Endothelin and platelet-activating factor: significance in the pathophysiology of ischemia/reperfusion-induced fetal growth restriction in the rat

Comparison of ET-1 and eNOS expressions in yak testes at different developmental stages

Yak has strong adaptability to plateau hypoxia environment. However, the endothelin-1 (ET-1) and endothelial nitric oxide synthase (eNOS) are important regulators in blood oxygen transportation. Yak testes: newborn (3 days), young (1 years), adult (4 years) and old (9 years) were collected for microscopic analyses using haematoxylin and eosin staining (H&E), immunohistochemistry and immunofluorescence, as well as Western blot to compare the expression of ET-1 and eNOS. Furthermore, the levels of ET-1 mRNA and eNOS mRNA was detected by real-time quantitative polymerase chain reaction (RT-qPCR). The results showed that ET-1 mRNA and eNOS mRNA in old yaks were higher than other developmental stages (p < .01). And the levels of ET-1 and eNOS protein increased with age. Immunohistochemistry and immunofluorescence showed that ET-1 and eNOS were mainly localized in gonocytes and spermatogenic membrane of newborn yaks. These two factors were expressed in both Leydig cells of young yaks and endothelial cells of adult yaks. In old yaks, ET-1 was mainly expressed in Sertoli cells, while eNOS was obviously positive in capillaries and Leydig cells. Therefore, the positive results of ET-1 and eNOS in gonocyte and spermatogenic basement were closely related to the development of testes. The expression of Leydig and Sertoli cells indicated that they played an important role in testes function. The expression in endothelial cells or interstitial capillaries, suggesting that they are involved in the regulation of microcirculation in yak testes. This study could provide clues for further revealing the regulation of yak testicular blood vessels in alpine cold and hypoxic environments.

Prenatal interventions for fetal growth restriction in animal models: A systematic review

Fetal growth restriction (FGR) in human pregnancy is associated with perinatal mortality, short- and long-term morbidities. No prenatal therapy is currently established despite decades of research. We aimed to review interventions in animal models for prenatal FGR treatment, and to seek the next steps for an effective clinical therapy. We registered our protocol and searched MEDLINE, Embase, and The Cochrane Library with no language restrictions, in accordance with the PRISMA guideline. We included all studies that reported the effects of any prenatal intervention in animal models of induced FGR. From 3257 screened studies, 202 describing 237 interventions were included for the final synthesis. Mice and rats were the most used animals (79%) followed by sheep (16%). Antioxidants (23%), followed by vasodilators (18%), nutrients (14%), and immunomodulators (12%) were the most tested therapy. Two-thirds of studies only reported delivery or immediate neonatal outcomes. Adverse effects were rarely reported (11%). Most studies (73%), independent of the intervention, showed a benefit in fetal survival or birthweight. The risk of bias was high, mostly due to the lack of randomization, allocation concealment, and blinding. Future research should aim to describe both short- and long-term outcomes across various organ systems in well-characterized models. Further efforts must be made to reduce selection, performance, and detection bias.

Serum metabolic profile characteristics of offspring rats before and after birth caused by prenatal caffeine exposure

Epidemiological investigations have confirmed that prenatal caffeine intake could increase the incidence rate of intrauterine growth retardation (IUGR) and multiple diseases after birth. Based on liquid chromatography-mass spectrometry, we analyzed serum metabolic profiles of offspring rats before and after birth in IUGR model induced by prenatal caffeine exposure (PCE). We discovered that differential metabolites in PCE fetuses mainly manifested as amino acids and lipid metabolism. In adulthood, PCE offspring showed less and inconsistent types of differential metabolites compared to those in utero, which still exhibited gender differences. The main differential metabolites induced by PCE, including phospholipids, platelet-activating factor, arachidonic acid, bile acid, sphingosine-1-phosphoric acid, indoxyl sulfuric acid, and cortexolone, may participate in the pathological and physiological processes of organ toxicities. This study demonstrated the short- and long-term developmental toxicity and gender differences of caffeine, providing new ideas for exploring the early warning and drug intervention targets of IUGR offspring.

