SB 239063, a Potent p38 MAP Kinase Inhibitor, Reduces Inflammatory Cytokine Production, Airways Eosinophil Infiltration, and Persistence

Abstract

The anti-inflammatory/antiallergic activity of a novel second-generation p38 mitogen-activated protein kinase inhibitor, SB 239063 [trans-1-(4-hydroxycyclohexyl)-4-(4-fluorophenyl)-5-(2-methoxypyridimidin-4-yl)imidazole], was investigated in vivo and in vitro. SB 239063 had an IC₅₀ of 44 nM for inhibition of recombinant purified human p38α. In lipopolysaccharide-stimulated human peripheral blood monocytes, SB 239063 inhibited interleukin-1 and tumor necrosis factor-α production (IC₅₀ values = 0.12 and 0.35 μM, respectively). A role for p38 kinase in cytokine-associated inflammation in the mouse was shown by p38 activation in the lung and inhibition of lipopolysaccharide-induced tumor necrosis factor-α production by SB 239063 (ED₅₀ = 5.8 mg/kg p.o.). Antiallergic activity was demonstrated by essential abolition (∼93% inhibition) of inhaled ovalbumin (OA)-induced airway eosinophilia by SB 239063 (12 mg/kg p.o.), measured by bronchoalveolar lavage (BAL) in OA-sensitized mice. In addition, p38 kinase was found by Western analysis to be activated in guinea pig lung. Administration of SB 239063 (10 or 30 mg/kg p.o.) in conscious guinea pigs markedly reduced (∼50% inhibition) OA-induced pulmonary eosinophil influx, measured by BAL 24 h after antigen. SB 239063 (10 mg/kg b.i.d. p.o.) administered after leukotriene D₄ inhalation, reduced by 60% the persistent airway eosinophilia seen at 4 days. Apoptosis of cultured eosinophils isolated from guinea pig BAL was increased by SB 239063 (1–10 μM) in the presence of interleukin-5. These results indicate that SB 239063 is a potent inhibitor of inflammatory cytokine production, inhibits eosinophil recruitment, in addition to enhancing apoptosis of these cells. Collectively, the results support the potential utility of p38 kinase inhibitors, such as SB 239063, for the treatment of asthma and other inflammatory disorders.