Involvement of cytokine production in pathogenesis of transient cerebral ischemic damage

High glucose stimulates GRO secretion from rat microglia via ROS, PKC, and NF-kappaB pathways

Hyperglycemia causes direct neuronal damage in diabetic encephalopathy. Microglia have been found to be activated in diabetic encephalopathy, presumably mediating and amplifying neuron degeneration. Chemokine IL-8 plays an important role in the pathogenesis of encephalopathy. Therefore, we investigated whether high glucose could activate microglia and stimulate IL-8 secretion and if so, the possible mechanisms that were involved. ELISA results showed that treatment with high glucose (35 mM) compared with treatment with low glucose (10 mM) time-dependently elevated secretion of GRO (the rat ortholog of human IL-8) in primary cultured rat microglia. Real-time PCR results showed GRO mRNA expression also increased in response to high glucose in a time-dependent manner. These effects were specific to high glucose because the osmolality control had no such effect. High-glucose treatment stimulated the formation of ROS, as seen in the DCF fluorescence assay, increased phosphorylation of PKC, as seen in the Western blot analysis, and activated NF-kappaB, as seen in the luciferase reporter assay. In addition, treatment with the ROS scavenger NAC (2 mM) significantly reduced the high glucose-induced phosphorylation of PKC and GRO secretion. Treatment with the PKC activator PMA (10-50 nM) stimulated GRO secretion, and the PKC inhibitors calphostin C (300 nM) or chelerythrine (1 microM) attenuated the high glucose-induced GRO secretion. Furthermore, the NF-kappaB inhibitors MG132 (10 microM) or PDTC (5 microM) completely blocked the high glucose-induced GRO secretion. In conclusion, high glucose induces GRO secretion and mRNA expression in activated rat microglia, which is mediated by the ROS, PKC, and NF-kappaB pathways. High glucose-induced IL-8 production by microglia may contribute to diabetic encephalopathy.

Detection of adiponectin in cerebrospinal fluid in humans

Adiponectin circulates in the body in high concentrations, and 100-fold lower amounts were described in the cerebrospinal fluid (CSF) of mice, whereas in humans, contradictory results have been published. To clarify whether adiponectin is present in human CSF and is derived from the circulation, it was determined in human CSF and plasma of 52 nonselected patients. Adiponectin was detected by immunoblot in CSF and was quantified in CSF and serum by ELISA. CSF adiponectin was positively correlated to systemic levels, and the CSF/serum adiponectin ratio was correlated to the CSF/serum albumin ratio. Furthermore, disturbed function of the blood-brain barrier (BBB) was associated with an elevated CSF/serum adiponectin ratio. Adiponectin mRNA was not found in the brain, indicating that adiponectin crosses the BBB and/or the blood-cerebrospinal fluid barrier (BCB). Rat adiponectin with a COOH-terminal tag was injected into the tail vein of rats and was detected 3 h later in CSF. However, CSF adiponectin in humans and rats was approximately 0.1% of the serum concentration and therefore was below the 0.5% expected in the CSF because of the residual leakage of an undisturbed BBB/BCB. Taken together, data from the present study show that adiponectin in human CSF is far below the level expected by the baseline BBB/BCB permeability, indicating that adiponectin enters the brain much less efficiently than albumin, thus supporting recent data that exclude adiponectin transport to the CSF. Additional studies are needed to reveal whether these low levels of adiponectin in CSF have a physiological function.

