Phyllanthin and hypophyllanthin inhibit function of P-gp but not MRP2 in Caco-2 cells.

OBJECTIVES: The purposes of this study were to investigate the inhibitory effects of two lignans, phyllanthin and hypophyllanthin, on the function of P-glycoprotein (P-gp) and multidrug resistance protein 2 (MRP2), using the in-vitro model of Caco-2 cells. In addition, the effect of prolonged exposure to these two compounds on the expression of active P-gp was also determined. METHODS: The activity of P-gp and MRP2 was determined in the uptake assays by monitoring the intracellular accumulation of their specific substrates (calcein acetoxymethyl ester and 5(6)-carboxy-2',7'-dichlorofluorescein diacetate, respectively) with fluorescence spectroscopy. KEY FINDINGS: Hypophyllanthin and phyllanthin inhibited P-gp function with comparable potencies, but neither compound affected MRP2 activity. When the lignans were washed out before addition of substrate, the inhibitory action of both compounds against P-gp function was lost. These results suggested the reversibility of the inhibition. Moreover, prolonged exposure of the Caco-2 cells to both lignans (up to 7 days) had no effect on P-gp function. CONCLUSIONS: Phyllanthin and hypophyllanthin directly inhibited P-gp activity and did not interfere with MRP2 activity. It was likely that both phyllanthin and hypophyllanthin could reversibly inhibit P-gp function.

Microemulsion-based oxyresveratrol for topical treatment of herpes simplex virus (HSV) infection: physicochemical properties and efficacy in cutaneous HSV-1 infection in mice.

The physicochemical properties of the optimized microemulsion and the permeating ability of oxyresveratrol in microemulsion were evaluated, and the efficacy of oxyresveratrol microemulsion in cutaneous herpes simplex virus type 1 (HSV-1) infection in mice was examined. The optimized microemulsion was composed of 10% w/w of isopropyl myristate, 35% w/w of Tween 80, 35% w/w of isopropyl alcohol, and 20% w/w of water. The mean particle diameter was 9.67 ± 0.58 nm, and the solubility of oxyresveratrol in the microemulsion was 196.34 ± 0.80 mg/ml. After accelerated and long-term stability testing, the microemulsion base and oxyresveratrol-loaded microemulsion were stable. The cumulative amount of oxyresveratrol permeating through shed snake skin from microemulsion at 6 h was 93.04 times compared to that of oxyresveratrol from Vaseline, determined at 20% w/w concentration. In cutaneous HSV-1 infection in mice, oxyresveratrol microemulsion at 20%, 25%, and 30% w/w, topically applied five times daily for 7 days after infection, was significantly effective in delaying the development of skin lesions and protecting from death (p < 0.05) compared with the untreated control. Oxyresveratrol microemulsion at 25% and 30% w/w was significantly more effective than that of 30% w/w of oxyresveratrol in Vaseline (p < 0.05) and was as effective as 5% w/w of acyclovir cream, topically applied five times daily (p > 0.05). These results demonstrated that topical oxyresveratrol microemulsion at 20-30% w/w was suitable for cutaneous HSV-1 mouse infection.

Endothelium-independent effects of phyllanthin and hypophyllanthin on vascular tension.

The purpose of this study was to investigate the modulating effects of phyllanthin and hypophyllanthin on vascular tension, using in the in vitro model of isolated rat aorta. Our results indicated that both phyllanthin and hypophyllanthin significantly relaxed the sustained contraction induced by phenylephrine (PE) in a concentration-dependent manner. In addition, endothelial removal had no significant influence on the vasorelaxation responses of the aortic rings toward these two compounds. Furthermore, both compounds inhibited the contraction of aortic muscle provoked by either PE (1 µM) or KCl (40 mM) as well as the spontaneous contraction of the Ca²âº-depleted muscle. In high K⁺-Ca²âº free solution, phyllanthin (100 µM), but not hypophyllanthin, significantly inhibited the contractile responses upon cumulative addition of CaCl2. Both compounds (100 µM) significantly inhibited PE-induced contraction in Ca²âº-free condition, but could not affect caffeine-induced contraction. Taken together, phyllanthin and hypophyllanthin could modulate the vascular tension via the endothelium-independent mechanisms. The modulating effects of both compounds were possibly involved with the blockade of Ca²âº entry into vascular smooth muscle cells and inhibition of PE-mediated Ca²âº release from sarcoplasmic reticulum.

Combination of multiplex PCR and DHPLC-based strategy for CYP2D6 genotyping scheme in Thais.

