Zhenming Lv

Acute exposure to waterborne cadmium induced oxidative stress and immunotoxicity in the brain, ovary and liver of zebrafish (Danio rerio)

Cadmium (Cd) is an environmental contaminant that poses serious risks to aquatic organisms and their associated ecosystem. The mechanisms underlying Cd-induced oxidative stress and immunotoxicity in fish remain largely unknown. In this study, adult female zebrafish were exposed to 0 (control), 1mgL-1 Cd for 24h and 96h, and the oxidative stress and inflammatory responses induced by Cd were evaluated in the brain, liver and ovary. Reactive oxygen species (ROS), nitric oxide (NO), and malondialdehyde (MDA) increased in a time-dependent manner after treatment with Cd in the brain and liver. The increase may result from the disturbance of genes including copper and zinc superoxide dismutase (Cu/Zn-SOD), catalase (CAT), inducible nitric oxide synthase (iNOS), and ciclooxigenase-2 (COX-2) at mRNA, protein and activity levels. Although ROS, NO and MDA were not significantly affected by Cd in the ovary, the up-regulation of Cu/Zn-SOD, CAT, iNOS, and COX-2 was observed. Exposure to Cd induced a sharp increase in the protein levels of tumor necrosis factor alpha (TNF-α) in the brain, liver and ovary, possibly contributing to activate inflammatory responses. Furthermore, we also found a dramatic increase in mRNA levels of NF-E2-related factor 2 (Nrf2) and nuclear transcription factor κB (NF-κB) at 24h in the liver and ovary. The corresponding changes in the mRNA levels of Kelch-like-ECH-associated protein 1 (Keap1a and Keap1b) and the inhibitor of κBα (IκBαa and IκBαb) may contribute to regulate the transcriptional activity of Nrf2 and NF-κB, respectively. Contrarily, mRNA levels of Nrf2, NF-κB, Keap1, Keap1b, IκBαa and IκBαb remained stable at 24 and 96h in the brain. Taken together, we demonstrated Cd-induced oxidative stress and immunotoxicity in fish, possibly through transcriptional regulation of Nrf2 and NF-κB and gene modifications at transcriptional, translational, post-translational levels, which would greatly extend our understanding on the Cd toxicity.

Negative effect of chronic cadmium exposure on growth, histology, ultrastructure, antioxidant and innate immune responses in the liver of zebrafish: Preventive role of blue light emitting diodes

The present study explored the possible preventive effects of blue light emitting diodes (LEDs) on cadmium (Cd)-induced oxidative stress and immunotoxicity in zebrafish. To this end, zebrafish were exposed to a white fluorescent bulb or blue LEDs (LDB, peak at 450nm, at an irradiance of 0.9W/m2), and 0 or 30µgL-1 waterborne Cd for 5 weeks. Growth performance, survival rate, and hepatic histology, ultrastructure, antioxidant and innate immune responses were determined in zebrafish. Cd exposure alone reduced growth and survival rate, and induced oxidative damage and changes in histology and ultrastructure. However, Cd exposure in combination with LDB apparently relieved these negative effects. The alleviation of adverse effects might result from the up-regulation of antioxidant and innate immune genes at transcriptional, translational, or post-translational levels. Cd exposure alone dramatically enhanced mRNA levels of nuclear transcription factor κB (NF-κB) and E2-related factor (Nrf2). However, compared to Cd exposure alone, Cd exposure in combination with LDB apparently down-regulated both genes. Taken together, our results suggest that chronic Cd exposure induced a negative effect on zebrafish, possibly involved in NF-κB-induced immunotoxicity and Nrf2-induced oxidative stress. Finally, for the first time, our data demonstrated that LDB could protect fish against Cd toxicity.

Circadian time-dependent antioxidant and inflammatory responses to acute cadmium exposure in the brain of zebrafish

Up to date, little information is available on effects of circadian rhythm on metal-induced toxicity in fish. In this study, zebrafish were acutely exposed to 0.97mgL-1 cadmium for 12h either at ZT0 (the light intensity began to reached maximum) or at ZT12 (light intensity began to reached minimum) to evaluate the temporal sensitivity of oxidative stress and inflammatory responses in the brain of zebrafish. Profiles of responses of some genes at mRNA, protein and activity levels were different between ZT0 and ZT12 in the normal water. Exposure to Cd induced contrary antioxidant responses and similar inflammatory responses between ZT0 and ZT12. However, the number of inflammatory genes which were up-regulated was significantly greater at ZT12 than at ZT0. And, the up-regulated inflammatory genes were more responsive at ZT12 than at ZT0. At ZT12, antioxidant genes were down-regulated at mRNA, protein and activity levels. Contrarily, antioxidant genes were not affected at mRNA levels but activated at the protein and/or activity levels at ZT0. Reactive oxygen species (ROS) sharply increased and remained relatively stable when fish were exposed to Cd at ZT12 and ZT0, respectively. Positive correlations between ROS levels and mRNA levels of nuclear transcription factor κB (NF-κB) and between mRNA levels of NF-κB and its target genes were observed, suggesting that ROS may play an essential role in regulating the magnitude of inflammatory responses. Taken together, oxidative stress and immunotoxicity in the brain were more serious when fish were exposed to Cd in the evening than in the morning, highlighting the importance of circadian rhythm in Cd-induced neurotoxicity in fish.

