Renal expression of ACE/AngⅡ in ACE2 knockout mice after tourniquet shock and its relationship with renal injury

AIM: To investigate the effect of angiotensin-converting enzyme 2 (ACE2) on tourniquet shock (TS)-induced acute renal injury by observing the renal expression of angiotensin-converting enzyme/angiotensin Ⅱ (ACE/AngⅡ) and injury severity in ACE2 knockout (KO) mice. METHODS: The TS animal model was produced by bilateral tourniquet ligation in the inguinal region on both hind legs for 2 h to induce ischemia, and reperfusion was initiated by cutting latex rings for 4 h. Six-month-old male wild-type (WT) and ACE2 KO C57BL/6 mice were selected, and divided into 4 groups (6 mice in each group) including WT group, WT+TS group, KO group and KO+TS group. The expression of ACE and AngⅡ in the renal tissues was determined by Western blotting and ELISA, respectively. The renal content of malondialdehyde (MDA) and activity of superoxide dismutase (SOD), blood urea nitrogen (BUN) and serum creatinine (Cr) were measured by chemical colorimetry. RESULTS: Compared with WT group, the expression of ACE/AngⅡ was obviously increased in WT+TS group, and significant renal oxidative stress injury was also observed. The expression of ACE/AngⅡ was elevated in KO mice, but no significant renal oxidative stress injury was found. Compared with WT+TS group, more highly increased expression of ACE/AngⅡ and more aggravated renal injury were exhibited in KO+TS group. CONCLUSION: Deletion of ACE2 gene exacerbates TS-induced renal oxidative stress injury by increasing local ACE/AngⅡ expression. The agonist targeting to ACE2 may be helpful for prevention and treatment of TS-induced acute renal injury.     

PP2A activation in mesenteric arteries of angiotensin Ⅱ-induced hypertensive rats

AIM: To investigate the mechanism of protein phosphatase 2A (PP2A) activation in mesenteric arteries of angiotensinⅡ(AngⅡ)-induced hypertensive rats. METHODS: Adult male Sprague-Dawley (SD) rats were subjected to AngⅡinfusion (500 ng·kg^-1·min^-1) using osmotic minipump up to 14 d to established the hypertension model. The rats (n=40) were randomly divided into 4 groups:control group (n=10), AngⅡgroup (n=10), candesartan (CAN; AngⅡtype 1 receptor blocker)+AngⅡgroup (n=10) and CAN group (n=10). The rats in CAN+AngⅡgroup and CAN group were administered with candesartan ester at the dose of 10 mg·kg^-1·d^-1 by gavage on the first day after implantation of osmotic minipump. The rats were sacrificed on the 15th day after minipump implantation. Serum and mesenteric arteries were collected. Systolic blood pressure was measured by tail-cuff method. The serum levels of AngⅡ were measured by ELISA. The protein levels of endothelial nitric oxide synthase (eNOS), phosphorylated eNOS (Ser1177), PP2A catalytic subunit (PP2Ac), phosphorylated PP2Ac (Tyr307) and PP2A inhibitor 2 (I₂^PP2A) in the mesenteric arteries were determined by Western blot. The activity of PP2A in the arteries was detected using PP2A activity assay kit. RESULTS: Compared with control group, the systolic blood pressure in AngⅡgroup was significantly increased(P<0.05), while those in CAN+AngⅡgroup and CAN group were significantly decreased (P<0.05). The serum levels of AngⅡ in AngⅡ group and CAN+AngⅡ group were significantly higher than that in control group (P<0.05). Compared with control group, the phosphorylation levels of eNOS Ser1177 were decreased in AngⅡgroup (P<0.05), but the activity of PP2A was significantly increased (P<0.05), and Pearson correlation analyses showed a negative correlation between PP2A activity and eNOS S1177 phosphorylation (r=-0.842, P<0.05). Compared with AngⅡgroup, the phosphorylation levels of eNOS Ser1177 in CAN+AngⅡgroup were significantly increased (P<0.05), but the activity of PP2A was reduced (P<0.05). Compared with control group, the protein levels of phosphorylated PP2Ac (Tyr307) and I₂^PP2A in the mesenteric arteries were decreased in AngⅡgroup (P<0.05), but increased in CAN+AngⅡgroup (P<0.05). No significant difference in all above-mentioned measures between control group and CAN group, nor in the levels of total eNOS and PP2Ac protein expression among all the groups was observed. CONCLUSION: AngⅡmay reduce the protein levels of phosphorylated PP2Ac (Tyr307) and I₂^PP2A in the mesenteric arteries of AngⅡ-induced hypertensive rats through AngⅡ/AngⅡ type 1 receptor-mediated signaling pathway, resulting in the activation of PP2A, then leading to down-regulation of eNOS S1177 phosphorylation, which ultimately mediates the occurrence of vascular endothelial dysfunction.     

