Showing papers by "Karin Thevissen published in 2014"
TL;DR: This review summarizes the mechanism of action of well-characterized antifungal plant defensins, including RsAFP2, MsDef1, MtDef4, NaD1 and Psd1, and points out the variety by which antifagal plantdefensins affect microbial cell viability.
Abstract: Plant defensins are small, cysteine-rich peptides that possess biological activity towards a broad range of organisms. Their activity is primarily directed against fungi, but bactericidal and insecticidal actions have also been reported. The mode of action of various antifungal plant defensins has been studied extensively during the last decades and several of their fungal targets have been identified to date. This review summarizes the mechanism of action of well-characterized antifungal plant defensins, including RsAFP2, MsDef1, MtDef4, NaD1 and Psd1, and points out the variety by which antifungal plant defensins affect microbial cell viability. Furthermore, this review summarizes production routes for plant defensins, either via heterologous expression or chemical synthesis. As plant defensins are generally considered non-toxic for plant and mammalian cells, they are regarded as attractive candidates for further development into novel antimicrobial agents.
177 citations
TL;DR: This review provides an overview of the different classes of antimycotics and novel antifungal compounds that induce ROS in fungal planktonic and biofilm cells and different strategies to further enhance the antibiofilm activity of such ROS-inducing antimyCotics will be discussed.
Abstract: Invasive fungal infections are associated with very high mortality rates ranging from 20–90% for opportunistic fungal pathogens such as Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus. Fungal resistance to antimycotic treatment can be genotypic (due to resistant strains) as well as phenotypic (due to more resistant fungal lifestyles, such as biofilms). With regard to the latter, biofilms are considered to be critical in the development of invasive fungal infections. However, there are only very few antimycotics, such as miconazole (azoles), echinocandins and liposomal formulations of amphotericin B (polyenes), which are also effective against fungal biofilms. Interestingly, these antimycotics all induce reactive oxygen species (ROS) in fungal (biofilm) cells. This review provides an overview of the different classes of antimycotics and novel antifungal compounds that induce ROS in fungal planktonic and biofilm cells. Moreover, different strategies to further enhance the antibiofilm act...
140 citations
TL;DR: An in vitro and in vivo enhancement of the antibiofilm activity of caspofungin by toremifene citrate is demonstrated, paving the way for implant-related applications of the identified enhancers.
Abstract: Results: Pre-incubation of C. albicans biofilms with subinhibitory concentrations of the enhancers drospirenone, perhexiline maleate or toremifene citrate significantly increased the activity of amphotericin B or caspofungin (FICI ,0.5) against C. albicans and Candida glabrata biofilms. Moreover, these enhancers did not affect the growth potential of osteoblasts. Interestingly, toremifene citrate also enhanced theinvitro activity of caspofungin in a mixed biofilm consisting ofC.albicans andStaphylococcusepidermidis. Furthermore, we demonstrate synergy between toremifene citrate and caspofungin in an in vivo worm C. albicans biofilm infection model. Conclusions: Our data demonstrate an in vitro and in vivo enhancement of the antibiofilm activity of caspofungin by toremifene citrate. Furthermore, our results pave the way for implant-related applications of the identified enhancers.
84 citations
TL;DR: The budding yeast protein kinase Sch9 is not only an effector, but also a regulator of sphingolipid metabolism, which provides a crucial link between nutrient and sphingalipid signaling.
Abstract: The Saccharomyces cerevisiae protein kinase Sch9 is an in vitro and in vivo effector of sphingolipid signaling. This study examines the link between Sch9 and sphingolipid metabolism in S. cerevisiae in vivo based on the observation that the sch9Δ mutant displays altered sensitivity to different inhibitors of sphingolipid metabolism, namely myriocin and aureobasidin A. Sphingolipid profiling indicates that sch9Δ cells have increased levels of long-chain bases and long-chain base-1 phosphates, decreased levels of several species of (phyto)ceramides, and altered ratios of complex sphingolipids. We show that the target of rapamycin complex 1–Sch9 signaling pathway functions to repress the expression of the ceramidase genes YDC1 and YPC1, thereby revealing, for the first time in yeast, a nutrient-dependent transcriptional mechanism involved in the regulation of sphingolipid metabolism. In addition, we establish that Sch9 affects the activity of the inositol phosphosphingolipid phospholipase C, Isc1, which is required for ceramide production by hydrolysis of complex sphingolipids. Given that sphingolipid metabolites play a crucial role in the regulation of stress tolerance and longevity of yeast cells, our data provide a model in which Sch9 regulates the latter phenotypes by acting not only as an effector but also as a regulator of sphingolipid metabolism.
