Rapamycin inhibits platelet-derived growth factor-induced collagen, but not fibronectin, synthesis in rat mesangial cells

Rapamycin, a macrocyclic lactone, is effective in reducing the incidence of acute rejection after renal transplantation. The inhibitory effects of rapamycin on lymphocyte proliferation and the molecular mechanisms that were involved have been described. However, its effects on glomerular mesangial cells have not been clearly understood, and here, we examined the effect of rapamycin on platelet-derived growth factor (PDGF)-induced extracellular matrix synthesis as well as cell proliferation in mesangial cells. Rat mesangial cells were isolated from the glomeruli of Sprague-Dawley rats and cultured with Dulbecco's modified Eagles medium containing 20% fetal bovine serum. Different concentrations of rapamycin were administered 1 hour before the addition of 10 ng/ml of PDGF into growth arrested and synchronized cells. Cell proliferation was assessed by [3H]thymidine incorporation, total collagen synthesis by [3H]proline incorporation, and fibronectin secretion into the medium by Western blot analysis. In the mesangial cells, PDGF increased cell proliferation by 4.6-fold, total collagen synthesis by 1.8-fold, and fibronectin secretion by 3.2-fold. Rapamycin above 10 nM significantly inhibited PDGF-induced proliferation and collagen synthesis, but the treatment of rapamycin up to 1 microM did not show any significant effects on PDGF-induced fibronectin secretion. These inhibitory effects of rapamycin on PDGF-induced mesangial cell proliferation and collagen synthesis reflect the potential value of rapamycin in the prevention and treatment of glomerulosclerosis in patients with chronic allograft nephropathy.     

Gas6 regulates mesangial cell proliferation through Axl in experimental glomerulonephritis

Proliferation of mesangial cells is a hallmark of glomerular disease, and understanding its regulatory mechanism is clinically important. Previously, we demonstrated that the product of growth arrest-specific gene 6 (Gas6) stimulates mesangial cell proliferation through binding to its cell-surface receptor Axl in vitro. We also showed that warfarin and the extracellular domain of Axl conjugated with Fc portion of human IgG1 (Axl-Fc) inhibit mesangial cell proliferation by interfering the Gas6/Axl pathway in vitro. In the present study, therefore, we examined in vivo roles of Gas6 and Axl in an experimental model of mesangial proliferative glomerulonephritis induced by the injection of anti-Thy1.1 antibody (Thy1 GN). In Thy1 GN, expression of Gas6 and Axl was markedly increased in glomeruli, and paralleled the progression of mesangial cell proliferation. Administration of warfarin or daily injection of Axl-Fc inhibited mesangial cell proliferation, and abolished the induction of platelet-derived growth factor-B mRNA and protein in Thy1 GN. Moreover, the anti-proliferative effect of warfarin was achieved at lower concentrations than those in routine clinical use. These findings indicate that the Gas6/Axl pathway plays a key role in mesangial cell proliferation in vivo, and could be a potentially important therapeutic target for the treatment of renal disease.     

醛糖还原酶基因转染对体外培养大鼠肾脏系膜细胞增殖的影响

目的观察醛糖还原酶(AR)基因转染对体外培养大鼠肾脏系膜细胞(MsC)增殖的影响,并对其机制进行初步探讨。方法脂质体转染法将AR基因转入大鼠MsC,蛋白印迹鉴定转染效率。四甲基偶氮唑盐(MTT)比色法检测细胞增殖,流式细胞术分析细胞周期与凋亡,对比正常MsC和AR转染MsC的生长速度及AR抑制剂(ARI)Sorbinil和Zopolrestat对血小板源性生长因子-BB(PDGF-BB)和小牛血清(NBS)促MsC增殖作用的影响。蛋白印迹检测PDGF-BB作用后AR和c-Jun表达的变化,EMSA检测转录因子AP-1的活性。结果(1)转染MsCAR表达较正常MsC明显增高;(2)AR转染MsC较正常MsC生长速度快(P<0.01);(3)ARI可部分抑制PDGF-BB对正常MsC、AR转染MsC以及NBS对AR转染MsC的促增殖作用(P<0.01,P<0.05),而对NBS促正常MsC的增殖无显著影响;(4)PDGF-BB刺激MsC后可上调AR和c-Jun蛋白的表达,ARI可减弱c-Jun的这种表达增高;(5)PDGF-BB可活化转录因子AP-1,而ARI可削弱此作用。结论AR可能参与了MsC在病理情况下的过度增殖过程,其作用机制与AP-1活化有一定关系。     

