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PMN stimulation by factors from IL-1-treated human synovial cell cultures
M L Watson1, G P Lewis, J Westwick
1Department of Pharmacology, Royal College of Surgeons, London, UK.
Abstract:
Following exposure of cultured human synovial cells to human recombinant interleukin 1 alpha (IL-1 alpha), we demonstrate the appearance of factors in the supernatant which stimulate human polymorphonuclear leukocyte (PMN) locomotion and elevate intracellular free calcium ([Ca++]i). The production of these factors can be abolished by actinomycin D or dexamethasone but not by cyclo-oxygenase or lipoxygenase inhibitors. In vivo, the supernatant induces a rapid accumulation of PMNs in rabbit skin following intradermal injection. These activities were not due to IL-1 itself, tumour necrosis factor (TNF alpha) or granulocyte-macrophage colony-stimulating factor (GM-CSF). Such factors may play an important role in inflammatory responses involving IL-1.
Insights
Interleukin 1 alpha (IL-1 alpha) exposure causes human synovial cells to release factors that attract polymorphonuclear leukocytes (PMNs) and increase intracellular calcium. These factors are crucial in IL-1-mediated inflammatory responses.
Area of Science:
- Immunology
- Cell Biology
- Inflammation Research
Background:
- Interleukin 1 alpha (IL-1 alpha) is a key mediator in inflammatory processes.
- Synovial cells play a role in joint inflammation.
- Polymorphonuclear leukocytes (PMNs) are critical immune cells involved in acute inflammation.
Purpose of the Study:
- To investigate the factors released by human synovial cells upon stimulation with IL-1 alpha.
- To determine the effect of these factors on PMN behavior and intracellular calcium levels.
- To assess the in vivo relevance of these IL-1 alpha-induced factors in an inflammatory model.
Main Methods:
- Cultured human synovial cells were exposed to human recombinant IL-1 alpha.
- Supernatants were analyzed for factors affecting PMN locomotion and intracellular calcium ([Ca++]i).
- In vivo studies involved intradermal injection of supernatants into rabbit skin to assess PMN accumulation.
Main Results:
- IL-1 alpha exposure induced the release of factors stimulating PMN locomotion and elevating [Ca++]i.
- Factor production was inhibited by actinomycin D and dexamethasone, but not by cyclo-oxygenase or lipoxygenase inhibitors.
- In vivo, supernatants caused rapid PMN accumulation in rabbit skin.
- The observed activities were distinct from IL-1 alpha, tumor necrosis factor alpha (TNF alpha), and granulocyte-macrophage colony-stimulating factor (GM-CSF).
Conclusions:
- Human synovial cells stimulated with IL-1 alpha produce novel factors that enhance PMN activity.
- These factors contribute to the inflammatory cascade initiated by IL-1.
- The findings suggest a significant role for these factors in IL-1-driven inflammatory conditions.