Chronic and persistent lung infections cause the majority of morbidity and mortality in patients with cystic fibrosis (CF). Galactosyl ceramide has been previously shown to be involved in Pseudomonas internalization. Therefore, we assessed ceramide levels in the plasma of patients with CF and compared them to healthy volunteers using high-performance liquid chromatography followed by mass spectrometry. Our results demonstrate that patients with CF display significantly lower levels of several ceramide sphingolipid species, specifically C14:0, C20:1, C22:0, C22:1, and C24:0 ceramides, and dihydroxy ceramide (DHC16:0). We report that Cftr-knockout mice display diminished ceramide levels in CF-related organs (lung, pancreas, ileum, and plasma) compared with their littermate controls. Since it has been previously reported that in vitro treatment with fenretinide induced ceramide in neuroblastoma cell lines, we decided to test this drug in vivo using our Cftr-knockout mice in an attempt to correct this newly identified defect in ceramide levels. We demonstrate that treatment with fenretinide is able to increase ceramide concentrations in CF-related organs. We further assessed the biological effect of fenretinide on the ability of Cftr-knockout mice to combat lung infection with P. aeruginosa. Our data show dramatic improvement in the ability of Cftr-knockout mice to control P. aeruginosa infection. Overall, these findings not only document a novel deficiency in several ceramide species in patients with CF, but also demonstrate a pharmacologic means to correct this defect in Cftr-knockout mice. Our data provide a strong rationale for clinical intervention that may benefit patients with CF suffering from CF lung disease.

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Whey protein isolates (WPI) may provide anti-inflammatory benefits to cystic fibrosis (CF), which could be mediated via peptides, as proteolytic digests of WPI enhance intracellular glutathione (GSH) concentrations. The objectives of this study were to investigate whether high hydrostatic pressure can (i) improve the in vitro digestibility of WPI; and (ii) generate low molecular weight (< 1 kDa) peptides from WPI hydrolysates that exert GSH-enhancing and anti-inflammatory properties in wild type and mutant CF transmembrane conductance regulator (CFTR) tracheal epithelial cells. Hydrostatic pressure processing enhanced the in vitro digestibility of WPI to proteolytic enzymes resulting in altered peptide profiles as assessed by CZE and GC-MS. The exposure of mutant CFTR cells to low molecular weight (< 1 kDa) peptides isolated from WPI hydrolysates exposed to pressure processing (pressurized WPI hydrolysates, pWPH), showed increased intracellular levels of reduced GSH and total GSH relative to treatment with peptides obtained from native WPI hydrolysates (nWPH). A tendency for decreased interleukin-8 secretion was associated with the pWPH and nWPH treatments in mutant CFTR cells, which was not observed in wild type cells. Hydrostatic pressure processing of whey proteins appears to enhance their impact on cellular GSH status in cells with the mutant CFTR condition.

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