Diverse immune functions of hemocyanins

Drosophila immune cells transport oxygen through PPO2 protein phase transition

Insect respiration has long been thought to be solely dependent on an elaborate tracheal system without assistance from the circulatory system or immune cells1,2. Here we describe that Drosophila crystal cells-myeloid-like immune cells called haemocytes-control respiration by oxygenating Prophenoloxidase 2 (PPO2) proteins. Crystal cells direct the movement of haemocytes between the trachea of the larval body wall and the circulation to collect oxygen. Aided by copper and a neutral pH, oxygen is trapped in the crystalline structures of PPO2 in crystal cells. Conversely, PPO2 crystals can be dissolved when carbonic anhydrase lowers the intracellular pH and then reassembled into crystals in cellulo by adhering to the trachea. Physiologically, larvae lacking crystal cells or PPO2, or those expressing a copper-binding mutant of PPO2, display hypoxic responses under normoxic conditions and are susceptible to hypoxia. These hypoxic phenotypes can be rescued by hyperoxia, expression of arthropod haemocyanin or prevention of larval burrowing activity to expose their respiratory organs. Thus, we propose that insect immune cells collaborate with the tracheal system to reserve and transport oxygen through the phase transition of PPO2 crystals, facilitating internal oxygen homeostasis in a process that is comparable to vertebrate respiration.

Antibacterial Properties of Peptide and Protein Fractions from Cornu aspersum Mucus

The discovery and investigation of new natural compounds with antimicrobial activity are new potential strategies to reduce the spread of antimicrobial resistance. The presented study reveals, for the first time, the promising antibacterial potential of two fractions from Cornu aspersum mucus with an MW < 20 kDa and an MW > 20 kDa against five bacterial pathogens-Bacillus cereus 1085, Propionibacterium acnes 1897, Salmonella enterica 8691, Enterococcus faecalis 3915, and Enterococcus faecium 8754. Using de novo sequencing, 16 novel peptides with potential antibacterial activity were identified in a fraction with an MW < 20 kDa. Some bioactive compounds in a mucus fraction with an MW > 20 kDa were determined via a proteomic analysis on 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and bioinformatics. High homology with proteins and glycoproteins was found, with potential antibacterial activity in mucus proteins named aspernin, hemocyanins, H-lectins, and L-amino acid oxidase-like protein, as well as mucins (mucin-5AC, mucin-5B, mucin-2, and mucin-17). We hypothesize that the synergy between the bioactive components determined in the composition of the fraction > 20 kDa are responsible for the high antibacterial activity against the tested pathogens in concentrations between 32 and 128 µg/mL, which is comparable to vancomycin, but without cytotoxic effects on model eukaryotic cells of Saccharomyces cerevisiae. Additionally, a positive effect, by reducing the levels of intracellular oxidative damage and increasing antioxidant capacity, on S. cerevisiae cells was found for both mucus extract fractions of C. aspersum. These findings may serve as a basis for further studies to develop a new antibacterial agent preventing the development of antibiotic resistance.

A comprehensive review on hemocyanin from marine products: Structure, functions, its implications for the food industry and beyond

Hemocyanin, an oxygen-transport protein, is widely distributed in the hemolymph of marine arthropods and mollusks, playing an important role in their physiological processes. Recently, hemocyanin has been recognized as a multifunctional glycoprotein involved in the immunological responses of aquatic invertebrates. Consequently, the link between hemocyanin functions and their potential applications has garnered increased attention. This review offers an integrated overview of hemocyanin's structure, physicochemical characteristics, and bioactivities to further promote the utilization of hemocyanin derived from marine products. Specifically, we review its implication in two aspects of food and aquaculture industries: quality and health. Hemocyanin's inducible phenoloxidase activity is thought to be an inducer of melanosis in crustaceans. New anti-melanosis agents targeted to hemocyanin need to be explored. The red-color change observed in shrimp shells is related to hemocyanin, affecting consumer preferences. Hemocyanin's adaptive modification in response to the aquatic environment is available as a biomarker. Additionally, hemocyanin is endowed with bioactivities encompassing anti-microbial, antiviral, and therapeutic activities. Hemocyanin is also a novel allergen and its allergenic features remain incompletely characterized.

Immunotherapeutic Potential of Mollusk Hemocyanins in Murine Model of Melanoma

The development of antitumor drugs and therapy requires new approaches and molecules, and products of natural origin provide intriguing alternatives for antitumor research. Gastropodan hemocyanins-multimeric copper-containing glycoproteins have been used in therapeutic vaccines and antitumor agents in many cancer models.

MATERIALS AND METHODS

We established a murine model of melanoma by challenging C57BL/6 mice with a B16F10 cell line for solid tumor formation in experimental animals. The anticancer properties of hemocyanins isolated from the marine snail Rapana thomasiana (RtH) and the terrestrial snail Helix aspersa (HaH) were evaluated in this melanoma model using various schemes of therapy. Flow cytometry, ELISA, proliferation, and cytotoxicity assays, as well as histology investigations, were also performed.

RESULTS

Beneficial effects on tumor growth, tumor incidence, and survival of tumor-bearing C57BL/6 mice after administration of the RtH or HaH were observed. The generation of high titers of melanoma-specific IgM antibodies, pro-inflammatory cytokines, and tumor-specific CTLs, and high levels of tumor-infiltrated M1 macrophages enhanced the immune reaction and tumor suppression.

DISCUSSION

Both RtH and HaH exhibited promising properties for applications as antitumor therapeutic agents and future experiments with humans.

Comparative Transcriptome Analysis of the Hepatopancreas from Macrobrachium rosenbergii Exposed to the Heavy Metal Copper

The contamination of aquatic ecosystems by the heavy metal copper (Cu) is an important environmental issue and poses significant risks to the physiological functions of aquatic organisms. Macrobrachium rosenbergii is one of the most important freshwater-cultured prawns in the world. The hepatopancreas of crustaceans is a key organ for immune defense, heavy metal accumulation, and detoxification, playing a pivotal role in toxicological research. However, research on the molecular response of the hepatopancreas in M. rosenbergii to Cu exposure is still lacking. In this study, the transcriptomic response in the hepatopancreas of M. rosenbergii was studied after Cu exposure for 3 and 48 h. Compared with the control group, 11,164 (7288 up-regulated and 3876 down-regulated genes) and 10,937 (6630 up-regulated and 4307 down-regulated genes) differentially expressed genes (DEGs) were identified after 3 and 48 h exposure, respectively. Most of these DEGs were up-regulated, implying that gene expressions were largely induced by Cu. Functional enrichment analysis of these DEGs revealed that immunity, copper homeostasis, detoxification, DNA damage repair, and apoptosis were differentially regulated by Cu. Seven genes involved in immunity, detoxification, and metabolism were selected for validation by qRT-PCR, and the results confirmed the reliability of RNA-Seq. All these findings suggest that M. rosenbergii attempts to resist the toxicity of Cu by up-regulating the expression of genes related to immunity, metabolism, and detoxification. However, with the excessive accumulation of reactive oxygen species (ROS), the antioxidant enzyme system was destroyed. As a result, DNA damage repair and the cellular stress response were inhibited, thereby exacerbating cell damage. In order to maintain the normal function of the hepatopancreas, M. rosenbergii removes damaged cells by activating the apoptosis mechanism. Our study not only facilitates an understanding of the molecular response mechanisms of M. rosenbergii underlying Cu toxicity effects but also helps us to identify potential biomarkers associated with the stress response in other crustaceans.

Characterization of a pseudohemocyanin gene (PtPhc1) and its immunity function in response to Vibrio parahaemolyticus infection in the swimming crab Portunus trituberculatus

Pseudohemocyanin is a member of the hemocyanin superfamily, but little research is available on its function in immunology. In this study, a Portunus trituberculatus pseudohemocyanin gene, named PtPhc1, was obtained by gene cloning. The PtPhc1 cDNA was 2312 bp in length, encoding 684 amino acids while exhibiting a characteristic hemocyanin structural domain. Tissue expression analysis revealed ubiquitous expression of PtPhc1 across all tissues, with the highest level of expression observed in the hepatopancreas. The expression pattern of PtPhc1 in response to Vibrio parahaemolyticus infection was clarified using RT-qPCR in swimming crabs. Notably, the expression peaked at 24 h, and increased 1435-fold compared to the control group in the hepatopancreas. While the expression level reached the maximum value at 72 h, which was 3.24 times higher than that of the control group in hemocytes. Remarkably, the reduction in PtPhc1 expression led to a noteworthy 30% increase in the mortality rate of P. trituberculatus when exposed to V. parahaemolyticus. In addition, in vitro bacterial inhibition assays exhibited a dose-dependent suppression of bacterial proliferation by recombinant PtPhc1 protein, with a notable inhibition rate of 48.33% against V. parahaemolyticus at a concentration of 0.03 mg/mL. To the best of our knowledge, the results establish the function of pseudohaemocyanin in immunity for the first time, contributing to a deeper comprehension of innate immune regulatory mechanisms in aquatic organisms and advancing strategies for disease-resistant breeding.

