Effect of Tapentadol on Splenic Cytokine Production in Mice

Neuroimmune Mechanisms of Opioid Use Disorder and Recovery: Translatability to Human Studies, and Future Research Directions

Opioid use disorder (OUD) is a major current cause of morbidity and mortality. Long-term exposure to short-acting opioids (MOP-r agonists such as heroin or fentanyl) results in complex pathophysiological changes to neuroimmune and neuroinflammatory functions, affected in part by peripheral mechanisms (e.g., cytokines in blood), and by neuroendocrine systems such as the hypothalamic-pituitary-adrenal (HPA) stress axis. There are important findings from preclinical models, but their role in the trajectory and outcomes of OUD in humans is not well understood. The goal of this narrative review is to examine available data on immune and inflammatory functions in persons with OUD, and to identify major areas for future research. Peripheral blood biomarker studies revealed a pro-inflammatory state in persons with OUD in withdrawal or early abstinence, consistent with available postmortem brain studies (which show glial activation) and diffusion tensor imaging studies (indicating white matter disruptions), with gradual abstinence-associated recovery. The mechanistic roles of these neuroimmune and neuroinflammatory changes in the trajectory of OUD (including recovery and medication management) cannot be examined practically with postmortem data. Collection of longitudinal data in larger-scale human cohorts would allow examination of these mechanisms associated with OUD stage and progression. Given the heterogeneity in presentation of OUD, a precision medicine approach integrating multi-omic peripheral biomarkers and comprehensive phenotyping, including neuroimaging, can be beneficial in risk stratification, and individually optimized selection of interventions for individuals who will benefit, and assessments under refractory therapy.

Modulation of the Inflammatory Response by Pre-emptive Administration of IMT504 Reduces Postoperative Pain in Rats and has Opioid-Sparing Effects

Despite the available knowledge on underlying mechanisms and the development of several therapeutic strategies, optimal management of postoperative pain remains challenging. This preclinical study hypothesizes that, by promoting an anti-inflammatory scenario, pre-emptive administration of IMT504, a noncoding, non-CpG oligodeoxynucleotide with immune modulating properties, will reduce postincisional pain, also facilitating therapeutic opioid-sparing. Male adult Sprague-Dawley rats with unilateral hindpaw skin-muscle incision received pre-emptive (48 and 24 hours prior to surgery) or postoperative (6 hours after surgery) subcutaneous vehicle (saline) or IMT504. Various groups of rats were prepared for pain-like behavior analyses, including subgroups receiving morphine or naloxone, as well as for flow-cytometry or quantitative RT-PCR analyses of the spleen and hindpaws (for analysis of inflammatory phenotype). Compared to vehicle-treated rats, pre-emptive IMT504 significantly reduced mechanical allodynia by 6 hours after surgery, and accelerated recovery of basal responses from 72 hours after surgery and onwards. Cold allodynia was also reduced by IMT504. Postoperative administration of IMT504 resulted in similar positive effects on pain-like behavior. In IMT504-treated rats, 3 mg/kg morphine resulted in comparable blockade of mechanical allodynia as observed in vehicle-treated rats receiving 10 mg/kg morphine. IMT504 significantly increased hindpaw infiltration of mesenchymal stem cells, CD4+T and B cells, and caused upregulated or downregulated transcript expressions of interleukin-10 and interleukin-1β, respectively. Also, IMT504 treatment targeted the spleen, with upregulated or downregulated transcript expressions, 6 hours after incision, of interleukin-10 and interleukin-1β, respectively. Altogether, pre-emptive or postoperative IMT504 provides protection against postincisional pain, through participation of significant immunomodulatory actions, and exhibiting opioid-sparing effects. PERSPECTIVE: This preclinical study introduces the noncoding non-CpG oligodeoxynucleotide IMT504 as a novel modulator of postoperative pain and underlying inflammatory events. The opioid-sparing effects observed for IMT504 appear as a key feature that could contribute, in the future, to reducing opioid-related adverse events in patients undergoing surgical intervention.