Fetal Growth Restriction Induced by Transient Uterine Ischemia-Reperfusion: Differential Responses in Different Mouse Strains

We characterized fetal and placental growth and uterine and placental inflammation in pregnant C3H/HeOuJ and C57BL/6J mice (strains with different sensitivities to metabolic and circulatory pathologies), using different uterine ischemia/reperfusion (I/R) protocols, to establish and refine a murine model of I/R-induced fetal growth restriction (FGR). Pregnant C3H/HeOuJ mice on gestation day 15 were subjected to unilateral uterine I/R by (1) total blood flow restriction (TFR) by occlusion of the right ovarian and uterine arteries for 30 minutes, (2) partial flow restriction (PFR) by occlusion of only the right ovarian artery for 30 minutes, or (3) sham surgery. Pregnant C57BL/6J mice were treated the same, but on gestation day 14 and with TFR for only 5 minutes due to high sensitivity of C57BL/6J mice to I/R. Four days post-I/R, the animals were euthanized to determine fetal and placental weight and fetal loss and to assay placental myeloperoxidase (MPO) activity. In C3H/HeOuJ mice, TFR/30 minutes induced significantly ( P < .05) lower fetal and placental weights and higher placental MPO activity, compared to controls. The PFR/30 minutes produced the same effects except placental weights were not reduced. In contrast, in C57BL/6J mice, TFR for only 5 minutes was sufficient to induce FGR and increase fetal loss; while PFR/30 minutes lowered fetal but not placental weights and increased fetal loss but not placental MPO activity. In summary, we present the first published model of I/R-induced FGR in mice. We find that mice of different strains have differing sensitivities to uterine I/R, therefore differing I/R response mechanisms.

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 ET_B and by SNAP. This phenomenon may play a role in rat models of gestational vasoactive systems dysregulation.

Endothelin-1 Attenuates Apoptosis in Cultured Trophoblasts From Term Human Placentas

The authors test the hypothesis that endothelin-1 (ET-1) modulates apoptosis in human term trophoblasts. Primary cultures of cytotrophoblasts from term human placentas (n = 5) were cultured for 16 hours total or 24 hours prior to harvest at 72 hours in atmospheres of <1%, 8%, and 20% oxygen, in the presence of 10% serum, ET-1 (1-100 pmol/mL), both, or neither. The apoptotic cleavage products of poly-ADP-ribose polymerase and cytokeratin 18 filaments were quantified by Western analysis and immunocytochemistry. The expression of BAD, pBAD-serine 112, p53, and 2 isoforms of MDM2 were quantified by immunoblotting, and endothelin A and B receptors were analyzed by immunocytochemistry. Compared to vehicle control, increasing concentrations of ET-1 reduce by 3- to 6-fold the level of apoptosis in cytotrophoblasts exposed to serum-free conditions at 20% oxygen. Similarly, syncytiotrophoblast cultures grown for 24 hours without serum in 100 pmol/mL ET-1 show a 3-fold lower level of apoptosis compared with vehicle control. ET-1 significantly reduces apoptosis in cultures exposed to 20% oxygen but not in cultures exposed to 8% or 1% oxygen. The effect of ET-1 on apoptosis in 20% oxygen is accompanied by reduced p53 expression and is correlated with enhanced expression of endothelin B receptor, compared to cultures in 8% or 1% oxygen. ET-1 reduces apoptosis in cultured human trophoblasts, and this finding suggests a role for ET-1 in protecting trophoblasts against injury.

