Klebsiella pneumoniae Induces Ferroptosis and Lactation Dysfunction in Bovine Mastitis via NCOA4-Mediated Ferritinophagy

Klebsiella pneumoniae, a major bovine mastitis pathogen, disrupts mammary gland function through poorly understood mechanisms. This study demonstrates that K. pneumoniae infection triggers ferroptosis in bovine mammary epithelial cells (BMECs) via nuclear receptor coactivator 4 (NCOA4)-mediated ferritinophagy, leading to lactation impairment. RNA sequencing revealed enrichment in ferroptosis, autophagy, and iron metabolism pathways. Infection time-dependently suppressed glutathione peroxidase 4 (GPX4) and solute carrier family 7 member 11 (SLC7A11) expression, causing mitochondrial membrane potential collapse and lipid peroxidation. Crucially, K. pneumoniae activated NCOA4-dependent ferritin degradation, elevating intracellular Fe2+. NCOA4 knockdown alleviated ferroptosis, restored GPX4/SLC7A11 expression, reduced the bacterial load, and partially rescued lactation markers (fatty acid synthase, acetyl-CoA carboxylase 1, and β-casein). In vivo, infected mammary glands showed iron overload, 4-hydroxynonenal accumulation, lactation protein suppression, and pathological damage, correlating with NCOA4/ferritin heavy chain 1 upregulation. These findings establish NCOA4-mediated ferritinophagy as a key driver of K. pneumoniae-induced ferroptosis and lactation dysfunction, suggesting novel therapeutic targets for mastitis.