Liza Haematocheila Research Articles

Molecular characterization of the evolutionary conserved signaling intermediate in Toll pathways (ECSIT) of soiny mullet (Liza haematocheila)

Mammalian evolutionary conserved signaling intermediate in Toll pathways (ECSIT) is an important intracellular protein that involves in innate immunity, embryogenesis, and assembly or stability of the mitochondrial complex I. In the present study, the ECSIT was characterized in soiny mullet (Liza haematocheila). The full-length cDNA of mullet ECSIT was 1860 bp, encoding 449 amino acids. Mullet ECSIT shared 60.4%∼78.2% sequence identities with its teleost counterparts. Two conserved protein domains, ECSIT domain and C-terminal domain, were found in mullet ECSIT. Realtime qPCR analysis revealed that mullet ECSIT was distributed in all examined tissues with high expressions in spleen, head kidney (HK) and gill. Further analysis showed that mullet ECSIT in spleen was up-regulated from 6 h to 48 h after Streptococcus dysgalactiae infection. In addition, the co-immunoprecipitation (co-IP) assay confirmed that mullet ECSIT could interact with tumor necrosis factor receptor-associated factor 6 (TRAF6). Molecular docking revealed that the polar interaction and hydrophobic interaction play crucial roles in the forming of ECSIT-TRAF6 complex. The resides of mullet ECSIT that involved in the interaction between ECSIT and TRAF6 were Arg107, Glu113, Phe114, Glu124, Lys120 and Lys121, which mainly located in the ECSIT domain. Our results demonstrated that mullet ECSIT involved in the immune defense against bacterial and regulation of TLRs signaling pathway by interaction with TRAF6. To the best of our knowledge, this is the first report on ECSIT of soiny mullet, which deepen the understanding of ECSIT and its functions in the immune response of teleosts.

Особенности развития личинок и молоди пиленгаса Liza haematocheilus (Temminck & Schlegel, 1845) = Mugil soiuy (Basilewsky, 1855) в искусственных условиях

Soiuy mullet of the family Mugilidae is a valuable commercial fish species introduced into the Azov-Black Sea basin. It is adapted to live both in fresh and oceanic saline waters; it fattens in shallow waters of bays and lagoons that warm up and cool down quickly and strongly and is one of the promising objects for artificial breeding. There are presented the research results on cultivating larvae and juveniles of soiuy mullet in 2017-2020 in the conditions of artificial reproduction at the experimental base of “Kerch” department of Russian Research Institute of Fish Industry and Oceanography (AzNIIRH) – Research Base Zavetnoe. The biological norms of larvae rearing to the end of metamorphosis were outlined. The larvae aged 4-12 days were fed only with zooplanktonic organisms. 10-12-day-old juveniles were fed with inert feed. There are given the data on development of eggs and juveniles of soiuy mullet in artificial conditions, main size and weight parameters, daily diets and amount of artificial feed used in its rearing from 
 5 to 120 days old. Using live feed in combination with artificial feed up to 30 days old is recommended. There are presented quantitative indicators on the expenditure of live and artificial feed and feed coefficients in soiuy mullet larvae farming until the completion of metamorphosis and yearlings. It has also been found that dietary intake of larvae considerably increases with growth, therefore it is expedient to work on using a wider range of artificial feed at earlier stages of rearing - in 10-15-day-old soiuy mullet larvae.

Assessment of the Effects of Salt and Salicornia herbacea L. on Physiochemical, Nutritional, and Quality Parameters for Extending the Shelf-Life of Semi-Dried Mullets (Chelon haematocheilus).

