On how insulin may influence ageing and become atherogenic throughout the insulin-like growth factor-1 receptor pathway: in vitro studies with human vascular smooth muscle cells

BACKGROUND: It is known that growth factors play a role in ageing and atherogenesis, and insulin develops mitogenic activity in vitro. OBJECTIVES: This study focuses on the pathway by which insulin induces proliferation and mobility in vascular smooth muscle cells (SMCs) compared with that of insulin-like growth factor-1 (IGF-1), because they are two basic phenomena for atherogenesis that could also help to understand the role of insulin in the ageing process. METHODS: Bromodeoxyuridine DNA incorporation, chemotaxis and the appearance of membrane ruffles were measured in cultured SMCs after incubation with insulin or IGF-1 in the presence of insulin or IGF-1 receptor-blocking antibodies. RESULTS: Insulin-induced SMC proliferation through the IGF-1 receptors; indeed, the blockade of insulin receptors does not inhibit the mitogenic influence of insulin. On the contrary, insulin-induced cell migration was inhibited by blocking the insulin receptor but not the IGF-1 receptor. Nevertheless, in less differentiated SMCs from non-confluent cultures, the migratory response was significantly higher and insulin lost its receptor specificity. It was stimulated through receptors both for insulin and IGF-1. In these cases the IGF-1 action was similar. Insulin-induced F-actin rearrangements took place through both types of receptors, but IGF-1 was a little more specific through its own receptors. CONCLUSION: The pathway activated by insulin to induce SMC proliferation is not different from that of IGF-1, whereas the unspecific mechanism inducing mobility in growing cells seems to be related to a higher sensitivity response. Cells with the highest mitotic activity have the highest mobility in which stimulation of receptor specificity is lost for either insulin or IGF-1. Extrapolating these results to in vivo, insulin could become relevant for inducing stabilization and also side effects in ageing.     

Smooth muscle cell matrix metalloproteinase production is stimulated via alpha(v)beta(3) integrin

This study tests the hypothesis that alpha(v)beta(3) integrin receptors play a critical role in smooth muscle cell (SMC) migration after arterial injury and facilitate migration through the upregulation of matrix metalloproteinase (MMP) activity. We showed that beta(3) integrin mRNA was upregulated by SMCs in the balloon-injured rat carotid artery in coincidence with MMP-1 expression and early SMC migration. Treatment with the beta(3) integrin-blocking antibody F11 significantly decreased SMC migration into the intima at 4 days after injury, from 110.8+/-30.8 cells/mm(2) in control rats to 10.29+/-7.03 cells/mm(2) in F11-treated rats (P=0.008). By contrast, there was no effect on medial SMC proliferation or on medial SMC number in the carotid artery at 4 days. In vitro, we found that human newborn SMCs produced MMP-1 but that adult SMCs did not. This was possibly due to the fact that newborn SMCs expressed alpha(v)beta(3) integrin receptors, whereas adult SMCs did not. Stimulation of newborn (alpha(v)beta(3)+) SMCs with osteopontin, a matrix ligand for alpha(v)beta(3), increased MMP-1 production from 114.4+/-35.8 ng/mL at 0 nmol/L osteopontin to 232.5+/-57.5 ng/mL at 100 nmol/L osteopontin. Finally, we showed that stimulation of newborn SMCs with platelet-derived growth factor-BB and osteopontin together increased the SMC production of MMP-9. Thus, our results support the hypothesis that SMC alpha(v)beta(3) integrin receptors play an important role in regulating migration by stimulating SMC MMP production.     

Serum starvation and growth factor receptor expression in vascular smooth muscle cells

BACKGROUND: Smooth muscle cell (SMC) proliferation in atherosclerosis is regulated through the interaction of growth factors like platelet-derived growth factor-BB (PDGF-BB) and insulin-like growth factor-1 (IGF-1) and their receptors (R). We hypothesized that serum starvation of SMCs may affect PDGFbeta-R and IGF-1-R expression and, consequently, the effect of their cognate ligands on SMC survival/proliferation. METHODS AND RESULTS: Serum starvation significantly increases PDGFbeta-R but not IGF-1-R mRNA and protein expression in SMCs. PDGF-BB stimulates cell survival but not proliferation in serum-starved SMCs of the synthetic phenotype, whereas SMCs of the contractile phenotype respond to PDGF-BB by a significant increase in proliferation. Immunohistochemical analysis of coronary atherosclerotic lesions reveals PDGFbeta-R expression in SMCs in the lamina fibromuscularis, but not in the media and in healthy parts of the arterial wall. No such differential expression was observed for IGF-1-R. CONCLUSIONS: Differential regulation of PDGFbeta-R and IGF-1-R expression by serum starvation might represent a mechanism for the control of SMC survival/proliferation in atherogenesis and restenosis. The distribution of PDGFbeta-Rs and IGF-1-Rs in atherosclerotic lesions may indicate an effect of serum starvation on SMCs in the arterial wall.     

