Susan Krezoski

Binding of cis-dichlorodiammine platinum(II) to metallothionein in Ehrlich cells.

The antitumor agent, cis-dichlorodiammine Pt(II), is cytotoxic to Ehrlich cells in culture. These cells contain a substantial amount of metallothionein in the absence of inducers of the protein. At concentrations of drug which cause 60% inhibition of cell proliferation, most of the platinum is found in the cytosol. Of this about 30% is bound in the metallothionein fraction. Isolated rat liver metallothionein reacts slowly with hydrolyzed cis-dichlorodiammine Pt(II). Thus, metallothionein is a major cellular site of binding of the platinum complex at concentrations which inhibit tumor growth.

Mammalian metallothionein in toxicology, cancer, and cancer chemotherapy

The present paper centers on mammalian metallothionein 1 and 2 in relationship to cell and tissue injury beginning with its reaction with Cd2+ and then considering its role in the toxicology and chemotherapy of both metals and non-metal electrophiles and oxidants. Intertwined is a consideration of MTs role in tumor cell Zn2+ metabolism. The paper updates and expands on our recent review by Petering et al. (Met Ions Life Sci 5:353–398, 2009).

Apo-Metallothionein Emerging as a Major Player in the Cellular Activities of Metallothionein

Observations of apo-metallothlonein (apo-MT) have been made under a variety of physiologic circumstances, including zinc deficiency in cell culture and in rodents, cellular induction of MT by dexamethasone with concurrent Zn deficiency, a variety of tumors under normal Zn conditions, MT induction by Zn and Bi citrate, induction of hepatic MT after tumor cell Injection into nude mice, and overexpression of cardiac MT in MT transgenic mice. Experiments demonstrating both the lability of Zn and Cu bound to MT and the cellular stability of apo-MT are described to help rationalize the widespread presence of this metal-depleted species. Finally, comparative in vitro and cellular experiments examined the relative reactivity of Zn- and apo-MT with nitric oxide species, showing that apo-MT is much more reactive chemically and that in cells it may be a principal reactive species within the MT pool.

Surface Chemistry and Biological Pathogenicity of Silicates: An X-Ray Photoelectron Spectroscopic Study

We extend our electron spectroscopy for chemical analysis studies of the chemistry of silicates to provide direct surface chemical information on the interactions involved in silicate-induced lung and tissue pathology. A total of five fibrous and non-fibrous silicate minerals, primarily amphiboles, have been studied: anthophyllite, tremolite, cummingtonite, hornblende and actinolite. We have followed the ‘in-lattice’ surface chemistry of these materials and monitored features such as the simultaneous presence of four- and six-coordinate (with respect to oxygen) structural aluminium, and the presence of iron in the M4 octahedral positions. In vitro experiments involving contact of the silicate with cultured murine Ehrlich cells have identified modifications in the surface chemistry of Al, Mg and Fe in the silicates and changes in cellular iron content.

Investigations of the surface chemistry of pathogenic silicates

The following is a continuation of our extensive investigations of the chemistry of complex silicate systems employing a combination of electron spectroscopy for chemical analysis and magic angle spinning nuclear magnetic resonance. In this case, we are beginning to provide unique chemical information that may have implications in the field of silicate‐induced pathogenesis (e.g., asbestosis). Select silicate materials (such as amphiboles) have been investigated both before and following alterations of their physical conditions (e.g., crushing) and also before and after contact with certain in vitro cell cultures. In our studies to date, we have been able to track the ‘‘in‐lattice’’ chemistry of the constituents of these, and related, silicates, determining such features as the simultaneous presence of aluminum in tetrahedral and octahedral sites of amphiboles, as well as the iron in M(4), as opposed to M(3) or M(1) octahedral positions of these amphiboles. We are comparing results for fibrous silicates wi...

Iron deficiency in growing male rats: a cause of development of cardiomyopathy.

Weanling male rats were fed a purified iron-adequate, a purified iron-deficient or a commercial diet for 12 weeks. At that time the rats were sacrificed, their hearts and livers were excised, and blood samples were taken. Heart and liver weights were recorded; organ tissue and serum samples were analyzed for Zn, Cu and Fe. Hemoglobin and hematocrit values were also obtained. The iron-deficient rats grew much more slowly than controls on the iron-adequate or commercial diets. The iron-deficient rats were severely anemic and had enlarged hearts (cardiomegaly). A histopathologic examination of the hearts of all animals showed that each heart of the iron-deficient rats had lesions characteristic of cardiomyopathy by dilatation, whereas none of the hearts of the iron-adequate group or the chow controls showed any lesions at all. The iron-deficient animals had only about 25% of the hepatic iron found in the iron-adequate animals but about 5 times the hepatic copper of the latter group or the chow controls. Heart iron of the iron-deficient group was 27% of the concentration found in hearts of the iron-adequate rats; heart copper was similar in all groups. Animals on the commercial stock diet accumulated significantly more iron in their hearts than did those on the purified iron-adequate diet but not in the livers. There was also a direct correlation of heart iron or heart zinc with log concentrations of dietary iron and consequently a direct correlation between heart iron and zinc concentrations.

