Zinc might prevent heat-induced hepatic injury by activating the Nrf2-antioxidant in mice

Zinc Ameliorates Tripterygium Glycosides-Induced Reproductive Impairment in Male Rats by Regulating Zinc Homeostasis and Expression of Oxidative Stress-Related Genes

Tripterygium glycosides (TG) can seriously damage male reproductive function, and the reproductive system is difficult to restore after stopping the administration of TG in male rats. Zinc (Zn) is one of the most important trace elements in the human body and plays an important role in maintaining male fertility. The aim of this study was to investigate whether zinc supplementation could improve the testicular reproductive damage induced by TG toxicity in rats and to investigate its mechanism of action. The results showed that zinc sulfate (ZnSO4) could improve testicular tissue structure and semen parameters, promote testosterone synthesis, increase zinc-containing enzyme activity, increase zinc concentration in serum and testicular tissues, and maintain zinc homeostasis in male rats induced by TG toxicity. Zinc supplementation activated relevant signalling molecules in the KEAP1-NRF2/ARE pathway and alleviated TG-induced oxidative stress. Therefore, this study concluded that zinc supplementation could improve reproductive damage by regulating zinc homeostasis and the expression of genes related to oxidative stress.

Effects of Macleaya cordata Extract on Blood Biochemical Indices and Intestinal Flora in Heat-Stressed Mice

Heat stress (HS) leads to disturbance of homeostasis and gut microbiota. Macleaya cordata extract (MCE) has anti-inflammatory, antibacterial, and gut health maintenance properties. Still, the specific effects of MCE on blood biochemical indices and gut microbiota homeostasis in heat-stressed mice are not entirely understood. This study aimed to investigate the impact of MCE on blood biochemical indices and gut microbiota in heat-stressed mice. A control group (CON) (25 °C, n = 6) and HS group (42 °C, n = 6) were gavaged with normal saline 0.2 mL/g body weight/day, and HS plus MCE group (HS-MCE) (42 °C, n = 6) was gavaged with 5 mg MCE/kg/day. HS (2 h/d) on 8–14 d. The experiment lasted 14 days. The results showed that HS increased mice’ serum aspartate transaminase, alanine transferase activities, heat shock protein 70 level, and malondialdehyde concentrations, and decreased serum catalase and superoxide dismutase activities. HS also disrupted microbiota diversity and community structure in mice, increasing the Bacteroidetes and decreasing Firmicutes and Lactobacillus; however, MCE can alleviate the disturbance of biochemical indicators caused by HS and regulate the flora homeostasis. Furthermore, MCE was able to moderate HS-induced metabolic pathways changes in gut microbiota. The Spearman correlation analysis implied that changes in serum redox status potentially correlate with gut microbiota alterations in HS-treated mice.

The adverse effect of heat stress and potential nutritional interventions

Heat stress can cause tissue damage and metabolic disturbances, including intestinal and liver dysfunction, acid-base imbalance, oxidative damage, inflammatory response, and immune suppression. Serious cases can lead to heatstroke, which can be life-threatening. The body often finds it challenging to counteract these adverse effects, and traditional cooling methods are limited by the inconvenience of tool portability and the difficulty of determining the cooling endpoint. Consequently, more research was conducted to prevent and mitigate the negative effect of heat stress via nutritional intervention. This article reviewed the pathological changes and altered metabolic mechanisms caused by heat stress and discussed the protein (amino acid), vitamin, trace element, and electrolyte action pathways and mechanisms to mitigate heat stress and prevent heat-related disease. The main food sources for these nutrients and the recommended micronutrient supplementation forms were summarized to provide scientific dietary protocols for special populations.

