Increased biomarkers of cardiovascular risk in HIV-1 viremic controllers and low persistent inflammation in elite controllers and art-suppressed individuals

HIV controllers (HICs) are models of HIV functional cure, although some studies have shown persistent inflammation and increased rates of atherosclerosis in HICs. Since immune activation/inflammation contributes to the pathogenesis of cardiovascular diseases (CVD), we evaluated clinical data and inflammation markers in HIV-1 viremic controllers (VC), elite controllers (EC), and control groups (HIV positive individuals with virological suppression by antiretroviral therapy—cART; HIV negative individuals—HIVneg) to assess whether they presented elevated levels of inflammation markers also associated with CVD. We observed the highest frequencies of activated CD8⁺ T cells in VCs, while EC and cART groups presented similar but slightly altered frequencies of this marker when compared to the HIVneg group. Regarding platelet activation, both HICs groups presented higher expression of P-selectin in platelets when compared to control groups. Monocyte subset analyses revealed lower frequencies of classical monocytes and increased frequencies of non-classical and intermediate monocytes among cART individuals and in EC when compared to HIV negative individuals, but none of the differences were significant. For VC, however, significant decreases in frequencies of classical monocytes and increases in the frequency of intermediate monocytes were observed in comparison to HIV negative individuals. The frequency of monocytes expressing tissue factor was similar among the groups on all subsets. In terms of plasma markers, VC had higher levels of many inflammatory markers, while EC had higher levels of VCAM-1 and ICAM-1 compared to control groups. Our data showed that VCs display increased levels of inflammation markers that have been associated with CVD risk. Meanwhile, ECs show signals of lower but persistent inflammation, comparable to the cART group, indicating the potential benefits of alternative therapies to decrease inflammation in this group.

When Leptin Is Not There: A Review of What Nonsyndromic Monogenic Obesity Cases Tell Us and the Benefits of Exogenous Leptin

Obesity is a pandemic condition of complex etiology, resulting from the increasing exposition to obesogenic environmental factors combined with genetic susceptibility. In the past two decades, advances in genetic research identified variants of the leptin-melanocortin pathway coding for genes, which are related to the potentiation of satiety and hunger, immune system, and fertility. Here, we review cases of congenital leptin deficiency and the possible beneficial effects of leptin replacement therapy. In summary, the cases presented here show clinical phenotypes of disrupted bodily energy homeostasis, biochemical and hormonal disorders, and abnormal immune response. Some phenotypes can be partially reversed by exogenous administration of leptin. With this review, we aim to contribute to the understanding of leptin gene mutations as targets for obesity diagnostics and treatment strategies.

Identification of a Rare and Potential Pathogenic MC4R Variant in a Brazilian Patient With Adulthood-Onset Severe Obesity

Background

The melanocortinergic pathway orchestrates the energy homeostasis and impairments in this system often lead to an increase in body weight. Rare variants in the melanocortin 4 receptor (MC4R) gene resulting in partial or complete loss of function have been described with autosomal co-dominant inheritance. These mutations are the most common cause of non-syndromic monogenic obesity. In this context, this study aimed to sequence the MC4R gene in a Brazilian cohort of adults with severe obesity.

Methods

This study included 163 unrelated probands with Body Mass Index (BMI) ≥ 35 kg/m², stratified into three groups, according to the period of obesity onset. From the total sample, 25 patients were enrolled in the childhood-onset group (0–11 years), 19 patients in the adolescence/youth-onset group (12–21 years), and 119 patients in the adult-onset group (>21 years). Blood pressure, anthropometric and biochemical characteristics were obtained, and the MC4R coding region of each subject’s DNA was assessed using automated Sanger sequencing.

Results

Significant anthropometric differences between the groups were observed. Higher body weight and BMI medians were found in patients with childhood-onset or adolescence/youth-onset when compared to the adulthood-onset obesity group. A total of five mutations were identified, including four missense variants: p.Ser36Thr, p.Val103Ile, p.Ala175Thr, and p.Ile251Leu. Additionally, we observed one synonymous variant (p.Ile198=). The p.Ala175Thr variant was identified in a female case with severe obesity and adulthood-onset. This variant was previously described as a partial loss-of-function mutation, in which the minor allele poses dominant-negative effect, probably resulting in reduced cAMP activity.

Conclusion

This study showed a prevalence of common and rare variants in a cohort of Brazilian adults with severe obesity and candidates to bariatric surgery. We have identified a rare potentially pathogenic MC4R variant in a Brazilian patient with severe and adulthood-onset obesity.

Adoptive Transfer of Bone Marrow-Derived Monocytes Ameliorates Schistosoma mansoni -Induced Liver Fibrosis in Mice

Liver diseases are a major health problem worldwide leading to high mortality rates and causing a considerable economic burden in many countries. Cellular therapies as potential treatments for liver diseases have proven beneficial in most of the conditions. In recent years, studies involving therapy with bone marrow cells have been implemented to promote liver regeneration and to reduce hepatic fibrosis, however identifying the cell population present in the bone marrow that is responsible for hepatic improvement after therapy is still necessary. The aim of the present study was the evaluation of the therapeutic efficacy of monocytes obtained from bone marrow in fibrosis resulting from S. mansoni infection in C57BL/6 mice. Monocytes were isolated by immunomagnetic separation and administered to the infected animals. The effects of treatment were evaluated through morphometric, biochemical, immunological and molecular analyzes. Monocyte therapy promoted reduction of liver fibrosis induced by S. mansoni infection, associated with a decrease in production of inflammatory and pro-fibrogenic mediators. In addition, monocyte infusion caused downregulation of factors associated with the M1 activation profile, as well as upregulation of M2reg markers. The findings altogether reinforce the hypothesis that the predominance of M2reg macrophages, producers of immunosuppressive cytokines, may favor the improvement of hepatic fibrosis in a preclinical model, through fibrous tissue remodeling, modulation of the inflammatory response and fibrogenesis.

PGL I expression in live bacteria allows activation of a CD206/PPARγ cross-talk that may contribute to successful Mycobacterium leprae colonization of peripheral nerves

Mycobacterium leprae, an obligate intracellular bacillus, infects Schwann cells (SCs), leading to peripheral nerve damage, the most severe leprosy symptom. In the present study, we revisited the involvement of phenolic glycolipid I (PGL I), an abundant, private, surface M. leprae molecule, in M. leprae-SC interaction by using a recombinant strain of M. bovis BCG engineered to express this glycolipid. We demonstrate that PGL I is essential for bacterial adhesion and SC internalization. We also show that live mycobacterium-producing PGL I induces the expression of the endocytic mannose receptor (MR/CD206) in infected cells in a peroxisome proliferator-activated receptor gamma (PPARγ)-dependent manner. Of note, blocking mannose recognition decreased bacterial entry and survival, pointing to a role for this alternative recognition pathway in bacterial pathogenesis in the nerve. Moreover, an active crosstalk between CD206 and the nuclear receptor PPARγ was detected that led to the induction of lipid droplets (LDs) formation and prostaglandin E2 (PGE2), previously described as fundamental players in bacterial pathogenesis. Finally, this pathway was shown to induce IL-8 secretion. Altogether, our study provides evidence that the entry of live M. leprae through PGL I recognition modulates the SC phenotype, favoring intracellular bacterial persistence with the concomitant secretion of inflammatory mediators that may ultimately be involved in neuroinflammation.

Nerve damage is the most severe symptom of leprosy, an ancient disease that continues to be a major health problem in several countries. Nerve damage is due to the ability of Mycobacterium leprae, the etiologic agent, to invade SCs, the glial cells of the peripheral nervous system. Understanding the molecular basis of M. leprae–SC interaction is essential for the creation of new tools aiming to treat and, above all, prevent leprosy neuropathy. This study demonstrates the critical role of PGL I, an M. leprae-abundant specific cell wall lipid, in establishing infection. PGL I is not only a prerequisite in initiating bacterial adhesion to and subsequent invasion of SCs, but also for changing the repertoire of cell surface proteins to allow for the entrance of bacteria via alternative pathways. These new invasive pathways induced by PGL I involve recognition of other bacterial cell surface glycolipids that, in turn, evoke functional changes in the infected cell, including the accumulation of host cell-derived lipids, which favor bacterial survival. These pathways also promote the secretion of inflammatory mediators that may contribute to nerve damage. In an era of translational-oriented research, exploring these receptors in depth could lead to the development of attractive strategies to ensure the targeted intracellular delivery of therapeutics aiming to prevent neuropathy.

Leishmania infantum lipophosphoglycan induced-Prostaglandin E2 production in association with PPAR-γ expression via activation of Toll like receptors-1 and 2

Lipophosphoglycan (LPG) is a key virulence factor expressed on the surfaces of Leishmania promastigotes. Although LPG is known to activate macrophages, the underlying mechanisms resulting in the production of prostaglandin E₂ (PGE₂) via signaling pathways remain unknown. Here, the inflammatory response arising from stimulation by Leishmania infantum LPG and/or its lipid and glycan motifs was evaluated with regard to PGE₂ induction. Intact LPG, but not its glycan and lipid moieties, induced a range of proinflammatory responses, including PGE₂ and nitric oxide (NO) release, increased lipid droplet formation, and iNOS and COX2 expression. LPG also induced ERK-1/2 and JNK phosphorylation in macrophages, in addition to the release of PGE₂, MCP-1, IL-6, TNF-α and IL-12p70, but not IL-10. Pharmacological inhibition of ERK1/2 and PKC affected PGE₂ and cytokine production. Moreover, treatment with rosiglitazone, an agonist of peroxisome proliferator-activated receptor gamma (PPAR-γ), also modulated the release of PGE₂ and other proinflammatory mediators. Finally, we determined that LPG-induced PPAR-γ signaling occurred via TLR1/2. Taken together, these results reinforce the role played by L. infantum-derived LPG in the proinflammatory response seen in Leishmania infection.

