Marc R. Del Bigio

Intracerebral hemorrhage induces macrophage activation and matrix metalloproteinases

Intracerebral hemorrhage (ICH) is characterized by parenchymal hematoma formation with surrounding inflammation. Matrix metalloproteinases (MMPs) have been implicated in the pathogenesis of neurological diseases defined by inflammation and cell death. To investigate the expression profile and pathogenic aspects of MMPs in ICH, we examined MMP expression in vivo using a collagenase‐induced rat model of ICH. ICH increased brain MMP‐2, ‐3, ‐7, and ‐9 mRNA levels relative to sham‐injected (control) animals in the vicinity of the hematoma, but MMP‐12 (macrophage metalloelastase) was the most highly induced MMP (>80‐fold). Immunohistochemistry showed MMP‐12 to be localized in activated monocytoid cells surrounding the hematoma. In vitro studies showed that thrombin, released during ICH, induced MMP‐12 expression in monocytoid cells, which was reduced by minocycline application. Similarly, in vivo minocycline treatment significantly reduced MMP‐12 levels in brain. Neuropathological studies disclosed marked glial activation and apoptosis after ICH that was reduced by minocycline treatment. Neurobehavioral outcomes also were improved with minocycline treatment compared with untreated ICH controls. Thus, select MMPs exhibit increased expression after ICH, whereas minocycline is neuroprotective after ICH by suppressing monocytoid cell activation and downregulating MMP‐12 expression.Ann Neurol 2003;53:731–742

The ependyma: A protective barrier between brain and cerebrospinal fluid

This review summarizes the current scientific literature concerning the ependymal lining of the cerebral ventricles of the brain with an emphasis on selective barrier function and protective roles for the common ependymal cell. Topics covered include the development, morphology, protein and enzyme expression including reactive changes, and pathology. Some cells lining the neural tube are committed at an early stage to becoming ependymal cells. They serve a secretory function and perhaps act as a cellular/axonal guidance system, particularly during fetal development. In the mature mammalian brain ependymal cells possess the structural and enzymatic characteristics necessary for scavenging and detoxifying a wide variety of substances in the CSF, thus forming a metabolic barrier at the brain‐CSF interface.

Experimental Intracerebral Hemorrhage in Rats Magnetic Resonance Imaging and Histopathological Correlates

BACKGROUND AND PURPOSE Intracerebral hemorrhage is associated with a considerable proportion of strokes and head injuries. The mechanism of brain cell injury associated with hemorrhage may be different from that due to pure ischemia. Therefore, it is essential that models of intracerebral hemorrhage be developed and well characterized. The purpose of this study was to obtain high-field MR images of rat brain at progressive times after induction of intracerebral hemorrhage and to correlate the images with behavior and histological evolution. METHODS Intracerebral hemorrhage was induced in rats by injection of bacterial collagenase and heparin into the caudate nucleus. Histopathological changes and corresponding MR images were studied from 30 minutes to 3 weeks after injection. Behavioral changes were also followed for 3 weeks. RESULTS Histological correlation showed that MR is capable of resolving the accumulation and degeneration of the hematoma, a centripetal wave of neutrophils infiltrating from the surrounding tissue beginning at 12 hours, and centripetal invasion of macrophages beginning at 48 hours. Widespread white matter edema was clearly evident on MR images for 1 week after the hemorrhage. Medium-sized striatal neurons were lost in the tissue surrounding the hematoma. Behavioral improvement was rapid during resolution of the edema but incomplete at 3 weeks. CONCLUSIONS MR images correlate very well with histological changes in this experimental model of intracerebral hemorrhage and can therefore be used to follow changes due to drug treatments in vivo. The intense neutrophilic response to this lesion may contribute to neuronal injury at the periphery of the hematoma.

Intracerebral injection of autologous whole blood in rats: time course of inflammation and cell death

Intracerebral hemorrhage is associated with stroke and head trauma. The purpose of this study was to study brain inflammation and cell death in adult rats 1 h to 4 weeks after injection of blood into the striatum. Terminal dUTP nick-end-labeling positive dying cells were evident 4 h to 4 weeks post-hemorrhage. Neutrophil infiltration was brief and peaked at 48 h. CD8a immunoreactive lymphocytes, possibly natural killer cells, became apparent at 48 h and persisted for 1 week. Microglial reaction was evident at 4 h and persisted for 4 weeks. We conclude that extravascular blood causes a mixed inflammatory cell reaction in brains that is maximal from 48-72 h following hemorrhage. This is associated with death of brain cells over a prolonged period of at least 4 weeks.

Expression of ataxin-2 in brains from normal individuals and patients with Alzheimer's disease and spinocerebellar ataxia 2

Spinocerebellar ataxia type 2 (SCA2) is caused by expansion of a CAG trinucleotide repeat located in the coding region of the human SCA2 gene. The SCA2 gene product, ataxin‐2, is a basic protein with two domains (Sm1 and Sm2) implicated in RNA splicing and protein interaction. However, the wild‐type function of ataxin‐2 is yet to be determined. To help clarify the function of ataxin‐2, we produced antibodies to three antigenic peptides of ataxin‐2 and analyzed the expression pattern of ataxin‐2 in normal and SCA2 adult brains and cerebellum at different developmental stages. These studies revealed that (1) both wild‐type and mutant forms of ataxin‐2 were synthesized; (2) the wild‐type ataxin‐2 was localized in the cytoplasm in specific neuronal groups with strong labeling of Purkinje cells; (3) the level of ataxin‐2 increased with age in Purkinje cells of normal individuals; and (4) ataxin‐2‐like immunoreactivity in SCA2 brain tissues was more intense than in normal brain tissues, and intranuclear ubiquitinated inclusions were not seen in SCA2 brain tissues. Ann Neurol 1999;45:232–241

