Characterization of neuronal cell death in normal and diabetic rats following exprimental focal cerebral ischemia

Neuroserpin, a crucial regulator for axogenesis, synaptic modelling and cell-cell interactions in the pathophysiology of neurological disease

Neuroserpin is an axonally secreted serpin that is involved in regulating plasminogen and its enzyme activators, such as tissue plasminogen activator (tPA). The protein has been increasingly shown to play key roles in neuronal development, plasticity, maturation and synaptic refinement. The proteinase inhibitor may function both independently and through tPA-dependent mechanisms. Herein, we discuss the recent evidence regarding the role of neuroserpin in healthy and diseased conditions and highlight the participation of the serpin in various cellular signalling pathways. Several polymorphisms and mutations have also been identified in the protein that may affect the serpin conformation, leading to polymer formation and its intracellular accumulation. The current understanding of the involvement of neuroserpin in Alzheimer's disease, cancer, glaucoma, stroke, neuropsychiatric disorders and familial encephalopathy with neuroserpin inclusion bodies (FENIB) is presented. To truly understand the detrimental consequences of neuroserpin dysfunction and the effective therapeutic targeting of this molecule in pathological conditions, a cross-disciplinary understanding of neuroserpin alterations and its cellular signaling networks is essential.

The defense system for Bidens pilosa root exudate treatments in Pteris multifida gametophyte

According to the novel weapons hypothesis, root exudates are the inhibition factors for native species growth and development through invasive plants. It is hypothesized that antioxidant system (AOS) presents an effective role in plant defense system. The allelopathy indexes of P. multifida gametophyte biomass and sporogonium conversions rates turn negative with the dose and time effects, and the synthetical allelopathic effect index was -55.07% at 100% treatments under root exudates treatments. Under transmission electron microscopy, the cell structures turn burry. Next, AOS and programmed cell death (PCD) were tested in this study. In AOS, strong activities of superoxide dismutase, catalase, glutathione reductase and glutathione S-transferase (GST) were identified in gametophyte cells under the treatments, as well as the contents of glutathione, ascorbic acid and reduced ascorbate, while GPX activity decreased. Based on the input (SOD activity) and the output (GST activity) of antioxidant system, and the decreasing system control would be a reason leading gametophyte death under root exudates. At day 10, PCD would get its peak of 46.93% at 100% root exudates. We found a dynamic balance of PCD and AOS under the exudates treatments. We detected hexadecanoic acid, ethylene glycol and undecane are three major chemicals in root exudates. Our results provide a reference of AOS and PCD working under root exudates treatments in plants and offer novel strategy for the native species protection and invasion plants control in environment science.

LncRNA MALAT1 promotes high glucose-induced inflammatory response of microglial cells via provoking MyD88/IRAK1/TRAF6 signaling

Although a large number of studies have confirmed from multiple levels that diabetes mellitus (DM) promotes cerebral ischemic reperfusion (I/R) injury, but the precise mechanism is still unclear. A cerebral I/R injury model in diabetic rats was established. The neurological deficit scores and brain edema were monitored at 24 and 72 hours after injury. The peri-infarct cortical tissues of rats were isolated for molecular biology detection. The rat primary microglia and microglia line HAPI were cultured to establish the cell model of DM-I/R by high glucose (HG) and hypoxia-reoxygenation (H/R). The endogenous expression of MALAT1 and MyD88 was regulated by the transfection with pcDNA-MALAT1, si-MALAT1 and si-MyD88, respectively. The cerebral I/R injury model in diabetic rats had more severe neuronal injury as shown by the significantly higher neurological deficit scores and an obvious increasing brain edema at 24 and 72 hours after injury. Moreover, the microglia were activated and induced a large number of inflammatory cytokines TNF-α, IL-1β and IL-6 in the peri-infarct cortical tissues during cerebral I/R injury associated with DM. The expression of MALAT1, MyD88, IRAK1 and TRAF6 protein were significantly up-regulated by DM-I/R in vitro and in vivo. Furthermore, the HG-H/R-induced MALAT1 promoted the inflammatory response in microglia via MyD88/IRAK1/TRAF6 signaling. Our results suggested that MALAT1 mediated the exacerbation of cerebral I/R injury induced by DM through triggering the inflammatory response in microglia via MyD88 signaling.

