Inhibitory Effect of Sestrin 2 on Hepatic Stellate Cell Activation and Liver Fibrosis

Aims: Hepatic fibrosis results from chronic liver injury and inflammatory responses. Sestrin 2 (Sesn2), an evolutionarily conserved antioxidant enzyme, reduces the severities of acute hepatitis and metabolic liver diseases. However, the role of Sesn2 in the pathogenesis of liver fibrosis remains obscure. Here, we used cultured hepatic stellate cells (HSCs) and chronic carbon tetrachloride (CCl₄) and bile duct ligation (BDL) murine models to investigate the effects of Sesn2 on fibrogenesis. Results: Sesn2 protein and mRNA levels were upregulated in activated primary HSCs, and by increasing transcription, transforming growth factor-β (TGF-β) also increased Sesn2 expression in HSCs. Furthermore, Smad activation was primarily initiated by TGF-β signaling, and Smad3 activation increased Sesn2 luciferase activity. In silico analysis of the 5' upstream region of the Sesn2 gene revealed a putative Smad-binding element (SBE), and its deletion demonstrated that the SBE between -964 and -956 bp within human Sesn2 promoter was critically required for TGF-β-mediated response. Moreover, ectopic expression of Sesn2 reduced gene expressions associated with HSC activation, and this was accompanied by marked decreases in SBE luciferase activity and Smad phosphorylation. Infection of recombinant adenovirus Sesn2 reduced hepatic injury severity, as evidenced by reductions in CCl₄- or BDL-induced alanine aminotransferase and aspartate aminotransferase, and inhibited collagen accumulation. Furthermore, HSC-specific lentiviral delivery of Sesn2 prevented CCl₄-induced liver fibrosis. Finally, Sesn2 expression was downregulated in the livers of patients with liver cirrhosis and in mouse models of hepatic fibrosis. Innovation and Conclusion: Our findings suggest that Sesn2 has the potential to inhibit HSC activation and hepatic fibrosis.

Synthesis and Biological Evaluation of PF-543 Derivative Containing Aliphatic Side Chain

The PF-543 is known as a potent and selective inhibitor of sphingosine kinase (SK) 1 amongst all the SK inhibitors known to date. In a recently reported study by Pfizer on the synthesis of PF-543 derivatives and the SK inhibitory effects, the introduction of propyl moiety into sulfonyl group of PF-543 in the case of 26b revealed an excellent result of 1.7 nM of IC₅₀ of SK1, suggesting the potential substitution of chain structure for benzenesulfonyl structure. In the present work, we aimed for identification of antitumor activity and inhibitory effects of PF-543 derivative containing aliphatic long chain (similar to known SK inhibitors) on SK1. The synthesized compound 2 exhibited an inhibitory effect on SK1 in a manner similar to that of PF-543; the PF-543 derivative manifested similar antitumor activity on HT29, HCT116 (colorectal cancer cell line), and AGS (gastric cancer cell line) cells. Also, from the docking study conducted with PF-543 and compound 2, it was apparent that the aliphatic chain in compound 2 could probably replace benzenesulfonyl structure of PF-543.

Cudrania Tricuspidata Extract and Its Major Constituents Inhibit Oxidative Stress-Induced Liver Injury

The fruits, leaves, and roots of Cudrania tricuspidata have been reported to contain large amounts of vitamin B, vitamin C, and flavonoids. They exhibit various physiological activities such as antitumor and anti-inflammatory effects. However, the hepatoprotective effects of C. tricuspidata extracts against oxidative stress-mediated liver injury have not yet been investigated. We thus examined whether C. tricuspidata leaf extracts (CTEs) protect against oxidative stress-mediated liver injury in vitro and in vivo and elucidated the underlying mechanism. The cytoprotective effects of CTE through the NF-E2-related factor 2 (Nrf2)/antioxidant response element (ARE) activation were presented and measured by biochemical analysis in HepG2 cells. To assess the protective effects of CTE in vivo, mice were administered with CTE (250 and 500 mg/kg; 5 days; p.o.) before a single dose of acetaminophen (APAP) (300 mg/kg; 24 h; i.p.). CTE increased ARE luciferase activity when compared with extracts of other parts of C. tricuspidata. CTE upregulated nuclear translocation of Nrf2 and its target gene expression. In addition, CTE inhibited the generation of reactive oxygen species (ROS) and cell death induced by arachidonic acid (AA) and iron (Fe) treatment in primary hepatocytes or HepG2 cells. The cytoprotective effects of CTE against oxidative stress might be due to kaempferol, the major flavonoid present in CTE. Kaempferol pretreatment blocked AA+Fe-induced ROS production and reversed glutathione depletion, which in turn led to decreased cell death. Furthermore, the protective effects of CTE against liver injury induced by excess APAP in mice or primary hepatocytes were observed. CTE could be a promising therapeutic candidate against oxidative stress-induced liver injury.

Synthesis of Novel FTY720 Analogs with Anticancer Activity through PP2A Activation

FTY720 inhibits various cancers through PP2A activation. The structure of FTY720 is also used as a basic structure for the design of sphingosine kinase (SK) inhibitors. We have synthesized derivatives using an amide chain in FTY720 with a phenyl backbone, and then compounds were screened by an MTT cell viability assay. The PP2A activity of compound 7 was examined. The phosphorylation levels of AKT and ERK, downstream targets of PP2A, in the presence of compound 7, were determined. Compound 7 may exhibit anticancer effects through PP2A activation rather than the mechanism by inhibition of SK1 in cancer cells. In the docking study of compound 7 and PP2A, the amide chain of compound 7 showed an interaction with Asn61 that was different from FTY720, which is expected to affect the activity of the compound.

Morphometric analysis of the maxillary root apex positions according to crowding severity

OBJECTIVES

To determine differences in arch forms derived from the root apices locations between individuals with <2 mm maxillary crowding and controls.

SETTING AND SAMPLE POPULATION

The Department of Orthodontics, Pusan National University. Cone-beam computed tomography (CBCT) images of 102 patients in the control group and 95 patients in the crowding group.

