[Study on the difference of curative effect of conventional mercury displacement treatment on mercury in brain and kidney]

Objective: To explore the expulsion effect of sodium dimercaptopropanesulfonate (DMPS) on mercury in different organs of mercury poisoning and the therapeutic effect of glutathione (GSH) combined with antioxidant therapy on mercury poisoning. Methods: In February 2019, 50 SPF male SD rats were randomly divided into 5 groups, 10 rats in each group: A (saline negative control group) , B (HgCL2 positive control group) , treatment group (C: intramuscular injection of DMPS 15 mg/kg treatment, D: intramuscular injection of DMPS30 mg/kg treatment, E: intramuscular injection of DMPS 15 mg/kg and intraperitoneal injection of GSH200 mg/kg treatment) . Rats in group B, C, D and E were subcutaneously injected with mercury chloride solution (1 mg/kg) to establish a rat model of subacute mercury poisoning kidney injury. Rats in group A were subcutaneously injected with normal saline. After the establishment of the model, rats in the treatment group were injected with DMPS and GSH. Rats in group A and group B were injected with normal saline. At 21 d (treatment 7 d) and 28 d (treatment 14 d) after exposure, urine and blood samples of 5 rats in each group were collected. Blood biochemistry, urine mercury, urine microalbumin and mercury content in renal cortex, cerebral cortex and cerebellum were detected. Results: After exposure to mercury, the contents of mercury in renal cortex, cerebrum and cerebellum of rats in group B, C, D and E increased, and urine microalbumin increased. Pathology showed renal tubular injury and renal interstitial inflammation. Compared with group B, urinary mercury and renal cortex mercury in group C, D and E decreased rapidly after DMPS treatment, and there was no significant decrease in mercury levels in cerebellum and cerebral cortex of rats, accompanied by transient increase in urinary albumin after DMPS treatment (P<0.05) ; the renal interstitial inflammation in group E was improved after GSH treatment. There was a positive correlation between urinary mercury and the contents of mercury in renal cortex, cerebral cortex and cerebellum (r=0.61, 0.47, 0.48, P<0.05) . Conclusion: DMPS mercury expulsion treatment can significantly reduce the level of metal mercury in the kidney, and there is no significant change in the level of metal mercury in the cortex and cerebellum.

Drug Repurposing of the Unithiol: Inhibition of Metallo-β-Lactamases for the Treatment of Carbapenem-Resistant Gram-Negative Bacterial Infections

The increasing antibiotic resistance is a clinical problem worldwide. Numerous Gram-negative bacteria have already become resistant to the most widely used class of antibacterial drugs, β-lactams. One of the main mechanisms is inactivation of β-lactam antibiotics by bacterial β-lactamases. Appearance and spread of these enzymes represent a continuous challenge for the clinical treatment of infections and for the design of new antibiotics and inhibitors. Drug repurposing is a prospective approach for finding new targets for drugs already approved for use. We describe here the inhibitory potency of known detoxifying antidote 2,3-dimercaptopropane-1-sulfonate (unithiol) against metallo-β-lactamases. Unithiol acts as a competitive inhibitor of meropenem hydrolysis by recombinant metallo-β-lactamase NDM-1 with the K_I of 16.7 µM. It is an order of magnitude lower than the K_I for l-captopril, the inhibitor of angiotensin-converting enzyme approved as a drug for the treatment of hypertension. Phenotypic methods demonstrate that the unithiol inhibits natural metallo-β-lactamases NDM-1 and VIM-2 produced by carbapenem-resistant K. pneumoniae and P. aeruginosa bacterial strains. The 3D full atom structures of unithiol complexes with NDM-1 and VIM-2 are obtained using QM/MM modeling. The thiol group is located between zinc cations of the active site occupying the same place as the catalytic hydroxide anion in the enzyme–substrate complex. The sulfate group forms both a coordination bond with a zinc cation and hydrogen bonds with the positively charged residue, lysine or arginine, responsible for proper orientation of antibiotics upon binding to the active site prior to hydrolysis. Thus, we demonstrate both experimentally and theoretically that the unithiol is a prospective competitive inhibitor of metallo-β-lactamases and it can be utilized in complex therapy together with the known β-lactam antibiotics.

Venom-Induced Blood Disturbances by Palearctic Viperid Snakes, and Their Relative Neutralization by Antivenoms and Enzyme-Inhibitors

Palearctic vipers are medically significant snakes in the genera Daboia, Macrovipera, Montivipera, and Vipera which occur throughout Europe, Central Asia, Near and Middle East. While the ancestral condition is that of a small-bodied, lowland species, extensive diversification has occurred in body size, and niche specialization. Using 27 venom samples and a panel of in vitro coagulation assays, we evaluated the relative coagulotoxic potency of Palearctic viper venoms and compared their neutralization by three antivenoms (Insoserp Europe, VIPERFAV and ViperaTAb) and two metalloprotease inhibitors (prinomastat and DMPS). We show that variation in morphology parallels variation in the Factor X activating procoagulant toxicity, with the three convergent evolutions of larger body sizes (Daboia genus, Macrovipera genus, and Vipera ammodytes uniquely within the Vipera genus) were each accompanied by a significant increase in procoagulant potency. In contrast, the two convergent evolutions of high altitude specialization (the Montivipera genus and Vipera latastei uniquely within the Vipera genus) were each accompanied by a shift away from procoagulant action, with the Montivipera species being particularly potently anticoagulant. Inoserp Europe and VIPERFAV antivenoms were both effective against a broad range of Vipera species, with Inoserp able to neutralize additional species relative to VIPERFAV, reflective of its more complex antivenom immunization mixture. In contrast, ViperaTAb was extremely potent in neutralizing V. berus but, reflective of this being a monovalent antivenom, it was not effective against other Vipera species. The enzyme inhibitor prinomastat efficiently neutralized the metalloprotease-driven Factor X activation of the procoagulant venoms. In contrast, DMPS (2,3-dimercapto-1-propanesulfonic acid), which as been suggested as another potential treatment option in the absence of antivenom, DMPS failed against all venoms tested. Overall, our results highlight the evolutionary variations within Palearctic vipers and help to inform clinical management of viper envenomation.

Dimercapto-1-propanesulfonic acid (DMPS) induces metaphase II mouse oocyte deterioration

In light of the recent lead contamination of the water in Flint, Michigan and its potential adverse outcomes, much research and media attention has turned towards the safety profile of commonly used chelators. Dimercapto-1-propanesulfonic acid (DMPS) typically used in the treatment of lead, mercury and arsenic poisoning also displays a high affinity towards transition metals such as zinc and copper, essential for biological functioning. It is given in series of dosages (0.2-0.4g/day) over a long period, and has the ability to enter cells. In this work, we investigated the mechanism through which increasing concentrations of DMPS alter oocyte quality as judged by changes in microtubule morphology (MT) and chromosomal alignment (CH) of metaphase II mice oocyte. The oocytes were directly exposed to increasing concentration of DMPS (10, 25, 50, 100 and 300μM) for four hours (time of peak plasma concentration after administration) and reactive oxygen species (mainly hydroxyl radical and superoxide) and zinc content were measured. This data showed DMPS plays an important role in deterioration of oocyte quality through a mechanism involving zinc deficiency and enhancement of reactive oxygen species a major contributor to oocyte damage. Our current work, for the first time, demonstrates the possibility of DMPS to negatively impact fertility. This finding can not only help in counseling reproductive age patients undergoing such treatment but also in the development of potential therapies to alleviate oxidative damage and preserve fertility in people receiving heavy metal chelators.

Effects of Zinc Chelators on Aflatoxin Production in Aspergillus parasiticus

Zinc concentrations strongly influence aflatoxin accumulation in laboratory media and in food and feed crops. The presence of zinc stimulates aflatoxin production, and the absence of zinc impedes toxin production. Initial studies that suggested a link between zinc and aflatoxin biosynthesis were presented in the 1970s. In the present study, we utilized two zinc chelators, N,N,N′,N′-tetrakis (2-pyridylmethyl) ethane-1,2-diamine (TPEN) and 2,3-dimercapto-1-propanesulfonic acid (DMPS) to explore the effect of zinc limitation on aflatoxin synthesis in Aspergillus parasiticus. TPEN but not DMPS decreased aflatoxin biosynthesis up to six-fold depending on whether A. parasiticus was grown on rich or minimal medium. Although we observed significant inhibition of aflatoxin production by TPEN, no detectable changes were observed in expression levels of the aflatoxin pathway gene ver-1 and the zinc binuclear cluster transcription factor, AflR. Treatment of growing A. parasiticus solid culture with a fluorescent zinc probe demonstrated an increase in intracellular zinc levels assessed by increases in fluorescent intensity of cultures treated with TPEN compared to controls. These data suggest that TPEN binds to cytoplasmic zinc therefore limiting fungal access to zinc. To investigate the efficacy of TPEN on food and feed crops, we found that TPEN effectively decreases aflatoxin accumulation on peanut medium but not in a sunflower seeds-derived medium. From an application perspective, these data provide the basis for biological differences that exist in the efficacy of different zinc chelators in various food and feed crops frequently contaminated by aflatoxin.

Amine oxidases as important agents of pathological processes of rhabdomyolysis in rats

In this study we have tested an idea on the important role of amine oxidases (semicarbazide-sensitive amine oxidase, diamine oxidase, polyamine oxidase) as an additional source of oxidative/carbonyl stress under glycerol-induced rhabdomyolysis, since the enhanced formation of reactive oxygen species and reactive carbonyl species in a variety of tissues is linked to various diseases. In our experiments we used the sensitive fluorescent method devised for estimation of amine oxidases activity in the rat kidney and thymus as targeted organs under rhabdomyolysis. We have found in vivo the multiple rises in activity of semicarbazide-sensitive amine oxidase, diamine oxidase, polyamine oxidase (2-4.5 times) in the corresponding cell fractions, whole cells or their lysates at the 3-6th day after glycerol injection. Aberrant antioxidant activities depended on rhabdomyolysis stage and had organ specificity. Additional treatment of animals with metal chelator ‘Unithiol’ adjusted only the activity of antioxidant enzymes but not amine oxidases in both organs. Furthermore the in vitro experiment showed that Fenton reaction (hydrogen peroxide in the presence of iron) products alone had no effect on semicarbazide-sensitive amine oxidase activity in rat liver cell fraction whereas supplementation with methylglyoxal resulted in its significant 2.5-fold enhancement. Combined action of the both agents had additive effect on semicarbazide-sensitive amine oxidase activity. We can assume that biogenic amine and polyamine catabolism by amine oxidases is upregulated by oxidative and carbonyl stress factors directly under rhabdomyolysis progression, and the increase in catabolic products concentration contributes to tissue damage in glycerol-induced acute renal failure and apoptosis stimulation in thymus.

