Antimicrobial Protein LECT2-b Helps Maintain Gut Microbiota Homeostasis via Selectively Targeting Certain Pathogenic Bacteria.

Antimicrobial peptides/proteins (AMPs) constitute a critical component of gut immunity in animals, protecting the gut from pathogenic bacteria. However, the interactions between AMPs and gut microbiota remain elusive. In this study, we show that leukocyte-derived chemotaxin-2 (LECT2)-b, a recently discovered AMP, helps maintain gut homeostasis in grass carp (Ctenopharyngodon idella), one of the major farmed fish species globally, by directly regulating the gut microbiota. Knockdown of LECT2-b resulted in dysregulation of the gut microbiota. Specifically, LECT2-b deficiency led to the dominance of Proteobacteria, consisting of proinflammatory bacterial species, over Firmicutes, which includes anti-inflammatory bacteria. In addition, the opportunistic pathogenic bacteria genus Aeromonas became the dominant genus replacing the probiotic bacteria Lactobacillus and Bacillus. Further analysis revealed that this effect was due to the direct and selective inhibition of certain pathogenic bacterial species by LECT2-b. Moreover, LECT2-b knockdown promoted biofilm formation by gut microbiota, resulting in tissue damage and inflammation. Importantly, LECT2-b treatment alleviated the negative effects induced by LECT2-b knockdown. These findings highlight the crucial role of LECT2-b in maintaining the gut microbiota homeostasis and mucosal health. Overall, our study provides important data for understanding the roles of AMPs in the regulation of gut homeostasis in animals.

LECT2 Is a Novel Antibacterial Protein in Vertebrates.

In vertebrates, leukocyte-derived chemotaxin-2 (LECT2) is an important immunoregulator with conserved chemotactic and phagocytosis-stimulating activities to leukocytes during bacterial infection. However, whether LECT2 possesses direct antibacterial activity remains unknown. In this article, we show that, unlike tetrapods with a single LECT2 gene, two LECT2 genes exist in teleost fish, named LECT2-a and LECT2-b Using grass carp as a research model, we found that the expression pattern of grass carp LECT2-a (gcLECT2-a) is more similar to that of LECT2 in tetrapods, while gcLECT2-b has evolved to be highly expressed in mucosal immune organs, including the intestine and skin. Interestingly, we found that gcLECT2-b, with conserved chemotactic and phagocytosis-stimulating activities, can also kill Gram-negative and Gram-positive bacteria directly in a membrane-dependent and a non-membrane-dependent manner, respectively. Moreover, gcLECT2-b could prevent the adherence of bacteria to epithelial cells through agglutination by targeting peptidoglycan and lipoteichoic acid. Further study revealed that gcLECT2-b can protect grass carp from Aeromonas hydrophila infection in vivo, because it significantly reduces intestinal necrosis and tissue bacterial load. More importantly, we found that LECT2 from representative tetrapods, except human, also possesses direct antibacterial activities, indicating that the direct antibacterial property of LECT2 is generally conserved in vertebrates. Taken together, to our knowledge, our study discovered a novel function of LECT2 in the antibacterial immunity of vertebrates, especially teleost fish, greatly enhancing our knowledge of this important molecule.

Insights into the Antibacterial Properties of Complement Peptides C3a, C4a, and C5a across Vertebrates.

