Role of 2-oxoglutarate dehydrogenase in brain pathologies involving glutamate neurotoxicity

Decreased activity of the mitochondrial thiamin-dependent 2-oxoglutarate dehydrogenase complex (OGDHC) is associated with a number of inborn and acquired neuropathologies. We hypothesized that perturbation in flux through the complex influences brain development and function, in particular, because the OGDHC reaction is linked to the synthesis/degradation of neurotransmitters glutamate and GABA. Developmental impact of this metabolic knot was studied by characterizing the brain OGDHC activity in offspring of rats exposed to acute hypobaric hypoxia at a critical organogenesis period of pregnancy. In this model, we detected the hypoxia-induced changes in the brain OGDHC activity and in certain physiologic and morphometric parameters. The changes were mostly abrogated by application of specific effector of cellular OGDHC, the phosphonate analog of 2-oxoglutarate (succinyl phosphonate), shortly before hypoxia. The glutamate excitotoxicity known to greatly contribute to hypoxic damage was alleviated by succinyl phosphonate in situ. That is, the delayed calcium deregulation, mitochondrial depolarization and reactive oxygen species (ROS) production became less pronounced in cultivated neurons loaded with succinyl phosphonate. In vitro, succinyl phosphonate protected OGDHC from the catalysis-induced inactivation. Thus, the protective effects of the phosphonate upon hypoxic insult in vivo may result from the preservation of mitochondrial function and Ca²⁺ homeostasis due to the phosphonate inhibition of both the OGDHC-dependent ROS production and associated OGDHC inactivation. As a result, we showed for the first time that the hypoxia- and glutamate-induced cerebral damage is linked to the function of OGDHC, introducing the phosphonate analogs of 2-oxoglutarate as promising diagnostic tools to reveal the role of OGDHC in brain function and development.     

Study on preparation and unique properties of a novel insulin analogue with N-terminal Arg-4, Pro-3, Lys-2, Pro-1extension at insulin B-chain

A novel insulin analog, PIns, with N-terminal Arg-4, Pro-3, Lys-2, Pro-1extension at human regular insulin B-chain was acquired through gene engineering. Preproinsulin for PIns was cloned and expressed using a bacterial expression system at a high level (72.1%) as fusion protein carrying a modified thioredoxin N-terminal region (1–21) linked to N-terminus of proinsulin by a lysine residue. Purified fusion protein was refolded and converted into PIns by a single enzymatic reaction. After PIns was purified, the homogeneity of it was characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis, isoelectronic focusing electrophoresis, amino acid composition analysis and mass spectrometry methods. A decreased tendency of self-association of PIns as compared with regular insulin was demonstrated by the size exclusion HPLC analysis. When subcutaneously administrated into normal rats, the PIns showed a faster rate of onset of action and a shorter duration of action compared with regular insulin, similar to the pharmacokinetic characteristics of insulin Lispro. These results showed that PIns is a rapid insulin analog. Furthermore, the N-terminal Arg-4, Pro-3, Lys-2, Pro-1extension at insulin B-chain can be excised by DPPIV and recombinant peptidase with DPPIV-like activities. It is suggested that PIns serves as an artificial insulin precursor and can be transformed to regular insulin in vivo due to the truncation of N-terminal sequence of PIns B-chain by DPPIV.     

An artificial redox coenzyme based on a triazine dye template

A series of nicotinamide-containing compounds based on the structure of a triazine dye, C.I. Reactive Blue 2, which is known to interact at the coenzyme-binding sites of several NAD(P)(H)-dependent dehydrogenases,^1,2 were designed, synthesized, and characterized. The preparation of these compounds is described. Reduction of the coenzyme mimics with sodium borohydride led to an increase in absorption at 356 nm, analogous to the behavior of the natural coenzyme, NAD⁺.³ When incubated with horse liver alcohol dehydrogenase and ethanol at 25°C and pH 9.0, one of the mimics, Blue N-3, was converted into a new compound with an increased absorption at 356 nm and an R_f value on thin-layer chromatography identical to that of the reduced form produced by treatment with sodium borohydride. The oxidized and reduced forms of Blue N-3 could be separated by reverse-phase ion pair high-performance liquid chromatography. This technique could be used to measure the extent of Blue N-3 reduction: Approximately 90 turnovers were calculated for each enzyme active site over a 48-h period. Gas chromatography analysis suggested that ethanol was simultaneously converted to acetaldehyde. Blue N-3 represents the first example of a new generation of potentially inexpensive, stable, and active biomimetic redox coenzymes.     

