Rubratoxin-B-induced secretion of chemokine ligands of cysteine-cysteine motif chemokine receptor 5 (CCR5) and its dependence on heat shock protein 90 in HL60 cells

To elucidate the mechanism underlying rubratoxin B toxicity, the effects of rubratoxin B on the secretion of CCR5 chemokines, CCL3, CCL4, and CCL5, in a human promyelocytic leukemia cell line, HL60, were investigated. In addition, to examine whether the molecular chaperone 90-kDa heat shock protein (Hsp90) contributes to rubratoxin B toxicity, the effects of Hsp90-specific inhibitors, radicicol and geldanamycin, were investigated. Exposure to rubratoxin B for 24 h induced secretion of each CCR5 chemokine, although the effect on CCL5 secretion was modest, and it enhanced secretion of proinflammatory cytokines tumor necrosis factor-α, CXCL8, and CCL2. Concomitant treatment with radicicol abolished the rubratoxin-induced secretion of all cytokines investigated. Geldanamycin antagonized the rubratoxin B-induced effects on CCL3 and CCL5, but not CCL4; the effects of geldanamycin were less than that of radicicol. Taken together, the results suggest that rubratoxin B, with the contribution of Hsp90, induces secretion of CCR5 chemokines.