While this work was in progress, Kelly-Aubert et al, studying the effects of a glutathione analog (GSH monoethyl ester), also found a reduced mCx-I activity in CF cells and KO mice [59], in agreement with our previous findings regarding a reduced CISD1[14] and MTND4[15] expression in CF cells, which prompted us to think again over the mitochondrial hypothesis of Shapiro and colleagues [10], [11], [12], [34], [35], [36], [37]. Here, MT-ND4 is linked to cystic fibrosis.