Melanomacrophage Centers Research Articles

Dietary curcumin supplementation can enhance health and resistance to ammonia stress in the greater amberjack (Seriola dumerili)

We evaluated the effect of dietary curcumin supplementation on the antioxidant capacity of the liver and the resistance of the liver and spleen to ammonia stress in the great amberjack (Seriola dumerili). Three isonitrogenous and isolipidic test diets were prepared by supplementing incremental levels of dietary curcumin at 0 mg/kg (CUR0%, control), 100 mg/kg (CUR0.01%), and 200 mg/kg (CUR0.02%), respectively. Each diet was randomly assigned to triplicate groups of 15 fish per tank. At the end of the feeding experiment, dietary curcumin supplementation positively modulated antioxidant-related genes and enzyme activity in liver tissues. After the ammonia challenge, dietary supplementation with the appropriate level of curcumin alleviated ammonia stress in liver tissue by upregulating the relative expression of GSH-Px and downregulating the relative expression of Keap1 and GR. Meanwhile, ammonia stress in spleen tissue could also be alleviated by upregulating the relative expression of CAT, downregulating the relative expression of GR, and increasing the activity of SOD and GSH. After the recovery, dietary supplementation with curcumin still alleviated ammonia stress in the liver tissue by upregulating the relative expression of CAT, downregulating the relative expression of Keap1 and GR, and increasing the activity of SOD and GSH. On the other hand, ammonia stress in spleen tissue was still alleviated by upregulating the relative expression of Mn-SOD and increasing the activity of SOD and GSH. The histological structure results also showed that liver cells in the curcumin-containing groups exhibited a positive impact on cell boundaries, alignment, and nuclei after the ammonia challenge and recovery. Spleen cells in the curcumin-containing groups exhibited greater aggregation of melano-macrophage centers after the ammonia challenge and recovery. These results suggest that dietary curcumin supplementation at 100 mg/kg can promote the health condition and resistance to ammonia stress of the greater amberjack.

Effect of Prenatal Hypoxia on the Liver of Rats

The state of the liver of one-month-old, three-month-old and six-month-old rats exposed to hypoxia during the embryonic period of intrauterine development was studied. It has been shown that prenatal hypoxia has a significant damaging effect on the liver, and the negative aspects of this factor can be traced in the later stages of ontogenesis. Histological study showed that in the liver of one-month-old experimental rats, hepatocyte hypertrophy, an increase in the size of their nuclei, and an increase in the number of binuclear hepatocytes were observed. In a comparative analysis of the data in the control and experimental groups of rats at the age of three months, no significant morphometric changes were observed. However, histological examination of the liver of three-month-old rats revealed small foci of extramedullary hematopoiesis in the parenchyma. Hemodynamic disturbances in the vessels of the liver were also determined. No significant changes in morphometric parameters were observed in the liver of the control and experimental groups of 6-month-old rats. However, melanomacrophage centers were found in the liver parenchyma, which indicates the presence of an inflammatory process. Despite the completion of the recovery processes in 6-month-old rats, the observed inflammatory processes and hemodynamic disturbances showed that prenatal hypoxia causes liver pathologies at later stages of ontogenesis. So, we can conclude that, under the influence of prenatal hypoxia, there are significant changes in the liver parenchyma, which affects the subsequent state of the body.

Device implant based on poly (lactic acid) with vitamin E for vaccine delivery system in Tilapia: Study for biocompatibility and biodegradation

