Toxicological Effects of Mercury Chloride on Laying Performance, Egg Quality, Serum Biochemistry, and Histopathology of Liver and Kidney in Laying Hens

Selenium represses microRNA-202-5p/MICU1 aixs to attenuate mercuric chloride-induced kidney ferroptosis

Mercuric chloride (HgCl2) is a nephrotoxic contaminant that is widely present in the environment. Selenium (Se) can effectively antagonize the biological toxicity caused by heavy metals. Here, in vivo and in vitro models of Se antagonism to HgCl2-induced nephrotoxicity in chickens were established, with the aim of exploring the specific mechanism. Morphological observation and kidney function analysis showed that Se alleviated HgCl2-induced kidney tissue injury and cytotoxicity. The results showed that ferroptosis was the primary mechanism for the toxicity of HgCl2, as indicated by iron overload and lipid peroxidation. On the one hand, Se significantly prevented HgCl2-induced iron overload. On the other hand, Se alleviated the intracellular reactive oxygen species (ROS) levels caused by HgCl2. Subsequently, we focused on the sources of ROS during HgCl2-induced ferroptosis. Mechanically, Se reduced ROS overproduction induced by HgCl2 through mitochondrial calcium uniporter (MCU)/mitochondrial calcium uptake 1 (MICU1)-mediated mitochondrial calcium ion (Ca2+) overload. Furthermore, a dual luciferase reporter assay demonstrated that MICU1 was the direct target of miR-202-5p. Overall, Se represses miR-202-5p/MICU1 axis to attenuate HgCl2-induced kidney ferroptosis.

Metabolisms of both inorganic and methyl-mercury in hens reveal eggs as an effective bioindicator for environmental Hg pollution

Mercury (Hg) is a globally distributed toxic metal and could pose serious harm to birds, which may ultimately threaten human health through poultry consumption. However, the avian Hg metabolism remains unclear. Poultry, like chickens, are more accessible human dietary sources than wild birds and are ideal proxies to study Hg metabolism in birds. In this study, the avian Hg metabolism is carefully investigated with hens fed by Hg-spiked (both inorganic mercury IHg and methylmercury MeHg) foods. Our results demonstrate that feces and eggs are the main removal pathways of Hg from hens, rather than feathers. Eggs show particularly rapid responses towards Hg exposures, thus could be more sensitive to environmental Hg pollution than feathers, feces or internal organs (and tissues). Egg yolk (with THg peak of 55.92 ng/g on Day 6) and egg white (THg peak of 1195.03 ng/g on Day 4) react as an effective bioindicator for IHg and MeHg exposure, respectively. In 90-day-single-dose exposure, IHg is almost completely excreted, while approximately 11% of MeHg remains in internal organs. Our study provides new insight into the metabolism and lifetime of IHg and MeHg in birds, advancing the understanding of the dynamics for human exposure to Hg through poultry products.

Dissecting the role of cadmium, lead, arsenic, and mercury in non-alcoholic fatty liver disease and non-alcoholic steatohepatitis

The objective of the present study was to review the existing epidemiological and laboratory findings supporting the role of toxic metal exposure in non-alcoholic fatty liver disease (NAFLD). The existing epidemiological studies demonstrate that cadmium (Cd), lead (Pb), arsenic (As), and mercury (Hg) exposure was associated both with an increased risk of NAFLD and altered biochemical markers of liver injury. Laboratory studies demonstrated that metal exposure induces hepatic lipid accumulation resulting from activation of lipogenesis and inhibition of fatty acid β-oxidation due to up-regulation of sterol regulatory element-binding protein 1 (SREBP-1), carbohydrate response element binding protein (ChREBP), peroxisome proliferator-activated receptor γ (PPARγ), and down-regulation of PPARα. Other metabolic pathways involved in this effect may include activation of reactive oxygen species (ROS)/extracellular signal-regulated kinase (ERK) and inhibition of AMP-activated protein kinase (AMPK) signaling. The mechanisms of hepatocyte damage during development of metal-induced hepatic steatosis were shown to involve oxidative stress, endoplasmic reticulum stress, pyroptosis, ferroptosis, and dysregulation of autophagy. Induction of inflammatory response contributing to progression of NAFLD to non-alcoholic steatohepatitis (NASH) upon toxic metal exposure was shown to be mediated by up-regulation of nuclear factor κB (NF-κB) and activation of NRLP3 inflammasome. Moreover, epigenetic effects of the metals, as well as their effect on gut microbiota and gut wall integrity were also shown to mediate their role in NAFLD development. Despite being demonstrated for Cd, Pb, and As, the contribution of these mechanisms into Hg-induced NAFLD is yet to be estimated. Therefore, further studies are required to clarify the intimate mechanisms underlying the relationship between heavy metal and metalloid exposure and NAFLD/NASH to reveal the potential targets for treatment and prevention of metal-induced NAFLD.