The Yin Yang 1 of Penaeus vannamei regulates transcription of the small subunit hemocyanin gene during Vibrio parahaemolyticus infection

Hemocyanin is a respiratory protein, it is also a multifunctional immune molecule that plays a vital role against pathogen invasion in shrimp. However, the regulation of hemocyanin gene expression in shrimp hemocytes and the mechanisms involved during pathogen infection remains unclear. Here, we used DNA pull-down followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify the Yin Yang 1 transcription factor homolog in Penaeus vannamei (PvYY1) as a key factor that modulates transcription of the small subunit hemocyanin gene of P. vannamei (PvHMCs) in hemocytes during Vibrio parahaemolyticus AHPND (VPAHPND) infection. Bioinformatics analysis revealed that the core promoter region of PvHMCs contains two YY1 motifs. Mutational and oligoprecipitation analyses confirmed that PvYY1 could bind to the YY1 motifs in the PvHMCs core promoter region, while truncation of PvYY1 revealed that the N-terminal domain of PvYY1 is essential for the transactivation of PvHMCs core promoter. Besides, the REPO domain of PvYY1 could repress the activity of the PvHMCs core promoter. Overexpression of PvYY1 significantly activates the promoter activity of PvHMCs core promoter, while PvYY1 knockdown significantly decreases the expression level of PvHMCs in shrimp hemocytes and survival rate of shrimp upon infection with VPAHPND. Our present study provides new insights into the transcriptional regulation of PvHMCs by PvYY1 in shrimp hemocytes during bacteria (VPAHPND) infection.

Abalone peptide increases stress resilience and cost-free longevity via SKN-1-governed transcriptional metabolic reprogramming in C. elegans

A major goal of healthy aging is to prevent declining resilience and increasing frailty, which are associated with many chronic diseases and deterioration of stress response. Here, we propose a loss-or-gain survival model, represented by the ratio of cumulative stress span to life span, to quantify stress resilience at organismal level. As a proof of concept, this is demonstrated by reduced survival resilience in Caenorhabditis elegans exposed to exogenous oxidative stress induced by paraquat or with endogenous proteotoxic stress caused by polyglutamine or amyloid-β aggregation. Based on this, we reveal that a hidden peptide ("cryptide")-AbaPep#07 (SETYELRK)-derived from abalone hemocyanin not only enhances survival resilience against paraquat-induced oxidative stress but also rescues proteotoxicity-mediated behavioral deficits in C. elegans, indicating its capacity against stress and neurodegeneration. Interestingly, AbaPep#07 is also found to increase cost-free longevity and age-related physical fitness in nematodes. We then demonstrate that AbaPep#07 can promote nuclear localization of SKN-1/Nrf, but not DAF-16/FOXO, transcription factor. In contrast to its effects in wild-type nematodes, AbaPep#07 cannot increase oxidative stress survival and physical motility in loss-of-function skn-1 mutant, suggesting an SKN-1/Nrf-dependent fashion of these effects. Further investigation reveals that AbaPep#07 can induce transcriptional activation of immune defense, lipid metabolism, and metabolic detoxification pathways, including many SKN-1/Nrf target genes. Together, our findings demonstrate that AbaPep#07 is able to boost stress resilience and reduce behavioral frailty via SKN-1/Nrf-governed transcriptional reprogramming, and provide an insight into the health-promoting potential of antioxidant cryptides as geroprotectors in aging and associated conditions.

Extracellular vesicle signatures and protein citrullination are modified in shore crabs (Carcinus maenas) infected with Hematodinium sp

Epizootiologists recurrently encounter symbionts and pathobionts in the haemolymph (blood equivalent) of shellfish. One such group is the dinoflagellate genus Hematodinium, which contains several species that cause debilitating disease in decapod crustaceans. The shore crab Carcinus maenas acts as a mobile reservoir of microparasites, including Hematodinium sp., thereby posing a risk to other co-located commercially important species, e.g. velvet crabs (Necora puber). Despite the widespread prevalence and documented seasonality of Hematodinium infection dynamics, there is a knowledge gap regarding host-pathogen antibiosis, namely, how Hematodinium avoids the host's immune defences. Herein, we interrogated the haemolymph of Hematodinium-positive and Hematodinium-negative crabs for extracellular vesicle (EV) profiles (a proxy for cellular communication), alongside proteomic signatures for post-translational citrullination/deimination performed by arginine deiminases, which can infer a pathologic state. Circulating EV numbers in parasitized crab haemolymph were reduced significantly, accompanied by smaller EV modal size profiles (albeit non-significantly) when compared to Hematodinium-negative controls. Differences were observed for citrullinated/deiminated target proteins in the haemolymph between the parasitized and control crabs, with fewer hits identified overall in the former. Three deiminated proteins specific to parasitized crab haemolymph were actin, Down syndrome cell adhesion molecule (DSCAM), and nitric oxide synthase - factors that contribute to innate immunity. We report, for the first time, Hematodinium sp. could interfere with EV biogenesis, and that protein deimination is a putative mechanism of immune-modulation in crustacean-Hematodinium interactions.

Assessment of Bacillus subtilis fermented Caulerpa microphysa byproduct as feed additive on the growth performance, immune regulation and disease resistance of white shrimp (Litopenaeus vannamei)

In this study, the immunomodulatory and antioxidant activity of fermented Caulerpa microphysa byproduct (FCMB) by Bacillus subtilis was evaluated, and its potential as a feed additive for white shrimp (Litopenaeus vannamei) was explored. In vitro experiments showed that the FCMB supernatant contained polysaccharides, polyphenols and flavonoids, and exhibited antioxidant properties as assessed by various antioxidant assays. Additionally, the FCMB supernatant was found to increase the production rate of reactive oxygen species and the activity of phenoloxidase in hemocytes in vitro. Furthermore, the results of the in vivo feeding trial showed that dietary 5 g kg-1 FCMB significantly improved the weight gain and specific growth rate of white shrimp after 56 days of feeding. Although there were no significant differences in total hemocyte count, phagocytosis, superoxide anion production rate, and phenoloxidase activity among the experimental groups, upregulation of immune-related genes was observed, particularly in the hepatopancreas and hemocytes of shrimps fed with 5 g or 50 g FCMB per kg feed, respectively. In the pathogen challenge assay, white shrimp fed with 5 % FCMB exhibited a higher survival rate compared to the control group following Vibrio parahaemolyticus challenge. Therefore, it is concluded that the fermented byproduct of C. microphysa, FCMB, holds potential as a feed additive for enhancing the growth performance and disease resistance against V. parahaemolyticus in white shrimp.

Quantification of proteomic profile changes in the hemolymph of crayfish during in vitro coagulation

Hemolymph is the circulatory fluid that fills the body cavity of crustaceans, analogous to blood in vertebrates. Hemolymph coagulation, similar to blood clotting in vertebrates, plays a crucial role in wound healing and innate immune responses. Despite extensive studies on the clotting process in crustaceans, no comparative quantitative analysis of the protein composition of non-clotted and clotted hemolymph in any decapod has been reported. In this study, we used label-free protein quantification with high-resolution mass spectrometry to identify the proteomic profile of hemolymph in crayfish and quantify significant changes in protein abundances between non-clotted and clotted hemolymph. Our analysis identified a total of two-hundred and nineteen proteins in both hemolymph groups. Furthermore, we discussed the potential functions of the top most high and low-abundant proteins in hemolymph proteomic profile. The quantity of most of the proteins was not significantly changed during coagulation between non-clotted and clotted hemolymph, which may indicate that clotting proteins are likely pre-synthesized, allowing for a swift coagulation response to injury. Four proteins still showed abundance differences (p < 0.05, fold change>2), including C-type lectin domain-containing proteins, Laminin A chain, Tropomyosin, and Reverse transcriptase domain-containing proteins. While the first three proteins were down-regulated, the last one was up-regulated. The down-regulation of structural and cytoskeletal proteins may affect the process of hemocyte degranulation needed for coagulation, while the up-regulation of an immune-related protein might be attributed to the phagocytosis ability of viable hemocytes during coagulation.

