Biomedical subjects

S R Patierno

Publications and source records attributed to S R Patierno.

52 records · Page 3Linked to original sources

PubMed1989

Study of the ability of phenacetin, acetaminophen, and aspirin to induce cytotoxicity, mutation, and morphological transformation in C3H/10T1/2 clone 8 mouse embryo cells.

Use of the analgesic compounds acetylsalicylic acid (aspirin), phenacetin, and acetaminophen has been correlated with increased risk of renal cancer in humans. Hence, we studied these compounds for ability to induce cytotoxicity, mutation to ouabain resistance, and morphological transformation in cultured C3H/10T1/2 clone 8 (10T1/2) mouse embryo cells. All three compounds were cytotoxic from 0.5-mg/ml to 2-mg/ml concentrations as evidenced by decreased plating efficiency. None of the compounds induced detectable base substitution mutations to ouabain resistance even at cytotoxic concentrations. Aspirin did not induce morphological transformation. Both phenacetin and acetaminophen induced low but concentration-dependent numbers of atypical, weak type II morphologically transformed foci; at equimolar concentrations, phenacetin was 1.1- to 3.0-fold more active in inducing these foci. Neither phenacetin nor acetaminophen was cotransforming with 3-methylcholanthrene, and neither compound promoted cell transformation when added to 3-methylcholanthrene-initiated 10T1/2 cells. The focus-inducing potency of both compounds was increased by addition of an Arochlor-induced hamster liver S9 fraction as an exogenous metabolizing system. However, seven putative metabolites of phenacetin and acetaminophen that were tested--N-hydroxyphenacetin, p-phenetidine, p-aminophenol, p-nitrosophenol, benzoquinone, acetamide, and N-acetyl-p-benzoquinoneimine--were inactive in transformation assays at the concentrations reducing plating efficiency of treated cells to 50% of the plating efficiency of nontreated (control) cells. Several acetaminophen- and phenacetin-induced foci were cloned, expanded into cell lines, and characterized. These cell lines stably formed type II foci when maintained at confluence for 2 to 4 wk in reconstruction experiments with nontransformed 10T1/2 cells; however, they did not exhibit significantly increased saturation density compared to 10T1/2 cells, and they did not grow in soft agarose. These results suggest that metabolic intermediates of high concentrations of phenacetin and acetaminophen induce a low frequency of nonneoplastic morphological transformation of 10T1/2 mouse embryo cells.

Acetaminophen↗

PubMed1989

Morphological and neoplastic transformation of C3H/10T1/2 Cl 8 mouse embryo cells by insoluble carcinogenic nickel compounds.

We studied induction of cytotoxicity and morphological transformation in C3H/10T1/2 Cl 8 (10T1/2) mouse embryo fibroblasts by soluble and insoluble carcinogenic nickel compounds. Soluble nickel sulfate and nickel chloride caused dose-dependent cytotoxicity in the concentration range from 0.5 microM to 100 microM after 48 hr treatments, but neither compound induced morphological transformation even at concentrations causing up to 94% cytotoxicity. Insoluble nickel subsulfide, nickel monosulfide, and nickel oxide caused dose-dependent cytotoxicity and a low, dose-dependent frequency of morphological transformation in the concentration ranges from 0.5 to 40 microM, 5 to 50 microM, and 50 to 400 microM, respectively, after 48 hr exposure of cells to these compounds. Foci were predominantly of type II morphology; type III foci were rare. The insoluble nickel compounds studied caused no induction of base substitution mutations to ouabain resistance in 10T1/2 cells over concentration ranges that induced morphological transformation. Nickel subsulfide and nickel monosulfide were taken into cells by phagocytosis, since particles were visible in intracytoplasmic vacuoles. Numerous nickel oxide particles were found associated with cells, but true phagocytic uptake was difficult to detect since no vacuoles were observed. We twice cloned type II and type III foci induced by insoluble nickel compounds, established independent cell lines, and characterized their phenotypes. Four of seven of these cell lines had three- to fourfold increased saturation densities compared to 10T1/2 cells, formed type II and type III foci in reconstruction assays, and grew in soft agarose. One cell line induced by nickel oxide formed tumors in nude mice. These data indicate that insoluble carcinogenic nickel compounds induced type II foci in 10T1/2 cells, some of which were tumorigenic, and that the 10T1/2 cell system is suitable for studying mechanisms of nickel compound-induced morphological transformation in mammalian cells.

