Browsing by Subject "Endothelium, Vascular"
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Item Acute Effect of High vs Low Dialysate Sodium on Endothelial Cell Function During Hemodialysis(2013-01-22) D'Silva, Kristin; Molina, Christopher; van Buren, Peter; Kim, Catherine; Inrig, JulaBACKGROUND: Intradialytic hypertension (HTN), a rise in blood pressure that occurs during hemodialysis (HD) treatments in up to 15% of patients, is associated with higher morbidity and mortality. The cause of intradialytic HTN is unknown but may be due to endothelial cell (EC) dysfunction. In vitro exposure of ECs to high sodium (Na+) concentration promotes EC stiffness and imbalances in vasoconstrictors (endothelin-1 [ET-1]) and vasodilators (nitric oxide [NO]). We hypothesized that, among patients with intradialytic HTN, exposure to high dialysate Na+ would lead to a decrease in NO and increase in ET-1 during HD. METHODS: We performed a 3-week, 2-arm, randomized crossover study among 16 HD patients with intradialytic HTN and compared the effects of high dialysate-to-serum Na+ gradients (5 mEq/L above participants' baseline Na+) vs low dialysate-to-serum Na+ gradients (5 mEq/L below baseline Na+ with lower limit of 134 mEq/L) on intradialytic changes in nitrite and ET-1. Differences between treatments were compared with repeated measures mixed linear regression and included randomization arm (high - low Na+ vs low - high Na+), treatment effect (high vs low Na+), subject, time and session. RESULTS: Study participants (N=16) had an average age of 58.8 years, 38% were black, 56% were Hispanic, and 94% were male. Intradialytic changes in NO and ET-1 with high and low dialysate-to-plasma Na+ gradients are shown in Figure 1. In the primary comparison of high vs low dialysate-to-serum Na+ gradient, there were no significant differences in intradialytic levels of NO or ET-1 (Table 1). However, when compared by randomization arm, participants who received the low dialysate-to-serum Na+ gradient followed by high compared to those who received the high dialysate-to-serum Na+ gradient followed by low had a significant decrease in ET-1 (parameter estimate -0.49 pg/mL, p=0.04) and significant increase in nitrite during hemodialysis (parameter estimate +0.16 nM, p=0.02) (Table 1). CONCLUSIONS: Patients who received the low dialysate-to-serum Na+ gradient before the high dialysate-to-serum Na+ gradient had higher levels of nitrite and lower levels of ET-1 throughout the three week study period compared to patients who received the high dialysate-to-serum Na+ gradient before the low dialysate-to-serum Na+ gradient. This suggests that the dialysate Na+ concentration may have longer-term effects on endothelial cell function.Item AIDS vasculopathy(2000-03-02) Terada, Lance S.Item Blood Vessel Development(2014-11-17) Koo, Yeon Seung; Carroll, Thomas J.; Cleaver, Ondine; Olson, Eric N.; Cobb, Melanie H.Cardiovascular system is the first developing functional organ in vertebrates, and one of the fundamental organ systems through adulthoods. Cardiovascular function depends on patent blood vessel formation by endothelial cells. In this dissertation, a careful analysis of different aspects of blood vessel development was conducted in order to expand our understandings of the biology of blood vessel. In brief, Chapter 2 provides an in depth description of vessel anatomy during formation of the first arteries and veins in developing murine embryos, and a stepwise acquisition of arteriovenous fate in these vessels. The dorsal aortae, the first intraembryonic vessels initiate arterial specification before complete circulation occurs, and gradually express a subset of arterial genes. The first veins then establish their fate later than the first arteries. It was also shown that the arteriovenous specification does not require hemodynamic flow, but the flow affects maintenance of select arterial genes. Chapter 3 focuses on the function of Rasip1 in vasculogenesis, angiogenesis and vessel maintenance in developing embryo and in adults. An observation of transient Rasip1 localization at apical membranes in endothelial cells during in vitro tube formation provided an insight where Rasip1 possibly functions. Mice lacking Rasip1 showed that Rasip1 is critical for lumen formation likely via recruiting Myosin to endothelial apical membranes to alter cell cytoskeleton during vasculogenesis. Rasip1 was also shown to be required for proper vessel remodeling and lumen formation during angiogenesis. I found, however, it is dispensable for adult established blood vessel lumen maintenance, making it a promising therapeutic target for anti-angiogenesis. Finally, in Chapter 4, I show my preliminary findings regarding the