The use of Poly (lactic acid) (PLA) as a slow-release vehicle for vaccines has attracted the attention of researchers, since its insertion improves the uptake of them, and reduces side effects or by stimulating recruited defense cells, assisting immunity without the need for booster vaccine doses. Seeking to develop new strategies for the administration of drugs and vaccines in aquaculture, we evaluated the biocompatibility and biodegradation of polymeric PLA devices and PLA plus vitamin E devices, implanted through subcutaneous (SC) and intraperitoneal (IP) routes in Nile tilapia. To carry out this study, 84 male tilapia (initial 243.82 ± 56.74 g; final 400.71 ± 100.54 g) were randomly distributed in 3 tanks (n = 28 fish per treatment/tank). The devices were prepared in two formulations: neat PLA (containing 100% PLA) and PLAVE (PLA plus vitamin E) implanted using a commercial AnimalTag® applicator, and non-implanted fish (control). Fish were sampled 15, 30, 60, and 120 days post-implantation (DPI). Blood analysis was used to access blood cells and blood smear for differential leucocytes count. Serum biochemistry to evaluated changes in serum proteins and glycemia. Histopathological investigation using hematoxylin-eosin (H&E) was used to assess polymer-tissue interaction. Histochemistry and immunohistochemistry was used to detection immune cells and phagocytes in capsule, and analyses of melanomacrophage centers (MMCs) to morphometric evaluation and percentage amount of melanin, hemosiderin and lipofucsin pigments. Histopathological study revealed an increase of capsular formation and inflammatory cell infiltration in PLAVE-implanted tilapia through SC route (15 DPI). Tilapia implanted with PLAVE and PLA (SC) presented mast cells and eosinophilic granular cells during 15, 30, and 60 DPI, with a decrease in these cells in the fibrous capsule around the polymer at 120 DPI. PLAVE implanted tilapia SC at 60 DPI showed significantly phagocytosis points than other groups. Phagocytic cells (F4/80+) were observed near to biopolymers in phagocytosis sites. Lipofuscin at 120 DPI in spleen melanomacrophage centers were significantly high in PLAVE implanted tilapias when compared to fish with PLA implants and control. The serum biochemical study of tilapia did not reveal changes in cytotoxicity and liver function in implanted fish. The absence of side effects in hematological and biochemical findings, including the absence of mortality after device implantation, proves its clinical safety. PLA implants in tilapia have demonstrated biocompatibility, biodegradation, clinical safety, and excellent evolution of foreign body inflammatory responses.

Experimental Infection of Goldfish (Carassius auratus L.) and Tilapia (Oreochromis niloticus L.) with Koi Ranavirus (KIRV)

Background: Ranaviruses are now emerging as serious pathogens for the amphibians, reptiles and fishes. The aim of this study was the determination of the susceptibility of goldfish (Carassius auratus L.) and tilapia (Oreochromis niloticus L.) to experimental infection with Koi ranavirus (KIRV). Methods: The experimental fishes were challenged with an infective dose of KIRV (106.8 TCID50/ml) by intraperitoneal injection (IP), while the control groups were injected with L-15 medium. Target tissues were collected from the experimental fishes infected with virus at 3, 7, 14, 21 and 28 dpi. Tissue samples were subjected to detection of KIRV by polymerase chain reaction (PCR), cell culture assay and histopathological technique. Result: This study reports no specific clinical signs and mortality due to virus infection during the experimental period. Experimentally infected goldfish and tilapia were tested positive for KIRV by PCR at 3 dpi, while target viral DNA was also detected in tilapia at 7 dpi by PCR. However, specific DNA of KIRV was not detected in tissues of experimental fish sampled at later experimental study periods. Cell culture assay revealed no cytopathic effect in the Epithelioma Papulosum Cyprini (EPC) cell line at all sampling time points. Histopathological study revealed focal necrosis, shrunken glomerulus and detached epithelium of tubules in kidney tissue at 3 and 7 dpi in gold fish and melanomacrophage cells and focal necrosis of glomerulus and detachment of the epithelium of tubules in kidney tissue at 3 and 7 dpi in tilapia. Melanomacrophage centers and necrosis were observed in spleen tissues of goldfish and tilapia at 3 and 7 dpi. The challenge study indicated that goldfish and tilapia are not the targeted species for KIRV.

