Platelet-activating factor receptor (PAFR) regulates neuronal maturation and synaptic transmission during postnatal retinal development

Introduction

Platelet-activating factor (PAF), PAF receptor (PAFR), and PAF- synthesis/degradation systems are involved in essential CNS processes such as neuroblast proliferation, differentiation, migration, and synaptic modulation. The retina is an important central nervous system (CNS) tissue for visual information processing. During retinal development, the balance between Retinal Progenitor Cell (RPC) proliferation and differentiation is crucial for proper cell determination and retinogenesis. Despite its importance in retinal development, the effects of PAFR deletion on RPC dynamics are still unknown.

Methods

We compared PAFR knockout mice (PAFR-/-) retinal postnatal development proliferation and differentiation aspects with control animals. Electrophysiological responses were analyzed by electroretinography (ERG).

Results and discussion

In this study, we demonstrate that PAFR-/- mice increased proliferation during postnatal retinogenesis and altered the expression of specific differentiation markers. The retinas of postnatal PAFR-/- animals decreased neuronal differentiation and synaptic transmission markers, leading to differential responses to light stimuli measured by ERG. Our findings suggest that PAFR signaling plays a critical role in regulating postnatal RPC cell differentiation dynamics during retinal development, cell organization, and neuronal circuitry formation.

The role of captopril in leukotriene deficient type 1 diabetic mice

T1D can be associated with metabolic disorders and several impaired pathways, including insulin signaling, and development of insulin resistance through the renin-angiotensin system (RAS). The main precursor of RAS is angiotensinogen (Agt) and this system is often linked to autophagy dysregulation. Dysregulated autophagy has been described in T1D and linked to impairments in both glucose metabolism, and leukotrienes (LTs) production. Here, we have investigated the role of RAS and LTs in both muscle and liver from T1D mice, and its effects on insulin and autophagy pathways. We have chemically induced T1D in 129sve and 129sve 5LO-/- mice (lacking LTs) with streptozotocin (STZ). To further inhibit ACE activity, mice were treated with captopril (Cap). In muscle of T1D mice, treatment with Cap increased the expression of RAS (angiotensinogen and angiotensin II receptor), insulin signaling, and autophagy markers, regardless of the genotype. In the liver of T1D mice, the treatment with Cap increased the expression of RAS and insulin signaling markers, mostly when LTs were absent. 5LO-/- T1D mice showed increased insulin sensitivity, and decreased NEFA, after the Cap treatment. Cap treatment impacted both insulin signaling and autophagy pathways at the mRNA levels in muscle and liver, indicating the potential role of ACE inhibition on insulin sensitivity and autophagy in T1D.

Platelet activating factor in the eye: Physiological roles, diseases and future perspectives

Platelet Activating Factor (PAF) is a known phospholipid mediator of inflammation. Since its first description in 1972, it has emerged as a key regulator of vital cellular signaling functions, as proliferation, cell adhesion, and apoptosis. Evidence suggests that interactions between PAF and its receptor (PAFR) play a critical role in nervous system tissues, including the retina. The retina is a very important constituent of the visual system, along with the cornea, sclera, choroid, iris, and ciliary body, that acts synergistically to provide vision and to maintain optical homeostasis. There is evidence that PAF may regulate a wide range of physiological functions in the visual system tissues, such as eye development, inflammation, epithelial wound healing, and synapsis. Due to their multiple functions, PAF and PAFR also have important pathological and clinical implications in ocular disorders such as Choroidal Neovascularization (CNV), Age Macular Degeneration, (AMD), Diabetic Retinopathy (DR), transplant responses, and pharmacological interactions. Studies with PAFR antagonists have shown promising results such as inhibition of neovascularization and chloroquine-induced retinopathies, as well as reducing inflammation and retinal cell death. Due to the importance of PAFR signaling in the visual system and ophthalmology research, this review aims to provide a general overview of current and future perspectives about PAF in eye biology.

Increased leukotriene B4 plasma concentration in type 2 diabetes individuals with cardiovascular autonomic neuropathy

BACKGROUND AND AIM

A low-grade inflammation is associated with cardiac autonomic neuropathy (CAN) and increased concentration of leukotriene B4 (LTB4) was found in individuals with type 1 diabetes and definitive CAN. This cross-sectional study evaluated plasma concentration of LTB4 and of other inflammatory mediators, namely, tumor necrosis factor (TNF), interleukin (IL)1B, and IL10 in individuals with type 2 diabetes (T2D) and different degrees of CAN, and correlated these inflammatory mediators with the degree of glycemic control and with a surrogate marker of insulin resistance.

METHODS

TNF, IL1B, IL10 and LTB4 plasma concentrations were measured in 129 T2D subjects (62% women with [median] age of 63 years, disease duration of 8 years and HbA1c of 7.3%) with or without CAN. The Lipid accumulation product index was used as a surrogate marker of insulin resistance.

RESULTS

LTB4 concentration was significantly higher in those presenting incipient CAN (69.7 ± 16.6 pg mL^-1) and definitive CAN (71.5 ± 15.7 pg mL^-1) versus those without CAN (57.0 ± 13.9 pg mL^-1). The groups without CAN and with incipient CAN were pooled (group without definitive CAN) and compared to those with definitive CAN. LTB4 concentration was higher in the latter group, as well as TNF concentration, while IL10 concentration was lower in this group. After adjustment for confounding variables, only LTB4 concentration remained significantly different between the groups with and without definitive CAN. Plasma concentration of LTB4 did not correlate with the degree of glycemic control. After sorting the participants by sex, a borderline weak correlation was found between LTB4 and the Lipid accumulation product index in women.

CONCLUSION

In the T2D setting, circulating LTB4 concentration seems to be associated with cardiovascular dysautonomia.

Leukotriene B4 modulation of murine dendritic cells affects adaptive immunity

Dendritic cells (DCs) link innate and adaptive immunity. The microenvironment generated during the innate immunity affects DCs and the type of adaptive immunity generated. Lipid mediators are released early in inflammation and could modify the functional state of DCs. Leukotriene B₄ (LTB₄) has a wide range of effects on macrophages and in the present study we investigated if it also affects DCs. Murine bone marrow-derived DCs were employed and it was found that stimulation of DCs with LTB4 (10 nM) increased the gene expression of the high affinity receptor BLT-1 but not of BLT-2. It also increased the co-stimulatory molecule CD86 expression but did not affect CD80 and CD40. LTB₄-stimulated DCs acquired the capacity to present antigen to T lymphocytes, evidenced by antigen-specific proliferation of CD4⁺ lymphocytes in co-cultures of ovalbumin-loaded DCs with DO11.10 splenocytes. LTB₄-stimulated DCs induced Treg proliferation and increased Th2 cytokine IL-13 in the co-cultures. Expression of transcription factor genes, Gata3 and Foxp3 (Th2 and Treg, respectively) were also found increased. However, the expression of Th1 transcription factor (Tbet) and Th17 (RorγT) were not affected. These results indicate that LTB₄ affects DCs and modulates the type of adaptive immune response.