Proteomics of the haemolymph of the terrestrial crustacean Porcellio scaber reveals components of its innate immunity under baseline conditions

The terrestrial crustacean Porcellio scaber is an established test organism in environmental research. We analysed the haemolymph proteome of P. scaber using a classical proteomic approach based on one-dimensional gel electrophoresis and tandem mass spectrometry. Using a publicly available protein database and our P. scaber transcriptome data, we have identified 76 proteins involved in cytoskeleton formation, protein degradation, vesicular transport, genetic information processing, detoxification, carbohydrate and lipid metabolism reflecting haemocyte metabolic activity, active intracellular transport, and intercellular communication. Compared with the data reported for other crustaceans, 28 of these P. scaber proteins have been linked to its immunity, among them hemocyanin, α-2-macroglobulin, phenoloxidase 3, superoxide dismutase, glutathione S-transferase, haemolymph clottable protein, and histones H4 and H2B. Our results thus provide a firm base for studying the innate immune response of P. scaber at the level of the haemolymph proteome. This knowledge is of particular importance in ecotoxicity studies with various environmental stressors where understanding physiological changes is important to reveal possible modes of action.

Exploring the Antimicrobial Potential and Biofilm Inhibitory Properties of Hemocyanin from Hemifusus pugilinus (Born, 1778)

The seafood industry plays a huge role in the blue economy, exploiting the advantage of the enriched protein content of marine organisms such as shrimps and molluscs, which are cultured in aquafarms. Diseases greatly affect these aquatic organisms in culture and, hence, there is need to study, in detail, their innate immune mechanisms. Hemocyanin is a non-specific innate defense molecule present in the blood cells of several invertebrates, especially molluscs, arthropods, and annelids. It is concerned with oxygen transport, blood clotting, and immune enhancement. In the present study, this macromolecular metalloprotein was isolated from the hemolymph of the marine snail Hemifusus pugilinus (Born, 1778) using Sephadex G-100 gel filtration column chromatography. It occurred as a single band (MW 80 kDa) on SDS-PAGE. High-performance liquid chromatography (HPLC) of the purified hemocyanin showed a single peak with a retention time of 4.3 min. The secondary structure and stability of the protein were detected using circular dichroism (CD), and the spectra demonstrated negative ellipticity bands close to 208 nm and 225 nm, indicating β-sheets. Further exploration of the purified hemocyanin revealed remarkable antimicrobial and antibiofilm activities against Gram-positive (Enterococcus faecalis and Staphylococcus aureus) and Gram-negative bacteria (Pseudomonas aeruginosa and Proteus vulgaris) at a concentration of 1-5 μg/mL. Spectrophotometric and in situ microscopic analyses (CLSM) unveiled the potential of the purified hemocyanin to inhibit biofilm formation in these bacteria with a minimal inhibitory concentration of 40 μg/mL. Furthermore, H. pugilinus hemocyanin (10 μg/mL concentration) displayed antifungal activity against Aspergillus niger. The purified hemocyanin was also assessed for cytotoxicity against human cancer cells using cell viability assays. Altogether, the present study shows that molluscan hemocyanin is a potential antimicrobial, antibiofilm, antifungal, anticancer, and immunomodulatory agent, with great scope for application in the enhancement of the immune system of molluscs, thereby facilitating their aquaculture.

Clodronate Liposome-Mediated Phagocytic Hemocyte Depletion Affects the Regeneration of the Cephalic Tentacle of the Invasive Snail, Pomacea canaliculata

After amputation, granular hemocytes infiltrate the blastema of regenerating cephalic tentacles of the freshwater snail Pomacea canaliculata. Here, the circulating phagocytic hemocytes were chemically depleted by injecting the snails with clodronate liposomes, and the effects on the cephalic tentacle regeneration onset and on Pc-Hemocyanin, Pc-transglutaminase (Pc-TG) and Pc-Allograft Inflammatory Factor-1 (Pc-AIF-1) gene expressions were investigated. Flow cytometry analysis demonstrated that clodronate liposomes targeted large circulating hemocytes, resulting in a transient decrease in their number. Corresponding with the phagocyte depletion, tentacle regeneration onset was halted, and it resumed at the expected pace when clodronate liposome effects were no longer visible. In addition to the regeneration progress, the expressions of Pc-Hemocyanin, Pc-TG, and Pc-AIF-1, which are markers of hemocyte-mediated functions like oxygen transport and immunity, clotting, and inflammation, were modified. After the injection of clodronate liposomes, a specific computer-assisted image analysis protocol still evidenced the presence of granular hemocytes in the tentacle blastema. This is consistent with reports indicating the large and agranular hemocyte population as the most represented among the professional phagocytes of P. canaliculata and with the hypothesis that different hemocyte morphologies could exert diverse biological functions, as it has been observed in other invertebrates.

Assessment of the In Vitro and In Vivo Antitumor Activity of Hemocyanins from Helix aspersa, Helix lucorum, and Rapana venosa in a Graffi Myeloid Tumor Model

Hemocyanins are oxygen-transporting glycoproteins in the hemolymph of some invertebrate species that attracted scientific interest as potential anticancer agents. The present study aims to assess the in vitro and in vivo anticancer activity of hemocyanins isolated from Helix aspersa, Helix lucorum, and Rapana venosa in the Graffi myeloid tumor model. The in vitro antitumor activity of the hemocyanins was determined by a MTT test and cytomorphological analysis by fluorescent and transmission electron microscopy. The in vivo effects of the hemocyanins were examined in hamsters transplanted with Graffi tumor. The serum antibody titers against the tested hemocyanins and tumor antigen were determined by ELISA. Histopathological assessment of the morphological features related to antitumor effect, immune system response, and toxicity in some internal organs was performed. The results of in vitro studies indicated that the tested hemocyanins induced significant antiproliferative and apoptogenic effects. The in vivo investigations demonstrated a protective antitumor effect, expressed in reduced transplantability, suppression of tumor growth and metastasis, reduced mortality, prolonged survival time, and absence of toxic side effects. The present study indicated that the antitumor activity of the studied hemocyanins was due to both immune stimulation and direct effects on the tumor cells, and they displayed their potential as therapeutic agents against hematological malignances.

Changes in Gene Expression of Whiteflies, Bemisia tabaci MED Feeding on Tomato Plants Infected by One of the Criniviruses, Tomato Chlorosis Virus through Transcriptome Analysis

Tomato chlorosis virus (ToCV), transmitted by the whitefly, Bemisia tabaci (Gennadius; Hemiptera: Aleyrodidae) has been continuously emerging on tomato plants and causing a significant economic loss throughout China. In the current study, RNA-Seq analysis was used to explore the gene expression profiles of B. tabaci Mediterranean (MED) that fed on both ToCV-infected and -uninfected tomato plants for 6, 12, 24, and 48 hours, respectively. The results revealed that dynamic changes occurred in the gene expressions of whiteflies at different time intervals after they acquired the virus. A total of 1709, 461, 4548, and 1748 differentially expressed genes (DEGs) were identified after a 6, 12, 24, and 48 hours feeding interval for the viral acquisition, respectively. The least number of expressed genes appeared in whiteflies with the 12 hours feeding treatment, and the largest numbers of those found in those with 24 hours feeding treatment. Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed that B. tabaci MED responded to ToCV acquisition through altering its nerve system development, fertility, detoxification, glucose metabolism, and immune function before it lost its ability to transmit the virus. The number of DEGs, degree of differential gene expressions, expression level of the same gene, involved biological processes, and metabolic functions in whiteflies post the 12 hours feeding, and viral acquisition were different from those from other three feeding treatments, which could be a significant finding suggesting an effective control of B. tabaci MED should be done less than 12 hours after whiteflies started feeding on ToCV-infected tomatoes. Our results further provided a clarified understanding in how B. tabaci was protected from viral acquisitions through comparison of the differential profile of gene expressions in whiteflies feeding on plants that were infected by semipersistent viruses.

Identification of Multiple Iron Uptake Mechanisms in Enterococcus faecalis and Their Relationship to Virulence

Among the unfavorable conditions bacteria encounter within the host is restricted access to essential trace metals such as iron. To overcome iron deficiency, bacteria deploy multiple strategies to scavenge iron from host tissues, with abundant examples of iron acquisition systems being implicated in bacterial pathogenesis. Yet the mechanisms utilized by the major nosocomial pathogen Enterococcus faecalis to maintain intracellular iron balance are poorly understood. In this study, we conducted a systematic investigation to identify and characterize the iron acquisition mechanisms of E. faecalis and to determine their contribution to virulence. Bioinformatic analysis and literature surveys revealed that E. faecalis possesses three conserved iron uptake systems. Through transcriptomics, we discovered two novel ABC-type transporters that mediate iron uptake. While inactivation of a single transporter had minimal impact on the ability of E. faecalis to maintain iron homeostasis, inactivation of all five systems (Δ5Fe strain) disrupted intracellular iron homeostasis and considerably impaired cell growth under iron deficiency. Virulence of the Δ5Fe strain was generally impaired in different animal models but showed niche-specific variations in mouse models, leading us to suspect that heme can serve as an iron source to E. faecalis during mammalian infections. Indeed, heme supplementation restored growth of Δ5Fe under iron depletion and virulence in an invertebrate infection model. This study revealed that the collective contribution of five iron transporters promotes E. faecalis virulence and that the ability to acquire and utilize heme as an iron source is critical to the systemic dissemination of E. faecalis.

