Risk factors for the development of essential hypertension in a Mongolian population of China: a case-control study.

Lifestyle, habits, diet, and genetics are all important factors associated with the prevalence of hypertension. Many association studies have been performed in the Chinese Han population, whereas data explaining the high prevalence of hypertension in the Mongolian population remain scarce. In the present study, we aimed to determine the factors associated with the development of essential hypertension in Mongolians. A total of 194 hypertensive cases and 201 controls from Dongwu County were enrolled in the study. Demographics, anthropometric and blood biochemical parameters, food intake, lifestyle, habits, education, occupation, and family history were recorded for each subject. Genotype and allele frequencies of six single nucleotide polymorphisms (SNPs) of the kallikrein 1 (KLK1) gene were also examined. Mean body mass index, waistline, hipline, blood sugar, blood urea nitrogen, creatinine, uric acid, total cholesterol, triglyceride, and low-density lipoprotein levels were all significantly higher in the hypertensive group (P<0.01). Hypertensives consumed less milk, vegetables, and fruits, and had higher cigarette, alcohol, and salt intake (P<0.05). There were also less regular physical exercisers and manual workers among the hypertensive group (P<0.05). The mean inheritance rank of the hypertensive group was higher than that of controls (P<0.05). There were no differences in the distribution of genotype and allele frequencies of the six SNPs between the hypertensive and control groups (P>0.05). These results suggest that dietary history and habits have the most important influence on the development of essential hypertension in the Mongolian population.

Potentiation of ibudilast inhibition of platelet aggregation in the presence of endothelial cells.

Although communications between platelets and endothelial cells or other blood cells are important in in vivo thrombus formation, laboratory platelet function tests are usually performed in isolation from these surrounding cells. In this study, we evaluated the effect of an antiplatelet drug, ibudilast (3-isobutyryl-2-isopropylpyrazolo[1,5-a]pyridine), on platelet aggregation in the presence and absence of human umbilical vein endothelial cells (HUVECs) and with the use of platelet-rich plasma (PRP) or whole blood as platelet samples. Stimulation-dependent platelet aggregation was weakened in the presence of HUVECs, which was especially prominent when the thrombin receptor-activating peptide SFLL (compared with ADP and epinephrine) was used as an aggregating agent. Ibudilast hardly affected SFLL-induced platelet aggregation (in PRP), while this antiplatelet agent was found to clearly inhibit this SFLL-induced response in a concentration-dependent manner, in the presence of HUVECs. Ibudilast tended to inhibit ADP- or epinephrine-induced platelet aggregation in the presence of HUVECs, but the effects were not statistically significant. Enhanced inhibition by ibudilast of SFLL-induced platelet aggregation (in the presence of HUVECs) was reproduced with the use of whole blood samples when a screen filtration pressure method was employed. It is suggested that the platelet aggregation studies in the presence of endothelial cells and/or other blood cells provide us with valuable information on platelet reactivity in vivo and improvement of antiplatelet therapy.

G(i)-mediated Cas tyrosine phosphorylation in vascular endothelial cells stimulated with sphingosine 1-phosphate: possible involvement in cell motility enhancement in cooperation with Rho-mediated pathways.