Osteoarthritis Pain in Old Mice Aggravates Neuroinflammation and Frailty: The Positive Effect of Morphine Treatment

Knee osteoarthritis is a common cause of pain and disability in old subjects. Pain may predispose to the development of frailty. Studies on mechanisms underlying pain in osteoarthritis models during aging are lacking. In this work, we used the monosodium iodoacetate model of osteoarthritis in adult (11-week-old) and old (20-month-old) C57BL/6J mice to compare hypersensitivity, locomotion, neuroinflammation, and the effects of morphine treatment. After osteoarthritis induction in adult and old mice, weight-bearing asymmetry, mechanical allodynia, and thermal hyperalgesia similarly developed, while locomotion and frailty were more affected in old than in adult animals. When behavioral deficits were present, the animals were treated for 7 days with morphine. This opioid counteracts the behavioral alterations and the frailty index worsening both in adult and old mice. To address the mechanisms that underlie pain, we evaluated neuroinflammatory markers and proinflammatory cytokine expression in the sciatic nerve, DRGs, and spinal cord. Overexpression of cytokines and glia markers were present in osteoarthritis adult and old mice, but the activation was qualitatively and quantitatively more evident in aged mice. Morphine was able to counteract neuroinflammation in both age groups. We demonstrate that old mice are more vulnerable to pain's detrimental effects, but prompt treatment is successful at mitigating these effects.

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.

Frailty and pain, human studies and animal models

The hypothesis that pain can predispose to frailty development has been recently investigated in several clinical studies suggesting that frailty and pain may share some mechanisms. Both pain and frailty represent important clinical and social problems and both lack a successful treatment. This circumstance is mainly due to the absence of in-depth knowledge of their pathological mechanisms. Evidence of shared pathways between frailty and pain are preliminary. Indeed, many clinical studies are observational and the impact of pain treatment, and relative pain-relief, on frailty onset and progression has never been investigated. Furthermore, preclinical research on this topic has yet to be performed. Specific researches on the pain-frailty relation are needed. In this narrative review, we will attempt to point out the most relevant findings present in both clinical and preclinical literature on the topic, with particular attention to genetics, epigenetics and inflammation, in order to underline the existing gaps and the potential future interventional strategies. The use of pain and frailty animal models discussed in this review might contribute to research in this area.

Association between chronic pain medications and the severity and mortality of COVID-19: Study protocol for a case-population study

In patients with coronavirus disease 2019 (COVID-19) infection, common drugs may exacerbate symptoms and negatively impact outcomes. However, the role of chronic medications on COVID-19 effects remains poorly understood. We hypothesized that certain chronic pain medications would influence outcomes in patients with COVID-19. The main aim is to assess the effect of these medications on the course of the disease in COVID-19 patients. Secondary aims are to compare disease severity and outcomes in patients with COVID-19 receiving chronic treatment with analgesics or other medications versus untreated patients and to determine prevalence of chronic pain medications in specific subgroups of hospitalized patients for COVID-19. Multicenter case-population study in 15 care centers for patients ≥18 years of age diagnosed and hospitalized with COVID-19. Controls will include patients treated at participating centers for chronic pain during the six-month period prior to March 15th, 2020. Each case will be age- and sex-matched to 10 controls. Patients will be grouped according to disease severity criteria. The primary outcome measures in patients admitted for COVID-19 will be: 1. statistical association between chronic pain medication and disease severity; 2. association between chronic pain treatment and survival. Secondary outcome measures include: 1. prevalence of chronic pain medications in patients with COVID-19 by age and sex; 2. prevalence of chronic pain medications in patients with COVID-19 vs controls. Patients and controls will be paired by age, sex, and geographic residence. Odds ratios with 95% confidence intervals will be calculated to determine the association between each drug and clinical status. Univariate and multivariate analyses will be performed. This is a study protocol. Data is actually being gathered and results are yet not achieved. There is no numerical data presented, so the conclusions cannot be considered solid at this point. Pain medications are likely to influence severity of COVID-19 and patient survival. Identifying those medications that are most closely associated with severe COVID-19 will provide clinicians with valuable data to guide treatment and reduce mortality rates and the long-term sequelae of the disease.

Opioid-Induced Immunomodulation: Consequences for the Experimental Coxsackievirus B3-Induced Myocarditis Model

Simple Summary

Myocarditis is an inflammatory disorder of the heart mainly caused by viruses. To investigate viral myocarditis, the Coxsackievirus B3 (CVB3)-induced myocarditis model is the experimental model used since more than sixty years. In the pathogeneses of viral myocarditis, the subtle balance between pro-and anti-inflammatory immune responses is of great importance for disease manifestation. Parallel to the infection of the heart, experimental CVB3-induced myocarditis results in an infection of the pancreas, causing a severe burden for the challenged animals. In frame of animal welfare, application of analgesics is mandatory. So far, positive as well as negative effects of opioids on the immune system have been described. However, the impact of opioid application on the pathogenesis of experimental CVB3-induced myocarditis has not been investigated yet. Since examinations on disease pathways and new treatment options rely on established models to generate reproducible data, applicability of opioids in experimental CVB3-induced myocarditis needs to be carefully evaluated. For this purpose, we summarized published studies for 13 different opioids and discussed their potential impact on the CVB3-induced myocarditis model.