Nanoparticles modulate autophagic effect in a dispersity-dependent manner

Autophagy plays a key role in human health and disease, especially in cancer and neurodegeneration. Many autophagy regulators are developed for therapy. Diverse nanomaterials have been reported to induce autophagy. However, the underlying mechanisms and universal rules remain unclear. Here, for the first time, we show a reliable and general mechanism by which nanoparticles induce autophagy and then successfully modulate autophagy via tuning their dispersity. Various well-designed univariate experiments demonstrate that nanomaterials induce autophagy in a dispersity-dependent manner. Aggregated nanoparticles induce significant autophagic effect in comparison with well-dispersed nanoparticles. As the highly stable nanoparticles may block autophagic degradation in autolysosomes, endocytosis and intracellular accumulation of nanoparticles can be responsible for this interesting phenomenon. Our results suggest dispersity-dependent autophagic effect as a common cellular response to nanoparticles, reveal the relationship between properties of nanoparticles and autophagy, and offer a new alternative way to modulate autophagy.

[Immune homeostasis impairment in acute carbon tetrachloride intoxicated rats corrected by administration of tocopherol acetate and unithiol]

The results of experiments on noninbred albino rats showed that the acute intoxication with carbon tetrachloride (CT) at a dose of 1 LD50 reduced the parameters of cellular immune response and function of Th1 cells more significantly than the levels of humoral immune response and Th2-lymphocyte function, decreases the blood content of immunoregulatory cytokines IFN-g, IL-2, IL-4 and anti-inflammatory cytokine IL-13, while not changing the concentration of anti-inflammatory cytokine IL-10 and increasing the concentration of pro-inflammatory cytokine IL-6. The application of unithiol, tocopherol acetate, and combinations partially restores the parameters examined. The combined effects of drugs during intoxication with CT does not exceed their separate action.

Influence of glutathione chemical effectors in the response of maize to arsenic exposure

To support the key role of glutathione (GSH) in the mechanisms of tolerance and accumulation of arsenic in plants, this work examines the impact of several effectors of GSH synthesis or action in the response of maize (Zea mays L.) to arsenic. Maize was exposed in hydroponics to iso-toxic rates of 150 μM arsenate or 75 μM arsenite for 9 days and GSH effectors, flurazole (an herbicide safener), l-buthionine-sulfoximine (BSO, a known inhibitor of GSH biosynthesis), and dimercaptosuccinate (DMS) and dimercaptopropanesulfonate (DMPS) (two thiols able to displace GSH from arsenite-GSH complexes) were assayed. The main responses of plants to arsenic exposure consisted of a biomass reduction (fresh weight basis) of about 50%, an increase of non-protein thiol (NPTs) levels (especially in the GSH precursor γ-glutamylcysteine and the phytochelatins PC₂ and PC₃) in roots, with little effect in shoots, and an accumulation of between 600 and 1000 ppm of As (dry weight basis) in roots with very little translocation to shoots. Growth inhibition caused by arsenic was partially or completely reversed in plants co-treated with flurazole and arsenate or arsenite, respectively, highly exacerbated in plants co-treated with BSO, and not modified in plants co-treated with DMS or DMPS. These responses correlated well with an increase of both NPTs levels in roots and glutathione transferase activity in roots and shoots due to flurazole treatment, the decrease of NPTs levels in roots caused by BSO and the lack of effect on NPT levels caused by both DMS and DMPS. Regarding to arsenic accumulation in roots, it was not modified by flurazole, highly reduced by BSO, and increased between 2.5- and 4.0-fold by DMS and DMPS. Therefore, tolerance and accumulation of arsenic by maize could be manipulated pharmacologically by chemical effectors of GSH.

[Antiviral activity of recombinant interferon-alpha-2b in combination with certain antioxidant]

In vitro activity of interferon-alpha-2b in combination with various antioxidants against the influenza virus and Herpes simplex was studied. The standard strains and a clinical strain of Herpes simplex isolated from a patient with resistance to acyclovir were used. The in vitro studie showed that antioxidants, such as alpho-tocoferol acetate (vitamin E), Unithiol and ascorbic acid had a significant antiinfluenzae and antiherpetic action on the influenza virus A/H5N1 and Herpes simplex variants. They protected up to 100% of the cell monolayer from the virus cytopathic effect. The taurin solutions had no antiviral activity irrespective of the infection dose. Combinations of interferon-alpha-2b with alpha-tocopherol acetate (vitamin E), Unithiol or ascorbic acid showed a significant synergistic effect: the antiviral activity of interferon increased several times. The antiinfluenza activity of interferon-a-2b in the presence of various concentrations of taurin did not change.

[Antioxidant properties of some sulfur-containing substances]

The antioxidant properties of sulfur-containing substances have been experimentally studied in vitro. Unithiol exhibits a wide spectrum us radicals. For this reason, unithiol can be considered, along with ascorbic acid, as a universal drug for the reduction of free radical reactions.

[Intervention effect of dimercaptopropansulfonate sodium on central toxic induced by bromoxynil in vivo]

OBJECTIVE

to investigate the changes of γ-aminobutyric acid (GABA) and glutamate (Glu) in the cerebral cortex following acute bromoxynil intoxication in mice and the protective effect of sodium dimercaptopropane sulfonate (Na-DMPS).

METHODS

30 ICR mice were randomly divided into blank control group (10), exposure group (10) and Na-DMPS protection group (10). The levels of GABA and Glu in the cerebral cortex were measured by RP-HPLC. The glutamine (Gln) level and the glutamine synthetase (GS), glutamate decarboxylation enzyme (GAD), γ-aminobutyric acid transaminase (GABA-T) activity in the cerebral cortex were determined by UV colorimetric.

RESULTS

compared with the control group [GABA: (3.41 ± 0.12) micromol/g, Glu (14.00 ± 0.16) micromol/g, Gln (1.25 ± 0.19) micromol/g, GAD (13.50 ± 0.25) micromol × g(-1) × h(-1), GABA-T (25.51 ± 0.21) micromol × g(-1) × h(-1), GS(142.19 ± 1.31) U/mg pro], the level of GABA [(3.14 ± 0.14) micromol/g] was decreased (P < 0.05), whereas the level of Glu [(17.54 ± 0.40) micromol/g] and Gln [(3.35 ± 0.27) micromol/g] were increased (P < 0.05), the activity of GAD [(11.93 ± 0.15 micromol × g(-1) × h(-1)], GABA-T [(24.15 ± 0.22) micromol × g(-1) × h(-1)], GS [(140.75 ± 1.01) U/mg pro] was decreased (P < 0.05) in acute intoxication group; Compared with the acute intoxication group, the level of GABA [(3.52 ± 0.30) micromol/g] was increased (P < 0.05), whereas the level of Glu [(14.20 ± 0.32) micromol/g] and Gln [(1.32 ± 0.17) micromol/g] were decreased (P < 0.05), the activity of GAD [(13.01 ± 0.45 micromol × g(-1) × h(-1)], GABA-T [(25.19 ± 0.26) micromol × g(-1) × h(-1), GS [(142.35 ± 1.20) U/mg pro] was increased (P < 0.05); In contrast, the levels of GABA, Glu, Gln and the activity of GAD, GABA-T, and GS in Na-DMPS protection group were not significantly different in comparison with control group (P > 0.05).

CONCLUSION

the central toxic effects of mice with acute bromoxynil intoxication may be related to the changes of GABA and Glu content in the cerebral cortex;Na-DMPS can protect mice from bromoxynil-induced central toxic effects and GABA and Glu abnormal change in the cerebral cortex.

Increased urinary excretion of carnitine and acylcarnitine by mercuric chloride is reversed by 2,3-dimercapto-1-propanesulfonic acid in rats

This investigation was aimed to study the effect of 2,3-dimercapto-1-propanesulfonic acid (DMPS) on mercuric chloride (HgCl(2))-induced alterations in urinary excretion of various carnitine fractions including free carnitine (FC), acylcarnitine (AC), and total carnitine (TC). Different groups of Wistar male rats were treated with HgCl(2) at the doses of 0.1, 0.5, 1.0, 2.0, and 3.0 mg/kg body weight, and the animals were sacrificed at 24 hours following HgCl(2) injection. A separate batch of animals received HgCl(2) (2 mg/kg) with or without DMPS (100 mg/kg) and sacrificed at 24 or 48 hours after dosing. Administration of HgCl(2) resulted in statistically significant and dose-dependent increase in the urinary excretion of FC, AC, and TC in rats. However, the ratio of urinary AC:FC was significantly decreased by HgCl(2). Pretreatment with DMPS offered statistically significant protection against HgCl(2)-induced alterations in various urinary carnitine fractions in rats.

[Expression of angiotensin converting enzyme and angiotensin converting enzyme 2 gene in lung of paraquat poisoning rats and protection of sodium dimercaptopropane sulfonate]

OBJECTIVE

To investigate the expression of angiotensin converting enzyme (ACE) and ACE2 Gene in lung of paraquat poisoning rats and the protection of sodium dimercaptopropane sulfonate (Na-DMPS).

METHODS

One hundred SD male rats were randomly equally divided into 4 groups:normal control group (10 rats), drug control group (40 rats), paraquat poisoning group (40 rats) and drug intervention group(40 rats). The paraquat poisoning and drug intervention group rats were injected intraperitoneally by paraquat (20 mg/kg). The rats in drug intervention group rats were protected by intraperitoneal injection with Na-DMPS (200 mg/kg) 15 min before exposure of paraquat. Behavioral changes of the rats and histological changes of lung tissues under light microscope were observed. And the expression of ACE and ACE2 mRNA in lung tissues of rats both in paraquat poisoned group and drug intervention group were measured by RT-PCR at different time of 6 h, 24 h, 3 and 7 d after poisoning.

