Regulation of neutrophil interleukin 8 gene expression and protein secretion by LPS, TNF‐α, and IL‐1β

Abstract

Neutrophils are possibly involved in the pathogenesis of various lung diseases through the release of numerous mediators. In the present study, we studied the regulation of IL-8 gene induction and protein secretion in human blood neutrophils. Northern blot analysis revealed that LPS increased IL-8 mRNA levels in neutrophils, with a maximal fivefold increase by 2 h. IL-8 mRNa levels returned to baseline values within 12 h. In contrast, LPS-stimulated monocytes demonstrated a sustained increase of IL-8 mRNA levels for more than 24 h. TNF-alpha, IL-1 beta, and phorbol myristate acetate also increased IL-8 mRNA levels in neutrophils. Immunohistochemical analysis confirmed that IL-8 was localized within stimulated neutrophils. IL-8 secretion by neutrophils and monocytes was quantified using a specific ELISA for IL-8. Resting neutrophils secreted minimal IL-8 activity. However when cells were stimulated with LPS, TNF-alpha, or IL-1B, neutrophils secreted IL-8. IL-8 secretion was most marked during the first 2 h after stimulation and decreased thereafter. In contrast, monocytes maintained a high rate of IL-8 secretion over 12 h. Although a single monocyte secreted 70-fold more IL-8 than did a single neutrophil after 4 h of incubation, the high abundance of neutrophils in peripheral blood made the neutrophil-secreted IL-8 more significant. During the first 2 h, neutrophils secreted approximately 40% of the IL-8 released by monocytes in the same volume of blood. This ratio decreased to 9% after 12 h. Neutrophil-secreted IL-8 may play an autocrine or paracrine role during the initial stage of inflammation.

Elevated serum and bronchoalveolar lavage fluid levels of interleukin 8 and granulocyte colony‐stimulating factor associated with the acute chest syndrome in patients with sickle cell disease

“…Inflammatory cytokines such as TNF-a or IL-1b released in response to infectious or other stimuli also have the ability to induce IL-8 production (Fujishima et al, 1992;Tilg et al, 1993). Even though we could not demonstrate elevated serum levels of TNF-a or IL-1b in patients with ACS, these factors may have been active locally in the lung.…”

Localization of human neutrophil interleukin-8 (CXCL-8) to organelle(s) distinct from the classical granules and secretory vesicles

“…However, over the past decade, it has become evident that neutrophils are capable of protein production. Cytokines, such as interleukin-8 (IL-8/CXCL-8) [48][49][50][51][52][53][54], and possibly also IL-1 , IL-1 receptor antagonist (IL-1ra) [55], and IL-6 [56] are produced upon stimulation with inflammatory stimuli, such as LPS. The view of the mature neutrophil as a rather static cell that is destined to exocytose its preformed granule proteins in appropriate situations has been partly re-evaluated.…”

“…The latter notion is supported by the fact that neutrophils synthesize considerable amounts of cytokines upon stimulation with certain inflammatory components or mediators. In vitro, the amount of CXCL-8 increases significantly over background levels when neutrophils are activated, e.g., by G protein-coupled receptors [48,51,115], by intracellular calcium increase [50], during phagocytosis [116], and by bacterial lipopolysaccharide [49,[117][118][119]. All these agonists/pathways induce both transcriptional and translational activation, resulting in increased levels of intracellular CXCL-8 with concomitant release of the cytokine to the surrounding milieu.…”

Lymphocyte activation after exposure to swine dust: a role of humoral mediators and phagocytic cells

“…Granulocytes have also been shown to release many of these cytokines, i.e. TNF-a, IL -1, and IL-8 upon lipopolysaccharide (LPS) stimulation [11][12][13][14][15], and monocytes can produce TNF-a [16], IL-1, [15,17,18] and IL-12 [19]. Many of these granulocytes and monocytes derived cytokines are involved in the activation of lymphocytes, either directly (IL-1, IL-6, IL-12) or indirectly (IFN-c).…”