Excessive exogenous cholesterol activating intestinal LXRα-ABCA1/G5/G8 signaling pathway can not reverse atherosclerosis in ApoE-/- mice.

BACKGROUND: The long-term excessive intake of exogenous cholesterol can lead to abnormally elevated blood lipid levels and induce cardiovascular and cerebrovascular diseases. However, the influence and relevance of exogenous cholesterol on plasma cholesterol components were still unclear, and the influence on intestinal lipid metabolism targets needs to be further explored. METHODS: In vivo, the C57BL/6 + NF group and ApoE-/- + NF group mice were fed a normal specific pathogen-free (SPF) diet; the ApoE-/- + HF group mice were fed a high-cholesterol SPF diet. The plasma and jejunum tissue homogenate were obtained for non-targeted lipid metabolomics. The lipid droplets in tissues were observed by transmission electron microscope and oil red O staining. Jejunum tissue morphology was observed by HE staining. The kits were used to detect lipid content in plasma, tissues, intestinal contents, and cells. Western blot, RT-PCR, immunohistochemistry (IHC), and immunofluorescence (IF) were used to observe the key target of lipid metabolism. In vitro, the final concentration of cholesterol was 100 µmol/L in Caco-cells. Oil red O staining, western blot, RT-PCR and immunofluorescence (IF) were used to observe the changes of lipid metabolism. Finally, the influence of liver X receptor alpha (LXRα) on intestinal cholesterol metabolism was clarified by applying the LXRα inhibitor GSK2033 and siRNA targeting LXRα. RESULTS: The aortic arch and intestinal villi of the two groups of ApoE-/- mice showed apparent lesions and lipid accumulation, and there were significant changes in a variety of lipids in the plasma and jejunum. Additionally, jejunum LXRα was markedly activated. High cholesterol can significantly activate LXRα in Caco-2 cells. After LXRα was inhibited, the protein level of ATP-binding cassette transporter A1/G5/G8 (ABCA1/G5/G8) decreased, and the quantity and volume of intracellular lipids soared. CONCLUSION: In a high-cholesterol environment, the intestine promotes the excretion of cholesterol from the cell through the LXRα-ABCA1/G5/G8 pathway, reduces the intestinal intake of a variety of exogenous cholesterol, and reduces the risk of AS.

Activation of estrogen receptor α inhibits TLR4 signaling in macrophages and alleviates the instability of atherosclerotic plaques in the postmenopausal stage.

Acute cardiovascular events increase significantly in postmenopausal women. The relationship between estrogen receptor (ER) and plaque stability in the postmenopausal stage remains to be elucidated. We aimed to explore whether ERα activation improves plaque instability in the postmenopausal stage. Here, we report that postmenopausal women showed increased macrophage activation and plaque instability with increased MCP-1, MMP9, TLR4, MYD88 and NF-κB p65 and decreased ERα and TIMP1 expression in the vascular endothelium. Moreover, ovariectomy in LDLR-/- mice resulted in a significant increase in plaque area and necrotic core area, as well as a significant decrease in collagen content and an increase in macrophage accumulation in the artery. Ovariectomy also reduced serum estrogen levels and ERα expression and upregulated TLR4 and MMP9 expression in arteries in LDLR-/- mice. Estrogen or phytoestrogen therapy upregulated the expression level of ERα in ovariectomized mice and increased plaque stability by inhibiting macrophage accumulation and TLR4 signaling. In vitro, LPS incubation of RAW264.7 cells resulted in a significant decrease in ERα and TIMP1 expression and an increase in TLR4 activation, and estrogen or phytoestrogen treatment increased ERα and TIMP1 expression and inhibited TLR4 activation and MMP9 expression in LPS-treated RAW264.7 cells. Compared to control siRNA transfected RAW264.7 cells, TLR4 siRNA promoted TIMP1 expression in RAW264.7 cells with LPS incubation, but did not affect ERα expression in RAW264.7 cells with or without LPS treatment. The ERα inhibitor MPP abolished the regulatory effect of estrogen or phytoestrogen on LPS-induced RAW264.7 cells. In conclusion, the present study demonstrates that decreased ERα expression promotes macrophage infiltration and plaque instability in the postmenopausal stage, and activation of ERα in the postmenopausal stage alleviates atherosclerotic plaque instability by inhibiting TLR4 signaling and macrophage-related inflammation.

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.

Catalpol Inhibits Macrophage Polarization and Prevents Postmenopausal Atherosclerosis Through Regulating Estrogen Receptor Alpha.

