Oxidative stress induced by tert-butylhydroperoxide interferes with the placental transport of glucose: in vitro studies with BeWo cells

Gallic acid markedly stimulates GLUT1-mediated glucose uptake by the AsPC-1 pancreatic cancer cell line

Phenolic acids are recognized as chemopreventive and chemotherapeutic agents. Altered glucose and glutamine metabolism are recognized hallmarks of cancer cells. We aimed to test the influence of phenolic acids on glucose and glutamine cellular uptake by a breast (MCF-7) and a pancreatic (AsPC-1) cancer cell line. Several phenolic acids (caffeic, ferrulic, proctocatechuic, coumaric and gallic acid) affected ³H-glutamine and/or ³H-deoxy-d-glucose (³H-DG) uptake. Gallic acid (100 µM) caused a 3-fold increase in ³H-DG uptake by AsPC-1 cells, associated with a 3.7-fold increase in lactic acid production. Gallic acid stimulated GLUT1-mediated ³H-DG uptake and increased the affinity of this transporter for ³H-DG. We further verified that gallic acid does not change GLUT1 transcription rates and cellular redox state and that its effect does not involve PI3K, mTOR and MAP kinases and is not associated with a proproliferative effect. Gallic acid also increased ³H-DG uptake by MCF-7 cells, although less potently. Further investigation is necessary to elucidate the cellular pathways involved in this effect of gallic acid.

Immunohistochemical evaluation of glucose transporter protein-1 density in the placenta in preeclampsia patients and its association with intrauterine growth retardation

Background/Aim: Preeclampsia (PE) complicates 2–8% of all pregnancies worldwide. Placental malperfusion and dysfunction are observed in PE. The supply of glucose, the main energy substrate for the fetus and placenta, is regulated by placental expression and activity of specific glucose transporter proteins (GLUTs), primarily GLUT1. GLUT1 expression is affected by uteroplacental malperfusion and oxidative stress, which are important components of PE. Very few studies have investigated GLUT1 expression in preeclamptic placentas. In this study, we aimed to compare GLUT1 staining intensity in the terminal villi of the placenta in healthy subjects and patients with E-PE or L-PE and determine whether there was a relationship between GLUT1 staining intensity and IUGR. Methods: This case-control study was carried out in our hospital’s gynecology and obstetrics clinic, a tertiary center for perinatology cases. A total of 94 placentas, 47 of which were preeclamptic and 47 were from uneventful pregnancies (controls), were included in the study. PE was diagnosed according to the American College of Obstetrics and Gynecologists 2019 diagnostic criteria for gestational hypertension and PE. Placentas in the control group were obtained from pregnancies without maternal, placental, or fetal pathology and resulted in spontaneous idiopathic preterm or term delivery. The PE group was divided into two subgroups as early onset PE (E-PE [≤33+6 gestational week]) and late-onset PE (L-PE [≥34+0 gestational week]), according to the gestational week of PE onset. Sections prepared from placental tissues were stained for GLUT-1 by immunohistochemical method. Slides were evaluated by light microscopy, and each slide was scored from 0 to 4 to determine the staining intensity. The results were compared between the control and PE group/PE sub-groups. Results: GLUT1 scores were significantly higher in both early- and late-onset PE subgroups compared to controls (P < 0.001 for both). In the late-onset PE subgroup, GLUT1 scores were significantly higher in those with severe PE features than those without them (P = 0.039). While intrauterine growth restriction (IUGR) was not found in any cases in the control group, IUGR was present in 11 (23.4%) of 47 pregnant women with PE, including eight (53.3%) of the 15 pregnant women with early-onset PE and 3 (9.38%) of the 32 pregnant women with late-onset PE. GLUT1 scores were similar in placentas obtained from pregnant women who had PE with and without IUGR (P = 0.756). In the late-onset PE subgroup, GLUT1 scores were correlated negatively with maternal body mass index (r = -0.377, P = 0.033) and positively with placental weight-to-fetal weight ratio (r = 0.444, P = 0.011). Conclusions: Our findings show that GLUT1 expression might be increased due to placental adaptation to new conditions in PE and, thus, is unlikely to be the main factor in PE-related IUGR.

Advanced glycation end products increased placental vascular permeability of human BeWo cells via RAGE/NF-kB signaling pathway

OBJECTIVE

This study aimed to investigate the mechanisms of advanced glycation end products (AGEs) on cell tight conjunction and placental vascular permeability in BeWo cells.