60 citations
TL;DR: The shortened alanine-substituted peptide at position 10 (AS10) was synthesized and inhibited C. albicans biofilm-inhibitory activity and did not affect the viability or functionality of different cell types involved in osseointegration of an implant, pointing to the potential of AS10 for further development as a lead peptide to coat implants.
Abstract: We identified a 26-amino-acid truncated form of the 34-amino-acid cathelicidin-related antimicrobial peptide (CRAMP) in the islets of Langerhans of the murine pancreas. This peptide, P318, shares 67% identity with the LL-37 human antimicrobial peptide. As LL-37 displays antimicrobial and antibiofilm activity, we tested antifungal and antibiofilm activity of P318 against the fungal pathogen Candida albicans. P318 shows biofilm-specific activity as it inhibits C. albicans biofilm formation at 0.15 μM without affecting planktonic survival at that concentration. Next, we tested the C. albicans biofilm-inhibitory activity of a series of truncated and alanine-substituted derivatives of P318. Based on the biofilm-inhibitory activity of these derivatives and the length of the peptides, we decided to synthesize the shortened alanine-substituted peptide at position 10 (AS10; KLKKIAQKIKNFFQKLVP). AS10 inhibited C. albicans biofilm formation at 0.22 μM and acted synergistically with amphotericin B and caspofungin against mature biofilms. AS10 also inhibited biofilm formation of different bacteria as well as of fungi and bacteria in a mixed biofilm. In addition, AS10 does not affect the viability or functionality of different cell types involved in osseointegration of an implant, pointing to the potential of AS10 for further development as a lead peptide to coat implants.
52 citations
TL;DR: It is shown that various tyrocidines have significant activity against planktonic Candida albicans in the low-micromolar range and are promising candidates for further research as antifungal drugs and as agents for combinatorial treatment.
Abstract: Tyrocidines are cationic cyclodecapeptides from Bacillus aneurinolyticus that are characterized by potent antibacterial and antimalarial activities. In this study, we show that various tyrocidines have significant activity against planktonic Candida albicans in the low-micromolar range. These tyrocidines also prevented C. albicans biofilm formation in vitro. Studies with the membrane-impermeable dye propidium iodide showed that the tyrocidines disrupt the membrane integrity of mature C. albicans biofilm cells. This membrane activity correlated with the permeabilization and rapid lysis of model fungal membranes containing phosphatidylcholine and ergosterol (70:30 ratio) induced by the tyrocidines. The tyrocidines exhibited pronounced synergistic biofilm-eradicating activity in combination with two key antifungal drugs, amphotericin B and caspofungin. Using a Caenorhabditis elegans infection model, we found that tyrocidine A potentiated the activity of caspofungin. Therefore, tyrocidines are promising candidates for further research as antifungal drugs and as agents for combinatorial treatment.
48 citations
01 Jan 2014
TL;DR: In this paper, the authors identified compounds that increase the activity of miconazole against Candida albicans biofilms, and they screened 1,600 compounds of a drug-repositioning library.
Abstract: ABSTRACT Mucosal biofilm-related fungal infections are very common, and the incidence of recurrent oral and vulvovaginal candidiasis is significant. As resistance to azoles (the preferred treatment) is occurring, we aimed at identifying compounds that increase the activity of miconazole against Candida albicans biofilms. We screened 1,600 compounds of a drug-repositioning library in combination with a subinhibitory concentration of miconazole. Synergy between the best identified potentiators and miconazole was characterized by checkerboard analyses and fractional inhibitory concentration indices. Hexachlorophene, pyrvinium pamoate, and artesunate act synergistically with miconazole in affecting C. albicans biofilms. Synergy was most pronounced for artesunate and structural homologues thereof. No synergistic effect could be observed between artesunate and fluconazole, caspofungin, or amphotericin B. Our data reveal enhancement of the antibiofilm activity of miconazole by artesunate, pointing to potential combination therapy consisting of miconazole and artesunate to treat C. albicans biofilm-related infections.
44 citations
TL;DR: It is demonstrated that OSIP108 activates the C. albicans cell wall integrity pathway and that its antibiofilm activity can be blocked by compounds inhibiting the yeast-to-hypha transition.
