This study plans to learn how endothelial cells, single cell lining of blood vessels may be dysfunctional after a spinal cord injury. Endothelial dysfunction will be measured by the capacity of blood vessels to vasodilate (increase in size) and alter blood flow is lower in adults with a spinal cord injury in comparison to adults without a spinal cord injury. The mechanisms which may alter this function may be critical in reducing the risk of heart attacks and strokes in people with spinal cord injuries.
Vascular endothelial dysfunction is prevalent after spinal cord injury (SCI) which predispose individuals with SCI to accelerated, atherosclerotic cardiovascular disease (ASCVD) and future myocardial infarctions and ischemic strokes. The central objective of this study is to determine whether adults with SCI exhibit impaired endothelial function. Specifically, if endothelium-dependent vasodilation is impaired and if endothelial cell derived microvesicles (EMVs) are elevated and dysfunctional in adults with paraplegia. Endothelium-dependent vasodilation will be assessed by pharmacologically manipulating endothelial vasodilator function in live conscious humans with SCI and determining the role of circulating EMVs as both a systemic biomarker and mediator of endothelial dysfunction.
Study Type
OBSERVATIONAL
Enrollment
40
A catheter is placed in the brachial artery of the non-dominant arm, and small doses of vasoactive drugs \[acetylcholine (Ach), isoproterenol (ISO), sodium nitroprusside (SNP)\] are infused. Forearm blood flow (FBF) is measured using venous occlusion plethysmography. The purpose of this procedure is to assess endothelium-dependent and independent vasodilation by stimulating different vascular pathways. The Ach infusion is to test muscarinic receptor, nitro oxide (NO) dependent, endothelium-dependent vasodilation. ISO infusion is to evaluate β-adrenergic, NO-dependent endothelium-dependent vasodilation. SNP infusion is to assess endothelium-independent vasodilation.
Vitamin C, a potent antioxidant, will be infused into the arm and forearm blood flow (FBF) will be re-evaluated to determine whether oxidative stress contributes to endothelial dysfunction.
Craig Hospital
Englewood, Colorado, United States
RECRUITINGEndothelium-dependent vasodilation
Total forearm blood flow with be measured by strain gauge venous plethysmography under baseline conditions and under pharmacological manipulation with acetylcholine and isoproterenol at increasing concentrations.
Time frame: Measured at baseline and immediately after each vasoactive dose for 3-5 minutes.
Endothelium-independent vasodilation
Total forearm blood flow with be measured by strain gauge venous plethysmography under baseline conditions and under pharmacological manipulation with sodium nitroprusside at increasing concentrations (1, 2, 4ug/ml).
Time frame: Measured at baseline (without sodium nitroprusside) and immediately after each sodium nitroprusside dose for 3-5 minutes.
Endothelial cell-derived microvesicles concentration
Endothelial cell-derived microvesicles will be collected from venous blood samples and counted used flow cytometry to determine a circulating concentration.
Time frame: Baseline
Endothelial cell-derived microvesicles effects of human coronary artery endothelial cells nitric oxide bioavailability
Endothelial cell-derived microvesicles will be sorted and collected by fluorescence-activated cell sorting (FACS) flow cytometry. The endothelial cell-derived microvesicles will be co-cultured with human coronary artery endothelial cells. Endothelial Nitric Oxide Synthase and phosphorylation sites of interest will be measured by intracellular protein expression quantification of whole cell lysates by capillary electrophoresis immunoassays. Nitric oxide production will be assessed by total nitric oxide and nitrate/nitrite parameter assays.
Time frame: Baseline
Endothelial cell-derived microvesicles effects of human coronary artery endothelial cells reactive oxygen species and antioxidant capacity
Endothelial cell-derived microvesicles will be sorted and collected by fluorescence-activated cell sorting (FACS) flow cytometry. The endothelial cell-derived microvesicles will be co-cultured with human coronary artery endothelial cells. Super oxide dismutase and catalase expression will be measured by intracellular protein expression quantification of whole cell lysates by capillary electrophoresis immunoassays. Intracellular oxidative stress will be assessed by ROS-Glo H2O2 assay.
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Blood will be sampled from the antecubital vein (\~50 mL) for biomarker analysis. This is to assess circulating biochemical and molecular indicators of vascular health and inflammation including levels of endothelial cell derived microvesicles (EMVs)
Time frame: Baseline