Cyclic AMP-Responsive Element-Binding Protein (CREB) is Critical in Autoimmunity by Promoting Th17 but Inhibiting Treg Cell Differentiation

The transition state for coupled folding and binding of a disordered DNA binding domain resembles the unbound state

The basic zippers (bZIPs) are one of two large eukaryotic families of transcription factors whose DNA binding domains are disordered in isolation but fold into stable α-helices upon target DNA binding. Here, we systematically disrupt pre-existing helical propensity within the DNA binding region of the homodimeric bZIP domain of cAMP-response element binding protein (CREB) using Ala-Gly scanning and examine the impact on target binding kinetics. We find that the secondary structure of the transition state strongly resembles that of the unbound state. The residue closest to the dimerization domain is largely folded within both unbound and transition states; dimerization apparently propagates additional helical propensity into the basic region. The results are consistent with electrostatically-enhanced DNA binding, followed by rapid folding from the folded zipper outwards. Fly-casting theory suggests that protein disorder can accelerate binding. Interestingly however, we did not observe higher association rate constants for mutants with lower levels of residual structure in the unbound state.

Deciphering the role of protein kinase A in the control of FoxP3 expression in regulatory T cells in health and autoimmunity

The molecular mechanisms that govern differential T cell development from CD4+CD25-conventional T (Tconv) into CD4+CD25+ forkhead-box-P3+ (FoxP3+) inducible regulatory T (iTreg) cells remain unclear. Herein, we investigated the relative contribution of protein kinase A (PKA) in this process. Mechanistically, we found that PKA controlled the efficiency of human iTreg cell generation through the expression of different FoxP3 splicing variants containing or not the exon 2. We found that transient PKA inhibition reduced the recruitment of cAMP-responsive element-binding protein (CREB) on regulatory regions of the FoxP3 gene, a condition that is associated with an impaired acquisition of their suppressive capacity in vitro. To corroborate our findings in a human model of autoimmunity, we measured CREB phosphorylation and FoxP3 levels in iTreg cells from treatment-naïve relapsing-remitting (RR)-multiple sclerosis (MS) subjects. Interestingly, both phospho-CREB and FoxP3 induction directly correlated and were significantly reduced in RR-MS patients, suggesting a previously unknown mechanism involved in the induction and function of human iTreg cells.

Aging as a Consequence of the Adaptation-Maladaptation Dilemma

In aging, the organism is unable to counteract certain harmful influences over its lifetime which leads to progressive dysfunction and eventually death, thus delineating aging as one failed process of adaptation to a set of aging stimuli. A central problem in understanding aging is hence to explain why the organism cannot adapt to these aging stimuli. The adaptation-maladaptation theory of aging proposes that in aging adaptation processes such as adaptive transcription, epigenetic remodeling, and metabolic plasticity drive dysfunction themselves over time (maladaptation) and thereby cause aging-related disorders such as cancer and metabolic dysregulation. The central dilemma of aging is thus that the set of adaptation mechanisms that the body uses to deal with internal and external stressors acts as a stressor itself and cannot be effectively counteracted. The only available option for the organism to decrease maladaptation may be a program to progressively reduce the output of adaptive cascades (e.g., via genomic methylation) which then leads to reduced physiological adaptation capacity and syndromes like frailty, immunosenescence, and cognitive decline. The adaptation-maladaptation dilemma of aging entails that certain biological mechanisms can simultaneously protect against aging as well as drive aging. The key to longevity may lie in uncoupling adaptation from maladaptation.

Protein kinase C signaling "in" and "to" the nucleus: Master kinases in transcriptional regulation

PKC is a multifunctional family of Ser-Thr kinases widely implicated in the regulation of fundamental cellular functions, including proliferation, polarity, motility, and differentiation. Notwithstanding their primary cytoplasmic localization and stringent activation by cell surface receptors, PKC isozymes impel prominent nuclear signaling ultimately impacting gene expression. While transcriptional regulation may be wielded by nuclear PKCs, it most often relies on cytoplasmic phosphorylation events that result in nuclear shuttling of PKC downstream effectors, including transcription factors. As expected from the unique coupling of PKC isozymes to signaling effector pathways, glaring disparities in gene activation/repression are observed upon targeting individual PKC family members. Notably, specific PKCs control the expression and activation of transcription factors implicated in cell cycle/mitogenesis, epithelial-to-mesenchymal transition and immune function. Additionally, PKCs isozymes tightly regulate transcription factors involved in stepwise differentiation of pluripotent stem cells toward specific epithelial, mesenchymal, and hematopoietic cell lineages. Aberrant PKC expression and/or activation in pathological conditions, such as in cancer, leads to profound alterations in gene expression, leading to an extensive rewiring of transcriptional networks associated with mitogenesis, invasiveness, stemness, and tumor microenvironment dysregulation. In this review, we outline the current understanding of PKC signaling "in" and "to" the nucleus, with significant focus on established paradigms of PKC-mediated transcriptional control. Dissecting these complexities would allow the identification of relevant molecular targets implicated in a wide spectrum of diseases.

