Functional analysis of MTF-1 and MT promoters and their transcriptional response to zinc (Zn) and copper (Cu) in yellow catfish Pelteobagrus fulvidraco

Role of zinc homeostasis in the prevention of prostate diseases

The prostate gland is the largest accessory sex gland in the male reproductive system, and is recognized for its elevated zinc concentration. Recently, the incidence of prostate diseases has increased, posing a significant threat to the health of men. Increasing evidence suggests that maintaining normal prostate function requires proper zinc homeostasis. Prostate disease can cause changes in the regulation of zinc levels in the prostate. Studies have indicated that patients with prostatitis, prostate enlargement, or prostate cancer experience an imbalance in zinc homeostasis, resulting in changes in zinc levels in the body and altered distribution of zinc in tissues. Zinc prevents the malignant transformation of normal prostate tissue by blocking citric acid oxidation, inducing apoptosis, and exhibiting antioxidant activity. Therefore, studying changes in zinc homeostasis in prostate diseases is of great clinical value for diagnosing and treating these diseases. This article reviews the distribution and content of zinc in the prostate, the mechanism underlying zinc homeostasis regulation, the role of zinc homeostasis in prostate diseases, and the clinical applications of zinc.

SENP1 mediates zinc-induced ZnT6 deSUMOylation at Lys-409 involved in the regulation of zinc metabolism in Golgi apparatus

Zinc (Zn) transporters contribute to the maintenance of intracellular Zn homeostasis in vertebrate, whose activity and function are modulated by post-translational modification. However, the function of small ubiquitin-like modifier (SUMOylation) in Zn metabolism remains elusive. Here, compared with low Zn group, a high-Zn diet significantly increases hepatic Zn content and upregulates the expression of metal-response element-binding transcription factor-1 (MTF-1), Zn transporter 6 (ZnT6) and deSUMOylation enzymes (SENP1, SENP2, and SENP6), but inhibits the expression of SUMO proteins and the E1, E2, and E3 enzymes. Mechanistically, Zn triggers the activation of the MTF-1/SENP1 pathway, resulting in the reduction of ZnT6 SUMOylation at Lys 409 by small ubiquitin-like modifier 1 (SUMO1), and promoting the deSUMOylation process mediated by SENP1. SUMOylation modification of ZnT6 has no influence on its localization but reduces its protein stability. Importantly, deSUMOylation of ZnT6 is crucial for controlling Zn export from the cytosols into the Golgi apparatus. In conclusion, for the first time, we elucidate a novel mechanism by which SUMO1-catalyzed SUMOylation and SENP1-mediated deSUMOylation of ZnT6 orchestrate the regulation of Zn metabolism within the Golgi apparatus.

Emerging perspectives of copper-mediated transcriptional regulation in mammalian cell development

Copper (Cu) is a vital micronutrient necessary for proper development and function of mammalian cells and tissues. Cu mediates the function of redox active enzymes that facilitate metabolic processes and signaling pathways. Cu levels are tightly regulated by a network of Cu-binding transporters, chaperones, and small molecule ligands. Extensive research has focused on the mammalian Cu homeostasis (cuprostasis) network and pathologies, which result from mutations and perturbations. There are roles for Cu-binding proteins as transcription factors (Cu-TFs) and regulators that mediate metal homeostasis through the activation or repression of genes associated with Cu handling. Emerging evidence suggests that Cu and some Cu-TFs may be involved in the regulation of targets related to development-expanding the biological roles of Cu-binding proteins. Cu and Cu-TFs are implicated in embryonic and tissue-specific development alongside the mediation of the cellular response to oxidative stress and hypoxia. Cu-TFs are also involved in the regulation of targets implicated in neurological disorders, providing new biomarkers and therapeutic targets for diseases such as Parkinson's disease, prion disease, and Friedreich's ataxia. This review provides a critical analysis of the current understanding of the role of Cu and cuproproteins in transcriptional regulation.

Recent advances on the influence of fipronil on insect behavior

Fipronil, a pesticide widely used to control agricultural and household insect pests, blocks insect GABAA and glutamate (GluCl) ionotropic receptors, resulting in uncontrolled hyperexcitation and paralysis that eventually leads to death. The use of fipronil is controversial because unintentional exposure to this compound may contribute to the ongoing global decline of insect pollinator populations. Although the sublethal effects of fipronil have been linked to aberrant behavior and impaired olfactory learning in insects, the precise mechanisms involved in these responses remain unclear. In this article, we highlight recent studies that have investigated the interaction among different pathways involved in the ability of fipronil to modulate insect behavior, with particular emphasis on the role of GABAergic neurotransmission in fine-tuning the integration of sensorial responses and insect behavior. Recent findings suggest that fipronil can also cause functional alterations that affect synaptic organization and the availability of metal ions in the brain.