Previous physical exercise alters the hepatic profile of oxidative-inflammatory status and limits the secondary brain damage induced by severe traumatic brain injury in rats

KEY POINTS

An early inflammatory response and oxidative stress are implicated in the signal transduction that alters both hepatic redox status and mitochondrial function after traumatic brain injury (TBI). Peripheral oxidative/inflammatory responses contribute to neuronal dysfunction after TBI Exercise training alters the profile of oxidative-inflammatory status in liver and protects against acute hyperglycaemia and a cerebral inflammatory response after TBI. Approaches such as exercise training, which attenuates neuronal damage after TBI, may have therapeutic potential through modulation of responses by metabolic organs. The vulnerability of the body to oxidative/inflammatory in TBI is significantly enhanced in sedentary compared to physically active counterparts.

ABSTRACT

Although systemic responses have been described after traumatic brain injury (TBI), little is known regarding potential interactions between brain and peripheral organs after neuronal injury. Accordingly, we aimed to investigate whether a peripheral oxidative/inflammatory response contributes to neuronal dysfunction after TBI, as well as the prophylactic role of exercise training. Animals were submitted to fluid percussion injury after 6 weeks of swimming training. Previous exercise training increased mRNA expression of X receptor alpha and ATP-binding cassette transporter, and decreased inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF)-α and interleukin (IL)-6 expression per se in liver. Interestingly, exercise training protected against hepatic inflammation (COX-2, iNOS, TNF-α and IL-6), oxidative stress (decreases in non-protein sulfhydryl and glutathione, as well as increases in 2',7'-dichlorofluorescein diacetate oxidation and protein carbonyl), which altered hepatic redox status (increases in myeloperoxidase and superoxide dismutase activity, as well as inhibition of catalase activity) mitochondrial function (decreases in methyl-tetrazolium and Δψ, as well as inhibition of citrate synthase activity) and ion gradient homeostasis (inhibition of Na⁺ ,K⁺ -ATPase activity inhibition) when analysed 24 h after TBI. Previous exercise training also protected against dysglycaemia, impaired hepatic signalling (increase in phosphorylated c-Jun NH2-terminal kinase, phosphorylated decreases in insulin receptor substrate and phosphorylated AKT expression), high levels of circulating and neuronal cytokines, the opening of the blood-brain barrier, neutrophil infiltration and Na⁺ ,K⁺ -ATPase activity inhibition in the ipsilateral cortex after TBI. Moreover, the impairment of protein function, neurobehavioural (neuromotor dysfunction and spatial learning) disability and hippocampal cell damage in sedentary rats suggests that exercise training also modulates peripheral oxidative/inflammatory pathways in TBI, which corroborates the ever increasing evidence regarding health-related outcomes with respect to a physically active lifestyle.

Neuroprotection of Gueichih-Fuling-Wan on cerebral ischemia/ reperfusion injury in streptozotocin-induced hyperglycemic rats via the inhibition of the cellular apoptosis pathway and neuroinflammation

Background: Risks of stroke link with complications of hyperglycemia. Gueichih-Fuling-Wan (GFW), according to Chinese Medical Code literature, has the promotion of blood circulation and attenuates the swollen plot. Recent pharmacological studies have pointed out its efficacy in patients with cerebral ischemia or diabetes. Therefore, this study determined whether GFW has the protection against cerebral ischemia/ reperfusion (I/R) injury in streptozotocin (STZ)-induced hyperglycemic rats and LPS-induced inflammation in BV-2 microglial cells.

Methods: Extracts of GFW were filtered and frozen to dry for use. Hyperglycemia was induced by intraperitoneal injection of 70 mg/kg STZ. Fourteen days after STZ injection, GFW (1, 2 and 4 g/kg) was orally administered once daily for seven days. Rats were subjected to cerebral ischemia/reperfusion and sacrificed for infarction analysis and neuronal apoptosis detection twenty-one days after STZ injection. MTT assay was used for cell viability; nitrite quantification and western blot analysis of iNOS and COX-2 were used to explore the effects of GFW on LPS-induced inflammation in BV-2 microglial cells.