Neuroprotective mechanisms of curcumin against cerebral ischemia-induced neuronal apoptosis and behavioral deficits

Increased oxidative stress has been regarded as an important underlying cause for neuronal damage induced by cerebral ischemia/reperfusion (I/R) injury. In recent years, there has been increasing interest in investigating polyphenols from botanical source for possible neuroprotective effects against neurodegenerative diseases. In this study, we investigated the mechanisms underlying the neuroprotective effects of curcumin, a potent polyphenol antioxidant enriched in tumeric. Global cerebral ischemia was induced in Mongolian gerbils by transient occlusion of the common carotid arteries. Histochemical analysis indicated extensive neuronal death together with increased reactive astrocytes and microglial cells in the hippocampal CA1 area at 4 days after I/R. These ischemic changes were preceded by a rapid increase in lipid peroxidation and followed by decrease in mitochondrial membrane potential, increased cytochrome c release, and subsequently caspase-3 activation and apoptosis. Administration of curcumin by i.p. injections (30 mg/kg body wt) or by supplementation to the AIN76 diet (2.0 g/kg diet) for 2 months significantly attenuated ischemia-induced neuronal death as well as glial activation. Curcumin administration also decreased lipid peroxidation, mitochondrial dysfunction, and the apoptotic indices. The biochemical changes resulting from curcumin also correlated well with its ability to ameliorate the changes in locomotor activity induced by I/R. Bioavailability study indicated a rapid increase in curcumin in plasma and brain within 1 hr after treatment. Together, these findings attribute the neuroprotective effect of curcumin against I/R-induced neuronal damage to its antioxidant capacity in reducing oxidative stress and the signaling cascade leading to apoptotic cell death.

Glutamine decreases lipopolysaccharide-induced intestinal inflammation in infant rats

Using a gastrostomy-fed (GF) rat infant "pup-in-a-cup" model, the effects of protein deprivation and supplemental glutamine (Gln) and glutamate (Glu) were examined to test the hypothesis that Gln decreases the proinflammatory response induced by LPS in the developing infant rat small intestine. Four groups of 6- to 7-day-old pups were fed a rat milk substitute (RMS), one providing 100% and three providing 25% of normal protein intake for another 6 days. Two of the 25% protein-fed groups received supplemental Gln or Glu. GF and LPS treatment blunted body growth and intestinal villus height and increased intestinal cytokine-induced neutrophil chemoattractant (CINC) mRNA in the protein-deprived, non-Gln-treated group compared with mother-fed pups (P < 0.05). Gln blunted intestinal CINC mRNA (P < 0.05), but Glu did not. Intestinal CINC peptide in the LPS-treated pups provided 100 and 25% protein was elevated approximately 13-fold compared with the mother-reared pups (P < 0.001). Gln and Glu decreased intestinal CINC peptide by 73 and 80%, respectively. GF, LPS-treated pups also had a higher level of plasma CINC peptide (P < 0.05). Gln but not Glu decreased plasma CINC peptide (P < 0.05). An approximate sixfold elevation of intestinal MPO activity in the GF, LPS-treated rats was decreased by Gln and Glu by 92% (P < 0.001) and 54% (P < 0.05), respectively. Intestinal and plasma TNF-alpha were increased in GF, LPS-treated pups (P < 0.01), and Gln and Glu both blunted this increase (P < 0.05) in the intestine but not in the plasma. The results indicate that Gln decreases the LPS-induced inflammatory response in infant rat intestine under different conditions of protein intake.

Early NFkappaB activation is inhibited during focal cerebral ischemia in interleukin-1beta-converting enzyme deficient mice

