Soo Jin Oh

Plasma pharmacokinetics and metabolism of the antitumour drug candidate 2′-benzoyloxycinnamaldehyde in rats

The pharmacokinetics and metabolism of 2′-benzoyloxycinnamaldehyde (BCA) was characterized in male Sprague–Dawley rats as part of the preclinical evaluations for developing this compound as an antitumour agent. BCA was not detected in the plasma following either intravenous or oral dose, whereas its putative metabolites 2′-hydroxycinnamaldehyde (HCA) and o-coumaric acid were present at considerable levels. In separate pharmacokinetics studies, HCA exhibited a high systemic clearance and a large volume of distribution, whereas both pharmacokinetic parameters were much lower for o-coumaric acid. The terminal half-life of both metabolites was approximately 2 h. BCA was converted rapidly to HCA in rat serum, liver microsomes and cytosol in vitro; HCA was subsequently converted to o-coumaric acid in a quantitative manner only in the liver cytosol. In addition, the formation of o-coumaric acid was inhibited significantly by menadione, a specific inhibitor for aldehyde oxidase. Taken collectively, the results suggest that the rapid systemic clearance of HCA is likely due mainly to hepatic clearance occurring from aldehyde oxidase-catalysed biotransformation to o- coumaric acid. In conclusion, the present work demonstrates that the anticancer drug candidate BCA is highly likely to work as its active metabolite HCA in the body.

Property-based optimization of hydroxamate-based γ-lactam HDAC inhibitors to improve their metabolic stability and pharmacokinetic profiles.

Hydroxamate-based HDAC inhibitors have promising anticancer activities but metabolic instability and poor pharmacokinetics leading to poor in vivo results. QSAR and PK studies of HDAC inhibitors showed that a γ-lactam core and a modified cap group, including halo, alkyl, and alkoxy groups with various carbon chain linkers, improved HDAC inhibition and metabolic stability. The biological properties of the γ-lactam HDAC inhibitors were evaluated; the compound designated 8f had potent anticancer activity and high oral bioavailability.

In vitro metabolism of KBH-A40, a novel δ-lactam-based histone deacetylase (HDAC) inhibitor, in human liver microsomes and serum

1.u2002The metabolism of KBH-A40, a novel δ-lactam-based histone deacetylase (HDAC) inhibitor, was investigated in vitro using human liver microsomes and serum. After 60-min incubation in human liver microsomes with β-nicotinamide adenine dinucleotide phosphate (NADPH) or uridine diphosphate glucuronic acid (UDPGA), the residual KBH-A40 was 90.6% ± 5.1% and 28.9% ± 2.0% (t1/2 = 26 min), respectively, suggesting that KBH-A40 is likely predominantly metabolized by glucuronidation, rather than by cytochrome P450 (CYP)-mediated oxidation. Consistently, KBH-A40 glucuronide was the only metabolite identified following incubations of KBH-A40 with human liver microsomes in the presence of both NADPH and UDPGA. 2.u2002KBH-A40 was not notably degraded when incubated with human serum for 60 min. In contrast, KBH-A40 was rapidly hydrolysed to its carboxylic acid form in rat serum (t1/2 = 13 min). 3.u2002Taken collectively, the results suggest that KBH-A40 is likely metabolized in man predominantly by glucuronidation of its hydroxamic acid moiety, with negligible biotransformation elsewhere in the molecule.

Prediction of Drug-Induced Liver Injury in HepG2 Cells Cultured with Human Liver Microsomes.