Glomerular mesangial cell migration in response to platelet-derived growth factor

Platelet-derived growth factor (PDGF) is a potent mitogenic and chemotactic protein for a variety of cell types. Glomerular mesangial cells also respond to PDGF in terms of proliferation, but, to date, have not been examined for migratory behavior in response to a specific growth factor. Here, we examine the ability of isolated rat mesangial cells to migrate toward gradients of purified PDGF. Chemotaxis assays were performed in two-compartment blind well chambers, each compartment separated by a 14-microns porous filter membrane. Human PDGF was added to 200 microliters of RPMI 1640 medium in the lower compartment beneath the filters to make incremental concentrations from 2.5 to 50 units/ml. Control compartments received diluent without PDGF. Mesangial cells in RPMI 1640 medium were added to the upper compartments and the chambers were incubated for 8 hours at 37 degrees C. After fixation, the number of cells on the underside of the filter were counted by scanning electron microscopy. A linear dose response of mesangial cell migration toward increasing concentrations of PDGF was observed, achieving cell numbers of 9-fold over controls at 50 units/ml. Migratory cells were verified as mesangial cells by fluorescence expression of actin, myosin, and desmin and absence of expression of leukocyte common antigen and Ia antigen. Addition of equimolar concentrations of PDGF on both sides of the filter or addition of anti-PDGF antibody to the lower chamber containing PDGF negated the chemotactic response. These studies indicate that mesangial cells migrate in response to PDGF. This mechanism may, in part, play a role in some forms of mesangial proliferative glomerular disease.     

Lipoxins inhibit Akt/PKB activation and cell cycle progression in human mesangial cells

Lipoxins (LX) are endogenously produced eicosanoids with a spectrum of bioactions that suggest anti-inflammatory, pro-resolution roles for these agents. Mesangial cell (MC) proliferation plays a pivotal role in the pathophysiology of glomerular inflammation and is coupled to sclerosis and tubulointerstitial fibrosis. We have previously reported that LXA4 acts through a specific G-protein-coupled-receptor (GPCR) to modulate MC proliferation in response to the proinflammatory mediators LTD4 and platelet-derived growth factor (PDGF). Further investigations revealed that these effects were mediated by modulation of receptor tyrosine kinase activity. Here we have explored the underlying mechanisms and report inhibition of growth factor (PDGF; epithelial growth factor) activation of Akt/PKB by LXA4. LXA4 (10 nmol/L) modulates PDGF-induced (10 ng/ml, 24 hours) decrements in the levels of cyclin kinase inhibitors p21Cip1 and p27Kip1. PDGF-induced increases in CDK2-cyclin E complex formation are also inhibited by LXA4. The potential of LXA4 as an anti-inflammatory therapeutic is compromised by its degradation; this has been circumvented by synthesis of stable analogs. We report that 15-(R/S)-methyl-LXA4 and 16-phenoxy-LXA4 mimic the native compound with respect to modulation of cell proliferation and PDGF-induced changes in cell cycle proteins. In vivo, MC proliferation in response to PDGF is associated with TGFbeta1 production and the subsequent development of renal fibrosis. Here we demonstrate that prolonged (24 to 48 hours) exposure to PDGF is associated with autocrine TGFbeta1 production, which is significantly reduced by LXA4. In aggregate these data demonstrate that LX inhibit PDGF stimulated proliferation via modulation of the PI-3-kinase pathway preventing mitogen-elicited G1-S phase progression and suggest the therapeutic potential of LX as anti-fibrotic agents.     