Mechanisms Underlying the Protective Effect of Maternal Zinc (ZnSO4 or Zn-Gly) against Heat Stress-Induced Oxidative Stress in Chicken Embryo

Environmental factors such as high temperature can cause oxidative stress and negatively affect the physiological status and meat quality of broiler chickens. The study was conducted to evaluate the effects of dietary maternal Zn-Gly or ZnSO4 supplementation on embryo mortality, hepatocellular mitochondrial morphology, liver antioxidant capacity and the expression of related genes involved in liver oxidative mechanisms in heat-stressed broilers. A total of 300 36-week-old Lingnan Yellow broiler breeders were randomly divided into three treatments: (1) control (basal diet, 24 mg zinc/kg); (2) inorganic ZnSO4 group (basal diet +80 mg ZnSO4/kg); (3) organic Zn-Gly group (basal diet +80 mg Zn-Gly/kg). The results show that maternal zinc alleviated heat stress-induced chicken embryo hepatocytes’ oxidative stress by decreasing the content of ROS, MDA, PC, 8-OHdG, and levels of HSP70, while enhancing T-SOD, T-AOC, CuZn-SOD, GSH-Px, CTA activities and the content of MT. Maternal zinc alleviated oxidative stress-induced mitochondrial damage in chick embryo hepatocytes by increasing mitochondrial membrane potential and UCP gene expression; and Caspase-3-mediated apoptosis was alleviated by increasing CuZn-SOD and MT gene expression and decreasing Bax gene expression and reducing the activity of caspase 3. Furthermore, maternal zinc treatment significantly increased Nrf2 gene expression. The results above suggest that maternal zinc can activate the Nrf2 signaling pathway in developing chick embryos, enhance its antioxidant function and reduce the apoptosis-effecting enzyme caspase-3 activities, thereby slowing oxidative stress injury and tissue cell apoptosis.

Inhibitory effects of zinc chloride (ZnCl2), n-acetyl-L-cysteine (NAC), and calcium/calmodulin dependent protein kinase II inhibitor (KN93) on Cd2+-induced abnormal cell morphology and membrane permeability

Cadmium (Cd) could reduce abnormal cell morphology and membrane permeability, however, there are few studies on the detoxification of Cd-reduced cell membrane toxicity. In the present study, we firstly studied the effects of zinc chloride (ZnCl₂), n-acetyl-L-cysteine (NAC), and calcium/calmodulin dependent protein kinase II inhibitor (KN93) on cell membrane permeability, respectively; then, we studied the inhibitory effects of ZnCl₂, NAC, and KN93 on Cd²⁺-induced abnormal cell membrane permeability by scanning electrochemical microscopy (SECM) scanning imaging, transverse scanning curve and DPV technology. Our results showed that 10 μmol·L^-1 ZnCl₂, 0.5 mmol·L^-1 NAC and 5 μmol·L^-1 KN93 could significantly improve the activity of MCF-7 cells, while did not destroy the cell morphology and membrane permeability. 0.5 mmol·L^-1 NAC and 5 μmol·L^-1 KN93 could significantly inhibit the effects of Cd²⁺ on the morphology and membrane permeability of MCF-7 cells (p < 0.01). 10 μmol·L^-1 ZnCl₂ could significantly inhibit the effect of Cd on the membrane permeability of MCF-7 cells, however, it cannot completely eliminate the morphological changes of MCF-7 cells caused by Cd²⁺. The results of cell activity experiment showed that 10 μmol·L^-1 ZnCl₂, 0.5 mmol·L^-1 NAC and 5 μmol·L^-1 KN93 could inhibit the effect of Cd²⁺ on the activity of MCF-7 cells. By comparing the inhibitory effects of ZnCl₂, NAC and KN93 on Cd²⁺- induced cytotoxicity, 5 μmol·L^-1 KN93 had the robust effect on the maintenance of MCF-7 cell morphology and cell membrane integrity. Our research provided evidence on Zn supplement, NAC as antioxidant drugs, and KN93 as special inhibitor for the detoxification of Cd²⁺-reduced abnormal cell morphology and membrane permeability.

