Mechanisms for vascular disease in women - Inflammation in pre-eclampsia and atherosclerosis

Women with preeclampsia have doubled risk for developing cardiovascular disease later in life. Pregnancy represents a metabolic stress test and abnormal changes in preeclampsia may represent an early sign of cardiovascular disease in some women. Both diseases are characterized as inflammatory and have shared risk factors. This project aims to understand the shared inflammatory processes in preeclampsia and cardiovascular disease. Inflammatory mechanisms and genetic risk factors have been studied by use of several Norwegian Biobanks and Health Registries. Preeclampsia most often begins with poor placental development and a central role for inflammation in this dysfunction is acknowledged, however the mechanisms and cell types involved are largely unknown. The body´s danger sensing system during disease, tissue damage and infection involves activation of a receptor system (Pathogen Recognition Receptors (PRRs)) that is essential for all inflammatory processes. Study of PRR expression and activation is required to determine which inflammatory mechanisms play a role, both in normal immune response to infection and tissue damage, and in inflammatory disease. In the placenta, specialized fetal cells (trophoblasts) form a protective cell layer against maternal blood, and this cell layer is particularly sensitive to immune activation. This project has shown that primary trophoblasts isolated from placentas broadly express functional PRRs and possess potent inflammatory characteristics. Importantly, characterization of PRRs in well-established trophoblast cell line models have demonstrated that they are less comparable to primary trophoblasts than expected, warranting caution for their use to study placental inflammation. Based on the existing knowledge of inflammation in atherosclerosis, central PRR mediated inflammatory mechanisms was selected for analysis. The main finding in the placenta was that the trophoblast cell layer showed the strongest expression of the central mechanisms HMGB1-activated TLR4 and crystal-activated inflammasome NLRP3. Moreover, the results indicated that these mechanisms play an important part of the harmful placental inflammation in preeclampsia. In preeclampsia, increased maternal levels of inflammatory signals such as cytokines reflect how the harmful inflammatory processes in the placenta contribute to systemic inflammation and disease development in the mother. A broad characterisation of many different cytokines in maternal blood from early pregnancy resulted in the ability to distinguish between women later developing preeclampsia and those later developing high blood pressure (pregnancy hyptertension). This method represents a new sensitive tool for detecting inflammatory changes in maternal blood even before clinical signs and has increased our understanding of pregnancy-related inflammatory disease. Furthermore, different variants of preeclampsia have been identified based on metabolic changes in blood and urine from pregnant women, providing a sensitive method to predict and characterize different subgroups of preeclampsia. A similar metabolic profiling of placental tissue has shown to be a novel method for classification of different variants of placenta diseases, a highly needed tool for more causal classification of preeclampsia, and providing a basis for a new rationale for biomarker discovery in preeclampsia. An important part of the project has been the investigations of gene variants associated with development of preeclampsia. Several gene variants (SNPs) associated with preeclampsia have been identified, and also shown related to genes and life style factors associated with cardiovascular disease. Extensive analysis of families with increased occurence of preeclampsia have shown that disease and life style factors associated with cardiovascular diseases are inheritable with preeclampsia. A collaborative epidemiologic study in the Cohort of Norway (CONOR) have identified that preeclampsia led to increased risk for cardiovascular disease later in life, especially for the preeclamptic women giving birth preterm and/or to small babies. By participating with a cohort from the HUNT Study and our Preeclampsia Biobank in the world largest preeclampsia related genetic analysis in the EU project InterPregGen, the first fetal gene variant associated with increased risk for preeclampsia has been identified. This gene variant is close to the gene regulating production of the protein sFlt, a trophoblast derived marker of placental disease.

Pre-eclampsia (PE) is a major cause of maternal disease/death in pregnancy and affects about 5% of pregnant women. In severe cases, PE may also involve the fetus, causing premature deliveries and fetal growth restriction. Enhanced systemic inflammation an d vascular endothelial activation are characteristic findings in pre-eclamptic women. Similar hallmarks are found in cardiovascular disease (CVD), and in accordance with this; women with previous pre-eclamptic pregnancies, have doubled risk for later-life CVD. In many ways pregnancy may be considered a metabolic stress test, and thus, PE may be the first clinical manifestation suggesting that an apparently healthy young woman in fact houses abnormal metabolic/inflammatory responses. In this project, mecha nisms underlying PE and CVD will be explored by focusing on inflammation. Both initiating signals (endogenous damage/danger signals and pathogen components) and receptivity (pattern recognition receptors (PRRs)) of cases/controls will be assessed. The g enetic influence will be assessed by genotyping PRR-related genes in women with/without PE and with/without CVD in several large Norwegian cohorts. In addition, levels of inflammatory signals and activation will be compared. The role of local inflammatory responses at the maternal-fetal site will be studied in placental/decidual tissues and in vitro studies of fetal trophoblasts. In the present project, the aim is to study, and compare, inflammatory mechanisms associated with both PE and CVD in women. F indings may potentially open for tests for risk assessment, useful for a maternity care aiming to increase attention to pregnant women at risk. In addition, findings may potentially open for new therapeutic approaches. Development of CVD appears to have g ender-specific mechanisms, which remain to be elucidated. Knowledge gained from the combined study of PE and CVD may generate useful insight in mechanisms underlying the female way of developing CVD.