Effects of opioid tolerance and withdrawal on the immune system

DeepBiomarker2: Prediction of Alcohol and Substance Use Disorder Risk in Post-Traumatic Stress Disorder Patients Using Electronic Medical Records and Multiple Social Determinants of Health

Prediction of high-risk events amongst patients with mental disorders is critical for personalized interventions. We developed DeepBiomarker2 by leveraging deep learning and natural language processing to analyze lab tests, medication use, diagnosis, social determinants of health (SDoH) parameters, and psychotherapy for outcome prediction. To increase the model's interpretability, we further refined our contribution analysis to identify key features by scaling with a factor from a reference feature. We applied DeepBiomarker2 to analyze the EMR data of 38,807 patients from the University of Pittsburgh Medical Center diagnosed with post-traumatic stress disorder (PTSD) to determine their risk of developing alcohol and substance use disorder (ASUD). DeepBiomarker2 predicted whether a PTSD patient would have a diagnosis of ASUD within the following 3 months with an average c-statistic (receiver operating characteristic AUC) of 0.93 and average F1 score, precision, and recall of 0.880, 0.895, and 0.866 in the test sets, respectively. Our study found that the medications clindamycin, enalapril, penicillin, valacyclovir, Xarelto/rivaroxaban, moxifloxacin, and atropine and the SDoH parameters access to psychotherapy, living in zip codes with a high normalized vegetative index, Gini index, and low-income segregation may have potential to reduce the risk of ASUDs in PTSD. In conclusion, the integration of SDoH information, coupled with the refined feature contribution analysis, empowers DeepBiomarker2 to accurately predict ASUD risk. Moreover, the model can further identify potential indicators of increased risk along with medications with beneficial effects.

DeepBiomarker2: Prediction of alcohol and substance use disorder risk in post-traumatic stress disorder patients using electronic medical records and multiple social determinants of health

Introduction

Prediction of high-risk events amongst patients with mental disorders is critical for personalized interventions. In our previous study, we developed a deep learning-based model, DeepBiomarker by utilizing electronic medical records (EMR) to predict the outcomes of patients with suicide-related events in post-traumatic stress disorder (PTSD) patients.

Methods

We improved our deep learning model to develop DeepBiomarker2 through data integration of multimodal information: lab tests, medication use, diagnosis, and social determinants of health (SDoH) parameters (both individual and neighborhood level) from EMR data for outcome prediction. We further refined our contribution analysis for identifying key factors. We applied DeepBiomarker2 to analyze EMR data of 38,807 patients from University of Pittsburgh Medical Center diagnosed with PTSD to determine their risk of developing alcohol and substance use disorder (ASUD).

Results

DeepBiomarker2 predicted whether a PTSD patient will have a diagnosis of ASUD within the following 3 months with a c-statistic (receiver operating characteristic AUC) of 0·93. We used contribution analysis technology to identify key lab tests, medication use and diagnosis for ASUD prediction. These identified factors imply that the regulation of the energy metabolism, blood circulation, inflammation, and microbiome is involved in shaping the pathophysiological pathways promoting ASUD risks in PTSD patients. Our study found protective medications such as oxybutynin, magnesium oxide, clindamycin, cetirizine, montelukast and venlafaxine all have a potential to reduce risk of ASUDs.

Discussion

DeepBiomarker2 can predict ASUD risk with high accuracy and can further identify potential risk factors along with medications with beneficial effects. We believe that our approach will help in personalized interventions of PTSD for a variety of clinical scenarios.

Natural Polyphenols-Resveratrol, Quercetin, Magnolol, and β-Catechin-Block Certain Aspects of Heroin Addiction and Modulate Striatal IL-6 and TNF-α

We have examined the effects of four different polyphenols in attenuating heroin addiction using a conditioned place preference (CPP) paradigm. Adult male Sprague Dawley rats received heroin (alternating with saline) in escalating doses starting from 10 mg/kg, i.p. up to 80 mg/kg/d for 14 consecutive days. The rats were treated with distilled water (1 mL), quercetin (50 mg/kg/d), β-catechin (100 mg/kg/d), resveratrol (30 mg/kg/d), or magnolol (50 mg/kg/d) through oral gavage for 7 consecutive days, 30 min before heroin administration, starting on day 8. Heroin withdrawal manifestations were assessed 24 h post last heroin administration following the administration of naloxone (1 mg/kg i.p). Heroin CPP reinstatement was tested following a single dose of heroin (10 mg/kg i.p.) administration. Striatal interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α) were quantified (ELISA) after naloxone-precipitated heroin withdrawal. Compared to the vehicle, the heroin-administered rats spent significantly more time in the heroin-paired chamber (p < 0.0001). Concomitant administration of resveratrol and quercetin prevented the acquisition of heroin CPP, while resveratrol, quercetin, and magnolol blocked heroin-triggered reinstatement. Magnolol, quercetin, and β-catechin blocked naloxone-precipitated heroin withdrawal and increased striatal IL-6 concentration (p < 0.01). Resveratrol administration was associated with significantly higher withdrawal scores compared to those of the control animals (p < 0.0001). The results of this study show that different polyphenols target specific behavioral domains of heroin addiction in a CPP model and modulate the increase in striatal inflammatory cytokines TNF-α and IL-6 observed during naloxone-precipitated heroin withdrawal. Further research is needed to study the clinical utility of polyphenols and to investigate the intriguing finding that resveratrol enhances, rather than attenuates naloxone-precipitated heroin withdrawal.

Estradiol Enhances the Development of Addiction-Like Features in a Female Rat Model of Opioid Use Disorder

INTRODUCTION

Women are more vulnerable than men in many aspects of opioid use disorder (OUD); a major theory of sex differences in substance use disorders is that these differences are due to ovarian hormones with estradiol enhancing vulnerability in females. However, most of this evidence is for psychostimulants and alcohol; evidence with opioids is sparse. Thus, the goal of this study was to determine the impact of estradiol on vulnerability in females in a rat model of OUD.

METHOD

Following self-administration training, ovariectomized (OVX) females with (E) or without (V) estradiol replacement were given extended (24 h/day), intermittent access (2, 5-min trials/h) to fentanyl for 10 days. Then, the development of three key features of OUD were assessed, including physical dependence, defined by the magnitude and time course of weight loss during withdrawal; an enhanced motivation for fentanyl, assessed using a progressive-ratio schedule; and relapse vulnerability, assessed using an extinction/cue-induced reinstatement procedure. These later two characteristics were examined following 14 days of withdrawal when the phenotypes are known to be highly expressed.

RESULTS

OVX+E females self-administered markedly higher levels of fentanyl under extended, intermittent-access conditions and showed a longer time course of physical dependence, a greater increase in motivation for fentanyl, and an enhanced sensitivity to the reinstating effects of fentanyl-associated cues compared to OVX+V rats. Severe health complications were also observed in OVX+E, but not OVX+V females, during withdrawal.

CONCLUSION

These results indicate that, as with findings with psychostimulants and alcohol, estradiol enhances vulnerability in females to developing opioid addiction-like features and serious opioid-related health complications.

