Opioids as modulators of cell death and survival--unraveling mechanisms and revealing new indications

The Role of Anesthetic Management in Lung Cancer Recurrence and Metastasis: A Comprehensive Review

Lung cancer remains a leading cause of cancer-related mortality worldwide. Although surgical treatment is a primary approach, residual cancer cells and surgery-induced pathophysiological changes may promote cancer recurrence and metastasis. Anesthetic agents and techniques have recently been shown to potentially impact these processes by modulating surgical stress responses, immune function, inflammatory pathways, and the tumor microenvironment. Anesthetics can influence immune-modulating cytokines, induce pro-inflammatory factors such as HIF-1α, and alter natural-killer cell activity, affecting cancer cell survival and spread. Preclinical studies suggest volatile anesthetics may promote tumor progression by triggering pro-inflammatory signaling, while propofol shows potential antitumor properties through immune-preserving effects and reductions in IL-6 and other inflammatory markers. Additionally, opioids are known to suppress immune responses and stimulate pathways that may support cancer cell proliferation, whereas regional anesthesia may reduce these risks by decreasing the need for systemic opioids and volatile agents. Despite these findings, clinical data remain inconclusive, with studies showing mixed outcomes across patient populations. Current clinical trials, including comparisons of volatile agents with propofol-based total intravenous anesthesia, aim to provide clarity but highlight the need for further investigation. Large-scale, well-designed studies are essential to validate the true impact of anesthetic choice on cancer recurrence and to optimize perioperative strategies that support long-term oncologic outcomes for lung cancer patients.

Insufficient autophagy enables the nuclear factor erythroid 2-related factor 2 (NRF2) to promote ferroptosis in morphine-treated SH-SY5Y cells

RATIONALE

While morphine has important therapeutic value it is also one of the most widely abused drugs in the world. As a newly discovered style of cell death, ferroptosis is involved in the occurrence and development of many diseases, however, the current understanding of the relationship between ferroptosis and morphine is still limited.

OBJECTIVE

To clarify the role of opioid receptors in morphine-induced ferroptosis and to investigate the role of NRF2 in morphine-induced ferroptosis.

METHODS

We first used different doses of morphine (0, 0.5, 1, and 1.5 mM) to investigate morphine-induced ferroptosis in SH-SY5Y cells, and we choose 1.5 mM morphine for subsequent experiments. We next inhibited opioid receptors and NRF2 separately and examined their influence on morphine-induced ferroptosis. Finally, we tested morphine-induced insufficient autophagy.

RESULTS

Morphine triggered ferroptosis in a dose-dependent manner, which could be significantly rescued by the ferroptosis-specific inhibitor DFO. Moreover, GPX4 rather than xCT antiporter might be involved in morphine-induced ferroptosis. We also found naloxone could inhibit morphine-induced ferroptosis. Interestingly, our results demonstrated that NRF2 could promote rather than defend morphine-induced ferroptosis; this may be due to the increased p62-related insufficient autophagy.

CONCLUSION

Morphine-induced ferroptosis is regulated by the opioid receptor and GPX4 rather than the xCT antiporter. NRF2-mediated ferroptosis in morphine-exposed cells may stem from increased p62-related insufficient autophagy.

Natural Products and Health

A natural product is an organic compound from a living organism that can be isolated from natural sources or synthesized [...].

Metabolic and functional substrates of impulsive decision-making in individuals with heroin addiction after prolonged methadone maintenance treatment

Elevated impulsivity has been frequently reported in individuals with opioid addiction receiving methadone maintenance therapy (MMT), but the underlying neural mechanisms and cognitive subprocesses are not fully understood. We acquired functional magnetic resonance imaging (fMRI) data from 37 subjects with heroin addiction receiving long-term MMT and 33 healthy controls who performed a probabilistic reversal learning task, and measured their resting-state brain glucose using fluorine-18-fluorodeoxyglucose positron emission tomography (18F-FDG PET). Subjects receiving MMT exhibited significantly elevated self-reported impulsivity, and computational modeling revealed a marked impulsive decision bias manifested as switching more frequently without available evidence. Moreover, this impulsive decision bias was associated with the dose and duration of methadone use, irrelevant to the duration of heroin use. During the task, the switch-related hypoactivation in the left rostral middle frontal gyrus was correlated with the impulsive decision bias while the function of reward sensitivity was intact in subjects receiving MMT. Using prior brain-wide receptor density data, we found that the highest variance of regional metabolic abnormalities was explained by the spatial distribution of μ-opioid receptors among 10 types of neurotransmitter receptors. Heightened impulsivity in individuals receiving prolonged MMT is manifested as atypical choice bias and noise in decision-making processes, which is further driven by deficits in top-down cognitive control, other than reward sensitivity. Our findings uncover multifaceted mechanisms underlying elevated impulsivity in subjects receiving MMT, which might provide insights for developing complementary therapies to improve retention during MMT.

Targeting the opioid remifentanil: Protective effects and molecular mechanisms against organ ischemia-reperfusion injury

Opioids are widely used in clinical practice by activating opioid receptors (OPRs), but their clinical application is limited by a series of side effects. Researchers have been making tremendous efforts to promote the development and application of opioids. Fortunately, recent studies have identified the additional effects of opioids in addition to anesthesia and analgesia, particularly in terms of organ protection against ischemia-reperfusion (I/R) injury, with unique advantages. I/R injury in vital organs not only leads to cell dysfunction and structural damage but also induces acute and chronic organ failure, even death. Early prevention and appropriate therapeutic targets for I/R injury are crucial for organ protection. Opioids have shown cardioprotective effects for over 20 years, especially remifentanil, a derivative of fentanyl, which is a new ultra-short-acting opioid analgesic widely used in clinical anesthesia induction and maintenance. In this review, we provide current knowledge about the physiological effects related to OPR-mediated organ protection, focusing on the protective effect and mechanism of remifentanil on I/R injury in the heart and other vital organs. Herein, we also explored the potential application of remifentanil in clinical I/R injury. These findings provide a theoretical basis for the use of remifentanil to inhibit or alleviate organ I/R injury during the perioperative period and provide insights for opioid-induced human organ protection and drug development.

Targeting Anti-Inflammatory Pathways to Treat Diabetes-Induced Neuropathy by 6-Hydroxyflavanone

It is evident that inflammation and metabolic syndrome instigated by diabetes mellitus can precipitate diabetes-induced neuropathy (DIN) and pain. In order to find an effective therapeutic method for diabetes-related problems, a multi-target-directed ligand model was used. 6-Hydroxyflavanone (6-HF) carrying anti-inflammatory and anti-neuropathic pain potential due to its quadruplicate mechanisms, targeting cyclooxygenase-2 (COX-2), 5-lipoxygenase (5-LOX), and opioid and GABA-A receptors was investigated. The anti-inflammatory potential of the test drug was confirmed utilizing in silico, in vitro, and in vivo tests. A molecular simulation approach was utilized to observe the interaction of 6-HF with the inflammatory enzyme COX-2 as well as opioid and GABA-A receptors. The same was confirmed via in vitro COX-2 and 5-LOX inhibitory assays. In vivo tests were performed to analyze the thermal anti-nociception in the hot-plate analgesiometer and anti-inflammatory action in the carrageenan-induced paw edema model in rodents. The potential anti-nociceptive effect of 6-HF was evaluated in the DIN model in rats. The Naloxone and Pentylenetetrazole (PTZ) antagonists were used to confirm the underlying mechanism of 6-HF. The molecular modeling studies revealed a favorable interaction of 6-HF with the identified protein molecules. In vitro inhibitory studies revealed that 6-HF inhibited the COX-2 and 5-LOX enzymes significantly. The 6-HF at dosages of 15, 30, and 60 mg/kg substantially reduced heat nociception in a hot plate analgesiometer as well as carrageenan-induced paw edema in rodent models. The authors discovered that 6-HF had anti-nociception properties in a streptozotocin-induced diabetic neuropathy model. According to the findings of this study, 6-HF was demonstrated to diminish inflammation caused by diabetes as well as its anti-nociception effect in DIN.

