Combined efficacies of lipoic acid and 2,3-dimercaptosuccinic acid against lead-induced lipid peroxidation in rat liver

Oxidative stress with subsequent lipid peroxidation has been postulated as one mechanism for lead toxicity. Hence in assessing the protective effects of lipoic acid (LA) and meso 2,3-dimercaptosuccinic acid (DMSA) on lead toxicity, they were tested either separately or in combination for their effects on selected indices of hepatic oxidative stress. Elevated levels of lipid peroxides were accompanied by altered antioxidant defense systems. Lead acetate (Pb - 0.2%) was administered in drinking water for five weeks to induce toxicity. LA (25 mg kg(-1) body wt. day(-1) i.p) and DMSA (20 mg kg(-1) body wt. day(-1) i.p) were administered individually and also in combination during the sixth week. Lead damage to the liver was evident in the decreases in hepatic enzymes alanine transaminase (-38%), aspartate transaminase (-42%) and alkaline phosphatase (-43%); increases in lipid peroxidation (+38%); decreases in the antioxidant enzymes catalase (-45%), superoxide dismutase (-40%), glutathione peroxidase (-46%) and decreases in glutathione (-43%) and decreases in glutathione metabolizing enzymes, glutathione reductase (-59%), glucose-6-phosphate dehydrogenase (-27%) and glutathione-S-transferase (-42%). In combination LA and DMSA completely ameliorated the lead induced oxidative damage. Either compound alone was however only partially protective against lead damage.     

New Methoxyflavone from Casimiroa sapota and the Biological Activities of Its Leaves Extract against Lead Acetate Induced Hepatotoxicity in Rats

Flavonoids are agents with strong antioxidant properties and ameliorate many diseases associated with oxidative stress. Leaves of Casimiroa sapota were investigated for components and antioxidant/anti‐inflammatory activities against lead acetate ((AcO)₂Pb) induced hepatotoxicity in rats. Three groups of male albino rats were administrated orally with vehicle or C. sapota (100 and 200 mg/kg b.w/day) for 28 days; other group was injected with sub‐acute dose (100 mg/kg b.w/day) of (AcO)₂Pb. Three protective groups were injected with (AcO)₂Pb (100 mg/kg b.w/day) for 7 days at day 22 after treatment with either C. sapota (100 or 200 mg/kg b.w/day) or silymarin (SILY) for 28 days. We isolated and identified, from C. sapota, a new compound for the 1st time in nature; 5,6,2′,3′‐tetramethoxyflavone in addition to the rare compound 5,6,3′‐trimethoxyflavone (second report of isolation from nature) and the known compound 5,6,2′,3′,4′‐pentamethoxyflavone. There is an improvement in all hemato‐biochemical parameters, antioxidant defense system and anti‐inflammatory cytokines of protective groups, which received C. sapota in dose dependent manner. The percentage of changes in all parameters measured in (AcO)₂Pb groups that received vehicle, CS100, CS200 or SILY were 109.2, 37.3, 12.5%, and 1.2% compared with the healthy control group. The C. sapota groups confer a better antioxidant activity by preventing oxidative stress and inflammation in (AcO)₂Pb treated rats. The compounds isolated are responsible at least in part for the observed protective effects.     

Lead-induced oxidative stress and role of antioxidant defense in wheat ( Triticum aestivum L.)

The aim of this study was to investigate soil lead pollution on biochemical properties and gene expression pattern of antioxidant enzymes in three wheat cultivars (Morvarid, Gonbad and Tirgan) at flag leaf sheath swollen stage. Lead (Pb(NO3)2) was used at four different concentrations (0, 15, 30 and 45 mg/kg of soil). The leaf and roots samples were taken at late-booting stage (Zadoks code, GS: 45). The results showed that lead heavy metal toxicity increased the expression of some genes and the activity of key enzymes of the antioxidant defense system in wheat. Moreover, the cell oxidation levels (MDA, LOX) enhanced under lead stress conditions. The relative gene expression and activity of antioxidant enzymes (CAT, SOD, GPX and APX) increased significantly in the both leaves and root tissues under lead stress conditions. The level of gene expression and enzymatic activity were higher in the root than the leaf tissue. There was no significant difference among cultivars in each of lead concentrations but Morvarid and Tirgan cultivars had more tolerance to toxic concentrations of lead when compared to Gonbad cultivar.     