RESULTS

The poisoning symptoms of shortness of breath, cramps appeared and deteriorated progressively in rats after paraquat exposure and the protection of NA-DMPS could delay and reduce these symptoms significantly. Histological appearance of disorganization of pulmonary capillary and alveolus, exudation in alveolar space, pulmonary edema, severe bleeding, and inflammatory cells infiltration were obvious in lungs of rats after paraquat poisoning, whereas the histological changes were extenuated by protection of NA-DMPS. As compared with normal control group (NC group), the expressions of ACE, ACE2 mRNA in lung tissue decreased, and the lowest level of ACE mRNA expressions appeared at 24 h (0.457 +/- 0.262), on 3 d (0.385 +/- 0.179) after Paraquat exposure (P < 0.05), while lowest level of ACE2 mRNA expressions appeared on 3 d (0.415 +/- 0.247), 7 d (0.365 +/- 0.215) (P < 0.05). As compared with paraquat poisoned group, the expressions of ACE mRNA in lung tissue of rats in NA-DMPS protected group increased significantly at 24 h (0.739 +/- 0.558) and 3 d (0.749 +/- 0.414) (P < 0.05), while the expressions of ACE2 mRNA increased markedly on 3 d (0.584 +/- 0.345) and 7 d (0.493 +/- 0.292) (P < 0.05). But the expression of ACEmRNA and ACE2 mRNA in lungs had no statistical significance between normal control group and drug intervention group (P > 0.05).

CONCLUSION

The expressions of ACE and ACE2 mRNA in lung tissue of the rats with paraquat poisoning are decreased. Na-DMPS can effectively improve the balance of RAS in local lung tissue and reduce the pathological changes of lung tissue, delay the poisoning symptoms and show protective effects for acute lung injury induced by paraquat.

[Antioxidant impact on specific antiviral activity of human recombinant interferon alpha-2b with respect to Herpes simplex in cell culture]

In vitro synergistic antiviral effect of interferon alpha-2b in combination with unithiol (an antioxidant) on diverse variants of Herpes simplex, including the clinical acyclovir-resistant isolates, was demonstrated. Unithiol showed immediate antiherpes activity in the cell culture. However, its activity was lower than that of ascorbic acid, another highly active antioxidant. It was also observed that the specific antiherpes activity of interferon alpha-2b in the presence of unithiol increased several times. The data could be useful in the clinical practice, since the drugs combinations or complex formulations provide higher efficacy of the herpetic infection therapy with the use of the same concentrations of the available agents.

[Oxidative stress of acute paraquat poisoned rats and sodium dimercaptopropane sulfonate intervention]

OBJECTIVE

to study the oxidative stress of rats with acute paraquat poisoning and the intervention of Sodium Dimercaptopropane Sulfonate (NA-DMPS).

METHODS

Eighty male SD rats were randomizedly divided into: the normal control group (n=8), NA-DMPS control group (n=8), the PQ group (n=32, the rats were intraperitoneally injected with 1% PQ solution at the dosage of 20 mg/kg) and the NA-DMPS protected group (n=32). The rats in the groups of normal and NA-DMPS control were sacrificed 1d after administration of NS or NA-DMPS. And the rats in the PQ group and the NA-DMPS protected group were sacrificed at 6h, 1, 3, 7d after poisoning. Samples of serum, bronchoalveolar lavage fluid (BALF) and lung tissue were gathered. The MDA and CAT in serum, BALF and lung homogenate, the glutathione (GSH) in serum and BALF were measured. And the expression of Nuclear factor E2-related factor 2 (Nrf2) mRNA in lung was tested with RT-PCR.

RESULTS

Compared with the normal control group, the activities of MDA and CAT in serum, BALF and lung homogenate are higher in both groups of PQ and NA-DMPS protected. And compared with the PQ group, the activities of MDA in serum, BALF and lung homogenate of the NA-DMPS protected group decreased significantly at 6h, 1d after poisoning, whereas the activities of CAT are higher at 6h, 1, 3d in serum and 1, 3d in BALF and lung homogenate (P<0.05 or P<0.001). The serum GSH at 6h, 3d of the NA-DMPS protected group [(730.07 +/- 16.23), (793.66 +/- 7.40)] were higher than those in the PQ group. And the BALF GSH at 1, 3d of the NA-DMPS protected group [(609.75 +/- 6.74), (631.83 +/- 12.03)] were also markedly higher than the PQ group (P<0.05 or P<0.001). The expression of NRF2 mRNA of the lung at 1, 3, 7d in the PQ group [(0.71 +/- 0.061), (1.023 +/- 0.158), (0.969 +/- 0.046)] and the NA-DMPS protected group [(1.005 +/- 0.06), (1.464 +/- 0.166), (1.066 +/- 0.191)] were significantly higher than those in the control groups. Compared with the PQ group, the expression of NRF2 mRNA of the lung increased markedly in the NA-DMPS protected group at 1, 3d (P<0.01).

CONCLUSION

Na-DMPS decreases the activity of MDA and increases the activity of CAT, GSH and the expression of Nrf2 mRNA. NA-DMPS can protected rats from PQ intoxication by improving the balance of redox reaction.

Increase of renal excretion of organo-mercury compounds like methlymercury by DMPS (2,3-Dimercapto-1-propanesulfonic acid, Dimaval®)

In a highly mercury-burdened, small scale gold mining area in the Philippines, spontaneous urine samples were taken from 75 Hg intoxicated volunteers before (U1), and 2-3 hours after (U2) the oral application of 200 mg DMPS (2,3-Dimercapto-1-propanesulfonic acid, Dimaval). In the urine samples, the concentrations of organic and inorganic bound mercury were determined separately by CV-AAS. In U1, median concentrations of 15.7 microg inorganic Hg/g crea. and 2.2 microg organic Hg/g crea. were found. In U2, these values increased to 262 for inorganic Hg and 14.5 for organic Hg. Maximum concentrations (microg/g crea.) as high as 7,593 for inorganic Hg and 2,011 for organic Hg were observed after DMPS. The mean (median) increasing factor (U2/U1) was 16.0 for inorganic Hg and 5.1 for organic Hg. There was a trend that females responded better to DMPS than males. It was concluded that DMPS increases the renal excretion of organic bound Hg as it does for inorganic Hg, but to a lesser extent.

Effects of 2,3-dimercapto-1-propanesulfonic acid (DMPS) on methylmercury-induced locomotor deficits and cerebellar toxicity in mice

Chelating therapy has been reported as a useful approach for counteracting mercurial toxicity. Moreover, 2,3-dimercapto-1-propanesulfonic acid (DMPS), a tissue-permeable metal chelator, was found to increase urinary mercury excretion and decrease mercury content in rat brain after methylmercury (MeHg) exposure. We evaluated the capability of DMPS to reduce MeHg-induced motor impairment and cerebellar toxicity in adult mice. Animals were exposed to MeHg (40 mg/L in drinking water, ad libitum) during 17 days. In the last 3 days of exposure (days 15-17), animals received DMPS injections (150 mg/kg, i.p.; once a day) in order to reverse MeHg-induced neurotoxicity. Twenty-four hours after the last injection (day 18), behavioral tests related to the motor function (open field and rotarod tasks) and biochemical analyses on oxidative stress-related parameters (cerebellar glutathione, protein thiol and malondyaldehyde levels, glutathione peroxidase and glutathione reductase activities) were carried out. Histological analyses for quantifying cellular damage and mercury deposition in the cerebellum were also performed. MeHg exposure induced a significant motor deficit, observed as decreased locomotor activity in the open field and decreased falling latency in the rotarod apparatus. DMPS treatment displayed an ameliorative effect toward such behavioral parameters. Cerebellar glutathione and protein thiol levels were not changed by MeHg or DMPS treatment. Conversely, the levels of cerebellar thiobarbituric acid reactive substances (TBARS), a marker for lipid peroxidation, were increased in MeHg-exposed mice and DMPS administration minimized such phenomenon. Cerebellar glutathione peroxidase activity was decreased in the MeHg-exposed animals, but DMPS treatment did not prevent such event. Histological analyses showed a reduced number of cerebellar Purkinje cells in MeHg-treated mice and this phenomenon was completely reversed by DMPS treatment. A marked mercury deposition in the cerebellar cortex was observed in MeHg-exposed animals (granular layer>Purkinje cells>molecular layer) and DMPS treatment displayed a significant ameliorative effect toward these phenomena. These findings indicate that DMPS displays beneficial effects on reversing MeHg-induced motor deficits and cerebellar damage in mice. Histological analyses indicate that these phenomena are related to its capability of removing mercury from cerebellar cortex.

[Effect of Gandou Decoction IV combined with short-term decoppering therapy with sodium dimercapto-sulphonate on serum indexes of hepatic fibrosis in patients with Wilson' s disease]

OBJECTIVE

To observe the effect of Gandou Decoction IV (GDIV) on serum indexes of hepatic fibrosis and liver function in patients with Wilson's disease (WD).

METHODS

Sixty-one WD patients were assigned to two groups, 30 patients in the sodium dimercaptosulphonate (DMPS) group and 31 patients in the GD IV group. Both groups received 8 courses of DMPS treatment with 6 days as one course, and the GD IV group was given GD IV additionally. Serum indexes of liver function were examined, serum matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of metalloproteinase-1 (TIMP-1) were detected by double antibody sandwish ABC enzyme-linked immunosorbent assay (ELISA), and serum hyaluronic (HA), laminin (LN), procollagen III (PC III) and collagen type IV (C-IV) were determined by radioimmunoassay (RIA).

RESULTS

After treatment, all indexes of hepatic fibrosis and liver function had no significant change in the DMPS group, while in the GD IV group, the serum TIMP-1 level markedly decreased (P <0.05), the ratio of MMP-1/TIMP-1 significantly increased (P <0.01), and serum indexes of liver function markedly decreased (P < 0.05), but the changes in serum levels of HA, LN and PCIII, as well as in serum MMP-1 and C-IV were insignificant (P> 0.05), though they showed a trend of decreasing or increasing, respectively.

CONCLUSION

Short-term decopper-ing treatment with DMPS alone has no significant effect on hepatic function and serum fibrosis indexes in WD patients, while combined with GD IV, it can improve liver function and display an anti-fibrosis effect through inhibiting the serum TIMP-1 level and increasing the ratio of MMP-1/TIMP-1.

