BF170 hydrochloride enhances the emergence of hematopoietic stem and progenitor cells.

Generation of hematopoietic stem and progenitor cells (HSPCs) ex vivo and in vivo, especially the generation of safe therapeutic HSPCs, still remains inefficient. In this study, we have identified compound BF170 hydrochloride as a previously unreported pro-hematopoiesis molecule, using the differentiation assays of primary zebrafish blastomere cell culture and mouse embryoid bodies (EBs), and we demonstrate that BF170 hydrochloride promoted definitive hematopoiesis in vivo. During zebrafish definitive hematopoiesis, BF170 hydrochloride increases blood flow, expands hemogenic endothelium (HE) cells and promotes HSPC emergence. Mechanistically, the primary cilia-Ca2+-Notch/NO signaling pathway, which is downstream of the blood flow, mediated the effects of BF170 hydrochloride on HSPC induction in vivo. Our findings, for the first time, reveal that BF170 hydrochloride is a compound that enhances HSPC induction and may be applied to the ex vivo expansion of HSPCs.

Hyperosmotic Stress Induces Inflammation and Excessive Th17 Response to Blunt T-Cell Immunity in Tilapia.

Despite the advances in study on osmotic physiology in bony fish, the mechanism by which the immune system, especially T-cell immunity, adapts and responds to osmotic stress remains unknown. In the current study, we investigated the response of T cells to hyperosmotic stress in the bony fish Nile tilapia (Oreochromis niloticus). As a euryhaline fish, tilapia was able to adapt to a wide range of salinities; however, hypertonic stress caused inflammation and excessive T-cell activation. Furthermore, hypertonic stress increased the expression of IL-17A in T cells, upregulated the transcription factor RORα, and activated STAT3 signaling, along with IL-6- and TGF-ß1-mediated pathways, revealing an enhanced Th17 response in this early vertebrate. These hypertonic stress-induced events collectively resulted in an impaired antibacterial immune response in tilapia. Hypertonic stress elevated the intracellular ROS level, which in turn activated the p38-MK2 signaling pathway to promote IL-17A production by T cells. Both ROS elimination and the p38-MK2 axis blockade diminished the increased IL-17A production in T cells under hypertonic conditions. Moreover, the produced proinflammatory cytokines further amplified the hypertonic stress signaling via the MKK6-p38-MK2 axis-mediated positive feedback loop. To our knowledge, these findings represent the first description of the mechanism by which T-cell immunity responds to hypertonic stress in early vertebrates, thus providing a novel perspective for understanding the adaptive evolution of T cells under environmental stress.

Fish Uses CTLA-4 Immune Checkpoint to Suppress mTORC1-Controlled T-Cell Glycolysis and Immunity.

As an immune checkpoint, cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) suppresses the activation, proliferation, and effector function of T cells, thus preventing an overexuberant response and maintaining immune homeostasis. However, whether and how this immune checkpoint functions in early vertebrates remains unknown. In the current study, using a Nile tilapia (Oreochromis niloticus) model, we investigated the suppression of T cell response by CTLA-4 in bony fish. Tilapia CTLA-4 is constitutively expressed in lymphoid tissues, and its mRNA and protein expression in lymphocytes are upregulated following PHA stimulation or Edwardsiella piscicida infection. Blockade of CTLA-4 signaling enhanced T cell activation and proliferation but inhibited activation-induced T cell apoptosis, indicating that CTLA-4 negatively regulated T cell activation. In addition, blocking CTLA-4 signaling in vivo increased the differentiation potential and cytotoxicity of T cells, resulting in an enhanced T cell response during E. piscicida infection. Tilapia CTLA-4 competitively bound the B7.2/CD86 molecule with CD28, thus antagonizing the CD28-mediated costimulatory signal of T cell activation. Furthermore, inhibition of mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling, c-Myc, or glycolysis markedly impaired the CTLA-4 blockade-enhanced T cell response, suggesting that CTLA-4 suppressed the T cell response of tilapia by inhibiting mTORC1/c-Myc axis-controlled glycolysis. Overall, the findings indicate a detailed mechanism by which CTLA-4 suppresses T cell immunity in tilapia; therefore, we propose that early vertebrates have evolved sophisticated mechanisms coupling immune checkpoints and metabolic reprogramming to avoid an overexuberant T cell response.

