Study on the osmotic response and function of myo-inositol oxygenase in euryhaline fish nile tilapia (Oreochromis niloticus).

To understand the role of myo-inositol oxygenase (miox) in the osmotic regulation of Nile tilapia, its expression was analyzed in various tissues. The results showed that the expression of miox gene was highest in the kidney, followed by the liver, and was significantly upregulated in the kidney and liver under 1 h hyperosmotic stress. The relative luminescence efficiency of the miox gene transcription starting site (-4,617 to +312 bp) under hyperosmotic stress was measured. Two fragments (-1,640/-1,619 and -620/-599) could induce the luminescence activity. Moreover, the -1,640/-1,619 and -620/-599 responded to hyperosmotic stress and high-glucose stimulation by base mutation, suggesting that osmotic and carbohydrate response elements may exist in this region. Finally, the salinity tolerance of Nile tilapia was significantly reduced after the knocking down of miox gene. The accumulation of myo-inositol was affected, and the expression of enzymes in glucose metabolism was significantly reduced after the miox gene was knocked down. Furthermore, hyperosmotic stress can cause oxidative stress, and MIOX may help maintain the cell redox balance under hyperosmotic stress. In summary, MIOX is essential in osmotic regulation to enhance the salinity tolerance of Nile tilapia by affecting myo-inositol accumulation, glucose metabolism, and antioxidant performance.NEW & NOTEWORTHY Myo-inositol oxygenase (MIOX) is the rate-limiting enzyme that catalyzes the first step of MI metabolism and determines MI content in aquatic animals. To understand the role of miox in the osmotic regulation of Nile tilapia, we analyzed its expression in different tissues and its function under hyperosmotic stress. This study showed that miox is essential in osmotic regulation to enhance the salinity tolerance of Nile tilapia by affecting myo-inositol accumulation, glucose metabolism, and antioxidant performance.

Evaluate the potential use of TonB-dependent receptor protein as a subunit vaccine against Aeromonas veronii infection in Nile tilapia (Oreochromis niloticus).

Aeromonas veronii is an emerging bacterial pathogen that causes serious systemic infections in cultured Nile tilapia (Oreochromis niloticus), leading to massive deaths. Therefore, there is an urgent need to identify effective vaccine candidates to control the spread of this emerging disease. TonB-dependent receptor (Tdr) of A. veronii, which plays a role in the virulence factor of the organism, could be useful in terms of protective antigens for vaccine development. This study aims to evaluate the potential use of Tdr protein as a novel subunit vaccine against A. veronii infection in Nile tilapia. The Tdr gene from A. veronii was cloned into the pET28b expression vector, and the recombinant protein was subsequently produced in Escherichia coli strain BL21 (DE3). Tdr was expressed as an insoluble protein and purified by affinity chromatography. Antigenicity test indicated that this protein was recognized by serum from A. veronii infected fish. When Nile tilapia were immunized with the Tdr protein, specific antibody levels increased significantly (p-value <0.05) at 7 days post-immunization (dpi), and peaked at 21 dpi compared to antibody levels at 0 dpi. Furthermore, bacterial agglutination activity was observed in the fish serum immunized with the Tdr protein, indicating that specific antibodies in the serum can detect Tdr on the bacterial cell surface. These results suggest that Tdr protein has potential as a vaccine candidate. However, challenging tests with A.veronii in Nile tilapia needs to be investigated to thoroughly evaluate its protective efficacy for future applications.

Genetic and morphological characterization of a new genotype of nervous necrosis virus circulating among Nile tilapia in the south of Egypt.

Nervous necrosis virus (NNV) is the causative agent of viral nervous necrosis in freshwater and marine fishes. In this study, NNV circulating among wild and farmed Nile tilapia (Oreochromis niloticus) was genetically and morphologically characterized using reverse transcription polymerase chain reaction (RT-PCR), sequencing analysis, and transmission electron microscopy (TEM). Brain, eye, and other organ (spleen, kidney, heart, and liver) specimens were collected from 87 wild (66) and farmed (21) Nile tilapia fish during their adult or juvenile stage at different localities in Qena and Sohag governorates in southern Egypt. Among them, 57/87 fish showed suspected NNV clinical signs, and 30/87 were healthy. The results revealed that NNV was detected in 66 out of 87 fish (58.62% in the wild and 17.24% in farmed Nile tilapia by RT-PCR), and the prevalence was higher among diseased (55.17%) than in healthy (20.69%) fish. NNV was detected in the brain, eye, and other organs. Using TEM, virion size variations based on the infected organs were observed. Nucleotide sequence similarity indicated that NNVs had a divergence of 75% from other fish nodaviruses sequenced in Egypt and worldwide. Phylogenetic analysis distinguished them from other NNV genotypes, revealing the emergence of a new NNV genotype in southern Egypt. In conclusion, NNV is circulating among diseased and healthy Nile tilapia, and a new NNV genotype has emerged in southern Egypt.