Complement peptides C3a, C4a, and C5a are important components of innate immunity in vertebrates. Although they diverged from a common ancestor, only C3a and C4a can act as antibacterial peptides in Homo sapiens, suggesting that C5a has evolved into a purely chemotactic molecule; however, the antibacterial properties of C3a, C4a, and C5a across vertebrates still require elucidation. In this article, we show that, unlike those in H. sapiens, Mus musculus C3a, C4a, and C5a all possess antibacterial activities, implying that the antibacterial properties of C3a, C4a, and C5a have evolved divergently in vertebrates. The extremely different net charge, a key factor determining the antibacterial activities of cationic antimicrobial peptides, of vertebrate C3a, C4a, and C5a supports this speculation. Moreover, the antibacterial activity of overlapping peptides covering vertebrate C3a, C4a, and C5a further strongly supports the speculation, because their activity is positively correlated with the net charge of source molecules. Notably, the structures of C3a, C4a, and C5a are conserved in vertebrates, and the inactive overlapping peptides can become antibacterial peptides if mutated to possess enough net positive charges, indicating that net charge is the only factor determining the antibacterial properties of vertebrate C3a, C4a, and C5a. More importantly, many vertebrate C3a-, C4a-, and C5a-derived peptides possess high antibacterial activities yet exhibit no hemolytic activities, suggesting the application potential in anti-infective therapy. Taken together, our findings reveal that vertebrate C3a, C4a, and C5a are all sources of antibacterial peptides that will facilitate the design of excellent peptide antibiotics.

Insights into the Antibacterial Properties of Complement Peptides C3a, C4a, and C5a across Vertebrates.

Complement peptides C3a, C4a, and C5a are important components of innate immunity in vertebrates. Although they diverged from a common ancestor, only C3a and C4a can act as antibacterial peptides in Homo sapiens, suggesting that C5a has evolved into a purely chemotactic molecule; however, the antibacterial properties of C3a, C4a, and C5a across vertebrates still require elucidation. In this article, we show that, unlike those in H. sapiens, Mus musculus C3a, C4a, and C5a all possess antibacterial activities, implying that the antibacterial properties of C3a, C4a, and C5a have evolved divergently in vertebrates. The extremely different net charge, a key factor determining the antibacterial activities of cationic antimicrobial peptides, of vertebrate C3a, C4a, and C5a supports this speculation. Moreover, the antibacterial activity of overlapping peptides covering vertebrate C3a, C4a, and C5a further strongly supports the speculation, because their activity is positively correlated with the net charge of source molecules. Notably, the structures of C3a, C4a, and C5a are conserved in vertebrates, and the inactive overlapping peptides can become antibacterial peptides if mutated to possess enough net positive charges, indicating that net charge is the only factor determining the antibacterial properties of vertebrate C3a, C4a, and C5a. More importantly, many vertebrate C3a-, C4a-, and C5a-derived peptides possess high antibacterial activities yet exhibit no hemolytic activities, suggesting the application potential in anti-infective therapy. Taken together, our findings reveal that vertebrate C3a, C4a, and C5a are all sources of antibacterial peptides that will facilitate the design of excellent peptide antibiotics.

CXCL20a, a Teleost-Specific Chemokine That Orchestrates Direct Bactericidal, Chemotactic, and Phagocytosis-Killing-Promoting Functions, Contributes to Clearance of Bacterial Infections.

The major role of chemokines is to act as a chemoattractant to guide the migration of immune cells to the infectious sites. In the current study, we found that CiCXCL20a, a teleost-specific chemokine from grass carp (Ctenopharyngodon idella), demonstrates broad-spectrum, potent, direct bactericidal activity and immunomodulatory functions to bacterial infections, apart from the chemotaxis. CiCXCL20a kills bacteria by binding, mainly targeting acid lipids, perforating bacterial membrane, resulting in bacterial cytoplasm leakage and death. CiCXCL20a aggregates and neutralizes LPS, agglutinates Gram-negative bacteria, and binds to peptidoglycan and Gram-positive bacteria, but not agglutinate them. All the complexes may be phagocytized and cleared away. CiCXCL20a chemoattracts leukocytes, facilitates phagocytosis of myeloid leukocytes, not lymphoid leukocytes, and enhances the bacteria-killing ability in leukocytes. We further identified its receptor CiCXCR3.1b1. Furthermore, we investigated the physiological roles of CiCXCL20a against Aeromonas hydrophila infection in vivo. The recombinant CiCXCL20a increases the survival rate and decreases the tissue bacterial loads, edema, and lesions. Then, we verified this function by purified CiCXCL20a Ab blockade, and the survival rate decreases, and the tissue bacterial burdens increase. In addition, zebrafish (Danio rerio) DrCXCL20, an ortholog of CiCXCL20a, was employed to verify the bactericidal function and mechanism. The results indicated that DrCXCL20 also possesses wide-spectrum, direct bactericidal activity through membrane rupture mechanism. The present study, to our knowledge, provides the first evidence that early vertebrate chemokine prevents from bacterial infections by direct bactericidal and phagocytosis-killing-promoting manners. The results also demonstrate the close functional relationship between chemokines and antimicrobial peptides.