An in vivo study of the toxic effects of triclosan on Xenopus laevis (Daudin, 1802) frog: Assessment of viability, tissue damage and mitochondrial dysfunction

The present study describes the in vivo effect of triclosan on the frog Xenopus laevis (Daudin, 1802). We have found a dose-dependence of the effect of triclosan on the survival of frogs. At a dose of 2 mg/L, the death of frogs was observed already on the 4th day of the experiment, while at a concentration of 0.5 mg/L, the frogs remained viable for 11 days. Triclosan caused damage to the liver tissue, which was expressed in an increase in the area of hemorrhage and the number of melanomacrophage centers. 0.5 mg/L of this agent did not affect the number of frog red blood cells, but reduced their osmotic resistance. Keeping animals in water containing triclosan (0.5 mg/L for 96 h) led to the suppression of the state 3 respiration rate of frog liver mitochondria. This effect was accompanied by suppression of the combined activity of complexes II and III of the mitochondrial respiratory chain. In parallel with this, we observed a reduction in the Ca2+ retention capacity of frog liver mitochondria, indicating a decrease in the resistance of organelles to mitochondrial permeability transition pore opening. The paper discusses the effects of triclosan on aquatic organisms.

Aggravation of hepatic lipidosis in red-footed tortoise Chelonoidis carbonaria with age is associated with alterations in liver mitochondria.

The occurrence of hepatic lipidosis is commonly reported in different reptilian species, especially in animals under captivity. Liver accumulation of fat is associated with disorders, better described in mammals as non-alcoholic fatty liver diseases (NAFLD), ranging from simple steatosis, to non-alcoholic steatohepatitis (NASH), and to more severe lesions of cirrhosis and hepatocellular carcinoma. Mitochondria play a central role in NAFLD pathogenesis, therefore in this study we characterized livers of ad libitum fed captive red-footed tortoise Chelonoidis carbonaria through histological and mitochondrial function evaluations of juvenile and adult individuals. Livers from adult tortoises exhibited higher levels of lipids, melanomacrophages centers and melanin than juveniles. The observed high score levels of histopathological alterations in adult tortoises, such as microvesicular steatosis, inflammation and fibrosis, indicated the progression to a NASH condition. Mitochondrial oxygen consumption at different respiratory states and with different substrates was 30 to 58% lower in adult when compared to juvenile tortoises. Despite citrate synthase activity was also lower in adults, cardiolipin content was similar to juveniles, indicating that mitochondrial mass was unaffected by age. Mitochondrial Ca2+ retention capacity was reduced by 70% in adult tortoises. Overall, we found that aggravation of NAFLD in ad libitum fed captive tortoises is associated with compromised mitochondrial function, indicating a critical role of the organelle in liver disease progression in reptiles.

Evaluation of the immune responses against enteric septicemia and determination of immune markers for selective breeding of pangasius families (Pangasianodon hypophthalmus)

The immune response of two groups of selective breeding panagasius families: susceptible (or sensitive) (S) and resistant (R) family groups, including red blood cell count (RBC count), white blood cell count (WBC count), neutrophil (NEU), monocyte (MONO), lymphocyte (LYM), and melano-macrophage centers (MMCs) count in liver, kidney and spleen tissue and antibody titers (ABT) against the bacteria Edwardsiella ictaluriwere evaluated in this research. Fish were sampled at five truncated points after infection with the bacteria Edwardsiella ictaluri including before the challenge, 24, 48, 264, and 312 hpi. The immune response of the R group was more effective than that of the S group, showing: (1) RBC decreased less during the challenge; (2) WBC, NEU, MONO, LYM increased more rapidly, especially at the truncated point 24-48 hpi; (3) MMCs in liver, kidney, and spleen of the R group increased faster up to the truncated point 48 hpi while the S group increased more slowly and only up to the truncated point 24 hpi; (4) ABT were higher in all stages of the challenge. The research developed a multivariable logistic regression model with immune markers such as NEU, ABT and MMCs in the liver at the truncated point of 24-48 hpi to identify individuals which were resistant to Enteric Septicemia of Catfish (ESC), with sensitivity and specificity of 91.7, 95.0%, respectively.