Cadmium inhibits δ-aminolevulinate dehydratase from rat lung in vitro: Interaction with chelating and antioxidant agents

The effect of cadmium (Cd(2+)) on delta-aminolevulinate dehydratase (delta-ALA-D) activity from rat lung in vitro was investigated. delta-ALA-D activity, a parameter for metal intoxication, has been reported as a target of Cd(2+) in different tissues. The protective effect of monotherapies with dithiol chelating (meso-2,3-dimercaptosuccinic acid (DMSA) and 2,3-dimercaptopropane-1-sulfonic acid (DMPS)) or antioxidant agents (ascorbic acid, diphenyl diselenide (PhSe)(2), and N-acetylcysteine (NAC)) was evaluated. The effect of a combined therapy (dithiol chelatingxantioxidant agent) was also studied. Zinc chloride (ZnCl(2)) and dithiothreitol (DTT) were used to investigate the mechanisms involved in cadmium, chelating and antioxidant effects on delta-ALA-D activity. Cadmium inhibited rat lung delta-ALA-D activity at low concentrations. DTT (3mM), but not ZnCl(2) (100microM), protected the inhibition of enzyme activity caused by Cd(2+). Chelating agents were not effective in restoring the enzyme activity. DMPS and DMSA presented inhibitory effect on enzyme activity. DTT restored the inhibition caused by both chelating agents, but ZnCl(2) restored only the inhibitory effect induced by DMSA. These compounds caused a marked potentiation of delta-ALA-D inhibition induced by Cd(2+). ZnCl(2) did not restore inhibition of enzyme activity caused by Cd(2+) plus chelating agents. Conversely, DTT restored the inhibition induced by Cd(2+)/DMSA, but not by Cd(2+)/DMPS. Antioxidants were not effective in ameliorating delta-ALA-D inhibition induced by Cd(2+), whereas ascorbic acid potentiated the enzyme inhibition induced by this metal. A combined effect of Cd(2+)xDMPSx(PhSe)(2) and Cd(2+)xDMPSxNAC was observed. There was no combined effect of Cd(2+)xchelatorxantioxidants when DMSA was used. This study demonstrated that Cd(2+)inhibited delta-ALA-D activity and chelating and antioxidant agents, alone or combined, did not restore the enzyme activity. In contrast, these compounds potentiated the inhibition induced by Cd(2+) in rat lung.

DMPS reverts morphologic and mitochondrial damage in OK cells exposed to toxic concentrations of HgCl2

Mercuric chloride (HgCl(2)) is a highly toxic compound, which can cause nephrotoxic damage. In the present study effects of HgCl(2) on mitochondria integrity and energy metabolism, as well as antidotal effects of 2,3-dimercaptopropane-1-sulfonate (DMPS) were investigated in the opossum kidney derived cell line (OK). OK cell monolayers were incubated during 0, 1, 3, 6, and 9 h in serum-free culture medium containing 15 microM HgCl(2), either in the absence or in the presence of 60 microM DMPS in a 1:4 ratio. Intracellular ATP content, MTT reduction, and HSP70/HSP90 induction were studied; confocal, transmission electron microscopy, and light microscopy studies were also performed. For confocal analysis, a mitochondrial selective probe (MitoTracker Red CMXH2Ros) was used. Antioxidant activity of DMPS was also studied by the scavenging of the free radical 2, 2-diphenyl-1-picrylhydrazyl (DPPH) technique. A decrease of ATP content, an impaired ability to reduce tetrazolium, and dramatic changes on cellular and mitochondrial morphology, and energetic levels were found after either 6 or 9 h of HgCl(2) exposure. Increased expression of HSP90 and HSP70 were also seen. When OK cells were co-incubated with HgCl(2) and DMPS, cellular morphology, viability, intracellular ATP, and mitochondrial membrane potential were partially restored; a protective effect on mitochondrial morphology was also seen. DMPS also showed potent antioxidant activity in vitro. Mitochondrial protection could be the cellular mechanism mediated by DMPS in OK cells exposed to a toxic concentration of HgCl(2).

DMPS and N-acetylcysteine induced renal toxicity in mice exposed to mercury

Acute effects of mercuric chloride (HgCl2) were evaluated on mice. Mice received a single dose of HgCl2 (4.6 mg/kg, subcutaneously) for three consecutive days. Thirty minutes after the last injection with HgCl2, mice received one single injection of 2,3-dimercapto-1-propanesulfonic acid (DMPS) or N-acetylcysteine (NAC) or diphenyl diselenide (PhSe)2. DMPS, NAC and (PhSe)2 were utilized as therapy against mercury exposure. At 24 h after the last HgCl2 injection, blood, liver and kidney samples were collected. delta-Aminolevulinate dehydratase (delta-ALA-D) and Na+, K- (+) ATPase activities, thiobarbituric acid-reactive substances (TBARS), non-protein thiols (NPSH) and ascorbic acid concentrations were evaluated. Plasma aspartate (AST) and alanine (ALT) aminotransferase activities, as well as urea and creatinine levels were determined. The group of mice exposed to Hg + (PhSe)2 presented 100% of lethality. Exposure with HgCl2 caused a decrease on the body weight gain and treatments did not modify this parameter. delta-ALA-D, AST and ALT activities, TBARS, ascorbic acid levels and NPSH (hepatic and erythrocytic) levels were not changed after HgCl2 exposure. HgCl2 caused an increase in renal NPSH content and therapies did not modify these levels. Mice treated with (PhSe)2, Hg + NAC and Hg + DMPS presented a reduction in plasma NPSH levels. Creatinine and urea levels were increased in mice exposed to Hg + NAC, while Hg + DMPS group presented an increase only in urea level. Na+, K- (+) ATPase activity was inhibited in mice exposed to Hg + DMPS and Hg + NAC. In conclusion, therapies with (PhSe)2, DMPS and NAC following mercury exposure must be better studied because the formation of more toxic complexes with mercury, which can mainly damage renal tissue.

Localization of the sulfate/anion exchanger in the rat liver

Although the sulfate/anion transporter (sat-1; SLC26A1) was isolated from a rat liver cDNA library by expression cloning, localization of sat-1 within the liver and its contribution to the transport of sulfate and organo sulfates have remained unresolved. In situ hybridization and immunohistochemical studies were undertaken to demonstrate the localization of sat-1 in liver tissue. RT-PCR studies on isolated hepatocytes and liver endothelial and stellate cells in culture were performed to test for the presence of sat-1 in these cells. In sulfate uptake and efflux experiments, the substrate specificity of sat-1 was evaluated. Sat-1 mRNA was found in hepatocytes and endothelial cells. Sat-1 protein was localized in sinusoidal membranes and along the borders of hepatocytes. The canalicular region and bile capillaries were not stained. Sulfate uptake was only slightly affected by sulfamoyl diuretics or organo sulfates. Sulfate efflux from sat-1-expressing oocytes was enhanced in the presence of bicarbonate, indicating sulfate/bicarbonate exchange. Estrone sulfate was not transported by sat-1. Sat-1 may be responsible for the uptake of inorganic sulfate from the blood into hepatocytes to enable sulfation reactions. In hepatocytes and endothelial cells, sat-1 may also supply sulfate for proteoglycan synthesis.

2,3-Dimercaptopropanol, 2,3-dimercaptopropane-1-sulfonic acid and meso-2,3-dimercaptosuccinic acid increase lead-induced inhibition of δ-aminolevulinate dehydratase in vitro and ex vivo

We investigated the effects of dimercaprol (BAL), meso-2,3-dimercaptosuccinic acid (DMSA) and 2,3-dimercapto-1-propanesulphonic acid (DMPS) on human blood delta-aminolevulinate dehydratase (delta-ALA-D) activity, the most reliable indicator of lead intoxication in humans, in the presence of lead in vitro. Furthermore, we studied the effects of the chelating agents, administered subcutaneously, on delta-ALA-D activity in blood and tissues of mice submitted to sub-acute lead exposure (50 mg/kg for 15 consecutive days, subcutaneously). In vitro results demonstrated that human blood delta-ALA-D activity was significantly inhibited (62%) by lead acetate. Lead acetate (1-1000 microM) pre-incubated with human blood increased the inhibitory potency of this compound on delta-ALA-D when compared to the assay without pre-incubation (89%). Chelating agents caused a marked potentiation of delta-ALA-D inhibition induced by lead, in vitro. One of the most notable observations in the present study was the correspondence between in vitro and ex vivo effects. In fact, BAL and DMPS increase the inhibitory effect of lead on delta-ALA-D activity from mice blood. The complexes formed (lead and chelators) were more inhibitory than lead alone in kidney and liver enzyme activity, ex vivo.

GEA3162, a nitric oxide-releasing agent, activates non-store-operated Ca2+ entry and inhibits store-operated Ca2+ entry pathways in neutrophils through thiol oxidation

We demonstrated that 5-amino-3-(3,4-dichlorophenyl)1,2,3,4-oxatriazolium (GEA3162), a nitric oxide (NO)-releasing agent, stimulated [Ca2+]i rise in rat neutrophils. This Ca2+ response was prevented by the thiol reducing agents, 2-mercaptoethanol, N-acetyl-L-cysteine, dithiothreitol, 2,3-dimercaptopropane-1-sulfonic acid (DMPS) and tris-(2-carboxyethyl)phosphine (TCEP), but slightly reduced by the antioxidant, 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox). GEA3162 also increased the formation of cellular reactive oxygen intermediates and decreased the cellular content of low molecular thiols. These responses were greatly reduced by Trolox, dithiothreitol and N-acetyl-L-cysteine. GEA3162 stimulated the protein tyrosine phosphorylation in neutrophils. The [Ca2+]i rise caused by formyl-Met-Leu-Phe (fMLP) and cyclopiazonic acid (CPA) was suppressed by GEA3162. TCEP prevented the inhibition of fMLP-induced [Ca2+]i rise by GEA3162. In the absence of external Ca2+, GEA3162 inhibited the CPA-induced [Ca2+]i rise, whereas it only slightly affected the fMLP-induced mobilization of the Ca2+ store. Application of GEA3162 after the stimulation with fMLP or CPA suppressed the robust Ca2+ entry followed by the readdition of Ca2+ into medium. Moreover, the Ca2+ entry was more susceptible to inhibition by treatment with GEA3162 prior to than after the fMLP stimulation. GEA3162 had no effect on the mitochondrial membrane potential. GEA3162 induced actin reorganization and condensed filament network at the cell periphery. These results indicate that GEA3162 exerted both the stimulation of Ca2+ entry and the inhibition of the store-operated Ca2+ entry in rat neutrophils. The dual effects of GEA3162 on the regulation of the external Ca2+ entry are mainly through the thiol modification of target protein(s) residing on the outside of the plasma membrane.

