Morphine inhibits AP-1 activity and CD14 expression in leukocytes by a nitric oxide and opioid receptor-dependent mechanism

Morphine alters the circulating proteolytic profile in mice: functional consequences on cellular migration and invasion

Opioids modulate the tumor microenvironment with potential functional consequences for tumor growth and metastasis. We evaluated the effects of morphine administration on the circulating proteolytic profile of tumor-free mice. Serum from morphine-treated (1 or 10 mg/kg, i.p. every 12 h) or saline-treated mice was collected at different time points and tested ex vivo in endothelial, lymphatic endothelial, and breast cancer cell migration assays. Serum from mice that were treated with 10 mg/kg morphine for 3 d displayed reduced chemotactic potential for endothelial and breast cancer cells, and elicited reduced cancer cell invasion through reconstituted basement membrane compared with serum from saline controls. This was associated with decreased circulating matrix metalloproteinase 9 (MMP-9) and increased circulating tissue inhibitor of metalloproteinase 1 (TIMP-1) and TIMP-3/4 as assessed by zymography and reverse zymography. By using quantitative RT-PCR, we confirmed morphine-induced alterations in MMP-9 and TIMP expression and identified organs, including the liver and spleen, in which these changes originated. Pharmacologic inhibition of MMP-9 abrogated the difference in chemotactic attraction between serum from saline-treated and morphine-treated mice, which indicated that reduced proteolytic ability mediated the decreased migration toward serum from morphine-treated mice. This novel mechanism may enable morphine administration to promote an environment that is less conducive to tumor growth, invasion, and metastasis.-Xie, N., Khabbazi, S., Nassar, Z. D., Gregory, K., Vithanage, T., Anand-Apte, B., Cabot, P. J., Sturgess, D., Shaw, P. N., Parat, M.-O. Morphine alters the circulating proteolytic profile in mice: functional consequences on cellular migration and invasion.

Neurobiological Aspects of Mindfulness in Pain Autoregulation: Unexpected Results from a Randomized-Controlled Trial and Possible Implications for Meditation Research

Background: Research has demonstrated that short meditation training may yield higher pain tolerance in acute experimental pain. Our study aimed at examining underlying mechanisms of this alleged effect. In addition, placebo research has shown that higher pain tolerance is mediated via endogenous neuromodulators: experimental inhibition of opioid receptors by naloxone antagonized this effect. We performed a trial to discern possible placebo from meditation-specific effects on pain tolerance and attention. Objectives: It was proposed that (i) meditation training will increase pain tolerance; (ii) naloxone will inhibit this effect; (iii) increased pain tolerance will correlate with improved attention performance and mindfulness. Methods: Randomized-controlled, partly blinded trial with 31 healthy meditation-naïve adults. Pain tolerance was assessed by the tourniquet test, attention performance was measured by Attention Network Test (ANT), self-perceived mindfulness by Freiburg Mindfulness Inventory. 16 participants received a 5-day meditation training, focusing on body/breath awareness; the control group (N = 15) received no intervention. Measures were taken before the intervention and on 3 consecutive days after the training, with all participants receiving either no infusion, naloxone infusion, or saline infusion (blinded). Blood samples were taken in order to determine serum morphine and morphine glucuronide levels by applying liquid chromatography-tandem mass spectrometry analysis. Results: The meditation group produced fewer errors in ANT. Paradoxically, increases in pain tolerance occurred in both groups (accentuated in control), and correlated with reported mindfulness. Naloxone showed a trend to decrease pain tolerance in both groups. Plasma analyses revealed sporadic morphine and/or morphine metabolite findings with no discernable pattern. Discussion: Main objectives could not be verified. Since underlying study goals had not been made explicit to participants, on purpose (framing effects toward a hypothesized mindfulness-pain tolerance correlation were thus avoided, trainees had not been instructed how to 'use' mindfulness, regarding pain), the question remains open whether lack of meditation effects on pain tolerance was due to these intended 'non-placebo' conditions, cultural effects, or other confounders, or on an unsuitable paradigm. Conclusion: Higher pain tolerance through meditation could not be confirmed.

Toll-like receptors expression and NF-κB activation in peritoneal leukocytes in morphine-mediated impairment of zymosan-induced peritonitis in swiss mice

Zymosan-induced peritonitis represents a well-described model of acute inflammation. The binding of zymosan with its specific Toll-like receptors (TLR2 and TLR6) on leukocytes initiates activation and phosphorylation of nuclear factor (NF)-κB, which leads to accumulation of NF-κB p65 subunits in the nucleus and subsequently up-regulation of the proinflammatory cytokine genes expression. Intraperitoneal co-administration of zymosan and morphine significantly inhibits peritonitis in several strains of mice by decreasing the influx of exudatory cells; however, mechanisms of this action still remain unclear. We aimed to verify the effects of morphine on NF-κB and TLRs expression at messenger RNA and protein levels during the early stages of zymosan-induced peritonitis. Peritonitis was induced by a single injection of zymosan A or zymosan supplemented with morphine in Swiss mice. At selected time points, after stimulation, peritoneal leukocytes were harvested. The TLRs and NF-κB expression was assessed by real-time PCR and flow cytometry. In comparison with the mice injected with zymosan only, morphine co-injection significantly decreased the expression of phospho-NF-κB and TLR2 in all investigated immunocompetent cells as well as up-regulated the levels of nitric oxide (NO) in peritoneal fluid. Moreover, supplementation of zymosan with morphine altered the TLR, NF-κB and some proinflammatory cytokines (keratinocyte-derived chemokine, tumor necrosis factor-α) gene expression during ongoing inflammation. We may postulate that after morphine stimulation peritoneal leukocytes recognize less effectively zymosan antigens because of impaired TLRs expression. The lower TLR expression attenuates TLR-mediated signal transduction, which prevents NF-κB activation. Additionally, during zymosan-induced peritonitis, morphine may modulate the NF-κB expression, at least partially, by an up-regulated release of NO, as suggested by others.

Endogenous morphine levels are increased in sepsis: a partial implication of neutrophils

Background

Mammalian 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.

Methodology

The 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 Findings

We 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.

Conclusions

Our 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.

Endogenous opiates and behavior: 2007

This paper is the thirtieth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2007 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Morphine induces apoptosis of human endothelial cells through nitric oxide and reactive oxygen species pathways

Morphine has been widely used for pain management. Other than analgesia, it has effects on vascular endothelial cells, including angiogenesis and apoptosis. An in vitro model of human umbilical vein endothelial cells (HUVECs) was made to investigate the effects and comprehensive mechanisms of morphine on vascular endothelial cells. Morphine enhanced apoptosis of HUVECs, increased intracellular reactive oxygen species (ROS), and reduced mitochondrial membrane potentials (MMPs). It also induced the release of NO and activated NF-kappaB in HUVECs. Naloxone, the opioid receptor antagonist, could reverse cell apoptosis and ROS generation, NO production, and MMP loss. Expression levels of Bak and Bax, and the activation of caspases 3 and 7 in HUVECs significantly increased when treated with morphine. Inhibition of NO production by NO synthase inhibitor reduced morphine-induced apoptosis. Morphine could induce apoptosis of HUVECs through both the NO and ROS pathways. Thus, inhibiting NO or ROS may be a potential target in blocking morphine-induced apoptosis of endothelial cells.