Hea-Young Cho

Acute toxicity and pharmacokinetics of 13 nm-sized PEG-coated gold nanoparticles

In general, gold nanoparticles are recognized as being as nontoxic. Still, there have been some reports on their toxicity, which has been shown to depend on the physical dimension, surface chemistry, and shape of the nanoparticles. In this study, we carry out an in vivo toxicity study using 13 nm-sized gold nanoparticles coated with PEG (MW 5000). In our findings the 13 nm sized PEG-coated gold nanoparticles were seen to induce acute inflammation and apoptosis in the liver. These nanoparticles were found to accumulate in the liver and spleen for up to 7 days after injection and to have long blood circulation times. In addition, transmission electron microscopy showed that numerous cytoplasmic vesicles and lysosomes of liver Kupffer cells and spleen macrophages contained the PEG-coated gold nanoparticles. These findings of toxicity and kinetics of PEG-coated gold nanoparticles may have important clinical implications regarding the safety issue as PEG-coated gold nanoparticles are widely used in biomedical applications.

Preparation and evaluation of tacrolimus-loaded nanoparticles for lymphatic delivery

In an effort to improve lymphatic targeting efficiency and reduce the toxicity of tacrolimus, the emulsification-diffusion method was used to load the drug into nanoparticles (NP). Poly(lactide-co-glycolide) (PLGA) and PLGA surface-modified with poly(ethylene glycol) (PEG) were used as polymers. Mean particle size and drug encapsulation efficiency of PLGA were 218+/-51nm and 60.0+/-1.2% and for PEG-PLGA NP were 220+/-33nm and 60.3+/-2.0%. NP were characterized by thermal analyzer and X-ray diffractometry (XRD), and their shapes were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In vitro release profiles were affected by the pH of dissolution media. The prepared NP and commercial product of tacrolimus (Prograf) inj.) were intravenously administered to rats to compare their pharmacokinetic characteristics and lymphatic targeting efficiency. The area under the whole blood concentration-time curve (AUC), mean residence time (MRT), and total clearance (CL(t)) of PEG-PLGA NP were significantly different (P<0.05) compared with those of Prograf inj., and lymphatic targeting efficiencies of both NP formulations at the mesenteric lymph node significantly increased (P<0.05). These results showed that the prepared tacrolimus-loaded NP are good possible candidates as a lymphatic delivery system of tacrolimus.

Gadd45β is a novel mediator of cardiomyocyte apoptosis induced by ischaemia/hypoxia

AIMS Because apoptotic death plays a critical role in cardiomyocyte loss during ischaemic heart injury, a detailed understanding of the mechanisms involved is likely to have a substantial impact on the optimization and development of treatment strategies. The goal of this study was to assess gene profiling during ischaemia/hypoxia and to evaluate the functions of ischaemia/hypoxia-responsive genes in in vivo and in vitro ischaemia/hypoxia-induced cardiomyocyte apoptosis models. METHODS AND RESULTS DNA microarray analysis and real-time polymerase chain reaction were performed on hearts obtained from an in vivo rat transient ischaemia model and on neonatal rat cardiomyocytes from an in vitro hypoxia model. Three genes, namely Ddit4, Gadd45beta and Atf3, were found to be up-regulated in vivo and in vitro. Using loss-of-function and gain-of-function techniques, the functions of these ischaemia/hypoxia-responsive genes were evaluated. Ischaemia/hypoxia-induced cardiomyocyte apoptosis was remarkably attenuated by the small interfering RNA-mediated down-regulation of Gadd45beta in vivo and in vitro, whereas ectopic Gadd45beta expression significantly aggravated hypoxia-induced apoptosis in vitro. CONCLUSION These results suggest that Gadd45beta is a key player in ischaemia/hypoxia-induced apoptotic cardiomyocyte death, and that strategies based on its inhibition might be of benefit in the treatment of acute ischaemic heart disease.

Influence of ABCB1 genetic polymorphisms on the pharmacokinetics of risperidone in healthy subjects with CYP2D6*10/*10

BACKGROUND AND PURPOSE The objective of this study was to investigate the combined influence of genetic polymorphisms in ABCB1 and CYP2D6 genes on risperidone pharmacokinetics.

