Effect of Tumor Necrosis Factor-α on Acyl Coenzyme A： Cholesteryl Acyltransferase Activity and ACAT1 Gene Expression in THP-1 Macrophages

In order to explore the effect and mechanisms of tumor necrosis factor-α (TNF-α) on the activity of the acyl coenzyme A: cholesteryl acyltransferase (ACAT), THP-1 monocytes were cul- tured and induced to differentiate into macrophages with phorbol ester. TNF-α (60 ng/mL) was added at different time points into the macrophage-containing medium and the ACAT enzyme activity was measured by quantifying the incorporation of 1-14C oleoyl CoA into cholesteryl esters. The expres- sion of ACAT-1 protein and mRNA was respectively detected by Western blotting and RT-PCR in THP-1 macrophages 24 h after treatment with TNF-α (60 ng/mL). The results indicated that ACAT activity in THP-1 macrophages treated with TNF-α was increased in a time-dependent manner. The expression levels of ACAT-1 protein and mRNA were significantly increased in THP-1 macrophages after treatment with TNF-α (P<0.05). It was suggested that TNF-α could increase the activity of ACAT in THP-1 macrophages by up-regulating the expression of ACAT-1 gene.     

不对称二甲基精氨酸上调THP-1来源的巨噬细胞和泡沫细胞内胆固醇酞基转移酶-1的表达

目的 观察不对称二甲基精氨酸(ADMA)对单核细胞THP-1来源的巨噬细胞和泡沫细胞中胆固醇酞基转移酶-1(ACAT-1)的表达及胆固醇含量的影响.方法 分别采用RT-PCR和Westem blot技术检测ACAT-1mRNA和蛋白表达水平.采用酶偶联比色法检测细胞内胆固醇含量.结果 不同浓度的ADMA (0,3.75,7.5,15,or30 μmol/L)对THP-1来源的巨噬细胞和泡沫细胞作用不同时间(6 12,24h)后,巨噬细胞和泡沫细胞内ACAT-1mRNA和蛋白的表达明显上调,细胞内总胆固醇的含量明显升高.结论 ADMA在巨噬细胞形成泡沫细胞过程中可能发挥了重要作用.抑制巨噬细胞和泡沫细胞内ACAT-1可能成为治疗动脉粥样硬化的潜在靶点.

Abstract：

Abstract:Objective To investigate the effects of asymmetric dimethylarginine(ADMA)on ACAT-I expression and cholesterol content in THP-1-derived macrophages and foam cells. Methods THP-1 cells were induced to differentiate into macrophages and further into foam ceIls.The macrophages and foam cells were exposed to different concentrations(0,3.75,7.5,15,and 30umol/K)of ADMA for varying time lengths(6,12,and 24 h),and the changes in ACAT-1 mRNA and protein levels in the cells were measured with RT-PCR and Western blotting.The cellular cholesterol content Was measured with enzyme-linked colorimetry assay.Results In THP-1-derived macrophages and foam cells,the expression levels of ACAT-1 mRNA and protein and cellular cholesterol content increased significantly in response to ADMA treatment in a time- and concentration-dependent manner. Conclusion ADMA may play all important role in inducing foam cell formation from macrophages. ACAT-1 inhibition targeting the macrophages and foam cells may serve as a potential therapeutic target IN the treatment of atherosclerosis.     

Increased expression and activity of MMP-9 in C-reactive protein- induced human THP-1 mononuclear cells is related to activation of nuclear factor kappa-B

The relation between the expression and activity of MMP-9 in C-reactive protein （CRP）-induced human THP-1 mononuclear cells and the activation of nuclear factor kappa-B （NF-κB） was studied to investigate the possible role of CRP in plaque destabilization. Human THP-1 cells were incubated in the presence of CRP at 0 （control group）, 25, 50 and 100 μg/mL （CRP groups） for 24 h. In PDTC （a specific NF-κB inhibitor） group, the cells were pre-treated with PDTC at 10 μmol/L and then with 100 μg/mL CRP. The conditioned media （CM） and human THP-1 cells in different groups were harvested. MMP-9 expression in CM and human THP-1 cells was measured by ELISA and Western blotting. MMP-9 activity was assessed by fluorogenic substrates. The expression of NF-κB inhibitor α （IκB-α） and NF-κB p65 was detected by Western blotting and ELISA respectively. The results showed that CRP increased the expression and activity of MMP-9 in a dose-dependent manner in the human THP-1 cells. Western blotting revealed that IiB-α expression was decreased in the cells with the concentrations of CRP and ELISA demonstrated that NF-κB p65 expression in the CRP-induced cells was increased. After pre-treatment of the cells with PDTC at 10 μmol/L, the decrease in IκB-α expression and the increase in NF-κB p65 expression in the CRP-induced cells were inhibited, and the expression and activity of MMP-9 were lowered too. It is concluded that increased expression and activity of MMP-9 in CRP-induced human THP-1 cells may be associated with activation of NF-κB. Down-regulation of the expression and activity of MMP-9 may be a new treatment alternative for plaque stabilization by inhibiting the NF-κB activation.     