Since blood platelets release sphingosine 1-phosphate (Sph-1-P) upon activation, it is important to examine the effects of this bioactive lipid on vascular endothelial cell functions from the viewpoint of platelet-endothelial cell interactions. In the present study, we examined Sph-1-P-stimulated signaling pathways related to human umbilical vein endothelial cell (HUVEC) motility, with a special emphasis on the cytoskeletal docking protein Crk-associated substrate (Cas). Sph-1-P stimulated tyrosine phosphorylation of Cas, which was inhibited by the G(i) inactivator pertussis toxin but not by the Rho inactivator C3 exoenzyme or the Rho kinase inhibitor Y-27632. Fyn constitutively associated with and phosphorylated Cas, suggesting that Cas tyrosine phosphorylation may be catalyzed by Fyn. Furthermore, upon HUVEC stimulation with Sph-1-P, Crk, through its SH2 domain, interacted with tyrosine-phosphorylated Cas, and the Cas-Crk complex translocated to the cell periphery (membrane ruffles), through mediation of G(i) (Fyn) but not Rho. In contrast, tyrosine phosphorylation of focal adhesion kinase, and formation of stress fibers and focal adhesion were mediated by Rho but not G(i) (Fyn). Finally, Sph-1-P-enhanced HUVEC motility, assessed by a phagokinetic assay using gold sol-coated plates and a Boyden's chamber assay, was markedly inhibited not only by pertussis toxin (or the Fyn kinase inhibitor PP2) but also by C3 exoenzyme (or Y-27632). In HUVECs stimulated with Sph-1-P, these data suggest the following: (i) cytoskeletal signalings may be separable into G(i)-mediated signaling pathways (involving Cas) and Rho-mediated ones (involving FAK), and (ii) coordinated signalings from both pathways are required for Sph-1-P-enhanced HUVEC motility. Since HUVECs reportedly express the Sph-1-P receptors EDG-1 (coupled with G(i)) and EDG-3 (coupled with G(13) and G(q)) and the EDG-3 antagonist suramin was found to block specifically Rho-mediated responses, it is likely that Cas-related responses following G(i) activation originate from EDG-1, whereas Rho-related responses originate from EDG-3.

Sphingosine 1-phosphate as a major bioactive lysophospholipid that is released from platelets and interacts with endothelial cells.

The serum-borne lysophospholipid mediators sphingosine 1-phosphate (Sph-1-P) and lysophosphatidic acid (LPA) have been shown to be released from activated platelets and to act on endothelial cells. In this study, we employed the repeated lipid extraction (under alkaline and acidic conditions), capable of detecting Sph-1-P, LPA, and possibly structurally similar lysophospholipids, whereby a marked formation of [(32)P]Sph-1-P, but not [(32)P]LPA, was observed in [(32)P]orthophosphate-labeled platelets. Platelet Sph-1-P release, possibly mediated by protein kinase C, was greatly enhanced in the presence of albumin, which formed a complex with Sph-1-P. This finding suggests that platelet Sph-1-P may become accessible to depletion by albumin when its transbilayer movement (flipping) across the plasma membrane is enhanced by protein kinase C. Although human umbilical vein endothelial cells expressed receptors for both Sph-1-P and LPA, Sph-1-P acted much more potently than LPA on the cells in terms of intracellular Ca(++) mobilization, cytoskeletal reorganization, and migration. The results suggest that Sph-1-P, rather than LPA, is a major bioactive lysophospholipid that is released from platelets and interacts with endothelial cells, under the conditions in which critical platelet-endothelial interactions (including thrombosis, angiogenesis, and atherosclerosis) occur. Furthermore, albumin-bound Sph-1-P may account for at least some of the serum biological activities on endothelial cells, which have been ascribed to the effects of albumin-bound LPA, based on the similarities between LPA and serum effects.

Rho-mediated phosphorylation of focal adhesion kinase and myosin light chain in human endothelial cells stimulated with sphingosine 1-phosphate, a bioactive lysophospholipid released from activated platelets.

Since sphingosine 1-phosphate (Sph-1-P) is stored in abundant amounts in blood platelets and released extracellularly upon stimulation, it is important to clarify the effects of this bioactive lysophospholipid on vascular endothelial cells from the viewpoint of platelet-endothelial cell interactions. In this study, we investigated the effects of Sph-1-P on the cytoskeletal remodeling of human umbilical vein endothelial cells (HUVECs). Of a focal adhesion kinase (FAK) family of non-receptor protein-tyrosine kinases, HUVECs were found to express FAK, but scarcely proline-rich tyrosine kinase 2. Sph-1-P induced FAK tyrosine phosphorylation, myosin light chain phosphorylation, and the formation of stress fibers in HUVECs. The specific Rho inactivator C3 transferase from Clostridium botulinum abolished all of these cytoskeletal responses induced by Sph-1-P, while pertussis toxin only partly inhibited FAK tyrosine phosphorylation, and hardly affected myosin light chain phosphorylation and stress fiber formation. In contrast, Sph-1-P-induced intracellular Ca(2)(+) mobilization was suppressed by pertussis toxin, but not at all by C3 exoenzyme. Our results suggest that Sph-1-P, a bioactive lipid released from activated platelets, induces endothelial cell cytoskeletal reorganization, mainly through Rho-mediated signaling pathways.