Decreased Intracranial Pressure Elevation and Cerebrospinal Fluid Outflow Resistance: A Potential Mechanism of Hypothermia Cerebroprotection Following Experimental Stroke

Background: Elevated intracranial pressure (ICP) occurs 18–24 h after ischaemic stroke and is implicated as a potential cause of early neurological deterioration. Increased resistance to cerebrospinal fluid (CSF) outflow after ischaemic stroke is a proposed mechanism for ICP elevation. Ultra-short duration hypothermia prevents ICP elevation 24 h post-stroke in rats. We aimed to determine whether hypothermia would reduce CSF outflow resistance post-stroke. Methods: Transient middle cerebral artery occlusion was performed, followed by gradual cooling to 33 °C. At 18 h post-stroke, CSF outflow resistance was measured using a steady-state infusion method. Results: Hypothermia to 33 °C prevented ICP elevation 18 h post-stroke (hypothermia ∆ICP = 0.8 ± 3.6 mmHg vs. normothermia ∆ICP = 4.4 ± 2.0 mmHg, p = 0.04) and reduced infarct volume 24 h post-stroke (hypothermia = 78.6 ± 21.3 mm3 vs. normothermia = 108.1 ± 17.8 mm3; p = 0.01). Hypothermia to 33 °C did not result in a significant reduction in CSF outflow resistance compared with normothermia controls (0.32 ± 0.36 mmHg/µL/min vs. 1.07 ± 0.99 mmHg/µL/min, p = 0.06). Conclusions: Hypothermia treatment was protective in terms of ICP rise prevention, infarct volume reduction, and may be implicated in CSF outflow resistance post-stroke. Further investigations are warranted to elucidate the mechanisms of ICP elevation and hypothermia treatment.

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Short-duration hypothermia completed prior to reperfusion prevents intracranial pressure elevation following ischaemic stroke in rats

Scientific Reports ◽

10.1038/s41598-021-01838-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Daniel Omileke ◽

Sara Azarpeykan ◽

Steven W. Bothwell ◽

Debbie Pepperall ◽

Daniel J. Beard ◽

...

Keyword(s):

Intracranial Pressure ◽

Ischaemic Stroke ◽

Short Duration ◽

Infarct Volume ◽

Arterial Occlusion ◽

Reperfusion Therapy ◽

Artery Occlusion ◽

Experimental Stroke ◽

Stroke Patients ◽

Post Stroke

AbstractReperfusion therapies re-establish blood flow after arterial occlusion and improve outcome for ischaemic stroke patients. Intracranial pressure (ICP) elevation occurs 18–24 h after experimental stroke. This elevation is prevented by short-duration hypothermia spanning the time of reperfusion. We aimed to determine whether hypothermia-rewarming completed prior to reperfusion, also prevents ICP elevation 24 h post-stroke. Transient middle cerebral artery occlusion was performed on male outbred Wistar rats. Sixty-minute hypothermia to 33 °C, followed by rewarming was induced prior to reperfusion in one group, and after reperfusion in another group. Normothermia controls received identical anaesthesia protocols. ΔICP from pre-stroke to 24 h post-stroke was measured, and infarct volumes were calculated. Rewarming pre-reperfusion prevented ICP elevation (ΔICP = 0.3 ± 3.9 mmHg vs. normothermia ΔICP = 5.2 ± 2.1 mmHg, p = 0.02) and reduced infarct volume (pre-reperfusion = 78.6 ± 23.7 mm3 vs. normothermia = 125.1 ± 44.3 mm3, p = 0.04) 24 h post-stroke. There were no significant differences in ΔICP or infarct volumes between hypothermia groups rewarmed pre- or post-reperfusion. Hypothermia during reperfusion is not necessary for prevention of ICP rise or infarct volume reduction. Short-duration hypothermia may be an applicable early treatment strategy for stroke patients prior to- during-, and after reperfusion therapy.

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Hypothermia and rewarming prior to reperfusion, prevents intracranial pressure elevation after ischaemic stroke in rats: an investigation to define the importance of cooling during reperfusion

10.21203/rs.3.rs-846595/v1 ◽

2021 ◽

Author(s):

Daniel Omileke ◽

Sara Azarpeykan ◽

Steven W Bothwell ◽

Debbie Pepperall ◽

Daniel J Beard ◽

...

