Stefanie König

Predicting Spontaneous Big Five Behavior with Implicit Association Tests

According to theories brought forward recently, implicit measures based on reaction times, for instance Implicit Association Tests (IATs), should predict spontaneous behavior better than explicit measures. We applied five IATs to the measurement of the Big Five personality factors and tested whether the IATs predicted spontaneous behavior. The results show that, although implicit and explicit measures of personality dimensions were related at times, the correlations between them and with behavior suggest that these constructs should be differentiated. IATs predicted spontaneous behavior, but explicit measures did not. In contrast, explicit measures, but not IATs, were related to transparent self-ratings of behavior.

Indirubin Core Structure of Glycogen Synthase Kinase-3 Inhibitors as Novel Chemotype for Intervention with 5-Lipoxygenase

The enzymes 5-lipoxygenase (5-LO) and glycogen synthase kinase (GSK)-3 represent promising drug targets in inflammation. We made use of the bisindole core of indirubin, present in GSK-3 inhibitors, to innovatively target 5-LO at the ATP-binding site for the design of dual 5-LO/GSK-3 inhibitors. Evaluation of substituted indirubin derivatives led to the identification of (3Z)-6-bromo-3-[(3E)-3-hydroxyiminoindolin-2-ylidene]indolin-2-one (15) as a potent, direct, and reversible 5-LO inhibitor (IC50 = 1.5 μM), with comparable cellular effectiveness on 5-LO and GSK-3. Together, we present indirubins as novel chemotypes for the development of 5-LO inhibitors, the interference with the ATP-binding site as a novel strategy for 5-LO targeting, and dual 5-LO/GSK-3 inhibition as an unconventional and promising concept for anti-inflammatory intervention.

Structure and Biosynthetic Assembly of Gulmirecins, Macrolide Antibiotics from the Predatory Bacterium Pyxidicoccus fallax

The gulmirecins constitute a new class of glycosylated macrolides that were isolated from the predatory bacterium Pyxidicoccus fallax HKI 727. Their structures were solved by a combination of NMR spectroscopic experiments and chemical derivatization. Analysis of the annotated gulmirecin gene cluster complemented the configurational assignment and provided insights into the stereochemical course of the biosynthetic assembly. The gulmirecins exhibit strong activity against staphylococci, including methicillin-resistant Staphylococcus aureus, but no cytotoxic effects on human cells.

Myxochelins target human 5-lipoxygenase.

Extracts of the predatory myxobacterium Pyxidicoccus fallax HKI 727 showed antiproliferative effects on leukemic K-562 cells. Bioactivity-guided fractionation led to the isolation of the bis-catechol myxochelin A and two new congeners. The biosynthetic origin of myxochelins C and D was confirmed by feeding studies with isotopically labeled precursors. Pharmacological testing revealed human 5-lipoxygenase (5-LO) as a molecular target of the myxochelins. In particular, myxochelin A efficiently inhibited 5-LO activity with an IC50 of 1.9 μM and reduced the proliferation of K-562 cells at similar concentrations.

Harnessing Enzymatic Promiscuity in Myxochelin Biosynthesis for the Production of 5‐Lipoxygenase Inhibitors

The siderophore myxochelin A is a potent inhibitor of human 5‐lipoxygenase (5‐LO). To clarify whether the iron‐chelating properties of myxochelin A are responsible for this activity, several analogues of this compound were generated in the native producer Pyxidicoccus fallax by precursor‐directed biosynthesis. Testing in a cell‐free assay unveiled three derivatives with bioactivity comparable with that of myxochelin A. Furthermore, it became evident that inhibition of 5‐LO by myxochelins does not correlate with their iron affinities.

Melleolides induce rapid cell death in human primary monocytes and cancer cells

The melleolides are structurally unique and bioactive natural products of the basidiomycete genus Armillaria. Here, we report on cytotoxic effects of melleolides from Armillaria mellea towards non-transformed human primary monocytes and human cancer cell lines, respectively. In contrast to staurosporine or pretubulysin that are less cytotoxic for monocytes, the cytotoxic potency of the active melleolides in primary monocytes is comparable to that in cancer cells. The onset of the cytotoxic effects of melleolides was rapid (within <1 h), as compared to the apoptosis inducer staurosporine, the protein biosynthesis inhibitor cycloheximide, and the DNA transcription inhibitor actinomycin D (>5 h, each). Side-by-side comparison with the detergent triton X-100 and staurosporine in microscopic and flow cytometric analysis studies as well as analysis of the viability of mitochondria exclude cell lysis and apoptosis as relevant or primary mechanisms. Our results rather point to necrotic features of cell death mediated by an as yet elusive but rapid mechanism.

