Induction and activation of mitogen-activated protein kinases of human lymphocytes as one of the signaling pathways of the immunomodulatory effects of morphine sulfate

Dubious effects of methadone as an "anticancer" drug on ovarian cancer cell-lines and patient-derived tumor-spheroids

BACKGROUND

The opioid agonist D,L-methadone exerts analgesic effects via the mu opioid receptor, encoded by OPRM1 and therefore plays a role in chronic pain management. In preclinical tumor-models D,L-methadone shows apoptotic and chemo-sensitizing effects and was therefore hyped as an off-label "anticancer" drug without substantiation from clinical trials. Its effects in ovarian cancer (OC) are completely unexplored.

METHODS

We analyzed OPRM1-mRNA expression in six cisplatin-sensitive, two cisplatin-resistant OC cell-lines, 170 OC tissue samples and 12 non-neoplastic control tissues. Pro-angiogenetic, cytotoxic and apoptotic effects of D,L-methadone were evaluated in OC cell-lines and four patient-derived tumor-spheroid models.

RESULTS

OPRM1 was transcriptionally expressed in 69% of OC-tissues and in three of eight OC cell-lines. D,L-methadone exposure significantly reduced cell-viability in five OC cell-lines irrespective of OPRM1 expression. D,L-methadone, applied alone or combined with cisplatin, showed no significant effects on apoptosis or VEGF secretion in cell-lines. Notably, in two of the four spheroid models, treatment with D,L-methadone significantly enhanced cell growth (by up to 121%), especially after long-term exposure. This is consistent with the observed attenuation of the inhibitory effects of cisplatin in three spheroid models when adding D,L-methadone. The effect of methadone treatment on VEGF secretion in tumor-spheroids was inconclusive.

CONCLUSIONS

Our study demonstrates that certain OC samples express OPRM1, which, however, is not a prerequisite for D,L-methadone function. As such, D,L-methadone may exert also detrimental effects by stimulating the growth of certain OC-cells and abrogating cisplatin's therapeutic effect.

The effects of long-term opioid treatment on the immune system in chronic non-cancer pain patients: A systematic review

BACKGROUND AND OBJECTIVE

Opioids have been increasingly prescribed for chronic non-cancer pain (CNCP). An association between long-term opioid treatment (L-TOT) of CNCP patients and suppression of both the innate and the adaptive immune system has been proposed. This systematic review aims at investigating the effects of L-TOT on the immune system in CNCP patients.

DATABASES AND DATA TREATMENT

A systematic search of MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials and the CINAHL for relevant articles was performed. Studies examining measures of both the innate and the adaptive immune system in adult CNCP patients in L-TOT (≥4 weeks of intake) were included. Outcomes and the level of evidence were analysed.

RESULTS

A total of 382 studies were identified; however, 376 were excluded (352 inappropriate methodology, 21 duplicates, three full-text could not be obtained) and one randomized controlled trial (RCT) and five cross-sectional studies were included and analysed. L-TOT compared with no treatment was associated with a lower percentage of natural killer (NK) cells, a lower absolute number of CD56^bright NK cells, a higher absolute number of IL-2-activated NK cells and a higher concentration of IL-1β as a response to toll-like receptor (TLR) agonists stimulation (Pam3CSK4, LPS, Imiquimod). No other significant differences were reported. Generalizability of the results was limited due to inconsistency of outcomes and an overall low quality of the studies.

CONCLUSIONS

L-TOT may alter the immune system in CNCP patients, but the level of evidence is still weak. More studies are needed to clarify the impact of L-TOT on immune system function.

SIGNIFICANCE

This systematic review found indication that long-term opioid treatment alters the immune system in chronic non-cancer pain patients. These alterations involved the NK cells and IL-1β production. However, the level of evidence is weak.

Up-regulation of μ-, δ- and κ-opioid receptors in concanavalin A-stimulated rat spleen lymphocytes

Regulation of μ-, δ- and κ-opioid receptor protein level in spleen lymphocytes when stimulated by mitogen is not known. To answer the question whether these cells do express opioid receptor (OR) proteins, primary, fresh rat spleen lymphocytes were prepared and stimulated for 48 h with mitogenic dose of Con A. The unstimulated lymphocytes did not express μ- and δ-OR proteins in detectable amounts, however, stimulation with Con A resulted in appearance of clearly detectable immunoblot signals of both μ-OR and δ-OR. κ-OR were detected already in primary cells and increased 2.4-fold in Con A-stimulated cells. These results were supported by data obtained by flow cytometry analysis indicating a dramatic increase in number of μ-, δ- and κ-OR expressing cells after mitogen stimulation. The newly synthesized μ-, δ- and κ-OR in Con A-stimulated spleen lymphocytes were present in the cells interior and not functionally mature, at least in terms of their ability to enhance activity of trimeric G proteins determined by three different protocols of agonist-stimulated, high-affinity [³⁵S]GTPγS binding assay. The up-regulation of μ-, δ- and κ-OR was associated with specific decrease of their cognate trimeric G proteins, G_i1α/G_i2α; the other Gα and Gβ subunits were unchanged. The level of β-arrestin-1/2 was also decreased in Con A-stimulated splenocytes. We conclude that up-regulation of OR expression level in spleen lymphocytes by Con A proceeds in conjunction with down-regulation of their intracellular signaling partners, G_i1α/G_i2α proteins and β-arrestin-1/2. These regulatory proteins are expressed in high amounts already in unstimulated cells and decreased by mitogen stimulation.