Dynamic immune and exosome transcriptomic responses in patients undergoing psychostimulant methamphetamine withdrawal

Methamphetamine (METH) addiction and withdrawal cause serious harm to both the immune system and nervous system. However, the pathogenesis remains largely unknown. Herein, we investigated the peripheral cytokines and exosomal transcriptome regulatory networks in the patients with METH use disorders (MUDs) undergoing withdrawal. Twenty-seven cytokines were simultaneously assessed in 51 subjects, including 22 at the acute withdrawal (AW) stage and 29 at the protracted withdrawal (PW) stage, and 31 age and gender-matched healthy controls (HCs). Compared to the HCs, significantly decreased levels of interleukin (IL)-1β, IL-9, IL-15, Basic FGF, and MIP1a, increased levels of IL-1rα, IL-6, Eotaxin IP-10, VEGF, and RANTES were identified in AW. These disturbances were mostly or partly restored to the baseline in PW. However, the cytokines IL-6, IL-7, and IL-12p70 were consistently increased even after one year of withdrawal. Besides, a significant decrease in CD3+T and CD4+T cell numbers was observed in AW, and the diminishment was restored to baseline in PW. Comparatively, there were no statistically significant changes in CD8+T, NK, and B cells. Furthermore, the exosomal mRNAs and long non-coding RNAs (lncRNA) were profiled, and the lncRNA-miRNA-mRNA networks were constructed and associated with METH AW and PW stages. Notably, the chemokine signaling was remarkably upregulated during AW. By contrast, the differentially expressed mRNAs/lincRNAs were significantly enriched in neurodegeneration-related diseases. Taken together, a group of METH withdrawal-related cytokines and exosomal mRNA/lncRNA regulatory networks were obtained, which provides a useful experimental and theoretical basis for further understanding of the pathogenesis of the withdrawal symptoms in MUDs.

Implant-related complications in patients with opioid use disorder undergoing primary shoulder arthroplasties: a matched-controlled analysis

BACKGROUND

The purpose of this study was to investigate whether patients undergoing primary shoulder arthroplasty with opioid use disorder have higher rates of (1) implant-related complications; (2) in-hospital lengths of stay; (3) readmission rates; and (4) costs of care.

METHODS

Opioid use disorder patients undergoing primary shoulder arthroplasty were queried and matched in a 1:5 ratio to controls by age, sex, and medical comorbidities within the Medicare database. The query yielded 25,489 patients with (n = 4253) and without (n = 21,236) opioid use disorder. Primary outcomes analyzed included: 2-year implant related complications, in-hospital lengths of stay, 90-day readmission rates, and 90-day costs of care. A p value less than 0.01 was considered statistically significant.

RESULTS

Opioid use disorder patients had significantly longer in-hospital lengths of stay (3 days vs. 2 days; p < 0.0001) compared to matched controls. Opioid use disorder patients were also found to have higher incidence and odds (OR) of readmission rates (12.84 vs. 7.45%; OR: 1.16, p < 0.0001) and implant-related complications (20.03 vs. 7.95%; OR: 1.82, p < 0.0001). Study group patients also incurred significantly higher 90-day costs of care ($16,918.85 vs. $15,195.37, p < 0.0001).

DISCUSSION

This study can be used to help further augment efforts to reduce opioid prescriptions from healthcare providers in shoulder arthroplasty settings.

Dynamics and correlations in multiplex immune profiling reveal persistent immune inflammation in male drug users after withdrawal

Drug withdrawal elicits immune responses that contribute to the development of withdrawal symptoms and relapse. The understanding of the immunologic dynamics after drug withdrawal is limited, precluding the finding of promising immune intervention measures. Here, we performed cytokine and multiplex immune profiling in heroin, methamphetamine (METH) and ephedrine users after withdrawal and identified the correlation between cytokines and other immune parameters. We showed that broad and strong inflammatory responses occurred at the early stage after drug withdrawal, and the inflammatory responses showed a downtrend with the extension of withdrawal time. Notably, immune dysregulation remained through and may last longer than 12 months after withdrawal in heroin and METH users. Our findings suggest that cytokines, immune cells, complement and immunoglobulin form a complex immune network that regulates immune responses after withdrawal. These data provide a reference for future scientific research and drug research and development.

Immunomodulatory effects of pharmaceutical opioids and antipyretic analgesics: Mechanisms and relevance to infection

Understanding how pharmaceutical opioids and antipyretic analgesics interact with the immune system potentially has major clinical implications for management of patients with infectious diseases and surgical and critical care patients. An electronic search was carried out on MEDLINE, EMBASE, PsycINFO, CENTRAL and the Cochrane library to identify reports describing the immunomodulatory effects of opioid analgesics and antipyretic analgesics, and their effects in infectious diseases. In adaptive immunity, nonsteroidal anti-inflammatory drugs have divergent effects: augmenting cell-mediated immunity but inhibiting humoral immunity. Nonsteroidal anti-inflammatory drugs have demonstrated a beneficial role in Mycobacterium tuberculosis infection and histoplasmosis in animals, and may be plausible adjuvants to antimicrobial agents in these diseases. There is a need to evaluate these findings rigorously in human clinical trials. There is preliminary evidence demonstrating antiviral effects of indomethacin in SARS CoV-2 in vitro; however, uncertainty regarding its clinical benefit in humans needs to be resolved in large clinical trials. Certain opioid analgesics are associated with immunosuppressive effects, with a developing understanding that fentanyl, morphine, methadone and buprenorphine suppress innate immunity, whilst having diverse effects on adaptive immunity. Morphine suppresses key cells of the innate immunity and is associated with greater risk of infection in the postsurgical setting. Efforts are needed to achieve adequate analgesia whilst avoiding suppression of the innate immunity in the immediate postoperative period caused by certain opioids, particularly in cancer surgery.

Preoperative Opioid Use Is Associated With Higher Revision Rates in Total Joint Arthroplasty: A Systematic Review

BACKGROUND

Although preoperative opioid use has been associated with poor postoperative patient-reported outcome measures and delayed return to work in patients undergoing total joint arthroplasty, direct surgery-related complications in patients on chronic opioids are still not clear. Thus, we sought to perform a systematic review of the literature to evaluate the influence of preoperative opioid use on postoperative complications and revision following primary total joint arthroplasty.

METHODS

Following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement, we queried PubMed, EMBASE, the Cochrane Library, and the ISI Web of Science for studies investigating the influence of preoperative opioid use on postoperative complications following total hip arthroplasty and total knee arthroplasty up to May 2020.

RESULTS

After applying exclusion criteria, 10 studies were included in the analysis which represented 87,165 opioid users (OU) and 5,214,010 nonopioid users (NOU). The overall revision rate in the OU group was 4.79% (3846 of 80,303 patients) compared to 1.21% in the NOU group (43,719 of 3,613,211 patients). There was a higher risk of aseptic loosening (odds ratio [OR] 1.30, 95% confidence interval [CI] 1.11-1.53, P = .002), periprosthetic fractures (OR 1.89, 95% CI 1.53-2.34, P < .00001), and dislocations (OR 1.26, 95% CI 1.14-1.39, P < .00001) in the OU group compared to the NOU group. Overall, 5 of 6 studies reporting on periprosthetic joint infection (PJI) rates showed statistically significant correlation between preoperative opioid use and higher PJI rates.

CONCLUSION

There is strong evidence that preoperative opioid use is associated with a higher overall revision rate for aseptic loosening, periprosthetic fractures, and dislocation, and an increased risk for PJI.

LEVEL OF EVIDENCE

Level III, systematic review.

Integration of Molecular Inflammatory Interactome Analyses Reveals Dynamics of Circulating Cytokines and Extracellular Vesicle Long Non-Coding RNAs and mRNAs in Heroin Addicts During Acute and Protracted Withdrawal

Heroin addiction and withdrawal influence multiple physiological functions, including immune responses, but the mechanism remains largely elusive. The objective of this study was to investigate the molecular inflammatory interactome, particularly the cytokines and transcriptome regulatory network in heroin addicts undergoing withdrawal, compared to healthy controls (HCs). Twenty-seven cytokines were simultaneously assessed in 41 heroin addicts, including 20 at the acute withdrawal (AW) stage and 21 at the protracted withdrawal (PW) stage, and 38 age- and gender-matched HCs. Disturbed T-helper(T_h)1/T_h2, T_h1/T_h17, and T_h2/T_h17 balances, characterized by reduced interleukin (IL)-2, elevated IL-4, IL-10, and IL-17A, but normal TNF-α, were present in the AW subjects. These imbalances were mostly restored to the baseline at the PW stage. However, the cytokines TNF-α, IL-2, IL-7, IL-10, and IL-17A remained dysregulated. This study also profiled exosomal long non-coding RNA (lncRNA) and mRNA in the plasma of heroin addicts, constructed co-expression gene regulation networks, and identified lncRNA-mRNA-pathway pairs specifically associated with alterations in cytokine profiles and T_h1/T_h2/T_h17 imbalances. Altogether, a large amount of cytokine and exosomal lncRNA/mRNA expression profiling data relating to heroin withdrawal was obtained, providing a useful experimental and theoretical basis for further understanding of the pathogenic mechanisms of withdrawal symptoms in heroin addicts.

