Antiproliferative mechanisms of quercetin in rat activated hepatic stellate cells

Quercetin, rich in fruits and vegetables, has been used as a nutritional supplement because of its anti-inflammatory and antioxidative properties. Its positive effects on anti-hepatic fibrosis have also been suggested. However the anti-hepatofibrotic mechanisms upon which quercetin acts have yet to be well characterized. In the present study, we investigated the anti-proliferative effect of quercetin on activated hepatic stellate cells (aHSCs), the central role of hepatofibrosis, and evaluated the proteins involved in growth inhibition by a 2D gel electrophoretic analysis. Activated HSCs were isolated from Sprague Dawley rats and were spontaneously activated in vitro. Quercetin restrained the proliferation of aHSCs rather than quiescent HSCs and heptotcytes by inducing a G(1) arrest as examined by cell cycle analysis and evidenced by increased levels of p53, p21(CIP1/WAF1), as well as p27(KIP1), and decreased abundance of cyclins (D(1), D(2), A, E). An apoptosis through extrinsic pathway as demonstrated by elevated expression of Fas/Fas ligand (FasL), annexin V labeling, chromatin condensation, sub-G(1) fraction (7.39%), caspase-3 activity, was also observed. The 2D electrophoresis analysis revealed that quercetin negatively regulated protein molecules associated with metabolism (α-enolase, phosphoglycerate kinase), survival, cytokinesis (tubulin), and protein folding (protein disulfide isomerase A3) leading to cell growth retardation. Furthermore, quercetin might restrain HSC activation through reducing the levels of inflammatory cytokines (CXCL10, Midkine). Taken together, quercetin exerted diverse mechanisms to inhibit the growth of aHSCs. Proper consumption of quercetin could be beneficial to control the progression of heptofibrosis.     

嗜酸乳杆菌胞外蛋白调控MAPK和PI3K-AKT信号途径关键蛋白活化水平

探讨并揭示嗜酸乳杆菌(Lactobacillus acidophilus)CICC6005分泌的相关蛋白质促进肠道健康及分子机制具有重要研究价值。本实验在确定了L.acidophilus CICC6005分泌的胞外蛋白抑制HT-29结肠癌细胞增殖的基础上,进一步探讨67 ku和37 ku的胞外蛋白通过何种途径发挥抑制结肠癌细胞增殖。研究以HT-29细胞作为靶细胞,用丝裂原激活的蛋白激酶(mitogen activated protein kinase,MAPK)和磷脂酰肌醇-3激酶-丝氨酸/苏氨酸蛋白激酶(phosphatidylinositol 3-kinase-protein kinase B,PI3K-AKT)信号通路为考察对象,以Western Blotting为手段,分析两个通路中关键的靶点蛋白p38、c-Jun氨基末端激酶(c-Jun N-terminal kinase,JNK)、胞外信号调节激酶(extracellular signal-regulated kinase,ERK)、磷酸化p38(phosphorylated p38,p-p38)、磷酸化c-Jun氨基末端激酶(phosphorylated c-Jun N-terminal kinase,p-JNK)、磷酸化的细胞外信号调节蛋白激酶(phosphorylated extracellular signal-regulated kinase,p-ERK)、磷酸化蛋白激酶B(phosphorylated AKT,p-AKT)、PI3K的表达水平,以探讨并阐述源于L.acidophilus CICC6005胞外蛋白调控结肠癌细胞增殖状况的分子机制。结果表明,不同质量浓度的67 ku和37 ku胞外蛋白分别作用HT-29细胞一定时间后,两种胞外蛋白均具有下调两个信号通路途径中p-ERK1/2、p-p38、p-AKT、PI3K蛋白的表达,且存在浓度依赖关系;但对p-JNK、ERK1/2、p38、JNK蛋白的表达没有影响。因此,源于L.acidophilus CICC6005分泌的37 ku和67 ku胞外蛋白表现出显著的抑制HT-29细胞增殖的功能,其机制可能与调控MAPK和PI3K-AKT两个信号通路中几个关键的靶点蛋白的活化水平相关。该研究结果提示,食用嗜酸乳杆菌其分泌的胞外蛋白质将达到维护肠道健康的目标。     