Achieving atomically ordered GaN/AlN quantum heterostructures: The role of surface polarity.

Interface engineering in heterostructures at the atomic scale has been a central research focus of nanoscale and quantum material science. Despite its paramount importance, the achievement of atomically ordered heterointerfaces has been severely limited by the strong diffusive feature of interfacial atoms in heterostructures. In this work, we first report a strong dependence of interfacial diffusion on the surface polarity. Near-perfect quantum interfaces can be readily synthesized on the semipolar plane instead of the conventional c-plane of GaN/AlN heterostructures. The chemical bonding configurations on the semipolar plane can significantly suppress the cation substitution process as evidenced by first-principles calculations, which leads to an atomically sharp interface. Moreover, the surface polarity of GaN/AlN can be readily controlled by varying the strain relaxation process in core-shell nanostructures. The obtained extremely confined, interdiffusion-free ultrathin GaN quantum wells exhibit a high internal quantum efficiency of ~75%. Deep ultraviolet light-emitting diodes are fabricated utilizing a scalable and robust method and the electroluminescence emission is nearly free of the quantum-confined Stark effect, which is significant for ultrastable device operation. The presented work shows a vital path for achieving atomically ordered quantum heterostructures for III-nitrides as well as other polar materials such as III-arsenides, perovskites, etc.

StructuralDPPIV: a novel deep learning model based on atom structure for predicting dipeptidyl peptidase-IV inhibitory peptides.

MOTIVATION: Diabetes is a chronic metabolic disorder that has been a major cause of blindness, kidney failure, heart attacks, stroke, and lower limb amputation across the world. To alleviate the impact of diabetes, researchers have developed the next generation of anti-diabetic drugs, known as dipeptidyl peptidase IV inhibitory peptides (DPP-IV-IPs). However, the discovery of these promising drugs has been restricted due to the lack of effective peptide-mining tools. RESULTS: Here, we presented StructuralDPPIV, a deep learning model designed for DPP-IV-IP identification, which takes advantage of both molecular graph features in amino acid and sequence information. Experimental results on the independent test dataset and two wet experiment datasets show that our model outperforms the other state-of-art methods. Moreover, to better study what StructuralDPPIV learns, we used CAM technology and perturbation experiment to analyze our model, which yielded interpretable insights into the reasoning behind prediction results. AVAILABILITY AND IMPLEMENTATION: The project code is available at https://github.com/WeiLab-BioChem/Structural-DPP-IV.

Comparative genomics on chloroplasts of Rubus (Rosaceae).

Rubus, the largest genus in Rosaceae, contains over 1400 species that distributed in multiple habitats across the world, with high species diversity in the temperate regions of Northern Hemisphere. Multiple Rubus species are cultivated for their valuable fruits. However, the intrageneric classification and phylogenetic relationships are still poorly understood. In this study, we sequenced, assembled, and characterized 17 plastomes of Rubus, and conducted comparative genomics integrating with 47 previously issued plastomes of this genus. The 64 plastomes of Rubus exhibited typical quadripartite structure with sizes ranging from 155,144 to 156,700 bp, and contained 132 genes including 87 protein-coding genes, 37 tRNA genes and eight rRNA genes. All plastomes are conservative in the gene order, the frequency of different types of long repeats and simple sequence repeats (SSRs), the codon usage, and the selection pressure of protein-coding genes. However, there are also some differences in the Rubus plastomes, including slight contraction and expansion of the IRs, a variation in the numbers of SSRs and long repeats, and some genes in certain clades undergoing intensified or relaxed purifying selection. Phylogenetic analysis based on whole plastomes showed that the monophyly of Rubus was strongly supported and resolved it into six clades corresponding to six subgenera. Moreover, we identified 12 highly variable regions that could be potential molecular markers for phylogenetic, population genetic, and barcoding studies. Overall, our study provided insight into plastomic structure and sequence diversification of Rubus, which could be beneficial for future studies on identification, evolution, and phylogeny in this genus.

