Specific nonopiate receptors for beta-endorphin

Modulation of chemiluminescence in a murine macrophage cell line by neuroendocrine hormones

This study determined the effects of neuropeptides and neuroendocrine hormones at the cellular level of the immune response using a murine macrophage cell line, J774, which exhibits a chemiluminescent oxidative burst upon acute stimulation with zymosan. We report that the zymosan-triggered oxidative burst of J774 cells can be modulated by the opioid peptides beta-endorphin (beta-END) and dynorphin A (DYN) in a naloxone-reversible fashion. Norepinephrine (NE) also modulated chemiluminescence (CL) emission of J774 cells, with dose-dependent suppression of CL dependent upon co-incubation with gamma-interferon (gamma-INF). Without gamma-INF co-incubation, NE shared with the opioid peptides beta-END and DYN the ability to modulate oxidative burst, producing an inverted-U dose response. These data indicate that J774 cells may be useful for explaining some mechanisms through which the neuroendocrine system interacts with the immune system.

The identity of the unconditioned stimulus to the central nervous system is interferon-beta

The specific mechanism of interaction between the central nervous system and immune system was examined using conditioned augmentation of natural killer (NK) cell activity. This study focused on the role of interferon-beta (IFN-beta) as the unconditioned stimulus (US). IFN-beta was found to be the signal responsible for the bidirectional communication which links the central nervous system with the immune system. This was substantiated by injection of small quantities of IFN-beta directly into the cisterna magna, which activated the effector pathway from the central nervous system to the immune system. More importantly, we found that when the conditioned stimulus (CS) was paired with an injection of IFN-beta into the cisterna magna, the conditioned animals were able to raise their natural killer cell activity in response to subsequent exposure to the conditioned stimulus. These studies show the unconditioned response must be the response of the central nervous system (CNS) to the unconditioned stimulus and not the direct effect of the substance injected into the periphery.

Boomerang effect between [Met]-enkephalin derivatives and human polymorphonuclear leukocytes

[Met]-enkephalin or its precursor, pre-[Met]-enkephalin, were exposed to activated oxygen species produced by human phorbol myristate acetate (PMA)-stimulated polymorphonuclear leukocytes (PMNs) and then analyzed by high-pressure liquid chromatography (HPLC). The chromatograms recorded at the tyrosine maximum wavelength (lambda em 300 nm and lambda ex 280 nm) showed the formation of new peptides by oxidation of methionyl residue in position 5 and ortho, meta, or para hydroxylation of phenylalanyl residue in position 4. The chromatograms recorded at the dityrosine maximum wavelength (lambda em 400 nm and lambda ex 325 nm) showed the formation of new dimeric peptides which contained two [Met]-enkephalin-derivatives linked by a dityrosyl group. These new peptides were tested for chemiluminescence response to PMA-stimulated PMNs. [Met]-enkephalin, pre-[Met]-enkephalin, and the methionyl-oxidized derivatives suppressed the PMA-induced respiratory burst of PMNs. Conversely, after hydroxylation by activated oxygen species released by stimulated PMNs, these peptides enhanced the PMA-induced respiratory burst of PMNs. In the same conditions, dimeric peptides had no effect.

Immunologic and viral markers in the circulation of anti-HIV negative heroin addicts

To assess the degree of immune system activation associated with addiction or hepatotropic viruses infection, we examined 60 HIV-negative heroin addicts for the presence of hepatitis B virus (HBV) infection markers, hepatitis C virus antibodies (anti-HCV), various auto-antibodies, and serum levels of soluble interleukin-2 receptors (sIL-2R). In addition, 28 anti-HCV positive patients comprising the disease control group, were also examined. Our results demonstrated a high prevalence of anti-HCV antibodies (61.7% and 90% with 1st and 2nd generation ELISA, respectively). Eighty-seven percent (87%) of the addicts positive for anti-HCV by the latter and 92.8% of the disease control patients, were also positive with 2nd generation recombinant immunoblot assay (RIBA-II). In 88.9% of anti-HCV positive addicts, antibody to C22-3 was the predominant (anti-C33c in 81.5%). Antibodies to C33c and C22-3 polypeptides were also more frequent in disease control group (92.8% and 85.7%, respectively). Anti-HCV antibodies were associated with increased transaminases (ALT or AST, P < 0.05), as well as with longer duration of addiction (P < 0.005). HBV infection markers (HBsAg, anti-HBc only and anti-HBs) were also present in the addicts (5%, 28.3% and 26.7%, respectively). Rheumatoid factors (RF) were detected in 36.7%, antinuclear antibodies (ANA) in 11.7%, antibodies (IgG and/or IgM) against cardiolipin (anti-CL) and double stranded DNA (anti-ds DNA) in 20% and 50%, respectively. RF, ANA, anti-CL and anti-dsDNA antibodies were also detected in the disease control group (32.1%, 89.3%, 28.5% and 28.5% respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Brain and gut neuropeptides in peripheral blood mononuclear cells

Neuropeptides, initially thought to be common features of gut and brain, are only synthesized in immune cells and modulate immune functions. The presence and possible functions of these peptides in immune cells in both physiological or pathological conditions have been investigated in our laboratory in the last years. Some of the data obtained are reviewed here, and future developments of the field are indicated.

