Effect of Ursolic and Oleanolic Acids on Lipid Membranes: Studies on MRSA and Models of Membranes

Staphylococcus aureus is an opportunistic pathogen and the major causative agent of life-threatening hospital- and community-acquired infections. A combination of antibiotics could be an opportunity to address the widespread emergence of antibiotic-resistant strains, including Methicillin-Resistant S. aureus (MRSA). We here investigated the potential synergy between ampicillin and plant-derived antibiotics (pentacyclic triterpenes, ursolic acid (UA) and oleanolic acid (OA)) towards MRSA (ATCC33591 and COL) and the mechanisms involved. We calculated the Fractional Inhibitory Concentration Index (FICI) and demonstrated synergy. We monitored fluorescence of Bodipy-TR-Cadaverin, propidium iodide and membrane potential-sensitive probe for determining the ability of UA and OA to bind to lipoteichoic acids (LTA), and to induce membrane permeabilization and depolarization, respectively. Both pentacyclic triterpenes were able to bind to LTA and to induce membrane permeabilization and depolarization in a dose-dependent fashion. These effects were not accompanied by significant changes in cellular concentration of pentacyclic triterpenes and/or ampicillin, suggesting an effect mediated through lipid membranes. We therefore focused on membranous effects induced by UA and OA, and we investigated on models of membranes, the role of specific lipids including phosphatidylglycerol and cardiolipin. The effect induced on membrane fluidity, permeability and ability to fuse were studied by determining changes in fluorescence anisotropy of DPH/generalized polarization of Laurdan, calcein release from liposomes, fluorescence dequenching of octadecyl-rhodamine B and liposome-size, respectively. Both UA and OA showed a dose-dependent effect with membrane rigidification, increase of membrane permeabilization and fusion. Except for the effect on membrane fluidity, the effect of UA was consistently higher compared with that obtained with OA, suggesting the role of methyl group position. All together the data demonstrated the potential role of compounds acting on lipid membranes for enhancing the activity of other antibiotics, like ampicillin and inducing synergy. Such combinations offer an opportunity to explore a larger antibiotic chemical space.

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Induction of Highly Curved Structures in Relation to Membrane Permeabilization and Budding by the Triterpenoid Saponins, α- and δ-Hederin

Journal of Biological Chemistry ◽

10.1074/jbc.m112.407635 ◽

2013 ◽

Vol 288 (20) ◽

pp. 14000-14017 ◽

Cited By ~ 34

Author(s):

Joseph Lorent ◽

Cécile S. Le Duff ◽

Joelle Quetin-Leclercq ◽

Marie-Paule Mingeot-Leclercq

Keyword(s):

Lipid Membranes ◽

Pore Formation ◽

Lateral Diffusion ◽

Molecular Shape ◽

Membrane Curvature ◽

Membrane Permeabilization ◽

Spontaneous Curvature ◽

Unilamellar Vesicles ◽

Generalized Polarization ◽

Triterpenoid Saponins

The interactions of triterpenoid monodesmosidic saponins, α-hederin and δ-hederin, with lipid membranes are involved in their permeabilizing effect. Unfortunately, the interactions of these saponins with lipid membranes are largely unknown, as are the roles of cholesterol or the branched sugar moieties (two for α-hederin and one for δ-hederin) on the aglycone backbone, hederagenin. The differences in sugar moieties are responsible for differences in the molecular shape of the saponins and the effects on membrane curvature that should be the most positive for α-hederin in a transbilayer direction. In large unilamellar vesicles and monocyte cells, we showed that membrane permeabilization was dependent on the presence of membrane cholesterol and saponin sugar chains, being largest for α-hederin and smallest for hederagenin. In the presence of cholesterol, α-hederin induced the formation of nonbilayer phases with a higher rate of Brownian tumbling or lateral diffusion. A reduction of Laurdan's generalized polarization in relation to change in order of the polar heads of phospholipids was observed. Using giant unilamellar vesicles, we visualized the formation of wrinkled borders, the decrease in liposome size, budding, and the formation of macroscopic pores. All these processes are highly dependent on the sugars linked to the aglycone, with α-hederin showing a greater ability to induce pore formation and δ-hederin being more efficient in inducing budding. Hederagenin induced intravesicular budding but no pore formation. Based on these results, a curvature-driven permeabilization mechanism dependent on the interaction between saponin and sterols and on the molecular shape of the saponin and its ability to induce local spontaneous curvature is proposed.