OBJECTIVE: To develop CYP2D6 genotyping scheme for accurate allele calling and reliable estimation of functional allele dosage in Thais. DESIGN AND METHODS: We analyzed CYP2D6 copy numbers by pentaplex PCR coupled with semi-quantitative denaturing high performance liquid chromatography (DHPLC)-based technique. Ten common SNPs were genotyped from CYP2D6 gene product using single base extension (SBE) followed by DHPLC analysis. This detection scheme was compared with real-time PCR and conventional PCR-RFLP for cost-effectiveness. RESULTS: The distribution of CYP2D6 gene copy numbers in our population ranged from zero (0.69%), one (7.99%), two (60.07%), three (28.13%) and four (3.13%). The most commonly detected SNPs were related to CYP2D6*10 haplotype. CYP2D6*36 in tandem with CYP2D6*10B is the major rearrangement type in Thais (18.75%). CONCLUSIONS: Multiplex PCR coupled with DHPLC-based strategy is convenient and reliable method for CYP2D6 genotyping offering sufficient allele coverage for Asians. Both cost and analytical time saving were shown and the method could potentially be modified to accommodate CYP2D6 genotyping in other ethnics.

Topical cream-based oxyresveratrol in the treatment of cutaneous HSV-1 infection in mice.

Anti-herpes simplex virus (HSV) activities of oxyresveratrol in vitro and topical administration in cutaneous HSV-1 infection in mice were examined. The inhibitory concentrations for 50% plaque formation (IC(50)) of oxyresveratrol against HSV-1 clinical isolates and HSV-2 clinical isolates were 20.9-29.5 and 22.2-27.5 µg/ml, respectively. In topical administration in cutaneous HSV-1 infection in mice, 2.5%, 5%, 10% and 20% oxyresveratrol in cream vehicle applied three times daily for 7 days after infection were evaluated and 10% and 20% oxyresveratrol cream were significantly effective in delaying the development of skin lesions and protection from death (P < 0.01). The concentration of 10% oxyresveratrol in cream was significantly more effective than that of 30% oxyresveratrol in vaseline applied three times daily (P < 0.01). Oxyresveratrol cream at 20% was as effective as 5% ACV cream applied three times daily (P < 0.01). Both 10% and 20% oxyresveratrol cream were as effective as that of 5% ACV cream applied two times daily (P > 0.05). Therapeutic efficacy of oxyresveratrol in cream vehicle was dose-dependent and the maximum efficacy observed on day 6 after infection was shown at 10% oxyresveratrol in cream applied three times daily. The frequency of application of 10% oxyresveratrol cream at three, four and five times daily was as effective as that of 5% ACV cream applied five times daily (P > 0.05). These results demonstrated that topical administration of oxyresveratrol in novel cream vehicle reduced the concentration of oxyresveratrol to 10% and was suitable for cutaneous HSV infection.

Protective activity of phyllanthin in ethanol-treated primary culture of rat hepatocytes.

AIM OF THE STUDY: To investigate the protective effect of phyllanthin (a known principal constituent of Phyllanthus amarus Schum. et Thonn.) on ethanol-induced rat liver cell injury. MATERIALS AND METHODS: Primary culture of rat hepatocytes (24h culturing) were pretreated with phyllanthin (1, 2, 3 and 4 microg/ml) for 24h. After 24h pretreatment, cells were treated with ethanol (80 microl/ml) for 2h. RESULTS: Ethanol decreased %MTT, increased the release of transaminases (ALT and AST) with the increase in the production of intracellular ROS and lipid peroxidation. Phyllanthin demonstrated its role in protection by antagonizing the above effect induced by ethanol. Phyllanthin also restored the antioxidant capability of rat hepatocytes including level of total glutathione, and activities of superoxide dismutase (SOD) and glutathione reductase (GR) which were reduced by ethanol. CONCLUSIONS: These results suggested the hepatoprotective effect of phyllanthin against ethanol-induced oxidative stress causing rat liver cell damage through its antioxidant activity.

Inhibitory activity of oxyresveratrol on wild-type and drug-resistant varicella-zoster virus replication in vitro.

The anti-herpes simplex virus (HSV) compound, oxyresveratrol, purified from a Thai traditional medicinal plant of Artocarpus lakoocha, was evaluated for its anti-varicella-zoster virus (VZV) activity. This compound exhibited IC(50) values (50%-inhibitory concentrations for virus plaque formation) of 12.82, 12.80, 12.99 and 12.82 microg/ml against wild type, thymidine kinase-deficient and two types of DNA polymerase mutants with acyclovir-resistance, respectively. Thus oxyresveratrol showed a broad spectrum of anti-VZV activity with a mechanism of action different from that of acyclovir.

