Expressions of P-selectin- and HSP72-like immunoreactivities in rat brain after transient middle cerebral artery occlusion

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

17beta-estradiol potentiates ischemia-reperfusion injury in diabetic ovariectomized female rats

To investigate the effect of 17beta-estradiol (E2) on ischemia-reperfusion (I/R) injury in diabetic ovariectomized female rats. Streptozotocin(STZ)-induced diabetic female rats received E2 treatment for 2 weeks after ovariectomy (OVX). A period of 90 min of temporary middle cerebral artery occlusion (tMCAO) was used for the study. Rats were evaluated for physiological data including plasma glucose, E2, MAP, PaCO2 and PaO2 before and after tMCAO. P-selectin expression, myeloperoxidase (MPO) enzyme activity and the cerebral infarct volume were analyzed.

RESULTS

The infarct volume in the E2-treated OVX rats is bigger than that in intact and OVX groups. However, there is not a significant different area of cerebral infarct between diabetic OVX and intact rats. Significant upregulation of P-selectin expression and MPO activity of the ischemia-reperfusion hemisphere were observed in E2 + OVX, intact and OVX groups at 8, 24, 72 h in time manner after tMCAO compared with that of the contralateral hemisphere of cerebral ischemia-reperfusion. Both P-selectin expression and MPO activity in the E2 + OVX and intact rats are significantly higher than that in the untreated OVX rats. Chronic estrogen replacement therapy (ERT) potentiates the I/R injury in diabetes female rats. This may be related to the increased expression of P-selectin and MPO activity.

Effect of P–selectin inhibition on leukocyteendothelium interaction and survival after global cerebral ischemia

Cerebral ischemia induces activation of leukocyte-endothelium interactions requiring upregulation of specific adhesion molecules including the selectins. The aim of the current study was to elucidate the therapeutic potency of P-selectin blockade on microcirculatory disturbances and secondary brain damage after global cerebral ischemia. Global cerebral ischemia for 15 minutes was induced in Mongolian gerbils. Functional blockade of P-selectin was achieved by pretreatment with the antibody RB 40.34 (2 mg/kg, n = 7). In vivo observation of brain microcirculation was performed by epifluorescence microscopy of a cranial window. Survival was assessed daily up to 4 days after ischemia. In the control group leukocyte rolling increased during reperfusion with a maximum at 3 h (28 +/- 14 x 100 microm(-1) x min(-1)) and was significantly reduced by the P-selectin antibody (13 +/- 9 x 100 microm(-1) x min(-1), p < 0.05). No effect on firm leukocyte adhesion was observed (4 +/- 3 vs. 2 +/- 1 x 100 microm(-1) x min(-1)). The survival of animals that received the Pselectin antibody (28 %) was significantly reduced compared with controls (71 %). Anti-P-selectin antibody reduces leukocyte rolling but has no positive effect on survival. Our data question the role of the inflammatory response in the development of secondary brain damage and do not support this kind of therapeutical approach in global cerebral ischemia.

Gene expression analysis of spontaneously hypertensive rat cerebral cortex following transient focal cerebral ischemia

Identification of novel modulators of ischemic neuronal death helps in developing new strategies to prevent the stroke-induced neurological dysfunction. Hence, the present study evaluated the gene expression changes in rat cerebral cortex at 6 and 24 h of reperfusion following transient middle cerebral artery occlusion (MCAO) by GeneChip analysis. Transient MCAO resulted in selective increased mRNA levels of genes involved in stress, inflammation, transcription and plasticity, and decreased mRNA levels of genes which control neurotransmitter function and ionic balance. In addition to a number of established ischemia-related genes, many genes not previously implicated in transient focal ischemia-induced brain damage [suppressor of cytokine signaling (SOCS)-3, cAMP responsive element modulator (CREM), cytosolic retinol binding protein (CRBP), silencer factor-B, survival motor neuron (SMN), interferon-gamma regulatory factor-1 (IRF-1), galanin, neurotrimin, proteasome subunit RC8, synaptosomal-associated protein (SNAP)-25 A and B, synapsin 1a, neurexin 1-beta, ras-related rab3, vesicular GABA transporter (VGAT), digoxin carrier protein, neuronal calcium sensor-1 and neurodap] were observed to be altered in the ischemic cortex. Real-time PCR confirmed the GeneChip results for several of these transcripts. SOCS-3 is a gene up-regulated after ischemia which modulates inflammation by controlling cytokine levels. Antisense knockdown of ischemia-induced SOCS-3 protein expression exacerbated transient MCAO-induced infarct volume assigning a neuroprotective role to SOCS-3, a gene not heretofore implicated in ischemic neuronal damage.

