Elevated D-glucose induces insulin insensitivity in human umbilical endothelial cells isolated from gestational diabetic pregnancies

The birth of cardiac disease: Mechanisms linking gestational diabetes mellitus and early onset of cardiovascular disease in offspring

Cardiovascular disease (CVD) is the biggest killer worldwide, composing a major economic burden for health care systems. Obesity and diabetes are dual epidemics on the rise and major risk factors predisposing for CVD. Increased obesity- and diabetes-related incidence is now observed among children, adolescents, and young adults. Gestational diabetes mellitus (GDM) is the most common metabolic pregnancy disorder, and its prevalence is rapidly increasing. During pregnancies complicated by GDM, the offspring are exposed to a compromised intrauterine environment characterized by hyperglycemic periods. Unfavorable in utero conditions at critical periods of fetal cardiac development can produce developmental adaptations that remodel the cardiovascular system in a way that can contribute to adult-onset of heart disease due to the programming during fetal life. Epidemiological studies have reported increased cardiovascular complications among GDM-descendants, highlighting the urgent need to investigate and understand the mechanisms modulated during fetal development of in utero GDM-exposed offspring that predispose an individual to increased CVD during life. In this manuscript, we overview previous studies in this area and gather evidence linking GDM and CVD development in the offspring, providing new insights on novel mechanisms contributing to offspring CVD programming by GDM, from the role of maternal-fetal interactions to their impact on fetal cardiovascular development, how the perpetuation of cardiac programming is maintained in postnatal life, and advance the intergenerational implications contributing to increased CVD premature origin. Understanding the perpetuation of CVD can be the first step to manage and reverse this leading cause of morbidity and mortality. This article is categorized under: Reproductive System Diseases > Molecular and Cellular Physiology Cardiovascular Diseases > Molecular and Cellular Physiology Metabolic Diseases > Genetics/Genomics/Epigenetics.

Gestational diabesity and foetoplacental vascular dysfunction

Gestational diabetes mellitus (GDM) shows a deficiency in the metabolism of D-glucose and other nutrients, thereby negatively affecting the foetoplacental vascular endothelium. Maternal hyperglycaemia and hyperinsulinemia play an important role in the aetiology of GDM. A combination of these and other factors predisposes women to developing GDM with pre-pregnancy normal weight, viz. classic GDM. However, women with GDM and prepregnancy obesity (gestational diabesity, GDty) or overweight (GDMow) show a different metabolic status than women with classic GDM. GDty and GDMow are associated with altered l-arginine/nitric oxide and insulin/adenosine axis signalling in the human foetoplacental microvascular and macrovascular endothelium. These alterations differ from those observed in classic GDM. Here, we have reviewed the consequences of GDty and GDMow in the modulation of foetoplacental endothelial cell function, highlighting studies describing the modulation of intracellular pH homeostasis and the potential implications of NO generation and adenosine signalling in GDty-associated foetal vascular insulin resistance. Moreover, with an increase in the rate of obesity in women of childbearing age worldwide, the prevalence of GDty is expected to increase in the next decades. Therefore, we emphasize that women with GDty and GDMow should be characterized with a different metabolic state from that of women with classic GDM to develop a more specific therapeutic approach for protecting the mother and foetus.

Myoinositol Reduces Inflammation and Oxidative Stress in Human Endothelial Cells Exposed In Vivo to Chronic Hyperglycemia

Myo-inositol (Myo) improves insulin resistance, glucose metabolism, and helps gestational diabetes (GDM) management. GDM is associated with a pro-inflammatory state and increased oxidative stress, which are both involved in vascular damage in diabetes. Our aim was to study Myo anti-inflammatory/antioxidant potential effects on an in vitro model of human umbilical vein endothelial cells (HUVECs). To this end, monocyte cell adhesion to HUVECs, adhesion molecule membrane exposure, and oxidative stress levels were determined in cells from control (C-) and GDM women treated during pregnancy either with diet only (GD-) or with diet plus Myo (GD+Myo). To deeply study the vascular effects of Myo, the same evaluations were performed in C- and GD-HUVECs following 48 h in vitro stimulation with Myo. Notably, we first observed that GD-HUVECs obtained from women assuming Myo supplementation exhibited a significantly decreased number of monocytes that adhered to endothelial cells, less adhesion molecule exposure, and lower intracellular reactive oxygen species (ROS) levels in the basal state as compared to GD-HUVECs obtained from women treated by diet only. This Myo anti-inflammatory/antioxidant effect was confirmed by 48 h in vitro stimulation of GD-HUVECs as compared to controls. Altogether, these results strongly suggest that Myo may exert protective actions against chronic inflammation induced by endothelial dysfunction in diabetes.

Insulin requires A2B adenosine receptors to modulate the L-arginine/nitric oxide signalling in the human fetoplacental vascular endothelium from late-onset preeclampsia