Transcriptional regulation of Znt family members znt4, znt5 and znt10 and their function in zinc transport in yellow catfish (Pelteobagrus fulvidraco)

The study characterized the transcriptionally regulatory mechanism and functions of three zinc (Zn) transporters (znt4, znt5 and znt10) in Zn2+ metabolism in yellow catfish (Pelteobagrus fulvidraco), commonly freshwater fish in China and other countries. We cloned the sequences of znt4 promoter, spanning from -1217 bp to +80 bp relative to TSS (1297 bp); znt5, spanning from -1783 bp to +49 bp relative to TSS (1832 bp) and znt10, spanning from -1923 bp to +190 bp relative to TSS (2113 bp). In addition, after conducting the experiments of sequential deletion of promoter region and mutation of potential binding site, we found that the Nrf2 binding site (-607/-621 bp) and Klf4 binding site (-5/-14 bp) were required on znt4 promoter, the Mtf-1 binding site (-1674/-1687 bp) and Atf4 binding site (-444/-456 bp) were required on znt5 promoter and the Atf4 binding site (-905/-918 bp) was required on znt10 promoter. Then, according to EMSA and ChIP, we found that Zn2+ incubation increased DNA affinity of Atf4 to znt5 or znt10 promoter, but decreased DNA affinity of Nrf2 to znt4 promoter, Klf4 to znt4 promoter and Mtf-1 to znt5 promoter. Using fluorescent microscopy, it was revealed that Znt4 and Znt10 were located in the lysosome and Golgi, and Znt5 was located in the Golgi. Finally, we found that znt4 knockdown reduced the zinc content of lysosome and Golgi in the control and zinc-treated group; znt5 knockdown reduced the zinc content of Golgi in the control and zinc-treated group and znt10 knockdown reduced the zinc content of Golgi in the zinc-treated group. High dietary zinc supplement up-regulated Znt4 and Znt5 protein expression. Above all, for the first time, we revealed that Klf4 and Nrf2 transcriptionally regulated the activities of znt4 promoter; Mtf-1 and Atf4 transcriptionally regulated the activities of znt5 promoter and Atf4 transcriptionally regulated the activities of znt10 promoter, which provided innovative regulatory mechanism of zinc transporting in yellow catfish. Our study also elucidated their subcellular location, and regulatory role of zinc homeostasis in yellow catfish.

Expression and Functional Analysis of the Metallothionein and Metal-Responsive Transcription Factor 1 in Phascolosoma esculenta under Zn Stress

Metallothioneins (MTs) are non-enzymatic metal-binding proteins widely found in animals, plants, and microorganisms and are regulated by metal-responsive transcription factor 1 (MTF1). MT and MTF1 play crucial roles in detoxification, antioxidation, and anti-apoptosis. Therefore, they are key factors allowing organisms to endure the toxicity of heavy metal pollution. Phascolosoma esculenta is a marine invertebrate that inhabits intertidal zones and has a high tolerance to heavy metal stress. In this study, we cloned and identified MT and MTF1 genes from P. esculenta (designated as PeMT and PeMTF1). PeMT and PeMTF1 were widely expressed in all tissues and highly expressed in the intestine. When exposed to 16.8, 33.6, and 84 mg/L of zinc ions, the expression levels of PeMT and PeMTF1 in the intestine increased first and then decreased, peaking at 12 and 6 h, respectively, indicating that both PeMT and PeMTF1 rapidly responded to Zn stress. The recombinant pGEX-6p-1-MT protein enhanced the Zn tolerance of Escherichia coli and showed a dose-dependent ABTS free radical scavenging ability. After RNA interference (RNAi) with PeMT and 24 h of Zn stress, the oxidative stress indices (MDA content, SOD activity, and GSH content) and the apoptosis indices (Caspase 3, Caspase 8, and Caspase 9 activities) were significantly increased, implying that PeMT plays an important role in Zn detoxification, antioxidation, and anti-apoptosis. Moreover, the expression level of PeMT in the intestine was significantly decreased after RNAi with PeMTF1 and 24 h of Zn stress, which preliminarily proved that PeMTF1 has a regulatory effect on PeMT. Our data suggest that PeMT and PeMTF1 play important roles in the resistance of P. esculenta to Zn stress and are the key factors allowing P. esculenta to endure the toxicity of Zn.

Vitamin D3 promotes fish oocyte development by directly regulating gonadal steroid hormone synthesis†

Vitamin D receptors and vitamin D3-metabolizing enzymes have been found to be highly expressed in the ovaries and spermatophores of fish. However, the role of vitamin D3 on fish gonadal development has rarely been reported. In this study, 2-month-old female zebrafish were fed with different concentrations of vitamin D3 diets (0, 700, 1400, and 11 200 IU/kg) to investigate the effects of vitamin D3 on ovarian development. The diet with 0 IU/kg vitamin D3 resulted in elevated interstitial spaces, follicular atresia, and reproductive toxicity in zebrafish ovaries. Supplementation with 700 and 1400 IU/kg of vitamin D3 significantly increased the oocyte maturation rate; upregulated ovarian gonadal steroid hormone synthesis capacity; and elevated plasma estradiol, testosterone, and ovarian vitellogenin levels. Furthermore, the current study identified a vitamin D response element in the cyp19a1a promoter and demonstrated that 1.25(OH)2D3-vitamin D response directly activated cyp19a1a production through activating the vitamin D response element. In conclusion, this study shows that an appropriate concentration of vitamin D3 can promote zebrafish ovarian development and affect vitellogenin synthesis through the vdr/cyp19a1a/er/vtg gene axis.