Inflammatory cell adhesion molecules in ischemic cerebrovascular disease

BACKGROUND

In this review we discuss the role of inflammatory cell adhesion molecules (CAMs) in ischemic stroke and in delayed cerebral ischemia after subarachnoid hemorrhage. Vascular endothelial cells and leukocytes express several inflammatory adhesion receptors, the most important of which are the selectins, immunoglobulin gene superfamily CAMs, and beta2 integrins. They mediate the transmigration process of leukocytes to the abluminal side of the endothelium.

SUMMARY OF REVIEW

There is ample evidence from animal models of middle cerebral artery occlusion that expression of CAMs is associated with cerebral infarct size. Absence of CAMs in knockout animals resulted in reduced infarct size. When middle cerebral artery occlusion in experimental stroke was followed by reperfusion, administration of anti-CAM antibodies decreased infarct size. Thus far, anti-CAM treatment has not been successful in patients with ischemic stroke. Inflammatory CAM may also play a role in the pathogenesis of delayed cerebral ischemia after subarachnoid hemorrhage. In animal models, increased expression of CAMs has been observed in vasospastic arteries. Increased concentrations of CAMs have also been found in cerebrospinal fluid of patients with subarachnoid hemorrhage.

CONCLUSIONS

Further research on the role of inflammatory CAMs in the pathogenesis of ischemic cerebrovascular disorders should lead to new diagnostic and therapeutic strategies.

Preconditioning the Brain and Heart: Implications for Cardiac Surgery

Despite many recent advances in emboli detection, aortic imaging, myocardial preservation, and perfusion equipment, ischemic injury to the heart and brain remains a serious complications after cardiac surgery. Hypoperfusion (particularly in the heart) and microem boli (particularly in the brain) during cardiopulmonary bypass constitute the etiology of ischemia. Although hypothermia has traditionally been the mainstay for systemic protection from transient ischemia, there has been a general trend to accept warmer heart and core temperatures during bypass, which increases the poten tial for ischemic injury to various organs. This article discusses recent advances in the understanding of myocardial and brain preconditioning and their poten tial role to provide additional protection during cardiac surgery.

Neuroglial activation repertoire in the injured brain: graded response, molecular mechanisms and cues to physiological function

Damage to the central nervous system (CNS) leads to cellular changes not only in the affected neurons but also in adjacent glial cells and endothelia, and frequently, to a recruitment of cells of the immune system. These cellular changes form a graded response which is a consistent feature in almost all forms of brain pathology. It appears to reflect an evolutionarily conserved program which plays an important role in the protection against infectious pathogens and the repair of the injured nervous system. Moreover, recent work in mice that are genetically deficient for different cytokines (MCSF, IL1, IL6, TNFalpha, TGFbeta1) has begun to shed light on the molecular signals that regulate this cellular response. Here we will review this work and the insights it provides about the biological function of the neuroglial activation in the injured brain.

Anti-P-selectin antibody attenuates rat brain ischemic injury

We examined a protective effect of anti-P-selectin monoclonal antibody against rat ischemic brain injury with 24 h of middle cerebral artery occlusion (MCAO). Anti-rat P-selectin monoclonal antibody, was intravenously injected at a dose of 1 mg/kg at 5 min before MCAO. Control animals received the same volume of vehicle. MCAO was accomplished by an insertion of nylon thread with silicone coating for 24 h. Application of anti-P-selectin antibody significantly reduced infarct size and brain water content at 24 h of MCAO. Although leukocyte infiltration was not normally detected, it became remarkably evident at 1 day of MCAO. However, treatment with ARP 2-4 significantly reduced the number of leukocytes. These results demonstrated that administration of monoclonal antibody against P-selectin attenuated infarct size and brain edema, which was associated with reduction of leukocyte infiltration.

