Molecular Mechanism By Which HSP70 Inhibits LPS-induced Expression Of Inflammatory Cytokines

In order to understand better the mechanism by which heat shock protein 70 (HSP70) negatively regulates endotoxin-induced production of proinflammatory cytokine, we investigated the effect of HSP70 on activation of inflammatory cytokine signaling pathways in RAW264.7 mouse macrophage cell line.Studies showed that elevation of HSP70 either by activation of the heat shock response (HSR) or through forced expression of the hsp70.1 gene down-regulated cytokine expression in RAW264.7 murine macrophages. Our experiments showed that activation of the HSR and HSP70 overexpression could inhibit lipopolysacchearide (LPS) mediated expression of proinflammatory cytokines such as tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β) and interleukin-15 (IL-15) at both mRNA and protein levels.There are several well-characterized signaling pathways that are likely to be involved in critical infection. Of these, the MAPK pathways might play exceptionally important roles because of the rapidity of activation and its unique regulation. So we investigated the effects of HSP70 elevation on MAPK signaling pathways. However, the result showed that HSP70 elevation had no marked effect on the LPS-induced phosphorylation of ERK, JNK, p38 MAPKs. Meanwhile, we designed bio-labelling DNA probe that could bind with transcription factor AP-1 to analyze the DNA binding activity of AP-1, a downstream transcription factor of MAPK. The result of electrophoretic mobility shift assay (EMSA) suggested that elevation of HSP70 had no marked effect on LPS-induced DNA binding activity of AP-1. Thus the inhibitory effect of HSP70 on LPS-induced inflammatory cytokine production appeared not...