Protective effect of green tea on lead-induced oxidative damage in rat’s blood and brain tissue homogenates

Recent studies have shown that lead (Pb) could disrupt tissue prooxidant/antioxidant balance which lead to physiological dysfunction. Natural antioxidants are particularly useful in such situation. Current study was designed to investigate efficacy of green tea extract (GTE), on oxidative status in brain tissue and blood caused by chronic oral Pb administration in rats. Four groups of adult male rats (each 15 rats) were utilized: control group; GTE-group (oral 1.5% w/v GTE for 6 weeks); Pb-group (oral 0.4% lead acetate for 6 weeks), and Pb+GTE-group (1.5% GTE and 0.4% lead acetate for 6 weeks). Levels of prooxidant/antioxidant parameters [lipid peroxides (LPO), nitric oxides (NO), total antioxidant capacity (TAC), glutathione (GSH), glutathione-S-transferase (GST), superoxide dismutase (SOD)] in plasma, erythrocytes, and brain tissue homogenate were measured using colorimetric methods. Pb concentrations in whole blood and brain tissue homogenate were measured by atomic absorption. In Pb-group, levels of LPO were higher while NO and GSH were lower in plasma, erythrocytes, and brain tissue than controls. TAC in plasma, SOD in erythrocytes, and GST in brain tissue homogenate were lower in Pb-group versus control. GTE co-administrated with Pb-reduced Pb contents, increased antioxidant status than Pb-group. In erythrocytes, Pb correlated positively with LPO and negatively with NO, GSH, SOD, and Hb. In brain tissue homogenate, Pb correlated positively with LPO and negatively with GSH. This study suggests that lead induce toxicity by interfering balance between prooxidant/antioxidant. Treatment of rats with GTE combined with Pb enhances antioxidant/ detoxification system which reduced oxidative stress. These observations suggest that GTE is a potential complementary agent in treatment of chronic lead intoxication.     

N-acetylcysteine exposure on lead-induced lipid peroxidative damage and oxidative defense system in brain regions of rats

Lead (Pb) is known to disrupt the pro-oxidant/antioxidant balance of tissues, which leads to biochemical and physiological dysfunction. Oxidative stress is considered a possible molecular mechanism involved in Pb neurotoxicity. Considering the vulnerability of the brain to oxidative stress under Pb neurotoxicity, this study investigated the effects of exposure of the thiol antioxidant N-acetylcysteine (NAC) on lead-induced oxidative damage and lipid peroxidation in brain regions of the rat. Wister strain rats were exposed to lead in the form of lead acetate (20 mg/kg body wt/d) for a period of 2 wk and the effects of NAC on lead-induced neurotoxicity in rat brain regions were assessed by postadministration of NAC (160 mg/kg body wt/d) for a period of 3 wk. The lipid peroxidation byproduct, malondialdehyde (MDA) increased following lead exposure in both of the regions, and the antioxidant capacities of the cell in terms of the activity of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) was diminished. Following NAC treatment, lead-induced lipid peroxidation decreased and antioxidant enzyme activities improved, with CAT showing enhancement in the cerebral region only and SOD showing enhancements in the cerebellar region. Our result suggests that thiol-antioxidant supplementation following Pb exposure might enhance the reductive status of brain regions by arresting the lipid peroxidative damage in brain regions.     