Late-onset preeclampsia (LOPE) associates with reduced umbilical vein reactivity and endothelial nitric oxide synthase (eNOS) activity but increased human cationic amino acid (hCAT-1)-mediated L-arginine transport involving A_2A adenosine receptor in the fetoplacental unit. This study addresses the A_2B adenosine receptor (A_2BAR)-mediated response to insulin in the fetoplacental vasculature from LOPE. Umbilical veins and HUVECs were obtained from women with normal (n = 37) or LOPE (n = 35) pregnancies. Umbilical vein rings reactivity to insulin was assayed in the absence or presence of adenosine and MRS-1754 (A_2BAR antagonist) in a wire myograph. HUVECs were exposed to insulin, MRS-1754, BAY60-6583 (A_2BAR agonist), NECA (general adenosine receptors agonist) or N^G-nitro-L-arginine methyl ester (NOS inhibitor). A_2BAR, hCAT-1, total and phosphorylated eNOS, Akt and p44/42^mapk protein abundance were determined by Western blotting. Insulin receptors A (IR-A) and B (IR-B), eNOS and hCAT-1 mRNA were determined by qPCR. Firefly/Renilla luciferase assay was used to determine -1606 bp SLC7A1 (hCAT-1) promoter activity. L-Citrulline content was measured by HPLC, L-[³H]citrulline formation from L-[³H]arginine by the Citrulline assay, and intracellular cGMP by radioimmunoassay. LOPE-reduced dilation of vein rings to insulin was restored by MRS-1754. HUVECs from LOPE showed higher A_2BAR, hCAT-1, and IR-A expression, Akt and p44/42^mapk activation, and lower NOS activity. MRS-1754 reversed the LOPE effect on A_2BAR, hCAT-1, Akt, and eNOS inhibitory phosphorylation. Insulin reversed the LOPE effect on A_2BAR, IR-A and eNOS, but increased hCAT-1-mediated transport. Thus, LOPE alters endothelial function, causing an imbalance in the L-arginine/NO signalling pathway to reduce the umbilical vein dilation to insulin requiring A_2BAR activation in HUVECs.

Inositol and antioxidant supplementation: Safety and efficacy in pregnancy

Pregnancies complicated by diabetes have largely increased in number over the last 50 years. Pregnancy is characterized by a physiologic increase in insulin resistance, which, associated with increased oxidative stress and inflammations, could induce alterations of glucose metabolism and diabetes. If not optimally controlled, these conditions have a negative impact on maternal and foetal outcomes. To date, one can resort only to diet and lifestyle to treat obesity and insulin resistance during pregnancy, and insulin remains the only therapeutic option to manage diabetes during pregnancy. However, in the last years, in a variety of experimental models, inositol and antioxidants supplementation have shown insulin-sensitizing, anti-inflammatory, and antioxidant properties, which could be mediated by some possible complementary mechanism of action. Different isomers and multiple combinations of these compounds are presently available: Aim of the present review article is to examine the existing evidence in order to clarify and/or define the effects of different inositol- and antioxidant-based supplements during pregnancy complicated by insulin resistance and/or by diabetes. This could help the clinician's evaluation and choice of the appropriate supplementation regimen.

Endothelial dysfunction in pregnancy metabolic disorders

In recent years, the vascular endothelium has gained attention as a key player in the initiation and development of pregnancy disorders. Endothelium acts as an endocrine organ that preserves the homeostatic balance by responding to changes in metabolic status. However, in metabolic disorders, endothelial cells adopt a dysfunctional function, losing their normal responsiveness. During pregnancy, several metabolic changes occur, in which endothelial function decisively participates. Similarly, when pregnancy metabolic disorders occur, endothelial dysfunction plays a key role in pathogenesis. This review outlines the main findings regarding endothelial dysfunction in three main metabolic pathological conditions observed during pregnancy: gestational diabetes, hypertensive disorders, and obesity and hyperlipidemia. Organ, histological and cellular characteristics were thoroughly described. Also, we focused in discussing the underlying molecular mechanisms involved in the cellular signaling pathways that mediate responses in these pathological conditions.

Anti-inflammatory Role of Carotenoids in Endothelial Cells Derived from Umbilical Cord of Women Affected by Gestational Diabetes Mellitus

Diabetes is associated with vascular inflammation, endothelial dysfunction, and oxidative stress, promoting the development of cardiovascular diseases (CVD). Several studies showed that a carotenoid-rich diet is associated to a reduced cardiovascular risk in healthy and diabetic subjects, although the mechanisms of action are still unknown. Here, the potential role of β-carotene (BC) and lycopene (Lyc) in human endothelial cells isolated from human umbilical cord vein (HUVECs) of women with gestational diabetes (GD) and respective controls (C) has been investigated. Results showed that BC and Lyc reduced the tumor necrosis factor alpha- (TNF-α-) stimulated monocyte-endothelium interaction (adhesion assay), membrane exposure (flow cytometry), and total expression levels (Western blot) of VCAM-1 and ICAM-1 in both cell types. Moreover, the treatment with BC and Lyc reduced the TNF-α-induced nuclear translocation of NF-κB (image flow cytometry) by preserving bioavailability of nitric oxide (NO, flow cytometry, and cGMP EIA kit assay), a key vasoactive molecule. Notably, BC and Lyc pretreatment significantly reduced peroxynitrite levels (flow cytometry), contributing to the redox balance protection. These results suggest a new mechanism of action of carotenoids which exert vascular protective action in diabetic condition, thus reinforcing the importance of a carotenoid-rich diet in the prevention of diabetes cardiovascular complications.

Insulin Is a Key Modulator of Fetoplacental Endothelium Metabolic Disturbances in Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is a disease of the mother that associates with altered fetoplacental vascular function. GDM-associated maternal hyperglycaemia result in fetal hyperglycaemia, a condition that leads to fetal hyperinsulinemia and altered L-arginine transport and synthesis of nitric oxide, i.e., endothelial dysfunction. These alterations in the fetoplacental endothelial function are present in women with GDM that were under diet or insulin therapy. Since these women and their newborn show normal glycaemia at term, other factors or conditions could be altered and/or not resolved by restoring normal level of circulating D-glucose. GDM associates with metabolic disturbances, such as abnormal handling of the locally released vasodilator adenosine, and biosynthesis and metabolism of cholesterol lipoproteins, or metabolic diseases resulting in endoplasmic reticulum stress and altered angiogenesis. Insulin acts as a potent modulator of all these phenomena under normal conditions as reported in primary cultures of cells obtained from the human placenta; however, GDM and the role of insulin regarding these alterations in this disease are poorly understood. This review focuses on the potential link between insulin and endoplasmic reticulum stress, hypercholesterolemia, and angiogenesis in GDM in the human fetoplacental vasculature. Based in reports in primary culture placental endothelium we propose that insulin is a factor restoring endothelial function in GDM by reversing ERS, hypercholesterolaemia and angiogenesis to a physiological state involving insulin activation of insulin receptor isoforms and adenosine receptors and metabolism in the human placenta from GDM pregnancies.

