A role for reactive oxygen species in endotoxin-induced elevation of MOR expression in the nervous and immune systems

Neuroprotective effects of naltrexone in a mouse model of post-traumatic seizures

Traumatic Brain Injury (TBI) induces neuroinflammatory response that can initiate epileptogenesis, which develops into epilepsy. Recently, we identified anti-convulsive effects of naltrexone, a mu-opioid receptor (MOR) antagonist, used to treat drug addiction. While blocking opioid receptors can reduce inflammation, it is unclear if post-TBI seizures can be prevented by blocking MORs. Here, we tested if naltrexone prevents neuroinflammation and/or seizures post-TBI. TBI was induced by a modified Marmarou Weight-Drop (WD) method on 4-week-old C57BL/6J male mice. Mice were placed in two groups: non-telemetry assessing the acute effects or in telemetry monitoring for interictal events and spontaneous seizures both following TBI and naltrexone. Molecular, histological and neuroimaging techniques were used to evaluate neuroinflammation, neurodegeneration and fiber track integrity at 8 days and 3 months post-TBI. Peripheral immune responses were assessed through serum chemokine/cytokine measurements. Our results show an increase in MOR expression, nitro-oxidative stress, mRNA expression of inflammatory cytokines, microgliosis, neurodegeneration, and white matter damage in the neocortex of TBI mice. Video-EEG revealed increased interictal events in TBI mice, with 71% mice developing post-traumatic seizures (PTS). Naltrexone treatment ameliorated neuroinflammation, neurodegeneration, reduced interictal events and prevented seizures in all TBI mice, which makes naltrexone a promising candidate against PTS, TBI-associated neuroinflammation and epileptogenesis in a WD model of TBI.

The effect of opioids on the efficacy of immunotherapy in recurrent/metastatic squamous cell carcinoma of the head and neck

OBJECTIVES

Head and neck squamous cell carcinoma (HNSCC) causes severe pain and opioids, the mainstay of pain management, may have immunomodulatory effects. We evaluated the effect of opioids on immunotherapy efficacy in recurrent/metastatic (R/M) HNSCC patients.

MATERIALS AND METHODS

In a retrospective study of 66 R/M HNSCC patients from 2015 to 2020, opioid dosage, calculated as mean morphine milligram equivalent per day, was assessed on the day of anti-PD-1 monoclonal antibody (mAb) treatment and most recent prior visit. Intratumoral T cells were evaluated by single cell RNAseq and immunohistochemistry prior to treatment. Univariable and multivariable Cox proportional hazards and logistic regression models were used to estimate the association between opioid usage, progression-free survival (PFS), overall survival (OS), disease control rate.

RESULTS

Patients were 79% male, 35% oropharynx, 35% oral cavity, 40% locoregional recurrence, and 56% platinum failure. Higher opioid dosage by continuous variable was significantly associated with lower PFS (p = 0.016) and OS (p < 0.001). In multivariable analysis, including platinum failure status and PD-L1, higher opioids were associated with lower OS. Opioid usage by categorical variable was associated with significantly lower intratumoral CD8+ T cells. Opioid receptor, OPRM1, expression was identified in intratumoral and circulating T cells.

CONCLUSIONS

In our study cohort of anti-PD-1 mAb treatment in R/M HNSCC patients, higher opioids were associated with significantly lower PFS and OS and lower CD8+ T cells in the tumor microenvironment. To our knowledge, this is the first analysis in R/M HNSCC patients and further research into the clinical and biologic effect of opioids is warranted.

Crosstalk between Mu-Opioid receptors and neuroinflammation: Consequences for drug addiction and pain

Mu-Opioid Receptors (MORs) are well-known for participating in analgesia, sedation, drug addiction, and other physiological functions. Although MORs have been related to neuroinflammation their biological mechanism remains unclear. It is suggested that MORs work alongside Toll-Like Receptors to enhance the release of pro-inflammatory mediators and cytokines during pathological conditions. Some cytokines, including TNF-α, IL-1β and IL-6, have been postulated to regulate MORs levels by both avoiding MOR recycling and enhancing its production. In addition, Neurokinin-1 Receptor, also affected during neuroinflammation, could be regulating MOR trafficking. Therefore, inflammation in the central nervous system seems to be associated with altered/increased MORs expression, which might regulate harmful processes, such as drug addiction and pain. Here, we provide a critical evaluation on MORs' role during neuroinflammation and its implication for these conditions. Understanding MORs' functioning, their regulation and implications on drug addiction and pain may help elucidate their potential therapeutic use against these pathological conditions and associated disorders.

