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Polymorphonuclear leucocyte (PMN)-derived inflammatory cytokines--regulation by oxygen tension and extracellular
A Derevianko1, R D'Amico, H Simms
1Department of Surgery, Rhode Island Hospital/Brown University School of Medicine, Providence, USA.
Abstract:
The kinetics of IL-8, tumour necrosis factor-alpha (TNF-alpha) and IL-1 beta release by PMN adhered to fibronectin, laminin or plastic for 24 h in response to continuous stimulation with lipopolysaccharide (LPS; 50 ng/ml), N-formyl-Met-Leu-Phe (fMLP; 100 mM), or phorbol myristate acetate (PMA; 10 ng/ml), was investigated under altered oxygen tension conditions. Cell supernatants were sampled for cytokine content every 6 h and measured by ELISA. IL-8 was the most abundant cytokine, produced in a range of up to 5.4 ng/ml; TNF-alpha and IL-1 beta were produced in a range of up to 1 ng/ml. During normoxia, LPS was the most potent stimulus, inducing the release of each cytokine, while fMLP showed a less pronounced effect on IL-8 and IL-1 beta production and markedly inhibited TNF-alpha production. PMA markedly suppressed IL-8 and IL-1 beta release and failed to induce any release of TNF-alpha. Hypoxia had an overall inhibitory effect on cytokine release except for PMA-induced IL-1 beta release, and hypoxia/reoxygenation had a significant up-regulating effect except for a further inhibition of fMLP-induced release of TNF-alpha. Integrinmatrix protein ligation differentiated both spontaneous and externally induced cytokine release and its sensitivity to alteration in oxygen tension. Thus the process of PMN elaboration of inflammatory cytokines is controlled on multiple levels of signal transduction, differentiated by integrin-extracellular matrix interactions, and is sensitive to alterations in microenvironmental oxygen tension.
Insights
Investigating inflammatory cytokine release from neutrophils (PMN) under varying oxygen levels revealed that lipopolysaccharide (LPS) is a potent stimulus. Integrin-matrix interactions and oxygen tension significantly control cytokine production.
Area of Science:
- Immunology
- Cell Biology
- Physiology
Background:
- Neutrophils (PMN) play a critical role in inflammatory responses.
- Cytokine release from PMN is a key component of inflammation.
- Oxygen tension is a crucial microenvironmental factor influencing cellular functions.
Purpose of the Study:
- To investigate the kinetics of IL-8, TNF-alpha, and IL-1 beta release by PMN.
- To examine the influence of oxygen tension on cytokine release.
- To understand the role of integrin-matrix interactions in modulating PMN inflammatory responses.
Main Methods:
- PMN were adhered to fibronectin, laminin, or plastic and stimulated with LPS, fMLP, or PMA.
- Cytokine release was measured by ELISA at 6-hour intervals over 24 hours.
- Experiments were conducted under normoxia, hypoxia, and hypoxia/reoxygenation conditions.
Main Results:
- IL-8 was the most abundant cytokine released, followed by TNF-alpha and IL-1 beta.
- Lipopolysaccharide (LPS) was the most potent stimulus under normoxia.
- Hypoxia generally inhibited cytokine release, while hypoxia/reoxygenation had a variable effect.
- Integrin-matrix protein ligation modulated both spontaneous and induced cytokine release and its sensitivity to oxygen tension.
Conclusions:
- PMN cytokine elaboration is regulated by multiple signaling pathways.
- Integrin-extracellular matrix interactions are critical in differentiating cytokine release.
- Microenvironmental oxygen tension significantly impacts PMN inflammatory cytokine production.