Cell Membrane Fluidity Research Articles

Mechanism analysis of calcium-induced low freeze-drying survival of probiotic encapsulated in alginate

Calcium alginate is widely used for probiotics encapsulation. In our previous report, low freeze-drying survival of probiotics encapsulated in calcium alginate was presented due to the damage by calcium with increased concentration during freeze-drying. The damage makes freeze-dried probiotic-loaded calcium alginate difficult to use in commercial foods. Therefore, it is urgent to analyze the mechanism of calcium-induced low survival of probiotics. In the present work, this mechanism was analyzed using Lactobacillus rhamnosus GG (LGG) as a research model. The results showed that calcium led to the emergence of 491 differential genes (300 up-regulated genes), 309 (175 up-regulated metabolites, positive ion) and 129 differential metabolites (33 up-regulated metabolites, negative ion). For one of the mechanisms, GO and KEGG analysis of differential genes indicated that calcium increased cardiolipin by downregulating glpO and upregulating LGG-RS07795 and cls genes in the glycerophospholipid metabolism pathway, increasing the fluidity of cell membrane, thereby causing the catabolism of cell membrane components. Additionally, the disturbances of differential genes/metabolites co-enrichment pathways by calcium were other mechanisms. Specifically, the correlation analysis of differential genes/metabolites that had upstream/downstream relationships in co-enrichment KEGG pathways showed consistently strong correlations, among which hisC gene regulated histidine metabolism pathway and phenylalanine, tyrosine and tryptophan biosynthesis pathway, ndk gene regulated pyrimidine metabolism pathway and purine metabolism pathway, and 3-phosphoserine, phenylalanine, and tyrosine were involved in multiple pathways including other differential genes/metabolites co-enrichment KEGG pathways. Based on the above mechanism analysis, the addition of small molecule sugar/sugar alcohol and down-regulated differential metabolites (ergothioneine and cytidine) in the co-enrichment pathway were effective strategies to improve the freeze-drying survival of LGG encapsulated in calcium alginate. Overall, these findings are expected to promote the application of dried calcium-based probiotics foods in the food industry.

AIE fluorescent probes for monitoring cell membrane fluidity /lipid droplet change during alcoholic liver disease

Alcoholic liver disease (ALD) has attracted widespread attention because of the ever-increasing alcohol consumption and high morbidity. However, there is still no effective detection method to prevent the deterioration of the disease. Cholesterol, as the main component of the cell membrane (CM), often transported to lipid droplets (LDs) for storage in hepatocytes. Meanwhile, abnormal changes of cholesterol could cause liver diseases, such as Tangier disease. Based on cholesterol could serve as a hub that affects the cell membrane fluidity (CMF) and the number of LDs, we planned to study the microscopic changes of CMF and LDs in ALD. As viscous media could limit the intramolecular motion of fluorescent probes, aggregation induced emission luminogens (AIEgens), which typically have rotators and vibrators in their structures and emit strongly in the aggregate state, may be promising candidates for CMF and LD study. So two AIE probes (TPCN and NDPB) were designed and synthesized based on the typical AIE skeleton, tetraphenylethylene (TPE), which could selectively target CMs and LDs, respectively. These probes exhibited high chemical stability, controllable emission, and excellent subcellular specificity. They successfully sensed the correlated changes of CMs and LDs in ALD model, which would contribute to understanding the microscopic process of ALD pathogenesis and further development of ALD therapeutic drugs.

Melatonin Preserves Fluidity in Cell and Mitochondrial Membranes against Hepatic Ischemia-Reperfusion.