Drug-induced liver injury (DILI) via metabolic activation by drug-metabolizing enzymes, especially cytochrome P450 (CYP), is a major cause of drug failure and drug withdrawal. In this study, an in vitro model using HepG2 cells in combination with human liver microsomes was developed for the prediction of DILI. The cytotoxicity of cyclophosphamide, a model drug for bioactivation, was augmented in HepG2 cells cultured with microsomes in a manner dependent on exposure time, microsomal protein concentration, and NADPH. Experiments using pan- or isoform-selective CYP inhibitors showed that CYP2B6 and CYP3A4 are responsible for the bioactivation of cyclophosphamide. In a metabolite identification study employing LC-ESI-QTrap and LC-ESI-QTOF, cyclophosphamide metabolites including phosphoramide mustard, a toxic metabolite, were detected in HepG2 cells cultured with microsomes, but not without microsomes. The cytotoxic effects of acetaminophen and diclofenac were also potentiated by microsomes. The potentiation of acetaminophen cytotoxicity was dependent on CYP-dependent metabolism, and the augmentation of diclofenac cytotoxicity was not mediated by either CYP- or UDP-glucuronosyltransferase-dependent metabolism. The cytotoxic effects of leflunomide, nefazodone, and bakuchiol were attenuated by microsomes. The detoxication of leflunomide by microsomes was attributed to mainly CYP3A4-dependent metabolism. The protective effect of microsomes against nefazodone cytotoxicity was dependent on both CYP-mediated metabolism and nonspecific protein binding. Nonspecific protein binding but not CYP-dependent metabolism played a critical role in the attenuation of bakuchiol cytotoxicity. The present study suggests that HepG2 cells cultured with human liver microsomes can be a reliable model in which to predict DILI via bioactivation by drug metabolizing enzymes.

Protective effect of silymarin against ethanol-induced gastritis in rats: role of sulfhydryls, nitric oxide and gastric sensory afferents.

Silymarin has been known to exert antioxidant, anti-carcinogenic and anti-inflammatory effects. In this study, we examined the effect of silymarin on gastritis in rats. Oral administration of silymarin dose-dependently decreased gastric lesions in ethanol-induced gastritis model. Silymarin also significantly suppressed the development of gastric lesions in aspirin- or water immersion-restraint stress-induced gastritis models. Further study demonstrated that the gastroprotective effect of silymarin was blocked by nitric oxide (NO) synthase inhibitor l-NAME, SH blocker N-ethylmaleimide or TRPV1 antagonist capsazepine in ethanol-induced gastritis model. In addition, ex vivo analysis revealed that ethanol-induced decrease in gastric mucus and non-protein sulfhydryl (NPSH) groups was significantly reversed by silymarin treatment and lipid peroxidation was also suppressed by silymarin in ethanol-induced gastritis model. Taken together, these results suggest that silymarin exerts gastroprotective effects and the gastroprotective effects of silymarin might be related to the protection of gastric mucosal NO and NP-SH and the modulation of capsaicin-sensitive gastric sensory afferents.

Discovery of Pyridone‐Based Histone Deacetylase Inhibitors: Approaches for Metabolic Stability

Histone deacetylases (HDACs) are important enzymes in epigenetic regulation and are therapeutic targets for cancer. Most zinc‐dependent HDACs induce proliferation, dedifferentiation, and anti‐apoptotic effects in cancer cells. We designed and synthesized a new series of pyridone‐based HDAC inhibitors that have a pyridone ring in the core structure and a conjugated system with an olefin connecting the hydroxamic acid moiety. Consequently, most of the selected pyridone‐based HDAC inhibitors showed similar or higher inhibition profiles in addition to remarkable metabolic stability against hydrolysis relative to the corresponding lactam‐based HDAC inhibitors. Furthermore, the selectivity of the novel pyridine‐based compounds was evaluated across all of the HDAC isoforms. One of these compounds, (E)‐N‐hydroxy‐3‐{1‐[3‐(naphthalen‐2‐yl)propyl]‐2‐oxo‐1,2‐dihydropyridin‐3‐yl}acrylamide, exhibited the highest level of HDAC inhibition (IC50=0.07u2005μM), highly selective inhibition of classu2005I HDAC1 and classu2005II HDAC6 enzymes, metabolic stability in mouse liver microsomal studies, and effective growth inhibition of various cancer cell lines. Docking studies indicated that a long alkyl linker and bulky hydrophobic cap groups affect inu2005vitro activities. Overall, the findings reported herein regarding pyridone‐based HDAC inhibitors can be used to guide future research efforts to develop new and effective anticancer therapeutics.