A CD6 homolog of Nile tilapia (Oreochromis niloticus) conserved binding bacteria involved in the regulation of Streptococcus agalactiae induced inflammation.

As a lymphocyte-specific surface receptor belonging to the cysteine-rich superfamily of scavenger receptors, CD6 acts as a pattern recognition receptor for microbial components and is involved in the regulation of inflammatory responses. However, the characteristics and functions of CD6 molecules in lower vertebrates represented by teleost fish are unknown. In this study, a CD6 homolog (designated OnCD6) was characterized from Nile tilapia (Oreochromis niloticus), and establishing its role as a PRRs that participates in immune recognition. OnCD6 contains an open reading frame of 1872 bp that encodes a peptide of 623 amino acids, and contains two conserved SR domain. Multiple sequence alignment revealed that OnCD6 shares a relatively high level of identity with those of other species. Transcriptional expression analysis revealed that OnCD6 was constitutively expressed in immunes tissues such as head kidney and thymus. The expression level of OnCD6 in mainly immune tissues were found significantly upregulated after the injection of Streptococcus agalactiae (S. agalactiae). Moreover, OnCD6 protein was located in the head kidney and brain, mainly over the plasma membrane of lymphocytes in these immune tissues. In vitro experiments showed that CD6 extracellular protein bound to and aggregated several Gram-positive and -negative bacterial strains through the recognition of bacterial surface conserved components LPS and LTA etc. In vivo experiments demonstrated that overexpression OnCD6 before S. agalactiae challenge significantly improved tilapia survival, and this was concomitant with reduced bacterial load and pro-inflammatory cytokines (IL-1ß and TNF-α). Taken together, our results illustrated the function of CD6 molecular pattern recognition receptors (PRRs) is conserved and plays an important role in antibacterial infection.

The role of HMGB2 in the immune response of Nile tilapia (Oreochromis niloticus) to streptococcal infection.

High mobility group protein B2 (HMGB2) is an abundant chromatin-associated protein with pivotal roles in transcription, cell proliferation, differentiation, inflammation, and tumorigenesis. However, its immune function in Nile tilapia (Oreochromis niloticus) remains unclear. In this study, we identified a homologue of HMGB2 from Nile tilapia (On-HMGB2) and investigated its functions in the immune response against streptococcus infection. The open reading frame (ORF) of On-HMGB2 spans 642 bp, encoding 213 amino acids, and contains two conserved HMG domains. On-HMGB2 shares over 80 % homology with other fish species and 74%-76 % homology with mammals. On-HMGB2 was widely distributed in various tissues, with its highest transcript levels in the liver and the lowest in the intestine. Knockdown of On-HMGB2 promoted the inflammatory response in Nile tilapia, increased the bacterial load in the tissues, and led to elevated mortality in Nile tilapia following Streptococcus agalactiae infection. Taken together, On-HMGB2 significantly influences the immune system of Nile tilapia in response to streptococcus infection.

Infection dynamics of Shewanella spp. in Nile tilapia under varied water temperatures: A hematological, biochemical, antioxidant-immune analysis, and histopathological alterations.

In aquaculture, fluctuating water temperatures can act as a potent stressor, influencing the virulence and transmission dynamics of pathogenic bacteria, potentially triggering outbreaks and impacting fish health. The purpose of this work was to examine the impact of Shewanella spp. infection on hematological, biochemical, and antioxidant-immune parameters of Nile tilapia (Oreochromis niloticus) under different water temperatures. For this purpose, 180 fish were divided into 6 groups in triplicate (30 fish per group; 10 fish per replicate). Group 1 (G1), G2, and G3 were reared at varying water temperatures (22 °C, 28 °C, and 31 °C, respectively) without infection. While G4, G5, and G6 were IP-injected with 0.2 mL of Shewanella spp. (0.14 × 105) and reared at 22 °C, 28 °C, and 31 °C, respectively. Shewanella spp. infection induced significant lowering (p < 0.05) in hematological parameters (red and white blood cells, hemoglobin, and packed cell volume%) and immune-antioxidant responses (phagocytic activity%, phagocytic index, lysozyme, nitric oxide), total antioxidant capacity, catalase, and reduced glutathione, especially at 22 °C. Moreover, a significant increase (p < 0.05) in the hepato-renal function indicators (alanine aminotransferase, aspartate aminotransferase, urea, and creatinine), stress biomarkers (glucose and cortisol), malondialdehyde, and pro-inflammatory cytokines (interleukin-1ß and tumor necrosis factor-α) were the consequences of the Shewanella spp. infection, especially at 22 °C. The Shewanella spp. infection exhibited marked histopathological changes in the hepatic and renal tissues. Worthily, Shewanella spp. can cause detrimental alterations in Nile tilapia's hematological, biochemical, and antioxidant-immune parameters at various water temperatures, but the major detrimental changes were observed at a water temperature of 22 °C. Consequently, we can conclude that the infection dynamics of Shewanella spp. are exaggerated at 22 °C. These outcomes could help in understanding the nature of such an infection in Nile tilapia.

