Sildenafil Therapy Normalizes the Aberrant Metabolomic Profile in the Comt(-/-) Mouse Model of Preeclampsia/Fetal Growth Restriction

Guidelines for assessing maternal cardiovascular physiology during pregnancy and postpartum

Maternal mortality rates are at an all-time high across the world and are set to increase in subsequent years. Cardiovascular disease is the leading cause of death during pregnancy and postpartum, especially in the United States. Therefore, understanding the physiological changes in the cardiovascular system during normal pregnancy is necessary to understand disease-related pathology. Significant systemic and cardiovascular physiological changes occur during pregnancy that are essential for supporting the maternal-fetal dyad. The physiological impact of pregnancy on the cardiovascular system has been examined in both experimental animal models and in humans. However, there is a continued need in this field of study to provide increased rigor and reproducibility. Therefore, these guidelines aim to provide information regarding best practices and recommendations to accurately and rigorously measure cardiovascular physiology during normal and cardiovascular disease-complicated pregnancies in human and animal models.

Function of sildenafil on diseases other than urogenital system: An umbrella review

Background: To investigate the function of sildenafil on diseases other than urogenital system, an umbrella review was conducted. Methods: Meta-analysis and systematic reviews on this topic were comprehensively evaluated in this umbrella review. Quality of evidence was evaluated through AMSTAR and the Grading of Recommendations, Assessment, Development and Evaluation system to generate a reliable and valid conclusion. Results: 77 out of 1164 meta-analysis were enrolled. 33 significant outcomes and 41 non-significant outcomes were extracted from all eligible articles. We found sildenafil did significant help in reducing arterial systolic pressure, mean pulmonary arterial pressure, pulmonary arterial pressure, systolic pulmonary arterial pressure in patients with pulmonary and cardiovascular diseases. Besides, sildenafil also improved exercise capacity or performance in patients with pulmonary and cardiovascular diseases. Other than these patients, this drug contributed great help in pregnant women with fetal growth restriction and preeclampsia by increasing the weight of newborns and lowering uterine and umbilical pulsatility indices. Additionally, it was reported that utilization of sildenafil has brought increased risk of melanoma. Conclusion: We can conclude from our study that sildenafil played an important role in many fields, especially in vascular protection. This finding provides a strong evidence for further expansion of sildenafil utilization in other diseases.

Prenatal interventions for fetal growth restriction in animal models: A systematic review

Fetal growth restriction (FGR) in human pregnancy is associated with perinatal mortality, short- and long-term morbidities. No prenatal therapy is currently established despite decades of research. We aimed to review interventions in animal models for prenatal FGR treatment, and to seek the next steps for an effective clinical therapy. We registered our protocol and searched MEDLINE, Embase, and The Cochrane Library with no language restrictions, in accordance with the PRISMA guideline. We included all studies that reported the effects of any prenatal intervention in animal models of induced FGR. From 3257 screened studies, 202 describing 237 interventions were included for the final synthesis. Mice and rats were the most used animals (79%) followed by sheep (16%). Antioxidants (23%), followed by vasodilators (18%), nutrients (14%), and immunomodulators (12%) were the most tested therapy. Two-thirds of studies only reported delivery or immediate neonatal outcomes. Adverse effects were rarely reported (11%). Most studies (73%), independent of the intervention, showed a benefit in fetal survival or birthweight. The risk of bias was high, mostly due to the lack of randomization, allocation concealment, and blinding. Future research should aim to describe both short- and long-term outcomes across various organ systems in well-characterized models. Further efforts must be made to reduce selection, performance, and detection bias.

The effect of phosphodiesterase-5 inhibitors on uteroplacental and fetal cerebral perfusion in pregnancies with fetal growth restriction: A systematic review and meta-analysis

OBJECTIVES

To evaluate the effect of phosphodiesterase-5 (PDE-5) inhibitors on uteroplacental and fetal cerebral perfusion in pregnancies complicated with fetal growth restriction (FGR).

MATERIAL AND METHODS

Relevant databases were searched from inception up to June 2021. The random-effects model was used to pool the weighted mean differences (WMDs) and the corresponding 95% confidence intervals (CIs). The primary outcomes were the effect of PDE-5 inhibitors on uterine (UtA-PI), umbilical (UA-PI) and middle cerebral artery (MCA-PI) pulsatility indices. Subgroup analyses were also performed based on the type of PDE-5 inhibitor medication, the dosage of medication, duration of treatment, sample size and onset of FGR.