Inhibition of angiotensin II and platelet-derived growth factor-induced vascular smooth muscle cell proliferation by calcium entry blockers

Summary Structural changes within the blood vessel wall such as hyperplasia and hypertrophy of vascular smooth muscle cells are important factors in the pathogenesis of hypertension. Humoral growth factors such as angiotensin II (AII) and platelet-derived growth factor BB (PDGF-BB) may participate in the remodelling of the blood vessel wall. Whether and by which mechanisms antihypertensive treatment is capable of influencing the structural blood vessel alterations to date remains unclear. In the present study, the effect of nifedipine and diltiazem on AII- and PDGF-BB-induced vascular smooth muscle cell proliferation was examined. Nifedipine and diltiazem at a concentration of 10 M did not affect baseline DNA synthesis in isolated vascular smooth muscle cells in culture. AII (final concentration 100 nM) and PDGF-BB (50 ng/ml) stimulated DNA synthesis by approximately 9.0- and 4.6-fold, respectively. Both AII- and PDGF-BB-induced DNA synthesis was significantly blunted by diltiazem and nifedipine in a concentration of 10 M, while no significant influence was seen with concentrations from 10 nM up to 1 M. In contrast, no significant influence of these drugs could be observed on fetal calf serum 5%-induced DNA synthesis. The findings indicate that calcium antagonists possess antimitogenic potential and that they may thus contribute to the regression of structural changes of the blood vessels associated with hypertension.Abbreviations PDGF-BB platelet-derived growth factor BB - AII angiotensin II - FCS fetal calf serum - VSMC vascular smooth muscle cells - ACE angiotensin I converting enzyme This work was supported by HEXAL-PHARMA, Holzkirchen, Federal Republic of Germany     

Vasopressin regulates rat mesangial cell growth by inducing autocrine secretion of vascular endothelial growth factor

Mesangial cell growth is a key feature of several glomerular diseases. Vascular endothelial growth factor (VEGF) is a potent mitogen of vascular endothelial cells and promoter of vascular permeability. Here, we examined the ability of vasopressin (AVP), which causes mesangial cell proliferation and hypertrophy, to stimulate VEGF secretion from cultured rat mesangial cells. AVP potently induced a time- and concentration-dependent increase in VEGF secretion in these cells, which was then inhibited by a V_1A receptor-selective antagonist, confirming this is a V_1A receptor-mediated event. VEGF also induced hyperplasia and hypertrophy in mesangial cells, which was completely abolished by an anti-VEGF antibody. In addition, AVP-induced hyperplasia and hypertrophy were completely inhibited by the V_1A receptor-selective antagonist and partially abolished by the anti-VEGF antibody. These results indicate that AVP increases VEGF secretion in rat mesangial cells via V_1A receptors and modulates mesangial cell growth not only by direct action but also through stimulation of VEGF secretion. This autocrine mechanism might contribute to glomerulosclerosis in renal diseases such as diabetic nephropathy.     

Bradykinin-induced inhibition of cell proliferation and tyrosine kinase activity in rat mesangial cells

The relationship between cell proliferation, protein tyrosine phosphorylation, phosphotyrosine kinase activity and bradykinin receptor activation in rat mesangial cells was investigated. We demonstrated that bradykinin (BK), through the B2 receptor, induced a dose-dependent inhibition of mesangial cell proliferation stimulated by fetal calf serum. We next found that BK induced a dose-dependent inhibition of phospho-tyrosine kinase activity. Treatments with pertussis-toxin, inhibition of phospholipase C and protein kinase C inhibitors and chelation of free cytosolic calcium did not change the bradykinin-induced inhibition of phosphotyrosine kinase. Western blot analysis of phosphotyrosinated proteins demonstrated that BK reduced tyrosine phosphorylation of several proteins among which we identified the 125-focal adhesion kinase. Taken together, these data suggest for the first time that, in proliferating rat mesangial cells, B2 receptor stimulation is able to induce, via a pertussis insensitive pathway, the inhibition of tyrosine kinase activity and mesangial cell proliferation.     

Epidermal growth factor-induced survival and proliferation of neuronal precursor cells from embryonic rat mesencephalon.