Identification and characterization of [125I]arginine vasopressin binding sites on human peripheral blood mononuclear cells

Arginine vasopressin (AVP) is a nonapeptide that has been shown to be released from the posterior pituitary during stress. Although noted primarily for its hemodynamic and homeostatic properties, AVP also appears to have an effect on the immune system. It may modulate cellular immunity via its enhancement of the autologous mixed lymphocyte response (AMLR), an effect which we have demonstrated to occur over a wide dose range with a maximum at 10(-7) M. In this study, we examined the binding of [125I]AVP, and AVP analogues to human peripheral blood mononuclear cells (PBMC). AVP inhibited [125I]AVP (0.2 nM) binding on PBMC in a dose-dependent manner with maximal inhibition being reached at 10(-8) M. Specific [125I]AVP binding, as defined as that which could be displaced by 1 x 10(-6) M AVP, was saturable, time-dependent, and linear to cell concentration. Specific binding reached saturation at approximately 1000 pM in 45 minutes. From Scatchard analysis of saturation experiments it appeared to be a homogeneous population of binding sites with KD of approximately 0.5 nM and Bmax of approximately 7.6 fmole/8 x 10(6) cells, corresponding to approximately 527 binding sites/cell. There was a good correlation between AVP binding and cell number. AVP failed to dissociate completely from its binding sites in 60 minutes, perhaps because of the formation of a high-affinity ligand-binding site complex. From competitive binding studies with various AVP antagonists and analogues, it was found that the AVP binding site appeared to be V1-like. AVP binding occurred predominantly on B-cells and macrophages. Having provided evidence for the existence of specific, high affinity, and saturable V1-like AVP binding sites, we suggest a potential modulatory role for AVP in the communication between the neuroendocrine and immune systems.

kappa-Opioid binding sites on a murine lymphoma cell line

As a first step in determining whether any subset of lymphocytes expresses opioid receptors, membranes prepared from mouse lymphoma cell lines were screened for [3H]naloxone binding sites. Membranes from the R1.1 cell line specifically bound [3H]naloxone. The Hill coefficient for [3H]naloxone binding was 0.93 +/- 0.18, and nonlinear regression analysis indicated that a one-site model was the best fit of the [3H[naloxone saturation binding data. Low concentrations of kappa-selective opioids, but neither mu nor delta opioids, inhibited [3H]naloxone binding. Saturation binding studies with the kappa-selective compound [3H]U69,593 revealed a single binding site with a KD value of 0.204 +/- 0.039 nM and a Bmax value of 31.7 +/- 3.1 fmol/mg of membrane protein. The Hill coefficient for [3H]U69,593 binding was 1.03 +/- 0.11, indicative of a single site. Time courses for the association and dissociation of [3H]U69,593 binding at 25 degrees C exhibited properties consistent with a single class of binding sites. Low concentrations of kappa-selective opioids, including dynorphin peptides, inhibited [3H]U69,593 binding, while high concentrations of mu opioids were needed to inhibit binding, and the delta-selective ligands were ineffective at concentrations up to 10 microM. Stereoselectivity of the binding site was demonstrated by the finding that the Ki value for (-)-pentazocine in inhibiting [3H]U69,593 binding was 25 times less than for the (+)-isomer. Based on its high affinity for U69,593, alpha-neo-endorphin, and dynorphin B, the kappa opioid binding site on R1.1 cell membranes belongs to the kappa 1b subtype. As observed with brain kappa opioid binding sites, sodium inhibited [3H]U69,593 binding to R1.1 cell membranes in a concentration-dependent manner. These data demonstrate that the murine lymphoma cell line R1.1 expresses kappa opioid binding sites that are very similar to brain kappa opioid binding sites.

Nerve growth factor receptor gene expression in human peripheral blood lymphocytes in aging

Nerve growth factor (NGF) has a modulating effect on immune function, which may occur as a consequence of binding to the NGF receptor (NGF-R). To determine if mRNA for the gene coding for p75NGFR (low affinity NGF-R) is present in lymphocytes, Northern blot analysis of mRNA from human peripheral blood lymphocytes (PBL) and purified T lymphocytes was initiated using cDNA probe for human p75NGFR. p75NGFR mRNA was present in PBL and T lymphocytes, and the mRNA in response to phytohemagglutinin stimulation showed maximum levels at 14 hr of stimulation. p75NGFR mRNA content when analyzed in PBL and T cells from volunteers of various ages showed that p75NGFR mRNA expression does not change with the age of the cell donor.

Regulation of beta-endorphin receptor expression in mouse spleen cells with Con A and rIL-2

The expression of the beta-endorphin receptor on both activated and unstimulated mouse spleen cells was studied. Results showed that unstimulated cells have only one type of beta-endorphin receptor with a specific low affinity (Kd = 1.034 +/- 0.0237 x 10(-7) M, 25,000 sites/cell). After Con A stimulation, cells express two types of receptors, one with a low affinity (Kd = 1.034 +/- 0.024 x 10(-7) M, 320,000 sites/cell) and the other with a high affinity (Kd = 1.052 +/- 0.033 x 10(-9) M, 49,000 sites/cell). The kinetic experiments during 4 days after Con A activation indicated that the receptor of high affinity emerged from 24 to 72 h, while the low affinity one increased in number after stimulation. The receptor numbers of both high and low affinity ones reached a maximum peak at 72 h, then began to decline. The addition of exogenous rIL-2 depressed the Con A-induced increment of the receptor numbers of both the high and low affinity ones, but enhanced the proliferative response of the cells. It is suggested that the degree of the expression of the receptors does not simply depend on the mitogenic degree of the cells. In addition, our experiment demonstrated that splenocytes cultured in medium with or without Con A or Con A + rIL-2 for 96 h did not secrete any detectable amount of beta-endorphin with use of the RIA assay, which is sensitive enough to detect the much lower levels of beta-endorphin than that necessary for biological effects. We suggest that the expression of the high affinity beta-endorphin receptor on the activated T-lymphocytes may have to precede the production of IL-2 to potentiate the T-cell proliferative response. The mechanisms and modes of interaction between the neuroendocrine system and the immune system were discussed.

Mind-body health: research, clinical, and policy applications

PURPOSE OF THE REVIEW. This critical review presents an overview of the development in the field of mind-body medicine over the last 10 years and has taken tentative steps toward suggesting the components of a new model of health based on psychoneuroimmunology. While documenting the major shortcomings of present research design, methodology, data analysis, and subsequent hypotheses, this article points out areas of sufficient promise for practical and responsible clinical applications of the research. SEARCH METHOD USED. A thorough review of the clinical and experimental medical literature related to the interaction between mind and body is presented, and the new and complex research in the field of psychoneuroimmunology is analyzed. SUMMARY OF IMPORTANT FINDINGS. Despite the mixed and sometimes conflicting findings in current research, there is an increasingly compelling body of scientific evidence indicating that mind-body interactions are at the root of both health and disease. Research demonstrates that psychological factors seem to play a causal role in the onset and course of many chronic disorders and that psychological, emotional, psychosocial, and behavioral interventions have at least as much proof of effectiveness as many purely medical treatments. MAJOR CONCLUSIONS. There is a substantial growing body of scientific and clinical knowledge which demonstrates an inextricable interaction between mind and body. Such an approach empowers individuals and organizations to assume greater responsibility for health as a basis for the development of a true health care system.

