Ambiguous Contribution of Glucocorticosteroids to Acute Neuroinflammation in the Hippocampus of Rat

Effects of modulation of glucocorticoid and mineralocorticoid receptors (GR and MR, respectively) on acute neuroinflammatory response were studied in the dorsal (DH) and ventral (VH) parts of the hippocampus of male Wistar rats. Local neuroinflammatory response was induced by administration of bacterial lipopolysaccharide (LPS) to the DH. The modulation of GR and MR was performed by dexamethasone (GR activation), mifepristone, and spironolactone (GR and MR inhibition, respectively). Experimental drugs were delivered to the dentate gyrus of the DH bilaterally by stereotaxic injections. Dexamethasone, mifepristone, and spironolactone were administered either alone (basal conditions) or in combination with LPS (neuroinflammatory conditions). Changes in expression levels of neuroinflammation-related genes and morphology of microglia 3 days after intrahippocampal administration of above substances were assessed. Dexamethasone alone induced a weak proinflammatory response in the hippocampal tissue, while neither mifepristone nor spironolactone showed significant effects. During LPS-induced neuroinflammation, GR activation suppressed expression of selected inflammatory genes, though it did not prevent appearance of activated forms of microglia. In contrast to GR activation, GR or MR inhibition had virtually no influence on LPS-induced inflammatory response. The results suggest glucocorticosteroids ambiguously modulate specific aspects of neuroinflammatory response in the hippocampus of rats at molecular and cellular levels.

N-Acetylcysteine in Mechanically Ventilated Rats with Lipopolysaccharide-Induced Acute Respiratory Distress Syndrome: The Effect of Intravenous Dose on Oxidative Damage and Inflammation

Treatment of acute respiratory distress syndrome (ARDS) is challenging due to its multifactorial aetiology. The benefit of antioxidant therapy was not consistently demonstrated by previous studies. We evaluated the effect of two different doses of intravenous (i.v.) N-acetylcysteine (NAC) on oxidative stress, inflammation and lung functions in the animal model of severe LPS-induced lung injury requiring mechanical ventilation. Adult Wistar rats with LPS (500 μg/kg; 2.2 mL/kg) were treated with i.v. NAC 10 mg/kg (NAC10) or 20 mg/kg (NAC20). Controls received saline. Lung functions, lung oedema, total white blood cell (WBC) count and neutrophils count in blood and bronchoalveolar lavage fluid, and tissue damage in homogenized lung were evaluated. NAC significantly improved ventilatory parameters and oxygenation, reduced lung oedema, WBC migration and alleviated oxidative stress and inflammation. NAC20 in comparison to NAC10 was more effective in reduction of oxidative damage of lipids and proteins, and inflammation almost to the baseline. In conclusion, LPS-instilled and mechanically ventilated rats may be a suitable model of ARDS to test the treatment effects at organ, systemic, cellular and molecular levels. The results together with literary data support the potential of NAC in ARDS.

Bacterial Lipopolysaccharide Augmented Malignant Transformation and Promoted the Stemness in Prostate Cancer Epithelial Cells

Purpose

To study bacterial lipopolysaccharide (LPS)-induced cancer stem-like transformation and to investigate the inhibitory effect of Trichostatin A (TSA) on the malignant transformation through targeting p-Stat3 signaling.

Methods

2D, 3D, and serum-free suspension culture system were used to study LPS-induced malignant transformation in series malignant grade of prostate cancer (PCa) epithelial cells. Flow cytometry assay and RT-PCR were utilized to evaluate the CD44⁺CD133⁺ stem cell population, the expression of inflammatory cytokines and series tumor stemness biomarkers. Meanwhile, Western blot was used to analyze the alteration of cell signaling associated-molecules by treatment with TSA, an original antifungal antibiotic and a panel inhibitor of histone deacetylase.

Results

Our study found that LPS promoted the migration, invasion and stem-like tumoroshpere forming in multiple PCa cell lines including DU145, PC3, 22RV1, LNCaP. LPS also enriched CD44⁺CD133⁺ stem cell population and increased the expression of series tumor stemness biomarkers (e.g., CD44, CD133, SOX-2, α-intergrin, Nestin, etc.). TSA was found to prevent tumor cell migration, invasion and tumorosphere forming in DU145 and PC3 cells with increasing tumor suppressive Maspin and reducing both phosphorylation of Stat3 (p-Stat3) and pro-oncogene c-Myc expression in LPS-treated DU145 cells. Furthermore, blocking Stat3 signaling pathway by treatment with TSA and/or small molecule compound Stattic of an p-Stat3 inhibitor effectively abrogated LPS-induced tumorosphere forming with decrease of IL-6, IL-8 and stemness biomarkers CD44, SOX-2 expression.

