marinobufagenin and bufogenin

The purpose of this review is to provide information detailing the existing evidence with regard to the hypothesis that marinobufagenin (MBG) is an important etiologic and predictive factor in preeclampsia (PE). In addition, evidence describing the role of the antagonist to MBG, resibufogenin (RBG), in the prevention and/or treatment of this disorder is provided.. The studies outlined were performed in an animal model of PE, in in vitro experiments, and in human studies.. Data have been obtained that strongly support the hypothesis that ~60 to 70% of PE patients demonstrate elevations in urinary and serum MBG levels. In the animal model, the entire syndrome can be prevented by the administration of RBG beginning early in pregnancy.. Expanded human trials of MBG as a predictor of the later development of PE are warranted as are studies of the efficacy and safety of RBG as a preventative/therapy.

Topics: Animals; Blood Pressure; Bufanolides; Capillary Permeability; Cardenolides; Clinical Trials as Topic; Disease Models, Animal; Endothelium, Vascular; Female; Hematocrit; Humans; Pre-Eclampsia; Pregnancy; Saponins; Treatment Outcome

The bufadienolides are a group of steroid hormones that circulate in blood and are excreted in urine. They have the ability to inhibit the adenosine triphosphatase sodium-potassium pump (Na(+)-K(+)-ATPase), with predilection for its alpha1 isoform. This capability enables them to share with other cardiac glycosides the facility to cause an increase in sodium excretion, produce vasoconstriction resulting in hypertension, and act as cardiac inotropes. Bufadienolides have been implicated in instances of volume expansion-mediated hypertension, syndromes in which they are considered capable of causing a vascular leak, interfering with cellular proliferation, and inhibiting cellular maturation. An antagonist to the most well-studied bufadienolide, marinobufagenin, is resibufogenin, a compound that provides promise for the treatment of disorders in which excessive levels of marinobufagenin are present and are etiopathogenetic.

Topics: Animals; Blood Volume; Bufanolides; Capillary Permeability; Cardiotonic Agents; Cytokines; Female; Heart Diseases; Humans; Hypertension; Molecular Structure; Pre-Eclampsia; Pregnancy; Renal Insufficiency, Chronic; Vascular Resistance; Vasoconstrictor Agents; Young Adult

Levels of leptin and marinobufagenin (MBG), a cardiotonic steroid, are elevated in the serum of women with pre-eclampsia. Besides this, leptin administration to pregnant rats increases systolic blood pressure (SBP), urinary protein excretion and serum markers of endothelial activation. The link between leptin and MBG is unknown and it is also unclear if leptin-induced increases in blood pressure and proteinuria in the pregnant rat could be prevented by an MBG antagonist. To ascertain this link, this study investigated the effect of resibufogenin (RBG), a marinobufagenin antagonist, on leptin-induced increases in blood pressure and proteinuria during pregnancy in rats. Four groups of Sprague-Dawley rats, aged 12 weeks, were given either normal saline (CONTROL) or 120 μg/kg/day of leptin (LEP), or 120 μg/kg/day of leptin+30 μg/kg/day of resibufogenin (L + RBG) or 30 μg/kg/day of resibufogenin (RBG) from Day 1-20 of pregnancy. Systolic blood pressure and urinary protein excretion (UPE) were measured during the study period. Animals were euthanized on day 21 of pregnancy and vascular cell adhesion molecule 1, (VCAM-1), soluble intracellular cell adhesion molecule 1 (sICAM-1), E-selectin and endothelin-1 (ET-1) were estimated in the serum. SBP, UPE, VCAM-1, sICAM-1 and ET-1 were significantly higher only in the LEP group when compared with those in CONT and in L + RBG and RBG groups. The prevention by RBG of leptin-induced increases in SBP, proteinuria, and endothelial activation during pregnancy seem to suggest a potential role for MBG in leptin-induced adverse effects on blood pressure, urinary protein excretion and endothelial activity during pregnancy in the rat.

