Beta-endorphin's modulation of lymphocyte proliferation is dose, donor, and time dependent

Serum IgG, IgA, IgM, and IgE Levels after Electroacupuncture and Diet Therapy in Obese Women

We investigated the effect of acupuncture therapy on obese women's body weight and peripheral blood levels of serum immunoglobulin G ( IgG ), immunoglobulin A ( IgA ), immunoglobulin M ( IgM ), and immunoglobulin E ( IgE ). Sixty-three healthy women were assigned into 3 groups: placebo electroacupuncture ( n = 13; mean age, 40.5 ± 4.2 years; body mass index [BMI], 33.5 ± 4.2), diet restriction ( n = 23; mean age, 42.9 ± 4.0 years; BMI, 34.6 ± 2.9), and electroacupuncture ( n = 24; mean age, 40.1 ± 5.9 years; BMI, 33.9 ± 2.7). Electroacupuncture was applied to the Hunger and Shen Men ear points and to the LI 4, LI 11, St 36, St 44, and Ren 6 body points for 30 min once daily for 20 days. A restricted diet of 1400 kilocalories was given to participants in all 3 groups for 20 days. Weight was lost significantly in subjects in the electroacupuncture group compared to those in the diet restriction and placebo electroacupuncture groups ( p < 0.000, Tukey test). Modulations in serum IgG ( p < 0.001) were apparent in women treated with electroacupuncture compared with women treated with placebo electroacupuncture and restricted diet only. No significant changes were seen in serum IgA , IgM , and IgE levels among the 3 groups. Our results suggest that electroacupuncture can be effectively used to treat obesity. We also observed a modulating effect of serum IgG , which is associated with weight loss, in patients in the electroacupuncture group.

Acupuncture and Immunomodulation

Acupuncture is a well-known form of Asian medical treatment and it is used not only as an effective curative method but also to prevent illness and mai ntain health. It is used for the production of analgesic effect; stress related physical-mental disorders and homeostasis. Electroacupuncture (EA) stimulation, an application of electrical current on acupuncture needles, is one of the most popular types of this traditional therapy. In recent years, intensive studies have been carried out to explain the underlying mechanisms of the efficacy of acupuncture. An increase in the release of endogen opioid peptides is generally accepted to be a keystone pathway that affects the immune system after the acupuncture application. To understand the huge gap between specific skin point applications and immune responses, a vast number of accumulating data of experimental and clinical studies in the literature have been collected. This paper reviews the data to explain the updated mechanisms related to immune modulation via acupuncture therapy.

The mechanism of acupuncture and clinical applications

This study presents the result of the studies explaining the effects of acupuncture on various systems and symptoms. It has been determined that endomorphin-1, beta endorphin, encephalin, and serotonin levels increase in plasma and brain tissue through acupuncture application. It has been observed that the increases of endomorphin-1, beta endorphin, encephalin, serotonin, and dopamine cause analgesia, sedation, and recovery in motor functions. They also have immunomodulator effects on the immune system and lipolithic effects on metabolism. Because of these effects, acupuncture is used in the treatment of pain syndrome illnesses such as migraine, fibromyalgia, osteoarthritis, and trigeminal neuralgia; of gastrointestinal disorders such as disturbance at gastrointestinal motility and gastritis; of psychological illnesses such as depression, anxiety, and panic attack; and in rehabilitation from hemiplegia and obesity.

Intravenous fentanyl increases natural killer cell cytotoxicity and circulating CD16(+) lymphocytes in humans

Opioids, including fentanyl, are often administered to patients who may be at risk for the consequences of impaired immune function. We performed a clinical study to test the effects of the synthetic opioid fentanyl on human immune function. Participants received an IV fentanyl initial dose of 3 microg/kg followed by a 2-h IV infusion of 1.2 microg x kg(-1) x h(-1). Peripheral blood was drawn before and after fentanyl administration to test for neutrophil phagocytic function, neutrophil antibody-dependent cell cytotoxicity, natural killer cell cytotoxicity, percentage of lymphocyte populations, T-lymphocyte proliferative response, and in vivo antibody response to a pneumococcal vaccine inoculation given at the end of the fentanyl infusion. Fentanyl exposure under the conditions of this study caused a rapid and significant increase in natural killer cell cytotoxicity, which was coincident with an increase in the percentage of CD16(+) and CD8(+) cells in peripheral blood. Fentanyl did not significantly affect any of the other immune measurements.