Heme oxygenase decreases the generation of ROS in AngⅡ induced proliferation and hypertrophy of cultured vascular smooth muscle cells

AIM:To investigate the role of heme oxygenase (HO) in AngⅡ induced proliferation and hypertrophy of cultured vascular smooth muscle cells.METHODS:(1) Western blotting analysis was carried out to detect protein level of HO-1 in the tissues.(2) ［3H］-TdR, ［3H］-leucine incorporation was measured in cultured vascular smooth muscle cells.(3) 2,7-dichlorofluorescin diacetate (DCFH-DA) as an index was used to determine the cellular reactive oxygen species (ROS) level.RESULTS:(1) No significant difference in HO-1 protein expression level between AngⅡ-stimulated and control groups was observed, but HO-1 protein level in Hemin-induced group was higher than that in other two groups (P<0.01).No significant increase in HO-1 protein expression was found in zinc-protoporphyrin IX (ZnPPIX) group.(2) After AngⅡ stimulation, ［3H］-TdR and ［3H］-leucine incorporations of vascular smooth muscle cells (VSMCs) were increased.Hemin inhibited this increase.The higher concentration of Hemin, the more significant was the inhibitory effect.On the contrary, ZnPPIX promoted the increase in the effect of AngⅡ by inhibiting HO.(3) Fluorescence intensity in AngⅡ group was obviously higher than that in control groups (P<0.01).Compared with AngⅡ group, Hemin group decreased 62.7%, but ZnPPIX group increased 39.5%.CONCLUSION:Hemin induces HO-1 expression and inhibits the effect of AngⅡ to stimulate proliferation and hypertrophy of VSMCs.The mechanism may be related to its inhibition of ROS production.     

Role of protein tyrosine phosphatase SHP-2 in cardiac fibroblasts proli-feration stimulated by Ang Ⅱ

AIM: To investigate the potential role of Src homology 2 domain-containing protein tyrosine phosphatase 2 (SHP-2) in the proliferation of cardiac fibroblasts induced by angiotensin Ⅱ (Ang Ⅱ). METHODS: The neonatal rat cardiac fibroblasts were separated by trypsin digestion. The cardiac fibroblasts were identified by vimentin of immunochemical staining. The proliferation of the cardiac fibroblasts with or without Ang Ⅱ stimulation was measured by MTT assay. Adenoviruses containing SHP-2 gene were transfected into cardiac fibroblasts to overexpress SHP-2. SHP-2 was inhibited by its inhibitor NSC-87877. RESULTS: The proliferation of the cardiac fibroblasts was increased in a dose-dependent manner by the stimulation of Ang Ⅱ and the maximum concentration of Ang II for cell proliferation was 10^-7 mol/L. SHP-2 promoted the proliferation of cardiac fibroblasts under the stimulation of Ang Ⅱ. The proliferation rate in mutant group was higher than that in wild-type group (P<0.01). Inhibition of SHP-2 by NSC-87877 attenuated the proliferation. CONCLUSION: The growth promoting effect of Ang Ⅱ on cardiac fibroblasts is regulated by SHP-2.     