Lacking estrogen increases the risk of atherosclerosis (AS) in postmenopausal women. Inflammation plays a vital role in the pathological process of AS, and macrophages are closely related to inflammation. Catalpol is an iridoid glucoside extracted from the fresh roots of the traditional Chinese herb Rehmanniae radix preparata. In this study, we aimed to evaluate the effects of catalpol on macrophage polarization and postmenopausal AS. In addition, we investigated whether the mechanism of catalpol was dependent on regulating the expression of estrogen receptors (ERs). In vitro, lipopolysaccharides (LPS) and interferon-γ (IFN-γ) were applied to induce M1 macrophage polarization. In vivo, the ApoE-/- mice were fed with a high-fat diet to induce AS, and ovariectomy was operated to mimic the estrogen cessation. We demonstrated catalpol inhibited M1 macrophage polarization induced by LPS and INF-γ, and eliminated lipid accumulation in postmenopausal AS mice. Catalpol not only suppressed the inflammatory response but also reduced the level of oxidative stress. Then, ERs (ERα and ERß) inhibitors and ERα siRNA were also applied in confirming that the protective effect of catalpol was mediated by ERα, rather than ERß. In conclusion, catalpol significantly inhibited macrophage polarization and prevented postmenopausal AS by increasing ERα expression.

The gut microbiota during the progression of atherosclerosis in the perimenopausal period shows specific compositional changes and significant correlations with circulating lipid metabolites.

Atherosclerosis (AS) is exacerbated in the perimenopausal period, which significantly increases the incidence rate of cardiovascular disease. The disruption of the gut microbiota has been associated with AS or menopause, but the specific changes of AS-associated gut microbiota in the perimenopausal period remain largely unknown. As lipid abnormalities are mainly responsible for AS, the relationship between lipid metabolism abnormalities and gut microbiota disruptions during menopause is rarely reported hitherto. In the present study, ApoE-/- mice fed with a high-fat diet (HFD) were subjected to ovariectomy and supplemented with estrogen. The ovariectomized HFD-fed ApoE-/- mice underwent significant AS damage, hepatic lipid damage, hyperlipidemia, and changes of lipid metabolism- and transport-related enzymes. There was significantly higher abundance of some lipid metabolites in the plasma of ovariectomized HFD-fed ApoE-/- mice than in non-ovariectomized ones, including cholesterol esters, triglycerides, phospholipids, and other types of lipids (free fatty acids, acylcarnitine, sphingomyelins, and ceramides). The administration of estrogen significantly reduced the contents of most lipid metabolites. The diversity and composition of gut microbiota evidently changed in ovariectomized HFD-fed ApoE-/- mice, compared to HFD-fed ApoE-/- mice without ovariectomy. In contrast, with estrogen supplementation, the diversity and composition of gut microbiota were restored to approach that of non-ovariectomized HFD-fed ApoE-/- mice, and the relative abundances of some bacteria were even like those of C57BL/6 mice fed with a normal diet. On the other hand, the transplantation of feces from C57BL/6 mice fed with normal diet to ovariectomized HFD-fed ApoE-/- mice was sufficient to correct the hyperlipidemia and AS damage, and to reverse the characteristics changing of lipid metabolomics in ovariectomized HFD-fed ApoE-/- mice. These phenomena were also been observed after transplantation of feces from estrogen-treated ovariectomized HFD-fed ApoE-/- mice to ovariectomized HFD-fed ApoE-/- mice. Moreover, the gut microbiota and lipid metabolites were significantly correlated, demonstrating that the changes of serum lipids may be associated with the gut microbiota disruptions in the perimenopausal period. In conclusion, the gut microbiota during the progression of AS in the perimenopausal period showed specific compositional changes and significant correlations with circulating lipid metabolites. Estrogen supplementation may exert beneficial effects on gut bacteria and lipid metabolism.

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.

Activation of estrogen receptor α (ERα) is required for Alisol B23-acetate to prevent post-menopausal atherosclerosis and reduced lipid accumulation.

