Cytokine gene regulation by PGE(2), LTB(4) and PAF

Integrated analysis of whole blood oxylipin and cytokine responses after bacterial, viral, and T cell stimulation reveals new immune networks

Oxylipins are major immunomodulating mediators, yet studies of inflammation focus mainly on cytokines. Here, using a standardized whole-blood stimulation system, we characterized the oxylipin-driven inflammatory responses to various stimuli and their relationships with cytokine responses. We performed a pilot study in 25 healthy individuals using 6 different stimuli: 2 bacterial stimuli (LPS and live BCG), 2 viral stimuli (vaccine-grade poly I:C and live H1N1 attenuated influenza), an enterotoxin superantigen and a Null control. All stimuli induced a strong production of oxylipins but most importantly, bacterial, viral, and T cell immune responses show distinct oxylipin signatures. Integration of the oxylipin and cytokine responses for each condition revealed new immune networks improving our understanding of inflammation regulation. Finally, the oxylipin responses and oxylipin-cytokine networks were compared in patients with active tuberculosis or with latent infection. This revealed different responses to BCG but not LPS stimulation highlighting new regulatory pathways for further investigations.

Lycopene attenuates LPS-induced liver injury by inactivation of NF-κB/COX-2 signaling

AIM

This study aimed to investigate the effect of lycopene on LPS-induced liver injury in mice and its mechanisms.

METHODS

Male C57bl/6 mice were randomly assigned to three groups: sham control group (S-C), LPS control group (L-C), lycopene treatment group (L-T). The mice from the L-T were treated with lycopene for 2 weeks, and the remaining mice with solvent. Afterwards, the mice from the L-C and the L-T received an intraperitoneal injection of LPS (20 mg/kg, dissolved in sterile saline), and the S-C mice were injected with sterile saline. Serum levels of alanine transaminase (ALT) and aspartate aminotransferase (AST) were determined for analysis of liver function. Levels of inflammatory cytokines including tumor necrosis factor (TNF)-α and interleukin (IL)-6, malondialdehyde (MDA) content, and the activity of superoxide dismutase (SOD), were detected in serum. Liver tissues were operated for morphologic analysis and determination of protein by western blot.

RESULTS

Pretreatment with lycopene significantly decreased levels of ALT, AST, and TNF-α and IL-6, reduced MDA content, and increased activity of SOD in serum compared with the L-C mice. Lycopene increased expression of nuclear factor-erythroid 2 related factor 2 (Nrf2), and reduced expression of cyclooxygenase (COX)-2, and phosphorylation of nuclear factor-kappa B (NF-κB) and extracellular regulated protein kinases 1/2 (ERK1/2).

CONCLUSION

The results showed that lycopene attenuates LPS-induced liver injury by reducing NF-κB/COX-2 signaling by upregulation of Nrf2/HO-1 activation.

Intrauterine Malnutrition Reduced Long Leptin Receptor Isoform Expression and Proinflammatory Cytokine Production in Male Rat Pulmonary Endothelial Cells Stimulated by Lipopolysaccharide

Background/Aims

We have previously shown that low birth weight (LBW) rats exposed to intrauterine malnutrition have an impaired lung inflammatory response and reduced levels of inflammatory mediators; however, circulating leptin levels were not increased. We evaluated long leptin receptor isoform (ObRb) expression in lung endothelial cells from low birth weight rats and examined its role in the production of lipid mediators and cytokines.

Methods

Lung endothelial cells were obtained from normal birth weight (NBW) rats or LBW rats subjected to intrauterine malnutrition. These cells were stimulated with leptin (10 ng/mL), LPS (lipopolysaccharide, 1 μg/mL), or leptin plus LPS. Six hours after stimulation, the production of inflammatory mediators (PGE₂, LTB₄, IL-1β, and IL-6) was evaluated using commercial ELISA kits, and Western blotting was performed to investigate p38MAPK, NF-κB, and ObRb expression.

Results

Leptin increased IL-1β levels in only cells from the NBW group, whereas LPS increased PGE₂ and LTB₄ levels in cells from both groups; leptin addition potentiated lipid mediator production induced by LPS in the NBW group. LPS enhanced the production of IL-1β and IL-6 in only endothelial cells from NBW rats. Leptin receptor expression was decreased (63%) in endothelial cells from LBW rats. None of the stimuli increased NF-κB or p38 signaling pathway expression in cells from LBW rats.

Conclusion

These results suggest that intrauterine malnutrition compromises leptin receptor expression and cytokine production in pulmonary endothelial cells stimulated by LPS; these effects seem to involve the NF-κB and p38MAPK signaling pathways.

