Background-Endothelin-1 (ET-1) plays an important role in the maintenance of vascular tone and pathological states such as ischemia/reperfusion (I/R) injury, coronary vasospasm, and cardiac allograft vasculopathy. We assessed the effects of elevated ET-1 levels as seen after I/R to determine if ET-1 modulates nitric oxide (NO) production via the translocation of specific protein kinase C (PKC) isoforms. Methods and Results-Human saphenous vein endothelial cells (HSVECs) (nϭ8) were incubated with ET-1 or phosphate-buffered saline (PBS) for 24 hours. NO production was determined in the supernatant by measuring nitrate/nitrite levels. Protein expression of endothelial nitric oxide synthase (eNOS), inducible NOS (iNOS), caveolin-1 and PKC were determined. Lastly, PKC translocation and activity were assessed after exposure to the drug of interest. HSVECs exposed to ET-1 displayed decreased NO production. PKC inhibition reduced NO production, whereas PKC activation increased production. NO production was maintained when HSVECs exposed to ET-1 were treated with the PKC agonist, PMA. eNOS protein expression was reduced after ET-1 treatment. PKC inhibition also downregulated eNOS protein expression, whereas PMA upregulated expression. ET-1 exposure led to a significant increase in PKC␦ and PKC translocation compared with control, whereas translocation of PKC was inhibited. ET-1 exposure significantly reduced overall PKC activity compared with control. Conclusions-Our study demonstrates that high levels of ET-1 impair endothelial NO production via an isoform-specific PKC-mediated inhibition of eNOS expression. ET-1 antagonism with bosentan stimulates translocation of PKC and leads to increased PKC activity and NO production. ET-1 antagonism may provide a novel therapeutic strategy to improve vascular homeostasis.

No abstract

Background-Epidermal growth factor-like domain 7 (Egfl7) is a chemoattractant for endothelial cells, and its expression is restricted to endothelial cells. Hypoxia/reoxygenation (H/R) induced endothelial injury that occurs during transplantation contributes to the subsequent development of allograft vasculopathy. We investigated the effect of Egfl7 on endothelial cell intercellular adhesion molecule 1 expression in response to H/R injury. Methods and Results-Human coronary artery endothelial cells were submitted to hypoxia (0.1% O 2 ) followed by normoxia (21% O 2 ) in the presence or absence of Egfl7 (100 ng/mL). Hypoxia alone increased the expression of Egfl7ϫ140Ϯ8% of control at 3 hours (nϭ6; PϽ0.05) and 385Ϯ50% of control at 6 hours (nϭ6; PϽ0.001). Incubation with Egfl7 during the reoxygenation period prevented intercellular adhesion molecule 1 upregulation (mean fluorescence intensity: 5.37Ϯ0.92 versus 3.81Ϯ0.21; PϽ0.05; nϭ4 per group). Nuclear factor-B nuclear localization on H/R injury was blocked by Egfl7 administration (cytosolic/nuclear ratio of 0.93Ϯ0.01 versus 1.44Ϯ0.24; PϽ0.05; nϭ4 per group). Inhibitor of nuclear factor-B protein level was significantly reduced on H/R injury (26Ϯ4.6% of control expression; PϽ0.05; nϭ4 per group); however, concurrent incubation with Egfl7 attenuated this reduction (46Ϯ6.2% of control expression; PϽ0.05 when compared with H/R injury alone; nϭ4 per group). Conclusions-Our study reveals the novel observation that hypoxia upregulates human coronary artery endothelial cells expression of Egfl7 and that Egfl7 inhibits expression of intercellular adhesion molecule 1 subsequent to H/R injury. Mechanistically, Egfl7 prevented nuclear factor-B nuclear localization and augmented inhibitor of nuclear factor-B protein levels, suggesting that it inhibits nuclear factor-B activation, a key step in the inflammatory activation of endothelial cells. Egfl7 may be protective against H/R injury incurred during transplantation and may modulate the events that lead to the development of graft vasculopathy. (Circulation. 2010;122[suppl 1]:S156 -S161.)

Background-Hypertonic saline (HTS) has been previously demonstrated to have immune modulatory and vascular protective effects. We assessed the effect of donor pretreatment with HTS on allograft preservation in a porcine model of orthotopic heart transplantation. Methods and Results-Orthotopic transplants were performed after 6 hours of cold static allograft storage. Donor pigs were randomly assigned to pretreatment with (nϭ7) or without (nϭ6) HTS (4.5 mL/kg of 7.5% NaCl) administered 1 hour before donor heart arrest. Administration of HTS increased serum sodium level from 138Ϯ2 mmol/L to 154Ϯ4 mmol/L, which normalized to 144Ϯ3 mmol/L 1 hour after infusion. Successful weaning from cardiopulmonary bypass was significantly greater in HTS-treated hearts (6/7 vs 1/6; Pϭ0.029).