Selenium nanoparticles: Enhanced nutrition and beyond

Selenium is a trace nutrient that has both nutritional and nutraceutical functions, whereas narrow nutritional range of selenium intake limits its use. Selenium nanoparticles (SeNPs) are less toxic and more bioavailable than traditional forms of selenium, suggesting that SeNPs have the potential to replace traditional selenium in food industries and/or biomedical fields. From the perspective of how SeNPs can be applied in health area, this review comprehensively discusses SeNPs in terms of its preparation, nutritional aspect, detoxification effect of heavy metals, nutraceutical functions and anti-pathogenic microorganism effects. By physical, chemical, or biological methods, inorganic selenium can be transformed into SeNPs which have increased stability and bioavailability as well as low toxicity. SeNPs are more effective than traditional selenium form in synthesizing selenoproteins like glutathione peroxidases. SeNPs can reshape the digestive system to facilitate digestion and absorption of nutrients. SeNPs have shown excellent potential to adjunctively treat cancer patients, enhance immune system, control diabetes, and prevent rheumatoid arthritis. Additionally, SeNPs have good microbial anti-pathogenic effects and can be used with other antimicrobial agents to fight against pathogenic bacteria, fungi, or viruses. Development of novel SeNPs with enhanced functions can greatly benefit the food-, nutraceutical-, and biomedical industries.

Role of Endoplasmic Reticulum Stress in Nano-Selenium Alleviating Prehierarchical Follicular Atresia Induced by Mercury in Laying Hens

This study investigated that the effect of nano-selenium (nano-Se) addition preventing prehierarchical follicular atresia induced by mercury (Hg) exposure in laying hens. Furthermore, endoplasmic reticulum (ER) stress pathway was explored to reveal the protective mechanism of nano-Se in vitro. The results revealed that Hg could significantly reduce laying performance (P < 0.05) and egg quality (P < 0.05), whereas nano-Se addition partially reversed the reductions. Besides, Hg significantly induced the deposition of Hg in prehierarchical follicles (P < 0.05) and prehierarchical follicular atresia (P < 0.05), whereas nano-Se addition could alleviate these toxicities in vitro. In addition, Hg exposure could significantly reduce cell viability (P < 0.05) and induce pyknotic nucleus in prehierarchical granulosa cells, while nano-Se addition reversed these effects. The levels of follicle-stimulating hormone (P < 0.05), luteinizing hormone (P < 0.05), progesterone (P < 0.05), and estradiol (P < 0.05) were significantly decreased after Hg exposure in vitro. However, nano-Se addition reversed the decreases of sex hormone levels. Furthermore, Hg exposure significantly increased the gene expressions of CHOP (P < 0.05), PERK (P < 0.05), ATF4 (P < 0.05), ATF6 (P < 0.05), ASK1 (P < 0.05), IRE1α (P < 0.05), TRAF2 (P < 0.05), caspase-9 (P < 0.05), caspase-3 (P < 0.05), and Bax/Bcl-2 (P < 0.05), whereas nano-Se addition reversed these increases of gene expressions in vitro. In summary, this study provides that Hg can induce prehierarchical follicular atresia, whereas nano-Se addition can ameliorate it, and elucidates an important role of ER stress in nano-Se alleviating prehierarchical follicular atresia induced by Hg in laying hens.