Quasi-Zero-Dimensional Ferroelectric Polarization Charges-Coupled Resistance Switching with High-Current Density in Ultrascaled Semiconductors.

Ferroelectric memristors hold immense promise for advanced memory and neuromorphic computing. However, they face limitations due to low readout current density in conventional designs with low-conductive ferroelectric channels, especially at the nanoscale. Here, we report a ferroelectric-mediated memristor utilizing a 2D MoS2 nanoribbon channel with an ultrascaled cross-sectional area of <1000 nm2, defined by a ferroelectric BaTiO3 nanoribbon stacked on top. Strikingly, the Schottky barrier at the MoS2 contact can be effectively tuned by the charge transfers coupled with quasi-zero-dimensional polarization charges formed at the two ends of the nanoribbon, which results in distinctive resistance switching accompanied by multiple negative differential resistance showing the high-current density of >104 A/cm2. The associated space charges in BaTiO3 are minimized to ∼3.7% of the polarization charges, preserving nonvolatile polarization. This achievement establishes ferroelectric-mediated nanoscale semiconductor memristors with high readout current density as promising candidates for memory and highly energy-efficient in-memory computing applications.

Ultrafast and Parts-per-Billion-Level MEMS Gas Sensors by Hetero-Interface Engineering of 2D/2D Cu-TCPP@ZnIn2S4 with Enriched Surface Sulfur Vacancies.

The primary challenge for resonant-gravimetric gas sensors is the synchronous improvement of the sensitivity and response time, which is restricted by low adsorption capacity and slow mass transfer in the sensing process and remains a great challenge. In this study, a novel 2D/2D Cu-TCPP@ZnIn2S4 composite is successfully constructed, in which Cu-TCPP MOF is used as a core substrate for the growth of 2D ultrathin ZnIn2S4 nanosheets with well-defined {0001} crystalline facets. The Cu-TCPP@ZnIn2S4 sensor exhibited high sensitivity (1.5 Hz@50 and 2.3 Hz@100 ppb), limit of detection (LOD: 50 ppb), and ultrafast (9 s @500 ppb) detection of triethylamine (TEA), which is the lowest LOD and the fastest sensor among the reported TEA sensors at room temperature, tackling the bottleneck for the ultrafast detection of the resonant-gravimetric sensor. These above results provide an innovative and easily achievable pathway for the synthesis of heterogeneous structure sensing materials.

Marsdenia tenacissima genome reveals calcium adaptation and tenacissoside biosynthesis.

Marsdenia tenacissima is a medicinal plant widely distributed in the calcium-rich karst regions of southwest China. However, the lack of a reference genome has hampered the implementation of molecular techniques in its breeding, pharmacology and domestication. We generated the chromosome-level genome assembly in Apocynaceae using combined SMRT sequencing and Hi-C. The genome length was 381.76 Mb, with 98.9% of it found on 11 chromosomes. The genome contained 222.63 Mb of repetitive sequences and 21 899 predicted gene models, with a contig N50 of 6.57 Mb. Phylogenetic analysis revealed that M. tenacissima diverged from Calotropis gigantea at least 13.43 million years ago. Comparative genomics showed that M. tenacissima underwent ancient shared whole-genome duplication. This event, together with tandem duplication, contributed to 70.71% of gene-family expansion. Both pseudogene analysis and selective pressure calculations suggested calcium-related adaptive evolution in the M. tenacissima genome. Calcium-induced differentially expressed genes (DEGs) were mainly enriched in cell-wall-related processes. Domains (e.g. Fasciclin and Amb_all) and cis-elements (e.g. MYB and MYC) frequently occurred in the coding and promoter regions of cell-wall DEGs, respectively, and the expression levels of these genes correlated significantly with those of calcium-signal-related transcription factors. Moreover, calcium addition increased tenacissoside I, G and H contents. The availability of this high-quality genome provides valuable genomic information for genetic breeding and molecular design, and lends insights into the calcium adaptation of M. tenacissima in karst areas.