Nelumbo nucifera synthesized selenium nanoparticles modulate the immune-antioxidants, biochemical indices, and pro/anti-inflammatory cytokines pathways in Oreochromis niloticus infected with Aeromonas veronii.

Bacterial infection is considered one of the major issues in fish culturing that results in economic losses. Metal nanoparticles are a cutting-edge and effective disease management and preventive strategy because of their antibacterial ability. In this investigation, the selenium nanoparticles were prepared by a biological method using Nelumbo nucifera leaves extract. The in-vitro antibacterial activity of N. nucifera synthesized selenium nanoparticles (NN-SeNPs) was tested against Aeromonas veronii. A treatment assay was conducted on 210 Oreochromis niloticus (average body weight: 27 ± 2.00 g). A preliminary approach was conducted on 90 fish for determination of the therapeutic concentration of NN-SeNPs which was found to be 4 mg/L. Fish (n = 120) were categorized into four groups for 10 days; G1 (control) and G2 (NN-SeNPs) were non-challenged and treated with 0 and 4 mg/L NN-SeNPs, respectively. While, G3 and G4 were infected with 2 × 106 CFU/mL of A. veronii and treated with 0 and 4 mg/L NN-SeNPs, respectively. NN-SeNPs exhibited an inhibition zone against A. veronii with a diameter of 16 ± 1.25 mm. The A. veronii infection increased the hepato-renal biomarkers (alanine and aspartate aminotransferases and creatinine) than the control group. An oxidative stress was the consequence of A. veronii infection (higher malondialdehyde and hydrogen peroxide levels with lower glutathione peroxidase superoxide, dismutase, and catalase activity). A. veronii infection resulted in lower immunological biomarker values (immunoglobulin M, lysozyme, and complement 3) with higher expression of the inflammatory cytokines (interleukin-1ß and tumor necrosis factor-ɑ) as well as lower expression of the anti-inflammatory cytokines (interleukin-10 and transforming growth factor-ß). Therapeutic application with 4 mg/L NN-SeNPs prevented the disease progression; and modulated the hepato-renal function disruptions, oxidant-immune dysfunction, as well as the pro/anti-inflammatory cytokines pathway in the A. veronii-infected fish. These findings suggest that NN-SeNPs, employed as a water therapy, can safeguard fish from the harmful effects of A. veronii and serve as a promising antibacterial agent for sustainable aquaculture.

Chlorella vulgaris extract conjugated magnetic iron nanoparticles in nile tilapia (Oreochromis niloticus): Growth promoting, immunostimulant and antioxidant role and combating against the synergistic infection with Ichthyophthirius multifiliis and Aeromonashydrophila.

Nile tilapia reared under intensive conditions was more susceptible for Ichthyophthirius multifilii (I. multifiliis) infection eliciting higher mortality, lower productive rate and further bacterial coinfection with Aeromonas hydrophila (A. hydrophila). The higher potency of magnetic field of iron oxide nanoparticles (NPs) can kill pathogens through inhibiting their viability. Herein, coating of Chlorella vulgaris extract (ChVE) with magnetic iron oxide NPs (Mag iron NPs) can create an external magnetic field that facilitates their release inside the targeted tissues. Thus, the current study is focused on application of new functionalized properties of Mag iron NPs in combination with ChVE and their efficacy to alleviate I. multifiliis and subsequent infection with A. hydrophila in Nile tilapia. Four hundred fingerlings were divided into: control group (with no additives), three groups fed control diet supplemented with ChVE, Mag iron NPs and ChVE@Mag iron NPs for 90 days. At the end of feeding trial fish were challenged with I. multifiliis and at 9 days post challenge was coinfected by A. hydrophila. A remarkable higher growth rate and an improved feed conversion ratio were detected in group fed ChVE@Mag iron-NPs. The maximum expression of antioxidant enzymes in skin and gills tissues (GSH-Px, CAT, and SOD) which came in parallel with higher serum activities of these enzymes was identified in groups received ChVE@Mag iron-NPs. Furthermore, group fed a combination of ChVE and Mag iron-NPs showed a boosted immune response (higher lysozyme, IgM, ACH50, and MPO) prior to challenge with I. multifiliis. In contrast, fish fed ChVE@Mag iron-NPs supplemented diet had lower infection (decreased by 62%) and mortality rates (decreased by 84%), as well as less visible white spots (decreased by 92 % at 12 dpi) on the body surfaces and mucous score. Interestingly, post I. multifiliis the excessive inflammatory response in gill and skin tissues was subsided by feeding on ChVE@Mag iron-NPs as proved by down regulation of IL-1ß, TNFα, COX-2 and iNOS and upregulation of IL-10, and IgM, IgT and Muc-2 genes. Notably, group exposed to I. multifiliis-showed higher mortality when exposed to Aeromonas hydrophilia (increased by 43 %) while group fed ChVE@Mag iron-NPs exhibited lower morality (2%). Moreover, the bacterial loads of A. hydrophilia in fish infected by I. multifiliis and fed control diet were higher than those received dietary supplement of ChVE, Mag iron-NPs and the most reduced load was obtained in group fed ChVE@Mag iron-NPs at 7 dpi. In conclusion, ChVE@Mag iron-NPs fed fish had stronger immune barrier and antioxidant functions of skin and gills, and better survival following I. multifiliis and A. hydrophilia infection.

