Pneumococcal meningitis in the rat: evaluation of peroxynitrite scavengers for adjunctive therapy

We evaluated the effect of different peroxynitrite scavengers for adjunctive therapy of experimental bacterial meningitis. Twenty hours after intracisternal injection of Streptococcus pneumoniae, rats were treated with ceftriaxone [100 mg/kg intraperitoneal (i.p.)] and either urate (300 mg/kg i.p.), Mn(III)tetrakis(4-benzoic acid)porphyrin (MnTBAP, 15 mg/kg i.p.), ascorbate (100 mg/kg i.p.), or urate (300 mg/kg i.p.) + ascorbate (100 mg/kg i.p.). Six hours after initiation of treatment, the cerebrospinal fluid (CSF) pleocytosis was significantly (p<0.05) reduced by urate (8697 +/- 1526 cells/microl) and MnTBAP (8542 +/- 4059 cells/microl) vs. ceftriaxone alone (15,793 +/- 3202 cells/microl). Brain concentrations of proinflammatory cytokines [interleukin-1beta (IL-beta), interleukin-6 (IL-6), and macrophage inflammatory protein-2 (MIP-2)] were also reduced by urate and MnTBAP. The intracranial hypertension was significantly reduced by MnTBAP (14.0 +/- 5.4 mm Hg), but not by urate (25.5 +/- 7.1 mm Hg) vs. ceftriaxone alone (22.5 +/- 5.9 mm Hg). Ascorbate alone had no effect on CSF pleocytosis (15,775 +/- 7058 cells/microl), intracranial pressure (25.6 +/- 8.8 mm Hg), and brain cytokine concentrations. However, the combination of urate and ascorbate was as effective as MnTBAP (CSF pleocytosis: 5392 +/- 4232 cells/microl, intracranial pressure: 13.3 +/- 6.9 mm Hg).