A novel treatment of cystic fibrosis acting on-target: cysteamine plus epigallocatechin gallate for the autophagy-dependent rescue of class II-mutated CFTR

Abstract

We previously reported that the combination of two safe proteostasis regulators, cysteamine and epigallocatechin gallate (EGCG), can be used to improve deficient expression of the cystic fibrosis transmembrane conductance regulator (CFTR) in patients homozygous for the CFTR Phe508del mutation. Here we provide the proof-of-concept that this combination treatment restored CFTR function and reduced lung inflammation (P<0.001) in Phe508del/Phe508del or Phe508del/null-Cftr (but not in Cftr-null mice), provided that such mice were autophagy-competent. Primary nasal cells from patients bearing different class II CFTR mutations, either in homozygous or compound heterozygous form, responded to the treatment in vitro. We assessed individual responses to cysteamine plus EGCG in a single-centre, open-label phase-2 trial. The combination treatment decreased sweat chloride from baseline, increased both CFTR protein and function in nasal cells, restored autophagy in such cells, decreased CXCL8 and TNF-α in the sputum, and tended to improve respiratory function. These positive effects were particularly strong in patients carrying Phe508del CFTR mutations in homozygosity or heterozygosity. However, a fraction of patients bearing other CFTR mutations failed to respond to therapy. Importantly, the same patients whose primary nasal brushed cells did not respond to cysteamine plus EGCG in vitro also exhibited deficient therapeutic responses in vivo. Altogether, these results suggest that the combination treatment of cysteamine plus EGCG acts ‘on-target' because it can only rescue CFTR function when autophagy is functional (in mice) and improves CFTR function when a rescuable protein is expressed (in mice and men). These results should spur the further clinical development of the combination treatment.

TG2 regulates the heat‐shock response by the post‐translational modification of HSF1

“…Intestinal HSP70 expression was increased in CFTR F508del /TG2 +/+ mice over WT (CFTR wt /TG2 +/+ ) controls, and this HSP70 overexpression was reduced in CFTR F508del /TG2 −/− mice (Fig A). Recently, it has been demonstrated that the administration of the TG2 inhibitor cysteamine restores CFTR function both in CF mice and patients bearing misfolded CFTR mutant proteins either in homozygous or in compound heterozygous form . By a computerized docking analysis, we found that cysteamine was able to interact with TG2 close to its active site, thus inhibiting the transamidating and the PDI activities (Fig EV4A).…”

“…According to this, phosphorylation of HSF1 at S326, a hallmark for HSF1 activation, occurred mainly in CF patients and largely decreased with cysteamine (Fig E and F). We also analysed freshly brushed nasal epithelial cells from two F508del CFTR homozygous patients who underwent a phase II clinical trial (EudraCT 2013‐001258‐82) with cysteamine bitartrate . Both patients, who showed functional rescue of mutant CFTR protein after 4 weeks of in vivo therapy , also manifested reduced HSP70 expression together with a decrease in TG2 protein (Fig EV4C).…”

“…We also analysed freshly brushed nasal epithelial cells from two F508del CFTR homozygous patients who underwent a phase II clinical trial (EudraCT 2013‐001258‐82) with cysteamine bitartrate . Both patients, who showed functional rescue of mutant CFTR protein after 4 weeks of in vivo therapy , also manifested reduced HSP70 expression together with a decrease in TG2 protein (Fig EV4C). Altogether, our data indicate a pivotal role of TG2 in favouring F508del CFTR degradation through regulation of HSP70‐HSF1 pathway.…”

“…Indeed, recent compelling evidence places TG2 within the regulation of main pathways controlling the proteome homeostasis as autophagy, proteasome and exosomes . In keeping with this, there is a vast literature describing the deregulation of this enzyme during the pathogenesis of major human diseases (neurodegenerative, liver and respiratory disorders as well as cancer) in which there is a deregulated proteostasis that can be improved by modulators of TG2 activity . In spite of differences related to cell‐ and tissue‐specific disease context, these disorders share common features of unbalanced cell adaptation to either cell autonomous or environmental stress.…”

A pathogenic role for cystic fibrosis transmembrane conductance regulator in celiac disease

“…Both FVB/129 and B6.129P2 littermates bearing WT‐CFTR are not sensitive to gliadin, as oral gliadin administration failed to stimulate inflammatory response and IFN‐γ production. Conversely, CFTR‐mutated mice (De Stefano et al , ; Tosco et al , ) fed with gliadin greatly increased both IL‐15 and IL‐17A levels in their small intestine and exhibited a 3.5‐fold increase in IFN‐γ production ( P < 0.01 vs. vehicle‐treated mice; Fig F; Appendix Fig S1D and E). These results indicate that the constitutive stress response and innate immunity activation in CFTR‐deficient intestines favor an immune response to gliadin.…”