Evaluation of therapeutic effect of low dose naltrexone in experimentally-induced Crohn's disease in rats

Unraveling the neuroprotective mechanisms of naltrexone against aluminum-induced neurotoxicity

Aluminum (Al) is a known neurotoxic trace element linked to Alzheimer's disease (AD). Naltrexone, an opioid antagonist, has shown promising effects in reducing neuroinflammation at lower doses than those prescribed for addiction. This study aimed to determine the neuroprotective effects of naltrexone on Al-induced neurotoxicity in an in vitro AD model. The SH-SY5Y cells were first cultivated in a standard growth medium. Subsequently, the cells were induced to differentiate by decreasing the concentration of fetal bovine serum and introducing retinoic acid (RA) into the culture media. Subsequently, the inclusion of brain-derived neurotrophic factor (BDNF) was implemented in conjunction with RA. The process of differentiation was concluded on the seventh day. Study groups (n = 3) were designed as the control group, naltrexone group, Al group, Al-Nal group, Alzheimer' model (AD) group, Alzheimer model + Al-exposed group (AD-Al), Alzheimer model + Nal applied group (AD-Nal) and Alzheimer model + Al-exposed + Nal applied group (AD-Al-Nal). Hyperphosphorylated Tau protein as the specific marker of AD was measured in all groups. Glycogen synthase kinase-3 (GSK-3)β, Protein phosphatase 2A (PP2A), Akt and Wnt signaling pathways were analyzed comparatively. In addition, oxidative stress parameters (total antioxidant capacity, lipid peroxidase, protein carbonyl and reactive oxygen species) were measured comparatively in the study groups. The results showed that naltrexone reduced hyperphosphorylated tau protein levels by regulating GSK-3β, PP2A, Akt and Wnt signaling. Also, exposure to naltrexone decreased oxidative stress parameters. Based on these results, naltrexone shows promise as a potential therapy for AD, subject to additional clinical assessments.

Pilot Study of Low-Dose Naltrexone for the Treatment of Chronic Pain Due to Arthritis: A Randomized, Double-blind, Placebo-Controlled, Crossover Clinical Trial

PURPOSE

Low-dose naltrexone (LDN) is commonly used to control pain and other symptoms, especially in patients with autoimmune diseases, but with limited evidence. This study tests the efficacy of LDN in reducing chronic pain in patients with osteoarthritis (OA) and inflammatory arthritis (IA), where existing approaches often fail to adequately control pain.

METHODS

In this randomized, double-blind, placebo-controlled, crossover clinical trial, each patient received 4.5 mg LDN for 8 weeks and placebo for 8 weeks. Outcome measures were patient reported, using validated questionnaires. The primary outcome was differences in pain interference during the LDN and placebo periods, using the Brief Pain Inventory (scale, 0-70). Secondary outcomes included changes in mean pain severity, fatigue, depression, and multiple domains of health-related quality of life. The painDETECT questionnaire classified pain as nociceptive, neuropathic, or mixed. Data were analyzed using mixed-effects models.

FINDINGS

Seventeen patients with OA and 6 with IA completed the pilot study. Most patients described their pain as nociceptive (n = 9) or mixed (n = 8) rather than neuropathic (n = 3). There was no difference in change in pain interference after treatment with LDN (mean [SD], -23 [19.4]) versus placebo (mean [SD], -22 [19.2]; P = 0.90). No significant differences were seen in pain severity, fatigue, depression, or health-related quality of life.

IMPLICATIONS

In this small pilot study, findings do not support LDN being efficacious in reducing nociceptive pain due to arthritis. Too few patients were enrolled to rule out modest benefit or to assess inflammatory or neuropathic pain.

CLINICALTRIALS

gov identifier: NCT03008590.

