Costimulation with interleukin-4 and interleukin-10 induces mast cell apoptosis and cell-cycle arrest: the role of p53 and the mitochondrion

Utilizing mast cells in a positive manner to overcome inflammatory and allergic diseases

Mast cells (MCs) are immune cells widely distributed in the body, accompanied by diverse phenotypes and functions. Committed mast cell precursors (MCPs) leave the bone marrow and enter the blood circulation, homing to peripheral sites under the control of various molecules from different microenvironments, where they eventually differentiate and mature. Partly attributable to the unique maturation mechanism, MCs display high functional heterogeneity and potentially plastic phenotypes. High plasticity also means that MCs can exhibit different subtypes to cope with different microenvironments, which we call “the peripheral immune education system”. Under the peripheral immune education system, MCs showed a new character from previous cognition in some cases, namely regulation of allergy and inflammation. In this review, we focus on the mucosal tissues, such as the gastrointestinal tract, to gain insights into the mechanism underlying the migration of MCs to the gut or other organs and their heterogeneity, which is driven by different microenvironments. In particular, the immunosuppressive properties of MCs let us consider that positively utilizing MCs may be a new way to overcome inflammatory and allergic disorders.

IL-10 in Mast Cell-Mediated Immune Responses: Anti-Inflammatory and Proinflammatory Roles

Mast cells (MCs) play critical roles in Th2 immune responses, including the defense against parasitic infections and the initiation of type I allergic reactions. In addition, MCs are involved in several immune-related responses, including those in bacterial infections, autoimmune diseases, inflammatory bowel diseases, cancers, allograft rejections, and lifestyle diseases. Whereas antigen-specific IgE is a well-known activator of MCs, which express FcεRI on the cell surface, other receptors for cytokines, growth factors, pathogen-associated molecular patterns, and damage-associated molecular patterns also function as triggers of MC stimulation, resulting in the release of chemical mediators, eicosanoids, and various cytokines. In this review, we focus on the role of interleukin (IL)-10, an anti-inflammatory cytokine, in MC-mediated immune responses, in which MCs play roles not only as initiators of the immune response but also as suppressors of excessive inflammation. IL-10 exhibits diverse effects on the proliferation, differentiation, survival, and activation of MCs in vivo and in vitro. Furthermore, IL-10 derived from MCs exerts beneficial and detrimental effects on the maintenance of tissue homeostasis and in several immune-related diseases including contact hypersensitivity, auto-immune diseases, and infections. This review introduces the effects of IL-10 on various events in MCs, and the roles of MCs in IL-10-related immune responses and as a source of IL-10.

Impact of inflammatory signaling on radiation biodosimetry: mouse model of inflammatory bowel disease

Background

Ionizing Radiation (IR) is a known pro-inflammatory agent and in the process of development of biomarkers for radiation biodosimetry, a chronic inflammatory disease condition could act as a confounding factor. Hence, it is important to develop radiation signatures that can distinguish between IR-induced inflammatory responses and pre-existing disease. In this study, we compared the gene expression response of a genetically modified mouse model of inflammatory bowel disease (Il10^−/−) with that of a normal wild-type mouse to potentially develop transcriptomics-based biodosimetry markers that can predict radiation exposure in individuals regardless of pre-existing inflammatory condition.

Results

Wild-type (WT) and Il10^−/− mice were exposed to whole body irradiation of 7 Gy X-rays. Gene expression responses were studied using high throughput whole genome microarrays in peripheral blood 24 h post-irradiation. Analysis resulted in identification of 1962 and 1844 genes differentially expressed (p < 0.001, FDR < 10%) after radiation exposure in Il10^−/− and WT mice respectively. A set of 155 genes was also identified as differentially expressed between WT and Il10^−/− mice at the baseline pre-irradiation level. Gene ontology analysis revealed that the 155 baseline differentially expressed genes were mainly involved in inflammatory response, glutathione metabolism and collagen deposition. Analysis of radiation responsive genes revealed that innate immune response and p53 signaling processes were strongly associated with up-regulated genes, whereas B-cell development process was found to be significant amongst downregulated genes in the two genotypes. However, specific immune response pathways like MHC based antigen presentation, interferon signaling and hepatic fibrosis were associated with radiation responsive genes in Il10^−/− mice but not WT mice. Further analysis using the IPA prediction tool revealed significant differences in the predicted activation status of T-cell mediated signaling as well as regulators of inflammation between WT and Il10^−/− after irradiation.

