Morphine synergizes with lipopolysaccharide in a chronic endotoxemia model

Increased LPS-Induced Fever and Sickness Behavior in Adult Male and Female Rats Perinatally Exposed to Morphine

As a result of the current opioid crisis, the rate of children born exposed to opioids has skyrocketed. Later in life, these children have an increased risk for hospitalization and infection, raising concerns about potential immunocompromise, as is common with chronic opioid use. Opioids can act directly on immune cells or indirectly via the central nervous system to decrease immune system activity, leading to increased susceptibility, morbidity, and mortality to infection. However, it is currently unknown how perinatal opioid exposure (POE) alters immune function. Using a clinically relevant and translatable model of POE, we have investigated how baseline immune function and the reaction to an immune stimulator, lipopolysaccharide, is influenced by in utero opioid exposure in adult male and female rats. We report here that POE potentiates the febrile and neuroinflammatory response to lipopolysaccharide, likely as a consequence of suppressed immune function at baseline (including reduced antibody production). This suggests that POE increases susceptibility to infection by manipulating immune system development, consistent with the clinical literature. Investigation of the mechanisms whereby POE increases susceptibility to pathogens is critical for the development of potential interventions for immunosuppressed children exposed to opioids in utero.

Impact of illicit opioid use on markers of monocyte activation and systemic inflammation in people living with HIV

INTRODUCTION

We hypothesize that illicit opioid use increases bacterial translocation from the gut, which intensifies systemic inflammation.

OBJECTIVE

To investigate the association between opioid use and plasma soluble CD14 [sCD14], interleukin-6 [IL-6] and D-dimer in people living with HIV (PLWH).

METHODS

We analyzed data from the Russia ARCH study-an observational cohort of 351 ART-naive PLWH in St. Petersburg, Russia. Plasma levels of sCD14 (primary outcome), IL-6 and D-dimer (secondary outcomes) were evaluated at baseline, 12, and 24 months. Participants were categorized into three groups based on illicit opioid use: current, prior, and never opioid use. Linear mixed effects models were used to evaluate associations.

RESULTS

Compared to never opioid use, sCD14 levels were significantly higher for participants with current opioid use (AMD = 197.8 ng/ml [11.4, 384.2], p = 0.04). IL-6 levels were also higher for participants with current vs. never opioid use (ARM = 2.10 [1.56, 2.83], p <0.001). D-dimer levels were higher for current (ARM = 1.95 [1.43, 2.64], p <0.001) and prior (ARM = 1.57 [1.17, 2.09], p = 0.004) compared to never opioid use.

CONCLUSIONS

Among PLWH, current opioid use compared to never use is associated with increased monocyte activation and systemic inflammation.

Opioids and Sepsis: Elucidating the Role of the Microbiome and microRNA-146

Sepsis has recently been defined as life-threatening organ dysfunction caused by the dysregulated host response to an ongoing or suspected infection. To date, sepsis continues to be a leading cause of morbidity and mortality amongst hospitalized patients. Many risk factors contribute to development of sepsis, including pain-relieving drugs like opioids, which are frequently prescribed post-operatively. In light of the opioid crisis, understanding the interactions between opioid use and the development of sepsis has become extremely relevant, as opioid use is associated with increased risk of infection. Given that the intestinal tract is a major site of origin of sepsis-causing microbes, there has been an increasing focus on how alterations in the gut microbiome may predispose towards sepsis and mediate immune dysregulation. MicroRNAs, in particular, have emerged as key modulators of the inflammatory response during sepsis by tempering the immune response, thereby mediating the interaction between host and microbiome. In this review, we elucidate contributing roles of microRNA 146 in modulating sepsis pathogenesis and end with a discussion of therapeutic targeting of the gut microbiome in controlling immune dysregulation in sepsis.

The Role of Opioid Receptors in Immune System Function

Research on the effects of opioids on immune responses was stimulated in the 1980s by the intersection of use of intravenous heroin and HIV infection, to determine if opioids were enhancing HIV progression. The majority of experiments administering opioid alkaloids (morphine and heroin) in vivo, or adding these drugs to cell cultures in vitro, showed that they were immunosuppressive. Immunosuppression was reported as down-regulation: of Natural Killer cell activity; of responses of T and B cells to mitogens; of antibody formation in vivo and in vitro; of depression of phagocytic and microbicidal activity of neutrophils and macrophages; of cytokine and chemokine production by macrophages, microglia, and astrocytes; by sensitization to various infections using animal models; and by enhanced replication of HIV in vitro. The specificity of the receptor involved in the immunosuppression was shown to be the mu opioid receptor (MOR) by using pharmacological antagonists and mice genetically deficient in MOR. Beginning with a paper published in 2005, evidence was presented that morphine is immune-stimulating via binding to MD2, a molecule associated with Toll-like Receptor 4 (TLR4), the receptor for bacterial lipopolysaccharide (LPS). This concept was pursued to implicate inflammation as a mechanism for the psychoactive effects of the opioid. This review considers the validity of this hypothesis and concludes that it is hard to sustain. The experiments demonstrating immunosuppression were carried out in vivo in rodent strains with normal levels of TLR4, or involved use of cells taken from animals that were wild-type for expression of TLR4. Since engagement of TLR4 is universally accepted to result in immune activation by up-regulation of NF-κB, if morphine were binding to TLR4, it would be predicted that opioids would have been found to be pro-inflammatory, which they were not. Further, morphine is immunosuppressive in mice with a defective TLR4 receptor. Morphine and morphine withdrawal have been shown to permit leakage of Gram-negative bacteria and LPS from the intestinal lumen. LPS is the major ligand for TLR4. It is proposed that an occult variable in experiments where morphine is being proposed to activate TLR4 is actually underlying sepsis induced by the opioid.

Effect of morphine and a low dose of ketamine on the T cells of patients with refractory cancer pain in vitro

The combination of morphine and ketamine is considered safe and efficacious in many patients. However, a considerable number of immunomodulatory effects have been reported to be produced by both morphine and ketamine. The aim of the present study was to assess the direct effect of morphine and a low dose of ketamine on the T cells of patients with refractory cancer pain in vitro. Venous blood was obtained from patients with refractory cancer pain and peripheral blood mononuclear cells were isolated using the Ficoll-Hypaque density gradient method. Anti-CD3 beads were used to isolate T cells by positive selection. Subsequently, the T cells were treated with vehicle, 200 ng/ml of morphine or 200 ng/ml of morphine + 100 ng/ml ketamine for 24 h, following which the cells were stimulated with anti-CD3 and anti-CD28. Flow cytometric analysis of CD3⁺ T cells, and interleukin (IL)-2 and interferon (IFN)-γ in the supernatant, reverse transcription-quantitative PCR analysis for the detection of IL-2 and IFN-γ and western blotting for the detection of p65 nuclear factor (NF)-κB were performed. In vitro, the CD4⁺ and CD8⁺ T cell counts, CD4⁺/CD8⁺ ratio, secretion of IL-2 and IFN-γ in the supernatant, mRNA expression levels of IL-2 and IFN-γ and expression of p65 NF-κB were significantly decreased following treatment with morphine and morphine + ketamine, compared with results in the control group (all P<0.05). However, there was no significant difference between treatment with morphine and that with morphine + ketamine. Treatment with morphine + ketamine in vitro decreased the immune functions of patients with refractory cancer pain, although the effect of treatment with morphine and a low dose of ketamine did not differ significantly from that with morphine treatment alone.