Lipid bodies accumulation in Leishmania infantum-infected C57BL/6 macrophages

Lipid bodies (LBs) are intracellular accumulations of neutral lipids surrounded by a single membrane. These organelles are involved in the production of eicosanoids, which modulate immunity by either promoting or dampening inflammatory responses. Leishmania infantum, the etiological agent of visceral leishmaniasis in Brazil, is an intracellular parasite that causes disease by suppressing macrophage microbicidal responses. C57BL/6 mouse bone marrow-derived macrophages infected with L. infantum strain LcJ had higher numbers of LB+ cells (P<.0001) and total LBs than noninfected cultures. Large (>3 μm) LBs were present inside parasitophorous vacuoles (PVs). These results contrast with those of L. infantum-infected BALB/c macrophages, in which the only LBs are derived from parasite, not macrophage origin. Increased LBs in C57BL/6 macrophages in close association with parasites would position host LBs where they could modulate L. infantum infection. These results imply a potential influence of the host genetics on the role of LBs in host-pathogen interactions. Overall, our data support a model in which the expression, and the role of LBs upon infection, ultimately depends on the specific combination of host-pathogen interactions.

Circulating Biomarkers of Immune Activation, Oxidative Stress and Inflammation Characterize Severe Canine Visceral Leishmaniasis

Clinical manifestations in canine visceral leishmaniasis (CVL) have not been clearly associated with immunological status or disease progression. We simultaneously assessed biomarkers of inflammation, immune activation, oxidative stress, and anti-sand fly saliva IgG concentrations in dog sera with different clinical manifestations to characterize a biosignature associated with CVL severity. In a cross-sectional exploratory study, a random population of 70 dogs from an endemic area in Brazil was classified according to CVL clinical severity and parasitological evaluation. A panel of biomarkers and anti-sand fly saliva IgG were measured in canine sera. Assessment of protein expression of profile biomarkers identified a distinct biosignature that could cluster separately animal groups with different clinical scores. Increasing severity scores were associated with a gradual decrease of LTB4 and PGE2, and a gradual increase in CXCL1 and CCL2. Discriminant analyses revealed that combined assessment of LTB4, PGE2 and CXCL1 was able to distinguish dogs with different clinical scores. Dogs with the highest clinical score values also exhibited high parasite loads and higher concentrations of anti-saliva antibodies. Our findings suggest CVL clinical severity is tightly associated with a distinct inflammatory profile hallmarked by a differential expression of circulating eicosanoids and chemokines.

Involvement of TLR6 in the induction of COX-2, PGE2 and IL-10 in macrophages by lipids from virulent S2P and attenuated R1A Babesia bovis strains

Toll like receptors (TLRs) are involved in the modulation of diverse host genes expression through a complex network of signalling events that allow for an appropriate response to a microbial pathogen. In the present work we used TLR6KO mice in order to study the role of TLR6 in the immune discrimination of lipids from two Babesia bovis strains, attenuated R1A (LA) and virulent S2P (LV), and the consequent macrophage activation. We demonstrated that TLR6 is required for lipid body induction in murine peritoneal macrophages by both LA and LV. Interestingly, as regards IL-10 and COX-2/PGE2 pathway induction by LA and LV, we observed differences in the biological effects produced by these lipid extracts. Our results indicate a role of TLR6 in the down-modulation of these immunoregulators only in the case of LA, whereas this receptor was not implicated in pro-inflammatory TNFα, IL-6 and KC release induced by LA. Remarkably, LV did not exert the down-modulatory effect observed for LA, supporting the notion that LA and LV possess different lipid composition that could correlate with the polar pathogenic effect of both B. bovis strains.

Omega-9 Oleic Acid Induces Fatty Acid Oxidation and Decreases Organ Dysfunction and Mortality in Experimental Sepsis

Sepsis is characterized by inflammatory and metabolic alterations, which lead to massive cytokine production, oxidative stress and organ dysfunction. In severe systemic inflammatory response syndrome, plasma non-esterified fatty acids (NEFA) are increased. Several NEFA are deleterious to cells, activate Toll-like receptors and inhibit Na⁺/K⁺-ATPase, causing lung injury. A Mediterranean diet rich in olive oil is beneficial. The main component of olive oil is omega-9 oleic acid (OA), a monounsaturated fatty acid (MUFA). We analyzed the effect of OA supplementation on sepsis. OA ameliorated clinical symptoms, increased the survival rate, prevented liver and kidney injury and decreased NEFA plasma levels in mice subjected to cecal ligation and puncture (CLP). OA did not alter food intake and weight gain but diminished reactive oxygen species (ROS) production and NEFA plasma levels. Carnitine palmitoyltransferase IA (CPT1A) mRNA levels were increased, while uncoupling protein 2 (UCP2) liver expression was enhanced in mice treated with OA. OA also inhibited the decrease in 5' AMP-activated protein kinase (AMPK) expression and increased the enzyme expression in the liver of OA-treated mice compared to septic animals. We showed that OA pretreatment decreased NEFA concentration and increased CPT1A and UCP2 and AMPK levels, decreasing ROS production. We suggest that OA has a beneficial role in sepsis by decreasing metabolic dysfunction, supporting the benefits of diets high in monounsaturated fatty acids (MUFA).

Murine lung injury caused by Leptospira interrogans glycolipoprotein, a specific Na/K-ATPase inhibitor

Background

Leptospiral glycolipoprotein (GLP) is a potent and specific Na/K-ATPase inhibitor. Severe pulmonary form of leptospirosis is characterized by edema, inflammation and intra-alveolar hemorrhage having a dismal prognosis. Resolution of edema and inflammation determines the outcome of lung injury. Na/K-ATPase activity is responsible for edema clearance. This enzyme works as a cell receptor that triggers activation of mitogen-activated protein kinase (MAPK) intracellular signaling pathway. Therefore, injection of GLP into lungs induces injury by triggering inflammation.

Methods

We injected GLP and ouabain, into mice lungs and compared their effects. Bronchoalveolar lavage fluid (BALF) was collected for cell and lipid body counting and measurement of protein and lipid mediators (PGE₂ and LTB₄). The levels of the IL-6, TNFα, IL-1B and MIP-1α were also quantified. Lung images illustrate the injury and whole-body plethysmography was performed to assay lung function. We used Toll-like receptor 4 (TLR4) knockout mice to evaluate leptospiral GLP-induced lung injury. Na/K-ATPase activity was determined in lung cells by nonradioactive rubidium incorporation. We analyzed MAPK p38 activation in lung and in epithelial and endothelial cells.

Results

Leptospiral GLP and ouabain induced lung edema, cell migration and activation, production of lipid mediators and cytokines and hemorrhage. They induced lung function alterations and inhibited rubidium incorporation. Using TLR4 knockout mice, we showed that the GLP action was not dependent on TLR4 activation. GLP activated of p38 and enhanced cytokine production in cell cultures which was reversed by a selective p38 inhibitor.

Conclusions

GLP and ouabain induced lung injury, as evidenced by increased lung inflammation and hemorrhage. To our knowledge, this is the first report showing GLP induces lung injury. GLP and ouabain are Na/K-ATPase targets, triggering intracellular signaling pathways. We showed p38 activation by GLP-induced lung injury, which was may be linked to Na/K-ATPase inhibition. Lung inflammation induced by GLP was not dependent on TLR4 activation.

Culture of mouse peritoneal macrophages with mouse serum induces lipid bodies that associate with the parasitophorous vacuole and decrease their microbicidal capacity against Toxoplasma gondii

Lipid bodies [lipid droplets (LBs)] are lipid-rich organelles involved in lipid metabolism, signalling and inflammation. Recent findings suggest a role for LBs in host response to infection; however, the potential functions of this organelle in Toxoplasma gondii infection and how it alters macrophage microbicidal capacity during infection are not well understood. Here, we investigated the role of host LBs in T. gondii infection in mouse peritoneal macrophages in vitro. Macrophages cultured with mouse serum (MS) had higher numbers of LBs than those cultured in foetal bovine serum and can function as a model to study the role of LBs during intracellular pathogen infection. LBs were found in association with the parasitophorous vacuole, suggesting that T. gondii may benefit from this lipid source. Moreover, increased numbers of macrophage LBs correlated with high prostaglandin E2 (PGE2) production and decreased nitric oxide (NO) synthesis. Accordingly, LB-enriched macrophages cultured with MS were less efficient at controlling T. gondii growth. Treatment of macrophages cultured with MS with indomethacin, an inhibitor of PGE2 production, increased the microbicidal capacity against T. gondii. Collectively, these results suggest that culture with MS caused a decrease in microbicidal activity of macrophages against T. gondii by increasing PGE2 while lowering NO production.