Reduction of cell proliferation and potentiation of Fas-induced apoptosis by the selective kappa-opioid receptor agonist U50 488 in the multiple myeloma LP-1 cells

As opioid receptors modulate proliferation and apoptosis of immune cells, we hypothesized that they could reduce malignant haematopoietic cells. After screening, we selected the human multiple myeloma LP-1 cells which express mu- (MOP-) and kappa-opioid receptors (KOP-R). U50 488 produces a modest but significant decrease in viability associated with an arrest in the G0/G1 phase, but not antagonized by NorBNI and not associated with modulation of p21(Cip1), p27(Kip1) or p53 expression. In contrast, no effect was observed with dynorphin, U69 593 and morphine. In conclusion, the anti-proliferative effects of U50 488 are not mediated by KOP-R in the LP-1 cells.

Single-nucleotide polymorphism (A118G) in exon 1 of OPRM1 gene causes alteration in downstream signaling by mu-opioid receptor and may contribute to the genetic risk for addiction

The opioid receptor mu1 (OPRM1) mediates the action of morphine. Although genetic background plays an important role in the susceptibility toward abuse of drugs as evident from familial, adoption and twin studies, association of specific single-nucleotide polymorphisms of OPRM1 gene with narcotic addiction is to be established. Here, we demonstrate the involvement of A118G polymorphism of exon1 of human OPRM1 gene (hOPRM1), with heroin and alcohol addiction, in a population in eastern India. Statistical analysis exhibited a significant association of G allele with both heroin and alcohol addiction with a risk factor of P(trend) < 0.05. The functional significance of G allele in A118G single-nucleotide polymorphisms was evaluated by studying the regulation of protein kinase A (PKA), pCREB, and pERK1/2 by morphine in Neuro 2A cells, stably transfected with either wild type or A118G mutant hOPRM1. Unlike acute morphine treatment, both chronic morphine exposure and withdrawal precipitated by naloxone were differentially regulated by A118 and G118 receptor isoforms when both PKA and pERK1/2 activities were compared. Results suggest that the association of A118G polymorphism to heroin and alcohol addiction may be because of the altered regulation of PKA and pERK1/2 during opioid and alcohol exposures.

Comparative analysis of mu-opioid receptor expression in immune and neuronal cells

Morphine modulates neuronal and immune cell functions via mu-opioid receptors. In primary and Jurkat T cells, and Raji B cells mu-opioid receptor transcripts were detected only after stimulation of the cells with IL-4 or TNF-alpha. Moreover, the amount of the induced mu-opioid receptor mRNA in the immune cells was 15 to 200 times less than those in primary cortical and SH SY5Y neuronal cells. Nevertheless, mu-opioid receptor mRNA in immune cells is processed to functional receptors, as demonstrated by morphine-mediated phosphorylation of mitogen activated protein kinase, morphine-mediated up-regulation of IL-4 mRNA and coupling to adenylyl cyclase in Jurkat cells.

The Complications of Scar Formation Associated With Intrathecal Pump Placement

A 40-year-old man had an intrathecal morphine-baclofen pump inserted for the treatment of severe dystonia affecting all limbs and severe low back pain. The etiology of his dystonic symptoms, despite thorough investigations, was uncertain. At age 45, the patient fell resulting in a cervical spinal cord injury. He underwent C2 through C5 instrumentation and fusion for cervical spine stabilization. Subsequently, an intrathecal morphine-baclofen pump was implanted to control pain and decrease spasticity. The patient ultimately died at age 48 from complications of pneumonia, and an autopsy was performed. Gross pathologic examination revealed that the intrathecal catheter entered the posterior aspect of the lumbar thecal sac, but coursed superiorly in the anterior intradural space. The catheter tip exited the thecal sac in the upper thoracic spine and became embedded in a fibrotic scar. Displacement of the catheter tip of the intrathecal morphine-baclofen pump and subsequent formation of scar tissue resulted in decreased drug delivery, contributing to diminished pain control and functional status. Catheter displacement and epidural scar formation must be considered as a potential cause of ineffective pain control and decreased functional status in patients with intrathecal morphine-baclofen pumps.

Nuclear factor kappaB signaling in opioid functions and receptor gene expression

Opiates are the most powerful of all known analgesics. The prototype opiate morphine has been used as a painkiller for several thousand years. Chronic usage of opiates not only causes drug tolerance, dependence, and addiction, but also suppresses immune functions and affects cell proliferation and cell survival. The diverse functions of opiates underscore the complexity of opioid receptor signaling. Several downstream signaling effector systems, including adenylyl cyclase, mitogen-activated protein kinase, Ca2+ channels, K+ channels, and phosphatidylinositol 3-kinase/Akt, have been identified to be critical in opioid functions. Nuclear factor-kappaB (NF-kappaB), one of the most diverse and critical transcription factors, is one of the downstream molecules that may either directly or indirectly transmit the receptor-mediated upstream signals to the nucleus, resulting in the regulation of the NF-kappaB-dependent genes, which are critical for the opioid-induced biological responses of neuronal and immune cells. In this minireview, we focus on current understanding of the involvement of NF-kappaB signaling in opioid functions and receptor gene expression in cells.

Cannabinoid receptor type 2 agonists induce transcription of the mu-opioid receptor gene in Jurkat T cells

Opioids and cannabinoids are both associated with analgetic, psychotropic, and immunomodulatory effects. It has been suggested that both systems interact on multiple levels. We hypothesized that cannabinoids induce opioid receptors and investigated cannabinoid-dependent expression of the mu-opioid receptor subtype in a human T cell model. We report that activation of the peripheral cannabinoid receptor type 2 leads to a de novo induction of mu-opioid receptor transcription in Jurkat E6.1 cells. We show that interleukin-4 is transcriptionally induced in response to cannabinoids and that an interleukin-4 receptor antagonist blocks cannabinoid-dependent induction of mu-opioid receptors, indicating that induced expression of interleukin-4 is required in this process. Induction of interleukin-4 is blocked by decoy oligonucleotides directed against STAT5, indicating the requirement of this transcription factor. In addition, we show cannabinoid-dependent phosphorylation of STAT5. Further experiments demonstrate that interleukin-4 then induces phosphorylation of STAT6, which directly transactivates the mu-opioid receptor gene. In addition, STAT6 induces expression of the transcription factor GATA3, which also contributes to mu-opioid receptor gene transcription. The responsive promoter region of the human mu-opioid receptor gene with the binding sites for both factors was mapped to nt -1001 to -950. To demonstrate functional mu-opioid receptor proteins, morphine-mediated phosphorylation of mitogen-activated protein kinase was investigated. We show that phosphorylation of mitogen-activated protein kinase occurs only in cannabinoid-prestimulated Jurkat E6.1 cells and that it is blocked by the mu-opioid receptor antagonist D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2. In summary, these findings provide a first example for cannabinoid-opioid-interactions in cells of the immune system.

