High-mobility group box 1 protein (HMGB1) has been studied as a key mediator of inflammatory diseases, including sepsis. Regulating secretion is important in the control of HMGB1-mediated inflammation. Previously, it was shown that HMGB1 needs to be phosphorylated for secretion. In this study, we show that HMGB1 is phosphorylated by the classical protein kinase C (cPKC) and is secreted by a calcium-dependent mechanism. For this study, RAW264.7 cells and human peripheral blood monocytes were treated with PI3K inhibitors wortmannin, LY294002, and ZSTK474, resulting in inhibition of LPS-stimulated HMGB1 secretion, whereas inhibitors of NF-κB and MAPKs p38 and ERK showed no inhibition. Akt inhibitor IV and mammalian target of rapamycin inhibitor rapamycin did not inhibit HMGB1 secretion. However, the PKC inhibitors Gö6983 (broad-spectrum PKC), Gö6976 (cPKC), and Ro-31-7549 (cPKC) and phosphoinositide-dependent kinase 1 inhibitor, which results in protein kinase C (PKC) inhibition, inhibited LPS-stimulated HMGB1 secretion. PKC activators, PMA and bryostatin-1, enhanced HMGB1 secretion. In an in vitro kinase assay, HMGB1 was phosphorylated by recombinant cPKC and by purified nuclear cPKC from LPS-stimulated RAW264.7 cells, but not by casein kinase II or cdc2. HMGB1 secretion was also induced by the calcium ionophore A23187 and inhibited by the Ca2+ chelators BAPTA-AM and EGTA. These findings support a role for Ca2+-dependent PKC in HMGB1 secretion. Thus, we propose that cPKC is an effector kinase of HMGB1 phosphorylation in LPS-stimulated monocytes and PI3K-phosphoinositide-dependent kinase 1 may act in concert to control HMGB1 secretion independent of the NF-κB, p38, and ERK pathways.

Lipopolysaccharide (LPS) triggers deleterious systemic inflammatory responses when released into the circulation. LPS-binding protein (LBP) in the serum plays an important role in modifying LPS toxicity by facilitating its interaction with LPS signaling receptors, which are expressed on the surface of LPS-responsive cells. We have previously demonstrated that high mobility group box 1 (HMGB1) can bind to and transfer LPS, consequently increasing LPSinduced TNF-a production in human peripheral blood mononuclear cells (PBMCs). We report here on the identification of two LPS-binding domains within HMGB1. Furthermore, using 12 synthetic HMGB1 peptides, we define the LPS-binding regions within each domain. Among them, synthetic peptides HPep1 and HPep6, which are located in the A and B box domains of HMGB1, bind to the polysaccharide and lipid A moieties of LPS respectively. Both HPep1 and HPep6 peptides inhibited binding of LPS to LBP and HMGB1, LBP-mediated LPS transfer to CD14, and cellular uptake of LPS in RAW264.7 cells. These peptides also inhibited LPS-induced TNF-a release in human PBMCs and induced lower levels of TNF-a in the serum in a subclinical endotoxemia mouse model. These results indicate that HMGB1 has two LPS-binding peptide regions that can be utilized to design anti-sepsis or LPS-neutralizing therapeutics.Keywords: Endotoxin shock . High mobility group box 1 . Inflammation . Lipopolysaccharide Supporting Information available online IntroductionLipopolysaccharide (LPS) is the main cause of Gram-negative bacterial sepsis. LPS consists of a lipid A component, a sugar moiety that forms the core, and an O-polysaccharide of variable length [1]. When LPS is introduced into the bloodstream, LPSbinding protein (LBP) recognizes the LPS molecules and catalyzes the movement of LPS from LPS aggregates. LBP transfers LPS to CD14, which in turn transfers LPS to the TLR4-MD2 receptor. Recently, the crystal structure of the TLR4-MD2-LPS complex has been determined [2]. Although there are several proteins that bind LPS, LBP is the first key protein that initiates and amplifies à These authors have contributed equally to this study. Eur. J. Immunol. 2011. 41: 2753-2762 DOI 10.1002 Innate immunity 2753 the LPS-mediated pro-inflammatory process that results in fatal septic shock syndrome. The nuclear protein high-mobility group box 1 protein (HMGB1) is involved in nucleosome stabilization, gene transcription, and neurite outgrowth [3]. HMGB1 can be actively or passively released into the extracellular space through acetylation [4], phosphorylation [5,6], methylation [7], or cell necrosis [8]. HMGB1 can trigger inflammation [8] and is a late mediator of endotoxemia and sepsis in both animal models and humans [9][10][11][12]. Although HMGB1 is a well-known mediator of endotoxemia and a proinflammatory cytokine-like protein in vivo, purified recombinant HMGB1 only has weak in vitro proinflammatory activity, such as the induction of TNF-a production [13,14]. HMGB1 can form highly inflammatory complexes with CpG DNA [15...

