Role of a synthetic pyrimidine compound, MS-818, in reduction of infarct size and amelioration of sensorimotor dysfunction following permanent focal cerebral ischemia in rats

Effect Produced by a Cyclooctyne Derivative on Both Infarct Area and Left Ventricular Pressure via Calcium Channel Activation

BACKGROUND

There are reports which indicate that some cyclooctyne derivatives may exert changes in cardiovascular system; however, its molecular mechanism is not very clear.

OBJECTIVE

The aim of this study was to evaluate the biological activity of four cyclooctyne derivatives (compounds 1: to 4: ) produced on infarct area and left ventricular pressure.

METHODS

Biological activity produced by cyclooctyne derivatives on infarct area was determinate using an ischemia/reperfusion injury model. In addition, to characterize the molecular mechanism of this effect, the following strategies were carried out as follows; i) biological activity produced by cyclooctyne derivative (compound 4: ) on either perfusion pressure or left ventricular pressure was evaluated using an isolated rat heart; ii) theoretical interaction of cyclooctyne derivative with calcium channel (1t0j protein surface) using a docking model.

RESULTS

The results showed that cyclooctyne derivative (compound 4: ) decrease infarct area of in a dose-dependent manner compared with compound 1: to 3: . Besides, this cyclooctyne derivative increase both perfusion pressure and left ventricular pressure which was inhibited by nifedipine. Other theoretical data suggests that cyclooctyne derivative could interact with some aminoacid residues (Met₈₃, Ile₈₅, Ser₈₆, Leu₁₀₈, Glu₁₁₄) involved in 1t0j protein surface.

CONCLUSIONS

All these data indicate that cyclooctyne derivative increase left ventricular pressure via calcium channel activation and this phenomenon could be translated as a decrease of infarct area.

Stem Cell Therapies for Neurodegenerative Diseases

Stem cell therapies have been proposed as a treatment option for neurodegenerative diseases, but the best stem cell source and therapeutic efficacy for neuroregeneration remain uncertain. Embryonic stem cells (ESCs) and neural stem cells (NSCs), which can efficiently generate neural cells, could be good candidates but they pose ethical and practical issues. Not only difficult to find the good source of those cells but also they alway pose immunorejection problem since they may not be an autologous cells. Even if we overcome the immunorejection problem, it has also been reported that transplantation of ESCs develop teratoma. Although adult stem cells are more accessible, they have a limited developmental potential. We developed technologies to increase potency of mesenchymal stem cells, which allow them to develop into neural cells, by over expression of the ESC gene, nanog. We also developed a small molecule compound, which significantly increases endogenous NSCs by peripheral administration, eliminating even the necessity of stem cell injection to the brain. These novel technologies may offer neuroregenerative therapies for Alzheimers disease (AD). However, we found that AD pathological condition prevent neurogenesis from NSCs. This chapter discusses how to overcome the problem associated stem cell therapy under AD pathology and introduces exosome as a tool to improve the modification of adult stem cells. These new technologies may open a door for the new era for AD therapy.

Discovery of a Small Molecule that Enhances Astrocytogenesis by Activation of STAT3, SMAD1/5/8, and ERK1/2 via Induction of Cytokines in Neural Stem Cells

Identification of small molecules that direct neural stem cells (NSCs) into specific cell types would be helpful to understand the molecular mechanisms involved in regulation of NSC fate, and facilitate the development of therapeutic applications. In the current study, we developed and screened small molecules that can modulate the fate of NSCs that are derived from rat fetal cortex. Among these compounds, compounds 5 and 6 successfully differentiated NSCs into astrocytes and neurons, respectively. Compound 5 induced astrocytogenesis by increasing expression of interleukin-6, bone morphogenetic protein 2 and leukemia inhibitory factor and through consequent phosphorylation of signal transducer and activator of transcription 3 and Sma- and Mad-related protein 1/5/8 in NSCs. In addition, compound 5 increased the expression of fibroblast growth factor (FGF) 2 and FGF8 which may regulate the branching and morphology of astrocytes. Taken together, our results suggest that these small molecules can serve as a useful tool to study cell fate determination in NSCs and be used as an inexpensive alternative to cytokines to study mechanisms of astrocytogenesis.

