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The limited number of medicinal products available to treat of fungal infections makes control of fungal pathogens problematic, especially since the number of fungal resistance incidents increases. Given the high costs and slow development of new antifungal treatment options, repurposing of already known compounds is one of the proposed strategies. The objective of this study was to perform in vitro experimental tests of already identified lead compounds in our previous in silico drug repurposing study, which had been conducted on the known Drugbank database using a seven-step procedure which includes machine learning and molecular docking. This study identifies siramesine as a novel antifungal agent. This novel indication was confirmed through in vitro testing using several yeast species and one mold. The results showed susceptibility of Candida species to siramesine with MIC at concentration 12.5 µg/mL, whereas other candidates had no antifungal activity. Siramesine was also effective against in vitro biofilm formation and already formed biofilm was reduced following 24 h treatment with a MBEC range of 50–62.5 µg/mL. Siramesine is involved in modulation of ergosterol biosynthesis in vitro, which indicates it is a potential target for its antifungal activity. This implicates the possibility of siramesine repurposing, especially since there are already published data about nontoxicity. Following our in vitro results, we provide additional in depth in silico analysis of siramesine and compounds structurally similar to siramesine, providing an extended lead set for further preclinical and clinical investigation, which is needed to clearly define molecular targets and to elucidate its in vivo effectiveness as well.

Drug addiction is a chronic, debilitating disease that affects millions of people around the world causing a substantial societal burden. Despite decades of research efforts, treatment possibilities remain limited and relapse represents the most treatment-resistant element. Neurosteroid sigma-1 receptors have been meticulously studied in psychostimulant reinforced Pavlovian learning, while the sigma-2 receptor subtype has remained unexplored. Recent development of selective sigma-2 receptor ligands have now made it possible to investigate if the sigma-2 receptor system is a potential target to treat drug addiction. We examined the effect of the sigma-2 receptor agonist Siramesine (Lu 28-179) on cocaine-associated locomotion, Pavlovian learning, and reward neurocircuitry using electrophysiology recordings and in vivo microdialysis. We found that Siramesine significantly attenuated conditioned place preference acquisition and expression, as well as it completely blocked cocaine-primed reinstatement. Siramesine, in a similar manner as the selective sigma-1 receptor antagonist BD 1063, decreased acute locomotor responses to cocaine. Immunohistochemistry suggests co-expression of progesterone receptor membrane component 1/sigma-2 receptors and vesicular glutamate transporter 1 in presynaptic boutons of the nucleus accumbens (NAc). Whole-cell voltage clamp recordings of neurons in the NAc indicated that Siramesine decreases the presynaptic release probability of glutamate. Further, we demonstrated, via in vivo microdialysis, that Siramesine significantly decreased cocaine-evoked dopamine release in the striatum of freely moving mice. Collectively, these findings demonstrate that sigma-2 receptors regulate neurocircuitry responsible for positive reinforcement and thereby play a role in cocaine-reinforced Pavlovian behaviors.

Drug addiction is a chronic, debilitating disease that affects millions of people around the world causing a substantial societal burden. Despite decades of research efforts, treatment possibilities remain limited and relapse represents the most treatmentresistant element. Neurosteroid sigma-1 receptors have been meticulously studied in psychostimulant reinforced Pavlovian learning, while the sigma-2 receptor subtype has remained unexplored. Recent development of selective sigma-2 receptor ligands have now made it possible to investigate if the sigma-2 receptor system is a potential target to treat drug addiction. We examined the effect of the sigma-2 receptor agonist Siramesine (Lu 28-179) on cocaine-associated locomotion, Pavlovian learning, and reward neurocircuitry using electrophysiology recordings and in vivo microdialysis. We found that Siramesine significantly attenuated conditioned place preference acquisition and expression, as well as it completely blocked cocaine-primed reinstatement. Siramesine, in a similar manner as the selective sigma-1 receptor antagonist BD 1063, decreased acute locomotor responses to cocaine. Immunohistochemistry suggests coexpression of progesterone receptor membrane component 1/sigma-2 receptors and vesicular glutamate transporter 1 in presynaptic boutons of the nucleus accumbens (NAc). Whole-cell voltage clamp recordings of neurons in the NAc indicated that Siramesine decreases the presynaptic release probability of glutamate. Further, we demonstrated, via in vivo microdialysis, that Siramesine significantly decreased cocaineevoked dopamine release in the striatum of freely moving mice. Collectively, these findings demonstrate that sigma-2 receptors regulate neurocircuitry responsible for positive reinforcement and thereby play a role in cocaine-reinforced Pavlovian behaviors. [ABSTRACT FROM AUTHOR]

