Cu2+-dependent hydrolysis of O-hexyl 2,5-dichlorophenyl phosphoramidate by reptile sera

This study shows the EDTA-resistant, Ca2+ and Cu2+-dependent hydrolysis of O-hexyl 2,5-dichlorophenyl phosphoramidate (HDCP) compound in reptiles sera determined by spectrophotometry UV/Vis and chiral chromatography. Samples of ten reptile species were incubated with aliquot of 100 or 400 μM HDCP in presence of 100 or 300 μM Cu2+, or 2.5 mM Ca2+ or 5 mM EDTA at 37 °C for 30-60 min. The results shown an activator effect of Cu2+ on HDCP hydrolysis in freshwater turtles sera (Trachemys scripta, Chelydra serpentina and Macrochelys temminckii) because the levels of 2,5-dichlorophenol (DCP; product hydrolysis) were similar (∼37 μM DCP) to chicken serum (positive control group). The marine turtles (Chelonia mydas and Eretmochelys imbricata) and crocodiles (Crocodylusacutus and Crocodylus moreletii) showed ∼50% less HDCPase activity (13-17 μM DCP) compared to the HDCPase activity of the freshwater turtle species. Terrestrial reptile species (snakes and lizards) showed around 25% of activity (7-13 μM DCP) with both copper concentrations. These Cu2+-dependent hydrolysis were stereospecific to R(+)-HDCP (p˂0.05) in the three freshwater turtle species that showed similar hydrolysis to the chicken serum. However, the Ca2+ did not show a significant activating effect on the HDCPase activity (1-8 μM DCP) in any reptile serum. Their hydrolysis levels were very similar to those of EDTA-resistant activity. The present study demonstrates a Cu2+-dependent A-esterase (HDCPase) activity in turtles and points serum albumin as the cuproprotein responsible for this activity, reinforcing its N-terminal sequence (DAEH) as a catalytic center.

Computational study to find the goat serum albumin (GSA) binding site as A-esterase

A-esterases are a classical term applied to enzymatic activity of the proteins by a mechanism not involving intermediate covalent phosphorylation, but requiring a divalent cation cofactor. Recently, a copper-dependent A-esterase activity has been identified in goat serum albumin (GSA) on the organophosphorus insecticide trichloronate. This hydrolysis was identified ex vivo with spectrophotometry and chromatography techniques. Albumin mechanism of action and catalytic site as Cu²⁺-dependent A-esterase are still unknown. Therefore, to know the copper bind to albumin is relevant. N-terminal sequence has been reported as the high affinity site for this cation, due to the histidine in position 3. The aim of this work In Silico is to explore how occurs this metallic binding and active the esterase catalytic function. The GSA crystallized structure (PDB: 5ORI) was chosen for molecular docking and dynamics. A site-directed docking, for N-terminal site and a blind docking was done with trichloronate as ligand. Root-mean-square deviation and frequency plot was calculated to find the most frequent predicted structure and visualize the amino acids involved in binding site. The affinity energy in the blind docking (-5.804 kcal/mol) is almost twice lower than site-directed docking (-3.816 kcal/mol) and N-terminal amino acids do not appear in the most repeated structure binding site, suggesting that the protein has a site with higher affinity to the trichloronate ligand. His145 could be involved in the binding site as has been reported in previous studies.

The acute systemic toxicity of thallium in rats produces oxidative stress: attenuation by metallothionein and Prussian blue

Thallium (TI) is one of the most toxic heavy metals. Human exposure to Tl occurs through contaminated drinking water and from there to food, a threat to health. Recently, environmental contamination by Tl has been reported in several countries, urging the need for studies to determine the impact of endogenous and exogenous mechanisms preventing thallium toxicity. The cytoprotective effect of metallothionein (MT), a protein with high capacity to chelate metals, at two doses (100 and 600 µg/rat), was tested. Prussian blue (PB) (50 mg/kg) was administered alone or in combination with MT. A dose of Tl (16mg/kg) was injected i.p. to Wistar rats. Antidotes were administered twice daily, starting 24h after Tl injection, for 4 days. Tl concentrations diminished in most organs (p < 0.05) by effect of PB, alone or in combination with MT, whereas MT alone decreased Tl concentrations in testis, spleen, lung and liver. Likewise, brain thallium also diminished (p < 0.05) by effect of PB and MT alone or in combination in most of the regions analyzed (p < 0.05). The greatest diminution of Tl was achieved when the antidotes were combined. Plasma markers of renal damage increased after Tl administration, while PB and MT, either alone or in combination, prevented the raise of those markers. Only MT increased the levels of reduced glutathione (GSH) in the kidney. Finally, increased Nrf2 was observed in liver and kidney, after treatment with MT alone or in combination with PB. Results showed that MT alone or in combination with PB is cytoprotective after thallium exposure.

