Comparative study on the effects of salinomycin, monensin and meso-2,3-dimercaptosuccinic acid on the concentrations of lead, calcium, copper, iron and zinc in lungs and heart in lead-exposed mice

BACKGROUND AND AIM

Environmental lead (Pb) exposure damages the lungs and is a risk factor for death from cardiovascular disease. Pb induces toxicity by a mechanism, which involves alteration of the essential elements homeostasis. In this study we compare the effects of salinomycin (Sal), monensin (Mon) and meso-2,3-dimercaptosuccinic acid (DMSA) on the concentrations of lead (Pb), calcium (Ca), copper (Cu), iron (Fe) and zinc (Zn) in the lungs and heart of lead-exposed mice.

METHODS

Sixty days old male ICR mice were divided into five groups: control (Ctrl) - untreated mice obtained distilled water for 28 days; Pb-intoxicated group (Pb) - exposed to 80 mg/kg body weight (BW) Pb(NO₃)₂ during the first 14 days of the experimental protocol; DMSA-treated (Pb + DMSA) - Pb-exposed mice, subjected to treatment with an average daily dose of 20 mg/kg BW DMSA for two weeks; Monensin-treated (Pb + Mon) - Pb-exposed mice, obtained an average daily dose of 20 mg/kg BW tetraethylammonium salt of monensic acid for 14 days; Pb + Sal - Pb-exposed mice, treated with an average daily dose of 20 mg/kg BW tetraethylammonium salt of salinomycinic acid for two weeks. On the 29^th day of the experiment the samples (lungs and heart) were taken for atomic absorption analysis.

RESULTS

The results revealed that exposure of mice to Pb for 14 days significantly increased the concentration of the toxic metal in both organs and elevated the cardiac concentrations of Ca, Cu and Fe compared to untreated mice. Pb exposure diminished the lung concentrations of Ca and Zn compared to that of untreated controls. DMSA, monensin and salinomycin decreased the concentration of Pb in the lungs and heart. Among the tested chelating agents, only salinomycin restored the cardiac Fe concentration to normal control values.

CONCLUSION

The results demonstrated the potential application of polyether ionophorous antibiotic salinomycin as antidote for treatment of Pb-induced toxicity in the lungs and heart. The possible complexation of the polyether ionophorous antibiotics with Ca(II) and Zn(II), which can diminish the endogenous concentrations of both ions in the lungs should be taken into account.

Chlorogenic Acid Ameliorates Lead-Induced Renal Damage in Mice

Lead (Pb) exposure is a global environmental problem and its exposure can lead to serious renal damage by disturbing the pro-oxidant/antioxidant balance and facilitating inflammation. Chlorogenic acid (CGA) is one of the most abundant polyphenols in the diet and has been reported to have many biological properties such as antioxidant and anti-inflammatory. In this study, we aimed to investigate the protective efficacy and mechanism of CGA against Pb-induced nephrotoxicity in mice. The results showed that CGA inhibited Pb-induced bodyweight loss, reduced kidney coefficients, and alleviated renal function and structure. Exploration on the potential mechanism demonstrated that CGA suppressed Pb-induced inflammation in the kidney by regulating NF-κB pathway activation. Furthermore, CGA significantly increased Pb-induced reduction in the activity of SOD and GSH-Px, and reduced Pb-induced increase in the content of MDA. The expression of Bax and Bcl-2 associated with apoptosis was also significantly regulated by CGA. These data indicated that CGA may play a potential treatment strategy for Pb toxicity.

The Protective Effect of Selenium on the Chicken Pancreas against Cadmium Toxicity via Alleviating Oxidative Stress and Autophagy