STUDY DESIGN

Monolayer permeability assay and transmission electron microscopy were employed to reveal the transformation of the placental vascular permeability and cell tight conjunction. Immunofluorescence, western blot and RT-qPCR were adopted to determine the protein and mRNA levels. Anti-RAGE and NF-kB inhibitor (PDTC) were used to inactivate the RAGE/NF-kB signaling pathway.

RESULTS

AGEs significantly decreased trans-epithelial electrical resistance (TEER), while increased paracellular permeability (P <  0.05). TEM showed that AGEs made cell junction loose. AGEs inhibited ZO-1 and Occludin expressions, while anti-RAGE or PDTC partially restored their levels. AGEs also significantly increased mRNA RAGE and NF-kB expressions in BeWo cells (P <  0.05), and their expressions were inhibited by anti-RAGEy or PDTC.

CONCLUSION

AGEs could reduce the expressions of ZO-1 and Occludin by activating RAGE/NF-kB signaling pathway, thus increasing placental vascular permeability.

Maternal 25-Hydroxyvitamin D Deficiency Promoted Metabolic Syndrome and Downregulated Nrf2/CBR1 Pathway in Offspring

Metabolic syndrome is a disorder of energy use and storage, which is characterized by central obesity, dyslipidemia, and raised blood pressure and blood sugar levels. Maternal 25-hydroxyvitamin D deficiency is known to cause metabolic changes, chronic disease, and increased adiposity in adulthood. However, the underlying mechanism of induced metabolic syndrome (MetS) in the offspring in vitamin D deficient pregnant mothers remains unclear. We identified that maternal 25-hydroxyvitamin D deficiency enhances oxidative stress, which leads to the development of MetS in the mother and her offspring. Further, immunohistochemical, Western blotting, and qRT-PCR analyses revealed that maternal 25-hydroxyvitamin D deficiency inhibited the activation of the Nrf2/carbonyl reductase 1 (CBR1) pathway in maternal placenta, liver, and pancreas, as well as the offspring's liver and pancreas. Further analyses uncovered that application of 25-hydroxyvitamin D activated the Nrf2/CBR1 pathway, relieving the oxidative stress in BRL cells, suggesting that 25-hydroxyvitamin D regulates oxidative stress in offspring and induces the activation of the Nrf2/CBR1 pathway. Taken together, our study finds that maternal 25-hydroxyvitamin D deficiency is likely to result in offspring's MetS probably via abnormal nutrition transformation across placenta. Depression of the Nrf2/CBR1 pathway in both mothers and their offspring is one of the causes of oxidative stress leading to MetS. This study suggests that 25-hydroxyvitamin D treatment may relieve the offspring's MetS.

Glut 1 in Cancer Cells and the Inhibitory Action of Resveratrol as A Potential Therapeutic Strategy

An important hallmark in cancer cells is the increase in glucose uptake. GLUT1 is an important target in cancer treatment because cancer cells upregulate GLUT1, a membrane protein that facilitates the basal uptake of glucose in most cell types, to ensure the flux of sugar into metabolic pathways. The dysregulation of GLUT1 is associated with numerous disorders, including cancer and metabolic diseases. There are natural products emerging as a source for inhibitors of glucose uptake, and resveratrol is a molecule of natural origin with many properties that acts as antioxidant and antiproliferative in malignant cells. In the present review, we discuss how GLUT1 is involved in the general scheme of cancer cell metabolism, the mechanism of glucose transport, and the importance of GLUT1 structure to understand the inhibition process. Then, we review the current state-of-the-art of resveratrol and other natural products as GLUT1 inhibitors, focusing on those directed at treating different types of cancer. Targeting GLUT1 activity is a promising strategy for the development of drugs aimed at treating neoplastic growth.

Placental mitochondria adapt developmentally and in response to hypoxia to support fetal growth

Mitochondria respond to a range of stimuli and function in energy production and redox homeostasis. However, little is known about the developmental and environmental control of mitochondria in the placenta, an organ vital for fetal growth and pregnancy maintenance in eutherian mammals. Using respirometry and molecular analyses, the present study examined mitochondrial function in the distinct transport and endocrine zones of the mouse placenta during normal pregnancy and maternal inhalation hypoxia. The data show that mitochondria of the two zones adopt different strategies in modulating their respiration, substrate use, biogenesis, density, and efficiency to best support the growth and energy demands of fetoplacental tissues during late gestation in both normal and hypoxic conditions. The findings have important implications for environmentally induced adaptations in mitochondrial function in other tissues and for compromised human pregnancy in which hypoxia and alterations in placental mitochondrial function are associated with poor outcomes like fetal growth restriction.

