Morphine modulates lymph node-derived T lymphocyte function: role of caspase-3, -8, and nitric oxide.

The major objective of this paper is to characterize the mechanism by which morphine modulates lymphocyte function and if these effects are mediated through the mu-opioid receptor. We evaluated the in vitro effects of morphine on lymphocytes that were freshly isolated from lymph nodes from wild type (WT) and mu-opioid receptor knock-out (MORKO) mice. Results show that morphine inhibits Con A-induced lymph node T-cell proliferation and IL-2 and IFN-gamma synthesis in a dose-dependent manner. This effect was abolished in lymph node cells isolated from MORKO mice. The inhibition of T-cell function with low-dose morphine was associated with an increase in caspase-3- and caspase-8-mediated apoptosis. The inhibition of T-cell function with high-dose morphine was associated with an increase in the inducible NO synthase mRNA expression. N(G)-nitro-L-arginine methyl ester (L-NAME) antagonized the apoptosis induced by high-dose morphine. Our results suggest that low-dose morphine, through the mu-opioid receptor, can induce lymph node lymphocyte apoptosis through the cleavage activity of caspase-3 and caspase-8. Morphine at high doses induces NO release. This effect of morphine is also mediated through the mu-opioid receptor present on the surface of macrophages.

Morphine synergizes with lipopolysaccharide in a chronic endotoxemia model.

Emergent or elective surgical procedures may be complicated by sepsis, resulting in critical illness that can lead to organ failure and death. The opioid drug, morphine is widely used to alleviate pain in post-surgical patients; however, it is well documented that chronic treatment of mice with morphine affects the proliferation, differentiation and function of immune cells. Thus, morphine might be expected to exacerbate the effects of sepsis, which also compromises the immune system. To test this notion, we investigated the effect on several immune functions of a clinical dose of morphine (4 mg/kg) superimposed upon a lipopolysaccharide (LPS)-induced infection model. Our results show that this relatively low dose of morphine, though generally having no effects on immune parameters by itself, significantly augmented LPS responses. A clinical dose of morphine (4 mg/kg body weight) superimposed upon an animal model of sepsis resulted in a significant increase in mortality at 48 h. In the absence of the drug, most septic animals died after 96 h. Phenotypic responses such as, decreased thymic cellularity, compromised mitogenic response and inhibition of IL-2 synthesis that are evident at 48-72 h after LPS injection appear as early as 24 h in animals that receive morphine in addition to LPS. In addition, our results show that in T cells there is a shift from TH1 type cytokine elaboration to a TH2 type cytokine elaboration in animals that receive both LPS and morphine.

MU-opioid receptor-knockout mice: role of mu-opioid receptor in morphine mediated immune functions.

The role of the mu-opioid receptor in immune function was investigated using mu-opioid receptor knockout mice (MOR-KO). Morphine modulation of several immune functions, including macrophage phagocytosis and macrophage secretion of TNF-alpha, was not observed in the MOR-KO animals, suggesting that these functions are mediated by the classical mu-opioid receptor. In contrast, morphine reduction of splenic and thymic cell number and mitogen-induced proliferation were unaffected in MOR-KO mice, as was morphine inhibition of IL-1 and IL-6 secretion by macrophages. These latter results are consistent with morphine action on a naloxone insensitive morphine receptor, a conclusion supported by previous studies characterizing a nonopioid morphine binding site on immune cells. Alternatively, morphine may act either directly or indirectly on these cells, by a mechanism mediated by either delta or kappa opioid receptors.

The Ca2+ second messenger system and interleukin-1-alpha modulation of hepatic gene transcription and mitochondrial fat oxidation.