Results: GFW significantly ameliorated cerebral infarction while dosage was more than 1 g/kg (by 38.03% at 2 g/kg and 52.44% at 4 g/kg), and attenuated neurological deficits by 23.48% (at 2 g/kg) and 47.25% (at 4 g/kg). Furthermore, GFW (2, 4 g/kg) notably decreased TUNEL- and cleaved caspase-3-positive cells in the immunohistochemical stain (P < 0.01 and P < 0.001, respectively). GFW remarkably increased in Bcl-2 and decreased in caspase-3 and Bax/Bcl-2 ratio protein expressions by Western blot. GFW (0.25, 0.5, 1 mg/ ml) significantly reduced LPS-induced NO production in BV-2 microglial cells. And GFW attenuated iNOS and COX-2 expression in LPS-treated BV-2 cells. Conclusions: In summary, GFW has good bioactivities to protect cerebral I/R injury in hyperglycemic rats, which might be due to inhibition of cellular apoptosis and neuroinflammation.

[A role of the Fas system in the pathogenesis of ischemic stroke]

The Fas system can promote several biological effects due to their activation after ischemic stroke: apoptosis, inflammation, proliferation, differentiation. Fas interacts with adapter proteins activating a number of signaling pathways, including MAPK, NFKB, JNK, ERK, phosphorylation of cytoskeletal proteins, and caspase-dependent apoptosis. Fas expressed by neuronal progenitor cells from the subventricular zone does not induce apoptosis in healthy adult humans. During motion and differentiation of these cells, Fas regulates their morphological structure by the phosphorylation/dephosphorylation of cytoskeletal elements. An increase in the Fas and Fas ligand expression is observed in response to stroke injury. Fas responsible not only for cell death and inflammation but also for neuronal plasticity which occupies a central place in the processes of sanogenesis.

Hyperglycemia / hypoglycemia-induced mitochondrial dysfunction and cerebral ischemic damage in diabetics

Enhancement of ischemic brain damage is one of the most serious complications of diabetes. Studies from various in vivo and in vitro models of cerebral ischemia have led to an understanding of the role of mitochondria and complex interrelated mitochondrial biochemical pathways leading to the aggravation of ischemic neuronal damage. Advancements in the elucidation of the mechanisms of ischemic brain damage in diabetic subjects have revealed a number of key mitochondrial targets that have been hypothesized to participate in enhancement of brain damage. The present review initially discusses the neurobiology of ischemic neuronal injury, with special emphasis on the central role of mitochondria in mediating its pathogenesis and therapeutic targets. Later it further details the potential role of various biochemical mediators and second messengers causing widespread ischemic brain damage among diabetics via mitochondrial pathways. The present review discusses preclinical data which validates the significance of mitochondrial mechanisms in mediating the aggravation of ischemic cerebral injury in diabetes. Exploitation of these targets may provide effective therapeutic agents for the management of diabetes-related aggravation of ischemic neuronal damage.

Buyang Huanwu Decoction fraction protects against cerebral ischemia/reperfusion injury by attenuating the inflammatory response and cellular apoptosis

Buyang Huanwu Decoction fraction extracted from Buyang Huanwu Decoction contains saponins of Astragalus, total paeony glycoside and safflower flavones. The aim of this study was to demonstrate the neuroprotective effect and mechanism of Buyang Huanwu Decoction fraction on ischemic injury both in vivo and in vitro. In vivo experiments showed that 50-200 mg/kg Buyang Huanwu Decoction fraction reduced infarct volume and pathological injury in ischemia/reperfusion rats, markedly inhibited expression of nuclear factor-κB and tumor necrosis factor-α and promoted nestin protein expression in brain tissue. Buyang Huanwu Decoction fraction (200 mg/kg) exhibited significant effects, which were similar to those of 100 mg/kg Ginkgo biloba extract. In vitro experimental results demonstrated that 10-100 mg/L Buyang Huanwu Decoction fraction significantly improved cell viability, decreased the release of lactate dehydrogenase and malondialdehyde levels, and inhibited the rate of apoptosis in HT22 cells following oxygen-glucose deprivation. Buyang Huanwu Decoction fraction (100 mg/L) exhibited significant effects, which were similar to those of 100 mg/L Ginkgo biloba extract. These findings suggest that Buyang Huanwu Decoction fraction may represent a novel, protective strategy against cerebral ischemia/reperfusion injury in rats and oxygen-glucose deprivation-induced damage in HT22 cells in vitro by attenuating the inflammatory response and cellular apoptosis.

