Alisol B 23-acetate adjusts bile acid metabolisim via hepatic FXR-BSEP signaling activation to alleviate atherosclerosis.

BACKGROUND: Postmenopausal women have a high incidence of atherosclerosis. Phytosterols have been shown to have cholesterol-lowering properties. Alisa B 23-acetate (AB23A) is a biologically active plant sterol isolated from Chinese herbal medicine Alisma. However, the atherosclerosis effect of AB23A after menopause and its possible mechanism have not been reported yet. PURPOSE: To explore whether AB23A can prevent atherosclerosis by regulating farnesoid X receptor and subsequently increasing fecal bile acid and cholesterol excretion to reduce plasma cholesterol levels. METHODS: Aortic samples from premenopausal and postmenopausal women with ascending aortic arteriosclerosis were analyzed, and bilateral ovariectomized (OVX) female LDLR-/- mice and free fatty acid (FFA)-treated L02 cells were used to analyze the effect of AB23A supplementation therapy. RESULTS: AB23A increased fecal cholesterol and bile acids (BAs) excretion dependent on activation of hepatic farnesoid X receptor (FXR) in ovariectomized mice. AB23A inhibited hepatic cholesterol 7α-hydroxylase (CYP7A1) and sterol 12α-hydroxylase (CYP8B1) via inducing small heterodimer partner (SHP) expression. On the other hand, AB23A increased the level of hepatic chenodeoxycholic acid (CDCA), and activated the hepatic BSEP signaling. The activation of hepatic FXR-BSEP signaling by AB23A in ovariectomized mice was accompanied by the reduction of liver cholesterol, hepatic lipolysis, and bile acids efflux, and reduced the damage of atherosclerosis. In vitro, AB23A fixed abnormal lipid metabolism in L02 cells and increased the expression of FXR, BSEP and SHP. Moreover, the inhibition and silencing of FXR canceled the regulation of BSEP by AB23A in L02 cells. CONCLUSION: Our results shed light into the mechanisms behind the cholesterol-lowering of AB23A, and increasing FXR-BSEP signaling by AB23A may be a potential postmenopausal atherosclerosis therapy.

Alisol B 23-acetate activates ABCG5/G8 in the jejunum via the LXRα/ACAT2 pathway to relieve atherosclerosis in ovariectomized ApoE-/- mice.

Phytosterols have been shown to improve blood lipid levels and treat atherosclerosis. This research investigated the effects of phytosterol Alisol B 23-acetate (AB23A) on jejunum lipid metabolism and atherosclerosis. The results show that intragastric administration of AB23A can significantly reduce atherosclerotic plaque area and lipid accumulation in the jejunum of ovariectomized ApoE-/- mice fed a high-fat diet and can also improve the lipid mass spectra of the plasma and jejunum. In vitro studies have shown that AB23A can increase cholesterol outflow in Caco-2 cells exposed to high fat concentrations and increase the expression of ATP-binding cassette transfer proteins G5/G8 (ABCG5/G8), the liver X receptor α (LXRα). Furthermore, inhibition of LXRα can significantly eliminate the active effect of AB23A on decreasing intracellular lipid accumulation. We also confirmed that AB23A has a negative effect on Acyl-CoA cholesterol acyltransferase 2 (ACAT2) in Caco-2 cells cultured in the high concentrations of fat, and we found that AB23A further reduces ACAT2 expression in cells treated with the ACAT2 inhibitor pyripyropene or transfected with ACAT2 siRNA. In conclusion, we confirmed that AB23A can reduce the absorption of dietary lipids in the jejunum by affecting the LXRα-ACAT2-ABCG5/G8 pathway and ultimately exert an anti-atherosclerotic effect.

Alisol B 23-Acetate Inhibits IgE/Ag-Mediated Mast Cell Activation and Allergic Reaction.

Alisol B 23-acetate (AB23A), a natural triterpenoid, has been reported to exert hepatoprotective and antitumor activities. Aiming to investigate the anti-inflammatory activity, this study examined the effect of AB23A on mast cells and allergic reaction. AB23A inhibited the degranulation of mast cells stimulated by immunoglobulin E/antigen (IgE/Ag), and also decreased the synthesis of leukotriene C4 (LTC4), production of interlukin-6 (IL-6), and expression of cyclooxygenase-2 (COX-2) in a concentration-dependent manner with no significant cytotoxicity in bone marrow-derived mast cells (BMMCs). AB23A inhibited spleen tyrosine kinase (Syk) and the downstream signaling molecules including phospholipase Cγ (PLCγ), serine-threonine protein kinase/inhibitor of nuclear factor kappa-B kinase/nuclear factor kappa-B (Akt/IKK/NF-κB), and mitogen-activated protein kinases/cytosolic phospholipase A2 (MAPK/cPLA2). Furthermore, AB23A blocked mobilization of Ca2+. Similar results were obtained in other mast cell lines Rat basophilic leukemia (RBL)-2H3 cells and a human mast cell line (HMC-1). In addition, AB23A attenuated allergic responses in an acute allergy animal model, passive cutaneous anaphylaxis (PCA). Taken together, this study suggests that AB23A inhibits the activation of mast cells and ameliorates allergic reaction, and may become a lead compound for the treatment of mast cell-mediated allergic diseases.