Construction of a Drug Release Evaluation System: Application of Mitochondrial Respiration to Monitor Drug Release.

BACKGROUND/AIM: Efficient drug encapsulation and regulation of drug release are important factors for sustained drug release and application for release-controlled anti-cancer and anti-inflammatory drug delivery. In the present study, a direct evaluation system for drug-release from model carrier (e.g., alginate-gel beads) was examined using the mitochondrial oxygen consumption rate as an index. MATERIALS AND METHODS: Alginate-gel beads were coated with the uncoupler SF6847 (SF beads) and used as a model microparticle-type drug. The real-time monitoring of SF6847 release from prepared alginate-gel beads was performed using the mitochondrial oxygen consumption rate. Release profiles of nonsteroidal anti-inflammatory drugs [NSAIDs, mefenamic acid (MEF) and diclofenac (DIC)] from alginate-gel beads as well as SF beads were investigated using the real time monitoring system. RESULTS: SF6847 release from alginate-gel beads was clearly detected using the rat liver mitochondrial oxygen consumption rate. The release features of MEF and DIC from alginate-gel beads were defined by the present trial monitoring system, and these NSAIDs exhibited different release profiles. CONCLUSION: The present drug monitoring system detected released drugs, and the release profile reflected the molecular properties of the test drugs. This system may be applied to the design and development of precise sustained drug release systems (e.g., anti-cancer and anti-inflammatory drugs).

Structure-associated Functional Control of TX-1877 Series by Glyco-conjugation.

BACKGROUND/AIM: Sugar molecules are often used as a tool to structurally modify chemical compounds. The features of synthesized sugar-conjugated TX-1877 derivatives were herein examined. MATERIALS AND METHODS: The molecular stabilities (reactivity) and hydrophobicities of sugar (e.g., monosaccharide and tetra-O-acetylated monosaccharide)-conjugated TXs were analyzed using a molecular simulation (e.g. molecular mechanics (MM) and molecular orbital (MO) analysis). RESULTS: The hydrophobicities of TX-1877 derivatives were increased by tetra-O-acetylation, and TX-2244 exhibited the most potent radiosensitizing activity (enhancement ratio: ER=2.30). CONCLUSION: The conformations and hydrophobicities of chemical compounds may be controlled by adding monosaccharide- and tetra-O-acetyl-conjugated sugars to TX-1877.

Effects of the Nonsteroidal Anti-inflammatory Drug Celecoxib on Mitochondrial Function.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used to treat inflammation and pain. In the present study, we examined the effects of celecoxib, a cyclooxygenase-2 (COX-2)-selective NSAID, on rat liver mitochondrial function. Celecoxib dose-dependently induced mitochondria swelling, which was not suppressed by cyclosporine A (CsA). The oxygen consumption rate in mitochondria-suspended solution was facilitated by the addition of celecoxib, and its uncoupling activity was observed. Celecoxib also suppressed SF6847-induced uncoupling, and appeared to exert inhibitory effects on the electron transport chain. Celecoxib suppressed the state 3 oxygen consumption rate in the presence of ADP. Protein release from the mitochondrial matrix was detected following the addition of celecoxib, and aldehyde dehydrogenase 2 (ALDH2) and hydroxymethylglutaryl-CoA (HMG-CoA) synthase 2 (HMGCS2) bands were confirmed in a Western blot analysis. On the other hand, protein release of cytochrome C (CytC), which is an inducer of apoptosis, from the intermembrane space was not observed. Celecoxib enhanced the membrane permeability of human erythrocytes and synthesized liposomes dose-dependently. It then induced the membrane-involving mitochondrial swelling and suppressed mitochondrial function.

Interactive Analysis of TX-1123 with Cyclo-oxygenase: Design of COX2 Selective TX Analogs.

BACKGROUND: To date, two cyclo-oxygenase (COX) isoforms, COX1 and COX2, have been identified. In the present study, the COX-inhibitory activities of TX-1123 derivatives with the 2-hydroxyarylidene-4-cyclopentene-1,3-dione structure were examined, and the binding profiles of TX-1123 to COXs were analyzed using docking simulations. MATERIALS AND METHODS: X-Ray data on COX1 [protein data bank (PDB) ID=1PGG] and COX2 (PDB ID=3LN1) were used for molecular interactive simulations. The interactive profiles of TX-1123 derivatives with COXs were examined using a molecular simulation technique with Molegro Virtual Docker (CLC bio, Aarhus, Denmark). RESULTS: TX-1123 exhibited COX1-inhibitory activity [half-maximal-inhibitory concentration (IC50)=1.57×10-5 M]. The COX2 inhibitory activity of TX-1123 was potent (IC50=1.16×10-6 M), and the ratio of COX1/COX2 inhibition was 13.5. TX-1123 bound to the COX2 molecule, and the oxygen atom of the 4-cyclopentene-1,3-dione region of TX-1123 interacted with Cys26 and Gln447 of COX2. CONCLUSION: The TX-1123-binding pocket of COX2 differs from that of the COX2-selective celecoxib-binding pocket. TX-1123 exhibited a different COX2-interactive mechanism from that of celecoxib.

