体外培养高糖、高脂喂养大鼠主动脉平滑肌细胞钙化的研究

目的 检测高糖、高脂喂养Goto-Kakizaki（GK）糖尿病大鼠主动脉平滑肌细胞（SMCs）的血管钙化指标,探讨糖尿病血管钙化的相关机制.方法 高糖、高脂喂养GK及Wistar大鼠2周,同时分离培养两组大鼠的主动脉SMCs,Wistar大鼠SMCs作为对照.通过细胞计数法观察细胞生长状况,以甲基百里香酚蓝比色法测定两组大鼠细胞层及培养上清中钙的含量,实时定量PCR检测两组细胞碱性磷酸酶（ALP）、骨桥蛋白（OPN）、核心结合因子α-1（Cbfα-1）、α-平滑肌肌动蛋白（α-SMA）的基因表达.结果 与Wistar大鼠SMCs相比,GK大鼠SMCs生长速度明显缓慢（F =363.392,P＜0.05）;细胞层钙含量[（0.56±0.22） vs.（0.39±0.09）,t=2.47,P＜0.05]明显增加,培养上清中钙含量[（0.82±0.22）vs.（1.20±0.17）,t=-22.573,P＜0.05]明显减少.GK大鼠SMCs中ALP （t=12.963,P＜0.05）、OPN（t=8.305,P＜0.05）及Cbfα-1（t=10.109,P＜0.05）的基因表达增加,同时α-SMA（t=-8.219,P＜ 0.05）的基因表达减少.结论 高糖、高脂喂养的GK糖尿病大鼠的主动脉平滑肌细胞易发生钙化.     

胰岛素对猪主动脉平滑肌细胞的增殖和前列环素合成的影响

以体外培养的猪主动脉平滑肌细胞为实验模型，研究了不同浓度胰岛素对其细胞增殖、前列环素合成的影响。结果显示胰岛素抑制平滑肌细胞的前列环素合成、促进细胞增殖都呈现剂量依赖性，提示高胰岛素血症可能是致动脉粥样样硬化的重要因素之一。     

High glucose-induced upregulation of Rho/Rho-kinase via platelet-derived growth factor receptor-beta increases migration of aortic smooth muscle cells

Small GTPase Rho and Rho-kinase, the target protein of Rho, play an important role in atherosclerosis. In diabetic macroangiopathy, one of the major pathogenic changes is the migration of vascular smooth muscle cells (SMCs). Platelet-derived growth factor (PDGF) is known to stimulate the migration of SMCs. In the current study, we have investigated the involvement of the Rho/Rho-kinase pathway in the increased migration of cultured human aortic SMCs under a high glucose condition. PDGF stimulated the activation and the protein level of Rho. The protein level of PDGF receptor-β (PDGFR-β) was increased under the high glucose condition concomitant with the increased protein level and activation of Rho. The increased protein level and activity of Rho were suppressed by an anti-PDGF neutralizing antibody or a PDGFR-β inhibitor, AG1433, under the high glucose condition. Furthermore, high glucose significantly increased the migration of SMCs. A specific inhibitor of Rho-kinase, Y-27632, or anti-PDGF neutralizing antibody inhibited increased migration of SMCs under the high glucose condition. The protein levels of Rho were increased in aortae of diabetic rats, which were abolished by the treatment of Imatinib, the inhibitor of PDGFR. These observations indicate that the upregulation of the PDGFR-β / Rho / Rho-kinase pathway increases the migration of SMCs under the high glucose condition. The inhibition of Rho/Rho-kinase may be a new target for the treatment of diabetic macroangiopathy.     