Immune response and protective efficacy of Streptococcus agalactiae vaccine coated with chitosan oligosaccharide for different immunization strategy in nile tilapia (Oreochromis niloticus).

In the past decade, the outbreak of Streptococcus agalactiae has caused significant economic losses in tilapia farming. Vaccine immunization methods and strategies have gradually evolved from single-mode to multi-mode overall prevention and control strategies. In this study, an inactivated vaccine of S. agalactiae with a chitosan oligosaccharide (COS) adjuvant was constructed using different administration methods: intraperitoneal injection (Ip), immersion combined with intraperitoneal injection (Im + Ip), immersion combined with oral administration (Im + Or), and oral administration (Or). Safety analysis revealed no adverse effects on tilapia, and the vaccine significantly promoted fish growth and development when administered through Im + Or or Or immunization. Following vaccination, innate immunity parameters including SOD, ACP and CAT activities were all significantly enhanced. Additionally, specific serum IgM antibodies reached their highest level at the 6th week post vaccination. Skin and intestinal mucus IgT antibodies reached peaked at the 6th and 7th week post vaccination, respectively. The relative peak expression values for IL-8, IL-12, MHC-I, MHC-II, IgM, IgT, CD4, CD8, TNFα, IFNγ from Im + Ip group were significantly higher than those in Ip group, Im + Or group and Or group in most cases (p < 0.05). Importantly, the relative protection survival of Im + Ip group was the highest (78.6%), followed by the Ip group (71.4%), the Or group (64.3%) and the Im + Or group (57.1%). In summary, this study encourages further research on multi-channel immunization strategies of other kinds of vaccines in other aquatic economic animals to improve their disease resistance.

Molecular characterization, expression and functional analysis of TAK1, TAB1 and TAB2 in Nile tilapia (Oreochromis niloticus).

The MAPK pathway is the common intersection of signal transduction pathways such as inflammation, differentiation and proliferation and plays an important role in the process of antiviral immunity. Streptococcus agalactiae will have a great impact on tilapia aquaculture, so it is necessary to study the immune response mechanism of tilapia to S. agalactiae. In this study, we isolated the cDNA sequences of TAK1, TAB1 and TAB2 from Nile tilapia (Oreochromis niloticus). The TAK1 gene was 3492 bp in length, contained an open reading frame (ORF) of 1809 bp and encoded a polypeptide of 602 amino acids. The cDNA sequence of the TAB1 gene was 4001 bp, and its ORF was 1491 bp, which encoded 497 amino acids. The cDNA sequence of the TAB2 gene was 4792 bp, and its ORF was 2217 bp, encoding 738 amino acids. TAK1 has an S_TKc domain and a coiled coil structure; the TAB1 protein structure contains a PP2C_SIG domain and a conserved PYVDXA/TXF sequence model; and TAB2 contains a CUE domain, a coiled coil domain and a Znf_RBZ domain. Homology analysis showed that TAK1 and TAB1 had the highest homology with Neolamprologus brichardi, and TAB2 had the highest homology with Simochromis diagramma (98.28 %). In the phylogenetic tree, TAK1, TAB1 and TAB2 formed a large branch with other scleractinian fishes. The tissue expression analysis showed that the expression of TAK1, TAB1 and TAB2 was highest in the muscle. The expression of TAK1, TAB1 and TAB2 was significantly induced in most of the tested tissues after stimulation with LPS, Poly I:C and S. agalactiae. The subcellular localization results showed that TAK1 was located in the cytoplasm, and TAB1 and TAB2 had certain distributions in the cytoplasm and nucleus. Coimmunoprecipitation (Co-IP) results showed that TRAF6 did not interact with the TAK1 protein but interacted with TAB2, while TAB1 did not interact with P38γ but interacted with TAK1. There was also an interaction between TAK1 and TAB2.

