Ultrastructural lesions in the small bowel of patients with cystic fibrosis

Alginate/Chitosan Particle-Based Drug Delivery Systems for Pulmonary Applications

Cystic fibrosis (CF) is a complex, potentially life-threatening disease that is most effectively treated through the administration of antibiotics (e.g., colistimethate sodium). Chronic infection with Pseudomonas aeruginosa is one of the most significant events in the pathogenesis of cystic fibrosis, and tobramycin is the treatment of choice for those patients with chronic P. aeruginosa infection who are deteriorating despite regular administration of colistimethate sodium. Effective treatment can be challenging due to the accumulation of thickened mucus in the pulmonary environment, and here we describe the results of our investigation into the development of alginate/chitosan particles prepared via precipitation for such environments. Tobramycin loading and release from the alginate/chitosan particles was investigated, with evidence of both uptake and release of sufficient tobramycin to inhibit P. aeruginosa in vitro. Functionalisation of the alginate/chitosan particles with secretory leukocyte protease inhibitor (SLPI) was shown to help inhibit the inflammatory response associated with lung infections (via inhibition of neutrophil elastase activity) and enhance their interaction with cystic fibrosis mucus (assayed via reduction of the depth of particle penetration into the mucus) in vitro, which have prospects to enhance their efficacy in vivo.

Pancreatic-like enzymes of microbial origin restore growth and normalize lipid absorption in a pig model with exocrine pancreatic insufficiency

INTRODUCTION

The standard therapy for exocrine pancreatic insufficiency (EPI) is porcine-derived pancreatic enzyme replacement therapy (PERT). In the present study we tested a new approach with a mixture of pancreatic-like enzymes of microbial origin (PLEM) in a 1-week efficacy study in EPI pigs. In addition to the conventionally used coefficient of fat and nitrogen absorption (CFA and CNA), parameters that more accurately reflect the nutritional and health status, such as changes in the lipemic index (LI), plasma triglyceride (TG) and non-esterified fatty acid (NEFA) levels, and somatic growth, were determined.

MATERIAL AND METHODS

A PLEM dose containing 120 000 active lipase units, 80 000 active protease units and 12 000 active amylase units (all from Sigma, St. Louis, MO) was given as a powder, twice daily with a meal (40 g fat/meal) to 8 EPI pigs for 7 days. Ten healthy pigs were used as a comparator.

RESULTS

The PLEM enhanced fat and protein digestion, and reversed growth impairment in EPI pigs. With treatment, CFA and CNA increased by 59% and 43% (p < 0.05), respectively. Although fat and protein absorption were lower than in the comparator, the postprandial blood lipid profile was normal as in healthy pigs. The mucosal thickness significantly increased by 27%, 50% and 26%, in the proximal, middle, and distal jejunum (p < 0.05) with treatment and resembled that of healthy animals.

CONCLUSIONS

Pancreatic-like enzymes of microbial origin supported somatic growth and normalized the postprandial lipid profile. As a measure of efficacy, postprandial LI, TG and NEFA are viable endpoints to be explored in human trials.

Targeted CFTR gene disruption with zinc-finger nucleases in human intestinal epithelial cells induces oxidative stress and inflammation

Cystic fibrosis (CF) is a multisystemic pathology caused by mutations of the CF transmembrane conductance regulator (CFTR) gene.

OBJECTIVES

As the intestine harbors the greatest number of CFTR transcripts after birth and since CFTR plays a role in glutathione transport, we hypothesized that CFTR deletion might produce oxidative stress (OxS) and inflammation in CF intestinal epithelial cell.

METHODS

CFTR gene was abrogated in Caco-2/15 enterocytes through the zinc-finger nuclease system. Their oxidative and inflammatory characteristics were appreciated under basal conditions and after the treatment with the pro-oxidant iron-ascorbate (Fe/Asc) complex and pro-inflammatory lipopolysaccharide (LPS).