Neuronal apoptosis induced by morphine withdrawal is mediated by the p75 neurotrophin receptor

Morphine withdrawal evokes neuronal apoptosis through mechanisms that are still under investigation. We have previously shown that morphine withdrawal increases the levels of pro-brain-derived neurotrophic factor (BDNF), a proneurotrophin that promotes neuronal apoptosis through the binding and activation of the pan-neurotrophin receptor p75 (p75NTR). In this work, we sought to examine whether morphine withdrawal increases p75NTR-driven signaling events. We employed a repeated morphine treatment-withdrawal paradigm in order to investigate biochemical and histological indicators of p75NTR-mediated neuronal apoptosis in mice. We found that repeated cycles of spontaneous morphine withdrawal promote an accumulation of p75NTR in hippocampal synapses. At the same time, TrkB, the receptor that is crucial for BDNF-mediated synaptic plasticity in the hippocampus, was decreased, suggesting that withdrawal alters the neurotrophin receptor environment to favor synaptic remodeling and apoptosis. Indeed, we observed evidence of neuronal apoptosis in the hippocampus, including activation of c-Jun N-terminal kinase (JNK) and increased active caspase-3. These effects were not seen in saline or morphine-treated mice which had not undergone withdrawal. To determine whether p75NTR was necessary in promoting these outcomes, we repeated these experiments in p75NTR heterozygous mice. The lack of one p75NTR allele was sufficient to prevent the increases in phosphorylated JNK and active caspase-3. Our results suggest that p75NTR participates in the neurotoxic and proinflammatory state evoked by morphine withdrawal. Because p75NTR activation negatively influences synaptic repair and promotes cell death, preventing opioid withdrawal is crucial for reducing neurotoxic mechanisms accompanying opioid use disorders.

Contributions of neuroimmune and gut-brain signaling to vulnerability of developing substance use disorders

Epidemiology and clinical research indicate that only a subset of people who are exposed to drugs of abuse will go on to develop a substance use disorder. Numerous factors impact individual susceptibility to developing a substance use disorder, including intrinsic biological factors, environmental factors, and interpersonal/social factors. Given the extensive morbidity and mortality that is wrought as a consequence of substance use disorders, a substantial body of research has focused on understanding the risk factors that mediate the shift from initial drug use to pathological drug use. Understanding these risk factors provides a clear path for the development of risk mitigation strategies to help reduce the burden of substance use disorders in the population. Here we will review the rapidly growing body of literature that examines the importance of interactions between the peripheral immune system, the gut microbiome, and the central nervous system (CNS) in mediating the transition to pathological drug use. While these systems had long been viewed as distinct, there is growing evidence that there is bidirectional communication between both the immune system and the gut microbiome that drive changes in neural and behavioral plasticity relevant to substance use disorders. Further, both of these systems are highly sensitive to environmental perturbations and are implicated in numerous neuropsychiatric conditions. While the field of study examining these interactions in substance use disorders is in its relative infancy, clarifying the relationship between gut-immune-brain signaling and substance use disorders has potential to improve our understanding of individual propensity to developing addiction and yield important insight into potential treatment options.

The Role of Opioid Receptors in Immune System Function

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

Opioid-sparing effects of cannabinoids on morphine analgesia: participation of CB1 and CB2 receptors

BACKGROUND AND PURPOSE

Much of the opioid epidemic arose from abuse of prescription opioid drugs. This study sought to determine if the combination of a cannabinoid with an opioid could produce additive or synergistic effects on pain, allowing reduction in the opioid dose needed for maximal analgesia.

EXPERIMENTAL APPROACH

Pain was assayed using the formalin test in mice and the carrageenan assay in rats. Morphine and two synthetic cannabinoids were tested: WIN55,212-2 (WIN), which binds to both CB1 and CB2 receptors, and possibly TRPV1 channels; and GP1a, which has activity at CB2 receptors and is reported to inhibit fatty acid amide hydrolase, thus raising levels of endogenous cannabinoids.

KEY RESULTS

Morphine in combination with WIN in the formalin test gave synergistic analgesia. Studies with selective antagonists showed that WIN was acting through CB1 receptors. Morphine in combination with GP1a in the formalin test was sub-additive. In the carrageenan test, WIN had no added effect when combined with morphine, but GP1a with morphine showed enhanced analgesia. Both WIN and Gp1a used alone had analgesic activity in the formalin pain test, but not in the carrageenan pain test.

CONCLUSIONS AND IMPLICATIONS

The ability of a cannabinoid to produce an additive or synergistic effect on analgesia when combined with morphine varies with the pain assay and may be mediated by CB1 or CB2 receptors. These results hold the promise of using cannabinoids to reduce the dose of opioids for analgesia in certain pain conditions.

A potential role for the gut microbiome in substance use disorders

Pathological substance use disorders represent a major public health crisis with limited effective treatment options. While much work has been done to understand the neuronal signaling networks and intracellular signaling cascades associated with prolonged drug use, these studies have yielded few successful treatment options for substance use disorders. In recent years, there has been a growing interest to explore interactions between the peripheral immune system, the gut microbiome, and the CNS. In this review, we will present a summary of existing evidence, suggesting a potential role for gut dysbiosis in the pathogenesis of substance use disorders. Clinical evidence of gut dysbiosis in human subjects with substance use disorder and preclinical evidence of gut dysbiosis in animal models of drug addiction are discussed in detail. Additionally, we examine how changes in the gut microbiome and its metabolites may not only be a consequence of substance use disorders but may in fact play a role in mediating behavioral response to drugs of abuse. While much work still needs to be done, understanding the interplay of gut microbiome in substance use disorders may offer a promising avenue for future therapeutic development.

G-Protein-Coupled Receptors Are Dynamic Regulators of Digestion and Targets for Digestive Diseases

G-protein-coupled receptors (GPCRs) are the largest family of transmembrane signaling proteins. In the gastrointestinal tract, GPCRs expressed by epithelial cells sense contents of the lumen, and GPCRs expressed by epithelial cells, myocytes, neurons, and immune cells participate in communication among cells. GPCRs control digestion, mediate digestive diseases, and coordinate repair and growth. GPCRs are the target of more than one third of therapeutic drugs, including many drugs used to treat digestive diseases. Recent advances in structural, chemical, and cell biology research have shown that GPCRs are not static binary switches that operate from the plasma membrane to control a defined set of intracellular signals. Rather, GPCRs are dynamic signaling proteins that adopt distinct conformations and subcellular distributions when associated with different ligands and intracellular effectors. An understanding of the dynamic nature of GPCRs has provided insights into the mechanism of activation and signaling of GPCRs and has shown opportunities for drug discovery. We review the allosteric modulation, biased agonism, oligomerization, and compartmentalized signaling of GPCRs that control digestion and digestive diseases. We highlight the implications of these concepts for the development of selective and effective drugs to treat diseases of the gastrointestinal tract.

Comparison of implant related complications amongst patients with opioid use disorder and non-users following total knee arthroplasty

BACKGROUND

The influence of opioid use disorder on implant related complications, infection and readmission rates, and total global episode-of-care costs following primary total knee arthroplasty (TKA) is limited.

AIM

To examine whether opioid abuse in patients undergoing primary TKA.