Arachidonic acid supplementation transiently augments the acute inflammatory response to resistance exercise in trained men

Strenuous exercise can result in skeletal muscle damage, leading to the systemic mobilization, activation, and intramuscular accumulation of blood leukocytes. Eicosanoid metabolites of arachidonic acid (ARA) are potent inflammatory mediators, but whether changes in dietary ARA intake influence exercise-induced inflammation is not known. This study investigated the effect of 4 wk of dietary supplementation with 1.5 g/day ARA ( n = 9, 24 ± 1.5 yr) or corn-soy oil placebo ( n = 10, 26 ± 1.3 yr) on systemic and intramuscular inflammatory responses to an acute bout of resistance exercise (8 sets each of leg press and extension at 80% one-repetition maximum) in previously trained men. Whole EDTA blood, serum, peripheral blood mononuclear cells (PMBCs), and skeletal muscle biopsies were collected before exercise, immediately postexercise, and at 2, 4, and 48 h of recovery. ARA supplementation resulted in higher exercise-stimulated serum creatine kinase activity [incremental area under the curve (iAUC) P = 0.046] and blood leukocyte counts (iAUC for total white cells, P < 0.001; neutrophils: P = 0.007; monocytes: P = 0.015). The exercise-induced fold change in peripheral blood mononuclear cell mRNA expression of interleukin-1β ( IL1B), CD11b ( ITGAM), and neutrophil elastase ( ELANE), as well as muscle mRNA expression of the chemokines interleukin-8 ( CXCL8) and monocyte chemoattractant protein 1 ( CCL2) was also greater in the ARA group than placebo. Despite this, ARA supplementation did not influence the histological presence of leukocytes within muscle, perceived muscle soreness, or the extent and duration of muscle force loss. These data show that ARA supplementation transiently increased the inflammatory response to acute resistance exercise but did not impair recovery. NEW & NOTEWORTHY Daily arachidonic acid supplementation for 4 wk in trained men augmented the acute systemic and intramuscular inflammatory response to a subsequent bout of resistance exercise. Greater exercise-induced inflammatory responses in men receiving arachidonic acid supplementation were not accompanied by increased symptoms of exercise-induced muscle damage. Although increased dietary arachidonic acid intake does not appear to influence basal inflammation in humans, the acute inflammatory response to exercise stress is transiently increased following arachidonic acid supplementation.

Carnitine and septic shock: a review

Most studies have reported reduced carnitine levels in the tissues of patients with sepsis, probably due to increased urinary excretion. Because of the increased utilization of fatty acids and ketone bodies as sources of energy in sepsis, the carnitine deficiency can further impair the fuel metabolism and contribute to the unregulated lipid metabolism in these patients.

Recently, experimental and clinical studies have shown that carnitine and its congeners are able to: (a) downmodulate the spontaneous and endotoxin (LPS)-triggered overproduction of tumor necrosis factor (TNF)-alpha; (b) ameliorate the lipid metabolism; and (c) reduce the severity of illness, accelerate recovery, and, in some cases, improve survival in experimental septic shock.

Many questions concerning the ultimate molecular mechanism of action of these compounds in endotoxaemia are still unanswered. Yet, these compounds may be helpful in patients with sepsis, when associated with conventional therapy, in that they can effectively reduce TNF-alpha levels and ameliorate the host's metabolic processes.

The role of host soluble inflammatory mediators induced by the BCG vaccine for the initiation of in vitro monocyte apoptosis in healthy Brazilian volunteers

Background

Tuberculosis (TB) is the second greatest killer worldwide that is caused by a single infectious agent. For its control, studies of TB vaccines are needed. Since Bacillus Calmette-Guerin (BCG) is the only vaccine against TB currently in use, studies addressing the protective role of BCG in the context of inducible inflammatory mediators are urgently required.

Methods

In this study, groups of HIV-negative adult healthy donors (HD; n = 42) and neonates (UV; n = 18) have been voluntarily enrolled, and BCG Moreau strain was used for the in vitro mononuclear cell infections for an initial period of 48 h. Subsequently, harvested conditioned medium (CM) was added to autologous resting cells for an additional 24, 48, and 120 h, and Annexin V, in conjunction with a vital dye, was then used for apoptosis detection. CM was also assayed for nitric oxide (NO), prostaglandin E2 (PGE₂), leukotriene B4 (LTB₄), interferon (IFN)-β, and transforming growth factor (TGF)-β1 levels. The p values were set up for any differences between two groups of individuals using Student’s t-test and considered significant when ≤ 0.05.

Results

At 120 h, CM induced the highest apoptosis levels in both group studied, but necrosis was high in UV group only (p-value < 0.05). NO was released equally during BCG infection in both groups, but higher levels were found in HD when compared with UV group (p-value < 0.05). Overall, BCG Moreau triggered high PGE₂, LTB₄ and IFN-β productions in macrophages from the UV group (p-value ≤ 0.05), whereas the prostanoid PGE₂ and TGF-β1 had an opposite pattern in the HD group.

Conclusions

This study uncovers critical roles for endogenous compounds in the instruction of host macrophage cell death patterns. Understanding the regulation of human immune responses is critical for vaccine development and the treatment of infectious diseases. These findings shed new light on the potential condition for a booster immunization in individuals already vaccinated with BCG for TB protection, and further studies are warranted.

Electronic supplementary material

The online version of this article (doi:10.1186/s12950-015-0105-0) contains supplementary material, which is available to authorized users.