Conclusion

Our data demonstrated that the inflammatory agent of bacterial LPS augmented malignant transformation and promoted the cancerous stemness in PCa epithelial cells. TSA could prevent, at least in part, the LPS-induced malignant transformation by targeting p-Stat3/c-Myc signaling pathway and reducing inflammatory IL-6, IL-8. In addition, the assay of LPS-induced tumorosphere forming could serve as a simple and an easy handling method for targeting cancer stem cells drug screening in vitro in clinical practice.

Targeting the Gut Microbiota for Remediating Obesity and Related Metabolic Disorders

The rate of obesity is rapidly increasing and has become a health and economic burden worldwide. As recent studies have revealed that the gut microbiota is closely linked to obesity, researchers have used various approaches to modulate the gut microbiota to treat the condition. Dietary composition and energy intake strongly affect the composition and function of the gut microbiota. Intestinal microbial changes alter the composition of bile acids and fatty acids and regulate bacterial lipopolysaccharide production, all of which influence energy metabolism and immunity. Evidence also suggests that remodeling the gut microbiota through intake of probiotics, prebiotics, fermented foods, and dietary plants, as well as by fecal microbiota transplantation, are feasible methods to remediate obesity.

Celecoxib treatment dampens LPS-induced periapical bone resorption in a mouse model

AIM

To evaluate the efficacy of selective and nonselective inhibitors of cyclooxygenase-2 enzymes in the treatment of experimental apical periodontitis induced by bacterial lipopolysaccharide (LPS) in vivo in a mouse model.

METHODOLOGY

Thirty-six C57BL/6 mice were used. After access cavity preparation, a solution containing E. coli LPS (1.0 µg µL^-1 ) was inoculated into the root canals of the mandibular and maxillary right first molars (n = 72) After 30 days, apical periodontitis was established and the animals were systemically treated with celecoxib, a selective COX-2 inhibitor (15 mg kg^-1 ), or indomethacin, a nonselective COX-2 inhibitor (5 mg kg^-1 ), for 7 and 14 days. Blocks containing teeth and bone were removed for histopathological and histometric analyses (haematoxylin and eosin), evaluation of osteoclasts numbers (tartrate-resistant acid phosphatase enzyme - TRAP) and immunohistochemistry for RANK, RANKL and OPG. Gene expression was performed using reverse transcription and real-time polymerase chain reaction (qRT-PCR) for RANK, RANKL, OPG, TRAP, MMP-9, cathepsin K and calcitonin receptor. Histopathological, histometric, TRAP, immunohistochemistry and qRT-PCR data were evaluated using Kruskal-Wallis followed by Dunn's test (α = 0.05).

RESULTS

Systemic administration of celecoxib for 7 and 14 days prevented periapical bone resorption (P < 0.0001), differently from indomethacin that exacerbated bone resorption at 7 days (P < 0.0001) or exerted no effect at 14 days (P = 0.8488). Celecoxib treatment reduced osteoclast formation in apical periodontitis, regardless of the period of treatment (P < 0.0001 for 7 days and P = 0.026 for 14 days). Administration of celecoxib or indomethacin differentially modulated the expression of genes involved in bone resorption. At 7 days, celecoxib and indomethacin treatment significantly inhibited expression of mRNA for cathepsin K (P = 0.0005 and P = 0.016, respectively) without changing TRAP, MMP-9 and calcitonin receptor gene expression. At 14 days, celecoxib significantly inhibited expression of mRNA for MMP-9 (P < 0.0001) and calcitonin receptor (P = 0.004), whilst indomethacin exerted no effect on MMP-9 (P = 0.216) and calcitonin receptor (P = 0.971) but significantly augmented cathepsin K gene expression (P = 0.001).

CONCLUSIONS

The selective COX-2 inhibitor celecoxib reduced osteoclastogenic signalling and activity that dampened bone resorption in LPS-induced apical periodontitis in mice, with greater efficacy than the nonselective inhibitor indomethacin.

