Plasma Membrane Lipid Research Articles

Molecular mechanisms of ferroptosis and its effects on bladder cancer.

Bladder cancer (BC) is one of the 3 common malignant tumors in the urinary system, with high incidence, easy metastasis, poor therapeutic efficacy, and poor prognosis, which seriously threatens the health of human. Tumor cells exhibit a strong demand for iron, and iron overload can induce ferroptosis, which is an iron dependent cell death caused by lipid peroxidation and cell membrane damage. Therefore, ferroptosis has strong anti-tumor potential. The molecular mechanisms of ferroptosis is associated with abnormalities in cellular phospholipid metabolism and iron metabolism, and dysregulation of antioxidant and non-antioxidant systems Xc-/glutathione (GSH)/glutathione peroxidase 4 (GPX4). Ferroptosis relevant molecules play important roles in the occurrence and development, metastasis, drug resistance, and immune response of BC, and are expected to become targets for the treatment of BC.

The synchronic, diachronic cell as the holism of consciousness

The cell is both synchronic and diachronic, based on ontogeny and phylogeny, respectively. As experimental evidence for this holism, absent gravitational force, differentiated lung and bone cells devolve, losing their phenotypes, losing their evolutionary status, reverting to their nonlocal status. Thus, when evolution is seen as serial homeostasis, it is homologous with Quantum Entanglement as the nonlocal means of maintaining homeostatic balance between particles. This monadic perspective on consciousness is one-hundred and eighty degrees out of synch with the conventional way of thinking about consciousness as a diad, or mind and brain. There have been many attempts to explain consciousness, virtually all of them based on the brain as mind. The working hypothesis is that consciousness is a holism constituted by the unicell, the lipid cell membrane forming a barrier between inside and outside of the cell's environment as a topology. Conceptually, both the unicell and ‘two hands clapping’ are holisms, but because the cell is constituted by the ambiguity of negative entropy, and ‘one hand clapping’ requires two hands, they are both pseudo-holisms, constantly striving to be whole again. In the case of the cell, it is incomplete in the sense that there are factors in the ever-changing environment that can homeostatically complete it. That process results in biochemical modification of specific DNA codes in the egg or sperm so that the offspring is able to adapt in subsequent generations epigenetically. The opportunity to trace the evolution of the breath from humans to fish opens up to the further revelation of the interplay between evolution and geological change, tracing it back to invertebrates, sponges, and ultimately to unicellular organisms. And therein is evidence that the Cosmos itself ‘breathes’, providing the ultimate celestial fundament for this trail of holisms.

Development of a bottom-up coarse-grained model for interactions of lipids with TiO nanoparticles.

Understanding interactions of inorganic nanoparticles with biomolecules is important in many biotechnology, nanomedicine, and toxicological research, however, the size of typical nanoparticles makes their direct modeling by atomistic simulations unfeasible. Here, we present a bottom-up coarse-graining approach for modeling titanium dioxide (TiO ) nanomaterials in contact with phospholipids that uses the inverse Monte Carlo method to optimize the effective interactions from the structural data obtained in small-scale all-atom simulations of TiO surfaces with lipids in aqueous solution. The resulting coarse-grained models are able to accurately reproduce the structural details of lipid adsorption on different titania surfaces without the use of an explicit solvent, enabling significant computational resource savings and favorable scaling. Our coarse-grained simulations show that small spherical TiO nanoparticles ( nm) can only be partially wrapped by a lipid bilayer with phosphoethanolamine headgroups, however, the lipid adsorption increases with the radius of the nanoparticle. The current approach can be used to study the effect of the size and shape of TiO nanoparticles on their interactions with cell membrane lipids, which can be a determining factor in membrane wrapping as well as the recently discovered phenomenon of nanoquarantining, which involves the formation of layered nanomaterial-lipid structures.

Detection and characterization of the Pichia manshurica biofilm on the traditionally produced homemade apple vinegar.