Hydrolysis and association of leucine enkephalin to lymphomic and erythroleukaemic cell lines--II

The relationship between the hydrolysis of labelled leucine enkephalin and the association of its radioactive label to the cells of lymphomic and erythroleukaemic cell lines have been studied using intact cells and resealed membranes obtained from these cells as models. Hydrolysis by cell enzymes and its effect on association have been analysed using protease inhibitors and non-hydrolysable enkephalin analogues. Results obtained confirm that hydrolysis of the pentapeptide is a prerequisite for association of the radiolabel to cells. The same results provide evidence of marked differences between enkephalin hydrolysis by whole cells and hydrolysis measured in the presence of resealed membranes, suggesting the existence in intact cells of proteolytic enzymes other than those bound to the membranes. The lack of reversibility of association and the intracellular localization of the radioactive label suggest that the association measured is prevailingly caused by internalization of a hydrolysis fragment, and not by binding to receptors. In order to determine the nature of the active fragment, association was measured in the presence of all four labelled N-terminal hydrolysis fragments of leu-enkephalin under conditions of nearly-total inhibition of proteolytic enzymes. Under these conditions, the label carried by Tyr, but not that carried by the other N-terminal fragments, was associated with cells. Free Tyr, furthermore, inhibits the association to cells of both labelled Tyr and leu-enkephalin. Data summarized above are consistent with the hypothesis that the radioactive label is taken up by the cells as Tyr, freed from the parent peptide by cell-related enzymes. The same data tend to exclude that a relevant fraction of the intact pentapeptide is bound to membrane receptors or that the radioactive label is carried into the cell by a N-terminal fragment other than Tyr.

Reciprocal effects between opioid peptides and human polymorphonuclear leukocytes--II. Enhancement of phorbol myristate acetate-induced respiratory burst in human polymorphonuclear leukocyte by opioid peptides previously exposed to activated oxygen species

Activated oxygen species (AOS) have often been shown to promote strong modifications in peptide structures and thus in their biological functions. In the present study, the immunomodulatory effects of Leu-enkephalin, beta-endorphin, dynorphin and some fragments are evaluated, before and after exposure of peptides to AOS, by studying their influence on human polymorphonuclear leukocyte (PMN) respiratory burst. None of the tested opioid peptides (modified or not) were shown to affect resting oxidative metabolism in the PMNs. The effects of peptides on phorbol myristate acetate (PMA)-stimulated production of AOS were measured in a lucigenin-enhanced chemiluminescence assay. Before AOS exposure, the opioid peptides suppressed the PMA-stimulated respiratory burst in human PMNs and a U-shaped dose-response relationship was observed. Conversely, after AOS exposure the opioid peptides enhanced the PMA-stimulated respiratory burst in human PMNs and an inverted U-shaped dose-response relationship was observed. In both cases, the maximal effect was reached at peptide concentrations of 10(-10)M-10(-12) M.

N-acetylation and C-terminal proteolysis of beta-endorphin in the anterior lobe of the horse pituitary

beta-Endorphin is post-translationally processed to both N-acetylated and C-terminally shortened derivatives in the anterior lobe of the horse pituitary, a processing pattern qualitatively different from that of the rat and virtually every other mammalian species. Thus, separation of the molecular forms of beta-endorphin using gel filtration and ion exchange chromatography showed that the horse anterior lobe primarily contains beta-endorphin-1-31 and N-acetyl-beta-endorphin-1-27 along with smaller amounts of beta-lipotropin, beta-endorphin-1-27, and N-acetyl-beta-endorphin-1-31 and -1-26, in contrast to the rat anterior lobe, which contains approximately equal amounts of beta-lipotropin and beta-endorphin-1-31. Immunohistochemical experiments using an antiserum which specifically recognizes N-acetylated beta-endorphin peptides confirmed that N-acetyl-beta-endorphin immunoreactivity is present in the anterior lobe of the horse, but not the rat. The intermediate lobe of both species primarily synthesizes N-acetylated, C-terminally shortened beta-endorphin peptides, and while distinct species differences do occur, they were relatively minor, consisting of quantitative differences in the relative proportion of each peptide. These results are consistent with earlier reports that beta-endorphin processing in the rat pituitary is tissue specific; the anterior and intermediate lobes produce entirely different sets of beta-endorphin peptides. In the equine pituitary, however, both pituitary lobes produce the same multiple beta-endorphin forms, possessing both opioid and nonopioid properties, although their relative amounts differ.

125I-beta-endorphin binding to neuroblastoma X glioma NG108-15 cells: distribution of delta opioid receptors

The mouse neuroblastoma x rat glioma hybrid NG108-15 was previously shown to express delta opioid receptors. Because neuroblastoma cells display different phenotypes and cloned cell lines are heterogenous, we studied the characteristics and distribution of human 125I-beta-endorphin (125I-beta E) binding sites in cultures of NG108-15 cells with the use of micro-autoradiography and light microscopy. 125I-beta E labeled delta sites in NG108-15 in the presence of the non-opioid blocking peptide, beta-endorphin (6-31) (beta E (6-31)). Silver grains resulting from 125I-beta E binding to the opioid sites occurred in diffuse patches over several cells, with preferential location in dense cell patches. Pretreatment of NG108-15 with the delta agonist DADLE, previously shown to decrease beta E binding to delta sites on intact cells, also reduced silver grain density; however, some cells located in dense cell clusters were resistant to substantial agonist induced loss of labeling. These results suggest that delta opioid binding has a heterogenous cellular distribution in NG108.

