Effect of prolonged exposure to morphine on responsiveness of human and invertebrate immunocytes to stimulatory molecules.
This study deals with a novel role of morphine in the modulation of cellular responsiveness to immunostimulatory substances that, at first glance, appears to be in contrast to the well documented immunoinhibitory short-term effects of opiate alkaloids on cells simultaneously exposed to stimulatory molecules. Vertebrate and invertebrate immunocytes pre-exposed to morphine (10(-6) M) in vitro for at least 24 h prior to the administration of lipopolysaccharide (LPS; 1.0 micrograms/ml) or other immunoactivating substances have revealed a distinct enhancement of their responsiveness to these signals, e.g. monocytes exposed to LPS alone resulted in 21% activation, whereas the morphine pretreated level was at 40% (P < 0.01). Prolonged pretreatment with morphine of naive human monocytes had the same effect on their sensitivity to plasma from patients having undergone cardiopulmonary bypass (CPB) operations followed by a diffuse inflammatory response. These results suggest that endogenous opiates may participate, in more than one way, in re-establishing an organism's readiness to meet a new demand on its immune system. Additional support for the concept of a role of endogenous opiates in immunomodulation was obtained by the results of in vivo tests with experimentally induced stress in Mytilus. Following their stress-induced stimulation, these animals' immunocytes could be shown to become exposed for some time to a measurable rise in endogenous morphine-like material (9 pmol/ml increasing to 59). These immunocytes, like those preincubated with exogenous morphine, displayed a heightened sensitivity to stimulation by LPS (control 21.3 +/- 3.1% activation compared to 47.2 +/- 5.1) when the morphine levels dropped. The mechanism of this enhancement of responsiveness to immunostimulation following the prolonged exposure of immunocytes to morphine, and its relationship with the known short-term immunoinhibitory opiate effects on the immune system, remains to be ascertained.
Stefano
G B
GB
Multidisciplinary Center for the Study of Aging, Old Westbury Neuroscience Research Institute, State University of New York 11568, USA.
Leung
M K
MK
Bilfinger
T V
TV
Scharrer
B
B
D000818:Animals; D049872:Bivalvia / Q000276:immunology*; D004744:Enkephalin, Methionine / Q000032:analysis; D006458:Hemolymph / Q000737:chemistry; D006801:Humans; D007114:Immunization; D007313:Insecta / Q000276:immunology*; D007375:Interleukin-1 / Q000494:pharmacology; D016209:Interleukin-8 / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000276:immunology*; D009020:Morphine / Q000276:immunology*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D007375:Interleukin-1; D016209:Interleukin-8; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D004744:Enkephalin, Methionine; D009240:N-Formylmethionine Leucyl-Phenylalanine; D009020:Morphine