Abstract

Myocarditis is an inflammatory disorder of the heart predominantly caused by infectious agents. Since more than sixty years, the Coxsackievirus B3 (CVB3)-induced myocarditis mouse model is the experimental model used to investigate viral myocarditis. The pathogenesis of viral myocarditis is conceptually a multiphase process, initiated by the infection of cardiomyocytes, followed by activation of the immune system, and resulting in myocardial fibrosis and left ventricular dysfunction. In parallel to the direct infection of the heart, CVB3 replicates in lymphatic organs such as the pancreas. Due to infection of the pancreas, the model of experimental CVB3-induced myocarditis is estimated as a severe burden for the challenged animals. Application of analgesics in frame of the animal welfare act (European directive 2010/63/EU) is more and more becoming a matter of debate. For this purpose, we summarized published studies for 13 different opioids and discussed their potential impact on CVB3-induced myocarditis. In addition, with this summary we also want to provide guidance for researchers beyond the myocarditis field to estimate the impact of opioids on the immune system for their specific model. In the literature, both immunosuppressive as well as immune-activating effects of opioids have been described, but examinations in experimental CVB3-induced myocarditis have still not been reported so far. Based on the existing publications, administration of opioids in experimental CVB3-induced myocarditis might result in more severe disease progression, including higher mortality, or a less pronounced myocarditis model, failing to be used for the establishment of new treatment options. Taken together, the applicability of opioids in experimental CVB3-induced myocarditis and in inflammatory models in general needs to be carefully evaluated and further investigated.

Modulation of sensitization processes in the management of pain and the importance of descending pathways: a role for tapentadol?

Objective: This paper presents and discusses recent evidence on the pathophysiological mechanisms of pain. The role of tapentadol - an opioid characterized by an innovative mechanism of action (i.e. µ-opioid receptor [MOR] agonism and inhibition of noradrenaline [NA] reuptake [NRI]) - in the modulation of pain, and the most recent pharmacological evidence on this molecule (e.g. the µ-load concept) are also presented and commented upon.Methods: Narrative review.Results: Solid evidence has highlighted the importance of central sensitization in the transition from acute to chronic pain. In particular, the noradrenergic system holds a major role in limiting central sensitization and the progression to chronic pain. Therefore, pharmacological modulation of the noradrenergic system appears to be a well-grounded strategy for the control of chronic pain. Tapentadol is characterized by a to-date-unique mechanism of action, since it acts both as a MOR agonist and as an inhibitor of NA reuptake. The synergistic interaction of these two mechanisms allows a strong analgesic effect by acting on both ascending and descending pathways. Of note, the reduced µ-load of tapentadol limits the risk of opioid-related adverse events, such as gastrointestinal disturbances. Moreover, the NA component becomes predominant, at least, in some types of pain, with consequent specific clinical efficacy in the treatment of neuropathic and chronic pain.Conclusions: According to these characteristics, tapentadol appears suitable in the treatment of severe uncontrolled chronic pain characterized by both a nociceptive and a neuropathic component, such as osteoarthritis or back pain.

Sublingual delivery of chondroitin sulfate conjugated tapentadol loaded nanovesicles for the treatment of osteoarthritis

Recent treatment approaches of osteoarthritis (OA) face a number of obstacles due to the progressive multitude of pain generators, nociceptive mechanisms, first pass mechanism, less efficacy and compromised safety. The present study was aimed to bring a novel approach for the effective management of OA, by developing sublingual targeted nanovesicles (NVs) bearing tapentadol HCl (TAP), surface modified with chondroitin sulfate (CS). Optimized nontargeted nanovesicle formulation (MB-NV) was developed by an ultrasound method, characterized as spherical in shape, nanometric in size (around 150 nm) with narrow size distribution (polydispersity index <0.5), and good entrapment efficiency (around 50%). MB-NV conjugated with CS which was confirmed by IR and ¹H NMR spectroscopy. C-MB-NV showed improved pharmacokinetics parameters i.e. increased t_1/2 (9.7 h), AUC (159.725 μg/mL*h), and MRT (14.99 h) of TAP than nontargeted formulation and plain drug soln. C-MB-NV in in vitro release studies proved sustained drug release pattern for more than 24 h following Higuchi model kinetics with Fickian diffusion (n ≤ 0.5).Targeted nanovesicles exhibited an improved bioavailability and enhanced analgesic activity in a disease-induced Wistar rat model which indicated the superior targeting potential of C-MB-NV exploiting CD44 receptors as mediators, overexpressed at the affected joints in the OA model. It could be a propitious approach to accustomed therapies for methodical and efficient management in advanced OA therapy.

