Haem oxygenase-1 induction protects against tumour necrosis factor α impairment of endothelial-dependent relaxation in rat isolated pulmonary artery

Background and purpose:

Disturbances in pulmonary vascular reactivity are important components of inflammatory lung disease. Haem oxygenase-1 (HO-1) is an important homeostatic enzyme upregulated in inflammation. Here we have investigated the potentially protective effect of HO-1 against cytokine-induced impairment in pulmonary artery relaxation.

Experimental approach:

Haem oxygenase-1 protein levels were assessed by immunofluorescence. HO activity was assessed by conversion of haemin to bilirubin. Rings of rat isolated pulmonary artery in organ baths were used to measure relaxant responses to the endothelium-dependent agent ACh and the endothelium-independent agent sodium nitroprusside (SNP). Production of nitric oxide (NO) and reactive oxygen species (ROS) was assessed by confocal fluorescence microscopy and fluorescent probes.

Key results:

Haem oxygenase-1 protein expression was strongly induced in pulmonary artery after 24-h incubation with either haemin (5 µM) or curcumin (2 µM), accompanied by a significant increase in HO activity. Incubation with tumour necrosis factor α (TNFα, 1 ng·mL⁻¹, 2 h) significantly decreased relaxation of arterial rings to ACh, without affecting responses to SNP. Induction of HO-1 by curcumin or haemin protected against TNFα-induced hyporesponsiveness to ACh. The competitive HO inhibitor, tin protoporphyrin (20 µM), abolished the protective effect of haemin. HO-1 induction prevented a TNFα-induced increase in NO generation without affecting the TNFα-induced increase in ROS generation. HO-1 induction prevented the TNFα-induced decrease in ACh-stimulated NO generation.

Conclusions and implications:

Induction of HO-1 protected against TNFα impairment of endothelium-dependent relaxation in pulmonary artery, by a mechanism involving a reduction in inducible NO synthase-derived NO production.     

Contrasting effects of an aminobisphosphonate,a potent inhibitor of bone resorption,on lipopolysaccharide-induced production of interleukin-1 and tumour necrosis factor α in mice

1. Aminobisphosphonates (aminoBPs), potent inhibitors of bone resorption, have been reported to induce inflammatory reactions such as fever and an increase in acute phase proteins in human patients, and to induce the histamine-forming enzyme, histidine decarboxylase, in mice. In the present study, we examined the effect of aminoBP, 4-amino-1-hydroxybutylidene-1,1-bisphosphonic acid (AHBuBP), on the production of the pro-inflammatory cytokines, IL-1 and TNFα, in mice.
2. Intraperitoneal injection of AHBuBP did not itself produce detectable levels of IL-1 (α and β) and TNFα in the serum. However, the elevation of serum IL-1 induced by lipopolysaccharide (LPS) was greatly augmented in mice injected with AHBuBP 3 days before the LPS injection, whereas the LPS-induced elevation of serum TNFα was almost completely abolished.
3. Spleen and bone marrow cells taken from mice injected with AHBuBP produced IL-1β in vitro spontaneously, and the production was augmented following the addition of LPS. Cells that accumulated in the peritoneal cavity in response to AHBuBP produced a particularly large amount of IL-1β. However, AHBuBP treatment of mice did not lead to an impairment of the in vitro production of TNFα by these three types of cells.
4. Liposomes encapsulating dichloromethylene bisphosphonate (a non-amino BP) selectively deplete phagocytic macrophages. When an intraperitoneal injection of these liposomes was given 2 days after an injection of AHBuBP, there was a marked decrease in the LPS-induced elevation of serum IL-1 (α and β) (LPS being injected 3 days after the injection of AHBuBP).
5. These results indicate that AHBuBP has contrasting effects on the in vivo LPS-induced production of IL-1 and TNFα in mice, enhancing the production of IL-1 by phagocytic macrophages and suppressing the production of TNFα, although underling mechanisms remain to be clarified.

