Prostaglandin E2 and thromboxane B2 release from human monocytes treated with bacterial lipopolysaccharide

TNF and PGE(2) in human monocyte-derived macrophages infected with Chlamydia trachomatis

In this study levels of prostaglandin E₂ (PGE₂), tumour necrosis factor (TNF) and interleukin-1 (IL-1) alpha in medium from monocyte derived macrophages (MdM) infected with Chlamydia trachomatis (L₂/434/Bu or K biovars). TNF and PGE₂ were found in both cases while IL-1 alpha was not detected. Both TNF and PGE₂ levels were higher in the medium of the MdM infected with K biovars. TNF reached maximum levels 24 h postinfection, and then declined, while PGE₂ levels increased continuously during the infection time up to 96 h post-infection. Addition of dexamethasone inhibited production of TNF and PGE₂. Inhibition of PGE₂ production by indomethacin resulted in increased production of TNF, while addition of PGE₂ caused partial inhibition of TNF production from infected MdM.

Biomarkers of inflammation in cattle determining the effectiveness of anti-inflammatory drugs

The impact of nonsteroidal anti-inflammatory drugs (NSAID) on prostaglandin E(2) (PGE(2)) production and cyclooxygenase 2 (COX-2) mRNA expression in bovine whole blood (WB) cultures stimulated by lipopolysaccharide (LPS) was determined, using the blood from six Holstein dairy cattle in various stages of lactation. Peak production of PGE(2) occurred 24 h after LPS stimulation but did not result in detectable concentrations of thromboxane B(2) (TXB(2)). The NSAID indomethacin, aspirin, flunixin meglumine, and 4-[5-phenyl-3-(trifluoromethyl)-1H-pyrazol-1-yl] benzene sulfonamide (PTPBS; celecoxib analogue), along with dexamethasone, were all equally effective in reducing the concentration of PGE(2) in the bovine WB culture supernatants. Bradykinin exhibited peak supernatant concentrations 1 h after LPS stimulation. Dexamethasone and the NSAID used in this study were equally effective at inhibiting bradykinin production. Peak induction of COX-2 mRNA occurred 3 h post-LPS stimulation. However, neither dexamethasone nor any of the NSAID used in this study altered COX-2 mRNA concentrations. In contrast, aspirin, flunixin meglumine, and PTPBS reduced tumor necrosis factor-alpha (TNFalpha) mRNA concentration. These results demonstrate that bovine blood cells respond to NSAID therapy like other mammalian cells with respect to inhibition of PGE(2) production and suppression of TNF mRNA induction, but do not inhibit induction of COX-2 mRNA.

Ellagic acid inhibits lipopolysaccharide-induced expression of enzymes involved in the synthesis of prostaglandin E2 in human monocytes

Ellagic acid, a natural polyphenol found in certain fruits, nuts and vegetables, has in recent years been the subject of intense research within the fields of cancer and inflammation. Pain, fever and swelling, all typical symptoms of inflammation, are ascribed to elevated levels of PGE2. In the present study, we have investigated the effects of ellagic acid on PGE2 release and on prostaglandin-synthesising enzymes in human monocytes. Ellagic acid was found to inhibit Ca ionophore A23187-, phorbol myristate acetate- and opsonised zymosan-induced release of PGE2 from monocytes pre-treated with the inflammatory agent lipopolysaccharide. Ellagic acid suppressed the lipopolysaccharide-induced increase in protein expression of cyclo-oxygenase-2 (COX-2), microsomal PGE synthase-1 (mPGEs-1) and cytosolic phospholipase A2α (cPLA2α), while it had no effect on the constitutively expressed COX-1 protein. Ellagic acid had no apparent inhibitory effect on these enzymes when the activities were determined in cell-free assays. We conclude that the inhibitory effect of ellagic acid on PGE2 release from monocytes is due to a suppressed expression of COX-2, mPGEs-1 and cPLA2α, rather than a direct effect on the activities of these enzymes.

