Morphine synergizes with lipopolysaccharide in a chronic endotoxemia model

Involvement of activator protein-1 in transcriptional regulation of the human mu-opioid receptor gene

mu-Opioid receptors mediate such opioid effects as analgesia, euphoria, and immunomodulation. Gene expression of mu-opioid receptors can be modulated by various substances, including cytokines, hormones, and drugs. Some of these stimuli (e.g., IL-1beta and cocaine) have been shown to activate members of the AP-1 transcription factor family. In addition, transcription of the mu-opioid receptor gene is induced by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C, which in turn is an activator of AP-1 transcription factors. This indicates that signaling pathways involving protein kinase C and activator protein 1 (AP-1) transcription factors are important for the specific expression pattern of the mu-opioid receptor gene. In this report, we show that TPA activates AP-1 as well as the transcription factor nuclear factor kappaB (NFkappaB) in the mu-opioid receptor expressing neuroblastoma cell line SH SY5Y. In transfection experiments performed in these cells, both factors trans-activate expression of reporter gene constructs containing the human mu-opioid receptor gene promoter. By excluding the effects of TPA on NFkappaB with the specific NFkappaB inhibitor sulfasalazine, AP-1 regulatory elements were localized. Two AP-1 elements, which differ in one nucleotide each from the classic AP-1 binding site, were delineated to positions -2388 and -1434 of the promoter. Independent of their orientation, these elements conferred TPA responsiveness on the heterologous thymidine kinase promoter. AP-1 binding to these elements was confirmed using electrophoretic mobility shift and immunoshift assays.

Increased production of inflammatory cytokines in patients with silent myocardial ischemia

OBJECTIVES

The aim of the study was to examine the inflammatory cytokines in patients with myocardial ischemia to evaluate whether silent ischemia patients exhibit any particular cytokine pattern.

BACKGROUND

Silent myocardial ischemia is frequently observed in patients with coronary artery disease. Various endogenous mechanisms control a patient's perceived intensity of pain. Among them, the inflammatory process and the related cytokine production are known to modulate the threshold for activating the primary afferent nociceptors.

METHODS

Seventy-eight patients with reproducible exercise-induced myocardial ischemia were studied: 34 symptomatic patients, with rest and/or stress angina; 44 asymptomatic patients, with no symptoms during daily life activities or during positive exercise stress test. Venous blood samples were taken from all patients to evaluate the expression of CD11b receptors both on neutrophils and monocytes. Frozen plasma samples (at -80 degrees C) were used to quantify the anti-inflammatory (interleukin-4 and -10, transforming growth factor-beta) and the proinflammatory cytokines (tumor necrosis factor-alpha, interferon-gamma, interleukin-1beta and -6).

RESULTS

In asymptomatic patients lower CD11b receptor expression and higher concentration of anti-inflammatory cytokines were observed. Proinflammatory cytokine production was similar in the two groups.

CONCLUSIONS

The data suggest that an "anti-inflammatory pattern" of cytokine production correlates with silent ischemia and that the immune and inflammatory system activation may be crucial for angina symptoms.

Regulation of mu-opioid receptor gene transcription by interleukin-4 and influence of an allelic variation within a STAT6 transcription factor binding site

Morphine and the endogenous opioid peptide beta-endorphin exert neuromodulatory as well as immunomodulatory effects, which are transduced by mu-opioid receptors. In this report we show that stimulation with interleukin-4 induces mu-opioid receptor transcripts in human primary blood cells (T cells and polymorphonuclear leukocytes), immune cell lines (Raji, U-937, and HMEC-1), and dendritic cells. In nonstimulated immune cells this gene is silent. In addition, mu receptor transcription is up-regulated by interleukin-4 in cultures of primary rat neurons. Transient transfection experiments in Raji and SH SY5Y neuronal cells with human and rat reporter gene constructs linked the interleukin-4 effect directly to cis-active mu receptor promoter elements located at nucleotide -997 on the human gene and nucleotide -727 on the rat gene. The interleukin-4 response elements function orientation independently. They bind STAT6 transcription factors as shown by electrophoretic mobility shift assays. In the human gene, a single nucleotide polymorphism within the interleukin-4 response element reduces the trans-activating potential of this element by 50%, which may affect the phenotype of persons carrying this variation. These findings provide a molecular basis for understanding bidirectional interactions between the opioid system and the immune system.

Morphine directs T cells toward T(H2) differentiation

BACKGROUND

Failure of cell-mediated immunity is thought to increase the morbidity and mortality rates after trauma and major surgical procedures and to be the result, in part, of a redirection of CD4(+) T cells toward T(H2) differentiation. We tested the hypothesis that morphine treatment after injury promotes T(H2) differentiation of precursor T cells through the mu-opioid receptor.