microRNAs: innovative targets for cerebral ischemia and stroke

Stroke is one of the leading causes of death and disability worldwide. Because stroke is a multifactorial disease with a short therapeutic window many clinical stroke trials have failed and the only currently approved therapy is thrombolysis. MicroRNAs (miRNA) are endogenously expressed noncoding short single-stranded RNAs that play a role in the regulation of gene expression at the post-transcriptional level, via degradation or translational inhibition of their target mRNAs. The study of miRNAs is rapidly growing and recent studies have revealed a significant role of miRNAs in ischemic disease. miRNAs are especially important candidates for stroke therapeutics because of their ability to simultaneously regulate many target genes and since to date targeting single genes for therapeutic intervention has not yet succeeded in the clinic. Although there are already quite a few review articles about miRNA in ischemic heart disease, much less is currently known about miRNAs in cerebral ischemia. This review summarizes current knowledge about miRNAs and cerebral ischemia, focusing on the role of miRNAs in ischemia, both changes in expression and identification of potential targets, as well as the potential of miRNAs as biomarkers and therapeutic targets in cerebral ischemia.

CoCl2 induces apoptosis through the mitochondria- and death receptor-mediated pathway in the mouse embryonic stem cells

Embryonic hypoxia/ischemia is a major cause of a poor fetal outcome and future neonatal and adult handicaps. However, biochemical cellular events in mouse embryonic stem (mES) cells during hypoxia remains unclear. This study investigated the underlying mechanism of apoptosis in mES cells under CoCl2-induced hypoxic/ischemic conditions. CoCl2 enhanced the expression of hypoxia-inducible factor-1α (HIF-1α) and the accumulation of reactive oxygen species in mES cells. The CoCl2-treated mES cells showed a decrease in cell viability as well as typical apoptotic changes, cell shrinkage, chromatin condensation, and nuclear fragmentation and an extended G2/M phase of the cell cycle. CoCl2 augmented the release of cytochrome c into the cytosol from the mitochondria with a concomitant loss of the mitochondrial transmembrane potential (ΔΨm) and upregulated the voltage-dependent anion channel. In addition, CoCl2-induced caspase-3, -8, and -9 activation and upregulation of p53 level, whereas downregulated Bcl-2 and Bcl-xL, a member of the anti-apoptotic Bcl-2 family in mES cells. Furthermore, CoCl2 led to the upregulation of Fas and Fas-ligand, which are the death receptor assemblies, as well as the cleavage of Bid in mES cells. These results suggest that CoCl2 induces apoptosis through both mitochondria- and death receptor-mediated pathways that are regulated by the Bcl-2 family in mES cells.

ER-Mitochondria Crosstalk during Cerebral Ischemia: Molecular Chaperones and ER-Mitochondrial Calcium Transfer

It is commonly believed that sustained elevations in the mitochondrial matrix Ca²⁺ concentration are a major feature of the intracellular cascade of lethal events during cerebral ischemia. The physical association between the endoplasmic reticulum (ER) and mitochondria, known as the mitochondria-associated ER membrane (MAM), enables highly efficient transmission of Ca²⁺ from the ER to mitochondria under both physiological and pathological conditions. Molecular chaperones are well known for their protective effects during cerebral ischemia. It has been demonstrated recently that many molecular chaperones coexist with MAM and regulate the MAM and thus Ca²⁺ concentration inside mitochondria. Here, we review recent research on cerebral ischemia and MAM, with a focus on molecular chaperones and ER-mitochondrial calcium transfer.

Potentiation of aspirin-induced cerebroprotection by minocycline: a therapeutic approach to attenuate exacerbation of transient focal cerebral ischaemia