A novel study of brain microvascular endothelial cells induced by astrocyte conditioned medium for constructing blood brain barrier model in vitro: A promising tool for meningitis of teleost.

The blood-brain barrier (BBB) is mainly composed of specialized endothelial cells, which can resist harmful substances, transport nutrients, and maintain the stability of the brain environment. In this study, an endothelial cell line from tilapia (Oreochromis niloticus) named TVEC-01 was successfully established. During the earlier establishment phase of the cell line, the TVEC-01 cells were persistently exposed to an astrocyte-conditioned medium (ACM). TVEC-01 cells were identified as an endothelial cell line. TVEC-01 cells retained the multiple functions of endothelial cells and were capable of performing various experiments in vitro. Furthermore, TVEC-01 cells efficiently expressed BBB-related tight junctions and key efflux transporters. From the results of the qRT-PCR, we found that the TVEC-01 cell line did not gradually lose BBB characteristics after persistent and repetitive passages, which was different from the vast majority of immortalized endothelial cells. The results showed that ACM induced up-regulation of the expression levels of multiple BBB-related genes in TVEC-01 cells. We confirmed that Streptococcus agalactiae was capable of invading the TVEC-01 cells and initiating a series of immune responses, which provided a theoretical basis for S. agalactiae to break through the BBB of teleost through the transcellular traversal pathway. In summary, we have successfully constructed an endothelial cell line of teleost, named TVEC-01, which can be used in many experiments in vitro and even for constructing BBB in vitro. Moreover, it was confirmed that S. agalactiae broke through the BBB of teleost through the transcellular traversal pathway and caused meningitis.

Antioxidant and antibacterial efficiency of the ethanolic leaf extract of Kratom (Mitragyna speciosa (Korth.) Havil) and its effects on growth, health, and disease resistance against Edwardsiella tarda infection in Nile tilapia (Oreochromis niloticus).

The research examined the impact of an ethanolic extract from the leaves of Kratom (Mitragyna speciosa (Korth.) Havil.) on the growth, antioxidant capacity, immune-related gene expression, and resistance to disease caused by Edwardsiella tarda in Nile tilapia (Oreochromis niloticus). The findings revealed that the extract had the important phytochemical content in the extract included total phenolics content, total flavonoids content, vitamin C, and total antioxidant capacity and 5.42 % of the crude extract was mitragynine. The extract demonstrated antioxidant activity, as evidenced by its IC50 values against ABTS and DPPH radicals and its ferric reducing power in vitro. Moreover, the MIC-IC50 value of 0.625 mg/mL indicated that the growth of the bacteria was reduced by approximately 50 %, and the MBC was 2.50 mg/mL against E. tarda. Furthermore, the orally administered Kratom leaf extract to fingerling tilapia for 8 weeks exhibited a noticeable increase in oxidative stress, as demonstrated by the increase in MDA production in the 10 and 25 g/kg groups. It also exhibited an increase in acetylcholinesterase (AChE) activity in muscle tissue at the 50 g/kg group. However, when administered at a feeding rate of 5-10 g/kg feed, the extract showed an increase in the expression of immune-related genes (IL1, IL6, IL8, NF-kB, IFNγ, TNFα, Mx, CC-chemokine, CD4, TCRß, MHC-IIß, IgM, IgT, IgD) and enhanced resistance to E. tarda infection in fish. Conversely, administering the extract at 25-50 g/kg feed resulted in contrasting effects, suppressing and reducing the observed parameters. Nevertheless, feeding the extract at all concentrations for 8 weeks did not produce any changes in the histology or systemic functioning of the liver and intestines, as indicated by blood biochemistry. These findings suggest that the ethanolic leaf extract from Kratom has the potential to be used as a substitute for antibiotics in the management of bacterial infections in Nile tilapia culture, with a recommended dosage of 5-10 g/kg feed/day for a maximum of 8 weeks.

Novel C-type lectin mediated non-specific cytotoxic cells killing activity through NCCRP-1 in nile tilapia (Oreochromis niloticus).

