Nano-delivery system of milk-derived exosomes loaded with Forsythiaside A: Studies on bovine mammary epithelial cells and mastitis induced mice.

Bovine mammary gland health is essential for sustaining milk yield and dairy production efficiency. Currently, antimicrobial resistance resulting from antibiotic treatment of mastitis severely constrains the sustainable development of the dairy industry. Forsythoside A (FTA), a natural phenylethanoid glycoside possessing potent anti-inflammatory and antioxidant activities, exhibits considerable therapeutic potential; however, its clinical translation remains hindered by poor bioavailability. To address this limitation, a milk-derived exosome-based nano-delivery system (FTA-mExos) was engineered. The therapeutic efficacy and underlying mechanisms of FTA-mExos were systematically evaluated in both in vitro and in vivo inflammatory models established using clinically isolated Staphylococcus chromogenes (S. chromogenes). In vitro, FTA-mExos significantly reduced reactive oxygen species (ROS) and malondialdehyde (MDA) levels in S. chromogenes-infected bovine mammary epithelial cells (BMECs), while enhancing glutathione peroxidase (GSH-Px) activity and restoring mitochondrial membrane potential. Mechanistically, FTA-mExos alleviated inflammatory responses by suppressing NF-κB signaling and downregulating the expression of pro-inflammatory cytokines, including IL-6, IL-1β, and TNF-α. In vivo studies revealed that FTA-mExos upregulated the expression of tight junction proteins (ZO-1, Occludin, and Claudin-3), leading to the restoration of blood-milk barrier (BMB) integrity and attenuation of oxidative stress injury and inflammatory responses. These findings demonstrate that FTA-mExos represent a promising nano-delivery strategy for the treatment of bovine mastitis.