Direct and indirect effects of pulsatile shear stress on the smooth muscle cell.

BACKGROUND: Anastomotic intimal hyperplasia is still an unsolved problem after small caliber prosthetic bypass grafting. Oscillatory turbulent flow occurs at the end to side anastomosis, and produces various effects on smooth muscle cells (SMCs) and endothelial cells (ECs), which compose intimal hyperplasia. We examined the influences of pulsatile oscillating shear stress on smooth muscle cells mitogenic activity induced by sheared endothelial cells. METHODS:1) Smooth muscle cells were cultured under three different pulsatile shear conditions (mean: 0, 6, and 60 dyne/cm2). 2) Endothelial cells were cultured under both static and sheared condition (mean: 60 dyne/cm2). Using the conditioned media from each well, SMCs were cultured under static and sheared conditions (60 dyne/cm2). Four groups of SMCs were devised by combining the two types of media and the two culture conditions. SMC colony spreading distances were measured as an index of combined migration and proliferation activity. An MTT assay and a cell counting assay were used to determine the proliferation activities of SMCs. RESULTS: 1) SMC spreading activity was suppressed by shear stress. SMC proliferative activity was stimulated by pulsatile turbulent shear stress. 2) SMC spreading activity was stimulated by mitogens derived from ECs under shear stress. However, this augmented SMC spreading activity was attenuated under sheared conditions. The mitogens derived from ECs under pulsatile shear stress had no effects on SMC proliferation activity. CONCLUSIONS: Pulsatile oscillating shear stress attenuates SMC migration activity induced by EC-denve mitogens and stimulates SMC proliferative activity.     

Galectin 1 modulates attachment, spreading and migration of cultured vascular smooth muscle cells via interactions with cellular receptors and components of extracellular matrix

Galectin 1 (Gal-1), a lactose-binding lectin, is a component of vascular extracellular matrix and secreted by human vascular smooth muscle cells (SMCs). The purpose of this study was to investigate a possible role of Gal-1 in controlling adhesion and migration of cultured human vascular SMCs. Gal-1 co-localised with laminin and cellular fibronectin in extracellular matrix (ECM) secreted by cultured human vascular SMCs. Recombinant glutathione S-transferase (GST)-Gal-1 fusion protein bound to laminin and cellular fibronectin in ELISA. GST-Gal-1 inhibited SMC attachment to laminin via interactions with both SMCs and laminin. GST-Gal-1 inhibited SMC spreading on plastic or on laminin, but not on cellular fibronectin. GST-Gal-1 modulated SMC migration on laminin and inhibited migration on cellular fibronectin. GST-Gal-1 bound to several 35S-labelled proteins in SMC extracts including laminin and alpha1beta1 integrin, identified by depletion of SMC protein extracts with respective antibodies. We conclude that Gal-1 is able to modulate SMC attachment, spreading and migration via interactions with ECM proteins and alpha1beta1 integrin.     

Production of tissue collagenase (matrix metalloproteinase 1) by human aortic smooth muscle cells in response to platelet-derived growth factor.

