Effects of oxidation on the physicochemical properties of polyunsaturated lipid membranes

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.

Brazilin-7-acetate, a novel potential drug of Parkinson's disease, hinders the formation of α-synuclein fibril, mitigates cytotoxicity, and decreases oxidative stress

Parkinson's disease (PD) is a prevalent neurodegenerative disorder characterized by the accumulation of α-synuclein (α-Syn) aggregates. However, there are currently no effective therapies for PD. Brazilin, an inhibitor of α-Syn aggregation, is unstable and toxic. Therefore, we have developed and synthesized derivatives of brazilin. One of these derivatives, called brazilin-7-acetate (B-7-A), has shown reduced toxicity and a stronger effect on inhibiting α-Syn aggregation. It showed that B-7-A prevented the formation of α-Syn fibers and disrupted existing fibers in a dosage-dependent manner. Additionally, B-7-A significantly reduced the cytotoxicity of α-Syn aggregates and alleviated oxidative stress in PC12 cells. The beneficial effects of B-7-A were also confirmed using the Caenorhabditis elegans model. These effects included preventing the accumulation of α-Syn clumps, improving behavior disorder, increasing lifespan, reducing oxidative stress, and protecting against lipid oxidation and loss. Finally, B-7-A showed good ADMET properties in silico. Based on these findings, B-7-A exhibits potential as a prospective treatment for PD.

Lipid peroxidation: Reactive carbonyl species, protein/DNA adducts, and signaling switches in oxidative stress and cancer

Under the exposure of lipids to reactive oxygen species (ROS), lipid peroxidation proceeds non-enzymatically and generates an extremely heterogeneous mixture of reactive carbonyl species (RCS). Among them, HNE, HHE, MDA, methylglyoxal, glyoxal, and acrolein are the most studied and/or abundant ones. Over the last decades, significant progress has been achieved in understanding mechanisms of RCS generation, protein/DNA adduct formation, and their identification and quantification in biological samples. In our review, we critically discuss the advancements in understanding the roles of RCS-induced protein/DNA modifications in signaling switches to provide adaptive cell response under physiological and oxidative stress conditions. At non-toxic concentrations, RCS modify susceptible Cys residue in c-Src to activate MAPK signaling and Cys, Lys, and His residues in PTEN to cause its reversible inactivation, thereby stimulating PI3K/PKB(Akt) pathway. RCS toxic concentrations cause irreversible Cys modifications in Keap1 and IKKβ followed by stabilization of Nrf2 and activation of NF-κB, respectively, for their nuclear translocation and antioxidant gene expression. Dysregulation of these mechanisms causes diseases including cancer. Alterations in RCS, RCS detoxifying enzymes, RCS-modified protein/DNA adducts, and signaling pathways have been implicated in various cancer types.

Puncturing lipid membranes: onset of pore formation and the role of hydrogen bonding in the presence of flavonoids

Products of lipid peroxidation induce detrimental structural changes in cell membranes, such as the formation of water pores, which occur in the presence of lipids with partially oxidized chains. However, the influence of another class of products, dicarboxylic acids, is still unclear. These products have greater mobility in the lipid bilayer, which enables their aggregation and the formation of favorable sites for the appearance of pores. Therefore, dodecanedioic acid (DDA) was selected as a model product. Additionally, the influence of several structurally different flavonoids on DDA aggregation via formation of hydrogen bonds with carboxyl groups was investigated. The molecular dynamics of DDA in DOPC lipid bilayer revealed the formation of aggregates extending over the hydrophobic region of the bilayer and increasing its polarity. Consequently, water penetration and the appearance of water wires was observed, representing a new step in the mechanism of pore formation. Furthermore, DDA molecules were found to interact with lipid polar groups, causing them to be buried in the bilayer. The addition of flavonoids to the system disrupted aggregate formation, resulting in the displacement of DDA molecules from the center of the bilayer. The placement of DDA and flavonoids in the lipid bilayer was confirmed by small-angle X-ray scattering. Atomic force microscopy and electron paramagnetic resonance were used to characterize the structural properties. The presence of DDA increased bilayer roughness and decreased the ordering of lipid chains, confirming its detrimental effects on the membrane surface, while flavonoids were found to reduce or reverse these changes.

