Hypoxia Differentially Regulates Arterial and Venous Smooth Muscle Cell Migration

OBJECTIVE

Intimal hyperplasia (IH) is a clinical concern leading to failure of up to 50% of vein grafts and 10% of arterial grafts after 10 years with no known current treatment. Recent studies have shown that hypoxia differentially regulates proliferation of vein derived smooth muscle cells (V-SMC) compared to artery derived smooth muscle cells (A-SMC). The objective of this study is to evaluate the effect of hypoxia on cellular migration and the mechanisms underlying the differential effects of hypoxia on A-SMC and V-SMC migration.

METHODS AND RESULTS

Hypoxic treatment (3-5% O2) of Smooth Muscle Cells (SMC) resulted in differential migration in scratch wound and electric cell substrate impedance sensing (ECIS) assays. Hypoxia led to greater migration compared to normoxia with venous derived wound closure (V-SMC 30.8% Normoxia to 67% Hypoxia) greater than arterial wound closure (A-SMC 6.2% Normoxia to 24.7% Hypoxia). Paracrine factors secreted by hypoxic endothelial cells induced more migration in SMC compared to factors secreted by normoxic endothelial cells. Migration of V-SMC was greater than A-SMC in the presence of paracrine factors. Neutralizing antibody to Vascular Endothelial Growth Factor Receptor -1 (VEGFR-1) completely inhibited V-SMC migration while there was only partial inhibition of A-SMC migration. A-SMC migration was completely inhibited by Platelet Derived Growth Factor BB (PDGF-BB) neutralizing antibody. p38 Mitogen Activated Protein kinase (p38 MAPK) inhibitor pre-incubation completely inhibited migration induced by paracrine factors in both A-SMC and V-SMC.

CONCLUSION

Our study determines that SMC migration under hypoxia occurs via both an autocrine and paracrine mechanism and is dependent on Vascular Endothelial Growth Factor-A (VEGF-A) in V-SMC and PDGF-BB in A-SMC. Migration of both A-SMC and V-SMC is inhibited by p38 MAPK inhibitor. These studies suggest that pharmacotherapeutic strategies directed at modulating p38 MAPK activity can be exploited to prevent IH in vascular grafts.

Morphine induces bacterial translocation in mice by compromising intestinal barrier function in a TLR-dependent manner

Opiates are among the most prescribed drugs for pain management. However, morphine use or abuse results in significant gut bacterial translocation and predisposes patients to serious infections with gut origin. The mechanism underlying this defect is still unknown. In this report, we investigated the mechanisms underlying compromised gut immune function and bacterial translocation following morphine treatment. We demonstrate significant bacterial translocation to mesenteric lymph node (MLN) and liver following morphine treatment in wild-type (WT) animals that was dramatically and significantly attenuated in Toll-like receptor (TLR2 and 4) knockout mice. We further observed significant disruption of tight junction protein organization only in the ileum but not in the colon of morphine treated WT animals. Inhibition of myosin light chain kinase (MLCK) blocked the effects of both morphine and TLR ligands, suggesting the role of MLCK in tight junction modulation by TLR. This study conclusively demonstrates that morphine induced gut epithelial barrier dysfunction and subsequent bacteria translocation are mediated by TLR signaling and thus TLRs can be exploited as potential therapeutic targets for alleviating infections and even sepsis in morphine-using or abusing populations.

Opioid drug abuse and modulation of immune function: consequences in the susceptibility to opportunistic infections

Infection rate among intravenous drug users (IDU) is higher than the general public, and is the major cause of morbidity and hospitalization in the IDU population. Epidemiologic studies provide data on increased prevalence of opportunistic bacterial infections such as TB and pneumonia, and viral infections such as HIV-1 and hepatitis in the IDU population. An important component in the intravenous drug abuse population and in patients receiving medically indicated chronic opioid treatment is opioid withdrawal. Data on bacterial virulence in the context of opioid withdrawal suggest that mice undergoing withdrawal had shortened survival and increased bacterial load in response to Salmonella infection. As the body of evidence in support of opioid dependency and its immunosuppressive effects is growing, it is imperative to understand the mechanisms by which opioids exert these effects and identify the populations at risk that would benefit the most from the interventions to counteract opioid immunosuppressive effects. Thus, it is important to refine the existing animal model to closely match human conditions and to cross-validate these findings through carefully controlled human studies. Better understanding of the mechanisms will facilitate the search for new therapeutic modalities to counteract adverse effects including increased infection rates. This review will summarize the effects of morphine on innate and adaptive immunity, identify the role of the mu opioid receptor in these functions and the signal transduction activated in the process. The role of opioid withdrawal in immunosuppression and the clinical relevance of these findings will also be discussed.