Immunization of Macaca fascicularis against experimental periodontitis using a vaccine containing cysteine proteases purified from Porphyromonas gingivalis

INTRODUCTION

Periodontitis is a common infectious disease to which Porphyromonas gingivalis has been closely linked, in which the attachment tissues of the teeth and their alveolar bone housing are destroyed. We conducted a study to determine if immunization using a purified antigen could alter the onset and progression of the disease.

METHODS

Using the ligature-induced model of periodontitis in Macaca fascicularis, we immunized five animals with cysteine protease purified from P. gingivalis and used an additional five animals as controls. Alveolar bone loss was measured by digital subtraction radiography.

RESULTS

Immunization induced high titers of specific immunoglobuin G serum antibodies that were opsonic. Total bacterial load, levels of P. gingivalis in subgingival plaque and levels of prostaglandin E(2) in gingival crevicular fluid were significantly reduced. Onset and progression of alveolar bone loss was inhibited by approximately 50%. No manifestations of toxicity were observed.

CONCLUSIONS

Immunization using a purified protein antigen from P. gingivalis inhibits alveolar bone destruction in a ligature-induced periodontitis model in M. fascicularis.

Angiopeptin, a somatostatin analogue, inhibits rat coronary artery and aorta smooth muscle cell proliferation induced by the thromboxane A2 mimetic U46619

Thromboxane A2 (TXA2) is a potent mitogenic agent. Its synthesis is increased in transplant patients during rejection episodes, which is the suspected etiology of accelerated transplant arteriosclerosis. Angiopeptin, a stable analogue of somatostatin, inhibits arterial myointimal thickening in a number of vascular balloon injury models of angioplasty and in vivo models of transplant arteriosclerosis. In this study, we investigated whether TXA2-induced smooth muscle cell proliferation is inhibited by Angiopeptin in vitro. Primary rat coronary and aorta smooth muscle cells were cultured in the presence of U46619, a TXA2 mimetic. Proliferation induced by U46619, as determined by 3H-thymidine incorporation, was abrogated by two specific thromboxane receptor antagonists, SQ 30741 and SQ 29548, indicating that the effect of U46619 on smooth muscle cells is a specific receptor-mediated response. We found Angiopeptin to inhibit proliferation following exposure of both coronary and aorta smooth muscle cells to varying concentrations of U46619 for 3 and 6 days. This study demonstrates that U46619 exerts a specific receptor-mediated response stimulating the rat coronary and aorta smooth muscle cell proliferation. This mitogenic effect is obtained by increasing the G1 to S transition rate. Angiopeptin inhibits thromboxane-induced cell proliferation to the same extent as a thromboxane antagonist. This inhibition is obtained by maintaining the noncycling fraction in that Angiopeptin prevents a progression from G0-G1 to S phase.

Risk assessment for periodontal diseases

Assessment of risk for periodontitis is still in its infancy. Nevertheless, a sufficient amount of dependable information exists to begin using risk assessment in the day to day practice of dentistry. The purpose of this paper is to summarise existing information about risks for periodontitis in a manner that is useful to practitioners. Risks for moderate to severe periodontitis that have been identified include cigarette smoking, advancing age, diabetes mellitus and certain other systemic conditions. These include, osteoporosis and HIV infection and conditions such as irradiation and immunosuppressive drugs that interfere with normal host defences, specific pathogenic bacteria in the subgingival flora, microbial deposits and poor oral hygiene status, bleeding on probing, previous disease experience and severity, and inheritance. Some risks such as pathogenic bacteria in the subgingival flora are strongly linked to causation of the disease while others such as bleeding on probing may indicate enhanced risk for future disease but are not known to be involved in causation and still others such as advancing age may be background factors that enhance susceptibility. While some risks such as cigarette smoking can be modified to lower the level of risk, others such as ageing are immutable and cannot be modified but need to be considered in overall risk assessment. A goal of periodontal diagnosis, treatment planning and therapy is to lower risk for future periodontal deterioration to the maximal extent. One approach to achieving this goal is described.