IMPLICATIONS

Many previous studies have suggested that opioid drugs can impair immune resistance in patients who may be at risk for infection. This study suggests that the opioid fentanyl, when given to healthy humans without coexisting diseases, does not suppress immune resistance. On the basis of these results, the use of fentanyl should not be restricted because of concerns that it may suppress immune function.

Effects of fentanyl on cellular immune functions in man

In order to analyze the effects of the opioid agonist fentanyl on cells of the innate immune system, seven healthy individuals were treated intravenously with the opioid fentanyl and five subjects received a placebo. Respiratory burst of polymorphonuclear cells (PMNC) and phenotypes of peripheral blood lymphocytes (PBL) were analyzed from blood samples drawn before, 15 and 30 min after fentanyl or placebo application. In addition, in vitro effects of fentanyl on natural killer (NK) activity was assessed. Fentanyl administration affected neither superoxide production of PMNC nor circulating numbers of B-and T-lymphocytes. In contrast, NK cell (CD16+/CD56+) numbers significantly increased in response to fentanyl. However, no direct influence of fentanyl on NK cell function in vitro could be detected. These results suggest a transient effect of fentanyl on NK cell circulation which seemed to be centrally mediated rather than a direct effect of this opioid on NK cells.

Effects of substance P on human T cell function and the modulatory role of peptidase inhibitors

Evidence has been presented for a modulatory role of surface peptidases on substance P-mediated immune responses. In this study, we first characterized the effects of substance P and its carboxy- and amino-terminal fragments on human lymphocyte proliferative responses to investigate whether peptidase inhibitors influence the effects of the neuropeptide. Substance P at 10(-7) M and the carboxy-terminal fragment SP(4-11) slightly enhanced the lymphocyte responses to phytohemagglutinin and concanavalin A. In contrast, the amino-terminal fragment SP(1-4) failed to have any positive effect. However, in the presence of dipeptidylpeptidase IV/CD26 and neutral endopeptidase/CD10 inhibitors (diprotin A and thiorphan, respectively), the effect of substance P on mitogen-induced proliferation was significantly increased. These data support the hypothesis that lymphocyte surface peptidases play a modulatory role in the effects of substance P on T cell function.

The immune effects of neuropeptides

Current evidence indicates that the neuroendocrine system is the highest regulator of immune/inflammatory reactions. Prolactin and growth hormone stimulate the production of leukocytes, including lymphocytes, and maintain immunocompetence. The hypothalamus-pituitary-adrenal axis constitutes the most powerful circuit regulating the immune system. The neuropeptides constituting this axis, namely corticotrophin releasing factor, adrenocorticotrophic hormone, alpha-melanocyte stimulating hormone, and beta-endorphin are powerful immunoregulators, which have a direct regulatory effect on lymphoid cells, regulating immune reactions by the stimulation of immunoregulatory hormones (glucocorticoids) and also by acting on the central nervous system which in turn generates immunoregulatory nerve impulses. Peptidergic nerves are major regulators of the inflammatory response. Substance P and calcitonin gene-related peptide are pro-inflammatory mediators and somatostatin is anti-inflammatory. The neuroendocrine regulation of the inflammatory response is of major significance from the point of view of immune homeostasis. Malfunction of this circuit leads to disease and often is life-threatening. The immune system emits signals towards the neuroendocrine system by cytokine mediators which reach significant blood levels (cytokine-hormones) during systemic immune/inflammatory reactions. Interleukin-1, -6, and TNF-alpha are the major cytokine hormones mediating the acute phase response. These cytokines induce profound neuroendocrine and metabolic changes by interacting with the central nervous system and with many other organs and tissues in the body. Corticotrophin releasing factor functions under these conditions as a major co-ordinator of the response and is responsible for activating the ACTH-adrenal axis for regulating fever and for other CNS effects leading to a sympathetic outflow. Increased ACTH secretion leads to glucocorticoid production. alpha-melanocyte stimulating hormone functions under these conditions as a cytokine antagonist and an anti-pyretic hormone. The sympathetic outflow, in conjunction with increased adrenal activity. leads to the elevation of catecholamines in the bloodstream and in tissues. Current evidence suggests that neuroimmune mechanisms are essential in normal physiology, such as tissue turnover, involution, atrophy, intestinal function, and reproduction. Host defence against infection, trauma and shock relies heavily on the neuroimmunoregulatory network. Moreover, abnormalities of neuroimmunoregulation contribute to the aetiology of autoimmune disease, chronic inflammatory disease, immunodeficiency, allergy, and asthma. Finally, neuroimmune mechanisms play an important role in regeneration and healing.

