Measurement of Nitric Oxide (NO) Generation Rate by Chloroplasts Employing Electron Spin Resonance (ESR)

ROS and RNS production, subcellular localization, and signaling triggered by immunogenic danger signals

Plants continuously monitor the environment to detect changing conditions and to properly respond, avoiding deleterious effects on their fitness and survival. An enormous number of cell surface and intracellular immune receptors are deployed to perceive danger signals associated with microbial infections. Ligand binding by cognate receptors represents the first essential event in triggering plant immunity and determining the outcome of the tissue invasion attempt. Reactive oxygen and nitrogen species (ROS/RNS) are secondary messengers rapidly produced in different subcellular localizations upon the perception of immunogenic signals. Danger signal transduction inside the plant cells involves cytoskeletal rearrangements as well as several organelles and interactions between them to activate key immune signaling modules. Such immune processes depend on ROS and RNS accumulation, highlighting their role as key regulators in the execution of the immune cellular program. In fact, ROS and RNS are synergic and interdependent intracellular signals required for decoding danger signals and for the modulation of defense-related responses. Here we summarize current knowledge on ROS/RNS production, compartmentalization, and signaling in plant cells that have perceived immunogenic danger signals.

Considerations of the importance of redox state for reactive nitrogen species action

Nitric oxide (NO) and other reactive nitrogen species (RNS) are immensely important signalling molecules in plants, being involved in a range of physiological responses. However, the exact way in which NO fits into signal transduction pathways is not always easy to understand. Here, some of the issues that should be considered are discussed. This includes how NO may interact directly with other reactive signals, such as reactive oxygen and sulfur species, how NO metabolism is almost certainly compartmentalized, that threshold levels of RNS may need to be reached to have effects, and how the intracellular redox environment may impact on NO signalling. Until better tools are available to understand how NO is generated in cells, where it accumulates, and to what levels it reaches, it will be hard to get a full understanding of NO signalling. The interaction of RNS metabolism with the intracellular redox environment needs further investigation. A changing redox poise will impact on whether RNS species can thrive in or around cells. Such mechanisms will determine whether specific RNS can indeed control the responses needed by a cell.

Electron Spin Resonance (ESR) for the study of Reactive Oxygen Species (ROS) on the isolated frog skin (Pelophylax bergeri): A non-invasive method for environmental monitoring

BACKGROUND

Reactive oxygen species (ROS) in biological tissues of elected biosentinels represent an optimal biomarker for eco-monitoring of polluted areas. Electron spin resonance (ESR) is the most definitive method for detecting, quantifying and possibly identifying radicals in complex systems.

OBJECTIVE

A non-invasive method for monitoring polluted areas by the quantitative determination of ROS in frog skin biopsy is presented.

METHODS

We assessed by ESR spectroscopy the ROS level in adult male of Pelophylax bergeri, specie not a risk of extinction, collected from the polluted Sarno River (SA, Italy) basin. The spin-trap ESR method was validated by immunohistochemical analysis of the well-assessed pollution biomarkers cytochrome P450 aromatase 1A (CYP1A) and glutathione S-transferase (GST), and by determining the poly(ADPribose) polymerase (PARP) and GST enzymatic activity.

RESULTS

ROS concentration in skin samples from frogs collected in the polluted area is significantly higher than that determined for the unpolluted reference area. Immunohistochemical analysis of CYP1A and GST supported the reliability of our approach, even in the absence of evident morphological and ultrastructural differences. PARP activity assay, connected to possible oxidative DNA damage, and the detoxification index by GST enzymatic assay give statistically significant evidence that higher levels of ROS are associated to alterations of the different biomarkers.

CONCLUSIONS

ROS concentration, measured by ESR on isolated frog skin, through the presented non-lethal method, is a reliable biomarker for toxicity screening and represents a useful basic datum for future modelling studies on environmental monitoring and biodiversity loss prevention.

Reactive oxygen species and glutathione antioxidants in the testis of the soil biosentinel Podarcis sicula (Rafinesque 1810)

Important toxicological achievements have been made during the last decades using reptiles. We focus our investigation on gonadal reproductive health of the soil biosentinel Podarcis sicula which is very sensitive to endocrine-disrupting chemicals. The aim of this study is to quantitatively detect, by sensitive microassays, reactive oxygen species and the glutathione antioxidants in the testis and investigate if they are differentially expressed before and after remediation of a site of the "Land of Fires" (Campania, Italy) subject to illicit dumping of unknown material. The oxidative stress level was evaluated by electron spin resonance spectroscopy applying a spin-trapping procedure able to detect products of lipid peroxidation, DNA damage and repair by relative mobility shift, and poly(ADP-ribose) polymerase enzymatic activity, respectively, the expression of glutathione peroxidase 4 transcript by real-time quantitative PCR analysis, the antioxidant glutathione S-transferase, a well-assessed pollution index, by enzymatic assay and the total soluble antioxidant capacity. Experimental evidences from the different techniques qualitatively agree, thus confirming the robustness of the combined experimental approach. Collected data, compared to those from a reference unpolluted site constitute evidence that the reproductive health of this lizard is impacted by pollution exposure. Remediation caused significant reduction of reactive oxygen species and downregulation of glutathione peroxidase 4 mRNAs in correspondence of reduced levels of glutathione S-transferase, increase of antioxidant capacity, and repair of DNA integrity. Taken together, our results indicate directions to define new screening approaches in remediation assessment.

Detection of Nitric Oxide via Electronic Paramagnetic Resonance in Mollusks

Electronic paramagnetic resonance (EPR) is an appropriate tool to identify free radicals formed in tissues under normal as well as stressful conditions. Since nitric oxide (NO) as a free radical has paramagnetic properties it can be detected by EPR. The use of spin traps highly improves the sensitivity allowing NO identification, detection and quantification at room temperature in vitro and in vivo conditions. NO production in animals is almost exclusively associated to an enzyme family known as Nitric Oxide Synthases (NOSs). The digestive glands of mollusks are a major target for oxidative disruption related to environmental stress. A simple EPR-methodology to asses both, the presence of NO and its rate of generation in tissues from different mollusk species, is reported here.