Protein phosphorylation in murine peritoneal macrophages induced by infection with Salmonella species

Infection of peritoneal macrophages from C3H/HeN and C3H/HeJ mice with Salmonella typhimurium or S. enteritidis induced extensive phosphorylation in a set of proteins with molecular masses of 85, 72, 35, 30, and 23 kDa, which were different from those induced by bacterial lipopolysaccharide. The phosphorylated proteins of 35, 30, and 23 kDa (pp35, pp30, and pp23, respectively) originated from the infecting bacteria, because living bacteria could induce these phosphorylated proteins themselves, and no induction of the proteins occurred in macrophages after phagocytosis of heat-killed or UV-irradiated organisms. When the infected macrophages were disrupted and separated into bacterial and macrophage debris fractions, pp85 and pp72 remained in the macrophage debris fraction, with none in the bacterial fraction. Induction of pp85 and pp72 in infected macrophages was inhibited in the presence of chloramphenicol but not cytochalasin D, suggesting that bacterial growth in the macrophages is necessary for induction of both proteins. Neither of these proteins could be detected in macrophages infected with Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, or Listeria monocytogenes. These results support the view that phosphorylation of the 85- and 72-kDa proteins occurs in the macrophages during the early phases of the interaction between Salmonella organisms and macrophages. The functions of specific proteins remain to be clarified.

Lipopolysaccharides prime whole human blood and isolated neutrophils for the increased synthesis of 5-lipoxygenase products by enhancing arachidonic acid availability: involvement of the CD14 antigen

Stimulation of heparinized blood with 1 microM formyl-methionyl-leucyl-phenylalanine (FMLP) resulted in the formation of < 30 pmol/ml plasma of 5-lipoxygenase (5-LO) products. The preincubation of blood with 1 microgram/ml of lipopolysaccharide (LPS) (Escherichia coli 0111-B4) for 30 min before stimulation with FMLP resulted in the accumulation of 250-300 pmol of 5-LO products per ml plasma. The major products detected were leukotriene B4 and (5S)-hydroxy-6,8,11,14-eicosatetraenoic acid which were produced in equivalent amounts. The priming activity was detectable with as little as 1-10 ng LPS per ml blood and was optimal using 1-10 micrograms LPS/ml blood. The priming for 5-LO product synthesis was optimal after 20-30 min of preincubation with LPS and declined at preincubation times > 30 min. The priming effect of LPS was also observed using the complement fragment C5a or interleukin 8 as agonists. Polymorphonuclear leukocytes (PMN) and peripheral blood mononuclear cells accounted for 80 and 20% of the synthesis of 5-LO products, respectively. The ability of LPS to prime isolated PMN was dependent on the presence of plasma and was inhibited by the anti-CD14 antibody IOM2, indicating a CD14-dependent priming mechanism. The priming of whole blood with tumor necrosis factor alpha (TNF-alpha) and LPS was additive and the presence of mononuclear cells did not enhance the ability of LPS to prime PMN, indicating that the priming activity of LPS is independent of LPS-induced TNF-alpha synthesis. The mechanism by which LPS enhance 5-LO product synthesis in PMN was investigated. Treatment of PMN with LPS strongly enhanced the release of arachidonic acid after stimulation with FMLP. The release of arachidonic acid was optimal 2-3 min after stimulation with FMLP, attaining levels 5-15-fold greater than those observed in unprimed cells stimulated with FMLP. These results demonstrate that LPS dramatically increases the ability of blood to generate 5-LO products, and support the putative role of leukotrienes in pathological states involving LPS.

Pathogenesis and pathophysiology of bacterial meningitis

Bacterial meningitis remains a disease with associated unacceptable morbidity and mortality rates despite the availability of effective bactericidal antimicrobial therapy. Through the use of experimental animal models of infection, a great deal of information has been gleaned concerning the pathogenic and pathophysiologic mechanisms operable in bacterial meningitis. Most cases of bacterial meningitis begin with host acquisition of a new organism by nasopharyngeal colonization followed by systemic invasion and development of a high-grade bacteremia. Bacterial encapsulation contributes to this bacteremia by inhibiting neutrophil phagocytosis and resisting classic complement-mediated bactericidal activity. Central nervous system invasion then occurs, although the exact site of bacterial traversal into the central nervous system is unknown. By production and/or release of virulence factors into and stimulation of formation of inflammatory cytokines within the central nervous system, meningeal pathogens increase permeability of the blood-brain barrier, thus allowing protein and neutrophils to move into the subarachnoid space. There is then an intense subarachnoid space inflammatory response, which leads to many of the pathophysiologic consequences of bacterial meningitis, including cerebral edema and increased intracranial pressure. Attenuation of this inflammatory response with adjunctive dexamethasone therapy is associated with reduced concentrations of tumor necrosis factor in the cerebrospinal fluid, with diminished cerebrospinal fluid leukocytosis, and perhaps with improvement of morbidity, as demonstrated in recent clinical trials. Further information on the pathogenesis and pathophysiology of bacterial meningitis should lead to the development of more innovative treatment and/or preventive strategies for this disorder.