Neuronal and glial precursor cells were isolated from primary cultures of embryonic rat mesencephalon. The separation of precursor cells from the neurons was accomplished by the resuspension of the primary cells by trypsinization, followed by replating. This procedure resulted in the death of differentiated neurons and the survival of precursor cells. The survival and proliferation of the replated precursor cells required the presence of epidermal growth factor (EGF) in the culture medium. The precursor cells differentiated into neurons and astrocytes, as determined by immunocytochemical staining with antibodies to neuron specific enolase (NSE) and tau protein or glial fibrillary acidic protein (GFAP) respectively.     

Basic fibroblast growth factor stimulates glomerular mesangial cell proliferation through a protein kinase C-independent pathway.

Basic Fibroblast Growth Factor (bFGF) is shown to be a potent mitogen for cultured glomerular mesangial cells. bFGF induces an increase in cell number and stimulates DNA synthesis measured by [3H]thymidine incorporation in normal as well as in protein kinase C-depleted cells. The ED50 observed in both cases are nearly identical (approximately 0.04 nM) and maximal responses are obtained at 1 nM. Staurosporine, a potent protein kinase C inhibitor, does not prevent bFGF from inducing mitogenesis. On the contrary, the tumour promoting phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) and the bradykinin derivative Des-Arg9bradykinin that we have previously shown as mitogens for mesangial cells, fail to trigger DNA synthesis or cell proliferation upon staurosporine treatment or in protein kinase C-depleted cells. bFGF is unable to induce the association of the enzyme to membranes, the so-called translocation process, although the growth factor induces a slight production of diacylglycerol. Using a highly resolutive two-dimensional electrophoresis, we show that bFGF, in contrast to TPA, is unable to stimulate the phosphorylation of a Mr 80,000/pI 4.5 protein, a major and specific protein kinase C substrate. By contrast, bFGF stimulates the phosphorylation of a Mr 28,000/pI 5.7-5.9 protein in normal as well as in protein kinase C-depleted cells while TPA induces this protein phosphorylation only in normal cells. Our results suggest that bFGF exerts its proliferative action on mesangial cells through a protein kinase C-independent pathway and that the growth factor does not activate anyway the enzyme in this cell type.     

抑制氯通道阻抑鼻咽癌细胞周期和细胞增殖

目的:研究Cl^-通道在鼻咽癌细胞调节性容积回缩(RVD)、增殖及细胞周期分布中的作用。方法:活细胞图像分析低分化鼻咽癌细胞(CNE－2Z)RVD,用台盼蓝拒染法检测细胞存活率,MTT法检测细胞增殖能力。用流式细胞仪测定细胞周期不同时相细胞百分率。结果:Cl^-通道抑制剂硝基苯丙胺基苯甲酸(NPPB)剂量依赖性抑制RVD和细胞增殖,100μmol/LNPPB明显阻抑细胞周期进程,使细胞停滞于G₁期,G₁期细胞百分率从54%提高到71%,但对细胞存活率没有显著性影响。结论:阻抑Cl^-通道可阻滞细胞于G₁期而抑制细胞增殖。提示Cl^-通道和RVD的激活是促进细胞从G₁期进入S期和维持增殖所必需的因素。     

Modulation of mesangial cell proliferation by endothelial cells in coculture.

The effects of direct cell contact between endothelial (ECs) and mesangial cells (MCs) on MCs proliferation were examined in a coculture system in vitro. Mitomycin C treated ECs (M-ECs) were plated on culture dishes and MCs were cocultured with these M-ECs. Cell number was measured at the end of days 1, 3, and 5. In the coculture system with direct contact, the growth of cocultured MCs was modulated as follows: 1) the growth of MCs was inhibited up to day 3, and 2) a high level of proliferation was observed between days 3 and 5. This biphasic pattern of growth could not be detected in coculture of fibroblasts with MCs. In coculture without direct contact, using intercup chambers, the kinetics in cell proliferation between cocultured MCs and MCs alone were essentially the same. Conditioned media derived from cocultures up to day 3 in a contact-dependent manner inhibited the 3H-thymidine uptake of MCs. From these results, it would thus appear that MCs proliferation is regulated by intercellular contact with ECs.     

