Inhibition of human catechol-O-methyltransferase-mediated dopamine O-methylation by daphnetin and its Phase II metabolites.

1. Finding and developing inhibitors of catechol-O-methyltransferase (COMT) from natural products is highly recommended. Daphnetin, a naturally occurring catechol from the family thymelaeaceae, has a chemical structure similar to several potent COMT inhibitors reported previously. Here the potential of daphnetin and its Phase II metabolites as inhibitors of COMT was investigated with human liver cytosol (HLC). 2. Daphnetin and its methylated metabolite (8-O-methyldaphnetin) were found to inhibit COMT-mediated dopamine O-methylation in a dose-dependent manner. The IC50 values for daphnetin (0.51∼0.53 µM) and 8-O-methyldaphnetin (22.5∼24.3 µM) were little affected by changes in HLC concentrations. Further kinetic analysis showed the differences in inhibition type and parameters (Ki) between daphnetin (competitive, 0.37 µM) and 8-O-methyldaphnetin (noncompetitive, 25.7 µM). Other metabolites, including glucuronidated and sulfated species, showed negligible inhibition against COMT. By using in vitro-in vivo extrapolation (IV-IVE), a 24.3-fold increase in the exposure of the COMT substrates was predicted when they are co-administrated with daphnetin. 3. With high COMT-inhibiting activity, daphnetin could serve as a lead compound for the design and development of new COMT inhibitors. Also, much attention should be paid to the clinical impact of combination of daphnetin and herbal preparations containing daphnetin with the drugs primarily cleared by COMT.

in vitro metabolism of daphnetin in rat liver S9 fractions / 药学学报

Daphnetin is quickly eliminated in rats after dosing, but the mechanism remains unclear. This study was aimed to investigate the in vitro metabolism of daphnetin using rat liver S9 fractions (RLS9). The metabolites formed in RLS9 were identified and the kinetic parameters for different metabolic pathways were determined. HPLC-DAD-MS analysis showed that daphnetin was biotransformed to six metabolites, which were identified as 7 or 8 mono-glucuronide and mono-sulfate, 8-methylate, and 7-suflo-8-methylate. Methylation and glucuronidation of daphnetin exhibited the Michaelis-Menten kinetic characteristics, whereas the substrate inhibition kinetic and the two-site kinetic were observed for 8-sulfate and 7-sulfate formations. Of the 3 conjugation pathways, the intrinsic clearance rate for sulfation was highest, followed by methylation and glucuronidation. By in vitro-in vivo extrapolation of the kinetic data measured in RLS9, the hepatic clearance were estimated to be 54.9 mL·min-1·kg-1 which is comparable to the system clearance (58.5 mL·min-1·kg-1) observed in rats. In conclusions, the liver might be the main site for daphnetin metabolism in rats. Sulfation, methylation and glucuronidation are important pathways of the hepatic metabolism of daphnetin in rats.

New drugs for gont: Research advances / 国际药学研究杂志

Gout is a common disease in the elderly men. The prevalence rate of gout is rising worldwide in recent years, and gout has become a serious metabolic disease threatening human health. Moreover, gout is also closely related to incidence of many diseases and symptoms such as hypertension, hyperlipidemia, atherosclerosis, obesity and insulin resistance. Recently, investigation and development of new drugs have attracted increasing attention. This paper summarizes the research advances in new agents for treatment of gout, including the uric acid reduction drugs that target the key enzymes of purine metabolism, the drugs which target the renal tubular urate transporters to lower the uric acid level, the dual inhibitors of xanthine oxidoreductase(XOR) and renal tubular urate transporters, and the uricase.

