Organic Selenium,Probiotics, and Prebiotics Effects on Growth,Blood Biochemistry,and Carcass Traits of Growing Rabbits During Summer and Winter Seasons

Lead (Pb) is a ubiquitous and toxic heavy metal and it can damage the immune system in humans and animals. Many researchers have reported that Selenium (Se) could possess various pharmacological effects in mammals. However, few studies have been carried out to investigate the protective role of Se in birds, especially in chickens. In this study, we investigated the protective effects of Se against Pb-induced inflammatory responses and the expression of heat shock proteins (HSPs) in peripheral blood neutrophils. One hundred eighty Hy-Line brown chickens were randomly divided into the control group (Con group), Se supplementation group (+Se group), Pb supplementation group (+Pb group), and the Se and Pb compound group (Se+Pb group). On the 90th day of the experiment, the peripheral blood was collected to extract neutrophils, and then, the levels of HSPs and cytokines were examined. The results showed that, after Pb treatment, the levels of IL-(1β, 1R, 4, 8, 10, and 12β), TGF-β4, and HSP (27, 40, 60, 70, and 90) mRNA were significantly increased and levels of IL-2 and IFN-γ mRNA were decreased compared with those in the control group. Compared with the control group, the protein levels of HSP60 and HSP70 were also increased in the Pb treatment group. Co-administration of Se (1 mg/kg/day) and Pb resulted in a reversal of the Pb-induced cytokine changes in neutrophils accompanied by a significant decrease in HSPs. Our study demonstrated that Pb could decrease the immune function via changing the expression of cytokines and HSPs in chicken neutrophils, but Se could relieve the toxic effect induced by Pb.     

Mechanisms behind Pb-induced disruption of Na+ and Cl- balance in rainbow trout (Oncorhynchus mykiss)

The mechanism of Pb-induced disruption of Na(+) and Cl(-) balance was investigated in the freshwater rainbow trout (Oncorhynchus mykiss). Na(+) and Cl(-) influx rates were reduced immediately in the presence of 2.40 +/- 0.24 and 1.25 +/- 0.14 muM Pb, with a small increase in efflux rates occurring after 24-h exposure. Waterborne Pb caused a significant decrease in the maximal rate of Na(+) influx without a change in transporter affinity, suggesting a noncompetitive disruption of Na(+) uptake by Pb. Phenamil and bafilomycin markedly reduced Na(+) influx rate but did not affect Pb accumulation at the gill. Time-course analysis in rainbow trout exposed to 0, 0.48, 2.4, and 4.8 microM Pb revealed time- and concentration-dependent branchial Pb accumulation. Na(+)-K(+)-ATPase activity was significantly reduced, with 4.8 microM exposure resulting in immediate enzyme inhibition and 0.48 and 2.4 microM exposures inhibiting activity by 24 h. Reduced activity was weakly correlated with gill Pb accumulation after 3- and 8-h exposures; this relationship strengthened by 24 h. Reduced Na(+) uptake was correlated with gill Pb burden after exposures of 3, 8, and 24 h. Immediate inhibition of branchial carbonic anhydrase activity occurred after 3-h exposure to 0.82 +/- 0.05 or 4.30 +/- 0.05 microM Pb and continued for up to 24 h. We conclude that Pb-induced disruption of Na(+) and Cl(-) homeostasis is in part a result of rapid inhibition of carbonic anhydrase activity and of binding of Pb with Na(+)-K(+)-ATPase, causing noncompetitive inhibition of Na(+) and Cl(-) influx.     

Antioxidant defense in a lead accumulating plant, Sesbania drummondii.

