Anti-HLA class I antibody-mediated activation of the PI3K/Akt signaling pathway and induction of Bcl-2 and Bcl-xL expression in endothelial cells

Anti-human leukocyte antigen (HLA) antibodies (Ab) have long been implicated in the process of acute and chronic allograft rejection, yet their mechanism(s) of action is not well understood. The aim of this study was to determine whether ligation of HLA class I molecules by anti-HLA Ab on the surface of human endothelial cells (EC) activates the PI3 Kinase (PI3K)/Akt signaling pathway and downstream target proteins of the cell death apparatus. We report that Ab ligation of major histocompatibility complex (MHC) class I molecules on the surface of EC triggers phosphorylation of Akt, PI3K, and recruitment of PI3K and Akt into a signaling unit with focal adhesion kinase. Signaling through class I also stimulated phosphorylation of Bad and upregulated expression of Bcl-2 and Bcl-xL. Pretreatment of EC with the PI3K inhibitor wortmannin blocked class I-mediated expression of Bcl-2, but not Bcl-xL, suggesting a role for the PI3K/Akt signaling pathway in regulation of class I-induced Bcl-2 expression. The intracellular events initiated by class I ligation were influenced by the concentration of the anti-HLA Ab with the lowest tested concentrations of Ab stimulating the highest level of Akt phosphorylation, Bcl-xL and Bcl-2 expression. Consistent with the in vitro experiments, analysis of biopsy samples from heart transplant recipients with evidence of Ab-mediated rejection exhibited increased Bcl-2 expression on the vascular endothelium. These results suggest that exposure of the graft endothelium to low concentrations of anti-HLA Ab may promote cell survival by transducing signals resulting in upregulation of cell survival genes.     

HLA Class I: An unexpected role in integrin β4 signaling in endothelial cells

The production of anti-donor antibodies to HLA class I and class II antigens following transplantation is associated with development of transplant vasculopathy and graft loss. Antibodies against HLA class I (HLA-I) molecules are thought to contribute to transplant vasculopathy by triggering signals that elicit the activation and proliferation of endothelial cells. The proximal molecular events that regulate HLA-I dependent signal transduction are not well understood. We demonstrated a mutual dependency between HLA-I and integrin β4 to stimulate signal transduction and cell proliferation. Similarly, we found that integrin β4-mediated cell migration was dependent upon its interactions with HLA-I molecules. Since integrin β4 has been implicated in angiogenesis and tumor formation, associations between integrin β4 and HLA-I may play an important role in cancer. Further characterization of interactions between HLA-I and integrin β4 may lead to the development of therapeutic strategies for the treatment and prevention of chronic allograft rejection and cancer.     

The PTEN tumor suppressor inhibits human airway smooth muscle cell migration

Airway remodeling in asthma is characterized by increased airway smooth muscle (ASM) mass, accompanied by cell migration. It is well known that the proliferation and migration of ASM cells (ASMCs) play a key role in airway remodeling, but the precise mechanism modulating these cellular events remains unclear. One of the genes most likely to be involved in this process is the phosphatase and tensin homolog (PTEN) gene, whose deletion from chromosome 10 can inhibit the proliferation and migration of many cell types. In this study, we investigated the effects of PTEN on human ASMCs. The cells were infected with recombinant adenovirus containing wild-type PTEN cDNA (Ad-PTEN), and the results were compared with those from the uninfected cells and those infected with the GFP-labeled adenovirus vector. Cell proliferation was measured using the MTT method. Cell migration was determined by wound-healing and transwell assays. The expressions of PTEN, phospho-Akt, Akt, phospho-ERK1/2, ERK1/2, phospho-focal adhesion kinase (FAK) and FAK, were examined by Western blot analysis. The results show that PTEN is expressed endogenously in ASMCs, and that Ad-PTEN inhibits the proliferation and migration of these cells. In addition, the Ad-PTEN treatment decreased the phosphorylation of Akt and FAK but not that of ERK1/2. In conclusion, this study demonstrates that PTEN overexpression inhibits the proliferation and migration of human ASMCs by down-regulating the activity of the Akt and FAK signaling pathways.     