Repurposing low-dose naltrexone for the prevention and treatment of immunothrombosis in COVID-19

Coronavirus disease 2019 (COVID-19) is characterized by striking dysregulation of the immune system, with evidence of hyperinflammation, an impaired induction of interferons, and delayed adaptive immune responses. In addition to dysfunctional immune responses, thrombosis is a hallmark of severe COVID-19. Because traditional anticoagulation strategies are associated with increased bleeding, novel strategies that address both the immune and thrombotic dysfunction associated with COVID-19 would be of tremendous benefit. In this commentary, we discuss the unique properties of low dose naltrexone (LDN) which could be leveraged to reduce the immune-mediated thrombotic complications in COVID-19. Mechanistically, LDN can blunt innate immune responses and Toll-like receptor (TLR) signaling, reducing interleukin1 (IL-1), tumor necrosis factor-alpha (TNF-α), and interferon (IFN) levels. Because of the immune-mediated thrombotic mechanisms that underlie COVID-19, we hypothesize that the immune-modulating and known pharmacologic properties of LDN could be leveraged as a novel therapeutic strategy in COVID-19.

Low-dose naltrexone for the induction of remission in patients with mild to moderate Crohn's disease: protocol for the randomised, double-blinded, placebo-controlled, multicentre LDN Crohn study

INTRODUCTION

Crohn's disease (CD) is an inflammatory bowel disease (IBD). Several drugs exist to induce and maintain remission, but a significant part of the patients is refractory to current IBD drugs or experiences side effects. Whether low-dose naltrexone (LDN) is a safe and easily accessible alternative treatment option for these patients needs to be investigated. The aim of this study is to assess the efficacy of LDN for the induction of remission in patients with mild to moderate CD.

METHODS AND ANALYSIS

The LDN Crohn study is a randomised, double-blinded, placebo-controlled multicentre trial. Patients with CD are randomised 1:1 to receive treatment with either LDN 4.5 mg once daily or placebo for 12 weeks. The primary objective is endoscopic remission at week 12, defined as Simple Endoscopic Score-CD≤2 and ulcerated surface subscore ≤1 in all five segments. Secondary aims include clinical and endoscopic response, changes in laboratory measures of inflammation, adverse events and patient-reported outcomes. To have 85% power to detect a true difference in the primary outcome measure between placebo and LDN, 61 patients will be needed in both groups.

ETHICS AND DISSEMINATION

The study is approved by the Medical Ethics Committee of the Erasmus MC, Rotterdam, the Netherlands (registration number NL69149.078.19, MEC-2019-0602). Results will be published in peer-reviewed journals and presented at international conferences.

TRIAL REGISTRATION NUMBERS

EudraCT2019-000852-32; NL9259.

NSAID-Associated Small Intestinal Injury: An Overview From Animal Model Development to Pathogenesis, Treatment, and Prevention

With the wide application of non-steroidal anti-inflammatory drugs (NSAIDs), their gastrointestinal side effects are an urgent health burden. There are currently sound preventive measures for upper gastrointestinal injury, however, there is a lack of effective defense against lower gastrointestinal damage. According to a large number of previous animal experiments, a variety of NSAIDs have been demonstrated to induce small intestinal mucosal injury in vivo. This article reviews the descriptive data on the administration dose, administration method, mucosal injury site, and morphological characteristics of inflammatory sites of various NSAIDs. The cells, cytokines, receptors and ligands, pathways, enzyme inhibition, bacteria, enterohepatic circulation, oxidative stress, and other potential pathogenic factors involved in NSAID-associated enteropathy are also reviewed. We point out the limitations of drug modeling at this stage and are also pleased to discover the application prospects of chemically modified NSAIDs, dietary therapy, and many natural products against intestinal mucosal injury.