     

Aminoguanidine and curcumin attenuated tumor necrosis factor (TNF)-α-induced oxidative stress, colitis and hepatotoxicity in mice

The up regulation of gut mucosal cytokines such as tumor necrosis factor (TNF)-α and oxidative stress have been related to inflammatory bowel diseases (IBD) such as ulcerative colitis (UC) and Crohn's disease (CD). This study investigated an immune-mediated model of colitis. TNF-α injected intraperitonally to mice induced a dose-dependent recruitment of neutrophils into abdominal mesentery. The leukocytes influx induced by TNF-α (10 μg kg(-1) body weight) increased by 3 fold liver and colon damage scores. TNF-α-colitis was characterized by hemorrhagic edemas and crypt abscesses massively infiltrated by inflammatory cells, namely neutrophils. Moreover, TNF-α-toxicity resulted in liver steatosis and foci of necrosis infiltrated by Kupffer cells and neutrophils in parenchyma and around the centrilobular veins. The involvement of oxidative stress was evaluated using aminoguanidine (AG) as selective inhibitor of inducible NO synthase (iNOS) and curcumin (Cur), the polyphenolic antioxidant of turmeric (Curcuma longa L.). TNF-α-toxicity led to significant increase in myeloperoxidase (MPO, an index of neutrophils infiltration), nitrites (stable nitric oxide metabolites) and malondialdehyde (MDA, a marker of lipid peroxides) levels and cell apoptosis in liver and colon. AG and Cur treatments significantly attenuated the hallmarks of oxidative stress, neutrophils influx and ROS-related cellular and histological damages, in TNF-α-treated mice. Taken together, our results provide insights into the role of phagocytes-derived oxidants in TNF-α-colitis in mice. Cur and AG, by inhibiting neutrophils priming and iNOsynthase could be effective against oxidative bowel damages induced in IBD by imbalanced gut immune response.     

Long-term toxicity of modified recombinant human tumor necrosis factor in Macaca mulata

目的：研究新型重组人肿瘤坏死因子（ｒｈＴＮＦＮＣ）ｉｖ对恒河猴的长期毒性，并与重组人肿瘤坏死因子（ｒｈＴＮＦ）作比较．方法：１６只恒河猴分４组分别每日ｉｖｒｈＴＮＦＮＣ９３和９３ＧＵ／ｍ２１个月和ｒｈＴＮＦ６３ＧＵ／ｍ２１０ｄ，检测其一般症状，血液学，血液化学和尿液生化指标，心电图，特异性抗体，骨髓，对组织器官作病理检查等．结果：ｉｖｒｈＴＮＦＮＣ后除大剂量组出现纳差和部分动物眼睑水肿之外，未见明显的药物性毒性反应，而ｒｈＴＮＦ组除上述反应外，还伴有肝肾受损，红系降低，注射局部有静脉炎及血栓形成等病理改变．此外两种ＴＮＦ均能使猴产生特异性抗体．结论：ｒｈＴＮＦＮＣ对恒河猴的毒性比ｒｈＴＮＦ要小得多．     

Modulation of tumor necrosis factor α expression in mouse brain after exposure to aluminum in drinking water

Aluminum, a known neurotoxic substance and a ground-water pollutant, is a possible contributing factor in various nervous disorders including Alzheimer's disease. It has been hypothesized that cytokines are involved in aluminum neurotoxicity. We investigated the alterations in mRNA expression of tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), and interferon γ (IFNγ), cytokines related to neuronal damage, in cerebrum and peripheral immune cells of mice after exposure to aluminum through drinking water. Groups of male BALB/c mice were administered aluminum ammonium sulfate in drinking water ad libitum at 0, 5, 25, and 125 ppm aluminum for 1 month. An additional group received 250 ppm ammonium as ammonium sulfate. After treatment, the cerebrum, splenic macrophages and lymphocytes were collected. The expression of TNFα mRNA in cerebrum was significantly increased among aluminum-treated groups compared with the control, in a dose-dependent manner. Other cytokines did not show any aluminum-related effects. In peripheral cells, there were no significant differences of cytokine mRNA expressions among treatment groups. Increased expression of TNFα mRNA by aluminum in cerebrum may reflect activation of microglia, a major source of TNFα in this brain region. Because the aluminum- induced alteration in cytokine message occurred at aluminum concentrations similar to those noted in contaminated water, these results may be relevant in considering the risk of aluminum neurotoxicity in drinking water. Received: 27 May 1999 / Accepted: 20 July 1999     

