sorbinil and fidarestat

Aldose reductase ([EC1.1.1.21]: AR) acts on the first step of the polyol metabolic pathway to catalyze the reduction of glucose to sorbitol with NADPH as a coenzyme. Hyperactivity of the pathway in individuals with high blood glucose level is closely related to the onset or progression of diabetic complications. AR inhibitors have therefore been noted as possible pharmacotherapeutic agents for the treatment of diabetic complications. One AR inhibitor has been on the market in Japan, while some potent inhibitors are in clinical trials. Reviewed are the physiological roles of AR, the chemical structures of AR inhibitors, interactions of AR inhibitors with AR using X-ray studies, and the following potencies of AR inhibitors: in vitro activities for AR, in vitro selectivities between AR and aldehyde reductase, their pharmacological effects in vivo, and their effectiveness in clinical trials. Also discussed are directions for the design of future AR inhibitors.

Topics: Aldehyde Reductase; Binding Sites; Clinical Trials as Topic; Crystallography, X-Ray; Diabetic Neuropathies; Enzyme Inhibitors; Humans; Imidazoles; Imidazolidines; Naphthalenes; Quinazolines

The purpose of this study was to evaluate the effect of aldose reductase (AR) inhibition on posterior capsular opacification (PCO) with the use of a pig eye capsular bag model.. Pig eye capsular bags were prepared by capsulorhexis and cultured in medium without or with AR inhibitors for 7 days. Immunostaining was performed in paraformaldehyde-fixed capsular bags to determine the expression of proliferating cell nuclear antigen (PCNA), alpha-smooth muscle actin (SMA), beta-crystallin, and intercellular adhesion molecule (ICAM)-1. The effect of AR inhibition on basic fibroblast growth factor (BFGF)-induced mitogenic signaling in cultured human lens epithelial cells (HLECs) was examined. Cell growth was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and cell counting, the expression of alpha-SMA, beta-crystallin, and ICAM-1 by Western blot and immunocytochemical analysis, protein kinases by Western blot analysis, and NF-kappaB activation by gel shift and reporter assays.. During culture of pig eye capsular bags, residual cells on both the anterior and the posterior capsule showed vigorous growth. Treatment with AR inhibitors significantly prevented the lens epithelial cell growth in capsular bags and expression of alpha-SMA, beta-crystallin, and ICAM-1. HLECs showed a dose-dependent response to BFGF, proliferation at lower concentrations (<20 ng/mL) and differentiation/transdifferentiation at higher concentrations (>50 ng/mL). Inhibition of AR also prevented the BFGF-induced activation of ERK1/2, JNK, and NF-kappaB in HLECs.. Results suggest that AR is required for lens epithelial cell growth and differentiation/transdifferentiation in the capsular bags, indicating that inhibition of AR could be a potential therapeutic target in the prevention of PCO.

Topics: Actins; Aldehyde Reductase; Animals; beta-Crystallins; Blotting, Western; Capsulorhexis; Cataract; Cell Count; Cell Differentiation; Cell Proliferation; Cells, Cultured; Electrophoretic Mobility Shift Assay; Enzyme Inhibitors; Epithelial Cells; Fibroblast Growth Factor 2; Imidazolidines; Immunoenzyme Techniques; Intercellular Adhesion Molecule-1; Lens Capsule, Crystalline; Microscopy, Fluorescence; NF-kappa B; Organ Culture Techniques; Proliferating Cell Nuclear Antigen; Signal Transduction; Swine

Phenolic marine natural product is a kind of new potential aldose reductase inhibitors (ARIs). In order to investigate the binding mode and inhibition mechanism, molecular docking and dynamics studies were performed to explore the interactions of six phenolic inhibitors with human aldose reductase (hALR2). Considering physiological environment, all the neutral and other two ionized states of each phenolic inhibitor were adopted in the simulation. The calculations indicate that all the inhibitors are able to form stable hydrogen bonds with the hALR2 active pocket which is mainly constructed by residues TYR48, HIS110 and TRP111, and they impose the inhibition effect by occupying the active space. In all inhibitors, only La and its two ionized derivatives La_ion1 and La_ion2, in which neither of the ortho-hydrogens of 3-hydroxyl is substituted by Br, bind with hALR2 active residues using the terminal 3-hydroxyl. While, all the other inhibitors, at least one of whose ortho-sites of 3- and 6-hydroxyls are substituted by Br substituent which take much electron-withdrawing effect and steric hindrance, bind with hALR2 through the lactone group. This means that the Br substituent can effectively regulate the binding modes of phenolic inhibitors. Although the lactone bound inhibitors have relatively high RMSD values, our dynamics study shows that both binding modes are of high stability. For each inhibitor molecule, the ionization does not change its original binding mode, but it does gradually increase the binding free energy, which reveals that besides hydrogen bonds, the electrostatic effect is also important to the inhibitor-hALR2 interaction.