组蛋白乙酰化酶调控MSCs经5-azaC诱导后的细胞周期和增殖特性

目的 阐述组蛋白乙酰化酶GCN5在间充质干细胞经5-氮杂胞苷诱导过程中的作用及其转录调控机制。方法 MTT法、流式细胞术检测细胞周期和细胞增殖;定量PCR检测P21基因表达;CHIP技术验证GCN5募集蛋白复合体与P21基因的相互作用及P21基因启动子区域的乙酰化水平;Co-IP技术分离、串联质谱技术鉴定GCN5募集蛋白复合体组成。结果 MSCs经5-azaC诱导3 d后G0/G1期细胞比例、P21基因表达量最高,此后逐渐降低,细胞增殖指数及G2/S期细胞比例与上述结果相反;筛选出GCN5募集蛋白复合体为：依赖ATP的染色质重塑复合体成分、转录起始复合体成分、转录因子和锌指结构蛋白;诱导组GCN5与P21基因启动子区域结合能力及P21基因启动子区域组蛋白H3乙酰化水平高于未诱导组。结论 GCN5募集蛋白复合体通过结合于P21基因启动子区域参与调控MSCs经5-azaC诱导体外分化过程中细胞周期G0/G1期和细胞增殖特性的调控。     

p38 mitogen-activated protein kinase regulates growth factor-induced mitogenesis of rat pulmonary myofibroblasts

Myofibroblast proliferation is a central feature of pulmonary fibrogenesis. Several growth factors, including platelet-derived growth factor (PDGF) and epidermal growth factor (EGF), stimulate myofibroblast growth by activating extracellular signal regulated kinases 1 and 2 (ERK1/2). In this report, we demonstrate that PDGF-BB and EGF also activate the p38 mitogen-activated protein (MAP) kinase. Inhibition of p38 activity with the pyridinylimidazole compound SB203580 enhanced both PDGF-BB and EGF-stimulated DNA synthesis in rat lung myofibroblasts. ERK1/2 phosphorylation in response to either PDGF-BB or EGF treatment was significantly increased by pretreatment of cells with SB203580. We also demonstrated that ERK1/2-induced phosphorylation of PHAS-1 substrate was enhanced by inhibition of p38 MAP kinase with SB203580. However, SB203580 did not significantly increase growth factor-induced activation of MEK, the upstream kinase that phosphorylates ERK1/2. p38 MAP kinase was co-immunoprecipitated with ERK-1/2 following growth factor stimulation. Collectively, these data demonstrate that p38 MAP kinase activation negatively regulates PDGF- and EGF-mediated growth responses by directly interacting with ERK1/2 and suppressing its phosphorylation.     

Hepatic stellate cell proliferation is an early platelet-derived growth factor-mediated cellular event in rat cholestatic liver injury.

SUMMARY: After liver injury, hepatic stellate cells (HSC) undergo a pleiotropic response termed "activation" that also occurs in culture models and ultimately leads to the conversion of HSC into myofibroblasts expressing smooth muscle alpha-actin (alpha-SMA). The onset of HSC proliferation in primary culture coincides with the induction of platelet-derived growth factor receptor-beta (PDGFR-beta) expression, while platelet-derived growth factor (PDGF) is the most potent mitogen for culture-activated HSC. Yet, the mechanisms and the stage of activation required for HSC proliferation in the intact liver are still uncertain. In the present study, we analyzed the proliferative response of HSC to rat cholestatic liver injury and the role of PDGF in this response. After in vivo incorporation of bromodeoxyuridine (BrdU), pure vitamin A-containing HSC were isolated at different time points after bile duct ligation (BDL) or sham operation and were analyzed by means of flow cytometry. The induction of HSC proliferation, as ascertained by BrdU incorporation, occurred between 24 and 48 hours and reached a plateau as soon as 48 hours after BDL. Flow cytometry and immunoblot analyses of HSC indicated that the induction of proliferation in HSC coincided with the up-regulation of PDGFR-beta protein on their surface but preceded that of alpha-SMA. A dose-dependent inhibition of PDGF-BB-induced HSC proliferation by STI571, a PDGF receptor tyrosine kinase inhibitor, was documented in vitro. Daily intraperitoneal injections of STI571 (20 mg/kg) caused a 60% reduction in BrdU positive isolated HSC and in the amount of desmin-immunoreactive sinusoidal cells on liver tissue sections in 48-hour bile duct-ligated rats. These results indicate that cholestatic liver injury elicits an early proliferative response in HSC that is mainly mediated by PDGF, and which precedes HSC phenotypic conversion into myofibroblasts.     