Animals↗

PubMed1988

Transformation of C3H/10T1/2 mouse embryo cells to focus formation and anchorage independence by insoluble lead chromate but not soluble calcium chromate: relationship to mutagenesis and internalization of lead chromate particles.

The genotoxicity of soluble and insoluble hexavalent chromium compounds was studied in mammalian cell assays which detect base substitution, deletion, addition, and frameshift mutations [6-thioguanine resistance in Chinese hamster ovary cells], primarily base substitution mutations [ouabain resistance in Chinese hamster ovary and C3H/10T1/2 Cl 8 mouse embryo fibroblasts (10T1/2)] and morphological transformation [focus formation] in 10T1/2 cells. Soluble hexavalent CaCrO4, administered in either acute (5-h) or subacute (24-h) dosing regimens, induced dose-dependent cytotoxicity and mutation to 6-thioguanine resistance in Chinese hamster ovary cells but no mutation to ouabain resistance or focus formation in transformation assays, although the acute treatment induced a high frequency of conversion of 10T1/2 cells to adipocytes. Cell lines established from cloned adipocytic cells were not morphologically transformed and did not grow in soft agarose. PbCrO4 did not induce mutation to either 6-thioguanine or ouabain resistance but did induce a reproducible dose-dependent, low frequency of focus formation in 10T1/2 cells. Cell lines established from PbCrO4-induced foci stably formed foci when coseeded with 10T1/2 cells, had 3-5-fold increased saturation densities relative to nontransformed 10T1/2 cells, and formed colonies in soft agarose, indicating their likelihood to be neoplastic. Long term exposure of 10T1/2 cells to either CaCrO4 or PbCl2, even at 85% cytotoxic concentrations, or pretreatment of cells with either CaCrO4 or PbCl2 followed by treatment with the alternate compound, did not induce morphological transformation. Treatment of cells with insoluble hexavalent PbCrO4 resulted in progressive and extensive vacuolization of cells in contact with the particles. Progressive cytoplasmic engulfment of PbCrO4 particles was observed using scanning electron microscopy, although PbCrO4 particles were not observed inside vacuoles. These results indicate that the soluble clastogens K2Cr2O7 and CaCrO4 were probably mutagenic by a non-base substitution mechanism but could not transform 10T1/2 cells. In contrast, PbCrO4 was not detectably mutagenic but induced transformation, which could not be explained solely by acute or chronic exposure to dissolution products of either lead or chromate alone. Since PbCrO4 particles were found to be intracytoplasmic in extensively vacuolated cells, we suggest that the unique physiochemical properties of PbCrO4 particles, leading to their internalization and the resultant associated cellular stress response, may be related to the transformation induced by this compound.

Adipose Tissue↗

PubMed1987

Increased expression of the glucose-regulated gene encoding the Mr 78,000 glucose-regulated protein in chemically and radiation-transformed C3H 10T1/2 mouse embryo cells.

Expression of the gene coding for the Mr 78,000 glucose-regulated protein (GRP78) was examined in nontransformed and chemically and radiation-transformed C3H 10T1/2 Cl 8 mouse embryo cells. When cells were grown in complete medium with 10% fetal bovine serum, GRP78 mRNA was increased 4- to 9-fold in 3-methylcholanthrene (MCA; Clones 15 and 16)-, bleomycin (Bleo 1)-, and ultraviolet light (UV-C3)-transformed cell lines compared to nontransformed 10T1/2 clone 8 cells (Cl 8) at similar cell number and growth phase. Increased steady-state levels of GRP78 protein in MCA Cl 15 compared to Cl 8 cells were confirmed by 2-dimensional gel electrophoresis. Under these conditions transformed MCA Cl 15 exhibited increased GRP78 RNA within 24 h after addition of fresh glucose-containing medium, whereas nontransformed Cl 8 cells did not increase expression of this gene even after 5 days of culture in conditioned medium. Incubation of Cl 8 and MCA Cl 15 in glucose-free medium for 16 h caused a 3- and 15-fold induction of GRP78 RNA, respectively. In addition, chemically transformed cells were highly sensitive to glucose deprivation and responded by rounding up and detaching from the substratum. Cl 8 cells exhibited no such sensitivity to glucose deprivation. These results extend earlier reports on virally transformed cells to include chemically and radiation-transformed cells and expand earlier reports to include mRNA expression and 2-dimensional gel electrophoresis of GRP78 protein.

