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HIF-1α Mediates Isoflurane-Induced Vascular Protection in Subarachnoid Hemorrhage.

Milner E, Johnson AW, Nelson JW, Harries MD, Gidday JM, Han BH, Zipfel GJ - Ann Clin Transl Neurol (2015)

Bottom Line: Isoflurane postconditioning provides strong HIF-1α-mediated macro- and microvascular protection in SAH, leading to improved neurological outcome.These results implicate cerebral vessels as a key target for the brain protection afforded by isoflurane postconditioning, and HIF-1α as a critical mediator of this vascular protection.They also identify isoflurane postconditioning as a promising novel therapeutic for SAH.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurological Surgery, Washington University School of Medicine St. Louis, Missouri, 63108 ; Program in Neuroscience, Washington University School of Medicine St. Louis, Missouri, 63108.

ABSTRACT

Objective: Outcome after aneurysmal subarachnoid hemorrhage (SAH) depends critically on delayed cerebral ischemia (DCI) - a process driven primarily by vascular events including cerebral vasospasm, microvessel thrombosis, and microvascular dysfunction. This study sought to determine the impact of postconditioning - the phenomenon whereby endogenous protection against severe injury is enhanced by subsequent exposure to a mild stressor - on SAH-induced DCI.

Methods: Adult male C57BL/6 mice were subjected to sham, SAH, or SAH plus isoflurane postconditioning. Neurological outcome was assessed daily via sensorimotor scoring. Contributors to DCI including cerebral vasospasm, microvessel thrombosis, and microvascular dysfunction were measured 3 days later. Isoflurane-induced changes in hypoxia-inducible factor 1alpha (HIF-1α)-dependent genes were assessed via quantitative polymerase chain reaction. HIF-1α was inhibited pharmacologically via 2-methoxyestradiol (2ME2) or genetically via endothelial cell HIF-1α- mice (EC-HIF-1α-). All experiments were performed in a randomized and blinded fashion.

Results: Isoflurane postconditioning initiated at clinically relevant time points after SAH significantly reduced cerebral vasospasm, microvessel thrombosis, microvascular dysfunction, and neurological deficits in wild-type (WT) mice. Isoflurane modulated HIF-1α-dependent genes - changes that were abolished in 2ME2-treated WT mice and EC-HIF-1α- mice. Isoflurane-induced DCI protection was attenuated in 2ME2-treated WT mice and EC-HIF-1α- mice.

Interpretation: Isoflurane postconditioning provides strong HIF-1α-mediated macro- and microvascular protection in SAH, leading to improved neurological outcome. These results implicate cerebral vessels as a key target for the brain protection afforded by isoflurane postconditioning, and HIF-1α as a critical mediator of this vascular protection. They also identify isoflurane postconditioning as a promising novel therapeutic for SAH.

No MeSH data available.


Related in: MedlinePlus

Postconditioning reverses SAH-induced microvascular dysfunction. Mice underwent sham surgery, subarachnoid hemorrhage (SAH) surgery, or SAH surgery followed 1 h later by isoflurane postconditioning (2% for 1 h, SAH-postC). On post surgery day 3, microvessel reactivity of the distal middle cerebral artery (MCA) was examined through an open cranial window. Pial arteriolar vasodilatory responses to hypercapnia (CO2), the endothelium-dependent vasodilator acetylcholine (ACh), and the endothelium-independent vasodilator S-nitroso-N-acetyl-penicillamine (SNAP) were assessed. N = 7 per group. Data represent mean ± SEM. *P < 0.05 by ANOVA.
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fig03: Postconditioning reverses SAH-induced microvascular dysfunction. Mice underwent sham surgery, subarachnoid hemorrhage (SAH) surgery, or SAH surgery followed 1 h later by isoflurane postconditioning (2% for 1 h, SAH-postC). On post surgery day 3, microvessel reactivity of the distal middle cerebral artery (MCA) was examined through an open cranial window. Pial arteriolar vasodilatory responses to hypercapnia (CO2), the endothelium-dependent vasodilator acetylcholine (ACh), and the endothelium-independent vasodilator S-nitroso-N-acetyl-penicillamine (SNAP) were assessed. N = 7 per group. Data represent mean ± SEM. *P < 0.05 by ANOVA.