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Increased Cardiovascular Risk Associated with Chemical Sensitivity to Perfluoro–Octanoic Acid: Role of Impaired Platelet Aggregation

International Journal of Molecular Sciences ◽

10.3390/ijms21020399 ◽

2020 ◽

Vol 21 (2) ◽

pp. 399 ◽

Cited By ~ 2

Author(s):

Luca De Toni ◽

Claudia Maria Radu ◽

Iva Sabovic ◽

Andrea Di Nisio ◽

Stefano Dall’Acqua ◽

...

Keyword(s):

Membrane Fluidity ◽

Octanoic Acid ◽

Specific Area ◽

Time Lapse ◽

Environmental Chemicals ◽

Aggregation State ◽

Low Exposure ◽

Aggregation Parameters ◽

Dose Dependent

Perfluoro–alkyl substances (PFAS), particularly perfluoro–octanoic acid (PFOA), are persisting environmental chemicals showing bioaccumulation in human tissues. Recently, exposure to PFAS has been associated with increased prevalence of cardiovascular diseases (CVDs). However, a causal role of PFAS in atherosclerosis pathogenesis is under-investigated. Here, we investigated the effect of PFOA exposure on platelets’ function, a key player in atherosclerosis process. PFOA accumulation in platelets was evaluated by liquid chromatography-mass spectrometry. Changes in platelets’ membrane fluidity and activation after dose-dependent exposure to PFOA were evaluated by merocyanine 540 (MC540) and anti P-Selectin immune staining at flow cytometry, respectively. Intracellular calcium trafficking was analyzed with Fluo4M probe, time-lapse live imaging. Platelets’ aggregation state was also evaluated with Multiplate® aggregometry analyzer in 48 male subjects living in a specific area of the Veneto region with high PFAS environmental pollution, and compared with 30 low-exposure control subjects. Platelets’ membrane was the major target of PFOA, whose dose-dependent accumulation was associated in turn with increased membrane fluidity, as expected by a computational model; increased activation at resting condition; and both calcium uptake and aggregation upon activation. Finally, exposed subjects had higher serum and platelets levels of PFOA, together with increased aggregation parameters at Multiplate®, compared with controls. These data help to explain the emerging association between PFAS exposure and CVD.

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Development of an In Vitro Membrane Model to Study the Function of EsxAB Heterodimer and Establish the Role of EsxB in Membrane Permeabilizing Activity of Mycobacterium tuberculosis

Pathogens ◽

10.3390/pathogens9121015 ◽

2020 ◽

Vol 9 (12) ◽

pp. 1015

Author(s):

Salvador Vazquez Reyes ◽

Supriyo Ray ◽

Javier Aguilera ◽

Jianjun Sun

Keyword(s):