Anti-herpes simplex virus (HSV-1) activity of oxyresveratrol derived from Thai medicinal plant: mechanism of action and therapeutic efficacy on cutaneous HSV-1 infection in mice.

Oxyresveratrol, a major compound purified from Artocarpus lakoocha, a Thai traditional medicinal plant, was evaluated for its mechanism of action and therapeutic efficacy on cutaneous herpes simplex virus (HSV) infection in mice. The inhibitory concentrations for 50% HSV-1 plaque formation of oxyresveratrol, three clinical isolates, thymidine kinase (TK)-deficient and phosphonoacetic acid (PAA)-resistant HSV-1 were 19.8, 23.3, 23.5, 24.8, 25.5 and 21.7microg/ml, respectively. Oxyresveratrol exhibited the inhibitory activity at the early and late phase of viral replication and inhibited the viral replication with pretreatment in one-step growth assay of HSV-1 and HSV-2. Oxyresveratrol inhibited late protein synthesis at 30microg/ml. The combination of oxyresveratrol and acyclovir (ACV) produced synergistic anti-HSV-1 effect, as characterized by the isobologram of plaque inhibition. Mice orally treated with oxyresveratrol (500mg/kg/dose) dose at 8 h before and three times daily had significant delay in herpetic skin lesion development (P<0.05). Topical application of 30% oxyresveratrol ointment five times daily significantly delayed the development of skin lesions and protected mice from death (P<0.0001).

Hepatoprotective activity of Phyllanthus amarus Schum. et. Thonn. extract in ethanol treated rats: in vitro and in vivo studies.

The present study was undertaken to investigate the protective effect and possible mechanism of aqueous extract from Phyllanthus amarus Schum. et. Thonn. (PA) on ethanol-induced rat hepatic injury. In the in vitro study, PA (1-4 mg/ml) increased %MTT reduction assay and decreased the release of transaminases (AST and ALT) in rat primary cultured hepatocytes being treated with ethanol. Hepatotoxic parameters studied in vivo included serum transaminases (AST and ALT), serum triglyceride (STG), hepatic triglyceride (HTG), tumor necrosis factor alpha (TNF-alpha), interleukin 1 beta (IL-1beta), together with histopathological examination. In acute toxicity study, single dose of PA (25, 50 and 75 mg/kg, p.o.) or SL (silymarin, a reference hepatoprotective agent, 5 mg/kg), 24h before ethanol (5 g/kg, p.o.) lowered the ethanol-induced levels of transaminases (AST and/or ALT). The 75 mg/kg PA dose gave the best result similar to SL. Treatment of rats with PA (75 mg/(kg day), p.o.) or SL (5 g/(kg day), p.o.) for 7 days after 21 days with ethanol (4 g/(kg day), p.o.) enhanced liver cell recovery by bringing the levels of AST, ALT, HTG and TNF-alpha back to normal. Histopathological observations confirmed the beneficial roles of PA and SL against ethanol-induced liver injury in rats. Possible mechanism may involve their antioxidant activity.

The protective effects of Phyllanthus emblica Linn. extract on ethanol induced rat hepatic injury.

This study was undertaken to investigate the protective effects of Phyllanthus emblica Linn. (PE) extract on ethanol induced rat hepatic injury. PE (0.5 and 1 mg/ml) increased cell viability of rat primary cultured hepatocytes being treated with ethanol (96 microl/m) by increasing % MTT and decreasing the release of transaminase. Hepatotoxic markers studied in rats included serum transaminases (AST and ALT), serum triglyceride (STG), hepatic triglyceride (HTG), TNF-alpha and IL-1beta together with histopathological examination. Pretreatment of rats with PE at oral dose of 25, 50 and 75 mg/kg or SL (silymarin, a reference hepatoprotective agent) at 5 mg/kg, 4 h before ethanol, lowered the ethanol induced levels of AST, ALT and IL-1beta. The 75 mg/kg PE dose gave the best result similar to SL. Treatment of rats with PE (75 mg/kg/day) or SL (5 mg/kg/day) for 7 days after 21 days with ethanol (4 g/kg/day, p.o.) enhanced liver cell recovery by bringing the levels of AST, ALT, IL-1beta back to normal. Histopathological studies confirmed the beneficial roles of PE and SL against ethanol induced liver injury in rats.

