Expression of c-fos and c-jun family genes after focal cerebral ischemia

Role of c-Fos in DNA damage repair

c-Fos, a member of the immediate early gene, serves as a widely used marker of neuronal activation induced by various types of brain damage. In addition, c-Fos is believed to play a regulatory role in DNA damage repair. This paper reviews the literature on c-Fos' involvement in the regulation of DNA damage repair and indicates that genes of the Fos family can be induced by various forms of DNA damage. In addition, cells lacking c-Fos have difficulties in DNA repair. c-Fos is involved in tumorigenesis and progression as a proto-oncogene that maintains cancer cell survival, which may also be related to DNA repair. c-Fos may impact the repair of DNA damage by regulating the expression of downstream proteins, including ATR, ERCC1, XPF, and others. Nonetheless, the underlying mechanisms necessitate further exploration.

l-borneol promotes neurovascular unit protection in the subacute phase of transient middle cerebral artery occlusion rats: p38-MAPK pathway activation, anti-inflammatory, and anti-apoptotic effect

Our previous study showed l-borneol reduced cerebral infarction in the acute stage after cerebral ischemia, but there is little about the study of subacute phase. We herein investigated the cerebral protective effects of l-borneol on neurovascular units (NVU) in the subacute phase after transient middle cerebral artery occlusion (t-MCAO). The t-MCAO model was prepared by the line embolus method. Zea Longa, mNss, HE, and TTC staining were used to evaluate the effect of l-borneol. We evaluated the mechanisms of l-borneol on inflammation, p38 MAPK pathway, and apoptosis, etc. through various technologies. l-borneol 0.2, 0.1, 0.05 g·kg-1 could significantly reduce cerebral infarction rate, alleviate the pathological injury, and inhibit inflammation reaction. l-borneol could also significantly increase brain blood supply, Nissl bodies, and the expression of GFAP. Additionally, l-borneol activated the p38 MAPK signaling pathway, inhibited cell apoptosis, and maintained BBB integrity. l-borneol had a neuroprotective effect, which was related to activating the p38 MAPK signaling pathway, inhibiting inflammatory response and apoptosis, and improving cerebral blood supply to protect BBB and stabilize and remodel NVU. The study will provide a reference for the use of l-borneol in the treatment of ischemic stroke in the subacute phase.

Lentiviral‑mediated inducible silencing of TLR4 attenuates neuropathic pain in a rat model of chronic constriction injury

An increasing body of evidence has indicated that spinal microglial Toll-like receptor 4 (TLR4) may serve a significant role in the development and maintenance of neuropathic pain (NP). In the present study, experiments were conducted to evaluate the contribution of a tetracycline inducible lentiviral-mediated delivery system for the expression of TLR4 small interfering (si)RNA to NP in rats with chronic constriction injury (CCI). Behavioral tests, including paw withdrawal latency and paw withdrawal threshold, and biochemical analysis of the spinal cord, including western blotting, reverse transcription-quantitative polymerase chain reaction and ELISA, were conducted following CCI to the sciatic nerve. Intrathecal administration of LvOn-si-TLR4 with doxycycline (Dox) attenuated allodynia and hyperalgesia. Biochemical analysis revealed that the mRNA and proteins levels of TLR4 were unregulated following CCI to the sciatic nerve, which was then blocked by intrathecal administration of LvOn-siTLR4 with Dox. The LvOn-siTLR4 was also demonstrated to have no effect on TLR4 or the pain response without Dox, which indicated that the expression of siRNA was Dox-inducible in the lentivirus delivery system. In conclusion, TLR4 may serve a significant role in neuropathy and the results of the present study provide an inducible lentivirus-mediated siRNA against TLR4 that may serve as a potential novel strategy to be applied in gene therapy for NP in the future.

Modulation of N-Methyl-D-Aspartate Receptors (NMDAR), Bcl-2 and C-Fos Gene Expressions on Exposure to Individual and Mixtures of Low Concentration Metals in Zebrafish (Danio rerio)

Currently, there is limited information on the toxicity of low concentration of metal mixtures in the environment. Of particular interest is the effect of low levels of metal mixtures on neurodevelopment of aquatic organisms. This study reports the neurological gene expressions after exposing zebrafish embryos to low concentration toxic heavy metals, 120 h post fertilization (hpf). Embryos were exposed to low concentration individual and mixtures of lead (Pb), mercury (Hg), arsenic (As), and cadmium (Cd). Quantitative real-time PCR was used to assess gene expressions. The findings of this study confirmed that exposure to low concentration heavy metals upregulated N-methyl-D-aspartate (NMDA) receptor subunits NMDAR2A (NR2A), NMDAR2B (NR2B), and NMDAR2D (NR2D) and B cell lymphoma (Bcl-2) genes. NR2A genes were significantly upregulated by 90 and 74%, respectively, on exposure to Pb + As and Pb + Cd. NR2B genes were upregulated by 85.3, 68.6, 62.7, and 62.7% on exposure to As, Pb + Hg, Pb + As, and Pb + Cd, respectively. Exposure to As, Pb + Cd, and Pb + Hg + As significantly upregulated Bcl-2 genes by 2.01-, 1.84-, and 1.80-fold, respectively. NR1A and C-fos gene expressions were not significantly different from control. Upregulation of NMDAR subunits and Bcl-2 genes in this study was largely a counter measure against insults from exposure to low concentration heavy metals. Principal component analysis confirmed the influence of low concentration individual and mixtures of Pb, Hg, As, and Cd on gene expression of NMDAR subunits and Bcl-2. These data suggest that altered expression of NMDA receptor subunits and Bcl-2 genes may explain toxicity of low concentration individual and mixtures of Pb, Hg, As, and Cd.

Quantitative Determination of Flexible Pharmacological Mechanisms Based On Topological Variation in Mice Anti-Ischemic Modular Networks

Targeting modules or signalings may open a new path to understanding the complex pharmacological mechanisms of reversing disease processes. However, determining how to quantify the structural alteration of these signalings or modules in pharmacological networks poses a great challenge towards realizing rational drug use in clinical medicine. Here, we explore a novel approach for dynamic comparative and quantitative analysis of the topological structural variation of modules in molecular networks, proposing the concept of allosteric modules (AMs). Based on the ischemic brain of mice, we optimize module distribution in different compound-dependent modular networks by using the minimum entropy criterion and then calculate the variation in similarity values of AMs under various conditions using a novel method of SimiNEF. The diverse pharmacological dynamic stereo-scrolls of AMs with functional gradient alteration, which consist of five types of AMs, may robustly deconstruct modular networks under the same ischemic conditions. The concept of AMs can not only integrate the responsive mechanisms of different compounds based on topological cascading variation but also obtain valuable structural information about disease and pharmacological networks beyond pathway analysis. We thereby provide a new systemic quantitative strategy for rationally determining pharmacological mechanisms of altered modular networks based on topological variation.

Review : Gene Expression after Cerebral Ischemia

Global and focal ischemias induce a variety of gene families, including immediate early genes, cytokines, neurotransmitter receptors, and heat-shock proteins. The Janus-like effects of several of these gene prod ucts promote neuronal survival and degeneration. Therefore, determining the molecular pathways respon sible for the differential regulation of these genes is of paramount importance. The discovery of apoptosis as a mediator of delayed neuronal death has led to the identification of a number of other genes involved in postischemic brain damage. Future neuroprotective therapies for cerebral ischemia may be directed at preventing alterations in gene expression. NEUROSCIENTIST 5:238-253, 1999

Inducible Lentivirus-Mediated siRNA against TLR4 Reduces Nociception in a Rat Model of Bone Cancer Pain

Although bone cancer pain is still not fully understood by scientists and clinicians alike, studies suggest that toll like receptor 4 (TLR4) plays an important role in the initiation and/or maintenance of pathological pain state in bone cancer pain. A promising treatment for bone cancer pain is the downregulation of TLR4 by RNA interference; however, naked siRNA (small interference RNA) is not effective in long-term treatments. In order to concoct a viable prolonged treatment for bone cancer pain, an inducible lentivirus LvOn-siTLR4 (tetracycline inducible lentivirus carrying siRNA targeting TLR4) was prepared and the antinociception effects were observed in bone cancer pain rats induced by Walker 256 cells injection in left leg. Results showed that LvOn-siTLR4 intrathecal injection with doxycycline (Dox) oral administration effectively reduced the nociception induced by Walker 256 cells while inhibiting the mRNA and protein expression of TLR4. Proinflammatory cytokines as TNF-α and IL-1β in spinal cord were also decreased. These findings suggest that TLR4 could be a target for bone cancer pain treatment and tetracycline inducible lentivirus LvOn-siTLR4 represents a new potential option for long-term treatment of bone cancer pain.

