CD40 ligation induces macrophage IL-10 and TNF-alpha production: differential use of the PI3K and p42/44 MAPK-pathways

Oligodeoxynucleotides containing CpG motifs (CpG-ODN) restores immune regulatory functions of airway macrophages of patients with asthma

Allergic asthma is characterized by the polarization of Th2 cells and impaired immune regulation. Macrophages occupy the largest proportion of airway immune cells. This study aims to discover the mechanism that hinders the immune regulatory functions of airway macrophages. In this study, macrophages were isolated from cells in bronchoalveolar lavage fluids (BALF) collected from asthma patients and normal control (NC) subjects. The results indicated that macrophages occupied the largest portion of the cellular components in BALF. The frequency of IL-10+ macrophage was significantly lower in asthma patients than in NC subjects. The expression of IL-10 in macrophages of BALF was associated with the levels of asthma-related parameters. The immune-suppressive functions of BALF M0 cells were defective in asthma patients. The inducibility of IL-10 expression was impaired in BALF macrophages of asthma patients, which could be restored by exposing to CpG. In conclusion, the induction of IL-10 in macrophages of BALF in asthma patients was impaired, and it could be restored by exposure to CpG.

The immune suppressive functions of macrophages are impaired in patients with ulcerative colitis

Chronic inflammation is the pathological feature of inflammatory bowel diseases (IBD), but its etiology is unknown. Macrophages are one of the major immune cell fractions in the colon. The objectives of this study are to characterize the immune regulatory functions of macrophages in the colon of patients with ulcerative colitis (UC). UC patients (n = 30) were recruited into this study. Colon lavage fluid (CLF) was collected. Macrophages are isolated from the cellular components of CLF. The immune suppressive functions of macrophages were assessed using immunological approaches. We observed that macrophages occupied about half of the proportions of the cellular components in CLF. Lower amounts of IL10 mRNA and proteins were detected in macrophages of the UC group than the normal control (NC) group. The expression of IL10 in CLF macrophages was positively correlated with the UC-associated cytokines, including tumor necrosis factor-α, interleukin (IL)-1β, IFN-γ, eosinophil-derived mediators, in CLF. The immune suppressive functions of CLF macrophages in UC patients were impaired. The inducibility of IL10 expression of UC M0 cells was defective as compared with NC M0 cells. Exposure to CpG restored the inducibility of IL10 expression in UC M0 cells, and gain the potential to acquire the immune suppressive functions. To sum up, the immune suppressive functions of UC macrophages are impaired. The inducibility of IL10 expression of M0 cells is impaired, which can be restored by the treatment with CpG.

Harnessing the potential of CD40 agonism in cancer therapy

CD40 is a member of the tumor necrosis factor (TNF) receptor superfamily of receptors expressed on a variety of cell types. The CD40-CD40L interaction gives rise to many immune events, including the licensing of dendritic cells to activate CD8+ effector T cells, as well as the facilitation of B cell activation, proliferation, and differentiation. In malignant cells, the expression of CD40 varies among cancer types, mediating cellular proliferation, apoptosis, survival and the secretion of cytokines and chemokines. Agonistic human anti-CD40 antibodies are emerging as an option for cancer treatment, and early-phase clinical trials explored its monotherapy or combination with radiotherapy, chemotherapy, immune checkpoint blockade, and other immunomodulatory approaches. In this review, we present the current understanding of the mechanism of action for CD40, along with results from the clinical development of agonistic human CD40 antibodies in cancer treatment (selicrelumab, CDX-1140, APX005M, mitazalimab, 2141-V11, SEA-CD40, LVGN7409, and bispecific antibodies). This review also examines the safety profile of CD40 agonists in both preclinical and clinical settings, highlighting optimized dosage levels, potential adverse effects, and strategies to mitigate them.

The roles of HDAC with IMPDH and mTOR with JAK as future targets in the treatment of rheumatoid arthritis with combination therapy

Various studies have shown that cytokines are important regulators in rheumatoid arthritis (RA). In synovial inflammation alteration of the enzyme HDAC, IMPDH enzyme, mTOR pathway, and JAK pathway increase cytokine level. These increased cytokine levels are responsible for the inflammation in RA. Inflammation is a physiological and normal reaction of the immune system against dangerous stimuli such as injury and infection. The cytokine-based approach improves the treatment of RA. To reach this goal, various researchers and scientists are working more aggressively by using a combination approach. The present review of combination therapy provides essential evidence about the possible synergistic effect of combinatorial agents. We have focused on the effects of HDAC inhibitor with IMPDH inhibitor and mTOR inhibitor with JAK inhibitor in combination for the treatment of RA. Combining various targeted strategies can be helpful for the treatment of RA.

Differential Spleen miRNA Expression Profile of Beagle Dogs Infected with Toxocara canis

Toxocara canis is an unnoticed zoonotic helminth that causes severe disease in animals and humans. The spleen has a wide range of immunological functions in protecting the host against infection by many pathogens, but the function of the spleen in T. canis infection is still to be clarified, especially for the role of spleen microRNAs (miRNAs). In this study, deep sequencing of spleen RNA samples of 18 Beagle puppies was conducted to uncover the miRNAs expression profiling at 24 h post-infection (hpi), 96 hpi, and 36 days post infection (dpi). A total of 20, 34, and 19 differentially expressed miRNAs (DEmiRNAs) were identified at 24 hpi, 96 hpi, and 36 dpi, respectively. These DEmiRNAs (e.g., cfa-miR-206, cfa-miR-331, and cfa-miR-339) could play critical roles in Beagle puppies against T. canis infection, such as influencing inflammatory and immune-related cells and cytokines, by regulating target genes that are tightly associated with host immune function and enriched in immune response and immune pathways based on GO annotation and KEGG enrichment analysis. The current study discovered marked alterations of spleen miRNAs after T. canis infection, with potential effects on the pathogenesis of toxocariasis.

Agonistic CD40 Antibodies in Cancer Treatment

Simple Summary

CD40 is a costimulatory molecule that is key for the activation of antigen-presenting cells and other innate immune cells. It plays an important role in anti-tumor immunity, and agonists of CD40 have been shown to eliminate tumors in both pre-clinical and clinical settings, alone and in combination with other treatment modalities. Here we assess the expression of CD40 and associations with other mediators of immunity in a variety of tumor types and review the potential of CD40 agonists for cancer treatment, given the promise of enhancing the interplay between innate and adaptive immunity.