Cadmium (Cd) is a highly toxic heavy metal that can affect human and animal health. Selenium (Se) is an essential microelement that can protect various organs against toxic heavy metals. Although many studies have investigated the adverse effect of Cd in rats and several other animals, little is known regarding the mechanisms of Cd-induced autophagy in the chicken pancreas and the antagonistic effect of Se on Cd. In the current study, we fed chickens Se, Cd, or Se and Cd supplements to establish the Se and Cd interaction model and to measure the concentrations of Se and Cd in the chicken pancreas. The ultrastructure changes of the chicken pancreas were also observed, and we detected oxidative stress indexes in each group. The expression levels of autophagy-related genes were also examined. We found that Cd exposure could increase the concentration of Cd, the activities of total superoxide dismutase (T-SOD), catalase (CAT), and glutathione peroxidase (GSH-Px); and the total antioxidant capacity (T-AOC) content in the chicken pancreas. The protein expression levels of dynein, Beclin1, LC3-1, LC3-2, and Atg5 were increased and that of TOR was decreased under Cd exposure conditions. However, the changes induced by Cd were significantly alleviated by Se. This study suggested that Cd could accumulate in the chicken pancreas and lead to oxidative stress and autophagy. Se was shown to antagonize Cd toxicity though reducing Cd accumulation, alleviating oxidative stress, and inhibiting autophagy. This study revealed a concrete mechanism for the Se antagonism of Cd and might provide a new clue for the detoxification of Cd poisoning.

Subchronic arsenism-induced oxidative stress and inflammation contribute to apoptosis through mitochondrial and death receptor dependent pathways in chicken immune organs

In many organ dysfunctions, arsenic and its compounds are well known to induce apoptosis by the mitochondria and death receptor apoptotic pathways in liver and airway. However, it is less reported that which signaling pathways contribute to excessive apoptosis of chicken immune organs, a major target of toxic metals biotransformation, which suffer from subchronic arsenism. In this study, we investigated whether the mitochondria or death receptor apoptotic pathways activated in the immune organs (spleen, thymus and bursa of Fabricius) of one-day-old male Hy-line chickens exposed to arsenic trioxide (As₂O₃), which were fed on diets supplemented with 0, 0.625, 1.25 and 2.5 mg/kg BW of As₂O₃ for 30, 60 and 90 days. We found that (1) Oxidative damage and inflammatory response were confirmed in the immune organs of chickens fed on As₂O₃ diet. (2) Subchronic arsenism induced typical apoptotic changes in ultrastructure. (3) TdT-mediated dUTP Nick-End Labeling (TUNEL) showed that the number of apoptotic cells significantly increased under subchronic arsenism. (4) As₂O₃-induced apoptosis of immune organs involved in mitochondrial pathway (decrease of B-cell lymphoma-2 (Bcl-2) and increase of protein 53 (p53), Bcl-2 Associated X Protein (Bax), caspase-9, caspase-3) and death receptor pathway (increase of factor associated suicide (Fas) and caspase-8). In conclusion, this work is the first to demonstrate that the activation of mitochondria and death receptor apoptosis pathways can lead to excessive apoptosis in immune organs of chickens, which suffer from subchronic arsenism, meanwhile, oxidative stress as well as subsequent inflammatory is a crucial driver of apoptosis.

Antagonistic effect of selenium on lead-induced inflammatory injury through inhibiting the nuclear factor-κB signaling pathway and stimulating selenoproteins in chicken hearts

In the chicken model of Pb and Se, Se alleviated Pb-induced the changes of inflammatory factors, selenoproteins, and histology. Se alleviated Pb-induced inflammatory injury through inhibiting NF-κB signaling pathway and stimulating selenoproteins in the chicken hearts.

Heavy Metal Ion Regulation of Gene Expression: MECHANISMS BY WHICH LEAD INHIBITS OSTEOBLASTIC BONE-FORMING ACTIVITY THROUGH MODULATION OF THE Wnt/β-CATENIN SIGNALING PATHWAY

Exposure to lead (Pb) from environmental sources remains an overlooked and serious public health risk. Starting in childhood, Pb in the skeleton can disrupt epiphyseal plate function, constrain the growth of long bones, and prevent attainment of a high peak bone mass, all of which will increase susceptibility to osteoporosis later in life. We hypothesize that the effects of Pb on bone mass, in part, come from depression of Wnt/β-catenin signaling, a critical anabolic pathway for osteoblastic bone formation. In this study, we show that depression of Wnt signaling by Pb is due to increased sclerostin levels in vitro and in vivo. Downstream activation of the β-catenin pathway using a pharmacological inhibitor of GSK-3β ameliorates the Pb inhibition of Wnt signaling activity in the TOPGAL reporter mouse. The effect of Pb was determined to be dependent on sclerostin expression through use of the SOST gene knock-out mice, which are resistant to Pb-induced trabecular bone loss and maintain their mechanical bone strength. Moreover, isolated bone marrow cells from the sclerostin null mice show improved bone formation potential even after exposure to Pb. Also, our data suggest that the TGFβ canonical signaling pathway is the mechanism by which Pb controls sclerostin production. Taken together these results support our hypothesis that the osteoporotic-like phenotype observed after Pb exposure is, in part, regulated through modulation of the Wnt/β-catenin pathway.