Selenium and vitamin E ameliorate lead acetate-induced hepatotoxicity in rats via suppression of oxidative stress,mRNA of heat shock proteins,and NF-kB production

BackgroundLead exposure results in a terrible rise in heat shock protein levels.ObjectiveThis research was conducted to look at the effects of lead poisoning on heat shock response, oxidative stress, and inflammatory markers in albino rats, as well as the power of selenium and vitamin E to resist lead toxic effects.MethodsEight groups of albino rats are used. Each group contained six rats where the first group represented the negative control, and the other groups were treated with olive oil, vitamin E, selenium, lead, (vitamin E + lead), (selenium + lead), and (vitamin E + selenium + lead). All the treatments lasted for 28 days. Then, the mRNA expression of interested heat shock proteins (HSP90, HSP70, and HSP60) was assessed. For oxidative stress disruption, we investigated nitric oxide (NO) and malondialdehyde (MDA) content, and enzymatic and non-enzymatic antioxidants activity respectively in rat livers.Resultsour results revealed the synergetic protective effect of the combination of two antioxidants (vitamin E and selenium) against lead poising. This was clear in regulating HSPs expression, inflammatory markers, glucose, lipid profile, liver functions, and antioxidant enzymes more than the treatment with one antioxidant.ConclusionPb is a toxic material that can induce HSPs and inflammatory markers expression. Selenium and vitamin E can give excellent effects in ameliorating Pb toxicity when used together.     

Potential of efficient and resistant plant growth‐promoting rhizobacteria in lead uptake and plant defence stimulation in Lathyrus sativus under lead stress

• The ability of plant growth‐promoting rhizobacteria (PGPR) to enhance Lathyrus sativus tolerance to lead (Pb) stress was investigated.
• Ten consortia formed by mixing four efficient and Pb‐resistant PGPR strains were assessed for their beneficial effect in improving Pb (0.5 mM) uptake and in inducing the host defence system of L. sativus under hydroponic conditions based on various physiological and biochemical parameters.
• Lead stress significantly decreased shoot (SDW) and root (RDW) dry weight, but PGPR inoculation improved both dry weights, with highest increases in SDW and RDW of plants inoculated with I5 (R. leguminosarum (M5) + P. fluorescens (K23) + Luteibacter sp. + Variovorax sp.) and I9 (R. leguminosarum (M5) + Variovorax sp. + Luteibacter sp. + S. meliloti) by 151% and 94%, respectively. Additionally, inoculation significantly enhanced both chlorophyll and soluble sugar content, mainly in I5 inoculated leaves by 238% and 71%, respectively, despite the fact that Pb decreased these parameters. We also found that PGPR inoculation helps to reduce oxidative damage and enhances antioxidant enzyme activity, phenolic compound biosynthesis, carotenoids and proline content. PGPR inoculation increased Pb uptake in L. sativus, with highest increase in shoots of plants inoculated with I5 and I7, and in roots and nodules of plants inoculated with I1. Moreover, PGPR inoculation enhanced mineral homeostasis for Ca, Cu and Zn under Pb stress, mainly in plants inoculated with I1, I5, I7 and I9.
• Results of our study suggest the potential of efficient and Pb‐resistant PGPR in alleviating harmful effects of metal stress via activation of various defence mechanisms and enhancing Pb uptake that promotes tolerance of L. sativus to Pb stress.

     

… -ome sweet -ome

Abstract

Arsenic-induced tissue damage is a major concern to the human population. An impaired antioxidant defense mechanism followed by oxidative stress is the major cause of arsenic-induced toxicity, which can lead to reproductive failure. The present study was carried out to investigate the preventive role of arjunolic acid, a triterpenoid saponin isolated from the bark of Terminalia arjuna, against arsenic-induced testicular damage in mice. Administration of arsenic (in the form of sodium arsenite, NaAsO₂, at a dose of 10 mg/kg body weight) for 2 days significantly decreased the intracellular antioxidant power, the activities of the antioxidant enzymes, as well as the levels of cellular metabolites. In addition, arsenic intoxication enhanced testicular arsenic content, lipid peroxidation, protein carbonylation and the level of glutathione disulfide (GSSG). Exposure to arsenic also caused significant degeneration of the seminiferous tubules with necrosis and defoliation of spermatocytes. Pretreatment with arjunolic acid at a dose of 20 mg/kg body weight for 4 days could prevent the arsenic-induced testicular oxidative stress and injury to the histological structures of the testes. Arjunolic acid had free radical scavenging activity in a cell-free system and antioxidant power in vivo. In summary, the results suggest that the chemopreventive role of arjunolic acid against arsenic-induced testicular toxicity may be due to its intrinsic antioxidant property.     