The Effect of Modified Porcine Surfactant Alone or in Combination with Polymyxin B on Lung Homeostasis in LPS-Challenged and Mechanically Ventilated Adult Rats

The study aimed to prove the hypothesis that exogenous surfactant and an antibiotic polymyxin B (PxB) can more effectively reduce lipopolysaccharide (LPS)-induced acute lung injury (ALI) than surfactant treatment alone, and to evaluate the effect of this treatment on the gene expression of surfactant proteins (SPs). Anesthetized rats were intratracheally instilled with different doses of LPS to induce ALI. Animals with LPS 500 μg/kg have been treated with exogenous surfactant (poractant alfa, Curosurf^®, 50 mg PL/kg b.w.) or surfactant with PxB 1% w.w. (PSUR + PxB) and mechanically ventilated for 5 hrs. LPS at 500 μg/kg increased lung edema, oxidative stress, and the levels of proinflammatory mediators in lung tissue and bronchoalveolar lavage fluid (BALF). PSUR reduced lung edema and oxidative stress in the lungs and IL-6 in BALF. This effect was further potentiated by PxB added to PSUR. Exogenous surfactant enhanced the gene expression of SP-A, SP-B, and SP-C, however, gene expression for all SPs was reduced after treatment with PSUR + PxB. In mechanically ventilated rats with LPS-induced ALI, the positive effect of exogenous surfactant on inflammation and oxidative stress was potentiated with PxB. Due to the tendency for reduced SPs gene expression after surfactant/PxB treatment topical use of PxB should be considered with caution.

Administration of Bacterial Lipopolysaccharide during Early Postnatal Ontogenesis Induces Transient Impairment of Long-Term Synaptic Plasticity Associated with Behavioral Abnormalities in Young Rats

Infectious diseases in early postnatal ontogenesis often result in cognitive impairments, particularly learning and memory. The essential foundation of learning and memory is long-term synaptic plasticity, which depends on N-methyl-D-aspartate (NMDA) receptors. In the present study, bacterial infection was modeled by treating rat pups with bacterial lipopolysaccharide (LPS, 25 µg/kg) three times, during either the first or the third week of life. These time points are critical for the maturation of NMDA receptors. We assessed the effects of LPS treatments on the properties of long-term potentiation (LTP) in the CA1 hippocampus of young (21–23 days) and adolescent (51–55 days) rats. LTP magnitude was found to be significantly reduced in both groups of young rats, which also exhibited investigative and motor behavior disturbances in the open field test. No changes were observed in the main characteristics of synaptic transmission, although the LTP induction mechanism was disturbed. In rats treated with LPS during the third week, the NMDA-dependent form of LTP was completely suppressed, and LTP switched to the Type 1 metabotropic glutamate receptor (mGluR1)-dependent form. These impairments of synaptic plasticity and behavior were temporary. In adolescent rats, no difference was observed in LTP properties between the control and experimental groups. Lastly, the investigative and motor behavior parameters in both groups of adult rats were similar.

Short-Term versus Long-Term Culture of A549 Cells for Evaluating the Effects of Lipopolysaccharide on Oxidative Stress, Surfactant Proteins and Cathelicidin LL-37

Alveolar epithelial type II (ATII) cells and their proper function are essential for maintaining lung integrity and homeostasis. However, they can be damaged by lipopolysaccharide (LPS) during Gram-negative bacterial infection. Thus, this study evaluated and compared the effects of LPS on short and long-term cultures of A549 cells by determining the cell viability, levels of oxidative stress and antimicrobial peptide cathelicidin LL-37 and changes in the expression of surfactant proteins (SPs). Moreover, we compared A549 cell response to LPS in the presence of different serum concentrations. Additionally, the effect of N-acetylcysteine (NAC) on LPS-induced oxidative stress as a possible treatment was determined. Our results indicate that A549 cells are relatively resistant to LPS and able to maintain integrity even at high LPS concentrations. Their response to endotoxin is partially dependent on serum concentration. NAC failed to lower LPS-induced oxidative stress in A549 cells. Finally, LPS modulates SP gene expression in A549 cells in a time dependent manner and differences between short and long-term cultures were present. Our results support the idea that long-term cultivation of A549 cells could promote a more ATII-like phenotype and thus could be a more suitable model for ATII cells, especially for in vitro studies dealing with surfactant production.

Extra-Virgin Olive Oil Modifies the Changes Induced in Non-Nervous Organs and Tissues by Experimental Autoimmune Encephalomyelitis Models