The effects of interferon-gamma and bacterial lipopolysaccharide on CD14 expression in human monocytes

CD14 has been reported to be the lipopolysaccharide (LPS)-LPS binding protein receptor. The effects of interferon-gamma (IFN-gamma) on CD14 expression have not been clearly established. The purpose of this investigation was to examine the effects of IFN-gamma alone and IFN-gamma followed by bacterial LPS on CD14 expression. Human peripheral blood monocytes were isolated by counterflow centrifugal elutriation (CCE). Monocytes were cultured for 48 h with IFN-gamma alone or for 24 h with IFN-gamma followed by LPS for a second 24 h. IFN-gamma alone caused a down-regulation of CD14 expression, as assessed by flow cytometry, relative to CD14 expression in untreated monocytes. In addition, CD14 expression was even more significantly down-regulated after IFN-gamma pretreatment followed by either Prevotella intermedia or Salmonella typhimurium LPS. Likewise, the percentage of CD14+ monocytes decreased after IFN-gamma alone and even more dramatically after IFN-gamma treatment followed by either LPS. This study clearly demonstrated that IFN-gamma down-regulates CD14 expression and that LPS following IFN-gamma pretreatment potentiates this effect.

Influence of mineral dust surface chemistry on eicosanoid production by the alveolar macrophage

It has been suggested that radicals on the surface of dust particles are key chemical factors in the pathophysiology that results from the occupational inhalation of coal and silica dust. In addition, oxygenated derivatives of arachidonic acid (eicosanoids) have been implicated as important biochemical mediators of mineral dust-induced lung disease through their role in bronchial and vascular smooth muscle reactivity, inflammation, and fibrosis. Therefore, we assessed eicosanoid production by the rat alveolar macrophage (AM) exposed in vitro to mineral dusts with varying surface chemical characteristics in order to determine if radicals associated with the mineral dust could influence the production of proinflammatory mediators in the lung environment. Primary cultures of rat AM were exposed to freshly fractured or "stale" bituminous coal dust, as well as untreated silica or silica calcined to 500 and 1100 degrees C. Prostaglandin E2 (PGE2), thromboxane A2 (TXA2), and leukotriene B4 (LTB4) levels in incubation medium were determined by specific radioimmunoassay. When AM were exposed to freshly fractured coal dust, PGE2 production was markedly increased. In contrast, exposure of AM to "stale" dust significantly reduced PGE2 production. Exposure of AM to freshly fractured coal dust resulted in a significant increase in production by AM, while exposure to stale coal dust did not influence AM TXA2 production. Neither "fresh" nor "stale" coal dust had any effect on LTB4 production. In vitro exposure of AM to untreated silica resulted in a significant increase in TXA2 PGE2, TXA2, and LTB4 production compared with control. However, exposure of AM to silica calcined to 1100 degrees C resulted in eicosanoid levels that were not significantly different from control. These effects were still apparent 8 wk after calcination of the silica particles. Silica was a more potent activator of AM eicosanoid production than was coal, and amorphous fumed silica was a more potent activator of AM eicosanoid production than was crystalline silica. These findings suggest that radicals associated with respirable coal and silica particles may play a key role in the ability of mineral dust to activate AM eicosanoid production and therefore may be important in the pathophysiological consequences of occupational mineral dust inhalation.

