Anja Tzschoppe

A mutation of the epithelial sodium channel associated with atypical cystic fibrosis increases channel open probability and reduces Na+ self inhibition

Increased activity of the epithelial sodium channel (ENaC) in the respiratory airways contributes to the pathophysiology of cystic fibrosis (CF), a genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. In some patients suffering from atypical CF a mutation can be identified in only one CFTR allele. We recently identified in this group of CF patients a heterozygous mutation (W493R) in the α‐subunit of ENaC. Here, we investigate the functional effects of this mutation by expressing wild‐type αβγENaC or mutant αW493RβγENaC in Xenopus oocytes. The αW493R mutation stimulated amiloride‐sensitive whole‐cell currents (ΔIami) by ∼4‐fold without altering the single‐channel conductance or surface expression of ENaC. As these data suggest that the open probability (Po) of the mutant channel is increased, we investigated the proteolytic activation of ENaC by chymotrypsin. Single‐channel recordings revealed that chymotrypsin activated near‐silent channels in outside‐out membrane patches from oocytes expressing wild‐type ENaC, but not in membrane patches from oocytes expressing the mutant channel. In addition, the αW493R mutation abolished Na+ self inhibition of ENaC, which might also contribute to its gain‐of‐function effects. We conclude that the αW493R mutation promotes constitutive activation of ENaC by reducing the inhibitory effect of extracellular Na+ and decreasing the pool of near‐silent channels. The resulting gain‐of‐function phenotype of the mutant channel might contribute to the pathophysiology of CF in patients carrying this mutation.

Microarray analysis of placental tissue in intrauterine growth restriction

Objective  Besides foetal or maternal disorders, placental dysfunction is a major cause of intrauterine growth restriction (IUGR). Although numerous macro‐ and histopathological changes have been described, little is known about the precise aetiology and the contribution of foetal/placental genes in this disorder.

Differences in gene expression dependent on sampling site in placental tissue of fetuses with intrauterine growth restriction

OBJECTIVE The human placenta as part of the feto-placental unit may influence fetal endocrine systems and may therefore represent a very important link between intrauterine growth restriction (IUGR) and metabolic disorders in later life. We aimed to analyze the effect of sample origin on gene expression of placental factors potentially involved in fetal programming in IUGR versus appropriate for gestational age growth (AGA) to standardize sample collection procedure for a multicenter approach. DESIGN Placental gene expression of insulin-like growth factor-binding protein (IGFBP)-1, prolactin, corticotropin releasing hormone (CRH) and leptin was measured and compared between proximal, intermediate and peripheral region of the placenta in 22 IUGR (proven by anomalous placental Doppler velocimetry) and 19 AGA neonates. RESULTS Whereas no difference in gene expression was seen in the proximal portion, in the intermediate placental region mRNA expression of IGFBP-1 (p = 0.01), prolactin (p = 0.04), CRH (p = 0.01) and leptin (p = 0.04) was increased in IUGR samples compared to controls. At the placental periphery, gene expression of these placental transcripts showed a higher expression level in IUGR placentas without statistical significance, except for leptin (p = 0.03). CONCLUSION Placental sampling site seems to be relevant for detecting differences in gene expression between IUGR and AGA neonates.

Intrauterine growth restriction (IUGR) is associated with increased leptin synthesis and binding capability in neonates.

Objective  Animal studies suggest pathological foetal programming of hypothalamic circuits regulating food intake in the setting of leptin deficiency and intrauterine growth restriction (IUGR). We aimed to compare placental leptin synthesis and leptin‐binding capability in venous cord blood between IUGR newborns and neonates born appropriate for gestational age (AGA).

Placental 11β-HSD2 Gene Expression at Birth Is Inversely Correlated With Growth Velocity in the First Year of Life After Intrauterine Growth Restriction

Intrauterine growth restriction (IUGR) is associated with an increased risk for short stature and diseases in adulthood thought to be inflicted by fetal programming. We hypothesized that placental endocrine systems involved in perinatal growth might also play a role in postnatal growth after IUGR. In a prospective controlled multicenter study, placental gene expression of IGF-binding protein-1 (IGFBP-1), leptin and 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) were measured in 14 IUGR infants and 15 children born appropriate for gestational age (AGA) proven by serial ultrasound examinations. Postnatally, IUGR infants experienced a significantly higher growth velocity than AGA neonates (at 1 y: p = 0.001). Gene expression of 11β-HSD2 at birth correlated positively with birth length (r = 0.55, p = 0.04) and inversely with growth velocity in the first year of life (r = −0.69, p = 0.01) in the IUGR, but not in the AGA group. There was no correlation between gene expression of placental IGFBP-1, leptin and birth weight, length and growth velocity during the first year of life. AGA infants showed significantly higher concentrations of cortisone in venous cord blood after birth (p = 0.02) as a surrogate of a higher 11β-HSD2 activity in the fetoplacental unit. In conclusion, placental 11β-HSD2 gene expression might predict postnatal growth in IUGR.