Differential effect of FGF and PDGF on cell proliferation and migration in osteoblastic cells

It has been known that growth factors such as fibroblast growth factor (FGF) and platelet-derived growth factor (PDGF) can promote proliferation and migration in a variety of cell types including osteoblastic cells. However, the mechanism underlying their action has not been clearly defined. The present study was undertaken to examine the effect of FGF and PDGF on cell proliferation and migration and to determine the role of extracellular signal-regulated kinase (ERK) and Akt in action of FGF and PDGF in osteoblastic cells. FGF enhanced proliferation in a dose- and time-dependent manner, whereas it did not affect cell migration. FGF induced a transient activation of ERK, but not Akt, which was inhibited by an inhibitor of MEK, the upstream kinase of ERK, but not by inhibitors of PI3K/Akt (LY294002), epidermal growth factor receptor (EGFR, AG1478), and Src (PP2). FGF-induced proliferation was inhibited by inhibitors of MEK/ERK and Src pathways. Exposure of cells to FGF stimulated transition of cell cycle from the G1 phase to S phase and increased phosphorylation of Rb. FGF-induced phosphorylation of Rb was attenuated by inhibitors of MEK/ERK and Src pathways. Cell migration studies indicated that PDGF stimulated migration, but it had no effect on cell proliferation. PDGF induced activation of ERK and Akt. The ERK activatin was inhibited by the Src inhibitor and the Akt activation was inhibited by inhibitors of EGFR and Src. PDGF-induced migration was inhibited by inhibitors of MEK/ERK, PI3K/Akt, EGFR and Src pathways. Taken together, these findings suggest that the MEK/ERK and Src pathways play an important role in the FGF-induced proliferation and signaling pathways involving MEK/ERK, EGFR, Src and PI3K/Akt mediate the PDGF-induced migration. These data are of importance in understanding the roles of these growth factors in osteoblastic cell proliferation and migration.     

Integrin-linked kinase in the vascular smooth muscle cell response to injury

Integrin-mediated interactions between smooth muscle cells (SMCs) and the extracellular matrix regulate cell migration and proliferation during neointimal hyperplasia. Integrin-linked kinase (ILK) is a serine-threonine kinase and scaffolding molecule that acts downstream of integrin receptors to modulate cell adhesion; therefore, we examined ILK function in SMCs during wound repair. Silencing of ILK expression with siRNA in vitro decreased cell adhesion to fibronectin and accelerated both cell proliferation and wound closure in the cell monolayer; it also resulted in the rearrangement of focal adhesions and diminished central actin stress fibers. Akt and GSK3beta are ILK substrates that are important in cell motility; however, ILK siRNA silencing did not attenuate injury-induced increases in Akt and GSK3beta phosphorylation. Following balloon catheter injury of the rat carotid artery in vivo, a dramatic decrease in ILK levels coincided with both the proliferation and migration of SMCs, which leads to the formation of a thickened neointima. Immunostaining revealed decreased ILK levels in the media and deep layers of the neointima, but increased ILK levels in the subluminal layers of the intima. Taken together, these results suggest that ILK functions to maintain SMC quiescence in the normal artery. A decrease in ILK levels after injury may permit SMC migration, proliferation, and neointimal thickening, and its re-expression at the luminal surface may attenuate this process during later stages of the injury response.     

Pre-exposure to sub-saturating concentrations of HLA class I antibodies confers resistance to endothelial cells against antibody complement-mediated lysis by regulating Bad through the phosphatidylinositol 3-kinase/Akt pathway

Allografts transplanted across HLA-sensitization results in an antibody-mediated rejection known as hyperacute rejection. Depleting anti-graft antibodies from the recipient by plasmapheresis prior to transplantation can prevent this rejection. We developed an in vitro model using polyclonal HLA class I antibodies obtained from highly sensitized patients awaiting transplantation,and analyzed their ability to provide signals following binding to human aortic endothelial cells (EC). Using this model, we show that EC undergo caspase 3-dependent cell death by apoptosis upon exposure to saturating concentrations of HLA class I antibodies and complement accompanied by loss of Akt activation and phosphorylation of Bad. In contrast, exposure of EC to sub-saturating concentrations of HLA class I antibodies conferred resistance towards antibody/complement-mediated lysis termed accommodation. Accommodated EC exhibited reduction in the expression of the adhesion molecules ICAM-1 and VCAM-1 and a significant increase in the expression of anti-apoptotic genes Bcl-xL, Bcl-2 and heme oxygenase-1. Further, induction of phosphatidylinositol 3-kinase (PI3K) and Akt activities that facilitate the phosphorylation of Bad were also noted. In conclusion, exposure of sub-saturating concentrations of HLA class I antibodies results in the induction of PI3K/Akt pathway that confers resistance to endothelial cells against antibody/complement-mediated cell death.     