Effect of lipid oxidation on the channel properties of Cx26 hemichannels: A molecular dynamics study

Intercellular communication plays a crucial role in cancer, as well as other diseases, such as inflammation, tissue degeneration, and neurological disorders. One of the proteins responsible for this, are connexins (Cxs), which come together to form a hemichannel. When two hemichannels of opposite cells interact with each other, they form a gap junction (GJ) channel, connecting the intracellular space of these cells. They allow the passage of ions, reactive oxygen and nitrogen species (RONS), and signaling molecules from the interior of one cell to another cell, thus playing an essential role in cell growth, differentiation, and homeostasis. The importance of GJs for disease induction and therapy development is becoming more appreciated, especially in the context of oncology. Studies have shown that one of the mechanisms to control the formation and disruption of GJs is mediated by lipid oxidation pathways, but the underlying mechanisms are not well understood. In this study, we performed atomistic molecular dynamics simulations to evaluate how lipid oxidation influences the channel properties of Cx26 hemichannels, such as channel gating and permeability. Our results demonstrate that the Cx26 hemichannel is more compact in the presence of oxidized lipids, decreasing its pore diameter at the extracellular side and increasing it at the amino terminus domains, respectively. The permeability of the Cx26 hemichannel for water and RONS molecules is higher in the presence of oxidized lipids. The latter may facilitate the intracellular accumulation of RONS, possibly increasing oxidative stress in cells. A better understanding of this process will help to enhance the efficacy of oxidative stress-based cancer treatments.

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, conformation and physicochemical properties of lipids, leading to major membrane alterations including bilayer thinning, altered fluidity, and increased permeability. 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 phase separation propensity of GPMVs into co-existing liquid ordered (raft) and liquid disordered (non-raft) domains and increases the relative abundance of the disordered, non-raft 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 raft and non-raft domains, and translocation of multiple classes of proteins out of rafts. These findings indicate that 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.

Insights into the mechanisms of interaction between inhalable lipid-polymer hybrid nanoparticles and pulmonary surfactant

Pulmonary delivery of small interfering RNA (siRNA) using nanoparticle-based delivery systems is promising for local treatment of respiratory diseases. We designed dry powder inhaler formulations of siRNA-loaded lipid-polymer hybrid nanoparticles (LPNs) with aerosolization properties optimized for inhalation therapy. Interactions between LPNs and pulmonary surfactant (PS) determine the fate of inhaled LPNs, but interaction mechanisms are unknown. Here we used surface-sensitive techniques to study how physicochemical properties and pathological microenvironments influence interactions between siRNA-loaded LPNs and supported PS layers. PS was deposited on SiO₂ surfaces as single bilayer or multilayers and characterized using quartz crystal microbalance with dissipation monitoring and Fourier-transform infrared spectroscopy with attenuated total reflection. Immobilization of PS as multilayers, resembling the structural PS organization in the alveolar subphase, effectively reduced the relative importance of interactions between PS and the underlying surface. However, the binding affinity between PS and LPNs was identical in the two models. The physicochemical LPN properties influenced the translocation pathways and retention time of LPNs. Membrane fluidity and electrostatic interactions were decisive for the interaction strength between LPNs and PS. Experimental conditions reflecting pathological microenvironments promoted LPN deposition. Hence, these results shed new light on design criteria for LPN transport through the air-blood barrier.

Chemical composition and anti-inflammatory activities of Castanopsis honey

Castanopsis is diffusely spread in tropical and subtropical regions and is an important nectar source plant in China. The Castanopsis honey (CH) is characterized by its bitter taste. However, its composition and functions remain unclear. In this study, the physicochemical parameters, chemical composition, and antioxidant capacity of CH were comprehensively investigated, with the anti-inflammatory effects of the Castanopsis honey extract (CHE) evaluated based on the RAW 264.7 cell inflammatory model. The results revealed a high level of quality in CH based on the quality standards. Among a total of 84 compounds identified in CH, 5 high response compounds and 29 phenols were further quantified by UPLC-Q/TOF-MS. The high content of phenylethylamine (117.58 ± 64.81 mg kg^-1) was identified as a potential marker of CH. Furthermore, the CH showed evident antioxidant activities, and the anti-inflammatory activities of CHE were observed to inhibit the release of nitric oxide (NO) and reduce the content of tumor necrosis factor alpha (TNF-α) and improve the content of interleukin-10 (IL-10) by regulating the NF-κB pathway. Our study indicates that CH has sound physicochemical properties and biological activities with a high level of quality, providing strong experimental evidence to support the further economic and agricultural development and application of CH.

