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Expression of vasoactive intestinal peptide binding sites in rat peritoneal macrophages is stimulated by inflammatory
J J Segura1, J M Guerrero, D Pozo
1Department of Physiology, University of Huelva, Spain.
Abstract:
Vasoactive intestinal peptide (VIP) binding to resident and stimulated-rat peritoneal macrophages was studied. No specific VIP binding was obtained with resident rat peritoneal macrophages. In contrast, VIP bound specifically to casein-elicited macrophages. The Scatchard analysis of binding data was consistent with the presence of two classes of VIP binding sites, but may represent a receptor site and internalized VIP. Both specific VIP binding and number of specific high affinity binding sites for VIP augmented progressively after sodium caseinate injection, reaching maximum at days 4-5. Macrophages obtained 1 day after injection showed a minimal specific VIP binding (0.3 +/- 0.1% of total), but cells obtained 4 days after injection showed a maximal binding to the peptide (3.1+/-0.2% of total). The number of high affinity binding sites per cell raised also progressively after sodium caseinate injection: 2650+/-301 at day 2, 4939 +/-723 at day 3, 6684+/-903 at day 4 and 9636+/-1626 at day 5 (P = 0.0035). The number of low affinity binding sites per cell exhibited the same changes. In contrast, the Kd values of both high and low affinity VIP binding sites did not vary significantly (P>0.05). These results demonstrate that VIP binding sites are only displayed by stimulated macrophages, suggesting that VIP binding sites could be considered to be a pre-activation marker in macrophages and could be used to recognize inflammatory or stimulated macrophages.
Insights
Vasoactive intestinal peptide (VIP) specifically binds to stimulated macrophages, not resident ones. VIP binding sites increase on macrophages after stimulation, suggesting they may serve as a marker for inflammatory cells.
Area of Science:
- Immunology
- Cell Biology
- Neuroendocrinology
Background:
- Vasoactive intestinal peptide (VIP) is a neuropeptide with immunomodulatory functions.
- Macrophages play critical roles in inflammation and immune responses.
- Understanding VIP-macrophage interactions is crucial for studying inflammatory processes.
Purpose of the Study:
- To investigate the presence and characteristics of VIP binding sites on rat peritoneal macrophages.
- To determine if VIP binding differs between resident and stimulated macrophages.
- To explore the potential of VIP binding as a marker for macrophage activation.
Main Methods:
- Peritoneal macrophages were isolated from rats.
- Macrophages were stimulated using sodium caseinate injection.
- VIP binding assays were performed on resident and stimulated macrophages.
- Scatchard analysis was used to characterize VIP binding sites.
Main Results:
- No specific VIP binding was observed on resident macrophages.
- Casein-elicited (stimulated) macrophages exhibited specific VIP binding.
- VIP binding and the number of high-affinity binding sites increased progressively after stimulation.
- Binding reached maximal levels at 4-5 days post-injection.
- Dissociation constants (Kd) for VIP binding sites remained unchanged.
Conclusions:
- VIP binding sites are selectively expressed on stimulated macrophages.
- VIP binding sites may serve as a pre-activation marker for macrophages.
- VIP binding could be a valuable tool for identifying inflammatory or activated macrophages.