METHODS

A retrospective analysis of the Medicare dataset, using the PearlDiver database, from 2005-2014 comparing outcomes in patients with opioid abusers (OUD) to non-opioid abusers (NOU) undergoing primary TKA was performed. Patient outcomes were analyzed including implant complications, readmission rates, and day-of-surgery and 90-d cost. Statistical analysis was performed with R (University of Auckland, New Zealand) calculating odds-ratio (OR) along with their respective 95% confidence interval (95%CI) and P-values.

RESULTS

The OUD group was at greater odds of having implant related complications overall (20.84% vs 11.25%; OR: 2.07; 95%CI: 1.93-2.23; P < 0.001). Revision (OR: 2.07; 95%CI: 1.11-3.84; P < 0.001), infection (OR: 1.92; 95%CI: 1.72–2.18; P < 0.001), periprosthetic fractures (OR: 1.83; 95%CI: 1.16-4.79; P < 0.001), and 90-d readmission rates (OR: 1.47, 95%CI: 1.35-1.61, P < 0.001) were also significantly increased. OUD patients also incurred in higher day-of-surgery and total global 90-d episode-of-care costs compared to NOU.

CONCLUSION

Patients with OUD show an increased risk of complications compared to the non-opioid users group. Appropriate recognition, pre-surgical optimization, and patient education are essential to mitigate these complications and improve patient outcome.

Preoperative Opioids Increase the Risk of Periprosthetic Joint Infection After Total Joint Arthroplasty

BACKGROUND

Opioids have well-known immunosuppressive properties and preoperative opioid consumption is relatively common among patients undergoing total joint arthroplasty (TJA). The hypothesis of this study was that utilization of opioids preoperatively would increase the incidence of subsequent periprosthetic joint infection (PJI) in patients undergoing primary TJA.

METHODS

A comparative cohort study design was set up that used a cohort of 23,754 TJA patients at a single institution. Patient records were reviewed to extract relevant information, in particular details of opioid consumption, and an internal institutional database of PJI was cross-referenced against the cohort to identify patients who developed a PJI within 2 years of index arthroplasty. Univariate and multivariate linear regression analyses were used to examine the potential association between preoperative opioid consumption and the development of PJI.

RESULTS

Among the total cohort of 23,754 patients, 5051 (21.3%) patients used opioids before index arthroplasty. Preoperative opioid usage overall was found to be a significant risk factor for development of PJI in the univariate (odds ratio, 1.63; P = .005) and multivariate analyses (adjusted odds ratio, 1.53 [95% confidence interval, 1.14-2.05], P = .005).

CONCLUSION

Preoperative opioid consumption is independently associated with a higher risk of developing a PJI after primary TJA. These findings underscore a need for caution when prescribing opioids in patients with degenerative joint disease who may later require arthroplasty.

The PPARγ Agonist Pioglitazone Fails to Alter the Abuse Potential of Heroin, But Does Reduce Heroin Craving and Anxiety

Possibly through its effects on glia, the peroxisome proliferator-activated gamma receptor (PPARγ) agonist pioglitazone (PIO) has been shown to alter the effects of heroin in preclinical models. Until now, these results have not been assessed in humans. Heroin-dependent participants were randomized to either active (45 mg, n = 14) or placebo (0 mg, n = 16) PIO maintenance for the duration of the three-week study. After stabilization on buprenorphine (8 mg), participants began a two-week testing period. On the first to fourth test days, participants could self-administer drug or money by making verbal choices for either option. On the fifth day, active heroin and money were administered and participants could work to receive heroin or money using a progressive ratio choice procedure. Test days 6-10 were identical to test days 1-5 with the exception that, during one of the test weeks, placebo was available on the first four days, and during the other week heroin was available. PIO failed to alter the reinforcing or positive subjective effects of heroin, but it did reduce heroin craving and overall anxiety. Although we were unable to replicate the robust effects found in preclinical models, these data provide an indication of drug effects that deserves further exploration.

CCR5 mediates HIV-1 Tat-induced neuroinflammation and influences morphine tolerance, dependence, and reward

The HIV-1 regulatory protein, trans-activator of transcription (Tat), interacts with opioids to potentiate neuroinflammation and neurodegeneration within the CNS. These effects may involve the C-C chemokine receptor type 5 (CCR5); however, the behavioral contribution of CCR5 on Tat/opioid interactions is not known. Using a transgenic murine model that expresses HIV-1 Tat protein in a GFAP-regulated, doxycycline-inducible manner, we assessed morphine tolerance, dependence, and reward. To assess the influence of CCR5 on these effects, mice were pretreated with oral vehicle or the CCR5 antagonist, maraviroc, prior to morphine administration. We found that HIV-1 Tat expression significantly attenuated the antinociceptive potency of acute morphine (2-64 mg/kg, i.p.) in non-tolerant mice. Consistent with this, Tat attenuated withdrawal symptoms among morphine-tolerant mice. Pretreatment with maraviroc blocked the effects of Tat, reinstating morphine potency in non-tolerant mice and restoring withdrawal symptomology in morphine-tolerant mice. Twenty-four hours following morphine administration, HIV-1 Tat significantly potentiated (∼3.5-fold) morphine-conditioned place preference and maraviroc further potentiated these effects (∼5.7-fold). Maraviroc exerted no measurable behavioral effects on its own. Protein array analyses revealed only minor changes to cytokine profiles when morphine was administered acutely or repeatedly; however, 24 h post morphine administration, the expression of several cytokines was greatly increased, including endogenous CCR5 chemokine ligands (CCL3, CCL4, and CCL5), as well as CCL2. Tat further elevated levels of several cytokines and maraviroc pretreatment attenuated these effects. These data demonstrate that CCR5 mediates key aspects of HIV-1 Tat-induced alterations in the antinociceptive potency and rewarding properties of opioids.

Bivariate genome-wide association analyses identified genetic pleiotropic effects for bone mineral density and alcohol drinking in Caucasians

Several studies indicated bone mineral density (BMD) and alcohol intake might share common genetic factors. The study aimed to explore potential SNPs/genes related to both phenotypes in US Caucasians at the genome-wide level. A bivariate genome-wide association study (GWAS) was performed in 2069 unrelated participants. Regular drinking was graded as 1, 2, 3, 4, 5, or 6, representing drinking alcohol never, less than once, once or twice, three to six times, seven to ten times, or more than ten times per week respectively. Hip, spine, and whole body BMDs were measured. The bivariate GWAS was conducted on the basis of a bivariate linear regression model. Sex-stratified association analyses were performed in the male and female subgroups. In males, the most significant association signal was detected in SNP rs685395 in DYNC2H1 with bivariate spine BMD and alcohol drinking (P = 1.94 × 10^-8). SNP rs685395 and five other SNPs, rs657752, rs614902, rs682851, rs626330, and rs689295, located in the same haplotype block in DYNC2H1 were the top ten most significant SNPs in the bivariate GWAS in males. Additionally, two SNPs in GRIK4 in males and three SNPs in OPRM1 in females were suggestively associated with BMDs (of the hip, spine, and whole body) and alcohol drinking. Nine SNPs in IL1RN were only suggestively associated with female whole body BMD and alcohol drinking. Our study indicated that DYNC2H1 may contribute to the genetic mechanisms of both spine BMD and alcohol drinking in male Caucasians. Moreover, our study suggested potential pleiotropic roles of OPRM1 and IL1RN in females and GRIK4 in males underlying variation of both BMD and alcohol drinking.