Conclusions

Using a mouse model we established that an inflammatory disease condition could affect the expression of many radiation responsive genes. Nevertheless, we identified a panel of genes that, regardless of disease condition, could predict radiation exposure. Our results highlight the need for consideration of pre-existing conditions in the population in the process of development of reliable biodosimetry markers.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5689-y) contains supplementary material, which is available to authorized users.

Apoptotic resistance of human skin mast cells is mediated by Mcl-1

Mast cells (MCs) are major effector cells of allergic reactions and contribute to multiple other pathophysiological processes. MCs are long-lived in the tissue microenvironment, in which they matured, but it remains ill-defined how longevity is established by the natural habitat, as research on human MCs chiefly employs cells generated and expanded in culture. In this study, we report that naturally differentiated skin MCs exhibit substantial resilience to cell death with considerable portions surviving up to 3 days in the complete absence of growth factors (GF). This was evidenced by kinetic resolution of membrane alterations (Annexin-V, YoPro), DNA degradation (propidium iodide), mitochondrial membrane disruption (Depsipher), and Caspase-3 activity. Because of the high basal survival, further protection by SCF was modest. Conversely, survival was severely compromised by staurosporine, implying functional caspase machinery. Contrary to the resistance of freshly purified MCs, their culture-expanded counterpart readily underwent cell death upon GF deprivation. Searching for the molecular underpinnings explaining the difference, we identified Mcl-1 as a critical protector. In fact, silencing Mcl-1 by RNAi led to impaired survival in skin MCs ex vivo, but not their cultured equivalent. Therefore, MCs matured in the skin have not only higher expression of Mcl-1 than proliferating MCs, but also greater reliance on Mcl-1 for their survival. Collectively, we report that human skin MCs display low susceptibility to cell death through vast expression of Mcl-1, which protects from mortality and may contribute to MC longevity in the tissue.

Comparative Assessment of Cytokine Pattern in Early and Late Onset of Neonatal Sepsis

Neonatal sepsis is a significant health issue associated with high mortality. Immune responses associated with neonatal sepsis, such as proinflammatory cytokine production, are believed to play a central role in the pathogenesis of this disease. In the present study, serum levels of the proinflammatory cytokines TNF-α, IL1-β, and IL-6 and the anti-inflammatory cytokines IL-4 and IL-10 were evaluated for 25 subjects with neonatal sepsis. We observed that subjects with late onset of sepsis (LOS), as well as those with early onset of sepsis (EOS), had a substantial increase in serum TNF-α. In contrast to EOS, subjects with LOS demonstrated a significant increase in serum levels IL-6 and IL-10. Additionally, we observed a significant difference in cytokine profiles between acute and postacute cases of neonatal sepsis. For instance, the level of proinflammatory cytokines, such as TNF-α and IL-6, was elevated in the acute phase, whereas the production of anti-inflammatory cytokines, such as IL-10, became substantially upregulated during the postacute phase. Additionally, no correlation was observed between cytokine levels and CRP levels or lymphocyte counts. Thus, in contrast to CRP levels and lymphocyte counts, examination of the cytokine profile can provide valuable information when determining the most effective therapy for treating neonatal sepsis. This information may be useful to physicians when determining if anti-inflammatory or immune stimulatory therapy is warranted.

Lentiviral-mediated multiple gene transfer to chondrocytes promotes chondrocyte differentiation and bone formation in rabbit bone marrow-derived mesenchymal stem cells

The aim of the present study was to provide a theoretical and experimental foundation on the differentiation of stem cells through the induction of multiple genes. The lentiviral vector carrying TGF-β1 and IL-10 genes was transfected to bone marrow-derived mesenchymal stem cells (BMSCs) which differentiated into chondrogenesis. Healthy New Zealand white rabbits, 2-3 months of age were used in the present study. A 6-8 ml of bone marrow was isolated from the iliac and tibial shaft of each rabbit. The BMSCs suspension was aspired following centrifugation of the bone marrow by percoll separating medium. The BMSCs were primarily cultured and subcultured in vitro, then divided into four groups according to the difference of lentivirus vectors: group A, receiving transforming growth factor β1 (TGF‑β1); group B, receiving TGF-β1 and Interleukin-10 (IL-10); group C, empty vector transfection; and group D, receiving no cell growth factor. Fluorescence expression was detected 12 h after transfecting the lentiviral vector carrying the TGF-β1 and IL-10 gene to BMSCs. The transfection efficiency was approximately 70% with a MOI=100 after 96 h. Expression of SOX-9 aggrecan and Type Ⅱ collagen in groups A-E on day 7 and 14 was detected by RT-PCR and western blot analysis. The expression level of three genes expressed in groups A and C were higher compared to the expression in groups B, D and E. The expression level of the three genes expressed in group B was higher compared to the expression in group D. The expression level of three genes expressed in group A and C showed no statistical difference. Cytokines therefore play an important role in cell proliferation and chondrogenic differentiation. TGF-β1 has a synergistic effect in the differentiation. In addition, IL-10 may have a protective role in the restoration of cartilaginous tissue.