Mesoporous silica as a matrix for photocatalytic titanium dioxide nanoparticles: lipid membrane interactions

In the present study, we investigate the combined interaction of mesoporous silica (SiO₂) and photocatalytic titanium dioxide (TiO₂) nanoparticles with lipid membranes, using neutron reflectometry (NR), cryo-transmission electron microscopy (cryo-TEM), fluorescence oxidation assays, dynamic light scattering (DLS), and ζ-potential measurements. Based on DLS, TiO₂ nanoparticles were found to display strongly improved colloidal stability at physiological pH of skin (pH 5.4) after incorporation into either smooth or spiky ("virus-like") mesoporous silica nanoparticles at low pH, the latter demonstrated by cryo-TEM. At the same time, such matrix-bound TiO₂ nanoparticles retain their ability to destabilize anionic bacteria-mimicking lipid membranes under UV-illumination. Quenching experiments indicated both hydroxyl and superoxide radicals to contribute to this, while NR showed that free TiO₂ nanoparticles and TiO₂ loaded into mesoporous silica nanoparticles induced comparable effects on supported lipid membranes, including membrane thinning, lipid removal, and formation of a partially disordered outer membrane leaflet. By comparing effects for smooth and virus-like mesoporous nanoparticles as matrices for TiO₂ nanoparticles, the interplay between photocatalytic and direct membrane binding effects were elucidated. Taken together, the study outlines how photocatalytic nanoparticles can be readily incorporated into mesoporous silica nanoparticles for increased colloidal stability and yet retain most of their capacity for photocatalytic destabilization of lipid membranes, and with maintained mechanisms for oxidative membrane destabilization. As such, the study provides new mechanistic information to the widely employed, but poorly understood, practice of loading photocatalytic nanomaterials onto/into matrix materials for increased performance.

Photocatalytic nanoparticles - From membrane interactions to antimicrobial and antiviral effects

As a result of increasing resistance among pathogens against antibiotics and anti-viral therapeutics, nanomaterials are attracting current interest as antimicrobial agents. Such materials offer triggered functionalities to combat challenging infections, based on either direct membrane action, effects of released ions, thermal shock induced by either light or magnetic fields, or oxidative photocatalysis. In the present overview, we focus on photocatalytic antimicrobial effects, in which light exposure triggers generation of reactive oxygen species. These, in turn, cause oxidative damage to key components in bacteria and viruses, including lipid membranes, lipopolysaccharides, proteins, and DNA/RNA. While an increasing body of studies demonstrate that potent antimicrobial effects can be achieved by photocatalytic nanomaterials, understanding of the mechanistic foundation underlying such effects is still in its infancy. Addressing this, we here provide an overview of the current understanding of the interaction of photocatalytic nanomaterials with pathogen membranes and membrane components, and how this translates into antibacterial and antiviral effects.

The Potential Role of Polyphenols in Oxidative Stress and Inflammation Induced by Gut Microbiota in Alzheimer's Disease

Gut microbiota (GM) play a role in the metabolic health, gut eubiosis, nutrition, and physiology of humans. They are also involved in the regulation of inflammation, oxidative stress, immune responses, central and peripheral neurotransmission. Aging and unhealthy dietary patterns, along with oxidative and inflammatory responses due to gut dysbiosis, can lead to the pathogenesis of neurodegenerative diseases, especially Alzheimer's disease (AD). Although the exact mechanism between AD and GM dysbiosis is still unknown, recent studies claim that secretions from the gut can enhance hallmarks of AD by disturbing the intestinal permeability and blood-brain barrier via the microbiota-gut-brain axis. Dietary polyphenols are the secondary metabolites of plants that possess anti-oxidative and anti-inflammatory properties and can ameliorate gut dysbiosis by enhancing the abundance of beneficial bacteria. Thus, modulation of gut by polyphenols can prevent and treat AD and other neurodegenerative diseases. This review summarizes the role of oxidative stress, inflammation, and GM in AD. Further, it provides an overview on the ability of polyphenols to modulate gut dysbiosis, oxidative stress, and inflammation against AD.

Does membrane curvature elastic energy play a role in mediating oxidative stress in lipid membranes?