Structural and Functional Aspects of the Spleen in Molly Fish Poecilia sphenops (Valenciennes, 1846): Synergistic Interactions of Stem Cells, Neurons, and Immune Cells.

Simple SummaryFish are free-living organisms who are dependent on their innate immune system for survival. This system is fundamental for the defense mechanisms against invading pathogens. The head kidney, spleen, and thymus are the main immune organs in fish, albeit with slightly different roles between species. This study aims to highlight the cellular components of the spleen in the molly fish (Poecilia sphenops) by providing some background on their potential role in the immune system of fish. The splenic parenchyma of molly fish is comprised mainly of red pulp intermingled with clusters of white pulp cells. The main cells identified in this study included: erythrocytes, neurons, dendritic cells, stem cells, epithelial reticular cells, lymphocytes, ellipsoids, and granular leukocytes (eosinophils, basophils, neutrophils), and macrophages. The current study demonstrated a variety of immune cell types with specific functions in the spleen of molly fish. The strong positive immunoreactivity of the cellular constituents of the spleen for APG-5, IL-1β, NF-κB, and TGF-β suggests its critical role in immunity.In fish, the spleen is the prime secondary lymphoid organ. It has a role in the induction of adaptive immune responses, in addition to its significance in the elimination of immune complexes. This study was conducted on 18 randomly obtained adult molly fish (Poecilia sphenops) of both sexes using histological, immunohistochemical, and ultrastructural studies to highlight the cellular components of the spleen and their potential role in the immune system. The spleen of molly fish was characterized by the presence of well-distinct melanomacrophage centers, and other basic structures present in higher vertebrates including red and white pulps, blood vessels, and ellipsoids. Some mitotic cells could also be identified in the red pulp. Mast cells with characteristic metachromatic granules could be seen among the splenic cells. Rodlet cells were randomly distributed in the spleen and were also observed around the ellipsoids. The white pulp of the spleen expressed APG5. The expressions were well distinct in the melanomacrophages, leukocytes, and macrophages. Myostatin was expressed in leukocytes and epithelial reticular cells. IL-1β showed immunoreactivity in monocytes and macrophages around the ellipsoids. NF-κB and TGF-β were expressed in macrophages and epithelial reticular cells. Nrf2 expression was detected in stem cells and rodlet cells. Sox-9 had a higher expression in epithelial reticular cells and stem cells. The high frequency of immune cells in the spleen confirmed its role in the regulation of both innate and adaptive immunity, cell proliferation, and apoptosis.

Biological responses of whitefish (Coregonus lavaretus L.) to reduced toxic impact: Metal accumulation, haematological, immunological, and histopathological alterations

Bioaccumulation of the main pollutants in the organs of whitefish, as well as their haematological parameters, were examined dynamically over a 40-year period in historically contaminated Lake Imandra. A quantitative histological analysis was performed to assess the physiological state of whitefish and histopathologies of organs, as well as their physiological and biochemical functions in the current period of toxic load decline. Biological reactions of whitefish from the historically contaminated area have been greatly modified in contrast to those of whitefish from the never contaminated area of the lake, and this shift persisted even after approximately 20 years of toxic load decline. First, high antioxidant status supports the body's systems, smoothing over the negative consequences of metal toxicity, phagocytosis and inflammatory reactions. Moreover, the defence mechanism of whitefish from the historically contaminated area actively uses the oxidative systems of nonspecific immunity. Second, the adaptive strategy is aimed at improving gas exchange without compensatory proliferation of gill structure, which increases their functional surface and reduces the distance to the bloodstream, as well as increasing haemoglobin in maturing erythrocytes. Third, the higher efficiency of endo- and phagocytosis was confirmed by detecting increased monocytes and macrophages in the peripheral blood and decreased melano-macrophage centres in the fish kidney. Elevated accumulation of Fe, Cu, and Se may serve a sign of liver pathology, while elevated accumulation of Zn and Co already indicates kidney pathology, which is confirmed by histopathological alterations.

Lympho-Hematopoietic Microenvironments and Fish Immune System.