MATERIALS AND METHODS

X, Y and Z coordinates of the tip of the crowns and the apex of the root of the maxillary teeth (except second molars) were determined on the CBCT images. The acquired three-dimensional (3D) coordinates were converted into two-dimensional (2D) coordinates via projection on the palatal plane, and the Procrustes analysis was employed to process the converted 2D coordinates. The mean shape of the arch form derived from the location of the tip of the crowns and the apex of the root was compared between groups using the statistical shape analysis.

RESULTS

There was a statistically significant difference (P = .046) between the groups for the mean shape of the root apex arch form, but the difference was small and clinically irrelevant as it is minor compared to the degree of crowding.

CONCLUSIONS

Maxillary arch from at the level of the maxillary apices only shows minor differences between crowded and non-crowded dentitions.

Induction of Lipin1 by ROS-Dependent SREBP-2 Activation

Lipin1 was identified as a phosphatidate phosphatase enzyme, and it plays a key role in lipid metabolism. Since free radicals contribute to metabolic diseases in the liver, this study investigated the effects of free radicals on the regulation of Lipin1 expression in Huh7 and AML12 cells. Hydrogen peroxide induced mRNA and protein expression of Lipin1 in Huh7 cells, which was assayed by quantitative RT-PCR and immunoblotting, respectively. Induction of Lipin1 by hydrogen peroxide was confirmed in AML12 cells. Hydrogen peroxide treatment significantly increased expression of sterol regulatory element-binding protein (SREBP)-2, but not SREBP-1. Moreover, nuclear translocation of SREBP-2 was detected after hydrogen peroxide treatment. Hydrogen peroxide-induced Lipin1 or SREBP-2 expression was significantly reduced by N-acetyl-l-cysteine treatment, indicating that reactive oxygen species (ROS) were implicated in Lipin1 expression. Next, we investigated whether the hypoxic environments that cause endogenous ROS production in mitochondria in metabolic diseases affect the expression of Lipin1. Exposure to hypoxia also increased Lipin1 expression. In contrast, pretreatment with antioxidants attenuated hypoxia-induced Lipin1 expression. Collectively, our results show that ROS activate SREBP-2, which induces Lipin1 expression.

Compound C Increases Sestrin2 Expression via Mitochondria-Dependent ROS Production

Compound C is a widely used chemical inhibitor that down-regulates AMP-activated protein kinase (AMPK) activity. However, it has been suggested that compound C exerts AMPK-independent effects in various cells. Here, we investigated whether compound C induces Sestrin2 (SESN2), an antioxidant enzyme induced by diverse stress. In addition, the mechanism responsible for SESN2 induction by compound C was determined. Our results showed that compound C increased SESN2 protein expression in HepG2 cells in a concentration- and time-dependent manner. The induction of SESN2 mRNA was also observed in cells treated with compound C. Increase of SESN2 luciferase activity confirmed transcriptional regulation by compound C and this substance also increased nuclear factor erythroid 2 (NF-E2)-related factor-2 (Nrf2) phosphorylation, which implies that Nrf2 was involved in SESN2 induction. Next, we sought to demonstrate whether production of reactive oxygen species (ROS) accompanied SESN2 expression. Compound C increased ROS production, but this effect was prevented by pretreatment with antioxidants or the mitochondrial complex I inhibitor. Moreover, cyclosporin A, an inhibitor of pore formation in the mitochondrial membrane, attenuated compound C-induced SESN2 induction. However, overexpression of a constitutively active form of AMPK was not able to abolish SESN2 induction by compound C, which implies that its action is independent of AMPK inhibition. In conclusion, this is the first study demonstrating that compound C alters mitochondrial function and induces ROS production, which ultimately leads to phosphorylation of Nrf2 and induction of SESN2.

Isorhamnetin Inhibits Reactive Oxygen Species-Dependent Hypoxia Inducible Factor (HIF)-1α Accumulation

Isorhamnetin is a flavonoid metabolite of quercetin and isolated from water dropwort (Oenanthe javanica, Umbelliferae). It has been reported that isorhamnetin exerts beneficial effects including antioxidant, anti-inflammatory, and anti-proliferative activities. The present study investigated whether the antioxidant activity of isorhamnetin is correlated with its anti-cancer effects on colorectal cancer cells. Isorhamnetin significantly repressed cobalt chloride (CoCl₂)- or hypoxia-induced hypoxia inducible factor-1α (HIF-1α) accumulation in HCT116 and HT29 cells. When compared with quercetin, isorhamnetin showed potent inhibition of HIF-1α. Moreover, it inhibited CoCl₂-induced activity of hypoxia response element reporter gene and HIF-1α-dependent transcription of genes such as glucose transporter 1, lactate dehydrogenase A, carbonic anhydrase-IX, and pyruvate dehydrogenase kinase 1. Isorhamnetin also blocked hydrogen peroxide (H₂O₂)-induced HIF-1α accumulation. The antioxidant effects of isorhamnetin were confirmed by observation of CoCl₂- or H₂O₂-induced reactive oxygen species (ROS) production. Consistently, overexpressed HIF-1α was decreased by isorhamnetin or N-acetyl-L-cysteine in HEK293 cells. In vitro migration and invasion assay further confirmed the inhibitory effects of isorhamnetin on cancer cells. Collectively, these results demonstrate that isorhamnetin inhibits ROS-mediated HIF-1α accumulation, which contributes to its anti-metastatic efficacy.