Protective effects of selenized yeast on the combination of cadmium-, lead-, mercury-, and chromium-induced toxicity in laying hens

The objective of this study was to investigate the toxic effects of a combination of cadmium (Cd), lead (Pb), mercury (Hg), and chromium (Cr) on laying performance, egg quality, serum biochemical parameters, and oxidative stress of laying hens, as well as the alleviating action of dietary supplementation of selenized yeast. A total of 160 Lohmann pink-shell laying hens (63-week-old) were randomly divided into four treatments with 10 replicates of four hens each. The treatments were the corn–soybean meal basal diet (control; CON), the CON diet supplemented with 0.4 mg selenium (Se)/kg from selenized yeast (Se); combined heavy metals group: the basal diet supplemented with 5 mg Cd/kg, 50 mg Pb/kg, 3 mg Hg/kg, and 5 mg Cr/kg (HEM), and the HEM diet supplemented with 0.4 mg Se/kg from selenized yeast (HEM+Se). The experimental period lasted for 12 weeks. The HEM diet decreased hen-day egg production, feed conversion ratio (FCR), and egg white quality (P < 0.05), but increased (P < 0.05) glutamic oxalacetic transaminase (AST) activity in the serum. HEM induced higher malondialdehyde (MDA) and reactive oxygen species (ROS) in the serum, liver, and ovary and significantly decreased (P < 0.05) the activity of total superoxide dismutase (SOD) and tended to decrease glutathione S-transferase (GST) (P = 0.09) in the serum. Meanwhile, HEM significantly decreased (P < 0.05) activity of SOD, GST, glutathione peroxidase (GPX), and glutathione (GSH) in the liver, and the activity of GPX and GSH in the ovary. Se addition of 0.4 mg/kg significantly (P < 0.05) improved hen-day egg production and FCR and decreased AST concentration and increased some enzyme activity in the serum, liver, and ovary. In conclusion, dietary HEM exposure depressed laying performance, and egg white quality was likely due to an impaired antioxidant capacity, disrupted hepatic function, and elevated HEM accumulation in the egg yolk and egg white of laying hens. Se addition of 0.4 mg/kg ameliorated toxic effects of HEM on laying performance, oxidative stress, and hepatic function.

Protective effect of nano-selenium on mercury-induced prehierarchical follicular atresia in laying hens

This study investigated the effect of nano-selenium (nano-Se) in protecting laying hens from mercury (Hg)-induced prehierarchical follicular atresia. Furthermore, the endoplasmic reticulum stress (ERS) was explored to reveal the molecular mechanism. In vivo, 720 Hyline-Brown laying hens were treated with Hg and nano-Se alone or in combination. In vitro, the prehierarchical follicles were treated with Hg, nano-Se and 4-phenyl butyric acid (4-PBA) alone or in combination (Control, 25 μM Hg group, 10 μM nano-Se group, 20 μM nano-Se group, 25 μM Hg + 10 μM nano-Se group, 25 μM Hg + 20 μM nano-Se group, 25 μM Hg + 4-PBA group, and 25 μM Hg + 20 μM nano-Se + 4-PBA group). The GCs were treated with Hg and nano-Se alone or in combination (Control, 15 μM Hg group, 6 μM nano-Se group, 12 μM nano-Se group, 15 μM Hg + 6 μM nano-Se group, 15 μM Hg + 12 μM nano-Se group). The results revealed that dietary Hg significantly reduced laying performance (P < 0.05) and egg quality (P < 0.05), whereas nano-Se addition prevented these reductions (P < 0.05). Hg exposure significantly induced the accumulation of Hg in PHFs (P < 0.05), prehierarchical follicular atresia (P < 0.05) and apoptosis in PHFs, whereas nano-Se addition significantly prevented these effects (P < 0.05). The levels of sex hormones (P < 0.05) were significantly decreased after Hg exposure in vivo and in vitro, while nano-Se addition prevented the reductions. Furthermore, the RNA-Seq results showed that the key factors of the ERS presented differential expression, including C/EBP homologous protein, protein kinase RNA-like endoplasmic reticulum kinase (PERK) and activating transcription factor 6 (ATF6) in GCs. Hg exposure significantly increased the key gene expression of endoplasmic reticulum stress in GCs, whereas nano-Se addition prevented the induction of expression of these genes. In addition, the protein levels of PERK, inositol requiring protein 1α (IRE1α) and ATF6 were significantly increased, whereas nano-Se addition prevented the enhancements of protein expression in GCs. In conclusion, this study shows that Hg exposure can reduce induce prehierarchical follicular atresia, whereas nano-Se can prevent these effects. Our results also elucidate a key role of ERS in these protective effects of nano-Se in laying hens.