Mycobacterium Tuberculosis ◽

Lipid Membranes ◽

Effect Of Temperature ◽

In Vitro Assays ◽

Vitro Model ◽

First Time ◽

Dose Dependent Increase ◽

Dose Dependent

EsxA and EsxB are secreted as a heterodimer and have been shown to play critical roles in phagosome rupture and translocation of Mycobacterium tuberculosis into the cytosol. Recent in vitro studies have suggested that the EsxAB heterodimer is dissociated upon acidification, which might allow EsxA insertion into lipid membranes. While the membrane permeabilizing activity (MPA) of EsxA has been well characterized in liposomes composed of di-oleoyl-phosphatidylcholine (DOPC), the MPA of EsxAB heterodimer has not been detected through in vitro assays due to its negligible activity with DOPC liposomes. In this study, we established a new in vitro membrane assay to test the MPA activity of N-terminal acetylated EsxA (N-EsxA). We established that a dose-dependent increase in anionic charged lipids enhances the MPA of N-EsxA. The MPA of both N-EsxA and EsxAB were significantly increased with this new liposome system and made it possible to characterize the MPA of EsxAB in more physiologically-relevant conditions. We tested, for the first time, the effect of temperature on the MPA of N-EsxA and EsxAB in this new system. Interestingly, the MPA of N-EsxA was lower at 37 °C than at RT, and on the contrary, the MPA of EsxAB was higher at 37 °C than at RT. Surprisingly, after incubation at 37 °C, the MPA of N-EsxA continuously decreased over time, while MPA of EsxAB remained stable, suggesting EsxB plays a key role in stabilizing N-EsxA to preserve its MPA at 37 °C. In summary, this study established a new in vitro model system that characterizes the MPA of EsxAB and the role of EsxB at physiological-relevant conditions.

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Recognition of intestinal epithelial HIF-1α activation by Pseudomonas aeruginosa

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00276.2006 ◽

2007 ◽

Vol 292 (1) ◽

pp. G134-G142 ◽

Cited By ~ 48

Author(s):

Nachiket J. Patel ◽

Olga Zaborina ◽

Licheng Wu ◽

Yingmin Wang ◽

Donald J. Wolfgeher ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Hypoxia Inducible Factor ◽

Opportunistic Pathogen ◽

Intestinal Epithelial ◽

Human Intestinal Epithelial Cell ◽

Cell Monolayers ◽

Dose Dependent Fashion ◽

Epithelial Cell Monolayers ◽

Dose Dependent

Human intestinal epithelial cell monolayers (Caco-2) subjected to hypoxia and reoxygenation release soluble factors into the apical medium that activate the virulence of the opportunistic pathogen Pseudomonas aeruginosa to express the potent barrier-dysregulating protein PA-I lectin/adhesin. In this study, we defined the role of hypoxia-inducible factor (HIF)-1α in this response. We tested the ability of medium from Caco-2 cells with forced expression of HIF-1α to increase PA-I expression in P. aeruginosa and found that medium from Caco-2 cells overexpressing HIF-1α increased PA-I expression compared with medium from control cells ( P < 0.001, ANOVA). To identify the components responsible for this response, medium was fractionated by molecular weight and subjected to mass spectroscopy, which identified adenosine as the possible mediator. Both adenosine and its immediate downstream metabolite inosine induced PA-I expression in P. aeruginosa in a dose-dependent fashion. Because inosine was not detectable in the medium of Caco-2 cells exposed to hypoxia or overexpressing HIF-1α, we hypothesized that P. aeruginosa itself might metabolize adenosine to inosine. Using mutant and parental strains of P. aeruginosa, we demonstrated that P. aeruginosa metabolized adenosine to inosine via adenosine deaminase and that the conditioned medium enhanced the extracellular accumulation of inosine. Together, these results provide evidence that P. aeruginosa can recognize and respond to extracellular end products of intestinal hypoxia that are released after activation of HIF-1α. The ability of P. aeruginosa to metabolize adenosine to inosine may represent a subversive microbial virulence strategy that deprives the epithelium of the cytoprotective actions of adenosine.