Effects of isoquinoline alkaloid berberine on lipid peroxidation,antioxidant defense system,and liver damage induced by lead acetate in rats

Objectives: Liver is considered a target organ affected by lead toxicity. Oxidative stress is among the mechanisms involved in liver damage. Here we investigated the effects of the natural alkaloid berberine on oxidative stress and hepatotoxicity induced by lead in rats.

Methods: Animals received an aqueous solution of lead acetate (500?mg Pb/l in the drinking water) and/or daily oral gavage of berberine (50?mg/kg) for 8 weeks. Rats were then weighed and used for the biochemical, molecular, and histological evaluations.

Results: Lead-induced oxidative stress, shown by increasing lipid peroxidation along with a concomitant decrease in hepatic levels of thiol groups, total antioxidant capacity, the activities of superoxide dismutase, catalase, glutathione peroxidase, and glutathione-S-transferase, and reduced versus oxidized glutathione ratio. Berberine corrected all the disturbances in oxidative stress markers induced by lead administration. Berberine also prevented the elevated levels of enzymes (alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase) and the decrease in body weight and albumin. The protective effects of berberine were comparable with silymarin. Furthermore, berberine attenuated liver damage, shown by decreased necrosis and inflammatory cell infiltration.

Discussion: Berberine represents a potential therapeutic option against lead-induced hepatotoxicity through inhibiting lipid peroxidation and enhancing antioxidant defenses.

Conclusion: Berberine exerted protective effects on lead-induced oxidative stress and hepatotoxicity in rats.     

Effect of 24-Epibrassinolide on Antioxidative Defence System Against Lead-Induced Oxidative Stress in The Roots of <Emphasis Type="Italic">Brassica juncea</Emphasis> L. Seedlings

Lead (Pb) toxicity causes oxidative stress by increasing the production of reactive oxygen species. The aim of the present study was to investigate the role of 24-epibrassinolide (24-EBL) on the antioxidant defence system as a response to Pb stress in Brassica juncea L. Surface-sterilized seeds were exposed to Pb ion (0 and 2 mM) toxicity in Petri dishes and subsequently, the seeds were sprayed with either (i) deionized water or (ii) different concentrations (10^–12, 10^–10, and 10^–8 M) of 24-EBL on alternate days. After nine days, the roots of the B. juncea seedlings were harvested to analyze the heavy metal content, root length, hydrogen peroxide level, lipid peroxidation, total protein content and activities of the antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase, peroxidase, glutathione reductase and glutathione-S-transferase). According to our results, the Pb ions accumulated by the B. juncea roots led to oxidative stress by increasing the level of H₂O₂ and malondialdehyde, and thus, increased the activity of the antioxidative enzymes (except for catalase) and the growth and total protein content decreased. Whereas, the 24-EBL treatment to the roots of Pb stressed seedlings was able to alleviate the Pb-induced oxidative stress. Upon the application of 24-EBL, a reduction in Pb accumulation, H₂O₂ and malondialdehyde levels as well as an increased total protein content and activity of antioxidative enzymes detoxifying hydrogen peroxide (catalase, ascorbate peroxidase and peroxidase) were observed. As a result, the stress protective properties of 24-EBL depending on concentration in B. juncea roots were revealed in this study.     

Effects of Cadmium,Chromium and Lead on Growth,Metal Uptake and Antioxidative Capacity in <Emphasis Type="Italic">Typha angustifolia</Emphasis>

This study investigates the modulation of antioxidant defence system of Typha angustifolia after 30 days exposure of 1 mM chromium (Cr), cadmium (Cd), or lead (Pb). T. angustifolia showed high tolerance to heavy metal toxicity with no visual toxic symptom when exposed to metal stress, and Cd/Pb addition also increased plant height and biomass especially in Pb treatment. Along with increased Cr, Cd, and Pb uptake in metal treatments, there was enhanced uptake of plant nutrients including Ca and Fe, and Zn in Pb treatment. A significant increase in malondialdehyde (MDA) content and superoxide dismutase (SOD) and peroxidase (POD) activities were recorded in plants subjected to Cr, Cd, or Pb stress. Furthermore, Pb stress also improved catalase (CAT), ascorbate peroxidase (APX), and glutathione peroxidase (GPX) activities; whereas Cr stress depressed APX and GPX. The results indicate that enzymatic antioxidants and Ca/Fe uptake were important for heavy metal detoxification in T. angustifolia, stimulated antioxidative enzymes, and Ca, Fe, and Zn uptake could partially explain its hyper-Pb tolerance.     