Mast cell production and response to IL-4 and IL-13

IL-4 was identified as the first cytokine to be produced by mast cells and is responsible for promoting mast cell IL-13 production. IL-4 and IL-13 play a prominent role in stimulating and maintaining the allergic response. As closely related genes, IL-4 and IL-13 share a common receptor subunit, IL-4Rα, necessary for signaling. Here we summarize the literature on mast cell activation associated with IL-4 and IL-13 production, including downstream signaling. We also describe the positive and negative roles each cytokine plays in mast cell immunity and detail the differences that exist between mouse and human mast cell responses to IL-4 and IL-13.

Cytokine signaling in the differentiation of innate effector cells

Innate effector cells, including innate effector cells of myeloid and lymphoid lineages, are crucial components of various types of immune responses. Bone marrow progenitors differentiate into many subsets of innate effector cells after receiving instructional signals often provided by cytokines. Signal transducer and activator of transcription (STATs) have been shown to be essential in the differentiation of various types of innate effector cells. In this review, we focus specifically on the differentiation of innate effector cells, particularly the role of cytokine signaling in the differentiation of innate effector cells.

Selective tumor cell killing by triptolide in p53 wild-type and p53 mutant ovarian carcinomas

Triptolide is a traditional Chinese medicinal herb-derived antineoplastic agent. However, its antitumor activity against gynecologic carcinomas has not yet been well described. It is the purpose of this article to investigate the effect and mechanism of triptolide in human ovarian cancer using both A2780 (p53 wild) and OVCAR-3 (p53 mutated) cells. Our results showed that triptolide exerted a potent inhibitory effect on the growth and proliferation of both cell lines in a dose- and time-dependent manner and that the effect was independent of the expression of p53. In contrast, triptolide had only a marginal cytotoxicity in noncancerous ovary cells, lung fibroblast cells, and macrophage cells, indicating differential inhibitory effects of the drug on cell growth between ovarian cancer cells and normal tissue cells. Exposure of the ovarian cancer cells to triptolide induced apoptosis, as evaluated by annexin V/propidium iodide-labeled flow cytometry. Triptolide-induced apoptosis was accompanied by cytochrome c release and caspase-3 activation and was associated with downregulation of Bcl-2 and upregulation of Bax. Cell cycle analysis demonstrated that treatment with triptolide induced cell cycle S phase arrest in A2780 cells and G2/M phase arrest in OVCAR-3 cells. Further detection by Western blotting revealed that the cell cycle arrest by triptolide in both cell lines occurred in concert with increased expression of p21(CIP1/WAF1). This study shows that triptolide selectively kills ovarian cancer cells with different p53 status predominantly through regulating the coordinate and dynamic cellular processes of proliferation and apoptosis, thereby making it a promising chemotherapeutic agent against a broad spectrum of ovarian carcinomas.

Effects of bacterial toxins on endothelial tight junction in vitro: a mechanism-based investigation

ABSTRACT Lipopolysaccharide (LPS) and lipoteichoic acid (LTA), principal cell wall components of Gram-negative and Gram-positive bacteria, respectively, play a central role in altering the blood-brain barrier and facilitate bacterial infection of the host brain. Despite the significance of bacterial toxins in disease pathogenesis, mechanisms by which toxins impair the barrier are not yet known. This study, using an in vitro cell culture model, showed that LPS and LTA interacted with the endothelial cells and disrupted the tight junction between the cells that increased the barrier's permeability. Both toxins increased inducible nitric oxide synthase (iNOS) mRNA that is indicative of an increase in intracellular NO release, disrupted architecture of the tight junction proteins, suppressed zonula occludens-1 (ZO-1) and occludin (OCL) and junctional adhesive molecules (JAM) mRNA levels, and increased tumor necrosis factor alpha (TNFalpha) and interleukin-1 beta (IL-1beta) mRNA levels. Anti-CD14 antibodies blocked the increase in TNFalpha and IL-1beta mRNA levels but did not affect either changes in the tight junction or iNOS, ZO-1, OCL, and JAM mRNA levels in endothelial cells and astrocytes. Although both toxins did not cross the endothelial barrier, the abluminal neurons exhibited high inflammatory activity characterized by a sequential increase in TNFalpha, IL-1beta, external receptor kinase (ERK), and RelA-p50 that induced inflammation, followed by an increase in anti-inflammatory/apoptotic factors including IL-10 and cysteine-aspartic acid protease-8 (CASPASE-8), which resolve inflammation and induce apoptosis. Anti-CD14 antibodies in luminal buffer blocked the pro- and anti-inflammatory effects of the toxins in neurons. Thus, the CD14-TLR cascade that participates in the inflammatory effects of toxins may not participate in the toxin-induced barrier disruption in vitro. Since the toxins did not cross the endothelial barrier, induction of inflammation in neurons was due to a release of proinflammatory cytokines in the abluminal fluid.

