Cystic fibrosis: a multiple exocrinopathy caused by dysfunctions in a multifunctional transport protein

Sweat induction using Pilocarpine microneedle patches for sweat testing in healthy adults

BACKGROUND

The sweat test using pilocarpine iontophoresis remains the gold standard for diagnosing cystic fibrosis, but access and reliability are limited by specialized equipment and insufficient sweat volume collected from infants and young children. These shortcomings lead to delayed diagnosis, limited point-of-care applications, and inadequate monitoring capabilities.

METHODS

We created a skin patch with dissolvable microneedles (MNs) containing pilocarpine that eliminates the equipment and complexity of iontophoresis. Upon pressing the patch to skin, the MNs dissolve in skin to release pilocarpine for sweat induction. We conducted a non-randomized pilot trial among healthy adults (clinicaltrials.gov, NCT04732195) with pilocarpine and placebo MN patches on one forearm and iontophoresis on the other forearm, followed by sweat collection using Macroduct collectors. Sweat output and sweat chloride concentration were measured. Subjects were monitored for discomfort and skin erythema.

RESULTS

Fifty paired sweat tests were conducted in 16 male and 34 female healthy adults. MN patches delivered similar amounts of pilocarpine into skin (1.1 ± 0.4 mg) and induced equivalent sweat output (41.2 ± 25.0 mg) compared to iontophoresis (1.2 ± 0.7 mg and 43.8 ± 32.3 mg respectively). Subjects tolerated the procedure well, with little or no pain, and only mild transient erythema. Sweat chloride concentration measurements in sweat induced by MN patches (31.2 ± 13.4 mmol/L) were higher compared to iontophoresis (24.0 ± 13.2 mmol/L). Possible physiological, methodological, and artifactual causes of this difference are discussed.

CONCLUSIONS

Pilocarpine MN patches present a promising alternative to iontophoresis to enable increased access to sweat testing for in-clinic and point-of-care applications.

Pilot study of inflammatory biomarkers in matched induced sputum and bronchoalveolar lavage of 2-year-olds with cystic fibrosis

BACKGROUND

In this pilot study, we investigated whether induced sputum (IS) could serve as a viable alternative to bronchoalveolar lavage (BAL) and yield robust inflammatory biomarkers in toddlers with cystic fibrosis (CF) featuring minimal structural lung disease.

METHODS

We collected IS, BAL (right middle lobe and lingula), and blood, and performed chest computed tomography (CT) scans from 2-year-olds with CF (N = 11), all within a single visit. Inflammatory biomarkers included 20 soluble immune mediators and neutrophil elastase (NE), as well as frequency and phenotype of T cells, monocytes/macrophages, and neutrophils.

RESULTS

At the molecular level, nine mediators showed similar levels in IS and BAL (CXCL1, CXCL8, IL-1α, IL-1RA, IL-6, CCL2, CXCL10, M-CSF, VEGF-A), four were higher in IS than in BAL (CXCL5, IL-1β, CXCL11, TNFSF10), and two were present in IS, but undetectable in BAL (IL-10, IFN-γ). Meanwhile, soluble NE had lower activity in IS than in BAL. At the cellular level, T-cell frequency was lower in IS than in BAL. Monocytes/macrophages were dominant in IS and BAL with similar frequencies, but differing expression of CD16 (lower in IS), CD115, and surface-associated NE (higher in IS). Neutrophil frequency and phenotype did not differ between IS and BAL. Finally, neutrophil frequency in IS correlated positively with air trapping.

CONCLUSIONS

IS collected from 2-year-olds with CF yields biomarkers of early airway inflammation with good agreement with BAL, notably with regard to molecular and cellular outcomes related to neutrophils and monocytes/macrophages.