Our previous study demonstrated that the inhibition of interleukin-1beta (IL-1beta) reduces ischemic brain injury; however, the molecular mechanism of the action of IL-1 in cerebral ischemia is unclear. We are investigating currently the role of NFkappaB during focal cerebral ischemia, using mutant mice deficient in the interleukin-1 converting enzyme gene (ICE KO) in a middle cerebral artery occlusion (MCAO) model. Adult male ICE KO and wild-type mice (n = 120) underwent up to 24 hr of permanent MCAO. Cytoplasmic phospho-NFkappaB/p65 expression in ischemic brain was examined using Western blot analysis and immunohistochemistry. NFkappaB DNA-binding activity was detected using electrophoretic mobility shift assay (EMSA). Furthermore, ICAM-1 expression was examined in both the ICE KO and wild-type mice (WT). Western blot analysis and immunostaining showed that the level of cytosolic phosphorylated NFkappaB/p65 increased after 2 and 4 hr of MCAO in WT mice; however, NFkappaB/p65 was significantly reduced after MCAO in the ICE KO mice (P < 0.05). EMSA showed that NFkappaB DNA-binding activity increased after MCAO in WT mice; but this effect was reduced in the ICE KO mice. The number of ICAM-1-positive vessels in the ischemic hemisphere was greatly attenuated in the ICE KO mice (P < 0.05), which paralleled the results of immunohistochemistry. Our results demonstrate that NFkappaB phosphorylation is reduced in ICE KO mice, suggesting that ICE or IL-1 are involved in early NFkappaB phosphorylation. Because cerebral ischemia induced infarction is significantly reduced in ICE KO mice, we conclude that early NFkappaB phosphorylation plays a disruptive role in the ischemic process.

Level of haem oxygenase does not obligatorily reflect the sensitivity of PC12 cells to an oxidative shock induced by glutathione depletion

In order to investigate the function of haem oxygenase in neuronal cell death or survival, we have determined in PC12 cells whether induction of haem oxygenase mRNA and protein or inhibition of haem oxygenase activity may be able to modulate the cell response to an oxidative stress. Inhibition of glutathione biosynthesis by buthionine sulfoximine (BSO) has indeed been demonstrated, in this cell line, to decrease the intracellular content of glutathione and to trigger a gradual and programmed cell death. Inhibition of haem oxygenase by zinc protoporphyrin IX, a potent inhibitor of this enzyme, or by a recently described peptidic inhibitor, induced a significant decrease in the toxicity of BSO. This protective action was not due to an alteration in the metabolism of glutathione and was still observed when the protecting agent was added several hours after BSO treatment. Induction of haem oxygenase-1 mRNA and protein by either haemin or pyrrolidine dithiocarbamate was associated with no protection or a significant reduction in the toxicity of BSO respectively. Our results indicate that induction of haem oxygenase-1 is not obligatorily associated with an improved resistance towards oxidative stress and suggest that a byproduct of haem degradation may also become detrimental.

Periventricular leukomalacia, inflammation and white matter lesions within the developing nervous system

Periventricular leukomalacia (PVL) occurring in premature infants, represents a major precursor for neurological and intellectual impairment, and cerebral palsy in later life. The disorder is characterized by multifocal areas of necrosis found deep in the cortical white matter, which are often symmetrical and occur adjacent to the lateral ventricles. There is no known cure for PVL. Factors predisposing to PVL include birth trauma, asphyxia and respiratory failure, cardiopulmonary defects, premature birth/low birthweight, associated immature cerebrovascular development and lack of appropriate autoregulation of cerebral blood flow in response to hypoxic-ischemic insults. The intrinsic vulnerability of oligodendrocyte precursors is considered as central to the pathogenesis of PVL. These cells are susceptible to a variety of injurious stimuli including free radicals and excitotoxicity induced by hypoxic-ischemic injury (resulting from cerebral hypoperfusion), lack of trophic stimuli, as well as secondary associated events involving microglial and astrocytic activation and the release of pro-inflammatory cytokines TNF-alpha and IL-6. It is yet unclear whether activated astrocytes and microglia act as principal participants in the development of PVL lesions, or whether they are representatives of an incidental pathological response directed towards repair of tissue injury in PVL. Nevertheless, the accumulated evidence points to a pathological contribution of microglia towards damage. The topography of lesions in PVL most likely reflects a combination of the relatively immature cerebrovasculature together with a failure in perfusion and/or hypoxia during the greatest period of vulnerability occurring around mid-to-late gestation. Mechanisms underlying the pathogenesis of PVL have so far been related to prenatal ischemic injury to the brain initiated within the third trimester, which result in global cognitive and developmental delay and motor disturbances. Over the past few years, several epidemiological and experimental studies have implicated intrauterine infection and chorioamnionitis as causative in the pathogenesis of PVL. In particular, recent investigations have shown that inflammatory responses in the fetus and neonate can contribute towards neonatal brain injury and development-related disabilities including cerebral palsy. This review presents current concepts on the pathogenesis of PVL and emphasizes the increasing evidence for an inflammatory pathogenic component to this disorder, either resulting from hypoxic-ischemic injury or from infection. These findings provide the basis for clinical approaches targeted at protecting the premature brain from inflammatory damage, which may prove beneficial for treating PVL, if identified early in pathogenesis.