Extracellular matrix marker LAMC2 targets ZEB1 to promote TNBC malignancy via up-regulating CD44/STAT3 signaling pathway.

BACKGROUND: Triple negative breast cancer (TNBC) is a heterogeneous and aggressive disease characterized by a high risk of mortality and poor prognosis. It has been reported that Laminin γ2 (LAMC2) is highly expressed in a variety of tumors, and its high expression is correlated with cancer development and progression. However, the function and mechanism by which LAMC2 influences TNBC remain unclear. METHODS: Kaplan-Meier survival analysis and Immunohistochemical (IHC) staining were used to examine the expression level of LAMC2 in TNBC. Subsequently, cell viability assay, wound healing and transwell assay were performed to detect the function of LAMC2 in cell proliferation and migration. A xenograft mouse model was used to assess tumorigenic function of LAMC2 in vivo. Luciferase reporter assay and western blot were performed to unravel the underlying mechanism. RESULTS: In this study, we found that higher expression of LAMC2 significantly correlated with poor survival in the TNBC cohort. Functional characterization showed that LAMC2 promoted cell proliferation and migration capacity of TNBC cell lines via up-regulating CD44. Moreover, LAMC2 exerted oncogenic roles in TNBC through modulating the expression of epithelial-mesenchymal transition (EMT) markers. Luciferase reporter assay verified that LAMC2 targeted ZEB1 to promote its transcription. Interestingly, LAMC2 regulated cell migration in TNBC via STAT3 signaling pathway. CONCLUSION: LAMC2 targeted ZEB1 via activating CD44/STAT3 signaling pathway to promote TNBC proliferation and migration, suggesting that LAMC2 could be a potential therapeutic target in TNBC patients.

Biological characteristics of pregnancy in captive Yangtze finless porpoises revealed by urinary metabolomics†.

The Yangtze finless porpoises (Neophocaena asiaeorientalis a.) are an endemic and critically endangered species in China. Intensive captive breeding is essential for understanding the biology of critically endangered species, especially their pregnancy characteristics, knowledge of which is crucial for effective breeding management. Urine metabolomics can reveal metabolic differences, arising from physiological changes across pregnancy stages. Therefore, we used the urinary metabolomic technology, to explore urinary metabolite changes in pregnant Yangtze finless porpoises. A total of 2281 metabolites were identified in all samples, which including organic acids and derivatives (24.45%), organoheterocyclic compounds (20.23%), benzenoids (18.05%), organic oxygen compounds (7.73%), and phenylpropanoids and polyketides (6.48%). There were 164, 387, and 522 metabolites demonstrating differential abundance during early pregnancy, mid pregnancy, and late pregnancy, respectively, from the levels observed in nonpregnancy. The levels of pregnenolone, 17α-hydroxyprogesterone, and tetrahydrocortisone were significantly higher during all pregnancy stages, indicating their important roles in fetal development. The differential metabolites between nonpregnancy and pregnancy were mainly associated with amino acid and carbohydrate metabolism. Moreover, metabolic activity varied across pregnancy stages; steroid hormone biosynthesis was predominant in early pregnancy, and amino acid biosynthesis and carbohydrate metabolism were predominant in mid pregnancy and late pregnancy, respectively. Our results provide new insights into metabolic characteristics in the Yangtze finless porpoises' urine during pregnancy, and indicate that the differential levels of urine metabolites can determine pregnancy in Yangtze finless porpoises, providing valuable information for the husbandry and management of pregnant Yangtze finless porpoises in captivity.

Integrated analysis of transcriptome and small RNAome reveals regulatory network of rapid and long-term response to heat stress in Rhododendron moulmainense.

