In VIVO HEAT SHOCK PROTEIN ASSEMBLES WITH SEPTIC LIVER NF-κB/I-κB COMPLEX REGULATING NF-κB ACTIVITY

Abstract

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-kappaB and nuclear factor-kappaB (NF-kappaB) declined in the cytosol of liver, whereas NF-kappaB increased in nucleus. NF-kappaB activity was significantly enhanced during sepsis, and the products of NF-kappaB target genes, such as TNF-alpha and inducible nitric oxide synthase (iNOS), were overexpressed. Heat shock treatment, inducing heat shock protein synthesis, prevented down-regulation of cytosolic I-kappaB and decreased translocation of NF-kappaB into the nucleus. Therefore, the sepsis-induced acceleration of NF-kappaB activation was inhibited. Expression of TNF-alpha and iNOS mRNA was also down-regulated. Coimmunoprecipitation with anti-NF-kappaB (p65) and anti-IkappaB antibodies verified an assembling phenomenon of heat shock protein (HSP) 72 with NF-kappaB and I-kappaB. We suggest that the mechanism preventing septic activation of NF-kappaB is that oversynthesized HSP72 forms a complex with NF-kappaB/I-kappaB, thus inhibiting nuclear translocation of NF-kappaB. HSP72 appears to play a crucial protective role in modulating the gene expression controlled by NF-kappaB in sepsis.

Expression of intracellular cytokines, HSP72, and apoptosis in monocyte subsets during exertional heat stress in trained and untrained individuals

“…NF-B DNA binding in the liver (11) and intestinal epithelial/mucosal cells (56) is an important source of inflammatory mediators during endotoxemia (11, 57) before spillover into the systemic circulation (28). It is possible, however, given the findings by Belge et al (6) and others (62, 64) regarding CD14 ϩ CD16 ϩ capacity for LPS-induced TNF-␣ production in vivo, that circulating inflammatory monocytes may be contributing to the changes in circulating cytokine profiles observed during EHS (68).Induction of the stress response plays a pivotal role in the regulation of the inducible transcription factor NF-B during inflammatory insult (10,11,56,79), improving survival during hyperthermia (70) and influencing both innate and adaptive immunity (41). Intracellular heat shock protein (HSP) 72 accumulation improves heat tolerance through cytoprotective effects (22, 37) such as the reduction of heat-induced cellular apoptosis (60) and protection against ischemia-reperfusion injury (42), yet limited data exist examining differences in HSP72 expression within monocyte subsets (4, 53).…”

“…It is well documented that HSP induction within the cell can downregulate the inflammatory cascade by reducing TNF-␣ production to inflammatory stimuli (11,18,36,73,79). The mechanism responsible for the upregulation of HSP during inflammatory stimuli results from serine kinase and mitogen-activated protein kinase (MAPK) activation of the NF-B pathway, coupled with the production of reactive oxygen species and subsequent oxidative stress in the mitochondria.…”

“…We recently reported that increases in circulating TNF-␣ and endotoxin during EHS are accompanied by nuclear factor (NF)-B translocation in peripheral blood mononuclear cells, suggestive of peripheral blood inflammatory cell activation (68). NF-B DNA binding in the liver (11) and intestinal epithelial/mucosal cells (56) is an important source of inflammatory mediators during endotoxemia (11,57) before spillover into the systemic circulation (28). It is possible, however, given the findings by Belge et al (6) and others (62,64) regarding CD14 ϩ CD16 ϩ capacity for LPS-induced TNF-␣ production in vivo, that circulating inflammatory monocytes may be contributing to the changes in circulating cytokine profiles observed during EHS (68).…”

“…Induction of the stress response plays a pivotal role in the regulation of the inducible transcription factor NF-B during inflammatory insult (10,11,56,79), improving survival during hyperthermia (70) and influencing both innate and adaptive immunity (41). Intracellular heat shock protein (HSP) 72 accumulation improves heat tolerance through cytoprotective effects (22,37) such as the reduction of heat-induced cellular apoptosis (60) and protection against ischemia-reperfusion injury (42), yet limited data exist examining differences in HSP72 expression within monocyte subsets (4,53).…”

Estrogen, NFκB, and the Heat Shock Response

“…Heat shock has been shown to inhibit IKK activation, and to increase IκB-α levels both by inhibition of its phosphorylation and degradation and by increased expression (110)(111)(112). Furthermore, phosphorylation of HSP 27 by p38 leads to association with IKK in HeLa cells upon TNF-α treatment, and suppression of NFκB activity (113).…”