Neutrophil signal transduction in Met-enkephalin modulated superoxide anion release

The present study explored the involvement of signal transduction system(s) in Met-enkephalin (MENK) modulated superoxide anion (O2-) release from human neutrophils. This opioid pentapeptide stimulated the O2- release in all samples if present at 10(-8) M concentration while in lower concentrations the stimulatory concentration was donor-dependent. The most abundant product of MENK degradation, Tyr-Gly-Gly (TGG), suppressed O2- release over a wide range of concentrations (10(-12)-10(-8) M). MENK induced O2- release was associated with a dose-dependent increase of diacylglycerol (DAG) concentration and protein-kinase C (PKC) translocation to the neutrophil membranes, with an increase of cytosolic Ca++, and could be abolished by H7, a PKC inhibitor. On the contrary, the suppressive effect of TGG was not associated with alteration of DAG concentration in neutrophil membranes. Superoxide anion release induced by low concentrations of MENK (10(12)-10(-10) M), could be blocked by NDGA, an inhibitor of the lipoxygenase pathway. We concluded that MENK-induced O2- release results mainly due to DAG/PKC pathway activation, although other secondary messengers might be involved.

Pretreatment of human peripheral blood lymphocytes with interleukin-2 or dexamethasone does not alter their response to Met-Enkephalin in a NK-cytotoxic assay

The effect of Met-Enkephalin (MENK; 10(-12) - 10(-8) M) on NK-activity of peripheral blood lymphocytes (PBL) after in vitro treatment (18 h, 37 degrees C) was examined in 30 young, healthy male donors. In the group as a whole (n = 30), no significant effect of MENK was detected. At the individual level, 18 of 30 donors (60%) responded to MENK either by mild enhancement (up to 8%, 8 responders), or by mild attenuation (up to 12%, 10 responders) of the basal NK-activity. The effect of MENK was donor-related regarding the dose-response, E/T ratio, and direction of MENK action. The influence of pretreatment of PBL (1 h) with either graded doses of interleukin-2 (IL-2; 3, 25, 50 U/ml) or dexamethasone (Dex; 2.5 x 10(-9), 2.5 x 10(-8), 2.5 x 10(-7) M), on the effect of MENK was also tested. The idea was that pretreatment of PBL would result in predictable, and/or stronger response to MENK. In the group as a whole again no significant effect of MENK was detected on the NK-activity of PBL prestimulated by IL-2 (n = 16), or inhibited by Dex (n = 12). Further, pretreatment of PBL with IL-2/Dex did not significantly alter the intensity of modulation by MENK, which was generally mild. The data obtained have shown that pretreatment of PBL with IL-2 or Dex, regardless of their concentrations, did not significantly alter the frequency of responders to MENK being 50%, 62.5% and 64.3% with 3, 25 or 50 U/ml IL-2, respectively, and 50% with all concentration of Dex used, as compared to that observed with resting PBL (60%). However, at the individual level physiological concentrations of MENK (10(-12) - 10(-9) M) induced enhancement or/and attenuation of the NK-activity pretreated with IL-2/Dex, respectively. The effect of MENK at the individual level was donor-related regarding the dose-response, E/T ratio, and direction of MENK action. Thus, pretreatment of PBL with graded concentrations of IL-2/Dex did not alter the effect of MENK on NK-activity, regarding the frequency and intensity, as well as the direction of modulation: it remained bidirectional, of low intensity, and independent of the grade of PBL preactivation/inhibition, therefore unpredictable.

