Jae-Hoon Chang

Protective effect of 7-O-succinyl macrolactin A against intestinal inflammation is mediated through PI3-kinase/Akt/mTOR and NF-κB signaling pathways.

Pro-inflammatory cytokines, such as tumor necrosis factor (TNF)-α, are pivotal for the development of inflammatory bowel disease (IBD), and down-regulation of the cytokines and cytokine-induced inflammatory responses therefore constitute pharmacological targets for the development of therapeutic strategies in IBD. In the current study, we found that 7-O-succinyl macrolactin A (SMA), a macrolide, potently inhibited TNF-α-induced adhesion of monocytes to colonic epithelial cells in a concentration-dependent manner, similar to rapamycin, a mTOR inhibitor. In addition, oral administration of SMA resulted in a significant suppression of clinical signs of TNBS-induced rat colitis, including weight loss, colon tissue edema, and myeloperoxidase activity, a marker for inflammatory cell infiltration, as well as microscopic damage score in a histomorphological examination of HE-stained colon tissue. More importantly, SMA was more efficacious in inhibition of intestinal inflammation than 5-aminosalicylic acid (5-ASA), an active metabolite of sulfasalazine, the most commonly prescribed agent for the treatment of IBD. Such anti-inflammatory activity showed correlation with significant suppression of adhesion molecules (ICAM-1 and VCAM-1), T-helper 1-type cytokines (TNF-α, IL-6), and chemokines (MCP-1, IL-8). In addition to inhibition of NF-κB nuclear translocation, SMA also caused significant suppression of TNF-α-induced phosphorylation of PI3K, Akt, mTOR and p70S6 kinase, similar to the effect of rapamycin, an immunosuppressant macrolide. Taken together, the current results suggest that managing both mTOR and NF-κB activation pathways using SMA may be a good therapeutic intervention for the treatment of IBD.

Regulatory T Cells in B Cell Follicles

Understanding germinal center reactions is crucial not only for the design of effective vaccines against infectious agents and malignant cells but also for the development of therapeutic intervention for the treatment of antibody-mediated immune disorders. Recent advances in this field have revealed specialized subsets of T cells necessary for the control of B cell responses in the follicle. These cells include follicular regulatory T cells and Qa-1-restricted cluster of differentiation (CD)8+ regulatory T cells. In this review, we discuss the current knowledge related to the role of regulatory T cells in the B cell follicle.

Regulatory T cell-targeted hybrid nanoparticles combined with immuno-checkpoint blockage for cancer immunotherapy

ABSTRACT Immunosuppression in tumor microenvironments induced by regulatory T (Treg) cells is regarded a critical mechanism of tumor immune escape and poses a major impediment to cancer immunotherapy. In this study, we developed tLyp1 peptide‐conjugated hybrid nanoparticles for targeting Treg cells in the tumor microenvironment. The tLyp1 peptide‐modified hybrid nanoparticles presented good stability and effective targeting to Treg cells, and they enhanced the effect of imatinib in downregulating Treg cell suppression through inhibition of STAT3 and STAT5 phosphorylation. In addition, an in vivo study revealed high tumor accumulation of the hybrid nanoparticle. Specifically, prolonged survival rate, enhanced tumor inhibition, reduced intratumoral Treg cells, and elevated intratumoral CD8+ T cells against tumor were observed when combined with checkpoint‐blockade by using anti‐cytotoxic T‐lymphocyte antigen‐4 antibody. This study provided groundwork for a repertoire of nanoparticle‐based drugs for targeting and modulating Treg cell function in the tumor microenvironment and for improving antitumor immunotherapy.

Globular Adiponectin Inhibits Lipopolysaccharide-Primed Inflammasomes Activation in Macrophages via Autophagy Induction: The Critical Role of AMPK Signaling

The inflammasome acts as a key platform for the activation of pro-inflammatory cytokines. Adiponectin exhibits potent anti-inflammatory properties. However, the effect of adiponectin on the modulation of the inflammasome has not been explored. Herein, we show that globular adiponectin (gAcrp) suppressed lipopolysaccharide (LPS)-primed inflammasomes activation in murine peritoneal macrophages judged by prevention of interleukin-1β (IL-1β) maturation, caspase-1 activation, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) speck formation, and pyroptotic cell death. Interestingly, pretreatment with 3-methyl adenine, a pharmacological inhibitor of autophagy, abrogated the suppressive effects of gAcrp on IL-1β secretion and caspase-1 activation, indicating the crucial role of autophagy induction in gAcrp-modulation of the inflammasome activation. In addition, inhibition of 5′Adenosine monophaspahate (AMP)-activated protein kinase (AMPK) signaling abolished suppressive effect of gAcrp on inflammasomes activation. Furthermore, autophagy induction or inhibition of the inflammasome activation by gAcrp was not observed in macrophages deficient in AMPK. Taken together, these results indicate that adiponectin inhibits LPS-primed inflammasomes activation in macrophages via autophagy induction and AMPK signaling-dependent mechanisms.