No abstract

Background-Human leukocyte antigen-G (HLA-G) expression in heart transplant patients has been negatively associated with acute cellular rejection and cardiac allograft vasculopathy. We assessed HLA-G expression in vascular human endothelial and smooth muscle cell cultures to determine if future therapeutic agents can be targeted toward inducing HLA-G expression to protect against allograft rejection and vasculopathy. Methods and Results-Human coronary artery endothelial, aortic endothelial, and coronary artery smooth muscle cell cultures were exposed to cytokines (interferon-␥ or interleukin-10), hypoxia/reoxygenation stress, immunosuppressive agents (cyclosporine, sirolimus, or tacrolimus), or progesterone. HLA-G was not expressed by untreated, normoxic cells. Furthermore, maximal doses of interferon-␥, interleukin-10, cyclosporine, sirolimus, or tacrolimus, as well as exposure to hypoxia/reoxygenation, failed to induce HLA-G expression. HLA-G, which has previously not been detected in adult vascular endothelial and smooth muscle cells, was detected by enzyme-linked immunosorbent assay and flow cytometry in human coronary artery endothelial, human coronary aortic endothelial, and human coronary artery smooth muscle cultures after incubation with progesterone in a dose-dependent manner (PϽ0.001) with no change in cellular proliferation ability or viability. This effect was partially blocked in the presence of mifepristone, a progesterone receptor antagonist (human coronary artery endothelial: 48.8Ϯ15.6%; human coronary aortic endothelial: 59.5Ϯ9.5%; human coronary artery smooth muscle: 59.8Ϯ9.8% of control; PϽ0.05). Progesterone-induced HLA-G expression was not protective against hypoxia/reoxygenation injury. Conclusions-HLA-G is not expressed at baseline in vascular endothelial and smooth muscle cells but can be induced by exposure to progesterone. Although tightly regulated, induction of HLA-G expression in these cells may represent a promising and novel therapeutic strategy to protect against rejection and cardiac allograft vasculopathy after heart transplantation.

Endothelial progenitor cells (EPCs) may contribute to rejection and cardiac allograft vasculopathy (CAV) by being intrinsically involved in the rejection process and causing neointimal hyperplasia. The mammalian target of rapamycin inhibitors (mTORi), sirolimus and everolimus, have been demonstrated to attenuate the progression of CAV and are cytotoxic to EPC. Thus, one mechanism by which mTORi may protect against CAV is by altering EPC function. Our study measured circulating EPC function and correlated this assessment with rejection episodes in heart transplant (HT) recipients. In addition, we examined the effect of mTORi on EPCs. Patients who received HT at our institution between 1995 and 2007 were included and stratified by International Society for Heart and Lung Transplantation (ISHLT) rejection grade. Group A (n = 13) consisted of patients with at least one moderate/severe rejection episode (grade > or = 2). Group B (n = 28) patients had no moderate/severe episodes (grade < 2). Patients were also independently stratified based on exposure as mTORi (n = 21) vs. non mTORi (n = 20). To assess EPC functional capacity, we counted the number of colony-forming units (CFU) of EPCs in peripheral blood samples from HT recipients. There were no significant differences in baseline characteristics between groups. The mean EPC-CFU counts/plate for group A (rejecting) were 30 +/- 6 vs.16 +/- 3 for group B (nonrejecting) (P = 0.03). The EPC-CFU counts/plate in the mTORi group (15 +/- 3) were lower compared to the non mTORi (27 +/- 5) group (P = 0.04). We found that EPC colony-forming capacity was higher in HT patients who experienced moderate/severe rejection episodes. Patients on mTORi showed a reduced EPC colony count consistent with our previous findings of EPC cytotoxicity. Detection of circulating EPC function post-transplant may reliably identify patient risk level for subsequent allograft rejection and allow for appropriate adjustments to immunosuppression. Converting to mTORi therapy may reduce EPC function and provide a novel mechanism to prevent rejection and possibly attenuate the development of CAV.

Cyclosporine A and hydrocortisone induce vasomotor dysfunction with a synergistic impairment observed after concomitant exposure. Our findings suggest that the resultant vasomotor dysfunction is the result of alterations in both nitric oxide and endothelin-1 regulation.