Role of tumor necrosis factor and nitric oxide in the protection of N-methyl-N-(3,4-methylenedioxybenzoyl) methyl-acetamide against immunological liver injury in mice

研究了Ｎ－甲基－Ｎ－（３，４－亚甲二氧基苯甲酰）甲基－乙酰胺（ＳＹ－６４０）的保肝作用及其机理．给小鼠ｉｖ活卡介苗（ＢＣＧ）１２ｄ后再ｉｖ脂多糖（ＬＰＳ）诱导小鼠血浆一氧化氮（ＮＯ），肿瘤坏死因子（ＴＮＦ），谷丙转氨酶（ＧＰＴ），谷草转氨酶（ＧＯＴ）剧烈升高及严重的肝损伤．以ＳＹ－６４０给小鼠ｉｇ（每日一次，连续１０ｄ），显著降低ＢＣＧ＋ＬＰＳ诱导的肝损伤小鼠血浆ＧＰＴ，ＧＯＴ和ＴＮＦ水平的升高，血浆ＮＯ水平的升高更加显著，肝损伤减轻．以单甲基精氨酸抑制ＮＯ的生成，ＳＹ－６４０的上述作用被抵消．ＳＹ－６４０对正常小鼠血浆ＮＯ，ＧＰＴ，ＧＯＴ水平无影响．可见，ＳＹ－６４０的保肝作用与其升高血浆ＮＯ，降低血浆ＴＮＦ水平有关．     

Tumor necrosis factor α up-regulates Giα and Gß proteins and adenylyl cyclase responsiveness in rat cardiomyocytes

Treatment of cultured rat cardiomyocytes in serum-free medium for 48 h with recombinant human tumor necrosis factor α (TNFα) led to a concentration-dependent increase in the level of membrane-inhibitory guanine nucleotide-binding protein (G₁) α-subunits and in pertussis toxin-catalyzed [³²P]ADP ribosylation of 40 kDa proteins. Both G_iα protein subtypes present in rat cardiac myocyte membranes, G_iα40 and G_iα41, were up-regulated by the cytokine, with the maximal increase occurring at 10 U/ml TNFα. In contrast to noradrenaline exposure, which causes a similar, but apparently exclusive, increase in α₁-subunits, treatment with TNFα in addition increased the level of membrane G protein ß₃₆-subunits. Furthermore, while noradrenaline exposure led to a decrease in receptor-dependent and -independent adenylyl cyclase activity, treatment of cardiomyocytes with TNFα caused a concentration-dependent increase in cyclase responsiveness to either forskolin, guanosine 5′-O-(3-thiotriphosphate) or isoproterenol, even though ß-adrenoceptor density was decreased by TNFα. The increase in adenylyl cyclase activity induced by TNFα was completely suppressed when the cells were cocultured with noradrenaline, a condition leading to an additive increase in G_iα level. The data indicate that the cytokine TNFα can potently modulate G protein-mediated signal transduction in rat cardiac myocytes. Although TNFα, like noradrenaline, exposure of the cells increased the level of membrane G_iα proteins, it did not decrease but rather caused an increase in adenylyl cyclase responsiveness. This hypertensitivity may be due to concomitant alterations of other components, e.g. G_ß, G_sα and/or the cyclase itself, of this multi-subunit signal transduction system following TNFα exposure.     

Tumor necrosis factor α decreases inositol phosphate formation and phosphatidylinositol-bisphosphate (PIP2) synthesis in rat cardiomyocytes