Population pharmacokinetic analysis of cilostazol in healthy subjects with genetic polymorphisms of CYP3A5, CYP2C19 and ABCB1

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT * The interindividual variability of the pharmacokinetic parameters of cilostazol is relatively large. * Cilostazol undergoes extensive hepatic metabolism via the P450 enzymes, primarily CYP3A and, to a lesser extent, CYP2C19. * Indeed, <1% of the administered dose of cilostazol is excreted unchanged in the urine. WHAT THIS STUDY ADDS * A population pharmacokinetic analysis of cilostazol was conducted to evaluate the impact of CYP3A, CYP2C19 and ABCB1 polymorphisms on cilostazol disposition in vivo. * Genetic polymorphisms of CYP3A5 and CYP2C19 explain the substantial interindividual variability in the pharmacokinetics of cilostazol. * ABCB1 genotypes do not to appear to be associated with the disposition of cilostazol. AIMS To investigate the influence of genetic polymorphisms in the CYP3A5, CYP2C19 and ABCB1 genes on the population pharmacokinetics of cilostazol in healthy subjects. METHODS Subjects who participated in four separate cilostazol bioequivalence studies with the same protocols were included in this retrospective analysis. One hundred and four healthy Korean volunteers were orally administered a single 50- or 100-mg dose of cilostazol. We estimated the population pharmacokinetics of cilostazol using a nonlinear mixed effects modelling (nonmem) method and explored the possible influence of genetic polymorphisms in CYP3A (CYP3A5*3), CYP2C19 (CYP2C19*2 and CYP2C19*3) and ABCB1 (C1236T, G2677T/A and C3435T) on the population pharmacokinetics of cilostazol. RESULTS A two-compartment model with a first-order absorption and lag time described the cilostazol serum concentrations well. The apparent oral clearance (CL/F) was estimated to be 12.8 l h(-1). The volumes of the central and the peripheral compartment were characterized as 20.5 l and 73.1 l, respectively. Intercompartmental clearance was estimated at 5.6 l h(-1). Absorption rate constant was estimated at 0.24 h(-1) and lag time was predicted at 0.57 h. The genetic polymorphisms of CYP3A5 had a significant (P < 0.001) influence on the CL/F of cilostazol. When CYP2C19 was evaluated, a significant difference (P < 0.01) was observed among the three genotypes (extensive metabolizers, intermediate metabolizers and poor metabolizers) for the CL/F. In addition, a combination of CYP3A5 and CYP2C19 genotypes was found to be associated with a significant difference (P < 0.005) in the CL/F. When including these genotypes, the interindividual variability of the CL/F was reduced from 34.1% in the base model to 27.3% in the final model. However, no significant differences between the ABCB1 genotypes and cilostazol pharmacokinetic parameters were observed. CONCLUSIONS The results of the present study indicate that CYP3A5 and CYP2C19 polymorphisms explain the substantial interindividual variability that occurs in the metabolism of cilostazol.

Influence of CYP3A and CYP2C19 Genetic Polymorphisms on the Pharmacokinetics of Cilostazol in Healthy Subjects

The objective of this study was to investigate the influence of genetic polymorphisms in the CYP3A and CYP2C19 genes on cilostazol pharmacokinetics, with the drug being administered orally as a 50‐mg single dose in healthy subjects. CYP2C19 genotypes in individuals with the CYP3A5*3/*3 genotype were associated with statistically significant differences (P < 0.05) in cilostazol pharmacokinetics parameters (apparent oral clearance (CL/F) and terminal half‐life (t1/2)). This indicates that CYP2C19 polymorphisms play an important role in the metabolism of cilostazol only in individuals with the CYP3A5*3/*3 genotype, which has low metabolic activity.