The effects of oxidative stress on cells are associated with a wide range of pathologies. Oxidative stress is predominantly initiated by the action of reactive oxygen species and/or lipoxygenases on polyunsaturated fatty acid containing lipids. The downstream products are oxidised phospholipids, bioactive aldehydes and a range of Schiff base by-products between aldehydes and lipids, or other biomacromolecules. In this review we assess the impact of oxidative stress on lipid membranes, focusing on the changes that occur to the curvature preference (lipid spontaneous curvature) and elastic properties of membranes, since these biophysical properties modulate phospholipid homeostasis. Studies show that the lipid products of oxidative stress reduce stored curvature elastic energy in membranes. Based upon this observation, we hypothesize that the effects of oxidative stress on lipid membranes will be reduced by compounds that increase stored curvature elastic energy. We find a strong correlation appears across literature studies that we have reviewed, such that many compounds like vitamin E, Curcumin, Coenzyme Q10 and vitamin A show behaviour consistent with this hypothesis. Finally, we consider whether age-related changes in lipid composition represent the homeostatic response of cells to compensate for the accumulation of in vivo lipid oxidation products.

Selenocompounds and Sepsis: Redox Bypass Hypothesis for Early Diagnosis and Treatment: Part A-Early Acute Phase of Sepsis: An Extraordinary Redox Situation (Leukocyte/Endothelium Interaction Leading to Endothelial Damage)

Significance: Sepsis is a health disaster. In sepsis, an initial, beneficial local immune response against infection evolves rapidly into a generalized, dysregulated response or a state of chaos, leading to multiple organ failure. Use of life-sustaining supportive therapies creates an unnatural condition, enabling the complex cascades of the sepsis response to develop in patients who would otherwise die. Multiple attempts to control sepsis at an early stage have been unsuccessful. Recent Advances: Major events in early sepsis include activation and binding of leukocytes and endothelial cells in the microcirculation, damage of the endothelial surface layer (ESL), and a decrease in the plasma concentration of the antioxidant enzyme, selenoprotein-P. These events induce an increase in intracellular redox potential and lymphocyte apoptosis, whereas apoptosis is delayed in monocytes and neutrophils. They also induce endothelial mitochondrial and cell damage. Critical Issues: Neutrophil production increases dramatically, and aggressive immature forms are released. Leukocyte cross talk with other leukocytes and with damaged endothelial cells amplifies the inflammatory response. The release of large quantities of reactive oxygen, halogen, and nitrogen species as a result of the leukocyte respiratory burst, endothelial mitochondrial damage, and ischemia/reperfusion processes, along with the marked decrease in selenoprotein-P concentrations, leads to peroxynitrite damage of the ESL, reducing flow and damaging the endothelial barrier. Future Directions: Endothelial barrier damage by activated leukocytes is a time-sensitive event in sepsis, occurring within hours and representing the first step toward organ failure and death. Reducing or stopping this event is necessary before irreversible damage occurs.

The roles of strawberry and honey phytochemicals on human health: A possible clue on the molecular mechanisms involved in the prevention of oxidative stress and inflammation

BACKGROUND

Oxidative stress and inflammation contribute to the etiopathogenesis of several human chronic diseases, such as cancer, diabetes, cardiovascular diseases and metabolic syndrome. Besides classic stimuli, such as reactive oxidant species, endotoxins (i.e., bacteria lipopolysaccharide), cytokines or carcinogens, oxidative stress and inflammation can be triggered by a poor diet and an excess of body fat and energy intake. Strawberry and honey are common rich sources of nutrients and bioactive compounds, widely studied for their roles exerted in health maintenance and disease prevention.

PURPOSE

This review aims to summarize and update the effects of strawberry and honey against oxidative stress and inflammation, with emphasis on metabolism and on the main molecular mechanisms involved in these effects.

METHODS

A wide range of literature, published in the last 10 years, elucidating the effects of strawberry and honey in preventing oxidative stress and inflammation both in vitro (whole matrix and digested fractions) and in vivo was collected from online electronic databases (PubMed, Scopus and Web of Science) and reviewed.

RESULTS

Strawberry and honey polyphenols may potentially prevent the chronic diseases related to oxidative stress and inflammation. Several in vitro and in vivo studies reported the effects of these foods in suppressing the oxidative stress, by decreasing ROS production and oxidative biomarkers, restoring the antioxidant enzyme activities, ameliorating the mitochondrial antioxidant status and functionality, among others, and the inflammatory process, by modulating the mediators of acute and chronic inflammation essential for the onset of several human diseases. These beneficial properties are mediated in part through their ability to target multiple signaling pathways, such as p38 MAPK, AMPK, PI3K/Akt, NF-κB and Nrf2.