Effects of advanced glycation end products on renal fibrosis and oxidative stress in cultured NRK-49F cells

Background Advanced glycation end products （AGEs） play a critical role in the development of diabetic nephropathy. Reactive oxygen species （ROS） may play a critical role in AGEs induced growth factor expression. In this study, the effects of AGEs on transforming growth factor β1 （TGF-β1）, connective tissue growth factor （CTGF） and fibronectin （Fn） mRNA expression and oxidative stress in cultured NRK-49F cells were examined. Methods NRK-49F cells were incubated with medium containing different doses of AGEs （50, 100 or 200 μg/ml） for 24 hours, or with AGEs 100 μg/ml for different times （0, 12, 24 or 48 hours）. Cells in the serum-free medium or medium containing 25 mmol/L glucose were controls. Cells were treated with 25 mmol/L glucose and 100 μg/ml AGEs for 24 hours to determine the effects between AGEs and glucose. We clarified the role of antioxidant by pretreating cells with N-acetylcysteine （10 mmol/L）, ginkgo biloba extract （50 or 100 mg/L） for 24 hours and with 100 μg/ml AGEs for further 24 hours. Alamarblue dye assay was used to analyze cell growth; intracellular ROS generation was measured by flow cytometry; intracellular glutathione by fluorescence spectrophotometry; expressions of TGF-β1, CTGF and Fn mRNA by semiquantitative RT-PCR. Results AGEs significantly increased the expressions of TGF-β1, CTGF, Fn mRNA and intracellular ROS generation, and decreased the glutathion level in NRK-49F cells in dose- and time-dependent manners. High glucose and AGEs together significantly increased the expression of TGF-β1, CTGF and Fn mRNA, compared with AGEs and high glucose separately. Preincubation with N-acetylcysteine or ginkgo biloba extract increased GSH level, suppressed AGEs-induced oxidative stress and TGF-β1, CTGF and Fn mRNA overexpression. Conclusions AGEs can significantly increase expression of TGF-β1, CTGF, Fn mRNA in NRK-49F cells through enhancement of oxidative stress. The accumulation of AGEs may play a pivotal role in the pathogenesis of tubulointerstitial fibrosis in diabetic nephropathy. Suppression of AGEs induced TGF-β1, CTGF and Fn mRNA overexpression in renal fibroblasts through inhibition of oxidative stress may be a mechanism underlying effect of ginkgo biloba extract in diabetic nephropathy. In addition, antioxidant therapy may help prevent AGEs accumulation and its induced damage.     

Role and mechanism of rosiglitazone on the impairment of insulin secretion induced by free fatty acids on isolated rat islets

Background Prolonged exposure of pancreatic β-cells to fatty acids increases basal insulin secretion but inhibits glucose-stimulated insulin secretion. Rosiglitazone is a new antidiabetic agent of the thiazolidinediones. However, the relationship between thiazolidinediones and insulin secretion is highly controversial. The aim of this study is to explore the effect and mechanism of rosiglitazone on insulin secretion of islets under chronic exposure to free fatty acids （FFA）. Methods Pancreatic islets were isolated from the pancreata of male Sprague-Dawley rats by the collagenase digestion and by the dextran gradient centrifugation method. The purified islets were cultured in the presence or absence of rosiglitazone and palmitate for 48 hours. The insulin secretion was measured by radioimmunoassay. The mRNA level of peroxisome proliferator-activated receptor y, uncoupling protein 2 0dCP-2） and insulin were determined by real-time polymerase chain reaction （PCR）. The cell cytotoxicity assay was measured by cell counting kit-8. Results Islets exposed to elevated palmitate for 48 hours showed an increased basal and a decreased glucose-stimulated insulin secretion （P〈0.01）. The mRNA level of UCP-2 was increased by 3.7 fold in the 0.5 mmol/L concentration of palmitate. When islets were cultured with palmitate （0.5 mmol/L） in the presence of rosiglitazone （1.0 pmol/L）, both basal and glucose-stimulated insulin secretion reversed to a pattern of control islets （P〈0.05, P〈0.0 1）. The addition of rosiglitazone in the culture medium decreased the mRNA level of UCP-2 by 2.2 fold, having a statistically significant difference （P〈0.05） as compared with islets cultured with palmitate alone. The cell viability was not affected. Conclusion The protective effects of rosiglitazone on insulin secretion of isolated pancreatic islets under chronic exposure to palmitate might be mediated through the downregulation of UCP-2 expression.     

