A new mitochondrial probe combining pyrene and a triphenylphosphonium salt for cellular oxygen and free radical detection via fluorescence lifetime measurements

To improve and diversify the quantification of reactive oxygen species (ROS) in mitochondria of single cells, we connected pyrene derivatives (PB) to a triphenylphosphonium salt (TPP⁺) as a mitochondrial vector forming PB-TPP⁺ probes. Two pyrene isomers with the n-butyltriphenylphosphonium moieties attached at their 1- or 2- positions were synthesized and characterized. Using the long fluorescence lifetime of pyrene, it was possible to monitor the variation of cellular free radicals and oxygen and to follow the reversibility of both quenchers in real-time. We compared the behavior of these new probes to the previously published pyrene-probes, functionalized by a mitochondrial-penetrating peptide, allowing their transfer to the mitochondria (Mito-PB) or to the cytosolic membrane for pyrene butyric acid (PBA). The high cellular uptake of the new probes allows cells to be loaded with an initial concentration 40 times lower than that for Mito-PB probes, without inducing perturbations in cell growth. The variation in free radicals and oxygen levels was monitored within cells under different stress conditions through the fluorescence lifetime of the new TPP⁺-based probes giving comparable results to those obtained for MPP-based probes. However, at a loading concentration as low as 25 nM, our technique allows the detection of increased production of free radicals in the mitochondria in the presence of the TPP⁺ vector, a warning to the user of this well-known vector.

A comparative study of Caesalpinia bonduc (L.) Roxb. root extracts on sexual behaviour in male Wistar rats

Caesalpinia bonduc is among the traditionally used plant in Benin, for its enhancement of male sexual activity. This study was undertaken to investigate the potential effect of C. bonduc root extracts on sexual behaviour of male Wistar rats. For that, thirty-six rats were allocated into six groups and orally treated with dimethyl sulfoxide (control), Sildenafil citrate (standard) and C. bonduc root extracts (hexane, ethyl acetate, ethanol and methanol) orally for twenty-eight days. Sexual behaviour parameters such as intromission frequency, intromission latency, mount latency and mount frequency were evaluated on day 0, 14 and 28. After the study completion, the body and reproductive organ weights as well as testicular histology and testosterone level were recorded. C. bonduc root extracts treatments had no significant effect on the body weight of rats. Enhancement in sexual behaviour was observed in ethanolic extract treated rats. An significant increase in mount frequency and intromission frequency as well as significant reduction in mount latency and intromission latency were noticed for ethanolic extract. The same extract caused an improvement in testosterone levels, relative testes weight and histological architecture. The findings demonstrate the aphrodisiac potential of C. bonduc root and lend support to the folkloric use as aphrodisiac.

Somatic production of reactive oxygen species does not predict its production in sperm cells across Drosophila melanogaster lines

OBJECTIVE

Sperm ageing has major evolutionary implications but has received comparatively little attention. Ageing in sperm and other cells is driven largely by oxidative damage from reactive oxygen species (ROS) generated by the mitochondria. Rates of organismal ageing differ across species and are theorized to be linked to somatic ROS levels. However, it is unknown whether sperm ageing rates are correlated with organismal ageing rates. Here, we investigate this question by comparing sperm ROS production in four lines of Drosophila melanogaster that have previously been shown to differ in somatic mitochondrial ROS production, including two commonly used wild-type lines and two lines with genetic modifications standardly used in ageing research.

RESULTS

Somatic ROS production was previously shown to be lower in wild-type Oregon-R than in wild-type Dahomey flies; decreased by the expression of alternative oxidase (AOX), a protein that shortens the electron transport chain; and increased by a loss-of-function mutation in dj-1β, a gene involved in ROS scavenging. Contrary to predictions, we found no differences among these four lines in the rate of sperm ROS production. We discuss the implications of our results, the limitations of our study, and possible directions for future research.