Evaluation of eicosanoids in nasal lavage as biomarkers of inflammation in patients with allergic rhinitis

INTRODUCTION

Cysteinyl leukotrienes (cys-LTs), 8-isoprostane and prostaglandin E2 (PGE2) constitute fundamental mediators in allergic inflammation; therefore we wanted to determine the utility of PGE2, 8-isoprostane and cys-LT levels in nasal lavage as biomarkers of allergic inflammation.

MATERIAL AND METHODS

Twenty-one patients with allergic rhinitis (AR) were included on the basis of a positive history of AR symptoms and positive results of skin prick tests to grass pollen allergens. The main exclusion criteria were: uncontrolled asthma, nasal polyps, respiratory infection, tuberculosis, neoplastic and autoimmune diseases, current smoking and immunotherapy. Both outside the pollen season and at the height of the pollen season, total nasal symptom score (TNS-4) was evaluated and the levels of cys-LTs, 8-isoprostane and PGE2 were measured in nasal lavage fluid (NALF).

RESULTS

Natural allergen stimulation resulted in a significant increase of TNS-4 (p < 0.001) and nasal eosinophilia (p < 0.001). The concentration of PGE2 dominated in the NALF outside the pollen season and decreased significantly at the height of natural exposure (p < 0.01). In contrast, lower baseline concentrations of cys-LTs and 8-isoprostane increased significantly upon allergen stimulation (p < 0.05). There was a significant correlation between mean concentration of PGE2 and eosinophil number in NALF (r = 0.67, p = 0.0439).

CONCLUSIONS

The NALF concentrations of cys-LTs and 8-isoprostane change simultaneously with TNS-4 and nasal eosinophilia. However, due to the lack of any significant correlation, their utility as markers of allergic rhinitis should be warily considered. The decrease of PGE2 concentration in NALF which correlated with nasal eosinophilia may participate in escalation of allergic inflammation and needs further evaluation.

Altered inhibitory function of the E-type prostanoid receptor 4 in eosinophils and monocytes from aspirin-intolerant patients

Prostaglandin (PG) E2 has been implicated in the pathogenesis of aspirin-exacerbated respiratory disease (AERD). E-type prostanoid (EP) receptor 4 is known to confer inhibitory signals to eosinophils and monocytes, amongst others. In this study, we investigated whether the responsiveness of eosinophils and monocytes to PGE2 and EP4 receptor activation is altered in AERD patients. While the expression of the EP4 receptor in eosinophils was unaltered in AERD patients, inhibition of eosinophil chemotaxis by PGE2 or the EP4 agonist CAY10598 was less pronounced in AERD patients as compared to healthy control subjects. In monocytes, we found no changes in basal or lipopolysaccharide (LPS)-stimulated PGE2 synthesis, but the response to EP4 receptor activation with respect to inhibition of LPS-induced tumor necrosis factor-α release was reduced in AERD patients, especially in the presence of aspirin (acetylsalicylic acid). Our data point towards a decreased sensitivity of inhibitory EP4 receptor that may play a role in AERD.

Current evidence linking polyunsaturated Fatty acids with cancer risk and progression

There is increasing evidence that polyunsaturated fatty acids (PUFAs) play a role in cancer risk and progression. The n-3 family of PUFAs includes alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) while the n-6 family includes linolenic acid (LA) and arachidonic acid (AA). EPA and DHA are precursors for anti-inflammatory lipid mediators while AA is a precursor for pro-inflammatory lipid mediators. Collectively, PUFAs play crucial roles in maintaining cellular homeostasis, and perturbations in dietary intake or PUFA metabolism could result in cellular dysfunction and contribute to cancer risk and progression. Epidemiologic studies provide an inconsistent picture of the associations between dietary PUFAs and cancer. This discrepancy may reflect the difficulties in collecting accurate dietary data; however, it also may reflect genetic variation in PUFA metabolism which has been shown to modify physiological levels of PUFAs and cancer risk. Also, host-specific mutations as a result of cellular transformation could modify metabolism of PUFAs in the target-tissue. Clinical trials have shown that supplementation with PUFAs or foods high in PUFAs can affect markers of inflammation, immune function, tumor biology, and prognosis. Pre-clinical investigations have begun to elucidate how PUFAs may mediate cell proliferation, apoptosis and angiogenesis, and the signaling pathways involved in these processes. The purpose of this review is to summarize the current evidence linking PUFAs and their metabolites with cancer and the molecular mechanisms that underlie this association. Identifying the molecular mechanism(s) through which PUFAs affect cancer risk and progression will provide an opportunity to pursue focused dietary interventions that could translate into the development of personalized diets for cancer control.

