Boldine enhances bile production in rats via osmotic and farnesoid X receptor dependent mechanisms.

Boldine, the major alkaloid from the Chilean Boldo tree, is used in traditional medicine to support bile production, but evidence to support this function is controversial. We analyzed the choleretic potential of boldine, including its molecular background. The acute- and long-term effects of boldine were evaluated in rats either during intravenous infusion or after 28-day oral treatment. Infusion of boldine instantly increased the bile flow 1.4-fold in healthy rats as well as in animals with Mrp2 deficiency or ethinylestradiol induced cholestasis. This effect was not associated with a corresponding increase in bile acid or glutathione biliary excretion, indicating that the effect is not related to stimulation of either bile acid dependent or independent mechanisms of bile formation and points to the osmotic activity of boldine itself. We subsequently analyzed bile production under conditions of changing biliary excretion of boldine after bolus intravenous administration and found strong correlations between both parameters. HPLC analysis showed that bile concentrations of boldine above 10 µM were required for induction of choleresis. Importantly, long-term pretreatment, when the bile collection study was performed 24-h after the last administration of boldine, also accelerated bile formation despite undetectable levels of the compound in bile. The effect paralleled upregulation of the Bsep transporter and increased biliary clearance of its substrates, bile acids. We consequently confirmed the ability of boldine to stimulate the Bsep transcriptional regulator, FXR receptor. In conclusion, our study clarified the mechanisms and circumstances surrounding the choleretic activity of boldine.

Cholesterol effects on endoglin and its downstream pathways in ApoE/LDLR double knockout mice.

BACKGROUND: The aim of the study was to evaluate whether cholesterol-rich diet affects transforming growth factor-ß-RIII (endoglin) levels in blood and 2 endoglin-related pathways in the aorta of ApoE/LDLR double knockout mice. METHODS AND RESULTS: Mice were fed either chow diet (CHOW) (n=8) or by 1% cholesterol-rich diet (CHOL) (n=8). Biochemical analysis of cholesterol and endoglin levels in blood, lesion size area, immunohistochemistry and Western blot analysis in mice aortas were performed. Biochemical analysis showed that cholesterol-rich diet resulted in a significant increase of cholesterol and endoglin levels in serum, and increased plaque size in the aorta. In addition, a cholesterol-rich diet significantly decreased the expressions of endoglin by 92%, activin receptor-like kinase (ALK)-1 by 71%, p-Smad2 by 21%, and vascular endothelial growth factor (VEGF) by 37% when compared to CHOW mice, but ALK-5, p-Smad1, and endothelial nitric oxide synthase were not significantly affected. CONCLUSIONS: Hypercholesterolemia increases endoglin levels in blood and simultaneously decreases its expression in aorta, together with atherosclerosis protective markers p-Smad2 and VEGF, followed by increased plaque size. Inhibition of endoglin signaling might be one of the mechanisms responsible for the promoting of endothelial dysfunction and atherogenesis. Moreover, the monitoring of endoglin serum levels might represent an attractive blood marker of progression of disease; however, the precise source and role of endoglin in blood serum remains to be elucidated.

Daunorubicin does not induce immunohistochemically detectable endothelial dysfunction in rabbit aorta and femoral artery.

Anthracyclines are one of the most effective anticancer drugs ever developed, but their clinical use has been hampered by the risk of severe cardiotoxicity. In this study, we investigated whether rabbits exposed to a different cumulative dose of anthracycline suffer from immunohistochemically detectable vascular toxicity and endothelial dysfunction. Daunorubicin (3 mg/kg, i.e. 50 mg/m²) was administered i.v. to rabbits once weekly for 1-10 weeks to reach different cumulative doses of the drug (50-500 mg/m²), while control rabbits received saline. The rabbits were sacrificed either 24 hours or 7 days after reaching each particular cumulative dose, and aortas and right femoral arteries were collected for immunohistochemical analysis. Immunohistochemical analysis showed ICAM-1 staining in many aortas from both saline and daunorubicin-treated rabbits without any relationship to the anthracycline treatment. On the contrary, unlike in the lipopolysaccharide-treated or hypercholesterolemic rabbits, no distinct immunoreactivity for other markers of inflammation, oxidative and nitrosative stress (VCAM-1, 4-HNE, iNOS and nitrotyrosine) were detected in aortas and femoral arteries from either control or daunorubicin-treated animals. No relationship to the cumulative dose of the drug or post-expose set up of harvesting was found. In this study, we have demonstrated that daunorubicin does not induce gross histopathological changes in the studied arteries and it fails to induce immunohistochemically detectable endothelial dysfunction. Thus, we propose that endothelial cells are much less susceptible to anthracycline toxicity than cardiac myocytes. In addition, our data suggest that vascular toxicity of anthracyclines plays rather a minor role in the cardiovascular complications of anthracycline chemotherapy.