Chitosan reduces the protective effects of IFN-γ2 on grass carp (Ctenopharyngodon idella) against Flavobacterium columnare infection due to excessive inflammation.

IFN-γ is an immunomodulatory factor that has been extensively studied in phenotypes of mammalian macrophages and multifarious inflammatory responses. Usually these studies relied on the classical synergistic activation of IFN-γ with LPS (LipoPolySaccharides). However, non-mammalian vertebrates, and in particular fish, are not very susceptible to LPS, and easily acquire tolerance upon repeated exposure. Therefore, for studies in fish, it is necessary to replace the classical IFN-γ+LPS immune system activation method, and find other pathogen-associated molecular patterns (PAMPs) capable of stimulating the fish immune system. Here we used an important farmed fish species, Ctenopharyngodon idella, to study the effects of CiIFN-γ2 (C. idella IFN-γ2) and chitosan (CS) on its immune responses in vivo and vitro. Our results showed that the combination of CS and CiIFN-γ2 significantly enhanced the activation of macrophages, with an activation intensity even stronger than in CiIFN-γ2 and CiIFN-γ2+LPS groups. In vivo, injection of CiIFN-γ2 could improve the survival rate of C. idella infected with Flavobacterium columnare, while a combined injection of CiIFN-γ2+CS only improved protection in the early stages after the challenge. Notably, both injections reduced the bacterial load of viscera and improved the levels of several plasma parameters (TP, T-SOD, LA, and NO). However, a dramatic up-regulation of inflammatory factors, severe inflammatory damage in the intestines and hepatopancreas, and increased mortality in late stages of infection were observed in the CiIFN-γ2+CS group. Our findings provide new insights into the macrophage activation phenotypes and inflammatory responses in fish. They also demonstrate that CiIFN-γ2 could be used as a potential immunopotentiator, but not in combination with CS. This suggests that selection of immunological adjuvants should be carefully tested experimentally.

Chemotactic effect of ß-defensin 1 on macrophages in Megalobrama amblycephala.

Besides their function as a physical barrier against pathogens, ß-defensins possess the ability to induce direct or indirect chemotaxis in leukocytes of mammals. However little is known about the ability of defensins to guide the migration of macrophages in fish. The objective of our study was to investigate whether ß-defensin 1 (maBD1) can recruit leukocytes (specifically macrophages) in vivo and in vitro in a farmed cyprinid fish Megalobrama amblycephala. The M. amblycephala ß-defensin 1 (maBD1) gene was amplified from the head-kidney transcriptome. Synthetic maBD1 polypeptide (as well as its N-terminus half, but not the C-terminus half) was capable of inducing the migration of leukocytes (specifically macrophages) at concentrations from 26.0 µg/mL to 52.0 µg/mL in head kidney tissue in vitro. When injected intraperitoneally in vivo, the number of leukocytes in the peritoneal cavity was in positive correlation with the maBD1 concentration. maBD1 also induced the expression of two proinflammatory cytokines (IL-1beta and TNF-alpha) in spleen, head and body kidney, and hepatopancreas. These results strongly indicate that BD1 has a chemoattractant capacity for macrophages, as well as the ability to modulate the expression of proinflammatory cytokines in fish.

Hepcidin protects grass carp (Ctenopharyngodon idellus) against Flavobacterium columnare infection via regulating iron distribution and immune gene expression.