Simple SummaryTeleost fish, the most abundant group of vertebrates, represent an excellent tool to establish possible correlations between the histological organization of their lymphoid organs and their immunological capacities. This approach allows us to analyze embryonic and larval lymphopoiesis, the remarkable organization of the teleost thymus, the role of the kidney as a true equivalent of the lympho-hematopoietic bone marrow of higher vertebrates, the mechanisms of antigen trapping in both ellipsoids and the so-called melano-macrophage centers (MMCs) and their relation with the generation of memory and the lack of germinal centers, and the extended development of the lymphoid tissue associated to mucosae.In the last 50 years information on the fish immune system has increased importantly, particularly that on species of marked commercial interest (i.e., salmonids, cods, catfish, sea breams), that occupy a key position in the vertebrate phylogenetical tree (i.e., Agnatha, Chondrichtyes, lungfish) or represent consolidated experimental models, such as zebrafish or medaka. However, most obtained information was based on genetic sequence analysis with little or no information on the cellular basis of the immune responses. Although jawed fish contain a thymus and lympho-hematopoietic organs equivalents to mammalian bone marrow, few studies have accounted for the presumptive relationships between the organization of these cell microenvironments and the known immune capabilities of the fish immune system. In the current review, we analyze this topic providing information on: (1) The origins of T and B lymphopoiesis in Agnatha and jawed fish; (2) the remarkable organization of the thymus of teleost fish; (3) the occurrence of numerous, apparently unrelated organs housing lympho-hematopoietic progenitors and, presumably, B lymphopoiesis; (4) the existence of fish immunological memory in the absence of germinal centers.

Multi-biomarkers approach to assess the toxicity of novel insecticide (Voliam flexi®) on Clarias gariepinus: From behavior to immunotoxicity

This study was conducted to determine for the first time the immunological, histopathological, histochemical, and ultrastructural changes; hematological and biochemical alterations; and poikilocytosis induced in Clarias gariepinus by Voliam flexi® 40% WG (thiamethoxam + chlorantraniliprole). Beside control fish, juvenile C. gariepinus were subjected to three sublethal concentrations of Voliam flexi® (43.5, 87.5, and 175 mg/L) for 15 days. Voliam flexi® induced immunotoxic impairments in C. gariepinus, such as a decrease in some immunity variables (lysozyme and phagocyte activity, immunoglobulin concentration, and nitro blue tetrazolium level). It also caused an extreme increase in the levels of primary cytokines (interleukin-1β and IL-6), compared with the control. The toxic effects of Voliam flexi® increased gradually with the increasing concentrations tested. Histological examination of the liver demonstrated necrosis, vacuolated hepatocytes (fatty deposition), melanomacrophage centers, foci of inflammatory cells, congested and dilated blood sinusoids, hepatic degeneration, fibrosis increment (Sirius Red stain), and glycogen depletion, as well as cytopathological alterations. We conclude that the toxic effects of Voliam flexi® must be restricted or prevented by using control mechanisms in aquatic systems.

Aggregation of IgM+, TCRβ+ and CD4+ Cells around melanomacrophage centers - evidence of an organized lymphoid structure in a teleost

Abstract The study of immunity in non-model organisms has the potential to reveal the evolved diversity of the immune system. However, such studies are hampered by the paucity of species-specific reagents. Advances in single-molecule RNA-ISH overcomes these setbacks and allows for the detection of potentially dozens of gene targets in a single tissue section. We examined the spatial expression of immune genes in the splenic tissue of a teleost, threespine stickleback, using the advanced multiplexed RNAScope Hiplex assay. Threespine stickleback, a small teleost found throughout the Northern Hemisphere, is an emerging immunologic model. It has been proposed that teleost humoral adaptive immunity initiates in the melanomacrophage center (MMC), a putative evolutionary precursor to germinal centers (GC), however this has not been directly tested. Teleosts lack GCs, yet still generate affinity matured antibodies in response to antigen challenge. We find that stickleback MMCs increase in size in response to antigen immunization but not to control injection, suggesting that MMC response is antigen driven, similar to the mammalian GC. Analysis of splenic tissue indicates that IgM mRNA expressing cells aggregate in discrete regions around stickleback MMCs. Similarly, CD4 and TCR-β expressing cells aggregate near IgM+ cells, comparable to the organization of B and T cells in mammalian GCs. These findings suggest that stickleback splenic tissues have an organized structure, focused around the MMCs, and support the hypothesis that MMCs could be the site of teleost adaptive immunity and the evolutionary precursors to GCs. This study also highlights the application of RNAScope in a non-model organism. Supported by NIH RO1AI146168