Effect of a hot water extract of Chlorella vulgaris on proliferation of IEC-6 cells

Chlorella vulgaris, a unicellular microalgae, exerts various biological effects; however their effect on proliferation signaling pathways in normal cells has not been studied. We investigated the effect of hot water extracts of Chlorella vulgaris (CVE) on cell proliferation and related signaling pathways in rat intestinal epithelial cells (IEC-6). CVE increased the expression of insulin-like growth factor-I receptor (IGF-IR) and the phosphorylation of focal adhesion kinase (FAK) and Src. In addition, CVE induced activation of the mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3K)/Akt pathways. We verified the increased phosphorylation of extracellular-signal-related kinase (ERK) and Akt and the increased expression of the PI3K regulatory subunit p85. CVE also influenced the canonical Wnt pathway through increased expression of the nuclear β-catenin, cyclin D1. Tyr-397 of FAK mediates interactions with Src homology?2 (SH2) domains in a number of other signaling proteins, including PI3K, PLC-γ, Shc, Grb7, Src and Nck2. Because CVE induced FAK activation, FAK may affect the Wnt pathway. Addition of a FAK inhibitor decreased the expression of nuclear β-catenin, cyclin D1 and c-myc, and increased the expression of cytosolic β-catenin. We conclude that CVE stimulated proliferation of IEC-6 cells via the MAPK, PI3K/Akt and canonical Wnt pathways, and that this affected the canonical Wnt pathway.     

Mechanisms of human smooth muscle cell proliferation and transplant vasculopathy induced by HLA class I antibodies: In vitro and in vivo studies

Vascular smooth muscle cells (SMC) play an important role in the pathophysiology of transplant vasculopathy (TV), a major cause of late death in patients receiving an organ transplant. In this review we describe the proliferative effect in vitro and in vivo of HLA class I antibodies on human SMC. We have developed an experimental model using segments of human mesenteric arteries transplanted in the position of the infrarenal aorta in immunodeficient mice (SCID/beige). Weekly injections of transplanted mice with a monoclonal antibody towards HLA class I provoked typical lesions of TV after 6 weeks in the human graft while transplanted mice receiving an irrelevant antibody did not develop any significant lesion. In vitro, the anti-HLA antibodies were mitogenic to SMC and we showed that they activate a stress-induced signaling pathway implicating matrix metalloproteinases (MMP) and neutral sphingomyelinase 2 (nSMase-2). The proliferative effect of anti-HLA antibodies could be blocked by pharmacological inhibitors or by siRNA. Administration of pharmacological inhibitors diminished the development of TV in grafted mice injected with anti-HLA antibodies demonstrating an important role of the MMP/nSMase-2 pathway in antibody-induced TV. This observation opens new perspectives for the management of TV in clinical settings.     

