AIM: To investigated the effects of urotensin Ⅱ(UII) on hepatic insulin resistance in Hep G2 cells and the potential mechanisms involved.METHODS: Human hepatoma Hep G2 cells were cultured with or without exogenous UI...AIM: To investigated the effects of urotensin Ⅱ(UII) on hepatic insulin resistance in Hep G2 cells and the potential mechanisms involved.METHODS: Human hepatoma Hep G2 cells were cultured with or without exogenous UII for 24 h, in the presence or absence of 100 nmol/L insulin for the last 30 min. Glucose levels were detected by the glucoseoxidase method and glycogen synthesis was analyzed by glycogen colorimetric/fluorometric assay. Reactive oxygen species(ROS) levels were detected with a multimode reader using a 2′,7′-dichlorofluorescein diacetate probe. The protein expression and phosphorylation levels of c-Jun N-terminal kinase(JNK), insulin signal essential molecules such as insulin receptor substrate-1(IRS-1), protein kinase B(Akt), glycogen synthase kinase-3β(GSK-3β), and glucose transporter-2(Glut 2), and NADPH oxidase subunits such as gp91 phox, p67 phox, p47 phox, p40 phox, and p22 phox were evaluated by Western blot.RESULTS: Exposure to 100 nmol/L UII reduced the insulin-induced glucose consumption(P < 0.05)and glycogen content(P < 0.01) in Hep G2 cells compared with cells without UII. UII also abolished insulin-stimulated protein expression(P < 0.01) and phosphorylation of IRS-1(P < 0.05), associated with down-regulation of Akt(P < 0.05) and GSK-3β(P < 0.05) phosphorylation levels, and the expression of Glut 2(P < 0.001), indicating an insulin-resistance state in Hep G2 cells. Furthermore, UII enhanced the phosphorylation of JNK(P < 0.05), while the activity of JNK, insulin signaling, such as total protein of IRS-1(P < 0.001), phosphorylation of IRS-1(P < 0.001) and GSK-3β(P < 0.05), and glycogen synthesis(P < 0.001) could be reversed by pretreatment with the JNK inhibitor SP600125. Besides, UII markedly improved ROS generation(P < 0.05) and NADPH oxidase subunit expression(P < 0.05). However, the antioxidant/NADPH oxidase inhibitor apocynin could decrease UII-induced ROS production(P < 0.05), JNK phosphorylation(P < 0.05), and insulin resistance(P < 0.05) in HepG 2 cells. CONCLUSION: UII induces insulin resistance, and this can be reversed by JNK inhibitor SP600125 and antioxidant/NADPH oxidase inhibitor apocynin targeting the insulin signaling pathway in HepG 2 cells.展开更多
OBJECTIVE The Ca2+-activated Cl-channel(Ca CC)plays a crucial role in various physiological functions.Recent evidences suggest TMEM16A encodes CaC C in various cells,including endothelial cells.However,the role of TME...OBJECTIVE The Ca2+-activated Cl-channel(Ca CC)plays a crucial role in various physiological functions.Recent evidences suggest TMEM16A encodes CaC C in various cells,including endothelial cells.However,the role of TMEM16A in the vascular endothelial dysfunction in hypertension is unclear.METHODS In the study,RT-PCR,Western blotting,co-immunopricipitation,confocal imaging,patch-clamp,and endothelial-specific TMEM16A transgenic and knockout mice were employed.RESULTS We found that TMEM16A was expressed abundantly and functioned as Ca CC in endothelial cells.AngiotensinⅡ(AngⅡ)induced endothelial dysfunction with an increase in TMEM16A expression,which was alleviated by TMEM16A inhibitor.Further studies revealed that TMEM16A endothelial-specific knockout significantly lowered the blood pressure and ameliorated endothelial dysfunction in AngⅡ-induced hypertension,whereas,TMEM16A endothelial-specific overexpression showed the opposite effects.These results were related to the increased reactive oxygen species(ROS)generation,NADPH oxidase activation,and Nox2,p22phox expression facilitated by TMEM16A upon AngⅡ-induced hypertensive challenges.Moreover,TMEM16A directly interacted with Nox2 monomer and reduced the degradation of Nox2 through the proteasome-dependent endoplasmic recticulum-associated degradation pathway.TMEM16A also potentiated the translocation of p47phox and p67phox from cytosol to cell membrane and the subsequent interaction with Nox2.CONCLUSION Our results demonstrated that TMEM16A,as Ca CC,is a positive regulator of ROS generation via upregulating the activation of Nox2 NADPH oxidase in the vascular endothelium,and therefore facilitates endothelial dysfunction and hypertension.Modification of TMEM16A may be a novel therapeutic strategy for endothelial dysfunction-associated cardiovascular diseases.展开更多
Endogenous elicitor, termed cellulase-degraded cell wall (CDW), was prepared from the cell wall of suspension-cultured ginseng (Panax ginseng C.A. Meyer) cells via cellulase degradation. CDW activated the NADPH oxidas...Endogenous elicitor, termed cellulase-degraded cell wall (CDW), was prepared from the cell wall of suspension-cultured ginseng (Panax ginseng C.A. Meyer) cells via cellulase degradation. CDW activated the NADPH oxidase activity of isolated plasma membranes and stimulated in vivo H2O2 generation in ginseng cell suspensions. CDW also increased the activity of phenylalanine ammonia lyase (PAL), expression of a P. ginseng squalene epoxidase (sqe) gene and saponin synthesis. NADPH oxidase inhibitors inhibited both in vitro NADPH oxidase activity and in vivo H2O2 generation. Induction of PAL activity, saponin synthesis and sqe gene expression were all inhibited by such inhibitor treatments and reduced by incubation with catalase and HA scavengers. These data indicate that activation of NADPH oxidase and generation of H2O2 are essential signalling events mediating defence responses induced by the endogenous elicitor(s) present in CDW.展开更多