Divergent enantioselective synthesis of (-)-galanthamine and (-)-morphine

An efficient divergent synthetic strategy for the synthesis of the opiate and amaryllidaceae alkaloids emerges by employing a Pd-catalyzed asymmetric allylic alkylation (AAA) to set the stereochemistry. Three generations of syntheses of galanthamine are discussed in detail with particular focus on the scope of the palladium-catalyzed AAA reactions and intramolecular Heck reactions. The pivotal tricyclic intermediate is available in six steps from 2-bromovanillin and the monoester of methyl 6-hydroxycyclohexene-1-carboxylate. This intermediate requires only two steps to convert to (-)-galanthamine. Using a Heck vinylation, we found that the fourth ring of codeine/morphine could be formed. The final ring formation involves a novel visible light-promoted hydroamination. Thus, six steps are required to convert the pivotal tricyclic intermediate into codeine, which has been demethylated in high yield to morphine.

Is paradoxical pain induced by sustained opioid exposure an underlying mechanism of opioid antinociceptive tolerance?

Opiates are the primary treatment for pain management in cancer patients reporting moderate to severe pain, and are being increasingly used for non-cancer chronic pain. However, prolonged administration of opiates is associated with significant problems including the development of antinociceptive tolerance, wherein higher doses of the drug are required over time to elicit the same amount of analgesia. High doses of opiates result in serious side effects such as constipation, nausea, vomiting, dizziness, somnolence, and impairment of mental alertness. In addition, sustained exposure to morphine has been shown to result in paradoxical pain in regions unaffected by the initial pain complaint, and which may also result in dose escalation, i.e. 'analgesic tolerance'. A concept that has been gaining considerable experimental validation is that prolonged use of opioids elicits paradoxical, abnormal pain. This enhanced pain state requires additional opioids to maintain a constant level of antinociception, and consequently may be interpreted as antinociceptive tolerance. Many substances have been shown to block or reverse antinociceptive tolerance. A non-inclusive list of examples of substances reported to block or reverse opioid antinociceptive tolerance include: substance P receptor (NK-1) antagonists, calcitonin gene-related peptide (CGRP) receptor antagonists, nitric oxide (NO) synthase inhibitors, calcium channel blockers, cyclooxygenase (COX) inhibitors, protein kinase C inhibitors, competitive and non-competitive antagonists of the NMDA (N-methyl-D-aspartate) receptor, AMPA (alpha-amino-3-hydroxy-5-methyl-4 isoxazolepropionic acid) antagonists, anti-dynorphin antiserum, and cholecystokinin (CCK) receptor antagonists. Without exception, these substances are also antagonists of pain-enhancing agents. Prolonged opiate administration indeed induces upregulation of substance P (SP) and calcitonin gene-related peptide (CGRP) within sensory fibers in vivo, and this is accompanied by an enhanced release of excitatory neurotransmitters and neuropeptides from primary afferent fibers upon stimulation. The enhanced evoked release of neuropeptides is correlated with the onset of abnormal pain states and opioid antinociceptive tolerance. Importantly, the descending pain modulatory pathway from the brainstem rostral ventromedial medulla (RVM) via the dorsolateral funiculus (DLF) is critical for maintaining the changes observed in the spinal cord, abnormal pain states and antinociceptive tolerance, because animals with lesion of the DLF did not show enhanced evoked neuropeptide release, or develop abnormal pain or antinociceptive tolerance upon sustained exposure to opiates. Microinjection of either lidocaine or a CCK antagonist into the RVM blocked both thermal and touch hypersensitivity as well as antinociceptive tolerance. Thus, prolonged opioid exposure enhances a descending pain facilitatory pathway from the RVM that is mediated at least in part by CCK activity and is essential for the maintenance of antinociceptive tolerance.

Signal transduction induced by opioids in immune cells: a review

New data regarding signal transduction triggered by opioid ligands in immune cells are reviewed, and the signal transduction in neuronal cells is documented. Similar signaling pathways are induced by opioids in immune as well as neuronal cells. Opioids altered second messenger cAMP, intracellular calcium, and second messenger-induced kinases in immune cells. Met-enkephalin, preferentially delta-opioid, was bimodally regulated, while kappa-opioids inhibited these second messengers. delta-, kappa- and micro-opioids altered nitric oxide secretion, inducing cGMP as the second messenger in immune cells. Coupling of opioid agonists to opioid receptors activated mitogen-activated protein/extracellular signal-regulated protein kinases and various transcription factors in immune cells. Activator protein 1 (AP-1), c-fos, and nuclear factor-kappaB (NF-kappaB) are transcription factors shared by neuronal and immune cells. Delta-opioids activated AP-1, c-fos, activating transcription factor 2, Ikaros-1 and Ikaros-2 transcription factors in immune cells. Induction of kappa-opioid receptor gene by retinoic acid resulted in increased binding of Sp1 transcription factor to the promoter of the kappa-opioid receptor. Micro-opioids inhibited synthesis of common transcription factors AP-1, c-fos, NF-kappaB, and nuclear factor of activated T cells in activated or stimulated immune cells, whereas micro-opioids activated NF-kappaB, GATA-3, and Kruppel-like factor 7 transcription factors in non-stimulated immune cells.

