Liposome encapsulating pine bark extract in Nile tilapia: Targeting interrelated immune and antioxidant defense to combat coinfection with Aeromonas hydrophila and Enterococcus faecalis

Application of smart delivery systems for encapsulation of natural ingredients provides novel avenues and is being frequently developed. Thus, we aimed to highlight the effects of cyclosome liposomal pine bark extract (CL-PBE) on Nile tilapia growth, immunomodulation, antioxidant capacity and resistance against coinfection with Aeromonas hydrophila and Enterococcus faecalis and their associated virulence genes. The experiment was conducted on four fish groups receiving a control diet (control) along with three baseline meals supplemented with 200, 400 and 600 mg/kg diet of CL-PBE (CL-PBE 200, 400 and 600, respectively). At the end of the 12-weeks feeding trial, the tilapias were intraperitoneally challenged with virulent A. hydrophila strain and five days later, E. faecalis challenge was carried out. The results revealed that tilapias fed diets fortified with CL-PBE displayed significantly enhanced growth rate and feed conversion ratio in a dose-dependent manner. Moreover, we demonstrated that CL-PBE had potent antioxidant property presented by modulation of several markers of oxidative stress; substantial reductions in reactive oxygen species, hydrogen peroxide and malondialdehyde levels, an elevation in total antioxidant capacity and boosting glutathione peroxidase (GSH-Px), catalase (CAT) and superoxide dismutase (SOD) activities in fish serum and muscle tissues. This was also correlated with augmenting the expression of CAT, SOD, GSH-Px, Nrf2 and caspase-1 genes alongside reducing those of COX-2, HSP70 and iNOS genes in response to CL-PBE. Our data demonstrated that CL-PBE fortification counteracted the overly pronounced inflammatory response-mediated induction of IL-1β, TNF-α, MHCII and TLR2 genes at the transcriptional levels post coinfection together with promotion in MUC2 and IL-10 genes expression. Notably, our findings displayed optimal well-functioning fish immune system post dietary supplementation of CL-PBE for the protection against coinfection with A. hydrophila and E. faecalis. This was evident from the decline of their counts and hence encompassing the capacity to reduce cumulative mortality percentage in conjunction with interference with their virulence via the significant downregulatory effects of CL-PBE on E. faecalis esp and gelE and A. hydrophila act and fla virulence genes. Taken together, our study strongly suggested dietary inclusion of CL-PBE for Nile tilapias with superior growth performance and significant economic benefits coupled with potent stimulatory effects on antioxidant capacity and immune response expediting our detailed understanding of how coinfection with A. hydrophila and E. faecalis was controlled.