Ketamine inhibits c-Jun protein expression in mouse hippocampus following cerebral ischemia/reperfusion injury

A model of cerebral ischemia and reperfusion was established in mice. Mice were treated with ketamine via intraperitoneal injection immediately following ischemia or ischemia/reperfusion. Ketamine did not remarkably change infarct volume in mice immediately following ischemia, but injection immediately following ischemia/reperfusion significantly decreased infarct volume. Ketamine injection immediately after ischemia or ischemia/reperfusion inhibited c-Jun protein expression in mouse hippocampus, but nuclear factor kappa B expression was unaltered. In addition, the Longa scale score for neural impairment was not reduced in mice following cerebral ischemia/reperfusion. These results indicate that ketamine can protect mice against cerebral ischemia and reperfusion injury by modulating c-Jun protein expression in mouse hippocampus.

Lentivirus mediated siRNA against GluN2B subunit of NMDA receptor reduces nociception in a rat model of neuropathic pain

Although neuropathic pain (NP) is still not fully understood by scientists and clinicians alike, studies suggest that N-methyl-D-aspartate (NMDA) receptors play an important role in the induction and maintenance of NP. A promising treatment for NP is through the downregulation of NMDA subunit GluN2B by RNA interference; however, naked siRNA (small interference RNA) is not effective in long-term treatments. In order to concoct a viable prolonged treatment for NP, Lv-siGluN2B (lentivirus carrying siRNA targeting GluN2B subunit) was prepared and the antinociception effects were observed in chronic constriction injury (CCI) rats in the present study. Results showed that Lv-siGluN2B was transduced into spinal cord cells after intrathecal injections and effectively reduced the nociception induced by sciatic nerve ligation while inhibiting the mRNA and protein expression of GluN2B. This antinociception effect lasted approximately 7 weeks. These findings suggest that GluN2B subunit could be a target for NP treatment and Lv-siGluN2B represents a new potential option for long-term treatment of NP.

AmotL2 disrupts apical-basal cell polarity and promotes tumour invasion

The establishment and maintenance of apical-basal cell polarity is essential for the functionality of glandular epithelia. Cell polarity is often lost in advanced tumours correlating with acquisition of invasive and malignant properties. Despite extensive knowledge regarding the formation and maintenance of polarity, the mechanisms that deregulate polarity in metastasizing cells remain to be fully characterized. Here we show that AmotL2 expression correlates with loss of tissue architecture in tumours from human breast and colon cancer patients. We further show that hypoxic stress results in activation of c-Fos-dependent expression of AmotL2 leading to loss of polarity. c-Fos/hypoxia-induced p60 AmotL2 interacts with the Crb3 and Par3 polarity complexes retaining them in large vesicles and preventing them from reaching the apical membrane. The resulting loss of polarity potentiates the response to invasive cues in vitro and in vivo in mice. These data provide a molecular mechanism how hypoxic stress deregulates cell polarity during tumour progression.

Timing of xenon-induced delayed postconditioning to protect against spinal cord ischaemia-reperfusion injury in rats

BACKGROUND

This study was designed to assess the neuroprotective effect of xenon-induced delayed postconditioning on spinal cord ischaemia-reperfusion injury (IRI) and to determine the time of administration for best neuroprotection in a rat model of spinal cord IRI.

METHODS

Fifty male rats were randomly divided equally into a sham group, control group, and three xenon postconditioning groups (n=10 per group). The control group underwent spinal cord IRI and immediately inhaled 50% nitrogen/50% oxygen for 3 h at the initiation of reperfusion. The three xenon postconditioning groups underwent the same surgical procedure and immediately inhaled 50% xenon/50% oxygen for 3 h at the initiation of reperfusion or 1 and 2 h after reperfusion. The sham operation group underwent the same surgical procedure without aortic occlusion, and inhaled 50% nitrogen/50% oxygen. Neurological function was assessed using the Basso, Beattie, and Bresnahan score at 4, 24, and 48 h of reperfusion. Histological examination was performed using Nissl staining and immunohistochemistry, and apoptosis was detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labelling staining.

RESULTS

Compared with the control group, the three xenon postconditioning groups showed improvements in neurological outcomes, and had more morphologically normal neurones at 48 h of reperfusion. Apoptotic cell death was reduced and the ratio of Bcl-2/Bax immunoreactivity increased in xenon-treated rats compared with controls.

CONCLUSIONS

Xenon postconditioning up to 2 h after reperfusion provided protection against spinal cord IRI in rats, but the greatest neuroprotection occurred with administration of xenon for 1 h at reperfusion.

Genetics and genomics of ischemic tolerance: focus on cardiac and cerebral ischemic preconditioning

A subthreshold ischemic insult applied to an organ such as the heart and/or brain may help to reduce damage caused by subsequent ischemic episodes. This phenomenon is known as ischemic tolerance mediated by ischemic preconditioning (IPC) and represents the most powerful endogenous mechanism against ischemic injury. Various molecular pathways have been implicated in IPC, and several compounds have been proposed as activators or mediators of IPC. Recently, it has been established that the protective phenotype in response to ischemia depends on a coordinated response at the genomic, molecular, cellular and tissue levels by introducing the concept of 'genomic reprogramming' following IPC. In this article, we sought to review the genetic expression profiles found in cardiac and cerebral IPC studies, describe the differences between young and aged organs in IPC-mediated protection, and discuss the potential therapeutic application of IPC and pharmacological preconditioning based on the genomic response.

Differential regulation of Nedd4 ubiquitin ligases and their adaptor protein Ndfip1 in a rat model of ischemic stroke

Ubiquitin-modification of proteins by E3 ubiquitin ligases is an important post-translational mechanism implicated in neuronal survival and injury following cerebral ischemia. However, of the 500 or so E3s thought to be present in mammalian cells, very few specific E3s have been identified and associated with brain ischemia. Here, we demonstrate endogenous induction of HECT-type E3 ligases of the Nedd4 family and their adaptor Nedd4-family interacting protein 1 (Ndfip1) following transient focal cerebral ischemia in rats. Ndfip1 is upregulated in surviving cortical neurons and its neuroprotective activity is correlated with Nedd4-2 upregulation, but not two other Nedd4 family members examined (Nedd4-1 and Itch). Immunoprecipitation assays confirmed biochemical binding of Ndfip1 with Nedd4-2 in the brain, with or without ischemic stroke, indicating their endogenous interaction. While Ndfip1 and Itch have been previously shown to interact outside of the nervous system, ischemic induction of Itch in the present study was associated with cellular survival independent of Ndfip1. Together, these findings demonstrate specific and differential regulation of Nedd4 family E3 ligases under ischemic conditions, and identify two E3 ligases and their adaptor that potentially regulate ubiquitination in ischemic stroke to provide neuroprotection.

Volumetric MRI and 1H MRS study of hippocampus in unilateral MCAO patients: relationship between hippocampal secondary damage and cognitive disorder following stroke

OBJECTIVE

To determine whether hippocampi alter in patients at the recovery stage of middle cerebral artery occlusion (MCAO) and whether the changes of hippocampi involve in the cognitive impairment in such patients.

MATERIALS AND METHODS

[corrected] Forty-four patients with unilateral infarction solely in MCAO territory and 44 age-, sex- and education background-matched healthy volunteers were enrolled in this study. All subjects underwent 3-dimensional fast spoiled gradient-echo (3D FSPGR) and sing-voxel proton magnetic resonance spectroscopy ((1)H MRS) protocols at a 1.5 T MR scanner. The ratios of n-acetylaspartate/creatine (NAA/Cr) and myo-inositol/creatine (mI/Cr) were obtained by using software integrated in the MR scanner. The hippocampal volumes were estimated by manually measurement.

RESULTS

The volume and NAA/Cr ratio were found significantly decreased and mI/Cr ratio significantly increased in the hippocampus ipsilateral to occluded middle cerebral artery (MCA) as compared with values in the contralateral hippocampus or healthy control. A reduced NAA/Cr ratio was also observed in contralateral hippocampus compared to controls. The shrinkage ratio of hippocampus ipsilateral to MCAO was found related to the Mini-Mental State Examination (MMSE) score.

