Differential effects of beta-endorphin fragments on human natural killing

Hormetic Dose-Response Relationships in Immunology: Occurrence, Quantitative Features of the Dose Response, Mechanistic Foundations, and Clinical Implications

This article provides an assessment of the occurrence of immune-system-related hormetic-like biphasic dose-response relationships. Such dose-response relationships are extensive, with over 90 different immune response-related endpoints reported, induced by over 70 endogenous agonists, over 100 drugs, and over 40 environmental contaminants. Such hormetic responses were reported in over 30 animal models, over a dozen mammalian and human cell lines. These findings demonstrate that immune-system-related hormetic-like biphasic dose-response relationships are common and highly generalizable according to model, endpoint, and chemical class. The quantitative features of the dose response are generally consistent with previously published examples of hormetic dose responses for other biological endpoints. These findings were generally recognized and explicitly discussed by the original authors, often with consideration given to possible mechanistic foundations as well as numerous clinical implications. Despite the recognition by individual authors of the hormetic nature of these observed responses, the overall widespread nature of immune-related hormetic responses has been only little appreciated, with a general lack of insight into the highly generalizable nature of this phenomenon as well as the complex regulatory networks affecting biological switching mechanisms that result in the hormetic responses.

Design and synthesis of single-nanoparticle optical biosensors for imaging and characterization of single receptor molecules on single living cells

At the cellular level, a small number of protein molecules (receptors) can induce significant cellular responses, emphasizing the importance of molecular detection of trace amounts of protein on single living cells. In this study, we designed and synthesized silver nanoparticle biosensors (AgMMUA-IgG) by functionalizing 11.6 +/- 3.5-nm Ag nanoparticles with a mixed monolayer of 11-mercaptoundecanoic acid (MUA) and 6-mercapto-1-hexanol (1:3 mole ratio) and covalently conjugating IgG with MUA on the nanoparticle surface. We found that the nanoparticle biosensors preserve their biological activity and photostability and can be utilized to quantitatively detect individual receptor molecules (T-ZZ), map the distribution of receptors (0.21-0.37 molecule/microm(2)), and measure their binding affinity and kinetics at concentrations below their dissociation constant on single living cells in real time over hours. The dynamic range of detection is 0-50 molecules per cell. We also found that the binding rate (2-27 molecules/min) is highly dependent upon the coverage of receptors on living cells and their ligand concentration. The binding association and dissociation rate constants and affinity constant are k1 = (9.0 +/- 2.6) x 10(3) M(-1) s(-1), k(-1) = (3.0 +/- 0.4) x 10(-4) s(-1), and KB = (4.3 +/- 1.1) x 10(7) M(-1), respectively.

Potent regulation of microglia-derived oxidative stress and dopaminergic neuron survival: substance P vs. dynorphin

Unregulated microglial activation has been implicated as a pivotal factor contributing to Parkinson's disease. Using mesencephalic neuron-glia cultures, we address the novel possibility that peptides endogenous to the substantia nigra (SN), substance P and dynorphin (10(-13)-10(-14) M), are opposing mediators of microglial activation and consequent DA neurotoxicity. Here, we identify that substance P (10(-13)-10(-14) M) is selectively toxic to DA neurons in a microglia-dependent manner. Mechanistically, substance P (10(-13)-10(-14) M) activated microglial NADPH oxidase to produce extracellular superoxide and intracellular reactive oxygen species (ROS). Neuron-glia cultures from mice lacking a functional NADPH oxidase complex (PHOX-/-) were insensitive to substance P (10(-13)-10(-14) M) -induced loss of DA neuron function. Mixed glia cultures from (PHOX-/-) mice failed to show a significant increase in intracellular ROS in response to substance P compared with control cultures (PHOX+/+). Further, dynorphin (10(-14) M) inhibited substance P (10(-13) M) -induced loss of [3H] DA uptake. Here we demonstrate a tightly regulated mechanism governing microglia-derived oxidative stress, where the neuropeptide balance of dynorphin and substance P is critical to DA neuron survival.

