the-inverted-heart-model-for-interstitial-transudate-collection-from

The Inverted Heart Model for Interstitial Transudate Collection from the Isolated Rat Heart

The present protocol describes a unique approach that enables the collection of cardiac transudate (CT) from the isolated, saline-perfused rat heart. ...

Heinrich Heine University

Two subsets of natural and adaptive regulatory T (T reg) cells have been described, but the identity of adaptive type 1 regulatory (Tr1)-like cells in humans is unclear. We analyzed a subset of human blood CD4(+) T cells--CD45RA(-)CD25(-)interleukin (IL)-7 receptor (R)(-) cells--that rapidly secreted high levels of IL-10 together with interferon gamma, but produced little IL-2. These IL-7R(-) T cells were rare, anergic, and largely Foxp3(-). They expressed low levels of Bcl-2 but high levels of Ki-67 and ICOS, suggesting that they have been recently activated in vivo. Consistently, they responded selectively to persistent foreign and self-antigens under steady-state conditions. Unlike natural CD25(+) T reg cells, IL-7R(-) cells suppressed naive and memory T cell proliferation in an IL-10-dependent fashion, and they required strong T cell receptor stimulation for suppression. To our knowledge, this is the first report that identifies Tr1-like cells in human blood. These IL-10-secreting cells have characteristics of chronically activated Th1 effector cells and are distinct from CD25(+) T reg cells.

Identification and characterization of IL-10/IFN-gamma-producing effector-like T cells with regulatory function in human blood.

Interleukin (IL)-10 produced by regulatory T cell subsets is important for the prevention of autoimmunity and immunopathology, but little is known about the phenotype and function of IL-10-producing memory T cells. Human CD4(+)CCR6(+) memory T cells contained comparable numbers of IL-17- and IL-10-producing cells, and CCR6 was induced under both Th17-promoting conditions and upon tolerogenic T cell priming with transforming growth factor (TGF)-beta. In normal human spleens, the majority of CCR6(+) memory T cells were in the close vicinity of CCR6(+) myeloid dendritic cells (mDCs), and strikingly, some of them were secreting IL-10 in situ. Furthermore, CCR6(+) memory T cells produced suppressive IL-10 but not IL-2 upon stimulation with autologous immature mDCs ex vivo, and secreted IL-10 efficiently in response to suboptimal T cell receptor (TCR) stimulation with anti-CD3 antibodies. However, optimal TCR stimulation of CCR6(+) T cells induced expression of IL-2, interferon-gamma, CCL20, and CD40L, and autoreactive CCR6(+) T cell lines responded to various recall antigens. Notably, we isolated autoreactive CCR6(+) T cell clones with context-dependent behavior that produced IL-10 with autologous mDCs alone, but that secreted IL-2 and proliferated upon stimulation with tetanus toxoid. We propose the novel concept that a population of memory T cells, which is fully equipped to participate in secondary immune responses upon recognition of a relevant recall antigen, contributes to the maintenance of tolerance under steady-state conditions.

CCR6 is expressed on an IL-10-producing, autoreactive memory T cell population with context-dependent regulatory function.

CCR6 is a chemokine receptor expressed on Th17 cells and regulatory T cells that is induced by T-cell priming with certain cytokines, but how its expression and stability are regulated at the molecular level is largely unknown. Here, we identified and characterized a noncoding region of the human CCR6 locus that displayed unmethylated CpG motifs (differentially methylated region [DMR]) selectively in CCR6(+) lymphocytes. CCR6 expression on circulating CD4(+) T cells was stable on cytokine-induced proliferation but partially down-regulated on T-cell receptor stimulation. However, CCR6 down-regulation was mostly transient, and the DMR within the CCR6 locus remained demethylated. Notably, in vitro induction of CCR6 expression with cytokines in T-cell receptor-activated naive CD4(+) T cells was not associated with a demethylated DMR and resulted in unstable CCR6 expression. Conversely, treatment with the DNA methylation inhibitor 5'-azacytidine induced demethylation of the DMR and led to increased and stable CCR6 expression. Finally, when cloned into a reporter gene plasmid, the DMR displayed transcriptional activity in memory T cells that was suppressed by DNA methylation. In summary, we have identified a noncoding region of the human CCR6 gene with methylation-sensitive transcriptional activity in CCR6(+) T cells that controls stable CCR6 expression via epigenetic mechanisms.