Platelet activating factor receptor antagonists improve the efficacy of experimental chemo- and radiotherapy

Platelet activating factor is a lipid mediator of inflammation, and in recent decades, it has emerged as an important factor in tumor outcomes. Platelet activating factor acts by specific binding to its receptor, which is present in both tumor cells and cells that infiltrate tumors. Pro-tumorigenic effects of platelet activating factor receptor in tumors includes promotion of tumor cell proliferation, production of survival signals, migration of vascular cells and formation of new vessels and stimulation of dendritic cells and macrophages suppressor phenotype. In experimental models, blocking of platelet activating factor receptor reduced tumor growth and increased animal survival. During chemotherapy and radiotherapy, tumor cells that survive treatment undergo accelerated proliferation, a phenomenon known as tumor cell repopulation. Work from our group and others showed that these treatments induce overproduction of platelet activating factor-like molecules and increase expression of its receptor in tumor cells. In this scenario, antagonists of platelet activating factor markedly reduced tumor repopulation. Here, we note that combining chemo- and radiotherapy with platelet activating factor antagonists could be a promising strategy for cancer treatment.

Nuclear PTEN enhances the maturation of a microRNA regulon to limit MyD88-dependent susceptibility to sepsis

Sepsis-induced organ damage is caused by systemic inflammatory response syndrome (SIRS), which results in substantial comorbidities. Therefore, it is of medical importance to identify molecular brakes that can be exploited to dampen inflammation and prevent the development of SIRS. We investigated the role of phosphatase and tensin homolog (PTEN) in suppressing SIRS, increasing microbial clearance, and preventing lung damage. Septic patients and mice with sepsis exhibited increased PTEN expression in leukocytes. Myeloid-specific Pten deletion in an animal model of sepsis increased bacterial loads and cytokine production, which depended on enhanced myeloid differentiation primary response gene 88 (MyD88) abundance and resulted in mortality. PTEN-mediated induction of the microRNAs (miRNAs) miR125b and miR203b reduced the abundance of MyD88. Loss- and gain-of-function assays demonstrated that PTEN induced miRNA production by associating with and facilitating the nuclear localization of Drosha-Dgcr8, part of the miRNA-processing complex. Reconstitution of PTEN-deficient mouse embryonic fibroblasts with a mutant form of PTEN that does not localize to the nucleus resulted in retention of Drosha-Dgcr8 in the cytoplasm and impaired production of mature miRNAs. Thus, we identified a regulatory pathway involving nuclear PTEN-mediated miRNA generation that limits the production of MyD88 and thereby limits sepsis-associated mortality.

Platelet-Activating Factor Receptor Ligands Protect Tumor Cells from Radiation-Induced Cell Death

Irradiation generates oxidized phospholipids that activate platelet-activating factor receptor (PAFR) associated with pro-tumorigenic effects. Here, we investigated the involvement of PAFR in tumor cell survival after irradiation. Cervical cancer samples presented higher levels of PAF-receptor gene (PTAFR) when compared with normal cervical tissue. In cervical cancer patients submitted to radiotherapy (RT), the expression of PTAFR was significantly increased. Cervical cancer-derived cell lines (C33, SiHa, and HeLa) and squamous carcinoma cell lines (SCC90 and SCC78) express higher levels of PAFR mRNA and protein than immortalized keratinocytes. Gamma radiation increased PAFR expression and induced PAFR ligands and prostaglandin E2 (PGE2) in these tumor cells. The blocking of PAFR with the antagonist CV3938 before irradiation inhibited PGE2 and increased tumor cells death. Similarly, human carcinoma cells transfected with PAFR (KBP) were more resistant to radiation compared to those lacking the receptor (KBM). PGE2 production by irradiated KBP cells was also inhibited by CV3988. These results show that irradiation of carcinoma cells generates PAFR ligands that protect tumor cells from death and suggests that the combination of RT with a PAFR antagonist could be a promising strategy for cancer treatment.

Imbalance between HDAC and HAT activities drives aberrant STAT1/MyD88 expression in macrophages from type 1 diabetic mice

AIMS

To investigate the hypothesis that alteration in histone acetylation/deacetylation triggers aberrant STAT1/MyD88 expression in macrophages from diabetics. Increased STAT1/MyD88 expression is correlated with sterile inflammation in type 1 diabetic (T1D) mice.

METHODS

To induce diabetes, we injected low-doses of streptozotocin in C57BL/6 mice. Peritoneal or bone marrow-differentiated macrophages were cultured in 5mM (low) or 25mM (high glucose). ChIP analysis of macrophages from nondiabetic or diabetic mice was performed to determine acetylation of lysine 9 in histone H3 in MyD88 and STAT1 promoter regions. Macrophages from diabetic mice were treated with the histone acetyltransferase inhibitor anacardic acid (AA), followed by determination of mRNA expression by qPCR.

RESULTS

Increased STAT1 and MyD88 expression in macrophages from diabetic but not naive mice cultured in low glucose persisted for up to 6days. Macrophages from diabetic mice exhibited increased activity of histone acetyltransferases (HAT) and decreased histone deacetylases (HDAC) activity. We detected increased H3K9Ac binding to Stat1/Myd88 promoters in macrophages from T1D mice and AA in vitro treatment reduced STAT1 and MyD88 mRNA expression.

CONCLUSIONS/INTERPRETATION

These results indicate that histone acetylation drives elevated Stat1/Myd88 expression in macrophages from diabetic mice, and this mechanism may be involved in sterile inflammation and diabetes comorbidities.

Platelet-activating factor (PAF) receptor as a promising target for cancer cell repopulation after radiotherapy

A major drawback of radiotherapy is the accelerated growth of the surviving tumor cells. Radiotherapy generates a variety of lipids that bind to the receptor for platelet-activating factor, expressed by cells in the tumor microenvironment. In the present study, using the TC-1 tumor cell line, we found that irradiation induced a twofold increase in receptor expression and generated agonists of receptor. Irradiated cells induced a 20-fold increase in live TC-1 proliferation in vitro. Furthermore, subcutaneous co-injection of irradiated TC-1 cells with TC-1 expressing luciferase (TC-1 fluc⁺) markedly increased TC-1 fluc⁺ proliferation in a receptor-dependent way. Moreover we used a human carcinoma cell line not expressing the PAF receptor (KBM) and the same cell transfected with the receptor gene (KBP). Following co-injection of live KBP cells with irradiated KBM in RAG mice, the tumor growth was significantly increased compared with tumor formed following co-injection of live KBM with irradiated KBM. This tumor cell repopulation correlated with increased infiltration of tumor-promoting macrophages (CD206+). We propose that receptor represents a possible target for improving the efficacy of radiotherapy through inhibition of tumor repopulation.

Gamma-Terpinene Modulation of LPS-Stimulated Macrophages is Dependent on the PGE2/IL-10 Axis

Gamma-terpinene is a monoterpene present in the essential oils of several plants, including those from the Eucalyptus genus. This molecule was recently described as anti-inflammatory and microbiocidal, but little is known about the mechanisms behind its effects. The aim of the present study was to investigate the effect of gamma-terpinene on the lipopolysaccharide-induced production of cytokines by murine peritoneal macrophages. Gamma-terpinene treatment was found to reduce the production of proinflammatory cytokines, such as interleukin-1β and interleukin-6, and enhance that of the anti-inflammatory cytokine interleukin-10. This was accompanied by increased levels of the enzyme cycloxygenase-2 and its product, the lipid mediator prostaglandin E₂. Inhibition of cycloxygenase-2 with nimesulide abolished the potentiating effect of gamma-terpinene on interleukin-10 production. Moreover, nimesulide treatment also abrogated the inhibitory effect of gamma-terpinene on interleukin-1β and interleukin-6. Furthermore, in macrophages from mice deficient in the interleukin-10 gene, gamma-terpinene failed to inhibit interleukin-1β and interleukin-6 production. These results suggest that this monoterpene promotes the prostaglandin E₂/interleukin-10 axis, which inhibits the production of these proinflammatory cytokines.

