Current therapies in ischemic stroke. Part B. Future candidates in stroke therapy and experimental studies

Noscapine alleviates cerebral damage in ischemia-reperfusion injury in rats

With high unmet medical needs, stroke remains an intensely focused research area. Although noscapine is a neuroprotective agent, its mechanism of action in ischemic-reperfusion (I-R) injury is yet to be ascertained. We investigated the effect of noscapine on the molecular mechanisms of cell damage using yeast, and its neuroprotection on cerebral I-R injury in rats. Yeast, both wild-type and Δtrx2 strains, was evaluated for cell growth and viability, and oxidative stress to assess the noscapine effect at 8, 10, 12, and 20 μg/ml concentrations. The neuroprotective activity of noscapine (5 and 10 mg/kg; po for 8 days) was investigated in rats using middle cerebral artery occlusion-induced I-R injury. Infarct volume, neurological deficit, oxidative stress, myeloperoxidase activity, and histological alterations were determined in I-R rats. In vitro yeast assays exhibited significant antioxidant activity and enhanced cell tolerance against oxidative stress after noscapine treatment. Similarly, noscapine pretreatment significantly reduced infarct volume and edema in the brain. The neurological deficit was decreased and oxidative stress biomarkers, superoxide dismutase activity and glutathione levels, were significantly increased while lipid peroxidation showed significant decrease in comparison to vehicle-treated I-R rats. Myeloperoxidase activity, an indicator of inflammation, was also reduced significantly in treated rats; histological changes were attenuated with noscapine. The study demonstrates the protective effect of noscapine in yeast and I-R rats by improving cell viability and attenuating neuronal damage, respectively. This protective activity of noscapine could be attributed to potent free radical scavenging and inhibition of inflammation in cerebral ischemia-reperfusion injury.

LIM kinase inhibitor T56-LIMKi protects mouse brain from photothrombotic stroke

Primary Objective: In an ischemic stroke, the damage spreads from the infarction core to surrounding tissues. The present work was aimed at the search of effective neuroprotectors that restrict injury propagation. Research Design: We studied possible protective effects of inhibitors of protein kinases LIMK2 (T56-LIMKi), DYRK1A (harmine), and tryptophan hydroxylase (4-chlorophenylalanine) on infarction size and morphology of peri-infarct area after photothrombotic stroke (a model of ischemic stroke) in mouse brain. Methods and Procedures: Photothrombotic stroke was induced by laser irradiation of mouse cortex after administration of photosensitizer Bengal Rose, which does not penetrate cells and remains in blood vessels. Under light exposure, it induces vessel occlusion. Infarct volume and histological changes in the cerebral cortex were evaluated 3, 7 and 14 days after photothrombotic impact. Main Outcomes and Results: Harmine and 4-chlorophenylalanine did not influence infarct volume and morphology of peri-infarct area in the mouse brain cortex after photothrombotic stroke. However, LIMK2 inhibitor T56-LIMKi significantly reduced infarct volume 7 and 14 days after photothrombotic stroke. It also increased the percent of normochromic neurons and decreased the fraction of altered cortical cells (hypochromic, hyperchromic and pyknotic neurons). Conclusions: T56-LIMK2i may be considered as a promising anti-stroke agent.

Validation of a stroke model in rat compatible with rt-PA-induced thrombolysis: new hope for successful translation to the clinic

The recent clinical trial (DAWN) suggests that recanalization treatment may be beneficial up to 24 h after stroke onset, thus re-opening avenues for development of new therapeutic strategies. Unfortunately, there is a continuous failure of drugs in clinical trials and one of the major reasons proposed for this translational roadblock is the animal models. Therefore, the purpose of this study was to validate a new thromboembolic stroke rat model that mimics the human pathology, and that can be used for evaluating new strategies to save the brain in conditions compatible with recanalization. Stroke was induced by injection of thrombin into the middle cerebral artery. Recombinant tissue-type plasminogen activator (rt-PA) or saline was administrated at 1 h/4 h after stroke onset, and outcome was evaluated after 24 h. Induced ischemia resulted in reproducible cortical brain injuries causing a decrease in neurological function 24 h after stroke onset. Early rt-PA treatment resulted in recanalization, reduced infarct size and improved neurological functions, while late rt-PA treatment showed no beneficial effects and caused hemorrhagic transformation in 25% of the rats. This validated and established model’s resemblance to human ischemic stroke and high translational potential, makes it an important tool in the development of new therapeutic strategies for stroke.