Contribution of the opioid system to depression and to the therapeutic effects of classical antidepressants and ketamine

Major depressive disorder (MDD) afflicts approximately 5 % of the world population, and about 30-50 % of patients who receive classical antidepressant medications do not achieve complete remission (treatment resistant depressive patients). Emerging evidence suggests that targeting opioid receptors mu (MOP), kappa (KOP), delta (DOP), and the nociceptin/orphanin FQ receptor (NOP) may yield effective therapeutics for stress-related psychiatric disorders. As depression and pain exhibit significant overlap in their clinical manifestations and molecular mechanisms involved, it is not a surprise that opioids, historically used to alleviate pain, emerged as promising and effective therapeutic options in the treatment of depression. The opioid signaling is dysregulated in depression and numerous preclinical studies and clinical trials strongly suggest that opioid modulation can serve as either an adjuvant or even an alternative to classical monoaminergic antidepressants. Importantly, some classical antidepressants require the opioid receptor modulation to exert their antidepressant effects. Finally, ketamine, a well-known anesthetic whose extremely efficient antidepressant effects were recently discovered, was shown to mediate its antidepressant effects via the endogenous opioid system. Thus, although opioid system modulation is a promising therapeutical venue in the treatment of depression further research is warranted to fully understand the benefits and weaknesses of such approach.

Plasma cell-free DNA methylome profiling in pre- and post-surgery oral cavity squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC), a highly heterogeneous disease that involves multiple anatomic sites, is a leading cause of cancer-related mortality worldwide. Although the utility of noninvasive biomarkers based on circulating cell-free DNA (cfDNA) methylation profiling has been widely recognized, limited studies have been reported so far regarding the dynamics of cfDNA methylome in oral cavity squamous cell carcinoma (OCSCC). It is hypothesized in this study that comparison of methylation profiles in pre- and postsurgery plasma samples will reveal OCSCC-specific prognostic and diagnostic biomarkers. As a strategy to further prioritize tumor-specific targets, top differential methylated regions (DMRs) were called by reanalyzing methylation data from paired tumor and normal tissue collected in the the cancer genome atlas head-neck squamous cell carcinoma (TCGA) head and neck cancer cohort. Matched plasma samples from eight patients with OCSCC were collected at Moffitt Cancer Center before and after surgical resection. Plasma-derived cfDNA was analyzed by cfMBD-seq, which is a high-sensitive methylation profiling assay. Differential methylation analysis was then performed based on the matched samples profiled. In the top 200 HNSCC-specific DMRs detected based on the TCGA data set, a total of 23 regions reached significance in the plasma-based DMR test. The top five validated DMR regions (ranked by the significance in the plasma study) are located in the promoter regions of genes PENK, NXPH1, ZIK1, TBXT, and CDO1, respectively. The genome-wide cfDNA DMR analysis further highlighted candidate biomarkers located in genes SFRP4, SOX1, IRF4, and PCDH17. The prognostic relevance of candidate genes was confirmed by survival analysis using the TCGA data. This study supports the utility of cfDNA-based methylome profiling as a promising noninvasive biomarker source for OCSCC and HNSCC.

Chronic exposure to methadone impairs memory, induces microgliosis, astrogliosis and neuroinflammation in the hippocampus of adult male rats

Methadone is a centrally-acting synthetic opioid analgesic widely used in methadone maintenance therapy (MMT) programs throughout the world. Given its neurotoxic effects, particularly on the hippocampus, this study aims to address the behavioral and histological alterations in the hippocampus associated with methadone administration. To do so, twenty-four adult male albino rats were randomized into two groups, methadone treatment and control. Methadone was administered subcutaneously (2.5-10 mg/kg) once a day for two consecutive weeks. A comparison was drawn with behavioral and structural changes recorded in the control group. The results showed that methadone administration interrupted spatial learning and memory function. Accordingly, treating rats with methadone not only induced cell death but also prompted the actuation of microgliosis, astrogliosis, and apoptotic biomarkers. Furthermore, the results demonstrated that treating rats with methadone decreased the complexity of astrocyte processes and the complexity of microglia processes. These findings suggest that methadone altered the special distribution of neurons. Also, a substantial increase was observed in the expression of TNF-α due to methadone. According to the findings, methadone administration exerts a neurodegenerative effect on the hippocampus via dysregulation of microgliosis, astrogliosis, apoptosis, and neuro-inflammation.

Morphine-induced changes in the function of microglia and macrophages after acute spinal cord injury

Background

Opioids are among the most effective and commonly prescribed analgesics for the treatment of acute pain after spinal cord injury (SCI). However, morphine administration in the early phase of SCI undermines locomotor recovery, increases cell death, and decreases overall health in a rodent contusion model. Based on our previous studies we hypothesize that morphine acts on classic opioid receptors to alter the immune response. Indeed, we found that a single dose of intrathecal morphine increases the expression of activated microglia and macrophages at the injury site. Whether similar effects of morphine would be seen with repeated intravenous administration, more closely simulating clinical treatment, is not known.

Methods

To address this, we used flow cytometry to examine changes in the temporal expression of microglia and macrophages after SCI and intravenous morphine. Next, we explored whether morphine changed the function of these cells through the engagement of cell-signaling pathways linked to neurotoxicity using Western blot analysis.

Results

Our flow cytometry studies showed that 3 consecutive days of morphine administration after an SCI significantly increased the number of microglia and macrophages around the lesion. Using Western blot analysis, we also found that repeated administration of morphine increases β-arrestin, ERK-1 and dynorphin (an endogenous kappa opioid receptor agonist) production by microglia and macrophages.

Conclusions

These results suggest that morphine administered immediately after an SCI changes the innate immune response by increasing the number of immune cells and altering neuropeptide synthesis by these cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12868-022-00739-3.

Pruritus in Chronic Kidney Disease: An Update

Chronic kidney disease-associated pruritus (CKDaP) is an often under-diagnosed and under-recognized condition, despite its considerable prevalence within the chronic kidney disease (CKD) population. Universally accepted guidelines are also lacking. The true prevalence of CKDaP worldwide therefore remains unknown, although its negative impact on mortality and health-related quality of life outcomes is very clear. The pathophysiological mechanisms leading to the onset of CKDaP are only partly understood. CKDaP is currently believed to be caused by a multifactorial process, from local skin changes, metabolic alterations, the development of neuropathy and dysregulation of opioid pathways, and psychological factors. Much work has been carried out towards a more systematic and structured approach to clinical diagnosis. Various tools are now available to assess the severity of CKDaP. Many of these tools require greater validation before they can be incorporated into the guidelines and into routine clinical practice. Further efforts are also needed in order to increase the awareness of clinicians and patients so that they can identify the CKDaP signs and symptoms in a timely manner. Currently established treatment options for CKDaP focus on the prevention of xerosis via topical emollients, the optimization of dialysis management, early referral to kidney transplantation if appropriate, oral antihistamine, and a variety of neuropathic agents. Other novel treatment options include the following: topical analgesics, topical tacrolimus, cannabinoid-containing compounds, antidepressants, oral leukotrienes, opioids, and non-pharmacological alternative therapies (i.e., phototherapy, dietary supplements, acupuncture/acupressure). We provide an updated review on the evidence relating to the epidemiology, the pathophysiology, the clinical assessment and diagnosis, and the management of CKDaP.