Endothelin Receptor A Antagonism Prevents Damage to Glycogen-Rich Placental Cells Following Uterine Ischemia-Reperfusion in the Rat

Fetal growth restriction (FGR) is a common cause of perinatal morbidity and mortality. Suboptimal uteroplacental perfusion is the most commonly identified cause of FGR, and ischemic lesions are often observed in placentas from pregnancies complicated by FGR. Ischemia followed by reperfusion is a strong stimulus to the production of the vasoconstrictor endothelin 1 (ET-1) which has been implicated in several models of FGR. We sought to investigate oxidative stress and placental morphology in a rat model of ischemia-reperfusion (I/R)-induced FGR and to evaluate the role of ET-1 in the observed pathology. Unilateral uterine I/R (30 min) was conducted, with and without simultaneous ET-1 receptor A (ET_A) antagonism, on pregnant rats at gestation day 17. Placental tissues collected 24 hours later were evaluated immunohistochemically for oxidative damage. Tissue pathology was studied using quantitative morphometry. Glycogen-rich cellular areas in the placental junctional zone exhibited only 50% intact cells (P < .001) in both uterine horns following unilateral I/R, compared to controls. ET_A antagonism prevented damage to the glycogen-rich cellular areas. Oxidative damage in response to I/R was prominent in the labyrinthine layer in both uterine horns and was not affected by ET_A antagonism. We conclude that glycogen-rich cellular areas of the placental junctional zone are particularly vulnerable to damage from uterine I/R in the rat. Nucleic acid oxidative damage in the labyrinth is a prominent effect of uterine I/R. ET_A antagonism protects placental cellular integrity during I/R challenge but does not prevent nucleic acid oxidative damage.

Endothelin Receptor A Antagonism and Fetal Growth in Endothelial Nitric Oxide Synthase Gene Knockout Maternal and Fetal Mice

Fetal growth restriction (FGR) is commonly associated with perinatal morbidity and mortality. Nitric oxide (NO) deficiency increases endothelin-1 (ET-1) production, and this increased ET-1 may contribute to the pathophysiology of NO deficiency-induced FGR. Using an endothelial NO synthase knockout mouse model of FGR, we sought to determine (a) the relative importance of maternal versus conceptus (fetal and placental) NO deficiency and (b) the contribution of ET-1 to the pathogenesis of FGR in this model. Fetal growth restriction occurred both with NO-deficient conceptuses in the setting of maternal NO production and with maternal NO deficiency in the setting of NO-producing conceptuses. Placental ET-1 expression was increased in NO-deficient dams, ET receptor A (ETA) production increased in endothelial nitric oxide synthase(+/-) placentas, and antagonism of ETA prevented FGR. These results demonstrate that both maternal and conceptus NO deficiency can contribute to FGR and suggest a role for ETA antagonists as therapeutic agents in FGR.

Maternal omega-3 fatty acid intake increases placental labyrinthine antioxidant capacity but does not protect against fetal growth restriction induced by placental ischaemia-reperfusion injury

Placental oxidative stress plays a key role in the pathophysiology of several placenta-related disorders. Oxidative stress occurs when excess reactive oxygen species (ROS) damages cellular components, an outcome limited by antioxidant enzymes; mitochondrial uncoupling protein 2 (UCP2) also limits ROS production. We recently reported that maternal dietary omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementation reduced placental oxidative damage and enhanced fetal and placental growth in the rats. Here, we examined the effect of n-3 PUFAs on placental antioxidant defences and whether n-3 PUFA supplementation could prevent growth restriction induced by placental ischaemia-reperfusion (IR), a known inducer of oxidative stress. Rats were fed either standard or high-n-3 PUFA diets from day 1 of pregnancy. Placentas were collected on days 17 and 22 in untreated pregnancies (term=day 23) and at day 22 following IR treatment on day 17. Expression of several antioxidant enzyme genes (Sod1, Sod2, Sod3, Cat, Txn1 and Gpx3) and Ucp2 was measured by quantitative RT-PCR in the placental labyrinth zone (LZ) and junctional zone (JZ). Cytosolic superoxide dismutase (SOD), mitochondrial SOD and catalase (CAT) activities were also analyzed. Maternal n-3 PUFA supplementation increased LZ mRNA expression of Cat at both gestational days (2- and 1.5-fold respectively; P<0.01) and female Sod2 at day 22 (1.4-fold, P<0.01). Cytosolic SOD activity increased with n-3 PUFA supplementation at day 22 (1.3-fold, P<0.05). Sod1 and Txn1 expression decreased marginally (30 and 22%, P<0.05). JZ antioxidant defences were largely unaffected by diet. Despite increased LZ antioxidant defences, maternal n-3 PUFA supplementation did not protect against placental IR-induced growth restriction of the fetus and placental LZ.