Clinical Features of Adult/Adolescent Atopic Dermatitis and Chinese Criteria for Atopic Dermatitis / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Atopic dermatitis (AD) is an inflammatory skin disease characterized by chronic recurrent dermatitis with profound itching. Most patients have personal and/or family history of atopic diseases. Several criteria have been proposed for the diagnosis of AD. Although the clinical features of childhood AD have been widely studied, there has been less large-scale study on adult/adolescent AD. The aim of this study was to investigate the clinical features of adult/adolescent patients with chronic symmetrical eczema/AD and to propose Chinese diagnostic criteria for adult/adolescent AD.</p><p><b>METHODS</b>A hospital-based study was performed. Forty-two dermatological centers participated in this study. Adult and adolescent patients (12 years and over) with chronic symmetrical eczema or AD were included in this study. Questionnaires were completed by both patients and investigators. The valid questionnaires were analyzed using EpiData 3.1 and SPSS 17.0 software.</p><p><b>RESULTS</b>A total of 2662 valid questionnaires were collected (1369 male and 1293 female). Of all 2662 patients, 2062 (77.5%) patients had the disease after 12 years old, while only 600 (22.5%) patients had the disease before 12 years old, suggesting late-onset eczema/AD is common. Two thousand one hundred and thirty-nine (80.4%) patients had the disease for more than 6 months. One thousand one hundred and forty-four (43.0%) patients had a personal and/or family history of atopic diseases. One thousand five hundred and forty-eight (58.2%) patients had an elevated total serum IgE and/or eosinophilia and/or positive allergen-specific IgE. Based on these clinical and laboratory features, we proposed Chinese criteria for adult/adolescent AD. Of all 2662 patients, 60.3% were satisfied with our criteria, while only 48.2% satisfied with Hanifin Rajka criteria and 32.7% satisfied with Williams criteria, suggesting a good sensitivity of our criteria in adult/adolescent AD patients.</p><p><b>CONCLUSION</b>Late-onset of eczema or AD is common. The clinical manifestations of AD are heterogeneous. We have proposed Chinese diagnostic criteria for adolescent and adult AD, which are simple and sensitive for diagnosis of adult/adolescent AD.</p>

Infliximab monotherapy for Chinese patients with moderate to severe plaque psoriasis: a randomized, double-blind, placebo-controlled multicenter trial / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Tumor necrosis factor-α is a key mediator in the pathogenesis of psoriasis. Infliximab is a monoclonal antibody that specifically binds to tumor necrosis factor-α. The purpose of this study was to validate the efficacy and safety of 5 mg/kg infliximab therapy in Chinese patients with moderate to severe plaque psoriasis.</p><p><b>METHODS</b>In this multicenter, double-blind, placebo-controlled trial, 129 patients with moderate-to-severe psoriasis were randomized to the induction therapy (weeks 0, 2 and 6) with infliximab 5 mg/kg (n = 84) or placebo (n = 45), followed with infliximab 5 mg/kg scheduled at week 14 and week 22 in the infliximab group, and infliximab 5 mg/kg scheduled at weeks 10, 12 and 16 in the placebo group. The primary end point was the proportion of patients who achieved at least 75% improvement in Psoriasis Area and Severity Index (PASI 75 response rate) from baseline at week 10.</p><p><b>RESULTS</b>At week 10, 81.0% of patients treated with infliximab (5 mg/kg) achieved a 75% or greater improvement compared with 2.2% of patients treated with placebo (P < 0.001). A significant improvement in PASI, Physician's Global Assessment (PGA) and Dermatology Life Quality Index (DLQI), was seen from week 6 through week 14 in the infliximab group compared with the placebo group. Through week 22, PASI, PGA, DLQI were well maintained. The incidence of adverse events for the infliximab treatment group was slightly higher in comparison to the placebo treatment group during the first 10 weeks without statistical significance. However, there were 3 cases of tuberculosis that developed during the 26 weeks treatment with infliximal.</p><p><b>CONCLUSIONS</b>Infliximab treatment was effective as induction and maintenance treatments for Chinese patients with moderate to severe plaque psoriasis. Most drug-induced adverse events were mild to moderate, and well tolerated. Screening for tuberculosis is essential and prophylactic treatment should be given if necessary.</p>