General toxicity and genotoxicity of alternariol: a novel 28-day multi-endpoint assessment in male Sprague-Dawley rats

Alternariol (AOH) is one of the toxins of Alternaria, and it has been widely detected in a variety of foods. It has been reported to be cytotoxic, dermally toxic, genotoxic, and potentially carcinogenic in vitro. However, in vivo toxicity data are lacking. This study used a novel in vivo 28-day multi-endpoint (Pig-a assay + micronucleus test + comet assay) genotoxicity evaluation system to evaluate the general toxicity and genotoxicity of AOH. A total of 42 male Sprague-Dawley rats were randomly distributed into three AOH-treated groups (5.51, 10.03, and 22.05 µg/kg bw), one AOH high-dose recovery group (AOH-HR, 22.05 µg/kg bw), one positive control group (N-ethyl-N-nitrosourea, 40 mg/kg bw), and two vehicle control groups (corn oil and PBS). Treatments were administered by oral gavage for 28 consecutive days. Histopathological lesions were observed in the liver, kidney, and spleen in all AOH-treated groups. No statistical difference was found in each genotoxicity index within 28 days in the AOH-treated groups compared with those in the corn oil group. On day 42, in the AOH-HR group, the rate of Pig-a mutant phenotype reticulocytes (RET^CD59-) significantly increased. On day 56, both RET^CD59- and the rate of Pig-a mutant phenotype erythrocytes (RBC^CD59-) were significantly reduced. These findings indicated that AOH might cumulatively induce genetic mutations.

Mercuric chloride induces sequential activation of ferroptosis and necroptosis in chicken embryo kidney cells by triggering ferritinophagy

Mercuric chloride (HgCl₂) is an environmental pollutant with serious nephrotoxic effects, but the underlying mechanism of HgCl₂ nephrotoxicity is not well understood. Ferroptosis and necroptosis are two programmed cell death (PCD) modalities that have been reported singly in heavy metal-induced kidney injury. However, the interaction between ferroptosis and necroptosis in HgCl₂-induced kidney injury is unclear. Here, we established a model of HgCl₂-exposed chicken embryo kidney (CEK) cells to dissect the progresses and mechanisms of these two PCDs. We found that ferroptosis was initially activated in CEK cells after HgCl₂ exposure for 12 h, and necroptosis was activated subsequently at 24 h. Importantly, further study indicated that the shift from ferroptosis to necroptosis was driven by ROS, which was produced by iron-dependent Fenton reaction, and the iron chelation by DFO prevented the sequential activation of both ferroptosis and necroptosis. To investigate the source of intracellular iron, the regulation of iron homeostasis was first explored and demonstrated a tendency for intracellular iron overload in CEK cells. Interestingly, the cellular ferritin, a free iron depository, decreased in a time-dependent manner. Further studies revealed that the degradation of ferritin was attributed to the activation of selective cargo receptor nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy, and the inhibition of ferritinophagy by CQ prevented the HgCl₂-induced cell death. In conclusion, our study demonstrated that HgCl₂ released excess free iron via ferritinophagy, led to a sustained accumulation of ROS and ultimately activated ferroptosis and necroptosis sequentially. These findings provide a new understanding for the nephrotoxic mechanism of HgCl₂.

