BDNF variability in opioid addicts and response to methadone treatment: preliminary findings

Brain-derived neurotrophic factor (BDNF) signaling pathways have been shown to be essential for opioid-induced plasticity. We conducted an exploratory study to evaluate BDNF variability in opioid addict responders and nonresponders to methadone maintenance treatment (MMT). We analyzed 21 single nucleotide polymorphisms (SNPs) across the BDNF genomic region. Responders and nonresponders were classified by means of illicit opioid consumption detected in random urinalysis. Patients were assessed by a structured interview (Psychiatric Research Interview for Substance and Mental Disorders (PRISM)-DSM-IV) and personality was evaluated by the Cloninger's Temperament and Character Inventory. No clinical, environmental and treatment characteristics were different between the groups, except for the Cooperativeness dimension ( P  < 0.001). Haplotype block analysis showed a low-frequency (2.7%) haplotype (13 SNPs) in block 1, which was more frequent in the nonresponder group than in the responder group (4/42 vs. 1/135; P _corrected = 0.023). Fine mapping in block 1 allows us to identify a haplotype subset formed by only six SNPs (rs7127507, rs1967554, rs11030118, rs988748, rs2030324 and rs11030119) associated with differential response to MMT (global P sim = 0.011). Carriers of the CCGCCG haplotype had an increased risk of poorer response, even after adjusting for Cooperativeness score (OR = 20.25 95% CI 1.46–280.50, P  = 0.025). These preliminary results might suggest the involvement of BDNF as a factor to be taken into account in the response to MMT independently of personality traits, environmental cues, methadone dosage and psychiatric comorbidity.     

Modification of the response to opioid and nonopioid drugs by chronic opioid antagonist treatment

Chronic exposure to opioid antagonists increases the analgesic actions of opioids such as morphine. In the present studies, morphine's analgesic potency was increased (supersensitivity) following an 8 day subcutaneous naltrexone implant in mice, but not following a 1 day implant. Supersensitivity was maximal 24hr following the 8 day implant and declined linearly and had returned to control levels by 120hr. Implantation of naltrexone pellets for 8 days was found to increase the relative analgesic potency of methadone by 120%, while the lethal potency of cocaine was slightly (19%), but significantly, decreased. In contrast, identical treatment did not alter the potency of the benzodiazepine alprazolam to induce ataxia.     

JWA regulates chronic morphine dependence via the delta opioid receptor

Opioid dependence is correlated with the adaptive changes at the cellular level following chronic opioid use, and believed to be the main cause for the relapse of drug taking behavior of addicts. Despite decades of intensive studies, the underlying mechanisms of morphine dependence are still unclear. Here, we present evidence that JWA was induced by chronic morphine treatment in specific brain regions, and knockdown of JWA expression significantly reduced the withdrawal response to chronic morphine treatment in rats. We further demonstrated that the morphine induced DOR expression, while activation of DARPP-32 and MAP kinase was suppressed by JWA knockdown. Through an in vitro cell model of chronic morphine exposure, we also found that JWA is required for maintaining the stability of DOR via the ubiquitin–proteasome pathway. These observations suggest that JWA is directly involved in the regulation of chronic morphine dependence.     

ATP,an attractive target for the treatment of refractory chronic cough

Purinergic Signalling - Chronic cough is the most common complaint in respiratory clinics. Most of them have identifiable causes and some may respond to common disease-modifying therapies. However,...     