Fluid shear stress-induced osteoarthritis: roles of cyclooxygenase-2 and its metabolic products in inducing the expression of proinflammatory cytokines and matrix metalloproteinases

The mechanical overloading of cartilage is involved in the pathophysiology of osteoarthritis (OA) by both biochemical and mechanical pathways. The application of fluid shear stress to chondrocytes recapitulates the earmarks of OA, as evidenced by the release of proinflammatory cytokines (PICs), matrix metalloproteinases (MMPs), and apoptotic factors. Dysregulations or mutations in these genes might directly cause OA in addition to determining the stage at which OA becomes apparent, the joint sites involved, and the severity of the disease and how rapidly it progresses. However, the underlying mechanisms remain unknown. In this review, we propose that the dysregulation of cyclooxygenase-2 (COX-2) is associated with fluid shear stress-induced OA via its metabolic products at different stages of the disease. Indeed, high fluid shear stress rapidly induces the production of PICs and MMPs via COX-2-derived prostaglandin (PG)E2 at the early stage of OA. In contrast, prolonged shear exposure (>12 h) aggravates the condition by concurrently up-regulating the expression of proapoptotic genes and down-regulating the expression of antiapoptotic genes in a 15-deoxy-Δ (12,14)-prostaglandin J2 (15d-PGJ2)-dependent manner at the late stage of disease. These observations may help to resolve long-standing questions in OA progression and provide insight for development of strategies to treat and combat OA.

Food components and the immune system: from tonic agents to allergens

The intestinal mucosa is the major site of contact with antigens, and it houses the largest lymphoid tissue in the body. In physiological conditions, microbiota and dietary antigens are the natural sources of stimulation for the gut-associated lymphoid tissues (GALT) and for the immune system as a whole. Germ-free models have provided some insights on the immunological role of gut antigens. However, most of the GALT is not located in the large intestine, where gut microbiota is prominent. It is concentrated in the small intestine where protein absorption takes place. In this review, we will address the involvement of food components in the development and the function of the immune system. Studies in mice have already shown that dietary proteins are critical elements for the developmental shift of the immature neonatal immune profile into a fully developed immune system. The immunological effects of other food components (such as vitamins and lipids) will also be addressed. Most of the cells in the GALT are activated and local pro-inflammatory mediators are abundant. Regulatory elements are known to provide a delicate yet robust balance that maintains gut homeostasis. Usually antigenic contact in the gut induces two major immune responses, oral tolerance and production of secretory IgA. However, under pathological conditions mucosal homeostasis is disturbed resulting in inflammatory reactions such as food hypersensitivity. Food allergy development depends on many factors such as genetic predisposition, biochemical features of allergens, and a growing array of environmental elements. Neuroimmune interactions are also implicated in food allergy and they are examples of the high complexity of the phenomenon. Recent findings on the gut circuits triggered by food components will be reviewed to show that, far beyond their role as nutrients, they are critical players in the operation of the immune system in health and disease.

Fish oil, but not soy bean or olive oil enriched infusion decreases histopathological severity of acute pancreatitis in rats without affecting eicosanoid synthesis

Different dietary fatty acids affect eicosanoid metabolism in different ways, thus influencing the pro- and anti-inflammatory balance of prostaglandins and leukotrienes. Therefore, we analyzed the impact of [n-3], [n-6], and [n-9] fatty acids on eicosanoid metabolism and histopathology in acute pancreatitis in rats. Seventy-five male Sprague-Dawley rats were randomized into five groups (n = 15). Group 1 underwent only laparotomy, while in groups, 2-5 pancreatitis was induced. Groups 1 and 2 were then given saline infusion, groups 3-5 received fat emulsion (group 3: rich in [n-6], group 4: rich in [n-9], group 5: rich in [n-3] fatty acids) for another 18 h. Infusion rich in [n-3] fatty acids significantly decreased histopathological severity of pancreatitis, compared to all other groups. There was no difference concerning the concentrations of prostaglandins and leukotrienes between all groups. Parenteral infusion rich in [n-3] fatty acids reduced histopathological severity of acute pancreatitis in rats without changing eicosanoid metabolism at the endpoint.

Deviations in circulating TNFα levels and TNFα production by mononuclear cells in healthy human populations

Objectives. Tumor necrosis factor alpha (TNFα) plays a pivotal role in the inflammatory host response. The serum-level of TNFα and the production of TNFα by lympho/monocytes, however, seem to show high individual variations. The goal of the present study was to investigate the variations and inducibility of TNFα-activity in two age-groups of healthy volunteers. Methods. Sixty elderly, healthy volunteers were studied. These persons were free of malignant diseases, and within three months, they did not have any trauma or inflammatory disease and were not taking any steroids or nonsteroid anti-inflammatory drugs. Thirty young volunteers were also included. Blood samples were taken; lympho/monocytes were separated and cultured with or without endotoxin (LPS) stimulation. Serum and culture supernatant TNFα levels were determined by bioassay using WEHI 164 cells. Results. The results indicated significant individual variations in TNFα levels of healthy volunteers irrespective of age. Subgroups with low, middle, and high serum TNF-levels were distinguished. In about 50% of volunteers with low serum-TNFα activity, LPS stimulation failed to increase the TNFα production by isolated lympho/monocytes. Conclusion. Our data suggest a chance to select individuals with enhanced sensitivity for septic complications.

Modulation of lipopolysaccharide-induced pro-inflammatory mediators by an extract of Glycyrrhiza glabra and its phytoconstituents

OBJECTIVE

To evaluate the inhibitory property of de-glycyrrhizinated extract of Glycyrrhiza glabra root and its phytoconstituents (glabridin, isoliquiritigenin and glycyrrhizin) on LPS-induced production of pro-inflammatory mediators.