Human supraphysiological gestational weight gain and fetoplacental vascular dysfunction

OBJECTIVE

Human foetal development and growth in an environment of maternal obesity associates with high risk of cardiovascular disease and adverse neonatal outcome. We studied whether supraphysiological gestational weight gain results in human fetoplacental endothelial dysfunction and altered fetoplacental vascular reactivity.

METHODS

Primary cultures of human umbilical vein endothelial cells (HUVECs) and umbilical vein rings were obtained from pregnant women (112 total of patients recruited, 7 patients dropped out) exhibiting prepregnancy normal weight that ended with a physiological (pGWG (n=67), total weight gain 11.5-16 kg, rates of weight gain ≤0.42 kg per week) or supraphysiological (spGWG (n=38), total weight gain >16 kg, rates of weight gain >0.42 kg per week) gestational weight gain (reference values from US Institute of Medicine guidelines). Vascular reactivity to insulin (0.1-1000 nmol l(-1), 5 min) in KCl-preconstricted vein rings was measured using a wire myograph. Protein levels of human equilibrative nucleoside transporter 1 (hENT1), total and Ser(1177)- or Thr(495)-phosphorylated endothelial nitric oxide synthase (eNOS) were detected by western blot or immunofluorescence, and adenosine transport (0-250 μmol l(-1) adenosine, 2 μCi ml(-1) [(3)H]adenosine, 20 s, 25 °C) was measured in the presence or absence of 1 μmol l(-1) nitrobenzylthioinosine (hENT1 inhibitor) or 10 μmol l(-1) chlorpromazine (CPZ, endocytosis inhibitor) in HUVECs.

RESULTS

spGWG associates with reduced NOS activity-dependent dilation of vein rings (P=0.001), lower eNOS expression and higher Thr(495) (P=0.044), but unaltered Ser(1177)eNOS phosphorylation. hENT1-adenosine maximal transport activity was reduced (P=0.041), but the expression was increased (P=0.001) in HUVECs from this group. CPZ increased hENT1-adenosine transport (P=0.040) and hENT1 plasma membrane accumulation only in cells from pGWG.

CONCLUSION

spGWG in women with a normal prepregnancy weight causes lower fetoplacental vascular reactivity owing to the downregulation of eNOS activity and adenosine transport in HUVECs. Maternal spGWG is a detrimental condition for human fetoplacental endothelial function and reducing these alterations could result in a better neonate outcome.

Features of endothelial dysfunction in umbilical cord vessels of women with gestational diabetes

BACKGROUND AND AIMS

Gestational diabetes (GDM) is associated with increased oxidative stress and overexpression of inflammatory cytokines, both of which might lead to endothelial dysfunction and vascular disease. As such, GDM could be viewed as a sort of ‘short lived’ metabolic syndrome. As umbilical cord vessels represent a suitable model for the study of vascular alterations brought about by GDM, the aim of the present work was to characterize the phenotype of human umbilical vein endothelial cells (HUVECs) chronically exposed to hyperglycaemia and to a pro-inflammatory environment during pregnancy so as to identify molecular modifications of cellular homoeostasis eventually impacting on endothelial dysfunction.

METHODS AND RESULT

Tissue specimens and HUVECs were obtained from umbilical cords of GDMand control women. As compared to controls, GD-HUVEC exhibited enhanced monocyte adhesion and vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1(ICAM-1) expression and exposure on plasma membrane after tumour necrosis factor-alpha(TNF-α) stimulation (Western blot, flow cytometer). As compared to control cells, GD-HUVEC in basal conditions exhibited enhanced monocyte adhesion, nitric oxide synthase (NOS) expression and activity (eNOS Real-Time polymerase chain reaction, Western Blot for eNOS total protein and monomers/dimers ratio, conversion of [3H]-L-arginine in [3H]-L-citrulline), increased O(-)(2)egeneration together with increased NT levels (immunofluorescence) and reduced NO bioavailability(guanosine 3',5'-monophosphate (cGMP) production, EIA). Furthermore, immunohistochemistry revealed increased eNOS and NT immunoreactivity in GD umbilical cords.

CONCLUSION

Endothelial cells exposed in vivo even transiently to hyperglycaemia, oxidative stress and inflammation exhibit durable pro-atherogenic modifications.

Immediate direct peripheral vasoconstriction in response to hyperinsulinemia and metformin in the anesthetized pig

Elevated levels of insulin have been reported to induce both an arterial vasodilation mediated by nitric oxide (NO), and vasoconstriction mediated by endothelin and reactive oxygen radicals. Metformin, used to control blood glucose levels in type 2 diabetes, has also been shown to cause NO-mediated dilation of conduit arteries. It is possible that these contradictory vascular effects are due to a non-direct action on arteries. Therefore, the direct effect of high levels of insulin and metformin infusion on resistance artery diameter was evaluated. Experiments were carried out on the anesthetized pig; blood flow and pressure were measured in the iliac artery. An adjustable snare was applied to the iliac above the pressure and flow measurement site to induce step decreases (3-4 occlusions at 5 min intervals were performed for each infusion) in blood flow, and hence iliac pressure, and the conductance (deltaflow / deltapressure) calculated. Saline, insulin (20 and 40 mUSP/l/min), and metformin (1 microg/ml/min) were infused separately downstream of the adjustable snare and their effect on arterial conductance assessed. Insulin at both infusion rates and metformin caused a significant reduction in peripheral vascular conductance. In conclusion, hyperinsulinemia and metformin infusion constrict resistance arterial vessels in vivo.

