Acute ischemic stroke (AIS) is a leading cause of disability and death worldwide. To date, intravenous tissue plasminogen activator and mechanical thrombectomy have been standards of care for AIS. There have been many advances in diagnostic imaging and endovascular devices for AIS; however, most neuroprotective therapies seem to remain largely in the preclinical phase. While many neuroprotective therapies have been identified in experimental models, none are currently used routinely to treat stroke patients. This review seeks to summarize clinical studies pertaining to neuroprotection, as well as the different preclinical neuroprotective therapies, their presumed mechanisms of action, and their future applications in stroke patients.
Gary B. Rajah and Yuchuan Ding
Ramin Eskandari, James P. McAllister II, Janet M. Miller, Yuchuan Ding, Steven D. Ham, David M. Shearer and John S. Way
Object. The authors of previous studies have suggested that connectivity within the cerebral cortex may be irreversibly altered by hydrocephalus. To examine connectivity-related changes directly, the authors conducted a study in which they used an axonal tracer in an animal model of infantile hydrocephalus.
Methods. In five hydrocephalic kittens low-pressure ventriculoperitoneal (VP) shunts were placed 10 to 14 days after induction of hydrocephalus by intracisternal kaolin injections. Wheat germ agglutinin-conjugated horseradish peroxidase was injected laterally into the motor cortex in hydrocephalic animals 9 to 15 days after kaolin injection, and 1, 2, and 4 weeks after VP shunt insertion in shunt-treated animals, and in age-matched controls.
Reduction of antero- and retrograde labeling was most profound within the contralateral cortex and portions of the midbrain. Thalamic nuclei exhibited reductions in anterograde and retrograde labeling. Labeling within cell bodies of the ventral tegmental area decreased greatly in animals with untreated hydrocephalus, in which retrograde labeling was reduced in the locus coeruleus but did not affect the raphe nucleus. Shunt treatment increased both antero- and retrograde labeling of contralateral motor cortex to near-normal levels. Thalamic relay nuclei recovered antero- and retrograde labeling, although not to levels exhibited in controls. Shunt therapy restored cellular labeling within the ventral tegmental area and locus coeruleus. Recovery of labeling occurred as early as 7 days after shunt insertion.
Conclusions. Collectively, analysis of these data indicates the following. 1) Cortical connectivity involving both afferent and efferent pathways was impaired in untreated hydrocephalic animals. 2) Shunt therapy improved both cortical afferent and efferent connectivity. 3) Complete reestablishment of the cortical efferent pathways, however, did not occur. Cortical pathway dysfunction, if permanent, could cause many of the motor and cognitive deficits seen clinically in children with hydrocephalus.
Yuchuan Ding, Bin Yao, Yandong Zhou, Hun Park, J. P. McAllister II and Fernando G. Diaz
Object. In ischemic stroke, the ischemic crisis activates a cascade of traumatic events that are potentiated by reperfusion and eventually lead to neuronal degeneration. The primary aim of this study was to investigate a procedure that could minimize this damage by interfering with the interactions between reestablished blood flow and ischemically damaged tissue, as well as by improving regional microcirculation.
Methods. Using a novel hollow filament, the authors flushed the ischemic territory with heparinized saline before vascular reperfusion after occlusion of the middle cerebral artery (MCA). The results demonstrate a statistically significant (p < 0.001) reduction in infarct volume (75%; from 45.3 ± 3.6% to 11.4 ± 1.7%, determined with Nissl staining) in rats in which a 2-hour MCA occlusion was followed by a 48-hour reperfusion. Infarction and neuronal degeneration were confirmed using silver staining, which revealed a significantly larger infarct (36.3%, p < 0.05) than that detected with Nissl staining. The long-term neuroprotection of the prereperfusion flushing was also evaluated. This was determined by a series of motor behavior tasks (foot placing, parallel bar traversing, rope and ladder climbing) performed up to 28 days after reperfusion. Motor deficits were found to be significantly ameliorated in animals that underwent the flushing procedure (p < 0.001). In addition, neurological outcome was also improved significantly (p < 0.001) in the same animals.
Conclusions. These results indicate that interaction between reperfusion and the metabolically and biochemically compromised tissue could be interrupted by the prereperfusion flushing procedure, which could lead to a reduction in brain injury from stroke. Mechanical reopening of the cerebral occlusion with local flushing and isolated reperfusion of the regionally injured brain might offer new treatment options for patients with stroke.