Effect of mercuric chloride on urinary excretion of free hydroxyproline

BACKGROUND

The present study was undertaken to study the effect of mercuric chloride (HgCl2) on the collagen metabolism in rats and the protective effect of 2, 3-dimercapto-1-propane sulfonic acid (DMPS) in HgCl2-treated rats.

MATERIAL/METHODS

The experimental groups studied were (i) a control group (ii) rats injected with a single intraperitoneal (ip) dose of 2 mg of HgCl2/kg body weight (HgCl2-treated group, n=10 rats), (iii) Rats injected with a single dose (ip) of 100 mg of DMPS/kg body weight (DMPS group, n=10 rats), (iv) rats injected with a single dose (ip) of 100 mg of DMPS/kg body weight followed by a single dose (ip) of 2 mg of HgCl2/kg body weight 1 hour after a 100-mg DMPS injection (DMPS + HgCl2-treated group, n=10 rats). Half of the rats from each group were sacrificed after 24 hours and the other half after 48 hours of treatment.

RESULTS

A dose of 2.0 mg HgCl2/kg body weight caused an impairment of glomerular function, which was reflected by significant increases in the levels of serum creatinine and serum urea nitrogen in HgCl2-treated rats compared with control rats. Administration of 2.0 mg of HgCl2/kg body weight significantly increased urinary excretion of free hydroxyproline in HgCI2-treated rats compared with the control rats, reflecting increased collagen breakdown.

CONCLUSIONS

Administration of DMPS one hour before HgCl2 treatment caused the restoration of altered parameters to near normal levels.

Efficacy of 2,3-dimercapto-1-propanesulfonic acid (DMPS) and diphenyl diselenide on cadmium induced testicular damage in mice

The deleterious effect of acute cadmium-intoxication in mice testes was evaluated. Animals received a single dose of CdCl2 (2.5 or 5 mg/kg, intraperitoneally) and a number of toxicological parameters in mice testes were examined, such as delta-aminolevulinic acid dehydratase (delta-ALA-D) activity, lipid peroxidation, hemoglobin and ascorbic acid contents. Furthermore, the parameters that indicate tissue damage such as plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were also determined. Thus, a possible protective effect of 2,3-dimercapto-1-propane-sulfonic acid (DMPS) and diphenyl diselenide (PhSe)2 were studied. The results demonstrated an inhibition of delta-ALA-D activity, a reduction of ascorbic acid and an increase of lipid peroxidation induced by cadmium, indicating testes damage. Furthermore, we observed an increase of plasma LDH, AST and ALT activities. DMPS (400 mol/kg) and (PhSe)2 (100 micromol/kg) partially protected from the inhibitory effect of 2.5 mg/kg CdCl2 on delta-ALA-D and from the increase of TBARS (thiobarbituric acid reactive species) levels. (PhSe)2 therapy was effective in ameliorate ascorbic acid content when the cadmium dose was 2.5 mg/kg. Treatment with DMPS and (PhSe)2, individually or combined, was inefficient in reducing cadmium-induced plasma LDH and ALT activity increase. The use of combined therapy (DMPS plus (PhSe)2) proved to be efficient in decreasing cadmium levels in testes and in ameliorating plasma AST activity from animals that received the highest dose of cadmium.

[Experimental study on the effects of BSO, GSH, vitamin C and DMPS on the nephrotoxicity induced by mercury]

OBJECTIVE

To study the renal toxicity caused by mercury administrated once and to observe the effects of buthionine sulfoximine (BSO), gluthionein (GSH), vitamin C (VC), and sodium 2,3-dimercato-1-propanesulfonate (DMPS) pretreatment on the nephrotoxicity of mercury.

METHODS

Sixty-four Wistar rats were divided randomly into eight groups, i. e., control group, low, middle and high dose mercury groups and BSO, GSH, VC, DMPS pretreatment groups. The low, middle, and high dose mercury group rats were subcutaneously (sc) injected with 0.75, 1.5, and 2.5 mg/kg HgCl2, respectively. The BSO pretreatment group rats were intraperitoneally (ip) injected with 0.5 mmol/kg BSO and four hours later sc administrated with 0.75mg/kg HgCl2. The GSH, VC and DMPS pretreatment group rats were ip injected with 3 mmol/kg GSH, 4mmol/kg VC, 200 micromol/kg DMPS, respectively, and two hours later sc administrated with 2.5 mg/kg HgCl2. The control group rats were sc injected with saline at corresponding time. The volume of injection was 5 ml/kg body weight. The 12 h urine samples were collected after 12 hours. After 48 hours, the blood samples were collected and then centrifuged to get the serum. The liver and renal cortex were also removed. Mercury contents in the liver, renal cortex, and urine samples were measured. Urinary NAG, ALP, LDH activities, urinary protein and BUN contents were also determined.

RESULTS

Mercury concentrations in the liver, renal cortex, and urine samples increased with mercury dose increasing. Mercury contents in the renal cortex presented evident dose-effect relationship. Mercury concentrations in the liver of high-dose mercury group were higher significantly than that of low, middle-dose mercury group, and control group. The concentrations of urinary mercury in the middle and high dose mercury groups were higher significantly than that of control group. Compared with 0.75mg/kg HgCl2 alone group, BSO pretreatment increased mercury concentrations in the liver, but decreased the concentrations in the renal cortex and urine. Mercury concentrations in the liver of GSH, VC and DMPS pretreatment groups were lower than that of 2.5 mg/kg HgCl2 alone group. Urinary NAG, ALP, LDH activities, urinary protein and BUN contents increased with mercury dose increasing, and the values in the animals of 2.5 mg/kg HgCl2 mercury group were higher significantly than that of control, 0.75 and 1.5 mg/kg HgCl2 groups. Urinary NAG, ALP activities, urinary protein and BUN contents in the rats of BSO pretreatment were higher than that of 0.75 mg/kg HgCl2 alone group and control group. Compared with 2.5 mg/kg HgCl2 alone group, urinary NAG, ALP, LDH activities, urinary protein and BUN contents decreased significantly.

CONCLUSION

Mercury concentrations in the liver, renal cortex, and urine of the rats increased with mercury dose increasing. BSO pretreatment could enhance the renal toxicity induced by mercury, however, GSH, VC, and DMPS pretreatment had antagonistic effects on nephrotoxicity of the mercury.

Effect of mercuric chloride on various hydroxyproline fractions in rat serum

Mercuric chloride (HgCl2) disturbs the collagen metabolism in the body which is reflected by altered hydroxyproline fractions in the serum. The aim of the present investigation was to study the effect of HgCl2 treatment on various hydroxyproline (Hyp) fractions in rat serum and the effect of 2,3-dimercapto-1-propane sulfonic acid (DMPS) treatment on serum Hyp fractions in HgCl2 treated rats. Other parameters studied included body weight, food intake, water intake and kidney weight. Doses of HgCl2 used were 0.1, 0.5, 1.0, 2.0, 3.0 mg/kg body weight and that of DMPS was 100 mg DMPS/kg body weight. All the doses of HgCl2 used caused significant (p < 0.01) alterations in free, peptide-bound and protein-bound Hyp in the serum when compared with control rats but a dose of 2 mg/kg body weight caused significant (p < 0.001) alteration even in the total serum Hyp when compared to control rats. Administration of DMPS prior HgCl2 treatment of rats sacrificed 24 h after the treatment caused a significant decrease of 52% (p < 0.01) in free Hyp when compared to similar HgCl2 treated rats. DMPS treatment with HgCl2 also caused an increase of 61% (p < 0.001) and 114% (p < 0.001) in peptide- and protein-bound Hyp respectively, when compared to HgCl2 treated rats sacrificed 24 h after mercuric chloride and DMPS treatment. Administration of DMPS followed by HgCl2 to rats which were sacrificed 48 h later caused no significant change in the total and free Hyp when compared to HgCl2 treated rats which were sacrificed 48 h after the treatment. But there was a significant decrease of 40% (p < 0.001) in peptide-bound Hyp and an increase in of 77% (p < 0.001) in protein-bound Hyp when compared to HgCl2 treated rats sacrificed 48 h after the treatment. The present study shows that HgCl2 treatment caused significant alterations in serum Hyp fractions reflecting disturbed composition of connective tissues which were not reversed by DMPS treatment.

Efforts to control the errant products of a targeted in vivo generator

Alpha-particle immunotherapy by targeted alpha-emitters or alpha-emitting isotope generators is a novel form of extraordinarily potent cancer therapy. A major impediment to the clinical use of targeted actinium-225 (225Ac) in vivo generators may be the radiotoxicity of the systemically released daughter radionuclides. The daughters, especially bismuth-213 (213Bi), tend to accumulate in the kidneys. We tested the efficacy of various pharmacologic agents and the effect of tumor burden in altering the pharmacokinetics of the 225Ac daughters to modify their renal uptake. Pharmacologic treatments in animals were started before i.v. administration of the HuM195-225Ac generator. 225Ac, francium-221 (221Fr), and 213Bi biodistributions were calculated in each animal at different time points after 225Ac generator injection. Oral metal chelation with 2,3-dimercapto-1-propanesulfonic acid (DMPS) or meso-2,3-dimercaptosuccinic acid (DMSA) caused a significant reduction (P < 0.0001) in the renal 213Bi uptake; however, DMPS was more effective than DMSA (P < 0.001). The results with DMPS were also confirmed in a monkey model. The renal 213Bi and 221Fr activities were significantly reduced by furosemide and chlorothiazide treatment (P < 0.0001). The effect on renal 213Bi activity was further enhanced by the combination of DMPS with either chlorothiazide or furosemide (P < 0.0001). Competitive antagonism by bismuth subnitrate moderately reduced the renal uptake of 213Bi. The presence of a higher target-tumor burden significantly prevented the renal 213Bi accumulation (P = 0.003), which was further reduced by DMPS treatment (P < 0.0001). Metal chelation, diuresis with furosemide or chlorothiazide, and competitive metal blockade may be used as adjuvant therapies to modify the renal accumulation of 225Ac daughters.

