title: The inhibition of LPS-induced production of inflammatory cytokines by HSP70 involves inactivation of the NF-kappaB pathway but not the MAPK pathways.
abstract: The objective of this study was to evaluate the negative regulatory role of heat shock protein 70 (HSP70) on endotoxin-induced activation of inflammatory cytokine signaling pathways in a macrophage cell line. Our studies show that elevation of HSP70 either by activation of the heat shock response (HSR) or through forced expression of the hsp70.1 gene downregulates cytokine expression. Our experiments showed that activation of the HSR and HSP70 overexpression could inhibit LPS-mediated expression of the proinflammatory cytokines TNF-alpha and IL-1 at the mRNA and protein levels. We also investigated the effects of HSP70 elevation on signaling pathways downstream of LPS and its receptors, including the NF-kappaB and mitogen-activated protein kinase (MAPK) pathways. The effects of HSP70 on cytokine expression were correlated with its effects on activation of NF-kappaB, a known activator of the tnfalpha and Il-1 genes. Overexpression of HSP70 inhibited the nuclear translocation of p65, the transcriptionally active component of the NF-kappaB complex, and prevented the degradation of IkappaBalpha, the regulator of NF-kappaB activity. However, HSP70 elevation did not markedly inhibit signaling through the MAPK arm of the LPS-induced pathway, suggesting that the effects of HSP70 are mediated primarily through the NF-kappaB cascade. Our experiments therefore suggested that elevated levels of HSP70 inhibit LPS-induced production of inflammatory cytokines by a mechanisms involving inactivation of NF-kappaB but cast doubt on significant role for the MAPK pathway in these effects.
authors.affiliation: Laboratory of Shock, Department of Pathophysiology, Xiangya School of Medicine, Central South University, Changsha, Hunan 410008, People's Republic of China.
authors.forename: Yongzhong
authors.initials: Y
authors.lastname: Shi
authors.forename: Zizhi
authors.initials: Z
authors.lastname: Tu
authors.forename: Daolin
authors.initials: D
authors.lastname: Tang
authors.forename: Huali
authors.initials: H
authors.lastname: Zhang
authors.forename: Meidong
authors.initials: M
authors.lastname: Liu
authors.forename: Kangkai
authors.initials: K
authors.lastname: Wang
authors.forename: Stuart K
authors.initials: SK
authors.lastname: Calderwood
authors.forename: Xianzhong
authors.initials: X
authors.lastname: Xiao
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D016207:Cytokines / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D018840:HSP70 Heat-Shock Proteins / Q000502:physiology*; D018869:Heat-Shock Response / Q000502:physiology; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D007375:Interleukin-1 / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000502:physiology*; D051996:Transcription Factor RelA / Q000378:metabolism; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism
chemical_list: D016207:Cytokines; D018840:HSP70 Heat-Shock Proteins; D020672:I-kappa B Proteins; D007375:Interleukin-1; D008070:Lipopolysaccharides; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; C440499:lipopolysaccharide, Escherichia coli O111 B4; D000072000:NF-KappaB Inhibitor alpha; D020928:Mitogen-Activated Protein Kinases; D010744:Phosphoric Monoester Hydrolases