Seedlings of Sesbania drummondii were grown in 500 mg l-1 Pb(NO3)2 in presence and absence of chelators: EDTA, DTPA and HEDTA for 4 weeks. Plants were assayed for activities of the antioxidant enzymes: ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT), superoxide dismutase (SOD) and glutathione (gamma-glutamyl-cysteinyl-glycine) content. Activities of antioxidant enzymes were elevated in the presence of Pb but were similar to controls in plants grown in the presence of Pb and EDTA, -DTPA or -HEDTA. Glutathione content was significantly elevated upon exposure to Pb, but lowered upon exposure to chelators. Chlorophyll a fluorescence kinetics were assessed by determination of Fv/Fm and Fv/Fo values. Seedling growth in Pb alone and Pb + chelators did not significantly affect photosynthetic integrity (Fv/Fo) and efficiency (Fv/Fm). The results suggest that Sesbania plants were able to tolerate Pb-induced stress using an effective antioxidant defense mechanism. This study also indicates a protective role of synthetic chelators in Pb-induced oxidative stress metabolism in a Pb-accumulating plant.     

Metabolic interactions between lead and copper in rats ingesting lead acetate

The effects of Pb ingestion with and without concurrent dietary Cu supplementation were determined on parameters associated with Cu deficiency in rats fed a nutritionally adequate diet. Groups of weanling male Sprague-Dawley rats were fed a purified (AIN-′76) diet and given Pb (0 or 500 ppm) and Cu (0, 6, or 12 ppm) as the acetate salt in deionized drinking water for 5 wk. A Pb-induced Cu deficiency resulted that was characterized by decreased levels of Cu in tissue and blood, decreased activities of the Cu-dependent enzymes, ceruloplasmin (serum) and Superoxide dismutase (erythocytes), and increased concentration of Fe in liver. These effects of Pb were prevented completely or in part by concurrent Cu supplementation. The Pb-induced decrease in hemoglobin and hematocrit values and the decrease in weight gain were not prevented by Cu supplementation of the diet and can therefore be assumed to be the direct result of a toxic effect of Pb. Although Pb ingestion resulted in decreased concentration of Cu in blood and tissue, additional dietary Cu had no effect on Pb levels.     

Exogenous Nitric Oxide (NO) Interferes with Lead (Pb)-Induced Toxicity by Detoxifying Reactive Oxygen Species in Hydroponically Grown Wheat (Triticum aestivum) Roots

Nitric Oxide (NO) is a bioactive signaling molecule that mediates a variety of biotic and abiotic stresses. The present study investigated the role of NO (as SNP [sodium nitroprusside]) in ameliorating lead (Pb)-toxicity in Triticum aestivum (wheat) roots. Pb (50 and 250 μM) alone and in combination with SNP (100 μM) was given to hydroponically grown wheat roots for a period of 0–8 h. NO supplementation reduced the accumulation of oxidative stress markers (malondialdehyde, conjugated dienes, hydroxyl ions and superoxide anion) and decreased the antioxidant enzyme activity in wheat roots particularly up to 6 h, thereby suggesting its role as an antioxidant. NO ameliorated Pb-induced membrane damage in wheat roots as evidenced by decreased ion-leakage and in situ histochemical localization. Pb-exposure significantly decreased in vivo NO level. The study concludes that exogenous NO partially ameliorates Pb-toxicity, but could not restore the plant growth on prolonged Pb-exposure.     

Effects of some sulfur-containing antioxidants on lead-exposed lenses

Lead (Pb) is known to negatively affect glutathione (GSH) metabolism in the lens. The present study examined the effects of Captopril, Taurine, and α-Lipoic acid on the Pb-induced GSH depletion and lipid peroxide increase in the lenticular system. Captopril administration returned the GSH, cysteine (CYS), and malondialdehyde (MDA) levels to near normal. Following Taurine administration the GSH, CYS and MDA levels were intermediate between the control group and the Pb group levels. α-Lipoic acid administration, however, only increased the CYS levels. No significant changes in oxidized glutathione (GSSG) levels were observed in any treatment group.     