Leukotriene B4-mediated sterile inflammation promotes susceptibility to sepsis in a mouse model of type 1 diabetes

Type 1 diabetes mellitus (T1DM) is associated with chronic systemic inflammation and enhanced susceptibility to systemic bacterial infection (sepsis). We hypothesized that low insulin concentrations in T1DM trigger the enzyme 5-lipoxygenase (5-LO) to produce the lipid mediator leukotriene B4 (LTB4), which triggers systemic inflammation that may increase susceptibility to polymicrobial sepsis. Consistent with chronic inflammation, peritoneal macrophages from two mouse models of T1DM had greater abundance of the adaptor MyD88 (myeloid differentiation factor 88) and its direct transcriptional effector STAT-1 (signal transducer and activator of transcription 1) than macrophages from nondiabetic mice. Expression of Alox5, which encodes 5-LO, and the concentration of the proinflammatory cytokine interleukin-1β (IL-1β) were also increased in peritoneal macrophages and serum from T1DM mice. Insulin treatment reduced LTB4 concentrations in the circulation and Myd88 and Stat1 expression in the macrophages from T1DM mice. T1DM mice treated with a 5-LO inhibitor had reduced Myd88 mRNA in macrophages and increased abundance of IL-1 receptor antagonist and reduced production of IL-β in the circulation. T1DM mice lacking 5-LO or the receptor for LTB4 also produced less proinflammatory cytokines. Compared to wild-type or untreated diabetic mice, T1DM mice lacking the receptor for LTB4 or treated with a 5-LO inhibitor survived polymicrobial sepsis, had reduced production of proinflammatory cytokines, and had decreased bacterial counts. These results uncover a role for LTB4 in promoting sterile inflammation in diabetes and the enhanced susceptibility to sepsis in T1DM.

Sepsis-induced lung inflammation is modulated by insulin

BACKGROUND

We have previously shown that diabetic rats are more susceptible to sepsis, but that the Acute lung injury (ALI) secondary to sepsis is less intense than in non-diabetics. In the present study, we further investigated the ALI-secondary to sepsis in diabetic rats and the effect of insulin treatment.

METHODS

Diabetes was induced in male Wistar rats by alloxan and sepsis by cecal ligation and puncture surgery (CLP). Some diabetic rats were given neutral protamine Hagedorn (NPH) insulin (4 IU, s.c.) 2 h before CLP. Six h later, the lungs were examined for edema, cell infiltration and prostaglandin-E2 (PGE2) levels in the bronchoalveolar lavage (BAL).

RESULTS

The results confirmed that leukocyte infiltration and edema were milder in diabetic rats with sepsis. After insulin treatment, the lung inflammation in diabetics increased to levels comparable to the non-diabetics. The BAL concentration of PGE2 was also lower in diabetics with sepsis, and increased after insulin treatment. Sepsis was followed by early fibroblast activation in the lung parenchyma, evaluated by increased transforming growth factor (TGF)-β and smooth muscle actin (α-SMA) expression, as well as an elevated number of cells with myofibroblasts morphology. These events were significantly lower in diabetic rats and increased after insulin treatment.

CONCLUSION

The results show that insulin modulates the early phase of inflammation and myofibroblast differentiation in diabetic rats.

Characterization of the inflammatory response during Ehrlich ascitic tumor development

INTRODUCTION

Ehrlich tumor is a mammary adenocarcinoma with aggressive behavior. Inoculated in mice peritoneal cavity, the Ehrlich tumor grows in ascitic form (EAT). Since inflammation modulates tumor progression we further investigated the inflammatory response during EAT growth.

METHODS

Balb/C mice were intraperitoneal inoculated with 5×10(5) Ehrlich cells and after every 2days, blood samples were collected for hemoglobin, hematocrit, platelets and leukocytes counts. The ascitic fluid was collected for protein concentration and cell count. Phenotype analysis of the peritoneal cells was made by FACS, prostaglandin E2 (PGE2) and cytokines by ELISA, nitric oxide (NO) by nitrate conversion protocol, and cyclooxygenase-1 (COX1), COX2 and inducible nitric oxide synthase (iNOS) by immunoblotting.

RESULTS

Following EAT inoculation into the peritoneal cavity there was a rapid increase in ascitis volume and protein concentration. The cell number in ascitis remained stable until day 8 (lag phase) followed by a sharp increase. As tumor progressed, blood leukocytes increased and erythrocyte decreased. Phenotypic analysis showed that during the lag phase the percentage of F4/80(+) cells remained similar to control levels and around 7% of this population was also positive for the GR1 marker. These double-positive cells (probably inflammatory monocytes) markedly increased at day 6. The percentage of F4/80-GR1(+)cells (probably neutrophils) was low and did not significantly vary during tumor progression. CD4(+) and CD8(+) cells were not detected in the time points analyzed. iNOS and COX1 expression increased after day 2 reaching peak levels on day 10. COX2 enzyme expression did not change significantly over time. Sustained increase in PGE2 and NO levels was observed. IL-10 and MCP-1 peaked at day 14 and IL-1β increased progressively till day 10. IFN-γ levels were low till day 10, increasing progressively after that.

DISCUSSION

These data extended the characterization of the inflammatory response during Ehrlich ascitis tumor growth, further validating it as a useful model for antitumor drugs screening.

Leukotriene B4 dictates sterile inflammation in type 1 diabetes (INM7P.424)

Type 1 diabetes (T1D) is characterized by chronic systemic inflammation that could be involved in the enhanced susceptibility to sepsis. The IL-1b/IL-1bR axis drives inflammation in a MyD88-dependent manner, but the molecular mechanisms involved in IL-1b actions in macrophages during T1D are unknown. We hypothesized that leukotriene (LT) B4 promotes IL-1b responsiveness in T1D by enhancing MyD88 expression. Peritoneal macrophages (PMs) from T1D mice expressed higher levels of MyD88 and its transcription factor STAT-1 than PMs from nondiabetic mice. 5-LO expression, LTB4 synthesis and IL-1b levels were also increased in both PM and serum from T1D mice. In vitro and in vivo insulin treatment restored LTB4 and STAT-1/MyD88 levels. Genetic and pharmacologic inhibition of the LTB4/BLT1 axis abolished MyD88 and STAT-1 induction in diabetic mice. ChIP assay showed that AP-1/cJun drove basal STAT-1 levels in an LTB4-dependent manner in T1D. We speculated that high LTB4 levels contribute to enhanced susceptibility to sepsis in T1D. Compared to WT or untreated T1D mice, genetic and pharmacologic inhibition of 5-LO prolonged T1D mice survival after polymicrobial sepsis; associated with decreased blood bacteria and reduced production of proinflammatory cytokines. We conclude that LTB4, by increasing MyD88 and IL-1b levels in a c-Jun/STAT-1 dependent manner, is the driving force involved in inflammation associated with T1D that contributes to high mortality associated to sepsis T1D.

