Pathogenesis Of Ischemic Brain Damage Research Articles

Current challenges for therapy of comorbid patients: a new look at celecoxib. A review

The use of non-steroidal anti-inflammatory drugs (NSAIDs) for a wide range of diseases is increasing, in part due to an increasing elderly population. Elderly patients are more vulnerable to adverse drug reactions, including side effects and adverse effects of drug-drug interactions, often occurring in this category of patients due to multimorbidity and polypharmacy. One of the most popular NSAIDs in the world is celecoxib. It is a selective cyclooxygenase (COX)-2 inhibitor with 375 times more COX-2 inhibitory activity than COX-1. As a result, celecoxib has a better gastrointestinal tract safety profile than non-selective NSAIDs. Gastrointestinal tolerance is an essential factor that physicians should consider when selecting NSAIDs for elderly patients. Celecoxib can be used in a wide range of diseases of the musculoskeletal system and rheumatological diseases, for the treatment of acute pain in women with primary dysmenorrhea, etc. It is also increasingly used as part of a multimodal perioperative analgesia regimen. There is strong evidence that COX-2 is actively involved in the pathogenesis of ischemic brain damage, as well as in the development and progression of neurodegenerative diseases, such as Alzheimer's disease. NSAIDs are first-line therapy in the treatment of acute migraine attacks. Celecoxib is well tolerated in patients with risk factors for NSAID-associated nephropathy. It does not decrease the glomerular filtration rate in elderly patients and patients with chronic renal failure. Many meta-analyses and epidemiological studies have not confirmed the increased risk of cardiovascular events reported in previous clinical studies and have not shown an increased risk of cardiovascular events with celecoxib, irrespective of dose. COX-2 activation is one of the key factors contributing to obesity-related inflammation. Specific inhibition of COX-2 by celecoxib increases insulin sensitivity in overweight or obese patients. Combination therapies may be a promising new area of treatment for obesity and diabetes.

Involvement immune response in the pathogenesis of ischemic stroke

Acute disorders of cerebral circulation are one of the leading problems of modern clinical medicine, due to their significant spread in the human population and the extremely negative impact exerted on the patient’s body. Currently available data allow us to talk about the multi-vector nature of the pathogenesis of ischemic brain damage. Within the framework of the cascade of developing pathochemical and pathophysiological processes, an essential role in the formation of ischemic stroke belongs to the inflammatory reaction occurring through the immune system’s response to cerebral tissue ischemia. One of the places of its implementation is the vessel wall located in the ischemic zone, where monocytes and neutrophils are attracted with the help of cell adhesion proteins. Complement activation plays a significant role, carried out mainly due to the C3 component or during the initialization of the mannose pathway. Activation of microglia and astrocytes plays a huge role directly in the focus of ischemia. It should be noted that in the process of activation, both microglia and astrocytes are able to acquire a pro-inflammatory or anti-inflammatory phenotype. The prevalence of the pro-inflammatory variant contributes to prolonged damage to brain tissue, while the predominance of the anti-inflammatory phenotype has a protective effect. An important role is played by a violation of the function of the blood-brain barrier, which provides an additional influx of leukocytes to the site of ischemia. In addition, individual subpopulations of T-lymphocytes penetrating through the damaged barrier also play a significant role in the organization and dynamics of the immuno-inflammatory response. The action of Th1 and Th2 cells, gamma-delta T lymphocytes, natural killer cells, as well as regulatory T lymphocytes has been most studied. The role of B-lymphocytes in the formation of a stroke focus is considered.

Comparative Characteristics of Changes in Neuron Organelles During Two-Stage Ligation of the Common Carotid Arteries in Phylogenetically Different Sections of the Brain Cortex of Outbreed White Rats

Ultrastructural characteristics of changes in neuronal organelles during two-stage ligation of the common carotid arteries in phylogenetically different sections are important indicators of the degree of brain damage during ischemic exposure, which necessitates the study of this aspect. Two-stage subtotal cerebral ischemia was performed on 24 outbred male rats by sequential ligation of both common carotid arteries with an interval of 7 days, 3 days and 1 day. This method of modeling subtotal ischemia makes it possible to study the dynamics of the consequences of severe cerebral ischemia and the pathogenesis of ischemic brain damage. Thus, compensatory changes in neuronal organelles during two-stage ligation of the common carotid arteries included expansion of the cisternae of the Golgi complex and hyperplasia of the endoplasmic reticulum, as a reflection of the activation of compensation mechanisms during hypoxia.