RESULTS

Intestinal epithelial cells with CFTR knockout spontaneously exhibited an increased lipid peroxidation level, reflected by malondialdehyde overproduction and reduced antioxidant defense characterized by low enzymatic activities of glutathione peroxidase and catalase. CFTR silencing also resulted in elevated protein expression of pro-inflammatory tumor necrosis Factor-α, interleukin-6, cyclooxygenase-2, and the transcription factor nuclear factor-κB. Moreover, exaggerated OxS and inflammation processes occurred in CFTR(-/-) cells in response to the addition of Fe/Asc and LPS, respectively.

CONCLUSIONS

Intestinal Caco-2/15 cells with CFTR deletion, display innate oxidative and inflammatory features while being more sensitive to pro-oxidant and pro-inflammatory stimuli. These two pathophysiological processes could be implicated in CF-related intestinal disorders.

Evidence for a Cystic Fibrosis Enteropathy

Background

Previous studies have suggested the existence of enteropathy in cystic fibrosis (CF), which may contribute to intestinal function impairment, a poor nutritional status and decline in lung function. This study evaluated enterocyte damage and intestinal inflammation in CF and studied its associations with nutritional status, CF-related morbidities such as impaired lung function and diabetes, and medication use.

Methods

Sixty-eight CF patients and 107 controls were studied. Levels of serum intestinal-fatty acid binding protein (I-FABP), a specific marker for enterocyte damage, were retrospectively determined. The faecal intestinal inflammation marker calprotectin was prospectively studied. Nutritional status, lung function (FEV1), exocrine pancreatic insufficiency (EPI), CF-related diabetes (CFRD) and use of proton pump inhibitors (PPI) were obtained from the medical charts.

Results

Serum I-FABP levels were elevated in CF patients as compared with controls (p<0.001), and correlated negatively with FEV1 predicted value in children (r-.734, p<0.05). Faecal calprotectin level was elevated in 93% of CF patients, and correlated negatively with FEV1 predicted value in adults (r-.484, p<0.05). No correlation was found between calprotectin levels in faeces and sputum. Faecal calprotectin level was significantly associated with the presence of CFRD, EPI, and PPI use.

Conclusion

This study demonstrated enterocyte damage and intestinal inflammation in CF patients, and provides evidence for an inverse correlation between enteropathy and lung function. The presented associations of enteropathy with important CF-related morbidities further emphasize the clinical relevance.

Defective goblet cell exocytosis contributes to murine cystic fibrosis-associated intestinal disease

Cystic fibrosis (CF) intestinal disease is associated with the pathological manifestation mucoviscidosis, which is the secretion of tenacious, viscid mucus that plugs ducts and glands of epithelial-lined organs. Goblet cells are the principal cell type involved in exocytosis of mucin granules; however, little is known about the exocytotic process of goblet cells in the CF intestine. Using intestinal organoids from a CF mouse model, we determined that CF goblet cells have altered exocytotic dynamics, which involved intrathecal granule swelling that was abruptly followed by incomplete release of partially decondensated mucus. Some CF goblet cells exhibited an ectopic granule location and distorted cellular morphology, a phenotype that is consistent with retrograde intracellular granule movement during exocytosis. Increasing the luminal concentration of bicarbonate, which mimics CF transmembrane conductance regulator-mediated anion secretion, increased spontaneous degranulation in WT goblet cells and improved exocytotic dynamics in CF goblet cells; however, there was still an apparent incoordination between granule decondensation and exocytosis in the CF goblet cells. Compared with those within WT goblet cells, mucin granules within CF goblet cells had an alkaline pH, which may adversely affect the polyionic composition of the mucins. Together, these findings indicate that goblet cell dysfunction is an epithelial-autonomous defect in the CF intestine that likely contributes to the pathology of mucoviscidosis and the intestinal manifestations of obstruction and inflammation.

Intestinal smooth muscle dysfunction develops postnatally in cystic fibrosis mice

OBJECTIVES

Intestinal dysmotility is one of the effects of cystic fibrosis (CF), but when and how this develops is not well understood. The goal of the present study was to use the Cftr knockout mouse to determine when in development circular smooth muscle of the small intestine becomes dysfunctional.