The effects of NMDA receptor antagonist MK-801 on lipid peroxidation during focal cerebral ischemia in rats

The effect of MK-801 on ischemic neuronal damage was studied in a rat model of permanent focal cerebral ischemia in terms of ipsilateral and contralateral cortical and cerebellar tissue lipid peroxides. Forty-five male Swiss Albino rats were assigned into one of four groups: sham operated as controls, subjected to right middle cerebral artery occlusion (MCAO) or injection of MK-801 (0.5 mg/kg i.p.) either 30 min before or just after right MCAO. Changes in lipid peroxides were expressed as nmol malondialdehyde (MDA) and conjugated diene (CD)/mg protein. MDA values after 60 min of ischemia relative to contralateral cortex and CD levels in 0, 10 and 60 min after ischemia were found to be higher in ipsilateral cortex than those in contralateral cortex. On the other hand, contralateral cerebellar MDA levels in 0 and 60 min of ischemia and CD levels in 0, 10 and 60 min after ischemia were found to be higher than those in ipsilateral cerebellum. Pharmacological inhibition of glutamate receptor by MK-801 before or just after permanent MCAO decreased significantly the MDA and CD levels in both cortex and cerebellum. Although no significant differences found in MDA values between rats pre- and posttreated with MK-801, CD levels in posttreated group seemed significantly lower than those in pretreated group. On the whole, these results suggest that MDA and CD represent early biochemical marker of lipid peroxidation in ischemic tissues, reflecting the radical-mediated tissue damage.

Cytokine production regulation in human astrocytes by a herbal combination (Yuldahansotang)

Yuldahansotang (YH-Tang), a Sasang Constitutional prescription composed of seven herbal mixtures, has been developed as a formula to prevent and treat cerebral infarction (CI) of Taeumins. However, the mechanisms by which this formula affects CI remain unknown. Previously, regulation of serum cytokine levels by YH-Tang has been observed in individuals at the acute stage of CI disease. It is uncertain whether this is a cause or a result of the disease process. In this study, we investigated whether YH-Tang inhibited secretion of inflammatory cytokines from human astrocytes. YH-Tang regulated the cytokine secretions in astrocytes stimulated with substance P (SP) and lipopolysaccharide (LPS). YH-Tang significantly inhibited interleukin (IL)-1, IL-4, IL-6 and tumor necrosis factor-alpha (TNF-alpha) secretion in astrocytes stimulated with SP and LPS, but did not inhibit interferon-y (IFN-gamma) and IL-2 secretion significantly. IL-1 has been shown to elevate TNF-alpha secretion from LPS-stimulated astrocytes while having no effect on astrocytes in the absence of LPS. Therefore, we investigated whether IL-1 mediated inhibition of TNF-alpha secretion from astrocytes by YH-Tang. Incubation of human astrocytes with IL-1 antibody abolished the synergistic cooperative effect of LPS and SP. These results suggest that YH-Tang may indirectly inhibit TNF-alpha secretion by inhibiting IL-1 secretion. Moreover, these findings indicate that YH-Tang has regulatory effects on cytokine secretion in an acute CI patient.