Effect of tramadol on apoptosis and synaptogenesis in hippocampal neurons: The possible role of µ-opioid receptor

Tramadol is a synthetic opioid with centrally acting analgesic activity that alleviates moderate to severe pain and treats withdrawal symptoms of the other opioids. Like other opioid drugs, tramadol abuse has adverse effects on central nervous system components. Chronic administration of tramadol induces maladaptive plasticity in brain structures responsible for cognitive function, such as the hippocampus. However, the mechanisms by which tramadol induces these alternations are not entirely understood. Here, we examine the effect of tramadol on apoptosis and synaptogenesis of hippocampal neuronal in vitro. First, the primary culture of hippocampal neurons from neonatal rats was established, and the purity of the neuronal cells was verified by immunofluorescent staining. To evaluate the effect of tramadol on neuronal cell viability MTT assay was carried out. The western blot analysis technique was performed for the assessment of apoptosis and synaptogenesis markers. Results show that chronic exposure to tramadol reduces cell viability of neuronal cells and naloxone reverses this effect. Also, the level of caspase-3 significantly increased in tramadol-exposed hippocampal neurons. Moreover, tramadol downregulates protein levels of synaptophysin and stathmin as synaptogenesis markers. Interestingly, the effects of tramadol were abrogated by naloxone treatment. These findings suggest that tramadol can induce neurotoxicity in hippocampal neuronal cells, and this effect was partly mediated through opioid receptors.

The consequences of neonatal pain, stress and opiate administration in animal models: An extensive meta-analysis concerning neuronal cell death, motor and behavioral outcomes

This systematic review and meta-analysis aimed to investigate the association of neonatal exposure to pain, stress, opiate administration alone, as well as opiate administration prior to a painful procedure on neuronal cell death, motor, and behavioral outcomes in rodents. In total, 36 studies investigating the effect of pain (n = 18), stress (n = 15), opiate administration (n = 13), as well as opiate administration prior to a painful event (n = 7) in rodents were included in our meta-analysis. The results showed a large effect of pain (g = 1.37, 95% CI 1.00-1.74, p < .001) on neuronal cell death. Moreover, higher number of neonatal pain events were significantly associated with increased neuronal cell death, increased anxiety (b = -1.18, SE = 0.43, p = .006), and depressant-like behavior (b = 1.74, SE = 0.51, p = .027) in rodents. Both opiates and pain had no impact on motor function (g = 0.26, 95% CI 0.18-0.70, p = .248).

The other side of the coin: Positive view on the role of opioids in cancer

Opioids have been used for medicinal purposes as an analgesic and recreational purposes as a euphorigenic throughout human history. Cancer patients are often treated with different doses of opioids concurrently with anti-cancer drugs for pain relief without exhibiting excessive adverse effects. The intersection of the biology of pain, opioid therapy, and disease progression represents the crux of the matters and is of potentially great importance in cancer care. For more than 20 years, multiple investigations have focused on the stimulatory effects of opioids on cancer cell growth, while in-depth studies on the inhibitory effects on cancer cell growth development have usually been neglected. This paper reviews the evidence regarding opioid therapies and their anti-cancer effects on various malignancies. Likewise, we have a glimpse into the molecular mechanisms necessary for pinpointing their positive or negative impacts on malignancies to raise awareness and stimulate more excellent dialogue regarding their carcinogenic/anticarcinogenic roles.

Dexamethasone Does not Compensate for Local Anesthetic Cytotoxic Effects on Tenocytes: Morphine or Morphine Plus Dexamethasone May Be a Safe Alternative

Purpose

The purposes of this in vitro study were to investigate whether the addition of dexamethasone can compensate for any cytotoxic effects of the amide-type local anesthetics (LA) bupivacaine and ropivacaine and whether morphine and morphine-6-glucuronide (M6G) may be a safe alternative for peritendinous application.

Methods

Biopsies of human biceps tendons (n = 6) were dissected and cultivated. Cells were characterized by the expression for tenocyte markers, collagen I, biglycan, tenascin C, scleraxis, and RUNX via reverse transcriptase-polymerase chain reaction and immunohistochemistry. Tenocytes were incubated with bupivacaine, ropivacaine, morphine, M6G, or a saline control with and without addition of dexamethasone for 15, 60, or 240 min. Cell viability was determined by quantifying the presence of adenosine-triphosphate.

Results

Significant time-dependent cytotoxic effects were observed for LA after all exposure times. After 15, 60, and 240 minutes, cell viability decreased to 81.1%, 49.4% and 0% (P < .001) for bupivacaine and to 81.4%, 69.6%, and 9.3% (P < .001) for ropivacaine compared to saline control. Dexamethasone did not compensate for these cytotoxic effects. Cell viability was not affected after 15, 60-min exposures to morphine and M6G but decreased significantly (P < .001) after 240 minutes compared to saline control. However, in combination with dexamethasone, tenocyte viability was significantly increased at all times for morphine (P < .01) and at 15 and 60 minutes for M6G (P < .01).

Conclusions

The results showed that amide-type LA have a time-dependent cytotoxic effect on human tenocytes in vitro, which could not be compensated for by dexamethasone, whereas morphine and M6G had no cytotoxic effects on tenocytes after 15 and 60 minutes. The addition of dexamethasone to morphine and M6G had a positive effect on viability, which increased significantly compared to the opioids.

Clinical Relevance

It is known that amide-type local anesthetics used for local joint analgesia have chondrotoxic side-effects. The combined application of morphine and dexamethasone may be a safe alternative.

Current Status and Prospects of Anesthesia and Breast Cancer: Does Anesthetic Technique Affect Recurrence and Survival Rates in Breast Cancer Surgery?

The relationship between the anesthetic technique and cancer recurrence has not yet been clarified in cancer surgery. Surgical stress and inhalation anesthesia suppress cell-mediated immunity (CMI), whereas intravenous (IV) anesthesia with propofol and regional anesthesia (RA) are known to be protective for CMI. Surgical stress, general anesthesia (GA) with inhalation anesthesia and opioids contribute to perioperative immunosuppression and may increase cancer recurrence and decrease survival. Surgical stress and GA activate the hypothalamic-pituitary-adrenal axis and release neuroendocrine mediators such as cortisol, catecholamines, and prostaglandin E₂, which may reduce host defense immunity and promote distant metastasis. On the other hand, IV anesthesia with propofol and RA with paravertebral block or epidural anesthesia can weaken surgical stress and GA-induced immunosuppression and protect the host defense immunity. IV anesthesia with propofol and RA or in combination with GA may reduce cancer recurrence and improve patient survival compared to GA alone. We review the current status of the relationship between anesthesia and breast cancer recurrence using retrospective and prospective studies conducted with animal models and clinical samples, and discuss the future prospects for reducing breast cancer recurrence and improving survival rates in breast cancer surgery.