虫草素通过ERK1/2、Ezrin和Akt信号通路抑制胆囊癌细胞SNU-308的增殖和迁移

目的:探讨虫草素对胆囊癌细胞SNU-308增殖和迁移的影响及其分子机制。方法:MTT法和平板集落形成实验检测不同浓度虫草素对胆囊癌SNU-308细胞活力和集落形成能力的影响;Annexin V/PI双染法检测细胞凋亡率;Western blot法检测细胞凋亡和自噬相关蛋白以及Akt、ERK1/2和Ezrin蛋白的磷酸化水平;免疫荧光染色法检测细胞内LC3的表达水平;划痕愈合实验和Transwell实验检测虫草素对胆囊癌细胞迁移能力的影响;划痕实验检测Akt抑制剂和ERK1/2抑制剂及Ezrin基因沉默对细胞迁移能力的影响。结果:虫草素可显著抑制胆囊癌细胞的活力和集落形成能力(P0.05)。流式细胞术结果显示,虫草素可诱导胆囊癌细胞凋亡(P0.05)。Western blot结果显示,虫草素处理后Bcl-2表达降低,Bax、细胞色素C(Cyto C)、Fas、Fas L和cleaved caspase-3蛋白水平升高,自噬标识蛋白LC3-II/I比例和beclin 1表达上调(P0.05)。免疫荧光染色结果显示,虫草素处理后SNU-308细胞胞浆中LC3荧光颗粒的数量明显增多。划痕实验和Transwell实验结果显示虫草素可抑制细胞迁移(P0.05)。虫草素明显抑制Akt、ERK1/2和Ezrin蛋白的磷酸化水平(P0.05)。Ezrin基因沉默及Akti-1/2和GDC-0994均可抑制胆囊癌细胞的迁移作用(P0.05)。结论:虫草素通过诱导凋亡和自噬抑制胆囊癌细胞的增殖和迁移,其机制可能与调控ERK1/2,Ezrin和Akt信号通路有关。     

CHK1抑制剂SCH900776抑制胶质瘤细胞U251的增殖及迁移

目的:本研究以胶质瘤细胞U251为实验用细胞株,探讨细胞周期检测点激酶1(CHK1)抑制剂SCH900776对其增殖及迁移的影响。方法:MTT法和细胞集落形成实验观察SCH900776对细胞增殖的影响;流式细胞术分析SCH900776对细胞周期分布的影响;划痕实验观察SCH900776对细胞迁移的影响;Western blot实验检测相关蛋白的表达水平。结果:SCH900776能够明显抑制U251细胞的增殖,诱导细胞发生S期或G2/M期阻滞,同时下调细胞分裂周期蛋白2(Cdc2)和p-Cdc2的水平;SCH900776对细胞迁移表现出明显的抑制作用;Western blot结果表明,SCH900776可升高p38丝裂原活化蛋白激酶(MAPK)的磷酸化水平,同时抑制蛋白激酶B(Akt)的磷酸化激活。结论:CHK1抑制剂SCH900776能够抑制胶质瘤细胞U251的增殖与迁移,其机制可能与其激活p38MAPK和抑制Akt活性相关。     

Curcumin inhibits oral squamous cell carcinoma proliferation and invasion via EGFR signaling pathways

Epidermal growth factor receptor (EGFR) is an effective molecular target of anti-cancer therapies. Curcumin is known to inhibit growth, invasion and metastasis by downregulating EGFR expression in some cancer cells. However, the mechanism underlying the effect of curcumin in human oral squamous cell carcinoma (OSCC) remains unclear. In this study, we investigated the efficacy of curcumin on proliferation and invasion in SCC-25 cell line. We also explored the effect of curcumin on the activition of EGFR and its downstream signaling molecules Akt, ERK1/2 and STAT3. Furthermore, we examined the inhibition effect of curcumin on EGF-induced EGFR phosphorylation and SCC-25 cells invasion. Our results showed that curcumin inhibited SCC-25 cells proliferation and induced G2/M phase arrest in a dose-dependent manner. Curcumin also inhibited SCC-25 cells invasion and downregulated MMP-2, MMP-9, uPA and uPAR expression. We further revealed that curcumin regulated the p-EGFR and EGFR downstream signaling molecules including Akt, ERK1/2 and STAT3. Finally, our data showed that crucumin reduced the EGF-induced phosphorylation of EGFR and suppressed EGF-triggered SCC-25 cells invasion. Taken together, our results suggest that curcumin reduced SCC-25 cells proliferation and invasion through inhibiting the phosphorylation of EGFR and EGFR downstream signaling molecules Akt, ERK1/2 and STAT3.     