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Background Irritable bowel syndrome (IBS), the most common functional gastrointestinal disorder, is characterized by chronic abdominal pain and bowel habit changes. Although diverse complicated etiologies are involved in its pathogenesis, a dysregulated gut–brain axis may be an important factor. Red ginseng (RG), a traditional herbal medicine, is proven to have anti-inflammatory effects and improve brain function; however, these effects have not been investigated in IBS. Methods Three-day intracolonic zymosan injections were used to induce post-infectious human IBS-like symptoms in mice. The animals were randomized to receive either phosphate-buffered saline (CG) or RG (30/100/300 mg/kg) for 10 days. Amitriptyline and sulfasalazine were used as positive controls. Macroscopic scoring was performed on day 4. Visceral pain and anxiety-like behaviors were assessed by colorectal distension and elevated plus maze and open field tests, respectively, on day 10. Next-generation sequencing of gut microbiota was performed, and biomarkers involved in gut–brain axis responses were analyzed. Results Compared to CG, RG significantly decreased the macroscopic score, frequency of visceral pain, and anxiety-like behavior in the IBS mice. These effects were comparable to those after sulfasalazine and amitriptyline treatments. Moreover, RG significantly increased the proliferation of beneficial microbes, including Lactobacillus johnsonii , Lactobacillus reuteri , and Parabacteroides goldsteinii . RG significantly suppressed expression of IL-1β and c-fos in the gut and prefrontal cortex, respectively. Further, it restored the plasma levels of corticosterone to within the normal range, accompanied by an increase in adrenocorticotropic hormone. Conclusion RG may be a potential therapeutic option for the management of human IBS.

Crotamiton is an anti-scabies drug, but it was recently found that crotamiton also suppresses non-scabietic itching in mice. However, the underlying mechanism is largely unclear. Therefore, aim of the study is to investigate mechanisms of the anti-pruritic effect of crotamiton for non-scabietic itching. Histamine and chloroquine are used as non-scabietic pruritogens. The effect of crotamiton was identified using fluorometric intracellular calcium assays in HEK293T cells and primary cultured dorsal root ganglion (DRG) neurons. Further in vivo effect was evaluated by scratching behavior tests. Crotamiton strongly inhibited histamine-induced calcium influx in HEK293T cells, expressing both histamine receptor 1 (H1R) and transient receptor potential vanilloid 1 (TRPV1), as a model of histamine-induced itching. Similarly, it also blocked chloroquine-induced calcium influx in HEK293T cells, expressing both Mas-related G-protein-coupled receptor A3 (MRGPRA3) and transient receptor potential A1 (TRPA1), as a model of histamine-independent itching. Furthermore, crotamiton also suppressed both histamine- and chloroquine-induced calcium influx in primary cultures of mouse DRG. Additionally, crotamiton strongly suppressed histamine- and chloroquine-induced scratching in mice. Overall, it was found that crotamiton has an anti-pruritic effect against non-scabietic itching by histamine and chloroquine. Therefore, crotamiton may be used as a general anti-pruritic agent, irrespective of the presence of scabies.