Characterization of phenoloxidase from the sea cucumber Apostichopus japonicus

Comparative study of three phenoloxidases in the sea cucumber Apostichopus japonicus

In order to preliminarily illustrate the functional differences of phenoloxidases (POs) in Apostichopus japonicus, the full-length cDNAs of two POs (named as AjPOⅡ and AjPOⅢ, respectively) were cloned from the coelomocytes of A. japonicus using 3'- and 5'-rapid amplification of cDNA ends method, and combined with the previously acquired full-length cDNA of a laccase-type PO from A. japonicus (Accession No. KF040052, named as AjPOⅠ), the sequence structure and phylogenic status of POs from A. japonicus (AjPOs) were comparatively analyzed, and the transcriptional expression of AjPOs in different tissues, at different developmental stages and after different bacterial challenges was determined with quantitative real-time PCR method. Sequence analysis indicated AjPOⅡ and AjPOⅢ were both laccase-type POs, coincident to the results of phylogenic analysis. Sequence analysis also showed that AjPOⅠ had a transmembrane domain (J. Jiang et al., 2014), AjPOⅡ contained a signal peptide, and AjPOⅢ possessed a signal peptide and a transmembrane domain, implying that three AjPOs might play different roles in immune and physiological processes. Transcriptional expression analysis showed that AjPOⅡ and AjPOⅢ were most abundant in tube feet, while AjPOⅠhad the highest expression level in coelomocytes (J. Jiang et al., 2014), suggesting that AjPOⅠ may be mainly involved in immune response, while AjPOⅡ and AjPOⅢ are probably responsible for other physiological processes in addition to immune response. Besides, three AjPOs were determined to have different expression patterns during organism development and different spectrums of response against bacteria, which further indicated that there might be immune and physiological functional differentiation among three AjPOs.

Effect of pH on temperature controlled degradation of reactive oxygen species, heat shock protein expression, and mucosal immunity in the sea cucumber Isostichopus badionotus

This study evaluated the effect of pH on the activity of antioxidant and immune enzymes in the sea cucumber Isostichopus badionotus exposed to different temperatures. The organisms (530 ±110 g) were exposed to 16, 20, 24, 28, 30, 34 and 36°C for 6 h to evaluate thermal limits at two water pH values (treatment = 7.70; control = 8.17). For the thermal tolerance experiment, the organisms were exposed to sublethal temperature of 34°C for 3, 6, 12, 24, and 48 h. I. badionotus showed signs of thermal stress by synthesizing heat shock protein 70 (hsp70) at the cold (16°C) and warm thermal limits (34°C). The glutathione peroxidase (GPx) showed a negative correlation with superoxide dismutase (SOD) activity in modulating the effect of oxidative stress at different temperature levels. Specifically, GPx activity was maximal at the extremes of the cold and warm temperatures (16, 20, and 36°C) tested, while contrarily, the SOD activity increased significantly in the narrow range of temperature between 28 and 30°C, as a part of a reaction to offset oxidative damage. The effect of pH on the expression of hsp70 was not significant, whereas the antioxidant enzymes activity was stimulated at pH 7.70. Mucosal immunity, evidenced by the activation of the phenoloxidase (PO) system, increased above the basal level at pH 7.70 and at 28, 30, and 34°C. Independent of pH, the temperature of 34°C was identified as the 12 h-sublethal upper limit for I. badionotus.

Comparative analysis of immunocompetence between females and males in the sea cucumber Apostichopus japonicus

