Damage induced by stannous chloride in plasmid DNA

Application of Diethylzinc/propyl Gallate Catalytic System for Ring-Opening Copolymerization of rac-Lactide and ε-Caprolactone

Biodegradable polyesters gain significant attention because of their wide potential biomedical applications. The ring-opening polymerization method is widely used to obtain such polymers, due to high yields and advantageous properties of the obtained material. The preparation of new, effective, and bio-safe catalytic systems for the synthesis of biomedical polymers is one of the main directions of the research in modern medical chemistry. The new diethylzinc/propyl gallate catalytic system was first used in the copolymerization of ε-caprolactone and rac-lactide. In this paper, the activity of the new zinc-based catalytic system in the copolymerization of cyclic esters depending on the reaction conditions was described. The microstructure analysis of the obtained copolyesters and their toxicity studies were performed. Resulted copolyesters were characterized by low toxicity, moderate dispersity (1.19–1.71), varying randomness degree (0.18–0.83), and average molar mass (5300–9800 Da).

Antioxidant study indicative of antibacterial and antimutagenic activities of an ellagitannin-rich aqueous extract from the leaves of Miconia latecrenata

Ethnopharmacological relevance; Several plant species of Miconia genus are commonly used in Brazilian folk medicine as anti-inflammatory agents and for the treatment of infectious diseases. Infusions and extracts of Miconia species are also reported as analgesic, antimicrobial, antimalarial, antioxidant, anti-inflammatory, antinociceptive, antimutagenic, and antitumoral. Aim of the study; To determine the phytochemical composition of an aqueous extract of Miconia latecrenata leaves and to evaluate its antioxidant, antibacterial, antimutagenic and antigenotoxic activities. Materials and Methods; The following methods were used for the different effects: I) antioxidant - β-carotene/linoleic acid, lipid peroxidation, and DPPH• radical scavenging; II) antibacterial - agar well diffusion and MIC methods); III) antimutagenic assays - Ames Test; and IV) antigenotoxic - Plasmid cleavage test. The phytochemical analysis and phenolic quantification were carried out by UPLC-DAD-ESI-MS/MS and colorimetry, respectively. In addition, statistical correlation analysis was performed aiming to evaluate the Pearson correlation between phenolic compounds and biological assays. Results; A high content of tannins was observed and the ellagitannin isomers of 1,2,3,5-tris-galloyl-4,6-HHDP-glucose were identified as the main constituents of the leaves aqueous extract. High antioxidant effect, in different tests, high antibacterial activity to gram-positive and negative strains, as well as high antimutagenic activity were observed. Statistical analysis showed a high Pearson correlation for the tannin content in relation to the results of the antioxidant and antibacterial tests. In general, the antioxidant action of the aqueous extract showed low correlation with the antimutagenic activity. Conclusions; The present results confirmed the expectations regarding the pharmacological profile of M. latecrenata supporting its therapeutic potential in relation to ROS/RNS related disorders. Furthermore, the phenolic compounds of M. latecrenata can act, in turn, minimizing or inhibiting the biological macromolecules damage, especially DNA.

Assessment of the phenolic content, mutagenicity and genotoxicity of ethanolic extracts of stem bark and leaves from Strychnos pseudoquina A. St.-hil

Strychnos pseudoquina is a plant species whose stem bark is used as bitter tonic beverage. The phytochemical analysis, as well as quantification of phenolic constituents and antioxidant activity of ethanolic extracts from S. pseudoquina stem bark, and leaves were conducted. The extracts were tested for mutagenicity (Ames test) and DNA-damaging activity (Plasmid Cleavage test). Leaves recorded the largest amount of flavonoids. The performed high-performance liquid chromatography (HPLC) showed flavonoids such as isorhamnetin and strychnobiflavone (phytochemical markers of the investigated species) in stem barks, but not in leaves. The proanthocyanidin content and antioxidant activity were significantly higher in stem barks than in leaves. Stem bark and leaf extracts presented mutagenic activity against TA98 and TA100 strains with, and without, metabolic activation (S9). The Plasmid Cleavage test did not indicate DNA-damaging activity. Our results suggest that extracts deriving from S. pseudoquina should be used with extreme caution, mainly the stem bark extract, which is widely used in folk medicine.

Phytochemical characterization and antioxidant, antibacterial and antimutagenic activities of aqueous extract from leaves of Alchornea glandulosa

Plant extracts exist as a complex matrix which serves as a source of numerous bioactive metabolites. The ultra performance liquid chromatography with diode-array detection-coupled electrospray ionization-mass spectrometry/mass spectrometry technique was used to characterize the aqueous extract from leaves of Alchornea glandulosa (EAG), a species popularly used to treat gastrointestinal problems as an antiulcer agent. Quantification of phenolic derivatives was determined using Folin-Ciocalteu and aluminum trichloride (AlCl₃) methods. In addition, antioxidant (2,2-diphenyl-1-picrylhydrazyl [DPPH^•] radical scavenging, β-carotene-linoleic acid, and lipid peroxidation), antibacterial (agar well diffusion method and minimum inhibitory concentration), antimutagenic (Ames test), and antigenotoxic (plasmid cleavage) assays were also performed on this plant extract. The ellagitannin tris-galloyl-hexahydroxydiphenic acid-glucose was identified as the predominant compound along with tannins as majority metabolites. EAG showed high antioxidant activity accompanied by moderate antibacterial activity against Staphylococcus aureus. The highest antimutagenic activity was observed for TA97 strain without metabolic activation (S9) and with metabolic activation, TA100 and TA102 were completely inhibited. In addition, EAG exhibited potential signs of antigenotoxic action. The high antioxidant and antimutagenic activity observed for EAG suggests important therapeutic uses that still need to be verified in future studies.