Phosphatase and Tension Homolog Overexpression in Insulin Resistant Diabetic Adipose Tissue

Objective To investigate the expression of phosphatase and tension homolog （PTEN） in adipose tissue of KKAy diabetic mice, a mouse model of type 2 diabetes. Methods KKAy diabetic mice were fed with high fat diet for 4 weeks. After blood glucose met the criteria of diabetes （over 16.7 mmol/L）, mice were randomly divided into 3 groups： a control group （without any treatment）, a rosiglitazone group （treated with rosiglitazone 12.5 mg/kg·d once per day）, and a metformin group （treated with metformin 3 g/kg·d twice daily）. After 4 weeks, we then determined the expression of PTEN and phosphoserine 473-Akt （pS473-Akt） in the epididymal adipose tissue with Western blots. The mice in each group were further divided into the insulin （-） subgroup and insulin （＋） subgroup, which were intraperitoneally injected with saline and insulin （5 mU/g body weight）, respectively. Results The expression of PTEN was elevated in the epididymal adipose tissue obtained from KKAy diabetic mice compared with that from the C57BL/6J mice （P〈0.001）. In accordance with the enhanced expression of PTEN, the level of pS473-Akt stimulated by insulin was decreased in the adipose tissue of KKAy mice compared to the C57BL/6J mice （P〈0.001）. Treatment with the insulin-sensitizing agents, rosiglitazone and metformin did not inhibit the elevated expression of PTEN in adipose tissue of KKAy diabetic mice. Conclusion PTEN may play an important role in the development of insulin resistance in adipose tissue of type 2 diabetes mice model.     

Aspirin inhibits tumor necrosis factor-α-stimulated fractalkine expression in human umbilical vein endothelial cells

Background Fractalkine is an important chemokine mediating local monocyte accumulation and inflammatory reactions in the vascular wall. Aspirin inhibits inflammatory cytokine expression closely related to atherosclerosis through the way independent of platelet and cyclooxygenase （COX）. There has been no report about the effect of aspirin on fractalkine expression. We aimed to determine the fractalkine expression in human umbilical vein endothelial cell （HUVEC） stimulated by tumor necrosis factor （TNF）-α and the effect of aspirin intervention.
Methods Six of 8 HUVEC groups received either different concentrations of aspirin （0.02, 0.2, 1.0, 5.0 mmol/L） or 40 μmol/L pyrrolidinecarbodithioc acid （PDTC） or 0.5 μmol/L NS-398. The other two groups were negative control and positive control （TNF-α-stimulated）. After being incubated for 24 hours, cells of the 8 groups except the negative control one were stimulated with TNF-α （4 ng/ml） for another 24 hours. After that, the cells were collected for RNA isolation and protein extraction.
Results Both mRNA and protein expressions of fractalkine in HUVEC were upregulated by 4 ng/ml TNF-α stimulation. Aspirin inhibited fractalkine expression in a dose-dependent manner at mRNA and protein levels. Nuclear factor-kappa B inhibitor, PDTC, effectively decreased the fractalkine expression. Fractalkine expression was not influenced by COX-2 selective inhibitor NS-398. COX-1 protein expression was not changed by either TNF-α stimulation or aspirin, PDTC, NS-398 intervention. Both mRNA and protein expression of COX-2 in HUVEC were upregulated by 4 ng/ml TNF-α stimulation. Aspirin decreased COX-2 expression in a dose-dependent manner at mRNA and protein levels.
Conclusions TNF-α-stimulated fractalkine expression is suppressed by aspirin in a dose-dependent manner through the nuclear factor-kappa B p65 pathway.     

