Several cytokines exhibit a high degree of temporal regulation as well as somnogenic potency (e.g., interleukin-1 [IL-1], tumor necrosis factor-alpha [TNF-alpha]). Seeking the underlying cause of obstructive sleep apnea syndrome (OSAS), we investigated whether circadian rhythms of cytokine release were altered in 10 patients with OSAS. Ten healthy volunteers served as the control population. Seven of the 10 OSAS patients were reexamined after 3 mo of therapy with nasal continuous positive airway pressure (nCPAP) mask ventilation. Circadian cytokine release (IL-1, IL-6, gamma-interferon [gamma-IFN], TNF-alpha) was investigated ex vivo by short-term culture of blood samples. The circadian rhythm of TNF-alpha release was significantly disturbed in OSAS patients: nocturnal physiologic peaks in this cytokine had almost disappeared and an additional daytime peak had developed. Circadian variations in IL-1, IL-6, and gamma-IFN, and in the immunoregulatory hormones melatonin and cortisol, did not differ from those in the controls. Because TNF-alpha is a known modulator of sleep, and nCPAP therapy did not normalize TNF rhythms, we assume that TNF-alpha could well play a pathophysiologic role in OSAS. Further studies should be directed at whether a physiopathologic and/or pathogenic link exists between TNF-alpha and OSAS.

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ABSTRACT:Epidermal growth factor (EGF) is a multifunctional growth factor known to play a major role in proliferation and differentiation processes. EGF-induced differentiation is a prerequisite for function of various cell types, among them cytotrophoblasts, a functionally important cellular fraction in human placenta. Stimulation of cytotrophoblasts with EGF results in formation of a multinuclear syncytium representing the feto-maternal interface, which protects the fetus against exogenous substances. It is well established that part of this protection system is based on ATP-binding cassette (ABC) transporters such as ABCG2 (breast cancer resistance protein, BCRP). However, little is known about regulation of transport proteins in the framework of EGF-mediated cellular differentiation. In the present work we show a significant increase of ABCG2 expression by EGF in cytotrophoblasts, BeWo, and MCF-7 cells on both mRNA and protein levels. This increase resulted in decreased sensitivity to the ABCG2 substrates mitoxantrone and topotecan. In each cell type, EGF increases expression of ABCG2 by activation of mitogen-activated protein kinase cascade via phosphorylation of extracellular regulated kinase (ERK)1/2 and c-jun NH-terminal kinase/stress-activated protein kinase (JNK/ SAPK). Consequently, the increase of ABCG2 by EGF was abolished by pretreatment of cells with the tyrosine kinase inhibitor 4-(3-chloroanillino)-6,7-dimethoxyquinazoline (AG1478) or the mitogen-activated protein kinase kinase inhibitor 2-amino-3me-thoxyflavone (PD 98059), thereby reestablishing sensitivity toward mitoxantrone. Moreover, analysis of ABCG2 expression during placental development revealed a significant increase in preterm versus term placenta. Taken together, our data show regulation of ABCG2 expression by EGF. In view of EGF signal transduction as a target for drugs (e.g., gefitinib), which are in turn substrates and/or inhibitors of ABCG2, this regulation has therapeutic consequences.

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ABSTRACT:L-carnitine is assumed to play an important role in fetal development, and there is evidence that carnitine is transported across the placenta. The protein involved in this transfer, however, has not been identified on a molecular level. We therefore characterized localization and function of the carnitine transporter OCTN2 in human placenta. Significant expression of OCTN2 mRNA was detected in human placenta applying real-time polymerase chain reaction technology. Confocal immunofluorescence microscopy using an antibody directed against the carboxy terminus of OCTN2 protein revealed that it is predominantly expressed in the apical membrane of syncytiotrophoblasts. This was confirmed by the costaining of organic anion-transporting polypeptide B and MRP2, which are known to be expressed mainly in the basal and apical syncytiotrophoblasts membrane, respectively. To further support this finding, we performed transport studies using basal and apical placenta membrane vesicles. We could demonstrate that the carnitine uptake into the apical vesicles was about eight times higher compared with the basal ones. Moreover, this uptake was sodiumand pH-dependent with an apparent K m value of 21 M and inhibited by verapamil, which is in line with published data for recombinant OCTN2. Finally, experiments using trophoblasts in cell culture revealed that expression of OCTN2 paralleled human choriogonadotropin production and thus is modulated by cellular differentiation. In summary, we show expression and function of OCTN2 in human placenta. Moreover, several lines of evidence indicate that OCTN2 is localized in the apical membrane of syncytiotrophoblasts, thereby suggesting a major role in the uptake of carnitine during fetal development.Carnitine plays an important physiological role, in particular, in ␤-oxidation because it facilitates long-chain fatty acid transport across the inner mitochondrial membrane. Moreover, carnitine is involved in intracellular coenzyme A homeostasis and functions as an antioxidant (Bremer, 1983;Arduini et al., 1992;Pons and De Vivo, 1995). Only a few organs like brain, liver, and kidney have the ability to biosynthesize carnitine (Bremer, 1983), whereas other tissues like skeletal and heart muscles, where ␤-oxidation plays a major role in energy metabolism, are highly dependent on active carnitine uptake from blood to maintain their carnitine steady-state concentration (Siliprandi et al., 1989).Recent studies describe the organic cation transporter novel type II (OCTN2) as a high affinity uptake system for carnitine. The OCTN2 cDNA codes for 557 amino acids consisting of 12 putative transmembrane domains with a predicted molecular mass of 63 kDa . The transport of carnitine is sodium-dependent (Tamai et al., 1998), whereas other compounds such as tetraethylammonium are transported by OCTN2 in a sodium-independent way (Ohashi et al., 2001).Besides its physiological function, OCTN2 is of pharmacological relevance. Drugs like verapamil, pyrilamine, and ␤-lactam antibiotics have been characte...