Raul Reyes, Miao Guo, Kathryn Swann, Siddharth U. Shetgeri, Shane M. Sprague, David F. Jimenez, Constance M. Barone and Yuchuan Ding
A relationship has been found between peripheral thermal injury and cerebral complications leading to injury and death. In the present study, the authors examined whether tumor necrosis factor–α (TNF-α) and matrix metalloproteinase–9 (MMP-9) play a causative role in blood-brain barrier (BBB) disruption after peripheral thermal injury.
Thirty-two male Sprague-Dawley rats were subjected to thermal injury. One hour later, 8 rats were injected with TNF-α neutralizing antibody, and 8 were injected with doxycycline, an inhibitor of the MMP family proteins; 16 rats did not receive any treatment. Brain tissue samples obtained 7 hours after injury in the treated animals were examined for BBB function by using fluorescein isothiocyanate–dextran and by assessing parenchymal water content. Protein expression of basement membrane components (collagen IV, laminin, and fibronectin) was quantified on Western blot analysis, and MMP-9 protein expression and enzyme activity were determined using Western blot and gelatin zymography. Thermally injured rats that did not receive treatment were killed at 3, 7, or 24 hours after injury and tested for BBB functioning at each time point. Histological analysis for basement membrane proteins was also conducted in untreated rats killed at 7 hours after injury. Results of testing in injured rats were compared with those obtained in a control group of rats that did not undergo thermal injury.
At 7 hours after thermal injury, a significant increase in the fluorescein isothiocyanate–dextran and water content of the brain was found (p < 0.05), but BBB dysfunction was significantly decreased in the rats that received TNF-α antibody or doxycycline (p < 0.05). In addition, the components of the basal lamina were significantly decreased at 7 hours after thermal injury (p < 0.01), and there were significant increases in MMP-9 protein expression and enzyme activity (p < 0.05). The basal lamina damage was reversed by inhibition of TNF-α and MMP-9, and the increase in MMP-9 protein was reduced in the presence of doxycycline (p < 0.05). The authors found that MMP-9 enzyme activity was significantly increased after thermal injury (p < 0.01) but decreased in the presence of either TNF-α antibody or doxycycline (p < 0.01).
The dual, inhibitory activity of both TNF-α and MMP-9 in brain injury suggests that a TNF-α and MMP-9 cascade may play a key role in BBB disruption. These results offer a better understanding of the pathophysiology of burn injuries, which may open new avenues for burn treatment beyond the level of current therapies.
Tony Wang, David Yu-Te Chou, Jamie Y. Ding, Vance Fredrickson, Changya Peng, Steven Schafer, Murali Guthikonda, Christian Kreipke, José A. Rafols and Yuchuan Ding
Previous studies have demonstrated that traumatic brain injury (TBI) causes brain edema by allowing excessive water passage through aquaporin (AQP) proteins. To establish the potential neuroprotective properties of ethanol as a post-TBI therapy, in the present study the authors determined the effect of ethanol on brain edema, AQP expression, and functional outcomes in a post-TBI setting.
Adult male Sprague-Dawley rats weighing between 425 and 475 g received a closed head TBI in which Maramarou's impact-acceleration method was used. Animals were given a subsequent intraperitoneal injection of 0.5 g/kg or 1.5 g/kg ethanol at 60 minutes post-TBI and were killed 24 hours after TBI. Brains were subsequently examined for edema along with AQP mRNA and protein expression. Additional animals treated with either 0.5 g/kg or 1.5 g/kg ethanol at 60 minutes post-TBI were designated for cognitive and motor testing for 3 weeks.
Ethanol administration post-TBI led to significantly (p < 0.05) lower levels of brain edema as measured by brain water content. This downregulation in brain edema was associated with significantly (p < 0.05) reduced levels of AQP mRNA and protein expression as compared with TBI without treatment. These findings concur with cognitive studies in which ethanol-treated animals exhibited significantly (p < 0.05) faster radial maze completion times. Motor behavioral testing additionally demonstrated significant (p < 0.05) beneficial effects of ethanol, with treated animals displaying improved motor coordination when compared with untreated animals.
The present findings suggest that acute ethanol administration after a TBI decreases AQP expression, which may lead to reduced cerebral edema. Ethanol-treated animals additionally showed improved cognitive and motor outcomes compared with untreated animals.
