Intermittent Hypoxia-Induced Activation of Endothelial Cells Is Mediated via Sympathetic Activation-Dependent Catecholamine Release

Figures

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  Figure 1. Intermittent hypoxia induces activation of aortic endothelial cells (ECs) in mice. We exposed C57BL/6 mice to either normoxia (N) or IH for 10 days and removed and flushed aorta with TRI Reagent to isolate RNA from aortic ECs and then assessed EC activation by measuring mRNA expression of markers of EC activation genes, including il6, kc, vcam1, and icam1. N = 5–6. Significance was determined by Student’s t-test. *p < 0.05, **p < 0.005, and ****p < 0.0001.

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  Figure 2. Intermittent hypoxia alone fails to induce aortic EC activation in vitro. We exposed human aortic ECs to either normoxia (N) or IH for 60 cycles and then assessed EC activation by measuring mRNA expression of markers of EC activation genes, including IL6, IL8, VCAM1, and ICAM1. N = 4–6.

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  Figure 3. Intermittent hypoxia increases systemic catecholamine levels. We exposed C57BL/6 mice to either normoxia (N) or IH for 10 days in the absence or presence of 6-hydroxydopamine (6OHDA), which depletes catecholamines. We also exposed adrenalectomized (Adr) mice to IH for 10 days. At the end of experiments, we collected plasma and measured catecholamine (epinephrine and norepinephrine) levels. N = 5–6. Significance was determined by one-way ANOVA using Bonferroni’s correction. ns, not significant. *p < 0.05, **p < 0.005, ***p < 0.001, and ****p < 0.0001.

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  Figure 4. Intermittent hypoxia-induced catecholamines are required for intermittent hypoxia-induced aortic EC activation in mice. We exposed C57BL/6 mice to normoxia (N) or IH for 10 days in the absence or presence of 6OHDA. We also exposed mice with adrenalectomy (Adr) and carotid body ablation (CBA) to IH for 10 days. We then assessed EC activation by measuring mRNA expression of markers of EC activation genes, including il6, kc, and vcam1. N = 5–6. Significance was determined by one-way ANOVA using Bonferroni’s correction. **p < 0.005; ****p < 0.0001.

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  Figure 5. Epinephrine alone is sufficient to induce EC activation and leukocyte adhesion in the absence of IH in vitro. We treated ECs with epinephrine (Epi; 10 μm) or vehicle control (C) under normoxia for 24 h and then (A) assessed EC activation by measuring mRNA expression of markers of EC activation genes, including IL6, VCAM1, and ICAM1 (N = 4; significance was determined by Student’s t-test) and (B) leukocyte adhesion (N = 8–10; significance was determined by one-way ANOVA using Bonferroni’s correction for multiple comparisons). ns, not significant. ***p < 0.001; ****p < 0.0001.

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  Figure 6. Epinephrine alone is sufficient to induce EC activation in vivo. We placed Alzet pumps in C57BL/6 mice to deliver epinephrine (Epi) or control vehicle (C) continuously for 10 days. We then assessed EC activation by measuring mRNA expression of markers of EC activation genes, including il6, kc, and vcam1. N = 4–5. Significance was determined by Student’s t-test. *p < 0.05; ****p < 0.0001.