Abstract

CD40 is expressed on a variety of antigen-presenting cells. Stimulation of CD40 results in inflammation by upregulation of other costimulatory molecules, increased antigen presentation, maturation (licensing) of dendritic cells, and activation of CD8+ T cells. Here we analyzed gene expression data from The Cancer Genome Atlas in melanoma, renal cell carcinoma, and pancreatic adenocarcinoma and found correlations between CD40 and several genes involved in antigen presentation and T cell function, supporting further exploration of CD40 agonists to treat cancer. Agonist CD40 antibodies have induced anti-tumor effects in several tumor models and the effect has been more pronounced when used in combination with other treatments (immune checkpoint inhibition, chemotherapy, and colony-stimulating factor 1 receptor inhibition). The reduction in tumor growth and ability to reprogram the tumor microenvironment in preclinical models lays the foundation for clinical development of agonistic CD40 antibodies (APX005M, ChiLob7/4, ADC-1013, SEA-CD40, selicrelumab, and CDX-1140) that are currently being evaluated in early phase clinical trials. In this article, we focus on CD40 expression and immunity in cancer, agonistic human CD40 antibodies, and their pre-clinical and clinical development. With the broad pro-inflammatory effects of CD40 and its ligand on dendritic cells and macrophages, and downstream B and T cell activation, agonists of this pathway may enhance the anti-tumor activity of other systemic therapies.

Immunoregulatory Effects of Porcine Plasma Protein Concentrates on Rat Intestinal Epithelial Cells and Splenocytes

Simple Summary

Blood contains proteins which have interest as products that may regulate immune function. For this reason some protein-based products are currently used as nutritional supplements for animals, for instance two porcine concentrates, spray dried serum (SDS), and an immunoglobulin concentrate (IC). These products have shown to protect against colonic inflammation in rodents. In the present study we characterize the ability of these products to modulate immune function in isolated cells, namely intestinal epithelial cells (IEC18 cells) and rat spleen cells. Our data indicate that both porcine protein concentrates indeed alter immune cell function, based on the secretion of the modulators known as cytokines. In intestinal epithelial IEC18 cells they promoted the secretion of GROα and MCP-1 cytokines. In spleen cells they mainly inhibited the production of TNF, a key proinflammatory cytokine. In addition, the IC product augmented the release of IL-10, an anti-inflammatory cytokine. Taken together, our data indicate that the immunomodulatory effects observed in vivo are consistent with the direct actions of the protein concentrates on epithelial cells, T lymphocytes, and monocytes.

Abstract

Serum protein concentrates have been shown to exert in vivo anti-inflammatory effects. Specific effects on different cell types and their mechanism of action remain unraveled. We aimed to characterize the immunomodulatory effect of two porcine plasma protein concentrates, spray dried serum (SDS) and an immunoglobulin concentrate (IC), currently used as animal nutritional supplements with established in vivo immunomodulatory properties. Cytokine production by the intestinal epithelial cell line IEC18 and by primary cultures of rat splenocytes was studied. The molecular pathways involved were explored with specific inhibitors and gene knockdown. Our results indicate that both products induced GROα and MCP-1 production in IEC18 cells by a MyD88/NF-κB-dependent mechanism. Inhibition of TNF production was observed in rat primary splenocyte cultures. The immunoglobulin concentrate induced IL-10 expression in primary splenocytes and lymphocytes. The effect on TNF was independent of IL-10 production or the stimulation of NF-kB, MAPKs, AKT, or RAGE. In conclusion, SDS and IC directly regulate intestinal and systemic immune response in murine intestinal epithelial cells and in T lymphocytes and monocytes.

Recruitment of monocytes and mature macrophages in mouse pubic symphysis relaxation during pregnancy and postpartum recovery†

Appropriate remodeling of the female lower reproductive tract and pelvic floor is essential during normal mammalian pregnancy, labor, and postpartum recovery. During mouse pregnancy, in addition to reproductive tract modifications, the pubic symphysis (PS) is remodeled into a soft interpubic ligament (IpL) to provide safe delivery of the offspring and fast postpartum recovery. Although temporal changes in the phenotypes of myeloid cells, such as mononuclear phagocytes, are crucial to remodeling the lower reproductive tract organs in preparation for a safe delivery, little is known about the involvement of recruited monocytes or macrophages in mouse PS remodeling. We used combined light microscopy, electron microscopy, and qPCR analysis to investigate the profile of recruited monocytes and macrophage polarization markers in C57Bl6 mouse interpubic tissues during pregnancy (D12, D18, and D19) and early days postpartum (1 dpp and 3 dpp) to better identify their presence in proper remodeling of the mouse PS. Our morphological data show that the number of recruited monocytes is increased in interpubic tissues and that recruited monocytes differentiate into proinflammatory or anti-inflammatory macrophage phenotypes from D18 to 3 dpp, which may contribute to dynamic changes in the gene expression of specific inflammatory mediators involved in interpubic tissue remodeling at these time points. Therefore, our morphological and quantitative gene expression data suggest that both differentiated macrophages from recruited monocytes and polarized macrophages may collaborate for IpL relaxation at labor and the appropriate repair of the PS after the first pregnancy.

IL-33 promotes IL-10 production in macrophages: a role for IL-33 in macrophage foam cell formation

We evaluated the role of IL-10- in IL-33-mediated cholesterol reduction in macrophage-derived foam cells (MFCs) and the mechanism by which IL-33 upregulates IL-10. Serum IL-33 and IL-10 levels in coronary artery disease patients were measured. The effects of IL-33 on intra-MFC cholesterol level, IL-10, ABCA1 and CD36 expression, ERK 1/2, Sp1, STAT3 and STAT4 activation, and IL-10 promoter activity were determined. Core sequences were identified using bioinformatic analysis and site-specific mutagenesis. The serum IL-33 levels positively correlated with those of IL-10. IL-33 decreased cellular cholesterol level and upregulated IL-10 and ABCA1 but had no effect on CD36 expression. siRNA-IL-10 partially abolished cellular cholesterol reduction and ABCA1 elevation by IL-33 but did not reverse the decreased CD36 levels. IL-33 increased IL-10 mRNA production but had little effect on its stability. IL-33 induced ERK 1/2 phosphorylation and increased the luciferase expression driven by the IL-10 promoter, with the highest extent within the −2000 to −1752 bp segment of the 5′-flank of the transcription start site; these effects were counteracted by U0126. IL-33 activated Sp1, STAT3 and STAT4, but only the STAT3 binding site was predicted in the above segment. Site-directed mutagenesis of the predicted STAT3-binding sites (CTGCTTCCTGGCAGCAGAA→CTGCCTGGCAGCAGAA) reduced luciferase activity, and a STAT3 inhibitor blocked the regulatory effects of IL-33 on IL-10 expression. Chromatin immunoprecipitation (CHIP) confirmed the STAT3-binding sequences within the −1997 to −1700 and −1091 to −811 bp locus regions. IL-33 increased IL-10 expression in MFCs via activating ERK 1/2 and STAT3, which subsequently promoted IL-10 transcription and thus contributed to the beneficial effects of IL-33 on MFCs.

