Drug Repurposing of the Unithiol: Inhibition of Metallo-ß-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, ß-lactams. One of the main mechanisms is inactivation of ß-lactam antibiotics by bacterial ß-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-ß-lactamases. Unithiol acts as a competitive inhibitor of meropenem hydrolysis by recombinant metallo-ß-lactamase NDM-1 with the KI of 16.7 µM. It is an order of magnitude lower than the KI 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-ß-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-ß-lactamases and it can be utilized in complex therapy together with the known ß-lactam antibiotics.

[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.

The effects of 2,3-dimercapto-1-propanesulfonic acid (DMPS) and meso-2,3-dimercaptosuccinic acid (DMSA) on the nephrotoxicity in the mouse during repeated cisplatin (CDDP) treatments.

Previously, we reported that specific lower dose of sodium 2,3-dimercapto-1-propanesulfonic acid (DMPS) which is an antidote to heavy metal intoxication, inversely enhanced cisplatin (CDDP)-induced antitumor activity to S-180 cell-bearing mouse. This activity was only weak with meso-2,3-dimercaptosuccinic acid (DMSA), however. This study investigated the effects of lower doses of DMPS or DMSA on the nephrotoxicity and kinetics of CDDP. Kidney and blood isolated from female mice which received CDDP with or without DMPS or DMSA once daily for 4 days were provided for measuring levels of blood urea nitrogen (BUN) and transporter proteins (OCT2: organic cation transporter; MATE1: multidrug and toxin extrusion) mRNA, and CDDP-originated platinum, and TUNEL staining of renal tubular cells. DMPS or DMSA reduced effectively CDDP-induced BUN, and caused a moderate reduction of platinum in kidney. Additionally, both dimercapto-compounds restored the CDDP-reduced mRNA levels of transporter proteins (OCT2 and MATE1), and apparently suppressed the CDDP-induced apoptosis. These results suggest that DMPS, as well as DMSA, at approximate 17-fold dose (µmol/kg) of CDDP, has an enough potential to reverse the CDDP nephrotoxicity, and concomitant use of DMPS considering both dose and timing for administration is potentially useful for preventing nephrotoxicity and enhancing antitumor activity during CDDP chemotherapy.

[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.

Keel venom: Rhabdophis subminiatus (Red-Necked Keelback) venom pathophysiologically affects diverse blood clotting pathways.

Venoms are evolutionary novelties that have real-world implications due to their impact upon human health. However, relative to the abundant studies of elapid and viperid snake venoms, fewer investigations have been undertaken on those of rear-fanged snakes as they are more problematic for obtaining venom. While most rear-fanged venomous snakes are not considered to be of great medical importance, several species are capable of producing fatalities. Most notable among these are snakes from the genus Rhabdophis, the Asian "keelback" snakes. Prior work have described potent procoagulant toxicity suggesting Factor X and prothrombin activation, but did not investigate the ability to activate other clotting factors. Here we show that in addition to activating both Factor X and prothrombin (with prothrombin twice that of FX), the venom of Rhabdophis subminiatus is able to more potently activate Factor VII (ten times that of prothrombin), while also activating FXII and FIX equipotently to prothrombin, and with FXI also activated but at a much lower level. The ability to activate FVII represents a third convergent evolution of this trait. The Australian elapid clade of [Oxyuranus (taipans) + Pseudonaja (brown snakes)] was the first identified to have evolved this trait. and only recently was it shown to be independently present in another lineage (the Central American viperid species Porthidium volcanicum). In addition, the abilities to activate FXI and FXII are also convergent between R. subminiatus and P. volcanicum, but with R. subminiatus being much more potent. By testing across amphibian, avian, and mammalian plasmas we demonstrate that the venom is potently procoagulant across diverse plasma types. However, consistent with dietary preference, R. subminiatus venom was most potent upon amphibian plasma. While a Rhabdophis antivenom is produced in Japan to treat R. tigrinus envenomings, it is scarce even within Japan and is not exported. As this genus is very wide-ranging in Asia, alternate treatment options are in need of development. Hence we tested the ability of candidate, broad-spectrum enzyme inhibitors to neutralize R. subminiatus venom: marimastat was more effective than prinomastat but both marimastat and prinomastat were significantly more effective than DMPS (2,3-Dimercapto-1-propanesulfonic acid). The findings of this study shed light on the evolution of these fascinating rear-fanged snakes as well as explored their systemic effects upon blood coagulation and point to potential treatment options for the rare, but potentially lethal encounters.

[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.

[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.

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.

Seventy-five percent nephrectomy and the disposition of inorganic mercury in 2,3-dimercaptopropanesulfonic acid-treated rats lacking functional multidrug-resistance protein 2.