The risk of atherosclerosis (AS) ascends among post-menopausal women, while current hormone replacement therapy exerts several adverse effects. Alisol B 23-acetate (AB23A), a tetracyclic triterpenoid isolated from the rhizome of Alisma orientale, was reported to show multiple physiological activities, including regulating lipid metabolism. According to molecular docking analysis, it was predicted to bind with estrogen receptor α (ERα). In this study, we aimed to observe the effect of AB23A on preventing post-menopausal AS and explore whether the mechanism was mediated by ERα. In vitro, free fatty acid (FFA) was applied to induce the abnormal lipid metabolism of L02 cells. In vivo, the ApoE-/- mice were ovariectomized to mimic the cessation of estrogen. The high-fat diet was also given to induce post-menopausal AS. We demonstrated AB23A attenuated the accumulation of total cholesterol and triglyceride induced by free fatty acids in hepatocytes. In high-fat diet-ovariectomy-treated ApoE-/- mice, AB23A eliminated lipids in blood and liver. AB23A not only reduced the synthesis of proprotein convertase subtilisin/kexin type 9 (PCSK9) through sterol-regulatory element binding proteins (SREBPs) but also suppressed the secretion of PCSK9 through silent information regulator 1 (SIRT1). Notably, AB23A promoted the expression of ERα in vivo and in vitro. The both ERα inhibitor and ERα siRNA were also applied in confirming whether the hepatic protective effect of AB23A was mediated by ERα. We found that AB23A significantly promoted the expression of ERα. AB23A could inhibit the synthesis and secretion of PCSK9 through ERα, lower the accumulation of triglyceride and cholesterol, and prevent post-menopausal AS.

ß-estradiol adjusts intestinal function via ERß and GPR30 mediated PI3K/AKT signaling activation to alleviate postmenopausal dyslipidemia.

Decreases in estrogen secretion and estrogen receptor function lead to an increase in the incidence of dyslipidemia and cardiovascular disease (CVD) in postmenopausal women. We previously reported that ß-estradiol has a significant regulatory effect on lipids in ApoE-/- mice with bilateral ovariectomy. In the present study, we investigated how ß-estradiol regulates intestinal function via estrogen receptors to alleviate postmenopausal dyslipidemia. Ovariectomized ApoE-/- mice were treated with ß-estradiol for 90 days, and we found that ß-estradiol reduced TC, TG, LDL-c, IL-1ß and IL-18 levels in serum and decreased lipid accumulation in the liver. ß-estradiol reduced injury and inflammation in the jejunum in ovariectomized mice, and promoted the expression of tight junction-related proteins. Moreover, ß-estradiol increased ERα, ERß, GPR30 and ABCG5 protein expression, and decreased the levels of NPC1L1 and SR-B1 in the jejunum of ovariectomized mice. In Caco-2 cells incubated with cholesterol, ß-estradiol up-regulated PI3K/AKT signaling, reduced cholesterol accumulation, suppressed inflammatory signaling, and increased the expression of tight junction-related proteins. ERß or GPR30 inhibition decreased the protective effect of ß-estradiol on cholesterol accumulation, tight junctions, and inflammation in cholesterol incubated Caco-2 cells, while silencing both ERß and GPR30 completely eliminated the protective effect of ß-estradiol. PI3K/AKT inhibition abolished the protective effect of ß-estradiol on cholesterol accumulation, tight junction-related protein expression, and inflammation, but had no influence on ERα, ERß or GPR30 expression in cholesterol incubated Caco-2 cells. Our results provide evidence that ß-estradiol regulates intestinal function via ERß and GPR30 mediated PI3K/AKT signaling activation to alleviate postmenopausal dyslipidemia.

The protective effects of liguzinediol on congestive heart failure induced by myocardial infarction and its relative mechanism.

BACKGROUND: Heart failure (HF) is one of the most common causes of cardiovascular diseases in the world. Currently, the drugs used to treat HF in the clinic may cause serious side effects. Liguzinediol, 2, 5-dimethyl-3, 6-dimethyl-pyrazine, is a compound synthesized after the structural modification of ligustrazine (one active ingredient of Szechwan Lovage Rhizome). We aimed to observe the effects of liguzinediol on preventing HF and explore the related mechanisms. METHODS: The ligation of left anterior descending coronary artery was operated to established the myocardial infarction (MI) model in Sprague-Dawley rats. Cardiac functions were recorded by echocardiography and hemodynamics. The changes in the Renin-Angiotensin-Aldosterone System (RAAS), inflammation, and oxidative stress were detected by radioimmunoassay and Elisa kits. Western blot and real-time PCR were applied to determine the expressions of the TGF-ß1/Smads pathway. RESULTS: Firstly, liguzinediol enhanced the systolic and diastolic functions of the heart in MI rats. Liguzinediol improved ventricular remodeling by reducing myocardial cell necrosis, as well as reducing collagen deposition and myocardial fibrosis. Then, liguzinediol suppressed the activation of RAAS, inhibited the synthesis of pro-inflammation factors, and reduced oxidative stress. In the end, liguzinediol also down-regulated the expressions of the TGF-ß1/Smads pathway. CONCLUSIONS: Liguzinediol could alleviate HF caused by MI in rats, and the protective effect was associated with the regulation of the TGF-ß1/Smads pathway.