CYTOKINE MRNA DECAY IS ACCELERATED BY AN INHIBITOR OF P38-MITOGEN-ACTIVATED PROTEIN KINASE

Objective: To identify the site(s) in tumor necrosis factor (TNFα), interleukin-6 (IL-6), and macrophage inflammatory protein-1α (MIP-1α) biosynthesis that is blocked by SB202190, a selective inhibitor of p38-mitogen 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 μM SB202190. Induced TNFα, IL-6, and MIP-1α protein and mRNA were measured by ELISA and quantitative RT-PCR, respectively. The half-lives of cytokine mRNA levels were determined following treatment of cells with actinomycin D or SB202190. ¶Results: SB202190 suppressed >60% of lipopolysaccharide-induced TNFα, IL-6, and MIP-1α protein and mRNA expression. Suppressed mRNA levels could be attributed to a >2 to 7-fold reduction in cytokine mRNA half-lives. In contrast, SB202190 did not destabilize mRNAs encoding interferon-induced gene 15 protein and glyceraldehyde-3-phosphate dehydrogenase. ¶Conclusions: Specific mRNA destabilization represents an important and novel site of action for the cytokine suppressive effects of p38 inhibitors.