Effects of Resistance, Endurance, and Concurrent Exercise on Oxidative Stress Markers and the Histological Changes of Intestine After Morphine Withdrawal in Rats

Objectives: The aim of this study was to evaluate the effects of resistance, endurance, and concurrent exercise on oxidative stress markers and histological changes of the intestine after morphine withdrawal in rats. Methods: A total of 30 male Wistar rats were randomly divided into 5 groups (n=6) including healthy control, withdrawal (rat received morphine for 21 days and 8 weeks of withdrawal period), withdrawal + endurance exercises, withdrawal + resistance exercises, and withdrawal + concurrent exercises. The rats practiced endurance, resistance, and concurrent exercises for 10 weeks. Then, their intestines were removed and used for biochemical and histological analysis. Next, several factors were measured such as total protein levels, malondialdehyde (MDA), reduced glutathione (GSH), total antioxidant capacity (TAC), and total oxidant status (TOS). Finally, the morphological alteration of intestine was examined under the light microscope. Results: Morphine withdrawal significantly increased the levels of MDA in the intestine of withdrawal rats compared to those of the control group while endurance, resistance, and concurrent exercise reduced the MDA levels in the intestine. In addition, morphine withdrawal led to a decrease in TAC and GSH levels in the intestine compared to control rats whereas endurance, resistance, and concurrent exercise noticeably increased TAC and GSH levels. Interestingly, the change in the concurrent group was more significant. Moreover, the levels of TOS demonstrated a significant increase in the addicted rat as compared to the control group. Conversely, endurance, resistance, and concurrent exercise significantly decreased TOS levels and the reduction was more significant in the concurrent group. Finally, the intestine of withdrawal rat was morphologically abnormal while it restored by the exercise. Conclusion: Overall, endurance, resistance, and concurrent exercise significantly normalized oxidative stress and the morphological changes of the intestine in withdrawal rats.

Ketamine, as adjuvant analgesics for patients with refractory cancer pain, does affect IL-2/IFN-γ expression of T cells in vitro?: A prospective, randomized, double-blind study

BACKGROUND

Ketamine has been used as an analgesic adjuvant with morphine in the treatment of refractory cancer pain recently. But both morphine and ketamine have been reported to produce a number of immunomodulatory effects. The current study was performed to assess whether the concentration of ketamine, as adjuvant analgesics for patient with refractory cancer pain, was related to its effect on T cells interleukin-2 (IL-2)/interferon-γ (IFN-γ) expression in vitro.

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from venous blood of patients with refractory cancer pain over a Ficoll-Hypaque density gradient. T cells were isolated from by positive selection using anti-CD3 beads. T cells were then treated with vehicle (C group), morphine (200 ng/mL, M group), morphine (200 ng/mL), and different dose of ketamine (100, 200, 1000 ng/mL; MK1, MK5, MK10 group) for 24 hours before stimulation with anti-CD3 and anti-CD28. Then supernatant IL-2 and IFN-γ protein analysis, quantitative reverse transcription polymerase chain reaction (RT-PCR) for IL-2 and IFN-γ were done.

RESULTS

There were no significant difference of supernatant IL-2 and IFN-γ among C group, M group, and MK1 group, but the mRNA of M group and MK1 group were decreased compared with C group (P < .05). Compared with C group, both of the supernatant protein and the mRNA of MK5 group and MK10 group were all significantly decreased (P < .01). Compared with M group, both of the supernatant protein and the mRNA of MK5 group and MK10 group were all decreased (P < .05), while supernatant IL-2 and the mRNA of MK10 group were significantly decreased (P < .01).

CONCLUSION

In conclusion, we confirmed that just as morphine, ketamine dose-dependently suppressed IL-2 and IFN-γ of activated T lymphocyte of patients with refractory cancer pain in vitro, but the inhibitory action of low dose ketamine could be neglected.

NLRP12 Inflammasome Expression in the Rat Brain in Response to LPS during Morphine Tolerance

Morphine, an effective but addictive analgesic, can profoundly affect the inflammatory response to pathogens, and long-term use can result in morphine tolerance. Inflammasomes are protein complexes involved in the inflammatory response. The nucleotide-binding oligomerization domain-like receptor (NLR) Family Pyrin Domain Containing (NLRP) 12 (NLRP12) inflammasome has been reported to have anti-inflammatory activity. In this study, we examined the expression of NLRP12 inflammasome related genes in the adult F344 rat brain in response to the bacterial endotoxin lipopolysaccharide (LPS) in the presence and absence of morphine tolerance. Morphine tolerance was elicited using the 2 + 4 morphine-pelleting protocol. On Day 1, the rats were pelleted subcutaneously with 2 pellets of morphine (75 mg/pellet) or a placebo; on Days 2 and 4 pellets were given. On Day 5, the animals were randomly assigned to receive either 250 µg/kg LPS or saline (i.p.). The expression of 84 inflammasome related genes in the rat brain was examined using a Ploymerase Chain Reaction (PCR) array. In response to LPS, there was a significant increase in the expression of the pro-inflammatory cytokine/chemokine genes interleukin-1 beta (Il-1β), interleukin-6 (Il-6), C-C motif chemokine ligand 2 (Ccl2), C-C motif chemokine ligand 7 (Ccl7), C-X-C motif chemokine ligand 1 (Cxcl1), and C-X-C motif chemokine ligand 3 (Cxcl3) and a significant decrease in the anti-inflammatory NLRP12 gene in both morphine-tolerant and placebo-control rats compared to saline-treated rats, although the changes were greater in the placebo-control animals. The Library of Integrated Network-Based Cellular Signatures’ (LINCS) connectivity map was used to analyze the list of affected genes to identify potential targets associated with the interactions of LPS and morphine tolerance. Our data indicate that, in the morphine tolerant state, the expression of NLRP12 and its related genes is altered in response to LPS and that the Vacuolar protein-sorting-associated protein 28 (VPS28), which is involved in the transport and sorting of proteins into sub-cellular vesicles, may be the key regulator of these alterations.