Experimental Chemotherapy in Paracoccidioidomycosis Using Ruthenium NO Donor

Paracoccidioidomycosis (PCM) is a granulomatous disease caused by a dimorphic fungus, Paracoccidioides brasiliensis (Pb). To determine the influence of nitric oxide (NO) on this disease, we tested cis-[Ru(bpy)2(NO)SO3](PF6), ruthenium nitrosyl, which releases NO when activated by biological reducing agents, in BALB/c mice infected intravenously with Pb 18 isolate. In a previous study by our group, the fungicidal activity of ruthenium nitrosyl was evaluated in a mouse model of acute PCM, by measuring the immune cellular response (DTH), histopathological characteristics of the granulomatous lesions (and numbers), cytokines, and NO production. We found that cis-[Ru(bpy)2(NO)SO3](PF6)-treated mice were more resistant to infection, since they exhibited higher survival when compared with the control group. Furthermore, we observed a decreased influx of inflammatory cells in the lung and liver tissue of treated mice, possibly because of a minor reduction in fungal cell numbers. Moreover, an increased production of IL-10 and a decrease in TNF-α levels were detected in lung tissues of infected mice treated with cis-[Ru(bpy)2(NO)SO3](PF6). Immunohistochemistry showed that there was no difference in the number of VEGF- expressing cells. The animals treated with cis-[Ru(bpy)2(NO)SO3](PF6) showed high NO levels at 40 days after infection. These results show that NO is effectively involved in the mechanism that regulates the immune response in lung of Pb-infected mice. These data suggest that NO is a resistance factor during paracoccidioidomycosis by controlling fungal proliferation, influencing cytokine production, and consequently moderating the development of a strong inflammatory response.     

Protective effect of quercetin on lead-induced oxidative stress and endoplasmic reticulum stress in rat liver via the IRE1/JNK and PI3K/Akt pathway

Abstract

Lead (Pb), a well-known environmental toxin, is one of the major hazards for human health. Quercetin (QE), a natural flavonoid, has been reported to have many benefits and medicinal properties. However, its protective effects against Pb-induced endoplasmic reticulum (ER) stress in liver have not been clarified. The aim of the present study was to investigate the effects of quercetin on hepatic ER stress in rats exposed to Pb. Wistar rats were exposed to lead acetate in the drinking water with or without quercetin co-administration for 75 days. Our data showed that quercetin significantly prevented Pb-induced hepatotoxicity in a dose-dependent manner, indicated by both diagnostic indicators of liver damage and histopathological analysis. Quercetin markedly decreased Pb contents in blood and liver. Western blot analysis showed that Pb-induced ER stress in rat liver was significantly inhibited by quercetin. In exploring the underlying mechanisms of quercetin action, we found quercetin markedly suppressed Pb-induced oxidative stress. Quercetin decreased reactive oxygen species (ROS) production and increased the total antioxidant capacity in rat livers. Additionally, quercetin dramatically increased Phosphoinositide-3-kinase (PI3K) and phosphorylated protein kinase B (PKB/Akt) levels in liver rats. In the examined unfolded protein response (UPR) pathways, quercetin markedly inhibited the Pb-induced increase of the phosphorylated inositol-requiring enzyme 1 (IRE1) and c-jun N-terminal kinase (JNK) in rat liver. Taken together, these results suggested that the inhibition of Pb-induced ER stress by quercetin is due at least in part to its anti-oxidant stress activity and its ability to modulate the PI3K/Akt and IRE1/JNK signaling pathway.     

Lead Induces Apoptosis and Histone Hyperacetylation in Rat Cardiovascular Tissues

Acute and chronic lead (Pb) exposure might cause hypertension and cardiovascular diseases. The purpose of this study was to evaluate the effects of early acute exposure to Pb on the cellular morphology, apoptosis, and proliferation in rats and to elucidate the early mechanisms involved in the development of Pb-induced hypertension. Very young Sprague-Dawley rats were allowed to drink 1% Pb acetate for 12 and 40 days. Western blot analysis indicated that the expression of proliferating cell nuclear antigen (PCNA) decreased in the tissues of the abdominal and thoracic aortas and increased in the cardiac tissue after 12 and 40 days of Pb exposure, respectively. Bax was upregulated and Bcl-2 was downregulated in vascular and cardiac tissues after 40 days of Pb exposure. In addition, an increase in caspase-3 activity was observed after 40 days of exposure to Pb. In terms of morphology, we found that the internal elastic lamina (IEL) of aorta lost the original curve and the diameter of cardiac cell was enlarged after 40 days. Furthermore, the exposure led to a marked increase in acetylated histone H3 levels in the aortas and cardiac tissue after 12 and 40 days, than that in the control group. These findings indicate that Pb might increase the level of histone acetylation and induce apoptosis in vascular and cardiac tissues. However, the mechanism involved need to be further investigated.     