Glycogen synthase kinase-3 (GSK3) regulates TNF production and haemocyte phagocytosis in the immune response of Chinese mitten crab Eriocheir sinensis

Glycogen synthase kinase-3 (GSK3) is a serine/threonine protein kinase firstly identified as a regulator of glycogen synthesis. Recently, it has been proved to be a key regulator of the immune reaction. In the present study, a GSK3 homolog gene (designated as EsGSK3) was cloned from Chinese mitten crab, Eriocheir sinensis. The open reading frame (ORF) was 1824 bp, which encoded a predicted polypeptide of 607 amino acids. There was a conserved Serine/Threonine Kinase domain and a DNA binding domain found in EsGSK3. Phylogenetic analysis showed that EsGSK3 was firstly clustered with GSK3-β from oriental river prawn Macrobrachium nipponense in the invertebrate branch, while GSK3s from vertebrates formed the other distinct branch. EsGSK3 mRNA transcripts could be detected in all tested tissues of the crab including haepatopancreas, eyestalk, muscle, gonad, haemocytes and haematopoietic tissue with the highest expression level in haepatopancreas. And EsGSK3 protein was mostly detected in the cytoplasm of haemocyte by immunofluorescence analysis. The expression levels of EsGSK3 mRNA increased significantly at 6 h after Aeromonas hydrophila challenge (p < 0.05) in comparison with control group, and then gradually decreased to the initial level at 48 h (p > 0.05). The mRNA expression of lipopolysaccharide-induced tumor necrosis factor (TNF)-α factor (EsLITAF) was also induced by A. hydrophila challenge. However, the mRNA expression of EsLITAF and TNF-α production was significantly suppressed after EsGSK3 was blocked in vivo with specific inhibitor lithium, while the phagocytosis of crab haemocytes was significantly promoted. These results collectively demonstrated that EsGSK3 could regulate the innate immune responses of E. sinensis by promoting TNF-α production and inhibiting haemocyte phagocytosis.

The cell-to-cell coordination between activated T cells and CpG-stimulated macrophages synergistically induce elevated levels of IL-10 via NF-κB1, STAT3, and CD40/CD154

Background

Studies into the regulation of interleukin-10 (IL-10), have focused only on the molecular or single-cell level. The cues that induce IL-10 in the context of cell-to-cell communication are scarce. To fill this gap, this study elucidates the cell-to-cell interaction dependent regulation of IL-10.

Results

The simultaneous activation of CD4⁺ T cells via CD3/CD28 and stimulation of macrophages via CpG and their intercellular communication with each other in the same microenvironment is necessary to induce a synergistic expression of IL-10. NF-κB1, ERK, and STAT3 are positive regulators of this cell-to-cell communication mediated molecular change of IL-10 induction. Strikingly, the activation of CD40/CD154 signaling is a negative regulator of IL-10 levels by CD3/CD28/CpG.

Conclusions

These findings are of prominence as CD3/CD28/CpG treatment can induce the anti-inflammatory cytokines IL-10 and IL-30, and the activation or inhibition of the CD40/CD154 acts as molecular rheostat of the expression of IL-10 or IL-30. More importantly, this not only serves as an example of IL-10 regulation at the cellular via coordination of two signals from two cell types, but these findings also lay the molecular and cellular groundwork for future studies to investigate how to manipulate IL-10 or IL-30 production during inflammation, cancer, or autoimmune diseases.

Rheumatoid factor positivity is associated with increased joint destruction and upregulation of matrix metalloproteinase 9 and cathepsin k gene expression in the peripheral blood in rheumatoid arthritic patients treated with methotrexate

We evaluated changes in gene expression of mTOR, p21, caspase-3, ULK1, TNFα, matrix metalloproteinase (MMP)-9, and cathepsin K in the whole blood of rheumatoid arthritic (RA) patients treated with methotrexate (MTX) in relation to their rheumatoid factor status, clinical, immunological, and radiological parameters, and therapeutic response after a 24-month follow-up. The study group consisted of 35 control subjects and 33 RA patients without previous history of MTX treatment. Gene expression was measured using real-time RT-PCR. Decreased disease activity in patients at the end of the study was associated with significant downregulation of TNFα expression. Downregulation of mTOR was observed in seronegative patients, while no significant changes in the expression of p21, ULK1, or caspase-3 were noted in any RA patients at the end of the study. The increase in erosion numbers observed in the seropositive patients at the end of the follow-up was accompanied by upregulation of MMP-9 and cathepsin K, while seronegative patients demonstrated an absence of significant changes in MMP-9 and cathepsin K expression and no increase in the erosion score. Our results suggest that increased expression of MMP-9 and cathepsin K genes in the peripheral blood might indicate higher bone tissue destruction activity in RA patients treated with methotrexate. The clinical study registration number is 0120.0810610.

Effect of N-salicyloyltryptamine (STP), a novel tryptamine analogue, on parameters of cell viability, oxidative stress, and immunomodulation in RAW 264.7 macrophages

Immunomodulatory actions exerted by some classes of tryptamines, such as benzoyltryptamine analogues, suggest these molecules as promising candidates to develop new therapies to treat conditions associated to acute and chronic pain and inflammation. N-salicyloyltryptamine (STP) was observed to act as an anticonvulsive agent and exert antinociceptive effects in mouse. In the present work, we performed a screening of cytotoxic, cytoprotective, immunomodulatory, and redox properties of STP in RAW 264.7 macrophages challenged with hydrogen peroxide and LPS. Our results show that STP presents no cytotoxicity in the range of 0.001 to 1 μg/mL, but doses of 50 and 100 μg/mL caused loss of cell viability (IC(50) = 22.75 μg/mL). Similarly, STP at 0.001 to 1 μg/mL did not cause oxidative stress to RAW 264.7 cells, although it did not prevent cell death induced by H(2)O(2) 0.5 mM. At 1 μg/mL, STP reversed some redox and inflammatory parameters induced by LPS. These include thiol (sulfhydryl) oxidation, superoxide dismutase activation, and morphological changes associated to macrophage activation. Besides, STP significantly inhibited LPS-induced TNF-α and IL-1β release, as well as CD40 and TNF-α protein upregulation. Signaling events induced by LPS, such as phosphorylation of ERK 1/2 and IκBα and p65 nuclear translocation (NF-kB activation) were also inhibited by STP. These data indicate that STP is able to modulate inflammatory parameters at doses that do not interfere in cell viability.

Anti-inflammatory and immune-modulating effect of Ulmus davidiana var. japonica Nakai extract on a macrophage cell line and immune cells in the mouse small intestine

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Oriental medicine has utilized the barks of the stem and root of Ulmus davidiana var. japonica Nakai (UD) to treat inflammatory disorders.

AIM OF THE STUDY

The purpose of the present study was to evaluate UD's anti-inflammatory and immune-modulating effects on a lipopolysaccharide (LPS)-stimulated macrophage cell line and small-intestinal lamina propria (LP) cells, respectively.

