Dusica Vasic

Ivabradine Reduces Chemokine-Induced CD4-Positive Lymphocyte Migration

Aims. Migration of CD4-positive lymphocytes into the vessel wall is a critical step in atherogenesis. Recent data suggest that ivabradine, a selective I(f)-channel blocker, reduces atherosclerotic plaque formation in apolipoprotein E-deficient mice, hitherto nothing is known about the mechanism by which ivabradine modulates plaque formation. Therefore, the present study investigated whether ivabradine regulates chemokine-induced migration of lymphocytes. Methods and results. Stimulation of CD4-positive lymphocytes with SDF-1 leads to a 2.0 ± 0.1 fold increase in cell migration (P < .01; n = 7). Pretreatment of cells with ivabradine reduces this effect to a maximal 1.2 ± 0.1 fold induction at 0.1 µmol/L ivabradine (P < .01 compared to SDF-1-treated cells, n = 7). The effect of ivabradine on CD4-positive lymphocyte migration was mediated through an early inhibition of chemokine-induced PI-3 kinase activity as determined by PI-3 kinase activity assays. Downstream, ivabradine inhibits activation of the small GTPase Rac and phosphorylation of the Myosin Light Chain (MLC). Moreover, ivabradine treatment reduces f-actin formation as well as ICAM3 translocation to the uropod of the cell, thus interfering with two important steps in T cell migration. Conclusion. Ivabradine inhibits chemokine-induced migration of CD4-positive lymphocytes. Given the crucial importance of chemokine-induced T-cell migration in early atherogenesis, ivabradine may be a promising tool to modulate this effect.

C-peptide promotes lesion development in a mouse model of arteriosclerosis

Patients with insulin resistance and early type 2 diabetes exhibit an increased propensity to develop a diffuse and extensive pattern of arteriosclerosis. Typically, these patients show elevated serum levels of the proinsulin cleavage product C‐peptide and immunohistochemical data from our group revealed C‐peptide deposition in early lesions of these individuals. Moreover, in vitro studies suggest that C‐peptide could promote atherogenesis. This study examined whether C‐peptide promotes vascular inflammation and lesion development in a mouse model of arteriosclerosis. ApoE‐deficient mice on a high fat diet were treated with C‐peptide or control injections for 12 weeks and the effect on lesion size and plaque composition was analysed. C‐peptide treatment significantly increased C‐peptide blood levels by 4.8‐fold without having an effect on glucose or insulin levels, nor on the lipid profile. In these mice, C‐peptide deposition in atherosclerotic plaques was significantly increased compared with controls. Moreover, lesions of C‐peptide–treated mice contained significantly more macrophages (1.6 ± 0.3% versus 0.7 ± 0.2% positive area; P < 0.01) and more vascular smooth muscle cells (4.8 ± 0.6% versus 2.4 ± 0.3% positive area; P < 0.01). Finally, lipid deposition measured by Oil‐red‐O staining in the aortic arch was significantly higher in the C‐peptide group compared with controls. Our results demonstrate that elevated C‐peptide levels promote inflammatory cell infiltration and lesion development in ApoE‐deficient mice without having metabolic effects. These data obtained in a mouse model of arteriosclerosis support the hypothesis that C‐peptide may have an active role in atherogenesis in patients with diabetes and insulin resistance.

Telmisartan Inhibits CD4-Positive Lymphocyte Migration Independent of the Angiotensin Type 1 Receptor via Peroxisome Proliferator-Activated Receptor-γ

Migration of CD4-positive lymphocytes into the vessel wall represents an important step in early atherogenesis. Telmisartan is an angiotensin type 1 receptor (AT1R) blocker with peroxisome proliferator-activated receptor (PPAR)-&ggr;–activating properties. The present study examined the effect of telmisartan on CD4-positive cell migration and the role of PPAR&ggr; in this context. CD4-positive lymphocytes express both the AT1R and PPAR&ggr;. Stimulation of CD4-positive lymphocytes with stromal cell-derived factor (SDF)-1 leads to a 4.1±3.1-fold increase in cell migration. Pretreatment of cells with telmisartan reduces this effect in a concentration-dependent manner to a maximal 1.6±0.7-fold induction at 10 &mgr;mol/L of telmisartan (P<0.01 compared with SDF-1–treated cells; n=22). Three different PPAR&ggr; activators, rosiglitazone, pioglitazone, and GW1929, had similar effects, whereas eprosartan, a non-PPAR&ggr;–activating AT1R blocker, did not affect chemokine-induced lymphocyte migration. Telmisartans effect on CD4-positive lymphocyte migration was mediated through an early inhibition of chemokine-induced phosphatidylinositol 3-kinase activity. Downstream, telmisartan inhibited F-actin formation, as well as intercellular adhesion molecule-3 translocation. Transfection of CD4-positive lymphocytes with PPAR&ggr; small interfering RNA abolished telmisartans effect on migration, whereas blockade of the AT1R had no such effect. Telmisartan inhibits chemokine-induced CD4-positive cell migration independent of the AT1R via PPAR&ggr;. These data provide a novel mechanism to explain how telmisartan modulates lymphocyte activation by its PPAR&ggr;-activating properties.

C-Peptide: A New Mediator of Atherosclerosis in Diabetes

Diabetes type 2 and insulin resistance are the risk factors for cardiovascular disease. It is already known that atherosclerosis is an inflammatory disease, and a lot of different factors are involved in its onset. C-peptide is a cleavage product of proinsulin, an active substance with a number of effects within different complications of diabetes. In this paper we discuss the role of C-peptide and its effects in the development of atherosclerosis in type 2 diabetic patients.

Proinflammatory Effects of C-Peptide in Different Tissues

Atherosclerosis is well known as an inflammatory disease that can lead to clinical complications such as heart attack or stroke. C-peptide as a cleavage product of proinsulin is in the last few decades known as an active peptide with a number of different effects on microvascular and macrovascular complications in type 2 diabetic patients. Patients with insulin resistance and early type 2 diabetes show elevated levels of C-peptide in blood. Several last findings demonstrated deposition of C-peptide in the vessel wall in ApoE-deficient mice and induction of local inflammation. Besides that, C-peptide has proliferative effects on human mesangial cells. This review discusses recently published proinflammatory effects of C-peptide in different tissues.

C-peptide induces human renal mesangial cell proliferation in vitro, activating Src-kinase, PI-3 kinase and ERK1/2

BACKGROUND Elevated levels of C-peptide have been found in patients with insulin resistance and early type 2 diabetes. These patients are at greater risk to develop micro- and macrovascular complications. Since diabetic nephropathy involves glomerular hyperproliferation, the present study evaluates the role of C-peptide on human renal mesangial cell proliferation. METHODS AND RESULTS C-peptide induces proliferation of human renal mesangial cells in a concentration-dependent manner with a maximal 2.6±0.4-fold induction at 10 nmol/L (P<0.05 compared with unstimulated cells; n=6), as revealed by [3H]-thymidine incorporation experiments. The proliferative effect of C-peptide is prevented by Src-kinase inhibitor-PP2, PI-3 kinase inhibitor-LY294002, and the ERK1/2 inhibitor-U126. Moreover, C-peptide induces phosphorylation of Src, as well as activation of PI-3 kinase and ERK1/2. Furthermore, C-peptide induces cyclin D1 expression as well as phosphorylation of retinoblastoma protein (Rb). CONCLUSIONS These results demonstrate an active role of C-peptide on the proliferation of human renal mesangial cells in vitro involving PI-3 kinase and MAP kinase signaling pathways, suggesting a possible role of C-peptide in glomerular hyperproliferation in patients with diabetic nephropathy.