P-selectin antibody reduces hemorrhage and infarct volume resulting from MCA occlusion in the rat

We investigated the effect of an anti-P-selectin antibody (RMP-1) on ischemic cell damage and hemorrhage after transient middle cerebral artery occlusion (MCAo) in the rat. Animals were divided into four groups: (1) antibody (Ab) 1 group (n = 14) RMP-1 (2 mg/kg) was administered to rats 1 h prior to induction of 2 h of MCA occlusion; (2) control-vehicle group Ab2 (n = 12) rats were subjected to the same experimental protocol, except that an isotype-matched control antibody was administered; (3) Abl group (n = 10) rats were subjected to 2 h of MCA occlusion and RMP-1 (2 mg/kg) was administered upon reperfusion; (4) control-vehicle group Ab2 (n = 10) rats were subjected to the same experimental protocol, except that an isotype-matched control antibody was administered. Animals were sacrificed 48 h after onset of the MCAo for histological evaluation of infarction and hemorrhage, and to quantify number of neutrophils. The lesion volume was significantly smaller only in pretreated rats (RMP-1 group, 18.7+/-3.1%) compared to the vehicle-treated (31.6+/-2.6%) group (P<0.01). Total area of hemorrhage (5.94 x 10(3)+/-2.86 x 10(3) microm2) in the pre MCAo RMP-1 treated group animals was significantly reduced (P<0.02) compared to the vehicle group (6.1 x 10(4)+/-3.42 x 10(4) microm2), respectively. Our data demonstrate that administration of the anti-P-selectin antibody before transient focal cerebral ischemia in rat brain reduces ischemic cell damage and petechial hemorrhage.

Oligonucleotide inhibitors of P-selectin-dependent neutrophil-platelet adhesion

P-selectin, an inducible cell adhesion molecule, mediates rolling of neutrophils on activated vascular endothelium. Because rolling is an early event of the inflammatory response, therapeutic applications of selectin antagonists have been of broad interest. There are, however, no truly satisfactory therapeutic candidates among known inhibitors. Consequently, we have used Systematic Evolution of Ligands by Exponential Enrichment (SELEX) technology, a process based on oligonucleotide combinatorial chemistry and in vitro selection, to develop aptamer antagonists of P-selectin. Equilibrium dissociation constants for aptamer/P-selectin binding range from 16 to 710 pM, a 10(5)-10(6)-fold improvement compared with the minimal carbohydrate ligand, sialyl Lewis X (sLeX). Aptamer binding is divalent cation dependent and, unlike sLeX, is specific for P-selectin. The selectivity for human P-selectin relative to human E-selectin or human L-selectin is 10(4)-10(5). In vitro, aptamers bind with subnanomolar affinities to P-selectin expressed on thrombin-activated platelets, inhibit the binding of P-selectin-IgG chimera to sLeX and to neutrophils, and block the binding activated platelets to neutrophils in flow cytometry and in hydrodynamic assays. Extrapolating from their in vitro characteristics, these novel P-selectin-specific antagonists may be suitable candidates for therapeutic development.

Inductions of hepatocyte growth factor and its activator in rat brain with permanent middle cerebral artery occlusion

Hepatocyte growth factor (HGF) is a potent pleiotrophic peptide which has a trophic role for neuronal cells. As it exerts its effect only after a conversion to its heterodimeric active form, the activation step, which is catalyzed by an enzyme serine protease named HGF activator (HGFA), is of great importance. HGF activated by HGFA may act as a protecting agent in injured brain. In the present study, we investigated expression of immunoreactive HGF and HGFA in rat brain after permanent middle cerebral artery (MCA) occlusion. By immunohistochemical analysis, HGF and HGFA were normally expressed only in ependymal cells and choroid plexus. At 1 h after MCA occlusion, neurons in the ischemic penumbra region of the cerebral cortex slightly expressed immunoreactive HGFA. HGF was not induced at that time. At 3 h of ischemia, however, immunoreactive HGF as well as HGFA became detectable in neurons of the ischemic cerebral cortex and caudate. Immunoreactivity for HGF continued to increase until 24 h, while that for HGFA remained almost constant from 3 to 24 h. No glial or vascular endothelial cells expressed HGF nor HGFA. By Western blot analysis for HGF, a single band of molecular weight (MW) 34 kDa became apparent at 24 h, corresponding to the light chain of the active form HGF. The present study suggests that HGF and HGFA were induced in neurons under permanent ischemia with slightly different temporal profiles. Through activation by HGFA, the active form of HGF could serve as a neurotrophic factor in ischemic brain.

