Tumour necrosis factor alpha induces only minor inflammatory changes in the central nervous system, but augments experimental meningitis

Abstract

Although tumour necrosis factor α is said to play a key role in bacterial meningitis and other CNS diseases, the effects of this proinflammatory cytokine have only been studied in part and incompletely understood. In a rat model, we investigated the effect of intracisternal injection of recombinant rat specific tumour necrosis factor α (5, 35, 70 and 280 μg tumour necrosis factor α) (i) alone, (ii) combined with pneumococcal cell wall components, on regional cerebral blood flow, intracranial pressure, white blood cell count in the cerebrospinal fluid, and brain water content. Tumour necrosis factor α dose-dependently caused an increase in regional cerebral blood flow (up to 221±43% of baseline values) over the six hours observation period and mild cerebrospinal fluid leukocytosis; intracranial pressure and brain water content were unchanged. Hypothesizing that regional cerebral blood flow changes are dependent on nitric oxide, tumour necrosis factor α induced regional cerebral blood flow increase was abolished by Aminoguanidine, a selective inhibitor of inducible nitric oxide synthase. Combination of the lowest tumour necrosis factor α dose and a low dose pneumococcal cell wall preparation magnified the inflammatory effect of either. We conclude that intrathecally-injected tumour necrosis factor α alone results in only minor inflammatory changes, whereas it augments dramatically experimental meningitis.