Zhi Tan

17β-Estradiol enhances breast cancer cell motility and invasion via extra-nuclear activation of actin-binding protein ezrin.

Estrogen promotes breast cancer metastasis. However, the detailed mechanism remains largely unknown. The actin binding protein ezrin is a key component in tumor metastasis and its over-expression is positively correlated to the poor outcome of breast cancer. In this study, we investigate the effects of 17β-estradiol (E2) on the activation of ezrin and its role in estrogen-dependent breast cancer cell movement. In T47-D breast cancer cells, E2 rapidly enhances ezrin phosphorylation at Thr567 in a time- and concentration-dependent manner. The signalling cascade implicated in this action involves estrogen receptor (ER) interaction with the non-receptor tyrosine kinase c-Src, which activates the phosphatidylinositol-3 kinase/Akt pathway and the small GTPase RhoA/Rho-associated kinase (ROCK-2) complex. E2 enhances the horizontal cell migration and invasion of T47-D breast cancer cells in three-dimensional matrices, which is reversed by transfection of cells with specific ezrin siRNAs. In conclusion, E2 promotes breast cancer cell movement and invasion by the activation of ezrin. These results provide novel insights into the effects of estrogen on breast cancer progression and highlight potential targets to treat endocrine-sensitive breast cancers.

Caveolin-3 is involved in the protection of resveratrol against high-fat-diet-induced insulin resistance by promoting GLUT4 translocation to the plasma membrane in skeletal muscle of ovariectomized rats.

Insulin resistance is recognized as a common metabolic factor which predicts the future development of both type 2 diabetes and atherosclerotic disease. Resveratrol (RSV), an agonist of estrogen receptor (ER), is known to affect insulin sensitivity, but the mechanism is unclear. Evidence suggests that caveolin-3 (CAV-3), a member of the caveolin family, is involved in insulin-stimulated glucose uptake. Our recent work indicated that estrogen via ER improves glucose uptake by up-regulation of CAV-3 expression. Here, we investigated the role of CAV-3 in the effect of RSV on insulin resistance in skeletal muscle both in vivo and in vitro. The results demonstrated that RSV ameliorated high-fat-diet (HFD)-induced glucose intolerance and insulin resistance in ovariectomized rats. RSV elevated insulin-stimulated glucose uptake in isolated soleus muscle in vivo and in C2C12 myotubes in vitro by enhancing GLUT4 translocation to the plasma membrane rather than increasing GLUT4 protein expression. Through ERα-mediated transcription, RSV increased CAV-3 protein expression, which contributed to GLUT4 translocation. Moreover, after knockdown of CAV-3 gene, the effects of RSV on glucose uptake and the translocation of GLUT4 to the plasma membrane, as well as the association of CAV-3 and GLUT4 in the membrane, were significantly attenuated. Our findings demonstrated that RSV via ERα elevated CAV-3 expression and then enhanced GLUT4 translocation to the plasma membrane to promote glucose uptake in skeletal muscle, exerting its protective effects against HFD-induced insulin resistance. It suggests that this pathway could represent an effective therapeutic target to fight against insulin resistance syndrome induced by HFD.

Effects of add-on lipid-modifying therapy on top of background statin treatment on major cardiovascular events: A meta-analysis of randomized controlled trials.