Morphine withdrawal stress modulates lipopolysaccharide-induced interleukin 12 p40 (IL-12p40) expression by activating extracellular signal-regulated kinase 1/2, which is further potentiated by glucocorticoids

Withdrawal stress is a common occurrence in opioid users, yet very few studies have examined the effects of morphine withdrawal (MW) on immune functioning or the role of glucocorticoids in MW-induced immunomodulation. This study investigated for the first time the role of glucocorticoids in MW modulation of LPS-induced IL-12p40, a key cytokine playing a pivotal role in immunoprotection. Using WT and μ-opioid receptor knock-out mice, we show that MW in vivo significantly attenuated LPS-induced IL-12p40 mRNA and protein expression. The role of glucocorticoids in MW modulation of IL-12p40 was investigated using a murine macrophage cell line, CRL2019, in an in vitro MW model. Interestingly, MW alone in the absence of glucocorticoids resulted in a significant reduction in IL-12p40 promoter activity and mRNA and protein expression. EMSA revealed a concurrent decrease in consensus binding to transcription factors NFκB, Activator Protein-1, and CCAAT/enhancer-binding protein and Western blot analysis demonstrated a significant activation of LPS-induced ERK1/2 phosphorylation. Interestingly, although glucocorticoid treatment alone also modulated these transcription factors and ERK1/2 activation, the addition of glucocorticoids to MW samples resulted in a greater than additive reduction in the transcription factors and significant hyperactivation of LPS-induced ERK1/2 phosphorylation. ERK inhibitors reversed MW and MW plus corticosterone inhibition of LPS-induced IL-12p40. The potentiating effects of glucocorticoids were non-genomic because nuclear translocation of glucocorticoid receptor was not significantly different between MW and corticosterone treatment. This study demonstrates for the first time that MW and glucocorticoids independently modulate IL-12p40 production through a mechanism involving ERK1/2 hyperactivation and that glucocorticoids can significantly augment MW-induced inhibition of IL-12p40.

Chronic morphine treatment inhibits LPS-induced angiogenesis: implications in wound healing

Delayed wound healing is a chronic problem in opioid drug abusers. We investigated the role chronic morphine plays on later stages of wound healing events using an angiogenesis model. Our results show that morphine treatment resulted in a significant decrease in inflammation induced angiogenesis. To delineate the mechanisms involved we investigate the role of hypoxia inducible factor 1 alpha (HIF-1 alpha), a potent inducer of angiogenic growth factor. Morphine treatment resulted in a significant decrease in the expression and nuclear translocation of HIF-1 alpha with a concurrent suppression in vascular endothelial growth factor (VEGF) synthesis. Cells of the innate immune system play a dominant role in the angiogenic process. Morphine treatment inhibited early recruitment of both neutrophils and monocytes towards an inflammatory signal with a significant decrease in the monocyte chemoattractant MCP-1. Taken together, our studies show that morphine regulates the wound repair process on multiple levels. Morphine acts both directly and indirectly in suppressing angiogenesis.

Chronic morphine administration delays wound healing by inhibiting immune cell recruitment to the wound site

Patients prescribed morphine for the management of chronic pain, and chronic heroin abusers, often present with complications such as increased susceptibility to opportunistic infections and inadequate healing of wounds. We investigated the effect of morphine on wound-healing events in the presence of an infection in an in vivo murine model that mimics the clinical manifestations seen in opioid user and abuser populations. We show for the first time that in the presence of an inflammatory inducer, lipopolysaccharide, chronic morphine treatment results in a marked decrease in wound closure, compromised wound integrity, and increased bacterial sepsis. Morphine treatment resulted in a significant delay and reduction in both neutrophil and macrophage recruitment to the wound site. The delay and reduction in neutrophil reduction was attributed to altered early expression of keratinocyte derived cytokine and was independent of macrophage inflammatory protein 2 expression, whereas suppression of macrophage infiltration was attributed to suppressed levels of the potent macrophage chemoattractant monocyte chemotactic protein-1. When the effects of chronic morphine on later wound healing events were investigated, a significant suppression in angiogenesis and myofibroblast recruitment were observed in animals that received chronic morphine administration. Taken together, our findings indicate that morphine treatment results in a delay in the recruitment of cellular events following wounding, resulting in a lack of bacterial clearance and delayed wound closure.

Morphine impairs intestinal immunity and barrier function leading to coagulase-negative staphylococcal bacteraemia (39.30)

Opiate abuse increases susceptibility to bacterial infection. However, if the intestine can be a potential source of bacterial infections in opiate abusers is not fully elucidated. Using an opiate abuse model, where mice were chronically treated with morphine or placebo pellet, we found that morphine treatment induced bacterial translocation and led to bacteraemia. After morphine exposure, group D Entercocci and coagulase negative Staphylococci were detected in the mesenteric lymph nodes and lungs. Morphine treatment enhanced bacterial growth in the intestine, and that such increased in bacteria was in direct proportion to coagulase-negative staphylococcal bacteraemia. Furthermore, our preliminary findings showed that morphine treatment modulated intestinal intraepithelial gammadelta T cells and impaired intestinal permeability. Moreover, morphine treatment induced dysfunction in intestinal intraepithelial gammadelta T cells was associated with the absence of phosphorylation of occludin and lack of claudin-3 and zona occludens-1 (ZO-1) proteins in tight junction complexes. Our studies suggest that bacterial translocation and bacteraemia occurs in opiate abusers, either on account of a breach of the mucosal barrier, impaired host immune defense, and/or bacterial overgrowth creating an ecologic imbalance in the indigenous intestinal microflora. Supported by R01 DA12104, P50 DA11806, and R03 DA023353.

