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Abstracts

Life Extension Magazine January 2014
Abstracts

Cytokine suppress

It Is Not Just Folklore: The Aqueous Extract of Mung Bean Coat Is Protective against Sepsis.

Mung bean (Vigna Radiata) has been traditionally used in China both as nutritional food and herbal medicine against a number of inflammatory conditions since the 1050s. A nucleosomal protein, HMGB1, has recently been established as a late mediator of lethal systemic inflammation with a relatively wider therapeutic window for pharmacological interventions. Here we explored the HMGB1-inhibiting capacity and therapeutic potential of mung bean coat (MBC) extract in vitro and in vivo. We found that MBC extract dose-dependently attenuated LPS-induced release of HMGB1 and several chemokines in macrophage cultures. Oral administration of MBC extract significantly increased animal survival rates from 29.4% (in saline group, N = 17 mice) to 70% (in experimental MBC extract group, N = 17 mice, P < 0.05). In vitro, MBC extract stimulated HMGB1 protein aggregation and facilitated both the formation of microtubule-associatedprotein-1-light-chain-3-(LC3-)containing cytoplasmic vesicles, and the production of LC3-II in macrophage cultures. Consequently, MBC extract treatment led to reduction of cellular HMGB1 levels in macrophage cultures, which was impaired by coaddition of two autophagy inhibitors (bafilomycin A1 and 3-methyladenine). Conclusion. MBC extract is protective against lethal sepsis possibly by stimulating autophagic HMGB1 degradation.

Evid Based Complement Alternat Med. 2012;2012:498467

A major ingredient of green tea rescues mice from lethal sepsis partly by inhibiting HMGB1.

BACKGROUND: The pathogenesis of sepsis is mediated in part by bacterial endotoxin, which stimulates macrophages/monocytes to sequentially release early (e.g., TNF, IL-1, and IFN-gamma) and late (e.g., HMGB1) pro-inflammatory cytokines. Our recent discovery of HMGB1 as a late mediator of lethal sepsis has prompted investigation for development of new experimental therapeutics. We previously reported that green tea brewed from the leaves of the plant Camellia sinensis is effective in inhibiting endotoxin-induced HMGB1 release. METHODS AND FINDINGS: Here we demonstrate that its major component, (-)-epigallocatechin-3-gallate (EGCG), but not catechin or ethyl gallate, dose-dependently abrogated HMGB1 release in macrophage/monocyte cultures, even when given 2-6 hours post LPS stimulation. Intraperitoneal administration of EGCG protected mice against lethal endotoxemia, and rescued mice from lethal sepsis even when the first dose was given 24 hours after cecal ligation and puncture. The therapeutic effects were partly attributable to: 1) attenuation of systemic accumulation of proinflammatory mediator (e.g., HMGB1) and surrogate marker (e.g., IL-6 and KC) of lethal sepsis; and 2) suppression of HMGB1-mediated inflammatory responses by preventing clustering of exogenous HMGB1 on macrophage cell surface. CONCLUSIONS: Taken together, these data suggest a novel mechanism by which the major green tea component, EGCG, protects against lethal endotoxemia and sepsis.

PLoS One. 2007 Nov 7;2(11):e1153

HMGB-1 as a target for inflammation controlling.

In the present study, we evaluated recent patents that describe products or methods able to down-regulate the pro-inflammatory action of HMGB-1, also called as amphoterin. High Mobility Group Box-1 (HMGB-1) has been implicated in the pathogenesis of inflammatory diseases. HMGB-1 has been proposed to be a crucial mediator in the pathogenesis of many diseases including sepsis, arthritis, cancer, autoimmunity diseases and diabetes. It has been suggested that HMGB-1 itself can signal through RAGEs (receptor for advanced glycation end products) and through the Toll-Like Receptors TLR2 and TLR4. Activation of these receptors results ultimately in the activation of Nuclear Factor-kappaB (NFkappaB), inducing the up-regulation of leukocyte adhesion molecules, production of pro-inflammatory cytokines and angiogenic factors in both hematopoietic and endothelial cells, thereby promoting inflammation. There are several patents proposed for controlling the production, secretion and neutralization of HMGB-1 and consequently the inflammatory process. We have divided the patents in six groups based on mechanism of action. The group 1 is associated with inhibition of HMGB-1 using anti-HMGB-1 antibodies; group 2: inhibition of HMGB-1 releases from the nucleus into the extracellular space; group 3: HMGB-A box as a competitive antagonist of HMGB-1; group 4: blockage of RAGE-HMGB-1 signaling using RAGE antagonists; group 5: blockage of TLR-HMGB-1 signaling using anti-TLR2 antibodies and group 6: other molecules that modulate HMGB-1 activity using e.g. human soluble thrombomodulin. The mechanism of HMGB-1 action, its role and efficiency of each group of patents proposed for controlling inflammation are discussed.