Cullin 7 and Fbxw 8 expression in trophoblastic cells is regulated via oxygen tension: implications for intrauterine growth restriction?

Objective: The F-box protein Fbxw8 is a cofactor of Cullin 7 (Cul7), which regulates protein transfer to the proteasome and cell growth. Cul7 or Fbxw8 deficiency is associated with intrauterine growth restriction (IUGR) due to abnormal placental development leading to poor oxygen supply to the fetus. We studied the role of hypoxia for Fbxw8 and Cul7 expression in trophoblastic cells. Methods: Immunomagnetic bead-separated extravillous trophoblast (EVT) and villous trophoblast (VT) and trophoblast cell lines were incubated with 1 or 8% O2. Fbxw8 and Cul7 expression was determined in IUGR versus matched control placentas. Results: Fbxw8 was expressed uniformly in trophoblasts, whereas Cul7 expression was most prominent in trophoblast cell lines. Hypoxia reduced expression of Cul7 and Fbxw8 in all trophoblastic cells, except for villous trophoblasts. In vivo, Cul7 and Fbxw8 were detected in syncytiotrophoblast cells, VT, and EVT cells. Although no significant changes in expression levels of Fbxw8 or Cul7 were noted in IUGR compared with control placentas, Fbxw8 expression correlated negatively with gestational age in the control, but not in the IUGR group. Conclusion: Fbxw8 and Cul7 expression reveals a complex regulation in trophoblastic cells. Our findings suggest that dysregulation of Cul7 and Fbxw8 expression might affect trophoblast turnover in IUGR.

Dexamethasone stimulates the expression of leptin and 11β-HSD2 in primary human placental trophoblastic cells

OBJECTIVES Fetal glucocorticoid excess is thought to play an important role in early-life programming, promoting growth restriction and contributing to adult metabolic, cardiovascular and neuroendocrine disease. We hypothesized that dexamethasone incubation of primary trophoblastic cells from human healthy placentas at term might induce altered gene and protein expression of several endocrine placental regulators. STUDY DESIGN Primary villous trophoblastic cells were incubated with 10 μM dexamethasone for 6, 12, 24, 48 and 72 h. Non-incubated trophoblastic cells served as vehicle control. Gene expression of leptin, 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) and insulin-like growth factor-binding protein-1 (IGFBP-1) was measured. Moreover, leptin, β-human chorionic gonadotropine (β-hCG) and lactate dehydrogenase (LDH) release into the culture medium was determined. RESULTS Leptin gene expression was significantly increased in dexamethasone-incubated trophoblastic cells after 24, 48 and 72 h. There was a significant increase in leptin concentration in the medium of the cell culture after 48 h. Gene expression of 11β-HSD2 was significantly higher in dexamethasone-stimulated trophoblastic cells compared to vehicle controls after 72 h. The expression rate of IGFBP-1 mRNA was basal throughout the incubation period. The concentration of β-HCG in the supernatant increased significantly after 72 h of dexamethasone incubation, while LDH concentrations remained stable. CONCLUSION Our findings suggest that dexamethasone incubation stimulates leptin and 11β-HSD2 gene expression in primary villous trophoblastic cells of healthy human placentas, while enhancing cytotrophoblast differentiation.

Differential effects of low birthweight and intrauterine growth restriction on umbilical cord blood insulin-like growth factor concentrations.

Alterations in the growth hormone–insulin‐like growth factor (IGF) axis have been considered as a causal factor for intrauterine growth restriction (IUGR) and for the increased risk of metabolic disease in later life. We compared members of the IGF axis in umbilical cord blood between IUGR neonates, small for gestational age without foetal restriction (SGA) and appropriate for gestational age (AGA) neonates.

DNA methylation of the p66Shc promoter is decreased in placental tissue from women delivering intrauterine growth restricted neonates

The adaptor protein p66Shc generates mitochondrial reactive oxygen species and translates oxidative signals into apoptosis. We aimed to analyze potential alterations in total methylation and in p66Shc activation in placental tissues from women delivering intrauterine growth restricted neonates (IUGR) versus appropriate for gestational age (AGA) and small for gestational age (SGA) neonates.

Sex‐specific differences in the concentration of tubular parameters in the amniotic fluid of second trimester fetuses

Renal dysplasia and obstructive uropathy are more common in males and are associated with an increased tubular loss of electrolytes. We aimed to compare the midtrimester concentration of tubular parameters in the prenatal period between healthy male and female fetuses.