Protein moonlighting: a new factor in biology and medicine

The phenomenon of protein moonlighting was discovered in the 1980s and 1990s, and the current definition of what constitutes a moonlighting protein was provided at the end of the 1990s. Since this time, several hundred moonlighting proteins have been identified in all three domains of life, and the rate of discovery is accelerating as the importance of protein moonlighting in biology and medicine becomes apparent. The recent re-evaluation of the number of protein-coding genes in the human genome (approximately 19000) is one reason for believing that protein moonlighting may be a more general phenomenon than the current number of moonlighting proteins would suggest, and preliminary studies of the proportion of proteins that moonlight would concur with this hypothesis. Protein moonlighting could be one way of explaining the seemingly small number of proteins that are encoded in the human genome. It is emerging that moonlighting proteins can exhibit novel biological functions, thus extending the range of the human functional proteome. The several hundred moonlighting proteins so far discovered play important roles in many aspects of biology. For example, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), heat-shock protein 60 (Hsp60) and tRNA synthetases play a wide range of biological roles in eukaryotic cells, and a growing number of eukaryotic moonlighting proteins are recognized to play important roles in physiological processes such as sperm capacitation, implantation, immune regulation in pregnancy, blood coagulation, vascular regeneration and control of inflammation. The dark side of protein moonlighting finds a range of moonlighting proteins playing roles in various human diseases including cancer, cardiovascular disease, HIV and cystic fibrosis. However, some moonlighting proteins are being tested for their therapeutic potential, including immunoglobulin heavy-chain-binding protein (BiP), for rheumatoid arthritis, and Hsp90 for wound healing. In addition, it has emerged over the last 20 years that a large number of bacterial moonlighting proteins play important roles in bacteria–host interactions as virulence factors and are therefore potential therapeutic targets in bacterial infections. So as we progress in the 21st Century, it is likely that moonlighting proteins will be seen to play an increasingly important role in biology and medicine. It is hoped that some of the major unanswered questions, such as the mechanism of evolution of protein moonlighting, the structural biology of moonlighting proteins and their role in the systems biology of cellular systems can be addressed during this period.

Chloride transport

Chloride transport along the nephron is one of the key actions of the kidney that regulates extracellular volume and blood pressure. To maintain steady state, the kidney needs to reabsorb the vast majority of the filtered load of chloride. This is accomplished by the integrated function of sequential chloride transport activities along the nephron. The detailed mechanisms of transport in each segment generate unique patterns of interactions between chloride and numerous other individual components that are transported by the kidney. Consequently, chloride transport is inextricably intertwined with that of sodium, potassium, protons, calcium, and water. These interactions not only allow for exquisitely precise regulation but also determine the particular patterns in which the system can fail in disease states.

mCLCA3 does not contribute to calcium-activated chloride conductance in murine airways

Ca(2+)-activated Cl(-) channels (CaCCs) contribute to airway Cl(-) and fluid secretion, and were implicated in the modulation of disease severity and as a therapeutic target in cystic fibrosis (CF). Previous in vitro studies suggested that members of the CLCA gene family, including the murine mCLCA3, contribute to CaCCs. However, the role of mCLCA3 in ion transport in native airway epithelia has not been studied, to the best of our knowledge. In this study, we used mCLCA3-deficient mice and determined bioelectric properties in freshly excised tracheal tissue, airway morphology, and gene expression studies, to determine the role of mCLCA3 in airway ion transport and airway structure. Bioelectric measurements did not detect any differences in basal short-circuit current, amiloride-sensitive Na(+) absorption, cyclic adenosine monophosphate-dependent Cl(-) secretion, and activation of Ca(2+)-activated (uridine-5'-triphosphate-mediated) Cl(-) secretion in mCLCA3-deficient mice compared with wild-type mice. Moreover, no histological changes were observed in the respiratory tract or any other tissues of mCLCA3-deficient mice when compared with wild-type control mice. The intratracheal instillation of IL-13 produced an approximately 30-fold up-regulation of mCLCA3 transcripts without inducing CaCC activity in wild-type airways, and induced goblet-cell hyperplasia and mucin gene expression to similar levels in both genotypes. Further, multiple specific reverse-transcriptase quantitative PCR assays for other CaCC candidates, including mCLCA1, mCLCA2, mCLCA4, mCLCA5, mCLCA6, mCLCA7, mBEST1, mBEST2, mCLC4, mTTYH3, and mTMEM16A, failed to identify the differential expression of genes in the respiratory tract that may compensate for a lack of mCLCA3 function. Together, these findings argue against a role of mCLCA3 in CaCC-mediated Cl(-) secretion in murine respiratory epithelia.