胰岛素样生长因子-1对大鼠结肠平滑肌细胞增殖、凋亡及MAPK通路的影响

目的 探讨胰岛素样生长因子-1(IGF-1)对大鼠结肠平滑肌细胞(SMCs)增殖、凋亡及丝裂原活化蛋白激酶(MAPK)信号转导通路的影响.方法 利用酶解法分离培养Sprague-Dawley大鼠结肠SMCs,进行免疫组化染色鉴定后,将其分为对照组、IGF-1组和IGF-1+ PD98059[细胞外信号调节激酶(ERK)抑制剂]组,分别采用噻唑蓝(MTT)法检测SMCs增殖,流式细胞术AnnexinV-FITC/PI检测SMCs凋亡,Western印迹检测磷酸化ERK、ERK、磷酸化p38MAPK、p38MAPK和磷酸化c-Jun氨基末端激酶(JNK)、JNK的表达.结果 分离培养的细胞经免疫组化鉴定为结肠SMCs,IGF-1组较对照组细胞增殖增强[(1.786 ±0.271)比(0.998±0.057),P＜0.01],凋亡率降低[(2.59±0.28)％比(20.68±2.48)％,P＜0.01],磷酸化ERK表达增强,磷酸化ERK/ERK比值升高[(42.71±3.74)％比(23.88±2.52％),P均＜0.01];磷酸化p38MAPK、p38MAPK、磷酸化JNK、JNK表达无差异(P均＞0.05).IGF-1+ PD98059组较对照组细胞增殖下降[(0.154±0.021)比(0.998±0.057),P＜0.01],凋亡率升高[(84.31±7.54)％比(20.68±2.48)％,P＜0.01],磷酸化ERK表达减弱,磷酸化ERK/ERK比值降低[(10.47±1.22)％比(23.88±2.52)％,P均＜0.01].结论 IGF-1可能通过激活结肠SMCs MAPK通路中的ERK途径,促进细胞增殖,抑制凋亡,可能与p38MAPK途径和JNK途径无关.     

氧化型胆固醇对血管平滑肌细胞的损伤作用

目的　以胆固醇为对照 ,观察 3 β 5α 6β 三羟胆固烷 (cholestane 3 β,5α,6β triol)、2 5 羟胆固醇 ( 2 5 hydroxycholesterol)、7 酮胆固醇 ( 7 ketocholesterol)及环氧胆固醇 (cholesterol 5α,6α epoxide)四种氧化型胆固醇对大鼠主动脉平滑肌细胞的损伤作用。方法　取 6～ 10代细胞 ,测定细胞存活率、细胞培养液乳酸脱氢酶活力 ,用电子自旋共振自旋标记检测膜脂流动性和膜蛋白构象。结果　氧化型胆固醇呈时间和剂量依赖性降低细胞存活率、增加培养液乳酸脱氢酶活力 ,以 3 β 5α 6β 三羟胆固烷损伤最重。氧化型胆固醇还使膜脂流动性降低、膜蛋白构象改变及运动减慢。胆固醇除改变膜脂流动性外 ,在相同剂量及相同作用时间的情况下 ,对细胞无损伤作用。结论　氧化型胆固醇对血管平滑肌细胞有损伤作用 ,其中以 3 β 5α 6β 三羟胆固烷损伤最重 ,胆固醇对细胞没有损伤作用。氧化型胆固醇的细胞损伤与膜物理性质改变有关。     

Effect of high glucose concentrations on prostacyclin-stimulating factor mRNA expression in cultured aortic smooth muscle cells

