Friedemann Gaube

Bivalent β-Carbolines as Potential Multitarget Anti-Alzheimer Agents

Alzheimers disease (AD) is a prevalent neurodegenerative disorder with multifactorial causes that requires multitargeted treatment. Inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) improve cholinergic signaling in the central nervous system and thus AChE inhibitors are well established in the therapy of AD to improve memory disturbances and other cognitive symptoms. On the other hand, AD patients benefit from reduction of pathologic glutamate-induced, Ca(2+)-mediated excitotoxicity by the N-methyl-d-aspartate receptor (NR) antagonist memantine. New drugs that simultaneously affect both cholinergic transmission and glutamate-induced excitotoxicity may further improve AD treatment. While connecting beta-carboline units by alkylene spacers in two different series of compounds and subsequent evaluation of their AChE/BChE-inhibitory potential, we found that several of these bivalent beta-carbolines were potent NR blockers. The most promising compound was a N(9)-homobivalent beta-carboline with a nonylene spacer, which displayed IC(50) values of 0.5 nM for AChE, 5.7 nM for BChE, and 1.4 microM for NR, respectively.

Gene expression profiling reveals effects of Cimicifuga racemosa (L.) NUTT. (black cohosh) on the estrogen receptor positive human breast cancer cell line MCF-7

BackgroundExtracts from the rhizome of Cimicifuga racemosa (black cohosh) are increasingly popular as herbal alternative to hormone replacement therapy (HRT) for the alleviation of postmenopausal disorders. However, the molecular mode of action and the active principles are presently not clear. Previously published data have been largely contradictory. We, therefore, investigated the effects of a lipophilic black cohosh rhizome extract and cycloartane-type triterpenoids on the estrogen receptor positive human breast cancer cell line MCF-7.ResultsBoth extract and purified compounds clearly inhibited cellular proliferation. Gene expression profiling with the extract allowed us to identify 431 regulated genes with high significance. The extract induced expression pattern differed from those of 17β-estradiol or the estrogen receptor antagonist tamoxifen. We observed a significant enrichment of genes in an anti-proliferative and apoptosis-sensitizing manner, as well as an increase of mRNAs coding for gene products involved in several stress response pathways. These functional groups were highly overrepresented among all regulated genes. Also several transcripts coding for oxidoreductases were induced, as for example the cytochrome P450 family members 1A1 and 1B1. In addition, some transcripts associated with antitumor but also tumor-promoting activity were regulated. Real-Time RT-PCR analysis of 13 selected genes was conducted after treatment with purified compounds – the cycloartane-type triterpene glycoside actein and triterpene aglycons – showing similar expression levels compared to the extract.ConclusionNo estrogenic but antiproliferative and proapoptotic gene expression was shown for black cohosh in MCF-7 cells at the transcriptional level. The effects may be results of the activation of different pathways. The cycloartane glycosides and – for the first time – their aglycons could be identified as an active principle in black cohosh.

Beta and gamma carboline derivatives as potential anti-Alzheimer agents: A comparison.

Nine novel β- and γ-carboline derivatives bearing either methyl-, propargyl- or phenethyl-residues at the indole nitrogen were synthesized and tested as potential anti-Alzheimer drugs. Antagonism of recombinantly expressed NMDA receptors, inhibition of cholinesterases, and radical scavenging properties were determined for all compounds. Some were additionally tested in vivo for their ability to reverse scopolamine-induced cognitive impairment in an 8-arm radial maze experiment with rats. For the most promising candidates, the interaction with muscarinic M1 receptors was also investigated. With this set of compounds assays the influence of the scaffold itself and the substituents can be investigated separately. 5-Methyl-γ-carboline (6) was the most potent (0.25 μmol/100 g b.w.) compound in the in vivo test and might be a good starting point for the development of novel anti-Alzheimer drugs.

Enantiomerically Pure 2-Methyltetrahydro-3-benzazepin-1-ols Selectively Blocking GluN2B Subunit Containing N-Methyl-d-aspartate Receptors

A chiral pool synthesis was developed to obtain all four stereoisomeric 2-methyl-3-(4-phenylbutyl)tetrahydro-3-benzazepin-1-ols 21, 31, and 32 in a seven- to eight-step sequence. The phenols 32 reveal slightly higher GluN2B affinity than the methyl ethers 21. The GluN2B affinity increases in the order (1R,2S) < (1S,2S) < (1S,2R) < (1R,2R). The stereoisomeric phenols (R,R)-32 and (S,R)-32 show the highest GluN2B affinity and the highest cytoprotective activity. Both compounds represent GluN2B selective allosteric NMDA receptor antagonists. Docking of the 3-benzazepin-1-ols into the ifenprodil binding site of the crystallized GluN1b/GluN2B N-terminal domains led to free binding energies, which correlate nicely with the experimentally determined GluN2B affinities. The similar GluN2B affinity of the stereoisomeric phenols (S,S)-32, (R,R)-32, and (S,R)-32 is explained by different binding modes of the 3-benzazepine scaffold. The benzyl ethers 31 reveal unexpectedly high GluN2B affinity but do not show cytoprotective effects. The additional benzyl moiety of 31 binds into a previously unrecognized lipophilic subpocket.

