Moderately lipophilic 2-(Het)aryl-6-dithioacetals, 2-phenyl-1,4-benzodioxane-6-dithioacetals and 2-phenylbenzofuran-5-dithioacetals: Synthesis and primary evaluation as potential antidiabetic AMPK-activators.

Since the 1950's, AMP-kinase (AMPK) has been used as a promising target for the development of antidiabetic drugs against Type 2 diabetes mellitus (T2D). Indeed, the canonical antidiabetic drug metformin recruits, at least partially, AMPK activation for its therapeutic effect. Herein we present design and synthesis of 20 novel relatively polar cyclic and acyclic dithioacetals of 2-(Het)arylchroman-6-carbaldehydes, 2-phenyl-1,4-benzodioxane-6-carbaldehyde, and 2-phenylbenzofuran-5-carbaldehyde, which were developed as potential AMPK activators. Three of the synthesized dithioacetals demonstrated significant enhancement (≥70%) of glucose uptake in rat L6 myotubes. Noteworthy, one of the dithioacetals, namely 4-(6-(1,3-dithian-2-yl)chroman-2-yl)pyridine, exhibited high potency comparing to other molecules. It increased the rate of glucose uptake in rat L6 myotubes and augmented insulin secretion from rat INS-1E cells in pharmacological relevant concentrations (up to 2 µM). Both effects were mediated by activation of AMPK. In addition, the compound showed excellent pharmacokinetic profile in healthy mice, including maximal oral bioavailability. Such bifunctionality (increased glucose uptake and insulin secretion) can be used as a starting point for the development of a novel class of antidiabetic drugs with dual activity that is relevant for T2D treatment.

Inhibiting the copper efflux system in microbes as a novel approach for developing antibiotics.

Five out of six people receive at least one antibiotic prescription per year. However, the ever-expanding use of antibiotics in medicine, agriculture, and food production has accelerated the evolution of antibiotic-resistant bacteria, which, in turn, made the development of novel antibiotics based on new molecular targets a priority in medicinal chemistry. One way of possibly combatting resistant bacterial infections is by inhibiting the copper transporters in prokaryotic cells. Copper is a key element within all living cells, but it can be toxic in excess. Both eukaryotic and prokaryotic cells have developed distinct copper regulation systems to prevent its toxicity. Therefore, selectively targeting the prokaryotic copper regulation system might be an initial step in developing next-generation antibiotics. One such system is the Gram-negative bacterial CusCFBA efflux system. CusB is a key protein in this system and was previously reported to play an important role in opening the channel for efflux via significant structural changes upon copper binding while also controlling the assembly and disassembly process of the entire channel. In this study, we aimed to develop novel peptide copper channel blockers, designed by in silico calculations based on the structure of CusB. Using a combination of magnetic resonance spectroscopy and various biochemical methods, we found a lead peptide that promotes copper-induced cell toxicity. Targeting copper transport in bacteria has not yet been pursued as an antibiotic mechanism of action. Thus, our study lays the foundation for discovering novel antibiotics.

Neuroligin-2-derived peptide-covered polyamidoamine-based (PAMAM) dendrimers enhance pancreatic ß-cells' proliferation and functions.

Pancreatic ß-cell membranes and presynaptic areas of neurons contain analogous protein complexes that control the secretion of bioactive molecules. These complexes include the neuroligins (NLs) and their binding partners, the neurexins (NXs). It has been recently reported that both insulin secretion and the proliferation rates of ß-cells increase when cells are co-cultured with full-length NL-2 clusters. The pharmacological use of full-length protein is always problematic due to its unfavorable pharmacokinetic properties. Thus, NL-2-derived short peptide was conjugated to the surface of polyamidoamine-based (PAMAM) dendrimers. This nanoscale composite improved ß-cell functions in terms of the rate of proliferation, glucose-stimulated insulin secretion (GSIS), and functional maturation. This functionalized dendrimer also protected ß-cells under cellular stress conditions. In addition, various novel peptidomimetic scaffolds of NL-2-derived peptide were designed, synthesized, and conjugated to the surface of PAMAM in order to increase the biostability of the conjugates. However, after being covered by peptidomimetics, PAMAM dendrimers were inactive. Thus, the original peptide-based PAMAM dendrimer is a leading compound for continued research that might provide a unique starting point for designing an innovative class of antidiabetic therapeutics that possess a unique mode of action.