The effect of thiamine deficiency on inflammation, oxidative stress and cellular migration in an experimental model of sepsis

Background

Sepsis is a prevalent condition in critically ill patients and may be associated with thiamine deficiency (TD). The aim of this study was to evaluate the effect of TD on inflammation, oxidative stress and cellular recruitment in a sepsis model.

Methods

The experimental sepsis model, cecal ligation and puncture (CLP), was utilized on mice in comparison with a sham procedure. The following four groups were compared against each other: SHAM with AIN93G complete chow, SHAM with thiamine deficient (TD) chow, CLP with AIN93G complete chow, and CLP with TD chow. Thiamine pyrophosphate (TPP) blood concentrations were determined, and blood and peritoneal fluid were evaluated for differences in TNF-alpha, IL-1, IL-6, KC and MCP-1/CCL2 levels. In addition, the levels of 4-HNE adducts in liver proteins were evaluated by Western Blot.

Results

The mean TPP blood concentration from the mice fed with the complete chow was 303.3 ± 42.6 nmol/L, and TD occurred within 10 days. TNF-α and MCP-1 concentrations in the peritoneal fluid were significantly greater in the CLP with TD chow group when compared with the other groups. The blood IL-1β level, however, was lower in the CLP with TD chow group. Liver 4-HNE levels were highest in the TD chow groups. Blood mononuclear cell numbers, as well as peritoneal total leukocyte, mononuclear cell and neutrophil numbers were greater in the CLP with TD chow group. Peritoneal bacterial colony forming units (CFU) were significantly lower in the CLP with TD chow group.

Conclusion

TD was associated with greater bacterial clearance, oxidative stress and inflammatory response changes.

Understanding the mechanisms controlling Leishmania amazonensis infection in vitro: the role of LTB4 derived from human neutrophils

Neutrophils are rapidly recruited to the site of Leishmania infection and play an active role in capturing and killing parasites. They are the main source of leukotriene B₄ (LTB₄), a potent proinflammatory lipid mediator. However, the role of LTB₄ in neutrophil infection by Leishmania amazonensis is not clear. In this study, we show that L. amazonensis or its lipophosphoglycan can induce neutrophil activation, degranulation, and LTB₄ production. Using pharmacological inhibitors of leukotriene synthesis, our findings reveal an LTB₄-driven autocrine/paracrine regulatory effect. In particular, neutrophil-derived LTB₄ controls L. amazonensis killing, degranulation, and reactive oxygen species production. In addition, L. amazonensis infection induces an early increase in Toll-like receptor 2 expression, which facilitates parasite internalization. Nuclear factor kappa B (NFkB) pathway activation represents a required upstream event for L. amazonensis–induced LTB₄ synthesis. These leishmanicidal mechanisms mediated by neutrophil-derived LTB₄ act through activation of its receptor, B leukotriene receptor 1 (BLT1).

Oleic acid inhibits lung Na/K-ATPase in mice and induces injury with lipid body formation in leukocytes and eicosanoid production

Background

Acute respiratory distress syndrome (ARDS) can emerge from certain pathologies, such as sepsis, fat embolism and leptospirosis, in which the levels of unesterified fatty acids are increased in the patient’s plasma. ARDS is characterized by edema formation, and edema resolution occurs mainly due to the pneumocyte Na/K-ATPase activity. As previously described, increased oleic acid (OA) plasma concentrations induce lung injury by interfering with sodium transport. The first aim of this study was to develop a radioactivity-free assay to detect Na,K-ATPase activity ex vivo using a model of OA-induced lung injury in mice. We also investigated the relationship between Na/K-ATPase inhibition and OA-induced lung injury using ouabain-induced lung injury as a comparison, because of the well-described effect of ouabain as a Na/K-ATPase inhibitor.

Methods

We developed a Na/K-ATPase assay based on the capture of non-radioactive Rb⁺ ions by mice lung tissue in the absence or presence of ouabain, a specific Na/K-ATPase inhibitor. Rb⁺ incorporation into the lung was measured by inductively coupled plasma-optical emission spectrometry (ICP-OES) after lung tissue mineralization. Na/K-ATPase activity was considered as the difference between Rb⁺ incorporation in the absence and in the presence of ouabain. Bronchoalveolar lavage fluid was collected for lung injury assessment. For this assessment, cell counting, lipid body enumeration and lipid mediator concentrations were measured. Histological analyses were used to determinate lung pathology. Whole body plethysmographic analysis was performed to assay lung function.

Results

The lung Na/K-ATPase activity of mice was completely inhibited by an OA dose of 10 μmol, an effect also obtained with 10^-3 μmol of ouabain, as demonstrated by the decreased Rb⁺ incorporation in the lungs. The same OA dose induced lung edema and inflammation with cell influx, lipid body formation, and leukotriene B₄ (LTB₄) and prostaglandin E₂ (PGE₂) production. Ouabain also induced lung inflammation, as detected by histological examinations. As far as we know, this is the first time that ouabain-induced lung injury was shown. Both OA and ouabain induced functional lung pathology in mice simultaneously with inhibition of the lung Na/K-ATPase activity.

Conclusions

We developed a new non-radioactive assay to quantified Na/K-ATPase in vivo. OA and ouabain inhibited in vivo Na/K-ATPase activity in the lungs and induced lung injury. Our data reinforce the idea that Na/K-ATPase inhibitors may worsen lung injury in specific pathological conditions.

Oleic acid induces lung injury in mice through activation of the ERK pathway

Oleic acid (OA) can induce acute lung injury in experimental models. In the present work, we used intratracheal OA injection to show augmented oedema formation, cell migration and activation, lipid mediator, and cytokine productions in the bronchoalveolar fluids of Swiss Webster mice. We also demonstrated that OA-induced pulmonary injury is dependent on ERK1/2 activation, since U0126, an inhibitor of ERK1/2 phosphorylation, blocked neutrophil migration, oedema, and lipid body formation as well as IL-6, but not IL-1β production. Using a mice strain carrying a null mutation for the TLR4 receptor, we proved that increased inflammatory parameters after OA challenges were not due to the activation of the TLR4 receptor. With OA being a Na/K-ATPase inhibitor, we suggest the possible involvement of this enzyme as an OA target triggering lung inflammation.

PPAR gamma activation protects the brain against microvascular dysfunction in sepsis

Sepsis is a severe disorder characterized by systemic inflammatory responses in the presence of an infection and may progress to multiple organ dysfunction and death. Alterations in cerebral microcirculation fulfill a crucial role in the pathogenesis of severe sepsis, and include a decrease in capillary density and disturbances in leukocyte movement along capillaries. Nevertheless, the mechanisms involved in sepsis-associated cerebral microcirculatory alterations have so far not been defined. We investigated the effect of the peroxisome proliferator-activated receptor gamma (PPARγ) selective agonist rosiglitazone on leukocyte/endothelial cell interaction and functional capillary density in the brain in the cecal ligation and puncture (CLP) model of sepsis. Anti-inflammatory effects of rosiglitazone on the cerebral microcirculation were marked. Functional capillary density increased and leukocyte rolling and adhesion were decreased in animals submitted to CLP and treated with rosiglitazone. Our data provide evidence for involvement of PPARγ activation in leukocyte-endothelium interactions and alterations in capillary density. Improved cerebral perfusion in animals treated with rosiglitazone, suggests that PPARγ activation is protective against cerebral microvascular dysfunction in sepsis.

Co-operative signalling through DP(1) and DP(2) prostanoid receptors is required to enhance leukotriene C(4) synthesis induced by prostaglandin D(2) in eosinophils

BACKGROUND AND PURPOSE

Prostaglandin (PG) D(2) has emerged as a key mediator of allergic inflammatory pathologies and, particularly, PGD(2) induces leukotriene (LT) C(4) secretion from eosinophils. Here, we have characterized how PGD(2) signals to induce LTC(4) synthesis in eosinophils.

EXPERIMENTAL APPROACH

Antagonists and agonists of DP(1) and DP(2) prostanoid receptors were used in a model of PGD(2) -induced eosinophilic inflammation in vivo and with PGD(2) -stimulated human eosinophils in vitro, to identify PGD(2) receptor(s) mediating LTC(4) secretion. The signalling pathways involved were also investigated.

KEY RESULTS

In vivo and in vitro assays with receptor antagonists showed that PGD(2) -triggered cysteinyl-LT (cysLT) secretion depends on the activation of both DP(1) and DP(2) receptors. DP(1) and DP(2) receptor agonists elicited cysLTs production only after simultaneous activation of both receptors. In eosinophils, LTC(4) synthesis, but not LTC(4) transport/export, was activated by PGD(2) receptor stimulation, and lipid bodies (lipid droplets) were the intracellular compartments of DP(1) /DP(2) receptor-driven LTC(4) synthesis. Although not sufficient to trigger LTC(4) synthesis by itself, DP(1) receptor activation, signalling through protein kinase A, did activate the biogenesis of eosinophil lipid bodies, a process crucial for PGD(2) -induced LTC(4) synthesis. Similarly, concurrent DP(2) receptor activation used Pertussis toxin-sensitive and calcium-dependent signalling pathways to achieve effective PGD(2) -induced LTC(4) synthesis.