role of Arhgap29, a Rasip1 binding partner, during embryonic development. Genetic ablation of Arhgap29 in mice led to allantois-chorion fusion and cardiovascular defects during embryonic development. Arhgap29 expression patterns were correlated with the sites of defects, as Arhgap29 transcripts were seen in allantois and cardiovascular tissues. From these results, its potential role in regulation of cell adhesion, likely via RhoA, was suggested. Overall, this thesis describes basic aspects of vascular development and uncharacterized molecules in different aspects of cardiovascular function.Item Endothelial dysfunction in the pathogenesis and treatment of myocardial ischemia(1997-09-25) Andrews, Thomas C.Item Endothelial dysfunction: mechanism, syndrome, artifact or myth?(1993-09-30) Meidell, Robert S.Item The endothelium: a key regulator of vascular tone(1991-02-28) Henrich, William L.Item Histone Deacetylase 7 and Transcriptional Regulatory Networks of the Vascular Endothelium(2010-05-14) Young, Bryan Daniel; Olson, Eric N.Cells respond to stimuli in part through the modulation of gene expression. Signal transduction from the environment to the nucleus culminates in the activation of factors that modify chromatin structure to either facilitate or inhibit gene transcription. Histone acetyltransferases (HATs) and histone deacetylases (HDACs) are two such classes of enzymes that regulate the epigenetic code. Their opposing actions – to activate transcription by histone acetylation and to inhibit transcription by deacetylation – are tightly regulated to coordinate the vast gene programs required for cellular growth and differentiation. The class II HDACs are restricted in their expression patterns, and each have unique developmental and physiological functions. The studies described here focus on HDAC7, a class II HDAC that is expressed in vascular endothelial cells and whose function is essential for the maintenance of vascular integrity during embryogenesis. Mice lacking HDAC7 die by e11.5 with complex cardiovascular malformations including endothelial, vascular smooth muscle, and myocardial defects. By generating HDAC7 conditional knockout mice, it was observed that all of these defects are recapitulated in mice bearing an endothelial-specific deletion of HDAC7, but no defects are observed upon deletion of HDAC7 in the other cell types that were affected in the HDAC7 nulls. This in vivo evidence demonstrated that HDAC7 acts cell autonomously to maintain normal vascular development, and lead to the identification of the genetic abnormalities and mechanism leading to cardiovascular failure in the HDAC7 knockout. Further, this work begins the investigation of HDAC7 in adult vascular physiology, the findings of which will reveal new mechanisms whereby the vasculature responds to stress signals or disease. To this end, methods have been developed for the deletion of HDAC7 in the adult mouse using an inducible cre recombinase system together with the HDAC7 conditional allele. Additionally, these studies present progress toward the identification of the enhancer elements driving the endothelial-specific expression pattern of HDAC7. Detailed characterization of this enhancer is likely to implicate new signaling pathways as being involved in the genetic regulation of vascular development and maintenance. Finally, this work investigates the role of microRNAmediated gene silencing in the vascular system by identifying microRNAs involved in MEF2-dependent signaling in endothelial cells.Item Investigating Vascular Patterning and Regression in Kidney Development and Organoids(December 2021) Ryan, Anne Regina; Marciano, Denise; Munshi, Nikhil; Dellinger, Michael T.; Cleaver, OndineChronic kidney disease (CKD) and end stage renal disease (ESRD) are increasingly frequent and devastating conditions that have driven a surge in the need for kidney transplantation. A stark shortage of organs has fueled interest in generating viable replacement tissues ex vivo for transplantation. One promising approach has been self-organizing organoids, which mimic developmental processes and yield multicellular, organ-specific tissues. However, a recognized roadblock to this approach is that many organoid cell types fail to acquire full maturity and function. I comprehensively assessed the vasculature in two distinct kidney organoid models as well as in explanted embryonic kidneys. Using a variety of methods, my work shows that while organoids can develop a wide range of kidney cell types, as previously shown, endothelial cells (ECs) initially arise but then rapidly regress overtime in culture. Vasculature of cultured embryonic kidneys exhibit similar regression. By contrast, engraftment of