Characterisation and expression analysis of two terminal complement components: C7 and C9 from large yellow croaker, Larimichthys crocea.

The large yellow croaker Larimichthys crocea, as one of the most economically important marine fish in China and East Asian countries, are facing the fatal attraction of various pathogens in recent years. Elucidation of the organism immunomodulatory mechanism of croaker response to pathogen infection is essential for the disease control. In present study, we reported for the first time the molecular characterization and expression analysis of two terminal complement components (TCCs) of croaker, Lc-C7 and Lc-C9. These two structural conserved TCCs were detected in many tissues in adult healthy fish, with highest levels detected in liver. The transcriptional expression analysis of Lc-C7 and Lc-C9 at different developmental stages showed a continuous increase towards hatch, however the two TCCs mRNA were not detected at the unfertilized stage, hinting the origination of these two TCCs after fertilization. Rapid and drastic responses to Vibrio alginolyticus challenge were observed for Lc-C7 and Lc-C9, suggesting the involvement of component C7 and C9 in innate immune responses to pathogenic invasion in teleost fish. These findings could deepen our understanding about immunomodulatory mechanisms of croaker and shed a new light to the role of component system in teleostean immunomodulation.

Changes in hemolymph characteristics of ark shell Scapharaca broughtonii dealt with Vibrio anguillarum challenge in vivo and various of anticoagulants in vitro

Abstract The ark shell Scapharca broughtonii is a commercially important shellfish in China. Alservers solution (AS), modified Alservers solution (MAS) and Heparin sodium solution (HSS) are common anticoagulants used for shellfish blood. To observe the immune response mediated by its hemocytes, we challenged in vivo S. broughtonii hemolymph with Vibrio anguillarum and dealt with the following three anticoagulants in vitro: Alservers solution (AS), modified Alservers solution (MAS) and Heparin sodium solution (HSS). The methodologies we used were immunostimulation with V. anguillarum, Wright‐Giemsa staining, micro‐examination, and flow cytometric and hydrolyzing enzyme activity analysis. The results showed that all three types of anticoagulants effectively prevented blood clotting in ark shellfish. The morphology of hemocytes did not significantly change 30 h after anticoagulant treatment, except for the shrinking of hemocytes after administering HSS. The size and permeability of hemocytes changed when treated with the anticoagulants and when stimulated with V. anguillarum. Both alkaline phosphatase (AKP) and acid phosphatase (ACP) in hemocytes and Plasma were measured at different times after they were stimulated with V. anguillarum in HSS and MAS. The AKP enzymatic activity in HSS was somewhat higher than in the MAS anticoagulant, but changes in response to V. anguillarum challenge of enzymatic activity were almost the same in HSS and MAS groups. In conclusion, all three types of anticoagulants may be used for ark shell blood preservation. They all changed the cell‐surface characteristics of hemocytes to inhibit clot formation. The AS anticoagulant was appropriate for maintaining white and red cell shapes, while MAS was ideal for retaining throbus cell function. Lastly, HSS was appropriate for maintaining enzymatic activity in hemolymph and function of hemocytes. Following this investigation, we gained insight into the changes in hemolymph characteristic during immune response. HighlightsWe studied Changes in hemolymph characteristics of shellfish hemolymph challenged with Vibrio anguillarum under various anticoagulants.All three types of anticoagulants may be used for ark shell blood preservation.The size and permeability of hemocytes changed when treated with the anticoagulants.Thrombus cells of S. brouthtonii may change in various anticoagulants solutions.

Preheating mitigates cadmium toxicity in zebrafish livers: Evidence from promoter demethylation, gene transcription to biochemical levels

The working hypothesis for this study was that moderate heat stress would alleviate the deleterious effects of subsequent cadmium (Cd) exposure on fish. Thus, zebrafish (Danio rerio) were subjected to water maintained at 26°C and 34°C for 4days, and then exposed to 0 or 200μg/L Cd for 1 week at 26°C. Multiple indicators were measured from livers of zebrafish at different levels, including DNA, RNA, protein and enzymatic activity associated with oxidative stress, inflammation and metal transport. The ameliorative effect of preheatinging on Cd toxicity was demonstrated. In the Cd-exposed groups, preheating decreased mortality and lipid peroxidation, increased activity levels of catalase (CAT) and copper/zinc-superoxide dismutase (Cu/Zn-SOD), and up-regulated mRNA levels of heat shock protein 70 (HSP70) and heat shock factor 2 (HSF2). Preheating also mitigated Cd-induced increases in protein and mRNA levels of metallothioneins (MTs), and mRNA levels of several inflammation-related genes. Furthermore, preheating alone dramatically up-regulated mRNA levels of genes related to antioxidant and immune defenses, zinc and copper transporters, protein folding, and reduced methylation levels in the HSF binding motif of the HSP70 promoter. Overall, preheating-induced accumulation of transcripts via demethylation might support the rapid defense responses at post-transcriptional levels caused by subsequent Cd exposure, indicating an adaptive mechanism for organisms exposed to one mild stressor followed by another.