The effect of intranasal administration of an IL-1b antagonist (RAIL) on the state of the nitroxydergic system of the brain during modeling of acute cerebrovascular accident

Introduction: This study was designed to evaluate the effect activity of RAIL-gel in comparison with Citicoline on nitroxydergic system during acute cerebrovascular accident. Methods: In this study, 80 white nonlinear rats were randomly assigned to 4 groups (20 rats in each): 1) intact; 2) control - untreated with acute cerebrovascular accident (ACVA), examined on the 4th day; 3) animals with ACVA, receiving RAIL, examined on the 18th day; 4) animals with ACVA, treated with Citicoline, examined on the 4th day. The expression of inducible NOS was determined by Western blotting. The nitrosative stress marker, nitrotyrosine, was determined using the ELISE kit NITROTYROSINE (kit no. HK501-02, series 12825k1212-k). To assess the state of iNOS mRNA expression, we used the method of polymerase chain reaction with reverse transcription in real time (RT-PCR). Results: Our research demonstrated that course administration of the RAIL and Citicoline to animals with ACVA for 4 days leads to the stabilization of the parameters of the brain nitroxydergic system. However, Citicoline does not provide a full effect on the shifts of the NO system in the brain. It does not have the proper effect on such an important link in the pathogenesis of ischemic brain damage as nitrosative stress. RAIL leads to a significant decrease in NOS activity due to its inducible form (decrease in the expression of iNOS and iNOS mRNA) and a decrease in NO metabolits, and inhibition of nitrosative stress (decrease in nitrotyrosine). Conclusion: IL-1b antagonist RAIL (Intranal Gel) significantly exceeds Citicoline in terms of the severity of the effect on the nitroxydergic system indicators.

Современные нейрохимические и молекулярно-генетические аспекты патогенеза неонатальных судорог

The article is devoted to the modern aspects of the pathogenesis of neonatal seizures (NS). The main mechanisms of the development of perinatal brain injuries, which are fundamental in the genesis of NS, are considered, the prospects for research devoted to the study of the possibilities of molecular genetic prediction of the individual risk of ischemia and the development of NS are outlined. The mechanisms of ischemic brain damage during the neonatal period and the role of glutamate, the main excitatory neurotransmitter acting on NMDA receptors that regulate the electrical activity of neurons, are described in detail. The review focuses on the involvement of metalloproteinases, primarily MMP-9, which destroys type IV collagen, which is the main component of the basement membrane of the cerebral endothelium, and creates conditions for cell migration across the BBB, thereby causing a cytokine storm and the development of inflammation, leading to NS. The possible role of calcium-dependent proteinases — calpains in the development of NS is analyzed, since in some forms of CNS pathology, uncontrolled hyperactivation of calpains is observed, leading to a disruption of the regulation of neurotransmitter transmission, which can, in turn, become an additional factor for the development of the neurodegenerative process in the brain and the development of seizures. Also are presented the results of studies devoted to the role of ion channels, providing synaptic transmission of excitation from an excited neuron to other cells. It has been shown that molecular defects in ion channels can be one of the factors that create prerequisites for the development of NS. The article shows the prospects for studying the genetic polymorphism of enzymes involved in the pathogenesis of ischemic brain damage, based on ideas about the pathogenesis of cerebral disorders in newborns, which are based on oxidative damage. The concluding part of the article outlines the modern principles of NS therapy, their main goal is to relieve the symptoms of the underlying disease, to ensure the normalization of blood circulation and brain metabolism, to optimize the conditions for the functioning of the preserved brain structures to prevent the formation of severe neurological complications, as well as to maintain optimal parameters of respiration, glucose-electrolyte composition of blood and thermal regime. Based on the data presented, it is concluded that early diagnosis of NS is necessary, which is determined by the fact that seizures in newborns are usually caused by serious damage to the child's brain, and in some cases — by life-threatening conditions, the timely diagnosis of which contributes to the early onset of specific treatment. No conflict of interest was declared by the author. Key words: newborn, cerebral ischemia, neonatal seizures.