Effects of ibudilast on oxycodone-induced analgesia and subjective effects in opioid-dependent volunteers

Opioid-induced glial activation is hypothesized to contribute to the development of tolerance to opioid-induced analgesia. This inpatient, double-blind, placebo-controlled, within-subject and between-groups pilot study investigated the dose-dependent effects of ibudilast, a glial cell modulator, on oxycodone-induced analgesia. Opioid-dependent volunteers were maintained on morphine (30mg, PO, QID) for two weeks and received placebo ibudilast (0mg, PO, BID) during the 1st week (days 1-7). On day 8, participants (N=10/group) were randomized to receive ibudilast (20 or 40mg, PO, BID) or placebo for the remainder of the study. On days 4 (week 1) and 11 (week 2), the analgesic, subjective, and physiological effects of oxycodone (0, 25, 50mg/70kg, PO) were determined. Analgesia was measured using the cold pressor test; participants immersed their hand in cold water (4°C) and pain threshold and pain tolerability were recorded. Oxycodone decreased pain threshold and tolerability in all groups during week 1. During week 2, the placebo group exhibited a blunted analgesic response to oxycodone for pain threshold and subjective pain ratings, whereas the 40mg BID ibudilast group exhibited greater analgesia as measured by subjective pain ratings (p≤0.05). Oxycodone also increased subjective drug effect ratings associated with abuse liability in all groups during week 1 (p≤0.05); ibudilast did not consistently affect these ratings. These findings suggest that ibudilast may enhance opioid-induced analgesia. Investigating higher ibudilast doses may establish the utility of pharmacological modulation of glial activity to maximize the clinical use of opioids.

Morphine Withdrawal Increases Brain-Derived Neurotrophic Factor Precursor

Morphine has been shown to increase the expression of brain-derived neurotrophic factor (BDNF) in the brain. However, little is known about the effect of morphine withdrawal on BDNF and its precursor protein, or proBDNF, which induces neuronal apoptosis. In this work, we examined whether BDNF and proBDNF levels change in rats chronically injected with escalating doses of morphine and those who undergo spontaneous withdrawal for 60 h. We observed, in the frontal cortex and striatum, that the ratio of BDNF to proBDNF changed depending upon the experimental paradigm. Morphine treatment and morphine withdrawal increased both BDNF and proBDNF levels. However, the increase in proBDNF immunoreactivity in withdrawal rats was more robust than that observed in morphine-treated rats. proBDNF is processed either intracellularly by furin or extracellularly by the tissue plasminogen activator (tPA)/plasminogen system or matrix metalloproteases (MMPs). To examine the mechanisms whereby chronic morphine treatment and morphine withdrawal differentially affects BDNF/proBDNF, the levels MMP-3 and MMP-7, furin, and tPA were analyzed. We found that morphine increases tPA levels, whereas withdrawal causes a decrease. To confirm the involvement of tPA in the morphine-mediated effect on BDNF/proBDNF, we exposed cortical neurons to morphine in the presence of the tPA inhibitor plasminogen activator inhibitor-1 (PAI-1). This inhibitor reversed the morphine-mediated decrease in proBDNF, supporting the hypothesis that morphine increases the availability of BDNF by promoting the extracellular processing of proBDNF by tPA. Because proBDNF could negatively influence synaptic repair, preventing withdrawal is crucial for reducing neurotoxic mechanisms associated with opioid abuse.

Impact of illicit opioid use on T cell subsets among HIV-infected adults

Objectives

Opioids have immunosuppressive properties, yet opioid effects on T cell abnormalities consistent with the immune risk phenotype among HIV-infected individuals are understudied.

Methods

To assess associations between illicit opioid use and T cell characteristics (CD4/CD8 ratio, memory profiles based on CD45RO and CD28 expression, and senescence based on CD57 expression), we conducted an exploratory cross-sectional analysis of Russia ARCH, a cohort of antiretroviral therapy (ART)-naïve HIV-infected individuals recruited 11/2012 to 10/2014 in St. Petersburg, Russia. The main independent variable was past 30 day illicit opioid use (yes vs. no). Secondary analyses evaluated none (0 days), intermittent (1 to 7 days), and persistent (8 to 30 days) opioid use. Outcomes were determined with flow cytometry. Analyses were conducted using linear regression models.

Results

Among 186 participants, 38% reported any illicit opioid use (18% intermittent and 20% persistent). Any illicit opioid use was not significantly associated with T cell characteristics. Intermittent opioid use appeared to be associated with decreased memory CD8+ T cells proportion (CD45RO+CD45RA- CD8+ T cells: adjusted mean difference [AMD] [95% CI] = -6.15 [-11.50, -0.79], p = 0.02) and borderline significant increased senescent T cells (%CD57+ of total CD28-CD8+ T cells (AMD [95% CI] = 7.70 [-0.06, 15.46], p = 0.05).

Conclusions

Among ART-naïve HIV-infected Russians, any illicit opioid use was not significantly associated with T cell abnormalities although intermittent illicit opioid use may be associated with CD8 T cell abnormalities. Longitudinal studies are warranted to confirm these findings given increased risk of infections and comorbidities seen among HIV-infected individuals with illicit opioid use.

Hormonal systems, human social bonding, and affiliation

Which hormones are implicated in human social bonding and affiliation? And how does field research speak to this issue? We begin by laying out a broad view of how endocrine hormones in general modulate life history allocations of energy and other resources, and the ways in which their neuromodulatory functions must be understood within a broader conceptualization of how they have been shaped to affect allocations. We then turn to four specific hormones or hormone families that have received much attention: oxytocin, opioids, prolactin, and progesterone. Each plays a role in regulating psychological capacities and propensities that underlie individuals' interactions with important social targets. Yet in no case is it clear exactly what regulatory roles these hormones play. We suggest several directions for future research.

Neuroendocrine-immune interaction: Evolutionarily conserved mechanisms that maintain allostasis in an ever-changing environment

It has now become accepted that the immune system and neuroendocrine system form an integrated part of our physiology. Immunological defense mechanisms act in concert with physiological processes like growth and reproduction, energy intake and metabolism, as well as neuronal development. Not only are psychological and environmental stressors communicated to the immune system, but also, vice versa, the immune response and adaptation to a current pathogen challenge are communicated to the entire body, including the brain, to evoke adaptive responses (e.g., fever, sickness behavior) that ensure allocation of energy to fight the pathogen. This phenomenon is evolutionarily conserved. Hence it is both interesting and important to consider the evolutionary history of this bi-directional neuroendocrine-immune communication to reveal phylogenetically ancient or relatively recently acquired mechanisms. Indeed, such considerations have already disclosed an extensive "common vocabulary" of information pathways as well as molecules and their receptors used by both the neuroendocrine and immune systems. This review focuses on the principal mechanisms of bi-directional communication and the evidence for evolutionary conservation of the important physiological pathways involved.

The impact of prescribed opioids on CD4 cell count recovery among HIV-infected patients newly initiating antiretroviral therapy

OBJECTIVES

Certain prescribed opioids have immunosuppressive properties, yet their impact on clinically relevant outcomes, including antiretroviral therapy (ART) response among HIV-infected patients, remains understudied.

METHODS

Using the Veterans Aging Cohort Study data, we conducted a longitudinal analysis of 4358 HIV-infected patients initiating ART between 2002 and 2010 and then followed them for 24 months. The primary independent variable was prescribed opioid duration, categorized using pharmacy data as none prescribed, short-term (< 90 days) and long-term (≥ 90 days). Outcomes included CD4 cell count over time. Analyses adjusted for demographics, comorbid conditions, ART type and year of initiation, and overall disease severity [ascertained with the Veterans Aging Cohort Study (VACS) Index]. Sensitivity analyses examined whether effects varied according to baseline CD4 cell count, achievement of viral load suppression, and opioid properties (i.e. dose and known immunosuppressive properties).

RESULTS

Compared to those with none, patients with short-term opioids had a similar increase in CD4 cell count (mean rise per year: 74 vs. 68 cells/μL; P = 0.11), as did those with long-term prescribed opioids (mean rise per year: 74 vs. 75 cells/μL; P = 0.98). In sensitivity analysis, compared with no opioids, the effects of short-term prescribed opioids were statistically significant among those with a baseline CD4 cell count ≥ 500 cells/μL (mean rise per year: 52 cells/μL for no opioids vs. 20 cells/μL for short-term opioids; P = 0.04); findings were otherwise unchanged.