CONCLUSION

Our study identified that the hippocampal secondary damage occurred in patients after MCAO, and it could be evaluated noninvasively by volumetric magnetic resonance imaging (MRI) and (1)H MRS. Moreover, the hippocampal secondary damage in MCAO patients indeed contributed to their cognitive impairment.

Mechanisms and prospects of ischemic tolerance induced by cerebral preconditioning

In the brain, brief episodes of ischemia induce tolerance against a subsequent severe episode of ischemia. This phenomenon of endogenous neuroprotection is known as preconditioning-induced ischemic tolerance. The purpose of this review is to summarize the current state of knowledge about mechanisms and potential applications of cerebral preconditioning and ischemic tolerance. Articles related to the terms ischemic preconditioning and ischemic tolerance were systematically searched via MEDLINE/PubMed, and articles published in English related to the nervous system were selected and analyzed. The past two decades have provided interesting insights into the molecular mechanisms of this neuroprotective phenomenon. Although both rapid and delayed types of tolerance have been documented in experimental settings, the delayed type has been found to be more prominent in the case of neuronal ischemic tolerance. Many intracellular signaling pathways have been implicated regarding ischemic preconditioning. Most of these are associated with membrane receptors, kinase cascades, and transcription factors. Moreover, ischemic tolerance can be induced by exposing animals or cells to diverse types of endogenous and exogenous stimuli that are not necessarily hypoxic or ischemic in nature. These cross-tolerances raise the hope that, in the future, it will be possible to pharmacologically activate or mimic ischemic tolerance in the human brain. Another promising approach is remote preconditioning in which preconditioning of one organ or system leads to the protection of a different (remote) organ that is difficult to target, such as the brain. The preconditioning strategy and related interventions can confer neuroprotection in experimental ischemia, and, thus, have promise for practical applications in cases of vascular neurosurgery and endo-vascular therapy.

Intrathecal siRNA against Toll-like receptor 4 reduces nociception in a rat model of neuropathic pain

BACKGROUND

Neuropathic pain is characterized by hyperalgesia, allodynia and spontaneous pain. It often occurs as a result of injury to peripheral nerves, dorsal root ganglions (DRG), spinal cord, or brain. Recent studies have suggested that Toll-like receptor 4 (TLR4) might play a role in neuropathic pain.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we investigated the role of TLR4 in a rat chronic constriction injury (CCI) model and explored the feasibility of treating neuropathic pain by inhibiting TLR4. Our results demonstrated that intrathecal siRNA-mediated suppression of TLR4 attenuated CCI-induced mechanical allodynia and thermal hyperalgesia through inhibiting the activation of NF-kappaB p65 and production of proinflammatory cytokines (e.g., TNF-alpha and IL-1 beta).

CONCLUSIONS/SIGNIFICANCE

These findings suggest that suppression of TLR4 mediated by intrathecally administered siRNA may be a new strategy for the treatment of neuropathic pain.

Protective effects of natrii sulfas on cerebral focal ischemia induced by MCAO in rats

This study examined the effect of Natrii sulfas, a treatment for stroke patients suffering constipation in Oriental medicine, on the physiological indices and brain edema of rats. Brain edema was induced by a middle cerebral artery occlusion (MCAO), Natrii sulfas was administered after the MCAO. At 3, 6, 15, 24, and 48 hours after reperfusion, the physiological indices such as the fecal weight, urine volume and water content in the stools were assessed. The edema index was measured 48 hours after reperfusion. At 48 hours, the expressions of iNOS, MMP9, VEGF, GFAP, Bax, Bcl-2, c-Fos, and HSP72 positive astrocytes were observed on the brain tissues by immunohistochemistry. Natrii sulfas significantly improved the decrease in fecal weight, urine volume and water content in the stool caused by the ischemic insult (p < 0.05) and attenuated the brain edema caused by the ischemia insult (p < 0.05). Natrii sulfas significantly down-regulated iNOS and MMP9 expressions and attenuated the astrocyte swelling due to brain edema in the penumbra of the cerebral cortex of MCAO rats. Natrii sulfas reduced the excess Bax and HSP72 expressions in ischemic brain, which was statistically significant in the penumbra of the cerebral cortex but not in the caudate putamen. These results suggest Natrii sulfas has a protective effect on ischemia-induced brain edema and improves the physiological symptoms.

Dexamethasone inhibits camptothecin-induced apoptosis in C6-glioma via activation of Stat5/Bcl-xL pathway

Dexamethasone (DX) induces apoptosis resistance in most solid malignant tumors during co-treatment with chemotherapy agents, such as camptothecin (CAM). In this study, we investigated the mechanism by which DX reduces chemotherapy efficiency in C6-glioma. DX reduced CAM-increased DNA fragmentation and caspase-3 activation. The DX's protection was negated by RU486, an antagonist of glucocorticoid receptor (GR). DX itself increased anti-apoptotic gene, Bcl-xL expression, and its transcription factor, signaling transducer and activator of transcription 5 (Stat5), DNA binding activity and phospho-Stat5 expression. DX blocked the CAM-decreased Bcl-xL and phospho-Stat5 expression, and Stat5 binding activity. RU486 negated DX's actions. To determine whether Stat5 regulates Bcl-xL expression in CAM-induced cell death, C6-glioma was infected with an adenovirus containing a constitutively activated Stat5-GFP (Ad-Stat5ca). Overexpression of Stat5ca increased Bcl-xL and decreased CAM-induced cell death compared to control adenovirus infected cells; whereas Stat5 siRNA decreased DX-induced Bcl-xL and increased cell death. Phospho-Stat5 expression was observed in the nuclear extract by co-immunoprecipitation with an anti-GR antibody, indicating that Stat5 and GR were interactive and formed a complex in the nuclei. These results suggest that DX's prevention from CAM-induced apoptosis and RU486's antagonism of DX's protection may be through Stat5/Bcl-xL signal pathway regulated by a GR.

Cellular and molecular neurobiology of brain preconditioning

The tolerant brain which is a consequence of adaptation to repeated nonlethal insults is accompanied by the upregulation of protective mechanisms and the downregulation of prodegenerative pathways. During the past 20 years, evidence has accumulated to suggest that protective mechanisms include increased production of chaperones, trophic factors, and other antiapoptotic proteins. In contrast, preconditioning can cause substantial dampening of the organism's metabolic state and decreased expression of proapoptotic proteins. Recent microarray analyses have also helped to document a role of several molecular pathways in the induction of the brain refractory state. The present review highlights some of these findings and suggests that a better understanding of these mechanisms will inform treatment of a number of neuropsychiatric disorders.

Transcription MRI: a new view of the living brain

Altered gene activities are underlying causes of many neurological disorders. The ability to detect, image, and report endogenous gene transcription using magnetic resonance (MR) holds great potential for providing significant clinical benefits. In this review, we present the development of conjugates consisting of gene-targeting short nucleic acids (oligodeoxynucleotides, or sODN) and superparamagnetic iron oxide nanoparticles (SPION, an MR susceptibility T(2) agent) for reporting gene activity using transcription MRI (tMRI). We will discuss 1) the target specificity of sODN, 2) selection of contrast agents for tMRI, 3) the distribution and uptake, 4) sequence specificity, 5) histology of SPION and sODN, 6) data acquisition and quantitative analysis for tMRI, and 7) application of gene transcript-targeting nanoparticles in biology and medicine. We will also discuss methods of validating the correlation between results from conventional assays (in situ hybridization, PCR, histology Prussian blue stain and immunohistochemistry) in postmortem samples and retention of SPION-sODN using tMRI. The application of our novel contrast probe to report and target gene transcripts in the mesolimbic pathways of living mouse brains after amphetamine exposure will be discussed. Because of the targeting ability in the nucleic acid sequence, the concept of tMRI probes with complementary nucleic acid (antisense DNA or short interfering RNA) allows not only tracking, targeting, binding to intracellular mRNA, and manipulating gene action but also tracing cells with specific gene action in living brains. Transcription MRI will lend itself to myriad applications in living organs.