The relevance of intact enkephalin molecule in predominantly delta opioid receptor mediated superoxide anion release

The effect of intact enkephalin (MENK) molecule or its metabolite Tyr-Gly-Gly (TGG) as well as the effect of synthetic agonist for opioid receptor subtypes (DADLE and DAGO) on superoxide anion release from human neutrophils has been investigated. In lower MENK concentrations, where MENK alone had no effect on O2- release, inhibition of enkephalinase by thiorphan significantly increased O2- production, while in higher concentrations, where MENK alone was effective, inhibition of enkephalinase had no effect. Aminopeptidase inhibition by bestatin did not influence O2- release from MENK treated PMNs. While MENK predominantly stimulated, TGG suppressed O2- release. Opioid antagonist naloxone (10(-5) M) abrogated the effect of MENK on O2- release. DADLE (delta receptor agonist) increased O2- release in 10(-11) M concentration, while DAGO (mu receptor agonist) had no effect in any concentration examined. Enkephalinase inhibition increased O2- production from DADLE but not from DAGO treated PMNs. It seems, therefore, that free radical production is mainly associated with the delta subtype of the opioid receptor. Also, our observations support the hypothesis that enkephalinase might be the enzyme selectively responsible for regulating effects of enkephalins.

Beta-endorphin and the immune system--possible role in autoimmune diseases

The immune system and the neuroendocrine system are closely interconnected having such means of bidirectional communication and regulation. In this review, a hypothesis is put forward regarding the possible role of beta-endorphins in the pathogenesis of autoimmune diseases: It is suggested that the increased cytokine production in immunoinflammatory disorders induces production of beta-endorphins from the pituitary and the lymphocytes; the enhanced level of beta-endorphin causes inhibition of human T helper cell function, which potentially down-regulate the antibody production. Also the beta-endorphin-induced enhancement of the natural killer cell activity may suppress the B cell function. In addition, beta-endorphin also exerts a direct inhibitory effect on the antibody production. Thus, in autoimmune disorders the enhanced cytokine level may via stimulation of the production of beta-endorphins exert a negative feed back on the antibody production and potentially so on the production of autoantibodies.

Characterization of binding sites for neuropeptide FF on T lymphocytes of the Jurkat cell line

Neuropeptide FF (NPFF) is a neuropeptide with antiopiate properties able to antagonize the action of both endogenous and exogenous opiates. Because we have recently shown that NPFF modulates the proliferation of human T lymphocytes, we have searched for binding sites for this peptide on T lymphocytes. Our study shows that T lymphocytes of the Jurkat cell line express binding sites for [125I]YLFQPQRFamide, an iodinated analogue of NPFF. This binding is time and dose dependent, reversible, saturable, and may be resolved in two distinct components of high and low affinity. The opiate receptor agonists mu, delta, and kappa, as well the antagonist naloxone, were unable to affect binding. Beside the effects of opiates on immune cells, our results suggest that an antiopiate peptide, such as NPFF, could play a role in the modulation of the immune system.

