Chronic hypoxia in pregnant mice impairs the placental and fetal vascular response to acute hypercapnia in BOLD-MRI hemodynamic response imaging.

INTRODUCTION: Brief hypercapnic challenge causes acute placental hypoperfusion with fetal brain sparing on BOLD-MRI. We hypothesize that this non-invasive imaging strategy can distinguish between normal pregnancy and chronic placental hypoperfusion (using the maternal hypoxia model). METHODS: Eighteen pregnant female ICR mice were randomized to three groups: normoxia, late-onset hypoxia (12%O2;E13.5-17.5) and early-onset hypoxia (12%O2;E10.5-17.5). On E17.5, animals were imaged in a 4.7-T Bruker-Biospec MRI scanner. Fast coronal True-FISP was performed to identify organs of interest (placenta and fetal heart, liver and brain). BOLD-MRI was performed at baseline and during a 4-min hypercapnic challenge (5%CO2). %-change in placental and fetal signal was analyzed from T2*-weighted gradient echo MR images. Following MRI, fetuses and placentas were harvested, weighed and immuno-stained. RESULTS: In normoxic mice, hypercapnia caused reduction in BOLD-MRI signal in placenta (-44% ± 7%; p < 0.0001), fetal liver (-32% ± 7%; p < 0.0001) and fetal heart (-54% ± 12%; p < 0.002), with relative fetal brain sparing (-12% ± 5%; p < 0.0001). These changes were markedly attenuated in both hypoxia groups. Baseline fetal brain/placenta SI ratio was highest in normoxic mice (1.14 ± 0.017) and reduced with increasing duration of hypoxia (late-onset hypoxia: 1.00 ± 0.026; early-onset hypoxia: 0.91 ± 0.016; p = 0.02). Both hypoxic groups exhibited fetal growth restriction with prominent placental glycogen-containing cells, particularly in early-onset hypoxia. There was increased fetal neuro- and intestinal-apoptosis in early-onset hypoxia only. CONCLUSIONS: BOLD-MRI with brief hypercapnic challenge distinguished between normoxia and both hypoxia groups, while fetal neuroapoptosis was only observed after early-onset hypoxia. This suggests that BOLD-MRI with hypercapnic challenge can identify chronic fetal asphyxia before the onset of irreversible brain injury.

Aberrant corin and PCSK6 in placentas of the maternal hyperinsulinemia IUGR rat model.

OBJECTIVES: Corin is a protease that converts pro-atrial natriuretic peptide (pro-ANP) to ANP. While the involvement of ANP in the cardiovascular regulation is well established, there is increasing evidence that the pregnant uterus produces ANP, which promotes spiral artery remodeling. The present study examines the alterations in corin and PCSK6, a key enzyme in the conversion of pro-corin to corin, in the placenta of hyperinsulinemic dams (HD) featuring pregnancy-induced hypertension (PIH). MATERIALS AND METHODS: The study was conducted on female Wistar rats. Rats were rendered hyperinsulinemic by subcutaneous insulin pellet, mated and followed to the twenty-first day of pregnancy. Normal pregnant dams (NPD) served as controls. Both groups were sacrificed on day 21 of gestation and their placentas were dissected along with the mesometrial triangle (MT). The tissue was then sectioned from the maternal surface to the base of the MT, and processed for histological and molecular biology analysis of Corin, PCSK6 and ANP expression/immunoreactivity. RESULTS: Hyperinsulinemic dams developed PIH, along lower placental and fetal weights. Corin expression and immunoreactivity were significantly decreased in the placenta by ~40-50%, but not in the MT. Similarly, placental but not MT PCSK6 immunoreactivity was lower in HD. Concomitantly with the downregulation of corin/PCSK6, proANP levels increased in the placenta of HD. CONCLUSIONS: Corin and PCSK6 are expressed in the placenta and MT. The decline in these two enzymes in the placenta of HD suggests a role of corin/PCSK6 machinery in the development of PIH and intrauterine growth restriction characterizing hyperinsulinemia.

The Effects of Chronic Iron Overload in Rats with Acute Acetaminophen Overdose.