Dose-dependent effects of morphine on lipopolysaccharide (LPS)-induced inflammation, and involvement of multixenobiotic resistance (MXR) transporters in LPS efflux in teleost fish

Opioid drugs, such as morphine (MO), detected in aquatic environments worldwide, may harm fish due to their semi-persistence and ability to potently interact with molecular targets conserved across vertebrates. Here, we established a waterborne bacterial lipopolysaccharide (LPS) challenge assay with zebrafish embryos as a model to investigate chemically-induced disruption of the innate immune system, and used it to study the effects of MO exposure. Exposure to 1 mg/L MO resulted in pronounced immunosuppression, reflected in downregulation of several inflammation-related genes, including myd88, trif, traf6, p38, nfκb2, il-1β, il-8 and ccl34a. Fish exposed to 1 mg/L MO accumulated 11.7 ng/g (wet weight) of MO, a concentration comparable to that reported in blood of chronic drug abusers subject to higher infection rates. Surprisingly, exposure to lower MO concentrations (100 ng/L-100 μg/L) led to exacerbation of LPS-induced inflammation. Two ATP-binding cassette (ABC) transporters known to be involved in the xenobiotic efflux - abcb4 and abcc2, also known as multixenobiotic resistance (MXR) transporters - were downregulated at 100 ng/L MO. We hypothesized that ABC/MXR transporters could modulate the severity of inflammation by being involved in efflux of LPS, thus regulating its accumulation in the organism. Indeed, we could demonstrate that blocking of ABC/MXR transporters by an inhibitor, cyclosporine A, results in stronger inflammation, coinciding with higher LPS accumulation, as visualized with fluorescently labeled LPS. Our work demonstrates that MO can disrupt fish innate immune responses at environmentally relevant concentrations. We also provide evidence for a role of ABC/MXR transporters in LPS efflux in fish. These finding may be applicable across other taxa, as ABC transporters are evolutionary conserved. Since diverse environmentally present chemicals are known to interfere with ABC/MXR transporters' expression or activity, our discovery raises concerns about potential adverse effects of such compounds on the immune system responses in aquatic organisms.

Disruption of gut homeostasis by opioids accelerates HIV disease progression

Cumulative studies during the past 30 years have established the correlation between opioid abuse and human immunodeficiency virus (HIV) infection. Further studies also demonstrate that opioid addiction is associated with faster progression to AIDS in patients. Recently, it was revealed that disruption of gut homeostasis and subsequent microbial translocation play important roles in pathological activation of the immune system during HIV infection and contributes to accelerated disease progression. Similarly, opioids have been shown to modulate gut immunity and induce gut bacterial translocation. This review will explore the mechanisms by which opioids accelerate HIV disease progression by disrupting gut homeostasis. Better understanding of these mechanisms will facilitate the search for new therapeutic interventions to treat HIV infection especially in opioid abusing population.

Morphine attenuates apically-directed cytokine secretion from intestinal epithelial cells in response to enteric pathogens

Epithelial cells represent the first line of host immune defense at mucosal surfaces. Although opioids appear to increase host susceptibility to infection, no studies have examined opioid effects on epithelial immune functions. We tested the hypothesis that morphine alters vectorial cytokine secretion from intestinal epithelial cell (IPEC-J2) monolayers in response to enteropathogens. Both entero-adherent Escherichia coli O157:H7 and entero-invasive Salmonella enterica serovar Typhimurium increased apically-directed IL-6 secretion and bi-directional IL-8 secretion from epithelial monolayers, but only IL-6 secretion evoked by E. coli was reduced by morphine acting through a naloxone-sensitive mechanism. Moreover, the respective type 4 and 5 Toll-like receptor agonists, lipopolysaccharide and flagellin, increased IL-8 secretion from monolayers, which was also attenuated by morphine pretreatment. These results suggest that morphine decreases cytokine secretion and potentially phagocyte migration and activation directed towards the mucosal surface; actions that could increase host susceptibility to some enteric infections.

Effects of opioids on phagocytic function, oxidative burst capacity, cytokine production and apoptosis in canine leukocytes

Opioids alter immune and apoptotic pathways in several species. They are commonly used in companion animals affected with infectious and/or inflammatory disease, but the immunomodulatory and apoptotic effects of these drugs in dogs are relatively unknown. The aim of the present study was to evaluate the effects of morphine, buprenorphine and fentanyl on canine phagocyte function, oxidative burst capacity, leukocyte cytokine production, and lymphocyte apoptosis. Blood from six healthy adult dogs was incubated in the presence or absence of morphine (200 ng/mL), buprenorphine (10 ng/mL) or fentanyl (10 ng/mL) for 3 h (phagocytic function; cytokine production) or 8 h (apoptosis). Neutrophil phagocytosis of opsonized Escherichia coli, respiratory burst capacity after stimulation with opsonized E. coli or phorbol 12-myristate 13-acetate (PMA), and Annexin V-FITC staining of apoptotic lymphocytes were evaluated using flow cytometry. Leukocyte production of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-10 was assessed after incubation with lipopolysaccharide (LPS), lipoteichoic acid (LTA) or peptidoglycan. Morphine promoted a more intense respiratory burst. Morphine, buprenorphine and fentanyl all promoted LPS- or LTA-induced TNF-α and IL-10 production. However, the opioids tested did not alter TNF-α:IL-10 ratios. Morphine, buprenorphine and fentanyl all inhibited neutrophil apoptosis, an effect that was not concentration dependent in nature. These data indicate that opioids alter immune and apoptotic pathways in dogs. The possible effects of opioids on immune and cellular responses should be considered when designing studies and interpreting outcomes of studies involving administration of opioids in dogs.

Involvement of the NLRP3 inflammasome in the modulation of an LPS-induced inflammatory response during morphine tolerance

BACKGROUND

Morphine is widely used for its analgesic effects. In addition to its high potential for addiction and tolerance, morphine also induces immunosuppression. Inflammasomes, NLRP3 being the most characterized, is a platform for activation of pro-inflammatory cytokines, particularly IL-1β. We have explored the effects of lipopolysaccharide (LPS) during morphine tolerance on expression of the NLRP3 inflammasome and related inflammatory genes.

METHODS

Morphine-pellet administration was used to induce morphine tolerance in F344 rats. Control rats were given a placebo. On day 5, the animals received either saline or 250 μg/kg LPS. LPS-induced protein expression of TNF-α, IL-1β, and IL- 6 was examined in the spleen of rats with and without morphine tolerance. A PCR array was used to examine LPS-induced expression of 84 inflammasome-related genes with and without morphine tolerance.

RESULTS

LPS-induced IL-1β and TNF-α protein expression was significantly lower in the spleen of the morphine-tolerant animals than in the placebo-control animals. In response to LPS, expression of 27 genes, including NLRP3, TNF-α, IL-1β, and IL-6, was significantly increased, and expression of 3 genes was significantly decreased in both the morphine-tolerant and placebo-control groups compared to the saline-treated animals. However, there was only a 2.7-fold increase in NLRP3 expression in response to LPS in the morphine-tolerant rats compared to a 4.5-fold increase in the placebo-control animals.

CONCLUSION

Our data indicate that, in the morphine-tolerant state, LPS-induced expression of NLRP3 is suppressed and cytokine/chemokine expression is inhibited, which may be one of the mechanisms involved in morphine-induced immunosuppression.

Morphine induces bacterial translocation in mice by compromising intestinal barrier function in a TLR-dependent manner

Opiates are among the most prescribed drugs for pain management. However, morphine use or abuse results in significant gut bacterial translocation and predisposes patients to serious infections with gut origin. The mechanism underlying this defect is still unknown. In this report, we investigated the mechanisms underlying compromised gut immune function and bacterial translocation following morphine treatment. We demonstrate significant bacterial translocation to mesenteric lymph node (MLN) and liver following morphine treatment in wild-type (WT) animals that was dramatically and significantly attenuated in Toll-like receptor (TLR2 and 4) knockout mice. We further observed significant disruption of tight junction protein organization only in the ileum but not in the colon of morphine treated WT animals. Inhibition of myosin light chain kinase (MLCK) blocked the effects of both morphine and TLR ligands, suggesting the role of MLCK in tight junction modulation by TLR. This study conclusively demonstrates that morphine induced gut epithelial barrier dysfunction and subsequent bacteria translocation are mediated by TLR signaling and thus TLRs can be exploited as potential therapeutic targets for alleviating infections and even sepsis in morphine-using or abusing populations.