In vivo bidirectional regulation of mouse natural killer (NK) cell cytotoxic activities by Leu-enkephalin: reversibility by naloxone

Intraperitoneal injection of Leu-enkephalin (LENK, 10 or 7.5 mg/kg) induced bidirectional modulation of natural cytotoxic activities in spleens of CBA mice (suppression followed by enhancement). NK-cytotoxic activity was more affected than the ADCC. Early suppression of NK activity could be reversed by 4 x M excess of naloxone injected 20 min before LENK, suggesting that the suppression was mediated by opioid receptors. Subsequent increase of NK activity could not be abrogated by naloxone, at least not completely. Naloxone itself decreased NK activity 12 hours after treatment, but enhanced ADCC at 24 and 48 hours. This increase was abrogated by LENK. In addition to functional alterations, LENK also induced phenotypic changes of spleen cells, i.e. a decrease in the percentage of asialo-GM-1+ cells 24 hours posttreatment. There was no correlation between LENK-induced alterations of cytotoxic function and the percentage of cells with NK phenotype (GM-1+). Thus, LENK modulates cytolytic functions and the phenotype of NK cells in vivo in a complex way, which besides opioid mechanisms may also include non-opioid ones.

Characteristics and kinetics of proopiomelanocortin mRNA expression by human leucocytes

Northern blot analysis of total and poly(A)+ RNA demonstrated that human leucocytes contain several proopiomelanocortin (POMC) mRNA species, including 0.8-, 1.2-, 1.5-, and 9.5-kb transcripts. Peripheral blood lymphocytes (PBL) were found to express all four species. The other cell types had either the 0.8-kb species alone or both 0.8- and 9.5-kb species. Neutrophils were the only cells to express the 9.5-kb transcript alone. In T cell clones, both interleukin (IL)-2 alone or the antigen for which the clone was specific induced POMC accumulation within 18-24 h. Cytoplasmic dot blot analysis of PBL RNA demonstrated that POMC expression could be induced by corticotrophin releasing factor, rIL-1, and phorbol ester, but not by calcium ionophore (A23187). In PBL activated in a mixed lymphocyte culture there was increased expression, particularly of the smaller species (0.8, 1.2, and 1.5 kb), within 1-3 days of activation. The intensity of the bands began to decline thereafter. The 9.5-kb POMC transcript essentially disappeared by Day 3.

Effect of high doses of morphine on Con-A induced lymphokine production in vitro

Morphine, a potent analgesic drug as well as the active metabolite derived from heroin, has been reported to affect a variety of immune functions. In vivo administration of high doses of morphine to animals has been shown to inhibit natural killer (NK) cell activity in the rat (Shavit et al., 1984) and splenic T cell mitogenic response in the mouse (Bryant et al., 1988). We report here on the effect of morphine sulfate (MS) (0.2-1.6 mM) on Concanavalin-A (Con-A) stimulated lymphokine production by mouse splenocytes in vitro. Twenty-four hour incubation of mouse splenocytes with MS, removal of the drug and activation with Con-A resulted in a significant (linear regression, P less than 0.001) dose-related inhibition of lymphokine production (IC50 = 0.8 mM) as measured by bioassay for interleukin-2 (IL-2)/interleukin-4 (IL-4). The inhibitory effect of MS on lymphokine production was not blocked by opiate antagonists nor was the inhibitory effect mimicked by equivalent concentrations of mu, delta or epsilon receptor-specific opiate agonists. Exposure to the concentrations of MS used did not reduce viability of mouse splenocytes as determined by Trypan Blue exclusion. Morphine did not inhibit protein synthesis or adenylate cyclase activity in a T cell clone under identical conditions, indicating that MS, in this concentration range, does not simply interfere with all cell functions in a nonspecific manner. These results suggest that (1) morphine directly inhibits splenocyte function, (2) the inhibitory effect is not mediated through classical opiate receptors, and (3) the inhibitory effect is not due to toxicity.

The posttranslational processing of beta-endorphin in human hypothalamus

beta-Endorphin is posttranslationally processed to six derivatives, which, although structurally similar, produce distinctly different biological effects. beta-Endorphin 1-31 is a potent opioid receptor agonist, but beta-endorphin 1-27 exhibits antagonist properties, and beta-endorphin 1-26 and the alpha-N-acetyl derivatives of all three peptides lack opioid receptor activity. In the present study, we identified the beta-endorphin peptides synthesized in human hypothalamus using cation exchange HPLC. First, we tested whether postmortem changes occur by storing rat hypothalami at 4 degrees C. This demonstrated that relative amounts of the six beta-endorphin forms did not change for up to 24 h, although total beta-endorphin immunoreactivity significantly declined after 6 h. HPLC analysis of human hypothalami revealed that beta-endorphin 1-31 was the principal form, constituting 58.4 +/- 5.4% of total immunoreactivity. Substantial amounts of beta-endorphin 1-27 (13.4 +/- 1.2%) and beta-endorphin 1-26 (13.1 +/- 1.6%) were also present, but alpha-N-acetylated forms were quantitatively minor, each comprising approximately 5% of total beta-endorphin. A similar processing pattern occurred in preoptic and suprachiasmatic areas of the hypothalamus. These results show that, despite differences in primary sequence, beta-endorphin is processed similarly in both rat and human hypothalamus. Opiate-active beta-endorphin 1-31 is the principal form in both species.

Beta-casomorphin (BCM) and human colonic lamina propria lymphocyte proliferation

BCM is a milk-derived peptide with opiate-like properties which is absorbed through the gastrointestinal mucosa. It has been shown to affect gastrointestinal motility, absorption and secretion. Recently, modulation of the immune system by BCM was also reported. In this study we investigated the in vitro effect of BCM on the human mucosal immune response as represented by lamina propria lymphocyte (LPL) proliferation. Results show that BCM significantly inhibited concanavalin A (ConA) stimulated LPL DNA synthesis. BCM also inhibited ornithine decarboxylase activity (ODC) in ConA-stimulated LPL. Although BCM also inhibited 12-O-tetradecanoyl phorbol-13-acetate (TPA) stimulated LPL DNA synthesis, the degree of inhibition was much lower than in ConA-stimulated LPL. The anti-proliferative effect of BCM was reversed by the opiate receptor antagonist, neloxone. Our results suggest that BCM may affect the human mucosal immune system, possibly via the opiate receptor.