Pichia yeasts are capable of forming biofilms during vinegar production and causing spoilage in various beverages. In addition, there exists a significant likelihood of encountering yeast contamination which can prevent vinegar production. The present study investigates the detection and characterization of the Pichia manshurica (P. manshurica) biofilm on traditionally produced homemade apple vinegar. The unique characteristics of vinegar were analyzed with a focus on the constituent, known as the "mother of vinegar", whose composition is comprised of cellulosic biofilm and acetic acid bacteria, including Gluconobacter oxydans (G. oxydans) Briefly, P. manshurica was isolated from apple vinegar and characterized in terms of the effect of biofilm formation on the surface of the cellulosic film on vinegar production. Microbial identification of vinegar with/without contamination by P. manshurica was analyzed through MALDI-TOF mass spectrometry (MS), and biofilm was characterized by Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), and crystal violet staining. Accordingly, MS spectrum of isolates was identified as G. oxydans and P. manshurica with a ratio of 2.01 and 1.94, respectively. The FTIR analysis indicated that the peaks within the range of 1150-900 cm-1 revealed a high content of polysaccharide in P. manchuria-contaminated biofilm, which is attributed to the stretching vibration of C-C and C-O bonds. The spectral region from 2921.51 to 2853.71 cm-1 exhibited the characteristic of lipids in bacterial cell walls and membranes. SEM images of bacterial biofilms revealed a three-dimensional network composed of ultrafine fibers with a ribbon-like shape; however, the condensed reticulated structure was observed in contaminated biofilms. The presence of two microbial populations was detected regarding the morphological analysis. Crystal violet staining of contaminated-cellulosic biofilms visualized bacterial and yeast colonization. Concisely, this study emphasizes that the proliferation of Pichia during apple fermentation has the potential to adversely affect the quality of the homemade vinegar, due to its distinct biofilm characteristics.

Lipid organization and turnover in the plasma membrane of human differentiating neural progenitor cells revealed by time-of-flight secondary ion mass spectrometry imaging

Membrane lipids have been known to influence multiple signalling and cellular processes. Dysregulation of lipids at the neuronal membrane is connected to a significant alteration of the brain function and morphology, leading to brain diseases and neurodegeneration. Understanding the lipid composition and turnover of neuronal membrane will provide a significant insight into the molecular events underlying the regulatory effects of these biomolecules in a neuronal system. In this study, we aimed to characterize the composition and turnover of the plasma membrane lipids in human neural progenitor cells (NPCs) at an early differentiation stage into midbrain neurons using ToF-SIMS imaging. Lipid composition of the native plasma membrane was explored, followed by an examination of the lipid turnover using different isotopically labelled lipid precursors, including 13C-choline, 13C-lauric acid, 15N-linoleic, and 13C-stearic. Our results showed that differentiating NPCs contain a high abundance of ceramides, glycerophosphoserines, neutral glycosphingolipids, diradylglycerols, and glycerophosphocholines at the plasma membrane. In addition, different precursors were found to incorporate into different membrane lipids which are specific for the short- or long-carbon chains, and the unsaturation or saturation stage of the precursors. The lipid structure of neuronal membrane reflects the differentiation status of NPCs, and it can be altered significantly using a particular lipid precursor. Our study illustrates a potential of ToF-SIMS imaging to study native plasma membrane lipids and elucidate complex cellular processes by providing molecular -rich information at a single cell level.

Molecular insight into thymoquinone mechanism of action against Mycobacterium tuberculosis.

Natural products are promising antimicrobials, usually having multiple and different cellular targets than synthetic antibiotics. Their influence on bacteria at various metabolic and functional levels contributes to higher efficacy even against drug-resistant strains. One such compound is a naturally occurring p-benzoquinone - thymoquinone. It is effective against different bacteria, including multidrug-resistant and extremely drug-resistant Mycobacterium tuberculosis. Its antibacterial mechanism of action was studied in several bacterial species except mycobacteria. To get an insight into the antimycobacterial activity of thymoquinone at the molecular level, we performed metabolomic and transcriptomic analyzes of bacteria exposed to this compound. The expression of genes coding stress-responsive sigma factors revealed that thymoquinone rapidly induces the production of sigE transcripts. At the same time, prolonged influence results in the overexpression of all sigma factor genes and significantly upregulates sigF. The metabolomic analysis confirmed that the antimycobacterial activity of thymoquinone was related to the depletion of NAD and ATP pools and the downregulation of plasma membrane lipids. This state was observed after 24 h and was persistent the next day, suggesting that bacteria could not activate catabolic mechanisms and produce energy. Additionally, the presence of a thymoquinone nitrogen derivative in the bacterial broth and the culture was reported.

