Autoantibody from women with preeclampsia induces soluble Fms-like tyrosine kinase-1 production via angiotensin type 1 receptor and calcineurin/nuclear factor of activated T-cells signaling

Preeclampsia is a pregnancy-specific hypertensive syndrome that causes substantial maternal and fetal morbidity and mortality. Recent evidence indicates that maternal endothelial dysfunction in preeclampsia results from increased soluble Fms-like tyrosine kinase-1 (sFlt-1), a circulating antiangiogenic protein. Factors responsible for excessive production of sFlt-1 in preeclampsia have not been identified. We tested the hypothesis that angiotensin II type 1 (AT1) receptor activating autoantibodies, which occur in women with preeclampsia, contribute to increased production of sFlt-1. IgG from women with preeclampsia stimulates the synthesis and secretion of sFlt-1 via AT1 receptor activation in pregnant mice, human placental villous explants, and human trophoblast cells. Using FK506 or short-interfering RNA targeted to the calcineurin catalytic subunit mRNA, we determined that calcineurin/nuclear factor of activated T-cells signaling functions downstream of the AT1 receptor to induce sFlt-1 synthesis and secretion by AT1-receptor activating autoantibodies. AT1-receptor activating autoantibody–induced sFlt-1 secretion resulted in inhibition of endothelial cell migration and capillary tube formation in vitro. Overall, our studies demonstrate that an autoantibody from women with preeclampsia induces sFlt-1 production via angiotensin receptor activation and downstream calcineurin/nuclear factor of activated T-cells signaling. These autoantibodies represent potentially important targets for diagnosis and therapeutic intervention.

Can the biology of VEGF and haem oxygenases help solve pre-eclampsia?

Pre-eclampsia, a pregnancy-specific multi-organ syndrome characterized by widespread endothelial damage, is a new risk factor for cardiovascular disease. No therapies exist to prevent or treat this condition, even to achieve a modest improvement in pregnancy length or birth weight. Co-administration of soluble VEGFR-1 [VEGF (vascular endothelial growth factor) receptor-1; more commonly known as sFlt-1 (soluble Fms-like tyrosine kinase-1)] and sEng (soluble endoglin) to pregnant rats elicits severe pre-eclampsia-like symptoms. These two anti-angiogenic factors are increased dramatically prior to the clinical onset of pre-eclampsia and are quite possibly the 'final common pathway' responsible for the accompanying signs of hypertension and proteinuria as they can be reversed by VEGF administration in animal models. HO-1 (haem oxygenase-1), an anti-inflammatory enzyme, and its metabolite, CO (carbon monoxide), exert protective effects in several organs against oxidative stimuli. In a landmark publication, we showed that the HO-1 pathway inhibits sFlt-1 and sEng in cultured cells and human placental tissue explants. Both CO and NO (nitric oxide) promote vascular homoeostasis and vasodilatation, and activation of VEGFR-1 or VEGFR-2 induced eNOS (endothelial nitric oxide synthase) phosphorylation, NO release and HO-1 expression. Our studies established the HO-1/CO pathway as a negative regulator of cytokine-induced sFlt-1 and sEng release and eNOS as a positive regulator of VEGF-mediated vascular morphogenesis. These findings provide compelling evidence for a protective role of HO-1 in pregnancy and identify it as a target for the treatment of pre-eclampsia. Any agent that is known to up-regulate HO-1, such as statins, may have potential as a therapy. Any intervention achieving even a modest prolongation of pregnancy or amelioration of the condition could have a significant beneficial health impact worldwide.

Targeting the glycoprotein 130 receptor subunit to control pain and inflammation

The glycoprotein 130 (gp130) is a shared signal-transducing-membrane-associated receptor for several hematopoietic cytokines. Its activation is implicated in pain and in a variety of diseases via signaling of proinflammatory cytokines. These include interleukin-6 (IL-6) subfamily cytokines, many of which play important roles in the pathogenesis of diseases such as rheumatoid arthritis, Castleman's disease, and Kaposi's sarcoma. Several strategies have been developed to block gp130-receptor-mediated signaling. These include the application of monoclonal antibodies, the creation of mutant form(s) of the gp130 with increased binding affinity for such ligands as IL-6/sIL-6R complex, and the generation of antagonists by selective mutagenesis of the specific cytokine/gp130 receptor binding site(s). Other strategies include targeting gp130-mediated signaling pathways such as that involving signal transducer and activator of transcription-3. This review provides a summary of the latest research pertaining to the role of gp130 in the pathogenesis of inflammatory and other diseases in which the gp130 receptor is implicated. An overview of antagonists targeting the gp130 receptor is included with particular emphasis on their mechanism of action and their limitations and potential for therapeutic application.

Induction of lipolysis in vitro and loss of body fat in vivo by zinc-alpha(2)-glycoprotein

Loss of adipose tissue in cancer cachexia has been associated with tumour production of a lipid-mobilizing factor (LMF) which has been shown to be homologous with the plasma protein zinc-a2-glycoprotein (ZAG). The aim of this study was to compare the ability of human ZAG with LMF to stimulate lipolysis in vitro and induce loss of body fat in vivo, and to determine the mechanisms involved. ZAG was purified from human plasma using a combination of Q Sepharose and Superdex 75 chromatography, and was shown to stimulate glycerol release from isolated murine epididymal adipocytes in a dose-dependent manner. The effect was enhanced by the cyclic AMP phosphodiesterase inhibitor Ro20-1724, and attenuated by freeze/thawing and the specific ß3-adrenoreceptor antagonist SR59230A. In vivo ZAG caused highly significant, time-dependent, decreases in body weight without a reduction in food and water intake. Body composition analysis showed that loss of body weight could be attributed entirely to the loss of body fat. Loss of adipose tissue may have been due to the lipolytic effect of ZAG coupled with an increase in energy expenditure, since there was a dose-dependent increase in expression of uncoupling protein-1 (UCP-1) in brown adipose tissue. These results suggest that ZAG may be effective in the treatment of obesity.