Impact of toll-like receptor 4 deficiency on the response to uterine ischemia/reperfusion in mice

Our objective was to determine the role of toll-like receptor 4 (TLR4) in uterine ischemia/reperfusion (I/R)-induced fetal growth restriction (FGR). Pregnant TLR4-deficient and wild-type mice were subjected to I/R or a sham procedure. Fetal and placental weights were recorded and tissues were collected. Pep-1 (inhibits low-molecular-weight hyaluronan (LMW-HA) binding to TLR4) was used to determine whether LMW-HA-TLR4 interaction has a role in FGR. TLR4-deficient mice exhibited significantly lower baseline fetal weights compared with wild-type mice (P<0.05), along with extensive placental calcification that was not present in wild-type mice. Following I/R, fetal and placental weights were significantly reduced in wild-type (P<0.05) but not in TLR4-deficient mice. However, I/R increased fetal loss (P<0.05) only in TLR4-deficient mice. Corresponding with the reduced fetal weights, uterine myeloperoxidase activity increased in wild-type mice (P<0.001), indicating an inflammatory response, which was absent in TLR4-deficient mice. TLR4 was shown to have a regulatory role for two anti-inflammatory cytokines: interferon-B1 decreased only in wild-type mice (P<0.01) and interleukin-10 increased only in TLR4-deficient mice (P<0.001), in response to I/R. Pep-1 completely prevented I/R-induced FGR (P<0.001), indicating a potential role for the endogenous TLR4 ligand LMW-HA in I/R-induced FGR. In conclusion, uterine I/R in pregnancy produces FGR that is dependent on TLR4 and endogenous ligand(s), including breakdown products of HA. In addition, TLR4 may play a role in preventing pregnancy loss after uterine I/R.

Unilateral uterine ischemia/reperfusion-induced bilateral fetal loss and fetal growth restriction in a murine model require intact complement component 5

The role of complement in ischemia/reperfusion-induced fetal growth restriction and fetal loss is unknown. C5-deficient or wild type timed-pregnant mice were subjected to unilateral uterine ischemia/reperfusion on gestation day 13, either by (1) partial flow restriction by right ovarian artery clamping for 30 min, or (2) total flow restriction by clamping both ovarian and uterine arteries for 5 min. Ischemia/reperfusion-challenged pregnancy outcomes were compared to sham-operated controls 5 days later. Ischemia/reperfusion-treated wild type mice exhibited significantly increased bilateral fetal loss, which was greater in total flow restriction than in partial flow restriction, and decreased fetal weights, which were the same in total flow restriction and partial flow restriction for the surviving fetuses. Placental weights were unchanged by treatments. Ischemia/reperfusion increased uterine, but not placental, myeloperoxidase activity, which correlated with fetal loss. In contrast, C5-deficient mice were protected from both fetal growth restriction and fetal loss, and exhibited no increase in myeloperoxidase activity. These results demonstrate that unilateral uterine ischemia/reperfusion results in bilateral fetal loss and fetal growth restriction, mediated by a systemic mechanism. In the current model, this pathological process is completely dependent on intact complement component 5.