Effects of flavonoids on the expression of the pro-inflammatory response in human monocytes induced by ligation of the receptor for AGEs

Increasing evidence has shown advanced glycation end products (AGEs) receptor ligation (RAGE) to be an important part of complex interactions of the oxidative stress and pro-inflammatory responses. In this study, flavonoids were used to monitor the protective effects against the oxidative damage and inflammation mediated by AGEs in human monocytes. S100B (RAGE ligand) treatment in human THP-1 monocytic cells (THP-1) significantly increased gene expression of the pro-inflammatory cytokines TNF-alpha and IL-1beta; chemokines MCP-1 and IP-10; adhesion factors platelet endothelial cell adhesion molecule (PECAM-1) and beta2-integrin; and pro-inflammatory cyclooxygenase-2 (COX-2). S100B treatment with quercetin and catechin in THP-1 cells had inhibitory effects on the expression of pro-inflammatory genes and protein levels. Quercetin and catechin could regulate S100B-activated oxidant stress-sensitive pathways through blocking p47phox protein expression. Treatment with quercetin and catechin could eliminate reactive oxygen species (ROS) to reduce oxidative stress stimulated by S100B in THP-1 cells. Quercetin and catechin also showed different regulatory abilities on mitogen-activated protein kinase (MAPK) signaling pathways by inhibiting protein expression in S100B-stimulated inflammatory responses in THP-1 cells. This study suggests that quercetin and catechin may be of benefit for diabetic vascular complications due to its antioxidant abilities against AGE-mediated oxidative stress through oxidative stress-sensitive and oxidative stress-responsive signaling pathways, which lead to inflammation in human monocytes.     

The stimulation of cell proliferation by quercetin is mediated by the estrogen receptor

Quercetin causes biphasic modulation of the proliferation of specific colon and mammary cancer cells. In this study, the possible involvement of the estrogen receptor (ER) in the stimulation of cell proliferation by quercetin was investigated. For this purpose, the effect of quercetin on cell proliferation was tested in ER-positive MCF-7 and T47D cells, and in ER-negative HCC-38 and MDA-MB231 cells. Quercetin stimulated proliferation of ER-positive cells only, suggesting this effect to be ER-dependent. In support of these results, quercetin induced ER-ERE-mediated gene expression in a reporter gene assay using U2-OS cells transfected with either ERalpha or ERbeta, with 10(5)-10(6) times lower affinity than 17beta-estradiol (E2) and 10(2)-10(3 )times lower affinity than genistein. Quercetin activated the ERbeta to a 4.5-fold higher level than E2, whereas the maximum induction level of ERalpha by quercetin was only 1.7 fold that of E2. These results point at the relatively high capacity of quercetin to stimulate supposed 'beneficial' ERbeta responses as compared to the stimulation of ERalpha, the receptor possibly involved in adverse cell proliferative effects. Altogether, the results of this study reveal that physiologically relevant concentrations of quercetin can exert phytoestrogen-like activity similar to that observed for the isoflavonoid genistein.     

Dietary quercetin alleviates diabetic symptoms and reduces streptozotocin‐induced disturbance of hepatic gene expression in mice

Quercetin is a food component that may ameliorate the diabetic symptoms. We examined hepatic gene expression of BALB/c mice with streptozotocin (STZ)‐induced diabetes to elucidate the mechanism of the protective effect of dietary quercetin on diabetes‐associated liver injury. We fed normal and STZ‐induced diabetic mice with diets containing quercetin for 2 wk and compared the patterns of hepatic gene expression in these groups of mice using a DNA microarray. Diets containing 0.1 or 0.5% quercetin lowered the STZ‐induced increase in blood glucose levels and improved plasma insulin levels. A cluster analysis of the hepatic gene expressions showed that 0.5% quercetin diet suppressed STZ‐induced alteration of gene expression. Gene set enrichment analysis (GSEA) and quantitative RT‐PCR analysis showed that the quercetin diets had greatest suppressive effect on the STZ‐induced elevation of expression of cyclin‐dependent kinase inhibitor p21(WAF1/Cip1) (Cdkn1a). Quercetin also suppressed STZ‐induced expression of Cdkn1a in the pancreas. Dietary quercetin might improve liver and pancreas functions by enabling the recovery of cell proliferation through the inhibition of Cdkn1a expression. Unexpectedly, in healthy control mice the 0.5 and 1% quercetin diets reduced the expression of ubiquitin C (Ubc), which has heat‐shock element (HSE) in the promoter region, in the liver.     