Columnaris disease (CD) caused by Flavobacterium columnare (F. columnare) is lack of knowledge on effective treatment measures. Bacterial pathogens require iron as an essential nutrient to infect the host. While hepcidin acts as a master regulator in iron metabolism, its contribution to host defense is emerging as complex and multifaceted. In vitro, recombinant Ctenopharyngodon idellus (C. idellus) hepcidin (CiHep) and synthetic CiHep both showed the ability to increase the expression of hepcidin and ferritin in C. idellus kidney cells, especially the recombinant CiHep. In vivo, recombinant CiHep improved the survival rate of C. idellus challenged with F. columnare. In addition, the fish fed diet containing recombinant CiHep (group H-1) had a higher survival rate than other pretreatment groups. The study showed that recombinant CiHep regulated iron metabolism causing iron redistribution, decreasing serum iron levels and increasing iron accumulation in the hepatopancreas. Moreover, the expression of iron-related genes was upregulated in various degrees at a different time except for group H-1. Immune-related genes were also evaluated, showing higher expression in the groups pretreated with CiHep at an early stage of infection. Of note, a clear upregulation of more immune genes occurred in the groups pretreated with recombinant CiHep than that pretreated with synthetic CiHep in the late stage of infection. In conclusion, the recombinant CiHep has a protective effect on the host response to bacterial pathogens. We speculate that hepcidin protects C. idellus against F. columnare infection via regulating the iron distribution and immune gene expression.

Transcriptome Analysis Provides Insights into the Markers of Resting and LPS-Activated Macrophages in Grass Carp (Ctenopharyngodon idella).

Macrophages are very versatile immune cells, with the characteristics of a proinflammatory phenotype in response to pathogen-associated molecular patterns. However, the specific activation marker genes of macrophages have not been systematically investigated in teleosts. In this work, leukocytes (WBC) were isolated using the Percoll gradient method. Macrophages were enriched by the adherent culture of WBC, then stimulated with lipopolysaccharide (LPS). Macrophages were identified by morphological features, functional activity and authorized cytokine expression. Subsequently, we collected samples, constructed and sequenced transcriptomic libraries including WBC, resting macrophage (Mø) and activated macrophage (M(LPS)) groups. We gained a total of 20.36 Gb of clean data including 149.24 million reads with an average length of 146 bp. Transcriptome analysis showed 708 differential genes between WBC and Mø, 83 differentially expressed genes between Mø and M(LPS). Combined with RT-qPCR, we proposed that four novel cell surface marker genes (CD22-like, CD63, CD48 and CD276) and two chemokines (CXCL-like and CCL39.3) would be emerging potential marker genes of macrophage in grass carp. Furthermore, CD69, CD180, CD27, XCL32a.2 and CXCL8a genes can be used as marker genes to confirm whether macrophages are activated. Transcriptome profiling reveals novel molecules associated with macrophages in C. Idella, which may represent a potential target for macrophages activation.

Comparative study on antibacterial characteristics of the multiple liver expressed antimicrobial peptides (LEAPs) in teleost fish.

Antimicrobial peptides are important components of the host innate immune system, forming the first line of defense against infectious microorganisms. Among them, liver-expressed antimicrobial peptides (LEAPs) are a family of antimicrobial peptides that widely exist in vertebrates. LEAPs include two types, named LEAP-1 and LEAP-2, and many teleost fish have two or more LEAP-2s. In this study, LEAP-2C from rainbow trout and grass carp were discovered, both of which are composed of 3 exons and 2 introns. The antibacterial functions of the multiple LEAPs were systematically compared in rainbow trout and grass carp. The gene expression pattern revealed that rainbow trout and grass carp LEAP-1, LEAP-2A, LEAP-2B and/or LEAP-2C were differentially expressed in various tissues/organs, mainly in liver. After bacterial infection, the expression levels of LEAP-1, LEAP-2A, LEAP-2B and/or LEAP-2C in the liver and gut of rainbow trout and grass carp increased to varying degrees. Moreover, the antibacterial assay and bacterial membrane permeability assay showed that rainbow trout and grass carp LEAP-1, LEAP-2A, LEAP-2B and LEAP-2C all have antibacterial activities against a variety of Gram-positive and Gram-negative bacteria with varying levels through membrane rupture. Furthermore, cell transfection assay showed that only rainbow trout LEAP-1, but not LEAP-2, can lead to the internalization of ferroportin, the only iron exporter on cell surface, indicating that only LEAP-1 possess iron metabolism regulation activity in teleost fish. Taken together, this study systematically compared the antibacterial function of LEAPs in teleost fish and the results suggest that multiple LEAPs can enhance the immunity of teleost fish through different expression patterns and different antibacterial activities to various bacteria.