Protective Effect of Nanoselenium on Renal Oxidative Damage Induced by Mercury in Laying Hens

This study investigated the effects of dietary nanoselenium (nano-Se) supplementation protecting from renal oxidative damages induced by mercury (Hg) exposure in laying hens. Furthermore, endoplasmic reticulum (ER) stress pathway was explored to reveal the protective mechanism of nano-Se. A total of 576 40-week-old Hyline-White laying hens were randomly allocated to 4 groups with 6 pens per group and 24 hens per pen. The experimental groups were as follows: control (basal diet), control + 27.0 mg/kg Hg, control + 5.0 mg/kg nano-Se, and Hg27.0 + 5.0 mg/kg nano-Se. The results revealed that dietary Hg exposure significantly reduced laying performance (P < 0.05) and egg quality (P < 0.05), whereas nano-Se supplementation partially reversed the reductions. Besides, dietary Hg exposure could induce histopathology damages and apoptosis in kidney, whereas nano-Se addition could alleviate these toxicities effectively. After Hg exposure, the activities and gene expressions of superoxidative dismutase (SOD) (P < 0.05), catalase (CAT) (P < 0.01), glutathione reductase (GR) (P < 0.05) and glutathione peroxidase (GSH-Px) (P < 0.05), and glutathione (GSH) content (P < 0.05) were significantly decreased, while the malondialdehyde (MDA) level was significantly increased (P < 0.05) in kidney. However, nano-Se supplementation partially reversed the levels and gene expressions of these antioxidant biomarkers in kidney. Furthermore, dietary Hg exposure significantly increased the gene expressions of PERK (P < 0.05), ATF4 (P < 0.05), CHOP (P < 0.05), IRE1α (P < 0.05), TRAF2 (P < 0.05), ASK1 (P < 0.05), Caspase-9 (P < 0.05), Caspase-8 (P < 0.05), Caspase-3 (P < 0.05), and Bax/Bcl-2 (P < 0.05), whereas nano-Se supplementation partially reversed these increases of gene expressions. In summary, this study provides evidence that dietary Hg exposure can induce renal oxidative damages, and elucidates an important role of ER stress pathway in nano-Se alleviating renal apoptosis in laying hens.

Effects of Selenium Supplementation on the Ion Homeostasis in the Reproductive Organs and Eggs of Laying Hens Fed With the Diet Contaminated With Cadmium, Lead, Mercury, and Chromium

The objective of this study was to explore the toxic effects of different heavy metals in combination with their deposition and ion homeostasis in the reproductive organs and eggs of laying hens, as well as the alleviating action of selenized yeast. A total of 160 Lohmann pink-shell laying hens (63-week-old) were randomly allocated into four treatments with 10 replicates of four hens each. The four dietary treatments were the corn-soybean meal basal dietary (control; CON); the CON dietary supplemented with 0.4 mg/kg selenium from selenized yeast (Se); the CON dietary supplemented with 5 mg/kg Cd + 50 mg/kg Pb +3 mg/kg Hg + 5 mg/kg Cr (HEM), and the HEM dietary supplemented with 0.4 mg/kg selenium from selenized yeast (HEM+Se). The dietary HEM significantly increased Cd, Pb, and Hg deposition in the egg yolk and ovary, and Cd and Hg deposition in the oviduct and in the follicular wall (p < 0.05). The HEM elevated Fe concentration in the egg yolk, ovary, and oviduct (p < 0.05). The HEM decreased Mn concentration in the egg yolk, Fe, Mn, and Zn concentrations in the egg white, Cu concentration in the ovary, Mg concentration in the oviduct, as well as Ca, Cu, Zn, and Mg concentrations in the follicular walls (p < 0.05). Dietary Se addition elevated Se concentration in the egg yolk, oviduct, and follicular walls and Mg concentration (p < 0.05) in the oviduct, whereas it reduced Fe concentration in the oviduct compared with the HEM-treated hens. Some positive or negative correlations among these elements were observed. Canonical Correlation Analysis showed that the concentrations of Pb and Hg in the egg yolk were positively correlated with those in the ovary. The concentration of Cd in the egg white was positively correlated with that in the oviduct. In summary, dietary Cd, Pb, Hg, and Cr in combination caused ion loss and deposition of HEM in reproductive organs of laying hens. Dietary Se addition at 0.4 mg/kg from selenized yeast alleviated the negative effects of HEM on Fe and Mg ion disorder in the oviduct and follicle wall of hens.