Endogenous opiates and behavior: 2017

This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Do All Opioid Drugs Share the Same Immunomodulatory Properties? A Review From Animal and Human Studies

Suppression of the immune system has been constantly reported in the last years as a classical side effect of opioid drugs. Most of the studies on the immunological properties of opioids refer to morphine. Although morphine remains the "reference molecule," other semisynthetic and synthetic opioids are frequently used in the clinical practice. The primary objective of this review is to analyze the available literature on the immunomodulating properties of opioid drugs different from morphine in preclinical models and in the human. A search strategy was conducted in PubMed, Embase, and the Cochrane databases using the terms "immunosuppression," "immune system," "opioids," "Natural killer cells," "cytokines," and "lymphocytes." The results achieved concerning the effects of fentanyl, methadone, oxycodone, buprenorphine, remifentanil, tramadol, and tapentadol on immune responses in animal studies, in healthy volunteers and in patients are reported. With some limitations due to the different methods used to measure immune system parameters, the large range of opioid doses and the relatively scarce number of participants in the available studies, we conclude that it is not correct to generalize immunosuppression as a common side effect of all opioid molecules.

Pharmacological rationale for tapentadol therapy: a review of new evidence

Chronic pain could be considered as a neurological disorder. Therefore, appropriate selection of the therapy, which should consider the pathophysiological mechanisms of pain, can result in a successful analgesic outcome. Tapentadol is an analgesic drug which acts both as a μ-opioid receptor (MOR) agonist and as a noradrenaline reuptake inhibitor (NRI), thereby generating a synergistic action in terms of analgesic efficacy, but not for the burden of adverse effects. Therefore, tapentadol can be defined as the first “MOR-NRI” drug. This molecule holds the potential to address at least some of the current limitations of analgesic therapy due to its unique mechanism of action and has shown to be safe and effective in the treatment of chronic pain of cancer and noncancer etiologies including nociceptive, neuropathic and mixed pain. In particular, the MOR component of tapentadol activity predominantly allows for analgesia in nociceptive pain; on the other hand, the NRI component contributes, now in a predominant manner, for analgesic efficacy in cases of neuropathic pain states. This paper will discuss recent pieces of evidence on the pathophysiology of pain, the background on tapentadol and then present some new studies on how the unique mechanism of action of tapentadol provides a key role in its analgesic efficacy in a number of pain states and with a favorable safety profile.

Tapentadol: an analgesic that differs from classic opioids due to its noradrenergic mechanism of action

Chronic pain treatment represents one of the most complex clinical challenges and even though opioids exhibit particular efficacy on nociceptive pain, their use must be controlled to avoid the risk of adverse reactions. A useful approach, aimed at maintaining analgesia and mitigating side effects, is represented by the use of a new class of analgesics endowed of µ-opioid (MOR) receptor agonism and noradrenaline reuptake inhibition (NRI) mechanisms. Tapentadol is the progenitor of this new class of drugs called MOP-NRI. A literature review has been conducted to gain information about the efficacy and the tolerability profile of tapentadol shifting from MOR agonism (acute pain) to NRI activity (chronic pain). The tolerability and therapeutic safety of tapentadol in neuropathic pain models, as well as in clinical settings, has been analyzed showing a good gastrointestinal tolerability profile, a moderate effect on hormone levels (in healthy volunteers and in patients) and on cognitive performance, a lack of significant alteration of the electrocardiogram recording and no changes of the QT/QTc interval, a minimal effect on serotonin reuptake in vivo with a low risk of serotonin syndrome, a longer time for the onset of analgesic tolerance and a less occurrence of abuse liability compared to formulations containing other comparator compounds. Tapentadol represents a great innovation in chronic pain therapy with a unique analgesic profile different form classical opioids, therefore, thanks to its synergistic MOR-NRI action, it may be a good option for the treatment of chronic, neuropathic and mixed pain.