Re-evaluation of stannous chloride (E 512) as food additive

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re‐evaluating the safety of stannous chloride and stannous chloride dihydrate (E 512) as food additives. The Panel considered that adequate exposure and toxicity data were available. Stannous chloride is only permitted as food additives in one food category and no reply on the actual use level of stannous chloride (E 512) as a food additive and on its concentration in food was provided by any interested party. According to the Mintel's Global New Products Database (GNPD), stannous chloride was not labelled on any products in the EU nor in Norway. The regulatory maximum level exposure assessment scenario is based on the maximum permitted levels (MPLs) for stannous chloride (E 512), which is 25 mg Sn/kg. The mean exposure to stannous chloride (E 512) from its use as a food additive was below 1.3 μg Sn/kg body weight (bw) per day for all age groups. The 95th percentile of exposure to stannous chloride (E 512) ranged from 0.0 μg Sn/kg bw per day in all groups to 11.2 μg Sn/kg bw per day in adults. Absorption of stannous chloride from the gastrointestinal tract is low there is no concern with respect to carcinogenicity and genotoxicity. Gastrointestinal irritation was reported in humans after ingestion of a bolus dose of 40 mg Sn. The Panel concluded that stannous chloride (E 512) is of no safety concern in this current authorised use and use levels.

Microbiota-based Signature of Gingivitis Treatments: A Randomized Study

Plaque-induced gingivitis can be alleviated by various treatment regimens. To probe the impacts of various anti-gingivitis treatments on plaque microflora, here a double blinded, randomized controlled trial of 91 adults with moderate gingivitis was designed with two anti-gingivitis regimens: the brush-alone treatment and the brush-plus-rinse treatment. In the later group, more reduction in both Plaque Index (TMQHI) and Gingival Index (mean MGI) at Day 3, Day 11 and Day 27 was evident, and more dramatic changes were found between baseline and other time points for both supragingival plaque microbiota structure and salivary metabonomic profiles. A comparison of plaque microbiota changes was also performed between these two treatments and a third dataset where 50 subjects received regimen of dental scaling. Only Actinobaculum, TM7 and Leptotrichia were consistently reduced by all the three treatments, whereas the different microbial signatures of the three treatments during gingivitis relieve indicate distinct mechanisms of action. Our study suggests that microbiota based signatures can serve as a valuable approach for understanding and potentially comparing the modes of action for clinical treatments and oral-care products in the future.

Role of OATP2A1 in PGE(2) secretion from human colorectal cancer cells via exocytosis in response to oxidative stress

Chronic inflammation induced by reactive oxygen species is associated with increased risk of developing colorectal cancer (CRC), and prostaglandin E2 (PGE2), which serves as a key mediator of inflammatory responses, plays an important role in CRC initiation and progression. Therefore, in the present study, we aimed to investigate the role of prostaglandin transporter OATP2A1/SLCO2A1 in the changes of PGE2 disposition in CRC cells in response to oxidative stress. H2O2 induced translocation of cytoplasmic OATP2A1 to plasma membranes in LoVo and COLO 320DM cells, but not in Caco-2 cells. The shift of subcellular OATP2A1 was abolished in the presence of anti-oxidant N-acetyl-L-cysteine or an inhibitor of protein kinase C, which evokes exocytosis. Exposure of LoVo cells to H2O2 caused an increase in the amount of extracellular PGE2 without changing the sum of intra- and extracellular PGE2. OATP2A1 knockdown decreased extracellular PGE2 in LoVo cells. In addition, extracellular PGE2 was significantly reduced by exocytosis inhibitor cytochalasin D, suggesting that H2O2-induced PGE2 release occurs in an exocytotic manner. Furthermore, mRNA expression of vascular endothelial growth factor (VEGF) was significantly reduced in LoVo cells by knockdown of OATP2A1. These results suggest that cytoplasmic OATP2A1 likely facilitates PGE2 loading into suitable intracellular compartment(s) for efficient exocytotic PGE2 release from CRC cells exposed to oxidative stress.

Intracellular accumulation of indium ions released from nanoparticles induces oxidative stress, proinflammatory response and DNA damage

Due to the widespread use of indium tin oxide (ITO), it is important to investigate its effect on human health. In this study, we evaluated the cellular effects of ITO nanoparticles (NPs), indium chloride (InCl3) and tin chloride (SnCl3) using human lung epithelial A549 cells. Transmission electron microscopy and inductively coupled plasma mass spectrometry were employed to study cellular ITO NP uptake. Interestingly, greater uptake of ITO NPs was observed, as compared with soluble salts. ITO NP species released could be divided into two types: 'indium release ITO' or 'tin release ITO'. We incubated A549 cells with indium release ITO, tin release ITO, InCl3 or SnCl2 and investigated oxidative stress, proinflammatory response, cytotoxicity and DNA damage. We found that intracellular reactive oxygen species were increased in cells incubated with indium release ITO, but not tin release ITO, InCl3 or SnCl2. Messenger RNA and protein levels of the inflammatory marker, interleukin-8, also increased following exposure to indium release ITO. Furthermore, the alkaline comet assay revealed that intracellular accumulation of indium ions induced DNA damage. Our results demonstrate that the accumulation of ionic indium, but not ionic tin, from ITO NPs in the intracellular matrix has extensive cellular effects.

