Yuba Raj Pokharel

Inhibition of liver fibrosis by solubilized coenzyme Q10: role of Nrf2 activation in inhibiting transforming growth factor-β1 expression.

Coenzyme Q10 (CoQ10), an endogenous antioxidant, is important in oxidative phosphorylation in mitochondria. It has anti-diabetic and anti-cardiovascular disease effects, but its ability to protect against liver fibrosis has not been studied. Here, we assessed the ability of solubilized CoQ10 to improve dimethylnitrosamine (DMN)-induced liver fibrogenesis in mice. DMN treatments for 3 weeks produced a marked liver fibrosis as assessed by histopathological examination and tissue 4-hydroxyproline content. Solubilized CoQ10 (10 and 30 mg/kg) significantly inhibited both the increases in fibrosis score and 4-hydroxyproline content induced by DMN. Reverse transcription-polymerase chain reaction and Western blot analyses revealed that solubilized CoQ10 inhibited increases in the transforming growth factor-beta1 (TGF-beta1) mRNA and alpha-smooth muscle actin (alpha-SMA) protein by DMN. Interestingly, hepatic glutamate-cysteine ligase (GCL) and glutathione S-transferase A2 (GSTA2) were up-regulated in mice treated with CoQ10. Solubilized CoQ10 also up-regulated antioxidant enzymes such as catalytic subunits of GCL and GSTA2 via activating NF-E2 related factor2 (Nrf2)/antioxidant response element (ARE) in H4IIE hepatoma cells. Moreover, CoQ10s inhibition of alpha-SMA and TGF-beta1 expressions disappeared in Nrf2-null MEF cells. In contrast, Nrf2 overexpression significantly decreased the basal expression levels of alpha-SMA and TGF-beta1 in Nrf2-null MEF cells. These results demonstrated that solubilized CoQ10 inhibited DMN-induced liver fibrosis through suppression of TGF-beta1 expression via Nrf2/ARE activation.

Ginsenoside Rg3 increases nitric oxide production via increases in phosphorylation and expression of endothelial nitric oxide synthase: essential roles of estrogen receptor-dependent PI3-kinase and AMP-activated protein kinase.

We previously showed that ginsenosides increase nitric oxide (NO) production in vascular endothelium and that ginsenoside Rg3 (Rg3) is the most active one among ginseng saponins. However, the mechanism for Rg3-mediated nitric oxide production is still uncertain. In this study, we determined whether Rg3 affects phosphorylation and expression of endothelial nitric oxide synthase (eNOS) in ECV 304 human endothelial cells. Rg3 increased both the phosphorylation and the expression of eNOS in a concentration-dependent manner and a maximal effect was found at 10μg/ml of Rg3. The enzyme activities of phosphatidylinositol 3-kinase (PI3-kinase), c-Jun N-terminal kinase (JNK), and p38 kinase were enhanced as were estrogen receptor (ER)- and glucocorticoid receptor (GR)-dependent reporter gene transcriptions in Rg3-treated endothelial cells. Rg3-induced eNOS phosphorylation required the ER-mediated PI3-kinase/Akt pathway. Moreover, Rg3 activates AMP-activated protein kinase (AMPK) through up-regulation of CaM kinase II and Rg3-stimulated eNOS phosphorylation was reversed by AMPK inhibition. The present results provide a mechanism for Rg3-stimulated endothelial NO production.

