Hypertension strengthens δ-ALA-D activity inhibition and increases it reactivation index in type 2 diabetic patients

AIMS

To assess the effect of hypertension on δ-aminolevulinate dehydratase (δ-ALA-D) activity of type 2 diabetic patients (T2DM).

METHODS

δ-ALA-D activity and reactivation index, as well as markers of oxidative stress, biochemical and anthropometrics parameters were determined in T2DM (n=23), type 2 diabetic patients with hypertension (T2DM/HT) (n=30) and controls (n=30).

RESULTS

T2DM/HT presented a greater inhibition of δ-ALA-D activity, a higher reactivation index (p<0.05) and a greater depletion of plasma protein thiol groups (P-SH) when compared to T2DM. Moreover, δ-ALA-D activity was positively associated with SH groups and negatively associated with serum protein carbonyl (PC) while its reactivation index was negatively associated with SH groups and positively associated with PC.

CONCLUSIONS

These results point out that there is a possible interference of hypertension on the mechanism of the δ-ALA-D activity suggesting that this condition aggravated the oxidative stress of diabetes mellitus.

The effects of resistance exercise and post-exercise meal timing on the iron status in iron-deficient rats

Resistance exercise increases heme synthesis in the bone marrow and the hemoglobin in iron-deficient rats. Post-exercise early nutrient provision facilitates skeletal muscle protein synthesis compared to late provision. However, the effects of post-exercise nutrition timing on hemoglobin synthesis are unclear. The current study investigated the effect of post-exercise meal timing on the activity of the key enzyme involved in hemoglobin synthesis, δ-aminolevulinic acid dehydratase (ALAD), in the bone marrow and examined the hemoglobin concentration in iron-deficient rats. Male 4-week-old Sprague-Dawley rats were fed an iron-deficient diet containing 12 mg iron/kg and performed climbing exercise (5 min × 6 sets/day, 3 days/week) for 3 weeks. The rats were divided into a group fed a post-exercise meal early after exercise (E) or a group fed the meal 4 h after exercise (L). A single bout of exercise performed after the 3-week training period increased the bone marrow ALAD activity, plasma iron concentration, and transferrin saturation. Although the plasma iron concentration and transferrin saturation were lower in the E group than the L group after a single bout of exercise, the basal hematocrit, hemoglobin, and TIBC after 3 weeks did not differ between the groups. Therefore, resistance exercise increases the bone marrow ALAD activity, while the post-exercise meal timing has no effect on the hemoglobin concentration in iron-deficient rats.

[Condition of erythron in newbord rats with disturbed sensorimotor reflexes]

Early adaptation issues of newborn rats of Wistar population and August line were examined. Absence of the connection between the condition of a female during the pregnancy and the birth, and newborn rats in early postnatal period was revealed.

A multibiomarker approach in the clam Ruditapes decussatus to assess the impact of pollution in the Ria Formosa lagoon, South Coast of Portugal

The Ria Formosa lagoon is an ecosystem whose water quality reflects the anthropogenic influence upon the surrounding areas. In this lagoon, the clam Ruditapes decussatus has a great economical importance and has been widely used as a biomonitor. A multibiomarker approach (δ-aminolevulinic acid dehydratase, metallothionein, lipid peroxidation, acetylcholinesterase, alkali-labile phosphates, DNA damage) was applied to assess the environmental quality of this ecosystem and the accumulation of contaminants and their potential adverse effects on clams. Clams were sampled in different shellfish beds in the period between July 2007 and December 2008 and abiotic parameters (temperature, salinity, pH and dissolved oxygen of seawater and organic matter in the sediment), condition index, metals (Cd, Cu, Zn, Ni, Pb), TBTs and PAHs concentrations were measured in clam tissues. Data was integrated using Principal Component Analyses and biomarker indices: IBR (Integrated Biomarker Response) and HSI (Health Status Index). This multibiomarker approach enabled discrimination of a time and space trend between sites with different degrees of anthropogenic contamination, identifying one of them (site 2) as the most stressful and summer months as the most critical period for clams due to an increase of environmental stress (anthropogenic pressure along with extreme environmental conditions, e.g. temperature, dissolved oxygen, organic matter in the sediments, etc). The selected biomarkers provided an integrated response to assess the environmental quality of the system, proving to be a useful approach when complex mixtures of contaminants occur.