The production of the precursor of tissue collagenase/matrix metalloproteinase 1 (proMMP-1) by cultured human aortic medial smooth muscle cells (SMCs) was significantly enhanced by the treatment of the cells with platelet-derived growth factor (PDGF), interleukin 1 or 12-O-tetradecanoylphorbol-13-acetate (TPA). The response to PDGF of SMCs exhibited a tendency to be age-dependent: only SMCs obtained from older individuals (age: 54, 56, 72 and 74 years) responded to PDGF and synthesized proMMP-1, but not SMCs from young individuals (age: 10, 16 and 41 years), and weak responsiveness with a 19-year-old individual. On the other hand, induction of proMMP-1 synthesis in SMCs by TPA was not discriminated by age. The synthesis of two other related matrix metalloproteinases was also examined. Matrix metalloproteinase 2 was found to be constitutively expressed in zymogen form in SMCs and its synthesis was not affected by the treatments with PDGF, interleukin 1 or TPA. The synthesis of matrix metalloproteinase 3 (stromelysin) was not detected in SMCs from both young and old individuals even after the treatment with PDGF, interleukin-1, prostaglandin E2 or TPA. The ability of SMCs to synthesize and secrete proMMP-1 in response to PDGF suggests that this enzyme plays an important role in the migration of PDGF-stimulated SMCs from the media into the intima of aorta and the eventual formation of atherosclerotic plaques.     

The expression of IGFs and IGF binding proteins in human carotid atherosclerosis, and the possible role of IGF binding protein-1 in the regulation of smooth muscle cell proliferation

ObjectiveProliferation of smooth muscle cells (SMCs) in the fibrous cap of atherosclerotic lesions has been proposed to be important for plaque stability. Since the insulin-like growth factor (IGF) system has been implicated to play a role in atherosclerosis and plaque stability, we investigated the expression of members of the IGF system in carotid plaques, in particular IGFBP-1 and its role in the regulation of SMC proliferation.Methods and resultsGene expression profiles of the IGF system in 164 human carotid plaques obtained from our Biobank of Karolinska Endarterectomies (BiKE) were analyzed. Expression of IGFBP-1 mRNA was significantly increased in carotid plaques compared with normal iliac arteries in contrast to IGF-1, IGF-2, and IGFBP-3 to IGFBP-6. The expression of IGFBP-1 mRNA correlated positively to that of CD163, CD68, IL-1β, IL-6, TNFα, IGFBP-4 and IGFBP-5. Immunohistochemistry demonstrated co-localization of IGFBP-1 with SMCs and macrophages. In vitro studies showed that IL-1β, IL-6 and TNFα stimulated IGFBP-1 mRNA expression in SMCs. IGFBP-1 stimulated SMC proliferation through ERK1/2 activation but independently of the IGF-1 receptor. In addition, IGFBP-1 modulated the effect of IGF-1 on SMC proliferation and ERK1/2 activation.ConclusionsOur results demonstrate that IGFBP-1 mRNA and protein is detected at increased levels in human carotid plaques, possibly as a consequence of plaque inflammation. IGFBP-1 affects SMC proliferation and may be involved in the regulation of plaque stability.     

胰岛素样生长因子-1对胃平滑肌细胞合成干细胞因子的作用

目的 探讨胰岛索样生长因子-1(IGF-1)对胃平滑肌细胞(SMC)及其合成的干细胞因子(SCF)的影响.方法 使用酶解法原代培养胃SMC,在进行-actin鉴定后,IGF-1组于细胞培养液中分别加入不同浓度的IGF-1(0、50、100、150ìg/L),抗IGF-1组于细胞培养液中加入IGF-1(100μg/L)和IGF-1α受体(IGF-1Rα)抗体(浓度分别为0、50、100,150μg/L),分别培养24 h.以四甲基偶氮唑盐(MTT)比色试验检测细胞增殖程度,以Western印迹法、逆转录(RT)-PCR、酶联免疫吸附试验(ELISA)检测细胞中及细胞上清中SCF的表达情况.结果 IGF-1可促进胃SMC增殖和SCF合成增加,离体实验中100μg/L可能是IGF-1促进胃SMC增殖和SCF合成的有效终浓度;IGF-1Rα抗体可抑制胃SMC增殖和SCF合成,抑制作用呈浓度依赖性.结论 IGF-1介导胃SMC合成SCF增加.     

