Diverse regulatory activity of human heat shock proteins 60 and 70 on endotoxin-induced inflammation

Tissue injury is often associated with bacterial infection. Intracellular heat shock proteins (HSPs) are released from damaged tissue, come in contact with cells of the immune system, and might affect the immune response against bacteria. In the present study, we investigated the capacity of highly purified human HSP60 and HSP70 to modulate the response of human peripheral blood-derived mononuclear cells (PBMC) to lipopolysaccharide (LPS). HSP70 but not HSP60 decreased the LPS-induced secretion of TNF-α when added simultaneously with LPS. In contrast, HSP60 and HSP70 primed PBMC for enhanced secretion of TNF-α when added 24 h prior to the stimulation with LPS. Neither HSP60 nor HSP70 alone induced the release of TNF-α. The capacity of LPS to bind to monocytes was not affected by HSPs, but HSP70 increased the expression of Toll-like receptor 4. Thus, HSP60 and HSP70 released upon tissue damage might play a role in the regulation of bacteria-induced inflammation.