RESULTS

Seven clinical trials were eligible, 6 trials using sildenafil, and one using tadalafil. The random-effects models indicated PDE-5 inhibitors significantly decrease UtA-PI (WMD = -0.28, 95% CI = -0.46,-0.11) and UA-PI (WMD = -0.07, 95% CI = -0.13, -0.01); however it failed to show a significant effect on MCA-PI (WMD = 0.24, 95% CI = -0.63, 1.11). Subgroup analyses showed similar significant effects of sildenafil on UtA-PI and UA-PI; however, no significant effect was observed after treatment with tadalafil.

CONCLUSION

PDE-5 inhibitors administration, especially sildenafil, may improve uteroplacental, but not fetal cerebral blood perfusion in pregnancies complicated by FGR.

Identification of potential crucial genes associated with early-onset preeclampsia via bioinformatic analysis

INTRODUCTION

Early-onset preeclampsia is a pregnancy complication associated with high maternal and perinatal morbidity, mortality. Intense efforts have been made to elucidate the pathogenesis, but the molecular mechanism is still elusive. This study aimed to identify potential key genes related to early-onset preeclampsia, and to obtain a better understanding of the molecular mechanisms of this disease.

METHODS

We performed a multi-step integrative bioinformatics analysis of microarray dataset GSE74341 downloaded from Gene Expression Omnibus (GEO) database including 7 early-onset preeclampsia and 5 gestational age matched normotensive controls. The differentially expressed genes (DEGs) were identified using the "limma" package, and their potential functions were predicted by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. Furthermore, the protein-protein interaction network (PPI) was obtained from the STRING database and the PPI network was visualized by Cytoscape software. Then, hub modules and hub genes were screened out from the PPI network, and enrichment analysis was performed for them. Also, validation of hub genes expression in early-onset PE was down by using microarray dataset GSE44711.

RESULTS

A total of 628 DEGs (256 down- and 372 up-regulated) were identified in early-onset PE compared to controls. A total of 4 significant hub modules and 26 significant hub genes were identified.

CONCLUSION

In conclusion, the DEGs related to cell-cell or cell-extracellular matrix interaction (ITGA5, SPP1, LUM, VCAN, APP), placenta metabolic or oxidative stress (CCR7, NT5E, CYBB) were predicted to be newly potential crucial genes that may play significant roles in the pathogenesis of early-onset PE.

Catechol-O-methyltransferase and Pregnancy Outcome: an Appraisal in Rat

Catechol-O-methyltransferase (COMT) has been shown to be a key regulator of pregnancy outcomes in mouse, and its deficiency is causative in the development of a preeclampsia-like disease process. Preeclampsia is a human pregnancy disorder associated with failure of intrauterine trophoblast cell invasion and trophoblast-guided uterine spiral artery remodeling, which are not well-developed in mouse. The purpose of this study was to investigate COMT in rat, a species with deep intrauterine trophoblast invasion. To accomplish this task, we used clustered regularly interspaced short palindromic repeats/Cas9-mediated genome editing of the rat Comt gene. A Comt null rat model was established and its fertility characterized. Comt null male and female rats were viable and fertile. COMT deficiency did not significantly impact pregnancy outcomes, including litter size, placental and fetal weights, Mendelian and sex ratios, or pregnancy-dependent adaptations to hypoxia. Collectively, our findings indicate that pregnancy-associated phenotypic outcomes of COMT deficiency are not equivalent in mouse and rat. In rat, COMT is not required for a successful pregnancy outcome.

Regulation of maternal-fetal metabolic communication

Pregnancy may be the most nutritionally sensitive stage in the life cycle, and improved metabolic health during gestation and early postnatal life can reduce the risk of chronic disease in adulthood. Successful pregnancy requires coordinated metabolic, hormonal, and immunological communication. In this review, maternal-fetal metabolic communication is defined as the bidirectional communication of nutritional status and metabolic demand by various modes including circulating metabolites, endocrine molecules, and other secreted factors. Emphasis is placed on metabolites as a means of maternal-fetal communication by synthesizing findings from studies in humans, non-human primates, domestic animals, rabbits, and rodents. In this review, fetal, placental, and maternal metabolic adaptations are discussed in turn. (1) Fetal macronutrient needs are summarized in terms of the physiological adaptations in place to ensure their proper allocation. (2) Placental metabolite transport and maternal physiological adaptations during gestation, including changes in energy budget, are also discussed. (3) Maternal nutrient limitation and metabolic disorders of pregnancy serve as case studies of the dynamic nature of maternal-fetal metabolic communication. The review concludes with a summary of recent research efforts to identify metabolites, endocrine molecules, and other secreted factors that mediate this communication, with particular emphasis on serum/plasma metabolomics in humans, non-human primates, and rodents. A better understanding of maternal-fetal metabolic communication in health and disease may reveal novel biomarkers and therapeutic targets for metabolic disorders of pregnancy.