DAEH N-terminal sequence of avian serum albumins as catalytic center of Cu (II)-dependent organophosphorus hydrolyzing A-esterase activity

O-hexyl O-2,5-dichlorophenyl phosphoramidate (HDCP) induces delayed neuropathy. The R (+)-HDCP inhibits and caused the so call "aging reaction" on inhibited-NTE. This enantiomer is not hydrolyzed by Ca(II)-dependent A-esterases in mammal tissues but is hydrolyzed by Cu(II)-dependent chicken serum albumin (CSA). With the aim of identifying HDCP hydrolysis by other vertebrate albumins, we incubated albumin with 400 μM racemic HDCP in the presence of 100 μM copper sulfate. HDCPase activity was assessed by measurement of HDCP with chiral chromatography. Human, sheep, dog, pig, lamprey or cobra serum albumin did not show a significant activity (~10%). Rabbit and bovine albumins hydrolyzed both enantiomers of HDCP (25% and 50% respectively). Turkey serum albumin had more HDCPase activity (~80 μM remaining) than the chicken albumin (~150 μM remaining). No animal albumins other than chicken showed stereoselective hydrolysis. Preincubation of chicken albumin with 1 mM the histidine modifying agents, 100 μM N-bromosuccinimide (NBS) and Zn(II), inhibited its Cu(II)-dependent R (+)-HDCPase activity, where as other mM amino acids modifiers had no inhibitory effects. . These results confirm that the stereoselective hydrolysis of (+)-HDCP is a specific A-esterase catalytic property of chicken albumin. The higher HDCPase activity by turkey albumin suggests the amino-terminal sequence of avian albumins (DAEHK) is the active center of this Cu(II)-dependent A-esterase activity.

Protection induced by estradiol benzoate in the MPP+ rat model of Parkinson's disease is associated with the regulation of the inflammatory cytokine profile in the nigro striatum

Previously, we have demonstrated that β-estradiol-3-benzoate (EB) has a protective effect on the neurodegenerative experimental model of Parkinson's disease. The protective effect is through the induction of the expression of paraoxonase-2 (PON2) in the striatum. PON2 has proven to have antioxidant and anti-inflammatory activity, this protein has a beneficial effect in MPP⁺ model in rats decreasing the lipid peroxidation and the oxidative stress. Furthermore, the molecular effect and the pathway by which EB induces protection were not further pursued. This study shows the regulation by EB of the anti-inflammatory effect through the modulation of cytokines, antioxidant enzymes and PON2 in the rat striatum. Rats were gonadectomized and 30 days after were randomly assigned into four experimental groups; only vehicles (Control group); EB treatment (EB group); MPP⁺ injury (M group); EB plus MPP⁺ injured (EB/M group). EB treatment consisted of 100 μg of the drug administered every 48 h for 11 days. Results showed that EB (group EB/M) treatment decrease significantly (40%) the number of ipsilateral turns respect to the M group and prevents significantly the dopamine (DA) decreased induced by MPP⁺ (~75%). This results are correlate with a significant decrease in the level of lipid peroxidation (60%) of the EB/M group respect to the M group. The EB treatment showed protection against neurotoxicity induced with MPP⁺, this could be due to EB capacity to prevent the increase in the expression level of proinflammatory cytokines TNF-α, IL-1 and IL-6 induced by MPP⁺. While, TGF-β1 and TGF-β3 expression was reduced in the rats treated only with MPP⁺, in the rats of EB/M group the expression of both cytokines was increased. EB protective effect against MPP⁺ neurotoxicity is related to antioxidant effect of PON2, pro-inflammatory cytokines and GSHR but not to SOD2, catalase, GPX1 or GPX4.

