Experimental Subarachnoid Hemorrhage Drives Catecholamine-Dependent Cardiac and Peripheral Microvascular Dysfunction

Subarachnoid hemorrhage (SAH) is a devastating cerebral event caused by an aneurysmal rupture. In addition to neurological injury, SAH has significant effects on cardiac function and the peripheral microcirculation. Since these peripheral complications may exacerbate brain injury, the prevention and management of these peripheral effects are important for improving the overall clinical outcome after SAH. In this investigation, we examined the effects of SAH on cardiac function and vascular reactivity in a well-characterized blood injection model of SAH. Standard echocardiographic and blood pressure measurement procedures were utilized to assess cardiac function and hemodynamic parameters in vivo; we utilized a pressure myography approach to assess vascular reactivity in cremaster skeletal muscle resistance arteries ex vivo. We observed that elevated catecholamine levels in SAH stun the myocardium, reduce cardiac output and augment myogenic vasoconstriction in isolated cremaster arteries. These cardiac and vascular effects are driven by beta- and alpha-adrenergic receptor signaling, respectively. Clinically utilized adrenergic receptor antagonists can prevent cardiac injury and normalize vascular function. We found that tumor necrosis factor (TNF) gene deletion prevents the augmentation of myogenic reactivity in SAH: since membrane-bound TNF serves as a mechanosensor in the arteries assessed, alpha-adrenergic signaling putatively augments myogenic vasoconstriction by enhancing mechanosensor activity.


Telemetric blood pressure measurements in mice with subarachnoid hemorrhage
Telemetric mean arterial blood pressure measurements in conscious mice indicate that mice with subarachnoid hemorrhage (SAH; n=3) do not develop hypertension within 1-week post-SAH induction (sham n=5). Baseline measurements were collected 1 day prior to SAH or sham surgery; the surgical window is delineated by dotted vertical lines. White and gray shading indicate "lights on" and "lights off" periods, respectively.

Representative diameter measurements
Stepwise increases in transmural pressure (20-100mmHg) are indicated in the boxes above the tracing. The active diameter tracing is acquired first ("diaactive"; black line), followed by measurement of passive diameter under calcium-free conditions ("diamax"; gray line). Shown are representative diameter tracings from cremaster skeletal muscle resistance arteries isolated from (A) sham-operated mice (diamax = 68 µm) and (B) mice with subarachnoid hemorrhage (SAH; diamax = 68 µm). Myogenic tone is calculated as the percent constriction in relation to the maximal diameter at each respective transmural pressure:

Post-operative bisoprolol treatment does not protect cardiac function following subarachnoid hemorrhage
When delivered immediately following experimental subarachnoid hemorrhage (SAH) induction, bisoprolol treatment (Bis; twice daily for 2 days with i.p. injections; 10 mg/kg initial pre-operative dose followed by 5 mg/kg for all subsequent injections) does not prevent the reduction in cardiac output at 2-days post-SAH (n=5 for all groups). The SAH and SAH+Bis groups were statistically compared with a Student's t test (P=N.S.).

Bisoprolol does not alter cremaster artery reactivity in sham animals
In sham-operated mice, in vivo bisoprolol treatment (Bis; twice daily for 2 days with i.p. injections; 10 mg/kg initial pre-operative dose followed by 5 mg/kg for all subsequent injections) has no effect on (A) myogenic reactivity or (B) phenylephrine responses in cremaster skeletal muscle resistance arteries isolated at 2 days post-surgery/treatment (sham diamax: 80±2 µm, n=13; Sham+Bis diamax: 70±4 µm, n=9). The sham data in both panels are reproduced from Figure 2  Control Bisoprolol

In vitro angiotensin II treatment does not alter cremaster artery myogenic reactivity or calcium sensitivity
Cremaster skeletal muscle resistance arteries isolated from naïve mice were treated for 4 hours with either 10 nmol/L angiotensin II or control buffer in vitro. The arteries were then washed and assessed in normal buffer. Angiotensin treatment does not affect (A) myogenic tone or (B) calcium sensitivity (control diamax: 69±4 µm, n=5; angiotensin II diamax: 78±5 µm, n=6). Data were statistically compared with a 2-way ANOVA.

SUPPLEMENTARY FIGURE 16
Terazosin does not alter olfactory cerebral artery reactivity in sham animals.

Echocardiographic measures in mice with subarachnoid hemorrhage
Data are means ± SEM (n=35 in both groups). * denotes P<0.05 for an unpaired comparison (Student's t test). Acronyms: LVEF − Left ventricular ejection fraction; SAH -subarachnoid hemorrhage.

Sham SAH
Mouse Body Weight (g)