Mullet, a coastal fish species, is commonly used as a salted dried fish in many countries, including Korea, Japan, and the southeastern United States. The purpose of this investigation was to develop high-quality products of salted semi-dried mullet (SSDM) using natural salt and Salicornia herbacea L. (SAL). The antioxidant activity of SAL was investigated by in vitro studies. The physicochemical and nutritional characteristics of fresh mullet (FM), salted control (SSDM-CON), and SAL-treated (SSDM-SAL) mullet groups were analyzed. The moisture, ash, and crude protein contents were significantly increased in the SSDM-SAL group, whereas the salinity was decreased when compared with the SSDM-CON group. Lipid oxidation occurred in the FM and SSDM groups, as indicated by the increase in peroxide (PV), acid (AV), and thiobarbituric acid reactive substance (TBARS) values during the storage period. The protein pattern on the sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed similarities between the groups, while the amino acid and fatty acid contents also varied in the FM and SSDM groups depending on their processing methods. Initially, the total bacterial count was significantly higher in the SSDM groups than in the FM group. However, the SSDM-SAL group had a markedly lower total bacteria count than the FM and SSDM-CON groups during 21 days of refrigerated storage. This result indicates that SAL treatment can improve mullet’s safety from microorganisms, includes beneficial biochemical parameters, and can extend their shelf-life through refrigerated storage.

Molecular characterization, expression profile, and antiviral activity of redlip mullet (Liza haematocheila) viperin.

Viperin is known to exhibit activity against RNA viral infection. Viral hemorrhagic septicemia virus (VHSV) is a negative-sense single-stranded RNA virus that causes severe loss in aquaculture species. Susceptible species include redlip mullets (Liza haematocheila), which has become an economically important euryhaline mugilid species in offshore aquaculture along the west coast of Korea. Although interferon-stimulated genes are suspected to act against VHSV, specific pathways or mechanisms of these antiviral actions in redlip mullets have not yet been established. In silico studies of the mullet viperin (Lhrsad2) revealed an S-adenosyl methionine binding conserved domain containing the 77CNYKCGFC84 sequence. In the tissue distribution, the highest levels of lhrsad2 expression were observed in the blood. When injected with poly(I:C), an approximately 17-fold upregulation (compared to the control) of viperin was detected in the blood after 24h. Furthermore, non-viral immune stimuli, including Lactococcus garvieae (L. garvieae) and lipopolysaccharide (LPS), that were injected into redlip mullets were not found to induce considerable levels of viperin expression. Subcellular analysis revealed that Lhrsad2 localized to the endoplasmic reticulum (ER). To investigate Lhrsad2's antiviral effects against VHSV, cells overexpressing lhrsad2 were infected with VHSV, and then the viral titer and viral gene expression were analyzed. Both assays revealed the potential of Lhrsad2 to significantly reduce VHSV transcription and replication. In brief, the current study illustrates the remarkable ability of viperin to weaken VHSV in redlip mullet.

Modulation of fish immune response by interferon regulatory factor 4 in redlip mullet (Liza haematocheilus): Delineation through expression profiling, antiviral assay, and macrophage polarization analysis

Interferon regulatory factor 4 (IRF4) is a crucial member of IRF family, which acts as an imperative transcription factor in the development and maturation of multiple lineages of blood cells and also plays a pivotal role in host defense against microbial infections. In the present study, we aimed to investigate the detailed structural and functional aspects of a redlip mullet IRF4 homolog (LhIRF4). The LhIRF4 open reading frame consists of 1347 base pairs encoding 449 amino acids, with the DNA-binding domain sharing significant homology with that of other vertebrate IRF4 homologs. The highest transcription levels of LhIRF4 were observed in the mullet intestine and spleen under normal physiological conditions. Furthermore, a time-dependent upregulation of LhIRF4 transcription was observed in the spleen and head kidney tissues upon pathogenic challenges. When overexpressed in mullet cells, LhIRF4 was localized to the nucleus and significantly stimulated the transcription of several host antiviral genes. Moreover, the overexpression of LhIRF4 strongly inhibited the replication of viral hemorrhagic septicemia virus (VHSV) in vitro. The function of LhIRF4 in regulation of macrophage M2 polarization has also been evidently demonstrated in RAW 264.7 cells. Taken together, our findings indicate the profound role of LhIRF4 in modulating immune responses against microbial infections in redlip mullet.

Mugil soiuy (so-iuy mullet)

This datasheet on Mugil soiuy covers Identity, Distribution, Further Information.

First morphological and phylogenetic data on Ligophorus kaohsianghsieni (Platyhelminthes: Monogenea) from the Black Sea and the Sea of Japan and molecular evidence of deep divergence of sympatric Ligophorus species parasitizing Planiliza haematocheilus.