Cerebrovascular disease is a major cause of mortality and disability in adults. Diabetes mellitus increases the risk of cerebral ischaemia and is associated with worse clinical outcome following an event. Upregulation of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) in diabetes appears to play a role in vascular complications of diabetes. We hypothesised that inhibition of MMP-2 and MMP-9 by minocycline can be potentiated by aspirin through inhibition of cyclooxygenase-2 and tissue plasminogen activator, resulting in amelioration of clinical cerebral ischaemia in diabetes. In the present study, cerebral ischaemia/reperfusion injury was induced in streptozotocin diabetic rats by 1 h middle cerebral artery occlusion and 24 h reperfusion. Infarct volume, cerebral oedema, neurological severity score and blood-brain barrier disruption were significantly increased in diabetic animals compared with the normoglycemic control group. The combination of aspirin and minocycline treatment significantly improved these parameters in diabetic animals. Moreover, this therapy was associated with significantly lower mortality and reduction in MMP-2 and MMP-9 levels. Our data indicate that combination of aspirin and minocycline therapy protects from the consequences of cerebral ischaemia in animal models of diabetes and is associated with inhibition of MMP-2 and MMP-9. Therefore, this combination therapy may represent a novel strategy to reduce the neurological complications of cerebral ischaemia in diabetes.

Inhibition by epigallocatechin gallate of CoCl2-induced apoptosis in rat PC12 cells

Epigallocatechin-3-gallate (EGCG) is a major constituent of green tea polyphenols. This study was aimed to investigate the possible mechanisms of EGCG-mediated inhibition against apoptosis in rat pheochromocytoma PC12 cells by exposure to CoCl(2). Exposure to CoCl(2) caused the generation of ROS and induced cell death with appearance of apoptotic morphology and DNA fragmentation. However, EGCG rescued the loss of viability in the cells exposed to CoCl(2) and led the reduction of DNA fragmentation and sub-G(1) fraction of cell cycle. Also, EGCG attenuated the CoCl(2)-induced disruption of mitochondrial membrane potential (DeltaPsim), release of cytochrome c from the mitochondria to cytosol and abolished the CoCl(2)-stimulated activities of the caspase cascades, caspase-9 and caspase-3. In addition, EGCG ameliorated the increase in the Bax to Bcl-2 ratio, a marker of apoptosis proceeding, induced by CoCl(2) treatment. Taken together, the present results suggest that EGCG inhibit the CoCl(2)-induced apoptosis of PC12 cells through the mitochondria-mediated apoptosis pathway involved in modulating the Bcl-2 family.

Diabetic Goto-Kakizaki rats display pronounced hyperglycemia and longer-lasting cognitive impairments following ischemia induced by cortical compression

Hyperglycemia has been shown to worsen the outcome of brain ischemia in several animal models but few experimental studies have investigated impairments in cognition induced by ischemic brain lesions in hyperglycemic animals. The Goto-Kakizaki (GK) rat naturally develops type 2 diabetes characterized by mild hyperglycemia and insulin resistance. We hypothesized that GK rats would display more severe cerebral damage due to hyperglycemia-aggravated brain injury and, accordingly, more severe cognitive impairments. In this study, recovery of motor and cognitive functions of GK and healthy Wistar rats was examined following extradural compression (EC) of the sensorimotor cortex. For this purpose, tests of vestibulomotor function (beam-walking) and combined tests of motor function and learning (locomotor activity from day (D) 1 to D5, operant lever-pressing from D14 to D25) were used. EC consistently reduced cerebral blood flow in both strains. Anesthesia-challenge and EC resulted in pronounced hyperglycemia in GK but not in Wistar rats. Lower beam-walking scores, increased locomotor activity, impairments in long-term habituation and learning of operant lever-pressing were more pronounced and observed at later time-points in GK rats. Fluoro-Jade, a marker of irreversible neuronal degeneration, revealed consistent degeneration in the ipsilateral cortex, hippocampus and thalamus at 2, 7 and 14 days post-compression. The amount of degeneration in these structures was considerably higher in GK rats. Thus, GK rats exhibited marked hyperglycemia during EC, as well as longer-lasting behavioral deficits and increased neurodegeneration during recovery. The GK rat is thus an attractive model for neuropathologic and cognitive studies after ischemic brain injury in hyperglycemic rats.

Effects of hypoxia reoxygenation in brain slices from rats with type 1-like diabetes mellitus

BACKGROUND

The aim of this study was to determine whether the brain tissue of type 1 diabetic animals is more susceptible to damage by hypoxia reoxygenation than healthy animals.

