Isotopic labelling for the characterisation of HNE-sequestering agents in plant-based extracts and its application for the identification of anthocyanidins in black rice with giant embryo

Dynamics of Reactive Carbonyl Species in Pea Root Nodules in Response to Polyethylene Glycol (PEG)-Induced Osmotic Stress

Drought dramatically affects crop productivity worldwide. For legumes this effect is especially pronounced, as their symbiotic association with rhizobia is highly-sensitive to dehydration. This might be attributed to the oxidative stress, which ultimately accompanies plants' response to water deficit. Indeed, enhanced formation of reactive oxygen species in root nodules might result in up-regulation of lipid peroxidation and overproduction of reactive carbonyl compounds (RCCs), which readily modify biomolecules and disrupt cell functions. Thus, the knowledge of the nodule carbonyl metabolome dynamics is critically important for understanding the drought-related losses of nitrogen fixation efficiency and plant productivity. Therefore, here we provide, to the best of our knowledge, for the first time a comprehensive overview of the pea root nodule carbonyl metabolome and address its alterations in response to polyethylene glycol-induced osmotic stress as the first step to examine the changes of RCC patterns in drought treated plants. RCCs were extracted from the nodules and derivatized with 7-(diethylamino)coumarin-3-carbohydrazide (CHH). The relative quantification of CHH-derivatives by liquid chromatography-high resolution mass spectrometry with a post-run correction for derivative stability revealed in total 194 features with intensities above 1 × 105 counts, 19 of which were down- and three were upregulated. The upregulation of glyceraldehyde could accompany non-enzymatic conversion of glyceraldehyde-3-phosphate to methylglyoxal. The accumulation of 4,5-dioxovaleric acid could be the reason for down-regulation of porphyrin metabolism, suppression of leghemoglobin synthesis, inhibition of nitrogenase and degradation of legume-rhizobial symbiosis in response to polyethylene glycol (PEG)-induced osmotic stress effect. This effect needs to be confirmed with soil-based drought models.

Lipid Peroxide-Derived Reactive Carbonyl Species as Mediators of Oxidative Stress and Signaling

Oxidation of membrane lipids by reactive oxygen species (ROS) or O₂/lipoxygenase leads to the formation of various bioactive compounds collectively called oxylipins. Reactive carbonyl species (RCS) are a group of oxylipins that have the α,β-unsaturated carbonyl structure, including acrolein and 4-hydroxy-(E)-2-nonenal. RCS provides a missing link between ROS stimuli and cellular responses in plants via their electrophilic modification of proteins. The physiological significance of RCS in plants has been established based on the observations that the RCS-scavenging enzymes that are overexpressed in plants or the RCS-scavenging chemicals added to plants suppress the plants' responses to ROS, i.e., photoinhibition, aluminum-induced root damage, programmed cell death (PCD), senescence, abscisic acid-induced stomata closure, and auxin-induced lateral root formation. The functions of RCS are thus a key to ROS- and redox-signaling in plants. The chemical species involved in distinct RCS signaling/damaging phenomena were recently revealed, based on comprehensive carbonyl determinations. This review presents an overview of the current status of research regarding RCS signaling functions in plants and discusses present challenges for gaining a more complete understanding of the signaling mechanisms.

Black rice with giant embryo ameliorates serum C-reactive protein in adults with metabolic syndrome

Metabolic syndrome is well known to increase the risk of cardiovascular diseases. We have reported that phytochemicals rich black rice with giant embryo reduced fat mass and metabolic disorders in an animal model. However, such effects have not been evaluated in humans. Subjects with metabolic syndrome (n = 49, 38 male, 44.3 ± 6.1 years) were randomly assigned into two groups and ingested roasted black-rice with giant embryo (BR, n = 26, 20 male) or white-rice (WR, n = 23, 18 male) powders mixed with water for breakfast for three months. Subjects were evaluated for various metabolic parameters before and after intervention. All parameters were not significantly different between groups before starting the intervention. After three months of consumption of either BR or WR, changes of body weight in BR vs WR groups (–1.54 kg vs –1.29 kg, p = 0.649) as well as waist circumference (–1.63 cm vs –1.02 cm, p = 0.365) were not significantly different between groups. However, changes in highly-sensitive C reactive proteins in BR vs WR groups (–0.110 mg/dl vs 0.017 mg/dl, p = 0.003) had significant differences. Three months of meal replacement with BR had a significant reduction of highly-sensitive C reactive protein compared to those with WR in adults with metabolic syndrome.

Reactive Carbonyl Species: A Missing Link in ROS Signaling

As reactive oxygen species (ROS) play critical roles in plants to determine cell fate in various physiological situations, there is keen interest in the biochemical processes of ROS signal transmission. Reactive carbonyl species (RCS), the ,-unsaturated aldehydes and ketones produced from lipid peroxides, due to their chemical property to covalently modify protein, can mediate ROS signals to proteins. Comprehensive carbonyl analysis in plants has revealed that more than a dozen different RCS, e.g., acrolein, 4-hydroxy-(E)-2-nonenal and malondialdehyde, are produced from various membranes, and some of them increase and modify proteins in response to oxidative stimuli. At early stages of response, specific subsets of proteins are selectively modified with RCS. The involvement of RCS in ROS signaling can be judged on three criteria: (1) A stimulus to increase the ROS level in plants leads to the enhancement of RCS levels. (2) Suppression of the increase of RCS by scavenging enzymes or chemicals diminishes the ROS-induced response. (3) Addition of RCS to plants evokes responses similar to those induced by ROS. On these criteria, the RCS action as damaging/signaling agents has been demonstrated for root injury, programmed cell death, senescence of siliques, stomata response to abscisic acid, and root response to auxin. RCS thus act as damage/signal mediators downstream of ROS in a variety of physiological situations. A current picture and perspectives of RCS research are presented in this article.

Oxygen in the tumor microenvironment: effects on dendritic cell function

Solid tumors grow at a high speed leading to insufficient blood supply to tumor cells. This makes the tumor hypoxic, resulting in the Warburg effect and an increased generation of reactive oxygen species (ROS). Hypoxia and ROS affect immune cells in the tumor micro-environment, thereby affecting their immune function. Here, we review the known effects of hypoxia and ROS on the function and physiology of dendritic cells (DCs). DCs can (cross-)present tumor antigen to activate naive T cells, which play a pivotal role in anti-tumor immunity. ROS might enter DCs via aquaporins in the plasma membrane, diffusion across the plasma membrane or via extracellular vesicles (EVs) released by tumor cells. Hypoxia and ROS exert complex effects on DCs, and can both inhibit and activate maturation of immature DCs. Furthermore, ROS transferred by EVs and/or produced by the DC can both promote antigen (cross-)presentation through phagosomal alkalinization, which preserves antigens by inhibiting proteases, and by direct oxidative modification of proteases. Hypoxia leads to a more migratory and inflammatory DC phenotype. Lastly, hypoxia alters DCs to shift the T- cell response towards a tumor suppressive T_h17 phenotype. From numerous studies, the concept is emerging that hypoxia and ROS are mutually dependent effectors on DC function in the tumor micro-environment. Understanding their precise roles and interplay is important given that an adaptive immune response is required to clear tumor cells.