The association of uniparental disomy (UPD) and short stature has been reported for diVerent chromosomes and in several conditions. Therefore, we investigated a cohort of 21 patients referred because of intrauterine and postnatal growth retardation for UPD of chromosomes 2, 7, 9, 14, 16, and 20. Typing of short tandem repeats showed maternal UPD(14) and maternal UPD(20) in two cases. In the first case, an interstitial UPD(14) was detected and the growth retarded newborn showed some additional clinical signs in common with the putative "maternal UPD(14) syndrome". The maternal UPD(20) patient showed minor features. However, since it is only the second maternal UPD(20) case it is too early to delineate a specific syndrome and the role of this constitution in growth remains to be investigated. Our data suggest that searching for UPD in growth retarded patients is a helpful approach to getting more information on the role of UPD in growth retardation. Based on our results, general considerations and indications for UPD testing are discussed. (J Med Genet 2001;38:86-89)

The placenta functions both as site for nutrition and protection of the fetus. Transport proteins, including members of the multidrug resistance protein (MRP)/ABCC subfamily, have been recognized to contribute to the latter function. MRP5 (ABCC5) was identified as transmembrane transport protein for cyclic nucleotides, especially 3',5'-cyclic GMP (cGMP), indicating an additional role in signal transduction and a potential role in placenta development. We therefore studied expression, localization, and function of MRP5 in placenta of different gestational ages. Quantitative real-time polymerase chain reaction revealed expression of MRP5 in all 60 samples from pre-term and term placenta, with a decreasing mean expression with gestational age (MRP5/18S-ratio x 1000; < 32 weeks: 2.91 +/- 0.73, n = 15; 32 to 37 weeks: 2.10 +/- 0.87, n = 15; > 37 weeks: 0.46 +/- 0.08, n = 30; P < 0.01). Immunofluorescence microscopy with an anti-MRP5 antibody indicated localization of MRP5 preferentially in the basal membrane of syncytiotrophoblasts and in and around fetal vessels. ATP-dependent [(3)H]cGMP transport as evidence for MRP5 function could be demonstrated in isolated basal membrane vesicles. Moreover, the influence of cellular differentiation on MRP5 expression was studied in isolated trophoblasts, revealing an increase of the MRP5 expression in parallel with the hCG production (MRP5/18S-ratio x 1000 was 2.4 +/- 0.5 at day 5 of culture and 1.45 +/- 0.5 at day 0 of culture, n = 3 preparations, significant difference with P < 0.05). In conclusion, MRP5 expression depends on gestational age and varies throughout the differentiation process. In view of the important role of cGMP for cellular differentiation, MRP5 may play a role in placental development in context with a specific need for cellular cGMP export.

There is clear evidence that the placenta produces leptin. However, it is still unclear to what extent leptin is released into the maternal and the fetal circulation. The aim of our study was to determine placental leptin release rates into these 2 compartments. In 10 term placentas, using dual in vitro perfusion of an isolated cotyledon, concentrations of leptin, hCG, and human placental lactogen (hPL) were determined in perfusates and in the tissue before and after perfusion. With perfusions lasting 270-840 min, total leptin production was 225 pg/g x min [median; interquartile range (IQR), 76-334 pg/g x min]. The release into the fetal circulation was very low (median, 2.5; IQR, 1.1-5.9 pg/g x min) compared with the release into the maternal circulation (median, 203; IQR, 79-373 pg/g x min) corresponding to 1.6% and 98.4% of net release. Only 0.05% of hPL and hCG were released into the fetal circulation and 99.95% into the maternal circulation, confirming previous results. Release into the fetal circulation correlated significantly with release into the maternal circulation for leptin (r = 0.648; P < 0.05) and hPL (r = 0.721; P < 0.05). Furthermore, release of leptin into the fetal circulation was positively correlated with release of fetal hCG (r = 0.661; P < 0.05). Most of the leptin produced by the placenta is released into the maternal circulation, but compared with other placental hormones (hCG and hPL), a considerably higher proportion of leptin is released into the fetal circulation. These findings may at least partially explain the marked increase in maternal serum leptin levels in pregnancy. The rapid postnatal decrease in leptin levels in both the mother and the neonate is also consistent with the concept of placental origin.