Opioids and HIV/HCV infection

Since human immunodeficiency virus (HIV) and hepatitis C virus (HCV) share the same modes of transmission and common risk factors for infection, co-infections with HIV and HCV are frequently found in injection drug users (IDUs). IDUs represent one of the largest reservoirs of HIV as well as HCV in the United States. These two pathogens are also likely to be responsible for the highest infectious disease morbidity and mortality rates among IDUs. IDUs frequently involve the abuse of heroin, the most common abused opiate. Opiates have been suggested to have a cofactor role in the immunopathogenesis of HIV disease, as they have the potential to compromise host immune responses and enhances microbial infections. Although in vitro studies have yielded relatively agreeable data that morphine, the active metabolite of heroin, exacerbate HIV infection/replication, epidemiologic studies as well as in vivo non-human primate investigations on the impact of opiate abuse on HIV disease progression have yielded the conflicting data. Given immunomodulation and immunocompromising effect as well as demonstrated impact to enhance HIV replication in vitro, it is reasonable to believe that opiate abuse is a facilitator in HIV and/or HCV disease progression. However, much remain to be learned about the mechanisms of opiate-mediated broad influence on host immunity and viral expression. Thus, more extensive studies are needed in order to determine the effects of different conditions of opiate abuse and to define the understanding of the role of opiate in modulating HIV and/or HCV disease progression.

Immunosuppressive effects of opioids--clinical relevance

Opioid-induced immunosuppression has been demonstrated in cell culture experiments and in animal models. This is in striking contrast to the paucity of confirmatory studies in humans. This review describes the basic pharmacokinetics and -dynamics of opioid use in patients. It summarizes the major findings on opioid use and infectious complications in intensive care unit (ICU) patients, in patients with acute or chronic non-malignant pain, and in intravenous drug users (IDU). The limitations of studies in each area are discussed. For example, ethical concerns may complicate randomized placebo-controlled trials (RCT) in acute postoperative pain and for a large part of ICU patients. Importantly, most studies in patients with chronic (non-malignant) pain only inadequately report infectious complications in relation to opioid use since their incidence is usually not considered to be drug related. Infectious complications in IDUs are very frequent but cannot easily be distinguished from risk behavior or risk environment. In summary, convincing clinical evidence is lacking that opioids per se increase the rate of infectious complications in most patient categories. From a clinical standpoint, important unresolved issues are i) selection of relevant animal models, ii) opioid selection and discontinuation, and iii) the role of coexisting diseases and concomitant other medications.

In vivo morphine treatment synergistically increases LPS-induced caspase activity in immune organs

Caspases are a family of proteins important for the elimination of infected cells through the induction of apoptosis as well as the initiation of inflammatory cytokines including IL-1β and IL-18. Morphine exposure to animals and/or cells has been associated with the induction of apoptosis. The most common practices of apoptosis detection have involved removing tissues from animal or humans and the analysis of apoptosis on cells or tissues. These methods can potentially induce spontaneous apoptosis that is unrelated to the actual treatment. The objective of this study was to develop an in vivo detection method for assessing caspase activity induced both by morphine directly and by morphine combined with lipopolysaccharide (LPS)-immune activation. Mice were administered saline, morphine, LPS, or a combination of morphine and LPS. Prior to sacrifice, mice were injected with a polycaspase-specific apoptosis detection probe to detect internal caspase activity in vivo. Results revealed that morphine alone did not directly induce caspase activity. However, morphine significantly enhanced the LPS-induced caspase activity in spleen, thymus, and bone marrow-derived immune cells. The use of a poly-caspase detection probe methodology to label caspase activity in vivo provides a powerful quantitative tool for the in vivo analysis of caspase activity.

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.

Anesthetics, immune cells, and immune responses

General anesthesia accompanied by surgical stress is considered to suppress immunity, presumably by directly affecting the immune system or activating the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system. Along with stress such as surgery, blood transfusion, hypothermia, hyperglycemia, and postoperative pain, anesthetics per se are associated with suppressed immunity during perioperative periods because every anesthetic has direct suppressive effects on cellular and neurohumoral immunity through influencing the functions of immunocompetent cells and inflammatory mediator gene expression and secretion. Particularly in cancer patients, immunosuppression attributable to anesthetics, such as the dysfunction of natural killer cells and lymphocytes, may accelerate the growth and metastases of residual malignant cells, thereby worsening prognoses. Alternatively, the anti-inflammatory effects of anesthetics may be beneficial in distinct situations involving ischemia and reperfusion injury or the systemic inflammatory response syndrome (SIRS). Clinical anesthesiologists should select anesthetics and choose anesthetic methods with careful consideration of the clinical situation and the immune status of critically ill patients, in regard to long-term mortality, morbidity, and the optimal prognosis.

Acute oral toxicity of colchicine in rats: effects of gender, vehicle matrix and pre-exposure to lipopolysaccharide

The oral toxicity of a single administration by gavage (10, 20 or 30 mg kg(-1) body weight) of colchicine (COL) was determined in young, mature male and female Sprague-Dawley rats. The effect of COL was evaluated in the presence or absence of additional treatment variables that included vehicle and lipopolysaccharide (LPS) pre-exposure. The vehicle for COL was either Half and Half cream (H & H) or saline, and each group included pretreatment with either saline or a low, minimally toxic dose (83 microg kg(-1) body weight) of LPS. Colchicine toxicity in both male and female age-matched rats was characterized by progressively more severe dose-related clinical signs of toxicity. These included mortality, decreased body weight and feed intake during the first several days after dosing, with recovery thereafter in surviving animals. There were differences in the severity of the toxic response to COL between male and female rats. The most notable sex-related difference was in COL lethality. Female rats were two times more susceptible to the lethal effects of COL than male rats. Saline or H & H delivery vehicles did not result in any apparent qualitative or quantitative differences in COL toxicity. LPS pretreatment significantly potentiated COL lethality in both males and females, although the potentiation in males was greater than in females. LPS pretreatment modestly increased the COL induced anorexic effect in surviving males, but not in surviving female animals. LPS did not appear to modulate either the body weights or clinical signs of COL induced toxicity in surviving males or females.

Morphine reciprocally regulates IL-10 and IL-12 production by monocyte-derived human dendritic cells and enhances T cell activation

We evaluated the effect of morphine on human dendritic cells (DCs). Interestingly, immature DCs were found to express all 3 (mu, kappa, delta) opioid receptors on the cell surface. Chronic morphine treatment (10(-8) to 10(-12) M) during the development of DCs from monocytes augmented LPS-induced upregulation of HLA-DR, CD86, CD80, and CD83 and increased the T cell stimulatory capacity of DCs, which could be inhibited by naloxone, an opioid receptor antagonist. The change in surface phenotype was paralleled by a p38 MAPK-dependent decrease in IL-10 and increase in IL-12 secretion. Our data indicate that morphine exerts an immunostimulatory effect by modulating LPS-induced DC maturation.