Blood Pb and δ-ALAD inhibition in cattle and sheep from a Pb-polluted mining area

The effects of Pb pollution on cattle and sheep raised in an ancient mining area were studied through the use of blood Pb (PbB) levels and δ-aminolevulinic acid dehydratase (δ-ALAD) activity. Lead levels in livestock blood from the mining area (n=110) were significantly elevated when compared to the controls (n=79). In 91.4% of cattle (n=58) and 13.5% of sheep (n=52) sampled in the mining area, PbB levels corresponded to subclinical exposure (6-35 μg/dl). Two young cattle (<2 years) from the mining area (n=5) had PbB levels indicative of clinical poisoning (>35 μg/dl). Elevated PbB was also accompanied by δ-ALAD activity inhibition in blood, which confirms that measurable effects of Pb poisoning were taking place. Observed PbB levels suggest that a potential risk to human consumers of beef from the Pb polluted areas may also exist, as has been shown previously for game meat from the same mining area.

Assessment of essential and nonessential metals and different metal exposure biomarkers in the human placenta in a population from the south of Portugal

The general population is exposed to metals as trace amounts of metallic compounds are present in air, water, and food. Information on background exposures and biomarker concentrations of environmental chemicals in the general Portuguese population is limited. Therefore, the purpose of this study was to determine the levels of important nonessential metals with recognized toxicity cadmium (Cd) and lead (Pb) and essential metals copper (Cu), nickel (Ni), chromium (Cr), and zinc (Zn) in placentas of mothers living in south Portugal (Algarve). Due to the difficulty in establishing the effects of chemicals in a complex and variable environment, this study also aimed to examine the response of biomarkers, such as biochemical changes that occurs at subcellular levels in the presence of contaminants. The investigated biomarkers in placentas indicative of metal exposure or damage included the metallothioneins (MT), delta-aminolevulinic acid dehydratase (ALAD) (specific for Pb), and lipid peroxidation (LPO) as an index of oxidative stress damage. Moreover, HJ-BIPLOT was applied in order to identify and categorize mothers vulnerable to environmental contamination in this region. Metal concentrations in the placenta were not excessive but within the range found in most European studies. In general, the biomarkers MT and LPO were positively correlated with metal levels, while with ALAD the opposite occurred, indicating the selected battery of biomarkers were suitable to study the effects of metals on human placenta. Further, the application of multivariate analysis with HJ-BIPLOT showed that most significant factors contributing to maternal and fetal exposures via placenta were dietary and smoking habits.

Characterization of three homoeologous cDNAs encoding chloroplast-targeted aminolevulinic acid dehydratase in common wheat

In the tetrapyrrole biosynthetic pathway of higher plants, 5-aminolevulinic acid (ALA) is metabolized by ALA dehydratase (ALAD). Here, we isolated ALAD1 cDNA from common wheat (Triticum aestivum L.) and its diploid progenitors, and produced transgenic tobacco plants expressing the wheat ALAD1 gene. The ALAD1 genes were highly conserved among wheat relatives, and three homoeologous loci of wheat ALAD1 (TaALAD1) were equally transcribed in common wheat. A transient expression assay of a TaALAD1-GFP (green fluorescent protein) fusion protein suggested that TaALAD1 is localized in chloroplasts. Overexpression of TaALAD1 in transgenic tobacco resulted in a significant increase in ALAD activity in leaves. Moreover, the transgenic tobacco showed vigorous growth and increased survival rate on medium containing ALA at herbicidal concentrations. These results indicate that wheat ALAD1 has catalytic activity in metabolizing ALA in plastids, and that ectopic expression of TaALAD1 in transgenic plants increases their tolerance to ALA application at high concentrations.