Role of epithelial HCO3⁻ transport in mucin secretion: lessons from cystic fibrosis

The invitation to present the 2010 Hans Ussing lecture for the Epithelial Transport Group of the American Physiological Society offered me a unique, special, and very surprising opportunity to join in saluting a man whom I met only once, but whose work was the basis, not only for my career, but also for finding the molecular defect in the inherited disease cystic fibrosis (CF). In this context, I will venture to make the tribute with a new explanation of why a mutation in a single gene that codes for an anion channel can cause devastation of multiple epithelial systems with pathogenic mucus. In so doing, I hope to raise awareness of a new role for that peculiar anion around which so much physiology revolves, HCO(3)(-). I begin by introducing CF pathology as I question the name of the disease as well as the prevalent view of the basis of its pathology by considering: 1) mucus, 2) salt, and 3) HCO(3)(-). I then present recent data showing that HCO(3)(-) is required for normal mucus discharge, and I will close with conjecture as to how HCO(3)(-) may support mucus discharge and why the failure to transport this electrolyte is pathogenic in CF.

In vitro and in vivo functional characterization of gutless recombinant SV40-derived CFTR vectors

In cystic fibrosis (CF) respiratory failure caused by progressive airway obstruction and tissue damage is primarily a result of the aberrant inflammatory responses to lung infections with Pseudomonas aeruginosa. Despite considerable improvement in patient survival, conventional therapies are mainly supportive. Recent progress towards gene therapy for CF has been encouraging; however, several factors such as immune response and transduced cell turnover remain as potential limitations to CF gene therapy. As alternative gene therapy vectors for CF we examined the feasibility of using SV40-derived vectors (rSV40s) which may circumvent some of these obstacles. To accommodate the large CFTR cDNA, we removed not only SV40 Tag genes, but also all capsid genes. We therefore tested whether “gutless” rSV40s could be packaged and were able to express a functional human CFTR cDNA. Results from our in vitro analysis determined that rSV40-CFTR was able to successfully result in the expression of CFTR protein which localized to the plasma membrane and restored channel function to CFTR deficient cells. Similarly in vivo experiments delivering rSV40-CFTR to the lungs of Cftr−/− mice resulted in a reduction of the pathology associated with intra-tracheal pseudomona aeruginosa challenge. rSV40-CFTR treated mice had had less weight loss when compared to control treated mice as well as demonstrably reduced lung inflammation as evidence by histology and reduced inflammatory cytokines in the BAL. The reduction in inflammatory cytokine levels led to an evident decrease in neutrophil influx to the airways. These results indicate that further study of the application of rSV40-CFTR to CF gene therapy is warranted.

Differential expression of calcium-activated chloride channels (CLCA) gene family members in the small intestine of cystic fibrosis mouse models

Members of the family of calcium-activated chloride channels (CLCA) have been implicated as modulators of the phenotype in cystic fibrosis (CF). Here, the expression levels of the murine mCLCA1, mCLCA2, mCLCA3 and mCLCA4 were quantified by real-time RT-PCR in the small intestines of CF (cftr (tm1Cam), cftr (TgH(neoim)1Hgu)) and wild type C57BL/6, BALB/c, DBA/2 and NMRI mice. Markedly different expression levels of all four CLCA homologs were observed between the different wild type strains. Expression of mCLCA1 and mCLCA4 was similar in CF versus wild type. In contrast, mCLCA3 mRNA copy numbers were increased up to threefold in all CF models. Immunohistochemical detection of mCLCA3 and PAS reactions on consecutive tissue sections identified a similar increase in mCLCA3 expressing goblet cells, suggesting that elevated mRNA copy numbers of mCLCA3 are due to goblet cell hyperplasia rather than transcriptional regulatory events. Increased mCLCA2 mRNA copy numbers, however, were considered more likely to be due to transcriptional upregulation. Changes in mRNA copy numbers were not associated with altered cell kinetics as determined by immunohistochemistry using antibodies to phospho-histone 3 and activated caspase-3. The results suggest that both mCLCA2 and mCLCA3 may act as modifiers of the intestinal phenotype in CF.

