Phenylthiazolyl-hydrazide and its derivatives are potent inhibitors of tau aggregation and toxicity in vitro and in cells

One of the key pathological features of Alzheimer's disease is the aggregation of tau protein. We are therefore searching for compounds capable of inhibiting this reaction. On the basis of an initial screen of 200000 compounds [Pickhardt, M., Gazova, Z., von Bergen, M., Khlistunova, I., Wang, Y., Hascher, A., Mandelkow, E. M., Biernat, J., and Mandelkow, E. (2005) Anthraquinones inhibit tau aggregation and dissolve Alzheimer's paired helical filaments in vitro and in cells, J. Biol. Chem. 280, 3628-3635], we performed an in silico screen and predicted a new phenylthiazolyl-hydrazide (PTH) compound as a possible hit [Larbig, G., Pickhardt, M., Lloyd, D. G., Schmidt, B., and Mandelkow, E. (2007) Screening for inhibitors of tau protein aggregation into Alzheimer paired helical filaments: A ligand based approach results in successful scaffold hopping. Curr. Alzheimer Res. 4 (3), 315-323.]. Synthesis of this compound showed that it was indeed active in terms of inhibiting de novo tau aggregation and disassembling preformed aggregates (IC50 = 7.7 microM and DC50 = 10.8 microM). We have now synthesized 49 similar structures and identified the core of the PTHs to be crucial for activity, thus representing a lead structure. Analysis of the binding epitope by saturation transfer difference NMR shows strong interactions between the tau protein and the ligand in the aromatic regions of the inhibitor. By chemical variation of the core, we improved the inhibitory potency five-fold. The compounds showed a low toxicity as judged by an N2A cell model of tau aggregation and lend themselves for further development.     

Ultrastructure of the Corynebacterium glutamicum cell wall

The cell wall structure of the Gram-positive Corynebacterium glutamicum was evaluated by electron microscopy of thin sections after freeze-substitution and conventional fixation with glutaraldehyde. For the cell wall an overall thickness of approximately 32 nm was determined, with 8.5 nm corresponding to an outer layer, 6.5 nm to an electron translucent region (ETR) as found in mycobacteria and 17 nm to the peptidoglycan. Knob-like surface structures previously observed in freeze-fracture experiments were detected when cells were conventionally processed with a fixation using glutaraldehyde. By mild treatment with detergents approximately 20 proteins were extracted from the cell wall. From seven of these N-terminal amino acid sequences were determined.     

Synthesis of novel benzamidine- and guanidine-derived polyazamacrocycles: Selective anti-protozoal activity for human African trypanosomiasis

Efficient synthetic routes have been developed for the preparation of two new polyazamacrocycles tagged with structural motifs recognised by the Trypanosoma brucei P2 aminopurine transporter. Biological testing of these compounds showed highly selective anti-protozoal activity against trypanosomes.     

Delay of acute intracellular pH recovery after acidosis decreases endothelial cell activation

Reperfusion after ischemic conditions induces massive endothelial cell (EC) activation, an initial step of reperfusion injury. Reperfusion is characterized by reoxygenation, realkalinization and a localized increase of inflammatory stimuli. In this study, we focused on the influence of extracellular realkalinization on human umbilical vein endothelial cell (HUVEC) activation. We examined intracellular pH (pH(in)) and intracellular free calcium concentration ([Ca(2+)](in)), a second messenger known to mediate von Willebrand factor (VWF) exocytosis in endothelium, upon realkalinization. Furthermore, we measured the agonist-stimulated exocytosis of VWF, Interleukin-8 and soluble P-selectin (sP-Selectin) as markers of EC activation. To verify a morphological correlate of EC activation, we finally observed platelet-endothelial adherence during realkalinization using shear flow. Realkalinization of HUVEC was simulated by switching from bicarbonate buffered Ringer solution of an acidotic pH(ex) of 6.4 to a physiologic pH(ex) of 7.4. Extracellular realkalinization was accompanied by pH(in) recovery from 6.5 to 7.2 within 10 min. Application of cariporide, an inhibitor of the Na(+)/H(+) exchanger subtype 1 (NHE), during extracellular realkalinization significantly delayed the early kinetics of intracellular realkalinization. Histamine stimulated [Ca(2+)](in) was significantly increased upon realkalinization compared to control cells. Also agonist-stimulated release of VWF, Interleukin-8 and sP-Selectin was massively enhanced during pH(in) recovery in comparison to control. Furthermore, we observed an increased platelet binding to endothelium. Interestingly, each of these realkalinization-induced effects were significantly reduced by early application of cariporide. Therefore, delay of acute NHE-dependent pH(in) recovery may represent a promising mechanism for inhibition of EC activation upon reperfusion.     