Increased expression of protein tyrosine phosphatase nonreceptor type 22 alters early T-cell receptor signaling and differentiation of CD4+ T cells in chronic heart failure

CD4+ T-cell counts are increased and activated in patients with chronic heart failure (CHF), whereas regulatory T-cell (Treg) expansion is inhibited, probably due to aberrant T-cell receptor (TCR) signaling. TCR signaling is affected by protein tyrosine phosphatase nonreceptor type 22 (PTPN22) in autoimmune disorders, but whether PTPN22 influences TCR signaling in CHF remains unclear. This observational case-control study included 45 patients with CHF [18 patients with ischemic heart failure versus 27 patients with nonischemic heart failure (NIHF)] and 16 non-CHF controls. We used flow cytometry to detect PTPN22 expression, tyrosine phosphorylation levels, zeta-chain-associated protein kinase, 70 kDa (ZAP-70) inhibitory residue tyrosine 292 and 319 phosphorylation levels, and CD4+ T cell and Treg proportions. We conducted lentivirus-mediated PTPN22 RNA silencing in isolated CD4+ T cells. PTPN22 expression increased in the CD4+ T cells of patients with CHF compared with that in controls. PTPN22 expression was positively correlated with left ventricular end-diastolic diameter and type B natriuretic peptide but negatively correlated with left ventricular ejection fraction in the NIHF group. ZAP-70 tyrosine 292 phosphorylation was decreased, which correlated positively with PTPN22 overexpression in patients with NIHF and promoted early TCR signaling. PTPN22 silencing induced Treg differentiation in CD4+ T cells from patients with CHF, which might account for the reduced frequency of peripheral Tregs in these patients. PTPN22 is a potent immunomodulator in CHF and might play an essential role in the development of CHF by promoting early TCR signaling and impairing Treg differentiation from CD4+ T cells.

Review on Monoclonal Antibodies (mAbs) as a Therapeutic Approach for Type 1 Diabetes

Monoclonal antibodies have been successfully utilized in a variety of animal models to treat auto-immune illnesses for a long time. Immune system responses will either be less active or more active depending on how the immune system is operating abnormally. Immune system hypoactivity reduces the body's capacity to fight off various invading pathogens, whereas immune system hyperactivity causes the body to attack and kill its own tissues and cells. For maximal patient compliance, we will concentrate on a variety of antibody therapies in this study to treat Type 1 diabetes (an autoimmune condition). T-cells are responsible for the auto-immune condition known as T1D, which causes irregularities in the function of β-cells in the pancreas. As a result, for the treatment and prevention of T1D, immunotherapies that selectively restore continuous beta cellspecific self-tolerance are needed. Utilizing monoclonal antibodies is one way to specifically target immune cell populations responsible for the auto-immune-driven disease (mAb). Numerous mAbs have demonstrated clinical safety and varied degrees of success in modulating autoimmunity, including T1D. A targeted cell population is exhausted by mAb treatments, regardless of antigenic specificity. One drawback of this treatment is the loss of obtained protective immunity. Immune effector cell function is regulated by nondepleting monoclonal antibodies (mAb). The antigenfocused new drug delivery system is made possible by the adaptability of mAbs. For the treatment of T1D and T-cell-mediated autoimmunity, different existing and potential mAb therapy methods are described in this article.

Inhibition of microRNA-34c reduces detrusor ROCK2 expression and urinary bladder inflammation in experimental cystitis

Interstitial cystitis (IC), also called painful bladder syndrome (PBS), is 2 to 5 times more common in women than in men, yet its cause and pathogenesis remain unclear. In our study using the cyclophosphamide (CYP)-induced mouse model of cystitis, histological evaluation of the urinary bladder (UB) lamina propria (LP) showed immune cell infiltrations, indicating moderate to severe inflammation. In this study, we noticed a differential expression of a subset of microRNAs (miRs) in the UB cells (UBs) of CYP-induced cystitis as compared to the control. UB inflammatory scores and inflammatory signaling were also elevated in CYP-induced cystitis as compared to control. We identified eight UBs miRs that exhibited altered expression after CYP induction and are predicted to have a role in inflammation and smooth muscle function (miRs-34c-5p, -34b-3p, -212-3p, -449a-5p, -21a-3p, -376b-3p, -376b-5p and - 409-5p). Further analysis using ELISA for inflammatory markers and real-time PCR (RT-PCR) for differentially enriched miRs identified miR-34c as a potential target for the suppression of UB inflammation in cystitis. Blocking miR-34c by antagomir ex vivo reduced STAT3, TGF-β1, and VEGF expression in the UBs, which was induced during cystitis as compared to control. Interestingly, miR-34c inhibition also downregulated ROCK2 but elevated ROCK1 expression in bladder and detrusor cells. Thus, the present study shows that targeting miR-34c can mitigate the STAT3, TGF-β, and VEGF, inflammatory signaling in UB, and suppress ROCK2 expression in UBs to effectively suppress the inflammatory response in cystitis. This study highlights miR-34c as a potential biomarker and/or serves as the basis for new therapies for the treatment of cystitis.

cAMP responsive element modulator α promotes effector T cells in systemic autoimmune diseases

T lymphocytes play a crucial role in adaptive immunity. Dysregulation of T cell-derived inflammatory cytokine expression and loss of self-tolerance promote inflammation and tissue damage in several autoimmune/inflammatory diseases, including systemic lupus erythematosus (SLE) and psoriasis. The transcription factor cAMP responsive element modulator α (CREMα) plays a key role in the regulation of T cell homeostasis. Increased expression of CREMα is a hallmark of the T cell-mediated inflammatory diseases SLE and psoriasis. Notably, CREMα regulates the expression of effector molecules through trans-regulation and/or the co-recruitment of epigenetic modifiers, including DNA methyltransferases (DNMT3a), histone-methyltransferases (G9a) and histone acetyltransferases (p300). Thus, CREMα may be used as a biomarker for disease activity and/or target for future targeted therapeutic interventions.