Effects of dietary tin on growth performance, hematology, serum biochemistry, antioxidant status, and tin retention in broilers

Tin (Sn) is widely used in daily life and distributed in many tissues and nutrients. Although over-ingestion of Sn can cause health problems, relatively little attention has been given to the toxic effects of Sn in livestock health and productivity. This study was performed to investigate the toxic effects of prolonged high intake of dietary Sn on broilers. 150 one-day-old Avian broilers were randomly divided into five treatment groups, with five replicates of six birds. For 6 weeks, each group was fed a corn-soybean basal diet (BD) or BD + Sn (as SnCl2) at 120, 240, 480, or 720 mg/kg, respectively. Compared with the control, hepatic glutathione peroxidase (GPX) and superoxide dismutase (SOD) activities were significantly decreased when supplemented with Sn up to 480 mg/kg, while malondialdehyde (MDA) was increased until Sn supplementation at 720 mg/kg. Moreover, dietary Sn supplementation at 720 mg/kg decreased BW gain, feed intake, and impaired feed conversion ratio. The 720 mg Sn/kg group also increased activities of alkaline phosphatase (AKP), while decreased hemoglobin (HGB), red blood cell (RBC), and hematocrit (HCT) in the blood. Furthermore, the accumulation of Sn in various tissues was dose dependent on Sn ingestion. It was found that the tibia and feather are the two main tissues for Sn accumulation, followed by the liver, kidney, and other tissues in broilers. In conclusion, the adverse effects on broilers were induced when diets supplemented with Sn up to 480 mg/kg. Sn levels also managed to accumulate in the tibia and feather of broilers.

The influence of chain microstructure of biodegradable copolyesters obtained with low-toxic zirconium initiator to in vitro biocompatibility

Because of the wide use of biodegradable materials in tissue engineering, it is necessary to obtain biocompatible polymers with different mechanical and physical properties as well as degradation ratio. Novel co- and terpolymers of various composition and chain microstructure have been developed and applied for cell culture. The aim of this study was to evaluate the adhesion and proliferation of human chondrocytes to four biodegradable copolymers: lactide-coglycolide, lactide-co-ε-caprolactone, lactide-co-trimethylene carbonate, glycolide-co-ε-caprolactone, and one terpolymer glycolide-colactide-co-ε-caprolactone synthesized with the use of zirconium acetylacetonate as a nontoxic initiator. Chain microstructure of the copolymers was analyzed by means of ¹H and ¹³C NMR spectroscopy and surface properties by AFM technique. Cell adhesion and proliferation were determined by CyQUANT Cell Proliferation Assay Kit. After 4 h the chondrocyte adhesion on the surface of studied materials was comparable to standard TCPS. Cell proliferation occurred on all the substrates; however, among the studied polymers poly(L-lactide-coglycolide) 85 : 15 that characterized the most blocky structure best supported cell growth. Chondrocytes retained the cell membrane integrity evaluated by the LDH release assay. As can be summarized from the results of the study, all the studied polymers are well tolerated by the cells that make them appropriate for human chondrocytes growth.

Evaluation of deoxyribonucleic acid toxicity induced by the radiopharmaceutical 99mTechnetium-Methylenediphosphonic acid and by stannous chloride in Wistar rats

Radiopharmaceuticals are employed in patient diagnostics and disease treatments. Concerning the diagnosis aspect, technetium-99m (^99mTc) is utilized to label radiopharmaceuticals for single photon computed emission tomography (SPECT) due to its physical and chemical characteristics. ^99mTc fixation on pharmaceuticals depends on a reducing agent, stannous chloride (SnCl₂) being the most widely-utilized. The genotoxic, clastogenic and anegenic properties of the ^99mTc-MDP(methylene diphosphonate used for bone SPECT) and SnCl₂ were evaluated in Wistar rat blood cells using the Comet assay and micronucleus test. The experimental approach was to endovenously administer NaCl 0.9% (negative control), cyclophosphamide 50 mg/kg b.w. (positive control), SnCl₂ 500 μg/mL or ^99mTc-MDP to animals and blood samples taken immediately before the injection, 3, and 24 h after (in the Comet assay) and 36 h after, for micronucleus test. The data showed that both SnCl₂ and ^99mTc-MDP-induced deoxyribonucleic acid (DNA) strand breaks in rat total blood cells, suggesting genotoxic potential. The ^99mTc-MDP was not able to induce a significant DNA strand breaks increase in in vivo assays. Taken together, the data presented here points to the formation of a complex between SnCl₂ in the radiopharmaceutical ^99mTc-MDP, responsible for the decrease in cell damage, compared to both isolated chemical agents. These findings are important for the practice of nuclear medicine.

The mutagenic, DNA-damaging and antioxidative properties of bark and leaf extracts from Coutarea hexandra (Jacq.) K. Schum

Coutarea hexandra is a species commonly known in Brazil as quina, and its bark is used in folk medicine. In this study, we assess the mutagenic and DNA-damaging effects of ethanol extracts from C. hexandra stem bark (SCH) and leaves (LCH) by employing the Ames test on the TA98 and TA100 strains of Salmonella typhimurium in addition to a plasmid treatment test. Furthermore, we performed a phytochemical analysis by TLC and HPLC, a quantification of the phenolic constituents and an assessment of the antioxidative activity. SCH and LCH showed mutagenic action in the Ames test for TA98 strains after metabolic activation. LCH also showed mutagenicity for the TA100 strain after metabolic activation. The findings from the plasmid treatment test did not indicate any DNA-damaging activity for either of the extracts with the tested dosages. SCH showed greater flavonoid content and greater antioxidative potential in relation to LCH. This study suggests that caution is advisable in the use of this plant. However, in vivo studies should be conducted to confirm these data.