Neuroimmune Mechanisms as Novel Treatment Targets for Substance Use Disorders and Associated Comorbidities

Recent studies examining the neurobiology of substance abuse have revealed a significant role of neuroimmune signaling as a mechanism through which drugs of abuse induce aberrant changes in synaptic plasticity and contribute to substance abuse-related behaviors. Immune signaling within the brain and the periphery critically regulates homeostasis of the nervous system. Perturbations in immune signaling can induce neuroinflammation or immunosuppression, which dysregulate nervous system function including neural processes associated with substance use disorders (SUDs). In this review, we discuss the literature that demonstrates a role of neuroimmune signaling in regulating learning, memory, and synaptic plasticity, emphasizing specific cytokine signaling within the central nervous system. We then highlight recent preclinical studies, within the last 5 years when possible, that have identified immune mechanisms within the brain and the periphery associated with addiction-related behaviors. Findings thus far underscore the need for future investigations into the clinical potential of immunopharmacology as a novel approach toward treating SUDs. Considering the high prevalence rate of comorbidities among those with SUDs, we also discuss neuroimmune mechanisms of common comorbidities associated with SUDs and highlight potentially novel treatment targets for these comorbid conditions. We argue that immunopharmacology represents a novel frontier in the development of new pharmacotherapies that promote long-term abstinence from drug use and minimize the detrimental impact of SUD comorbidities on patient health and treatment outcomes.

Current overview of opioids in progression of inflammatory bowel disease; pharmacological and clinical considerations

Inflammatory bowel diseases (IBD) belong to a subgroup of persistent, long-term, progressive, and relapsing inflammatory conditions. IBD may spontaneously develop in the colon, resulting in tumor lesions in inflamed regions of the intestine, such as invasive carcinoma. The benefit of opioids for IBD treatment is still questionable, thereby we investigated databases to provide an overview in this context. This review demonstrates the controversial role of opioids in IBD therapy, their physiological and pharmacological functions in attenuating the IBD symptoms, and in improving inflammatory, oxidative stress, and the quality of life factors in IBD subjects. Data were extracted from clinical, in vitro, and in vivo studies in English, between 1995 and 2019, from PubMed, Google Scholar, Scopus, and Cochrane library. Based on recent reports, there are promising opportunities to target the opioid system and control the IBD symptoms. This study suggests a novel approach for future treatment of functional and inflammatory disorders such as IBD.

Opioid agonist and antagonist use and the gut microbiota: associations among people in addiction treatment

Murine models suggest that opioids alter the gut microbiota, which may impact opioid tolerance and psychopathology. We examined how gut microbiota characteristics related to use of opioid agonists and antagonists among people receiving outpatient addiction treatment. Patients (n = 46) collected stool samples and were grouped by use of opioid agonists (heroin, prescription opioids), antagonists (naltrexone), agonist-antagonist combinations (buprenorphine-naloxone), or neither agonists nor antagonists within the month before enrollment. We sequenced the V4 region of the 16S rRNA gene using Illumina MiSeq to examine how alpha diversity, enterotypes, and relative abundance of bacterial genera varied by opioid agonist and antagonist exposures. Compared to 31 participants who used neither agonists nor antagonists, 5 participants who used opioid agonists (without antagonists) had lower microbiota diversity, Bacteroides enterotypes, and lower relative abundance of Roseburia, a butyrate producing genus, and Bilophila, a bile acid metabolizing genus. There were no differences in gut microbiota features between those using agonist + antagonists (n = 4), antagonists only (n = 6), and neither agonists nor antagonists. Similar to murine morphine exposure models, opioid agonist use was associated with lower microbiota diversity. Lower abundance of Roseburia and Bilophila may relate to the gut inflammation/permeability and dysregulated bile acid metabolism observed in opioid-exposed mice.