Gestational diabetes mellitus impairs Nrf2-mediated adaptive antioxidant defenses and redox signaling in fetal endothelial cells in utero

In utero exposure to gestational diabetes mellitus (GDM) is associated with an increased risk of type 2 diabetes and cardiovascular disease in later life, yet the underlying mechanisms remain to be elucidated. We examined the effects of GDM on the proteome, redox status, and nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant gene expression in human fetal endothelial cells. Proteomic analysis revealed that proteins involved in redox homeostasis were significantly altered in GDM and associated with increased mitochondrial superoxide generation, protein oxidation, DNA damage, and diminished glutathione (GSH) synthesis. In GDM cells, the lipid peroxidation product 4-hydroxynonenal (HNE) failed to induce nuclear Nrf2 accumulation and mRNA and/or protein expression of Nrf2 and its target genes NAD(P)H:quinone oxidoreductase 1 (NQO1), Bach1, cystine/glutamate transporter, and glutamate cysteine ligase. Although methylation of CpG islands in Nrf2 or NQO1 promoters was unaltered by GDM, decreased DJ-1 and increased phosphorylated glycogen synthase kinase 3β levels may account for impaired Nrf2 signaling. HNE-induced increases in GSH and NQO1 levels were abrogated by Nrf2 small interfering RNA in normal cells, and overexpression of Nrf2 in GDM cells partially restored NQO1 induction. Dysregulation of Nrf2 in fetal endothelium may contribute to the increased risk of type 2 diabetes and cardiovascular disease in offspring.

The placenta and gestational diabetes mellitus

By its location between maternal and fetal bloodstreams the human placenta not only handles the materno-fetal transport of nutrients and gases, but may also be exposed to intrauterine conditions adversely affecting placental and fetal development. Such adverse conditions exist in pregnancies complicated by gestational diabetes mellitus (GDM), and have been associated with alterations in placental anatomy and physiology. These alterations are mainly based on changes on the micro-anatomical and/or even molecular level including aberrant villous vascularization, a disbalance of vasoactive molecules, and enhanced oxidative stress. The consequence thereof may be impaired fetal oxygenation and changes in transplacental nutrient supply. Although transplacental glucose flux is flow limited and independent of glucose transporter availability, transport of essential and nonessential amino acids and expression of genes involved in lipid transport and metabolism are significantly affected by GDM.

The role of oxidative stress in the pathophysiology of gestational diabetes mellitus

Normal human pregnancy is considered a state of enhanced oxidative stress. In pregnancy, it plays important roles in embryo development, implantation, placental development and function, fetal development, and labor. However, pathologic pregnancies, including gestational diabetes mellitus (GDM), are associated with a heightened level of oxidative stress, owing to both overproduction of free radicals and/or a defect in the antioxidant defenses. This has important implications on the mother, placental function, and fetal well-being. Animal models of diabetes have confirmed the important role of oxidative stress in the etiology of congenital malformations; the relative immaturity of the antioxidant system facilitates the exposure of embryos and fetuses to the damaging effects of oxidative stress. Of note, there are only a few clinical studies evaluating the potential beneficial effects of antioxidants in GDM. Thus, whether or not increased antioxidant intake can reduce the complications of GDM in both mother and fetus needs to be explored. This review provides an overview and updated data on our current understanding of the complications associated with oxidative changes in GDM.

Placental vascular dysfunction in diabetic pregnancies: intimations of fetal cardiovascular disease?

In the human placenta, the angioarchitecture of fetal vessels lying in maternal blood is useful for nutrient uptake, but it makes the synthesis, maturation and functioning of placental vessels vulnerable to any alterations in the fetal and maternal environment. This review discusses how the maternal diabetic milieu, and the resultant fetal hyperglycemia and hyperinsulinemia, may act together to produce an altered placental vascular phenotype, which includes increased angiogenesis, altered junctional maturity, increased vascular endothelial-like growth factor (VEGF), altered VEGF and insulin receptor profiles, and upregulation of genes involved in signal transduction, transcription and mitosis in placental endothelial cells. The placental vascular dysfunction does extend to other fetal vascular beds including endothelial cells from umbilical vessels, where there are reports of elevated basal iNOS activity and altered sensitivity to insulin. There is emerging evidence of epigenetic modulation of fetal endothelial genes in diabetes and long-term vascular consequences of this. Thus, placental vascular dysfunction in diabetes may be contributing to and describing disturbances in the fetal vasculature, which may produce an overt pathological response in later life if challenged with additional cardiovascular stresses.

Insulin restores gestational diabetes mellitus-reduced adenosine transport involving differential expression of insulin receptor isoforms in human umbilical vein endothelium

OBJECTIVE

To determine whether insulin reverses gestational diabetes mellitus (GDM)-reduced expression and activity of human equilibrative nucleoside transporters 1 (hENT1) in human umbilical vein endothelium cells (HUVECs).

RESEARCH DESIGN AND METHODS

Primary cultured HUVECs from full-term normal (n = 44) and diet-treated GDM (n = 44) pregnancies were used. Insulin effect was assayed on hENT1 expression (protein, mRNA, SLC29A1 promoter activity) and activity (initial rates of adenosine transport) as well as endothelial nitric oxide (NO) synthase activity (serine(1177) phosphorylation, l-citrulline formation). Adenosine concentration in culture medium and umbilical vein blood (high-performance liquid chromatography) as well as insulin receptor A and B expression (quantitative PCR) were determined. Reactivity of umbilical vein rings to adenosine and insulin was assayed by wire myography. Experiments were in the absence or presence of l-N(G)-nitro-l-arginine methyl ester (l-NAME; NO synthase inhibitor) or ZM-241385 (an A(2A)-adenosine receptor antagonist).