Lung remodeling in a mouse model of asthma involves a balance between TGF-β1 and BMP-7

A key event in chronic allergic asthma is the TGF-β-induced activation of fibroblasts into α-SMA-positive myofibroblasts which synthesize type-I collagen. In the present study we investigated the effect of the anti-fibrotic molecule BMP-7 in asthma. Balb/c mice were immunized i.p. with ovalbumin in alum and challenged every 2 days with ovalbumin aerosol (two or six challenges for acute and chronic protocols, respectively). The lung was evaluated for: α-SMA and type-I collagen by immunohistochemistry; BMP-7 and TGF- β1 gene expression by qRT-PCR; type-I collagen and Smads 2 and 3 by immunoblotting; mucus by PSA staining. Type-I collagen around bronchi, α-SMA, mucus secretion, TGF- β1 and BMP-7 gene expression were all increased in asthma. The TGF- β1/BMP-7 ratio was higher in the chronic group and correlated with higher levels of collagen. Fibroblasts isolated from asthmatic and healthy lungs produced type-I collagen upon stimulation with TGF- β1 via phosphorylation of Smad-2, Smad-3. Pre-treatment of the fibroblasts with BMP-7 reduced collagen production and Smads phosphorylation. Intranasal treatment of asthmatic mice with recombinant BMP-7 during the immunization protocol reduced lung inflammation and type I collagen deposition. These results suggest a protective role for BMP-7 in lung allergic inflammation, opposing the pro-fibrotic effects of TGF- β1.

Activation of platelet-activating factor receptor exacerbates renal inflammation and promotes fibrosis

Platelet-activating factor (PAF) is a lipid mediator with important pro-inflammatory effects, being synthesized by several cell types including kidney cells. Although there is evidence of its involvement in acute renal dysfunction, its role in progressive kidney injury is not completely known. In the present study, we investigated the role of PAF receptor (PAFR) in an experimental model of chronic renal disease. Wild-type (WT) and PAFR knockout (KO) mice underwent unilateral ureter obstruction (UUO), and at kill time, urine and kidney tissue was collected. PAFR KO animals compared with WT mice present: (a) less renal dysfunction, evaluated by urine protein/creatinine ratio; (b) less fibrosis evaluated by collagen deposition, type I collagen, Lysyl Oxidase-1 (LOX-1) and transforming growth factor β (TGF-β) gene expression, and higher expression of bone morphogenetic protein 7 (BMP-7) (3.3-fold lower TGF-β/BMP-7 ratio); (c) downregulation of extracellular matrix (ECM) and adhesion molecule-related machinery genes; and (d) lower levels of pro-inflammatory cytokines. These indicate that PAFR engagement by PAF or PAF-like molecules generated during UUO potentiates renal dysfunction and fibrosis and might promote epithelial-to-mesenchymal transition (EMT). Also, early blockade of PAFR after UUO leads to a protective effect, with less fibrosis deposition. In conclusion, PAFR signaling contributes to a pro-inflammatory environment in the model of obstructive nephropathy, favoring the fibrotic process, which lately will generate renal dysfunction and progressive organ failure.

Leukotriene B4 enhances the generation of proinflammatory microRNAs to promote MyD88-dependent macrophage activation

MicroRNAs are known to control TLR activation in phagocytes. We have shown that leukotriene (LT) B4 (LTB4) positively regulates macrophage MyD88 expression by decreasing suppressor of cytokine signaling-1 (SOCS-1) mRNA stability. In this study, we investigated the possibility that LTB4 control of MyD88 expression involves the generation of microRNAs. Our data show that LTB4, via its receptor B leukotriene receptor 1 (BLT1) and Gαi signaling, increased macrophage expression of inflammatory microRNAs, including miR-155, miR-146b, and miR-125b. LTB4-mediated miR-155 generation was attributable to activating protein-1 activation. Furthermore, macrophage transfection with antagomirs against miR-155 and miR-146b prevented both the LTB4-mediated decrease in SOCS-1 and increase in MyD88. Transfection with miR-155 and miR-146b mimics decreased SOCS-1 levels, increased MyD88 expression, and restored TLR4 responsiveness in both wild type and LT-deficient macrophages. To our knowledge, our data unveil a heretofore unrecognized role for the GPCR BLT1 in controlling expression of microRNAs that regulate MyD88-dependent activation of macrophages.

PAF receptor and tumor growth

The receptor for the lipid mediator PAF (PAFR) is a G-protein coupled receptor expressed in several cell types. Besides PAF, a series of oxidized phospholipids can also bind to PAFR. Dying cells also express PAFR-ligands and, in both situations, scavenger receptors are involved as well. There is evidence that the scavenger receptor CD36 and PAFR associate in the macrophages membrane and signal in conjunction to induce a regulatory phenotype. In the tumor microenvironment, apoptotic cells are abundant due to hypoxia, and PAF-like phospholipids are generated. Engagement of PAFR expressed by tumor macrophages and dendritic cells induces a regulatory/tolerogenic phenotype and subverts the innate and adaptive immune response to the tumor. During cancer therapies, PAFR-ligands can be generated, further aggravating the immune suppression. Moreover, some tumor cells express PAFR and its activation by PAFR-ligands generated during chemotherapy induce anti-apoptotic factors, which protect the tumor cells from death induced by these treatments. It is proposed that PAFR antagonists, administered in combination with chemotherapy, may represent a promising strategy for cancer treatment.

Uptake of oxLDL and IL-10 production by macrophages requires PAFR and CD36 recruitment into the same lipid rafts

Macrophage interaction with oxidized low-density lipoprotein (oxLDL) leads to its differentiation into foam cells and cytokine production, contributing to atherosclerosis development. In a previous study, we showed that CD36 and the receptor for platelet-activating factor (PAFR) are required for oxLDL to activate gene transcription for cytokines and CD36. Here, we investigated the localization and physical interaction of CD36 and PAFR in macrophages stimulated with oxLDL. We found that blocking CD36 or PAFR decreases oxLDL uptake and IL-10 production. OxLDL induces IL-10 mRNA expression only in HEK293T expressing both receptors (PAFR and CD36). OxLDL does not induce IL-12 production. The lipid rafts disruption by treatment with βCD reduces the oxLDL uptake and IL-10 production. OxLDL induces co-immunoprecipitation of PAFR and CD36 with the constitutive raft protein flotillin-1, and colocalization with the lipid raft-marker GM1-ganglioside. Finally, we found colocalization of PAFR and CD36 in macrophages from human atherosclerotic plaques. Our results show that oxLDL induces the recruitment of PAFR and CD36 into the same lipid rafts, which is important for oxLDL uptake and IL-10 production. This study provided new insights into how oxLDL interact with macrophages and contributing to atherosclerosis development.

Activation of PAF-receptor induces regulatory dendritic cells through PGE2 and IL-10

Activation of the platelet-activating factor receptor (PAFR) in macrophages is associated with suppressor phenotype. Here, we investigated the PAFR in murine dendritic cells (DC). Bone marrow-derived dendritic cells (BALB/c) were cultured with GM-CSF and maturation was induced by LPS. The PAFR antagonists (WEB2086, WEB2170, PCA4248) and the prostaglandin (PG) synthesis inhibitors (indomethacin, nimesulide and NS-398) were added before LPS. Mature and immature DCs expressed PAFR. LPS increased MHCII, CD40, CD80, CD86, CCR7 and induced IL-10, IL-12, COX-2 and PGE2 expression. IL-10, COX-2 and PGE2 levels were reduced by PAFR antagonists and increased by cPAF. The IL-10 production was independent of PGs. Mature DCs induced antigen-specific lymphocyte proliferation. PAFR antagonists or PG-synthesis inhibitors significantly increased lymphocyte proliferation. It is proposed that PAF has a central role in regulatory DC differentiation through potentiation of IL-10 and PGE2 production.

