Chromium-induced production of reactive oxygen species, DNA single-strand breaks, nitric oxide production, and lactate dehydrogenase leakage in J774A.1 cell cultures

Cigarette Smoke-Induced Reactive Oxygen Species Formation: A Concise Review

Smoking is recognized as a significant risk factor for numerous disorders, including cardiovascular diseases, respiratory conditions, and various forms of cancer. While the exact pathogenic mechanisms continue to be explored, the induction of oxidative stress via the production of excess reactive oxygen species (ROS) is widely accepted as a primary molecular event that predisposes individuals to these smoking-related ailments. This review focused on how cigarette smoke (CS) promotes ROS formation rather than the pathophysiological repercussions of ROS and oxidative stress. A comprehensive analysis of existing studies revealed the following key ways through which CS imposes ROS burden on biological systems: (1) ROS, as well as radicals, are intrinsically present in CS, (2) CS constituents generate ROS through chemical reactions with biomolecules, (3) CS stimulates cellular ROS sources to enhance production, and (4) CS disrupts the antioxidant system, aggravating the ROS generation and its functions. While the evidence supporting these mechanisms is chiefly based on in vitro and animal studies, the direct clinical relevance remains to be fully elucidated. Nevertheless, this understanding is fundamental for deciphering molecular events leading to oxidative stress and for developing intervention strategies to counter CS-induced oxidative stress.

The role of chromium supplementation in cardiovascular risk factors: A comprehensive reviews of putative molecular mechanisms

In the recent years, micronutrients play an important role in improving body health with preventing and treating of chronic diseases. Chromium is one of the vital minerals involved in the regulation of insulin action. According to abundant evidences this mineral seems to be an essential factor involved in the reduction of insulin resistance and decreasing the risk of type 2 diabetes mellitus (T2DM) and cardiovascular diseases (CVDs). Moreover, it has been proposed that Chromium supplementation affects mechanisms involved in blood pressure, lipid metabolism, inflammation, and oxidative stress. For instance, it may affect blood pressure through alteration of the renin-angiotensin system, as well as reducing the angiotensin-converting enzyme activity. Furthermore, Chromium supplementation might help reduce the coronary heart disease rates. This study aims to provide a comprehensive review regarding to the effects of Chromium supplementation on CVDs risk factors with an emphasis on possible molecular mechanisms.

Effects of cobalt and chromium ions on oxidative stress and energy metabolism in macrophages in vitro

Cobalt and chromium ions released from cobalt-chromium-molybdenum (CoCrMo)-based implants are a potential health concern, especially since both ions have been shown to induce oxidative stress in macrophages, the predominant immune cells in periprosthetic tissues. Ions of other transition metals (Cd, Ni) have been reported to inhibit the activity of mitochondrial enzymes in the electron transport chain. However, the effects of Co and Cr ions on the energy metabolism of macrophages remain largely unknown. The objective of the present study was to analyze the effects of Co²⁺ and Cr³⁺ on oxidative stress and energy metabolism in macrophages in vitro. RAW 264.7 murine macrophages were exposed to 6-18 ppm Co²⁺ or 50-150 ppm Cr³⁺ . Results showed a significant increase in two markers of oxidative stress, reactive oxygen species level and protein carbonyl content, with increasing concentrations of Co²⁺ , but not with Cr³⁺ . In addition, oxygen consumption rates (OCR; measured using an extracellular flux analyzer) showed significant decreases in both mitochondrial respiration and non-mitochondrial oxygen consumption with increasing concentrations of Co²⁺ , but not with Cr³⁺ . OCR results further showed that Co²⁺ , but not Cr³⁺ , induced mitochondrial dysfunction, including a decrease in oxidative phosphorylation capacity. Overall, this study suggests that mitochondrial dysfunction may contribute to Co²⁺ -induced oxidative stress in macrophages, and thereby to the inflammatory response observed in periprosthetic tissues. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3178-3187, 2018.