Morphine reciprocally regulates IL-10 and IL-12 production by monocyte-derived human dendritic cells and enhances T cell activation

We evaluated the effect of morphine on human dendritic cells (DCs). Interestingly, immature DCs were found to express all 3 (mu, kappa, delta) opioid receptors on the cell surface. Chronic morphine treatment (10(-8) to 10(-12) M) during the development of DCs from monocytes augmented LPS-induced upregulation of HLA-DR, CD86, CD80, and CD83 and increased the T cell stimulatory capacity of DCs, which could be inhibited by naloxone, an opioid receptor antagonist. The change in surface phenotype was paralleled by a p38 MAPK-dependent decrease in IL-10 and increase in IL-12 secretion. Our data indicate that morphine exerts an immunostimulatory effect by modulating LPS-induced DC maturation.

Morphine modulates gammadelta lymphocytes cytolytic activity following BCG vaccination

Chronic opioid administration modulates lymphocytes' functional capabilities increasing susceptibility to infectious diseases. Bacille-Calmette-Guérin (BCG) vaccination initiates a non-specific and specific cell-mediated immunity orchestrated by T lymphocytes including gammadelta T lymphocytes. gammadelta T lymphocytes increase in natural killer and antigen-directed cytolytic response following BCG vaccination. The objective of this study was to determine morphine effects on gammadelta T lymphocytes' cytolytic activity. Pigs were chronically administered morphine and subsequently vaccinated with Mycobacterium bovis BCG. By administering morphine prior to BCG vaccination, natural killer response was significantly suppressed (p=.034). Furthermore, innate cytolytic response against M. bovis-infected monocytes (p=.002) as well as antigen specific cytolytic functions (p=.04) were significantly altered due to morphine administration. It was concluded that administering morphine prior to BCG vaccination significantly altered gammadelta T lymphocyte cytolytic responses.

Morphine withdrawal lowers host defense to enteric bacteria: spontaneous sepsis and increased sensitivity to oral Salmonella enterica serovar Typhimurium infection

Understanding the consequences of drug withdrawal on immune function and host defense to infection is important. We, and others, previously demonstrated that morphine withdrawal results in immunosuppression and sensitizes to lipopolysaccharide-induced septic shock. In the present study, the effect of morphine withdrawal on spontaneous sepsis and on oral infection with Salmonella enterica serovar Typhimurium was examined. Mice were chronically exposed to morphine for 96 h by implantation of a slow-release morphine pellet. Abrupt withdrawal was induced by removal of the pellet. In the sepsis model, bacterial colonization was examined and bacterial species were identified by necropsy of various tissues. It was found that at 48 h postwithdrawal, morphine-treated mice had enteric bacteria that were detected in the Peyer's patches (4/5), mesenteric lymph nodes (4/5), spleens (4/10), livers (6/10), and peritoneal cavities (8/10). In placebo pellet-withdrawn mice, only 2/40 cultures were positive. The most frequently detected organisms in tissues of morphine-withdrawn mice were Enterococcus faecium followed by Klebsiella pneumoniae. Both organisms are part of the normal gastrointestinal flora. In the infection model, mice were orally inoculated with S. enterica 24 h post-initiation of abrupt withdrawal from morphine. Withdrawal significantly decreased the mean survival time and significantly increased the Salmonella burden in various tissues of infected mice compared to placebo-withdrawn animals. Elevated levels of the proinflammatory cytokines were observed in spleens of morphine-withdrawn mice, compared to placebo-withdrawn mice. These findings demonstrate that morphine withdrawal sensitizes to oral infection with a bacterial pathogen and predisposes mice to bacterial sepsis.

Altered subcellular signaling in murine peritoneal macrophages upon chronic morphine exposure

Alterations in opioid signaling that take place in murine peritoneal macrophages in vitro are variably dependent on opiate exposure conditions. Acute exposure to morphine inhibits Fc-mediated phagocytosis by a pertussis toxin (PT)-sensitive mechanism, but has no effect on cAMP levels. In contrast, chronic exposure to morphine results in a "tolerant" state, wherein test and control values for both phagocytosis and cAMP are equivalent. However, drug withdrawal after chronic exposure to morphine results in inhibition of phagocytosis and a concomitant 4-fold increase in cAMP by a PT-insensitive mechanism. This increase is causally related to inhibition of phagocytosis since an artificial increase in cAMP inhibits phagocytosis in non-withdrawn cells exposed chronically to morphine. We suggest that macrophage opioid receptors signaling switches from a Gi/o-mediated mechanism that does not involve adenylate cyclase in acute exposure to a non-Gi/o-mediated adenylate cyclase superactivation during chronic exposure.

Effects of opioid tolerance and withdrawal on the immune system

Review of the robust literature using acute drug injection paradigms points clearly to the conclusion that morphine is immunosuppressive. In contrast, studies of the effect of subacute or chronic administration of morphine on immune function is limited, with variable results. In some cases tolerance to the immunosuppressive effects of the drug is clearly demonstrated, but in other cases, selected immune parameters do not demonstrate tolerance. Discrepancies in findings may result from differences in species or route and manner of drug administration. Even fewer studies (total of 10) have been published on the effects of withdrawal on immune function. Most immune parameters tested are suppressed following drug withdrawal. Recovery time to baseline response levels varies in the studies. In the single report of withdrawal in humans, immune function was suppressed for up to 3 years. It is clearly established that withdrawal suppresses capacity of murine spleen cells to make an ex vivo antibody response, which contrasts with evidence of polarization of the lymphocytes towards a Th2 phenotype. Several laboratories have shown that subacute and chronic exposure to morphine, as well as drug withdrawal, sensitize to the lethal effects of bacterial lipopolysaccharide. Underlying sepsis, combined with morphine-induced hypofunction of the hypothalamic-pituitary-adrenal (HPA) axis, may be occult variables modulating immune responses during opioid administration and withdrawal. As episodes of withdrawal are common among drug abusers, more intensive investigation is warranted on the effects of withdrawal on immune function, on mechanisms of immune modulation, and on sensitization to infection.

Subclass opioid receptors associated with the cardiovascular depression after traumatic shock and the antishock effects of its specific receptor antagonists

The present available opioid receptor antagonists such as naloxone and naltrexone are not highly receptor selective. They may antagonize mu opioid receptors to affect the pain threshold of the patients with traumatic shock while they exert antishock effects. Therefore, they are not suitable for traumatic shock. It is very important to elucidate the subclass of opioid receptors that are closely associated with cardiovascular depression of traumatic shock and then choose their specific receptor antagonists to treat it. Traumatic shock was used in pentobarbital-anesthetized Wistar rats by right femur fracture plus hemorrhage (fixed hemorrhage at a rate of 20 mL/kg in experiment 1 or hemorrhage to 40 mmHg mean arterial blood pressure for 60 min in experiments 2 and 3), and the changes of myocardial and brain opioid receptors after traumatic shock, the antagonizing effects of mu, delta, and kappa opioid receptor antagonists on the cardiovascular depression of traumatic shock and the antishock effects of delta and kappa opioid receptor antagonists ICI174,864 and Nor-binaltorphimine (Nor-BNI) were observed. The results indicate that after traumatic shock, the number of myocardial and brain delta and kappa opioid receptors were significantly increased that were significantly associated with the decreased cardiovascular functions. mu Opioid receptors in the heart and brain did not change significantly. Intracerebral ventricular administration of ICI174,864 and Nor-BNI significantly antagonized the decreased cardiovascular function after traumatic shock and increased the survival rate of traumatic shock rats, but mu opioid receptor antagonist beta-funaltrexamine did not. Meanwhile, intravenous administration of delta and kappa opioid receptor antagonists ICI174,864 and Nor-BNI also significantly increased the mean arterial blood pressure, improved the hemodynamic parameters, and prolonged the survival rate of traumatic shock rats. These findings suggest that opioid receptors are involved in the cardiovascular depression of traumatic shock, and the subclass receptors are mainly delta and kappa opioid receptors. delta and kappa opioid receptor antagonists have good beneficial effects on traumatic shock.