INFLUENCE OF ABCB1 GENETIC POLYMORPHISMS ON THE PHARMACOKINETICS OF LEVOSULPIRIDE IN HEALTHY SUBJECTS

The purposes of this study were to clarify the involvement of P-glycoprotein in the absorption of levosulpiride in knockout mice that lack the Abcb1a/ 1b gene, and to evaluate the relationship between genetic polymorphisms in ABCB1 (exon 12, 21 and 26) and levosulpiride disposition in healthy subjects. The plasma and brain samples were obtained after oral administration (10 microg/g) of levosulpiride to abcb1a/1b(-/-) and wild-type mice (n=3 approximately 6 at each time point). The average brain-to-plasma concentration ratio and blood-brain barrier partitioning of levosulpiride were 2.3- and 2.0-fold higher in Abcb1a/1b(-/-) mice than in wild-type mice, respectively. A total of 58 healthy Korean volunteers receiving a single oral dose of 25 mg levosulpiride participated in this study. The subjects were evaluated for polymorphisms of the ABCB1 exon 12 C1236T, exon 21 G2677A/T (Ala893Ser/Thr) and exon 26 C3435T using polymerase chain reaction restriction fragment length polymorphism. The PK parameters (AUC(0-4h), AUC(0-infinity) and C(max.)) of ABCB1 2677TT and 3435TT subjects were significantly higher than those of subjects with at least one wild-type allele (P<0.05). The results indicate that levosulpiride is a P-glycoprotein substrate in vivo, which is supported by the effects of SNPs 2677G>A/T in exon 21 and 3435C>T in exon 26 of ABCB1 on levosulpiride disposition.

Simultaneous determination of puerarin and its active metabolite in human plasma by UPLC-MS/MS: application to a pharmacokinetic study.

A rapid, selective and sensitive ultra-performance liquid chromatography (UPLC)-tandem mass spectrometry method about the simultaneous determination of puerarin and its major active metabolite, daidzein, in human plasma was developed and validated in order to investigate the pharmacokinetics (PKs) of Gegen after the usual oral dose administration to human. Chromatography was carried out on a Kinetex C18 column (2.1mm×50mm, 1.7μm) using 0.05% acetic acid in water and 0.05% acetic acid in methanol as mobile phase with a gradient elution. Liquid-liquid extraction with ethyl acetate in acidic condition could remove the interference and minimize the matrix effect of human plasma. The lower limit of quantification in human plasma was 0.2ng/mL for both of compounds, puerarin and daidzein. The calibration curves for puerarin and daidzein in human plasma were linear over all the concentration range of 0.2-100ng/mL with correlation coefficients greater than 0.998. This assay procedure was successfully applied to the PKs of puerarin and daidzein, after the usual oral dose of Gegen extract powder (2.56g, containing 9.984mg puerarin) in human subjects.

Scrub typhus meningoencephalitis occurring during doxycycline therapy for Orientia tsutsugamushi

We report on a scrub typhus patient who contracted meningoencephalitis during doxycycline administration. This is the first case of scrub typhus in which doxycycline concentrations were measured in serum and cerebrospinal fluid. Clinicians should be alerted to the possibility that meningoencephalitis can occur because of inadequate maintenance of serum doxycycline level caused by antacids administered along with doxycycline.

Effect of saikosaponin A on maintenance of intravenous morphine self-administration.

In this study, we investigated the effects of saikosaponin A (SSA), a major compound of Bupleurum falcatum L., on morphine self-administration behavior. Male Sprague-Dawley rats were trained to self-administer intravenous morphine (0.1mg/kg per injection over 5s) during daily 1-h sessions under a fixed-ratio 1 schedule. Rats were pretreated with SSA (0.25, 0.5, 1.0mg/kg) by intraperitoneal injection 30 min prior to the start of the test session. Results demonstrated that pretreatment with SSA reduced morphine-maintained responding dose-dependently. Additionally, SSA inhibition of morphine-reinforced behavior was blocked by the selective GABA(B) receptor antagonist (2S)(+)-5,5-dimethyl-2-morpholineacetic acid (SCH 50911), but not the selective GABA(A) receptor antagonist bicuculline. Together, these results suggest that SSA may effectively suppress morphine-reinforced behavior by activating GABA(B) receptors.