We evaluated the in vivo effects of melatonin treatment on oxidative damage in the liver in an experimental model of ischemia-reperfusion. A total of 37 male Sprague-Dawley rats were randomly divided into four groups: control, ischemia, ischemia + reperfusion, and ischemia + reperfusion + melatonin. Hepatic ischemia was maintained for 20 min, and the clamp was removed to initiate vascular reperfusion for 30 min. Melatonin (50 mg/kg body weight) was intraperitoneally administered. Fluidity was measured by polarization changes in 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene-p-toluene sulfonate). After 20 min of ischemia, no significant changes were observed in cell and mitochondrial membrane fluidity levels, lipid peroxidation, and protein carbonylation. However, after 30 min of reperfusion, membrane fluidity decreased compared to controls. Increases in lipid and protein oxidation were also seen in hepatic homogenates of animals exposed to reperfusion. Melatonin injected 30 min before ischemia and reperfusion fully prevented membrane rigidity and both lipid and protein oxidation. Livers from ischemia-reperfusion showed histopathological alterations and positive labeling with antibodies to oxidized lipids and proteins. Melatonin reduced the severity of these morphological changes and protected against in vivo ischemia-reperfusion-induced toxicity in the liver. Therefore, melatonin might be a candidate for co-treatment for patients with hepatic vascular occlusion followed by reperfusion.

Mining of key genes for cold adaptation from Pseudomonas fragi D12 and analysis of its cold-adaptation mechanism.

The psychrotroph Pseudomonas fragi D12, which grew strongly under low temperatures, was screened from tundra soil collected from the permanent alpine zone on Changbai Mountain. To mine the genes critical for cold tolerance and to investigate the cold-adaptation mechanism, whole-genome sequencing, comparative genomic analysis, and transcriptome analysis were performed with P. fragi. A total of 124 potential cold adaptation genes were identified, including nineteen unique cold-adaptive genes were detected in the genome of P. fragi D12. Three unique genes associated with pili protein were significantly upregulated at different degrees of low temperature, which may be the key to the strong low-temperature adaptability of P. fragi D12. Meanwhile, we were pleasantly surprised to find that Pseudomonas fragi D12 exhibited different cold-adaptation mechanisms under different temperature changes. When the temperature declined from 30°C to 15°C, the response included maintenance of the fluidity of cell membranes, increased production of extracellular polymers, elevation in the content of compatibility solutes, and reduction in the content of reactive oxygen species, thereby providing a stable metabolic environment. When the temperature decreased from 15°C to 4°C, the response mainly included increases in the expression of molecular chaperones and transcription factors, enabling the bacteria to restore normal transcription and translation. The response mechanism of P. fragi D12 to low-temperature exposure is discussed. The results provide new ideas for the cold-adaptation mechanism of cold-tolerant microorganisms.

Cholesterol depletion decreases adhesion of non-small cell lung cancer cells to E-selectin.

Lipid microdomains, ordered membrane phases containing cholesterol and glycosphingolipids, play an essential role in cancer cell adhesion and ultimately metastasis. Notably, elevated levels of cholesterol-rich lipid microdomains are found in cancer cells relative to their normal counterparts. Therefore, alterations of lipid microdomains through cholesterol modulation could be used as a strategy to prevent cancer metastasis. In this study, methyl-beta-cyclodextrin (MβCD), sphingomyelinase (SMase), and simvastatin (Simva) were used to investigate the effects of cholesterol on the adhesive behaviors of four non-small cell lung cancer (NSCLC) cell lines (H1299, H23, H460, and A549) and a small cell lung cancer (SCLC) cell line (SHP-77) on E-selectin, a vascular endothelial molecule that initiates circulating tumor cell recruitment at metastatic sites. Under hemodynamic flow conditions, the number of adherent NSCLC cells on E-selectin significantly decreased by MβCD and Simva treatments, whereas SMase treatment did not show a significant effect. Significant increases in rolling velocities were detected only for H1299 and H23 cells after MβCD treatment. In contrast, cholesterol depletion did not affect SCLC cell attachment and rolling velocities. Moreover, cholesterol depletion by MβCD and Simva induced CD44 shedding and resulted in an enhanced membrane fluidity in the NSCLC cells, whereas it did not affect the membrane fluidity of the SCLC cells which lacked detectable expression of CD44. Our finding suggests that cholesterol regulates the E-selectin-mediated adhesion of NSCLC cells by redistributing the CD44 glycoprotein and thus modulating the membrane fluidity.NEW & NOTEWORTHY This study investigates the effects of cholesterol on the adhesive behaviors of lung cancer cells in recruitment at metastatic sites. Using cholesterol-modulating compounds, we found that reducing cholesterol decreases the adhesion of non-small cell lung cancer (NSCLC) cells while having no significant effect on small cell lung cancer (SCLC) cells. The study suggests that cholesterol regulates NSCLC cell metastasis by redistributing the adhesion proteins on the cells and modulating cells' membrane fluidity.