Different potency of bacterial antigens TLR2 and TLR4 ligands in stimulating mature mast cells to cysteinyl leukotriene synthesis

The aim of study was to compare the potency of different bacterial antigens to induce rat mature mast cell to cysteinyl leukotriene (cysLT) generation. We examined Toll-like receptor (TLR)2 agonists, i.e. lipoteichoic acid (LTA) Staphylococcus faecalis, Streptococcus pyogenes, Bacillus subtilis and Staphylococcus aureus, lipoarabinomannan (LAM) Mycobacterium smegmatis, peptydoglican (PGN) Staphylococcus aureus, as well as TLR4 agonists, i.e. lipopolysaccharide (LPS) Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella enteritidis, Pophyromonas gingivalis and Escherichia coli. We also estimated the effect of tumor necrosis factor (TNF)-, interleukin (IL)-6-, CCL5-, and IL-10-priming on mast cell cysLT synthesis following bacterial antigen activation. We found that all bacterial antigens activated mast cells to cysLT generation; however, the extent of cysLT release in response to stimulation varied. Out of the examined antigens LPS P. gingivalis exhibited the highest potency, as it induced cysLT generation acting at a very low concentration (10(-4) ng/mL). Other LPSs affected mast cells at higher (up to 10(5) -fold) concentrations. LTAs were the most effective at concentrations of 5 × 10(2) ng/mL, while LAM and PGN stimulated mast cells to maximal cysLT generation at concentrations as high as 10(5) ng/mL. Anti-TLR2 and anti-TLR4 antibodies, as well as nuclear factor κB (NF-κB) inhibitor significantly diminished cysLT generation in response to bacterial antigen stimulation. Priming with TNF, IL-6 and CCL5 did not affect bacterial antigen-induced cysLT generation, while IL-10-pretreatment caused significant decrease in cysLT synthesis by mast cells. These observations might have a great pathophysiological importance; inasmuch cysLTs strongly influence the development and intensity of inflammation during bacterial infection.

The Fyn-STAT5 Pathway: A New Frontier in IgE- and IgG-Mediated Mast Cell Signaling

Mast cells are central players in immune surveillance and activation, positioned at the host–environment interface. Understanding the signaling events controlling mast cell function, especially those that maintain host homeostasis, is an important and still less understood area of mast cell-mediated disease. With respect to allergic disease, it is well established that IgE and its high affinity receptor FcεRI are major mediators of mast cell activation. However, IgG-mediated signals can also modulate mast cell activities. Signals elicited by IgG binding to its cognate receptors (FcγR) are the basis for autoimmune disorders such as lupus and rheumatoid arthritis. Using knowledge of IgE-mediated mast cell signaling, recent work has begun to illuminate potential overlap between FcεRI and FcγR signal transduction. Herein we review the importance of Src family kinases in FcεRI and FcγR signaling, the role of the transcription factor STAT5, and impingement of the regulatory cytokines IL-4, IL-10, and TGFβ1 upon this network.

Inflamed gut mucosa: downstream of interleukin-10

BACKGROUND

Interleukin-10 is a pleiotropic cytokine, whose main function is limitation and ultimately termination of immune responses. This is especially true for environmental interfaces such as the gastrointestinal tract. IL-10 acts as a key mediator for maintaining gut homeostasis. IL-10 knockout mice are well established as a genetic model for inflammatory bowel disease (IBD), and sequence variants in the IL-10 locus contribute to ulcerative colitis (UC).

DESIGN

This review covers the significance of IL-10 signalling in the intestinal immune response both in health and disease. It explains the biological role of IL-10, its deregulation in IBD and its contribution to intestinal inflammation via endoplasmic reticulum stress response.