Neuroimmune and Mu-Opioid Receptor Alterations in the Mesocorticolimbic System in a Sex-Dependent Inflammatory Pain-Induced Alcohol Relapse-Like Rat Model

Evidence concerning the role of alcohol-induced neuroinflammation in alcohol intake and relapse has increased in the last few years. It is also proven that mu-opioid receptors (MORs) mediate the reinforcing properties of alcohol and, interestingly, previous research suggests that neuroinflammation and MORs could be related. Our objective is to study neuroinflammatory states and microglial activation, together with adaptations on MOR expression in the mesocorticolimbic system (MCLS) during the abstinence and relapse phases. To do so, we have used a sex-dependent rat model of complete Freund's adjuvant (CFA)-induced alcohol deprivation effect (ADE). Firstly, our results confirm that only CFA-treated female rats, the only experimental group that showed relapse-like behavior, exhibited specific alterations in the expression of phosphorylated NFκB, iNOS, and COX2 in the PFC and VTA. More interestingly, the analysis of the IBA1 expression revealed a decrease of the microglial activation in PFC during abstinence and an increase of its expression in the relapse phase, together with an augmentation of this activation in the NAc in both phases that only occur in female CFA-treated rats. Additionally, the expression of IL1β also evidenced these dynamic changes through these two phases following similar expression patterns in both areas. Furthermore, the expression of the cytokine IL10 showed a different profile than that of IL1β, indicating anti-inflammatory processes occurring only during abstinence in the PFC of CFA-female rats but neither during the reintroduction phase in PFC nor in the NAc. These data indicate a downregulation of microglial activation and pro-inflammatory processes during abstinence in the PFC, whereas an upregulation can be observed in the NAc during abstinence that is maintained during the reintroduction phase only in CFA-female rats. Secondly, our data reveal a correlation between the alterations observed in IL1β, IBA1 levels, and MOR levels in the PFC and NAc of CFA-treated female rats. Although premature, our data suggest that neuroinflammatory processes, together with neural adaptations involving MOR, might play an important role in alcohol relapse in female rats, so further investigations are warranted.

The Endogenous Opioid System in Schizophrenia and Treatment Resistant Schizophrenia: Increased Plasma Endomorphin 2, and κ and μ Opioid Receptors Are Associated with Interleukin-6

BACKGROUND

activation of the immune-inflammatory response system (IRS) and the compensatory immune-regulatory system (CIRS) plays a key role in schizophrenia (SCZ) and treatment resistant SCZ. There are only a few data on immune and endogenous opioid system (EOS) interactions in SCZ and treatment resistant SCZ.

METHODS

we examined serum β-endorphin, endomorphin-2 (EM2), mu-opioid (MOR) and kappa-opioid (KOR) receptors, and interleukin (IL)-6 and IL-10 in 60 non responders to treatment (NRTT), 55 partial RTT (PRTT) and 43 normal controls.

RESULTS

serum EM2, KOR, MOR, IL-6 and IL-10 were significantly increased in SCZ as compared with controls. β-endorphin, EM2, MOR and IL-6 were significantly higher in NRTT than in PRTT. There were significant correlations between IL-6, on the one hand, and β-endorphin, EM2, KOR, and MOR, on the other, while IL-10 was significantly correlated with MOR only. A large part of the variance in negative symptoms, psychosis, hostility, excitation, mannerism, psychomotor retardation and formal thought disorders was explained by the combined effects of EM2 and MOR with or without IL-6 while increased KOR was significantly associated with all symptom dimensions. Increased MOR, KOR, EM2 and IL-6 were also associated with neurocognitive impairments including in episodic, semantic and working memory and executive functions.

CONCLUSION

the EOS contributes to SCZ symptomatology, neurocognitive impairments and a non-response to treatment. In SCZ, EOS peptides/receptors may exert CIRS functions, whereas increased KOR levels may contribute to the pathophysiology of SCZ and EM2 and KOR to a non-response to treatment.