MATERIALS AND METHODS

Inhibitory effect of G. glabra extract and its phytoconstituents were studied on lipopolysaccharide (LPS)-induced nitric oxide (NO), interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) levels in J774A.1 murine macrophages.

RESULTS

G. glabra and isoliquiritigenin significantly inhibited LPS stimulated NO, IL-1 beta and IL-6 production. Glabridin showed significant inhibition of NO and IL-1 beta release, but failed to attenuate IL-6 levels at the tested concentrations. In addition, glycyrrhizin did not exhibit inhibitory response towards any of the LPS-induced pro-inflammatory mediators at the tested concentrations.

CONCLUSION

From the results we speculate that the inhibitory effect of G. glabra extract on LPS-induced pro-inflammatory mediators is influenced by glabridin and isoliquiritigenin and is not contributed by glycyrrhizin.

Optimization of cell-based assays to quantify the anti-inflammatory/allergic potential of test substances in 96-well format

OBJECTIVE

There is an insistent need for robust, reliable, and optimized assays for screening novel drugs targeting the inflammatory/allergic markers. The present study describes about the optimization of eight cell-based assays utilizing mammalian cell lines in 96-well format for quantifying anti-inflammatory/allergic drug candidates.

MATERIALS AND METHODS

We estimated the inhibitory response of reference compounds: 1400 W dihydrochloride on LPS-induced NO release, celecoxib on LPS-induced PGE(2) production and dexamethasone on LPS-induced pro-inflammatory cytokines IL-1 beta, IL-6, and TNF-alpha production by J774A.1 murine macrophages. Response of acetylsalicylic acid and celecoxib was studied on A23187-induced TXB(2) production; captopril on A23187-stimulated LTB(4) production by HL-60 cells. Effect of ketotifen fumarate was evaluated on A23187-elicited histamine release by RBL-2H3 cells. Each experiment was repeated twice to assess the reproducibility and suitability of the assays by determining appropriate statistical tools viz. %CV, S/B and Z' factor.

RESULTS

1400 W dihydrochloride was capable of inhibiting LPS-induced NO levels (IC(50) = 10.7 μM). Dexamethasone attenuated LPS-induced IL-1 beta (IC(50) = 70 nM), IL-6 (IC(50) = 58 nM) and TNF-alpha (IC(50) = 44 nM) release, whereas celecoxib, a specific COX-2 inhibitor showed marked reduction in LPS-induced PGE(2) (IC(50) = 23 nM) production. Captopril (IC(50) = 48 μM) and ketotifen fumarate (IC(50) = 36.4 μM) demonstrated potent inhibitory effect against A23187-stimulated LTB(4) and histamine levels, respectively. Both acetylsalicylic acid (IC(50) = 5.5 μM) and celecoxib (IC(50) = 7.9 nM) exhibited concentration-dependent decrease in TXB(2) production. Results for all the cell assays from two experiments showed a Z' factor varying from 0.30 to 0.99; the S/B ratio ranged from 2.39 to 24.92; %CV ranged between 1.52 and 20.14.

CONCLUSION

The results proclaim that these cell-based assays can act as ideal tools for screening new anti-inflammatory/anti-allergic compounds.

Determination of the eicosanoid response to inflammatory stimuli in whole blood and its pharmacological modulation ex vivo

Recognition of pathogens by immune cells initiates the release of numerous signaling molecules, including cytokines and eicosanoids. Here, we describe a simple procedure by which eicosanoids such as prostaglandin E(2) (PGE(2)), leukotriene B(4) (LTB(4)) and thromboxane B(2) (TxB(2)) can be measured using commercial enzyme immunoassays (EIAs) in the supernatant of whole blood stimulated with inflammatory stimuli. This is illustrated for numerous stimuli. The kinetics by which lipopolysaccharide (LPS) induces cyclooxygenase (COX)-2 expression in this setup were determined by quantitative reverse transcription polymerase chain reaction (RT-PCR). The eicosanoid response of the blood of 160 healthy volunteers to 1 microg/ml LPS was measured. To determine whether the action of a drug in vivo is represented ex vivo in the eicosanoid response of blood, one volunteer took a standard dose of a number of commercially available cyclooxygenase inhibitors on different days and the eicosanoid response of his blood to LPS was determined before ingestion as well as 2 and 6 h afterwards. The efficacy of the different pharmaceuticals on cyclooxygenase but not lipoxygenase products or cytokines could be monitored ex vivo. Similarly, ex vivo eicosanoid release was measured in blood from 10 volunteers who had taken 50 mg flurbiprofen. The method described extends approaches for studying whole blood cytokine release to the lipid mediators formed from arachidonic acid. These important signaling molecules represent targets for pharmacological intervention, which can now be monitored in vitro, as well as ex vivo employing the same model. Furthermore, the assay could be used to characterize the immune status of patient groups or to monitor the course of disease.