RESULTS

Many IBD susceptibility genes have been discovered in the past years, linking fundamental biological systems, like innate and adaptive immunity, stress responses, autophagy and mucosal barrier to the pathogenesis of Crohn's disease (CD) and UC. IL-10 has long been known for its substantial role in regulating gut immunity, but its contribution to IBD was somewhat elusive. A recent study identified mutations in either IL-10 receptor subunits that are associated with early-onset enterocolitis, a severe phenotype of IBD. Other than genetic variants of IL-10 receptors, IL-10 and STAT3 genes are also associated with IBD, emphasizing the involvement of the IL-10 signalling cascade in the pathogenesis of CD and UC.

CONCLUSIONS

  The discovery of inherited deregulations in the IL-10 signalling cascade is not only considered the missing link between IL-10 and intestinal homeostasis, but also demonstrates how findings made in animal models help explaining human disease.

IL-10-induced gp130 expression in mouse mast cells permits IL-6 trans-signaling

It is reported that human and mouse mast cells express the IL-27R, which consists of WSX-1 (the IL-27Rα subunit) and the signal-transducing subunit gp130. Although it has been proposed that IL-27 may negatively regulate mast cell-dependent, immediate hypersensitivity responses directly, this has yet to be examined specifically. We found that mouse BMMC and primary peritoneal mast cells are unresponsive to IL-27. Consistent with this, gp130 protein in resting BMMC was not on the cell surface to a measurable degree but was found intracellularly, and data are consistent with incompletely processed N-linked glycosylation. Furthermore, BMMC constitutively expressed SOCS3, a major negative regulator of gp130 signaling. However, BMMC stimulation with IL-10 and consequential STAT3 activation increased gp130 expression, which resulted in a functional gp130 receptor on the BMMC cell surface. IL-10 has not been previously shown to regulate gp130 expression, which on the BMMC surface, permitted IL-6 trans-signaling, found to increase survival under limiting conditions and enhance IL-13 and TNF-α secretion. This study identifies factors that regulate mouse mast cell gp130 expression and signaling and makes conspicuous the limitations of using cultured mouse mast cells to study the effects of the IL-6/IL-12 cytokine family on mast cell biology.

Endogenous suppression of mast cell development and survival by IL-4 and IL-10

Mast cell development is an important component of atopic and chronic inflammatory diseases such as asthma, multiple sclerosis, rheumatoid arthritis, and atherosclerosis. In this study, we found that IL-4 and IL-10 were produced constitutively in cultures of developing mast cells, correlating with mast cell purity. Deletion of either gene increased mast cell numbers and Fc epsilon RI expression during culture in IL-3 + stem cell factor (SCF). By adding exogenous IL-4 and IL-10 to bone marrow (BM) cultures containing IL-3 + SCF, we found that IL-4 + IL-10 suppressed mast cell development through mechanisms not used by either cytokine alone. IL-4 + IL-10 elicited a rapid cell death coincidental with reduced Kit receptor expression and signaling and enhanced mitochondrial damage and caspase activation. IL-4 or IL-10 costimulation, unlike either cytokine alone, altered mast cell ontogeny to yield predominantly macrophages in cultures that typically produce mast cells. This effect was observed consistently with unseparated BM cells, purified mouse BM stem cells, and erythrocyte-depleted human umbilical cord blood cells. These experiments demonstrated a major role for Stat6 and Stat3, but not the Stat3-induced transcriptional repressor Ets variant gene 3. Genetic background was also a critical factor, as BALB/c-derived BM cells were completely resistant to IL-10-mediated killing and expressed lower levels of IL-10R. Collectively, these results support the theory that IL-4 and IL-10 function as endogenous regulators of mast cell progenitor development, consistent with a role in immune homeostasis. Loss of this homeostasis, perhaps via genetic polymorphism, could contribute to the etiology of mast cell-associated disease.

Interleukin (IL)-10 inhibits RANTES-, tumour necrosis factor (TNF)- and nerve growth factor (NGF)-induced mast cell migratory response but is not a mast cell chemoattractant

Interleukin (IL)-10 is an important immunoregulatory cytokine with multiple biologic effects on different cell types. This cytokine also affects mast cell development, survival and activity. Mast cells are well known for their role in diverse pathophysiological processes including inflammatory events. Mast cell number in tissues is high and relatively constant. However, it is well established that these cells accumulate at the sites of inflammation in response to chemoattractants, e.g. RANTES, tumour necrosis factor (TNF) and nerve growth factor (NGF). In the present study, we examined whether IL-10 influenced RANTES-, TNF- and NGF-induced rat peritoneal mast cell migration. We also studied whether IL-10 could act as mast cell chemoattractant. We provided evidence, for the first time ever, that IL-10 influenced mature mast cell migration, i.e. it strongly decreased RANTES-induced mast cell migration and completely inhibited mast cell migratory response to TNF and NGF. The effective concentration of IL-10 that inhibited RANTES-, TNF- and NGF-induced mast cell migratory response was in the nanomolar range. The inhibitory effect of IL-10 on cytokine-stimulated mast cell migration was specific, as it was completely blocked by anti-IL-10R antibodies, and STAT3-dependent. In addition, our results have shown that IL-10 was not a mast cell chemoattractant. Thus, our findings clearly demonstrated that IL-10 may affect mast cell number within tissue by inhibiting local mast cell accumulation stimulated by chemotactic factors.

