SIRT1 mediates hypoxic postconditioning- and resveratrol-induced protection against functional connectivity deficits after subarachnoid hemorrhage

Abstract

Functional connectivity (FC) is a sensitive metric that provides a readout of whole cortex coordinate neural activity in a mouse model. We examine the impact of experimental SAH modeled through endovascular perforation, and the effectiveness of subsequent treatment on FC, through three key questions: 1) Does the endovascular perforation model of SAH induce deficits in FC; 2) Does exposure to hypoxic conditioning provide protection against these FC deficits and, if so, is this neurovascular protection SIRT1-mediated; and 3) does treatment with the SIRT1 activator resveratrol alone provide protection against these FC deficits? Cranial windows were adhered on skull-intact mice that were then subjected to either sham or SAH surgery and either left untreated or treated with hypoxic post-conditioning (with or without EX527) or resveratrol for 3 days. Mice were imaged 3 days post-SAH/sham surgery, temporally aligned with the onset of major SAH sequela in mice. Here we show that the endovascular perforation model of SAH induces global and network-specific deficits in FC by day 3, corresponding with the time frame of DCI in mice. Hypoxic conditioning provides SIRT1-mediated protection against these network-specific FC deficits post-SAH, as does treatment with resveratrol. Conditioning-based strategies provide multifaceted neurovascular protection in experimental SAH.

Keywords: Functional connectivity; delayed cerebral ischemia; experimental subarachnoid hemorrhage; optical intrinsic signal; sirtuins.

Figure 1.

Optical Intrinsic Signal (OIS) Imaging of Subarachnoid Hemorrhage (SAH). (a) Timeline outlining the surgical, treatment, behavior recording, and imaging schedule for the present study. (b) Final number of mice used in the analysis for each condition.

Figure 2.

SAH results in decreased Neuroscore and FC score compared to Sham mice. (a) Average Neuroscore for Sham and SAH mice at baseline and Days 1–3. Error bars are SEM. (b) Group average bilateral homotopic connectivity maps for Sham and SAH, their difference when Sham is subtracted from SAH, and the t-statistic and significantly changed pixels after a cluster-based correction. (c) Left, every Pearson correlation coefficient value per pixel plotted between Sham and SAH groups. Right, only Pearson correlation coefficients within the black outline plotted between Sham and SAH groups. (d) Global average Pearson correlation coefficient from each mouse within each condition. Grey horizontal bar is the median, each box edge marks the 25th/75th percentile, whiskers extend to most extreme values not considered outliers (*p < 0.05, two sample student’s t-test). e) Linear fit of Neuroscore vs the global FC average plotted in d). Dotted grey line corresponds to confidence bounds (n = 19 Sham, 29 SAH).

Figure 3.

Hypoxic conditioning protects against SAH through a SIRT1 mediated mechanism. (a) Average Neuroscore for Sham and SAH mice compared to SAH mice that have been treated with Hypoxic conditioning with or without the SIRT1 inhibitor EX527 at baseline and Days 1–3. Error bars are SEM. (b) Group average bilateral homotopic connectivity maps for Hypoxia and SAH, their difference when SAH is subtracted from Hypoxia, and the t-statistic and significantly changed pixels after a cluster-based correction. (c) Group average bilateral homotopic connectivity maps for Hypoxia + EX527 and SAH, their difference when SAH is subtracted from Hypoxia + EX527, and the t-statistic and significantly changed pixels after a cluster-based correction. (d) Pearson correlation coefficient values per pixel plotted between Sham, SAH, Hypoxia, and Hypoxia + EX527 groups using the same ROI delineated in Figure 2(c). (e) Global average Pearson correlation coefficient from each mouse within each condition. Grey horizontal bar is the median, each box edge marks the 25th/75th percentile, whiskers extend to most extreme values not considered outliers. (f) Linear fit of Neuroscore vs the global FC average plotted in e). Dotted grey line corresponds to confidence bounds (n = 19 Sham, 29 SAH, 14 SAH:PostC, 12 SAH:PostC + EX527).

Figure 4.

SIRT1 agonist Resveratrol protects against FC deficits in SAH. (a) Average Neuroscore for Sham and SAH mice compared to SAH mice that have been treated with RSV at baseline and Days 1–3. Error bars are SEM. (b) Group average bilateral homotopic connectivity map for RSV and SAH, their difference when RSV is subtracted from SAH, and the t-statistic and significantly changed pixels after a cluster-based correction. (c) Pearson correlation coefficient values per pixel plotted between Sham, SAH, and RSV groups using the same ROI delineated in Figure 2(c). (d) Global average Pearson correlation coefficient from each mouse within each condition. Grey horizontal bar is the median, each box edge marks the 25th/75th percentile, whiskers extend to most extreme values not considered outliers (*p < 0.05, two sample student’s t-test). (e) Linear fit of Neuroscore vs the global FC average plotted in d). Dotted grey line corresponds to confidence bounds (n = 19 Sham, 29 SAH, 16 SAH:RSV).