Plasmablasts induced by chitosan oligosaccharide secrete natural IgM to enhance the humoral immunity in grass carp.

Chitosan oligosaccharide (COS) is an attractive immunopotentiator capable of driving humoral immunity in vertebrates, but its cellular and molecular mechanisms still require elucidation. In this study, COS induced the proliferation and differentiation of splenic IgM+ B cells into IgMlo and IgMhi B cell subsets in grass carp (Ctenopharyngodon idella). The IgMlo B cells were further identified as short-lived plasmablasts that secreted natural IgM with binding-abilities to lipopolysaccharide (LPS) and peptidoglycan (PGN). Moreover, the mannose receptor (MR) and integrins were discovered and identified as the binding-receptors of COS on IgMlo plasmablasts. The MR synergized with integrins to trigger intracellular signal transduction to boost plasmablast generation and expansion. Notably, IgMlo plasmablasts originally generated in spleen but they migrated into blood to secrete natural IgM, which augmented the serum bactericidal activity. Taken together, this study revealed the cellular and molecular mechanisms of COS-triggered humoral immunity in fish.

Conserved function of crucian carp cGAS in the MITA-mediated interferon signaling.

Mammalian cyclic GMP-AMP synthase (cGAS) is pivotal for cytosolic DNA-triggered interferon (IFN) response. However, the function of cGAS in fish IFN response remains unclear. Our recent study has reported that cGAS from crucian and grass carps downregulates the IFN response by attenuating the K63-linked ubiquitination of retinoic acid-inducible gene-I (RIG-I) and its interaction with mitochondrial antiviral signaling protein (MAVS). Here, the function of crucian carp cGAS was further investigated. We found that crucian carp cGAS directly binds to poly deoxyadenylic-deoxythymidylic acid (poly (dA:dT)) and exhibits mediator of IFN regulatory factor 3 (IRF3) activation (MITA)-dependent activation of the IFN response, indicating a conserved function of crucian carp cGAS in the MITA-mediated IFN signaling. However, crucian carp cGAS could suppress the IFN activation stimulated by polyinosinic: polycytidylic acid (poly (I:C)) in time- and dose-dependent manners. These data collectively suggest complicated functions of crucian carp cGAS in the IFN antiviral response.

Interfacial Microstructure and Mechanical Properties of 1Cr18Ni9Ti/1Cr21Ni5Ti Stainless Steel Joints Brazed with Mn-Based Brazing Filler.

The problem of stainless steel brazing is still the focus of scientific research. In this work, the Mn-based brazing filler was used to braze 1Cr18Ni9Ti and 1Cr21Ni5Ti stainless steel. The typical microstructure of the 1Cr18Ni9Ti/1Cr21Ni5Ti joint was analyzed in detail, and the interface structure of the joint was determined to be 1Cr18Ni9Ti/Mn(s, s)/1Cr21Ni5Ti. The brazing temperature and holding time were shown to have a great influence on the microstructure of the brazed joint. The tensile strength of brazed joints first increased and then decreased with the rising of the brazing temperature and the holding time. The maximum tensile strength was 566 MPa when the joints were brazed at 1125 °C for 15 min. The diffusion of Mn and Cr was an important factor affecting the quality of the joints. The diffusion distances of Mn and Cr at different brazing temperatures and holding times were measured, and the diffusion activation energy and diffusion coefficient were achieved by the Arrhenius equation.