Morphine induces defects in early response of alveolar macrophages to Streptococcus pneumoniae by modulating TLR9-NF-kappa B signaling

Resident alveolar macrophages and respiratory epithelium constitutes the first line of defense against invading lung pneumococci. Results from our study showed that increased mortality and bacterial outgrowth and dissemination seen in morphine-treated mice were further exaggerated following depletion of alveolar macrophages with liposomal clodronate. Using an in vitro alveolar macrophages and lung epithelial cells infection model, we show significant release of MIP-2 from alveolar macrophages, but not from lung epithelial cells, following 4 h of exposure of cells to pneumococci infection. Morphine treatment reduced MIP-2 release in pneumococci stimulated alveolar macrophages. Furthermore, morphine treatment inhibited Streptococcus pneumoniae-induced NF-kappaB-dependent gene transcription in alveolar macrophages following 2 h of in vitro infection. S. pneumoniae infection resulted in a significant induction of NF-kappaB activity only in TLR9 stably transfected HEK 293 cells, but not in TLR2 and TLR4 transfected HEK 293 cells, and morphine treatment inhibited S. pneumoniae-induced NF-kappaB activity in these cells. Moreover, morphine treatment also decreased bacterial uptake and killing in alveolar macrophages. Taken together, these results suggest that morphine treatment impairs TLR9-NF-kappaB signaling and diminishes bacterial clearance following S. pneumoniae infection in resident macrophages during the early stages of infection, leading to a compromised innate immune response.

Morphine withdrawal inhibits IL-12 induction in a macrophage cell line through a mechanism that involves cAMP

There are very few studies that examine the effects that morphine withdrawal has on immune functioning, and of these even fewer describe the mechanisms by which withdrawal brings about these changes. Our previous work demonstrated that morphine withdrawal contributed to Th cell differentiation by biasing cells toward the Th2 lineage. A major finding from these studies was that IL-12 was decreased following withdrawal, and it was concluded that this decrease may be a mechanism by which morphine withdrawal is mediating Th2 polarization. Therefore, it was the aim of the current studies to develop an in vitro model to examine the process of morphine withdrawal and to understand the signaling mechanisms that withdrawal may use to effect IL-12 production through the use of this model. It was demonstrated and concluded that morphine withdrawal may be effecting IL-12 production by increasing cAMP levels, which activates protein kinase A. Protein kinase A activation then prevents the phosphorylation and subsequent degradation of IkappaB, which in turn prevents translocation of the NF-kappaB p65 subunit to the nucleus to transactivate the IL-12 p40 gene, ultimately resulting in decreased IL-12 production following LPS stimulation.

Transcriptional and Epigenetic Regulation of Interleukin-2 Gene in Activated T Cells by Morphine

Chronic morphine inhibits interleukin-2 (IL-2) at both the transcriptional and protein synthesis levels. The molecular mechanisms by which morphine decreases IL-2 are not fully understood. The production of IL-2 is tightly regulated by several transcription factors that bind to the IL-2 promoter. Herein, we show that chronic morphine treatment results in an increase in cAMP levels with a concurrent up-regulation of the cAMP inducible repressor inducible cAMP early repressor (ICER)/cAMP response element modulator (CREM) and down-regulation of p-cAMP-response element-binding protein (CREB) in activated T cells. Furthermore, ICER competes for p-CREB binding to the cAMP-responsive elements (CREs) site. This leads to the uncoupling of CBP/p300 thereby abrogating IL-2 transcription. Overexpression of either antisense CREM or CREB plasmid rescued morphine-induced inhibition of IL-2 promoter activity and protein production. In addition, we also found that chronic morphine treatment inhibited the acetylation and trimethylation of histones and decreased both DNA demethylation and accessibility of the IL-2 promoter. These findings suggest that chronic morphine treatment may function through both transcriptional and epigenetic mechanisms to inhibit IL-2 production.