MATERIALS AND METHODS

RAW 264.7 cells were stimulated with LPS in the presence of various concentrations of a UD water-soluble extract. Cell viability, nitric oxide (NO) production, and the level of inflammatory cytokines synthesis were measured. Among the mice receiving the UD water-soluble extract, changes in the LP cell populations and immunoglobulin (Ig)A production were evaluated.

RESULTS

The UD water-soluble extract inhibited LPS-induced NO synthesis and inflammatory cytokine production in a RAW264.7 macrophage-like cell line. Small-intestinal LP cells isolated from mice that received the UD extract displayed a decrease in the side scatter of medium-to-high cells. Those LP cells isolated from the UD-treated mice also showed a marked decrease of intracellular IgA. However, UD administration had no apparent effect on the synthesis of systemic inflammatory cytokines.

CONCLUSIONS

These results suggest that UD water-soluble extracts have anti-inflammatory properties and, as such, can be used to promote intestinal immune-homeostatic conditions.

Metformin: the hidden chronicles of a magic drug

Metformin, a biguanide is well known treatment for type 2 diabetes mellitus that has diverse mechanism of actions. Various studies have elucidated the role of this drug in different pathologies. The well-known United Kingdom Prospective Diabetic Study (UKPDS) has observed its survival benefits in a large cohort of individuals. Data has been conclusive that metformin also has beneficial role in lipid disorders as it improves the markers of metabolic syndrome. Studies have also shown the beneficial roles in antipsychotic induced weight gain as well as HIV lipodystrophy syndrome. Evidence is accumulating that metformin also improves the fertility in females with Polycystic Ovarian Syndrome (PCOS). It also delays aging and is effective in aging related disorders and is equally effective in inflammation related disorders at least in different rodent studies. Metformin's major effect has been shown in various cancers ranging from solid to hematological malignancies. Researchers are working to reveal more benefits of this magic drug but it remains an unexplored territory for the medical community.

Modeling and experimental analyses reveals signaling plasticity in a bi-modular assembly of CD40 receptor activated kinases

Depending on the strength of signal dose, CD40 receptor (CD40) controls ERK-1/2 and p38MAPK activation. At low signal dose, ERK-1/2 is maximally phosphorylated but p38MAPK is minimally phosphorylated; as the signal dose increases, ERK-1/2 phosphorylation is reduced whereas p38MAPK phosphorylation is reciprocally enhanced. The mechanism of reciprocal activation of these two MAPKs remains un-elucidated. Here, our computational model, coupled to experimental perturbations, shows that the observed reciprocity is a system-level behavior of an assembly of kinases arranged in two modules. Experimental perturbations with kinase inhibitors suggest that a minimum of two trans-modular negative feedback loops are required to reproduce the experimentally observed reciprocity. The bi-modular architecture of the signaling pathways endows the system with an inherent plasticity which is further expressed in the skewing of the CD40-induced productions of IL-10 and IL-12, the respective anti-inflammatory and pro-inflammatory cytokines. Targeting the plasticity of CD40 signaling significantly reduces Leishmania major infection in a susceptible mouse strain. Thus, for the first time, using CD40 signaling as a model, we show how a bi-modular assembly of kinases imposes reciprocity to a receptor signaling. The findings unravel that the signalling plasticity is inherent to a reciprocal system and that the principle can be used for designing a therapy.

Phosphatidylinositol-3-kinase activity during in vitro dendritic cell generation determines suppressive or stimulatory capacity

Modulating PI3K at different stages of dendritic cells (DC) generation could be a novel means to balance the generation of immunosuppressive versus immunostimulatory DC. We show that PI3K inhibition during mouse DC generation in vitro results in cells that are potently immunosuppressive and characteristic of CD8alpha- CD11c+ CD11b+ DC. These DC exhibited low surface class I and class II MHC, CD40, and CD86 and did not produce TNF-alpha. In allogeneic MLR, these DC were suppressive. Although in these mixed cultures, there was no increase in the frequency of CD4+ CD25+ Foxp3+ cells, the Foxp3 content on a per cell basis was significantly increased. Sustained TLR9 signaling in the presence of PI3K inhibition during DC generation overrode the cells' suppressive phenotype.

Sustained T cell Rap1 signaling is protective in the collagen-induced arthritis model of rheumatoid arthritis

OBJECTIVE

Defective activation of T cell receptor-proximal signaling proteins, such as the small GTPase Rap1, is thought to contribute to the pathologic behavior of rheumatoid arthritis (RA) synovial T cells. This study was undertaken to determine whether maintaining Rap1 signaling in murine T cells modifies disease onset or severity in collagen-induced arthritis (CIA).

METHODS

CIA experiments were conducted using wild-type and RapV12-transgenic mice, which express an active mutant of Rap1 in the T cell compartment. Mice were assessed using macroscopic, microscopic, and radiologic measures, and serum levels of anticollagen antibodies were measured by enzyme-linked immunosorbent assay. Phenotypic and functional characterization of wild-type and RapV12-transgenic T cells under homeostatic conditions and during disease onset was performed by flow cytometry.

RESULTS

Disease incidence and severity, synovial infiltration, joint destruction, and anticollagen antibody production were significantly reduced in RapV12-transgenic mice. Although the numbers and percentages of CD3+, CD4+, and CD8+ (naive, effector, and memory) T cells, Treg cells, and Th17 cells were equivalent in wild-type and RapV12-transgenic mice, a significant decrease in the percentage of tumor necrosis factor α-secreting CD8+ T cells was observed in RapV12-transgenic mice during CIA. RapV12-transgenic T cells also inefficiently expressed inducible costimulator and CD40L costimulatory proteins involved in B cell immunoglobulin class switching.

CONCLUSION

Our findings indicate that maintenance of T cell Rap1 signaling in murine T cells reduces disease incidence and severity in CIA, which are associated with specific defects in T cell effector function. Therefore, the restoration of Rap1 function in RA synovial T cells may have therapeutic benefit in RA.

Mammalian target of rapamycin signaling is crucial for joint destruction in experimental arthritis and is activated in osteoclasts from patients with rheumatoid arthritis

OBJECTIVE

Activation of the mammalian target of rapamycin (mTOR) pathway is important for immune cell activation and bone metabolism. To date, the contribution of mTOR signaling to joint inflammation and structural bone and cartilage damage is unknown. The aim of this study was to investigate the potential of inhibiting mTOR as a treatment of inflammatory arthritis.

METHODS

Human tumor necrosis factor-transgenic mice in which inflammatory arthritis was developing were treated with 2 different mTOR inhibitors, sirolimus or everolimus. The effects of treatment on clinical disease activity, inflammation, and localized joint and cartilage destruction were studied. In addition, the effects of mTOR inhibition on osteoclast survival and expression of key molecules of osteoclast function were analyzed in vitro. Moreover, synovial tissue from patients with rheumatoid arthritis (RA) was assessed for activation of the mTOR pathway.