Effect of qi-tonifying and stasis-eliminating therapy (益气活血法) on expression of vascular endothelial growth factor and its receptors Flt-1, Flk-1 in the brain of intracerebral hemorrhagic rats

Objective： To investigate the effects and mechanism of qi-tonifying and stasiseliminating （QTSE） therapy on the expression of vascular endothelial growth factor （VEGF） and its receptors Fit-1 and FIk-1 in the brains of intracerebral hemorrhagic （model） rats. Methods： One hundred and eighty Sprague-Dawley rats were randomly divided into six groups： the normal group （n=5）, the sham-operative （SO） group （n=35）, the model group （n=35）, the QTSE group （n=35）, the QT group （n=35） and the SE group （n=35）. All the rats except those in the normal group and SO group were established into an intracerebral hemorrhage（ICH） model by intracerebral injection of collagenase type Ⅶ and the latter three were orally administered with Buyang Huanwu Decoction （补阳还五汤, a classical recipe for QTSE） or with some of its components for qi-tonification and for stasis-elimination, respectively. To the other three groups, normal saline solutions were given instead. Behavioral tests were carried out in the animals randomly chosen from each group on days 1, 2, 4, 7, 14, 21 and 28 after modeling. The expressions of VEGF, FIk-1 and Fit-1 were determined by immunohistochemistry and the number of vascular segments with positive expression in the injured brain area of the rats was calculated. Results： From day 7 onwards, the asymmetric forelimb use rate in the QTSE group recovered more significantly than that in the other model groups. In the model group, the expressions of VEGF, FIk-1 and Fit-1 appeared on day 1 and reached a peak on day 21, then weakened gradually. In the QTSE group, as compared with the other model groups, a higher level of VEGF expression was shown from day 7 （P〈0.01） and a higher level of Fit-1 expression was shown from the 7th day to the 21st day （P〈0.01）. Conclusion： QTSE therapy can up-regulate the expressions of VEGF and its receptors （FIk-1 and Fit-l） and improve the recovery of kinetic function in the ICH rats, which may be correlated with its action in modulating vascular regeneration to promote the reconstruction of microvascular networks in the damaged areas.     

Role of liver X receptors alpha agonist on expressions of LPS-induced inflammatory response associated factor IRAK-4 and NF-kappaB in Kupffer cells

Objective： To explore the role of activated liver X receptor α （LXRα） on the expressions of interleukin-1 receptor associated kinase-4 （IRAK-4） and NF-kappaB （NF-κB） in the inflammatory response which induced by LPS in the Kupffer cells and to investigate the possible mechanisms of LXRα negative regulation of inflammatory response. Methods： The Kupffer cells were isolated from male Kunming mice by collagen perfusion in situ. And these cells were divided into 4 groups： normal control group, LPS treatment group, LXRct agonist T0901317 treatment group, LPS and T0901317 combined treatment group. The LPS treatment group were treated with a final concentration of 1 μg/ml LPS in RPMI 1640 and cultured for 6 h, the T0901317 treatment group were treated with a final concentration of 5 μg/ml in RPMI 1640 and cultured for 24 h, and the combined treatment group received pre-culture for 24 h with a final concentration of 1μg/ml T0901317 in RPMI 1640 and then cultured for 6 h with a final concentration of 5 μg/ml LPS in RPMI 1640. All groups were cultured for 30 h. The expression of LXRα, IRAK-4 and NF-κB at mRNA and protein levels were detected by real-time PCR and Western blotting, and the TNF-α and IL-1β levels were detected by ELISA. Results： The levels of LXRα mRNA and protein were highest in T0901317 group, and lowest in LPS group （P〈0.05）. The level of IRAK4 and NF-κB mRNAs and proteins were evidently lower in the Combined-treated group than in LPS group （P〈0.05）. And the level of TNF-α and IL-1 were observed highest in LPS group （P〈0.05）, but no difference among the Control group, T0901317 group and Combined-treated group （P〉0.05）. Conclusion： These date suggest that the LXR agonists can effectively up-regulate the expressions of LXRα mRNA and protein and inhibit the inflammatory response. This may be via down-regulating the expressions of IRAK4 and NF-κB at mRNA and protein levels.     

Effect of advanced glycosylation end products on activity of protein kinase C in human peripheral blood mononuclear cells