Peptide Vectors Carry Pyrene to Cell Organelles Allowing Real-Time Quantification of Free Radicals in Mitochondria by Time-Resolved Fluorescence Microscopy

Real-time quantification of reactive nitrogen and oxygen species (ROS) in cells is of paramount importance as they are essential for cellular functions. Their excessive formation contributes to the dysfunction of cells and organisms, ultimately leading to cell death. As ROS are mostly produced in the mitochondria, we have synthesized a fluorescent probe able to reach this organelle to detect and quantify, in real time, the variation of ROS by time-resolved microfluorimetry. The new probes are based on the long fluorescence lifetime of pyrene butyric acid (PBA). Two PBA isomers, attached at their 1- or 2-positions to a peptide vector to target mitochondria, were compared and were shown to allow the measurement of free radical species and oxygen, but not non-radical species such as H₂ O₂ .

Synthetic Sensors for Reactive Oxygen Species Detection and Quantification: A Critical Review of Current Methods

SIGNIFICANCE

Redox reactions play important roles in both physiological and pathological processes, highlighting the importance of quantifying and localizing intracellular redox-active components. Most research has focused on direct investigation of reactive oxygen species (ROS). Intensity-based fluorescent methods are very sensitive and easy to use, but they lack specificity and can produce artifacts. In this article, we focus on synthetic sensors, describing experimental pitfalls associated with their use. We also present alternative methods for the detection of free radicals.

RECENT ADVANCES

New approaches have been developed to overcome the main artifact of intensity-based methods: spurious changes in fluorescence intensity caused by oxidation. These new approaches are based on analytical measurements of the oxidized sensors or techniques that are not susceptible to oxidation, such as electron spin resonance and fluorescence lifetime-based methods. Regardless of the approach, the need for detection of ROS on the subcellular level, especially in the mitochondria, has motivated the development of new probes.

CRITICAL ISSUES

Flow cytometry systems and confocal microscopes are now available to the majority of biologists, and commercially available probes are, therefore, more widely used. The fact that these new applications are cited in thousands of publications makes these sensors even more attractive.

FUTURE DIRECTIONS

The field of ROS detection by synthetic sensors continues to expand, bringing needed additional research to the development of robust techniques that are applicable both in vitro and in vivo. Antioxid. Redox Signal. 25, 520-533.

Oxidative stress does not play a primary role in the toxicity induced with clinical doses of doxorubicin in myocardial H9c2 cells

The implication of oxidative stress as primary mechanism inducing doxorubicin (DOX) cardiotoxicity is still questionable as many in vitro studies implied supra-clinical drug doses or unreliable methodologies for reactive oxygen species (ROS) detection. The aim of this study was to clarify whether oxidative stress is involved in compliance with the conditions of clinical use of DOX, and using reliable tools for ROS detection. We examined the cytotoxic mechanisms of 2 μM DOX 1 day after the beginning of the treatment in differentiated H9c2 rat embryonic cardiac cells. Cells were exposed for 2 or 24 h with DOX to mimic a single chronic dosage or to favor accumulation, respectively. We found that apoptosis was prevalent in cells exposed for a short period with DOX: cells showed typical hallmarks as loss of anchorage ability, mitochondrial hyperpolarization followed by the collapse of mitochondrial activity, and nuclear condensation. Increasing the exposure period favored a shift to necrosis as the cells preferentially exhibited early DNA impairment and nuclear swelling. In either case, measuring the fluorescence lifetime of 1-pyrenebutyric acid or the intensities of dihydroethidium or amplex red showed a consistent pattern in ROS production which was a slight increased level far from representative of an oxidative stress. Moreover, pre-treatment with dexrazoxane provided a cytoprotective effect although it failed to detoxify ROS. Our data support that oxidative stress is unlikely to be the primary mechanism of DOX cardiac toxicity in vitro.