IL-10 suppresses mast cell IgE receptor expression and signaling in vitro and in vivo

Mast cells are known for their roles in allergy, asthma, systemic anaphylaxis, and inflammatory disease. IL-10 can regulate inflammatory responses and may serve as a natural regulator of mast cell function. We examined the effects of IL-10 on in vitro-cultured mouse and human mast cells, and evaluated the effects of IL-10 on FcepsilonRI in vivo using mouse models. IgE receptor signaling events were also assessed in the presence or absence of IL-10. IL-10 inhibited mouse mast cell FcepsilonRI expression in vitro through a Stat3-dependent process. This down-regulation was consistent in mice tested in vivo, and also on cultured human mast cells. IL-10 diminished expression of the signaling molecules Syk, Fyn, Akt, and Stat5, which could explain its ability to inhibit IgE-mediated activation. Studies of passive systemic anaphylaxis in IL-10-transgenic mice showed that IL-10 overexpression reduced the IgE-mediated anaphylactic response. These data suggest an important regulatory role for IL-10 in dampening mast cell FcepsilonRI expression and function. IL-10 may hence serve as a mediator of mast cell homeostasis, preventing excessive activation and the development of chronic inflammation.

STAT6 mediates apoptosis of human coronary arterial endothelial cells by interleukin-13

Interleukin (IL)-13 is a cytokine produced by type 2 helper T cells that has pathophysiological roles in allergic inflammation and fibrosis formation. IL-13 shares many functional properties with IL-4, which promotes apoptosis of endothelial cells (ECs). We here investigated the effects of IL-13 on apoptosis using human coronary artery endothelial cells (HCAECs). Assessment by WST-1 assay demonstrated that IL-13 as well as IL-4 significantly inhibited cell growth. IL-13 significantly attenuated the cell viability and induced apoptosis of HCAECs as well. Expression of mRNA for vascular endothelial cell growth factor, which maintains survival of ECs, was significantly diminished by IL-13. The effects of IL-13 and IL-4 were abolished by depletion of STAT6 using RNA interference. These results suggest that IL-13 attenuates EC viability by inducing apoptosis, and that STAT6 plays pivotal roles on IL-13- and IL-4-induced apoptosis in ECs.

Interleukin-10 modulates pro-apoptotic effects of TNF-alpha in human articular chondrocytes in vitro

The aim of this study is to determine if there is an antagonistic effect between tumour necrosis factor (TNF)-alpha and the immunoregulatory interleukin (IL)-10 on chondrocytes survival. Serum-starved primary human articular chondrocytes were stimulated with either 10 ng/ml recombinant TNF-alpha, IL-10 or a combination of both (at 10 ng/ml each). Chondrocyte apoptosis was determined by measuring caspase-3/7, -8 and -9 activities using caspase assays. Mitochondrial apoptotic inducer bax, and the suppressor bcl-2 were evaluated using western blotting at 48 h. Results indicated that TNF-alpha increased caspase activities and resulted in a significant (p = 0.001) increase in bax/bcl-2 ratio. Stimulation with IL-10 did not alter caspase activities, while co-treatment with IL-10 and TNF-alpha inhibited TNF-alpha induced caspase activities and significantly (p > 0.004) impaired bax/bcl-2 ratio. At 24 h, mRNA levels for collagen type II, TNF-alpha and IL-10 were determined using real-time RT-PCR. Stimulation with TNF-alpha or TNF-alpha and IL-10 significantly inhibited collagen type II and increased IL-10 and TNF-alpha mRNA expression. IL-10 modulated the pro-apoptotic capacity of TNF-alpha in chondrocytes as shown by the decrease in caspase activities and bax/bcl-2 ratio compared to TNF-alpha stimulated chondrocytes, suggesting a mostly antagonistic interplay of IL-10 and TNF-alpha on mitochondrial apoptotic pathways.