Cytokines have been implicated in the modulation of fat metabolism after sepsis. Carnitine palmitoyltransferase (CPT), the regulatory enzyme of hepatic mitochondrial long-chain fatty-acid oxidation, is involved in the control of hepatic fat oxidation in sepsis. Using either H4IIe rat hepatoma cells or rat hepatocytes in primary culture, we tested the hypothesis that interleukin-1-alpha (IL-1 alpha) would modulate CPT transcription (CPT mRNA), CPT translation (35S-methionine CPT protein incorporation), and hepatic mitochondrial oxidation of 1-Carbon 14-labeled (14C) palmitate to ketone bodies (acid soluble products). We showed that IL-1 alpha significantly increased CPT mRNA, 35S-methionine incorporation CPT protein, and hepatic mitochondrial oxidation of 1-14C-palmitate to acid soluble products. We further hypothesized that the Ca2+ second messenger system may play a role in the IL-1 alpha induction of hepatic CPT gene transcription. We showed that either calcium ionophore (A23187) or phorbol myristate acetate increased CPT gene transcription and that either calcium chelation, protein kinase C inhibition (acridine orange), or chronic exposure to phorbol myristate acetate significantly inhibited IL-1 alpha induction of CPT mRNA. We conclude that the IL-1 alpha increases in hepatic mitochondrial fatty-acid oxidation may be, in part, secondary to increased CPT gene transcription and translation and that the Ca2+ second messenger system may play an important role in IL-1 alpha induction of CPT gene transcription.

Interleukin-4 regulates macrophage interleukin-12 protein synthesis through a c-fos mediated mechanism.

BACKGROUND: Interleukin-4 (IL-4) treatment after lipopolysaccharide (LPS) induction inhibits macrophage (Mphi) IL-12 synthesis; however, IL-4 pretreatment (PreTx) primes the Mphi for increased LPS-induced IL-12 production. In this study we study the role of c-fos in the IL-4 priming of Mphi IL-12 synthesis. METHODS: With a murine in vitro peritoneal M phi model, we studied the effect of either c-fos deficiency (wild type, WT; homozygous c-fos knockout, Homo KO) or c-fos overexpression to study the role of c-fos in IL-4 priming of LPS-induced M phi IL-12 synthesis. RESULTS: (1) We first show that IL-4 PreTx results in a 72% decrease in Mphi c-fos mRNA compared with vehicle PreTx. (2) With respect to IL-12 p70 protein, IL-4 PreTx in the WT group increased LPS-induced Mphi IL-12 p70 2.2-fold compared with vehicle PreTx. Compared with vehicle PreTx in the WT group, vehicle PreTx in the Homo KO group followed by LPS stimulation resulted in a 2.8-fold increase in IL-12 p70 in the Homo KO group. IL-4 PreTx did not significantly increase IL-12 p70 over vehicle PreTx in the Homo KO group. (3) We studied the effect of c-fos overexpression on LPS-induced Mphi IL-12 production when primed with IL-4. Overexpression of c-fos completely inhibited IL-4 primed LPS-induced IL-12 p70 protein synthesis. CONCLUSIONS: These data demonstrated that down-regulation of c-fos is an integral part of the IL-4 priming process for Mphi IL-12 production.

The possible inhibitory role of the leucine-zipper DNA binding protein c-fos in the regulation of hepatic gene expression after sepsis.

BACKGROUND: The leucine-zipper c-fos has been implicated in the regulation of gene expression. We investigated the possible role of c-fos in the regulation of hepatic gene expression after sepsis. Based on previous data demonstrating that sepsis inhibits hepatic gene expression of carnitine palmitoyltransferase (CPT), we hypothesized that c-fos may play a role in the inhibition of CPT gene expression after sepsis. METHODS: We studied c-fos gene expression after peritoneal sepsis induced by cecal ligation and puncture (CLP) or sham-CLP. To investigate the possible inhibitory role of c-fos on CPT gene transcription, we investigated the effect of c-fos on c-jun-driven CPT promoter-chloramphenicol acyltransferase reporter gene expression in a HepG2 hepatoma cell cotransfection model. To investigate the possible role of cyclic adenosine monophosphate (cAMP) in the regulation of c-fos in vivo, we treated either the sham-CLP group or the CLP group with either vehicle or cAMP. RESULTS: Peritoneal sepsis in the rat model resulted in a four-fold increase in hepatic c-fos mRNA and c-fos protein. In the cotransfection model, c-fos significantly inhibited c-jun-induced chloramphenicol acyltransferase activity. Treatment with cAMP resulted in a 50% decrease in c-fos protein in either the sham-CLP or CLP group. CONCLUSIONS: We conclude that (1) sepsis increases hepatic c-fos transcription and translation, (2) c-fos inhibits c-jun-induced CPT gene expression, and (3) cAMP probably does not directly mediate the increase in c-fos after sepsis.

Sepsis-induced release of interleukin-6 may activate the immediate-early gene program through a hypothalamic-hypophyseal mechanism.