Effects of Sanionia uncinata extracts in protecting against and inducing DNA cleavage by reactive oxygen species

When mosses are exposed to increased quantities of ultraviolet (UV) radiation, they produce more secondary metabolites. Antarctica moss Sanionia uncinata (Hedw.) Loeske has presented high carotenoid contents in response to an increase in UVB radiation. This moss has been recommended as a potential source of antioxidants. In the present work, the protective and enhancing effects of aqueous (AE) and hydroalcoholic (HE) extracts of S. uncinata on the cleavage of supercoiled DNA were evaluated through topological modifications, quantified by densitometry after agarose gel electrophoresis. Total phenolic contents reached 5.89 mg/g. Our data demonstrated that the extract does not induce DNA cleavage. Furthermore, both extracts showed antioxidant activity that protected the DNA against cleavage induced by (i) O(2)(•-), 89% (AE) and 94% (HE) (P<0.05), and (ii) (.)OH, 17% (AE) and 18% (HE). However, the extracts intensified cleavage induced by Fenton-like reactions: (i) Cu(2+)/H(2)O(2), 94% (AE) and 100% (HE) (P<0.05), and (ii) SnCl(2), 62% (AE) and 56% (HE). DNA damages seem to follow different ways: (i) in the presence of Fenton-like reactions could be via reactive oxygen species generation and (ii) with HE/Cu(2+) could have also been triggered by other mechanisms.

Endonuclease IV is the main base excision repair enzyme involved in DNA damage induced by UVA radiation and stannous chloride

Stannous chloride (SnCl₂) and UVA induce DNA lesions through ROS. The aim of this work was to study the toxicity induced by UVA preillumination, followed by SnCl₂ treatment. E. coli BER mutants were used to identify genes which could play a role in DNA lesion repair generated by these agents. The survival assays showed (i) The nfo mutant was the most sensitive to SnCl₂; (ii) lethal synergistic effect was observed after UVA pre-illumination, plus SnCl₂ incubation, the nfo mutant being the most sensitive; (iii) wild type and nfo mutants, transformed with pBW21 plasmid (nfo⁺) had their survival increased following treatments. The alkaline agarose gel electrophoresis assays pointed that (i) UVA induced DNA breaks and fpg mutant was the most sensitive; (ii) SnCl₂-induced DNA strand breaks were higher than those from UVA and nfo mutant had the slowest repair kinetics; (iii) UVA + SnCl₂ promoted an increase in DNA breaks than SnCl₂ and, again, nfo mutant displayed the slowest repair kinetics. In summary, Nfo protects E. coli cells against damage induced by SnCl₂ and UVA + SnCl₂.

Interaction of tin(II) and arsenic(III) with DNA at the nanostructure film modified electrodes

Biosensors based on DNA and DNA-carbon nanotubes film immobilized at the surface of a screen-printed carbon electrode were used for simple in vitro tests of chemical toxicity. The damage to DNA caused by tin(II) and arsenic(III) compounds as components of specific reaction media was evaluated by means of an electrochemical DNA marker, [Co(phen)3](3+), as the portion of original dsDNA which survives an incubation of the biosensor in the cleavage medium. The results were confirmed by the electrically heated electrode and by the measurement of the DNA guanine moiety signal.

Study of the protective effect of ascorbic acid against the toxicity of stannous chloride on oxidative damage, antioxidant enzymes and biochemical parameters in rabbits

Stannous chloride (SnCl2) is a reducing chemical agent used in several man-made products. SnCl2 can generate reactive oxygen species (ROS). Therefore, the present study has been carried out to investigate the antioxidant action of l-ascorbic acid (AA) in minimizing SnCl2 toxicity on lipid peroxidation, antioxidant enzyme, and biochemical parameters in male New Zealand white rabbits. Animals were assigned to one of four treatment groups: 0mg AA and 0mg SnCl2/kg BW (control); 40 mg AA/kg BW; 20mg SnCl2/kg BW; 20mg SnCl2 plus 40 mg AA/kg BW. Rabbits were orally administered the respective doses every other day for 12 weeks. Results obtained showed that SnCl2 significantly (P<0.05) induced thiobarbituric acid-reactive substances (TBARS; the marker of lipid peroxidation) in plasma, while the activities of glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT), and the level of sulfhydryl groups (SH-group) were decreased (P<0.05) in blood plasma. Aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (AlP), acid phosphatase (AcP) and lactate dehydrogenase (LDH) activities were decreased (P<0.05). Stannous chloride significantly (P<0.05) increased the levels of plasma total lipid (TL), cholesterol, triglyceride (TG), low-density lipoprotein (LDL) and very low-density lipoprotein (VLDL), glucose, urea and total bilirubin. On the other hand, the level of plasma high-density lipoprotein (HDL), total protein (TP), albumin (A) and globulin (G) were significantly (P<0.05) decreased. Ascorbic acid alone significantly decreased the levels of TBARS, lipids and urea, and increased the activities of GST, SOD and CAT, and the levels of SH-group and proteins. While the rest of the tested parameters were not affected. Also, the presence of AA with SnCl2 alleviated its harmful effects on most of the tested parameters. Therefore, the present results revealed that treatment with AA could minimize the toxic effects of stannous chloride.