Zeta (zeta), a growth-related opioid receptor in developing rat cerebellum: identification and characterization

Endogenous opioids and opioid receptors (i.e. endogenous opioid systems) are expressed during neural ontogeny, and play a role in the development of the nervous system. Using [3H][Met5]-enkephalin, a potent ligand involved in neural growth, particularly cell proliferation, specific and saturable binding was detected in homogenates of 6-day-old rat cerebellum; the data were consistent with a single binding site. Scatchard analysis yielded a binding affinity (Kd) of 2.2 nM and a binding capacity (Bmax) of 22.3 fmol/mg protein. Binding was linear with protein concentration, dependent on time, temperature, and pH, and was sensitive to Na+, Mg2+, and guanyl nucleotides. Optimal binding required protease inhibitors, and pretreatment of the homogenates with trypsin markedly reduced binding, suggesting that the binding site was proteinaceous in character. The [Met5]-enkephalin binding site was an integral membrane protein located in the nuclear fraction. Competition experiments indicated that [Met5] enkephalin was the most potent displacer of [3H][Met5]-enkephalin, and that binding was stereospecific. In the adult rat cerebellum, non-opioid receptor binding of [3H][Met5]-enkephalin was recorded, mu and kappa receptors were also found in the developing rat cerebellum, while mu, delta, and kappa receptors were recorded in adult cerebellar tissue. The function, pharmacological and biochemical characteristics, subcellular distribution, and temporal expression of the [Met5]-enkephalin binding site suggest the presence of a unique opioid receptor, termed zeta (zeta), in the developing nervous system.

A further exploration of the relationships between immune parameters and the HPA-axis activity in depressed patients

In order to investigate the relationship between the immune apparatus and the hypothalamic-pituitary-adrenal (HPA)-axis activity in depressed patients, we measured in vitro lymphocyte responses to the mitogens Phytohaemagglutinin (PHA), Pokeweed (PWM) and Concanavalin A (Con A) and 8 a.m. baseline cortisol values in plasma, free cortisol excretion in 24 h urine (UFC), basal and post-dexamethasone beta-endorphin values. Major depressed patients with melancholia/psychotic features exhibited a significantly lower mitogen-induced blast transformation as compared to minor and simple major depressed patients. The lymphocyte responses to the three mitogens were significantly inversely related to baseline cortisol values and postdexamethasone beta-endorphin values. The proliferative capacity of lymphocytes to stimulation with PHA and PWM was significantly and positively related to UFC excretion. Up to 45% of the variance in the immune-responses to the mitogens was explained by the baseline cortisol, post-dexamethasone beta-endorphin and UFC values.

Chronic morphine treatment selectively suppresses macrophage colony formation in bone marrow

Opioids have been shown to have diverse effects on the immune system, both in vivo and in vitro, but their interactions on immature progenitor cells have been little studied. We have examined the effects of chronic morphine treatment of mice on colony formation by bone marrow cells in vitro. Bone marrow cells from mice implanted with morphine pellets for 72 h showed a 65% decrease in their response to macrophage colony stimulating factor (M-CSF). In contrast, chronic morphine treatment had no effect on the response of bone marrow cells to granulocyte/macrophage colony stimulating factor (GM-CSF). Removal of the morphine pellets from the mice resulted in a time-dependent reversal of the inhibition of macrophage colony formation, and the inhibition was completely blocked by simultaneous administration of naloxone and morphine pellets to the mice. No inhibition of colony formation was observed in bone marrow cells from mice treated with a single acute dose of morphine. Incubation of bone marrow cells from untreated mice for 7 days with in vitro morphine concentrations as low as 25 microM also reduced macrophage colony formation, and the opioid peptide beta-endorphin was even more potent, significantly reducing macrophage colony formation at concentrations as low as 0.25 microM. In agreement with the in vivo effects, neither opioid in vitro had a significant effect on granulocyte/macrophage colony formation. These results suggest that opioids may significantly alter the maturation of immune cells, which could result in potent effects on overall immune competence.

Melatonin-induced enhancement of antibody-dependent cellular cytotoxicity

Antibody-dependent cellular cytotoxicity (ADCC) is a lytic mechanism in which a specific antibody acts cooperatively with leukocytic effector cells to induce target cell lysis. In this paper, the effect of exogenous melatonin on ADCC was examined. It was found that two evening intravenous injections of melatonin (1 mg/kg b.w.) was sufficient to enhance the capacity of splenocytes to mediate ADCC. This augmented activity returned to normal levels by day 6. Moreover, the opioid antagonist, naloxone, was unable to inhibit the ADCC enhancement, suggesting that melatonin did not operate through a naloxone-sensitive opiatergic mechanism. These results further support the modulatory action of melatonin on immune responses.

N-acetyl-beta-endorphin1-31 antagonizes the suppressive effect of beta-endorphin1-31 on murine splenocyte proliferation via a naloxone-resistant receptor

High affinity binding sites for beta-endorphin1-31 (beta-EP) have been observed on transformed mononuclear cells such as the human U937 monocyte-like cell line and the murine EL4-thymoma line, and on normal murine splenocytes. Binding of beta-EP at these sites is resistant to competition by naloxone and other opiate receptor ligands but sensitive to N-acetyl-beta-endorphin1-31 (N-Ac), cations and GTP-gamma-sulfate. Thus, the following studies were done to determine the functional significance of binding beta-EP and N-Ac. beta-EP suppressed phytohemagglutinin (PHA)-stimulated [3H]thymidine uptake in a dose-dependent, naloxone-insensitive fashion. beta-Endorphin1-27, (des)-tyrosine beta-endorphin2-31, or N-Ac failed to duplicate the suppressive effect of beta-EP. However, N-Ac, which is equipotent to beta-EP at displacing 125I-beta-EP bound to murine splenocytes or U937 cells, antagonized the suppressive effect of beta-EP. Taken together with previous binding studies, the present observations suggest that beta-EP effects receptor-mediated responses on normal immunocytes that do not depend on the activation of neuronal-like opiate receptors which are naloxone-sensitive. N-Ac, which shows minimal binding to such brain opiate receptors, is a potent functional antagonist of the naloxone-insensitive immunocyte receptor for beta-EP.

