Cytokine mRNA decay is accelerated by an inhibitor of p38-mitogen-activated protein kinase

Objective: To identify the site(s) in tumor necrosis factor (TNF alpha), in terleukin-6 (IL-6), and macrophage inflammatory protein-1 alpha (MIP-1 alph a) biosynthesis that is blocked by SB202190, a selective inhibitor of p38-m itogen activated protein kinase (p38). Materials: Human blood monocytes isolated by centrifugal elutriation. Methods: Monocytes were stimulated with lipopolysaccharide in the presence of 0, 0.3, 1 and 3 mu M SB202190. Induced TNF alpha; IL-6, and MIP-1 alpha protein and mRNA were measured by ELISA and quantitative RT-PCR, respective ly. The half-lives of cytokine mRNA levels were determined following treatm ent of cells with actinomycin D or SB202190, Results: SB202190 suppressed >60% of lipopolysaccharide-induced TNF alpha, IL-6, and MIP-1 alpha protein and mRNA expression. Suppressed mRNA levels c ould be attributed to a >2 to 7-fold reduction in cytokine mRNA half-lives. In contrast, SB202190 did not destabilize mRNAs encoding interferon-induce d gene 15 protein and glyceraldehyde-3-phosphate dehydrogenase. Conclusions: Specific mRNA destabilization represents an important and nove l site of action for the cytokine suppressive effects of p38 inhibitors.