Involvement of AMPK/mTOR/HIF-1α in anticancer control of quercetin in hypoxic MCF-7 cells

Quercetin has been reported to possess therapeutic effects in the treatment of cancers. In this study, the molecular action of quercetin, with emphasis on its ability to control the intracellular signaling cascades of hypoxia inducible factor-1α (HIF-1α), mammalian target of rapamycin (mTOR), and AMP-activated protein kinase (AMPK), responsible for survival or induction of apoptosis in hypoxic MCF-7 cells, was investigated. The effects of quercetin on apoptosis in relation to its ability to prevent HIF-1α induction were investigated. The involvement of HIF-1α reduction in quercetin-based cancer control was clearly shown in conditions of mTOR inhibition by rapamycin, an mTOR inhibitor. Surprisingly, quercetin induced an AMPK-suppressed state in a CoCl₂-induced hypoxic condition. It is speculated that quercetin is capable of inhibiting AMPK to decrease HIF-1α, which is a critical survival factor in hypoxia. A complex control of HIF-1α, mTOR, and AMPK is necessary in inducing apoptosis of MCF-7 breast cancer cells under hypoxia.     

Oleuropein and hydroxytyrosol inhibit MCF‐7 breast cancer cell proliferation interfering with ERK1/2 activation

The growth of many breast tumors is stimulated by estradiol (E2), which activates a classic mechanism of regulation of gene expression and signal transduction pathways inducing cell proliferation. Polyphenols of natural origin with chemical similarity to estrogen have been shown to interfere with tumor cell proliferation. The aim of this study was to investigate whether hydroxytyrosol (HT) and oleuropein (OL), two polyphenols contained in extra‐virgin olive oil, can affect breast cancer cell proliferation interfering with E2‐induced molecular mechanisms. Both HT and OL inhibited proliferation of MCF‐7 breast cancer cells. Luciferase gene reporter experiments, using a construct containing estrogen responsive elements able to bind estrogen receptor alpha (ERα) and the study of the effects of HT or OL on ERα expression, demonstrated that HT and OL are not involved in ERα‐mediated regulation of gene expression. However, further experiments pointed out that both OL and HT determined a clear inhibition of E2‐dependent activation of extracellular regulated kinase1/2 belonging to the mitogen activating protein kinase family. Our study demonstrated that HT and OL can have a chemo‐preventive role in breast cancer cell proliferation through the inhibition of estrogen‐dependent rapid signals involved in uncontrolled tumor cell growth.     

槲皮素对氧化条件下猪肉肌原纤维蛋白结构及凝胶特性的影响

为研究槲皮素对氧化条件下猪肉肌原纤维蛋白结构及凝胶特性的影响,建立肌原纤维蛋白氧化体系（40 mg/mL蛋白、10 μmol/L FeCl3、100 μmol/L VC、1 mmol/L H2O2）,加入不同量的槲皮素（10、50、100、150 μmol/g）,测定蛋白的巯基含量、表面疏水性、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳、凝胶强度、保水性、微观结构、流变特性以及水合特性。结果表明,槲皮素使肌原纤维蛋白的总巯基含量显著降低（P＜0.05）;10 μmol/g槲皮素使表面疏水性降低,随后表面疏水性略有增加;槲皮素导致肌球蛋白重链（myosin heavy chain,MHC）条带强度减弱,添加量为100、150 μmol/g时,肌动蛋白条带强度也减弱,MHC和肌动蛋白参与了蛋白质大分子聚集体的形成,并且该聚集体是可被还原的;槲皮素提高了凝胶强度和保水性,凝胶微观结构更加致密,部分自由水转化为不易流动水,蛋白质对水的束缚能力增强,且槲皮素提高了蛋白的G’和G”。因此,槲皮素通过与肌原纤维蛋白巯基的共价交联及适度提高蛋白的表面疏水性,改善了蛋白的凝胶特性,且槲皮素添加量越高,蛋白形成凝胶的能力越强。     

