Pil-Hoon Park

Short-term treatment of RAW264.7 macrophages with adiponectin increases TNF-α expression via ERK1/2 activation and EGR-1 expression: Role of TNF-α in adiponectin-stimulated IL-10 production

Adiponectin is an adipokine with potent anti-inflammatory properties. However, the mechanisms by which adiponectin suppresses macrophage function are not well understood. Treatment of RAW264.7 macrophages with adiponectin for 18 h decreased lipopolysaccharide (LPS)-stimulated tumor necrosis factor-α (TNF-α) production. Here we demonstrate that globular adiponectin (gAcrp) initially increased TNF-α expression in RAW264.7 macrophages; this TNF-α then contributed to increased expression of interleukin-10, which in turn was required for the development of tolerance to subsequent LPS exposure. gAcrp-mediated increases in TNF-α mRNA accumulation were associated with increased TNF-α promoter activity. gAcrp increased the DNA binding activity of both Egr-1 and NFκB; mutation of either the Egr-1 or NFκB binding sites in the TNF-α promoter decreased gAcrp-stimulated promoter activity. Further, co-transfection with either dominant negative Egr-1 or the IκB super-repressor prevented gAcrp-stimulated TNF-α promoter activity. gAcrp also increased Egr-1 promoter activity, mRNA accumulation, and DNA binding activity. Inhibition of ERK1/2 with U0126 potently suppressed gAcrp-stimulated Egr-1 promoter activity, as well as TNF-α promoter activity. In summary, these data demonstrate that adiponectin initially increases TNF-α production by macrophages via ERK1/2→Egr-1 and NFκB-dependent mechanisms; these increases in TNF-α in turn lead to increased expression of interleukin-10 and an eventual dampening of LPS-mediated cytokine production in macrophages.

Activation of autophagy by globular adiponectin attenuates ethanol-induced apoptosis in HepG2 cells: involvement of AMPK/FoxO3A axis.

Hepatocellular apoptosis is an important pathological entity of alcoholic liver disease. Previously, we have shown that globular adiponectin (gAcrp) protects liver cells from ethanol-induced apoptosis by modulating an array of signaling pathways. In the present study, we investigated the role of autophagy induction by gAcrp in the suppression of ethanol-induced apoptosis and its potential mechanism(s) in liver cells. Here, we demonstrated that gAcrp significantly restores ethanol-induced suppression of autophagy-related genes, including Beclin-1 and microtubule-associated protein light chain (LC3B) both in primary rat hepatocytes and human hepatoma cell line (HepG2). Globular adiponectin also restored autophagosome formation suppressed by ethanol treatment in HepG2. Furthermore, inhibition of gAcrp-induced autophagic process by knock-down of LC3B prevented protection from ethanol-induced apoptosis. In particular, the autophagic process induced by gAcrp was involved in the suppression of ethanol-induced activation of caspase-8 and expression of Bax. Moreover, knock-down of AMPK by small interfering RNA (siRNA) blocked gAcrp-induced expression of genes related to autophagy, which in turn prevented protection from ethanol-induced apoptosis, suggesting that AMPK plays an important role in the induction of autophagy and protection of liver cells by gAcrp. Finally, we also showed that gAcrp treatment induces translocation of the forkhead box O member protein, FoxO3A, into the nucleus, which may play a role in the induction of autophagy-related genes. Taken together, our data demonstrated that gAcrp protects liver cells from ethanol-induced apoptosis via induction of autophagy. Further, the AMPK-FoxO3A axis plays a cardinal role in gAcrp-induced autophagy and subsequent inhibition of ethanol-induced apoptosis.