Immunomodulatory activity of TNF-alpha during acute liver injury induced by D-galactosamine and its protection by PGE1 in rats

Tumour necrosis factor-alpha (TNF-alpha) mediates hepatocyte cell death by D-galactosamine (D-GalN) and its protection by prostaglandin E(1) (PGE(1)). The activation of immune system plays an important role in the development of liver injury. TNF-alpha and PGE(1) regulate the activity and cytokine release of different inflammatory cells. The present study was undertaken to determine if the noxious or hepatic protective properties of TNF-alpha during D-GalN-induced liver injury was related to an alteration by PGE(1) of the immunoregulatory activity of TNF-alpha. The role of TNF-alpha was assessed by anti-TNF-alpha antibodies to D-GalN-treated rats in the presence or absence of PGE(1). D-GalN enhanced the percentage of monocytes and T lymphocytes in the total peripheral blood mononuclear cells (PBMCs). D-GalN enhanced the activation degree of monocytes, but reduced that of T lymphocytes. D-GalN also enhanced TNF-alpha, IL-1alpha, IL-6 and IFN-gamma concentrations in blood. Anti-TNF-alpha antibodies abolished all immunological changes and greatly reduced liver damage induced by D-GalN. The protection by PGE(1) against D-GalN liver injury was associated with an increase in TNF-alpha concentration and a reduction of IL-1alpha and IL-6. These changes were associated with a reduction of monocyte activation degree and a recovery of that of T lymphocytes. Although anti-TNF-alpha antibodies abolished the protection by PGE(1) against D-GalN-liver injury, they did not essentially counteract the effect of the prostanoid in all immunological parameters studied. The present study showed that the protection against D-GalN liver damage by PGE(1) or anti-TNF-alpha was associated with similar effects on the inflammatory parameters studied. Nevertheless, the abolishment of liver protection by PGE(1) with anti-TNF-alpha in D-GalN-treated rats in the presence of a protective cytokine profile suggests that the release of TNF-alpha induced by PGE(1) pre-administration was exerting a direct protective effect on hepatocytes against D-GalN injury. Consequently, the effect of PGE(1) on inflammatory parameters studied during liver injury was unrelated to TNF-alpha.

Dietary modification of inflammation with lipids

The n-3 polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are found in high proportions in oily fish and fish oils. The n-3 PUFA are structurally and functionally distinct from the n-6 PUFA. Typically, human inflammatory cells contain high proportions of the n-6 PUFA arachidonic acid and low proportions of n-3 PUFA. The significance of this difference is that arachidonic acid is the precursor of 2-series prostaglandins and 4-series leukotrienes, which are highly-active mediators of inflammation. Feeding fish oil results in partial replacement of arachidonic acid in inflammatory cell membranes by EPA. This change leads to decreased production of arachidonic acid-derived mediators. This response alone is a potentially beneficial anti-inflammatory effect of n-3 PUFA. However, n-3 PUFA have a number of other effects which might occur downstream of altered eicosanoid production or might be independent of this activity. For example, animal and human studies have shown that dietary fish oil results in suppressed production of pro-inflammatory cytokines and can decrease adhesion molecule expression. These effects occur at the level of altered gene expression. This action might come about through antagonism of the effects of arachidonic acid-derived mediators or through more direct actions on the intracellular signalling pathways which lead to activation of transcription factors such as nuclear factor kappa B (NFB). Recent studies have shown that n-3 PUFA can down regulate the activity of the nuclear transcription factor NFB. Fish oil feeding has been shown to ameliorate the symptoms in some animal models of chronic inflammatory disease and to protect against the effects of endotoxin and similar inflammatory challenges. Clinical studies have reported that oral fish oil supplementation has beneficial effects in rheumatoid arthritis and among some patients with asthma, supporting the idea that the n-3 PUFA in fish oil are anti-inflammatory. There are indications that inclusion of n-3 PUFA in enteral and parenteral formulas might be beneficial to patients in intensive care or post-surgery.

Modulatory effects of dietary lipids on immune system functions

Dietary lipid manipulation may affect a great number of immune parameters, such as lymphocyte proliferation, cytokine synthesis, natural killer (NK) cell activity, phagocytosis and so on. The immunomodulation induced by dietary fatty acids may be applied in the amelioration of inflammatory disorders, such as autoimmune diseases. However, the mechanisms that participate in these processes are still poorly understood. It is probable that modulation of immune system by fatty acids of the diet may occur by alteration of membrane fluidity, lipid peroxide formation, eicosanoid production or regulation of gene expression. However, recent studies have reported the effects of several free fatty acids on apoptosis induction of in vitro cultures. In fact, a possible explanation of the effects that fatty acids promote on the immune system cells could be associated with an apoptotic process performed in an irreversible way. In vivo studies have demonstrated the ability of fatty acids to alter the survival of animals fed diets containing oils and infected with a pathogenic bacterium. Experimental infection in animals fed dietary lipids produces a modification of resistance to micro-organisms. The present review analyses all of these parameters that dietary fatty acids are capable of altering in order to modify the immune response. Further studies will be needed to establish the mechanisms involved in immune system regulation, reduction of symptoms derived from autoimmune pathologies and so on.