Activation of vascular smooth muscle cells by TNF and PDGF: overlapping and complementary signal transduction mechanisms

OBJECTIVE: Because tumor necrosis factor-alpha (TNF) has been implicated in the pathogenesis of vein graft neointimal hyperplasia, we sought to determine mechanisms by which TNF could induce proliferative and migratory responses in smooth muscle cells (SMCs). METHODS AND RESULTS: In rabbit jugulocarotid interposition vein grafts, SMCs expressed TNF as early as four days postoperatively. In rabbit aortic SMCs, TNF and platelet-derived growth factor (PDGF) elicited comparable migration (1.7-fold/basal), and their effects were partially additive. In contrast, while TNF failed to promote SMC [(3)H]thymidine incorporation alone, it doubled the [(3)H]thymidine incorporation observed with PDGF alone. To gain mechanistic insight into these phenomena, we found that TNF and PDGF each activated p38(mapk) equivalently in SMCs, but that PDGF was two to three times more efficacious than TNF in activating SMC extracellular signal-regulated kinases (ERK) 1 and 2 and phosphoinositide 3-kinase. However, only TNF activated NF kappa B. SMC [(3)H]thymidine incorporation that depended on TNF, but not PDGF, was abolished by overexpression of a dominant-negative I kappa B alpha mutant. Inhibition of ERK activation by U0126 reduced SMC migration stimulated only by PDGF (by 35%, P<0.05), but not by TNF. Inhibition of phosphoinositide 3-kinase by LY294002, however, significantly reduced both TNF- and PDGF-stimulated chemotaxis (by 38-54%, P<0.05). In contrast, both U0126 and LY294002 abolished SMC [(3)H]thymidine incorporation induced by either TNF, PDGF, or both agonists. CONCLUSIONS: In primary rabbit SMCs, TNF promotes migration and mitogenesis through signaling mechanisms that are both distinct from and overlapping with those employed by PDGF. TNF-induced SMC mitogenesis requires complementary co-stimulation with other growth factors.     

Expression levels and functional aspects of the hyaluronan receptor CD44. Effects of insulin, glucose, IGF-I, or growth hormone on human arterial smooth muscle cells

An increased amount of hyaluronan (HA) in the arterial wall is a feature of the diabetic macroangiopathy. The functional consequences of accumulated HA are mediated through binding to CD44. The regulation of this receptor by diabetic metabolic and hormonal factors is, however unknown. The objective of this study was to examine the influence of glucose, insulin, insulin-like growth factor I (IGF-I), and human growth hormone (hGH) on the formation and function of the HA receptor CD44 in cultures of human aortic smooth muscle cells (SMCs). Migration of nonproliferating SMCs were determined by estimating the area covered by cells 6 days after removal of a barrier. Cellular content of standard CD44 and its isoforms, CD44v3 and CD44v6, and HA-binding capacity were measured using a modified enzyme-linked immunosorbent assay procedure. The analysis is made either with antibodies against CD44 or with HA as a ligand. The migration assay showed that glucose, insulin, and IGF-I were able to stimulate SMC migration (2 P < .01). Anti-CD44 antibody inhibited the stimulated migration at most concentrations. Insulin increased HA binding at 100 to 1000 micro U/mL insulin (2 P < .03). CD44 expression was only elevated at 1000 micro U/mL insulin (2 P < .03), whereas CD44 content decreased at 2 ng/mL hGH and increased at 16 ng/mL hGH (2 P < .01). Glucose and IGF-I reduced the amount of the variant isoform CD44v3 (2 P < .01) but did not change the amount of total CD44. CD44v6 was not present on human arterial SMCs. In conclusion, the present data obtained with human arterial SMCs in vitro support a role of CD44 and its isoform, CD44v3, in the SMC response to the metabolic and hormonal disorders of diabetes.     

Inhibition of vascular smooth muscle cell adhesion and migration by c7E3 Fab (abciximab): a possible mechanism for influencing restenosis