BACKGROUND: The immediate-early gene c-fos has been implicated in transcriptional regulation after sepsis. We test the hypothesis that sepsis-induced central nervous system release of interleukin (IL)-6 regulates hepatic c-fos gene expression. METHODS: Using a stereotaxically placed intracerebral-ventricular (ICV) catheter in rats with and without hypophysectomy, we measured hepatic c-fos protein accumulation after treatment with either IL-6 or vehicle control. Using a rat cecal ligation and puncture (CLP) model, we studied the following groups: (1) sham-CLP, (2) CLP, (3) hypophysectomized sham-CLP, and (4) hypophysectomized CLP and measured hepatic c-fos mRNA. RESULTS: ICV IL-6 treatment increased hepatic c-fos protein in the IL-6-treated group compared with the vehicle-treated group, and hypophysectomy inhibited the ICV IL-6-mediated increase in c-fos protein. After peritoneal sepsis, CLP increased hepatic c-fos messenger RNA compared to either the sham-CLP or the hypophysectomized sham-CLP group, and hypophysectomy before CLP inhibited hepatic c-fos mRNA compared with the CLP group. CONCLUSIONS: ICV IL-6 results in an increase in hepatic fos protein that is mediated through a hypothalamic-hypophyseal mechanism. Peritoneal sepsis results in an increase in hepatic c-fos gene expression that may be, in part, mediated by central nervous system release of IL-6 through a hypothalamic-hypophyseal mechanism.

Deficiency of the transcription factor c-fos increases lipopolysaccharide-induced macrophage interleukin 12 production.

BACKGROUND: Interleukin 12 (IL-12) p70 is a heterodimeric protein (p35, p40 subunits) that promotes T-helper TH1-type cytokine response. In critically ill patients, after severe trauma or sepsis, IL-12 production is markedly impaired. We tested the hypothesis that deficiency of the transcription factor c-fos will increase macrophage IL-12 production. METHODS: We harvested adherent peritoneal macrophages harvested from wild-type (WT), heterozygous c-fos knockout (Hetero KO), or homozygous c-fos knockout (Homo KO) mice and investigated lipopolysaccharide (LPS)-induced IL-12 p70 protein synthesis (by enzyme-linked immunosorbent assay), IL-12 p35 and IL-12 p40 messenger RNA accumulation (mRNA) (by reverse transcriptase-polymerase chain reaction), and the transcription rate (by nuclear runoff). RESULTS: (1) LPS treatment compared with vehicle increases c-fos mRNA accumulation 5-fold and AP-1 DNA protein binding (electrophoretic mobility shift assay), which precedes either IL-12 p35 or IL-12 p40 mRNA accumulation. (2) LPS induces a significant increase in IL-12 p70 protein, IL-12 p40 mRNA, and the transcription rate in the Homo KO group compared with either the Hetero KO or WT groups. (3) Compared with vehicle control, we demonstrate that interferon gamma priming increases LPS-stimulated macrophage IL-12 p70 protein in the Hetero KO or WT groups to the level of the Homo KO group but has no significant effect on the Homo KO group. CONCLUSIONS: These data suggest that deficiency of the transcription factor c-fos increases LPS-induced macrophage IL-12 production, possibly by simulating the effect of interferon gamma priming.

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.

Mechanisms of the adjuvant effect of hemoglobin in experimental peritonitis. VII. Hemoglobin does not inhibit clearance of Escherichia coli from the peritoneal cavity.

Hemoglobin has been shown to be a potent adjuvant in experimental Escherichia coli peritonitis, although a satisfactory mechanistic rationale is still obscure. Hemoglobin has been thought to impair intraperitoneal neutrophil function, delay clearance of bacteria from the peritoneal cavity by the normal absorptive mechanisms, or directly enhance bacterial growth. Using highly purified stroma-free hemoglobin (SFHgb), we have largely discounted any direct effect of hemoglobin on peritoneal white blood cell function. In the present study, we confirmed that uncontrolled proliferation of bacteria takes place in the presence of hemoglobin in the peritoneal cavity. Nonviable 5-iododeoxyuridine 125I-labelled bacteria were then used to directly study peritoneal clearance kinetics, eliminating the problem of bacterial growth. SFHgb had no influence on the removal of intraperitoneal bacteria. The rate of bloodstream appearance of radiolabel was similar with or without intraperitoneal SFHgb. Thus, SFHgb does not prevent clearance of bacteria from the peritoneal cavity by interfering with normal host clearance mechanisms. SFHgb may act as a bacterial growth adjuvant, either by serving as a bacterial nutrient or by suitably modifying the environment so that extensive bacterial proliferation can occur. The latter hypothesis appears to be an area in which investigation concerning the adjuvant effect of hemoglobin may prove most fruitful.