Insights into Common Octopus (Octopus vulgaris) Ink Proteome and Bioactive Peptides Using Proteomic Approaches

The common octopus (Octopus vulgaris) is nowadays the most demanded cephalopod species for human consumption. This species was also postulated for aquaculture diversification to supply its increasing demand in the market worldwide, which only relies on continuously declining field captures. In addition, they serve as model species for biomedical and behavioral studies. Body parts of marine species are usually removed before reaching the final consumer as by-products in order to improve preservation, reduce shipping weight, and increase product quality. These by-products have recently attracted increasing attention due to the discovery of several relevant bioactive compounds. Particularly, the common octopus ink has been described as having antimicrobial and antioxidant properties, among others. In this study, the advanced proteomics discipline was applied to generate a common octopus reference proteome to screen potential bioactive peptides from fishing discards and by-products such as ink. A shotgun proteomics approach by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) using an Orbitrap Elite instrument was used to create a reference dataset from octopus ink. A total of 1432 different peptides belonging to 361 non-redundant annotated proteins were identified. The final proteome compilation was investigated by integrated in silico studies, including gene ontology (GO) term enrichment, pathways, and network studies. Different immune functioning proteins involved in the innate immune system, such as ferritin, catalase, proteasome, Cu/Zn superoxide dismutase, calreticulin, disulfide isomerase, heat shock protein, etc., were found in ink protein networks. Additionally, the potential of bioactive peptides from octopus ink was addressed. These bioactive peptides can exert beneficial health properties such as antimicrobial, antioxidant, antihypertensive, and antitumoral properties and are therefore considered lead compounds for developing pharmacological, functional foods or nutraceuticals.

Purification and characterization of a hemocyanin with lectin-like activity isolated from the hemolymph of speckled shrimp, Metapenaeusmonoceros

Lectins or agglutinins are mainly proteins or glycoproteins, reported to uphold an ability to agglutinate the red blood cells (RBCs) with a known sugar specificity in a diverse group of organisms. In the present study, we purified a hemocyanin (named as MmHc) from a shrimp, Metapenaeus monoceros by size-exclusion chromatography. Further characterization revealed that the purified MmHc showed hemagglutination activity that was found to be specifically inhibited by Lewis B and Lewis Y tetrasaccharides. The MmHc displayed two oligomers of molecular weight approximately ∼78 and ∼85 kDa in SDS-PAGE. The native molecular mass of MmHc was found to be ∼457 kDa as determined by size-exclusion chromatography which indicated that the purified MmHc is an oligomeric protein. MmHc showed a maximum activity within pH 7.0-8.0, while a wide range of temperature stability was observed between 4 to 55 °C, however, it did not show any dependency on metal ions for binding. Subsequently, the analysis of the peptides by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) identified the purified MmHc as shrimp hemocyanin showing significant similarity to the hemocyanin of Penaeus vannamei. The results of multiple sequence alignment and detailed analysis of the molecular interactions predicted by AutoDock suggested that besides the oxygen carrier function, this MmHc may have multiple roles and can interact well with the Lewis Y antigen through a typical sugar binding motif containing the similar hydrophilic amino acids as the conserved residues.

Cloning, identification, and functional characterization of novel prophenoloxidases (ShproPO) from the freshwater crab Sinopotamon henanense in response to cadmium exposure and Aeromonas hydrophila infection

Prophenoloxidase (proPO) is essential in the prophenoloxidase-activating system (proPO-AS) which is important for defense against foreign infection in crustaceans. However, most studies have focused on expression in the presence of a single pathogenic bacterium, and very few have addressed the presence of environmental contaminants simultaneously, such as cadmium (Cd) and Aeromonas hydrophila. Our study aimed to investigate the function of proPO in the freshwater crab Sinopotamon henanense and the changes in its expression by Cd and infection of A. hydrophila. A novel proPO from the hemocytes of S. henanense (ShproPO) was found in this research, the full-length cDNA of ShproPO was 2620 bp of encoding a protein of 678 amino acids containing three typical hemocyanin domains. The ShproPO protein could be found in both the granular (GHc) and the semi-granular hemocytes (SGHc). The ShproPO mRNA was found to be abundantly expressed in hemocytes and could be influenced by A. hydrophila infection. These results indicate that ShproPO could be involved in the antibacterial process. Further research found that low concentrations of Cd could promote its expression after infection with A. hydrophila. Therefore, it was hypothesized that Cd disrupted the response of crabs to A. hydrophila infection. Subsequently, PO enzyme activity was found to be significantly reduced through in vivo RNA interference with ShproPO, and the results suggested that ShproPO is likely to be a key enzyme in the melanization response. Finally, ShproPO was found to significantly enhance the phagocytosis of A. hydrophila-infected hemocytes by in vitro recombination, confirming that ShproPO is involved in hemocyte-mediated melanization and phagocytosis. Our findings reveal completely new insight into the immunotoxicity of Cd and the immune function of ShproPO in S. henanense.

Effects of chronic exposure to cadmium and copper on the proteome profile of hemolymph in false widow spider Steatoda grossa (Theridiidae)

The aim of this study was to evaluate the quantitative and qualitative changes in the proteome of the hemolymph of female Steatoda grossa spiders (Theridiidae) that were chronically exposed to cadmium and copper in food and were additionally immunostimulated (phorbol 12-myristate 13-acetate (PMA); bacterial suspensions: Staphylococcus aureus (G+), Pseudomonas fluorescens (G-). It was found that the expression of nearly 90 proteins was altered in cadmium-intoxicated spiders and more than 60 in copper-exposed individuals. Regardless of the type of metal used, these proteins were mainly overexpressed in the hemolymph of the exposed spiders. On the other hand, immunostimulation did not significantly change the number of proteins with altered expression in metal-intoxicated individuals. Hemocyanin (Hc) was found to be the most abundant of the proteins identified with altered expression. In copper-intoxicated spiders, immunostimulation increased the expression of A-, E-, F-, and G-chain-containing proteins, while in the case of cadmium-intoxicates spiders, it decreased the expression of E- and A-chain-containing Hc and increased the expression of G-chain-containing Hc. Regardless of the type of metal and immunostimulant used, there was an increase in the expression of actin. In addition, cadmium increased the expression of cullin, vimentin, and ceruloplasmin. The changes observed in the expression of hemolymph proteins indicate their protective function in S. grossa (Theridiidae) spiders under conditions of metal exposure.

Effects of dietary Ginkgo biloba leaf extract on growth performance, immunity and environmental stress tolerance of Penaeus vannamei

Ginkgo biloba leaf extract (GBE) has been extensively used in the treatment of diseases due to its anti-inflammatory, antioxidant, and immunomodulatory effects. In aquaculture, GBE is widely used as a feed additive, which is important to enhance the immunity of aquatic animals. The current study evaluated the effects of adding GBE to the diet of Penaeus vannamei (P. vannamei) under intensive aquaculture. The GBE0 (control group), GBE1, GBE2, and GBE4 groups were fed a commercial feed supplemented with 0.0, 1.0, 2.0, and 4.0 g/kg GBE for 21 days, respectively. The results showed that dietary GBE could alleviate hepatopancreas tissue damage and improve the survival rate of shrimp, and dietary 2 g/kg GBE could significantly increase the total hemocyte count (THC), the hemocyanin content, the antioxidant gene's expression, and the activity of their encoded enzymes in P. vannamei. Furthermore, transcriptome data revealed that immunity-related genes were upregulated in the GBE2 group compared with the GBE0 group after 21 days of culture. Drug metabolism-cytochrome P450, sphingolipid metabolism, linoleic acid metabolism, glycerolipid metabolism, fat digestion and protein digestion and absorption pathways were significantly enriched, according to KEGG results. Surprisingly, all of the above KEGG-enriched pathways were significantly upregulated. These findings demonstrated that supplementing P. vannamei with 2 g/kg GBE improved its environmental adaptability by improving immunity, lipid metabolism, and detoxification. In this study, a comprehensive evaluation of the effects of dietary GBE on the intensive aquaculture of P. vannamei was conducted to provide a reference for the healthy culture of P. vannamei.