Enhancement of germ tube formation in Candida albicans by beta-endorphin

Candida albicans is a dimorphic yeast that causes vaginal infections after its transition from a budding yeast to a germinating hyphal form. We report here that physiologic concentrations of beta-endorphin, a neuropeptide with immunomodulating activity produced during stress or physical exercise, stimulates germ tube formation in C. albicans. The percent of germination was proportional to the endorphin concentration, over the 5 x 10(-12) to 5 x 10(-10) mol/L range tested. beta-Endorphin modified by removal of the 4-carboxy-terminal amino acids and (D-Ala2)-beta-endorphin, a peptide with a protease-resistant amino terminal end, were equally effective in stimulating germination. In contrast, N-acetylated beta-endorphin did not stimulate germination. Antisera to beta-endorphin also completely blocked beta-endorphin-stimulated germ tube formation. Two clinical isolates of C. albicans were also responsive to beta-endorphin. Stimulation of germ tube formation by beta-endorphin occurred only in sera from ovulating women. Germination in sera from women using oral contraceptives, in sera from men, or in glucose beef extract broth was not influenced by beta-endorphin. Thus C. albicans may be able to recognize and respond to neuroendocrine signals in ovulating women.

Beta-endorphin C-terminal peptide evokes arachidonic acid release from cortical neurones

The release of free [3H]arachidonic acid and its metabolites (AAM) from mouse embryo cortical neurones cultured in serum-free medium stimulated by beta-endorphin C-terminal dipeptide (glycl-L-glutamine, Gly-Gln) was investigated. Gly-Gln but not the related dipeptide, glycyl-glutamic acid, caused a 2-fold elevation of AAM release which was blocked in the absence of extracellular calcium, in the presence of 5 mM magnesium and by the phospholipase A2 (PLA2) inhibitor, mepacrine. Other proopiomelanocortin (POMC) peptides did not elicit AAM release. The response to Gly-Gln was unaffected by D-amino-2-phospho-5-valeric acid (AP5) and 7-chlorokynurenic acid (7-ClKY), antagonists respectively at the ligand and allosteric glycine binding sites of the NMDA glutamate receptor subtype. However, it was inhibited in a dose-dependent manner by antagonists at the phencyclidine (PCP) and sigma sites. The results suggest that Gly-Gln causes AAM release by activating PLA2 through the mediation of a PCP/sigma-like receptor.

Peptide opioids and morphine effects on inflammatory process

Morphine was found to inhibit human granulocyte aggregation and ATP, thromboxane B2 (TxB2), and leukotriene B4 (LTB4) secretion during cell aggregation. None of the opioid peptides tested [(D-Ala2, D-Leu5)-enkephalin (DADL), (D-Ala2, N-Me-Phe4, Gly-ol5)-enkephalin (DAGO) or dynorphin 1-9 (Dyn 1-9)] was capable of mimicking morphine effects, while Dyn 1-9 per se induced TxB2 and LTB4 secretion from granulocytes. Morphine inhibition of both cell aggregation and ATP, but not of arachidonic acid metabolism product secretion, was prevented by naloxone. The naloxone-sensitive impairment by morphine of CD11b-CD18 complex surface expression observed could play a role in opioid inhibition of granulocyte activation.

Examination of the neuroendocrine basis for the social conflict-induced enhancement of immunity in mice

Intruder DBA/2 and C57BL/6 mice, which display different neuroendocrine responses to social conflict, evidence a pronounced increase in splenocyte phagocytosis of opsonized zymosan particles as a consequence of social conflict-induced stress. Interruption of the hypothalamic-pituitary-adrenal axis prior to social conflict results in an abrogation of the stress-induced enhancement of phagocytosis in DBA/2, but not in C57BL/6, mice. Administration of the opiate antagonists naloxone and naltrexone resulted in a potentiation of the stress-induced enhancement of phagocytosis in both strains. Similarly, administration of the alkylating antagonist beta-chlornaltrexamine which irreversibly blocks opioid binding sites potentiated the immune-enhancing effects of social conflict stress. Mitogen-induced T and B lymphocyte proliferation was unaffected by any of the experimental procedures with the exception of beta-chlornaltrexamine which suppressed activity equally in stressed and nonstressed groups. These results demonstrate the necessity of employing inbred murine strains in the dissection of the neuroendocrine pathways which govern stress-induced modulation of the immune system.

Differential effects of beta-endorphin on cAMP levels in human peripheral blood mononuclear cells

In the present paper we demonstrate that one of the early effects of the opioid peptide beta-endorphin on human peripheral blood mononuclear cells is the induction of a change in the intracellular cAMP level. However, the effect of beta-endorphin on cAMP levels is not uniform; increases as well as decreases in cAMP level are observed. It appears that beta-endorphin is a true modulator of intracellular cAMP level: the peptide will increase cAMP levels in cells with a low baseline level. In contrast, beta-endorphin tends to decrease cAMP levels is cells with a high cAMP concentration. Moreover, beta-endorphin modulates the rise in cAMP induced by beta-adrenergic activation. The effect of beta-endorphin on cAMP level correlates negatively with the magnitude of the change in cAMP level induced by beta-adrenergic activation.

Interleukins counteract opioid agonists immunosuppression

A centrally acting novel analgesic, PM, added to murine lymphocyte cultures abrogated the mitogenic response to Con A, as well as, interleukin 2 production, in a dose-dependent manner. Simultaneous presence of interleukin 1 (IL-1) and interleukin 2 (IL-2) into the cultures counteracted, in a dose-dependent manner, as naloxone does, the immunosuppressive action of PM as well as of Pethidine, a known opioid agonist. These results show that IL-1 and IL-2 together exhibit classical agonist-antagonist opioid receptor interactions and support the hypothesis that these lymphokines might play a role as endogenous opioid receptor antagonists against endogenous opioid agonists.

