Barone FC. Arvin B. White RF. Miller A. Webb CL. Willette RN. Lysko PG. Feuerstein GZ.
Tumor necrosis factor-alpha. A mediator of focal ischemic brain injury, Stroke. 28(6) :1233-44, 1997.
Abstract
BACKGROUND AND PURPOSE: Tumor necrosis factor-alpha (TNF-alpha) is a pleiotropic cytokine that rapidly upregulates in the brain after injury. The present study was
designed to explore the pathophysiological significance of brain TNF-alpha in the ischemic brain by systematically evaluating the effects of lateral cerebroventricular administration
of exogenous TNF-alpha and agents that block the effects of TNF-alpha on focal stroke and by examining the potential direct toxic effects of TNF-alpha on cultured neurons to
better understand how TNF-alpha might mediate stroke injury. METHODS: TNF-alpha (2.5 or 25 pmol) was administered intracerebroventricularly to spontaneously
hypertensive rats 24 hours before permanent or transient (80 minutes and 160 minutes) middle cerebral artery occlusion (MCAO). Animals were examined 24 hours later for
neurological deficits and ischemic hemisphere necrosis and swelling. In some of these studies, neutralizing anti-TNF-alpha monoclonal antibody (mAb) (60 pmol) was injected
intracerebroventricularly 30 minutes before exogenous TNF-alpha (25 pmol). In addition, the effects of blocking endogenous TNF-alpha on permanent focal ischemic injury were
determined with the use of either mAb (60 pmol) or soluble TNF receptor I (sTNF-RI) (0.3 or 0.7 nmol) administered intracerebroventricularly 30 minutes before and 3 and 6
hours after MCAO. Finally, the direct neurotoxic effects of TNF-alpha were studied in cultured rat cerebellar granule cells exposed to TNF-alpha (10 to 2000 U/mL for 6 to 24
hours), and neurotransmitter release, glutamate toxicity, and oxygen radical toxicity were studied. RESULTS: TNF-alpha increased the percent hemispheric infarct induced by
permanent MCAO in a dose-related manner from 13.1 +/- 1.3% (vehicle) to 18.9 +/- 1.7% at 2.5 pmol (P < .05) and 27.1 +/- 1.3% at 25 pmol (P < .0001). The high dose of
TNF-alpha increased ischemia-induced forelimb deficits from 1.6 +/- 0.2 to 2.3 +/- 0.2 (P < 0.1). TNF-alpha (2.5 pmol) also increased the infarction induced by 80 or 160
minutes of transient MCAO from 1.9 +/- 0.9% to 4.3 +/- 0.4% (P < .01) and from 14.2 +/- 1.3% to 21.6 +/- 2.2% (P < .05), respectively. The exacerbation of infarct size,
swelling, and neurological deficit after exogenous TNF-alpha was reversed by preinjection of 60 pmol mAb. Blocking endogenous TNF-alpha also significantly reduced focal
ischemic brain injury. Treatment with 60 pmol mAb before and after permanent MCAO significantly reduced infarct size compared with control (nonimmune) antibody treatment by
20.2% (P < .05). Reduced brain infarction also was produced by brain administration of 0.3 nmol (decreased 18.2%) or 0.7 nmol (decreased 26.1%, P < .05) sTNF-RI before
and after focal stroke. The intracerebroventricular administration of TNF-alpha or sTNF-RI did not alter brain or body temperature, blood gases or pH, blood pressure, blood
glucose, or general blood chemistry. In cultured cerebellar granule cells, the application of TNF-alpha did not directly affect neurotransmitter release or glutamate or oxygen free
radical toxicity. CONCLUSIONS: These studies demonstrate that exogenous TNF-alpha exacerbates focal ischemic injury and that blocking endogenous TNF-alpha is
neuroprotective. The specificity of the action(s) of TNF-alpha was demonstrated by antagonism of its effects with specific anti-TNF-alpha tools (ie, mAb and sTNF-RI).
TNF-alpha toxicity does not appear to be due to a direct effect on neurons or modulation of neuronal sensitivity to glutamate or oxygen radicals and apparently is mediated
through nonneuronal cells. These data suggest that inhibiting TNF-alpha may represent a novel pharmacological strategy to treat ischemic stroke.
Important Points:
-Model: cultured rat cerebellar granule cells
-TNF-alpha (10 to 2000 U/mL for 6 to 24 hours), 24h before ischemia, increased neural damage
-the effect could be specifically blocked using anti-TNF antibody
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