CONCLUSIONS

Available scientific literature show that strawberry and honey may be effective in preventing oxidative stress and inflammation. The deep evaluation of the factors that affect their metabolism as well as the assessment of the main molecular mechanisms involved are of extreme importance for the possible therapeutic and preventive benefit against the most common human diseases. However, published literature is still scarce so that deeper studies should be performed in order to evaluate the bioavailability of these food matrices and their effects after digestion.

Composition effects on photooxidative membrane destabilization by TiO2 nanoparticles

Membrane interactions and photooxidative membrane destabilization of titanium dioxide (TiO₂) nanoparticles were investigated, focusing on the effects of membrane composition, notably phospholipid headgroup charge and presence of cholesterol. For this, we employed a battery of state-of-the-art methods for studies of bilayers formed by zwitterionic palmitoyloleoylphosphatidylcholine (POPC) containing also polyunsaturated palmitoylarachidonoylphosphocholine (PAPC), as well as its mixtures with anionic palmitoyloleoylphosphatidylglycerol (POPG) and cholesterol. It was found that the TiO₂ nanoparticles display close to zero charge at pH 7.4, resulting in aggregation. At pH 3.4, in contrast, the 6 nm TiO₂ nanoparticles are well dispersed due to a strongly positive ζ-potential. Mirroring this pH dependence, TiO₂ nanoparticles were observed to bind to negatively charged lipid bilayers at pH 3.4, but much less so at pH 7.4. While nanoparticle binding has some destabilizing effect alone, illumination with ultraviolet (UV) light accentuates membrane destabilization, a result of oxidative stress caused by generated reactive oxygen species (ROS). Neutron reflectivity (NR), quartz crystal microbalance (QCM), and small-angle X-ray scattering (SAXS) results all demonstrate that membrane composition strongly influences membrane interactions and photooxidative destabilization of lipid bilayers. In particular, the presence of anionic POPG makes the bilayers more sensitive to oxidative destabilization, whereas a stabilizing effect was observed in the presence of cholesterol. Also, structural aspects of peroxidation were found to depend strongly on membrane composition, notably the presence of anionic phospholipids. The results show that membrane interactions and UV-induced ROS generation act in concert and need to be considered together to understand effects of lipid membrane composition on UV-triggered oxidative destabilization by TiO₂ nanoparticles, e.g., in the context of oxidative damage of bacteria and cells.

Tail-Oxidized Cholesterol Enhances Membrane Permeability for Small Solutes

Cholesterol renders mammalian cell membranes more compact by reducing the amount of voids in the membrane structure. Because of this, cholesterol is known to regulate the ability of cell membranes to prevent the permeation of water and water-soluble molecules through the membranes. Meanwhile, it is also known that even seemingly tiny modifications in the chemical structure of cholesterol can lead to notable changes in membrane properties. The question is, how significantly do these small changes in cholesterol structure affect the permeability barrier function of cell membranes? In this work, we applied fluorescence methods as well as atomistic molecular dynamics simulations to characterize changes in lipid membrane permeability induced by cholesterol oxidation. The studied 7β-hydroxycholesterol (7β-OH-chol) and 27-hydroxycholesterol (27-OH-chol) represent two distinct groups of oxysterols, namely, ring- and tail-oxidized cholesterols, respectively. Our previous research showed that the oxidation of the cholesterol tail has only a marginal effect on the structure of a lipid bilayer; however, oxidation was found to disturb membrane dynamics by introducing a mechanism that allows sterol molecules to move rapidly back and forth across the membrane-bobbing. Herein, we show that bobbing of 27-OH-chol accelerates fluorescence quenching of NBD-lipid probes in the inner leaflet of liposomes by dithionite added to the liposomal suspension. Systematic experiments using fluorescence quenching spectroscopy and microscopy led to the conclusion that the presence of 27-OH-chol increases membrane permeability to the dithionite anion. Atomistic molecular dynamics simulations demonstrated that 27-OH-chol also facilitates water transport across the membrane. The results support the view that oxysterol bobbing gives rise to successive perturbations to the hydrophobic core of the membrane, and these perturbations promote the permeation of water and small water-soluble molecules through a lipid bilayer. The observed impairment of permeability can have important consequences for eukaryotic organisms. The effects described for 27-OH-chol were not observed for 7β-OH-chol which represents ring-oxidized sterols.