RESULTS

Inhibition of mTOR by sirolimus or everolimus reduced synovial osteoclast formation and protected against local bone erosions and cartilage loss. Clinical signs of arthritis improved after mTOR inhibition, and histologic evaluation showed a decrease in synovitis. In vitro, mTOR inhibition down-regulated the expression of digestive enzymes and led to osteoclast apoptosis. Moreover, mTOR signaling was shown to be active in the synovial membrane of patients with RA, particularly in synovial osteoclasts.

CONCLUSION

Signaling through mTOR is an important link between synovitis and structural damage in inflammatory arthritis. Current pharmacologic inhibitors of mTOR could be effective in protecting joints against structural damage.

A Rac1 inhibitory peptide suppresses antibody production and paw swelling in the murine collagen-induced arthritis model of rheumatoid arthritis

INTRODUCTION

The Rho family GTPase Rac1 regulates cytoskeletal rearrangements crucial for the recruitment, extravasation and activation of leukocytes at sites of inflammation. Rac1 signaling also promotes the activation and survival of lymphocytes and osteoclasts. Therefore, we assessed the ability of a cell-permeable Rac1 carboxy-terminal inhibitory peptide to modulate disease in mice with collagen-induced arthritis (CIA).

METHODS

CIA was induced in DBA/1 mice, and in either early or chronic disease, mice were treated three times per week by intraperitoneal injection with control peptide or Rac1 inhibitory peptide. Effects on disease progression were assessed by measurement of paw swelling. Inflammation and joint destruction were examined by histology and radiology. Serum levels of anti-collagen type II antibodies were measured by enzyme-linked immunosorbent assay. T-cell phenotypes and activation were assessed by fluorescence-activated cell sorting analysis. Results were analyzed using Mann-Whitney U and unpaired Student t tests.

RESULTS

Treatment of mice with Rac1 inhibitory peptide resulted in a decrease in paw swelling in early disease and to a lesser extent in more chronic arthritis. Of interest, while joint destruction was unaffected by Rac1 inhibitory peptide, anti-collagen type II antibody production was significantly diminished in treated mice, in both early and chronic arthritis. Ex vivo, Rac1 inhibitory peptide suppressed T-cell receptor/CD28-dependent production of tumor necrosis factor alpha, interferon gamma and interleukin-17 by T cells from collagen-primed mice, and reduced induction of ICOS and CD154, T-cell costimulatory proteins important for B-cell help.

CONCLUSIONS

The data suggest that targeting of Rac1 with the Rac1 carboxy-terminal inhibitory peptide may suppress T-cell activation and autoantibody production in autoimmune disease. Whether this could translate into clinically meaningful improvement remains to be shown.

Oxaprozin-induced apoptosis on CD40 ligand-treated human primary monocytes is associated with the modulation of defined intracellular pathways

The modulation of CD40L activity might represent a promising therapeutic target to reduce monocyte inflammatory functions in chronic diseases, such as rheumatoid arthritis. In the present study, we investigated the possible influence of nonsteroidal anti-inflammatory drugs (NSAIDs) on CD40L-induced monocyte survival. Monocytes were isolated from buffy coats by using Ficoll-Percoll gradients. Monocyte apoptosis was evaluated by fluorescence microscopy on cytopreps stained with acridine orange or using flow cytometry analysis of Annexin-V and Propidium Iodide staining. Akt and NF-κB activation was assessed using western blot. Caspase 3 activity was determined spectrophotometrically. Among different NSAIDs, only oxaprozin dose-dependently increased apoptosis of CD40L-treated monocytes. Oxaprozin pro-apoptotic activity was associated with the inhibition of CD40L-triggered Akt and NF-κB phosphorylation and the activation of caspase 3. In conclusion, our data suggest that oxaprozin-induced apoptosis in CD40L-treated human monocytes is associated with previously unknown cyclooxygenase (COX)-independent pathways. These intracellular proteins might be promising pharmacological targets to increase apoptosis in CD40L-treated monocytes.

Latent membrane protein 1 of EBV activates phosphatidylinositol 3-kinase to induce production of IL-10

EBV is a B lymphotrophic gamma-herpesvirus that is associated with multiple human malignancies, including posttransplant lymphoproliferative disorder. The EBV-encoded protein, latent membrane protein 1 (LMP1), is required for oncogenic transformation of human B cells by EBV. An important consequence of LMP1 expression in EBV-infected B cells is the induction of cellular IL-10, which acts as an autocrine growth factor for B cell lymphomas. However, the mechanisms by which LMP1 induces IL-10 are incompletely understood. We previously showed that rapamycin, a clinically relevant immunosuppressant and mammalian target of rapamycin inhibitor, could suppress IL-10 production by EBV-infected B cell lines. To test the hypothesis that PI3K, which acts upstream of mammalian target of rapamycin, might also be involved in LMP1-dependent IL-10 production, we generated B cell lines expressing signaling-inducible chimeric LMP1. Our results show that induced LMP1 signaling elicits both p38- and PI3K-dependent IL-10 production in EBV- B cells. Moreover, distinct regions of the LMP1 signaling tail are associated with p38- vs PI3K-dependent IL-10 induction. We also demonstrate that the LMP1-dependent p38 and PI3K activation regulates IL-10 induction through discrete mechanisms. Whereas p38 activation is critical for the phosphorylation of the transcription factor CREB, PI3K activation is required for the inactivation of glycogen synthase kinase 3beta (GSK3beta), an inhibitory kinase that can regulate CREB function. We find that GSK3beta regulates LMP1-dependent IL-10 induction, with GSK3beta inhibition by pharmacologic or small interfering RNA strategies enhancing LMP1-induced IL-10 induction. These findings demonstrate that LMP1 uses both p38 and PI3K activation for maximal up-regulation of IL-10.

Interaction between Transmembrane TNF and TNFR1/2 Mediates the Activation of Monocytes by Contact with T Cells

Monocytes and monocytic cells produce proinflammatory cytokines upon direct cell contact with activated T cells. In the autoimmune disease rheumatoid arthritis, the pivotal role of TNF-alpha implies that the interaction between transmembrane TNF-alpha (mTNF) and the TNF receptors (TNFR1 and TNFR2) might participate in the T cell contact-dependent activation of monocytes. Accordingly, treatment of rheumatoid arthritis by administration of a TNF-alpha-blocking Ab was found to significantly decrease TNF-alpha production by monocytes. Several lines of evidence indicated that signaling through TNFR1/2 and through mTNF (reverse signaling) is involved in TNF-alpha production by monocytes after T cell contact: 1) blocking mTNF on activated T cells leads to a significant reduction in TNF-alpha production; 2) down-regulation of TNFR1/2 on monocytes by transfection with small interfering RNA results in diminished TNF-alpha production; 3) blocking or down-regulating TNFR2 on activated T cells inhibits TNF-alpha production, indicating that mTNF on the monocyte surface mediates signaling; 4) ligation of mTNF on monocytes by surface TNFR2 transfected into resting T cells induces TNF-alpha production due to reverse signaling by mTNF; and 5) ligation of mTNF on monocytes by a soluble TNFR2:Ig receptor construct induces TNF-alpha production due to reverse signaling. In conclusion, we identified mTNF and TNFR1/2 as interaction partners contributing to TNF-alpha production in monocytes. Both pathways initiated by mTNF-TNFR interaction are likely to be inhibited by treatment with anti-TNF-alpha Abs.