RESULTS

Umbilical vein blood adenosine concentration was higher, and the adenosine- and insulin-induced NO/endothelium-dependent umbilical vein relaxation was lower in GDM. Cells from GDM exhibited increased insulin receptor A isoform expression in addition to the reported NO-dependent inhibition of hENT1-adenosine transport and SLC29A1 reporter repression, and increased extracellular concentration of adenosine and NO synthase activity. Insulin reversed all these parameters to values in normal pregnancies, an effect blocked by ZM-241385 and l-NAME.

CONCLUSIONS

GDM and normal pregnancy HUVEC phenotypes are differentially responsive to insulin, a phenomenon where insulin acts as protecting factor for endothelial dysfunction characteristic of this syndrome. Abnormal adenosine plasma levels, and potentially A(2A)-adenosine receptors and insulin receptor A, will play crucial roles in this phenomenon in GDM.

Impact of dietary soy isoflavones in pregnancy on fetal programming of endothelial function in offspring

Epidemiological evidence suggests that soy-based diets containing phytoestrogens (isoflavones) afford protection against cardiovascular diseases (CVDs); however, supplementation trials have largely reported only marginal health benefits. The molecular mechanisms by which the isoflavones genistein, daidzein, and equol afford protection against oxidative stress remain to be investigated in large scale clinical trials. Isoflavones are transferred across the placenta in both rodents and humans, yet there is limited information on their actions in pregnancy and the developmental origins of disease. Our studies established that feeding a soy isoflavone-rich diet during pregnancy, weaning, and postweaning affords cardiovascular protection in aged male rats. Notably, rats exposed to a soy isoflavone-deficient diet throughout pregnancy and adult life exhibited increased oxidative stress, diminished antioxidant enzyme and eNOS levels, endothelial dysfunction, and elevated blood pressure in vivo. The beneficial effects of refeeding isoflavones to isoflavone-deficient rats include an increased production of nitric oxide and EDHF, an upregulation of antioxidant defense enzymes and lowering of blood pressure in vivo. This review focuses on the role that isoflavones in the fetal circulation may play during fetal development in affording protection against CVD in the offspring via their ability to activate eNOS, EDHF, and redox-sensitive gene expression.

Pathological aspects of lipid peroxidation

Lipid peroxidation (LPO) product accumulation in human tissues is a major cause of tissular and cellular dysfunction that plays a major role in ageing and most age-related and oxidative stress-related diseases. The current evidence for the implication of LPO in pathological processes is discussed in this review. New data and literature review are provided evaluating the role of LPO in the pathophysiology of ageing and classically oxidative stress-linked diseases, such as neurodegenerative diseases, diabetes and atherosclerosis (the main cause of cardiovascular complications). Striking evidences implicating LPO in foetal vascular dysfunction occurring in pre-eclampsia, in renal and liver diseases, as well as their role as cause and consequence to cancer development are addressed.

Nitric oxide regulates neurogenesis in adult olfactory epithelium in vitro

Nitric oxide regulates neurogenesis in the developing and adult brain. The olfactory epithelium is a site of neurogenesis in the adult and previous studies suggest a role for nitric oxide in this tissue during development. We investigated whether neuronal precursor proliferation and differentiation is regulated by nitric oxide using primary cultures of olfactory epithelial cells and an immortalized, clonal, neuronal precursor cell line derived from adult olfactory epithelium. In these cultures NOS inhibition reduced cell proliferation and stimulated neuronal differentiation, including expression of a voltage-dependent potassium conductance of the delayed rectifier type. In the neuronal precursor cell line, differentiation was associated with a significant decrease in nitric oxide release. In contrast, addition of nitric oxide stimulated proliferation and reduced neuronal differentiation. Nitric oxide regulated olfactory neurogenesis independently of added growth factors. Taken together these results indicate that nitric oxide levels can regulate cell proliferation and neuronal differentiation of olfactory precursor cells.

Chronic hyperglicemia and nitric oxide bioavailability play a pivotal role in pro-atherogenic vascular modifications

Diabetes is associated with accelerated atherosclerosis and macrovascular complications are a major cause of morbidity and mortality in this disease. Although our understanding of vascular pathology has lately greatly improved, the mechanism(s) underlying enhanced atherosclerosis in diabetes remain unclear. Endothelial cell dysfunction is emerging as a key component in the pathophysiology of cardiovascular abnormalities associated with diabetes. Although it has been established that endothelium plays a critical role in overall homeostasis of the vessels, vascular smooth muscle cells (vSMC) in the arterial intima have a relevant part in the development of atherosclerosis in diabetes. However, high glucose induced alterations in vSMC behaviour are not fully characterized. Several studies have reported that impaired nitric oxide (NO) synthesis and/or actions are often present in diabetes and endothelial dysfunction. Furthermore, although endothelial cells are by far the main site of vascular NO synthesis, vSMC do express nitric oxyde synthases (NOSs) and NO synthesis in vSMC might be important in vessel's function. Although it is known that vSMC contribute to vascular pathology in diabetes by their change from a quiescent state to an activated proliferative and migratory phenotype (termed phenotypic modulation), whether this altered phenotypic modulation might also involve alterations in the nitrergic systems is still controversial. Our recent data indicate that, in vivo, chronic hyperglycemia might induce an increased number of vSMC proliferative clones which persist in culture and are associated with increased eNOS expression and activity. However, upregulation of eNOS and increased NO synthesis occur in the presence of a marked concomitant increase of O(2-) production. Since NO bioavailabilty might not be increased in high glucose stimulated vSMC, it is tempting to hypothesize that the proliferative phenotype observed in cells from diabetic rats is associated with a redox imbalance responsible quenching and/or trapping of NO, with the consequent loss of its biological activity. This might provide new insight on the mechanisms responsible for accelerated atherosclerosis in diabetes.

