Exaggerated apoptosis andNF‐KBactivation in pancreatic and tracheal cystic fibrosis cells

Abstract

The pathophysiologic mechanisms causing inflammation in cystic fibrosis (CF) remain obscure. The effects of proapoptotic agents on pancreatic and tracheal cell lines expressing wild-type CFTR (PANC-1 and NT-1, respectively) or the homozygous CFTRDeltaF508 mutation (CFPAC-1 and CFT-2, respectively) were assessed. An increased susceptibility to apoptosis was observed in CFPAC-1 and CFT-2 cells. Apoptosis was reduced by treatment with a pan-caspase inhibitor and by incubation at 27 degrees C, allowing recruitment of CFTR deltaF508 at the plasma membrane. Inhibition of CFTR function in wild-type cells induced an increase of apoptosis. Apoptosis in CFPAC-1, but not in CFT-2 cells, was associated with overexpression of the proinflammatory mediators interleukin-6 and interleukin-8. In CF cells, apoptosis was linked to NF-kappaB pathway activation. Conditioned medium from actinomycin D-treated CFPAC-1 cells produced an increase in apoptosis of wild-type cells, suggesting that proinflammatory mediators secreted by mutant cells promote apoptosis. This was confirmed through the induction of apoptosis in wild-type cells by exogenous interleukin-6 and interleukin-8. These results suggest that CFTR deltaF508 mutation, apoptosis, and activation of the NF-kappaB pathway contribute to the self-perpetuating inflammatory cycle, at least in pancreatic cells, and provide evidence that excessive apoptosis may account for the exaggerated proinflammatory response observed in CF patients.

Inhibition of acinar apoptosis occurs during acute pancreatitis in the human homologue ΔF508 cystic fibrosis mouse

“…Furthermore, observations from multiple nonpancreatic studies indicate that resistance to apoptosis occurs in CF (2,6,27,31,37,38,50,83). This concept remains controversial (33,35,65,75), possibly because the predominant mode of cell death is tissue dependent (74) and because the CFTR-dependent effect on cell death may differ based on cell type, injury model, trigger, and the end points measured. For example, Rottner et al (65) observed that actinomycin D increased apoptosis in a mutant CFTR pancreatic ductal cell line and also in WT and mutant ductal cell lines pretreated with the CFTR inhibitor CFTR inh -172.…”

“…This concept remains controversial (33,35,65,75), possibly because the predominant mode of cell death is tissue dependent (74) and because the CFTR-dependent effect on cell death may differ based on cell type, injury model, trigger, and the end points measured. For example, Rottner et al (65) observed that actinomycin D increased apoptosis in a mutant CFTR pancreatic ductal cell line and also in WT and mutant ductal cell lines pretreated with the CFTR inhibitor CFTR inh -172. The effects of actinomycin D, however, are not likely generalizable; a variety of apoptosisinducing drugs (aphidicilin, pacitaxel, doxorubicin, puromycin, staurosporin) do not unmask a pro-or antiapoptotic phenotype in ⌬F508-CF respiratory epithelial cells (6).…”

“…It remains controversial whether CFTR mutations impair (2,6,15,27,31,37,38,50,83) or increase (33,35,65,75) cellular apoptosis in response to cell injury. That apoptosis execution machinery is impaired in models of CF is supported by in vivo studies (6,15), including ours in UNC-CF mice (15) and those performed by Cannon et al (6) in respiratory epithelial cells from ⌬F508-CF mice.…”

Development and Investigation of Dry Powder Inhalers for Cystic Fibrosis

“…As a consequence, NF-κB dimers can localize into the nucleus and positively regulate the transcription of proinflammatory genes (37). This pathway is overactivated also in absence of any infection (38)(39)(40) in CF cells. In our experiments, CuFi1 cells exhibit higher expression levels of IKK and phosphoIKB proteins compared to their normal counterpart NuLi1 cells (data from Western Blot analysis not shown).…”

Lack of Cystic Fibrosis Transmembrane Conductance Regulator in CD3+Lymphocytes Leads to Aberrant Cytokine Secretion and Hyperinflammatory Adaptive Immune Responses

“…The mechanisms by which CFTR mutations cause chronic lung disease in CF are not fully defined, but may include the combined effects of altered ion and water transport across the airway epithelium (5-7), increased binding or decreased clearance of P. aeruginosa (8,9), as well as increased proinflammatory cytokine production in the CF airway (10)(11)(12)(13)(14). CF cell lines demonstrate increased NF-kB activation and increased IL-8 secretion in response to P. aeruginosa exposure as compared with control cells (14,15). Furthermore, CFTR mutant mice demonstrate a greater cytokine response (keratinocyte chemoattractant [KC], macrophage inflammatory protein-2 [MIP2], IL-1b), greater mortality, and greater weight loss after airway challenge with a P. aeruginosa-agarose bead slurry as compared with control mice (16)(17)(18)(19).…”