Mitigation of Lead-Induced Neurotoxicity by the Naringin: Erythrocytes as Neurons Substitute Markers

This study aimed to investigate the effect of lead (Pb) on neuronal nitric oxide synthase (nNOS) activity using erythrocytes as neurons surrogate markers. Moreover, the protective effect of naringin (NAR) against lead acetate (PbAc)-induced neurotoxicity was investigated. Human erythrocytes were incubated with l-arginine (l-Arg), N ^ω-nitro-l-Arginine methyl ester ( l-NAME), NAR, PbAc, PbAc + l-Arg, PbAc + NAR, or PbAc + l-Arg +NAR. The present results revealed that incubation of erythrocytes with PbAc inhibited NOS activity and decreased nitrite levels as an index for nitric oxide (NO) production to values similar that of l-NAME as known NOS inhibitor. Likewise, PbAc induced a significant decrease in activities of ATPases and acetylcholinesterase compared to control cells. Furthermore, PbAc exposure significantly increased protein carbonyl content (PCC) and malondialdehyde (MDA) levels while significantly decrease the levels of reduced glutathione (GSH). On the contrary, incubation of erythrocytes with PbAc in the presence of l-Arg + NAR synergistically ameliorated the investigated parameters compared to erythrocytes incubated with PbAc alone. These data suggest that NAR can restore NO bioavailability in a situation of Pb-induced cellular damage. This attributed to antioxidant activity and restoration NOS activity.     

Effects of Lead Exposure on Nitric Oxide-associated Gene Expression in the Olfactory Bulb of Mice

Lead (Pb) is known to have toxic effects on the brain; however, data regarding its specific toxic effects on the olfactory bulb are lacking. Therefore, we investigated the relationship between acute Pb exposure and alterations in gene expression associated with the nitric oxide signaling pathway in the olfactory bulb of mice. After administration of Pb (intraperitoneal injections of 1 or 10 mg/kg Pb(CH₃CO₂)₂ · 3H₂O once per day for 4 days), body weight, motor activity, and gene expression in the olfactory bulb of mice were examined. High doses of Pb resulted in significant decreases in body weight, but motor coordination was not significantly altered until 11 days after the end of Pb treatment. The expression patterns of dimethylarginine dimethylaminohydrolase 1 (Ddah1), superoxide dismutase 1 (Sod1), and superoxide dismutase (Ccs) were increased, whereas expression of the Stratifin (Sfn) gene was significantly decreased following treatment with 10 mg/kg Pb. The expression patterns of nitric oxide synthases at the mRNA and protein levels, however, were not significantly altered by treatment with 10 mg/kg Pb. These findings indicate that Pb-induced neurotoxicity may be modulated in part by the expression of Ddah1, Sod1, Ccs, and Sfn in the olfactory bulb.     

Preferential Vulnerability of Nucleus Accumbens Dopamine Binding Sites to Low-Level Lead Exposure: Time Course of Effects and Interactions with Chronic Dopamine Agonist Treatments

