SB 239063, a second-generation p38 mitogen-activated protein kinase inhibitor, reduces brain injury and neurological deficits in cerebral focal ischemia.

The stress-activated mitogen-activated protein kinase (MAPK) p38 has been linked to the production of inflammatory cytokines/mediators/inflammation and death/apoptosis following cell stress. In these studies, a second-generation p38 MAPK inhibitor, SB 239063 (IC(50) = 44 nM), was found to exhibit improved kinase selectivity and increased cellular (3-fold) and in vivo (3- to 10-fold) activity over first-generation inhibitors. Oral SB 239063 inhibited lipopolysaccharide-induced plasma tumor necrosis factor production (IC(50) = 2.6 mg/kg) and reduced adjuvant-induced arthritis (51% at 10 mg/kg) in rats. SB 239063 reduced infarct volume (48%) and neurological deficits (42%) when administered orally (15 mg/kg, b.i.d.) before moderate stroke. Intravenous SB 239063 exhibited a clearance of 34 ml/min/kg, a volume of distribution of 3 l/kg, and a plasma half-life of 75 min. An i.v. dosing regimen that provided effective plasma concentrations of 0.38, 0.75, or 1.5 microg/ml (i.e., begun 15 min poststroke and continuing over the initial 6-h p38 activation period) was used. Significant and dose-proportional brain penetration of SB 239063 was demonstrated during these infusion periods. In both moderate and severe stroke, intravenous SB 239063 produced a maximum reduction of infarct size by 41 and 27% and neurological deficits by 35 and 33%, respectively. No effects of the drug were observed on cerebral perfusion, hemodynamics, or body temperature. Direct neuroprotective effects from oxygen and glucose deprivation were also demonstrated in organotypic cultures of rat brain tissue. This robust in vitro and in vivo SB 239063-induced neuroprotection emphasizes the potential role of MAPK pathways in ischemic stroke and also suggests that p38 inhibition warrants further study, including protection in other models of nervous system injury and neurodegeneration.