Generation of hydroxyl radicals by nucleohistone-bound metal-adriamycin complexes

Colocalization of Aluminum and Iron in Nuclei of Nerve Cells in Brains of Patients with Alzheimer's Disease

Increasing evidence indicates that metal-induced oxidative stress plays a pivotal role in the pathogenesis of Alzheimer's disease (AD). Recently, the presence of 8-hydroxydeoxyguanosine, a biomarker of oxidative DNA damage, was demonstrated in nuclear DNA (nDNA) in the AD brain. Iron (Fe) is a pro-oxidant metal capable of generating hydroxyl radicals that can oxidize DNA, and aluminum (Al) has been reported to facilitate Fe-mediated oxidation. In the present study, we examined the elements contained in the nuclei of nerve cells in AD brains using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS). Our results demonstrated that Al and Fe were colocalized in the nuclei of nerve cells in the AD brain. Within the nuclei, the highest levels of both Al and Fe were measured in the nucleolus. The SEM-EDS analysis also revealed the colocalization of Al and Fe in the heterochromatin and euchromatin in neuronal nuclei in the AD brain. Notably, the levels of Al and Fe in the nucleus of nerve cells in the AD brain were markedly higher than those in age-matched control brains. We hypothesize that the colocalization of Al and Fe in the nucleus of nerve cells might induce oxidative damage to nDNA and concurrently inhibit the repair of oxidatively damaged nDNA. An imbalance caused by the increase in DNA damage and the decrease in DNA repair activities might lead to the accumulation of unrepaired damaged DNA, eventually causing neurodegeneration and the development of AD.

Synthesis of Coumarin–Polyamine-Based Molecular Probe for the Detection of Hydroxyl Radicals Generated by Gamma Radiation

To develop a molecular probe for detection of hydroxyl radicals in the vicinity of DNA, the coumarin-polyamine complexes, N(1),N(12)-bis[2-oxo-2H-chromene-3-carbonyl]-1,12-diamine-4,9-diazadodecane (5) and tris[2-(2-oxo-2H-chromene-3-carboxamido)ethyl]amine (7), and their hydroxylated derivatives, N(1),N(12)-bis[7-hydroxy-2-oxo-2H-chromene-3-carbonyl]-1,12-diamine-4,9-diazadodecane (6) and tris[2-(7-hydroxy-2-oxo-2H-chromene-3-carboxamido)ethyl]amine (8), have been synthesized. Using computer-generated molecular modeling, the derivatives have been docked onto DNA dodecamer d(CGCGAATTCGCG)(2), the ligand-DNA complexes have been minimized, and the free binding energies (DeltaG(binding)) and inhibition constants (K(i)) have been calculated. Compound 7 is not water-soluble at the concentrations required for the project. When aqueous solutions of 5 are irradiated with gamma rays, the relationship between induced fluorescence and dose is linear in the range of 0 to 10 Gy. The fluorescence emission spectrum of irradiated 5 is similar to that of its dihydroxy derivative 6, indicating conversion of 5 to 6, and induction of fluorescence records formation of hydroxyl radicals in aqueous solution. The dicoumarin-polyamine 5, a novel compound for the detection of hydroxyl radicals close to DNA, is a sensitive and quantitative probe with potential for applications in biological systems.

Potentiation of Doxorubicin cardiotoxicity by iron loading in a rodent model

OBJECTIVES

The role of iron toward doxorubicin (DOX) cardiotoxicity was studied using a rodent model of dietary carbonyl iron loading.

BACKGROUND

Doxorubicin, a commonly used anticancer drug, is known to cause serious and potentially life-threatening cardiotoxicity. Doxorubicin cardiotoxicity is thought to be mediated through free-radical injury.

METHODS

Male Sprague Dawley rats fed iron-rich chow (n = 8) and regular chow (n = 8) were treated with DOX or saline (4 animals in each arm). Cardiotoxicity was assessed using mortality, weight changes, Tc-99m annexin-V imaging, histopathology, and immunohistochemistry.

RESULTS

Animals fed iron-rich chow showed significantly higher DOX cardiotoxicity as evidenced by greater weight loss (107 +/- 14 g vs. 55 +/- 10 g weight loss, p < 0.05), higher annexin uptake (0.14 +/- 0.01% vs. 0.08 +/- 0.01% injected dose/g of myocardium, p < 0.05), more severe myocyte injury on electron microscopy, and significantly higher cleaved caspase-3 staining compared with regular chow fed rats given DOX. Feeding iron-rich chow alone did not result in any cardiotoxicity.

CONCLUSIONS

Dietary iron loading resulted in a substantially increased DOX cardiotoxicity in rats. Body iron stores as well as its bioavailability in tissue may be important independent predictors of susceptibility to DOX cardiotoxicity in man. Further clinical studies are warranted.

Chromatin as a target for the DNA-binding anticancer drugs

Chemotherapy has been a major approach to treat cancer. Both constituents of chromatin, chromosomal DNA and the associated chromosomal histone proteins are the molecular targets of the anticancer drugs. Small DNA binding ligands, which inhibit enzymatic processes with DNA substrate, are well known in cancer chemotherapy. These drugs inhibit the polymerase and topoisomerase activity. With the advent in the knowledge of chromatin chemistry and biology, attempts have shifted from studies of the structural basis of the association of these drugs or small ligands (with the potential of drugs) with DNA to their association with chromatin and nucleosome. These drugs often inhibit the expression of specific genes leading to a series of biochemical events. An overview will be given about the latest understanding of the molecular basis of their action. We shall restrict to those drugs, synthetic or natural, whose prime cellular targets are so far known to be chromosomal DNA.

Fluorescence probes used for detection of reactive oxygen species

Endogenously produced pro-oxidant reactive species are essential to life, being involved in several biological functions. However, when overproduced (e.g. due to exogenous stimulation), or when the levels of antioxidants become severely depleted, these reactive species become highly harmful, causing oxidative stress through the oxidation of biomolecules, leading to cellular damage that may become irreversible and cause cell death. The scientific research in the field of reactive oxygen species (ROS) associated biological functions and/or deleterious effects is continuously requiring new sensitive and specific tools in order to enable a deeper insight on its action mechanisms. However, reactive species present some characteristics that make them difficult to detect, namely their very short lifetime and the variety of antioxidants existing in vivo, capable of capturing these reactive species. It is, therefore, essential to develop methodologies capable of overcoming this type of obstacles. Fluorescent probes are excellent sensors of ROS due to their high sensitivity, simplicity in data collection, and high spatial resolution in microscopic imaging techniques. Hence, the main goal of the present paper is to review the fluorescence methodologies that have been used for detecting ROS in biological and non-biological media.

Structure and function of "metalloantibiotics"

Although most antibiotics do not need metal ions for their biological activities, there are a number of antibiotics that require metal ions to function properly, such as bleomycin (BLM), streptonigrin (SN), and bacitracin. The coordinated metal ions in these antibiotics play an important role in maintaining proper structure and/or function of these antibiotics. Removal of the metal ions from these antibiotics can cause changes in structure and/or function of these antibiotics. Similar to the case of "metalloproteins," these antibiotics are dubbed "metalloantibiotics" which are the title subjects of this review. Metalloantibiotics can interact with several different kinds of biomolecules, including DNA, RNA, proteins, receptors, and lipids, rendering their unique and specific bioactivities. In addition to the microbial-originated metalloantibiotics, many metalloantibiotic derivatives and metal complexes of synthetic ligands also show antibacterial, antiviral, and anti-neoplastic activities which are also briefly discussed to provide a broad sense of the term "metalloantibiotics."