Activation of the spinal ERK signaling pathway contributes naloxone-precipitated withdrawal in morphine-dependent rats

Extracellular signal-regulated kinase (ERK), a mitogen-activated protein kinases (MAPK), transduces a broad range of extracellular stimuli into diverse intracellular responses. Recent studies have showed that ERK activation in the supraspinal level involved in the development of drug dependence, especially in psychological dependence. In this study, we reported that the spinal ERK signaling pathway was activated by chronic morphine injection. There was a further increase in ERK activation after naloxone-precipitated withdrawal. Furthermore, attenuation of the spinal ERK phosphorylation by intrathecal a MAPK kinase (MEK) inhibitor U0126 or knockdown of the spinal ERK by antisense oligonucleotides not only decreased the scores of morphine withdrawal, but also attenuated withdrawal-induced allodynia, which were accompanied by decreased ERK phosphorylation in the spinal cord. The spinal ERK inhibition or knockdown also reduced morphine withdrawal-induced phosphorylation of cAMP response element binding protein (CREB), which is one of the important downstream substrates of ERK pathway, and Fos expression. The involvement of the spinal ERK in morphine withdrawal was supported by our finding that intrathecal N-methyl-D-aspartate receptor antagonist MK-801 or protein kinase C inhibitor chelerythrine chloride suppressed withdrawal-induced ERK activation in the spinal cord and attenuated morphine withdrawal symptoms. These findings suggest activation of the spinal ERK signaling pathway contributes naloxone-precipitated withdrawal in morphine-dependent rats.

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

Opioids are powerful analgesics but also drugs of abuse. Because opioid addicts are susceptible to certain infections, opioids have been suspected to suppress the immune response. This was supported by the finding that various immune-competent cells express opioid receptors and undergo apoptosis when treated with opioid alkaloids. Recent evidence suggests that opioids may also effect neuronal survival and proliferation or migrating properties of tumor cells. A multitude of signaling pathways has been suggested to be involved in these extra-analgesic effects of opioids. Growth-promoting effects were found to be mediated through Akt and Erk signaling cascades. Death-promoting effects have been ascribed to inhibition of nuclear factor-kappaB, increase of Fas expression, p53 stabilization, cytokine and chemokine release, and activation of nitric oxide synthase, p38, and c-Jun-N-terminal kinase. Some of the observed effects were inhibited with opioid receptor antagonists or pertussis toxin; others were unaffected. It is still unclear whether these properties are mediated through typical opioid receptor activation and inhibitory G-protein-signaling. The present review tries to unravel controversial findings and provides a hypothesis that may help to integrate diverse results.

Inflammatory masses associated with intrathecal drug infusion: a review of preclinical evidence and human data

OBJECTIVES

The phenomenon of inflammatory masses at the tips of intrathecal drug administration catheters was the subject of a recent case-compilation report and a number of animal studies. We sought to synthesize current clinical and preclinical data to formulate hypotheses about the etiology of catheter-tip masses.

METHODS

We reviewed the published human clinical data, new unpublished clinical data, and the results of preclinical studies in two mammalian species, beagle dogs and sheep.

RESULTS

Intrathecal morphine sulfate studies in beagle dogs suggested that the observed inflammatory reaction was dose or concentration dependent. Masses occurred after 28 days in one of three animals at 1.5 mg/day (the lowest morphine dose tested); in two of three animals at 3 and 9 mg/day; and in three of three animals at 12 mg/day. The addition of various amounts of clonidine to 1.5 mg/day of morphine revealed no mass formation when the clonidine dose was>0.25 mg/day. A morphine sulfate study that was performed in sheep using a commercially marketed drug administration system found catheter tip masses in two of three animals that received 12 or 18 mg/day of morphine, the highest doses tested. Human cases have occurred only in pain patients who received intrathecal opioids, alone or mixed with other drugs, or in patients who received investigational agents (such as superoxide dismutase or the partial micro-opioid-receptor agonist, tramadol) that were not labeled for long-term intrathecal use.

DISCUSSION/CONCLUSIONS

The evidence suggests that the long-term administration of opioids, especially morphine, caused the masses that were observed in humans and in two species of animals. A relationship probably exists between mass formation and intrathecal morphine doses or concentration. Other factors remain to be investigated.

Endogenous formation of morphine in human cells

Morphine is a plant (opium poppy)-derived alkaloid and one of the strongest known analgesic compounds. Studies from several laboratories have suggested that animal and human tissue or fluids contain trace amounts of morphine. Its origin in mammals has been believed to be of dietary origin. Here, we address the question of whether morphine is of endogenous origin or derived from exogenous sources. Benzylisoquinoline alkaloids present in human neuroblastoma cells (SH-SY5Y) and human pancreas carcinoma cells (DAN-G) were identified by GC/tandem MS (MS/MS) as norlaudanosoline (DAN-G), reticuline (DAN-G and SH-SY5Y), and morphine (10 nM, SH-SY5Y). The stereochemistry of reticuline was determined to be 1-(S). Growth of the SH-SY5Y cell line in the presence of (18)O(2) led to the [(18)O]-labeled morphine that had the molecular weight 4 mass units higher than if grown in (16)O(2), indicating the presence of two atoms of (18)O per molecule of morphine. Growth of DAN-G cells in an (18)O(2) atmosphere yielded norlaudanosoline and (S)-reticuline, both labeled at only two of the four oxygen atoms. This result clearly demonstrates that all three alkaloids are of biosynthetic origin and suggests that norlaudanosoline and (S)-reticuline are endogenous precursors of morphine. Feeding of [ring-(13)C(6)]-tyramine, [1-(13)C, N-(13)CH(3)]-(S)-reticuline and [N-CD(3)]-thebaine to the neuroblastoma cells led each to the position-specific labeling of morphine, as established by GC/MS/MS. Without doubt, human cells can produce the alkaloid morphine. The studies presented here serve as a platform for the exploration of the function of "endogenous morphine" in the neurosciences and immunosciences.