Lycopene inhibits growth of human colon cancer cells via suppression of the Akt signaling pathway

The aberrant regulation of the phosphoinositide 3-kinase/Akt survival signaling pathway in cancer has prompted significant interest in suppression of this pathway to treat cancer. Previous studies identified an important role for phosphoinositide 3-kinase/Akt in colon cancer progression. Lycopene, a major component in tomato, exhibited potential anti-carcinogenic activity. Consumption of tomato has been associated with reduced risk of several types of human cancer. However, the inhibitory mechanisms of lycopene on the proliferation of human colon cancer have not been studied well yet. Thus we investigated the inhibitory effects of lycopene on the Akt signaling pathway in human colon cancer HT-29 cells. Lycopene inhibited cell proliferation in human colon cancer HT-29 cells with a IC(50) value of 10 microM. Lycopene treatment suppressed Akt activation and non-phosphorylated beta-catenin protein level in human colon cancer cells. Immunocytochemical results indicated that lycopene increased the phosphorylated form of beta-catenin proteins. These effects were also associated with reduced promoter activity and protein expression of cyclin D1. Furthermore, lycopene significantly increased nuclear cyclin-dependent kinase inhibitor p27(kip)abundance and inhibited phosphorylation of the retinoblastoma tumor suppressor protein in human colon cancer cells. In conclusion, lycopene inhibited cell proliferation of human colon cancer cells via suppression of the Akt signaling pathway and downstream targeted molecules.     

Quercetin Mitigates Hepatic Insulin Resistance in Rats with Bile Duct Ligation Through Modulation of the STAT3/SOCS3/IRS1 Signaling Pathway

Insulin resistance (IR) and inflammatory mediators are correlated with hepatic fibrosis. Quercetin is a bioflavonoid with well‐known antidiabetic and antifibrotic properties. Bile duct ligation (BDL) is a surgical model performed on animals to produce a murine model in which increased oxidative stress occurs, which results in liver fibrosis. Our study aimed to determine whether quercetin improves hepatic IR as well as hepatic fibrosis in rats experiencing BDL. Male Wistar rats were allocated to four groups according to a random pattern, including a sham group, a sham and quercetin group (30 mg/kg/day), a BDL alone group, and a BDL and quercetin group (30 mg/kg/day). Evaluation of STAT3, SOCS3, IRS1, Rac1, Rac1‐GTP, Sp1, NOX1, HIF‐1α, and ERK1 expression was performed by RT‐PCR along with the western blot analytical technique in liver tissue. The antidiabetic impact of quercetin was associated with reduction in mRNA and expression of protein in STAT3 and SOCS3, along with an increase in IRS1. The antifibrotic effect of quercetin was also determined by downregulation of mRNA or the levels of protein expression of Rac1‐GTP, Rac1, HIF‐1α, NOX1, and Sp1, along with ERK1. Our study indicates that quercetin may improve hepatic fibrosis via inhibiting ROS‐associated inflammation as well as ameliorating hepatic IR by beneficial regulation of the STAT3/SOCS3/IRS1 signaling pathway.     