Microglial NADPH oxidase is a novel target for femtomolar neuroprotection against oxidative stress

Inflammation has been increasingly recognized to contribute to the pathogenesis of Parkinson's disease. Several compounds are neuroprotective at femtomolar concentrations through the inhibition of inflammation. However, the mechanisms mediating femtomolar-acting compounds are poorly understood. Here we show that both gly-gly-phe (GGF), a tri-peptide contained in the dynorphin opioid peptide, and naloxone are neuroprotective at femtomolar concentrations against LPS-induced dopaminergic neurotoxicity through the reduction of microglial activation. Mechanistic studies demonstrated the critical role of NADPH oxidase in the GGF and naloxone inhibition of microglial activation and associated DA neurotoxicity. Pharmacophore analysis of the neuroprotective dynorphin peptides and naloxone revealed common chemical properties (hydrogen bond acceptor, hydrogen bond donor, positive ionizable, hydrophobic) of these femtomolar-acting compounds. These results support a common high-affinity site of action for several femtomolar-acting compounds, where NADPH oxidase is the critical mechanism governing neuroprotection, suggesting a novel avenue of anti-inflammatory and neuroprotective therapy.

Stochastic description of the ligand-receptor interaction of biologically active substances at extremely low doses

Signalling molecules can be effective at extraordinarily low concentrations (down to attomolar levels). To handle such cases, probabilistic methods have been used to describe the formal kinetics of action of biologically active substances in these low doses, although it has been necessary to review what is meant by such a term. The mean numbers of transformed/degraded molecules and their dispersions were calculated for the possible range of ligand-receptor binding schemes. We used both analytical equations and numerical simulations to calculate the coefficients of variation (ratio of standard deviation to mean) and demonstrated that the distribution of the coefficient is highly dependent on the reaction scheme. It may, therefore, be used as an additional factor for discriminating between cooperative and noncooperative models of ligand-receptor interaction over extreme ranges of ligand dilution. The relevance to signalling behaviour is discussed.

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.

Antisense inhibition of pro-opiomelanocortin and proenkephalin A messenger RNA translation alters rat immune cell function in vitro

Pro-opiomelanocortin (POMC) and proenkephalin A (PEA) antisense oligodeoxynucleotides respectively reduced and enhanced proliferation of rat splenocytes incubated with concanavalin A in vitro. Nonsense base sequences used as controls were without effect. Coincubation with the exogenous synthetic opioid peptides, ACTH, beta-endorphin, met-enkephalin or [D-ala,D-leu]-enkephalin did not significantly alter either the POMC or PEA antisense response, indicating potential differences in bioactivity of immunocyte opioid peptides compared with synthetic equivalents. Levels of the POMC opioid products, ACTH and beta-endorphin, were significantly reduced in splenocytes incubated with POMC antisense probes. These data provide evidence for functional effects of endogenous opioid peptides on rat splenocyte proliferation in vitro.

beta-Endorphin and natural killer cell cytolytic activity during prolonged exercise. is there a connection?

This study was designed to test whether a single 50-mg dose of the opioid antagonist naltrexone hydrochloride, ingested 60 min before 2 h of moderate-intensity exercise (i.e., 65% peak O2 consumption), influenced the exercise-induced augmentation of peripheral blood natural killer cell cytolytic activity (NKCA). Ten healthy male subjects were tested on four occasions separated by intervals of at least 14 days. A rested-state control trial was followed by three double-blind exercise trials [placebo (P), naltrexone (N), and indomethacin] arranged according to a random block design. The indomethacin exercise trial is discussed elsewhere (S. G. Rhind, G. A. Gannon, P. N. Shek, and R. J. Shepherd. Med. Sci. Sports Exerc. 30: S20, 1998). For both the P and N trials, plasma levels of beta-endorphin were increased (P < 0.05) at 90 and 120 min of exercise but returned to resting (preexercise) levels 2 h postexercise. CD3(-)CD16(+)CD56(+) NK cell counts and NKCA were significantly (P < 0.05) elevated at each 30-min interval of exercise compared with correspondingly timed resting control values. However, there were no differences in NK cell counts or NKCA between P and N trials at any time point during the two trials. Changes in NKCA reflected mainly changes in NK cell count (r = 0.72; P < 0.001). The results do not support the hypothesis that the enhancement of NKCA during prolonged submaximal aerobic exercise is mediated by beta-endorphin.