The intracellular growth of the vacuolar pathogen Legionella pneumophila is dependent on the acyl chain composition of host membranes

Legionella pneumophila is an accidental human bacterial pathogen that infects and replicates within alveolar macrophages causing a severe atypical pneumonia known as Legionnaires’ disease. As a prototypical vacuolar pathogen L. pneumophila establishes a unique endoplasmic reticulum (ER)-derived organelle within which bacterial replication takes place. Bacteria-derived proteins are deposited in the host cytosol and in the lumen of the pathogen-occupied vacuole via a type IVb (T4bSS) and a type II (T2SS) secretion system respectively. These secretion system effector proteins manipulate multiple host functions to facilitate intracellular survival of the bacteria. Subversion of host membrane glycerophospholipids (GPLs) by the internalized bacteria via distinct mechanisms feature prominently in trafficking and biogenesis of the Legionella-containing vacuole (LCV). Conventional GPLs composed of a glycerol backbone linked to a polar headgroup and esterified with two fatty acids constitute the bulk of membrane lipids in eukaryotic cells. The acyl chain composition of GPLs dictates phase separation of the lipid bilayer and therefore determines the physiochemical properties of biological membranes - such as membrane disorder, fluidity and permeability. In mammalian cells, fatty acids esterified in membrane GPLs are sourced endogenously from de novo synthesis or via internalization from the exogenous pool of lipids present in serum and other interstitial fluids. Here, we exploited the preferential utilization of exogenous fatty acids for GPL synthesis by macrophages to reprogram the acyl chain composition of host membranes and investigated its impact on LCV homeostasis and L. pneumophila intracellular replication. Using saturated fatty acids as well as cis- and trans- isomers of monounsaturated fatty acids we discovered that under conditions promoting lipid packing and membrane rigidification L. pneumophila intracellular replication was significantly reduced. Palmitoleic acid – a C16:1 monounsaturated fatty acid – that promotes membrane disorder when enriched in GPLs significantly increased bacterial replication within human and murine macrophages but not in axenic growth assays. Lipidome analysis of infected macrophages showed that treatment with exogenous palmitoleic acid resulted in membrane acyl chain reprogramming in a manner that promotes membrane disorder and live-cell imaging revealed that the consequences of increasing membrane disorder impinge on several LCV homeostasis parameters. Collectively, we provide experimental evidence that L. pneumophila replication within its intracellular niche is a function of the lipid bilayer disorder and hydrophobic thickness.

RAS G-domains allosterically contribute to the recognition of lipid headgroups and acyl chains.

Mutant RAS are major contributors to cancer and signal primarily from nanoclusters on the plasma membrane (PM). Their C-terminal membrane anchors are main features of membrane association. However, the same RAS isoform bound to different guanine nucleotides spatially segregate. Different RAS nanoclusters all enrich a phospholipid, phosphatidylserine (PS). These findings suggest more complex membrane interactions. Our electron microscopy-spatial analysis shows that wild-types, G12V mutants, and membrane anchors of isoforms HRAS, KRAS4A, and KRAS4B prefer distinct PS species. Mechanistically, reorientation of KRAS4B G-domain exposes distinct residues, such as Arg 135 in orientation state 1 (OS1) and Arg 73/Arg 102 in OS2, to the PM and differentially facilitates the recognition of PS acyl chains. Allele-specific oncogenic mutations of KRAS4B also shift G-domain reorientation equilibrium. Indeed, KRAS4BG12V, KRAS4BG12D, KRAS4BG12C, KRAS4BG13D, and KRAS4BQ61H associate with PM lipids with headgroup and acyl chain specificities. Distribution of these KRAS4B oncogenic mutants favors different nanoscale membrane topography. Thus, RAS G-domains allosterically facilitate membrane lateral distribution.

Antifungal Activities of L-Methionine and L-Arginine Treatment In Vitro and In Vivo against Botrytis cinerea.