Hydroxytyrosol inhibits MAO isoforms and prevents neurotoxicity inducible by MPP+ invivo

Parkinson's disease is considered to be due to an increase in the catabolism of dopamine by the action of monoamine oxidase (MAO) enzymes which leads to an increase in reactive oxygen species (ROS) and loss of dopaminergic neurons. Here, in a model of neurotoxicity inducible by 1-methyl-4-phenylpyridinium (MPP+), we tested the effect of hydroxytyrosol (HTy), a potent antioxidant, on generation of ROS. Five minutes after a single intravenous administration of 1.5 mg/Kg of Hty, Wistar rats received an intrastriatal micro-injection of 10 micrograms of MPP+ while control animals received saline solution. Six days later, all animals were treated with apomorphine (1 mg/Kg), subcutaneously and ipsilateral rotations were assessed within an hour. Then, the rats were sacrificed, striatal tissues were removed and their catecholamines and MAO-A and B activities were quantitated. Pretreatment with HTy significantly diminished the number of ipsilateral rotations. This recovery correlated with significant preservation of striatal dopamine and significant inhibition of of the MAO activity. These results are consistent with the inhibitory effect of HTy on the MAO isoforms and form a basis for the neuroprotective mechanism of this phenylpropanoid in MPP+ induced Parkinson's disease.

Paraoxonase-1 polymorphisms and cerebral ischemic stroke: a pilot study in mexican patients

Background:

The serum paraoxonase-1 (PON1) associated to HDL presents two common polymorphisms in the positions 192 and 55. These polymorphisms are considered determinant of the capacity of HDL to protect LDL from their oxidative modification. In this context, the PON1 genotype has been associated with cardiovascular diseases, including stroke.

Objective:

To determine the allelic and genotypic frequencies of PON1 L55M and Q192R as well as the enzymatic activities of PON1 in subjects with and without atherothrombotic stroke.

Methods:

There were included 28 people with atherothrombotic stroke and 29 without stroke. The genotyping was carried out by PCR-RFLP and the phenotyping by measurement of the activities of paraoxonase and arylesterase in serum.

Results:

For the polymorphism Q192R, the allelic frequencies (Q/R) were 0.46/0.54 and 0.48/0.52 (p= 0.843) for the control group and the group with stroke, respectively. While for the polymorphism L55M, the allelic frequencies (L/M) were 0.81/0.19 for the control group, and 0.78/0.22 for the group with stroke (p= 0.610). The activity levels of paraoxonase were not significantly different between the control and stroke groups (450 vs. 348 UI/mL, p= 0.093) While the activity levels of arylesterase were significantly different between the studied groups (90 vs. 70 UI/mL, p= 0.001); however, upon adjustment by multiple linear regression, it was not longer significant.

Conclusion:

The polymorphisms Q192R and L55M, and the paraoxonase activity of PON1 are not risk factors for atherothrombotic stroke according to the results of this study.

Relationship Between Paraoxonase-1 and Butyrylcholinesterase Activities and Nutritional Status in Mexican Children

BACKGROUND

The enzymes butyrylcholinesterase (BuChE) and paraoxonase-1 (PON1) are the primary bioscavenging enzymes in serum and exhibit antioxidant and anti-inflammatory activities. PON1 has been associated with diseases caused by high oxidative stress, whereas BuChE appears to be involved in the pathophysiology of the metabolic syndrome and related disorders. It has been suggested that children from rural communities in Mexico may have a predisposition to develop obesity or type 2 diabetes during adolescence or adulthood. The objective of this study was to determine whether associations exist between the paraoxonase (PONase)/arylesterase (AREase) activity of PON1, its PON1-Q192R and PON1-L55M polymorphisms, and BuChE activity with the nutritional status and lipid profiles in a group of children from rural communities in Mexico.

METHODS

A group of 97 boys and girls from a rural community in Mexico were assessed for body mass index, the enzymatic activities of BuChE, PONase, and AREase were measured in serum, and their lipid profiles were determined. Genetic polymorphisms of PON1-L55M and PON1-Q192R were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).

RESULTS

The children were classified into four groups: thinness, normal weight, overweight, and obese. Of the children studied, 34.4% were overweight and obese. The mean age of the participants was 9.5 years (standard deviation = 1.8). The L allele of the PON1-L55M genotype was the most frequent (83.3%), and the R allele of the PON1-Q192R genotype was the most frequent (61.8%). Overweight and obese children had higher values of BuChE, total cholesterol, triglycerides (TG), and lower high-density lipoprotein (HDL-C) values than children with thinness or normal weight (P = 0.028, P = 0.019, P = 0.004, P = 0.069 and P = 0.021, respectively). The levels of AREase and PONase and the prevalence of PON1-L55M and PON1-Q192R genotypes were similar between groups (P = 0.484 and P = 0.380, respectively).

CONCLUSIONS

This study establishes a positive association of BuChE activity with nutritional status and serum TG.