Abstract: We previously identified a decapeptide from the model plant Arabidopsis thaliana, OSIP108, which is induced upon fungal pathogen infection. In this study, we demonstrated that OSIP108 interferes with biofilm formation of the fungal pathogen Candida albicans without affecting the viability or growth of C. albicans cells. OSIP108 displayed no cytotoxicity against various human cell lines. Furthermore, OSIP108 enhanced the activity of the antifungal agents amphotericin B and caspofungin in vitro and in vivo in a Caenorhabditis elegans-C. albicans biofilm infection model. These data point to the potential use of OSIP108 in combination therapy with conventional antifungal agents. In a first attempt to unravel its mode of action, we screened a library of 137 homozygous C. albicans mutants, affected in genes encoding cell wall proteins or transcription factors important for biofilm formation, for altered OSIP108 sensitivity. We identified 9 OSIP108-tolerant C. albicans mutants that were defective in either components important for cell wall integrity or the yeast-to-hypha transition. In line with these findings, we demonstrated that OSIP108 activates the C. albicans cell wall integrity pathway and that its antibiofilm activity can be blocked by compounds inhibiting the yeast-to-hypha transition. Furthermore, we found that OSIP108 is predominantly localized at the C. albicans cell surface. These data point to interference of OSIP108 with cell wall-related processes of C. albicans, resulting in impaired biofilm formation.
31 citations
TL;DR: In this article, the in vitro activity of toremifene to inhibit biofilm formation of different fungal and bacterial pathogens, including Candida albicans, Candida glabrata, C. dubliniensis, CandIDA krusei, Pseudomonas aeruginosa, Staphylococcus aureus, and S. epidermidis, was reported.
Abstract: We here report on the in vitro activity of toremifene to inhibit biofilm formation of different fungal and bacterial pathogens, including Candida albicans, Candida glabrata, Candida dubliniensis, Candida krusei, Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis. We validated the in vivo efficacy of orally administered toremifene against C. albicans and S. aureus biofilm formation in a rat subcutaneous catheter model. Combined, our results demonstrate the potential of toremifene as a broad-spectrum oral antibiofilm compound.
25 citations
TL;DR: Recent research shows that S. cerevisiae is an invaluable model to investigate SLs as signaling molecules in modulating mitochondrial function, but can also be used as a tool to further enhance current knowledge on SLs and mitochondria in mammalian cells.
Abstract: Mitochondrial dysfunction is a hallmark of several neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease, but also of cancer, diabetes and rare diseases such as Wilson's disease (WD) and Niemann Pick type C1 (NPC). Mitochondrial dysfunction underlying human pathologies has often been associated with an aberrant cellular sphingolipid metabolism. Sphingolipids (SLs) are important membrane constituents that also act as signaling molecules. The yeast Saccharomyces cerevisiae has been pivotal in unraveling mammalian SL metabolism, mainly due to the high degree of conservation of SL metabolic pathways. In this review we will first provide a brief overview of the major differences in SL metabolism between yeast and mammalian cells and the use of SL biosynthetic inhibitors to elucidate the contribution of specific parts of the SL metabolic pathway in response to for instance stress. Next, we will discuss recent findings in yeast SL research concerning a crucial signaling role for SLs in orchestrating mitochondrial function, and translate these findings to relevant disease settings such as WD and NPC. In summary, recent research shows that S. cerevisiae is an invaluable model to investigate SLs as signaling molecules in modulating mitochondrial function, but can also be used as a tool to further enhance our current knowledge on SLs and mitochondria in mammalian cells.
23 citations
TL;DR: The potential of OSIP108 to prevent Cu-induced apoptosis, possibly via its effects on sphingolipid homeostasis is indicated, as it decreased the levels of several sphingoid bases and ceramide species.
TL;DR: A medium-throughput screen of a small-molecule collection resulting in the identification of the N-alkylated 3,6-dihalogenocarbazol 1-(sec-butylamino)-3-dichloro-9H-carbazol-9-yl)propan-2-ol shows no cytotoxicity against various human cell types, pointing to its potential for further development as a novel antibacterial drug.
TL;DR: A pivotal signaling role for SLs in maintaining correct mitochondrial function in budding yeast is suggested, and the retrograde response, a signaling event originating from mitochondria to the nucleus, which results in the induction of nuclear target genes is described.
TL;DR: OSIP108 prevents Cu-induced toxicity in in vitro models and in a Cu-toxicity zebrafish larvae model applicable to Wilson disease, indicating the potential of OSIP108 as a drug lead for further development as a novel WD treatment.
Patent•
29 Apr 2014
TL;DR: In this article, the authors present agrochemical and biological control compositions for combating pests, more specifically plant pests, comprising at least one polypeptide which specifically binds to a pest, and provide methods for protecting or treating a plant or a part of a plant from an infection or other biological interaction with a plant pathogen.