Effects of Acute Stress or Centrally Injected Interleukin-1beta on Neuropeptide Expression in the Immune System

Acute stress stimulates the expression and release of corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) from the hypothalamus, and the pro-opiomelanocortin products beta-endorphin and ACTH from the anterior pituitary. These neuropeptides are also expressed in immune tissues, and it has been proposed that they may modulate immune responses to stress through paracrine mechanisms. We subjected rats to restraint stress or central injection of interleukin (IL)-1beta to determine whether these acute stimuli can alter the expression of neuropeptides in the spleen and thymus. Restraint stress significantly increased the contents of all these neuropeptides in thymic, but not splenic, extracts. A single icv injection of IL-1beta increased contents of CRH, AVP, ACTH and beta-endorphin in the spleens of both sham-operated and adrenalectomised (ADX) rats. IL-1beta increased thymic contents of CRH and ACTH in sham-operated rats but these increases were not observed in ADX rats. These results suggest that the effects of IL-1beta on neuropeptide expression in the spleen are independent of glucocorticoids, whereas IL-1beta stimulation of neuropeptide expression in the thymus is dependent on circulating glucocorticoids. There were significant correlations between increases in CRH, ACTH and beta-endorphin in the spleen, and between CRH and ACTH in the thymus, consistent with the suggestion that IL-1beta-induced increases in ACTH and beta-endorphin may be mediated through CRH. These results provide evidence that stressors can directly influence neuropeptide expression in immune tissues. Thus stress may influence immune functions through paracrine mechanisms involving locally synthesised neuropeptides as well as through activation of the hypothalamo-pituitary-adrenal axis.

Retinoids and the control of growth/death decisions in human neuroblastoma cell lines

Cell proliferation, the balance between mitosis and apoptosis is the result of the continuous integration of a number of different signal transduction pathways stimulated in a cell at any given point in its life. Neuroblastoma cells regulate the switch between mitosis and death, according both to intrinsic factors and extrinsic factors, such as growth factor withdrawal and action of the vitamin A derivative, retinoic acid. In this review, we describe the balance of some factors regulating growth and death of human neuroblastoma cells in vitro. These dynamic studies are necessarily-performed on cell lines, which offer controlled conditions enabling the disection of the complex stimuli mediating survival and growth (IGF, trk, BDNF) and death (transglutaminase, free radicals, Bcl-2). Although the conclusions drawn may therefore not be directly applicable to tumour cells in vivo, the results herein discussed are of sufficient significance to warrant in vivo relevance.

Release of alpha-melanocyte-stimulating hormone from rat splenocytes in vitro is dependent on protein synthesis

The pro-opiomelanocortin (POMC) peptide product alpha-melanocyte-stimulating hormone (alpha-MSH) has a variety of anti-inflammatory effects within the immune system. Using an antiserum specific for alpha-MSH, we have now demonstrated for the first time that this peptide is secreted from splenocytes. Basal secretion of alpha-MSH from the spleen in vitro was some 300-fold less than that detected from the neurointermediate lobe. Secretion of alpha-MSH from the spleen was increased 5-fold in the presence of puromycin, indicating that splenocyte alpha-MSH secretion is under the regulation of a product of endogenous protein synthesis. ACTH and beta-endorphin were also released from splenocytes in vitro, but their release was not affected by incubation with puromycin. Secretion of the POMC peptides from splenocytes or NIL was not affected by corticosterone. These data show that the many anti-inflammatory effects within the immune system ascribed to alpha-MSH may actually be mediated through paracrine effects of immune alpha-MSH.

Effects of a chronic inflammatory stress on levels of pro-opiomelanocortin-derived peptides in the rat spleen and thymus

Adjuvant-induced arthritis (AA) in specific strains of rats is an immunologically mediated inflammatory disease which is also characterised by activation of the endocrine system. To further investigate the effects of AA on processing of the pro-opiomelanocortin (POMC) precursor in rat immune tissues, we utilised radioimmunoassays for adrenocorticotrophin (ACTH), beta-endorphin and alpha-melanocyte-stimulating hormone (alpha-MSH) to measure these peptides in the spleen and thymus. 14 days following adjuvant injection, spleen levels of ACTH were elevated in the AA group (4.47 +/- 1.04 ng/g tissue, n = 9) compared to controls (2.42 +/- 0.4 ng/g) and exacerbation of the disease by removal of circulating glucocorticoids through bilateral adrenalectomy (ADX) resulted in further elevation of spleen ACTH (5.11 +/- 1.22 ng/g). beta-Endorphin levels in both the AA (10.60 +/- 1.61 ng/g) and AA/ADX (13.37 +/- 2.36 ng/g) groups were higher than controls (5.57 +/- 0.65 ng/g). Conversely, alpha-MSH spleen levels were decreased in the AA (2.89 +/- 0.22 ng/g) and AA/ADX (2.22 +/- 0.33 ng/g) groups compared to controls (4.62 +/- 0.45 ng/g) and were also decreased following adrenalectomy. In the thymus, ACTH levels were elevated in the AA group (8.95 +/- 1.41 ng/g) compared to controls (5.79 +/- 0.63 ng/g), and the same pattern was evident for thymic alpha-MSH (0.64 +/- 0.08 ng/g in AA animals compared to control levels of 0.35 +/- 0.03 ng/g). Following G50 gel filtration, ACTH and beta-endorphin immunoreactivities (ir) were present in both spleen and thymus as two peaks, one which eluted near the void volume and one which eluted in a lower molecular mass position than the standards.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes of natural killer cells during acute psychological stress

