New class of inhibitors of amyloid-beta fibril formation. Implications for the mechanism of pathogenesis in Alzheimer's disease

The amyloid hypothesis suggests that the process of amyloid-beta protein (Abeta) fibrillogenesis is responsible for triggering a cascade of physiological events that contribute directly to the initiation and progression of Alzheimer's disease. Consequently, preventing this process might provide a viable therapeutic strategy for slowing and/or preventing the progression of this devastating disease. A promising strategy to achieve prevention of this disease is to discover compounds that inhibit Abeta polymerization and deposition. Herein, we describe a new class of small molecules that inhibit Abeta aggregation, which is based on the chemical structure of apomorphine. These molecules were found to interfere with Abeta1-40 fibrillization as determined by transmission electron microscopy, Thioflavin T fluorescence and velocity sedimentation analytical ultracentrifugation studies. Using electron microscopy, time-dependent studies demonstrate that apomorphine and its derivatives promote the oligomerization of Abeta but inhibit its fibrillization. Preliminary structural activity studies demonstrate that the 10,11-dihydroxy substitutions of the D-ring of apomorphine are required for the inhibitory effectiveness of these aporphines, and methylation of these hydroxyl groups reduces their inhibitory potency. The ability of these small molecules to inhibit Abeta amyloid fibril formation appears to be linked to their tendency to undergo rapid autoxidation, suggesting that autoxidation product(s) acts directly or indirectly on Abeta and inhibits its fibrillization. The inhibitory properties of the compounds presented suggest a new class of small molecules that could serve as a scaffold for the design of more efficient inhibitors of Abeta amyloidogenesis in vivo

Alanine Stimulation of Water and Sodium Absorption in a Model of Secretory Diarrhea

We investigated the effectiveness of L-alanine (Ala) addition to oral hydration solutions (OHSs) during secretory conditions induced by ileal instillation of 10 m M theophylline in anesthetized rats using a perfusion procedure, and monitoring water and sodium transport. Ala was added to two hypotonic OHSs in which the sodium:glucose ratio was 2:1, and compared with the OHS recommended by the World Health Organization (WHO), which has a sodium:glucose ratio of 0.81:1. Theophylline had the expected secretory effect on water and sodium absorption in the WHO-recommended OHS, and on sodium transport in a formula containing 60 m M sodium and 30 m M glucose. However, an OHS with 90 m M sodium and 45 m M glucose canceled the secretory effect of the-ophylline and yielded a greater rate of net water absorption than the WHO formula. Addition to this solution of either 15 or 30 m M Ala enhanced water and sodium absorption of both control and theophylline-treated rats. In the hypotonic OHS with 60 m M sodium and 30 m M glucose, Ala had little effect on both sodium and water transport. Therefore, the data support the view that Ala added to solutions with 90 m M sodium, containing sufficient glucose to maintain a sodium:glucose ratio of not less than 2:1, is most effective at compensating fluid and sodium losses under secretory conditions. Ala presumably exerts its sodium-sparing effect because of its cotransport with sodium and the consequent water influx into the intestinal cells

Metabolic and Structural Effects of Insulin-like Growth Factor-I and High-Protein Diet on Dystrophic Hamster Skeletal Muscle

Abstract In muscular dystrophy (MD) there is an imbalance between muscle protein synthesis and protein degradation, which results in a net muscle catabolism, along with muscle wasting and weakness. Using a dystrophic hamster model (BIO 53.58), we examined the chronic (8 weeks) effects of two factors that may enhance muscle protein synthesis and inhibit protein degradation, namely, insulin-like growth factor-I (rhlGF-I) and high-protein diet (HPD). Protein synthesis was determined by measuring the incorporation of 14C phenylalanine into perfused leg muscle, while protein degradation was calculated from the release of tyrosine from the same perfused muscle. Urinary 3-methylhistidine excretion was used as an indicator of myofibrillar degradation. Treatment of dystrophic hamsters with rhlGF-I, HPD, or a combination of the two for 8 weeks resulted in significant decreases in total and myofibrillar degradation when compared with untreated dystrophic animals (P< 0.05) but had minimal effects on protein synthesis. Significant morphologic improvements (P< 0.05), including a normalization and greater uniformity of muscle fibers, were also seen in rhlGF-l- and rhlGF-l + HPD-treated animals. rhlGF-l and HPD were effective in reducing the excessive proteolysis seen in dystrophic muscle, and this reduced proteolysis resulted in improvement of muscle morphology

ANG II promotes autophagy in podocytes

Podocytes are an integral and important constituent of the glomerular filtration barrier (GFB) and are exposed to a higher concentrations of ANG II in diseased states; consequently, podocytes may accumulate oxidized proteins and damaged mitochondria. In the present study, we evaluated the effect of ANG II on the podocyte autophagic process, which is likely to be triggered in order to degrade unwanted proteins and damaged organelles. To quantitate the occurrence of autophagy, electron microscopic studies were carried out on control and ANG II-treated conditionally immortalized mouse podocytes (CIMPs). ANG II-treated cells showed a fivefold greater number of autophagosomes/field compared with control cells. This proautophagic effect of ANG II was inhibited by pretreatment with 3-methyladenine, an inhibitor of autophagy. ANG II also enhanced podocyte expression of autophagic genes such as LC3-2 and beclin-1. Since oxidative stress is often associated with the induction of autophagy, we examined the effect of ANG II on podocyte reactive oxygen species (ROS) generation. ANG II enhanced podocyte ROS generation in a time-dependent manner. To determine whether there is a causal relationship between ANG II-induced oxidative stress and induction of autophagy, we evaluated the effect of antioxidants on ANG II-induced autophagy. As expected, the proautophagic effect of ANG II was inhibited by antioxidants. We conclude that ANG II promotes podocyte autophagy through the generation of ROS