AMP-activated protein kinase activator AICAR attenuates hypoxia-induced murine fetal growth restriction in part by improving uterine artery blood flow

KEY POINTS

Pregnancy at high altitude is associated with a greater incidence of fetal growth restriction due, in part, to lesser uterine artery blood flow. AMP-activated protein kinase (AMPK) activation vasodilates arteries and may increase uterine artery blood flow. In this study, pharmacological activation of AMPK by the drug AICAR improved fetal growth and elevated uterine artery blood flow. These results suggest that AMPK activation is a potential strategy for improving fetal growth and raising uterine artery blood flow in pregnancy, which may be important in pregnancy disorders characterized by uteroplacental ischaemia and/or fetal hypoxia.

ABSTRACT

Uteroplacental hypoxia is associated with pregnancy disorders such as intrauterine growth restriction and preeclampsia, which are characterized by uteroplacental ischaemia and/or fetal hypoxia. Activation of AMP-activated protein kinase (AMPK) results in vasodilatation and is therefore a potential therapeutic strategy for restoring uteroplacental perfusion in pregnancy disorders. In this study, C57Bl/6 mice were treated with subcutaneous pellets containing vehicle, the AMPK activator AICAR (200 mg kg^-1 day^-1 ), or the AMPK inhibitor Compound C (20 mg kg^-1 day^-1 ) beginning on gestational day 13.5, and were exposed to hypoxia starting on gestational day 14.5 that induced intrauterine growth restriction. Pharmacological AMPK activation by AICAR partially prevented hypoxia-induced fetal growth restriction (P < 0.01), due in part to increased uterine artery blood flow (P < 0.0001). The proportion of total cardiac output flowing through the uterine artery was increased with AICAR in hypoxic mice (P < 0.001), suggesting that the vasodilator effect of AICAR was selective for the uterine circulation. Further, pharmacological inhibition of AMPK with Compound C reduced uterine artery diameter and increased uterine artery contractility in normoxic mice, providing evidence that physiological levels of AMPK activation are necessary for vasodilatation in healthy pregnancy. Two-way ANOVA analyses indicated that hypoxia reduced AMPK activation in the uterine artery and placenta, and AICAR increased AMPK activation in these tissues compared to vehicle. These findings provide support for further investigation into the utility of pharmacological AMPK activation for treatment of fetal growth restriction.

The kynurenine pathway; A new target for treating maternal features of preeclampsia?

In preeclampsia, vasospasm, oxidative stress, endothelial dysfunction, and immune dysregulation are key mediators of maternal disease. A new time-of-disease treatment is needed with the potential to treat these areas of pathophysiology. A review of the literature has indicated that metabolites of the kynurenine pathway have the potential to; (i) induce vasorelaxation of resistance arteries and reduce blood pressure; (ii) exert antioxidant effects and reduce the effects of poly-ADP ribose polymerase activation (iii) prevent endothelial dysfunction and promote endothelial nitric oxide production; (iv) cause T cell differentiation into tolerogenic regulatory T cells and induce apoptosis of pro-inflammatory Th1 cells. This has led to the hypothesis that increasing Kynurenine pathway activity may offer a new treatment strategy for preeclampsia.

A double-hit pre-eclampsia model results in sex-specific growth restriction patterns

Pre-eclampsia is a multifactorial pregnancy-associated disorder characterized by angiogenic dysbalance and systemic inflammation; however, animal models that combine these two pathophysiological conditions are missing. Here, we introduce a novel double-hit pre-eclampsia mouse model that mimics the complex multifactorial conditions present during pre-eclampsia and allows for the investigation of early consequences for the fetus. Adenoviral overexpression of soluble fms-like tyrosine kinase (sFlt-1) and lipopolysaccharide (LPS) administration at mid-gestation in pregnant mice resulted in hypertension and albuminuria comparable to that of the manifestation in humans. A metabolomics analysis revealed that pre-eclamptic dams have increased plasma concentrations of phosphadytilcholines. The fetuses of both sexes were growth restricted; however, in males a brain-sparing effect was seen as compensation for this growth restriction. According to the plasma metabolomics, male fetuses showed changes in amino acid metabolism, while female fetuses showed pronounced alterations in lipid metabolism. Our results show that combined exposure to sFlt-1 and LPS mimics the clinical symptoms of pre-eclampsia and affects fetal growth in a sex-specific manner, with accompanying metabolome changes.