Insulin restores glucose inhibition of adenosine transport by increasing the expression and activity of the equilibrative nucleoside transporter 2 in human umbilical vein endothelium

L-Arginine transport and nitric oxide (NO) synthesis (L-arginine/NO pathway) are stimulated by insulin, adenosine or elevated extracellular D-glucose in human umbilical vein endothelial cells (HUVEC). Adenosine uptake via the human equilibrative nucleoside transporters 1 (hENT1) and 2 (hENT2) has been proposed as a mechanism regulating adenosine plasma concentration, and therefore its vascular effects in human umbilical veins. Thus, altered expression and/or activity of hENT1 or hENT2 could lead to abnormal physiological plasma adenosine level. We have characterized insulin effect on adenosine transport in HUVEC cultured in normal (5 mM) or high (25 mM) D-glucose. Insulin (1 nM) increased overall adenosine transport associated with higher hENT2-, but lower hENT1-mediated transport in normal D-glucose. Insulin increased hENT2 protein abundance in normal or high D-glucose, but reduced hENT1 protein abundance in normal D-glucose. Insulin did not alter the reduced hENT1 protein abundance, but blocked the reduced hENT1 and hENT2 mRNA expression induced by high D-glucose. Insulin effect on hENT1 mRNA expression in normal D-glucose was blocked by N(G)-nitro-L-arginine methyl ester (L-NAME, NO synthase inhibitor) and mimicked by S-nitroso-N-acetyl-L,D-penicillamine (SNAP, NO donor). L-NAME did not block insulin effect on hENT2 expression. In conclusion, insulin stimulation of overall adenosine transport results from increased hENT2 expression and activity via a NO-independent mechanism. These findings could be important in hyperglycemia-associated pathological pregnancies, such as gestational diabetes, where plasma adenosine removal by the endothelium is reduced, a condition that could alter the blood flow from the placenta to the fetus affecting fetus growth and development.

HUVECs from newborns with a strong family history of diabetes show diminished ROS synthesis in the presence of high glucose concentrations

BACKGROUND

A family history of type 2 diabetes mellitus (DM) increases the probability to develop DM and endothelial dysfunction. The probable mechanism involves augmented reactive oxygen species (ROS) synthesis. The aim of this study was to evaluate the synthesis of ROS in human umbilical vein endothelial cells (HUVECs) obtained from healthy newborns with (experimental) and without (control) a strong family history of type 2 DM, exposed to different glucose concentrations.

METHODS

HUVECs were exposed to various glucose concentrations for 24 and 48 h periods, before cell proliferation, mitochondrial activity, and mitochondrial membrane potential were determined. Intracellular ROS synthesis in the presence or absence of the mitochondrial uncoupler CCCP, cytochalasin B, or diphenyleneiodonium (DPI) was also evaluated.

RESULTS

As opposed to control HUVECs, we found that experimental HUVECs exposed to 30 mmol/L glucose showed a 50% decrease in cell proliferation, a 90% reduction in mitochondrial activity, and a statistically significant inhibition of ROS synthesis in the presence of CCCP or cytochalasin B; DPI had no effect.

CONCLUSIONS

Our results suggest that mitochondria and NAD(P)H-oxidase from HUVECs obtained from healthy newborns with a family history of DM have an innate deficient response to high glucose concentrations.

Gestational diabetes and the adenosine/L-arginine/nitric oxide (ALANO) pathway in human umbilical vein endothelium

Altered endothelial cell function is a key factor associated with vascular disorders and is critical in the fetal growth and development. Pregnancies affected by diseases such as gestational diabetes are associated with human umbilical vein endothelial dysfunction, a finding that has been associated with a high incidence of vascular complications during the adult life. Limited information is available addressing cellular mechanisms associated with altered human umbilical vein endothelial function in gestational diabetes. One of the key signalling pathways associated with altered vascular physiology is the synthesis of the vasodilator nitric oxide (NO) from the cationic amino acid L-arginine by the endothelium (i.e. the endothelial L-arginine/NO pathway). The activity of this signalling pathway is modulated by D-glucose, adenosine, insulin, and ATP, among other molecules, and is upregulated (transcriptional, post-transcriptional and post-translational levels) in gestational diabetes. This review focuses on the cellular and molecular mechanisms involved with elevated adenosine levels in fetal umbilical vein blood and the endothelial L-arginine/NO pathway activity in gestational diabetes. We suggest that a lower capacity of adenosine transport by the fetal endothelium in gestational diabetes leads to extracellular accumulation of this nucleoside and its higher bio-availability activates endothelial P1 type purinoceptors. A functional association between A2a purinoceptor subtype signalling and the activity of the l-arginine transport mediated by human cationic amino acid transporters and endothelial NO synthase activity (i.e. 'ALANO pathway') is proposed, revealing in part the mechanisms that account for human umbilical vein endothelial cell dysfunction programmed through the development of the fetus in gestational diabetes.

Possible involvement of facilitated polyol pathway in augmentation of intimal hyperplasia in rabbits with alloxan-induced hyperglycemia

Present experiments were designed to investigate whether the facilitated polyol pathway is involved in the augmentation of intimal hyperplasia with hyperglycemia. Twelve weeks after a single bolus intravenous injection of alloxan (100 mg/kg) or saline, rabbits underwent a unilateral endothelial denudation of the carotid artery. Intimal hyperplasia was evident 4 weeks after denudation and significantly augmented in hyperglycemic animals treated with alloxan. This effect was accompanied by the enhanced accumulation of endogenous NOS inhibitors (N(G)-monomethyl-l-arginine [l-NMMA] and asymmetric, N(G),N(G)-dimethyl-l-arginine [ADMA]) in regenerated endothelial cells, impairment of NO production and release, and enhanced accumulation of endothelin-1 (ET-1) within the vessel wall. Sorbitol levels in aortic endothelial cells and within the smooth muscle layer were significantly increased with hyperglycemia. All these changes associated with hyperglycemia were significantly reduced in animals treated with the selective aldose reductase inhibitor fidarestat (3 mg/kg/d). These findings suggest that the facilitated polyol pathway possibly plays an important role for the augmentation of intimal hyperplasia caused by the hyperglycemic state.