Disturbed immunoregulatory properties of the neuropeptide substance P on lymphocyte proliferation in HIV infection

The neuropeptide substance P (SP) is known to increase cell-mediated immune responses in animal models and healthy subjects. Several studies have suggested an involvement of neuropeptides in the immunopathogenesis of some diseases. The study of the immunomodulatory effects of neuropeptides, namely SP, may represent a model for the analysis of immunoregulatory defects in HIV infection at the level of the interaction between the immune and nervous systems, both of which are known to be affected by the virus. In the present study, we investigate the possibility of a disturbance in the immunomodulatory properties of SP in HIV infection by analysing the effects of SP (10(-10)-10(-6) M) on the lymphocyte proliferative responses to concanavalin A (Con A) and phytohaemagglutinin (PHA) assessed by 3H-thymidine incorporation in peripheral blood lymphocytes from 34 HIV-infected patients (16 asymptomatic (ASY)/persistent generalized lymphadenopathy (PGL); 18 ARC/AIDS) and in 37 healthy subjects. In ASY/PGL HIV-infected patients, SP 10(-7) M was identified as the concentration inducing the maximal increase in the lymphocyte responses to Con A and PHA, similarly to what was observed in healthy subjects. In ARC/AIDS patients, SP appeared to inhibit the mitogenic responses, particularly those induced by Con A, in contrast to the effects found either in healthy subjects or in ASY/PGL patients. These results suggest the existence of an alteration in the in vitro immunomodulatory properties of SP in ARC/AIDS patients compared with healthy subjects and ASY/PGL patients. In conclusion, the unexpected finding of an inhibitory effect of SP on lymphocyte proliferation from ARC/AIDS patients justifies further investigation of the neuropeptide-dependent immunoregulatory systems in HIV infection.

Central nervous system-immune system interactions: psychoneuroendocrinology of stress and its immune consequences

Psychoneuroimmunology is a relatively new discipline which deals with CNS-immune system interactions. The evidence for such interactions was reviewed, as was the neuroendocrinologic response to stress. Recent evidence indicates that the behavioral, nervous system, and neuroendocrine responses to stress are mediated by hypothalamic CRF, which acts on both the sympathetic nervous system and the HPA axis, resulting in increased levels of corticosteroids, catecholamines, and certain opiates, substances which are generally immunosuppressive. Concentrations of growth hormone and prolactin, which are immunoenhancing, are elevated early during the response to stress but are later suppressed. Although several other neuromediators may also be released with stress, the net effect of a variety of acute stressors is down regulation of the immune system function. In the following minireview, I consider whether stress alters the resistance of the host to infection as well as the immunomodulatory effects of released immune system mediators on the brain.

The role of brain-immune interactions in immunotoxicology

Certain xenobiotics (or the metabolites) can damage immunocompetence by directly interacting with one or more of the cells of the immune system and adversely affecting its function. It has also been proposed that xenobiotics may indirectly affect immune function by affecting other organ systems that will in turn affect immunocompetence. This review surveys evidence that supports the existence of a functional link between the brain and the immune system. In addition, we review data that support the concept that a xenobiotic-induced dysfunction in the neuroendocrine system may be associated with an immune dysfunction as well. Such chemicals do not necessarily interact directly with immunocompetent cells but would instead act to disrupt regulatory brain-immune interactions. This class of indirectly acting immunotoxic xenobiotics would not be detected in the typical in vitro screening assays.

Effect of synthetic thymic hormones on the cocaine-induced inhibition of the primary immune response in mice

The effects of thymosin alpha 1 (T alpha 1) and thymopentin (TP5) on the cocaine-induced impairment of the primary antibody response to sheep red blood cells (SRBC) was studied. The administration of cocaine from day -4 to the day of immunization (day 0) induced a significant impairment of the response to the T-dependent antigen SRBC, as evaluated on day 5 post-immunization by the Splenocyte-Induced SRBC Hemolysis (SIH) assay. The analysis of the responses to immunogen elicited from each single mouse indicated that, under the experimental conditions used, cocaine acted by exerting more an "all or nothing" effect rather than by modulating the strength of the immune response. Both T alpha 1 and TP5, injected into mice during cocaine administration and for 4 days after, induced a significant recovery of the response to SRBC. Our experiments did not show any great differences in the overall efficacy of the two drugs, although they showed quite a different dose-response effect. The results of the present investigation demonstrated the capability of TP5 and T alpha 1 to reverse the cocaine-induced impairment of the response to SRBC and suggested that the effect of the two peptides may be related to their immunomodulating activities on T-cell functions.

