Wntless, a conserved Wnt-transport protein, is involved in the innate immune response of Macrobrachium rosenbergii

Roles of β-catenin in innate immune process and regulating intestinal flora in Qi river crucian carp (Carassius auratus)

In mammals, β-catenin participates in innate immune process through interaction with NF-κB signaling pathway. However, its role in teleost immune processes remains largely unknown. We aimed to clarify the function of β-catenin in the natural defense mechanism of Qi river crucian carp (Carassius auratus). β-catenin exhibited a ubiquitous expression pattern in adult fish, as indicated by real-time PCR analysis. Following lipopolysaccharide (LPS), Polyinosinic-polycytidylic acid (polyI: C) and Aeromonas hydrophila (A. hydrophila) challenges, β-catenin increased in gill, intestine, liver and kidney, indicating that β-catenin likely plays a pivotal role in the immune response against pathogen infiltration. Inhibition of the β-catenin pathway using FH535, an inhibitor of Wnt/β-catenin pathway, resulting in pathological damage of the gill, intestine, liver and kidney, significant decrease of innate immune factors (C3, defb3, LYZ-C, INF-γ), upregulation of inflammatory factors (NF-κB, TNF-α, IL-1, IL-8), and downregulation of glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT) activities, increase of Malondialdehyde (MDA) content. Following A. hydrophila invasion, the mortality rate in the FH535 treatment group exceeded that of the control group. In addition, the diversity of intestinal microflora decreased and the community structure was uneven after FH535 treatment. In summary, our findings strongly suggest that β-catenin plays a vital role in combating pathogen invasion and regulating intestinal flora in Qi river crucian carp.

Cineole regulates Wnt/β-catenin pathway through Nrf2/keap1/ROS to inhibit bisphenol A-induced apoptosis, autophagy inhibition and immunosuppression of grass carp hepatocytes

Bisphenol A (BPA), an environmental pollutant, can cause multiple organ tissue damage by inducing oxidative stress. Cineole (CIN) is a terpene oxide existing in a variety of plant essential oils, which has anti-inflammatory, analgesic, and antioxidant effects. This study examined the effects of 200 nM BPA and 20 μM CIN on apoptosis, autophagy, and immunology in grass carp hepatocytes (L8824). The treatments were categorized as NC, CIN, BPA + CIN, and BPA. The findings demonstrated that BPA exposure could increase ROS levels and oxidative stress-related indicators, decrease the expression of the Nrf2/keap1 pathway and the Wnt/β-catenin pathway, increase the expression of genes involved in the apoptotic pathway (Bax and Caspase3), and decrease the expression of the anti-apoptotic gene Bcl-2 by lowering mitochondrial membrane potential. BPA also reduced the expression of genes linked to autophagy (ATG5, Beclin1, LC3). Changes in immunological function after BPA exposure were also shown by changes in the amounts of antimicrobial peptides (HEPC, β-defensin, LEAP2) and cytokines (INF-γ, IL-1β, IL-2, and TNF-α). After the co-treatment of CIN and BPA, CIN can inhibit BPA-induced apoptosis and recover from autophagy and immune function to a certain extent by binding to keap1 to exert an anti-oxidative regulatory effect of Nrf2 incorporation into the nucleus. Molecular docking provides strong evidence for the interaction of CIN ligands with keap1 receptors. Therefore, these results indicated that CIN could inhibit BPA-induced apoptosis, autophagy inhibition and immunosuppression in grass carp hepatocytes by regulating the Wnt/β-catenin pathway with Nrf2/keap1/ROS. This study provided further information to the risk assessment of the neuroendocrine disruptor BPA on aquatic organisms and offered suggestions and resources for further research into the function of natural extracts in the body's detoxification process.

Identification of wnt2 in the pearl mussel Hyriopsis cumingii and its role in innate immunity and gonadal development

Wnt2 is a significant factor in the Wnt signaling pathway, which is associated with a variety of physiological activities, including inflammatory response, cell apoptosis, reproductive system development, and cell differentiation. Hyriopsis cumingii is the main pearl breeding mussel in China. However, the role of wnt2 in this species remains unclear. In this study, wnt2 from H. cumingii was cloned and identified. The full-length cDNA of wnt2 is 1524 bp, containing a 963 bp open reading frame (ORF), encoding 320 amino acid residues. The tissue distribution of H. cumingii indicated that wnt2 was predominantly highly expressed in the ovary and gill. And the expression profile after Aeromonas hydrophila or LPS injection indicated that wnt2 was up-regulated in gill, suggesting its role in the innate immune response. The expression of wnt2 was high at 4-month-old of early gonadal development and throughout ovarian development. In situ hybridization (ISH) showed significant hybridization signals on the gills and mature eggs of female gonads. In addition, miR-1988b-5p was found to negatively regulate wnt2 to affect the expression of key genes (frizzled-5, ctnnb1, and tcf7l) in the Wnt signaling pathway. Thus, these findings suggest a key role for wnt2 in immune regulation and gonadal development in H. cumingii.

Involvement of tetraspanin 8 in the innate immune response of the giant prawn, Macrobrachium rosenbergii

The tetraspanins, representing a conserved superfamily of four-span membrane proteins, are highly involved in viral and bacterial infections. Thus far, the function of the tetraspanins in crustaceans remains largely unknown. In this study, we report the cloning and expression analysis of a tetraspanin 8 from the giant freshwater prawn, Macrobrachium rosenbergii (named as MrTspan8). MrTspan8 contains a 720-bp open reading frame encoding a 239-amino acids protein, which exhibits four transmembrane domains and two extracellular loops that are typical for tetraspanins. MrTspan8 was found to be widely expressed in a variety of prawn tissues including heart, gill, muscle, gut, and hepatopancreas. Additionally, MrTspan8 expression was significantly increased in the hepatopancreas and gill of the prawns challenged by the bacterial pathogen Aeromonas hydrophila. Moreover, we show that pre-incubation of the peptides from the large extracellular loop of MrTSPAN8 protein reduced the cell death caused by A. hydrophila infection in prawn tissue, suggesting that MrTSPAN8 could be a mediator for bacterial infection to prawn.