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Wine JJ, Char JE, Chen J, Cho HJ, Dunn C, Frisbee E, Joo NS, Milla C, Modlin SE, Park IH, Thomas EAC, Tran KV, Verma R, Wolfe MH. In vivo readout of CFTR function: ratiometric measurement of CFTR-dependent secretion by individual, identifiable human sweat glands. PLoS One 2013; 8:e77114. [PMID: 24204751 PMCID: PMC3811985 DOI: 10.1371/journal.pone.0077114] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 08/29/2013] [Indexed: 12/14/2022] Open
Abstract
To assess CFTR function in vivo, we developed a bioassay that monitors and compares CFTR-dependent and CFTR-independent sweat secretion in parallel for multiple (~50) individual, identified glands in each subject. Sweating was stimulated by intradermally injected agonists and quantified by optically measuring spherical sweat bubbles in an oil-layer that contained dispersed, water soluble dye particles that partitioned into the sweat bubbles, making them highly visible. CFTR-independent secretion (M-sweat) was stimulated with methacholine, which binds to muscarinic receptors and elevates cytosolic calcium. CFTR-dependent secretion (C-sweat) was stimulated with a β-adrenergic cocktail that elevates cytosolic cAMP while blocking muscarinic receptors. A C-sweat/M-sweat ratio was determined on a gland-by-gland basis to compensate for differences unrelated to CFTR function, such as gland size. The average ratio provides an approximately linear readout of CFTR function: the heterozygote ratio is ~0.5 the control ratio and for CF subjects the ratio is zero. During assay development, we measured C/M ratios in 6 healthy controls, 4 CF heterozygotes, 18 CF subjects and 4 subjects with 'CFTR-related' conditions. The assay discriminated all groups clearly. It also revealed consistent differences in the C/M ratio among subjects within groups. We hypothesize that these differences reflect, at least in part, levels of CFTR expression, which are known to vary widely. When C-sweat rates become very low the C/M ratio also tended to decrease; we hypothesize that this nonlinearity reflects ductal fluid absorption. We also discovered that M-sweating potentiates the subsequent C-sweat response. We then used potentiation as a surrogate for drugs that can increase CFTR-dependent secretion. This bioassay provides an additional method for assessing CFTR function in vivo, and is well suited for within-subject tests of systemic, CFTR-directed therapeutics.
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Affiliation(s)
- Jeffrey J. Wine
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California, United States of America
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, United States of America
- Department of Psychology, Stanford University, Stanford, California, United States of America
| | - Jessica E. Char
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California, United States of America
| | - Jonathan Chen
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California, United States of America
| | - Hyung-ju Cho
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California, United States of America
| | - Colleen Dunn
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Eric Frisbee
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California, United States of America
| | - Nam Soo Joo
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California, United States of America
| | - Carlos Milla
- Department of Pediatrics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Sara E. Modlin
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California, United States of America
| | - Il-Ho Park
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California, United States of America
| | - Ewart A. C. Thomas
- Department of Psychology, Stanford University, Stanford, California, United States of America
| | - Kim V. Tran
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California, United States of America
| | - Rohan Verma
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California, United States of America
| | - Marlene H. Wolfe
- Cystic Fibrosis Research Laboratory, Stanford University, Stanford, California, United States of America
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Abstract
Cystic fibrosis transmembrane conductance regulator-related disorders encompass a disease spectrum from focal male reproductive tract involvement in congenital absence of the vas deferens to multiorgan involvement in classic cystic fibrosis. The reproductive, gastrointestinal, and exocrine manifestations of cystic fibrosis transmembrane conductance regulator deficiency are correlated with CFTR genotype, whereas the respiratory manifestations that are the main cause of morbidity and mortality in cystic fibrosis are less predictable. Molecular genetic testing of CFTR has led to new diagnostic strategies and will enable targeting of molecular therapies now in development. Older diagnostic methods that measure sweat chloride and nasal potential difference nonetheless remain important because of their sensitivity and specificity. In addition, the measurement of immunoreactive trypsinogen and the genotyping of CFTR alleles are key to newborn screening programs because of low cost. The multiorgan nature of cystic fibrosis leads to a heavy burden of care, thus therapeutic regimens are tailored to the specific manifestations present in each patient. The variability of cystic fibrosis lung disease and the variable expressivity of mild CFTR alleles complicate genetic counseling for this autosomal recessive disorder. Widespread implementation of newborn screening programs among populations with significant cystic fibrosis mutation carrier frequencies is expected to result in increasing demands on genetic counseling resources.
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da Costa MZG, Guarita DR, Ono-Nita SK, Nogueira JDA, Nita ME, Paranaguá-Vezozzo DC, de Souza MT, do Carmo EP, Teixeira ACDS, Carrilho FJ. CFTR polymorphisms in patients with alcoholic chronic pancreatitis. Pancreatology 2008; 9:173-81. [PMID: 19077469 DOI: 10.1159/000178889] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Accepted: 07/01/2008] [Indexed: 12/11/2022]
Abstract
INTRODUCTION Pancreas susceptibility to alcohol is variable and only 5-10% of chronic alcohol abusers develop chronic pancreatitis; the role of genetic factors in this process is unknown. The CFTR gene encodes a protein that acts on epithelial cells and plays a key role in normal exocrine pancreatic function. METHODS This study investigated the frequency of polymorphisms in intron 8 of the CFTR gene in patients with alcoholic chronic pancreatitis. Three groups of patients were studied: group A - 68 adult alcoholics with a diagnosis of chronic pancreatitis; group B - 68 adult alcoholics without pancreatic disease or liver cirrhosis and group C - 104 healthy nonalcoholic adults. RESULTS T5/T7 genotype was more frequent in group A (11.8%) than in group B (2.9%) (p = 0.0481), and there was no statistical difference when groups A and C (5.8%) were compared (p = 0.1317). The haplotype combination (TG)10-T7/(TG)11-T7 was more frequent in groups B (23.5%) and C (20.2%) than in group A (7.3%) (p = 0.0080 and 0.0162). CONCLUSION There are differences when these three groups are compared and individuals with T5/T7 genotype might have a greater risk of developing chronic pancreatitis when they become chronic alcoholics.
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