Summary Prostacyclin (PGI₂) is a potent vasoactive prostanoid regulating vascular tone. We recently purified and cloned a PGI₂-stimulating factor (PSF), which stimulates PGI₂ production by vascular endothelial cells (ECs). Previous study demonstrated that PSF is predominantly located in vascular smooth muscle cells (SMCs) and present in serum. PSF may act on vascular ECs to regulate PGI₂ synthesis for maintaining vessel wall homeostasis. Decreased PSF production in the vessel wall may result in an imbalance of prostanoid synthesis, leading to the development of vascular lesions such as diabetic angiopathy. In the present study, to investigate the regulatory mechanisms of PSF gene expression, we examined the effect of high glucose concentrations on PSF mRNA expression in cultured bovine aortic SMCs. Expression of PSF mRNA was significantly decreased to 66 ± 6 % of control value (p < 0.01), when the glucose level was raised from 5.5 to 27.8 mmol/l. We also examined the effect of osmolarity on PSF mRNA expression by addition of an appropriate dose of mannitol to the culture medium. We confirmed that high glucose concentration itself reduced the expression of PSF mRNA and glucose had much more effect than the osmolarity control. The expression of PSF mRNA was significantly decreased to 72 ± 5 % of control value (p < 0.05) by a protein kinase C (PKC) activator, phorbol-12-myristate-13-acetate (PMA). The decreased expression of PSF mRNA in the presence of high glucose or PMA was restored by co-incubation with a PKC-specific inhibitor (GF109203X). These results suggest that PSF gene expression in vascular SMCs may be decreased via a specific effect of high glucose concentrations. High glucose-induced activation of PKC is suggested to participate partly in the regulation of PSF gene expression. [Diabetologia (1998) 41: 134–140] Received: 22 July 1997 and in revised form: 19 September 1997     

PDGF通过AKT/FoxO信号通路促进血管平滑肌细胞增殖

目的探讨血小板源生长因子(PDGF)促进血管平滑肌细胞增殖的分子机制方法用PDGF处理体外培养的大鼠动脉平滑肌细胞A10,MTT检测TPDGF对平滑肌细胞增殖的影响;用Western Blot检测AKT、FoxO1/3a的总蛋白和磷酸化水平。结果 PDGF可促进平滑肌细胞的增殖,且呈明显的剂量恶化时间依赖关系。PDGF可明显升高AKT和FoxO1/3a的磷酸化水平,呈时间依赖的关系。PI3K抑制剂可阻断PDGF促进平滑肌细胞的增殖和增高AKT和FoxO1/3a磷酸化的作用,但MEK和JNK信号通路抑制剂无明显作用。结论 PDGF通过激活AKT/FoxO1/3a信号途径促进血管平滑肌细胞的增殖。     

The possible role of hydrogen sulfide as a smooth muscle cell proliferation inhibitor in rat cultured cells

Hydrogen sulfide (H₂S) was recently suggested to be a possible endogenous gasotransmitter in physiological concentration. For the purpose of understanding its possible role in the regulation of the cardiovascular system, we explored the potential effect of H₂S on the proliferation of cultured aortic vascular smooth muscle cells (VSMCs) of rats and mitrogen-activated protein kinase (MAPK) as a signaling transduction pathway. Vascular smooth muscle cells were cultured in vitro and the cells were divided into six groups: (1) control group, (2) serum group, (3) endothelin group, (4) NaHS group, (5) serum + NaHS group, and (6) endothelin + NaHS group. VSMC proliferation was measured by [³H]thymidine ([³H]TdR) incorporation and MAPK activity in the VSMCs was determined by radioactivity assay. The results showed that endothelin-1 increased VSMC [³H]TdR incorporation 2.39-fold (P 0.01) and MAPK activity 1.62-fold (P 0.01), as compared with controls. Hydrogen sulfide at 5 × 10^–5mol/l, 1 × 10^–4mol/l, and 5 × 10^–4mol/l decreased VSMC [³H]TdR incorporation by 16.8%, 26.60%, and 37.40%, respectively, and reduced MAPK activity by 7.37% (P 0.05), 23.39%, and 33.57%, respectively (P 0.01). The results demonstrated that H₂S could dose-dependently suppress the proliferation of VSMCs through the MAPK pathway.     

