Magnolol mitigates polystyrene microplastic-induced oviductal toxicity in laying hens via immunomodulation and microbiota regulation

Environmental contamination with polystyrene microplastics (PS) has been shown to trigger inflammation and impair reproductive function in animals. Magnolol (MAG) is a natural compound with anti-inflammatory properties. However, the protective role of MAG against PS-induced oviductal damage remains unclear. This study aimed to investigate the protective effects and underlying mechanisms of dietary MAG supplementation in laying hens exposed to PS. A total of 270 Hy-Line white hens were randomly assigned to three groups: control group (CK), PS-exposed group (PS), and MAG protective group against PS exposure (PM). Hens in the PM group were fed a MAG-supplemented diet, while hens in the CK and PS groups received a basal diet. After eight weeks of dietary treatment, hens in PS and PM groups were treated with 1 mg/mL PS by gavage, and the CK group received phosphate-buffered saline for four weeks. The results revealed that PS exposure significantly reduced albumen quality and eggshell strength, which was associated with decreased abundance of the beneficial bacterium Lactobacillus crispatus, disrupted mucosal barrier integrity, enhanced oxidative stress, and increased inflammation and apoptosis in the oviduct. MAG supplementation alleviated these adverse effects by improving antioxidant status, reducing mucosal inflammation and apoptosis, enhancing epithelial barrier markers, and restoring the microbial balance in the oviduct. In vitro cell culture experiments also confirmed MAG could inhibit macrophage M1-type polarization via suppressing NF-κB signaling pathway activation. Consequently, MAG reduced mucosal inflammation and apoptosis, enhanced the expression of epithelial barrier markers (Claudin and MUC-2), and restored the microbial balance in the oviduct. These findings demonstrate that dietary MAG mitigates PS-induced oviductal damage through immunomodulation and microbiota regulation, ultimately improving reproductive performance in laying hens. This study highlights MAG as a promising dietary strategy to counteract microplastic-induced reproductive toxicity in poultry.