Angiogenesis after stroke is correlated with increased numbers of macrophages: the clean-up hypothesis

Brain cells manufacture and secrete angiogenic peptides after focal cerebral ischemia, but the purpose of this angiogenic response is unknown. Because the maximum possible regional cerebral blood flow is determined by the quantity of microvessels in each unit volume, it is possible that angiogenic peptides are secreted to generate new collateral channels; other possibilities include neuroprotection, recovery/regeneration, and removal of necrotic debris. If the brain attempts to create new collaterals, microvessel density should increase significantly after ischemia. Conversely, if angiogenic-signaling molecules serve some other purpose, microvessel densities may increase slightly or not at all. To clarify, the authors measured microvessel densities with quantitative morphometry. Left middle cerebral arteries of adult male Sprague-Dawley rats were occluded with intraluminal nylon suture for 4 hours followed by 7, 14, 19, or 30 days of reperfusion. Controls received no surgery or suture occlusion. Changes in microvessel density and macrophage numbers were measured by light microscopic morphometry using semiautomated stereologic methods. Microvessel density increased only in the ischemic margin adjacent to areas of pannecrosis and was always associated with increased numbers of macrophages. Ischemic brain areas without macrophages displayed no vascularity changes compared with normal animals. These data suggest that ischemia-induced microvessels are formed to facilitate macrophage infiltration and removal of necrotic brain.

Role of astrocytes in pathogenesis of ischemic brain injury

Astrocytes play an important role in the homeostasis of the CNS both in normal conditions and after ischemic injury. The swelling of astrocytes is observed during and several seconds after brain ischemia. Then ischemia stimulates sequential morphological and biochemical changes in glia and induces its proliferation. Reactive astrocytes demonstrate stellate morphology, increased glial fibrillary acidic protein (GFAP) immunoreactivity, increased number of mitochondria as well as elevated enzymatic and non-enzymatic antioxidant activities. Astrocytes can re-uptake and metabolize glutamate and in this way they control its extracellular concentration. The ability of astrocytes to protect neurons against the toxic action of free radicals depends on their specific energy metabolism, high glutathione level, increased antioxidant enzyme activity (catalase, superoxide dismutase, glutathione peroxidase) and overexpression of antiapoptotic bcl-2 gene. Astrocytes produce cytokines (TNF-alpha, IL-1, IL-6) involved in the initiation and maintaining of immunological response in the CNS. In astrocytes, like in neurones, ischemia induces the expression of immediate early genes: c-fos, c-jun, fos B, jun B, jun D, Krox-24, NGFI-B and others. The protein products of these genes modulate the expression of different proteins, both destructive ones and those involved in the neuroprotective processes.

Stimulation of adenosine A3 receptors in cerebral ischemia. Neuronal death, recovery, or both?

The role of the adenosine A3 receptor continues to baffle, and, despite an increasing number of studies, the currently available data add to, rather than alleviate, the existing confusion. The reported effects of adenosine A3 receptor stimulation appear to depend on the pattern of drug administration (acute vs. chronic), dose, and type of the target tissue. Thus, while acute exposure to A3 receptor agonists protects against myocardial ischemia, it is severely damaging when these agents are given shortly prior to cerebral ischemia. Mast cells degranulate when their A3 receptors are stimulated. Degranulation of neutrophils is, on the other hand, impaired. While reduced production of reactive nitrogen species has been reported following activation of A3 receptors in collagen-induced arthritis, the process appears to be enhanced in cerebral ischemia. Indeed, immunocytochemical studies indicate that both pre- and postischemic treatment with A3 receptor antagonist dramatically reduces nitric oxide synthase in the affected hippocampus. Even more surprisingly, low doses of A3 receptor agonists seem to enhance astrocyte proliferation, while high doses induce their apoptosis. This review concentrates on the studies of cerebral A3 receptors and, based on the available evidence, discusses the possibility of adenosine A3 receptor serving as an integral element of the endogenous cerebral neuroprotective complex consisting of adenosine and its receptors.

