Increased splenocyte proliferative response and cytokine production in beta-endorphin-deficient mice

Mechanisms Underlining Inflammatory Pain Sensitivity in Mice Selected for High and Low Stress-Induced Analgesia-The Role of Endocannabinoids and Microglia

In this work we strived to determine whether endocannabinoid system activity could account for the differences in acute inflammatory pain sensitivity in mouse lines selected for high (HA) and low (LA) swim-stress-induced analgesia (SSIA). Mice received intraplantar injections of 5% formalin and the intensity of nocifensive behaviours was scored. To assess the contribution of the endocannabinoid system, mice were intraperitoneally (i.p.) injected with rimonabant (0.3–3 mg/kg) prior to formalin. Minocycline (45 and 100 mg/kg, i.p.) was administered to investigate microglial activation. The possible involvement of the endogenous opioid system was investigated with naloxone (1 mg/kg, i.p.). Cannabinoid receptor types 1 and 2 (Cnr1, Cnr2) and opioid receptor subtype (Oprm1, Oprd1, Oprk1) mRNA levels were quantified by qPCR in the structures of the central nociceptive circuit. Levels of anandamide (AEA) and 2-arachidonoylglycerol (2-AG) were measured by liquid chromatography coupled with the mass spectrometry method (LC-MS/MS). In the interphase, higher pain thresholds in the HA mice correlated with increased spinal anandamide and 2-AG release and higher Cnr1 transcription. Downregulation of Oprd1 and Oprm1 mRNA was noted in HA and LA mice, respectively, however no differences in naloxone sensitivity were observed in either line. As opposed to the LA mice, inflammatory pain sensitivity in the HA mice in the tonic phase was attributed to enhanced microglial activation, as evidenced by enhanced Aif1 and Il-1β mRNA levels. To conclude, Cnr1 inhibitory signaling is one mechanism responsible for decreased pain sensitivity in HA mice in the interphase, while increased microglial activation corresponds to decreased pain thresholds in the tonic inflammatory phase.

Pathogenesis of psoriasis in the "omic" era. Part I. Epidemiology, clinical manifestation, immunological and neuroendocrine disturbances

Psoriasis is a common, chronic, inflammatory, immune-mediated skin disease affecting about 2% of the world's population. According to current knowledge, psoriasis is a complex disease that involves various genes and environmental factors, such as stress, injuries, infections and certain medications. The chronic inflammation of psoriasis lesions develops upon epidermal infiltration, activation, and expansion of type 1 and type 17 Th cells. Despite the enormous progress in understanding the mechanisms that cause psoriasis, the target cells and antigens that drive pathogenic T cell responses in psoriatic lesions are still unproven and the autoimmune basis of psoriasis still remains hypothetical. However, since the identification of the Th17 cell subset, the IL-23/Th17 immune axis has been considered a key driver of psoriatic inflammation, which has led to the development of biologic agents that target crucial elements of this pathway. Here we present the current understanding of various aspects in psoriasis pathogenesis.

Affinity Purification of Neuropeptide Precursors from Mice Lacking Carboxypeptidase E Activity

Peptidomic techniques are powerful tools to identify peptides in a biological sample. This protocol describes a targeted peptidomic approach that uses affinity chromatography to purify peptides that are substrates of carboxypeptidase E (CPE), an enzyme present in the secretory pathway of neuroendocrine cells. Many CPE products function as neuropeptides and/or peptide hormones, and therefore represent an important subset of the peptidome. Because CPE removes C-terminal Lys and Arg residues from peptide-processing intermediates, organisms lacking CPE show a large decrease in the levels of the mature forms of most neuropeptides and peptide hormones, and a very large increase in the levels of the processing intermediates that contain C-terminal Lys and/or Arg (i.e., the CPE substrates). These CPE substrates can be purified on an anhydrotrypsin-agarose affinity resin, which specifically binds peptides with C-terminal basic residues. Not all peptides with basic C-terminal residues within a cell are CPE substrates, and these other peptides will also be purified on the anhydrotrypsin affinity column. However, a comparison of peptides purified from wild-type mice and from mice lacking CPE allows for the rapid identification of CPE substrates based on their large increase in the absence of CPE.