Hyperglycemia triggers epigenetic machinery to enhance MyD88 expression in macrophages from type 1 diabetes mice (P1350)

Type I diabetes (T1DM) is characterized by hyperglycemia and insulin deficiency. T1DM is associated with constitutive production of pro-inflammatory cytokine such as the members of IL-1 family. IL-1β binding to its MyD88-associated receptor IL-1R is a major cause of tissue injury in T1DM. We hypothesize that hyperglycemia (HG) enhances MyD88 in macrophages (MA) amplifying IL-1βR responsiveness. We found that both in vitro and in vivo HG increases the expression of MyD88 and its transcription factor STAT-1. Speculating that enhanced MyD88/STAT-1 levels could be due to epigenetic changes, we analyzed the expression of enzymes involved in DNA methylation (DNMT) and Histone deacetylation (HDAC) in MA from T1DM mice. We observed that diabetic mice expressed at least 2 times more HDAC 8, 10 and 11, and DNMT 3b than nondiabetic mice. In vitro inhibition of HDAC (TSA) or DNMT (5-azacyd) in MA impaired HG-enhanced MyD88 and STAT-1 expression. These data suggest a heretofore unrecognized epigenetic changes associated with hyperinflammatory pattern of MA from T1DM, leading to high MyD88 expression and possibly allowing overly IL-1β receptor and other MyD88-dependent receptor activation

Oxidized LDL induces alternative macrophage phenotype through activation of CD36 and PAFR

OxLDL is recognized by macrophage scavenger receptors, including CD36; we have recently found that Platelet-Activating Factor Receptor (PAFR) is also involved. Since PAFR in macrophages is associated with suppressor function, we examined the effect of oxLDL on macrophage phenotype. It was found that the presence of oxLDL during macrophage differentiation induced high mRNA levels to IL-10, mannose receptor, PPAR γ and arginase-1 and low levels of IL-12 and iNOS. When human THP-1 macrophages were pre-treated with oxLDL then stimulated with LPS, the production of IL-10 and TGF- β significantly increased, whereas that of IL-6 and IL-8 decreased. In murine TG-elicited macrophages, this protocol significantly reduced NO, iNOS and COX2 expression. Thus, oxLDL induced macrophage differentiation and activation towards the alternatively activated M2-phenotype. In murine macrophages, oxLDL induced TGF- β , arginase-1 and IL-10 mRNA expression, which were significantly reduced by pre-treatment with PAFR antagonists (WEB and CV) or with antibodies to CD36. The mRNA expression of IL-12, RANTES and CXCL2 were not affected. We showed that this profile of macrophage activation is dependent on the engagement of both CD36 and PAFR. We conclude that oxLDL induces alternative macrophage activation by mechanisms involving CD36 and PAFR.

Sepsis-induced acute lung injury (ALI) is milder in diabetic rats and correlates with impaired NFkB activation

Acute lung injury (ALI) develops in response to a direct insult to the lung or secondarily to a systemic inflammatory response, such as sepsis. There is clinical evidence that the incidence and severity of ALI induced by direct insult are lower in diabetics. In the present study we investigated whether the same occurs in ALI secondarily to sepsis and the molecular mechanisms involved. Diabetes was induced in male Wistar rats by alloxan and sepsis by caecal ligation and puncture surgery (CLP). Six hours later, the lungs were examined for oedema and cell infiltration in bronchoalveolar lavage. Alveolar macrophages (AMs) were cultured in vitro for analysis of IκB and p65 subunit of NFκB phosphorylation and MyD88 and SOCS-1 mRNA. Diabetic rats were more susceptible to sepsis than non-diabetics. In non-diabetic rats, the lung presented oedema, leukocyte infiltration and increased COX2 expression. In diabetic rats these inflammatory events were significantly less intense. To understand why diabetic rats despite being more susceptible to sepsis develop milder ALI, we examined the NFκB activation in AMs of animals with sepsis. Whereas in non-diabetic rats the phosphorylation of IκB and p65 subunit occurred after 6 h of sepsis induction, this did not occur in diabetics. Moreover, in AMs from diabetic rats the expression of MyD88 mRNA was lower and that of SOCS-1 mRNA was increased compared with AMs from non-diabetic rats. These results show that ALI secondary to sepsis is milder in diabetic rats and this correlates with impaired activation of NFκB, increased SOCS-1 and decreased MyD88 mRNA.

A novel murine model of late-phase reaction of immediate hypersensitivity

We describe here a novel experimental model of late-phase reaction of immediate hypersensitivity developed in mice. It consists of introducing small fragments of heat-coagulated hen egg white into the subcutaneous tissue of mice. After 14 days, animals challenged with purified ovalbumin into the footpad presented an immediate swelling of the paw peaking at 30 min, followed by two peaks of swelling at 6 and 24 h. Histological examination of the paws showed a massive eosinophil infiltration (more than 800 cells/5 microscopic fields). This intense infiltration persisted for more than 14 days after the challenge. Furthermore, in mice immunized with coagulated egg white the delayed swelling of the paws and eosinophilic infiltration were significantly higher than in mice immunized with the classical protocol of ovalbumin in alumen adjuvant. Transfer of lymph node cells obtained from mice implanted with heat-coagulated hen egg white induced footpad swelling and eosinophil infiltration in response to ovalbumin. High levels of ovalbuminspecific IgG1 but not of IgE were detected in the serum of these animals. The advantages of this model for the experimental study of late-phase reaction per se and its relevance to the study of allergic diseases such as asthma are discussed.

Co-stimulation of PAFR and CD36 is required for oxLDL-induced human macrophages activation

The oxidative process of LDL particles generates molecules which are structurally similar to platelet-activating factor (PAF), and some effects of oxidized LDL (oxLDL) have been shown to be dependent on PAF receptor (PAFR) activation. In a previous study, we showed that PAFR is required for upregulation of CD36 and oxLDL uptake. In the present study we analyzed the molecular mechanisms activated by oxLDL in human macrophages and the contribution of PAFR to this response. Human adherent monocytes/macrophages were stimulated with oxLDL. Uptake of oxLDL and CD36 expression were determined by flow cytometry; MAP kinases and Akt phosphorylation by Western blot; IL-8 and MCP-1 concentration by ELISA and mRNA expression by real-time PCR. To investigate the participation of the PI3K/Akt pathway, Gαi-coupled protein or PAFR, macrophages were treated with LY294002, pertussis toxin or with the PAFR antagonists WEB2170 and CV3988, respectively before addition of oxLDL. It was found that the addition of oxLDL to human monocytes/macrophages activates the PI3K/Akt pathway which in turn activates the MAPK (p38 and JNK). Phosphorylation of Akt requires the engagement of PAFR and a Gαi-coupled protein. The upregulation of CD36 protein and the uptake of oxLDL as well as the IL-8 production are dependent on PI3K/Akt pathway activation. The increased CD36 protein expression is dependent on PAFR and Gαi-coupled protein. Transfection studies using HEK 293t cells showed that oxLDL uptake occurs with either PAFR or CD36, but IL-8 production requires the co-transfection of both PAFR and CD36. These findings show that PAFR has a pivotal role in macrophages response to oxLDL and suggest that pharmacological intervention at the level of PAFR activation might be beneficial in atherosclerosis.