Intraventricular injection of human immunodeficiency virus type 1 (HIV-1) Tat protein causes inflammation, gliosis, apoptosis, and ventricular enlargement

To determine the role of the Tat protein of the human immunodeficiency virus type 1 (HIV-1) in the pathogenesis of HIV-1 associated dementia, recombinant Tat was injected intraventricularly as a single or repeated dose into male Sprague- Dawley rats. Histopathological evaluation showed an initial infiltration of neutrophils one day after Tat injection, followed by macrophages and lymphocytes by 7 days. Tat-injected brains also exhibited astrocytosis, apoptotic cells, and ventricular enlargement 7 days following the last injection. Nuclear magnetic resonance spectroscopic analysis of tissue extracts of hippocampi from Tat-injected rats showed a decrease in the glutamate/g aminobutyric acid ratio. We conclude that the transient extracellular exposure of the central nervous system to Tat protein of HIV can cause a cascade of events leading to the influx of inflammatory cells, glial cell activation, and neurotoxicity.

Chronic hydrocephalus in rats and humans: White matter loss and behavior changes

Chronic hydrocephalus that begins in childhood and progresses only very gradually is sometimes called “arrested” hydrocephalus. Data suggest that this state eventually can become symptomatic and may be treatable by shunting. However, the pathological substrate of the disorder is not entirely understood. We studied chronic hydrocephalus in rats, 9 months after induction by kaolin injection into the cisterna magna, and in humans. In both circumstances, destruction of periventricular white matter structures was worst in those with the largest ventricles. Structures damaged include the corpus callosum, corticospinal tract, and fimbria/fornix projections from the hippocampus. Myelin turnover was increased. These changes were associated with deficits of motor and cognitive function. The cerebral cortex was largely spared. There appears to be a threshold of ventricle size beyond which functional changes manifest, but this undoubtedly is modified by factors such as age of onset and rate of enlargement. These data support the need for persistent follow‐up of patients with chronic, apparently stable hydrocephalus. A slight increase in size of already enlarged ventricles might cause significant axonal damage.

Adenosine A2A receptor activation reduces proinflammatory events and decreases cell death following intracerebral hemorrhage

The ubiquitous neuromodulator adenosine inhibits the production of several proinflammatory cytokines through activation of specific cell‐surface adenosine receptors. We demonstrated recently that antisense oligonucleotides to tumor necrosis factor‐α (TNF‐α) are neuroprotective in a rat model of intracerebral hemorrhage. Therefore, we hypothesized that activation of adenosine receptors would provide protection against intracerebral hemorrhage‐induced TNF‐α production and inflammatory events. In vitro experiments showed that adenosine A1, A2A, and A3 receptor subtypes were present on U937 cells, and activation of these subtypes inhibited TNF‐α production with a rank order of A2A >> A1 > A3. Prolonged treatment of U937 cells with the A2A receptor agonist 2‐p‐(carboxyethyl)phenethylamino‐5′‐N‐ethylcarboxamidoadenosine hydrochloride (CGS 21680) desensitized adenosine A2A, A1, and A3 receptors. CGS 21680 administration directly into the striatum immediately prior to the induction of intracerebral hemorrhage inhibited TNF‐α mRNA and, 24 hours following induction, reduced parenchymal neutrophil infiltration (p < 0.001) and TUNEL‐positive cells (p < 0.002) within and bordering the hematoma. These results suggest that pharmacological strategies targeting A2A receptors may provide effective inhibition of acute neurotoxic proinflammatory events that occur following intracerebral hemorrhage.

Efficacy of disodium 4-[(tert-butylimino)methyl]benzene-1,3-disulfonate N-oxide (NXY-059), a free radical trapping agent, in a rat model of hemorrhagic stroke.

Because free radical mechanisms may contribute to brain injury in hemorrhagic stroke, the effect of the free radical trapping agent disodium 4-[(tert-butylimino)methyl]benzene-1,3-disulfonate N-oxide (NXY-059) was investigated on outcome following intracerebral hemorrhage (ICH) in rat. ICH was induced in 20 adult rats by infusion of collagenase into the caudate-putamen. Thirty minutes later rats were treated with NXY-059 (50 mg/kg subcutaneous plus 8.8 mg/kg/h for 3 days subcutaneous delivered via implanted osmotic pumps) or saline (equivalent volumes). Magnetic resonance imaging 24 h after ICH confirmed that the hemorrhage was uniform in the two groups, and subsequent imaging at 7 and 42 days post-ICH showed that the hematoma resolved similarly in the two groups. Behavioral testing on days 1, 3, 7, 14, and 21 after ICH showed that rats treated with NXY-059 had significantly decreased neurological impairment at all times. Deficits in skilled forelimb use 4-5 weeks post-ICH, and in striatal function 6 weeks post-ICH, were not reduced by treatment with NXY-059. Treatment with NXY-059 significantly reduced the neutrophil infiltrate observed 48 h post-hemorrhage in the vicinity of the hematoma, and the number of TUNEL-positive cells 48 h post-hemorrhage at the hematoma margin. However, by 6 weeks there were no differences in neuronal densities in treated and control rats.

Fatty acid transport protein expression in human brain and potential role in fatty acid transport across human brain microvessel endothelial cells

J. Neurochem. (2011) 117, 735–746.