Molecular mechanisms of excitatory signaling upon chronic opioid agonist treatment

Opioid receptor agonists mediate their analgesic effects by interacting with Gi/o protein-coupled opioid receptors. Acute treatment with opioid agonists is thought to mediate analgesia by hyperpolarization of presynatic neurons, leading to the inhibition of excitatory (pain) neurotransmitters release. After chronic treatment however, the opioid receptors gradually become less responsive to agonists, and increased drug doses become necessary to maintain the therapeutic effect (tolerance). Analgesic tolerance is the result of two, partially overlapping processes: a gradual loss of inhibitory opioid function is accompanied by an increase in excitatory signaling. Recent data indicate that chronic opioid agonist treatment simultaneously desensitizes the inhibitory-, and augments the stimulatory effects of the opioids. In the present paper we review the molecular mechanisms that may have a role in the augmentation of the excitatory signaling upon chronic opioid agonist treatment. We also briefly review our recent experimental data on the molecular mechanism of chronic opioid agonist-mediated functional sensitization of forskolin-stimulated cAMP formation, in a recombinant Chinese hamster ovary cell line stably expressing the human delta-opioid receptor (hDOR/CHO). To interpret the experimental data, we propose that chronic hDOR activaton leads to activation of multiple redundant signaling pathways that converge to activate the protein kinase, Raf-1. Raf-1 in turn phosphorylates and sensitizes the native adenylyl cyclase VI isoenzyme in hDOR/CHO cells, causing a rebound increase in forskolin-stimulated cAMP formation upon agonist withdrawal.     

Genomewide linkage scan for opioid dependence and related traits

Risk of opioid dependence is genetically influenced. We recruited a sample of 393 small nuclear families (including 250 full-sib and 46 half-sib pairs), each with at least one individual with opioid dependence. Subjects underwent a detailed evaluation of substance dependence-related traits. As planned a priori to reduce heterogeneity, we used cluster analytic methods to identify opioid dependence-related symptom clusters, which were shown to be heritable. We then completed a genomewide linkage scan (with 409 markers) for the opioid-dependence diagnosis and for the two cluster-defined phenotypes represented by >250 families: the heavy-opioid-use cluster and the non-opioid-use cluster. Further exploratory analyses were completed for the other cluster-defined phenotypes. The statistically strongest results were seen with the cluster-defined traits. For the heavy-opioid-use cluster, we observed a LOD score of 3.06 on chromosome 17 (empirical pointwise P = .0002) for European American (EA) and African American (AA) subjects combined, and, for the non-opioid-use cluster, we observed a LOD score of 3.46 elsewhere on chromosome 17 (empirical pointwise P = .00002, uncorrected for multiple traits studied) for EA subjects only. We also identified a possible linkage (LOD score 2.43) of opioid dependence with chromosome 2 markers for the AA subjects. These results are an initial step in identifying genes for opioid dependence on the basis of a genomewide investigation (i.e., a study not conditioned on prior physiological candidate-gene hypotheses).     

Methadone maintenance in the treatment of opioid dependence. A current perspective.

We describe the historical underpinnings of negative attitudes towards methadone and how these affect medical decisions. Current developments have increased the understanding of the origins of opioid addiction, such as how receptor system dysfunction may affect the ability to remain abstinent once out of treatment. Specialized topics include the pregnant addict, the role of methadone maintenance in limiting the spread of the acquired immunodeficiency syndrome, and patients with a dual diagnosis. We also describe issues that arise when methadone is used in conjunction with prescribed or abused drugs, noting pharmacologic alternatives and adjuncts to methadone treatment. Finally, we comment on treatment issues such as methadone patients in 12-step programs and the growing legitimacy of this treatment method.     

Effect of chronic oral methadone treatment on the growth of maturing monkeys.

Three male rhesus monkeys drank methadone hydrochloride (1.0-2.5 mg/kg/day) in Tang orange drink from age two to four years. Their rate of body weight gain was faster than that found by other experimenters. In a second study one male monkey drank 2.0 mg/kg/day methadone while two others drank only Tang from age 21/2 to 31/2 years. The rate of body weight gain was identical for the three monkeys, and was the same as that found in the previous study. The apparent augmentation of body weight gain in the first study was probably due to inter-laboratory differences in housing and feeding conditions.     