Effects of mu, kappa or delta opioids administered by pellet or pump on oral Salmonella infection and gastrointestinal transit

Our laboratory has shown previously that subcutaneously implanted, slow-release morphine pellets markedly enhanced susceptibility to oral infection with Salmonella typhimurium. Further, morphine, kappa and delta opioid receptor agonists infused via osmotic minipumps were immunosuppressive. The present study compared morphine pellets to morphine pumps and also examined the differential effects of morphine versus U50,488H (kappa agonist), deltorphin II (delta2 agonist), and (D-Pen2, D-Pen5)-enkephalin (DPDPE, delta1 agonist), administered via Alzet minipumps, on oral Salmonella infection and on gastrointestinal transit. The results show that all morphine-pelleted mice (26/26) had a marked increase in Salmonella burden in the Peyer's Patches, mesenteric lymph nodes and spleen. In comparison, only 8/20 mice receiving morphine by minipump at doses ranging from 1 to 25 mg/kg/day had any culturable Salmonella in their organs and the number of bacteria was very low. The level of Salmonella colonization correlated with blood morphine levels and gut transit measured using an intragastric charcoal meal. Morphine pellets inhibited gut transit by 38%, while mice receiving morphine by minipump at doses of 1 to 25 mg/kg/day showed only a dose-dependent 7% to 17% inhibition. Mice receiving various doses of U50,488H or DPDPE had no culturable Salmonella in the three sites. Deltorphin II given by minipump resulted in a moderate level of Salmonella in the spleen. Deltorphin II and U50,488H (0.1 to 10 mg/kg/day) did not suppress gut transit. The present studies indicate that a predominantly mu opioid receptor agonist, morphine, given by slow-release pellet, potentiated Salmonella infection and inhibited gastrointestinal transit. In contrast, morphine in pumps slightly inhibited intestinal transit, but did not sensitize to Salmonella infection. A delta1 opioid receptor agonist did not sensitize to infection, and a delta2 and a kappa opioid receptor agonist had minimal effects on either parameter.

Morphine-induced degradation of the host defense barrier role of intestinal mucosal injury

The effect of morphine on intestinal ulcer formation and on the degradation of the host defense barrier was studied. Mice receiving morphine (MRM) showed mucosal ulcer formation in the ileum and in the upper third of the colon. In in vitro studies, morphine enhanced apoptosis of cultured human colonic cells (HCC). Nitric oxide synthase (NOS) inhibitors attenuated the proapoptotic effect of morphine. Moreover, morphine stimulated NO generation by HCCs. MRM also showed a breach in the host defense barrier as well as injury to peritoneal macrophages. Although NOS inhibitors completely prevented morphine-induced intestinal ulcer formation, it provided only partial protection against a breach in the host defense barrier and peritoneal macrophage injury. Propranolol did not inhibit the induction of intestinal ulcer formation in MRM; nevertheless, propranolol prevented a breach in the host defense barrier as well as macrophage injury in MRM, whereas hemin exacerbated macrophage injury as well as the breach in the host defense barrier of MRM. These findings suggest that morphine-induced intestinal injury is mediated through NO generation. However, the degradation of the host defense barrier correlates with macrophage injury, but not intestinal injury.

Morphine withdrawal contributes to Th cell differentiation by biasing cells toward the Th2 lineage

The consequences that drug withdrawal has on immune functioning has only recently been appreciated; however, given the wide variety of use and abuse of opiate analgesics, understanding the decrements to immune function that withdrawal from these drugs causes is of crucial importance. In previous work, we have demonstrated that morphine treatment contributes to immunosuppression by polarizing Th cells toward the Th2 lineage. In the current study, it was hypothesized that morphine withdrawal would result in Th2 differentiation and subsequent immune dysfunction. To address this hypothesis, mice were chronically treated with morphine for 72 h followed by a 24-h withdrawal period. It was determined that 24-h morphine withdrawal resulted in a decrease in IFN-gamma, the Th1 signature cytokine, whereas the Th2 cytokine, IL-4, was increased. In addition, Western blot and EMSA experiments revealed that morphine withdrawal-induced Th2 differentiation was mediated through the classical Th2 transcription factors Stat-6 and GATA-3. In addition, the consequence of morphine withdrawal in the presence of an immune stimulation was also examined by treating mice in vivo with LPS before morphine withdrawal. Following withdrawal, it was found that the Th1-polarizing cytokine IL-12 was significantly decreased, providing further support for the observation that withdrawal results in Th2 differentiation by possibly impacting the generation of an appropriate innate immune response which directs subsequent adaptive Th1/Th2 responses.

Morphine withdrawal sensitizes mice to lipopolysaccharide: Elevated TNF-α and nitric oxide with decreased IL-12

Mice made dependent on morphine using slow-release morphine pellets for 96 h were withdrawn by removal of pellets, followed by a sublethal dose of LPS 24 h later. These animals exhibited 100% lethality. Animals withdrawn from placebo pellets receiving LPS all survived, as did morphine-withdrawn mice receiving saline. Morphine-withdrawn LPS-treated animals had elevated serum TNF-alpha and nitric oxide levels, and depressed IL-12 levels compared to controls. Anti-TNF-alpha antibody given prior to LPS challenge afforded significant protection to morphine-withdrawn animals. These studies show that morphine withdrawal sensitizes to LPS lethality via increased production of TNF-alpha.

Interleukin-1 antagonizes morphine analgesia and underlies morphine tolerance

Pain sensitivity reflects a balance between pain facilitatory and inhibitory systems. To characterize the relationships between these systems we examined the interactions between the analgesic effects of morphine and the anti-analgesic effects of the pro-inflammatory cytokine interleukin-1 (IL-1). We report that administration of a neutral dose of IL-1beta abolished morphine analgesia in mice, whereas acute or chronic blockade of IL-1 signaling by various IL-1 blockers (IL-1 receptor antagonist (IL-1ra), alpha-melanocyte-stimulating hormone, or IL-1 tri-peptide antagonist) significantly prolonged and potentiated morphine analgesia. Morphine-induced analgesia was also extended in strains of mice genetically impaired in IL-1 signaling (mice with transgenic over-expression of IL-1 receptor antagonist, deletion of the IL-1 receptor type I, or deletion of the IL-1 receptor accessory protein). The finding that IL-1 produces a marked anti-analgesic effect, suggests that it may also be involved in the development of opiate tolerance. Indeed, genetic or pharmacological blockade of IL-1 signaling prevented the development of tolerance following repeated morphine administration. Moreover, acute administration of IL-1ra in wild type mice, either immediately following the cessation of acute morphine analgesia, or following the development of chronic morphine tolerance, re-instated the analgesia, suggesting that blockade of the IL-1 system unmasks the analgesic effect of morphine. These findings suggest that morphine produces an IL-1-mediated homeostatic response, which serves to limit the duration and extent of morphine analgesia and which underlies the development of tolerance.