BACKGROUND In patients at high risk of atherosclerotic cardiovascular diseases (ASCVDs), residual cardiovascular risk persists despite the achievement of target LDL cholesterol levels with statin therapy. It is still unclear whether adding lipid-modifying agent to statin treatment can further improve clinical outcomes. METHODS Randomized controlled trials (RCTs) in terms of adding lipid-modifying agent to statin versus statin monotherapy in patients at high risk of ASCVD were identified by electronic and manual searches. Results were expressed as relative risk (RR) with 95% confidence intervals (CIs). RESULTS Eleven RCTs with 109,244 patients were included in this meta-analysis. Overall, the incidences of major adverse cardiovascular events (MACEs) were 9.70% in the statin combination groups and 9.92% in the statin monotherapy groups. No significant difference was observed in the risk of MACEs either in overall (RR 0.99, 95% CI 0.93-1.05, P=0.76) or subgroup analysis (CETP inhibitor: RR 1.07, 95% CI 0.93-1.23, P=0.37; niacin: RR 1.03, 95% CI 0.85-1.25, P=0.79; n-3 fatty acid: RR 0.98, 95% CI 0.88-1.09, P=0.70; fenofibrate: RR 0.93, 95% CI 0.80-1.09, P=0.38), with the exception of the statin/ezetimibe combination subgroup (RR 0.92, 95% CI 0.87-0.97, P=0.004). Adding lipid-modifying agent to statin significantly increased liver injury risk. Adding ezetimibe to statin did not alter side effect profile. CONCLUSION Adding niacin, CETP inhibitors, n-3 fatty acid or fibrates to statin therapy has all failed to achieve a clinical benefit. Adding ezetimibe to statin therapy further lowers LDL-cholesterol safely and translates into a clinical benefit in patients at high risk of ASCVD.

Progesterone enhances vascular endothelial cell migration via activation of focal adhesion kinase.

The mechanisms of progesterone on endothelial cell motility are poorly investigated. Previously we showed that progesterone stimulated endothelial cell migration via the activation of actin‐binding protein moesin, leading to actin cytoskeleton remodelling and the formation of cell membrane structures required for cell movement. In this study, we investigated the effects of progesterone on the formation of focal adhesion complexes, which provide anchoring sites for cell movement. In cultured human umbilical endothelial cells, progesterone enhanced focal adhesion kinase (FAK) phosphorylation at Tyr397 in a dose‐ and time‐dependent manner. Several signalling inhibitors interfered with progesterone‐induced FAK activation, including progesterone receptor (PR) antagonist ORG 31710, specific c‐Src kinase inhibitor PP2, phosphatidylinosital‐3 kinase (PI3K) inhibitor wortmannin as well as ρ‐associated kinase (ROCK‐2) inhibitor Y27632. It suggested that PR, c‐Src, PI3K and ROCK‐2 are implicated in this action. In line with this, we found that progesterone rapidly promoted c‐Src/PI3K/Akt activity, which activated the small GTPase RhoA/ρ‐associated kinase (ROCK‐2) complex, resulting in FAK phosphorylation. In the presence of progesterone, endothelial cells displayed enhanced horizontal migration, which was reversed by small interfering RNAs abrogating FAK expression. In conclusion, progesterone promotes endothelial cell movement via the rapid regulation of FAK. These findings provide new information on the biological actions of progesterone on human endothelial cells that are relevant for vascular function.

E2–BSA activates caveolin-1 via PI3K/ERK1/2 and lysosomal degradation pathway and contributes to EPC proliferation

BACKGROUND The mechanism that estrogen (E(2)) increases the number of endothelial progenitor cells (EPC) is largely unknown. Here we used E(2)-conjugated bovine serum albumin (E(2)-BSA, membrane impermeable) to investigate whether the membrane estrogen receptor (mER) and its related protein caveolin-1 (CAV-1) are involved in these processes. METHODS AND RESULTS E(2)-BSA promoted [(3)H]-thymidine incorporation of EPC through increasing CAV-1 expression via mER (ERα, but not ERβ or GPR30). Both cholesterol depletion and CAV-1 knockdown with use of CAV-1 siRNA significantly attenuated E(2)-BSA-induced [(3)H]-thymidine incorporation. Western blot showed that E(2)-BSA increased membrane CAV-1 protein expression 12h after treatment, whereas mRNA levels of CAV-1 were augmented until 24h after E(2)-BSA treatment. Furthermore, pre-incubated EPC with ICI 182780 (a specific ER antagonist), LY 294002 (a selective PI(3)K inhibitor) or PD 98059 (a specific ERK1/2 inhibitor) before E(2)-BSA inhibited the late-stage effect of E(2)-BSA (≥24 h) on up-regulation of CAV-1 mRNA and protein expression. Pulse chase results demonstrated that E(2)-BSA inhibited lysosome-mediated degradation of CAV-1 protein at the early stage (≤12 h), and then resulted in the increased CAV-1 protein. CONCLUSION In the present work we demonstrated that E(2)-BSA promotes EPC proliferation through mER (ERα) in CAV-1-dependent manner: prolonging the stability of CAV-1 protein through quick inhibition of the lysosomal degradation pathway at the early stage (≤12 h) and up-regulating CAV-1 at transcription levels through PI(3)K/ERK1/2 signaling pathway at the late stage (≥24 h). These data indicated that a there is a novel mechanism of E(2)-BSA in the regulation of EPC proliferation through CAV-1.