CONCLUSIONS AND IMPLICATIONS

Based on pivotal roles of cysLTs in allergic inflammatory pathogenesis and the collaborative interaction between PGD(2) receptors described here, our data suggest that both DP(1) and DP(2) receptor antagonists might be attractive candidates for anti-allergic therapies.

Histopathological analysis of initial cellular response in TLR-2 deficient mice experimentally infected by Leishmania (L.) amazonensis

Tegumentary leishmaniasis is an important public health problem in several countries. The capacity of the Leishmania species, at the initial moments of the infection, to invade and survive inside the host cells involves the interaction of surface molecules that are crucial in determining the evolution of the disease. Using C57BL/6 wild-type and TLR-2(-/-) mice infected with L. (L.) amazonensis, we demonstrated that TLR-2(-/-) mice presented eosinophilic granuloma in the ear dermis, different from C57BL/6 wild-type mice that presented a cellular profile characterized mainly by mononuclear cell infiltrates, besides neutrophils and eosinophils, during the two first week of infection. When the parasite load was evaluated, we found that the absence of TLR-2 lead to a significant reduction of the infection in deficient mice, when compared with C57BL/6 mice which were more susceptible to the infection. Using TLR-2 deficient mice, it was possible to show that the absence of this receptor determined the reduction of the parasite load and the recruitment of inflammatory cells during the two first weeks after L. (L.) amazonensis infection.

Lipids from attenuated and virulent Babesia bovis strains induce differential TLR2-mediated macrophage activation

Babesia bovis is an intraerythrocytic apicomplexan protozoa of cattle that causes an acute infection with parasite persistence. Babesiosis limitation depends on macrophages, essential effector cells of the host innate defense, which generate inflammatory cytokines and nitric oxide. Herein, we report quantitative differences in the lipid composition of merozoites from two B. bovis strains with polar behaviour: attenuated R1A and virulent S2P. Accordingly, we observed a distinct inflammatory response induced by the total lipids of R1A (L(A)) and S2P (L(V)) in murine peritoneal macrophages. L(A) and particularly its fractions phosphatidic acid and phosphatidylserine+phosphatidylinositol (PS+PI), produced a strong activation of these cells with lipid body formation, cyclooxygenase-2 expression and pro-inflammatory TNFalpha, IL-6 and KC secretion. Although L(V) did not activate these cells, the corresponding PS+PI fraction induced TNFalpha, IL-6 and KC release. Therefore, these facts might be suggesting the presence of an inhibitor in L(V). Furthermore, the employment of wild type and toll like receptor 2 knockout (TLR2KO) mice allowed us to demonstrate that macrophage activation by the stimulating lipid fractions was mediated through TLR2. Interestingly, only L(A) activated the extracellular signal-regulated kinases 1 and 2 (ERK1/2). Inhibitory studies employing UO126, indicated that the ERK pathway was required for TNFalpha, IL-6 and KC release. In conclusion, the absence of inflammatory response observed with the lipids of S2P virulent strain could constitute an evasion mechanism of the innate immune response enabling parasite establishment in the host.

Histoplasma capsulatum cell wall {beta}-glucan induces lipid body formation through CD18, TLR2, and dectin-1 receptors: correlation with leukotriene B4 generation and role in HIV-1 infection

Histoplasma capsulatum (Hc) is a facultative, intracellular parasite of worldwide significance. Infection with Hc produces a broad spectrum of diseases and may progress to a life-threatening systemic disease, particularly in individuals with HIV infection. Resolution of histoplasmosis is associated with the activation of cell-mediated immunity, and leukotriene B(4) plays an important role in this event. Lipid bodies (LBs) are increasingly being recognized as multifunctional organelles with roles in inflammation and infection. In this study, we investigated LB formation in histoplasmosis and its putative function in innate immunity. LB formation in leukocytes harvested from Hc-infected C57BL/6 mice peaks on day 2 postinfection and correlates with enhanced generation of lipid mediators, including leukotriene B(4) and PGE(2). Pretreatment of leukocytes with platelet-activating factor and BLT1 receptor antagonists showed that both lipid mediators are involved in cell signaling for LB formation. Alveolar leukocytes cultured with live or dead Hc also presented an increase in LB numbers. The yeast alkali-insoluble fraction 1, which contains mainly beta-glucan isolated from the Hc cell wall, induced a dose- and time-dependent increase in LB numbers, indicating that beta-glucan plays a signaling role in LB formation. In agreement with this hypothesis, beta-glucan-elicited LB formation was inhibited in leukocytes from 5-LO(-/-), CD18(low) and TLR2(-/-) mice, as well as in leukocytes pretreated with anti-Dectin-1 Ab. Interestingly, human monocytes from HIV-1-infected patients failed to produce LBs after beta-glucan stimulation. These results demonstrate that Hc induces LB formation, an event correlated with eicosanoid production, and suggest a role for these lipid-enriched organelles in host defense during fungal infection.

Arrest of oogenesis in the bug Rhodnius prolixus challenged with the fungus Aspergillus niger is mediated by immune response-derived PGE2

In this work we characterized the immune response of the insect Rhodnius prolixus to a direct injection into the hemocoel of the non-entomopathogenic fungus Aspergillus niger, and evaluated its consequences on host oogenesis. These animals were able to respond by mounting effective cellular and humoral responses to this fungus; these responses were shown, however, to have reproductive fitness costs, as the number of eggs laid per female was significantly reduced. The disturbance of egg formation during infectious process correlated with an elevation in the titer of hemolymph prostaglandin E2 48 h post-challenge. Administration of Zymosan A as an immunogenic non-infectious challenge produced similar effects on phenoloxidase and prophenoloxidase activities, oocyte development and prostaglandin E2 titer, precluding the hypothesis of an effect mediated by fungal metabolites in animals challenged with fungus. Ovaries at 48 h post-challenge showed absence of vitellogenic ovarian follicles, and the in vivo administration of prostaglandin E2 or its receptor agonist misoprostol, partially reproduced this phenotype. Together these data led us to hypothesize that immune-derived prostaglandin E2 raised from the insect response to the fungal challenge is involved in disturbing follicle development, contributing to a reduction in host reproductive output and acting as a host-derived adaptive effector to infection.

Inflammatory response and bacterial dissemination afterlaparotomy and abdominal CO2 insufflation in a murine model of peritonitis

BACKGROUND

The immunologic repercussions due to cavity insufflation are the focus of great discussion. The aim of this study was to compare the inflammatory response and bacterial dissemination after laparotomy and abdominal CO2 insufflation in a murine model of peritonitis.

METHODS

Swiss mice were inoculated intraperitoneally with 0.5 ml of a solution containing 1 x 10(8) colony-forming units (CFU)/ml of Escherichia coli and were divided into three groups as follow: control (anesthesia for 30 min), laparotomy (2.5-cm midline incision for 30 min), and CO2 pneumoperitoneum (CO2 cavity insufflation for 30 min). The number of leukocytes, CFU/ml counting, and the levels of interleukin (IL)-6, tumor necrosis factor-alpha (TNF-alpha), and IL-10 were evaluated in blood, peritoneal, and pleural fluid samples obtained at 90 min and 18 h after the procedures.

RESULTS

The laparotomy group showed a greater bacterial dissemination to the blood, peritoneum, and pleural cavity and also greater neutrophil migration to the peritoneal cavity compared to the CO2 insufflated and control groups. The 24-h mortality was also significantly higher in the laparotomy group. The IL-6 levels showed a precocious rise in all groups submitted to bacterial inoculation at the 90-min time point. At the 18-h time point, IL-6 levels in the peritoneum were significantly higher in the laparotomy group than in the control or CO2 insufflated groups. At the same time, TNF-alpha levels were higher in the laparotomy and CO2 insufflated groups than in controls; IL-10 levels showed no differences among the groups.

CONCLUSIONS

Our results suggest that cavity insufflation with CO2 is a more effective method of access, inducing less bacterial dissemination and also a less intense inflammatory response. Cavity insufflation with CO2 may present a good option for the surgical treatment of patients with bacterial peritonitis.

Anti-inflammatory activity in the aqueous crude extract of the leaves of Nidularium procerum: A bromeliaceae from the Brazilian coastal rain forest

Nidularium procerum LINDMAN, a common bromeliaceae from the Brazilian flora, remains poorly studied regarding its chemical and pharmacological properties. We have recently published that N. procerum has potent analgesic and anti-inflammatory activities. In the present work, we have investigated potential mechanisms involved in the anti-inflammatory effects of N. procerum aqueous extract on lipopolysaccharide (LPS)-, platelet activating factor (PAF)- or formyl-methionyl-leucyl-phenylalanine (fMLP)-induced pleurisy models of inflammation. We found that the aqueous extract of N. procerum leaves (leaf aqueous extract; LAE) inhibits the neutrophil migration, production of inflammatory cytokines interleukin-1 and -6 (IL-1 and IL-6) and the generation of prostaglandin E2 (PGE2) in LPS-induced pleural inflammation in mice. Such inhibitory effect of N. procerum on PGE2 generation was tightly correlated to the inhibition of formation of new cytoplasmic lipid bodies within recruited leukocytes. N. procerum also blocked the in vivo neutrophil influx induced by injection of PAF or fMLP into the mouse pleural cavity and directly inhibited PAF-induced neutrophil chemotaxis in vitro. The data obtained in this study indicate that N. procerum LAE exerts its anti-inflammatory effects by interfering with the capacity of the host to respond to injury at different levels. Among the different functions affected by N. procerum LAE, lipid body formation, PGE2 and cytokine production and neutrophil chemotaxis are readily evidenced in relevant surrogate models. The N. procerum bioactive profile makes it an attractive candidate for future development as a drug or phytomedicine.

