Cholinergic regulation of morphine release from human white blood cells: evidence for a novel nicotinic receptor via pharmacological and microarray analysis.

Recent work from our laboratory has demonstrated that human white blood cells make morphine and that substances of abuse, i.e. nicotine, alcohol and cocaine have the ability to release this endogenous substance, suggesting a common mechanism of action. We now demonstrate that the nicotinic process is more complex than formerly envisioned. The incorporation rate of 125I-labeled morphine into PMN and MN are 7.85+/-0.36%, 1.42+/-0.19%, respectfully, suggesting in MN this process is of low activity. Separate incubations of PMN with varying concentrations of nicotine or the nicotine agonist epibatidine resulted in a statistically significant enhancement of 125I-trace labeled morphine released into the extracellular medium. In order to ascertain the specificity of the nicotine stimulated morphine release the following experiments were performed. Co-incubation of hexamethonium dichloride (5 microg/ml and at 10 microg/ml), which preferentially blocks nicotinic receptors at autonomic ganglia, with nicotine, exerted a very weak inhibitory effect. Co-incubation of alpha-BuTx or atropine or chlorisondamine diiodide or dihydro-Beta-erythroidine hydrobromide, an alpha4Beta2 receptor antagonist, did not block nicotine induced morphine release alone or in combination, suggesting either the response was not specific or it was mediated by a novel nicotinic receptor. Human leukocyte total RNA isolated from whole blood were analyzed, using the Human Genome Survey microarray (Applied Biosystems), for cholinergic receptor expression. PMN nicotinic receptor gene expression was present and contained numerous variants (eight). The number of variants suggests that indeed a novel nicotinic receptor may be mediating this effect, while simultaneously demonstrating the significance of the cholinergic receptor expression in these immune cells.

HIV gp120 and morphine alter mu opiate receptor expression in human vascular endothelium.

We find that chronic exposure of human saphenous vein, atria and internal thoracic artery endothelium to the human immunodeficiency virus surface glycoprotein gp120, results in an increase in endothelial mu opioid receptor expression (52%). gp120 acts, in this regard, as a proinflammatory cytokine (e.g. interleukin-1-alpha) by increasing endothelial mu opioid receptor expression. In contrast, morphine decreases mu opioid receptor expression by 90% in a dose dependent fashion. Pretreatment of these tissues with the respective antagonists e.g., naloxone and anti-gp120 blocks the opiate decrease and increase gp120 induced increase in mu expression, respectively. Further, pretreatment of these endothelia with morphine inhibits gp120-stimulated mu transcript expression. Therefore, the immune down-regulating action of morphine may prevent viral replication because this process requires immune activation that can, in part, be provided for by gp120 proinflammatory actions.