Transforming growth factor-β1 and eosinophil-derived neurotoxins contribute to the development of work-related respiratory symptoms in bakery workers

Background

In baker's asthma previous studies suggest that adaptive and innate immunity are involved in the development of work-related respiratory symptoms (WRS), where we hypothesized that epithelial cells derive airway inflammation through modulating the release of inflammatory cytokines. Thus, we conducted this study to investigate the role of epithelial cell-derived cytokines in the development of WRS among bakery workers.

Methods

We recruited 385 wheat-exposed subjects with WRS (WRS+)/without WRS (WRS-) working in a single industry and 243 unexposed controls from Ajou Medical Center (Suwon, South Korea). Levels of epithelial cell-derived cytokines (interleukin [IL-8], transforming growth factor-β1 [TGF-β1], eotaxin-2) and inflammatory mediators (eosinophil-derived neurotoxins [EDN]) in sera or cell-free supernatants were measured by ELISA. Human airway epithelial cells (HAECs), A549, were stimulated by wheat flour extracts and co-cultured with peripheral blood neutrophils isolated from 4 asthmatic patients.

Results

Serum TGF-β1 levels were significantly lower in exposed subjects than in unexposed controls, in the WRS+ group than in the WRS- group (P < 0.001 for each). The WRS+ group had a significantly higher level of serum EDN than the WRS- group (P < 0.001). Serum TGF-β1 and EDN levels predicted the development of WRS in exposed subjects (area under the curve [AUC] = 0.719, 72.4% sensitivity/70% specificity; AUC = 0.759, 78.6% sensitivity/60% specificity). From wheat-stimulated HAECs, TGF-β1 release peaked at 6 hours after wheat exposure, while eotaxin-2 peaked at 12 hours. Co-culture of HAECs with neutrophils did not affect TGF-β1 release.

Conclusions

Our results suggest that TGF-β1 may contribute to develop type-2 airway inflammation and WRS. Serum TGF-β1/EDN levels may be potential serum biomarkers for predicting WRS among bakery workers.

Binge-Like Exposure to Ethanol Enhances Morphine's Anti-nociception in B6 Mice

Elevation of the blood ethanol concentration (BEC) to > 80 mg/dL (17.4 mM) after binge drinking enhances inflammation in brain and neuroimmune signaling pathways. Morphine abuse is frequently linked to excessive drinking. Morphine exerts its actions mainly via the seven transmembrane G-protein-coupled mu opioid receptors (MORs). Opioid use disorders (OUDs) include combination of opioids with alcohol, leading to opioid overdose-related deaths. We hypothesized that binge drinking potentiates onset and progression of OUD. Using C57BL/6J (B6) mice, we first characterized time-dependent inflammatory gene expression change as molecular markers using qRT-PCR within 24 h after binge-like exposure to high-dose, high-concentration ethanol (EtOH). The mice were given one injection of EtOH (5 g/kg, 42% v/v, i.g.) and sacrificed at 2.5 h, 5 h, 7.5 h, or 24 h later. Inflammatory cytokines interleukin (IL)-1β, IL-6, and IL-18 were elevated in both the striatum (STr) and the nucleus accumbens (NAc) of the mice. We then investigated the expression profile of MOR in the STr at 2 min, 5 h, or 24 h after the first EtOH injection and at 24 h and 48 h after the third injection. This binge-like exposure to EtOH upregulated MOR expression in the STr and NAc, an effect that could enhance morphine's anti-nociception. Therefore, we examined the impact of binge-like exposure to EtOH on morphine's anti-nociception at the behavioral level. The mice were treated with or without 3-d binge-like exposure to EtOH, and the anti-nociceptive changes were evaluated using the hot-plate test 24 h after the final (3rd) EtOH injection with or without a cumulative subcutaneous dose (0, 0.1, 0.3, 1.0, and 3.0 mg/kg) of morphine at intervals of 30 min. The response curve of the mice given EtOH was shifted to the left, showing enhanced latency to response to morphine up to 3 mg/kg. Furthermore, co-treatment with the MOR antagonist naltrexone blocked morphine's anti-nociception in animals given either EtOH or saline. This confirms that MOR is involved in binge-like exposure to EtOH-induced changes in morphine's anti-nociception. Our results suggest that EtOH enhanced latency to analgesic response to morphine, and such effect might initiate the onset and progression of OUDs.