Baicalein induces autophagic cell death through AMPK/ULK1 activation and downregulation of mTORC1 complex components in human cancer cells

Baicalein, a flavonoid and aglycon hydrolyzed from baicalin, has anticancer properties in several human carcinomas, but its molecular mechanisms of action remain unclear. Here, we show that baicalein leads to human cancer cell death by inducing autophagy rather than apoptosis, because cell death induced by baicalein was completely reversed by suppressing the expression levels of key molecules in autophagy such as Beclin 1, vacuolar protein sorting 34 (Vps34), autophagy‐related (Atg)5 and Atg7, but not by pan‐caspase inhibitor. Our data revealed that baicalein significantly increased the number of green fluorescence protein–cytosol‐associated protein light chain 3 (GFP–LC3)‐containing puncta and LC3B‐II expression levels, which were further enhanced by chloroquine treatment. Furthermore, a luciferase‐based reporter assay showed that the ratio of RLuc–LC3wt/RLuc–LC3G120A was greatly reduced. The data suggested that baicalein induced not only autophagosome formation, but also autophagic flux. Experiments using short interfering RNAs and pharmacological inhibitors revealed that Beclin 1, Vps34, Atg5, Atg7 and UNC‐51 (Caenorhabditis elegans)‐like kinase 1 (ULK1) play pivotal roles in mediating baicalein‐induced autophagy. Moreover, baicalein activated AMP‐activated protein kinase (AMPK)α, leading to ULK1 activation through phosphorylation at Ser555, whereas both protein and mRNA levels of mammalian target of rapamycin (mTOR) and Raptor, upstream inhibitors of ULK1 and autophagy, were markedly downregulated by baicalein. Our data suggest that the anticancer effects of baicalein are mainly due to autophagic cell death through activation of the AMPK/ULK1 pathway and inhibition of mTOR/Raptor complex 1 expression. These results provide new mechanistic insights into the anticancer functions of autophagy inducers, such as baicalein, which may be used as potential therapeutics for cancer treatment.

Dihydroxylated 2,4,6-triphenyl pyridines: Synthesis, topoisomerase I and II inhibitory activity, cytotoxicity, and structure—activity relationship study

Twelve dihydroxylated 2,4,6-triphenyl pyridines were designed and synthesized which contain hydroxyl groups at ortho, meta or para position of 2- and 6-phenyl, or 2- and 4-phenyl rings attached to the central pyridine. They were evaluated for topoisomerase I and II inhibitory activity, and cytotoxicity against several human cancer cell lines for the development of novel anticancer agents. Generally, dihydroxylated 2,4,6-triphenyl pyridines exhibited stronger topoisomerase II inhibitory activity, and cytotoxicity compared to those of monohydroxylated 2,4,6-triphenyl pyridines. The concrete structure-activity relationship was observed that dihydroxylated 2,4,6-triphenyl pyridines with hydroxyl group at meta or para position of 2-phenyl ring displayed significant topoisomerase II inhibitory activity as well as cytotoxicity. Positive correlation between topoisomerase II inhibitory activity and cytotoxicity was observed for compounds 10, 12, 13, 17-20 and 22.

Globular adiponectin inhibits ethanol-induced apoptosis in HepG2 cells through heme oxygenase-1 induction.

Hepatocellular apoptosis is an essential pathological feature of alcoholic liver disease. Adiponectin, an adipokine predominantly secreted from adipose tissue, has been shown to play beneficial roles in alcoholic liver disease against various inflammatory and pro-apoptotic molecules. However, the effects of adiponectin on ethanol-induced apoptosis in liver cells are largely unknown. Herein, we investigated the role of globular adiponectin (gAcrp) in the prevention of ethanol-induced apoptosis and further tried to decipher the potential mechanisms involved. In the present study, we demonstrated that gAcrp significantly inhibits both ethanol-induced increase in Fas ligand expression and activation of caspase-3 in human hepatoma cell lines (HepG2 cells), suggesting that gAcrp plays a protective role against ethanol-induced apoptosis in liver cells. This protective effect of gAcrp was mediated through adiponectin receptor R1 (adipoR1). Further, globular adiponectin treatment caused induction of heme oxygenase-1 (HO-1) through, at least in part, nuclear factor (erythroid-derived 2)-like 2, (Nrf2) signaling. Treatment with SnPP, a pharmacological inhibitor of HO-1, and knockdown of HO-1 with small interfering RNA (siRNA) restored caspase-3 activity suppressed by gAcrp, indicating a critical role of HO-1 in mediating the protective role of gAcrp in ethanol-induced apoptosis in liver cells. In addition, carbon monoxide, a byproduct obtained from the catabolism of free heme was found to contribute to the anti-apoptotic effect of adiponectin. In conclusion, these data demonstrated that globular adiponectin prevents ethanol-induced apoptosis in HepG2 cells via HO-1 induction and revealed a novel biological response of globular adiponectin in the protection of liver injury from alcohol consumption.