Antidepressant fluvoxamine reduces cerebral infarct volume and ameliorates sensorimotor dysfunction in experimental stroke

The sigma-1 receptor has been reported to be associated with diverse biological activities including cellular differentiation, neuroplasticity, neuroprotection, and cognitive functioning of the brain. Fluvoxamine, one of the currently known antidepressants, is a sigma-1 receptor agonist; its effectiveness in treating acute cerebral ischemia has not been reported. We studied the in-vivo effects of this compound using an animal model of focal cerebral ischemia. Forty male Sprague-Dawley rats were subjected to right middle cerebral artery occlusion and assigned to five treatment groups (n=8 each). Postischemic neurological deficits and infarct volume were determined 24 h after stroke-inducing surgery. Significant reductions in infarct volume (total and cortical) were found in group 2 (fluvoxamine 20 mg/kg given 6 h before and immediately after ischemic onset) and group 3 (fluvoxamine given immediately after ischemic onset and 2 h later) compared with controls. Fluvoxamine induced significant amelioration of sensorimotor dysfunction, as indicated by the scores of forelimb and hindlimb placing tests. Moreover, NE-100, a selective sigma-1 receptor antagonist, completely blocked the neuroprotective effect of fluvoxamine. The present findings suggest that the sigma-1 receptor agonist fluvoxamine reduces infarct volume and ameliorates neurological impairment even on postischemic treatment. From the clinical viewpoint, fluvoxamine may be a promising new therapeutic approach for cerebral infarction.

Modified permanent middle cerebral artery occlusion rat model aiming to reduce variability in infarct size

In animal cerebral infarct experiments, the most important aspect is to produce consistent infarct size and localization. In an attempt to improve the conventional middle cerebral artery (MCA) coagulation technique, we developed a new animal model using a microclip to reduce variability in infarct size. Male Sprague-Dawley rats were subjected to right MCA occlusion. The animals were divided into two groups; conventional MCA occlusion group (Group 1; n = 9) and modified clip occlusion group (Group 2; n = 9). In Group 2, the proximal portion of MCA was occluded by applying a small clip just proximal to the olfactory nerve, and the MCA from the clipped position to the position just proximal to the level of the inferior cerebral vein was electrocoagulated using a bipolar diathermy in the same manner as in Group 1. In other words, the only difference between these two groups was the manner of occlusion of the most proximal portion of the MCA. Rats were killed 24 hours after the stroke-inducing surgery, and infarct volume was determined by an image analysis program following staining with 2,3,5-triphenyltetrazolium chloride. The cortical infarct volumes were 51.0 +/- 13.8% in Group 1 and 46.3 +/- 6.2% in Group 2. The scattering of cortical infarct volume was significantly small in Group 2 (p=0.0176). The differences in scattering of striatal and total infarct volumes did not reach statistical significance. The present results demonstrated that the new MCA occlusion model using a clip significantly reduces the variability in cortical infarct volume, solving the problems of the model using coagulation alone. That permanent MCA occlusion model using a clip is an excellent method that produces more consistent and reproducible infarction.

