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Tumor necrosis factor-alpha-stimulated polymorphonuclear leukocytes suppress migration and bactericidal activity of
Patricia S Grutkoski1, Ron D'Amico, Alfred Ayala
1Division of Surgical Research, Rhode Island Hospital, and Brown University School of Medicine, Providence, USA.
Objective:
Polymorphonuclear leukocytes (PMN) and tumor necrosis factor-alpha (TNF-alpha) play prominent roles in acute respiratory distress syndrome, ischemia-reperfusion injury, trauma, and sepsis. Whereas direct effects of TNF-alpha on PMN function and viability are well documented, little data are available addressing the ability of PMN to communicate with each other in response to cytokine stimulation. Therefore, the aim of this study was to determine whether TNF-alpha can modulate PMN function by inducing PMN to secrete products upon stimulation, which would affect other PMN in vitro in a manner independent of cell contact.
Methods:
PMN were purified daily from blood obtained from a pool of 22 healthy volunteers. Conditioned media (CM-TNF) was prepared by incubating PMN in Hanks' balanced salt solution plus TNF-alpha for 1-4 hrs. Freshly isolated PMN were resuspended in CM-TNF and analyzed for 1) phagocytosis of opsonized Escherichia coli, 2) oxidative metabolism as measured as an index of DCF-DA activation, and 3) migration to chemoattractants through Transwell inserts.
Results:
CM-TNF decreased PMN phagocytotic activity by 8% to 15% and completely suppressed oxidative metabolism but did not modulate the expression of receptors associated with these functions. CM-TNF suppressed the migration of PMN to two biologically relevant agents, N-formyl-methionyl-leucyl-phenylalanine and leukotriene B4, by approximately 65%, but had no effect on PMN migration to interleukin-8. This suppression was observed for migration across plastic filters as well as extracellular matrix proteins.
Conclusion:
Our data demonstrate that PMN stimulated with TNF-alpha suppress the immunologic function and migration of other PMN independent of cell-cell contact and suggest that TNF-alpha may participate in a negative feedback loop by inducing a PMN-derived factor that counteracts its activity.
Insights
Tumor necrosis factor-alpha (TNF-alpha) stimulation induces polymorphonuclear leukocytes (PMN) to release factors that suppress the function and migration of other PMN. This suggests TNF-alpha may create a negative feedback loop in immune responses.
Area of Science:
- Immunology
- Cell Biology
Background:
- Polymorphonuclear leukocytes (PMN) and tumor necrosis factor-alpha (TNF-alpha) are key players in inflammatory conditions like sepsis and acute respiratory distress syndrome.
- While TNF-alpha's direct effects on PMN are known, how PMN communicate with each other upon cytokine stimulation is less understood.
Purpose of the Study:
- To investigate if TNF-alpha can modulate PMN function by inducing PMN to secrete factors that affect other PMN independently of cell contact.
Main Methods:
- PMN were isolated from healthy volunteers.
- Conditioned media (CM-TNF) was created by incubating PMN with TNF-alpha.
- Fresh PMN were exposed to CM-TNF and assessed for phagocytosis, oxidative metabolism, and migration.
Main Results:
- CM-TNF reduced PMN phagocytosis by 8-15% and completely suppressed oxidative metabolism.
- PMN migration to N-formyl-methionyl-leucyl-phenylalanine and leukotriene B4 was suppressed by ~65%, but not to interleukin-8.
- These suppressive effects occurred independently of cell-cell contact.
Conclusions:
- TNF-alpha-stimulated PMN release factors that suppress the immune function and migration of other PMN.
- This suggests a potential negative feedback mechanism where TNF-alpha induces a PMN-derived factor that counteracts its own activity.