MR contrast probes that trace gene transcripts for cerebral ischemia in live animals

The aim of this research was to validate transcription magnetic resonance (MR) imaging (MRI) for gene transcript targeting in acute neurological disorders in live subjects. We delivered three MR probe variants with superparamagnetic iron oxide nanoparticles (SPION, a T2 susceptibility agent) linked to a phosphorothioate-modified oligodeoxynucleotide (sODN) complementary to c-fos mRNA (SPION-cfos) or beta-actin mRNA (SPION-beta-actin) and to sODN with random sequence (SPION-Ran). Each probe (1 microg Fe in 2 microl) was delivered via intracerebroventricular infusion to the left cerebral ventricle of male C57Black6 mice. We demonstrated SPION retention, measured as decreased T2* signal or increased R2* value (R2* = 1/T2*). Animals that received the SPION-beta-actin probe exhibited the highest R2* values, followed (in descending order) by SPION-cfos and SPION-Ran. SPION-cfos retention was localized in brain regions where SPION-cfos was present and where hybrids of SPION-cfos and its target c-fos mRNA were detected by in situ reverse transcription PCR. In animals that experienced cerebral ischemia, SPION-cfos retention was significantly increased in locations where c-fos mRNA increased in response to the ischemic insult; these elevations were not observed for SPION-beta-actin and SPION-Ran. This study should enable MR detection of mRNA alteration in disease models of the central nervous system.

Molecular targets in cerebral ischemia for developing novel therapeutics

Cerebral ischemia (stroke) triggers a complex series of biochemical and molecular mechanisms that impairs the neurologic functions through breakdown of cellular integrity mediated by excitotoxic glutamatergic signalling, ionic imbalance, free-radical reactions, etc. These intricate processes lead to activation of signalling mechanisms involving calcium/calmodulin-dependent kinases (CaMKs) and mitogen-activated protein kinases (MAPKs) such as extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal kinase (JNK). The distribution of these transducers bring them in contact with appropriate molecular targets leading to altered gene expression, e.g. ERK and JNK mediated early gene induction, responsible for activation of cell survival/damaging mechanisms. Moreover, inflammatory reactions initiated at the neurovascular interface and alterations in the dynamic communication between the endothelial cells, astrocytes and neurons are thought to substantially contribute to the pathogenesis of the disease. The damaging mechanisms may proceed through rapid nonspecific cell lysis (necrosis) or by active form of cell demise (apoptosis or necroptosis), depending upon the severity and duration of the ischemic insult. A systematic understanding of these molecular mechanisms with prospect of modulating the chain of events leading to cellular survival/damage may help to generate the potential strategies for neuroprotection. This review briefly covers the current status on the molecular mechanisms of stroke pathophysiology with an endeavour to identify potential molecular targets such as targeting postsynaptic density-95 (PSD-95)/N-methyl-d-aspartate (NMDA) receptor interaction, certain key proteins involved in oxidative stress, CaMKs and MAPKs (ERK, p38 and JNK) signalling, inflammation (cytokines, adhesion molecules, etc.) and cell death pathways (caspases, Bcl-2 family proteins, poly (ADP-ribose) polymerase-1 (PARP-1), apoptosis-inducing factor (AIF), inhibitors of apoptosis proteins (IAPs), heat shock protein 70 (HSP70), receptor interacting protein (RIP), etc., besides targeting directly the genes itself. However, selecting promising targets from various signalling cascades, for drug discovery and development is very challenging, nevertheless such novel approaches may lead to the emergence of new avenues for therapeutic intervention in cerebral ischemia.

Endovascular middle cerebral artery occlusion in rats as a model for studying vascular dementia

Vascular dementia (VaD), incorporating cognitive dysfunction with vascular disease, ranks as the second leading cause of dementia in the United States, yet no effective treatment is currently available. The challenge of defining the pathological substrates of VaD is complicated by the heterogeneous nature of cerebrovascular disease and coexistence of other pathologies, including Alzheimer's disease (AD) types of lesion. The use of rodent models of ischemic stroke may help to elucidate the type of lesions that are responsible for cognitive impairment in humans. Endovascular middle cerebral artery (MCA) occlusion in rats is considered to be a convenient and reliable model of human cerebral ischemia. Both sensorimotor and cognitive dysfunction can be induced in the rat endovascular MCA occlusion model, yet sensorimotor deficits induced by endovascular MCA occlusion may improve with time, whereas data presented in this review suggest that in rats this model can result in a progressive course of cognitive impairment that is consistent with the clinical progression of VaD. Thus far, experimental studies using this model have demonstrated a direct interaction of cerebral ischemic damage and AD-type neuropathologies in the primary ischemic area. Further, coincident to the progressive decline of cognitive function, a delayed neurodegeneration in a remote area, distal to the primary ischemic area, the hippocampus, has been demonstrated in a rat endovascular MCA occlusion model. We argue that this model could be employed to study VaD and provide insight into some of the pathophysiological mechanisms of VaD.

Expression of tumor necrosis factor-α and c-fos mRNA in immature rats' model of gut ischemia/reperfusion injury

AIM: To analyze the expression patterns of tumor necrosis factor-a (TNF-a) and c-fos mRNA in immature rats after gut ischemia/reperfusion (I/R) injury.

METHODS: The left laparotomy was performed and the superior mesenteric artery (SMA) was occluded by artery clamp to establish the model of gut I/R injury. The expression of TNF-a and c-fos mRNA were detected by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS: In comparison with sham operation group, an increase in TNF-a mRNA was detected after 30-min ischemia (1.55 ± 0.33 vs 1.07 ± 0.08, P < 0.05) and the maximal increase was detected after 30-min reperfusion (3.05 ± 0.11). TNF-a mRNA expression after 60-min reperfusion (2.02 ± 0.10) remained above the control level. The expression of c-fos mRNA in the intestinal tissues was rapidly induced by ischemia, and it increased obviously 30 min after ischemia as compared with that in sham operation group (0.95 ± 0.13 vs 0.12 ± 0.02, P < 0.05). The expression of c-fos mRNA also reached the peak level 30 min after reperfusion (1.53 ± 0.11), and it declined markedly 60 min after reperfusion. After 90-min reperfusion, c-fos mRNA expression returned to the normal level.

CONCLUSION: Gut I/R induces the mRNA expression of both TNF-a and c-fos, suggesting that there is possibly a correlation between the expression of c-fos and TNF-a.

Evolving Paradigms for Neuroprotection: Molecular Identification of Ischemic Penumbra

Ischemic penumbra defines the existence of tissue at risk of infarction and which is, hence, potentially salvageable and the target for current stroke reperfusion and neuroprotective therapies. Penumbral tissue evolves toward irreversibly damaged tissue at different rates in individual stroke patients yielding different therapeutic windows depending on the individual duration of risk of infarction of this tissue. An accurate identification of the penumbra is then necessary in order to individualize the window of opportunity for therapeutic interventions. Imaging techniques, although helpful, may not give the most accurate information as to the existence of penumbra given that the threshold for identification of penumbra varies depending on the technique used. A better identification of the true penumbral tissue might be based on the cascade of molecular events that are responsible for the evolution of the penumbra toward infarcted tissue. Multiple penumbras can be defined in molecular terms taking into account which vessel is occluded, the time of evolution of the ischemia, the degree of the ischemia, and the sensitivity to ischemia of the different cells. Future studies are necessary to clarify whether the enhancement of cytoprotective mechanisms, and/or the block of cytotoxic mechanisms confirming the existence of penumbra at different times of ischemic evolution, are effective neuroprotective strategies.

Increased expression of c-fos and c-jun in the rat small intestinal epithelium after ischemia-reperfusion injury: a possible correlation with the proliferation or apoptosis of intestinal epithelial cells

BACKGROUND AND PURPOSE

An increased expression of immediate early genes, such as the c-fos and c-jun, is observed in some organs after ischemia-reperfusion (I/R) injury. These factors have been revealed to potentially induce apoptosis and proliferation of the postischemic cells. The purpose of this study is to analyze the relationship between the expression patterns of such immediate early genes and the cellular responses in the intestinal epithelial cells (IECs) after I/R stress.

METHODS

The rat small intestine was reperfused after 30 minutes ischemia. Semiquantitative reverse transcription-polymerase chain reaction was used to quantify c-fos and c-jun messenger RNAs. The proliferation and apoptosis of IECs were detected by immunohistochemistry and the in situ terminal deoxynucleotidyl transferase-mediated dUTP biotin nick-end labeling method, respectively.

RESULTS

The messenger RNA levels of the c-fos and c-jun showed characteristic patterns in the IECs after the I/R stress. The proliferation of the cells was initially observed after the I/R stress, followed by apoptosis of the cells.

CONCLUSIONS

The sequential expression patterns of these factors are possibly related to the proliferation and apoptosis of the IECs.