Hepatic CCAAT/enhancer binding protein (C/EBP-alpha and C/EBP-beta) expression changes with riboflavin deficiency, diet restriction and starvation in rats

To study the role of nuclear regulatory proteins in mediating dietary effects, hepatic CCAAT/enhancer binding protein (C/EBP), mRNA and transcription rate were measured for C/EBP-alpha and C/EBP-beta in nutritional states that profoundly alter energy metabolism and growth. Weanling male Sprague-Dawley rats were fed riboflavin-sufficient (R+) or deficient (R-) diets for 4 wk. A diet-restricted, pair-fed (RP) group was maintained concurrently, because riboflavin-deficient rats voluntarily decrease food consumption by approximately 50% compared with controls. Half of each group was deprived of food for 48 h. The 4-wk treatment altered hepatic levels of both proteins (P < 0.05). C/EBP-alpha protein levels were increased -twofold by diet restriction. C/ EBP-beta protein levels were increased nearly threefold by riboflavin deficiency. Starvation had no significant effect on the expression of either protein. We investigated the mechanism responsible for increased protein by measuring steady-state mRNA levels and transcription rates for C/EBP-alpha and C/EBP-beta. In both isoforms, increases in mRNA were parallel to increases in transcription rates. The nutrient-induced changes in protein, mRNA and transcription rates could not be attributed only to alterations in serum glucagon or insulin concentrations. We conclude that 1) C/EBP-alpha and C/EBP-beta expression responds to diet but may involve different dietary signals for diet restriction vs. riboflavin deficiency; 2) the dietary regulation of C/EBP-alpha and C/EBP-beta expression seems to be controlled in part at the level of gene transcription; and 3) C/EBP-alpha and C/EBP-beta nuclear proteins, by virtue of their increased quantities, may participate in regulating altered energy metabolism and growth by influencing hepatic transcription of key metabolic enzymes.

Morphine withdrawal contributes to Th cell differentiation by biasing cells toward the Th2 lineage

The consequences that drug withdrawal has on immune functioning has only recently been appreciated; however, given the wide variety of use and abuse of opiate analgesics, understanding the decrements to immune function that withdrawal from these drugs causes is of crucial importance. In previous work, we have demonstrated that morphine treatment contributes to immunosuppression by polarizing Th cells toward the Th2 lineage. In the current study, it was hypothesized that morphine withdrawal would result in Th2 differentiation and subsequent immune dysfunction. To address this hypothesis, mice were chronically treated with morphine for 72 h followed by a 24-h withdrawal period. It was determined that 24-h morphine withdrawal resulted in a decrease in IFN-gamma, the Th1 signature cytokine, whereas the Th2 cytokine, IL-4, was increased. In addition, Western blot and EMSA experiments revealed that morphine withdrawal-induced Th2 differentiation was mediated through the classical Th2 transcription factors Stat-6 and GATA-3. In addition, the consequence of morphine withdrawal in the presence of an immune stimulation was also examined by treating mice in vivo with LPS before morphine withdrawal. Following withdrawal, it was found that the Th1-polarizing cytokine IL-12 was significantly decreased, providing further support for the observation that withdrawal results in Th2 differentiation by possibly impacting the generation of an appropriate innate immune response which directs subsequent adaptive Th1/Th2 responses.

Morphine Induces CD4+ T Cell IL-4 Expression through an Adenylyl Cyclase Mechanism Independent of the Protein Kinase A Pathway

Impaired host defense mechanisms after major operative procedures and trauma are recognized as important factors in the development of infectious complication. Trauma is associated with impaired cellular immunity and CD4+ T cell Th2 differentiation. We have previously implicated morphine treatment as a possible mechanism for Th2 differentiation after injury. In this investigation we first establish that morphine treatment in vivo results in Th2 differentiation and that this effect is mediated through a naltrexone-sensitive opioid receptor. We investigated the intracellular mechanism by which morphine controls CD4+ T cell differentiation and demonstrate that morphine treatment in vitro 1) increases anti CD3/CD28 Ab-induced CD4+ T cell IL-4 protein synthesis, IL-4 mRNA, and GATA-3 mRNA accumulation through a pertussis toxin-sensitive receptor; 2) results in a dose-dependent increase in anti-CD3/CD28 Ab-induced CD4+ T cell cytoplasmic cAMP concentration; and 3) increases the forskolin-stimulated cytoplasmic cAMP level through a pertussis toxin-sensitive receptor. We also demonstrate that chronic morphine treatment increases anti-CD3/CD28 Ab-induced IL-4 promoter activity and IL-4 immunoprotein expression through a p38 MAPK-dependent, but protein kinase A- and Erk1/Erk2-independent, mechanism.

Morphine Impairs Host Innate Immune Response and Increases Susceptibility toStreptococcus pneumoniaeLung Infection

Chronic morphine use impairs host innate immune response and increases susceptibility to bacteria and virus. In this study a novel mouse model of chronic morphine treatment, followed by intranasal inoculation with Streptococcus pneumoniae, was used to investigate microbial events and host innate immune response. Our results show that chronic morphine treatment markedly delayed neutrophil recruitment and increased bacterial burden in the lung, spleen, and blood with a subsequent increase in mortality. In morphine-treated animals, before neutrophil recruitment, a significant decrease in TNF-alpha, IL-1, IL-6, MIP-2, and KC was observed both in bronchoalveolar lavage fluids and in lung tissue. In the early phase of infection, we found that accumulation of galectin-3 in the alveolar space of streptococcus-infected lungs was decreased after morphine treatment. The transcription factor NF-kappaB in lung resident cells was also inhibited after morphine treatment. Taken together, these results suggest that chronic morphine treatment in an S. pneumoniae infection model suppresses NF-kappaB gene transcription in lung resident cells, which, in turn, modulates the transcriptional regulation of MIP-2 and inflammatory cytokines. The decreased synthesis of MIP-2 and inflammatory cytokines coupled with the decreased release of galectin-3 result in reduced migration of neutrophils to the site of infection, thereby increasing susceptibility to S. pneumoniae infection after morphine treatment.