METHODS

Human peripheral blood mononuclear cells (PBMCs) or splenocytes from either wild type or mu-opioid receptor knock-out mice were treated in vitro with either vehicle or morphine and then stimulated with anti-CD3/anti-CD28. The supernatant was assayed for T(H1) (interleukin-2 [IL-2], interferon gamma [IFN gamma]) and T(H2) (IL-4, IL-5) cytokines (enzyme-linked immunosorbent assay). Morphine regulation of IL-4 transcription was investigated in PBMCs (IL-4 messenger RNA, nuclear factor of activated T-cells) and Jurkat T cells transfected with a murine IL-4 promoter-luciferase construct. Morphine-induced nuclear factor of activated T-cell (NFAT) binding was assayed with the electromobility shift assay in Jurkat T cells.

RESULTS

Morphine treatment of PBMCs decreases IL-2 and IFN gamma and increases IL-4 and IL-5 as a function of morphine concentration. Morphine treatment in wild type splenocytes inhibited IFN gamma and stimulated IL-4 protein synthesis. Changes in cytokine synthesis were abolished in mu-opioid receptor knockout mice. Morphine treatment increases IL-4 messenger RNA accumulation in PBMCs and increases IL-4 promoter activity in Jurkat T cells. Morphine increases NFAT nuclear protein binding to an NFAT DNA response element.

CONCLUSIONS

We conclude that morphine treatment promotes T(H2) differentiation through a mu-opioid receptor mechanism and that morphine treatment increases IL-4 transcription, in part, through an NFAT mechanism.

CD8(+) T cells express a T-helper 1--like phenotype after burn injury

BACKGROUND

Previous studies suggest that CD8(+) T cells are immunosuppressive after burn injury, but recent reports indicate that CD8(+) T cells have several functions similar to CD4(+) T cells, including the secretion of cytokines. This study uses HY male antigen in transgenic HY female mice to determine the antigen-specific response of activated CD8(+) T cells after burn injury.

METHODS

HY TCR transgenic female mice underwent burn or sham injury. Seventy-two hours after the burn, splenocytes were stimulated with 20 micromol/L HY peptide for 16, 48, and 64 hours; cellular proliferation, intracellular interferon-gamma and interleukin-2, and apoptosis were measured.

RESULTS

Burn injury significantly impaired proliferation to HY antigen (P < or =.05). Activated CD8(+) T cells from burned mice showed increased intracellular interferon-gamma and interleukin-2 16 hours after stimulation compared with sham (P < or =.05) and at no time was less than control mice. The percent of CD8(+) T cells decreased with the time of stimulation but was not due to apoptosis by Annexin V staining.

CONCLUSIONS

Activated CD8(+) T cells express a T(h1)-like phenotype after burn injury. This provides evidence that CD8(+) T cells are not simply suppressive and that is consistent with data that CD4(+) T cells are primed for a T(h1) response after burn injury.

Effect of central and peripheral administration of a nitric oxide synthase inhibitor on morphine hyperthermia in rats

The effect of central and peripheral administration of a nitric oxide synthase inhibitor, N-nitro-L-arginine methyl ester (L-NAME), on morphine hyperthermia was studied in male Sprague-Dawley rats. The first series of experiments examined the effect of subcutaneous (s.c.) administration of L-NAME on the hyperthermia induced by morphine given s.c. in doses of 4 and 15 mg/kg. L-NAME, at a s.c. dose of 50 mg/kg, per se, had no influence on body temperature (T(b)). Coadministration of L-NAME (50 mg/kg, s.c.) with the higher dose of morphine (15 mg/kg, s.c.) caused a significant suppression of morphine hyperthermia during the first 30 min and then produced hypothermia. In contrast, s.c. injection of L-NAME (50 mg/kg, s.c.) failed to alter the hyperthermic response induced by the lower dose of morphine (4 mg/kg). In the second series of experiments, we investigated the effect of intracerebroventricular (i.c.v.) administration of L-NAME on the hyperthermia induced by morphine given s.c. L-NAME, itself, given i.c.v. at a dose of 1 mg did not evoke any change in T(b). Intracerebroventricular administration of L-NAME (1 mg) blocked the hyperthermia induced by 15 mg/kg morphine during the first 30 min and induced a slight hypothermia but did not alter the hyperthermia induced by 4 mg/kg morphine. The results indicate that either central or peripheral NO synthesis is required for the production of hyperthermia induced by 15 mg/kg of morphine. However, NO synthesis does not seem to be involved in the hyperthermic process induced by 4 mg/kg of morphine.