Abstract: The present invention relates to agrochemical and biological control compositions for combating pests, more specifically plant pests, comprising at least one polypeptide, which specifically binds to a pest. The invention further provides methods for protecting or treating a plant or a part of a plant from an infection or other biological interaction with a plant pathogen, at least comprising the step of applying directly or indirectly to a plant or to a part of a plant, an agrochemical composition, under conditions effective to protect or treat a plant or a part of a plant against a infection or biological interaction with a plant pathogen. Further provided are methods for producing such agrochemical compositions and formulations, to polypeptides with a specific pesticidal activity comprised within an agrochemical formulation, to nucleic acids encoding such polypeptide and to plants comprising chimeric genes comprising such nucleic acids.
TL;DR: The 2N-substituted 5-aryl-2-aminoimidazoles consistently showed the lowest toxicity and allowed survival of the bone cells for up to 4 weeks, and did not negatively affect the osteogenic differentiation potential of theBone cells.
Abstract: Previously, we have synthesized several series of compounds based on the 5-aryl-2-aminoimidazole scaffold, which showed a preventive activity against microbial biofilms. We here studied the cytotoxicity of the most active compounds of each series. First, the cytostatic activity was investigated against a number of tumor cell lines (L1210, CEM and HeLa). A subset of monosubstituted 5-aryl-2-aminoimidazoles showed a moderate safety window, with therapeutic indices (TIs) ranging between 3 and 20. Whereas introduction of a (cyclo-)alkyl chain at the N1-position strongly reduced the TI, introduction of a (cyclo-)alkyl chain or a triazole moiety at the 2N-position increased the TI up to 370. Since a promising application of preventive anti-biofilm agents is their use in anti-biofilm coatings for orthopedic implants, their effects on cell viability and functional behavior of human osteoblasts and bone marrow derived mesenchymal stem cells were tested. The 2N-substituted 5-aryl-2-aminoimidazoles consistently showed the lowest toxicity and allowed survival of the bone cells for up to 4 weeks. Moreover they did not negatively affect the osteogenic differentiation potential of the bone cells. Finally, we examined the effect of the compounds on the survival of Caenorhabditis elegans, which confirmed the higher safety window of 2N-substituted 5-aryl-2-aminoimidazoles.
TL;DR: By combining the most promising amino acid substitutions, it was found that the double-substituted OSIP108 analogue Q6R/G7K had an 8-fold-increased antibiofilm activity.
Abstract: We performed a structure-activity relationship study of the antibiofilm plant-derived decapeptide OSIP108. Introduction of positively charged amino acids R, H, and K resulted in an up-to-5-fold-increased antibiofilm activity against Candida albicans compared to native OSIP108, whereas replacement of R9 resulted in complete abolishment of its antibiofilm activity. By combining the most promising amino acid substitutions, we found that the double-substituted OSIP108 analogue Q6R/G7K had an 8-fold-increased antibiofilm activity.
TL;DR: The data indicate that OSIP108 and its cyclic derivatives can protect against Cp-induced toxicity and, thus, show potential as treatment options for mitochondrial dysfunction- and apoptosis-related conditions.
Abstract: We investigated the effect of the Arabidopsis thaliana-derived decapeptide OSIP108 on human cell tolerance to the chemotherapeutic agent cisplatin (Cp), which induces apoptosis and mitochondrial dysfunction. We found that OSIP108 increases the tolerance of HepG2 cells to Cp and prevents Cp-induced changes in basic cellular metabolism. More specifically, we demonstrate that OSIP108 reduces Cp-induced inhibition of respiration, decreases glycolysis and prevents Cp-uptake in HepG2 cells. Apart from its protective action against Cp in human cells, OSIP108 also increases the yeast Saccharomyces cerevisiae tolerance to Cp. A limited yeast-based study of OSIP108 analogs showed that cyclization does not severely affect its activity, which was further confirmed in HepG2 cells. Furthermore, the similarity in the activity of the D-stereoisomer (mirror image) form of OSIP108 with the L-stereoisomer suggests that its mode of action does not involve binding to a stereospecific receptor. In addition, as OSIP108 decreases Cp uptake in HepG2 cells and the anti-Cp activity of OSIP108 analogs without free cysteine is reduced, OSIP108 seems to protect against Cp-induced toxicity only partly via complexation. Taken together, our data indicate that OSIP108 and its cyclic derivatives can protect against Cp-induced toxicity and, thus, show potential as treatment options for mitochondrial dysfunction- and apoptosis-related conditions.