Animals↗

PubMed1987

Effect of nickel(II) on DNA-protein binding, thymidine incorporation, and sedimentation pattern of chromatin fractions from intact mammalian cells.

Nuclear uptake and chromatin binding of nickel(II) was investigated in Chinese hamster ovary (CHO) cells. The cytoplasmic:nuclear ratio of nickel immediately following treatment was 5:1, but by 24 and 48 hours this ratio decreased to 4:1 and 2:1, respectively, indicating that nickel is retained longer in the nucleus than cytoplasmic nickel. Chromatin was fractionated by sonication and centrifugation into fast-sedimenting, magnesium-insoluble, or magnesium-soluble components. The magnesium-insoluble portion bound more nickel ions and retained the metal longer than either the magnesium-soluble or the fast-sedimenting fractions. Treatment of cells with nickel chloride (NiCl2) decreased the amount of DNA in the magnesium-insoluble fraction but increased the amount of DNA in the fast-sedimenting chromatin fraction. The magnesium-insoluble fraction isolated from nickel-treated cells contained approximately ten times more [35-S]-methionine-labeled protein per milligram DNA compared with untreated cells. The magnesium-soluble and the fast-sedimenting fractions isolated from the nickel-treated cells did not exhibit a similar increase in [35-S]-methionine-labeled protein per milligram of DNA. Nickel treatment suppressed [14-C]-thymidine incorporation into total DNA by 30% compared with untreated cells. However, the magnesium-insoluble chromatin fraction from nickel-treated cells had a tenfold to 20-fold increase in thymidine incorporation, while the other chromatin fractions did not exhibit an increase in thymidine incorporation. These findings indicate that nickel induced widespread alterations in chromatin conformation and preferentially interacted with an Mg-insoluble component of chromatin.

Animals↗

PubMed1987

Physicochemical characteristics and biological effects of nickel oxides.

Ten nickel oxides and nickel-copper oxides, which all contained NiO (bunsenite) as the predominant crystalline phase, were assayed as follows: in vitro dissolution tests in water and body fluids; in vitro phagocytosis tests in Chinese hamster ovary and C3H-10T1/2 cells; morphological transformation and cytotoxicity tests in cultured Syrian hamster embryo (SHE) cells; erythropoiesis stimulation assay by intrarenal administration to Fischer-344 rats; and scoring the renal histopathologic responses in rats killed 3 months post-injection. The test compounds differed substantially in their biological effects when tested in the various experimental systems. Based upon highly significant concordance of ranked results in the assays (P less than 0.001), six colligative biological attributes of the compounds were identified: (i) dissolution half-times in rat serum and renal cytosol; (ii) phagocytosis by C3H-10T1/2 cells; (iii) morphological transformation of SHE cells; (iv) erythropoiesis stimulation in rats; (v) induction of tubular hyperplasia in rat kidneys; and (vi) induction of arteriosclerosis in rat kidneys. Strong rank correlation (P less than 0.01) between results of the cell transformation and erythropoiesis stimulation assays is especially notable, since the compounds were tested by blind protocols in independent laboratories. The presence of high surface area and demonstrable Ni(III) were two physicochemical characteristics that were associated with the greatest biological effects of nickel oxides.

Animals↗

PubMed1987

Effects of nickel(II) on nuclear protein binding to DNA in intact mammalian cells.