Beta-endorphin stimulates rat T lymphocyte proliferation

beta-Endorphin 1-31 and several structurally related peptides were tested for their ability to alter mitogen-induced T cell proliferation. Rat beta-endorphin 1-31 and human beta-endorphin 1-27 increased phytohemagglutinin (PHA)-induced [3H]thymidine incorporation into rat lymph node cells. However, when PHA-induced proliferation was suppressed by the inclusion of prostaglandin E1 (PGE1), human beta-endorphin 1-31 and a number of structurally similar peptides, including some peptides that did not alter mitogen-induced proliferation, significantly reduced the PGE1 inhibition of PHA-stimulated T cell proliferation. Although the N-terminus of beta-endorphin was necessary for potency, inclusion of the opioid antagonist naloxone together with beta-endorphin 1-31 did not alter the blockage of PGE1 inhibition of PHA-induced proliferation caused by beta-endorphin. The inhibition of mitogen-stimulated proliferation by either cholera toxin or forskolin, two additional compounds that like PGE1 also elevate cyclic AMP levels, was not blocked by beta-endorphin. Verapamil suppression of proliferation was not modified by beta-endorphin, indicating that the beta-endorphin stimulatory effect was probably not due to Ca2+ influx through verapamil-sensitive Ca2+ channels. These data suggest that beta-endorphin, acting through a nonopioid beta-endorphin receptor, may modulate immunocompetence by stimulating T cell proliferation and by counteracting the inhibitory effects of PGE1.

Beta-endorphin alters the course of central nervous system disease induced by a temperature-sensitive vesicular stomatitis virus in reconstituted nude mice

A 100 plaque forming unit (pfu) dose of a temperature-sensitive (ts) mutant of vesicular stomatitis virus (VSV), tsG31 KS5, engendered a slowly progressive paralytic central nervous system (CNS) disease that killed all BALB/c nude mice within 28 days. Reconstitution of nude mice with 10(7) syngeneic splenocytes 24 h before intracerebral inoculation with tsG31 KS5 VSV, however, protected 92% of the animals from death. When these reconstituted animals were injected intracerebroventricularly with 14 pmol of beta-endorphin 24 h after reconstitution with splenocytes and 24 h before inoculation with tsG31 KS5 VSV, only 72% of the animals survived. Furthermore, whereas 40% of the afflicted reconstituted nude mice given intracerebroventricular injections of sterile water were able to recover from the symptoms of disease, those surviving animals which received beta-endorphin were unable to do so. A single intravenous injection of 14 pmol beta-endorphin, or repeated postinfection administration of 28 pmol of beta-endorphin intravenously into nude mice reconstituted with syngeneic splenocytes, which were pretreated with beta-endorphin, did not alter the course of CNS disease induced by tsG31 KS5 VSV. The effect induced by intracerebroventricular injection of beta-endorphin was antagonized by naloxone, but not by the neuropeptide fragment beta-endorphin-(1-27). A simultaneous intracerebroventricular injection of reconstituted nude mice with 1220 pmol of naloxone and 14 pmol of beta-endorphin resulted in a 89% survival rate, and 33% of the afflicted animals were able to overcome the symptoms of the disease induced by tsG31 KS5 VSV. Intracerebroventricular injection of reconstituted nude mice with 330 pmol of beta-endorphin-(1-27) and 14 pmol of beta-endorphin resulted in a 72% survival rate and the surviving animals were unable to improve appreciably the clinical status of their disease. Injection of reconstituted nude mice with either 1220 pmol of naloxone or 330 pmol of beta-endorphin-(1-27) alone did not alter the course of the CNS disease in any way. A single intracerebroventricular injection of 29 pmol of another psychoactive peptide, [Des-Tyr]-endorphin, 24 h after reconstitution of nude mice with splenocytes and 24 h prior to infection with virus, resulted in 74% survival; and 39% of the afflicted animals were able to recover from the clinical symptoms.

The enhancement of polyclonal T cell proliferation by beta-endorphin

Beta-endorphin (beta-end) is a naturally occurring opioid peptide that has been implicated as a modulator of immune function. In this communication, data are presented to illustrate that beta-end enhances proliferation of murine splenocytes stimulated by the T cell mitogen, Con A. The T cell sensitivity of this effect was demonstrated in cell preparations enriched for T cells by nylon wool separation. The opioid specificity of the enhancement indicates that the C-terminus of the 31 amino acid peptide contributed significantly to the effect. In addition, the magnitude and the incidence of the enhancement was highly dependent on the concentration of Con A, the density of the tested cells and the timing of the addition of beta-end relative to that of Con A. These observations suggest that the state of activation of the T cell is a principal determinant of its sensitivity to beta-end. Overall, the data provide compelling evidence for the existence of an immunomodulatory role for beta-end.

Stimulation of human peripheral lymphocytes by methionine enkephalin and delta-selective opioid analogues

The opioid peptide methionine enkephalin was shown to stimulate human peripheral lymphocyte proliferation in vitro in the absence of mitogen. A study of the time course of stimulation revealed a maximum proliferative response, measured by [3H]thymidine incorporation, after 4-5 days incubation. The kinetics of the response are similar to those for in vitro T cell responses to antigen rather than via polyclonal activation through lectin or anti-CD3 triggering, suggesting a physiological basis for the phenomenon. The stimulatory influence was blocked by the delta-selective antagonist ICI-174864, suggesting the mediation of classical opioid delta receptors. The opioid receptor specificity is further demonstrated using delta- and mu-selective agonists. The delta-selective agonists DSLET and DPDPE stimulate proliferation, whereas the mu-selective agonist DAGON was without effect.

