Biomedical subjects

L Poston

Publications and source records attributed to L Poston.

At least 19 recordsLinked to original sources

PubMed2007

Mechanical stretch regulates TRPC expression and calcium entry in human myometrial smooth muscle cells.

Stretch is known to stimulate myometrial hyperplasia and hypertrophy in early pregnancy and uterine contraction at term. We propose that transduction of the stretch signal involves alteration of intracellular calcium signalling, including changes in transient receptor potential canonical (TRPC) isoform expression. The aim of the present study was to investigate the effect of prolonged mechanical (tonic) stretch in vitro on human myometrial smooth muscle cell calcium signalling and TRPC expression. Cells were cultured from myometrial biopsies, obtained from women undergoing elective Caesarean section at term, grown on Flexiplates and subjected to 25% tonic mechanical stretch for 1, 4 and 14 h. Time-matched control cells were not stretched. Mechanical stretch (14 h) increased basal calcium entry and cyclopiazonic acid (CPA)-induced calcium/Mn(2+) entry (P < 0.05) in Fura-2 loaded cells. The calcium selectivity of CPA-thapsigarin induced inward currents, measured by patch clamp electrophysiology, was also increased in stretched cells compared with control cells (P < 0.05). Real time PCR and Western blot data demonstrated that TRPC3 and TRPC4 mRNA and TRPC3 protein expression were increased by stretch (P < 0.05), respectively. These data support the hypothesis that uterine stretch modulates uterine growth and contractility in pregnancy via alterations in calcium signalling.

Blotting, Western↗

PubMed2006

Developmental programming of obesity in mammals.

Converging lines of evidence from epidemiological studies and animal models now indicate that the origins of obesity and related metabolic disorders lie not only in the interaction between genes and traditional adult risk factors, such as unbalanced diet and physical inactivity, but also in the interplay between genes and the embryonic, fetal and early postnatal environment. Whilst studies in man initially focused on the relationship between low birth weight and risk of adult obesity and metabolic syndrome, evidence is also growing to suggest that increased birth weight and/or adiposity at birth can also lead to increased risk for childhood and adult obesity. Hence, there appears to be increased risk of obesity at both ends of the birth weight spectrum. Animal models, including both under- and overnutrition in pregnancy and lactation lend increasing support to the developmental origins of obesity. This review focuses upon the influence of the maternal nutritional and hormonal environment in pregnancy in permanently programming appetite and energy expenditure and the hormonal, neuronal and autocrine mechanisms that contribute to the maintenance of energy balance in the offspring. We discuss the potential maternal programming 'vectors' and the molecular mechanisms that may lead to persistent pathophysiological changes resulting in subsequent disease. The perinatal environment, which appears to programme subsequent obesity, provides a potential therapeutic target, and work in this field will readily translate into improved interventional strategies to stem the growing epidemic of obesity, a disease which, once manifest, has proven particularly resistant to treatment.

Adiposity↗

PubMed2006

Vitamin C and vitamin E in pregnant women at risk for pre-eclampsia (VIP trial): randomised placebo-controlled trial.

BACKGROUND: Oxidative stress could play a part in pre-eclampsia, and there is some evidence to suggest that vitamin C and vitamin E supplements could reduce the risk of the disorder. Our aim was to investigate the potential benefit of these antioxidants in a cohort of women with a range of clinical risk factors. METHODS: We did a randomised, placebo-controlled trial to which we enrolled 2410 women identified as at increased risk of pre-eclampsia from 25 hospitals. We assigned the women 1000 mg vitamin C and 400 IU vitamin E (RRR alpha tocopherol; n=1199) or matched placebo (n=1205) daily from the second trimester of pregnancy until delivery. Our primary endpoint was pre-eclampsia, and our main secondary endpoints were low birthweight (<2.5 kg) and small size for gestational age (<5th customised birthweight centile). Analyses were by intention to treat. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN 62368611 . FINDINGS: Of 2404 patients treated, we analysed 2395 (99.6%). The incidence of pre-eclampsia was similar in treatment placebo groups (15% [n=181] vs 16% [n=187], RR 0.97 [95% CI 0.80-1.17]). More low birthweight babies were born to women who took antioxidants than to controls (28% [n=387] vs 24% [n=335], 1.15 [1.02-1.30]), but small size for gestational age did not differ between groups (21% [n=294] vs 19% [n=259], 1.12 [0.96-1.31]). INTERPRETATION: Concomitant supplementation with vitamin C and vitamin E does not prevent pre-eclampsia in women at risk, but does increase the rate of babies born with a low birthweight. As such, use of these high-dose antioxidants is not justified in pregnancy.