Morphine negatively regulates interferon-gamma promoter activity in activated murine T cells through two distinct cyclic AMP-dependent pathways

To explore the mechanism by which morphine promotes the incidence of HIV infection, we evaluated the regulatory role of morphine on the interferon-gamma (IFN-gamma) promoter in activated T cells from wild type and mu-opioid receptor knockout mice. Our results show that morphine inhibited anti-CD3/CD28-stimulated IFN-gamma promoter activity in a dose-dependent manner. Chronic morphine treatment of T cells increased intracellular cAMP. To evaluate the role of cAMP in morphine's modulatory function, the effects of dibutyryl cyclic AMP and forskolin were investigated. Both dibutyryl cyclic AMP and forskolin treatment inhibited IFN-gamma promoter activity. Treatment with pertussis toxin, but not with a protein kinase A inhibitor, antagonized morphine's inhibitory effects. Morphine inhibited phosphorylation of ERK1/2 and p38 MAPK; in addition, morphine treatment in the presence of either ERK1/2 or p38 MAPK inhibitor (PD98059 or SB203580) resulted in an additive inhibition of IFN-gamma promoter activity. The transcription factor activator protein-1, NF-kappaB, and nuclear factor of activated T cells (NFAT) were negatively regulated by morphine. Overexpression of NF-kappaB p65 rescued the inhibitory effect of morphine on IFN-gamma promoter activity. However, only when NFATc1 was co-overexpressed with c-fos was the inhibitory effect of morphine on IFN-gamma promoter counteracted. The inhibitory effects of morphine were not observed in T cells obtained from mu-opioid receptor knockout mice, suggesting that morphine modulation of IFN-gamma promoter activity is mediated through the mu-opioid receptor. In summary, our data indicate that morphine modulation of IFN-gamma promoter activity is mediated through two distinct cAMP-dependent pathways, the NF-kappaB signaling pathway and the ERK1/2, p38 MAPK, AP-1/NFAT pathway.

Morphine suppresses lymphocyte apoptosis by blocking p53-mediated death signaling

Opiates such as morphine or heroin may promote cell apoptosis and cause dysfunction of immune cells. In simian immunodeficiency virus (SIV)-infected lymphocytic cells, however, morphine may protect the cells from apoptotic lysis and allow the virus to continue to replicate. To further explore this apparently antithetical effect of opiates, we evaluated in the present study the effects of morphine on human lymphocytic CEM x174 cells induced to undergo apoptosis in the presence of actinomycin D. It was found that induction of apoptosis (characterized by DNA laddering) by actinomycin D was accompanied by a stimulation of the expression of active (phosphorylated) form of p53. Pretreatment of the cells with 10nM morphine caused a transient, naloxone-reversible suppression of the appearance of activated p53 and the generation of DNA laddering. Parallel evaluation of the growth of CEM x174 indicated that morphine treatment delays the inception of cell death triggered by actinomycin D. Inasmuch as Bcl-2 suppresses while Bax accelerates apoptosis, treatment of cells with morphine reduced the expression of Bax and enhanced the expression of Bcl-2. Taken together, morphine, through binding at the opioid receptor, may protect lymphocytic cells from apoptotic lysis if cell death is initiated by apoptosis-inducing agents such as human immunodeficiency virus (HIV), SIV or actinomycin D.

Morphine inhibits VEGF expression in myocardial ischemia

BACKGROUND

Vascular endothelial growth factor (VEGF) may contribute to the resolution of myocardial ischemia by stimulating collateral circulation. Morphine analgesia after myocardial ischemia is thought to increase infarct size. We hypothesize that morphine inhibits myocardial VEGF expression by inhibiting hypoxia-induced factor 1alpha (HIF-1alpha) and the signal transduction mechanisms involving Erk-1,2 MAP kinase (p42/p44), and PI3 kinase activity (phospho-Akt).

METHODS

(1) In vitro: primary cultures of rat cardiac myocytes; (2) in vivo: rat coronary ligation model; (3) mRNA measurement: real-time reverse transcriptase-polymerase chain reaction; (4) protein measurements: enzyme-linked immunosorbent assay, Western immunoblot, electromobility shift assay (EMSA), and immunohistochemistry.

RESULTS

Using rat cardiac myocytes in vitro, we show that morphine: (1) decreases hypoxia-induced VEGF(121) and VEGF(165) mRNA expression and VEGF protein concentration through an opioid receptor mechanism; (2) decreases HIF-1alpha protein expression (immunoblot) and nuclear protein binding to the VEGF HIF-1alpha DNA response element (EMSA); and (3) inhibits phospho-Erk-1,2 MAP kinase (immunoblot) and phospho-Akt kinase activity (immunoblot). Using a rat coronary ligation model, we show that morphine treatment: (1) decreases myocardial VEGF protein expression (immunohistochemistry); (2) decreases HIF-1alpha protein expression (immunoblot); and (3) decreases phospho-Erk-1,2 and phospho-Akt expression.

CONCLUSIONS

(1) Morphine inhibits hypoxia-induced VEGF transcription, in part, through an HIF-1alpha-mediated mechanism and (2) morphine inhibition of hypoxia-induced HIF-1alpha may be mediated by inhibition of ERK 1,2 MAP kinase activity and PI3 kinase activity.

Management of Intrathecal Catheter-Tip Inflammatory Masses: A Consensus Statement

OBJECTIVES

In a companion article, we synthesized current clinical and preclinical data to formulate hypotheses about the etiology of drug administration catheter-tip inflammatory masses. In this article, we communicate our recommendations for the detection, treatment, mitigation, and prevention of such masses.

METHODS

We reviewed published and unpublished case reports and our own experiences to find methods to diagnose and treat catheter-tip inflammatory masses in a manner that minimized adverse neurological sequelae. We also formulated hypotheses about theoretical ways to mitigate, and possibly, prevent the formation of such masses.