Effects of GA3 on Plant Physiological Properties,Extraction, Subcellular Distribution and Chemical Forms of Pb in Lolium perenne

The effects of growth-promoting hormone gibberellic acid 3 (GA₃) on physiology, Pb phytoextraction, and metal detoxification mechanisms in Lolium perenne were studied. Results showed that addition of GA₃ alone at lower doses (1 or 10 μM) facilitated antioxidant defense of L. perenne under Pb stress, decreased the toxicity of Pb in plant shoot by increasing the proportion of Pb in cell wall, hence significantly enhanced photosynthesis and plant growth, as well as Pb uptake and accumulation in L. perenne (P < 0.05). However, these indicators showed the opposite changes when treated with GA₃ at a higher dose (100 μM). Of the total Pb in plant shoot, 36–51% was associated with cell wall, and 31–40% was soluble fraction, while 41.4–49.7% was NaCl extractable, 24.6–35.4% HAc extractable followed by other fractions. These findings suggest that Pb fixation by pectates and proteins in cell wall and sequestration in vacuole are responsible for Pb detoxification in plant, and the GA₃ at 1 μM appears to be optimal for enhancing Pb phytoextraction by L. perenne from Pb polluted soils.     

Effects of Montmorillonite on Pb Accumulation,Oxidative Stress,and DNA Damage in Tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>) Exposed to Dietary Pb

In order to investigate the effects of montmorillonite (MMT) on reducing dietary lead (Pb) toxicity to tilapia (Oreochromis niloticus), 240 fish were randomly divided into four treatments denominated as follows: control treatment (fed with a basal diet), MMT treatment (fed with a basal diet added with 0.5% MMT), Pb treatment (fed with a basal diet added with 100 mg Pb per kilogram dry weight (dw)), and Pb + MMT treatment (fed with a basal diet added with 100 mg Pb per kilogram dw and 0.5% MMT). Changes in Pb accumulation, oxidative stress, and DNA damage in tilapia were measured after 60 days. DNA damage was assessed using comet assay. The results showed that MMT supplemented in diet significantly reduced Pb accumulation in kidney and blood of tilapia exposed to dietary Pb (P < 0.05). Malondialdehyde level decreased insignificantly while levels of total antioxidant capacity and glutathione (GSH), activities of glutathione peroxidase, and superoxide dismutase increased insignificantly in kidney of tilapia in Pb + MMT treatment as compared to Pb treatment (P > 0.05). Significant decreases in tail length, tail DNA, tail moment, and Olive tail moment of peripheral blood cells in Pb + MMT treatment were observed when compared with Pb treatment (P < 0.05). The results indicated that dietary MMT supplementation could alleviate dietary Pb toxicity to tilapia effectively.     

Protective Effect of Naringenin Against Lead-Induced Oxidative Stress in Rats

Oxidative stress is thought to be involved in lead-induced toxicity. The aim of this study was to investigate the possible protective role of naringenin on lead-induced oxidative stress in the liver and kidney of rats. In the present investigation, lead acetate (500 mg Pb/L) was administered orally for 8 weeks to induce hepatotoxicity and nephrotoxicity. The levels of hepatic and renal markers such as alanine aminotransferase, aspartate aminotransferase, urea, uric acid, and creatinine were significantly (P < 0.05) increased following lead acetate administration. Lead-induced oxidative stress in liver and kidney tissue was indicated by a significant (P < 0.05) increase in the level of maleic dialdehyde and decreased levels of reduced glutathione, superoxide dismutase, catalase, and glutathione peroxidase. Naringenin markedly attenuated lead-induced biochemical alterations in serum, liver, and kidney tissues (P < 0.05). The present study suggests that naringenin shows antioxidant activity and plays a protective role against lead-induced oxidative damage in the liver and kidney of rats.     

