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Modulation of human neutrophil adherence by beta-endorphin and met-enkephalin
Abstract:
Early events in an acute inflammatory response include the adherence of neutrophils (PMN) to capillary endothelial cells and the migration of these cells into tissues. This study was designed to determine if the opioid peptides beta-endorphin or met-enkephalin would induce a concentration-dependent increase in PMN adherence to serum-coated glass. Results show that PMN adherence is increased with both beta-endorphin and met-enkephalin and this increase may be partially blocked by the opiate antagonist naloxone. Binding of opioid peptides to the formyl peptide receptor was ruled out as a mechanism of increased adherence by showing that the opioids failed to block the binding of f-met-leu-phe-lys to PMN. These studies suggest that alterations in circulating opioid concentrations may modulate the adherence of PMN and thereby influence acute inflammatory reactions.
Insights
Opioid peptides like beta-endorphin and met-enkephalin increase neutrophil adherence during inflammation. This effect, potentially modulated by circulating opioid levels, can be partially blocked by naloxone.
Area of Science:
- Immunology
- Neuroscience
- Pharmacology
Background:
- Acute inflammation involves neutrophil (PMN) adherence to endothelial cells and migration into tissues.
- Opioid peptides are endogenous molecules with diverse physiological roles.
Purpose of the Study:
- To investigate the effect of opioid peptides (beta-endorphin, met-enkephalin) on PMN adherence.
- To determine if opioid-induced PMN adherence is mediated by the formyl peptide receptor.
Main Methods:
- Assessing PMN adherence to serum-coated glass in the presence of varying opioid concentrations.
- Utilizing the opiate antagonist naloxone to block potential opioid receptor interactions.
- Testing the competitive binding of opioid peptides against f-met-leu-phe-lys for the formyl peptide receptor.
Main Results:
- Both beta-endorphin and met-enkephalin significantly increased PMN adherence in a concentration-dependent manner.
- Naloxone partially inhibited the opioid-induced increase in PMN adherence.
- Opioid peptides did not block the binding of f-met-leu-phe-lys, ruling out formyl peptide receptor involvement.
Conclusions:
- Circulating opioid peptides can modulate neutrophil adherence, a key step in acute inflammation.
- The mechanism of opioid-induced PMN adherence is independent of the formyl peptide receptor.
- Findings suggest a potential role for endogenous opioids in regulating inflammatory responses.