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9. Type 1 pseudohypoaldosteronism: Lung symptoms resembling cystic fibrosis are associated with deficiency of the α-subunit of the epithelial sodium channel
Supplement / The Netherlands Journal of Medicine 54 (1999) S3 –S84 induced negative I sc gradually reversed to a positive response when the tissues were incubated with indomethacin. In the presence of indomethacin CCH activated a luminal K 1 conductance in non-CF and CF rectal biopsies that was blocked by luminal Ba 21 . Interestingly, in 16 out of 41 CF tissues, we observed a CFTR-mediated residual Cl 2 secretion in the range of 2–3% of the maximum Cl 2 conductance in non-CF. We conclude that using proper experimental conditions, this method can be used for functional in vitro diagnosis of cystic fibrosis and may even allow for detection of very little residual Cl 2 conductance caused by mutant CFTR. Supported by DFG KU1228 / 1-1 and ZKF 1 Freiburg.
S25
current in rectal biopsies after stimulation with carbachol (10 24 M) and classified according to Veeze 1994. Residual chloride secretion (Type I to III)
I no
II low
III high
High risk patients (n 5 14) (Mean6SE) DI SC net mA/cm 2 Low risk patients (n 5 10) (Mean6SE) DI SC net mA/cm 2
2/14* 2 6.99 7/10* 2 10.97
6/14 2 1.92 1/10 2 3.01
6/14 3.66 2/10 6.81
* P , 005 (high vs low risk group).
Within DF508 homozygous patients residual chloride secretion is not related to a reduced risk of early PSA colonization. 7. CFTR-mediated inhibition of epithelial sodium conductance in human colon is defective in cystic fibrosis. M. Mall 1 , M. 2 ¨ 1 , M. Brandis 1 , R. Greger 2 , K. Kunzelmann 2 . Bleich , J. Kuhr 1 Children’ s Hospital and 2 Institute of Physiology, Albert-LudwigsUniversity Freiburg, Germany. 1 In cystic fibrosis (CF) airways, Na conductance is typically enhanced besides the defect in cAMP-dependent Cl 2 conductance. We previously demonstrated that the amiloride sensitive epithelial Na 1 channel (ENaC) is downregulated by CFTR and that this regulatory function is lost in CF airways. In the present study we examined this regulatory mechanism in human colon by measuring short circuit current (I sc ) in rectal biopsies from non-CF (n 5 68) and CF patients (n 5 25) in a modified Ussing chamber. Inhibition of I sc by amiloride was significantly increased in CF compared to non-CF tissues. When endogenous cAMP-synthesis was inhibited by indomethacin, the amiloride sensitive I sc was significantly increased in non-CF but not in CF. CFTR-activation with IBMX and forskolin induced Cl 2 secretion in non-CF. Under these conditions, the amiloride sensitive I sc was significantly inhibited. In CF, cAMP-mediated Cl 2 conductance was defective and amiloride sensitive Na 1 conductance was not altered by cAMP-activation. We conclude that CFTR acts as a down-regulator of ENaC in human distal colon. The loss of CFTR-mediated inhibition of ENaC in CF colon could lead to hyperabsorption, increased mucus viscosity and meconius ileus. Supported by DFG KU1228 / 1-1 and ZKF 1 Freiburg.