Tolerance develops to the effect of lipopolysaccharides on movement-evoked hyperalgesia when administered chronically by a systemic but not an intrathecal route

Single exposures to lipopolysaccharides (LPS) produce deep tissue pain in humans and cutaneous hyperalgesia in rodents. While tolerance develops to many effects of LPS, sensitization to hyperalgesia is documented after a single injection. To determine the effect of long-term exposure to LPS, we explored the chronic effect of LPS on movement-evoked pain using a new assay based on grip force in mice. We found that a single systemic injection of LPS (i.p. or s.c.) induced a dose-related decrease in forelimb grip force responses beginning 6-8 h after injection and peaking between 9 and 24 h. The consequence of LPS is likely hyperalgesia rather than weakness as these decreases were rapidly attenuated by either 10 mg/kg of morphine i.p. or 10 microg of morphine injected intrathecally (i.t.). Complete tolerance to this hyperalgesia developed after repeated injections of LPS at doses of 0.9 mg/kg i.p. or 5 mg/kg s.c. Tolerance began after a single injection and was fully developed after as few as four injections of 5 mg/kg of LPS delivered s.c. The concentration of circulating LPS 5 h after a single parenteral injection was less in LPS-tolerant mice than naïve controls, suggesting that tolerance may result from a more efficient clearance of LPS from the circulation. Injected i.t., LPS also induced hyperalgesia, however, tolerance did not develop to multiple injections by this route. There was no cross-tolerance between s.c. and i.t. injections of LPS. These data indicate that decreases in grip force are a sensitive measure of LPS-induced movement-evoked hyperalgesia and that tolerance develops to parenteral but not central hyperalgesic effects of LPS.

The opioid antagonist naltrexone blocks acute endotoxic shock by inhibiting tumor necrosis factor-alpha production

Septic shock is believed to be a consequence of excessive stimulation of the immune system by bacterial toxins that results in systemic overproduction of proinflammatory cytokines, including tumor necrosis factor-alpha (TNF-alpha), IL-1, and IL-6. Various studies have shown that TNF-alpha, a major mediator of septic shock, induces tissue injury, loss of blood pressure, organ failure, and ultimately death. Administration of the opioid antagonist naloxone has been reported to reverse opiate-mediated hypotension, promote organ perfusion and increase patient survival. In this study, we examined the mechanism by which the opioid receptor antagonist, naltrexone, modulates the septic shock response in BALB/c mice after injection with lipopolysaccharide (LPS) or staphylococcal enterotoxin B (SEB) in combination with d-galactosamine (d-gal), or with agonistic anti-Fas antibody (Jo2) alone. Each of these treatments induced rapid-onset, acute shock, and ultimately mortality (6-9h after injection), although different mechanisms are involved. Administration of the opioid antagonist naltrexone protected mice from shock induced by LPS+d-gal, but not SEB+d-gal or Jo2 antibody, a protective effect that was reversed by morphine. Naltrexone significantly inhibited the production of TNF-alpha induced by LPS, but not SEB in vivo. When bone marrow-derived, splenic or peritoneal macrophages were treated with LPS in vitro, administration of naltrexone had no direct effect on TNF-alpha production. These results suggest that naltrexone is capable of preventing LPS-induced septic shock mortality by indirect inhibition of TNF-alpha production in vivo.

Morphine-induced macrophage apoptosis: oxidative stress and strategies for modulation

Occurrence of macrophage apoptosis has been implicated for the altered immune function found in an opiate milieu. In the present study, we evaluated the role of oxidative stress in morphine-induced macrophage apoptosis. Morphine promoted the apoptosis of macrophages. This effect of morphine was associated with the production of superoxide and nitric oxide (NO). Antioxidants provided protection against morphine-induced macrophage injury. In addition, diphenyleneiodonium chloride, an inhibitor of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation, attenuated the proapoptotic effect of morphine. Antitransforming growth factor-beta (anti-TGF-beta) antibody and propranolol (an inhibitor of the phospholipase D pathway) inhibited morphine-induced superoxide generation as well as apoptosis. N'-Tetraacetic acid tetra (acetoxymethyl) ester, a calcium-chelating agent, inhibited morphine-induced apoptosis, whereas thapsigargin (a calcium agonist) stimulated macrophage apoptosis under basal as well as morphine-stimulated states. These studies suggest that morphine-induced macrophage apoptosis is mediated through downstream signaling involving TGF-beta and NO production. Moreover, there is NADPH oxidation activation involving phospholipase D and Ca(2+), leading to the generation of superoxide. In in vivo studies, administration of N-acetyl cysteine and preinduction of heme oxygenase activity and epoetin alpha prevented morphine-induced peritoneal macrophage apoptosis, thus further confirming the role of oxidative stress in morphine-induced macrophage apoptosis.

Chronic morphine treatment differentiates T helper cells to Th2 effector cells by modulating transcription factors GATA 3 and T-bet

Chronic morphine treatment in animal models has been shown to alter a number of immune parameters including suppression of cellular immunity. T helper cell differentiation into Th2 effector cell may be a major contributing factor to impaired cellular immunity following chronic drug abuse. We had previously shown that chronic morphine treatment in vivo and in vitro decreases IL-2 and IFNgamma (Th1) protein levels and increases IL-4 and IL-5 (Th2) protein levels in a time-dependent manner. In addition in this paper, we show that chronic morphine treatment resulted in a decrease in IFNgamma and IL-2 mRNA and an increase in IL-4 and IL-5 mRNA accumulation in murine splenocytes. Furthermore, chronic morphine treatment inhibited IFNgamma promoter activity and increased IL-4 promoter activity in respective promoter transfected primary T cells. In addition, we also demonstrate that chronic morphine treatment resulted in an increase in GATA 3 binding to DNA consensus elements in electromobility shift assays and an increase in GATA 3 protein and mRNA levels. In contrast, chronic morphine treatment resulted in a decrease in T-bet mRNA levels. From these data, we conclude that chronic morphine treatment differentiates T helper cell to Th2 effector cells by modulating key master switches that results in committing T helper cell to a Th2 phenotype.

