Chun-Jung Lin

Complex haplotypic effects of the ABCB1 gene on epilepsy treatment response.

OBJECTIVES The aim of this study was to investigate the association of the complex haplotype system of the adenosine triphosphate-binding cassette B1 (ABCB1) gene with the epilepsy treatment response. METHODS AND RESULTS Ten polymorphisms were genotyped in 108 drug-resistant epileptic patients, 223 seizure-free patients and 287 normal controls. Highly significant linkage disequilibrium was shown among exon 12 C1236T, exon 21 G2677T and exon 26 C3435T. Haplotypic analysis demonstrated that patients with the CGC, TGC, and TTT haplotypes were more likely to be drug resistant. Further analysis of haplotype combinations demonstrated that drug-resistant patients tended to have the CGC/CGC, CGC/TGC, CGC/TTT, and TGC/TTT haplotype combinations over the seizure-free patients and controls (all p-values < 0.0001). In contrast, patients with the TTC/TTC, TTC/CGT, TTC/TGT, CGT/CGT and TGT/CGT haplotype combinations were more likely to be seizure-free (all p-values<0.0001 except CGT/CGT [p=0.0063]). CONCLUSION Our results showed that the three loci, C1236T, G2677T and C3435T, jointly influenced the treatment response for epileptic patients. They should be regarded together as a complex polymorphic drug-response system. These findings suggest that examination of the haplotypes of the three loci could be useful in predicting drug resistance in epilepsy.

Inhibition of Hypoxia-Induced Increase of Blood-Brain Barrier Permeability by YC-1 through the Antagonism of HIF-1α Accumulation and VEGF Expression

Cerebral microvascular endothelial cells form the anatomical basis of the blood-brain barrier (BBB), and the tight junctions of the BBB are critical for maintaining brain homeostasis and low permeability. Ischemia/reperfusion is known to damage the tight junctions of BBB and lead to permeability changes. Here we investigated the protective role of 3-(5′-hydroxymethyl-2′-furyl)-1-benzylindazole (YC-1), against chemical hypoxia and hypoxia/reoxygenation (H/R)-induced BBB hyperpermeability using adult rat brain endothelial cell culture (ARBEC). YC-1 significantly decreased CoCl2- and H/R-induced hyperpermeability of fluorescein isothiocyanate (FITC)-dextran in cell culture inserts. It was found that the decrease and disorganization of tight junction protein zonular occludens-1 (ZO-1) in response to CoCl2, and H/R was antagonized by YC-1. The protection of YC-1 may result from the inhibition of HIF-1α accumulation and production of its downstream target vascular endothelial growth factor (VEGF). VEGF alone significantly increased FITC-dextran permeability and down-regulated mRNA and protein levels of ZO-1 in ARBECs. We further used animal model to examine the effect of YC-1 on BBB permeability after cerebral ischemia/reperfusion. It was found that YC-1 significantly protected the BBB against ischemia/reperfusion-induced injury. Taken together, these results indicate that YC-1 may inhibit HIF-1α accumulation and VEGF production, which in turn protect BBB from injury caused by hypoxia.

Dosage Recommendation of Phenytoin for Patients with Epilepsy with Different Cyp2c9/cyp2c19 Polymorphisms

To search for the optimal dosage of phenytoin in patients with epilepsy based on the metabolic activities of CYP2C9 and CYP2C19 polymorphisms, a total of 169 patients receiving phenytoin treatment for more than 1 month were recruited. Phenytoin concentration, serum albumin, liver function tests, and renal function tests were measured. CYP2C9 and CYP2C19 polymorphisms were genotyped by PCR-RFLP analysis, and NONMEM models were built to evaluate factors that would affect phenytoin metabolism. Patients were divided into 5 groups according to genotyping results (G1 to G5). Compared with extensive metabolizers in both CYP2C9 and CYP2C19 (G1), the Vmax (mg/kg/d) was 8.29% and 36.96% lower in CYP2C19 poor metabolizers (G3) and CYP2C9 poor metabolizers (G4), respectively. For the patient who was identified as a poor metabolizer in both CYP2C19 and CYP2C9 (G5), the Vmax was 45.75% lower than that of G1. In respect to Km (mg/L), it was 15.09% higher in G3 and 27.36% higher in G4 compared with that in G1. The Km of G5 was 91.71% higher than that of G1. The results revealed that the CYP2C9 and CYP2C19 polymorphisms have dramatic effects on the population pharmacokinetic parameters of phenytoin, especially for CYP2C9. Based on the Vm and Km values obtained in this study, the recommended dose ranges for G1, G2, G3, G4, and G5 patients would be 5.5–7, 5–7, 5–6, 3–4, and 2–3 mg/kg/d, respectively.