Unravelling the pathophysiology of chronic kidney disease-associated pruritus

For decades, itch related to chronic kidney disease (CKDaP) has been a clinical problem, but the aetiology and pathophysiology of CKDaP are still not yet fully understood—currently the underlying pathophysiological mechanisms are thought to be multifactorial. As new therapeutic targets have recently been identified and clinical trials have shown promising results, our current understanding of the interrelationships has expanded significantly. Here we review the pathophysiology and recent findings on modulation and sensitization of itch contributing to the development of CKDaP, covering hypothesis regarding immune system dysfunction, metabolic changes, uremic toxin deposition, peripheral neuropathy and imbalances in the endogenous opioid system.

Effects of Anesthesia and Anesthetic Techniques on Metastasis of Lung Cancers: A Narrative Review

Purpose

Tumor recurrence and metastasis are essential for the mortality and morbidity of cancer. Surgical resection of solid tumors is the conventional treatment approach for malignant tumors. However, even after undergoing radical surgery, certain patients develop local or distant metastasis, which may contribute to treatment failure. Anesthesia and anesthetic techniques are widely used in the perioperative period. Emerging evidence indicates that anesthetics influence tumor recurrence and metastasis. Therefore, the current review summarizes the effects of anesthesia and anesthetic techniques on tumor recurrence and lung metastasis.

Methods

Relevant literature was retrieved from the following databases: Medline/PubMed, CNKI and Wanfang. A total of 109 articles were selected and analyzed in this research.

Results

(1) A variety of intravenous anesthetics may affect metastasis or tumor growth, though the evidence is contradictory and inconsistent, and the clinical data are still inconclusive. (2) Volatile anesthetics have proinflammatory effects and may have direct and indirect effects on the survival of cancer cells. (3) Although the relevant clinical data are limited, there is strong evidence in vitro that local anesthetics have a protective effect on cancer recurrence. (4) No mode of anesthesia has been determined to be beneficial to patients with cancer, but clinical studies are currently recommended for anesthesia modality and composite use.

Conclusion

Available data suggest that anesthesia and anesthetic techniques might play an important role in tumor progression and lung metastasis, the understanding of which will help in designing more effective management of the tumor and attaining fewer side effects.

miR-506-loaded gelatin nanospheres target PENK and inactivate the ERK/Fos signaling pathway to suppress triple-negative breast cancer aggressiveness

Triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancer. Some microRNAs (miRNAs) were abnormally expressed in TNBC, and they are closely related to the occurrence and progression of TNBC. Here, we found that miR-506 was significantly downregulated in TNBC and relatively lower miR-506 expression predicted a poorer prognosis. Moreover, we found that miR-506 could inhibit MDA-MB-231 cell viability, colony formation, migration, and invasion, and suppress the ERK/Fos oncogenic signaling pathway through upregulating its direct target protein proenkephalin (PENK). Therefore, miR-506 was proposed as a nucleic acid drug for TNBC therapy. However, miRNA is unstable in vivo, which limiting its application as a therapeutic drug via conventional oral or injected therapies. Here, a gelatin nanosphere (GN) delivery system was applied for the first time to load exogenous miRNA. Exogenous miR-506 mimic was loaded on GNs and injected into the in situ TNBC animal model, and the miR-506 could achieve sustained and controlled release. The results confirmed that overexpression of miR-506 and PENK in vivo through loading on GNs inhibited in situ triple-negative breast tumor growth and metastasis significantly in the xenograft model. Moreover, we indicated that the ERK/Fos signaling pathway was intensively inactivated after overexpression of miR-506 and PENK both in vitro and in vivo, which was further validated by the ERK1/2-specific inhibitor SCH772984. In conclusion, this study demonstrates that miR-506-loaded GNs have great potential in anti-TNBC aggressiveness therapy.

Biphalin, a dimeric opioid peptide, reduces neonatal hypoxia-ischemia brain injury in mice by the activation of PI3K/Akt signaling pathway

Previous studies have demonstrated that the activation of delta opioid receptors is neuroprotective against neonatal hypoxia-ischemia (HI) brain injury. The aim of this study was to investigate the neuroprotective effects of biphalin, a dimeric opioid peptide, in a mouse model of neonatal HI and the underlying mechanisms. On postnatal day 10, mouse pups were subjected to unilateral carotid artery ligation followed by 1 h of hypoxia (10 % O₂ in N₂). For treatment, biphalin (5 mg/kg, 10 mg/kg, 20 mg/kg) was administered intraperitoneally immediately after HI. The opioid antagonist naloxone or phosphatidylinositol-3-kinase inhibitor Ly294002 was administered to determine the underlying mechanisms. Infarct volume, brain edema, phosphorylated Akt and apoptosis-related proteins levels were evaluated by using a combination of 2,3,5-triphenyltetrazolium chloride staining, brain water content and Western blotting at 24 h after HI. The long-term effects of biphalin were evaluated by brain atrophy measurement, Nissl staining and neurobehavioral tests at 3 weeks post-HI. Biphalin (10 mg/kg) significantly reduced the infarct volume and ameliorated brain edema. Biphalin also had long-term protective effects against the loss of ipsilateral brain tissue and resulted in improvements in neurobehavioral outcomes. However, naloxone or Ly294002 abrogated the neuroprotective effects of biphalin. Furthermore, biphalin treatment significantly preserved phosphorylated Akt expression, increased Bcl-2 levels, and decreased Bax and cleaved caspase 3 levels after HI. These effects were also reversed by naloxone and Ly294002 respectively. In conclusion, biphalin protects against HI brain injury in neonatal mice, which might be through activation of the opioid receptor/phosphatidylinositol-3-kinase/Akt signaling pathway.

PENK inhibits osteosarcoma cell migration by activating the PI3K/Akt signaling pathway

Background

This article reports the effects of proenkephalin (PENK) on osteosarcoma (OS) cell migration.

Methods

A Gene Expression Omnibus (GEO) dataset was used to identify differentially expressed genes (DEGs) in OS tumor samples and normal human osteoblasts. Tumor tissue and adjacent normal tissue were collected from 40 OS patients. MG63 cells were transfected with si-PENK. Transwell migration assays and wound healing assays were performed to compare the effect of PENK on migration. Moreover, LY294002 was used to identify the potential mechanism. Gene expression was examined via qRT-PCR and Western blotting.

Results

Bioinformatic analysis revealed that PENK was downregulated in OS tumor samples compared with normal human osteoblasts. Moreover, PENK was identified as the hub gene of the DEGs. The PI3K/Akt signaling pathway was significantly enriched in the DEGs. Moreover, PENK was downregulated in OS and MG63 cells compared with the corresponding control cells. Silencing PENK promoted MG63 cell migration; however, treatment with LY294002 partially attenuated PENK silencing-induced OS cell migration.

Conclusion

PENK inhibits OS cell migration by activating the PI3K/Akt signaling pathway.

Hsp90β positively regulates μ-opioid receptor function

AIMS

Many μ-opioid receptor (MOR)-associated proteins can regulate the MOR signaling pathway. Using a bacterial two-hybrid screen, we found that the C-terminal of the MOR associated with heat shock protein 90 isoform β (Hsp90β). Here, we explored the effect of Hsp90β on MOR signaling transduction and function.

MAIN METHODS

The interaction of Hsp90β with MOR was detected by co-immunoprecipitation and immunofluorescence. The effects of Hsp90β on MOR signaling induced by opioids were studied in vitro and in vivo. The effects of the Hsp90β inhibitor 17-N-allylamino-17-demethoxygeldanamycin (17-AAG) on morphine tolerance and dependence were studied via a hot plate test and CPP test.