Gemcitabine induced cytotoxicity, DNA damage and hepatic injury in laboratory mice

The present study was conducted to demonstrate cytotoxicity, apoptosis and hepatic damage induced by gemcitabine in laboratory mice. Animals were treated with a single dose of gemcitabine (415 mg/kg body wt), equivalent to a human therapeutic dose, and sacrificed after 1, 2 and 3 weeks. A significant decrease in mean body weight and absolute liver weight was registered. The levels of alkaline phosphatase (ALP), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were increased as a result of this induced stress. Various structural changes were observed in the liver tissue of treated mice, as evident in the histological sections. Specifically, gemcitabine exposure was able to induce apoptosis in liver cells, and the incidence of TUNEL positive liver cells was increased compared to the control group. DNA fragmentation appeared on agarose gel and flow cytometry analysis confirmed the induction of apoptosis. These findings in gemcitabine-treated animal tissues suggest that inhibition or disruption of cells' DNA synthesis may be the mechanism by which this drug induces toxicity in the animal body.

Chromium-induced genotoxicity and interference in human lymphoblastoid cell (TK6) repair processes

Two model chromium (Cr) compounds, one hexavalent (sodium chromate) and one trivalent (chromium chloride), were investigated in a human lymphoblastoid cell line (TK6) to increase our knowledge regarding Cr-induced genotoxicity mechanisms. Both selected compounds were genotoxic using the comet assay, although the percentage of DNA in tail obtained after treatment with Cr(VI) was significantly higher than that obtained with Cr(III), at the higher concentrations tested. To determine the nature of the induced damage, enzymes recognizing oxidized bases were used. Treatments with formamidopyrimidine (FPG) and endonuclease III (EndoIII) displayed a greater degree of DNA damage, indicating that the induction of oxidized bases accounts for an important proportion of the damage induced by Cr compounds. In addition, the kinetic repair studies showed that generated DNA damage is removed in approximately 8 h, with the damage induced by Cr(III) being removed/repaired more rapidly than damage produced by Cr(VI). To detect Cr interferences with the repair process, a post-treatment was applied after exposure to 2 Gy gamma radiation. Post-treatment significantly delayed the repair kinetics of DNA damage induced by radiation. This interference effect induced by Cr(VI) was more pronounced. In conclusion, evidence indicates that a high proportion of the Cr-induced DNA damage is correlated with oxidative damage, and that both Cr compounds interfere with repair mechanisms involved in repair of DNA damage induced by gamma radiation.

Chromium III exposure inhibits brain Na+K+ATPase activity of Clarias batrachus L. involving lipid peroxidation and deficient mitochondrial electron transport chain activity

The present study elucidated the role of lipid peroxidation and diminished mitochondrial electron transport chain activity in partial dysfunction of brain Na+K+ATPase of Clarias batrachus exposed to chromium III ions. The fish were exposed to 10% and 20% of the derived 96 h LC50 value, 5.69 mg/L and 11.38 mg/L, respectively, and sampled on 20, 40 and 60 days. Exposure to chromium III on fish brain demonstrated an increased lipid peroxidation, production of protein carbonyl and reactive oxygen species and loss of protein thiol groups in synaptosomal fraction with decreased activity of Na+K+ATPase, partial inactivation of mitochondrial electron transport chain activity and energy depletion.

Carcinogenic metal compounds: recent insight into molecular and cellular mechanisms

Mechanisms of carcinogenicity are discussed for metals and their compounds, classified as carcinogenic to humans or considered to be carcinogenic to humans: arsenic, antimony, beryllium, cadmium, chromium, cobalt, lead, nickel and vanadium. Physicochemical properties govern uptake, intracellular distribution and binding of metal compounds. Interactions with proteins (e.g., with zinc finger structures) appear to be more relevant for metal carcinogenicity than binding to DNA. In general, metal genotoxicity is caused by indirect mechanisms. In spite of diverse physicochemical properties of metal compounds, three predominant mechanisms emerge: (1) interference with cellular redox regulation and induction of oxidative stress, which may cause oxidative DNA damage or trigger signaling cascades leading to stimulation of cell growth; (2) inhibition of major DNA repair systems resulting in genomic instability and accumulation of critical mutations; (3) deregulation of cell proliferation by induction of signaling pathways or inactivation of growth controls such as tumor suppressor genes. In addition, specific metal compounds exhibit unique mechanisms such as interruption of cell-cell adhesion by cadmium, direct DNA binding of trivalent chromium, and interaction of vanadate with phosphate binding sites of protein phosphatases.