Isosteviol Sodium Protects Against Permanent Cerebral Ischemia Injury in Mice via Inhibition of NF-κB–Mediated Inflammatory and Apoptotic Responses

Isosteviol sodium (STVNa) has been reported to have neuroprotective effects against ischemia/reperfusion (I/R) injury in rats. Furthermore, recanalization treatments, including thrombolytic therapy, have several limitations. Excessive inflammation and apoptosis contribute to the pathogenesis of ischemic brain damage. Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is critical to these processes and is associated with cerebral ischemia. Therefore, we studied the potential therapeutic effects and mechanisms of STVNa on permanent cerebral ischemia in mice. Permanent middle cerebral artery occlusion (pMCAO) was established via the suture method, followed by intravenous STVNa (7.5, 15, 30, 45, and 60 mg/kg). Neurobehavioral deficits, infarct volume, and histology were examined 24 hours after cerebral ischemia. In addition, the messenger RNA (mRNA) expression of NF-κB-related genes was detected using real-time quantitative polymerase chain reaction (qPCR). STVNa (30 mg/kg) had significant neuroprotective effects 24 hours after pMCAO, including the reduction of the infarct volume and the improvement of the neurological severity score. Immunohistochemistry demonstrated that STVNa significantly increased the number of restored neurons and decreased the number of astrocytes. qPCR also demonstrated that the mRNA expression of inhibitor of nuclear factor kappa-B kinase-α, inhibitor of nuclear factor kappa-B kinase-β, NF-κB, inhibitor of NF-κB-α, tumor necrosis factor-α, interleukin-1 beta, Bcl2-associated X protein, and caspase-3 were significantly downregulated, whereas B-cell CLL/lymphoma 2 mRNA was upregulated with STVNa treatment compared with vehicle. These findings demonstrate a neuroprotective role of STVNa during cerebral ischemia, which may result from interactions with the NF-κB signaling pathway and the associated inflammatory and apoptotic responses.

Complex application 2-ethyl-6-methyl-3-hydroxypyridine-succinate and vinpocetine in cerebrovascular disorder.

Developing brain ischemia due to cerebral vascularization leads to disruption of brain metabolism. Chronic cerebral hypoperfusion leads to irreversible brain damage and plays an important role in the development of some types of dementia. Early use of antioxidants such as ethyl ether apovincamine acid (vinpocetine) and 2-ethyl-6-methyl-3-hydroxypyridine-succinate in the treatment of this pathology is seen as a real pathogenetically based method of correction of cerebral metabolism with cerebral vascular disorders, demonstrating the increase in cerebral blood flow and also neuroprotective effects. Clinical studies and studies on biological models show that the main mechanisms of action of vinpocetine and 2-ethyl-6-methyl-3-hydroxypyridine-succinate, although have a similar focus, but implementing neuroprotective and nootropic effects via various links in the pathogenesis of ischemic brain damage.

The role of connexin structures (gap-junction and hemichannels) in the pathogenesis of ischemic brain damage: status update on the problem

This review is devoted to a discussion of the dual role of connexin intercellular structures and gap junction (GJ) in normal and cerebral ischemia. The review describes the structure and form of connexin structures such as gap junctions and hemichannels. It is shown that the properties of connexin structures depend on the connexins. We describe a substance that can be transported through connexin structure. The data on the possible increase in the number of GJ after ischemia/cerebral hypoxia. A hypothesis about the development of post-ischemic neuronal syncytium formation by GJ. We discuss ways of blocking of GJ to reduce post-ischemic brain damage.