5-Fluorouracil inhibits cell migration by induction of Sestrin2 in colon cancer cells

5-Fluorouracil (5-FU) is a chemotherapeutic agent used in the treatment of colorectal cancer. In this study, we investigated whether 5-FU induces Sestrin2 (SESN2), an antioxidant enzyme, and the role of SESN2 in 5-FU action in colon cancer cells. We found that 5-FU upregulated SESN2 protein expression in both HCT116 and HT29 cells. It also increased transcripts of SESN1 and SESN2, but not of SESN3. Furthermore, we investigated whether production of reactive oxygen species (ROS) was involved in 5-FU-induced SESN2 expression. 5-FU did not increase ROS production nor affect Nrf2 phosphorylation and expression levels. Moreover, SESN2 upregulation by 5-FU was not prevented by pretreatment with antioxidants. Next, we investigated p53 levels after 5-FU treatment to elucidate the regulation of SESN2 by 5-FU. An increase in p53 levels was detected following 5-FU treatment; pifithrin-α, an inhibitor of p53 activation, reversed 5-FU-induced SESN2 expression. 5-FU prevented serum-induced in vitro cell migration, but knockdown of SESN2 or treatment with pifithrin-α reversed a 5-FU-mediated decrease in cell migration. Taken together, our results suggest that 5-FU increases SESN2 levels via a p53-dependent pathway, which contributes to inhibition of cancer cell migration in vitro.

Sestrin2 inhibits hypoxia-inducible factor-1α accumulation via AMPK-mediated prolyl hydroxylase regulation

Sestrin2 (SESN2) is an antioxidant protein that modulates cellular redox homeostasis through regeneration of peroxiredoxins. It has beneficial effects in oxidative or metabolic stress conditions as an upstream regulator of AMP-activated protein kinase (AMPK). Since hypoxia causes oxidative and metabolic stress, this study investigated the effect of SESN2 on signaling pathways altered by hypoxia in colon cancer cells. SESN2 overexpression in HEK293 cells inhibited hypoxia-inducible factor-1α (HIF-1α), which plays a crucial role in tumor growth and development in hypoxia. Moreover, infection with adenovirus-SESN2 (Ad-SESN2) decreased hypoxia or CoCl₂-induced HIF-1α accumulation in colorectal cancer cells. Ad-SESN2 also reduced CoCl₂-induced hypoxia response element (HRE)-luciferase activity and mRNA level of HIF-1α-driven genes. Furthermore, Ad-SESN2 infected cells showed anti-metastatic effects in serum-induced cell migration and invasion in vitro. Ad-SESN2 facilitated the ubiquitination of HIF-1α protein and increased hydroxyl-HIF-1α (OH-HIF-1α) level. In contrast, treatment with dimethyloxalylglycine (DMOG), an inhibitor of prolyl hydroxylase (PHD), reversed Ad-SESN2-induced OH-HIF-1α and subsequently suppressed HIF-1α level. The inhibitory effects of SESN2 on the serum-induced in vitro cell migration and invasion were also abrogated by DMOG treatment. Furthermore, knockdown of AMPKα reversed Ad-SESN2-mediated increase of OH-HIF-1α and inhibition of HIF-1α. Dominant-negative form of AMPK also restored the Ad-SESN2 mediated decrease in HIF-1α accumulation. Lastly, Ad-SESN2 suppressed tumor growth in a mouse xenograft model. Taken together, these results suggest that SESN2 increases degradation of HIF-1α via AMPK-PHD regulation that contributes to inhibition of in vitro and in vivo tumorigenesis.

The Role of Lipin-1 in the Regulation of Fibrogenesis and TGF-β Signaling in Hepatic Stellate Cells

The adipogenic transcriptional regulation was reported to inhibit transdifferentiation of hepatic stellate cells (HSCs), which constitute the main fibrogenic cell type in the liver. Lipin-1 exhibits a dual function: an enzyme that catalyzes the conversion of phosphatidate to diacylglycerol and a transcriptional regulator. However, the involvement of Lipin-1 in the regulation of transforming growth factor-β (TGF-β) signaling and fibrogenesis in HSCs is not fully understood. Here, we showed that Lipin-1 was downregulated in activated primary HSCs and TGF-β-treated LX-2 cells, immortalized human HSC cell lines. The downregulation of Lipin-1 by TGF-β was not dependent on altered mRNA stability but rather on protein stability. Treatment of LX-2 cells with the proteasome inhibitor led to the accumulation of Lipin-1. Moreover, we observed a significant increase in Lipin-1 polyubiquitination. Overexpression of Lipin-1 attenuated TGF-β-induced fibrogenic gene expression. In addition, Lipin-1 inhibited TGF-β-mediated activation of Sma and Mad-related family (SMAD), a major transcription factor that transduces intracellular signals from TGF-β. Resveratrol, a well-known natural polyphenolic antioxidant, is known to inhibit liver fibrosis, although its mechanism of action remains unknown. Our data showed that resveratrol significantly increased the levels of Lipin-1 protein and mRNA in HSCs. Further investigation revealed that resveratrol blocked the polyubiquitination of Lipin-1. Resveratrol inhibited TGF-β-induced fibrogenic gene expression. TGF-β-induced SMAD binding element-luciferase reporter activity was significantly diminished by resveratrol with a simultaneous decrease in SMAD3 phosphorylation. Consistently, knockdown of the Lipin-1 gene using siRNA abolished the inhibitory effect of resveratrol. We conclude that Lipin-1 can antagonize HSC activation through the inhibition of TGF-β/SMAD signaling and that resveratrol may affect Lipin-1 gene induction and contribute to the inhibition of TGF-β-mediated hepatic fibrogenesis.

Sestrin2: A Promising Therapeutic Target for Liver Diseases

Sestrin2 (Sesn2), a highly conserved antioxidant protein, is induced by various stresses, including oxidative and energetic stress, and protects cells against those stresses. In normal physiological conditions, redox-homeostasis plays an essential role in cell survival and performs the cellular functions to protect the cells against oxidative damage. The liver is susceptible to oxidative stress, since it is responsible for xenobiotic detoxification and energy metabolism. For this reason, oxidative stress is associated with the pathogenesis of liver diseases. Recently, the role of Sesn2 has been investigated in liver injury and related diseases. In this paper, we review the role of Sesn2 in the pathophysiology of liver diseases and the potential clinical applications of Sesn2 as a therapeutic target to prevent/treat liver diseases. This article promotes our understanding of liver disease progression and advances the development of strategies for pharmacological intervention.

