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Human alveolar macrophage gene expression of interleukin-8 by tumor necrosis factor-alpha, lipopolysaccharide, and
R M Strieter1, S W Chensue, M A Basha
1Department of Pathology, University of Michigan Medical School, Ann Arbor.
Abstract:
The alveolar macrophage (AMO) in its pivotal position for pulmonary host defense may play a prominent role in the orchestration of polymorphonuclear leukocyte (PMN) diapedesis. We demonstrate that the human AMO may participate in these inflammatory events through the production of a novel neutrophil chemotactic factor, interleukin-8 (IL-8). The induction of AMO-derived IL-8 by tumor necrosis factor (TNF), lipopolysaccharide (LPS), and interleukin-1 (IL-1 beta) was shown to be both dose and time dependent. Maximal IL-8 gene expression, as assessed by Northern blot analyses, was achieved with 20 ng/ml and 1 microgram/ml, respectively, for each of the cytokines and LPS. A kinetic study of TNF-, IL-1 beta-, and LPS-treated AMOs showed significant steady-state IL-8 mRNA accumulation post-stimulation at 1 h, peaking by 8 h, with a decline over the next 16 h. Immunohistochemical staining using rabbit anti-human IL-8 antibody demonstrated significant immunolocalization of cell-associated IL-8 antigen at 4 h, with persistence over the next 20 h. Chemotactic bioactivity peaked by 8 h, with continued production over the next 16 h. Chemotactic bioactivity from AMO-conditioned media was inhibited by IL-8 antiserum by 2, 31, 44, and 47%, respectively, for unstimulated control, LPS-, IL-1 beta-, and TNF-treated cells. Preimmune serum had no effect on chemotactic activity. These data support the central role of the AMO in the elicitation of PMNs into the lung via the production of IL-8.
Insights
Alveolar macrophages (AMOs) produce interleukin-8 (IL-8), a neutrophil chemotactic factor, in response to inflammatory stimuli. This IL-8 production by AMOs is crucial for recruiting polymorphonuclear leukocytes (PMNs) to the lungs during host defense.
Area of Science:
- Immunology
- Pulmonary Biology
- Cellular Inflammation
Background:
- Alveolar macrophages (AMOs) are key immune cells in the lungs.
- Their role in orchestrating polymorphonuclear leukocyte (PMN) recruitment is under investigation.
Purpose of the Study:
- To investigate the role of human AMOs in PMN diapedesis.
- To determine if AMOs produce neutrophil chemotactic factors, specifically interleukin-8 (IL-8).
Main Methods:
- Stimulation of AMOs with tumor necrosis factor (TNF), lipopolysaccharide (LPS), and interleukin-1 beta (IL-1 beta).
- Assessment of IL-8 gene expression using Northern blot analysis.
- Immunohistochemical staining for cell-associated IL-8 antigen.
- Measurement of chemotactic bioactivity in conditioned media.
- Inhibition studies using IL-8 antiserum.
Main Results:
- AMO-derived IL-8 production was induced by TNF, LPS, and IL-1 beta in a dose- and time-dependent manner.
- Maximal IL-8 gene expression occurred at specific concentrations of stimuli, with mRNA accumulation peaking at 8 hours.
- Cell-associated IL-8 antigen and chemotactic bioactivity were detected and persisted over time.
- IL-8 antiserum significantly inhibited the chemotactic activity of AMO-conditioned media.
Conclusions:
- Human AMOs produce IL-8 in response to inflammatory cytokines and LPS.
- AMO-derived IL-8 plays a significant role in attracting PMNs to the lung.
- AMOs are central to initiating PMN recruitment through IL-8 production.