Norepinephrine regulates TNF expression via the A1AR-p38 MAPK-Relish pathway in granulocytes of oyster Crassostrea gigas

Norepinephrine (NE) is involved in regulating cytokine expression and phagocytosis of immune cells in the innate immunity of vertebrates. In the present study, the modulation mechanism of NE on the biosynthesis of TNFs in oyster granulocytes was explored. The transcripts of CgTNF-1, CgTNF-2 and CgTNF-3 were highly expressed in granulocytes, and they were significantly up-regulated after LPS stimulation, while down-regulated after NE treatment. The phagocytic rate and apoptosis index of oyster granulocytes were also triggered by LPS stimulation and suppressed by NE treatment. The mRNA expressions of CgMAPK14 and CgRelish were significantly induced after NE treatment, and the translocation of CgRelish from cytoplasm to nucleus was observed. The concentration of intracellular Ca2+ in granulocytes was significantly up-regulated upon NE incubation, and this trend reverted after the treatment with DOX (specific antagonist for NE receptor, CgA1AR-1). No obvious significance was observed in intracellular cAMP concentrations in the PBS, NE and NE + DOX groups. Once CgA1AR-1 was blocked by DOX, the mRNA expressions of CgMAPK14 and CgRelish were significantly inhibited, and the translocation of CgRelish from cytoplasm to nucleus was also dramatically suppressed, while the mRNA expression of CgTNF-1 and the apoptosis index increased significantly to the same level with those in LPS group, respectively. These results collectively suggested that NE modulated TNF expression in oyster granulocyte through A1AR-p38 MAPK-Relish signaling pathway.

Unravelling the main immune repertoire of Paracentrotus lividus following Vibrio anguillarum bath challenge

Paracentrotus lividus is the most abundant echinoid species in the North East Atlantic Ocean and Mediterranean Sea. Although there is abundant genomic information of the species, there is no deep characterisation of the genes involved in the immune response. Here, a reference transcriptome of male and female coelomocytes was produced. The generated P. lividus transcriptome assembly has 203,511 transcripts, N50 transcript length of 1079 bp, and more than 90% estimated gene completeness in Eukaryota and Metazoa BUSCO databases, respectively. Differential gene expression analyses showed 54 and 55 up-regulated genes in P. lividus female and male coelomocyte tissues, respectively. These results suggest a similar immune gene repertoire between sexes. To examine the immune response, P. lividus was challenged with Vibrio anguillarum, one of the candidate pathogens for bald disease. Immune parameters were evaluated at cell and humoral levels, as well as the expression analysis of immune related genes at an early response stage. No differences were found at cellular and humoral levels with the exception of the increase of nitric oxide in perivisceral fluid of challenged animals. At the gene expression level, a total of 2721 genes were upregulated in challenged animals, 13.6 times higher expression than control group. Our analysis revealed that four major KEGG pathways were enriched in challenged animals: Autophagy (KEGG:04140), Endocytosis (KEGG:04144), Phagosome (KEGG:04145) and Protein processing in endoplasmic reticulum (KEGG:04141). Several toll-like receptors (TLR), scavenger receptors cysteine-rich (SRCR) or nucleotide-binding oligomerisation domain like receptors (NLR) were identified as major family genes for pathogen recognition and immune defence. This study provides a valuable transcriptomic resource and unfolds the molecular basis of immune response to V. anguillarum exposure. Overall, our findings contribute to the conservation effort of the P. lividus populations, as well as its sustainable exploitation in an aquaculture context.