Role of sestrin2 in the regulation of proinflammatory signaling in macrophages

Sestrins (Sesns) are conserved antioxidant proteins that accumulate in cells in response to various stresses. However, the regulatory roles of Sesn2 in the immune system and in inflammatory responses remain obscure. In the present study, we investigated whether Sesn2 regulates Toll like receptor (TLR)-mediated inflammatory signaling and sought to identify the molecular mechanism responsible. In cells expressing Sesn2, it was found that Sesn2 almost completely inhibited lipopolysaccharide (LPS)-induced NO release and iNOS expression. A gene knockdown experiment confirmed the role of Sesn2 in LPS-activated RAW264.7 cells. Consistently, proinflammatory cytokine (e.g., TNF-α, IL-6, and IL-1β) release and expression were inhibited in Sesn2-expressing cells. Furthermore, Sesn2 prevented LPS-elicited cell death and ROS production via inhibition of NADPH oxidase. NF-κB and AP-1 are redox-sensitive transcription factors that regulate the expressions of diverse inflammatory genes. Surprisingly, Sesn2 specifically inhibited AP-1 luciferase activity and its DNA binding, but not those of NF-κB. AP-1 inhibition by Sesn2 was found to be due to a lack of JNK, p38, and c-Jun phosphorylation. Next, we investigated whether Sesn2 protects galactosamine (Gal)/LPS-induced liver injury in mice infected with a recombinant adenovirus Sesn2 (Ad-Sesn2). Ad-Sesn2 present less severe hepatic injury as supported by decreases in the ALT, AST, and hepatocyte degeneration. Moreover, Ad-Sesn2 attenuated Gal/LPS-induced proinflammatory gene expression in mice. The study shows that Sesn2 inhibits TLR-induced proinflammatory signaling and protects cells by inhibiting JNK- or p38-mediated c-Jun phosphorylation.

The skeletal maturation status estimated by statistical shape analysis: axial images of Japanese cervical vertebra

OBJECTIVES

To evaluate axial cervical vertebral (ACV) shape quantitatively and to build a prediction model for skeletal maturation level using statistical shape analysis for Japanese individuals.

METHODS

The sample included 24 female and 19 male patients with hand-wrist radiographs and CBCT images. Through generalized Procrustes analysis and principal components (PCs) analysis, the meaningful PCs were extracted from each ACV shape and analysed for the estimation regression model.

RESULTS

Each ACV shape had meaningful PCs, except for the second axial cervical vertebra. Based on these models, the smallest prediction intervals (PIs) were from the combination of the shape space PCs, age and gender. Overall, the PIs of the male group were smaller than those of the female group. There was no significant correlation between centroid size as a size factor and skeletal maturation level.

CONCLUSIONS

Our findings suggest that the ACV maturation method, which was applied by statistical shape analysis, could confirm information about skeletal maturation in Japanese individuals as an available quantifier of skeletal maturation and could be as useful a quantitative method as the skeletal maturation index.

Methylglyoxal induces mitochondrial dysfunction and cell death in liver

Degradation of glucose is aberrantly increased in hyperglycemia, which causes various harmful effects on the liver. Methylglyoxal is produced during glucose degradation and the levels of methylglyoxal are increased in diabetes patients. In this study we investigated whether methylglyoxal induces mitochondrial impairment and apoptosis in HepG2 cells and induces liver toxicity in vivo. Methylglyoxal caused apoptotic cell death in HepG2 cells. Moreover, methylglyoxal significantly promoted the production of reactive oxygen species (ROS) and depleted glutathione (GSH) content. Pretreatment with antioxidants caused a marked decrease in methylglyoxal-induced apoptosis, indicating that oxidant species are involved in the apoptotic process. Methylglyoxal treatment induced mitochondrial permeability transition, which represents mitochondrial impairment. However, pretreatment with cyclosporin A, an inhibitor of the formation of the permeability transition pore, partially inhibited methylglyoxal-induced cell death. Furthermore, acute treatment of mice with methylglyoxal increased the plasma levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), indicating liver toxicity. Collectively, our results showed that methylglyoxal increases cell death and induces liver toxicity, which results from ROS-mediated mitochondrial dysfunction and oxidative stress.

Resveratrol inhibits LXRα-dependent hepatic lipogenesis through novel antioxidant Sestrin2 gene induction

Liver X receptor-α (LXRα), a member of the nuclear receptor superfamily of ligand-activated transcription factors, regulates de novo fatty acid synthesis that leads to stimulate hepatic steatosis. Although, resveratrol has beneficial effects on metabolic disease, it is not known whether resveratrol affects LXRα-dependent lipogenic gene expression. This study investigated the effect of resveratrol in LXRα-mediated lipogenesis and the underlying molecular mechanism. Resveratrol inhibited the ability of LXRα to activate sterol regulatory element binding protein-1c (SREBP-1c) and thereby inhibited target gene expression in hepatocytes. Moreover, resveratrol decreased LXRα-RXRα DNA binding activity and LXRE-luciferase transactivation. Resveratrol is known to activate Sirtuin 1 (Sirt1) and AMP-activated protein kinase (AMPK), although its precise mechanism of action remains controversial. We found that the ability of resveratrol to repress T0901317-induced SREBP-1c expression was not dependent on AMPK and Sirt1. It is well established that hepatic steatosis is associated with antioxidant and redox signaling. Our data showing that expression of Sestrin2 (Sesn2), which is a novel antioxidant gene, was significantly down-regulated in the livers of high-fat diet-fed mice. Moreover, resveratrol up-regulated Sesn2 expression, but not Sesn1 and Sesn3. Sesn2 overexpression repressed LXRα-activated SREBP-1c expression and LXRE-luciferase activity. Finally, Sesn2 knockdown using siRNA abolished the effect of resveratrol in LXRα-induced FAS luciferase gene transactivation. We conclude that resveratrol affects Sesn2 gene induction and contributes to the inhibition of LXRα-mediated hepatic lipogenesis.

