Impact of ergosterol content on acetic and lactic acids toxicity to Saccharomyces cerevisiae.

Organic acid stress often represents a major hurdle in industrial bio-based microbial processes. Organic acids can be released from lignocellulosic feedstocks pretreatment and can also be desirable products obtained by microbial fermentation with applications in different industrial sectors. Yeasts are prominent cell factories. However, the presence of organic acids can compromise yeast metabolism, impairing fermentation performances and limiting the economic feasibility of the processes. Plasma membrane remodeling is deeply involved in yeast tolerance to organic acids, but the detailed mechanisms and potentials of this phenomenon remain largely to be studied and exploited. We investigated the impact of ergosterol on Saccharomyces cerevisiae tolerance against organic acid stress by coupling in vitro and in vivo assays. In the in vitro assay, synthetic lipid vesicles were prepared containing different concentrations of ergosterol. We observed changes in organic acids diffusion through the membrane as a function of ergosterol content. Then, we extended our approach in vivo, engineering S. cerevisiae with the aim of changing the ergosterol content of cells. We focused on ECM22, an important transcription factor, involved in the regulation of ergosterol biosynthesis. The overexpression of ECM22 was sufficient to increase ergosterol levels in S. cerevisiae, resulting in an enhanced tolerance toward lactic acid stress. In this work we propose an in vitro approach, using synthetic lipid vesicles, as a complementary method to be used when studying the impact of the plasma membrane lipid composition on the diffusion of organic acids.

Chemotherapy in pancreatic ductal adenocarcinoma: When cytoreduction is the aim. A systematic review and meta-analysis.

BACKGROUND: In pancreatic ductal adenocarcinoma cytoreduction can be curative, or palliative. FOLFIRINOX and GEM-NAB are the two FDA/EMA approved regimens for advanced disease. We aim to identified the most cytoreductive regimen on the basis of current literature. MATERIAL AND METHODS: PUBMED was searched for studies published to April 2021. Abstracts of annual meetings ASCO 2009-2021, and ESMO 2015-2020, were searched as well. Phase II, phase III clinical trials, prospective, observational and retrospective studies, reporting overall response rate (complete + partial response) (ORR) in patients treated either with FOLFIRINOX or GEM-NAB were included. The meta-analysis was performed using a randomized-effects model. Main outcome was cytoreduction with each regimen reported as ORR according to RECIST. RESULTS: Among 2183 studies identified, 40 fulfilled the selection criteria (22 FOLFIRINOX, 18 GEM-NAB), totaling 2883 patients. Pooling of data found similar ORR between regimens: FOLFIRINOX [30% (95 CI 26-34%)] and GEM-NAB [30% (95 CI 26-35%),] P = 0.928. Disease control rate (DCR) was significantly higher with FOLFIRINOX [85% (95CI 82-88%)] compared to GEM-NAB [80% (95CI 77-84%)], P = 0.012. A significantly higher ORR irrespective of the regimen was observed in stage IV [36% (95CI 32-40%)] versus stage II-III [25% (95CI 20-31%)], P = 0.002. CONCLUSIONS AND RELEVANCE: Our meta-analysis did not find significant superiority of one regimen over the other in terms of RECIST-based cytoreduction both in palliative and curative setting of patients with pancreatic adenocarcinoma. The significantly better DCR with FOLFIRINOX compared with GEM-NAB deserves further investigation including waterfall plot and correlations with potential predictive factors.

The impact of preinfarct angina on the incidence of acute kidney injury in patients with myocardial infarction: interaction with pre-existent chronic kidney disease.