Zinc glycinate alleviates LPS-induced inflammation and intestinal barrier disruption in chicken embryos by regulating zinc homeostasis and TLR4/NF-κB pathway

The effect of an immune challenge induced by a lipopolysaccharide (LPS) exposure on systemic zinc homeostasis and the modulation of zinc glycinate (Zn-Gly) was investigated using a chicken embryo model. 160 Arbor Acres broiler fertilized eggs were randomly divided into 4 groups: CON (control group, injected with saline), LPS (LPS group, injected with 32 µg of LPS saline solution), Zn-Gly (zinc glycinate group, injected with 80 µg of zinc glycinate saline solution) and Zn-Gly+LPS (zinc glycinate and LPS group, injected with the same content of zinc glycinate and LPS saline solution). Each treatment consisted of eight replicates of five eggs each. An in ovo feeding procedure was performed at 17.5 embryonic day and samples were collected after 12 hours. The results showed that Zn-Gly attenuated the effects of LPS challenge-induced upregulation of pro-inflammatory factor interleukin 1β (IL-1β) level (P =0.003). The LPS challenge mediated zinc transporter proteins and metallothionein (MT) to regulate systemic zinc homeostasis, with increased expression of the jejunum zinc export gene zinc transporter protein 1 (ZnT-1) and elevated expression of the import genes divalent metal transporter 1 (DMT1), Zrt- and Irt-like protein 3 (Zip3), Zip8 and Zip14 (P < 0.05). A similar trend could be observed for the zinc transporter genes in the liver, which for ZnT-1 mitigated by Zn-Gly supplementation (P =0.01). Liver MT gene expression was downregulated in response to the LPS challenge (P =0.004). These alterations caused by LPS resulted in decreased serum and liver zinc levels and increased small intestinal, muscle and tibial zinc levels. Zn-Gly reversed the elevated expression of the liver zinc finger protein A20 induced by the LPS challenge (P =0.025), while Zn-Gly reduced the gene expression of the pro-inflammatory factors IL-1β and IL-6, decreased toll-like receptor 4 (TLR4) and nuclear factor kappa-B p65 (NF-κB p65) (P < 0.05). Zn-Gly also alleviated the LPS-induced downregulation of the intestinal barrier gene Claudin-1. Thus, LPS exposure prompted the mobilization of zinc transporter proteins and MT to perform the remodeling of systemic zinc homeostasis, Zn-Gly participated in the regulation of zinc homeostasis and inhibited the production of pro-inflammatory factors through the TLR4/NF-κB pathway, attenuating the inflammatory response and intestinal barrier damage caused by an immune challenge.

Copper Metabolism and Cuproptosis: Molecular Mechanisms and Therapeutic Perspectives in Neurodegenerative Diseases

Copper is an essential trace element, and plays a vital role in numerous physiological processes within the human body. During normal metabolism, the human body maintains copper homeostasis. Copper deficiency or excess can adversely affect cellular function. Therefore, copper homeostasis is stringently regulated. Recent studies suggest that copper can trigger a specific form of cell death, namely, cuproptosis, which is triggered by excessive levels of intracellular copper. Cuproptosis induces the aggregation of mitochondrial lipoylated proteins, and the loss of iron-sulfur cluster proteins. In neurodegenerative diseases, the pathogenesis and progression of neurological disorders are linked to copper homeostasis. This review summarizes the advances in copper homeostasis and cuproptosis in the nervous system and neurodegenerative diseases. This offers research perspectives that provide new insights into the targeted treatment of neurodegenerative diseases based on cuproptosis.

Cellular zinc metabolism and zinc signaling: from biological functions to diseases and therapeutic targets

Zinc metabolism at the cellular level is critical for many biological processes in the body. A key observation is the disruption of cellular homeostasis, often coinciding with disease progression. As an essential factor in maintaining cellular equilibrium, cellular zinc has been increasingly spotlighted in the context of disease development. Extensive research suggests zinc's involvement in promoting malignancy and invasion in cancer cells, despite its low tissue concentration. This has led to a growing body of literature investigating zinc's cellular metabolism, particularly the functions of zinc transporters and storage mechanisms during cancer progression. Zinc transportation is under the control of two major transporter families: SLC30 (ZnT) for the excretion of zinc and SLC39 (ZIP) for the zinc intake. Additionally, the storage of this essential element is predominantly mediated by metallothioneins (MTs). This review consolidates knowledge on the critical functions of cellular zinc signaling and underscores potential molecular pathways linking zinc metabolism to disease progression, with a special focus on cancer. We also compile a summary of clinical trials involving zinc ions. Given the main localization of zinc transporters at the cell membrane, the potential for targeted therapies, including small molecules and monoclonal antibodies, offers promising avenues for future exploration.

Regulatory effect of NK homeobox 1 (NKX2.1) on melanocortin 4 receptor (Mc4r) promoter in Mandarin fish

The melanocortin 4 receptor (MC4R) is a G protein-coupled transporter that mediates the regulation of thyroid hormones and leptin on energy balance and food intake. However, the mechanisms of transcriptional regulation of Mc4r by thyroid hormone and leptin in fish have been rarely reported. The messenger RNA expression of Mc4r gene was significantly higher in brain than those in other tissues of mandarin fish. We analyzed the structure and function of a 2029 bp sequence of Mc4r promoter. Meanwhile, overexpression of NKX2.1 and incubation with leptin significantly increased Mc4r promoter activity, but triiodothyronine showed the opposite effect. In addition, mutations in the NKX2.1 binding site abolished not only the activation of Mc4r promoter activity by leptin but also the inhibitory effect of thyroid hormones on Mc4r promoter activity. In summary, these results suggested that thyroid hormones and leptin might regulate the transcriptional expression of Mc4r through NKX2.1.