Protective Effects of Mangiferin in Subchronic Developmental Lead-Exposed Rats

Lead is a ubiquitous environmental and industrial pollutant. Exposure to excessive amounts of lead is especially harmful to the central nervous systems of infants and young children, and oxidative stress has been reported as a major mechanism of lead-induced toxicity. To evaluate the ameliorative potential of antioxidant mangiferin (MGN) on lead-induced toxicity, Morris water maze test, determination of blood and bone lead concentration, determination of antioxidant status in plasma, as well as observation of ultrastructural changes in the hippocampus were carried out. In the present study, under a transmission electron microscope, ameliorated morphological damages in the hippocampus were observed in MGN-treated groups. Blood and bone lead concentration in MGN-treated groups lowered to some extent (p?<?0.05, p?<?0.01). The activities of antioxidant enzymes, glutathione (GSH) content, and the GSH/oxidized glutathione ratio in MGN-treated groups were increased, respectively. Further studies are needed to establish whether the observed differences were a direct cause of mangiferin on lead-induced toxicity or not. This study might provide clues for the treatment of lead-induced toxicity.     

Antioxidant enzymes activities and bilirubin level in adult rat treated with lead

Lead toxicity is closely related to its accumulation in several tissues and its interference with bioelements, whose role is critical for several biological processes. Recently, oxidative stress has been proposed as a possible mechanism involved in lead toxicity. This study was carried out to investigate the effect of dose-dependent lead exposure on haematological and oxidative stress parameters. Adult male 'Wistar' rats (150-200 g) were divided into three groups: group [Pb 5] and group [Pb 15] received respectively 5 mg Pb(2+) (n=16) and 15 mg Pb(2+)/kg b.w. (n=16) as lead acetate solution i.p. for a period of seven days. Group [T] (n= 16) served as control and received 15 mg Na(+)/kg b.w. as sodium acetate solution i.p. for the same period. All animals were sacrificed 24 h after the last injection. Blood superoxide dismutase (SOD) and blood glutathione peroxidase (GPx) activities and plasma bilirubin level were measured. Liver was quickly excised for the estimation of alteration in lipid peroxidation indices (MDA). Lead exposure induces, in both treated groups, a marked decline in haematocrit and haemoglobin levels (p<0.01) when compared to control. The results show also a significant decrease (p<0.01) in SOD activity, but only in group [Pb 15]. SOD activity did not decrease in group [Pb 5] in comparison with control (p>0.05). However, lead exposure caused a light increase in GPx activity in group [Pb 15], which remains non-significant (p>0.05) compared to control. Group [Pb 5] did not record significant changes in the activity of GPx. Lead exposure for a period of seven days resulted in a significant (p<0.05) increase in bilirubin level in group [Pb 15] compared to control. The bilirubin level from rats of group [Pb 5] did not reach a statistical significance. Changes in liver MDA content in lead-exposed rats from [Pb 5] and [Pb 15] groups did not reach a statistical (p<0.05) significance. It is concluded that lead induces oxidative stress in a dose-dependent manner. No dose-dependent response was observed in blood GPx activity and liver MDA content. These results could be due to the short duration of the treatment.     

Effect of lead on the physiological,biochemical and ultrastructural properties of Leucaena leucocephala

• Heavy metals are characterised by a relatively high density and cause genotoxic, cytotoxic and mutagenic effects on plants, animals and humans. Lead (Pb) is one of the heavy metals that causes toxicity to plants and animals.
• This experiment was conducted using a hydroponic technique to study the effects of Pb(NO₃)₂ on physiological, biochemical and ultrastructural characteristics in Leucaena leucocephala seedlings. Plants were grown in a growth chamber for 21 days in Hoagland’s solution supplemented with 0 (control), 25, 50, 100, 300, 500 and 700 µm Pb(NO₃)₂.
• Shoot heights as well as root lengths decreased significantly in Pb‐treated plants with 300, 500 and 700 µm . In Pb‐treated plants with high Pb concentrations, photosynthesis rate (P_N), stomatal conductance (g_s) and transpiration rate (E) decreased. Total protein and carbohydrate content in Pb‐treated plants with 300, 500 and 700 µm increased significantly in leaves. Moreover, in Pb‐treated plants with 300, 500 and 700 µm Pb(NO₃)₂, mesophyll cells had enlarged chloroplasts with disrupted thylakoid membranes associated with large starch grains. In contrast, Pb treatments with 25, 50 µm and 100 µm were not toxic to the plants. Thick sections of roots of Pb‐treated plants with 300, 500 and 700 µm Pb showed distinct changes in structure of epidermal and cortical cells. Moreover, thin sections of roots of Pb‐treated plants with 300, 500 and 700 µm Pb had thickened walls of xylem cells.
• These results will shed more light in understanding the effects of heavy metal stress on plants.