Effect of resistance exercise on iron status in moderately iron-deficient rats

Resistance exercise increases heme synthesis in the bone marrow, but it does not improve the hemoglobin status in severe iron-deficient rats on a diet containing less than 5 mg iron/kg. The current study investigated whether resistance exercise could mitigate hemoglobin status via increasing heme synthesis in moderately iron-deficient rats. Male 4-week-old Sprague-Dawley rats were fed an iron-deficient diet containing 12 mg iron/kg for 3 weeks. The rats were divided into two groups: a sedentary (S) group (n = 7) or an exercise (E) group (n = 7). The rats in the E group performed a climbing exercise (5 min × 6 sets/day, 3 days/week). The aminolevulinic acid dehydratase activity, hematocrit, and hemoglobin tended to be higher in group E than S. The iron content in the flexor hallucis longus muscle was significantly higher in E than S, whereas the content in the liver, spleen, kidney, and heart did not significantly differ between the groups. Therefore, resistance exercise appears to improve hemoglobin via increasing heme synthesis in the bone marrow in moderately iron-deficient rats.

A multi-biomarker approach in cross-transplanted mussels Mytilus galloprovincialis

The present work integrates the active biomonitoring (ABM) concept in mussels Mytilus galloprovincialis from the South coast of Portugal transplanted during 28 days between two sites with different sources of contamination, and vice versa, in order to assess biological effects in these mussels. For that purpose a multibiomarker approach was used. The suit of biomarkers indicative of metal contamination were metallothioneins (MT) and the enzyme δ-aminolevulinic acid dehydratase (ALAD), for organic contamination mixed function oxidase system (MFO), glutathione-S-transferase (GST) and acetylcholinesterase (AChE), as oxidative stress biomarkers superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and lipid peroxidation (LPO). These biomarkers were used to determine an index to evaluate the stress levels in these two sites. Site A is strongly influenced by metallic contamination, with higher Cu, Cr and Pb in M. galloprovincialis, as well as higher MT levels, antioxidant enzymes activities and LPO concentrations, and lower ALAD activity. In site B organic compounds (PAHs) are prevalent and native mussels show higher activities of the MFO system components and GST. Transplanted mussels had significant alterations in some biomarkers that reflect the type of contaminants present in each site, which demonstrates the primary role of the environment in determining the physiological characteristics of resident mussels. Therefore the application of ABM using a battery of biomarkers turns out to be a useful approach in sites where usually complex mixtures of contaminants occurs. In this study the biomarkers that better differentiate the impact of different contaminants at each site were MT, CYP450, SOD and CAT.

δ-Aminolevulinic acid dehydratase single nucleotide polymorphism 2 and peptide transporter 2*2 haplotype may differentially mediate lead exposure in male children

Child low-level lead (Pb) exposure is an unresolved public health problem and an unaddressed child health disparity. Particularly in cases of low-level exposure, source removal can be impossible to accomplish, and the only practical strategy for reducing risk may be primary prevention. Genetic biomarkers of increased neurotoxic risk could help to identify small subgroups of children for early intervention. Previous studies have suggested that, by way of a distinct mechanism, δ-aminolevulinic acid dehydratase single nucleotide polymorphism 2 (ALAD(2)) and/or peptide transporter 2*2 haplotype (hPEPT2*2) increase Pb blood burden in children. Studies have not yet examined whether sex mediates the effects of genotype on blood Pb burden. Also, previous studies have not included blood iron (Fe) level in their analyses. Blood and cheek cell samples were obtained from 306 minority children, ages 5.1 to 12.9 years. (208)Pb and (56)Fe levels were determined with inductively coupled plasma-mass spectrometry. General linear model analyses were used to examine differences in Pb blood burden by genotype and sex while controlling for blood Fe level. The sample geometric mean Pb level was 2.75 μg/dl. Pb blood burden was differentially higher in ALAD(2) heterozygous boys and hPEPT2*2 homozygous boys. These results suggest that the effect of ALAD(2) and hPEPT2*2 on Pb blood burden may be sexually dimorphic. ALAD(2) and hPEPT2*2 may be novel biomarkers of health and mental health risks in male children exposed to low levels of Pb.

