Molecular Insights into the Role of Sterols in Microtuber Development of Potato Solanum tuberosum L.

Potato tubers are reproductive and storage organs, enabling their survival. Unraveling the molecular mechanisms that regulate tuberization is crucial for understanding how potatorespond to environmental stress situations and for potato breeding. Previously, we did a transcriptomic analysis of potato microtuberization without light. This showed that important cellular processes like ribosomal proteins, cell cycle, carbon metabolism, oxidative stress, fatty acids, and phytosterols (PS) biosynthesis were closely connected in a protein-protein interaction (PPI) network. Research on PS function during potato tuberization has been scarce. PS plays a critical role in regulating membrane permeability and fluidity, and they are biosynthetic precursors of brassinosteroids (BRs) in plants, which are critical in regulating gene expression, cell division, differentiation, and reproductive biology. Within a PPI network, we found a module of 15 genes involved in the PS biosynthetic process. Darkness, as expected, activated the mevalonate (MVA) pathway. There was a tight interaction between three coding gene products for HMGR3, MVD2, and FPS1, and the gene products that synthetize PS, including CAS1, SMO1, BETAHSD, CPI1, CYP51, FACKEL, HYDRA1, SMT2, SMO2, STE1, and SSR1. Quantitative real-time polymerase chain reaction (qRT-PCR) confirmed the expression analysis of ten specific genes involved in the biosynthesis of PS. This manuscript discusses the potential role of genes involved in PS biosynthesis during microtuber development.

Mitochondrial dysfunction on Leishmania (Leishmania) amazonensis induced by ketoconazole: insights into drug mode of action

BACKGROUND Leishmania parasites cause leishmaniasis that range from self-limiting cutaneous lesions to more serious forms of the disease. The search for potential drug targets focusing on biochemical and metabolic pathways revealed the sterol biosynthesis inhibitors (SBIs) as a promising approach. In this class of inhibitors is found ketoconazole, a classical inhibitor of 14α-methysterol 14-demethylase. OBJECTIVE The present study aimed to better understand the biological response of Leishmania (Leishmania) amazonensis promastigotes at the cellular level after ketoconazole treatment. METHODS Herein, techniques, such as fluorimetry, flow cytometry, fluorescence microscopy, electron and scanning microscopy were used to investigate the cellular structures and to identify organelles affected by ketoconazole treatment. FINDINGS The study demonstrated, for the first time, the effect of ketoconazole on mitochondrion functioning and its probable relationship to cell cycle and death on L. (L.) amazonensis promastigotes (IFLA/BR/67/PH8 strain). MAIN CONCLUSIONS Ketoconazole-induced mitochondrial damages led to hyperpolarisation of this single organelle and autophagic vacuoles formation, as a parasite survival strategy. These damages did not reflect directly on the parasite cell cycle, but drove the parasites to death, making them susceptible to ketoconazole treatment in in vitro models.

Cross-Resistance Among Demethylation Inhibitor Fungicides With Brazilian Monilinia fructicola Isolates as a Foundation to Discuss Brown Rot Control in Stone Fruit.

Despite the resistance problems in Monilinia fructicola, demethylation inhibitor fungicides (DMIs) are still effective for the disease management of brown rot in commercial stone fruit orchards in Brazil. This study aims to investigate the sensitivity of M. fructicola isolates and efficiency of DMIs to reduce brown rot. A set of 93 isolates collected from Brazilian commercial orchards were tested for their sensitivities to tebuconazole, propiconazole, prothioconazole, and myclobutanil. The isolates were analyzed separately according to the presence or absence of the G461S mutation in MfCYP51 gene, determined by allele-specific test. The mean EC50 values for G461S mutants and wild-type isolates were respectively 8.443 and 1.13 µg/ml for myclobutanil, 0.236 and 0.026 µg/ml for propiconazole, 0.115 and 0.002 µg/ml for prothioconazole, and 1.482 and 0.096 µg/ml for tebuconazole. The density distribution curves of DMI sensitivity for both genotypes showed that myclobutanil and prothioconazole curves were mostly shifted toward resistance and sensitivity, respectively. Incomplete cross-resistance was detected among propiconazole and tebuconazole in both wild-type (r = 0.45) and G461S (r = 0.38) populations. No cross-sensitivity was observed among wild-type isolates to prothioconazole and the others DMIs tested. Fungicide treatments on detached fruit inoculated with M. fructicola genotypes showed significant DMI efficacy differences when fruit were inoculated with wild-type and G461S isolates. Protective applications with prothioconazole were more effective for control of both G461S and wild-type isolates compared with tebuconazole. Curative applications with tebuconazole were most effective in reducing the incidence and lesion size of G461S isolates. Sporulation occurred only for G461S isolates treated with tebuconazole under curative and preventative treatments. The differences found among the performance of triazoles against M. fructicola isolates will form the basis for recommendations of rational DMI usage to control brown rot in Brazil.

Synthesis and trypanocidal activity of novel pyridinyl-1,3,4-thiadiazole derivatives.