Effects of opioid peptides on the cellular immunity in spleen cells from intact nude mice or nude mice bearing human ovarian carcinoma

The present study was designed to explore the effects of opioid peptides on the lytic activity of spleen cells from intact nude mice or nude mice bearing human ovarian cancer cells (KF). When the spleen cells from intact nude mice were incubated with various concentrations of opioid peptides, the ability of the spleen cells to lyse the KF cells was significantly stimulated between 0.05 nM and 50 nM concentrations of all opioid peptides used in this study. The degree of stimulation was most marked at 5 nM opioid peptides and the most marked stimulatory effect was obtained by alpha-endorphin. On the other hand, the lytic activity of spleen cells from nude mice challenged with the KF cells was about two-fold higher than that of intact nude mice, suggesting that spleen cells from nude mice challenged with KF cells have KF-cell-specific cytotoxicity. Even if the spleen cells were incubated with any concentration of alpha-endorphin or [Met]enkephalin indicated, the lytic activity remained unchanged. In contrast, only beta-endorphin resulted in a significant increase of the lytic activity between 0.5 nM and 50 nM. These results suggest that opioid peptides play a crucial role in immune surveillance mechanisms.

Beta-endorphin modulation of IL-1-induced IL-2 production

We have studied the effects of natural opioids on interleukin-1 (IL-1) -induced interleukin 2 (IL-2) production by the lymphoid cell line EL-4. beta-Endorphin (beta-end) significantly enhanced IL-2 production by IL-1-stimulated EL-4 cells. Similar results were obtained using the LBRM33-1A5 cell line. beta-End induced significant enhancement (35-100%) of IL-1-induced IL-2 production at all concentrations of IL-1 tested (2-0.25 U/ml) and the effects were seen with both IL-1 alpha and IL-1 beta. The dose response of beta-end augmentation of IL-1-induced IL-2 production was bimodal, with peak activities seen at high (10(-8)-10(-10) M) and low (10(-16) M) beta-end concentrations. The specificity of beta-end effect was studied using the opioid antagonist naloxone. Naloxone completely abolished the enhancing effects of beta-end, indicating that the effects might be mediated through binding to opioid receptors. In addition, other opioid peptides, including gamma-endorphin and enkephalins, elicited similar effects. Northern blotting analysis revealed higher levels of IL-2 mRNA in beta-end-treated IL-1-induced EL-4 cells than in IL-1-induced control cells. Thus, beta-end might enhance IL-2 production by either augmenting the transcription rate or increasing IL-2 mRNA stability. These results suggest that beta-end might play an important role in the regulation of lymphokine production in the periphery in addition to its known interactions with IL-1 in the central nervous system.

Neuroendocrine control of thymic hormonal production. II. Stimulatory effects of endogenous opioids on thymulin production by cultured human and murine thymic epithelial cells

Data have now accumulated to strongly demonstrate that several neuropeptides, including endogenous opioids, can have immunomodulatory functions. Most of the studies have so far focused on the direct action of these substances on lymphocytes. We decided to investigate whether thymic epithelial cells (TEC) - the major component of the thymic microenvironment - could also be modulated by endogenous opioids. Primary cultures of human and murine TEC were subjected to several opioids (alpha-beta- or gamma-endorphins, as well as met- or leuenkephalins) applied in concentrations ranging from 10(-6) to 10(-9) M. On the following days we measured the levels of thymulin (a chemically-defined thymic hormone known to stimulate some steps of T-cell differentiation) in the culture supernatants, as well as the numbers of thymulin containing cells, evaluated by immunofluorescence with an anti-thymulin monoclonal antibody. After treatment of TEC cultures with beta-endorphin or leu-enkephalin a significant increase in the levels of thymulin in the culture media was observed, paralleled by a rise in the percentage of thymulin containing cells. In addition, this stimulatory effect was dose-dependent. Preincubation of the opioids with the specific antibodies abrogated the opioid-induced stimulatory effect on TEC. Moreover, naloxone, an opioid receptor antagonist, blocked the effect of beta-endorphin on thymulin production, suggesting that the effect of this neuropeptide on epithelial cells was mediated by an opioid receptor. Importantly, no effect on thymulin production was observed with the other opioids used, whatever the dose. These results suggest that, at least in vitro, beta-endorphin and leu-enkephalin stimulate the hormonal function of the thymic epithelium. These findings lead to the general concept that the modulatory role of endogenous opioids on the immune system is not restricted to lymphocytes but can also take place at the level of cells belonging to T-cell differentiating microenvironments.

Hydrolysis and binding of leucine enkephalin to lymphomic and erythroleukaemic cell lines

Hydrolysis and binding of labelled leucine enkephalin have been measured in the presence of cell lines of lymphoid and erythroid origin. The radioactive label was found to be associated to all lines studied. In the presence of these cells, enkephalin is rapidly hydrolyzed, forming three tyrosine-containing peptides: Tyr, Tyr-Gly and Tyr-Gly-Gly. Conversely, the presence of selective protease inhibitors reduces both enkephalin degradation and binding. Data obtained suggest the involvement in enkephalin hydrolysis of aminopeptidases, dypeptidylaminopeptidases and dypeptidylcarboxypeptidases. In addition, they suggest that the radioactive label associated to cells can be related to the peptides formed by the enzyme degradation of enkephalin and not to the intact pentapeptide.

Plasma beta-endorphin and beta-lipotropin levels increase in well trained athletes after competition and non competitive exercise

Plasma beta-endorphin (beta-EP) and beta-lipotropin (beta-LPH) levels were measured in 15 healthy trained marathon runners. These hormones were evaluated in two different conditions: 1-before (1h) and after a marathon race (n = 10); 2-before, during and after a prolonged (90 min) submaximal exercise (bicycle ergometer at 50% VO2 max) (n = 5). In these latter group plasma beta-EP and beta-LPH levels were measured every 15 min for 165 min. In all the athletes, both plasma beta-EP and beta-LPH levels were significantly higher after the end of the marathon race than in basal conditions (p less than 0.01). The prolonged exercise with bicycle ergometer significantly stimulated plasma beta-EP and beta-LPH levels. Starting 60 min after the beginning of the exercise, plasma beta-EP and beta-LPH levels resulted significantly higher than basal values until the end of the exercise (p less than 0.01 at 60, 75 and 90 min). These data confirming that marathon running is a potent stress stimulus, showed that the duration and related factors but not the work load may be considered critical in stimulating beta-EP and beta-LPH release during physical exercise.