High-affinity naloxone binding to filamin a prevents mu opioid receptor-Gs coupling underlying opioid tolerance and dependence

Ultra-low-dose opioid antagonists enhance opioid analgesia and reduce analgesic tolerance and dependence by preventing a G protein coupling switch (Gi/o to Gs) by the mu opioid receptor (MOR), although the binding site of such ultra-low-dose opioid antagonists was previously unknown. Here we show that with approximately 200-fold higher affinity than for the mu opioid receptor, naloxone binds a pentapeptide segment of the scaffolding protein filamin A, known to interact with the mu opioid receptor, to disrupt its chronic opioid-induced Gs coupling. Naloxone binding to filamin A is demonstrated by the absence of [(3)H]-and FITC-naloxone binding in the melanoma M2 cell line that does not contain filamin or MOR, contrasting with strong [(3)H]naloxone binding to its filamin A-transfected subclone A7 or to immunopurified filamin A. Naloxone binding to A7 cells was displaced by naltrexone but not by morphine, indicating a target distinct from opioid receptors and perhaps unique to naloxone and its analogs. The intracellular location of this binding site was confirmed by FITC-NLX binding in intact A7 cells. Overlapping peptide fragments from c-terminal filamin A revealed filamin A(2561-2565) as the binding site, and an alanine scan of this pentapeptide revealed an essential mid-point lysine. Finally, in organotypic striatal slice cultures, peptide fragments containing filamin A(2561-2565) abolished the prevention by 10 pM naloxone of both the chronic morphine-induced mu opioid receptor-Gs coupling and the downstream cAMP excitatory signal. These results establish filamin A as the target for ultra-low-dose opioid antagonists previously shown to enhance opioid analgesia and to prevent opioid tolerance and dependence.     

Immunohistochemical study of opioid receptors after chronic morphine treatment in rats

Previously, we have used the biochemical receptor binding method to investigate whether down-regulation of the opioid receptor is a mechanism for morphine tolerance, and we were led to a negative conclusion. In the current study, we further used immunohistochemistry to reinvestigate this issue. Male Sprague-Dawley rats (250-300 g) were chronically treated with morphine s.c. for 2, 4 or 6 days, using an escalating dosage paradigm (5-45 mg), which resulted in a 1.8 to 4.0-fold increase in AD50. Rat brains were removed, frozen, coronally sectioned (14 microm) and processed for mu- or delta-opioid receptor immunohistochemistry using the Avidin-Biotin Complex (ABC) method. No significant decrease in mu-opioid receptor (MOR) immunodensity was found in most of the brain regions, which were enriched with MOR after chronic treatment with morphine except for the anteroventral thalamic nucleus in the ventrolateral part (AVVL). No significant change in delta-opioid receptor (DOR) immunodensity after chronic treatment with morphine was found either. Therefore, our conclusion is that down regulation of opioid receptors may not be an important mechanism for morphine tolerance.     

Method for determination of methadone in exhaled breath collected from subjects undergoing methadone maintenance treatment

At present drugs of abuse testing using exhaled breath as specimen is only possible for alcohol. However, we recently discovered that using modern liquid chromatography–mass spectrometry technique amphetamine and methamphetamine is detectable in exhaled breath following intake in drug addicts. We therefore undertook to develop a method for determination of methadone in exhaled breath from patients undergoing methadone maintenance treatment. Exhaled breath was collected from 13 patients after intake of the daily methadone dose. The compounds were trapped by filtering the air through a C18 modified silica surface. After elution of any trapped methadone the extract was analysed by a combined liquid chromatography–tandem mass spectrometry method. Recovery of trapped methadone from the filter surface was 96%, no significant matrix effect was observed, and the quantification using methadone-d3 as an internal standard was accurate (<10% bias) and precise (coefficient of variation 1.6–2.0%). Methadone was indisputably identified by means of the mass spectrometry technique in exhaled breath samples from all 13 patients. Identification was based on monitoring two product ions in selected reaction monitoring mode with correct relative ratio (±20%) and correct retention time. Excretion rates ranged from 0.39 to 78 ng/min. No methadone was detected in 10 control subjects. This finding confirms that breath testing is a new possibility for drugs of abuse testing. Collection of exhaled breath specimen is likely to be more convenient and safe as compared to other matrices presently in use.     