The β2-adrenergic receptor agonist terbutaline upregulates T helper-17 cells in a protein kinase A-dependent manner

BACKGROUND

T helper 17 (Th17) cells produce IL-17A cytokine and can exacerbate autoimmune diseases and asthma. The β2 adrenergic receptor is a g protein-coupled receptor that induces cAMP second messenger pathways. We tested the hypothesis that terbutaline, a β2-adrenergic receptor-specific agonist, promotes IL-17 secretion by memory Th17 cells in a cAMP and PKA-dependent manner.

METHODS

Venous peripheral blood mononuclear cells (PBMC) from healthy human participants were activated with anti-CD3 and anti-CD28 antibodies. Secreted IL-17A was measured by enzyme linked immunosorbent assay, intracellular IL-17A, and RORγ were measured using flow cytometry, and RORC by qPCR. Memory CD3+CD4+CD45RA-CD45RO+ T cells were obtained by immunomagnetic negative selection and activated with tri-antibody complex CD3/CD28/CD2. Secreted IL-17A, intracellular IL-17A, RORC were measured, and phosphorylated-serine133-CREB was measured by western blotting memory Th cells.

RESULTS

Terbutaline increased IL-17A (p < 0.001), IL-17A+ cells (p < 0.05), and RORC in activated PBMC and memory Th cells. The PKA inhibitors H89 (p < 0.001) and Rp-cAMP (p < 0.01) abrogated the effects of terbutaline on IL-17A secretion in PBMC and memory T cells. Rolipram increased IL-17A (p < 0.01) to a similar extent as terbutaline. P-Ser133-CREB was increased by terbutaline (p < 0.05) in memory T cells.

CONCLUSION

Terbutaline augments memory Th17 cells in lymphocytes from healthy participants. This could exacerbate autoimmune diseases or asthma, in cases where Th17 cells are considered to be pro-inflammatory.

Soluble adenylyl cyclase contributes to imiquimod-mediated inflammation and is a potential therapeutic target in psoriasis

Cyclic AMP (cAMP) has a key role in psoriasis pathogenesis, as indicated by the therapeutic efficacy of phosphodiesterase inhibitors that prevent the degradation of cAMP. However, whether soluble adenylate cyclase (sAC) (encoded by the ADCY10 gene), which is an important source for cAMP, is involved in Th17 cell-mediated inflammation or could be an alternative therapeutic target in psoriasis is unknown. We have utilized the imiquimod model of murine psoriasiform dermatitis to address this question. Adcy10-/- mice had reduced erythema, scaling and swelling in the skin and reduced CD4+ IL17+ cell numbers in the draining lymph nodes, compared with wild-type mice after induction of psoriasiform dermatitis with imiquimod. Keratinocyte-specific knock out of Adcy10 had no effect on imiquimod-induced ear swelling suggesting keratinocyte sAC has no role in imiquimod-induced inflammation. During Th17 polarization in vitro, naive T cells from Adcy10-/- mice exhibited reduced IL17 secretion and IL-17+ T-cell proliferation suggesting that differentiation into Th17 cells is suppressed without sAC activity. Interestingly, loss of sAC did not impact the expression of Th17 lineage-defining transcription factors (such as Rorc and cMaf) but rather was required for CREB-dependent gene expression, which is known to support Th17 cell gene expression. Finally, topical application of small molecule sAC inhibitors (sACi) reduced imiquimod-induced psoriasiform dermatitis and Il17 gene expression in the skin. Collectively, these findings demonstrate that sAC is important for psoriasiform dermatitis in mouse skin. sACi may provide an alternative class of topical therapeutics for Th17-mediated skin diseases.

Mettl3-m6A-Creb1 forms an intrinsic regulatory axis in maintaining iNKT cell pool and functional differentiation

N6-methyladenosine (m6A) methyltransferase Mettl3 is involved in conventional T cell immunity; however, its role in innate immune cells remains largely unknown. Here, we show that Mettl3 intrinsically regulates invariant natural killer T (iNKT) cell development and function in an m6A-dependent manner. Conditional ablation of Mettl3 in CD4+CD8+ double-positive (DP) thymocytes impairs iNKT cell proliferation, differentiation, and cytokine secretion, which synergistically causes defects in B16F10 melanoma resistance. Transcriptomic and epi-transcriptomic analyses reveal that Mettl3 deficiency disturbs the expression of iNKT cell-related genes with altered m6A modification. Strikingly, Mettl3 modulates the stability of the Creb1 transcript, which in turn controls the protein and phosphorylation levels of Creb1. Furthermore, conditional targeting of Creb1 in DP thymocytes results in similar phenotypes of iNKT cells lacking Mettl3. Importantly, ectopic expression of Creb1 largely rectifies such developmental defects in Mettl3-deficient iNKT cells. These findings reveal that the Mettl3-m6A-Creb1 axis plays critical roles in regulating iNKT cells at the post-transcriptional layer.