Quercetin对人气道平滑肌细胞增殖和迁移的影响及机制

目的 体外培养人气道平滑肌细胞(human airway smooth muscle cells,HASMCs),探讨槲皮素(Quercetin,Que)对血小板源性生长因子BB(PDGF-BB)刺激的HASMCs增殖和迁移的影响及其机制.方法体外培养HASMCs,分为六组;对照组、PdGF-BB组、Que与PDGF-BB联合干预组、Que组、U0126组、U0126与PDGF-BB联合干预组.四甲基偶氮唑蓝(MTT)微量比色法测定HASMCs增殖,transwell法观察细胞迁移,Western blot法检测ERK的磷酸化及Cyclin D1表达水平.结果 与对照组相比,PDGF-BB(20μg/L)显著诱导HASMCs增殖和迁移(P＜0.05),Que(20～80μmol/L)呈浓度依赖性抑制PDGF-BB诱导的HASMCs的增殖和迁移(P＜0.05).PDGF-BB组ERK磷酸化及Cyclin D1 表达水平较对照组明显增高(P＜0.05).Que(80μmol/L)及PDGF-BB干预组其表达量低于PDGF-BB组,此抑制作用与ERK特异性拮抗剂U0126作用相当(P＞0.05).结论 Que抑制PDGF-BB诱导的HASMCs的增殖和迁移,可能是通过调节ERK/Cyelin D1通路起作用.     

Glucose-induced hyperproliferation of cultured rat aortic smooth muscle cells through polyol pathway hyperactivity

Aims/hypothesis. The protein kinase C (PKC), platelet-derived growth factor (PDGF) and polyol pathway play important parts in the hyperproliferation of smooth muscle cells, a characteristic feature of diabetic macroangiopathy. The precise mechanism, however, remains unclear. This study investigated the relation between polyol pathway, protein kinase C and platelet-derived growth factor in the development of diabetic macroangiopathy. Methods. Smooth muscle cells were cultured with 5.5 or 20 mmol/l glucose with or without an aldose reductase inhibitor, epalrestat, or a PKC-β specific inhibitor, LY333 531. Protein kinase C activities, the expression of PKC-βII isoform and PDGF-β receptor protein, free cytosolic NAD⁺:NADH ratio, the contents of reduced glutathione, and proliferation activities were measured. Results. Smooth muscle cells cultured with 20 mmol/l glucose showed statistically significant increases in protein kinase C activities, the expression of PKC-βII isoform and PDGF-β receptor protein, and proliferation activities, compared with smooth muscle cells cultured with 5.5 mmol/l glucose. Although epalrestat and LY333 531 inhibited protein kinase C activation induced by glucose to the same degree, the effects of epalrestat on proliferation activities and expression of the PDGF-β receptor were more prominent than those of LY333 531. Epalrestat improved the glucose-induced decrease in free cytosolic NAD⁺:NADH ratio and reduced glutathione content, but LY333 531 did not. The increased expression of membranous PKC-βII isoform was normalized by epalrestat. Conclusion/interpretation. These observations suggest that polyol pathway hyperactivity contributes to the development of diabetic macroangiopathy through protein kinase C, PDGF-β receptor, and oxidative stress, and that an aldose reductase inhibitor has a therapeutic value for this complication. [Diabetologia (2001) 44: 480–487] Received: 2 October 2000 and in revised form: 13 December 2000     

Relative insensitivity to glucagon of sterol synthesis in cultured rat aortic smooth muscle cells

Summary The smooth muscle cell plays an important role in the process of atherogenesis. In these experiments the effect of glucagon and dibutyryl cyclic AMP on sterol synthesis in cultured rat arterial smooth muscle cells was studied. Glucagon in concentrations of 1×10⁻⁹ mol/l inhibited the incorporation of sodium (2−¹⁴C)acetate into non-saponifiable lipids and digitonin precipitable sterols but lower concentrations of glucagon had no effect. In cells which were exposed to serum, dibutyryl cyclic AMP also resulted in a decrease in the incorporation of labelled acetate into sterols but when the cells were grown in serum free medium, dibutyryl cyclic AMP had no inhibitory effect on sterol synthesis. These results provide further evidence that sterol metabolism in arterial smooth cells may be influenced by hormones but suggest that glucagon is relatively less important than insulin in this respect.     

