Related Experiment Videos
Felodipine-induced inhibition of polymorphonuclear leukocyte functions
1Department of Medical Biochemistry, University of Leiden, Sylvius Laboratories, The Netherlands.
Abstract:
Felodipine inhibits fMet-Leu-Phe or ionophore A23187-induced exocytosis in rabbit peritoneal polymorphonuclear leukocytes (PMNs), in the concentration range 1-50 microM. Activation of the metabolic burst, and migration of PMNs towards fMet-Leu-Phe are equally inhibited by felodipine in the same concentration range. The effect is not due to blocking of calcium channels in the plasma membrane, because the degree of inhibition remains the same when Ca2+ is omitted from the medium. Felodipine interferes with ionophore A23187-induced association of 45Ca with the PMN but this interference occurs at lower concentrations than the inhibition of exocytosis. Hypotonic hemolysis of erythrocytes is inhibited by felodipine; maximal protection against hemolysis occurs at a concentration of 50 microM felodipine. It is suggested that at least a part of the inhibiting effect on PMN functions might be due to an anesthetic-like membrane effect of felodipine.
Insights
Felodipine inhibits key functions of polymorphonuclear leukocytes (PMNs), including exocytosis and metabolic burst, suggesting a membrane-level effect rather than calcium channel blockade.
Area of Science:
- Immunology
- Pharmacology
- Cell Biology
Background:
- Polymorphonuclear leukocytes (PMNs) play a crucial role in inflammatory responses.
- Understanding the mechanisms by which drugs modulate PMN function is vital for developing targeted therapies.
Purpose of the Study:
- To investigate the effects of felodipine on PMN functions, specifically exocytosis, metabolic burst, and migration.
- To elucidate the mechanism of felodipine's action on PMNs, differentiating between calcium channel blockade and other cellular effects.
Main Methods:
- Rabbit peritoneal PMNs were isolated and treated with felodipine.
- Exocytosis, metabolic burst activation, and PMN migration were measured in response to stimuli like fMet-Leu-Phe and ionophore A23187.
- Calcium-45 (45Ca) uptake and erythrocyte hemolysis assays were performed.
Main Results:
- Felodipine inhibited fMet-Leu-Phe or A23187-induced exocytosis in PMNs (1-50 microM).
- Activation of the metabolic burst and PMN migration towards fMet-Leu-Phe were also inhibited by felodipine.
- Inhibition persisted even without extracellular calcium, indicating the effect is not solely due to plasma membrane calcium channel blockade.
- Felodipine interfered with 45Ca association with PMNs at lower concentrations than exocytosis inhibition.
- Felodipine inhibited hypotonic hemolysis of erythrocytes, with maximal protection at 50 microM.
Conclusions:
- Felodipine exerts inhibitory effects on PMN functions, including exocytosis, metabolic burst, and migration.
- The mechanism of inhibition appears to involve a non-calcium channel-dependent pathway, potentially an anesthetic-like membrane effect.
- Felodipine's membrane-stabilizing properties may contribute to its observed effects on PMN and erythrocyte functions.