酒糟粗提物对肝癌细胞HepG2增殖的抑制作用

为了解酒糟粗提物对人体肝癌细胞株HepG2细胞增殖和凋亡的影响,首先采用液相色谱-质谱联用仪（LC-MS）分析酒糟粗提物成分,再利用不同浓度的酒糟提取物分别处理HepG2细胞,采用RTCA检测其对HepG2细胞增殖的影响,采用流式细胞术检测其对HepG2细胞周期的影响,采用实时荧光定量PCR检测其对CyclinA、CDK2、Bax、Bcl-2基因表达的影响,采用Western Blot检测其对9种凋亡相关蛋白表达量的影响。研究发现浓香型白酒酒糟粗提物主要含有43种物质,酒糟粗提物可明显抑制HepG2细胞的增殖且呈浓度依赖;酒糟粗提物可以显著下调S期相关周期蛋白CyclinA及其激酶CDK2的mRNA及蛋白的表达,同时使抗凋亡蛋白Bcl-2的mRNA及蛋白的表达减少,促凋亡蛋白Bax的mRNA及蛋白的表达增加（P<0.05）;CYTC、Cleaved-Caspase-9及Cleaved-Caspase-3表达量逐渐升高（P<0.05）,Caspase-9、Caspase-3表达量逐渐降低（P<0.05）。结果表明酒糟粗提物含多种活性物质,可抑制HepG2细胞的增殖,并通过激活介导凋亡的线粒体通路诱导肝癌HepG2细胞发生凋亡。     

苦荞清蛋白酶解物对高糖诱导的HepG2细胞胰岛素抵抗的保护作用

目的:建立胰岛素抵抗HepG2细胞模型,观察苦荞清蛋白酶解物(tartary buckwheat albumin hydrolysate,TBAH)对HepG2细胞胰岛素抵抗的影响.方法:采用碱性蛋白酶水解苦荞清蛋白制备TBAH,超滤法截留分子质量小于3 kDa的TBAH;利用高糖高胰岛素诱导HepG2细胞36 h建立...     

Cellular assessment of the extract of bambangan (Mangifera pajang) as a potential cytoprotective agent for the human hepatocellular HepG2 cell line

This study was conducted to investigate the potential of bambangan (Mangifera pajang) fruit extracts in the protection against oxidative damage caused by tert-butyl hydroperoxide in the human hepatocellular HepG2 cell line. Proteins which might be involved in the cytoprotective mechanism were investigated using western blotting technique. Quercetin was used as a positive control. The results showed that only the kernel extract of M. pajang and quercetin displayed cytoprotective activity in HepG2 cells, with EC₅₀ values of 1.2 and 5.3 μg/ml, respectively. Expression of quinone reductase, glutathione reductase and methionine sulfoxide reductase A proteins were significantly up-regulated by quercetin, suggesting their involvement in the cytoprotective activity of quercetin. However, expressions of only glutathione reductase and methionine sulfoxide reductase A proteins were significantly up-regulated by the kernel extract, again suggesting their involvement in the cytoprotective activity of bambangan kernel extract. Future study is needed to investigate the involvement of other cytoprotective proteins in the cytoprotection mechanism.     

糖苷结构对苦荞黄酮促进葡萄糖在C2C12小鼠骨骼肌细胞中摄取作用的影响

苦荞是芦丁含量最高的粮食作物,但不同的加工过程会导致芦丁降解为单糖苷结构的异槲皮素及其前体槲皮素,进而影响生物活性。本研究比较芦丁及其降解产物（槲皮素、异槲皮素）这三类含有不同糖苷结构的黄酮在C2C12小鼠骨骼肌细胞中促进葡萄糖摄取的功效差异,并探究其作用机制。研究结果表明,苦荞与水接触会导致苦荞中的核心黄酮组分-芦丁降解为槲皮素。芦丁及其降解产物（槲皮素、异槲皮素）均能有效促进C2C12细胞对葡萄糖的摄取,作用顺序为:槲皮素>异槲皮素>芦丁。糖苷键的增加会降低槲皮素促进骨骼肌细胞糖摄取的效果。芦丁和异槲皮素不能激活胰岛素依赖型信号通路中的IRS-1表达及AKT的磷酸化,但高浓度下（400 μmol/L）,芦丁和异槲皮素可以通过非胰岛素依赖型的信号通路中的p-AMPK/p-ACC促进葡萄糖摄取作用,且异槲皮素的作用大于芦丁。槲皮素虽然抑制了IRS-1的表达及AKT的磷酸化,但槲皮素通过AMPK/ACC的磷酸化显著了促进C2C12细胞对葡萄糖的摄取。本研究揭示芦丁及其降解产物在细胞水平上的降血糖作用及机理的差异,对于充分理解苦荞黄酮降血糖机制提供了科学依据。     