Enhancement of Glucose Transporter Expression of Brain Endothelial Cells by Vascular Endothelial Growth Factor Derived from Glioma Exposed to Hypoxia

Increased need for glycolysis and glucose uptake for ATP production is observed in tumor cells, particularly in cells lacking of oxygen supply. Because glucose is transported from blood to tumor, glucose molecules must be delivered across glucose transporters of the vascular endothelium and tumor cells. Here we found that glioma suffered from hypoxic insults can secrete factor(s) to regulate glucose transporter expression in brain endothelium. It was found that conditioned medium from rat C6 glioma cells under hypoxia up-regulated glucose transporter type 1 (GLUT1) expression in rat brain endothelial cells, whereas conditioned medium from C6 cells under normoxia caused no significant effect. We further investigated whether the observed potentiating effect was caused by vascular endothelial growth factor (VEGF) production from C6 cells, because secreted VEGF was markedly increased under hypoxic condition. By transfection of C6 cells with VEGF small interfering RNA, it was found that conditioned medium from transfected cells under hypoxia no longer up-regulated GLUT1 expression of endothelial cells. Moreover, the addition of VEGF-neutralizing antibody to the hypoxic conditioned medium could also exert similar inhibitory effects. Furthermore, it was found that the VEGF-induced increase of GLUT1 expression in endothelial cells was mediated by the phosphoinositide-3 kinase/Akt pathway. Our results indicate that hypoxic brain glioma may secrete VEGF to increase glucose transport across blood-brain barrier.

Cellular localization of the organic cation transporters, OCT1 and OCT2, in brain microvessel endothelial cells and its implication for MPTP transport across the blood-brain barrier and MPTP-induced dopaminergic toxicity in rodents

J. Neurochem. (2010) 114, 717–727.

A new drug design targeting the adenosinergic system for Huntington's disease.

Background Huntingtons disease (HD) is a neurodegenerative disease caused by a CAG trinucleotide expansion in the Huntingtin (Htt) gene. The expanded CAG repeats are translated into polyglutamine (polyQ), causing aberrant functions as well as aggregate formation of mutant Htt. Effective treatments for HD are yet to be developed. Methodology/Principal Findings Here, we report a novel dual-function compound, N 6-(4-hydroxybenzyl)adenine riboside (designated T1-11) which activates the A2AR and a major adenosine transporter (ENT1). T1-11 was originally isolated from a Chinese medicinal herb. Molecular modeling analyses showed that T1-11 binds to the adenosine pockets of the A2AR and ENT1. Introduction of T1-11 into the striatum significantly enhanced the level of striatal adenosine as determined by a microdialysis technique, demonstrating that T1-11 inhibited adenosine uptake in vivo. A single intraperitoneal injection of T1-11 in wildtype mice, but not in A2AR knockout mice, increased cAMP level in the brain. Thus, T1-11 enters the brain and elevates cAMP via activation of the A2AR in vivo. Most importantly, addition of T1-11 (0.05 mg/ml) to the drinking water of a transgenic mouse model of HD (R6/2) ameliorated the progressive deterioration in motor coordination, reduced the formation of striatal Htt aggregates, elevated proteasome activity, and increased the level of an important neurotrophic factor (brain derived neurotrophic factor) in the brain. These results demonstrate the therapeutic potential of T1-11 for treating HD. Conclusions/Significance The dual functions of T1-11 enable T1-11 to effectively activate the adenosinergic system and subsequently delay the progression of HD. This is a novel therapeutic strategy for HD. Similar dual-function drugs aimed at a particular neurotransmitter system as proposed herein may be applicable to other neurotransmitter systems (e.g., the dopamine receptor/dopamine transporter and the serotonin receptor/serotonin transporter) and may facilitate the development of new drugs for other neurodegenerative diseases.

High-dose dual therapy is superior to standard first-line or rescue therapy for Helicobacter pylori infection.

BACKGROUND & AIMS The efficacy of treatment of Helicobacter pylori infection has decreased steadily because of increasing resistance to clarithromycin, metronidazole, and levofloxacin. Resistance to amoxicillin is generally low, and high intragastric pH increases the efficacy of amoxicillin, so we investigated whether a combination of a high-dose proton pump inhibitor and amoxicillin (dual therapy) was more effective than standard first-line or rescue therapies in eradicating H pylori. METHODS We performed a large-scale multihospital trial to compare the efficacy of a high-dose dual therapy (HDDT) with that of standard therapies in treatment-naive (n = 450) or treatment-experienced (n = 168) patients with H pylori infection. Treatment-naive patients were randomly assigned to groups given HDDT (rabeprazole 20 mg and amoxicillin 750 mg, 4 times/day for 14 days, group A1), sequential therapy for 10 days (group B1), or clarithromycin-containing triple therapy for 7 days (group C1). Treatment-experienced patients were randomly assigned to groups given HDDT for 14 days (group A2), sequential therapy for 10 days (B2), or levofloxacin-containing triple therapy for 7 days (C2). H pylori infection was detected by using the (13)C-urea breath test. We evaluated factors associated with treatment outcomes. RESULTS In the intention-to-treat analysis, H pylori was eradicated in 95.3% of patients in group A1 (95% confidence interval [CI], 91.9%-98.8%), 85.3% in B1 (95% CI, 79.6%-91.1%), and 80.7% in group C1 (95% CI, 74.3%-87.1%). Infection was eradicated in 89.3% of patients in group A2 (95% CI, 80.9%-97.6%), 51.8% in group B2 (95% CI, 38.3%-65.3%), and 78.6% (95% CI, 67.5%-89.7%) in group C2. The efficacy of HDDT was significantly higher than that of currently recommended regimens, irrespective of CYP2C19 genotype. Bacterial resistance to drugs was associated with treatment failure. There were no significant differences between groups in adverse events or patient adherence. CONCLUSIONS HDDT is superior to standard regimens as empirical first-line or rescue therapy for H pylori infection, with similar safety profiles and tolerability. ClinicalTrials.gov number: NCT01163435.

