Lysosomal enzyme pattern in Holothuria polii coelomocytes

Synergistic Effects of Dietary Selenomethionine and Vitamin C on the Immunity, Antioxidant Status, and Intestinal Microbiota in Sea Cucumber (Apostichopus japonicus)

A 30-day feeding trial was carried out to investigate the interactive effects of dietary selenium (selenomethionine) and vitamin C (Vc) in Apostichopus japonicus. Two selenium (0 and 5 mg/kg) and three vitamin C (0, 5000, and 10,000 mg/kg) combined groups of feed were formulated (Designated as LSeLVc, LSeMVc, LSeHVc, HSeLVc, HSeMVc and HSeHVc, respectively) and fed the sea cucumbers. Our results showed no significant effects on the growth-related parameters in sea cucumber (P > 0.05). Furthermore, the reciprocal action between Se and Vc had significant (P < 0.05) effects on Se accumulation in the respiratory tree and intestines. Also, the lysozyme, glutathione peroxidase activity, and the relative expression levels such as LZM, GPX, Hsp70, and Hsp90 in different tissues were significantly increased in the group of sea cucumber fed diet with 5 mg Se in combination with 5000 mg Vc compared with the control group (P < 0.05). However, MDA and H2O2 contents in the body wall were significantly reduced in the HSeHVc group (P < 0.05). In addition, analysis of intestinal flora revealed that Haloferula abundance was highest in the LSeMVc group than other treatment groups, and Vibrio abundance was decreased with combined Se and Vc supplement. Finally, the species diversity of the gut microbial community of sea cucumber in HSeMVc group was lower than those in other treatment groups. The results showed that the interaction of selenium and vitamin C had positive effects on improving the immune status, antioxidant capacity, and digestive ability of A. japonicus.

Changes in Symbiotic Microbiota and Immune Responses in Early Development Stages of Rapana venosa (Valenciennes, 1846) Provide Insights Into Immune System Development in Gastropods

The symbiotic microbiota can stimulate modulation of immune system, which also can promote immune system mature in critical developmental periods. In this study, we have investigated the symbiotic microbiota in Rapana venosa at five early development stages using Illumina high-throughput sequencing, and detected immune responses in larvae. Analysis of the symbiotic microbiota sequences identified that the most abundant phylum was Proteobacteria. Beta diversity analysis indicated that the structure of the symbiotic microbiota dramatically shifted in early development stages. The abundance of immune-related KEGG Orthologs (KOs) also increased in competent larval (J4, 30-day post-hatching) and postlarval after 3 days of metamorphosis (Y5, 33-day post-hatching) stages. Acid phosphatase activity decreased significantly in the Y5 stage, and alkaline phosphatase activity also at a lower level in Y5 stage, whereas lysozyme activities exhibited no remarkable change. Also, the activities of catalase and superoxide dismutase activities decreased dramatically during early development stages of R. venosa. Dramatic changes in the symbiotic microbiota and the immune response mainly occurred in the initially hatched veliger (C1), competent larval (J4) and postlarval (Y5) stages, during which the hosts might experience substantial environmental changes or changes in physiological structure and function. These findings expand our understanding of the stage-specific symbiotic microbiota in R. venosa and the close association between immune system and symbiotic microbiota in mollusks, however, the specific relationship may need more researches are needed to investigated in the future.

Impact of hypoxia stress on the physiological responses of sea cucumber Apostichopus japonicus: respiration, digestion, immunity and oxidative damage