Epigenetic regulation of T cell lineages in skin and blood following hematopoietic stem cell transplantation

Allogeneic hematopoietic stem-cell transplantation (HSCT) seeks to reconstitute the host's immune system from donor stem cells. The success of HSCT is threatened by complications including leukemia relapse or graft-versus-host-disease (GvHD). To investigate the underlying regulatory processes in central and peripheral T cell recovery, we performed sequential multi-omics analysis of T cells of the skin and blood during HSCT. We detected rapid effector T cell reconstitution, while emergence of regulatory T cells was delayed. Epigenetic and gene-regulatory programs were associated with recovering T cells and diverged greatly between skin and blood T cells. The BRG1/BRM-associated factor chromatin remodeling complex and histone deacetylases (HDACs) were epigenetic regulators involved in restoration of T cell homeostasis after transplantation. In isolated T cells of patients after HSCT, we observed class I HDAC-inhibitors to modulate their dysbalance. The present study highlights the importance of epigenetic regulation in the recovery of T cells following HSCT.

Transcriptional regulatory networks of circulating immune cells in type 1 diabetes: A community knowledgebase

Investigator-generated transcriptomic datasets interrogating circulating immune cell (CIC) gene expression in clinical type 1 diabetes (T1D) have underappreciated re-use value. Here, we repurposed these datasets to create an open science environment for the generation of hypotheses around CIC signaling pathways whose gain or loss of function contributes to T1D pathogenesis. We firstly computed sets of genes that were preferentially induced or repressed in T1D CICs and validated these against community benchmarks. We then inferred and validated signaling node networks regulating expression of these gene sets, as well as differentially expressed genes in the original underlying T1D case:control datasets. In a set of three use cases, we demonstrated how informed integration of these networks with complementary digital resources supports substantive, actionable hypotheses around signaling pathway dysfunction in T1D CICs. Finally, we developed a federated, cloud-based web resource that exposes the entire data matrix for unrestricted access and re-use by the research community.

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Re-use of transcriptomic type 1 diabetes (T1D) circulating immune cells (CICs) datasets

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We generated transcriptional regulatory networks for T1D CICs

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Use cases generate substantive hypotheses around signaling pathway dysfunction in T1D CICs

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Networks are freely accessible on the web for re-use by the research community

SPRC Suppresses Experimental Periodontitis by Modulating Th17/Treg Imbalance

Object: The aims of the study were to explore the protective effects of S-propargyl-cysteine (SPRC) on periodontitis and to determine the underlying mechanisms.

Methods: A rat periodontitis model was constructed by injecting LPS and SPRC (0, 25, and 50 mg/kg/d) was administered intraperitoneally. H2S and CSE level were detected. The alveolar bone level was evaluated by micro-CT, HE staining and methylene blue staining analysis. Inflammation-related factors, Treg and Th17 cells were detected by immunohistochemistry, RT-PCR, immunofluorescence, Western blot and flow cytometry. Phosphorylation levels of ERK1/2 and CREB were analysed.

Results: The administration of SPRC significantly increased the expression of CSE in the gingival tissue and the concentration of endogenous H2S in the peripheral blood. Simultaneously, SPRC significantly inhibited the resorption of alveolar bone based on the H&E staining, micro-CT and methylene blue staining analysis. Compared with the periodontitis group, the levels of IL-17A, IL-10 were downregulated and IL-6,TGF-β1 were upregulated in the SPRC groups. In the SPRC group, the percentage of TH17 cells and the expression of ROR-γt were downregulated, while the percentage of Tregs and the expression of Foxp3 were upregulated accompanied with inhibition of phosphorylation ERK1/2 and CREB.

Conclusion: SPRC can prevent the progression of periodontitis by regulating the Th17/Treg balance by inhibition of the ERK/CREB signalling pathway.

Prostaglandin E2 directly inhibits the conversion of inducible regulatory T cells through EP2 and EP4 receptors via antagonizing TGF-β signalling

Regulatory T (Treg) cells are essential for control of inflammatory processes by suppressing effector T-cell functions. The actions of PGE2 on the development and function of Treg cells, particularly under inflammatory conditions, are debated. In this study, we employed pharmacological and genetic approaches to examine whether PGE2  had a direct action on T cells to modulate de novo differentiation of Treg cells. We found that TGF-β-induced Foxp3 expression and iTreg cell differentiation in vitro is markedly inhibited by PGE2 , which was mediated by the receptors EP2 and EP4. Mechanistically, PGE2 -EP2/EP4 signalling interrupts TGF-β signalling during iTreg differentiation. Moreover, EP4 deficiency in T cells impaired iTreg cell differentiation in vivo. Thus, our results demonstrate that PGE2 negatively regulates iTreg cell differentiation through a direct action on T cells, highlighting the potential for selectively targeting the PGE2 -EP2/EP4 pathway to control T cell-mediated inflammation.