基金Supported by National Natural Science Foundation of China,No.81272757the Project of Construction of Innovative Teams and Teacher Career Development for Universities and Colleges under Beijing Municipality,No.IDHT20150502
文摘AIM: To investigated the effects of urotensin Ⅱ(UII) on hepatic insulin resistance in Hep G2 cells and the potential mechanisms involved.METHODS: Human hepatoma Hep G2 cells were cultured with or without exogenous UII for 24 h, in the presence or absence of 100 nmol/L insulin for the last 30 min. Glucose levels were detected by the glucoseoxidase method and glycogen synthesis was analyzed by glycogen colorimetric/fluorometric assay. Reactive oxygen species(ROS) levels were detected with a multimode reader using a 2′,7′-dichlorofluorescein diacetate probe. The protein expression and phosphorylation levels of c-Jun N-terminal kinase(JNK), insulin signal essential molecules such as insulin receptor substrate-1(IRS-1), protein kinase B(Akt), glycogen synthase kinase-3β(GSK-3β), and glucose transporter-2(Glut 2), and NADPH oxidase subunits such as gp91 phox, p67 phox, p47 phox, p40 phox, and p22 phox were evaluated by Western blot.RESULTS: Exposure to 100 nmol/L UII reduced the insulin-induced glucose consumption(P < 0.05)and glycogen content(P < 0.01) in Hep G2 cells compared with cells without UII. UII also abolished insulin-stimulated protein expression(P < 0.01) and phosphorylation of IRS-1(P < 0.05), associated with down-regulation of Akt(P < 0.05) and GSK-3β(P < 0.05) phosphorylation levels, and the expression of Glut 2(P < 0.001), indicating an insulin-resistance state in Hep G2 cells. Furthermore, UII enhanced the phosphorylation of JNK(P < 0.05), while the activity of JNK, insulin signaling, such as total protein of IRS-1(P < 0.001), phosphorylation of IRS-1(P < 0.001) and GSK-3β(P < 0.05), and glycogen synthesis(P < 0.001) could be reversed by pretreatment with the JNK inhibitor SP600125. Besides, UII markedly improved ROS generation(P < 0.05) and NADPH oxidase subunit expression(P < 0.05). However, the antioxidant/NADPH oxidase inhibitor apocynin could decrease UII-induced ROS production(P < 0.05), JNK phosphorylation(P < 0.05), and insulin resistance(P < 0.05) in HepG 2 cells. CONCLUSION: UII induces insulin resistance, and this can be reversed by JNK inhibitor SP600125 and antioxidant/NADPH oxidase inhibitor apocynin targeting the insulin signaling pathway in HepG 2 cells.
基金The project supported by National Natural Science Foundation of China(81230082,81302771,81525025,81573422,81500226)Natural Science Foundation of Guangdong Province(2014A030313087)by Science and Technology program of Guangzhou City(201607010255)
文摘OBJECTIVE The Ca2+-activated Cl-channel(Ca CC)plays a crucial role in various physiological functions.Recent evidences suggest TMEM16A encodes CaC C in various cells,including endothelial cells.However,the role of TMEM16A in the vascular endothelial dysfunction in hypertension is unclear.METHODS In the study,RT-PCR,Western blotting,co-immunopricipitation,confocal imaging,patch-clamp,and endothelial-specific TMEM16A transgenic and knockout mice were employed.RESULTS We found that TMEM16A was expressed abundantly and functioned as Ca CC in endothelial cells.AngiotensinⅡ(AngⅡ)induced endothelial dysfunction with an increase in TMEM16A expression,which was alleviated by TMEM16A inhibitor.Further studies revealed that TMEM16A endothelial-specific knockout significantly lowered the blood pressure and ameliorated endothelial dysfunction in AngⅡ-induced hypertension,whereas,TMEM16A endothelial-specific overexpression showed the opposite effects.These results were related to the increased reactive oxygen species(ROS)generation,NADPH oxidase activation,and Nox2,p22phox expression facilitated by TMEM16A upon AngⅡ-induced hypertensive challenges.Moreover,TMEM16A directly interacted with Nox2 monomer and reduced the degradation of Nox2 through the proteasome-dependent endoplasmic recticulum-associated degradation pathway.TMEM16A also potentiated the translocation of p47phox and p67phox from cytosol to cell membrane and the subsequent interaction with Nox2.CONCLUSION Our results demonstrated that TMEM16A,as Ca CC,is a positive regulator of ROS generation via upregulating the activation of Nox2 NADPH oxidase in the vascular endothelium,and therefore facilitates endothelial dysfunction and hypertension.Modification of TMEM16A may be a novel therapeutic strategy for endothelial dysfunction-associated cardiovascular diseases.
文摘Endogenous elicitor, termed cellulase-degraded cell wall (CDW), was prepared from the cell wall of suspension-cultured ginseng (Panax ginseng C.A. Meyer) cells via cellulase degradation. CDW activated the NADPH oxidase activity of isolated plasma membranes and stimulated in vivo H2O2 generation in ginseng cell suspensions. CDW also increased the activity of phenylalanine ammonia lyase (PAL), expression of a P. ginseng squalene epoxidase (sqe) gene and saponin synthesis. NADPH oxidase inhibitors inhibited both in vitro NADPH oxidase activity and in vivo H2O2 generation. Induction of PAL activity, saponin synthesis and sqe gene expression were all inhibited by such inhibitor treatments and reduced by incubation with catalase and HA scavengers. These data indicate that activation of NADPH oxidase and generation of H2O2 are essential signalling events mediating defence responses induced by the endogenous elicitor(s) present in CDW.