Benchmark dose approach for low-level lead induced haematogenesis inhibition and associations of childhood intelligences with ALAD activity and ALA levels

Lead (Pb) levels, delta-aminolevulinic acid dehydratase (ALAD) activities, zinc protoporphyrin (ZPP) levels in blood, and urinary delta-aminolevulinic acid (ALA) and coproporphyrin (CP) concentrations were measured for 318 environmental Pb exposed children recruited from an area of southeast China. The mean of blood lead (PbB) levels was 75.0μg/L among all subjects. Benchmark dose (BMD) method was conducted to present a lower PbB BMD (lower bound of BMD) of 32.4μg/L (22.7) based on ALAD activity than those based on the other three haematological indices, corresponding to a benchmark response of 1%. Childhood intelligence degrees were not associated significantly with ALAD activities or ALA levels. It was concluded that blood ALAD activity is a sensitive indicator of early haematological damage due to low-level Pb exposures for children.

Delayed biochemical changes induced by mercury intoxication are prevented by zinc pre-exposure

This work evaluated the delayed effects of mercury and the effectiveness of zinc in preventing such effects. Pups were pre-treated with 1 daily dose of ZnCl(2) (27 mg/kg/day, by subcutaneous injections) from 3rd to 7th postnatal day and received 1 daily dose of 5 mg/kg of HgCl(2), for 5 subsequent days (8-12 days old). Animals were euthanized 21 days after the end of Hg-exposure. Porphobilinogen-synthase activity as well as zinc and mercury contents was determined in the liver and kidneys. Alanine aminotransferase, aspartate aminotransferase and lactic dehydrogenase activities as well as urea, creatinine and glucose levels were analyzed in plasma or serum. Some animals were considered more sensitive to mercury, since they did not recover the body weight gain and presented an increase of renal and hepatic mercury content, urea and creatinine levels; a decrease in renal porphobilinogen-synthase and alanine aminotransferase activities, as well as a decrease in the liver and an increase in kidney weights. Some animals were considered less sensitive to mercury because they recovered the body weight and presented no biochemical alterations in spite of mercury in the tissues. Zinc prevents partially or totally the alterations caused by mercury even those that persisted for a long time after the end of exposure. These findings suggest that there is difference among the animals regarding the sensitivity to mercury.

Acute exposure to diphenyl ditelluride causes oxidative damage in rat lungs

The present study evaluated the effect of acute exposure to diphenyl ditelluride [(PhTe)(2)] on oxidative status in lungs of rats. Rats were exposed to a single subcutaneous application of (PhTe)(2) at the doses of 0.3, 0.6, 0.9 μmol/kg or vehicle. After 72 h of exposure to (PhTe)(2), biochemical parameters of oxidative stress were carried out in lungs of rats. The lungs of rats exposed to (PhTe)(2) showed an increase in the levels of lipid peroxidation, reactive species and non-protein thiol. Alterations in superoxide dismutase activity were observed at all tested doses. (PhTe)(2) caused an increase in catalase activity and a reduction in ascorbic acid levels at the dose of 0.9 μmol/kg. The oxidative damage was more pronounced in animals treated with the highest dose of (PhTe)(2). Thus, this study demonstrated that acute exposure to (PhTe)(2) induced oxidative damage and an adaptive response of antioxidants in pulmonary tissue of rats.

Source and impact of lead contamination on δ-aminolevulinic acid dehydratase activity in several marine bivalve species along the Gulf of Cadiz