Treatment of neonatal rat cardiomyocytes for 72 h in the presence of tumor necrosis factor (TNF) (10 U/ml) lead to a decrease in basal and ₁-adrenoceptor-induced formation of the calcium-mobilizing second messenger inositol trisphosphate (IP₃) and its metabolites, IP₂ and IP₁, by 35 and 26%, respectively. The synthesis of phosphatidylinositol bisphosphate (PIP₂), the substrate of PI-specific phospholipase C, was decreased by 45% following the TNF (10 U/ml) exposure. Time courses of TNF (10 U/ml)-induced alterations in rat cardiomyocytes showed a parallel decline of basal inositol phosphate formation and PIP₂ synthesis suggesting that the decrease in inositol phosphate formation was due to the reduction in PIP₂ synthesis. As the TNF-induced decrease of PIP₂ synthesis was associated with a decreased synthesis of the phospholipid phosphatidylinositol (PI), the precursor of PIP₂, by 33%, the decreased availability of PIP₂ is apparently, at least in part, the result of the decreased synthesis of PI. As an apparent functional consequence of the decrease in IP₃ formation following the TNF exposure, the ₁-adrenoceptor-mediated induction of arrhythmias by 100 mol/l noradrenaline + 10 mol/l timolol was abolished in TNF-pretreated rat cardiomyocytes.To investigate one of the possible mechanisms of the TNF-induced decrease of PIP₂ formation, the effect of TNF pretreatment on glycerol-3-phosphate dehydrogenase (GDH), a key enzyme of lipogenesis, was studied: Exposure of the rat cardiomyocytes for 72 h to TNF induced a concentration-dependent decrease in GDH activity by maximally 55%.The result presented are consistent with the hypothesis that the decreased basal and ₁-adrenoceptor-induced formation of the second messenger IP₃ observed in chronic endotoxinemia and sepsis may be mediated by a TNF-induced decrease in the synthesis of PIP₂, the substrate of PI-specific phospholipase C. This mechanism occurs following long-term exposure to low TNF/ha concentrations and is apparently distinct from the short-term cardiac effects induced by high concentrations of TNF. Correspondence to: C. Reithmann at the above address     

The rewarding action of acute cocaine is reduced in β-endorphin deficient but not in μ opioid receptor knockout mice

Cognitive impairment is a multidimensional concept that subsumes the attention and concentration, learning and memory, problem-solving ability, visuospatial abilities, mental flexibility, psychomotor efficiency and manual dexterity. The intrinsic mechanisms of the behavioural effects may involve neuronal damage in the brain structure. A lower concentration of glutamate receptor co-agonists in the striatum indicates the general malfunction of the brain glutamatergic system. It is suggested that a selective decrease in hippocampal glutamate concentration may account for deterioration in learning and memory process, considering the important role of this neurotransmitter in the cognitive functions. Nootropic agents like piracetam and anticholinesterase inhibitors are commonly used for improving memory, mood and behaviours. The present study was undertaken to assess the nootropic potential of menthol on learning and memory employing exteroceptive and interoceptive behavioral model in young and aged mice. To delineate the mechanism by which menthol decreases cognitive impairment and protect the brain, various biochemical parameters such as brain glutamate, glycine, glutathione and thiobarbituric acid reactive substances were determined. Menthol produced significant improvement in learning and memory. Menthol exhibited excellent antioxidant effect and maintain glutamate concentration in various region of the mouse brain for management of preliminary symptoms of memory impairment.     

The involvement of tumour necrosis factor-α in the protective effects of 17β oestradiol in splanchnic ischaemia-reperfusion injury

1. Tumour necrosis factor-α (TNF-α) is a cytokine that is implicated in the pathogenesis of ischaemic states and atherosclerosis. We tested the hypothesis that the vasoprotective effects of the oestrogens may be mediated in vivo by inhibition of the formation of TNF-α.
2. Anaesthetized rats, subjected to total occlusion of the superior mesenteric artery and the coeliac trunk for 45 min developed a severe shock state resulting in a fatal outcome within 75–90 min after the release of occlusion. Sham-operated animals were used as controls.
3. Splanchnic artery occlusion (SAO) shocked rats had a marked hypotension, enhanced levels of TNF-α in serum and macrophages, leukopenia and increased ileal leukocyte accumulation, studied by means of myeloperoxidase activity (MPO). Furthermore, aortae from SAO rats showed a marked hyporeactivity to phenylephrine (PE, 1 nM–10 μM), reduced responsiveness to acetylcholine (ACh, 10 nM–10 μM) and an increased staining for intercellular adhesion molecule-1 (ICAM-1).
4. In vivo administration of 17β oestradiol (500 μg kg⁻¹, i.m., three hours before the induction of SAO) increased survival rate (100%, 4 h after SAO), enhanced mean arterial blood pressure; reduced serum TNF-α (25±5 u ml⁻¹ vs 379±16 u ml⁻¹), ameliorated leukopaenia and reduced ileal MPO (0.7±0.02 u 10⁻³ g⁻¹ tissue vs 4.2±0.4 u 10⁻³ g⁻¹ tissue). Furthermore aortae from SAO rats treated with 17β oestradiol exhibited a greater contractile response to phenylephrine, improved responsiveness to ACh and a blunted staining of ICAM-1. Finally 17β oestradiol, added in vitro to peritoneal macrophages collected from untreated SAO rats, significantly reduced TNF-α production.
5. Our results suggest that inhibition of TNF-α in vivo may explain, at least in part, the vasoprotective effects of oestrogens.