β-Estradiol-3-benzoate confers neuroprotection in Parkinson MPP+ rat model through inhibition of lipid peroxidation

Estradiol (E2), in addition to its known hormone function, is a neuroactive steroid that has shown neuroprotective profile in several models of neurological diseases. The present study explores the antioxidant effect of β-estradiol-3-benzoate (EB) on the neurotoxicity elicited by MPP⁺ in rat striatum. Male Wistar rats, that were gonadectomized 30days prior to EB, were given 100µgEB per rat every 48h for 11days and animals were infused with MPP⁺ via intrastriatal at day six after beginning EB treatment. EB treatment completely prevented the fall in dopamine caused by MPP⁺, such result was related with decreased lipid peroxidation, a marker of oxidative stress; diminished number of ipsilateral-to-lesion turns and increased signal of the dopamine-synthesizing enzyme Tyrosin Hydroxylase in substantia nigra. The protection elicited by EB was not related to Mn or Cu-Zn superoxide dismutase enzymatic activities or glutathione modulation since none of these parameters were influenced by EB at the times assayed. Whereas, increased expression of PON2 as a result of EB treatment was observed, this phenomenon could be one of the mechanism by which the steroid conferred protection to dopaminergic cells against MPP⁺ injury.

Copper sulfate pretreatment prevents mitochondrial electron transport chain damage and apoptosis against MPP+-induced neurotoxicity

Intrastriatal injection of 1-methyl-4-phenylpyridinium (MPP⁺) is considered a model to reproduce some biochemical alterations observed in Parkinson's disease (PD) patients. Among those alterations, inhibition of mitochondrial complex I activity, increased free radical production and reduced antioxidant responses have been reported. Copper (Cu) plays an important role in the metabolism and antioxidative responses through its participation as a cofactor in the cytochrome c oxidase enzyme (COX), Cu/Zn-superoxide dismutase (Cu/Zn-SOD), and metallothioneins. We tested the effect of copper sulfate (CuSO₄) pretreatment on the mitochondrial electron transport chain (METC) in the striatum after MPP⁺ toxicity in rats. The results showed that the MPP⁺ intrastriatal injection reduced mitochondrial complex I, II, IV and V activities; while 10 μmol of CuSO₄ pretreatment counteracted this damage. Activities of complexes I, II and IV, were coincident with ATP recovery. Moreover, Cu/Zn-SOD activity was reduced as a consequence of MPP⁺ damage; however, copper pre-treatment kept the striatal Cu/Zn-SOD activity unchanged in MPP⁺-damaged animals. We observed that MPP⁺ also reduced the metallothionein (MT) content and that CuSO₄ pretreatment maintained baseline values. CuSO₄ pretreatment also reduced the striatal caspase-3 and caspase-9 activities that were increased three days after MPP⁺-induced damage. The present study provided evidence that copper pretreatment reduced MPP⁺-induced apoptotic damage, probably through direct action on copper-dependent proteins or indirectly on proteins in the apoptotic pathway.

Preclinical evaluation of anti-Helicobacter spp. activity of Hippocratea celastroides Kunth and its acute and sub-acute toxicity

Background

Hippocratea celastroides Kunth, commonly known as “cancerina”, is used in Mexican Traditional Medicine for the treatment of gastric and intestinal infections, systemic and skin inflammation, injuries and gastritis. The aim of this research was to assess the anti-Helicobacter pylori activities of hydro-ethanolic root-bark extracts from Hippocratea celastroides Kunth in naturally infected dogs, after testing their acute and subacute toxicities in mice.

Methods

To determine in vivo acute toxicity, a hydro-ethanolic extract was obtained and administered orally in female and male Balb-C mice, at doses ranging from 2000 to 5000 mg/kg. For the subacute study, a hydro-ethanolic extract was given to male and female Balb-C mice at doses ranging from 200 to 2000 mg/kg body weight. The animals were observed daily over a period of 42 days for signs of toxicity. In the pre-clinical anti-Helicobacter spp. assay, 60 dogs were included. Eighteen and 19 dogs for the experimental and control groups respectively, concluded the study. The experimental treatment consisted of H. celastroides hydro-ethanolic extract and the control treatment of amoxicillin-clarithromycin-omeprazole.

Results

Oral LD₅₀ (lethal dose 50) values for hydro-ethanolic extract were indeterminable at the highest tested doses. Under the subacute administration, neither mortality nor any sign of toxicity were observed when the hydro-ethanolic extract was administered. There were no significant alterations in biochemical parameters. The prevalence of Helicobacter spp. infection in dogs was 97.1 % for the experimental group and 100 % for the control group. Effectiveness was of 33.3 and 55 % in the experimental and control group respectively. The oral administration of H. celastroides was well-tolerated and safe.