Complement C3a Enhances the Phagocytic Activity of B Cells Through C3aR in a Fish.

The complement system is an important part of the immune system of teleost fish. Besides, teleost B cells possess both phagocytic activity and adaptive humoral immune function, unlike mammalian B1 cells with phagocytic activity and B2 cells specific to adaptive humoral immunity. However, the cross talk between complement system and phagocytic B cells in teleost fish still requires elucidation. Here, we show that, unlike tetrapods with a single C3 gene, nine C3 genes were identified from the grass carp (Ctenopharyngodon idella) genome, named C3.1-C3.9. Expression analysis revealed that C3.1 is the dominant C3 molecule in grass carp, for its expression was significantly higher than that of the other C3 molecules both at the mRNA and protein levels. The C3a fragment of C3.1 (C3a.1) was determined after the conserved C3 convertase cleavage site. Structural analysis revealed that C3a.1 consists of four α-helixes, with the C-terminal region forming a long α-helix, which is the potential functional region. Interestingly, we found that the recombinant GST-C3a.1 protein and the C-terminal α-helix peptide of C3a.1 both could significantly enhance the phagocytic activity of IgM+ B cells. Further study revealed that the C3a receptor (C3aR) was highly expressed in grass carp IgM+ B cells, and the phagocytosis-stimulating activity of C3a.1 could be dramatically inhibited by the anti-C3aR antibodies, indicating that C3a.1 performed the stimulating function through C3aR on IgM+ B cells. Taken together, our study not only uncovered the novel phagocytosis-stimulating activity of C3a, but also increased our knowledge of the cross talk between complement system and phagocytic B cells in teleost fish.

Hamp Type-1 Promotes Antimicrobial Defense via Direct Microbial Killing and Regulating Iron Metabolism in Grass Carp (Ctenopharyngodon idella).

Hepcidin is an antimicrobial peptide and regulator of iron homeostasis which has two isoforms in most fishes and some mammals. Previous studies have reported that the two hepcidin isoforms have different roles. Hamp type-1 plays a regulatory role in iron metabolism and hamp type-2 mostly performs an antimicrobial role. In this study, we found that Ctenopharyngodon idella (C. idella) have only one hepcidin isoform (hamp type-1), which showed both broad-spectrum antibacterial and iron regulatory functions. C. idella hepcidin mature peptide (hepcidin-25) and truncated peptide (hepcidin-20) exhibited bactericidal activities against both Gram-positive and Gram-negative bacteria in a dose-dependent manner in part through membrane rupture and binding to bacterial genomic DNA. The data from challenge tests demonstrated that the administration of hepcidin-25 significantly reduced mortality rates of C. idella by A. hydrophila infection, probably due to direct bactericidal activities of the peptide and a reduction of iron content in the fish serum. In addition, a comparison between hepcidin-20 and -25 suggests that the N terminal 5 amino acids play a critical role in reducing iron content in fish serum. Our findings revealed an important role of hamp type-1 in maintaining iron homeostasis and fighting against bacterial infections, suggesting the hepcidin has implications for the prevention and control of bacterial infection in aquaculture.

N-acetylcysteine alleviates fluoride-induced testicular apoptosis by modulating IRE1α/JNK signaling and nuclear Nrf2 activation.