MAIN CONCLUSION: The post-transcriptional gene regulatory pathway and small RNA pathway play important roles in regulating the rapid and long-term response of Rhododendron moulmainense to high-temperature stress. The Rhododendron plays an important role in maintaining ecological balance. However, it is difficult to domesticate for use in urban ecosystems due to their strict optimum growth temperature condition, and its evolution and adaptation are little known. Here, we combined transcriptome and small RNAome to reveal the rapid response and long-term adaptability regulation strategies in Rhododendron moulmainense under high-temperature stress. The post-transcriptional gene regulatory pathway plays important roles in stress response, in which the protein folding pathway is rapidly induced at 4 h after heat stress, and alternative splicing plays an important role in regulating gene expression at 7 days after heat stress. The chloroplasts oxidative damage is the main factor inhibiting photosynthesis efficiency. Through WGCNA analysis, we identified gene association patterns and potential key regulatory genes responsible for maintaining the ROS steady-state under heat stress. Finally, we found that the sRNA synthesis pathway is induced under heat stress. Combined with small RNAome, we found that more miRNAs are significantly changed under long-term heat stress. Furthermore, MYBs might play a central role in target gene interaction network of differentially expressed miRNAs in R. moulmainense under heat stress. MYBs are closely related to ABA, consistently, ABA synthesis and signaling pathways are significantly inhibited, and the change in stomatal aperture is not obvious under heat stress. Taken together, we gained valuable insights into the transplantation and long-term conservation domestication of Rhododendron, and provide genetic resources for genetic modification and molecular breeding to improve heat resistance in Rhododendron.

Construction and interpretation of high-order image information based on NV optical magnetic vector detection.

Tensor imaging can provide more comprehensive information about spatial physical properties, but it is a high-dimensional physical quantity that is difficult to observe directly. This paper proposes a fast-transform magnetic tensor imaging method based on the NV magnetic detection technique. The Euler deconvolution interprets the magnetic tensor data to obtain the target three-dimensional (3D) boundary information. Fast magnetic vector imaging was performed using optical detection of magnetic resonance (ODMR) to verify the method's feasibility. The complete tensor data was obtained based on the transformation of the vector magnetic imaging data, which was subsequently solved, and the contour information of the objective was restored. In addition, a fast magnetic moment judgment model and an angular transformation model of the observation space are developed in this paper to reduce the influence of the magnetic moment direction on the results and to help interpret the magnetic tensor data. Finally, the experiment realizes the localization, judgment of magnetic moment direction, and 3D boundary identification of a micron-sized tiny magnet with a spatial resolution of 10 µm, a model accuracy of 90.1%, and a magnetic moment direction error of 4.2°.

Imaging electromagnetic boundary of microdevice using a wide field quantum microscope.

Imaging of electronic device surface or sub-surface electromagnetic fields under operating conditions is important for device design and diagnosis. In this study, we proposed a method to characterize specific magnetic field properties of electromagnetic devices at micron-scale using a solid-state quantum sensor, namely diamond nitrogen-vacancy (NV) centers. By employing a wide-field magnetic field measurement technique based on NV centers, we rapidly obtain the first-order magnetic field distribution of anomalous regions. Furthermore, we approximate the second-order magnetic field (magnetic gradient tensor) using the differential gradient method. To visualize the electromagnetic anomalous regions boundary, we utilize the tensor invariants of the magnetic gradient tensor components, along with their nonlinear combinations. The identification error rate of the anomalous regions is within 12.5%. Additionally, the electromagnetic field of anomalous regions is simulated showing the measurement accuracy. Our study shows that the experimental results are very similar to the theoretical simulation of the electromagnetic field (error: 7%). This work is essential for advancing electromagnetic field characterization of electronic devices and the advancement of quantum magnetic sensor applications.

Short-Process Regeneration of Highly Stable Spherical LiCoO2 Cathode Materials from Spent Lithium-Ion Batteries through Carbonate Precipitation.

