Shoei-Sheng Lee

Atherogenicity and carcinogenicity of high-arsenic artesian well water. Multiple risk factors and related malignant neoplasms of blackfoot disease.

The objective of this study was to examine multiple risk factors and correlated malignant neoplasms of blackfoot disease (BFD), a unique peripheral vascular disease related to continuous exposure to high-arsenic artesian well water. A total of 241 BFD cases, Including 169 with spontaneous or surgical amputations of affected extremities, and 759 age-sex-resldence-matched healthy community controls were studied to explore the risk factors of BFD. Multiple logistic regression analysis showed that artesian well water consumption, arsenic poisoning, familial history of BFD, and undernourishment were significantly associated with the development of BFD. The life-table method used to analyze cancer mortality of 789 BFD patients followed for 15 years showed a significantly higher mortality from cardiovascular diseases, peripheral vascular diseases, and cancers of bladder, skin, lung, and liver among BFD patients as compared with the general population In Taiwan or residents In the BFD-endemic area. The results Imply the atherogenicity and carcinogenicity of the artesian well water In the BFD-endemic area.

Differential inhibition of reverse transcriptase and cellular DNA polymerase-α activities by lignans isolated from Chinese herbs, Phyllanthus myrtifolius Moon, and tannins from Lonicera japonica Thunb and Castanopsis hystrix

Two lignans, phyllamycin B and retrojusticidin B isolated from Phyllanthus myrtifolius Moon have been demonstrated to have a strong inhibitory effect on human immunodeficiency virus-1 reverse transcriptase activity (HIV-1 RT), but much less inhibitory effect on human DNA polymerase-alpha (HDNAP-alpha) activity. Fifty percent inhibitory concentrations of phyllamycin B and retrojusticidin B were determined to be 3.5 and 5.5 microM for HIV-1 RT, and 289 and 989 microM for HDNAP-alpha, respectively. The mode of inhibition was found to be non-competitive inhibition with respect to template-primer and triphosphate substrate. Several tannins such as caffeoylquinates (CQs) isolated from Lonicera japonica Thunb, galloylquinates (GQs) and galloylshikimates (GSs) purified from Castanopsis hystrix were shown to have a much less selective inhibitory effect on HIV-1 RT.

Lignans from Phyllanthus urinaria

Chemical investigation on the aerial and the root parts of Phyllanthus urinaria L. culminated in the isolation of four lignans, namely 5-demethoxyniranthin, urinatetralin, dextrobursehernin, urinaligran, together with nine known lignans. Their structures, including the absolute stereochemistry, were elucidated by spectral analysis (NMR and CD) and chemical correlation.

Synergistic interactions between sorafenib and bortezomib in hepatocellular carcinoma involve PP2A-dependent Akt inactivation

BACKGROUND & AIMS Previously we reported that Akt inactivation determines the sensitivity of hepatocellular carcinoma (HCC) cells to bortezomib. Here we report that combined treatment with sorafenib and bortezomib shows synergistic effects in HCC. METHODS HCC cell lines (PLC/PRF/5, Huh-7, and Hep3B) were treated with sorafenib and/or bortezomib and analyzed in terms of apoptosis signal transduction. In vivo efficacy was determined in nude mice with PLC/PRF/5 xenografts. RESULTS Pretreatment with sorafenib enhanced bortezomib-induced apoptotic cell death by restoring bortezomibs ability to inactivate Akt in PLC/PRF/5 cells. Knocking down Akt1 by RNA-interference overcame apoptotic resistance to bortezomib in PLC/PRF/5 cells and ectopic expression of active Akt in HCC cells abolished the bortezomib sensitizing effect of sorafenib, indicating Akt inactivation plays a key role in mediating the combinational effects. Moreover, okadaic acid, a protein phosphatase 2A (PP2A) inhibitor, reversed down-regulation of phospho-Akt (P-Akt) expression induced by co-treatment with sorafenib and bortezomib, and 1, 9 di-deoxy-forskolin, a PP2A agonist, restored bortezomibs effect on P-Akt and apoptosis. Importantly, silencing of PP2A by RNA-interference reduced the apoptotic effect induced by sorafenib-bortezomib co-treatment, indicating that PP2A is indispensable for mediating the effects of these drugs. Notably, sorafenib with bortezomib increased PP2A activity in PLC/PRF/5 cells without altering protein levels of PP2A complex or the interaction between PP2A and Akt proteins. Finally, sorafenib plus bortezomib significantly suppressed PLC/PRF/5 xenograft tumor growth, down-regulated P-Akt expression, and up-regulated PP2A activity. CONCLUSIONS The combination of sorafenib and bortezomib shows synergy in HCC through PP2A-dependent Akt inactivation.