RNA-sequencing identifies differentially expressed genes in T helper 17 cells in peritoneal fluid of patients with endometriosis

Innate and adaptive immune factors play significant roles in the pathophysiology of endometriosis. T helper 17 (Th17) cells, a pro-inflammatory T cell subset, were considered to contribute to the progression of endometriosis lesions. However, the regulatory mechanisms of Th17 cells in endometriosis remain unidentified, partially due to the difficulty in recovering live Th17 cells from endometriosis patients. In this study, by flow cytometry analysis of a set of chemokine receptors including CXCR3, CCR4, CCR10, and CCR6, live RORγt-and-IL-17A-expressing Th17 cells were enriched from peritoneal fluid (PF) of patients with different stages of endometriosis for the first time, RNA-sequencing (RNA-Seq) of these PF Th17 cells revealed significantly up-regulated genes and down-regulated genes in stage I-II and stage III-IV endometriosis, compared with their counterparts in normal PF. In conclusion, this study provides a novel method to isolate live Th17 cells from endometriosis patients, unveils an array of differentially expressed genes in endometriosis Th17 cells, and offers valuable gene expression profile information for endometriosis clinical research.

Buserelin Inhibits the Immunosuppressive Activity of Regulatory T Cells through the Protein Kinase A Signaling in a Central Precocious Puberty Model

Background: Gonadotropin-releasing hormone analogs (GnRHas) are used for treating central precocious puberty (CPP). However, their roles in the regulation of immune cells especially regulatory T cells (Tregs) remains elusive. Therefore, we characterized buserelin-induced phenotypical and functional changes of Tregs.Methods: A rat CPP model was established followed by administration of buserelin acetate. Flow cytometry was used to evaluate the expression of functional molecules in splenic Tregs. The suppressive activity of Tregs was determined by the suppression assay. GnRHR expression in Tregs was assessed by flow cytometry analysis and Immunoblotting. Normal Tregs were then stimulated and treated with buserelin acetate in vitro. After that, Foxp3 expression, Treg proliferation, and cytokine production were analyzed by flow cytometry. Intracellular signaling was evaluated by Immunoblotting, and Treg function was determined by the suppression assay.Results: After in vivo buserelin treatment, the frequency of splenic Tregs was decreased, with the reduction in the expression of Foxp3, IL-10, and TGF-β. The suppressive activity of Tregs was weakened. Buserelin down-regulated Foxp3 expression while promoting the expression of RORγt and IL-17 in Tregs through activating the protein kinase A (PKA) pathway in vitro. The PKA inhibitor H-89 abolished the effect of buserelin and enhanced Treg function.Conclusion: Buserelin impaired the immunosuppressive activity of Tregs through the PKA signal pathway. Buserelin-induced activation of PKA signaling down-regulated Foxp3 expression while promoting RORγt expression in Tregs, and subsequently weakened Treg function. Our study indicates the necessity of monitoring Treg activity in CPP patients to avoid potential autoimmunity or inflammation.

IL-15 Upregulates Telomerase Expression and Potently Increases Proliferative Capacity of NK, NKT-Like, and CD8 T Cells

Interleukin-15 (IL-15) is a cytokine that has been shown to expand CD8 T cell and natural killer (NK) cell populations, and therefore has potential for potentiating adoptive immune cell therapy for cancer. Previously, IL-15 has been shown to induce proliferation of CD8 memory T cells through activation of telomerase. Here, we investigated whether telomerase is also activated during the IL-15 mediated proliferation of NK and NKT-like (CD56+CD3+) cells. We also examined the extent that each of the three signaling pathways known to be stimulated by IL-2/IL-15 (JAK-STAT, PI3K-AKT Ras-RAF/MAPK) were activated and involved in the telomerase expression in the three cell types NK, NKT, or CD8 T cells. To assess cell proliferation and doubling, peripheral blood mononuclear cells (PBMCs) or isolated NK, NKT-like or CD8 T cells were incubated with varying concentrations of IL-15 or IL-2 for 7 days. CD8 T, NK, and NKT cell expansion was determined by fluorophore-conjugated antibody staining and flow cytometry. Cell doubling was investigated using carboxyfluorescein-succinimidyl-ester (CFSE). Telomerase expression was investigated by staining cells with anti-telomerase reverse transcriptase (anti-TERT). Telomerase activity in CD56+ and CD8 T cells was also measured via Telomerase Repeat Amplification Protocol (TRAP). Analysis of cellular expansion, proliferation and TERT expression concluded that IL-15 increased cellular growth of NK, NKT, and CD8 T cells more effectively than IL-2 using low or high doses. IL-15, increased TERT expression in NK and NKT cells by up to 2.5 fold, the same increase seen in CD8 T cells. IL-2 had effects on TERT expression only at high doses (100–1000 ng/ml). Proteome profiling identified that IL-15 activated selected signaling proteins in the three pathways (JAK-STAT, PI3K-AKT, Ras-MAPK) known to mediate IL-2/IL-15 signaling, more strongly than IL-2. Evaluation by signaling pathway inhibitors revealed that JAK/STAT and PI3K/AKT pathways are important in IL-15’s ability to upregulate TERT expression in NK and NKT cells, whereas all three pathways were involved in CD8 T cell TERT expression. In conclusion, this study shows that IL-15 potently stimulates TERT upregulation in NK and NKT cells in addition to CD8 T cells and is therefore a valuable tool for adoptive cell therapies.