Effect of N-acetylcysteine administration on the expression and activities of antioxidant enzymes and the malondialdehyde level in the blood of lead-exposed workers

We investigated whether treatment with N-acetylcysteine (NAC) reduces oxidative stress intensity and restores the expression and activities of superoxide dismutase (Sod1, SOD), catalase (Cat, CAT) and glutathione peroxidase (Gpx1, GPx) in lead-exposed workers. The exposed population was divided randomly into two groups. Workers in the first group (reference group, n=49) were not administered any drugs, while workers in the second group (n=122) were treated with NAC at three doses for 12 weeks (200 mg, 400 mg, 800 mg/day). NAC administered orally to lead-exposed workers normalized antioxidant enzyme activities in blood cells. Oxidative stress intensity measured as malondialdehyde (MDA) levels in serum, leukocytes and erythrocytes significantly decreased after NAC administration. NAC may be an alternative therapy for chronic lead intoxication.

Puerarin protects against lead-induced cytotoxicity in cultured primary rat proximal tubular cells

Puerarin, a potent free radicals scavenger, has been demonstrated to have protective efficacy in oxidative damage induced by nephrotoxins. In the present study, the attenuating effect of puerarin (PU) on lead (Pb)-induced apoptosis and oxidative stress was investigated in cultured primary rat proximal tubular (rPT) cells. Results showed that exposure to 0.5 µM Pb induced a decrease in cell viability accompanied with obvious cellular morphological alterations and caused an increase in apoptotic rate and apoptotic morphological changes. Simultaneously, depletion of mitochondrial membrane potential (ΔΨ) and intracellular glutathione (GSH); elevation of caspase-3 activity, intracellular reactive oxygen species, and malondialdehyde levels; and inhibition of GSH peroxidase (GSH-Px) activity were revealed in the cells exposed to Pb alone. However, simultaneous supplementation with PU (50 and 100 µM) protected rPT cells from Pb-induced cytotoxicity through inhibiting apoptosis, attenuating lipid peroxidation, renewing mitochondrial function, and elevating the intracellular antioxidants (nonenzymatic and enzymic) levels. In conclusion, these findings suggested that PU, as a widely distributed dietary antioxidant, contributes potentially to inhibition of Pb-induced cytotoxicity in rPT cells.

Cytoprotective and antioxidant effects of the edible halophyte Sarcocornia perennis L. (swampfire) against lead-induced toxicity in renal cells

Lead (Pb) exposure is considered as a risk factor responsible for renal impairment in humans. On the other hand, the halophyte Sarcocornia perennis is a fresh vegetable crop suitable for leafy vegetable production. This study was designed to evaluate the in vitro protective activity of S. perennis against lead-induced damages in HEK293 kidney cells. Morphological and biochemical indicators were used to assess cytotoxicity and oxidative damages caused by Pb treatment on the cells. Our results showed that lead induced (1) a decrease in cell viability (MTT), (2) cell distortion and cohesion loss, (3) superoxide anion production and lipid peroxidation. Conversely, addition of S. perennis extract to the lead-containing medium alleviated every above syndrome. Thus, cell survival was increased and the production of reactive oxygen species caused by Pb treatment was inhibited. Taken together, our study revealed that S. perennis has potent cytoprotective effect against Pb-induced toxicity in HEK 293 cell. Such action would proceed through the decrease in ROS levels and resulting oxidative stress, which suggests a potential interest of this halophyte in the treatment of oxidative-stress related diseases.