Anti-inflammatory and Antiapoptotic Effects of Mesenchymal Stem Cells Transplantation in Rat Brain with Cerebral Ischemia

Excessive inflammation and apoptosis contribute to the pathogenesis of ischemic brain damage. Nuclear factor-kappa B (NF-κB) is considered to be a key protein complex involved in this cascade of events. The aim of the present study was to clarify the protection mechanism of the mesenchymal stem cells (MSCs). Lewis rats (N = 90) were randomly assigned to three groups: (1) the sham-operated group; (2) the saline group, in which the animals underwent rat transient middle cerebral artery occlusion (tMCAO, for 2 hours) and were treated with saline through the tail vein; and (3) the MSCs group, in which the animals underwent tMCAO (for 2 hours) and were infused with cultured human MSCs (4 × 10(6)/0.4 ml PBS) through the tail vein. At days 1 and 3 post-MSCs infusion, real-time PCR, and Western blot, immunohistochemical analyses were applied for tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and P-IKKβ, p53, and B-cell lymphoma 2 (Bcl-2) expression levels. TNF-α, IL-1β messenger RNA (mRNA) and P-IκB-α, P-IKKβ, p53 protein expression levels were significantly increased in the saline group compared with the sham group. However, IκB-α and Bcl-2 protein expression levels were markedly decreased in the saline group. After injection of BrdU(+) MSCs, the expression levels of TNF-α, IL-1β mRNA and P-IκB-α, P-IKKβ, p53 protein were significantly decreased. Contrary to these findings, IκB-α, Bcl-2 protein expression levels were markedly increased. In addition, we found that infarct area was significantly reduced in MSCs group. These results suggest that MSCs' neuroprotection is attributable to its anti-inflammatory and antiapoptotic effect through inhibition of NF-κB.

Serum levels of renin-angiotensin system components in acute stroke patients

The renin-angiotensin system (RAS) is involved in the pathogenesis of ischemic brain damage, and is suggested to have therapeutic potential in stroke by large clinical trials. However, the changes of serum RAS components in patients with acute stroke are totally unknown. We assessed the serum levels of RAS components in acute stroke patients, and investigated the relationship between RAS and stroke subtype. Levels of angiotensin-converting enzyme (ACE), ACE2 and angiotensin II in serum from patients with acute stroke (n=117; male 75, female 42, age 69 ± 13 years) were measured by an established enzyme-linked immunosorbent assay method. Diagnosis of subtypes of ischemic stroke was based on the Trial of Org10172 in Acute Stroke Treatment classification. The Kruskal-Wallis test with post-hoc Mann-Whitney U-test with Bonferroni correction was carried out for statistical analysis. Classification of stroke was as follows: large-artery atherosclerosis (n=44), cardioembolism (n=33), small-vessel occlusion (n=31), stroke of other determined etiology (n=9). Levels of angiotensin II and ACE did not show significant differences among each group. However, serum ACE2 level was significantly higher in the cardioembolism group than in the small-vessel occlusion group (cardioembolism 13 ± 9.3 ng/mL, large-artery atherosclerosis 10.2 ± 6.8 ng/mL, small-vessel occlusion 7.2 ± 3.7 ng/mL, stroke of other determined etiology 10.2 ± 7.3 ng/mL). ACE2 level showed a positive correlation with serum brain natriuretic peptide level (P=0.031). In contrast, angiotensin II concentration showed a negative correlation with National Institute of Health Stroke Scale score on admission (P=0.023). These findings suggest that changes of serum RAS components could reflect stroke subtypes and predict stroke severity.