     

Cooperative role of tumour necrosis factor-α, interleukin-1β and neutrophils in a novel behavioural model that concomitantly demonstrates articular inflammation and hypernociception in mice

BACKGROUND AND PURPOSE

Chronic joint inflammation and pain are the hallmarks of disease in patients with inflammatory arthritis, notably rheumatoid arthritis. The aim of the present study was to investigate the relative contribution of tumour necrosis factor (TNF)-α, interleukin (IL)-1β and neutrophil influx for joint inflammation and nociception in a novel murine model of antigen-induced arthritis (AIA).

EXPERIMENTAL APPROACH

AIA was induced by administration of antigen into knee joint of previously immunized mice. Neutrophil accumulation was determined by counting neutrophils in the joints and assessing myeloperoxidase activity in tissues surrounding the joints. TNF-α, IL-1β and CXCL-1 were measured by elisa. Mechanical hypernociception was assessed in parallel, using an electronic pressure meter.

KEY RESULTS

Hypernociception was dependent on antigen dose and the time after its administration; it was prevented by treatment with morphine and associated with neutrophil infiltration and local production of TNF-α, IL-1β and CXCL-1. Administration of a chimeric monoclonal antibody to TNF-α (infliximab) or IL-1receptor antagonist prevented neutrophil influx and hypernociception, and this was comparable to the effects of dexamethasone. Treatment with fucoidin (a leucocyte adhesion inhibitor) greatly suppressed neutrophil influx and local production of TNF-α and IL-1β, and hypernociception.

CONCLUSIONS AND IMPLICATIONS

In conclusion, the present study describes a new model that allows for the concomitant evaluation of articular hypernociception and inflammation. Using this system, we demonstrated that a positive feedback loop involving neutrophil influx and the pro-inflammatory cytokines TNF-α and IL-1β is necessary for articular hypernociception after antigen challenge of immunized mice.     

Investigation on the effect of nanoparticle size on the blood–brain tumour barrier permeability by in situ perfusion via internal carotid artery in mice

The blood–brain barrier (BBB) is a limiting factor in nanoparticle drug delivery to the brain, and various attempts have been made to overcome it for efficient drug delivery. Nowadays, it was considered as further issue for brain–drug delivery that the nanoparticle delivered to brain through the BBB reach cancer cells in tumour tissue. In this study, we investigated the effect of nanoparticle size on blood–brain tumour barrier (BBTB) permeation of fluorescence-labelled gold nanoparticles (AuNPs) in a mouse model of orthotopic glioblastoma multiforme (GBM), established by intracranial implantation of luciferase-expressing human glioblastoma U87MG cells. AuNPs sized 10, 50, and 100?nm were perfused into the GBM mice via internal carotid artery (ICA) for 5?min. Immediately after perfusion, the brains were fixed and prepared for LSCM observation. The AuNPs distribution in the normal and tumorous brain tissues was analysed qualitatively and quantitatively. Higher distribution of AuNPs was observed in the tumorous tissue than in the normal tissue. Furthermore, the smallest nanoparticle, 10?nm AuNPs, was widely distributed in the brain tumour tissue, whereas the 50 and 100?nm AuNPs were located near the blood vessels. Therefore, nanoparticle size affected the permeation of nanoparticles from the blood into brain tumour tissue.     

How is sesamin metabolised in the human liver to show its biological effects?