kidney organoids under the kidney capsule results in the formation of a stable, perfused vasculature that integrates into the organoid. This work demonstrates that kidney organoids offer a promising model system to define the complexities of vascular-nephron interactions, but the establishment and maintenance of a vascular network present unique challenges when grown ex vivo. The future of the field necessitates the inclusion of flow and perhaps additional factors into in vitro culture methods. Future studies investigating endothelial heterogeneity in the developing kidney will aid in forwarding our mission of creating a functional organoid vasculature.Item Mechanisms of Intradialytic Hypertension(2012-08-15) Kim, Bohyun Catherine; Inrig, JulaIntradialytic Hypertension and Its Association with Endothelial Cell Dysfunction BACKGROUND: Intradialytic hypertension is associated with adverse outcomes, yet the mechanism is uncertain. Patients with intradialytic hypertension exhibit imbalances in endothelial-derived vasoregulators nitric oxide and endothelin-1, indirectly suggesting endothelial cell dysfunction. We hypothesized that intradialytic hypertension is associated in vivo with endothelial cell dysfunction, a novel predictor of adverse cardiovascular outcomes. DESIGN, SETTINGS, PARTICIPANTS, & MEASUREMENTS: We performed a case-control cohort study including 25 hemodialysis (HD) subjects without (controls) and 25 with intradialytic hypertension (an increase in systolic BP pre- to postdialysis greater than or equal to 10 mmHg greater than or equal to 4/6 consecutive HD sessions). The primary outcome was peripheral blood endothelial progenitor cells (EPCs) assessed by aldehyde dehydrogenase activity (ALDHbr) and cell surface marker expression (CD34+CD133+). We also assessed endothelial function by ultrasonographic measurement of brachial artery flow-mediated vasodilation (FMD) normalized for shear stress. Parametric and nonparametric t tests were used to compare EPCs, FMD, and BP. RESULTS: Baseline characteristics and comorbidities were similar between groups. Compared with controls, 2-week average predialysis systolic BP was lower among subjects with intradialytic hypertension (144.0 versus 155.5 mmHg), but postdialysis systolic BP was significantly higher (159.0 versus 128.1 mmHg). Endothelial cell function was impaired among subjects with intradialytic hypertension as measured by decreased median ALDHbr cells and decreased CD34+CD133+ cells (ALDHbr, 0.034% versus 0.053%; CD34+CD133+, 0.033% versus 0.059%). FMD was lower among subjects with intradialytic hypertension (1.03% versus 1.67%). CONCLUSIONS: Intradialytic hypertension is associated with endothelial cell dysfunction. We propose that endothelial cell dysfunction may partially explain the higher event rates observed in these patients. ----- Probing the Mechanisms of Intradialytic Hypertension: a Pilot Study Targeting Endothelial Cell Dysfunction BACKGROUND: Intradialytic hypertension may be caused by an impaired endothelial cell response to hemodialysis. Carvedilol has been shown to improve endothelial cell function in vivo and in vitro to block endothelin-1 release. Among patients with intradialytic hypertension, we hypothesized that carvedilol would improve endothelial cell function and reduce the occurrence of intradialytic hypertension. DESIGN, SETTINGS, PARTICIPANTS & MEASUREMENTS: We performed a prospective 12-week pilot study of carvedilol titrated to 50 mg twice daily among 25 hemodialysis participants with intradialytic hypertension. Each patient served as their own control. Changes in endothelial cell function (assessed by flow-mediated vasodilation, endothelial progenitor cells (EPCs by aldehyde dehydrogenase activity and CD34+CD133+), asymmetric dimethylarginine (ADMA) and endothelin-1) and blood pressure (BP) from baseline to study-end were analyzed by paired tests. RESULTS: Flow-mediated vasodilation was significantly improved with carvedilol (from 1.03% to 1.40%, p=0.02). There was no significant change in EPCs, endothelin-1 or ADMA. At baseline, participants exhibited a significant increase in endothelin-1 pre to postdialysis that resolved by study-end. While pre-hemodialysis systolic BP was unchanged (144 to 146 mmHg, p=0.5), post-hemodialysis systolic BP, 44-hour ambulatory systolic BP, and the frequency of intradialytic hypertension decreased with carvedilol (159 to 142 mmHg, p<0.0001; 155 to 148 mmHg, p=0.05; 77% (4.6/6) to 28% (1.7/6), p<0.0001, respectively). CONCLUSIONS: Among hemodialysis participants with intradialytic hypertension, targeting endothelial cell dysfunction with carvedilol was associated with modest improvements in endothelial cell function, improved intra and interdialytic