Efficacy of cattle encephalon glycoside and ignotin in patients with acute cerebral infarction: a randomized, double-blind, parallel-group, placebo-controlled study

Cattle encephalon glycoside and ignotin (CEGI) injection is a compound preparation formed by a combination of muscle extract from healthy rabbits and brain gangliosides from cattle, and it is generally used as a neuroprotectant in the treatment of central and peripheral nerve injuries. However, there is still a need for high-level clinical evidence from large samples to support the use of CEGI. We therefore carried out a prospective, multicenter, randomized, double-blind, parallel-group, placebo-controlled study in which we recruited 319 patients with acute cerebral infarction from 16 centers in China from October 2013 to May 2016. The patients were randomized at a 3:1 ratio into CEGI (n = 239; 155 male, 84 female; 61.2 ± 9.2 years old) and placebo (n = 80; 46 male, 34 female; 63.2 ± 8.28 years old) groups. All patients were given standard care once daily for 14 days, including a 200 mg aspirin enteric-coated tablet and 20 mg atorvastatin calcium, both taken orally, and intravenous infusion of 250–500 mL 0.9% sodium chloride containing 40 mg sodium tanshinone IIA sulfonate. Based on conventional treatment, patients in the CEGI and placebo groups were given 12 mL CEGI or 12 mL sterile water, respectively, in an intravenous drip of 250 mL 0.9% sodium chloride (2 mL/min) once daily for 14 days. According to baseline National Institutes of Health Stroke Scale scores, patients in the two groups were divided into mild and moderate subgroups. Based on the modified Rankin Scale results, the rate of patients with good outcomes in the CEGI group was higher than that in the placebo group, and the rate of disability in the CEGI group was lower than that in the placebo group on day 90 after treatment. In the CEGI group, neurological deficits were decreased on days 14 and 90 after treatment, as measured by the National Institutes of Health Stroke Scale and the Barthel Index. Subgroup analysis revealed that CEGI led to more significant improvements in moderate stroke patients. No drug-related adverse events occurred in the CEGI or placebo groups. In conclusion, CEGI may be a safe and effective treatment for acute cerebral infarction patients, especially for moderate stroke patients. This study was approved by the Ethical Committee of Peking University Third Hospital, China (approval No. 2013-068-2) on May 20, 2013, and registered in the Chinese Clinical Trial Registry (registration No. ChiCTR1800017937).

Neuropeptide Y Y2 and Y5 receptors as promising targets for neuroprotection in primary neurons exposed to oxygen-glucose deprivation and in transient focal cerebral ischemia in rats

It was postulated that neuropeptide Y (NPY)-ergic system could be involved in the ischemic pathophysiology, however, the role of particular subtypes of NPY receptors (YRs) in neuroprotection against ischemia is still not well known. Therefore, we investigated the effect of NPY and YR ligands using in vitro and in vivo experimental ischemic stroke models. Our in vitro findings showed that NPY (0.5-1μM) and specific agonists of Y2R (0.1-1μM) and Y5R (0.5-1μM) but not that of Y1R produced neuroprotective effects against oxygen-glucose deprivation (OGD)-induced neuronal cell death, being also effective when given 30min after the end of OGD. The neuroprotective effects of Y2R and Y5R agonists were reversed by appropriate antagonists. Neuroprotection mediated by NPY, Y2R and Y5R agonists was accompanied by the inhibition of both OGD-induced calpain activation and glutamate release. Data from in vivo studies demonstrated that Y2R agonist (10μg/6μl; i.c.v.) not only diminished the infarct volume in rats subjected to transient middle cerebral artery occlusion (MCAO) but also improved selected gait parameters in CatWalk behavioral test, being also effective after delayed treatment. Moreover, we found that a Y5R agonist (10μg/6μl; i.c.v.) did not reduce MCAO-evoked brain damage but improved stride length, when it was given 30min after starting the occlusion. In conclusion, our studies indicate that Y5 and especially Y2 receptors may be promising targets for neuroprotection against ischemic damage.