叶酸通过下调ERK1/2信号通路抑制血管平滑肌细胞增殖和迁移

目的:探讨叶酸(folic acid,FA)对血管平滑肌细胞(VSMCs)增殖和迁移的影响及其机制。方法:取SD大鼠的主动脉,采用组织贴块法培养VSMCs,随机分组进行实验。采用CCK-8和Ed U法检测叶酸对VSMCs活力和增殖能力的影响。采用划痕实验和Transwell法检测叶酸对VSMCs迁移和侵袭的影响。采用Western blot法检测细胞增殖核抗原(PCNA)蛋白表达以及血小板源性生长因子受体(PDGFR)和细胞外信号调节激酶1/2(ERK1/2)蛋白的磷酸化水平。结果:叶酸抑制血小板源性生长因子(PDGF)诱导的VSMCs的活力,并呈浓度依赖性(P0.05)。叶酸抑制PDGF诱导的VSMCs的迁移,并呈浓度依赖性(P0.05)。叶酸降低PCNA表达和PDGFR磷酸化水平,并抑制PDGF激活的ERK1/2信号通路。结论:叶酸降低PDGF诱导的VSMCs PCNA和p-PDGFR蛋白水平,下调ERK1/2信号通路,从而抑制VSMCs的增殖和迁移。     

Specificity and function of immunoglobulin superfamily NK cell inhibitory and stimulatory receptors

Summary: Human NK cells express clonally distributed receptors specific for HLA-A, -B and -C molecules. These receptors belong to the immunoglobulin superfamily and can be functionally distinguished as inhibitory or stimulatory Inhibitory receptors block NK-cell-mediated cytotoxicity upon binding to HLA class I ligands. This function is mediated by phosphorylation of cytoplasmic tyrosines, which recruit the protein tyrosine phosphatase SHP-1. Stimulatory receptors also bind HLA class I, lack cytoplasmic tyrosine-based motifs, and trigger NK cytotoxicity and proliferation. Both types of receptor are characterized by a limited diversity allowing for recognition of distinct class I supertypic epitopes. This limited diversity is counterbalanced by the expression of different combinations ill inhibitory and stimulatory receptors with self and/or non-self HLA class I specificities on distinct NK cell clones. This peculiar strategy allows NK cells to detect loss of MHC class I molecules on autologous transformed and virally infected cells with maximal sensitivity.     

Retinoic acid inhibits airway smooth muscle cell migration

Airway remodeling in chronic asthma is characterized by increased smooth muscle mass that is associated with the reduction of the bronchial lumen as well as airway hyperresponsiveness. The development of agents that inhibit smooth muscle growth is therefore of interest for therapy to prevent asthma-associated airway remodeling. All-trans retinoic acid (ATRA) suppresses growth of vascular smooth muscle cells (SMCs) from the systemic and pulmonary circulation. The present study investigated the effects of ATRA on human bronchial (airway) SMCs. Human bronchial SMCs were found to express mRNAs for retinoic acid receptor (RAR)-alpha, -beta, -gamma, and retinoid X receptor (RXR)-alpha, -beta, but not RXR-gamma. Although ATRA was not effective in inhibiting proliferation or in inducing apoptosis in airway SMCs, we found that ATRA (0.2-2 microM) inhibited the SMC migration in response to platelet-derived growth factor (PDGF), as determined in a modified Boyden chamber assay. Both RAR and RXR agonists also blocked PDGF-induced airway SMC migration. ATRA also inhibited PDGF-induced actin reorganization associated with migration. PDGF-induced actin reorganization and migration were blocked by inhibitors of phosphatidylinositol 3 kinase (PI3K) and Akt. However, migration was blocked by inhibitors of the MEK/ERK pathway, with no effect on cytoskeletal reorganization. ATRA suppressed PDGF-induced Akt activation without influencing ERK activation. RAR was found to form protein-protein interactions with the p85 PI3K subunit. These results suggest that retinoic acid inhibits airway SMC migration through the modulation of the PI3K/Akt pathway.     

