15-hydroxyeicosatetraenoic acid (15-HETE) plays an important role in hypoxia-induced pulmonary vasoconstriction. Release of nitric oxide (NO) is apparently decreased and activity of endothelial nitric oxide synthase (eNOS) is impaired in chronic hypoxia. However, little is known whether 15-HETE contributes to eNOS/NO pathway in the constriction induced by 15-HETE. We examined the response of rat pulmonary artery (PA) rings to 15-HETE, the production of NO, total eNOS expression and the phosphorylation of eNOS in bovine pulmonary artery endothelial cells (BPAECs) stimulated by 15-HETE. Rat PA rings were divided into three groups: endothelium intact group, endothelium denuded group, and nitro-L-arginine methyl ester (L-NAME, 0.1 mmol/L, an inhibitor of eNOS) group. Constrictions to 15-HETE were significantly enhanced in endothelium denuded group and L-NAME group (both P< 0.05 vs endothelium intact group, n= 9); BPAECs were incubated in different conditions to test nitrite production by Greiss method. Nitrite production was significantly reduced by 1 mumol/L 15-HETE (P<0.05), and increased by the lipoxygenase inhibitors, 10 mumol/L cinnamyl 3,4- dihydroxy-[alpha] -cyanocinnamate (CDC, P< 0.05) and 0.1 mmol/L nordihydroguiairetic acid (NDGA, P< 0.01 ); Western blot analysis of extracts from BPAECs incubated with 15-HETE in different time was carried out to test total eNOS expression, and the expression was changed unobviously. Immunoprecipitation (IP) and Western blot analysis of cell extracts from BPAECs treated with 2 mumol/L 15-HETE in different length of time were accomplished, using phospo-eNOS-threonine 495 (Thr495, an inhibitory site) antibody for IP, and eNOS or 15-lipoxygenase (15-LO) antibodies for Western blot. 15-HETE depressed eNOS activity by increasing the levels of phospho-eNOS-Thr 495. The data suggest that eNOS/NO pathway is involved in PA constrictions induced by 15-HETE and that 15-HETE depresses eNOS activity by phosphorylation in Thr495 site. The protein interaction between phospho-eNOS (Thr495) and 15-LO is discovered for the first time.
Animals ; Cattle ; Down-Regulation ; drug effects ; Endothelium, Vascular ; cytology ; drug effects ; enzymology ; Hydroxyeicosatetraenoic Acids ; pharmacology ; In Vitro Techniques ; Male ; Nitric Oxide Synthase Type III ; metabolism ; Pulmonary Artery ; cytology ; enzymology ; physiology ; Rats ; Rats, Wistar

Fluid shear stress plays a critical role in vascular health and disease. While protein kinase A (PKA) has been implicated in shear-stimulated signaling events in endothelial cells, it remains unclear whether and how PKA is stimulated in response to shear stress. This issue was addressed in the present study by monitoring the phosphorylation of endogenous substrates of PKA. Shear stress stimulated the phosphorylation of cAMP responsive element binding protein (CREB) in a PKA-dependent manner. Western blot analysis using the antibody reactive against the consensus motif of PKA substrates detected two proteins, P135 and P50, whose phosphorylation was increased by shear stress. The phosphorylation of P135 was blocked by a PKA inhibitor, H89, but not by a phosphoinositide 3-kinase inhibitor, wortmannin. Expression of a constitutively active PKA subunit stimulated P135 phosphorylation, supporting the potential of P135 as a PKA substrate. P135 was identified as endothelial nitric oxide synthase (eNOS) by immunoprecipitation study. PKA appeared to mediate shear stress-stimulated eNOS activation. Shear stress stimulated intracellular translocation of PKA activity from 'soluble' to 'particulate' fractions without involving cellular cAMP increase. Taken together, this study suggests that shear stress stimulates PKA-dependent phosphorylation of target proteins including eNOS, probably by enhancing intracellular site-specific interactions between protein kinase and substrates.
Animals ; Aorta, Thoracic/cytology ; Blotting, Western ; Cattle ; Cell Culture Techniques ; Cell Extracts ; Cells, Cultured ; Comparative Study ; Cyclic AMP-Dependent Protein Kinases/analysis/*metabolism ; Endothelium, Vascular/cytology/*enzymology/*metabolism ; Nitric Oxide Synthase Type III/analysis/*metabolism ; Phosphorylation ; Precipitin Tests ; Research Support, Non-U.S. Gov't ; Stress, Mechanical ; Time Factors

OBJECTIVETo explore the postburn adhesion properties of polymorphonuclear leukocyte (PMN) onto pulmonary vascular endothelial cells (PVEC) in burn patients with acute lung injury (ALI), so as to determine the role of C5a on PVEC-PMN adhesion.