LOW-DOSE NALTREXONE REVERSES FACIAL MECHANICAL ALLODYNIA IN A RAT MODEL OF TRIGEMINAL NEURALGIA

Trigeminal neuralgia (TN) is a type of neuropathic pain characterized by intense pain; although anticonvulsants are used as an option to relieve pain, adverse side effects can decrease patient adherence. In this context, a low dose of naltrexone is effective in relieving pain in other pain conditions. Thus, the objective of the present study was to evaluate the analgesic effect of low-dose naltrexone on facial mechanical allodynia in a rat model of TN, as well as its effect(s) on biomarkers in the central nervous system (tumor necrosis factor-alpha, brain-derived neurotrophic factor [BDNF], interleukin [IL]-10, and toll-like receptor-4). Fifty-nine adult male Wistar rats (CEUA-HCPA#2017-0575) were allocated to following groups: control; sham-pain + vehicle; sham-pain + carbamazepine (100 mg/kg); sham-pain + naltrexone (0.5 mg/kg); pain + vehicle; pain + carbamazepine; and pain + naltrexone. TN was induced using chronic constriction of the infraorbital nerve. Facial allodynia was assessed using von Frey test. Drugs were administered by gavage 14 days after surgery for 10 days. At baseline, the mechanical threshold was similar between groups (P > 0.05; generalized estimating equation). Seven days after surgery, facial allodynia was observed in sham-TN and pain-TN groups (P < 0.05). Fourteen days after surgery, only pain-TN groups exhibited facial allodynia. The first dose of low-dose naltrexone or carbamazepine partially reversed facial allodynia. After 10 days of treatment, both drugs completely reversed it. Spinal cord levels of BDNF and IL-10 were modulated by low-dose naltrexone. Thus, low-dose naltrexone may be suitable to relieve TN; however, the exact mechanisms need to be clarified.

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).

Role of the δ-Opioid Receptor in 2 Murine Models of Colitis

Crohn disease and ulcerative colitis, collectively referred to as inflammatory bowel disease (IBD), are chronic inflammatory disorders of the gastrointestinal tract. Currently, the etiology of IBD is unknown, and immunosuppressive therapies have become the standard of care to reduce the inflammation; however, these agents only induce remission 50% of the time in patients and can have serious side effects. Recently, endogenous opioids and opioid receptors have been shown to play a role in the mediation of inflammation. In addition, opioid receptor blockade with a nonselective antagonist, naltrexone, has been shown to reduce colitis in both murine models and human subjects. The goal of the current study was to determine if the antiinflammatory effects of naltrexone are mediated through the delta (δ) opioid receptor. Male C57BL/6NCrl (6 to 8 wk.; n = 110) and female BALB/cAnNCrl (6-8 wk.; n = 91) mice were studied using 2 animal models of chemically induced colitis: dextran sodium sulfate (DSS) and 2, 4, 6-trinitrobenzenesulfonic acid (TNBS). The selective δ-receptor antagonists naltrindole and 7-benzylidenenaltrexone were administered to examine the role of the δ-opioid receptor in colonic inflammation. The quantitative measurement of colitis activity, colon weight and length, Hct, WBC count, and gross and microscopic aberrations were analyzed. Administration of naltrexone in the DSS colitis model significantly improved overall disease activity indices on day 5 of therapy. The use of δ-antagonists and naltrexone had limited to no effect on TNBS colitis. Similar findings were obtained by using the DSS colitis model. Based on the current findings, the authors conclude that naltrexone therapy has limited effect on the improvement of colitis in 2 murine models; however, the δ-opioid receptor was not responsible for mediating the effects.

Low-Dose Naltrexone (LDN)-Review of Therapeutic Utilization

Naltrexone and naloxone are classical opioid antagonists. In substantially lower than standard doses, they exert different pharmacodynamics. Low-dose naltrexone (LDN), considered in a daily dose of 1 to 5 mg, has been shown to reduce glial inflammatory response by modulating Toll-like receptor 4 signaling in addition to systemically upregulating endogenous opioid signaling by transient opioid-receptor blockade. Clinical reports of LDN have demonstrated possible benefits in diseases such as fibromyalgia, Crohn’s disease, multiple sclerosis, complex-regional pain syndrome, Hailey-Hailey disease, and cancer. In a dosing range at less than 1 μg per day, oral naltrexone or intravenous naloxone potentiate opioid analgesia by acting on filamin A, a scaffolding protein involved in μ-opioid receptor signaling. This dose is termed ultra low-dose naltrexone/naloxone (ULDN). It has been of use in postoperative control of analgesia by reducing the need for the total amount of opioids following surgery, as well as ameliorating certain side-effects of opioid-related treatment. A dosing range between 1 μg and 1 mg comprises very low-dose naltrexone (VLDN), which has primarily been used as an experimental adjunct treatment for boosting tolerability of opioid-weaning methadone taper. In general, all of the low-dose features regarding naltrexone and naloxone have been only recently and still scarcely scientifically evaluated. This review aims to present an overview of the current knowledge on these topics and summarize the key findings published in peer-review sources. The existing potential of LDN, VLDN, and ULDN for various areas of biomedicine has still not been thoroughly and comprehensively addressed.