Epigenetic modification of the human CCR6 gene is associated with stable CCR6 expression in T cells.

Dendritic cells (DC) have the unique capacities to induce primary T-cell responses. In mice, CD8α(+)DC are specialized to cross-prime CD8(+) T cells and produce interleukin-12 (IL-12) that promotes cytotoxicity. Human BDCA-3(+)DC share several relevant characteristics with CD8α(+)DC, but the capacities of human DC subsets to induce CD8(+) T-cell responses are incompletely understood. Here we compared CD1c(+) myeloid DC (mDC)1, BDCA-3(+)mDC2, and plasmacytoid DC (pDC) in peripheral blood and lymphoid tissues for phenotype, cytokine production, and their capacities to prime cytotoxic T cells. mDC1 were surprisingly the only human DC that secreted high amounts of IL-12p70, but they required combinational Toll-like receptor (TLR) stimulation. mDC2 and pDC produced interferon-λ and interferon-α, respectively. Importantly, mDC1 and mDC2 required different combinations of TLR ligands to cross-present protein antigens to CD8(+) T cells. pDC were inefficient and also expressed lower levels of major histocompatibility complex and co-stimulatory molecules. Nevertheless, all DC induced CD8(+) memory T-cell expansions upon licensing by CD4(+) T cells, and primed naive CD8(+) T cells following appropriate TLR stimulation. However, because mDC1 produced IL-12, they induced the highest levels of cytotoxic molecules. In conclusion, CD1c(+)mDC1 are the relevant source of IL-12 for naive T cells and are fully equipped to cross-prime cytotoxic T-cell responses.

Human CD1c+ dendritic cells secrete high levels of IL-12 and potently prime cytotoxic T-cell responses.

Extracellular nucleotides and nucleosides have been implicated as important signaling molecules in the pathogenesis of acute lung injury (ALI). While adenosine is known to inhibit T cell activation, little information is available as to ATP and NAD degrading enzymes, the expression of ATP and adenosine receptors/transporters in different T cell subsets. ALI was induced by challenging mice with intra-tracheal instillation of 60 µl (3 µg/g) LPS. After 3 d and 7 d blood, lung tissue and bronchoalveolar lavage was collected and immune cells were analyzed using flow cytometry. The transcriptional phenotype of T helper cells, cytotoxic and regulatory T cells sorted by FACS was assessed by measuring the expression profile of 28 genes related to purinergic signaling using TaqMan Array Micro Fluidic Cards. Catabolism of ATP, NAD and cAMP by activated CD4+ T cells was evaluated by HPLC. CD73 was found to be highly abundant on lymphoid cells with little abundance on myeloid cells, while the opposite was true for CD39. After ALI, the abundance of CD39 and CD73 significantly increased on all T cell subsets derived from lung tissue and bronchoalveolar space. Expression analysis in T cell subsets of the lung revealed ATP (Cd39, Cd73) and NAD (Cd38, Cd157, Cd296, Pc-1) degrading enzymes. However, only transcription of Cd38, Cd39, Cd73, Ent1 and A2a receptor was significantly upregulated after ALI in T helper cells. CD4+ T cells from injured lung rapidly metabolized extracellular ATP to AMP and adenosine but not NAD or cAMP. These findings show that lung T cells--the dominant cell fraction in the later phase of ALI--exhibit a unique expression pattern of purinergic signaling molecules. Adenosine is formed by T cells at an enhanced rate from ATP but not from NAD and together with upregulated A2a receptor is likely to modulate the healing process after acute lung injury.

Purinergic signaling on leukocytes infiltrating the LPS-injured lung.