Phosphoinositide 3-kinase signalling and FoxO transcription factors in rheumatoid arthritis

Although the mechanisms leading to the induction of RA (rheumatoid arthritis) are poorly understood, improper activation, proliferation, survival and retention of neutrophils, macrophages, lymphocytes and other leucocytes contribute to perpetuation of inflammation and eventual joint destruction through activation of stromal fibroblast-like synoviocytes. Fundamental studies in developmental biology, cellular biology and immunology have established critical roles for PI3K (phosphoinositide 3-kinase) signal transduction pathways in cellular chemotactic responses, proliferation, apoptosis and survival. Despite profound alteration of these cellular processes in RA, involvement of PI3K signalling pathways in this chronic inflammatory disease, and their assessment as potential therapeutic targets, has until recently received scant attention. This review highlights recent advances in our understanding of PI3K signalling pathways, in particular regulation of FoxO (forkhead box O) transcription factors, and their relevance to RA.

Inhibition of forkhead box class O family member transcription factors in rheumatoid synovial tissue

OBJECTIVE

Phosphatidylinositol 3-kinase-dependent activation of protein kinase B (PKB) has been observed in rheumatoid arthritis (RA) synovial tissue, and mechanisms that interfere with this process are protective in animal models of arthritis. PKB can regulate cell survival and proliferation via phosphorylation-dependent inactivation of forkhead box class O (FoxO) transcription factors. The present study was undertaken to examine whether FoxO transcription factors are differentially inactivated in RA synovial tissue, and whether this inactivation correlates with laboratory and clinical parameters of disease activity.

METHODS

The expression and phosphorylation of FoxO family members were assessed in synovial biopsy tissue from 12 patients with RA and 9 patients with inflammatory osteoarthritis (OA), by immunohistochemistry and quantitative computer-assisted image analysis. Immunoblotting was used to assess the interleukin-1beta (IL-1beta)- and tumor necrosis factor alpha (TNFalpha)-induced phosphorylation of FoxO1 and FoxO4 in cultured fibroblast-like synoviocytes (FLS) and macrophages.

RESULTS

FoxO1, FoxO3a, and FoxO4 were expressed and phosphorylated in synovial tissue from both RA patients and OA patients. In RA synovial tissue, phosphorylation of FoxO1 was observed in both FLS and macrophages, FoxO3a in T lymphocytes, and FoxO4 in macrophages alone. Following stimulation with IL-1beta and TNFalpha, FoxO1 and FoxO4 were phosphorylated in both RA and OA FLS and synovial macrophages, respectively. Inactivation of FoxO4 was significantly enhanced in the RA as compared with the OA synovial sublining. There was a strong negative correlation between inactivation of FoxO4 in RA synovial tissue and increased serum C-reactive protein levels and a raised erythrocyte sedimentation rate in RA patients.

CONCLUSION

All 3 FoxO family members examined were phosphorylated in both RA and OA synovial tissue; in particular, inactivation of FoxO4 was significantly enhanced in macrophages from RA synovial tissue. Thus, cell-specific inactivation of FoxO family members appears to differentially regulate cell survival and proliferation in the RA synovium.

Differential regulation of interleukin-12 and tumour necrosis factor-alpha by phosphatidylinositol 3-kinase and ERK 1/2 pathways during Mycobacterium tuberculosis infection

Interleukin (IL)-12 and tumour necrosis factor (TNF)-alpha are both thought to be critical factors in the defence against mycobacteria but are known to play different roles. In this study, we investigated the regulatory pathways for IL-12 and TNF-alpha expression in human monocyte-derived macrophages (MDMs) after treatment with Mycobacterium tuberculosis H37Rv or the Triton X-100 solubilized proteins (TSP) purified from M. tuberculosis. We found a rapid phosphorylation of Akt and extracellular signal-regulated kinase (ERK), albeit with differential activation kinetics, in human MDMs treated with M. tuberculosis or TSP. Studies using inhibitors selective for phosphatidylinositol 3-kinase (PI 3-K) and ERK 1/2 show that both pathway plays an essential role in the induction of TNF-alpha at both the transcriptional and translational levels in human MDMs. In contrast, blockade of the PI 3-K/Akt or ERK 1/2 pathways significantly increased M. tuberculosis- or TSP-induced IL-12 p40 and p35 mRNA and bioactive p70 protein. The enhancement of IL-12 levels by inhibition of PI 3-K and ERK 1/2 was not reversed by neutralization of TNF-alpha or addition of rhTNF-alpha, suggesting that the negative regulation of IL-12 is not mediated by concomitant TNF-alpha suppression. Further, PI 3-K activity is required for the M. tuberculosis- or TSP-induced phosphorylation of ERK 1/2 activation. TSP from M. tuberculosis shows a similar dependency on the PI 3-K and ERK 1/2 pathways to those by M. tuberculosis. Collectively, these data suggest that the Th1-driving cytokine IL-12 and proinflammatory cytokine TNF-alpha are differentially regulated by PI 3-K and ERK 1/2 pathways in human MDMs during mycobacterial infection. These results may provide therapeutic targets for precise and specific fine-tuning of cytokine responses.

Alternative signaling pathways: when, where and why?

Alternative cell signal transduction pathways have been demonstrated in some experimental systems. The importance of their existence has not been completely appreciated. In this review we present the cases of alternative pathways resulted from a survey of the available experimental data. The alternative pathways could show different relationships, i.e., synergistic, redundant, additive, opposite and competitive effects. They could have distinct time courses and cell, organ, sex or species specification. Further, they could happen during physiological or pathological situations, and display differentiated sensitivity. These case studies together imply that alternative signal pathways could be involved in the regulation of cell functions at the pathway level. In-depth understanding of the importance of the alternative pathways will rely on building and exploration of mathematical models.