This study reveals the existence of oxidative stress (reactive oxygen species (ROS)) in non-nervous organs and tissues in multiple sclerosis (MS) by means of a model of experimental autoimmune encephalomyelitis (EAE) in rats. This model reproduces a similar situation to MS, as well as its relationship with intestinal microbiota starting from the changes in bacterial lipopolysaccharide levels (LPS) in the outer wall of the gram-negative bacteria. Finally, the administration of extra-virgin olive oil (EVOO), hydroxytirosol (HT), and oleic acid (OA) exert beneficial effects. Twenty-five Dark Agouti two-month-old male rats, weighing around 190 g, were distributed into the following groups: Control, EAE (experimental autoimmune encephalomyelitis group), EAE + EVOO, EAE + HT, and EAE + OA. The glutathione redox system with the EAE was measured in heart, kidney, liver, and small and large intestines. The LPS and the correlation with oxidative stress in the small and large intestines were also investigated. The results showed that (1) the oxidative damage in the EAE model affects non-nervous organs and tissues; (2) The LPS is related to inflammatory phenomena and oxidative stress in the intestinal tissue and in other organs; (3) The administration of EVOO, HT, and OA reduces the LPS levels at the same time as minimizing the oxidative damage; (4) EVOO, HT, and OA improve the disease's clinical score; and (5) on balance, EVOO offers a better neuroprotective effect.

Alveolar-Capillary Membrane-Related Pulmonary Cells as a Target in Endotoxin-Induced Acute Lung Injury

The main function of the lungs is oxygen transport from the atmosphere into the blood circulation, while it is necessary to keep the pulmonary tissue relatively free of pathogens. This is a difficult task because the respiratory system is constantly exposed to harmful substances entering the lungs by inhalation or via the blood stream. Individual types of lung cells are equipped with the mechanisms that maintain pulmonary homeostasis. Because of the clinical significance of acute respiratory distress syndrome (ARDS) the article refers to the physiological role of alveolar epithelial cells type I and II, endothelial cells, alveolar macrophages, and fibroblasts. However, all these cells can be damaged by lipopolysaccharide (LPS) which can reach the airspaces as the major component of the outer membrane of Gram-negative bacteria, and lead to local and systemic inflammation and toxicity. We also highlight a negative effect of LPS on lung cells related to alveolar-capillary barrier and their response to LPS exposure. Additionally, we describe the molecular mechanism of LPS signal transduction pathway in lung cells.

Dual Role of Toll-like Receptors in Human and Experimental Asthma Models

Asthma is a chronic airway inflammatory disease that is influenced by the interplay between genetic factors and exposure to environmental allergens, microbes, or microbial products where toll-like receptors (TLRs) play a pivotal role. TLRs recognize a wide range of microbial or endogenous molecules as well as airborne environmental allergens and act as adjuvants that influence positively or negatively allergic sensitization. TLRs are qualitatively and differentially expressed on hematopoietic and non-hematopoietic stromal or structural airway cells that when activated by TLRs agonists exert an immune-modulatory role in asthma development. Therefore, understanding mechanisms and pathways by which TLRs orchestrate asthma outcomes may offer new strategies to control the disease. Here, we aim to review and critically discuss the role of TLRs in human asthma and murine models of allergic airway inflammation, highlighting the complexity of TLRs function in development, exacerbation, or control of airway allergic inflammation.

Acute induction of anomalous and amyloidogenic blood clotting by molecular amplification of highly substoichiometric levels of bacterial lipopolysaccharide

It is well known that a variety of inflammatory diseases are accompanied by hypercoagulability, and a number of more-or-less longer-term signalling pathways have been shown to be involved. In recent work, we have suggested a direct and primary role for bacterial lipopolysaccharide (LPS) in this hypercoagulability, but it seems never to have been tested directly. Here, we show that the addition of tiny concentrations (0.2 ng l⁻¹) of bacterial LPS to both whole blood and platelet-poor plasma of normal, healthy donors leads to marked changes in the nature of the fibrin fibres so formed, as observed by ultrastructural and fluorescence microscopy (the latter implying that the fibrin is actually in an amyloid β-sheet-rich form that on stoichiometric grounds must occur autocatalytically). They resemble those seen in a number of inflammatory (and also amyloid) diseases, consistent with an involvement of LPS in their aetiology. These changes are mirrored by changes in their viscoelastic properties as measured by thromboelastography. As the terminal stages of coagulation involve the polymerization of fibrinogen into fibrin fibres, we tested whether LPS would bind to fibrinogen directly. We demonstrated this using isothermal calorimetry. Finally, we show that these changes in fibre structure are mirrored when the experiment is done simply with purified fibrinogen and thrombin (±0.2 ng l⁻¹ LPS). This ratio of concentrations of LPS : fibrinogen in vivo represents a molecular amplification by the LPS of more than 10⁸-fold, a number that is probably unparalleled in biology. The observation of a direct effect of such highly substoichiometric amounts of LPS on both fibrinogen and coagulation can account for the role of very small numbers of dormant bacteria in disease progression in a great many inflammatory conditions, and opens up this process to further mechanistic analysis and possible treatment.

