41 research outputs found
Lithocholic Acid Is an Eph-ephrin Ligand Interfering with Eph-kinase Activation
Eph-ephrin system plays a central role in a large variety of human cancers. In
fact, alterated expression and/or de-regulated function of Eph-ephrin system
promotes tumorigenesis and development of a more aggressive and metastatic
tumour phenotype. In particular EphA2 upregulation is correlated with tumour
stage and progression and the expression of EphA2 in non-trasformed cells
induces malignant transformation and confers tumorigenic potential. Based on
these evidences our aim was to identify small molecules able to modulate
EphA2-ephrinA1 activity through an ELISA-based binding screening. We identified
lithocholic acid (LCA) as a competitive and reversible ligand inhibiting
EphA2-ephrinA1 interaction (Ki = 49 µM). Since each
ephrin binds many Eph receptors, also LCA does not discriminate between
different Eph-ephrin binding suggesting an interaction with a highly conserved
region of Eph receptor family. Structurally related bile acids neither inhibited
Eph-ephrin binding nor affected Eph phosphorylation. Conversely, LCA inhibited
EphA2 phosphorylation induced by ephrinA1-Fc in PC3 and HT29 human prostate and
colon adenocarcinoma cell lines (IC50 = 48 and
66 µM, respectively) without affecting cell viability or other receptor
tyrosine-kinase (EGFR, VEGFR, IGFR1β, IRKβ) activity. LCA did not
inhibit the enzymatic kinase activity of EphA2 at 100 µM (LANCE method)
confirming to target the Eph-ephrin protein-protein interaction. Finally, LCA
inhibited cell rounding and retraction induced by EphA2 activation in PC3 cells.
In conclusion, our findings identified a hit compound useful for the development
of molecules targeting ephrin system. Moreover, as ephrin signalling is a key
player in the intestinal cell renewal, our work could provide an interesting
starting point for further investigations about the role of LCA in the
intestinal homeostasis
Analyzing the regulation of metabolic pathways in human breast cancer
<p>Abstract</p> <p>Background</p> <p>Tumor therapy mainly attacks the metabolism to interfere the tumor's anabolism and signaling of proliferative second messengers. However, the metabolic demands of different cancers are very heterogeneous and depend on their origin of tissue, age, gender and other clinical parameters. We investigated tumor specific regulation in the metabolism of breast cancer.</p> <p>Methods</p> <p>For this, we mapped gene expression data from microarrays onto the corresponding enzymes and their metabolic reaction network. We used Haar Wavelet transforms on optimally arranged grid representations of metabolic pathways as a pattern recognition method to detect orchestrated regulation of neighboring enzymes in the network. Significant combined expression patterns were used to select metabolic pathways showing shifted regulation of the aggressive tumors.</p> <p>Results</p> <p>Besides up-regulation for energy production and nucleotide anabolism, we found an interesting cellular switch in the interplay of biosynthesis of steroids and bile acids. The biosynthesis of steroids was up-regulated for estrogen synthesis which is needed for proliferative signaling in breast cancer. In turn, the decomposition of steroid precursors was blocked by down-regulation of the bile acid pathway.</p> <p>Conclusion</p> <p>We applied an intelligent pattern recognition method for analyzing the regulation of metabolism and elucidated substantial regulation of human breast cancer at the interplay of cholesterol biosynthesis and bile acid metabolism pointing to specific breast cancer treatment.</p
Differences in Spontaneously Avoiding or Approaching Mice Reflect Differences in CB1-Mediated Signaling of Dorsal Striatal Transmission