Application of the lithium and magnesium initiators for the synthesis of glycolide, lactide, and epsilon-caprolactone copolymers biocompatible with brain tissue

The subject of this work is new method of the synthesis of biodegradable copolymers compatible with brain tissue. Copolymerization of glycolide with lactide was conducted in solution or in bulk in the presence of LiBu, LiAcac, MgBu(2), Mg(acac)(2) as initiators. In all cases, copolymers with molecular weight of 20000-40000 were obtained, which enables to use them as drug carriers. During the reactions of copolymer chain growth, the intermolecular transesterification occurs, changing the distribution of comonomeric units in copolymer chain. Magnesium initiators showed a lower contribution to transesterification in comparison with lithium and calcium compounds. The copolymerization of glycolide with epsilon-caprolactone using magnesium compounds as initiators was also described. The random glycolide/epsilon-caprolactone copolymer (10/90) obtained with MgBu(2) was used in in vivo study in the forms of microspheres and foils. Complete degradation of microspheres during 6 weeks was observed after the implantation to brain tissue. All implanted copolymers are compatible with brain tissue.

Cytotoxic and genotoxic effects induced by stannous chloride associated to nuclear medicine kits

At present, more than 75% of routine nuclear medicine diagnostic procedures use technetium-99m (99mTc). The binding between 99mTc and the drug to obtain the radiopharmaceutical needs a reducing agent, with stannous chloride (SnCl2) being one of the most used. There are controversies about the cytotoxic, genotoxic and mutagenic effects of SnCl2 in the literature. Thus, the approaches below were used to better understand the biological effects of this salt and its association in nuclear medicine kits [methylenediphosphonate (MDP) bone scintigraphy and diethylenetriaminepentaacetic acid (DTPA) kidney and brain scintigraphy]: (i) bacterial inactivation experiments; (ii) agarose gel electrophoresis of supercoiled and linear plasmid DNA and (iii) bacterial transformation assay. The Escherichia coli strains used here were AB1157 (wild type) and BW9091 (xthA mutant). Data obtained showed that both MDP and SnCl2 presented a high toxicity, but this was not observed when they were assayed together in the kit, thereby displaying a mutual protect effect. DTPA salt showed a moderate toxicity, and once more, the DTPA kit provided protection, compared to the SnCl2 effect alone. The results suggest a possible complex formation, either MDP-SnCl2 or DTPA-SnCl2, originating an atoxic compound. On the other hand, SnCl2-induced cell inactivation and the decrease in bacterial transformation generated by DTPA found in XthA mutant strain suggest that the lack of this enzyme could be responsible for the effects observed, being necessary to induce DNA damage repair.

Biological effects of stevioside on the survival of Escherichia colistrains and plasmid DNA

Stevioside is widely used daily in many countries as a non-caloric sugar substitute. Its sweetening power is higher than that of sucrose by approximately 250-300 times, being extensively employed as a household sweetener, or added to beverages and food products. The purpose of this study was to ascertain stevioside genotoxic and cytotoxic potentiality in different biological systems, as its use continues to increase. Agarose gel electrophoresis and bacterial transformation were employed to observe the occurrence of DNA lesions. In addition to these assays, Escherichia coli strains were incubated with stevioside so that their survival fractions could be obtained. Results show absence of genotoxic activity through electrophoresis and bacterial transformation assays and drop of survival fraction of E. coli strains deficient in rec A and nth genes, suggesting that stevioside (i) is cytotoxic; (ii) could need metabolization to present deleterious effects on cells; (iii) is capable of generating lesions in DNA and pathways as base excision repair, recombination and SOS system would be important to recover these lesions.

Interaction of stannous chloride leads to alteration in DNA, triphosphate nucleotides and isolated bases

Stannous chloride (SnCl2) is a reducing chemical agent used in several man-made products. SnCl2 can generate reactive oxygen species (ROS); therefore, studies have been carried out in order to better understand its damaging action in biological systems. In this work, calf thymus DNA, triphosphate nucleotides and isolated bases were incubated with SnCl2 and the results were analyzed through UV spectrophotometry. The presence of stannous ions altered the absorption spectra of all three isolates. The amount of stannous ions associated to DNA was measured by atomic absorption spectrophotometry. Data showed that more than 40% of the initial SnCl2 concentration was present in the samples. Our results are in accordance with the damaging potential of this salt and present evidence that stannous ions can complex with DNA, inducing ROS in its vicinity, which may be responsible for the observed lesions.

Stannous chloride induces alterations in enzyme activities, lipid peroxidation and histopathology in male rabbit: antioxidant role of vitamin C

Stannous chloride (SnCl2) is widely used in daily human life to conserve soft drinks, in food manufacturing and biocidal preparations. It had genotoxicity, immunotoxicity, neurotoxicity and oxidative stress. Therefore, the present experiment was carried out to determine the effectiveness of l-ascorbic acid (AA) in alleviating the toxicity of SnCl2 on some enzyme activities and oxidative damage in male New Zealand white rabbits. Six rabbits per group were assigned to 1 of 4 treatment groups: 0 mg AA and 0 mg SnCl2/kg BW (control); 40 mg AA/kg BW; 20 mg SnCl2/kg BW (1/500 LD50); 20 mg SnCl2 plus 40 mg AA/kg BW. Rabbits were orally administered the respective doses every other day for 12 weeks. Liver and kidney specimens were processed for histopathologic studies. Results obtained showed that SnCl2 significantly (P < 0.05) induced free radicals in rabbit liver, testes, kidney, lung, brain and heart. While, the activity of glutathione S-transferase (GST) and the level of sulfhydryl groups (SH-group) were decreased (P < 0.05) in all tested organs except brain and heart. Aspartate aminotransferase (AST) activity was increased (P < 0.05) in liver and decreased in testes, but alanine aminotransferase (ALT) did not change. The activities of alkaline phosphatase (AlP) and acid phosphatase (AcP) were decreased (P < 0.05) in liver, testes, kidney and lung. Also, the activity of acetylcholinesterase (AChE) was significantly decreased in brain and plasma of rabbits treated with SnCl2 compared to control group. Histopathologic studies showed marked changes in hepatocytes as well as proliferation of duct epithelium, dilatation and congestion of blood vessels as well as mononuclear inflammatory infiltrate. The kidney were also severely affected by SnCl2 the Bowman's space was increased, with infiltration of renal parenchyma by mononuclear inflammatory infiltrate and changes in cells lining convoluted tubule. Ascorbic acid alone significantly decreased the levels of free radicals, and increased the activity of GST and the levels of SH groups in tested organs except brain and heart. While, the rest of the tested parameters were not affected. Results showed that AA alleviated the harmful effects of SnCl2. This was proved histopathologically by the great improvement in liver and kidney histology where hepatocytes retained normal architecture with mild dilatation and congestion of blood vessels. Bowman's space of kidney was almost normal, with normal lining of proximal and distal convoluted tubules. In conclusion AA could be effective in the protection against stannous chloride toxicity.