METHODS

This study used rats with diabetes of 1, 2 and 3 months (N = 15 rats/group). Brain slices were subjected to hypoxia and reoxygenation for 180 min in vitro. We measured oxidative stress (lipid peroxidation, glutathione concentration and enzyme activities related to glutathione), concentration of prostaglandin E(2) (PGE(2)) and nitric oxide (NO) pathway (nitrite + nitrate, activities of constitutive (cNOS) and inducible (iNOS) nitric oxide synthase). As a parameter of cell death we measured the efflux of lactate dehydrogenase (LDH).

RESULTS

After reoxygenation LDH activity increased in comparison to nondiabetic animals by 40, 40.6 and 68.9% in animals with diabetes of 1, 2 and 3 months duration, respectively. These changes were accompanied by greater increases in lipid peroxides (25.4, 93.7 and 92.8%). PGE(2) accumulated in significantly larger amounts in diabetic animals (62.5, 85.5 and 114%), and nitrite + nitrate accumulation was significantly greater in rats with diabetes of 2 (40.2%) and 3 months duration (24.0%). iNOS activity increased significantly in all the groups of diabetic animals, with the largest increases in rats with diabetes of 2 (18.6%) and 3 months duration (21.1%).

CONCLUSIONS

The biochemical pathways involved in oxidative stress and neuronal death are more sensitive to hypoxia reoxygenation in type 1-like diabetic, as compared to normal, rats.

Effects of aspirin plus alpha-tocopherol on brain slices damage after hypoxia-reoxygenation in rats with type 1-like diabetes mellitus

Diabetes mellitus is a risk factor for cerebrovascular ischemic disease. Aspirin (acetylsalicylic acid) is the most widely used drug for the secondary prevention of thrombotic phenomena. It has been also recently demonstrated that alpha-tocopherol influenced in vitro the antiplatelet effect of aspirin. The aim of the present study is to evaluate the effects aspirin plus alpha-tocopherol on cerebral oxidative stress, prostaglandin production and the nitric oxide pathway in a model of hypoxia-reoxygenation in rat brain slices. Our results show an imbalance in brain oxidative status (reflected mainly as the increase in lipid peroxides) as a result of diabetes itself rather than a failure of the glutathione-based antioxidant system. Moreover, our results also show a higher concentration of prostaglandins in the brain of diabetic animals and a higher nitric oxide concentration, mainly through a high iNOS activity. After 180 min of post-hypoxia reoxygenation, LDH activity was 40.6% higher in animals with diabetes, in comparison to non-diabetic animals. The increase of the LDH efflux observed in non-treated rats was reduced by 31.2% with aspirin, by 34.7% with alpha-tocopherol and by 69.8% with the association aspirin-alpha-tocopherol. The accumulation of prostaglandin E2 observed in diabetic non-treated rats was reduced statistically after the treatment with aspirin (34.2% inhibition), alpha-tocopherol (19.3% inhibition) or the association aspirin-alpha-tocopherol (54.4% inhibition). Nitric oxide production after 180 min reoxygenation was significantly reduced in aspirin (36.4%), alpha-tocopherol (22.7%) and aspirin-alpha-tocopherol (77.8%) treated rats with respect to diabetic non-treated animals; this was related mainly with a reduction in iNOS activity. The association between aspirin and alpha tocopherol could protects against brain ischemic-reperfusion damage with a better profile than aspirin alone.

Involvement of mitochondrial- and Fas-mediated dual mechanism in CoCl2-induced apoptosis of rat PC12 cells

Hypoxic/ischemic condition induces neuronal apoptotic events, which consequently lead to neuronal cell death. However, its specific mechanistic pathways remain obscure. Cobalt chloride (CoCl(2)) could mimic the hypoxic condition including the production of reactive oxygen species (ROS). In this report, we investigated the signal pathway of CoCl(2)-induced apoptosis in PC12 cells. The main mechanism for these apoptosis appeared to be mitochondria-mediated pathway accompanied with loss of the mitochondrial transmembrane potential (Delta Psi m) followed by cytochrome c release from the mitochondria into the cytosol, resulting in the activation of caspase-9 and caspase-3. Also, upregulation of pro-apoptotic protein Bax, and downregulation of anti-apoptotic protein Bcl-2 by presence of CoCl(2) appeared significantly and it might result in activating mitochondria-mediated apoptosis. We showed that expression of Fas and Fas ligand was upregulated and caspase-8 was significantly activated in CoCl(2)-induced apoptotic cells. In addition, ZB4, an antagonistic Fas-antibody, inhibited the activation of caspase-8 by CoCl(2), indicating that Fas receptor was involved in this pathway. These results demonstrate that CoCl(2) induce apoptosis in PC12 cells via different dual apoptosis pathway through death receptor as well as mitochondria.