An Antitumor 2-Hydroxyarylidene-4-cyclopentene-1,3-Dione as a Protein Tyrosine Kinase Inhibitor: Interaction Between TX-1123 Derivatives and Src Kinase.

BACKGROUND: Protein tyrosine kinases (PTKs) play major roles in signal transduction during cell proliferation and apoptosis. Tyrphostin AG17 was previously shown to be a potent tumor growth inhibitor, while AG17 induced apoptosis and inhibited activity of cyclin-dependent kinase 2. We herein describe the binding features of tyrphostin AG17 analogs, such as TX-1123, with Src kinase (Src-K). MATERIALS AND METHODS: Structural data for Src-K were obtained from a protein data bank (ID=2SRC), and the molecular interactions between Src-K and TX-1123 derivatives were examined. RESULTS: TX-1123 exihibited potent Src-K inhibitory activity (half maximal-inhibitory concentration=2.2 µM), and fit into the pocket of the Src-K molecule as well as c-AMP did. CONCLUSION: The binding profiles of TX-1123 derivatives differed from each other, while their Src-K inhibitory activities were affected by their fit in the Src-K molecule.

Effect of N-Phenylanthranilic Acid Scaffold Nonsteroidal Anti-inflammatory Drugs on the Mitochondrial Permeability Transition.

Hepatotoxicity is a known side effect of nonsteroidal anti-inflammatory drugs (NSAIDs). In the present study, the effects of N-phenylanthranilic acid (NPA) scaffold NSAIDs on rat liver mitochondria were examined. Mefenamic acid (MEF, 200 µM) induced mitochondrial swelling, which was inorganic phosphate (Pi)-dependent and suppressed by cyclosporin A (CsA, 2.5 µM), similar to calcium-induced swelling. Mitochondrial swelling was also observed following the addition of 200 µM flufenamic acid (FLU), meclofenamic acid (MCL), and tolfenamic acid (TOL). Less swelling was observed with the addition of 200 µM diclofenac (DIC) or NPA. Diphenylamine (DPA)-induced swelling occurred in a Pi-independent manner and was not sensitive to CsA. The mechanism by which DPA interacted with the mitochondrial inner membrane differed from those of the other NPA scaffold NSAIDs. The addition of 50 µM MEF, MCL, TOL, and FLU had uncoupling effects in mitochondrial inner membrane. These NSAIDs dose-dependently obstructed electron transport in the respiratory chain. NSAIDs are known to have various dynamic structures, and the solvation free energies (dGWs: an index of stereo-hydrophobicity) of the conformers obtained were determined using a molecular orbital analysis. The relationship between the dynamic structures and swelling induced by NPA scaffold NSAIDs was also examined.

Cytolytic Activity and Molecular Feature of Cardiotoxin and Cardiotoxin-like Basic Protein: The Electrostatic Potential Field Is an Important Factor for Cell Lytic Activity.

BACKGROUND/AIM: Cardiotoxin (CT) is a well-known cell lytic protein and has been purified from cobra venom. Cardiotoxin-like basic protein (CLBP) has two amino acid insertions and does not exhibit cell lytic activity. The molecular features of these CT family proteins were examined in the present study using molecular modeling and molecular simulation techniques. MATERIALS AND METHODS: Molecular models of CT and CLBP were constructed based on the X-ray data of Naja mossambica mossambica CT VII4 (Protein Data Bank ID: 1CDT). The structural features of these models were examined using molecular orbital and electrostatic potential parameters. RESULTS: The stereo-hydrophobicities and molecular torsions of CT and CLBP, which are indexes of structural features, were similar. Electrostatic potential fields (ESP) differed between CT and CLBP and this was considered one of the critical factors in molecular titer. CONCLUSION: The distribution of ESP fields may affect the cytolytic activity of the CT family.