Chronic morphine treatment differentiates T helper cells to Th2 effector cells by modulating transcription factors GATA 3 and T-bet

Chronic morphine treatment in animal models has been shown to alter a number of immune parameters including suppression of cellular immunity. T helper cell differentiation into Th2 effector cell may be a major contributing factor to impaired cellular immunity following chronic drug abuse. We had previously shown that chronic morphine treatment in vivo and in vitro decreases IL-2 and IFNgamma (Th1) protein levels and increases IL-4 and IL-5 (Th2) protein levels in a time-dependent manner. In addition in this paper, we show that chronic morphine treatment resulted in a decrease in IFNgamma and IL-2 mRNA and an increase in IL-4 and IL-5 mRNA accumulation in murine splenocytes. Furthermore, chronic morphine treatment inhibited IFNgamma promoter activity and increased IL-4 promoter activity in respective promoter transfected primary T cells. In addition, we also demonstrate that chronic morphine treatment resulted in an increase in GATA 3 binding to DNA consensus elements in electromobility shift assays and an increase in GATA 3 protein and mRNA levels. In contrast, chronic morphine treatment resulted in a decrease in T-bet mRNA levels. From these data, we conclude that chronic morphine treatment differentiates T helper cell to Th2 effector cells by modulating key master switches that results in committing T helper cell to a Th2 phenotype.

Morphine negatively regulates interferon-gamma promoter activity in activated murine T cells through two distinct cyclic AMP-dependent pathways

To explore the mechanism by which morphine promotes the incidence of HIV infection, we evaluated the regulatory role of morphine on the interferon-gamma (IFN-gamma) promoter in activated T cells from wild type and mu-opioid receptor knockout mice. Our results show that morphine inhibited anti-CD3/CD28-stimulated IFN-gamma promoter activity in a dose-dependent manner. Chronic morphine treatment of T cells increased intracellular cAMP. To evaluate the role of cAMP in morphine's modulatory function, the effects of dibutyryl cyclic AMP and forskolin were investigated. Both dibutyryl cyclic AMP and forskolin treatment inhibited IFN-gamma promoter activity. Treatment with pertussis toxin, but not with a protein kinase A inhibitor, antagonized morphine's inhibitory effects. Morphine inhibited phosphorylation of ERK1/2 and p38 MAPK; in addition, morphine treatment in the presence of either ERK1/2 or p38 MAPK inhibitor (PD98059 or SB203580) resulted in an additive inhibition of IFN-gamma promoter activity. The transcription factor activator protein-1, NF-kappaB, and nuclear factor of activated T cells (NFAT) were negatively regulated by morphine. Overexpression of NF-kappaB p65 rescued the inhibitory effect of morphine on IFN-gamma promoter activity. However, only when NFATc1 was co-overexpressed with c-fos was the inhibitory effect of morphine on IFN-gamma promoter counteracted. The inhibitory effects of morphine were not observed in T cells obtained from mu-opioid receptor knockout mice, suggesting that morphine modulation of IFN-gamma promoter activity is mediated through the mu-opioid receptor. In summary, our data indicate that morphine modulation of IFN-gamma promoter activity is mediated through two distinct cAMP-dependent pathways, the NF-kappaB signaling pathway and the ERK1/2, p38 MAPK, AP-1/NFAT pathway.

Mu-opioid receptor mediates chronic restraint stress-induced lymphocyte apoptosis

Psychological stress is associated with immunosuppression in both humans and animals. Although it was well established that psychological stressors stimulate the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system, resulting in the release of various hormones and neurotransmitters, the mechanisms underlying these phenomena are poorly understood. In this study, mu-opioid receptor knockout (MORKO) mice were used to investigate whether the mu-opioid receptor mediates the immunosuppression induced by restraint stress. Our results showed that wild-type (WT) mice subjected to chronic 12-h daily restraint stress for 2 days exhibited a significant decrease in splenocyte number with a substantial increase in apoptosis and CD95 (Fas/APO-1) expression of splenocytes. The effects are essentially abolished in MORKO mice. Furthermore, inhibition of splenic lymphocyte proliferation, IL-2, and IFN-gamma production induced by restraint stress in WT mice was also significantly abolished in MORKO mice. Interestingly, both stressed WT and MORKO mice showed a significant elevation in plasma corticosterone and pituitary proopiomelanocortin mRNA expression, although the increase was significantly lower in MORKO mice. Adrenalectomy did not reverse restraint stress-induced immunosuppression in WT mice. These data clearly established that the mu-opioid receptor is involved in restraint stress-induced immune alterations via a mechanism of apoptotic cell death, and that the effect is not mediated exclusively through the glucocorticoid pathway.