Ligophorus kaohsianghsieni (Gusev, ) Gusev, was collected from the so-iuy mullet Planiliza haematocheilus (Temminck & Schlegel, 1845) from the Black Sea and the Sea of Japan. DNA sequences data for L. kaohsianghsieni, as well as its morphological characters from the Sea of Japan were obtained for the first time. Significant morphometric and genetic diversity between specimens of L. kaohsianghsieni from the Black-Azov Sea region and the Sea of Japan were not found. For the first time, the molecular phylogeny of L. kaohsianghsieni based on three fragments of the nuclear DNA ribosomal cluster (18S, internal transcribed spacer 1 and 28S) was reconstructed. Molecular analysis of Ligophorus species from the Atlantic and Pacific Oceans revealed a significant phylogenetic distance between L. kaohsianghsieni and two others species (Ligophorus pilengas and Ligophorus llewellyni) from the same host (P. haematocheilus) and region. This result indicates the lack of correspondence between the phylogenetic and geographical closeness of the hosts and the relation of their parasites from the genus Ligophorus.

Assessment of physiological and biochemical indicators of the state of the so-iuy mullet Liza haematocheilus (Temminck & Shlegel, 1845) in the Azov-Black Sea Basin

A comprehensive analysis of the physiological state of the so-iuy mullet, inhabiting the Sea of Azov, has been carried out during its pre-spawning period in 2020–2021. The hematological characteristics of the investigated individuals have been evaluated. It has been revealed that the content of protein and lipids in fish tissues was at the level of average longterm values. The content of protein and lipids in the gonads of females was significantly higher than that of males, which is explained by the forthcoming stage of spawning. It has been determined that the contribution of albumin to the total blood serum protein was minimal, which could be a consequence of the low feeding rate of the fish. At the same time, no stress effect was identified-glucose was within its normal range.

Length–weight relationships of three fish species from Dayang River, northeast China

Length–weight relationships (LWRs) were determined for three fish species from Dayang River, northeast China. The specimens were collected using drift gillnets (80 × 2 m, four mesh sizes: 4, 5, 6 and 8 cm) seasonally from April to November 2020. All LWRs were statistically significant (p < .01), with r2 values being ≥0.95. This study provides a new record of LWR for Takifugu xanthopterus and the new size ranges for Planiliza haematocheila (15.6–66.2 cm) and Lateolabrax japonicus (29.9–45.4 cm).

A new method for quantifying the value of ecological environment damage caused by illegal fishing: A case study

Illegal fishing may trigger structural disruption of the food chain and even damage the entire marine ecosystem. This paper proposes a new method for quantifying the value of eco-environment damage caused by illegal fishing; as an example, we used an illegal fishing case of anchovies in the vicinity of the Yellow River Delta National Nature Reserve. Based on the data from the field investigation and literature, we estimated the number and age distribution of illegally harvested anchovies. Additionally, the potential number of the offspring was calculated according to the potential number and survival rate of anchovy eggs. Due to the unavailability of commercial anchovy fries, “alternative stock enhancement” was recommended to restore the damaged eco-environment. Notably, the alternative species should have similar economic value, status in the food chain, and living areas to anchovies. Eventually, we selected Liza haematocheilus as the alternative species and calculated the total eco-environment recovery cost.

Cytosolic β-catenin is involved in macrophage M2 activation and antiviral defense in teleosts: Delineation through molecular characterization of β-catenin homolog from redlip mullet (Planiliza haematocheila)