Oxidation of Polyunsaturated Lipid Membranes by Photocatalytic Titanium Dioxide Nanoparticles: Role of pH and Salinity

In the present study, UV-induced membrane destabilization by TiO₂ (anatase) nanoparticles was investigated by neutron reflectometry (NR), small-angle X-ray scattering (SAXS), quartz crystal microbalance with dissipation (QCM-D), dynamic light scattering (DLS), and ζ-potential measurements for phospholipid bilayers formed by zwitterionic palmitoyloleoylphosphatidylcholine (POPC) containing biologically relevant polyunsaturations. TiO₂ nanoparticles displayed pH-dependent binding to such bilayers. Nanoparticle binding alone, however, has virtually no destabilizing effects on the lipid bilayers. In contrast, UV illumination in the presence of TiO₂ nanoparticles activates membrane destabilization as a result of lipid oxidation caused by the generation of reactive oxygen species (ROS), primarily ^•OH radicals. Despite the short diffusion length characterizing these, the direct bilayer attachment of TiO₂ nanoparticles was demonstrated to not be a sufficient criterion for an efficient UV-induced oxidation of bilayer lipids, the latter also depending on ROS generation in bulk solution. From SAXS and NR, minor structural changes were seen when TiO₂ was added in the absence of UV exposure, or on UV exposure in the absence of TiO₂ nanoparticles. In contrast, UV exposure in the presence of TiO₂ nanoparticles caused large-scale structural transformations, especially at high ionic strength, including gradual bilayer thinning, lateral phase separation, increases in hydration, lipid removal, and potential solubilization into aggregates. Taken together, the results demonstrate that nanoparticle-membrane interactions ROS generation at different solution conditions act in concert to induce lipid membrane destabilization on UV exposure and that both of these need to be considered for understanding the performance of UV-triggered TiO₂ nanoparticles in nanomedicine.

Enhanced antioxidant, anti-inflammatory and α-glucosidase inhibitory activities of citrus hesperidin by acid-catalyzed hydrolysis

Hesperidin hydrolysates (HHS) was produced by the hydrolysis of hesperidin (HDN) in previous studies. The potential components in HHS were identified by LC-MS, and minor components (MCS) in HHS were isolated. Antioxidant activities by radical-scavenging capacities, reducing capacity and β-carotene-linoleate assay, anti-inflammatory effects by inhibiting NO production of RAW 264.7 cells, and α-glucosidase inhibitory effects of HDN, HHS, MCS and henperetin (HTN) were investigated in present study. HHS showed higher radical scavenging activities, higher reducing capacity, and higher inhibitory activity in the β-carotene-linoleate assay than HDN. HHS inhibited the production of NO and pro-inflammatory cytokines of RAW 264.7 cells more strongly than HDN. HHS also intensively inhibited α-glucosidase activity whereas HDN showed little activity. In addition, the effects of MCS on above activities showed it play a synergistic part with HTN. This work suggested that hydrolyzation of HDN enhance the activities, and provided valuable information on effective utilization of HDN.

Redox (phospho)lipidomics of signaling in inflammation and programmed cell death

In addition to the known prominent role of polyunsaturated (phospho)lipids as structural blocks of biomembranes, there is an emerging understanding of another important function of these molecules as a highly diversified signaling language utilized for intra- and extracellular communications. Technological developments in high-resolution mass spectrometry facilitated the development of a new branch of metabolomics, redox lipidomics. Analysis of lipid peroxidation reactions has already identified specific enzymatic mechanisms responsible for the biosynthesis of several unique signals in response to inflammation and regulated cell death programs. Obtaining comprehensive information about millions of signals encoded by oxidized phospholipids, represented by thousands of interactive reactions and pleiotropic (patho)physiological effects, is a daunting task. However, there is still reasonable hope that significant discoveries, of at least some of the important contributors to the overall overwhelmingly complex network of interactions triggered by inflammation, will lead to the discovery of new small molecule regulators and therapeutic modalities. For example, suppression of the production of AA-derived pro-inflammatory mediators, HXA3 and LTB4, by an iPLA2 γ inhibitor, R-BEL, mitigated injury associated with the activation of pro-inflammatory processes in animals exposed to whole-body irradiation. Further, technological developments promise to make redox lipidomics a powerful approach in the arsenal of diagnostic and therapeutic instruments for personalized medicine of inflammatory diseases and conditions.