Appetite regulatory mechanisms and food intake in mice are sensitive to mismatch in diets between pregnancy and postnatal periods

Human and animal studies suggest that obesity in adulthood may have its origins partly during prenatal development. One of the underlying causes of obesity is the perturbation of hypothalamic mechanisms controlling appetite. We determined mRNA levels of genes that regulate appetite, namely neuropeptide Y (NPY), pro-opiomelanocortin (POMC) and the leptin receptor isoform Ob-Rb, in the hypothalamus of adult mouse offspring from pregnant dams fed a protein-restricted diet, and examined whether mismatched post-weaning high-fat diet altered further expression of these gene transcripts. Pregnant MF1 mice were fed either normal protein (C, 18% casein) or protein-restricted (PR, 9% casein) diet throughout pregnancy. Weaned offspring were fed to adulthood a high-fat (HF; 45% kcal fat) or standard chow (21% kcal fat) diet to generate the C/HF, C/C, PR/HF and PR/C groups. Food intake and body weight were monitored during this period. Hypothalamic tissues were collected at 16 weeks of age for analysis of gene expression by real time RT-PCR. All HF-fed offspring were observed to be heavier vs. C groups regardless of the maternal diet during pregnancy. In the PR/HF males, but not in females, daily energy intake was reduced by 20% vs. the PR/C group (p <0.001). In PR/HF males, hypothalamic mRNA levels were lower vs. the PR/C group for NPY (p <0.001) and Ob-Rb (p <0.05). POMC levels were similar in all groups. In females, mRNA levels for these transcripts were similar in all groups. Our results suggest that adaptive changes during prenatal development in response to maternal dietary manipulation may have long-term sex-specific consequences on the regulation of appetite and metabolism following post-weaning exposure to an energy-rich nutritional environment. © 2008 Elsevier B.V. All rights reserved.

The coupling mechanism of P-glycoprotein involves residue L339 in the sixth membrane spanning segment

The transmembrane (TM) domains in P-glycoprotein (P-gp) contain the drug binding sites and undergo conformational changes driven by nucleotide catalysis to effect translocation. However, our understanding of exactly which regions are involved in such events remains unclear. A site-directed labelling approach was used to attach thiol-reactive probes to cysteines introduced into transmembrane segment 6 (TM6) in order to perturb function and infer involvement of specific residues in drug binding and/or interdomain communication. Covalent attachment of coumarin-maleimide at residue 339C within TM6 resulted in impaired ATP hydrolysis by P-gp. The nature of the effect was to reduce the characteristic modulation of basal activity caused by transported substrates, modulators and the potent inhibitor XR9576. Photoaffinity labelling of P-gp with [(3)H]-azidopine indicated that residue 339C does not alter drug binding per se. However, covalent modification of this residue appears to prevent conformational changes that lead to drug stimulation of ATP hydrolysis.

Angiotensin II induces soluble fms-Like tyrosine kinase-1 release via calcineurin signaling pathway in pregnancy

Maternal endothelial dysfunction in preeclampsia is associated with increased soluble fms-like tyrosine kinase-1 (sFlt-1), a circulating antagonist of vascular endothelial growth factor and placental growth factor. Angiotensin II (Ang II) is a potent vasoconstrictor that increases concomitant with sFlt-1 during pregnancy. Therefore, we speculated that Ang II may promote the expression of sFlt-1 in pregnancy. Here we report that infusion of Ang II significantly increases circulating levels of sFlt-1 in pregnant mice, thereby demonstrating that Ang II is a regulator of sFlt-1 secretion in vivo. Furthermore, Ang II stimulated sFlt-1 production in a dose- and time-dependent manner from human villous explants and cultured trophoblasts but not from endothelial cells, suggesting that trophoblasts are the primary source of sFlt-1 during pregnancy. As expected, Ang II-induced sFlt-1 secretion resulted in the inhibition of endothelial cell migration and in vitro tube formation. In vitro and in vivo studies with losartan, small interfering RNA specific for calcineurin and FK506 demonstrated that Ang II-mediated sFlt-1 release was via Ang II type 1 receptor activation and calcineurin signaling, respectively. These findings reveal a previously unrecognized regulatory role for Ang II on sFlt-1 expression in murine and human pregnancy and suggest that elevated sFlt-1 levels in preeclampsia may be caused by a dysregulation of the local renin/angiotensin system.

Growing better brains? Pregnancy and neuroscience discourses in English social and welfare policies

In recent years, English welfare and health policy has started to include pregnancy within the foundation stage of child development. The foetus is also increasingly designated as ‘at risk’ from pregnant women. In this article, we draw on an analysis of a purposive sample of English social and welfare policies and closely related advocacy documents to trace the emergence of neuroscientific claims-making in relation to the family. In this article, we show that a specific deterministic understanding of the developing brain that only has a loose relationship with current scientific evidence is an important component in these changes. We examine the ways in which pregnancy is situated in these debates. In these debates, maternal stress is identified as a risk to the foetus; however, the selective concern with women living in disadvantage undermines biological claims. The policy claim of neurological ‘critical windows’ also seems to be influenced by social concerns. Hence, these emerging concerns over the foetus’ developing brain seem to be situated within the gendered history of policing women’s pregnant bodies rather than acting on new insights from scientific discoveries. By situating these developments within the broader framework of risk consciousness, we can link these changes to wider understandings of the ‘at risk’ child and intensified surveillance over family life.