METHODS

Wild-type (WT) and CF mice were used at postnatal day 5 (P5) through adult. Pieces of small intestine were used to measure contractile activity of the circular muscle. Bacterial overgrowth was measured by quantitative polymerase chain reaction (PCR) of the bacterial 16S gene. Intestinal gene expression was determined by quantitative reverse transcription polymerase chain reaction (RT-PCR). Prostaglandin E2 (PGE2) and its metabolites were measured by enzyme immunoassay.

RESULTS

CF circular muscle response to cholinergic stimulation was similar to WT at P5, became somewhat impaired at P7, and was severely impaired by P14. In the CF intestine, bacterial overgrowth occurred by P4 and was maintained into adulthood. Eicosanoid metabolic gene expression in the CF intestine did not differ from WT shortly after birth. The phospholipase A2 genes, Pla2g4c and Pla2g5 exhibited increased expression in CF mice at P24. Prostaglandin degradative genes, Hpgd and Ptgr1, showed lower expression in CF as compared with WT at P16 and P24, respectively. PGE2 levels were significantly greater in CF mice at most ages from P7 through adulthood.

CONCLUSIONS

The results clearly demonstrate that lack of CFTR itself does not cause smooth muscle dysfunction, because the circular muscle from P5 CF mice had normal activity and dysfunction developed between P7 and P14.

Persistent fat malabsorption in cystic fibrosis; lessons from patients and mice

Fat malabsorption in pancreatic insufficient cystic fibrosis (CF) patients is classically treated with pancreatic enzyme replacement therapy (PERT). Despite PERT, intestinal fat absorption remains insufficient in most CF patients. Several factors have been suggested to contribute to the persistent fat malabsorption in CF (CFPFM). We reviewed the current insights concerning the proposed causes of CFPFM and the corresponding intervention studies. Most data are obtained from studies in CF patients and CF mice. Based on the reviewed literature, we conclude that alterations in intestinal pH and intestinal mucosal abnormalities are most likely to contribute to CFPFM. The presently available data indicate that acid suppressive drugs and broad spectrum antibiotics could be helpful in individual CF patients for optimizing fat absorption and/or nutritional status.

Investigation of adipose tissues in Zucker rats using in vivo and ex vivo magnetic resonance spectroscopy

In vivo single-voxel magnetic resonance spectroscopy (MRS) at 4.7T and ex vivo high-resolution proton magnetic resonance spectroscopy (HR-NMR) at 500 MHz were used to study the composition of adipose tissues in Zucker obese and Zucker lean rats. Lipid composition was characterized by unsaturation and polyunsaturation indexes and mean chain lengths. In vitro experiments were conducted in known mixtures of triglycerides and oils in order to validate the method. To avoid inaccuracies due to partial peak overlapping in MRS, peak quantification was performed after fitting of spectral peaks by using the QUEST algorithm. The intensity of different spectral lines was also corrected for T2 relaxation. Albeit with different sensitivity and accuracy, both techniques revealed that white adipose tissue is characterized by lower unsaturation and polyunsaturation indexes in obese rats compared with controls. HR-NMR revealed similar differences in brown adipose tissue. The present findings confirm the hypothesis that obese and lean Zucker rats have different adipose tissue composition.

CFTR knockdown stimulates lipid synthesis and transport in intestinal Caco-2/15 cells

Cystic fibrosis transmembrane conductance regulator (CFTR) is a chloride channel highly expressed in epithelial cells of the gastrointestinal tract. Mutations in the CFTR gene cause cystic fibrosis (CF), a disease characterized by pancreatic insufficiency, fat malabsorption, and steatorrhea. Despite the administration of pancreatic enzymes to normalize malabsorption, CF patients still experienced lipid fecal loss, nutritional deficiencies, and abnormalities in serum lipid profile, suggesting the presence of intrinsic defects in the intestinal handling of nutrients. The objective of the present study was to assess the impact of CFTR gene knockdown on intracellular lipid metabolism of the intestinal Caco-2/15 cell line. Partial CFTR gene inactivation led to cellular lipid accretion of phospholipids, triglycerides, and cholesteryl esters. Likewise, secretion of these lipid fractions was significantly increased following CFTR gene manipulation. As expected from these findings, the output of triglyceride-rich lipoproteins showed the same increasing pattern. Investigation of the mechanisms underlying these changes revealed that CFTR knockdown resulted in raised levels of apolipoproteins in cells and media and microsomal transfer protein activity, two important factors for the efficient assembly and secretion of lipoproteins. Similarly, scrutiny of the enzymatic monoacylglycerol acyltransferase and diacylglycerol acyltransferase, which exhibit dynamic function in triacylglycerol resynthesis and chylomicron formation in enterocytes, revealed a significant augmentation in their activity. Conversely, cholesterol uptake mediated by Niemann-Pick C1 like 1, Scavenger Receptor Class B Type I, and ATP-binding cassette G8 remains unaffected by genetic modification of CFTR. Collectively, these results highlight the role played by CFTR in intestinal handling of lipids and may suggest that factors other than defective CFTR are responsible for the abnormal intracellular events leading to fat malabsorption in CF patients.