Efficacy of sauchinone as a novel AMPK-activating lignan for preventing iron-induced oxidative stress and liver injury

Iron-overload disorders cause hepatocyte injury and inflammation by oxidative stress, possibly leading to liver fibrosis and hepatocellular carcinoma. This study investigated the efficacy of sauchinone, a bioactive lignan, in preventing iron-induced liver injury and explored the mechanism of sauchinone's activity. To create iron overload, mice were injected with phenylhydrazine, and the effects on hepatic iron and histopathology were assessed. Phenylhydrazine treatment promoted liver iron accumulation and ferritin expression, causing hepatocyte death and increased plasma arachidonic acid (AA). Sauchinone attenuated liver injury (EC(50)=10 mg/kg) and activated AMPK in mice. Treatment of hepatocytes with iron and AA simulated iron overload conditions: iron + AA synergistically amplified cytotoxicity, increasing H(2)O(2) and the mitochondrial permeability transition. Sauchinone protected hepatocytes from iron + AA-induced cytotoxicity, preventing the induction of mitochondrial dysfunction and apoptosis (EC(50)=1 microM), similar to the result using metformin. Sauchinone treatment activated LKB1, which led to AMPK activation: these events contributed to cell survival. Evidence of cytoprotection by LKB1 and AMPK activation was revealed in the reversal of sauchinone's restoration of the mitochondrial membrane potential by either dominant negative mutant AMPKalpha or chemical inhibitor. In conclusion, sauchinone protects the liver from toxicity induced by iron accumulation, and sauchinone's effects may be mediated by LKB1-dependent AMPK activation.

Resveratrol protects mitochondria against oxidative stress through AMP-activated protein kinase-mediated glycogen synthase kinase-3beta inhibition downstream of poly(ADP-ribose)polymerase-LKB1 pathway

Arachidonic acid (AA, a proinflammatory fatty acid) in combination with iron promotes excess reactive oxygen species (ROS) production and exerts a deleterious effect on mitochondria. We have shown previously that activation of AMP-activated protein kinase (AMPK) protects hepatocytes from AA + iron-induced apoptosis. Resveratrol, a polyphenol in grapes, has beneficial effects mediated through SIRT1, LKB1, and AMPK. This study investigated the potential of resveratrol to protect against the mitochondrial impairment induced by AA + iron and the underlying mechanism for this cytoprotection. Resveratrol treatment inhibited apoptosis, ROS production, and glutathione depletion elicited by AA + iron in HepG2 cells. In addition, resveratrol attenuated superoxide generation in mitochondria and inhibited mitochondrial dysfunction induced by AA + iron. Overall, AMPK activation by resveratrol contributed to cell survival, as supported by the reversal of its restoration of mitochondrial membrane potential by either overexpression of a dominant-negative mutant of AMPKalpha or compound C treatment. Resveratrol increased inhibitory phosphorylation of glycogen synthase kinase-3beta (GSK3beta) downstream of AMPK, which contributed to mitochondrial protection and cell survival. Likewise, small interfering RNA knockdown of LKB1, an upstream kinase of AMPK, reduced the ability of resveratrol to protect cells from mitochondrial dysfunction. Furthermore, this LKB1-dependent mitochondrial protection resulted from resveratrol's poly(ADP-ribose)polymerase activation, but not SIRT1 activation, as supported by the experiment using 3-aminobenzamide, a poly(ADP-ribose)polymerase inhibitor. Other polyphenols, such as apigenin, genistein, and daidzein, did not activate AMPK or protect mitochondria against AA + iron. Thus, resveratrol protects cells from AA + iron-induced ROS production and mitochondrial dysfunction through AMPK-mediated inhibitory phosphorylation of GSK3beta downstream of poly(ADP-ribose)polymerase-LKB1 pathway.

Oxidized metabolites of oltipraz exert cytoprotective effects against arachidonic acid through AMP-activated protein kinase-dependent cellular antioxidant effect and mitochondrial protection

Oltipraz protects cells from chemical-induced carcinogenesis partly because of phase 2 enzyme induction. Certain oltipraz metabolites also induce phase 2 enzymes. This study investigated the cytoprotective effects of the oxidized metabolites of oltipraz against arachidonic acid (AA), a proinflammatory fatty acid that causes cellular reactive oxygen species (ROS) production and mitochondrial impairment, and the mechanistic basis of their action in HepG2 cells. Treatment with 4-methyl-5-(pyrazin-2-yl)-3H-1,2-dithiol-3-one (M1) or 7-methyl-6,8-bis(methylthio)H-pyrrolo[1,2-a]-pyrazine (M2), but not 7-methyl-8-(methylsulfinyl)-6-(methylthio)H-pyrrolo[1,2-a]pyrazine (M3) or 7-methyl-6,8-bis(methylsulfinyl)H-pyrrolo[1,2-a]pyrazine (M4), enabled cells to protect against AA-induced apoptosis. M1 and M2 treatment protected cells from ROS produced by AA and inhibited AA-induced glutathione depletion. Moreover, both M1 and M2 effectively inhibited mitochondrial dysfunction induced by AA, although M2 alone slightly elicited it at a relatively high concentration. M1 and M2 activated AMP-activated protein kinase (AMPK), but M3 and M4 failed to do so. AMPK activation by M1 and M2 contributed to cell survival against AA through a decrease in cellular ROS production and prevention of mitochondrial dysfunction, as shown by the reversal of the metabolites' restoration of mitochondrial membrane potential by compound C treatment or overexpression of a dominant-negative mutant AMPK. Consistently, 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside, an AMPK activator, also had a cytoprotective and antioxidant effect against AA. Our results demonstrate that, of the major metabolites of oltipraz, M1 and M2 are capable of protecting cells from AA-induced ROS production and mitochondrial dysfunction, which may be associated with AMPK activation.