INTRODUCTION: Sesamin is a major lignan found in sesame and is known to have various biological effects. Some of these biological effects occur following its metabolic conversion to corresponding catechols and, therefore, the study of sesamin metabolism is quite important. There is currently a need to identify the enzymes responsible for metabolism of sesamin so that scientists will be more able to predict sesamin-drug interactions. AREAS COVERED: The authors reviewed all the published literature with a focus on papers that dealt with metabolism of sesamin by drug-metabolising enzymes in rat and/or human liver, such as cytochrome P450 and UDP-glucuronosyltransferase. The article also reviews papers that dealt with the inhibition of enzymes by sesamin including drug-metabolising enzymes and other physiologically important enzymes. Additionally, the authors discuss the species-based differences in the metabolism of sesamin between rats and humans. EXPERT OPINION: A remarkable species-based difference was found in sesamin metabolism between humans and other animals; thus, it is very important that precautions are taken when predicting the physiological effects in humans from animal data. A mechanism-based inhibition of human CYP2C9 by sesamin was recently discovered, suggesting that it is important to evaluate the interaction between sesamin and drugs that are mainly metabolised by CYP2C9. Furthermore, further analysis of sesamin and episesamin and their molecular mechanisms are needed to make better use of sesamin supplements.     

Ochratoxin A and human chronic nephropathy in Tunisia: is the situation endemic?

Ochratoxin A (OTA) is a nephrotoxic mycotoxin that is being increasingly considered as the main causal agent of Balkan endemic nephropathy (BEN), a fatal kidney disease associated with the end stage of urothelial tumours. However, despite the considerable amount of data, it is still controversial whether OTA plays a causative or only a subordinate role in the induction of this human nephropathy. Tunisia for years had to confront a very similar human nephropathy, which is tentatively called chronic interstitial nephropathy of unknown cause. This study tends firstly to consolidate the suspected link between this Tunisian chronic interstitial nephropathy (CIN) of unknown cause and the presence of OTA in the blood and food of such patients, and second to enlighten the endemic character of this particular nephropathy. Therefore, in four consecutive inquiries, performed within the period 1991-2000, blood and food OTA contaminations were assayed and compared for 954 nephropathy patients and 205 healthy subjects from the Tunisian general population. This survey was also designed to show that, although the whole population is likely to be exposed to OTA, specific people living in conditions showing similarities with the Balkans do have a kidney disease apparently linked to ochratoxin in food. The results showed that the highest incidences were found in patients with CIN of unknown cause. Indeed, the percentages of OTA-positive samples ranged from 93% to 100%, whereas it was only from 62% to 82% in healthy subjects. Mean OTA concentrations were also higher in patients with CIN of unknown cause than in controls (44.4 +/- 19 microg/L to 55.6 +/- 19 microg/L as opposed to 1.22 +/- 1.2 microg/L to 3.35 +/- 2.32 microg/L, respectively). This study emphasizes further the implication of OTA on this particular human nephropathy and underlines the probable causative role of OTA in the onset of this disease. It is important to note that the highest levels of food OTA contamination were found in the group presenting with CIN of unknown cause, indicating that, similar to the case in the Balkans, people are exposed to OTA essentially by their food.     

Characterization of the prostanoid receptor(s) on human blood monocytes at which prostaglandin E2 inhibits lipopolysaccharide-induced tumour necrosis factor-α generation