IL-21 promotes Th17 differentiation, and Th17 cells that upregulate T-bet, IFN-γ, and GM-CSF drive experimental autoimmune diseases in mice. Anti-IL-21 treatment of autoimmune patients is therefore a therapeutic option, but the role of IL-21 in human T cell differentiation is incompletely understood. IL-21 was produced at high levels by human CD4(+) central memory T cells, suggesting that it is associated with early T cell differentiation. Consistently, it was inhibited by forced expression of T-bet or RORC2, the lineage-defining transcription factors of Th1 and Th17 effector cells, respectively. Although IL-21 was efficiently induced by IL-12 in naive CD4(+) T cells, it inhibited the generation of Th1 effector cells in a negative feedback loop. IL-21 was also induced by IL-6 and promoted Th17 differentiation, but it was not absolutely required. Importantly, however, IL-21 promoted IL-10 secretion but inhibited IFN-γ and GM-CSF production in developing Th17 cells, and consequently prevented the generation of polyfunctional Th1/17 effector cells. Moreover, in Th17 memory cells, IL-21 selectively inhibited T-bet upregulation and GM-CSF production. In summary, IL-21 is a central memory T cell-associated cytokine that promotes Th17 differentiation and IL-10 production, but inhibits the generation of potentially pathogenic Th1/17 effector cells. These findings shed new light on the role of IL-21 in T cell differentiation, and have relevant implications for anti-IL-21 therapy of autoimmune diseases.

IL-21 is a central memory T cell-associated cytokine that inhibits the generation of pathogenic Th1/17 effector cells.

IL-17 production defines Th17 cells, which orchestrate immune responses and autoimmune diseases. Human Th17 cells can be efficiently generated with appropriate cytokines from precommitted precursors, but the requirements of uncommitted T cells are still ill defined. In standard human Th17 cultures, IL-17 production was restricted to CCR6(+)CD45RA(+) T cells, which expressed CD95 and produced IL-17 ex vivo, identifying them as Th17 memory stem cells. Uncommitted naive CD4(+) T cells upregulated CCR6, RORC2, and IL-23R expression with Th17-promoting cytokines but in addition required sustained TCR stimulation, late mammalian target of rapamycin (mTOR) activity, and HIF-1α to produce IL-17. However, in standard high-density cultures, nutrients like glucose and amino acids became progressively limiting, and mTOR activity was consequently not sustained, despite ongoing TCR stimulation and T cell proliferation. Sustained, nutrient-dependent mTOR activity also induced spontaneous IL-22 and IFN-γ production, but these cytokines had also unique metabolic requirements. Thus, glucose promoted IL-12-independent Th1 differentiation, whereas aromatic amino acid-derived AHR ligands were selectively required for IL-22 production. The identification of Th17 memory stem cells and the stimulation requirements for induced human Th17/22 differentiation have important implications for T cell biology and for therapies targeting the mTOR pathway.

Signal Strength and Metabolic Requirements Control Cytokine-Induced Th17 Differentiation of Uncommitted Human T Cells.