Hypoxia is one of the most frequently occurring stressors confronted by industrial cultures of sea cucumber and can cause large economic losses and resource degradation. However, its responsive mechanisms are still lacking. In this paper, the physiological responses of Apostichopus japonicus to oxygen deficiency was illustrated, including induced oxidative response and immune defense and changed digestive enzymes activities. Significantly increased activities of alpha-amylase (AMS), acid phosphatase (ACP), lactate dehydrogenase, catalase, peroxidase, succinate dehydrogenase and higher content of malondialdehyde, and decreased activities of lipase and trypsin (TRY) were observed after hypoxia exposure (dissolved oxygen [DO] 2 mg/L). Expressions of key genes showed that AMS, peptidase, ACP, alkaline phosphatase, lysozyme, heat shock protein 70 and glutathione peroxidase were increased and TRY was decreased under hypoxia. With the decline of the DO level, the decreased tendency of oxygen consumption rates was different in varied weight groups. Moreover, respiratory trees were observed degraded under long-term hypoxia stress, thus leading a negative effect of respiration. These results could help to develop a better understanding of the responsive mechanism of sea cucumber under hypoxia stress and provide a theoretical basis for the prevention of hypoxia risk.

Immune-related proteins detected through iTRAQ-based proteomics analysis of intestines from Apostichopus japonicus in response to tussah immunoreactive substances

Apostichopus japonicus is a species of sea cucumber that is extensively bred as a marine delicacy because of its high nutritive and medicinal value. Immunostimulants are usually used to enhance the immunity of sea cucumber against diseases, but the physiological function of immunostimulants is poorly understood. In this study, we fed A. japonicus individuals with a diet supplemented with different concentrations of tussah immunoreactive substances (TIS), and then subjected their intestines to iTRAQ-based proteomic analysis. A total of 51 differentially expressed proteins were detected in response to TIS, 13 proteins were upregulated, while 38 proteins were reduced. These proteins are involved in phagocytosis, tissue protection, cell apoptosis and energy metabolism. Among these 51 proteins, 7 proteins (GLO2, ACOX, CTTN, MARK, FADD, CSTA and CASP6) related to immunity with functional annotation in sea cucumber were further analyzed. In addition, the upregulated expression of 4 immune-related proteins (GLO2, ACOX, CTTN and MARK) was validated by qRT-PCR. The findings of this study gave further insight into the mechanism by which TIS might enhance the immunity of A. japonicus.

Dietary Cordyceps militaris protects against Vibrio splendidus infection in sea cucumber Apostichopus japonicus

Vibrio splendidus is the common pathogen that causes infectious diseases widely spread in cultured sea cucumber in China. Therefore, we investigated the ability of Cordyceps militaris to protect against infection caused by V. splendidus. In this study, sea cucumbers were fed with a diet containing 0 (control), 1%, 2% or 3% C. militaris for 28 days, and subsequently challenged with V. splendidus by injection with 1.0 × 10(9) cfu per animal. Parameters of immune response such as phagocytosis (PC), lysozyme (LSZ) activity, superoxide dismutase (SOD) activity, alkaline phosphatase (AKP) activity and acid phosphatase (ACP) activity were determined on days 0, 1, 3, 5 and 7 after injection. The results showed that dietary C. militaris at a dose of 2% or 3% significantly up-regulated (P < 0.05) all the immune parameters on day 0. One day after injection with V. splendidus, all the immune indices except ACP exhibited a tendency to decrease and then increase again, returning to the initial level on days 5 and/or 7 after injection. All the immune parameters of those fed with C. militaris were found significantly higher (P < 0.05) than those of the control group on day 1 after injection. Only LSZ activity of those fed with 1%- or 3%-C. militaris diet on day 5 showed significantly increases (P < 0.05) than the controls. As for ACP activity, the values remained steady with time, but with significant increase (P < 0.05) seen in sea cucumbers fed with 2%-C. militaris diet, and lasted for up to 7 days after V. splendidus injection. The cumulative mortality of sea cucumbers fed with the basal diet followed V. splendidus infection was significantly higher (P < 0.05) than those fed with 2% and 3% C. militaris diet. Under the experimental conditions, dietary C. militaris could enhance the immune responses of Apostichopus japonicus and improve its resistance to infection by V. splendidus.