Inhibition of NF-κB activation is associated with anti-inflammatory and anti-apoptotic effects of Ginkgolide B in a mouse model of cerebral ischemia/reperfusion injury

Ginkgolide B (GB) has potent neuroprotective effects against ischemia-induced brain injury in vivo and in vitro. However, the underlying mechanisms of GB’s neuroprotection remain poorly understood. Excessive inflammation and apoptosis contribute to the pathogenesis of ischemic brain damage, and NF-κB is considered to be a key player in these processes. In the present study, we examined the detailed mechanisms underlying the inhibitory effects of GB on inflammatory and apoptotic responses induced by focal cerebral ischemia/reperfusion (I/R). Transient middle cerebral artery occlusion (tMCAO) model was produced by using an intraluminal filament technique in mice. GB (10, 20 and 40mg/kg) was administered intravenously (i.v.) 2h after MCAO. The results demonstrated that MCAO-induced cerebral injury was associated with an upregulation of p-IKK, p-IκB-α and degradation of IκB-α, indicating of NF-κB activation. Meanwhile activation of microglial and increases in levels of TNF-α, IL-1β and iNOS were observed. Furthermore upregulation of the expression of NF-κB target gene p53 and p53 downstream gene Bax, but downregulation of Bcl-2 and activation of caspase-3 were found. GB treatment showed marked reduction in infarction volume, brain edema and neurological deficits. GB also inhibited I/R induced NF-κB, microglia activation and production of pro-inflammatory cytokines. We also demonstrated that GB reduced Bax protein levels and increased Bcl-2 protein levels in the post-ischemic brains. These results suggest that GB’s neuroprotection is attributable to its anti-inflammatory and anti-apoptotic effect through inhibition of NF-κB.

Neuron Protection as a Therapeutic Target in Acute Ischemic Stroke

Involvement of various neurotransmitters and neuromodulators have been shown to contribute to the ischemic injury and neuronal death associated with stroke Role of excitatory amino acid receptor activation, calcium overload, nitric oxide, and oxidative stress in the pathogenesis of ischemic brain damage is well established. Several new strategies are currently emerging, based on recent advances in our understanding of molecular pathways that could be considered as potential therapeutic targets. For example reactive oxygen species (ROS) are important contributors to the secondary injury cascade following traumatic brain injury (TBI), and ROS inhibition has consistently been shown to be neuroprotective following experimental TBI and brain ischemia. Furthermore, more recently, some authors concluded that nonanticoagulant 3K3A-APC exhibits greater neuroprotective efficacy with no risk for bleeding compared with drotrecogin-alfa activated, a hyperanticoagulant form of APC. Excessive calcium entry into depolarized neurons contributes significantly to cerebral tissue damage after ischemia. Included in the sequence of events leading to neuronal death in ischemic tissue following stroke is an excessive and toxic rise in the intracellular Ca(2+)-concentration, predominantly due to an influx of Ca2+ through nonselective cation-channels as well as Ca(2+)-channels.. Some authros conducted a study to investigate whether the enhancement of GABA receptor activity could inhibit NMDA receptor-mediated nitric oxide (NO) production by neuronal NO synthase (nNOS) in brain ischemic injury. The results showed that both the GABA(A) receptor agonist muscimol and the GABA(B) receptor agonist baclofen had neuroprotective effect, and the combination of two agonists could significantly protect neurons against death induced by ischemia/reperfusion. On this basis we conclude that neuroprotection for ischemic stroke refers to strategies, applied singly or in combination, that antagonize the injurious biochemical and molecular events that eventuate in irreversible ischemic injury. There has been a recent explosion of interest in this field, with over 1000 experimental papers and over 400 clinical articles appearing within the past 6 years. These studies, in turn, are the outgrowth of three decades of investigative work to define the multiple mechanisms and mediators of ischemic brain injury, which constitute potential targets of neuroprotection.

Selective neuron loss after cerebral ischemia in the rat: possible role of transmitter glutamate.

Male Wistar rats were subjected to 20 min of cerebral ischemia by means of 4-vessel occlusion. The topography of regional, selective neuron loss in this model corresponded to areas with pronounced glutamate high affinity uptake (presynaptic receptors), suggesting that transmitter glutamate is involved in the mechanism of neuron damage. One group of animals was injected with the glutamate antagonist, glutamic acid diethyl ester (GDEE) before ischemia. The regional neuron loss was rated using a semiquantitative scale. No statistically significant difference was found between the groups. The results do not exclude a possible role of transmitter glutamate in the pathogenesis of ischemic brain damage. More specific and potent glutamate antagonists are needed in order to clarify such a mechanism.