Copper induces liver lipotoxicity disease by up-regulating Nrf2 expression via the activation of MTF-1 and inhibition of SP1/Fyn pathway

Excessive copper (Cu) intake leads to hepatic lipotoxicity disease, which has adverse effects on health, but the underlying mechanism is unclear. We found that Cu increased lipotoxicity by promoting Nrf2 recruitment to the ARE site in the promoters of five lipogenic genes (g6pd, 6pgd, me, icdh and pparγ). We also found that Cu affected the Nrf2 expression via different pathways: metal regulatory transcription factor 1 (MTF-1) mediated the Cu-induced Nrf2 transcriptional activation; Cu also enhanced the expression of Nrf2 by inhibiting the SP1 expression, which was achieved by inhibiting the negative regulator Fyn of Nrf2. These promoted the enrichment of Nrf2 in the nucleus and ultimately affected lipotoxicity. Thus, for the first time, we elucidated that Cu induced liver lipotoxicity disease by up-regulating Nrf2 expression via the MTF-1 activation and the inhibition of SP1/Fyn pathway. Our study elucidates the Cu-associated obesity and NAFLD for fish and possibly humans.

ZnO-NPs alleviate aflatoxin B1-induced hepatoxicity in ducklings by promoting hepatic metallothionein expression

Aflatoxin B₁ (AFB₁) is a mycotoxin widely present in animal feed and human food, posing a serious threat to animal and human health. This study was aim to illustrate the mechanism of the protective role of MT against AFB₁-induced hepatotoxicity, as well as to explore the feasibility of enhancing the tolerance of poultry to AFB₁ by upregulating the expression of hepatic MT. After being exposed to AFB₁ (50 ng/kg) primary duckling hepatocytes, the cell viability, the antioxidant index (SOD and GPx) and the mRNA levels of MT downstream genes (PTGR, p53, TrxR, AR and Bcl-2) significantly (p < 0.05) decreased, while the intracellular formation of (AFBO)-DNA adduct content, apoptosis, and MDA content significantly (p < 0.05) increased. Interestingly, overexpression of MT in primary duckling hepatocytes markedly (p < 0.05) reversed the detrimental impact of AFB₁ and increased the expression of MT downstream genes. HepG2 cells were applied to study the mechanism how MT works to relieve the hepatic toxicity of AFB₁. The ZnO-NPs (20 μg/mL) + AFB₁ (20 μg/mL) group significantly (p < 0.05) increased the cell viability, the expression of NRF2, NQO1 and SOD, and expression of MT and MTF-1, as well as significantly (p < 0.05) decreased LDH, ROS and apoptotic rate, comparing with the AFB₁ group. While joint treatment with AFB₁ and ZnO-NPs, the hepatic toxicity exerted by AFB₁ alone was reversed, along with the translocation of MTF-1 from the cytoplasm to the nucleus and upregulated its expression. Duckling trails were further carried out. A total number of 96 1-day-old healthy Cherry Valley commercial ducklings were randomly allocated according to a 2 by 2 factorial arrangement of treatments with the main factors including oral administration of AFB₁ (0 vs. 40 μg/kg) and dietary supplementation of ZnO-NPs (0 vs. 60 mg/kg) for 7 days. It showed that AFB₁ exposure caused body weight loss (p < 0.05), impaired liver structure and failure in hepatic function (activity of ALT, AST and concentration of TP and GLU) (p < 0.05), and decreases in antioxidant capacity(activity of SOD, CAT and concentration of GSH) (p < 0.05), along with the decrease in hepatic concentration of Zn, increase in expression of apoptosis-related genes and protein CAS3 and mRNA Bcl-2 expression (p < 0.05), and suppressed mRNA levels of antioxidant-related genes MT, SOD1, NRF2, and NQO1 (p < 0.05). In accordance with the cell test, dietary supplementation with ZnO-NPs mitigated the toxicity exerted by AFB₁. In conclusion, ZnO-NPs has the protective effects against AFB₁-induced hepatocyte injury by activating the expression of MTF-1 and the ectopic induction of MT expression, providing detailed information on the detoxification ability of MT on AFB₁.

Zinc promotes cell proliferation via regulating metal-regulatory transcription factor 1 expression and transcriptional activity in pulmonary arterial hypertension

Metal responsive transcription factor 1 (MTF-1) is a zinc-dependent transcription factor involved in the development of pulmonary arterial hypertension (PAH), which is a life-threatening disease characterized by elevated pulmonary artery pressure and pulmonary vascular remodeling. However, little is known about the role and regulatory signaling of MTF-1 in PAH. This study aimed to investigate the effect and mechanism of MTF-1 on the proliferation of pulmonary arterial smooth muscle cells (PASMCs). Several techniques including intracellular-free zinc detected by fluorescent indicator-fluozinc-3-AM, western blot, luciferase reporter, and cell proliferation assay were conducted to perform a comprehensive analysis of MTF-1 in proliferation of PASMCs in PAH. Increased cytosolic zinc was shown in monocrotaline (MCT)-PASMCs and ZnSO₄-treated PASMCs, which led to overexpression and overactivation of MTF-1, followed by the up-regulation of placental growth factor (PlGF). Elevated MTF-1 and PlGF were observed in western blot, and high transcriptional activity of MTF-1 was confirmed by luciferase reporter in ZnSO4-treated cells. Further investigation of cell proliferation revealed a favorable impact of zinc ions on PASMCs proliferation, with the deletion of Mtf-1/Plgf attenuating ZnSO4-induced proliferation. Flow cytometry analysis showed that blockade of PKC signaling inhibited the cell cycle of MCT-PASMCs and ZnSO4-treated PASMCs. The Zinc/PKC/MTF-1/PlGF pathway is involved in the up-regulatory effect on the PASMCs proliferation in the process of PAH. This study provided novel insight into zinc homeostasis in the pathogenesis of PAHs, and the regulation of MTF-1 might be a potential target for therapeutic intervention in PAH.