Hepatoprotective Effects of Selenium-Enriched Probiotics Supplementation on Heat-Stressed Wistar Rat Through Anti-Inflammatory and Antioxidant Effects

The purpose of this study was to elucidate the effects of selenium-enriched probiotics on the liver of heat-stressed Wistar rats. Ten-week-old male rats were assigned to four groups: control (Con); high temperature (HT); high temperature plus probiotics (HT + P: 10¹¹ CFU/mL Lactobacillus acidophilus and 10⁹ CFU/mL Saccharomyces cerevisiae); or high temperature plus selenium-enriched probiotics (HT + SeP: 0.3 mg/kg Se, 10¹¹ CFU/mL L. acidophilus and 10⁹ CFU/mL S. cerevisiae). The HT, HT + P, and HT + SeP groups were maintained at higher ambient temperature (40-42 °C), while the control group was kept at room temperature (25 °C). After 42 days of thermal exposure, blood and liver tissues were collected and analyzed for morphological and molecular markers of liver physiology. The body weight of rats in the HT group decreased but liver weight and live index were increased. Histological examination showed dilation of liver sinusoids and congestion of interstitial veins in HT group. Moreover, the histomorphology of the liver in HT + P and HT + SeP groups was restored, and the serum AST, ALT, ALP, LDH, and hepatic MDA level decreased significantly, but the serum total protein level and the liver SOD, T-AOC, and GSH-PX activities were increased significantly relative to the HT group. In addition, the mRNA level of Gpx1, SOD1, Nrf2, and Bcl-2 was significantly increased, while the expression level of Bax, IL-6, TNF-α, COX-2, NF-κB, α-SMA, TGFβ1, Collagen I, HSP70, and HSP90 was significantly decreased in liver tissues after SeP supplementation. We concluded that SeP can protect Wistar rats from oxidative stress, inflammation, apoptosis, and liver fibrosis induced by heat stress.

Sphingosine kinase inhibitor, SKI-II confers protection against the ionizing radiation by maintaining redox homeostasis most likely through Nrf2 signaling

Exposure to ionizing radiation (IR) set a series of deleterious events causing acute radiation syndrome and mortality, posing the need for a potent and safe radio-protective drug. IR induces cell death predominantly by causing oxidative stress and macromolecular damage. The pre-existing antioxidant defence machinery of the cellular system plays a crucial role in protecting the cells against oxidative stress by activation of Nrf2. The current study was undertaken to investigate the radio-protective potential of sphingosine kinase inhibitor (SKI-II), which was demonstrated to activate Nrf2 signaling. The safety and efficacy of SKI-II were evaluated with cell cytotoxicity, proliferation index, and clonogenic survival assays in different cell lines, namely Raw 264.7, INT-407, IEC-6 and NIH/3T3 cell lines. A safe dose of SKI-II was found radio-protective in all the cell lines linked with the activated antioxidant defence system, thereby resulting in the amelioration of IR induced oxidative stress. SKI-II pretreatment also significantly reduced DNA damage, micronuclei expression, and accelerated DNA repair kinetics as compared to IR exposed cells. Reduced oxidative stress and enhanced DNA repair significantly reduced apoptosis and suppressed the pro-death signaling associated with IR exposure. Furthermore, the in-vitro observation was verified in the in-vivo model (C57 BL/6). The Intra-peritoneal (IP) administration of SKI-II, 2 h before a lethal dose of IR exposure (7.5 Gy) resulted in 75% survival. These results imply that SKI-II ameliorates IR-induced oxidative stress and cell death by inducing anti-oxidant defence system and DNA repair pathways, thus strengthening its potential to be used as radiation countermeasure.