Human sFLT1 Leads to Severe Changes in Placental Differentiation and Vascularization in a Transgenic hsFLT1/rtTA FGR Mouse Model

The anti-angiogenic soluble fms-like tyrosine kinase 1 (sFLT1) is one of the candidates in the progression of preeclampsia, often associated with fetal growth restriction (FGR). Therapeutic agents against preeclampsia with/without FGR, as well as adequate transgenic sFLT1 mouse models for testing such agents, are still missing. Much is known about sFLT1-mediated endothelial dysfunction in several tissues; however, the influence of sFLT1 on placental and fetal development is currently unknown. We hypothesize that sFLT1 is involved in the progression of FGR by influencing placental differentiation and vascularization and is a prime candidate for interventional strategies. Therefore, we generated transgenic inducible human sFLT1/reverse tetracycline-controlled transactivator (hsFLT1/rtTA) mice, in which hsFLT1 is ubiquitously overexpressed during pregnancy in dams and according to the genetics in hsFLT1/rtTA homozygous and heterozygous fetuses. Induction of hsFLT1 led to elevated hsFLT1 levels in the serum of dams and on mRNA level in all placentas and hetero-/homozygous fetuses, resulting in FGR in all fetuses at term. The strongest effects in respect to FGR were observed in the hsFLT1/rtTA homozygous fetuses, which exhibited the highest hsFLT1 levels. Only fetal hsFLT1 expression led to impaired placental morphology characterized by reduced placental efficiency, enlarged maternal sinusoids, reduced fetal capillaries, and impaired labyrinthine differentiation, associated with increased apoptosis. Besides impaired placental vascularization, the expression of several transporter systems, such as glucose transporter 1 and 3 (Glut-1; Glut-3); amino acid transporters, solute carrier family 38, member one and two (Slc38a1; Slc38a2); and most severely the fatty acid translocase Cd36 and fatty acid binding protein 3 (Fabp3) was reduced upon hsFLT1 expression, associated with an accumulation of phospholipids in the maternal serum. Moreover, the Vegf pathway showed alterations, resulting in reduced Vegf, Vegfb, and Plgf protein levels and increased Bad and Caspase 9 mRNA levels. We suggest that hsFLT1 exerts an inhibitory influence on placental vascularization by reducing Vegf signaling, which leads to apoptosis in fetal vessels, impairing placental differentiation, and the nutrient exchange function of the labyrinth. These effects were more pronounced when both the dam and the fetus expressed hsFLT1 and ultimately result in FGR and resemble the preeclamptic phenotype in humans.

Sildenafil for the treatment of preeclampsia, an update: should we still be enthusiastic?

Preeclampsia is a hypertensive disorder of pregnancy and the clinical manifestation of severe endothelial dysfunction associated with maternal and foetal morbidity and mortality. The primum movens of the disease is the defect of invasion of the uterine arteries by foetal syncytiotrophoblasts, which causes a maladaptive placental response to chronic hypoxia and the secretion of the soluble form of type 1 vascular growth endothelial factor receptor, also called soluble fms-like tyrosine kinase 1 (sFlt-1), the major player in the pathophysiology of the disease. Among its different effects, sFlt-1 induces abnormal sensitivity of the maternal vessels to the vasoconstrictor angiotensin II. This leads to the hypertensive phenotype, recently shown to be abrogated by the administration of sildenafil citrate, which can potentiate the vasodilatory mediator nitrite oxide. This review focuses on the mechanisms of maternal endothelial dysfunction in preeclampsia and discusses the therapeutic window of sildenafil use in the context of preeclampsia, based on the results from preclinical studies and clinical trials. Safety issues recently reported in neonates have considerably narrowed this window.