Investigating the internal system of defense of Gastropoda Aplysia depilans (Gmelin, 1791): Focus on hemocytes

The internal defense system of mollusks represents an efficient protection against pathogens and parasites, involving several biological immune processes, such as phagocytosis, encapsulation, cytotoxicity, and antigenic recognition of self/non-self. Mollusks possess professional, migratory, and circulating cells that play a key role in the defense of the organism, the hemocytes. Several studies have been performed on hemocytes from different mollusks, but, to date, these cells are still scarcely explored. Different hemocyte populations have been found, according to the presence or absence of granules, size, and the species of mollusks studied. Our study aims to deepen the knowledge of the hemocytes of the gastropod Aplysia depilans using morphological techniques and light and confocal microscopy, testing Toll-like receptor 2, inducible nitric oxide synthetase, and nicotinic acetylcholine receptor alpha 7 subunit. Our results show two hemocyte populations distinguishable by size, and presence/absence of granules in the cytoplasm, strongly positive for the antibodies tested, suggesting for the first time the presence of these receptors on the surface of sea hare hemocytes by immunohistochemistry. These data help in the understanding of the immune system of this gastropod, providing additional data for comprehending the evolution of the defense response in metazoan phylogenesis.

Role of the Neuroendocrine System of Marine Bivalves in Their Response to Hypoxia

Mollusks comprise one of the largest phylum of marine invertebrates. With their great diversity of species, various degrees of mobility, and specific behavioral strategies, they haveoccupied marine, freshwater, and terrestrial habitats and play key roles in many ecosystems. This success is explained by their exceptional ability to tolerate a wide range of environmental stresses, such as hypoxia. Most marine bivalvemollusksare exposed to frequent short-term variations in oxygen levels in their marine or estuarine habitats. This stressfactor has caused them to develop a wide variety of adaptive strategies during their evolution, enabling to mobilize rapidly a set of behavioral, physiological, biochemical, and molecular defenses that re-establishing oxygen homeostasis. The neuroendocrine system and its related signaling systems play crucial roles in the regulation of various physiological and behavioral processes in mollusks and, hence, can affect hypoxiatolerance. Little effort has been made to identify the neurotransmitters and genes involved in oxygen homeostasis regulation, and the molecular basis of the differences in the regulatory mechanisms of hypoxia resistance in hypoxia-tolerant and hypoxia-sensitive bivalve species. Here, we summarize current knowledge about the involvement of the neuroendocrine system in the hypoxia stress response, and the possible contributions of various signaling molecules to this process. We thusprovide a basis for understanding the molecular mechanisms underlying hypoxic stress in bivalves, also making comparisons with data from related studies on other species.

Apextrin from Ruditapes philippinarum functions as pattern recognition receptor and modulates NF-κB pathway

Apextrin belongs to ApeC-containing proteins (ACPs) and features a signal-peptide, an N-terminal membrane attack complex component/perforin (MACPF) domain, and a C-terminal ApeC domain. Recently, apextrin-like proteins were identified as pattern recognition receptor (PRR), which recognize the bacterial cell wall component and participate in innate immunity. Here, an apextrin (Rpape) was identified and characterized in Ruditapes philippinarum. Our results showed that Rpape mRNA was significantly induced under bacterial challenges. The Rpape recombinant protein exhibited a significant inhibitory effect on gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) and bound with Vibrio anguillarum, S. aureus and B. subtilis. We found Rpape protein positively activated the NF-κB signaling cascade and increased the activity of Nitric oxide (NO). This study revealed the immunity role of apextrin in R. philippinarum and provided a reference for further study on the role of apextrin in bivalves.

The potential role of eyestalk in the immunity of Litopenaeus vannamei to Vibrio parahaemolyticus infection II. From the perspective of long non-coding RNA