Design of a potent anticancer lead inspired by natural products from traditional Indian medicine

Abstract

Among the plant constituents of Clerodendrum colebrookianum Walp., acteoside, martinoside, and osmanthuside β6 interact with ROCK, a drug target for cancer. In this study, aglycone fragments of these plant constituents (caffeic acid, ferulic acid, and p-coumaric acid) along with the homopiperazine ring of fasudil (standard ROCK inhibitor) were used to design hybrid molecules. The designed molecules interact with the key hinge region residue Met156/Met157 of ROCK I/II in a stable manner according to our docking and molecular dynamics simulations. These compounds were synthesized and tested in vitro in SW480, MDA-MB-231, and A-549 cancer cell lines. The most promising compound was chemically optimized to obtain a thiourea analog, 6a (IC₅₀ = 25?µM), which has >3-fold higher antiproliferative activity than fasudil (IC₅₀ = 87?µM) in SW480 cells. Treatment with this molecule also inhibits the migration of colon cancer cells and induces cell apoptosis. Further, SPR experiments suggests that the binding affinity of 6a with ROCK I protein is better than that of fasudil. Hence, the drug-like natural product analog 6a constitutes a highly promising new anticancer lead.

Communicated by Ramaswamy H. Sarma     

Analog synthesis of DAMASCENOLIDETM,an important aroma component of roses,and their odor properties

ABSTRACT

DAMASCENOLIDE^TM [1, 4-(4-methylpent-3-en-1-yl)furan-2(5H)-one], which has a citrus-like odor, is an important aroma component of roses. We have previously reported on the synthesis and odor evaluation of double-bond isomers of 1 and concluded that the position and the geometric isomerism of the double-bond had a significant effect on the odor. For the purpose of deepening knowledge about structure–odor relationships, we synthesized 13 analogs of compound 1 and evaluated their odors. As a result, it was found that the presence of two double-bonds and branched methyl group at the terminal position in the side chain was essential in order to have a citrus-like odor. Substitution of the side chain with appropriate length at the appropriate 4-position of the 2(5H)-furanone ring was also an important factor in determining the quality of the odor.     

Identification of two different Q-binding sites in QH2-cytochrome c oxidoreductase,using the Q analogue n-heptadecylmercapto-6-hydroxy-5,8-quinolinequinone

The pK and mid-point redox potential of the Q-analogue 7-(n-heptadecyl)mercapto-6-hydroxy-5,8-quinolinequinone (HMHQQ) in aqueous medium are so low that under the experimental conditions used for studying the inhibition of electron transfer in submitochondrial particles only the oxidized, anionic form is present. The K_D of the analogue, determined by comparing its inhibitory effect with that of n-heptyl-4-hydroxyquinolineN-oxide, is (0.003+0.24×mg protein/ml) μM. The inhibition of succinate oxidation is pH dependent, due to a pH-dependent change in the overcapacity of the QH₂-oxidizing system above the Q-reducing system. If the terminal part of the respiratory chain is reduced with ascorbate, the analogue inhibits the reduction of cytochrome b by substrate in the presence of antimycin with a similar K_D value. In the absence of ascorbate the K_D value is 100-times higher. The reduction of cytochrome b by substrate in particles treated with 2,3-dimercaptopropanol (BAL)+O₂ is also sensitive to HMHQQ, with a K_D value in between the two values given above. It is concluded that the QH₂ oxidase system contains two different sites for interaction with ubiquinone. The site responsible for the inhibition of steady-state electron transfer is near the Fe-S cluster, as is shown by the sensitivity to the redox state of this cluster and by the effect of HMHQQ on the EPR signal of the reduced cluster. The second site, which is similar to the antimycin-binding site, is occupied only at higher concentrations of inhibitor. The affinity of HMHQQ for this site is not affected by the redox state of the Fe-S cluster.     