Histological and Chemical Analysis of Heavy Metals in Kidney and Gills of Boops boops: Melanomacrophages Centers and Rodlet Cells as Environmental Biomarkers.

Industrialization has resulted in a massive increase in garbage output, which is frequently discharged or stored in waterways like rivers and seas. Due to their toxicity, durability, bioaccumulation, and biomagnification, heavy metals (such as mercury, cadmium, and lead) have been identified as strong biological poisons. Their presence in the aquatic environment has the potential to affect water quality parameters and aquatic life in general. Teleosts’ histopathology provides a sensitive indicator of pollutant-induced stress, because their organs have a central role in the transformation of different active chemical compounds in the aquatic environment. In particular, the gills, kidneys, and liver are placed at the center of toxicological studies. The purpose of this study is to examine the morphological changes caused by heavy metals in the kidney and gills of Boops boops, with a focus on melanomacrophages centers (MMCs) and rodlet cells (RCs) as environmental biomarkers, using histological and histochemical stainings (hematoxylin/eosin, Van Gieson trichrome, Periodic Acid Schiff reaction, and Alcian Blue/PAS 2.5), and immunoperoxidase methods. Our findings show an increase of MMCs and RCs linked to higher exposure to heavy metals, confirming the role of these aggregates and cells as reliable biomarkers of potential aquatic environmental changes reflected in fish fauna. The cytological study of RCs and MMCs could be important in gaining a better understanding of the complicated immune systems of teleosts.

Deleting ORF71L of infectious spleen and kidney necrosis virus (ISKNV) resulted in virulence attenuation in Mandarin fish

Infectious spleen and kidney necrosis virus (ISKNV), the type species of the genus Megalocytivirus, infects a variety of teleost fish species and causes substantial losses in the aquaculture industry worldwide. ISKNV ORF71L is 1611 bp in length, encodes a 537-amino-acid peptide and was previously identified as a viral structural protein in the ISKNV virion. In this study, the ORF71L deletion mutant virus strain ISKNV-Δ71 was obtained through a homologous recombination approach. The multistep growth curves showed that ISKNV-Δ71 replication was faster than ISKNV-WT replication in mandarin fish fry cells (MFF-1 cells) before 48 h post-infection (hpi). The cumulative mortality of ISKNV-Δ71-infected mandarin fish (Siniperca chuatsi) was lower than that of fish infected with ISKNV-WT. The copy numbers of viral genome equivalents (GEs) in ISKNV-Δ71-infected mandarin fish spleens were also lower than those in ISKNV-WT-infected spleens. Deletion of ORF71L resulted in ISKNV virulence attenuation in mandarin fish. Furthermore, we found that the number of melanomacrophage centers (MMCs) in ISKNV-Δ71-infected mandarin fish spleens was higher than that in ISKNV-WT-infected mandarin fish spleens. Transcriptomic analysis showed that the cytokine–cytokine receptor interaction pathway had the most significant change between ISKNV-Δ71- and ISKNV-WT-infected MFF-1 cells. These results indicated ORF71L is a virulence-related gene of ISKNV. ORF71L could be considered as a potential target for the development of engineered attenuated live vaccines via multigene deletion or as a potential insertion site for exogenous protein expression.