A System Dynamics Model to Predict the Human Monocyte Response to Endotoxins

System dynamics is a powerful tool that allows modeling of complex and highly networked systems such as those found in the human immune system. We have developed a model that reproduces how the exposure of human monocytes to lipopolysaccharides (LPSs) induces an inflammatory state characterized by high production of tumor necrosis factor alpha (TNFα), which is rapidly modulated to enter into a tolerant state, known as endotoxin tolerance (ET). The model contains two subsystems with a total of six states, seven flows, two auxiliary variables, and 14 parameters that interact through six differential and nine algebraic equations. The parameters were estimated and optimized to obtain a model that fits the experimental data obtained from human monocytes treated with various LPS doses. In contrast to publications on other animal models, stimulation of human monocytes with super-low-dose LPSs did not alter the response to a second LPSs challenge, neither inducing ET, nor enhancing the inflammatory response. Moreover, the model confirms the low production of TNFα and increased levels of C-C motif ligand 2 when monocytes exhibit a tolerant state similar to that of patients with sepsis. At present, the model can help us better understand the ET response and might offer new insights on sepsis diagnostics and prognosis by examining the monocyte response to endotoxins in patients with sepsis.

Molecular Signaling and Dysfunction of the Human Reactive Enteric Glial Cell Phenotype: Implications for GI Infection, IBD, POI, Neurological, Motility, and GI Disorders

BACKGROUND

Clinical observations or animal studies implicate enteric glial cells in motility disorders, irritable bowel syndrome, inflammatory bowel disease, gastrointestinal (GI) infections, postoperative ileus, and slow transit constipation. Mechanisms underlying glial responses to inflammation in human GI tract are not understood. Our goal was to identify the "reactive human enteric glial cell (rhEGC) phenotype" induced by inflammation, and probe its functional relevance.

METHODS

Human enteric glial cells in culture from 15 GI-surgical specimens were used to study gene expression, Ca, and purinergic signaling by Ca/fluo-4 imaging and mechanosensitivity. A nanostring panel of 107 genes was designed as a read out of inflammation, transcription, purinergic signaling, vesicular transport protein, channel, antioxidant, and other pathways. A 24-hour treatment with lipopolysaccharide (200 μg/mL) and interferon-γ (10 μg/mL) was used to induce inflammation and study molecular signaling, flow-dependent Ca responses from 3 mL/min to 10 mL/min, adenosine triphosphate (ATP) release, and ATP responses.

RESULTS

Treatment induced a "rhEGC phenotype" and caused up-regulation in messenger RNA transcripts of 58% of 107 genes analyzed. Regulated genes included inflammatory genes (54%/IP10; IFN-γ; CxCl2; CCL3; CCL2; C3; s100B; IL-1β; IL-2R; TNF-α; IL-4; IL-6; IL-8; IL-10; IL-12A; IL-17A; IL-22; and IL-33), purine-genes (52%/AdoR2A; AdoR2B; P2RY1; P2RY2; P2RY6; P2RX3; P2RX7; AMPD3; ENTPD2; ENTPD3; and NADSYN1), channels (40%/Panx1; CHRNA7; TRPV1; and TRPA1), vesicular transporters (SYT1, SYT2, SNAP25, and SYP), transcription factors (relA/relB, SOCS3, STAT3, GATA_3, and FOXP3), growth factors (IGFBP5 and GMCSF), antioxidant genes (SOD2 and HMOX1), and enzymes (NOS2; TPH2; and CASP3) (P < 0.0001). Treatment disrupted Ca signaling, ATP, and mechanical/flow-dependent Ca responses in human enteric glial cells. ATP release increased 5-fold and s100B decreased 33%.

CONCLUSIONS

The "rhEGC phenotype" is identified by a complex cascade of pro-inflammatory pathways leading to alterations of important molecular and functional signaling pathways (Ca, purinergic, and mechanosensory) that could disrupt GI motility. Inflammation induced a "purinergic switch" from ATP to adenosine diphosphate/adenosine/uridine triphosphate signaling. Findings have implications for GI infection, inflammatory bowel disease, postoperative ileus, motility, and GI disorders.

