Hemodynamic and metabolic effects of the beta-phosphorylated nitroxide 2-diethoxyphosphoryl-2,5,5-trimethylpyrrolidinoxyl during myocardial ischemia and reperfusion

In vivo fluorescence bioimaging of ascorbic acid in mice: Development of an efficient probe consisting of phthalocyanine, TEMPO, and albumin

After a groundbreaking study demonstrated that a high dose of ascorbic acid selectively kills cancer cells, the compound has been tested in the clinic against various forms of cancers, with some success. However, in vivo tracing of intravenously injected ascorbic acid has not been achieved. Herein, we successfully imaged ascorbic acid intravenously injected into mice based on the discovery of a novel, highly sensitive, and appropriately selective fluorescent probe consisting of silicon phthalocyanine (SiPc) and two 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) radicals, i.e., R2c. The radicals in this R2c were encapsulated in dimeric bovine serum albumin, and the sensitivity was >100-fold higher than those of other R2c-based probes. Ascorbic acid intravenously injected into mice was efficiently transported to the liver, heart, lung, and cholecyst. The present results provide opportunities to advance the use of ascorbic acid as cancer therapy.

Indole-TEMPO conjugates alleviate ischemia-reperfusion injury via attenuation of oxidative stress and preservation of mitochondrial function

Mitochondrial oxidative damage contributes to a wide range of pathologies including ischemia/reperfusion injury. Accordingly, protecting mitochondria from oxidative damage should possess therapeutic relevance. In the present study, we have designed and synthesized a series of novel indole-TEMPO conjugates that manifested good anti-inflammatory properties in a murine model of xylene-induced ear edema. We have demonstrated that these compounds can protect cells from simulated ischemia/reperfusion (s-I/R)-induced reactive oxygen species (ROS) overproduction and mitochondrial dysfunction. Furthermore, we have demonstrated that indole-TEMPO conjugates can attenuate organ damage induced in rodents via intestinal I/R injury. We therefore propose that the pharmacological profile and mechanism of action of these indole-TEMPO conjugates involve convergent roles, including the ability to decrease free radical production via lipid peroxidation which couples to an associated decrease in ROS-mediated activation of the inflammatory process. We further hypothesize that the protective effects of indole-TEMPO conjugates partially reside in maintaining optimal mitochondrial function.

The line asymmetry of electron spin resonance spectra as a tool to determine the cis:trans ratio for spin-trapping adducts of chiral pyrrolines N-oxides: the mechanism of formation of hydroxyl radical adducts of EMPO, DEPMPO, and DIPPMPO in the ischemic-reperfused rat liver

Nonstereospecific addition of free radicals to chiral nitrones yields cis/trans diastereoisomeric nitroxides often displaying different electron spin resonance (ESR) characteristics. Glutathione peroxidase-glutathione (GPx-GSH) reaction was applied to reduce the superoxide adducts (nitrone/*OOH) to the corresponding hydroxyl radical (HO*) adducts (nitrone/*OH) of two nitrones increasingly used in biological spin trapping, namely 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO) and 5-ethoxycarbonyl-5-methyl-1-pyrroline N-oxide, and of 5-diisopropoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DIPPMPO), a sterically hindered DEPMPO analogue. The method offered improved conditions to record highly resolved ESR spectra and by accurate simulation of line asymmetry we obtained clear evidence for the existence of previously unrecognized isomer pairs of cis- and trans-[DEPMPO/*OH] and [DIPPMPO/*OH]. Additional nitrone/*OH generation methods were used, i.e. photolysis of hydrogen peroxide and the Fenton reaction. We developed a kinetic model involving first- and second-order decay and a secondary conversion of trans to cis isomer to fully account for the strongly configuration-dependent behavior of nitrone/*OH. In the reductive system and, to a lower extent, in the Fenton or photolytic systems cis-nitrone/*OH was the more stable diastereoisomer. In various biologically relevant milieu, we found that the cis:trans-nitrone/*OH ratio determined right after the spin adduct formation significantly differed upon the GPx-GSH vs (Fenton or photolytic) systems of formation. This new mechanistic ESR index consistently showed for all nitrones that nitrone/*OH signals detected in the postischemic effluents of ischemic isolated rat livers are the reduction products of primary nitrone/*OOH. Thus, ESR deconvolution of cis/trans diastereoisomers is of great interest in the study of HO* formation in biological systems.

In vitro photodynamic effects of phthalocyaninatosilicon covalently linked to 2,2,6,6-tetramethyl-1-piperidinyloxy radicals on cancer cells

In this paper, we have investigated the ability to sensitize the phototoxicity toward HeLa cells in vitro, of tetra-tert-butylphthalocyaninatosilicon (SiPc) covalently linked to one or two 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) radicals (R1c or R2c), which are shown as photosensitizers efficiently producing singlet oxygen (1Delta(g)). Addition of R1c or R2c encapsulated in liposomes to cultures, followed by irradiation with a 680-nm dye laser, resulted in a highly significant phototoxicity toward HeLa cells, in contrast to negligible phototoxicity observed with (dihydroxy)SiPc (R0). EPR measurements indicate that R1c and R2c exist in some degree as nitroxide radicals even in HeLa cells. Electronic absorption spectra indicate that the degree of aggregation increases in the order R2c<R1c<R0. Thus, the high phototoxicity of R1c and R2c toward HeLa cells is reasonably interpreted by both the large singlet oxygen yield and the inhibition of aggregation due to the bulky TEMPO radicals. This increase in photodynamic effect on HeLa cells is an unusual and important example for increasing the photobiological reaction yields using paramagnetic radicals.

Insulin-like growth factor-1 protects ischemic murine myocardium from ischemia/reperfusion associated injury

INTRODUCTION

Ischemia/reperfusion occurs in myocardial infarction, cardiac dysfunction during sepsis, cardiac transplantation and coronary artery bypass grafting, and results in injury to the myocardium. Although reperfusion injury is related to the nature and duration of ischemia, it is also a separate entity that may jeopardize viable cells and ultimately may impair cardiac performance once ischemia is resolved and the organ heals.

METHOD

The present study was conducted in an ex vivo murine model of myocardial ischemia/reperfusion injury. After 20 min of ischemia, isolated hearts were perfused for up to 2 hours with solution (modified Kreb's) only, solution plus insulin-like growth factor (IGF)-1, or solution plus tumor necrosis factor (TNF)-alpha. Cardiac contractility was monitored continuously during this period of reperfusion.

RESULTS

On the basis of histologic evidence, IGF-1 prevented reperfusion injury as compared with TNF-alpha; TNF-alpha increased perivascular interstitial edema and disrupted tissue lattice integrity, whereas IGF-1 maintained myocardial cellular integrity and did not increase edema. Also, there was a significant reduction in detectable creatine phosphokinase in the perfusate from IGF-1 treated hearts. By recording transduced pressures generated during the cardiac cycle, reperfusion with IGF-1 was accompanied by markedly improved cardiac performance as compared with reperfusion with TNF-alpha or modified Kreb's solution only. The histologic and functional improvement generated by IGF-1 was characterized by maintenance of the ratio of mitochondrial to nuclear DNA within heart tissue.

CONCLUSION

We conclude that IGF-1 protects ischemic myocardium from further reperfusion injury, and that this may involve mitochondria-dependent mechanisms.