Molecular cloning, characterization, and expression level analysis of a marine teleost homolog of catalase from big belly seahorse (Hippocampus abdominalis)

Antioxidant Defence in Labeo rohita to Biotic and Abiotic Stress: Insight from mRNA Expression, Molecular Characterization and Recombinant Protein-Based ELISA of Catalase, Glutathione Peroxidase, CuZn Superoxide Dismutase, and Glutathione S-Transferase

Fish possess numerous enzymatic antioxidant systems as part of their innate immunity. These systems have been poorly studied in Labeo rohita (rohu). The present study characterized and investigated the role of antioxidant genes in the defence mechanisms against two types of stressors, including infection and ammonia stress. Four key genes associated with antioxidant activity-catalase, glutathione peroxidase, glutathione S-transferase, and CuZn superoxide dismutase were successfully cloned and sequenced. These genes were found to be expressed in different tissues and developmental stages of rohu. The expression levels of these antioxidant genes in the liver and anterior kidney tissues of rohu juveniles were modulated in response to bacterial infection (Aeromonas hydrophila), parasite infection (Argulus siamensis), poly I:C stimulation and ammonia stress. Additionally, the recombinant proteins derived from these genes exhibited significant antioxidant and antibacterial activities. These proteins also demonstrated a protective effect against A. hydrophila infection in rohu and had an immunomodulatory role. Furthermore, indirect ELISA assay systems were developed to measure these protein levels in healthy as well as A. hydrophila and ammonia-induced rohu serum. Overall, this study characterized and emphasised the importance of the antioxidant mechanism in rohu's defence against oxidative damage and microbial diseases.

Multiple biomarkers response of Astyanax lacustris (Teleostei: Characidae) exposed to manganese and temperature increase

The present study aimed to evaluate the toxicity of Mn (6.65 mg/L) at different exposure times (96 h, 7, 14, and 21 days) and evaluate its possible toxic effects on the fish Astyanax lacustris through multi-biomarkers and the maximum critical temperature (CT Max). The results show an increase in the Mn accumulation (liver and gills) with increasing exposure time. The glutathione S-transferase (GST) activity showed differences in the group exposed to Mn for 96 h compared to the group exposed for 21 days. The acetylcholinesterase (AChE) activity increased in the fish exposed for 7 days compared to the control group. On the other hand, no genotoxic changes were observed. The CT Max showed that the loss of equilibrium of 50% of the fish occurs at a temperature of 39ºC, with and without the Mn presence. Furthermore, the catalase gene expression (oxidative stress) did not show alterations.

Molecular Cloning and Functional Characterization of Catalase in Stress Physiology, Innate Immunity, Testicular Development, Metamorphosis, and Cryopreserved Sperm of Pacific Abalone

Catalase is a crucial enzyme of the antioxidant defense system responsible for the maintenance of cellular redox homeostasis. The aim of the present study was to evaluate the molecular regulation of catalase (Hdh-CAT) in stress physiology, innate immunity, testicular development, metamorphosis, and cryopreserved sperm of Pacific abalone. Hdh-CAT gene was cloned from the digestive gland (DG) of Pacific abalone. The 2894 bp sequence of Hdh-CAT had an open reading frame of 1506 bp encoding 501 deduced amino acids. Fluorescence in situ hybridization confirmed Hdh-CAT localization in the digestive tubules of the DG. Hdh-CAT was induced by different types of stress including thermal stress, H₂O₂ induction, and starvation. Immune challenges with Vibrio, lipopolysaccharides, and polyinosinic-polycytidylic acid sodium salt also upregulated Hdh-CAT mRNA expression and catalase activity. Hdh-CAT responded to cadmium induced-toxicity by increasing mRNA expression and catalase activity. Elevated seasonal temperature also altered Hdh-CAT mRNA expression. Hdh-CAT mRNA expression was relatively higher at the trochophore larvae stage of metamorphosis. Cryopreserved sperm showed significantly lower Hdh-CAT mRNA expression levels compared with fresh sperm. Hdh-CAT mRNA expression showed a relationship with the production of ROS. These results suggest that Hdh-CAT might play a role in stress physiology, innate immunity, testicular development, metamorphosis, and sperm cryo-tolerance of Pacific abalone.