β-catenin is a structural protein that makes the cell-cell connection in adherence junctions. Besides the structural functions, it also plays a role as a central transducer of the canonical Wnt signaling cascade, regulating nearly four hundred genes related to various cellular processes. Recently the immune functions of β-catenin during pathogenic invasion have gained more attention. In the present study, we elucidated the immune function of fish β-catenin by identifying and characterizing the β-catenin homolog (PhCatβ) from redlip mullet, Planiliza haematocheila. The complete open reading frame of PhCatβ consists of 2352 bp, which encodes a putative β-catenin homolog (molecular weight: 85.7 kDa). Multiple sequence alignment analysis revealed that β-catenin is highly conserved in vertebrates. Phylogenetic reconstruction demonstrated the close evolutionary relationship between PhCatβ and other fish β-catenin counterparts. The tissue distribution analysis showed the highest mRNA expression of PhCatβ in heart tissues of the redlip mullet under normal physiological conditions. While in response to pathogenic stress, the PhCatβ transcription level was dramatically increased in the spleen and gill tissues. The overexpression of PhCatβ stimulated M2 polarization and cell proliferation of murine RAW 264.7 macrophage. In fish cells, the overexpression of PhCatβ resulted in a significant upregulation of antiviral gene transcription and vice versa. Moreover, the overexpression of PhCatβ could inhibit the replication of VHSV in FHM cells. Our results strongly suggest that PhCatβ plays a role in macrophage activation and antiviral immune response in redlip mullet.

Effects of replacing fish meal with soybean meal on growth performance, feed utilization and physiological status of juvenile redlip mullet Liza haematocheila

The purpose of this study was carried out to elucidate the effects of replacing fish meal (FM) with soybean meal (SBM) on growth performance, feed utilization, and physiological status of juvenile redlip mullet Liza haematocheila. Five test diets were formulated to replace FM protein by SBM at the levels of 0% (SBM0), 25 %(SBM25), 50 %(SBM50), 75 %(SBM75), or 100 % (SBM100). Each treatment was triplicated (20 fish per tank, initial average weight 5.08 ± 0.11 g fish−1). No significant differences were observed in weight gain (WG), feed efficiency (FE), and protein efficiency ratio (PER) between fish fed with SBM0 and SBM75 diets. However, the WG, FE, and PER values showed a decreased trend with fish fed diet containing more than 75 % SBM protein. The value of HSI decreased significantly with increasing dietary SBM levels. An increase of dietary SBM level linearly decreased energy retention (ER) and lipid retention (LR). Concentrations of serum triacylglycerol (TG) and total cholesterol (T−CHO) decreased significantly with increasing the dietary SBM levels. FM substitution with different levels of SBM had no statistical differences in the activities of trypsin, lipase (LPS), and amylase (AMS) on the intestine. Activities of superoxide dismutase (SOD), catalase (CAT), and glutamyl oxaloacetic transaminase (GOT) in the liver increased significantly with increasing dietary SBM levels. The content of malondialdehyde (MDA) in the liver was significant higher in fish fed SBM100 diet than other treatments. Based on the model of broken-line model of WG and FE, it showed that SBM can replace 51.18–52.46% FM in juvenile L. haematocheila.

A copper-zinc-superoxide dismutase (CuZnSOD) from redlip mullet, Liza haematocheila: Insights to its structural characteristics, immune responses, antioxidant activity, and potent antibacterial properties

Copper–zinc superoxide dismutase (CuZnSOD) is a nuclear-encoded metalloenzyme responsible for scavenging harmful reactive oxygen species (ROS). In this study, the CuZnSOD homolog from redlip mullet (Liza haematochelia) (MuCuZnSOD) was structurally and functionally characterized to evaluate its antioxidant capacity, antibacterial properties, and protective level in various pathogenic stress conditions. Structural characteristics of MuCuZnSOD were evaluated using different bioinformatics tools. Pairwise sequence comparison and evolutionary tree structure revealed that the MuCuZnSOD sequence was closely related to the CuZnSOD sequence of Oplegnathus fasciatus with a 94.2% sequence identity. Sequence alignment analysis indicated that the CuZnSOD domain was well conserved. The highest transcriptional expression of MuCuZnSOD was identified in the blood. Immune challenge with lipopolysaccharide (LPS), Lactococcus garvieae, and polyinosinic-polycytidylic acid (poly I:C) exhibited an increased MuCuZnSOD mRNA expression in the blood and liver. Transfected green fluorescent protein-fused MuCuZnSOD was localized in the cytoplasm. Recombinant MuCuZnSOD (rMuCuZnSOD) was overexpressed in a bacterial system. The rMuCuZnSOD possessed significant antioxidant properties as determined by conventional xanthine oxidase assay. The optimum pH and temperature of rMuCuZnSOD were found to be pH 9 and 25 °C, respectively. rMuCuZnSOD enzyme activity increased in a concentration-dependent manner. Treatment with potassium cyanide highly inhibited the rMuCuZnSOD activity. rMuCuZnSOD possessed a significant peroxidation activity in the presence of HCO3ˉ ions as demonstrated by the increased viability in cells treated with the enzyme in the presence of hydrogen peroxide. Antibacterial assays showed that rMuCuZnSOD had significant growth-inhibitory effects on both gram-positive and gram-negative bacteria. Collectively, our findings demonstrate that MuCuZnSOD is an essential antioxidant protein, which regulates the host defense mechanisms and innate immunity under oxidative stress.