Gray mold caused by Botrytis cinerea is a common postharvest fungal disease in fruit and vegetables. The prevention and treatment of postharvest gray mold has been one of the hot research issues addressed by researchers. This study aimed to investigate the effect of L-methionine and L-arginine on Botrytis cinerea in vitro and on cherry tomato fruit. The results of the in vitro experiment showed that L-methionine and L-arginine had significant inhibitory effects on the mycelial growth and spore germination of Botrytis cinerea, and the inhibitory effects were enhanced with increasing L-methionine or L-arginine concentration. In addition, L-methionine and L-arginine treatment increased the leakage of Botrytis cinerea electrolytes, proteins and nucleic acids. The experiment involving propidium iodide staining and malondialdehyde content assay also confirmed that L-methionine and L-arginine treatment could lead to cell membrane rupture and lipid peroxidation. The results of scanning electron microscopy further verified that the morphology of hyphae was damaged, deformed, dented and wrinkled after treatment with L-methionine or L-arginine. Fruit inoculation experiments displayed that L-methionine and L-arginine treatments significantly inhibited the occurrence and development of gray mold in postharvest cherry tomato. Therefore, treatment with L-methionine or L-arginine might be an effective means to control postharvest gray mold in fruit and vegetables.

Mitigative Effect of Rare Earth Element Cerium on the Growth of Zinc-stressed Wheat （Triticum aestivum L.）Seedlings

This research aimed to clarify the mitigative effect of exogenously applied rare earth element cerium （Ce） on the growth， zinc （Zn） accumulation， and physiological characteristics of wheat （Triticum aestivum L.） seedlings under Zn stress. The wheat variety studied was Bainong307 （BN307）， and Zn stress was achieved by growing seedlings in a hydroponic culture experiment with 500 μmol·L-1 Zn2 + added to the culture solution. It was found that Zn stress at 500 μmol·L-1 significantly inhibited the chlorophyll content， photosynthesis， and biomass accumulation of wheat seedlings. Seedling roots became shorter and thicker， and the lateral roots decreased under Zn stress. The Zn stress also increased MDA accumulation and the degree of cell membrane lipid peroxidation and reduced soluble protein contents and the activities of antioxidant enzymes such as superoxide dismutase （SOD）， catalase （CAT）， and ascorbate peroxidase （APX）. On the contrary， exogenous Ce decreased the adsorption and transport of Zn by the root system and alleviated the damage of Zn stress to wheat seedlings. Specifically， the increase in chlorophyll content （chlorophyll a， chlorophyll b， and total chlorophyll） and photosynthetic parameters， the enhancement of antioxidant enzymes activities and soluble protein levels， and the reduction in MDA content and the damage of lipid peroxidation to the cell membrane were all driven by exogenous Ce， which ultimately led to the increase in dry matter biomass of the root system and shoot. In summary， these results provide basic data for the application of exogenous Ce to alleviate Zn toxicity to plants.

Hippocampus and jejunum biochemical parameters related to physiological ageing of neurons in rats fed diets with copper nanoparticles and different fiber types

Abstract One of the more important factors responsible for synaptic dysfunction of neurons is a neurological ageing. It is a natural consequence of occurrence of biochemical pathways in cells, promoting oxidation processes, an increase in the amount of free oxygen radicals that damage DNA, disorders in calcium ion homeostasis, interactions between lipids of cell membranes, formation of neurofibrillary tangles and deposition of toxic protein deposits. Diet modifications can delay neurometabolism disorders that occur as a result of aging, as well as limit the development of neurodegenerative diseases. The aim of this study on rats was to verify the hypothesis regarding the effect of dietary addition of copper nanoparticles (CuNPs; instead of standard CuCO3) in combination with various dietary fibers on changes in hippocampus and jejunum biochemical parameters related to metabolic disorders appearing with neurological ageing in rats. Male rats were fed a control diet with containing fiber α-cellulose and a standard or enhanced content of Cu provided as CuCO3 (6.5 or 13 mg/kg diet). The diets of other groups were deprived of CuCO3 and the animals were fed diets supplemented with two CuNPs aforementioned doses, and additionally combined with four different types of dietary fiber: α-cellulose (control fiber), pectin, inulin or psyllium (Plantago psyllium). The addition of dietary CuNPs increased the level of acetylcholinesterase (AChE) and decreased the levels of Tau protein, glycosylated AChE (GAChE) and Ca/calmodulin dependent protein kinase II alpha (CAMK2α) in the examined organs. To sum up, both applied doses of CuNPs, 6.5 mg and 13 mg per kg of a diet, can beneficially modulate some important parameters describing metabolic and neurodevelopmental status in the hippocampal and small intestinal tissue of rats. With regard to the fiber type added to rats’ diet, the Plantago psyllium fiber strengthened the mentioned effects of copper nanoparticles. The observed effects should be confirmed in a model study of neurodegeneration.

