Oxidative and nitrosative stress in association with DNA damage in coronary heart disease

INTRODUCTION

Oxidative and nitrosative stress caused by a disturbance in the homeostasis of pro-oxidants and antioxidants play a vital role in the pathogenesis of coronary heart disease (CHD). Enhanced formation of reactive oxygen species/reactive nitrogen species may also affect the oxidation/nitration of biomolecules such as lipids, proteins and DNA. The present study was undertaken to estimate oxidative and nitrosative stress, and to evaluate oxidative DNA damage.

METHODS

The study population consisted of 120 patients with angiographically documented CHD and an equal number of age- and gender-matched healthy controls. Lipid profiles were estimated using Glaxo kits. Estimation of plasma malondialdehyde (MDA), nitrite/nitrate and comet assay were carried out using previously published methods.

RESULTS

Lipid profiles were significantly different in patients with coronary artery disease compared to the controls (p-value less than 0.01). The levels of MDA, nitrite/nitrate and DNA damage in the patients were significantly higher compared to the controls, and a strong correlation was found between the comet tail length and the MDA and nitrite/nitrate levels. Further analysis revealed that the influence of nitrite/nitrate was greater than that of MDA.

CONCLUSION

Our results indicate that abnormal levels of lipid profiles, along with increased oxidative and nitrosative stress as well as somatic DNA damage, could be important pathogenic factors that act as additional prognostic predictors. They may also serve as potential targets for therapeutic strategies in CHD for early management and prevention of the disease.

Ascorbic acid, garlic extract and taurine alleviate cadmium-induced oxidative stress in freshwater catfish (Clarias batrachus)

An experiment was conducted to investigate bioaccumulation potential of cadmium (Cd) and changes in oxidative stress indices in liver and kidney tissues from Cd-exposed catfish (Clarias batrachus) with or without simultaneous treatment of water with ascorbic acid, garlic extract or taurine. C. batrachus (n=324) with average length of 20+/-4 cm and weight of 86+/-5 g were used for the present investigation. Fishes were divided into nine groups (I to IX) each comprising 36 fishes. The fishes of groups II, III, IV and V were challenged with 5 ppm of cadmium chloride monohydrate (CdCl2.H2O), whereas groups VI, VII, VIII and IX were exposed to 10 ppm CdCl2.H2O solution for a period of 45 days. Group I was kept as negative control and the fishes of this group were maintained in water containing no added Cadmium. Group II and VI were maintained as Cd exposed non treated control to serve as positive controls. Fishes of III and VII, IV and VIII, V and IX received ascorbic acid (5 ppm), extract of dried garlic (5 ppm) or taurine (5 ppm), respectively during the entire experiment period. The concentrations of Cd in liver and kidney increased significantly following exposure to Cd and the level continued to rise with the increase in exposure duration. Treatment of tank water with ascorbic acid, garlic or taurine significantly reduced the Cd concentrations in tissues compared to the positive control group, but the level in Cd exposed groups was greater than the negative control group. Fishes exposed to Cd and treated with ascorbic acid, garlic or taurine had reduced oxidative stress as evidenced from lower concentration of lipid peroxides and higher activities of superoxide dismutase and catalase in liver, kidney and erythrocytes compared to fishes exposed to Cd. The reduction in Cd induced oxidative stress was highest in ascorbic acid treated group followed by garlic and taurine treatment. The results suggest that ascorbic acid, garlic and taurine have potential to reduce tissue accumulation of Cd and associated oxidative stress in freshwater catfish.

CNS-Specific Ribozyme Expression

Targeted genetic deletion is a powerful tool for analysis of gene function, but the standard approaches carry certain inescapable disadvantages. First, deletion is ubiquitous; tissue-specific knockout cannot be obtained. Second, temporal regulation of depletion is unattainable; the deleted functions are absent throughout the animal's development. As a consequence, during ontogeny, other gene products may be able to compensate, filling the functional gap. Furthermore bifunctional proteins exist that fulfill one role during development and another in the mature organism; deletion will remove the early function and, if this is lethal, the later function will remain undetected. Third, if genes utilize alternative splicing to control protein expression, it is difficult to target one spliced mRNA while leaving intact its related, but different, siblings. We review how these problems may be circumvented using ribozymes to diminish gene expression in a tissue-specific and temporally regulated manner and provide guidelines for the design and delivery of active ribozymes in vivo. Such methods may be particularly useful for analysis of genes involved in ontogeny and function of the central nervous system, in which individual genes may be expressed with alternative splicing patterns, or at differentially regulated levels, at different stages of CNS development.

Evidence that alternate foldings of the hepatitis delta RNA confer varying rates of self-cleavage

The pentapurine sequence GGAGA, located between 80 and 84 nucleotides downstream of the cleavage site in the self-cleaving antigenomic RNA of hepatitis delta virus, is necessary for highly efficient cleavage and for stability in up to 20 M formamide. Yet much of the cleavage activity lost upon its removal from the 3' end of an 84-nucleotide RNA can be restored by elongation of the 5' end of the RNA with the polypyrimidine sequence found in the virus. We propose that this sequence alteration causes a refolding of the RNA, resulting in a "structural compensation" of the active core of the molecule. Restoration of the self-cleavage activity did not restore the ability to cleave in high concentrations of formamide. Deletion mutagenesis was carried out and supported the alternate RNA folding. The ability to assume more than one active conformation and for one RNA structure to compensate for another in supporting ribozyme activity may be unique to RNA enzymes and could be a useful adaptation in viruses or in prebiotic RNAs.

Deriving a 67-nucleotide trans-cleaving ribozyme from the hepatitis delta virus antigenomic RNA

RNAs derived from the genomic and antigenomic hepatitis delta virus are capable of self-cleavage, and thus have the potential for serving as ribozymes in a trans-cleaving reaction. Because the catalytic core of such an enzymatic RNA was not evident from phylogenetic data, we took a step-wise approach to identifying the core, reducing the RNA in size, and characterizing various properties for each size class. Thus, a 186-nucleotide antigenomic RNA (termed Ag180) was found to be capable of cleaving well in 20 M formamide (Smith and Dinter-Gottlieb, 1991), and this unusual stability in formamide was lost by reducing the 3' end of the molecule, leaving a 140-nucleotide RNA (Ag 140). Both RNAs showed only intramolecular cleavage at a wide range of concentrations, and a number of conformers could be seen in the Ag140 RNA, some of which were resistant to cleavage at 37 degrees C. Since Ag140 could not cleave in 20 M formamide, the 5' and 3' termini of Ag180 were truncated and produced Ag5-84, which cleaved to 100% at 37 degrees C in less than 0.25 min. Internal deletions of the Stem IV region resulted in Ag5-73, still capable of efficient cleavage, although with a lessened stability in formamide. A trans-cleaving enzyme-substrate pair was finally derived from this RNA, and it consisted of a 67-nucleotide enzyme that cleaved a 13-nucleotide RNA substrate.