HMGB1 and LPS induce distinct patterns of gene expression and activation in neutrophils from patients with sepsis-induced acute lung injury.

Objectives: Circulating levels of the proinflammatory mediator High Mobility Group Box Protein 1 (HMGB1) are increased in septic patients and may contribute to sepsis-induced organ dysfunction. Although HMGB1 has been shown to activate neutrophils from healthy volunteers, the responses of neutrophils from septic patients to HMGB1 have not been reported. In the present study we evaluated gene expression and activation of major intracellular signaling pathways in peripheral blood neutrophils obtained from patients with sepsis-induced acute lung injury after culture with HMGB1 or LPS.

Functional and genomic changes induced by alveolar transmigration in human neutrophils.

Although the accumulation of neutrophils in the lungs and airways is common to many inflammatory lung diseases, including acute lung injury, the alterations that neutrophils undergo as they leave the peripheral circulation and migrate into the lungs have not been well characterized. Human volunteers were exposed to endotoxin by bronchoscopic instillation. The resulting air space neutrophil accumulation and peripheral blood neutrophils were isolated 16 h later, compared with circulating neutrophils isolated before or after to the pulmonary endotoxin exposure, and compared with circulating neutrophils exposed to endotoxin in vitro.

Peripheral blood neutrophil activation patterns are associated with pulmonary inflammatory responses to lipopolysaccharide in humans.

Increased nuclear accumulation of NF-kappaB in LPS-stimulated peripheral blood neutrophils has been shown to be associated with more severe clinical course in patients with infection associated acute lung injury. Such observations suggest that differences in neutrophil response may contribute to the pulmonary inflammation induced by bacterial infection. To examine this question, we sequentially measured LPS-induced DNA binding of NF-kappaB in neutrophils collected from healthy humans on at least three occasions, each separated by at least 2 wk, and then determined pulmonary inflammatory responses after instillation of LPS into the lungs.

Variant IRAK-1 haplotype is associated with increased nuclear factor-kappaB activation and worse outcomes in sepsis.

Rationale: The IL-1 receptor-associated kinase (IRAK-1) plays a central role in TLR2- and TLR4-induced activation of nuclear factor (NF)-kappaB, a critical event in the transcriptional regulation of many sepsis-associated proinflammatory mediators. There are two haplotypes for the IRAK-1 gene in Caucasians, with the variant haplotype consisting of five intron single-nucleotide polymorphisms (SNPs) and three exon SNPs.

Objectives: To examine the functional significance of the IRAK-1 variant haplotype in modifying nuclear translocation of NF-kappaB and affecting outcomes from sepsis.

High mobility group box 1 protein interacts with multiple Toll-like receptors.

High mobility group box 1 (HMGB1), originally described as a DNA-binding protein, can also be released extracellularly and functions as a late mediator of inflammatory responses. Although recent reports have indicated that the receptor for advanced glycation end products (RAGE) as well as Toll-like receptor (TLR)2 and TLR4 are involved in cellular activation by HMGB1, there has been little evidence of direct association between HMGB1 and these receptors. To examine this issue, we used fluorescence resonance energy transfer (FRET) and immunoprecipitation to directly investigate cell surface interactions of HMGB1 with TLR2, TLR4, and RAGE.

Involvement of toll-like receptors 2 and 4 in cellular activation by high mobility group box 1 protein.

High mobility group box 1 (HMGB1) protein, originally described as a DNA-binding protein that stabilizes nucleosomes and facilitates transcription, can also be released extracellularly during acute inflammatory responses. Exposure of neutrophils, monocytes, or macrophages to HMGB1 results in increased nuclear translocation of NF-kappaB and enhanced expression of proinflammatory cytokines. Although the receptor for advanced glycation end products (RAGE) has been shown to interact with HMGB1, other putative HMGB1 receptors are known to exist but have not been characterized.