Conclusion

The root-bark of H. celastroides produced no signs of toxicity, and manifested pharmacological activity that indicated the possibility of an alternative treatment for H. pylori infection. Effectiveness is still low so it is necessary to continue research.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-1412-6) contains supplementary material, which is available to authorized users.

[Proposal for early detection of ethanol consumption in students of the Universidad Autónoma del Estado de Morelos]

The present study determined through analytic techniques the quantification of some biomarkers that have been useful to detect early ethanol consumption in a college population. A group of 117 students of recent entry to the Universidad Autónoma del Estado de Morelos was analyzed. The enzyme determination of aspartate aminotransferase, alanine aminotransferase, and gamma glutamyltransferase as metabolic markers of ethanol, as well as the carbohydrate-deficient transferrin (CDT) detected by high chromatographic liquid (up to 1.8% of CDT), allowed us to identify that 6% of the college population presented a potential risk of alcohol consumption. The use of the biochemical-analytical method overall with the psychological drug and a risk factor instrument established by the Universidad Autónoma del Estado de Morelos permit us to identify students whose substance abuse consumption puts their terminal efficiency at risk as well as their academic level. The timely detection on admission to college can monitor and support a student consumer's substance abuse.

The neuroprotective effect of lovastatin on MPP(+)-induced neurotoxicity is not mediated by PON2

Parkinson's disease (PD) is a neurodegenerative disorder characterized by loss of the pigmented dopaminergic neurons in the substantia nigra pars compacta with subsequent striatal dopamine (DA) deficiency and increased lipid peroxidation. The etiology of the disease is still unclear and it is thought that PD may be caused by a combination of genetic and environmental factors. In the search of new pharmacological options, statins have been recognized for their potential application to treat PD, due to their antioxidant effect. The aim of this work is to contribute in the characterization of the neuroprotective effect of lovastatin in a model of PD induced by 1-methyl-4-phenylpyridinium (MPP(+)). Male Wistar rats (200-250 g) were randomly allocated into 4 groups and administered for 7 days with different pharmacological treatments. Lovastatin administration (5 mg/kg) diminished 40% of the apomorphine-induced circling behavior, prevented the striatal DA depletion and lipid peroxides formation by MPP(+) intrastriatal injection, as compared to the group of animals treated only with MPP(+). Lovastatin produced no change in paraoxonase-2 (PON2) activity. It is evident that lovastatin conferred neuroprotection against MPP(+)-induced protection but this effect was not associated with the induction of PON2 in the rat striatum.

Neuroprotective effect of Buddleja cordata methanolic extract in the 1-methyl-4-phenylpyridinium Parkinson's disease rat model

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the irreversible loss of dopaminergic neurons in the nigrostriatal pathway with subsequent dopamine deficiency. Environmental causes have been proposed through molecules, such as 1-methyl-4-phenylpyridinium (MPP(+)), to induce oxidative stress. The methanolic extract of plants of the genus Buddleja has been reported to have in vitro and in vivo antioxidant properties to protect against neuronal death. In the present study, the neuroprotective effect of Buddleja cordata methanolic extract in the MPP(+) PD rat model was investigated. Animals were administered orally with 50 or 100 mg/kg of methanolic extract every 24 h for 14 days. Twenty hours later, rats were infused with an intrastriatal stereotaxic microinjection of 10 µg MPP(+) in 8 μl sterile saline solution. Six days later, the animals were treated with 1 mg/kg apomorphine to record ipsilateral rotations for 1 h. All the rats were killed by decapitation and the lesioned striatum was dissected for dopamine and lipid peroxidation quantifications. Both methanolic extract doses led to a significantly lower (P < 0.05) number of ipsilateral rotations (75-80 %). This behavioral protection was corroborated with 60 % level of dopamine preservation (P < 0.05) and 90 % decrease in the formation of lipidic fluorescent products in the striatum (P < 0.05). This study demonstrates the antioxidant and neuroprotective effect of Buddleja cordata methanolic extract in the MPP(+) PD rat model, possibly due to the involvement of phenylpropanoids.