Insight into the molecular structure and function of peptidoglycan recognition protein SC2 (PGRP-SC2) from Amphiprion clarkii: Investigating the role in innate immunity

Peptidoglycan recognition proteins (PGRPs) belong to the pattern recognition receptor (PRR) family and are conserved from insects to mammals. PGRPs show specific binding abilities to peptidoglycans (PGNs) in various microbes. In this study, molecular and functional analyses of PGRP-SC2 from Amphiprion clarkii (AcPGRP-SC2) were conducted. The 492 bp ORF of AcPGRP-SC2 encoded a protein of 164 amino acids with a molecular weight of 17.58 kDa and pI of 8.9. The PGRP superfamily domain was identified from the protein sequence of AcPGRP-SC2 and sequence similarities were observed with homologous proteins. Quantitative polymerase chain reaction (qPCR) analysis revealed that AcPGRP-SC2 transcripts were ubiquitously expressed in all tested tissues, with high levels in the skin, and transcript expression was significantly modulated by immune stimulation with lipopolysaccharide (LPS), Polyinosinic:polycytidylic acid (poly I:C), and Vibrio harveyi post-immune challenge. Recombinant AcPGRP-SC2 with the maltose-binding protein fusion (rAcPGRP-SC2) was used to evaluate LPS-, PGN-, and bacterial-binding activities and to conduct bacterial agglutination assays, and the results demonstrated that AcPGRP-SC2 exhibited bacterial recognition, binding, and colonization abilities to a range of Gram-positive and Gram-negative bacterial strains. Moreover, rAcPGRP-SC2-pre-treated Fat Head Minnow (FHM) cells exhibited significant upregulation in NF-ĸB1, NF-ĸB2, and stat3 expression upon treatment with killed bacteria. Taken together, our findings suggest that AcPGRP-SC2 plays an important role in the immune response against microbial pathogens in A. clarkii.

Antioxidant Effects and Potential Molecular Mechanism of Action of Limonium aureum Extract Based on Systematic Network Pharmacology

Oxidative stress is the redox imbalance state of organisms that involves in a variety of biological processes of diseases. Limonium aureum (L.) Hill. is an excellent wild plant resource in northern China, which has potential application value for treating oxidative stress. However, there are few studies that focused on the antioxidant effect and related mechanism of L. aureum. Thus, the present study combining systematic network pharmacology and molecular biology aimed to investigate the antioxidant effects of L. aureum and explore its underlying anti-oxidation mechanisms. First, the antioxidant activity of L. aureum extracts was confirmed by in vitro and intracellular antioxidant assays. Then, a total of 11 bioactive compounds, 102 predicted targets, and 70 antioxidant-related targets were obtained from open source databases. For elucidating the molecular mechanisms of L. aureum, the PPI network and integrated visualization network based on bioinformatics assays were constructed to preliminarily understand the active compounds and related targets. The subsequent enrichment analysis results showed that L. aureum mainly affect the biological processes involving oxidation-reduction process, response to drug, etc., and the interference with these biological processes might be due to the simultaneous influence on multiple signaling pathways, including the HIF-1 and ERBB signaling pathways. Moreover, the mRNA levels of predicted hub genes were measured by qRT-PCR to verify the regulatory effect of L. aureum on them. Collectively, this finding lays a foundation for further elucidating the anti-oxidative damage mechanism of L. aureum and promotes the development of therapeutic drugs for oxidative stress.

Responses of Aquatic Nontarget Organisms in Experiments Simulating a Scenario of Contamination by Imidacloprid in a Freshwater Environment

Several studies have indicated the presence of the neonicotinoid insecticide imidacloprid (IMI) in aquatic ecosystems in concentrations up to 320.0 µg L^-1. In the present study, we evaluated the effects of the highest IMI concentration detected in surface water (320.0 µg L^-1) on the survival of Chironomus sancticaroli, Daphnia similis, and Danio rerio in three different scenarios of water contamination. The enzymatic activities of glutathione S-transferase (GST), catalase (CAT), and ascorbate peroxidase (APX) in D. rerio also were determined. For this evaluation, we have simulated a lotic environment using an indoor system of artificial channels developed for the present study. In this system, three scenarios of contamination by IMI (320.0 µg L^-1) were reproduced: one using reconstituted water (RW) and the other two using water samples collected in unpolluted (UW) and polluted (DW) areas of a river. The results indicated that the tested concentration was not able to cause mortality in D. similis and D. rerio in any proposed treatment (RW, UW, and DW). However, C. sancticaroli showed 100% of mortality in the presence of IMI in the three proposed treatments, demonstrating its potential to impact the community of aquatic nontarget insects negatively. Low IMI concentrations did not offer risks to D. rerio survival. However, we observed alterations in GST, CAT, and APX activities in treatments that used IMI and water with no evidence of pollution (i.e., RW and UW). These last results demonstrated that fish are more susceptible to the effects of IMI in unpolluted environments.