Dietary supplementation of synbiotic Leuconostoc mesenteroide B4 and dextran improves immune regulation and disease resistance of Penaeus vannamei against Vibrio parahaemolyticus

White shrimp (Penaeus vannamei) is an important culture species in Taiwan but often encounters disease infection by Vibrio parahaemolyticus that cause acute hepatopancreatic necrosis disease (AHPND). This study investigates the effects of dietary supplementation of Leuconostoc mesenteroide B4 and its fermentate (dextran) on the immune response, intestinal morphology, disease resistance, and immune-related gene expression in white shrimp. In comparison to the control group, the shrimp fed with a diet containing B4+dextran (10⁷ CFU B4/g feed and 0.05% dextran) for 14, 28, 42 and 56 days had a significantly higher feed efficiency, weight gain and specific growth rate. A significantly higher villus height in the intestine and higher survival rate after challenging with V. parahaemolyticus was recorded for the B4+dextran group. Flow cytometry analysis demonstrated that the group that had ingested B4+dextran had a higher total hemocyte count and a higher proportion of semi-granulocytes, but a lower percentage of granulocytes compared to the control group. The shotgun metagenomic results in the midgut revealed that Leuco. mesenteroides was barely found in the midgut of the shrimp, suggesting that this microbe and its transient presence in the midgut is not the direct mechanism underlying the improved shrimp growth in the treated sample. Instead, dextran, a key ingredient in the B4 fermentate, on the dynamic of the microbial populations in shrimp, possibly promoting the diversity of gut microbes, especially the beneficial microbes, and thereby rendering protection against AHPND. In terms of comparing the gene expression between the control and synbiotic groups, pre- and post-bacterial challenge, a higher expression level of immune genes was mostly found in the B4+dextran group after challenging it with V. parahaemolyticus (group B4+dextran-VP) in the hepatopancreas and hemocyte. In contrast, the transcript level of immune-related genes was found to be higher in the B4+dextran group than other combinations in the midgut. Taken together, this study found that dietary addition of synbiotic Leuco. mesenteroides B4 and dextran can improve the growth performance, intestinal morphology and microbiome, regulation of immune genes and disease resistance against V. parahaemolyticus infection in white shrimp.

Immunological and biochemical changes in Pacific white shrimp, Litopenaeus vannamei, challenged with Vibrioparahaemolyticus

Vibrio parahaemolyticus (Vpara) is the causative agent of Acute Hepatopancreatic Necrosis Disease (AHPND), or Early Mortality Syndrome (EMS) in shrimp. Shrimp, like other invertebrates, lack an adaptive immune system and depend solely on innate immunity against invading pathogens. To better understand the defense mechanisms of shrimp to this problematic pathogen, we evaluated the changes in hematology, immunology and biochemical values of the hemolymph from shrimp challenged with V. parahaemolyticus up to 8 days post-challenge. Thirty-six shrimp (12 g) were distributed in 9 tanks (75 L), divided into three groups (non-challenged, challenged with 5 × 10² cfu/shrimp and challenged with 1 × 10³ cfu/shrimp) in triplicate. Pacific white shrimp, Litopenaeus vannamei, were administered an inoculum of V. parahaemolyticus under the shell between the 5th and 6th abdominal segment to assess cellular and humoral immune responses. Total hemocyte count (THC) significantly decreased in shrimp challenged with Vpara at 6 h, 12 h and 24 h-post infection. Hemocyte lysate phenoloxidase (PO) activity in Vpara-challenged shrimp at 48 h post challenge was significantly increased compared to that of control shrimp. No significant differences were observed in total plasma protein between plasma from control and Vpara-challenged shrimp. However, shrimp challenged with 5 × 10^2, and 1 × 10³ cfu/shrimp had significantly lower hemocyanin at 6 h and 48 h sampling point, respectively. At 24 h post-challenge, the ≥140 kDa and 70 kDa bands from SDS-PAGE of hemocyanin-concentrated hemolymph lysate samples showed a higher and lower intensity, respectively, in Vpara-challenged group than those of the control group. Plasma from Vpara-challenged shrimp at 6 h and 12 h-post infection significantly suppressed V. parahaemolyticus growth. However, significantly less bacterial growth suppression was observed in plasma of shrimp challenged with higher dose compared to control shrimp at the 192 h post-challenge point. Plasma chemistry parameters did not significantly differ among treatments. The changes observed in hemolymph parameters may be useful indicators of the health status of shrimp.

Comparative transcriptomics reveals the immune dynamics during the molting cycle of swimming crab Portunus trituberculatus

Molting is one of the most important biological processes of crustacean species, and a number of molecular mechanisms facilitate this complex procedure. However, the understanding of the immune mechanisms underlying crustacean molting cycle remains very limited. This study performed transcriptome sequencing in hemolymph and hepatopancreas of the swimming crab (Portunus trituberculatus) during the four molting stages: post-molt (AB), inter-molt (C), pre-molt (D), and ecdysis (E). The results showed that there were 78,572 unigenes that were obtained in the hemolymph and hepatopancreas of P. trituberculatus. Further analysis showed that 98 DEGs were involved in immunity response of hemolymph and hepatopancreas, and most of the DEGs participated in the process of signal transduction, pattern recognition proteins/receptors, and antioxidative enzymes system. Specifically, the key genes and pathway involved in signal transduction including the GPCR126, beta-integrin, integrin, three genes in mitogen-activated protein kinase (MAPK) signaling cascade (MAPKKK10, MAPKK4, and p38 MAPK), and four genes in Toll pathway (Toll-like receptor, cactus, pelle-like kinase, and NFIL3). For the pattern recognition proteins/receptors, the lowest expression level of 11 genes was found in the E stage, including C-type lectin receptor, C-type lectin domain family 6 member A and SRB3/C in the hemolymph, and hepatopancreatic lectin 4, C-type lectin, SRB, Down syndrome cell adhesion molecule homolog, Down syndrome cell adhesion molecule isoform, and A2M. Moreover, the expression level of copper/zinc superoxide dismutase isoform 4, glutathione peroxidase, glutathione S-transferase, peroxiredoxin, peroxiredoxin 6, and dual oxidase 2 in stage C or stage D significantly higher than that of stage E or stage AB. These results fill in the gap of the continuous transcriptional changes that are evident during the molting cycle of crab and further provided valuable information for elucidating the molecular mechanisms of immune regulation during the molting cycle of crab.

Immune Defense in Hypoxic Waters: Impacts of CO2 Acidification

AbstractPeriodic episodes of low oxygen (hypoxia) and elevated CO₂ (hypercapnia) accompanied by low pH occur naturally in estuarine environments. Under the influence of climate change, the geographic range and intensity of hypoxia and hypercapnic hypoxia are predicted to increase, potentially jeopardizing the survival of economically and ecologically important organisms that use estuaries as habitat and nursery grounds. In this review we synthesize data from published studies that evaluate the impact of hypoxia and hypercapnic hypoxia on the ability of crustaceans and bivalve molluscs to defend themselves against potential microbial pathogens. Available data indicate that hypoxia generally has suppressive effects on host immunity against bacterial pathogens as measured by in vitro and in vivo assays. Few studies have documented the effects of hypercapnic hypoxia on crustaceans or bivalve immune defense, with a range of outcomes suggesting that added CO₂ might have additive, negative, or no interactions with the effects of hypoxia alone. This synthesis points to the need for more partial pressure of O₂ × low pH factorial design experiments and recommends the development of new host∶pathogen challenge models incorporating natural transmission of a wide range of viruses, bacteria, and parasites, along with novel in vivo tracking systems that better quantify how pathogens interact with their hosts in real time under laboratory and field conditions.

Structure-Function Relationships of Oxygen Transport Proteins in Marine Invertebrates Enduring Higher Temperatures and Deoxygenation

AbstractPredictions for climate change-to lesser and greater extents-reveal a common scenario in which marine waters are characterized by a deadly trio of stressors: higher temperatures, lower oxygen levels, and acidification. Ectothermic taxa that inhabit coastal waters, such as shellfish, are vulnerable to rapid and prolonged environmental disturbances, such as heatwaves, pollution-induced eutrophication, and dysoxia. Oxygen transport capacity of the hemolymph (blood equivalent) is considered the proximal driver of thermotolerance and respiration in many invertebrates. Moreover, maintaining homeostasis under environmental duress is inextricably linked to the activities of the hemolymph-based oxygen transport or binding proteins. Several protein groups fulfill this role in marine invertebrates: copper-based extracellular hemocyanins, iron-based intracellular hemoglobins and hemerythrins, and giant extracellular hemoglobins. In this brief text, we revisit the distribution and multifunctional properties of oxygen transport proteins, notably hemocyanins, in the context of climate change, and the consequent physiological reprogramming of marine invertebrates.