Pharmacological Activity of Cepharanthine.

Cepharanthine, a natural bisbenzylisoquinoline (BBIQ) alkaloid isolated from the plant Stephania Cephalantha Hayata, is the only bisbenzylisoquinoline alkaloid approved for human use and has been used in the clinic for more than 70 years. Cepharanthine has a variety of medicinal properties, including signaling pathway inhibitory activities, immunomodulatory activities, and antiviral activities. Recently, cepharanthine has been confirmed to greatly inhibit SARS-CoV-2 infection. Therefore, we aimed to describe the pharmacological properties and mechanisms of cepharanthine, mainly including antitumor, anti-inflammatory, anti-pathogen activities, inhibition of bone resorption, treatment of alopecia, treatment of snake bite, and other activities. At the same time, we analyzed and summarized the potential antiviral mechanism of cepharanthine and concluded that one of the most important anti-viral mechanisms of cepharanthine may be the stability of plasma membrane fluidity. Additionally, we explained its safety and bioavailability, which provides evidence for cepharanthine as a potential drug for the treatment of a variety of diseases. Finally, we further discuss the potential new clinical applications of cepharanthine and provide direction for its future development.

Supramolecular Photothermal Cascade Nano-Reactor Enables Photothermal Effect, Cascade Reaction, and In Situ Hydrogelation for Biofilm-Associated Tooth-Extraction Wound Healing.

Due to the emergence of drug resistance in bacteria and biofilm protection, achieving a satisfactory therapeutic effect for bacteria-infected open wounds with conventional measures is problematic. Here, we construct a photothermal cascade nano-reactor (CPNC@GOx-Fe2+ ) through a supramolecular strategy through hydrogen bonding and coordination interactions between chitosan-modified palladium nano-cube (CPNC), glucose oxidase (GOx), and ferrous iron (Fe2+ ). CPNC@GOx-Fe2+ exhibits excellent photothermal effect and powers the GOx-assisted cascade reaction to generate hydroxyl radicals, enabling photothermal and chemodynamic combination therapy against bacteria and biofilms. Further proteomics, metabolomics, and all-atom simulation results indicate that the damage of hydroxyl radical to the function and structure of the cell membrane and the thermal effect enhances the fluidity and inhomogeneity of the bacterial cell membrane, resulting in the synergistic anti-bacterial effect. In the biofilm-associated tooth extraction wound model, hydroxyl radical generated from the cascade reaction process could initiate the radical polymerization process to form a hydrogel in situ for wound protection. In vivo experiments confirm synergistic anti-bacterial and wound protection can accelerate the healing of infected tooth-extraction wounds without affecting the oral commensal microbiota. This study provides a way to propose a multifunctional supramolecular system for the treatment of open wound infection. This article is protected by copyright. All rights reserved.

Membrane Phenotypic, Metabolic and Genotypic Adaptations of Streptococcus oralis Strains Destined to Rapidly Develop Stable, High-Level Daptomycin Resistance during Daptomycin Exposures.

The Streptococcus mitis-oralis subgroup of viridans group streptococci are important human pathogens. We previously showed that a substantial portion of S. mitis-oralis strains (>25%) are 'destined' to develop rapid, high-level, and stable daptomycin (DAP) resistance (DAP-R) during DAP exposures in vitro. Such DAP-R is often accompanied by perturbations in distinct membrane phenotypes and metabolic pathways. The current study evaluated two S. oralis bloodstream isolates, 73 and 205. Strain 73 developed stable, high-level DAP-R (minimum inhibitory concentration [MIC] > 256 µg/mL) within 2 days of in vitro DAP passage ("high level" DAP-R [HLDR]). In contrast, strain 205 evolved low-level and unstable DAP-R (MIC = 8 µg/mL) under the same exposure conditions in vitro ("non-HLDR"). Comparing the parental 73 vs. 73-D2 (HLDR) strain-pair, we observed the 73-D2 had the following major differences: (i) altered cell membrane (CM) phospholipid profiles, featuring the disappearance of phosphatidylglycerol (PG) and cardiolipin (CL), with accumulation of the PG-CL pathway precursor, phosphatidic acid (PA); (ii) enhanced CM fluidity; (iii) increased DAP surface binding; (iv) reduced growth rates; (v) decreased glucose utilization and lactate accumulation; and (vi) increased enzymatic activity within the glycolytic (i.e., lactate dehydrogenase [LDH]) and lipid biosynthetic (glycerol-3-phosphate dehydrogenase [GPDH]) pathways. In contrast, the 205 (non-HLDR) strain-pair did not show these same phenotypic or metabolic changes over the 2-day DAP exposure. WGS analyses confirmed the presence of mutations in genes involved in the above glycolytic and phospholipid biosynthetic pathways in the 73-D2 passage variant. These data suggest that S. oralis strains which are 'destined' to rapidly develop HLDR do so via a conserved cadre of genotypic, membrane phenotypic, and metabolic adaptations.