CONCLUSIONS

Despite immunosuppressive properties intrinsic to opioids, prescribed opioids appeared to have no effect on CD4 cell counts over 24 months among HIV-infected patients initiating ART.

Survey on Hypothermia and Hyperthermia in Poisoned Patients in a Unique Referral Hospital, Tehran, Iran

Background

Body temperature is a critical criterion of health. Drugs and a variety of poisons can affect body temperature in poisoned patients, causing hyperthermia and hyperpyrexia.

Objectives

Our previous study’s findings in patients poisoned with organophosphate led us to the goal of this study: obtaining the initial tympanic temperature in patients poisoned by a variety of toxins.

Materials and Methods

A cross-sectional study reviewed the records of poisoned patients who were admitted to the toxicological intensive care unit (TICU) at Loghman Hakim hospital poison center (LHHPC) from February 2014 to February 2015. The data collected included gender, age, type of poisoning, the season during which poisoning occurred, vital signs, initial tympanic temperature (first four hours), presence of seizures, white blood cell (WBC) count, creatinine phosphokinase (CPK), length of stay and patient outcome. We determined the mean (SD) for normally distributed continuous variables, the median and interquartile range for non-normally distributed continuous variables, and the absolute and relative frequency (%) for categorical variables. All were determined using SPSS version 16.

Results

Data were collected from 310 eligible patients. The mean patient age was 32.65 (with a standard deviation of 14.40). Of the patients in the study, 183 (59%) were male. Intentional poisoning in an attempted suicide was documented in 253 (81.6%) patients. The most prevalent poisoning agent was aluminum phosphate (18.70%), followed by methadone (10%) and opium (10%). Seventy percent of the patients (n = 217) were diagnosed and classified with fever or hyperthermia. A temperature ≥ 40°C was detected in just three cases. The highest mean temperature was found in patients poisoned with amphetamine, organophosphate and tramadol. Patients with alcohol and phenobarbital poisoning were included in the sample, but these patients were not diagnosed with hypothermia. WBC ≥ 10,000 cells/mL and CPK ≥ 975 IU/L were recorded in 57.7% and 13.2% of subjects, respectively.

Conclusions

Body temperature changes in human poisonings are a matter in need of special attention. A literature review did not reveal any controversy over hypothermia, but poisoning cases exhibit a variety of patterns of fever and hyperthermia. If there are no limits to the diagnosis of fever and hyperthermia, all cases with a poor prognosis which fail to respond to treatment could be categorized as drug-induced hyperthermia. Therefore, a different approach is needed for poisoning cases.

Pathogenesis of infection in surgical patients

Purpose of review

Despite the application of prophylactic antimicrobial therapy and advanced technologies, infection remains one of the most common causes of morbidity and mortality in surgical patients. Understanding the pathogenesis of surgical infection would offer new insights into the development of biomarkers to predict and stratify infection in patients, and to explore specific strategies to minimize this serious postoperative complication.

Recent findings

The acute nonspecific inflammatory response triggered by endogenous danger signals evoked by surgical insult is beneficial, while paradoxically associated with reduced resistance to infection. There is growing evidence indicating that primed inflammation by surgical insult exaggerates the dysregulation of the immune-inflammatory response to the invasion of pathogens postoperatively. Innate immune receptors, such as Toll-like receptors (TLRs), contribute to detecting both pathogen-associated molecular patterns and endogenous damage-associated molecular patterns, and to further amplifying inflammatory responses to infection. Current evidence shows the fascinating role of non-TLRs in the process of infection. Non-TLRs, such as membrane-associated triggering receptor expressed on myeloid cells family, cytosolic nucleotide-binding oligomerization domain-like receptors and nuclear receptor nuclear family 4 subgroup A receptors, are also crucial in triggering the immune responses and mounting an effective defense against surgical insults and the second hit of infection.

Summary

Understanding the pivotal role of non-TLRs in sensing exogenous and endogenous molecules, and the influence of primed systemic inflammation and depressed immune status on the defense against pathogen after surgical insult, would be helpful to fully explore the relevant sophisticated phenomena of surgical infection, and to elucidate the occurrence of heterogeneous constellations of clinical signs and symptoms among this special population.

The effects of pioglitazone, a PPARγ receptor agonist, on the abuse liability of oxycodone among nondependent opioid users

AIMS

Activation of PPARγ by pioglitazone (PIO) has shown some efficacy in attenuating addictive-like responses in laboratory animals. The ability of PIO to alter the effects of opioids in humans has not been characterized in a controlled laboratory setting. The proposed investigation sought to examine the effects of PIO on the subjective, analgesic, physiological and cognitive effects of oxycodone (OXY).

METHODS

During this investigation, nondependent prescription opioid abusers (N=17 completers) were maintained for 2-3weeks on ascending daily doses of PIO (0mg, 15mg, 45mg) prior to completing a laboratory session assessing the aforementioned effects of OXY [using a within-session cumulative dosing procedure (0, 10, and 20mg, cumulative dose=30mg)].

RESULTS

OXY produced typical mu opioid agonist effects: miosis, decreased pain perception, and decreased respiratory rate. OXY also produced dose-dependent increases in positive subjective responses. Yet, ratings such as: drug "liking," "high," and "good drug effect," were not significantly altered as a function of PIO maintenance dose.

DISCUSSION

These data suggest that PIO may not be useful for reducing the abuse liability of OXY. These data were obtained with a sample of nondependent opioid users and therefore may not be applicable to dependent populations or to other opioids. Although PIO failed to alter the abuse liability of OXY, the interaction between glia and opioid receptors is not well understood so the possibility remains that medications that interact with glia in other ways may show more promise.

Heroin Use and HIV Disease Progression: Results from a Pilot Study of a Russian Cohort

Opioids have immunosuppressive properties, yet their impact on HIV disease progression remains unclear. Using longitudinal data from HIV-infected antiretroviral therapy-naïve Russian individuals (n = 77), we conducted a pilot study to estimate the effect of heroin use on HIV disease progression. Heroin use was categorized based on past 30 days self-reported use at baseline, 6 and 12 months as none, intermittent or persistent. We estimated the effect of heroin use on HIV disease progression, measured as change in CD4 count from baseline to 12 months, using multivariable linear regression. Those with intermittent (n = 21) and no heroin use (n = 39) experienced mean decreases in CD4 count from baseline to 12 months (-103 and -10 cells/mm(3), respectively; adjusted mean difference (AMD) -93; 95 % CI -245, 58). Those with persistent use (n = 17) showed a mean increase of 53 cells/mm(3) (AMD 63; 95 % CI -95, 220). Future studies exploring the effects of heroin withdrawal on HIV disease progression are warranted.

Opioids and cancer recurrence

PURPOSE OF REVIEW

With the majority of deaths from cancer because of their metastases, strategies to reduce this from occurring are at the forefront of treatment. It has been hypothesized that morphine may result in an increase in cancer metastases, following many in-vitro and animal studies, but the evidence from human retrospective data is inconclusive. This article will explore the possible mechanisms by which opioids can impact on the natural history of the cancer cell and whether they are likely to be harmful in individuals with cancer.

RECENT FINDINGS

Although there have been trials demonstrating benefits with regional anaesthesia techniques (opioid sparing) in the surgical population, it is not clear whether the source of the benefit arises directly from the avoidance of opioids or an added benefit afforded by regional anaesthesia. Research has shown that in particular cancer cell types, morphine may actually be beneficial and that the μ-opioid receptor (MOR) plays a role in cancer disease. With the crystal structure of the MOR having recently been elucidated, this may offer new opportunities for treatments aimed at reducing cancer metastasis.