Reactivity of Zn-, Cd-, and Apo-Metallothionein with Nitric Oxide Compounds: In Vitro and Cellular Comparison

The reactivity of Zn(7)- and Cd(7)-metallothionein (MT) with S-nitrosopenicillamine (SNAP), S-nitrosoglutathione (GSNO), and 2-(N,N-diethylamino)-diazenolate-2-oxide (DEA/NO) was investigated to explore the hypothesis that metallothionein is a signficant site of cellular reaction of nitric oxide or NO compounds. Zn(7)-MT reacted with SNAP or GSNO only under aerobic conditions and in the presence of light, which stimulates the decomposition of S-nitrosothiolates to NO. Zn(2+) is released, and protein thiols are modified. DEA/NO, which degrades spontaneously to release NO, also reacted with Zn(7)-MT only when oxygen was present. Anaerobically, DEA/NO reacted with Zn(7)-MT in the presence of 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, which converts NO to NO(2). Glutathione competed effectively with Zn(7)-MT for reactive nitrogen oxide species in reaction mixtures. Reaction of Cd(7)-MT with SNAP also required oxygen and light to react. In this case, only a fraction of the Cd(2+) bound to Cd(7)-MT was displaced by SNAP. Apo-metallothionein was much more reactive with SNAP and DEA-NO than Zn(7)- or Cd(7)-MT. TE671 and LLC-PK(1) cell lines were incubated with DEA/NO to examine the role that MT might play in the cellular reactions of this NO donor compound. Incubation of cells with 0-80 microM Zn(2+) for 24 h resulted in progressively increasing concentrations of Zn-unsaturated MT. One hour of cellular exposure to a range of DEA/NO concentrations followed by 24 h of incubation caused no evident acute toxicity at less than 0.45 mM. Preinduction of MT did not alter this response. The effects of DEA/NO on proteomic, metallothionein, and low molecular weight (LMW) thiol pools, including glutathione (GSH), were measured. Substantial fractions of the proteomic and LMW thiol pools underwent reaction with little dislocation of Zn(2+). In addition, one-third of the MT thiol pool reacted without labilizing any of the bound Zn(2+). These results demonstrated that it was free thiols associated with MT that reacted with DEA/NO not those bound to Zn(2+). Moreover, under the conditions of the experiments, DEA/NO reacted with the spectrum of cellular thiols in proportion to their fraction in the cytosol and did not preferentially react with MT sulfhydryl groups.

Surface modification of silicon and silica in biological environment: an X-ray photoelectron spectroscopy study

Abstract The Earth’s crust is primarily made of various silicate materials upon which we successfully dwell everyday. Numerous biomedical studies, however, have documented the toxicity of some of these materials when interacted with biological cells. It has become apparent that the surface chemistry of these silicates plays a key role in the cell pathogenesis, thus enhancing the value of the use of electron spectroscopy for chemical analysis (ESCA) or X-ray photoelectron spectroscopy (XPS) as a key method for analysis. Recent studies suggest that many common silicates, including silica itself, may not be innocuous to cell pathogenecity, thus suggesting their inclusion in these XPS studies. This paper presents a detailed study of the surface chemical modification of silicon and silica when interacting with Ehrlich cells. XPS studies at selected stages of cell treatment reveal cell-induced alteration in the carbon, silicon, and oxygen of these silicon-based materials as well as changes in the carbon, iron, and nitrogen of the cell chemistry. Supporting results from the atomic absorption spectroscopy show similar changes.

12:Metallothionein Toxicology: Metal Ion Trafficking and Cellular Protection

The literature is replete with reports about the involvement of metallothionein in host defense against injurious chemical, biological, and physical agents. Yet, metallothioneins functional roles are still being debated. This review addresses the issues that have left the physiological significance of metallothionein in doubt and moves on to assess the MTs importance in cell toxicology. It is evident that the protein is broadly involved in protecting cells from injury due to toxic metal ions, oxidants, and electrophiles. Attention is focused on MTs structural and chemical properties that confer this widespread role in cell protection. Particular emphasis is placed on the implications of finding that metal ion unsaturated metallothionein is commonly present in many cells and tissues and the question, how does selectivity of reaction with metallothionein take place in the cellular environment that includes large numbers of competing metal binding sites and high concentrations of protein and glutathione sulfhydryl groups?

Surface chemical interaction of fibrous asbestos with biocells: An ESCA study

Abstract High-resolution X-ray Photoelectron Spectroscopy (XPS), also known as ESCA (Electron Spectroscopy for Chemical Analysis), has been used to monitor the surface chemistry of silicate minerals exposed to living cells. We have followed the chemical changes in the silicates induced by changes in elemental composition (reflected in the Si Al and Si Mg ratios) and structure. Changes in bond strength which occur in the process were monitored via the line shifts in the ESCA spectra. As it is likely that differences in surface chemistry affect the interactions of silicates with cellular systems, we have embarked on a systematic study of well-characterized silicates exposed to murine tumour Ehrlich cells under controlled conditions. ESCA identifies changes in the surface chemistry of asbestos caused by interactions with cells, while atomic absorption spectrometry (AAS) monitors silicate-induced changes in the cell iron content. There is a significant increase in iron concentration in the cells and in the Si Mg ratio on the surface of asbestos after contact with the cells. The complex C(1s) and Si(2p) ESCA spectral features and the presence of trace elements in freeze-dried cell-asbestos mixtures indicate the presence of chemical interactions of asbestos with the cells. We believe that such studies may eventually help in the identification of pathogenic mechanisms involving mineral dusts.