Gyrodactylus molweni sp. n. (Monogenea: Gyrodactylidae) from Chelon richardsonii (Smith, 1846) (Mugilidae) from Table Bay, South Africa.

Gyrodactylus molweni sp. n. is described from the body surface and fins of the South African mullet, Chelon richardsonii (Smith, 1846) collected from Table Bay Harbour, Cape Town and is compared to five other Gyrodactylus species described from grey mullets globally namely G. zhukovi Ling, 1963 and G. mugili Zhukov, 1970 from Planiliza haematocheila (Temminck and Schlegel, 1845); G. mugelus Rawson, 1973 from Mugil cephalus L.; G. curemae Conroy and Conroy, 1985 from Mugil curema Valenciennes, 1836 and G. xiamenensis Zang,Yang and Liu, 2001 from Planiliza macrolepis (Smith, 1846). Morphologically, G. molweni sp. n. has prominent ventral bar processes that near cover the hamulus roots, marginal sickles with large rhomboid heels, slender shafts and fine points that extend beyond the sickle toes. Gyrodactylus molweni sp. n. can, however, be readily differentiated: G. mugili and G. xiamenensis have ventral bars with small ventral processes; G. zhukovi has marginal hooks sickles with slender shafts and proportionately short points and open-faced blades; G. mugelus possesses marginal hook sickles with deep, rounded heels, forward slanting shafts and an angular, square line to the inner face of the blades. Although the length of the marginal hooks of G. curemae are similar to G. molweni sp. n., their hamuli are double the size. A GenBank BlastN search with the 931 bp sequence covering ITS1, 5.8S and ITS2 gave no close hits; the nearest species for which sequences are available is G. nipponensis Ogawa and Egusa, 1978 (identity 96.56%, 899/931 bp). The proposal of G. molweni sp. n. as a new species, therefore, is well supported by both the molecular and morphological analyses presented herein. This Gyrodactylus species is the first to be described from C. richardsonii and only the second Gyrodactylus species to be described from the marine environment off the African continent.

Alien fishes in the Black Sea waters of Crimea (Ukraine)

The paper is devoted to alien fish species that have appeared in coastal waters of the Black Sea near Crimea for the past 50 years. The fish fauna of the Black Sea mainly comprises species that represent the Ponto-Caspian and Atlantic-Mediterranean faunal complexes. According to the generalised literature data, 158 fish species of 107 genera of 60 families have been recorded in the Black Sea since the publication of K. F. Kessler’s work (Kessler 1877), all of them representing the Atlantic-Mediterranean complex. In waters of Crimea, 116 species of 86 genera of 51 families have been recorded for the same period. A full checklist of fishes of this complex is presented indicating 31 alien species that have appeared since the 1970s and which belong to 27 genera and 16 families. In waters of Crimea, alien fishes make up 26.5 % of all species, 31.0 % of all genera, and 31.4 % of all families of the Atlantic-Medirranean complex. According to the level of their occurrence in marine waters of Crimea, all recently introduced species are grouped into three categories: regular, sporadic, and casual. Their brief characterisics are given, including synonymy, representation in the fish collection of the NMNH NASU, brief description, distribution, and vector of introduction. It was found that benthic species predominate among introduced fishes that occur regularly in waters of Crimea (12 species, or 80.0 %), while bentho-pelagic and pelagic species are less represented (6.7 % and 13.3 %, respectively). Pelagic and bentho-pelagic species prevail (50.0 % and 37.5 %, respectively) among fishes that occur sporadically. Bentho-pelagic species predominate (57.1 %) among fishes that occur casually. It was discovered that among the 31 alien fishes recorded in the Black Sea waters of Crimea for the past 50 years predominate those that have appeared here due to the natural process of mediterranisation (22 species, 71.0 %). It was imposibble to determine the vector of introduction of 4 species (12.9 %). The appearance of 5 species, which represent 16.1 % of all alien species, is related to anthropogenic factors. It can be also concluded that benthic species predominate among the alien fishes (14 species, or 45.2 %), while bentho-pelagic (9 species) and pelagic (8 species) fishes make up 29.0 % and 25.8 %, respectively. Of the 31 introduced fishes, 10 (32.2 %) have naturalised and acclimatised in marine waters of Crimea and have founded independent breeding populations. Among them, representatives of the family Gobiidae notably prevail, followed by the taxonomically close family Oxudercidae, whereas one species belongs to the family Blenniidae. The so-iuy mullet, which is the only representative of the pelagic ecological group, was introduced intentionally.

