Dietary Cinnamaldehyde Alleviates Chlorpyrifos-Induced Immunotoxicity in Nile Tilapia and Modulates Apoptosis-, Autophagy-, and AKT/mTOR-Related Gene Expression.

Abstract

This study investigated the immunotoxic effects of chronic waterborne chlorpyrifos (CPO) exposure in Nile tilapia (Oreochromis niloticus) and evaluated the protective efficacy of dietary cinnamaldehyde (CA). Fish were exposed to 15 μg/L CPO for 60 days, while CIN was incorporated into the diet at 0.42 g/kg feed. Immune function was comprehensively assessed through hematological profiling, serum innate immune responses, splenic oxidative stress and apoptotic biomarkers, expression of immune- and cell survival-related genes, and histopathological examination of the spleen. Chronic CPO exposure caused marked hematological disturbances, characterized by significant reductions in erythrocyte count, hematocrit, hemoglobin concentration, and platelet count, together with pronounced leukocytosis and alterations in differential leukocyte populations. Moreover, CPO significantly suppressed innate immune responses, as proved by decreased serum lysozyme activity and nitric oxide production. Splenic oxidative injury was confirmed by elevated malondialdehyde, accompanied by marked depletion of reduced glutathione, catalase, and superoxide dismutase. At the molecular level, CPO markedly dysregulated the expression of akt-1, mtor, becn-1, jnk, bcl-2, and caspase-3. Histopathological examination further revealed severe splenic lesions, including lymphoid depletion, melanomacrophage center activation, vascular congestion, and disruption of normal splenic architecture. In contrast, dietary CA markedly alleviated CPO-induced immunotoxicity by restoring hematological indices, enhancing innate immune responses, reinforcing antioxidant defenses, and normalizing the expression of akt-1, mtor, becn-1, jnk, caspase-3, and bcl-2 toward physiological levels. Histological observations corroborated these biochemical and molecular findings, demonstrating substantial preservation of splenic architecture in CA-treated fish. Collectively, these findings indicate that dietary CA effectively protects Nile tilapia against CPO-induced immunotoxicity through enhancement of antioxidant capacity, restoration of innate immune competence, inhibition of apoptosis, modulation of autophagy, and regulation of the AKT/mTOR signaling pathway.