Eicosanoid-mediated proinflammatory activity of Pseudomonas aeruginosa ExoU

As Pseudomonas aeruginosa ExoU possesses two functional blocks of homology to calcium-independent (iPLA(2)) and cytosolic phospholipase A(2) (cPLA(2)), we addressed the question whether it would exhibit a proinflammatory activity by enhancing the synthesis of eicosanoids by host organisms. Endothelial cells from the HMEC-1 line infected with the ExoU-producing PA103 strain exhibited a potent release of arachidonic acid (AA) that could be significantly inhibited by methyl arachidonyl fluorophosphonate (MAFP), a specific PLA(2) inhibitor, as well as significant amounts of the cyclooxygenase (COX)-derived prostaglandins PGE(2) and PGI(2). Cells infected with an isogenic mutant defective in ExoU synthesis did not differ from non-infected cells in the AA release and produced prostanoids in significantly lower concentrations. Infection by PA103 induced a marked inflammatory response in two different in vivo experimental models. Inoculation of the parental bacteria into mice footpads led to an early increase in the infected limb volume that could be significantly reduced by inhibitors of both COX and lipoxygenase (ibuprofen and NDGA respectively). In an experimental respiratory infection model, bronchoalveolar lavage (BAL) from mice instilled with 10(4) cfu of PA103 exhibited a marked influx of inflammatory cells and PGE(2) release that could be significantly reduced by indomethacin, a non-selective COX inhibitor. Our results suggest that ExoU may contribute to P. aeruginosa pathogenesis by inducing an eicosanoid-mediated inflammatory response of host organisms.

Antinociceptive effect of Nidularium procerum: a Bromeliaceae from the Brazilian coastal rain forest

Nidularium procerum, a common plant of the Brazilian flora, has not yet been studied for its pharmacological properties. We report here that extracts of N. procerum show both analgesic and anti-inflammatory properties. Oral (p.o.) or intraperitoneal (i.p.) administration of an aqueous crude extract from leaves of N. procerum (LAE) inhibited the writhing reaction induced by acetic acid (ED50 value = 0.2 mg/kg body weight, i.p.) in a dose-dependent manner. This analgesic property was confirmed in rats using two different models of bradykinin-induced hyperalgesia; there was 75% inhibition of pain in the modified Hargreaves assay, and 100% inhibition in the classical Hargreaves assay. This potent analgesic effect was not blocked by naloxone, nor was it observed in the hot plate model, indicating that the analgesic effect is not associated with the activation of opioid receptors in the central nervous system. By contrast, we found that LAE (0.02 microg/ml) selectively inhibited prostaglandin E2 production by cyclooxygenase (COX)-2, but not COX-1, which is a plausible mechanism for the analgesic effect. A crude methanol extract from the leaves also showed similar analgesic activity. An identical extract from the roots of N. procerum did not, however, block acetic acid-induced writhes, indicating that the analgesic compounds are concentrated in the leaves. Finally, we found that LAE inhibited an inflammatory reaction induced by lipopolysaccharide in the pleural cavity of mice.

Macrophage lipid body induction by Chagas disease in vivo: putative intracellular domains for eicosanoid formation during infection

Lipid bodies (LB), lipid-rich inclusions abundantly present in cells engaged in inflammation, are specialized intracellular domains involved in generating inflammatory mediators, the eicosanoids. Since the acute Trypanosoma cruzi infection triggers a potent inflammatory reaction characterized by a great increase of peripheral blood monocyte (PBM) and macrophage numbers, we investigated the LB occurrence in these cells. The experimental rat infection by T. cruzi (Y strain) induced significant increase of the LB numbers in peritoneal macrophages at day 6 and 12, accompanied by significant enhancement of Prostaglandin E(2) (PGE(2)) production, as measured by EIA. At day 12, ultrastructural analysis of the heart, a target organ of the disease, showed numerous macrophages with LB prominently increased in number (mean of 8.3 per section view, range of 1-25) compared to controls (mean of 2.6 per section view, range of 0-3) and size. PBM from all groups rarely showed LB. Our results demonstrate, for the first time, that T. cruzi infection in rats elicits important LB formation in inflammatory macrophages but not in PBM. The increase in LB numbers during infection positively correlates with increased generation of PGE(2), suggesting that LB may have a role in the heightened eicosanoid production observed during T. cruzi infection.

NS-398: cyclooxygenase-2 independent inhibition of leukocyte priming for lipid body formation and enhanced leukotriene generation

Because the induction of new lipid body formation in leukocytes correlates with and likely contributes to their enhanced 'primed' prostaglandin and leukotriene formation, we evaluated two selective cyclooxygenase (COX)-2 inhibitors. Three types of stimuli, cis -unsaturated fatty acids, platelet activating factor and protein kinase C activators, stimulate lipid body formation. NS-398 (0.1-10 microM), but not another COX-2 inhibitor, SC58125 (0.1- 10 microM), blocked leukocyte lipid body formation elicited by all three types of stimuli and also blocked priming for enhanced LTB(4) production and PGE(2) production. The effect of NS-398 on lipid body formation was independent of its inhibitory effects on COX-2 since arachidonate-induced lipid body formation in COX-2-deficient mouse leukocytes was also inhibited by NS-398. By means of its ability to inhibit leukocyte lipid body formation, NS-398 may exert actions independent of its COX-2 inhibition and more broadly contribute to the suppression of formation of COX-1 and lipoxygenase-derived eicosanoids.

LPS induces eosinophil migration via CCR3 signaling through a mechanism independent of RANTES and Eotaxin

Mounting evidence suggests that lipopolysaccharide (LPS) modulates bronchoconstriction and eosinophil function in asthma. We have investigated the role of different chemokines in the eosinophil influx to the pleural cavity after LPS stimulation. Expression of mRNA for eotaxin, regulated on activation, normal T cells expressed and secreted (RANTES), macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, MIP-2, and monocyte chemotactic protein (MCP)-1 was increased in cells recovered from the mouse pleural cavity 6 h after LPS administration. Eotaxin and RANTES, but not MIP-1alpha, protein levels were also increased in cell-free pleural washes recovered 6 h after LPS stimulation (LPW). Antimurine eotaxin and antimurine RANTES antibodies (Abs) failed to inhibit LPS-induced eosinophil influx into mouse pleural cavity in vivo. Pertussis toxin inhibited LPW-induced eosinophil shape change in vitro, suggesting the involvement of G protein-coupled receptors in LPW signaling. Blockade of CCR3 receptors diminished eosinophil shape change induced by LPW fractions in vitro and LPS-induced eosinophil accumulation in vivo. To investigate further contribution of CC chemokines, we administered a 35-kD CC chemokine neutralizing protein (vCKBP) in vivo. vCKBP inhibited the eosinophil accumulation induced by eotaxin and ovalbumin, but did not block that induced by LPS or LPW. Our data suggest that LPS-induced eosinophil accumulation depends on G protein-coupled CCR3 receptor activation, through a mechanism independent of eotaxin, RANTES, or other vCKBP-inhibitable CC chemokines.

Apoptotic mimicry by an obligate intracellular parasite downregulates macrophage microbicidal activity

Programmed cell death by apoptosis of unnecessary or potentially harmful cells is clearly beneficial to multicellular organisms. Proper functioning of such a program demands that the removal of dying cells proceed without an inflammatory reaction. Phosphatidylserine (PS) is one of the ligands displayed by apoptotic cells that participates in their noninflammatory removal when recognized by neighboring phagocytes. PS ligation induces the release of transforming growth factor-beta (TGF-beta), an antiinflammatory cytokine that mediates the suppression of macrophage-mediated inflammation. In Hydra vulgaris, an organism that stands at the base of metazoan evolution, the selective advantage provided by apoptosis lies in the fact that Hydra can survive recycling apoptotic cells by phagocytosis. In unicellular organisms, it has been proposed that altruistic death benefits clonal populations of yeasts and trypanosomatids. Now we show that advantageous features of the apoptotic process can operate without death as the necessary outcome. Leishmania spp are able to evade the killing activity of phagocytes and establish themselves as obligate intracellular parasites. Amastigotes, responsible for disease propagation, similar to apoptotic cells, inhibit macrophage activity by exposing PS. Exposed PS participates in amastigote internalization. Recognition of this moiety by macrophages induces TGF-beta secretion and IL-10 synthesis, inhibits NO production, and increases susceptibility to intracellular leishmanial growth.