[Daphnia magna Straus: a new model for evaluating the antioxidant acton of water-soluble preparations in vivo]

Hydrobionta species of Daphnia magna Straus were used as a test objects for in vivo evaluation of the antioxidant activity of three hydrophilic thiol compounds: reduced gluthatione, unithiol, and cysteine. These compounds exhibited significant differences in activity under oxidative stress conditions, in the dynamics of observed effects, and in the probability of inversion from anti- to pro-oxidant action. The main advantage of the proposed test objects in comparison to the conventional in vitro experiments (where the antioxidant effect is evaluated over a period of time from several minutes to several hours) is that the development of drug activity (pro- and antioxidant effects) can be monitored over a prolonged period of time (up to several days). In comparison to the tests on mammals, the new method is much simpler and allows the entire antioxidant protection (rather than separate systems) to be evaluated. It is recommended to use Daphnia magna Straus species for comparative evaluation of the antioxidant action of water-soluble preparations in vivo.

Intracellular redistribution of heme in rat liver under oxidative stress: the role of heme synthesis

Heme distribution in subcellular fractions of rat liver was studied first hours under the action of several agents causing oxidative stress in vivo. Total and post-mitochondrial heme content in liver was found to depend on both the level of hemolysis products in blood and agent's capacity to modify heme and hemoproteins. The increase of activity of 5-aminolevulinate synthase (ALAS) and/or heme accumulation in mitochondria was accompanied by increase of tryptophan-2,3-dioxygenase (TDO) heme saturation. Membrane stabilisation by tocopherol or prevention of early ALAS induction by cycloheximide prevented both mitochondrial heme accumulation and increase of TDO heme saturation. Modification of heme fully prevented the alterations of total heme content even under severe hemolysis as well as the increase of TDO heme saturation if no increase of heme synthesis occurred. Thus heme synthesis can greatly contribute to heme intracellular redistribution under oxidative stress.

Simultaneous administration of sodium selenite and mercuric chloride decreases efficacy of DMSA and DMPS in mercury elimination in rats

Two chelating agents meso-2,3-dimercaptosuccinic acid (DMSA) and sodium 2,3-dimercapto-propane-1-sulphonate (DMPS) were tested for their efficiency in mercury removal from the body of rats in the presence and in the absence of selenium. Female Wistar rats were given a single intraperitoneal injection of mercuric chloride or an equimolar mixture of mercuric chloride and sodium selenite (1.5 micromol/kg body weight). The chelating agents were given orally, in excess (500 micromol DMSA/kg body weight; 300 micromol DMPS/kg body weight), 30 min after the administration of mercury and selenium. The animals were euthanized 24 h after the treatment and mercury in the kidney, liver, and 24 h urine was determined using cold vapour atomic absorption spectrometry (CV-AAS). The simultaneous administration of mercuric chloride and sodium selenite led to a redistribution of mercury in the organs, so that accumulation of mercury in the kidneys was decreased and in the liver increased. Selenite also caused decrease in the level of urinary mercury excretion. Both chelating agents were effective in mercury removal from the body, by increasing its urinary excretion. However, when animals were simultaneously treated with mercury and selenite, the rise of mercury excreted in the urine due to the treatment with chelating agents was lower when compared to animals receiving mercury without selenite. It is concluded that sodium selenite decreases the efficiency of DMSA and DMPS in mercury removal from the body of rats.

Conformational regulation of alpha 4 beta 1-integrin affinity by reducing agents. "Inside-out" signaling is independent of and additive to reduction-regulated integrin activation

The alpha(4)beta(1)-integrin (very late antigen-4 (VLA-4), CD49d/CD29) is an adhesion receptor involved in the interaction of lymphocytes, dendritic cells, and stem cells with the extracellular matrix and endothelial cells. This and other integrins have the ability to regulate their affinity for ligands through a process termed "inside-out" signaling that affects cell adhesion avidity. Several mechanisms are known to regulate integrin affinity and conformation: conformational changes induced by separation of the C-terminal tails, divalent ions, and reducing agents. Recently, we described a fluorescent LDV-containing small molecule that was used to monitor VLA-4 affinity changes in live cells (Chigaev, A., Blenc, A. M., Braaten, J. V., Kumaraswamy, N., Kepley, C. L., Andrews, R. P., Oliver, J. M., Edwards, B. S., Prossnitz, E. R., Larson, R. S., and Sklar, L. A. (2001) J. Biol. Chem. 276, 48670-48678). Using the same molecule, we also developed a fluorescence resonance energy transfer-based assay to probe the "switchblade-like" opening of VLA-4 upon activation. Here, we investigated the effect of reducing agents on the affinity and conformational state of the VLA-4 integrin simultaneously with cell activation initiated by inside-out signaling through G protein-coupled receptors or Mn(2+) in live cells in real time. We found that reducing agents (dithiothreitol and 2,3-dimercapto-1-propanesulfonic acid) induced multiple states of high affinity of VLA-4, where the affinity change was accompanied by an extension of the integrin molecule. Bacitracin, an inhibitor of the reductive function of the plasma membrane, diminished the effect of dithiothreitol, but had no effect on inside-out signaling. Based on this result and differences in the kinetics of integrin activation, we conclude that conformational activation of VLA-4 by inside-out signaling is independent of and additive to reduction-regulated integrin activation.

2,3-Dimercaptopropanol, 2,3-dimercaptopropane-1-sulfonic acid, and meso-2,3-dimercaptosuccinic acid inhibit delta-aminolevulinate dehydratase from human erythrocytes in vitro

The effects of dithiol chelating agents meso-2,3-dimercaptosuccinic acid (DMSA), 2,3-dimercaptopropane-1-sulfonic acid (DMPS), and 2,3-dimercaptopropanol (BAL) on delta-aminolevulinate dehydratase (delta-ALA-D) from human erythrocytes were evaluated. Furthermore, possible protective effects of zinc chloride (ZnCl(2)), dithiothreitol (DTT), and cysteine were studied. delta-ALA-D activity from human erythrocytes was inhibited by dithiol chelating agents in a concentration-dependent manner. Cysteine, at all concentrations tested, did not protect the inhibitory effect of 1 and 4 mM DMPS and DMSA, but protected 1 mM BAL inhibition. Dithiotreitol was able to protect the inhibition caused by 1 mM BAL (28%), DMPS (56%), and DMSA (40%) in a concentration-dependent manner. Zinc chloride protected and restored 1 mM BAL inhibitory effect on delta-ALA-D. Zinc chloride at 500 microM and 1 mM, respectively, protected inhibitory effects of DMPS and DMSA (1 and 4 mM), but did not reverse its effects. The preincubation of dithiol chelating agents with enzyme demonstrated that DMSA was the most potent delta-ALA-D inhibitor of human erythrocytes. These data are in agreement with delta-ALA-D activity from purified enzyme. ZnCl(2) (1 microM) added, in the reaction mixture, increased enzyme activity and DTT (100 microM) totally restored the enzyme activity for all chelating agents tested.

The Outer Pore of the Glutamate Receptor Channel Has 2-Fold Rotational Symmetry

The ligand binding domain of glutamate receptors (GluRs) has 2-fold rotational symmetry. The structure including the symmetry of the GluR ion channel remains undefined. Here we used substituted cysteines in the pore-lining M3 segment of the AMPAR GluR-A subunit and various cysteine-reactive agents to study the structure of the channel during gating. We find that cysteines substituted at A+6, located in the highly conserved SYTANLAAF motif, are grouped in pairs consistent with a 2-fold symmetry in the extracellular part of the pore. To account for this symmetry and crosslinking, we propose that the M3 segments in two neighboring GluR subunits are kinked within SYTANLAAF in opposite directions relative to the central axis of the pore. Our results extend the 2-fold rotational symmetry from the ligand binding domain to at minimum the extracellular part of the channel and suggest a model of gating movements in GluR pore-forming domains.

Zinc chelators inhibit eotaxin, RANTES, and MCP-1 production in stimulated human airway epithelium and fibroblasts

Asthma is characterized by an increased production of eosinophil-active C-C chemokines by the airway epithelium. Recent studies have identified the presence of important quantities of labile zinc in the conducting airways. We hypothesized that modulation of this labile zinc could influence the production of proinflammatory chemokines in respiratory epithelial cells. The zinc chelator N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) and the heavy metal chelator 2,3-dimercapto-1-propanesulfonic acid (DMPS) were used to reduce the labile zinc content of A549, BEAS-2B, and HFL-1 cells. Northern blot analysis and RNase protection assay were used to study the effects of the zinc chelators on mRNA expression. DMPS and TPEN specifically inhibited the production of eotaxin, regulated on activation, normal T-cell expressed, and presumably secreted, and monocyte chemotactic protein-1 in TNF-alpha-stimulated respiratory epithelial cells and fibroblasts through labile zinc chelation. The inhibitory effects of DMPS and TPEN were associated with the decreased binding of the zinc-finger transcription factor GATA-1, whereas no change in NF-kappaB activation was observed. Together these results demonstrate that modulation of the labile pool of zinc can regulate gene expression and protein synthesis of C-C chemokines in lung epithelial cells and fibroblasts.

Anticopper efficacy of captopril and sodium dimercaptosulphonate in patients with Wilson's disease

The aim of this study was to explore and compare initial treatment effects of captopril (Tensiomin) and sodium dimercaptosulphonate (DMPS) on a relatively large series of Wilson's disease inpatients. Two important markers of anticopper efficacy: serum sulphydryl and 24 h urinary copper levels in the patients were evaluated before and after treatment. The patients were randomly subdivided into 4 groups to allow statistical analysis (ANOVA) of the values recorded. The protocol was an open-label study of all the patients treated for 8 weeks (i.e., all the patients except those in the no-drug group), and a further six-month follow-up (post hospitalization) of the 14 patients administered captopril. Several copper-related variables were studied to evaluate the effect of the drugs on copper, and several biochemical and clinical variables were studied to evaluate potential toxic effects. Captopril was found to have a significant anticopper effect and did not markedly raise serum sulphydryl levels within this limited patient sample; the anticopper efficacy of captopril was, however, found to be markedly lower than that of DMPS; DMPS was found to raise the patients' serum sulphydryl and urinary copper levels. Evaluation of data from individual patients revealed evidence of a toxic side effect in only 1 patient, treated with DMPS, who exhibited transiently raised serum alanine aminotransferases, while no serious adverse events, upstanding syncope, irritating cough and leukopenia induced by captopril were noted. The results obtained in this four-group sample suggest that captopril might be a mild anticopper agent for Wilson's disease, possibly relieving the hepatic portal hypertension, but that DMPS has a greater field of anticopper efficiency than captopril. The authors also discuss recent experience of the overall treatment in China.