Recent Pat Endocr Metab Immune Drug Discov. 2012 Sep;6(3):201-9

HMGB1: endogenous danger signaling.

While foreign pathogens and their products have long been known to activate the innate immune system, the recent recognition of a group of endogenous molecules that serve a similar function has provided a framework for understanding the overlap between the inflammatory responses activated by pathogens and injury. These endogenous molecules, termed alarmins, are normal cell constituents that can be released into the extracellular milieu during states of cellular stress or damage and subsequently activate the immune system. One nuclear protein, High mobility group box-1 (HMGB1), has received particular attention as fulfilling the functions of an alarmin by being involved in both infectious and non-infectious inflammatory conditions. Once released, HMGB1 signals through various receptors to activate immune cells involved in the immune process. Although initial studies demonstrated HMGB1 as a late mediator of sepsis, recent findings indicate HMGB1 to have an important role in models of non-infectious inflammation, such as autoimmunity, cancer, trauma, and ischemia reperfusion injury. Furthermore, in contrast to its pro-inflammatory functions, there is evidence that HMGB1 also has restorative effects leading to tissue repair and regeneration. The complex functions of HMGB1 as an archetypical alarmin are outlined here to review our current understanding of a molecule that holds the potential for treatment in many important human conditions.

Mol Med. 2008 Jul-Aug;14(7-8):476-84

Human macrophage and dendritic cell-specific silencing of high-mobility group protein B1 ameliorates sepsis in a humanized mouse model.

Hypersecretion of cytokines by innate immune cells is thought to initiate multiple organ failure in murine models of sepsis. Whether human cytokine storm also plays a similar role is not clear. Here, we show that human hematopoietic cells are required to induce sepsis-induced mortality following cecal ligation and puncture (CLP) in the severely immunodeficient nonobese diabetic (NOD)/SCID/IL2Rg(-/-) mice, and siRNA treatment to inhibit HMGB1 release by human macrophages and dendritic cells dramatically reduces sepsis-induced mortality. Following CLP, compared with immunocompetent WT mice, NOD/SCID/IL2Rg(-/-) mice did not show high levels of serum HMGB1 or murine proinflammatory cytokines and were relatively resistant to sepsis-induced mortality. In contrast, NOD/SCID/IL2Rg(-/-) mice transplanted with human hematopoietic stem cells [humanized bone marrow liver thymic mice (BLT) mice] showed high serum levels of HMGB1, as well as multiple human but not murine proinflammatory cytokines, and died uniformly, suggesting human cytokines are sufficient to induce organ failure in this model. Moreover, targeted delivery of HMGB1 siRNA to human macrophages and dendritic cells using a short acetylcholine receptor (AchR)-binding peptide [rabies virus glycoprotein (RVG)-9R] effectively suppressed secretion of HMGB1, reduced the human cytokine storm, human lymphocyte apoptosis, and rescued humanized mice from CLP-induced mortality. siRNA treatment was also effective when started after the appearance of sepsis symptoms. These results show that CLP in humanized mice provides a model to study human sepsis, HMGB1 siRNA might provide a treatment strategy for human sepsis, and RVG-9R provides a tool to deliver siRNA to human macrophages and dendritic cells that could potentially be used to suppress a variety of human inflammatory diseases.

Proc Natl Acad Sci U S A. 2012 Dec 18;109(51):21052-7

HMGB1 is associated with atherosclerotic plaque composition and burden in patients with stable coronary artery disease.