Effect of potential probiotic Rhodotorula benthica D30 on the growth performance, digestive enzyme activity and immunity in juvenile sea cucumber Apostichopus japonicus

The effects of dietary addition of yeast Rhodotorula benthica (R. benthica) D30 which isolated from local sea mud at levels of 0 (control), 10(5), 10(6) and 10(7) CFU/g feed on the growth performance, digestive enzyme activity, immunity and disease resistance of juvenile sea cucumber Apostichopus japonicus were investigated. It was shown that dietary addition of R. benthica D30 significantly increased the growth rates of sea cucumbers (p < 0.05). The amylase activity, cellulase activity and alginase activity were increased for the animals from three probiotics treated groups. And with the supplemented concentration increased, the values of those digestive enzyme activities increased as well. Dietary addition of R. benthica D30 at the level of 10(7) CFU significantly increased the lysozyme, phagocytic and total nitric oxide synthase activity of A. japonicus (p < 0.05). While, the highest values of the phenoloxidase and alkaline phosphatase activity were found in sea cucumbers fed with R. benthica D30 at the level of 10(6) CFU. Whereas adding R. benthica D30 to diet had no significant effects on the total coelomocyte counts and acid phosphatase activity of A. japonicus (p > 0.05). It was observed that adding R. benthica D30 could significantly decrease the cumulative mortality of sea cucumbers. The present study demonstrated that dietary addition of R. benthica D30 could increase growth performance and some digestive enzyme activities, improve immunity and disease resistance of A. japonicus. And the medium (10(6) CFU) and high (10(7) CFU) additional levels showed better effects. It suggests that yeast R. benthica D30 could be a good probiotic for aquaculture.

Effects of dietary live yeast Hanseniaspora opuntiae C21 on the immune and disease resistance against Vibrio splendidus infection in juvenile sea cucumber Apostichopus japonicus

A feeding experiment was conducted to determine effects of Hanseniaspora opuntiae C21 on immune response and disease resistance against Vibrio splendidus infection in juvenile sea cucumbers Apostichopus japonicus. Sea cucumbers were fed with either diets containing C21 at 10(4), 10(5) and 10(6) CFU g(-1) feed or a control diet for 30-50 days, respectively. After feeding for 30 days and 45 days, five sea cucumbers from each tank were sampled for immunological analyses. Results indicated that C21 significantly improved the phagocytic activity in coelomocytes of sea cucumbers (P < 0.05). Moreover, C21 administration significantly enhanced lysozyme (LSZ), phenoloxidase activity (PO), total nitric oxide synthase (T-NOS), superoxide dismutase (SOD), alkaline phosphatase (AKP) and acid phosphatase (ACP) activities in coelomic fluid, and LSZ, T-NOS, AKP and ACP activities in coelomocytes lysate supernatant (CLS) of sea cucumbers (P < 0.05). After feeding for 45 days, 10 sea cucumbers from each dose group were challenged with V. splendidus NB13. Cumulative incidence and mortality of sea cucumbers fed with C21 were found to be lower than those of control group. After feeding for 50 days, sea cucumbers in 10(4) CFU g(-1) C21 treatment and control tanks were subjected to acute salinity changes (from 30 to 20) for 24 h in the laboratory, and the immunological parameters were measured to evaluate the immune capacities of the A. japonicus. Phagocytic, LAZ and T-NOS activities of C21-treated group were higher than those of control group, indicating that salinity stress tolerance of sea cucumber was enhanced by C21. The present results showed that a diet supplemented with C21 could stimulate the immune system of juvenile A. japonicus thus enhancing their resistance against V. splendidus.

Enhancement of non-specific immune response in sea cucumber (Apostichopus japonicus) by Astragalus membranaceus and its polysaccharides