Abstract: This study examined the hypotheses that low-level lead (Pb) exposure would increase dopamine (DA) binding sites, would do so preferentially in nucleus accumbens, and that such effects would be modified by concurrent DA agonist treatment. D₁-like and D₂-like binding sites and the dopamine transporter (DT) were measured autoradiographically in caudate-putamen and nucleus accumbens of rats exposed from weaning to 0, 50, or 150 ppm Pb acetate drinking solutions with or without concurrent chronic intermittent intraperitoneal injections of the D₁-like agonist SKF 82958 or the DA agonist apomorphine after 2 weeks (no injections), 8 months, or 12 months of Pb exposure. Pb selectively decreased DA binding in nucleus accumbens. Decreases in D₂-like and DT sites were sustained across the 12-month exposure, whereas D₁-like sites evidenced recovery at 12 months. Chronic intermittent DA agonist treatments reversed these effects of Pb in nucleus accumbens, restoring receptor and DT binding levels to normal, despite decreasing binding sites of non-Pb-treated rats. These studies implicate increased DA availability as a mechanism of Pb-induced DA system changes. They also raise the possibility that Pb exposure could serve as a predisposing factor in neurodegenerative diseases associated with DA system dysfunction or could alter the course of DA-based therapeutic treatments.     

The Involvement of Copper Transporter in Lead-induced Oxidative Stress in Astroglia

Lead (Pb), depositing primarily in astroglia in the brain, is a well-known neurotoxicant and a risk factor for neurologic disorders. Pb has been reported to induce oxidative stress by probably the disturbance of copper (Cu) homeostasis in astroglia. Thus, we hypothesized that Pb-induced oxidative stress is initiated by interfering with Cu transporter in astroglia. In this study, we observed Pb-induced oxidative stress as indicated by reactive oxygen species (ROS) augmentation and GRP78 and GRP94 protein induction, and it was parallel to Cu accumulation intracellularly by Pb. To further address Cu transporter as a potential Pb target, a heavy metal-binding (HMB) domain of Cu-transporting ATPase (Atp7a) was overexpressed and purified. Evidence showed that one molecule of HMB chelated 11 Pb ions or seven Cu ions and that Pb competed with Cu for binding to HMB. These findings suggest that Pb-induced oxidative stress results from the impairment of Cu metabolism by Pb targeting of Atp7a.     

Nitric oxide donors selectively potentiate thrombin-stimulated p70(S6k) activity and morphological changes in Swiss 3T3 cells

Thrombin stimulates both DNA synthesis and cell morphological changes in Swiss 3T3 cells, although the mechanism of signal coordination leading to these responses is unknown. We report here that nitric oxide (NO) donors selectively enhance thrombin-stimulated p70(S6k) activity by 40-60%, an effect that was sustained for 24 h. Potentiation of p70(S6k) also was observed with cGMP analogues indicating that this effect is mediated by cGMP-activated protein kinase. NO donors also induced morphological changes characterized by spindle-shaped cells in confluent, nondividing cells or by extended protrusions from the trailing edge in subconfluent, polarized cells. NO donors had no significant effects on intracellular Ca(2+) mobilization, DNA synthesis, proliferation, or ERKs 1 and 2 and p90RSK activities, indicating that mitogenic responses and cell division are not altered by NO donors. We conclude that NO donors modulate the morphological changes associated with cellular motility in response to thrombin stimulation through selective enhancement of p70(S6k) activity.     

Neurodegeneration,demyelination, and astrogliosis in rat spinal cord by chronic lead treatment

Early exposure to lead (Pb) has been associated with an elevated risk of developing neurodegenerative diseases. There is evidence that neuronal damage in chronic Pb exposure can be caused by the convergence of glial damage. Apoptosis may be a possible mechanism of Pb‐induced cell death in the central nervous system. We tested cellular damage and apoptosis in the spinal cord of Wistar rats treated with Pb. Twelve rats were divided into two groups (n = 6): the control group was treated with only drinking water and the other group received 500 ppm of Pb acetate. After 3 months of Pb treatment, all animals were euthanized and spinal cords were extracted. Morphology was evaluated by Nissl and Kluver‐Barrera stainings. Apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Specific antibodies were used to evaluate Pb damage in oligodendrocytes, astrocytes, and microglia. A large number of apoptotic bodies was observed in the white matter of the Pb‐treated group. The Pb‐treated group also showed a reduced number of neurons and oligodendrocytes but had an increased number of astrocytes compared with the nontreated group. Our results demonstrate that chronic Pb treatment induces neurodegeneration, demyelination, and astrogliosis in the rat spinal cord.     