Sequential Capecitabine/Temozolomide and Sunitinib Treatment in Patients With Metastatic Well-Differentiated Grade 1/Grade 2 Pancreatic Neuroendocrine Tumors

ObjectiveThe role of alternate sequential administration of sunitinib and capecitabine/temozolomide (CAPTEM) in metastatic pancreatic neuroendocrine tumors (PanNETs) remains unexplored. We thus aimed to analyze the efficacy and tolerability of this strategy in advanced grade 1/grade 2 PanNETs.MethodsIn total, data of 43 patients with metastatic PanNET were collected from a real-world database of a cancer center. Twenty-four patients were treated with sunitinib followed by CAPTEM (group 1), and 19 patients were treated with CAPTEM followed by sunitinib (group 2).ResultsTwenty-three patients were treated with first-line sunitinib or CAPTEM, and 20 patients were pretreated with somatostatin analog (SSA) or SSA in combination with transcatheter arterial chemoembolization. The objective response rate with first-line treatment was similar in both groups, whereas that with second-line treatment was higher in group 1 than in group 2, albeit with no significant differences (21.1% vs 5.3%, respectively; P = .205). Median progression-free survival (mPFS) for first-line and second-line treatments did not differ between the 2 groups (11 and 12 months vs 12 and 8 months, respectively). Following subgroup analyses, treatment with first-line sunitinib and sunitinib after pretreated SSA had a longer mPFS than that with second-line sunitinib after CAPTEM (11 months vs 8 months, respectively; P = .046), whereas treatment with first-line CAPTEM and CAPTEM after pretreated SSA had an mPFS similar to that of second-line CAPTEM after sunitinib treatment. CAPTEM and sunitinib had similar tolerability.ConclusionAlternating sunitinib and CAPTEM were well tolerated and associated with similar mPFS in grade 1/grade 2 PanNETs. However, larger prospective studies are required to investigate the efficacy of alternate sequential therapies for metastatic PanNET.     

Efficacy and Safety of Analog Insulin in Comparison With Human Insulin for Hyperglycemia in Hospitalized Patients With Acute Stroke: A Randomized,Open-Label,Single-Center Trial

ObjectiveTo assess the efficacy and safety of analog insulins in comparison with human insulins for hyperglycemia in hospitalized patients with acute stroke.MethodsIn this single-center, open-label, randomized trial, 102 patients (age 59.4 ± 11.7 years, 54 women) admitted with acute stroke (52 ischemic, 50 hemorrhagic) and hyperglycemia were assigned to analog insulin (n = 52) or human insulin (n = 50) group during February to June 2021. Insulin was initiated and titrated according to the predefined standard protocol. The capillary blood glucose (BG) level was monitored by standardized glucometers. The primary outcomes were mean daily BG and the number of hypoglycemic events.ResultsBetween the 2 treatment groups, there was no significant difference in the mean daily BG (P >.05 for all days) or in the frequency of hypoglycemic episodes (P =.727). Four participants experienced severe hypoglycemia; all were receiving human insulin (P =.054). In the analog insulin group, there was a tendency toward lower daily total requirement for insulin (P =.053). The difference in bolus insulin dose was significantly lower in the analog insulin group (P =.029), but the difference in basal insulin dose was similar (P =.167). Between the 2 groups, there were no significant differences in the hospital mortality rate, modified Rankin Scale score on outcome, or length of hospital stay (P =.729,.658, and.918, respectively).ConclusionHospitalized patients acute stroke and hyperglycemia exhibited similar mean BG but a trend of lower incidence of severe hypoglycemia when treated with analog insulins in comparison with human insulin.