Antisense in vivo knockdown of synaptotagmin I by HVJ–liposome mediated gene transfer attenuates ischemic brain damage in neonatal rats

Synaptic release of the excitatory amino acid glutamate is considered as an important mechanism in the pathogenesis of ischemic brain damage in neonates. Synaptotagmin I is one of exocytosis-related proteins at nerve terminals and considered to accelerate the exocytosis of synaptic vesicles by promoting fusion between the vesicles and plasma membrane. To test the possibility that antisense in vivo knockdown of synaptotagmin I modulates the exocytotic release of glutamate, thus suppressing the excitotoxic intracellular processes leading to neuronal death following ischemia in the neonatal brain, we injected antisense oligodeoxynucleotides (ODNs) targeting synaptotagmin I (0.3 (AS), 0.15 (0.5 AS), or 0.03 μg (0.1 AS), or vehicle) into the lateral ventricles of 7-day-old rats by using a hemagglutinating virus of Japan (HVJ)–liposome mediated gene transfer technique. At 10 days of age, these rats were subjected to an electrical coagulation of the right external and internal carotid arteries, then the insertion of a solid nylon thread into the right common carotid artery toward the ascending aorta up to 10–12 mm from the upper edge of the sternocleidomastoid muscle. Cerebral ischemia was induced by clamping the left external and internal carotid arteries with a clip, and ended by removing the clip 2 h later. Twenty-four hours after the end of ischemia, the extent of ischemic brain damage was neuropathologically and quantitatively evaluated in the neocortex and striatum. While the relative volume of damage in the cerebral cortex and striatum of the vehicle group was extended to 40% and 13.7%, respectively, that in the AS group was significantly reduced to 4.8% and 0.6%. In the 0.5 AS group, the relative volume of ischemic damage in the cerebral cortex and striatum was reduced to 20.5% and 15.4%, respectively, and the difference between the 0.5 AS group and vehicle group was statistically significant in the neocortex, but not in the striatum. These results indicated that antisense in vivo knockdown of synaptotagmin I successfully attenuated ischemic brain damage in neonatal rats and that the effect was dose-dependent. It was also suggested that this treatment was more effective in the neocortex than in the striatum in neonatal rats.

Neuronal and Glial Responses to Polyamines in the Ischemic Brain

The polyamines, putrescine, spermidine and spermine are present in most living cells, with the essentiality for normal cell function, cellular growth and differentiation. In the mammalian brain, polyamines are also present at relatively high concentrations with different regional distribution profiles. Cerebral ischemia is a leading cause of disability and mortality in humans, and believed to yield a cascade of cytotoxic molecules responsible for the death of viable cells in the brain. Polyamines have been implicated in the pathogenesis of ischemic brain damage. For example, polyamine biosynthesis is increased after the onset of cerebral ischemia through an induction of ornithine decarboxylase, a key enzyme in the polyamine biosynthetic pathway. The administration of a drug that inhibits ornithine decarboxylase activity prevents the development of ischemic brain damage, suggesting a critical role of the accumulation of polyamines in the ischemic brain in the pathogenesis of stroke. Both spermine and spermidine are linked to the development of glutamate-mediated neurotoxicity, for they can bind to the N-methyl-D-aspartate (NMDA)-sensitive subtype of glutamate receptors to potentiate cellular responses to glutamate. Moreover, polyamines are metabolized by polyamine oxidases after acetylation to produce different cytotoxic aldehydes and reactive oxygen species such as hydrogen peroxide, which possibly damage proteins, DNA and lipids. Polyamines have been extensively studied in the ischemic brain, particularly with respect to neuronal responses such as NMDA receptor-mediated excitotoxicity. However, little is known about glial responses to polyamines in the ischemic brain to date. In this review, we would summarize previous studies related to neuronal and glial responses to polyamines in the ischemic brain.

