Enhancement of chemiluminescence associated with lipid peroxidation by rhodamine dyes

The use of a chemiluminescence in the assessment of the nanomaterials antioxidant activity

Nanomaterials are one of the most promising classes of advanced materials with fine-tuned biological activities. This is evidenced by the presence of redox activity of a number of nanoparticles aimed at inhibiting free radicals and/or mimicking the functions of enzymes. At the same time, it is impossible to study the expression of these biological properties without the use of well-standardized, representative techniques that provide availability, high precision, sensitivity, and selectivity of the measured characteristics. A method that satisfies these requirements is chemiluminescence analysis, which is widely used both in clinical analysis and to characterize the antioxidant activity of substances of natural or synthetic origin. Recently, a trend of using chemiluminescence analysis to study the biological activity of nanomaterials has appeared as a suitable alternative to spectroscopic and electrochemical techniques. This review briefly describes the examples of successful applications of chemiluminescence methods to study radical-binding and enzyme-like activities of nanomaterials. We discuss the data about the effect of the used reagents (radical-generating systems, chemiluminescence activators) and experimental conditions on the obtained values characterizing the nanomaterials activity.

Graphical Abstract

Assessing Photosensitized Membrane Damage: Available Tools and Comprehensive Mechanisms

Lipids are important targets of the photosensitized oxidation reactions, forming important signaling molecules, disorganizing and permeabilizing membranes, and consequently inducing a variety of biological responses. Although the initial steps of the photosensitized oxidative damage in lipids are known to occur by both Type I and Type II mechanisms, the progression of the peroxidation reaction, which leads to important end-point biological responses, is poorly known. There are many experimental tools used to study the products of lipid oxidation, but neither the methods nor their resulting observations were critically compared. In this article, we will review the tools most frequently used and the key concepts raised by them in order to rationalize a comprehensive model for the initiation and the progression steps of the photoinduced lipid oxidation.

Chemiluminescence as a method for detection and study of free radicals in biological systems

Chemiluminescence observed during LPO or reactions of nitric oxide and oxygen radicals and was named "ultraweak luminescence". In the presence of chemiluminescence activators (luminol, lucigenin, rhodamine G, or coumarine C-525) the appearance of radicals is associated with intensive fluorescence; the registration of this fluorescence is widely used in biomedical and clinical studies.

Unifying mechanism for anticancer agents involving electron transfer and oxidative stress: Clinical implications

Extensive evidence supports involvement of electron transfer (ET), reactive oxygen species (ROS) and oxidative stress (OS) in the mechanism of many anticancer drugs. The common ET functionalities, usually present in the drug metabolites, are quinones (or precursors), metal complexes (or complexors), aromatic nitro compounds (or reduced hydroxylamine and nitroso derivatives), and conjugated imines (or iminium species). The ET agents function catalytically in redox cycling with formation of ROS from oxygen. Electrochemical data add support to the mechanistic viewpoint. The generated metabolites generally possess reduction potentials amenable to ET in vivo, thus giving rise to ROS. The resulting OS is a participant in destruction of the cancer cell. It is important to recognize that drug action is often multipronged. The various modes of action are summarized. Most research has been devoted to development of new and improved chemotherapeutic agents. The need for more attention to measures for cancer prevention is addressed. One of the most promising involves use of antioxidants.

A sensitive chemiluminescence method to measure the lipoxygenase catalyzed oxygenation of complex substrates

Oxidative modification of low-density lipoprotein (LDL) has been implicated as a patho-physiological process in early atherogenesis and 15-lipoxygenases (15-LOX) may be involved. While studying the in vitro kinetics of the 15-LOX/LDL interaction, we found that the conventional spectrophotometric assays failed in the range of substrate saturation owing to the high optical density of concentrated LDL solutions. Therefore, we developed a much more sensitive assay system which was based on peroxide induced isoluminol enhanced chemiluminescence. With this method reliable kinetic data were obtained at LDL concentrations of up to 1 mg/ml. To validate this luminometric method the kinetic parameters of 15-LOX catalyzed oxygenation of linoleic acid (Km=3.7 microM, kcat=17 s-1) were determined and we observed a good agreement with previously published data obtained with a spectrophotometric assay. Moreover, we found that the kinetic constants of 15-LOX catalyzed LDL oxidation (Km=0.64 microM, kcat=0.15 s-1) are quite different from those of free fatty acid oxygenation and that the cholesterol esters are preferentially oxidized during 15-LOX/LDL interaction. Vitamin E depletion does not reduce the rate of LDL oxidation and analysis of the structure of the oxygenation products suggests that the majority of the products were formed via direct LOX catalyzed oxidation of LDL ester lipids. The luminometric method described here is not restricted to the measurement of LOX catalyzed LDL oxidation, but may also be used to determine kinetic constants for the oxidation of other complex substrates such as biomembranes or liposomes.

Measurement of lipid hydroperoxides in plasma lipoproteins by a new highly-sensitive 'single photon counting' luminometer

The lipid hydroperoxide content of isolated, native human plasma lipoproteins, was measured, by the luminol-based chemiluminescent reaction, using a highly sensitive single photon counting instrument. The reaction was specific for lipid hydroperoxides since the signal completely disappeared after treatment with the selenoperoxidase specific for lipidic substrates. In this analytical procedure the whole kinetic of photon emission induced by lipid hydroperoxides and hemin in the presence of luminol is integrated, taking advantage of the mono-exponential fitting of the decay of photon emission. The addition of a detergent to the reaction mixture improved the precision of the measurements apparently by preventing oxidative chain reactions affecting the shape of the decay of photon emission. The sensitivity of the instrument allowed measurements on samples containing just a few picomoles of hydroperoxides, small enough to minimize the effect of antioxidants and quenchers possibly present in the sample (as in the case of lipoproteins). Thus, by using an internal calibration with a phospholipid hydroperoxide, the evaluation of the lipid hydroperoxide content in whole, native lipoproteins was possible without previous extraction and chromatographic separation. Data obtained from plasma lipoproteins isolated by different procedures suggest that lipid hydroperoxide content increases during ultracentrifugation.

Chemiluminescent measurement of increased free radical formation after ischemia/reperfusion. Mechanisms of free radical formation in the liver

It has been proposed that xanthine oxidase-derived superoxide mediates reperfusion injury in the liver; however, there is a little direct evidence to support this hypothesis. In this paper we describe a model system to directly and noninvasively measure oxyradical formation and hepatic injury in isolated perfused rat liver. Using this sensitive chemiluminescent technique, we clearly demonstrate the theorized burst in oxygen radical production upon reperfusion of previously ischemic liver, without perturbing the system with chemical luminescence enhancers. This increase in chemiluminescence (CL) upon reperfusion was diminished by the free radical scavengers trolox and ascorbate, as well as N-2-mercaptoproprionyl-glycine (MPG), thereby confirming the oxyradical nature of this signal. Additionally, superoxide dismutase and the xanthine oxidase inhibitor allopurinol, but not catalase, attenuated the reperfusion effect, providing the most direct evidence so far that XOD derived superoxide anion is formed during liver reperfusion. Hepatic injury (AST release) did not appear to relate to increased CL, supporting the notion that the oxyradical flux may serve as a signal for other events leading to tissue injury. Further studies using this sensitive chemiluminescent technique should aid in delineating the detailed mechanism(s) of reperfusion injury.