Orexin receptor agonist Yan 7874 is a weak agonist of orexin/hypocretin receptors and shows orexin receptor-independent cytotoxicity

Two promising lead structures of small molecular orexin receptor agonist have been reported, but without detailed analyses of the pharmacological properties. One of them, 1(3,4-dichloropheny1)-242-imino-3-(4-methylbenzy1)-2,3-dihydro-1H-benzo[climidazol-1-yl] ethan-1-ol (Yan 7874), is commercially available, and we set out to analyze its properties. As test system we utilized human OX1 and OX2 orexin receptor -expressing Chinese hamster ovary (CHO) K1 cells as well as control CHO-K1 and neuro-2a neuroblastoma cells. Gq-coupling was assessed by measurement of intracellular Ca2+ and phospholipase C activity, and the coupling to G(i) and G(s) by adenylyl cyclase inhibition and stimulation, respectively. At concentrations above 1 pM, strong Ca' and low phospholipase C responses to Yan 7874 were observed in both OX1- and OX2-expressing cells. However, a major fraction of the response was not mediated by orexin receptors, as determined utilizing the nonselective orexin receptor antagonist N-biphenyl-2-y1-1-{[(1-methyl-1H-benzimidazol-2-y1) sulfanyl]acetyl}-L-prolinamide (TCS 1102) as well as control CHO-K1 cells. Yan 7874 did not produce any specific adenylyl cyclase response. Some experiments suggested an effect on cell viability by Yan 7874, and we thus analyzed this. Within a few hours of exposure, Yan 7874 markedly changed cell morphology (shrunken, rich in vacuoles), reduced growth, promoted cell detachment, and induced necrotic cell death. The effect was equal in cells expressing orexin receptors or not. Thus, Yan 7874 is a weak partial agonist of orexin receptors. It also displays strong off -target effects in the same concentration range, culminating in necrotic cell demise. This makes Yan 7874 unsuitable as orexin receptor agonist.Peer reviewe

Prolyl oligopeptidase inhibition by KYP-2407 increases alpha-synuclein fibril degradation in neuron-like cells

Growing evidence emphasizes insufficient clearance of pathological alpha-synuclein (alpha SYN) aggregates in the progression of Parkinson's disease (PD). Consequently, cellular degradation pathways represent a potential therapeutic target. Prolyl oligopeptidase (PREP) is highly expressed in the brain and has been suggested to increase alpha SYN aggregation and negatively regulate the autophagy pathway. Inhibition of PREP with a small molecule inhibitor, KYP-2407, stimulates autophagy and reduces the oligomeric species of alpha SYN aggregates in PD mouse models. However, whether PREP inhibition has any effects on intracellular alpha SYN fibrils has not been studied before. In this study, the effect of KYP2407 on alpha SYN preformed fibrils (PFFs) was tested in SH-SY5Y cells and human astmcytes. Immunostaining analysis revealed that both cell types accumulated alpha SYN PFFs intracellularly but KYP-2047 decreased intracellular alpha SYN deposits only in SH-SY5Y cells, as astrocytes did not show any PREP activity. Western blot analysis confirmed the reduction of high molecular weight alpha SYN species in SH-SY5Y cell lysates, and secretion of aSYN from SH-SY5Y cells also decreased in the presence of KYP-2407. Accumulation of alpha SYN inside the SH-SY5Y cells resulted in an increase of the auto-lysosomal proteins p62 and LC3BII, as well as calpain 1 and 2, which have been shown to be associated with PD pathology. Notably, treatment with KYP-2407 significantly reduced p62 and LC3BII levels, indicating an increased autophagic flux, and calpain 1 and 2 levels returned to normal in the presence of KYP-2407. Our findings indicate that PREP inhibition can potentially be used as therapy to reduce the insoluble intracellular alpha SYN aggregates

Prolyl oligopeptidase inhibition by KYP-2407 increases alpha-synuclein fibril degradation in neuron-like cells

Corrigendum: Biomedicine & Pharmacotherapy 133 (2021) 111019 WOS:000604603600003Growing evidence emphasizes insufficient clearance of pathological alpha-synuclein (alpha SYN) aggregates in the progression of Parkinson's disease (PD). Consequently, cellular degradation pathways represent a potential therapeutic target. Prolyl oligopeptidase (PREP) is highly expressed in the brain and has been suggested to increase alpha SYN aggregation and negatively regulate the autophagy pathway. Inhibition of PREP with a small molecule inhibitor, KYP-2407, stimulates autophagy and reduces the oligomeric species of alpha SYN aggregates in PD mouse models. However, whether PREP inhibition has any effects on intracellular alpha SYN fibrils has not been studied before. In this study, the effect of KYP2407 on alpha SYN preformed fibrils (PFFs) was tested in SH-SY5Y cells and human astmcytes. Immunostaining analysis revealed that both cell types accumulated alpha SYN PFFs intracellularly but KYP-2047 decreased intracellular alpha SYN deposits only in SH-SY5Y cells, as astrocytes did not show any PREP activity. Western blot analysis confirmed the reduction of high molecular weight alpha SYN species in SH-SY5Y cell lysates, and secretion of aSYN from SH-SY5Y cells also decreased in the presence of KYP-2407. Accumulation of alpha SYN inside the SH-SY5Y cells resulted in an increase of the auto-lysosomal proteins p62 and LC3BII, as well as calpain 1 and 2, which have been shown to be associated with PD pathology. Notably, treatment with KYP-2407 significantly reduced p62 and LC3BII levels, indicating an increased autophagic flux, and calpain 1 and 2 levels returned to normal in the presence of KYP-2407. Our findings indicate that PREP inhibition can potentially be used as therapy to reduce the insoluble intracellular alpha SYN aggregates.Peer reviewe