Functional induction of P-glycoprotein in the blood-brain barrier of streptozotocin-induced diabetic rats: evidence for the involvement of nuclear factor-kappaB, a nitrosative stress-sensitive transcription factor, in the regulation

The objective of this study was to investigate the transport kinetics of cyclosporin A, a well known substrate for P-glycoprotein (P-gp), across the blood-brain barrier (BBB), and the expression of the transporter in the brain of streptozotocin-induced diabetic rats. The in vivo transport clearance of cyclosporin A was significantly reduced in diabetic rats compared with that in the control. The decreased transport was associated with the increased level of mRNA and the protein for P-glycoprotein in the rat brain. The functional activity of the efflux transporter in mouse brain capillary endothelial (MBEC4) cells, an in vitro model of the BBB, was also stimulated when slow nitric oxide (NO)-releasing donors were present, whereas the stimulation was absent in the case of rapid NO-releasing donors (e.g., S-nitroso-N-acetyl-dl-penicillamine and diethylenetriamine). The stimulatory effect was highest for sodium nitroprusside (SNP) and the functional induction associated with the increased mRNA and protein level of the transporter. The pretreatment of the cell with SNP along with ascorbate, methylene blue, or superoxide dismutase attenuated the induction of function and expression for P-glycoprotein, suggesting that the reaction product between superoxide and NO is involved in the induction of function and expression. The level of nuclear translocation of nuclear factor-kappaB (NF-kappaB) and DNA binding activity of nuclear extracts to the NF-kappaB consensus oligonucleotide was increased in MBEC4 cells pretreated with SNP. Taken together, these observations suggest that nitrosative stress leads to the up-regulation of the message for the efflux transporter and, ultimately, to the enhanced function, probably via a NF-kappaB-dependent mechanism.

Identifying drugs needing pharmacogenetic monitoring in a Korean hospital

PURPOSE

A decision matrix for identifying drugs for which pharmacogenetic drug monitoring (PDM) provides the greatest benefit in a Korean setting is described.

SUMMARY

We developed a decision matrix including the ethnic frequency of clinically relevant polymorphic cytochrome P-450 (CYP) enzymes, and the metabolic profiles and adverse drug reactions of drugs. Using the developed decision matrix based on the population allele frequencies of CYP enzymes, we identified potential candidates for PDM among the most commonly used drugs at Seoul National University Hospital (SNUH). Collectively, 17 of these drugs were largely metabolized by at least one polymorphic CYP enzyme. Pharmacogenetic information was used to identify CYP2C9, CYP2C19, and CYP2D6 as the major CYP enzymes of clinical importance for pharmacologic effect and safety in Koreans. The frequencies of poor and intermediate metabolizers among Koreans were 0% and 2.3-12% for CYP2C9, 12% and 42% for CYP2C19, and 0.44% and 28% for CYP2D6, respectively. The frequency of ultrarapid metabolizers of CYP2D6 was 2.28%. The decision matrix and pharmacogenetic information were used to identify seven drugs for PDM: warfarin, glimepiride, diazepam, amitriptyline, nortriptyline, codeine, and oxycodone. This approach can be applied to other institutional hospitals or other ethnic populations and would be helpful for advancing pharmacy practice. Further work is required to assess the practical and potential clinical relevance of pharmacogenetic variations on drugs of interest before the implementation of PDM.

CONCLUSION

A decision matrix helped identify drugs for which PDM provides the greatest potential benefit at one Korean hospital.

Gene expression signatures associated with the resistance to imatinib

Imatinib (imatinib mesylate, STI-571, Gleevec) is a selective BCR-ABL tyrosine kinase inhibitor that has been used as a highly effective chemoagent for treating chronic myelogenous leukemia. However, the initial response to imatinib is often followed by the recurrence of a resistant form of the disease, which is major obstacle to many therapeutic modalities. The aim of this study was to identify the gene expression signatures that confer resistance to imatinib. A series of four resistant K562 sublines was established with different imatinib dosage (200, 400, 600 and 800 nM) and analyzed using microarray technology. The transcripts of the genes showing universal or dose-dependent expression changes across the resistant sublines were identified. The gene sets associated with the imatinib-resistance were also identified using gene set enrichment analysis. In the resistant K562 sublines, the transcription- and apoptosis-related expression signatures were upregulated, whereas those related to the protein and energy metabolism were downregulated. Several genes identified in this study such as IGF1 and RAB11A have the potential to become surrogate markers useful in a clinical evaluation of imatinib-resistant patients without BCR-ABL mutation. The expression signatures identified in this study provide insights into the mechanism of imatinib-resistance and are expected to facilitate the development of an effective diagnostic and therapeutic strategy.

CCAAT/enhancer binding protein activation by PD98059 contributes to the inhibition of AhR-mediated 3-methylcholanthrene induction of CYP1A1

2'-Amino-3'-methoxyflavone (PD98059), an MKK1 inhibitor, negatively regulates the induction of the CYP1A1 gene by polycyclic aromatic hydrocarbons. In view of the observations that PD98059 inhibits AhR-mediated CYP1A1 induction and has the capability to activate C/EBPbeta, the study investigated whether the inhibition by PD98059 of 3-MC induction of CYP1A1 results from C/EBP activation. 3-MC induction of the CYP1A1 and the CYP1A1 promoter-luciferase gene were inhibited by treatment of H4IIE cells with PD98059. PD98059 treatment inhibited 3-MC-induced AhR binding to the XRE, but increased protein binding to the CYP1A1 C/EBP binding site. PD98059 inhibited 3-MC induction of CYP1A1 in cells stably transfected with a dominant negative mutant of MKK1, indicating that PD98059 represses CYP1A1 induction by 3-MC irrespective of its MKK1 inhibition. The role of C/EBP activation by PD98059 in repressing CYP1A1 induction was supported by the observation that a dominant-negative mutant C/EBP abolished the ability of PD98059 to suppress 3-MC induction of CYP1A1.