Mitigation of Insulin Resistance by Natural Products from a New Class of Molecules, Membrane-Active Immunomodulators.

Insulin resistance (IR), accompanied by an impaired cellular glucose uptake, characterizes diverse pathologies that include, but are not limited to, metabolic disease, prediabetes and type 2 diabetes. Chronic inflammation associated with deranged cellular signaling is thought to contribute to IR. The key molecular players in IR are plasma membrane proteins, including the insulin receptor and glucose transporter 4. Certain natural products, such as lipids, phenols, terpenes, antibiotics and alkaloids have beneficial effects on IR, yet their mode of action remains obscured. We hypothesized that these products belong to a novel class of bioactive molecules that we have named membrane-active immunomodulators (MAIMs). A representative MAIM, the naturally occurring medium chain fatty acid ester diethyl azelate (DEA), has been shown to increase the fluidity of cell plasma membranes with subsequent downstream effects on cellular signaling. DEA has also been shown to improve markers of IR, including blood glucose, insulin and lipid levels, in humans. The literature supports the notion that DEA and other natural MAIMs share similar mechanisms of action in improving IR. These findings shed a new light on the mechanism of IR mitigation using natural products, and may facilitate the discovery of other compounds with similar activities.

The regulation of carbon dioxide on food microorganisms: A review

This review presents a survey of two extremely important technologies about CO2 with the effectiveness of controlling microorganisms - atmospheric pressure CO2-based modified atmosphere packaging (MAP) and high pressure CO2 non-thermal pasteurization (HPCD). CO2-based MAP is effectively in delaying the lag and logarithmic phases of microorganisms by replacing the surrounding air, while HPCD achieved sterilization by subjecting food to either subcritical or supercritical CO2 for some time in a continuous, batch or semi-batch way. In addition to the advantages of healthy, eco-friendly, quality-preserving, effective characteristic, some challenges such as the high drip loss and packaging collapse associated with higher concentration of CO2, the fuzzy mechanisms of oxidative stress, the unproven specific metabolic pathways and biomarkers, etc., in CO2-based MAP, and the unavoidable extraction of bioactive compounds, the challenging application in solid foods with higher efficiency, the difficult balance between optimal sterilization and optimal food quality, etc., in HPCD still need more efforts to overcome. The action mechanism of CO2 on microorganisms, researches in recent years, problems and future perspectives are summarized. When dissolved in solution medium or cellular fluids, CO2 can form carbonic acid (H2CO3), and H2CO3 can further dissociate into bicarbonate ions (HCO3–), carbonate (CO32−) and hydrogen cations (H+) ionic species following series equilibria. The action mode of CO2 on microorganisms may be relevant to changes in intracellular pH, alteration of proteins, enzyme structure and function, alteration of cell membrane function and fluidity, and so on. Nevertheless, the effects of CO2 on microbial biofilms, energy metabolism, protein and gene expression also need to be explored more extensively and deeply to further understand the action mechanism of CO2 on microorganisms.