An intracellular effect of nickel(II) which may be involved in its carcinogenic action is the alteration of normal DNA-protein binding. This effect of ionic nickel was studied in Chinese hamster ovary cells using several chromatin isolation methods in combination with SDS-polyacrylamide gel electrophoresis. DNA from cells incubated with (35S)-methionine or (35S)-cysteine to radiolabel protein was prepared by three methods: (solation of nuclei or nucleoids followed by chloroform-isoamyl alcohol (24:1 v/v) extraction and in some cases an additional extraction in the absence or presence of 2M NaCl, 40 mM EDTA or SDS; by isopycnic centrifugation through Cs2SO4 gradients containing 0.8% sarkosyl, 2.2 MCs2SO4, 1 mM NaCl and 10 mM EDTA; or by chromatin disaggregation and denaturation using 9 M urea, 2% 2-mercaptoethanol, 4% Nonidet P-40 +/- 2 M NaCl. DNA from nickel-treated cells consistently had more (35S)-methionine radioactivity associated with it than did DNA from untreated cells. This radioactivity was resistant to ribonuclease but sensitive to protease. Differential extraction using denaturing agents and high ionic strength followed by SDS-polyacrylamide gel electrophoresis revealed that most of the tightly bound proteins were nonhistone chromosomal proteins, and possibly histone 1. The enhancement of DNA-protein binding from nickel-treated cells was disrupted by SDS, suggesting that nickel ions do not function as classical bifunctional crosslinking agents. Since regulation of DNA replication and gene expression is dependent upon DNA-protein interactions, the effect of nickel in altering the extent of DNA-protein binding may interfere with this regulation and may contribute to the carcinogenic activity of nickel compounds.

Animals↗

PubMed1986

Enhanced expression of c-myc and decreased expression of c-fos protooncogenes in chemically and radiation-transformed C3H/10T1/2 Cl 8 mouse embryo cell lines.

c-abl, c-fos, c-Ha-ras, c-myc, and c-mos were expressed whereas c-sis, c-fms, c-rel, c-src, and c-myb expression was not detectable in C3H/10T1/2 Cl 8 (10T1/2) cells and in eight chemically and radiation-transformed 10T1/2 cell lines. The expression of c-abl, c-fos, c-Ha-ras, and c-myc was growth-related in nontransformed 10T1/2 cells. c-abl and c-fos expression increased at confluence by 5- and 9-fold, respectively, compared to that in log phase cells. c-Ha-ras and c-myc transcripts were most abundant in log phase cells and decreased by 70 and 50%, respectively, in confluent cells. There were no significant growth-related changes in the expression of c-Ha-ras, c-myc, or c-abl in methylcholanthrene-transformed Cl 15 cells. The c-fos transcript was not detected in Cl 15 cell cultures. c-abl, c-fos, c-ras, and c-myc were expressed in whole C3H mouse embryo tissue, mouse liver, and 10T1/2 cells. Sizes of these protooncogene transcripts in 10T1/2 cells were the same as those in whole embryo tissue, except that 10T1/2 cells did not express the 8.2-kilobase abl transcript. At subconfluence, equivalent low levels of c-mos expression were observed in nontransformed and in the eight transformed 10T1/2 cell lines. The level of c-abl expression was similar in the nontransformed and in the eight transformed cell lines, but there was a new 8.2-kilobase transcript in the transformed MCA Cl 15 cell line. c-fos was expressed in 10T1/2 cells but was not detectable or greatly reduced in eight transformed cell lines. c-Ha-ras was expressed to a similar extent in eight transformed cell lines and in nontransformed 10T1/2 cells. In the UVC-4 transformed cell line, extra 3.3-kilobase Ha-ras and 7.5-kilobase Ki-ras transcripts were observed. c-myc was expressed at 4- to 7-fold higher levels in six transformed cell lines compared to 10T1/2 cells. There were no major rearrangements in or amplification of the c-myc gene in three transformed cells overexpressing this gene 5-fold. These studies show that enhanced expression of c-myc and decreased expression of c-fos correlate with the chemically and radiation transformed states of 10T1/2 cells. Changes in c-fos and c-myc oncogene expression may be casually linked to late stages of neoplastic transformation in these chemically and radiation transformed 10T1/2 cell lines.

Animals↗

PubMed1986

Characterization of DNA lesions induced by CaCrO4 in synchronous and asynchronous cultured mammalian cells.