The role of programmed cell death (apoptosis) in thymic involution following sepsis.

OBJECTIVE: To test the hypothesis that thymic involution following peritoneal sepsis is secondary to thymocyte programmed cell death. DESIGN: We investigated the temporal response of thymic weight and thymic DNA fragmentation following peritoneal sepsis induced by cecal ligation and puncture in a rat model. We investigated the possible role of decreased interleukin (IL)-2 synthesis in the induction of apoptosis using rat thymocytes in primary culture. Finally, we studied IL-2 gene expression and IL-2 protein synthesis in phytohemagglutinin and IL-1 beta-treated thymocytes derived from the cecal ligation and puncture model of sepsis. RESULTS: We demonstrated that (1) there is a significant decrease in thymic weight and an increase in thymic DNA fragmentation with the characteristic apoptotic DNA "ladder" fragmentation pattern on agarose gel electrophoresis following peritoneal sepsis; (2) thymocytes in primary culture sustain a significant increase in thymocyte apoptosis following IL-2 withdrawal; and (3) peritoneal sepsis results in inhibition of phytohemagglutinin and IL-1 beta-induced thymocyte IL-2 messenger RNA accumulation and protein synthesis. CONCLUSIONS: Thymic involution following peritoneal sepsis is associated with increased thymocyte programmed cell death. Thymocyte apoptosis induced by sepsis may be the result, in part, of inhibition of IL-2 gene expression.

Macrophages and translymphatic absorption represent the first line of host defense of the peritoneal cavity.

To quantitate the host defenses of the rat peritoneal cavity, nonviable radiolabeled Escherichia coli were injected intraperitoneally and clearance, leukocyte influx, and phagocytosis were examined. Macrophages (MCs) were present initially and remained relatively constant in number. The polymorphonuclear leukocyte (PMN) response began at one to two hours and was maximal at 24 to 72 hours. A previously unidentified inoculum-dependent PMN response was defined. Clearance and phagocytosis were extremely rapid, and few (less than 3%) free bacteria were present after two hours. Phagocytic activity of MCs and PMNs was identical, but MCs were numerically predominant initially and thus accounted for the majority of early phagocytosis. Thus, MC phagocytosis and clearance represent the primary line of host peritoneal defenses. We hypothesize that the subsequent inoculum-dependent PMN response may have evolved to cope with those larger inocula for which this initial response is inadequate.

The possible role of a central nervous system dopaminergic mechanism in hepatic c-fos protein expression following peritoneal sepsis.

OBJECTIVE: To investigate the hypothesis that a central dopaminergic mechanism may regulate hepatic c-fos and c-jun gene expression following peritoneal sepsis. METHODS: First, dopamine or vehicle was instilled into a stereotaxically placed intracerebral-ventricular (ICV) cannula with or without D1 (SCH 23390) or D2 (haloperidol) antagonist pretreatment in a rat model, and the effect on hepatic c-fos or c-jun protein expression was investigated. Second, we investigated the effect of haloperidol and vehicle treatment following cecal ligation and puncture (CLP)-induced sepsis with respect to hepatic c-fos protein expression, c-jun protein expression, and survival. RESULTS: Intracerebral-ventricular dopamine treatment increased hepatic c-fos immunoreactive protein but had no effect on hepatic c-jun immunoreactive protein expression. Pretreatment with SCH 23390 inhibited ICV dopamine treatment-induced hepatic c-fos immunoreactive protein expression. Haloperidol pretreatment synergized with ICV dopamine treatment to overexpress hepatic c-fos protein. Haloperidol treatment significantly increased CLP-induced hepatic c-fos and c-jun protein expression and improved survival following CLP. CONCLUSIONS: Hepatic c-fos protein expression may be regulated, in part, by a central nervous system-mediated dopaminergic D1 receptor mechanism. Treatment with the D2 receptor antagonist, haloperidol, increases sepsis-induced hepatic c-fos and c-jun protein expression and improves survival following peritoneal contamination.