Physiological and muscle tissue responses in Litopenaeus vannamei under hypoxic stress via iTRAQ

White L. vannamei have become the most widely cultivated shrimp species worldwide. Cultivation of L. vannamei is one of the predominant sectors in China’s aquaculture industry. This study focused on the physiological and biochemical responses, differential protein expression, and expression characteristics of the related crucial functional protein genes under low oxygen conditions among different strains of L. vannamei. It was found that 6 h of hypoxic stress caused a significant reduction in the total hemocyte number in both strains, while the hypoxia-sensitive strain showed a stronger reduction. In contrast, the hemocyanin concentration showed only an overall upward trend. Proteomic analysis of L. vannamei muscle tissue revealed 3,417 differential proteins after 12 h of hypoxic stress. Among them, 29 differentially expressed proteins were downregulated and 244 were upregulated in the hypoxia-sensitive strain. In contrast, there were only 10 differentially expressed proteins with a downregulation pattern and 25 with an upregulation pattern in the hypoxia-tolerant strain. Five protein genes that responded significantly to hypoxic stress were selected for quantitative real-time PCR analysis, namely, hemocyanin, chitinase, heat shock protein 90 (HSP 90), programmed death protein, and glycogen phosphorylase. The results showed that the gene expression patterns were consistent with proteomic experimental data except for death protein and glycogen phosphorylase. These results can enrich the general knowledge of hypoxic stress in L. vannamei and the information provided differentially expressed proteins which may be used to assist breeding programs of L. vannamei of new strains with tolerance to hypoxia.

Embryonic and post-embryonic development of the spider Polybetes pythagoricus (Sparassidae): A biochemical point of view

Analysis of energy expense during development has achieved special interest through time on account of the crucial role of the consumption of resources required for offspring survival. Spider eggs have a fixed composition as well as some initial energy that is supplied by mothers. These resources are necessary to support the metabolic expense not only through the embryonic period but also during the post-embryonic period, as well as for post emerging activities before spiderlings become self-sustaining. Depletion of these resources would be critical for spiders since it could give rise to prey competition as well as filial cannibalism. Even though spiders represent a megadiverse order, information regarding the metabolic requirements during spiders development is very scarce. In this study, we analyse the changes in protein, lipid and carbohydrate content as well as the variation in lipovitellin reserves and hemocyanin content during Polybetes pythagoricus development. Our results show that lipovitellins and phospholipids represent the major energy source throughout embryonic and post-embryonic development. Lipovitellin apolipoproteins are gradually consumed but are later depleted after dispersion. Phosphatidylethanolamine is mainly consumed during the post-embryonic period, while triacylglycerides are consumed after juveniles' dispersion. Finally, hemocyanin concentration starts to increase in postembryonic stages.

Deacetylation of K481 and K484 on Penaeid Shrimp Hemocyanin Is Critical for Antibacterial Activity

Although invertebrates' innate immunity relies on several immune-like molecules, the diversity of these molecules and their immune response mechanisms are not well understood. Here, we show that Penaeus vannamei hemocyanin (PvHMC) undergoes specific deacetylation under Vibrio parahaemolyticus and LPS challenge. In vitro deacetylation of PvHMC increases its binding capacity with LPS and antibacterial activity against Gram-negative bacteria. Lysine residues K481 and K484 on the Ig-like domain of PvHMC are the main acetylation sites modulated by the acetyltransferase TIP60 and deacetylase HDAC3. Deacetylation of PvHMC on K481 and K484 allows PvHMC to form a positively charged binding pocket that interacts directly with LPS, whereas acetylation abrogates the positive charge to decrease PvHMC-LPS attraction. Besides, V. parahaemolyticus and LPS challenge increases the expression of Pvhdac3 to induce PvHMC deacetylation. This work indicates that, during bacterial infections, deacetylation of hemocyanin is crucial for binding with LPS to clear Gram-negative bacteria in crustaceans.

Microplastics in decapod crustaceans: Accumulation, toxicity and impacts, a review

The presence of microplastics in the aquatic environment poses a serious threat not only to aquatic organisms but also to human beings that consume them. The uptake and effects of microplastics have been studied in almost all groups of aquatic organisms. This review details the different aspects of microplastics exposure in an ecologically and economically important group of crustaceans, the Decapods. A majority of Decapod crustaceans such as prawns, shrimp, crabs, lobsters and crayfish are consumed as seafood and play important roles in food chains and food webs. Numerous studies are available on the accumulation of microplastics in tissues such as the gills, hepatopancreas and gastrointestinal tract in these organisms. Experimental studies have also highlighted the toxic effects of microplastics such as oxidative stress, immunotoxicity and reproductive and developmental toxicity in them. This review also summarizes the ecological impacts and implications in human beings as well as lacunae with regard to microplastic uptake in Decapods.

Immune Response to Natural and Experimental Infection of Panulirus argus Virus 1 (PaV1) in Juveniles of Caribbean Spiny Lobster

Simple Summary

Experimental immunological challenges are widely used to corroborate the success of breeding programs for lines resistant to specific pathogens, to test the efficiency of new vaccines, and to improve immunity of cultured animals. The validation of experimental infection protocols is complex because it requires comparison with naturally infected organisms at different stages of the infection. The present study compares the immune response of lobsters under a natural process of viral infection (PaV1), versus the defense response of experimentally infected organisms. Innate immunity for infected lobsters was measured through cellular and plasmatic components. The results indicate that the immune response of organisms naturally or experimentally infected by PaV1 was similar, and provides the bases to corroborate that the immunological challenge was not exacerbated. Appropriate infection protocols can be useful for research aimed at increasing resistance to infectious diseases and reducing the use of antibiotics in aquaculture.

Abstract

Experimental infections have been used to better comprehend the immune system of organisms, and to probe for additives that generate greater resistance and help reduce antibiotic use in aquaculture. We compared the immune response of juveniles of the Caribbean spiny lobster, Panulirus argus, infected naturally with Panulirus argus virus 1 (PaV1) versus organisms infected experimentally, to determine the analogy between both infectious processes. The immunological response was measured by hemagglutination activity, hemocyte count, and total phenoloxidase activity in plasma and hemocytes in 211 individuals that were either naturally infected (110), or had been injected with viral inoculum and followed for six months (101). The samples were classified into the following four groups according to the severity of the infection: 0, uninfected; 1, lightly; 2, moderately; and 3, severely infected), which was determined on the basis of PCR and histological criteria. A permutational MANOVA showed that both the origin (natural and experimental), and the severity of the infection contributed significantly to explain the variation in the immune response of lobsters. The lack of significance of the interaction term indicated that the immunological response changed with the severity of the infection in a similar way, regardless of its origin. The results of the present study suggest that the experimental viral infection of PaV1 produces a defense response similar to the natural pathways of contagion, and provides the bases to validate an immunological challenge protocol for the first time in crustaceans. The discussion includes the perspective of the conceptual models of immune response within an ecological context.

Functional Characterization, Antimicrobial Effects, and Potential Antibacterial Mechanisms of NpHM4, a Derived Peptide of Nautilus pompilius Hemocyanin

Hemocyanins present in the hemolymph of invertebrates are multifunctional proteins that are responsible for oxygen transport and play crucial roles in the immune system. They have also been identified as a source of antimicrobial peptides during infection in mollusks. Hemocyanin has also been identified in the cephalopod ancestor Nautilus, but antimicrobial peptides derived from the hemocyanin of Nautilus pompilius have not been reported. Here, the bactericidal activity of six predicted peptides from N. pompilius hemocyanin and seven mutant peptides was analyzed. Among those peptides, a mutant peptide with 15 amino acids (1RVFAGFLRHGIKRSR15), NpHM4, showed relatively high antibacterial activity. NpHM4 was determined to have typical antimicrobial peptide characteristics, including a positive charge (+5.25) and a high hydrophobic residue ratio (40%), and it was predicted to form an alpha-helical structure. In addition, NpHM4 exhibited significant antibacterial activity against Gram-negative bacteria (MBC = 30 μM for Vibrio alginolyticus), with no cytotoxicity to mammalian cells even at a high concentration of 180 µM. Upon contact with V. alginolyticus cells, we confirmed that the bactericidal activity of NpHM4 was coupled with membrane permeabilization, which was further confirmed via ultrastructural images using a scanning electron microscope. Therefore, our study provides a rationalization for the development and optimization of antimicrobial peptide from the cephalopod ancestor Nautilus, paving the way for future novel AMP development with broad applications.