Differential phosphorylation of functional tyrosines in CD19 modulates B‐lymphocyte activation

CD19 is a B‐cell transmembrane molecule that is critical for B‐cell activation. CD19 serves as a scaffold protein for key signal transduction molecules including Lyn, PI3K, and Vav, by providing docking sites for these molecules via phosphorylation of CD19‐Y⁵¹³, CD19‐Y⁴⁸², and CD19‐Y³⁹¹. We investigated the process of CD19 tyrosine phophorylation during B‐cell activation using Ab specific for each of these phosphorylated tyrosines. BCR engagement induced differential tyrosine phosphorylation, as CD19‐Y⁵¹³ phophorylation occurred first, and CD19‐Y⁴⁸² phosphorylation was delayed and transient. Different BCR isotypes exhibited distinct patterns of CD19 phosphorylation: IgG‐BCR ligation resulted in faster phosphorylation of CD19‐Y⁵¹³ and more intense phosphorylation of CD19‐Y³⁹¹ than IgM‐BCR ligation. This affected CD19‐mediated downstream pathways involving Vav, PI3K, and Akt. Additionally, the phosphorylation profile of CD19 differed distinctly according to its plasma membrane location. CD19 phosphorylated at Y⁵¹³ was almost exclusively located within lipid rafts, whereas phosphorylated Y⁴⁸² and Y³⁹¹ were found both inside and outside of the rafts. Furthermore, the phosphorylation of all three tyrosines was remarkably enhanced and prolonged following the simultaneous stimulation of BCR and CD40. Thus, variations in phosphorylation patterns may contribute to the complexity of CD19‐regulated signal transduction.     

Quantification by flow cytofluorimetry of HLA class I molecules at the surface of murine cells transformed by cloned HLA genes

A method allowing quantitative analysis of the expression of foreign antigens at the surface of transformed cells is described. Aminoethyl-Sephadex G-25 beads labelled with different amounts of fluorescein isothiocyanate (FITC) were used to calibrate an Epics V cell sorter. The quantity of FITC molecules bound per bead was found to be a linear function of relative fluorescence intensity expressed by channel number for intermediate and high levels of fluorescence and a non-linear function for low levels. The lowest limit of detectable fluorescence was 3400 FITC molecules bound per bead. Using FITC-conjugated monoclonal antibodies (m.Ab.) the number of HLA class I molecules expressed at the surface of murine LMTK- (H-2Kk) cells transfected by cloned HLA class I genes was estimated and compared with the amount expressed on human B (Raji) and T (MOLT 4) lymphoblastoid reference cells. Murine transformed cells expressed approximately 3 times less HLA class I determinants per surface unit (micrometer 2) than Raji cells and 1.4 times less than MOLT 4 cells. Similar results were obtained by Scatchard analysis of the same populations using radiolabelled m.Ab. A detailed analysis of fluorescent cells showed that 5-20% of transformed cells expressed less than 33,000 HLA class I molecules/cell whereas most MOLT 4 cells exhibited at least 280,000 molecules/cell and the majority of Raji cells more than 700,000 molecules/cell. The expression of foreign antigen did not reduce the amount of H-2Kk molecules at the surface of transformed cells (mean of 350,000 molecules/cell).     

Calpain-mediated regulation of the distinct signaling pathways and cell migration in human neutrophils

We studied the mechanisms underlying calpain inhibition-mediated human neutrophil migration. MAPKs, including ERK, p38, and JNK, MEK1/2, MAPK kinase 3/6 (MKK3/6), PI-3K/Akt, c-Raf, and p21-activated kinase (PAK; an effector molecule of Rac) were rapidly (within 30 s) activated in neutrophils upon exposure to calpain inhibitors (PD150606 and N-acetyl-Leu-Leu-Nle-CHO) but not PD145305 (inactive analog of PD150606). Following activation of these pathways, neutrophils displayed active migration (chemotaxis), which was sustained for more than 45 min. The studies with pharmacological inhibitors suggest that calpain inhibition-mediated neutrophil migration is mediated by activation of MEK/ERK, p38, JNK, PI-3K/Akt, and Rac. NSC23766 (Rac inhibitor) and pertussis toxin (PTX) suppressed calpain inhibitor-induced phosphorylation of distinct signaling molecules (PAK, c-Raf, MEK1/2, ERK, MKK3/6, p38, JNK, and Akt) as well as cell migration, suggesting that the PTX-sensitive G protein and Rac axis may be a possible key target of calpain inhibitors. Differentiated neutrophil-like HL-60 cells but not undifferentiated cells displayed cell migration and activation of MAPKs and PI-3K/Akt on calpain inhibition. These findings suggest that constitutively active calpain negatively regulates activation of the distinct signaling pathways and cell migration in resting neutrophils, and this regulatory system develops during differentiation into mature neutrophils.     