Effects of high and low 17β-estradiol doses on focal cerebral ischemia in rats

The majority of the numerous animal studies of the effects of estrogens on cerebral ischemia have reported neuroprotective results, but a few have shown increased damage. Differences in hormone administration methods, resulting in highly different 17β-estradiol levels, may explain the discrepancies in previously reported effects. The objective of the present study was to test the hypothesis that it is the delivered dose per se, and not the route and method of administration, that determines the effect, and that high doses are damaging while lower doses are protective. One hundred and twenty ovariectomized female Wistar rats (n = 40 per group) were randomized into three groups, subcutaneously administered different doses of 17β-estradiol and subjected to transient middle cerebral artery occlusion. The modified sticky tape test was performed after 24 h and the rats were subsequently sacrificed for infarct size measurements. In contrast to our hypothesis, a significant negative correlation between 17β-estradiol dose and infarct size was found (p = 0.018). Thus, no support was found for the hypothesis that 17β-estradiol can be both neuroprotective and neurotoxic merely depending on dose. In fact, on the contrary, the findings indicate that the higher the dose of 17β-estradiol, the smaller the infarct.

Variation of pathways and network profiles reveals the differential pharmacological mechanisms of each effective component to treat middle cerebral artery ischemia-reperfusion mice

Using a system pharmacology strategy, this study evaluated the unique pharmacological characteristics of three different neuroprotective compounds for the treatment of cerebral ischemia-reperfusion. A microarray including 374 brain ischemia-related genes was used to identify the differentially expressed genes among five treatment groups: baicalin, jasminoidin, ursodeoxycholic acid, sham, and vehicle, and MetaCore analysis software was applied to identify the significantly altered pathways, processes and interaction network parameters. At pathway level, 46, 25, and 31 pathways were activated in the baicalin, jasminoidin, and ursodeoxycholic acid groups, respectively. Thirteen pathways mainly related with apoptosis and development were commonly altered in the three groups. Additionally, baicalin also targeted pathways related with development, neurophysiologic process and cytoskeleton remodeling, while jasminoidin targeted pathways related with cell cycle and ursodeoxycholic acid targeted those related with apoptosis and development. At process level, three processes were commonly regulated by the three groups in the top 10 processes. Further interaction network analysis revealed that baicalin, jasminoidin, and ursodeoxycholic acid displayed unique features either on network topological parameters or network structure. Additional overlapping analysis demonstrated that compared with ursodeoxycholic acid, the pharmacological mechanism of baicalin was more similar with that of jasminoidin in treating brain ischemia. The data presented in this study may contribute toward the understanding of the common and differential pharmacological mechanisms of these three compounds.

Inhibiting histone deacetylase 6 partly protects cultured rat cortical neurons from oxygen‑glucose deprivation‑induced necroptosis

Necroptosis has an important role in ischemia-reperfusion damage. The expression of histone deacetylase 6 (HDAC6) is upregulated in neurons following ischemia-reperfusion, however, whether HDAC6 is closely involved in the necroptosis, which occurs during ischemia-reperfusion damage remains to be elucidated. In the present study, the roles of HDAC6 in the necroptosis of cultured rat cortical neurons were investigated in a oxygen-glucose deprivation (OGD) model. The results demonstrated that OGD induced marked necroptosis of cultured rat cortical neurons and upregulated the expression of HDAC6 in the cultured neurons, compared with the control (P<0.05). The necroptosis inhibitor, necrostatin-1 (Nec-1), decreased The expression of HDAC6 in the OGD-treated cultured neurons, accompanied by the inhibition of necroptosis. Further investigation revealed that, compared with OGD treatment alone, inhibiting the activity of HDAC6 with tubacin, a specific HDAC6 inhibitor, reduced the OGD-induced necroptosis of the cultured rat cortical neurons (P<0.05), which was similar to the change following treatment with Nec-1 (P>0.05). In addition, inhibiting the activity of HDAC6 reversed the OGD-induced increase of reactive oxygen species (ROS) and the OGD-induced decrease of acetylated tubulin in the cultured rat cortical neurons (P<0.05), compared with the neurons treated with OGD alone). The levels of acetylated tubulin in the cultured neurons following treatment with OGD and tubacin were significantly higher than those in the control (P<0.05). These results suggested that HDAC6 was involved in the necroptosis of neurons during ischemia-reperfusion by modulating the levels of ROS and acetylated tubulin.