Keyword(s):

Intracranial Pressure ◽

Ischaemic Stroke ◽

Short Duration ◽

Infarct Volume ◽

Arterial Occlusion ◽

Reperfusion Therapy ◽

Artery Occlusion ◽

Experimental Stroke ◽

Stroke Patients ◽

Post Stroke

Abstract Reperfusion therapies re-establish blood flow after arterial occlusion and improve outcome for ischaemic stroke patients. Intracranial pressure (ICP) elevation occurs 18–24 h after experimental stroke. This elevation is prevented by short-duration hypothermia spanning the time of reperfusion. We aimed to determine whether hypothermia-rewarming completed prior to reperfusion, also prevents ICP elevation 24 h post-stroke. Transient middle cerebral artery occlusion was performed on male outbred Wistar rats. Sixty-minute hypothermia to 33℃, followed by rewarming was induced prior to reperfusion in one group, and after reperfusion in another group. Normothermia controls received identical anaesthesia protocols. ΔICP from pre-stroke to 24 h post-stroke was measured, and infarct volumes were calculated. Rewarming pre-reperfusion prevented ICP elevation (ΔICP = 0.3 ± 3.9 mmHg vs. normothermia ΔICP = 5.2 ± 2.1 mmHg, p = 0.02) and reduced infarct volume (pre-reperfusion = 78.6 ± 23.7 mm3 vs. normothermia = 125.1 ± 44.3 mm3, p = 0.04) 24 h post-stroke. There were no significant differences in ΔICP or infarct volumes between hypothermia groups rewarmed pre-or post-reperfusion. Hypothermia during reperfusion is not necessary for prevention of ICP rise or infarct volume reduction. Short-duration hypothermia is a broadly applicable potential early treatment strategy for stroke patients prior to- during-, and after reperfusion therapy.

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Ultra-Short Duration Hypothermia Prevents Intracranial Pressure Elevation Following Ischaemic Stroke in Rats

Frontiers in Neurology ◽

10.3389/fneur.2021.684353 ◽

2021 ◽

Vol 12 ◽

Author(s):

Daniel Omileke ◽

Debbie Pepperall ◽

Steven W. Bothwell ◽

Nikolce Mackovski ◽

Sara Azarpeykan ◽

...

Keyword(s):

Intracranial Pressure ◽

Ischaemic Stroke ◽

Short Duration ◽

Animal Studies ◽

Infarct Volume ◽

Artery Occlusion ◽

Rapid Cooling ◽

Long Duration ◽

Intracranial Pressure Elevation ◽

Cooling Methods

There is a transient increase in intracranial pressure (ICP) 18–24 h after ischaemic stroke in rats, which is prevented by short-duration hypothermia using rapid cooling methods. Clinical trials of long-duration hypothermia have been limited by feasibility and associated complications, which may be avoided by short-duration cooling. Animal studies have cooled faster than is achievable in patients. We aimed to determine whether gradual cooling at a rate of 2°C/h to 33°C or 1°C/h to 34.5°C, with a 30 min duration at target temperatures, prevented ICP elevation and reduced infarct volume in rats. Transient middle cerebral artery occlusion was performed, followed by gradual cooling to target temperature. Hypothermia to 33°C prevented significant ICP elevation (hypothermia ΔICP = 1.56 ± 2.26 mmHg vs normothermia ΔICP = 8.93 ± 4.82 mmHg; p = 0.02) and reduced infarct volume (hypothermia = 46.4 ± 12.3 mm3 vs normothermia = 85.0 ± 17.5 mm3; p = 0.01). Hypothermia to 34.5°C did not significantly prevent ICP elevation or reduce infarct volume. We showed that gradual cooling to 33°C, at cooling rates achievable in patients, had the same ICP preventative effect as traditional rapid cooling methods. This suggests that this paradigm could be translated to prevent delayed ICP rise in stroke patients.

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Glyceryl trinitrate for the treatment of ischaemic stroke: Determining efficacy in rodent and ovine species for enhanced clinical translation

Journal of Cerebral Blood Flow & Metabolism ◽

10.1177/0271678x211018901 ◽

2021 ◽

pp. 0271678X2110189

Author(s):

Annabel J Sorby-Adams ◽

Annastazia E Learoyd ◽

Philip M Bath ◽

Fiona Burrows ◽

Tracy D Farr ◽

...