KEY FINDINGS

Hsp90β, instead of Hsp90α, interacted with the MOR in HEK293 cells and SH-SY5Y cells, and the interaction was augmented after morphine pretreatment. The interaction of Hsp90β and MOR increased the inhibition of cAMP and decreased PKA activity under opioid treatment. The functional Hsp90β-MOR complex also promoted the phosphorylation and internalization of the MOR induced by DAMGO in MOR-CHO cells. 17-AAG blocked Hsp90β-MOR interactions and decreased the effect of Hsp90β on the MOR signal transduction. In C57BL/6 mice, 17-AAG decreased morphine-induced acute anti-nociception in the hot plate test, with an increase in phosphorylated PKA and phosphorylated JNK and a decrease in phosphorylated CREB and phosphorylated ERK in murine brains. Chronic morphine treatment induced tolerance, and dependence was inhibited by 17-AAG co-administration.

SIGNIFICANCE

Hsp90β is a positive co-regulator of the MOR via the activation of a G-protein-dependent and β-arrestin-dependent pathway. Hsp90β has the potential to improve the pharmacologic profile of existing opiates. It is conceivable that in future clinical treatments, the Hsp90β inhibitor, 17-AAG, could decrease the tolerance and dependence in cancer patients induced by opioids.

Restoration of Cyclo-Gly-Pro-induced salivary hyposecretion and submandibular composition by naloxone in mice

Cyclo-Gly-Pro (CGP) attenuates nociception, however its effects on salivary glands remain unclear. In this study, we investigated the acute effects of CGP on salivary flow and composition, and on the submandibular gland composition, compared with morphine. Besides, we characterized the effects of naloxone (a non-selective opioid receptor antagonist) on CGP- and morphine-induced salivary and glandular alterations in mice. After that, in silico analyses were performed to predict the interaction between CGP and opioid receptors. Morphine and CGP significantly reduced salivary flow and total protein concentration of saliva and naloxone restored them to the physiological levels. Morphine and CGP also reduced several infrared vibrational modes (Amide I, 1687-1594cm^-1; Amide II, 1594-1494cm^-1; CH₂/CH₃, 1488-1433cm^-1; C = O, 1432-1365cm^-1; PO₂ asymmetric, 1290-1185cm^-1; PO₂ symmetric, 1135-999cm^-1) and naloxone reverted these alterations. The in silico docking analysis demonstrated the interaction of polar contacts between the CGP and opioid receptor Cys219 residue. Altogether, we showed that salivary hypofunction and glandular changes elicited by CGP may occur through opioid receptor suggesting that the blockage of opioid receptors in superior cervical and submandibular ganglions may be a possible strategy to restore salivary secretion while maintaining antinociceptive action due its effects on the central nervous system.

Evaluation of Receptor Affinity, Analgesic Activity and Cytotoxicity of a Hybrid Peptide, AWL3020

In the present contribution we report design, synthesis and evaluation of receptor affinity, analgesic activity and cytotoxicity of a hybrid peptide, AWL3020. The peptide includes two pharmacophores, one of δ-opioid receptor (δOR) agonists and one of neurokinin-1 receptor (NK1R) antagonists. The design was motivated by the desire to obtain a compound with strong analgesic action and potential additional antiproliferative action. The compound displays high δOR affinity (IC50 = 29.5 nM). On the other hand, it has only poor affinity for the NK1R (IC50 = 70.28 μM). The substance shows good analgesic action which is however weaker than that of morphine. Regarding the effect on proliferation, the compound exhibits no pro-proliferative action in the assayed range. In higher concentrations, it has also cytotoxic activity. This effect is however not selective. The strongest effect of AWL3020 was found for melanoma MeW164 cell line (EC50 = 46.27 μM in reduction of cell numbers after a few days of incubation; EC50 = 37.78 μM in MTT assay).

Mu Opioid Receptor 1 (MOR-1) Expression in Colorectal Cancer and Oncological Long-Term Outcomes: A Five-Year Retrospective Longitudinal Cohort Study

Preclinical evidence has shown increased expression of mu opioid receptor 1 (MOR-1) in colorectal cancer although its association with disease-free and overall survival (DFS and OS) has not been investigated. We hypothesized that MOR-1 was overexpressed in tumor samples compared to normal tissue and this was associated with decreased DFS and OS. We carried out a retrospective study assessing the association of MOR-1 tumor expression with long-term outcomes by immunohistochemistry in normal and tumor samples from 174 colorectal cancer patients. The primary endpoint was five years of DFS. Secondary endpoints were five years of OS, the difference in MOR-1 expression between normal and tumor tissue and the occurrence of postoperative complications. Multivariable Cox regression showed no significant association between MOR-1 expression and DFS (HR 0.791, 95% CI 0.603–1.039, p = 0.092). MOR-1 expression was higher in tumor tissue compared to non-tumor tissue. No associations were found between MOR-1 expression and OS or postoperative complications. These findings suggest that although MOR-1 is over-expressed in colorectal cancer samples there is no association to increased risk of recurrence or mortality. Future studies are warranted to elucidate the role of cancer stage, genetic polymorphism, and quantitative assessment of MOR-1 over-expression on long-term outcomes in colorectal cancer.

Nociceptin Receptor Is Overexpressed in Non-small Cell Lung Cancer and Predicts Poor Prognosis

Classic opioid receptors, mu (μ), delta (δ), and kappa (κ), have been reported to be expressed in non-small cell lung cancer (NSCLC) cell lines and tumor tissues and to play a role in tumor prognosis. However, the expression and role of the non-classic opioid receptor, nociceptin receptor (NOP) in cancer are unclear. Our hypothesis was that NOP was also highly expressed in NSCLC tumor tissues and this could be correlated with patients' prognostic characters. Expression of NOP was examined in archived cancer tissues from 129 enrolled NSCLC patients by immunohistochemistry and was further analyzed with the patients' outcomes. NOP expression in NSCLC cell lines was also detected. The dataset from Kaplan-Meier Plotter was used to explore the correlation between the levels of NOP mRNA in cancerous tissue and the prognosis of NSCLC patients. Cell functional assays were performed to detect the effect of NOP activation on tumor aggressive furthers. Results showed NOP expression was highly expressed in cancer tissues and human cancer cell lines. NOP expression was not associated with patients' opioid requirement but closely with some clinicopathological indicators which reflected the malignancy. Moreover, NOP staining level was the independent poor prognostic factor for NSCLC patients receiving lobectomy, which was further verified by determining the mRNA expression levels through the online dataset. In vitro experiments revealed that NOP activation promotes the proliferation and invasion of A549 cells via PI3K/Akt signaling pathway. We conclude that NOP is overexpressed in NSCLC and is inversely correlated with patient's postoperative survival.

Design, synthesis and evaluation of 111In labeled DOTA-conjugated tetrapeptides having high affinity and selectivity for mu opioid receptors

INTRODUCTION

Peripheral mu (μ) opioid receptors are implicated in pain, bowel dysfunction and the progression of certain cancers. In an effort to identify radioligands well suited for imaging these peripheral sites, we have prepared and evaluated four hydrophilic ¹¹¹In labeled DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) conjugated μ tetrapeptides.

METHODS

Peptides were prepared by solid-phase techniques, using orthogonal strategies to achieve branching to DOTA, and then characterized by HPLC, mass spectroscopy and amino acid analysis. Scaffolds included novel peptide H-Dmt-D-Ala-Phe-Orn-NH₂ (DAPO), where Dmt = 2',6'-dimethyltyrosine, and known peptide H-Dmt-D-Arg-Phe-Lys-NH₂ ([Dmt¹]DALDA). Constructs had DOTA conjugation at the Orn⁴ or Lys⁴ side chains, or to the C-terminal through a hexanoic acid-lysine linker. Indium(III) complexation and ¹¹¹In radiolabeling were accomplished by standard methods. Protein binding and Log D_7.4 were determined. Binding and pharmacological profiles were obtained in vitro. Biodistribution and radiometabolite studies were conducted using male CD-1 mice.