Pharmacological profile and efficiency in vivo of diflapolin, the first dual inhibitor of 5-lipoxygenase-activating protein and soluble epoxide hydrolase

Arachidonic acid (AA) is metabolized to diverse bioactive lipid mediators. Whereas the 5-lipoxygenase-activating protein (FLAP) facilitates AA conversion by 5-lipoxygenase (5-LOX) to pro-inflammatory leukotrienes (LTs), the soluble epoxide hydrolase (sEH) degrades anti-inflammatory epoxyeicosatrienoic acids (EETs). Accordingly, dual FLAP/sEH inhibition might be advantageous drugs for intervention of inflammation. We present the in vivo pharmacological profile and efficiency of N-[4-(benzothiazol-2-ylmethoxy)-2-methylphenyl]-N′-(3,4-dichlorophenyl)urea (diflapolin) that dually targets FLAP and sEH. Diflapolin inhibited 5-LOX product formation in intact human monocytes and neutrophils with IC50 = 30 and 170 nM, respectively, and suppressed the activity of isolated sEH (IC50 = 20 nM). Characteristic for FLAP inhibitors, diflapolin (I) failed to inhibit isolated 5-LOX, (II) blocked 5-LOX product formation in HEK cells only when 5-LOX/FLAP was co-expressed, (III) lost potency in intact cells when exogenous AA was supplied, and (IV) prevented 5-LOX/FLAP complex assembly in leukocytes. Diflapolin showed target specificity, as other enzymes related to AA metabolism (i.e., COX1/2, 12/15-LOX, LTA4H, LTC4S, mPGES1, and cPLA2) were not inhibited. In the zymosan-induced mouse peritonitis model, diflapolin impaired vascular permeability, inhibited cysteinyl-LTs and LTB4 formation, and suppressed neutrophil infiltration. Diflapolin is a highly active dual FLAP/sEH inhibitor in vitro and in vivo with target specificity to treat inflammation-related diseases.

Myxochelin-Inspired 5-Lipoxygenase Inhibitors - Synthesis and Biological Evaluation

A total of 48 analogues of the natural product myxochelin A were prepared and evaluated for their inhibitory effects on human 5‐lipoxygenase in both cell‐free and cell‐based assays. Structure–activity relationship analysis revealed that the secondary alcohol function and only chiral center of myxochelin A is not required for biological activity. By expanding the diaminoalkane linker of the two aromatic residues it was possible to generate a myxochelin derivative with superior activity against 5‐lipoxygenase in intact cells.

Endogenous metabolites of vitamin E limit inflammation by targeting 5-lipoxygenase

Systemic vitamin E metabolites have been proposed as signaling molecules, but their physiological role is unknown. Here we show, by library screening of potential human vitamin E metabolites, that long-chain ω-carboxylates are potent allosteric inhibitors of 5-lipoxygenase, a key enzyme in the biosynthesis of chemoattractant and vasoactive leukotrienes. 13-((2R)-6-hydroxy-2,5,7,8-tetramethylchroman-2-yl)-2,6,10-trimethyltridecanoic acid (α-T-13′-COOH) can be synthesized from α-tocopherol in a human liver-on-chip, and is detected in human and mouse plasma at concentrations (8–49 nM) that inhibit 5-lipoxygenase in human leukocytes. α-T-13′-COOH accumulates in immune cells and inflamed murine exudates, selectively inhibits the biosynthesis of 5-lipoxygenase-derived lipid mediators in vitro and in vivo, and efficiently suppresses inflammation and bronchial hyper-reactivity in mouse models of peritonitis and asthma. Together, our data suggest that the immune regulatory and anti-inflammatory functions of α-tocopherol depend on its endogenous metabolite α-T-13′-COOH, potentially through inhibiting 5-lipoxygenase in immune cells.Vitamin E metabolites are proposed to have signalling capacity, but how they may regulate immune responses is still unclear. Here the authors show that a vitamin E metabolite, α-T-13′-COOH, can inhibit 5-lipoxygenase and thereby suppress the synthesis of lipid mediators of immune activation and inflammatory responses.

Triterpene Acids from Frankincense and Semi-Synthetic Derivatives That Inhibit 5-Lipoxygenase and Cathepsin G

Age-related diseases, such as osteoarthritis, Alzheimer’s disease, diabetes, and cardiovascular disease, are often associated with chronic unresolved inflammation. Neutrophils play central roles in this process by releasing tissue-degenerative proteases, such as cathepsin G, as well as pro-inflammatory leukotrienes produced by the 5-lipoxygenase (5-LO) pathway. Boswellic acids (BAs) are pentacyclic triterpene acids contained in the gum resin of the anti-inflammatory remedy frankincense that target cathepsin G and 5-LO in neutrophils, and might thus represent suitable leads for intervention with age-associated diseases that have a chronic inflammatory component. Here, we investigated whether, in addition to BAs, other triterpene acids from frankincense interfere with 5-LO and cathepsin G. We provide a comprehensive analysis of 17 natural tetra- or pentacyclic triterpene acids for suppression of 5-LO product synthesis in human neutrophils. These triterpene acids were also investigated for their direct interference with 5-LO and cathepsin G in cell-free assays. Furthermore, our studies were expanded to 10 semi-synthetic BA derivatives. Our data reveal that besides BAs, several tetra- and pentacyclic triterpene acids are effective or even superior inhibitors of 5-LO product formation in human neutrophils, and in parallel, inhibit cathepsin G. Their beneficial target profile may qualify triterpene acids as anti-inflammatory natural products and pharmacological leads for intervention with diseases related to aging.