Molecular cloning, mRNA expression and functional characterization of a catalase from Chinese black sleeper (Bostrychus sinensis)

In this study, the catalase gene of Chinese black sleeper Bostrychus sinensis (termed as BsCat) was sequenced and characterized. The BsCat, which encodes 525 amino acids, contains a catalase proximal active site signature domain (⁶⁴FDRERIPERVVHAKGAG⁸⁰) and a catalase proximal heme-ligand signature domain (³⁵⁴RLFAYPDTH³⁶²). The BsCat exhibits high sequence similarity with Cat of other species. Phylogenetic tree reconstruction revealed a close evolutionary relationship of BsCat to catalase genes of other fishes. The results of Real-time PCR showed that the BsCat gene was constitutively expressed in most organs of B. sinensis, with predominant expression detected in liver, followed by peripheral blood and spleen. Moreover, the BsCat gene was significantly changed after either poly (I:C) stimulation or Vibrio parahemolyticus infection in peripheral blood, head kidney, liver and spleen. The enzymatic activity of purified recombinant BsCat (rBsCat) was 2261 ± 96 U/mg. The rBsCat exhibits optimum enzymatic activity at 15 °C and pH 7.0. Our results suggested that the BsCat is involved in the antioxidant defense and host immune response of Chinese black sleeper during pathogen invasion.

Best practices for non-lethal blood sampling of fish via the caudal vasculature

Blood sampling through the caudal vasculature is a widely used technique in fish biology for investigating organismal health and physiology. In live fishes, it can provide a quick, easy and relatively non-invasive method for obtaining a blood sample (cf. cannulation and cardiac puncture). Here, a general set of recommendations are provided for optimizing the blood sampling protocol that reflects best practices in animal welfare and sample integrity. This includes selecting appropriate use of anaesthetics for blood sampling as well as restraint techniques for situations where sedation is not used. In addition, ideal sampling environments where the fish can freely ventilate and strategies for minimizing handling time are discussed. This study summarizes the techniques used for extracting blood from the caudal vasculature in live fishes, highlighting the phlebotomy itself, the timing of sampling events and acceptable blood sample volumes. This study further discuss considerations for selecting appropriate physiological metrics when sampling in the caudal region and the potential benefits that this technique provides with respect to long-term biological assessments. Although general guidelines for blood sampling are provided here, it should be recognized that contextual considerations (e.g., taxonomic diversity, legal matters, environmental constraints) may influence the approach to blood sampling. Overall, it can be concluded that when done properly, blood sampling live fishes through the caudal vasculature is quick, efficient and minimally invasive, thus promoting conditions where live release of focal animals is possible.

Molecular and functional insights into a novel teleost malectin from big-belly seahorse Hippocampus abdominalis

Malectin is a carbohydrate-binding lectin protein found in the endoplasmic reticulum (ER). It selectivity binds to Glc₂-N-glycan and is involved in a glycoprotein quality control mechanism. Even though malectin may play a role in immunity, its role in innate immunity is not fully known. In the present study, we identified and characterized the malectin gene from Hippocampus abdominalis (HaMLEC). We analyzed sequence features, spatial expression levels, temporal expression profiles upon immune responses, bacterial and carbohydrate binding abilities and anti-viral properties to investigate the potential role of HaMLEC in innate immunity. The molecular weight and isoelectric point (pI) were estimated to be 31.99 kDa and 5.17, respectively. The N-terminal signal peptide, malectin superfamily domain and C-terminal transmembrane region were identified from the amino acid sequence of HaMLEC. The close evolutionary relationship of HaMLEC with other teleosts was identified by phylogenetic analysis. According to quantitative PCR (qPCR) results, HaMLEC expression was observed in all the examined tissues and high expression was observed in the ovary and brain, compared to other tested tissues. Temporal expression of HaMLEC in liver and blood tissues were significant modulated upon exposure to immunogens Edwardasiella tarda, Streptococcus iniae, polyinosinic:polycytidylic and lipopolysaccharide. The presence of carbohydrate binding modules (CBMs) of bacterial glycosyl hydrolases were functionally confirmed by a bacterial binding assay. Anti-viral activity significantly reduced viral hemorrhagic septicemia virus (VHSV) replication in cells overexpressing HaMLEC. The observed results suggested that HaMLEC may have a significant role in innate immunity in Hippocampus abdominalis.