Adult↗

PubMed2006

Cardiovascular consequences of life-long exposure to dietary isoflavones in the rat.

Dietary soy intake in man is proposed to provide cardiovascular protection, but it is not established whether this property is attributable to the soy protein per se or to associated dietary isoflavones. This investigation aimed to establish whether the dietary isoflavones in soy protein affect cardiovascular function. Ten days prior to mating, male and female Wistar rats were habituated to either a soy based isoflavone rich diet (plasma concentration 1.87 micromol l(-1) isoflavones) or the same diet after isoflavone elution (plasma isoflavone not detectable). Offspring were weaned onto and maintained on the same diet as their dam and sire for 6 months. Blood pressure, and constrictor and dilator responses in the aorta and mesenteric resistance arteries were assessed at 3 and 6 months of age. There was no effect of isoflavone removal from the diet on blood pressure, heart rate, aortic function or mesenteric artery contractile function, at either 3 or 6 months of age. Resistance mesenteric arteries from 6-month-old female rats fed the isoflavone rich diet demonstrated a modest increase in arterial distensibility compared with those fed the depleted diet, and mesenteric arteries from male and female rats fed the isoflavone rich diet showed increased sensitivity to acetylcholine. In summary, the isoflavone content of soy protein has no influence on blood pressure in healthy rats fed a diet based on soy protein, but influences small artery function.

Animals↗

PubMed2005

Enhanced vascular responses to adrenomedullin in mice overexpressing receptor-activity-modifying protein 2.

Adrenomedullin (AM) levels are elevated in cardiovascular disease, but little is known of the role of specific receptor components. AM acts via the calcitonin receptor-like receptor (CLR) interacting with a receptor-activity-modifying protein (RAMP). The AM1 receptor is composed of CLR and RAMP2, and the calcitonin gene-related peptide (CGRP) receptor of CLR and RAMP1, as determined by molecular and cell-based analysis. This study examines the relevance of RAMP2 in vivo. Transgenic (TG) mice that overexpress RAMP2 in smooth muscle were generated. The role of RAMP2 in the regulation of blood pressure and in vascular function was investigated. Basal blood pressure, acute angiotensin II-raised blood pressure, and cardiovascular properties were similar in wild-type (WT) and TG mice. However, the hypotensive effect of IV AM, unlike CGRP, was enhanced in TG mice (P<0.05), whereas a negative inotropic action was excluded by left-ventricular pressure-volume analysis. In aorta relaxation studies, TG vessels responded in a more sensitive manner to AM (EC50, 8.0+/-1.5 nmol/L) than WT (EC50, 17.9+/-3.6 nmol/L). These responses were attenuated by the AM receptor antagonist, AM(22-52), such that residual responses were identical in all mice. Remaining relaxations were further inhibited by CGRP receptor antagonists, although neither affected AM responses when given alone. Mesenteric and cutaneous resistance vessels were also more sensitive to AM in TG than WT mice. Thus RAMP2 plays a key role in the sensitivity and potency of AM-induced hypotensive responses via the AM1 receptor, providing evidence that this receptor is a selective target for novel therapeutic approaches.

Adrenomedullin↗

PubMed2005

The placental bed in pregnancies complicated by primary antiphospholipid syndrome.