Cells immersed in collagen matrices show a decrease in plasma membrane fluidity as the matrix stiffness increases

Cells are constantly adapting to maintain their identity in response to the surrounding media's temporal and spatial heterogeneity. The plasma membrane, which participates in the transduction of external signals, plays a crucial role in this adaptation. Studies suggest that nano and micrometer areas with different fluidities at the plasma membrane change their distribution in response to external mechanical signals. However, investigations linking fluidity domains with mechanical stimuli, specifically matrix stiffness, are still in progress. This report tests the hypothesis that the stiffness of the extracellular matrix can modify the equilibrium of areas with different order in the plasma membrane, resulting in changes in overall membrane fluidity distribution. We studied the effect of matrix stiffness on the distribution of membrane lipid domains in NIH-3 T3 cells immersed in matrices of varying concentrations of collagen type I, for 24 or 72 h. The stiffness and viscoelastic properties of the collagen matrices were characterized by rheometry, fiber sizes were measured by Scanning Electron Microscopy (SEM) and the volume occupied by the fibers by second harmonic generation imaging (SHG). Membrane fluidity was measured using the fluorescent dye LAURDAN and spectral phasor analysis. The results demonstrate that an increase in collagen stiffness alters the distribution of membrane fluidity, leading to an increasing amount of the LAURDAN fraction with a high degree of packing. These findings suggest that changes in the equilibrium of fluidity domains could represent a versatile and refined component of the signal transduction mechanism for cells to respond to the highly heterogeneous matrix structural composition. Overall, this study sheds light on the importance of the plasma membrane's role in adapting to the extracellular matrix's mechanical cues.

Breaking Down Tumor Drug Resistance: The Link Between Cell Membrane Changes and Treatment Efficacy

Abstract There have been significant advances in our understanding of how changes in the fluidity and permeability of the cell membrane can affect drug resistance in cancer. Research has shown that cancer cells often have changes in the fluidity and permeability of their cell membrane that contribute to their resistance to drugs used to treat cancer. These changes may be due to changes in the composition and organization of the lipid bilayer that makes up the membrane, as well as changes in the expression or localization of proteins and other molecules embedded in the membrane. The lipid composition in the tumor cell membrane changes with drug resistance, which can affect the fluidity and permeability of the cell membrane. Reversal of drug resistance can be achieved by altering cell membrane fluidity and permeability. In recent years, there have been numerous studies aimed at understanding the mechanisms underlying these changes and identifying strategies to overcome drug resistance in cancer. This research has led to the development of new drugs and drug delivery systems that are designed to target specific changes in the cell membrane of cancer cells and improve the effectiveness of chemotherapy. Overall, the advances in our understanding of the role of cell membrane fluidity and permeability in drug resistance in cancer have led to the development of new approaches to treat cancer and improve patient outcomes and further research is needed to continue to improve the understanding of these mechanisms and to identify new strategies to overcome drug resistance in cancer. This article highlights the research status and detection methods of cell membrane fluidity and permeability affecting tumor drug resistance.

The lipidomic profiles of donkey semen present greater diversity and abundance than horse semen

While donkeys and horses belong to the same family and are able to cross-mate to produce hybrids, there are many unique features of either species regarding their sexual behavior, semen characteristics, and tolerance to cryopreservation; therefore, a better understanding of the physiology of either species can enhance semen processing and fertility. Lipids play a paramount role in the fluidity and flexibility of the sperm plasma membrane and are intrinsically related to sperm motility and plasma membrane integrity. This study aimed to determine the lipid profile of donkey and horse semen. Semen from 19 jacks and 25 stallions was collected by artificial vagina, and gel-free semen was assessed for motility, morphology, concentration, and volume. An aliquot of gel-free semen (50 million sperm/mL) was placed in cryovials and then plunged into liquid nitrogen until lipidomic analysis. The lipidomic profile of the gel-free semen was performed with MALDI-MS with no addition of an extender. The analyses were performed with MetaboAnalyst 2.0 and the discriminating analyses of PLS-DA to demonstrate differences between horses and donkeys. The lipid types that were differentially expressed were analyzed by ANOVA followed by Tukey test. The Volcano plot was used to compare species, using the criteria values of P<0.05 andfold-change (FC) ≥1.5. A total of 101 ion lipids were found in horse semen and 105 in donkey semen. Five ion-lipids with mass charge (mz) 762, 822, 865, 867, and 879 were uniquely present in horse semen, but not identified in the databases (www.lipidmaps.org), whereas 9-ion-lipid were present in donkey semen (m/z 709.4, 731, 753, 756, 778, 796, 798, 811 and 880) with only 709.4 being identified (Phosphatidylglycerol). The donkeys showed 18 ion-lipid with greater relative abundance (P<0.05 and fold-change>1.5), 12 identified in the database (4 triacylglycerols, 2 phosphatidylglycerols, 2 phosphatidylcholine, 2 phosphatidylinositols and 2 sphingolipids); whereas the horse had ten ion-lipid with greater abundance (P<0.05 and fold-change >1.5) but only 4 identified (2 diacylglycerols, 1 triacylglycerol and 1 phosphatidylglycerol). Among these identified lipids, 10 have one or more double bonds, making them mono- or polyunsaturated, while in horses only 1 was polyunsaturated. This may be one of the underlying reasons for lower tolerance to cryopreservation/cooling of donkey semen. In conclusion, the lipidomic profile of donkey and stallion semen differ with regard to relative abundance and diversity.