转化生长因子α对小鼠气道平滑肌细胞的促增殖作用

目的 探讨转化生长因子α(transforming growth factog alphg,TGF-α)对小鼠气道平滑肌细胞(airway smooth muscle cells,ASMC)促增殖作用及其机制.方法 用四唑盐(MTT)比色法和3H-TdR掺人法测定加入TGF-α后小鼠ASMC的增殖情况.本实验采用3H-TdR掺入法和MTT比色法观察选择性表皮生长因子受体(epidermal growth factor receptor,EGFR)酪氨酸激酶抑制剂(AG1478)、EGFR中和抗体225(225mAb)、MEK抑制剂(U0126)、PI-3K抑制剂(Wonmannin)对加入TGF-α后促ASMC增殖的影响.通过Western Blot方法测定加入TGF-α及加用AG1478、225mAb后ASMC磷酸化EGFR蛋白表达.结果 用MTT比色法和3H-TdR掺入法测定ASMC培养液中加入TGF-α后ASMC增殖情况比对照组明显增加.加入AG1478、225mAb、U0126、Wortmannin可抑制TGF-α促ASMC增殖作用(P＜0.01).经Western Blot检测,TGF-α引起ASMC磷酸化EGFR蛋白表达增高.AG1478、225mAb抑制TGF-α所致ASMC磷酸化EGFR蛋白表达的增加(P＜0.01).结论 TGF-α激活EGFR为磷酸化EGFR,从而通过:①ras-raf-MEK-erk/MAPK途径;②PI3K-PKC-IKK途径;促进体外培养的小鼠ASMC的增殖.     

一氧化氮对大鼠主动脉血管平滑肌细胞骨桥蛋白表达的影响

目的:观察一氧化氮(NO)对培养的大鼠主动脉血管平滑肌细胞(VSMC)骨桥蛋白(OPN)表达的影响。方法:体外培养大鼠主动脉VSMC,随机分为对照组,不同浓度NO供体S-亚硝基-N-乙酰青霉胺(SNAP,0.5,1,2,5mmol)干预组,应用RT-PCR及Western blot技术结合光密度扫描分析,观察SNAP对VSMC的OPN表达的影响。结果:不同浓度SNAP均明显抑制VSMC的OPN mRNA和蛋白的表达,且具有剂量依赖性抑制作用。结论:NO能抑制VSMC的OPN表达。     

高糖条件下腺苷酸活化蛋白激酶对大鼠胃平滑肌细胞能量代谢调控机制的研究

目的探讨高糖条件下腺苷酸活化蛋白激酶(AMPK)对大鼠胃平滑肌细胞能量代谢调控机制的影响。方法制备并确定糖尿病胃轻瘫(DGP)大鼠模型,实验分为正常对照(NC)组和DGP组,抗体芯片观察AMPK磷酸化通路的变化,确定能量代谢相关功能蛋白;SeahorseXFe细胞能量代谢分析系统观察2-脱氧-D-葡萄糖(2-DG)与化合物C(Compound C)对高糖条件下大鼠胃平滑肌细胞耗氧率(OCR)与细胞外酸化率(ECAR)的影响;沉默AMPK后,观察高糖条件下大鼠胃平滑肌细胞能量代谢相关功能蛋白变化。结果高糖条件下AMPK抑制大鼠胃平滑肌细胞OCR的基础呼吸、最大呼吸值、三磷酸腺苷产量(P<0.05),促进大鼠胃平滑肌细胞ECAR的糖酵解水平和能力(P<0.01)。抗体蛋白芯片发现18个磷酸化差异抗体,涉及与能量代谢相关蛋白包括:p53、Ca²⁺/CaM依赖性蛋白激酶Ⅱ(CaMKⅡ)、Ca²⁺/CaM依赖性蛋白激酶Ⅳ(CaMKⅣ)、磷脂酰肌醇特异性磷酯酶C-β3(PLC-β3)、蛋白激酶A(PKA)、乙酰CoA羧化酶1(ACC1)、真核延伸因子2(eEF2)、真核延伸因子激酶2(eEF2K)。与HG(24 h)组比较,HG(48 h)组p53、ACC1、eEF2表达升高(P<0.05或P<0.01),PLC-β3表达降低(P<0.01)。与HG(48 h)组比较,HG(48 h)+siRNA组p53、ACC1表达降低(P<0.01)。与HG(24 h)组比较,HG(48 h)组p-CaMKⅡThr³⁰⁵/CaMKⅡ与p-CaMKⅣThr^196/200/CaMKⅣ比值升高(P<0.01)。与HG(48 h)组比较,HG(48 h)+siRNA组p-CaMKⅡThr³⁰⁵/CaMKⅡ比值降低(P<0.01)。HG(48 h)组PKA活性高于HG(24 h)组(P<0.01)。结论高糖条件下AMPK通过调控p53、ACC1、eEF2、CaMKⅡ、CaMKⅣ、PLC-β3及PKA生物学作用,抑制大鼠胃平滑肌细胞线粒体代谢途径及促进糖酵解途径。     