Loss of placental growth factor ameliorates maternal hypertension and preeclampsia in mice

Preeclampsia remains a clinical challenge due to its poorly understood pathogenesis. A prevailing notion is that increased placental production of soluble fms-like tyrosine kinase-1 (sFlt-1) causes the maternal syndrome by inhibiting proangiogenic placental growth factor (PlGF) and VEGF. However, the significance of PlGF suppression in preeclampsia is uncertain. To test whether preeclampsia results from the imbalance of angiogenic factors reflected by an abnormal sFlt-1/PlGF ratio, we studied PlGF KO (Pgf-/-) mice and noted that the mice did not develop signs or sequelae of preeclampsia despite a marked elevation in circulating sFLT-1. Notably, PlGF KO mice had morphologically distinct placentas, showing an accumulation of junctional zone glycogen. We next considered the role of placental PlGF in an established model of preeclampsia (pregnant catechol-O-methyltransferase-deficient [COMT-deficient] mice) by generating mice with deletions in both the Pgf and Comt genes. Deletion of placental PlGF in the context of COMT loss resulted in a reduction in maternal blood pressure and increased placental glycogen, indicating that loss of PlGF might be protective against the development of preeclampsia. These results identify a role for PlGF in placental development and support a complex model for the pathogenesis of preeclampsia beyond an angiogenic factor imbalance.

Phosphodiesterase Inhibition in the Treatment of Preeclampsia: What Is New?

PURPOSE OF REVIEW

The present study intends to review the possibility of using phosphodiesterase inhibitors as a treatment option for preeclampsia, addressing potential risks and benefits.

RECENT FINDINGS

Preeclampsia is the most common hypertensive disorder of pregnancy, often responsible for severe maternal and fetal complications, which can lead to early pregnancy termination and death. Despite the numerous studies, its pathophysiology is still unclear, although it seems to involve a multiplicity of complex factors related to angiogenesis, ineffective vasodilation, oxidative stress, inflammatory cytokines, and endothelial dysfunction. It has been hypothetically suggested that the use of phosphodiesterase inhibitors is capable of improving placental and fetal perfusion, contributing to gestational scenario, by decreasing the symptomatology and severity of this syndrome. In this literature review, it has been found that most of the studies were conducted in animal models, and there is still lack of evidence supporting its use in clinical practice. Research in human indicates conflicting findings; randomized controlled trials were scarce and did not demonstrate any benefit in morbidity or mortality. Data regarding to pathophysiological and interventional research are described and commented in this review. The use of phosphodiesterase inhibitors in the treatment of preeclampsia is controversial and should not be encouraged taking into account recent data.

A Family Based Study of Carbon Monoxide and Nitric Oxide Signalling Genes and Preeclampsia

BACKGROUND

Preeclampsia is thought to originate during placentation, with incomplete remodelling and perfusion of the spiral arteries leading to reduced placental vascular capacity. Nitric oxide (NO) and carbon monoxide (CO) are powerful vasodilators that play a role in the placental vascular system. Although family clustering of preeclampsia has been observed, the existing genetic literature is limited by a failure to consider both mother and child.

METHODS

We conducted a nested case-control study within the Norwegian Mother and Child Birth Cohort of 1545 case-pairs and 995 control-pairs from 2540 validated dyads (2011 complete pairs, 529 missing mother or child genotype). We selected 1518 single-nucleotide polymorphisms (SNPs) with minor allele frequency >5% in NO and CO signalling pathways. We used log-linear Poisson regression models and likelihood ratio tests to assess maternal and child effects.

RESULTS

One SNP met criteria for a false discovery rate Q-value <0.05. The child variant, rs12547243 in adenylate cyclase 8 (ADCY8), was associated with an increased risk (relative risk [RR] 1.42, 95% confidence interval [CI] 1.20, 1.69 for AG vs. GG, RR 2.14, 95% CI 1.47, 3.11 for AA vs. GG, Q = 0.03). The maternal variant, rs30593 in PDE1C was associated with a decreased risk for the subtype of preeclampsia accompanied by early delivery (RR 0.45, 95% CI 0.27, 0.75 for TC vs. CC; Q = 0.02). None of the associations were replicated after correction for multiple testing.

CONCLUSIONS

This study uses a novel approach to disentangle maternal and child genotypic effects of NO and CO signalling genes on preeclampsia.