Hypoxia-ischemia in the immature brain

The immature brain has long been considered to be resistant to the damaging effects of hypoxia and hypoxia-ischemia (H/I). However, it is now appreciated that there are specific periods of increased vulnerability, which relate to the developmental stage at the time of the insult. Although much of our knowledge of the pathophysiology of cerebral H/I is based on extensive experimental studies in adult animal models, it is important to appreciate the major differences in the immature brain that impact on its response to, and recovery from, H/I. Normal maturation of the mammalian brain is characterized by periods of limitations in glucose transport capacity and increased use of alternative cerebral metabolic fuels such as lactate and ketone bodies, all of which are important during H/I and influence the development of energy failure. Cell death following H/I is mediated by glutamate excitotoxicity and oxidative stress, as well as other events that lead to delayed apoptotic death. The immature brain differs from the adult in its sensitivity to all of these processes. Finally, the ultimate outcome of H/I in the immature brain is determined by the impact on the ensuing cerebral maturation. A hypoxic-ischemic insult of insufficient severity to result in rapid cell death and infarction can lead to prolonged evolution of tissue damage.

Diabetes enhances apoptosis induced by cerebral ischemia

The aim of this study is to explore the mechanism by which diabetes exaggerates cerebral stroke and its outcome. Since ischemia can be related to not only necrosis but apoptosis as well, we compared the development of apoptosis in STZ-diabetic rats and STZ-diabetic rats subjected to occlusion of the middle cerebral artery (MCA). 24-48 hr following MCA occlusion the animals were killed, the brain removed and prepared for evaluation by several indexes of apoptosis: nucleosomal DNA fragmentation, TUNEL staining, activation of caspase-3 and alteration in the expression of Bax and Bcl2. DNA fragmentation was not detected in the cortex of normal and diabetic animals, but was evident following MCA occlusion in diabetic rats. Bax expression was increased in the cortex of normal rats following MCA occlusion and this expression was further increased in the cortex of MCA occluded diabetic rats. Bcl2 expression was not changed in any of the groups. In the hippocampus, DNA fragmentation was not evident in control rats but was observed in diabetic rats. Ischemic injury did not enhance DNA laddering in diabetic animals. The expression of Bax was increased in diabetic rats but was not increased following MCA occlusion. Bcl2 expression was not changed by ischemia in any of the animal models. These data suggest that diabetes may enhance the development of stroke via increased cortical apoptotic activity but this was not additive in the hippocampus following ischemic injury.

Reductions in mRNA of the neuroprotective agent, neuroserpin, after cerebral ischemia/reperfusion in diabetic rats

The aim of this study is to investigate disturbances in fibrinolytic components in diabetic rats with middle cerebral artery occlusion (MCAO). Comparison of cerebral injury at 23 h after reperfusion indicated that infarction volumes were increased in diabetic rats as compared with normal rats. Cerebral ischemia/reperfusion in normal and diabetic rats was accompanied by increased expression of tissue plasminogen activator (t-PA), urokinase plasminogen activator (u-PA), plasminogen activator inhibitor 1 (PAI-1) and neuroserpin (NSP) mRNA after reperfusion. Most importantly, the expression of NSP mRNA, but not t-PA, u-PA and PAI-1 mRNA, was reduced to undetectable levels at 11 and 23 h after reperfusion in diabetic rats as compared with normal rats. Although activity of PA (t-PA and u-PA) and the ratio of PA/PAI were increased at 5 h after reperfusion in both ischemic brains of diabetic and normal rats, the levels in diabetic rats were lower than that in normal rats. We speculate that the exacerbation of ischemic injury in diabetic rats may be related to the reduction of fibrinolytic component and the neuroprotective role of NSP. Further study of the efficacy of NSP in the pathogenesis and treatment of cerebral ischemia may provide novel insights.