Hepatoprotective activity of Thunbergia laurifolia Linn extract in rats treated with ethanol: in vitro and in vivo studies.

Primary cultures of rat hepatocyte and rats were used as the in vitro and in vivo models to evaluate the hepatoprotective activity of aqueous extract from Thunbergia laurifolia (TLE). Ethanol was selected as hepatotoxin. Silymarin (SL) was the reference hepatoprotective agent. In the in vitro study, MTT reduction assay and release of transaminases (ALT and AST) were the criteria for cell viability. Primary cultures of rat hepatocyte (24 h culturing) were treated with ethanol (96 microl/ml) and various concentrations of TLE (2.5, 5.0, 7.5 and 10.0 mg/ml) or SL (1, 2 and 3 mg/ml) for 2 h. Ethanol decreased MTT (%) nearly by half. Both TLE and SL increased MTT reduction and brought MTT (%) back to normal. Ethanol induced release of ALT and AST was also reduced by TLE (2.5 and 5.0 mg/ml) and SL (1 mg/ml). In the in vivo study, serum transaminases, serum triglyceride (STg) together with hepatic triglyceride (HTg) and histopathological examination were the criteria for evidences of liver injury. Ethanol (4 g/(kg day), po for 14 days) caused the increase in ALT, AST, HTg and centrilobular hydropic degeneration of hepatocytes. TLE at 25 mg/(kg day), po, or SL at 5 mg/(kg day), po, for 7 days after ethanol enhanced liver cell recovery by bringing HTg, ALT and/or AST back to normal. These results suggest that TLE and SL possess the hepatoprotective activity against ethanol induced liver injury in both primary cultures of rat hepatocyte and rats.

Hepatotoxic effect of (+)usnic acid from Usnea siamensis Wainio in rats, isolated rat hepatocytes and isolated rat liver mitochondria.

Hepatotoxic effect of (+)usnic acid, the active constituent of Usnea siamensis Wainio was studied in rats, isolated rat hepatocytes and isolated rat liver mitochondria. In rats, after treatment with high dose of (+)usnic acid (200 mg/kg per day, i.p.) for 5 days, there was no significant change in serum transaminase activity (serum AST, ALT) while the electron micrographs showed apparent morphological damage of mitochondria and endoplasmic reticulum. (+)Usnic acid at high dose (1 mM) as well as carbon tetrachloride (CCl4, the reference hepatotoxin) induced loss of cell membrane integrity in isolated rat hepatocytes by increasing the release of cellular transaminases (AST, ALT). Increase in lipid peroxidation, decrease in glutathione (GSH) content and increase in aniline hydroxylase activity (CYP 2E1) were also found. Combination of (+)usnic acid and CCl4 showed the additive results. (+)Usnic acid (0.15-6 microM) possessed uncoupling activity in isolated rat liver mitochondria. It stimulated respiration by mitochondria respiring with glutamate plus malate or succinate as substrates and activated ATPase activity. Increasing concentration of (+)usnic acid (>6 microM) exhibited loss of respiratory control and ATP synthesis. In conclusion, hepatotoxic effect of high dose (+)usnic acid may involve its reactive metabolite(s), causing loss of integrity of membrane like structures, resulting in destruction of mitochondrial respiration and oxidative phosphorylation.

Efficacy of Thai medicinal plant extracts against herpes simplex virus type 1 infection in vitro and in vivo.

Twenty Thai medicinal plant extracts were evaluated for anti-herpes simplex virus type 1 (HSV-1) activity. Eleven of them inhibited plaque formation of HSV-1 more than 50% at 100microg/ml in a plaque reduction assay. Aglaia odorata, Moringa oleifera, and Ventilago denticulata among the 11 were also effective against thymidine kinase-deficient HSV-1 and phosphonoacetate-resistant HSV-1 strains. These therapeutic efficacies were characterized using a cutaneous HSV-1 infection in mice. The extract of M. oleifera at a dose of 750mg/kg per day significantly delayed the development of skin lesions, prolonged the mean survival times and reduced the mortality of HSV-1 infected mice as compared with 2% DMSO in distilled water (P<0.05). The extracts of A. odorata and V. denticulata were also significantly effective in limiting the development of skin lesions (P<0.05). There were no significant difference between acyclovir and these three plant extracts in the delay of the development of skin lesions and no significant difference between acyclovir and M. oleifera in mean survival times. Toxicity of these plant extracts were not observed in treated mice. Thus, these three plant extracts may be possible candidates of anti-HSV-1 agents.