8. Correlation between residual chlorid secretion and the risk of early chronical Pseudomonas aeruginosa infection in DF508 homozygosity. N. Derichs, M. Ballmann, H. von der Hardt. Medical School Hannover, Paed. Dept., Hannover, Germany. In CF with mild mutations (A445E) more often residual chlorid secretion was observed than in more severe mutations (DF508). To investigate whether this difference in the clinical phenotype is related to residual chloride secretion we compared within the same genotype chlorid secretion and risk of early chronic Pseudomonas aeruginosa (PSA) infection as a parameter of clinical phenotype. In the low-risk group (n 5 10) patients were at least free of PSA till the age of 13 years and in the high-risk group (n 5 14) patients were chronic PSA colonised before the age of 7 years. Residual chloride secretion was calculated by measuring short circuit
9. Type 1 pseudohypoaldosteronism: Lung symptoms resembling cystic fibrosis are associated with deficiency of the asubunit of the epithelial sodium channel. C. Schaedel, L. ¨ B. Orlenius, L. Marthinsen, A.-C. Kristoffersson, R. Kornfalt, ¨ Holmberg. Department of Paediatrics in Lund, Malmo¨ , Linkoping and Halmstad, Sweden. Objective: To study four Swedish patients with autosomal recessive type 1 pseudohypoaldosteronism (PHA1) with focus on pulmonary pathology which has been claimed to mimic cystic fibrosis; to relate the clinical picture to gene mutations in the epithelial sodium channel (ENaC). Methods: The genes for ENaC and CFTR were scrutinized for gene mutations with methods including DNA sequencing. Results: Three novel mutations were found in the a gene of ENaC, two frame-shifts (1449delC and 729delA) and a missense mutation (S562L). The 1449delC mutation was found in all patients in either homo- or heterozygous form and seems to be the predominant cause of PHA1 in Sweden. The allele coding for S562L also contained a rare polymorphism, W493R. All patients had lung symptoms to various degrees. The bacterial findings were similar to those in cystic fibrosis but development of chronic lung disease and progressive decline in lung function were not observed. Conclusions: Deficiencies of the a-subunit of the ENaC are associated with prominent lung symptoms which are, however, clearly different from those in cystic fibrosis.
10. Nitric oxide donors, cGMP, genistein and quercetin do not 1 ¨ affect human nasal epithelium. C. Ruckes-Nilges , H. Lin1 2 1,2 1 demann , W. Van Driessche , W.-M. Weber . CF Working Group Giessen, Wartweg 95, D-35392 Giessen, Germany, 2 Laboratory for Physiology, K.U. Leuven, Campus Gasthuisberg, B-3000 Leuven, Belgium. Nitric oxide (NO) is a potent activator of guanylate cyclase and mediates its effects by production of cGMP. Since the NO donors sodium nitroprusside (SNP) and spermine NONOate (SNO) had only minor effects on transepithelial current (I sc ), conductance (G t ) and capacitance (C t ) of primary cultured human nasal epithelium, we tested directly the effects of cGMP (8-Br-cGMP, 100 mM). Basolateral application of cGMP led to slight inhibition
S25
current in rectal biopsies after stimulation with carbachol (10 24 M) and classified according to Veeze 1994. Residual chloride secretion (Type I to III)
I no
II low
III high
High risk patients (n 5 14) (Mean6SE) DI SC net mA/cm 2 Low risk patients (n 5 10) (Mean6SE) DI SC net mA/cm 2
2/14* 2 6.99 7/10* 2 10.97
6/14 2 1.92 1/10 2 3.01
6/14 3.66 2/10 6.81
* P , 005 (high vs low risk group).
Within DF508 homozygous patients residual chloride secretion is not related to a reduced risk of early PSA colonization. 7. CFTR-mediated inhibition of epithelial sodium conductance in human colon is defective in cystic fibrosis. M. Mall 1 , M. 2 ¨ 1 , M. Brandis 1 , R. Greger 2 , K. Kunzelmann 2 . Bleich , J. Kuhr 1 Children’ s Hospital and 2 Institute of Physiology, Albert-LudwigsUniversity Freiburg, Germany. 1 In cystic fibrosis (CF) airways, Na conductance is typically enhanced besides the defect in cAMP-dependent Cl 2 conductance. We previously demonstrated that the amiloride sensitive epithelial Na 1 channel (ENaC) is downregulated by CFTR and that this regulatory function is lost in CF airways. In the present study we examined this regulatory mechanism in human colon by measuring short circuit current (I sc ) in rectal biopsies from non-CF (n 5 68) and CF patients (n 5 25) in a modified Ussing chamber. Inhibition of I sc by amiloride was significantly increased in CF compared to non-CF tissues. When endogenous cAMP-synthesis was inhibited by indomethacin, the amiloride sensitive I sc was significantly increased in non-CF but not in CF. CFTR-activation with IBMX and forskolin induced Cl 2 secretion in non-CF. Under these conditions, the amiloride sensitive I sc was significantly inhibited. In CF, cAMP-mediated Cl 2 conductance was defective and amiloride sensitive Na 1 conductance was not altered by cAMP-activation. We conclude that CFTR acts as a down-regulator of ENaC in human distal colon. The loss of CFTR-mediated inhibition of ENaC in CF colon could lead to hyperabsorption, increased mucus viscosity and meconius ileus. Supported by DFG KU1228 / 1-1 and ZKF 1 Freiburg.
