Moringa oleifera Leaf Powder Dietary Inclusion Differentially Modulates the Antioxidant, Inflammatory, and Histopathological Responses of Normal and Aeromonas hydrophila-Infected Mono-Sex Nile Tilapia (Oreochromis niloticus)

Abstract

This study aimed to detect the impact of <i>Moringa oleifera</i> leaf powder dietary inclusion on the antioxidant and innate immune responses of mono-sex Nile tilapia fingerlings. A total of 180 fingerlings were allocated in a random method into three groups with triplicate each. One group (1^st group) received the control diet (basal diet (BD) free of moringa) and the other groups (2^nd and 3^rd) fed BD containing <i>M. oleifera</i> leaf powder at 5 and 10% of the diet, respectively. After 6 weeks of feeding, fish were randomly redistributed into four replicates and rested for 24 h. Then, each fish in the first two replicates was injected with 0.2 mL of PBS, while the others were injected with 0.2 mL of <i>A. hydrophila</i> suspension (1.8 × 10⁶ CFU/mL). Healthy fish fed on <i>M. oleifera</i> leaf powder showed enhanced immune response manifested by significant increases in phagocytic and lysozyme activities with a marked H/L ratio (<i>P</i> < 0.05). In addition, significant alterations of the lymphocytic and heterophilic population in circulation with increasing infiltration in tissue such as the spleen were noticed. Also, <i>M. oleifera</i> significantly upregulated the antioxidants, <i>CAT</i> and <i>GPx</i>, proinflammatory cytokines, <i>IL1-</i>β<i>, IL-8</i>, and <i>IFN-</i>γ relative mRNA levels. On the other hand, following <i>A. hydrophila</i> challenging conditions<i>, M. oleifera</i> caused downregulations of <i>IL1-</i>β<i>, IL-8</i>, and <i>IFN-</i>γ transcription levels, and also lowered the <i>CAT</i> and <i>GPx</i> mRNA levels. In addition, a marked reduction of leukocytic infiltration plus a significant improvement of the degenerative changes in intestinal architecture has occurred. So, <i>M. oleifera</i> leaf powder can be included in the fish diet to enhance immune response under normal health conditions and lower the infection-associated inflammatory response.