Spreading depression induces expression of calcium-independent protein kinase C subspecies in ischaemia-sensitive cortical layers: regulation by N-methyl-D-aspartate receptors and glucocorticoids

Spreading depression is a wave of sustained depolarization challenging the energy metabolism of the cells without causing irreversible damage. In the ischaemic brain, sreading depression-like depolarization contributes to the evolution of ischaemia to infarction. The depolarization is propagated by activation of N-methyl-D-aspartate receptors, but changes in signal transduction downstream of the receptors are not known. Because protein phosphorylation is a general mechanism whereby most cellular processes are regulated, and inhibition of N-methyl-D-aspartate receptors or protein kinase C is neuroprotective, the expression of protein kinase C subspecies in spreading depression was examined. Cortical treatment with KCl induced an upregulation of protein kinase Cdelta and zeta messenger RNA at 4 and 8 h, whereas protein kinase Calpha, beta, gamma and epsilon did not show significant changes. The gene induction was the strongest in layers 2 and 3, and was followed by an increased number of protein kinase Cdelta-immunoreactive neurons. Protein kinase Cdelta and zeta inductions were inhibited by pretreatment with an N-methyl-D-aspartate receptor antagonist, dizocilpine maleate, which also blocked spreading depression propagation, and with dexamethasone, which acted without blocking the propagation. Quinacrine, a phospholipase A2 inhibitor, reduced only protein kinase C5 induction. In addition, N(G)(-nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, did not influence protein kinase Cdelta or zeta induction, whereas 6-nitro-7-sulphamoylbenzo[f]quinoxaline-2,3-dione, an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate/kainate receptor antagonist, and the cyclo-oxygenase inhibitors indomethacin and diclophenac tended to increase gene expression. The data show that cortical spreading depression induces Ca2(+)-independent protein kinase C subspecies delta and zeta, but not Ca(2+)-dependent subspecies, through activation of N-methyl-D-aspartate receptors and phospholipase A2. Even though the signal pathway is similar to the induction described previously in ischaemia for genes implicated in delayed neuronal death, the gene inductions observed here are not necessarily pathogenetic, but may represent a general reaction to metabolic stress.

Free radical scavengers: chemical concepts and clinical relevance

Free radicals are involved in the pathology of many CNS disorders, like Parkinson's disease, Alzheimer's disease, or stroke. This discovery lead to the development of many radical scavengers for the clinical treatment of neurodegenerative diseases. In this review, the different chemical concepts for free radical scavenging will be discussed: nitrons, thiols, iron chelators, phenols, and catechols. Especially catechols, like the naturally occurring flavonols, the synthetic drug nitecapone, or the endogenous catacholamines and their metabolites, are of great interest, as they combine iron chelating with radical scavenging activity. We present data on the radical scvenging activity of dopamine and apomorphine, which prevent lipid peroxidation in rat brain mitochondria and protect PC12 cells against H2O2-toxicity.

Adenosine and cerebral ischemia: therapeutic future or death of a brave concept?

Numerous studies have consistently shown that agonist stimulation of adenosine A1 receptors results in a significant reduction of morbidity and mortality associated with global and focal brain ischemia in animals. Based on these observations, several authors have suggested utilization of adenosine A1 receptors as targets for the development of clinically viable drugs against ischemic brain disorders. Recent advent of adenosine A1 receptor agonists characterized by lowered cardiovascular effects added additional strength to this argument. On the other hand, although cardioprotective, adenosine A3 receptor agonists proved severely cerebrodestructive when administered prior to global ischemia in gerbils. Moreover, stimulation of adenosine A3 receptors appears to reduce the efficacy of some of the neuroprotective actions mediated by adenosine A1 receptors. The review discusses the possible role of adenosine receptor subtypes (A1, A2, and A3) in the context of their involvement in the pathology of cerebral ischemia, and analyzes putative strategies for the development of clinically useful strategies based on adenosine and its receptors. It also stresses the need for further experimental studies before definitive conclusions on the usefulness of the adenosine concept in the treatment of brain ischemia can be made.