The immunosuppressive effects of chronic morphine treatment are partially dependent on corticosterone and mediated by the mu-opioid receptor

Wild-type and mu-opioid receptor knockout (MORKO) mice were used to investigate the role of corticosterone (CORT) and the mu-opioid receptor (MOR) in chronic morphine-mediated immunosuppression. We found that although plasma CORT concentrations in CORT infusion (10 mg/kg/day) and morphine-pellet implantation (75 mg) mice were similar (400-450 ng/ml), chronic morphine treatment resulted in a significantly higher (two- to threefold) inhibition of thymic, splenic, and lymph node cellularity; inhibition of thymic-lymphocyte proliferation; inhibition of IL-2 synthesis; and activation of macrophage nitric oxide (NO) production when compared with CORT infusion. In addition, results show that the inhibition of IFN-gamma synthesis and splenic- and lymph node-lymphocyte proliferation and activation of macrophage TNF-alpha and IL-1beta synthesis occurred only with chronic morphine treatment but not with CORT infusion. These morphine effects were abolished in MORKO mice. The role of the sympathetic nervous system on morphine-mediated effects was investigated by using the ganglionic blocker chlorisondamine. Our results show that chlorisondamine was able to only partially reverse morphine's inhibitory effects. The results clearly show that morphine-induced immunosuppression is mediated by the MOR and that although some functions are amplified in the presence of CORT or sympathetic activation, the inhibition of IFN-gamma synthesis and activation of macrophage-cytokine synthesis is CORT-independent and only partially dependent on sympathetic activation.

Morphine sulfate inhibits hypoxia-induced vascular endothelial growth factor expression in endothelial cells and cardiac myocytes

Vascular endothelial growth factor (VEGF) is an angiogenic mitogen, specific for endothelial cells. Hypoxia-induced VEGF in endothelial cells and cardiomyocytes leads to autocrine and paracrine stimulation, respectively. During myocardial ischemia, VEGF is upregulated in the endothelium and myocardium, and may mediate angiogenesis. Morphine sulfate is commonly used in pain relief for patients with acute myocardial infarction. We investigated the effect of morphine sulfate on VEGF expression in cultured endothelial cells and cardiac myocytes subjected to hypoxia. Enzyme-linked immunosorbent assays showed that morphine sulfate significantly inhibited hypoxia-induced VEGF expression in mouse heart microvascular endothelial cells (SMHEC4), primary cultures of human umbilical vein endothelial cells (HUVECs) and in primary cultures of rat cardiac myocytes (P<0.05). Real time reverse transcriptase polymerase chain reaction showed that morphine treatment (100 ng/ml) of hypoxic HUVECs resulted in a significant reduction in mRNA levels of VEGF(121) and VEGF(165) isoforms. Transfection of HUVECs with a human VEGF promoter-luciferase construct showed that hypoxia-induced transcriptional activation of VEGF was markedly inhibited by morphine sulfate (P<0.05). Phosphatidyl inositol-3 kinase and protein kinase C-mediated activation of the VEGF promoter was also inhibited by morphine. The opioid antagonist naloxone significantly reversed the inhibitory effects of morphine in endothelial cells suggesting the involvement of opioid receptors. Our results show that the inhibitory effects of morphine on hypoxia-induced VEGF expression in endothelial cells and cardiac myocytes can lead to a decrease in the autocrine and paracrine stimulation and hence limit neovascularization of the ischemic myocardium.

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 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.

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.

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.

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 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.

Morphine modulates NF kappa B activation in macrophages

Chronic use of morphine affects the immune system and predisposes an individual to opportunistic infections. Macrophages play an important role in conferring a first line of defense against invading pathogens. Understanding the mechanisms by which morphine affects the functioning of macrophages would have significant therapeutic benefit in treatment against infections such as HIV and AIDS related syndromes. Two of the major cytokines secreted by activated macrophages are Interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha). Our studies show that morphine differentially modulates lipopolysaccharide (LPS) induced expression of IL-6 and TNF-alpha. Nanomolar concentrations of morphine synergize with LPS and augment the secretion of both IL-6 and TNF-alpha. However, at micromolar concentrations morphine inhibits LPS induced synthesis of IL-6 and TNF-alpha. Expression of both these cytokine genes is dependent on the activation of a transcription factor, NF kappa B. Interestingly, morphine treatment also modulated the activation of NF kappa B by LPS. Pretreatment with a low dose of morphine (nanomolar) resulted in an increase in NF kappa B activation. In contrast pretreatment with a high dose of morphine (micromolar) led to a significant decrease in NF kappa B activation. Furthermore unlike the augmentation which was naloxone reversible, the inhibition of NF kappa B by morphine was not reversed by naloxone, suggesting the involvement of a nonclassical opioid receptor.