AIM: Remote ischemic conditioning may reduce acute kidney injury (AKI) in patients undergoing a coronary intervention. As preinfarct angina (PIA) might act as a preconditioning stimulus in patients with ST-elevation myocardial infarction (STEMI), we aimed to study whether PIA reduces AKI in accordance to pre-existing chronic kidney disease. PATIENTS AND METHODS: We conducted a retrospective study including 891 consecutive STEMI patients who underwent primary coronary intervention from January 2008 to March 2016. AKI was determined on the basis of KDIGO criteria. The impact of PIA was evaluated in three groups according to the baseline glomerular filtration rate: less than 45 ml/min/1.73 m (group 1, n = 89), 45-59 ml/min/1.73 m (group 2, n = 117), and greater than or equal to 60 ml/min/1.73 m (group 3, n = 642). Univariate and multivariate predictors for AKI were determined. RESULTS: AKI developed in 13.8% of patients (n = 117) and was more prevalent in patients with worse baseline renal function (35% in group 1; 22% in group 2; and 9% in group 3, P < 0.01). The prevalence of PIA was similar across groups (28-34%, P = 0.2). Only in group 1 did patients with PIA have a significantly lower rate of AKI than patients without PIA (19 vs. 42%, P = 0.033). In multivariate analysis, the absence of PIA in group 1 patients conferred an almost three-fold risk of developing AKI (odds ratio = 2.92, P = 0.009), whereas no differences were found for the other groups. Age, total ischemic time, and intra-aortic balloon pump utilization were also related independently to AKI. CONCLUSION: In our series, STEMI patients with at least stage 3B chronic kidney disease had a three-fold risk of developing AKI in the absence of PIA. These findings suggest that patients with worse renal function may be more susceptible to the renoprotective effect of myocardial ischemic preconditioning.

Phenolic Imidazole Derivatives with Dual Antioxidant/Antifungal Activity: Synthesis and Structure-Activity Relationship.

BACKGROUND: Previous publications show that the addition of a phenolic antioxidant to an antifungal agent, considerably enhances the antifungal activity. OBJECTIVE: Synthesis of novel compounds combining phenolic units with linear or cyclic nitrogencontaining organic molecules with antioxidant/antifungal activity using methodologies previously developed in the group. METHODS: Several N- [1,2-dicyano-2- (arylidenamino) vinyl]-O-alkylformamidoximes 3 were synthesized and cyclized to 4,5-dicyano-N- (N´-alcoxyformimidoyl)-2-arylimidazoles 4 upon reflux in DMF, in the presence of manganese dioxide or to 6-cyano-8-arylpurines 5 when the reagent was refluxed in acetonitrile with an excess of triethylamine. These compounds were tested for their antioxidant activity by cyclic voltammetry, DPPH radical (DPPH•) assay and deoxyribose degradation assay. The minimum inhibitory concentration (MIC) of all compounds was evaluated against two yeast species, Saccharomyces cerevisiae and Candida albicans, and against bacteria Bacillus subtilis (Gram-positive) and Escherichia coli (Gram negative). Their cytotoxicity was evaluated in fibroblasts. RESULTS: Among the synthetised compounds, five presented higher antioxidant activity than reference antioxidant Trolox and from these compounds, four presented antifungal activity without toxic effects in fibroblasts and bacteria. CONCLUSION: Four novel compounds presented dual antioxidant/antifungal activity at concentrations that are not toxic to bacteria and fibroblasts. The active molecules can be used as an inspiration for further studies in this area.

Contacts in Death: The Role of the ER-Mitochondria Axis in Acetic Acid-Induced Apoptosis in Yeast.

Endoplasmic reticulum-mitochondria contact sites have been a subject of increasing scientific interest since the discovery that these structures are disrupted in several pathologies. Due to the emerging data that correlate endoplasmic reticulum-mitochondria contact sites function with known events of the apoptotic program, we aimed to dissect this interplay using our well-established model of acetic acid-induced apoptosis in Saccharomyces cerevisiae. Until recently, the only known tethering complex between ER and mitochondria in this organism was the ER-mitochondria encounter structure (ERMES). Following our results from a screening designed to identify genes whose deletion rendered cells with an altered sensitivity to acetic acid, we hypothesized that the ERMES complex could be involved in cell death mediated by this stressor. Herein we demonstrate that single ablation of the ERMES components Mdm10p, Mdm12p and Mdm34p increases the resistance of S. cerevisiae to acetic acid-induced apoptosis, which is associated with a prominent delay in the appearance of several apoptotic markers. Moreover, abrogation of Mdm10p or Mdm34p abolished cytochrome c release from mitochondria. Since these two proteins are embedded in the mitochondrial outer membrane, we propose that the ERMES complex plays a part in cytochrome c release, a key event of the apoptotic cascade. In all, these findings will aid in targeted therapies for diseases where apoptosis is disrupted, as well as assist in the development of acetic acid-resistant strains for industrial processes.