Altered eicosanoid metabolism in the cystic fibrosis mouse small intestine

OBJECTIVES

Imbalances in essential fatty acid levels have been reported in cystic fibrosis (CF), which may relate to elevated proinflammatory eicosanoid generation. The aim of this work was to better define eicosanoid metabolism in the CF intestine.

MATERIALS AND METHODS

We used the small intestine of the cystic fibrosis transmembrane conductance regulator knockout mouse (CF mouse) to measure eicosanoid metabolic gene expression by quantitative reverse transcription polymerase chain reaction and Western blot, and eicosanoid levels by enzyme immunoassay, as compared with wild-type (WT) littermates.

RESULTS

In the CF small intestine, expression of the secretory phospholipase A2 Pla2g5 mRNA was upregulated to 980% of WT levels. The following were downregulated: leukotriene C4 synthase Ltc4s (mRNA 55% of WT); omega-hydroxylase cytochrome P450s Cyp2c40 (mRNA 54% of WT), and Cyp4a10 (mRNA 4% of WT); and the major prostaglandin degradative enzymes prostaglandin dehydrogenase Hpgd (mRNA 27% of WT) and leukotriene B4 12-hydroxydehydrogenase/15-oxo-prostaglandin 13-reductase Ltb4dh (mRNA 64% and protein 30% of WT). The prostaglandins PGE2 and PGF2alpha were increased to 400% to 600% of WT levels in the CF mouse intestine, and the hydroxyeicosatetraenoic acids (HETEs) 12-, 15-, and 20-HETE were decreased to 3% to 20% of WT levels.

CONCLUSIONS

There are changes in eicosanoid metabolic gene expression that are accompanied by significant changes in specific eicosanoid levels. These changes are expected to play important roles in the pathophysiology of CF in the intestine.

Fat absorption in cystic fibrosis mice is impeded by defective lipolysis and post-lipolytic events

Cystic fibrosis (CF) is frequently associated with progressive loss of exocrine pancreas function, leading to incomplete digestion and absorption of dietary fat. Supplementing patients with pancreatic lipase reduces fat excretion, but it does not completely correct fat malabsorption, indicating that additional pathological processes affect lipolysis and/or uptake of lipolytic products. To delineate the role of such (post) lipolytic processes in CF-related fat malabsorption, we assessed fat absorption, lipolysis, and fatty acid uptake in two murine CF models by measuring fecal fat excretion and uptake of oleate- and triolein-derived lipid. Pancreatic and biliary function was investigated by determining lipase secretion and biliary bile salt (BS) secretion, respectively. A marked increase in fecal fat excretion was observed in cftr null mice but not in homozygous DeltaF508 mice. Fecal BS loss was enhanced in both CF models, but biliary BS secretion rates were similar. Uptake of free fatty acid was delayed in both CF models, but only in null mice was a specific reduction in lipolytic activity apparent, characterized by strongly reduced triglyceride absorption. Impaired lipolysis was not due to reduced pancreatic lipase secretion. Suppression of gastric acid secretion partially restored lipolytic activity and lipid uptake, indicating that incomplete neutralization of gastric acid impedes fat absorption. We conclude that fat malabsorption in cftr null mice is caused by impairment of lipolysis, which may result from aberrant duodenal pH regulation.