Manganese-Induced Oxidative Stress Contributes to Intestinal Lipid Deposition via the Deacetylation of PPARγ at K339 by SIRT1

Aims: Excessive manganese (Mn) exposure is toxic, and induces lipid deposition, but the underlying mechanisms remain elusive. Herein, we explored how dietary Mn supplementation affects lipid deposition and metabolism in the intestine of vertebrates using the yellow catfish Pelteobagrus fulvidraco as the model. Results: High-Mn (H-Mn) diet increased intestinal Mn content, promoted lipid accumulation and lipogenesis, and inhibited lipolysis. In addition, it induced oxidative stress, upregulated metal-response element-binding transcription factor-1 (MTF-1), and peroxisome proliferator-activated receptor gamma (PPARγ) protein expression in the nucleus, induced PPARγ acetylation, and the interaction between PPARγ and retinoid X receptor alpha (RXRα), while it downregulated sirtuin 1 (SIRT1) expression and activity. Mechanistically, Mn activated the MTF-1/divalent metal transporter 1 (DMT1) pathway, increased Mn accumulation in the mitochondria, and induced oxidative stress. This in turn promoted lipid deposition via deacetylation of PPARγ at K339 by SIRT1. Subsequently, PPARγ mediated Mn-induced lipid accumulation through transcriptionally activating fatty acid translocase, stearoyl-CoA desaturase 1, and perilipin 2 promoters. Innovation: These studies uncover a previously unknown mechanism by which Mn induces lipid deposition in the intestine via the oxidative stress-SIRT1-PPARγ pathway. Conclusion: High dietary Mn intake activates MTF-1/DMT1 and oxidative stress pathways. Oxidative stress-mediated PPARγ deacetylation at K339 site contributes to increased lipid accumulation. Our results provided a direct link between Mn and lipid metabolism via the oxidative stress-SIRT1-PPARγ axis. Antioxid. Redox Signal. 37, 417-436.

Cuproptosis and cuproptosis-related genes in rheumatoid arthritis: Implication, prospects, and perspectives

Rheumatoid arthritis (RA) is an autoimmune disease that severely affects patients' physical and mental health, leading to chronic synovitis and destruction of bone joints. Although various available clinical treatment options exist, patients respond with varying efficacies due to multiple factors, and there is an urgent need to discover new treatment options to improve clinical outcomes. Cuproptosis is a newly characterized form of cell death. Copper causes cuproptosis by binding to lipid-acylated components of the tricarboxylic acid cycle, leading to protein aggregation, loss of iron-sulfur cluster proteins, and eventually proteotoxic stress. Targeting copper cytotoxicity and cuproptosis are considered potential options for treating oncological diseases. The synovial hypoxic environment and the presence of excessive glycolysis in multiple cells appear to act as inhibitors of cuproptosis, which can lead to excessive survival and proliferation of multiple immune cells, such as fibroblast-like synoviocytes, effector T cells, and macrophages, further mediating inflammation and bone destruction in RA. Therefore, in this study, we attempted to elaborate and summarize the linkage of cuproptosis and key genes regulating cuproptosis to the pathological mechanisms of RA and their effects on a variety of immune cells. This study aimed to provide a theoretical basis and support for translating preclinical and experimental results of RA to clinical protocols.

Transcriptional Regulation and Protein Localization of Zip10, Zip13 and Zip14 Transporters of Freshwater Teleost Yellow Catfish Pelteobagrus fulvidraco Following Zn Exposure in a Heterologous HEK293T Model

Zip family proteins are involved in the control of zinc (Zn) ion homeostasis. The present study cloned the promoters and investigated the transcription responses and protein subcellular localizations of three LIV-1 subfamily members (zip10, zip13, and zip14) from common freshwater teleost yellow catfish, Pelteobagrus fulvidraco, using in vitro cultured HEK293T model cells. The 2278 bp, 1917 bp, and 1989 bp sequences of zip10, zip13, and zip14 promoters, respectively, were subcloned into pGL3-Basic plasmid for promoter activity analysis. The pcDNA3.1 plasmid coding EGFP tagged pfZip10, pfZip13, and pfZip14 were generated for subsequent confocal microscope analysis. Several potential transcription factors' binding sites were predicted within the promoters. In vitro promoter analysis in the HEK293T cells showed that high Zn administration significantly reduced the transcriptional activities of the zip10, zip13, and zip14 promoters. The -2017 bp/-2004 bp MRE in the zip10 promoter, the -360 bp/-345 bp MRE in the zip13 promoter, and the -1457 bp/-1442 bp MRE in the zip14 promoter were functional loci that were involved in the regulation of the three zips. The -606 bp/-594 bp KLF4 binding site in the zip13 promoter was a functional locus responsible for zinc-responsive regulation of zip13. The -1383 bp/-1375 bp STAT3 binding site in the zip14 promoter was a functional locus responsible for zinc-responsive regulation of zip14. Moreover, confocal microscope analysis indicated that zinc incubation significantly reduced the fluorescence intensity of pfZip10-EGFP and pfZip14-EGFP but had no significant influence on pfZip13-EGFP fluorescence intensity. Further investigation found that pfZip10 localizes on cell membranes, pfZip14 colocalized with both cell membranes and lysosome, and pfZip13 colocalized with intracellular ER and Golgi. Our research illustrated the transcription regulation of zip10, zip13, and zip14 from P. fulvidraco under zinc administration, which provided a reference value for the mechanisms involved in Zip-family-mediated control of zinc homeostasis in vertebrates.