Copper‐Catalyzed Monooxygenation of Phenols: Evidence for a Mononuclear Reaction Mechanism

The Cu^I salts [Cu(CH₃CN)₄]PF and [Cu(oDFB)₂]PF with the very weakly coordinating anion Al(OC(CF₃)₃)₄⁻ (PF) as well as [Cu(NEt₃)₂]PF comprising the unique, linear bis‐triethylamine complex [Cu(NEt₃)₂]⁺ were synthesized and examined as catalysts for the conversion of monophenols to o‐quinones. The activities of these Cu^I salts towards monooxygenation of 2,4‐di‐tert‐butylphenol (DTBP‐H) were compared to those of [Cu(CH₃CN)₄]X salts with “classic” anions (BF₄⁻, OTf⁻, PF₆⁻), revealing an anion effect on the activity of the catalyst and a ligand effect on the reaction rate. The reaction is drastically accelerated by employing Cu^II‐semiquinone complexes as catalysts, indicating that formation of a Cu^II complex precedes the actual catalytic cycle. This result and other experimental observations show that with these systems the oxygenation of monophenols does not follow a dinuclear, but a mononuclear pathway analogous to that of topaquinone cofactor biosynthesis in amine oxidase.

Beneficial Effects of Snail Helix aspersa Extract in an Experimental Model of Alzheimer’s Type Dementia

Background: Alzheimer’s disease (AD) is a complex neurodegenerative disease with multifactorial etiology, unsatisfactory treatment, and a necessity for broad-spectrum active substances for cure. The mucus from Helix aspersa snail is a mixture of bioactive molecules with antimicrobial, anti-inflammatory, antioxidant, and anti-apoptotic effects. So far there are no data concerning the capacity of snail extract (SE) to affect neurodegenerative disorders. Objective: The effects of SE from Helix aspersa on learning and memory deficits in Alzheimer’s type dementia (ATD) induced by scopolamine (Sco) in male Wistar rats were examined and some mechanisms of action underlying these effects were evaluated. Methods: SE (0.5 mL/100 g) was applied orally through a food tube for 16 consecutive days: 5 days before and 11 days simultaneously with Sco (2 mg/kg, intraperitoneally). At the end of Sco treatment, using behavioral methods, we evaluated memory performance. Additionally, in cortex and hippocampus the acetylcholinesterase (AChE) activity, acetylcholine and monoamines (dopamine, noradrenaline, and serotonin) content, levels of main oxidative stress markers, and expression of brain-derived neurotrophic factor (BDNF) and cAMP response element-binding protein (CREB) were determined. Results: We demonstrated that, according to all behavioral tests used, SE significantly improved the cognitive deficits induced by Sco. Furthermore, SE possessed AChE inhibitory activity, moderate antioxidant properties and the ability to modulate monoamines content in two brain structures. Moreover, multiple SE applications not only restored the depressed by Sco expression of CREB and BDNF, but significantly upregulated it. Conclusion: Summarizing results, we conclude that complex mechanisms underlie the beneficial effects of SE on impaired memory in Alzheimer’s type dementia.

Molecular dating of the blood pigment hemocyanin provides new insight into the origin of animals

The Neoproterozoic included changes in oceanic redox conditions, the configuration of continents and climate, extreme ice ages (Sturtian and Marinoan), and the rise of complex life forms. A much-debated topic in geobiology concerns the influence of atmospheric oxygenation on Earth and the origin and diversification of animal lineages, with the most widely popularized hypotheses relying on causal links between oxygen levels and the rise of animals. The vast majority of extant animals use aerobic metabolism for growth and homeostasis; hence, the binding and transportation of oxygen represent a vital physiological task. Considering the blood pigment hemocyanin (Hc) is present in sponges and ctenophores, and likely to be present in the common ancestor of animals, we investigated the evolution and date of Hc emergence using bioinformatics approaches on both transcriptomic and genomic data. Bayesian molecular dating suggested that the ancestral animal Hc gene arose approximately 881 Ma during the Tonian Period (1000-720 Ma), prior to the extreme glaciation events of the Cryogenian Period (720-635 Ma). This result is corroborated by a recently discovered fossil of a putative sponge ~890 Ma and modern molecular dating for the origin of metazoans of ~1,000-650 Ma (but does contradict previous inferences regarding the origin of Hc ~700-600 Ma). Our data reveal that crown-group animals already possessed hemocyanin-like blood pigments, which may have enhanced the oxygen-carrying capacity of these animals in hypoxic environments at that time or acted in the transport of hormones, detoxification of heavy metals, and immunity pathways.

Effects of copper on non-specific immunity and antioxidant in the oriental river prawn (Macrobrachium nipponense)

The copper, as heavy metal has important impacts on the antioxidant and immune defense systems in aquatic organisms, and the toxic effects of copper can be accumulated and magnified with the food chain, thus posing a threat to food safety as well as ecosystems. This study explored the response of the antioxidant system and non-specific immunity in M. nipponense to copper stress. Low concentration of copper (0.05, 0.1 mg L^-1) had positive effects on the non-specific immunity in M. nipponense, while the non-specific immunity in M. nipponense could be affect negatively or even be inhibited by high copper concentration (0.15 mg L^-1). Even low concentrations of copper could cause oxidative stress, and high copper concentration (0.15 mg L^-1) could induce oxidative damage and even apoptosis, and thus causing damage to the antioxidant defense system in M. nipponense. Low concentration of copper could affect the gill and hepatopancreas structure in M. nipponense, but high level oxidative stress caused by high copper concentration could cause oxidative damage to these tissue, resulting in the destruction of gill and hepatopancreas. This study provides the safety concentration for using copper-containing fish drugs in the actual culture of M. nipponense and provides basic data for the toxicity mechanism of copper to M. nipponense.

Comprehensive Transcriptomic and Metabolomic Analysis of the Litopenaeus vannamei Hepatopancreas After WSSV Challenge

Litopenaeus vannamei is the major farmed shrimp species worldwide. White spot disease due to white spot syndrome virus (WSSV) is severely affecting shrimp worldwide, causing extensive economic losses in L. vannamei culture. This is the first study that applied combined transcriptomic and metabolomic analysis to study the effects on the L. vannamei hepatopancreas after WSSV challenge. Our transcriptomic data revealed differentially expressed genes (DEGs) associated with immunity, apoptosis, the cytoskeleton and the antioxidant system in the hepatopancreas of L. vannamei. Metabolomic results showed that WSSV disrupts metabolic processes including amino acid metabolism, lipid metabolism and nucleotide metabolism. After challenged by WSSV, immune-related DEGs and differential metabolites (DMs) were detected in the hepatopancreas of L. vannamei, indicating that WSSV may damage the immune system and cause metabolic disorder in the shrimp. In summary, these results provide new insights into the molecular mechanisms underlying L. vannamei's response to WSSV.

Cold acclimation increases Asian citrus psyllid Diaphorina citri (Hemiptera: Liviidae) survival during exposure to freezing temperatures

The Asian citrus psyllid, Diaphorina citri, is the vector of the pathogenic bacteria that causes Huanglongbing, the most devasting disease affecting citrus worldwide. As cultivation of citrus tends to expand northward, the tolerance of psyllids to freezing temperatures needs to be investigated. While mortality of D. citri to cold temperature has been previously studied, much less is known regarding the acclimation potential of psyllids to cold temperatures. We first evaluated cold resistance of D. citri depending on color morph and sex. Subsequently, we compared mortality of D. citri at -4 °C for 10 hours between unacclimated psyllids, psyllids that were gradually acclimated to cold over 1 or 2 weeks, and psyllids intermittently acclimated also for 1 or 2 weeks. We did not find major differences in cold resistance between color morphs and sex. We found that after 1 week of gradual acclimation, the survival of psyllids at -4 °C increased to 86%, compared to 20% in the control group. Survival did not increase after the second week of gradual acclimation. Although intermittent acclimation improved survival compared to the control group, it was less effective than gradual acclimation with a survival at 30% and 70% after 1 and 2 weeks of acclimation, respectively, although this difference with gradual acclimation was not significant at week 2. These data show that gradual cold acclimation allows D. citri to survive brief periods below freezing. It may serve as a mechanism responsible for increasing northern establishment of this pest.

Fipronil use and associated effects on hematological and biochemical parameters of blue land crab (Cardisoma guanhumi Latreille): Ecological implication

Fipronil is used to control pests to improve farm yield, however, indiscriminate use of fipronil has been reported to endanger crabs leading to their extinction. Therefore, this study investigated the impact of fipronil on several hematological and biochemical parameters of blue land crabs. We exposed blue land crabs to either fipronil or to a control treatment; fipronil reduced the protein content of the crab and also led to hematological and oxidative damages to the crabs' oxy-hemocyanin. Based on our results, there is need for guided use of agrochemicals such as fipronil to avoid/reduce their adverse effects on economically important species such as crabs.