Alternariol monomethyl ether toxicity and genotoxicity in male Sprague-Dawley rats: 28-Day in vivo multi-endpoint assessment

Alternariol monomethyl ether (AME), a typical Alternaria toxin, has often been detected in grains. We have measured the general toxicity and genotoxicity of AME with a 28-day multi-endpoint (Pig-a assay + in vivo micronucleus [MN] test + comet assay) platform. Male Sprague-Dawley rats were administered AME (1.84, 3.67, or 7.35 μg/kg body weight/day), N-Ethyl-N-nitrosourea (40 mg/kg body weight/day), or corn oil by gavage for 28 consecutive days. Another group (AME-high-dose + recovery) was maintained for a further 14 days after the end of the AME administration. Hematology and serum biochemistry results suggested that AME might compromise the immune system. The histopathology results indicated that AME can cause liver (inflammatory cell infiltration, steatosis, and edema), kidney (renal glomerular atrophy), and spleen (white pulp atrophy) damage. The genotoxicity results showed that AME can induce gene mutations, chromosome breakage, and DNA damage, but the effects were diminished after the recovery period. According to point-of-departure analysis (BMDL₁₀), the risk to the population of exposure to AME cannot be ignored and further assessment is needed.

Tolerance and safety evaluation of sodium sulfate: A subchronic study in laying hens

Sodium sulfate (Na₂SO₄) is a readily available chlorine-free source of sodium, which could be used to reduce sodium chloride to maintain the ratio between chlorine and sodium in poultry diets. Dietary supplementation with excessive levels of Na₂SO₄ might be detrimental to bird's health and performance. A subchronic study was carried out to investigate the potential adverse effects of an accidental oversupply of Na₂SO₄ in the diets of laying hens. Four hundred and fifty 21-week-old Hy-Line White layers were randomly assigned to 5 treatments with 6 replicates. The birds were fed diets supplemented with 0 (control), 0.3%, 0.6%, 1.5%, and 3.0% Na₂SO₄ for 8 weeks. Laying performance, egg quality parameters, clinical blood parameters, histopathology, intestinal barrier functions, and intestinal microflora composition were measured. No clinical signs of intoxication or mortality were observed during the experimental period. The results of this study showed that the optimal levels of Na₂SO₄ (0.3% to 0.6%) significantly improved the laying rates, average daily egg mass, and eggshell quality of hens compared to the control (P < 0.05). However, 3.0% Na₂SO₄ produced negative effects on laying performance, eggshell quality, blood biochemistry, and particularly on liver and kidney pathology, and intestinal morphology and barrier functions compared with the controls. Although minor changes were observed in clinical blood parameters of hens receiving 1.5% Na₂SO₄, these were not considered to be of toxicological significance due to the absence of any organ pathological changes in hens. In conclusion, our results indicated that a Na₂SO₄ concentration of 1.5% was non-deleterious to laying hens after a daily administration for 56 d, namely that dietary supplementation of up to 5 times the maximum recommended dose is safely tolerated by laying hens.

Apoptosis induced by mercuric chloride is associated with upregulation of PERK-ATF4-CHOP pathway in chicken embryonic kidney cells

Mercuric chloride (HgCl₂) is a serious environmental toxicant. So far, the toxicity mechanism of HgCl₂ in chicken embryonic kidney (CEK) cells is not still fully understood. In this study, the possible molecular mechanisms of HgCl₂ on apoptosis of CEK cells were investigated. Results showed that the cell morphology changed, and cell viability was significantly decreased (P < 0.05) after HgCl₂ exposure. Besides, apoptosis rate was significantly increased after HgCl₂ exposure (P < 0.05). The gene and protein expressions of B-cell lymphoma-2 associate X/B-cell lymphoma-2 (P < 0.05), caspase-3 (P < 0.05), and caspase-9 (P < 0.05) were significantly enhanced by HgCl₂ in CEK cells. We also found that intracellular reactive oxygen species level was significantly enhanced (P < 0.05), and the flux of calcium ion to mitochondria occurred after HgCl₂ exposure. In terms of molecular mechanisms, the mRNA and protein expressions associated with endoplasmic reticulum (ER) stress were significantly increased after HgCl₂ exposure (P < 0.05), including glucose regulated protein 78, protein kinase RNA-like endoplasmic reticulum kinase (PERK), activating transcription factor 4 (ATF4), and C/EBP homologous protein (CHOP). However, pretreated with 1-μmol/L 4-phenylbutyrate (ER stress inhibitor) alleviated the apoptosis and downregulated PERK-ATF4-CHOP pathway in CEK cells. Taken together, upregulation of PERK-ATF4-CHOP pathway of ER stress induced by HgCl₂ is associated with apoptosis in CEK cells.