OBJECTIVES: Brief intravenous administration of chimeric antibody c7E3 Fab during coronary angioplasty has been shown in some studies to provide long term protection against coronary events. Smooth muscle cell (SMC) adhesion and migration are key initial steps in the development of restenosis. The purpose of this study was to investigate the effect of c7E3 Fab on adhesion and migration of SMC to the extracellular matrix (ECM) proteins osteopontin (Opn) and vitronectin (Vn). METHODS: Adhesion of human vascular SMCs to ECM proteins was quantified using a CyQUANT assay kit. Migration of SMCs to Vn, Opn and PDGF was studied using a modified Boyden's chamber migration assay. Integrin expression was determined by immunoprecipitation. RESULTS: c7E3 Fab reduced SMC adhesion on Vn and Opn to 69.2+/-3.3% (P<0.001) and 52.5+/-4.8% (P<0.001) respectively, compared to adhesion without antibody present. This reduction was the same as that for anti-alpha(v)beta(3) integrin antibody LM609 (P=0.5). The combination of anti-alpha(v)beta(5) integrin antibody and c7E3 Fab had a greater effect than either antibody alone (P<0.001). c7E3 Fab reduced SMC migration to Vn and Opn to 51.6+/-8.9% (P<0.001) and 20.3+/-6.1% (P<0.001) respectively, compared to migration in the absence of antibodies. Again, similar results were seen with LM609. PDGF-induced SMC migration was also inhibited by c7E3 Fab (P=0.004) and LM609 (P=0.001), but to much less an extent. The migration SMCs from a culture found not to express the alpha(v)beta(3) integrin was unaffected by these antibodies, strengthening the argument that c7E3 Fab inhibits SMC function via this integrin. CONCLUSIONS: c7E3 Fab inhibits the adhesion and migration of SMCs via the alpha(v)beta(3) integrin. The inhibition, however, is partial, and varied depending on type of ECM protein and alpha(v)beta(3) integrin expression. Some of the clinical benefits of c7E3 Fab may be due to its effect on SMCs.     

JTT-705 blocks cell proliferation and angiogenesis through p38 kinase/p27(kip1) and Ras/p21(waf1) pathways

The excessive proliferation and migration of vascular smooth muscle cells (SMCs) participate in the growth and instability of atherosclerotic plaque. We examined the direct role of a newly developed chemical inhibitor of cholesteryl ester transfer protein, JTT-705, on SMC proliferation and angiogenesis in endothelial cells (ECs). JTT-705 inhibited human coronary artery SMC proliferation. JTT-705 induced the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and extracellular-signal-regulated kinases (ERK) in SMCs. In addition, the anti-proliferative effects of JTT-705 in SMCs were blocked by p38 MAPK inhibitor. JTT-705 induced the upregulation of p-p21(waf1), and this effect was blocked by dominant-negative Ras (N17), but not by inhibitors of p38 MAPK or ERK. In addition, JTT-705 also induced the upregulation of p27(kip1), and this effect was blocked by p38 MAPK inhibitor. Interestingly, culture medium from JTT-705-treated SMCs blocked human coronary artery EC tube formation in an in vitro model of angiogenesis indirectly via a decrease in vascular endothelial growth factor (VEGF) from SMCs and directly via an anti-proliferative effect in ECs. JTT-705 blocked the proliferation of SMCs through the activation of p38 kinase/p27(kip1) and Ras/p21(waf1) pathways, and simultaneously blocked EC tube formation associated with a decrease in VEGF production from SMCs and an anti-proliferative effect in ECs. Our results indicate that JTT-705 may induce a direct anti-atherogenic effect in addition to its inhibitory effect of CETP activity.     

Regulation of Src homology 2-containing protein tyrosine phosphatase by advanced glycation end products: the role on atherosclerosis in diabetes

Advanced glycation end products (AGEs), among the most important causes of atherosclerosis in diabetes mellitus, stimulate the proliferation of smooth muscle cells (SMCs). Smooth muscle cells are central in the formation of atherosclerotic lesions, where they show both increased migration and accelerated proliferation. In investigating how AGEs stimulate SMC proliferation, we focused on protein tyrosine phosphatase, especially Src homology 2-containing protein tyrosine phosphatase (SHP2), which is considered important in regulating cell proliferation. Advanced glycation end products increased activity of SHP2 in the membrane fraction of rat aortic SMCs compared with control bovine serum albumin (P < .05). Upon characterizing the genomic and promoter structure of SHP2, we detected nuclear factor-kappaB (NF-kappaB) binding sites in the promoter area. Advanced glycation end product stimulation increased luciferase activity in cells transfected with SHP2 promoter region including NF-kappaB binding sites (P < .05) and increased SHP2 expression (P < .05). These data indicate that AGE stimulation appears to activate NF-kappaB. Activated NF-kappaB binds to sites on the SHP2 promoter, resulting in increased SHP2 expression, SHP2 activity, and, ultimately, SMC proliferation. It suggests that AGE stimulation induces SMC proliferation via SHP2, underscoring the importance of control of AGE for suppressing macroangiopathy in diabetes mellitus.     