Insights into the mechanisms of tris(2-chloroethyl) phosphate-induced growth inhibition in juvenile yellow catfish Pelteobagrus fulvidraco

With the gradual elimination of brominated flame retardants (BFRs), the production and application of tris (2-chloroethyl) phosphate (TCEP), as a substitute of BFRs, has increased greatly. The objective of the present study was to comprehensively explore the potential adverse effects of TCEP on fish growth and the possible underlying mechanisms. To this end, juvenile yellow catfish (Pelteobagrus fulvidraco) were exposed to environmentally relevant concentrations of TCEP (0, 1, 10 and 100 µg/L) for 30 days. The results showed that exposure to high concentrations of TCEP (10 and 100 µg/L) significantly decreased body weight, body length and specific growth rate (SGR). Plasma IGF-I levels and hepatic mRNA levels of igf1 and igf1r were all reduced, while the transcriptional levels of IGFBPs (igfbp2, igfbp3, igfbp5) were significantly up-regulated in the liver of yellow catfish under exposure to 10 and 100 µg/L TCEP. TCEP-induced growth inhibition might be related to somatostatin (SS) signaling system, as evidenced by elevated mRNA transcriptions of ss in brain and its receptors (sstr2, sstr3, sstr5) in liver. In addition, fish exposed to high concentrations of TCEP displayed multiple histological alterations in liver. Taken together, these findings suggested that TCEP (>10 µg/L) might exert its inhibitory effect on fish growth through interfering with the GH/IGF axis and SS signaling system, and by impairing hepatic structures.

Combined effects of polystyrene microplastics and copper on antioxidant capacity, immune response and intestinal microbiota of Nile tilapia (Oreochromis niloticus)

Microplastics (MPs) coexist with other pollutants (such as heavy metals) in water, adversely impacting aquatic organisms, which might cause unpredictable ecological risks. This study aims to evaluate the effect of copper (Cu²⁺) and polystyrene microplastics (PS-MPs) on antioxidant capacity, immune response and intestinal microbiota of Nile tilapia. Cu²⁺ and PS-MPs co-exposure enhanced Cu²⁺ bioaccumulation in the liver of fish compared with Cu²⁺-alone exposure. Fish exposed to PS-MPs and Cu²⁺ displayed histopathologic alterations in the liver, intestine and gill. Exposure at low concentrations of Cu²⁺ in the C0 and CP0 groups can improve antioxidant capacity and immune response, while oxidative damage and inflammation existed in the high concentration of Cu²⁺ groups. Intestinal microbiota results showed that the diversity and structure were changed by Cu²⁺ and PS-MPs exposure, and harmful bacterium even increased at high concentration of Cu²⁺ and PS-MPs exposure groups. All in all, PS-MPs aggravate the accumulation of Cu²⁺ and lead to perturbations in biological systems of Nile tilapia.

Mitochondria-Dependent Oxidative Stress Mediates ZnO Nanoparticle (ZnO NP)-Induced Mitophagy and Lipotoxicity in Freshwater Teleost Fish

Due to many special characteristics, zinc oxide nanoparticles (ZnO NPs) are widely used all over the world, leading to their wide distribution in the environment. However, the toxicities and mechanisms of environmental ZnO NP-induced changes of physiological processes and metabolism remain largely unknown. Here, we found that addition of dietary ZnO NPs disturbed hepatic Zn metabolism, increased hepatic Zn and lipid accumulation, downregulated lipolysis, induced oxidative stress, and activated mitophagy; N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN, Zn²⁺ ions chelator) alleviated high ZnO NP-induced Zn and lipid accumulation, oxidative stress, and mitophagy. Mechanistically, the suppression of mitochondrial oxidative stress attenuated ZnO NP-activated mitophagy and ZnO NP-induced lipotoxicity. Taken together, our study elucidated that mitochondrial oxidative stress mediated ZnO NP-induced mitophagy and lipotoxicity; ZnO NPs could be dissociated to free Zn²⁺ ions, which partially contributed to ZnO NP-induced changes in oxidative stress, mitophagy, and lipid metabolism. Our study provides novel insights into the impacts and mechanism of ZnO NPs as harmful substances inducing lipotoxicity of aquatic organisms, and accordingly, metabolism-relevant parameters will be useful for the risk assessment of nanoparticle materials in the environment.