EGF-induced trophoblast secretion of MMP-9 and TIMP-1 involves activation of both PI3K and MAPK signalling pathways

Epidermal growth factor (EGF) is present in the maternal-fetal environment and has an important role in placental development. Matrix metalloproteinase-9 (MMP-9) expression/activation is a pre-requisite in extravillous trophoblast invasion. Whereas EGF up-regulates MMP-9 activity in a variety of cell types, there is no direct evidence for the stimulation of MMP-9 and tissue inhibitor of metalloproteinase-1 (TIMP-1) secretion by EGF in extravillous trophoblasts. In addition, the signalling pathways involved in this regulation are not clear. In the present study, we have examined the possible involvement of the phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways in the regulation of the MMP-9/TIMP-1 system by EGF in vitro. We used a well-established invasive extravillous trophoblast cell line (HTR8/Svneo) and measured gene and protein expression by semi-quantitative RT-PCR and western analysis respectively. MMP activity was determined by zymography. We showed for the first time that EGF activated both PI3K/Akt and MAPK/extracellular-signal regulated kinase (ERK) signalling in HTR8/SVneo, and increased both MMP-9 and TIMP-1 mRNAs and protein concentrations. Interfering with either signalling pathway via PI3K inhibitor LY294002 or MEK inhibitor U0126 in EGF-stimulated HTR8/SVneo cells blocked the induction of MMP-9 and TIMP-1. LY294002 inhibited Akt phosphorylation, but had no effect on ERK phosphorylation; U0126 suppressed ERK phosphorylation without interfering with the phosphorylation of Akt. In addition, expression of constitutively active Akt (Myr-Akt1, Myr-Akt2, Myr-Akt3) was not sufficient to induce proMMP-9 and TIMP-1 secretion. Our results suggest that the activation of both PI3K and MAPK pathways in extravillous trophoblasts is necessary for the up-regulation of MMP-9 and TIMP-1 expression by EGF.     

Participation of phosphatidyl inositol 3-kinase/protein kinase B and ERK1/2 pathways in interleukin-1beta stimulation of lactate production in Sertoli cells

Interleukin-1beta (IL1beta ) belongs to a set of intratesticular regulators that provide the fine-tuning of cellular processes implicated in the maintenance of spermatogenesis. The aim of the present study was to analyze the signaling pathways that may participate in IL1beta regulation of Sertoli cell function. Sertoli cell cultures from 20-day-old rat were used. Stimulation of the cultures with IL1beta showed increments in phosphorylated protein kinase B (PKB), P70S6K, and ERK1/2 levels. A phosphatidyl inositol 3-kinase (PI3K) inhibitor (wortmannin (W)), a mammalian target of rapamycin inhibitor (rapamycin (R)), and a MEK inhibitor (PD98059 (PD)) were utilized to evaluate the participation of PI3K/PKB, P70S6K, and ERK1/2 pathways in the regulation of lactate production by IL1beta . PD and W, but not R, decreased IL1beta-stimulated lactate production. The participation of these pathways in the regulation of glucose uptake and lactate dehydrogenase (LDH) A mRNA levels by IL1beta was also analyzed. It was observed that W decreased IL1beta-stimulated glucose uptake, whereas PD and R did not modify it. On the other hand, PD decreased the stimulation of LDH A mRNA levels by IL1beta , whereas W and R did not modify it. In summary, results presented herein demonstrate that IL1beta stimulates PI3K/PKB-, P70S6K-, and ERK1/2-dependent pathways in rat Sertoli cells. Moreover, these results show that while IL1beta utilizes the PI3K/PKB pathway to regulate glucose transport, it utilizes the ERK1/2 pathway to regulate LDH A mRNA levels. This study reveals that IL1beta utilizes different signal transduction pathways to modify the biochemical steps that are important to regulate lactate production in rat Sertoli cells.     