Extracellular adenosine formation from ATP is controlled by ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase/CD39) and ecto-5'-nucleotidase (e-5NT/CD73); the latter converts AMP to adenosine and inorganic phosphate, representing the rate limiting step controlling the ratio between extracellular ATP and adenosine. Evidence that cellular expression and activity of CD39 and CD73 may be subject to changes under pathophysiological conditions has identified this pathway as an endogenous modulator in several diseases and was shown to be involved in the molecular mechanism of drugs, such as methotrexate, salicylates , interferon-β. We evaluated whether CD73/adenosine/A2A signalling pathway is involved in nimesulide anti-inflammatory effect, in vivo and in vitro. We found that the adenosine A2A agonist, 4-[2-[[6-amino-9-(N-ethyl-β-d-ribofuranuronamidosyl)-9H-purin-2-yl]amino]ethyl]benzenepropanoic acid hydrochloride (CGS21680, 2mg/kg ip.), inhibited carrageenan-induced rat paw oedema and the effect was reversed by co-administration of the A2A antagonist -(2-[7-amino-2-[2-furyl][1,2,4]triazolo[2,3-a][1,3,5]triazin-5-yl-amino]ethyl)phenol (ZM241385; 3mg/kg i.p.). Nimesulide (5mg/kg i.p.) anti-inflammatory effect was inhibited by pre-treatment with ZM241385 (3mg/kg i.p.) and by local administration of the CD73 inhibitor, adenosine 5'-(α,β-methylene)diphosphate (APCP; 400μg/paw). Furthermore, we found increased activity of 5'-nucleotidase/CD73 in paws and plasma of nimesulide treated rats, 4h following oedema induction. In vitro, the inhibitory effect of nimesulide on nitrite and prostaglandin E2 production by lipopolysaccharide-activated J774 cell line was reversed by ZM241385 and APCP. Furthermore, nimesulide increased CD73 activity in J774 macrophages while it did not inhibit nitrite accumulation by lipopolysaccharide-activated SiRNA CD73 silenced J774 macrophages. Our data demonstrate that the anti-inflammatory effect of nimesulide in part is mediated by CD73-derived adenosine acting on A2A receptors.

Adenosine signalling mediates the anti-inflammatory effects of the COX-2 inhibitor nimesulide.

Background -T-cells are required for proper healing after myocardial infarction. The mechanism of their beneficial action, however, is unknown. The pro-inflammatory "danger signal" adenosine triphosphate (ATP), released from damaged cells, is degraded by the ectonucleotidases CD39 and CD73 to the anti-inflammatory mediator adenosine. Here, we investigate the contribution of CD73-derived adenosine produced by T-cells to cardiac remodeling after ischemia/reperfusion and define its mechanism of action. Methods -Myocardial ischemia (50 min /reperfusion) was induced in global CD73(-/-) and CD4-CD73(-/-) mice. Tissue injury, T-cell purinergic signaling, cytokines and cardiac function (MRT at 9.4 T over four weeks) were analyzed. Results -Changes in functional parameters of CD4-CD73(-/-) mice were identical to global CD73 knockouts. T-cells infiltrating the injured heart significantly upregulated at the gene (qPCR) and protein levels (enzymatic activity) critical transporters and enzymes (Cx43, Cx37, Panx1, ENT1, CD39, CD73, ENNP 1+3, CD157, CD38) for the accelerated release and hydrolysis of ATP, cAMP, AMP and NAD to adenosine. Surprisingly, lack of CD39 on T-cells (from CD39(-/-) mice) did not alter ATP hydrolysis and very likely involves pyrophosphatases (ENNP 1+3). Circulating T cells predominantly expressed A2aR transcripts. Following MI, A2bR transcription was induced in both T cells and myeloid cells in the heart. Thus A2aR and A2bR signaling may both contribute to myocardial responses after MI. In the case of T-cells, this was associated with an accelerated secretion of proinflammatory and profibrotic cytokines (Il-2, IFN-γ and IL-17) when CD73 was lacking. Cytokine production by T-cells from peripheral lymph nodes was inhibited by A2aR activation (CGS-21680). The A2bR agonist BAY 60-6583 showed off-target effects. The adenosine receptor agonist NECA inhibited IFN-γ and stimulated IL-6 production, each of which was antagonized by a specific A2bR antagonist (PSB-603). Conclusions -This work demonstrates that CD73 on T-cells plays a crucial role in the cardiac wound healing process after MI. The underlying mechanism involves a profound increase in the hydrolysis of ATP/NAD and AMP, due primarily tothe upregulation of pyrophosphatases and CD73. We also define A2bR/A2aR-mediated autacoid feed-back inhibition of proinflammatory/ profibrotic cytokines by T-cell-derived CD73.

Bodo Steckel

Department of Molecular Cardiology

Heinrich Heine University

The Inverted Heart Model for Interstitial Transudate Collection from the Isolated Rat Heart