Effect of inhibiting nuclear factor-kappa B on TNF-α-induced expression of angiotensinogen and production of angiotensinⅡ in glomerular mesangial cells

AIM: To study the effect of inhibiting nuclear factor-kappa B (NF-κB) activity on the expression of angiotensinogen (AGT) and the production of angiotensinⅡ (AngⅡ) induced by tumor necrosis factor-α (TNF-α) in glomerular mesangial cells (MCs) of SD rats. METHODS: The MCs of SD rats were isolated and divided into three groups as follows: control; MCs treated with TNF-α, and the MCs treated with TNF-α + pyrrolidinedithiocarbamate (PDTC). The activity of nuclear factor-kappa B was measured by electrophoretic mobility shift assay. The expression of AGT was determined by RT-PCR for mRNA and Western blotting for protein. The concentration of angiotensinⅡ in supernatant was measured by RIA. RESULTS: The NF-κB activity in the MCs treated with TNF-α (20.67±9.14)×102 μg/cell was significantly higher than that in control cells ［(8.25±4.35)×102 μg/cell, P<0.01］ and the MCs treated with TNF-α+PDTC ［(7.20±4.57)×102 μg/cell, P<0.01］, and no significant difference was found between control and the MCs treated with TNF-α＋PDTC (P>0.05). The AGT mRNA level in the MCs treated with TNF-α (0.27±0.05) was higher than that in the control cells (0.20±0.05, P<0.05), and no significant difference was observed when compared with that in the MCs treated with TNF-α＋PDTC (0.22±0.06, P>0.05). The expression of AGT protein in the MCs treated with TNF-α (0.60±0.19) μg/cell was higher than that in the control ［(0.37±0.15)μg/cell, P＜0.05］ and the MCs treated with TNF-α＋PDTC ［(0.37±0.17)μg/cell, P<0.05］, and no significance was found between the MCs treated TNF-α＋PDTC and the control (P>0.05). The AngⅡ level in supernatant of cultured MCs treated with TNF-α ［(9.73±2.38)×10-5 ng·L-1/cell］ was significantly higher than that in the control ［(7.50±1.51)×10-5 ng·L-1/cell, P<0.05］ and in the MCs treated with TNF-α＋PDTC ［(6.94±1.46)×10-5 ng·L-1/cell, P<0.05］, however, the difference between the MCs treated with TNF-α＋PDTC and the control was of no significance (P>0.05). CONCLUSION: TNF-α activates the NF-κB in glomerular MCs, induces the AGT expression and the production of AngⅡ. Inhibition of NF-κB decreases the AGT expression and the production of AngⅡ. Therefore, the effects of TNF-α on AGT and AngⅡ may be mediated by NF-κB.     

Role of nephrin in preventing angiotensinⅡ-induced cytoskeletal rearrangement in glomerular podocytes

AIM: To investigate the role of nephrin, a slit diaphragm-associated protein, in angiotensinⅡ (AngⅡ)-induced cytoskeleton rearrangement in podocytes. METHODS: Immortalized mouse podocytes were exposed to AngⅡ (10^-8 mol/L) with or without AngⅡ receptor antagonist lorsatan and Akt inhibitor LY294002. FITC-conjugated phalloidin was used to stain F-actin, and semi-quantitative system with cortical F-actin score (CFS) was introduced to analyze the degree of actin cytoskeleton arrangement. The expression of nephrin was assessed by quantitative real-time RT-PCR,RT-PCR and Western blotting. Undifferentiated podocytes were transfected with pcDNA3.1-mNPHS1 plasmid containing the full length of nephrin. The stably transfected cell line was generated by G418 selection. Phosphorylation level of Akt was assessed by Western blotting, and F-actin distribution was further evaluated in transfected cells exposed to AngⅡ or not. RESULTS: Cytoskeletal rearrangements including cortical F-actin ring formation and stress fiber attenuation were observed in Ang II-and LY294002-stimulated podocytes. Pretreatment with losartan significantly prevented Ang II-induced actin cytoskeleton reorganization. The mRNA and protein levels of nephrin and phosphorylation of Akt were obviously decreased in the podocytes exposed to Ang II, which were dramatically reversed by pcDNA3.1-mNPHS1 transfection. Transfection of pcDNA3.1- mNPHS1 induced the formation of short filopodia and partially prevented AngⅡ-induced F-actin remodeling. CONCLUSION: PI3K/Akt signaling is a common downstream pathway of nephrin and Ang Ⅱ. Nephrin is able to stabilize AngⅡ-induced cytoskeletal rearrangement via PI3K/Akt signaling pathway.     