Relationship between obesity, insulin resistance and cell membrane properties

Introduction and aim. The obesity is one of the greatest public health problems in developing countries and it is a triggering factor for diabetes associated with insulin resistance. The importance of cell membrane lipids as essential regulators of insulin resistance, since changes in the dynamic properties of the cell membrane (e.g., membrane fluidity), could be one of the events by which obesity affects insulin sensitivity. Thus, the insulin resistance may not only be a cause but also a consequence of lipid disorders such as dyslipidemia and/or cell membrane phospholipid composition change. The modification of plasma membrane lipid composition can change membrane biophysical properties and thus influencing protein-lipid interactions, enzymatic activity and regulation of surface receptors. Alterations in the lipid composition modify the fluidity of plasma membranes and the expression of membrane functions, such as receptor binding and enzyme activities. This review summarizes the current knowledge on the effects of the modulation of plasma membrane lipid composition and membrane fluidity in the functionality of membrane proteins involved in insulin activity, including the insulin receptor, glucose transport and Na + /K + ATPase and, in turn, the key features of the metabolic syndrome. Material and methods. References for that article were found through PubMed and Google Scholar, using terms: “obesity”, “insulin resistance” and “membrane properties”. The research was limited to abstracts and available full-text articles. Analysis of the literature. There is a strong relationship between dietary lipids, membrane lipid profiles and insulin resistance. The changes in the dynamic properties of the cell membrane (e.g., membrane fluidity), could be one of the events by which obesity affects insulin sensitivity. The modification of plasma membrane lipid composition can change membrane biophysical properties and thus influencing protein–lipid interactions, enzymatic activity, and regulation of surface receptors. Modifications of membrane phospholipid composition could have a role in the insulin action by altering membrane fluidity and, as a consequence, the insulin signaling pathway. Conclusion. As conclusion the membrane-lipid therapy approach can be used to treat important pathologies such as obesity and many others diseases such as : cancer, cardiovascular pathologies, neurodegenerative processes, obesity, metabolic disorders, inflammation, and infectious and autoimmune diseases. This pharmacological strategy aims to regulate cell functions by influencing lipid organization and membrane fluidity, inducing a concomitant modulation of membrane protein localization and activity which might serve to reverse the pathological state. Through this review we suggest an in-depth analysis of the membrane lipid therapy field, especially its molecular bases and its relevance to the development of innovative therapeutic approaches.

Sperm Cryopreservation Today: Approaches, Efficiency, and Pitfalls.

The cryopreservation of human spermatozoa has been an option for patients undergoing chemo or radiotherapies since the late 1950s. Presently, there are different techniques for the cryopreservation of spermatozoa. The most commonly used techniques are programmable slow freezing and freezing on liquid nitrogen vapors, while the use of vitrification is still not accepted as clinically relevant. Although there have been many improvements, the ideal technique for achieving better post-thaw sperm quality continues to be a mystery. A major obstacle during cryopreservation is the formation of intracellular ice crystals. Cryodamage generated by cryopreservation causes structural and molecular alterations in spermatozoa. Injuries can happen because of oxidative stress, temperature stress, and osmotic stress, which then result in changes in the plasma membrane fluidity, motility, viability, and DNA integrity of the spermatozoa. To prevent cryodamage as much as possible, cryoprotectants are added, and in some clinical trial cases, even antioxidants that may improve post-thaw sperm quality are added. This review discusses cryopreservation techniques, cryodamage on molecular and structural levels, and cryoprotectants. It provides a comparison of cryopreservation techniques and describes recent advances in those techniques.