Epigallocatechin suppression of proliferation of vascular smooth muscle cells: correlation with c-jun and JNK

1 The mechanisms of the antiproliferative effect of epigallocatechin, one of the catechin derivatives found in green tea, in vascular smooth muscle cells were studied. The proliferative response was determined from the uptake of tritiated thymidine. 2 In the concentration range of 10−6 to 10−4 m, catechin, epicatechin, epigallocatechin, epicatechin gallate and epigallocatechin, epigallocatechin gallate, concentration‐dependently inhibited the proliferative response stimulated by serum in rabbit cultured vascular smooth muscle cells. Catechin and epicatechin were less effective in inhibiting the serum‐stimulated smooth muscle cell proliferation, indicating that the galloyl group may be important for full inhibitory activity. 3 Epigallocatechin (EGC) inhibited the proliferative responses in different cells including rat aortic smooth muscle cells (A7r5 cells), rabbit cultured aortic smooth muscle cells, human coronary artery smooth muscle cells, and human CEM lymphocytes in a concentration‐dependent manner. The possible mechanisms of the antiproliferative effect of EGC were further studied in A7r5 cells. 4 The membranous protein tyrosine kinase activity stimulated by serum in A7r5 cells was significantly reduced by 10−5 m EGC. In contrast, the cytosolic protein kinase C activity stimulated by phorbol ester was unaffected by directly incubating with EGC (10−6−10−4 m). 5 We also performed Western blot analysis using the anti‐phosphotyrosine monoclonal antibody PY‐20. EGC (10−5 m) reduced the levels of tyrosine phosphorylated proteins with different molecular weights, indicating that EGC may inhibit the protein tyrosine kinase activity or stimulate the protein phosphatase activity. 6 Reverse transcription‐polymerase chain reaction analysis of c‐fos, c‐jun and c‐myc mRNA levels demonstrated that c‐jun mRNA level after serum‐stimulation was significantly reduced by 10−5 m EGC. However, the reduction of c‐fos and c‐myc mRNA levels by 10−5 m EGC did not achieve significance. 7 Western blot analysis using the antibody against JNK (c‐jun N‐terminal kinase) and ERK (extracellular signal‐regulated kinase) demonstrated that the level of phosphorylated JNK1, but not phosphorylated ERK1 and ERK2, was reduced by 10−5 m EGC. Direct measurement of kinase activity by immune complex kinase assay confirmed that JNK1 activity was inhibited by EGC treatment. These results demonstrate that EGC preferentially reduced the activation of JNK/SAPK (stress‐activated protein kinase) signal transduction pathway. 8 It is suggested that the antiproliferative effect of epigallocatechin on vascular smooth muscle cells may partly be mediated through inhibition of protein tyrosine kinase activity, reducing c‐jun mRNA expression and inhibiting JNK1 activation. Tea catechins may be useful as a template for the development of drugs to prevent the pathological changes of atherosclerosis and post‐angioplasty restenosis.

Oregonin inhibits lipopolysaccharide-induced iNOS gene transcription and upregulates HO-1 expression in macrophages and microglia

Oregonin isolated from Alnus formosana is a diarylheptanoid derivative, which appears to have antioxidative and anti‐inflammatory activities. In this study, our data demonstrated inhibitory actions of oregonin on the LPS‐induced iNOS protein in RAW264.7 macrophages and BV‐2 microglial cells. We also suggested that HO‐1 induction by oregonin might contribute to this action. Oregonin is able to dose‐dependently reduce NO production, iNOS protein and iNOS promoter activity stimulated by LPS in RAW264.7 and BV‐2 cells. Oregonin also showed inhibition of LPS‐mediated NF‐κB promoter activity and DNA‐binding ability, as well as p65 nuclear translocation and phosphorylation. However, oregonin had no effect on IKK activity. AP‐1 promoter activity and p38 MAPK activation but not PKC, ERK and JNK activation induced by LPS were attenuated by oregonin. Accompanying with iNOS protein reduction, moreover, we found that oregonin was able to induce HO‐1 protein level. Results using a CO donor, [Ru(CO)3Cl2]2 further showed the ability of CO in reduction of iNOS protein level induced by LPS through the blockade of NF‐κB and AP‐1. Taken together, these results provide new evidences into the anti‐inflammatory actions of oregonin, which include the inhibition of iNOS gene transcription via suppressing transcriptional activity of NF‐κB and AP‐1, as well as the upregulation of anti‐inflammatory molecule HO‐1. The HO‐1‐derived CO may also be involved in the suppressive effect on iNOS gene regulation.

