title: Implications of proteasome inhibition: an enhanced macrophage phenotype.
abstract: The objective of this study was to elucidate the role of the cellular proteasome on endotoxin-mediated activation of the macrophage. To study this role, THP-1 cells were stimulated with lipopolysaccharide (LPS) with selective cells being pretreated with the proteasome inhibitor, lactacystin or MG-132. LPS stimulation led to the phosphorylation and degradation of IRAK, followed by activation of JNK/SAPK, ERK 1/2, and p38. Subsequently, LPS induced the degradation of IkappaB, and the nuclear activation of NF-kappaB and AP-1. Activation of these pathways was associated with the production of IL-6, IL-8, IL-10, and TNF-alpha. Proteasome inhibition with either lactacystin or MG-132 attenuated LPS-induced IRAK degradation, and enhanced activation of JNK/SAPK, ERK 1/2, and p38. Proteasome inhibition, also, led to increased LPS-induced AP-1 activation, and attenuated LPS-induced IkappaB degradation resulting in abolished NF-kappaB activation. Proteasome inhibition led to significant modulation of LPS-induced cytokine production; increased IL-10, no change in IL-6, and decreased IL-8, and TNF-alpha. Thus, this study demonstrates that cellular proteasome is critical to regulation of LPS-induced signaling within the macrophage, and inhibition of the proteasome results in a conversion to an anti-inflammatory phenotype.
authors.affiliation: Department of Surgery, University of Cincinnati, 231 Albert Sabin Way, ML 558 Cincinnati, OH 45267-0558, USA. cuschij@ucmail.uc.edu
authors.forename: Joseph
authors.initials: J
authors.lastname: Cuschieri
authors.forename: David
authors.initials: D
authors.lastname: Gourlay
authors.forename: Iris
authors.initials: I
authors.lastname: Garcia
authors.forename: Sandra
authors.initials: S
authors.lastname: Jelacic
authors.forename: Ronald V
authors.initials: RV
authors.lastname: Maier
mesh_terms: D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000502:physiology*; D004731:Endotoxins / Q000494:pharmacology; D004789:Enzyme Activation; D006801:Humans; D051550:I-kappa B Kinase; D053592:Interleukin-1 Receptor-Associated Kinases; D016209:Interleukin-8 / Q000096:biosynthesis; D008262:Macrophage Activation; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000502:physiology*; D016328:NF-kappa B / Q000378:metabolism; D010641:Phenotype; D046988:Proteasome Endopeptidase Complex; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis
chemical_list: D004731:Endotoxins; D016209:Interleukin-8; D009097:Multienzyme Complexes; D016328:NF-kappa B; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D011494:Protein Kinases; D053592:Interleukin-1 Receptor-Associated Kinases; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; D020928:Mitogen-Activated Protein Kinases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex