Publications by authors named "Hun T Chung"

Neurotrophic factors are endogenous proteins that promote the survival of various neuronal cells. Increasing evidence has suggested a key role for brain-derived neurotrophic factor (BDNF) in the dopaminergic neurotoxicity associated with Parkinson's Disease (PD). This study explores the therapeutic potential of filbertone, a bioactive compound found in hazelnuts, in neurodegeneration, focusing on its effects on neurotrophic factors and the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway.

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Hepatic glucose production by glucagon is crucial for glucose homeostasis during fasting, yet the underlying mechanisms remain incompletely delineated. Although CD38 has been detected in the nucleus, its function in this compartment is unknown. Here, we demonstrate that nuclear CD38 (nCD38) controls glucagon-induced gluconeogenesis in primary hepatocytes and liver in a manner distinct from CD38 occurring in the cytoplasm and lysosomal compartments.

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Aging can increase the risk of various hepatic diseases, especially non-alcoholic fatty liver disease (NAFLD). Although the mechanisms underlying the pathogenesis of age-related disorders such as NAFLD remain incompletely understood, recent studies have implicated the accumulation of senescent cells as a contributing factor. Here, we show that tristetraprolin (TTP) deficiency accelerates NAFLD during aging by enhancing the senescence-associated secretory phenotype (SASP) as well as several hallmarks of senescence.

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The molecular mechanisms underlying the pathogenesis of neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease (PD), and Huntington's disease remain enigmatic, resulting in an unmet need for therapeutics development. Here, we suggest that filbertone, a key flavor compound found in the fruits of hazel trees of the genus Corylus, can ameliorate PD via lowering the abundance of aggregated α-synuclein. We previously reported that inhibition of hypothalamic inflammation by filbertone is mediated by suppression of nuclear factor kappa-B.

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Objective: Emerging evidence suggests that crosstalk between Kupffer cells (KCs) and hepatocytes protects against non-alcoholic fatty liver disease (NAFLD). However, the underlying mechanisms that lead to the reduction of steatosis in NAFLD remain obscure.

Methods: Ttp and Ttp mice were fed with a high-fat diet.

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Article Synopsis
  • The study explores how phosphorylation of EIF2S1/eIF2α plays a crucial role in linking macroautophagy and unfolded protein response (UPR) pathways during endoplasmic reticulum (ER) stress, aiding in restoring ER homeostasis.
  • It was found that cells lacking phosphorylation at residue 51 of EIF2S1 showed impaired autophagic processes, specifically in the formation of autophagosomes and autolysosomes, due to disrupted activities of transcription factors TFEB and TFE3.
  • Overexpressing certain activated forms of transcription factors like ATF6, XBP1s, and ATF4 was able to partially rescue autophagy defects in EIF2S1 phosphorylation-deficient cells
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The protein kinase R (PKR)-like endoplasmic reticulum (ER) kinase (PERK), a key ER stress sensor of the unfolded protein response (UPR), can confer beneficial effects by facilitating the removal of cytosolic aggregates through the autophagy-lysosome pathway (ALP). In neurodegenerative diseases, the ALP ameliorates the accumulation of intracellular protein aggregates in the brain. Transcription factor-EB (TFEB), a master regulator of the ALP, positively regulates key genes involved in the cellular degradative pathway.

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Sepsis is characterized by an initial net hyperinflammatory response, followed by a period of immunosuppression, termed immunoparalysis. During this immunosuppressive phase, patients may have difficulty eradicating invading pathogens and are susceptible to life-threatening secondary hospital-acquired infections. Due to progress in antimicrobial treatment and supportive care, most patients survive early sepsis.

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To improve the potential treatment strategies of incurable renal cell carcinoma (RCC), which is highly resistant to chemotherapy and radiotherapy, the present study established a combination therapy with immunostimulatory factor (ISTF) and anti-4-1BB monoclonal antibodies (mAbs) to augment the antitumor response in a murine RCC model. ISTF isolated from stimulates macrophages, dendritic cells and B cells to produce IL-6, TNF-α, nitric oxide and major histocompatibility complex class II expression. 4-1BB (CD137) is expressed in activated immune cells, including activated T cells, and is a promising target for cancer immunotherapy.

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Background/aims: Heme oxygenase-1 (HO-1) plays a central role in cellular defense against inflammatory insults, and its induction in macrophages potentiates their efferocytic activity. In this study, we explored the potential role of macrophage HO-1 in the resolution of experimentally induced colitis.

Methods: To induce colitis, male C57BL/6 mice were treated with 2% dextran sulfate sodium (DSS) in the drinking water for 7 days.

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Tumor-associated macrophages (TAMs) represent one of the most abundant components of the tumor microenvironment and play important roles in tumor development and progression. TAMs display plasticity and functional heterogeneity as reflected by distinct phenotypic subsets. TAMs with an M1 phenotype have proinflammatory and anti-tumoral properties whereas M2-like TAMs exert anti-inflammatory and pro-tumoral functions.

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Chemotherapy is commonly used as a major therapeutic option for breast cancer treatment, but its efficacy is often diminished by disruption of patient's anti-tumor immunity. Chemotherapy-generated tumor cell debris could hijack accumulated tumor-associated macrophages (TAMs), provoking tumor recurrence. Therefore, reprogramming TAMs to acquire an immunocompetent phenotype is a promising strategy to potentiate therapeutic efficacy.