Effects of a biodegradable polymer synthesized with inorganic tin on the chondrogenesis of human articular chondrocytes

Recent study has shown that biodegradable polymers are attractive candidates for chondrocyte fixation and further transplantation in cartilage tissue engineering. Poly (glycolic acid) (PGA), a polymer of glycolic acid, is widely used in orthopedic applications as a biodegradable polymer. Organotin, lead, antimony, and zinc are catalysts commonly used in synthesizing PGA. Here, we investigated the biocompatibility of PGA, synthesized with and without inorganic tin as a catalyst in chondrogenesis of human articular chondrocytes in a micromass culture system. Significant enhancement of chondrocyte proliferation and expression of the collagen type II protein gene were observed in cultures treated with PGA synthesized with a tin catalyst. However, aggrecan gene expression was very similar to the control culture. Amount of collagen type II protein was also increased in the same group of cultured chondrocytes. In contrast, PGA without a catalyst caused overall inhibition of chondrogenesis. Despite several positive findings, extensive investigations are essential for the feasibility of this PGA(Sn) in future clinical practice.

Assessment of Aloe vera (L.) genotoxic potential on Escherichia coli and plasmid DNA

Aloe vera is a tropical plant, known in Brazil as babosa and several reputable suppliers produce a stabilized aloe gel for topic use. Since people use Aloe vera topically, they could be exposed to solar ultraviolet light in addition and it might cause a cross damage effect between these agents. The aim of this work was to investigate the biological effects of Aloe vera pulp extract, associated or not to UVA radiation, on Escherichia coli-deficient repair mutants and plasmid DNA, in order to test its genotoxic potential. Data obtained from analysis of survival fractions, bacterial transformation and agarose gel electrophoresis suggest that Aloe vera has genotoxic properties, but it seems not to be able to damage the cell membrane.

Genotoxicity of stannous chloride in yeast and bacteria

Stannous chloride was found genotoxic in microbial test systems of the yeast Saccharomyces cerevisiae, in one strain of Salmonella typhimurium and in the Mutoxitest of Escherichia coli. Five isogenic haploid yeast strains differing only in a particular repair-deficiency had the following ranking in Sn2+ -sensitivity: rad52delta>rad6delta>rad2delta>rad4delta>RAD, indicating a higher relevance of recombinogenic repair mechanisms than nucleotide excision in repair of Sn2+ -induced DNA damage. Sn2+ -treated cells formed aggregates that lead to gross overestimation of toxicity when not undone before diluting and plating. Reliable inactivation assays at exposure doses of 25-75 mM SnCl2 were achieved by de-clumping with either EDTA- or phosphate buffer. Sn2+ -induced reversion of the yeast his1-798, his1-208 and lys1-1 mutant alleles, in diploid and haploid cells, respectively, and putative frameshift mutagenesis (reversion of the hom3-10 allele) was observed. In diploid yeast, SnCl2 induced intra-genic mitotic recombination while inter-genic (reciprocal) recombination was very weak and not significant. Yeast cells of exponentially growing cultures were killed to about the same extend at 0.1% of SnCl2 than respective cells in stationary phase, suggesting a major involvement of physiological parameters of post-diauxic shift oxidative stress resistance in enhanced Sn2+ -tolerance. Superoxide dismutases, but not catalase, protected against SnCl2-induced reactive oxygen species as sod1delta had a three-fold higher sensitivity than the WT while the sod2delta mutant was only slightly more sensitive but conferred significant sensitivity increase in a sod1delta sod2delta double mutant. In the Salmonella reversion assay, SnCl2 did not induce mutations in strains TA97, TA98 or TA100, while a positive response was seen in strain TA102. SnCl2 induced a two-fold increase in mutation in the Mutoxitest strain IC203 (uvrA oxyR), but was less mutagenic in strain IC188 (uvrA). We propose that the mutagenicity of SnCl2 in yeast and bacteria occurs via error-prone repair of DNA damage that is produced by reactive oxygen species.

Protective role of ascorbic acid to enhance reproductive performance of male rabbits treated with stannous chloride

The objective of this study was to determine the protective role of ascorbic acid (AA, 40 mg/kg BW) on reproductive performance of male New Zealand White rabbits given sublethal dose (20 mg/kg BW every other day for 12 weeks) of stannous chloride (SnCl2). Results showed that treatment with SnCl2 caused a decrease (P<0.05) in libido (by increasing the reaction time), ejaculate volume, sperm concentration, total sperm output, sperm motility (%), total motile sperm per ejaculate (TMS), packed sperm volume (PSV), total functional sperm fraction (TFSF), normal and live sperm and semen initial fructose. Dead sperm and initial hydrogen ion concentration (pH) were increased. While, relative weights of testes (RTW) and epididymis (REW) were decreased. On the other hand, live body weight (LBW) and dry matter intake (DMI) did not change. Treatment with AA alone caused significant increase in LBW, DMI, RTW, REW and semen characteristics compared to control group. Also, the presence of AA with SnCl2 minimized its harmful effects. Results obtained revealed suggest that assessment of reproductive toxicity of stannous chloride needs to be addressed, and may presently be underestimated. Also, the beneficial influences of AA in counteracting the toxic effects of SnCl2 and improved the reproductive performance of male rabbit was demonstrated.

