Involvement of Rac GTPase activation in phosphatidylcholine hydroperoxide-induced THP-1 cell adhesion to ICAM-1

Lipid hydroperoxides in nutrition, health, and diseases

Research on lipid peroxidation in food degradation, oil and fat nutrition, and age-related diseases has gained significant international attention for the view of improvement of societal health and longevity. In order to promote basic studies on these topics, a chemiluminescence detection-high performance liquid chromatography instrument using a high-sensitivity single photon counter as a detector was developed. This instrument enabled us to selectively detect and quantify lipid hydroperoxides, a primary product of lipid peroxidation reactions, as hydroperoxide groups at the lipid class level. Furthermore, an analytical method using liquid chromatography-tandem mass spectrometry has been established to discriminate the position and stereoisomerization of hydroperoxide groups in lipid hydroperoxides. Using these two methods, the reaction mechanisms of lipid peroxidation in food and in the body have been confirmed.

Determination of triacylglycerol oxidation mechanisms in canola oil using liquid chromatography-tandem mass spectrometry

Triacylglycerol (TG), the main component of edible oil, is oxidized by thermal- or photo- oxidation to form TG hydroperoxide (TGOOH) as the primary oxidation product. Since TGOOH and its subsequent oxidation products cause not only the deterioration of oil quality but also various toxicities, preventing the oxidation of edible oils is essential. Therefore understanding oxidation mechanisms that cause the formation of TGOOH is necessary. Since isomeric information of lipid hydroperoxide provides insights about oil oxidation mechanisms, we focused on dioleoyl-(hydroperoxy octadecadienoyl)-TG (OO-HpODE-TG) isomers, which are the primary oxidation products of the most abundant TG molecular species (dioleoyl-linoleoyl-TG) in canola oil. To secure highly selective and sensitive analysis, authentic OO-HpODE-TG isomer references (i.e., hydroperoxide positional/geometrical isomers) were synthesized and analyzed with HPLC-MS/MS. With the use of the method, photo- or thermal- oxidized edible oils were analyzed. While dioleoyl-(10-hydroperoxy-8E,12Z-octadecadienoyl)-TG (OO-(10-HpODE)-TG) and dioleoyl-(12-hydroperoxy-9Z,13E-octadecadienoyl)-TG (OO-(12-HpODE)-TG) were characteristically detected in photo-oxidized oils, dioleoyl-(9-hydroperoxy-10E,12E-octadecadienoyl)-TG and dioleoyl-(13-hydroperoxy-9E,11E-octadecadienoyl)-TG were found to increase depending on temperature in thermal-oxidized oils. These results prove that our methods not only evaluate oil oxidation in levels that are unquantifiable with peroxide value, but also allows for the determination of oil oxidation mechanisms. From the analysis of marketed canola oils, photo-oxidized products (i.e., OO-(10-HpODE)-TG and OO-(12-HpODE)-TG) were characteristically accumulated compared to the oil analyzed immediately after production. The method described in this paper is valuable in the understanding of oil and food oxidation mechanisms, and may be applied to the development of preventive methods against food deterioration.

Edible oils become rancid when reacting with oxygen under light or heat, degrading into different products depending on the pathway. Kiyotaka Nakagawa at Tohoku University, Japan, and co-workers used instruments that can separate and identify by weight components in mixtures to study light- and heat-induced oxidation of canola oil. Using authentic samples of possible oxidation products as references, the team found that each process generated two unique species from triacylglycerol, the main ingredient in edible oils. These signature compounds allowed the researchers to reveal that heat-oxidation sped up as temperature increased and that light-oxidized products gradually accumulated in off-the-shelf canola oil after production. This method is more sensitive than conventional protocols and can tell exactly how oils are oxidized, useful for developing techniques for food preservation.

