Expression, localization, and function of the carnitine transporter octn2 (slc22a5) in human placenta.

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 sodium- and pH-dependent with an apparent K(m) value of 21 muM 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.     

High 123I-MIBG uptake in neuroblastic tumours indicates unfavourable histopathology

Purpose

Scintigraphy using ¹²³I-metaiodobenzylguanidine (¹²³I-MIBG) is widely used for the detection of neuroblastic tumours. The aim of this study was to identify a possible correlation between the uptake intensity on ¹²³I-MIBG SPECT and histopathology of neuroblastic tumours.

Methods

¹²³I-MIBG SPECT examinations were performed in 55 paediatric patients with neuroblastic tumour and compared to histopathology after surgical resection or biopsy at a mean of 2 weeks after SPECT. For each lesion International Neuroblastoma Pathology Classification System (INPC) stage, mitosis karyorrhexis index (MKI), location and a semiquantitative tumour-to-liver count-rate ratio (TLCRR) were determined. Also, the presence or absence of MYCN amplification, p1 deletion, urine catecholamine and neuron-specific enolase blood levels at the time of scanning were recorded.

Results

In the 55 patients, 61 lesions were evaluated with ¹²³I-MIBG SPECT and corresponding histopathological findings were reviewed (11 ganglioneuroma, 11 ganglioneuroblastoma and 39 neuroblastoma). TLCRR was significantly higher in the neuroblastoma group (mean TLCRR 2.7) than in the ganglioneuroblastoma group (mean TLCRR 1.0) and ganglioneuroma group (mean TLCRR 0.7) at the time of primary diagnosis (p?<?0.001) and at follow-up (p?=?0.039). Intense ¹²³I-MIBG uptake was found in tumour tissue with a high mitotic activity (MKI-high or MKI-intermediate) after treatment. Four ganglioneuromas (36 %), three ganglioneuroblastomas (27 %) and six neuroblastomas (15 %) were ¹²³I-MIBG-negative.

Conclusion

In paediatric patients with peripheral neuroblastic tumours, strong ¹²³I-MIBG uptake indicates unfavourable histopathology. High uptake was seen in neuroblastomas and in tumours with a high mitotic activity.     

Attenuated Purinergic Receptor Function in Patients With Type 2 Diabetes

OBJECTIVE

Extracellular nucleotides and nucleosides are involved in regulation of skeletal muscle blood flow. Diabetes induces cardiovascular dysregulation, but the extent to which the vasodilatatory capacity of nucleotides and nucleosides is affected in type 2 diabetes is unknown. The present study investigated 1) the vasodilatatory effect of ATP, uridine-triphosphate (UTP), and adenosine (ADO) and 2) the expression and distribution of P2Y² and P2X¹ receptors in skeletal muscles of diabetic subjects.

RESEARCH DESIGN AND METHODS

In 10 diabetic patients and 10 age-matched control subjects, leg blood flow (LBF) was measured during intrafemoral artery infusion of ATP, UTP, and ADO, eliciting a blood flow equal to knee-extensor exercise at 12 W (∼2.6 l/min).

RESULTS

The vasodilatatory effect of the purinergic system was 50% lower in the diabetic group as exemplified by an LBF increase of 274 ± 37 vs. 143 ± 26 ml/μmol ATP × kg, 494 ± 80 vs. 234 ± 39 ml/μmol UTP × kg, and 14.9 ± 2.7 vs. 7.5 ± 0.6 ml/μmol ADO × kg in control and diabetic subjects, respectively, thus making the vasodilator potency as follows: UTP control subjects (100) > ATP control subjects (55) > UTP diabetic subjects (47) > ATP diabetic subjects (29) > ADO control subjects (3) > ADO diabetic subjects (1.5). The distribution and mRNA expression of receptors were similar in the two groups.

CONCLUSIONS

The vasodilatatory effect of the purinergic system is severely reduced in type 2 diabetic patients. The potency of nucleotides varies with the following rank order: UTP > ATP > ADO. This is not due to alterations in receptor distribution and mRNA expression, but may be due to differences in receptor sensitivity.The net balance between vasoconstrictor and vasodilator activity in patients with type 2 diabetes is abnormal, and the ability of adjusting vascular tone during conditions with increased demands for blood flow is affected (1,2). The level of secretion and bioavailability of the potent vasodilators nitric oxide (NO) and prostacyclin (prostaglandin [PG]) are diminished, and there is an increase in the synthesis, secretion, and action of vasoconstrictors including prostanoids, angiotensin II, endothelin, and noradrenalin (3). This leads to impaired vascular reactivity, which may limit exercise capacity in patients with type 2 diabetes.In the last decade, the purinergic system and its impact on blood flow regulation have come more into focus. Several studies have shown that extracellular nucleotides and nucleosides such as ATP, uridine-triphosphate (UTP), and adenosine (ADO) are factors in the local control of vessel tone (4) and regulation of exercise-induced hyperemia (5). Interestingly, reduced ATP release has been shown in diabetic patients (6).Whereas UTP and ADO are pure vasodilators, ATP possesses the ability to induce both vasodilatation and vasoconstriction; ATP-induced vasodilatation is assumed to be a result of intravascular release of ATP from endothelial cells or erythrocytes, leading to release of NO and PG via endothelial purinergic receptors (7,8), whereas extravascular ATP leads to vasoconstriction by direct action on receptors on smooth muscle cells (9). Nucleotides and nucleosides mediate a biological response via two main categories of cell surface receptors: P1 receptor for ADO and P2 receptor recognizing primarily ATP, UTP, ADP, and uridine-diphosphate. P2 receptors are subdivided into P2X and P2Y, based on their pharmacological properties; P2Y is a family of G-protein–coupled receptors, whereas P2X is a group of ligand-gated ion channel receptors (10,11).Attenuated function of purinergic receptors is implicated in multiple diseases (12). The aim of the present study was therefore to evaluate whether the endothelial dysfunction in type 2 diabetic patients is associated with impairment of the vascular sensitivity to extracellular nucleotides and nucleosides. We hypothesized that purinergic-mediated vasodilation is diminished in type 2 diabetic patients because of decreased receptor density and/or sensitivity. We determined localization of P2Y₂ and P2X₁ receptors and measured levels of mRNA of P2Y₂ receptors to investigate potential downregulation.     

The Effect of Pain on Major Cognitive Impairment in Older Adults

Older adults frequently report pain; cross-sectional studies have shown that pain is associated with worse cognitive function. However, longitudinal studies are lacking. We prospectively studied 441 participants without dementia, including 285 with pain, aged 65 years and older, enrolled in the Central Control of Mobility in Aging study, a prospective cohort study. We analyzed the longitudinal association between pain (measured with the Medical Outcomes Study pain severity scale) and major cognitive impairment (measured with the Repeatable Battery for the Assessment of Neuropsychological Status and the Trail Making Test Delta) using Cox regression analysis adjusted for age, gender, ethnicity, and education. Over a mean follow-up of 2.75 years (standard deviation?=?1.94), there was no difference in the risk of developing cognitive impairment between participants with pain and participants without pain. However, among those with pain, risk for developing major memory impairment was higher among those with high levels of pain than those with low levels of pain (adjusted hazard ratio?=?3.47, 95% confidence interval?=?1.42–8.46). The association with pain and incident impairments in attention or executive function was not significant. We did not find that pain is associated with incident cognitive impairment in general, but among older adults with pain, a high level of pain is associated with increased risk of developing incident memory impairment.