Abnormalities in the pulmonary innate immune system in cystic fibrosis

Pulmonary infection is the dominant clinical feature of cystic fibrosis (CF), but the basis for this susceptibility remains incompletely understood. One hypothesis is that CF airway surface liquid (ASL) is abnormal and interferes with neutrophil function. To study this possibility, we developed an in vitro system in which we collected ASL from primary cultures of normal and CF airway epithelial cells. Microbial killing was less efficient when bacteria were incubated with neutrophils in the presence of ASL from CF epithelia compared with normal ASL. Antimicrobial functions of human neutrophils were assessed in ASL from CF and normal epithelia using a combination of quantitative bacterial culture, flow cytometry, and microfluorescence imaging. The results of these assays of neutrophil function were indistinguishable in CF and normal ASL. In contrast, the direct bactericidal activity of ASL to Escherichia coli and to clinical isolates of Staphylococcus aureus and Pseudomonas aeruginosa was substantially less in CF than in normal ASL, even when highly diluted in media of identical ionic strength. Together, these observations indicate that the antimicrobial properties of ASL in CF are compromised in a manner independent of ionic strength of the ASL, and that this effect is not mediated through a direct effect of the ASL on phagocyte function.

Responses of well-differentiated airway epithelial cell cultures from healthy donors and patients with cystic fibrosis to Burkholderia cenocepacia infection

Well-differentiated cultures established from airway epithelia of patients with cystic fibrosis (CF cultures) exhibited goblet cell hyperplasia, increased secretion of mucus, and higher basal levels of interleukin-8 than similarly cultured cells from healthy donors. Upon apical infection with low doses (10(4) to 10(5) CFU) of Burkholderia cenocepacia isolate BC7, the two cultures gave different responses. While normal cultures trapped the added bacteria in the mucus layer, killed and/or inhibited bacterial replication, and prevented bacterial invasion of the cells, CF cultures failed to kill and/or supported the growth of bacteria, leading to invasion of underlying epithelial cells, compromised transepithelial permeability, and cell damage. Depletion of the surface mucus layer prior to bacterial infection rendered the normal cultures susceptible to bacterial invasion, but the invading bacteria were mainly confined to vacuoles within the cells and appeared to be nonviable. In contrast, bacteria that invaded cells in CF cultures were found free in the cytoplasm surrounded by intermediate filaments and also between cells. Cultured CF airway epithelium was therefore more susceptible to infection than normal epithelium. This mimics CF tissue in vivo and illustrates differences in the way epithelia in CF patients and normal subjects handle bacterial infection. In addition, we found that the CF and normal cell cultures responded differently not only to isolate BC7 but also to isolates of other B. cepacia complex species. We therefore conclude that this cell culture model is suitable for investigation of B. cepacia complex pathogenesis in CF patients.

The CepIR quorum-sensing system contributes to the virulence of Burkholderia cenocepacia respiratory infections

The cepIR genes encode an N-acyl homoserine lactone (AHL)-dependent quorum-sensing system consisting of an AHL synthase that directs the synthesis of N-octanoyl-L-homoserine lactone (ohl) and n-hexanoyl-L-homoserine lactone and a transcriptional regulator. The virulence of cepIR mutants was examined in two animal models. Rats were infected with agar beads containing Burkholderia cenocepacia K56-2, K56-I2 (cepI : : Tp(r)) or K56-R2 (cepR : : Tn5-OT182). At 10 days post-infection, the extent of lung histopathological changes was significantly lower in lungs infected with K56-I2 or K56-R2 compared to the parent strain. Intranasal infections were performed in Cftr((-/-)) mice and their wild-type siblings. K56-2 was more virulent in both groups of mice. K56-I2 was the least virulent strain and was not invasive in the Cftr((-/-)) mice. OHL was readily detected in lung homogenates from Cftr((-/-)) mice infected with K56-2 but was only detected at levels slightly above background in a few mice infected with K56-I2. Lung homogenates from mice infected with K56-2 had significantly higher levels of the inflammatory mediators murine macrophage inflammatory protein-2, KC/N51, interleukin-1beta and interleukin-6 than those from K56-I2-infected animals. These studies indicate that a functional CepIR quorum-sensing system contributes to the severity of B. cenocepacia infections. A zinc metalloprotease gene (zmpA) was shown to be regulated by CepR and may be one of the factors that accounts for the difference in virulence between the cepI mutant and the parent strain.

