Beneficial Effects of Metolazone in a Rat Model of Preeclampsia

Animal Models of Preeclampsia: Causes, Consequences, and Interventions

Preeclampsia is a common pregnancy complication, affecting 2% to 8% of pregnancies worldwide, and is an important cause of both maternal and fetal morbidity and mortality. Importantly, although aspirin and calcium are able to prevent preeclampsia in some women, there is no cure apart from delivery of the placenta and fetus, often necessitating iatrogenic preterm birth. Preclinical models of preeclampsia are widely used to investigate the causes and consequences of preeclampsia and to evaluate safety and efficacy of potential preventative and therapeutic interventions. In this review, we provide a summary of the published preclinical models of preeclampsia that meet human diagnostic criteria, including the development of maternal hypertension, together with new-onset proteinuria, maternal organ dysfunction, and uteroplacental dysfunction. We then discuss evidence from preclinical models for multiple causal factors of preeclampsia, including those implicated in early-onset and late-onset preeclampsia. Next, we discuss the impact of exposure to a preeclampsia-like environment for later maternal and progeny health. The presence of long-term impairment, particularly cardiovascular outcomes, in mothers and progeny after an experimentally induced preeclampsia-like pregnancy, implies that later onset or reduced severity of preeclampsia will improve later maternal and progeny health. Finally, we summarize published intervention studies in preclinical models and identify gaps in knowledge that we consider should be targets for future research.

Thiazide-like diuretic drug metolazone activates human pregnane X receptor to induce cytochrome 3A4 and multidrug-resistance protein 1

Human pregnane X receptor (hPXR) regulates the expression of drug-metabolizing enzyme cytochrome P450 3A4 (CYP3A4) and drug transporters such as multidrug-resistance protein 1 (MDR1). PXR can be modulated by small molecules, including Federal Drug Administration (FDA)-approved drugs, thus altering drug metabolism and causing drug-drug interactions. To determine the role of FDA-approved drugs in PXR-mediated regulation of drug metabolism and clearance, we screened 1481 FDA-approved small-molecule drugs by using a luciferase reporter assay in HEK293T cells and identified the diuretic drug metolazone as an activator of hPXR. Our data showed that metolazone activated hPXR-mediated expression of CYP3A4 and MDR1 in human hepatocytes and intestine cells and increased CYP3A4 promoter activity in various cell lines. Mammalian two-hybrid assays showed that hPXR recruits its co-activator SRC-1 upon metolazone binding in HepG2 cells, explaining the mechanism of hPXR activation. To understand the role of other commonly-used diuretics in hPXR activation and the structure-activity relationship of metolazone, thiazide and non-thiazide diuretics drugs were also tested but only metolazone activates hPXR. To understand the molecular mechanism, docking studies and mutational analysis were carried out and showed that metolazone binds in the ligand-binding pocket and interacts with mostly hydrophobic amino acid residues. This is the first report showing that metolazone activates hPXR. Because activation of hPXR might cause drug-drug interactions, metolazone should be used with caution for drug treatment in patients undergoing combination therapy.

Urine iodine levels in preeclamptic and normal pregnant women

The aim of this study was to investigate the urine iodine concentration in women with severe preeclampsia and in healthy women in Erzurum, Turkey. Urine specimens were obtained from 40 severe preeclampsia and 18 healthy pregnant women. Urinary iodine levels were determined by the Foss method based on the Sandell-Kolthoff reaction. The urinary iodine level for women with severe preeclampsia was 4.25 +/- 2.7 microg/dL, lower than 20.89 +/- 6.4 microg/dL of urinary iodine for healthy pregnant women (p < 0.001). Blood magnesium concentration was found to be 1.63 +/- 0.05 mg/dL for women with severe preeclampsia, which is lower than that of healthy pregnant women (1.87 +/- 0.05 mg/dL; p < 0.001). There was a positive correlation between urinary iodine level and blood magnesium level in pregnant women with preeclampsia (Pearson correlation coefficient = 0.43; p < 0.01). However, there was no correlation between urinary iodine level and blood magnesium level in healthy pregnant women. There was no difference in thyroid hormone levels (T4, TSH, FT4) between women with severe preeclampsia and healthy pregnant women. However, there was a difference in T3 thyroid hormone levels between women with severe preeclampsia (1.86 +/- 0.4 microg/dL) and healthy pregnant women (1.45 +/- 0.3 microg/dL; p < 0.001). There was also a difference in FT3 between women with severe preeclampsia (2.77 +/- 0.4 pg/mL) and healthy pregnant women (2.41 +/- 0.5 microg/dL; p < 0.01). Urinary iodine excretion is currently the most convenient laboratory marker of iodine deficiency. The method is useful for the rapid and low-cost assessment of iodine deficiency. Our results suggested that urinary iodine concentration might be a useful marker for prediagnosing preeclamptic women. In addition, iodine supplementation may also be considered for preeclamptic therapy.

Marinobufagenin, resibufogenin and preeclampsia

The bufodienolides are cardiac glycosides which have the ability to inhibit the enzyme, Na(+)/K(+) ATPase (sodium potassium adenosine triphosphatase). They are cardiac inotropes, cause vasoconstriction (and, potentially, hypertension) and are natriuretic. Evidence has accrued over time which supports the view that they are mechanistically involved in volume expansion-mediated hypertension. In this communication, the authors summarize data which support the view that the bufodienolides and, in particular, marinobufagenin (MBG) are involved in the pathogenesis of preeclampsia. In a rat model of the syndrome, MBG causes hypertension, proteinuria, intrauterine growth restriction and increased weight gain. All of these phenotypic characteristics are prevented by an antagonist to MBG, resibufogenin (RBG). The "preeclamptic" animals also develop a vascular leak syndrome, resulting in hemoconcentration. Abnormalities in the MAPK (mitogen-activated protein kinase) system play a role in the mechanism by which MBG produces the abnormalities in the pregnant rat. Studies to discover the relevance of these findings to human preeclampsia are currently underway in several laboratories and clinics.