Zinc protects against cadmium-induced toxicity in neonatal murine engineered cardiac tissues via metallothionein-dependent and independent mechanisms

Cadmium (Cd) is a nonessential heavy metal and a prevalent environmental toxin that has been shown to induce significant cardiomyocyte apoptosis in neonatal murine engineered cardiac tissues (ECTs). In contrast, zinc (Zn) is a potent metallothionein (MT) inducer, which plays an important role in protection against Cd toxicity. In this study, we investigated the protective effects of Zn against Cd toxicity in ECTs and explore the underlying mechanisms. ECTs were constructed from neonatal ventricular cells of wild-type (WT) mice and mice with global MT gene deletion (MT-KO). In WT-ECTs, Cd (5-20 μM) caused a dose-dependent toxicity that was detected within 8 h evidenced by suppressed beating, apoptosis, and LDH release; Zn (50-200 μM) dose-dependently induced MT expression in ECTs without causing ECT toxicity; co-treatment of ECT with Zn (50 µM) prevented Cd-induced toxicity. In MT-KO ECTs, Cd toxicity was enhanced; but unexpectedly, cotreatment with Zn provided partial protection against Cd toxicity. Furthermore, Cd, but not Zn, significantly activated Nrf2 and its downstream targets, including HO-1; inhibition of HO-1 by a specific HO-1 inhibitor, ZnPP (10 µM), significantly increased Cd-induced toxicity, but did not inhibit Zn protection against Cd injury, suggesting that Nrf2-mediated HO-1 activation was not required for Zn protective effect. Finally, the ability of Zn to reduce Cd uptake provided an additional MT-independent mechanism for reducing Cd toxicity. Thus, Zn exerts protective effects against Cd toxicity for murine ECTs that are partially MT-mediated. Further studies are required to translate these findings towards clinical trials.

Antioxidant and Anti-Inflammatory Effects of Different Zinc Sources on Diquat-Induced Oxidant Stress in a Piglet Model

Zinc (Zn) plays a crucial role in reducing oxidative stress and diarrhea in postweanling piglets. This study is aimed at comparing the effects of zinc chelate of 2-hydroxy-4 methyl-thio butanoic acid (HMZn) and ZnSO₄ on the oxidative stress in weaned piglets. A total of 32 piglets were randomly divided into 4 treatments: CON: basal diet+80 mg/kg Zn as ZnSO₄; DIQ: basal diet+80 mg/kg Zn as ZnSO₄; HMZn: basal diet+200 mg/kg Zn as HMZn; and ZnSO₄: basal diet+200 mg/kg Zn as ZnSO₄. On day 15, the DIQ, HMZn, and ZnSO₄ groups were injected intraperitoneally with diquat except for the CON group. The trial lasted 21 days. The results showed that zinc sources did not influence the growth performance during the first 14 days. But HMZn increased activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), and total antioxidant capacity (T-AOC) in serum (P < 0.05). After diquat injection, the fecal score was decreased in the HMZn group. Both HMZn and ZnSO₄ increased the activities of GPX and T-AOC in serum and the relative mRNA expressions of hepatic and renal Nrf2, SOD1, and GPX compared with the DIQ group (P < 0.05). Moreover, the relative mRNA expression of inflammatory factors in the small intestine, liver, and kidney was downregulated; the phosphorylation of NF-κB protein was inhibited in the HMZn group compared with the DIQ and ZnSO₄ groups (P < 0.05). In general, HMZn showed notable advantage over ZnSO₄ in reducing diarrhea and improving antioxidant and anti-inflammatory ability in piglets challenged with diquat.

Zinc-induced protective effect for testicular ischemia-reperfusion injury by promoting antioxidation via microRNA-101-3p/Nrf2 pathway