The central response to ovarian carcinoma simulates the response to sepsis

BACKGROUND

Animal models of stress and sepsis demonstrate increased hypophyseal gene expression of the transcription factor c-fos and the cytokines interleukin-1 and interleukin-6. Chronic central nervous system exposure to interleukin-1 results in hypermetabolism, accelerated nitrogen loss, anorexia, and cachexia. We test the hypothesis that the host response to ovarian carcinoma recapitulates the host response to sepsis regarding the elaboration of the transcription factors and cytokines in the central nervous system, liver, and lung.

MATERIALS AND METHODS

Nude mice were seeded intraperitoneally with either ovarian carcinoma (MA-148) or vehicle. The animal subjects were observed for 5 weeks and sacrificed for brain, pituitary, lung, and liver mRNA. We studied the mRNA accumulation of the transcription factors c-fos, c-jun, and C/EBP alpha and the cytokines interleukin-1 and interleukin-6 using reverse-transcriptase polymerase chain reaction.

RESULTS

Compared with the control, ovarian carcinoma in the mouse model resulted in the following: (1) Pituitary c-fos and c-jun mRNA increased 3-fold (P = 0.012) and 6-fold (P < 0.001), respectively; (2) pituitary IL-1 and IL-6 mRNA increased 4-fold (P < 0.001) and 8-fold (P = 0.037), respectively; (3) liver c-fos mRNA increased > 8-fold (P < 0.001); and (4) lung C/EBP alpha mRNA decreased greater than 10-fold (P < 0.001).

CONCLUSIONS

We conclude that the host response to ovarian carcinoma in this animal model recapitulates many aspects of the host response to bacterial sepsis especially concerning pituitary gene expression. These data suggest that, as in sepsis, a hypothalamic-hypophyseal-mediated cytokine response in ovarian carcinoma may result in hypermetabolism, accelerated nitrogen loss, anorexia, and cachexia.

Morphine inhibits transcriptional activation of IL-2 in mouse thymocytes

Chronic treatment of mice with morphine affects the proliferation, differentiation, and function of immune cells. In the present study, we investigated the mechanism by which morphine inhibits phytohemagglutinin (PHA)/interleukin-1 (IL-1)-induced thymocyte proliferation. When compared to control cultures, morphine-treated thymocytes showed decreased steady-state levels of bioactive IL-2 and IL-2 mRNA. The reduced IL-2 concentration and reduced transcript levels correlated well with a decreased rate of synthesis of IL-2 mRNA as determined by nuclear runoff assays. Subsequent studies showed that morphine treatment affected transcriptional control elements of the IL-2 promoter by inhibiting the synthesis of a specific trans-activating nuclear factor, c-Fos. c-Fos mRNA levels measured by semiquantitative RT-PCR were significantly decreased in thymocytes following treatment with morphine and activation with PHA and IL-1. Under identical conditions, c-Jun mRNA levels were not altered. Electrophoretic mobility shift studies with the AP-1 consensus oligonucleotide showed significantly decreased levels of AP-1-protein complex formation in nuclear extracts prepared from morphine-treated cells. These studies demonstrate for the first time that opioid alkaloids such as morphine can impair mitogen-lymphokine-activated thymocyte proliferation by interfering with transcriptional activation of the IL-2 gene.

Differential effects of opioids on the proliferation of a macrophage cell line, Bac 1.2F5

Chronic treatment of mice with morphine selectively abrogates the terminal differentiation of committed bone marrow progenitor cells to form macrophage colony forming units. To understand the molecular mechanisms involved in morphine-mediated suppression of myeloid cell differentiation, we investigated the use of a macrophage cell line, Bac 1.2 F5. In vitro proliferation of this cell line is dependent on the exogenous supply of macrophage colony stimulating factor. Treatment of Bac 1.2F5 cells in vitro with morphine showed a dose-dependent inhibition of proliferation which was associated with morphological changes. Characterization of the binding site revealed that the binding site for morphine on these cells is different from the classical opioid receptors described in the brain. In addition to the putative novel class of morphine receptors, Bac 1.2F5 cells also expressed the delta opioid receptors as determined by RT-PCR analyses. These studies show that Bac 1.2F5 cells are suitable for the molecular characterization of opioid effects on the proliferation and differentiation of myeloid progenitor cells.

