Kristo Hakala

Transfer of proinflammatory cytokines across term placenta.

OBJECTIVE: Increased concentrations of proinflammatory cytokines in amniotic fluid indicate the presence of intra-amniotic inflammation and increase the risk of preterm birth, cerebral palsy, and bronchopulmonary dysplasia. The purpose of this study was to find out if the proinflammatory cytokines, tumor necrosis factor alpha (TNF-&agr;), interleukin (IL)-1&bgr;, and IL-6, transfer across the placenta, and thereby determine whether intra-amniotic inflammatory response, measured from the amniotic fluid, is of maternal or fetal origin. METHODS: Nineteen placentas from healthy women undergoing elective cesarean delivery at term with intact membranes and without labor, were dually perfused ex vivo in an open circulation system for either 30 minutes or 2 hours. Tumor necrosis factor-&agr;, IL-1&bgr;, and IL-6 were added to maternal or fetal circulation in a concentration usually found in chorioamnionitis. As a reference, placentas without added cytokine were also perfused. The concentrations of cytokines were determined by enzyme immunoassays (enzyme-linked immunosorbent assay [ELISA]). RESULTS: After the addition of the cytokine to the arterial perfusate, the venous concentration on the same side of the placenta increased rapidly and reached a plateau at 10 minutes. No transfer of any cytokine in either direction was detected. Some endogenous release of IL-6 was observed in response to the perfusion. CONCLUSION: Proinflammatory cytokines do not cross normal term placenta. LEVEL OF EVIDENCE: II-1

Functional role of P-glycoprotein in the human blood-placental barrier

In vitro and animal experiments suggest that P‐glycoprotein forms a functional barrier between maternal and fetal blood circulation in the placenta, thus protecting the fetus from exposure to xenobiotics during pregnancy. In this study we aimed to characterize the role of P‐glycoprotein in the blood‐placental barrier by use of dually perfused human placenta.

Effects of Low and High Plasma Concentrations of Dexmedetomidine on Myocardial Perfusion and Cardiac Function in Healthy Male Subjects

Background:Dexmedetomidine, a selective &agr;2-adrenoceptor agonist, has counteracting effects on the cardiovascular system. It mediates sympatholysis by activating &agr;2 adrenoceptors in the central and peripheral nervous system, and vasoconstriction and vasorelaxation by activating postsynaptic &agr;2 adrenoceptors in blood vessels. The goal of this study was to determine the effects of therapeutic and high concentrations of dexmedetomidine on myocardial perfusion and cardiac function in healthy subjects. Methods:The authors studied 12 healthy young men. Myocardial blood flow (assessed with positron emission tomography), myocardial function (by echocardiography), and hemodynamic data were collected before and during low (measured mean plasma concentration, 0.5 ng/ml) and high (5 ng/ml) plasma concentrations of dexmedetomidine. Results:The low concentration of dexmedetomidine reduced myocardial perfusion (mean difference, −27% from baseline [95% confidence interval, −31 to −23%], P < 0.001) in parallel with a reduction in myocardial oxygen demand (estimated by the rate–pressure product (−23% [−28 to −18%], P < 0.001). The high dexmedetomidine plasma concentration did not further attenuate myocardial perfusion (−3% [−12 to +6%] from low dexmedetomidine, P > 0.05; −29% [−39 to −18%] from baseline, P < 0.001) or statistically significantly affect the rate–pressure product (+5% [0 to +10%], P > 0.05). Systolic myocardial function was attenuated by sympatholysis during the low infusion rate and was further attenuated by a combination of the sustained sympatholysis and increased afterload during the high infusion rate. Conclusions:In healthy subjects, plasma concentrations of dexmedetomidine that significantly exceed the recommended therapeutic level do not seriously attenuate myocardial perfusion below the level that is observed with usual therapeutic concentrations and do not induce evident myocardial ischemia.

Liquid chromatographic–tandem mass spectrometric method for the plant lignan 7-hydroxymatairesinol and its potential metabolites in human plasma

A HPLC-MS-MS method was developed for the determination of the plant lignan 7-hydroxymatairesinol and its potential metabolites matairesinol, oxomatairesinol, alpha-conidendrin, 7-hydroxyenterolactone, enterodiol, and enterolactone in human plasma. The method included sample cleanup by solid-phase extraction (SPE) and analysis using a PE Sciex API3000 triple quadrupole mass spectrometer with electrospray ionisation. The lignans were quantified using two deuterated internal standards. They showed good chromatographic linearity, analysis repeatability, and SPE recovery in the presence of plasma. In pooled plasma and in plasma samples collected from two individual subjects lignan glucuronides and sulfates were enzymatically hydrolysed to free lignans and then analysed. All the lignans could be detected in the samples.