BJ-3105, a 6-Alkoxypyridin-3-ol Analog, Impairs T Cell Differentiation and Prevents Experimental Autoimmune Encephalomyelitis Disease Progression

CD4+ T cells are essential in inflammation and autoimmune diseases. Interferon-γ (IFN-γ) secreting T helper (Th1) and IL-17 secreting T helper (Th17) cells are critical for several autoimmune diseases. To assess the inhibitory effect of a given compound on autoimmune disease, we screened many compounds with an in vitro Th differentiation assay. BJ-3105, a 6-alkoxypyridin-3-ol analog, inhibited IFN-γ and IL-17 production from polyclonal CD4+ T cells and ovalbumin (OVA)-specific CD4+ T cells which were activated by T cell receptor (TCR) engagement. BJ-3105 ameliorated the experimental autoimmune encephalomyelitis (EAE) model by reducing Th1 and Th17 generation. Notably, Th cell differentiation was significantly suppressed by BJ-3105 treatment without inhibiting in vitro proliferation of T cells or inducing programmed cell death. Mechanistically, BJ-3105 inhibited the phosphorylation of JAK and its downstream signal transducer and activator of transcription (STAT) that is critical for Th differentiation. These results demonstrated that BJ-3105 inhibits the phosphorylation of STAT in response to cytokine signals and subsequently suppressed the differentiation of Th cell responses.

BJ-1108, a 6-Amino-2,4,5-trimethylpyridin-3-ol analogue, regulates differentiation of Th1 and Th17 cells to ameliorate experimental autoimmune encephalomyelitis

BackgroundCD4+ T cells play an important role in the initiation of an immune response by providing help to other cells. Among the helper T subsets, interferon-γ (IFN-γ)-secreting T helper 1 (Th1) and IL-17-secreting T helper 17 (Th17) cells are indispensable for clearance of intracellular as well as extracellular pathogens. However, Th1 and Th17 cells are also associated with pathogenesis and contribute to the progression of multiple inflammatory conditions and autoimmune diseases.ResultsIn the current study, we found that BJ-1108, a 6-aminopyridin-3-ol analogue, significantly inhibited Th1 and Th17 differentiation in vitro in a concentration-dependent manner, with no effect on proliferation or apoptosis of activated T cells. Moreover, BJ-1108 inhibited differentiation of Th1 and Th17 cells in ovalbumin (OVA)-specific OT II mice. A complete Freund’s adjuvant (CFA)/OVA-induced inflammatory model revealed that BJ-1108 can reduce generation of proinflammatory Th1 and Th17 cells. Furthermore, in vivo studies showed that BJ-1108 delayed onset of disease and suppressed experimental autoimmune encephalomyelitis (EAE) disease progression by inhibiting differentiation of Th1 and Th17 cells.ConclusionsBJ-1108 treatment ameliorates inflammation and EAE by inhibiting Th1 and Th17 cells differentiation. Our findings suggest that BJ-1108 is a promising novel therapeutic agent for the treatment of inflammation and autoimmune disease.

Tanshinone IIA suppresses FcεRI-mediated mast cell signaling and anaphylaxis by activation of the Sirt1/LKB1/AMPK pathway

Graphical abstract Figure. No Caption available. ABSTRACT AMP‐activated protein kinase (AMPK) and its upstream mediators liver kinase B1 (LKB1) and sirtuin 1 (Sirt1) are generally known as key regulators of metabolism. We have recently reported that the AMPK pathway negatively regulates mast cell activation and anaphylaxis. Tanshinone IIA (Tan IIA), an active component of Salvia miltiorrhiza extract that is currently used for the treatment of cardiovascular and cerebrovascular diseases, shows anti‐diabetic activity and improves insulin resistance in db/db mice through activation of AMPK. The aim of this study was to evaluate the anti‐allergic activity of Tan IIA in vivo and to investigate the underlying mechanism in vitro in the context of AMPK signaling. The anti‐allergic effect of Tan IIA was evaluated using mouse bone marrow‐derived mast cells (BMMCs) from AMPK&agr;2−/− or Sirt1−/− mice, or BMMCs transfected with siRNAs specific for AMPK&agr;2, LKB1, or Sirt1. AMPK&agr;2−/− and Sirt1−/− mice were used to confirm the anti‐allergic effect of Tan IIA in anaphylaxis in vivo. Tan IIA dose‐dependently inhibited Fc&egr;RI‐mediated degranulation and production of eicosanoids and cytokines in BMMCs. These inhibitory effects were diminished by siRNA‐mediated knockdown or genetic deletion of AMPK&agr;2 or Sirt1. Moreover, Tan IIA inhibited a mast cell‐mediated local passive anaphylactic reaction in wild‐type mice, but not in AMPK&agr;2−/− or Sirt1−/− mice. In conclusion, Tan IIA suppresses Fc&egr;RI‐mediated mast cell activation and anaphylaxis through activation of the inhibitory Sirt1‐LKB1‐AMPK pathway. Thus, Tan IIA may be useful as a new therapeutic agent for mast cell‐mediated allergic diseases.