Long non-coding RNAs (lncRNAs) have been linked to immunological modulation. Unfortunately, little is known about the processes of immune control in shrimp. In crustaceans such as Litopenaeus vannamei, a prominent aquaculture species, the X-organ-sinus gland complex (XO-SG) in the eyestalk is an essential neuroendocrine regulatory organ. Eyestalk ablation is commonly employed in aquaculture to accelerate ovarian maturation in shrimp. It does, however, have a negative impact on the shrimps' immunocompetence and causes death. As a result, we used RNA-seq to profile the transcriptomes of L. vannamei hemocytes infected with Vibrio parahaemolyticus after the eyestalk ablation. Following strict transcript screening procedures, 2307 lncRNAs were identified from L. vannamei hemocytes in this study. Pearson correlation analysis was finally used to uncover 535 DElncRNAs and 1566 DEmRNA targets. According to the Venn diagram analysis, 326 non-eyestalk regulatory lncRNAs (NElncRNAs) with a target of 1014 non-eyestalk regulatory genes (NEmRNAs), 47 eyestalk negative regulatory lncRNAs (ENRlncRNAs) with a target of 95 eyestalk negative regulatory genes (ENRmRNAs), and 162 eyestalk positive regulatory lncRNAs (EPRlncRNAs) with a target of 457 eyestalk positive regulatory genes (EPRmRNAs) were screened. The bioinformatics analysis revealed that lncRNAs were associated with Axon regeneration, Rap1 signaling pathway, Thyroid hormone signaling pathway, TGF-beta signaling pathway, and PI3K-Akt signaling pathway, implying that lncRNAs may play a role in the regulation of the neuroendocrine-immune (NEI) system. Furthermore, several lncRNAs targeting HSP70, YWHAZ, FER2, HIF1α, and Notch were discovered and verified by qRT-PCR. These findings showed that regulation of lncRNAs in hemocytes which were controlled by the eyestalk might be one of the impact variables in controlling the differential expression of mRNAs associated with immune response in L. vannamei infected with V. parahaemolyticus.

The Complexity of Sesquiterpene Chemistry Dictates Its Pleiotropic Biologic Effects on Inflammation

Sesquiterpenes (SQs) are volatile compounds made by plants, insects, and marine organisms. SQ have a large range of biological properties and are potent inhibitors and modulators of inflammation, targeting specific components of the nuclear factor-kappaB (NF-κB) signaling pathway and nitric oxide (NO) generation. Because SQs can be isolated from over 1600 genera and 2500 species grown worldwide, they are an attractive source of phytochemical therapeutics. The chemical structure and biosynthesis of SQs is complex, and the SQ scaffold represents extraordinary structural variety consisting of both acyclic and cyclic (mono, bi, tri, and tetracyclic) compounds. These structures can be decorated with a diverse range of functional groups and substituents, generating many stereospecific configurations. In this review, the effect of SQs on inflammation will be discussed in the context of their complex chemistry. Because inflammation is a multifactorial process, we focus on specific aspects of inflammation: the inhibition of NF-kB signaling, disruption of NO production and modulation of dendritic cells, mast cells, and monocytes. Although the molecular targets of SQs are varied, we discuss how these pathways may mediate the effects of SQs on inflammation.

Effect of Air Exposure-Induced Hypoxia on Neurotransmitters and Neurotransmission Enzymes in Ganglia of the Scallop Azumapecten farreri

The nervous system expresses neuromolecules that play a crucial role in regulating physiological processes. Neuromolecule synthesis can be regulated by oxygen-dependent enzymes. Bivalves are a convenient model for studying air exposure-induced hypoxia. Here, we studied the effects of hypoxia on the expression and dynamics of neurotransmitters, and on neurotransmitter enzyme distribution, in the central nervous system (CNS) of the scallop Azumapecten farreri. We analyzed the expression of the neurotransmitters FMRFamide and serotonin (5-HT) and the choline acetyltransferase (CHAT) and universal NO-synthase (uNOS) enzymes during air exposure-induced hypoxia. We found that, in early-stage hypoxia, total serotonin content decreased in some CNS regions but increased in others. CHAT-lir cell numbers increased in all ganglia after hypoxia; CHAT probably appears de novo in accessory ganglia. Short-term hypoxia caused increased uNOS-lir cell numbers, while long-term exposure led to a reduction in their number. Thus, hypoxia weakly influences the number of FMRFamide-lir neurons in the visceral ganglion and does not affect peptide expression in the pedal ganglion. Ultimately, we found that the localization and level of synthesis of neuromolecules, and the numbers of cells expressing these molecules, vary in the scallop CNS during hypoxia exposure. This indicates their possible involvement in hypoxia resistance mechanisms.