NRF2 inhibition represses ErbB2 signaling in ovarian carcinoma cells: Implications for tumor growth retardation and docetaxel sensitivity

NF-E2-related factor 2 (NRF2) is a transcription factor that regulates the expression of various antioxidant and detoxifying enzymes. Although the benefit of NRF2 in cancer prevention is well established, its role in cancer pathobiology was recently discovered. In this study, the role of NRF2 in tumor growth and docetaxel sensitivity was investigated in ErbB2-overexpressing ovarian carcinoma SKOV3 cells. Interfering RNA-mediated stable inhibition of NRF2 in SKOV3 cells repressed NRF2 signaling, resulting in cell growth arrest at G(0)/G(1) phase and tumor growth retardation in mouse xenografts. Microarray analysis revealed that ErbB2 expression is substantially reduced in NRF2-inhibited SKOV3 and this was further confirmed by RT-PCR and immunoblot analysis. Repression of ErbB2 led to a decrease in phospho-AKT and enhanced p27 protein, reinforcing the effect of NRF2 knockdown on SKOV3 growth. Furthermore, NRF2 inhibition-mediated ErbB2 repression increases the sensitivity of these cells to docetaxel cytotoxicity and apoptosis. The linkage between NRF2 and ErbB2 was confirmed in the ErbB2-positive breast cancer cell line BT-474: NRF2 knockdown suppressed ErbB2 expression and enhanced docetaxel sensitivity. Our results provide insight into the coordinated regulation of signaling molecules responding to environmental stress and suggest that NRF2 modulation might be a therapeutic strategy to limit tumor growth and enhance sensitivity to taxane-based chemotherapy.

Salvia plebeia extract inhibits the inflammatory response in human rheumatoid synovial fibroblasts and a murine model of arthritis

Salvia plebeia R. Br. has been used to treat a variety of inflammatory diseases and as an antioxidant in many countries, including Korea and China. In this study, we investigated the effects of S. plebeia extract (SPE) on inflammatory arthritis and the underlying mechanisms of action. We used a collagen-induced arthritis (CIA) mouse model. TNF-α-stimulated rheumatoid arthritis (RA) synovial fibroblasts were used to elucidate the underlying mechanisms of action. Oral administration of SPE improved the clinical arthritis score, footpad thickness, and histologic changes, as well as serum IgG1 and IgG2a levels. SPE administration inhibited Th1/Th2/Th17 phenotype CD4(+) T lymphocyte expansion in inguinal lymph node and expression of inflammatory mediators such as cytokines, MMP-1, and MMP-3 in the ankle joint tissue. SPE significantly suppressed the expression of cytokines and MMP-1 by down-regulating NF-κB, Akt, and mitogen-activated protein kinases in RA synovial fibroblasts. Taken together, these results indicate that SPE is therapeutically efficacious against chronic inflammatory arthritis, suggesting that SPE is a candidate for treating RA.

Autocrine and paracrine modulation of microRNA-155 expression by globular adiponectin in RAW 264.7 macrophages: involvement of MAPK/NF-κB pathway.