Dendritic cells from X-linked hyper-IgM patients present impaired responses to Candida albicans and Paracoccidioides brasiliensis

BACKGROUND

Patients with X-linked hyper-IgM syndrome (X-HIGM) due to CD40 ligand (CD40L) mutations are susceptible to fungal pathogens; however, the underlying susceptibility mechanisms remain poorly understood.

OBJECTIVE

To determine whether monocyte-derived dendritic cells (DCs) from patients with X-HIGM exhibit normal responses to fungal pathogens.

METHODS

DCs from patients and controls were evaluated for the expression of costimulatory (CD80 and CD86) and MHC class II molecules and for their ability to produce IL-12 and IL-10 in response to Candida albicans and Paracoccidioides brasiliensis. We also evaluated the ability of C albicans- and P brasiliensis-pulsed mature DCs to induce autologous T-cell proliferation, generation of T helper (T(H)) 17 cells, and production of IFN-γ, TGF-β, IL-4, IL-5, and IL-17.

RESULTS

Immature DCs from patients with X-HIGM showed reduced expression of CD80, CD86, and HLA-DR, which could be reversed by exogenous trimeric soluble CD40L. Most important, mature DCs from patients with X-HIGM differentiated by coculturing DCs with fungi secreted minimal amounts of IL-12 but substantial amounts of IL-10 compared with mature DCs from normal individuals. Coculture of mature DCs from X-HIGM patients with autologous T cells led to low IFN-γ production, whereas IL-4 and IL-5 production was increased. T-cell proliferation and IL-17 secretion were normal. Finally, in vitro incubation with soluble CD40L reversed the decreased IL-12 production and the skewed T(H)2 pattern response.

CONCLUSION

Absence of CD40L during monocyte/DC differentiation leads to functional DC abnormalities, which may contribute to the susceptibility to fungal infections in patients with X-HIGM.

Airway remodeling in murine asthma correlates with a defect in PGE2 synthesis by lung fibroblasts

Asthma is a chronic lung disease characterized by local inflammation that can result in structural alterations termed airway remodeling. One component of airway remodeling involves fibroblast accumulation and activation, resulting in deposition of collagen I around small bronchi. Prostaglandin E(2) (PGE(2)) is the main eicosanoid lipid mediator produced by lung fibroblasts, and it exerts diverse anti-fibrotic actions. Dysregulation of the PGE(2) synthesis/response axis has been identified in human pulmonary fibrotic diseases and implicated in the pathogenesis of animal models of lung parenchymal fibrosis. Here we investigated the relationship between the fibroblast PGE(2) axis and airway fibrosis in an animal model of chronic allergic asthma. Airway fibrosis increased progressively as the number of airway challenges with antigen increased from 3 to 7 to 12. Compared with cells from control lungs, fibroblasts grown from the lungs of asthmatic animals, regardless of challenge number, exhibited no defect in the ability of PGE(2) or its analogs to inhibit cellular proliferation and collagen I expression. This correlated with intact expression of the EP(2) receptor, which is pivotal for PGE(2) responsiveness. However, cytokine-induced upregulation of PGE(2) biosynthesis as well as expression of cyclooxygenase-2 (COX-2) and microsomal PGE synthase-1 declined with increasing numbers of antigen challenges. In addition, treatment with the COX-2-selective inhibitor nimesulide potentiated the degree of airway fibrosis following repeated allergen challenge. Because endogenous COX-2-derived PGE(2) acts as a brake on airway fibrosis, the inability of fibroblasts to upregulate PGE(2) generation in the inflammatory milieu presented by repeated allergen exposure could contribute to the airway remodeling and fibrosis observed in chronic asthma.

Leukotrienes target F-actin/cofilin-1 to enhance alveolar macrophage anti-fungal activity

Candida albicans is the most common opportunistic fungal pathogen and causes local and systemic disease in immunocompromised patients. Alveolar macrophages (AMs) are pivotal for the clearance of C. albicans from the lung. Activated AMs secrete 5-lipoxygenase-derived leukotrienes (LTs), which in turn enhance phagocytosis and microbicidal activity against a diverse array of pathogens. Our aim was to investigate the role of LTB(4) and LTD(4) in AM antimicrobial functions against C. albicans and the signaling pathways involved. Pharmacologic and genetic inhibition of LT biosynthesis as well as receptor antagonism reduced phagocytosis of C. albicans when compared with untreated or WT controls. Conversely, exogenous LTs of both classes augmented base-line C. albicans phagocytosis by AMs. Although LTB(4) enhanced mainly mannose receptor-dependent fungal ingestion, LTD(4) enhanced mainly dectin-1 receptor-mediated phagocytosis. LT enhancement of yeast ingestion was dependent on protein kinase C-δ (PKCδ) and PI3K but not PKCα and MAPK activation. Both LTs reduced activation of cofilin-1, whereas they enhanced total cellular F-actin; however, LTB(4) accomplished this through the activation of LIM kinases (LIMKs) 1 and 2, whereas LTD(4) did so exclusively via LIMK-2. Finally, both exogenous LTB(4) and LTD(4) enhanced AM fungicidal activity in an NADPH oxidase-dependent manner. Our data identify LTB(4) and LTD(4) as key mediators of innate immunity against C. albicans, which act by both distinct and conserved signaling mechanisms to enhance multiple antimicrobial functions of AMs.

Mycoplasmal lipid-associated membrane proteins and Mycoplasma arthritidis mitogen recognition by serum antibodies from patients with rheumatoid arthritis

Mycoplasmal lipid-associated membrane proteins (LAMPs) and Mycoplasma arthritidis mitogen (MAM superantigen) are potent stimulators of the immune system. The objective of this work was to detect antibodies to MAM and LAMPs of Mycoplasma hominis and M. fermentans in the sera of patients affected by rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) to identify mycoplasmal products that can be involved in the etiopathogenesis of these autoimmune diseases. Serum samples from female RA and SLE patients and controls, recombinant MAM, and LAMPs of M. hominis PG21 and M. fermentans PG18 were used in Western blot assays. A similar frequency of sera from patients and controls reactive to MAM was detected. A larger number of M. hominis and M. fermentans LAMPs were recognized by sera from RA patients than controls, but no differences were detected between sera from SLE patients and controls. Among the LAMPs recognized by IgG antibodies from RA patients, proteins of molecular masses in a range of <49 and ≥20 KDa (M. hominis) and <102 and ≥58 KDa (M. fermentans) were the most reactive. These preliminary results demonstrate the strong reactivity of antibodies of RA patients with some M. hominis and M. fermentans LAMPs. These LAMPs could be investigated as mycoplasmal antigens that can take part in the induction or amplification of human autoimmune responses.