Patent•
13 Feb 2014
TL;DR: In this article, the authors proposed methods and compositions comprising a compound, preferably perhexiline (maleate), drospirenone or toremiphene (citrate), which increases the susceptibility and sensitivity of bio-films to antifungal drugs such as amphotericin B and caspofungin.
Abstract: The present invention relates to novel methods and compositions comprising a compound, preferably perhexiline (maleate), drospirenone or toremiphene (citrate), which increases the susceptibility and sensitivity of biofi!ms to antifungal drugs such as amphotericin B and caspofungin. Accordingly, the present invention relates to use of said composition for the treatment or prevention of biofilms, particularly fungal or yeast biofilms, such as Candida biofilms, in a subject or on a surface or other medium susceptible to biofilm formation. Coating of medical devices, like implants and plastics with said compounds, in combination with conventional antifungal therapy for the treatment or prevention of biofilms is also contemplated.
01 Jan 2014
TL;DR: The results demonstrate the potential of toremifene as a broad-spectrum oral antibiofilm compound and validate the in vivo efficacy of orally administered to Remifene against C. albicans and S. aureus biofilm formation in a rat subcutaneous catheter model.
Abstract: ABSTRACT We here report on the in vitro activity of toremifene to inhibit biofilm formation of different fungal and bacterial pathogens, including Candida albicans, Candida glabrata, Candida dubliniensis, Candida krusei, Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis. We validated the in vivo efficacy of orally administered toremifene against C. albicans and S. aureus biofilm formation in a rat subcutaneous catheter model. Combined, our results demonstrate the potential of toremifene as a broad-spectrum oral antibiofilm compound.
01 Jan 2014
TL;DR: 2 members of the drug class of Angiotensin II Type 1 receptor blockers (ARBs) that could increase yeast tolerance to Cu and/or the chemotherapeutic agent cisplatin are identified, and it is demonstrated that specific ARBs can prevent the prevalence of Cu-induced apoptotic markers in yeast.
Abstract: The human pathology Wilson disease (WD) is characterized by toxic copper (Cu) accumulation in brain and liver, resulting in, among other indications, mitochondrial dysfunction and apoptosis of hepatocytes. In an effort to identify novel compounds that can alleviate Cu-induced toxicity, we screened the Pharmakon 1600 repositioning library using a Cu-toxicity yeast screen. We identified 2 members of the drug class of Angiotensin II Type 1 receptor blockers (ARBs) that could increase yeast tolerance to Cu, namely Candesartan and Losartan. Subsequently, we show that specific ARBs can in- crease yeast tolerance to Cu and/or the chemotherapeutic agent cisplatin (Cp). The latter also induces mitochondrial dysfunction and apoptosis in mammalian cells. We further demonstrate that specific ARBs can prevent the prevalence of Cu-induced apoptotic markers in yeast, with Candesartan Cilex- etil being the ARB which demonstrated most pronounced reduction of apop- tosis-related markers. Next, we tested the sensitivity of a selection of yeast knockout mutants affected in detoxification of reactive oxygen species (ROS) and Cu for Candesartan Cilexetil rescue in presence of Cu. These data indicate that Candesartan Cilexetil increases yeast tolerance to Cu irrespectively of major ROS-detoxifying proteins. Finally, we show that specific ARBs can in- crease mammalian cell tolerance to Cu, as well as decrease the prevalence of Cu-induced apoptotic markers. All the above point to the potential of ARBs in
01 Jan 2014
TL;DR: This paper presents the results of a two-year research project aimed at determining the phytochemical properties of E. coli A.A. Dendrobatics, which has shown promising results in relation to agricultural pests and disease.
Abstract: 1 Phalguni Tewari Kumar*, 2 Kim Vriens*, 3 Matteo Cornaglia, 3 Martin Gijs, 1,4 Tadej Kokalj, 2 Karin Thevissen, 1 Annemie Geeraerd, 2,5 Bruno P.A. Cammue, 6 Robert Puers, and 1 Jeroen Lammertyn 1 BIOSYST-MEBIOS, KU Leuven, Leuven, Belgium, 2 Centre of Microbial and Plant Genetics, KU Leuven, Leuven, Belgium, 3 Laboratory of Microsystems, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne, Switzerland, 4 Institute of Metals and Technology, Ljubljana, Slovenia, 5 Department of Plant Systems Biology, VIB, Ghent, Belgium, 6 MICAS-ESAT, KU Leuven, Leuven, Belgium