连翘苷对食管上皮恶性转变细胞和食管癌Eca-109细胞的抑制作用及机制

目的：探究连翘苷对食管上皮恶性转变细胞和食管癌Eca-109细胞增殖、周期、凋亡、迁移、侵袭的影响,分析其对这两种细胞的抑制效果及其作用机制。方法：取食管上皮恶性转变细胞和食管癌Eca-109细胞,使用不同浓度（10、100μmol/L）的连翘苷处理干预细胞24 h,采用细胞计数试剂盒-8(cell counting kit-8,CCK8)法检测细胞增殖,流式细胞术检测细胞周期、凋亡,Transwell实验检测细胞迁移、侵袭,蛋白免疫印迹法（Western blotting）检测细胞中磷脂酰肌醇-3-激酶（phosphoinositide 3-kinase,PI3K）、蛋白激酶B(protein kinase B,PKB),（也称为AKT）、磷酸化磷脂酰肌醇3-激酶（phosphorylated phosphatidylinositol-3-kinase,p-PI3K）、磷酸化蛋白激酶B(phosphorylated protein kinase B,p-PKB)（也称为p-AKT）、p21蛋白、B淋巴细胞瘤-2(B-cell lymphoma-2,Bcl-2)和基质金属蛋白酶9(ma...     

Cruciferous vegetable phytochemical sulforaphane affects phase II enzyme expression and activity in rat cardiomyocytes through modulation of Akt signaling pathway

The isothiocyanate sulforaphane (SF), abundant in Cruciferous vegetables, is known to induce antioxidant/detoxification enzymes in many cancer cell lines, but studies focused on its cytoprotective action in nontransformed cells are just at the beginning. Since we previously demonstrated that SF elicits cardioprotection through an indirect antioxidative mechanism, the aim of this study was to analyze the signaling pathways through which SF exerts its protective effects. Using cultured rat cardiomyocytes, we investigated the ability of SF to activate Akt/protein kinase B (PKB) and extracellular signal-regulated kinase 1 and 2 (ERK1/2) signaling pathways, which are implicated in cardiac cell survival, and to increase the phosphorylation of Nuclear factor E2-related factor 2 (Nrf2) and its binding to the antioxidant response element. By means of specific inhibitors, we demonstrated that the Phosphatidylinositol 3-kinase (PI3K)/Akt pathway represents a mechanism through which SF influences both expression and activity of glutathione reductase, glutathione-S-transferase, thioredoxin reductase, and NAD(P)H:quinone oxidoreductase-1, analyzed by western immunoblotting and spectrophotometric assay, respectively, and modulates Nrf2 binding and phosphorylation resulting in a cytoprotective action against oxidative damage. Results of this study confirm the importance of phase II enzymes modulation as cytoprotective mechanism and support the nutritional assumption of Cruciferous vegetables as source of nutraceutical cardioprotective agents.     

Saffron (Crocus sativus L.) increases glucose uptake and insulin sensitivity in muscle cells via multipathway mechanisms

Saffron (Crocus sativus Linn.) has been an important subject of research in the past two decades because of its various biological properties, including anti-cancer, anti-inflammatory, and anti-atherosclerotic activities. On the other hand, the molecular bases of its actions have been scarcely understood. Here, we elucidated the mechanism of the hypoglycemic actions of saffron through investigating its signaling pathways associated with glucose metabolism in C₂C₁₂ skeletal muscle cells. Saffron strongly enhanced glucose uptake and the phosphorylation of AMPK (AMP-activated protein kinase)/ACC (acetyl-CoA carboxylase) and MAPKs (mitogen-activated protein kinases), but not PI 3-kinase (Phosphatidylinositol 3-kinase)/Akt. Interestingly, the co-treatment of saffron and insulin further improved the insulin sensitivity via both insulin-independent (AMPK/ACC and MAPKs) and insulin-dependent (PI 3-kinase/Akt and mTOR) pathways. It also suggested that there is a crosstalk between the two signaling pathways of glucose metabolism in skeletal muscle cells. These results could be confirmed from the findings of GLUT4 translocation. Taken together, AMPK plays a major role in the effects of saffron on glucose uptake and insulin sensitivity in skeletal muscle cells. Our study provides important insights for the possible mechanism of action of saffron and its potential as a therapeutic agent in diabetic patients.