雌激素对PDGF诱导的血管平滑肌细胞增殖及细胞周期的影响

目的探讨17β-雌二醇（E2）对血管平滑肌细胞（VSMC）增殖及细胞周期的影响。方法分离培养VSMC,血小板源生长因子（PDGF）诱导其增殖,应用MTT法及流式细胞仪检测不同浓度E2（10和100 nmol/L）对传代VSMC增殖活性及细胞周期的影响。结果E2（10和100 nmol/L）作用下VSMC增殖活性下降,且与浓度有关;对VSMC细胞周期的分布影响主要表现为处于G0/G1期细胞数增多,G2/S期的细胞数减少（P<0.01）。结论E2具有抑制VSMC增殖的作用,其部分机制可能是通过阻滞VSMC G0/G1期向S的转化有关。     

PD098059及N-乙酰半胱氨酸在缓激肽引起血管平滑肌细胞增殖反应中的调节作用

目的 :研究丝裂原活化蛋白激酶 （MAPK ）信号途径在缓激肽 （BK）介导的大鼠血管平滑肌细胞 （VSMC）增殖中的作用。方法 :通过 3H -胸苷 （3H- Td R）掺入率与 SMC3H-亮氨酸掺入率分别反映 VSMC的 DNA代谢与蛋白质合成代谢速率 ;并通过给予 PD0 980 5 9及 N-乙酰半胱氨酸预处理 ,观察其对细胞增殖的影响。结果 :1BK（10 nm ol/L ）处理 30 min,VSMC3H-胸苷掺入率和 3H-亮氨酸掺入率均明显增高 ;2 BK增高 3H -胸苷掺入的作用可明显被PD0 980 5 9所抑制 ,对 3H -亮氨酸掺入的作用可部分被 PD0 980 5 9所抑制 ;3BK增高 3H -胸苷掺入和 3H -亮氨酸掺入的作用均可部分被 N-乙酰所抑制 ,完全被 N-乙酰 +PD0 980 5 9所抑制。结论 :细胞外信号调节激酶 （ERKs）激活在缓激肽介导的 VSMC增殖中具有重要作用 ,并可通过 ERKs信号途径的特异性抑制剂影响血管平滑肌细胞的增殖效应。     

Insulin induces PKC-dependent proliferation of mesenteric vascular smooth muscle cells from hypertensive patients

Background and objectives Proliferation of human vascular smooth muscle cells (VSMCs) induced by hyperinsulinemia is a very common clinical pathology. Extensive research has focused on PKC (Protein kinase C)-MAPK (mitogen-activated protein kinase) intracellular signal transduction and the phenotypic modulation accompanied by reorganization of intracellular F-actins in VSMCs. Methods DNA synthesis, signaling of ERK1/2 MAPKs, and changes in a-smooth muscle (SM) actin and F-actin were studied in hypertensive and normotensive human arterial VSMCs exposed to insulin and PMA with and without the PKC inhibitor, GF109203X. Results Differences among cell types in MAPK signaling, a-SM actin, and F-actin isoforms in VSMCs harvested from the arteries of patients with essential hypertension (EH) and normotension (NT) were identified in response to insulin treatment. Proliferation and activation of MAPK were more pronounced in EH VSMCs than in NEH VSMCs. Insulin exposure decreased expression of a-SM actin and was accompanied by rearrangement of intracellular F-actins in VSMCs, especially in the EH group. These effects were reversed by treatment with the PKC inhibitor. Conclusions Human mesenteric VSMCs of EH and NT patients differed in proliferation, MAPK signaling, and degree of changes in a-SM actin and F-actin isoforms immediately following insulin exposure in vitro.     