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Amelioration of Carbon Tetrachloride-Induced Liver Injury by Citrus Leaf Extract

Current Topics in Nutraceutical Research ◽

10.37290/ctnr2641-452x.17:426-431 ◽

2019 ◽

Vol 17 (4) ◽

pp. 426-431

Author(s):

Jin Xuezhu ◽

Li Jitong ◽

Nie Leigang ◽

Xue Junlai

Keyword(s):

Carbon Tetrachloride ◽

Leaf Extract ◽

Hepatic Injury ◽

The Body ◽

Dependent Manner ◽

Weight Changes ◽

Citrus Leaf ◽

Dose Dependent ◽

And Oxidative Stress

The main purpose of this study is to investigate the role of citrus leaf extract in carbon tetrachloride-induced hepatic injury and its potential molecular mechanism. Carbon tetrachloride was used to construct hepatic injury animal model. To this end, rats were randomly divided into 4 groups: control, carbon tetrachloride-treated, and two carbon tetrachloride + citrus leaf extract-treated groups. The results show that citrus leaf extract treatment significantly reversed the effects of carbon tetrachloride on the body weight changes and liver index. Besides, treatment with citrus leaf extract also reduced the levels of serum liver enzymes and oxidative stress in a dose-dependent manner. H&E staining and western blotting suggested that citrus leaf extract could repair liver histological damage by regulating AMPK and Nrf-2.

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Investigation on the antibacterial activity of electronic cigarette liquids (ECLs): a proof of concept study

Current Pharmaceutical Biotechnology ◽

10.2174/1389201021666200903121624 ◽

2020 ◽

Vol 21 ◽

Cited By ~ 1

Author(s):

Virginia Fuochi ◽

Massimo Caruso ◽

Rosalia Emma ◽

Aldo Stivala ◽

Riccardo Polosa ◽

...

Keyword(s):

Antibacterial Activity ◽

Bacterial Species ◽

A549 Cells ◽

Bactericidal Effect ◽

Minimal Bactericidal Concentration ◽

Viability Assay ◽

Dependent Inhibition ◽

Dose Dependent Inhibition ◽

Dose Dependent

Background: The key ingredients of e-cigarettes liquid are commonly propane-1,2-diol (also called propylene glycol) and propane-1,2,3-triol (vegetal glycerol) and their antimicrobial effects are already established. The nicotine and flavors which are often present in e-liquids can interfere with the growth of some microorganisms. Objective: The effect of the combining these elements in e-liquids is unknown. The aim of the study was to investigate the possible effects of these liquids on bacterial growth in the presence or absence of nicotine and flavors. Methods: Susceptibilities of pathogenic strains (Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli, Enterococcus faecalis and Sarcina lutea) were studied by means of a multidisciplinary approach. Cell viability and antioxidant assays were also evaluated. Results: All e-liquids investigated showed antibacterial activity against at least one pathogenic strain. A higher activity was correlated to the presence of flavors and nicotine. Discussion: In most cases the value of minimal bactericidal concentration is equal to the value of minimal inhibitory concentration showing that these substances have a bactericidal effect. This effect was observed in concentrations up to 6.25% v/v. Antioxidant activity was also correlated to presence of flavors. Over time, the viability assay in human epithelial lung A549 cells showed a dose-dependent inhibition of cell growth. Conclusion: Our results have shown that flavors considerably enhance the antibacterial activity of propane-1,2-diol and propane-1,2,3-triol. This study provides important evidence that should be taken into consideration in further investigative approaches, to clarify the different sensitivity of the various bacterial species to e-liquids, including the respiratory microbiota, to highlight the possible role of flavors and nicotine.

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The Role of the Pathogen Dose and PI3Kγ in Immunometabolic Reprogramming of Microglia for Innate Immune Memory

International Journal of Molecular Sciences ◽

10.3390/ijms22052578 ◽

2021 ◽

Vol 22 (5) ◽

pp. 2578

Author(s):

Trim Lajqi ◽

Christian Marx ◽

Hannes Hudalla ◽

Fabienne Haas ◽

Silke Große ◽

...