Non-specific cytotoxic cells (NCCs) are vital immune cells involved in teleost's non-specific immunity. As a receptor molecule on the NCCs' surface, the non-specific cytotoxic cell receptor protein 1 (NCCRP-1) is known to play a crucial role in mediating their activity. Nevertheless, there have been limited studies on the signal molecule that transmits signals via NCCRP-1. In this study, a yeast two-hybrid (Y2H) library of tilapia liver and head kidney was constructed and subsequently screened with the bait vector NCCRP-1 of Oreochromis niloticus (On-NCCRP-1) to obtain a C-type lectin (On-CTL) with an interacting protein sequence. Consequently, the full-length sequence of On-CTL was cloned and analyzed. The expression analysis revealed that On-CTL is highly expressed in the liver and is widely distributed in other tissues. Furthermore, On-CTL expression was significantly up-regulated in the brain, intestine, and head kidney following a challenge with Streptococcus agalactiae. A point-to-point Y2H method was also used to confirm the binding between On-NCCRP-1 and On-CTL. The recombinant On-CTL (rOn-CTL) protein was purified. In vitro experiments demonstrated that rOn-CTL can up-regulate the expression of killer effector molecules in NCCs via its interaction with On-NCCRP-1. Moreover, activation of NCCs by rOn-CTL resulted in a remarkable enhancement in their ability to eliminate fathead minnow cells, indicating that rOn-CTL effectively modulates the killing activity of NCCs through the NCC receptor molecule On-NCCRP-1. These findings significantly contribute to our comprehension of the regulatory mechanisms governing NCC activity, paving the way for future research in this field.

A novel metabolite of Streptomyces coeruleorubidus exhibits antibacterial activity against Streptococcus agalactiae through modulation of physiological performance, inflammatory cytokines, apoptosis, and oxidative stress-correlated gene expressions in Nile tilapia (Oreochromis niloticus).

Using the unique structures found in natural materials to produce new antibacterial drugs is crucial. Actinobacteria is well-known for its ability to produce naturally occurring chemicals with a variety of structural features that can be used as weapons against infectious bacteria. In the present study, the Streptomyces coeruleorubidus metabolites were characterized and their efficacy in suppressing Streptococcus agalactiae growth was carried out both in vitro and in vivo. The metabolites of S. coeruleorubidus were purified and identified as octasiloxane-hexadecamethyl (OHM). In vivo antibacterial activity of OHM revealed an inhibitory minimum concentration value of 0.5 µg/ml against S. agalactiae and induced ultrastructural cell changes revealed by scanning electron microscope. The safe concentration of OHM was determined as 0.8 mg/L for Nile tilapia. Four in vivo treatments were treated with 0 and 0.8 mg/L OHM and with or without challenge by S. agalactiae (1 × 107 CFU/mL) named control, OHM, S. agalactiae, and S. agalactiae + OHM groups. The OHM treatment improved the survival of Nile tilapia by 33.33% than S. agalactiae challenge group. Waterborne OHM treatment significantly mitigated the deleterious effects of S. agalactiae on hematological, hepato-renal functions, stress indicators, and antioxidant balance. OHM significantly alleviated nitric oxide levels, complement 3, IgM, and lysozyme activity, downregulation of liver antioxidant genes expression in S. agalactiae group. Furthermore, the addition of OHM to challenged fish with S. agalactiae-significantly reversed dramatic negative regulation of inflammatory, apoptosis, and immune related gene expression (caspase-3, bax, pcna, tnf-α, ifn-γ, il-8 il-1ß, il-10, tgf-ß, and bcl-2 in the Nile tilapia spleen. Additionally, the damaged hepatic and splenic structure induced by bacterial infection was restored with OHM treatment. Finally, S. coeruleorubidus metabolites (mainly OHM) revealed in vitro and in vivo antibacterial activity and showed alleviated effects on the physiological status of S. agalactiae infected tilapia.

Single nucleotide polymorphisms in the MRFs gene family associated with growth in Nile tilapia.

BACKGROUND: Muscle occupies most of the fish body, promoting the proliferation of fish muscle fibers can facilitate rapid growth and increase the body weight of fish. Some studiesSeveral previous suggest that Myogenic regulatory factors (MRFs) play an important role in the growth of fish. OBJECTIVE: To investigate the association between the polymorphism of MRFs gene family and growth traits in Nile tilapia (Oreochromis niloticus), get more molecular markers for growth. METHODS: Amplified the Nile tilapia MRFs family gene, including Myogenic determination 1 (Myod1), Myogenic determination 2 (Myod2), Myogenin (Myog), Myogenic factor 5 (Myf5), and Myogenic factor 6 (Myf6), single nucleotide polymorphism (SNP) were screened by Sanger sequencing. RESULTS: A total of 16 SNP loci were screened, including six for Myf5, six for Myf6, one for Myog, one for Myod1 and two for Myod2. The growth traits were analyzed in relation to these 16 SNP loci, and the results indicated significant associations between all 16 SNP loci and the growth traits (P < 0.05). The linkage disequilibrium analysis revealed that D1 and D2 diplotypes of Myf5 gene, E1, E2, E3 and E4 of Myf6 gene, and F1 diplotype of Myod2 gene were significantly associated with superior growth traits. CONCLUSION: There were 6, 6, 1, 1 and 2 growth-related molecular markers in Myf5, Myf6, Myog, Myod1 and Myod2 genes, respectively, which could be applied to the breeding of Nile tilapia.

