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

FIGURE 1. Subarachnoid hemorrhage (SAH) induces a cardiovascular phenotype. At 2-days post-SAH induction, (A) plasma epinephrine levels are elevated (sham n = 8, SAH n = 10), (B) cardiac output is reduced (sham n = 35, SAH n = 35) and (C) total peripheral resistance is elevated (sham n = 7, SAH n = 8). (D) The elevated peripheral resistance correlates with augmented cremaster skeletal muscle resistance artery myogenic tone (sham diamax: 78 ± 2 μm, n = 26; SAH 78 ± 2 μm, n = 22). (E) Phenylephrine-stimulated vasoconstriction is also greater in cremaster arteries isolated from SAH mice (sham diamax: 78 ± 2 μm, n = 26; SAH 78 ± 2 μm, n = 22); however, (F) calcium sensitivity is unaffected (sham diamax: 72 ± 5 μm, n = 7; SAH diamax: 80 ± 3 μm, n = 8). *P < 0.05.

FIGURE 2. β-Adrenergic signaling drives the cardiac phenotype in SAH, but not the vascular phenotype. (A) Bisoprolol (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) prevents the compromised cardiac function observed at 2-days post-SAH induction (sham n = 12, SAH n = 11, SAH + Bis n = 10). (B) However, bisoprolol treatment does not prevent the augmentation of myogenic reactivity in cremaster skeletal muscle resistance arteries isolated from SAH mice, nor (C) does it alter vasoconstriction in response to phenylephrine (sham diamax: 80 ± 2 μm, n = 13; SAH diamax: 80 ± 2 μm, n = 10; SAH + Bis diamax: 76 ± 2 μm, n = 7). (D) In naïve mice, the β-adrenergic receptor agonist isoproterenol (150 mg/kg i.p. for 2 days) reduces cardiac output (control n = 5, Isoproterenol n = 9). However, in contrast to SAH, both (E) myogenic reactivity and (F) phenylephrine responses in cremaster skeletal muscle resistance arteries isolated from isoproterenol-treated mice are attenuated (control diamax: 80 ± 4 μm, n = 8; isoproterenol diamax: 79 ± 2 μm, n = 8). *P < 0.05.

FIGURE 3. α-Adrenergic signaling drives the vascular phenotype in SAH, but not the cardiac phenotype. (A) Terazosin (TZ; twice daily for 2 days with i.p. injections; 1 mg/kg initial pre-operative dose followed by 0.5 mg/kg for all subsequent injections) has no effect on the compromised cardiac function observed at 2-days post-SAH induction (sham n = 16, SAH n = 16, SAH + TZ n = 12). (B) However, terazosin treatment successfully normalizes the augmented myogenic reactivity in cremaster skeletal muscle arteries isolated from SAH mice. (C) Phenylephrine responses are enhanced in cremaster arteries isolated from SAH mice; this augmentation is also normalized by terazosin treatment (sham diamax: 76 ± 3 μm, n = 13; SAH diamax: 76 ± 3 μm, n = 12; SAH + TZ diamax: 74 ± 2 μm, n = 13). (D) Calcium sensitivity is not altered by terazosin treatment (SAH diamax: 80 ± 3 μm, n = 8; SAH + TZ diamax: 78 ± 4 μm, n = 7). The SAH curve in (D) is reproduced from Figure 1E for comparison to the SAH + TZ curve. *P < 0.05.