RESULTS

Human cases have occurred only in patients with chronic pain who received intrathecal opioid drugs, alone or mixed with other drugs, or in patients who received agents that were not labeled for long-term intrathecal use. Most patients had noncancer pain owing to their large representation among the population with implanted pumps. Such patients also had a longer life expectancy and exposure to intrathecal drugs, and they received higher daily doses than patients with cancer pain. Clues to diagnosis included the loss of analgesic drug effects accompanied by new, gradually progressive neurological symptoms and signs. When a mass was diagnosed before it filled the spinal canal or before it caused severe neurological symptoms, open surgery to remove the mass often was not required. Anecdotal reports and the authors' experiences suggest that cessation of drug administration through the affected catheter was followed by shrinkage or disappearance of the mass over a period of 2-5 months.

CONCLUSIONS

Attentive follow-up and maintenance of an index of suspicion should permit timely diagnosis, minimally invasive treatment, and avoidance of neurological injury from catheter-tip inflammatory masses. Whenever it is feasible, positioning the catheter in the lumbar thecal sac and/or keeping the daily intrathecal opioid dose as low as possible for as long possible may mitigate the seriousness, and perhaps, reduce the incidence of such inflammatory masses.

Effects of beta-endorphin and Naloxone on in vitro maturation of bovine oocytes

Bovine cumulus-oocyte complexes (COCs) and mural granulosa cells express the mRNA coding for the micro-opioid receptor. The addition of beta-endorphin (beta-end) to oocytes cultured in hormonally-supplemented in vitro maturation (IVM) medium had no effect on the rates of oocytes reaching the metaphase II (MII) stage, but significantly decreased the maturation rate (P < 0.05) and arrested oocytes at metaphase I (MI) after culture in hormone-free medium (P < 0.001). Naloxone (Nx) reverted this inhibitory effect of beta-end. Moreover, Nx "per se" showed a dose-dependent dual effect. When added at high concentration (10 x (-3) M), it significantly reduced the rate of oocytes in MII (P < 0.001), thus increasing the rate of oocytes arrested in MI. However, Nx added at low concentration (10 x (-8) M) significantly increased oocyte maturation (P < 0.001). High concentration of Nx induced an increase in both intracellular calcium concentration ([Ca(2+)](i)) and in the activity of the mitogen-activated protein kinase (MAPK) also called extracellular-regulated kinase (ERK) in cumulus cells of bovine COCs. Blocking the rise in [Ca(2+)](i) with the calcium chelator acetoxymethylester-derived form of bis (o-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM) reversed the Nx-dependent inhibition of meiotic maturation observed at high Nx concentrations. Whereas blocking ERK with the MAPK/ERK kinase (MEK) inhibitor, PD98059, had no effect on this process. Therefore, we concluded that the mocro-opioid receptor, by inducing [Ca(2+)](i) increase, participates in the cumulus-oocyte coupled signaling associated with oocyte maturation.

Chemokine receptor CCR5: polymorphism at protein level

Polymorphisms in chemokine receptor CCR5 genes have been implicated in HIV disease progression, resistance, or non-progressive infection. Multiple CCR5 transcripts and mRNA diversity have also been identified. This study presents evidence to show that two distinct forms of CCR5 protein, 62 and 42k Da, are present in human lymphocytic cells and monkey peripheral blood mononuclear cells. The ratio of these two forms of CCR5 changes with cell growth. The 62k Da CCR5 predominates if the electrophoresis sample buffer does not contain reducing agent. However, the 62 and the 42 kDa CCR5 are not interconvertible. Morphine sulfate induces the formation and expression of both forms of CCR5 whereas RANTES, MIP-1alpha or MIP-1beta inhibits them. Localization studies indicate that the 62 kDa CCR5 resides mainly on the cell membrane and the 42 kDa CCR5 is present solely in the cytoplasm of the cells.

Methadone induces CCR5 and promotes AIDS virus infection

Methadone, a regimen for the treatment of opioid dependency, was found to induce the expression of CCR5, a co-receptor for human immunodeficiency virus (HIV)/simian form of HIV (SIV) entry, on human CEM x174 lymphocytes. Both CCR5 mRNA and protein were elevated in methadone-treated cells. A concomitant increase of mu opioid receptors was also observed. Upon methadone exposure, SIVmac239-infected CEM x174 cells released greater amounts of virus particles as revealed by both the number of syncytia formation and reverse transcriptase activities. Similar methadone effect was not observed on CEM x174 cells infected with other simian retroviruses that do not depend on CCR5 for cellular entry. These studies raise concerns considering methadone as an innocuous morphine substitute.

Inflammatory mass lesions associated with intrathecal drug infusion catheters: report and observations on 41 patients

OBJECTIVE

Several reports have described inflammatory mass lesions at the tip of intraspinal drug administration catheters. We evaluated the number of patients reported with this condition and whether data support hypotheses that have been put forth regarding the cause of these lesions.

METHODS

Information that was reported in the medical literature, and by Medtronic, Inc., to the United States Food and Drug Administration as of November 30, 2000, was reviewed.

RESULTS

Forty-one cases were identified, including 16 from the literature and 25 that were not published previously in the literature. Because of voluntary reporting and other methodological limitations, the actual number of cases must be higher than reported. All of the patients had chronic pain. The mean duration of therapy was 24.5 months. Most masses were located in the thoracic region. Intrathecal drugs included morphine or hydromorphone, either alone or mixed with other drugs, in 39 of 41 cases. No masses were reported in patients who received baclofen as the only intrathecal medication. Thirty patients underwent surgery to relieve spinal cord or cauda equina compression. Eleven patients were nonambulatory at last follow-up, and one died of a pulmonary embolus. Surgical specimens revealed noninfectious chronic inflammation, granuloma formation, and fibrosis or necrosis.