BP, and reduced frequency of intradialytic hypertension. Randomized controlled trials are required to confirm these findings. ----- The Role of Dialysate Exposure in Intradialytic Hypertension BACKGROUND: Intradialytic hypertension is associated with endothelial dysfunction, but the cause of vascular impairment is unknown. Exposure to high concentration sodium has been shown in vitro to promote endothelial stiffness and imbalances in markers of vascular function. We hypothesized that, among patients with intradialytic hypertension, exposure to dialysate sodium would lead to increases in endothelin-1, decreases in nitric oxide, and an intradialytic increase in systolic blood pressure. DESIGN, SETTINGS, PARTICIPANTS & MEASUREMENTS: We performed a 6-week crossover study of 10 hemodialysis patients with intradialytic hypertension. Changes in blood pressure, endothelin-1, and nitric oxide levels were measured during three different, midweek dialysis treatments consisting of: 1) regular hemodialysis with standard dialysate sodium (140 mEq/L); 2) ultrafiltration only without dialysate exposure; and 3) hemodialysis (Na 140 mEq/L) without ultrafiltration. These changes were analyzed using mixed model analyses. RESULTS: Serum sodium levels rose with dialysate exposure during regular HD and HD without UF sessions (+1.6 and +3 mEq/L, respectively), and fell during UF only session (-0.9 mEq/L). Endothelin-1 level also rose with dialysate exposure during regular HD and HD without UF (+0.15 and +0.25pg/mL, respectively), but fell during UF only session (-0.02 pg/mL). Plasma nitrite levels fell with all treatment types, most significantly with regular HD (-123.25 nM), then HD without UF (-52.77 nM), with lowest decrease seen during UF only session without dialysate exposure (-48.48 nM). Systolic BP rose during all treatments, most significantly with HD without UF (13.3%), followed by regular dialysis (6.9%), and UF only (5.7%). CONCLUSIONS: Among hemodialysis patients prone to intradialytic hypertension, there was an association between dialysate exposure and increases in endothelin-1, decreases in nitric oxide, and increases in systolic blood pressure during dialysis. We propose that high dialysate to plasma sodium gradient may contribute to intradialytic hypertension.Item Targeting Aminophospholipids Exposed on Tumor Endothelium for Tumor Imaging(2012-07-20) Stafford, Jason Hugh; Thorpe, Philip E.Advances in noninvasive imaging of human cancer are crucial to improving diagnosis and therapeutic planning. My project was aimed at developing novel imaging agents that target the aminophospholipidsphosphatidylserine (PS) and phosphatidylethanolamine (PE). PS and PE arenormally intracellular, but become exposed on the surface of tumor endothelial cells (EC). Anti-tumor therapies promote exposure of PS and PE on tumor EC and the tumor cells as well. Therefore, I tested the hypothesis that 1N11, a PS-binding antibody, and duramycin, a PE-binding peptide, could function as tumor imaging agents. I labeled the F(ab')₂ fragment of 1N11 with the near-infrared fluophore 800CW for optical imaging and the positron emitting isotope iodine-124 (¹²⁴I) for PET imaging. 800CW-1N11 F(ab')₂ clearly imaged subcutaneous and orthotopic U87 gliomas growing in mice with optimal tumor contrast obtained at 24 h post-injection (p.i.). Uptake of 800CW-1N11 F(ab')₂ was approximately 2-fold higher in irradiated U87 tumors. ¹²⁴I-1N11 F(ab')₂ clearly imaged subcutaneous and orthotopic PC3 prostate carcinomas growing in mice with optimal tumor contrast obtained at 48 hr p.i. Importantly, 800CW- and ¹²⁴I-1N11 F(ab')₂ exhibited low uptake in non-target organs (i.e. liver and kidneys). Unlike PS, PE had not been established as a specific marker of tumor vasculature in the literature. To demonstrate PE was such a marker, I biotinylated duramycin, characterized its binding properties, and used it to determine the distribution of PE on EC in vitro and in vivo. Exposure of cultured EC to hypoxia, acidity, reactive oxygen species, or irradiation resulted in the formation of membrane blebs that were intensely PE-positive. When biotinylated duramycin was intravenously injected into tumor-bearing mice it preferentially localized to the luminal surface of the vascular endothelium in multiple tumor models. PE-positive vessels were observed in and around hypoxic regions of the tumor. With the exception of intertubular vessels of the kidney, normal vessels remained unstained. I also conjugated duramycin to 800CW and used it for optical imaging of RM-9 and TRAMP prostate carcinomas. These results demonstrate that both 1N11 and duramycin can be used to image a variety of tumors and warrant further study as imaging agents.