In vivo heat shock protein assembles with septic liver NF-κB/I-κB complex regulating NF-κB activity

This study elucidates the mechanism through which heat shock treatment influences the outcome of sepsis. Post-heat shock sepsis was induced in rats by CLP 24 h after whole-body hyperthermia. Liver cytosolic and nuclear fractions were collected and analyzed in early and late sepsis rats (sacrificed 9 and 18 h after CLP, respectively). During sepsis, levels of I-kappa B and nuclear factor-kappa B (NF-kappa B) declined in the cytosol of liver, whereas NF-kappa B increased in nucleus. NF-kappa B activity was significantly enhanced during sepsis, and the products of NF-kappa B target genes, such as TNF-alpha and inducible nitric oxide synthase (NOS), were overexpressed. Heat shock treatment, inducing heat shock protein synthesis, prevented down-regulation Of cytosolic I-kappa B and decreased translocation of NF-kappa B into the nucleus. Therefore, the sepsisinduced acceleration of NF-kappa B activation was inhibited. Expression of TNF-a and NOS mRNA was also down-regulated. Coirnmunoprecipitation with anti-NF-kappa B (p65) and anti-I kappa B antibodies verified an assembling phenomenon of heat shock protein (HSP) 72 with NF-kappa B and I-kappa B. We suggest that the mechanism preventing septic activation of NF-kappa B is that oversynthesized HSP72 forms a complexwith NF-kappa B/l-kappa B, thus inhibiting nuclear translocation of NF-kappa B. HSP72 appears to play a crucial protective role in modulating the gene expression controlled by NF-kappa B in sepsis.