Search

Circulating endothelial cells (CEC) are thought to be markers of endothelial injury. We hypothesized that the numbers of CEC may provide a novel means for predicting long-term survival and cardiovascular events in hemodialysis patients. 54 hemodialysis patients underwent enumeration of their CEC number. We retrospectively analyzed their survival and incidence of adverse cardiovascular events. 22 deaths (41%) were noted over the median follow up period of 3.56 years (IQR 1.43-12) and 6 were attributed to cardiovascular deaths (11%) of which 1 (4%) was in the low CEC (CEC20 cells/ml) and 5 (19%) in the high CEC (CEC≥20 cells/ml) group. High CEC was associated with worse cardiovascular survival (p = 0.05) and adverse cardiac events (p = 0.01). In multivariate analysis, CEC20 cells/ml was associated with a 4-fold increased risk of adverse cardiac events (OR, 4.16 [95% CI,1.38-12.54],p = 0.01) while all-cause mortality and cardiovascular mortality were not statistically different. In this hemodialysis population, a single measurement of CEC was a strong predictor of long term future adverse cardiovascular events. We propose that CEC may be a novel biomarker for assessing cardiovascular risk in dialysis patients.

Introduction and Hypothesis: Acute kidney injury (AKI), even if renal function returns to normal, is associated with an increased risk of cardiovascular disease. We have developed a novel, mouse model that allows investigation into the mechanism of this clinical scenario. We hypothesized that AKI, particular at a severe level, may result in a permanent change to the vasculature that would promote atherosclerotic lesions. Methods and Results: AKI was induced by clamping the bilateral renal vessels of male, C57/BL mice for 28-30 minutes. The creatinine (Cr) was measured two days later to determine the severity of the AKI. An increase in the Cr of at least three-fold, was defined as severe damage, corresponding to Kidney Disease Improving Global Outcomes (KDIGO) AKI Stage 3. If the Cr increased less than three times, this was defined as mild/moderate AKI. Ten weeks after AKI, the Cr was measured to determine if renal function returned to baseline and the femoral artery was injured by repeated introduction of a guidewire. After four weeks, the animals were sacrificed and the neointima lesions were analyzed. Immunohistochemistry for smooth muscle myosin heavy chain revealed that the neointima was mostly composed of smooth muscle cells. The re-endothelialization was almost complete, as determined by anti-CD31 staining. More interestingly, the narrowing rate of the injured artery in animals who suffered severe AKI was higher than in the mild/moderate AKI animals (53.2% vs 27.2%; P= 0.04). There is no difference between the sham-AKI animals and the mild/moderate AKI animals (34.9 % vs 27.2%, see picture). Conclusions: Severe AKI induces a permanent change to the vasculature and/or the immune cells that hastens the development of neointima even after renal function recovers. This work has implications for the development of human atherosclerosis in the clinical setting after AKI. Potential mechanisms for this increased propensity will be discussed.

In short-term animal models of ischemia, erythropoietin (EPO) signaling through the heterodimeric EPO receptor (EPOR)/β-common receptor (βCR) is believed to elicit tissue protective effects. However, large, randomized, controlled trials demonstrate that targeting a higher hemoglobin level by administering higher doses of EPO, which are more likely to activate the heterodimeric EPOR/βCR, is associated with an increase in adverse cardiovascular events. Thus, inhibition of long-term activation of the βCR may have therapeutic implications. This study aimed to design and evaluate the efficacy of novel computationally designed βCR inhibitory peptides (βIP). These novel βIPs were designed based on a truncated portion of Helix-A from EPO, specifically residues 11–26 (VLERYLLEAKEAEKIT). Seven novel peptides (P1 to P7) were designed. Peptide 7 (P7), VLERYLHEAKHAEKIT, demonstrated the most robust inhibitory activity. We also report here the ability of P7 to inhibit βCR-induced nitric oxide (NO) production and angiogenesis in human umbilical vein endothelial cells (HUVECs). Specifically, we found that P7 βIP completely abolished EPO-induced NO production. The inhibitory effect could be overcome with super physiological doses of EPO, suggesting a competitive inhibition. βCR-induced angiogenesis in HUVEC’s was also abolished with treatment of P7 βIP, but P7 βIP did not inhibit vascular endothelial growth factor (VEGF)-induced angiogenesis. In addition, we demonstrate that the novel P7 βIP does not inhibit EPO-induced erythropoiesis with use of peripheral blood mononuclear cells (PBMCs). These results, for the first time, describe a novel, potent βCR peptide inhibitor that inhibit the actions of the βCR without affecting erythropoiesis.

