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Byline: Uwe Senftleben (1) Keywords: Nuclear factor-IoB; Signal transduction; Inflammation; Sepsis/SIRS; Multiple organ failure; Pyrrolidine dithiocarbamate Author Affiliation: (1) Department of Anesthesiology and Intensive Care, University of Ulm, Steinhovelstrasse 9, 89075 , Ulm, Germany Article History: Received Date: 27/06/2003 Accepted Date: 15/07/2003 Online Date: 04/09/2003

Research demonstrates that p38alpha mitogen-activated protein kinase activity is stimulated by environmental and hematopoietic growth factors in line with general activation of specialized signal transduction pathways. Results show that the kinase links developmental and stress-induced erythropoiesis through erythropoietin expression.

Activation of NF-κB is known to prevent apoptosis but may also act as proapoptotic factor in order to eliminate inflammatory cells. Here, we show that classical NF-κB activation in RAW 264.7 and bone marrow-derived macrophages upon short E. coil coculture is necessary to promote cell death at late time points. At 48 hours subsequent to short-term, E. coli challenge increased survival of NF-κB-suppressed macrophages was associated with pattern of autophagy whereas macrophages with normal NF-κB signalling die. Cell death of normal macrophages was indicated by preceding downregulation of autophagy associated genes atg5 and bedin1. Restimulation of macrophages with LPS at 48 hours after E. coil treatment results in augmented proinflammatory cytokine production in NF-κB-suppressed macrophages compared to control cells. We thus demonstrate that classical NF-κB activation inhibits autophagy and promotes delayed programmed cell death. This mechanism is likely to prevent the recovery of inflammatory cells and thus contributes to the resolution of inflammation. [ABSTRACT FROM AUTHOR]

Investigates the role of enzyme IKB kinase (IKK) alpha in canonical nuclear factor kappa B (NF-[sub K]B) activation pathway. B cells maturation; Formation of secondary lymphoid organs; Expression of NF-[sub k]B target genes; Processing of NF-[sub K]B2 precursors; Phosphorylation of NF-[sub K]B2.

Sepsis induces extensive lymphocyte apoptosis that contributes to immunosuppression and mortality. Activation of the canonical NF-kappaB pathway, however, prevents TNF-alpha-induced lymphocyte apoptosis. In this study the function of canonical NF-kappaB in T cells was studied in the context of murine sepsis. Upon cecal ligation and puncture (CLP), NF-kappaB DNA binding activity in thymocytes declines relative to sham-operated mice. This decline in NF-kappaB activity is most likely due to posttranslational modifications such as deacetylation of p65. In parallel, cleavage of procaspase-3 is increased, whereas expression of NF-kappaB-dependent antiapoptotic genes Bcl-xL and c-IAP2 is suppressed upon sepsis induction. Interestingly, adoptive transfer of IkappaBalpha-deficient fetal liver stem cells into sublethally irradiated lymphopenic host mice reduced the decline in thymocyte survival, increased peripheral T cell numbers, and improved the mortality rate relative to wild-type reconstituted hosts after cecal ligation and puncture. In conclusion, lymphocyte-directed augmentation of canonical NF-kappaB ameliorates immunosuppression during murine sepsis. These data provide evidence for a new approach in sepsis therapy.

NF-kappaB is a crucial mediator of macrophage inflammatory responses, but its role in the context of pathogen-induced adaptive immune responses has yet to be elucidated. Here, we demonstrate that classical NF-kappaB activation delays phagocytosis-induced cell death (PICD) in Raw 264.7 and bone marrow-derived macrophages (BMDMs) upon ingestion of bacteria from the Escherichia coli laboratory strain Top10. By expression of a nondegradable form of IkappaBalpha (superrepressor) and pyrrolidine dithiocarbamate treatment, prolonged activation of NF-kappaB upon bacterial coculture is suppressed, whereas initial induction is only partially inhibited. This activation pattern results in partial inhibition of cellular activation and reduced expression of costimulatory CD86. Notably, suppression of classical NF-kappaB activation does not influence bacterial uptake rates but is followed by increased production of oxygen radicals and enhanced intracellular killing in Raw macrophages. This is associated with reduced expression of NF-kappaB-dependent antiapoptotic c-IAP-2 and a loss of the mitochondrial transmembrane potential. Accordingly, NF-kappaB inhibition in Raw cells and BMDMs causes increased apoptotic rates within 12 h of bacterial ingestion. Interestingly, accelerated eradication of E. coli in NF-kappaB-inhibited macrophages is associated with reduced antigen-specific T-cell activation in macrophage-lymphocyte cocultures. These data suggest that E. coli inhibits PICD of macrophages via classical, antiapoptotic NF-kappaB activation and thus facilitates signaling to T cells. Subsequently, a proper adaptive immune response is likely to be generated. Conclusively, therapeutic inhibition of classical NF-kappaB activation in macrophages may hamper the initiation of adaptive immunity.