Senescence of endothelial cells and gene expression associated with apoptosis induced by angiotensinⅡ

AIM: To study the senescence of human umbilical vein endothelial cells (HUVECs) and Bcl-2, Bax gene expression associated with apoptosis induced by angiotensinⅡ (AngⅡ).METHODS: HUVECs were cultured in vitro and the cell viability was observed by methyl thiazolyl tetrazolium (MTT). HUVECs were intervened by AngⅡ and valsartan (AngⅡ type 1 receptor blocking) and divided into 3 groups: the control group, AngⅡ group (stimulated with AngⅡ10^-6mol/L for 48 h), valsartan group (valsartan was added to cells 1 h before 10^-6mol/L AngⅡ treatment). β-gal staining and cell cycle analysis were used to identify the cell aging status. Morphologic changes and percentage of apoptosis were assayed with Hoechst33258 under fluorescent microscope. The expressions of Bcl-2 and Bax, and the apoptosis-associated genes were detected by immunocytochemical staining, RT-PCR and Western blotting. RESULTS: The cell viability by AngⅡ-induced cells was (81.9%±4.1)%, the positive cell number of β-gal staining was significantly higher in AngⅡ-induced cells (80.10%±6.81)% than that in the control cells. The cell cycle was at G₀-G₁(91.36%±6.45)%, the apoptotic cells significantly increased (31.84±2.86)% under fluorescent microscope. In valsartan group, Bcl-2 mRNA and protein expression increased markedly (P<0.05), but Bax mRNA and protein expression decreased evidently (P<0.05) compared to those in the AngⅡ group.CONCLUSION: Cell apoptosis is possibly an important factor for endothelial cell senescence and vascular aging induced by AngⅡ. One of its molecular mechanisms might be associated with decreasing the expression level of Bcl-2 and increasing that of Bax, which regulate the imbalance between mRNA and protein expression of Bcl-2 and Bax. Valsartan improves endothelial cell aging.     

Effects of PPARα activation on AngⅡ-induced cardiomyocyte hypertrophy and interaction of NFATc4 with p65-NFκB

AIM：To investigate the effects of fenofibrate on angiotensin Ⅱ (AngⅡ)-induced cardiomyocyte hypertrophy. METHODS：Primary neonatal cardiomyocytes were pretreated with fenofibrate (10 μmol/L) for 1 h followed by stimulation with AngⅡ (100 nmol/L). The mRNA levels of ANF, BNP and β-MHC were measured by real-time PCR. Western blotting was employed to determine the nuclear translocations of NFATc4 and p65-NFκB. Co-immunoprecipitation was used to investigate the interaction of NFATc4 with p65-NFκB in the nucleus of cardiomyocytes. In addition, the DNA binding activity of NFATc4 on the BNP promoter was determined by EMSA. RESULTS：Fenofibrate significantly inhibited AngⅡ-induced cardiomyocyte hypertrophy. Fenofibrate treatment inhibited the nuclear translocations of NFATc4 and p65-NFκB, as well as the interactions of NFATc4 with p65-NFκB in the nucleus of cardiomyocytes induced by AngⅡ. Fenofibrate inhibited the binding activity of NFATc4 with the BNP promoter, which was strengthened by AngⅡ. CONCLUSION： Fenofibrate enhances the interaction of NFATc4 with PPARα, decreases the interaction of NFATc4 with p65-NFκB in the nucleus of cardiomyocytes, and inhibits the DNA binding activity of NFATc4 induced by AngⅡ, which may be the important mechanisms of fenofibrate on inhibiting cardiac hypertrophy.     

Effects of aldosterone on expression of angiotensin Ⅱ receptors in cultured rat mesangial cells