Additive effect of DL-penicillamine plus Prussian blue for the antidotal treatment of thallotoxicosis in rats

DL-penicillamine (DL-P) and Prussian blue (PB) given alone or in combination were tested as possible treatments against acute thallium toxicity. Rats were intoxicated by i.p. injection of thallium (I) acetate at LD(50) (32 mg/kg). A day later, pharmacological treatment was administered until day 4 as follows: (1) vehicles, (2) PB 50mg/kg, by oral route, twice a day, (3) DL-P 25mg/kg i.p. route, twice daily and (4) PB+DL-P. The Estimated Probability Survival (EPS) was recorded during the experiment for each treatment. DL-P alone did not show a significant effect on survival. However, when it was used in combination with PB, it increased the survival significantly (EPS=0.8, P<0.05) as compared to the control group (EPS=0.4). In a different experiment, using 16 mg/kg of Thallium I acetate, the metal levels were analyzed in blood, body organs and brain regions after treatments. DL-P given alone decreased slightly the thallium content in blood, organs and brain. Meanwhile, its administration in combination with PB diminished the thallium levels significantly (P<0.05) in the majority of tissues, at levels lower than those achieved in the PB group. Those results indicate that DL-P administered alone did not prevent the mortality nor accumulation of the metal in body tissues. Its combination with PB could be considered an alternative antidotal treatment in thallium toxicity, because this chelating agent given alone did not cause thallium redistribution to the brain. When given in combination with PB it has an additive effect in the treatment of acute thallotoxicosis.

Relationship between the paraoxonase (PON1) L55M and Q192R polymorphisms and obesity in a Mexican population: a pilot study

The aim of this study was to examine the relationship between the L55M and Q192R paraoxonase (PON1) polymorphisms and obesity in a population of adult Mexican workers. The study population included 127 adult individuals from the Universidad Autónoma del Estado de Morelos, ranging in age from 20 to 56 years and representing both sexes. Based on body mass index, 63 individuals were classified as obese and 64 as normal weight. The PON1-Q192R and PON1-L55M polymorphisms were determined by restriction fragment length polymorphism PCR analysis. Both arylesterase and paraoxonase activity levels were similar in both groups, whereas systolic pressure, triglyceride, total cholesterol, low-density lipoprotein cholesterol, very-low-density lipoprotein cholesterol, glucose, and insulin levels were higher in the obese group than in the normal-weight group (P < 0.05). An exception was the high-density lipoprotein cholesterol (HDL-C) levels, which were lower in the obese group (P < 0.05). Although the PON1-Q192R polymorphism was not associated with either group, the frequency of the homozygous L genotype for the PON1-L55M polymorphism was higher in the obese group than in the normal-weight group (P < 0.05). In conclusion, this study established a positive association between the PON1-L55M homozygous L genotype and obesity.

Endogenous thiols enhance thallium toxicity

Either L-methionine (L-met) or L-cysteine (L-cys), given alone and in combination with Prussian blue (PB) was characterized as treatment against acute thallium (Tl) toxicity in rats. Animals were intoxicated with 32 mg/kg Tl acetate corresponding to rat LD(50). Antidotal treatments were administered during 4 days, as follows: (1) vehicle, (2) L-met 100 mg/kg i.p. twice a day, (3) L-cys 100 mg/kg i.p. twice a day, (4) PB 50 mg/kg oral, twice a day, (5) L-met + PB and (6) L-cys + PB. Mortality was as follows: control 50%; L-met 80%; L-cys 80%; PB 20%; L-met + PB 90% and L-cys + PB 100%. In a different experiment, using 16 mg/kg of Tl, tissue levels of this metal were analyzed. PB treatment statistically diminished Tl content in body organs and brain regions (P<0.01). Whereas, separate treatments of L-met and L-cys failed to decrease Tl content in organs and brain regions; while its administration in combination with PB (L-met + PB and L-cys + PB groups) lowered Tl levels in body organs in the same extent as PB group. Results indicate that L-met and L-cys administered alone or in combination with PB should not be considered suitable treatments against acute Tl toxic effects because this strategy failed to prevent mortality and Tl accumulation in brain.