Down-regulation of A3AR signaling by IL-6-induced GRK2 activation contributes to Th17 cell differentiation

IL-6-triggered Th17 cell expansion is responsible for the pathogenesis of many immune diseases including rheumatoid arthritis (RA). Traditionally, IL-6 induces Th17 cell differentiation through JAK-STAT3 signaling. In the present work, PKA inhibition reduces in vitro induction of Th17 cells, while IL-6 stimulation of T cells facilitates the internalization of A₃AR and increased cAMP production in a GRK2 dependent manner. Inhibition of GRK2 by paroxetine (PAR) or genetic depletion of GRK2 restored A₃AR distribution and prevented Th17 cell differentiation. Furthermore, in vivo PAR treatment effectively reduced the splenic Th17 cell proportion in a rat model of collagen-induced arthritis (CIA) which was accompanied by a significant improvement in clinical manifestations. These results indicate that IL-6-induced Th17 cell differentiation not only occurs through JAK-STAT3-RORγt but is also mediated through GRK2-A₃AR-cAMP-PKA-CREB/ICER-RORγt. This elucidates the significance of GRK2-controlled cAMP signaling in the differentiation of Th17 cells and its potential application in treating Th17-driven immune diseases such as RA.

A Novel, Pan-PDE Inhibitor Exerts Anti-Fibrotic Effects in Human Lung Fibroblasts via Inhibition of TGF-β Signaling and Activation of cAMP/PKA Signaling

Phosphodiesterase (PDE) inhibitors are currently a widespread and extensively studied group of anti-inflammatory and anti-fibrotic compounds which may find use in the treatment of numerous lung diseases, including asthma and chronic obstructive pulmonary disease. Several PDE inhibitors are currently in clinical development, and some of them, e.g., roflumilast, are already recommended for clinical use. Due to numerous reports indicating that elevated intracellular cAMP levels may contribute to the alleviation of inflammation and airway fibrosis, new and effective PDE inhibitors are constantly being sought. Recently, a group of 7,8-disubstituted purine-2,6-dione derivatives, representing a novel and prominent pan-PDE inhibitors has been synthesized. Some of them were reported to modulate transient receptor potential ankyrin 1 (TRPA1) ion channels as well. In this study, we investigated the effect of selected derivatives (832—a pan-PDE inhibitor, 869—a TRPA1 modulator, and 145—a pan-PDE inhibitor and a weak TRPA1 modulator) on cellular responses related to airway remodeling using MRC-5 human lung fibroblasts. Compound 145 exerted the most considerable effect in limiting fibroblast to myofibroblasts transition (FMT) as well as proliferation, migration, and contraction. The effect of this compound appeared to depend mainly on its strong PDE inhibitory properties, and not on its effects on TRPA1 modulation. The strong anti-remodeling effects of 145 required activation of the cAMP/protein kinase A (PKA)/cAMP response element-binding protein (CREB) pathway leading to inhibition of transforming growth factor type β₁ (TGF-β₁) and Smad-dependent signaling in MRC-5 cells. These data suggest that the TGF-β pathway is a major target for PDE inhibitors leading to inhibitory effects on cell responses involved in airway remodeling. These potent, pan-PDE inhibitors from the group of 7,8-disubstituted purine-2,6-dione derivatives, thus represent promising anti-remodeling drug candidates for further research.

Double-faced implication of CD4+ Foxp3+ regulatory T cells expanded by acute dengue infection via TLR2/MyD88 pathway

Dengue infection causes dengue fever (DF) and dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS). CD4⁺ Foxp3⁺ Tregs are expanded in patients during dengue infection, and appear to be associated with clinical severity. However, molecular pathways involved in Treg proliferation and the reason for their insufficient control of severe diseases are poorly understood. Here, dengue infection induced the proliferation of functional CD4⁺ Foxp3⁺ Tregs via TLR2/MyD88 pathway. Surface TLR2 on Tregs was responsible for their proliferation, and dengue-expanded Tregs subverted in vivo differentiation of effector CD8⁺ T cells. An additional interesting finding was that dengue-infected hosts displayed changed levels of susceptibility to other diseases in TLR2-dependent manner. This change included enhanced susceptibility to tumors and bacterial infection, but highly enhanced resistance to viral infection. Further, the transfer of dengue-proliferated Tregs protected the recipients from dengue-induced DHF/DSS and LPS-induced sepsis. In contrast, dengue-infected hosts were more susceptible to sepsis, an effect attributable to early TLR2-dependent production of proinflammatory cytokines. These facts may explain the reason why in some patients, dengue-proliferated Tregs is insufficient to control DF and DHF/DSS. Also, our observations lead to new insights into Treg responses activated by dengue infection in a TLR2-dependent manner, which could differentially act on subsequent exposure to other disease-producing situations.

