Showing papers by "Youn-Chul Kim published in 2011"

Butein from Rhus verniciflua Protects Pancreatic β Cells against Cytokine-Induced Toxicity Mediated by Inhibition of Nitric Oxide Formation

Abstract: Butein (3,4,2',4'-tetrahydroxychalcone), a plant polyphenol, is a major component in isolate of Rhus verniciflua STOKES (Anacardiaceae). It is shown to exert various potent effects such as antioxidant, antiinflammatory induction of apoptosis among many properties. In this study, we investigated the effect of butein on cytokine-induced β-cell damage. Pre-treatment with butein is shown to increase the viability of cytokine-treated INS-1 cells at concentrations of 15-30 µM. Butein prevented cytokine-mediated cell death, as well as nitric oxide (NO) production, and these effects correlated well with reduced levels of protein expression of the inducible nitric oxide synthase (iNOS). Furthermore, the molecular mechanisms by which butein inhibits iNOS gene expression appeared to be through the inhibition of nuclear factor-κB (NF-κB) translocation. In a second set of experiments, rat islets were used to demonstrate the protective effects of butein and the results were essentially the same as those observed in Beutin pretreated INS-1 cells. Butein prevented cytokine-induced NO production, iNOS expression, and NF-κB translocation and inhibition of glucose-stimulated insulin secretion (GSIS). In conclusion, these results suggest that butein can be used for the prevention of functional β-cell damage and preventing the progression of Type 1 diabetes mellitus (T1DM).

Sauchinone suppresses pro-inflammatory mediators by inducing heme oxygenase-1 in RAW264.7 macrophages.

Abstract: Sauchinone, a biologically active lignan isolated from the roots of Saururus chinensis (LOUR.) BAILL. (Saururaceae), is reported to exert a variety of biological activities, such as hepatoprotective, anti-inflammatory actions and inhibitory effects on bone resorption. In this study, we investigated the effect of sauchinone in suppressing cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expression, leading to a reduction in COX-2-derived prostaglandin E(2) (PGE(2)) and iNOS-derived nitric oxide (NO) production in lipopolysaccharide (LPS) stimulated RAW264.7 macrophages. Present study also demonstrates the effects of sauchinone in inducing heme oxygenase-1 (HO-1) expression and an increase in heme oxygenase (HO) activity in RAW264.7 macrophages. The effects of sauchinone on LPS-induced PGE(2), NO, tumor necrosis factor-α (TNF-α) and interlukine-1β (IL-1β) production were partially reversed by the HO-1 inhibitor Tin protoporphyrin was also seen in this study. In addition, we found that treatment with extracellular signal-regulated kinase (ERK) inhibitor (PD98059) reduced sauchinone-induced HO-1 expression. Sauchinone also increased ERK phosphorylation. These results suggest that sauchinone inhibits pro-inflammatory mediators through expression of anti-inflammatory HO-1 via ERK pathway.

Involvement of heme oxygenase-1 induction in inhibitory effect of ethyl gallate isolated from Galla Rhois on nitric oxide production in RAW 264.7 macrophages.

Abstract: In the present study, we investigated an anti-inflammatory effect of ethyl gallate (EG) isolated from Galla Rhois as evaluated by inhibition of nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression, and a potential role of heme oxygenase-1 (HO-1) in the inhibition of NO production elicited by EG. Treatment of RAW264.7 macrophages with EG significantly inhibited the production of NO and iNOS expression stimulated by lipopolysaccharide (LPS). We also demonstrated that EG treatment increased HO-1 mRNA and protein expression, as assessed by quantitative RT-PCR and Western blot analysis. EG treatment also increased the levels of nuclear factor-erythroid 2-related factor 2, which is critical for transcriptional induction of HO-1. In addition, treatment with SnPP (tin protoporphyrin IX), a selective HO-1 inhibitor, counteracted the inhibitory effect of EG on nitrite production, suggesting that HO-1 is, at least in part, implicated in the inhibition of NO production induced by EG treatment. Taken together, these results indicate that EG isolated from Galla Rhois suppresses NO production in LPS-stimulated RAW 264.7 macrophages via HO-1 induction.

Bakuchicin induces Vascular Relaxation via Endothelium-dependent NO-cGMP Signaling

Abstract: Bakuchicin is a furanocoumarin derived from the seeds of Psoralea corylifolia. The aim of the present study was to investigate the effect of bakuchicin on vascular tone in rat aortic tissue. Bakuchicin induced a dose-dependent relaxation of phenylephrine-precontracted rat aorta which was abolished by removal of the endothelium. Pretreatment of the endothelium-intact aortic tissues with NG-nitro-L-arginine methylester (L-NAME) or 1H-[1,2,4]-oxadiazole-[4,3-α]-quinoxalin-1-one (ODQ) significantly inhibited the vascular relaxation induced by bakuchicin. Incubation with bakuchicin increased the production of cGMP in a concentration-dependent manner, and this effect was blocked by pretreatment with both L-NAME and ODQ. Vascular relaxation induced by bakuchicin was significantly inhibited by pretreatment with verapamil and diltiazem, but not by several other inhibitors including tetraethylammonium (TEA), glibenclamide, indomethacin, atropine or propranolol. These results suggested that bakuchicin-induced vasodilatation is closely associated with the endothelium-dependent nitric oxide (NO)/cGMP signaling pathway, with the possible involvement of L-type Ca(2+) channels.

Inhibition of Nitric Oxide Production by Ethyl Digallates Isolated from Galla Rhois in RAW 264.7 Macrophages

Abstract: Galla Rhois and its components are known to possess anti-infl ammatory properties. In the present study, we prepared equilibrium mixture of ethyl m-digallate and ethyl p-digallate isomers (EDG) from Galla Rhois and examined its effect on nitric oxide (NO) production in murine macrophage cell line. Treatment of RAW264.7 macrophages with EDG signifi cantly inhibited NO production and inducible nitric oxide synthase (iNOS) expression stimulated by LPS, as assessed by Western blot and quantitative RTPCR analyses. We also demonstrated that EDG treatment led to an increase in heme oxygenase-1 (HO-1) mRNA and protein expression. EDG treatment also enhanced expression level of nuclear factor-erythroid 2-related factor 2 (Nrf2) in nucleus, which is critical for transcriptional induction of HO-1. Treatment with SnPP (tin protoporphyrin IX), a selective HO-1 inhibitor, reversed EDG-mediated inhibition of nitrite production, suggesting that HO-1 plays an important role in the suppression of NO production by EDG. Taken together, these results indicate that EDG isolated from Galla Rhois suppresses LPS-stimulated NO production in RAW 264.7 macrophages via HO-1 induction.