FIGURE 4. α-Adrenergic signals augment myogenic reactivity in vitro. In (A–C), cremaster skeletal muscle resistance arteries isolated from naïve mice were treated for 4 h with either 1 μmol/L phenylephrine or control buffer in vitro. The arteries were then washed and assessed in normal buffer. (A) Arteries treated with phenylephrine possess higher myogenic reactivity than control arteries. Although in vitro phenylephrine treatment (B) does not affect subsequent phenylephrine-stimulated vasoconstriction responses, (C) calcium sensitivity is increased (control diamax: 69 ± 2 μm, n = 10; phenylephrine diamax: 73 ± 3 μm, n = 9). (D) Phenylephrine-stimulated vasoconstriction is abolished in cremaster skeletal muscle resistance arteries isolated from smooth muscle cell-targeted Gq11 knockout mice [sm-Gq11(KO); diamax: 96 ± 10, n = 6], relative to wild-type littermate controls [sm-Gq11(WT); diamax: 83 ± 6, n = 6]. (E) In addition to eliminating phenylephrine responses, smooth muscle cell-targeted Gq11 gene deletion also attenuates myogenic tone [sm-Gq11(WT) diamax: 83 ± 6, n = 6; sm-Gq11(KO) diamax: 88 ± 12, n = 4]. *P < 0.05.

FIGURE 5. Tumor necrosis factor (TNF) gene deletion abolishes the SAH-induced myogenic tone augmentation. In cremaster skeletal muscle resistance arteries isolated from germline tumor necrosis factor knockout mice (TNF KO), neither (A) myogenic tone nor (B) phenylephrine responses are affected by SAH (at 2-days post-SAH induction; sham diamax: 69 ± 4 μm, n = 7; SAH diamax: 71 ± 6 μm, n = 6). Accordingly, in cremaster skeletal muscle resistance arteries isolated from smooth muscle cell-targeted tumor necrosis factor knockout mice (sm-TNF KO), neither (C) myogenic tone (sham diamax: 90 ± 4, n = 6; SAH diamax: 77 ± 7, n = 6) nor (D) phenylephrine responses are affected by SAH (sham diamax: 90 ± 4, n = 6; SAH diamax: 72 ± 6, n = 7).

FIGURE 6. ∝-adrenergic signaling augments myogenic reactivity and calcium sensitivity despite tumor necrosis factor (TNF) gene deletion. Cremaster skeletal muscle resistance arteries isolated from TNF KO mice were treated for 4 h with either 1 μmol/L phenylephrine or control buffer in vitro. The arteries were then washed and assessed in normal buffer. Arteries treated with phenylephrine display higher (A) myogenic reactivity (control diamax: 71 ± 4 μm, n = 5; phenylephrine diamax: 70 ± 3 μm, n = 6) and (B) calcium sensitivity (control diamax: 68 ± 6 μm, n = 5; phenylephrine diamax: 69 ± 4 μm, n = 5) than control arteries; however, the treatment does not affect (C) responses to phenylephrine (control diamax: 68 ± 6 μm, n = 5; phenylephrine diamax: 69 ± 4 μm, n = 5). *P < 0.05.

FIGURE 7. Cerebral and cremaster resistance arteries have distinct phenotypes. (A) Terazosin (TZ; twice daily for 2 days with i.p. injections; 1 mg/kg initial pre-operative dose followed by 0.5 mg/kg for all subsequent injections) does not normalize the augmented myogenic reactivity observed in olfactory cerebral arteries isolated from mice at 2-days post-SAH induction (sham diamax: 108 ± 4 μm, n = 6; SAH diamax: 104 ± 7 μm, n = 5; SAH + TZ diamax: 101 ± 9 μm, n = 5). (B) Phenylephrine responses in olfactory cerebral arteries are unaffected by SAH or terazosin treatment (sham diamax: 110 ± 4 μm, n = 5; SAH diamax: 104 ± 7 μm, n = 5; SAH + TZ diamax: 108 ± 10 μm, n = 6). (C) Phenylephrine-stimulated vasoconstriction is abolished in olfactory cerebral resistance arteries isolated from smooth muscle cell-targeted Gq11 knockout mice [sm-Gq11(KO); diamax = 156 ± 5 μm, n = 10], relative to wild-type littermate controls [sm-Gq11(WT); diamax = 144 ± 5, n = 5]. However, (D) there is no effect of the targeted Gq11 gene deletion on myogenic tone. *P < 0.05.