Deciphering the functional role of plasma membrane lipid asymmetry and its regulated release in mast cell activation and degranulation

Deciphering the functional role of plasma membrane lipid asymmetry and its regulated release in mast cell activation and degranulation

Сравнение липидных изменений в астроцитомах по мере роста их злокачественности

The use of ambient ionization mass spectrometry methods is one of the promising approaches to the impovement of glial tumor resection completeness by using an additional method to improve the tumor margin identification accuracy during the neurosurgical intervention itself. The amounts of data accumulated when testing such techniques can be also used in fundamental research to identify metabolic alterations associated with the tumor growth. The study was aimed to assess changes in the cell membrane lipid composition of diffuse and anaplastic astrocytomas based on the data acquired by ambient ionization mass spectrometry profiling of the tissues excised during the elective neurosurgical intervention. The lipid profiles obtained when assessing the tumor tissue samples (n = 43) by flow microextraction in a cartridge were subjected to shrinkage linear discriminant analysis enabling extraction of a number of lipids, the levels of which changed with increasing tumor grade. The lipid diversity decreased with increasing grade. Thus, the levels of 13 phospholipids belonging to six different subclasses turned out to be decreased in anaplastic tumors compared to diffuse ones. Both average size of the polar lipid fatty acid residues and their degree of unsaturation decrease with increasing tumor grade. The findings agree well with the data of the earlier study of high-grade glial tumors and confirm the biochemical view of metabolic reprogramming associated with malignant transformation of neuroglia.

Biodegradable Ferric Phosphate Nanocarriers with Tumor‐Specific Activation and Glutathione Depletion for Tumor Self‐Enhanced Ferroptosis and Chemotherapy

AbstractFerroptosis is a regulatory cell death that is dependent on iron‐mediated lipid peroxidation and cell membrane damage. The use of iron‐based nanocarriers to activate ferroptosis is of great significance in oncotherapy. However, the limited endogenous hydrogen peroxide (H2O2) and high expression of glutathione (GSH) in tumor cells restrict the efficiency of iron‐based nanocarriers in inducing ferroptosis. Herein, a ferric phosphate nanotherapeutic system (denoted as FeP@HCPT‐HA) is reported with H2O2‐supply and GSH‐elimination properties for tumor self‐enhanced ferroptosis and chemotherapy. FeP@HCPT‐HA is obtained by a coprecipitation method with the in situ loading of 10‐hydroxycamptothecin (HCPT), followed by the modification of hyaluronic acid (HA). FeP@HCPT‐HA actively targets CD44‐overexpressed tumor cells and degrades in acidic tumor microenvironment to release HCPT, Fe2+ and Fe3+. As a chemotherapy drug, HCPT not only induces tumor cell apoptosis but also supplies H2O2 for Fe2+‐mediated Fenton reaction to enhance ferroptosis. The released Fe3+ depletes GSH by the redox reaction between Fe3+ and GSH, which down‐regulates the expression of glutathione peroxidase 4 (GPX4) and enhances lipid peroxidation, resulting in enhanced ferroptosis. The integration of tumor targeting and tumor‐specific activation, as well as H2O2‐supply and GSH‐elimination, endow the FeP@HCPT‐HA with effective tumor growth inhibition by the enhanced ferroptosis and chemotherapy.

Antagonistic activity of secondary metabolites from rhizofunctional bacteria extracts against <i>Fusarium</i>species