AIM: To investigate the effect of aldosterone (ALD) on the mRNA expression of angiotensin Ⅱ (Ang II) type 1 (AT-1a R and AT-1bR) and 2 (AT-2R) receptors in cultured rat mesangial cells (RMCs) treated with high glucose. METHODS: Rat mesangial cells were cultured in high glucose medium containing different concentrations of ALD (10-8-10-6 mol/L). The antagonists of ALD and Ang II receptors including pironolactone (10-7 mol/L, aldosterone receptor antagonist, SPI), losartan (10-7 mol/L, Ang II type 1 receptor blocker, Los) or PD123319 (10-9 mol/L, Ang II type 2 receptor antagonist, PD) were added in the cell culture for 12 h. The control cells were only treated with high (30 mmol/L) or normal (5.6 mmol/L) glucose medium. The viability and proliferation of the RMCs were evaluated by MTT assay. The mRNA expression of AT-1aR, AT-1b R and AT-2R was detected by semi-quantitative RT- PCR. The expression of MCP-1 in cultured RMCs was detected by ELISA. RESULTS: The mRNA expression of AT-1aR, AT-1b R and AT-2R was increased significantly by treatment with ALD in a dose-dependent manner (1.62-1.77, 9.61-9.89 and 7.26-7.35 folds of high glucose control, respectively, P<0.01). SPI significantly reduced the mRNA expression of AT-1aR and AT-1b R (P<0.01) but not affected the mRNA expression of AT-2R. The ratio of AT-1aR/AT-1b R in cultured RMCs treated with high glucose decreased significantly after stimulated with ALD (P<0.01). However, the effect of ALD was inhibited by SPI (P<0.01). Aldosterone treatment induced a significant upregulation of MCP-1 expression in a dose-dependent manner, and previous treatment with spironolactone, losartan or PD123319 abolished this aldosterone-induced MCP-1 expression. CONCLUSION: The results suggest that aldosterone is involved in the inflammatory response by up-regulating the expression of AT-1aR, AT-1bR and AT-2R, changing the proportion of AT-1R subtype, and inducing MCP-1 overproduction in cultured RMCs treated with high glucose.     

Role of IGF-Ⅱ in proliferation and migration of hepatocellular carcinoma Huh7 cells

AIM: To observe the effects of insulin-like growth factorⅡ (IGF-Ⅱ) at different expression levels on hepatocellular carcinoma Huh7 cell proliferation and migration, and to explore the role of IGF-Ⅱ in the development of HCC. METHODS: The Huh7 cells were transfected with the over-expression plasmid pcDNA3.1(+)- IGF-Ⅱ or RNA interference plasmid pLVX-shRNA-IGF-Ⅱ by Lipofectamine 2000. The quantitative real-time PCR and Western blotting were used to verify the expression of IGF-II. The biological behaviors of the Huh7 cells were analyzed by CCK-8 assay, plate clone formation assay, cell scratch test and Transwell chamber experiment.RESULTS: Over-expression of IGF-II promoted the growth and migration of hepatocellular carcinoma cells (P < 0.05), and the cell proliferation was significantly inhibited in the Huh7 cells with low IGF-II expression (P < 0.05).CONCLUSION: IGF-II is involved in the regulation of biological behavior of hepatocellular carcinoma Huh7 cells in vitro, which may play a promoting role in the development of hepatocellular carcinoma.     

Early treatment with aminoguanidine on level of plasma and renal AngⅡ in diabetic rats

AIM: To investigate the effect of aminoguanidine (AG) on plasma and renal levels of angiogenesis Ⅱ (AngⅡ), and to identify the relationship of AGEs with AngⅡ in STZ-induced diabetic rats. METHODS: Wistar rats were randomly assigned to three groups. Diabetes was induced, rats were then received AG in treatment group. At the end of 12th week, urine albumin excretion rate (UAER) and calculate creatinine clearance (Ccr) were detected. Periodic acid-Schiff reagent was used to evaluate renal pathology. Plasma and renal AngⅡ were analyzed by radioimmunoassay and immunohistochemistry, respectively. RESULTS: AG treatment significantly prevented the increase in UAER (P<0.01), renal pathology (P<0.01), and level of renal AngⅡ (P<0.01). However, plasma concentration of AngⅡ was higher than that in diabetic rats without AG treatment (P<0.01). CONCLUSION: AG down-regulates renal Ang Ⅱ level, probably by reducing the formation of AGEs, which may be one of the renoprotective factors in diabetic nephropathy. More proofs are needed to identify the result that plasma AngⅡ concentration increases in DMA group.     

Melatonin alleviates cold-induced oxidative damage by regulation of ascorbate–glutathione and proline metabolism in melon seedlings (Cucumis melo L.)