Coastal areas and estuaries are particularly sensitive to metal contamination from anthropogenic sources and in the last few decades the study of space-time distribution and variation of metals has been extensively researched. The Gulf of Cadiz is no exception, with several rivers draining one of the largest concentrations of sulphide deposits in the world, the Iberian Pyrite Belt (IPB). Of these rivers, the Guadiana, one of the most important in the Iberian Peninsula, together with smaller rivers like the Tinto and Odiel, delivers a very high metal load to the adjacent coastal areas. The purpose of this work was to study the source and impact of lead (Pb) drained from historical or active mining areas in the IPB on the activity of a Pb inhibited enzyme (δ-aminolevulinic acid dehydratase, ALAD) in several bivalve species along the Gulf of Cadiz. Seven marine species (Chamelea gallina, Mactra corallina, Donax trunculus, Cerastoderma edule, Mytilus galloprovincialis, Scrobicularia plana and Crassostrea angulata) were collected at 12 sites from Mazagón, near the mouth of the rivers Tinto and Odiel (Spain), to Cacela Velha (Ria Formosa lagoon system, Portugal). Lead concentrations, ALAD activity and lead isotope ratios ((206)Pb/(204)Pb, (207)Pb/(204)Pb and (208)Pb/(204)Pb) were determined in the whole soft tissues. The highest Pb concentrations were determined in S. plana (3.50±1.09 μg g(-1) Pb d.w.) and D. trunculus (1.95±0.10 μg g(-1) Pb d.w.), while M. galloprovincialis and C. angulata showed the lowest Pb levels (<0.38 μg g(-1) Pb d.w.). In general, ALAD activity is negatively correlated with total Pb concentration. However this relationship is species dependent (e.g. linear for C. gallina ALAD=-0.36[Pb]+0.79; r=0.837; or exponential for M. galloprovincialis ALAD=2.48e(-8.3[Pb]); r=0.911). This indicates that ALAD activity has considerable potential as a biomarker of Pb and moreover, in marine bivalve species with different feeding habits. Lead isotope data showed significant seasonal and spatial changes in bivalve isotopic composition reflecting seasonal and geographic differences in bioaccumulation. Within the study area, Pb can be modelled as a mixing between geogenic Pb and mine-related, discharges of Pb from the IPB. For some sites at the mouth of the Guadiana River, the bivalves show contamination from other anthropogenic sources, such as leaded boat/aviation fuel and/or leaded paint. Finally, the study demonstrates convincingly the need to consider species-specific variation when using bivalve ALAD activity as a biomarker for Pb.

Therapeutic efficiency of succimer used with calcium and ascorbic acid in the treatment of mild lead-poisoning

The aim of this study was to explore therapeutic efficiency of succimer used with calcium and ascorbic acid in the treatment of mildly lead-poisoned mice and preschool children. Mice were exposed to lead by drinking water, and then treated with saline solution, 50mg/kg body weight (b.w.) succimer, 100mg/kg b.w. succimer, or 50mg/kg b.w. succimer plus calcium and ascorbic acid by gavage. Seventy-two children aged 48-72 months were randomly assigned into combined treatment or nutritional intervention group. Lead levels in blood and bone were analyzed by atomic absorption spectrophotometry. Activities of aminolevulinic acid dehydratase (ALAD) in blood were determined by colorimetric method. Results of animal experiment showed that succimer used alone could reduce lead levels in blood and bone and reverse activities of ALAD in blood, however, a better therapeutic efficiency in mobilizing bone lead could be achieved by succimer used with calcium and ascorbic acid. Findings from the clinical study showed that reduction of blood lead levels (BLLs) between the end and initiation of therapy in the combined treatment group was significantly greater than that in the nutritional intervention group. Percentage of children with BLLs less than 10μg/dL at the end of therapy and the eighth week after therapy in the combined treatment group was significantly higher than that in the nutritional intervention group. In conclusion, combined use of succimer with calcium and ascorbic acid seemed to be a choice in the treatment of mildly lead poisoned children.

delta-Aminolevulinic acid dehydratase of Haloarcula argentinensis isolated from Tuz Lake in Turkey

The delta-aminolevulinic acid dehydratase (ALAD) enzyme of a novel record for Turkish microbial flora was studied. The isolate I-113 was obtained from Tuz Lake in Turkey and identified as Haloarcula argentinensis. The ALAD enzyme of the isolate was assayed in order to determine its requirements and to be used as biomarker for lead pollution in it's ambient. In enzymic studies, the effects of various metals (Cd, Co, Mg, Mn, Ni, Pb, and Zn), pH (3-11), temperatures (25-55 degrees C), and salinity (15-25%) conditions have been examined. The data obtained from the studies were analyzed statistically by using Kruskal-Wallis, Mann-Whitney, correlation, regression, variance analysis, and significance tests were performed by using SPSS 10.0 for Windows. Although its optimum pH was determined as 7, it was still active at pH 3-11. The optimal temperature for the enzyme was observed to be 30 degrees C. Mn and Pb inhibited its activity significantly (p < 0.05) while Zn increased it slightly. The ALAD enzyme in H. argentinensis could be used as a biomarker for Pb contamination.