Topics: Aldehyde Reductase; Enzyme Inhibitors; Hydrogen Bonding; Imidazolidines; Molecular Dynamics Simulation; Naphthalenes; Protein Structure, Secondary; Rhodanine; Thiazolidines

Structure determination of porcine aldehyde reductase holoenzyme in complex with the potent aldose reductase inhibitor fidarestat was carried out to explain the difference in the potency of the inhibitor for aldose and aldehyde reductases. The hydrogen bonds between the active-site residues Tyr50, His113, and Trp114 and fidarestat are conserved in the two enzymes. In aldose reductase, Leu300 forms a hydrogen bond through its main-chain nitrogen atom with the exocyclic amide group of the inhibitor, which when replaced with a Pro in aldehyde reductase, cannot form a hydrogen bond, thus causing a loss in binding energy. Furthermore, in aldehyde reductase, the side chain of Trp220 occupies a disordered split conformation that is not observed in aldose reductase. Molecular modeling and inhibitory activity measurements suggest that the difference in the interaction between the side chain of Trp220 and fidarestat may contribute to the difference in the binding of the inhibitor to the enzymes.

Topics: Alcohol Oxidoreductases; Aldehyde Reductase; Animals; Binding Sites; Crystallography, X-Ray; Holoenzymes; Imidazolidines; Models, Molecular; Protein Binding; Protein Structure, Tertiary; Stereoisomerism; Structure-Activity Relationship; Swine

Structure of the Leu300Pro mutant of human aldose reductase (ALR2) in complex with the inhibitor fidarestat is determined. Comparison with the hALR2-fidarestat complex and the porcine aldehyde reductase (ALR1)-fidarestat complex indicates that the hydrogen bond between the Leu300 amino group of the wild-type and the exocyclic amide group of the inhibitor is the key determinant for the specificity of fidarestat for ALR2 over ALR1. Thermodynamic data also suggest an enthalpic contribution as the predominant difference in the binding energy between the aldose reductase mutant and the wild-type. An additional selectivity-determining feature is the difference in the interaction between the inhibitor and the side chain of Trp219, ordered in the present structure but disordered (corresponding Trp220) in the ALR1-fidarestat complex. Thus, the hydrogen bond ( approximately 7 kJ/mol) corresponds to a 23-fold difference in inhibitor potency while the differences in the interactions between Trp219(ALR2) and fidarestat and between Trp220(ALR1) and fidarestat can account for an additional 10-fold difference in potency.

Topics: Aldehyde Reductase; Binding Sites; Calorimetry; Crystallization; Holoenzymes; Humans; Imidazolidines; Models, Molecular; Mutation; Protein Binding; Protein Conformation; Thermodynamics

The absolute configuration of the aldose reductase (AR) inhibitor, (+)-(2S,4S)-6-fluoro-2',5'-dioxospiro¿chroman-4, 4'-imidazolidine-2-carboxamide (fidarestat), was established indirectly by single-crystal X-ray analysis of (+)-(2S, 4S)-8-bromo-6-fluoro-2',5'-dioxospiro¿chroman-4, 4'-imidazolidine-2-carboxylic acid (1). The crystal structure of human AR complexed with fidarestat was determined, and the specific inhibition activity was discussed on the basis of the three-dimensional interactions between them. The structure clarified that fidarestat was located in the active site by hydrophilic and hydrophobic interactions and that the carbamoyl group of fidarestat was a very effective substituent for affinity to AR and for selectivity between AR and aldehyde reductase (AHR). Explanations for the differences between the observed activities of fidarestat and its stereoisomer 2 were suggested by computer modeling.

Topics: Aldehyde Reductase; Binding Sites; Crystallography, X-Ray; Enzyme Inhibitors; Humans; Imidazoles; Imidazolidines; Models, Molecular; Molecular Structure; Stereoisomerism