Effects Of Monocrotaline Research Articles

Abstract P141: Gender Differences in the Development of Severe Pulmonary Hypertension and Right Ventricular Dysfunction in Apolipoprotein E--Deficient Mice Are Eliminated with Increasing Age

Apolipoprotein E (ApoE) is a multifunctional protein and its deficiency leads to the development of atherosclerosis in mice. Patients with pulmonary hypertension (PH) have reduced expression of ApoE in lung tissue. ApoE is known to inhibit endothelial and smooth muscle cell proliferation and has anti-inflammatory and anti-platelet aggregation properties. Young ApoE deficient mice have been shown to develop high fat diet-induced PH in a gender specific manner. Estrous cyclicity peaks at 7–8 months and declines by 9 months of age in mice. Here we investigated the effects of monocrotaline (MCT) on young and middle-aged ApoE deficient mice.Middle-Aged (MA) (11–12 month old) male (n=4) and female (n=4) and young (7–8 month old) male (n=5) and female (n=5) ApoE deficient mice were injected with a single intraperitoneal dose of MCT (60 mg/kg). Mice were closely monitored for ∼4 weeks with serial echocardiography for cardiopulmonary hemodynamic assessment. Direct cardiac catheterisation was performed terminally to record peak systolic right ventricular pressure (RVP). RV, LV, IVS and lung tissue was dissected and weighed. Trichrome staining and histochemical analyses were performed. At ∼4 weeks after MCT, MA male and female and young male mice developed severe PH (RVP: MA male=64±5 mmHg, MA female=71±4 mmHg, young male=60±5 mmHg, p=n.s between all the groups) whereas young females developed significantly less severe PH (RVP: 37±5 mmHg, P<0.05 vs. MA male and female, and young male). MA male and female and young male mice developed severe RV dysfunction (RV ejection fraction (RVEF): MA male=31±2%, MA female=28±4%, young male=36±1%, p=n.s between all the groups) whereas young females showed significantly better RV function (RVEF: 43±2%, P<0.05 vs. MA male and female, and young male). MA male and female mice also developed more severe RV hypertrophy (RV/LV+Septum, MA male=0.49, MA female=0.53, young female=0.39). MA male and female mice also manifested increased peripheral pulmonary artery muscularization and pulmonary fibrosis. Interestingly, the gender differences witnessed between young ApoE deficient male and female mice in the development of severe PH and RV dysfunction are abolished as the mice increase in age.

The possible toxic effects of monocrotaline on rat humoral immune response

The possible toxic effects of monocrotaline on rat humoral immune response

Effects of monocrotaline on energy metabolism in the rat liver

Monocrotaline (MCT) is a pyrrolizidine alkaloid present in the plants of the Crotalaria species that causes cytotoxicity and genotoxicity in animals and humans, and it is hepatically metabolized to the alkylating agent dehydromonocrotaline by cytochrome P-450. The exact cellular and molecular mechanisms of MCT-induced tissue injury remain unclear. We previously demonstrated that dehydromonocrotaline, but not monocrotaline, inhibits the activity of NADH-dehydrogenase at micromolar concentrations in isolated liver mitochondria, an effect associated with significantly reduced ATP synthesis. Impairment of energy metabolism is expected to lead to several alterations in cell metabolism. In this work, the action of different concentrations of monocrotaline (250, 500, and 750 μM) on energy metabolism-linked parameters was investigated in isolated perfused rat livers. In the fed state, monocrotaline increased glycogenolysis and glycolysis, whereas in the livers of fasted rats, it decreased gluconeogenesis and urea synthesis from l-alanine. These metabolic alterations were only found in livers of phenobarbital-treated rats, indicating that active metabolites including dehydromonocrotaline were responsible for the observed activity. Our findings indicate that hepatic metabolic changes may be implicated, partly at least, in the hepatotoxicity of monocrotaline in animals and humans.

Pathology of pulmonary hypertension: a human and experimental study.

To clarify the histopathological characteristics of pulmonary hypertension (PH) in Japan, and to clarify the role of serotonin and endothelin in monocrotaline induced PH, human histopathological studies and experimental studies were carried out. An epidemiological study based on the Annual of the Pathological Autopsy Cases in Japan, and a morphological study on autopsy cases of congenital heart disease and idiopathic PH were performed. Plasma levels of serotonin and endothelin, vascular responsiveness to serotonin, and the effects of a selective serotonin antagonist, DV-7028, were investigated after monocrotaline injection. Plexogenic pulmonary arteriopathy was prevalent, and recurrent pulmonary thromboembolism and pulmonary veno-occlusive disease extremely rare among primary pulmonary hypertension in Japan. In secondary PH, systemic lupus erythematosus and mixed connective tissue disease were frequent and showed particularly severe intimal and medial thickening. After an injection of monocrotaline, plasma serotonin and endothelin levels were raised, and pulmonary arteries showed hyperreactivity to serotonin. DV-7028 (5-HT2 receptor antagonist) attenuated the rise in pulmonary artery pressure and the various effects of monocrotaline. There may be some genetic difference between PH in Japan and other countries. Roles for serotonin and endothelin in the initiation and progression of monocrotaline induced PH are suggested.

Neither anticoagulant nor nonanticoagulant heparin affects monocrotaline lung injury.

The administration of monocrotaline to rats causes pulmonary vascular leak within 1 wk followed in 2-3 wk by perivascular proliferation and fatal pulmonary hypertension. Possibly blocking the proliferation might block the pulmonary hypertension, providing insight into its mechanism. Because heparin, given as an antiproliferative agent, reduced hypoxic pulmonary hypertension in mice, it might also block monocrotaline-induced pulmonary hypertension. Alternatively, anticoagulation could worsen the lung injury. We found that heparin (300 and 600 U/kg sc twice daily) inhibited clotting in rats given monocrotaline but did not change the vascular leak, the right ventricular pressure, the right ventricular hypertrophy, the increased medial thickness of the pulmonary arterioles, or the production of a slow-reacting substance of anaphylaxis-like material by the lungs. A nonanticoagulant heparin fragment (2 mg/kg sc twice daily), given to avoid anticoagulation also did not influence the monocrotaline injury. Thus neither anticoagulant nor nonanticoagulant heparin either attenuated or worsened the measured effects of monocrotaline.