Defibrinogenating effect of batroxobin (Defibrase) in rats and inhibition of migration of human vascular smooth muscle cells by the plasma of batroxobin-treated rats in vitro

The defibrinogenating effect of batroxobin (Defibrase) in male Wistar rats and the inhibitory effects of the plasma of batroxobin-treated rats on the migration of human vascular smooth muscle cells (SMCs) were investigated in vitro. At 1 h after a single intravenous injection of 3.0, 10.0 or 30.0 BU/kg batroxobin (ten rats in each group), the fibrinogen levels in the plasma of the rats decreased to 88.3, 66.2 and 16.5%, respectively, of that in the plasma of control saline-treated rats (261.0+/-26.7 mg/dl). When the plasma from the batroxobin-treated rats was added to Dulbecco's modified Eagle's medium at a concentration of 0.2% for a vascular SMC migration assay and incubated in a modified Boyden's chamber system at 37 degrees C for 24 h, significant inhibitory effects on vascular SMC migration were observed in the 10.0 (P<0.05) and 30.0 BU/kg (P<0.01) batroxobin-treated rats. The plasma of batroxobin-treated rats as well as standard rat fibrinogen induced vascular SMC migration in a fibrinogen content-dependent manner except the plasma of the 30.0 BU/kg batroxobin-treated rats. Moreover, the rat serum (0.1 approximately 5.0%) did not show any activity on vascular SMC migration in the present experimental system. These results indicate that the plasma fibrinogen significantly influences vascular SMC migration, and that the inhibitory effect of the plasma of batroxobin-treated rats on vascular SMC migration is related to the defibrinogenating action of batroxobin in vivo.     

Periostin mediates vascular smooth muscle cell migration through the integrins ανβ3 and ανβ5 and focal adhesion kinase (FAK) pathway

Smooth muscle cell (SMC) migration involves interactions of integrin receptors with extracellular matrix (ECM) and is an important process of neointimal formation in atherosclerosis and restenosis after vascular interventions. Previous studies have shown that periostin (PN), a novel ECM protein, is upregulated in rat carotid artery after balloon injury, and growth factor-stimulated expression of PN promotes SMC migration in vitro. Here, we address the mechanism by which PN–integrin interaction mediates SMC migration in vitro. Aortic SMCs isolated from PN null mice exhibited a significantly reduced ability to migrate and proliferate in vitro. Endogenous PN protein was absent and very low in the culture medium from the primary cultures of PN?/? and wildtype SMCs, respectively. In both types of SMCs, adenovirus-mediated overexpression of HA-tagged PN to a similar extent, which induced a robust cell migration concomitantly with an increase in β3-integrin expression and phosphorylation of FAK (Tyr397). Furthermore, in cultured human SMCs, specific integrin blocking antibodies showed that interactions of PN-ανβ3 and PN-ανβ5, but not PN-β1 integrins, are required for SMC migration. Inhibition of FAK signaling by overexpression of an endogenous FAK inhibitor termed FRNK (FAK-related nonkinase) significantly attenuated FAK (Tyr397) phosphorylation and the SMC migration induced by PN. These results reveal a mechanism whereby PN mediates vascular SMC migration through an interaction with alphaV-integrins (mainly ανβ3) and subsequent activation of FAK pathway.     

Treatment with insulin glargine does not suppress serum IGF-1.

AIMS: A 6-8-fold higher insulin-like growth factor 1 (IGF-1) receptor binding affinity in vitro is reported for the insulin analogue glargine compared with human insulin. This study evaluates the in vivo significance by exploring the growth hormone (GH)-IGF-1 axis. Assuming a higher binding affinity of insulin glargine to pituitary IGF-1 receptors, serum IGF-1 concentrations should decrease via negative feedback. METHODS: In a crossover study, insulin glargine or NPH insulin, respectively, were used in identical doses as basal insulins in treatment periods of 3 weeks. RESULTS: Overall glycaemic control was not different between the treatment regimens. In contrast to the hypothesis, serum IGF-1 concentrations were higher during insulin glargine treatment compared with NPH insulin in patients with Type 1 diabetes (177 +/- 18 vs. 159 +/- 18 microg/l, P < 0.02, n = 17, age 28 +/- 2 years). The effect on IGF-1 was most pronounced in male patients with Type 1 diabetes (174 +/- 11 vs. 146 +/- 10 microg/l, P < 0.02, n = 10), but was not significant in patients with Type 2 diabetes (92 +/- 9 vs. 86 +/- 8 microg/l, NS, n = 25, age 66 +/- 2 years). CONCLUSIONS: In contrast to our hypothesis, serum IGF-1 did not decrease, but rose during insulin glargine treatment, suggesting an absence of relevant IGF-1-like activity of glargine at the level of the pituitary. Improved plasma glucose at dawn during glargine treatment may intensify growth hormone surges and increase IGF-1 synthesis. Significant increases were seen in younger patients, compatible with the higher activity of the GH-IGF-1 axis in this age group.     