Ekologicheskoye sostoyaniye akvatorii Vostochnogo Sivasha v ranneletniy sezon 2020 goda

The paper studies the ecosystem of the Eastern Sivash in the context of natural and anthropogenic influence. The data collected during the expedition of the Azov-Black Sea Branch of the FSBSI “VNIRO” conducted in early summer 2020 were used as original empirical evidence. Specific features of hydrological and hydrochemical conditions, as well as species composition, distribution, and abundance of ichthyoplankton were indicated. It was shown that the values of pH, nitrates, nitrites, and phosphates did not exceed MPCs established for fishery water bodies within the entire water area under study; the range of dissolved oxygen content was wide: 3.63–9.13 mg/dm3 . By comparison of the environmental status of the biocoenoses during early summer 2020 with the data collected during a similar survey in 2019, it was found that the water temperature at site 4 is lower by 1.9–2.7 °C. Further salinization of the Sivash was recorded: the lowest salinity in 2019 ranged within 32–38 ‰ and the highest one ranged within 83–86 ‰; in 2020, these values were 36–43 ‰ and 91–97 ‰, respectively. In terms of spatial distribution, the range of the increase in salinity was 4.36–16.69 ‰, with the highest value being recorded at site 2 (11.51–16.69 ‰) and the eastern part of site 3 (13.22 ‰). To a lesser extent (by 4.36–6.26 ‰), an increase in salinity was recorded at site 4 and the western part (5.27 ‰) of site 3. The results of plankton net surveys showed that ichthyoplankton was represented almost exclusively by larvae of big-scale send smelt, which had the densest distribution at site 1 at a salinity of 89 ‰, and on the border between sites 2 and 3 at a salinity of 74 ‰. The upper limit of salinity at which this fish reproduction is possible lies within the range 75–90 ‰. The absence of so-iuy mullet eggs and juveniles at a salinity higher than 32–36 ‰ in May – June of 2019–2020 during the peak of so-iuy mullet spawning does not provide a reason to include the Sivash Bay among the Azov Sea areas important for reproduction of this fish species

Государственные меры по развитию рыбохозяйственного комплекса Российской Федерации. Политика кластеризации. Потенциал развития рыбопромышленных кластеров в Азово-Черноморском бассейне полуострова Крым

The issues of state regulation and clustering policy in the Russian fisheries complex are considered, organizational shortcomings, obstacles to the full use of the biological potential of fisheries, difficulties in financing the business of cluster participants are revealed, and the need for an adaptation period for the formation of intra-cluster relations is justified. The need for leveraged sources of financing requires the development of financial models with affordable loans under the current investment lending mechanism. A special credit product will provide a transparent system of relations between state structures, participants of the fishing cluster and credit institutions. The proposed scheme of lending to clusters with real estate collateral and collateral for manufactured products is aimed at stable relations with credit institutions. This will lead to the formation of a collective share capital and the creation of management structures responsible for operational management and interaction with investors and financial institutions. The Azov-Black Sea basin of the Crimean Peninsula has the potential to restore biological resources, develop aquaculture, and produce feed for aquaculture. Clusters for targeted programs of artificial breeding in the marine area of rainbow trout, so-iuy mullet, oysters, mussels and other valuable biological resources successfully implement the projects «Valuable seafood», «Food pelagic». The renewal of the fishing fleet will increase the volume of fish production by 2.5-3 times and expand the raw material base of processing enterprises. The development of various forms and channels of sales of fish products with high added value will increase the profitability of the business and meet consumer demand in the domestic market.