Topics: Animals; Blood Pressure; Bufanolides; Endothelin-1; Endothelium, Vascular; Female; Intercellular Adhesion Molecule-1; Leptin; Pre-Eclampsia; Pregnancy; Proteinuria; Rats; Rats, Sprague-Dawley; Vascular Cell Adhesion Molecule-1

The acute respiratory distress syndrome (ARDS) represents a major challenge for clinicians as well as basic scientists. The mortality rate for ARDS has been maintained within the range of 40-52%. The authors have examined the involvement of the "cardiotonic steroids" in the pathogenesis and therapy of ARDS. We have studied the possible role of the bufadienolide, marinobufagenin (MBG), in the pathogenesis of ARDS in both a rat model of ARDS and in patients afflicted with that disorder. In addition, the potential therapeutic benefit of an antagonist of MBG, resibufogenin (RBG), in an animal model has been evaluated.. A syndrome resembling human ARDS was produced in the rat by exposing the animals to 100% oxygen for 48 h. In other animals, RBG was administered to these "hyperoxic" rats, and the serum MBG was measured. In human ICU patients, urinary samples were examined for levels of MBG, and the values were compared to those obtained from other ICU patients admitted with diagnoses other than ARDS.. (1) Exposure of rats to hyperoxia produced a histologic picture which resembled that of human ARDS. (2) Serum levels of MBG in the "hyperoxic" rats substantially exceeded those obtained in animals exposed to ambient oxygen levels and were reduced to normal by RBG. (3) In ARDS patients, substantial elevations in urinary MBG were obtained compared to those in non-ARDS ICU patients.. MBG may serve as an important biomarker for the development of ARDS, and RBG may represent a preventative/therapy in this disorder.

Topics: Acute Lung Injury; Animals; Biomarkers; Bufanolides; Case-Control Studies; Disease Models, Animal; Humans; Hyperoxia; Pulmonary Alveoli; Pulmonary Edema; Rats; Respiratory Distress Syndrome; Up-Regulation

Resibufogenin (RB), one of the major active compounds of the traditional Chinese medicine Chansu, has displayed great potential as a chemotherapeutic agent in oncology. However, it is a digoxin-like compound that also exhibits extremely cardiotoxic effects. The present study aimed to characterize the metabolic behaviors of RB in humans as well as to evaluate the metabolic effects on its bioactivity and toxicity. The phase I metabolic profile in human liver microsomes was characterized systemically, and the major metabolite was identified as marinobufagenin (5β-hydroxylresibufogenin, 5-HRB) by liquid chromatography-mass spectrometry and nuclear magnetic imaging techniques. Both cytochrome P450 (P450) reaction phenotyping and inhibition assays using P450-selective chemical inhibitors demonstrated that CYP3A4 was mainly involved in RB 5β-hydroxylation with much higher selectivity than CYP3A5. Kinetic characterization demonstrated that RB 5β-hydroxylation in both human liver microsomes and human recombinant CYP3A4 obeyed biphasic kinetics and displayed similar apparent kinetic parameters. Furthermore, 5-HRB could significantly induce cell growth inhibition and apoptosis in A549 and H1299 by facilitating apoptosome assembly and caspase activation. Meanwhile, 5-HRB displayed very weak cytotoxicity of human embryonic lung fibroblasts, and in mice there was a greater tolerance to acute toxicity. In summary, CYP3A4 dominantly mediated 5β-hydroxylation and was found to be a major metabolic pathway of RB in the human liver, whereas its major metabolite (5-HRB) displayed better druglikeness than its parent compound RB. Our findings lay a solid foundation for RB metabolism studies in humans and encourage further research on the bioactive metabolite of RB.