The potential role of eyestalk in the immunity of Litopenaeus vannamei to Vibrio infection

The X-organ-sinus gland complex (XO-SG) in the eyestalk is an important neuroendocrine regulatory organ of crustaceans such as Litopenaeus vannamei, a prominent aquaculture species. The current study found significant changes in the enzyme activities of ALP, ACP, and T-SOD of hepatopancreatic in response to Vibrio parahaemolyticus exposure following eyestalk ablation, indicating that they were all involved in the immunological regulation of shrimps against V. parahaemolyticus infection. A total of 52,656 unigenes were obtained after RNA-Seq, with an average length of 1036 bp and an N50 of 1847 bp. Subsequently, 1899 eyestalk positive regulation genes (EPRGs), 745 eyestalk negative regulation genes (ENRGs), and 2077 non-eyestalk regulatory genes (NEGs) were identified. KEGG analysis of EPRGs revealed that eyestalk ablation might activate the neuroendocrine-immune (NEI) system. The RNA-Seq data were validated using quantitative real-time PCR (qRT-PCR). The findings suggested that eyestalk ablation might affect the expression of genes involved in the prophenoloxidase-activating system, the TLR signaling pathway, and numerous other immune-related genes in L. vannamei. All of these findings revealed that the eyestalk might have a role in the immune response of L. vannamei. The genes and pathways discovered in this study will help to elucidate the molecular mechanisms of hemocytes' immune response to V. parahaemolyticus following eyestalk ablation in shrimp, as well as provide the framework for building crustacean immunity theory.

The role of emerging micro-scale vegetables in human diet and health benefits-an updated review based on microgreens

Increasing public concern about health has prompted humans to find new sources of food. Microgreens are young and immature plants that have been recently introduced as a new category of vegetables, adapting their production at the micro-scale. In this paper, the chemical compositions including micro-nutrients and some typical phytochemicals of microgreens are summarized. Their edible safety and potential health benefits are also reviewed. Microgreens play an increasingly vital role in health-promoting diets. They are considered good sources of nutritional and bioactive compounds, and show potential in the prevention of malnutrition and chronic diseases. Some strategies in the pre- or post-harvest stages of microgreens can be further applied to obtain better nutritional, functional, and sensorial quality with freshness and extended shelf life. This review provides valuable nutrient data and health information for microgreens, laying a theoretical foundation for people to consume microgreens more wisely, and providing great value for the development of functional products with microgreens.

Bivalves are NO different: nitric oxide as negative regulator of metamorphosis in the Pacific oyster, Crassostrea gigas

BACKGROUND

Nitric oxide (NO) is presumed to be a regulator of metamorphosis in many invertebrate species, and although NO pathways have been comparatively well-investigated in gastropods, annelids and crustaceans, there has been very limited research on the effects of NO on metamorphosis in bivalve shellfish.

RESULTS

In this paper, we investigate the effects of NO pathway inhibitors and NO donors on metamorphosis induction in larvae of the Pacific oyster, Crassostrea gigas. The nitric oxides synthase (NOS) inhibitors s-methylisothiourea hemisulfate salt (SMIS), aminoguanidine hemisulfate salt (AGH) and 7-nitroindazole (7-NI) induced metamorphosis at 75, 76 and 83% respectively, and operating in a concentration-dependent manner. Additional induction of up to 54% resulted from exposures to 1H-[1,2,4]Oxadiazole[4,3-a]quinoxalin-1-one (ODQ), an inhibitor of soluble guanylyl cyclase, with which NO interacts to catalyse the synthesis of cyclic guanosine monophosphate (cGMP). Conversely, high concentrations of the NO donor sodium nitroprusside dihydrate in combination with metamorphosis inducers epinephrine, MK-801 or SMIS, significantly decreased metamorphosis, although a potential harmful effect of excessive NO unrelated to metamorphosis pathway cannot be excluded. Expression of CgNOS also decreased in larvae after metamorphosis regardless of the inducers used, but intensified again post-metamorphosis in spat. Fluorescent detection of NO in competent larvae with DAF-FM diacetate and localisation of the oyster nitric oxide synthase CgNOS expression by in-situ hybridisation showed that NO occurs primarily in two key larval structures, the velum and foot. cGMP was also detected in the foot using immunofluorescent assays, and is potentially involved in the foot's smooth muscle relaxation.