The present study was performed to determine the protective effect of Zinc on the rat testicular ischemia-reperfusion (I/R) injury and its mechanism. In vivo, the pathological changes and the apoptosis index were significantly relieved in the rats with Low-dose Zinc pretreatment, compared to the I/R group. After Low-dose Zinc treatment, the levels of tissue Malondialdehyde (MDA) were significantly decreased, while tissue antioxidant indices were significantly increased. Meanwhile, the level of NF-κB was significantly lower compared to I/R group, while the levels of Nrf2-dependent antioxidant enzymes were significantly higher in Low-dose Zinc+I/R group. In vitro, Low-dose Zinc markedly increased Leydig cell (TM3) cell viability, and relieved testicular oxidative damage via down-regulating ROS. A total of 22 differently expressed microRNAs were screened out using microRNA microarray in rat testicular tissue caused by I/R injury, especially showing that miR-101-3p was selected as the target miRNA. Furthermore, the levels of Nrf2 and NF-κB were apparently increased/decreased in TM3 cells treated with Hypoxic/Reoxygenation (H/R) after miR-101-3p mimics/inhibitor. In addition, H/R-induced testicular oxidative damage was recovered in TM3 administrated with miR-101-3p inhibitor and si-Nrf2. Therefore, this study provided a novel insight for investigating protective effect of Zinc on testicular I/R injury by promoting antioxidation via miR-101-3p/Nrf2.

Effects of Dietary Zinc on Carcass Traits, Meat Quality, Antioxidant Status, and Tissue Zinc Accumulation of Pekin Ducks

This study investigated the effects of dietary zinc on carcass traits, meat quality, antioxidant capacity, and tissue zinc accumulation of Pekin ducks. A total of 768 1-day-old Pekin ducks were randomly allocated to six dietary treatments and penned in groups of 16 with 8 pens per treatment. Ducks were fed a basal corn-soybean meal diet supplemented with graded levels of zinc sulfate (0, 15, 30, 60, 120, 240 mg zinc/kg) for 35 days. The slaughter weight, carcass weight, eviscerated weight, and breast and leg muscle weight of Pekin ducks were increased with increasing dietary zinc levels (P < 0.05). Zinc supplementation increased the pH value at 24-h postmortem and the intramuscular fat (IMF) (P < 0.05), but decreased the lightness value, drip loss, and shear force in breast meat of ducks (P < 0.05). Increasing dietary zinc increased the activity of superoxide dismutase (SOD), glutathione peroxidase (GPX), glutathione reductase (GR), catalase (CAT), and the content of glutathione (GSH), as well as decreased the malondialdehyde (MDA) level in breast muscle (P < 0.05). RT-qPCR analysis demonstrated that supplemental zinc notably enhanced the transcription of SOD, GPX, GR, CAT, and nuclear factor erythroid 2-related factor 2 (Nrf2) (P < 0.05). Meanwhile, zinc accumulation in plasma, breast muscle, liver, and tibia were linearly increased with increasing zinc supplementation (P < 0.05). These results indicated that zinc supplementation could improve carcass traits and meat quality and increase the activities and mRNA levels of antioxidant enzymes in breast muscle of Pekin duck. Base on broken-line regression analysis that 91.32 mg/kg of dietary zinc was suggested for optimal carcass traits, meat quality, antioxidant capacity, and zinc deposition of Pekin duck.

Response of the Chinese Soft-Shelled Turtle to Acute Heat Stress: Insights From the Systematic Antioxidant Defense

Understanding the responses of animals to acute heat stress can help to reveal and predict the effect of more frequent extreme hot weather episodes on animal populations and ecosystems in the content of global climate change. Antioxidant defenses can help to protect animals against oxidative stress caused by intense temperature variation. In the present study, systematic antioxidant responses to acute heat stress (Δ15°C and maintained for 12 h) and subsequent recovery were assessed by evaluating gene transcript levels and relative enzyme activities in tissues of Pelodiscus sinensis, a subtropical freshwater turtle. Targets included nuclear factor erythroid 2-related factor 2 (Nrf2, the upstream transcription factor), antioxidant enzymes, and the glutathione (GSH) and ascorbic acid (AA) systems. Results showed three main patterns of expression change among antioxidant genes: (1) gene expression of Mn-superoxide dismutase (Mn-SOD), glutathione peroxidase 4 (GPx 4), and catalase (CAT) increased in response to heat stress or recovery in the liver; (2) transcripts of most genes did not change in brain, liver, and kidney of P. sinensis; and (3) expression of several GST isoforms were affected by heat stress or recovery in brain and kidney. However, relative enzyme activities involved in antioxidant defense were little affected by acute heat stress and recovery, indicating a relatively conservative antioxidant response in P. sinensis. Furthermore, results for malondialdehyde (MDA) levels indicated that acute heat stress and recovery did not cause a net increase in oxidative damage in turtle tissues and, in particular, MDA levels in spleen decreased along with increased splenic ascorbic acid concentration. Overall, the present study revealed a conservative antioxidant response in P. sinensis, which may be indicative of a high basal stress tolerance and relate with adaptation to climate change in freshwater turtles.