The brain and muscle aryl hydrocarbon receptor nuclear translocator–like protein (BMAL)-1 constitutes a major transcriptional regulator of the circadian clock. Here, we explored the impact of conditional deletion of Bmal1 in endothelium and hematopoietic cells in murine models of microvascular and macrovascular injury. We used two models of Bmal1 fx/fx ; Tek-Cre mice, a retinal ischemia/reperfusion model and a neointimal hyperplasia model of the femoral artery. Eyes were enumerated for acellular capillaries and were stained for oxidative damage markers using nitrotyrosine immunohistochemistry. LSK (lineage-negative, stem cell antigen-1–positive, c- Kit –positive) cells were quantified and proliferation assessed. Hematopoiesis is influenced by innervation to the bone marrow, which we assessed using IHC analysis. The number of acellular capillaries increased threefold, and nitrotyrosine staining increased 1.5-fold, in the retinas of Bmal1 fx/fx ; Tek-Cre mice. The number of LSK cells from the Bmal1 fx/fx ; Tek-Cre mice decreased by 1.5-fold and was accompanied by a profound decrease in proliferative potential. Bmal1 fx/fx ; Tek-Cre mice also exhibited evidence of bone marrow denervation, demonstrating a loss of neurofilament-200 staining. Injured femoral arteries showed a 20% increase in neointimal hyperplasia compared with similarly injured wild-type controls. Our study highlights the importance of the circadian clock in maintaining vascular homeostasis and demonstrates that specific deletion of BMAL1 in endothelial and hematopoietic cells results in phenotypic features similar to those of diabetes.

Objective— Patients with systemic lupus erythematosis are at risk for premature atherosclerosis and half of the patients with systemic lupus erythematosis have elevated type I interferon (IFN-I) levels. We hypothesized that IFN-I would induce premature atherosclerosis by increasing the number of smooth muscle progenitor cells (SMPC) in the bloodstream and promoting atherosclerotic lesions within the vasculature. Approach and Results— SMPC isolated from wild-type and IFN receptor knockout animals were cultured in medium±IFN-I. In vivo, we used electroporation to generate stable IFN-I expression for as long as 4 months. The number of SMPC was determined in mice that expressed IFN-I and in control mice and sections from the bifurcation of the abdominal aorta were analyzed 3 months after electroporation of an IFN-I expression plasmid or a control plasmid. Adding IFN-I to the media increased the number of cultured wild-type SMPC and increased mRNA for SM22, but had no effect on SMPC isolated from IFN receptor knockout mice. Our in vivo results demonstrated a positive relationship between the preatherosclerotic-like lesions and endothelial damage. Although, there were no significant differences in smooth muscle cell density or thickness of the medial layer between groups, the IFN-I–expressing mice had a significant increase in preatherosclerotic-like lesions and immature smooth muscle cells, cells that expressed CD34 and smooth muscle α-actin; but lacked smooth muscle myosin heavy chain. Conclusions— IFN-I seems to enhance SMPC number in vitro. In vivo IFN-I expression may maintain SMPC in an immature state. These immature smooth muscle cells could give rise to macrophages and eventually foam cells.

Clinically, erythropoietin (EPO) is known to increase systemic vascular resistance and arterial blood pressure. However, EPO stimulates the production of the potent vasodilator, nitric oxide (NO), in culture endothelial cells. The mechanism by which EPO causes vasoconstriction despite stimulating NO production may be dependent on its ability to activate two receptor complexes, the homodimeric EPO (EPOR 2) and the heterodimeric EPOR/β‐common receptor (β CR). The purpose of this study was to investigate the contribution of each receptor to the vasoactive properties of EPO. First‐order, mesenteric arteries were isolated from 16‐week‐old male C57BL/6 mice, and arterial function was studied in pressure arteriographs. To determine the contribution of each receptor complex, EPO‐stimulating peptide (ESP), which binds and activates the heterodimeric EPOR/β CR complex, and EPO, which activates both receptors, were added to the arteriograph chamber 20 min prior to evaluation of endothelium‐dependent (acetylcholine, bradykinin, A23187) and endothelium‐independent (sodium nitroprusside) vasodilator responses. Only ACh‐induced vasodilation was impaired in arteries pretreated with EPO or ESP. EPO and ESP pretreatment abolished ACh‐induced vasodilation by 100% and 60%, respectively. EPO and ESP did not affect endothelium‐independent vasodilation by SNP. Additionally, a novel β CR inhibitory peptide (β IP), which was computationally developed, prevented the impairment of acetylcholine‐induced vasodilation by EPO and ESP, further implicating the EPOR/β CR complex. Last, pretreatment with either EPO or ESP did not affect vasoconstriction by phenylephrine and KCl. Taken together, these findings suggest that acute activation of the heterodimeric EPOR/β CR in endothelial cells leads to a selective impairment of ACh‐mediated vasodilator response in mouse mesenteric resistance arteries.