Cold stress is one of the most detrimental environmental factors affecting plant growth and development. Melatonin (MEL), a natural indoleamine compound, responds to various environmental cues. To explore the role of MEL in the response of melon (Cucumis melo L.) seedlings to cold stress, the effects of exogenous MEL on the ascorbate–glutathione (AsA–GSH) cycle and proline metabolism were investigated. Melon seedlings were sprayed with various concentrations of MEL (0, 50, 100, 200, or 400 μM), then exposed to cold stress, 12/6°C (day/night) for 7 d, followed by recovery at 28/18°C for another 7 d. The results showed that MEL, especially the 200 μM treatment, dramatically alleviated growth inhibition caused by cold stress, manifested by increased plant growth and decreased O₂^?¯ production rate and malondialdehyde content. Importantly, exogenous application of MEL enhanced the ratios of reduced and oxidized forms of AsA (AsA/DHA) and GSH (GSH/GSSG), and the activities of ascorbate peroxidase (APX), glutathione reductase (GR), and dehydroascorbate reductase (DHAR) involved in the ascorbate–glutathione (AsA–GSH) cycle in melon seedings grown under cold stress. Besides, MEL pretreatment further increased the contents of proline and soluble protein under cold stress. The results reveal that protective effects of MEL against cold stress in melon seedlings are most likely associated with the regulation of the AsA–GSH cycle and proline metabolism as an effective antioxidant system.     

AngⅡ/AT1R pathway activates PP2A to down-regulate p-eNOS (Ser1177) in human umbilical vein endothelial cells

AIM: To investigate whether angiotensinⅡ (AngⅡ)/angiotensin Ⅱ type 1 receptor (AT₁R) pathway down-regulates endothelial nitric oxide synthase (eNOS) Ser1177 phosphorylation level in human umbilical vein endothelial cells by activating protein phosphatase 2A (PP2A).METHODS: Human umbilical vein endothelial cells were randomly divided into normal control (control) group, Ang Ⅱ group, candesartan (CAN; specific AT₁R blocker) group and CAN pretreatment+AngⅡ group. The protein levels of total eNOS, p-eNOS (Ser1177), PP2Ac, I₂^PP2A and p-PP2Ac (Tyr307) were determined by Western blot. The content of NO in the cell culture medium was detected by chemical colorimetry.RESULTS: Compared with control group, the level of p-eNOS (Ser1177) and the content of NO decreased (P<0.05). Compared with the same concentration of AngⅡ group, CAN pretreatment increased the level of p-eNOS (Ser1177) and the content of NO (P<0.05), but the protein expression of eNOS showed no significant difference. Compared with control group, the levels of p-PP2Ac (Tyr307) and I₂^PP2A decreased (P<0.05). Compared with the same concentration of AngⅡ group, CAN pretreatment increased the levels of p-PP2Ac (Tyr307) and I₂^PP2A (P<0.05), but the protein expression of PP2Ac showed no significant difference.CONCLUSION: AngⅡ down-regulates the level of p-eNOS (Ser1177), and decreases the production of NO in human umbilical vein endothelial cells via AT₁R pathway. This effect may be related to the reduction of p-PP2Ac (Tyr307) and protein expression of I₂^PP2A, which results in the enhancement of PP2A activity. Pretreatment with AT₁R blocker CAN increases p-PP2Ac (Tyr307) level and I₂^PP2A protein expression, thus reducing the PP2A activity, and ultimately restoring eNOS Ser1177 phosphorylation level and eNOS activity.     

Effects of curcumin on actinomycin D/TNF-α-induced injury in PC12 cells and rat hippocampal neurons

AIM: To study the possible mechanism of curcumin on actinomycin D (ActD)/tumor necrosis factor α (TNF-α)-induced injury in PC12 cells and rat hippocampal neurons. METHODS: PC12 cells were divided into control group, TNF-α group, ActD group, curcumin group, ActD/TNF-α group and curcumin+ActD/TNF-α group. The cells were cultured for 24 h. Inverted fluorescence microscopy was used to observe the morphological changes of the cells in each group. Annexin V/PI double staining was applied to analyze the apoptosis of PC12 cells. The level of intracellular Ca²⁺ was detected by Fluo-3 AM staining. Rat hippocampal slices were prepared and divided into the same groups as the PC12 cells. Extracellular microelectrode recording technique was used to observe and calculate the changes of long-term potentiation (LTP) in different groups. RESULTS: Apoptosis of PC12 cells was induced by ActD/TNF-α. Curcumin protected the PC12 cells from ActD/TNF-α-induced apoptosis (P<0.05). ActD/TNF-α increased the intracellular Ca²⁺ concentration. Curcumin significantly reduced ActD/TNF-α-induced apoptosis by decreasing the intracellular Ca²⁺ concentration (P<0.05), inversed the effect of ActD/TNF-α on LTP in hippocampal slices, and improved the synaptic plasticity (P<0.05). CONCLUSION: Curcumin protects ActD/TNF-α-induced neuronal damage by depressing the intracellular Ca²⁺ concentration and maintaining the homostasis of intracellular calcium.     