ALA-D and ALA-D reactivated as biomarkers of lead contamination in the fish Prochilodus lineatus

ALA-D activity and lead concentrations were measured in blood and liver tissues of the fish Prochilodus lineatus, collected from three locations along the coast of the La Plata River, Argentina. Two of them, Berazategui and Berisso, were located nearby the main ducts that discharge the urban and domestic waste disposal from Buenos Aires and La Plata cities, respectively, while the third station (Atalaya) was free of sewage discharges. For both tissues, the levels of lead in fish from Berazategui and Berisso were higher than those found in the samples from Atalaya. For blood, but not for liver, a significant negative correlation was found between ALA-activity and tissue levels of lead considering all the data. However, no good correlations were observed at each location. Therefore, an enzyme reactivation technique was optimized. The blood enzyme, but not the liver one, could be effectively reactivated with zinc (Zn(II)). The values of the reactivated ALA-D in samples from Berazategui and Berisso, but not from Atalaya, were significantly higher than the original values, indicating that the enzyme was actually inhibited. In addition, the reactivation index showed significant correlations with the blood lead levels. It is proposed that the reactivation index, rather than the ALA-D activity, may reflect better the extent of lead contamination, especially for field monitoring programs where many confounding factors may affect the biomarker response.

Modification by ALAD of the association between blood lead and blood pressure in the U.S. population: results from the Third National Health and Nutrition Examination Survey

BACKGROUND

Environmental lead exposure has been found to be associated with an increased risk of hypertension. Individuals vary greatly in susceptibility to lead toxicity, and genetic susceptibility has often been cited as the probable cause for such variation.

OBJECTIVE

The main objective is to determine the role of the aminolevulinic acid dehydratase (ALAD) gene, which encodes the main carrier protein of lead in blood, in the association between lead exposure and blood pressure (BP) and hypertension in the U.S. population.

METHODS

We analyzed data from individuals >or= 17 years of age who participated in the Third National Health and Nutrition Examination Survey for whom DNA was available (n = 6,016). Multivariable logistic and linear regressions stratified by race/ethnicity were used to examine whether hypertension and BP were associated with ALAD and blood lead levels (BLL).

RESULTS

BLL was associated with systolic BP in non-Hispanic whites and with hypertension and systolic and diastolic BP in non-Hispanic blacks. BLL was not associated with BP outcomes in Mexican Americans. Non-Hispanic white ALAD2 carriers in the highest BLL quartile (3.852.9 microg/dL) had a significantly higher adjusted prevalence odds ratio for hypertension compared with ALAD1 homozygous individuals. We also found a significant interaction between lead concentration and the ALAD2 allele in non-Hispanic whites and non-Hispanic blacks in relation to systolic BP.

CONCLUSIONS

BLL may be an important risk factor for hypertension and increased systolic and diastolic BP. These associations may be modified by ALAD genotype.

Diphenyl diselenide protects against glycerol-induced renal damage in rats

In this study we evaluated the effect of diphenyl diselenide (PhSe)(2) on glycerol-induced acute renal failure in rats. Rats were pre-treated by gavage every day with (PhSe)(2 )(7.14 mg kg(-1)) for 7 days. On the eighth day, rats received an intramuscular injection of glycerol (8 mL kg(-1)). Twenty-four hours afterwards, rats were euthanized and the levels of urea and creatinine were measured in plasma. Catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), delta-aminolevulinate dehydratase (delta-ALA-D) and Na(+), K(+)-ATPase activities and ascorbic acid levels were evaluated in renal homogenates. Histopathological evaluations were also performed. The results demonstrated that (PhSe)(2) was able to protect against the increase in urea and creatinine levels and histological alterations in kidney induced by glycerol. (PhSe)(2) protected against the inhibition in delta-ALA-D, CAT and GPx activities and the reduction in ascorbic acid levels induced by glycerol in kidneys of rats. In conclusion, the present results indicate that (PhSe)(2) was effective in protecting against acute renal failure induced by glycerol.