CONCLUSION

Together, these results suggest that the NO pathway acts as a negative regulator of metamorphosis in Pacific oyster larvae, and that NO reduction induces metamorphosis by inhibiting swimming or crawling behaviour, in conjunction with a cascade of additional neuroendocrine downstream responses.

Transcriptional changes of Pacific oyster Crassostrea gigas reveal essential role of calcium signal pathway in response to CO2-driven acidification

There is increasing evidence that ocean acidification (OA) has a significant impact on marine organisms. However, the ability of most marine organisms to acclimate to OA and the underlying mechanisms are still not well understood. In the present study, whole transcriptome analysis was performed to compare the impacts of short- (7 days, named as short group) and long- (60 days, named as long group) term CO₂ exposure (pH 7.50) on Pacific oyster Crassostrea gigas. The responses of C. gigas to short- and long-term CO₂ exposure shared common mechanisms in metabolism, membrane-associated transportation and binding processes. Long-term CO₂ exposure induced significant expression of genes involved in DNA or RNA binding, indicating the activated transcription after long-term CO₂ exposure. Oysters in the short-term group underwent significant intracellular calcium variation and oxidative stress. In contrast, the intracellular calcium, ROS level in hemocytes and H₂O₂ in serum recovered to normal levels after long-term CO₂ exposure, suggesting the compensation of physiological status and mutual interplay between calcium and oxidative level. The compensation was supported by the up-regulation of a series of calcium binding proteins (CBPs) and calmodulins (CaMs) related signal pathway. The results provided valuable information to understand the molecular mechanism underlying the responses of Pacific oyster to the acidified ocean and might have implications for predicting the possible effects of global climate changes on oyster aquaculture.

Caveolin1 Tyrosine-14 Phosphorylation: Role in Cellular Responsiveness to Mechanical Cues

The plasma membrane is a dynamic lipid bilayer that engages with the extracellular microenvironment and intracellular cytoskeleton. Caveolae are distinct plasma membrane invaginations lined by integral membrane proteins Caveolin1, 2, and 3. Caveolae formation and stability is further supported by additional proteins including Cavin1, EHD2, Pacsin2 and ROR1. The lipid composition of caveolar membranes, rich in cholesterol and phosphatidylserine, actively contributes to caveolae formation and function. Post-translational modifications of Cav1, including its phosphorylation of the tyrosine-14 residue (pY14Cav1) are vital to its function in and out of caveolae. Cells that experience significant mechanical stress are seen to have abundant caveolae. They play a vital role in regulating cellular signaling and endocytosis, which could further affect the abundance and distribution of caveolae at the PM, contributing to sensing and/or buffering mechanical stress. Changes in membrane tension in cells responding to multiple mechanical stimuli affects the organization and function of caveolae. These mechanical cues regulate pY14Cav1 levels and function in caveolae and focal adhesions. This review, along with looking at the mechanosensitive nature of caveolae, focuses on the role of pY14Cav1 in regulating cellular mechanotransduction.

In-Depth In Silico Search for Cuttlefish (Sepia officinalis) Antimicrobial Peptides Following Bacterial Challenge of Haemocytes

Cuttlefish (Sepia officinalis) haemocytes are potential sources of antimicrobial peptides (AMPs). To study the immune response to Vibrio splendidus and identify new AMPs, an original approach was developed based on a differential transcriptomic study and an in-depth in silico analysis using multiple tools. Two de novo transcriptomes were retrieved from cuttlefish haemocytes following challenge by V. splendidus or not. A first analysis of the annotated transcripts revealed the presence of Toll/NF-κB pathway members, including newly identified factors such as So-TLR-h, So-IKK-h and So-Rel/NF-κB-h. Out of the eight Toll/NF-κB pathway members, seven were found up-regulated following V. splendidus challenge. Besides, immune factors involved in the immune response were also identified and up-regulated. However, no AMP was identified based on annotation or conserved pattern searches. We therefore performed an in-depth in silico analysis of unannotated transcripts based on differential expression and sequence characteristics, using several tools available like PepTraq, a homemade software program. Finally, five AMP candidates were synthesized. Among them, NF19, AV19 and GK28 displayed antibacterial activity against Gram-negative bacteria. Each peptide had a different spectrum of activity, notably against Vibrio species. GK28—the most active peptide—was not haemolytic, whereas NF19 and AV19 were haemolytic at concentrations between 50 and 100 µM, 5 to 10 times higher than their minimum inhibitory concentration.