Boron Affects the Development of the Kidney Through Modulation of Apoptosis, Antioxidant Capacity, and Nrf2 Pathway in the African Ostrich Chicks

The nuclear-related factor 2 (Nrf2) pathway is the most important mechanism in antioxidant capacity, which regulates the cell's redox homeostasis. In addition, Nrf2 pathway also can inhibit cell apoptosis. The mechanism of boron actions on various organs is well documented. But, it is not known whether boron can also regulate the Nrf2 pathway in the kidneys. Therefore, in this research, the actions of boron on the kidneys of ostrich chicks, especially the antioxidant effects, have been studied. The ostrich chicks were divided into six groups and supplemented with boric acid (BA) (source of boron) in the drinking water (0, 40, 80, 160, 320, 640 mg respectively) to examine apoptotic, antioxidant, biochemical, and histochemical alterations induced by boron administration in the ostrich chick's kidney. The cellular apoptosis was assessed by terminal deoxynucleotidyl transferase dUTP Nick-End Labeling (TUNEL) assay. The relative antioxidant enzymes (T-AOC, MDA, GSH-Px, SOD, GR, CAT) and biochemical indices (ALT, AST, ALP, CK, LDH, BUN, CREA, UA) in the kidney were determined by spectrophotometric method. The expression of three important genes in the antioxidant pathway (Nrf2, HO-1, GCLc) was measured by quantitative real-time PCR (qPCR), and the localization of key regulator Nrf2 was examined by immunohistochemistry (IHC) method. Western blotting was also performed to further validate our results. Our results revealed that low doses of boron (up to 160 mg) had positive effect, while high doses (especially 640 mg) caused negative effect on the development of the kidney. The cellular apoptosis was in a biphasic manner by altering the boron quantities. The low doses regulate the oxidative and enzyme activity in the kidney. The IHC and western blot showed maximum localization of Nrf2 in 80 mg/L BA dose group. Furthermore, supplementation of boron at low doses upregulated the expression of genes involved in the antioxidant pathway. Taken together, the study demonstrated that low levels of boron (up to 160 mg) inhibited the cell apoptosis, regulate the enzyme activity, and improved the antioxidant system, thus may encourage the development of the ostrich chick's kidney, while a high amount of boron especially 640 mg/L promoted cell apoptosis and reduced the antioxidant capacity, thus caused negative effect to the ostrich chick's kidney.

Metabonomics Approach to Assessing the Modulatory Effects of Kisspeptin-10 on Liver Injury Induced by Heat Stress in Rats

The protective effects of Kisspeptin on heat-induced oxidative stress in rats were investigated by using a combination of biochemical parameters and metabonomics. Metabonomic analyses were performed using gas chromatography/mass spectrometry in conjunction with multivariate and univariate statistical analyses. At the end point of the heat stress experiment, histological observation, ultrastructural analysis and biochemical parameters were measured. Metabonomic analysis of liver tissue revealed that Kisspeptin mainly attenuated the alteration of purine metabolism and fatty acid metabolism pathways. Futhermore, Kisspeptin also increased the levels of GSH, T-AOC as well as SOD activities, and upregulated MDA levels. These results provide important mechanistic insights into the protective effects of Kisspeptin against heat-induced oxidative stress.