In order to preliminarily understand the immune difference between females and males in the sea cucumber Apostichopus japonicus, the activities assay of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), phenoloxidase (PO), acid phosphatase (ACP) and alkaline phosphatase (ALP) with biochemical methods, the detection of PO isozymes with native-PAGE and catechol staining, and the test of antibacterial activities with bacterial growth curve determination method were performed in this study using cell-free coelomic fluid (CCF) and coelomocyte lysate supernatant (CLS) from females and males as the samples. The PO activities were not detected in the CLS and showed no significant difference between the CCF from females and males. However, totally five PO isozyme bands were detected in the CLS of females while only four were detected in the CLS of males after zymogram analysis. These results implied that the PO isozymes in the coelomocytes of viripotent A. japonicus were inactive under natural condition and may be activated by some certain treatments during native-PAGE, and PO might play different immune and physiological roles between females and males. In addition, the activities of SOD, CAT, POD and ALP in the CCF and the activities of CAT, POD, ACP and ALP in the CLS from males were all significantly higher than those from females. The results collectively suggested that in viripotent A. japonicus, the gender had a remarkable effect on the immunity, and the immunocompetence of males might have an advantage over that of females. Furthermore, the activities of all determined enzymes except PO and the number of detected PO isozymes showed higher values in CLS than in CCF, implying that in viripotent A. japonicus, the coelomocytes might take more immune responsibility in comparison with CCF.

Effects of thermal stress on the immune and oxidative stress responses of juvenile sea cucumber Holothuria scabra

Holothuria scabra is the most valued and cultured tropical sea cucumber, given the great demand of this species for human consumption. However, despite its ecological and economic relevance, little is known regarding its immune responses under thermal stress. Here, the main goal was to study the response of sea cucumbers to temperature stress, assessing sub-organismal alterations and acclimation capacities of juveniles to temperature changes. After changing temperature (1 °C/day) for 6 days, organisms were exposed to temperature conditions of 21 °C (cold), 27 °C (control), and 33 °C (warm) over a 30 day period. At each 15-day interval (T0, T15, and T30), six replicates per condition were killed for biochemical analysis. Immune responses were addressed by studying the activity of phenoloxidase (PO) and prophenoloxidase (ProPO) in the coelomic fluid. Antioxidant defence responses-catalase (CAT), superoxide dismutase (SOD), and glutathione reductase (GR) enzymatic activities-were measured in the muscle and respiratory tree tissues, whereas oxidative damage was evaluated by measuring levels of superoxide radicals (ROS), DNA-strand breaks and lipid peroxidation (LPO). Juvenile H. scabra increased SOD and PO activities when temperature was elevated, and revealed low levels of ROS and damage in both cold and warm treatments throughout the experiment, confirming the organism's moderate thermal stress. After the short acclimation period, the immune and antioxidant responses prevented damage and maintained homeostasis. This multi-biomarker approach highlights its usefulness to monitor the health of H. scabra and to gain insight concerning the use of this high-valued species in global-scale aquaculture from different temperature regions.

Immune indices and identical functions of two prophenoloxidases from the haemolymph of green tiger shrimp Penaeus semisulcatus and its antibiofilm activity

In the present study, we purified two prophenoloxidases (proPO) from haemolymph of green tiger shrimp, Penaeus semisulcatus by gel fermentation chromatography using blue Sepharose matrix. The two purified prophenoloxidase macromolecules are of about 76 and 75 kDa determined through SDS-PAGE and named as Penaeus semisulcatus prophenoloxidase I (PSproPO I) and Penaeus semisulcatus prophenoloxidase II (PSproPO II). It was further characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Circular Dichroism (CD) and High Performance Liquid Chromatography (HPLC) analysis. The purified PSproPO I and PSproPO II showed the strongest agglutination titre against human erythrocytes compared to goat RBC. The PSproPO I and PSproPO II showed phagocytic activity against yeast Saccharomyces cerevisiae and encapsulation activity against Sepharose CL 6B beads compared to CM Sepharose and Sodium alginate beads. The functional analysis of purified PSproPO I and PSproPO II showed enhanced PO activity when added with the triggering molecules such as pathogen associated molecular patterns (PAMPs), metals and chemicals. In addition, eluted fraction containing PSproPO I and PSproPO II showed antibiofilm activity against Gram positive and Gram negative bacteria. The above results concluded that no significant differences were found between the purified PSproPO I and PSproPO II immune indices and functions. This study might provide a sensitive platform to understand more about the critical roles of PSproPO I and PSproPO II in crustacean immune system.