Alkaline elution studies demonstrated CaCrO4-induced DNA single strand breaks and DNA-protein crosslinks. DNA single strand breaks increased following treatment with 10-400 microM CaCrO4 in Chinese hamster ovary cells maintained with a minimal salts/glucose medium. DNA single strand breaks were rapidly repaired when extracellular CaCrO4 was removed even following exposure levels of CaCrO4 (200 microM for 2 hr) which reduced survival to 0.6%. Under these exposure conditions the trypan blue exclusion was greater than 80%, whereas cell growth was inhibited by 46% within 24 hr. The DNA-protein crosslinks induced by 10 microM CaCrO4 were repaired in the absence of metal within 24 hr. In contrast, the amount of DNA-protein crosslinks measured 24 hr after a 2-hr treatment with 50, 100, and 200 microM CaCrO4 remained unchanged at the 50 microM level or increased at the two higher concentrations. Thus, at concentrations of 50 microM or greater there was no repair of the DNA protein crosslinks, and this may have been due to cytotoxicity of the metal. CaCrO4 at 10 or 25 microM exposure for 6 hr also induced DNA-protein crosslinking in Chinese hamster ovary cells maintained in normal tissue culture growth media. The lack of repair of DNA-protein crosslinks at the 25 microM level, which did not substantially reduce cell survival, indicated the persistence of these lesions in a noncytotoxic form. Uptake of CaCrO4 was linear with all of the concentrations tested. Analysis of the cell cycle sensitivity to CaCrO4 revealed that cells in early S phase were the most sensitive to the cytotoxic and strand breaking activity of CaCrO4. Compared with other phases of the cell cycle, there was also an elevated level of DNA-protein crosslinks when cells were treated in early S phase and incubated 24 hr without CaCrO4. These results implicate the DNA-protein crosslink as an important lesion that may be responsible for the cytotoxic and carcinogenic properties of chromate.

Animals↗

PubMed1985

DNA-protein cross-links induced by nickel compounds in intact cultured mammalian cells.

The carcinogenic activity of crystalline NiS has been attributed to phagocytosis and intracellular dissolution of the particles to yield Ni2+ which is thought to enter the nucleus and damage DNA. In this study the extent and type of DNA damage in Chinese hamster ovary CHO cells treated with various nickel compounds was assessed by alkaline elution. Both insoluble (crystalline NiS) and soluble (NiCl2) nickel compounds induced single strand breaks and DNA protein cross-links. The single strand breaks were repaired relatively quickly but the DNA-protein cross-links were present and still accumulating 24 h after exposure to nickel. Single strand breakage occurred at both non-cytotoxic and cytotoxic concentrations of nickel, however, DNA-protein cross-linking was absent when cells were exposed to toxic nickel levels. The concentration of nickel that induced DNA-protein cross-linking correlated with those metal concentrations that reversibly inhibited cellular replication.

Animals↗

PubMed1985

Preferential DNA-protein cross-linking by NiCl2 in magnesium-insoluble regions of fractionated Chinese hamster ovary cell chromatin.

Intracellular nickel ions (Ni2+) have been shown to cause single-strand breaks in DNA, that were rapidly repaired, and DNA-protein cross-links, that persisted for at least 24 h following removal of extracellular ionic nickel. In this study, we have used the techniques of alkaline elution, chromatin fractionation, and sodium dodecyl sulfate:polyacrylamide gel electrophoresis to examine the DNA-protein cross-linking induced by NiCl2 in Chinese hamster ovary cells. Continuous treatment of logarithmically growing Chinese hamster ovary cells with 2.5 mM NiCl2 in complete medium resulted in DNA single-strand breaks within 1 h, followed by a time-dependent increase in the induction of DNA-protein cross-links at 2, 3, and 6 h. Since the entry of nickel into cells was maximal within 2 h of exposure, the time delay for the formation of DNA-protein cross-links was not limited by metal uptake. The nickel-induced DNA-protein cross-linking appeared to require active cell cycling, since single-strand breaks but no cross-linking could be detected in confluent cells treated with 1, 2.5, or 5 mM NiCl2 for 3 h. DNA-protein cross-linking induced by nickel occurred in late S phase of the cell cycle. High-molecular-weight nonhistone chromatin proteins and possibly histone H1 migrating at the Mr 30,000 range became cross-linked to DNA after treatment of cells with NiCl2. All nickel-cross-linked proteins were concentrated in the magnesium-insoluble regions of fractionated chromatin and were stable to urea, 2-mercaptoethanol, and Nonidet P-40. Some proteins (Mr 48,000, 52,000, 55,000, 70,000, and 95,000), the association of which with DNA was also stable to Sarkosyl, salt, and EDTA, were detectable in DNA rigorously fractionated from untreated cells. Nickel therefore appeared to cause the cross-linking of proteins that normally reside in close association with DNA. Alterations of the normal association of these proteins with DNA by nickel may be an early event in the nickel transformation process.