Free radical-mediated neurotoxicity may be caused by inhibition of mitochondrial dehydrogenases in vitro and in vivo

We previously demonstrated that copper facilitated the formation of reactive oxygen species, and inhibited pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase in vitro and in animal models of Wilson's disease in vivo. However, direct Cu(2+) toxicity has only been demonstrated for Wilson's disease. We now hypothesize that inhibition of these mitochondrial dehydrogenases might also contribute to many other injuries and disorders that are reactive oxygen species-mediated. We have modeled reactive oxygen species-mediated injuries using inducers of reactive oxygen species such as hydrogen peroxide, ethacrynic acid or menadione, or another redox active metal (Cd(2+)). Here we demonstrated that these toxic exposures were accompanied by an early marked reduction in both pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase activities, followed by a decrease in neuronal mitochondrial transmembrane potential and ATP, prior to murine cortical neuronal death. Thiamine (6 mM), and dihydrolipoic acid (50 microM), required cofactors for pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase (thiamine as thiamine pyrophosphate), attenuated the reactive oxygen species-induced reductions in these enzyme activities, as well as subsequent loss of mitochondrial transmembrane potential and ATP, and neuronal death. We next tested the effect of thiamine supplementation on an in vivo model of reactive oxygen species-mediated injury, transient middle cerebral artery occlusion, and reperfusion in rats. Oral or i.p. thiamine administration reduced the middle cerebral artery occlusion-induced infarct. These data suggest that reactive oxygen species-induced neuronal death may be caused in part by reactive oxygen species-mediated inhibition of pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase in vitro and in vivo, and that thiamine or dihydrolipoic acid may constitute potential therapeutic agents not just against Cu(2+) neurotoxicity, but may reduce neuronal degeneration in the broader range of diseases mediated by free radical stress.

Amyloid beta peptide increases DP5 expression via activation of neutral sphingomyelinase and JNK in oligodendrocytes

There is growing recognition that white matter pathology is a common feature in Alzheimer's disease. We have previously reported that the amyloid beta peptide (Abeta) induces apoptosis in oligodendrocytes (OLG), via activation of neutral sphingomyelinase (nSMase) and resultant generation of ceramide. In the current study, we report that both Abeta and ceramide increased expression of the proapoptotic protein DP5/Hrk (DP5), and release of cytochrome C from mitochondria to cytoplasm in OLGs. We provide evidence that the Jun N-terminal kinase (JNK) signaling pathway mediates Abeta- and ceramide-induced apoptosis: Both Abeta and ceramide activated JNK phosphorylation, and subsequent AP-1 DNA binding activity; JNK siRNA decreased AP-1 DNA binding, DP5 expression and reduced cell death. Furthermore, inhibition of nSMase attenuated Abeta-induced JNK phosphorylation, AP-1 DNA binding activity, DP5 expression, and cytochrome C release. Collectively, these results suggest that Abeta-induced apoptosis involves the sequential activation of nSMase with ceramide generation, JNK activation, AP-1 DNA binding, and DP5 expression.

15d-prostaglandin J2 protects brain from ischemia-reperfusion injury

OBJECTIVE

Brain expresses abundant lipocalin-type prostaglandin (PG) D2 (PGD2) synthase but the role of PGD2 and its metabolite, 15-deoxy-Delta(12,14) PGJ2 (15d-PGJ2) in brain protection is unclear. The aim of this study is to assess the effect of 15d-PGJ2 on neuroprotection.

METHODS AND RESULTS

Adenoviral transfer of cyclooxygenase-1 (Adv-COX-1) was used to amplify the production of 15d-PGJ2 in ischemic cortex in a rat focal infarction model. Cortical 15d-PGJ2 in Adv-COX-1-treated rats was increased by 3-fold over control, which was correlated with reduced infarct volume and activated caspase 3, and increased peroxisome proliferator activated receptor-gamma (PPARgamma) and heme oxygenase-1 (HO-1). Intraventricular infusion of 15d-PGJ2 resulted in reduction of infarct volume, which was abrogated by a PPARgamma inhibitor. Rosiglitazone infusion had a similar effect. 15d-PGJ2 and rosiglitazone at low concentrations suppressed H2O2-induced rat or human neuronal apoptosis and necrosis and induced PPARgamma and HO-1 expression. The anti-apoptotic effect was abrogated by PPARgamma inhibition.

CONCLUSIONS

15d-PGJ2 suppressed ischemic brain infarction and neuronal apoptosis and necrosis in a PPARgamma dependent manner. 15d-PGJ2 may play a role in controlling acute brain damage induced by ischemia-reperfusion.

Cerebral Blood Flow Thresholds for mRNA Synthesis After Focal Ischemia and the Effect of MK-801

BACKGROUND AND PURPOSE

MK-801 is a noncompetitive antagonist of N-methyl-d-aspartate subtype glutamate receptors with protective efficacy in experimental stroke. This study examined the impact of MK-801 on cerebral blood flow (CBF) and its relationship to gene expression changes during focal ischemia.

METHODS

Spontaneously hypertensive rats were subjected to surgical occlusion of the middle cerebral artery and ipsilateral common carotid artery after 30 minutes pretreatment with 5 mg/kg MK-801 or saline vehicle. After 2.5 hours of ischemia, regional CBF was evaluated by [14C]iodoantipyrine autoradiography and compared with distributions of gene expression changes evaluated by in situ hybridization detection of mRNAs encoding several immediate-early genes and the stress protein, hsp72.

RESULTS

MK-801 increased CBF in contralateral cortex from 93+/-15 to 187+/-37 mL/100 g per minute and produced a significant 25% reduction in the volume of ischemic cortex ipsilateral to occlusion. The extent of cortex failing to express inducible mRNAs correspondingly decreased, but the CBF threshold for mRNA synthesis remained unchanged (25 to 30 mL/100 g per minute). Widespread immediate-early gene expression in the neocortex became restricted to periinfarct regions after MK-801 treatment, and hybridization patterns in the striatum and hippocampus reflected the altered topography of cortical activation after drug treatment.

CONCLUSIONS

MK-801 alters ischemia-induced gene expression by 2 distinct mechanisms. Generalized increases in CBF reduce the volume of cortex falling below ischemic injury thresholds, protecting tissue and facilitating transcription of inducible genes proximal to the ischemic focus. In addition, MK-801 attenuates the signals that induce expression of immediate-early genes in cortical and subcortical regions remote from the middle cerebral artery territory.

Regional expression of constitutive and inducible transcription factors following transient focal ischemia in the neonatal rat: influence of hypothermia

Ischemia is a potent modulator of gene expression. Differential expression of transcription factors after focal ischemia may reflect the potential for neuronal recovery in peri-ischemic regions. Previously, we demonstrated that hypothermia reduces the volume of damage in a model of neonatal focal ischemia. In the present study, immunocytochemistry was used to assess the temporal and spatial profiles of the transcription factors Fos and pCREB under normal and hypothermic conditions in this neonatal model of focal ischemia. At 7 days of age, rat pups underwent a permanent middle cerebral artery occlusion (MCAo) coupled with a temporary 1-h occlusion of the common carotid artery (CCAo). They were maintained at 37 degrees C throughout ischemia and reperfusion (Normothermic), or given 1 h of hypothermic conditions (28 degrees C) either during the occlusion (Intraischemic Hypothermia) or during the second hour of reperfusion (postischemic hypothermia). In normothermic pups, Fos immunoreactivity peaked at early time points (4-8 h post-ischemia) in a narrow band in peri-ischemic regions. By later stages of reperfusion (12-24 h), there was a more widespread induction in peri-ischemic regions including the ipsilateral cortex. In contrast with Fos, the constitutive transcription factor pCREB was reduced in core regions at all time points examined. Both the c-fos induction in peri-ischemic regions and the reduction of pCREB in the core were attenuated by intraischemic hypothermia. Postischemic hypothermia altered the distribution of Fos immunoreactivity without significantly changing the number of Fos- and pCREB-immunoreactive cells compared to normothermic rats. Both intra- and postischemic hypothermia reduced the number of caspase-immunoreactive cells. Thus, focal ischemia in the P7 rat produces different distributions of Fos and pCREB than what has been observed in adult rats subjected to focal ischemia, and expression of these transcription factors can be altered by hypothermia.

Ischemic tolerance in the brain

Endogenous tolerance to cerebral ischemia is nature's strategy for neuroprotection. Exploring the physiologic and molecular mechanism of this phenomenon may give us new means of protection against ischemia and other degenerative disorders. This article reviews the currently available experimental methods to induce ischemic tolerance in the brain and gives a brief summary of the potential mode of action.