UNLABELLED: Pregnancy in women with primary antiphospholipid syndrome (APS) is frequently associated with placental insufficiency leading to intrauterine growth restriction (IUGR)+/-fetal death, pre-eclampsia, placental abruption, premature delivery or thrombosis. The aim of this study was to investigate the placental bed in APS pregnancies for evidence of impaired trophoblast invasion, endothelial cell activation (ECA) and macrophage infiltration. METHODS: Biopsies from the presumed site of the placental bed were obtained from 12 women with treated primary APS and 16 controls. Immunohistochemical methods were employed to investigate expression of cytokeratin (trophoblasts), alpha-actin (smooth muscle), CD68 (macrophages) and VCAM-1 (as marker of ECA). Fibrinoid and elastin distribution and expression were determined by periodic acid/Schiff and orcein stain, respectively. RESULTS: Three APS pregnancies developed IUGR, one with concurrent pre-eclampsia. Eight of 12 APS biopsies were confirmed to be from the placental bed; one patient failed to meet APS criteria and was excluded from analysis; six included spiral arteries in the biopsy; 11 of 16 controls' biopsies were from the placental bed. APS biopsies had a higher concentration of inflammatory cells (p=0.0001), particularly macrophages (p=0.014). Three APS biopsies showed necrosis with hyperplastic vessels; one demonstrated arterial thromboses, but none had profound vasculopathy/atherosis or ECA. CONCLUSION: Inflammatory mechanisms in the placental bed may contribute to APS pregnancy complications.

Antiphospholipid Syndrome↗

PubMed2005

Amino thiols, detoxification and oxidative stress in pre-eclampsia and other disorders of pregnancy.

New knowledge of placental development and function suggests that several common complications of pregnancy could share a similar origin. It is suggested that impaired placental development in early pregnancy may lead to placental oxidative stress and subsequently to the maternal syndromes such as recurrent early pregnancy loss and pre-eclampsia. Oxidative stress has been most extensively investigated in pre-eclampsia, resulting in hundreds of publications and many reviews. In general the literature points to the presence of placental and maternal oxidative stress. However, conformity amongst the relevant data is not absolute, most probably the result of the diversity of biomarkers investigated and the methods employed to assess oxidative stress, which generally depend on the assessment of end products of oxidative stress. Recently, new techniques have been developed that use different approaches based on the "real-time" measurement of oxidative stress by the redox status of thiols or the assessment of superoxide generation, whereas the role of Phase I/Phase II biotransformation pathways in oxidative stress was recognised. This review focuses on this biotransformation system, the thiol redox status and the involvement of these systems in oxidative stress associated with reproduction and pregnancy disorders, with the emphasis being laid on the syndrome of pre-eclampsia.

Adult↗

PubMed2004

A high-fat diet during rat pregnancy or suckling induces cardiovascular dysfunction in adult offspring.

Epidemiological and animal studies suggest that diet-induced epigenetic modifications in early life can contribute to development of the metabolic syndrome in adulthood. We previously reported features of the metabolic syndrome in adult offspring of rats fed a diet rich in animal fat during pregnancy and suckling. We now report a study to compare the relative effects of high-fat feeding during 1) pregnancy and 2) the suckling period in the development of these disorders. As observed previously, 6-mo-old female offspring of fat-fed dams suckled by the same fat-fed dams (OHF) demonstrated raised blood pressure, despite being fed a balanced diet from weaning. Female offspring of fat-fed dams "cross fostered" to dams consuming a control diet during suckling (OHF/C) demonstrated raised blood pressure compared with controls (OC) [systolic blood pressure (SBP; mmHg) means +/- SE: OHF/C, 132.5 +/- 3.0, n = 6 vs. OC, 119.0 +/- 3.8, n = 7, P < 0.05]. Female offspring of controls cross fostered to dams consuming the fat diet (OC/HF) were also hypertensive [SBP (mmHg) 131.0 +/- 2.5 mmHg, n = 6 vs. OC, P < 0.05]. Endothelium-dependent relaxation (EDR) of male and female OHF and OHF/C mesenteric small arteries was similar and blunted compared with OC (P < 0.001). OC/HF arteries showed profoundly impaired EDR (OC/HF vs. OHF, P < 0.001). OHF/C and OC/HF demonstrated hyperinsulinemia and increased adiposity. Features of the metabolic syndrome in adult offspring of fat-fed rats can be acquired both antenatally and during suckling. However, exposure during pregnancy confers adaptive protection against endothelial dysfunction induced by maternal fat feeding during suckling.

Animals↗

PubMed2004

Impaired EDHF-mediated vasodilatation in adult offspring of rats exposed to a fat-rich diet in pregnancy.