Regulation of amino acid and glucose transporters in endothelial and smooth muscle cells

While transport processes for amino acids and glucose have long been known to be expressed in the luminal and abluminal membranes of the endothelium comprising the blood-brain and blood-retinal barriers, it is only within the last decades that endothelial and smooth muscle cells derived from peripheral vascular beds have been recognized to rapidly transport and metabolize these nutrients. This review focuses principally on the mechanisms regulating amino acid and glucose transporters in vascular endothelial cells, although we also summarize recent advances in the understanding of the mechanisms controlling membrane transport activity and expression in vascular smooth muscle cells. We compare the specificity, ionic dependence, and kinetic properties of amino acid and glucose transport systems identified in endothelial cells derived from cerebral, retinal, and peripheral vascular beds and review the regulation of transport by vasoactive agonists, nitric oxide (NO), substrate deprivation, hypoxia, hyperglycemia, diabetes, insulin, steroid hormones, and development. In view of the importance of NO as a modulator of vascular tone under basal conditions and in disease and chronic inflammation, we critically review the evidence that transport of L-arginine and glucose in endothelial and smooth muscle cells is modulated by bacterial endotoxin, proinflammatory cytokines, and atherogenic lipids. The recent colocalization of the cationic amino acid transporter CAT-1 (system y(+)), nitric oxide synthase (eNOS), and caveolin-1 in endothelial plasmalemmal caveolae provides a novel mechanism for the regulation of NO production by L-arginine delivery and circulating hormones such insulin and 17beta-estradiol.

Intrauterine growth retardation is associated with reduced activity and expression of the cationic amino acid transport systems y+/hCAT-1 and y+/hCAT-2B and lower activity of nitric oxide synthase in human umbilical vein endothelial cells

Intrauterine growth retardation (IUGR) is associated with vascular complications leading to hypoxia and abnormal fetal development. The effect of IUGR on L-arginine transport and nitric oxide (NO) synthesis was investigated in cultures of human umbilical vein endothelial cells (HUVECs). IUGR was associated with membrane depolarization and reduced L-arginine transport (V(max)= 5.8+/-0.2 versus 3.3+/-0.1 pmol/microg protein per minute), with no significant changes in transport affinity (K(m)=159+/-15 versus 137+/-14 micromol/L). L-Arginine transport was trans-stimulated (8- to 9-fold) in cells from normal and IUGR pregnancies. IUGR was associated with reduced production of L-[3H]citrulline from L-[3H] arginine, lower nitrite and intracellular L-arginine, L-citrulline, and cGMP. IUGR decreased hCAT-1 and hCAT-2B mRNA, and increased eNOS mRNA and protein levels. IUGR-associated inhibition of L-arginine transport and NO synthesis, and membrane depolarization were reversed by the NO donor S-nitroso-N-acetyl-L,D-penicillamine. In summary, endothelium from fetuses with IUGR exhibit altered L-arginine transport and NO synthesis (L-arginine/NO pathway), reduced expression and activity of hCAT-1 and hCAT-2B and reduced eNOS activity. Alterations in L-arginine/NO pathway could be critical for the physiological processes involved in the etiology of IUGR in human pregnancies.

Modulation of adenosine transport by insulin in human umbilical artery smooth muscle cells from normal or gestational diabetic pregnancies

1. Adenosine transport was measured in human cultured umbilical artery smooth muscle cells, isolated from non-diabetic or gestational diabetic pregnancies, under basal conditions and after pretreatment in vitro with insulin. 2. Adenosine transport in non-diabetic smooth muscle cells was significantly increased by insulin (half-maximal stimulation at 0.33 +/- 0.02 nM, 8 h) and characterized by a higher maximal rate (V(max)) for nitrobenzylthioinosine (NBMPR)-sensitive (es) saturable nucleoside transport (17 +/- 5 vs. 52 +/- 12 pmol (microg protein)(-1) min(-1), control vs. insulin, respectively) and maximal binding sites (B(max)) for [(3)H]NBMPR (0.66 +/- 0.07 vs. 1.1 +/- 0.1 fmol (microg protein)(-1), control vs. insulin, respectively), with no significant changes in Michaelis-Menten (K(m)) and dissociation (K(d)) constants. 3. In contrast, in smooth muscle cells from diabetic pregnancies, where the values of V(max) for adenosine transport (59 +/- 4 pmol (microg protein)(-1) min(-1)) and B(max) for [(3)H]NBMPR binding (1.62 +/- 0.16 fmol (microg protein)(-1)) were significantly elevated by comparison with non-diabetic cells, insulin treatment (1 nM, 8 h) reduced the V(max) for adenosine transport and B(max) for [(3)H]NBMPR binding to levels detected in non-diabetic cells. 4. In non-diabetic cells, the stimulatory effect of insulin on adenosine transport was mimicked by dibutyryl cGMP (100 nM) and reduced by inhibitors of phosphatidylinositol 3-kinase (10 nM wortmannin), nitric oxide synthase (100 microM N (G)-nitro-L-arginine methyl ester, L-NAME) or protein synthesis (1 microM cycloheximide), whereas inhibition of adenylyl cyclase (100 microM SQ-22536) had no effect. 5. Wortmannin or SQ-22536, but not L-NAME or cycloheximide, attenuated the inhibitory action of insulin on the diabetes-induced stimulation of adenosine transport. 6. Protein levels of inducible NO synthase (iNOS) were similar in non-diabetic and diabetic cells, but were increased by insulin (1 nM, 8 h) only in non-diabetic smooth muscle cells. 7. Our results suggest that adenosine transport via the es nucleoside transporter is modulated differentially by insulin in either cell type. Insulin increased adenosine transport in non-diabetic cells via NO and cGMP, but inhibited the diabetes-elevated adenosine transport via activation of adenylyl cyclase, suggesting that the biological actions of adenosine may be altered under conditions of sustained hyperglycaemia in uncontrolled diabetes.