The Role of Anti-Viral Effector Molecules in Mollusc Hemolymph

Molluscs are major contributors to the international and Australian aquaculture industries, however, their immune systems remain poorly understood due to limited access to draft genomes and evidence of divergences from model organisms. As invertebrates, molluscs lack adaptive immune systems or ‘memory’, and rely solely on innate immunity for antimicrobial defence. Hemolymph, the circulatory fluid of invertebrates, contains hemocytes which secrete effector molecules with immune regulatory functions. Interactions between mollusc effector molecules and bacterial and fungal pathogens have been well documented, however, there is limited knowledge of their roles against viruses, which cause high mortality and significant production losses in these species. Of the major effector molecules, only the direct acting protein dicer-2 and the antimicrobial peptides (AMPs) hemocyanin and myticin-C have shown antiviral activity. A better understanding of these effector molecules may allow for the manipulation of mollusc proteomes to enhance antiviral and overall antimicrobial defence to prevent future outbreaks and minimize economic outbreaks. Moreover, effector molecule research may yield the description and production of novel antimicrobial treatments for a broad host range of animal species.

LvHemB1, a novel cationic antimicrobial peptide derived from the hemocyanin of Litopenaeus vannamei, induces cancer cell death by targeting mitochondrial voltage-dependent anion channel 1

Current cancer treatment regimens such as chemotherapy and traditional chemical drugs have adverse side effects including the appearance of drug-resistant tumor cells. For these reasons, it is imperative to find novel therapeutic agents that overcome these factors. To this end, we explored a cationic antimicrobial peptide derived from Litopenaeus vannamei hemocyanin (designated LvHemB1) that induces cancer cell death, but sparing normal cells. LvHemB1 inhibits the proliferation of human cervical (HeLa), esophageal (EC109), hepatocellular (HepG2), and bladder (EJ) cancer cell lines, but had no significant effect on normal liver cell lines (T-antigen-immortalized human liver epithelial (THLE-3) cells). In addition to its antiproliferative effects, LvHemB1 induced apoptosis, by permeating cells and targeting mitochondrial voltage-dependent anion channel 1 (VDAC1). Colocalization studies revealed the localization of LvHemB1 in mitochondria, while molecular docking and pull-down analyses confirmed LvHemB1-VDAC1 interaction. Moreover, LvHemB1 causes loss in mitochondrial membrane potential and increases levels of reactive oxygen species (ROS) and apoptotic proteins (caspase-9, caspase-3, and Bax (Bcl-2-associated X)), which results in mitochondrial-mediated apoptosis. Thus, peptide LvHemB1 has the potential of being used as an anticancer agent due to its antiproliferation effect and targeting to VDAC1 to cause mitochondrial dysfunction in cancer cells, as well as its ability to induce apoptosis by increasing ROS levels, and the expression of proapoptotic proteins.

Determination of tyrosinase-cyanidin-3-O-glucoside and (-/+)-catechin binding modes reveal mechanistic differences in tyrosinase inhibition

Tyrosinase, exquisitely catalyzes the phenolic compounds into brown or black pigment, inhibition is used as a treatment for dermatological or neurodegenerative disorders. Natural products, such as cyanidin-3-O-glucoside and (-/+)-catechin, are considered safe and non-toxic food additives in tyrosinase inhibition but their ambiguous inhibitory mechanism against tyrosinase is still elusive. Thus, we presented the mechanistic insights into tyrosinase with cyanidin-3-O-glucoside and (-/+)-catechin using computational simulations and in vitro assessment. Initial molecular docking results predicted ideal docked poses (- 9.346 to - 5.795 kcal/mol) for tyrosinase with selected flavonoids. Furthermore, 100 ns molecular dynamics simulations and post-simulation analysis of docked poses established their stability and oxidation of flavonoids as substrate by tyrosinase. Particularly, metal chelation via catechol group linked with the free 3-OH group on the unconjugated dihydropyran heterocycle chain was elucidated to contribute to tyrosinase inhibition by (-/+)-catechin against cyanidin-3-O-glucoside. Also, predicted binding free energy using molecular mechanics/generalized Born surface area for each docked pose was consistent with in vitro enzyme inhibition for both mushroom and murine tyrosinases. Conclusively, (-/+)-catechin was observed for substantial tyrosinase inhibition and advocated for further investigation for drug development against tyrosinase-associated diseases.

Antibacterial, Antibiofilm and Anti-Virulence Activity of Biactive Fractions from Mucus Secretion of Giant African Snail Achatina fulica against Staphylococcus aureus Strains

Staphylococcus aureus is an important etiological agent that causes skin infections, and has the propensity to form biofilms, leading to significant mortality and morbidity in patients with wounds. Mucus secretion from the Giant African snail Achatina fulica is a potential source of biologically active substances that might be an important source for new drugs to treat resistant and biofilm-forming bacteria such as S. aureus. This study evaluated the effect of semi-purified fractions from the mucus secretion of A. fulica on the growth, biofilm formation and virulence factors of S. aureus. Two fractions: FMA30 (Mw >30 kDa) and FME30 (Mw 30−10 kDa) exhibited antimicrobial activity against S. aureus with a MIC₅₀ of 25 and 125 µg/mL, respectively. An inhibition of biofilm formation higher than 80% was observed at 9 µg/mL with FMA30 and 120 µg/mL with FME30. Furthermore, inhibition of hemolytic and protease activity was determined using a concentration of MIC₂₀, and FME30 showed a strong inhibitory effect in the formation of clots. We report for the first time the effect of semi-purified fractions of mucus secretion of A. fulica on biofilm formation and activity of virulence factors such as α-hemolysin, coagulase and proteases produced by S. aureus strains.

The Microbial Composition of Penaeid Shrimps' Hepatopancreas Is Modulated by Hemocyanin

Aquatic organisms have to produce proteins or factors that help maintain a stable relationship with microbiota and prevent colonization by pathogenic microorganisms. In crustaceans and other aquatic invertebrates, relatively few of these host factors have been characterized. In this study, we show that the respiratory glycoprotein hemocyanin is a crucial host factor that modulates microbial composition and diversity in the hepatopancreas of penaeid shrimp. Diseased penaeid shrimp (Penaeus vannamei), had an empty gastrointestinal tract with atrophied hepatopancreas, expressed low hemocyanin, and high total bacterial abundance, with Vibrio as the dominant bacteria. Similarly, shrimp depleted of hemocyanin had mitochondrial depolarization, increased reactive oxygen species (ROS) levels, and dysregulation of several energy metabolism-related genes. Hemocyanin silencing together with ROS scavenger (N-acetylcysteine) treatment improved microbial diversity and decreased Vibrio dominance in the hepatopancreas. However, fecal microbiota transplantation after hemocyanin knockdown could not restore the microbial composition in the hepatopancreas. Collectively, our data provide, to our knowledge, new insight into the pivotal role of hemocyanin in modulating microbial composition in penaeid shrimp hepatopancreas via its effect on mitochondrial integrity, energy metabolism, and ROS production.

A proteomics evaluation of the primary and secondary immune response of Biomphalaria straminea challenged by Schistosoma mansoni

Biomphalaria spp. snails are intermediary hosts of Schistosoma mansoni, etiologic agent of intestinal schistosomiasis, one of the most important neglected tropical diseases. Biomphalaria straminea is an important intermediary host that possess a different phenotype to parasite infection but shows a large geographic distribution and high capacity of new ecologic niche invasion. Our purpose was to characterize for the first time the differentially expressed proteome in B. straminea during two times intervals after primary and secondary exposure to S. mansoni. The hemolymph was collected at 1 and 15 days after primary and secondary exposure of snails to the parasite. Total proteins were extracted and digested with trypsin. LC-MS/MS label-free quantification was performed and analyzed using Maxquant and Perseus software. Proteins were identified and annotated using Blast2GO tools. After 1 day of exposure, most of upregulated proteins are hemoglobin type 2, C and H type lectins, molecules related to cell adhesion, and response to oxidative stress. After 15 days, we found a similar pattern of upregulated proteins but some fibrinogen-related proteins (FREPs) and TEPs homologs were downregulated. Regarding the differentially expressed proteins during secondary response, the principal immune-related proteins upregulated were C and H type lectins, cellular adhesion molecules, biomphalysin, and FREP3. We noted a several upregulated biological processes during both responses that could be the one of the key points of efficacy in the immune response to parasite. Our data suggests different immune mechanisms used by B. straminea snails challenged with S. mansoni.

Inter-Subunit Dynamics Controls Tunnel Formation During the Oxygenation Process in Hemocyanin Hexamers

Hemocyanin from horseshoe crab in its active form is a homo-hexameric protein. It exists in open and closed conformations when transitioning between deoxygenated and oxygenated states. Here, we present a detailed dynamic atomistic investigation of the oxygenated and deoxygenated states of the hexameric hemocyanin using explicit solvent molecular dynamics simulations. We focus on the variation in solvent cavities and the formation of tunnels in the two conformational states. By employing principal component analysis and CVAE-based deep learning, we are able to differentiate between the dynamics of the deoxy- and oxygenated states of hemocyanin. Finally, our results identify the deoxygenated open conformation, which adopts a stable, closed conformation after the oxygenation process.