The Effect of Low-Dose Naltrexone on Medication in Inflammatory Bowel Disease: A Quasi Experimental Before-and-After Prescription Database Study

BACKGROUND AND AIMS

Low-dose naltrexone [LDN] is a controversial off-label treatment used by many Crohn's disease [CD] and ulcerative colitis [UC] patients. A small number of preliminary studies indicate that LDN might be beneficial in CD, but evidence is too scarce to demonstrate efficacy. We sought to examine whether initiation of LDN therapy by patients with inflammatory bowel disease [IBD] was followed by changes in dispensing of relevant medication.

METHODS

We performed a quasi-experimental before-and-after study following a sudden increase in LDN use in the Norwegian population in 2013. IBD patients were identified from among all the patients who had at least one LDN prescription recorded in the Norwegian Prescription Database [NorPD] in 2013. Drug dispensing 2 years before and after the first LDN prescription was compared.

RESULTS

We identified 582 IBD patients who had received LDN. Of the 256 patients who became persistent LDN users, there were reductions in the number of users for [i] all examined drugs [-12%], [ii] intestinal anti-inflammatory agents [-17%], [iii] other immunosuppressants [-29%], [iv] intestinal corticosteroids [-32%] and [v] aminosalicylates [-17%]. In subgroups of identified CD and UC patients, there were significant reductions in the number of users of intestinal corticosteroids [CD: -44%, UC: -53%] and systemic corticosteroids [UC: -24%]. No significant differences in cumulative defined daily doses were observed.

CONCLUSIONS

Our findings imply that the initiation of LDN in IBD is followed by reduced dispensing of several drugs considered essential in the treatment of CD and UC.

Low dose Naltrexone for induction of remission in inflammatory bowel disease patients

BACKGROUND

Around 30% of patients with inflammatory bowel disease (IBD) are refractory to current IBD drugs or relapse over time. Novel treatments are called for, and low dose Naltrexone (LDN) may provide a safe, easily accessible alternative treatment option for these patients. We investigated the potential of LDN to induce clinical response in therapy refractory IBD patients, and investigated its direct effects on epithelial barrier function.

METHODS

Patients not in remission and not responding to conventional therapy were offered to initiate LDN as a concomitant treatment. In total 47 IBD patients prescribed LDN were followed prospectively for 12 weeks. Where available, endoscopic remission data, serum and biopsies were collected. Further the effect of Naltrexone on wound healing (scratch assay), cytokine production and endoplasmic reticulum (ER) stress (GRP78 and CHOP western blot analysis, immunohistochemistry) were investigated in HCT116 and CACO2 intestinal epithelial cells, human IBD intestinal organoids and patient samples.

RESULTS

Low dose Naltrexone induced clinical improvement in 74.5%, and remission in 25.5% of patients. Naltrexone improved wound healing and reduced ER stress induced by Tunicamycin, lipopolysaccharide or bacteria in epithelial barriers. Inflamed mucosa from IBD patients showed high ER stress levels, which was reduced in patients treated with LDN. Cytokine levels in neither epithelial cells nor serum from IBD patients were affected.

CONCLUSIONS

Naltrexone directly improves epithelial barrier function by improving wound healing and reducing mucosal ER stress levels. Low dose Naltrexone treatment is effective and safe, and could be considered for the treatment of therapy refractory IBD patients.