Endogenous fecal losses of calcium compromise calcium balance in pancreatic-insufficient girls with cystic fibrosis

OBJECTIVE

Bone mineral density is compromised in individuals with cystic fibrosis (CF); calcium is the major bone mineral. This study examined the impact of endogenous fecal calcium (V(endo)) losses on calcium balance in girls with CF. Study design V(endo) was measured in 12 girls with CF (aged 7-18 years): 7 younger, premenarcheal girls with compromised nutritional status; and 5 older, postmenarcheal girls with adequate nutritional status. V(endo) was measured as the amount of intravenously administered (42)Ca, a calcium stable isotope, in stool relative to urine over 6 days. V(endo) was compared between pre- and postmenarcheal girls by Student's t test. Actual calcium balance [absorbed calcium-(urinary calcium (V(u))+V(endo))] was compared with estimated balance (assuming V(endo)=1.6 mg/kg/day calcium) by paired t test.

RESULTS

V(endo) was 99.3+/-42.3 mg/day. By body weight, V(endo) was highest among premenarcheal girls (3.37+/-1.09 mg/kg/day), resulting in excess losses (>1.6 mg/kg/day) of 55.0+/-45.7 mg/day. Over 1 year, this represents 20.1+/-16.7 g of unattained bone calcium or 6.7+/-4.2% of the bone calcium content of these girls.

CONCLUSIONS

V(endo) is a significant source of calcium loss in individuals with CF and may limit calcium availability for bone mineral deposition.

Effects of therapy with lansoprazole on intestinal permeability and inflammation in young cystic fibrosis patients

BACKGROUND

Defective pancreatic bicarbonate secretion with low intestinal pH or intestinal inflammation of any origin increase intestinal permeability in cystic fibrosis (CF).

METHODS

In this open study, the authors evaluated the effect of a proton-pump inhibitor on intestinal permeability and inflammation in 14 young, pancreatic-insufficient CF patients. Permeability was measured by a three-sugar permeability test before and after 1 year of lansoprazole use, and urinary nitric oxide (NO) oxidation products were assessed before and during that year as a marker of inflammation.

RESULTS

After 1 year of lansoprazole use, median urinary recovery percentages changed from 2.5% to 1.7% (P = 0.064), from 24.9% to 24.5% (no significance), and from 10.5% to 11.1% (no significance) for lactulose, mannitol, and L-rhamnose, respectively. Despite the fact that the median urinary excretion ratios decreased from 0.108 to 0.083 (P = 0.03) and from 0.246 to 0.176 (P = 0.016) for lactulose and mannitol and for lactulose and rhamnose, respectively, they both remained increased. Median urinary NO products-to-creatinine ratios were 0.287 for CF patients before lansoprazole and 0.130 for healthy control participants (P = 0.002). Although there was a tendency toward a decrease in the NO products-to-creatinine ratio during treatment, this was not significant at the end point.

CONCLUSIONS

Intestinal permeability is considerably increased in CF patients and is partly corrected after the use of a proton-pump inhibitor for 1 year, which may point to a harmful effect of the acid luminal contents on the tight junctional related paracellular permeability pathway. The start and end values for the NO products-to-creatinine ratio in CF patients were not significantly different, but were considerably increased when compared with control participants (P = 0.002).

Physiological basis of cystic fibrosis: a historical perspective

Physiological Basis of Cystic Fibrosis: A Historical Perspective. Physiol. Rev. 79, Suppl.: S3-S22, 1999. - Cystic fibrosis made a relatively late entry into medical physiology, although references to conditions probably reflecting the disease can be traced back well into the Middle Ages. This review begins with the origins of recognition of the symptoms of this genetic disease and proceeds to briefly review the early period of basic research into its cause. It then presents the two apparently distinct faces of cystic fibrosis: 1) as that of a mucus abnormality and 2) as that of defects in electrolyte transport. It considers principal findings of the organ and cell pathophysiology as well as some of the apparent conflicts and enigmas still current in understanding the disease process. It is written from the perspective of the author, whose career spans back to much of the initial endeavors to explain this fatal mutation.