Blood mercury following DMPS administration to subjects with and without dental amalgam

The use of DMPS as a diagnostic tool in patients with symptoms allegedly caused by mercury from dental amalgam fillings is disputed. We have previously shown that the mercury concentrations in urine cannot be used in such a way. In the present study, we wished to evaluate the effect on blood mercury levels (B-Hg) following intravenously injected DMPS in four groups of subjects: 19 controls without amalgam experience; 21 healthy controls with amalgam fillings; 20 patients with self-reported symptoms from existing dental amalgams; and 20 patients who had removed amalgam fillings. A single dose of DMPS (2 mg/kg) was injected. Blood samples were collected prior to the injection and after 15, 30, 120 min, and after 24 h, and mercury was analyzed by cold vapor atomic absorption spectrophotometry. All groups showed an initial drop of 24 to 30% in the blood levels, approaching baseline values (2.5-5.5 microg/l) after 2 h. The subjects with no amalgam experience had the lowest mercury values. There was no significant difference between the three groups with such experience. There were no significant differences between the two groups with amalgam fillings present. Patients with symptoms allegedly caused by amalgam were not different from the control groups. There were indications that part of the urinary mercury excreted during the first 30 min originated from blood.

Metal chelators change the human sperm motility pattern

OBJECTIVE

To investigate the influence of zinc on the generation of motility.

DESIGN

Prospective study.

SETTINGS

Outpatient clinic of the Center of Dermatology and Andrology.

PATIENT(S)

Seventy-three patients and 10 sperm donors.

INTERVENTION(S)

Motile spermatozoa were isolated by swim-up and incubated for 1, 2, 4 or 6 hours with DL-penicillamine, 2,3-dimercaptopropan-1-sulfonate, and meso-2,3-dimercapto-succinimic acid at concentrations of 1, 10, and 100 micro mol/L.

MAIN OUTCOME MEASURE(S)

Motility was analyzed by means of computer-assisted semen analysis (CASA).

RESULT(S)

Significant dose-dependent changes in nonlinear motility, progressive motility, and velocity straight line (VSL) were observed. After only 1 hour of incubation, nonlinear motility decreased, and progressive motility and VSL increased. The percentage of immotile spermatozoa was not affected. Time-dependent changes in motility were observed on a significantly higher or lower level as compared to the control. Comparing the chelators after 2 hours revealed that DL-penicillamine showed the strongest effect on the sperm.

CONCLUSION(S)

The results imply that chelators can eliminate at least some part of the zinc from the flagellum. This zinc elimination appears to lead to comparable changes of the outer dense fibers as seen in vivo during epididymal maturation, finally resulting in improved motility.

The Mt. Diwata study on the Philippines 2000-treatment of mercury intoxicated inhabitants of a gold mining area with DMPS (2,3-dimercapto-1-propane-sulfonic acid, Dimaval)

Ninty-five inhabitants of the gold mining area of Mt. Diwata (on Mindanao, Philippines), who were diagnosed to be mercury (Hg) intoxicated, were orally treated with 2 x 200 mg of the chelating agent DMPS (Dimaval, Co. Heyl, Germany) for 14 days in the course of a UNIDO project focusing on mercury pollution abatement. Blood and urine samples before and after treatment, urine after the first application of DMPS and a hair sample were collected and analyzed for Hg. Before and after treatment extensive anamnestic data were collected, medical and neurological investigations and some neuro-psychological tests were performed. In spite of the short time of treatment most of the patients reported a marked improvement of the complaints which were stated by them before the therapy and which are characteristic for a chronic Hg intoxication, for example tremor, loss of memory, sleeplessness, metallic taste, etc. But even in some of the objective neurological parameters like hypo-mimia, Romberg test and tests for tremor/ataxia a statistical significant improvement could be found. Significant improvements could also be found in two neuro-psychological tests (pencil tapping and Frostig). In some cases an extreme high urinary Hg excretion was found under the chelating therapy with DMPS, and by this a distinct reduction of the Hg body burden. Nevertheless, in most cases Hg in blood and urine was not markedly decreased by the treatment. This shows that the duration of the treatment (14 days) was not sufficient for a permanent decrease in Hg. As DMPS excretes Hg mainly through the kidney, it can be concluded that in most cases even after 14 days of treatment there was an ongoing redistribution of Hg from other tissues to the kidney. In conclusion, this study proves that a chelating therapy with DMPS is highly effective even in the case of a mixed chronic and acute intoxication with an unknown combination of Hg vapor, inorganic Hg and organic Hg=methylmercury (MeHg), as characteristic for gold mining areas in the third world. Adverse side effects were rarely reported. Only in one case the medication had to be terminated after the first application due to an allergic skin reaction.

2,3-Dimercaptopropane-1-sulfonic acid and meso-2,3-dimercaptosuccinic acid increase mercury- and cadmium-induced inhibition of delta-aminolevulinate dehydratase

Compounds derived from Dimercaprol, such as meso-2,3-dimercaptosuccinic acid (DMSA) and 2,3-dimercaptopropane-1-sulfonic acid (DMPS), are becoming common agents for treating humans exposed to heavy metals. Heavy metals such as Pb(2+), Hg(2+) and Cd(2+) can inhibit delta-aminolevulinate dehydratase (delta-ALA-D) activity. Delta-ALA-D catalyzes the condensation of two delta-aminolevulinic acid (delta-ALA) molecules with the formation of porphobilinogen, a heme precursor. The effects of DMSA and DMPS alone or in combination with Cd(2+), Hg(2+), or Pb(2+) on hepatic delta-ALA-D were examined. DMPS and DMSA caused a dose-dependent inhibition of hepatic delta-ALA-D. In the presence of Hg(2+) or Cd(2+) the inhibitory potency of DMPS increased. Similarly, the inhibitory effects of Hg(2+) and Cd(2+) were markedly increased in the presence of DMSA. In contrast, the inhibitory effect of DMPS was not changed by inclusion of Pb(2+). As observed with DMSA, Zn(2+) did not modified the inhibitory effect of DMPS. Data of the present report support the idea that the complexes formed (metals-DMSA or DMPS) were more inhibitory than the metal (Hg(2+) and Cd(2+)) or the chelating agent alone to the hepatic delta-ALA-D activity, in vitro. The mechanism of hepatic delta-ALA-D inhibition by Hg(2+)-DMPS/DMSA and Cd(2+)-DMPS/DMSA complexes involve the essential thiol groups of the enzyme.

Effect of sodium 2,3-dimercaptopropane-1-sulphonate (DMPS) on chronic daunorubicin toxicity in rabbits: comparison with dexrazoxane

A possible protective action of DMPS (a dithiol chelating agent) against chronic daunorubicin toxicity in rabbits in comparison with dexrazoxane was investigated. The rabbits were divided into five groups: control (saline, 1 ml/kg i.v.), daunorubicin (3 mg/kg i.v.), DMPS (50 mg/kg i.v.); the remaining two groups were pre-treated either with dexrazoxane (60 mg/kg i.p.) or DMPS (50 mg/kg i.v.) 30 min before administration of daunorubicin (3 mg/kg i.v.). Drugs were given once a week for 10 weeks. Routine biochemical parameters were determined in weeks 1, 5 and 11. In the 11th week, invasive haemodynamic parameters were measured, then the rabbits underwent autopsy, cardiac tissue was examined by light microscopy and scored semiquantitatively. The contents of calcium, potassium, magnesium, iron and selenium were measured in the left heart ventricle. DMPS administered alone was well tolerated and did not cause any major signs of toxicity. It decreased the cardiac content of calcium, but did not affect the iron concentration. In contrast to dexrazoxane, DMPS pre-treatment did not prevent the decline in body weight in weeks 8-11 caused by daunorubicin, actually worsened mortality (26.7% vs 40.0%), did not ameliorate daunorubicin-induced nephrotic syndrome, and did not prevent the occurrence of the severe myocardial lesions. Unlike dexrazoxane, a lack of protective effect of DMPS against chronic daunorubicin toxicity in rabbits was demonstrated. The underlying cause may consist in the fact that DMPS does not efficiently chelate tissue iron and thus may not prevent the formation of oxygen free radicals.

Redox control of platelet aggregation

Sulfhydryl and disulfide metabolism in platelet function has recently reemerged as a focus of platelet research. In this study we tested the effect of redox buffer on platelet aggregation and the effect of reduced glutathione (GSH) and platelet activation on sulfhydryl exposure in the platelet fibrinogen receptor, alpha IIb beta 3. In the presence of subthreshold concentrations of agonist, physiologic concentrations of GSH (10 microM) stimulated platelet aggregation and secretion. These effects were found with more than one platelet agonist and with different low molecular weight thiols, including homocysteine. The effect of low molecular weight thiols was reproduced with the peptide LSARLAF which directly activates platelets through alpha IIb beta 3, suggesting that the mechanism is at the level of this integrin. After determining optimal sulfhydryl labeling conditions for alpha IIb beta 3 (5 mM EDTA, 37 degrees C, 60 min), we found that GSH (10 microM) generated sulfhydryls in the beta 3 subunit. To determine if the requirement was for reducing equivalents or for a redox potential (ratio of GSH to GSSG), aggregation was further studied with the addition of low concentrations of GSSG to the GSH. With a ratio of GSH/GSSG of 5/1, similar to that of blood, the addition of GSSG potentiated the stimulatory effect as compared to GSH alone. This indicates that, for potentiation of aggregation, GSH is not simply reducing disulfide bonds; there is rather a requirement for a certain redox potential. Additional studies performed in the absence of added glutathione showed an increase in sulfhydryl labeling in the beta 3 subunit during platelet activation. Finally, we show that vicinal dithiols of platelet surface proteins are involved in the sulfhydryl-dependent pathways of platelet activation. In summary, these data imply that the redox potential of blood regulates activation of the alpha IIb beta 3 integrin and together with other reports in the literature suggest that disulfide bond cleavage with sulfhydryl generation in beta 3 is involved in activation of this receptor.