Herein, we present the design, synthesis and trypanocidal evaluation of sixteen new 1,3,4-thiadiazole derivatives from N-aminobenzyl or N-arylhydrazone series. All derivatives were assayed against the trypomastigote form of Trypanosoma cruzi, showing IC50 values ranging from 3 to 226 µM, and a better trypanocidal profile was demonstrated for the 1,3,4-thiadiazole-N-arylhydrazones (3a-g). In this series, the 2-pyridinyl fragment bound to the imine subunit of the hydrazine moiety presented pharmacophoric behavior for trypanocidal activity. Compounds 2a, 11a and 3e presented remarkable activity and excellent selectivity indexes. Compound 2a was also active against the intracellular amastigote form of T. cruzi. Moreover, its corresponding hydrochloride, compound 11a, showed the most promising profile, producing phenotypic changes similar to those caused by posaconazole, a well-known inhibitor of sterol biosynthesis. Thus, 1,3,4-thiadiazole derivative 11a could be considered a good prototype for the development of new drug candidates for Chagas disease therapy.

Δ(24)-Sterol Methyltransferase Plays an Important Role in the Growth and Development of Sporothrix schenckii and Sporothrix brasiliensis.

Inhibition of Δ(24)-sterol methyltransferase (24-SMT) in Sporothrix schenckii sensu stricto and Sporothrix brasiliensis was investigated in vitro. The effects on fungal growth and sterol composition of the 24-SMT inhibitor 22-hydrazone-imidazolin-2-yl-chol-5-ene-3ß-ol (H3) were compared to those of itraconazole. MIC and MFC analysis showed that H3 was more effective than itraconazole against both species in both their filamentous and yeast forms. H3 showed fungistatic activity in a time-kill assay, with inhibitory activity stronger than that of itraconazole. GC analysis of cell sterol composition showed that sterols present in control cells (ergosterol and precursors) were completely replaced by 14α-methylated sterols after H3 exposure. Itraconazole only partially inhibited ergosterol synthesis but completely arrested synthesis of other sterols found in control cells, promoting accumulation of nine 14α-methyl sterols. Based on these results, we propose a schematic model of sterol biosynthesis pathways in S. schenckii and S. brasiliensis. Effects on cell morphology due to 24-SMT inhibition by H3 as analyzed by SEM and TEM included irregular cell shape, reduced cytoplasmic electron-density, and reduced thickness of the microfibrillar cell wall layer. Moreover, 24-SMT inhibition by H3 promoted mitochondrial disturbance, as demonstrated by alterations in MitoTracker(®) Red CMXRos fluorescence intensity evaluated by flow cytometry. When used in conjunction with itraconazole, H3 enhanced the effectiveness of itraconazole against all tested strains, reducing at least half (or more) the MIC values of itraconazole. In addition, cytotoxicity assays revealed that H3 was more selective toward these fungi than was itraconazole. Thus, 24-SMT inhibition by H3 was an effective antifungal strategy against S. schenckii and S. brasiliensis. Inhibition of the methylation reaction catalyzed by 24-SMT has a strong antiproliferative effect via disruption of ergosterol homeostasis, suggesting that this enzyme is a promising target for novel antifungal therapies against sporotrichosis, either as sole treatments or in combination with itraconazole.

3-H-[1,2]Dithiole as a New Anti-Trypanosoma cruzi Chemotype: Biological and Mechanism of Action Studies.

The current pharmacological Chagas disease treatments, using Nifurtimox or Benznidazole, show limited therapeutic results and are associated with potential side effects, like mutagenicity. Using random screening we have identified new chemotypes that were able to inhibit relevant targets of the Trypanosoma cruzi. We found 3H-[1,2]dithioles with the ability to inhibit Trypanosoma cruzi triosephosphate isomerase (TcTIM). Herein, we studied the structural modifications of this chemotype to analyze the influence of volume, lipophilicity and electronic properties in the anti-T. cruzi activity. Their selectivity to parasites vs. mammalian cells was also examined. To get insights into a possible mechanism of action, the inhibition of the enzymatic activity of TcTIM and cruzipain, using the isolated enzymes, and the inhibition of membrane sterol biosynthesis and excreted metabolites, using the whole parasite, were achieved. We found that this structural framework is interesting for the generation of innovative drugs for the treatment of Chagas disease.

Ergosterol biosynthesis and drug development for Chagas disease

This article presents an overview of the currently available drugs nifurtimox (NFX) and benznidazole (BZN) used against Trypanosoma cruzi, the aetiological agent of Chagas disease; herein we discuss their limitations along with potential alternatives with a focus on ergosterol biosynthesis inhibitors (EBI). These compounds are currently the most advanced candidates for new anti-T. cruzi agents given that they block de novo production of 24-alkyl-sterols, which are essential for parasite survival and cannot be replaced by a host's own cholesterol. Among these compounds, new triazole derivatives that inhibit the parasite's C14± sterol demethylase are the most promising, as they have been shown to have curative activity in murine models of acute and chronic Chagas disease and are active against NFX and BZN-resistant T. cruzi strains; among this class of compounds, posaconazole (Schering-Plough Research Institute) and ravuconazole (Eisai Company) are poised for clinical trials in Chagas disease patients in the short term. Other T. cruzi-specific EBI, with in vitro and in vivo potency, include squalene synthase, lanosterol synthase and squalene epoxidase-inhibitors as well as compounds with dual mechanisms of action (ergosterol biosynthesis inhibition and free radical generation), but they are less advanced in their development process. The main putative advantages of EBI over currently available therapies include their higher potency and selectivity in both acute and chronic infections, activity against NFX and BZN-resistant T. cruzi strains, and much better tolerability and safety profiles. Limitations may include complexity and cost of manufacture of the new compounds. As for any new drug, such compounds will require extensive clinical testing before being introduced for clinical use, and the complexity of such studies, particularly in chronic patients, will be compounded by the current limitations in the verification of true parasitological...