Keyword(s):

Oxygen Consumption ◽

Immune Tolerance ◽

Immune Cells ◽

Low Dose ◽

Innate Immune ◽

Immune Memory ◽

Innate Immune Cells ◽

Atp Production ◽

Dose Dependent

Microglia, the innate immune cells of the CNS, exhibit long-term response changes indicative of innate immune memory (IIM). Our previous studies revealed IIM patterns of microglia with opposing immune phenotypes: trained immunity after a low dose and immune tolerance after a high dose challenge with pathogen-associated molecular patterns (PAMP). Compelling evidence shows that innate immune cells adopt features of IIM via immunometabolic control. However, immunometabolic reprogramming involved in the regulation of IIM in microglia has not been fully addressed. Here, we evaluated the impact of dose-dependent microglial priming with ultra-low (ULP, 1 fg/mL) and high (HP, 100 ng/mL) lipopolysaccharide (LPS) doses on immunometabolic rewiring. Furthermore, we addressed the role of PI3Kγ on immunometabolic control using naïve primary microglia derived from newborn wild-type mice, PI3Kγ-deficient mice and mice carrying a targeted mutation causing loss of lipid kinase activity. We found that ULP-induced IIM triggered an enhancement of oxygen consumption and ATP production. In contrast, HP was followed by suppressed oxygen consumption and glycolytic activity indicative of immune tolerance. PI3Kγ inhibited glycolysis due to modulation of cAMP-dependent pathways. However, no impact of specific PI3Kγ signaling on immunometabolic rewiring due to dose-dependent LPS priming was detected. In conclusion, immunometabolic reprogramming of microglia is involved in IIM in a dose-dependent manner via the glycolytic pathway, oxygen consumption and ATP production: ULP (ultra-low-dose priming) increases it, while HP reduces it.

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Pro-Inflammatory and Neurotrophic Factor Responses of Cells Derived from Degenerative Human Intervertebral Discs to the Opportunistic Pathogen Cutibacterium acnes

International Journal of Molecular Sciences ◽

10.3390/ijms22052347 ◽

2021 ◽

Vol 22 (5) ◽

pp. 2347

Author(s):

Manu N. Capoor ◽

Anna Konieczna ◽

Andrew McDowell ◽

Filip Ruzicka ◽

Martin Smrcka ◽

...

Keyword(s):

Neurotrophic Factor ◽

Acne Vulgaris ◽

Opportunistic Pathogen ◽

Intervertebral Discs ◽

Disc Disease ◽

Gene Target ◽

Cutibacterium Acnes ◽

Pre Treatment

Previously, we proposed the hypothesis that similarities in the inflammatory response observed in acne vulgaris and degenerative disc disease (DDD), especially the central role of interleukin (IL)-1β, may be further evidence of the role of the anaerobic bacterium Cutibacterium (previously Propionibacterium) acnes in the underlying aetiology of disc degeneration. To investigate this, we examined the upregulation of IL-1β, and other known IL-1β-induced inflammatory markers and neurotrophic factors, from nucleus-pulposus-derived disc cells infected in vitro with C. acnes for up to 48 h. Upon infection, significant upregulation of IL-1β, alongside IL-6, IL-8, chemokine (C-C motif) ligand 3 (CCL3), chemokine (C-C motif) ligand 4 (CCL4), nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), was observed with cells isolated from the degenerative discs of eight patients versus non-infected controls. Expression levels did, however, depend on gene target, multiplicity and period of infection and, notably, donor response. Pre-treatment of cells with clindamycin prior to infection significantly reduced the production of pro-inflammatory mediators. This study confirms that C. acnes can stimulate the expression of IL-1β and other host molecules previously associated with pathological changes in disc tissue, including neo-innervation. While still controversial, the role of C. acnes in DDD remains biologically credible, and its ability to cause disease likely reflects a combination of factors, particularly individualised response to infection.