8. Correlation between residual chlorid secretion and the risk of early chronical Pseudomonas aeruginosa infection in DF508 homozygosity. N. Derichs, M. Ballmann, H. von der Hardt. Medical School Hannover, Paed. Dept., Hannover, Germany. In CF with mild mutations (A445E) more often residual chlorid secretion was observed than in more severe mutations (DF508). To investigate whether this difference in the clinical phenotype is related to residual chloride secretion we compared within the same genotype chlorid secretion and risk of early chronic Pseudomonas aeruginosa (PSA) infection as a parameter of clinical phenotype. In the low-risk group (n 5 10) patients were at least free of PSA till the age of 13 years and in the high-risk group (n 5 14) patients were chronic PSA colonised before the age of 7 years. Residual chloride secretion was calculated by measuring short circuit
9. Type 1 pseudohypoaldosteronism: Lung symptoms resembling cystic fibrosis are associated with deficiency of the asubunit of the epithelial sodium channel. C. Schaedel, L. ¨ B. Orlenius, L. Marthinsen, A.-C. Kristoffersson, R. Kornfalt, ¨ Holmberg. Department of Paediatrics in Lund, Malmo¨ , Linkoping and Halmstad, Sweden. Objective: To study four Swedish patients with autosomal recessive type 1 pseudohypoaldosteronism (PHA1) with focus on pulmonary pathology which has been claimed to mimic cystic fibrosis; to relate the clinical picture to gene mutations in the epithelial sodium channel (ENaC). Methods: The genes for ENaC and CFTR were scrutinized for gene mutations with methods including DNA sequencing. Results: Three novel mutations were found in the a gene of ENaC, two frame-shifts (1449delC and 729delA) and a missense mutation (S562L). The 1449delC mutation was found in all patients in either homo- or heterozygous form and seems to be the predominant cause of PHA1 in Sweden. The allele coding for S562L also contained a rare polymorphism, W493R. All patients had lung symptoms to various degrees. The bacterial findings were similar to those in cystic fibrosis but development of chronic lung disease and progressive decline in lung function were not observed. Conclusions: Deficiencies of the a-subunit of the ENaC are associated with prominent lung symptoms which are, however, clearly different from those in cystic fibrosis.
10. Nitric oxide donors, cGMP, genistein and quercetin do not 1 ¨ affect human nasal epithelium. C. Ruckes-Nilges , H. Lin1 2 1,2 1 demann , W. Van Driessche , W.-M. Weber . CF Working Group Giessen, Wartweg 95, D-35392 Giessen, Germany, 2 Laboratory for Physiology, K.U. Leuven, Campus Gasthuisberg, B-3000 Leuven, Belgium. Nitric oxide (NO) is a potent activator of guanylate cyclase and mediates its effects by production of cGMP. Since the NO donors sodium nitroprusside (SNP) and spermine NONOate (SNO) had only minor effects on transepithelial current (I sc ), conductance (G t ) and capacitance (C t ) of primary cultured human nasal epithelium, we tested directly the effects of cGMP (8-Br-cGMP, 100 mM). Basolateral application of cGMP led to slight inhibition