Emotional stress is often followed by increased susceptibility to infections. One major role in the immediate immune response to infection is played by natural killer (NK) cells. This study was designed to establish whether acute psychological stress influences cellular immune functions and to elucidate the role of endocrine parameters as potent mediators of stress induced alterations of the immune system. Forty-five first-time tandem parachutists were examined continuously for their plasma concentrations of cortisol and catecholamines from 120 min before to 60 min after jumping. Lymphocyte subsets, NK activity, and ADCC were determined 2 hr before, immediately after, and 1 hr after jumping. There was a significant increase in sympathetic-adrenal hormones during (adrenaline, noradrenaline) and shortly after jumping (cortisol). Lymphocyte subsets and the functional capacity of NK cells revealed an increase immediately after jumping followed by a decrease significantly below starting values 1 hr later. These changes were significantly correlated to plasma concentrations of noradrenaline. Thus, quick mobilization of NK cells is suggested as one major mechanism for this effective adaptation of the immune system to stress situations.

Opioids, receptors, and immunity

The results achieved by those seeking to determine whether opioids and other drugs of abuse can affect immunity are quite astonishing given the short period of time that research has focused on this area. Despite the fact that there is no longer any question that opioids produce a variety of effects on the immune system, the extent and significance of these changes in the drug-abusing population remains to be determined. Whether or not the findings in mice and in in vitro preparations can be extrapolated to man is not yet known. Of major significance is the question of whether the endogenous opioid system is involved in immunoregulation. Given the multitude of drugs taken by drug abusers and the varying patterns of drug administration, the significance of the findings in the literature is still an open question. However, it is only by continuing studies such as those discussed at this meeting that we will find the answers.

Psychoneuroimmunological aspects of disease progression among women with human papillomavirus-associated cervical dysplasia and human immunodeficiency virus type 1 co-infection

OBJECTIVE

Psychosocial associations have been observed with level of cervical dysplasia or "pre-cancer" and invasive cervical cancer [related to human papillomavirus (HPV) infection]. Psychoneuroimmunological relationships have been observed in human immunodeficiency virus type 1 (HIV-1) infection, which is being described in an increasing number of women. Our objective was to review these relationships regarding effects that might be expected in HIV-1 and HPV co-infected women.

METHOD

This review was based on a Medline literature search supplemented by a manual search of selected journals unrepresented in that database.

RESULTS

Relationships of psychosocial factors and level of cervical dysplasia were similarly observed with reference to immunological and health status in asymptomatic and early symptomatic HIV-1 infected homosexual men, suggesting that a potentiating effect may occur in HIV-1 and HPV co-infected women. Consistency of relationships across studies appeared to be enhanced by the use of a biopsychosocial model integrating the effects of life stressors, social support and coping style as well as psychiatric disorders.

CONCLUSIONS

Research is indicated on the relationships between psychosocial factors, immunological status and clinical health status in this group of women. Because of the high prevalence of psychosocial risk factors for chronic psychological distress in these women and the known immunological and health status decrements occurring with progression of these two infections, a clinical screening program based on the biopsychosocial model is recommended as a means of secondary prevention. If effective in generating treatment referrals, such a program would likely improve quality of life and could aid in the determination of relationships with immunological and health status as well.

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.

Beta-endorphin and related peptides suppress phorbol myristate acetate-induced respiratory burst in human polymorphonuclear leukocytes