Identification and characterization of proteins with phenoloxidase-like activities in the sea urchin Strongylocentrotus nudus

Three proteins with PO-like activities in the coelomocytes of sea urchin Strongylocentrotus nudus were identified using electrophoretic method and named as SnPO1, SnPO2 and SnPO3 according to their molecular mass from high to low. The SnPOs were characterized for substrate specificity and the effects of temperature, pH, divalent metal ions and inhibitors on PO activities. They showed oxidative activities to L-3,4-dihydroxyphenylalanine. (l-DOPA), dopamine and hydroquinone, but failed to oxidize tyrosine, which illustrated the three proteins had laccase-like PO activities. The optimum temperature for the activities of SnPO1, SnPO2 and SnPO3 was 75 °C, 70 °C, 40 °C, and the optimum pH was 7.0, 9.0, 8.0, respectively. The SnPOs were notably activated after being incubated in boiled water for 60 min, suggesting that the three proteins are thermophilic. The activity of SnPO1 was greatly enhanced by Cu(2+), Mn(2+) and Fe(2+) and inhibited by Pb(2+), Cd(2+), EDTA, DETC, sodium sulfite and ascorbic acid, but SnPO2 and SnPO3 were not obviously affected by Pb(2+) and Cd(2+), suggesting the three proteins are copper-containing, and the catalytic properties of SnPO1 might be different from those of SnPO2 and SnPO3. Taken together, SnPO1, SnPO2 and SnPO3 might play different roles in the immune and physiological processes of S. nudus.

A review of the immune molecules in the sea cucumber

It is very important to identify and characterize the immune-related genes that respond to pathogens. Until recently, only some of the immune-related genes in sea cucumbers had been characterized. Their expression patterns after pathogen challenges have been analyzed via expressed sequence tag libraries, microarray studies and proteomic approaches. These genes include lectins, antimicrobial peptides, lysozyme, enzymes, clotting protein, pattern recognition proteins, Toll receptors, complement C3 and other humoral factors that might participate in the innate immune system of sea cucumbers. Although the participation of some of these immune molecules in the sea cucumber's innate immune defense against invading pathogens has been demonstrated, the functions of many of the molecules remain unclear. This review focuses on the discovery and functional characterization of the immune-related molecules from the sea cucumber for the first time and provides new insights into the immune mechanisms of the sea cucumber, which opens new possibilities for developing drugs for novel anti-bacterial and antiviral applications in fisheries.

In vitro antibacterial analysis of phenoloxidase reaction products from the sea cucumber Apostichopus japonicus

Three phenoloxidases (POs) of Apostichopus japonicus, AjPOs (AjPO1, AjPO2 and AjPO3), were partially purified from the coelomocytes with an electrophoretic method, and then employed for the in vitro antibacterial analysis. Using L-3,4-dihydroxyphenylalanine (L-DOPA) as a substrate, AjPO1 and AjPO2-derived compounds inhibited the growth of Vibrio splendidus and Staphylococcus aureus, while AjPO3-derived compounds only inhibited the growth of V. splendidus. When dopamine was used as a substrate, AjPO1 and AjPO3-derived compounds inhibited the growth of V. splendidus and Vibrio harveyi, while AjPO2-derived compounds only inhibited the growth of V. splendidus. Moreover, AjPO1-derived compounds showed stronger inhibition in V. harveyi than AjPO3-derived compounds did. However, all of the three AjPO reaction products showed no inhibitions on the growth of Pseudoalteromonas nigrifaciens, Shewanella baltica, Micrococcus lysodeikticus, Streptococcus dysgalactiae and Nocardiopsis sp. with L-DOPA or dopamine as a substrate. Scanning electron microscope (SEM) observation of V. harveyi treated by AjPOs and dopamine showed that AjPO1-derived compounds resulted in massive bacteriolysis, AjPO2-derived compounds caused no obvious alteration on bacterial morphology, and AjPO3-derived compounds increased the ratio of spheroidal bacteria. All these results suggested that AjPO reaction products derived by L-DOPA and dopamine had different but limited antibacterial spectrum, and the different antibacterial effects observed among three AjPOs resulted from the different reaction products generated by AjPOs with the same substrate.