meso-dihydroguaiaretic acid from Machilus thunbergii down-regulates TGF-beta1 gene expression in activated hepatic stellate cells via inhibition of AP-1 activity

meso-dihydroguaiaretic acid (DGA), naturally occurring in plants such as Machilus thunbergii and Myristica fragrans, exhibits a neuroprotective effect and also exerts cytotoxicity to certain cancer cells. Activated hepatic stellate cells (HSCs) play an important role in liver fibrogenesis through the production of transforming growth factor beta1 (TGF-beta1) after injuries. TGF-beta1 mediates the deposition of extracellular matrix and the inhibition of collagenase activity in the liver. This study has investigated the inhibitory effect of DGA on the activation of rat HSCs in culture and TGF-beta1 production from HSCs. The level of alpha-smooth muscle actin (alpha-SMA), a representative marker of stellate cell transdifferentiation, was decreased upon treatment of activated HSCs with DGA (1 - 10 microM). Immunoblot analysis revealed that DGA inhibited the expression of TGF-beta1 in activated HSCs. Consistently, DGA down-regulated the transactivation of the TGF-beta1 promoter linked to the luciferase reporter gene in HSCs. Promoter deletion analysis revealed that the region located between -731 bp and -323 bp in the TGF-beta1 promoter, which is comprised of AP-1 response elements, conferred the inhibition of TGF-beta1 expression by DGA. DGA also inhibited AP-1-mediated gene transactivation in HSCs to a comparable extent, indicating that down-regulation of the TGFbeta1 gene by DGA might result from its inhibition of AP-1 activity. We found in addition that DGA inhibited DNA synthesis in HSCs stimulated by platelet-derived growth factor. The data provide evidence that DGA directly inhibits activation of HSCs and down-regulates TGF-beta1 gene expression through inhibition of AP-1 activity.

Effects of angiotensin II on the renal antioxidant activities of borderline hypertensive rats

This study was aimed to study the angiotensin II (Ang II)-induced antioxidant changes in the kidney of borderline-hypertensive rats (BHR). We measured renal antioxidant enzyme activities, and glutathione (GSH) contents and lipid peroxide levels in relation to the age of subjects. In the antioxidant enzyme assays, consistent changes were not observed in relation to age. However, in the assay for reduced GSH, nonenzymatic antioxidant, contents of adult and aged rats were much greater than those of weanling rats. Subcutaneous injection of pressor dose of human Ang II (200 microg/kg over 90 min) significantly reduced enzymatic activities in the weanling (4-week-aged) and adult (10-week-aged) BHR. However, in the relatively aged (16-week-aged) rats, Ang II did not alter enzymatic activities. Renal GSH contents of aged BHR, were highly increased by Ang II. Renal lipid peroxide levels of weanling and adult BHR were increased by Ang II, but decreased in the aged rats. However, these characteristic changes of renal antioxidant due to Ang II of the BHR could not be observed in the age-matched control, Wistar-Kyoto rats (WKR). From these results, it can be concluded that impacts of oxidative stress on the kidney of BHR may be greater in the young rats.

In vitro effects of hydroxybenzaldehydes from Gastrodia elata and their analogues on GABAergic neurotransmission, and a structure-activity correlation

The present study was designed to characterize the modulatory effects of the constituents of Gastrodia elata and their analogues on the GABAergic neurotransmission. 4-Hydroxybenzaldehyde (1) and 4-hydroxy-3-methoxybenzaldehyde (4) inhibited potently the activity of GABA transaminase (IC(50) = 4.1 and 5.4 microg/ml, respectively), while the activity of another constituent, 4-hydroxybenzyl alcohol (2), was very weak. Further investigation with 10 analogues revealed a structure-activity correlation, suggesting that the aldehyde group and the hydroxy group at C-4 are necessary for the inhibitory effect on the enzyme activity. Some potent enzyme inhibitors were examined for the effect on the radioligands to the GABA(A) receptor complexes of rat cerebral cortices. Among them, the component 4 dose-dependently increased (20 - 30 %) the binding of [(3)H]flunitrazepam in the presence of GABA.

Near infrared spectroscopic monitoring of secondary cerebral energy failure after transient global hypoxia-ischemia in the newborn piglet

The present study was done to establish whether the secondary cerebral energy failure could be reproduced in the newborn piglet subjected to transient global hypoxia-ischemia, and whether the evolution of secondary cerebral energy failure could be monitored by measuring the changes of Cyt aa3 using NIRS. Fifteen anesthetized, ventilated newborn piglets (< 3 day) were divided into 2 groups. Eight of hypoxia-ischemia (HI) group were induced transient HI by breathing 8% oxygen and complete occlusion of bilateral common carotid arteries for 30 min followed by release of occluders and reoxygenation and maintained for up to 48 h. Seven were given sham operation and maintained for 48 h also. Monitoring of cerebral Hb, HbO, HbT and Cyt aa3 were continued throughout the experiment using near infrared spectroscopy. Na+, K(+)-ATPase activity, lipid peroxidation products (conjugated dienes), tissue high energy phosphates (ATP and phosphocreatine) levels and brain glucose and lactate levels were determined biochemically in the cerebral cortex harvested at the termination of experiment. HbT as an index of a cerebral blood volume increased at 2 h after resuscitation significantly in HI group. During hypoxia-ischemia Cyt aa3 fell to -2.0 +/- 0.5 mu l-1 (p < 0.01), returned to baseline on resuscitation, but decreased again progressively from 33 h, and finally fell to -2.2 +/- 0.9 mumol l-1 (p < 0.01) at 48 h in spite of normal physiologic values. There were no changes in control animals. Cerebral level of ATP and PCr in HI group decreased significantly compared to control and ATP concentrations were correlated with the final levels of Cyt aa3. In HI group, cerebral Na+, K(+)-ATPase activity decreased, but the cerebral level of conjugated dienes, glucose, lactate was not different compared to controls. These findings suggest that secondary cerebral energy failure was successfully reproduced in the newborn piglets after transient hypoxia-ischemia and the continuous in vivo NIRS monitoring can be used as a useful tool for the monitoring of delayed cerebral injury.