OBJECTIVES: The role of inflammation in atherosclerosis is widely appreciated. High mobility group box 1 (HMGB1), an injury-associated molecular pattern molecule acting as a mediator of inflammation, has recently been implicated in the development of atherosclerosis. In this study, we sought to investigate the association of plasma HMGB1 with coronary plaque composition in patients with suspected or known coronary artery disease (CAD). DESIGN: HMGB1, high sensitive troponin T (hsTnT) and high sensitive C-reactive protein (hsCRP) were determined in 152 consecutive patients with suspected or known stable CAD who underwent clinically indicated 256-slice coronary computed tomography angiography (CCTA). Using CCTA, we assessed 1) coronary calcification, 2) non-calcified plaque burden and 3) the presence of vascular remodeling in areas of non-calcified plaques. RESULTS: Using univariate analysis, hsCRP, hsTnT and HMGB1 as well as age, and atherogenic risk factors were associated with non-calcified plaque burden (r = 0.21, p = 0.009; r = 0.48, p<0.001 and r = 0.34, p<0.001, respectively). By multivariate analysis, hsTnT and HMGB1 remained independent predictors of the non-calcified plaque burden (r = 0.48, p<0.01 and r = 0.34, p<0.001, respectively), whereas a non-significant trend was noticed for hs-CRP (r = 0.21, p = 0.07). By combining hsTnT and HMGB1, a high positive predictive value for the presence of non-calcified and remodeled plaque (96% and 77%, respectively) was noted in patients within the upper tertiles for both biomarkers, which surpassed the positive predictive value of each marker separately.CONCLUSIONS: In addition to hs-TnT, a well-established cardiovascular risk marker, HMGB1 is independently associated with non-calcified plaque burden in patients with stable CAD, while the predictive value of hs-CRP is lower. Complementary value was observed for hs-TnT and HMGB1 for the prediction of complex coronary plaque.

PLoS One. 2012;7(12):e52081

HDAC4/5-HMGB1 signalling mediated by NADPH oxidase activity contributes to cerebral ischaemia/reperfusion injury.

Histone deacetylases (HDACs)-mediated epigenetic mechanisms play critical roles in the homeostasis of histone acetylation and gene transcription. HDAC inhibitors have displayed neuroprotective properties in animal models for various neurological diseases including Alzheimer’s disease and ischaemic stroke. However, some studies have also reported that HDAC enzymes exert protective effects in several pathological conditions including ischaemic stress. The mixed results indicate the specific roles of each HDAC protein in different diseased states. However, the subtypes of HDACs associated with ischaemic stroke keep unclear. Therefore, in this study, we used an in vivo middle cerebral artery occlusion (MCAO) model and in vitro cell cultures by the model of oxygen glucose deprivation to investigate the expression patterns of HDACs and explore the roles of individual HDACs in ischaemic stroke. Our results showed that inhibition of NADPH oxidase activity ameliorated cerebral ischaemia/reperfusion (I/R) injury and among Zn(2+) -dependent HDACs, HDAC4 and HDAC5 were significantly decreased both in vivo and in vitro, which can be reversed by NADPH oxidase inhibitor apocynin. We further found that both HDAC4 and HDAC5 increased cell viability through inhibition of HMGB1, a central mediator of tissue damage following acute injury, expression and release in PC12 cells. Our results for the first time provide evidence that NADPH oxidase-mediated HDAC4 and HDAC5 expression contributes to cerebral ischaemia injury via HMGB1 signalling pathway, suggesting that it is important to elucidate the role of individual HDACs within the brain, and the development of HDAC inhibitors with improved specificity is required to develop effective therapeutic strategies to treat stroke.

J Cell Mol Med. 2013 Apr;17(4):531-42

HMGB1: the missing link between diabetes mellitus and heart failure.