The involvement of a regucalcin in suppressing hemocyte apoptosis in Pacific oyster Crassostrea gigas

Regucalcin (RGN), also known as senescence marker protein-30 (SMP30), plays a vital role in the regulation of Ca²⁺ homeostasis. In the present study, a regucalcin (designated as CgRGN) was identified from Pacific oyster Crassostrea gigas. The complete cDNA sequence of CgRGN was of 1059 bp, containing an open reading frame of 933 bp which encoded a protein of 310 amino acids. The deduced amino acid sequence of CgRGN shared similarity with other RGNs from the genome of C. gigas as well as other species. The mRNA transcripts of CgRGN were universally detected in all tested tissues, with higher level in hepatopancreas, labial palp, and gills. The relative expression level of CgRGN in hemocytes was significantly up-regulated (p < 0.05) at 3, 12, 72, and 96 h after the stimulation of lipopolysaccharide (LPS). After CgRGN expression was interfered by specific CgRGN-dsRNA, the hemocytes apoptosis rate increased dramatically at 12 h post LPS stimulation (1.56 fold, p < 0.01), compared to the control group. The caspase-3 activity in hemocytes and NO concentration in hemolymph increased significantly (p < 0.05) in dsCgRGN injection oysters. These results collectively indicated that CgRGN could suppress LPS-induced apoptosis and be involved in the immune response of oysters.

A Signaling Pathway to Mediate the Combined Immunomodulation of Acetylcholine and Enkephalin in Oyster Crassostrea gigas

Molluscs have evolved a primitive but complete neuroendocrine-immune (NEI) system with a vast array of neurotransmitters to conduct both humoral and cellular immunomodulation. Previous studies have illustrated the immune functions of several key neurotransmitters. However, the combined effects of multiple neurotransmitters and the signaling pathway to mediate such immunomodulation have not been well-understood. In the present study, iTRAQ and LC-ESI-MS/MS approaches were employed to investigate the combined immunomodulation functions of two crucial neurotransmitters, acetylcholine (ACh), and [Met⁵]-enkephalin (ENK), in oyster Crassostrea gigas. A total number of 5,379 proteins were identified from hemocytes of oysters after the treatments with Ach and ENK separately or simultaneously, and 1,475 of them were found to be significantly up-regulated, while 1,115 of them were significantly down-regulated. The protein expression patterns in the groups treated by ACh and ENK separately were quite similar, which were dramatically different from that in the group treated by ACh+ENK. One hundred seventy-two proteins were found to be differentially expressed in all the three neurotransmitter treatment groups. Functional validation suggested that ACh and ENK possibly modulate the immune response in oyster hemocytes by enhancing pathogen recognition, cell apoptosis, and the enzyme activities of superoxide dismutase (SOD). Moreover, GO enrichment and co-expression network analyses implied that the combined immunomodulation of ACh and ENK might be mediated by p53, EGF-R–ErbB, and Fc gamma R (FcγR) signaling pathways. These results collectively indicated that multiple neurotransmitters executed a combined and ordered immune regulation through common signaling cascades in molluscs, which was under delicate control to maintain the homeostasis.

