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Met-enkephalin induced alterations of macrophage functions
Abstract:
Met-enkephalin /Met-enk/ was found to stimulate IgG2a-mediated antibody dependent cytotoxicity /ADCC/ of thioglycollate elicited rat peritoneal macrophages /PM/ through naloxone-sensitive opiate receptors in concentrations ranging from 10(-9) - 14(-7) M. Phagocytosis of IgG2a coated 51Cr-sheep red blood cell /SRBC/ was suppressed by M-enk in the same concentration range. In the same range of concentrations, M-enk was observed to induce a significant increase in the generation of luminol dependent chemiluminescence /LDCL/. The observed stimulation of ADCC was abolished by calmodulin inhibitor triflouroperazine /TFP/ in 10(-6) M concentration. The involvement of cyclic nucleotides in the M-enk induced functional alterations is indicated by finding cGMP accumulation to be augmented in M-enk treated PMs.
Insights
Met-enkephalin stimulates antibody-dependent cell-mediated cytotoxicity in rat macrophages via opiate receptors. This peptide also affects phagocytosis and chemiluminescence, indicating complex immunomodulatory roles.
Area of Science:
- Immunology
- Neuroendocrinology
- Cellular Biology
Background:
- Opioid peptides, such as Met-enkephalin, are known to modulate immune cell functions.
- Rat peritoneal macrophages are key effector cells in cellular immunity.
Purpose of the Study:
- To investigate the effects of Met-enkephalin on rat peritoneal macrophage functions, specifically antibody-dependent cell-mediated cytotoxicity (ADCC).
- To explore the receptor pathways and intracellular mechanisms involved in Met-enkephalin's immunomodulatory actions.
Main Methods:
- Assessing Met-enkephalin's effect on IgG2a-mediated ADCC using 51Cr-labeled sheep red blood cells.
- Measuring phagocytosis of antibody-coated target cells.
- Quantifying luminol-dependent chemiluminescence (LDCL) as an indicator of oxidative burst.
- Utilizing naloxone to block opiate receptors and trifluoperazine (TFP) to inhibit calmodulin.
- Analyzing cyclic guanosine monophosphate (cGMP) levels in treated macrophages.
Main Results:
- Met-enkephalin (10^-9 - 10^-7 M) significantly stimulated IgG2a-mediated ADCC in rat peritoneal macrophages through naloxone-sensitive opiate receptors.
- Phagocytosis of IgG2a-coated SRBC was suppressed by Met-enkephalin in the same concentration range.
- Met-enkephalin induced a significant increase in LDCL generation.
- The Met-enkephalin-induced stimulation of ADCC was abolished by the calmodulin inhibitor TFP (10^-6 M).
- Met-enkephalin treatment led to augmented cGMP accumulation in peritoneal macrophages.
Conclusions:
- Met-enkephalin modulates rat peritoneal macrophage functions, enhancing ADCC and LDCL while suppressing phagocytosis.
- The effects are mediated via naloxone-sensitive opiate receptors and involve calmodulin and cGMP signaling pathways.
- These findings highlight the intricate interplay between the neuroendocrine and immune systems.