Endogenous Morphine Levels Are Increased in Sepsis: A Partial Implication of Neutrophils

Abstract

BackgroundMammalian cells synthesize morphine and the respective biosynthetic pathway has been elucidated. Human neutrophils release this alkaloid into the media after exposure to morphine precursors. However, the exact role of endogenous morphine in inflammatory processes remains unclear. We postulate that morphine is released during infection and can be determined in the serum of patients with severe infection such as sepsis.MethodologyThe presence and subcellular immunolocalization of endogenous morphine was investigated by ELISA, mass spectrometry analysis and laser confocal microscopy. Neutrophils were activated with Interleukin-8 (IL-8) or lipopolysaccharide (LPS). Morphine secretion was determined by a morphine-specific ELISA. μ opioid receptor expression was assessed with flow cytometry. Serum morphine concentrations of septic patients were determined with a morphine-specific ELISA and morphine identity was confirmed in human neutrophils and serum of septic patients by mass spectrometry analysis. The effects of the concentration of morphine found in serum of septic patients on LPS-induced release of IL-8 by human neutrophils were tested.Principal FindingsWe confirmed the presence of morphine in human neutrophil extracts and showed its colocalisation with lactoferrin within the secondary granules of neutrophils. Morphine secretion was quantified in the supernatant of activated human polymorphonuclear neutrophils in the presence and absence of Ca2+. LPS and IL-8 were able to induce a significant release of morphine only in presence of Ca2+. LPS treatment increased μ opioid receptor expression on neutrophils. Low concentration of morphine (8 nM) significantly inhibited the release of IL-8 from neutrophils when coincubated with LPS. This effect was reversed by naloxone. Patients with sepsis, severe sepsis and septic shock had significant higher circulating morphine levels compared to patients with systemic inflammatory response syndrome and healthy controls. Mass spectrometry analysis showed that endogenous morphine from serum of patient with sepsis was identical to poppy-derived morphine.ConclusionsOur results indicate that morphine concentrations are increased significantly in the serum of patients with systemic infection and that morphine is, at least in part, secreted from neutrophils during sepsis. Morphine concentrations equivalent to those found in the serum of septic patients significantly inhibited LPS-induced IL-8 secretion in neutrophils.

Mapping of endogenous morphine‐like compounds in the adult mouse brain: Evidence of their localization in astrocytes and GABAergic cells

“…This antibody has been used in previous studies (Muller et al, 2008;Glattard et al, 2010) to determine the presence of morphine/M6G by immunohistochemistry, with results consistent with those described here (i.e. basket cell labeling in cerebellar cortex).…”

“…The Journal of Comparative Neurology | Research in Systems Neuroscience presence of morphine and/or codeine and/or morphine glucuronides in astrocytic foot processes around blood vessels suggests the possibility of uptake from the blood or release into the blood (Brix-Christensen et al, 1997Glattard et al, 2010). Finally, our results indicate that astrocytes may be responsible for morphine catabolism in the CNS, mechanisms that now require our attention because of the extensive use of morphine in clinics and as drug of abuse.…”

“…It is also likely that the level of endogenous morphine being produced and secreted can vary with physiological conditions, notably stressful conditions such as fasting (Lee and Spector, 1991;Molina et al, 1995;Goumon et al, 2000;Glattard et al, 2010). Nevertheless, based on the effects of exogenous morphine, coupled with the localization of MOR and the precise distribution of endogenous morphine and/or glucuronides and/or codeine described in this study, several cellular and physiological roles of endogenous morphine-like compounds can be hypothesized.…”

“…Recent data have indicated that high endogenous morphine levels are present in the blood during stressful situations including pathological states such as sepsis (Brix-Christensen et al, 1997Glattard et al, 2010;Madbouly et al, 2010). However, these fluctuations in morphine levels and their consequences for brain function remain to be fully elucidated .…”

Involvement of μ-opioid receptors in antinociceptive action of botulinum toxin type A

“…(1) Modulation of pain by endogenous opioid peptides as a consequence of their enhanced synthesis/release has been observed in some conditions like stress (Parikh et al, 2011), placebo administration (Eippert et al, 2009;Zubieta et al, 2005), infections (Glattard et al, 2010) and exercise (Goldfarb and Jamurtas, 1997). Possibility that BTX-A enhances spinal opioid peptide synthesis may be supported by studies which reported that intramuscular injection of BTX-A induces the enkephalin mRNA synthesis in the spinal cord ventral horn (Humm et al, 2000;Jung et al, 1997).…”