SUMMARY

The role opioids play in the development of cancer metastasis and recurrence is far from clear and appears to differ depending on the cancer cell type in question. Prospective randomized controlled trials are currently underway in humans to help clarify the situation further and there results are awaited with anticipation. The negative impact of pain on the immune system is well documented and it appears that appropriate analgesia is paramount in minimizing this. Opioids still constitute a central role in the management of moderate-to-severe cancer pain.

Dissociation of immunosuppressive and nociceptive effects of fentanyl, but not morphine, after repeated administration in mice: fentanyl-induced sensitization to LPS

Immunosuppressive morphine actions are well characterized, but other opiates are less studied. The objectives of this work were: (a) to compare the acute effects of morphine and fentanyl to inhibit early peritoneal LPS-induced TNFα release; (b) to find if, as in the case of morphine, intraperitoneal mast cells (MCs) are the target of fentanyl's immunosuppressive actions; and (c) to analyze if repeated opiate administration induces tolerance to opiate immunosuppressive effects. Independent groups of mice received a single i.p. injection of morphine (0.1-10mg/kg) or fentanyl (0.001-0.1mg/kg) 10min prior to LPS (1mg/kg). Peritoneal TNFα levels were determined 1h later. The effects of fentanyl were analyzed in MC-deficient mice (W-sh) and in W-sh mice reconstituted with bone marrow-derived MCs. Other animals received 6 or 10 doses of morphine (10mg/kg, 3×/day) or fentanyl (0.1mg/kg 3×/day) and were then challenged with LPS. Fentanyl was equally effective and 1000× more potent than morphine to inhibit i.p. LPS-induced TNFα release and this was dependent on intraperitoneal MCs. Repeated morphine administration induced tolerance to both antinociception and inhibition of response to endotoxin. Repeated fentanyl injection did not induce significant antinociceptive tolerance, but, interestingly, produced sensitization to LPS.

IN CONCLUSION

(1) opiates with different analgesic potency also differ in their potency to induce immunosuppression; (2) MCs are the cellular target of the immunosuppressive actions of fentanyl here studied; (3) in contrast with morphine, tolerance to fentanyl's immunosuppressive actions can be dissociated from tolerance to its antinociceptive effects.

Comparison and analysis of the animal models used to study the effect of morphine on tumour growth and metastasis

The effect of opioids on tumour growth and metastasis has been debated for many years, with recent emphasis on the possibility that they might influence the rate of disease-free survival after tumour resection when used in the perioperative pain management of cancer surgery patients. The literature presents conflicting and inconclusive in vitro and in vivo data about the potential effect of opioids, especially morphine, on tumour growth and metastasis. To inform clinical practice, appropriate animal models are needed to test whether opioids alter the course of tumour growth and metastasis. Here, we review the literature on animal-based studies testing the effect of morphine on cancer so far, and analyse differences between the models used that may explain the discrepancies in published results. Such analysis should elucidate the role of opioids in cancer and help define ideal pre-clinical models to provide definitive answers.

LINKED ARTICLES

This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.

Opioid administration following spinal cord injury: implications for pain and locomotor recovery

Approximately one-third of people with a spinal cord injury (SCI) will experience persistent neuropathic pain following injury. This pain negatively affects quality of life and is difficult to treat. Opioids are among the most effective drug treatments, and are commonly prescribed, but experimental evidence suggests that opioid treatment in the acute phase of injury can attenuate recovery of locomotor function. In fact, spinal cord injury and opioid administration share several common features (e.g. central sensitization, excitotoxicity, aberrant glial activation) that have been linked to impaired recovery of function, as well as the development of pain. Despite these effects, the interactions between opioid use and spinal cord injury have not been fully explored. A review of the literature, described here, suggests that caution is warranted when administering opioids after SCI. Opioid administration may synergistically contribute to the pathology of SCI to increase the development of pain, decrease locomotor recovery, and leave individuals at risk for infection. Considering these negative implications, it is important that guidelines are established for the use of opioids following spinal cord and other central nervous system injuries.

Differences between opioids: pharmacological, experimental, clinical and economical perspectives

Clinical studies comparing the response and side effects of various opioids have not been able to show robust differences between drugs. Hence, recommendations of the regulatory authorities have been driven by costs with a general tendency in many countries to restrict physician's use of opioids to morphine. Although this approach is recognized as cost-effective in most cases there is solid evidence that, on an individual patient basis, opioids are not all equal. Therefore it is important to have an armamentarium of strong analgesics in clinical practice to ensure a personalized approach in patients who do not respond to standard treatment. In this review we highlight differences between opioids in human studies from a pharmacological, experimental, clinical and health economics point of view. We provide evidence that individuals respond differently to opioids, and that general differences between classes of opioids exist. We recommend that this recognition is used to individualize treatment in difficult cases allowing physicians to have a wide range of treatment options. In the end this will reduce pain and side effects, leading to improved quality of life for the patient and reduce the exploding pain related costs.

μ opioid receptor agonist-selective regulation of interleukin-4 in T lymphocytes

Opioids are irreplaceable for the treatment of severe pain. However, opioid-induced immunomodulation affects therapies. Here we report that treatment of human T lymphocytes with the opioids fentanyl, methadone, loperamide and beta-endorphin resulted in a strong induction of the cytokine interleukin-4. In contrast, morphine and buprenorphine induced markedly and significantly lower levels of interleukin-4 mRNA and protein. These findings suggest agonist-biased μ opioid receptor signaling in T cells. In the future, better knowledge about agonist-specific immunomodulatory effects of opioids offers the possibility to select drugs for a therapy with more favorable and/or less detrimental side effects in immune cells.

Serum biochemical parameters following heroin withdrawal: an exploratory study

BACKGROUND

Long-term consumption of opioid compounds, even after withdrawal, affects serum biochemical parameters. Investigating these alterations is a new approach in substance abuse studies.

METHOD

This study investigated clinical laboratory results in men who are currently active, recently abstinent and non-heroin users. Participants (N = 240) of this matched cohort study included heroin dependent men referred for abstinence treatment, volunteer men who did not abuse opioids matched for age, sex, body mass index, and educational level (control group). The groups were further sub-divided for analysis into (a) continuous heroin users for more than 2 years (N = 70), the dependent group; (b) heroin abusers with 1 month abstinence period (N = 70), identified as ex-heroin dependents; and (c) a matched, non-dependent control group (N = 100). All participants were tested for fasting blood sugar (FBS), sodium, potassium, calcium, uric acid (UA), blood urea nitrogen (BUN), creatinine, total cholesterol, triglycerides (TGs), total protein, fibrinogen, and prothrombin.

RESULTS

Compared to the control group, ex-heroin dependents showed decreased FBS and significantly higher sodium, creatinine, and cholesterol levels. Compared to the heroin dependent group, the ex-heroin dependents showed significant differences in FBS, sodium, calcium, creatinine, UA, and thrombin time. No significant differences were noted between ex-heroin dependents and controls in potassium, calcium, UA, BUN, TGs, total protein, and thrombin time.

CONCLUSION

These results demonstrate altered laboratory markers in long-term heroin dependents as well as ex-heroin dependents and suggest the need for further identification, population distribution, and etiological understanding of these biomarkers in individuals who have abused heroin.

