Through experiments performed in vivo, using a water-soluble, less toxic hsp90-specific inhibitor, 17-DMAG, we show that hsp90 inhibition decreases proinflammatory cytokine production and alleviates LPS-induced liver injury. Previous limitations for in vivo use of geldanamycin and its derivatives have been their dose-limiting toxicity, leading to weight loss, hematologic, hepatic, and renal toxicity, and cell death.38, 39 Pharmacodynamic studies showed that the medium tolerated dose of 17-DMAG in vivo is 75 mg/kg with minimal toxicity.40, 41 Here, we used a single dose of 17-DMAG, ranging from 2.5 mg/kg to 30

mg/kg, with less concern Bafilomycin A1 research buy for nonspecific or toxic effects. Our data here suggest hsp90 as an attractive therapeutic target in liver diseases. Although

inhibitors of hsp90 were primarily identified for their therapeutic importance in cancer, their role in inflammatory diseases,42 such as rheumatoid arthritis,28 endotoxin-mediated uveitis,18 sepsis,43 and atherosclerosis,44, 45 is emerging. Because LPS-mediated this website inflammatory responses are crucial to the development of liver diseases, strategies that prevent this response in the liver could have a beneficial effect. The inhibitory function of hsp90 inhibitors on liver inflammatory responses could be a dual mechanism: either loss of client proteins resulting (-)-p-Bromotetramisole Oxalate from loss of chaperone function19, 21 or induction of anti-inflammatory transcription factor HSF1 and hsp70 expression.46 Here, we report that inhibition of hsp90 in the liver induces HSF1 and inhibits LPS-induced NFκB activation and proinflammatory cytokine production, thereby alleviating liver injury (Fig. 8). The chaperone function of

hsp90 on LPS-signaling intermediates explains its effect on the expression of down-stream proinflammatory cytokines. In this context, 17-DMAG could affect the transcription of cytokine genes and their production. We observed that the proinflammatory cytokines, TNFα and IL-6, were significantly inhibited, both at the mRNA and protein level, in whole livers treated with 17-DMAG and LPS. Concomitant reduction of serum TNFα and IL-6 paralleled the liver cytokine profile. We predict that hsp90 inhibition in the liver alters LPS-signaling events proximal to proinflammatory cytokine gene transcription. The transcription factor, NFκB, is a key downstream signaling intermediate of the LPS receptors, CD14 and TLR4. Earlier studies showed that 17-DMAG reduces NFκB activity in respiratory epithelial cells,47 either directly or through inhibition of upstream the LPS receptors, CD14 and TLR4.14 Hsp90 associates with the LPS receptor complex,14 and its inhibition decreases CD14 expression.48 Our results showed significant down-regulation in CD14 mRNA without changes in TLR4 mRNA in the liver.