Influence of opioids on immune function in patients with cancer pain: from bench to bedside

In patients with cancer, opioids are principally used for the management of acute surgical and chronic cancer-related pain. However, opioids have many non-analgesic effects, including direct and indirect effects on cancer cells and on anti-tumour immunity (NK cells, macrophages and T-cells). Direct effects on immune cells are manifested via opioid and non-opioid toll-like receptors, whereas indirect effects are manifested via the sympathetic nervous system and hypothalamic-pituitary-adrenal axis. Opioids can also decrease/alter immune cell infiltration into the tumour micro-environment. Animal models have shown that this is not a class effect, in that morphine and fentanyl suppress NK cell cytotoxicity; buprenorphine does not affect NK cell cytotoxicity, whereas tramadol increases NK cell cytotoxicity, reducing metastasis. In healthy individuals, morphine suppresses and fentanyl enhances NK cell cytotoxicity. In patients undergoing surgery, fentanyl decreased and tramadol increased NK cell cytotoxicity; clinical outcomes were not determined. Meta-analyses of opioid-sparing surgical studies report an association between improved recurrence-free and/or overall survival with regional/neuraxial anaesthesia compared with systemic opioids. In patients receiving opioids for non-surgical cancer-related pain, morphine has variable effects on immunity; clinical outcomes were not assessed. Although there is a potential association between systemic opioid administration and shorter survival in cancer patients with a prognosis of months to years, studies have not been designed to primarily assess survival, as a consequence of which causality cannot be apportioned. Pain is immunosuppressive, so analgesia is important. Opioids for cancer-related pain will continue to be recommended until definitive data on the effects of opioids on clinical outcomes in specific patient groups becomes available.

LINKED ARTICLES

This article is part of a themed section on Emerging Areas of Opioid Pharmacology. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.14/issuetoc.

Toll-like receptor 4 contributes to the inhibitory effect of morphine on colonic motility in vitro and in vivo

Opioids rank among the most potent analgesic drugs but gastrointestinal side effects, especially constipation, limit their therapeutic utility. The adverse effects of opioids have been attributed to stimulation of opioid receptors, but emerging evidence suggests that opioids interact with the innate immune receptor Toll-like receptor 4 (TLR4) and its signalling pathway. As TLR4 signalling affects gastrointestinal motility, we examined the involvement of TLR4 in morphine-induced depression of peristaltic motility in the guinea-pig intestine in vitro and male C57BL/6N mice in vivo. While the TLR4 antagonist TAK-242 (0.1 μM and 1 μM) did not alter the morphine-induced inhibition of peristalsis in the isolated guinea-pig small intestine, the morphine-induced decrease in pellet propulsion velocity in colonic segments was attenuated by TAK-242 (0.1 μM). The ability of TAK-242 (4 mg/kg) to mitigate the morphine-induced suppression of colonic motility was replicated in mice in vivo by measuring the expulsion time of beads inserted in the distal colon. The inhibition of upper gastrointestinal transit of mice by morphine was not affected by pre-treatment with TAK-242 (4 mg/kg) in vivo. This is the first report that morphine-induced inhibition of colonic peristalsis is alleviated by TLR4 antagonism. We therefore conclude that TLR4 may contribute to opioid-induced constipation.

Opioid signaling in mast cells regulates injury responses associated with heterotopic ossification

INTRODUCTION

Previous studies found that neuron specific enolase promoter (Nse-BMP4) transgenic mice have increased expression of the nociceptive mediator, substance P and exaggerated local injury responses associated with heterotopic ossification (HO). It is of interest great to know the pain responses in these mice and how the opioid signaling is involved in the downstream events such as mast cell (MC) activation.

MATERIALS AND METHODS

This study utilized a transgenic mouse model of HO in which BMP4 is expressed under the control of the Nse-BMP4. The tactile sensitivity and the cold sensitivity of the mice were measured in a classic inflammatory pain model (carrageenan solution injected into the plantar surface of the left hind paw). The MC activation and the expression profiles of different components in the opioid signaling were demonstrated through routine histology and immunohistochemistry and Western blotting, in the superficial and deep muscle injury models.