17beta-estradiol attenuates pressure overload-induced myocardial hypertrophy through regulating caveolin-3 protein in ovariectomized female rats

Our findings indicate that in ovariectomized female rats abdominal aortic constriction led to significant increases in left ventricular mass, myocyte diameter and heart weight/body weight (HW/BW) value, and decreases in interventricular septal thickness at diastole (IVSd), left ventricular percent fractional shortening (FS) and ejection fraction (EF). These pathophysiological alterations were largely reversed by administration with 17β-estradiol for eight weeks. Furthermore, the enhanced expression of extracellular signal-regulated kinases 1/2 and decreased expression of caveolin-3 were found in left ventricle of AAC group. 17β-estradiol (E2) administration increased the expression of caveolin-3 and reduced the level of ERK phosphorylation in these pressure-overloaded rats. Moreover, in cultured neonatal rat cardiomyocytes, E2 inhibited the hypertrophic response to angiotensin II. This effect was reinforced by the addition of extracellular signal-regulated kinases 1/2 inhibitor PD98059, but was impaired when the cells were pretreated with caveolae disruptor, methyl-β-cyclodextrin (M-β-CD). In conclusion, our data indicate that estrogen attenuates the hypertrophic response induced by pressure overload through down-regulation of extracellular signal-regulated kinases 1/2 phosphorylation and up-regulation of caveolin-3 expression.

Oestrogen exerts anti-inflammation via p38 MAPK/NF-κB cascade in adipocytes

BACKGROUND Oestrogen has anti-inflammatory property in obesity. However, the mechanism is still not defined. OBJECTIVE To investigate the effect of oestrogen on LPS-induced monocyte chemoattractant protein-1 (MCP-1) production in adipocytes. METHODS Lipopolysaccharides (LPS) was used to imitate inflammatory responses and monocyte chemotactic protein-1 (MCP-1) was selected as an inflammatory marker to observe. 17β-Estradiol (E2), SB203580 (SB), pyrrolidine dithiocarbamate (PDTC), pertussis toxin (PTX), wortmannin (WM), p65 siRNA and p38 MAPK siRNA were pre-treated respectively or together in LPS-induced MCP-1. Then p38 MAPK and NF-κB cascade were silenced successively to observe the change of each other. Lastly, oestrogen receptor (ER) α agonist, ERβ agonist and ER antagonist were utilised. RESULTS LPS-induced MCP-1 largely impaired by pre-treatment with E2, SB, PDTC or silencing NF-κB subunit. E2 inhibited LPS-induced MCP-1 in a time- and dose-dependent manner, which was related to the suppression of p65 translocation to nucleus. Furthermore, LPS rapidly activated p38 MAPK, while E2 markedly inhibited this activation. It markedly attenuated LPS-stimulated p65 translocation to nucleus and MCP-1 production by transfecting with p38 MAPK siRNA or using p38 MAPK inhibitor. The oestrogens inhibitory effect was mimicked by the ERα agonist, but not by the ERβ agonist. The inhibition of E2 on p38 MAPK phosphorylation was prevented by ER antagonist. CONCLUSIONS E2 inhibits LPS-stimulated MCP-1 in adipocytes. This effect is related to the inhibition of p38 MAPK/NF-κB cascade, and ERα appears to be the dominant ER subtype in these events.

17β-Estradiol attenuates diet-induced insulin resistance and glucose intolerance through up-regulation of caveolin-3.