Natural variability and potential use of melanomacrophage centres as indicators of pollution in fish species from the NW Mediterranean Sea

The present study provides a baseline assessment of the prevalence and densities of splenic melanomacrophage centres (MMCs) in 18 fish species from the NW Mediterranean Sea related to spatiotemporal and environmental factors and fish traits. Their correlation with other established health indicators, such as body condition indices (condition factor, hepatosomatic and gonadosomatic indices), parasite community descriptors and histological assessment of target organs (gills, liver and spleen) is also assessed. Despite MMCs variability is mainly attributed to the species identity and fish size, their potential use as generic biomarkers of health condition is pointed out for certain species (e.g. Spicara maena and Micromesistius poutassou) in which an increased response was identified, and whose potential drivers are discussed. Most importantly, present results provide a comprehensive assessment of MMCs in the fish community for future studies in the area.

Behavioral and histo-pathological indices of striped catfish (Pangasionodon hypophthalmus) exposed to different salinities

Salinity intrusion due to climate changes in the coastal area is substantially jeopardized for sustainable aquaculture. This study was focused on behavioral and histo-pathological changes (gills, liver and kidney) of striped catfish (Pangasionodon hypopththalmas) exposed to four salinities (0, 4, 8 and 12 ppt), each with three replications for 56 days. Both behavioral and histological analyses were carried out for durations of 7, 14, 28 and 56 days of exposure. Mild to moderate behavioral abnormalities such as rate of swimming, food intake, gill motion and convulsions were observed in 8 ppt, but pronounced alterations were detected at higher salinity (12 ppt), increasing with longer exposures. Similarly, mild to moderate histological anomalies in gills (hypertrophy of the chloride cell, telangiectasia at the tips of secondary lamellae, epithelial necrosis, fusion of some secondary lamellae and lifting of the lamellar epithelium), liver (vacuolation, blood congestion, melanomacrophage centers, patchy degeneration, necrosis and hypertrophy nucleus) and kidney (degeneration of renal tubule, enlarged Bowman's capsule, increased space in between glomerulus center, melanomacrophage centers, vacuolation and necrotic cell in the hematopoetic tissue) were detected in 8 ppt but pronounced alterations were detected at higher salinity (12 ppt) with increasing the days of exposure. This preliminary study revealed more profound responses to higher salinity exposure in the striped catfish, and this species could serve as a model bio-indicator in costal aquaculture.

Apelin participates in host defense against bacterial infection and promotes bacterial clearance in large yellow croaker (Larimichthys crocea)

Apelin, a pleiotropic cytokine with various biological activities, plays important roles in both infectious and noninfectious inflammatory diseases in mammals by regulating immune responses. However, the effect of apelin on the host defenses against microbial infections in teleosts is still unknown. Therefore, this study aimed to characterize the molecular features of apelin in Larimichthys crocea (designated LCapelin ) and to investigate the roles of LCapelin in bacterial infection in vivo. The complete open reading frame (ORF) of LCapelin , which encodes a 77-amino acid precursor, was cloned and identified. In healthy fish, LCapelin was constitutively expressed in all 10 tissues examined, and the highest expression level was observed in muscle tissue. Following a challenge with Vibrio parahemolyticus , the mRNA expression of LCapelin was significantly increased at 4 hpi in the spleen. However, in the liver, the expression of LCapelin decreased initially but gradually returned to normal. Furthermore, pretreatment with the synthetic peptide LCapelin-13 prior to Vibrio parahaemolyticus challenge significantly ameliorated clinical signs, inhibited the expression of inflammatory cytokines (TNF-α, IL-1β, and IL-6) in the spleen and liver, decreased the proliferation of splenocytes and melanomacrophage centers (MMCs) in the spleen, and promoted bacterial clearance. Taken together, our results show that LCapelin participates in host defense against V. parahaemolyticus infection in L. crocea and may have potential application in the development of new strategies to combat infectious diseases in teleosts. • LCapelin expression responded to Vibro parahaemolyticus challenge in spleen and liver. • LCapelin significantly ameliorated the clinical signs of experimental vibriosis. • LCapelin inhibited Vibrio parahaemolyticus induced-expression of inflammatory cytokines. • LCapelin promoted bacterial clearance in vivo.

