Investigation of BECN1-Mediated Autophagy Mechanisms Triggered by External Stimuli in Clinical Mastitis of Dairy Cows

Disruption of the blood-milk barrier and inhibition of enzymatic activity caused by abnormal external stimuli, accompanied by the occurrence of autophagy, are among the major factors contributing to the onset of clinical mastitis (CM) in dairy cows. However, the molecular mechanisms through which external stimuli and autophagy regulate CM in dairy cows are not fully understood. This study examined mammary gland (MG) tissue samples collected from healthy dairy cows and those with CM caused by <i>Staphylococcus aureus</i> (<i>n</i> = 3 per group) to observe histological changes and autophagic phenomena, identify candidate biomolecular targets involved in external stimuli in dairy cows affected by mastitis through proteomic and bioinformatic analyses, and analyze their expression and distribution patterns in MG tissues. Pathological examination revealed that the MG tissues of the CM group exhibited significant alveoli collapse and inflammatory cell infiltration, accompanied by autolysosome and phagolysosome activation, and elevated expression of lysosomal and autophagic markers. Bioinformatic analysis identified five biological processes (BPs) and 144 differentially expressed proteins (DEPs) associated with external stimuli, among which beclin 1 (BECN1) was involved in all five BPs. Pathway enrichment analysis revealed that BECN1 participated in six autophagy-related signaling pathways. BECN1 was localized in the cytoplasm of mammary epithelial cells, and both mRNA and protein levels of <i>BECN1</i> were significantly upregulated in the CM group compared with those in the controls (<i>p</i> < 0.01). These findings suggest that BECN1 expression is closely associated with CM in dairy cows and correlates with autophagy-related responses to external stimuli, and its elevated expression is positively correlated with <i>Staphylococcus aureus</i>-induced CM severity. Our results offer preliminary observations relevant to the molecular mechanisms by which BECN1, the autophagy-regulating biomolecule BECN1 influences the development of CM.