Excision repair is required for genotoxin-induced mutagenesis in mammalian cells

Certain hexavalent chromium [Cr(VI)] compounds are human lung carcinogens. Although much is known about Cr-induced DNA damage, very little is known about mechanisms of Cr(VI) mutagenesis and the role that DNA repair plays in this process. Our goal was to investigate the role of excision repair (ER) pathways in Cr(VI)-mediated mutagenesis in mammalian cells. Repair-proficient Chinese hamster ovary cells (AA8), nucleotide excision repair (NER)-deficient (UV-5) and base excision repair (BER)-inhibited cells were treated with Cr(VI) and monitored for forward mutation frequency at the hypoxanthine-guanine phosphoribosyltransferase (HPRT) locus. BER was inhibited using methoxyamine hydrochloride (Mx), which binds to apurinic/apyrimidinic sites generated during BER. Notably, we found that both NER-deficient (UV-5 and UV-41) and BER-inhibited (AA8 + Mx) cells displayed attenuated Cr(VI) mutagenesis. To determine whether this was unique to Cr(VI), we included the alkylating agent, methylmethane sulfonate (MMS) and ultraviolet (UV) radiation (260 nm) in our studies. Similar to Cr(VI), UV-5 cells exhibited a marked attenuation of MMS mutagenesis, but were hypermutagenic following UV exposure. Moreover, UV-5 cells expressing human xeroderma pigmentosum complementation group D displayed similar sensitivity to Cr(VI) and MMS-induced mutagenesis as AA8 controls, indicating that the genetic loss of NER was responsible for attenuated mutagenesis. Interestingly, Cr(VI)-induced clastogenesis was also attenuated in NER-deficient and BER-inhibited cells. Taken together, our results suggest that NER and BER are required for Cr(VI) and MMS-induced genomic instability. We postulate that, in the absence of ER, DNA damage is channeled into an error-free system of DNA repair or damage tolerance.

Impairment of cell and plasma redox state in subjects professionally exposed to chromium

BACKGROUND

Chromium (Cr) is widely used in chemical, tannery, building, and metal industries. More recently, it has been demonstrated that Cr induces oxidative stress in mouse brain. Nevertheless very few data exist on in vivo oxidative damage in humans exposed to Cr.

METHODS

Changes in antioxidant parameters both in plasma (acid ascorbic redox state and total antioxidant capacity) and in red blood cells (glutathione (GSH) redox state) of 40 subjects (age 37.65 +/- 7.46; M/F 20/20) professionally exposed to Cr who were recruited from metal, chemistry, and building industries were evaluated. We also evaluated the levels of lipoperoxidation (thiobarbituric acid-reactive material, TBA-RM) and thiol levels in plasma to assess the extent of oxidative stress state. To evaluate Cr exposure rate, we measured urinary-chromium (U-Cr) by an electrothermic atomization-atomic absorption spectrometry (ETA-AAS) method.

RESULTS

In this study, we found that Cr exposure induced a decrease both in GSH (P < 0.0005) and GSH/oxidized glutathione (GSSG) ratio (P < 0.0001) in red blood cells from workers with respect to control subjects. Furthermore, we also demonstrated a significant decrease of plasma acid ascorbic levels (45.7 +/- 14.9 vs. 53.5 +/- 16.5 micromol/L; P < 0.05) and in total plasma antioxidant capacity (1,126.3 +/- 212.2 vs. 1,266.9 +/- 207.8 micromol/L; P < 0.05) in subjects exposed to Cr. No difference was found with regard to TBA-RM and thiol levels.

CONCLUSIONS

This study demonstrated that in humans, an oxidative stress occurs for Cr exposures as low as those considered safe. This oxidative stress appears to be able to affect intracellular and plasmatic antioxidant defense.

Urinary 8-hydroxydeoxyguanosine and sister chromatid exchanges in patients with total hip replacements

Ion release from metal implants has been suspected to increase the risk of genotoxic effects in patients wearing orthopedic metal devices. In this study we used urinary 8-hydroxydeoxyguanosine (8-OHdG) as marker of oxidative DNA damage and the frequency of sister chromatid exchanges in lymphocytes to test a possible relationship between the concentrations of chromium or cobalt and the induction of cytogenetic modifications in 46 patients with total hip replacements. A broad range of individual levels of metals has been observed in these patients: chromium in blood, 1.59-14.11 microg/L; chromium in urine, 0.79-93.80 microg/24 h; cobalt in blood, 0.77-37.80 microg/L; cobalt in urine, 2.59-166.94 microg/24 h. By linear regression analysis, no significant correlation between urinary 8OHdG or sister chromatid exchange (SCE) and the concentrations of metals was found. However, cobalt in blood as well as 8-OHdG in urine were higher in patients with implants 3-4 yr old as compared to patients with implants 1-2 yr old. Smoking significantly increased the frequency of SCE. Our data do not indicate a dependence of 8-OHdG in urine or SCE on the levels of chromium or cobalt in patients with total hip replacements.