Heart function in magnetic resonance imaging and the mesenteric artery reactivity in rats receiving lead-contaminated drinking water

The aim of this study was to evaluate the effect of lead (Pb)-contaminated drinking water on magnetic resonance imaging (MRI)-estimated cardiac function, vascular reactivity, and serum lipids in rats. For 3 months, male Wistar rats, aged 4–6 weeks, were given drinking water with the addition of lead acetate at a concentration of 100 ppm Pb (10 rats) or water free from Pb (8 control rats). The cardiac MRI was performed at rest and under β-adrenergic stimulation on a 4.7 T scanner using electrocardiogram-triggered gradient echo (FLASH) cine sequence. After 1–2 weeks of the MRI test, experiments were performed ex vivo. After stabilization of perfusion pressure (PP), norepinephrine at doses from 0.01 to 5.0 μg was dissolved in Krebs solution, injected in a volume of 100 μl, and next infused at a concentration of 0.5 μg/ml into the isolated mesenteric artery. In this manner, preconstricted mesenteric bed was used to determine PP changes induced by acetylcholine, given at doses from 0.05 to 5.0 μg, before and during the infusion of nitric oxide synthase inhibitor (1.0 μg/ml). At the end, dobutamine (5 mg), followed by potassium chloride (10.5 mg), was injected. Lipid levels were determined enzymatically, blood Pb level was measured by the atomic absorption spectrophotometer. This study showed that Pb impairs the left ventricular systolic and diastolic function. Pb-induced changes in response to resistance of vessels to vasoactive agents may be secondary to the reduced left ventricular ejection fraction. The high-density lipoprotein subfraction 2 (HDL2) is involved in the cardiovascular effect of Pb.

The administration of N-acetylcysteine reduces oxidative stress and regulates glutathione metabolism in the blood cells of workers exposed to lead

CONTEXT AND OBJECTIVE

The aim of the study was to investigate whether treatment with N-acetylcysteine (NAC) is able to restore erythrocyte glutathione (GSH) content in workers exposed to lead. Additionally, we measured the leukocyte and erythrocyte activities of GSH-related enzymes, such as glutathione reductase (GR), glutathione-S-transferase (GST), and glucose-6-phosphate dehydrogenase (G6PD), and estimated the influence of NAC administration on oxidative stress intensity, which was measured as the lipofuscin (LPS) level in erythrocytes.

METHODS

The exposed population consisted of 171 healthy males randomly divided into four groups. Workers in the first group (n = 49) were not administered any antioxidants, drugs, vitamins, or dietary supplements, while workers in the remaining groups were treated with NAC at three doses for 12 weeks (1 × 200 mg per day, 2 × 200 mg per day, and 2 × 400 mg per day). All workers continued to work during the study. The blood of all examined workers was drawn two times: at the beginning of the study and after 12 weeks of treatment.

RESULTS AND CONCLUSION

Blood lead levels decreased significantly in all groups receiving NAC compared to those in baseline. Erythrocyte GSH concentrations were significantly elevated in workers receiving 400 and 800 mg of NAC compared to those in baseline by 5% and 6%, respectively. Erythrocyte G6PD activity was significantly elevated in workers receiving 200, 400, and 800 mg of NAC compared to those in baseline by 24%, 14%, and 14%, respectively. By contrast, there were no significant differences in leukocyte G6PD or leukocyte and erythrocyte glutathione reductase (GR) activities before and after treatment. Leukocyte GST activities decreased significantly after treatment in workers receiving 200 mg of NAC by 34%, while LPS levels decreased significantly in workers receiving 200, 400, and 800 mg of NAC compared to those in baseline by 5%, 15%, and 13%, respectively. In conclusion, NAC decreases oxidative stress in workers exposed to lead via stimulating GSH synthesis.

Decreased blood lead levels after calcitriol treatment in hemodialysis patients with secondary hyperparathyroidism

OBJECTIVE

Secondary hyperparathyroidism (SHP) is characterized by high bone turnover, which may, in turn, result in increased release of lead from bone stores. This study investigated the effects of intravenous calcitriol on blood lead (BL) levels in patients with SHP.

METHODS

Intravenous calcitriol therapy was administered for 16 wk to 28 patients who were on maintenance hemodialysis (HD) and had intact parathyroid hormone (iPTH) plasma levels of >300 pg/mL. Blood was drawn at baseline and every 4 wk for 16 wk to determine the levels of iPTH; bone remodeling markers, including bone-specific alkaline phosphatase (bAP) and type 5b tartrate-resistant acid phosphatase (TRAP); and BL.