Effect of hyperglycemia on brain cell membrane function and energy metabolism during hypoxia-ischemia in newborn piglets

The purpose of this study was to test the hypothesis that hyperglycemia ameliorates changes in brain cell membrane function and preserves cerebral high energy phosphates during hypoxia-ischemia in newborn piglets. A total of 42 ventilated piglets were divided into 4 groups, normoglycemic/normoxic(group 1, n=9), hyperglycemic/normoxic(group 2, n=8), normoglycemic/hypoxic-ischemic(group 3, n=13) and hyperglycemic/hypoxic-ischemic(group 4, n=12) group. Cerebral hypoxia-ischemia was induced by occlusion of bilateral common carotid arteries and simultaneous breathing with 8% oxygen for 30 min. Hyperglycemia (blood glucose 350-400 mg/dl) was maintained for 90 min before and throughout hypoxia-ischemia using modified glucose clamp technique. Changes in cytochrome aa3 were continuously monitored using near infrared spectroscopy. Blood and CSF glucose and lactate were monitored. Na+, K+-ATPase activity, lipid peroxidation products (conjugated dienes), tissue high energy phosphates (ATP and phosphocreatine) levels and brain glucose and lactate levels were determined biochemically in the cerebral cortex. During hypoxia-ischemia, glucose levels in blood and CSF were significantly elevated in hyperglycemic/hypoxic-ischemic group compared with normoglycemic/hypoxic-ischemic group, but lactate levels in blood and CSF were not different between two groups. At the end of hypoxia-ischemia of group 3 and 4, triangle up Cyt aa3, Na+, K+-ATPase activity, ATP and phosphocreatine values in brain were significantly decreased compared with normoxic groups 1 and 2, but were not different between groups 3 and 4. Levels of conjugated dienes and brain lactate were significantly increased in groups 3 and 4 compared with groups 1 and 2, and were significantly elevated in group 4 than in group 3 (0.30+/-0.11 vs. 0.09+/-0.02 micromol g-1 protein, 26.4+/-7.6 vs. 13.1+/-2.6 mmol kg-1, p<0.05). These findings suggest that hyperglycemia does not reduce the changes in brain cell membrane function and does not preserve cerebral high energy phosphates during hypoxia-ischemia in newborn piglets. We speculate that hyperglycemia may be harmful during hypoxia-ischemia due to increased levels of lipid peroxidation in newborn piglet.

Effect of indomethacin phonophoresis on the relief of temporomandibular joint pain

The pain-relieving effect of indomethacin phonophoresis on temporomandibular (TMJ) joint pain was evaluated in a double-blind, placebo-controlled clinical trial. Twenty subjects, who have TMJ pain, were included for this study and randomly assigned to either the experimental group (n = 10) or the control group (n = 10). Each treatment consisted of the application of ultrasound massage (1.0 MHz, 0.8 to 1.5 W/cm2 continuous output) for 15 minutes to the painful temporomandibular joint. As a conducting medium, 1% indomethacin cream was used for the experimental group and placebo cream for the control group respectively. Pre- and post-treatment pain levels and pain sensitivity were assessed with visual analogue scales (VAS) and pressure pain threshold (PPT). Mean data indicated that post-treatment VAS was significantly decreased and post-treatment PPT was significantly increased in the experimental group, not in the control group. The results of this study suggest that indomethacin phonophoresis provides significant pain relieving effect over the TMJ pain.

Protective effect of alpha-tocopherol on brain cell membrane function during cerebral cortical hypoxia in newborn piglets

Protective effect of alpha-tocopherol on the structure and function of brain cell membranes was investigated by measuring Na+,K(+)-ATPase activity and products of lipid peroxidation (fluorescent compounds) in brain cell membranes obtained from newborn piglets. Four groups of anesthetized, ventilated piglets were studied: five hypoxic piglets and five normoxic piglets were pretreated with free alpha-tocopherol (20 mg/kg/dose i.m.), five additional hypoxic piglets received i.m. placebo and five normoxic piglets served as control. Placebo and alpha-tocopherol were given 48 and 3 h prior to onset of hypoxia. Hypoxic hypoxia was induced and cerebral hypoxia was documented as a decrease in the ratio of phosphocreatine to inorganic phosphate (PCr/P(i)) using 31P NMR spectroscopy. PCr/P(i) decreased from baseline of 2.62 +/- 0.54 to 1.05 +/- 0.27 in alpha-tocopherol-pretreated and from 2.44 +/- 0.48 to 1.14 +/- 0.30 in the placebo-pretreated group during hypoxia. Na+,K(+)-ATPase activity was unchanged in both normoxic and hypoxic alpha-tocopherol-pretreated groups. However, in placebo-pretreated hypoxic group, Na+,K(+)-ATPase activity decreased as compared with control (44.9 +/- 9.7 vs. 61.8 +/- 5.7 mumol P(i)/mg protein/h, P < 0.005). The level of fluorescent compounds increased in placebo-pretreated but not in alpha-tocopherol-pretreated group as compared with control. During hypoxia, serum alpha-tocopherol levels were higher in alpha-tocopherol-pretreated groups as compared with placebo-pretreated hypoxic group. The present data indicates that alpha-tocopherol protects brain cell membranes in newborn piglets from lipid peroxidative damage during tissue hypoxia probably by being incorporated in cell membrane and also as circulating antioxidant.

[Experimental activation of cryptosporidiosis in mice by immunosuppression]

Cryptosporidium, a coccidian parasite first described by Tyzzer (1907) from a laboratory mouse, has become an important human enteric pathogen causing overwhelming diarrhea especially in immunocompromised patients such as AIDS. This parasite has been reported from over 20 countries and is recognized as a cosmopolitan species. In Korea, however, there has been no report on human as well as animal cryptosporidiosis. This study was performed so as to verify the presence of Cryptosporidium in Korea by activating the parasite from laboratory mice by immunosuppression. Total 65 conventionally-bred ICR mice including a control (5 mice) and 3 experimental groups (20 each) were used for this study. Group I was immunosuppressed with prednisolone injection (1 mg IM, every other day) for 7 weeks. Group II (prednisolone injection and tetracycline administration) and Group III (prednisolone injection and trimethoprim-sulfamethoxazole administration) were prepared to observe the effect of antibacterial agents on the activation of cryptosporidiosis. In fecal examinations of mice Cryptosporidium oocysts (4-6 microns in size) were detected from 1 week after the start of immunosuppression and the mice began to die. In H-E stained tissue sections of the lower jejunum, numerous very small (2-4 microns), dense, ovoid or spherical, slightly basophilic bodies were seen attached on the free border of mucosal epithelial cells. In scanning and transmission electron microscopic observations, these organisms were identified as various developmental stages of Cryptosporidium. The species is considered to be C. parvum.(ABSTRACT TRUNCATED AT 250 WORDS)