Background: Fusarium species remain important fugal pathogens that produce several mycotoxins with adverse effects on both plant and animals. This work aimed to identify biocontrol agent from rhizofunctional bacteria and assess its antagonistic activity against Fusarium sp. using dual culture technique.
 Methodology: Briefly a circular disc of the Fusarium sp. was inoculated at the center of Potato Dextrose Agar (PDA) plate and incubated for three days. The bacterial isolates were then inoculated about 2cm from the Fusarium hyphal tips and incubated for three days, and zone of inhibition was examined. Isolates that showed antagonistic activities against the fungi were subculture in nutrient broth for three days and the metabolites were extracted using ethyl acetate. The metabolic extracts were tested against the fungi using the agar disc diffusion method.
 Results: Of the 20 rhizofunctional bacterial isolates screened for antagonistic activities against Fusarium sp., 5 showed active antagonism against the fungi with observed clear zone of inhibition in the dual culture, and microscopic examination of the fungal hyphae showed excessive and diffused hyphal branching with hyphal swelling. Ethyl acetate extracts from nutrient broth cultures did not show any zone of inhibition in dual culture against the Fusarium sp. All the 5 bacterial isolates were Gram positive strains but only 2 isolates (2a and 3K) were lipase positive, which may indicate that the mechanisms of antagonism could be due to the production of enzymes that have the ability to hydrolyze the cell wall and membrane lipids of the fungi.
 Conclusion: The rhizoplane and rhizosphere of plants could be great sources of biocontrol agents and that bacterial isolates 2a and 3K have the potential to be used as antifungal agents against Fusarium sp. Molecular identification of 2a and 3K bacterial isolates to the species level is recommended.

In Vitro and In Vivo Evaluation of the Pathology and Safety Aspects of Three- and Four-Way Junction RNA Nanoparticles.

RNA therapeutics has advanced into the third milestone in pharmaceutical drug development, following chemical and protein therapeutics. RNA itself can serve as therapeutics, carriers, regulators, or substrates in drug development. Due to RNA's motile, dynamic, and deformable properties, RNA nanoparticles have demonstrated spontaneous targeting and accumulation in cancer vasculature and fast excretion through the kidney glomerulus to urine to prevent possible interactions with healthy organs. Furthermore, the negatively charged phosphate backbone of RNA results in general repulsion from negatively charged lipid cell membranes for further avoidance of vital organs. Thus, RNA nanoparticles can spontaneously enrich tumor vasculature and efficiently enter tumor cells via specific targeting, while those not entering the tumor tissue will clear from the body quickly. These favorable parameters have led to the expectation that RNA has low or little toxicity. RNA nanoparticles have been well characterized for their anticancer efficacy; however, little detail on RNA nanoparticle pathology and safety is known. Here, we report the in vitro and in vivo assessment of the pathology and safety aspects of different RNA nanoparticles including RNA three-way junction (3WJ) harboring 2'-F modified pyrimidine, folic acid, and Survivin siRNA, as well as the RNA four-way junction (4WJ) harboring 2'-F modified pyrimidine and 24 copies of SN38. Both animal models and patient serum were investigated. In vitro studies include hemolysis, platelet aggregation, complement activation, plasma coagulation, and interferon induction. In vivo studies include hematoxylin and eosin (H&E) staining, hematological and biochemical analysis as the serum profiling, and animal organ weight study. No significant toxicity, side effect, or immune responses were detected during the extensive safety evaluations of RNA nanoparticles. These results further complement previous cancer inhibition studies and demonstrate RNA nanoparticles as an effective and safe drug delivery vehicle for future clinical translations.

Salicylic acid mitigates 'Hayward' kiwifruit chilling injury by regulating hormone and proline metabolism, as well as maintaining cellular structure

The 'Hayward' kiwifruit is extremely susceptible to chilling injury (CI) during the late stages of cold storage, thus limiting its storage quality and life. Therefore, mitigating the losses caused by CI is imperative. Salicylic acid (SA) has been demonstrated to mitigate CI in fruit and vegetables. In this study, we conducted a comparative analysis of proline metabolism, key endogenous hormone levels, as well as the effects on cell structure and membrane lipid oxidation in kiwifruit treated with 1 mM SA during low-temperature storage. The results showed that SA could attenuate lipoxygenase (LOX) activity, enhance catalase (CAT) activity, suppress the elevation of malondialdehyde (MDA) content, mitigate starch granule degradation in cells, and preserve cell structure integrity. Moreover, SA was found to enhance proline biosynthesis by activating ornithine transaminase (OAT) and pyrroline-5-carboxylate synthase (P5CS) while concurrently suppressing proline dehydrogenase (PDH) activity. Additionally, exogenous SA increased endogenous levels of both SA and abscisic acid (ABA), while simultaneously decreasing the concentration of gibberellic acid (GA) in fruit. In conclusion, exogenous SA treatment could alleviate the development of CI in kiwifruit by maintaining cell structure, promoting proline synthesis, and balancing endogenous hormone content. Our study offers a theoretical foundation for understanding the mechanism by which SA mitigates cold damage in kiwifruit, and provides novel insights into the low-temperature preservation of kiwifruit.