Time- and concentration-dependent production of superoxide anion, nitric oxide, DNA damage and cellular death by ricin in the J774A.1 macrophage cells

The time- and concentration-dependent effects of ricin on some biomarkers of cellular toxicity, including production of superoxide anion (O2-), nitric oxide (NO), and DNA single strand breaks (SSB), as well as cellular death, have been examined in the J774A.1 macrophage cell cultures. Various concentrations of ricin have been added to various cell cultures, and the cells were incubated for 12, 24, 36, and 48 hours. Following 12 hour incubation, ricin did not cause significant increases in any of those biomarkers. However, time- and concentration-dependent increases were observed in the induction of all the biomarkers after incubation for 24-48 hours. Approximately twofold increases in the production of O2- were observed after incubation with 1 and 10 ng/mL of ricin for 24 and 36-48 hours, respectively. The concentrations of ricin that caused approximately twofold increases in the rate of DNA-SSB are 10 and 1-10 ng/mL after 24 and 36-48 hours incubation, respectively. Approximately twofold increases in NO production were only observed after incubation of the cultures with 1-10 ng/mL of ricin for 36-48 hours. Fifty percent reductions in cellular viability were also observed with ricin concentrations of 10-100, 10, and 1-10 ng/mL, after incubation for 24, 36, and 48 hours, respectively.

The role of glutathione in chronic adaptation to oxidative stress: studies in a normal rat kidney epithelial (NRK52E) cell model of sustained upregulation of glutathione biosynthesis

Reduced glutathione (GSH) is considered to play a central role in protection of cells from oxidant injury. However, the question remains as to whether sustained elevation of intracellular GSH levels, as compared with the ability to rapidly upregulate GSH synthesis, is more important with respect to protection of cell constituents from oxidative stress. To address this question, we conducted studies to evaluate the direct influence of chronically increased endogenous GSH content on chemically induced intracellular free radical formation and oxidative stress using a kidney epithelial cell model adapted to sustain intracellular GSH concentrations in excess of eightfold that observed in unadapted parent kidney cells. Elevated GSH levels in adapted cells were found to be attributable, at least in part, to coordinately increased amounts of both the regulatory and catalytic subunits of gamma-glutamylcysteine synthetase (GCS), the rate-limiting enzyme in GSH synthesis. Studies using electron spin resonance (ESR) spectroscopy and scanning laser cytometry demonstrated that cells having sustained elevation of GSH levels did not attenuate free radical formation and associated oxidative stress compared with parent cells when treated with the prooxidant chemicals, menadione or potassium dichromate. In contrast, nonadapted kidney parent cells treated 18 h after initial prooxidant challenge displayed significantly attenuated free radical signals. Additionally, cells adapted to sustain excess GSH were somewhat more sensitive than parent cells in terms of resistance to prooxidant (chromate) toxicity, as determined by cell viability assays. These findings suggest that the capacity of cells to rapidly upregulate GSH synthesis, rather the ability to chronically sustain elevated intracellular GSH levels, may play a more important role in terms of protection from cytotoxicity associated with prooxidant chemical exposures.

The nutritional supplement chromium(III) tris(picolinate) cleaves DNA

Chromium(III) tris(picolinate) [Cr(pic)3] is currently a very popular nutritional supplement; however, its safety has recently been questioned, especially with regard to its ability to act as a clastogen. At physiologically relevant concentrations, Cr(pic)3 is reduced by biological reductants, including ascorbate and thiols, to Cr(II)-containing species. These species are susceptible to air oxidation, resulting in the catalytic generation of the potent DNA-damaging agent hydroxyl radical. In the absence of reductants, H2O2 can interact with Cr(pic)3 to produce hydroxyl radicals by a second, less efficient mechanism. Cr(pic)3 is extremely stable, which allows the complex to be readily absorbed but also to potentially be incorporated into cells intact. In this form, Cr(pic)3 is primed by its redox potential to enter into the generation of hydroxyl radicals. This study suggests that investigation of the long-term effects of supplementation of the diet with Cr(pic)3 are needed to assess the safety of this material.