Hepatic transcriptomic and histopathological responses of common carp, Cyprinus carpio, to copper and microplastic exposure

The combined effects of copper and polyvinyl chloride (PVC) microparticles were investigated on the metal accumulation, histopathological biomarkers, and targeted transcriptomics in Cyprinus carpio liver. The fish were exposed to 0.25 mg/L copper and/or 0.5 mg/L PVC microparticles over a 14-d period. The results showed that hepatic copper accumulation is facilitated by the PVC microparticles presence in water. All treatments induced significant hepatic stress and inflammation; however, the transcriptional responses involving in detoxification pathways and apoptotic mechanisms were mixed and often down-regulated in the fish exposed to copper and/or PVC microparticles. Exposure to copper and/or PVC microparticles induced hypermeia, leukocyte infiltration and increase in melanomacrophage centers number and area. Generally, the severity of the lesions was in the following order: PVC microparticles < copper < copper+ PVC microparticles. In conclusion, PVC MPs act as a copper vector, facilitating accumulation of copper in the fish liver and increasing the tissue damage.

Assessment of the immune responses of macrophages in selective breeding pangasius families (Pangasianodon hypophthalmus) resistant to enteric septicemia of catfish (ESC)

This study aimed to evaluate the non-specific immune responses of macrophages in two selective breeding pangasius family groups: high disease-resistant (A) and low disease-resistant (B) to Enteric Septicemia of Catfish (ESC) caused by Edwardsiella ictaluri. Fish were sampled at five different time points after infection with the bacteria E. ictaluri including before the infection process, 24hpi, 48hpi, 264hpi and 312hpi. There were 372 samples including 192 samples of fish in group A and 180 samples in group B. All of them were used to analyze the amount of melano-macrophage centers in the tissues of liver, kidney and spleen; phagocytosis activity (PA) and phagocytosis index (PI) of the anterior kidney macrophages. Results showed that (1) the number of melano-macrophages of group A fish was higher than that of group B at survey points during the challenge and the difference was significant at 48hpi; (2) PA and PI of group A were higher than that of group B in the period from 48 to 264hpi, specifically, the PI of group A was higher than that of group B, which was statistically significant at 48hpi. The results of this study showed that the differences in non-specific immune responses through melano-macrophages can improve the survival rate and life span of the high disease-resistant family compared to the low disease-resistant family after the challenge with Edwardsiella ictaluri.

The effect of nonylphenol exposure on the stimulation of melanomacrophage centers, estrogen and testosterone level, and ERα gene expression in goldfish

The present study tried to measure the formation of melanomacrophage centers (MMCs) in various organs of male and female goldfish exposed to nonylphenol (NP) and aimed to assess its relationship with the main sexual hormones, estrogen receptor expression, and the pigment content of the MMCs. Immature goldfish were exposed to 10−6 and 10−7 M NP for 25 days. After obtaining blood for measuring testosterone and estrogen (E2) levels, tissue samples were collected from various organs for histological studies, quantifying pigments using ImageJ software and chemical analysis, and measuring ERα gene expression. Results showed that the order of forming MMCs in various organs exposed to NP was liver > spleen > kidney, and the order of ERα gene expression was liver > testes > spleen > kidney in the male, and liver > spleen > kidney > ovaries in the female. Among the three pigments present in MMCs after exposure to the two doses of NP, melanin was more obvious (especially in the liver) and increased mostly in a dose-dependent manner in both sexes (especially in the male). Chemical analyses confirmed these results. Measurement of testosterone and E2 level in male and female goldfish showed that NP had more effect on the concentration of these hormones in male fish, indicating more endocrine-disrupting potential of NP against the male fish. Generally, the increase of melanin content of melanomacrophage centers coincided with the increase of ERα gene expression and decrease of testosterone level in goldfish after exposure to NP.