Implications of ammonia stress for the pathogenicity of Shewanella spp. in Oreochromis niloticus: effects on hematological, biochemical, immunological, and histopathological parameters.

Environmental stressors (such as ammonia) in aquaculture could increase the risk of pathogenicity, posing a more severe threat to farmed fish. The aim of this study was to investigate the effects of ammonia stress on the pathogenicity of Shewanella spp. in Oreochromis niloticus. First, a 96-hour static test was used to determine the median lethal concentration (LC50) of unionized ammonia to Nile tilapia. After 96 h of exposure, the Un-ionized ammonia (UIA) LC50 was estimated to be 4.26 mg/L. Second, an experiment was conducted to test the effect of unionized ammonia stress on the pathogenicity of Shewanella spp. in O. niloticus for 30 days. A study involved 180 fish divided into six groups, with the first group serving as a control. The second group (AMN1/10) and the third group (AMN1/20) were not challenged and were exposed to 1/10 (0.42 mg/L) and 1/20 (0.21 mg/L) of the 96-hour LC50 of UIA, respectively. Then 0.2 mL (0.14 × 105) of Shewanella spp. was intraperitoneally injected into the fourth (SH), fifth (SH + AMN1/10), and sixth (SH + AMN1/20) groups, which were subjected to 0, 1/10 (0.42 mg/L), and 1/20 (0.21 mg/L) of the 96-hour LC50 of UIA, respectively. The survival rate, hematological indices, immunological parameters, and antioxidant activity of the fish significantly decreased when they were exposed to ammonia and Shewanella infection separately or together. Histopathological changes were also observed in the kidney and liver. Furthermore, both individual and combined exposures significantly altered renal and hepatic function, with notable increases in glucose and cortisol levels, as well as in the expression of proinflammatory cytokine genes (TNF-α and IL-1ß). However, the detrimental effects of co-exposure to ammonia stress and Shewanella infection were greater than those of separate exposures. As a result, we may say that increased ammonia concentrations enhance the infection of Shewanella spp. These findings could contribute to a better understanding of Shewanella infection in Nile tilapia.

The effects of dietary Spirulina platensis or curcumin nanoparticles on performance, body chemical composition, blood biochemical, digestive enzyme, antioxidant and immune activities of Oreochromis niloticus fingerlings.

CONTEXT: Recently, prioritize has been given to using natural phytogenic or nano compounds as growth promoters and immunostimulants in fish diets as an alternative to antibiotics. AIMS: The main propose of this trial was to determine the impact of supplementing diets with spirulina or curcumin nanoparticles on the performance and health indicators of Nile tilapia fingerlings. METHODS: In a 56-day feeding trial, 180 tilapia fingerlings were assigned into three main groups, as follows: 1st, control group, 2nd, Spirulina platensis (SP; 5 g kg-1 diet) and 3rd, curcumin nanoparticles (CUR-NPs; 30 mg kg-1 diet). KEY RESULTS: Incorporating tilapia diets with SP or CUR-NPs significantly improved performance, body chemical analysis, blood biochemical and hematological indices, digestive enzyme activities, and antioxidant and immunostimulant features compared to the control. CONCLUSION: Fortified tilapia diets with CUR-NPs or SP efficiently boost the productivity and health of Nile tilapia fingerlings. IMPLICATIONS: The research introduces new practical solutions for applying safe feed additives as alternatives to antibiotics in tilapia farming.

Pseudomonas putida infection induces immune-antioxidant, hepato-renal, ethological, and histopathological/immunohistochemical disruptions in Oreochromis niloticus: the palliative role of titanium dioxide nanogel.

BACKGROUND: Pseudomonas putida is a pathogenic bacterium that induces great losses in fishes, including Nile tilapia (Oreochromis niloticus). Currently, the application of nanomaterials in aquaculture practices has gained more success as it endows promising results in therapies compared to traditional protocols. OBJECTIVE: Therefore, the current perspective is considered the first report to assess the anti-bacterial efficacy of titanium dioxide nanogel (TDNG) against Pseudomonas putida (P. putida) in Nile tilapia. METHODS: The fish (n = 200; average body weight: 47.50±1.32 g) were allocated into four random groups (control, TDNG, P. putida, and TDNG + P. putida), where 0.9 mg/L of TDNG was applied as bath treatment for ten days. RESULTS: Outcomes revealed that P. putida infection caused ethological alterations (surfacing, abnormal movement, and aggression) and depression of immune-antioxidant variables (complement 3, lysozyme activity, total antioxidant capacity, superoxide dismutase, and reduced glutathione content). Additionally, a substantial elevation in hepatorenal biomarkers (aspartate and alanine aminotransferases and creatinine) with clear histopathological changes and immuno-histochemical alterations (very weak BCL-2 and potent caspase-3 immuno-expressions) were seen. Surprisingly, treating P. putida-infected fish with TDNG improved these variables and obvious restoration of the tissue architectures. CONCLUSION: Overall, this report encompasses the key role of TDNG as an anti-bacterial agent for controlling P. putida infection and improving the health status of Nile tilapia.