In this study, the immunostimulatory effect of oral administration of different preparations (conventional fine powder [CP] and superfine powder [SP]) of Astragalus membranaceus root or its polysaccharides (APS) in sea cucumber (Apostichopus japonicus) was investigated. Sea cucumbers with an average initial weight of 49.3 +/- 5.65 g were fed with a diet containing 3% CP or SP or 0.3% APS over a period of 60 days. The non-specific humoral (phenoloxidase, lysozyme and agglutination titer) and cellular (phagocytic capacity and reactive oxygen species) responses were determined and compared with controls (no supplement) after 20, 40 and 60 days of feeding. Variation in the levels of responses was evident among different supplements. SP and APS significantly enhanced most of the immune parameters tested. Among the humoral responses, lysozyme activity significantly increased after feeding with SP-supplemented diet for 20, 40 or 60 days. Furthermore, lectin titer showed significant enhancement after 20 and 60 days of feeding with APS-supplemented diet. Significant increase in the production of reactive oxygen species was evident for all three supplements after 20 days of feeding, but no significant change in serum phenoloxidase activity was observed for any of the three supplements over the three different periods. Overall, significant modulation of the cellular responses was only noticed after 20 days of feeding with SP- or APS-supplemented diet. After 60 days, these two groups also exhibited a decrease in the cumulative symptom rates compared to the controls when challenged with Vibrio splendidus. These results indicated that dietary intake containing A. membranaceus root or its polysaccharides could enhance the immune responses of A. japonicus and improve its resistance to infection by V. splendidus.

The effects of chronic inorganic and organic phosphate exposure on bactericidal activity of the coelomic fluid of the sea urchin Lytechinus variegatus (Lamarck) (Echinodermata: Echinoidea)

The sea urchin Lytechinus variegatus can survive chronic exposure to sodium phosphate (inorganic phosphate) concentrations as high as 3.2 mg L-1, and triethyl phosphate (organic phosphate) concentrations of 1000 mg L-1. However, chronic exposure to low (0.8 mg L-1 inorganic and 10 mg L-1 organic phosphate), medium (1.6 mg L-1 inorganic and 100 mg L-1 organic phosphate) or high (3.2 mg L-1 inorganic and 1000 mg L-1 organic phosphate) sublethal concentrations of these phosphates inhibit bactericidal clearance of the marine bacterium Vibrio sp. Bacteria were exposed to coelomic fluid collected from individuals maintained in either artificial seawater, or three concentrations of either inorganic phosphate or organic phosphate. Sterile marine broth, natural seawater and cell free coelomic fluid (cfCF) were employed as controls. Bacterial survival indices were measured at 0, 24 and 48 h periods once a week for four weeks. Bacteria were readily eliminated from the whole coelomic fluid (wCF) of individuals maintained in artificial seawater. Individuals maintained in inorganic phosphates were able to clear bacteria following a two week exposure period, while individuals maintained at even low concentrations of organic phosphates failed to clear all bacteria from their coelomic fluid. Exposure to phosphates represses antimicrobial defenses and may ultimately compromise survival of L. variegatus in the nearshore environment.

Polysaccharides from Astragalus membranaceus promote phagocytosis and superoxide anion (O2-) production by coelomocytes from sea cucumber Apostichopus japonicus in vitro

The potential immunostimulatory effects of Astralagus membranaceus polysaccharides (APS) on sea cucumber, Apostichopus japonicus (Selenka), were investigated in vitro. Phagocytosis and superoxide anion (O(2)(-)) production by phagocytic amoebocytes (PA) from A. japonicus coelomic fluid were measured during incubation at 18 degrees C, 22 degrees C, or 25 degrees C with APS at 0, 10, 20, or 40 microg mL(-1) (n=3). Phagocytic activity against yeast cells was quantified by direct visualization, and O(2)(-) production by nitroblue tetrazolium (NBT) reduction assay. Compared with controls, including APS at 20 microg mL(-1) significantly increased (P<0.05) the percentage of phagocytic capacity (PC) and phagocytic index (PI) at 18 degrees C and 22 degrees C, but no significant enhancement was observed at 25 degrees C. In contrast, the coelmocytes of A. japonicus can have an obvious generation of O(2)(-) after the stimulation. The concentration of 20 microg mL(-1) APS resulted in a significant increase in nitroblue tetrazolium (NBT) positive cells (P<0.05) at different temperature and even 10 microg mL(-1) APS could increase O(2)(-) generation significantly at 18 degrees C and 22 degrees C. Both phagocytosing and O(2)(-) production increased with the increase of APS concentration from 0 to 20 microg mL(-1) at different temperature, and when APS at 40 microg mL(-1), they were decreased. It suggested that immunocytes activity in A. japonicus decreased with the temperature increasing from 18 degrees C to 25 degrees C, and APS could be an effective immunostimulant to enhance phagocytic activity and O(2)(-) production.