Erythropoietin (EPO) increases systemic vascular resistance and blood pressure. However, endothelial cells cultured in the presence of EPO demonstrate increased production of the potent vasodilator, nitric oxide (NO). The mechanism by which EPO causes vasoconstriction despite stimulating NO production may be dependent on its ability to differentially activate the two receptor complexes, the homodimeric EPO (EPOR 2 ) and the heterodimeric EPOR/β-common receptor (βCR). Objective: The purpose of this study was to investigate the contribution of the EPOR 2 and βCR receptor to the vasoactive properties of EPO. Methods: First order, mesenteric arteries isolated from 16-week old male C57BL/6 mice were cannulated and perfused using a pressure arteriography system. To determine the contribution of each receptor complex, arteries were incubated with EPO stimulating peptide (ESP) which binds and activates only the heterodimeric EPOR/βCR complex or EPO which activates both receptors, 20 min prior to evaluation of vasoconstrictor (phenylephrine and potassium chloride), endothelium-dependent (acetylcholine, bradykinin, A23187) and -independent (sodium nitroprusside) vasodilator responses. Additionally, we studied the effect of a novel βCR inhibitory peptide (βIP) which was developed in silico and validated by demonstrating that it selectively inhibits binding of ligands to the βCR. Results: Acetylcholine induced vasodilation was impaired in arteries pretreated with EPO or ESP by 100% and 60%, respectively. EPO and ESP did not affect endothelium-dependent vasodilation by Bradykinin or A23187, endothelium-independent vasodilation by sodium nitroprusside, or vasoconstriction by phenylephrine and KCl. The βIP prevented the impairment of acetylcholine-induced vasodilation by EPO and ESP. Conclusion: Together, our findings suggest that activation of the heterodimeric EPOR/βCR leads to selective impairment of ACh-mediated vasodilator response in mouse mesenteric resistance arteries. Thus the βCR might have a role in mediating hypertensive effects of EPO. Therapeutic inhibition of the βCR might prevent vascular complications of EPO without affecting erythropoiesis.

The ovarian peptide hormone, relaxin, circulates during pregnancy, contributing to profound maternal vasodilation through endothelial and nitric oxide (NO)–dependent mechanisms. Circulating numbers of bone marrow–derived endothelial cells (BMDECs), which facilitate angiogenesis and contribute to repair of vascular endothelium, increase during pregnancy. Thus, we hypothesized that relaxin enhances BMDEC NO production, circulating numbers, and function. Recombinant human relaxin-2 (rhRLX) stimulated PI3K/Akt B-dependent NO production in human BMDECs within minutes, and activated BMDEC migration that was inhibited by L-NG-nitroarginine methyl ester. In BMDECs isolated from relaxin/insulin-like family peptide receptor 2 gene (Rxfp2) knockout and wild-type mice, but not Rxfp1 knockout mice, rhRLX rapidly increased NO production. Similarly, rhRLX increased circulating BMDEC number in Rxfp2 knockout and wild-type mice, but not Rxfp1 knockout mice as assessed by colony formation and flow cytometry. Taken together, these results indicate that relaxin effects BMDEC function through the RXFP1 receptor. Finally, both vascularization and incorporation of GFP-labeled BMDECs were stimulated in rhRLX-impregnated Matrigel pellets implanted in mice. To conclude, relaxin is a novel regulator of BMDECs number and function, which has implications for angiogenesis and vascular remodeling in pregnancy, as well as therapeutic potential in vascular disease.