Functional evaluation of polymorphisms in the human abcb1 gene and the impact on clinical responses of antiepileptic drugs

Objective The ABCB1 haplotype combinations have been demonstrated to be associated with epilepsy treatment outcomes. The aim of this study is to investigate whether ABCB1 haplotype combinations would affect P-glycoprotein (Pgp) function and impact the clinical responses of antiepileptic drugs (AEDs). Methods and results Transport of substrate rhodamine 123 and calcein-AM by human Pgp carrying 12 haplotype combinations of 1236C>T, 2677G>T/A and 3435C>T were assayed in the absence and presence of known inhibitors and AEDs. The inhibitory potency of the tested drugs from the dose–response relationships was cyclosporin A>verapamil> phenytoin> carbamazepine> lamotrigine>phenobarbital>valproic acid, levetiracetam, gabapentin. The silent polymorphisms combination (1236T-3435T) and triple haplotypes (1236T-2677A/T-3435T) resulted in profoundly less effective inhibition against substrates with significantly lower intracellular substrate concentration. These results confirmed that ABCB1 polymorphisms were associated with clinical responses of AEDs. Conclusion Our findings demonstrated that human ABCB1 polymorphisms may alter the interactions between Pgp and substrates, and provided functional evidence for ABCB1 haplotypes-associated epilepsy treatment responses.

Treatment of Helicobacter pylori infection: Current status and future concepts

Helicobacter pylori (H. pylori) infection is highly associated with the occurrence of gastrointestinal diseases, including gastric inflammation, peptic ulcer, gastric cancer, and gastric mucosa-associated lymphoid-tissue lymphoma. Although alternative therapies, including phytomedicines and probiotics, have been used to improve eradication, current treatment still relies on a combination of antimicrobial agents, such as amoxicillin, clarithromycin, metronidazole, and levofloxacin, and antisecretory agents, such as proton pump inhibitors (PPIs). A standard triple therapy consisting of a PPI and two antibiotics (clarithromycin and amoxicillin/metronidazole) is widely used as the first-line regimen for treatment of infection, but the increased resistance of H. pylori to clarithromycin and metronidazole has significantly reduced the eradication rate using this therapy and bismuth-containing therapy or 10-d sequential therapy has therefore been proposed to replace standard triple therapy. Alternatively, levofloxacin-based triple therapy can be used as rescue therapy for H. pylori infection after failure of first-line therapy. The increase in resistance to antibiotics, including levofloxacin, may limit the applicability of such regimens. However, since resistance of H. pylori to amoxicillin is generally low, an optimized high dose dual therapy consisting of a PPI and amoxicillin can be an effective first-line or rescue therapy. In addition, the concomitant use of alternative medicine has the potential to provide additive or synergistic effects against H. pylori infection, though its efficacy needs to be verified in clinical studies.

Competitive inhibition of glycylsarcosine transport by enalapril in rabbit renal brush border membrane vesicles: interaction of ACE inhibitors with high-affinity H+/peptide symporter.

AbstractPurpose. To examine the inhibitory potential of enalapril [and other angiotensin converting enzyme (ACE) inhibitors] on glycylsarcosine (GlySar) transport by the high-affinity renal peptide transporter. Methods. Studies were performed in rabbit renal brush border membrane vesicles in which the uptake of radiolabeled GlySar was examined in the absence and presence of captopril, enalapril, enalaprilat, fosinopril, lisinopril, quinapril, quinaprilat, ramipril and zofenopril. Results. Kinetic analyses demonstrated that enalapril inhibited the uptake of GlySar in a competitive manner (Ki ≈ 6 mM). Fosinopril and zofenopril had the greatest inhibitory potency (IC50 values of 55 and 81 μM, respectively) while the other ACE inhibitors exhibited low-affinity interactions with the renal peptide transporter. With respect to structure-function, ACE inhibitor affinity was strongly correlated with drug lipophilicity (r = 0.944, p < 0.001 for all ACE inhibitors; r = 0.983, p < 0.001 without enalaprilat, quinaprilat and quinapril). Conclusions. The data suggest that enalapril and GlySar compete for the same substrate-binding site on the high-affinity peptide transporter in kidney, and that ACE inhibitors can interact with the renal carrier and inhibit dipeptide transport.