Inflammation in areas of remote changes following focal brain lesion

Focal brain lesions can lead to metabolic and structural changes in areas distant from but connected to the lesion site. After focal ischemic or excitotoxic lesions of the cortex and/or striatum, secondary changes have been observed in the thalamus, substantia nigra pars reticulata, hippocampus and spinal cord. In all these regions, inflammatory changes characterized by activation of microglia and astrocytes appear. In the thalamus, substantia nigra pars reticulata and hippocampus, an expression of proinflammatory cytokine like tumor necrosis factor-alpha and interleukin-1beta is induced. However, time course of expression and cellular localisation differ between these regions. Neuronal damage has consistently been observed in the thalamus, substantia nigra and spinal cord. It can be present in the hippocampus depending on the procedure of induction of focal cerebral ischemia. This secondary neuronal damage has been linked to antero- and retrograde degeneration. Anterograde degeneration is associated with somewhat later expression of cytokines, which is localised in neurons. In case of retrograde degeneration, the expression of cytokines is earlier and is localised in astrocytes. Pharmacological intervention aiming at reducing expression of tumor necrosis factor-alpha leads to reduction of secondary neuronal damage. These first results suggest that the inflammatory changes in remote areas might be involved in the pathogenesis of secondary neuronal damage.

Neuroprotection against focal ischemic brain injury by inhibition of c-Jun N-terminal kinase and attenuation of the mitochondrial apoptosis-signaling pathway

c-Jun N-terminal kinase (JNK) is an important stress-responsive kinase that is activated by various forms of brain insults. In this study, we have examined the role of JNK activation in neuronal cell death in a murine model of focal ischemia and reperfusion; furthermore, we investigated the mechanism of JNK in apoptosis signaling, focusing on the mitochondrial-signaling pathway. We show here that JNK activity was induced in the brain 0.5 to 24 h after ischemia. Systemic administration of SP600125, a small molecule JNK-specific inhibitor, diminished JNK activity after ischemia and dose-dependently reduced infarct volume. c-Jun N-terminal kinase inhibition also attenuated ischemia-induced expression of Bim, Hrk/DP5, and Fas, but not the expression of Bcl-2 or FasL. In strong support of a role for JNK in promoting the mitochondrial apoptosis-signaling pathway, JNK inhibition prevented ischemia-induced mitochondrial translocation of Bax and Bim, release of cytochrome c and Smac, and activation of caspase-9 and caspase-3. The potential mechanism by which JNK promoted Bax translocation after ischemia was further studied using coimmunoprecipitation, and the results revealed that JNK activation caused serine phosphorylation of 14-3-3, a cytoplasmic sequestration protein of Bax, leading to Bax disassociation from 14-3-3 and subsequent translocation to mitochondria. These results confirm the role of JNK as a critical cell death mediator in ischemic brain injury, and suggest that one of the mechanisms by which JNK triggers the mitochondrial apoptosis-signaling pathway is via promoting Bax and Bim translocation.

Oxygen free radical-dependent activation of extracellular signal-regulated kinase mediates apoptosis-like cell death after traumatic brain injury

Mitogen-activated protein kinase (MAPK) cascades are membrane-to-nucleus signaling modules that recently have been implicated as mediators of cellular injury. In this study, we investigated the involvement of the MAP kinase p44/p42 (extracellular signal-regulated kinase [ERK1/2]) in traumatic brain injury (TBI) in rats. There was a strong increase in activated, phosphorylated ERK 1/2 (p-ERK 1/2) protein at 10 min up to 24 h after the injury. Expression of p-ERK occurred in cells identified as neurons, astrocytes, and microglia. Most of the cells expressing p-ERK were TUNEL positive at later time points. Treatment with the MEK inhibitor U0126 or the free radical scavenger S-PBN, both with neuroprotective properties in TBI, attenuated the early activation of ERK and resulted in less activation of caspase-3 and subsequent DNA fragmentation. Post-treatment with U0126 resulted in a significant decrease (-60%) in cortical cavity size and cortical atrophy at 2 weeks after trauma. Overall, the results suggest that ERK activation is initiated by increased oxygen radical activity and that overactivation of ERK sets off secondary cell death mechanisms in TBI. Clinical studies are warranted to evaluate the concept of MEK inhibition in head-injured patients.

Specific Inhibition of IkappaB kinase reduces hyperalgesia in inflammatory and neuropathic pain models in rats

Phosphorylation of IkappaB through IkappaB kinase (IKK) is the first step in nuclear factor kappaB (NF-kappaB) activation and upregulation of NF-kappaB-responsive genes. Hence, inhibition of IKK activity may be expected to prevent injury-, infection-, or stress-induced upregulation of various proinflammatory genes and may thereby reduce hyperalgesia and inflammation. In the present study, we tested this hypothesis using a specific and potent IKK inhibitor (S1627). In an IKK assay, S1627 inhibited IKK activity with an IC50 value of 10.0 +/- 1.2 nm. In cell culture experiments, S1627 inhibited interleukin (IL)-1beta-stimulated nuclear translocation and DNA-binding of NF-kappaB. Plasma concentration time courses after intraperitoneal injection revealed a short half-life of 2.8 hr in rats. Repeated intraperitoneal injections were, therefore, chosen as the dosing regimen. S1627 reversed thermal and mechanical hyperalgesia at 3x 30 mg/kg in the zymosan-induced paw inflammation model and reduced the inflammatory paw edema at 3x 40 mg/kg. S1627 also significantly reduced tactile and cold allodynia in the chronic constriction injury model of neuropathic pain at 30 mg/kg once daily. The drug had no effect on acute inflammatory nociception in the formalin test and did not affect responses to heat and tactile stimuli in naive animals. As hypothesized, S1627 prevented the zymosan-induced nuclear translocation of NF-kappaB in the spinal cord and the upregulation of NF-kappaB-responsive genes including cyclooxygenase-2, tumor necrosis factor-alpha, and IL-1beta. Our data indicate that IKK may prove an interesting novel drug target in the treatment of pathological pain and inflammation.

The release of tumor necrosis factor-alpha is associated with ischemic tolerance in human stroke

Tumor necrosis factor (TNF)-alpha overexpression has been related to experimental ischemic tolerance when transient ischemia precedes cerebral infarction. We investigated TNF-alpha and interleukin (IL)-6 plasma concentrations in 283 patients with an acute stroke within 24 hours after symptom onset. An ipsilateral transient ischemic attack (TIA) within 72 hours before stroke was recorded in 38 patients. The infarct volume measured on computed tomography on days 4 to 7 and the frequency of poor outcome (Barthel Index score < 85) at 3 months were significantly lower in patients with prior TIA. Plasma concentrations of TNF-alpha were higher (42.5 +/- 9.9 vs 13.1 +/- 6.4pg/ml, p < 0.0001) and IL-6 levels were lower (10.1 +/- 6.2 vs 28.3 +/- 17.3pg/ml, p < 0.0001) in patients with prior TIA. A new variable termed TNF-alpha/IL-6 index was considered positive when TNF-alpha was greater than 30pg/ml and IL-6 was less than 30pg/ml. Positive TNF-alpha/IL-6 index was found in 92% of patients with prior TIA and in 1% of those without. TNF-alpha/IL-6 index (p = 0.0003) and TIA (p = 0.0001) were associated with good outcome in logistic regression analysis after adjusting for potential confounding factors. Ischemic tolerance in acute stroke is associated with increased plasma levels of TNF-alpha in the presence of reduced concentrations of IL-6.

Evaluation of MCAO stroke models in normotensive rats: standardized neocortical infarction by the 3VO technique

The temporary three-vessel occlusion (3VO) technique with a surgical approach for middle cerebral artery (MCA) produces consistent cerebral infarction in the neocortex in normotensive rats. The intraluminal thread-occlusion technique with an endovascular approach targeting the MCA occlusion (MCAO) is more widely used since it does not require complicated intracranial procedures. The aim of this study was to review the methods/models for MCAO stroke in normotensive rats and to evaluate a 3VO stroke model that provides consistent degrees and variance of cortical stroke injury for additional discussion. First, we analyzed a model with modified temporary 3VO technique requiring less complicated procedures than the temporary 3VO model, i.e., temporary occlusion of the bilateral common carotid arteries (CCAs) superimposed on a permanent occlusion of the MCA, in Sprague-Dawley rats or C57BL/6J mice. In the microvascular tissue (cerebral) perfusion study, significant reductions in regional cerebral perfusion during the 3VO accompanied a rapid return to baseline after release of the CCAs, showing that the technique induces temporary focal ischemia. The average sizes and variances of the neocortical infarction in this model, together with those in the other normotensive rat models caused by the 3VO technique in the literature, indicated a standard size and variance of infarcted lesion in the control groups relative to the specific ischemic period. However, stroke injuries in the neocortex induced by the thread occlusion technique showed greater variability with less consistent lesion sizes. Inclusion/exclusion criteria to avoid inappropriate cases with too mild (no/faint infarction) or too great (huge/fatal infarction) severity in the ischemic injury may differ between laboratories in the thread occlusion model.