Determination of natural resistance of mice fed dietary lipids to experimental infection induced by Listeria monocytogenes

Current understanding based on the effect of dietary lipid manipulation upon immune system function indicates that fatty acids are involved in the modulation of the immune response through different and complex pathways. Reduction of several immune parameters by fatty acid action may be applied in the treatment of diseases characterised by an overactivation of the immune system. As a consequence, a reduction of host resistance against infectious agents has been reported in animals fed dietary lipids. The present study confirms the action of dietary lipids on the survival of mice infected with the pathogenic bacterium Listeria monocytogenes. A significant increase in peritoneal cells from mice fed a hydrogenated coconut oil diet was found, while a significant reduction of bacterial recovery from spleens of these mice was observed in this group. In addition, both eicosanoid and phospholipase inhibitors did not promote any modification of lymphocyte proliferation from mice fed olive oil or fish oil.

Effect of PGE1 on TNF-alpha status and hepatic D-galactosamine-induced apoptosis in rats

Prostaglandin E1 has hepatoprotective properties in several clinical and experimental models of liver dysfunction. Hepatotoxicity induced by D-galactosamine (D-GalN) is a suitable animal model of human acute hepatic failure. The aim of the study was to investigate if prostaglandin E1 (PGE1) protection against hepatic D-GalN-induced apoptosis was related to tumour necrosis factor-alpha (TNF-alpha) content in serum. This cytokine is associated with in vitro apoptosis and general inflammatory disorders. In this study, PGE1 was administered 30 min before D-GalN to rats. In other experiments, several doses of TNF-alpha were administered 15min after PGE1 to D-Ga1N-treated rats. Several parameters related to apoptosis and necrosis were measured by flow cytometry, gel electrophoresis, biochemical analysis, and optical and electron microscopy. Tumour necrosis factor-alpha was quantified by competitive enzyme-linked immunosorbent assay (ELISA). PGE1 by itself did not modify the cell cycle of hepatocytes and liver toxicity, but increased TNF-alpha in serum in comparison with the control group. D-Galactosamine increased the percentage of hepatocytes in apoptosis and in the S phase of the cell cycle, and decreased those in G0/G1. Such an increase of hepatocytes in apoptosis was correlated with a higher number of apoptotic bodies and DNA fragmentation in liver than control samples. Also, D-GalN increased alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase and TNF-alpha in serum compared with the control group. Pre-administration of PGE1 to D-GalN-treated rats reduced all the parameters of apoptosis and necrosis in liver, and increased additionallyTNF-alpha content in serum. In those experiments where low doses of TNF-alpha were administered to PGE1 and D-GalN-treated rats an inverse relationship appeared between TNF-alpha and ALT content in serum. In conclusion, the protective effects of PGE1 on D-GalN-induced apoptosis may be linked to its capacity to modulate cell division and/or its immunomodulatory activity. In this sense, our experimental results suggest that TNF-alpha could be involved in protection or exacerbation of liver damage in relation to the pathophysiological status of the liver.

Regulation of macrophage cytokine production by prostaglandin E2. Distinct roles of cyclooxygenase-1 and -2

Prostaglandin E2 (PGE2) modulates a variety of physiological processes including the production of inflammatory cytokines. There are two cyclooxygenase (Cox) enzymes, Cox-1 and Cox-2, that are responsible for initiating PGE2 synthesis. These isozymes catalyze identical biosynthetic reactions but are regulated by different mechanisms in the cell. This report examines differences in the roles of Cox-1 and Cox-2 in regulating cytokine synthesis in macrophages. We employed agents that selectively modulate the activity of each isozyme and measured their effects on synthesis of interleukin (IL)-6, IL-1, and tumor necrosis factor-alpha by peritoneal macrophages. Among these three cytokines, only IL-6 synthesis was stimulated by production of endogenous PGE2. This effect was specifically linked to activation of Cox-2 and not Cox-1. The specificity derives, partly, from the timing of the production of PGE2 following stimulation of each isozyme and from induction of ancillary signals that control the response to PGE2. The experimental findings demonstrate that the effects of Cox-1 and Cox-2 activity on macrophage IL-6 synthesis are segregated. This provides a mechanism for IL-6 to be induced selectively during inflammation.

Peripheral blood neutrophil leukotriene B4 release and migration in rheumatoid arthritis