Property based optimization of δ-lactam HDAC inhibitors for metabolic stability

The novel δ-lactam based HDAC inhibitor, KBH-A118 (3) shows a good HDAC enzyme and cancer cell growth inhibitory activities but has undesirable pharmacokinetics profiles because of instability in mouse liver microsome. To improve metabolic stability, various analogues were prepared with substituents on aromatic ring of cap group and various chain lengths between the cap group and δ-lactam core. The newly prepared analogues showed moderate to potent in vitro activities. Among them six compounds (8a, 8e, 8j, 8n, 8t, and 8v) were evaluated on mouse liver microsome assay and it turned out that the microsomal stabilities were dependent on lipophilicity and the number of the rotatable bonds. Finally, the animal pharmacokinetic profiles of 8e displayed improving oral exposure and oral bioavailability.

Artemisinin inhibits lipopolysaccharide-induced interferon-β production in RAW 264.7 cells: Implications on signal transducer and activator of transcription-1 signaling and nitric oxide production

Artemisinin is a well-known anti-malarial drug and has been shown to inhibit nitric oxide (NO) production. In this study, we investigated the effect of artemisinin on lipopolysaccharide (LPS)-induced production of IFN-β and characterized the potential relationship between artemisinin-mediated inhibition of IFN-β and NO production. Artemisinin suppressed IFN-β production and mRNA expression in a dose-dependent manner in LPS-stimulated RAW 264.7 cells. LPS-induced phosphorylation of signal transducer and activator of transcription-1 (STAT-1) was also inhibited by artemisinin treatment in RAW 264.7 cells. In addition, artemisinin suppressed LPS-induced production of NO in RAW 264.7 cells. Further study demonstrated that artemisinin-mediated inhibition of NO production and STAT-1 phosphorylation was reversed by addition of exogenous IFN-β. Moreover, artemisinin does not affect IFN-β-induced STAT-1 phosphorylation in RAW 264.7 cells. Collectively, these results suggest that the inhibition of IFN-β production by artemisinin and concomitant attenuation of STAT-1 activation might be involved in artemisinin-mediated inhibition of NO production in macrophages.

Effects of palmitic acid on TNF-α-induced cytotoxicity in SK-Hep-1 cells.

Non-alcoholic steatohepatitis (NASH) is an increasingly common cause of chronic liver disease; however, no specific pharmacologic therapy has been shown to be effective in its treatment. The present study was designed to develop an experimental cell culture model of NASH using four kinds of fatty acids - palmitic acid (PA), stearic acid (SA), linoleic acid (LA), and oleic acid (OA) - and TNF-α, according to the two-hit hypothesis. The saturated fatty acids PA and SA are more cytotoxic than the unsaturated fatty acids OA and LA. Cellular lipid accumulation without cytotoxicity was more easily induced with the unsaturated fatty acids than with the saturated fatty acids. PA augmented TNF-α-induced cytotoxicity, while the unsaturated fatty acids attenuated TNF-α-induced cytotoxicity. In a mechanistic study, PA enhanced TNF-α-mediated apoptosis in the absence of oxidative stress, as determined by measuring the cellular glutathione and malondialdehyde levels. Moreover, PA inhibited the TNF-α-induced phosphorylation of AKT, but not c-Jun N-terminal kinase, indicating that inhibition of survival signaling pathways activated by TNF-α may explain the effects of PA on TNF-α-induced cytotoxicity. The in vitro NASH model established in this study may be used to screen drug candidates for suitability for the treatment of NASH.

Cardiovascular protective effect of glabridin: Implications in LDL oxidation and inflammation

Atherosclerosis is one of the most common causes of death in Western countries and now considered as a chronic inflammatory disease in broad outline. Glaridin, a flavonoid isolated from licorice root, has been shown to exert a variety of biological activities, including antimicrobial, antioxidant, anti-inflammatory and cardiovascular protective effects. Among these, the most extensive research area in the past two decades was a cardiovascular protection-related activity of glabridin. The protective effect of glabridin on LDL oxidation, which is one of the important processes involved in the development of atherosclerosis, was demonstrated in vitro and in vivo and the mechanisms involved in this process were established well. Structure-activity relationship of glabridin derivatives on LDL oxidation was also reported. In addition, the inhibitory effects of glabridin on early inflammatory processes, including the expression of adhesion molecules on endothelial cells and the activation of macrophages and dendritic cells, were also demonstrated previously. In this review, we summarized the cardiovascular protection-related activities of glabridin and the mechanism of action involved in these activities. Collectively, it is hoped that glabridin or glabridin derivatives might be used as a therapeutic agent for the treatment of cardiovascular diseases in the future.