RESULTS

We found that the pain responses in these mice were paradoxically attenuated or unchanged, and we also found increased expression of both Methionine Enkephalin (Met-Enk), and the μ-opioid receptor (MOR). Met-Enk and MOR both co-localized within activated MCs in limb tissues. Further, Nse-BMP4;MOR(-/-) double mutant mice showed attenuated MC activation and had a significant reduction in HO formation in response to injuries.

CONCLUSIONS

These observations suggest that opioid signaling may play a key role in MC activation and the downstream inflammatory responses associated with HO. In addition to providing insight into the role of MC activation and associated injury responses in HO, these findings suggest opioid signaling as a potential therapeutic target in HO and possibly others disorders involving MC activation.

Schizophrenia is primed for an increased expression of depression through activation of immuno-inflammatory, oxidative and nitrosative stress, and tryptophan catabolite pathways

Schizophrenia and depression are two common and debilitating psychiatric conditions. Up to 61% of schizophrenic patients have comorbid clinical depression, often undiagnosed. Both share significant overlaps in underlying biological processes, which are relevant to the course and treatment of both conditions. Shared processes include changes in cell-mediated immune and inflammatory pathways, e.g. increased levels of pro-inflammatory cytokines and a Th1 response; activation of oxidative and nitrosative stress (O&NS) pathways, e.g. increased lipid peroxidation, damage to proteins and DNA; decreased antioxidant levels, e.g. lowered coenzyme Q10, vitamin E, glutathione and melatonin levels; autoimmune responses; and activation of the tryptophan catabolite (TRYCAT) pathway through induction of indoleamine-2,3-dioxygenase. Both show cognitive and neurostructural evidence of a neuroprogressive process. Here we review the interlinked nature of these biological processes, suggesting that schizophrenia is immunologically primed for an increased expression of depression. Such a conceptualization explains, and incorporates, many of the current perspectives on the nature of schizophrenia and depression, and has implications for the nature of classification and treatment of both disorders. An early developmental etiology to schizophrenia, driven by maternal infection, with subsequent impact on offspring immuno-inflammatory responses, creates alterations in the immune pathways, which although priming for depression, also differentiates the two disorders.

Endogenous opiates and behavior: 2011

This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 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 (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).

Interleukin-1 beta-induced up-regulation of opioid receptors in the untreated and morphine-desensitized U87 MG human astrocytoma cells

Background

Interleukin-1beta (IL-1β) is a pro-inflammatory cytokine that can be produced in the central nervous system during inflammatory conditions. We have previously shown that IL-1β expression is altered in the rat brain during a morphine tolerant state, indicating that this cytokine may serve as a convergent point between the immune challenge and opiate mediated biological pathways. We hypothesized that IL-1β up-regulates opioid receptors in human astrocytes in both untreated and morphine-desensitized states.

Methods

To test this hypothesis, we compared the basal expression of the mu (MOR), delta (DOR), and kappa (KOR) opioid receptors in the human U87 MG astrocytic cell line to SH-SY5Y neuronal and HL-60 immune cells using absolute quantitative real time RT-PCR (AQ-rt-RT-PCR). To demonstrate that IL-1β induced up-regulation of the MOR, DOR and KOR, U87 MG cells (2 x 10⁵ cells/well) were treated with IL-1β (20 ng/mL or 40 ng/mL), followed by co-treatment with interleukin-1 receptor antagonist protein (IL-1RAP) (400 ng/mL or 400 ng/mL). The above experiment was repeated in the cells desensitized with morphine, where U87 MG cells were pre-treated with 100 nM morphine. The functionality of the MOR in U87 MG cells was then demonstrated using morphine inhibition of forksolin-induced intracellular cAMP, as determined by radioimmunoassay.

Results

U87 MG cells treated with IL-1β for 12 h showed a significant up-regulation of MOR and KOR. DOR expression was also elevated, although not significantly. Treatment with IL-1β also showed a significant up-regulation of the MOR in U87 MG cells desensitized with morphine. Co-treatment with IL-1β and interleukin-1 receptor antagonist protein (IL-1RAP) resulted in a significant decrease in IL-1β-mediated MOR up-regulation.

Conclusion

Our results indicate that the pro-inflammatory cytokine, IL-1β, affects opiate-dependent pathways by up-regulating the expression of the MOR in both untreated and morphine-desensitized U87 MG.