Astaxanthin protected against the adverse effects induced by diesel exhaust particulate matter via improving membrane stability and anti-oxidative property

Diesel exhaust particulate matter (DPM), which has been clarified as a Group I carcinogenic agent, is still challenging in its detoxification due to the complex composition and toxic mechanisms. Astaxanthin (AST) is a pleiotropic small biological molecule widely used in medical and healthcare with surprising effects and applications. The present study aimed to investigate the protective effects of AST on DPM-induced injury and the underlying mechanism. Our results indicated that AST significantly suppressed the generation of phosphorylated histone H2AX (γ-H2AX, marker of DNA damage) and inflammation caused by DPM both in vitro and in vivo. Mechanistically, AST prevented the endocytosis and intracellular accumulation of DPM via regulating the stability and fluidity of plasma membranes. Moreover, the oxidative stress elicited by DPM in cells could also be effectively inhibited by AST, together with protecting the structure and function of mitochondria. These investigations provided clear evidence that AST notably reduced DPM invasion and intracellular accumulation by modulating the membrane-endocytotic pathway, which eventually reduced intracellular oxidative stress caused by DPM. Our data might provide a novel clue for curing and treating the harmful effects of particulate matter.

Co-encapsulation of probiotics with acylglycerols in gelatin-gum arabic complex coacervates: Stability evaluation under adverse conditions

Co-encapsulation of acylglycerols and probiotics may improve the resistance of probiotics to adverse conditions. In this study, three probiotic microcapsule models were constructed using gelatin (GE)-gum arabic (GA) complex coacervate as wall material: microcapsules containing only probiotics (GE-GA), microcapsules containing triacylglycerol (TAG) oil and probiotics (GE-T-GA) and microcapsules containing diacylglycerol (DAG) oil and probiotics (GE-D-GA). The protective effects of three microcapsules on probiotic cells under environmental stresses (freeze-drying, heat treatment, simulated digestive fluid and storage) were evaluated. The results of cell membrane fatty acid composition and Fourier transform infrared (FTIR) spectroscopy revealed that GE-D-GA could improve the fluidity of cell membrane, maintain the stability of protein and nucleic acid structure, and decrease the damage of cell membrane. These characteristics supported the high freeze-dried survival rate (96.24 %) of GE-D-GA. Furthermore, regardless of thermotolerance or storage, GE-D-GA showed the best cell viability retention. More importantly, GE-D-GA provided the best protection for probiotics under simulated gastrointestinal conditions, as the presence of DAG reduced cell damage during freeze-drying and the degree of contact between probiotics and digestive fluids. Therefore, co-microencapsulation of DAG oil and probiotics is a promising strategy to resist adverse conditions.

Antibacterial properties of citral against Staphylococcus aureus: From membrane damage to metabolic inhibition

Citral, a natural antimicrobial agent, has been found to induce severe membrane damage resulting in bacterial death. Despite its effectiveness, there is a lack of in-depth research on its interaction with bacterial cells, especially at low concentrations. This work aimed to investigate the impact of citral concentration on its antibacterial effect against Staphylococcus aureus (S. aureus) and to analyze the relevance between membrane damage and cell death. In this study, the minimal inhibitory concentration of citral against S. aureus was measured at 0.25 mg/mL. At a concentration of 0.5 mg/mL, citral significantly disturbed the cell membrane fluidity and permeability, leading to the leakage of intracellular macromolecules and rapid cell death. However, when the concentration was decreased to 0.25 mg/mL, the membrane damage was greatly reduced, and a complex biological process between citral and membrane components was found. Under continuous drug exposure, the cell membrane underwent gradual rigidification, concomitant with the loss of membrane function, ultimately causing cell death. Despite the fact that no notable disturbance to membrane functions was discovered, the presence of 0.125 mg/mL citral could still weaken the metabolic vitality and growth of S. aureus. Therefore, it was suggested that there could be multiple mechanisms of citral action on S. aureus cells, with drug concentration being a critical factor affecting the mode of action. Overall, the findings of this study provide valuable insights into the antibacterial mechanisms of natural compounds and broaden the potential applications of citral as a natural antimicrobial.