Animals↗

PubMed1983

Application of a modified 203Hg binding assay for metallothionein.

A sensitive and rapid method to estimate concentrations of functional metallothionein in small biological samples, based upon the acid stability of 203Hg binding and solubility of this protein in trichloroacetic acid is described. Sephadex G-10 minicolumns supported in centrifuge tubes afforded separation and quantitation of isotope bound metallothionein from unbound metal. Elution of metallothionein bound 203Hg was achieved by short term-low speed centrifugation that segregated chelator-ligand complex into the eluate while unbound ligand remained in the gel. A well characterized standard of pure metallothionein protein was utilized to verify the specificity and sensitivity of the modified assay. Metallothionein levels were estimated by 203Hg binding in extracts of wild type and cadmium resistant Chinese hamster ovary cells treated with maximum tolerable concentrations of CdCl2. Similar separation methods demonstrated [35S]-cysteine incorporation into induced metallothionein. Additionally, induction of metallothionein was observed after treatment with particulate CdS but not crystalline NiS particles. These results demonstrate that the modified assay system is easily applied to serial measurement of metallothionein levels in multiple small biological samples.

Animals↗

PubMed1983

Inhibition of LPS toxicity for macrophages by metallothionein-inducing agents.

Parenteral administration of adrenal corticosteroids or particular transition metal salts are known to protect mice from the lethal effects of bacterial lipopolysaccharides (LPS). To determine if both groups of substances act through similar biologic mechanisms, their capacity to protect macrophages from the direct toxic effects of LPS was examined in vitro. When added simultaneously with LPS at culture initiation, 10 to 100 microM cortisone increased the viability of normal peritoneal macrophages as determined by trypan blue exclusion. Prednisolone and corticosterone protected LPS-treated macrophages at even lower concentrations (0.1 to 1 microM); estradiol and testosterone failed to alter cell viability at any concentration tested. Protection was dependent on de novo synthesis because inclusion of 20 nM actinomycin C1 or 1 microM cycloheximide with 10 microM corticosterone during a 4-hr pretreatment period blocked induction of the protective effect. Murine macrophages were also protected by micromolar concentrations of zinc, cadmium, mercury, and manganese, but not by calcium or lead. As was obtained with corticosteroids, heavy metal-induced protection depended on de novo RNA and protein synthesis. Because all substances that protected against LPS are known inducers of metallothionein in somatic cells, peritoneal macrophages were assayed for the presence of this unique, cytoplasmic protein. Within 2 to 8 hr, 10 microM cadmium caused three to fivefold increases in the incorporation of 35S-cysteine and in the binding of 203Hg into the TCA-soluble fraction of cell lysates that was excluded on centrifugally accelerated Sephadex G-10 columns. These results suggest macrophages may be protected from LPS-mediated cytotoxicity through synthesis of a sulfhydryl-rich, metal-binding protein. Although its mechanism of action remains unknown, it is proposed that metallothionein may function homeostatically by altering intracellular concentrations of zinc or may play a regulatory role by facilitating transfer of heavy metals among metal-requiring apoproteins.

Animals↗

PubMed1983

Growth inhibition and metallothionein induction in cadmium-resistant cells by essential and non-essential metals.

Essential and non-essential metal ions were compared on the basis of their growth-inhibitory potency and their mediation of metallothionein induction in a Chinese hamster ovary cell line resistant to cadmium. Cadmium-resistant cells were found to be 20-fold and 6-fold more resistant than wild-type Chinese hamster ovary cells to the non-essential metals CdCl2 and HgCl2, respectively. In contrast, cadmium-resistant cells showed 2-fold or less resistance to growth inhibition due to the metals with known or possible biological essentiality, ZnCl2, CuSO4, CoCl2, and NiCl2. Resistance to either cadmium or mercury was not due to decreased uptake as measured isotopically or by X-ray fluorescence. At concentrations near the threshold of growth inhibition, CdCl2 and ZnCl2 induced metallothionein 8- to 10-fold above background levels in cadmium-resistant cells within 8-10 hr. A 2- to 3-fold induction of this protein was produced in resistant cells by levels of HgCl2, CuSO4, and CoCl2 near the threshold of growth inhibition whereas NiCl2 produced no measurable elevations of metallothionein at concentrations below, near, and above those that inhibit cell growth. Induction of metallothionein was measured by a modified 203Hg binding assay and by [35S]cysteine incorporation. No measurable induction of metallothionein was evident in wild-type cells with any metal treatment using a reasonable quantity of cells consistent with our assay. These results in cadmium-resistant cells demonstrate selective induction of metallothionein by various metals and suggest that induction of this protein alone is not solely responsible for differences in the growth-inhibitory potential of these elements.