RESULTS

All four indium(III)-DOTA conjugates derived from DAPO and [Dmt¹]DALDA showed good selectivity and subnanomolar affinity for μ opioid receptors. One radioligand, H-Dmt-D-Ala-Phe-Orn(δ-[¹¹¹In]In-DOTA)-NH₂, showed 25% specific binding in vivo to μ sites in mouse gut. Notably, this was the least polar of the series, and also showed low sensitivity to modulation of binding by sodium ions. All radioligands showed high kidney uptake of radiometabolites.

CONCLUSIONS

Visualizing peripheral μ opioid receptors using ¹¹¹In labeled DOTA-conjugated tetrapeptides appears feasible, but structural modifications to enhance specific binding and metabolic stability, as well as to reduce kidney uptake, will be required.

ADVANCES IN KNOWLEDGE

This study shows in vivo labeling of peripheral μ opioid receptors by a tetrapeptide radioligand, and provides information that should prove useful in the design of peptide radioligands having optimal properties.

Fentanyl Induces Cerebellar Internal Granular Cell Layer Apoptosis in Healthy Newborn Pigs

Background

Opioids like fentanyl are regularly used in neonates for analgesia and sedation. So far, they have been reported to be safe and eligible to use. The cerebellum has become a focus of neurodevelopmental research within the last years, as it is known to play an important role in long-lasting motor, cognitive, and other behavioral changes. The cerebellar cortex is of major importance in the coordinative role of the cerebellum and highly vulnerable to injury and impaired growth.

Objective

This study was performed to evaluate the apoptotic effect of intravenous fentanyl infusion on the cerebellum in healthy newborn pigs.

Methods

Thirteen healthy pigs (<median 12 h old) were randomized into (1) 24 h of intravenous fentanyl at normothermia (NTFe, n = 6) or (2) non-ventilated controls at normothermia (NTCTR, n = 7). Cerebellar sections were morphologically assessed after staining with hematoxylin–eosin. In addition, paired sections were immuno-stained for cell death [Cleaved caspase-3 and terminal deoxynucleotidyl transferase-mediated deoxyuridine-triphosphate nick-end labeling (TUNEL)], and positive cells were counted in defined areas of the internal granular cell layer. In total, cells in three cerebellar gyri were counted.

Results

We found that there was an increase in cells with apoptotic morphology in the internal granular cell layer in the NTFe group. For quantification, we found a significant increase in cell death in group (1) [median (range) number of caspase-3-positive cell group (1) 8 (1–22) vs. group (2) 1 (1–6) and TUNEL-positive cells (1) 6 (1–10) vs. (2) 1 (0–4)]. In both groups, there was no difference in the number of Purkinje cells. Both groups had comparable and stable physiological parameters throughout the 24 h period.

Conclusion

Twenty-four hours of continuous intravenous fentanyl infusion increased apoptosis in the internal granular cell layer in the cerebellum of healthy newborn pigs.

Methadone against cancer: Lost in translation

Recently, the opioid analgesic d,l-methadone has gained much attention as a potential antineoplastic compound, considerably triggered through lay press and media. In consequence, physicians and pharmacists are currently confronted with numerous patients willing to use d,l-methadone against their malignancies. Well-performed in vitro and in vivo models have in fact shown pro-apoptotic effects of d,l-methadone or other opioids, but also proliferation-stimulating properties. Moreover, the mechanisms of proposed opioid-stimulated apoptosis are incompletely described or contradicting. Finally, the receptors mostly responsible for induction of apoptosis by d,l-methadone remain unclear as contributions of both µ-opioid receptors, Fas cell death receptors, toll-like receptors, N-Methyl-d-aspartate receptors and opioid growth factor receptors were suggested. Such ambiguity prevents rational application of d,l-methadone or patient stratification to enhance beneficial antineoplastic effects. From a clinical point of view, d,l-methadone and other opioids might in fact prolong survival, but such effects likely originate from their analgesic and neuro-psychotropic properties and, thus, improvements of quality of life. Crucial obstacles to the administration of d,l-methadone are incomplete knowledge about its systemic disposition, highly variable pharmacokinetics, profound drug-drug- or drug-disease interaction and QT-prolongation potential. This article summarizes and rates the pharmacological basis of d,l-methadone as an antineoplastic agent and puts its administration in clinical oncology into perspective. Despite enthralling experimental findings about d,l-methadone-mediated apoptosis in cancerous cells or tissues, clinicians should realize the current lack of evidence for the use of d,l-methadone as an antineoplastic agent. Its administration against cancer pain is, however, tenable, albeit restricted to certain clinical situations.

Opioids: Modulators of angiogenesis in wound healing and cancer

Opioids are potent drugs that are widely used to control wound or cancer pain. Increasing evidence suggest that opioids mediate clinically relevant effects that go beyond their classical role as analgesics. Of note, opioids appear to modulate angiogenesis - a process that is critical in wound healing and cancer progression. In this review, we focus on pro- and anti-angiogenic facets of opioids that arise from the activation of individual opioid receptors and the usage of individual concentrations or application routes. We overview the still incompletely elucidated mechanisms of these angiogenic opioid actions. Moreover, we describe plausible opioids effects, which - although not primarily studied in the context of vessel formation - may be related to the opioid-driven processes of angiogenesis. Finally we discuss the use of opioids as an innovative therapeutic avenue for the treatment of chronic wounds and cancer.

Incorporation of new neurons in the olfactory bulb after paced mating in the female rat

One of the regions that constantly produces neurogenesis in the adult brain is the subventricular zone (SVZ), whose new cells migrate to the olfactory bulbs (OB). When the females regulate the copulatory events (paced mating) the number of new cells in the SVZ increases, as well as those observed in the OB 15 days later. However, no changes were observed in the number of cells 45 days after the females paced the sexual interaction. Constant sensory stimulation is an important promoter of cell survival in the OB circuit. Hence, we increased the number of mating sessions in this study to cover the period where stimulation of the new cells is critical for their incorporation into pre-existing circuits in the OB. Ovariectomized female Wistar rats, were injected with the mitotic marker 5-bromo-2'-deoxyuridine (BrdU, 100 mg/kg, per injection) before, at the end and one hour after mating. Sexual behavior was recorded for 1 h in 10 weekly sessions. After the last mating session, brain sections were processed to determine BrdU immunoreactivity. Our results indicate that females that paced the sexual interaction for 10 sessions had a higher number of cells in the glomerular layer (GL) of the accessory olfactory bulb (AOB) and a higher number of neurons in the granular layer (GrL) of the main olfactory bulb (MOB) in comparison to the control group. These results indicate that continued sexual interaction contributes to the integration of new cells and neurons, induced in the first sexual experience, into pre-exiting circuits of the OB.

Effects of surgery and anesthetic choice on immunosuppression and cancer recurrence

Background

The relationship between surgery and anesthetic-induced immunosuppression and cancer recurrence remains unresolved. Surgery and anesthesia stimulate the hypothalamic–pituitary–adrenal (HPA) axis and sympathetic nervous system (SNS) to cause immunosuppression through several tumor-derived soluble factors. The potential impact of surgery and anesthesia on cancer recurrence was reviewed to provide guidance for cancer surgical treatment.