Filtrate of Phellinus linteus Broth Culture Reduces Infarct Size Significantly in a Rat Model of Permanent Focal Cerebral Ischemia

Phellinus linteus, a natural growing mushroom, has been known to exhibit anti-tumor, anti-inflammatory, anti-allergic and anti-oxidant effects. Aiming to exploit the neuroprotective effects of P. linteus, we evaluated its effects on infarct volume reduction in a rat model of focal cerebral ischemia. Male Sprague-Dawley rats were subjected to right middle cerebral artery occlusion. Filtrate of P. linteus broth culture (various doses), fractionated filtrate (based on molecular weight) or control medium was administered intraperitoneally to rats before or after ischemia induction. Rats were killed at 24 h after the stroke surgery. Cortical and caudoputaminal infarct volumes were determined separately using an image analysis program following staining with 2,3,5-triphenyltetrazolium chloride. Significant cortical infarct volume reductions were found in the pre-treatment groups (30 and 60 minutes before onset of cerebral ischemia) compared with the control group, showing dose dependence. Posttreatment (30 minutes after ischemic onset) also significantly reduced cortical infarct volume. Furthermore, the higher molecular weight (≥12 000) fraction of the culture filtrate was more effective compared with the lower molecular weight fraction. The present findings suggest that P. linteus may be a new promising approach for the treatment of focal cerebral ischemia, with the additional benefit of a wide therapeutic time window since significant infarct volume reduction is obtained by administration even after the ischemic event. Our finding that the higher molecular weight fraction of the P. linteus culture filtrate demonstrated more prominent effect may provide a clue to identify the neuroprotective substances and mechanisms.

MS-818 Accelerates Mobilization of Endothelial Progenitor Cells and Differentiation to Endothelial Cells

MS-818 that is a synthetic pyrimidine compound and shown to have neurotrophic actions, enhanced basic fibroblast growth factor (bFGF)-induced angiogenesis in vivo. However, the mechanism and whether MS-818 affects endothelial cells (ECs) directly is not known. Here, the authors investigated whether MS-818 alone could induce angiogenesis and tried to clarify the mechanism of neovascularization by MS-818 in terms of angiogenesis and vasculogenesis. The authors show that MS-818 affects ECs directly and induces migration of and tube formation by ECs in vitro (angiogenesis). Furthermore, the authors demonstrate that MS-818 mobilizes endothelial progenitor cells (EPCs) from the bone marrow and potentiates their differentiation to ECs (vasculogenesis). The effect of MS-818 on the endothelial differentiation was further confirmed with an in vitro differentiation system using mouse embryonic stem cells. MS-818 activates the mitogen-activated protein kinase (MAPK) pathway but not the phosphoinositol 3-kinase (PI3K)-Akt pathway in ECs. These results indicate that MS-818, a synthetic compound, promotes both angiogenesis and vasculogenesis.

Pravastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, reduces delayed neuronal death following transient forebrain ischemia in the adult rat hippocampus

Recent evidence indicates that statins have beneficial effects on the brain in the ischemic condition. However, there is a lack of studies related to the effect of statins on delayed neuronal death. We investigated the effect of prophylactic therapy with pravastatin on delayed neuronal death in the rat hippocampus. The rats were given a daily dose of 20 mg/kg of pravastatin orally for 14 days. Transient forebrain ischemia was induced by the four-vessel occlusion method. Three days after ischemia, surviving neurons of the hippocampal CA1 subfield were counted. Our results demonstrated that prophylactic statin treatment significantly reduced delayed neuronal death after transient forebrain ischemia. Our findings suggest that prophylactic statin treatment may be useful in preventing functional neurological disorders after transient cerebral ischemic insult.

Neuroprotective agents for the treatment of acute ischemic stroke

Neuroprotective treatments are therapies designed to interrupt the cellular, biochemical, and metabolic elaboration of injury during or following exposure to ischemia; they encompass a rapidly expanding array of pharmacologic interventions. Various classes of neuroprotective agents have reached phase III efficacy trials in focal ischemic stroke, but none has proven effective, despite successful preceding animal studies. This notwithstanding, recent favorable results of hypothermia in human cardiac arrest trials have validated the general concept of neuroprotection. In addition, the promise of neuroprotective therapy for focal acute ischemic stroke has been renewed by innovations in strategies of preclinical drug development and clinical trial design that rectify past defects, including trial testing of combination therapies rather than single agents and novel approaches to accelerating time to initiation of experimental treatment.