C/EBPα is involved in transcriptional regulation of mVGLUT2 gene expression

AIM: The main purpose of this study is to investigate the regulatory role of C/EBPα in mouse vesicular glutamate transporter 2(mVGLUT2) gene expression. METHODS: The promoter region of mVGLUT2 was cloned to PGL3-basic vector. Site-direction mutation was used to identify the CCAAT-enhancer-binding protein α(C/EBPα) binding site. The promoter activity was observed by luciferase system. The binding between C/EBPα protein and mVGLTU2 promoter region was determined by EMSA. The C/EBPα gene expression was inhibited by its specific siRNA. RESULTS: mVGLUT2 promoter activity decreased about 50% after mutation of C/EBPα binding site. EMSA showed that C/EBPα protein bound onto mVGLUT2 promoter region. Meanwhile, when C/EBPα gene expression was inhibited by its specific siRNA, mVGLUT2 promoter activity, mRNA level and protein level were decreased about 60%, 40% and 45%, respectively. CONCLUSION: C/EBPα is involved in the regulation of mVGLUT2 gene expression.     

Role of retinoic acid X receptor in regulation of autophagy in rat alveolar type Ⅱ epithelial cells induced by hypoxia/reoxygenation

AIM To investigate the regulatory effect of retinoic acid X receptor （RXR） on autophagy induced by hypoxia/reoxygenation （H/R） in rat alveolar type Ⅱ epithelial cells （AEC Ⅱ） and its molecular mechanism. METHODS AEC Ⅱ were cultured in normoxia. The cells growing to logarithmic growth phase were randomly divided into 5 groups： （1） control （Con） group： cells were cultured for 30 h under normal operation; （2） H/R group： cells were cultured in hypoxia condition for 6 h and then in reoxygenation condition for 24 h; （3） DMSO group： cells were pretreated 1.5 h with medium containing less than 0.1% DMSO before modeling, and the rest were treated the same as the H/R group; （4） 9-cis-retinoic acid （9-RA） group： cells were pretreated for 1 h with 9-RA （100 nmol/L） before hypoxia; （5） HX531 group： cells were treated with 9-RA （100 nmol/L） for 0.5 h, then treatment with HX531 （2.5 μmol/L） for 1 h. CCK-8 assay was used to detect the cell viability. Immunofluorescence staining was used to observe the expression of RXRα. Transmission electron microscope was used to observe the changes of intracellular ultrastructure, and the mRNA expression of adenosine AMP-activated protein kinase （AMPK）, beclin 1, LC3, mammalian target of rapamycin （mTOR） and P62 was detected by RT-PCR. Western blot was used to detected the protein levels of p-AMPK, beclin 1, LC3-Ⅱ, p-mTOR and P62. RESULTS Compared with Con group, the cell viability in H/R, DMSO, 9-RA and HX531 groups were significantly decreased. The mRNA expression of AMPK, beclin 1 and LC3 was significantly increased, and the protein levels of p-AMPK, beclin 1 and LC3-Ⅱ were also increased. The mRNA expression of mTOR and P62 was decreased, and the protein levels of p-mTOR and P62 were also decreased （P<0.05）. The cell injury in 9-RA group was alleviated and autophagy level was significantly lower than that in H/R, DMSO and HX531 groups （P<0.05）, and no significant difference among H/R, DMSO and HX531 groups was observed （P>0.05）. CONCLUSION H/R induces autophagy of AEC Ⅱ. Activating RXR reduce the damage of AEC Ⅱ cells induced by H/R, and its mechanism may be related to the inhibition of autophagy.