Biphasic expression of activating transcription factor-3 in neurons after cerebral infarction

It has been demonstrated that some of immediate early genes such as c-Jun are induced immediately and transiently following focal cerebral ischemia. Here we newly characterize the activating transcription factor (ATF)-3 as a focal ischemia associated immediate early gene. Using in situ hybridization and immunohistochemistry, we compared the expression profile of ATF-3 with those of ATF-2 and c-Jun after middle cerebral artery (MCA) occlusion. Focal cerebral ischemia induced two temporal and spatial patterns of ATF-3 expression. Early and transient induction of ATF-3 mRNA was observed in the core and margins of the cortex immediately after MCA occlusion. Late-onset and prolonged expression of ATF-3 mRNA and its protein were specifically identified in the peri-infarct cortex and thalamus where neurons survive at least 1 month. The expression profiles of ATF-3 and c-Jun were virtually similar, but c-Jun expression was also observed in other regions of the brain in control rats. Expression of ATF-2 was ubiquitously seen in neuronal cells throughout the brain in normal rats, but was suppressed in ischemic regions. Double immunohistochemical labeling revealed concurrent expression of ATF-3 and phospho-c-Jun in neurons. We conclude that the transcription factor ATF-3 is a suitable marker of neurons subjected to ischemic insult directly and indirectly, and that cooperative works of ATF-3 and c-Jun may be crucial triggers of various transcriptional responses to the ischemic insult.

Desflurane and sevoflurane attenuate oxygen and glucose deprivation-induced neuronal cell death

Neuronal cell death may occur via two pathways: those causing necrosis or those causing apoptosis. Apoptosis can be activated during periods of stress such as oxygen and glucose deprivation. Anesthetic agents such as desflurane or sevoflurane can attenuate early neuronal necrotic death, but their effect on oxygen and glucose deprivation-induced apoptosis has not been investigated. Neuronal cell cultures were prepared from neonatal rat cortex and were used between 10 and 14 days in vitro. The neuronal cell cultures were pretreated 30 minutes prior to oxygen and glucose deprivation with either desflurane or sevoflurane (N = 18). Three concentrations of each anesthetic were evaluated. The cultures were then deprived of oxygen and glucose for 30, 60, or 90 minutes. Treatment with desflurane or sevoflurane was continued during the period of oxygen and glucose deprivation. Forty-eight hours after exposure, the cells were examined for apoptosis using TUNEL and DNA gel electrophoresis. Comparisons were made to neuronal cortical cell cultures exposed to oxygen and glucose deprivation alone (N = 9). This in vitro model of oxygen and glucose deprivation was successful in producing neuronal cell death during the exposure times examined. During 30-, 60-, and 90-minute periods of oxygen and glucose deprivation, both desflurane and sevoflurane significantly ( approximately 98%) attenuated neuronal cell death regardless of concentration.

Effect of intra-ischemic hypothermia on the expression of c-Fos and c-Jun, and DNA binding activity of AP-1 after focal cerebral ischemia in rat brain

It is unknown whether immediate early gene (IEG) induction and subsequent late gene regulation after ischemia is beneficial or deleterious. The aim of this study was to examine the effect of hypothermia on expression of c-Fos and c-Jun, and AP-1 DNA binding activity, after transient focal cerebral ischemia in rat brain, and clarify the role of IEGs and AP-1 after insults. Male Wistar rats underwent right middle cerebral artery occlusion for 1 h with the intraluminal suture method. During ischemia, animals were assigned to either normothermic (NT) or hypothermic (HT) groups. In the NT group, brain temperature was observed to spontaneously increase to 40 degrees C during ischemia. In the HT group, brain temperature decreased to 30 degrees C. Infarct volume in cortex was decreased in the HT group, compared with that in the NT group (P<0.001). Increased c-Fos immunoreactivity in the cortex was observed at 3 h after reperfusion in the HT, but not the NT group, while c-Jun expression was not affected by HT treatment. There was also a significant increase in AP-1 DNA binding activity at 3 h in the HT group when compared to the NT group (P<0.01). In conclusion, hypothermia decreased cerebral infarction in association with early increases in c-Fos expression and AP-1 DNA binding activity in peri-infarct cortex. It remains to be established whether such responses are a cause or consequence of cell survival, but these results clearly establish that altered transcription is a key feature of tissue spared following hypothermic focal ischemia.

Differential regulation of thrombospondin-1 and thrombospondin-2 after focal cerebral ischemia/reperfusion

BACKGROUND AND PURPOSE

Angiogenesis occurs after cerebral ischemia, and the extent of angiogenesis has been correlated with survival in stroke patients. However, postischemic angiogenesis is short-lived and may be completely terminated within a few weeks after ischemic insult. The molecular mechanism underlying the dissolution of postischemic angiogenic processes is poorly understood. Although the expression of angiogenic genes has been studied in ischemic stroke models, the activation of angiostatic genes after cerebral ischemia has not been investigated. Thrombospondin (TSP)-1 and TSP-2 are naturally occurring angiostatic factors, which inhibit angiogenesis in vivo. The aim of the present study was to explore the expression of TSP-1 and TSP-2 in relation to the evolution of angiogenic process in a focal ischemia model in rats.

METHODS

Rats underwent cortical ischemia in the middle cerebral artery territory for 60 minutes and reperfusion for up to 2 weeks. Northern and Western blot analysis were used to study the temporal profile of TSP-1 and TSP-2 expression at the mRNA and protein level, respectively. In situ hybridization and immunohistochemical studies were used to examine the spatial expression patterns. Double immunostaining was applied to define the cellular origins of TSP-1 and TSP-2.

RESULTS

A biphasic expression of TSP-1 was noted after ischemia, peaking at 1 and 72 hours. Endothelial cells in the leptomeninges were the only source of the first TSP-1 peak, whereas endothelial, glial, neuronal, and macrophage cells contributed to the second peak of TSP-1 expression. TSP-2 expression occurred much later and in a monophasic manner, peaking 2 weeks after ischemia. TSP-2 immunoreactivity was observed in endothelial, neuronal, and macrophage, but not glial, cells. TSP-1 was expressed before the peak of angiogenesis, whereas robust TSP-2 expression occurred at the peak of angiogenesis and continued into the period when angiogenesis had completely resolved.

CONCLUSIONS

Robust expression of TSP-1 and TSP-2, 2 major angiostatic factors, was noted in the ischemic brain with different temporal expression profiles from different cellular origins. The expression of these angiostatic factors, especially TSP-2, likely contributes to the spontaneous resolution of postischemic angiogenesis. Further studies are needed to explore the molecular mechanisms that regulate the balance of angiogenic and angiostatic factors in the ischemic brain.

Ischemia-reperfusion-related repair deficit after oxidative stress: implications of faulty transcripts in neuronal sensitivity after brain injury

Diseases of the heart are the No. 1 killer in industrialized countries. Brain injury can develop as a result of cerebral ischemia-reperfusion due to stroke (brain attack) and other cardiovascular diseases. Learning about the disease is the best way to reduce disability and death. We present here whether gene repair activities are associated with neuronal death in an ischemia-reperfusion model that simulates stroke in male Long-Evans rats. This experimental stroke model is known to induce necrosis in the ischemic cortex. Cerebral ischemia causes overactivation of membrane receptors and accumulation of extracellur glutamate and intracellular calcium, which activates neuronal nitric oxide synthase, causing damage to lipids, proteins, and nucleic acids, and reduces energy sources with consequent functional deterioration, leading to cell death. Restoration processes normally repair genes with few errors. However, ischemia elevates oxidative DNA lesions despite these repair mechanisms. These episodes concurrently occur with the induction of immediate-early genes that critically activate other late genes in the signal transduction pathway. Damage, repair, and transcription of the c-FOS gene are presented here as examples, because Fos peptide, one of the components of activator protein 1, activates nerve growth factor and repair mechanisms. The results of our studies show that treatments with 7-nitroindazole, a specific inhibitor of nitric oxide synthase known to attenuate nitric oxide, oxidative DNA lesions, and necrosis, increase intact c-fos mRNA levels after stroke. This suggests that the accuracy of gene expression could be accounted for the recovery of cellular function after cerebral injury.

