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Rifampin affects polymorphonuclear leukocyte interactions with bacterial and synthetic chemotaxins but not
Abstract:
Three independent experimental approaches support the hypothesis that rifampin competes for receptors on polymorphonuclear leukocytes (PMLs) with small peptide chemoattractants, e.g., N-formylmethionylleucylphenylalanine (FMLP), but not with serum-derived chemoattractants (C5a). First, rifampin inhibited chemotaxis induced with FMLP but reversed the immobilization of PMLs that occurred at high FMLP concentrations. Second, rifampin competed with radiolabeled FMLP for binding sites on PMLs and displaced already-bound radiolabeled FMLP. Third, rifampin blocked and reversed the bipolar shape changes induced in PMLs by FMLP. These effects occurred at concentrations attained during rifampin therapy and were not due to rifampin toxicity. In contrast, no effect of rifampin was observed on serum-derived chemoattractants (C5a) in any of the three systems. The evidence suggests, therefore, that rifampin is a ligand for FMLP-type receptors on PMLs.
Insights
Rifampin interferes with how polymorphonuclear leukocytes (PMLs) respond to certain signals. This antibiotic acts as a ligand for N-formylmethionylleucylphenylalanine (FMLP) receptors, impacting immune cell function.
Area of Science:
- Immunology
- Pharmacology
Background:
- Polymorphonuclear leukocytes (PMLs) are crucial immune cells involved in host defense.
- Chemoattractants like N-formylmethionylleucylphenylalanine (FMLP) and complement component 5a (C5a) regulate PML function.
- Rifampin is an antibiotic commonly used to treat bacterial infections.
Purpose of the Study:
- To investigate the interaction between rifampin and chemoattractant receptors on PMLs.
- To determine if rifampin affects PML chemotaxis and signaling pathways.
Main Methods:
- Three experimental approaches were used: chemotaxis assays, radioligand binding studies, and assessment of PML shape changes.
- PMLs were exposed to FMLP and/or rifampin, and their responses were measured.
- Competition assays were performed using radiolabeled FMLP and C5a.
Main Results:
- Rifampin inhibited FMLP-induced chemotaxis and reversed PML immobilization at high FMLP concentrations.
- Rifampin competed with radiolabeled FMLP for binding sites on PMLs and displaced bound FMLP.
- Rifampin blocked and reversed FMLP-induced bipolar shape changes in PMLs.
- Rifampin did not affect responses to C5a.
Conclusions:
- Rifampin acts as a ligand for FMLP-type receptors on PMLs.
- These interactions occur at therapeutic concentrations of rifampin and are not due to toxicity.
- Rifampin's effects on PMLs may have implications for immune responses during treatment.