Mentions: To determine the temporal window for postconditioning-induced protection, we exposed mice to isoflurane at various times after SAH surgery. Nonpostconditioned mice served as controls. All mice subjected to SAH surgery were found to have SAH at the time of animal sacrifice; no mice subjected to sham surgery were found to have SAH at the time of animal sacrifice. Mortality was not significantly different between groups (nonpostconditioned = 6.1%; postconditioned = 6.9%). Substantial DCI protection, however, was noted between postconditioned and nonpostconditioned mice. Specifically, SAH-induced vasospasm was eliminated when postconditioning was initiated 15 min, 1 h, or 3 h after SAH; this protection was lost when postconditioning began 6 h after SAH (Fig.1A and B; P < 0.05, ANOVA). Given the robust protection seen with postconditioning starting at 1 h, this time point was used for subsequent experiments. Other vascular contributors to DCI were also significantly improved by postconditioning. Extensive cortical microvessel thrombosis was noted in MCA-territory of the cerebral cortex after SAH, which was significantly reduced by postconditioning (Fig.2A and B; P < 0.05, ANOVA). SAH-induced microvascular dysfunction was also attenuated by postconditioning (Fig.3). Cerebral microvascular function was significantly impaired after SAH as assessed by responses to physiologic hypercapnia, as well as to local application of the endothelium-dependent and endothelium-independent dilators ACh and SNAP, respectively, compared to sham animals. Postconditioning fully restored the vasodilatory responses to hypercapnia and SNAP (Fig.3; P < 0.05, ANOVA). Together, these results show that isoflurane postconditioning after experimental SAH positively impacts multiple vascular contributors to DCI. This is direct evidence that isoflurane postconditioning induces strong protection of the cerebrovasculature and indicates this strategy is a novel and promising therapeutic approach toward ameliorating the devastating effects of SAH-induced DCI.


HIF-1α Mediates Isoflurane-Induced Vascular Protection in Subarachnoid Hemorrhage.

Milner E, Johnson AW, Nelson JW, Harries MD, Gidday JM, Han BH, Zipfel GJ - Ann Clin Transl Neurol (2015)

Postconditioning reverses SAH-induced microvascular dysfunction. Mice underwent sham surgery, subarachnoid hemorrhage (SAH) surgery, or SAH surgery followed 1 h later by isoflurane postconditioning (2% for 1 h, SAH-postC). On post surgery day 3, microvessel reactivity of the distal middle cerebral artery (MCA) was examined through an open cranial window. Pial arteriolar vasodilatory responses to hypercapnia (CO2), the endothelium-dependent vasodilator acetylcholine (ACh), and the endothelium-independent vasodilator S-nitroso-N-acetyl-penicillamine (SNAP) were assessed. N = 7 per group. Data represent mean ± SEM. *P < 0.05 by ANOVA.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4402079&req=5