Diabetes mellitus (DM) is a major independent risk factor for cardiovascular disease, but also leads to cardiomyopathy. However, the etiology of the cardiac disease is unknown. Therefore, the aim of this study was to identify molecular mechanisms underlying diabetic heart disease. High glucose treatment of isolated cardiac fibroblasts, macrophages and cardiomyocytes led to a sustained induction of HMGB1 on the RNA and protein level followed by increased NF-kB binding activity with consecutively sustained TNF-a and IL-6 expression. Short interference (si) RNA knock-down for HMGB1 and RAGE in vitro confirmed the importance of this axis in diabetes-driven chronic inflammation. In a murine model of post-myocardial infarction remodeling in type 1 diabetes, cardiac HMGB1 expression was significantly elevated both on RNA and protein level paralleled by increased expression of pro-inflammatory cytokines up to 10 weeks. HMGB1-specific blockage via box A treatment significantly reduced post-myocardial infarction remodeling and markers of tissue damage in vivo. The protective effects of box A indicated an involvement of the mitogen-activated protein-kinases jun N-terminal kinase and extracellular signal-regulated kinase 1/2, as well as the transcription factor nuclear factor-kappaB. Interestingly, remodeling and tissue damage were not affected by administration of box A in RAGE (-/-) mice. In conclusion, HMGB1 plays a major role in DM and post-I/R remodeling by binding to RAGE, resulting in activation of sustained pro-inflammatory pathways and enhanced myocardial injury. Therefore, blockage of HMGB1 might represent a therapeutic strategy to reduce post-ischemic remodeling in DM.

Basic Res Cardiol. 2010 Nov;105(6):805-20

HMGB1 in development and diseases of the central nervous system.

High mobility group box 1 (HMGB1) is widely expressed in cells of vertebrates in two forms: a nuclear “architectural” factor and a secreted inflammatory factor. During early brain development, HMGB1 displays a complex temporal and spatial distribution pattern in the central nervous system. It facilitates neurite outgrowth and cell migration critical for processes, such as forebrain development. During adulthood, HMGB1 serves to induce neuroinflammation after injury, such as lesions in the spinal cord and brain. Receptor for advanced glycation end products and Toll-like receptors signal transduction pathways mediate HMGB1-induced neuroinflammation and necrosis. Increased levels of endogenous HMGB1 have also been detected in neurodegenerative diseases. However, in Huntington’s disease, HMGB1 has been reported to protect neurons through activation of apurinic/apyrimidinic endonuclease and 5’-flap endonuclease-1, whereas in other neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, and multiple sclerosis, HMGB1 serves as a risk factor for memory impairment, chronic neurodegeneration, and progression of neuroinflammation. Thus, HMGB1 plays important and double-edged roles during neural development and neurodegeneration. The HMGB1-mediated pathological mechanisms have remained largely elusive. Knowledge of these mechanisms is likely to lead to therapeutic targets for neurological diseases.

Mol Neurobiol. 2012 Jun;45(3):499-506

The role of HMGB1 in the pathogenesis of rheumatic disease.

HMGB1 is a ubiquitous nuclear protein that can be released by any damaged cell or by activated macrophages and certain other cell types. HMGB1 has been successfully therapeutically targeted in multiple preclinical models of infectious and sterile diseases including arthritis. Extracellular HMGB1 mediates inflammation via induction of cytokine and metalloproteinase production and recruitment and activation of dendritic cells needed for priming of naïve T helper type 1 lymphocytes. HMGB1 can bind endogenous molecules such as IL-1beta and nucleosomes and exogenous agents like endotoxin and microbial DNA. These complexes synergistically increase the capacity for activation of adaptive and innate immunity. HMGB1-nucleosome complexes induce autoantibody formation against double-stranded DNA and nucleosomes, which does not occur if HMGB1 is absent. These antibodies are central in the pathogenesis of systemic lupus erythematosus and patients with active disease have both increased HMGB1 and HMGB1-nucleosome levels in circulation. Furthermore, HMGB1 is strongly bipolar charged, enabling cell membrane passage and intracellular transport of complexed molecules including DNA. Rheumatoid arthritis patients have excessive extracellular HMGB1 levels in joints and serum. The HMGB1 release is caused by cytokines, activated complement and hypoxia. The most prominent HMGB1 protein and mRNA expression arthritis is present in pannus regions, where synovial tissue invades articular cartilage and bone. HMGB1 promotes the activity of proteolytic enzymes, and osteoclasts need HMGB1 for functional maturation. Neutralizing HMGB1 therapy in preclinical models of arthritis confers striking protection against structural damage. This review summarizes selected aspects of HMGB1 biology relevant for induction and propagation of some autoimmune conditions.

Biochim Biophys Acta. 2010 Jan-Feb; 1799(1-2):141-8