Abnormal passive chloride absorption in cystic fibrosis jejunum functionally opposes the classic chloride secretory defect

Due to genetic defects in apical membrane chloride channels, the cystic fibrosis (CF) intestine does not secrete chloride normally. Depressed chloride secretion leaves CF intestinal absorptive processes unopposed, which results in net fluid hyperabsorption, dehydration of intestinal contents, and a propensity to inspissated intestinal obstruction. This theory is based primarily on in vitro studies of jejunal mucosa. To determine if CF patients actually hyperabsorb fluid in vivo, we measured electrolyte and water absorption during steady-state perfusion of the jejunum. As expected, chloride secretion was abnormally low in CF, but surprisingly, there was no net hyperabsorption of sodium or water during perfusion of a balanced electrolyte solution. This suggested that fluid absorption processes are reduced in CF jejunum, and further studies revealed that this was due to a marked depression of passive chloride absorption. Although Na+-glucose cotransport was normal in the CF jejunum, absence of passive chloride absorption completely blocked glucose-stimulated net sodium absorption and reduced glucose-stimulated water absorption 66%. This chloride absorptive abnormality acts in physiological opposition to the classic chloride secretory defect in the CF intestine. By increasing the fluidity of intraluminal contents, absence of passive chloride absorption may reduce the incidence and severity of intestinal disease in patients with CF.

CFTR gene mutations in Japanese individuals with congenital bilateral absence of the vas deferens

Congenital bilateral absence of the vas deferens (CBAVD) is a monosymptomatic disease confined to the male reproductive system with similarity to the phenotype of cystic fibrosis (CF), and mutations in the CFTR gene are highly prevalent in Caucasian CBAVD patients. While CF is very rare in Japan, CBAVD is not. Our previous study demonstrated high prevalence of the 5T allele in the CFTR gene in Japanese CBAVD patients. We analyzed whole exons of the CFTR gene in 19 CBAVD patients and 53 normal individuals using polymerase chain reaction amplification-single strand conformation polymorphism analysis and direct sequencing. Three missense mutations (W216X, G1349S, Q1352H) were found in seven CFTR alleles, and the 5T allele was positive in 11 of 38 CFTR patient alleles. Consequently, 47% of CFTR chromosomes in the patients were affected, and 11 individuals (58%) had at least one mutated CFTR allele. In contrast, three of 53 normal individuals (5.7%) had a missense mutation in one of the CFTR genes, but no 5T allele was detected (both P<0.0001). Mutations of the CFTR gene are closely associated with Japanese patients with CBAVD.

Different activation mechanisms of cystic fibrosis transmembrane conductance regulator expressed in Xenopus laevis oocytes

The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP sensitive Cl- channel that is defective in cystic fibrosis (CF). The most frequent mutation, namely deltaF508-CFTR, accounts for 66% of CF. Here we show that cAMP-activation of CFTR occurs via at least two distinct pathways: activation of CFTR molecules already present in the plasma membrane and protein kinase A (PKA)-mediated vesicular transport of new CFTR molecules to the plasma membrane and functional insertion into the membrane. We investigated the mechanisms that are responsible for these activation pathways using the Xenopus laevis oocytes expression system. We expressed CFTR and recorded continuously membrane current (Im), conductance (Gm) and capacitance (Cm), which is a direct measure of membrane surface area. Expression of CFTR alone did not change the plasma membrane surface area. However, activation of CFTR with cAMP increased Im, Gm and Cm while deltaF508-CFTR-expressing oocytes showed no response on cAMP. Inhibition of protein kinase A or buffering intracellular Ca2+ abolished the cAMP-induced increase in Cm while increases of Im and Gm were still present. ATP or the xanthine derivative 8-cyclopentyl-1,3-dipropylxanthine (CPX) did not further activate CFTR. Insertion of pre-formed CFTR into the plasma membrane could be prevented by compounds that interfere with intracellular transport mechanisms such as primaquine, brefeldin A, nocodazole. From these data we conclude that cAMP activates CFTR by at least two distinct pathways: activation of CFTR already present in the plasma membrane and exocytotic delivery of new CFTR molecules to the oocyte membrane and functional insertion into it.