Histopathological and ultrastructural studies of a Henneguya species (Myxozoa: Myxosporea) infesting the intestine of Clarias gariepinus from Benin (West Africa)

Fish culture is the best alternative to fill the gap between natural fish catches and estimated needs of populations in animal protein consumption. In West Africa, this goal required to have suitable fishes for aquaculture which are Clariidae and Tilapia. Clarias gariepinus (Clariidae) fetches a higher price than tilapias as it can be sold alive at the market but a high infestation by Henneguya leads to decrease this commercial value. Those reasons lead us to perform studies on seasonal variations, histopathological aspects and life cycle of Henneguya sp. infecting the intestine of C. gariepinus using light and electron microscope. From November 2011 to December 2012, 339 specimens were collected from Ouémé River (Benin) and examined. An overall prevalence of 7.37 % was recorded for plasmodia of Henneguya sp. Parasite occurrence did not vary significantly between seasons (χ(2) = 12.235; df = 3; p > 0.05), nor sexes (χ(2) = 2.992; df = 7; p > 0.05) while differences were significant between classes of weight (χ(2) = 39.929; df = 5; p < 0.05). The highest prevalence was recorded in host ranging from 300 to 374 g. Histopathological analysis showed that the mass continuous development of the plasmodium produced thickening of the intestine wall and compressed neighboring tissues and destroyed villi and smooth muscle layers. The stages of the parasite development including sporogenesis, capsulogenesis, and valvogenesis were asynchronous. Investigations are still running by molecular approaches in order to identify accurately this species.

Adriamycin dose and time effects on cell cycle, cell death, and reactive oxygen species generation in leukaemia cells

We investigate the relative importance of the different mechanisms of Adriamycin, an anthracycline, and their interrelations, in particular the link between cell cycle arrest, cell death, and generation of reactive oxygen species (ROS) that is suspected to be the origin of cardiotoxic side-effects. We introduced a lifetime fluorescence based technology and used videomicrofluorometry, two efficient analytical methods. We show that depending on the doses and time after incubation, ADR will not reach the same compartments (nucleus, mitochondria, cytosol) in the cells, having consequences on the production of ROS, growth arrest pathways and cell death pathways.

Reduced metabolic rate and oxygen radicals production in stored insect sperm

Females of internally fertilizing species can significantly extend sperm lifespan and functionality during sperm storage. The mechanisms for such delayed cellular senescence remain unknown. Here, we apply current hypotheses of cellular senescence developed for diploid cells to sperm cells, and empirically test opposing predictions on the relationship between sperm metabolic rate and oxygen radical production in an insect model, the cricket Gryllus bimaculatus. Using time-resolved microfluorimetry, we found a negative correlation between metabolic rate (proportion of protein-bound NAD[P]H) and in situ intracellular oxygen radicals production in freshly ejaculated sperm. In contrast, sperm stored by females for periods of 1 h to 26 days showed a positive correlation between metabolic rate and oxygen radicals production. At the same time, stored sperm showed a 37 per cent reduced metabolic rate, and 42 per cent reduced reactive oxygen species (ROS) production, compared with freshly ejaculated sperm. Rank differences between males in ROS production and metabolic rate observed in ejaculated sperm did not predict rank differences in stored sperm. Our method of simultaneously measuring ROS production and metabolic rate of the same sample has the advantage of providing data that are independent of sperm density and any extracellular antioxidants that are proteins. Our method also excludes effects owing to accumulated hydrogen peroxide. Our results unify aspects of competing theories of cellular ageing and suggest that reducing metabolic rate may be an important means of extending stored sperm lifespan and functionality in crickets. Our data also provide a possible explanation for why traits of ejaculates sampled from the male may be rather poor predictors of paternity in sexual selection studies and likelihood of pregnancy in reproductive medicine.

Variation of 1-pyrenebutyric acid fluorescence lifetime in single living cells treated with molecules increasing or decreasing reactive oxygen species levels

1-Pyrenebutyric acid (PBA) is a fluorescent probe whose fluorescence lifetime depends on local oxygen and free radical concentrations. We propose to use PBA fluorescence lifetime to quantify reactive oxygen species (ROS) in biological samples. Time-resolved microfluorimetry was used to record the fluorescence decay of single living cells loaded with this probe. We measured intracellular PBA fluorescence lifetimes and reduced nicotinamide adenine dinucleotide phosphate intensities under various oxygen concentrations. To confirm the feasibility of the new method, CCRF-CEM cells were treated with drugs that are known to increase or decrease ROS production. After treatment with adriamycin, we observed a decrease of PBA fluorescence lifetime. This corresponded to an increase of ROS concentration (80%). After treatment with cysteamine, we observed a reduction of the ROS concentration by 67%. Moreover, addition of exogenous H(2)O(2) solution resulted in a decrease of PBA fluorescence lifetime due to a raising of the intracellular ROS concentration. These results support our hypothesis linking a part of PBA fluorescence lifetime variations to intracellular fluctuation of ROS.