[T cell-dependent monocyte activation, TNFalpha and apolipoprotein A-I in autoimmunity and inflammation]

Rheumatoid arthritis is characterized by a massive overproduction of monokines like TNFalpha, IL-6 and IL-1beta, which are predominantly produced by monocytes and macrophages. To date, the exact mechanisms of monocyte/macrophage activation have not been fully elucidated. One possible mechanism is their cell contact-dependent activation by activated T cells. The direct cell contact of monocytes/macrophages and T cells leads to an increased production of pro-inflammatory cytokines such as TNFalpha and IL-1beta. Stringent control of this mechanism by inhibitory factors appears mandatory under physiological conditions in order to avoid systemic cytokine release syndromes. The presence of inhibitory factors in the serum could represent such a mechanism. In healthy donors, apolipoprotein A-I was identified as such an inhibitory serum protein. In patients with rheumatoid arthritis, apolipoprotein A-I is found in decreased concentrations, possibly due to its role as a negative acute phase protein. The role of this and other inhibitory serum molecules are discussed.

The contact-mediated response of peripheral-blood monocytes to preactivated T cells is suppressed by serum factors in rheumatoid arthritis

Stimulation of monocytes/macrophages after cell contact with preactivated T cells has been suggested to contribute to the excessive TNF-α production in rheumatoid arthritis (RA). In this study, T cell-contact-dependent TNF-α production by peripheral-blood monocytes in vitro was investigated and found to be significantly lower in treated and untreated patients with RA than in healthy controls. This suppression was not due to a general deficiency of monocytes to respond, because responses to lipopolysaccharide were comparable in patients and controls. In agreement with the pivotal role of TNF-α in RA, T cell-dependent induction of TNF-α in synovial macrophages was fivefold to tenfold higher than in peripheral-blood monocytes from either patients or controls. The decreased response of peripheral-blood monocytes from patients with RA was found to be mediated by inhibitory serum factors, because the addition of patient sera to monocytes from healthy controls suppressed TNF-α response in the co-culture assay. Preincubation of monocytes from healthy controls with RA serum was sufficient to suppress the subsequent TNF-α response in T cell co-cultures, indicating that inhibitory factors do indeed bind to monocyte surfaces, which might represent a regulatory counter-action of the immune system to the long-standing and consuming autoimmune process in RA. There are some indications that apolipoprotein A-1 might be part of this regulatory system.

CD40 ligation activates murine macrophages via an IFN-gamma-dependent mechanism resulting in tumor cell destruction in vitro

We have shown previously that agonistic anti-CD40 mAb induced T cell-independent antitumor effects in vivo. In this study, we investigated mechanisms of macrophage activation with anti-CD40 mAb treatment, assessed by the antitumor action of macrophages in vitro. Intraperitoneal injection of anti-CD40 mAb into C57BL/6 mice resulted in activation of peritoneal macrophages capable of suppressing B16 melanoma cell proliferation in vitro, an effect that was greatly enhanced by LPS and observed against several murine and human tumor cell lines. Anti-CD40 mAb also primed macrophages in vitro to mediate cytostatic effects in the presence of LPS. The tumoristatic effect of CD40 ligation-activated macrophages was associated with apoptosis and killing of tumor cells. Activation of macrophages by anti-CD40 mAb required endogenous IFN-gamma because priming of macrophages by anti-CD40 mAb was abrogated in the presence of anti-IFN-gamma mAb, as well as in IFN-gamma-knockout mice. Macrophages obtained either from C57BL/6 mice depleted of T and NK cells by Ab treatment, or from scid/beige mice, were still activated by anti-CD40 mAb to mediate cytostatic activity. These results argued against the role of NK and T cells as the sole source of exogenous IFN-gamma for macrophage activation and suggested that anti-CD40 mAb-activated macrophages could produce IFN-gamma. We confirmed this hypothesis by detecting intracytoplasmic IFN-gamma in macrophages activated with anti-CD40 mAb in vivo or in vitro. IFN-gamma production by macrophages was dependent on IL-12. Taken together, the results show that murine macrophages are activated directly by anti-CD40 mAb to secrete IFN-gamma and mediate tumor cell destruction.

Fc receptor γ-chain activation via hOSCAR induces survival and maturation of dendritic cells and modulates Toll-like receptor responses

We previously reported the characterization of human osteoclast-associated receptor (hOSCAR), a novel Fc receptor γ-chain (FcRγ)–associated receptor expressed by myeloid cells. Here we show that ligation of hOSCAR by specific antibodies promotes dendritic cell (DC) survival by an extracellular signal-regulated kinase (ERK)- and phosphatidylinositol 3-kinase (PI3K)–dependent pathway, linked to expression of the Bcl-2 and Bcl-xL antiapoptotic molecules. Crosslinking of hOSCAR leads to maturation of DCs, as demonstrated by up-regulation of maturation markers, decrease in dextran uptake capacity, and secretion of immunesystem effectors such as interleukin-8 (IL-8)/CXC chemokine ligand 8 (CXCL8), IL-12 p40, monocyte chemoattractant protein-1 (MCP-1)/chemokine receptor ligand 2 (CCL2) and macrophage-derived chemokine (MDC)/CCL22. Stimulation of hOSCAR acts in conjunction with the Toll-like receptor (TLR) ligands, lipopolysaccharide (LPS), R-848, and polyinosinic-polycytidylic acid (poly(I:C)), to increase the expression of maturation markers, and to modulate cytokine release. A PI3K-dependent up-regulation of IL-10 release is observed with all the TLR ligands used, whereas regulation of IL-12 production is variable depending on the TLR stimulated. hOSCAR engagement on DCs did not significantly increase the proliferation of naive T cells; however, when co-incubated with TLR ligands, an enhanced proliferation was observed. The percentage of interferon (IFN)–γ–producing T cells is decreased when hOSCAR engagement is combined with LPS stimulation. Altogether, these data suggest that hOSCAR may modulate the responses of both innate resistance and adaptive immunity.

The production of IL-1 receptor antagonist in IFN-beta-stimulated human monocytes depends on the activation of phosphatidylinositol 3-kinase but not of STAT1

IFN-beta induces the production of secreted IL-1R antagonist (sIL-1Ra) without triggering synthesis of the agonist IL-1beta in human monocytes. This might account for its anti-inflammatory properties. Canonically, IFN-beta signals through activation of JAK/STAT pathway, although PI3K and MAPK have also been involved. In this study, the role of PI3K, MEK1, and STAT1 in IFN-beta-induced sIL-1Ra production is investigated in freshly isolated human blood monocytes. PI3K, but not MEK1 activation is essential for sIL-1Ra production in monocytes treated with IFN-beta, as demonstrated by using the respective inhibitors of PI3K and MEK1, Ly294002 and PD98059. The use of cycloheximide and actinomycin D shows that sIL-1Ra was an immediate early gene induced by IFN-beta and that PI3K was controlling sIL-1Ra gene transcription. Although both inhibitors of PI3K and MEK1 diminished the Ser(727) phosphorylation of STAT1 induced by IFN-beta, only Ly294002 inhibited sIL-1Ra production. Furthermore, the inhibition of STAT1-Ser(727) phosphorylation by Ly294002 did not affect STAT1 translocation, suggesting that STAT1 was not involved in sIL-1Ra gene induction. This was confirmed in monocytes that were transfected with small interfering RNA specifically targeting STAT1. Indeed, monocytes in which effective STAT1 gene knockdown was achieved were fully responsive to IFN-beta in terms of sIL-1Ra production. Taken together, the present data demonstrate that the induction of sIL-1Ra transcription and production by IFN-beta in human monocytes involved PI3K, but not STAT1 activation.