High-efficacy recycling of spent lithium cobalt oxide (LiCoO2 ) batteries is one of the key tasks in realizing a global resource security strategy due to the rareness of lithium (Li) and cobalt (Co) resources. However, it is of great significance to develop the innovative recycle methods for spent LiCoO2 , simultaneously realizing the efficient recovery of valuable elements and the regeneration of high-performance LiCoO2 . Herein, a novel strategy of regenerating LiCoO2 cathode is proposed, which involves the preparation of micro-spherical aluminum (Al)-doped lithium-lacked precursor (Li2x Co1-x-y Al2/3y CO3, remarked as "PLCAC") via ammonium bicarbonate coprecipitation. The comprehensive conditions affecting particle growth kinetics, morphology and particle size the has been investigated in detail by physical characterizations and electrochemical measurements. And the optimized Al-doped LiCoO2 materials with high-density sphericity (LiCo1-z Alz O2 , remarked as "LCAO") shows a high initial specific capacity of 161 mAh g-1 at 0.1 C and excellent capacity retention of 99.5 % within 100 cycles at 1 C in the voltage range of 2.8 to 4.3 V. Our work provides valuable insights into the featured design of LiCoO2 precursors and cathode materials from spent LiCoO2 batteries, potentially guaranteeing the high-efficacy recycling and utilization of strategic resources.

Constructing Hollow Microcubes SnS2 as Negative Electrode for Sodium-ion and Potassium-ion Batteries.

Sodium/potassium-ion batteries (NIBs and KIBs) are considered the most promising candidates for lithium-ion batteries in energy storage fields. Tin sulfide (SnS2) is regarded as an attractive negative candidate for NIBs and KIBs thanks to its superior power density, high-rate performance and natural richness. Nevertheless, the slow dynamics, the enormous volume change and the decomposition of polysulfide intermediates limit its practical application. Herein, microcubes SnS2 were prepared through sacrificial MnCO3 template-assisted and a facile solvothermal reaction strategy and their performance was investigated in Na and K-based cells. The unique hollow cubic structure and well-confined SnS2 nanosheets play an important role in Na+/K+ rapid kinetic and alleviating volume change. The effect of the carbon additives (Super P/C65) on the electrochemical properties were investigated thoroughly. The in operando and ex-situ characterization provide a piece of direct evidence to clarify the storage mechanism of such conversion-alloying type negative electrode materials.

Mitochondrial quality control in abdominal aortic aneurysm: From molecular mechanisms to therapeutic strategies.

Mitochondria are the energy supply sites of cells and are crucial for eukaryotic life. Mitochondrial dysfunction is involved in the pathogenesis of abdominal aortic aneurysm (AAA). Multiple mitochondrial quality control (MQC) mechanisms, including mitochondrial DNA repair, biogenesis, antioxidant defense, dynamics, and autophagy, play vital roles in maintaining mitochondrial homeostasis under physiological and pathological conditions. Abnormalities in these mechanisms may induce mitochondrial damage and dysfunction leading to cell death and tissue remodeling. Recently, many clues suggest that dysregulation of MQC is closely related to the pathogenesis of AAA. Therefore, specific interventions targeting MQC mechanisms to maintain and restore mitochondrial function have become promising therapeutic methods for the prevention and treatment of AAA.

Glutathione Consumptive Dual-Sensitive Lipid-Composite Nanoparticles Induce Immunogenic Cell Death for Enhanced Breast Tumor Therapy.

Although chemotherapy remains the standard therapy for tumor treatment, serious side effects can occur because of nontargeted distribution and damage to healthy tissues. Hollow mesoporous silica nanoparticles (HMSNs) modified with lipids offer potential as delivery systems to improve therapeutic outcomes and reduce adverse effects. Herein, we synthesized HMSNs with integrated disulfide bonds (HMSN) for loading with the chemotherapeutic agent oxaliplatin (OXP) which were then covered with the synthesized hypoxia-sensitive lipid (Lip) on the surface to prepare the dual-sensitive lipid-composite nanoparticles (HMSN-OXP-Lip). The empty lipid-composite nanoparticles (HMSN-Lip) would consume glutathione (GSH) in cells because of the reduction of disulfide bonds in HMSN and would also inhibit GSH production because of NADPH depletion driven by Lip cleavage. These actions contribute to increased levels of ROS that induce the immunogenic cell death (ICD) effect. Simultaneously, HMSN-Lip would disintegrate in the presence of high concentrations of GSH. The lipid in HMSN-OXP-Lip could evade payload leakage during blood circulation and accelerate the release of the OXP in the tumor region in the hypoxic microenvironment, which could significantly induce the ICD effect to activate an immune response for an enhanced therapeutic effect. The tumor inhibitory rate of HMSN-OXP-Lip was almost twice that of free OXP, and no apparent side effects were observed. This design provides a dual-sensitive and efficient strategy for tumor therapy by using lipid-composite nanoparticles that can undergo sensitive drug release and biodegradation.