Transcriptional responses of four slc30a/znt family members and their roles in Zn homeostatic modulation in yellow catfish Pelteobagrus fulvidraco

The study characterized their regulatory functions of four znt members (znt1, znt2, znt6 and znt8) in Zn homeostasis in vertebrates. We found that the -1281/-1296 bp locus on the znt1 promoter, the -1/-16 bp locus on the znt2 promoter, the -825/-839 bp locus on the znt6 promoter, the -165/-180 bp locus and the -274/-292 bp STAT3 locus on the znt8 promoter were functional MTF-1 binding sites and had metal responsive element (MRE). Zn incubation increased activities of four znt promoters, which was mediated by MRE sites on znt1, znt2, znt6 and znt8 promoters and by STAT3 binding site on znt8 promoter. Moreover, Zn activated the transcription of these znts genes through MTF-1-MRE-dependent pathway. Zn incubation up-regulated the mRNA and total protein expression of ZnT1, ZnT2 and ZnT8 at both 24 h and 48 h. Overall, for the first time, this study offered novel insights for regulatory mechanism of Zn homeostasis in vertebrates.

Functional Analysis of the Promoter Regions of Two Apoptosis-Related Genes (Bcl-2 and Cycs) and Their Regulation by Zn in Yellow Catfish

B-cell lymphoma 2 (Bcl-2) and cytochrome c (Cycs) are two important proteins relevant to cellular apoptosis. In this study, we characterized the functions of the promoter regions of two apoptosis-related genes, Bcl-2 and Cycs, in yellow catfish Pelteobagrus fulvidraco. We obtained a 1989 bp Bcl-2 promoter and an 1830 bp Cycs promoter and predicted several key transcription factor binding sites (TFBSs) on the promoters, such as Kruppel-like factor 4 (KLF4), signal transducer and activator of transcription factor 3 (STAT3), forkhead box O (FOXO), metal-responsive element (MRE) and hepatocyte nuclear factor 1α (HNF-1α). Zinc (Zn) increased the activities of the Bcl-2 promoter but decreased the activities of the Cycs promoter. Metal-responsive transcription factor 1 (MTF-1) and HNF-1α directly bound with Bcl-2 and Cycs promoters, and they positively regulated the activity of the Bcl-2 promoter but negatively regulated the activity of the Cycs promoter. Zn promoted the binding ability of HNF-1α to the Bcl-2 promoter but decreased its binding ability to the Cycs promoter. However, Zn had no significant effect on the binding capability of MTF-1 to the regions of Bcl-2 and Cycs promoters. Zn upregulated the mRNA and total protein expression of Bcl-2 but downregulated the mRNA and total protein expression of Cycs. At the same time, Annexin V-FITC/PI staining showed that Zn significantly reduced the apoptosis of primary hepatocytes. For the first time, our study provides evidence for the MRE and HNF-1α response elements on the Bcl-2 and Cycs promoters, offering new insight into the mechanism by which Zn affects apoptosis in vertebrates.

Zn Induces Lipophagy via the Deacetylation of Beclin1 and Alleviates Cu-Induced Lipotoxicity at Their Environmentally Relevant Concentrations

In this study, the mechanisms of environmentally relevant doses of Cu and Zn mixtures influencing lipid deposition and metabolism were investigated in freshwater teleost yellow catfish Pelteobagrus fulvidraco (2 months old, 4.95 (t0.01 g, mean ± SEM). Our study indicated that waterborne Cu exposure increased lipid content, while Zn activated lipophagic flux and alleviated Cu-induced lipid accumulation. Yellow catfish hepatocytes treated with Zn or Zn + Cu activated autophagy-specific lipophagy, decreased lipid storage, and increased nonesterified fatty acid (NEFA) release, suggesting a causal relationship between lipophagy and lipid droplet (LD) breakdown under Zn and Zn + Cu conditions. Our further investigation found that Beclin1 deacetylation by sirtuin 1 (SIRT1) was required for Zn- and Zn + Cu-induced lipophagy and lipolysis, and lysine residues 427 and 434 were key sites for Beclin1 deacetylation. Taken together, these findings show that the Zn-induced deacetylation of Beclin1 promotes lipophagy as an important pathway to alleviate Cu-induced lipid accumulation in fish, which reveals a previously unidentified mechanism for understanding the antagonistic effects of Cu and Zn on metabolism at their environmentally relevant concentrations. Our results highlight the importance of combined exposure when the biological effects of heavy metals are evaluated during environmental risk assessments.

Characterization of cadmium-responsive transcription factors in wolf spider Pardosa pseudoannulata

Transcription factors (TFs) act on the regulation of gene expression, which is prevalent in all organisms, and their characterization may provide important clues for understanding the regulatory mechanism of gene expression. In this research, inhibited growth (delayed developmental time and decreased body weight) and increased activities of antioxidant enzymes (peroxidase, superoxide dismutase, and catalase) were recorded in Pardosa pseudoannulata in response to cadmium burden. Expression profiles of TFs were analyzed based on the transcriptome profiling of P. pseudoannulata, and 1711 TFs genes were differentially expressed with 995 up-regulated and 716 down-regulated. Most of the differentially expressed TFs belonged to zf-C2H2, ZBTB, Homeobox, and bHLH families. Interestingly, hub genes smads, TCF7L2, EGR1, and GATA5 were identified to be the candidate Cd-responsive TFs related to growth of spider. The expression level of Sod2 (superoxide dismutase) was regulated by the up-regulated TF foxo3, implying its important role in the antioxidant defense of spider. Moreover, sequence analysis demonstrated that smads and foxo3 were conserved among spiders and insects. This study revealed for the first time the role of TFs in molecular response of P. pseudoannulata to Cd stress, providing the basis for the protection of tarantula under Cd stress.