METHODSMicrotubule sucking technique was employed to determine the PVEC-PMN adhesion. The myeloperoxidase (MPO) was also assayed to reflect the magnitude of PVEC-PMN adhesion.

RESULTSThe magnitude of PVEC-PMN adhesion increased and the adhesion force increased along with an increase in rh-C5a concentration. Simultaneously, the MPO activity was increased, which could be inhibited by anti-C5aR McAb in a concentration 1:104.

CONCLUSIONBoth C5a and C5aR participated in PVEC-PMN adhesion, which might be important in the pathogenesis of ALI.

Acute Disease ; Antibodies, Monoclonal ; pharmacology ; Antigens, CD ; immunology ; Burns ; blood ; complications ; Cell Adhesion ; drug effects ; Cells, Cultured ; Complement C5a ; pharmacology ; Dose-Response Relationship, Drug ; Endothelium, Vascular ; cytology ; drug effects ; Fetus ; Humans ; Lung ; Lung Diseases ; complications ; Neutrophils ; cytology ; drug effects ; enzymology ; Peroxidase ; antagonists & inhibitors ; drug effects ; metabolism ; Receptor, Anaphylatoxin C5a ; Receptors, Complement ; immunology

Leptin, the product of ob gene, is an endocrine hormone that regulates adipose tissue mass. Recently, leptin has been found to generate a growth signal involving a tyrosine kinase-dependent intracellular pathway and promote angiogenic processes via activation of leptin receptor (Ob-R) in endothelial cells. However, it is not clear how leptin functions to promote multi-step processes involved in the neovascularization at the atherosclerotic plaque. We have examined the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) and Ob-R in human atherosclerotic lesions, leptin-mediated angiogenesis in vivo and in vitro. Immunohistochemical analysis of human atherosclerotic aorta revealed an increased expression of Ob-R in the intima of neorevascularized regions and of both MMPs and TIMPs predominantly in the endothelial lining of intimal neovessels and macrophages/foam cells. In the rat corneal angiogenesis assay, leptin elicited a comparable sensitivity of angiogenic activity to those of vascular endothelial growth factor (VEGF). The immunohistological analysis of the leptin-treated rat cornea showed definitive rises in Ob-R, MMPs and TIMPs expression as well as those of VEGF receptor (VEGFR-1). Leptin (10-40 ng/ml) induced proliferation of the human umbilical vein endothelial cells (HUVECs) and elevation of MMP-2, MMP-9, TIMP-1, and TIMP-2 expression in a dose-dependent manner. Leptin also induced increases of MMP-2, MMP-9, TIMP-1, and Up-regulated the human coronary artery smooth muscle cells (HCASMCs). These findings suggest that leptin, a hormone with pluralistic properties including a mitogenic activity on vascular endothelial cells, plays a role in matrix remodeling by regulating the expression of MMPs and TIMPs. Taken together, our findings further provide evidences for leptin's role as an angiogenesis inducer in the normal organ (rat cornea) and in aberrant vasculature under duress like atherosclerosis.
Animal ; Arteriosclerosis/metabolism ; Blotting, Western ; Cell Division ; Cells, Cultured ; Dose-Response Relationship, Drug ; Endothelial Growth Factors/metabolism ; Endothelium, Vascular/*cytology/*enzymology ; Enzyme-Linked Immunosorbent Assay ; Fibroblast Growth Factor 2/metabolism ; Immunohistochemistry ; Leptin/*chemistry/metabolism/*physiology ; Lymphokines/metabolism ; Matrix Metalloproteinases/*biosynthesis ; *Neovascularization, Pathologic ; Rats ; Receptor Protein-Tyrosine Kinases/metabolism ; Receptors, Growth Factor/metabolism ; Recombinant Proteins/metabolism ; Support, Non-U.S. Gov't ; Tissue Inhibitor of Metalloproteinases/metabolism ; Umbilical Veins/metabolism ; Up-Regulation