Pharmacological characterization of the orexin/hypocretin receptor agonist Nag 26

One promising series of small-molecule orexin receptor agonists has been described, but the molecular pharmacological properties, i.e. ability and potency to activate the different orexin receptor-regulated signal pathways have not been reported for any of these ligands. We have thus here assessed these properties for the most potent ligand of the series, 4'-methoxy-N,N-dimethyl-3'4N-(3-{[2-(3-methylbenzamido)ethyl]amino}phenyl sulfamoy1]-(1,1'-biphenyl)-3-carboxamide (Nag 26). Chinese hamster ovary-K1 cells expressing human orexin receptor subtypes OX1 and OX2 were used. Ca2+ elevation and cell viability and death were assessed by fluorescent methods, the extracellular signal-regulated kinase pathway by a luminescent Elk-1 reporter assay, and phospholipase C and adenylyl cyclase activities by radioactive methods. The data suggest that for the G(q)-dependent responses, Ca2+, phospholipase C and Elk-1, Nag 26 is a full agonist for both receptors, though of much lower potency. However, saturation was not always reached for OX1, partially due to Nag 26s low solubility and partially because the response decreased at high concentrations. The latter occurs in the same range as some reduction of cell viability, which is independent of orexin receptors. Based on the EC50, Nag 26 was OX2 selective by 20-200 fold in different assays, with some indication of biased agonism (as compared to orexin-A). Nag 26 is a potent orexin receptor agonist with a largely similar pharmacological profile as orexin-A. However, its weaker potency (low-mid micromolar) and low water solubility as well as the non-specific effect in the mid-micromolar range may limit its usefulness under physiological conditions.Peer reviewe

Characterization of a putative orexin receptor in Ciona intestinalis sheds light on the evolution of the orexin/hypocretin system in chordates

Abstract Tunicates are evolutionary model organisms bridging the gap between vertebrates and invertebrates. A genomic sequence in Ciona intestinalis (CiOX) shows high similarity to vertebrate orexin receptors and protostome allatotropin receptors (ATR). Here, molecular phylogeny suggested that CiOX is divergent from ATRs and human orexin receptors (hOX1/2). However, CiOX appears closer to hOX1/2 than to ATR both in terms of sequence percent identity and in its modelled binding cavity, as suggested by molecular modelling. CiOX was heterologously expressed in a recombinant HEK293 cell system. Human orexins weakly but concentration-dependently activated its Gq signalling (Ca2+ elevation), and the responses were inhibited by the non-selective orexin receptor antagonists TCS 1102 and almorexant, but only weakly by the OX1-selective antagonist SB-334867. Furthermore, the 5-/6-carboxytetramethylrhodamine (TAMRA)-labelled human orexin-A was able to bind to CiOX. Database mining was used to predict a potential endogenous C. intestinalis orexin peptide (Ci-orexin-A). Ci-orexin-A was able to displace TAMRA-orexin-A, but not to induce any calcium response at the CiOX. Consequently, we suggested that the orexin signalling system is conserved in Ciona intestinalis, although the relevant peptide-receptor interaction was not fully elucidated

Different types of cell death in CHO cells.

<p>Ctrl CHO cells (not expressing orexin receptor), stained with Hoechst, FDA and PI, were photographed after 24 h of treatment with 10 μM Yan 7874 or 100 nM staurosporine. The brightfield images were taken with differential interference contrast; however, this effect is not very strong as 96-well plates were used.</p

Morphological indications of cell death.

<p>Ctrl CHO cells (not expressing orexin receptor) were photographed under a phase contrast microscope after a 5-h treatment with 10 and 30 μM Yan 7874.</p

Quantitation of cell viability and demise upon Yan 7874 exposure in CHO cells.

<p>(A) Concentration-response relationship of Yan 7874. (B) The impact of the inhibition of caspases and protein synthesis. Ctrl CHO cells (not expressing orexin receptors) were cultured on 96-well plates for 24 after which they were treated with the compounds as indicated. After another 24 h, the cells were stained with Hoechst for total cell number, FDA for living cells, and PI for necrotic cells. (A) The values for total and living cells were normalized to the control, where essentially all cells are alive (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0178526#pone.0178526.g006" target="_blank">Fig 6</a>) and thus the specific fluorescence is maximal. PI-stained cells could not be normalized in this way, since the specific PI fluorescence in control cells was essentially 0, and thus small deviations in the background subtraction would have introduced much noise. Therefore, the values were normalized to the PI fluorescence (or PI/Hoechst fluorescence ratio) in cells treated with 30 μM Yan 7874. "FDA/Hoechst" stands for the FDA reading divided by the Hoechst reading, indicating the proportion of living cells of all cells. "PI/Hoechst" similarly gives the proportion of necrotic/secondary necrotic cells among all cells. <i>N</i> = 6. (B) The effect of the pan-caspase inhibitor Q-VD-Oph and the protein synthesis inhibitor CHX on the response to Yan 7874 (10 μM). For the sake of clarity, only the PI/Hoechst fluorescence ratios, normalized to the control response to 10 μM Yan 7874 (in the absence of Q-VD-Oph or CHX), are shown. The ratios were always calculated separately for each independent sample before averaging. <i>N</i> = 8.</p