DISCUSSION

The most plausible hypothesis with regard to the cause of intrathecal catheter tip mass lesions implicates the administration of relatively high-concentration or high-dose opiate drugs or the use of drugs and admixtures that are not labeled for intrathecal use.

CONCLUSION

Patients who require high-dose intraspinal opioid therapy and those who receive drugs or admixtures that are not approved for intrathecal use should be monitored closely for signs of an extra-axial mass or catheter malfunction. Prompt diagnosis and treatment may preserve neurological function.

Chronic morphine exposure increases the phosphorylation of MAP kinases and the transcription factor CREB in dorsal root ganglion neurons: an in vitro and in vivo study

Tolerance to opiates reduces their effectiveness in the treatment of severe pain. Although the mechanisms are unclear, overactivity of pro-nociceptive systems has been proposed to contribute to this phenomenon. We have reported that the development of morphine tolerance significantly increased calcitonin-gene-related-peptide-like immunoreactivity (CGRP-IR) in primary sensory afferents of the spinal dorsal horn, suggesting that changes in pain-related neuropeptides in the dorsal root ganglion (DRG) neurons may be involved (Menard et al., 1996, J. Neurosci., 16, 2342-2351). Recently, we have shown that repeated morphine treatments induced increases in CGRP- and substance P (SP)-IR in cultured DRG, mimicking the in vivo effects (Ma et al., 2000, Neuroscience, 99, 529-539). In this study, we investigated the intracellular signal transduction pathways possibly involved in morphine-induced increases in CGRP- and SP-IR in DRG neurons. Repeated morphine exposure (10-20 microm) for 6 days increased the number of neurons expressing phosphorylated (p) mitogen-activated protein (MAP) kinases, including the extracellular signal-regulated kinase (pERK), c-jun N-terminal kinase (pJNK) and P38 (pP38 MAPK). The number of neurons expressing phosphorylated cAMP responsive element binding protein (pCREB) was also markedly increased in morphine-exposed cultured DRG neurons. pERK-, pP38-, pJNK- and pCREB-IR were colocalized with CGRP-IR in cultured DRG neurons. Naloxone effectively blocked these actions of morphine, whereas a selective MEK1 inhibitor, PD98059, inhibited the morphine-induced increase in the phosphorylation of ERK and CREB, and the expression of CGRP and SP. Moreover, in morphine-tolerant rats, the number of pCREB-, CGRP- and SP-IR neurons in the lumbar DRG was also significantly increased. These in vitro and in vivo data suggest that the phosphorylation of MAP kinases and CREB plays a role in the morphine-induced increase in spinal CGRP and SP levels in primary sensory afferents, contributing to the development of tolerance to opioid-induced analgesia.

Morphine upregulates mu opioid receptors of human and monkey lymphocytes

Opioid receptors of subtypes delta, kappa, and mu similar to those found in brain cells have been identified in immune cells. The current study demonstrates by competitive polymerase chain reaction the treatment of human lymphocytic cells with morphine resulting in an increased amount of gene expression of mu opioid receptors. Antibodies against the MOR-1, the neuronal mu opioid receptor, were used in Western blot analysis of mu proteins and the results revealed a single band of approximately 50 kDa, the intensity of which was increased by morphine treatment. Similar results of mu opioid receptor activation were observed when monkey lymphocytes were treated with morphine. These studies suggest that in addition to causing an immune effect through communication with the neuroendocrine system, the psychoactive drug morphine may modulate immune functions by acting directly on the mu opioid receptors expressed on lymphocytes.

Morphine induces gene expression of CCR5 in human CEMx174 lymphocytes

All HIV-1 strains studied to date use CCR5, CXCR4, or both receptors to enter cells. Simian immunodeficiency virus (SIV) infection of non-human primates has served as a useful model for understanding AIDS pathogenesis in humans. Research on several genetically divergent SIV isolates has revealed that SIV uses CCR5, and not CXCR4, for entry. CEM x174, a human lymphoid cell line, has been routinely used to cultivate and maintain various SIV strains. However, questions have arisen about how CEM x174, which reportedly was unable to express detectable amounts of CCR5 transcripts, efficiently supports the growth of SIV. In searching for an answer, we resorted to a sensitive competitive reverse transcriptase-polymerase chain reaction procedure in an attempt to detect as well as quantify the amount of CCR5 expression. Here we present our findings, which indicate that CEM x174 indeed expresses CCR5 and that the amount of CCR5 is increased in cells pretreated with morphine. These results correlate well with our previous observations that morphine treatment causes CEM x174 cells to be more susceptible to SIV infection. Similar morphine effect was not observed on CEM x174 cells infected with simian retroviruses, which do not depend on CCR5 for entry. These findings suggest a plausible mechanism whereby opiate drug users render themselves more susceptible to HIV infection, thereby explaining the vast prevalence of HIV infection among endemic drug use populations.

Endogenous morphine

It is now well accepted that endogenous morphine is present in animals, both in invertebrates and vertebrates. It is a key signaling molecule that plays an important role in downregulating physiological responses, such as those in the immune system, including immune elements in the CNS. It has been demonstrated that a specific mu-opiate-receptor subtype, mu3, mediates these downregulatory effects through release of NO. This article examines morphine as an endogenous signaling molecule, in terms of its role in neural and immune regulation.

Molecular mechanisms and regulation of opioid receptor signaling

Cloning of multiple opioid receptors has presented opportunities to investigate the mechanisms of multiple opioid receptor signaling and the regulation of these signals. The subsequent identification of receptor gene structures has also provided opportunities to study the regulation of receptor gene expression and to manipulate the concentration of the gene products in vivo. Thus, in the current review, we examine recent advances in the delineation basis for the multiple opioid receptor signaling, and their regulation at multiple levels. We discuss the use of receptor knockout animals to investigate the function and the pharmacology of these multiple opioid receptors. The reasons and basis for the multiple opioid receptor are addressed.