Three triterpene esters from Zizyphus jujuba

Abstract Further separation of the water-insoluble fraction of the ethanol extract from the root of Zizyphus jujuba var. spinosa led to the isolation of three new triterpene esters: 2-O-protocatechuoylaliphitolic acid, 2α-hydroxypyracrenic acid and 3-O-protocatechuoylceanothic acid. The latter two compounds were charcterized as the triacetate and tetra-O-methylated derivative, respectively.

Borapetoside C from Tinospora crispa improves insulin sensitivity in diabetic mice

Diabetes mellitus (DM) often leads to disability from vascular complications and neurological complications. Tinospora crispa has been widely used in Asia and Africa as a remedy for diabetes and other diseases. In this study, we investigated the hypoglycemic actions of borapetoside C isolated from T. crispa, and the mechanisms underlying its actions. Acute treatment with borapetoside C (5mg/kg, i.p.) attenuated the elevated plasma glucose induced by oral glucose in normal and type 2 DM (T2DM) mice. Compared to the effect of injected insulin (0.5 IU/kg), borapetoside C caused a more prominent increase of glycogen content in skeletal muscle of T2DM mice, but a less increase in type 1 DM (T1DM) mice. Combined treatment of a low dose borapetoside C (0.1mg/kg, i.p.) plus insulin enhanced insulin-induced lowering of the plasma glucose level and insulin-induced increase of muscle glycogen content. Continuous treatment with 5mg/kg borapetoside C (twice daily) for 7 days increased phosphorylation of insulin receptor (IR) and protein kinase B (Akt) as well as the expression of glucose transporter-2 (GLUT2) in T1DM mice. Combined treatment of a low dose borapetoside C (0.1mg/kg, twice daily) plus insulin for 7 days enhanced insulin-induced IR and Akt phosphorylation and GLUT2 expression in the liver of T1DM mice. This study proved that borapetoside C can increase glucose utilization, delayed the development of insulin resistance and enhanced insulin sensitivity. The activation of IR-Akt-GLUT2 expression and the enhancement of insulin sensitivity may contribute to the hypoglycemic action of borapetoside C in diabetic mice.

Antiplatelet effects of some aporphine and phenanthrene alkaloids in rabbits and man

Two aporphines (boldine and laurolitsine) and five phenanthrene alkaloids (litebamine, secoboldine, N‐cyanosecoboldine, N‐methylsecoglaucine and N‐methylsecopredicentrine) were evaluated in‐vitro for their ability to inhibit platelet aggregation.

Thaliporphine, a positive inotropic agent with a negative chronotropic action.

The effects of thaliporphine on contractions and electrophysiological properties of cardiac tissues were examined. In driven rat left atria and right ventricular strips, thaliporphine (1-30 microM) increased twitch tension dose-dependently. The positive inotropic effect of thaliporphine was unaffected by atenolol (3 microM) and prazosin (1 microM) but was significantly suppressed by verapamil (1 microM). An electrophysiological study revealed that thaliporphine (3-10 microM) markedly inhibited the action potential upstroke and prolonged the action potential duration (APD50) in rat and guinea pig atrial and ventricular cells. At 1-30 microM, thaliporphine reduced the transient outward current (Ito) of the rat ventricular cells in a dose-dependent manner. The peak Ito in rat ventricular cells and the delayed rectifying K+ current (Ik in guinea pig ventricular cells were reduced by thaliporphine (10 microM) to 37.3 +/- 2.1% (n = 8) and 45.3 +/- 1.8% (n = 4), respectively. In rat ventricular cells and guinea pig atrial cells, thaliporphine (1.5 microM) reduced the Na+ inward current (INa) with a negative shift (4-5 mV) relative to its half inactivation potential. For the Ca2+ inward current (ICa) in rat ventricular cells, 10 microM of thaliporphine caused a smaller increase in the peak ICa than 0.5 microM of Bay K 8644. The increase in ICa elicited by both agents was associated with a negative shift of its half activation potential from -10 +/- 2 mV to -18 +/- 2 mV (n = 6) by thaliporphine and -11 +/- 2 to -19 +/- 2 mV (n = 4) by Bay K 8644. These results indicate that thaliporphine is a weak Ca2+ channel agonist with strong Na+ and K+ channel blocking activities. The positive inotropic effect may be due to an increase in calcium entry mediated via partial activation of calcium channels or by inhibition of K+ efflux. Inhibition of K+ efflux would result in prolongation of APD50 and contribute to the negative chronotropic effect of thaliporphine.