Adenosine and cerebral ischemia: therapeutic future or death of a brave concept?

Numerous studies have consistently shown that agonist stimulation of adenosine A1 receptors results in a significant reduction of morbidity and mortality associated with global and focal brain ischemia in animals. Based on these observations, several authors have suggested utilization of adenosine A1 receptors as targets for the development of clinically viable drugs against ischemic brain disorders. Recent advent of adenosine A1 receptor agonists characterized by lowered cardiovascular effects added additional strength to this argument. On the other hand, although cardioprotective, adenosine A3 receptor agonists proved severely cerebrodestructive when administered prior to global ischemia in gerbils. Moreover, stimulation of adenosine A3 receptors appears to reduce the efficacy of some of the neuroprotective actions mediated by adenosine A receptors. The review discusses the possible role of adenosine receptor subtypes (A1, A2, and A3) in the context of their involvement in the pathology of cerebral ischemia, and analyzes putative strategies for the development of clinically useful strategies based on adenosine and its receptors. It also stresses the need for further experimental studies before definitive conclusions on the usefulness of the adenosine concept in the treatment of brain ischemia can be made.

Reperfusion injury after focal cerebral ischemia: the role of inflammation and the therapeutic horizon

Recent evidence indicates that thrombolysis may be an effective therapy for the treatment of acute ischemic stroke. However, the reperfusion of ischemic brain comes with a price. In clinical trials, patients treated with thrombolytic therapy have shown a 6% rate of intracerebral hemorrhage, which was balanced against a 30% improvement in functional outcome over controls. Destruction of the microvasculature and extension of the infarct area occur after cerebral reperfusion. We have reviewed the existing data indicating that an inflammatory response occurring after the reestablishment of circulation has a causative role in this reperfusion injury. The recruitment of neutrophils to the area of ischemia, the first step to inflammation, involves the coordinated appearance of multiple proteins. Intercellular adhesion molecule-1 and integrins are adhesion molecules that are up-regulated in endothelial cells and leukocytes. Tumor necrosis factor-alpha, interleukin-1, and platelet-activating factor also participate in leukocyte accumulation and subsequent activation. Therapies that interfere with the functions of these factors have shown promise in reducing reperfusion injury and infarct extension in the experimental setting. They may prove to be useful adjuncts to thrombolytic therapy in the treatment of acute ischemic stroke.

Chemokines, receptors, and their role in cardiovascular pathology

A superfamily of leukocyte chemotactic proteins, known as chemokines, has been identified during the past decade. Chemokines selectively attract and activate different leukocyte subpopulations and are key mediators of a variety of patho-physiological states, including hematopoiesis, inflammation, infection, allergy, atheroslerosis, reperfusion injury, as well as malignant tumors. Chemokines bind and activate a number of specific or promiscuous, G-protein-coupled seven-transmembrane receptors. Some of these receptors are utilized by human immuno-deficiency virus type 1 as essential fusion co-factors. Further understanding of the role of chemokines and their receptors in host defense will help develop means by which the beneficial versus detrimental effects of these molecules can be balanced.

Colocalization of Bcl-2 and 4-hydroxynonenal modified proteins in microglial cells and neurons of rat brain following transient focal ischemia

Bcl-2 has a role in suppressing the production of reactive oxygen species and lipid peroxidation. To explore the in situ localization of 4-hydroxy-2-nonenal (HNE)-modified proteins and the Bcl-2 oncoprotein, we used double immunofluorescence labeling and confocal imaging in the rat brain after 3 h of middle cerebral artery (MCA) occlusion followed by reperfusion. Immunoreactivity for HNE or Bcl-2 was not detected at 1 h, but appeared in some intact neurons in the boundary between the infarcted and non-infarcted zones at 12 h. At 48 h, HNE-positive microglia were colocalized with Bcl-2 in the infarcted area and the boundary zone. Bcl-2 may play an important role in the antioxidant system promoting survival of the neurons and activated microglia following reperfusion injury.