Opioids suppress chemokine-mediated migration of monkey neutrophils and monocytes - an instant response

Opioid users having acquired human immunodeficiency syndrome (AIDS) are at a greater risk than non-users of contracting opportunistic infections. Opioid-administered and simian immunodeficiency virus (SIV)-infected rhesus monkeys have been an excellent model for studying AIDS and drug abuse in humans. In this study, chemotaxis of monkey leukocytes was evaluated using the chemokines interleukin-8 (IL-8) and regulated upon activation, normal T cell expressed (RANTES) as the chemoattractants, and the effects of various opioid agonists and antagonists on the efficiency of chemotaxis were examined. Opioids were either incubated with monkey leukocytes or added directly to chemokines, and the number of cells migrating toward IL-8 (for neutrophils) or RANTES (for monocytes) was scored. Inhibition of chemotaxis was seen with both assay conditions, and the inhibition was mediated by opioids binding to mu or kappa receptors. Binding to delta opiod receptors was rarely, if ever, observed. Although opioids themselves may act as weak chemoattractants for monkey leukocytes, addition of opioid agonists to chemokines would reduce the chemoattractant ability of the chemokines. Opioids did not cause the same inhibitory effect on the chemotactic migration of neutrophils when the complement component C5a or the chemotactic peptide N-formyl-MET-LEU-PHE (fMLP) was used as chemoattractant. These studies suggest that the presence of opioids during SIV infection immediately alters chemokine-mediated immune functions.

Involvement of mitogen-activated protein kinase in agonist-induced phosphorylation of the mu-opioid receptor in HEK 293 cells

Agonist exposure of many G protein-coupled receptors stimulates an activation of extracellular signal-regulated protein kinases (ERKs) 1 and 2, members of the mitogen-activated protein kinase (MAPK) family. Here, we show that treatment of human embryonic kidney (HEK) 293 cells stably transfected to express the rat micro-opioid receptor (MOR1) with [D-Ala2,MePhe4,Gly5-ol]enkephalin (DAMGO) stimulated a rapid and transient (3-5-min) activation and nuclear translocation of MAPK. Exposure of these cells to the MAPK kinase 1 inhibitor PD98059 not only prevented MAPK activation but also inhibited homologous desensitization of the mu-opioid receptor. We have therefore determined the effect of PD98059 on agonist-induced mu-receptor phosphorylation. DAMGO stimulated a threefold increase in MOR1 phosphorylation within 20 min that could be reversed by the antagonist naloxone. PD98059 produced a dose-dependent inhibition of agonist-promoted mu-receptor phosphorylation with an IC50 of 20 microM. DAMGO also induced MOR1 internalization that peaked at 30 min. Confocal microscopy revealed that DAMGO-induced MOR1 internalization was also largely inhibited in the presence of PD98059. U0126, another chemically unrelated inhibitor of the MAPK cascade, mimicked the effect of PD98059 on mu-receptor phosphorylation and desensitization. MOR1 itself, however, appears to be a poor substrate for MAPK because mu-receptors immunoprecipitated from stably transfected HEK 293 cells were not phosphorylated by exogenous ERK 2 in vitro. The fact that morphine also triggered MAPK activation but did not induce MOR1 internalization indicates that receptor internalization was not required for MOR1-mediated mitogenic signaling. We conclude that MOR1 stimulates a rapid and intemalization-independent MAPK activation. Activation of the MAPK cascade in turn may not only relay mitogenic signals to the nucleus but also trigger initial events leading to phosphorylation and desensitization of the mu-opioid receptor.

Inhibition of alanyl aminopeptidase induces MAP-kinase p42/ERK2 in the human T cell line KARPAS-299

Inhibition of alanyl aminopeptidase (EC 3.4.11.2, aminopeptidase N, CD13) expression, or activity compromise cell proliferation in a number of cell systems [1, 2, 3, 4, 5, 6]. The underlying mechanisms and the molecular components involved have not been identified as yet. In this study we show that inhibition of alanyl aminopeptidase enzymatic activity decreases the proliferation rate of the CD13-positive T cell line Karpas-299. By using the ATLAS cDNA expression array (Clontech) we identified the p42/ERK2 MAP kinase as one downstream target of probestin, a potent inhibitor of alanyl aminopeptidase. Probestin and another specific aminopeptidase inhibitor, actinonin, in addition to their capability of inducing erk-2 mRNA levels, significantly increase p42 phosphorylation state. This is the first report on signal transduction components possibly mediating the growth-modulatory effects of alanyl aminopeptidase inhibitors.

Heptachlor and the mitogen-activated protein kinase module in human lymphocytes

The organochlorine pesticide heptachlor constitutes a potential health hazard because of its persistence in nature, its reported contamination in food and milk, and its possible carcinogenic effects. As a tumor promoter, heptachlor induces human myeloblastic leukemia cells to differentiate, and also down-regulates the tumor suppressor gene p53 in human immune cells. In this study, the heptachlor signaling pathway in human lymphocytes was studied. Addition of heptachlor to human CEM x174 lymphocytic cells reduced the cellular levels of MAP kinase (MAPK, mitogen-activated protein kinase) cascade proteins, including ERK1 (a 44-kDa MAPK), ERK2 (a 42-kDa MAPK), a 85-kDa and a 54-kDa MAP kinase, MEK1 (a 45-kDa ERK kinase) and MEKK (a 78-kDa MEK kinase). However, heptachlor treatment caused a marked increase in the expression of the activated (Thr- and Tyr-dually phosphorylated) ERK1 and ERK2 in the cells. These studies indicate that mitogen-activated protein kinases are important intermediates in the signal transduction pathway of immune cells upon heptachlor exposure, and the observation of stimulation of activated MAP kinases without a simultaneous accumulation of basal enzymes may suggest the involvement of a negative feedback control mechanism in the pathway.