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Nicotinic acid adenine dinucleotide phosphate (NAADP) is the most potent Ca mobilizing second messenger whose formation has remained elusive. In vitro, CD38-mediated NAADP synthesis requires an acidic pH and a nonphysiological concentration of nicotinic acid (NA). We discovered that CD38 catalyzes synthesis of NAADP by exchanging the nicotinamide moiety of nicotinamide adenine dinucleotide phosphate (NADP ) for the NA group of nicotinic acid adenine dinucleotide (NAAD) inside endolysosomes of interleukin 8 (IL8)-treated lymphokine-activated killer (LAK) cells.

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The translocation of transcription factor EB (TFEB) to the nucleus plays a pivotal role in the regulation of basic cellular processes, such as lysosome biogenesis and autophagy. Autophagy is an intracellular degradation system that delivers cytoplasmic constituents to the lysosome, which is important in maintaining cellular homeostasis during environmental stress. Furthermore, oxidative stress is a critical cause for the progression of neurodegenerative diseases.

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Oxidative stress is recognised as a key factor that can lead to cellular senescence and aging. Carbon monoxide (CO) is produced by haemoxygenase-1 (HO-1), which exerts cytoprotective effects in aging-related diseases, whereas the effect of CO on cellular senescence and aging has not been elucidated. In the current study, we clearly demonstrated that CO delays the process of cellular senescence and aging through regulation of miR-34a and Sirt1 expression.

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The resolution phase of acute inflammation is essential for tissue homeostasis, yet the underlying mechanisms remain unclear. We demonstrate that resolution of inflammation involves interactions between CD38 and tristetraprolin (TTP). During the onset of acute inflammation, CD38 levels are increased, leading to the production of Ca-signaling messengers, nicotinic acid adenine dinucleotide phosphate (NAADP), ADP ribose (ADPR), and cyclic ADPR (cADPR) from NAD(P).

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Endothelial senescence is the main risk factor that contributes to vascular dysfunction and the progression of vascular disease. Carbon monoxide (CO) plays an important role in preventing vascular dysfunction and in maintaining vascular physiology or homeostasis. The application of exogenous CO has been shown to confer protection in several models of cardiovascular injury or disease, including hypertension, atherosclerosis, balloon-catheter injury, and graft rejection.

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Acetaminophen (APAP) is widely used as an antifebrile and analgesic drug at recommended doses, whereas an overdose of APAP can cause severe liver damage. The molecular mechanisms underlying APAP-induced liver damage remain incompletely understood. Carbon monoxide (CO), an end-product of heme oxygenase (HO)-1 activity, can confer anti-inflammatory and antiapoptotic properties in cellular models of toxicity regulation of mitochondrial function.

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Chung Hun Wha Dam Tang (CHWDT), a traditional Korean herbal formula, has been used for hundreds of years for alleviating dizziness, phlegm, and inflammation. The inhibitory effects of CHWDT on obesity have been reported. However, the effects of CHWDT in atherosclerosis have not yet been explored.

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Background: Obesity-induced skeletal muscle inflammation is a major contributor of skeletal muscle loss/atrophy and is implicated in metabolic complications such as insulin resistance. Fibroblast growth factor 21 (FGF21) is known to be an important metabolic regulator with anti-inflammatory properties. However, the effect of FGF21 on skeletal muscle atrophy is unclear.

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Immunometabolism, defined as the interaction of metabolic pathways with the immune system, influences the pathogenesis of metabolic diseases. Metformin and carbon monoxide (CO) are two pharmacological agents known to ameliorate metabolic disorders. There are notable similarities and differences in the reported effects of metformin and CO on immunometabolism.

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Stress granules (SGs) are membraneless and phase-dense organelles that form transiently in response to a variety of harmful stimuli, including oxidative, heat, osmotic, ultraviolet light and chemotoxic stresses, and thus providing protective effects, allowing survivals. Carbon monoxide (CO), a gaseous second messenger, is synthesized by heme-oxygenases, and exerts anti-inflammatory, anti-proliferative and anti-apoptotic effects in a variety of cellular- and tissue-injury models. Several reports indicate that low levels of mitochondrial reactive oxygen species (mtROS) generated by CO can selectively activate PERK-eIF2α integrated stress response (ISR) to preserve the cellular homeostasis.

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Objective And Design: Hypothalamic inflammation is closely associated with metabolic dysregulation. Fibroblast growth factor 21 (FGF21) is known to be an important metabolic regulator with anti-inflammatory properties. In this study, we investigated the effects of FGF21 deficiency on obesity-induced hypothalamic inflammation and thermogenic responses.

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UVB-induced skin damage is attributable to reactive oxygen species, which are triggered by intracellular Ca signals. However, exactly how the reactive oxygen species are triggered by intracellular Ca upon UVB irradiation remains obscure. Here, we show that UVB induces Ca signals via sequential generation of the following Ca messengers: inositol 1,4,5-trisphosphate, nicotinic acid adenine dinucleotide phosphate, and cyclic ADP-ribose.

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