Effects of PCBs on reactive oxygen species (ROS) production by the immune cells of Paracentrotus lividus (Echinodermata)

The impact of four PCB congeners: 3,3',4,4'-tetrachlorobiphenyl (IUPAC congener #77), 3,3',4,4',5-pentachlorobiphenyl (IUPAC #126), 2,2',4,4',5,5'-hexachlorobiphenyl (IUPAC #153) and 3,3',4,4',5,5'-hexachlorobiphenyl (IUPAC #169) was investigated on the reactive oxygen species (ROS) production by coelomocytes of the echinoid Paracentrotus lividus, an important species in marine benthic ecosystems. PCBs were found to increase ROS production and to delay the time of peak production. These effects were stronger on bacteria-stimulated cells and were congener-specific: coplanar congeners (#77, 126 and 169) had more effect than the non-coplanar PCB #153. Among coplanar congeners, PCB #169 showed dose-dependent effects whereas PCB #77 and 126 were more toxic at high and low doses, respectively. The relative immunotoxicity of the different PCB congeners is discussed in the light of their structural properties and biological affinities.

Echinoderm immunity and the evolution of the complement system

Our understanding of inflammatory responses in humans has its roots in the comparative approach to immunology. In the late 1900s, research on echinoderms provided the initial evidence for the importance of phagocytic cells in reactions to foreign material. Studies of allograft rejection kinetics have shown that echinoderms have a non-adaptive, activation type of immune response. Coelomocytes mediate the cellular responses to immune challenges through phagocytosis, encapsulation, cytotoxicity, and the production of antimicrobial agents. In addition, a variety of humoral factors found in the coelomic fluid, including lectins, agglutinins, and lysins, are important in host defense against pathogens and other foreign substances. Recently, a simple complement system has been identified in the purple sea urchin that is homologous to the alternative pathway in vertebrates. The sea urchin [corrected] homologue of C3, is inducible by challenge with lipopolysaccharide, which is known to activate coelomocytes. Complement components have been identified in all vertebrate classes, and now have been characterized in protochordates and echinoderms indicating the primordial nature of the complement system. Because it is thought that the complement system evolved from a few primordial genes by gene duplication and divergence, the origin of this system appears to have occurred within the common ancestor of the deuterostomes.

The echinoderm immune system. Characters shared with vertebrate immune systems and characters arising later in deuterostome phylogeny

In summary, the characters of the echinoderm immune system that we review here can be considered to illuminate the baseline nonadaptive immune systems that were our original deuterostome heritage. We still retain--and greatly rely upon--similarly functioning, nonadaptive cellular defense systems. It is worth stressing that sea urchins are long lived, normally healthy animals that display remarkable abilities to heal wounds and combat major infections. From an external point of view, their immune systems obviously work very well. Thus, their cellular defense systems are extremely sensitive, and they respond rapidly to minor perturbations, all without any specific adaptive capabilities. These systems probably function through the transduction of signals conveying information on injury and infection, just as do the equivalent systems that underlie and back up our own adaptive immune systems, and that provide the initial series of defenses against pathogenic invasions. Many extremely interesting questions remain regarding the evolution of the deuterostome immune response. Are the echinoderm and tunicate systems the same, or have the protochordates augmented the basic phagocyte system with an as yet unidentified chordate-like character? Do the jawless fishes produce Igs that would make them similar to the sharks, or are they vertebrates without an Ig system that essentially rely on an invertebrate-like, nonspecific, activated phagocyte type of immune system? How do sharks regulate their immune system without T cells and MHC class I? How do they avoid producing autoantibodies? Future research will not only answer these questions, but those answers will also be enlightening with regard to the origins of the mammalian immune system in which ancient functions and subsystems remain.