Methods

PubMed was searched up to December 31, 2016 using search terms such as, “anesthetic technique and cancer recurrence,” “regional anesthesia and cancer recurrence,” “local anesthesia and cancer recurrence,” “anesthetic technique and immunosuppression,” and “anesthetic technique and oncologic surgery.”

Results

Surgery-induced stress responses and surgical manipulation enhance tumor metastasis via release of angiogenic factors and suppression of natural killer (NK) cells and cell-mediated immunity. Intravenous agents such as ketamine and thiopental suppress NK cell activity, whereas propofol does not. Ketamine induces T-lymphocyte apoptosis but midazolam does not affect cytotoxic T-lymphocytes. Volatile anesthetics suppress NK cell activity, induce T-lymphocyte apoptosis, and enhance angiogenesis through hypoxia inducible factor-1α (HIF-1α) activity. Opioids suppress NK cell activity and increase regulatory T cells.

Conclusion

Local anesthetics such as lidocaine increase NK cell activity. Anesthetics such as propofol and locoregional anesthesia, which decrease surgery-induced neuroendocrine responses through HPA-axis and SNS suppression, may cause less immunosuppression and recurrence of certain types of cancer compared to volatile anesthetics and opioids.

Toll-like Receptor-Dependent Negative Effects of Opioids: A Battle between Analgesia and Hyperalgesia

Our understanding of the pathophysiology of the pathological pain and the pharmacology of analgesic treatments has progressed tremendously over the past two decades. Among the well-documented pro-algesic factors, glia and other toll-like receptors (TLRs)-expressing cells in the neuroimmune interface have been recognized for their role in the development of neuropathic pain and for compromising the analgesic effects of opioids. Here, we comprehensively review the molecular mechanisms of pain initiation and progression, the role of TLRs in these processes, and the molecular mechanisms of morphine and morphine-3-glucuronide in TLR-dependent central immune signaling. The data reviewed here suggest that, while targeting glia to treat neuropathic pain, both analgesic and analgesia-opposing effects of opioids must be considered by acknowledging their role in TLR-mediated signaling.

Opiate Drugs with Abuse Liability Hijack the Endogenous Opioid System to Disrupt Neuronal and Glial Maturation in the Central Nervous System

The endogenous opioid system, comprised of multiple opioid neuropeptide and receptor gene families, is highly expressed by developing neural cells and can significantly influence neuronal and glial maturation. In many central nervous system (CNS) regions, the expression of opioid peptides and receptors occurs only transiently during development, effectively disappearing with subsequent maturation only to reemerge under pathologic conditions, such as with inflammation or injury. Opiate drugs with abuse liability act to modify growth and development by mimicking the actions of endogenous opioids. Although typically mediated by μ-opioid receptors, opiate drugs can also act through δ- and κ-opioid receptors to modulate growth in a cell-type, region-specific, and developmentally regulated manner. Opioids act as biological response modifiers and their actions are highly contextual, plastic, modifiable, and influenced by other physiological processes or pathophysiological conditions, such as neuro-acquired immunodeficiency syndrome. To date, most studies have considered the acute effects of opiates on cellular maturation. For example, activating opioid receptors typically results in acute growth inhibition in both neurons and glia. However, with sustained opioid exposure, compensatory factors become operative, a concept that has been largely overlooked during CNS maturation. Accordingly, this article surveys prior studies on the effects of opiates on CNS maturation, and also suggests new directions for future research in this area. Identifying the cellular and molecular mechanisms underlying the adaptive responses to chronic opiate exposure (e.g., tolerance) during maturation is crucial toward understanding the consequences of perinatal opiate exposure on the CNS.

High-Intensity Swimming Exercise Decreases Glutamate-Induced Nociception by Activation of G-Protein-Coupled Receptors Inhibiting Phosphorylated Protein Kinase A

Several studies in humans have reported that improved pain control is associated with exercise in a variety of painful conditions, including osteoarthritis, fibromyalgia, and neuropathic pain. Despite the growing amount of experimental data on physical exercise and nociception, the precise mechanisms through which high-intensity exercise reduces pain remain elusive. Since the glutamatergic system plays a major role in pain transmission, we firstly analyzed if physical exercise could be able to decrease glutamate-induced nociception through G-protein-coupled receptor (G-PCR) activation. The second purpose of this study was to examine the effect of exercising upon phosphorylation of protein kinase A (PKA) isoforms induced by intraplantar (i.pl.) glutamate injection in mice. Our results demonstrate that high-intensity swimming exercise decreases nociception induced by glutamate and that i.pl. or intrathecal injections of cannabinoid, opioid, and adenosine receptor antagonists, AM281, naloxone, and 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), respectively, prevent this effect. Furthermore, the peripheral A₁ and opioid receptors, but not CB₁, are also involved in exercise's effect. We also verified that glutamate injection increases levels of phosphorylated PKA (p-PKA). High-intensity swimming exercise significantly prevented p-PKA increase. The current data show the direct involvement of the glutamatergic system on the hyponociceptive effect of high-intensity swimming exercise as well as demonstrate that physical exercise can activate multiple intracellular pathways through G-PCR activation, which share the same endogenous mechanism, i.e., inhibition of p-PKA.

Synthesis and opioid receptor binding of indium (III) and [111In]-labeled macrocyclic conjugates of diprenorphine: novel ligands designed for imaging studies of peripheral opioid receptors

Radiolabeled diprenorphine (DPN) and analogs are widely used ligands for non-invasive brain imaging of opioid receptors. To develop complementary radioligands optimized for studies of the peripheral opioid receptors, we prepared a pair of hydrophilic DPN derivatives, conjugated to the macrocyclic chelator DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid), for complexation with trivalent metals. The non-radioactive indium (III) complexes, tethered to the C6-oxygen position of the DPN scaffold by 6- to 9-atom spacers, displayed high affinities for binding to μ, δ and κ opioid receptors in vitro. Use of the 9-atom linker conferred picomolar affinities equipotent to those of the parent ligand DPN. The [¹¹¹In]-labeled complexes were prepared in good yield (>70%), with high radiochemical purity (~99%) and high specific radioactivity (>4000 mCi/μmol). Their log D_7.4 values were -2.21 to -1.66. In comparison, DPN is lipophilic, with a log D_7.4 of +2.25. Further study in vivo is warranted to assess the suitability of these [¹¹¹In]-labeled DPN-DOTA conjugates for imaging trials.

Sexual Behavior Increases Cell Proliferation in the Rostral Migratory Stream and Promotes the Differentiation of the New Cells into Neurons in the Accessory Olfactory Bulb of Female Rats

We have previously demonstrated, that 15 days after female rats pace the sexual interaction, there is an increase in the number of new cells that reach the granular cell layer (GrL) of the accessory olfactory bulb (AOB). The aim of the present study was to evaluate, if the first sexual experience in the female rat increases cell proliferation in the subventricular zone (SVZ) and the rostral migratory stream (RMS). We also tested if this behavior promotes the survival of the new cells that integrate into the main olfactory bulb (MOB) and AOB 45 days after the behavioral test. Sexually, naive female rats were injected with the DNA synthesis marker 5'-bromo-2'-deoxyuridine (BrdU) on the day of the behavioral test. They were randomly divided into the following groups: Female rats placed alone in the mating cage (1); Females exposed to amyl acetate odor [banana scent, (2)]; Females that could see, hear, and smell the male but physical contact was not possible [exposed to male, (3)]; Female rats that could pace the sexual interaction (4); and females that mated without the possibility of pacing the sexual interaction (5). Animals were sacrificed 2 days after the behavioral test (proliferation) or 45 days later (survival). Our results show that 2 days after females were exposed to banana scent or to the male, they had a higher number of cells in the SVZ. Females, that mated in pace and no-paced conditions had more new cells in the RMS. At 45 days, no significant differences were found in the number of new cells that survived in the MOB or in the AOB. However, mating increased the percentage of new cells, that differentiated into neurons in the GrL of the AOB. These new cells expressed c-Fos after a second sexual encounter just before the females were sacrificed. No significant differences in plasma levels of estradiol and progesterone were observed between groups. Our results indicate that the first sexual experience increases cell proliferation in the RMS and mating 45 days later enhances the number of new cells that differentiate into neurons in the AOB. These new neurons are activated by sexual stimulation.