fig03: Postconditioning reverses SAH-induced microvascular dysfunction. Mice underwent sham surgery, subarachnoid hemorrhage (SAH) surgery, or SAH surgery followed 1 h later by isoflurane postconditioning (2% for 1 h, SAH-postC). On post surgery day 3, microvessel reactivity of the distal middle cerebral artery (MCA) was examined through an open cranial window. Pial arteriolar vasodilatory responses to hypercapnia (CO2), the endothelium-dependent vasodilator acetylcholine (ACh), and the endothelium-independent vasodilator S-nitroso-N-acetyl-penicillamine (SNAP) were assessed. N = 7 per group. Data represent mean ± SEM. *P < 0.05 by ANOVA.
Mentions: To determine the temporal window for postconditioning-induced protection, we exposed mice to isoflurane at various times after SAH surgery. Nonpostconditioned mice served as controls. All mice subjected to SAH surgery were found to have SAH at the time of animal sacrifice; no mice subjected to sham surgery were found to have SAH at the time of animal sacrifice. Mortality was not significantly different between groups (nonpostconditioned = 6.1%; postconditioned = 6.9%). Substantial DCI protection, however, was noted between postconditioned and nonpostconditioned mice. Specifically, SAH-induced vasospasm was eliminated when postconditioning was initiated 15 min, 1 h, or 3 h after SAH; this protection was lost when postconditioning began 6 h after SAH (Fig.1A and B; P < 0.05, ANOVA). Given the robust protection seen with postconditioning starting at 1 h, this time point was used for subsequent experiments. Other vascular contributors to DCI were also significantly improved by postconditioning. Extensive cortical microvessel thrombosis was noted in MCA-territory of the cerebral cortex after SAH, which was significantly reduced by postconditioning (Fig.2A and B; P < 0.05, ANOVA). SAH-induced microvascular dysfunction was also attenuated by postconditioning (Fig.3). Cerebral microvascular function was significantly impaired after SAH as assessed by responses to physiologic hypercapnia, as well as to local application of the endothelium-dependent and endothelium-independent dilators ACh and SNAP, respectively, compared to sham animals. Postconditioning fully restored the vasodilatory responses to hypercapnia and SNAP (Fig.3; P < 0.05, ANOVA). Together, these results show that isoflurane postconditioning after experimental SAH positively impacts multiple vascular contributors to DCI. This is direct evidence that isoflurane postconditioning induces strong protection of the cerebrovasculature and indicates this strategy is a novel and promising therapeutic approach toward ameliorating the devastating effects of SAH-induced DCI.

Bottom Line: Isoflurane postconditioning provides strong HIF-1α-mediated macro- and microvascular protection in SAH, leading to improved neurological outcome.These results implicate cerebral vessels as a key target for the brain protection afforded by isoflurane postconditioning, and HIF-1α as a critical mediator of this vascular protection.They also identify isoflurane postconditioning as a promising novel therapeutic for SAH.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurological Surgery, Washington University School of Medicine St. Louis, Missouri, 63108 ; Program in Neuroscience, Washington University School of Medicine St. Louis, Missouri, 63108.

ABSTRACT

Objective: Outcome after aneurysmal subarachnoid hemorrhage (SAH) depends critically on delayed cerebral ischemia (DCI) - a process driven primarily by vascular events including cerebral vasospasm, microvessel thrombosis, and microvascular dysfunction. This study sought to determine the impact of postconditioning - the phenomenon whereby endogenous protection against severe injury is enhanced by subsequent exposure to a mild stressor - on SAH-induced DCI.

Methods: Adult male C57BL/6 mice were subjected to sham, SAH, or SAH plus isoflurane postconditioning. Neurological outcome was assessed daily via sensorimotor scoring. Contributors to DCI including cerebral vasospasm, microvessel thrombosis, and microvascular dysfunction were measured 3 days later. Isoflurane-induced changes in hypoxia-inducible factor 1alpha (HIF-1α)-dependent genes were assessed via quantitative polymerase chain reaction. HIF-1α was inhibited pharmacologically via 2-methoxyestradiol (2ME2) or genetically via endothelial cell HIF-1α- mice (EC-HIF-1α-). All experiments were performed in a randomized and blinded fashion.

Results: Isoflurane postconditioning initiated at clinically relevant time points after SAH significantly reduced cerebral vasospasm, microvessel thrombosis, microvascular dysfunction, and neurological deficits in wild-type (WT) mice. Isoflurane modulated HIF-1α-dependent genes - changes that were abolished in 2ME2-treated WT mice and EC-HIF-1α- mice. Isoflurane-induced DCI protection was attenuated in 2ME2-treated WT mice and EC-HIF-1α- mice.

Interpretation: Isoflurane postconditioning provides strong HIF-1α-mediated macro- and microvascular protection in SAH, leading to improved neurological outcome. These results implicate cerebral vessels as a key target for the brain protection afforded by isoflurane postconditioning, and HIF-1α as a critical mediator of this vascular protection. They also identify isoflurane postconditioning as a promising novel therapeutic for SAH.

No MeSH data available.


Related in: MedlinePlus