FK419, a Nonpeptide Platelet Glycoprotein IIb/IIIa Antagonist, Ameliorates Brain Infarction Associated with Thrombotic Focal Cerebral Ischemia in Monkeys: Comparison with Tissue Plasminogen Activator

The binding of platelet glycoprotein (GP) IIb/IIIa to fibrinogen is the final common pathway in platelet aggregation, a process known to play a key role in the pathogenesis of ischemic brain damage. We compared the effects of FK419, a novel nonpeptide GPIIb/IIIa antagonist, with recombinant tissue plasminogen activator (rt-PA) on middle cerebral artery (MCA) patency and ischemic brain damage in a thrombotic stroke model in squirrel monkeys. FK419 not only inhibited in vitro platelet aggregation (IC50: 88 nmol/L), but also showed disaggregatory activity to aggregated platelet (EC50: 286 nmol/L). FK419 dose-dependently reduced the time to first reperfusion and total occlusion time of MCA blood flow when administered immediately after the termination of photoirradiation. FK419 reduced cerebral infarction and ameliorated neurologic deficits with similar dose-dependency. Although rt-PA reduced the time to first reperfusion, total occlusion time, and cerebral infarction, it did not significantly ameliorate neurologic deficits and induced petechial intracerebral hemorrhages. These results indicate: (1) FK419 restored cerebral blood flow after thrombotic occlusion of MCA, (2) FK419 reduced ischemic brain injury by its thrombolytic actions in a non-human primate stroke model, and (3) FK419 has superior antithrombotic efficacy and is safer than rt-PA.

Antithrombotic effects of FK419, a novel nonpeptide platelet GPIIb/IIIa antagonist, in a guinea pig photochemically induced middle cerebral artery thrombosis model: comparison with ozagrel and argatroban.

Platelet activation and subsequent aggregation play a key role in the pathogenesis of ischemic brain damage. Recent studies revealed that enhanced platelet activation is also observed after ischemia, suggesting that secondary thrombus formation might participate in the development of cerebral infarction. The binding of platelet glycoprotein GPIIb/IIIa (integrin alpha(IIb)beta3) to fibrinogen is the final common pathway in platelet aggregation. Therefore, GPIIb/IIIa antagonists might be useful in acute ischemic stroke as well as in the secondary prevention of ischemic stroke. In the present study, we evaluated the effect of three compounds, FK419 ((S)-2-acetylamino-3-[(R)-[1-[3-(piperidin-4-yl) propionyl] piperidin-3-ylcarbonyl] amino] propionic acid trihydrate), a novel nonpeptide GPIIb/IIIa antagonist, ozagrel, a selective thromboxane A(2) synthase inhibitor, and argatroban, a thrombin inhibitor, on middle cerebral artery (MCA) patency and ischemic brain damage using photochemically induced MCA thrombosis model in guinea pigs. FK419, ozagrel, or argatroban was administered 5 min after the termination of photoirradiation. FK419 dose-dependently improved MCA patency by decreasing the total occlusion time, time to continuous reperfusion, and the number of cyclic flow reductions, at doses that inhibited ADP-induced platelet aggregation ex vivo. In contrast, ozagrel only improved total occlusion time, and argatroban showed no improvement in MCA patency. FK419 also reduced ischemic brain damage in a dose-dependent fashion, whereas ozagrel and argatroban did not. Finally, FK419 ameliorated neurological deficits, whereas ozagrel and argatroban did not. These results indicate that FK419, a GPIIb/IIIa antagonist, ameliorates ischemic brain damage by improving MCA patency after occlusion and that FK419 is a promising candidate for the treatment of acute ischemic stroke.

Measurement of volume of cerebral blood flow in healthy preterm and term neonates with ultrasound

Changes in cerebral blood flow are important in the pathogenesis of ischaemic brain damage, but standard methods cannot measure volume of cerebral blood flow quantitatively in neonates. We used colour duplex sonography of the extracranial cerebral arteries to measure volume of global cerebral blood flow in 67 healthy preterm and term neonates. Volume of cerebral blood flow increased between the postmenstrual ages of 34 weeks (median 33 mL/min [range 23-43]) and 42 weeks (85 mL/min [57-104]). However, intersession and interobserver variability was quite large. This non-invasive method will allow quantitative bedside monitoring of global brain perfusion in preterm and term neonates with pathological disorders, and could also be used to monitor effects of neuroprotective measures.

