator, CFTR）突变体F508del的功能性表达，并减轻CftrF508del纯合子小鼠的肺部炎症。半胱胺（cysteamine）作为胱胺的还原形式，是美国食品药品监督管理局（FDA）批准的药物。本研究报道，半胱胺口服给药可显著降低携带F508del-CFTR突变的新生小鼠的死亡率，并改善其表型。半胱胺还可提升F508del纯合型囊性纤维化患者鼻腔上皮细胞中F508del-CFTR蛋白的质膜表达水平，且该效应在停药后仍可持续24小时。值得注意的是，在小鼠体内实验及囊性纤维化患者原代上皮细胞的体外实验中，序贯给予绿茶黄酮类化合物表没食子儿茶素没食子酸酯（epigallocatechin gallate, EGCG）可进一步维持半胱胺停药后的上述效应。在一项纳入10例F508del-CFTR纯合型囊性纤维化患者的先导临床试验中，半胱胺与EGCG联合给药可在体内恢复鼻腔上皮细胞的BECN1表达、降低SQSTM1水平并改善CFTR功能，且该效应与汗液氯离子浓度降低相关，同时与鼻腔刷取样本中肿瘤坏死因子（tumor necrosis factor, TNF/TNF-α）及趋化因子C-X-C基序配体8（CXCL8）的转录本丰度下降、痰液中TNF及CXCL8蛋白水平降低相关。综上，本研究结果提示，优化半胱胺联合EGCG的给药方案，可用于治疗由F508del-CFTR突变引发的囊性纤维化。