L'hyperplasie myointimale est un processus pathologique d'importance majeure intervenant dans l'echec des greffons veineux des patients diabetiques. Dans cette etude, nous avons teste l'hypothese selon laquelle l'effet inhibiteur de l'aminoguanidine sur l'hyperplasie myointimale serait lie a une diminution de l'expression des produits terminaux de glycation (PTG), et de leur recepteur (RAGE) sur un modele de diabete induit par la streptozotocine. Pour induire l'hyperplasie myointimale, une veine jugulaire externe autologue etait greffee au niveau de l'aorte sous-renale de 52 rats Sprague-Dawley de sexe masculin. Chez les rats diabetiques, de l'eau distillee avec ou sans aminoguanidine etait administree, tandis que les rats non diabetiques recurent de l'eau distillee seule. Les greffons veineux etaient preleves a 1 et 4 semaines post-operatoires pour analyse morphologique et reaction en chaine par polymerase en transcription inverse (RT-PCR) pour le recepteur RAGE et le facteur nucleaire κB (NF-κB) p65. Le niveau serique de PTG etait determine par fluorospectrophotometrie. En comparaison aux rats non diabetiques, les taux seriques de PTG chez les rats diabetiques ayant recu de l'eau distillee etaient significativement augmentes. L'expression de RAGE et de NF-κB p65, le rapport intima-media, et le pourcentage de cellules positives pour l'antigene nucleaire de proliferation cellulaire (CPAN) etaient significativement augmentes dans les greffons veineux. Chez les rats diabetiques traites par aminoguanidine, les niveaux seriques de PTG et d'expression de NF-κB p65, le rapport intima-media, et le pourcentage de cellules CPAN-positives dans les greffons veineux etaient tous significativement diminues. Cependant, aucune difference dans l'expression de RAGE n'etait retrouvee en comparaison au groupe de rats diabetiques ayant recu de l'eau distillee. Nos resultats suggerent que le complexe PTG-RAGE pourrait jouer un role majeur dans l'hyperplasie myointimale des greffons veineux des diabetiques. Cette hyperplasie myointimale pourrait etre supprimee par l'aminoguanidine.

La hiperplasia intimal es uno de los principales procesos patologicos involucrados en el fracaso del implante de injertos venosos en pacientes con diabetes mellitus. En el presente estudio, probamos la hipotesis de que en la diabetes inducida por estreptozotocina el efecto supresor de la aminoguanidina sobre la hiperplasia intimal esta mediado por la expresion regulada a la baja de los productos finales de glicosilacion avanzada (advanced glycation end products [AGE]) y su receptor (RAGE). Para inducir la hiperplasia intimal, se implanto un injerto autologo de vena yugular externa en la aorta abdominal infrarrenal de 52 ratas macho Sprague-Dawley. En ratas diabeticas, se administro agua destilada con o sin aminoguanidina, mientras que en no diabeticas solo se administro agua destilada. Los injertos venosos se recuperaron a las 1 y 4 semanas despues de la cirugia para un analisis morfologico y un analisis semicuantitativo mediante reaccion en cadena de la polimerasa retrotranscriptasa para RAGE y la subunidad p65 del factor nuclear kappaB (NF-kappaB). Mediante fluoroespectrofotometria se determino la concentracion serica de AGE. Comparado con ratas no diabeticas, en animales diabeticos que recibieron agua destilada la concentracion serica de AGE aumento significativamente. En el injerto venoso se identifico un aumento significativo de la expresion de RAGE y de p65 de NF-kappaB, cociente de area intimal:medial, y porcentaje de celulas positivas al antigeno de proliferacion nuclear celular (PCNA). En ratas diabeticas tratadas con aminoguanidina, la concentracion serica de AGE, la expresion de p65 de NF-kappaB, cociente area intimal:medial y porcentaje de celulas PCNA positivas disminuyeron significativamente. Sin embargo, en estos animales no se identifico una diferencia en la expresion de RAGE comparado con el grupo diabetico que recibio agua destilada. Los datos del presente estudio sugieren que los AGE y su receptor (RAGE) podrian desempenar un papel clave en la hiperplasia intimal venosa en la diabetes mellitus y la hiperplasia intimal suprimida por aminoguanidina a traves de la inhibicion de esta via.

Intimal hyperplasia of autologous vein grafts is a critical problem affecting the long-term patency of many types of vascular reconstruction. Within intimal hyperplasia lesions, smooth muscle cells are a major component, playing an essential role in the pathological process. Given that bone marrow-derived cells may differentiate into smooth muscle cells in the neointima of injured arteries, we hypothesized that the bone marrow may serve as a source for some of the smooth muscle cells within intimal hyperplasia lesions of vein grafts. To test this hypothesis, we used an established mouse model for intimal hyperplasia in wild-type mice that had been transplanted with bone marrow from a green fluorescent protein (GFP+/+) transgenic mouse. High-resolution confocal microscopy analysis performed 2 and 8 weeks after grafting demonstrated expression of GFP in 5.4 +/- 0.8% and 11.9 +/- 2.3%, respectively, of smooth muscle cells within intimal hyperplasia lesions. By 16 weeks, GFP expression in smooth muscle cells was not detected by immunohistochemistry; however, real-time PCR revealed that 20.2 +/- 1.7% of the smooth muscle cells captured from the neointima lesion by laser capture microdissection at 16 weeks contained GFP DNA. Our results suggest that bone marrow-derived cells differentiated into smooth muscle cells within the intimal lesion and may provide a novel clinical approach for decreasing intimal hyperplasia in vein grafts.