Pivotal role for platelet-activating factor receptor in CD36 expression and oxLDL uptake by human monocytes/macrophages

The uptake of oxLDL by CD36 is not regulated by intracellular levels of cholesterol, leading to macrophage differentiation into foam cells which play a major role in atherosclerosis. Furthermore, oxLDL competes with PAF in macrophages for binding to PAF receptors (PAFR). Here we investigated the involvement of PAFR in CD36 expression and uptake of oxLDL by human monocytes/macrophages. Adherent peripheral blood mononuclear cells were treated with PAFR-antagonists (WEB2170, CV3988); inhibitors of ERK1/2 (PD98059), p38 (SB203580), JNK (SP600125) or diluents, before stimulation with oxLDL or PAF. After 24 h, uptake of FITC-oxLDL and expression of CD36 was determined by flow cytometry and phosphorylation of MAP-kinases by Western blot. It was shown that the uptake of oxLDL was reduced by PAFR antagonists. CD36 expression was up-regulated by oxLDL, an effect reversed by PAFR antagonists. The up-regulation of CD36 and oxLDL uptake both required MAP-kinases activation. The oxLDL-induced ERK1/2 and JNK but not p38 phosphorylation was reversed by PAFR-antagonists suggesting that oxLDL signalling involves PAFR dependent and independent pathways. In macrophages from PAFR(-/-) mice, oxLDL was unable to up-regulate CD36 expression and the oxLDL uptake was reduced compared to wild type. These results suggest that oxLDL interacts with PAFR in macrophages to increase CD36 expression and oxLDL uptake. Whereas pharmacological intervention at the level of PAFR would be beneficial in atherosclerosis remains to be determined.

Leukotriene B4 amplifies NF-κB activation in mouse macrophages by reducing SOCS1 inhibition of MyD88 expression

Activation of NF-κB and 5-lipoxygenase-mediated (5-LO-mediated) biosynthesis of the lipid mediator leukotriene B4 (LTB4) are pivotal components of host defense and inflammatory responses. However, the role of LTB4 in mediating innate immune responses elicited by specific TLR ligands and cytokines is unknown. Here we have shown that responses dependent on MyD88 (an adaptor protein that mediates signaling through all of the known TLRs, except TLR3, as well as IL-1β and IL-18) are reduced in mice lacking either 5-LO or the LTB4 receptor BTL1, and that macrophages from these mice are impaired in MyD88-dependent activation of NF-κB. This macrophage defect was associated with lower basal and inducible expression of MyD88 and reflected impaired activation of STAT1 and overexpression of the STAT1 inhibitor SOCS1. Expression of MyD88 and responsiveness to the TLR4 ligand LPS were decreased by Stat1 siRNA silencing in WT macrophages and restored by Socs1 siRNA in 5-LO-deficient macrophages. These results uncover a pivotal role in macrophages for the GPCR BLT1 in regulating activation of NF-κB through Stat1-dependent expression of MyD88.

Insulin modulates cytokine release and selectin expression in the early phase of allergic airway inflammation in diabetic rats

BACKGROUND

Clinical and experimental data suggest that the inflammatory response is impaired in diabetics and can be modulated by insulin. The present study was undertaken to investigate the role of insulin on the early phase of allergic airway inflammation.

METHODS

Diabetic male Wistar rats (alloxan, 42 mg/Kg, i.v., 10 days) and controls were sensitized by s.c. injection of ovalbumin (OA) in aluminium hydroxide 14 days before OA (1 mg/0.4 mL) or saline intratracheal challenge. The following analyses were performed 6 hours thereafter: a) quantification of interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha and cytokine-induced neutrophil chemoattractant (CINC)-1 in the bronchoalveolar lavage fluid (BALF) by Enzyme-Linked Immunosorbent Assay, b) expression of E- and P- selectins on lung vessels by immunohistochemistry, and c) inflammatory cell infiltration into the airways and lung parenchyma. NPH insulin (4 IU, s.c.) was given i.v. 2 hours before antigen challenge.

RESULTS

Diabetic rats exhibited significant reduction in the BALF concentrations of IL-1beta (30%) and TNF-alpha (45%), and in the lung expression of P-selectin (30%) compared to non-diabetic animals. This was accompanied by reduced number of neutrophils into the airways and around bronchi and blood vessels. There were no differences in the CINC-1 levels in BALF, and E-selectin expression. Treatment of diabetic rats with NPH insulin, 2 hours before antigen challenge, restored the reduced levels of IL-1beta, TNF-alpha and P-selectin, and neutrophil migration.

CONCLUSION

Data presented suggest that insulin modulates the production/release of TNF-alpha and IL-1beta, the expression of P- and E-selectin, and the associated neutrophil migration into the lungs during the early phase of the allergic inflammatory reaction.

Platelet-activating factor receptor (PAF-R)-dependent pathways control tumour growth and tumour response to chemotherapy

Background

Phagocytosis of apoptotic cells by macrophages induces a suppressor phenotype. Previous data from our group suggested that this occurs via Platelet-activating factor receptor (PAF-R)-mediated pathways. In the present study, we investigated the impact of apoptotic cell inoculation or induction by a chemotherapeutic agent (dacarbazine, DTIC) on tumour growth, microenvironmental parameters and survival, and the effect of treatment with a PAF-R antagonist (WEB2170). These studies were performed in murine tumours: Ehrlich Ascitis Tumour (EAT) and B16F10 melanoma.

Methods

Tumour growth was assessed by direct counting of EAT cells in the ascitis or by measuring the volume of the solid tumour. Parameters of the tumour microenvironment, such as the frequency of cells expressing cyclo-oxygenase-2 (COX-2), caspase-3 and galectin-3, and microvascular density, were determined by immunohistochemistry. Levels of vascular endothelium growth factor (VEGF) and prostaglandin E2 (PGE2) were determined by ELISA, and levels of nitric oxide (NO) by Griess reaction. PAF-R expression was analysed by immunohistochemistry and flow cytometry.

Results

Inoculation of apoptotic cells before EAT implantation stimulated tumour growth. This effect was reversed by in vivo pre-treatment with WEB2170. This treatment also reduced tumour growth and modified the microenvironment by reducing PGE2, VEGF and NO production. In B16F10 melanoma, WEB2170 alone or in association with DTIC significantly reduced tumour volume. Survival of the tumour-bearing mice was not affected by WEB2170 treatment but was significantly improved by the combination of DTIC with WEB2170. Tumour microenvironment elements were among the targets of the combination therapy since the relative frequency of COX-2 and galectin-3 positive cells and the microvascular density within the tumour mass were significantly reduced by treatment with WEB2170 or DTIC alone or in combination. Antibodies to PAF-R stained the cells from inside the tumour, but not the tumour cells grown in vitro. At the tissue level, a few cells (probably macrophages) stained positively with antibodies to PAF-R.

Conclusions

We suggest that PAF-R-dependent pathways are activated during experimental tumour growth, modifying the microenvironment and the phenotype of the tumour macrophages in such a way as to favour tumour growth. Combination therapy with a PAF-R antagonist and a chemotherapeutic drug may represent a new and promising strategy for the treatment of some tumours.

Bradykinin B(1) receptor antagonist R954 inhibits eosinophil activation/proliferation/migration and increases TGF-beta and VEGF in a murine model of asthma

In the present study the effects of bradykinin receptor antagonists were investigated in a murine model of asthma using BALB/c mice immunized with ovalbumin/alum and challenged twice with aerosolized ovalbumin. Twenty four hours later eosinophil proliferation in the bone marrow, activation (lipid bodies formation), migration to lung parenchyma and airways and the contents of the pro-angiogenic and pro-fibrotic cytokines TGF-beta and VEGF were determined. The antagonists of the constitutive B(2) (HOE 140) and inducible B(1) (R954) receptors were administered intraperitoneally 30min before each challenge. In sensitized mice, the antigen challenge induced eosinophil proliferation in the bone marrow, their migration into the lungs and increased the number of lipid bodies in these cells. These events were reduced by treatment of the mice with the B(1) receptor antagonist. The B(2) antagonist increased the number of eosinophils and lipid bodies in the airways without affecting eosinophil counts in the other compartments. After challenge the airway levels of VEGF and TGF-beta significantly increased and the B(1) receptor antagonist caused a further increase. By immunohistochemistry techniques TGF-beta was found to be expressed in the muscular layer of small blood vessels and VEGF in bronchial epithelial cells. The B(1) receptors were expressed in the endothelial cells. These results showed that in a murine model of asthma the B(1) receptor antagonist has an inhibitory effect on eosinophils in selected compartments and increases the production of cytokines involved in tissue repair. It remains to be determined whether this effects of the B(1) antagonist would modify the progression of the allergic inflammation towards resolution or rather towards fibrosis.