1. The prostanoid receptor(s) that mediates inhibition of bacterial lipopolysaccharide (LPS)-induced tumour necrosis factor-α (TNFα) generation from human peripheral blood monocytes was classified by use of naturally occurring and synthetic prostanoid agonists and antagonists.
2. In human monocytes that were adherent to plastic, neither prostaglandin D₂ (PGD₂), prostaglandin E₂ (PGE₂), prostaglandin F_2α (PGF_2α) nor the stable prostacyclin and thromboxane mimetics, cicaprost and U-46619, respectively, promoted the elaboration of TNFα-like immunoreactivity, as assessed with a specific ELISA, indicating the absence of excitatory prostanoid receptors on these cells.
3. Exposure of human monocytes to LPS (3 ng ml⁻¹, ∼ EC₈₄) resulted in a time-dependent elaboration of TNFα which was suppressed in cells pretreated with prostaglandin E₁ (PGE₁), PGE₂ and cicaprost. This effect was concentration-dependent with mean pIC₅₀ values of 7.14, 7.34 and 8.00 for PGE₁, PGE₂ and cicaprost, respectively. PGD₂, PGF_2α and U-46619 failed to inhibit the generation of TNFα at concentrations up to 10 μM.
4. With respect to PGE₂, the EP-receptor agonists, 16,16-dimethyl PGE₂ (non-selective), misoprostol (EP₂/EP₃-selective), 11-deoxy PGE₁ (EP₂-selective) and butaprost (EP₂-selective) were essentially full agonists as inhibitors of LPS-induced TNFα generation with mean pIC₅₀ values of 6.21, 6.02, 5.67 and 5.59, respectively. In contrast to the results obtained with butaprost and 11-deoxy PGE₁, another EP₂-selective agonist, AH 13205, inhibited TNFα generation by only 21% at the highest concentration (10 μM) examined. EP-receptor agonists which have selectivity for the EP₁- (17-phenyl-ω-trinor PGE₂) and EP₃-receptor (MB 28,767, sulprostone) were inactive or only weakly active as inhibitors of TNFα generation.
5. Pretreatment of human monocytes with the TP/EP₄-receptor antagonist, AH 23848B, at 10, 30 and 100 μM suppressed LPS-induced TNFα generation by 10%, 28% and 77%, respectively, but failed to shift significantly the location of the PGE₂ concentration-response curves.
6. Given that AH 13205 was a poor inhibitor of TNFα generation, studies were performed to determine if it was a partial agonist and whether it could antagonize the inhibitory effect of PGE₂. Pretreatment of human monocytes with 10 and 30 μM AH 13205 inhibited the generation of TNFα by 31% and 53%, respectively, but failed to shift significantly the location of the PGE₂ concentration-response curves at either concentration examined.
7. Since PGD₂ and 17-phenyl-ω-trinor PGE₂ (EP₁-agonist) did not suppress TNFα generation, the EP₁/EP₂/DP-receptor antagonist, AH 6809, was employed to assess if EP₂-receptors mediated the inhibitory effect of PGE₂. Pretreatment of human monocytes with 10 μM AH 6809 did not affect LPS-induced TNFα generation but produced a parallel 3.5 fold rightwards shift of the PGE₂ concentration-response curve.
8. Collectively, these data suggest that human peripheral blood monocytes express at least two distinct populations of inhibitory prostanoid receptors that mediate inhibition of LPS-induced TNFα generation. One of these probably represents IP receptors based upon the selectivity of cicaprost for this subtype. The other population has the pharmacology of EP-receptors, but the rank order of potency for a range of synthetic EP-receptor agonists was inconsistent with an interaction with any of the currently defined subtypes. Given the pharmacological behaviour of butaprost, AH 6809 and AH 23848B in these cells, we propose that multiple (EP₂- and/or EP₄- and/or IP) or novel EP-receptors mediate the inhibitory effect of PGE₂ on TNFα generation.

     

Dextran sulphate sodium colitis in C57BL/6J mice is alleviated by Lactococcus lactis and worsened by the neutralization of Tumor necrosis Factor α

TNFα has a well-established role in inflammatory bowel disease that affects the gastrointestinal tract and is usually manifested as Crohn's disease or ulcerative colitis. We have compared Lactococcus lactis NZ9000 displaying TNFα-binding affibody with control Lactococcus lactis and with anti-TNFα antibody infliximab for the treatment of mice with dextran sulphate sodium (DSS)-induced colitis. L. lactis NZ9000 alleviated the colitis severity one week after colitis induction with DSS, more effectively when administered in preventive fashion prior to, during and after DSS administration. TNFα-binding L. lactis was less effective than control L. lactis, particularly when TNFα-binding L. lactis was administered in preventive fashion. Similarly, an apparently detrimental effect of TNFα neutralization was observed in mice that were intraperitoneally administered anti-TNFα monoclonal antibody infliximab prior to colitis induction. The highest concentrations of tissue TNFα were observed in groups without DSS colitis that were treated either with TNFα-binding L. lactis or infliximab. To conclude, we have confirmed that L. lactis exerts a protective effect on DSS-induced colitis in mice. Contrary to expectations, but in line with some reports, the neutralization of TNFα aggravated disease symptoms in the acute phase of colitis and increased TNFα concentration in colon tissue of healthy mice. Nevertheless, we have demonstrated that oral administration of bacteria with surface displayed TNFα-binding affibody can interfere significantly with TNFα signaling and mimic the infliximab response in the given animal model of colitis.