Enterococcal sepsis and lung microvascular injury in sheep.

In a common bile duct contamination model, we studied the effect of Streptococcus faecalis compared with Escherichia coli in sheep with chronic lymph fistulas to investigate the role of enterococcus in acute lung injury and acute sepsis. Early pulmonary hypertension in the E coli group was not expressed in the S faecalis group, probably due to a failure of S faecalis to illicit a thromboxane A2 response. In the late period, E coli was associated with significantly greater lung microvascular damage compared with S faecalis. The lack of difference between groups with respect to complement activation suggests the action of chemotactic factors, in addition to complement, mediating granulocyte aggregation, and neutropenia. In this model, S faecalis demonstrated limited pathogenicity as expressed in lung microvascular injury compared with E coli.

Effects of biliary obstruction on hepatic clearance of bacteria.

High surgical mortality in patients with obstructive jaundice and sepsis have been attributed to reticuloendothelial system (RES) depression. The purpose of this study was to clarify the effects of mechanical biliary obstruction on RES clearance of pathogenic bacteria by comparing the phagocytic index (K) with the directly measured hepatic uptake of indium 111-labeled bacteria injected into the portal vein of normal dogs and dogs with partial (PBO) or complete biliary obstruction (CBO). No significant difference was observed between the K in normal dogs (0.19 +/- 0.08; n = 6) and that in dogs with PBO (0.24 +/- 0.06; n = 5) or CBO (0.21 +/- 0.03; n = 4). There was no significant difference in uptake of radiolabel by the liver among the three groups of dogs. In our model, biliary obstruction had no effect on hepatic RES function and may not represent a significant determinant of mortality in patients with obstructive jaundice.

Comparative pulmonary effects of intraperitoneal inoculation of live v dead Escherichia coli.

We studied the effect of 2.5 X 10(9) live Escherichia coli per kilogram v 2.7 X 10(9) dead E coli per kilogram injected into the peritoneal cavity of sheep with chronic pulmonary lymph fistulas. The effects of dead E coli were compared with those of live E coli, with respect to (1) pulmonary hypertension, (2) hemodynamic failure, (3) damage to the pulmonary microvasculature, (4) systemic arterial hypoxemia, (5) neutropenia and lymphopenia, (6) thrombocytopenia and platelet aggregation, (7) plasma fibrinogen concentration, and (8) classic- and alternative-pathway hemolytic complement. The time after injection of the bacteria was divided into an early period (zero to two hours) and a late period (two to seven hours). We made two conclusions: (1) The early period effects, with the exception of the absolute neutrophil count and Pao2, were independent of bacterial viability, whereas the late period effects were strongly dependent on bacterial viability. (2) The early notable difference between the live v dead groups, with respect to the absolute neutrophil count and Pao2, could not be explained on the basis of an increase in bacterial numbers alone.

The association of Escherichia coli virulence and pulmonary microvascular damage.

Bacterial virulence indicates the degree of pathogenicity of a given strain of microbe for a given host. The effect of Escherichia coli virulence on lung microvascular permeability was studied in sheep with chronic pulmonary lymph fistulas following peritoneal contamination. The study was divided into four groups: (1) wild-type E coli (WT group, 2.5 x 10(9) colony-forming units [CFUs]/kg); (2) virulent E coli (PV group, 2.3 x 10(9) CFUs/kg); (3) nonvirulent E coli (PNV group, 2.6 x 10(9) CFUs/kg); (4) high-inoculum wild-type E coli (HIWT group, 6.1 x 10(9) CFUs/kg). In the late period (two to six hours), the increase in lung lymph flow in the PV group was significantly greater than the WT, PNV, and HIWT groups, with no difference noted among groups with respect to the pulmonary artery pressure, pulmonary wedge pressure, or albumin lymph/plasma ratio. It was concluded that (1) increased E coli virulence results in increased lung microvascular damage and (2) increased lung microvascular damage as a function of E coli virulence may not be solely due to increased bacterial numbers as a function of time.

Gram-negative bacterial sepsis and the sepsis syndrome.

Gram-negative sepsis syndrome is an increasingly common complication in medical and surgical patients. The molecular and cellular mechanisms underlying this dreaded complication are yielding to investigation. These studies have led to a multiplicity of targets for novel therapies. Despite highly promising results in many animal studies, clinical studies have been disappointing.