VDAC regulates AAC-mediated apoptosis and cytochrome c release in yeast.

Mitochondrial outer membrane permeabilization is a key event in apoptosis processes leading to the release of lethal factors. We have previously shown that absence of the ADP/ATP carrier (AAC) proteins (yeast orthologues of mammalian ANT proteins) increased the resistance of yeast cells to acetic acid, preventing MOMP and the release of cytochrome c from mitochondria during acetic acid - induced apoptosis. On the other hand, deletion of POR1 (yeast voltage-dependent anion channel - VDAC) increased the sensitivity of yeast cells to acetic acid. In the present work, we aimed to further characterize the role of yeast VDAC in acetic acid - induced apoptosis and assess if it functionally interacts with AAC proteins. We found that the sensitivity to acetic acid resulting from POR1 deletion is completely abrogated by the absence of AAC proteins, and propose that Por1p acts as a negative regulator of acetic acid - induced cell death by a mechanism dependent of AAC proteins, by acting on AAC - dependent cytochrome c release. Moreover, we show that Por1p has a role in mitochondrial fusion that, contrary to its role in apoptosis, is not affected by the absence of AAC, and demonstrate that mitochondrial network fragmentation is not sufficient to induce release of cytochrome c or sensitivity to acetic acid - induced apoptosis. This work enhances our understanding on cytochrome c release during cell death, which may be relevant in pathological scenarios where MOMP is compromised.

Cell wall dynamics modulate acetic acid-induced apoptotic cell death of Saccharomyces cerevisiae.

Acetic acid triggers apoptotic cell death in Saccharomyces cerevisiae, similar to mammalian apoptosis. To uncover novel regulators of this process, we analyzed whether impairing MAPK signaling affected acetic acid-induced apoptosis and found the mating-pheromone response and, especially, the cell wall integrity pathways were the major mediators, especially the latter, which we characterized further. Screening downstream effectors of this pathway, namely targets of the transcription factor Rlm1p, highlighted decreased cell wall remodeling as particularly important for acetic acid resistance. Modulation of cell surface dynamics therefore emerges as a powerful strategy to increase acetic acid resistance, with potential application in industrial fermentations using yeast, and in biomedicine to exploit the higher sensitivity of colorectal carcinoma cells to apoptosis induced by acetate produced by intestinal propionibacteria.

Synthesis of naphtho[2,3-a]phenoxazinium chlorides: structure-activity relationships of these heterocycles and benzo[a]phenoxazinium chlorides as new antimicrobials.

Synthesised functionalised naphtho[2,3-a]phenoxazinium chlorides revealed great fluorescence with maximum emission wavelengths between 630 and 676 nm, in ethanol and water at physiological pH. Naphtho[2,3-a]phenoxazines, as well as a series of benzo[a]phenoxazines, were evaluated against Saccharomyces cerevisiae, in a broth microdilution assay. This family of compounds exhibited antifungal activity depending both on the substituents of the heterocycle nucleus as well as on its size. The best activities were obtained for four-ring systems, and particularly for 5,9-diaminobenzo[a]phenoxazines with R=Me, R(1)=H and R(2)=Et. As for R(3) substitution, the greatest efficiency was obtained for R(3)=(CH(2))(3)Cl, with a MIC of 3.75 microM. The linkage of different amino acids to the functional group of the 5-amino position of diaminobenzo[a]phenoxazinium moiety resulted in compounds with diverse antimicrobial efficiencies, depending on the polar character of the amino acid, on its linkage position and on the size of the alkyl chain linker.