Role of IL-1α and IL-1β in Ischemic Brain Damage

The cytokine interleukin-1 (IL-1) has been strongly implicated in the pathogenesis of ischemic brain damage. Evidence to date suggests that the major form of IL-1 contributing to ischemic injury is IL-1beta rather than IL-1alpha, but this has not been tested directly. The objective of the present study was to compare the effects of transient cerebral ischemia [30 min middle cerebral artery occlusion (MCAO)] on neuronal injury in wild-type (WT) mice and in IL-1alpha, IL-1beta, or both IL-1alpha and IL-1beta knock-out (KO) mice. Mice lacking both forms of IL-1 exhibited dramatically reduced ischemic infarct volumes compared with wild type (total volume, 70%; cortex, 87% reduction). Ischemic damage compared with WT mice was not significantly altered in mice lacking either IL-1alpha or IL-1beta alone. IL-1beta mRNA, but not IL-1alpha or the IL-1 type 1 receptor, was strongly induced by MCAO in WT and IL-1alpha KO mice. Administration (intracerebroventricularly) of recombinant IL-1 receptor antagonist significantly reduced infarct volume in WT (-32%) and IL-1alpha KO (-48%) mice, but had no effect on injury in IL-1beta or IL-1alpha/beta KO mice. These data confirm that IL-1 plays a major role in ischemic brain injury. They also show that chronic deletion of IL-1alpha or IL-1beta fails to influence brain damage, probably because of compensatory changes in the IL-1 system in IL-1alpha KO mice and changes in IL-1-independent mediators of neuronal death in IL-1beta KO mice.

Possible role of the superoxide anion in the development of neuronal tolerance following ischaemic preconditioning in rats.

There is a large body of evidence that reactive oxygen species play a major role in the pathogenesis of ischaemic brain damage. On the other hand, it has recently been suggested that superoxide anions participate in the development of neuronal tolerance against lethal ischaemia following ischaemic preconditioning (PC). The present study aimed to examine whether or not the intravenous administration of human recombinant Cu/Zn superoxide dismutase (hr SOD) prior to PC would affect the subsequent development of neuronal tolerance. Animals were randomly assigned to the following three groups: group 1, sham PC treated with vehicle; group 2, PC treated with hr SOD and group 3, PC treated with vehicle. For PC, 10 min occlusion of the middle cerebral artery (MCA) by a modified intraluminal suture method was followed by 60 min recirculation and this procedure was successively repeated three times. The procedures were similar for sham PC except that the MCA was kept unoccluded. Just prior to PC or sham PC, a bolus of hr SOD (6 x 103 IU/2 ml/kg) was administered intravenously. Seventy-two hours thereafter, rats were subjected to lethal ischaemia, i.e. MCA occlusion for 100 min followed by recirculation for 48 h. The infarct area and volume were assessed with the 2,3,5-triphenyltetrazolium stain. A significant difference in the infarct volume was revealed between the sham PC/vehicle and the PC/vehicle groups (total and cortex P < 0.01; striatum P < 0.05), showing that PC induced a marked neuronal tolerance against lethal ischaemia. The infarct volume in the PC/SOD group was close to that in the sham PC/vehicle group, being significantly greater than that in the PC/vehicle group (total and cortex P < 0.01) and showing that the administration of hr SOD suppressed the development of neuronal tolerance induced by PC. In a parallel experiment, expression of 72-kDa heat-shock protein (hsp 72) at 72 h after PC was considerably reduced in rats treated with hr SOD compared with those treated with vehicle. These results suggest that superoxide anions intraluminally generated within cerebral microvessels participate in the development of neuronal tolerance as well as the induction of hsp 72 following PC.