RXR-induced TNF-alpha suppression is reversed by morphine in activated U937 cells

Deficiency in vitamin A has been associated with adverse clinical outcomes in drug users with HIV-1 infection. Retinoids have been demonstrated to suppress proinflammatory cytokine production by immune cells in vitro. These effects are induced by ligand-mediated activation of the retinoid receptors--retinoic acid receptor (RAR) and retinoid X receptor (RXR). In these studies, the effects of all-trans-retinoid acid (ATRA, a RAR agonist), 9-cis-retinoic acid (9cis RA; RAR and RXR agonist), LG101305 (RXR agonist), LG100815 (RAR antagonist) and LG101208 (RXR antagonist) on TNF-alpha production by phytohemagglutanin-activated U937 cells and the modulation of these effects by morphine were examined. TNF-alpha production was suppressed in all cultures exposed to retinoid agonist and antagonist agents. For cells exposed to RXR agonists or RAR antagonist, incubation with morphine resulted in the reversal of TNF-alpha suppression and this effect was inhibited by naloxone. These data suggest that interactions between RXR and morphine are involved in the immune effects of retinoids on TNF-alpha production by activated U937 cells. Such information may be important for understanding interactions between drugs of abuse and immune function in individuals with chronic proinflammatory states such as HIV-1 infection.

Dual effects of morphine on permeability and apoptosis of vascular endothelial cells: morphine potentiates lipopolysaccharide-induced permeability and apoptosis of vascular endothelial cells

Vascular endothelial cells (VEC) provide an essential protective barrier between the vascular system and underlying tissues. Using VEC barrier models of human coronary artery cells and human and rat brain microvascular endothelial cells, we investigated the mechanism by which morphine affects lipopolysaccharide (LPS)-induced VEC permeability. We demonstrated that co-administration of morphine and LPS induced greater VEC apoptosis and permeability than morphine or LPS alone. The extent of induced apoptosis appeared to be cell-type dependent. Furthermore, RT-PCR analysis revealed that morphine and LPS up-regulated Fas expression. These data suggest potential crosstalk between the signaling pathways that mediate morphine- and LPS-triggered apoptosis in brain VEC.

Immune, neuroendocrine, and somatic alterations in animal models of human heroin abuse

We investigated immune, endocrine, and somatic alterations using two animal models of human heroin administration. In a heroin self-administration paradigm, we observed changes in immune function which suggest that the cycle of intermittent drug use is actually a stressor, which in turn not only exacerbates craving and drug-seeking behavior but also collaterally causes suppression of immune function and therefore susceptibility to disease. In another model of rats made physically dependent to heroin, we show that immune function is more broadly compromised, leading to evidence of infection, followed by chronic activation of innate immune function, cachexia, and weight loss.

The Role of Nuclear Factor κB in Tumor Necrosis Factor-Regulated Transcription of the Human μ-Opioid Receptor Gene

Opioids and their receptors are key players in a cross-talk between the nervous and immune systems. For example, the endogenous opioid system is activated during inflammation as a physiological feedback mechanism to attenuate inflammatory pain. Herein, we report that in primary human T lymphocytes, Raji B cells, U937 monocytes, primary human polymorphonuclear leukocytes, and mature dendritic cells, the proinflammatory cytokine tumor necrosis factor induced mu-opioid receptor gene transcription. Transcriptional induction of the gene in immune cells was mediated via tumor necrosis factor receptor type 2. Using selective in vivo disruption of possibly involved transcription factors with decoy oligonucleotides, nuclear factor-kappaB was identified as the factor responsible for induction of the gene in immune cells, whereas activator protein-1 was found to be uninvolved. Nuclear factor-kappaB also mediates up-regulation of mu-opioid receptors in neuronal cells stimulated with tumor necrosis factor. Among six putative nuclear factor-kappaB binding sites on the mu-opioid receptor gene promoter, three cis-active elements at nt -2174, -557, and -207 were identified using transfection experiments of reporter gene constructs, electrophoretic mobility shift assays, and in vivo binding studies with decoy oligonucleotides. An allelic variation within the -557 element significantly reduced its trans-activating potency, which may affect regulation of the mu-opioid receptor gene in persons carrying this mutation. This study suggests a regulatory function of tumor necrosis factor in opioid-mediated processes in neuronal and immune cells, with possible impact on the complex of inflammation-induced analgesia.

Anti-inflammatory properties of the mu opioid receptor support its use in the treatment of colon inflammation

The physiologic role of the mu opioid receptor (MOR) in gut nociception, motility, and secretion is well established. To evaluate whether MOR may also be involved in controlling gut inflammation, we first showed that subcutaneous administration of selective peripheral MOR agonists, named DALDA and DAMGO, significantly reduces inflammation in two experimental models of colitis induced by administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS) or peripheral expansion of CD4(+) T cells in mice. This therapeutic effect was almost completely abolished by concomitant administration of the opioid antagonist naloxone. Evidence of a genetic role for MOR in the control of gut inflammation was provided by showing that MOR-deficient mice were highly susceptible to colon inflammation, with a 50% mortality rate occurring 3 days after TNBS administration. The mechanistic basis of these observations suggests that the anti-inflammatory effects of MOR in the colon are mediated through the regulation of cytokine production and T cell proliferation, two important immunologic events required for the development of colon inflammation in mice and patients with inflammatory bowel disease (IBD). These data provide evidence that MOR plays a role in the control of gut inflammation and suggest that MOR agonists might be new therapeutic molecules in IBD.

Anti-inflammatory properties of the mu opioid receptor support its use in the treatment of colon inflammation

The physiologic role of the mu opioid receptor (MOR) in gut nociception, motility, and secretion is well established. To evaluate whether MOR may also be involved in controlling gut inflammation, we first showed that subcutaneous administration of selective peripheral MOR agonists, named DALDA and DAMGO, significantly reduces inflammation in two experimental models of colitis induced by administration of 2,4,6-trinitrobenzene sulfonic acid (TNBS) or peripheral expansion of CD4(+) T cells in mice. This therapeutic effect was almost completely abolished by concomitant administration of the opioid antagonist naloxone. Evidence of a genetic role for MOR in the control of gut inflammation was provided by showing that MOR-deficient mice were highly susceptible to colon inflammation, with a 50% mortality rate occurring 3 days after TNBS administration. The mechanistic basis of these observations suggests that the anti-inflammatory effects of MOR in the colon are mediated through the regulation of cytokine production and T cell proliferation, two important immunologic events required for the development of colon inflammation in mice and patients with inflammatory bowel disease (IBD). These data provide evidence that MOR plays a role in the control of gut inflammation and suggest that MOR agonists might be new therapeutic molecules in IBD.

Microbial infections, immunomodulation, and drugs of abuse

The use of recreational drugs of abuse has generated serious health concerns. There is a long-recognized relationship between addictive drugs and increased levels of infections. Studies of the mechanisms of actions of these drugs became more urgent with the advent of AIDS and its correlation with abused substances. The nature and mechanisms of immunomodulation by marijuana, opiates, cocaine, nicotine, and alcohol are described in this review. Recent studies of the effects of opiates or marijuana on the immune system have demonstrated that they are receptor mediated, occurring both directly via specific receptors on immune cells and indirectly through similar receptors on cells of the nervous system. Findings are also discussed that demonstrate that cocaine and nicotine have similar immunomodulatory effects, which are also apparently receptor mediated. Finally, the nature and mechanisms of immunomodulation by alcohol are described. Although no specific alcohol receptors have been identified, it is widely recognized that alcohol enhances susceptibility to opportunistic microbes. The review covers recent studies of the effects of these drugs on immunity and on increased susceptibility to infectious diseases, including AIDS.