Galectin 1 is involved in vascular smooth muscle cell proliferation

OBJECTIVE: Smooth muscle cell (SMC) migration and proliferation are the key steps in the development of atherosclerosis and restenosis. Matricellular proteins have been implicated in cell adhesion, migration and proliferation. Here we investigated the role of the matricellular protein galectin-1 (Gal-1), a beta-galactoside-binding lectin, in SMC proliferation in atheroma and DNA synthesis in cell culture. METHODS: Protein expression was visualised by tissue section immunostaining. RNA expression was analysed using Northern blot analysis. DNA synthesis of human vascular SMCs was determined by 3H-thymidine incorporation. Recombinant glutathione S-transferase-galectin-1 fusion protein (Gal FP) binding to extracellular matrix (ECM) proteins was measured by ELISA. Gal-1 binding to cells and ECM was estimated using 125I-labelled Gal FP. RESULTS: Prominent Gal-1 staining coincided with SMC proliferation in human coronary endarterectomy samples in organoid culture. In cell culture, Gal-1 mRNA was upregulated in growing SMCs. Gal FP increased serum-induced DNA synthesis of human SMCs on plastic or endogenous ECM, but not of a rat PAC1 SM cell line. Also, Gal FP slightly increased SMC adhesion to ECM. SMCs exhibited a complex pattern of receptor-ligand interactions with Gal FP. The Gal-1 binding to SMCs was much stronger than to ECM, produced by these SMCs. We identified new ECM proteins: thrombospondin, vitronectin and osteopontin, which bound to Gal FP in a dose- and beta-galactoside-dependent manner in ELISA. CONCLUSIONS: Gal-1 binding to SMCs was stronger than to ECM, although ECM of atherosclerotic blood vessels contained additional ECM proteins which bound to Gal-1. Gal-1 was upregulated during SMC growth and Gal FP enhanced serum-induced DNA synthesis in SMCs. Overall, Gal-1 upregulation is likely to provide a reinforcement of serum-induced events during vascular injury.     

Phenotypic expression of surface antigens of rabbit aortic smooth muscle cells in culture. Monoclonal antibody, 2P1A2, characteristic of smooth muscle cells present in atherosclerotic plaque, is not correlated with cell proliferation

The expression of smooth muscle cell (SMC) antigens was studied in culture by immunofluorescence and immunoelectron microscopy. As specific SMC markers, we used 2 monoclonal antibodies (MAb), 1PC1 and 2P1A2 which are able to detect atherosclerotic plaques in the rabbit. MAb 1PC1 recognizes an antigen expressed on the cell surface, starting on the 7th day in primary culture after serum activation, and then secreted. On a confluent SMC monolayers this antigen appears outside the cell as an important filamentous network. The kinetics of secretion of this external protein recognized by 1PC1 corresponds to the kinetics of the secretory phenotype described by Chamley-Campbell and Campbell (Atherosclerosis, 40 (1981) 347). 2P1A2 MAb is specific for SMCs exclusively present in the rabbit atherosclerotic plaque. We studied the degree of reactivity of 2P1A2 with SMCs during primary cell culture. This "atherosclerotic" antigen of SMCs recognized by 2P1A2 is expressed in culture conditions by SMCs from rabbit normal media. This antigen appears after 3 days of serum activation, and heparin growth inhibition does not interfere with its expression. 2P1A2 recognized antigen is expressed during all cell cycle phases without amplification. 3 days after fetal calf serum (FCS) stimulation of cells which are in G0/G1, 89% are labelled by 2P1A2, 4 days later G0/G1 positive cells constitute 49%. We conclude that 2P1A2 immunolabelling on the SMC surface reflects an activated state which is not correlated with SMC proliferation.