     

Isolation and Identification of Lead (Pb) Solubilizing Bacteria from Automobile Waste and Its Potential for Recovery of Lead from End of Life Waste Batteries

Abstract

End of life waste Lead (Pb) acid batteries are one of the largest sources of secondary lead production globally. Recycling lead by melting down used batteries is a commercial trade all over the world; but, regrettably, reprocessing lead from end of life batteries is reported for anthropogenic lead exposures causing harsh human health consequence and environmental pollution. The current research intends to isolate and identify Lead (Pb) solubilizing bacteria from automobile waste deposits from Agartala city in Tripura state of India. Scanning Electron Microscope equipped with energy-dispersive X-ray characterization of the grounded lead sample was carried out, and the micrographs demonstrated scattered structures across the matrix. The X-ray diffraction (XRD) spectrum indicates the presence of Lead Oxide (PbO), Lead dioxide (PbO₂), and Lead sulfate (PbSO₄) in the collected samples. A single bacterium viewing observable growth on Pb supplemented plates was isolated and its Pb recovering capability was estimated through ICP AES analysis. Molecular characterization of the bacterium was investigated using 16S rRNA sequencing along with isolated culture was taxonomically grouped as Cupriavidus sp. The genomic DNA sequences were submitted in NCBI GenBank with the accession number MG171197. In the present case of inspection, the ability of the bacterial strain to recover Pb from end life battery waste was carried out in laboratory scale on a shake flask for 20?days. The experiment conducted under optimum bioleaching parameters with initial pH 6, 5% w/v of microbial culture, 2% pulp density and 2?g/100?mL dextrose concentration at 30?°C temperature with a speed of 200?RPM resulted in 67% Pb recovery from the battery sample. This investigation emphasizes the significance of Pb recycling ability of native bacterial isolate for efficient Pb bio-recovery from end of life waste batteries.     

Improvement of element uptake and antioxidative defense in Brassica napus under lead stress by application of hydrogen sulfide

Heavy metal pollution is one of the major constraints in oilseed rape (Brassica napus L.) production. In this study, protective role of hydrogen sulfide (H₂S) on plant growth under lead (Pb) stress was studied in B. napus. Plants were grown hydroponically in greenhouse conditions under three levels (0, 100, and 400 μM) of Pb and three levels (0, 100 and 200 μM) of H₂S donor sodium hydrosulfide. Outcomes demonstrated that Pb stress significantly reduced the plant biomass, leaf chlorophyll contents, nutrients uptake in the leaves and roots of B. napus plants. Exogenous application of H₂S significantly improved the plant biomass, chlorophyll contents and concentration of macro- and micronutrients in the leaves and roots of B. napus plants under Pb-toxicity conditions. The data indicated that application of Pb alone significantly increased the reactive oxygen species (ROS) as well as malondialdehyde (MDA) in the leaves and roots of plants. Meanwhile, application of H₂S decreased the production of MDA and ROS in the leaves and roots by increasing antioxidant activities under Pb stress. Moreover, this study also revealed that plants treated with H₂S at different concentrations enhanced the contents of total glutathione and glutathione reduced/glutathione oxidized ratio in leaves and roots under different levels of Pb. The results depicted that H₂S improved the plant biomass, uptake of nutrients in the leaves and roots of B. napus plants and enhanced the performance of antioxidant defense system due to its ameliorative potential under Pb stress conditions.