Mass cytometry reveals systemic and local immune signatures that distinguish inflammatory bowel diseases

Inflammatory bowel disease (IBD) includes Crohn's disease and ulcerative colitis. Each disease is characterized by a diverse set of potential manifestations, which determine patients' disease phenotype. Current understanding of phenotype determinants is limited, despite increasing prevalence and healthcare costs. Diagnosis and monitoring of disease requires invasive procedures, such as endoscopy and tissue biopsy. Here we report signatures of heterogeneity between disease diagnoses and phenotypes. Using mass cytometry, we analyze leukocyte subsets, characterize their function(s), and examine gut-homing molecule expression in blood and intestinal tissue from healthy and/or IBD subjects. Some signatures persist in IBD despite remission, and many signatures are highly represented by leukocytes that express gut trafficking molecules. Moreover, distinct systemic and local immune signatures suggest patterns of cell localization in disease. Our findings highlight the importance of gut tropic leukocytes in circulation and reveal that blood-based immune signatures differentiate clinically relevant subsets of IBD.

Targeting Adenosine in Cancer Immunotherapy to Enhance T-Cell Function

T cells play a critical role in cancer control, but a range of potent immunosuppressive mechanisms can be upregulated in the tumor microenvironment (TME) to abrogate their activity. While various immunotherapies (IMTs) aiming at re-invigorating the T-cell-mediated anti-tumor response, such as immune checkpoint blockade (ICB), and the adoptive cell transfer (ACT) of natural or gene-engineered ex vivo expanded tumor-specific T cells, have led to unprecedented clinical responses, only a small proportion of cancer patients benefit from these treatments. Important research efforts are thus underway to identify biomarkers of response, as well as to develop personalized combinatorial approaches that can target other inhibitory mechanisms at play in the TME. In recent years, adenosinergic signaling has emerged as a powerful immuno-metabolic checkpoint in tumors. Like several other barriers in the TME, such as the PD-1/PDL-1 axis, CTLA-4, and indoleamine 2,3-dioxygenase (IDO-1), adenosine plays important physiologic roles, but has been co-opted by tumors to promote their growth and impair immunity. Several agents counteracting the adenosine axis have been developed, and pre-clinical studies have demonstrated important anti-tumor activity, alone and in combination with other IMTs including ICB and ACT. Here we review the regulation of adenosine levels and mechanisms by which it promotes tumor growth and broadly suppresses protective immunity, with extra focus on the attenuation of T cell function. Finally, we present an overview of promising pre-clinical and clinical approaches being explored for blocking the adenosine axis for enhanced control of solid tumors.

CREB signals as PBMC-based biomarkers of cognitive dysfunction: A novel perspective of the brain-immune axis

To date, there is no reliable biomarker for the assessment or determination of cognitive dysfunction in Alzheimer's disease and related dementia. Such a biomarker would not only aid in diagnostics, but could also serve as a measure of therapeutic efficacy. It is widely acknowledged that the hallmarks of Alzheimer's disease, namely, amyloid deposits and neurofibrillary tangles, as well as their precursors and metabolites, are poorly correlated with cognitive function and disease stage and thus have low diagnostic or prognostic value. A lack of biomarkers is one of the major roadblocks in diagnosing the disease and in assessing the efficacy of potential therapies. The phosphorylation of cAMP Response Element Binding protein (pCREB) plays a major role in memory acquisition and consolidation. In the brain, CREB activation by phosphorylation at Ser133 and the recruitment of transcription cofactors such as CREB binding protein (CBP) is a critical step for the formation of memory. This set of processes is a prerequisite for the transcription of genes thought to be important for synaptic plasticity, such as Egr-1. Interestingly, recent work suggests that the expression of pCREB in peripheral blood mononuclear cells (PBMC) positively correlates with pCREB expression in the postmortem brain of Alzheimer's patients, suggesting not only that pCREB expression in PBMC might serve as a biomarker of cognitive dysfunction, but also that the dysfunction of CREB signaling may not be limited to the brain in AD, and that a link may exist between the regulation of CREB in the blood and in the brain. In this review we consider the evidence suggesting a correlation between the level of CREB signals in the brain and blood, the current knowledge about CREB in PBMC and its association with CREB in the brain, and the implications and mechanisms for a neuro-immune cross talk that may underlie this communication. This Review will discuss the possibility that peripheral dysregulation of CREB is an early event in AD pathogenesis, perhaps as a facet of immune system dysfunction, and that this impairment in peripheral CREB signaling modifies CREB signaling in the brain, thus exacerbating cognitive decline in AD. A more thorough understanding of systemic dysregulation of CREB in AD will facilitate the search for a biomarker of cognitive function in AD, and also aid in the understanding of the mechanisms underlying cognitive decline in AD.