The significance of endothelin in platelet-activating factor-induced fetal growth restriction

The significance of endothelin-1 (ET-1) in platelet-activating factor (PAF)-induced fetal growth restriction (FGR) was evaluated in timed-pregnant rats receiving intravenous carbamyl-PAF (c-PAF; 0.5, 1.0, or 2.5 µg/kg per h) or vehicle, with or without ET-1 receptor A (ET(A)) antagonist (10 or 20 mg/kg per d) for 7 days beginning on gestation day 14. Tissues were collected on day 21. Carbamyl-PAF reduced fetal weights dose dependently. Placental weights were significantly reduced but not dose dependently. ET(A) antagonism prevented FGR at the 0.5, but not the 1.0 and 2.5 µg/kg per h c-PAF doses. Correspondingly, placental, but not uterine, preproET-1 messenger RNA (mRNA) expression (determined by reverse transcription-polymerase chain reaction) was increased at 0.5 µg/kg per h but not at higher c-PAF doses. In summary, c-PAF infusion results in fetal and placental growth restriction in the rat. At low doses of c-PAF, ET-1 is central to the pathophysiology of PAF-induced FGR. At higher c-PAF doses, FGR is induced by mechanisms other than ET-1 action.

Hyperinsulinemia increases placenta endothelin-converting enzyme-1 expression in trophoblasts

BACKGROUND

Exogenous hyperisulinemia causes pregnancy, induced hypertension and intrauterine growth restriction (IUGR) in pregnant rats. Hyperinsulinemia may increase production of endothelin-1 (ET-1), produced by sequential proteolysis of the big endothelin by the endothelin-converting enzyme (ECE)-1, the expression of which is examined here in the placenta, kidney, heart, and liver.

METHODS

Rats were rendered hyperinsulinemic by subcutaneous insulin pellet, mated and followed to the twenty-first day of pregnancy. They were then killed, and their fetuses and placentas were examined.

RESULTS

Hyperinsulinemic dams (HD) had higher blood pressure (BP) (130 ± 17 mm Hg in HD vs. 115 ± 16 mm Hg in normal pregnant dams (NPD), P < 0.05), lower placenta weight (0.44 ± 0.08 g in HD vs. 0.47 ± 0.08 NPD, P < 0.05) and lower fetus weight: males 4.9 ± 0.4 g in HD vs. 5.5 ± 0.4 g in NPD, P < 0.0001; females 4.7 ± 0.4 g in HD vs. 5.2 ± 0.4 g in NPD (P < 0.0001). ECE-1 expression as determined by western blot was significantly increased in the placenta and its implantation site, i.e., the mesometrial triangle (MT) of HD by 46 and 48%, respectively. In the kidney and heart of HD ECE-1, protein expression was increased by 230 and 220%, respectively, but its level in the liver was similar in both groups. Immunohistochemical staining revealed ECE-1 expression in endothelial cells and trophoblastic cells of the placenta and MT. Endothelin receptor A (ET-A), a mediator of vasoconstriction by ET-1, was also expressed in the endothelium and in trophoblasts of the placenta and MT. The expression of both ECE-1 and ET-A, as measured by automated image analysis, was generally stronger in placentas of HD.

CONCLUSIONS

ECE-1 and ET-A are expressed in the trophoblastic cells of the placenta and MT. This may affect local endothelin levels, BP and IUGR.

Hypertension induced by episodic reductions in uteroplacental blood flow in gravid rat

BACKGROUND

The etiology of preeclampsia remains unclear. Animal modeling of preeclampsia has been useful; however, no model to date represents episodic changes in uteroplacental blood flow that may occur in preeclampsia.

OBJECTIVE

To develop a gravid rat model characterized by episodic reductions in uteroplacental blood flow.

METHOD

Pregnant Sprague Dawley rats were used and subjected to SHAM, reduced uterine perfusion pressure (RUPP), or aortic occlusion on gestational Day 14. Aortic occlusion surgery consisted of implantation of a silastic vascular occluder around the abdominal aorta and silver clips around the uterine-ovarian arteries. Aortic occlusion animals were subjected to five consecutive days of occlusion (40% reduction) each session lasting 1 h. On Day 21, maternal mean arterial pressure (MAP) and fetal morphology were assessed. For isolated blood vessels, resistance-sized mesenteric arteries were harvested and mounted on a pressure arteriograph.