The effect of surgical treatment following peritoneal sepsis on hepatic gene expression

Peritoneal sepsis results in downregulation of the gene that codes for the hepatic mitochondrial enzyme carnitine palmitoyltransferase (CPT). The inhibition of hepatic CPT transcription by sepsis is thought to be mediated, in part, by increased expression of the leucine-zipper DNA transcription factor c-fos. In a cecal ligation and puncture (CLP) model, we examined the temporal effect of surgical treatment (cecal excision) on sepsis-induced inhibition of CPT gene expression. We investigated the hypothesis that Fos protein level will inversely correlate with the regulation of CPT gene expression. Specifically, we studied hepatic Fos nucleoprotein accumulation and CPT gene expression as measured by total mitochondrial CPT activity, CPT protein, and CPT mRNA. We investigated the following groups: (i) CLP followed by cecal excision 6, 12, or 24 hr following initial insult, (ii) concurrent CLP control group, and (iii) concurrent sham CLP reference group. When measured 48 hr following initial surgical insult, we conclude that: (i) in the absence of surgical treatment, peritoneal contamination results in a decrease in hepatic CPT gene expression and an increase in Fos nucleoprotein accumulation; (ii) surgical treatment at 6 or 12 hr following initial insult prevents the downregulation in hepatic CPT gene expression and does not result in Fos nucleoprotein accumulation; and (iii) surgical treatment at 24 hr following insult did not prevent the downregulation of hepatic CPT gene expression and results in an increase in hepatic Fos nucleoprotein accumulation. These data are consistent with the hypothesis that sepsis-induced regulation of hepatic c-fos gene expression, in part, is responsible for the downregulation of CPT gene expression.

Recurrent amiodarone pulmonary toxicity

Amiodarone, a widely used antiarrhythmic drug, is associated with pulmonary toxicity, with an estimated mortality of 1% to 33%. Standard treatment for amiodarone pulmonary toxicity (APT) has been discontinuance of the drug and steroid therapy. We report a case of APT that recurred after withdrawal of steroids and failed to respond to reinstatement of steroid therapy. Recurrent APT is a rare clinical entity that has been reported only twice in recent literature.

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.

Regulation of the transcription factor C/EBP alpha following peritoneal sepsis

The transcription factors C/EBP alpha and C/EBP beta belong to the leucine-zipper C/EBP (CCAAT/enhancer binding protein) family of DNA-binding proteins. C/EBP alpha and C/EBP beta are expressed in the liver and are implicated in the control of transcriptional events following following sepsis. It is hypothesized that inhibition of C/EBP alpha gene expression following sepsis may lead to some of the phenotypic features we recognize as sepsis syndrome such as decreased visceral protein (albumin) synthesis. In this study we demonstrate that C/EBP alpha mRNA accumulation is transiently inhibited 12 hr following peritoneal insult, consistent with previous data. However, we demonstrate that (1) there is increased binding of hepatic nuclear protein to the C/EBP alpha DNA response element 48 hr following insult, (2) a marked increase in C/EBP alpha protein is observed 48 hr following CLP insult compared with no increase in hepatic C/EBP alpha protein at 12 hr postinsult, (3) the increase in hepatic C/EBP alpha protein at 48 hr following cecal ligation and puncture is not associated with an increase in C/EBP alpha mRNA accumulation, (4) the increase in hepatic C/EBP alpha protein is associated with an increase in C/EBP beta protein, and (5) hepatic albumin mRNA accumulation is decreased at 12 and 48 hr following insult and does not correlate with the C/EBP alpha protein synthesis. We conclude that the possible role of the transcription factor C/EBP alpha with respect to decreased albumin gene expression following sepsis must be reevaluated.

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.

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.

The regulation of mitochondrial fatty acid oxidation and hepatic gene expression by catecholamine

We hypothesized that dopamine or dobutamine may alter hepatic mitochondrial fatty acid oxidation secondary to an effect on hepatic gene expression. We investigated the effect of dopamine or dobutamine on hepatic fat oxidation and gene transcription by studying the enzyme carnitine palmitoyltransferase (CPT), the rate-limiting step in hepatic mitochondrial long-chain fat oxidation. We incubated either H4IIE rat hepatoma cells or rat hepatocytes in primary cell culture with either dopamine (1, 0.1, 0.01 microgram/ml), dobutamine (1, 0.1, 0.01 microgram/ml), or vehicle control for 1, 2, 3, or 4 hr. We investigated the effect on (1) CPT mRNA (Northern or dot blotting) and the possible regulatory mechanism by incubating dopamine (0.1 microgram/ml) or dobutamine (0.1 microgram/ml) with propranolol or phentolamine, (2) CPT translation (CPT [35S]methionine incorporation), and (3) hepatic mitochondrial fatty acid oxidation ([1-14C]-palmitate oxidation to acid-soluble products). We conclude that (1) dopamine or dobutamine increases both hepatic CPT mRNA and CPT protein translation, (2) the effect on CPT mRNA is mediated by the beta-receptor, (3) the increase in hepatic mitochondrial fat oxidation induced by dopamine or dobutamine may be, in part, secondary to increased CPT transcription and translation, and (4) the significant difference in hepatic fat oxidation induced by dopamine as compared with that by dobutamine is secondary to factors other than transcriptional or translational mechanisms. We speculate that dopamine treatment in the critically ill may increase hepatic mitochondrial fatty acid oxidation and ketogenesis and that this increase in beta-oxidation may be, in part, secondary to increased CPT gene expression.

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.

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.

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.

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.