Estrogen promotes autophagy in the mammary epithelial cells of dairy sheep via the CXCL12/CXCR4 axis.

Mammary gland development and lactation in dairy sheep are regulated by hormones and autophagy; however, the role of estrogen-mediated autophagy remains unclear. This study determined that estrogen enhances autophagy, promotes CXCR4 and CXCL12 gene expression, and increases the number of autolysosomes in sheep mammary epithelial cells. Co-treatment with a CXCR4 overexpression vector and the small-molecule alternative of CXCL12, NUCC-390, significantly upregulated ATG5 and LC3 gene expression, increased the abundance of the autophagy-associated protein ATG5 and the LC3II/I ratio, and increased the consumption of the autophagy substrate P62. These results suggest that CXCR4 and CXCL12 signaling promotes autophagy in mammary epithelial cells. Conversely, co-treatment with a CXCR4-specific blocker and estrogen inhibited autophagic changes in ATG5, P62, and LC3 levels, reducing the number of autophagosomes and autolysosomes. Overall, this study demonstrated that estrogen promotes autophagy in sheep mammary epithelial cells through the CXCL12/CXCR4 signaling axis, revealing the underlying mechanisms behind estrogen-mediated autophagy.