Cystic fibrosis transmembrane regulator regulates uptake of sphingoid base phosphates and lysophosphatidic acid: modulation of cellular activity of sphingosine 1-phosphate

Sphingolipids have been implicated in the regulation of cell growth, differentiation, and programmed cell death. Sphingosine 1-phosphate (SPP) has recently emerged as an important lipid messenger and a ligand for the endothelial differentiation gene receptor family of proteins through which it mediates its biologic effects. Recent studies in Saccharomyces cerevisiae in our laboratory implicated the yeast oligomycin resistance gene (YOR1), a member of the ATP binding cassette family of proteins, in the transport of SPP. The cystic fibrosis transmembrane regulator is a unique member of the ATP binding cassette transporter family and has high homology with YOR1. We therefore set out to investigate if this member of the family can regulate SPP transport. We demonstrate that C127/cystic fibrosis transmembrane regulator (CFTR) cells, expressing wild type CFTR, exhibited significantly higher uptake of sphingosine 1-phosphate than either cells expressing a mutant CFTR C127/DeltaF508 or C127/mock-transfected cells. This effect was specific, dose-dependent, and competed off by dihydrosphingosine 1-phosphate and lysophosphatidic acid. There was no difference in uptake of sphingosine, C(16)-ceramide, sphingomyelin, lysophingomyelin, phosphatidylcholine, lysophosphatidylcholine, or phosphatidic acid among the different cell lines. Pretreatment with forskolin or isobutylmethylxanthine to stimulate cAMP did not affect the uptake in any of the cell lines. Moreover, we found that mitogen-activated protein kinase activation by SPP was less responsive in C127/CFTR as compared with C127/mock-transfected cells, suggesting that uptake of SPP by CFTR may divert it from interacting with its cell surface receptors and attenuate signaling functions. Taken together, these data implicate CFTR in uptake of SPP and the related phosphorylated lipids dihydrosphingosine 1-phosphate and lysophosphatidic acid. This uptake influences the availability of SPP to modulate biologic activity via endothelial differentiation gene receptors. These studies may have important implications to cystic fibrosis.

Enhanced susceptibility to pulmonary infection with Burkholderia cepacia in Cftr(-/-) mice

Progressive pulmonary infection is the dominant clinical feature of cystic fibrosis (CF), but the molecular basis for this susceptibility remains incompletely understood. To study this problem, we developed a model of chronic pneumonia by repeated instillation of a clinical isolate of Burkholderia cepacia (genomovar III, ET12 strain), an opportunistic gram-negative bacterium, from a case of CF into the lungs of Cftr (m1unc-/-) (Cftr(-/-)) and congenic Cftr(+/+) controls. Nine days after the last instillation, the CF transmembrane regulator knockout mice showed persistence of viable bacteria with chronic severe bronchopneumonia while wild-type mice remained healthy. The histopathological changes in the lungs of the susceptible Cftr(-/-) mice were characterized by infiltration of a mixed inflammatory-cell population into the peribronchiolar and perivascular spaces, Clara cell hyperplasia, mucus hypersecretion in airways, and exudation into alveolar airspaces by a mixed population of macrophages and neutrophils. An increased proportion of neutrophils was observed in bronchoalveolar lavage fluid from the Cftr(-/-) mice, which, despite an increased bacterial load, demonstrated minimal evidence of activation. Alveolar macrophages from Cftr(-/-) mice also demonstrated suboptimal activation. These observations suggest that the pulmonary host defenses are compromised in lungs from animals with CF, as manifested by increased susceptibility to bacterial infection and lung injury. This murine model of chronic pneumonia thus reflects, in part, the situation in human patients and may help elucidate the mechanisms leading to defective host defense in CF.

