Sucrose-induced cardiomyocyte dysfunction is both preventable and reversible with clinically relevant treatments

We recently identified cardiomyocyte dysfunction in the early stage of type 2 diabetes (i.e., diet-induced insulin resistance). The present investigation was designed to determine whether a variety of clinically relevant interventions are sufficient to prevent and reverse cardiomyocyte dysfunction in sucrose (SU)-fed insulin-resistant rats. Subsets of animals were allowed to exercise (free access to wheel attached to cage) or were treated with bezafibrate in drinking water to determine whether these interventions would prevent the adverse effects of SU feeding on cardiomyocyte function. After 6-8 wk on diet and treatment, animals were surgically prepared to assess whole body insulin sensitivity (intravenous glucose tolerance test), and isolated ventricular myocyte mechanics were evaluated (video edge recording). SU feeding produced hyperinsulinemia and hypertriglyceridemia, with euglycemia, and induced characteristic whole body insulin resistance. Both exercise and bezafibrate treatment prevented these metabolic abnormalities. Ventricular myocyte shortening and relengthening were slower in SU-fed rats (42-63%) compared with starch (ST)-fed controls, and exercise or bezafibrate completely prevented cardiomyocyte dysfunction in SU-fed rats. In separate cohorts of animals, after 5 wk of SU feeding, animals were either switched back to an ST diet or given menhaden oil for an additional 7-9 wk to determine whether the cardiomyocyte dysfunction was reversible. Both interventions have previously been shown to have favorable metabolic effects, and both improved myocyte mechanics, but only the ST diet reversed all indications of cardiomyocyte dysfunction induced by SU feeding. Thus phenotypic changes in cardiomyocyte mechanics associated with early stages of type 2 diabetes were found to be both preventable and reversible with clinically relevant treatments, suggesting that the cellular processes contributing to this dysfunction are modifiable.     

Expression of lysosomal protective protein/cathepsin A in a stably transformed human neuroblastoma cell line during bi-directional differentiation into neuronal and Schwannian cells

Human neuroblastoma GOTO cell lines were established that stably express recombinant human lysosomal protective protein/cathepsin A (PPCA) cDNA by transfection. Intracellular cathepsin A (acid serine carboxypeptidase) activity increased four-fold compared with in those of the parent and mock-transfected cell lines. The immunoreactive 54 kDa precursor/zymogen and mature 32/20 kDa two-chain forms were produced in the cells. The amount of the latter form expressed in the GOTO cells was significantly larger than those in the PPCA-overexpressing CHO cell lines previously established. The intracellular proteins showed a typical lysosomal granular distribution and the glycosylated 54 kDa precursor was secreted into the culture medium without the addition of an alkalizing agent. The PPCA-overexpressing cell lines also retained the ability to differentiate bi-directionally as well as the parent cells; into neuronal cells on induction by dibutyryl cAMP in serum-free medium and into Schwannian cells on induction by bromodeoxyuridine. During the course of differentiation into neuronal and Schwannian cells, the intracellular cathepsin A activity further increased two and five times, respectively, which was associated with an increase in the expression of the 32/20 kDa two-chain form. The glycosylated precursor proteins were taken up via the mannose 6-phosphate receptors, and the cathepsin A, alpha-neuraminidase and beta-galactosidase (beta-Gal) activities deficient in the fibroblasts derived from a patient with PPCA deficiency (galactosialidosis) were restored. These results suggest that the bi-directional differentiation of GOTO cell lines stably expressing the recombinant human PPCA gene could be a model system for analyzing the functions of PPCA in peripheral neuronal cells and Schwannian cells as well as the recombinant PPCA could be a useful source for enzyme replacement therapy (ERT) for galactosialidosis patients.     