Background To investigate the molecular mechanism of autologous venous graft intimal hyperplasia, a mouse model is needed. Currently only vein to carotid artery mouse models are available and are hampered by a high thrombosis rate. We hypothesized that operating on the aorta would lead to intimal hyperplasia with decreased risk of thrombosis. Materials and methods In C57BL/6J mice, the left external jugular vein was grafted into the infrarenal abdominal aorta by end-to-end anastomosis with 11-0 Ethilon. Grafts harvested at 1, 2, 4, 8, and 16 weeks postoperatively were subjected to histological and immunohistochemical analysis. Results Thirty-one of 35 mice survived; 2 mice were sacrificed secondary to thrombosis. The percentage lumen narrowing (±SE) was 7.8 ± 0.3, 16.4 ± 0.9, 19.2 ± 0.9, 22.3 ± 0.8, and 23.9 ± 1.6% at 1, 2, 4, 8 and 16 weeks, respectively. Nuclear density decreased with each successive time point. The percentage of α-smooth-muscle actin-positive cells within the neointima peaked at 16 weeks (53%), and the percentage of cells positive for proliferating cell nuclear antigen peaked at 2 weeks (39%). Conclusions We thus report on a novel mouse model of intimal hyperplasia in autologous venous grafts with a low thrombosis rate. Further studies using this model, coupled with genetic and bone marrow transplantation mouse models, should lead to significant enhancement in understanding of the mechanism of intimal hyperplasia.

Vascular endothelial growth factor (VEGF) and erythropoietin (EPO) have profound effects on the endothelium and endothelial progenitor cells (EPCs), which originate from the bone marrow and differentiate into endothelial cells. Both EPO and VEGF have demonstrated an ability to increase the number and performance properties of EPCs. EPC behavior is highly dependent on nitric oxide (NO), and both VEGF and EPO can stimulate intracellular NO. EPO can bind to the homodimeric EPO receptor (EPO-R) and the heterodimeric receptor, EPO-R and the common β receptor (βC-R). Although VEGF has several receptors, VEGF-R2 appears most critical to EPC function. We demonstrate that EPO induction of NO is dependent on the βC-R and VEGF-R2, that VEGF induction of NO is dependent on the expression of the βC-R, and that the βC-R and VEGF-R2 interact. This is the first definitive functional and structural evidence of an interaction between the 2 receptors and has implications for the side effects of EPO.

To investigate the molecular mechanism of autologous venous graft intimal hyperplasia, a mouse model is needed. Currently only vein to carotid artery mouse models are available and are hampered by a high thrombosis rate. We hypothesized that operating on the aorta would lead to intimal hyperplasia with decreased risk of thrombosis.In C57BL/6J mice, the left external jugular vein was grafted into the infrarenal abdominal aorta by end-to-end anastomosis with 11-0 Ethilon. Grafts harvested at 1, 2, 4, 8, and 16 weeks postoperatively were subjected to histological and immunohistochemical analysis.Thirty-one of 35 mice survived; 2 mice were sacrificed secondary to thrombosis. The percentage lumen narrowing (+/-SE) was 7.8 +/- 0.3, 16.4 +/- 0.9, 19.2 +/- 0.9, 22.3 +/- 0.8, and 23.9 +/- 1.6% at 1, 2, 4, 8 and 16 weeks, respectively. Nuclear density decreased with each successive time point. The percentage of alpha-smooth-muscle actin-positive cells within the neointima peaked at 16 weeks (53%), and the percentage of cells positive for proliferating cell nuclear antigen peaked at 2 weeks (39%).We thus report on a novel mouse model of intimal hyperplasia in autologous venous grafts with a low thrombosis rate. Further studies using this model, coupled with genetic and bone marrow transplantation mouse models, should lead to significant enhancement in understanding of the mechanism of intimal hyperplasia.