SPARC is expressed by mesangial cells in experimental mesangial proliferative nephritis and inhibits platelet-derived-growth-factor-medicated mesangial cell proliferation in vitro.

Mesangial cell proliferation is a characteristic feature of many glomerular diseases and often precedes extracellular matrix expansion and glomerulosclerosis. This study provides the first evidence that SPARC (secreted protein acidic and rich in cysteine) could be an endogenous factor mediating resolution of experimental mesangial proliferative nephritis in the rat. SPARC is a platelet-derived-growth-factor-binding glycoprotein that inhibits proliferation of endothelial cells and fibroblasts. We now show that SPARC is synthesized by mesangial cells in culture and that SPARC mRNA levels are increased by platelet-derived growth factor and basic fibroblast growth factor. Recombinant SPARC or the synthetic SPARC peptide 2.1 inhibited platelet-derived-growth-factor-induced mesangial cell DNA synthesis in vitro. In a model of experimental mesangioproliferative glomerulonephritis, SPARC mRNA was increased 5-fold by day 7 and was identified in the mesangium by in situ hybridization. Similarly, SPARC was increased in glomerular mesangial cells and visceral epithelial cells by day 5 and reached maximal expression levels by day 7. Mesangial cell proliferation increased by 36-fold on day 5 and decreased abruptly on day 7. Maximal expression of SPARC was correlated with the resolution of mesangial cell proliferation. We propose that SPARC functions in part as an endogenous inhibitor of platelet-derived-growth-factor-mediated mesangial cell proliferation in glomerulonephritis and that it could account for the resolution of cellular proliferation in this disease.     

高浓度葡萄糖对大鼠肾小球系膜细胞增殖的影响

目的: 观察高糖环境对系膜细胞增殖的影响。方法: 用高浓度葡萄糖刺激系膜细胞, 采用MTT比色法观察系膜细胞的增殖情况。结果: 葡萄糖对系膜细胞的增殖效应呈现浓度和时间依赖性, 其中20 mmol/L的葡萄糖为最佳刺激增殖浓度, 反应最佳时点为48 h。10 mmol/L、20 mmol/L和30 mmol/L在72 h和96 h有抑制增殖作用。结论: 高糖在一定浓度和一定时段内有刺激大鼠系膜细胞增殖的效应, 随着时间的延长此效应消失。     

血小板衍化生长因子在细胞增殖和组织修复中的作用及机制

背景：细胞增殖和组织修复是一个复杂的过程,这期间有大量生长因子参与,并且这些因子在发挥本身功效时,同时还相互影响和制约,从而更好地促进细胞增殖和组织修复。 目的：总结血小板衍化生长因子在细胞增殖和组织修复愈合过程中发挥的作用及其机制。 方法：检索PubMed数据库、EMbase数据库1960-01/2010-10期间相关文章,检索词为“platelet-derived growth factor,cell proliferation,tissue repair”。同时检索中国生物医学文献数据库、中文科技期刊全文数据库、中文学术期刊全文数据库2000-01/2010-10期间相关文章,检索词为“血小板衍化生长因子”。 结果与结论：血小板衍化生长因子是一种重要的促细胞分裂剂,可刺激各种类型细胞的分裂增殖。血小板衍化生长因子及其受体存在于机体的多种组织细胞,当机体受到一定的刺激时,血小板衍化生长因子与其受体结合,发挥作用,因此许多研究发现,在外科手术后和损伤修复过程中常伴随有局部血小板衍化生长因子基因表达量的升高和受体的上调,被称为损伤修复因子。但是它的具体作用机制尚不太明确,对细胞组织的增殖修复的认识还处于起始、发展阶段,还有许多的问题需要去探索研究。