Morphine, a potential antagonist of cisplatin cytotoxicity, inhibits cisplatin-induced apoptosis and suppression of tumor growth in nasopharyngeal carcinoma xenografts

Morphine is an opioid analgesic drug often used for pain relief in cancer patients. However, there is growing evidence that morphine may modulate tumor growth, progression and metastasis. In this study, we evaluated whether morphine modulates cisplatin-induced apoptosis in human nasopharyngeal carcinoma CNE-2 cells and whether morphine affects the antitumor activity of cisplatin on tumor growth in human nasopharyngeal carcinoma CNE-2 xenografts in nude mice. We showed that a pretreatment with morphine (1 μg/ml) inhibited the sensitivity of CNE-2 cells to cisplatin by inhibiting cisplatin-induced CNE-2 cell apoptosis, decreasing caspase-3 activity and increasing the Bcl-2/Bax ratio. However, a high dose of morphine (1000 μg/ml) had the opposite effect. We also showed that at a low dose, morphine enhances chemoresistance in an in vivo nasopharyngeal carcinoma (NPC) model by inhibiting cisplatin-induced apoptosis and decreasing neovascularization. Taken together, our results indicate that a low dose of morphine may lead to chemoresistance of cisplatin in NPC models in vitro and in vivo by inhibiting cisplatin-induced apoptosis and decreasing neovascularization.

Activation of μ opioid receptors modulates inflammation in acute experimental colitis

BACKGROUND

μ opioid receptors (μORs) are expressed by neurons and inflammatory cells, and mediate immune response. We tested whether activation of peripheral μORs ameliorates the acute and delayed phase of colitis.

METHODS

C57BL/6J mice were treated with 3% dextran sodium sulfate (DSS) in water, 5 days with or without the peripherally acting μOR agonist, [D-Ala2, N-Me-Phe4, Gly5-ol]-Enkephalin (DAMGO) or with DAMGO+μOR antagonist at day 2-5, then euthanized. Other mice received DSS followed by water for 4 weeks, or DSS with DAMGO starting at day 2 of DSS for 2 or 3 weeks followed by water, then euthanized at 4 weeks. Disease activity index (DAI), histological damage, and myeloperoxidase assay (MPO), as index of neutrophil infiltration, were evaluated. Cytokines and μOR mRNAs were measured with RT-PCR, and nuclear factor-kB (NF-kB), the antiapoptotic factor Bcl-xL, and caspase 3 and 7 with Western blot.

KEY RESULTS

DSS induced acute colitis with elevated DAI, tissue damage, apoptosis and increased MPO, cytokines, μOR mRNA, and NF-kB. DAMGO significantly reduced DAI, inflammatory indexes, cytokines, caspases, and NF-kB, and upregulated Bcl-xL, effects prevented by μOR antagonist. In DSS mice plus 4 weeks of water, DAI, NF-kB, and μOR were normal, whereas MPO, histological damage, and cytokines were still elevated; DAMGO did not reduce inflammation, and did not upregulate Bcl-xL.

CONCLUSIONS & INFERENCES

μOR activation ameliorated the acute but not the delayed phase of DSS colitis by reducing cytokines, likely through activation of the antiapoptotic factor, Bcl-xL, and suppression of NF-kB, a potentiator of inflammation.

Involvement of neuronal TGF-β activated kinase 1 in the development of tolerance to morphine-induced antinociception in rat spinal cord

BACKGROUND AND PURPOSE

Tolerance induced by morphine and other opiates remains a major unresolved problem in the clinical management of pain. There is now good evidence for the importance of MAPKs in morphine-induced antinociceptive tolerance. A member of the MAPK kinase kinase family, TGF-β activated kinase 1 (TAK1) is the common upstream kinase of MAPKs. Here, we have assessed the involvement of TAK1 in the development of tolerance to morphine-induced analgesia.

EXPERIMENTAL APPROACH

The effects of an antagonist of TAK1 on morphine tolerance were investigated in vivo using the Randall-Selitto test, and the mechanism was investigated using Western blot and immunohistochemistry. The expression of TAK1 after chronic morphine exposure was also evaluated in vitro by immunohistochemistry.

KEY RESULTS

Chronic intrathecal morphine exposure up-regulated protein levels and phosphorylation of spinal TAK1. TAK1 immunoreactivity was co-localized with the neuronal marker NeuN. Intrathecal administration of 5Z-7-oxozeaenol (OZ), a selective TAK1 inhibitor, attenuated the loss of morphine analgesic potency and morphine-induced TAK1 up-regulation. Furthermore, OZ decreased the up-regulated expression of spinal p38 and JNK after repeated morphine exposure. In vitro studies demonstrated that sustained morphine treatment induced TAK1 up-regulation, which was reversed by co-administration of OZ. A bolus injection of OZ showed some reversal of established morphine antinociceptive tolerance.

CONCLUSIONS AND IMPLICATIONS

TAK1 played a pivotal role in the development of morphine-induced antinociceptive tolerance. Modulation of TAK1 activation by the selective inhibitor OZ in the lumbar spinal cord may prove to be an attractive adjuvant therapy to attenuate such tolerance.

Redox-based epigenetic status in drug addiction: a potential contributor to gene priming and a mechanistic rationale for metabolic intervention

Alcohol and other drugs of abuse, including psychostimulants and opioids, can induce epigenetic changes: a contributing factor for drug addiction, tolerance, and associated withdrawal symptoms. DNA methylation is a major epigenetic mechanism and it is one of more than 200 methylation reactions supported by methyl donor S-adenosylmethionine (SAM). Levels of SAM are controlled by cellular redox status via the folate and vitamin B12-dependent enzyme methionine synthase (MS). For example, under oxidative conditions MS is inhibited, diverting its substrate homocysteine (HCY) to the trans sulfuration pathway. Alcohol, dopamine, and morphine, can alter intracellular levels of glutathione (GSH)-based cellular redox status, subsequently affecting SAM levels and DNA methylation status. Here, existing evidence is presented in a coherent manner to propose a novel hypothesis implicating the involvement of redox-based epigenetic changes in drug addiction. Further, we discuss how a “gene priming” phenomenon can contribute to the maintenance of redox and methylation status homeostasis under various stimuli including drugs of abuse. Additionally, a new mechanistic rationale for the use of metabolic interventions/redox-replenishers as symptomatic treatment of alcohol and other drug addiction and associated withdrawal symptoms is also provided. Hence, the current review article strengthens the hypothesis that neuronal metabolism has a critical bidirectional coupling with epigenetic changes in drug addiction exemplified by the link between redox-based metabolic changes and resultant epigenetic consequences under the effect of drugs of abuse.