A novel circular RNA circPRIM2 revealed by circular RNA profile inhibits mammary epithelial cell proliferation and immune response in bovine mastitis.

BACKGROUND

Bovine mastitis is a major inflammatory disease that impairs mammary epithelial function, milk production, and animal health. Circular RNAs (circRNAs) are involved in many physiological and pathological processes, but their roles in pathogen-induced bovine mammary epithelial dysfunction remain unclear.

AIM: This study aimed to identify mastitis-associated circRNAs and determine whether circPRIM2 regulates mammary epithelial cell proliferation, β-casein secretion, and inflammatory responses.

METHODS

An inflammatory model was established in bovine mammary alveolar cell-T (MAC-T) cells by heat-inactivated Staphylococcus aureus or Escherichia coli stimulation. circRNA profiles were analyzed by high-throughput sequencing and bioinformatic prediction. The stability and function of circPRIM2 were further validated by RNase R digestion, RT-qPCR, CCK-8, EdU, Western blot, and ELISA assays.

RESULTS

A total of 5043 circRNAs were identified in S. aureus-treated MAC-T cells, and 31 circRNAs were differentially expressed between S. aureus-treated and control cells. circPRIM2, a novel circRNA derived from the PRIM2 locus, was down-regulated under inflammatory conditions and resistant to RNase R digestion. circPRIM2 overexpression reduced MAC-T cell viability and EdU incorporation, increased β-casein expression and secretion, and decreased LTA-induced TNF-α and IL-1β secretion as well as p65 phosphorylation.

CONCLUSION

These findings suggest that circPRIM2 may act as an epithelial regulatory circRNA linking cell growth, secretory function, and immune response during bovine mastitis. This study provides a basis for further exploring circPRIM2 as a potential biomarker or molecular target for mastitis management.