The TAK1/JNK axis participates in adaptive immunity by promoting lymphocyte activation in Nile tilapia.

The transforming growth factor beta-activated kinase 1 (TAK1)/c-Jun N-terminal kinase (JNK) axis is an essential MAPK upstream mediator and regulates immune signaling pathways. However, whether the TAK1/JNK axis harnesses the strength in regulation of signal transduction in early vertebrate adaptive immunity is unclear. In this study, by modeling on Nile tilapia (Oreochromis niloticus), we investigated the potential regulatory function of TAK1/JNK axis on lymphocyte-mediated adaptive immune response. Both OnTAK1 and OnJNK exhibited highly conserved sequences and structures relative to their counterparts in other vertebrates. Their mRNA was widely expressed in the immune-associated tissues, while phosphorylation levels in splenic lymphocytes were significantly enhanced on the 4th day post-infection by Edwardsiella piscicida. In addition, OnTAK1 and OnJNK were significantly up-regulated in transcriptional level after activation of lymphocytes in vitro by phorbol 12-myristate 13-acetate plus ionomycin (P + I) or PHA, accompanied by a predominant increase in phosphorylation level. More importantly, inhibition of OnTAK1 activity by specific inhibitor NG25 led to a significant decrease in the phosphorylation level of OnJNK. Furthermore, blocking the activity of OnJNK with specific inhibitor SP600125 resulted in a marked reduction in the expression of T-cell activation markers including IFN-γ, CD122, IL-2, and CD44 during PHA-induced T-cell activation. In summary, these findings indicated that the conserved TAK1/JNK axis in Nile tilapia was involved in adaptive immune responses by regulating the activation of lymphocytes. This study enriched the current knowledge of adaptive immunity in teleost and provided a new perspective for understanding the regulatory mechanism of fish immunity.

Inducible IL-2 production and IL-2+ cell expansion are landmark events for T-cell activation of teleost.

As a multipotent cytokine, interleukin (IL)-2 plays important roles in activation, differentiation and survival of the lymphocytes. Although biological characteristics and function of IL-2 have been clarified in several teleost species, evidence regarding IL-2 production at the cellular and protein levels is still scarce in fish due to the lack of reliable antibody. In this study, we developed a mouse anti-Nile tilapia IL-2 monoclonal antibody (mAb), which could specifically recognize IL-2 protein and identify IL-2-producing lymphocytes of tilapia. Using this mAb, we found that CD3+ T cells, but not CD3- lymphocytes, are the main cellular source of IL-2 in tilapia. Under resting condition, both CD3+CD4-1+ T cells and CD3+CD4-1- T cells of tilapia produce IL-2. Moreover, the IL-2 protein level and the frequency of IL-2+ T cells significantly increased once T cells were activated by phytohemagglutinin (PHA) or CD3 plus CD28 mAbs in vitro. In addition, Edwardsiella piscicida infection also induces the IL-2 production and the expansion of IL-2+ T cells in the spleen lymphocytes. These findings demonstrate that IL-2 takes part in the T-cell activation and anti-bacterial adaptive immune response of tilapia, and can serve as an important marker for T-cell activation of teleost fish. Our study has enriched the knowledge regarding T-cell response in fish species, and also provide novel perspective for understanding the evolution of adaptive immune system.