Melatonin prevents experimental preterm labor and increases offspring survival

Preterm delivery is the leading cause of neonatal mortality and contributes to delayed physical and cognitive development in children. At present, there is no efficient therapy to prevent preterm labor. A large body of evidence suggests that intra-amniotic infections may be a significant and potentially preventable cause of preterm birth. This work assessed the effect of melatonin in a murine model of inflammation-associated preterm delivery which mimics central features of preterm infection in humans. For this purpose, preterm labor was induced in BALB/c mice by intraperitoneal injections of bacterial lipopolysaccharide (LPS) at 10.00 hr (10 μg LPS) and 13.00 hr (20 μg LPS) on day 15 of pregnancy. On day 14 of pregnancy, a pellet of melatonin (25 mg) had been subcutaneously implanted into a group of animals. In the absence of melatonin, a 100% incidence of preterm birth was observed in LPS-treated animals, and the fetuses showed widespread damage. By comparison, treatment with melatonin prevented preterm birth in 50% of the cases, and all pups from melatonin-treated females were born alive and their body weight did not differ from control animals. Melatonin significantly prevented the LPS-induced rises in uterine prostaglandin (PG) E2 , PGF2α, and cyclooxygenase-2 protein levels. In addition, melatonin prevented the LPS-induced increase in uterine nitric oxide (NO) production, inducible NO synthase protein, and tumor necrosis factor-alpha (TNFα) levels. Collectively, our results suggest that melatonin could be a new therapeutic tool to prevent preterm labor and to increase offspring survival.

An ethyl acetate fraction of Moringa oleifera Lam. Inhibits human macrophage cytokine production induced by cigarette smoke

Moringa oleifera Lam. (MO) has been reported to harbor anti-oxidation and anti-inflammatory activity and useful in the treatment of inflammatory diseases. However, despite these findings there has been little work done on the effects of MO on immune cellular function. Since macrophages, TNF and related cytokines play an important pathophysiologic role in lung damage induced by cigarette smoke, we examined the effects of MO on cigarette smoke extract (CSE)-induced cytokine production by human macrophages. An ethyl acetate fraction of MO (MOEF) was prepared from fresh leaves extract of Moringa and shown to consist of high levels of phenolic and antioxidant activities. Human monocyte derived macrophages (MDM) pre-treated with varying concentrations of MOEF showed decreased production of TNF, IL-6 and IL-8 in response to both LPS and CSE. The decrease was evident at both cytokine protein and mRNA levels. Furthermore, the extract inhibited the expression of RelA, a gene implicated in the NF-κB p65 signaling in inflammation. The findings highlight the ability of MOEF to inhibit cytokines (IL-8) which promote the infiltration of neutrophils into the lungs and others (TNF, IL-6) which mediate tissue disease and damage.

Regulation of cocaine- and amphetamine-regulated transcript-synthesising neurons of the hypothalamic paraventricular nucleus by endotoxin; implications for lipopolysaccharide-induced regulation of energy homeostasis

Infectious diseases and the administration of bacterial lipopolysaccharide (LPS) result in decreased food intake and increased energy expenditure. Because the hypothalamic paraventricular nucleus (PVN) has pivotal roles in the regulation of energy homeostasis and expresses an anorexic peptide, cocaine- and amphetamine-regulated transcript (CART), we hypothesised that increased CART synthesis in this nucleus may contribute to LPS-induced changes in energy homeostasis. Therefore, we studied the effects of intraperitoneal administration of LPS on CART gene expression in the PVN by semiquantitative in situ hybridisation. LPS caused a rapid increase in CART mRNA levels in the PVN. One hour after treatment, the density of silver grains was increased by three-fold in the PVN, and remained elevated 3 h after treatment. Because the dorsal vagal complex, an important vegetative centre in the brainstem, is heavily innervated by CART-containing axons, we determined whether the retrograde tracer, cholera toxin B subunit (CTB), accumulates in CART neurons in the PVN following stereotaxic injection of the tracer into the dorsal vagal complex. One week after injection, CTB accumulated in CART neurons in the ventral, medial, and lateral parvocellular subdivisions of the PVN. In addition, LPS administration induced c-fos expression in a population of CART neurons in the PVN that project to the dorsal vagal complex. These data indicate that increased CART gene expression in neurons of PVN may contribute to LPS-induced anorexia, and suggest that this action may be mediated, at least in part, through a PVN-dorsal vagal complex pathway.

Inhibition of ornithine decarboxylase potentiates nitric oxide production in LPS-activated J774 cells

