The protective effect of apolipoprotein in models of trophoblast invasion and preeclampsia.

Preeclampsia is a hypertensive disorder of pregnancy. It is associated with abnormal placentation via poor placental invasion of the uterine vasculature by trophoblast cells, leading to poor placental perfusion, oxidative stress, and inflammation, all of which are implicated in its pathogenesis. A dyslipidemia characterized by low plasma levels of high-density lipoproteins (HDL) and elevated triglycerides has been described in preeclampsia. Apolipoprotein A-I (apoA-I), a constituent of HDL is an anti-inflammatory agent. This study investigated whether apoA-I protects against hypertension and adverse placental changes in a proinflammatory cytokine (TNF-α)-induced model of preeclampsia. Further, this study investigated whether apoA-I protects against the inhibitory effect of TNF-α in a human in vitro model of trophoblast invasion. Administration of apoA-I to pregnant mice before infusion with TNF-α resulted in a significant reduction in the cytokine-induced increase in systolic blood pressure. MRI measurement of T2 relaxation, a parameter that is tissue specific and sensitive to physiological changes within tissues, showed a reversal of TNF-α-induced placental changes. Preincubation of endothelial cells with apoA-I protected against the TNF-α-induced inhibition of HTR-8/SVneo (trophoblast) cell integration into endothelial (UtMVEC) networks. These data suggest that a healthy lipid profile may affect pregnancy outcomes by priming endothelial cells in preparation for trophoblast invasion.

Cardiovascular risk, lipids and pregnancy: preeclampsia and the risk of later life cardiovascular disease.

It has been widely thought that the effects of hypertension in pregnancy reversed after delivery and hypertension values returned to their pre-pregnancy level as it was seen as a disease of short duration in otherwise healthy young women. However, recent studies have demonstrated that the principal underlying abnormality, endothelial dysfunction, remains in women who had preeclampsia and that it is this damage that increases the risk of developing cardiovascular disease (CVD) in later life. The contributions of hypertension and dyslipidaemia before and during the pregnancy are also important and contribute to future risk. Serum lipids are complex and change dramatically in pregnancy. In general there is an increase in most plasma lipid components, notably triglycerides, total cholesterol and the major particles of HDL and LDL. Aberrations or exaggerations in this shift (i.e. decrease HDL and a greater increase in LDL) are associated with poor outcomes of pregnancy such as preeclampsia. Long term cardiovascular disease is influenced by preeclampsia and in part potentially by the lipid changes which escalate late in disease. Whether we can influence the risk of preeclampsia by controlling cardiovascular risk factors preceding or during preeclampsia, or cardiovascular disease after preeclampsia is yet to be determined. Ultimately, strategies to control lipid concentrations will only be viable when we understand the safety to the mother at the time of the pregnancy, and to the foetus both immediately and in the very long term. Strategies to control blood pressure are well established in the non-pregnant population, and previous preeclampsia and gestational hypertension should be considered in any cardiovascular risk profile. Whether control of blood pressure in the pregnancy per se is of any longer term benefit is also yet to be determined.

The low resolution structure of ApoA1 in spherical high density lipoprotein revealed by small angle neutron scattering.

Spherical high density lipoprotein (sHDL), a key player in reverse cholesterol transport and the most abundant form of HDL, is associated with cardiovascular diseases. Small angle neutron scattering with contrast variation was used to determine the solution structure of protein and lipid components of reconstituted sHDL. Apolipoprotein A1, the major protein of sHDL, forms a hollow structure that cradles a central compact lipid core. Three apoA1 chains are arranged within the low resolution structure of the protein component as one of three possible global architectures: (i) a helical dimer with a hairpin (HdHp), (ii) three hairpins (3Hp), or (iii) an integrated trimer (iT) in which the three apoA1 monomers mutually associate over a portion of the sHDL surface. Cross-linking and mass spectrometry analyses help to discriminate among the three molecular models and are most consistent with the HdHp overall architecture of apoA1 within sHDL.

Evidence that niacin inhibits acute vascular inflammation and improves endothelial dysfunction independent of changes in plasma lipids.

OBJECTIVE: To determine if niacin can confer cardiovascular benefit by inhibiting vascular inflammation and improving endothelial function independent of changes in plasma lipid and lipoprotein levels. METHODS AND RESULTS: New Zealand white rabbits received normal chow or chow supplemented with 0.6% or 1.2% (wt/wt) niacin. This regimen had no effect on plasma cholesterol, triglyceride, or high-density lipoprotein levels. Acute vascular inflammation and endothelial dysfunction were induced in the animals with a periarterial carotid collar. At the 24-hour postcollar implantation, the endothelial expression of vascular cell adhesion molecule-1, intercellular adhesion molecule-1, and monocyte chemotactic protein-1 was markedly decreased in the niacin-supplemented animals compared with controls. Niacin also inhibited intima-media neutrophil recruitment and myeloperoxidase accumulation, enhanced endothelial-dependent vasorelaxation and cyclic guanosine monophosphate production, increased vascular reduced glutathione content, and protected against hypochlorous acid-induced endothelial dysfunction and tumor necrosis factor alpha-induced vascular inflammation. CONCLUSION: Previous human intervention studies have demonstrated that niacin inhibits coronary artery disease. This benefit is thought to be because of its ability to reduce low-density lipoprotein and plasma triglyceride levels and increase high-density lipoprotein levels. The present study showed that niacin inhibits vascular inflammation and protects against endothelial dysfunction independent of these changes in plasma lipid levels.

Antihypertensive drugs methyldopa, labetalol, hydralazine, and clonidine improve trophoblast interaction with endothelial cellular networks in vitro.