Dynamics of bacterial colonisation in the respiratory tract of patients with cystic fibrosis

Mutations in the human genome may result in altered phenotypes. The cystic fibrosis (CF) patient, for instance, suffers from an aberrant composition of the epithelial lining of the gastrointestinal and respiratory tract. In this particular case, a single point mutation in the cystic fibrosis conductance regulator (CFTR) gene results in major physiological changes resulting in ecological changes that generate a niche particularly attractive to a selected set of microbial pathogens. We here present a review on the dynamics of the bacterial populations inhabiting the CF lung. Studies focusing on Staphylococcus aureus, Haemophilus influenzae and Pseudomonas aeruginosa will be summarised and discussed, whereas the technology used for microbial characterisation will be shortly highlighted. Emphasis, however, will be on those studies that assessed the genetic diversity among clinical isolates that were obtained over prolonged periods of time, enabling the distinction between persistent colonisation versus frequent re-infection by the selected pathogens. Evolutionary adaptation of pathogens to the CF lung is a common theme in many of these studies.

Inflammation and infection in naive human cystic fibrosis airway grafts

Exacerbated inflammation is now recognized as an important component of cystic fibrosis (CF) airway disease. Whether inflammation is part of the basic defect in CF or a response to persistent infection remains controversial. We addressed this question using human fetal tracheal grafts in severe combined immunodeficient mice. This model yields histologically mature, and most importantly, naive CF and non-CF surrogate airways. Significant inflammatory imbalance was found in naive CF airway grafts, including a highly increased intraluminal interleukin 8 content (CF: 10.1 +/- 2.2 ng/ml; non-CF: 1.2 +/- 0.6 ng/ml; P < 0.05) and consistent accumulation of leukocytes in the subepithelial region (P < 0.001). CF airway grafts were not histologically affected until challenged with Pseudomonas aeruginosa, which provoked: (1) early (before 3 h) and massive leukocyte transepithelial migration, (2) intense epithelial exfoliation, and (3) rapid progression of bacteria toward the lamina propria. In non-CF grafts, these three sets of events were not observed before 6 h. Using a model of naive human airways, we thus demonstrate that before any infection, CF airways are in a proinflammatory state. After infection, the basal inflammatory imbalance contributes to exert severe damage to the mucosa, paving the way for bacterial colonization and subsequent steps of CF airway disease.

Mutations of the cystic fibrosis gene, but not cationic trypsinogen gene, are associated with recurrent or chronic idiopathic pancreatitis

OBJECTIVE

We investigated whether mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene and cationic trypsinogen gene are associated with recurrent acute, or chronic idiopathic pancreatitis.

METHODS

Twenty patients with idiopathic pancreatitis (11 women, nine men; mean age, 30 yr) were studied for the presence of a CFTR mutation by screening the genomic DNA for more than 30 mutations and variants in the CFTR gene. Selected mutations of the cationic trypsinogen gene were screened by Afl III restriction digestion or by a mutation-specific polymerase chain reaction (PCR). In each patient exons 1, 2, and 3 of the cationic trypsinogen gene were sequenced. Patients with a CFTR mutation underwent evaluation of further functional electrophysiological test (intestinal current measurement).

RESULTS

No mutation of the cationic trypsinogen gene was detected. A CFTR mutation was detected in 6/20 (30.0%) patients. Three patients (15.0%) had a cystic fibrosis (CF) mutation on one chromosome (deltaF508, I336K, Y1092X), which is known to cause phenotypical severe cystic fibrosis. One patient was heterozygous for the 5T allele. In addition, two possibly predisposing CFTR variants (R75Q, 1716G-->A) were detected on four patients, one of these being a compound heterozygous for the missense mutation I336K and R75Q. No other family member (maternal I336K; paternal R75Q; sister I1336K) developed pancreatitis. An intestinal current measurement in rectum samples of patients with a CFTR mutation revealed no CF-typical constellations.

CONCLUSIONS

CFTR mutations are associated with recurrent acute, or chronic idiopathic pancreatitis, whereas mutations of the cationic trypsinogen mutation do not appear to be a frequent pathogenetic factor.

Ion channels and the control of blood pressure

Ion channels exist in all cells and are enormously varied in structure, function and regulation. Some progress has been made in understanding the role that ion channels play in the control of blood pressure, but the discipline is still in its infancy. Ion channels provide many different targets for intervention in disorders of blood pressure and exciting advances have been made in this field. It is possible that new drugs, as well as antisense nucleotide technology or gene therapy directed towards ion channels, may form a new class of treatments for high and low blood pressure in the future.