RESULTS

Of the 28 patients, 25 responded to calcitriol therapy; they exhibited significant decrements in serum iPTH levels by the end of 4 wk of therapy and thereafter. After 16 wk of therapy, these patients had significant reductions in serum iPTH levels (p<0.01) and significant and parallel decreases in the levels of bAP (p<0.01), TRAP (p<0.01), and BL (p<0.01). Further analysis showed a significant positive correlation between the levels of BL and serum iPTH (r=0.34, p<0.01) and BL and serum TRAP (r=0.22, p<0.05). However, there was no significant correlation between the levels of BL and serum bAP.

CONCLUSION

Elevated levels of BL and serum bone remodeling markers, which are common features of SHP, can be effectively suppressed by calcitriol therapy. This indicates that hyperparathyroidism not only accelerates bone remodeling but may also enhance bone lead mobilization in patients on maintenance HD.

Effects of lead and/or cadmium on the distribution patterns of some essential trace elements in immature female rats

Lead acetate (300 mg/L) and/or cadmium chloride (50 mg/L) were administered as drinking water to Sprague-Dawley rats for 9 weeks to investigate the effects of concurrent exposure to lead and cadmium on the distribution patterns of five essential trace elements. Inductively coupled plasma mass spectrometry was used to determine the concentrations of zinc, copper, manganese, selenium and iron in the urine at different exposure times, as well as their levels in the renal cortex and serum at the end of treatment. Compared with the control group, exposure to lead and/or cadmium resulted in a significant increase in the urinary excretion of these five elements during the experiment, whereas significant decreased levels of these elements were found in kidney and serum. In conclusion, increased urinary loss of antioxidant trace elements due to lead and/or cadmium exposure induced the deficiency of antioxidants in the body, which could result in further oxidative damage. Moreover, there was an obvious synergistic effect of lead combined with cadmium on the distribution patterns of these essential trace elements, which may be related to the severity of co-exposure to these two metals.

Quercetin protects the rat kidney against oxidative stress-mediated DNA damage and apoptosis induced by lead

Quercetin, a flavonoid, effectively improved the lead-induced histology changes including structure damage and leukocyte infiltration in rat kidney. The present study was designed to explore the protective mechanism of quercetin against lead-induced oxidative DNA damage and apoptosis in rat kidney. We found that quercetin markedly decreased the ROS level and lowered the GSH/GSSG ratio in the kidney of lead-treated rat. The increase of 8-hydroxydeoxyguanosine level in the kidney of lead-treated rat was effectively suppressed by quercetin. Furthermore, quercetin markedly restored Cu/Zn-SOD, CAT and GPx activities in the kidney of lead-treated rat. TUNEL assay showed that lead-induced apoptosis in rat kidney was significantly inhibited by quercetin, which might be attributed to its antioxidant property. In conclusion, these results suggested that quercetin could protect the rat kidney against lead-induced injury by improving renal function, attenuating histopathologic changes, reducing ROS production, renewing the activities of antioxidant enzymes, decreasing DNA oxidative damage and apoptosis.

Prophylactic effect of N-acetylcysteine against sodium fluoride-induced blood oxidative stress in mice

Ninety female Balb/c mice were used. The animals were allocated to evenly six groups. While the first group was maintained as control, Groups 3, 4, 5, and 6 were administered 750 ppm, 1500 ppm, 3000 ppm, and 6000 ppm of N-acetylcysteine, respectively, for a period of 15 days. After day 15, Groups 2-6 were administered sodium fluoride, containing 100 ppm fluoride in drinking water, for another 15 days. Plasma malondialdehyde (MDA) levels and erythrocyte superoksid dismutase (SOD) and catalase (CAT) activities were determined at the beginning of the trial and on days 15 and 30. According to the data obtained in the present study, N-acetylcysteine, when administered at the indicated doses, did not produce a significant alteration in any of the three parameters investigated. On the other hand, while the plasma MDA level was determined to have increased significantly, erythrocyte SOD and CAT activities were ascertained to have decreased significantly in the group, which was administered sodium fluoride alone on day 30. In the groups, which were administered N-acetylcysteine prior to sodium fluoride, however, it was observed that, after sodium fluoride administration, plasma MDA levels and erythrocyte SOD and CAT activities drew closer to the values of the control group.