Objectives To investigate the effect of advanced glycosylation end products (AGEs) on the a ctivity of protein kinase C (PKC) in human peripheral blood mononuclear cells (P BMC) and to observe whether aminoguanidine (AG) can influence the effect of AGEs .Methods After PBMC were isolated from human peripheral blood and incubated with differen t concentrations of AGEs-BSA for various periods, total PKC activity in PBMC wa s determined by measuring the incorporation of (32)P from ［γ-(32) P］ ATP into a special substrate using Promega PKC assay kit.Results AGEs-BSA increased the total PKC activity in PBMC from 83.43±6.57 pmol/min/ mg protein to 116.8±13.82 pmol/min/mg protein with a peak at 15 min. AGEs -BSA also increased the total PKC activity in a concentration-dependent manner fro m 83.1±6.4 pmol/min/mg protein (control) to 119.1±13.3 pmol/min/mg prote in (control vs AGEs-BSA 400 mg/L, P&lt;0.01).Furthermore, AGEs-BSA induc ed an elevation of PKC activity in a glycosylating time-related manner, from 80 .9±8.2 (control) to 118.3±11.5 pmol/min/mg protein (glycosylation for 12 wk, P&lt;0.01).The total PKC activity stimulated by AGEs-BSA pretreated wi th AG (100, 200 mg/L) was markedly lower than that of AGEs-BSA group not pretr eated with AG (P&lt;0.05, P&lt;0.01).Conclusions AGEs-BSA increased the total PKC activity in PBMC in a concentration and incuba tion time dependent manner. The ability of AGEs-BSA to stimulate PKC activity was markedly decreased by pretreatment of AGEs-BSA with AG.     

Effects of Rosiglitazone on Adiponectin Expression in 3T3- L1 Adipocytes at High Levels of Both Testosterone and Insulin In Vitro Culture

Objective To evaluate effects of rosiglitazone （RSG） on the expression of adiponectin in mature adipocytes at high levels of both testosterone （T） and insulin in vitro culture. Methods Mouse 3T3-L1 preadipocytes were induced to be mature adipocytes and used in this study. According to RSG concentrations, the cells added with T （10^-5 mol/L） and insulin （10^-4 mol/L） were divided into 4 groups： free-RSG group （0 mol/L RSG, FR-TI）, low-dose group （10^-9 mol/L RSG, LR-TI）, middle-dose group （lO-7mol/L RSG, MR-T1） and high-dose group （10^-6 mol/L RSG, HR-TI）. Besides, the cells added with RSG without T and insulin were also divided into 4 groups： FR, LR, MR, and HR. These 8 groups were incubated for 42 h. Cell viability was determined by MTT assay. Expression of adiponectin was detected by Western blotting. Results The maximum viability in FR-TI group was observed at point of 42 h. The growth of the adipocytes was significantly inhibited in MR-TI group compared with FR-TI （P〈0.01）. The level of adiponectin in MR-TI group was higher than that in LR- TI group （P〈0.01）. However, with RSG increasing; HR-TI group showed the lowest level of adiponectin among three treatment groups （P〈0.01）. In addition, adiponectin expression in MR-TI group was significantly higher than that in MR group （P〈0.01）. Conclusion RSG could increase the expression of adiponectin in 3T3-L1 adipocytes under high levels of both T and insulin, but it acts in a narrow concentration range.     

Effect of Sodium Tanshinone ⅡA Sulfonate on Phosphorylation of Extracellular Signal-regulated Kinasel/2 in Angiotensin Ⅱ-induced Hypertrophy of Myocardial Cells

Objective： To observe the effects of sodium tanshinone ⅡA sulfonate （STS） on angiotensin Ⅱ （Ang Ⅱ）-induced hypertrophy of myocardial cells through the expression of phosphorylated extracellular signal-regulated kinase （p-ERK1/2）. Methods： In the primary culture of neonatal rat myocardial cells, the total protein content in myocardial cells was determined by coomassie brilliant blue and the protein synthesis rate was measured by [3H]-Leucine incorporation as indexes for hypertrophy of myocardial cells. The expression of p-ERK1/2 was determined using Western blot and immunofluorescence labeling. Results： （1） The total protein and protein synthesis rate increased significantly in contrast to the control group after the myocardial cells were stimulated by Ang Ⅱ （1 μ mol/L） for 24 h; STS markedly inhibited the increment of the total protein level induced by Ang Ⅱ and the syntheses of protein. （2） After pretreatment of myocardial cells with Ang Ⅱ （1 μmol/L） for 5 min, the p-ERK1/2 protein expression was increased, with the most obvious effect shown at about 10 min; pretreatment of myocardial cells with STS at different doses （2, 10, 50μmol/L） for 30 min resulted in obvious inhibition of the expression of p-ERK1/2 stimulated by Ang Ⅱ in a dose-dependent manner. （3） After the myocardial cells were stimulated by AngⅡ （1 μ mol/L）, the immunofluorescence of ERK1/2 rapidly appeared in the nucleus. The activation and translocation process of ERK1/2 induced by Ang Ⅱ was blocked distinctly by STS. （Conclusion： STS inhibited the myocardial cell hypertrophy induced by Ang Ⅱ, and the mechanism may be associated with the inhibition of p-ERK1/2 expression.