Met-enkephalin induced escape from dexamethasone immunosuppression

The present study was undertaken to examine whether and what type of interaction occurs between a synthetic glucocorticoid, dexamethasone (DEX) and an opioid peptide, met-enkephalin (MENK) upon superoxide anion (O2-) release from human polymorphonuclear cells (PMN). MENK (10(-8) M) abolished suppressed O2- release from PMNs treated with 10(-7) M DEX. This was the case in unstimulated but not in PMNs stimulated with PMA. The effect of MENK was mediated through pertussis-toxin (PTX) sensitive G-protein and since it was abolished by H7 probably involves protein kinase C (PKC) as a second messenger system. Thus, MENK can abolish DEX induced suppression of O2- release from human PMNs possibly through the interaction of second messenger pathways.

Leu-enkephalin modulates the migration inhibition of mouse splenocytes induced by cAMP-elevating agents

The ability of Leu-enkephalin (LENK) to alter random migration of mouse spleen cells was tested in vitro and in vivo. Incubation of the cells with LENK (10(-14) M-10(-7) M) for 1 h at 37 degrees C suppressed the migration. The dose-response was irregular, showing two peaks in the physiological concentration range: 10(-10) M, and 10(-13)-10(-14) M. Intraperitoneal (i.p.) injection of LENK (7.5 mg/kg body wt) depressed the migratory capacity of the splenocytes harvested 2 and 24 h later. In contrast to the inhibitory effect of LENK on the migration of native cells, its effect on cells pretreated with the cAMP-elevating agents theophylline, 3-isobutyl-1-methyl-xanthine (IBMX) and forskolin was predominantly a stimulatory one. The addition of LENK resulted in attenuation or even full reversion of the migration-inhibition caused by those agents. Occasionally, potentiation of the suppression was also observed. There was no discrimination between the phosphodiesterase (PDE) inhibitors IBMX and theophylline, and the adenylate cyclase activator forskolin. Specificity of LENK effects was tested by using naloxone (10(-6) M), an opioid-receptor antagonist. Migration-inhibition induced by LENK was reversed in about two-thirds of the experiments. In contrast, migration-inhibition induced by cAMP-elevating agents, could not be reversed by naloxone. Naloxone itself was not inert, usually suppressing the locomotor ability of splenocytes. The data suggest that LENK-induced modulation of cell migration is (at least partly) mediated via opioid receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Naloxone modulates NK-cell activity of human peripheral blood lymphocytes like an opioid agonist

Naloxone at concentrations 10(-6) M to 10(-10) M modulated endogenous NK-activity in 11 of 14 samples of human peripheral blood lymphocytes after 18-hour incubation. The dose response usually showed two peaks, which varied with the donor. Enhancement was obtained in 6, suppression in 4, and both effects (depending on naloxone concentration) in 1 example; 3 donors were nonresponders. However, the overall effect of naloxone on endogenous NK activity was not statistically significant in the population as a whole. IL-2-stimulated NK-activity, was also altered by naloxone. The direction of the alteration depended on the degree of IL-2-induced NK-stimulation, and was donor-dependent. For example, naloxone enhanced NK-activity that had been stimulated by low IL-2 concentration (3 U/ml), but decreased NK-activity which had been stimulated by high (50 U/ml) IL-2 concentration. Naloxone 10(-7) M significantly reversed medium stimulation of NK activity, induced by 25 U/ml, in a group as a whole. Naloxone (10(-7) M to 10(-12) M) also modulated NK-activity stimulated by exogenous IFN alpha, as well as by endogenous, Poly-I.C-induced IFN. Decrease, or enhancement, depended on the degree of baseline NK-stimulation and varied with the donor. Short (2-hours) incubation with naloxone also resulted in the modulation of basal and IFN-stimulated NK-activity. Again, the effect varied with the donor and with the degree of lymphocyte activation. Thus, naloxone, the opioid receptor antagonist, modulated the NK-cell activity like opioid peptides, i.e. resembled an opioid agonist, in an individual, donor dependent fashion.