Metabolic changes of arachidonic acid after cerebral ischemia–reperfusion in diabetic rats

The purpose of this study is to discuss an important component-arachidonic acid (AA) cascade of inflammatory reaction in diabetic rats with cerebral ischemia. Using the model of middle cerebral artery occlusion (MCAO), we have compared the expression of cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX), and measured the levels of their products prostaglandin E2 (PGE(2)) and cysteine-containing leukotrienes (cys-LTs) after different reperfusion periods in diabetic and normal rats. Cerebral ischemia-reperfusion was accompanied by increased expression of COX-2 and release of PGE(2), peaking at 12 h after reperfusion. The expression of COX-2 was maintained at a high level until 24 h after reperfusion, while the levels of PGE(2) were declined rapidly to baseline. The expression of 5-LOX and levels of cys-LTs reached a peak at 6 and 12 h after reperfusion, respectively, and was returned to baseline at 24 h after reperfusion. Compared with normal rats, the expression of COX-2 and 5-LOX as well as release of PGE(2) and cys-LTs was elevated in the brains of diabetic rats, revealing a possible mechanism for hyperglycemia-mediated aggravation of cerebral ischemic injury. A reduction of arachidonic acid metabolites mediated by inhibitors of its metabolites could be helpful in preventing ischemic brain injury in diabetic rats.

Influence of specific stroke diagnosis on prognostication, recovery, and early management

Strokes are focal lesions in the brain and as such bring about deficits and portend a course of recovery depending on the nature of the lesion. Given the large number of possible combinations of locations, sizes, and types of lesions, a clear and reliable formula for predicting outcomes based on these characteristics has been statistically difficult, particularly early in the course of recovery. Severity of deficit and age of the patient accounts for sufficient variability that the influence of other factors becomes statistically harder to illustrate.

Apoptosis and brain ischaemia

There is increasing evidence that some neuronal death after brain ischaemia is mediated by the action of cysteine-requiring aspartate-directed proteases (caspases), the proteases responsible for apoptosis in mammals, although this form of neuronal death is not always accompanied by the morphological changes that are typical of apoptosis in other tissues. Caspase-mediated neuronal death is more extensive after transient than permanent focal brain ischaemia and may contribute to delayed loss of neurons from the penumbral region of infarcts. The activation of caspases after brain ischaemia is largely consequent on the translocation of Bax, Bak, and other BH3-only members of the Bcl-2 family to the mitochondrial outer membrane and the release of cytochrome c, procaspase-9, and apoptosis activating factor-1 (Apaf-1) from the mitochondrial intermembrane space. How exactly ischaemia induces this translocation is still poorly understood. NF-kappaB, the c-jun N-terminal kinase-c-Jun pathway, p53, E2F1, and other transcription factors are probably all involved in regulating the expression of BH3-only proteins after brain ischaemia, and mitochondrial translocation of Bad from sequestering cytosolic proteins is promoted by inactivation of the serine-threonine kinase, Akt. Other processes that are probably involved in the activation of caspases after brain ischaemia include the mitochondrial release of the second mitochondrial activator of caspases (Smac) or direct inhibitor-of-apoptosis-binding protein with low pI (DIABLO), the accumulation of products of lipid peroxidation, a marked reduction in protein synthesis, and the aberrant reentry of neurons into the cell cycle. Non-caspase-mediated neuronal apoptosis may also occur, but there is little evidence to date that this makes a significant contribution to brain damage after ischaemia. The intracellular processes that contribute to caspase-mediated neuronal death after ischaemia are all potential targets for therapy. However, anti-apoptotic interventions in stroke patients will require detailed evaluation using a range of outcome measures, as some such interventions seem simply to delay neuronal death and others to preserve neurons but not neuronal function.

Dissociative increase of oligodendrocyte progenitor cells between young and aged rats after transient cerebral ischemia

To investigate the effect of aging on the oligodendrocyte progenitor cells (OPCs) after cerebral ischemia, neuron-glia antigen 2 (NG2) chondroitin sulfate proteoglycan was examined at 1, 3 and 7 days after 90 min of transient middle cerebral artery occlusion in young and aged brains. The number of NG2 positive cells increased in the ischemic penumbra at 3 and 7 days after reperfusion, while those decreased in the ischemic core. At 7 days, the number of NG2 positive cells was significantly greater in the young than the aged brains, and the processes of NG2 positive cells enlarged and were highly branched in the young than the aged brains. These results suggest that the young brain showed a higher potential of proliferation and process branching of OPCs than the aged brains.