Tetsuhiro Higashida, Christian W. Kreipke, José A. Rafols, Changya Peng, Steven Schafer, Patrick Schafer, Jamie Y. Ding, David Dornbos III, Xiaohua Li, Murali Guthikonda, Noreen F. Rossi and Yuchuan Ding
The present study investigated the role of hypoxia-inducible factor-1α (HIF-1α), aquaporin-4 (AQP-4), and matrix metalloproteinase-9 (MMP-9) in blood-brain barrier (BBB) permeability alterations and brain edema formation in a rodent traumatic brain injury (TBI) model.
The brains of adult male Sprague-Dawley rats (400–425 g) were injured using the Marmarou closed-head force impact model. Anti–AQP-4 antibody, minocycline (an inhibitor of MMP-9), or 2-methoxyestradiol (2ME2, an inhibitor of HIF-1α), was administered intravenously 30 minutes after injury. The rats were killed 24 hours after injury and their brains were examined for protein expression, BBB permeability, and brain edema. Expression of HIF-1α, AQP-4, and MMP-9 as well as expression of the vascular basal lamina protein (laminin) and tight junction proteins (zona occludens-1 and occludin) was determined by Western blotting. Blood-brain barrier disruption was assessed by FITC-dextran extravasation, and brain edema was measured by the brain water content.
Significant (p < 0.05) edema and BBB extravasations were observed following TBI induction. Compared with sham-operated controls, the injured animals were found to have significantly (p < 0.05) enhanced expression of HIF-1α, AQP-4, and MMP-9, in addition to reduced amounts (p < 0.05) of laminin and tight junction proteins. Edema was significantly (p < 0.01) decreased after inhibition of AQP-4, MMP-9, or HIF-1α. While BBB permeability was significantly (p < 0.01) ameliorated after inhibition of either HIF-1α or MMP-9, it was not affected following inhibition of AQP-4. Inhibition of MMP reversed the loss of laminin (p < 0.01). Finally, while inhibition of HIF-1α significantly (p < 0.05) suppressed the expression of AQP-4 and MMP-9, such inhibition significantly (p < 0.05) increased the expression of laminin and tight junction proteins.
The data support the notion that HIF-1α plays a role in brain edema formation and BBB disruption via a molecular pathway cascade involving AQP-4 and MMP-9. Pharmacological blockade of this pathway in patients with TBI may provide a novel therapeutic strategy.
Feng Yan, Gary Rajah, Yuchuan Ding, Yang Hua, Hongqi Zhang, Liqun Jiao, Guilin Li, Ming Ren, Ran Meng, Feng Lin and Xunming Ji
Symptomatic intracranial hypertension can be caused by cerebral venous sinus stenosis (CVSS) and cerebral venous sinus thrombotic (CVST) stenosis, which is usually found in some patients with idiopathic intracranial hypertension (IIH). Recently, at the authors’ center, they utilized intravascular ultrasound (IVUS) as an adjunct to conventional venoplasty or stenting to facilitate diagnosis and accurate stent placement in CVSS.
The authors designed a retrospective review of their prospective database of patients who underwent IVUS-guided venous sinus stenting between April 2016 and February 2017. Clinical, radiological, and ophthalmological information was recorded and analyzed. IVUS was performed in 12 patients with IIH (9 with nonthrombotic CVSS, 3 with secondary stenosis combined with CVST) during venoplasty through venous access. The IVUS catheter was used from a proximal location to the site of stenosis. Post-stenting follow-up, including symptomatic improvement, stent patency, and adjacent-site stenosis, was assessed at 1 year.
Thirteen stenotic cerebral sinuses in 12 patients were corrected using IVUS-guided stenting. No technical or neurological complications were encountered. The IVUS images were excellent for the diagnosis of the stenosis, and intraluminal thrombi were clearly visualized by using IVUS in 3 (25%) of the 12 patients. A giant arachnoid granulation was demonstrated in 1 (8.3%) of the 12 patients. Intravenous compartments or septations (2 of 12, 16.7%) and vessel wall thickening (6 of 12, 50%) were also noted. At 1-year follow-up, 10 of 12 patients were clinically symptom-free in our series.
IVUS is a promising tool with the potential to improve the diagnostic accuracy in IIH, aiding in identification of the types of intracranial venous stenosis, assisting in stent selection, and guiding stent placement. Further study of the utility of IVUS in venous stenting and venous stenosis pathology is warranted.