Vasoactive mediator release by fetal endothelial cells in intrauterine growth restriction and preeclampsia

OBJECTIVE

Preeclampsia and fetal growth restriction are associated with poor placental perfusion, which may be accompanied by a compensatory release of vasoactive substances in the fetoplacental circuit. This study examines the effects of preeclampsia and fetal growth restriction on nitric oxide and prostacyclin signaling pathways in fetal endothelial cells.

STUDY DESIGN

Human umbilical vein endothelial cells from 30 control pregnancies, 18 pregnancies with preeclampsia, and 9 pregnancies with intrauterine growth restriction were cultured. Intracellular cyclic guanosine monophosphate accumulation and 6-keto-prostaglandin F1alpha production were determined.

RESULTS

Intracellular accumulation of cyclic guanosine monophosphate was significantly higher in the preeclampsia group and lower in the growth restriction group than in the control group (9.8, 1.8, and 3.9 pmol/microg protein for 5 minutes, respectively), whereas 6-keto-prostaglandin F1alpha production was not significantly different in the 3 groups.

CONCLUSION

The data suggest that the fetoplacental vascular response to preeclampsia is to increase production of cyclic guanosine monophosphate, perhaps to maintain vessel dilatation and maximum flow through placental villi. In fetal growth restriction the umbilical vein endothelial cells do not or cannot respond to chronic hypoxia by increasing cyclic guanosine monophosphate, which may lead to fetoplacental vasoconstriction.

Regulation of adenosine transport by D-glucose in human fetal endothelial cells: involvement of nitric oxide, protein kinase C and mitogen-activated protein kinase

The effects of elevated D-glucose on adenosine transport were investigated in human cultured umbilical vein endothelial cells isolated from normal pregnancies. Elevated D-glucose resulted in a time- (8-12 h) and concentration-dependent (half-maximal at 10+/-2 mM) inhibition of adenosine transport, which was associated with a reduction in the Vmax for nitrobenzylthioinosine (NBMPR)-sensitive (es) saturable nucleoside with no significant change in Km. d-Fructose (25 mM), 2-deoxy-D-glucose (25 mM) or D-mannitol (20 mM) had no effect on adenosine transport. Adenosine transport was inhibited following incubation of cells with the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA; 100 nM, 30 min to 24 h). D-Glucose-induced inhibition of transport was abolished by calphostin C (100 nM, an inhibitor of PKC), and was not further reduced by PMA. Increased PKC activity in the membrane (particulate) fraction of endothelial cells exposed to D-glucose or PMA was blocked by calphostin C but was unaffected by NG-nitro-L-arginine methyl ester (L-NAME; 100 microM, an inhibitor of nitric oxide synthase (NOS)) or PD-98059 (10 microM, an inhibitor of mitogen-activated protein kinase kinase 1). D-Glucose and PMA increased endothelial NOS (eNOS) activity, which was prevented by calphostin C or omission of extracellular Ca2+ and unaffected by PD-98059. Adenosine transport was inhibited by S-nitroso-N-acetyl-l, d-penicillamine (SNAP; 100 microM, an NO donor) but was increased in cells incubated with L-NAME. The effect of SNAP on adenosine transport was abolished by PD-98059. Phosphorylation of mitogen-activated protein kinases p44mapk (ERK1) and p42mapk (ERK2) was increased in endothelial cells exposed to elevated D-glucose (25 mM for 30 min to 24 h) and the NO donor SNAP (100 microM, 30 min). The effect of D-glucose was blocked by PD-98059 or L-NAME, which also prevented the inhibition of adenosine transport mediated by elevated D-glucose. Our findings provide evidence that D-glucose inhibits adenosine transport in human fetal endothelial cells by a mechanism that involves activation of PKC, leading to increased NO levels and p42-p44mapk phosphorylation. Thus, the biological actions of adenosine appear to be altered under conditions of sustained hyperglycaemia.

Accelerated intimal hyperplasia and increased endogenous inhibitors for NO synthesis in rabbits with alloxan-induced hyperglycaemia

1. We examined whether endogenous inhibitors of NO synthesis are involved in the augmentation of intimal hyperplasia in rabbits with hyperglycaemia induced by alloxan. 2. Four weeks after the endothelial denudation of carotid artery which had been performed 12 weeks after alloxan, the intimal hyperplasia was greatly augmented with hyperglycaemia. The degree of hyperplasia was assessed using three different parameters of histopathological findings as well as changes in luminal area and intima: media ratio. 3. There were positive and significant correlations between intima:media ratio, plasma glucose, and concentrations of N(G)-monomethyl-L-arginine (L-NMMA) and N(G), N(G)-dimethyl-L-arginine (ADMA) in endothelial cells, that is, the intima:media ratio became greater as plasma glucose and endothelial L-NMMA and ADMA were increased. Furthermore, endothelial L-NMMA and ADMA were increased in proportion to the increase in plasma glucose. 4. In contrast, there were inverse and significant correlations between cyclic GMP production by carotid artery strips with endothelium and plasma glucose, between cyclic GMP production and endothelial L-NMMA and ADMA, and between the intima:media ratio and cyclic GMP production. 5. Exogenously applied L-NMMA and ADMA inhibited cyclic GMP production in a concentration-dependent manner. IC50 values were determined to be 12.1 microM for the former and 26.2 microM for the latter. The cyclic GMP production was abolished after the deliberate removal of endothelium from the artery strips. 6. These results suggest that the augmentation of intimal hyperplasia with hyperglycaemia is closely related to increased accumulation of L-NMMA and ADMA with hyperglycaemia, which would result in an accelerated reduction in NO production/release by endothelial cells.