RESULT

Occluder animals experienced a 10 mmHg rise in MAP as compared to SHAM (p < 0.05), and RUPP MAP was significantly increased as compared to control subjects (p < 0.05). Pups from Occluder animals exhibited a decrease in fetal weight as compared to SHAM (p < 0.05), but an increase in fetal weight as compared to RUPP (p < 0.05). Myogenic reactivity of second-order mesenteric arteries increased in Occluder animals as compared to SHAM (p < 0.05), but were similar to that of RUPP.

CONCLUSION

Episodic reductions in uteroplacental blood flow play a crucial role in the altered vascular reactivity seen in Occluder animals and may represent a new model to investigate the mechanisms associated with episodic reductions in uteroplacental blood flow in pathological pregnancies.

Impact of endothelin A receptor antagonist selectivity in chronic nitric oxide synthase inhibition-induced fetal growth restriction in the rat

OBJECTIVE

Endothelin receptor A (ETA) antagonism improves fetal and placental growth and placental perfusion on days 1 and 4, but not day 7 of a 7-day infusion of a nitric oxide synthase (NOS) inhibitor. Our purpose was to evaluate the significance of the degree of ETA antagonist selectivity on uteroplacental perfusion and fetal growth on day 7 of chronic NOS inhibition.

METHODS

Timed-pregnant rats were treated with the NOS inhibitor nitro-L-arginine methyl ester (L-NAME, 2.5 mg/kg/h) with and without one of the following ETA antagonists or their respective vehicles for 7 days beginning on day 14 of gestation: A-127722 (2,000-fold selective for ETA over ETB), FR139317 (8,000-fold ETA-selective), or ABT-546 (28,000-fold ETA-selective). Uterine and placental perfusion, as well as fetal and placental weight, was evaluated at the 7th day of treatment (gestation day 21).

RESULTS

L-NAME administration resulted in a significant reduction in uterine and placental perfusion as well as fetal and placental growth. In the setting of NOS inhibition, ETA antagonism did not improve uterine or placental perfusion or fetal growth after 7 days of infusion irrespective of the degree of selectivity of the antagonist used.

CONCLUSIONS

ETA antagonism, irrespective of the degree of receptor selectivity, does not improve fetal growth or uteroplacental perfusion on day 7 of chronic NOS inhibition.

Pyometra in an inguinal hernia in a bitch

Pyometra in an inguinal hernia was diagnosed in a 10-year-old intact cross-bred bitch which had had dysorexia, depression and inguinal distension. The hernia contained caudal portions of the two uterine horns, uterine cervix and cranial part of the vagina. As the organs were enlarged and full of pus, manual attempt to push back the uterine horns and the vagina in the abdominal cavity through the inguinal canal was unsuccessful. Herniated uterine horns were ligated and cut in their median portion, so it became possible to remove the cervix and the caudal portion of the horns through the hernial orifice, and the ovaries and the cranial part of the horns through a peritoneal midline incision. This bitch was not intended for breeding purposes and, given the presence of a huge pyometra associated with an inguinal hernia, an ovario-hysterectomy was recommended. Uterine herniation should be considered as a differential diagnosis of a caudal lateral inguinal mass. When pushing the uterus back in the abdominal cavity is impossible, a surgical procedure should be performed to detect ischemia–reperfusion injury and/or a septic risk.

The fetal response to chronic placental insufficiency

Fetal growth restriction is most commonly caused by failure of the placenta to meet the increasing demands for oxygen and substrate of the developing fetus, resulting in common fetal compensatory responses. Understanding these responses is helpful in developing a management strategy that will optimize pregnancy outcome.