BACKGROUND AND AIMS: Rats are resistant to acetaminophen (APAP) hepatotoxicity. In this study, we evaluated whether by augmentation of the hepatic oxidative stress, through the induction of hepatic iron overload (IO), it will be feasible to overcome the resistance of rats to the toxic effects of APAP. METHOD: Rats with no or increased hepatic IO. RESULTS: Providing iron by diet induced hepatocellular IO, while parenteral iron administration induced combined hepatocellular and sinusoidal cell IO. APAP administration to rats with no IO caused an increase in hepatic oxidative stress and a decrease in the hepatic antioxidative markers but no hepatic cell damage. APAP administration to rats with hepatocellular IO further amplified the hepatic oxidative stress but induced only hepatocyte feathery degeneration without any increase in serum aminotransaminases. APAP administration to rats with combined hepatocellular and sinusoidal cell IO caused an unexpected decrease in hepatic oxidative stress and increase in the hepatic antioxidative markers and no hepatic cell damage. No hepatic expression of activated c-jun-N-terminal kinase was detected in any of the rats. CONCLUSIONS: The hepatic distribution of iron may affect its oxidative/antioxidative milieu. Augmentation of hepatic oxidative stress did not increase the rats' vulnerability to APAP.

Vasoactivity of the rat endovascular trophoblast.

INTRODUCTION: Rat endovascular trophoblasts (EVasT) express smooth muscle (SM) proteins and contract ex vivo upon exposure to endothelin-1 (ET1) via receptors A and B (ETA, ETB). Presently, we investigated the EVasT response to NOS inhibition (N-Nitro-l-arginine methyl ester hydrochloride, l-NAME), and potentiation by NO donor [S-Nitroso-N-Acetyl-D,l-Penicillamine (SNAP)] following KCl precontraction. M&M: Luminal surface area (LSA) of remodeled spiral artery rings (SAR) devoid of SM was measured ex vivo upon exposure to l-NAME alone; l-NAME and ET1 representing the combined contractile effect of both ET1 receptors; l-NAME with ET1 and ETA antagonist, representing the isolated contractile effect via ETB. In another experiment we administered SNAP to KCl precontracted SAR. Statistical analysis was performed using 2-way mixed ANOVA and repeated measures. RESULTS: l-NAME reduced LSA by 2.22%, 95% CI [0.83%, 3.60%] compared with control. ET1 and l-NAME reduced LSA immediately, compared with a plateau at 60min by ET1 alone. The isolated ET1 constrictive effect via ETB, reduced LSA by 5.94%; 95% CI [3.47%, 8.41%], significantly more than that obtained via ETA following 36 min of the experiment by 0.88%; 95%CI [0.09%, 1.67%]. Addition of KCl reduced LSA by 11.9%, 95% CI [9.6%, 14.1%]. Addition of SNAP increased LSA by 3.0%, 95% CI [1.7%, 4.3%]. CONCLUSIONS: EVasT of the rat remodeled spiral artery react to ET1 and KCl similar to vascular SM: contract via both ET1 receptors and KCl and relax by ET1 via ETB and by SNAP. This phenomenon may play a role in rat models of gestational vasoactive systems dysregulation.

Effects of antihypertensive and triglyceride-lowering agents on hepatic copper concentrations in rats with fatty liver disease.

Copper deficiency had been suggested to link between fructose-enriched diet (FED) and the development of non-alcoholic fatty liver disease (NAFLD). In this study, we characterized changes in hepatic copper concentrations and hepatic oxidative milieu, in rats with the metabolic syndrome and NAFLD as a result of FED with pharmacological manipulations to reduce blood pressure or plasma triglycerides. Changes in plasma and hepatic copper concentrations were correlated with changes observed in the immunohistochemical hepatic expression of copper-zinc-superoxide dismutase (CuZnSOD; SOD1), metallothionein (MT) and nitrotyrosine (NITT). FED administration was associated with a 2.2-fold reduction in hepatic copper concentrations, a decrease in the hepatic SOD1 expression, disappearance of the hepatic MT expression and increase in the hepatic NITT expression. Bezafibrate administration restored the hepatic copper concentrations and the hepatic SOD1 expression to levels that were observed in the control rats. A significant positive correlation between hepatic copper concentrations and the values of hepatic SOD1 expression of each animal included in this study was found. Administration of either captopril or bezafibrate increased hepatic MT expression, however, to levels that were lower than those observed in the control group. Administration of either amlodipine, or captopril or bezafibrate to the FED rats, had no effect on hepatic NITT expression. NAFLD development in FED rats is associated with a decrease in hepatic copper concentrations that is associated with a decrease in the hepatic SOD1 expression. Bezafibrate administration increases hepatic copper concentrations and restores the hepatic SOD1 expression.