TSG-14 transgenic mice have improved survival to endotoxemia and to CLP-induced sepsis

Tumor necrosis factor-stimulated gene 14 (TSG-14)/PTX3 was identified originally as a TNF-alpha and IL-1beta-stimulated gene from normal, human foreskin fibroblasts and vascular endothelial cells, respectively. TSG-14 gene encodes a 42-kDa-secreted glycoprotein with a carboxy-terminal half that shares homology with the entire sequence of C-reactive protein (CRP) and serum amyloid P component (SAP), acute-phase proteins of the pentraxin family. Some experimental evidence suggests that TSG-14 plays a role in inflammation, yet its function and mechanism of action remain unclear. We have generated transgenic mice that overexpress the murine TSG-14 gene under the control of its own promoter. From eight transgenic founders, two lineages were derived and better characterized: Tg2 and Tg4, carrying two and four copies of the transgene, respectively. TSG-14 transgenic mice were found to be more resistant to the endotoxic shock induced by LPS and to the polymicrobial sepsis caused by cecal ligation and puncture (CLP). Moreover, macrophages derived from the transgenic mice produced higher amounts of nitric oxide in response to IFN-gamma, TNF-alpha, and LPS as compared with macrophages from wild-type animals, and the augmented response appears to be the consequence of a higher responsiveness of transgenic macrophages to IFN-gamma. The data shown here are the first in vivo evidence of the involvement of TSG-14 in the inflammatory process and suggest a role for TSG-14 in the defense against bacterial infections.

Mechanisms of allergen- and LPS-induced bone marrow eosinophil mobilization and eosinophil accumulation into the pleural cavity: a role for CD11b/CD18 complex

OBJECTIVE

The mechanisms involved in bone marrow eosinophil emigration and recruitment to inflammatory sites are not fully understood. The involvement of CD11b/CD18 in marrow eosinophil release induced by lipopolysaccharide (LPS) or allergen was investigated in mice.

METHODS

Eosinophil and neutrophil counts in the pleural cavity, blood and bone marrow were performed at different time intervals after the intrathoracic injection of LPS (250 ng/cavity) or ovalbumin (OVA, 12 microg/cavity; into actively sensitized mice) and compared to anti-CD11b/CD 18 (5C6, 1 mg/mouse) or anti-IL-5 (TRFK-5, 500 microg/kg) treated mice.

RESULTS

LPS induced local eosinophil influx, that peaked within 24 h and that was preceded by a decrease in marrow eosinophils at 4 h. Antigenic challenge induced a decrease in marrow eosinophils within 4 h, followed by a long lasting pleural eosinophil accumulation and a persistent increase in marrow eosinophil numbers. Pretreatment with anti-CD11b/CD18 abolished LPS-induced neutrophil and eosinophil accumulation in the pleural cavity at 4 and 24 h, respectively. This pretreatment failed to modify neutrophil emigration from bone marrow, but significantly inhibited marrow eosinophil release at 4 h post-LPS or OVA challenge. Anti-IL-5 pretreatment failed to inhibit LPS-induced pleural eosinophil accumulation and mobilization from bone marrow, but it abolished allergen-induced effects, indicating a role for IL-5 in marrow eosinophil mobilization induced by antigen, but not by LPS challenge.

CONCLUSIONS

Our results suggest that eosinophil migration induced by antigen or LPS into the pleural cavity is preceded by bone marrow eosinophil release through a mechanism that depends on CD11b/CD18.

Arachidonyl trifluoromethyl ketone induces lipid body formation in leukocytes

Leukocyte lipid bodies, abundant in cells associated with inflammation, can be induced to form in response to stimuli that include cis -unsaturated, but not saturated, fatty acids. Arachidonyl trifluoromethyl ketone (AACOCF(3)), a non-esterifiable arachidonate analog and an inhibitor of cytosolic phospholipase A(2)enzymes (PLA(2)), dose-dependently (0-20 microM) stimulated neutrophil lipid body formation, but this stimulation was not attributable to PLA(2)inhibition. Palmitoyl trifluoromethyl ketone, also a PLA(2)inhibitor, failed to stimulate lipid body formation, like palmitic acid itself, and did not inhibit stimulated lipid body formation. Moreover, aspirin, indomethacin and ibuprofen, which inhibit cis -unsaturated fatty acid-induced lipid body formation, inhibited AACOCF(3)-induced lipid body formation. Lipid body induction with AACOCF(3)reflected its structural basis as a cis -unsaturated fatty acid analog. These results indicate that cytosolic PLA(2)enzymes are not active in lipid body induction and cis -fatty acid stimulation of lipid body formation does not require esterification of cis -fatty acids into glycerolipids.

A role for adrenoceptors in the regulation of pleural neutrophilia induced by LPS

The role of catecholamines in regulating pleural neutrophilia evoked by intrathoracic (i.t.) injection of lipopolysaccharide (LPS) was investigated in Wistar rats by means of surgical adrenalectomy, depletion of catecholamine stores or adrenoceptor blockade. Treatment of animals with a single dose of LPS evoked a dramatic increase in the number of pleural neutrophils concomitant with an increase in the number of these cells in blood at 4 h. Although blood neutrophilia was drastically reduced when catecholamine stores were depleted with intraperitoneal (i.p.) injection of reserpine, pleural neutrophilia was not modified. However, the i.t. injection of reserpine reduced the increase in pleural neutrophils after LPS stimulation. Adrenalectomy failed to inhibit the increase in neutrophil counts in the blood or pleural cavity after LPS challenge. Pretreatment with intravenous (i.v.) injection of prazosin, an alpha(1)/alpha(2B) antagonist, reduced LPS-induced blood but not pleural neutrophilia. On the other hand, although pleural neutrophilia was not affected by systemic pretreatment with the alpha(2)-adrenoceptor antagonist, yohimbine, the local treatment (i. t. injection) with this antagonist markedly reduced the increase in pleural neutrophil counts observed after stimulation by LPS. In contrast, pleural neutrophilia induced by i.t injection of formyl-methionyl-leucyl-phenylalanine (fMLP) was not modified by local treatment with yohimbine. Taken together, our results suggest that catecholamines, through activation of alpha(1) and alpha(2)-adrenoceptors, play a role in the regulation of blood and pleural neutrophilia observed during the inflammatory response evoked by LPS in the pleural cavity.

Yangambin, a lignan obtained from Ocotea duckei, differentiates putative PAF receptor subtypes in the gastrointestinal tract of rats

We investigated the presence of PAF receptor subtypes in the tissues of the gastrointestinal tract, airways, blood vessels and in murine macrophages. For this purpose we have used a competitive PAF receptor antagonist, yangambin (YAN), extracted from the Brazilian plant "louro de cheiro" (Ocotea duckei Vattimo). Rat duodenum, jejunum, ileum, colon, stomach fundus, trachea and bronchia were removed and 1.5-2 cm muscle segments from those regions were mounted in a 10 ml organ bath with aerated physiological solution at 37 degrees C. PAF evoked a contraction of the rat jejunum, ileum, colon and stomach fundus. The contraction was slow and resistant to wash and was followed by desensitization to further doses of PAF. Contractions induced by PAF (10(-6) M) were inhibited by YAN (10(-7) to M-2 x 10(-5) M) and WEB 2086 (10(-6) m to M-5 M) in rat jejunum, ileum and colon but not in the stomach fundus. In the rat stomach fundus only WEB 2086 (5 x 10(-6) M) was able to block PAF-induced contraction. The contractions induced by acetylcholine, histamine, 5-hydroxytryptamine and vasopressin were not inhibited by prior administration of YAN. Yangambin also significantly inhibited PAF-induced vascular permeability in rat duodenum, jejunum, ileum, colon, and mesentery. Yangambin significantly inhibited PAF-induced lipid body formation in mice peritoneal macrophages. We suggest that YAN is a selective PAF antagonist which is able to discriminate putative PAF receptors subtypes present in the stomach fundus.

Cutting edge: lipoxin (LX) A4 and aspirin-triggered 15-epi-LXA4 block allergen-induced eosinophil trafficking

Tissue eosinophilia prevention represents one of the primary targets to new anti-allergic therapies. As lipoxin A4 (LXA4) and aspirin-triggered 15-epi-LXA4 (ATL) are emerging as endogenous "stop signals" produced in distinct pathologies including some eosinophil-related pulmonary disorders, we evaluated the impact of in situ LXA4/ATL metabolically stable analogues on allergen-induced eosinophilic pleurisy in sensitized rats. LXA4/ATL analogues dramatically blocked allergic pleural eosinophil influx, while concurrently increasing circulating eosinophilia, inhibiting the earlier edema and neutrophilia associated with allergic reaction. The mechanisms underlying this LXA4/ATL-driven allergic eosinophilia blockade was independent of mast cell degranulation and involved LXA4/ATL inhibition of both IL-5 and eotaxin generation, as well as platelet activating factor action. These findings reveal LXA4/ATL as a novel class of endogenous anti-allergic mediators, capable of preventing local eosinophilia.