Global SUMOylation is a molecular mechanism underlying hypothermia-induced ischemic tolerance

The molecular mechanisms underlying hypothermic neuroprotection have yet to be fully elucidated. Herein we demonstrate that global SUMOylation, a form of post-translational modification with the Small Ubiquitin-like MOdifer, participates in the multimodal molecular induction of hypothermia-induced ischemic tolerance. Mild (32°C) to moderate (28°C) hypothermic treatment(s) during OGD (oxygen-glucose-deprivation) or ROG (restoration of oxygen/glucose) increased global SUMO-conjugation levels and protected cells (both SHSY5Y and E18 rat cortical neurons) from OGD and ROG-induced cell death. Hypothermic exposure either before or after permanent middle cerebral artery occlusion (pMCAO) surgery in wild type mice increased global SUMO-conjugation levels in the brain and in so doing protected these animals from pMCAO-induced ischemic damage. Of note, hypothermic exposure did not provide an additional increase in protection from pMCAO-induced ischemic brain damage in Ubc9 transgenic (Ubc9 Tg) mice, which overexpress the sole E2 SUMO conjugating enzyme and thereby display elevated basal levels of global SUMOylation under normothermic conditions. Such evidence suggests that increases in global SUMOylation are critical and may account for a substantial part of the observed increase in cellular tolerance to brain ischemia caused via hypothermia.

Soluble or soluble/membrane TNF-α inhibitors protect the brain from focal ischemic injury in rats

Tumor Necrosis Factor-alpha (TNF-α) is an immunomodulatory and proinflammatory cytokine implicated in neuro-inflammation and neuronal damage in response to cerebral ischemia. The present study tested the hypothesis that anti-TNF-α agents may be protective against cerebral infarction. Transient focal ischemia was artificially induced in anesthetized adult male Wistar rats (300-350 g) by middle cerebral artery occlusion (MCAO) with an intraluminal suture. TNF-α function was interfered with either a chimeric monoclonal antibody against TNF-α (infliximab-7 mg/kg) aiming to TNF-α soluble and membrane-attached form; or a chimeric fusion protein of TNF-α receptor-2 with a fragment crystallizable (Fc) region of IgG1 (etanercept-5 mg/kg) aiming for the TNF-α soluble form. Both agents were administered intraperitoneally 0 or 6 h after inducing ischemia. Infarct volume was measured by 2,3,5-triphenyltetrazolium chloride staining. Cerebral infarct volume was significantly reduced in either etanercept or infliximab-treated group compared with non-treated MCAO rats 24 h after reperfusion. These results suggest that anti-TNF-α agents may reduce focal ischemic injury in rats.

Therapeutic potential of midkine in cardiovascular disease

Ischaemic heart disease, stroke and their pathological consequences are life-threatening conditions that account for about half of deaths in developed countries. Pathology of these diseases includes cell death due to ischaemia/reperfusion injury, vascular stenosis and cardiac remodelling. The growth factor midkine plays a pivotal role in these events. Midkine shows an acute cytoprotective effect in ischaemia/reperfusion injury at least in part via its anti-apoptotic effect. Moreover, while midkine promotes endothelial cell proliferation, it also recruits inflammatory cells to lesions. These activities eventually enhance angiogenesis, thereby preventing cardiac tissue remodelling. However, midkine's activity in recruiting inflammatory cells into the vascular wall also triggers neointima formation, and consequently, vascular stenosis. Moreover, midkine is induced in cancer tissues where it enhances angiogenesis. Therefore, midkine may promote tumour formation through its angiogenic and anti-apoptotic activity. This review focuses on the roles of midkine in ischaemic cardiovascular disease and their pathological consequences, that is angiogenesis, vascular stenosis, and cardiac remodelling, and discusses the possible therapeutic potential of modulation of midkine in these diseases.