Genotoxic potentiality of aqueous extract prepared from Chrysobalanus icaco L. leaves

Plants have been related to our lives, being used as medicine, regardless of scientific evidence of side effects. This work analyses the toxicological effects of Chrysobalanus icaco L. aqueous extract, used in different pathologies. It was studied through: (i) alteration of plasmid pUC 9.1 topology; (ii) survival of bacterial strains submitted, or not, to previous treatment with SnCl2; (iii) transformation efficiency of E. coli strain by the treatment with the plasmid pUC 9.1. In (i), the treatment of the plasmid resulted in DNA single-strand breaks (SSB). A decrease of the lethal effect induced by SnCl2 in presence of the extract was found, while no C. icaco bacterial survival reduction was observed. The transformation efficiency of the plasmid was also reduced. Results suggest that the extract could present a potential genotoxic effect, as demonstrated either by the induction of SSB in plasmid or in transformation efficiency experiments. Finally, it presents an antioxidant action.

Role of PSO genes in repair of DNA damage of Saccharomyces cerevisiae

Photoactivated psoralens used in treatment of skin diseases like Psoriasis and Vitiligo cause DNA damage, the repair of which may lead to mutations and thus to higher risk to have skin cancer. The simple eukaryote Saccharomyces cerevisiae was chosen to investigate the cells' genetic endowment with repair mechanisms for this type of DNA damage and to study the genetic consequences of such repair. Genetic studies on yeast mutants sensitive to photoactivated psoralens, named pso mutants, showed their allocation to 10 distinct loci. Cloning and molecular characterization allowed their grouping into three functional classes: (I) the largest group comprises seven PSO genes that are either generally or specifically involved in error-prone DNA repair and thus affect induced mutability and recombination; (II) one PSO gene that represents error-free excision repair, and (III) two PSO genes encoding proteins not influencing DNA repair but physiological processes unrelated to nucleic acid metabolism. Of the seven DNA repair genes involved in induced mutagenesis three PSO loci [PSO1/REV3, PSO8/RAD6, PSO9/MEC3] were allelic to already known repair genes, whereas three, PSO2/SNM1, PSO3/RNR4, and PSO4/PRP19 represent new genes involved in DNA repair and nucleic acid metabolism in S. cerevisiae. Gene PSO2 encodes a protein indispensable for repair of interstrand cross-link (ICL) that are produced in DNA by a variety of bi- and polyfunctional mutagens and that appears to be important for a likewise repair function in humans as well. In silico analysis predicts a putative endonucleolytic activity for Pso2p/Snm1p in removing hairpins generated as repair intermediates. The absence of induced mutation in pso3/rnr4 mutants indicates an important role of this subunit of ribonucleotide reductase (RNR) in regulation of translesion polymerase zeta in error-prone repair. Prp19p/Pso4p influences efficiency of DNA repair via splicing of pre-mRNAs of intron-containing repair genes but also may function in the stability of the nuclear scaffold that might influence DNA repair capacity. The seventh gene, PSO10 which controls an unknown step in induced mutagenesis is not yet cloned. Two genes, PSO6/ERG3 and PSO7/COX11, are responsible for structural elements of the membrane and for a functional respiratory chain (RC), respectively, and their function thus indirectly influences sensitivity to photoactivated psoralens.

Evaluation of the phytic acid effect on the labeling of blood elements with technetium-99m and on the survival of a strain of Escherichia coli treated with stannous fluoride

The labeling of red blood cells with technetium-99m (99mTc) depends on a reducing agent and stannous ions, as chloride or fluoride, are widely utilized. This labeling may also be altered by drugs. Moreover, some authors have reported that the survival of Escherichia coli (E. coli) cultures decreases in presence of stannous ions. Phytic acid is present in the daily diet and we evaluated its influence on: (i) the labeling of blood elements with 99mTc and (ii) on the survival of an E. coli strain treated with stannous fluoride. Heparinized whole blood was withdrawn from Wistar rats and it was incubated with stannous chloride and with 99mTc, as sodium pertechnetate, centrifuged and plasma (P) and blood cells (BC) were isolated. Samples of P and BC were also precipitated with trichloroacetic acid, centrifuged and soluble (SF) and insoluble fractions (IF) isolated. E. coli culture was treated with stannous fluoride in presence of phytic acid. As phytic acid altered the fixation of 99mTc on BC, on IF-P and on IF-BC and, moreover, it abolished the lethal effect of stannous fluoride on the E. coli culture, we can suggest that, probably, phytic acid would have chelating properties to the stannous ions.