Stereospecific hydrolysis of a phosphoramidate as a model to understand the role of biotransformation in the neurotoxicity of chiral organophosphorus compounds

Calcium-dependent and EDTA-resistant hydrolyses of R and S isomers of O-hexyl O-2,5-dicholorophenyl phosphoramidate (HDCP) were observed in serum and subcellular fractions of liver, kidney and brain from hen, rat and rabbit. In serum, the Ca(2+)-dependent hydrolysis was much higher in rabbit than in other species. Liver showed a higher activity than kidney and brain. The S-HDCP isomer was hydrolysed to a higher extent than the other isomer. The fact that this stereospecificity favours the S-isomer is more clearly observed in rabbit serum, and in rat and rabbit liver particulate fractions. In such tissues and species, the EDTA-resistant hydrolysis was not stereospecific. Soluble fractions of rat brain and of hen liver, kidney and brain, showed a lower total activity but with a higher proportion of EDTA-resistant activity and a higher hydrolysis of the R-HDCP isomer. The Ca(2+)-dependent stereoselective biodegradation of S-HDCP is dominant in the most active tissues in rabbit and rat. It can therefore be concluded that S-HDCP would be biodegraded faster than R-HDCP. Furthermore, R-HDCP is the isomer that will remain at a higher proportion to be available for interaction with the target of neurotoxicity.

Comparative hydrolysis of O-hexyl O-2,5-dichlorophenyl phosphoramidate and paraoxon in different tissues of vertebrates

The Ca(2+)-dependent and EDTA-resistant hydrolysis of O-hexyl O-2,5-dichlorophenyl phosphoramidate (HDCP) and paraoxon was studied in serum and subcellular fractions of liver, kidney and brain of hen, rat and rabbit. HDCP was the best substrate among all the tissues studied, except that of rabbit serum which showed the highest Ca(2+)-dependent paraoxon hydrolysing activity (paraoxonase). High HDCP hydrolysing activity (HDCPase) was detected in the brain tissue of the three species studied, whereas low or no paraoxonase was found. The HDCPase/paraoxonase ratio of Ca(2+)-dependent hydrolysing activities ranged from 0.5 to 83 for tissues of the same species. EDTA-resistant HDCPase activity was more than 50% of the total activities in hen tissues, with an almost undetectable Ca(2+)-dependent paraoxonase activity in most organs. The same response was observed in rat tissues, except for serum where the Ca(2+)-dependent HDCPase and paraoxonase activities were higher (70 and 25% of total activities, respectively). EDTA-resistant HDCPase and paraoxonase activities represented less than 25% of all activities in rabbit tissues. Paraoxon has traditionally been the substrate for measuring organophosphorus hydrolysing activities. However, HDCP could be a good substrate in addition to paraoxon for monitoring other phosphotriesterases in biological tissues.

EGb761 Pretreatment Reduces Monoamine Oxidase Activity in Mouse Corpus Striatum During 1-Methyl-4-Phenylpyridinium Neurotoxicity

EGb761 produces reversible inhibition of both monoamine oxidase (MAO) isoforms in the central nervous system. 1-Methyl-4-phenylpyridinium (MPP+) neurotoxicity is prevented by treatment with the MAO inhibitor pargyline. We investigated EGb761's effect on striatal MAO activity during MPP+ neurotoxicity. C-57 black mice were pretreated with EGb761 (10 mg/kg) daily for 17 days followed by administration of MPP+ (0.72 mg/kg). MPP+ enhanced striatal MAO (30%) activity at 6 h, and EGb761 prevented this effect. MAO-B activity in striatum was enhanced (70%) 6 h after MPP+ administration and was reduced to almost normal levels in EGb761 + MPP+ group compared to MPP+ group. Pretreatment with EGb761 partially prevented (32%) the striatal dopamine-depleting effect of MPP+ and prevented the reduction in striatal tyrosine hydroxylase activity (100%). Results suggest that EGb761 supplements may be effective in reducing MAO activity as well as enhancement in dopamine metabolism, thereby preventing MPP+-neurotoxicity.

Dichlorophenyl phosphoramidates as substrates for avian and mammalian liver phosphotriesterases: activity levels, calcium dependence and stereospecificity

The present study shows the existence of both Ca2+-dependent and EDTA-resistant hydrolysing activities against HDCP and paraoxon in the particulate and soluble fractions of hen, rat and rabbit liver. HDCP was more extensively hydrolysed than paraoxon in both subcellular fractions and each of three individuals of the three animal species under study in spite of wide interindividual variations. However the ratio of HDCP versus paraoxon hydrolysing activity (HDCPase/paraoxonase), although within the same order of magnitude, cannot be considered as constant as it ranges one- to seven-fold between individuals of the same species. Also there is no constant ratio of Ca2+-dependent/EDTA-resistant activities. Rabbit liver showed the highest rates of Ca2+-dependent hydrolysis for both organophosphorus compounds whereas the hen paraoxonase activity was not inhibited by EDTA. The stereospecific hydrolysis of HDCP was mostly a Ca2+-dependent one, the S-HDCP isomer being hydrolysed faster than the R-HDCP one. The suggestion is made that HDCP could be conveniently used to measure PTE activity in the liver.