IL-10 confers protection from mast cell degranulation in a mouse model of allergic conjunctivitis

IL-10 is a regulatory cytokine known to inhibit allergic and inflammatory events. Mast cells (MC) are effector cells which when stimulated release histamine, chemokines and cytokines that initiate the allergic inflammatory response. Recent studies have shown that IL-10 regulates MC function by affecting cytokine production and expression of FcvarepsilonR1 in in vitro assays. Using IL-10 knockout (IL10KO) mice, we examined the effect of its absence on MC susceptibility to degranulation by the basic secretagogue, Compound 48/80 (C48/80). C48/80 is a receptor mimetic that directly activates G proteins and stimulates vigorous MC degranulation. For these studies we stimulated conjunctival MC with C48/80 and found that conjunctival MC of IL10KO mice exhibit increased degranulation compared with wild type mice. Reconstitution of IL10KO mice by adding rIL-10 24h prior to challenge with C48/80 conferred increased resistance of MC to the degranulatory effects of C48/80. The protective effect therefore appears to be due to the presence of IL-10. This is the first in vivo rodent study which reports a novel role of IL-10 in stabilizing mast cells from degranulation by a secretagogue, by as of yet an unknown mechanism.

Interleukin-4 induces human hepatocyte apoptosis through a Fas-independent pathway

IL-4 is overexpressed in liver grafts during severe recurrent hepatitis C and rejection. Hepatocyte apoptosis is involved in both these phenomena. We therefore examined the proapoptotic effect of IL-4 on HepG2 cells and human hepatocytes in vitro, together with the underlying mechanisms. We first measured IL-4 receptor expression, STAT6 activation by IL-4, and STAT6 inhibition by an anti-IL-4 antibody or by STAT6 siRNA transfection. We then focused on the pathways involved in IL-4-mediated apoptosis and the role of STAT6 activation in apoptosis initiation. The IL-4 receptor was expressed on both cell types, and STAT6 was activated by IL-4. Both anti-IL-4 and STAT-6 siRNA inhibited this activation. IL-4 induced apoptosis of both HepG2 cells (P=0.008 vs. untreated control) and human hepatocytes (P<0.001 vs. untreated control). IL-4 reduced the mitochondrial membrane potential, activated Bid and Bax, and augmented caspase 3, 8, and 9 activity. STAT6 blockade inhibited IL-4-induced apoptosis. Expression of Fas and Fas ligand was unaffected when HepG2 cells and hepatocytes were cultured with IL-4, and Fas/FasL pathway blockade failed to inhibit IL-4-induced apoptosis. These results show that IL-4 induces apoptosis of human hepatocytes through IL-4 receptor binding, STAT6 activation, decreased mitochondrial membrane potential, and increased caspase activation, independently of the Fas pathway. IL-4 might thus contribute to the progression of severe liver graft damage.

A functional comparison of canine and murine bone marrow derived cultured mast cells

Disorders involving mast cells are extremely common in dogs, ranging from allergic diseases to neoplastic transformation resulting in malignant mast cell tumors. Relatively little is known regarding the basic biologic properties of normal canine mast cells, largely due to the difficulty in reliably purifying large numbers from canine skin. In vitro generated bone marrow derived cultured mast cells (BMCMCs) are routinely used in both human and murine studies as a ready source of material for in vitro and in vivo studies. We previously developed a technique to generate canine BMCMCs from bone marrow derived CD34+ cells and demonstrated that these cells exhibit the phenotypic properties characteristic of mast cells and release histamine in response to IgE cross-linking. The purpose of the following study was to characterize the functional properties of these canine BMCMCs and contrast these with the functional properties of murine BMCMCs. Our work demonstrates that both IL-4 and IL-10 promote canine BMCMC proliferation, possibly through upregulation of Kit expression, while TGFbeta inhibits proliferation. The canine BMCMCs produce a variety of cytokines and chemokines in response to IgE cross-linking and chemical stimulation including IL-3, IL-4, IL-13, GM-CSF, RANTES, and MIP1alpha. Interestingly, the canine BMCMCs released significantly larger amounts of MCP-1 and tryptase and significantly smaller amounts of IL-6 following chemical stimulation and IgE cross-linking when compared to murine BMCMCs. Lastly, the canine BMCMCs produced larger amounts of active MMP9 than their murine counterparts. In summary, canine BMCMCs exhibit unique functional properties that distinguish them from murine BMCMCs and provide insight into the contribution of these cells to mast cell disorders in the dog.