Isolation and Characterization of Three Sodium-Phosphate Cotransporter Genes and Their Transcriptional Regulation in the Grass Carp Ctenopharyngodon idella

It is important to explore the regulatory mechanism of phosphorus homeostasis in fish, which help avoid the risk of P toxicity and prevent P pollution in aquatic environment. The present study obtained the full-length cDNA sequences and the promoters of three SLC20 members (slc20a1a, slc20a1b and slc20a2) from grass carp Ctenopharyngodon idella, and explored their responses to inorganic phosphorus (Pi). Grass carp SLC20s proteins possessed conservative domains and amino acid sites relevant with phosphorus transport. The mRNAs of three slc20s appeared in the nine tissues, but their expression levels were tissue-dependent. The binding sites of three transcription factors (SREBP1, NRF2 and VDR) were predicted on the slc20s promoters. The mutation and EMSA analysis indicated that: (1) SREBP1 binding site (-783/-771 bp) negatively but VDR (-260/-253 bp) binding site positively regulated the activities of slc20a1a promoter; (2) SREBP1 (-1187/-1178 bp), NRF2 (-572/-561 bp) and VDR(615/-609 bp) binding sites positively regulated the activities of slc20a1b promoter; (3) SREBP1 (-987/-977 bp), NRF2 (-1469/-1459 bp) and VDR (-1124/-1117 bp) binding sites positively regulated the activities of the slc20a2 promoter. Moreover, Pi incubation significantly reduced the activities of three slc20s promoters, and Pi-induced transcriptional inactivation of slc20s promoters abolished after the mutation of the VDR element but not SREBP1 and NRF2 elements. Pi incubation down-regulated the mRNA levels of three slc20s. For the first time, our study elucidated the transcriptional regulatory mechanisms of SLC20s and their responses to Pi, which offered new insights into the Pi homeostatic regulation and provided the basis for reducing phosphorus discharge into the waters.

Functional Analysis of Two Zinc (Zn) Transporters (ZIP3 and ZIP8) Promoters and Their Distinct Response to MTF1 and RREB1 in the Regulation of Zn Metabolism

ZIP (zinc-regulated transporters, iron-regulated transporter-like protein) family plays an important role in organism Zn balance. This research identified the promoter regions of ZIP3 and ZIP8, two members of ZIP family, from a freshwater teleost yellow catfish Pelteobagrus fulvidraco, characterized the binding sequences of the metal-responsive transcription factor-1 (MTF-1) and Ras responsive element binding protein 1 (RREB1) on their promoter regions. The present study cloned and obtained the 2027 bp of ZIP3 promoter and 1664 bp of ZIP8 promoter, and predicted several key elements on their promoters, such as the binding sites of CREB (cAMP-response element binding protein), KLF4 (Kruppel like factor 4), MTF-1 and RREB1. The sequence deletion from −361 bp to −895 bp down-regulated the luciferase activity of ZIP3 promoter, and the deletion from −897 bp to −1664 bp down-regulated the luciferase activity of ZIP8 promoter. Within different deletion plasmids, the relative luciferase activities of ZIP3 and ZIP8 promoters changes to Zn incubation in a Zn concentration-dependent manner. The site mutagenesis and EMSA (electrophoretic mobility shift assay) found that the −1327 bp/−1343 bp MTF-1 binding site and the −248 bp/−267 bp RREB1 binding site on the ZIP3 promoter, and the −1543 bp/−1557 bp MTF-1 binding site on the ZIP8 promoter are functional sites. Low Zn increased the binding capability between MTF-1 and its responsive site on the ZIP3 promoter, and high Zn increased the transcriptional activation ZIP3 by RREB1; Zn also promoted the binding ability between MTF-1 and its responsive element on the ZIP8 promoter. This study provides the first direct evidence for the response elements of MTF-1 and RREB1 on ZIP3 and MTF-1 on ZIP8 to Zn, which are very important for the evaluation of Zn nutrition and toxicity in vertebrates.

miR-101b Regulates Lipid Deposition and Metabolism of Primary Hepatocytes in Teleost Yellow Catfish Pelteobagrus fulvidraco

Excessive fat deposition in the hepatocytes, associated with excess dietary fat intake, was related to the occurrence of fatty livers in fish. miR-101b plays the important roles in controlling lipid metabolism, but the underlying mechanism at the post-transcriptional level remains unclear. The purpose of this study is to explore the roles and mechanism of miR-101b-mediating lipid deposition and metabolism in yellow catfish Pelteobagrus fulvidraco. We found that miR-101b directly targeted fatty acid translocase (cd36), caspase9 (casp9) and autophagy-related gene 4A (atg4a). Furthermore, using palmitic acid (PA) or oleic acid (OA) to incubate the primary hepatocytes of yellow catfish, we demonstrated that miR-101b inversely regulated cd36, casp9, and atg4a expression at the transcriptional level; the inhibition of miR-101b aggravated fatty acids (FAs, PA or OA)-induced lipid accumulation, indicating that miR-101b mediated FAs-induced variations of lipid metabolism in yellow catfish. Taken together, our study gave novel insight into the regulatory mechanism of lipid deposition and metabolism and might provide potential targets for the prevention and treatment of fatty livers in fish.