Copper, zinc, and selenium in human blood and urine after injection of sodium 2,3-dimercaptopropane-1-sulfonate: a study on subjects with dental amalgam

This study investigated the effects of a single dose of intravenously administered sodium 2,3-dimercaptopropane-1-sulfonate (DMPS) on the essential elements copper, zinc, and selenium in human blood and urine. The possible role of dental amalgam was also addressed. Eighty individuals, divided in four groups according to the presence or absence of dental amalgam fillings and symptoms self-related to such fillings, were given DMPS (2 mg/kg body wt) and 500 mL Ringer's acetate intravenously. Urine and blood were collected prior to the injection, and thereafter at intervals over a 24-h period. Cu, Zn, and Se concentrations were determined by atomic absorption spectrometry methods. A statistically significant increase in the concentrations of Cu and Zn in urine was observed 30 and 120 min after the DMPS injection compared to the preinjection concentrations. The concentrations of Se were not affected. The cumulated excretion over 24 h after DMPS injection constitutes only from 0.1% to 0.7% of the body content of these elements. There was no effect of different amalgam statuses on Cu and Zn excretion. We found a temporary decrease (4-7%) in the concentrations of Cu, Zn, and Se in blood 15 and 30 min after DMPS, but this seems to be the result of dilution factors. Administration of a single dose of DMPS does not affect the body stores of the essential elements Cu, Zn, and Se.

[The activity of blood cholinesterase in rats exposed to dimethypo after drug intervention]

OBJECTIVE

To investigate the activity of ChE in rats poisoned by dimehypo and then treated with pralidoxime methylchloride or unithiol.

METHOD

Rats were divided into control group (dimehypo); intervention groups [dimehypo plus pralidoxime methylchloride or dimehypo plus unithiol (sodium dimercaptopropanesulphonate)]. Rats were dosed with 4 different doses of dimehypo: 1/16, 1/8, 1/4 and 1/2 of LD50 respectively(the LD50 of dimehypo is 342 mg/kg). After being poisoned with dimehypo orally, rats were immediately injected intramuscularly with pralidoxime methylchloride or unithiol. The activity of ChE in blood was detected before and 1/2, 1, 2, 4 and 24 h after poisoning in dimehypo and intervention groups.

RESULT

The ChE activity of four dose subgroups at 1 h after poisoning were (1.04 +/- 0.21), (0.84 +/- 0.12), (0.71 +/- 0.12), (0.66 +/- 0.07) U/ml respectively; the ChE activity of pralidoxime methylchloride intervention groups were (1.01 +/- 0.18), (1.17 +/- 0.11), (1.01 +/- 0.04), (1.03 +/- 0.12) U/ml respectively; and the ChE activity of unithiol intervention groups were (1.15 +/- 0.15), (1.26 +/- 0.27), (1.08 +/- 0.08), (1.04 +/- 0.12) U/ml respectively. The inhibited ChE in blood was recovered by either treatment with pyraldoxime methylchloride or unithiol. These two drugs had similar effects of recovering the activity of ChE(P > 0.05), but at higher doses(1/4 and 1/2 of LD50) the effects of both were not so good.

CONCLUSION

Pralidoxime methylchloride and unithiol could partly recover the activity of ChE inhibited by dimehypo.

Interaction of the metal chelator 2,3-dimercapto-1-propanesulfonate with the rabbit multispecific organic anion transporter 1 (rbOAT1)

The metal chelator DMPS (2,3-dimercapto-1-propanesulfonate) is used to treat heavy metal intoxication because it increases renal excretion of these toxins, which are accumulated in proximal tubule cells. To evaluate the involvement of the organic anion transporter 1 (OAT1) in the renal flux of DMPS, we examined the effect of DMPS on transport mediated by the rabbit ortholog of OAT1 and compared these characteristics with those observed in intact isolated rabbit proximal tubules. The rabbit OAT1 (rbOAT1) cDNA consisted of 2124 base pairs encoding a protein of 551 amino acids. Heterologous expression in COS-7 cells revealed rbOAT1-mediated transport of p-aminohippurate (PAH; K(t) = 16 microM). A 1 mM concentration of unlabeled PAH, alpha-ketoglutarate, urate, or probenecid inhibited [(3)H]PAH uptake by 70 to 90%. cis-Inhibition and trans-stimulation experiments using several Krebs cycle intermediates implicated alpha-ketoglutarate as the main intracellular exchange anion. Reduced DMPS inhibited rbOAT1-mediated fluorescein transport with an apparent K(i) of 102 microM. These characteristics paralleled those observed in isolated rabbit proximal tubules. PAH was transported into nonperfused single proximal tubule S(2) segments with a K(t) of 76 microM. DMPS inhibited FL uptake into single tubule segments with a K(i-app) of 71 microM. Fluorescein efflux from preloaded tubules was trans-stimulated by 1 mM PAH and 1 mM DMPS, consistent with DMPS entry into tubule cells by rbOAT1. In summary, rbOAT1 mediates basolateral uptake of DMPS into proximal tubule cells, implicating this process in the detoxification process of heavy metals in the kidneys.

Determination of arsenic metabolic complex excreted in human urine after administration of sodium 2,3-dimercapto-1-propane sulfonate

Sodium 2,3-dimercapto-1-propane sulfonate (DMPS) has been used to treat acute arsenic poisoning. Presumably DMPS functions by chelating some arsenic species to increase the excretion of arsenic from the body. However, the excreted complex of DMPS with arsenic has not been detected. Here we describe a DMPS complex with monomethylarsonous acid (MMA(III)), a key trivalent arsenic in the arsenic methylation process, and show the presence of the DMPS-MMA(III) complex in human urine after the administration of DMPS. The DMPS-MMA(III) complex was characterized using electrospray tandem mass spectrometry and determined by using HPLC separation with hydride generation atomic fluorescence detection (HGAFD). The DMPS-MMA(III) complex did not form a volatile hydride with borohydride treatment. On-line digestion with 0.1 M sodium hydroxide following HPLC separation decomposed the DMPS-MMA(III) complex and allowed for the subsequent quantification by hydride generation atomic fluorescence. Arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MMA(V)), dimethylarsinic acid (DMA(V)), MMA(III), and DMPS-MMA(III) complex were analyzed in urine samples from human subjects collected after the ingestion of 300 mg of DMPS. The administration of DMPS resulted in a decrease of the DMA(V) concentration and an increase of the MMA(V) concentration excreted in the urine, confirming the previous results. The finding of the DMPS-MMA(III) complex in human urine after DMPS treatment provides an explanation for the inhibition of arsenic methylation by DMPS. Because MMA(III) is the substrate for the biomethylation of arsenic from MMA(V) to DMA(V), the formation of DMPS-MMA(III) complex would reduce the availability of MMA(III) for the subsequent biomethylation.

Selenoprotein P in subjects exposed to mercury and other stress situations such as physical load or metal chelation treatment

In plasma, Se is found in plasma glutathione peroxidase (pGSH-Px), selenoprotein P (Sel-P), and albumins. The aim of the present study was to determine the influence of lifelong exposure to various levels of mercury vapor (Hg0) on plasma Se content and the fraction bound to Sel-P. Second, a pilot study was performed on the influence of short-term excessive physical stress and metal chelation (DIMAVAL) treatment. Samples of human plasma/serum obtained from a control group, Idrija residents living in a Hg-polluted environment because of the vicinity of the Idrija mercury mine (closed 1994), a few Idrija residents exposed to excessive physical stress, and two retired miners treated with the drug DIMAVAL were investigated. Selenoprotein P was isolated by affinity chromatography (heparin-Sepharose), and the concentrations of selenium were determined by radiochemical neutron activation analysis and hydride generation-atomic fluorescence spectrometry. Regardless of the group investigated, plasma Se average values were very similar (about 70-90 ngSe/g). A significant change of Sel P (7-24% decrease) was noted only in the group exposed to physical stress as compared to the same subjects before the test, to the control group, and to the Hg exposed group. The decrease of Se bound on Sel-P was accompanied by its increase in fraction of pGSH-Px with albumin.

Identification of a mechanism by which the methylmercury antidotes N-acetylcysteine and dimercaptopropanesulfonate enhance urinary metal excretion: transport by the renal organic anion transporter-1

N-Acetylcysteine (NAC) and dimercaptopropanesulfonate (DMPS) are sulfhydryl-containing compounds that produce a dramatic acceleration of urinary methylmercury (MeHg) excretion in poisoned animals, but the molecular mechanism for this effect is unknown. NAC and DMPS are themselves excreted in urine in high concentrations. The present study tested the hypothesis that the complexes formed between MeHg and these anionic chelating agents are transported from blood into proximal tubule cells by the basolateral membrane organic anion transporters (Oat) 1 and Oat3. Xenopus laevis oocytes expressing rat Oat1 showed increased uptake of [(14)C]MeHg when complexed with either NAC or DMPS but not when complexed with L-cysteine, glutathione, dimercaptosuccinate, penicillamine, or gamma-glutamylcysteine. In contrast, none of these MeHg complexes were transported by Oat3-expressing oocytes. The apparent K(m) values for Oat1-mediated transport were 31 +/- 2 microM for MeHg-NAC and 9 +/- 2 microM for MeHg-DMPS, indicating that these are relatively high-affinity substrates. Oat1-mediated uptake of [(14)C]MeHg-NAC and [(14)C]MeHg-DMPS was inhibited by prototypical substrates for Oat1, including p-aminohippurate (PAH), and was trans-stimulated when oocytes were preloaded with 2 mM glutarate but not glutamate. Conversely, efflux of [(3)H]PAH from Oat1-expressing oocytes was trans-stimulated by glutarate, PAH, NAC, DMPS, MeHg-NAC, MeHg-DMPS, and a mercapturic acid, indicating that these are transported solutes. [(3)H]PAH uptake was competitively inhibited by NAC (K(i) of 2.0 +/- 0.3 mM) and DMPS (K(i) of 0.10 +/- 0.02 mM), providing further evidence that these chelating agents are substrates for Oat1. These results indicate that the MeHg antidotes NAC and DMPS and their mercaptide complexes are transported by Oat1 but are comparatively poor substrates for Oat3. This is the first molecular identification of a transport mechanism by which these antidotes may enhance urinary excretion of toxic metals.