Placental transfer of quetiapine in relation to P-glycoprotein activity.

Atypical antipsychotic drugs are well tolerated and thus often preferred in women of fertile age; yet the information on their placental transfer and use during the prenatal period is limited. The aim of this study was to study the placental transfer of quetiapine, a widely used atypical antipsychotic, with special reference to the role of the placental transporter protein, P-glycoprotein (P-gp). This was performed in 18 dually perfused placentas, using the well established P-gp inhibitors PSC833 (valspodar) and GG918 to inhibit the function of P-gp. We also aimed to clarify the significance of two potentially functional ABCB1 single nuclear polymorphisms (SNPs), 2677G>T/A and 3435C>T, on the transplacental transfer (TPT) of quetiapine. The placental transfer of quetiapine in the control group as measured by TPTAUC % (absolute fraction of the dose crossing placenta) was 3.7%, which is 29% less than the transfer of the freely diffusible antipyrine, which was 5.2%. The P-gp inhibitors had no significant effect on the transfer of quetiapine as measured by TPTAUC % (P = 0.77). No correlation was found between the transplacental transfer of quetiapine (TPTAUC %) and placental P-gp expression (P = 0.61). The 3435T allele in exon 26 was associated with significantly higher placental transfer of quetiapine (P = 0.04). We conclude that quetiapine passes the human placenta but that the blood—placental barrier partially limits the transplacental transfer of quetiapine. Administration of P-gp inhibiting drugs with quetiapine is not likely to increase fetal exposure to quetiapine, although the ABCB1 C3435T polymorphism may contribute to inter-individual variation in fetal exposure to quetiapine.

Influence of adenosine triphosphate and ABCB1 (MDR1) genotype on the P-glycoprotein-dependent transfer of saquinavir in the dually perfused human placenta

Background: The ATP-dependent drug-efflux pump, P-glycoprotein (P-gp) encoded by ABCB1 (MDR1), plays a crucial role in several tissues forming blood–tissue barriers. Absence of a normally functioning P-gp can lead to a highly increased tissue penetration of a number of clinically important drugs. Methods: We have studied the dose–response effect of exogenous ATP on the placental transfer of the well-established P-gp substrate saquinavir in 17 dually perfused human term placentas. We have also studied the influence of the ABCB1 polymorphisms 2677G>T/A and 3435C>T on placental P-gp expression (n = 44) and the transfer (n = 16) of saquinavir. Results: The present results indicate that the addition of exogenous ATP to the perfusion medium does not affect the function of P-gp as measured by saquinavir transfer across the human placenta. The variant allele 3435T was associated with significantly higher placental P-gp expression than the wild-type alleles. However, neither polymorphism affected placental transfer of saquinavir nor there was any correlation between P-gp expression and saquinavir transfer. Conclusions: Our results indicate that addition of exogenous ATP is not required for ATP-dependent transporter function in a dually perfused human placenta. Although the ABCB1 polymorphism 3435C>T altered the expression levels of P-gp in the human placenta, this did not have any consequences on P-gp–mediated placental transfer of saquinavir.

The effect of probenecid and MK-571 on the feto-maternal transfer of saquinavir in dually perfused human term placenta.

Human placenta, particularly the blood-placenta barrier, with various transporters has crucial role to protect the fetus and, on the other hand, to facilitate movement of compounds towards the fetal circulation. This study aimed to characterize the role of basal transporters of the syncytiotrophoblast, which appear to be yet less studied, in the fetal-to-maternal transfer of saquinavir by use of dually perfused human placentas. A dual perfusion of human placenta was performed to study effect of MK-571 and probenecid, inhibitors of the MRP1 and OATP transporters, expressed in the basal trophoblast membrane, on the transfer of saquinavir. The fetal-to-maternal placental transfer of saquinavir in the control group as measured by TPT(AUC)% (absolute fraction of the dose crossing placenta) was 14.0%, which is 73% less than the transfer of the freely diffusible antipyrine. The two inhibitors, MK-571 and probenecid caused a non-significant (P = 0.34 for ANOVA) reduction of 43% and 24%, respectively, in the mean amount of saquinavir transferred from the fetal to the maternal side. MK-571 also somewhat (by 31%) reduced the TPT(AUC)% of antipyrine, but this finding did not reach statistical significance (P = 0.25). Neither of the employed inhibitors had an effect on the placental transfer index of saquinavir transfer (P = 0.77). The present results indicated lack of significant effect by MK-571 and probenecid on the fetal-to-maternal transfer of saquinavir and suggest that MRP1 and, possibly, OATP2B1 do not play a significant role in the fetal-to-maternal transfer of saquinavir.