Activation of extracellular signal-regulated kinases is essential for pressure-induced proliferation of vascular smooth muscle cells.

In hypertension, increased transmural pressure directly influences vascular smooth muscle cells and causes cell proliferation. However, the mechanisms of transmural pressure-induced proliferation of vascular smooth muscle cells are unknown. We investigated the role of various protein kinases in pressure-induced proliferation of vascular smooth muscle cells. Pressure was applied to quiescent rat vascular smooth muscle cells in culture by compressed helium gas in a loading apparatus. Pressure application increased [3H]thymidine incorporation in a time- and pressure-dependent manner and significantly increased the cell number. The pressor response was significantly suppressed by various protein kinase inhibitors for protein kinase C (bisindolylmaleimide I), tyrosine kinase (genistein), extracellular signal-regulated kinase kinase (PD98059; 2'-amino-3'-methoxyflavone) and p38 mitogen-activated protein kinases (MAPK) (SB203580; 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole). Pressure rapidly increased the phosphorylation and activity of extracellular signal-regulated kinases (ERK). Pressure also caused increment of phosphorylation level of p38 MAPK but not that of c-JUN N-terminal protein kinase (JNK). In ERK-deficient cells prepared by transfection of an antisense oligonucleotide for ERK, pressure-induced DNA synthesis was almost abolished. Our results suggest that activation of ERK is essential for pressure-induced DNA synthesis in rat vascular smooth muscle cells, in addition to activation of protein kinase C, tyrosine kinase and p38 MAPK. These processes could be involved in the pathogenesis of hypertension-related atherosclerosis.

Association between plasma lipoprotein(a) and endothelial dysfunction in normocholesterolemic and non-diabetic patients with angiographically normal coronary arteries.

The present study was designed to examine whether elevated levels of lipoprotein(a) (Lp(a)) are related to the impairment of the endothelium-dependent vasoresponse to acetylcholine (ACh) in normocholesterolemic and non-diabetic human normal coronary arteries. ACh (30 microg) was injected into the left main coronary artery of 31 patients (serum low-density cholesterol <160mg/dl and fasting plasma glucose <126mg/dl) with angiographically normal coronary arteries, and the relation between diameter change and lipid levels was analyzed. The mean diameter change of all coronary segments examined (segments 6, 8, 11 and 13) was reduced by 14.6+/-26.5% in response to ACh, but increased by 23.3+/-6.0% in response to nitroglycerin, suggesting endothelial dysfunction in those arteries. The mean diameter change of the left anterior descending artery or left circumflex artery in each patient was negatively correlated only with the level of Lp(a). Stepwise multiple regression analysis also revealed that only Lp(a) among the lipids showed significant correlation with impaired vasodilation (p=0.033). These findings suggest that elevated levels of plasma Lp(a) might be a strong predictor of endothelial dysfunction in normocholesterolemic and non-diabetic subjects.

Expression of profilin, an actin-binding protein, in rat experimental glomerulonephritis and its upregulation by basic fibroblast growth factor in cultured rat mesangial cells.

Profilin binds to actin monomer to regulate actin polymerization, and to phosphatidylinositol 4,5-bisphosphate to inhibit hydrolysis by phospholipase Cgamma1. This study investigated the expression of profilin in rat anti-Thy-1.1 mesangial proliferative glomerulonephritis (GN) and examined the effect of growth factors on its expression in cultured rat mesangial cells. Profilin mRNA was constitutively expressed in isolated glomeruli of untreated rats. However, in glomeruli of anti-Thy-1.1 GN rats, its expression was upregulated beginning on day 1, reaching a peak level on day 4 (3.9-fold versus control glomeruli), and decreased on day 14, as determined by competitive reverse transcription-PCR. Increased expression of profilin protein was confirmed using immunoblotting and immunohistochemistry. Immunoelectron microscopy revealed the presence of profilin in plasma membrane and the rough endoplasmic reticulum of mesangial cells, indicating that profilin was produced in mesangial cells. In cultured rat mesangial cells, expression of profilin mRNA and protein was upregulated by basic fibroblast growth factor but not by platelet-derived growth factor or transforming growth factor-beta. Suppression of profilin expression using an antisense oligonucleotide against profilin inhibited [3H]thymidine uptake. These findings indicated the involvement of profilin in anti-Thy-1.1 GN and suggest that the upregulation of profilin might be involved in the progression of anti-Thy-1.1 GN possibly by affecting cell growth.