The role of opioid receptor phosphorylation and trafficking in adaptations to persistent opioid treatment

Mu-opioid receptor activation underpins clinical analgesia and is the central event in the abuse of narcotics. Continued opioid use produces tolerance to the acute effects of the drug and adaptations that lead to physical and psychological dependence. Continued mu-receptor signaling provides the engine for these adaptations, with most evidence suggesting that chronic agonist treatment produces only limited alterations in primary mu-opioid receptor signaling. Here we examine agonist regulation of mu-opioid receptor function, and whether this is altered by chronic treatment. Receptor phosphorylation is thought to be the key initial event in agonist regulation of the mu-opioid receptor, providing a signal for acute receptor desensitization and also subsequent receptor resensitization. Morphine appears to produce qualitatively and quantitatively different mu-receptor phosphorylation than other agonists, but the consequences of this remain obscure, at least in neurons. There is no evidence that agonist-induced mu-opioid receptor phosphorylation changes in chronically morphine-treated animals, although receptor regulation appears to be altered. Thus, as receptor phosphorylation and resensitization appear to maintain continued signaling through the mu-opioid receptor, these two events are crucial in facilitating adaptations to chronic opioid treatment, and the possibility that agonist-specific phosphorylation can contribute to the development of different adaptations remains open.     

Circulating opioid peptides in chronic renal failure: acute effect of dialysis treatment

In 14 patients affected by chronic renal failure (7 males and 7 females) it has been evaluated the secretion of beta LPH, beta EP, ACTH and Cortisol in basal conditions and immediately after a dialytic treatment. For beta LPH and beta EP measurements on each thawed plasma a silic acid extraction and a successive peptides separation by a Sephadex G-75 column chromatography preceeded the two specific RIAs. Basal beta LPH plasma levels resulted significantly higher than in normal controls, while that of beta EP, ACTH and Cortisol were in the normal range. The dialytic treatment was able to increase ACTH and Cortisol plasma levels, without to modified beta LPH and beta EP plasma levels.     

阿片依赖及戒断的信号转导机制

药物依赖是一种慢性、复发性的脑疾病,可引起大脑发生病理性变化.在我国滥用的毒品主要是阿片类物质,阿片类物质依赖包括身体依赖(表现为停药后的戒断症状)和精神依赖(表现为满足感和重新用药的渴求).与阿片依赖及耐受相关的因素有内源性阿片肽、阿片受体及其受体后信号转导系统功能状态的适应性改变等.本文就与阿片依赖有关的细胞内信号转导机制作一综述.     

Sunitinib treatment for refractory malignant pheochromocytoma

We report the clinical response and adverse events of a female patient treated for recurrent malignant pheochromocytoma using the tyrosine kinase inhibitor sunitinib. A 41-year-old woman underwent adrenectomy and nephrectomy forpotentially malignant adrenal pheochromocytoma. Fifty-four months after surgery, abdominal computed tomography (CT) and Iodine-131 metaiodobenzylguanidine((131)I-MIBG) scintigraphy revealed multiple tumors in the liver. Two chemotherapy protocols were administered in succession (first line: cyclophosphamide/vinblastine/dacarbazine; second line: cisplatin/docetaxel/ifomide). Despite these treatments, however, the tumors continued to progress. Treatment with sunitinib was initiated, but the patient quickly developed critical hypertension caused by tumor lysis syndrome. The sunitinib dose was reduced, and a partial response, as defined by the Response Evaluation Criteria in Solid Tumors (RECIST), was observed after 6 treatment cycles. Moreover, no severe adverse events occurred during this lower-dose sunitinib treatment. Unfortunately, sunitinib treatment became unaffordable for the patient, who eventually resorted to palliative care and died 37 months later. This case study is consistent with previous reports indicating that appropriate doses of sunitinib can induce a partial antitumor response in patients with refractory pheochromocytoma.