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Ischaemic Stroke ◽

Glyceryl Trinitrate ◽

Infarct Volume ◽

Imaging Spectroscopy ◽

Artery Occlusion ◽

Laser Speckle ◽

Post Stroke ◽

Physiological Outcomes

Hypertension is a leading risk factor for death and dependency after ischaemic stroke. However, administering anti-hypertensive medications post-stroke remains contentious with concerns regarding deleterious effects on cerebral blood flow and infarct expansion. This study sought to determine the effect of glyceryl trinitrate (GTN) treatment in both lissencephalic and gyrencephalic pre-clinical stroke models. Merino sheep underwent middle cerebral artery occlusion (MCAO) followed by GTN or control patch administration (0.2 mg/h). Monitoring of numerous physiologically relevant measures over 24 h showed that GTN administration was associated with decreased intracranial pressure, infarct volume, cerebral oedema and midline shift compared to vehicle treatment (p < 0.05). No significant changes in blood pressure or cerebral perfusion pressure were observed. Using optical imaging spectroscopy and laser speckle imaging, the effect of varying doses of GTN (0.69–50 µg/h) on cerebral blood flow and tissue oxygenation was examined in mice. No consistent effect was found. Additional mice undergoing MCAO followed by GTN administration (doses varying from 0–60 µg/h) also showed no improvement in infarct volume or neurological score within 24 h post-stroke. GTN administration significantly improved numerous stroke-related physiological outcomes in sheep but was ineffective in mice. This suggests that, whilst GTN administration could potentially benefit patients, further research into mechanisms of action are required.

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Abstract WP151: Rapamycin Improves Post-Recanalization Blood Flow After Acute Experimental Stroke in Rats

Stroke ◽

10.1161/str.51.suppl_1.wp151 ◽

2020 ◽

Vol 51 (Suppl_1) ◽

Author(s):

Anna Maria Schneider ◽

Daniel Beard ◽

Alastair Buchan

Keyword(s):

Blood Flow ◽

Infarct Volume ◽

Mammalian Target Of Rapamycin ◽

Volume Measurement ◽

Artery Occlusion ◽

Experimental Stroke ◽

Stroke Outcome ◽

Doppler Flowmetry ◽

Rapamycin Treatment ◽

Post Stroke

Background and Purpose: In the era of thrombectomy, there is evidence suggesting that successful recanalization is not always accompanied by complete reperfusion, the so called “no-reflow phenomenon”. Given the importance of reperfusion as a predictor of stroke outcome, this represents a potential target for stroke therapy. Rapamycin, a clinically approved inhibitor of Mammalian Target of Rapamycin (mTOR) has been shown to improve cerebral blood flow (CBF) in Alzheimer’s disease. However, there has been little investigation into the effect of rapamycin on post-stroke microvascular perfusion. The aim of this study was to investigate the effects of rapamycin treatment on post-recanalisation CBF and stroke outcome in an experimental animal model of stroke. Methods: Male Wistar rats (300-350g) were subjected to 90min of transient middle cerebral artery occlusion (tMCAo) followed by randomized administration of 250μg/kg intravenous rapamycin (n=8) or vehicle (n=6), 30min after the onset of MCAo. Laser Doppler flowmetry was used to continuously measure changes in MCA perfusion during MCAo and for min after recanalisation. Neurobehavioral tests were performed 24hrs after MCAo before tissue was collected for infarct volume measurement. Results: MCAo was confirmed by a 70% reduction in MCA perfusion. Rapamycin treatment significantly improved post-recanalization CBF at 55min after recanalization (p<0.01). Rapamycin significantly increased average CBF during the 60min post-recanalization period (p<0.01). Rapamycin showed a trend towards reduced final infarct volume. Rapamycin significantly improved neuroscores (p<0.05). Post-recanalization CBF was significantly inversely correlated with infarct volume (R 2 =0.4994, p<0.05). Conclusion: Rapamycin significantly improved post-recanalization CBF and behavioural outcomes after MCAo. These results suggest that rapamycin may be an effective acute intervention to improve post-recanalisation blood flow to improve stroke outcome. However, further studies are need to determine the mechanism of improved CBF and if improvements in post-stroke CBF and neurological outcome are sustained long-term post-stroke.