Preprotachykinin-A gene disruption attenuates nociceptive sensitivity after opioid administration and incision by peripheral and spinal mechanisms in mice

The preprotachykinin A gene (ppt-A) codes for Substance P (SP), supports nociceptive sensitization, and modulates inflammatory responses after incision. Repeated opioid use produces paradoxical pain sensitization-termed opioid-induced hyperalgesia (OIH) -which can exacerbate pain after incision. Here the contribution of SP to peri-incisional nociceptive sensitization and nociceptive mediator production after opioid treatment was examined utilizing ppt-A knockout (-/-) mice and the neurokinin (NK1) receptor antagonist LY303870. Less mechanical allodynia was observed in ppt-A(-/-) mice compared to wild types (wt) after morphine treatment both before and after incision. Moreover, LY303870 administered with morphine reduced incisional hyperalgesia in wt mice. Incision after saline or escalating morphine treatment upregulated skin IL-1β, IL-6, G-CSF and MIP-1α levels in ppt-A(-/-) and wt mice similarly. However, chronic morphine treatment greatly exacerbated increases in skin nerve growth factor levels after incision, an effect entirely dependent upon intact SP signaling. Additionally, SP dependent upregulation of prodynorphin, NMDA1 and NK1 receptor expression in spinal cord was seen after morphine treatment and incision. A similar pattern was seen for 5-HT3 receptor expression in tissue from dorsal root ganglia. Therefore, SP may work at both central and peripheral sites to enhance nociceptive sensitization after morphine treatment and incision.

PERSPECTIVE

These studies show that SP signaling modulates enhanced nerve growth factor production and changes in neuronal gene expression seen after incision in mice previously exposed to morphine.

Hematological changes in opium addicted diabetic rats

Background

Chronic opioid treatment in animal models has shown to alter hematological parameters.

Objectives

The aim of this study was to evaluate the biological effects of opium on the number of peripheral blood cells and red blood cells (RBCs) indices in diabetic rats.

Materials and Methods

Peripheral blood samples were collected from diabetic, opium-addicted, diabetic opium-addicted and normal male and female rats and hematological parameters were measured.

Results

The mean number of white blood cells (WBCs) was significantly higher in diabetic opium-addict females compared to diabetic non-addict female group. In both male and female, the mean number of neutrophils was significantly higher and the mean number of lymphocytes was lower in diabetic opium-addicted rats than those observed in diabetic non-addicted group. In diabetic opium-addicted male group the mean counts of RBC significantly increased as compared with diabetic male group. However, in diabetic addicted female, the mean number of RBCs was significantly lower than diabetic non-addicted female group. In both males and females, the mean number of platelets was significantly lower in diabetic addict rats compared to diabetic non-addict group.

Conclusions

Generally, the results indicated that opium addiction has different effects on male and female rats according to the number of WBC, RBC and RBC indices. It could also be concluded that in the opium-addicts the risk of infection is enhanced due to the weakness of immune system as a result of the imbalance effect of opium on the immune cells.

Current research on opioid receptor function

The use of opioid analgesics has a long history in clinical settings, although the comprehensive action of opioid receptors is still less understood. Nonetheless, recent studies have generated fresh insights into opioid receptor-mediated functions and their underlying mechanisms. Three major opioid receptors (μ-opioid receptor, MOR; δ-opioid receptor, DOR; and κ-opioid receptor, KOR) have been cloned in many species. Each opioid receptor is functionally sub-classified into several pharmacological subtypes, although, specific gene corresponding each of these receptor subtypes is still unidentified as only a single gene has been isolated for each opioid receptor. In addition to pain modulation and addiction, opioid receptors are widely involved in various physiological and pathophysiological activities, including the regulation of membrane ionic homeostasis, cell proliferation, emotional response, epileptic seizures, immune function, feeding, obesity, respiratory and cardiovascular control as well as some neurodegenerative disorders. In some species, they play an essential role in hibernation. One of the most exciting findings of the past decade is the opioid-receptor, especially DOR, mediated neuroprotection and cardioprotection. The upregulation of DOR expression and DOR activation increase the neuronal tolerance to hypoxic/ischemic stress. The DOR signal triggers (depending on stress duration and severity) different mechanisms at multiple levels to preserve neuronal survival, including the stabilization of homeostasis and increased pro-survival signaling (e.g., PKC-ERK-Bcl 2) and antioxidative capacity. In the heart, PKC and KATP channels are involved in the opioid receptor-mediated cardioprotection. The DOR-mediated neuroprotection and cardioprotection have the potential to significantly alter the clinical pharmacology in terms of prevention and treatment of life-threatening conditions like stroke and myocardial infarction. The main purpose of this article is to review the recent work done on opioids and their receptor functions. It shall provide an informative reference for better understanding the opioid system and further elucidation of the opioid receptor function from a physiological and pharmacological point of view.

Impact of opiate addiction on neuroinflammation in HIV

To investigate the independent and interactive effects of opiate addiction and HIV on neuroinflammation, we measured microglial/macrophage activation and astrogliosis in multiple regions of human brain. Samples of thalamus, frontal gray matter, and frontal white matter were obtained from 46 individuals categorized as: HIV negatives, HIV-negative opiate addicts, HIV positives, HIV-positive opiate addicts, HIV encephalitis (HIVE), and HIVE opiate addicts. Activated brain microglia/macrophages and astrocytosis were quantified by morphometric analysis of immunohistochemical stains for CD68, HLA-D, CD163, and GFAP. The effects of HIV grouping, opiate addiction, and their interaction on expression of the markers were examined in a series of two-way ANOVAs. In opiate addicts, there was generally higher baseline expression of CD68 and HLA-D in HIV negatives, and lower expression in HIV and HIVE, compared to individuals without opiate abuse. Thus, for these markers, and for GFAP in frontal gray, opiates were associated with attenuated HIV effect. In contrast, for CD163, opiates did not significantly alter responses to HIV, and HIV effects were variably absent in individuals without opiate abuse. The divergent impact that opiate addiction displays on these markers may suggest a generally immunosuppressive role in the CNS, with decreased HIV-associated activation of markers CD68 and HLA-D that potentially reflect neurotoxic pathways, and preservation of CD163, thought to be an indicator of neuroprotective scavenger systems. These results suggest a complex impact of opiates on neuroinflammation in baseline and virally stimulated states.

Depletion and recovery of lymphoid subsets following morphine administration

BACKGROUND AND PURPOSE

Opioid use and abuse has been linked to significant immunosuppression, which has been attributed, in part, to drug-induced depletion of lymphocytes. We sought to define the mechanisms by which lymphocyte populations are depleted and recover following morphine treatment in mice.

EXPERIMENTAL APPROACH

Mice were implanted with morphine pellets and B- and T-cell subsets in the bone marrow, thymus, spleen and lymph nodes were analysed at various time points. We also examined the effects of morphine on T-cell development using an ex vivo assay.

KEY RESULTS

The lymphocyte populations most susceptible to morphine-induced depletion were the precursor cells undergoing selection. As the lymphocytes recovered, more lymphocyte precursors proliferated than in control mice. In addition, peripheral T-cells displayed evidence that they had undergone homeostatic proliferation during the recovery phase of the experiments.

CONCLUSIONS AND IMPLICATIONS

The recovery of lymphocytes following morphine-induced depletion occurred in the presence of morphine and via increased proliferation of lymphoid precursors and homeostatic proliferation of T-cells.

Withdrawal from morphine reduces cell-mediated immunity against herpes simplex virus generated by natural immunization

In a previous study, the authors have shown that herpes simplex virus type 1 (HSV-1) glycoprotein B DNA vaccine but not live vaccine (non-virulent KOS strain) failed to induce protective immunity against acute HSV-1 challenge in morphine-dependent mice. The present study reports the effect of morphine withdrawal on protective immunity induced by live HSV-1 immunization. BALB/c mice were vaccinated with KOS strain as a live vaccine. Three weeks later, they were exposed to morphine for 14 days. On day 14, withdrawal was induced by administration of normal saline instead of morphine. One day later, immune responses against HSV-1 were assessed by measuring cytotoxicity, lymphocyte proliferation and interferon-γ production. Protection against HSV-1 was assessed by measuring the mortality rate after acute HSV-1 challenge. The results showed that withdrawal from morphine reduces protective immunity against acute HSV-1 challenge. These findings raise the possibility that withdrawal from morphine may increase the susceptibility of drug addicts to infectious diseases.

Opioids and HIV/HCV infection

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