3-(7-Azaindolyl)-4-arylmaleimides as potent, selective inhibitors of glycogen synthase kinase-3

A novel series of acyclic 3-(7-azaindolyl)-4-(aryl/heteroaryl)maleimides was synthesized and evaluated for activity against GSK-3beta and selectivity versus PKC-betaII, as well as a broad panel of protein kinases. Compounds 14 and 17c potently inhibited GSK-3beta (IC(50)=7 and 26 nM, respectively) and exhibited excellent selectivity over PKC-betaII (325 and >385-fold, respectively). Compound 17c was also highly selective against 68 other protein kinases. In a cell-based functional assay, both 14 and 17c effectively increased glycogen synthase activity by inhibiting GSK-3beta.     

MexAB-OprM specific efflux pump inhibitors in Pseudomonas aeruginosa. Part 3: Optimization of potency in the pyridopyrimidine series through the application of a pharmacophore model

The addition of substituents to the pyridopyrimidine scaffold of MexAB-OprM specific efflux pump inhibitors was explored. As predicted by a pharmacophore model, the incorporation substituents at the 2-position improved potency. Piperidines were found to be optimal, and further introduction of polar groups without compromising the activity was shown to be feasible. Careful positioning of the essential acidic moiety of the pharmacophore relative to the scaffold led to the discovery of vinyl tetrazoles with still greater potency.     

Synthesis and biological evaluation of taxinine analogues as orally active multidrug resistance reversal agents in cancer

Three novel taxinine analogues were prepared and tested for their activity as multidrug resistance (MDR) reversal agents in comparison with verapamil. In vitro testing demonstrated that compounds 8-10 possess MDR-reversal activity in the KB/V cell line. Half-hour after treatment with 5, 10, and 20 micromol/L compound 9, the intracellular rhodamine123 concentration increased 2.3, 2.9, and 3.2-fold, respectively, higher than 1.88-fold of 10 micromol/L verapamil in KB/V cell line. In vivo studies with VCR-resistant KB/V tumor xenografts showed that compound 9 in combination with VCR significantly inhibited tumor growth. Treatment with VCR or 9 alone did not result in growth inhibition. These results reveal that three taxinine analogues are good modifiers of MDR in tumor cells.     

Identification of promoters bound by c-Jun/ATF2 during rapid large-scale gene activation following genotoxic stress

The NH2-terminal Jun kinases (JNKs) function in diverse roles through phosphorylation and activation of AP-1 components including ATF2 and c-Jun. However, the genes that mediate these processes are poorly understood. A model phenotype characterized by rapid activation of Jun kinase and enhanced DNA repair following cisplatin treatment was examined using chromatin immunoprecipitation with antibodies against ATF2 and c-Jun or their phosphorylated forms and hybridization to promoter arrays. Following genotoxic stress, we identified 269 genes whose promoters are bound upon phosphorylation of ATF2 and c-Jun. Binding did not occur following treatment with transplatin or the JNK inhibitor SP600125 or JNK-specific siRNA. Of 89 known DNA repair genes represented on the array, 23 are specifically activated by cisplatin treatment within 3-6 hr. Thus, the genotoxic stress response occurs at least partly via activation of ATF2 and c-Jun, leading to large-scale coordinate gene expression dominated by genes of DNA repair.     

Crystal structure of the hypothetical protein TA1238 from Thermoplasma acidophilum: a new type of helical super-bundle

The crystal structure of the hypothetical protein TA1238 from Thermoplasma acidophilum was solved with multiple-wavelength anomalous diffraction and refined at 2.0 A resolution. The molecule consists of a typical four-helix antiparallel bundle with overhand connection. However, its oligomerization into a trimer leads to a coiled "super-helix" which is novel for such bundles. Its central feature, a six-stranded coiled coil, is also novel for proteins. TA1238 does not have strong sequence homologues in databases, but shows strong structural similarity with some proteins in the Protein Data Bank. The function could not be inferred from the sequence but the structure, with some rearrangement, bears some resemblance to the active site region of cobalamin adenosyltransferase (TA1434). Specifically, TA1238 retains Arg104, which is structurally equivalent to functionally critical Arg119 of TA1434. For such conformational change, the overhand connection of TA1238 might need to be involved in a gating mechanism that might be modulated by ligands and/or by interactions with the physiological partners. This allowed us to hypothesize that TA1238 could be involved in cobalamin biosyntheses.