Sirt1 negatively regulates FcεRI-mediated mast cell activation through AMPK- and PTP1B-dependent processes

Sirt1, a key regulator of metabolism and longevity, has recently been implicated in the regulation of allergic reactions, although the underlying mechanism remains unclear. Here we show that Sirt1 negatively regulates FcεRI-stimulated mast cell activation and anaphylaxis through two mutually regulated pathways involving AMP-activated protein kinase (AMPK) and protein tyrosine phosphatase 1B (PTP1B). Mast cell-specific knockout of Sirt1 dampened AMPK-dependent suppression of FcεRI signaling, thereby augmenting mast cell activation both in vitro and in vivo. Sirt1 inhibition of FcεRI signaling also involved an alternative component, PTP1B, which attenuated the inhibitory AMPK pathway and conversely enhanced the stimulatory Syk pathway, uncovering a novel role of this phosphatase. Moreover, a Sirt1 activator resveratrol stimulated the inhibitory AMPK axis, with reciprocal suppression of the stimulatory PTP1B/Syk axis, thus potently inhibiting anaphylaxis. Overall, our results provide a molecular explanation for the beneficial role of Sirt1 in allergy and underscore a potential application of Sirt1 activators as a new class of anti-allergic agents.

BJ-2266 ameliorates experimental autoimmune encephalomyelitis through down-regulation of the JAK/STAT signaling pathway

CD4+ T cells differentiate into distinct effector subsets upon antigenic stimulation. Cytokines, and micro‐environmental factors present during T‐cell priming, direct differentiation of naïve CD4+ T cells into pro‐inflammatory Th1 and Th17 cells. From extensive screening of 2,4,5‐trimethylpyridin‐3‐ol derivatives with various functional groups at C(6)‐position, BJ‐2266, a 6‐thioureido‐derivative, showed potent inhibitory activity on in vitro T helper (Th)‐cell differentiation. This compound inhibited IFN‐γ and IL‐17 production from polyclonal CD4+ T cells and ovalbumin (OVA)‐specific CD4+ T cells that were activated by T‐cell receptor (TCR) engagement. We assessed the inhibitory effect of BJ‐2266 in experimental autoimmune encephalomyelitis (EAE). Our results suggest that BJ‐2266 treatment significantly suppresses EAE disease progression with reduced generation of Th1 and Th17 cells. Notably, Th‐cell differentiation was significantly suppressed by BJ‐2266 treatment with no effect on apoptosis, activation and proliferation of activated T cells. Furthermore, adoptive transfer of BJ‐2266 treated MOG‐reactive Th1 and Th17 cells led to a lower EAE disease score and better clinical recovery from EAE. The underlying mechanism of BJ‐2266 effect involved the inhibition of JAK/STAT phosphorylation that is critical for Th‐cell differentiation. We conclude that BJ‐2266 regulates the JAK/STAT pathway in response to cytokine signals and subsequently suppresses the differentiation of Th‐cell responses.

15,16-Dihydrotanshinone I suppresses IgE-Ag stimulated mouse bone marrow-derived mast cell activation by inhibiting Syk kinase

ETHNOPHARMACOLOGICAL RELEVANCE 15,16-Dihydrotanshinone I (DHT-I), isolated from the dried root of Salvia miltiorrhiza Bung, which is traditionally used to treat cardiovascular and inflammatory diseases agent in Chinese medicine. DHT-I has been reported to have a broad range of biological activities, including antibacterial activity, and has been used to treat circulatory disorders, hepatitis, inflammation, cancer, and neurodegenerative diseases. AIM OF THE STUDY The aim of this study was to evaluate the anti-allergic inflammatory effects of DHT-I on degranulation and on the generation of eicosanoids, such as, prostaglandin D2 (PGD2) and leukotriene C4 (LTC4), in IgE/Ag-stimulated bone marrow-derived mast cells (BMMCs). MATERIALS AND METHODS The anti-allergic inflammatory activity of DHT-I was evaluated using BMMCs. The effects of DHT-I on mast cell activation were investigated by following degranulation and eicosanoid generation using ELISA and immunoblotting and immunoprecipitation techniques. RESULTS DHT-I at a concentration of 20μM markedly inhibited degranulation and the generation of PGD2 and LTC4 in IgE/Ag-stimulated BMMCs (about 90% inhibitions, respectively). Analyses of FcεRI-mediated signaling pathways demonstrated that DHT-I inhibited the phosphorylations of spleen tyrosine kinase (Syk) and linker for activation of T cells (LAT), and inhibited downstream signaling process, including [Ca(2+)]i mobilization induced by the phosphorylation of phospholipase Cγ1 (PLCγ1), and the activations of mitogen-activated protein kinases (MAPKs) and the Akt-nuclear factor-κB (NF-κB) pathway. CONCLUSIONS DHT-1 inhibits the release of allergic inflammatory mediators from IgE/Ag-stimulated mast cells by suppressing a FcεRI-mediated Syk-dependent signal pathway. This result suggests DHT-I offers a novel developmental basis for drugs targeting allergic inflammatory diseases.