Evaluation of Homobivalent Carbolines as Designed Multiple Ligands for the Treatment of Neurodegenerative Disorders.

Neurodegenerative diseases represent a challenge for biomedical research due to their high prevalence and lack of mechanism-based treatments. Because of the complex pathology of neurodegenerative disorders, multifunctional drugs have been increasingly recognized as potential treatments. We identified homobivalent γ-carbolinium salts as potent inihitors of both cholinesterases, N-methyl-D-aspartate receptors, and monoamine oxidases. Homobivalent γ-carbolines displayed similar structure-activity relationships on all tested targets and may present promising designed multiple ligands for the treatment of neurodegenerative disorders.

Developmental gene regulation by an ancient intercellular communication system in social amoebae

The social amoebae (Dictyostelia) use quorum sensing-like communication systems to coordinate the periodic transition from uni- to multicellularity. The monophyletic descent of the Dictyostelia provides a unique opportunity to study the origin and adaptive evolution of such intercellular communication systems. We determined that the ability of aggregation-competent cells to respond to the intercellular messenger glorin occurred in the most ancient taxa of the Dictyostelia. We show using Illumina sequencing technology that glorin mediates rapid changes in gene expression at the transition from vegetative growth to aggregation. We conclude that peptide-based communication is the most ancient form of intercellular signaling in the evolution of multicellularity in the social amoebae, but has been repeatedly replaced by other communication systems during the monophyletic evolution of the social amoebae. Glorin communication has parallels with quorum sensing in that the molecule diffuses into the field, stimulates gene expression in receptive cells and coordinates a population-wide response.

Effects of Leuzea carthamoides on human breast adenocarcinoma MCF-7 cells determined by gene expression profiling and functional assays.

Products derived from roots of Leuzea carthamoides (Maral root) are being promoted as dietary supplements with anti-aging, adaptogenic and anabolic activity, without much scientific evidence. We investigated the effects of a lipophilic Leuzea root extract and the major phytoecdysteroid, 20-hydroxyecdysone, in human breast adenocarcinoma MCF-7 cells. Cell proliferation was inhibited by the extract (IC50 = 30 microg/mL) but not by 20-hydroxyecdysone. Genome-wide expression profiling using Affymetrix HG U133 Plus 2.0 microarrays was carried out to analyse effects at the transcriptional level. 241 genes appeared to be differentially expressed after Leuzea treatment, more than after treatment with either 17beta-estradiol or tamoxifen. Transcripts linked to cell cycle regulation and DNA replication were highly over-represented and regulated in an anti-proliferative manner. Genes involved in apoptosis were regulated in a pro-apoptotic manner. Expression levels of several oxidoreductase transcripts were strongly induced, most prominent CYP1A1, known to be regulated via the aryl hydrocarbon receptor pathway. An XRE-dependent reporter gene assay confirmed the AhR-agonistic activity of the Leuzea root extract, whereas 20-hydroxyecdysone was not active. Leuzea extract also inhibited 5alpha-reductase, type II. While the extract significantly modulates cellular activities, the phytoecdysteroids, are most likely not the active principles of L. carthamoides.

1‐Benzyl‐1,2,3,4‐Tetrahydro‐β‐Carboline as Channel Blocker of N‐Methyl‐d‐Aspartate Receptors

N‐methyl‐d‐aspartate (NMDA) receptors belong to the family of ligand‐gated ion channels and are important for synaptic plasticity and memory function. The NMDA receptor consists of a voltage‐dependent channel permeable to Ca2+ and Na+. In Alzheimer’s disease, neuronal degeneration is thought to cause an excessive release of glutamate to the extracellular space, which may in turn mediate prolonged stimulation of the NMDA receptor complex and, as a consequence, excessive calcium influx into neuronal cells, leading to subsequent cell death. This process is called glutamate‐induced excitotoxicity, and its inhibition may present an effective antidementive therapy. We found that 1‐benzyl‐1,2,3,4‐tetrahydro‐β‐carboline (1a) blocked NMDA receptor–mediated, glutamate‐induced excitotoxicity with an IC50 value of 27.4 μm, whereas the closely related 1‐phenyl‐1,2,3,4‐tetrahydro‐β‐carboline (1b) had no effect. The binding modes of the reported compounds were studied by in silico docking simulations. We demonstrate that compounds (S)‐1a and (R)‐1a, but not (S)‐1b and (R)‐1b, have the same characteristics of potent NMDA receptor blockers, because they establish the main interactions inside the vestibule region of the receptor described previously for the high‐affinity NMDA receptor blocker, MK‐801.

Antimicrobial, antiproliferative, cytotoxic, and tau inhibitory activity of rubellins and caeruleoramularin produced by the phytopathogenic fungus Ramularia collo-cygni.

Photodynamically active anthraquinone derivatives produced by the phytopathogenic fungus Ramularia collo-cygni are known to cause a barley leaf-spot disease, but data about light-dependent and independent bioactivity have been sparse to date. We therefore conducted for the first time a broad bioactivity profiling of rubellins B, C, D, and E and caeruleoramularin. Antibacterial but not antiviral activity is reported with light-dependent increase. Furthermore, when tested without illumination, compounds exerted antiproliferative and cytotoxic activity in a series of human tumor cell lines. Inhibition of tau protein assembly was observed as well.