Effects of β-endorphin on the production of reactive oxygen species, IL-1β, Tnf-Α, and IL-10 by murine peritoneal macrophages in vivo

It has been demonstrated that β-endorphin stimulates the zymosan-induced secretion of reactive oxygen species and suppresses the spontaneous production of IL-1β and IL-10 by murine peritoneal macrophages in vivo.

Endogenous opioid peptides in regulation of innate immunity cell functions

Endogenous opioid peptides comprise a group of bioregulatory factors involved in regulation of functional activity of various physiological systems of an organism. One of most important functions of endogenous opioids is their involvement in the interaction between cells of the nervous and immune systems. Summary data on the effects of opioid peptides on regulation of functions of innate immunity cells are presented.

Nonopioid effect of β-endorphin

This review presents the generalized literature data and the results of our own research of the nonopioid effect of β-endorphin, an opioid neuropeptide interacting not only with opioid but also with nonopioid (insensitive to the opioid antagonist naloxone) receptors. The roles of the hormone and its receptors in regulation of the immune, nervous, and endocrine systems are discussed. The effect of neuromediator on the immune system mediated by both opioid and nonopioid receptors is considered in detail. The data on distribution and function of the nonopioid β-endorphin receptor in human and animal organisms are presented. All available data on the characteristics of the nonopioid β-endorphin receptor obtained by means of radioligand analysis are given. The discussed information is supposed to extend our conceptions of the role of β-endorphin in mammals and to be of extensive use in medicine and pharmacology.

Inhibition of cartilage damage by pro-opiomelanocortin prohormone overexpression in a rat model of osteoarthritis

Pro-opiomelanocortin (POMC) is a precursor of various neuropeptides. POMC-derived neuropeptides are potent inflammation inhibitors and immunosuppressants. Evidence that osteoarthritis (OA) is an inflammatory disease is accumulating. We assessed whether intra-articular gene delivery of POMC ameliorates experimentally induced OA in a rat model. OA was induced in Wistar rats by anterior cruciate ligament-transection (ACLT) in the knee of one hind limb. Adenoviral vector encoding human POMC (AdPOMC) was injected intra-articularly into the knee joints after ACLT. The transgene expression and the inflammatory responses were evaluated using immunoblotting, immunohistochemistry and enzyme-linked immunosorbent assay. The treated joints were assessed histologically for manifestations of the disease. Human POMC was expressed in the chondrocytes and synovial membrane after the intra-articular injection. POMC gene transfer reduced nuclear factor- κB activity and the levels of interleukin-1 β in HTB-94 chondrosarcoma cells and Raw 264.7 macrophages; it also reduced microvessel density in the synovium. Histological examination showed that symptoms of OA in AdPOMC-treated rats were less severe than in rats treated with either empty adenoviral vector (AdNull) or normal saline. Intra-articular injection of adenoviral vectors expressing POMC significantly suppressed the progression and severity of OA, and reduced inflammatory responses and angiogenesis. POMC gene delivery may offer novel therapeutic approach for treating OA.

Endogenous μ-opioid peptides modulate immune response towards malignant melanoma

Opioids exert major effects not only in the central nervous system but also in immune responses. We investigated the effects of μ-opioid peptides, secreted by tumor cells, on anti-tumor immune responses. For this purpose, tumor growth was studied in wild-type and μ-opioid receptor-deficient (MOR-/-) mice injected with B16 melanoma cells. The ability of these cells to produce opioids was studied by Western blots in vitro. Finally, biopsy material from human melanomas was investigated by immunohistochemistry for ß endorphin expression. Injection of B16 melanoma cells, producing endogenous ß endorphin, in the flank of MOR-/- mice revealed a profound reduction in tumor growth, paralleled by a significantly higher infiltration of immune cells into the tumors, when compared to tumor growth after injection of B16 melanoma cells into wild-type mice. Opioids present in B16 cell supernatant significantly reduced the proliferation of normal but not MOR-/- leucocytes. Immunohistochemical analyses of biopsies from human melanoma tissues showed a positive correlation between expression of ß endorphin and tumor progression. Our data provide evidence that μ-opioid peptides may play a major role in cancer progression by modulating immune response. This finding may have implications for the future optimization of immunointerventions for cancer.