Protein kinase MARK/PAR-1 is required for neurite outgrowth and establishment of neuronal polarity

Protein kinases of the microtubule affinity-regulating kinase (MARK) family were originally discovered because of their ability to phosphorylate certain sites in tau protein (KXGS motifs in the repeat domain). This type of phosphorylation is enhanced in abnormal tau from Alzheimer brain tissue and causes the detachment of tau from microtubules. MARK-related kinases (PAR-1 and KIN1) occur in various organisms and are involved in establishing and maintaining cell polarity. Herein, we report the ability of MARK2 to affect the differentiation and outgrowth of cell processes from neuroblastoma and other cell models. MARK2 phosphorylates tau protein at the KXGS motifs; this results in the detachment of tau from microtubules and their destabilization. The formation of neurites in N2a cells is blocked if MARK2 is inactivated, either by transfecting a dominant negative mutant, or by MARK2 inhibitors such as hymenialdisine. Alternatively, neurites are blocked if the target KXGS motifs on tau are rendered nonphosphorylatable by point mutations. The results suggest that MARK2 contributes to the plasticity of microtubules needed for neuronal polarity and the growth of neurites.     

Estimates of Genetic Differentiation Measured by F(ST) Do Not Necessarily Require Large Sample Sizes When Using Many SNP Markers

Population genetic studies provide insights into the evolutionary processes that influence the distribution of sequence variants within and among wild populations. F_ST is among the most widely used measures for genetic differentiation and plays a central role in ecological and evolutionary genetic studies. It is commonly thought that large sample sizes are required in order to precisely infer F_ST and that small sample sizes lead to overestimation of genetic differentiation. Until recently, studies in ecological model organisms incorporated a limited number of genetic markers, but since the emergence of next generation sequencing, the panel size of genetic markers available even in non-reference organisms has rapidly increased. In this study we examine whether a large number of genetic markers can substitute for small sample sizes when estimating F_ST. We tested the behavior of three different estimators that infer F_ST and that are commonly used in population genetic studies. By simulating populations, we assessed the effects of sample size and the number of markers on the various estimates of genetic differentiation. Furthermore, we tested the effect of ascertainment bias on these estimates. We show that the population sample size can be significantly reduced (as small as n = 4–6) when using an appropriate estimator and a large number of bi-allelic genetic markers (k>1,000). Therefore, conservation genetic studies can now obtain almost the same statistical power as studies performed on model organisms using markers developed with next-generation sequencing.     

Nucleolipids as potential organogelators

Four different series of nucleolipids or bola-nucleolipids were synthesized or re-synthesized. Most of the compounds were studied with respect to their gelation properties toward either water or aromatic, hetero-aromatic, and aliphatic hydrocarbons. Bola-nucleolipids 6 and 7 do not gelate any solvent tested, neither as sole additive nor by adding up to 10 wt% of a 1:1 mixture. The nucleolipid 22 carrying the antiviral acyclovir as a head group proved to be a potent organogelator for aromatic hydrocarbons such as toluene, but not for hetarenes, aliphatic hydrocarbons or water. The mono-tailed nucleolipid 24 exhibits excellent organogelator properties for both aromatic and aliphatic hydrocarbons. These were studied as a function of concentration and temperature.