Novel Role of Pin1 Induction in Type II Collagen-Mediated Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation in joints and subsequent destruction of cartilage and bone. Inflammatory mediators such as PGs and proinflammatory cytokines contribute to RA progress. Pin1, a peptidyl prolyl isomerase, plays important pathophysiological roles in several diseases, including cancer and neurodegeneration. We found that both Pin1 and cyclooxygenase-2 (COX-2) were highly expressed in ankle tissues of type II collagen-induced RA mice. HTB-94 cells overexpressing Pin1 and primary cultured human chondrocytes showed increased basal expression of proinflammatory proteins (COX-2, inducible NO synthase, TNF-α, and IL-1β). Site-directed mutagenesis revealed that Pin1-mediated transcriptional activation of COX-2 was coordinately regulated by NF-κB, CREB, and C/EBP. Gel shift, reporter gene, and Western blot analyses confirmed that NF-κB, CREB, and C/EBP were consistently activated in chondrocytes overexpressing Pin1. Treatment of RA mice with juglone, a chemical inhibitor of Pin1, significantly reduced RA progress and COX-2 expression in the ankle tissues. Moreover, juglone dose dependently decreased the basal COX-2 expression in primary cultured chondrocytes from RA patients. These results demonstrate that Pin1 induction during RA progress stimulates proinflammatory protein expression by activating NF-κB, CREB, and C/EBP, and suggest that Pin1 is a potential therapeutic target of RA.

Sopungyangjae-Tang Inhibits Development of Dermatitis in Nc/Nga Mice

Sopungyangjae-Tang (SYT) is a traditional Korean decoction used for the treatment of dermatitis. The aim of this study was to confirm whether or not SYT has a preventive effect on the development of atopic dermatitis in dinitrochlorobenzene-applied Nc/Nga mice. SYT was administered orally to Nc/Nga mice, which led to the remarkable suppression of the development of dermatitis, as determined by a histological examination and the serum IgE levels. Moreover, SYT inhibited the production of thymus- and activation-regulated chemokine (TARC) and its mRNA expression in a keratinocyte cell line, HaCaT, which had been stimulated with tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ). Activation of the nuclear factor-κB (NF-κB) or activator protein-1 (AP-1) is one of the key steps in the signaling pathways mediating induction of TARC. In this study, SYT selectively suppressed NF-κB activation, which may be essential for TARC expression in TNF-α/IFN-γ treated keratinocytes. The inhibitory effect of SYT on NF-κB activation and TARC production might be associated with the anti-dermatitic effects of SYT.

Increased Ubiquitination of Multidrug Resistance 1 by Ginsenoside Rd

MCF-7/ADR cells, a doxorubicin-resistant human breast cancer cell line, acquires resistance to several chemotherapeutic agents, such as anthracylines and taxol, via overexpression of the multidrug resistance1 (MDR1) gene. The present study was designed to clarify whether ginsenosides affect the expression of the MDR1 gene in MCF-7/ADR cells. Ginsenoside Rd, Re, Rb1, and Rg1 (100 μ g/ml) decreased MDR1 protein levels in MCF-7/ADR cells. In particular, ginsenoside Rd most potently inhibited MDR1 protein expression without cytotoxicity, but did not change mRNA levels or nuclear levels of key transcriptional factors for MDR1 gene expression, hypoxia inducible factor-1α, CCAAT-enhancer binding protein β, Forkhead box-containing protein, O subfamily1, or Y-box binding protein-1. Reporter gene analyses showed that ginsenoside Rd did not decrease MDR1 gene transcription or the pregnane X receptor reporter. MDR1 protein stability is dependent on ubiquitin-dependent protein degradation. We further found that ginsenosides Rd increased ubiquitination of MDR1. Moreover, doxorubicin resistance in MCF-7/ADR cells was reversed by ginsenoside Rd treatment. These results propose that ginseng administration with other anti-cancer agents may be useful for the treatment of chemotherapy-resistant breast cancer through down-regulating MDR1 protein.