Bradykinin inducible receptor is essential to lipopolysaccharide-induced acute lung injury in mice

Lipopolysaccharides from gram-negative bacteria are amongst the most common causative agents of acute lung injury, which is characterized by an inflammatory response, with cellular infiltration and the release of mediators/cytokines. There is evidence that bradykinin plays a role in lung inflammation in asthma but in other types of lung inflammation its role is less clear. In the present study we evaluated the role of the bradykinin B1 receptor in acute lung injury caused by lipopolysaccharide inhalation and the mechanisms behind bradykinin actions participating in the inflammatory response. We found that in C57Bl/6 mice, the bradykinin B1 receptor expression was up-regulated 24h after lipopolysaccharide inhalation. At this time, the number of cells and protein concentration were significantly increased in the bronchoalveolar lavage fluid and the mice developed airway hyperreactivity to methacholine. In addition, there was an increased expression of tumor necrosis factor-alpha, interleukin-1 beta and interferon-gamma and chemokines (monocytes chemotactic protein-1 and KC) in the bronchoalveolar lavage fluid and in the lung tissue. We then treated the mice with a bradykinin B1 receptor antagonist, R-954 (Ac-Orn-[Oic2, alpha-MePhe5, D-betaNal7, Ile8]desArg9-bradykinin), 30 min after lipopolysaccharide administration. We observed that this treatment prevented the airway hyperreactivity as well as the increased cellular infiltration and protein content in the bronchoalveolar lavage fluid. Moreover, R-954 inhibited the expression of cytokines/chemokines. These results implicate bradykinin, acting through B1 receptor, in the development of acute lung injury caused by lipopolysaccharide inhalation.

Role of PPAR-gamma in the modulation of CD36 and FcgammaRII induced by LDL with low and high degrees of oxidation during the differentiation of the monocytic THP-1 cell line

Scavenger or Fcgamma receptors are important for capture and clearance of modified LDL particles by monocytes/macrophages. Uptake via scavenger receptors is not regulated by intracellular levels of cholesterol and in consequence, macrophages develop into foam cells in the arterial intima. The levels of scavenger receptor CD36 are increased in atherosclerotic lesions and there is evidence that some components of oxLDL auto-regulate the expression of this receptor. Fcgamma receptor expression is increased in cardiovascular diseases but it is not known weather their expression is regulated by oxLDL. The biological properties of oxLDLs vary depending on the degree of oxidation. In the present study we investigated the effect of LDL particles showing extensive or low oxidation (HoxLDL and LoxLDL) on the expression of CD36 and FcgammaRII in a human monocytic cell line (THP-1), differentiated or not to macrophage, and the involvement of PPARgamma. It was found that both forms of oxLDL are able to increase the expression of CD36 and FcgammaRII and that this effect is dependent on the degree of oxidation and of the stage of cell differentiation (monocyte or macrophage). We also showed that the increased expression of FcgammaRII is dependent on PPARgamma whereas that of the CD36 is independent of PPARgamma.

Crucial cytokine interactions in nitric oxide production induced by Mycoplasma arthritidis superantigen

Mycoplasma arthritidis causes autoimmune arthritis in rodents. It produces a superantigen (MAM) that simultaneously activates antigen presenting cells and T cells inducing nitric oxide and cytokine release. Nitric oxide is a key inducer and regulator of the immune system activation. Here, we investigated nitric oxide and cytokine production and interactions of these molecules in MAM-stimulated co-cultures of macrophages (J774A.1 cell line) with spleen lymphocytes. We found that: a) MAM-induced nitric oxide, interferon-gamma, membrane-associated tumor necrosis factor and interleukin-2 production in co-cultures of macrophages with lymphocytes from BALB/c and C3H/HePas but not from C57Bl/6 mice; b) production of nitric oxide was dependent on interferon-gamma whereas that of interferon-gamma was dependent on interleukin-2 and membrane-associated tumor necrosis factor; c) these cytokines up regulated MAM-induced nitric oxide production. Unraveling the mechanisms of cell activation induced by MAM might be helpful to design strategies to prevent immune system activation by superantigens and therefore in seeking amelioration of associated immunopathologies.

Endothelin A receptor antagonist modulates lymphocyte and eosinophil infiltration, hyperreactivity and mucus in murine asthma

Levels of endothelins are particularly high in the lung, and there is evidence that these peptides are involved in asthma. Asthma is a chronic inflammatory disease associated with lymphocyte infiltration. In the present study, we used a murine model of asthma to investigate the role of endothelins in lymphocyte and eosinophil infiltration into the airway hyperreactivity and mucus secretion. Sensitized C57Bl/6 mice were treated with endothelin ETA receptor antagonist (BQ123) or endothelin ETB receptor antagonist (BQ788) 30 min before an antigen aerosol challenge. After 24 h, dose response curves to methacholine were performed in isolated lungs, FACS analysis of lymphocytes and eosinophil counts were performed in bronchoalveolar lavage fluid and mucus index was determined by histopathology. In sensitized and antigen-challenged mice there is a marked increase in the T CD4+, T CD8+, B220+, Tgammadelta+ and NK1.1+ lymphocyte subsets. Treatment with BQ123 further increased these cell populations. The number of eosinophils, airway hyperreactivity and mucus were all reduced by BQ123 treatment. The BQ 788 had no significant effect on the parameters analyzed. Treatment with BQ123 reduced the endothelin concentration in lung homogenates, suggesting that endothelins exert a positive feedback on their synthesis. We show here that in murine asthma the ETA receptor antagonist up-regulates lymphocyte infiltration and reduces eosinophils, hyperreactivity and mucus.

Bradykinin [corrected] B1 receptor antagonism is beneficial in renal ischemia-reperfusion injury

Previously we have demonstrated that bradykinin B1 receptor deficient mice (B1KO) were protected against renal ischemia and reperfusion injury (IRI). Here, we aimed to analyze the effect of B1 antagonism on renal IRI and to study whether B1R knockout or antagonism could modulate the renal expression of pro and anti-inflammatory molecules. To this end, mice were subjected to 45 minutes ischemia and reperfused at 4, 24, 48 and 120 hours. Wild-type mice were treated intra-peritoneally with antagonists of either B1 (R-954, 200 µg/kg) or B2 receptor (HOE140, 200 µg/kg) 30 minutes prior to ischemia. Blood samples were collected to ascertain serum creatinine level, and kidneys were harvested for gene transcript analyses by real-time PCR. Herein, B1R antagonism (R-954) was able to decrease serum creatinine levels, whereas B2R antagonism had no effect. The protection seen under B1R deletion or antagonism was associated with an increased expression of GATA-3, IL-4 and IL-10 and a decreased T-bet and IL-1β transcription. Moreover, treatment with R-954 resulted in lower MCP-1, and higher HO-1 expression. Our results demonstrated that bradykinin B1R antagonism is beneficial in renal IRI.