Background: Glioblastoma is the most frequent and most malignant brain tumor with the patients having a median survival of only 14.6 months. Although glioblastoma patients are treated with surgery, radiation and chemotherapy recurrence is inevitable. A stem-like population of radio- and chemoresistant brain tumor-initiating cells combined with the invasive properties of the tumors is believed to be critical for treatment resistance. In the present study, the aim was to investigate the effect of a novel therapeutic strategy using the lysosomotropic detergent siramesine on glioblastomas.Methods: Standard glioma cell lines and patient-derived spheroids cultures with tumor-initiating stem-like cells were used to investigate effects of siramesine on proliferation and cell death. Responsible mechanisms were investigated by inhibitors of caspases and cathepsins. Effects of siramesine on migrating tumor cells were investigated by a flat surface migration assay and by implanting spheroids into organotypic rat brain slice cultures followed by confocal time-lapse imaging. Finally the effect of siramesine was investigated in an orthotopic mouse glioblastoma model. Results obtained in vitro and in vivo were confirmed by immunohistochemical staining of histological sections of spheroids, spheroids in brain slice cultures and tumors in mice brains.Results: The results showed that siramesine killed standard glioma cell lines in vitro, and loss of acridine orange staining suggested a compromised lysosomal membrane. Co-treatment of the cell lines with inhibitors of caspases and cathepsins suggested differential involvement in cell death. Siramesine caused tumor cell death and reduced secondary spheroid formation of patient-derived spheroid cultures. In the flat surface migration model siramesine caused tumor cell death and inhibited tumor cell migration. This could not be reproduced in the organotypic three dimensional spheroid-brain slice culture model or in the mice xenograft model.Conclusions: In conclusion the in vitro results obtained with tumor cells and spheroids suggest a potential of lysosomal destabilizing drugs in killing glioblastoma cells, but siramesine was without effect in the organotypic spheroid-brain slice culture model and the in vivo xenograft model. [ABSTRACT FROM AUTHOR]

Mast cells are known to have a detrimental impact on numerous types of inflammatory skin diseases such as contact dermatitis, atopic eczema and cutaneous mastocytosis. Regimens that dampen skin mast cell-mediated activities can thus offer an attractive therapeutic option under such circumstances. As mast cells are known to secrete a large array of potentially pathogenic compounds, both from preformed stores in secretory lysosomes (granules) and after de novo synthesis, mere inhibition of degranulation or interference with individual mast cell mediators may not be sufficient to provide an effective blockade of harmful mast cell activities. An alternative strategy may therefore be to locally reduce skin mast cell numbers. Here, we explored the possibility of using lysosomotropic agents for this purpose, appreciating the fact that mast cell granules contain bioactive compounds prone to trigger apoptosis if released into the cytosolic compartment. Based on this principle, we show that incubation of human skin punch biopsies with the lysosomotropic agents siramesine or Leu-Leu methyl ester preferably ablated the mast cell population, without causing any gross adverse effects on the skin morphology. Subsequent analysis revealed that mast cells treated with lysosomotropic agents predominantly underwent apoptotic rather than necrotic cell death. In summary, this study raises the possibility of using lysosomotropic agents as a novel approach to targeting deleterious mast cell populations in cutaneous mastocytosis and other skin disorders negatively influenced by mast cells. [ABSTRACT FROM AUTHOR]