Prostaglandin-cytokine crosstalk in chronic inflammation

Chronic inflammation underlies various debilitating disorders including autoimmune, neurodegenerative, vascular and metabolic diseases as well as cancer, where aberrant activation of the innate and acquired immune systems is frequently seen. Since non-steroidal anti-inflammatory drugs exert their effects by inhibiting COX and suppressing PG biosynthesis, PGs have been traditionally thought to function mostly as mediators of acute inflammation. However, an inducible COX isoform, COX-2, is often highly expressed in tissues of the chronic disorders, suggesting an as yet unidentified role of PGs in chronic inflammation. Recent studies have shown that in addition to their short-lived actions in acute inflammation, PGs crosstalk with cytokines and amplify the cytokine actions on various types of inflammatory cells and drive pathogenic conversion of these cells by critically regulating their gene expression. One mode of such PG-mediated amplification is to induce the expression of relevant cytokine receptors, which is typically observed in Th1 cell differentiation and Th17 cell expansion, events leading to chronic immune inflammation. Another mode of amplification is cooperation of PGs with cytokines at the transcription level. Typically, PGs and cytokines synergistically activate NF-κB to induce the expression of inflammation-related genes, one being COX-2 itself, which makes PG-mediated positive feedback loops. This signalling consequently enhances the expression of various NF-κB-induced genes including chemokines to macrophages and neutrophils, which enables sustained infiltration of these cells and further amplifies chronic inflammation. In addition, PGs are also involved in tissue remodelling such as fibrosis and angiogenesis. In this article, we review these findings and discuss their relevance to human diseases.

Leukocyte-Associated Ig-like Receptor 1 Inhibits Th1 Responses but Is Required for Natural and Induced Monocyte-Dependent Th17 Responses

Leukocyte-associated Ig-like receptor 1 (LAIR1) is an ITIM-bearing collagen receptor expressed by leukocytes and is implicated in immune suppression. However, using a divalent soluble LAIR1/Fc recombinant protein to block interaction of cell surface LAIR1 with matrix collagen, we found that whereas T_h1 responses were enhanced as predicted, T_h17 responses were strongly inhibited. Indeed, LAIR1 on both T cells and monocytes was required for optimal T_h17 responses to collagen type (Col)V. For pre-existing "natural" T_h17 response to ColV, the LAIR1 requirement was absolute, whereas adaptive T_h17 and T_h1/17 immune responses in both mice and humans were profoundly reduced in the absence of LAIR1. Furthermore, the addition of C1q, a natural LAIR1 ligand, decreased T_h1 responses in a dose-dependent manner, but it had no effect on T_h17 responses. In IL-17-dependent murine organ transplant models of chronic rejection, LAIR1^+/+ but not LAIR1^-/- littermates mounted strong fibroproliferative responses. Surface LAIR1 expression was higher on human T_h17 cells as compared with T_h1 cells, ruling out a receptor deficiency that could account for the differences. We conclude that LAIR1 ligation by its natural ligands favors T_h17 cell development, allowing for preferential activity of these cells in collagen-rich environments. The emergence of cryptic self-antigens such as the LAIR1 ligand ColV during ischemia/reperfusion injury and early acute rejection, as well as the tendency of macrophages/monocytes to accumulate in the allograft during chronic rejection, favors T_h17 over T_h1 development, posing a risk to long-term graft survival.

Cholera toxin enhances interleukin-17A production in both CD4+ and CD8+ cells via a cAMP/protein kinase A-mediated interleukin-17A promoter activation

Cholera toxin (CT) is a bacterial component that increases intracellular cAMP levels in host cells and suppresses T-cell activation. Recently, CT was reported to induce T helper type 17-skewing dendritic cells and activate interleukin-17A (IL-17A) production in CD4⁺ T cells through a cAMP-dependent pathway. However, the underlying mechanism by which cAMP regulates IL-17A production in T cells is not completely defined. In this study, we took advantage of a small molecule protein kinase A (PKA) inhibitor (H89) and different cAMP analogues: a PKA-specific activator (N6-benzoyl-adenosine-cAMP), an exchange protein activated by cAMP-specific activator (Rp-8-chlorophenylthio-2'-O-methyl cAMP), and a PKA inhibitor (Rp-8-bromo-cAMP), to elucidate the signalling cascade of cAMP in IL-17A regulation in T cells. We found that CT induced IL-17A production and IL-17A promoter activity in activated CD4⁺ T cells through a cAMP/PKA pathway. Moreover, this regulation was via cAMP-response element binding protein (CREB) -mediated transcriptional activation by using the transfection of an IL-17A promoter-luciferase reporter construct and CREB small interfering RNA in Jurkat cells. Also, we showed that CREB bound to the CRE motif located at -183 of the IL-17A promoter in vitro. Most interestingly, not only in CD4⁺ T cells, CT also enhanced cAMP/PKA-dependent IL-17A production and CREB phosphorylation in CD8⁺ T cells. In conclusion, our data suggest that CT induces an IL-17A-dominated immune microenvironment through the cAMP/PKA/CREB signalling pathway. Our study also highlights the potentials of CT and cAMP in modulating T helper type 17 responses in vivo.

Dual Mechanisms for Balancing Th17 and Treg Cell Fate by CREB

Th17 cells, which express the cytokine IL-17A, and master regulator RORγt, are important in the inflammatory response to fungal and bacterial pathogens, but also have a pathogenic role in many inflammatory disorders. In contrast, regulatory T cells (Treg), expressing the Foxp3 transcription factor, have a suppressive function and can dampen an immune response. The appropriate balance of these distinct effector functions is critical for an effective immune response and autoimmunity can arise if this process goes awry. In this issue, Wang et al. demonstrate a critical role for the transcription factor CREB (cyclic AMP-responsive element binding protein) in regulating the balance between inflammatory Th17 and suppressive Treg cells with implications for autoimmunity.