Native fluorescence and mag-indo-1-protein interaction as tools for probing unfolding and refolding sequences of the bovine serum albumin subdomain in the presence of guanidine hydrochloride

Changes in the fluorescence spectrum of tryptophans Trp 134 and Trp 212 in bovine serum albumin (BSA) and of Trp 214 of human serum albumin in the presence of the chaotropic agent guanidine hydrochloride (Gnd) were studied. A detailed analysis of the fluorescence spectrum of native BSA yielded the fluorescence spectrum for each tryptophan of BSA. Modifications in the binding of Mag-indo-1 to BSA, which results in a specific quenching of the fluorescence spectrum of Trp 134 associated with an energy transfer from Trp 134 to the protein-bound Mag-indo-1, were also investigated. Changes occurring when the Gnd concentration is decreased stepwise cover a larger concentration scale of Gnd than the reverse protocol, allowing one to suggest that the resulting conformational changes in the subdomain IA of BSA involve at least three different steps.

Interaction of a protein, BSA, and a fluorescent probe, Mag-Indo-1, influence of EDTA and calcium on the equilibrium

Recent findings indicate that ion-chelator probes with tetracarboxylate structure bind proteins. It was suggested that these fluorescent probes are valuable tools to gain information on protein structure through the energy transfer from tryptophans to the bound probe. Here, the binding of the fluorescent probe Mag-Indo-1 to bovine serum albumin (BSA) was investigated. Mag-Indo-1 was reported previously to serve as a probe for magnesium cations (Kd = 2.8 x 10(-4) M for zero ionic strength) which can also interact with calcium cations (Kd = 7.5 x 10(-7) M). Probe complexation with protein results in a shift of the emission fluorescence spectrum of the probe from 480 to 457 nm. We used emission fluorescence techniques to monitor this interaction. Computational resolution of the complex fluorescence spectra and a new software to test the theoretical model were developed in our laboratory. This enabled us to calculate the number of interacting sites and the dissociation constants. The fluorescent probe Mag-Indo-1 binds at a singular site with high affinity (Kd = 1.8 x 10(-7) M) to bovine serum albumin (BSA). Since proteins are known to bind several compounds unspecifically, we have studied the influence of EDTA as a competitor of the probe. Our findings suggest that the BSA binding site is identical for both Mag-Indo-1 and EDTA. We found that EDTA binds the protein with Kd = 0.4 x 10(-3) M. We studied the influence of calcium and found that Mag-Indo-1 does not bind the calcium free Apo-protein anymore.

Intervalence Electron Transfer in Mixed Valence Diferrocenylpolyenes. Decay Law of the Metal-Metal Coupling with Distance

A series of diferrocenylpolyenes of general formula Fc(CH=CH)(n)()Fc with n = 1-6 (Fc = ferrocenyl group) has been prepared and studied from the point of view of intervalence transitions in the mixed valence state. Well-resolved intervalence transitions are observed in dichloromethane upon partial electrolytic oxidation. Comproportionation constants have been determined from redox titration data and in some cases from electrochemical wave splitting. The corrected spectra of the mixed valence species have been deconvoluted to extract the parameters (position, intensity, width) of the intervalence bands, which allowed the determination of the metal-metal coupling (V(ab)) through the bridging unit using Hush's formula. The decay of V(ab) with distance is close to an exponential law with an exponent of 0.087 Å(-)(1), constituting one of the smallest attenuations reported so far. A small deviation to the exponential law is detected.