Abstract: Mast cells (MCs) are well known for their detrimental effects in the context of allergic disorders. Strategies that limit MC function can therefore have a therapeutic value. Previous studies have shown that siramesine, a sigma-2 receptor agonist originally developed as an anti-depressant, can induce cell death in transformed cells through a mechanism involving lysosomal destabilization. Since MCs are remarkably rich in lysosome-like secretory granules we reasoned that MCs might be sensitive to siramesine. Here we show that murine and human MCs are highly sensitive to siramesine. Cell death was accompanied by secretory granule permeabilization, as shown by reduced acridine orange staining and leakage of granule proteases into the cytosol. Wild type siramesine-treated MCs underwent cell death with typical signs of apoptosis but MCs lacking serglycin, a proteoglycan crucial for promoting the storage of proteases within MC secretory granules, died predominantly by necrosis. A dissection of the underlying mechanism suggested that the necrotic phenotype of serglycin−/− cells was linked to defective Poly(ADP-ribose) polymerase-1 degradation. In vivo, siramesine treatment of mice caused a depletion of the MC populations of the peritoneum and skin. The present study shows for the first time that MCs are highly sensitive to apoptosis induced by siramesine and introduces the possibility of using siramesine as a therapeutic agent for treatment of MC-dependent disease. [Copyright &y& Elsevier]

1′-[4-[1-(4-Fluorophenyl)-1H-indol-3-yl]-1-butyl]spiro[isobenzofuran-1(3H),4′-piperidine] (Lu 28-179) or Siramesine is a σ-ligand with high specificity for σ2-sites, has been tritiated to directly label these sites in brain. [3H]Lu 28-179 bound in a saturable manner to homogenates prepared from rat brain or human cortices with high affinity (Kd=2.2 and 1.1 nM, respectively) and moderate capacity (Bmax=50±12 and 26±3 fmol mg tissue−1, respectively). The rank order of affinity for [3H]Lu 28-179 binding to homogenates from human and rat brain was: Lu 28-179>ifenprodil=haloperidol>1,3-di(2-tolyl)-guanidine (DTG)>(−)pentazocine≫(+)pentazocine. Using in vitro receptor autoradiography to rat brain sections [3H]Lu 28-179 binding was shown to be most predominant in the cerebral cortex, piriform cortex, hippocampal formation (CA1–CA3 and dentate gyrus), superior colliculus, molecular layer of the cerebellar cortex and locus coeruleus. Overall, these data are consistent with [3H]Lu 28-179 labelling a σ2-like binding site. [Copyright &y& Elsevier]

The limited number of medicinal products available to treat of fungal infections makes control of fungal pathogens problematic, especially since the number of fungal resistance incidents increases. Given the high costs and slow development of new antifungal treatment options, repurposing of already known compounds is one of the proposed strategies. The objective of this study was to perform in vitro experimental tests of already identified lead compounds in our previous in silico drug repurposing study, which had been conducted on the known Drugbank database using a seven-step procedure which includes machine learning and molecular docking. This study identifies siramesine as a novel antifungal agent. This novel indication was confirmed through in vitro testing using several yeast species and one mold. The results showed susceptibility of Candida species to siramesine with MIC at concentration 12.5 µg/mL, whereas other candidates had no antifungal activity. Siramesine was also effective against in vitro biofilm formation and already formed biofilm was reduced following 24 h treatment with a MBEC range of 50–62.5 µg/mL. Siramesine is involved in modulation of ergosterol biosynthesis in vitro, which indicates it is a potential target for its antifungal activity. This implicates the possibility of siramesine repurposing, especially since there are already published data about nontoxicity. Following our in vitro results, we provide additional in depth in silico analysis of siramesine and compounds structurally similar to siramesine, providing an extended lead set for further preclinical and clinical investigation, which is needed to clearly define molecular targets and to elucidate its in vivo effectiveness as well. [ABSTRACT FROM AUTHOR]