Bioactivity of Macronutrients from Chlorella in Physical Exercise

Chlorella is a marine microalga rich in proteins and containing all the essential amino acids. Chlorella also contains fiber and other polysaccharides, as well as polyunsaturated fatty acids such as linoleic acid and alpha-linolenic acid. The proportion of the different macronutrients in Chlorella can be modulated by altering the conditions in which it is cultured. The bioactivities of these macronutrients make Chlorella a good candidate food to include in regular diets or as the basis of dietary supplements in exercise-related nutrition both for recreational exercisers and professional athletes. This paper reviews current knowledge of the effects of the macronutrients in Chlorella on physical exercise, specifically their impact on performance and recovery. In general, consuming Chlorella improves both anaerobic and aerobic exercise performance as well as physical stamina and reduces fatigue. These effects seem to be related to the antioxidant, anti-inflammatory, and metabolic activity of all its macronutrients, while each component of Chlorella contributes its bioactivity via a specific action. Chlorella is an excellent dietary source of high-quality protein in the context of physical exercise, as dietary proteins increase satiety, activation of the anabolic mTOR (mammalian Target of Rapamycin) pathway in skeletal muscle, and the thermic effects of meals. Chlorella proteins also increase intramuscular free amino acid levels and enhance the ability of the muscles to utilize them during exercise. Fiber from Chlorella increases the diversity of the gut microbiota, which helps control body weight and maintain intestinal barrier integrity, and the production of short-chain fatty acids (SCFAs), which improve physical performance. Polyunsaturated fatty acids (PUFAs) from Chlorella contribute to endothelial protection and modulate the fluidity and rigidity of cell membranes, which may improve performance. Ultimately, in contrast to several other nutritional sources, the use of Chlorella to provide high-quality protein, dietary fiber, and bioactive fatty acids may also significantly contribute to a sustainable world through the fixation of carbon dioxide and a reduction of the amount of land used to produce animal feed.

Exposure to dietary fatty acids oleic and palmitic acid alters structure and mechanotransduction of intestinal cells in vitro

Intestinal cells are continuously exposed to food constituents while adapting to peristaltic movement and fluid shear stress. Oleic acid (OA) and palmitic acid (PA) are among the most prevalent fatty acids with respect to dietary lipids. Despite the central importance of dietary lipids for a balanced diet, awareness about potential detrimental effects related to excessive consumption is increasing; this includes toxicity, metabolic deregulation, and, particularly for cancer cells, a benefit from the uptake of fatty acids related to promotion of metastasis. Expanding on this, we started elucidating the effects of OA and PA (25–500 µM) on non-transformed human intestinal epithelial cells (HCEC-1CT) in comparison to colon carcinoma cells (HCT116), with regard to the mechanosensory apparatus. Hence, intestinal cells’ motility is on the one side essential to ensure adaption to peristaltic movement and barrier function, but also to enable metastatic progression. Incubation with both OA and PA (≥ 25 µM) significantly decreased membrane fluidity of HCT116 cells, whereas the effect on HCEC-1CT was more limited. Application of rhodamine-labelled PA demonstrated that the fatty acid is incorporated into the plasma membrane of HCT116, which could not be observed in the non-tumorigenic cell line. Down-streaming into the intracellular compartment, a pronounced rearrangement of actin cytoskeleton was evident in both cell lines (OA and PA; 25 and 100 µM). This was accompanied by a variation of translocation efficiency of the mechanosensitive co-transcription factor YAP1, albeit with a stronger effect seen for PA and the cancer cells. Untargeted proteomic analysis confirmed that exposure to OA and PA could alter the response capacity of HCT116 cells to fluid shear stress. Taken together, OA and PA were able to functionally modulate the mechanosensory apparatus of intestinal cells, implying a novel role for dietary fatty acids in the regulation of intestinal pathophysiology.