Therapeutic effects of white poplar (Populus alba) leave extract on hepatorenal, stress, and antioxidant-immune parameters of Oreochromis niloticus challenged with Aeromonas veronii

Abstract

Herbal plants have gained enormous interest due to their immune, antioxidant, and antibacterial activities. The present study proposed that white poplar (Populus alba) leave extract (WPE) might provide a promising alternative to traditional antibiotics to treat Aeromonas veronii infection in Nile tilapia (Oreochromis niloticus). WPE showed an in vitro antibacterial activity [22 ± 0.45 mm inhibition zone, with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 60 µg/mL] against A. veronii. For the in-vivo study, a factorial (2 × 2) design was used to investigate the therapeutic effects of WPE on the antioxidant/immune status and blood biochemical parameters of Nile tilapia challenged with A. veronii. One-hundred sixty fish (33 ± 1.5 g) were assigned into four experimental groups, each with four replicates (4 glass tanks/group, 40 fish/group, 10 fish/tank) for 10 days. In the first (1st) and 2nd groups, 0 and 1.5 mg/L WPE were applied in tank water, respectively, without fish being challenged. In the 3rd and 4th groups, 0 and 1.5 mg/L WPE were applied in tank water, respectively, with fish intraperitoneal inoculated with 0.2 mL of A. veronii (0.5 × 10⁷ CFU). Aeromonas veronii infection significantly diminished the survivability, hepatic catalase, lysozyme activity, nitric oxide, immunoglobulin M, phagocytic %, total protein, albumin, and globulin. Moreover, a significant rise in the hepatic malondialdehyde, serum hepatorenal function indicators, cortisol, and glucose levels were consequences of A. veronii challenge. Interestingly, the interaction between bacterial challenge and WPE application increased the survivability, antioxidant activity, and immune responses and reduced ALT levels of fish treated with WPE during the bacterial challenge. The serum creatinine, cortisol, and glucose levels were decreased in fish treated with WPE during the infection but still higher than in the non-infected fish either treated or not treated with WPE. In conclusion, WPE (1.5 mg/L) can be used as an antibacterial substance in fish farming to alleviate the detrimental impacts of A. veronii infection by enhancing the antioxidant/immune status of the infected fish. These outcomes could help reduce antibiotic usage in fish farms, which is conducive to the sustainable development of aquaculture.

HIGHLIGHTS

• White poplar extract (WPE) had an in vitro antibacterial activity against Aeromonas veronii.

• Aeromonas veronii infection inhibited the antioxidant/immune functions of Nile tilapia.

• Aeromonas veronii infection altered the hepatorenal functions and biochemical parameters of Nile tilapia.

• WPE at a level of 1.5 mg/L displayed a therapeutic effect in Nile tilapia against A. veronii.

Keywords:

• Aeromonas veronii
• antibacterial activity
• antioxidant-immune status
• hepato-renal function
• Populus alba

Acknowledgements

This work was supported by the Researches Supporting Project (RSP2024R36), King Saud University, Riyadh, Saudi Arabia. The authors thank Professor Rasha M. Reda for her kind help and providing the A. veronii strain. The authors thank the Aquatic Animal Medicine Department, Faculty of Veterinary Medicine, Zagazig University, for their kind help during the experimental procedures.

Ethical approval

The experimental protocol received ethical approval from Zagazig University’s Institutional Animal Care and Use Committee (Approval No. ZU-IACUC/2/F/136/2021). All animal experiments were carried out in accordance with the instructions outlined in ‘The Guide for the Care and Use of Laboratory Animals in Scientific Investigations’, and the study followed the relevant institutional standards. All animal experiments were carried out in accordance with the ARRIVE guidelines.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The datasets generated or analysed during the current study are not publicly available but are available upon reasonable request from the corresponding author.