Human placental glucose transport in fetoplacental growth and metabolism

While efficient glucose transport is essential for all cells, in the case of the human placenta, glucose transport requirements are two-fold; provision of glucose for the growing fetus in addition to the supply of glucose required the changing metabolic needs of the placenta itself. The rapidly evolving environment of placental cells over gestation has significant consequences for the development of glucose transport systems. The two-fold transport requirement of the placenta means also that changes in expression will have effects not only for the placenta but also for fetal growth and metabolism. This review will examine the localization, function and evolution of placental glucose transport systems as they are altered with fetal development and the transport and metabolic changes observed in pregnancy pathologies.

The effect of oxidative stress upon intestinal sugar transport: an in vitro study using human intestinal epithelial (Caco-2) cells

The pathogenesis of various gastrointestinal diseases, including gastrointestinal cancers and inflammatory bowel disease, is associated with increased oxidative stress levels. We aimed to investigate the effect of oxidative stress induced by tert-butylhydroperoxide (TBH) on the uptake of 3H-deoxy-d-glucose (3H-DG) and 14C-fructose by the human intestinal Caco-2 cell line. TBH (500 μM; 24 h) increased lipid peroxidation (TBARS) levels and was not cytotoxic. TBH (500 μM; 24 h) increased uptake of both low (SGLT1-mediated) and high concentrations (SGLT1- and GLUT2-mediated) of 3H-DG, but did not affect absorption of 14C-fructose (GLUT2- and GLUT5-mediated). The polyphenol chrysin abolished the increase in TBARS levels and the increase in uptake of both low and high concentrations of 3H-DG induced by TBH. On the other hand, TBH blocked the inhibitory effect of chrysin on 14C-fructose uptake. 3H-DG uptake, but not 14C-fructose uptake, was sensitive to sweet taste receptor (STRs) inhibition (with lactisole). The inhibitory effect of lactisole in relation to uptake of 3H-DG (10 nM) (SGLT1-mediated), but not in relation to uptake of 3H-DG (50 mM) (SGLT1- and GLUT2-mediated), was abolished in the presence of TBH. So, these results show that the stimulatory effect of STRs on SGLT1-mediated transport is dependent on oxidative stress levels. In conclusion, this work shows that uptake of both 3H-DG and 14C-fructose is sensitive to oxidative stress levels. Moreover, it suggests that the three distinct transporters involved in the intestinal absorption of glucose and fructose (SGLT1, GLUT2 and GLUT5) have different sensitivities to oxidative stress levels, SGLT1 being the most sensitive and GLUT5 the least.

Oxidative Stress in Preeclampsia and Placental Diseases

Preeclampsia is a persistent hypertensive gestational disease characterized by high blood pressure and proteinuria, which presents from the second trimester of pregnancy. At the cellular level, preeclampsia has largely been associated with the release of free radicals by the placenta. Placenta-borne oxidative and nitrosative stresses are even sometimes considered as the major molecular determinants of the maternal disease. In this review, we present the recent literature evaluating free radical production in both normal and pathological placentas (including preeclampsia and other major pregnancy diseases), in humans and animal models. We then assess the putative effects of these free radicals on the placenta and maternal endothelium. This analysis was conducted with regard to recent papers and possible therapeutic avenues.

The effect of oxidative stress induced by tert-butylhydroperoxide under distinct folic acid conditions: An in vitro study using cultured human trophoblast-derived cells

Preeclampsia is a pregnancy disorder characterized by high maternal blood pressure, fetal growth restriction and intrauterine hypoxia. Folic acid is a vitamin required during pregnancy. In this work, we investigated the relationship between preeclampsia and the intake of distinct doses of folic acid during pregnancy. Considering that preeclampsia is associated with increased placental oxidative stress levels, we investigated the effect of oxidative stress induced by tert-butylhydroperoxide (TBH) in human trophoblast-derived cells cultured upon deficient/low, physiological and supra-physiological folic acid levels. The negative effect of TBH upon thiobarbituric acid reactive substances (TBARS), total, reduced and oxidized glutathione, cell viability, cell proliferation, culture growth and cell migration was more marked under folic acid excess. This study suggests more attention on the dose administered, and ultimately, on the overall folic acid levels during pregnancy, in the context of preeclampsia risk.