Apoptosis of motor neurons with induction of caspases in the spinal cord after ischemia

BACKGROUND AND PURPOSE

Some neuronal subpopulations are especially vulnerable to ischemic injury. In the spinal cord, large motor neurons are vulnerable to ischemia and are selectively lost after transient ischemia. However, the mechanisms of the neuronal loss have been uncertain. We hypothesized that spinal motor neurons might be lost by apoptosis and investigated a possible mechanism of neuronal death by detection of double-strand breaks in genomic DNA and immunohistochemical analysis for caspases, ie, interleukin-1beta converting enzyme (ICE), Nedd-2, and CPP32.

METHODS

We used a rabbit spinal cord ischemia model created with a balloon catheter. The spinal cord was removed at 8 hours, 1, 2, or 7 days after 15 minutes of transient ischemia, and histological changes were studied with hematoxylin-eosin staining. To detect double-strand breaks in DNA, a staining with terminal deoxynucleotidyl transferase-mediated dUTP-biotin in situ nick end labeling (TUNEL) was performed. Furthermore, expression of ICE, Nedd-2, and CPP32 was investigated by Western blotting and immunohistochemical analysis.

RESULTS

Motor neurons were selectively lost at 7 days after transient ischemia. TUNEL study demonstrated that no cells were positively labeled until 1 day after ischemia, but nuclei of some motor neurons were positively labeled at 2 days. Western blot analysis revealed no immunoreactivity for ICE and slight immunoreactivities for Nedd-2 and CPP32 in the sham-operated spinal cords. However, immunoreactivity became apparent at 8 hours after transient ischemia, decreased at 1 day, and returned to baseline level at 2 days. Immunohistochemical analysis demonstrated that motor neurons were responsible for induction of those caspases.

CONCLUSIONS

Double-strand breaks in genomic DNA and induction of three caspases were demonstrated. These results indicate that motor neuron death in the spinal cord after transient ischemia is profoundly associated with activation of apoptotic processes.

Rapid induction of vascular endothelial growth factor gene expression after transient middle cerebral artery occlusion in rats

BACKGROUND AND PURPOSE

Vascular endothelial growth factor (VEGF) is a mitogen for endothelial cells and also has the potential to increase vascular permeability. Therefore, it may contribute to the recovery of brain cells from ischemic insult through potentiating neovascularization or may exacerbate brain damage by forming brain edema. However, the exact role of this protein in cerebral ischemia is not fully understood. We investigated temporal, spatial, and cellular profiles of the induction of VEGF gene expression after transient focal cerebral ischemia at both mRNA and protein levels.

METHODS

We used a transient middle cerebral artery (MCA) occlusion model. Northern blot analysis was performed to assess the chronological pattern of induction and the impact of length of ischemia on mRNA expression. Western blot analysis was performed to ensure the selective detection of immunoreactive VEGF with an antibody. Temporal, spatial, and cellular changes of immunohistochemical VEGF expression were compared with different periods of reperfusion from 1 hour to 7 days after transient MCA occlusion.

RESULTS

(1) Northern blot analysis revealed no detectable VEGF mRNA in the control brains. The mRNA became evident at 1 hour after reperfusion, peaked at 3 hours, and then decreased. The length of ischemia from 1 to 3 hours made no differences in the degree and temporal profile of the subsequent induction of VEGF mRNA. (2) Western blot analysis showed no band in the control brain, but two bands with molecular weights of 38 and 45 kD, corresponding to VEGF121 and VEGF165, were induced at 1 hour of reperfusion, peaked at 3 hours of reperfusion, and then decayed. (3) Neurons in the cerebral cortex of the MCA territory expressed VEGF at 1 hour after reperfusion with a peak at 3 hours and then diminished by 1 day. Pial cells of the MCA territory also expressed immunoreactive VEGF from 1 hour of reperfusion that was sustained until 3 to 7 days after reperfusion.

CONCLUSIONS

Rapid induction of VEGF gene expression after transient MCA occlusion was demonstrated at both mRNA and protein levels. Cortical neurons and pial cells were the source of VEGF production in this model, but the temporal profiles of the induction between these cells were different. The early but dissociative induction of VEGF between neuronal and pial cells suggests different roles of the protein in their cells after transient MCA occlusion.