Immunology, signal transduction, and behavior in hypothalamic-pituitary-adrenal axis-related genetic mouse models

A classical view of the neuroendocrine-immune network assumes bidirectional interactions where pro-inflammatory cytokines influence hypothalamic-pituitary-adrenal (HPA) axis-derived hormones that subsequently affect cytokines in a permanently servo-controlled circle. Nevertheless, this picture has been continuously evolving over the last years as a result of the discovery of redundant expression and extended functions of many of the molecules implicated. Thus, cytokines are not only expressed in cells of the immune system but also in the central nervous system, and many hormones present at hypothalamic-pituitary level are also functionally expressed in the brain as well as in other peripheral organs, including immune cells. Because of this intermingled network of molecules redundantly expressed, the elucidation of the unique roles of HPA axis-related molecules at every level of complexity is one of the major challenges in the field. Genetic engineering in the mouse offers the most convincing method for dissecting in vivo the specific roles of distinct molecules acting in complex networks. Thus, various immunological, behavioral, and signal transduction studies performed with different HPA axis-related mutant mouse lines to delineate the roles of beta-endorphin, the type 1 receptor of corticotropin-releasing hormone (CRHR1), and its ligand CRH will be discussed here.

Association of catastrophizing with interleukin-6 responses to acute pain

Catastrophizing exerts its deleterious effects on pain via multiple pathways, and some researchers have reported that high levels of catastrophizing are associated with enhanced physiological reactivity to painful stimulation. In this project, 42 generally healthy adults underwent a series of psychophysical pain testing procedures assessing responses to noxious mechanical, heat, and cold stimuli. Pain catastrophizing cognitions were assessed prior to and then immediately after the various pain induction procedures. Blood samples were taken at baseline and then at several time points from the end of the procedures to 1h post-testing. Samples were assayed for serum levels of cortisol and interleukin-6 (IL-6). Both cortisol and IL-6 increased from baseline during the post-testing period (p's<.05), with cortisol returning to baseline by 1h post-testing and IL-6 remaining elevated. Pain catastrophizing, measured immediately after the pain procedures, was unrelated to cortisol reactivity, but was strongly related to IL-6 reactivity (p<.01), with higher levels of catastrophizing predicting greater IL-6 reactivity. In multivariate analyses, the relationship between catastrophizing and IL-6 reactivity was independent of pain ratings. Collectively, these findings suggest that cognitive and emotional responses during the experience of pain can shape pro-inflammatory immune system responses to noxious stimulation. This pathway may represent one important mechanism by which catastrophizing and other psychosocial factors shape the experience of both acute and chronic pain in a variety of settings.

Naloxone, an opioid receptor antagonist, enhances induction of protective immunity against HSV-1 infection in BALB/c mice

The immunomodulatory effects of exogenous opioids on induction of acquired immunity during microbial infection are now well known; however, our knowledge about the relationship between endogenous opioid response and microbial infections is rudimentary. Here, we report the effect of administration of Naloxone (NLX), an opioid receptor antagonist, on induction of acquired immunity during primary herpes simplex virus type 1 (HSV-1) infection. BALB/c mice received NLX, twice daily, 2 h before infection with HSV-1 until 7 days after infection. Cell-mediated immunity was assessed by evaluating lymphocyte proliferation, interferon-gamma (IFN-gamma) production, delayed type hypersensitivity (DTH) and mortality rate after acute HSV-1 challenge. The findings showed that a higher level of cell-mediated immunity was induced in the NLX-treated animals compared to the control group after induction of HSV-1 infection. However, the data indicate similar neutralizing antibody production in NLX-treated animals and control animals. This observation and further studies in this field may lead to the use of NLX as an adjuvant for designing microbial vaccines and adjunctive therapy of viral infections.

Battle of animal models

This is a brief summary of the animal models session held during the 12th Annual Meeting of the Society on NeuroImmune Pharmacology, Santa Fe, NM, USA. This session provided important information for participants on availability and utility of animal models for the studies of HIV-1 central nervous system infection and drug abuse. It highlighted animal model relevance to human disease/condition, its utility for the studies of pathogenesis, potential importance for the development of therapeutics, and demonstrated limitations/pitfalls.