Biological effects of stannous chloride, a substance that can produce stimulation or depression of the central nervous system

It was demonstrated that tin, as stannous chloride (SnCl(2)), can facilitate the neuromuscular transmission by accelerating the transmitter release from the nerve terminals in the mouse. When this salt is injected into laboratory animals, it can produce stimulation or depression of the central nervous system. Because calcium (Ca(2+)) influx into the cytoplasm is indispensable to release the transmitter, it would be possible that SnCl(2) increases the Ca(2+) influx at the nerve terminals but not by blocking the K(+) channels. SnCl(2) is known to inhibit the immune response in rodents and to induce tumor generation in thyroid gland. There is no general agreement regarding its genotoxicity and it was discussed that the effects of this salt might depend on the physicochemical conditions and the route of its administration. SnCl(2) has been used in many sectors of human interest, such as food industry and nuclear medicine. This salt is directly administered to human beings endovenously, when it is used as a reducing agent to prepare 99mTc-radiopharmaceuticals which are also used for cerebral studies. SnCl(2) is capable to promote the generation of reactive oxygen species (ROS) that are responsible for the oxidative stress. Oxidative stress has been related with aging and other neurological diseases. So, it is relevant to evaluate other biological effects of SnCl(2). We decided to study these effects using Escherichia coli mutant strains, deficient in DNA repair genes, and supercoiled plasmid DNA. We evaluated the influence of medicinal plants, metal chelating agents, and ROS scavengers against the SnCl(2) deleterious effects. Our results show that SnCl(2) produced lesions in vitro as well as in vivo. This inactivation may be due to the production of ROS. We observed that the genotoxic effect of SnCl(2) was partly inhibited or disappeared, when the treatments were done in the presence of medicinal plants, metal chelating agents, and ROS scavengers. In conclusion, these findings suggest that the SnCl(2) biological effects may be associated with the generation of ROS. Moreover, we can speculate that ROS could be associated with the detrimental effects in the brain due to exogenous or endogenous metals.

Genotoxic effects of stannous chloride (SnCl2) in K562 cell line

The toxic effects of SnCl2 in K562 cells were analyzed in this study. This cell line is resistant to reactive oxygen species (ROS) making it suitable to evaluate the impact of SnCl2 in culture either through ROS or by direct toxicity using Trypan blue dye exclusion, comet and flow cytometry assays. An important loss of viability induced by SnCl2 in a dose-response manner was observed in cells treated in Tris-buffered saline (TBS). This necrotic cell death was further confirmed by flow cytometry. On the other hand, there was no loss of viability when cells were treated in rich medium (RPMI). DNA damage was visualized in SnCl2-treated K562 cells in both tested conditions. The data indicate that SnCl2 induces DNA damage and reduces K562 viability. Both actions seem to be correlated with ROS formation and direct linkage to DNA.

Effect of an extract of cauliflower (leaf) on the labeling of blood elements with technetium-99m and on the survival of Escherichia coli AB1157 submitted to the treatment with stannous chloride

The labeling of red blood cells (RBC) with technetium-99m (99mTc) depends on a reducing agent and stannous chloride (SnCl(2)) and is widely utilized. This labeling may also be altered by drugs, and SnCl(2) reduces the survival of Escherichia coli cultures. Cauliflower (Brassica oleracea L. var. botrytis) is used in folk medicine and we evaluated its influence on (i) the labeling of blood elements with 99mTc, and (ii) on the survival of an E. coli strain. Blood was withdrawn from rats that drank the extract of cauliflower (15 days). Blood was incubated with SnCl(2) and with 99mTc, as sodium pertechnetate, centrifuged and plasma (P) and RBC were isolated. Samples of P and RBC were also precipitated, centrifuged and soluble and insoluble fractions isolated. E. coli culture was treated with SnCl(2) in the presence of cauliflower. The extract of cauliflower did not alter the fixation of 99mTc on blood fractions; however, it abolished the lethal effect of SnCl(2) on the E. coli culture. We suggest that the substances present in the extract of cauliflower probably, would have redox property with different mechanisms of action. The oxidant action of the substances of the extract would not be strong enough to oxidise the stannous ions altering the 99mTc-labeling. However, the referred substances could oxidise these ions sufficiently to protect the E. coli culture against the lethal effect of the stannous ion.

Adaptive response to H(2)O(2) protects against SnCl(2) damage: the OxyR system involvement

The stannous ion, mainly the stannous chloride (SnCl(2)) salt form, is widely used as a reducing agent to label radiotracers with technetium-99m ((99m)Tc). These radiotracers can be employed as radiopharmaceuticals in nuclear medicine procedures. In this case, there is no doubt about absorption of this complex, because it is intravenously administered in humans, although biological effects of these agents have not been fully understood. In this work we used a bacterial system to study the cytotoxic potential of stannous chloride. It is known that SnCl(2) induces lesions that could be mediated by reactive oxygen species (ROS). We, thus, investigated the existence of cross-adaptive response between hydrogen peroxide (H(2)O(2)) and SnCl(2) and the role of the OxyR system known to promote cellular protection against oxidative damages. Here we describe the results obtained with prior treatment of different Escherichia coli strains with sub-lethal doses of H(2)O(2), followed by incubation with SnCl(2). Our data show that H(2)O(2) is capable of inducing cross-adaptive response against the lethality promoted by SnCl(2), suggesting the OxyR system participation through catalase, alkyl hydroperoxide reductase and superoxide dismutase enzymes

Study of perrhenate reduction by capillary electrophoresis

The influence of perrhenate concentration, the concentration of the reducing agent and pH of the reaction mixture on the yield of perrhenate reduction were studied to find a possibility to decrease the stannous chloride concentration in the reaction mixture without negative changes on the yield of perrhenate reduction. Britton-Robinson buffer solutions were selected as the background electrolytes because of their buffering capacity in a wide pH interval. The highest degree of perrhenate reduction was obtained at pH 2 at perrhenate concentrations ranging from 10(-4) to 10(-3) mol/L. The stability of reduced rhenium against pH change from 2 to 5.5 and against dilution of rhenium in the reaction mixture to the concentration suitable for the application in radiotherapy were studied as well. The results obtained by capillary electrophoresis and by thin-layer chromatography with radiometric detection were compared.