In vitro phencyclidine-induced inhibition of lymphocyte proliferation: prevention by cell activation

The proliferative response of phytohemagglutinin (PHA)- and interleukin 2 (IL-2)-activated murine splenocytes was studied in the presence of phencyclidine (PCP), a potent psychotomimetic drug of abuse. PCP inhibited [3H]-thymidine incorporation in lymphocytes treated with PHA or IL-2. This inhibitory action was dependent upon the drug doses and the time of incubation with the cultures. There was no significant inhibitory activity of PCP when it was added 24 hrs or 48 hrs after mitogenic stimuli. Parallel, a lower inhibitory effect was observed when IL-2 or PHA were simultaneously present in the incubation medium. Moreover, the pretreatment for 18 hrs with IL-2 completely counteracted PCP-induced depression of PHA-stimulated lymphocytes. We suggest that PCP affects some pathway that regulates the activation of resting T cells rather than affecting already cycling cells.

Modulation of human lymphocyte proliferation by FLFQPQRFamide, a FMRFamide-like peptide with anti-opiate properties

The octapeptide Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2 (F8Fa), originally detected in mammalian brain by antisera raised against the invertebrate peptide Phe-Met-Arg-Phe-NH2 (FMRFamide) is a neuropeptide able to antagonize the actions of both endogenous and exogenous opiates. Since it is well accepted that lymphocytes are targets for opiates, we have tested the effect of F8Fa on T cell proliferation from normal human peripheral blood lymphocytes. Our study shows that F8Fa exerts a concentration-dependent diphasic modulation of human T lymphocyte proliferation. Thus, despite a great variability between individuals, 10(-13) M F8Fa was found to enhance the proliferation of T cells induced by phytohemagglutinin or anti-CD2 monoclonal antibodies, while 10(-7) M F8Fa inhibited T cell proliferation, without affecting cell viability. When F8Fa was tested on monocyte-depleted cell preparations, only the inhibitory effect was observed. These results indicate that F8Fa may stimulate T cells via monocytes, but may also directly inhibit T lymphocyte proliferation. Given the presence of F8Fa-like peptide in human plasma, we suggest that F8Fa may act as a neurohormone in the control of the immune system.

Effect of morphine and beta-endorphin on human Fc receptor-dependent and natural killer cell functions

Interactions between opiates and the human immune system have important clinical implications. To further evaluate these interactions, we studied in vitro and in vivo effects of morphine sulfate (morphine) and beta-endorphin (Bend) on antibody-dependent cell cytotoxicity (ADCC), natural killer cell cytotoxicity (NKCC), and effector cell expression of antibody Fc receptors. Morphine and Bend had no potent in vivo or in vitro effect on FcR expression nor did they have a significant in vitro effect on ADCC by monocytes or polymorphonuclear cells. Bend enhancement of NKCC in vitro was inhibited by coincubation of effector cells with morphine. After taking 90 to 150 mg of oral morphine, study volunteers demonstrated a significant decrease in ADCC by peripheral blood mononuclear cells. The same individuals demonstrated a consistent increase in NKCC and no change in the expression of Fc receptors. Effector cells from these individuals responded normally to in vitro incubation with interferon-gamma (IFN-gamma).

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.

Endogenous opiates: 1990

This paper, an examination of works published during 1990, is thirteenth in a series of our annual reviews of the research involving the behavioral, nonanalgesic, effects of the endogenous opiate peptides. The specific topics this year include stress; tolerance and dependence, eating; drinking; gastrointestinal, renal, and hepatic functions; mental illness; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; locomotor activity; sex, pregnancy, development, and aging; immunological responses; and other behavior.