Lipid Peroxidation Drives Liquid-Liquid Phase Separation and Disrupts Raft Protein Partitioning in Biological Membranes.

The peroxidation of membrane lipids by free radicals contributes to aging, numerous diseases, and ferroptosis, an iron-dependent form of cell death. Peroxidation changes the structure and physicochemical properties of lipids, leading to bilayer thinning, altered fluidity, and increased permeability of membranes in model systems. Whether and how lipid peroxidation impacts the lateral organization of proteins and lipids in biological membranes, however, remains poorly understood. Here, we employ cell-derived giant plasma membrane vesicles (GPMVs) as a model to investigate the impact of lipid peroxidation on ordered membrane domains, often termed membrane rafts. We show that lipid peroxidation induced by the Fenton reaction dramatically enhances the phase separation propensity of GPMVs into coexisting liquid-ordered (Lo) and liquid-disordered (Ld) domains and increases the relative abundance of the disordered phase. Peroxidation also leads to preferential accumulation of peroxidized lipids and 4-hydroxynonenal (4-HNE) adducts in the disordered phase, decreased lipid packing in both Lo and Ld domains, and translocation of multiple classes of raft proteins out of ordered domains. These findings indicate that the peroxidation of plasma membrane lipids disturbs many aspects of membrane rafts, including their stability, abundance, packing, and protein and lipid composition. We propose that these disruptions contribute to the pathological consequences of lipid peroxidation during aging and disease and thus serve as potential targets for therapeutic intervention.

Adapting lipidomic sample processing methods for boars housed in commercial settings.

Multiple reaction monitoring (MRM) profiling is a sensitive method of lipid screening that has the capability to distinguish between different fertility phenotypes in gilts. However, MRM profiling has not yet been utilized to evaluate fertility phenotypes in boars. Markers indicative of fertility status in boars would be valuable as inclusion of subfertile boars in breeding programs results in a loss of efficiency and negative economic consequences. In addition, semen samples for lipidomic analysis are transported in liquid nitrogen or on dry ice to suspend metabolic activity within the sperm cells, however, these cryopreservation techniques are not commonly available at commercial boar studs. Therefore, the objective of this study was to develop a method of sample processing for MRM profiling that suspends metabolic activity within semen without freezing the sample. Five, sexually mature boars of similar genetics enrolled in a commercial breeding program were collected for the study. Following collection, ejaculates were aliquoted into methanol to suspend metabolic activity and shipped to Purdue University overnight for lipid extraction. Lipids were extracted using the Bligh and Dyer method and MRM profiling was used for lipid screening. A total of 329 ion transitions (MRMs) related to lipids were detected with most lipids being characterized as plasma membrane lipids (74%) which were comprised of phosphatidylcholines (40%), ceramides (16%), phosphatidylethanolamines (11%), and phosphatidylserines (7%). acylcarnitines (AC) represented approximately 8% of the ejaculate lipidome. Hierarchical cluster and principal component analysis revealed that boars have a distinct ejaculate lipidome profile based on major plasma membrane lipid classes. In addition, we observed that one boar was unique in his abundance of AC which are related to progressive motility and sperm cell metabolism. These results indicate that this method of sample processing for MRM profiling is suitable to be used to evaluate the lipidome of ejaculates from commercial boars and has the potential for broader applications across different livestock species in commercial environments.

MαCD-based plasma membrane outer leaflet lipid exchange in mammalian cells to study insulin receptor activity.

Signaling receptors on the plasma membrane, such as insulin receptor, can have their activity modulated to some extent by their surrounding lipids. Studying the contribution of membrane lipid properties such as presence of ordered lipid domains or bilayer thickness on the activity of receptors has been a challenging objective in living cells. Using methyl-alpha cyclodextrin-mediated lipid exchange, we are able to alter the lipids of the outer leaflet plasma membrane of mammalian cells to investigate the effect of the properties of the exchanged lipid upon receptor function in live cells. In this article, we describe the technique of lipid exchange in detail and how it can be applied to better understand lipid-mediated regulation of insulin receptor activity in cells.