Approach or avoidance behaviors are accompanied by perceptual vigilance for, affective reactivity to and behavioral predisposition towards rewarding or punitive stimuli, respectively. We detected three subpopulations of C57BL/6J mice that responded with avoiding, balancing or approaching behaviors not induced by any experimental manipulation but spontaneously displayed in an approach/avoidance conflict task. Although the detailed neuronal mechanisms underlying the balancing between approach and avoidance are not fully clarified, there is growing evidence that endocannabinoid system (ECS) plays a critical role in the control of these balancing actions. The sensitivity of dorsal striatal synapses to the activation of cannabinoid CB1 receptors was investigated in the subpopulations of spontaneously avoiding, balancing or approaching mice. Avoiding animals displayed decreased control of CB1 receptors on GABAergic striatal transmission and in parallel increase of behavioral inhibition. Conversely, approaching animals exhibited increased control of CB1 receptors and in parallel increase of explorative behavior. Balancing animals reacted with balanced responses between approach and avoidance patterns. Treating avoiding animals with URB597 (fatty acid amide hydrolase inhibitor) or approaching animals with AM251 (CB1 receptor inverse agonist) reverted their respective behavioral and electrophysiological patterns. Therefore, enhanced or reduced CB1-mediated control on dorsal striatal transmission represents the synaptic hallmark of the approach or avoidance behavior, respectively. Thus, the opposite spontaneous responses to conflicting stimuli are modulated by a different involvement of endocannabinoid signaling of dorsal striatal neurons in the range of temperamental traits related to individual differences
Anticonvulsant potencies of the enantiomers of the neurosteroids androsterone and etiocholanolone exceed those of the natural forms
RATIONALE: Androsterone [(3α,5α)-3-hydroxyandrostan-17-one; 5α,3α-A] and its 5β-epimer etiocholanolone [(3α,5β)-3-hydroxyandrostan-17-one; 5β,3α-A)], the major excreted metabolites of testosterone, are neurosteroid positive modulators of GABA(A) receptors. Such neurosteroids typically show enantioselectivity in which the natural form is more potent than the corresponding unnatural enantiomer. For 5α,3α-A and 5β,3α-A, the unnatural enantiomers are more potent at GABA(A) receptors than the natural forms. OBJECTIVES: The aim of this study was to compare the anticonvulsant potencies and time courses of 5α,3α-A and 5β,3α-A with their enantiomers in mouse seizure models. METHODS: Steroids were administered intraperitoneally to male NIH Swiss mice 15 min (or up to 6 h in time course experiments) prior to administration of an electrical stimulus in the 6-Hz or maximal electroshock (MES) seizure tests or the convulsant pentylenetetrazol (PTZ). RESULTS: In the 6-Hz test, the ED(50) values of ent-5α,3α-A was 5.0 mg/kg whereas the value for 5α,3α-A was 12.1 mg/kg; the corresponding values in the PTZ seizure test were 22.8 and 51.8 mg/kg. Neurosteroid GABA(A) receptor positive allosteric modulators are generally weak in the MES test and this was confirmed in the present study. However, the atypical relative potency relationship was maintained with ED(50) values of 140 and 223 mg/kg for ent-5α,3α- A and 5α,3α-A, respectively. Similar relationships were obtained for the 5β-isomers, except that the enantioselectivity was accentuated. In the 6-Hz and PTZ tests, the ED(50) values of ent-5β,3α-A were 11.8 and 20.4 mg/kg whereas the values for 5β,3α-A were 57.6 and 109.1 mg/kg. Protective activity in the 6-Hz test of ent-5α,3α-A persisted for somewhat longer (~5 h) than for 5α,3α-A (~4 h); protection by ent-5β,3α-A also persisted longer (~3 h) than for 5β,3α-A (~2 h). CONCLUSIONS: The unnatural enantiomers of 17-keto androgen class neurosteroids have greater in vivo potency and a longer duration of action than their natural counterparts. The more prolonged duration of action of the unnatural enantiomers could reflect reduced susceptibility to metabolism. Unnatural enantiomers of androgen class neurosteroids could have therapeutic utility and may provide advantages over the corresponding natural isomers due to enhanced potency and improved pharmacokinetic characteristics