A novel tumor necrosis factor in the Pacific oyster Crassostrea gigas mediates the antibacterial response by triggering the synthesis of lysozyme and nitric oxide

Tumor necrosis factors (TNFs) are a group of multifunctional inflammatory cytokines involved in various pathological and immune processes. Recently, a few primitive TNFs have been characterized from molluscs, which play important roles in modulating cell apoptosis, phagocytosis and production of immune-related enzymes. In the present study, a novel TNF (named as CgTNF-2) with the activity to mediate antibacterial response was identified from the Pacific oyster Crassostrea gigas. The open reading frame of CgTNF-2 was of 783 bp encoding a putative polypeptide of 261 amino acids with a typical TNF domain. The deduced amino acid sequence of CgTNF-2 shared high identity with that of TNFs previously identified from other molluscs, such as 96.1% identity with that in oyster C. hongkongensis, 33.7% identity with that in scallop Mizuhopecten yessoensis and 33.0% identity with CgTNF-1 in oyster C. gigas. There were two distinct TNF branches of vertebrate and invertebrate in the phylogenetic tree, and CgTNF-2 was firstly clustered with TNF-14 from C. hongkongensis, and then clustered with other molluscan TNFs. The mRNA transcripts of CgTNF-2 were widely expressed in various oyster tissues, with the highest expression level in hemocytes. The expression level of CgTNF-2 increased significantly at 6 h (2.45-fold and 6.20-fold, respectively, p < 0.05) after peptidoglycan and lipopolysaccharides treatments, and peaked at 12 h (31.86-fold and 7.90-fold, respectively, p < 0.05). The recombinant protein of CgTNF-2 (rCgTNF-2) inhibited the growth of human alveolar basal epithelial (A549) cells at a concentration of 800 ng/mL. After the oysters received an injection of rCgTNF-2, the serum from those oysters exhibited significantly higher antibacterial activity compared to that from control group, evidenced by inhibiting the growth of Vibrio splendidus. Moreover, the lysozyme activity as well as the contents of nitric oxide in the oyster serum also increased significantly. The above results collectively suggested that CgTNF-2 was a novel member of bivalve TNF-α family, which could prompt the antibacterial activity by inducing the lysozyme activity and the production of nitric oxide in the innate immune response of oyster.

The Neuroendocrine-Immune Regulation in Response to Environmental Stress in Marine Bivalves

Marine bivalves, which include many species worldwide, from intertidal zones to hydrothermal vents and cold seeps, are important components of the ecosystem and biodiversity. In their living habitats, marine bivalves need to cope with a series of harsh environmental stressors, including biotic threats (bacterium, virus, and protozoan) and abiotic threats (temperature, salinity, and pollutants). In order to adapt to these surroundings, marine bivalves have evolved sophisticated stress response mechanisms, in which neuroendocrine regulation plays an important role. The nervous system and hemocyte are pillars of the neuroendocrine system. Various neurotransmitters, hormones, neuropeptides, and cytokines have been also characterized as signal messengers or effectors to regulate humoral and cellular immunity, energy metabolism, shell formation, and larval development in response to a vast array of environmental stressors. In this review substantial consideration will be devoted to outline the vital components of the neuroendocrine system identified in bivalves, as well as its modulation repertoire in response to environmental stressors, thereby illustrating the dramatic adaptation mechanisms of molluscs.

Annual assessment of the sea urchin (Paracentrotus lividus) humoral innate immune status: Tales from the north Portuguese coast

Innate immune status of the sea urchin Paracentrotus lividus population from two different rocky shore beaches in the northern Portuguese coast was evaluated for a period of one year. Although some ecological studies regarding the effect of toxics on the immune parameters of the sea urchin were made in Portuguese waters, there is a current lack of knowledge concerning their immune status all over the year. In perspective of a changing ecosystem in these waters due to global warming and colonization of new species, it is important to assess the status of the major species living in the area. In this way, immune parameters such as total protein content, nitric oxide concentration, haemolytic activity, protease activity, lysozyme concentration and bactericidal activity were evaluated in the perivisceral coelomic fluid, and were correlated with the gonadal index of the population and water parameters. Also, the spawning period can upset some immune status parameters, and others such as haemolytic activity and bactericidal activity against Vibrio anguillarum, showed a clear correlation with the gonad maturation status. The knowledge of the basal immune status of the species could serve as ecological indicator of some stress agent or contaminant into the field; also, coelomic fluid is suggested as good quality marker to assess the immune status of sea urchins.