The present study was designed to compare peripheral blood neutrophil migration and leukotriene (LT) release between patients with rheumatoid arthritis (RA) and healthy controls and to correlate the neutrophil functions with clinical disease activity. Nineteen patients with moderately active RA and 19 age and sex matched healthy volunteers participated in this study. Isolated peripheral blood neutrophils from RA patients released equal amounts of LTB4 but their random migration was enhanced as compared with neutrophils from healthy controls. LTB4 release in whole blood was significantly lower in samples from RA patients than in those from the healthy volunteers (13.5 +/- 1.4 and 19.1 +/- 1.4 ng/10(6) neutrophils respectively; P < 0.001). LTB4 release from isolated RA neutrophils correlated with the levels of C-reactive protein, duration of morning stiffness and Ritchie articular swelling index. Concentrations of hyaluronate, cyclic AMP and 13, 14-dihydro-15-keto prostaglandin were not different between patients with RA and healthy volunteers. Neither was there any difference in TXB2 production by platelets during blood clotting. In conclusion, peripheral blood neutrophils of RA patients seem to be primed and/or activated as their random migration is enhanced as compared with those of healthy volunteers. In RA, LTB4 release from peripheral blood neutrophils seems to reflect the clinical activity of the disease. However, RA neutrophils released smaller (in whole blood) or equal (isolated cells) amount of LTB4 as compared with the respective controls. These contradictory findings suggest that LTB4 release from peripheral blood neutrophils has no major role in the regulation of disease activity in rheumatoid arthritis.

Inhibition of leukotriene formation and IL-8 release by the paf-receptor antagonist SM-12502

We analyzed the effect of the PAF receptor antagonist (+)-cis-3,5-dimethyl-2-(3-pyridyl)thiazolidin-4-one hydrochloride (SM-12502) on the release of leukotriene B4 and IL-8 from human leukocytes. Peripheral blood from healthy donors was separated in two different fractions: polymorphonuclear leukocytes (PMN) and a lymphocyte, monocyte and basophil granulocyte cell fraction (LMB). After incubation of the cell population with different concentrations of SM-12502 the cells were subsequently stimulated with either the Ca ionophore A23187, the bacterial derived peptide fMLP, or with an activator of heterotrimetric G-proteins, the sodium fluoride (NaF, in the presence of Al3+). The PAF receptor antagonist led to a concentration and time dependent inhibition of LTB4 formation and IL-8 release from PMN and LMB. Our data clearly indicate an inhibitory effect of the PAF receptor antagonist SM-12502 on the formation of mediators of the lipoxygenase pathway and on the release of IL-8.

Production of inflammatory mediators by human macrophages obtained from ascites

Ascites is a readily available source of human macrophages (M phi), which can be used to study M phi functions in vitro. We characterized the mediators of inflammation produced by human peritoneal M phi (hp-M phi) obtained from patients with portal hypertension and ascites. The production of the cytokines interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) was found to be lipopolysaccharide (LPS) concentration dependent (0-10 micrograms/ml) with a maximal production at 10 micrograms/ml and also dependent on the time of exposure to the stimulus (0-36 h). IL-1 beta, IL-6 and TNF-alpha production after LPS administration reached a plateau at 24 h. In vitro stimulation for 24 h with LPS does not influence the eicosanoid production from endogenous arachidonate. 13 min of exposure of the cells to the calcium ionophore A23187 gives a significant increase in eicosanoid production from both exogenous and endogenous arachidonate. The main eicosanoids produced are the 5-lipoxgenase products LTB4 and 5-hydroxyeicosatetraenoic acid (HETE). The increase in production of the other eicosanoids is not significant. The eicosanoid production depends on the stimulus concentration. The optimal A23187 concentration is 1 microM. Oxygen radical production was measured in the M phi by a flowcytometric method. The fluorescence intensity of phorbol 12-myristate 13-acetate stimulated and dihydro-rhodamine 123 loaded hp-M phi increases significantly after 15 min. We conclude that LPS stimulation of hp-M phi from liver disease results in similar production of IL-1 beta, IL-6 and TNF-alpha, but that the profile of the eicosanoid production of these M phi stimulated with LPS and A23187 differs from M phi of other origin and species.

Leukotriene B4 and platelet-activating factor in human skin

Acute inflammatory reactions are characterized by leukocyte infiltration associated with increases in vascular permeability and in local blood flow. Leukocyte infiltration can be induced by chemotactic factors such as leukotriene B4 (LTB4) and paf-acether (formerly known as platelet-activating factor) that can be generated within inflammatory lesions. Vascular permeability and increase in blood flow are also affected by LTB4 and paf-acether, as well as by several other substances, including histamine and prostaglandins. Derived from arachidonic acid via the 5 lipo-oxygenase pathway, LTB4 is one of the most potent leukocyte chemotactic substances known. Intradermal injections of LTB4 induce dermal neutrophil infiltration in animal models and in humans. Topical application of LTB4 to human skin induces intraepidermal micro-abscesses containing numerous intact neutrophils. LTB4 has been found to be increased in psoriatic lesions, but its synthesis by epidermal cells remains undecided. Like other leukotrienes, LTB4 can stimulate DNA synthesis in cultured human epidermal keratinocytes. However, receptors for LTC4 but not for LTB4 have been found on human keratinocytes in culture. Paf-acether is an ether-linked phospholipid identified as 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine and is considered to be one of the most potent mediators of acute allergic and inflammatory reactions. For instance, intradermal injection of paf-acether induces inflammatory events such as neutrophil infiltration and increase in vascular permeability. Recent data suggest that cutaneous cells, such as fibroblasts and keratinocytes, are capable of producing paf and that paf is released during the development of allergic cutaneous reactions.(ABSTRACT TRUNCATED AT 250 WORDS)