The hepatoprotective effects of adenine nucleotide translocator-2 against aging and oxidative stress

Mitochondrial adenine nucleotide translocator (ANT) plays important roles in the regulation of mitochondrial permeability transition and cell bioenergetics. The mouse has three ANT isoforms (1, 2 and 4) showing tissue-specific expression patterns. Although ANT1 is known to have a pro-apoptotic property, the specific functions of ANT2 have not been well determined. In the present study, ANT2 expression was significantly lower in the aged rat liver and in a liver fibrosis model. To explore the protective role of ANT2 in the liver, we established a hepa1c1c7 cell line overexpressing ANT2. Overexpression of ANT2 caused hepa1c1c7 cells to be more resistant to oxidative stress, and mitochondrial membrane potential (MMP, ∆Ψm) was relatively intact in ANT2-overexpressing cells under oxidative stress. In addition, ANT2 was found to increase ATP production by influencing mitochondrial bioenergetics. These results imply that the hepatoprotective effect of ANT2 is due to the stabilization of MMP and enhanced ATP production, and thus, maintaining ANT2 levels in the liver might be important to enhance resistance to aging and oxidative stress.

Immunomodulatory Studies on Triterpenoids from Scoparia dulcis Linn

Glutinone (1), coixol (2), friedelin (3), glutinol (4), and betulinic acid (5) were isolated from the plant Scoparia dulcis. Their structures were identified using mass and 1D- and 2D- NMR techniques. All the compounds were tested for their immunomodulatory potential in oxidative burst assay. Compound 1 showed a significant inhibitory effect on the release of reactive oxygen species (ROS) from zymosan activated cells from whole blood (IC50 = 4.3 ± 0.6 μg/mL) as well as from isolated PMNs (IC50 = 5.0 ± 0.3 μg/mL) as compared to standard drug ibuprofen in whole blood (IC50 = 11.2± 1.9 μg/ mL) and in isolated PMNs (IC50 = 2.5± 0.6 μg/mL) shows that it is more active in whole blood as compared with isolated PMNs. Compound 1 when further tested for its effect on pro-inflammatory cytokines TNF-α, IL-1β and on nitric oxide (NO), was found to moderately inhibiting the production of TNF-α (19%) at a concentration 25 μg/mL. On the other hand a weak inhibitory effect of this compound was also observed on the production of IL-1β and NO production, whereas, compounds 2-5 showed no effect (IC50 = >100) on the release of ROS from zymosan activated cells.

Inhibition of Dermatitis Development by Sopungsan in Nc/Nga Mice

Sopungsan (SS) is a traditional Korean decoction used for the treatment of dermatitis. The aim of this study is to confirm whether or not SS has a preventive effect on the development of atopic dermatitis in dinitrochlorobenzene-applied Nc/Nga mice. SS was administered orally to Nc/Nga mice, which led to the remarkable suppression of the development of dermatitis, as determined by a histological examination and the serum IgE levels. Moreover, SS inhibited the production of thymus- and activation-regulated chemokine (TARC) and its mRNA expression in a keratinocyte cell line, HaCaT, which had been stimulated with tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ). Activation of the nuclear factor-κB (NF-κB) or activator protein-1 (AP-1) is one of key steps in the signaling pathways mediating induction of TARC. In this study, SS selectively suppressed NF-κB activation which may be essential for TARC expression in TNF-α/IFN-γ treated keratinocytes. The inhibitory effect of SS on NF-κB activation and TARC production might be associated with the anti-dermatitic effects of SS.

Inhibition of the Induction of Nitric Oxide Synthase by Kobusin

We isolated a lignan, kobusin from Geranium thunbergii and studied its effect on the expression of inducible nitric oxide synthase (iNOS) gene in a monocyte/macrophage cell line, RAW264.7 cells. Kobusin inhibited lipopolysaccharide (LPS)-stimulated NO production and the expression of inducible nitric oxide synthase (iNOS) in a concentration-dependent manner. To identify the mechanistic basis for its inhibition of iNOS induction, we examined the effect of kobusin on both the luciferase reporter activity using NF-kB minimal promoter and the nuclear translocation of p65. Kobusin suppressed the reporter gene activity and the LPS-induced movement of p65 in to nucleus. NF-κB activation is controlled by the phosphorylation and subsequent degradation of I-κBα, and in the present study, we found that I-κBα phosphorylation was also inhibited by kobusin. Our findings indicate that kobusin may provide a developmental basis for an agent against inflammatory diseases.