HSP90 inhibition by 17-DMAG reduces inflammation in J774 macrophages through suppression of Akt and nuclear factor-κB pathways

This study was designed to determine whether inhibition of heat shock protein 90 (HSP90) reduces pro-inflammatory mediator production by decreasing the nuclear factor (NF)-kappa B and Akt signaling pathways in immune-stimulated macrophages. J774A.1 murine macrophages were treated with the HSP90 inhibitor 17-DMAG (0.01, 0.1 or 1 mu M) prior to immune stimulation with lipopolysaccharide and interferon-gamma. Expression of Akt, inhibitor of kappa B kinase (IKK), and heat shock proteins were measured in whole cell lysates by Western blotting. Phosphorylated Akt and inhibitor of kappa B (I kappa B) were measured in whole cell lysates by ELISA. Cell supernatants were analyzed for interleukin (IL)-6, tumor necrosis factor (TNF)-alpha and nitric oxide (NO). Translocation of NF-kappa B and heat shock factor (HSF)-1 was assessed by immunofluorescence. Treating cells with 17-DMAG reduced expression of Akt and IKK in immune-stimulated cells. 17-DMAG reduced nuclear translocation of NF-kappa B and reduced immune-stimulated production of IL-6, TNF-alpha and NO, but did not decrease inducible nitric oxide synthase expression. Our studies show that the immune-mediated NF-kappa B inflammatory cascade is blocked by the HSP90 inhibitor 17-DMAG. Due to the broad interaction of HSP90 with many pro-inflammatory kinase cascades, inhibition of HSP90 may provide a novel approach to reducing chronic inflammation.