Acute Pressor Response to Psychosocial Stress Is Dependent on Endothelium-Derived Endothelin-1

Abstract

Background: Acute psychosocial stress provokes increases in circulating endothelin-1 (ET-1) levels in humans and animal models. However, key questions about the physiological function and cellular source of stress-induced ET-1 remain unanswered. We hypothesized that endothelium-derived ET-1 contributes to the acute pressor response to stress via activation of the endothelin A receptor.

Methods and results: Adult male vascular endothelium-specific ET-1 knockout mice and control mice that were homozygous for the floxed allele were exposed to acute psychosocial stress in the form of cage switch stress (CSS), with blood pressure measured by telemetry. An acute pressor response was elicited by CSS in both genotypes; however, this response was significantly blunted in vascular endothelium-specific ET-1 knockout mice compared with control mice that were homozygous for the floxed allele. In mice pretreated for 3 days with the endothelin A antagonist, ABT-627, or the dual endothelin A/B receptor antagonist, A-182086, the pressor response to CSS was similar between genotypes. CSS significantly increased plasma ET-1 levels in control mice that were homozygous for the floxed allele. CSS failed to elicit an increase in plasma ET-1 in vascular endothelium-specific ET-1 knockout mice. Telemetry frequency domain analyses suggested similar autonomic responses to stress between genotypes, and isolated resistance arteries demonstrated similar sensitivity to α₁-adrenergic receptor-mediated vasoconstriction.

Conclusions: These findings specify that acute stress-induced activation of endothelium-derived ET-1 and subsequent endothelin A receptor activation is a novel mediator of the blood pressure response to acute psychosocial stress.

Keywords: cage switch stress; endothelin‐1; endothelium‐derived factors; psychosocial stress; stress; vascular endothelium‐specific ET‐1 knockout mice.

Figure 1

Blood pressure responses to cage switch stress (CSS) in vascular endothelium‐specific endothelin‐1 knockout (VEETKO) mice and control mice that were homozygous for the floxed allele (flox) receiving normal drinking water. Mean arterial pressure (A), systolic pressure (B), diastolic pressure (C), heart rate (D), and locomotor activity (E) in VEETKO (n=9) and flox (n=7) mice exposed to CSS.

Figure 2

Blood pressure responses to cage switch stress (CSS) in vascular endothelium‐specific endothelin‐1 knockout (VEETKO) mice and control mice that were homozygous for the floxed allele (flox) receiving water containing ABT‐627 for 3 days before CSS exposure. Mean arterial pressure (A), systolic pressure (B), diastolic pressure (C), heart rate (D), and locomotor activity (E) in VEETKO (n=6) and flox (n=9) mice.

Figure 3

Blood pressure responses to cage switch stress (CSS) in vascular endothelium‐specific endothelin‐1 knockout (VEETKO) mice and control mice that were homozygous for the floxed allele (flox) receiving water containing A‐182086 for 3 days before CSS exposure. Mean arterial pressure (A), systolic pressure (B), diastolic pressure (C), heart rate (D), and locomotor activity (E) in VEETKO (n=8) and flox (n=8) mice.

Figure 4

Plasma endothelin‐1 (ET‐1) peptide level in response to cage switch stress (CSS) and endothelin B (ET_B) receptor expression in lung membrane–enriched homogenates of vascular endothelium‐specific ET‐1 knockout (VEETKO) mice and control mice that were homozygous for the floxed allele (flox). A, Plasma ET‐1 level is significantly elevated 30 minutes after the onset of CSS in flox control mice, but it is unchanged from baseline in VEETKO mice. *P<0.05 vs flox baseline; P _stress=0.014, P _genotype <0.001, P _interaction=0.278; flox baseline (n=5), flox CSS (n=5), VEETKO baseline (n=6), VEETKO CSS (n=5); 2‐way ANOVA with Bonferroni post hoc test. B, Calculated ET_B receptor expression, P=0.174, 2‐tailed, unpaired, Student t test. C, ET‐1–specific binding in flox and VEETKO mice (maximal binding [B_Max]: 580.8±112.6 vs 597.9±67.1 fmol/mg protein [P=0.901]; K_d: 0.11±0.03 vs 0.09±0.02 nmol/L [P=0.584]; 2‐tailed, unpaired, Student t test). D, ET‐3 specific binding in flox (n=4) and VEETKO (n=4) mice (B_{M ax}: 784.4±60.0 vs 623.7±84.9 fmol/mg protein [P=0.173]; K_d: 0.20±0.05 vs 0.11±0.03 nmol/L [P=0.166]; 2‐tailed, unpaired, Student t test). K_d indicates dissociation constant.

Figure 5

Heart rate variability and frequency blood pressure variability responses to cage switch stress (CSS) in vehicle, ABT‐627, and A‐182086 treated vascular endothelium‐specific endothelin‐1 knockout (VEETKO) mice and control mice that were homozygous for the floxed allele (flox). Systolic blood pressure variability low‐/high‐frequency ratio (Systolic LF/HF) in vehicle (n=7 flox, n=9 VEETKO; A), ABT‐627 (n=8 flox, n=6 VEETKO; C), and A‐182086 (n=8 flox, n=8 VEETKO; E) treated mice. Root means squared of the successive differences (RMSSD) relative to baseline in vehicle (n=6 flox, n=8 VEETKO; B), ABT‐627 (n=8 flox, n=6 VEETKO; D), and A‐182086 (n=8 flox, n=7 VEETKO; F) treated mice. G, Adrenal norepinephrine content at baseline and following 30 minutes of CSS exposure (n=4 flox baseline, n=4 flox CSS, n=6 VEETKO baseline, n=5 VEETKO CSS). H, Two‐way repeated‐measures ANOVA results (A through F) and ordinary 2‐way ANOVA results (G).

Figure 6

Vascular reactivity of isolated aorta and third‐order mesenteric arteries of vascular endothelium‐specific endothelin‐1 knockout (VEETKO) mice and control mice that were homozygous for the floxed allele (flox). A, Cumulative concentration‐response curves to phenylephrine (PE) in aorta of flox (n=4) and VEETKO (n=5) mice (Emax: 89.76±0.48% KCl vs 88.26±2.05% KCl [P=0.545]; EC ₅₀: −7.089±0.062 vs −7.029±0.064 log [PE] [P=0.532]; 2‐tailed, unpaired, Student t test). B, Cumulative concentration‐response curves to PE in third‐order mesenteric arteries of flox (n=4) and VEETKO (n=5) mice (Emax: 91.25±4.65% KCl vs 97.84±6.95% KCl [P=0.482]; EC ₅₀: −5.982±0.108 vs −6.169±0.106 log [PE] [P=0.262]; 2‐tailed, unpaired, Student t test). C, Acute constriction to 10⁻⁴ mol/L PE in aorta of flox (n=3) and VEETKO (n=5) mice (maximum contraction: 44.52±1.91% KCl and 44.01±1.05% KCl [P=0.805]; 2‐tailed, unpaired, Student t test). D, Acute constriction to 10⁻⁴ mol/L PE in third‐order mesenteric arteries of flox (n=4) and VEETKO (n=5) mice (maximum contraction: 95.54±5.60% KCl vs 103.58±3.50% KCl [P=0.244]; 2‐tailed, unpaired, Student t test). Emax indicates maximal effective concentration.