Molecular cloning, expression analysis and cellular localization of an LFRFamide gene in the cuttlefish Sepiella japonica.

Neuropeptides are important regulators of physiological processes in metazoans, such as feeding, reproduction, and heart activities. In this study, an LFRFamide gene was identified from the cuttlefish Sepiella japonica (designated as SjLFRFamide). The full-length sequence of SjLFRFamide cDNA has 841bp, and the open reading frame contains 567bp encoding 188 amino acids, which shared high similarity with precursor SOFaRP2 from Sepia officinalis. The deduced SjLFRFamdie precursor protein contains a signal peptide and four different FLPs (FMRFamide-like peptides): one pentapeptide (TIFRFamide), two hexapeptides (NSLFRFamide and GNLFRFamide) and one heptapeptide (PHTPFRFamide). Multiple sequence alignment showed that SjLFRFamide contains rather conserved mature peptides, which all ended in FRF. The phylogenetic analysis suggests that SjLFRFamide belongs to the LFRFamide subfamily. The tissue distribution analysis through quantitative real-time PCR method showed that SjLFRFamide mRNA is significantly expressed in the brain, and slight trace are detected in female nidamental gland and accessory nidamental gland. In situ hybridization assay of the brain indicated that SjLFRFamide is transcribed in several different functional lobes, suggesting SjLFRFamide might associate with multiple physiological regulations, such as feeding, chromatophore regulation and reproduction. This is the first study describing LFRFamide in S. japonica, which might have great importance for cuttlefish artificial breeding.

Complete mitochondrial genome of the spineless cuttlefish Sepiella inermis (Sepioidea, Sepiidae)

Abstract In this study, we determined the complete mitochondrial genome of the spineless cuttlefish Sepiella inermis. The genome was 16,191 bp in length and contained 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes, and 2 main non-coding regions [both are control regions (CR)]. The composition and order of genes, for the mitogenome found in S. inermis were similar to most other invertebrates. The overall base composition of S. inermis is T 35.6%, C 16.4%, A 40.0% and G 8.0%, with a highly A + T bias of 75.6%. Two control regions contain both termination-associated sequences and conserved sequence blocks. Thus, mitogenome sequence data would play an important role in the investigation of phylogenetic relationship, taxonomic resolution and phylogeography of the Sepiidae.

Identification and functional characterisation of 5-HT4 receptor in sea cucumber Apostichopus japonicus (Selenka)

Serotonin (5-HT) is an important neurotransmitter and neuromodulator that controls a variety of sensory and motor functions through 5-HT receptors (5-HTRs). The 5-HT4R subfamily is linked to Gs proteins, which activate adenylyl cyclases (ACs), and is involved in many responses in peripheral organs. In this study, the 5-HT4R from Apostichopus japonicus (Aj5-HT4R) was identified and characterised. The cloned full-length Aj5-HT4R cDNA is 1,544 bp long and contains an open reading frame 1,011 bp in length encoding 336 amino acid proteins. Bioinformatics analysis of the Aj5-HT4R protein indicated this receptor was a member of class A G protein coupled receptor (GPCR) family. Further experiments using Aj5-HT4R-transfected HEK293 cells demonstrated that treatment with 5-HT triggered a significant increase in intracellular cAMP level in a dose-dependent manner and induced a rapid internalisation of Aj5-HT4R fused with enhanced green fluorescent protein (Aj5-HT4R-EGFP) from the cell surface into the cytoplasm. In addition, the transcriptional profiles of Aj5-HT4R in aestivating A. japonicas and phosphofructokinase (AjPFK) in 5-HT administrated A. japonicus have been analysed by real-time PCR assays. Results have led to a basic understanding of Aj5-HT4R in A. japonicus, and provide a foundation for further exploration of the cell signaling and regulatory functions of this receptor.

Complete mitochondrial genome of the needle cuttlefish Sepia aculeata (Sepioidea, Sepiidae)

Abstract In this study, we determined the complete mitochondrial genome of the needle cuttlefish Sepia aculeata. The genome was 16,219 bp in length and contained 13 protein-coding genes, 22 transfer RNA genes, 2 ribosomal RNA genes and 2 main non-coding regions [both are control regions (CR)]. The composition and order of genes, for the mitogenome found in S. aculeate, were similar to most other invertebrates. The overall base composition of S. aculeata is T 34.0%, C 17.0%, A 40.5% and G 8.5%, with a highly A + T bias of 74.5%. Two control regions (CR) both contain termination-associated sequences and conserved sequence blocks. This mitogenome sequence data would play an important role in the investigation of phylogenetic relationship, taxonomic resolution and phylogeography of the Sepiidae.