In the present study, the immunomodulatory effect of beta-endorphin (beta-E) and shorter pro-opiomelanocortin (POMC) fragments was evaluated by assessing their influence on respiratory burst in human polymorphonuclear leukocytes (PMN). The effect of the peptides (10(-17)M - 10(-10)M) on phorbol myristate acetate (PMA)-stimulated production of reactive oxygen metabolites was measured in a lucigenin-enhanced chemiluminescence (CL) assay. Both POMC peptides with opiate-like activity (i.e. alpha-endorphin (alpha-E), beta-E and gamma-endorphin (gamma-E] and their non-opioid derivatives (i.e. des-TYR1-beta-endorphin (dT beta E), des-TYR1-gamma-endorphin (dT gamma E), and des-ENK-gamma-endorphin (dE gamma E] were tested. With the exception of alpha-E, PMA-stimulated respiratory burst was suppressed by all POMC fragments tested. A U-shaped dose-response relation was observed. Doses lower than 10(-17)M and higher than 10(-8)M were without effect. beta-E and dT beta E both suppressed PMA-induced oxidative burst in human PMN at physiological concentrations (10(-16)M - 10(-10)M). gamma-E and dT gamma E proved to be less potent inhibitors, reaching maximal effect at higher concentrations (10(-12)M - 10(-10)M). DE gamma E exerted an even less pronounced but still significant suppressive effect at the concentration of 10(-10)M. None of the endorphins tested was shown to affect resting oxidative metabolism in the PMN. The modulatory effects of the opioid peptides could not be blocked by the opioid antagonist naloxone (10(-8)M). These data show that fragments derived from the POMC-precursor molecule modulate the activation of PMN by suppressing PMA-stimulated oxidative metabolism and that this activity does not involve a classical opiate-like receptor.

Biology of natural killer cells

Studies of cytotoxicity by human lymphocytes revealed not only that both allogeneic and syngeneic tumor cells were lysed in a non-MHC-restricted fashion, but also that lymphocytes from normal donors were often cytotoxic. Lymphocytes from any healthy donor, as well as peripheral blood and spleen lymphocytes from several experimental animals, in the absence of known or deliberate sensitization, were found to be spontaneously cytotoxic in vitro for some normal fresh cells, most cultured cell lines, immature hematopoietic cells, and tumor cells. This type of nonadaptive, non-MHC-restricted cellmediated cytotoxicity was defined as “natural” cytotoxicity, and the effector cells mediating natural cytotoxicity were functionally defined as natural killer (NK) cells. The existence of NK cells has prompted a reinterpretation of both the studies of specific cytotoxicity against spontaneous human tumors and the theory of immune surveillance, at least in its most restrictive interpretation. Unlike cytotoxic T cells, NK cells cannot be demonstrated to have clonally distributed specificity, restriction for MHC products at the target cell surface, or immunological memory. NK cells cannot yet be formally assigned to a single lineage based on the definitive identification of a stem cell, a distinct anatomical location of maturation, or unique genotypic rearrangements.

Psychoneuroimmunology for the psychoneuroendocrinologist: a review of animal studies of nervous system-immune system interactions

Evidence for interactions between the nervous and immune systems arises from a number of experimental observations: the behavioral conditioning of immune responses, the effects of stimulation or lesion of brain sites on immune system function, the effects of stressors on immune responses and tumor growth, and physiological and neurochemical changes in the brain during immune responses. The links between the nervous and immune systems probably include glucocorticoids secreted from the adrenal gland, catecholamines and neuropeptides secreted by sympathetic terminals and the adrenal medulla, certain pituitary and gonadal hormones, and polypeptides produced by cells of the immune system. The effect of glucocorticoids is not exclusively immunosuppressive, nor is it adequate to explain all the effects of stress. The effects of opiates on immune function are complex; in vitro, endogenous opiates most often facilitate immune activity, but in vivo, opiates appear to inhibit immune responses and impair tumor rejection. The in vitro effects are rarely prevented by naloxone pretreatment and appear to require the integrity of the C- rather than the N-terminal of beta-endorphin, suggesting a nonopiate character. Infections or the administration of antigens increase circulating concentrations of glucocorticoids and activate cerebral catecholaminergic metabolism, especially in the hypothalamus. These responses suggest that challenges to the immune system are physiologic stressors. Interleukin-1 (IL-1) produced by immune cells may be the mediator of these effects, thus acting as an "immunoneurotransmitter". The cerebral responses suggest that the brain can monitor the progress of immune responses. IL-1 and the glucocorticoids together may form a regulatory feedback mechanism for immune responses.

Effect of neuropeptides and monoamines on lymphocyte activation

Neuropeptides and monoamines have been found in tissues where immune reactions are initiated such as the skin, gut, and respiratory tract, and in these tissues neuropeptides and monoamines might be involved in the regulation of lymphocyte activation. Studies both in in vitro and in vivo showing that various neuropeptides and monoamines may influence reactions such as T lymphocyte proliferation, B lymphocyte proliferation, and antibody synthesis, lymphocyte migration, and cytotoxicity will be reviewed.