Selective Targeting of a Novel Vasodilator to the Uterine Vasculature to Treat Impaired Uteroplacental Perfusion in Pregnancy

Fetal growth restriction (FGR) in pregnancy is commonly caused by impaired uteroplacental blood flow. Vasodilators enhance uteroplacental perfusion and fetal growth in humans and animal models; however, detrimental maternal and fetal side effects have been reported. We hypothesised that targeted uteroplacental delivery of a vasodilator would enhance drug efficacy and reduce the risks associated with drug administration in pregnancy. Phage screening identified novel peptides that selectively accumulated in the uteroplacental vasculature of pregnant mice. Following intravenous injection, the synthetic peptide CNKGLRNK selectively bound to the endothelium of the uterine spiral arteries and placental labyrinth in vivo; CNKGLRNK-decorated liposomes also selectively bound to these regions. The nitric oxide donor 2-[[4-[(nitrooxy)methyl]benzoyl]thio]-benzoic acid methyl ester (SE175) induced significant relaxation of mouse uterine arteries and human placental arteries in vitro; thus, SE175 was encapsulated into these targeted liposomes and administered to healthy pregnant C57BL/6J mice or endothelial nitric oxide synthase knockout (eNOS-/-) mice, which exhibit impaired uteroplacental blood flow and FGR. Liposomes containing SE175 (0.44mg/kg) or PBS were administered on embryonic (E) days 11.5, 13.5, 15.5 and 17.5; fetal and placental weights were recorded at term and compared to mice injected with free PBS or SE175. Targeted uteroplacental delivery of SE175 had no effect on fetal weight in C57BL/6J mice, but significantly increased fetal weight and mean spiral artery diameter, and decreased placental weight, indicative of improved placental efficiency, in eNOS-/- mice; free SE175 had no effect on fetal weight or spiral artery diameter. Targeted, but not free SE175 also significantly reduced placental expression of 4-hydroxynonenal, cyclooxygenase-1 and cyclooxygenase-2, indicating a reduction in placental oxidative stress. These data suggest that exploiting vascular targeting peptides to selectively deliver SE175 to the uteroplacental vasculature may represent a novel treatment for FGR resulting from impaired uteroplacental perfusion.

Targeting STOX1 in the therapy of preeclampsia

INTRODUCTION

Preeclampsia is a major pregnancy disease, explained partly by genetic predispositions. STOX1, a transcription factor discovered in 2005, was the first gene directly associated with genetic forms of the disease. Alterations of STOX1 expression as well as STOX1 variants have also been associated to Alzheimer's disease. These observations make of this gene a putative therapeutic target. Area covered: Two major isoforms (STOX1A and STOX1B) are encoded by the gene and are theoretically able to compete for the same binding site, while only the most complete (STOX1A) is supposed to be able to activate gene expression. This makes the ratio between STOX1A and STOX1B as well as their position inside the cell (nucleus or cytoplasm) crucial to understand how STOX1 functions. STOX1 appears to have multiple gene targets, especially in pathways connected to inflammation, oxidative stress, and cell cycle. Expert opinion: STOX1-directed therapies, could be directed either towards its targets (genes or pathways), or directly at STOX1. For this the addressing of STOX1 to various cell compartments could theoretically be modified; also it could be possible of altering the balance between the two isoforms, through selectively inhibiting one of them, possibly improving the outcomes in severe preeclampsia.

A Dormant Microbial Component in the Development of Preeclampsia

Preeclampsia (PE) is a complex, multisystem disorder that remains a leading cause of morbidity and mortality in pregnancy. Four main classes of dysregulation accompany PE and are widely considered to contribute to its severity. These are abnormal trophoblast invasion of the placenta, anti-angiogenic responses, oxidative stress, and inflammation. What is lacking, however, is an explanation of how these themselves are caused. We here develop the unifying idea, and the considerable evidence for it, that the originating cause of PE (and of the four classes of dysregulation) is, in fact, microbial infection, that most such microbes are dormant and hence resist detection by conventional (replication-dependent) microbiology, and that by occasional resuscitation and growth it is they that are responsible for all the observable sequelae, including the continuing, chronic inflammation. In particular, bacterial products such as lipopolysaccharide (LPS), also known as endotoxin, are well known as highly inflammagenic and stimulate an innate (and possibly trained) immune response that exacerbates the inflammation further. The known need of microbes for free iron can explain the iron dysregulation that accompanies PE. We describe the main routes of infection (gut, oral, and urinary tract infection) and the regularly observed presence of microbes in placental and other tissues in PE. Every known proteomic biomarker of "preeclampsia" that we assessed has, in fact, also been shown to be raised in response to infection. An infectious component to PE fulfills the Bradford Hill criteria for ascribing a disease to an environmental cause and suggests a number of treatments, some of which have, in fact, been shown to be successful. PE was classically referred to as endotoxemia or toxemia of pregnancy, and it is ironic that it seems that LPS and other microbial endotoxins really are involved. Overall, the recognition of an infectious component in the etiology of PE mirrors that for ulcers and other diseases that were previously considered to lack one.