Blockade of integrin beta3-FAK signaling pathway activated by osteopontin inhibits neointimal formation after balloon injury.

BACKGROUND: Osteopontin (OPN) promotes the migration and adhesion of vascular smooth muscle cells (VSMCs) through cell surface receptor, integrin beta3. In order to elucidate the signaling pathway by which OPN is involved in neointimal formation, we focused on integrin beta3-focal adhesion kinase (FAK) upon VSMC migration. METHODS: The integrin beta3 and FAK expression in VSMC and in neointima was detected by Western blot and immunohistochemistry staining. FAK phosphorylation induced by OPN was verified using a linear OPN 13 peptide containing RGD motif and anti-OPN antibody. The role of integrin beta3-FAK pathway in VSMC adhesion and migration induced with OPN was tested by the overexpression of FAK-related nonkinase and integrin beta3 cytoplasmic domain. RESULTS: The results showed that OPN increased integrin beta3 expression and induced rapid and transient FAK phosphorylation. Inhibition of the phosphorylation of FAK significantly suppressed VSMC migration induced by OPN. Similarly, blockade of the interaction of integrin beta3 with OPN inhibited VSMC adhesion induced by OPN. The experiment, in vivo, demonstrated that OPN expression level was consistent with neointimal thickening. Administration of anti-OPN antibody for blocking OPN function suppressed integrin beta3 and FAK expression induced by balloon injury, and neointimal thickening was inhibited. CONCLUSIONS: These data indicate that integrin beta3-FAK signaling modulates OPN-induced VSMC migration during neointimal formation.     

Modulation of cell spreading and migration by pp125FAK phosphorylation.

We provide evidence for both matrix-dependent and pp60v-src tyrosine kinase-dependent modulation of cell migration via tyrosine phosphorylation of pp125FAK, a focal adhesion kinase, thought to be involved in integrin-mediated signaling. Enhanced pp125FAK tyrosine phosphorylation and cell spreading was associated with decreased migration. Cells plated on type I collagen were less spread and exhibited lower levels of pp125FAK tyrosine phosphorylation and faster migration rates compared with cells on fibronectin that were well spread, which exhibited enhanced levels of pp125FAK tyrosine phosphorylation and slower migration rates. Inside-out signaling via expression of pp60v-src or its kinase-negative mutant caused a decrease in cell migration by changing the extent of pp125FAK tyrosine phosphorylation to above or below the levels obtained with control cells plated on fibronectin. Hence, pp125FAK tyrosine phosphorylation appears to play a role in the signaling cascade pathway involved in regulation of extracellular matrix-modulated, integrin-mediated cell migration.     

重组人促红细胞生成素与骨髓间充质干细胞的迁移及黏附

背景：促红细胞生成素可促进内皮祖细胞的增殖分化并增强其黏附性。 目的：观察重组人促红细胞生成素干预对人骨髓间充质干细胞迁移和黏附能力及相关细胞信号传导通路的影响。 方法：体外培养人骨髓间充质干细胞,使用重组人促红细胞生成素干预第6代人骨髓间充质干细胞。分别用PI3K/Akt通路特异抑制剂Ly294002或p38MAPK通路特异激动剂anisomycin或ERK1/2通路特异抑制剂U0126预处理。 结果与结论：重组人促红细胞生成素可使人骨髓间充质干细胞的PI3K/Akt通路磷酸化水平升高,抑制p38MAPK通路磷酸化水平,对人骨髓间充质干细胞的ERK通路和总Akt、总p38MAPK水平无明显影响。重组人促红细胞生成素作用组中迁移细胞数目显著高于对照组(P < 0.01),黏附细胞数亦明显增加(P < 0.01),PI3K/AKT通路特异抑制剂Ly294002预处理后重组人促红细胞生成素对迁移能力的作用消失,p38MAPK通路特异激动剂anisomycin预处理对两种作用影响均不明显。提示重组人促红细胞生成素具有增强人骨髓间充质干细胞迁移和黏附能力的作用,其增强迁移能力的作用与激活人骨髓间充质干细胞的PI3K/Akt通路有关,但是它对黏附能力的作用与PI3K/Akt和p38MAPK通路均无关。