We recently reported vascular dysfunction in adult offspring of rats fed a fat-rich (animal lard) diet in pregnancy. This study reports further characterization of constrictor and dilator function in mesenteric and caudal femoral arteries from 180-day-old offspring of dams fed the high fat diet (OHF). Endothelium-dependent relaxation in response to acetylcholine (10(-9)-10(-5)m) was impaired in mesenteric small arteries from male and female OHF compared with offspring of dams fed normal chow (males (maximum percentage relaxation): OHF 67.92 +/- 2.89, n= 8 versus control 92.08 +/- 2.19, n= 8, P < 0.01). Substantial relaxation in response to acetycholine in control mesenteric arteries remained after inhibition of nitric oxide synthase, soluble guanylate cyclase and cyclo-oxygenase but was blocked by 25 mm potassium. This component of relaxation, attributed to EDHF, was significantly reduced in OHF mesenteric arteries compared with controls. However, EDHF played a minor role in acetylcholine-induced relaxation in both control and OHF femoral caudal arteries (male and female). In these arteries, in contrast to mesenteric vessels, acetylcholine-induced relaxation was significantly enhanced in OHF but only in males (ACh (maximum percentage relaxation): OHF 58.40 +/- 4.39, n= 8 versus male controls 32.18 +/- 6.36, P < 0.05). This was attributable to enhanced nitric oxide-mediated relaxation. In conclusion, reduced endothelium-dependent relaxation in OHF mesenteric arteries is due to impaired EDHF-mediated relaxation. This defect was not apparent in femoral arteries in which EDHF has a less prominent role.

Acetylcholine↗

PubMed2004

Aortic adaptation to pregnancy: elevated expression of matrix metalloproteinases-2 and -3 in rat gestation.

The maternal aorta undergoes substantial functional and structural adaptation in pregnancy. Both aortic diameter and compliance are increased and studies of animal and human gestation indicate that these changes are initiated in early pregnancy and maintained until delivery. The mechanisms underlying aortic adaptation in normal pregnancy remain largely unknown but matrix metalloproteinase enzymes (MMP) are likely to play a key role. Gene expression of candidate MMP and specific tissue inhibitors of MMP (TIMP) were investigated in non-pregnant, pregnant (days 7, 14, 21) and postpartum (day 7) rat aorta using real-time PCR. Of the gene transcripts studied (MMP-2, -3, -7, -9, -12, -13, MT1MMP, TIMP-1, -2) in rat aorta, only MMP-3 was significantly elevated with a 24-fold increase observed in late gestation compared to virgin control (P = 0.0001). MMP-2 mRNA appeared constitutively expressed and unchanged at time-points studied, but MMP-2 activity as assessed by gelatin zymography suggested further modulation after transcription and/or post-translation in rat aorta with activity increased in early pregnancy (P < 0.01, compared to virgin control). These data suggest that MMP-2 and MMP-3 may contribute to adaptive processes in the maternal rat aorta at different gestations and further support a role for this family of enzymes in physiological vascular remodelling.

Animals↗

PubMed2004

Trophoblast oxidative stress, antioxidants and pregnancy outcome--a review.

Placental oxidative stress has been implicated in pre-eclampsia and miscarriage. The review briefly summarizes the definition of oxidative stress, methods of estimation and likely sources in the placenta. Experimental evidence favouring a role for trophoblast oxidative stress in pre-eclampsia includes reports of lipid peroxidation and deficiencies in antioxidant defences. The potential sources of free radical generation include enhanced enzymatic synthesis of superoxide by xanthine oxidase and NAD(P)H oxidase. Studies employing immunohistochemical markers of oxidative stress also implicate free radical induced damage in placentae from women with early pregnancy loss. The overwhelming evidence for oxidative stress in the placenta and the maternal circulation in pre-eclampsia has led to the suggestion that antioxidant prophylaxis may prevent oxidant stress and so ameliorate or prevent the disease. Several clinical trials currently underway will not only determine whether antioxidants are of use in pre-eclampsia prevention but also provide an ideal opportunity to investigate the aetiology and consequences of trophoblast oxidative stress.

Adult↗

PubMed2004

NAD(P)H oxidase associated superoxide production in human placenta from normotensive and pre-eclamptic women.