CD40 signaling induces reciprocal outcomes in Leishmania-infected macrophages; roles of host genotype and cytokine milieu

We investigated the influence of CD40-CD40 ligand-mediated signaling on induction of microbicidal activity against Leishmania major in macrophages from resistant (B6) and susceptible (BALB) mouse strains. CD40 engagement induced leishmanicidal activity in resistant macrophages, but increased parasite replication in susceptible macrophages. CD40 engagement induced comparable TNF-alpha production in macrophages from both strains. However, increased IL-10 production was restricted to susceptible macrophages. Increased parasite replication in susceptible macrophages was prevented by a neutralizing anti-IL-10 antibody. In the presence of IFN-gamma, CD40 engagement induced Leishmania killing by macrophages from both strains. Therefore, the outcome of CD40 signaling on effector responses against L. major depends on host genotype and the cytokine milieu, and a source of IFN-gamma is required for a protective response.

Diminished bacterial clearance is associated with decreased IL-12 and interferon-gamma production but a sustained proinflammatory response in a murine model of postseptic immunosuppression

After a major illness or injury, immune status in critically ill patients may fluctuate between a marked proinflammatory response and an immunosuppressed state. Postinflammatory immunosuppression can result in increased susceptibility to infection. Alterations of cytokine production, such as suppression of IFNgamma and elevation of the anti-inflammatory cytokine IL-10, are believed to contribute to postinflammatory immunosuppression. We examined antimicrobial immunity in mice that had previously been subjected to a sublethal cecal ligation and puncture (CLP) as a model of major injury. Mice were challenged with Pseudomonas aeruginosa (5 x 10(7) CFU i.v.) on day 5 after CLP or sham surgery. Bacterial clearance in mice after CLP was impaired and associated with decreased production of IFNgamma and increased production of IL-10 in the early response to the Pseudomonas challenge. Pseudomonas-induced production of the IFNgamma-inducing factor IL-12 was also decreased in post-CLP mice. However, splenocytes from post-CLP mice remained responsive to exogenous stimulation with the IFNgamma-inducing cytokines IL-12, IL-15, and IL-18 as well as T-cell receptor activation. Furthermore, production of the proinflammatory cytokines TNF-alpha, IL-1beta, and IL-6 were as high, or higher, in the post-CLP group compared with sham mice after P. aeruginosa challenge. Blockade of IL-10 did not reverse IL-12 and IFNgamma suppression in splenocytes from post-CLP mice. These studies show that suppressed bacterial clearance in post-CLP mice is associated with decreased production of IFNgamma and IL-12 and with increased production of IL-10 and proinflammatory cytokines.

Conventional protein kinase C and atypical protein kinase Czeta differentially regulate macrophage production of tumour necrosis factor-alpha and interleukin-10

In chronic inflammatory diseases such as rheumatoid arthritis, joint macrophages/monocytes are the major source of pro- and anti-inflammatory cytokines. Little is understood regarding the signalling pathways which determine the production of the pro-inflammatory cytokine, tumour necrosis factor-alpha (TNF-alpha) and the anti-inflammatory cytokine, interleukin-10 (IL-10). Two pathways integral to macrophage function are the protein kinase C (PKC)- and the cAMP-dependent pathways. In this report, we have investigated the involvement of PKC and cAMP in the production of TNF-alpha and IL-10 by peripheral blood monocyte-derived macrophages. The utilization of the PKC inhibitors Go6983, Go6976 and RO-32-0432 demonstrated a role for conventional PKCs (alpha and beta) in the production of TNF-alpha in response to stimulation by lipopolysaccharide and phorbol 12-myristate 13-acetate (PMA)/ionomycin. PKC stimulation resulted in the downstream activation of the p42/44 mitogen-activated protein kinase (MAPK) pathway which differentially regulates TNF-alpha and IL-10. The addition of cAMP however, suppressed activation of this MAPK and TNF-alpha production. Cyclic-AMP augmented IL-10 production and cAMP response element binding protein activation upon stimulation by PMA/ionomycin. In addition, cAMP activated PKCzeta; inhibition of which, by a dominant negative adenovirus construct, selectively suppressed IL-10 production. These observations suggest that pro-inflammatory and anti-inflammatory cytokines are differentially regulated by PKC isoforms; TNF-alpha being dependent on conventional PKCs (alpha and beta) whereas IL-10 is regulated by the cAMP-regulated atypical PKCzeta.

PI3K inhibitors block skeletogenesis but not patterning in sea urchin embryos

Skeletogenesis in the sea urchin embryo is a simple model of biomineralization, pattern formation, and cell-cell communication during embryonic development. The calcium carbonate skeletal spicules are secreted by primary mesenchyme cells (PMCs), but the skeletal pattern is dictated by the embryonic ectoderm. Although the process of skeletogenesis is well characterized, there is little molecular understanding of the basis of patterning within this system. In this study, we examined the contribution of phosphatidylinositide 3-kinase (PI3K)-mediated signaling to the skeletogenic process in sea urchin embryos by using the well-established PI3K inhibitors LY294002 and wortmannin. Our results show that PI3K inhibitors specifically and reversibly block skeletogenesis, and that this blockade occurs within the PMCs rather than in the ectoderm, because the inhibitors block spiculogenesis in cultured micromeres. Our results are consistent with a model in which PI3K signaling is required, not for pattern sensing or interpretation but rather for the biomineralization process itself in the sea urchin embryo.

Interleukin-10 and the regulation of mitogen-activated protein kinases: are these signalling modules targets for the anti-inflammatory action of this cytokine?

The many specific, yet overlapping and redundant activities of individual cytokines have been the basis for current concepts of therapeutical intervention. Cytokines are powerful two-edged weapons that can trigger a cascade of reactions and may show activities that often go beyond the single highly specific property that it is hoped they possess. Nevertheless, it can be stated that our new, though burgeoning, understanding of the biological mechanisms governing cytokine actions is an important contribution to medical knowledge. The crucial role of the anti-inflammatory cytokine, interleukin (IL)-10, in regulating potential molecular pathway mediating injury and cell death has attracted paramount attention in recent years. In this respect, the mitogen-activated protein kinase (MAPK) components have emerged as potential signalling cascades that regulate a plethora of cell functions, including inflammation and cell death. The biochemistry and molecular biology of cytokine actions, particularly IL-10, explain some well known and sometimes also some of the more obscure clinical aspects of the evolution of diseases.