Analytical assessment of the so-iuy mullet in the Azov Sea using XSA cohort model

Analytical assessment of the so-iuy mullet in the Azov Sea using XSA cohort model

β-hydroxybutyrate (β-HB) exerts anti-inflammatory and antioxidant effects in lipopolysaccharide (LPS)-stimulated macrophages in Liza haematocheila

Poly-β-hydroxybutyrate (PHB) can be hydrolyzed to β-hydroxybutyrate (β-HB) in the intestinal tract of animals, and dietary PHB supplementation could enhance the immunity and disease resistance of aquatic animals. Antioxidant system is responsive to PHB stimuli via MAPK/PI3K-Akt/TNF/NF-κB/TCR/TLR signaling pathways. However, the precise immunopotentiation mechanism needs further study. In this study, macrophages from spleen in Liza haematocheila was used to study the effect of β-HB on cell viability and antioxidant function to illustrate the immunopotentiation mechanism of PHB. The results showed that β-HB (100 μg/mL) promoted the viability of macrophages and balanced the production of reactive oxygen species, but inhibited the excessive production of intracellular nitric oxide. In order to further explore the immunopotentiation mechanism of β-HB, LPS (100 μg/mL) was used to induce the inflammation and investigated the inhibitory effect of β-HB on inflammation. The results showed that LPS could induce inflammation successfully, and β-HB exerted anti-inflammatory and antioxidant effects in LPS-stimulated macrophages. Compared with LPS stimuli alone, the expression of anti-inflammatory genes NF-κBIA, MAP3K8 and TLR5 in β-HB pretreatment group was up-regulated, and the expression of pro-inflammatory genes TNFSF6, TNF-α, PI3K, NF-κB and TLR1 down-regulated. It suggested that β-HB inhibited the inflammatory response by up-regulation of anti-inflammatory genes such as NF-κBIA, thereby enhancing the immunity of the body.

Structural analysis of toll-like receptor 18 from soiny mullet (Liza haematocheila): Giving insights on the ligand binding mechanism of fish specific TLRs

Toll-like receptors (TLRs) are important pattern recognition receptors (PRRs) of innate immune system, playing crucial roles in immune defense against pathogens. TLR18, a member of TLR1 family, is fish-specific TLR and involves in the immune response against bacterial infection. Currently, the structural biology of fish TLR18 is poorly elaborated. In this study, the structure and ligand binding of TLR18 (smTLR18) of soiny mullet (Liza haematocheila), an economically valuable aquaculture mugilid species, were analyzed. The extracellular domain (ECD) of smTLR18 formed an open-loop horseshoe-shaped structure with the concave surfaces made up of 19 parallel β-strands (LRR1-LRR19), lacking Z-loop that seen in human TLR9. The intracellular Toll/interleukin (IL)-1 (TIR) domain contained a central 4-parallel β-sheet (βA-βD) surrounded by 5 α-helices (αA-αE). Molecular docking analysis revealed that both ECD domain and TIR domain of smTLR18 could form homodimers. For the ECD homodimer, the main residues involved in dimer formation were located from LRR10 to LRR14. For the TIR homodimer, the residues involved in dimer formation were located in BB loop, αB helix, αC helix and DD loop. Ligand binding analyses revealed that peptidoglycans (PGNs) and lipopolysaccharides (LPS), two main bacterial pathogen-associated molecular patterns (PAMPs), were the potential ligands of smTLR18. The van der Waals and Coulombic interactions contributed to the interactions between smTLR18 and PGNs, while only van der Waals dominated the interactions between smTLR18 and LPS. The residues involved in ligands binding were located from LRR9 to LRR13. Our results provided the structural bases for elucidate the ligand binding of fish TLR18.