Topics: Animals; Antineoplastic Agents; Bufanolides; Cytochrome P-450 CYP3A; Cytochrome P-450 Enzyme System; Dogs; Guinea Pigs; Humans; Hydroxylation; Kinetics; Liver; Macaca fascicularis; Male; Metabolic Detoxication, Phase I; Mice; Mice, Inbred ICR; Microsomes, Liver; Rats; Rats, Sprague-Dawley

Marinobufagenin (MBG) is a cardiotonic steroid that is increased in preeclampsia. An analog of MBG, resibufogenin (RBG), prevents the development of preeclampsia in a rat model. Oxidative stress is a concomitant of endothelial dysfunction in the latter disorder. The objective of the current studies was to evaluate the status of oxidative stress in a rat model of preeclampsia.. We measured the aortic AT(1) receptor expression and urinary excretion of 8-isoprostane (8IP) in rats rendered "preeclamptic" and compared the findings to those obtained in normal pregnant animals, pregnant rats injected with MBG, and preeclamptic rats treated with RBG.. Aortic AT(1) receptor expression and the urinary excretion of 8IP were significantly augmented in "preeclamptic" and MBG-injected pregnant rats compared to normal pregnant animals. RBG prevented evidence of oxidative stress in "preeclamptic" rats.. MBG is involved in the causation of oxidative stress in our rat model and RBG attenuates this change.

Topics: Animals; Bufanolides; Disease Models, Animal; Female; Oxidative Stress; Pre-Eclampsia; Pregnancy; Rats; Rats, Sprague-Dawley

Preeclampsia (PE) is a hypertensive disorder of pregnancy, in which marinobufagenin (MBG), a circulating cardiotonic steroid, is increased. The Gadd45a stress sensor protein is an upstream modulator of the pathophysiological changes observed in PE. However, the effects of MBG on Gadd45a stress signaling remain unknown. We examined the expression of Gadd45a, the sFlt-1 receptor, and p38, as well as caspase 3 and 8 activities in placental samples from four groups of rats. These were: normal pregnant (NP, n=8); pregnant rats which received weekly injections of desoxycorticosterone acetate and 0.9% saline as their drinking water (PDS, n=9); normal pregnant rats injected with MBG (NPM, n=8); and PDS rats injected with resibufogenin (RBG), an in vivo antagonist of MBG (PDSR, n=8). Utilizing human cytotrophoblast (CTB) cells, we examined the effect of MBG on these stress signaling proteins in vitro. Placental Gadd45a expression, caspase 3 and 8 activities, sFlt-1 concentrations, and sFlt-1 receptor expression were significantly higher in PDS and NPM compared to NP and PDSR rats. Gadd45a protein was significantly upregulated in the CTB cells when MBG was present in concentrations ≥1nM. Treatment with MBG (≥1nM) also significantly arrested cell cycle progression and activated the expression of the Gadd45a-mediated stress signaling proteins. Inhibition of Gadd45a through RNAi-mediation attenuated MBG-induced CTB cell stress signaling. In conclusion, MBG is involved in the alteration in Gadd45a stress signaling both in vivo and in vitro and RBG prevents these changes when administered in vivo.

Topics: Animals; Apoptosis; Blotting, Western; Bufanolides; Caspase 3; Caspase 8; Cell Cycle; Cell Cycle Proteins; Cells, Cultured; Female; Humans; Male; Nuclear Proteins; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Placenta; Pre-Eclampsia; Pregnancy; Rats; Rats, Sprague-Dawley; RNA Interference; Signal Transduction; Trophoblasts; Vascular Endothelial Growth Factor Receptor-1; Vasoconstrictor Agents

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.

Topics: Animals; Bufanolides; Disease Models, Animal; Female; Fetal Growth Retardation; Humans; Mitogen-Activated Protein Kinase Kinases; Pre-Eclampsia; Pregnancy; Proteinuria; Rats; Sodium-Potassium-Exchanging ATPase