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Spinal cerebrospinal fluid flow is increased in rats with elevated intracranial pressure 18 hours after cortical ischaemic stroke

10.21203/rs.3.rs-84123/v1 ◽

2020 ◽

Author(s):

Steven William Bothwell ◽

Daniel Omileke ◽

Debbie-Gai Pepperall ◽

Adjanie Patabendige ◽

Neil J Spratt

Keyword(s):

Cerebrospinal Fluid ◽

Intracranial Pressure ◽

Infarct Volume ◽

Compensatory Mechanism ◽

Tracer Transport ◽

Cerebrospinal Fluid Flow ◽

Post Stroke ◽

Spinal Subarachnoid Space ◽

Infarct Expansion ◽

Underlying Mechanisms

Abstract Background A dramatic oedema-independent intracranial pressure (ICP) rise occurs 24 hours post-stroke in rats and may explain infarct expansion. Underlying mechanisms of this rise are unknown but evidence suggests cerebrospinal fluid (CSF) dynamics are involved. Methods We investigated how CSF flow changes post-stroke and how this relates to ICP by infusing CSF tracer into the lateral ventricles of rats and assessing transport time and total tracer transport to the spinal subarachnoid space over a 90 minute period. Results Stroke animals with ICP rise had faster tracer transit when compared with stroke animals without ICP rise (27.6 ± 4, n = 6, vs 48.6 ± 4.5 mins, n = 6) or animals subjected to a sham procedure (47.9 ± 4 mins, n = 8), F(2,17) = 0.1, p≤0.01. There was a correlation between tracer transit time and ΔICP (R = -0.52, p=0.02) and infarct volume (R = -0.6, p=0.04). There was no difference in total tracer observed. Conclusions Faster tracer transit in stroke animals may be explained by impairment of other CSF outflow pathways, whereby, spinal drainage acts as a compensatory mechanism. Investigation into the disruption of other CSF drainage routes post-stroke may offer insight into the underlying mechanisms of infarct expansion post-stroke.

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Abstract P746: Sex Differences in Cognitive and Psychological Outcomes of Stroke: Impact of Diabetes

Stroke ◽

10.1161/str.52.suppl_1.p746 ◽

2021 ◽

Vol 52 (Suppl_1) ◽

Author(s):

Victoria L Wolf ◽

Aunay Miller ◽

Raghavendar Chandran ◽

Weiguo Li ◽

Adviye Ergul

Keyword(s):

Artery Occlusion ◽

Psychological Outcomes ◽

Experimental Stroke ◽

Dark Light ◽

Stroke Outcomes ◽

Post Stroke ◽

Stroke Research ◽

Y Maze ◽

Male Animal ◽

The Impact

Diabetes increases risk and severity of post-stroke cognitive impairment (PSCI), a major cause of disability worldwide. While it is known that females suffer more from PSCI, psychological outcomes and underlying reasons are poorly understood. From a preclinical perspective, potential explanations include 1) use of otherwise healthy animals in experimental stroke research without integration of common comorbid diseases like diabetes into the study design, and 2) optimization of most behavioral tests for sensorimotor and cognitive functions using only male animal models. Our hypothesis is that post-stroke outcomes are sex and comorbid disease-dependent. To test this, we validated the Novel Object Recognition (NOR), Y-maze, and Passive Avoidance (PAT) behavioral paradigms in Ctrl and Diabetic (DM) male (M) and female (F) rats pre- and post-stroke (S) via 60 min. middle cerebral artery occlusion (MCAO). We tested the PAT paradigm with a multi-trial method where the animals were habituated to the dark/light chambers without foot shock and then trained in 3 trials where they received foot shock upon entering the dark. We then tested retention following MCAO for their memory of foot shock 2 weeks prior. Multitrial results suggested that there was no difference between groups in learning to associate the dark chamber with the shock, so we revised the multitrial method into a single-trial method for ongoing retention tests to compare the impact of stroke on shock memory recall. PAT revealed (Table 1) disease- and sex-dependent responses to aversive stimulus. NOR revealed that M-DM-S and F-DM-S rats have decreased exploration time, suggesting that they are unmotivated or depressed. Y-maze indicated that males displayed spatial memory recovery, while females remained impaired. In summary, we have observed numerous sex- and disease-dependent post-stroke outcomes with standard behavioral paradigms, causing us to carefully consider how we evaluate preclinical outcomes.