We have examined whether modulation of the polyamine biosynthetic pathway, through inhibition by alpha-difluoromethylornithine (DFMO) of the rate limiting enzyme, ornithine decarboxylase (ODC), modulates NO synthesis in J774 macrophages. DFMO potentiated LPS-stimulated nitrite production in both a concentration- and time-dependent manner, increasing nitrite levels by 48+/-5% at 10 mM. This effect was observed in cells pre-treated with DFMO for 24 h prior to stimulation with LPS. Addition of DFMO 12 h after LPS failed to potentiate LPS-induced nitrite production. Supplementation of the culture medium with horse serum (10%) in place of foetal calf serum (10%) caused no significant change in either LPS-induced nitrite production or in the ability of DFMO (10 mM) to potentiate LPS-induced NO synthesis. Metabolism of L-[3H]arginine to L-[3H]citrulline by partially purified inducible nitric oxide synthase (iNOS) was not significantly altered by either DFMO (1-10 mM) or by putrescine (0.001-1 mM), spermidine (0.001-1 mM) or spermine (0.001-1 mM). iNOS activity was also unaffected by 1 mM EGTA but was markedly attenuated (70+/-0.07%) by L-NMMA (100 microM). Pre-incubation of cells with DFMO (10 mM; 24 h) prior to activation with LPS resulted in enhanced (approximately 2 fold) iNOS protein expression. These results show that DFMO potentiates LPS-induced nitrite production in the murine macrophage cell line J774. Since the only known mechanism of action of DFMO is inhibition of ODC, and thus polyamine biosynthesis, we conclude that expression of iNOS can be critically regulated by endogenous polyamines.

Mechanisms of acute vasodilator response to bacterial lipopolysaccharide in the rat coronary microcirculation

1. In this study the mechanisms of the acute vasodilator action of bacterial lipopolysaccharide (LPS) were investigated in the rat Langendorff perfused heart. 2. Infusion of LPS (5 microg ml(-1)) caused a rapid and sustained fall in coronary perfusion pressure (PP) of 59 +/- 4 mmHg (n = 12) and a biphasic increase in NO levels determined in the coronary effluent by chemiluminescent detection. Both the fall in PP and the increase in NO release were completely abolished (n = 3) by pretreatment of hearts with the NO synthase inhibitor L-NAME (50 microM). 3. LPS-induced vasodilatation was markedly attenuated to 5 +/- 4 mmHg (n 3) by pretreatment of hearts with the B2 kinin receptor antagonist Hoe-140 (100 nM). 4. Vasodilator responses to LPS were also blocked by brief pretreatment with mepacrine (0.5 microM, n = 3) or nordihydroguaiaretic acid (0.1 microM, n = 4) and markedly attenuated by WEB 2086 (3 microM, n = 4). 5. Thirty minutes pretreatment of hearts with dexamethasone (1 nM), but not progesterone (1 microM), significantly modified responses to LPS. The action of dexamethasone was time-dependent, having no effect when applied either simultaneously with or pre-perfused for 5 min before the administration of LPS but inhibiting the response to LPS by 91 +/- 1% (n = 4) when pre-perfused for 15 min. The inhibition caused by dexamethasone was blocked by 15 min pretreatment with the glucocorticoid receptor antagonist RU-486 (100 nM) or by 2 min pre-perfusion of a 1:200 dilution of LCPS1, a selective antilipocortin 1 (LC1) neutralizing antibody. 6. Treatment with the protein synthesis inhibitor, cycloheximide (10 microM, for 15 min) selectively blunted LPS-induced vasodilatation, reducing the latter to 3 +/- 5 mmHg (n = 3), while having no effect on vasodilator responses to either bradykinin or sodium nitroprusside. 7. These results indicate that LPS-induced vasodilatation in the rat heart is dependent on activation of kinin B2 receptors and synthesis of NO. In addition, phospholipase A2 (PLA2) is activated by LPS resulting in the release of platelet-activating factor (PAF) and lipoxygenase but not cyclo-oxygenase products. These effects are dependent on de novo synthesis of an intermediate protein which remains to be identified.

Lipopolysaccharide induces expression of tumour necrosis factor alpha in rat brain: inhibition by methylprednisolone and by rolipram

1. We have investigated the effects of the phosphodiesterase (PDE) type IV inhibitor rolipram and of the glucocorticoid methylprednisolone on the induction of tumour necrosis factor alpha (TNF-alpha) mRNA and protein in brains of rats after peripheral administration of lipopolysaccharide (LPS). 2. After intravenous administration of LPS, a similar time-dependent induction of both TNF-alpha mRNA and protein was observed in rat brain. Peak mRNA and protein levels were found 7 h after administration of LPS. 3. In situ hybridization experiments with a specific antisense TNF-alpha riboprobe suggested that the cells responsible for TNF-alpha production in the brain were microglia. 4. Intraperitoneal administration of methylprednisolone inhibited the induction of TNF-alpha protein in a dose-dependent manner. A maximal inhibition of TNF-alpha protein production by 42.9+/-10.2% was observed at a dose regimen consisting of two injections of each 30 mg kg(-1) methylprednisolone. 5. Intraperitoneal administration of rolipram also inhibited the induction of TNF-alpha protein in a dose-dependent manner. The maximal inhibition of TNF-alpha protein production was 96.1+/-12.2% and was observed at a dose regimen of three separate injections of each 3 mg kg(-1) rolipram. 6. In situ hybridization experiments showed that the level of TNF-alpha mRNA induced in rat brain by LPS challenge was reduced by intraperitoneal administration of methylprednisolone (2 x 15 mg kg(-1)) and of rolipram (3 x 3 mg kg(-1)). 7. We suggest that peripheral administration of LPS induces a time-dependent expression of TNF-alpha in rat brain, presumably in microglial cells, and that methylprednisolone and rolipram inhibit LPS-induced expression of TNF-alpha in these cells via a decrease of TNF-alpha mRNA stability and/or TNF-alpha gene transcription.