Carbon nanotubes physicochemical properties influence the overall cellular behavior and fate

The unique properties of single walled carbon nanotubes (SWCNTs) make them viable candidates for versatile implementation in the next generation of biomedical devices for targeted delivery of chemotherapeutic agents or cellular-sensing probes. Such implementation requires user-tailored changes in SWCNT's physicochemical characteristics to allow for efficient cellular integration while maintaining nanotubes' functionality. However, isolated reports showed that user-tailoring could induce deleterious effects in exposed cells, from decrease in cellular proliferation, to changes in cellular adhesion, generation of reactive oxygen species or phenotypical variations, just to name a few. Before full implementation of SWCNTs is achieved, their toxicological profiles need to be mechanistically correlated with their physicochemical properties to determine how the induced cellular fate is related to the exposure conditions or samples' characteristics. Our study provides a comprehensive analysis of the synergistic cyto- and genotoxic effects resulted from short-term exposure of human lung epithelial cells to pristine (as manufactured) and user-tailored SWCNTs, as a function of their physicochemical properties. Specifically, through a systematic approach we are correlating the nanotube uptake and nanotube-induced cellular changes to the sample's physicochemical characteristics (e.g., metal impurities, length, agglomerate size, surface area, dispersion, and surface functionalization). By identifying changes in active hallmarks involved in cell-cell connections and maintaining epithelial layer integrity, we also determine the role that short-term exposure to SWCNTs plays in the overall cellular fate and cellular transformation. Lastly, we assess cellular structure-function relationships to identify non-apoptotic pathways induced by SWCNTs exposure that could however lead to changes in cellular behavior and cellular transformation. Our results show that the degree of cell transformation is a function of the physicochemical properties of the SWCNT, with the nanotube with higher length, higher metal content and larger agglomerate size reducing cell viability to a larger extent. Such changes in cell viability are also complemented by changes in cell structure, cycle and cell-cell interactions, all responsible for maintaining cell fate.

Small GTPase and regulation of inflammation response in atherogenesis

Small GTPases are key signal transducers from extracellular stimuli to the nucleus that regulate a variety of cellular responses, including changes in gene expression and cell adhesion and migration. Accumulating data have demonstrated that abnormal activation of these small GTPases plays a critical role in the atherosclerosis characterized by vascular abnormalities, especially endothelial dysfunction and inflammation. Here, we discuss the linkage between small GTPases, inflammation, and atherogenesis. First, small GTPases affect gene expression of inflammatory cytokines through proinflammatory signaling pathways, such as nuclear factor-κB, vascular cell adhesion molecule-1, intercellular adhesion molecule-1, interlukin-8, and monocyte chemoattractant protein-1. Then, these molecules regulate the vascular inflammation through cell adhesion and migration. In turn, small GTPases are also regulated by extracellular stimuli, such as L-selectin, thrombin, oxidized phospholipids, and interleukins. Thus, these inflammatory cytokines generate a vicious cycle for small GTPases and inflammatory responses in the atherogenesis.

Inflammation-related gene expression by lipid oxidation-derived products in the progression of atherosclerosis

Vascular areas of atherosclerotic development persist in a state of inflammation, and any further inflammatory stimulus in the subintimal area elicits a proatherogenic response; this alters the behavior of the artery wall cells and recruits further inflammatory cells. In association with the inflammatory response, oxidative events are also involved in the development of atherosclerotic plaques. It is now unanimously recognized that lipid oxidation-derived products are key players in the initiation and progression of atherosclerotic lesions. Oxidized lipids, derived from oxidatively modified low-density lipoproteins (LDLs), which accumulate in the intima, strongly modulate inflammation-related gene expression, through involvement of various signaling pathways. In addition, considerable evidence supports a proatherogenic role of a large group of potent bioactive lipids called eicosanoids, which derive from oxidation of arachidonic acid, a component of membrane phospholipids. Of note, LDL lipid oxidation products might regulate eicosanoid production, modulating the enzymatic degradation of arachidonic acid by cyclooxygenases and lipoxygenases; these enzymes might also directly contribute to LDL oxidation. This review provides a comprehensive overview of current knowledge on signal transduction pathways and inflammatory gene expression, modulated by lipid oxidation-derived products, in the progression of atherosclerosis.