Polystyrene nanoplastic and engine oil synergistically intensify toxicity in Nile tilapia, Oreochromis niloticus : Polystyrene nanoplastic and engine oil toxicity in Nile tilapia.

Polystyrene nanoplastic (PS-NPs) and Engine oil (EO) pose multiple ecotoxic effects with increasing threat to fish ecosystems. The current study investigated the toxicity of 15 days exposure to PS-NPs and / or EO to explore their combined synergistic effects on Nile tilapia, Oreochromis niloticus (O. niloticus). Hematobiochemical parameters, proinflammatory cytokines, and oxidative stress biomarkers as well as histological alterations were evaluated. The experimental design contained 120 acclimated Nile tilapia distributed into four groups, control, PS-NPs (5 mg/L), EO (1%) and their combination (PS-NPs + EO). After 15-days of exposure, blood and tissue samples were collected from all fish experimental groups. Results indicated that Nile tilapia exposed to PS-NPs and / or EO revealed a significant decrease in almost all the measured hematological parameters in comparison to the control, whereas WBCs and lymphocyte counts were significantly increased in the combined group only. Results clarified that the combined PS-NPs + EO group showed the maximum decrease in RBCs, Hb, MCH and MCHC, and showed the maximum significant rise in interleukin-1ß (IL-1ß), and interleukin-6 (IL-6) in comparison to all other exposed groups. Meanwhile, total antioxidant capacity (TAC) showed a significant (p < 0.05) decline only in the combination group, whereas reduced glutathione (GSH) showed a significant decline in all exposed groups in comparison to the control. Both malondialdehyde (MDA) and aspartate aminotransferase (AST) showed a significant elevation only in the combination group. Uric acid showed the maximum elevation in the combination group than all other groups, whereas creatinine showed significant elevation in the EO and combination group when compared to the control. Furthermore, the present experiment proved that exposure to these toxicants either individually or in combination is accompanied by pronounced histomorpholgical damage characterized by severe necrosis and hemorrhage of the vital organs of Nile tilapia, additionally extensively inflammatory conditions with leucocytes infiltration. We concluded that combination exposure to both PS-NPs and EO caused severe anemia, extreme inflammatory response, oxidative stress, and lipid peroxidation effects, thus they can synergize with each other to intensify toxicity in fish.

Skin histopathological responses of Oreochromis niloticus (Nile tilapia) to transportation in water with and without salt.

Oreochromis niloticus (Nile tilapia) is a well-known economic fish species that can thrive under the right environmental circumstances. The transport of live fish, either for food or as companion animals, presents a big issue for animal welfare at the same time it is considered one of stressful conditions. Hence, the present study investigated the skin histopathological responses of O. niloticus that were attributed to stress and salt addition during transportation. Three experimental groups of O. niloticus the 1st is the control non-transported group (CG), the 2nd is transport in water without salt (PT-S) and the 3rd is transport in water containing 5gL- 1salt (PT + S), the last 2 groups were transported in 5 h transport model. Results indicate that the skin of PT-S fish showed a marked decrease in epidermal thickness, decreased number of goblet cells, and an increase in the sub-epidermal and dermal pigments with the presence of large edematous vacuoles. Fish skin from PT + S demonstrated mild hydropic swelling in epidermal cells with normal goblet (mucous) cells density, and more or less normal melanin pigment distribution in sub epidermis and on the dermis layers, however, dermis showed mild edematous spaces. Scanning microscopy of PT-S skin tissue showed few scratched white patches among normal regions that may represent a thickened surface with the decreased number of goblets cell opening, while the PT + S group showed moderate preservation of surface skin architectures with the presence of goblet (mucous) cells opening in spite of presence of slight thickened white patches. The estimated total lesion changes present in PT-S group showed a significant increase (P < 0.001) compared with the control (CG) group. On the other hand, PT + S showed significant (P < 0.001) improvement in the overall previously recorded changes compared with the PT-S group, and a non- significant change in the histological architectures compared with the control group. Our findings underlined the importance of skin and its mucous cover health during transportation. The use 5 gL- 1salt during O. niloticus transportation appears to preserve the surface skin features, and keep the goblet (mucous) cells open to the external surface, and may act as a deterrent for the release of mucus from goblet (mucous) cells in response to stress and lessen the stress of transportation.