A Novel Phenylchromane Derivative Increases the Rate of Glucose Uptake in L6 Myotubes and Augments Insulin Secretion from Pancreatic Beta-Cells by Activating AMPK.

PURPOSE: A series of novel polycyclic aromatic compounds that augment the rate of glucose uptake in L6 myotubes and increase glucose-stimulated insulin secretion from beta-cells were synthesized. Designing these molecules, we have aimed at the two main pathogenic mechanisms of T2D, deficient insulin secretion and diminished glucose clearance. The ultimate purpose of this work was to create a novel antidiabetic drug candidate with bi-functional mode of action. METHODS: All presented compounds were synthesized, and characterized in house. INS-1E cells and L6 myoblasts were used for the experiments. The rate of glucose uptake, mechanism of action, level of insulin secretion and the druggability of the lead compound were studied. RESULTS: The lead compound (6-(1,3-dithiepan-2-yl)-2-phenylchromane), dose- and time-dependently at the low µM range increased the rate of glucose uptake in L6 myotubes and insulin secretion in INS-1E cells. The compound exerted its effects through the activation of the LKB1 (Liver Kinase B1)-AMPK pathway. In vitro metabolic parameters of this lead compound exhibited good druggability. CONCLUSIONS: We anticipate that bi-functionality (increased rate of glucose uptake and augmented insulin secretion) will allow the lead compound to be a starting point for the development of a novel class of antidiabetic drugs.

Mimicking Neuroligin-2 Functions in ß-Cells by Functionalized Nanoparticles as a Novel Approach for Antidiabetic Therapy.

Both pancreatic ß-cell membranes and presynaptic active zones of neurons include in their structures similar protein complexes, which are responsible for mediating the secretion of bioactive molecules. In addition, these membrane-anchored proteins regulate interactions between neurons and guide the formation and maturation of synapses. These proteins include the neuroligins (e.g., NL-2) and their binding partners, the neurexins. The insulin secretion and maturation of ß-cells is known to depend on their 3-dimensional (3D) arrangement. It was also reported that both insulin secretion and the proliferation rates of ß-cells increase when cells are cocultured with clusters of NL-2. Use of full-length NL-2 or even its exocellular domain as potential ß-cell functional enhancers is limited by the biostability and bioavailability issues common to all protein-based therapeutics. Thus, based on molecular modeling approaches, a short peptide with the potential ability to bind neurexins was derived from the NL-2 sequence. Here, we show that the NL-2-derived peptide conjugates onto innovative functional maghemite (γ-Fe2O3)-based nanoscale composite particles enhance ß-cell functions in terms of glucose-stimulated insulin secretion and protect them under stress conditions. Recruiting the ß-cells' "neuron-like" secretory machinery as a target for diabetes treatment use has never been reported before. Such nanoscale composites might therefore provide a unique starting point for designing a novel class of antidiabetic therapeutic agents that possess a unique mechanism of action.

Antiproliferative Effect of Novel Aminoacridine-based Compounds.

We tested the antiproliferative activity and mechanism of the action of several novel aminoacridine derivatives. Six different cancer cell lines were used to evaluate the potential cytotoxic effect of eleven aminoacridine-based molecules. A standard MTT assay was used for cell bioavailability analysis. Additionally, the potential cytotoxic effect of the tested compounds on non-cancer cells was investigated in rat skeletal muscle myotubes (L6) and in bovine aortic smooth muscle cells. In order to investigate whether the DNA binding activity of tested compounds correlated with their cytotoxic effect, circular dichroism (CD) measurement and DNA T4 ligase assay were performed. Finally, the potential mutagenic activity of the lead compound 5 was investigated. The cytotoxic effect of compound 5 in cancer cells was obtained in lower concentrations than the well-known: 9- aminoacridine based drug, amsacrine. The lead compound binds to DNA, but in a different mode than the parent molecules. Additionally, compound 5 was not cytotoxic in the effective range of concentrations in non-cancer cells. In identical concentrations, the parent compound (9-aminoacridine) and amsacrine were extremely toxic for both types of these normal cells. Finally, based on CD measurement and T4 ligase assay, it was confirmed that 5 binds to DNA but in different from the parent compounds manner. Important to mention, that compound 5 might have increased mutagenic activity which must be verified in vivo. Based on these in vitro results, we conclude that 5 is a more potent and more selective antiprolifirative compound than amsacrine. Compound 5 was also more effective in HepG2 and P-12 cells. Thus, 5 is suitable for future in vivo biological evaluation and its structure might be used as a basis for developing novel anticancer drugs.