Effects of varying dietary intoxication with lead on the performance and ovaries of laying hens

In this study, we explored the effect of dietary lead nitrate on zootechnical performance, egg quality, accumulation of ovarian plumbum (Pb), follicular atresia rate, and ovarian oxidative stress in laying hens. Furthermore, the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling molecule was studied to reveal the molecular mechanism of the stress. A total of 512 Hy-Line Brown laying hens aged 40 wk were randomly allocated to 4 groups (with 8 pens per group and 16 hens per pen). The Pb concentrations used to treat the 4 groups were 3.20, 33.20, 63.20, and 93.20 mg/kg. The results revealed that dietary Pb exposure significantly linearly reduced the zootechnical performance (P < 0.01) but significantly linearly increased the feed conversion ratio (P < 0.01). The dietary Pb exposure significantly linearly reduced the Haugh units (P < 0.01), albumen height (P < 0.01), eggshell thickness (P < 0.01), and eggshell strength (P < 0.01). In addition, the dietary Pb exposure significantly enhanced the follicular atresia rate (P < 0.01). After dietary Pb exposure, superoxide dismutase (P < 0.01) and glutathione peroxidase (GSH-Px) (P < 0.01) activities and glutathione (P < 0.01) contents were significant decreased quadratically, and there were significant linear decreases in the activities of catalase (CAT) (P < 0.01) and glutathione reductase (GR) (P < 0.01), whereas malondialdehyde content was significantly linearly increased (P < 0.01). In addition, except for manganese superoxide dismutase, the gene expressions of copper-zinc superoxide dismutase (P < 0.01), CAT (P < 0.01), and GR (P < 0.01) were significant decreased linearly. In addition, there were significantly quadratic decreases in the mRNA expressions of GSH-Px (P < 0.01) and Nrf2 (P < 0.01). By way of contrast, the Kelch-like ECH-associated protein 1 (Keap1) gene expression was significantly linearly increased (P < 0.01). In conclusion, dietary Pb exposure could induce oxidative stress by impairing the Nrf2-Keap1 signal pathway in the ovaries of laying hens.

Selenium relieves oxidative stress, inflammation, and apoptosis within spleen of chicken exposed to mercuric chloride

Mercuric chloride (HgCl₂) is a widely distributed environmental pollutant with multiorgan toxicity including immune organs such as spleen. Selenium (Se) is an essential trace element in animal nutrition and exerts biological activity to antagonize organ toxicity caused by heavy metals. The objective of this study was to explore the underlying mechanism of the protective effects of Se against spleen damage caused by HgCl₂ in chicken. Ninety male Hyline brown chicken were randomly divided into 3 groups namely Cont, HgCl₂, and HgCl₂+Se group. Chicken were provided with the standard diet and nontreated water, standard diet and HgCl₂-treated water (250 ppm), and sodium selenite-treated diet (10 ppm) plus HgCl₂-treated water (250 ppm), respectively. After being fed for 7 wk, the spleen tissues were collected, and spleen index, the microstructure of the spleen, and the indicators of oxidative stress, inflammation, apoptosis as well as heat shock proteins (HSP) were detected. First, the results of spleen index and pathological examination confirmed that Se exerted an antagonistic effect on the spleen injury induced by HgCl₂. Second, Se ameliorated HgCl₂-induced oxidative stress by decreasing the level of malondialdehyde and increasing the levels of glutathione, glutathione peroxidase, and total antioxidant capacity. Third, Se attenuated HgCl₂-induced inflammation by decreasing the protein expression of nuclear factor kappa-B, inducible nitric oxide synthase, and cyclooxygenase-2, and the gene expression of interleukin (IL)-1β, IL-6, IL-8, IL-12β, IL-18 as well as tumor necrosis factor-α. Fourth, Se inhibited HgCl₂-induced apoptosis by downregulating the protein expression of BCL2 antagonist/killer 1 and upregulating the protein expression of B-cell lymphoma-2. Finally, Se reversed HgCl₂-triggered activation of HSP 60, 70, and 90. In conclusion, Se antagonized HgCl₂-induced spleen damage in chicken, partially through the regulation of oxidative stress, inflammatory, and apoptotic signaling.