Nitric oxide production by hemocytes of larva and pharate prepupa of Galleria mellonella in response to bacterial lipopolysaccharide: Cytoprotective or cytotoxic?

Nitric oxide production by the hemocytes of the last instar larvae and sessile pharate prepupa of Galleria mellonella (Lepidoptera: Pyralidae) was demonstrated in vitro in response to preparations of bacterial lipopolysaccharide (LPS) from Escherichia coli using the Griess reaction. Augmented, dose dependent nitric oxide production was observed in the pharate prepupal hemocytes compared with larval hemocytes. This was partially reversed in a dose dependent manner with S-methyl thiourea (SMT), a specific inhibitor of inducible nitric oxide synthase (iNOS). A decrease in NO production was also observed when non-selective inhibitors such as N(G)-nitro-L-arginine (L-NAME) and N-omega-nitro-L-arginine (L-NNA) were used, albeit the inhibition was not to the extent of SMT. Challenge with the entomopathogenic Gram-negative bacterium Photorhabdus asymbiotica also enhanced NO production by hemocytes of both stages. SMT, alone or in combination with P. asymbiotica significantly decreased levels of NO production. However, it was observed that phenoloxidase activity (a cascade for innate immune responses) was independent of NO production stimulation. NO donors, S-nitroso-N-acetyl-penicillamine (SNAP) and diethylenetriamine NO adduct (DETA/NO) at various concentrations (100-500 microM) resulted in the lysis of hemocytes dose dependently. The nitrite production in these cases was however similar to LPS stimulation (10 microg/mL) and 1.5-3 fold lower than those observed upon P. asymbiotica (2.5 x 10(7) cfu/mL) stimulation. Survival analysis (Kaplan-Meier) following injection of P. asymbiotica alone or in combination with SMT revealed that only 12.5% (median survival 25.5 h) of co-injected larvae of G. mellonella survived in comparison to 28.6% (median survival 29 h) survivors in P. asymbiotica alone-injected groups till the end of the study. In contrast, co-injected pharate prepupa survived longer (median survival 28 h) than the P. asymbiotica alone-injected individuals (median survival 24 h); however, both co-injected and P. asymbiotica-injected groups showed 100% mortality at the end of the study. Based on the above, we propose that although NO production is involved in cellular immune responses of this insect to bacterial infection it does not appear to be a part of the signalling pathway that initiates the prophenoloxidase (PPO) cascade, and the extended NO production/overproduction by pharate prepupal hemocytes could result in cytotoxic rather than cytoprotective effects compared with larval hemocytes.     

Activation of PERK-eIF2α-ATF4-CHOP axis triggered by excessive ER stress contributes to lead-induced nephrotoxicity

Lead (Pb) is a known nephrotoxicant that causes damage to proximal tubular cells. PERK pathway plays an important role in the pathogenesis of renal diseases, but its role in Pb-induced nephrotoxicity remains largely unknown. In this study, data showed that Pb could induce ER stress as shown by increased phosphorylation of PERK with subsequent activation of the eIF2α-ATF4-CHOP axis in primary rat proximal tubular (rPT) cells, indicating the activation of PERK-eIF2α-ATF4-CHOP pathway due to excessive ER stress. Pb-activated PERK pathway can be effectively inhibited by 4-phenylbutyric acid and PERK gene silencing, respectively; whereas continuously up-regulated by tunicamycin (TM) treatment. Moreover, Pb-induced apoptosis and inhibition of autophagic flux in rPT cells were significantly augmented and aggravated by co-treatment with TM, respectively. Pharmacological or genetic inhibition of the PERK pathway results in alleviation of apoptosis and restoration of autophagy inhibition in Pb-exposed rPT cells. Mechanistically, activation of PERK-eIF2α-ATF4-CHOP axis triggered by excessive ER stress in rPT cells leads to Pb-induced apoptosis and blockage of autophagic flux, resulting in nephrotoxicity.