Oxidative stress plays an important role in the development of pre-eclampsia. Recently, the superoxide producing enzyme NAD(P)H oxidase was shown to be present in placental trophoblast. In this pilot-study we investigated the NAD(P)H oxidase associated superoxide production as modulator of placental oxidative stress in normotensive pregnancy (n = 19; gestational age 38(+6)+/-0(+1)weeks(+days)) and pre-eclampsia (n = 15; gestational age 34(+3)+/-1(+5)weeks(+days)) using a lucigenin assay. Specificity of superoxide generation by NAD(P)H oxidase was assessed using the inhibitors L-NAME, rotenone, allopurinol, DPI and TIRON. Superoxide production was measurable in all placenta tissues and was inhibited by DPI and TIRON. No significant differences for total superoxide production (O2*total), maximal superoxide production (O2*max), or the rate of superoxide production were found between normotensive and pre-eclamptic women. However, women with early onset of disease had a higher O2*total as compared to those with a late onset disease. We conclude that human placenta contains a functional NAD(P)H oxidase that is highly active, which could be an important source of superoxide during pregnancy and pre-eclampsia. These data justify more detailed investigation of the role of NAD(P)H oxidase and placental oxidative stress in complicated pregnancies.

Adult↗

PubMed2004

Physiological induction of transient receptor potential canonical proteins, calcium entry channels, in human myometrium: influence of pregnancy, labor, and interleukin-1 beta.

This study investigated gestational regulation of transient receptor potential canonical (TrpC) proteins, putative calcium entry channels in human myometrium, and the potential modulation of TrpC expression by IL-1 beta, a cytokine implicated in labor. Total RNA and proteins were isolated from myometrial biopsies obtained from NP women, pregnant women at term not in labor (TNL), or term active labor (TAL) and from primary cultured human myometrial smooth muscle cells incubated with IL-1 beta or IL-1 beta with or without nimesulide. Semiquantitative RT-PCR demonstrated significant up-regulation of TrpC1 in TAL and TNL (P < or = 0.01) and TrpC6 (P < or = 0.01) and TrpC7 (P < or = 0.05) in TAL samples. TrpC3 and TrpC4 mRNA expression was unaffected. Western blot demonstrated significant up-regulation of TrpC1 in TAL and TNL (P < or = 0.05) and TrpC3 (P < or = 0.01), TrpC4 (P < or = 0.05), and TrpC6 (P < or = 0.01) in TAL samples. IL-1 beta did not alter TrpC1, 3, 4, 6, or 7 mRNA expression; but IL-1 beta exclusively up-regulated TrpC3 protein expression (P < or = 0.05). TrpC3 up-regulation was unaffected by cyclooxygenase blockade. These data demonstrate physiological regulation of TrpC mRNA and protein and suggest an important role for TrpC proteins in human myometrium during labor.

Calcium Channels↗

PubMed2003

Glycine rectifies vascular dysfunction induced by dietary protein imbalance during pregnancy.

Protein restriction in rat pregnancy programmes the development of elevated systolic blood pressure and vascular dysfunction in the offspring. A recent study has shown that hypertension is reversed by maternal glycine supplementation. Whether this protective effect is exerted directly on the embryo and fetus, or indirectly via effects on the mother, is unknown although we have previously shown abnormalities in the maternal vasculature. We tested the hypothesis that dietary glycine repletion would reverse endothelial dysfunction in protein-restricted pregnant rat dams using wire myography. Impaired acetylcholine- (P < 0.01) and isoprenaline-induced (P < 0.05) vasodilatation in isolated mesenteric arteries (MA) from protein-restricted pregnant dams was accompanied by reduced vascular nitric oxide (NO) release (P < 0.05). Dietary glycine supplementation reversed vascular dysfunction in MA (P < 0.05) and improved NO release thus potentially protecting the maternal circulation. The impaired NO release in the MA of low protein diet dams was not accompanied by reduced eNOS mRNA expression, suggesting that eNOS activity was altered. Protein restriction did not alter the vascular function of a conduit artery, the thoracic aorta. These results provide evidence that adequate provision of glycine, a conditionally essential amino acid in pregnancy, may play a role in the vascular adaptations to pregnancy, protecting the fetus from abnormal programming of the cardiovascular system.

Animals↗

PubMed2003

The potential role for arachidonic and docosahexaenoic acids in protection against some central nervous system injuries in preterm infants.