Pre-eclampsia is a disorder that results in significant feto-maternal complications with yet no definitive pharmacologic intervention. One postulated etiologic mechanism is an imbalance between circulating pro-angiogenic and anti-angiogenic factors. We investigated these factors sequentially throughout pregnancy (19-21 days) in our rat model of pre-eclampsia, which involves the imposition of excessive volume expansion.. We evaluated the status of the pro-angiogenic and anti-angiogenic factors at the following time points: 3-5, 7-10 and 17-20 days of gestation.. We have previously determined that the urinary excretion of the circulating bufodienolide, marinobufagenin, is elevated at the 3- to 5-day time period, prior to the advent of hypertension and proteinuria. At 3-5 days of pregnancy, there was no evidence of angiogenic imbalance in the normal pregnant (NP) and 'pre-eclamptic' (PDS) rats. At the 7- to 10-day time point, plasma PlGF was greater in the NP rats than in the PDS group (p < 0.05). The plasma sFlt-1/PlGF ratio in the PDS animals was greater than that in the NP rats (p < 0.05). The placental sFlt-1 and sFlt-1/PlGF ratio were greater in the PDS rats than in NP rats (p < 0.05). These changes were also present at the 17- to 20-day time point in both plasma and placenta. The administration of resibufogenin, an antagonist of marinobufagenin, early in pregnancy, prevented angiogenic imbalance.. We conclude that angiogenic imbalance plays a role in the pathogenesis of pre-eclampsia in this rat model. Furthermore, the earliest event in the pathogenetic sequence appears to be the secretion and elaboration of marinobufagenin.

Topics: Analysis of Variance; Angiogenic Proteins; Animals; Blood Pressure; Bufanolides; Creatinine; Endoglin; Female; Gestational Age; Hematocrit; Intracellular Signaling Peptides and Proteins; Models, Animal; Placenta Growth Factor; Pre-Eclampsia; Pregnancy; Pregnancy Proteins; Proteinuria; Rats; Rats, Sprague-Dawley; Transforming Growth Factor beta; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factor Receptor-1

There are two major pathophysiologic processes involved in the development of hypertension: (1) expanded extracellular fluid volume and (2) vasoconstriction. We have developed a model of preeclampsia in the rat, in which excessive volume expansion (VE) plays a role. These animals excrete increased amounts of the bufodienolide, marinobufagenin (MBG), even before their hypertension and proteinuria become established. Furthermore, their hypertension is corrected by administration of resibufogenin (RBG), a compound structurally similar to MBG.. We studied two models of experimental hypertension in the nonpregnant animal, produced either by deoxycorticosterone acetate (DOCA)-salt administration or by angiotensin infusion.. RBG administered to the DOCA-salt rats lowered blood pressure and reduced proteinuria in the VE animals, but had no affect on the rats infused with angiotensin. Furthermore, although the production of superoxide anion in the aortas of both groups of hypertensive rats was increased over control, RBG reduced these levels to normal in the VE (DOCA-salt) animals only. RBG had no effect in the angiotensin-infused rats. The urinary excretion of angiotensinogen did not rise in VE-mediated hypertension, but did increase in the angiotensin-infused rats.. MBG plays an important role in the causation of hypertension in the VE rats, but not in the vasoconstrictive model. RBG is effective only in VE-mediated hypertension.

Topics: Angiotensin II; Angiotensinogen; Animals; Blood Pressure; Bufanolides; Creatinine; Desoxycorticosterone; Disease Models, Animal; Hypertension, Renal; Male; Mineralocorticoids; Proteinuria; Rats; Rats, Inbred Strains; Sodium Chloride; Superoxides; Vasoconstrictor Agents

The study of the pathogenesis of preeclampsia has been hampered by a relative dearth of animal models. We developed a rat model of preeclampsia in which the excretion of a circulating inhibitor of Na/K ATPase, marinobufagenin (MBG), is elevated. These animals develop hypertension, proteinuria, and intrauterine growth restriction. The administration of a congener of MBG, resibufogenin (RBG), reduces blood pressure to normal in these animals, as is the case when given to pregnant animals rendered hypertensive by the administration of MBG. Studies of Na/K ATPase inhibition by MBG and RBG reveal that these agents are equally effective as inhibitors of the enzyme.

Topics: Animals; Blood Pressure; Bufanolides; Disease Models, Animal; Enzyme Inhibitors; Female; Humans; Hypertension; Isoenzymes; Molecular Structure; Ouabain; Pre-Eclampsia; Pregnancy; Rats; Sodium-Potassium-Exchanging ATPase