OBJECTIVES: The interaction between trophoblasts and maternal endothelium is important for placental vascular modeling. Failure of uterine spiral artery transformation is linked to the etiopathology of preeclampsia. Antihypertensive medications used to control hypertension in early pregnancy can alter placental and circulating cytokines. This study investigated whether selected antihypertensive drugs can modulate the interaction between trophoblast and endothelial cells. METHODS: Human uterine myometrial microvascular endothelial cells were preincubated with (or without) low-dose tumor necrosis factor-α (TNF-α; 0.5 ng/ml) or TNF-α and soluble fms-like tyrosine kinase 1 (sFlt-1; 100 ng/ml). Red fluorescent-labeled endothelial cells were then cultured on Matrigel. After appearance of endothelial cellular networks, green fluorescent-labeled HTR-8/SVneo trophoblast cells were cocultured in the presence of pharmacological doses of methyldopa, labetalol, hydralazine, and clonidine. Images were captured after 24 h and drug effects on HTR-8/SVneo cell integration were quantified by Image Analysis software. The conditioned medium was collected to measure sFlt-1, vascular endothelial growth factor (VEGF), placental growth factor, interleukin-10, and interleukin-6 by ELISA. RESULTS: Methyldopa, labetalol, hydralazine, and clonidine increased trophoblast integration into TNF-α-preincubated endothelial cellular networks. In conditioned medium, sFlt-1 was reduced by methyldopa, hydralazine, and clonidine alone. VEGF was increased by methyldopa. A decrease in placental growth factor was seen by methyldopa and also in nontreated endothelial cell coculture of the other three drugs. CONCLUSION: Some antihypertensive drugs used in pregnancy may improve the cellular interaction between trophoblast and endothelial cells exposed to TNF-α. Methyldopa, hydralazine, and clonidine reduced sFlt-1 concentration in culture medium, whereas labetalol increased trophoblast integration independently of sFlt-1. Methyldopa increased VEGF concentration. Some pregnancy-related antihypertensives may affect placental vascularization.

Molecular basis of PCSK9 function.

The LDL receptor (LDLr) inhibitor Proprotein Convertase Subtilisin Kexin type 9 (PCSK9) has emerged as a genetically validated target for lowering plasma LDL cholesterol levels. In 2007, PCSK9 was found to act as a chaperone that binds the LDLr, thereby targeting it for lysosomal degradation. The enzymatic activity of PCSK9 is not involved in that process, but rather permits proper intramolecular processing of PCSK9. This was demonstrated by both site directed mutagenesis and independent reports of the PCSK9 crystal structure. These reports also elucidated the mode of action of several naturally occurring mutants of PCSK9 associated with hyper- or hypocholesterolemia. The present review summarizes studies published or in print before May 2008 investigating the functional significance of PCSK9 and its promising aspects as a prognostic tool and a drug target.

Identification and characterization of two non-secreted PCSK9 mutants associated with familial hypercholesterolemia in cohorts from New Zealand and South Africa.

We analysed the Proprotein Convertase Subtilisin Kexin type 9 (PCSK9) exons and intronic junctions of 71 patients with familial hypercholesterolemia (FH) in whom LDL receptor (LDLR) or apolipoprotein B100 mutations were excluded. The previously reported S127R and R237W mutations were found in South African families, whereas new missense mutations D129G and A168E were found in families from New Zealand. Only, the S127R and D129G mutations modify a highly conserved residue and segregate with the FH phenotype. We overexpressed those mutants in hepatoma cells and found that both S127R and D129G have reduced autocatalytic activity compared with wild-type PCSK9, whereas the A168E mutant is processed normally. The S127R and D129G mutants were not secreted from cells, unlike the A168E mutant and wild-type PCSK9. By immunoblot, we showed that the expression of the LDLR was reduced by 40% in cells overexpressing wild-type or A168E PCSK9 and further reduced by 30% when the S127R or D129G mutants were used. Paralleling the LDLR levels, LDL cellular binding decreased by 25% upon wild-type PCSK9 or A168E overexpression, and by 45% with both S127R and D129G mutants. Our study therefore indicates that PCSK9 mediated inhibition of the LDLR does not require PCSK9 autocatalytic cleavage or secretion, suggesting that PCSK9 may also function intracellularly.

Plasma PCSK9 concentrations correlate with LDL and total cholesterol in diabetic patients and are decreased by fenofibrate treatment.

BACKGROUND: Proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes the degradation of the LDL receptor (LDLr) in hepatocytes, and its expression in mouse liver has been shown to decrease with fenofibrate treatment. METHODS: We developed a sandwich ELISA using recombinant human PCSK9 protein and 2 affinity-purified polyclonal antibodies directed against human PCSK9. We measured circulating PCSK9 concentrations in 115 diabetic patients from the FIELD (Fenofibrate Intervention and Event Lowering in Diabetes) study before and after fenofibrate treatment. RESULTS: We found that plasma PCSK9 concentrations correlate with total (r = 0.45, P = 0.006) and LDL (r = 0.54, P = 0.001) cholesterol but not with triglycerides or HDL cholesterol concentrations in that cohort. After 6 weeks of treatment with comicronized fenofibrate (200 mg/day), plasma PCSK9 concentrations decreased by 8.5% (P = 0.041 vs pretreatment). This decrease correlated with the efficacy of fenofibrate, as judged by a parallel reduction in plasma triglycerides (r = 0.31, P = 0.015) and LDL cholesterol concentrations (r = 0.27, P = 0.048). CONCLUSIONS: We conclude that this decrease in PCSK9 explains at least in part the LDL cholesterol-lowering effects of fenofibrate. Fenofibrate might be of interest to further reduce cardiovascular risk in patients already treated with a statin.