TGFbeta1 induces mast cell apoptosis

Mast cells are potent effectors of the inflammatory response, playing an important role in atopy, bacterial immunity, and animal models of arthritis, multiple sclerosis, and heart disease. Hence controlling mast cell numbers and responsiveness is essential for preventing inflammatory disease. We demonstrate that the cytokine transforming growth factor (TGF) beta1 is a potent inducer of mast cell apoptosis, a finding that was consistent in cultured mouse bone marrow-derived mast cells, peritoneal mast cells, and human mast cells. Cell death appeared to be caused by TGF-mediated repression of interleukin-3 (IL-3) receptor expression and function, leading to mitochondrial damage and activation of an apoptotic cascade acting via p53 and caspases. Although IL-3 receptor expression was reduced within 1 day of TGFbeta1 stimulation, apoptosis required at least 3 days to occur. This delay in onset is postulated to allow protective mast cell effector functions, protecting the host from infection while preventing the establishment of chronic inflammation. Our data support the theory that TGFbeta1 is an inhibitor of mast cell survival. The widespread expression of TGFbeta1 offers this cytokine as an ideal candidate for control of mast cell homeostasis.

Tetrazolium violet induces G0/G1 arrest and apoptosis in brain tumor cells

Tetrazolium violet (TV), a potent anticancer agent, has been shown to induce cell growth-inhibition in tumor cells. However, the related mechanism has not been revealed yet. In this report we assessed the influence of TV on cell growth and cell cycle in brain tumor cells. Treatment of C6 tumor cells with TV (5-15 microM for 24-72 h) resulted in a growth inhibition in a dose and time-dependent manner and G0/G1 phase arrest, determined by flow cytometry analysis. These effects were accompanied by apoptosis other than necrosis, evidenced by nuclear condensation, terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) assay and trypan blue exclusion assay plus lactate dehydrogenase (LDH) release assay. Treatment of cells with TV at 15 microM for 24 h resulted in an increase in the activity of caspase-3, evidenced by colorimetric assay, and a dramatic up-regulation of p53, accompanied with a significant increase of Bax/Bcl-2 ratio, as evidenced by immunofluorescence assay. These results suggest that TV induces growth inhibition of C6 cells through p53-midiated apoptotic pathway and G0/G1 checkpoint mechanism. Although detailed mechanisms remain to be explored, selective blockage of tumor cells in G0/G1 phase accompanied by p53-associated apoptosis makes tetrazolium violet a promising anticancer agent, meriting further investigations.

Immunotherapy of hypersensitivity to hymenoptera venom

Insect sting allergy is a common condition with a risk of life-threatening anaphylaxis. After a severe reaction, the fear of being restung can significantly reduce quality of life. Venom immunotherapy (VIT) is a highly effective treatment of the underlying type I-sensitisation. This review addresses the mechanisms of immune modulation by VIT and outlines current clinical application. Although highly effective in the majority of patients, VIT fails in a few individuals. It can also cause systemic allergic side effects, restricting its application to physicians trained in the treatment of anaphylaxis. This review discusses several new strategies to overcome these problems, which are presently a promising focus of research. These include the use of new adjuvants, of recombinant and genetically engineered venom allergens, as well as vaccination with peptides.

IFN-gamma induces apoptosis in developing mast cells

Mast cells are critical effectors of allergic disease, and are now implicated in immune responses observed in arthritis, multiple sclerosis, and heart disease. Because of their role in inflammation, understanding how mast cells develop is of clinical importance. In this study we determined the effects of IFN-gamma on mast cell survival. Using in vitro culture of bone marrow cells in IL-3 plus stem cell factor, we found that the addition of IFN-gamma induced apoptosis, as exhibited by the presence of subdiploid DNA and caspase activation. IFN-gamma-mediated apoptosis was Stat1-dependent, and was accompanied by loss of mitochondrial membrane potential. Apoptosis was reduced in cultures of bone marrow cells derived from p53- or Bax-deficient mice, as well as H2K-Bcl-2 transgenic mice. IFN-gamma hyperresponsiveness has been shown to result in inflammatory disease and death in mice lacking the regulatory protein suppressor of cytokine signaling (SOCS)-1. Bone marrow cells from SOCS-1 knockout (KO) mice failed to give rise to viable mast cells after culture in IL-3 plus stem cell factor, with profound apoptosis occurring as the cultures matured. However, bone marrow cells lacking both SOCS-1 and IFN-gamma survived normally. This in vitro defect in mast cell development was recapitulated in vivo. SOCS-1 KO mice demonstrated a 67% decrease in peritoneal mast cell numbers relative to wild-type mice, a deficiency that was reversed in SOCS-1/IFN-gamma KO mice. These data demonstrate the potent regulatory effects of IFN-gamma on mast cell survival and show that this cytokine can elicit mast cell death in vitro and in vivo.