In the present study, we evaluated the disposition of inorganic mercury (Hg(2+)) in sham-operated and 75% nephrectomized (NPX) Wistar and transport-deficient (TR(-)) rats treated with saline or the chelating agent meso-2,3-dimercaptosuccinic acid (DMSA). Based on previous studies, DMSA and TR(-) rats were used as tools to examine the potential role of multidrug-resistance protein 2 (MRP2) in the disposition of Hg(2+) during renal insufficiency. All animals were treated with a low dose (0.5 mumol/kg i.v.) of mercuric chloride (HgCl(2)). At 24 and 28 h after exposure to HgCl(2), matched groups of Wistar and TR(-) rats received normal saline or DMSA (intraperitoneally). Forty-eight hours after exposure to HgCl(2), the disposition of Hg(2+) was examined. A particularly notable effect of 75% nephrectomy in both strains of rats was enhanced renal accumulation of Hg(2+), specifically in the outer stripe of the outer medulla. In addition, hepatic accumulation, fecal excretion, and blood levels of Hg(2+) were enhanced in rats after 75% nephrectomy, especially in the TR(-) rats. Treatment with DMSA increased both the renal tubular elimination and urinary excretion of Hg(2+) in all rats. DMSA did not, however, affect hepatic content of Hg(2+), even in the 75% NPX TR(-) rats. We also show with real-time polymerase chain reaction that after 75% nephrectomy and compensatory renal growth, expression of MRP2 (only in Wistar rats) and organic anion transporter 1 is enhanced in the remaining functional proximal tubules. We conclude that MRP2 plays a significant role in the renal and corporal disposition of Hg(2+) after a 75% reduction of renal mass.

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.

[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.

[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.

[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.

A study of susceptibility-weighted imaging in patients with Wilson disease during the treatment of metal chelator.

OBJECTIVE: A randomized-controlled trial comparing study of the changes in brain sensitive-weighted imaging (SWI) of Wilson disease (WD) patients during the treatment with metal chelator was done. METHODS: 100 untreated WD patients (80 cases of cerebral type, 20 cases of hepatic type, age 20.13 ± 9.12 years old) and 20 normal controls were selected. Neurological symptoms were scored using the modified Young scale. Liver function tests and copper indices were collected. All study objects received SWI test of the brain. The values of corrected phase (CP) were calculated on SWI. Cerebral-type WD patients were treated with D-penicillamine (DPA) (group 1) or Dimercaptopropane Sulfonate (DMPS) + Dimercaptosuccinic Acid (DMSA) (group 2). Hepatic-type WD patients were treated with DPA (group 3). All patients received annual neurological symptom score, liver function, copper indices, and SWI examination. RESULTS: At the first year of treatment, score of the modified Young scale in group 2 was lower than that in group 1 (P = 0.023) and lower than that before treatment (P = 0.040). After 2 years of treatment, the score of the modified Young scale in group 1 was lower than that before treatment (P = 0.012). At the second year after treatment, the urinary copper in group 2 was higher than that in group 1 (P = 0.014). Urinary copper was maintained at 200 µg/day in group 1 and 300 µg/day in group 2 after 3 years of treatment. At the first year of treatment, serum copper in group 1 was lower than that in group 2 (P = 0.032). At the first year of treatment, CP values of the pallidum and substantia nigra in group 2 were higher than those in group 1 (P = 0.026, 0.040). At the second year of treatment, CP value of substantia nigra in group 2 was higher than that in group 1 (P = 0.037). After 3 years of treatment, there was no difference in CP values between WD patients and normal controls. CONCLUSIONS: Therapy with DMPS and DMSA improves neurological symptoms of WD patients more quickly and leads to less aggravation, compared with therapy with DPA. The metal content in the brain of WD patients was at a low level after 3 years of treatment. DMPS and DMSA can remove metal from brain tissue faster than DPA.

Arsenic Toxicity: Molecular Targets and Therapeutic Agents.

: High arsenic (As) levels in food and drinking water, or under some occupational conditions, can precipitate chronic toxicity and in some cases cancer. Millions of people are exposed to unacceptable amounts of As through drinking water and food. Highly exposed individuals may develop acute, subacute, or chronic signs of poisoning, characterized by skin lesions, cardiovascular symptoms, and in some cases, multi-organ failure. Inorganic arsenite(III) and organic arsenicals with the general formula R-As2+ are bound tightly to thiol groups, particularly to vicinal dithiols such as dihydrolipoic acid (DHLA), which together with some seleno-enzymes constitute vulnerable targets for the toxic action of As. In addition, R-As2+-compounds have even higher affinity to selenol groups, e.g., in thioredoxin reductase that also possesses a thiol group vicinal to the selenol. Inhibition of this and other ROS scavenging seleno-enzymes explain the oxidative stress associated with arsenic poisoning. The development of chelating agents, such as the dithiols BAL (dimercaptopropanol), DMPS (dimercapto-propanesulfonate) and DMSA (dimercaptosuccinic acid), took advantage of the fact that As had high affinity towards vicinal dithiols. Primary prevention by reducing exposure of the millions of people exposed to unacceptable As levels should be the prioritized strategy. However, in acute and subacute and even some cases with chronic As poisonings chelation treatment with therapeutic dithiols, in particular DMPS appears promising as regards alleviation of symptoms. In acute cases, initial treatment with BAL combined with DMPS should be considered.