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Lumican Inhibits Osteoclastogenesis and Bone Resorption by Suppressing Akt Activity

International Journal of Molecular Sciences ◽

10.3390/ijms22094717 ◽

2021 ◽

Vol 22 (9) ◽

pp. 4717

Author(s):

Jin-Young Lee ◽

Da-Ae Kim ◽

Eun-Young Kim ◽

Eun-Ju Chang ◽

So-Jeong Park ◽

...

Keyword(s):

Bone Resorption ◽

Bone Formation ◽

Map Kinases ◽

Osteoclast Differentiation ◽

Dependent Manner ◽

Dual Action ◽

Dose Dependent ◽

Resorptive Activity

Lumican, a ubiquitously expressed small leucine-rich proteoglycan, has been utilized in diverse biological functions. Recent experiments demonstrated that lumican stimulates preosteoblast viability and differentiation, leading to bone formation. To further understand the role of lumican in bone metabolism, we investigated its effects on osteoclast biology. Lumican inhibited both osteoclast differentiation and in vitro bone resorption in a dose-dependent manner. Consistent with this, lumican markedly decreased the expression of osteoclastogenesis markers. Moreover, the migration and fusion of preosteoclasts and the resorptive activity per osteoclast were significantly reduced in the presence of lumican, indicating that this protein affects most stages of osteoclastogenesis. Among RANKL-dependent pathways, lumican inhibited Akt but not MAP kinases such as JNK, p38, and ERK. Importantly, co-treatment with an Akt activator almost completely reversed the effect of lumican on osteoclast differentiation. Taken together, our findings revealed that lumican inhibits osteoclastogenesis by suppressing Akt activity. Thus, lumican plays an osteoprotective role by simultaneously increasing bone formation and decreasing bone resorption, suggesting that it represents a dual-action therapeutic target for osteoporosis.

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A zebrafish model of infection-associated acute kidney injury

AJP Renal Physiology ◽

10.1152/ajprenal.00328.2017 ◽

2018 ◽

Vol 315 (2) ◽

pp. F291-F299 ◽

Cited By ~ 7

Author(s):

Xiaoyan Wen ◽

Liyan Cui ◽

Seth Morrisroe ◽

Donald Maberry ◽

David Emlet ◽

...

Keyword(s):

Acute Kidney Injury ◽

Unmet Need ◽

Kidney Injury ◽

Edwardsiella Tarda ◽

Adult Zebrafish ◽

Zebrafish Model ◽

Pericardial Edema ◽

Kidney Injury Molecule 1 ◽

Dose Dependent

Sepsis-associated acute kidney injury (S-AKI) independently predicts mortality among critically ill patients. The role of innate immunity in this process is unclear, and there is an unmet need for S-AKI models to delineate the pathophysiological response. Mammals and zebrafish ( Danio rerio) share a conserved nephron structure and homologous innate immune systems, making the latter suitable for S-AKI research. We introduced Edwardsiella tarda to the zebrafish. Systemic E. tarda bacteremia resulted in sustained bacterial infection and dose-dependent mortality. A systemic immune reaction was characterized by increased mRNA expressions of il1b, tnfa, tgfb1a, and cxcl8-l1 ( P < 0.0001, P < 0.001, P < 0.001, and P < 0.01, respectively). Increase of host stress response genes ccnd1 and tp53 was observed at 24 h postinjection ( P < 0.0001 and P < 0.05, respectively). Moderate E. tarda infection induced zebrafish mortality of over 50% in larvae and 20% in adults, accompanied by pericardial edema in larvae and renal dysfunction in both larval and adult zebrafish. Expression of AKI markers insulin-like growth factor-binding protein-7 (IGFBP7), tissue inhibitor of metalloproteinases 2 (TIMP-2), and kidney injury molecule-1 (KIM-1) was found to be significantly increased in the septic animals at the transcription level ( P < 0.01, P < 0.05, and P < 0.05) and in nephric tubules compared with noninfected animals. In conclusion, we established a zebrafish model of S-AKI induced by E. tarda injection, with both larval and adult zebrafish showing nephron injury in the setting of infection.

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