Dapsone attenuates kainic acid-induced seizures in rats

We tested the ability of dapsone (4,4'-diamino-diphenyl sulfone) to attenuate kainic acid-induced seizures. We observed that 9.375 and 12.5 mg/kg doses of dapsone administered 30 min before a single kainic acid (10 mg/kg) i.p. injection were able to decrease the time of electroencephalographic seizures by 52% and 82%, respectively, as compared with rats administered with 10 mg/kg kainic acid only. The 12.5 mg/kg dose of dapsone was also able to diminish both kainic acid-evoked body and head shakes (58%) and kainic acid-induced mortality (75%). These results suggest that dapsone could be used in clinical trials as anticonvulsant.

Combined D-penicillamine and prussian blue as antidotal treatment against thallotoxicosis in rats: evaluation of cerebellar lesions

Rats were treated with a single dose of thallium acetate (32 mg/kg i.p.) and the antidotal effect of D-penicillamine and prussian blue given alone or in combination was assessed by means of evaluation of the thallium-induced cerebellar histological lesions. After thallium poisoning (24 h), antidotes were administered for 4 days as follows: D-penicillamine (DP) 25 mg/kg, i.p. twice daily; prussian blue (PB), 50 mg/kg p.o., twice daily. Mortality among the treatment groups was as follows: control, 87.5%; DP, 100%; PB, 56.25%; DP+PB, 25%. Three days after these treatments, rats treated with the combination DP+PB presented a significantly lower number of altered Purkinje cells in cerebellum as compared with those of the thallium alone treated animals, indicating adequate protection by this antidote treatment against thallium neurotoxicity. Prussian blue protected against thallium-induced neurotoxicity to a lesser extent as compared with the effects obtained by the DP+PB protection. DP did not protect against thallium-induced alterations of Purkinje cells. These results confirm the efficacy of the combined antidotal treatment of DP and PB against thallium toxicity in rats, and support the possible application in human cases of thallotoxicosis.

Relationship between physicochemical properties of prussian blue and its efficacy as antidote against thallium poisoning

In the present work we established a relationship between some physicochemical properties of two different batches of Prussian blue (PB) and their in vivo efficacy as an antidote against thallium poisoning. The physicochemical properties studied were crystallite size and thallium-adsorbing capacity. One of the batches was synthesized and the other was obtained from commercial sources. The synthesized PB batch with the smallest crystallite size had both the highest adsorption capacity and antidotal efficacy. Synthesized PB protected 100% of the animals against one LD50 thallium dose, whereas the commercial PB batch protected only 80%. Thallium content in blood and tissues (liver, kidney, brain) was also analysed after antidotal PB treatment in rats previously intoxicated with a sublethal dose of T1+. Animals treated with synthesized PB showed significantly less thallium in blood and tissue contents than those values of commercial PB-treated rats, indicating better antidotal properties of the synthesized PB. According to the present study we suggest an in vivo evaluation of the compound before distribution of the product to toxicological units, if X-ray diffractometric analysis is not available, in order to identify and determine the crystallite size of the compound as it plays an important role in the efficacy of PB.

D-penicillamine and prussian blue as antidotes against thallium intoxication in rats

D-penicillamine (DP) and prussian blue (PB), given alone and in combination, were evaluated in rats as treatments against acute thallotoxicosis. Animals were poisoned by intraperitoneal (i.p.) injection of thallium(I) acetate at different doses (16, 30, 40, 50 and 70 mg/kg). Later (24 h), treatments were administered until day 5, as follows: D-penicillamine (DP), 25 mg/kg, i.p. route, twice daily; prussian blue (PB), 50 mg/kg, oral route, twice daily. LD50 values were estimated for each treatment with the following results: control, 32 mg/kg; DP, 27 mg/kg; PB, 42 mg/kg; PB + DP, 64 mg/kg. Thallium content was analyzed in six body organs and eight brain regions after treatments. PB administration induced significant elimination of thallium from all tissues. DP treatment diminished thallium content in body organs, but increased it in brain regions, indicating a redistributive effect of DP. DP + PB treatment decreased thallium content in all body organs and brain regions. Renal thallium content in the DP + PB group was significantly lower than that of PB alone group, suggesting accelerated urinary excretion of thallium as a result of DP action. Results indicate that DP administered alone may be dangerous because of its redistributive effect, but given in combination with PB may be useful as treatment against thallium poisoning.