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Complementary DNA cloning of a mu-opioid receptor from rat peritoneal macrophages
M Sedqi1, S Roy, S Ramakrishnan
1University of Minnesota, Department of Pharmacology, Minneapolis 55455, USA.
Abstract:
Treatment with opioid agonists in vitro and in vivo has been shown to affect the function of the immune system. Several investigators have suggested that immune cells may express opioid receptors, but it had been very difficult to demonstrate their presence on these cells by direct binding assays. Our earlier studies have shown that macrophage progenitor cells are highly sensitive to morphine treatment in vitro and in vivo. In the current investigation, we determined, unequivocally, the expression of mu-opioid receptor related transcripts in rat peritoneal macrophages by reverse transcriptase-polymerase chain reaction (RT-PCR) studies. In order to further characterize the transcript, the RT-PCR product was cloned and sequenced. The sequence analyses indicate that the transcripts from rat peritoneal macrophages are identical to those for the mu-opioid receptor described in the rat brain. To further confirm the presence of mu-opioid receptors, immunoreactivity to an antiserum raised against the carboxyl terminal fifteen amino acid residues of the mu-opioid receptor was determined. These studies show for the first time that rat peritoneal macrophages express a mu-opioid receptor.
Insights
This study confirms that rat peritoneal macrophages express mu-opioid receptors, which are key targets for opioid drugs. This finding advances our understanding of opioid effects on the immune system.
Area of Science:
- Immunology
- Neuroscience
- Pharmacology
Background:
- Opioid agonists impact immune function, with suggestions of opioid receptors on immune cells.
- Direct binding assays have historically struggled to confirm opioid receptor presence on immune cells.
- Previous research indicated macrophage progenitor cells are sensitive to morphine.
Purpose of the Study:
- To unequivocally demonstrate the expression of mu-opioid receptors in rat peritoneal macrophages.
- To characterize the mu-opioid receptor transcripts in these immune cells.
- To confirm the presence of functional mu-opioid receptors.
Main Methods:
- Reverse transcriptase-polymerase chain reaction (RT-PCR) to detect receptor transcripts.
- Cloning and sequencing of RT-PCR products for transcript characterization.
- Immunoreactivity assays using specific antiserum against the mu-opioid receptor.
Main Results:
- RT-PCR confirmed the expression of mu-opioid receptor related transcripts in rat peritoneal macrophages.
- Sequence analysis revealed these transcripts are identical to rat brain mu-opioid receptors.
- Immunoreactivity studies provided further confirmation of mu-opioid receptor presence.
Conclusions:
- Rat peritoneal macrophages express mu-opioid receptors.
- This study provides the first definitive evidence of mu-opioid receptors on rat peritoneal macrophages.
- This discovery opens avenues for understanding opioid-immune system interactions.