Green tea (-)-epigallocatechin gallate inhibits the growth of human villous trophoblasts via the ERK, p38, AMP-activated protein kinase, and protein kinase B pathways

Green tea catechins, especially (-)-epigallocatechin gallate (EGCG), have been reported to circulate in the placenta of animals and blood of humans after consumption. Whether EGCG regulates activity of human villous trophoblasts (HVT) is unknown. This study investigated the pathways involved in EGCG modulation of trophoblast mitogenesis. EGCG inhibited trophoblast proliferation in a dose-dependent and time-dependent manner, as indicated by the number of cells and incorporation of bromodeoxyuridine (BrdU). EGCG was more effective than other green tea catechins in inhibiting cell growth. EGCG also increased the phosphorylation of the MAPK pathway proteins, ERK1/2, and p38, but not JNK. Furthermore, EGCG had no effects on the total amounts of ERK1/2, p38 MAPK, and JNK proteins. This suggests that EGCG selectively affects particular MAPK subfamilies. Pretreatment with specific inhibitors of ERK1/2, p38 MAPK, and AMP-activated protein kinase (AMPK) antagonized EGCG-induced decreases in both cell number and BrdU incorporation. These inhibitors also blocked EGCG-induced increases in the levels of phospho-ERK1/2, phospho-p38, and phospho-AMPK proteins, respectively. Moreover, EGCG was similar to the phosphatidylinositol 3-kinase inhibitors wortmannin and LY-294002 to decrease protein kinase B (AKT) phosphorylation, cell number, and BrdU incorporation. These data imply that EGCG inhibits the growth of HVT through the ERK, p38, AMPK, and AKT pathways.

The chemopreventive effect of the dietary compound kaempferol on the MCF-7 human breast cancer cell line is dependent on inhibition of glucose cellular uptake

Our aim was to investigate the effect of several dietary polyphenols on glucose uptake by breast cancer cells. Uptake of (3)H-deoxy-D-glucose ((3)H-DG) by MCF-7 cells was time-dependent, saturable, and inhibited by cytochalasin B plus phloridzin. In the short-term (26 min), myricetin, chrysin, genistein, resveratrol, kaempferol, and xanthohumol (10-100 µM) inhibited (3)H-DG uptake. Kaempferol was found to be the most potent inhibitor of (3)H-DG uptake [IC50 of 4 µM (1.6-9.8)], behaving as a mixed-type inhibitor. In the long-term (24 h), kaempferol (30 µM) was also able to inhibit (3)H-DG uptake, associated with a 40% decrease in GLUT1 mRNA levels. Interestingly enough, kaempferol (100 µM) revealed antiproliferative (sulforhodamine B and (3)H-thymidine incorporation assays) and cytotoxic (extracellular lactate dehydrogenase activity determination) properties, which were mimicked by low extracellular (1 mM) glucose conditions and reversed by high extracellular (20 mM) glucose conditions. Finally, exposure of cells to kaempferol (30 µM) induced an increase in extracellular lactate levels over time (to 731 ± 32% of control after a 24 h exposure), due to inhibition of MCT1-mediated lactate cellular uptake. In conclusion, kaempferol potently inhibits glucose uptake by MCF-7 cells, apparently by decreasing GLUT1-mediated glucose uptake. The antiproliferative and cytotoxic effect of kaempferol in these cells appears to be dependent on this effect.

Impact of gestational diabetes mellitus in the maternal-to-fetal transport of nutrients

Gestational diabetes mellitus (GDM) is a metabolic disorder prevalent among pregnant women. This disease increases the risk of adverse perinatal outcomes and diseases in the offspring later in life. The human placenta, the main interface between the maternal and fetal blood circulations, is responsible for the maternal-to-fetal transfer of nutrients essential for fetal growth and development. In this context, the aim of this article is to review the latest advances in the placental transport of macro and micronutrients and how they are affected by GDM and its associated conditions, such as elevated levels of glucose, insulin, leptin, inflammation, and oxidative stress. Data analyzed in this article suggest that GDM and its associated conditions, particularly high levels of glucose, leptin, and oxidative stress, disturb placental nutrient transport and, consequently, fetal nutrient supply. As a consequence, this disturbance may contribute to the fetal and postnatal adverse health outcomes associated with GDM.