We previously investigated excessive fluoride exposure elicited intracellular endoplasmic reticulum (ER) stress and led to Sertoli cells dysfunction in vitro. However, the mechanisms underlying fluoride-mediated male reproductive damage in vivo remain largely unknown. Considerable evidence has now revealed ER stress is closely linked with testicular oxidative damage. Hence, we aimed to explore whether ER stress signaling was involved in the testicular protective effects of antioxidant N-acetylcysteine (NAC) against testicular apoptosis induced by fluoride. Male SD rats were oral gavaged with sodium fluoride (NaF) for 7 weeks to induce fluorosis. The animals were pretreatment with or without NAC (150 mg/Bw•d). Our results demonstrated that sub-chronic NaF exposure triggered testicular apoptosis and sex hormonal disturbance in pituitary-testicular (PT) axis, promoted oxidative stress and the expression of ER stress mediators. Antioxidant NAC, however, prevented NaF-induced testicular apoptosis accompanied by activating Nrf2-mediated antioxidant potential. Simultaneously, NAC pretreatment downregulated XBP1 splicing, reduced JNK phosphorylation and further blocked cleavage of caspase-3, all these might contribute to the inhibition of testicular cell apoptosis. Collectively, the present results suggested that prolonged administration of NAC preserved testicular function and normalized sex hormonal disruption induced by NaF via the inhibition of Nrf2-associated oxidative damage and Ire1α-JNK-mediated apoptosis in rat testis.

Latent role of in vitro Pb exposure in blocking Aß clearance and triggering epigenetic modifications.

Both ß-amyloid (Aß) catabolism and epigenetic regulation play critical roles in the onset of neurodegeneration. The latter also contribute to Pb neurotoxicity. The present study explored the role of epigenetic modifiers and Aß degradation enzymes in Pb-induced latent effects on Aß overproduction in vitro. Our results indicated that in SH-SY5Y cells exposed to Pb, the expression of NEP and IDE remained declined during the recovery period, accompanied with abnormal increase of Aß1-42 and amyloid oligomer. A disruption of selective global post-translational histone modifiers including the decrease of H3K9ac and H4K12ac and the induction of H3K9me2 and H3K27me2 dose dependently was also showed in recovery cells. Moreover, histone deacetylase inhibitor VPA could attenuate latent Aß accumulation and HDAC activity induced by Pb, which might be by regulating the expression of NEP and IDE epigenetically. Overall, our results suggest sustained reduction of NEP and IDE expression in response to Pb sensitizes recovery SH-SY5Y cells to Aß accumulation; however, administration of VPA is demonstrated to be beneficial in modulating Aß clearance.

Early-Life Exposure to Lead Induces Cognitive Impairment in Elder Mice Targeting SIRT1 Phosphorylation and Oxidative Alterations.

Pb is a potential risk factor for cognition, mainly mediated by enhanced oxidative stress. Resveratrol, a natural polyphenol with crucial anti-oxidative property, is recently implicated in preventing cognitive deficits in normal aging and neurodegenerative disorders. Its beneficial effects have been linked to sirtuin 1(SIRT1) activation. The aim of this work is to investigate the possible linkage between alterations in Pb-induced oxidative damage and cognitive impairment by prolonged treatment of resveratrol. Male C57BL/6 mice were given Pb(Ac)2 treatment or deionized H2O for 12 weeks, and subjected to resveratrol gavage at the dose of 50 mg/kgBw•d or vehicle after Pb exposure. Results from biochemical analysis and immunohistofluorescence showed that Pb induced oxidative DNA damage and decreased cortical antioxidant biomarker. As expected, these abnormalities were improved by resveratrol treatment. Morris water maze test, Western blotting, immunohistofluorescence staining and RT-qPCR indicated that resveratrol ameliorated spatial learning and memory deficits with alterations in hippocampal BDNF-TrkB signaling, promoted nuclear localization and phosphorylation of hippocampal SIRT1, partly increased protein levels of AMPK and PGC-1α involving in modulation of antioxidant response in Pb-exposed mice. Our results support the hypothesis that resveratrol could attenuate Pb-induced cognitive impairment which was associated with activating SIRT1 via modulation of oxidative stress. Additionally, resveratrol also repressed the Pb-induce amyloidogenic processing with resultant decline in cortical Aß1--40. Noteworthy, such effects were not mediated by resveratrol treatment alone. These findings emphasize the potential of SIRT1 activator as an efficacious dietary intervention to downgrade the Pb-induced neurotoxic lesion.