Geldanamycin inhibits the production of inflammatory cytokines in activated macrophages by reducing the stability and translation of cytokine transcripts.

OBJECTIVE: Heat-shock protein 90 (Hsp90) is critical in the intracellular signaling pathways that promote inflammatory cytokine production. Geldanamycin (GD) is a benzoquinone ansamycin that inhibits the function of Hsp90. GD inhibits the production of tumor necrosis factor alpha (TNFalpha) in activated macrophages and suppresses the progression of adjuvant-induced arthritis and experimental allergic encephalomyelitis in rodents. GD has been used to investigate the mechanisms by which Hsp90 regulates inflammatory cytokine production.
METHODS: The macrophage cell line RAW264.7 (or primary peritoneal macrophages) was activated with lipopolysaccharide in the absence or presence of GD. The effect of GD on the transcription, stability, and translation of inflammatory cytokine messenger RNA (mRNA) was determined using nuclear run-on assays, mRNA decay assays, and sucrose gradient polysome profiles, respectively.
RESULTS: Our data revealed that GD potently inhibits the production of TNFalpha, interleukin-6 (IL-6), and IL-1beta in activated macrophages. Although GD did not significantly reduce the transcription of inflammatory cytokine mRNA, it significantly decreased the stability of these transcripts. Polysome profiles indicated that GD also inhibited the translation of TNFalpha and IL-6 transcripts. These effects may be due, in part, to inhibition of p38 mitogen-activated protein kinase, a kinase known to regulate the stability and translation of inflammatory cytokine transcripts.
CONCLUSION: These results indicate that the function of Hsp90 is important in the posttranscriptional control of inflammatory cytokine production.