Adiponectin, a hormone produced from adipose tissue, regulates various biological responses, including inflammation and many metabolic processes. MicroRNAs control expression of diverse target genes and various physiological responses. Many of these responses are commonly regulated by adiponectin. However, effects of adiponectin on microRNAs regulation are largely unknown. Herein we demonstrated that globular adiponectin induces increase in miR-155 expression, which plays an important role in inflammatory response, in RAW 264.7 macrophages. We further showed that this effect was modulated by and MAPK/NF-κB dependent mechanisms. These results suggest that miR-155 would be a novel promising target mediating adiponectin-induced various biological responses.

Gene-Selective Histone H3 Acetylation in the Absence of Increase in Global Histone Acetylation in Liver of Rats Chronically Fed Alcohol

AIMS The aim of this study was to determine the effect of chronic ethanol feeding on acetylation of histone H3 at lysine 9 (H3-Lys9) at promoter and coding regions of genes for class I alcohol dehydrogenase (ADH I), inducible nitric oxide synthase (iNOS), Bax, p21, c-met and hepatocyte growth factor in the rat liver. METHODS Rats were fed ethanol-containing liquid diet (5%, w/v) for 1-4 weeks. The global level of acetylation of H3-Lys9 in the liver was examined by western blot analysis. The levels of mRNA for various genes were measured by real-time reverse transcriptase-polymerase chain reaction. The association of acetylated histone H3-Lys9 with the different regions of genes was monitored by chromatin immunoprecipitation assay. RESULTS Chronic ethanol treatment increased mRNA expression of genes for iNOS, c-jun and ADH 1. Chronic ethanol treatment did not cause increase in global acetylation of H3-Lys9, but significantly increased the association of acetylated histone H3-Lys9 in the ADH I gene, both in promoter and in coding regions. In contrast, chronic ethanol treatment did not significantly increase the association of acetylated histone H3-Lys9 with iNOS and c-jun genes. CONCLUSION Chronic ethanol exposure increased the gene-selective association of acetylated H3-Lys9 in the absence of global histone acetylation. Thus, not all genes expressed by ethanol are linked to transcription via histone H3 acetylation at Lys9.

Critical Role of AMPK/FoxO3A Axis in Globular Adiponectin‐Induced Cell Cycle Arrest and Apoptosis in Cancer Cells

Adiponectin predominantly secreted from adipose tissue has exhibited potent anti‐proliferative properties in cancer cells via modulating cell cycle and apoptosis. FoxO3A, a Forkhead box O member of the transcription factor, plays a critical role in modulating expression of genes involved in cell death and/or survival. In this study, we investigated the role of FoxO3A signaling in anti‐cancer activities of adiponectin. Herein, we have shown that treatment with globular adiponectin (gAcrp) increases p27 but decreases cyclinD1 expression in human hepatoma (HepG2) and breast (MCF‐7) cancer cells. Gene ablation of FoxO3A prevented gAcrp‐induced increase in p27 and decreased in cyclin D1 expression, and further ameliorated cell cycle arrest by gAcrp, indicating a critical role of FoxO3A in gAcrp‐induced cell cycle arrest of cancer cells. Moreover, treatment with gAcrp also induced caspase‐3/7 activation and increased Fas ligand (FasL) expression in both HepG2 and MCF‐7 cells. Transfection with FoxO3A siRNA inhibited gAcrp‐induced caspase‐3/7 activation and FasL expression, suggesting that FoxO3A signaling also plays an important role in gAcrp‐induced apoptosis of cancer cells. We also found that gene silencing of AMPK prevented gAcrp‐induced nuclear translocation of FoxO3A in HepG2 and MCF‐7 cells. In addition, suppression of AMPK also blocked gAcrp‐induced cell cycle arrest and further attenuated gAcrp‐induced caspase‐3/7 activation, indicating that AMPK signaling plays a pivotal role in both gAcrp‐induced cell cycle arrest and apoptosis via acting as an upstream signaling of FoxO3A. Taken together, our findings demonstrated that AMPK/FoxO3A axis plays a cardinal role in anti‐proliferative effect of adiponectin in cancer cells. J. Cell. Physiol. 231: 357–369, 2016.