LINKED ARTICLES

This article is part of a themed section on Midkine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-4.

Acute neuromuscular adaptation at the spinal level following middle cerebral artery occlusion-reperfusion in the rat

The purpose of the study was to highlight the acute motor reflex adaptation and to deepen functional deficits following a middle cerebral artery occlusion-reperfusion (MCAO-r). Thirty-six Sprague-Dawley rats were included in this study. The middle cerebral artery occlusion (MCAO; 120 min) was performed on 16 rats studied at 1 and 7 days, respectively (MCAO-D1 and MCAO-D7, n = 8 for each group). The other animals were divided into 3 groups: SHAM-D1 (n = 6), SHAM-D7 (n = 6) and Control (n = 8). Rats performed 4 behavioral tests (the elevated body swing test, the beam balance test, the ladder-climbing test and the forelimb grip force) before the surgery and daily after MCAO-r. H-reflex on triceps brachii was measured before and after isometric exercise. Infarction size and cerebral edema were respectively assessed by histological (Cresyl violet) and MRI measurements at the same time points than H-reflex recordings. Animals with cerebral ischemia showed persistent functional deficits during the first week post-MCAO-r. H-reflex was not decreased in response to isometric exercise one day after the cerebral ischemia contrary to the other groups. The motor reflex regulation was recovered 7 days post-MCAO-r. This result reflects an acute sensorimotor adaptation at the spinal level after MCAO-r.

Small molecule inhibitors in the treatment of cerebral ischemia

INTRODUCTION

Stroke is the world's second leading cause of death. Although recombinant tissue plasminogen activator is an effective treatment for cerebral ischemia, its limitations and ischemic stroke's complex pathophysiology dictate an increased need for the development of new therapeutic interventions. Small molecule inhibitors (SMIs) have the potential to be used as novel therapeutic modalities for stroke, since many preclinical and clinical trials have established their neuroprotective capabilities.

AREAS COVERED

This paper provides a summary of the pathophysiology of stroke as well as clinical and preclinical evaluations of SMIs as therapeutic interventions for cerebral ischemia. Cerebral ischemia is broken down into four mechanisms in this article: thrombosis, ischemic insult, mitochondrial injury and immune response. Insight is provided into preclinical and current clinical assessments of SMIs targeting each mechanism as well as a summary of reported results.

EXPERT OPINION

Many studies demonstrated that pre- or post-treatment with certain SMIs significantly ameliorated adverse effects from stroke. Although some of these promising SMIs moved on to clinical trials, they generally failed, possibly due to the poor translation of preclinical to clinical experiments. Yet, there are many steps being taken to improve the quality of experimental research and translation to clinical trials.

Ginsenoside Rd for acute ischemic stroke: translating from bench to bedside

Numerous studies have identified pathophysiological mechanisms of acute ischemic stroke and have provided proof-of-principle evidence that strategies designed to impede the ischemic cascade, namely neuroprotection, can protect the ischemic brain. However, the translation of these therapeutic agents to the clinic has not been successful. Ginsenoside Rd, a dammarane-type steroid glycoside extracted from ginseng plants, has exhibited an encouraging neuroprotective efficacy in both laboratory and clinical studies. This article attempts to provide a synopsis of the physiochemical profile, pharmacokinetics, pharmacodynamics, clinical efficacy, safety and putative therapeutic mechanisms of Rd. Finally, the authors discuss the validity of Rd as a neuroprotective agent for acute ischemic stroke.