Absence of modulation of monokine production via endogenous cyclooxygenase or 5-lipoxygenase metabolites: MK-886 (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2- dimethylpropanoic acid), indomethacin, or arachidonate fail to alter immunoreactive interleukin-1 beta, or TNF-alpha production by human monocytes in vitro

Human peripheral blood monocytes exposed to MK-886 (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2- dimethylpropanoic acid) at doses which abolish formation of 5-lipoxygenase metabolites showed unaltered interleukin-1 beta (IL-1 beta) or tumor necrosis factor-alpha (TNF-alpha) levels in response to phorbol ester, concanavalin A, serum-treated zymosan, or lipopolysaccharide. Indomethacin (10 microM), alone or in combination with MK-886, also failed to modulate monokine production in response to any stimulus. Exogenous arachidonate (3-30 microM) which augmented the formation of PGE2 and LTB4 in the absence of stimulation, also had no effect on monokine production. LPS-induced IL-1 and TNF production occurred despite stimulation of PGE2 synthesis. The results make a role for endogenous prostaglandins and leukotrienes in the regulation of monocyte IL-1 beta and TNF-alpha production unlikely. These data also indicate that MK-886, a novel inhibitor of 5-lipoxygenase product formation, is a potentially useful leukotriene inhibitor which does not affect monokine production.

Prostaglandin E release from human monocytes treated with lipopolysaccharides isolated from Bacteroides intermedius and Salmonella typhimurium: potentiation by gamma interferon

The purpose of this investigation was to examine gamma interferon potentiation of lipopolysaccharide (LPS) responses in human monocytes by using phenol-water-extracted (unfractionated) and highly purified LPS preparations isolated from Bacteroides intermedius and Salmonella typhimurium. Phenol-water-extracted LPS preparations from these bacteria were further purified by chromatography over Sepharose-CL-4B. LPS enrichment in pooled column fractions was assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and quantitation of hydroxy-fatty acid and 2-keto-3-deoxyoctulosonic acid content, protein contamination, and anthrone-reactive material. Monocyte stimulation by LPS, measured as prostaglandin E (PGE) release, was assessed with and without gamma interferon treatment. Cells were either treated simultaneously with gamma interferon and LPS or pretreated with gamma interferon prior to LPS stimulation. PGE release from counterflow-isolated monocytes was quantitated during the 0- to 24-h and 24- to 48-h culture intervals. Contrary to previous results from this laboratory, phenol-water-extracted LPS preparations from B. intermedius and S. typhimurium were similar in their capacities to stimulate PGE release from monocytes. Molecular sieve chromatography was found to remove substantial amounts of high-molecular-weight polysaccharide contaminants only from the B. intermedius LPS but did not significantly alter the potency of either B. intermedius or S. typhimurium LPS. Gamma interferon cotreatment did not potentiate the release of PGE with any of the LPS preparations tested. However, 24-h pretreatment of monocytes with gamma interferon followed by a 24-h exposure to LPS resulted in significant potentiation of PGE release over LPS alone. In addition, B. intermedium preparations were approximately threefold more potent than similarly prepared LPS isolates from S. typhimurium following gamma interferon pretreatment. These results indicate that gamma interferon can selectively potentiate the effects of B. intermedius LPS in human monocyte isolates.

Tumor necrosis factor alpha and prostaglandin E2 production by human monocyte-derived macrophages infected with spotted fever group rickettsiae

Infection of macrophages by intracellular parasites might modulate production of tumor necrosis factor (TNF) and prostaglandin E2 (PGE2), which, in turn, might have a profound effect on the outcome of the infection in vivo. In this study we examined in an in vitro system, the rickettsial yield in human monocyte-derived macrophages (MdM) and the PGE2 and TNF production by MdM infected with Rickettsia conorii RC, Casablanca strain) or Israeli spotted fever (ISF, G-212 strain). TNF and PGE2 were determined in the media of MdM infected with RC or ISF. TNF reached maximum levels 24 h post-infection and then declined, while PGE2 levels increased continuously during the infection up to 96 h post-infection. Addition of dexamethasone inhibited both TNF and PGE2 production and enhanced rickettsial yield in MdM. Inhibition of PGE2 production by indomethacin resulted in increased production of TNF from rickettsial-infected MdM, while addition of PGE2 caused partial inhibition of TNF production from infected MdM.