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Abstract WP118: The Flavanol (-)-Epicatechin Improves Functional Recovery In Mice Subjected To Experimental Stroke

Stroke ◽

10.1161/str.44.suppl_1.awp118 ◽

2013 ◽

Vol 44 (suppl_1) ◽

Author(s):

Christopher C Leonardo ◽

Sean Robbins ◽

Abdullah A Ahmad ◽

Sylvain Dore

Keyword(s):

Functional Recovery ◽

Transcriptional Activation ◽

Infarct Volume ◽

Epidemiological Studies ◽

Artery Occlusion ◽

Experimental Stroke ◽

Adhesive Tape ◽

Dietary Consumption ◽

Therapeutic Doses ◽

Cerebral Artery Occlusion

Background: Epidemiological studies indicate that flavanol consumption reduces the propensity to develop cerebrovascular disease. Available data suggest actions on multiple pro-inflammatory pathways, yet it remains unclear which pathways mediate functional recovery after stroke. Our goal is to begin identifying the mechanisms by which the flavanol (-)-epicatechin (EC) improves anatomical and functional outcomes. Based upon data from initial dose-response experiments, ongoing studies are investigating hypothesized protective pathways involving matrix metalloproteinase-mediated blood brain barrier protection and Nrf2 transcriptional activation. Methods: Male, 8-10wk old C57BL/6 mice were pretreated with EC 90m prior to permanent distal middle cerebral artery occlusion. Vehicle or EC was administered by oral gavage to mimic dietary consumption. Mice were evaluated 1, 4 and 7d post-stroke for performance on various sensorimotor tasks prior to histological assessments. Results: Initial experiments demonstrated that mice treated with 15mg/kg EC showed reduced latency to remove adhesive tape at 1d compared to vehicle controls (n=12, p<0.01). Similarly, immunoreactivity for the microglia/macrophage marker Iba1 was increased in the ipsilateral hemispheres of mice 7d after treatment with vehicle (p<0.01), whereas pretreatment with 15mg/kg blocked this effect (n=4). Mice treated with 15mg/kg also showed a trend toward reduced infarct volume relative to vehicle controls (n=5-9 per group). In subsequent reduced dosing studies, vehicle-treated mice again showed deficiencies in removing adhesive tape at 1d (n=8, p<0.01). Remarkably, mice treated with 15, 10 or 5mg/kg EC showed no deficits. Similarly, vehicle control mice showed grip strength impairments up to 7d (n=8, p<0.05) that were absent in all groups of EC-treated mice. Conclusions: Preventative administration of EC promotes functional recovery in mice subjected to experimental stroke. Investigations are underway to determine the pathways mediated by EC following administration at these therapeutic doses. Together, these data will provide insights into the potential for (-)-epicatechin as a clinical therapeutic.

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Impact of Key Nicotinic AChR Subunits on Post-Stroke Pneumococcal Pneumonia

Vaccines ◽

10.3390/vaccines8020253 ◽

2020 ◽

Vol 8 (2) ◽

pp. 253

Author(s):

Sandra Jagdmann ◽

Claudia Dames ◽

Daniel Berchtold ◽

Katarzyna Winek ◽

Luis Weitbrecht ◽

...

Keyword(s):

Artery Occlusion ◽

Experimental Stroke ◽

Medical Complication ◽

Α7 Nicotinic Acetylcholine Receptor ◽

Post Stroke ◽

Cholinergic Signaling ◽

Cerebral Artery Occlusion ◽

Pathogen Clearance ◽

The Impact ◽

Alveolar Capillary

Pneumonia is the most frequent severe medical complication after stroke. An overactivation of the cholinergic signaling after stroke contributes to immunosuppression and the development of spontaneous pneumonia caused by Gram-negative pathogens. The α7 nicotinic acetylcholine receptor (α7nAChR) has already been identified as an important mediator of the anti-inflammatory pathway after stroke. However, whether the α2, α5 and α9/10 nAChR expressed in the lung also play a role in suppression of pulmonary innate immunity after stroke is unknown. In the present study, we investigate the impact of various nAChRs on aspiration-induced pneumonia after stroke. Therefore, α2, α5, α7 and α9/10 nAChR knockout (KO) mice and wild type (WT) littermates were infected with Streptococcus pneumoniae (S. pneumoniae) three days after middle cerebral artery occlusion (MCAo). One day after infection pathogen clearance, cellularity in lung and spleen, cytokine secretion in bronchoalveolar lavage (BAL) and alveolar-capillary barrier were investigated. Here, we found that deficiency of various nAChRs does not contribute to an enhanced clearance of a Gram-positive pathogen causing post-stroke pneumonia in mice. In conclusion, these findings suggest that a single nAChR is not sufficient to mediate the impaired pulmonary defense against S. pneumoniae after experimental stroke.

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