Animals↗

PubMedDate not supplied

Soluble vs insoluble hexavalent chromate. Relationship of mutation to in vitro transformation and particle uptake.

Soluble CaCrO4 and insoluble PbCrO4 were tested for induction of mutation to 6-thioguanine (base-substitution, deletion, addition, and frameshift mutations) or ouabain (base-substitution mutations) resistance in Chinese hamster ovary cells and morphological transformation in C3H/10(1/2) mouse embryo cells. CaCrO4 induced dose-dependent cytotoxicity and mutation to 6-thioguanine resistance, but did not induce mutation to ouabain resistance or morphological transformation. Highly cytotoxic amounts of CaCrO4 induced conversion of 10T1/2 cells to adipocytes, but cell lines derived from such cells were not transformed. PbCrO4 was not mutagenic in either mutation assay but induced a dose-dependent, low frequency of focus formation. Cell lines established from these foci had a 3-5-fold increased saturation density, grew in soft agarose, and were tumorigenic in nude mice. Chronic exposure to CaCrO4 or PbCl2 did not induce transformation, PbCl2 was inactive even at acutely cytotoxic concentrations, and sequential treatments with CaCrO4 and PbCl2 did not induce transformation. Light and scanning electron microscopy showed progressive cytoplasmic engulfment of PbCrO4 particles and extensive vacuolization of cells in contact with the particles. No particles were observed inside of vacuoles. We suggest that internalization of PbCrO4 and the associated cellular stress response may be related to PbCrO4-induced neoplastic transformation of 10T1/2 cells.

Animals↗

PubMedDate not supplied

Chromium-induced genotoxicity and apoptosis: relationship to chromium carcinogenesis (review).

The adverse health effects linked with chromium (Cr) exposure, the role of solubility and chemical speciation of Cr compounds, and the diverse cellular and molecular effects of Cr make the study of Cr carcinogenesis and toxicology very interesting and complex. Certain Cr compounds are prominent metal carcinogens in both occupational and environmental settings. Inhaled particulate forms of hexavalent Cr [Cr(VI)] cause lung cancer as well as lung toxicity. Some of the important factors in determining the biological outcome of Cr exposure include the bioavailability, chemical speciation and solubility of Cr compounds, intracellular reduction, and interaction of Cr with DNA. The stable oxidation states of Cr found in nature are Cr(III) and Cr(VI). Cr(III) is unable to enter cells but Cr(VI) enters into cells through membrane anionic transporters. Intracellular Cr(VI) is metabolically reduced to the ultimate Cr(III). Cr(VI) does not react with macromolecules such as DNA, RNA, proteins and lipids. However, both Cr(III) and the reductional intermediate Cr(V) are capable of co-ordinate covalent interactions with macromolecules. At the genomic level, Cr genotoxicity manifests as gene mutations, several types of DNA lesions and inhibition of macromolecular synthesis. At the cellular level, Cr exposure may lead to cell cycle arrest, apoptosis, premature terminal growth arrest, or neoplastic transformation. Cr-induced DNA-DNA interstrand crosslinks (DDC), the tumor suppressor gene p53 and oxidative processes are some of the major factors that may play a significant role in determining the cellular outcome in response to Cr exposure. We have utilized cellular, molecular, pharmacological, and genetic approaches to understand the interrelationship between Cr-induced genotoxicity, apoptosis and carcinogenesis. This review is based on the results and inferences of this research. We hope this review will clarify existing concepts and also introduce novel perspectives in chromium carcinogenesis research.

Animals↗