Uptake of apoptotic cells drives the growth of a pathogenic trypanosome in macrophages

After apoptosis, phagocytes prevent inflammation and tissue damage by the uptake and removal of dead cells. In addition, apoptotic cells evoke an anti-inflammatory response through macrophages. We have previously shown that there is intense lymphocyte apoptosis in an experimental model of Chagas' disease, a debilitating cardiac illness caused by the protozoan Trypanosoma cruzi. Here we show that the interaction of apoptotic, but not necrotic T lymphocytes with macrophages infected with T. cruzi fuels parasite growth in a manner dependent on prostaglandins, transforming growth factor-beta (TGF-beta) and polyamine biosynthesis. We show that the vitronectin receptor is critical, in both apoptotic-cell cytoadherence and the induction of prostaglandin E2/TGF-beta release and ornithine decarboxylase activity in macrophages. A single injection of apoptotic cells in infected mice increases parasitaemia, whereas treatment with cyclooxygenase inhibitors almost completely ablates it in vivo. These results suggest that continual lymphocyte apoptosis and phagocytosis of apoptotic cells by macrophages have a role in parasite persistence in the host, and that cyclooxygenase inhibitors have potential therapeutic application in the control of parasite replication and spread in Chagas' disease.

In vitro and in vivo responses of murine granulocytes to human complement-derived, haemolytically inactive C5b67 (iC5b67)

Haemolytically inactive C5b67 (iC5b67), which was made from purified human components and decayed to a haemolytically inactive form, was evaluated as an agonist for murine leucocytes both in vitro and in vivo. In an in vitro assay, iC5b67 stimulated chemotaxis for both neutrophils purified from mouse bone marrow and splenic eosinophils of IL-5 transgenic mice. The stimulation was dose-dependent, with high dose inhibition. As with human neutrophils, iC5b67 also failed to up-regulate CR3 (CD11b/CD18) expression and to stimulate superoxide generation in murine bone marrow neutrophils, in vitro. In vivo, iC5b67 elicited an inflammatory response in a mouse model of pleuritis. A marked infiltration of neutrophils, which peaked at 4 h, was followed by an infiltration of eosinophils and mononuclear leucocytes. This inflammatory response was dose- and time-dependent. However, the protein concentration in the pleural wash fluid did not increase, indicating that iC5b67 did not induce a capillary leak. Although the infiltration of neutrophils could not be reproduced by pure C7 or human serum albumin (HSA), C5b6 did induce an influx of neutrophils. We were able to document the existence of C7, both antigenically and functionally, in pleural washes of normal mice, making it likely that the activity of C5b6 resulted from the in situ formation of C5b67 and iC5b67. The mouse model of pleuritis promises to be a useful in vivo system in which to evaluate the pro- and anti-inflammatory effects of iC5b67 that have been noted in vitro.

Bradykinin down-regulates LPS-induced eosinophil accumulation in the pleural cavity of mice through type 2-kinin receptor activation: a role for prostaglandins

1. The role of both exogenously administered and endogenously generated bradykinin (BK) on LPS-induced eosinophil accumulation in the mice pleural cavity was investigated by means of treatment with BK selective receptor agonists/antagonists and captopril. 2. Intrathoracic (i.t.) injection of LPS (250 ng cavity(-1)) induced eosinophil influx at 24 h as previously described (Bozza et al., 1993). Pretreatment with the B1 receptor antagonist des-Arg9-[leu-8]BK (0.025 and 0.25 nmol cavity(-1)) showed no effect on this phenomenon, whereas pretreatment with the B2 receptor antagonists, NPC 17731 (0.025 and 0.25 nmol cavity(-1)) or HOE 140 (2.5 nmol cavity(-1)), increased LPS-induced eosinophil influx. Accordingly, pretreatment with captopril at 10 mg kg(-1) i.p., inhibited eosinophil infiltration induced by LPS in the pleural cavity, suggesting that endogenous BK is down-regulating LPS-induced eosinophil accumulation. 3. BK administered at 15 and 25 nmol cavity(-1), i.t. or i.p. also inhibited LPS-induced eosinophil accumulation. BK alone had no effect on the basal number of leucocytes in the pleural or peritoneal cavity in doses up to 25 nmol cavity(-1). Nevertheless, when injected at doses of 50 and 100 nmol cavity(-1) BK induced leucocyte influx characterized by neutrophil and eosinophil accumulation at 24 h. 4. Similarly to what was observed with BK, a specific B2 receptor agonist, Tyr8BK, administered at 0.25 nmol cavity(-1) i.p., significantly inhibited the eosinophil influx induced by LPS. 5. The mechanism by which B2 receptor agonists inhibit LPS-induced eosinophil accumulation was investigated by pretreating the animals with indomethacin or a selective cyclooxygenase-2 inhibitor, NS-398. Pretreatment with either indomethacin or NS-398 had no effect on eosinophil influx induced by LPS alone, but those drugs were able to restore the LPS-induced eosinophil influx in Tyr8BK (0.25 nmol cavity(-1)) injected mice. 6. In conclusion, endogenously generated bradykinin seems to modulate, through activation of B2 receptors, eosinphil accumulation induced by LPS via a mechanism dependent on prostanoid synthesis.

Cytoplasmic lipid bodies in eosinophils: central roles in eicosanoid generation

BACKGROUND

Lipid bodies are lipid-rich cytoplasmic inclusions which form in diverse cell types, including eosinophils. Lipid body numbers increase in vivo in leukocytes participating in inflammatory processes. Our interest in lipid bodies relates to the roles that these structures play in arachidonate metabolism by eosinophils and other leukocytes involved in inflammation.

METHODS

Specific agonists, platelet-activating factor (PAF), two cis-unsaturated fatty acids (arachidonic and oleic acids) and a diglyceride (1-oleyl-2-acetyl-glycerol (OAG)), were used to stimulate lipid body formation in human eosinophils. Lipid bodies were enumerated and eosinophils were stimulated with submaximal calcium ionophore to generate leukotriene C4 (LTC4), which was quantitated by immunoassay.

RESULTS

Lipid body formation was rapidly inducible in eosinophils by specific intracellular signaling pathways. PAF, the two cis-unsaturated fatty acids and OAG each stimulated lipid body formation in eosinophils. Increased numbers of lipid bodies correlated quantitatively with the 'priming' response of eosinophils to form enhanced amounts of the 5-lipoxygenase-derived eicosanoid, LTC4.

CONCLUSION

Lipid bodies in eosinophils function as intracellular domains that are both depots of esterified arachidonate and sites at which regulated enymatic events relevant to arachidonate metabolism can occur. In conjunction with our findings that key eicosanoid-forming enzzymes, including cyclooxygenase, 5- and 15-lipoxygenase and LTC4 synthase, are localized at lipid bodies in eosinophils, the finding that induction of lipid body formation correlated quantitatively with enhanced LTC4 production indicate that lipid bodies are structurally distinct, inducible, non-nuclear sites for enhanced synthesis of paracrine eicosanoid mediators of inflammation.

The PACAP-type I receptor agonist maxadilan from sand fly saliva protects mice against lethal endotoxemia by a mechanism partially dependent on IL-10

Sand fly saliva contains maxadilan, a peptide that causes vasodilation and modifies the secretion of pro-inflammatory cytokines by macrophages. We show that 1 to 10 microg maxadilan protected BALB/c mice against a lethal dose of LPS. Maxadilan reduced serum levels of TNF-alpha by approximately tenfold, while it caused a threefold increase in IL-6 and IL-10. The protective effect of maxadilan is partially dependent on its ability to induce IL-10 production since maxadilan did not prevent death from endotoxic shock in IL-10(-/-) mice. Finally, maxadilan is a selective agonist of the pituitary adenylate cyclase-activating peptide (PACAP) type I receptor, and we found that the natural ligand of this receptor (PACAP 38) also protected mice against lethal endotoxemia. These results indicate that activation of the PACAP type I receptor may contribute to the control of systemic inflammation by a mechanism that is partially dependent on IL-10.

Pathways for eosinophil lipid body induction: differing signal transduction in cells from normal and hypereosinophilic subjects

Although lipid bodies, inducible cytoplasmic inclusions active in arachidonic acid metabolism, are abundant in activated leukocytes, including eosinophils, mechanisms for eosinophil lipid body formation are not certain. Eosinophils from hypereosinophilic syndrome (HES) donors contained about twice (approximately 18/cell) as many lipid bodies as eosinophils froin normal donors (approximately 10/cell). By immunocytochemistry both 5- and 15-lipoxygenases were localized at lipid bodies in HES eosinophils. Platelet-activating factor (PAF) induced rapid, receptor-mediated increases in lipid bodies in normal and HES eosinophils. Protein kinase C (PKC) inhibitors, chelerythrine and calphostin C, inhibited PAF-induced lipid body formation partially in normal and HES eosinophils. In HES, but not normal, eosinophils, PAF-induced lipid body formation was completely blocked by two tyrosine kinase inhibitors, herbimycin A and genistein, which were not acting on 5-lipoxygenase because they also blocked 5-HETE-induced lipid body formation in HES, and not normal, eosinophils. After 24 h culture with eosinophil growth factor cytokines [interleukin (IL)-3, IL-5, and granulocyte-macrophage colony-stimulating factor (GM-CSF) or GM-CSF alone but not IL-5 or IL-3 alone], normal eosinophils were induced to exhibit an HES-like phenotype, including increased lipid body numbers and tyrosine kinase-dependent signaling for PAF-induced lipid body formation. Thus, signal transduction mechanisms involved in PAF-induced lipid body formation in eosinophils can be differentially recruited. Tyrosine kinase-dependent signaling is not involved in normal eosinophils, but is active in HES eosinophils and in normal eosinophils cultured with GM-CSF. PKC- and tyrosine kinase-dependent pathways are involved in the formation of eosinophil lipid bodies, which may facilitate enhanced synthesis of lipoxygenase-derived eicosanoids.