Gene transfer of pro-opiomelanocortin prohormone suppressed the growth and metastasis of melanoma: involvement of alpha-melanocyte-stimulating hormone-mediated inhibition of the nuclear factor kappaB/cyclooxygenase-2 pathway

Pro-opiomelanocortin (POMC) is a prohormone of various neuropeptides, including corticotropin, alpha-melanocyte-stimulating hormone (alpha-MSH), and beta-endorphin (beta-EP). POMC neuropeptides are potent inflammation inhibitors and immunosuppressants and may exert opposite influences during tumorigenesis. However, the role of POMC expression in carcinogenesis remains elusive. We evaluated the antineoplastic potential of POMC gene delivery in a syngenic B16-F10 melanoma model. Adenovirus-mediated POMC gene delivery in B16-F10 cells increased the release of POMC neuropeptides in cultured media, which differentially regulated the secretion of pro- and anti-inflammatory cytokines in lymphocytes. POMC gene transfer significantly reduced the anchorage-independent growth of melanoma cells. Moreover, pre- or post-treatment with POMC gene delivery effectively retarded the melanoma growth in mice. Intravenous injection of POMC-transduced B16-F10 cells resulted in reduced foci formation in lung by 60 to 70% of control. The reduced metastasis of POMC-transduced B16-F10 cells could be attributed to their attenuated migratory and adhesive capabilities. POMC gene delivery reduced the cyclooxygenase-2 (COX-2) expression and prostaglandin (PG) E(2) synthesis in melanoma cells and tumor tissues. In addition, application of NS-398, a selective COX-2 inhibitor, mimicked the antineoplastic functions of POMC gene transfer in melanoma. The POMC-mediated COX-2 down-regulation was correlated with its inhibition of nuclear factor kappaB (NFkappaB) activities. Exogenous supply of alpha-MSH inhibited NFkappaB activities, whereas application of the alpha-MSH antagonist growth hormone-releasing peptide-6 (GHRP-6) abolished the POMC-induced inhibition of NFkappaB activities and melanoma growth in mice. In summary, POMC gene delivery suppresses melanoma via alpha-MSH-induced inhibition of NFkappaB/COX-2 pathway, thereby constituting a novel therapy for melanoma.

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

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

Chronic psychosocial stress-induced down-regulation of immunity depends upon individual factors

The effect of chronic stress on immune functions is strongly biased by individual factors. Mice were subjected to a new model of chronic psychosocial stress in which four different subcategories of stressed animals may be identified: Resident Dominants (RD), Resident Subordinates (RS), Intruder Dominants (InD), and Intruder Subordinates (InS). After 7 days of stress, mice were immunized with keyhole limpet hemocyanine (KLH). Their immune functions were investigated 14 days later with stress continuing trough. Importantly, RS mice, which are mice losing territory ownership, were the more affected, having lower IgG, proliferation, and IL-2. RD and InD showed lower IgG while InS showed no immune alteration. In conclusion, loss of resources could be a key factor in determining individual vulnerability to stressful events.

Endogenous opiates and behavior: 2002

This paper is the twenty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2002 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Enhanced humoral response in kappa-opioid receptor knockout mice

Opiates are major analgesics and addictive drugs described also as immunomodulators. Here, we investigated the contribution of kappa-opioid receptor (KOR) activity in immunity in vivo by studying immune responses in KOR knockout mice. These animals displayed a modest reduction in thymus cellularity and CD4(+) cell ratio, parallel to a slight increase in immature CD4(+)CD8(+) lymphocytes. In spleen, KOR null animals showed augmented cell number with no change in cell distribution. T and B lymphocyte proliferative capabilities in vitro, Natural Killer activity and steady-state Ig levels were unchanged in KOR-/- mice. We immunized the mice with the antigen keyhole limpet hemocyanin (KLH). Compared to wild-type (WT) mice, KOR-/- animals produced significant higher levels of antigen-specific total Ig, IgM, IgG1 and IgG2a antibodies. This enhancement of humoral activity was not observed in mu-opioid receptor and delta-opioid receptor knockout animals. These results show that endogenous activation of kappa-opioid receptors may exert a tonic inhibition of antibody (Ab) response.