Allosteric inhibition of human porphobilinogen synthase

Porphobilinogen synthase (PBGS) catalyzes the first common step in tetrapyrrole (e.g. heme, chlorophyll) biosynthesis. Human PBGS exists as an equilibrium of high activity octamers, low activity hexamers, and alternate dimer configurations that dictate the stoichiometry and architecture of further assembly. It is posited that small molecules can be found that inhibit human PBGS activity by stabilizing the hexamer. Such molecules, if present in the environment, could potentiate disease states associated with reduced PBGS activity, such as lead poisoning and ALAD porphyria, the latter of which is associated with human PBGS variants whose quaternary structure equilibrium is shifted toward the hexamer (Jaffe, E. K., and Stith, L. (2007) Am. J. Hum. Genet. 80, 329-337). Hexamer-stabilizing inhibitors of human PBGS were identified using in silico prescreening (docking) of approximately 111,000 structures to a hexamer-specific surface cavity of a human PBGS crystal structure. Seventy-seven compounds were evaluated in vitro; three provided 90-100% conversion of octamer to hexamer in a native PAGE mobility shift assay. Based on chemical purity, two (ML-3A9 and ML-3H2) were subjected to further evaluation of their effect on the quaternary structure equilibrium and enzymatic activity. Naturally occurring ALAD porphyria-associated human PBGS variants are shown to have an increased susceptibility to inhibition by both ML-3A9 and ML-3H2. ML-3H2 is a structural analog of amebicidal drugs, which have porphyria-like side effects. Data support the hypothesis that human PBGS hexamer stabilization may explain these side effects. The current work identifies allosteric ligands of human PBGS and, thus, identifies human PBGS as a medically relevant allosteric enzyme.

Biomarkers of exposure to metal contamination and lipid peroxidation in the benthic fish Cathorops spixii from two estuaries in South America, Brazil

Biomarkers as lipid peroxidation, metallothionein and delta-aminolevulinic acid dehydratase were determined in Cathorops spixii to compare the biological responses of this fish from estuaries with distinct anthropogenic influence. Three areas were selected in two estuaries in accordance with the levels of contamination for the polluted (Santos/São Vicente) and with the hydrodynamic characteristics for the non-polluted (Cananéia) estuary. Water characteristics and mercury levels in C. spixii confirmed a high human influence in the polluted system. In general, the biomarkers showed differences between the estuaries, suggesting disturbances in the specific cell mechanisms due to the presence of multiple xenobiotics in the contaminated system. Therefore, these biomarkers are recommended to promote more accurate information about the exposure to pollutants. Additionally, the study of the effect of the multiple xenobiotics on resident species such as the benthic fish C. spixii can favor a better assessment of the environmental quality of these systems.

Phylogenetic analysis of ALAD and MGP genes related to lead toxicity

Experimental studies in our laboratory have established the role of delta-aminolevulinic acid dehydratase (ALAD) and matrix gamma-carboxyglutamic acid (MGP) gene polymorphisms in the etiology of lead toxicity. Polymorphisms in these genes influenced the levels of lead in subjects exposed to this metal. In extension to our studies, we aimed to investigate the possible role of these proteins in evolution by studying the phylogenetic relationship and divergence of ALAD and MGP genes using computational phylogenetic methods. The human ALAD and MGP protein sequences from various species were retrieved from Swiss-Prot database and were compared using Basic Local Alignment Search Tool. Multiple sequence alignment was carried out using ClustalW with defaults, and phylogenetic trees for both the genes were built using neighbor-joining method as in Mega software. Our study indicated that ALAD is a highly conserved protein with the same metal binding site distributed in all the phyla (from archaea to chordates). Phylogenetic analysis of MGP gene revealed that it had an important role in the evolution of endogenous skeleton in contrast to exoskeleton of insects. Occurrence of these genes in evolution with conserved metal binding sites strengthens the role of ALAD and MGP genes in regulating heme biosynthesis and mineralization, respectively, in evolution and helps in better understanding of lead poisoning.