Transcripts of damaged genes in the brain during cerebral oxidative stress

Recent studies using ischemia/reperfusion models of brain injury suggest that there is a period of time during which the formation of oxidative DNA lesions (ODLs) exceeds removal. This interval is a window of opportunity in which to study the effect of gene damage on gene expression in the brain, because the presence of excessive ODLs mimics a deficiency in gene repair, which has been shown to be associated with neurological disorders. Evidence from studies using similar models indicates that expression of faulty transcripts from ODL-infested genes and non-sense mutation in repaired genes occur before the process of cell death. Preventing the formation of ODLs and enhancing ODL repair are shown to increase the expression of intact transcripts and attenuate cell death. Understanding this mechanism could lead to the development of therapeutic techniques (physiologic, pharmacological, and/or genomic) that can enhance recovery.

Dynamic changes in cerebral blood flow and angiogenesis after transient focal cerebral ischemia in rats. Evaluation with serial magnetic resonance imaging

BACKGROUND AND PURPOSE

Angiogenesis occurs after cerebral ischemia, but the relationship between angiogenesis and cerebral hemodynamic change is unknown. The aim of the present study was to investigate the relationship between ischemia-induced angiogenesis and hemodynamics in a well-defined 3-vessel occlusion model of the rat by using diffusion- (DWI), perfusion-, and T2-weighted MRI (T2WI).

METHODS

Rats were subjected to 60 minutes of transient middle cerebral artery occlusion or sham operation. DWI and T2WI were used to characterize the extent of the ischemic lesion from 4.5 hours to 14 days after reperfusion. A flow-sensitive alternating inversion recovery method and dynamic susceptibility contrast MRI were used to evaluate the temporal changes in relative cerebral blood flow (CBF) and cerebral blood volume (CBV), respectively. Rats were randomly selected and killed at each time point for investigation of vascular density and for hematoxylin-eosin staining.

RESULTS

Ischemic lesions developed in the ipsilateral cortex, as demonstrated by DWI and T2WI. CBF was significantly increased in the ipsilateral cortex, especially in the cortical outer layer from day 1 to day 14, and peaked on day 7 (P<0.05), while CBV was significantly increased on day 7 (P<0.01). The vascular density on the ipsilateral brain surface was gradually increased from day 1 to day 5, peaked on day 7, and then decreased on day 14. Histology study showed pannecrosis in the cortex from day 1 to day 5 and partial liquefaction of the necrotic tissues on days 7 and 14.

CONCLUSIONS

A delayed increase in both CBF and CBV is documented in the ipsilateral cortex after transient focal brain ischemia, and such an increase may be associated with angiogenesis.

Amyloid-beta induces Smac release via AP-1/Bim activation in cerebral endothelial cells

Insoluble fibrils of amyloid-beta peptide (Abeta) are the major component of senile and vascular plaques found in the brains of Alzheimer's disease (AD) patients. Abeta has been implicated in neuronal and vascular degeneration because of its toxicity to neurons and endothelial cells in vitro; some of these cells die with characteristic features of apoptosis. We used primary cultures of murine cerebral endothelial cells (CECs) to explore the mechanisms involved in Abeta-induced cell death. We report here that Abeta(25-35), a cytotoxic fragment of Abeta, induced translocation of the apoptosis regulator termed second-mitochondria-derived activator of caspase (Smac) from the intramembranous compartment of the mitochondria to the cytosol 24 hr after exposure. In addition, we demonstrated that X chromosome-linked inhibitor-of-apoptosis protein (XIAP) coimmunoprecipitated with Smac, suggesting that the two proteins bound to one another subsequent to the release of Smac from the mitochondria. Abeta(25-35) treatment also led to rapid AP-1 activation and subsequent expression of Bim, a member of the BH3-only family of proapoptotic proteins. Bim knockdown using an antisense oligonucleotide strategy suppressed Abeta(25-35)-induced Smac release and resulted in attenuation of CEC death. Furthermore, AP-1 inhibition, with curcumin or c-fos antisense oligonucleotide, reduced bim expression. These results suggest that Abeta activates an apoptotic cascade involving AP-1 DNA binding, subsequent bim induction, followed by Smac release and binding to XIAP, resulting in CEC death.

Expression profiling following traumatic brain injury: a review

Traumatic brain injury (TBI) elicits a complex sequence of putative autodestructive and neuroprotective cellular cascades. It is hypothesized that the genomic responses of cells in the injured brain serve as the basis for these cascades. Traditional methods for analyzing differential gene expression following brain trauma demonstrate that immediate early genes, cytokines, transcription factors, and neurotrophic factors can all participate in the brain's active and directed response to injury, and may do so concurrently. It is this complexity and multiplicity of interrelated molecular mechanisms that has demanded new methods for comprehensive and parallel evaluation of putative as well as novel gene targets. Recent advances in DNA microarray technology have enabled the simultaneous evaluation of thousands of genes and the subsequent generation of massive amounts of biological data relevant to CNS injury. This emerging technology can serve to further current knowledge regarding recognized molecular cascades as well as to identify novel molecular mechanisms that occur throughout the post-traumatic period. The elucidation of the complex alterations in gene expression underlying the pathological sequelae following TBI is of central importance in the design of future therapeutic agents.

The association between neuronal nitric oxide synthase and neuronal sensitivity in the brain after brain injury

Injury to the central nervous system is the leading cause of disability in the United States. Neuronal death is one of the causes of disability. Among patients who survive this type of injury, various degrees of recovery in brain function are observed. The molecular basis of functional recovery is poorly understood. Clinical observations and research using experimental injury models have implicated several metabolites in the cascade of events that lead to neuronal degeneration. The levels of intracellular ATP (energy source) and pH are decreased, whereas levels of extracellular glutamate, intracellular calcium ions, and oxidative damage to RNA/DNA, protein, and lipid are increased. These initiating events can be associated with energy failure and mitochondrial dysfunction, resulting in functional or structural brain damage. The injured brain is known to express immediate early genes. Recent studies show that reactive oxygen species (ROS) cause lesions in genes from which mRNA is transcribed as part of the endogenous neuroprotective response. Although degenerating proteins and lipids may contribute to necrosis significantly after severe injury, abnormalities in genetic material, if not repaired, disturb cellular function at every level by affecting replication, transcription, and translation. These lesions include abnormal nucleic acids, known as oxidative lesions of DNA (ODLs) or of RNA (ORLs). In this review, we focus on our current understanding of the various effects of neuronal nitric oxide synthase on the formation of modified bases in DNA and RNA that are induced in the brain after injury, and how ODLs and ORLs affect cell function.

Cyclooxygenase-1 and bicistronic cyclooxygenase-1/prostacyclin synthase gene transfer protect against ischemic cerebral infarction

BACKGROUND

We tested the hypothesis that bicistronic cyclooxygenase-1 (COX-1)/prostacyclin synthase (PGIS) and COX-1 gene transfer reduce cerebral infarct volume by augmenting synthesis of protective prostaglandins.

METHODS AND RESULTS

We infused into lateral ventricle of a rat stroke model recombinant adenoviruses (rAd) containing COX-1 (Adv-COX-1), COX-1 and PGIS (Adv-COX-1/PGIS), or Adv-PGK control vector, and we determined COX-1 and PGIS protein and eicosanoid levels and infarct volume. COX-1 and PGIS proteins were increased in a time-dependent manner. Adv-COX-1/PGIS infusion selectively augmented prostacyclin levels, with reduction of other eicosanoids in ischemic cortex and a significant reduction of infarct volume, even when the rAd was administered 5 hours after ischemia. Infusion of Adv-COX-1 also increased prostacyclin, suppressed leukotriene levels, and achieved a similar degree of cerebral protection. Its neuroprotection was abrogated by treatment with a selective COX-1 inhibitor.

CONCLUSIONS

COX-1/PGIS and COX-1 gene transfer reduce cerebral infarct volume by augmenting prostacyclin and suppressing leukotriene productions. COX-1-based gene transfer has potential for treating ischemic stroke.