Effect of non-toxic mercury, zinc or cadmium pretreatment on the capacity of human monocytes to undergo lipopolysaccharide-induced activation

1. Metal salts can inhibit cell activity through direct toxicity to critical cellular molecules and structures. On the other hand, they can also change cell behaviour by inducing specific genes (including genes encoding members of the metallothionein [MT] gene family). Therefore, transition metals may affect cell functions either by acting as a toxin, or by transmitting or influencing signals controlling gene expression. 2. To explore the latter possibility, we measured the ability of low, non-toxic metal pretreatment to alter immune cell behaviour. We previously found that pretreatment of human monocytes with zinc induces metallothionein gene expression and alters their capacity to undergo a bacterial lipopolysaccharide-induced respiratory burst. We showed here that cadmium and mercury salts, at concentrations that exert no discernible toxicity, inhibit activation of human monocytic leukemia (THP-1) cells. CdCl2 1 microM, ZnCl2 20-40 microM or HgCl2 2 microM pretreatment for 20 h induced MT-2 mRNA and total MT protein accumulation and had no effect on proliferation potential or metabolic activity, but significantly inhibited the ability of subsequent lipopolysaccharide treatment to induce the oxidative burst, increased adhesion to plastic, and MT-2 and interleukin-1 beta (IL-1 beta) mRNA accumulation. 3. The phenomenon of metal-induced suppression of monocyte activation, at metal concentrations that have no effect on cell viability, has important implications for assessment of acceptable levels of human exposure to cadmium, zinc and mercury.

Induction of tumoricidal macrophages from bone marrow cells of normal mice or mice bearing a colony-stimulating-factor-producing tumor

Nonadherent cells of the bone marrow of C3H/HeN mice were incubated for 3 days with the culture supernatant of an L-929 cell line containing macrophage-colony-stimulating factor. Approximately, 70% of the cells became phagocytic, adherent to plastic dishes and positive for nonspecific esterase staining. The adherent cells exhibited a weak tumoricidal activity against syngeneic mammary carcinoma cells, and the cytotoxicity was strongly augmented by the addition of bacterial lipopolysaccharide to the cytotoxicity assay. The cytotoxicity induced by lipopolysaccharide was also shown to be mediated by Thy1.2- and asialo-GM1+ cells, and was abrogated by the addition of carrageenan. Macrophage-colony-stimulating-factor-producing (D66) and nonproducing (A23) variants were separated from the MM48 tumor line in in vitro culture following limiting dilution. There was no difference between these two variants in either the in vitro growth rate or the susceptibility to macrophage-mediated cytotoxicity. C3H/HeN mice inoculated i.p. with D66 survived longer than did those inoculated i.p. with A23. C3H/HeN mice bearing D66 or A23 as an ascitic form were given i.p. injections of Nocardia rubra cell wall skeleton (N-CWS). N-CWS significantly prolonged the survival period of mice bearing D66, whereas it exhibited no apparent antitumor effect on mice bearing A23. The increase in the cell number of D66 in the peritoneal cavity was significantly retarded, compared with that of A23. In contrast, the number of peritoneal macrophages increased more in D66-bearing mice than in A23-bearing mice. The increase in the peritoneal macrophage number was further augmented by an i.p. injection of N-CWS. Peritoneal macrophages of D66-bearing mice exhibited apparent tumoricidal activity against MM48 tumor cells in the presence of lipopolysaccharide, and the cytotoxicity was significantly augmented by i.p. injection of N-CWS. On the other hand, the responsiveness of peritoneal macrophages to lipopolysaccharide was found to be poor in A23-bearing mice and the tumoricidal activity was only weakly augmented by N-CWS. These results strongly suggest that M-CSF plays an important role not only in the maturation of macrophage progenitors but also in the induction and the accumulation of activated macrophages.