Toxicological investigation and antinociceptive property of potassium thiophene-3-trifluoroborate

The aim of the present study was to evaluate pharmacological and toxicological properties of potassium thiophene-3-trifluoroborate (RBF(3)K). The acute effect of RBF(3)K was evaluated on mice. To this end, mice received a single dose of RBF(3)K (25, 50, and 100 mg/kg, by oral route, p.o.) and after 72 hrs, blood, liver, and kidney samples were collected. delta-Aminolevulinate dehydratase, catalase and glutathione-S-transferase activities, thiobarbituric acid-reactive substances and vitamin C levels, as well as plasma aspartate and alanine aminotransferase activities and creatinine levels were determined. Hepatic and renal lipid peroxidation levels in treated mice did not differ from those in control mice. No significant differences between treated and control mice were detected in hepatic and renal delta-aminolevulinate dehydratase activity. Aspartate and alanine aminotransferase activities as well as urea and creatinine levels were similar among the groups. In contrast, results obtained from in vivo experiments revealed that RBF(3)K, orally administered, reduced peritoneovisceral pain induced by acetic acid administered i.p. Doses of 1, 5, 10, 25, 50, and 100 mg/kg of RBF(3)K were assessed in the antinociceptive investigation and the effect was significantly different than control groups from 5 mg/kg. It was observed that alpha(2-)adrenergic and serotonergic, but not opioidergic, receptors appear to be involved in orally administered RBF(3)K. Mice treated with RBF(3)K did not reveal any motor impairment in the open field. This is a promising compound for more detailed pharmacological studies involving organotrifluoroborate compounds.

Relationships between physiology, tissue contaminants, and biomarker responses in Atlantic cod (Gadus morhua L.)

It is generally assumed that there should be some relationship between tissue residues of contaminants and related biomarker responses in the same individual, with a possible additional modulation through physiological processes. The main basis for such assumptions originated from experimental studies, but it has been less easy to detect and quantify any such relationships in field-collected material. The aim of the current study was to clarify whether the responses of selected biomarkers (cytochrome P-4501A [CYP1A], delta-aminolevulinic acid dehydratase [ALA-D], metallothionein [MT]) could be correlated with physiological parameters and/or contaminant levels. Atlantic cod (Gadus morhua L.) were sampled over a decade at a number of locations along the Norwegian coast. The locations included both polluted and reference areas. In addition to contaminant-related responses (biomarkers), physiological characteristics were registered for each individual and the contaminant load determined. There were clear relationships between responses in all three biomarkers and tissue contaminants, but additional factors such as age or size and liver lipid or liver somatic index also contributed in multiple-regression models. The results indicated that responses in all three biomarkers reflected relevant, contaminant-related processes in the cod even though none of them provided a simple separation between polluted and pristine locations.

Involvement of non-enzymatic antioxidant defenses in the protective effect of diphenyl diselenide on testicular damage induced by cadmium in mice

The involvement of non-enzymatic antioxidant defenses in the protective effect of diphenyl diselenide (PhSe)(2) on testicular damage caused by cadmium in mice was investigated. Mice received a single dose of CdCl(2) (5mg/kg, intraperitoneally). Thirty minutes after the CdCl(2) injection, they received a single oral dose of (PhSe)(2) (400micromol/kg). Twenty-four hours after CdCl(2) administration, blood samples were collected and mice were killed and had their testes dissected. Parameters in plasma (aspartate (AST) and alanine (ALT) aminotransferases and lactato dehydrogenase (LDH) activities as well as creatinine levels) were determined. The activity of delta-aminolevulinate dehydratase (delta-ALA-D), the levels of thiobarbituric acid-reactive substances (TBARS), ascorbic acid and nonprotein thiols (NPSH) and histological analysis were determined in collected samples. Results demonstrated that (PhSe)(2) protected against toxicity induced by CdCl(2) on delta-ALA-D activity, ascorbic acid and NPSH levels. (PhSe)(2) protected against the increase in plasma AST, ALT and LDH activities caused by CdCl(2). Testes of mice exposed to CdCl(2) showed marked histopathological alterations that were ameliorated by administration of (PhSe)(2). (PhSe)(2) protected against toxicity induced by CdCl(2) in testes of mice. Ascorbic acid and NPSH, non-enzymatic antioxidant defenses, are involved in the protective effect of (PhSe)(2) against testicular damage caused by CdCl(2) in mice.