Effects of chelators on mercury, iron, and lead neurotoxicity in cortical culture.

Chelation therapy for the treatment of acute, high dose exposure to heavy metals is accepted medical practice. However, a much wider use of metal chelators is by alternative health practitioners for so called "chelation therapy". Given this widespread and largely unregulated use of metal chelators it is important to understand the actions of these compounds. We tested the effects of four commonly used metal chelators, calcium disodium ethylenediaminetetraacetate (CaNa2EDTA), D-penicillamine (DPA), 2,3 dimercaptopropane-1-sulfonate (DMPS), and dimercaptosuccinic acid (DMSA) for their effects on heavy metal neurotoxicity in primary cortical cultures. We studied the toxicity of three forms of mercury, inorganic mercury (HgCl2), methyl mercury (MeHg), and ethyl mercury (thimerosal), as well as lead (PbCl2) and iron (Fe-citrate). DPA had the worst profile of effects, providing no protection while potentiating HgCl2, thimerosal, and Fe-citrate toxicity. DMPS and DMSA both attenuated HgCl2 toxicity and potentiated thimerosal and Fe toxicity, while DMPS also potentiated PbCl2 toxicity. CaNa2EDTA attenuated HgCl2 toxicity, but caused a severe potentiation of Fe-citrate toxicity. The ability of these chelators to attenuate the toxicity of various metals is quite restricted, and potentiation of toxicity is a serious concern. Specifically, protection is provided only against inorganic mercury, while it is lacking against the common form of mercury found in food, MeHg, and the form found in vaccines, thimerosal. The potentiation of Fe-citrate toxicity is of concern because of iron's role in oxidative stress in the body. Potentiation of iron toxicity could have serious health consequences when using chelation therapy.

[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.

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.

Multidrug resistance proteins and the renal elimination of inorganic mercury mediated by 2,3-dimercaptopropane-1-sulfonic acid and meso-2,3-dimercaptosuccinic acid.

Current therapies for inorganic mercury (Hg(2+)) intoxication include administration of a metal chelator, either 2,3-dimercaptopropane-1-sulfonic acid (DMPS) or meso-2,3-dimercaptosuccinic acid (DMSA). After exposure to either chelator, Hg(2+) is rapidly eliminated from the kidneys and excreted in the urine, presumably as an S-conjugate of DMPS or DMSA. The multidrug resistance protein 2 (Mrp2) has been implicated in this process. We hypothesize that Mrp2 mediates the secretion of DMPS- or DMSA-S-conjugates of Hg(2+) from proximal tubular cells. To test this hypothesis, the disposition of Hg(2+) was examined in control and Mrp2-deficient TR(-) rats. Rats were injected i.v. with 0.5 mumol/kg HgCl(2) containing (203)Hg(2+). Twenty-four and 28 h later, rats were injected with saline, DMPS, or DMSA. Tissues were harvested 48 h after HgCl(2) exposure. The renal and hepatic burden of Hg(2+) in the saline-injected TR(-) rats was greater than that of controls. In contrast, the amount of Hg(2+) excreted in urine and feces of TR(-) rats was less than that of controls. DMPS, but not DMSA, significantly reduced the renal and hepatic content of Hg(2+) in both groups of rats, with the greatest reduction in controls. A significant increase in urinary and fecal excretion of Hg(2+), which was greater in the controls, was also observed following DMPS treatment. Experiments utilizing inside-out membrane vesicles expressing MRP2 support these observations by demonstrating that DMPS- and DMSA-S-conjugates of Hg(2+) are transportable substrates of MRP2. Collectively, these data support a role for Mrp2 in the DMPS- and DMSA-mediated elimination of Hg(2+) from the kidney.

Influence of DMPS on the water retention capacity of electroporated stratum corneum: ATR-FTIR study.

Anionic lipids like phosphatidylserine are known to significantly enhance electroporation mediated transepidermal transport of polar solutes of molecular weights up to 10kDa. The underlying mechanism of the effect of anionic lipids on transdermal transport is not fully understood. The main barrier to transdermal transport lies within the intercellular lipid matrix (ILM) of the stratum corneum (SC) and our previous studies indicate that dimyristoyl phosphatidylserine (DMPS) can perturb the packing of this lipid matrix. Here we report on our investigation on water retention in the SC following electroporation in the presence and the absence of DMPS. The water content in the outer most layers of the SC of full thickness porcine skin was determined using ATR-FTIR-spectroscopy. The results show that in the presence of DMPS, the SC remains in a state of enhanced hydration for longer periods after electroporation. This increase in water retention in the SC by DMPS is likely to play an important role in trans-epidermal transport, since improved hydration of the skin barrier can be expected to increase the partitioning of polar solutes and possibly the permeability.