The risk of central nervous, visual, and auditory damage increases from 2/1000 live births in the normal birthweight to > 200/1000 as birthweight falls below 1500 g. Such babies are most likely to be born preterm. Advances in infant care have led to increasing numbers of very-low-birthweight, preterm infants surviving to school age with moderate to severe brain damage. Steroids are one of the current treatments, but they cause significant, long-term problems. The evidence reported here suggests an additional approach to protecting the very preterm infant by supporting neurovascular membrane integrity. The complications of preterm, very-low-birthweight babies include bronchopulmonary dysplasia, retinopathy of prematurity, intraventricular hemorrhage, periventricular leukomalacia, and necrotizing enterocolitis, all of which have a vascular component. Arachidonic acid (AA) and DHA are essential, structural, and functional constituents of cell membranes. They are especially required for the growth and function of the brain and vascular systems, which are the primary biofocus of human fetal growth. Molecular dynamics and experimental evidence suggest that DHA could be the ligand for the retinoid X receptor (RXR) in neural tissue. RXR activation is an obligatory step in signaling to the nucleus and in the regulation of gene expression. Very preterm babies are born with minimal fat stores and suboptimal circulating levels of these nutrients. Postnatally, they lose the biomagnification of the proportions of AA and DHA by the placenta for the fetus. No current nutritional management repairs these deficits. The placental biomagnification profile highlights AA rather than DHA. The resultant fetal FA profile closely resembles that of the vascular endothelium and not the brain. Without this nourishment, cell membrane abnormalities would be predicted. We present a scientific rationale for a common pathogenic process in the complications of prematurity.

Animals↗

PubMed2003

Mechanisms underlying the programming of small artery dysfunction: review of the model using low protein diet in pregnancy in the rat.

Human and animal studies have shown that unbalanced maternal nutrition is associated with the development of cardiovascular and metabolic disease in adulthood. In the Southampton maternal low protein model (SMLP), protein deprivation (50%) throughout pregnancy in rats leads to elevated blood pressure in adult offspring. Impaired peripheral arterial function may contribute to the cardiovascular dysfunction observed in these offspring. This review discusses the impact of such a dietary insult on the vascular function of resistance arteries from pregnant rats (pF(o)), their offspring (F(1)), the pregnant offspring (pF(1)) and the second generation (F(2)). At each stage, disturbances in endothelium-dependent relaxation were observed, implicating changes in endothelial nitric oxide (NO)-guanylate cyclase (GC) signalling pathway in the vascular adaptations to pregnancy and the programmed effects on offspring.

Animals↗

PubMed2003

Fetal programming for adult disease: where next?

The Barker hypothesis of fetal programming for adult cardiovascular and metabolic diseases has attracted much interest over the past few years. In this review, we summarize the main studies in this field, give a brief outline of some of the laboratory models used to investigate this hypothesis and discuss potential mechanisms underlying these clinical observations that are amenable to future research.

Birth Weight↗

PubMed2003

Gestational profile of matrix metalloproteinases in rat uterine artery.

Mechanisms underlying structural reorganization of the uterine artery in pregnancy remain largely unknown. Matrix metalloproteinases (MMPs) which are involved in degradation of vascular wall matrix are likely to play a key role. In this investigation of rat uterine artery, key MMPs and the specific tissue inhibitors of MMPs (TIMPs) together with three housekeeping genes were studied before, during and after pregnancy, using real time PCR. Data were analysed by partial least squares analysis as well as by conventional univariate methods. Each gene studied [MMP-2, MMP-3, MMP-7, MMP-9, MMP-12, MMP-13, membrane-type 1 (MT1)-MMP, TIMP-1, TIMP-2, GAPDH, cyclophilin and beta-actin] increased in late pregnancy (day 21). MMP-2, MT1MMP, MMP-3 and TIMP-1 transcripts were also elevated at day 7. TIMP-1 and MMP-3 mRNA expression returned to virgin control values in the post-partum, whereas others remained elevated or increased further (MMP-9, MMP-13). Gelatin zymography showed maximum elevation of MMP-2 at day 21. A novel 43-45 kDa gelatinolytic doublet was observed which increased in density with gestation and may represent an active MMP-2 fragment. Together, these data strongly suggest that MMPs and TIMPs are likely to play an important role in remodelling uterine arteries in rat pregnancy and may represent means by which vasodilatation is maintained in later pregnancy. Continued elevated levels of some MMPs post-partum may contribute to vessel regression and return to a non-pregnant physiological state.

Animals↗