Effect of iron glycine chelate supplementation on egg quality and egg iron enrichment in laying hens

This study was conducted to evaluate the effects of iron glycine chelate (Fe-Gly) on egg quality of laying hens. A total of 810 laying hens (HyLine Variety White, 26 wk old) were randomly assigned to 6 groups, and each group consisting of 135 hens (5 replicates of 27 hens each). Hens in the control group received a diet supplemented with 60 mg Fe/kg as FeSO4, whereas hens in the other 5 groups received diets supplemented with 0, 20, 40, 60, and 80 mg Fe/kg from Fe-Gly, respectively. The study showed that dietary Fe-Gly treatments influenced (P < 0.05) the internal egg quality (egg weight, Haugh unit, albumen height), compared with the control group. However, dietary Fe-Gly supplementation showed few effects on the ultrastructure of eggshell in this study. The group of 60 mg Fe/kg as Fe-Gly was promoted (P < 0.05) in succinate dehydrogenase levels of liver and spleen compared with the 0 mg Fe-Gly/kg group, whereas the control (Fe/kg as FeSO4) group has no differences compared with the 0 mg Fe-Gly/kg group. The concentrations of Fe in the eggshell, yolk, and albumen were increased with increasing concentrations of Fe-Gly, where Fe-Gly (60, 80 mg Fe/kg) had higher (P < 0.01) Fe concentration than the control in yolk and albumen. The Fe-Gly groups (60, 80 mg Fe/kg) were influenced (P < 0.05) in transferrin, divalent mental transport 1, and ferroportin 1, compared with the control (FeSO4). In conclusion, Fe-Gly (60 mg Fe/kg) improved egg quality and egg iron enrichment. In general, there were no significant differences between Fe-Gly (40) and the control group in albumen height, Haugh unit, Fe concentration in eggshell and yolk. It revealed that FeSO4 could be substituted by a lower concentration of Fe-Gly and Fe-Gly may be superior to FeSO4 for egg quality in laying hens.

The Effect of Mercury Chloride and Boric Acid on Rat Erythrocyte Enzymes

The aim of this study was to investigate the effects of mercury chloride and boric acid on rat (Wistar albino) erythrocyte: glucose 6-phosphate dehydrogenase (G6PD), 6-phosphoglucona-te dehydrogenase (6PGD), thioredoxin reductase (TrxR), glutathione reductase (GR) and glutathione S-transferase (GST) enzymes in vivo, and the rat erythrocyte G6PD enzyme in vitro. In the in vivo study, 24 male rats were divated into three different groups: control (C), mercury chloride (M), and mercury chloride + boric acid (M + BA). At the completion of this study, a significant degree of inhibition for both G6PD and GST enzyme activity was observed in the M groups when compared to the C group (p < 0.05), and no significant effect was observed in the 6PGD enzyme. However, there was significantly increased TrxR and GR enzyme activity of both the M and M + BA groups (p < 0.05). In the in vitro study, the G6PD enzyme from rat erythrocytes was purified with 2',5'-ADP Sepharose-4B affinity chromatography, and the effect of both mercury chloride and boric acid on the enzyme activity was investigated. The results showed that boric acid increased the G6PD enzyme activity while the mercury ions that inhibited the enzyme activity (IC₅₀ values of 346 μM and K_i values of 387 μM) were noncompetitive.