p38MAPK信号途径与血管损伤后平滑肌细胞增殖关系的研究

目的检测大鼠颈动脉球囊损伤后平滑肌细胞增殖及p38丝裂素活化蛋白激酶(MAPK)的表达,探讨血管损伤后平滑肌细胞增殖的信号途径.方法雄性Sprague-dawley大鼠30只,体重250～300 g.随机分为假手术组、手术后7 d组、手术后14d组,每组10只大鼠,进行球囊血管损伤术,术后7、14 d分别取15 mm颈动脉作为实验标本.血管组织行苏木精-伊红染色、免疫组化和免疫印迹,检测血管壁增生、增殖细胞核抗原(PCNA)和p38MAPK表达情况.结果术后7、14d组有动脉壁增厚、新生内膜形成和中膜平滑肌胶原化,PCNA细胞阳性率分别是(39.5±7.9)%和(44.8±9.9)%,与假手术组[(1.3±0.4)%]相比明显增加(P＜0.01);p38MAPK表达明显高于假手术组(P＜0.05).p38MAPK表达与血管平滑肌细胞增殖率呈正相关(r=0.714,P＜0.05).结论球囊损伤血管能促进血管平滑肌细胞增殖和血管内膜增生;血管损伤后p38MAPK表达明显增强,与平滑肌细胞增殖呈正相关;p38MAPK信号途径参与了血管平滑肌细胞的增殖.     

Saturated non-esterified fatty acids stimulate de novo diacylglycerol synthesis and protein kinase c activity in cultured aortic smooth muscle cells

Aims/hypothesis. Insulin resistance is linked with a cluster of multiple risk factors and excessive acceleration of atherosclerosis. The underlying mechanism is not, however, fully understood. Methods. To determine the link between insulin resistance and altered vascular function, we focused on the effect of various non-esterified fatty acids on diacylglycerol-protein kinase C pathway and mitogen-activated protein kinase activity in cultured aortic smooth muscle cells. Results.Incubation of the cells with saturated non-esterified fatty acids (200 μmol/l) for 24 h, such as palmitate or stearate, induced a significant increase in diacylglycerol concentrations by about fivefold or eightfold, respectively, whereas oleate induced a slight increase in diacylglycerol concentrations by 1.8-fold and arachidonate induced none. In addition, the increased diacylglycerol concentrations induced by palmitate were completely restored to control concentrations by triacsin C, acyl-CoA synthetase inhibitor. These results suggest that saturated non-esterified fatty acids may increase diacylglycerol concentrations through de novo pathway by stepwise acylation. In parallel with the increased diacylglycerol, incubation of the cells with saturated non-esterified fatty acids significantly induced the activation of protein kinase C and mitogen-activated protein kinase. The palmitate-induced increase in mitogen-activated protein kinase activity was restored to control concentrations by GF109203X (5 · 10^–7 mol/l), a specific protein kinase C inhibitor, suggesting a protein kinase C-dependent activation of mitogen-activated protein kinase. Conclusion/interpretation. Saturated non-esterified fatty acids induced an increase in de novo diacylglycerol synthesis and subsequent activation of protein kinase C and mitogen-activated protein kinase in cultured aortic smooth muscle cells. This could contribute to the altered vascular functions in the insulin resistant state. [Diabetologia (2001) 44: 614–620] Received: 29 September 2000 and in revised form: 11 January 2001