BackgroundAlthough estrogen contributes to glucose homeostasis, its mechanisms remain unclear.AimsTo investigate the role of caveolin-3 in estrogen’s effects on glucose metabolism.MethodsOvariectomized (OVX) and sham-operated rats, fed with normal chow diet (NCD) or high-calorie diet (HCD), received 17β-estradiol (E2) or placebo. Fasting plasma glucose (FPG) was detected and HOMA-IR was calculated. Primary cultured skeletal muscle cells were treated with E2, in the presence or absence of β-methyl-cyclodextrin and tamoxifen. Glucose consumption and transportation and expression of caveolin-3 were examined.ResultsIn NCD-fed rats, OVX or E2 had no effects on FPG or HOMA-IR. In HCD-fed rats, OVX led to the increase of FPG and HOMA-IR, which was attenuated by E2. In cultured cells, E2 improved glucose consumption and transportation and enhanced caveolin-3 expression, which were blocked by β-methyl-cyclodextrin and tamoxifen.ConclusionCaveolin-3 plays an important role in the mechanism by which E2 attenuates diet-induced glucose intolerance.

Nicotinic Acetylcholine Receptor Alpha7 Subunit Mediates Vagus Nerve Stimulation-Induced Neuroprotection in Acute Permanent Cerebral Ischemia by a7nAchR/JAK2 Pathway

Background The role of nicotinic acetylcholine receptor alpha7 subunit (a7nAchR) in the treatment of acute cerebral ischemia by VNS has not been thoroughly clarified to date. Therefore, this study aimed to investigate the specific role of a7nAchR and explore whether this process is involved in the mechanisms of VNS-induced neuroprotection in rats undergoing permanent middle cerebral artery occlusion (PMCAO) surgery. Material/Methods Rats received a7nAChR antagonist (A) or antagonist placebo injection for control (AC), followed by PMCAO and VNS treatment, whereas the a7nAChR agonist (P) was utilized singly without VNS treatment but only with PMCAO pretreatment. The rats were randomly divided into 6 groups: sham PMCAO, PMCAO, PMCAO+VNS, PMCAO+VNS+A, PMCAO+VNS+AC, and PMCAO+P. Neurological function and cerebral infarct volume were measured to evaluate the level of brain injury at 24 h after PMCAO or PMCAO-sham. Moreover, the related proteins levels of a7nAChR, p-JAK2, and p-STAT3 in the ischemic penumbra were assessed by Western blot analysis. Results Rats pretreated with VNS had significantly improved neurological function and reduced cerebral infarct volume after PMCAO injury (p<0.05). In addition, VNS enhanced the levels of a7nAchR, p-JAK2, and p-STAT3 in the ischemic penumbra (p<0.05). However, inhibition of a7nAchR not only attenuated the beneficial neuroprotective effects induced by VNS, but also decreased levels of p-JAK2 and p-STAT3. Strikingly, pharmacological activation of a7nAchR can partially substitute for VNS-induced beneficial neurological protection. Conclusions These results suggest that a7nAchR is a pivotal mediator of VNS-induced neuroprotective effects on PMCAO injury, which may be related to suppressed inflammation via activation of the a7nAchR/JAK2 anti-inflammatory pathway.

Topical delivery of l -theanine ameliorates TPA-induced acute skin inflammation via downregulating endothelial PECAM-1 and neutrophil infiltration and activation

l-theanine, the most abundant free amino acid in tea, has been documented to possess many different bioactive properties through oral or intragastrical delivery. However, little is known about the effect of topical delivery of l-theanine on acute inflammation. In the present study, by using 12-O-tetradecanoylphorbol-13-acetate (TPA, 2.5 μg/ear)-induced ear edema model in mice, we first found that single-dose local pretreatment of l-theanine 30 min before TPA time- and dose-dependently suppressed the increases in both skin thickness and weight. Subsequently l-theanine ameliorated TPA-induced erythema, vascular permeability increase, epidermal and dermal hyperplasia, neutrophil infiltration and activation via downregulating the expression of PECAM-1 (a platelet endothelial adhesion molecule-1) in blood vessels and the production of pro-inflammatory cytokines IL-1β, TNF-α, and mediator cyclooxygenase-2 (COX-2), which is mainly expressed in neutrophils. It highlighted the potential of l-theanine as a locally administrable therapeutic agent for acute cutaneous inflammation.