Mechanisms of formation and function of eosinophil lipid bodies: inducible intracellular sites involved in arachidonic acid metabolism

Lipid bodies, inducible lipid-rich cytoplasmic inclusions, are characteristically abundant in cells associated with inflammation, including eosinophils. Here we reviewed the formation and function of lipid bodies in human eosinophils. We now have evidence that the formation of lipid bodies is not attributable to adverse mechanisms, but is centrally mediated by specific signal transduction pathways. Arachidonic acid and other cis fatty acids by an NSAID-inhibitable process, diglycerides, and PAF by a 5-lipoxygenase dependent pathway are potent stimulators of lipid body induction. Lipid body formation develops rapidly by processes that involve PKC, PLC, and de novo mRNA and protein synthesis. These structures clearly serve as repositories of arachidonyl-phospholipids and are more than inert depots. Specific enzymes, including cytosolic phospholipase A2, MAP kinases, lipoxygenases and cyclooxygenases, associate with lipid bodies. Lipid bodies appear to be dynamic, organelle-like structures involved in intracellular pathways of lipid mobilization and metabolism. Indeed, increases in lipid body numbers correlated with enhanced production of both lipoxygenase- and cyclooxygenase-derived eicosanoids. We hypothesize that lipid bodies are distinct inducible sites for generating eicosanoids as paracrine mediators with varied activities in inflammation. The capacity of lipid body formation to be specifically and rapidly induced in leukocytes enhances eicosanoid mediator formation, and conversely pharmacologic inhibition of lipid body induction represents a potential novel and specific target for anti-inflammatory therapy.

A role for lymphocytes and cytokines on the eosinophil migration induced by LPS

In the present work we review the existing evidence for a LPS-induced cytokine-mediated eosinophil accumulation in a model of acute inflammation. Intrathoracic administration of LPS into rodents (mice, rats or guinea pigs) induces a significant increase in the number of eosinophils recovered from the pleural fluid 24 hr later. This phenomenon is preceded by a neutrophil influx and accompanied by lymphocyte and monocyte accumulation. The eosinophil accumulation induced by LPs is not affected by inhibitors of cyclo or lipoxygenase nor by PAF antagonists but can be blocked by dexamethasone or the protein synthesis inhibitor cycloheximide. Transfer of cell-free pleural wash from LPS injected rats (LPS-PW) to naive recipient animals induces a selective eosinophil accumulation within 24 hr. The eosinophilotactic activity present on the LPS-PW has a molecular weight ranging between 10 and 50 kDa and its effect is abolished by trypsin digestion of the pleural wash indicating the proteic nature of this activity. The production of the eosinophilotactic activity depends on the interaction between macrophages and T-lymphocytes and its effect can not be blocked by anti-IL-5 monoclonal antibodies. Accumulated evidence suggest that the eosinophil accumulation induced by LPS is a consequence of a eosinophilotactic cytokine produced through macrophage and T-cell interactions in the site of a LPS-induced inflammatory reaction.

Regulation of allergic inflammation and eosinophil recruitment in mice lacking the transcription factor NFAT1: role of interleukin-4 (IL-4) and IL-5

Transcription factors of the NFAT (nuclear factor of activated T cells) family regulate the expression of many genes encoding immunoregulatory cytokines and cell surface proteins during the immune response. The NFAT protein NFAT1 (NFATp) is expressed and functional in T cells, B cells, mast cells, and natural killer cells. Here we report a detailed analysis of the enhanced eosinophil responses of NFAT1-deficient mice, observed in an in vivo model of allergic inflammation. In addition to the pleural eosinophilia described previously, NFAT1-/- mice that have been sensitized with antigen display a significant increase, relative to wild-type mice, in the numbers of eosinophils in bone marrow and peripheral blood. After restimulation with antigen in vitro, antigen-responsive T cells from the draining lymph nodes of NFAT1-/- mice show increased expression of mRNA encoding the Th2 cytokines interleukin-4 (IL-4), IL-5, and IL-13. Consistent with this finding, there is a pronounced increase in the levels of IL-5 and IL-13 in the pleural cavities of sensitized NFAT1-/- mice after allergen challenge in vivo. Furthermore, development of eosinophilia depends on overexpression of IL-4 and IL-5, because it is strongly inhibited by administration of neutralizing antibodies to either of these cytokines. These results indicate that NFAT1-deficient mice are prone to develop a classically allergic phenotype characterized by eosinophilia and increased production of Th2 cytokines. Thus, the presence of NFAT1 might inhibit the allergic response, perhaps by interfering with the development of Th2 immune responses, and the lack or dysfunction of NFAT1 could potentially underlie certain cases of atopic disease.

Co-compartmentalization of MAP kinases and cytosolic phospholipase A2 at cytoplasmic arachidonate-rich lipid bodies

Lipid bodies are inducible lipid domains abundantly present in leukocytes engaged in inflammation. They are rich in esterified arachidonate and are also potential sites for eicosanoid-forming enzyme localization. It is therefore of interest to know whether arachidonate-releasing cytosolic phospholipase A2 (cPLA2) localizes at lipid bodies. Here, we present evidence that cPLA2 and its activating protein kinases, mitogen-activated protein (MAP) kinases, co-localize at lipid bodies. U937 cells express high levels of cPLA2 and contain numerous cytoplasmic lipid bodies. Using double-labeling immunocytochemistry we demonstrated punctate cytoplasmic localizations of both cPLA2 and MAP kinases in U937 cells that were perfectly concordant with fluorescent fatty-acid-labeled lipid bodies. The co-localization of cPLA2 and MAP kinases at lipid bodies was confirmed by subcellular fractionation and immunoblot. Lipid body fractions free of cytosol and other organelles contained significant amounts of [14C]arachidonate-labeled phosphatidylcholine and cPLA2 enzymatic activities. Immunoblotting with specific antibodies identified cPLA2 as well as MAP kinases, including ERK1, ERK2, p85, and p38, in lipid bodies. The co-compartmentalization within arachidonate-rich lipid bodies of cPLA2 and its potentially activating protein kinases suggests that lipid bodies may be structurally distinct intracellular sites active in extracellular ligand-induced arachidonate release and eicosanoid formation.

Eosinophil lipid bodies: specific, inducible intracellular sites for enhanced eicosanoid formation

The specific intracellular sites at which enzymes act to generate arachidonate-derived eicosanoid mediators of inflammation are uncertain. We evaluated the formation and function of cytoplasmic lipid bodies. Lipid body formation in eosinophils was a rapidly (<1 h) inducible response which was platelet-activating factor (PAF) receptor-mediated, involved signaling through protein kinase C, and required new protein synthesis. In intact and enucleated eosinophils, the PAF-induced increases in lipid body numbers correlated with enhanced production of both lipoxygenase- and cyclooxygenase-derived eicosanoids. All principal eosinophil eicosanoid-forming enzymes, 5-lipoxygenase, leukotriene C4 synthase, and cyclooxygenase, were immunolocalized to native as well as newly induced lipid bodies in intact and enucleated eosinophils. Thus, lipid bodies are structurally distinct, inducible, nonnuclear sites for enhanced synthesis of paracrine eicosanoid mediators of inflammation.

The role of gammadelta T lymphocytes in lipopolysaccharide-induced eosinophil accumulation into the mouse pleural cavity

LPS induces an accumulation of eosinophils in the pleural cavity that requires resident macrophages and lymphocytes, but is independent of IL-5 production. In the present study we investigated the involvement of different T lymphocyte subsets on the modulation of LPS-induced eosinophil accumulation into the pleural cavity of mice. Within 4 h after LPS injection the number of neutrophils in the pleural cavity increased significantly. Mononuclear cell counts increased after 12 h, while a significant rise on eosinophil counts was observed only after 24 h. T lymphocytes counts were increased in the pleural cavity 24 and 48 h after LPS administration. This T lymphocyte accumulation was accounted for by an influx of the gammadelta+ subset, while CD4+ and CD8+ subsets did not accumulate in the pleural cavity after LPS stimulation. All those changes had resolved 96 h after LPS injection. Depletion of T lymphocytes by treatment with mAb anti-Thy 1.0 inhibited the eosinophil accumulation triggered by LPS. Aiming to clarify which T lymphocyte subset would be involved in the LPS-induced eosinophil accumulation, we depleted mice of various T lymphocyte subpopulations using specific Abs. Depletion of either CD4+ or CD8+ subsets failed to inhibit LPS-induced eosinophil migration. In contrast, when mice were treated with anti-gammadelta+ T lymphocyte mAb, a significant reduction of LPS-induced eosinophil accumulation was observed. Similarly, the administration of LPS in BALB/c-nu/nu mice induced the expected significant influx of eosinophils into the pleural cavity. Our results indicate that the gammadelta+ T lymphocytes are centrally involved in LPS-induced eosinophil accumulation in mice.