Overexpression of angiotensin-converting enzyme 2 contributes to the amelioration of Streptococcus uberis-induced inflammatory injury in mammary epithelial cells.

Streptococcus uberis (S. uberis) is an environmentally important pathogenic bacterium and is the main pathogenic microorganism responsible for mastitis, which causes significant economic losses worldwide. Currently, there is no particularly effective treatment other than antibiotic therapy. Angiotensin-converting enzyme 2 (ACE2) plays an anti-inflammatory as well as an anti-injury role in numerous inflammatory diseases. Therefore, this study aimed to assess the hypothesis that S. uberis-induced mammary epithelial cells injury associated with ACE2, angiotensin II (Ang II) as well as angiotensin 1-7 (Ang-(1-7)) imbalance and that overexpression of ACE2 can repair S. uberis-induced mammary epithelial cells injury. We observed that the expression level of ACE2 was significantly downregulated after treatment of EpH4-Ev cells with S. uberis. Next, this assay verified the role of ACE2 in S. uberis-induced inflammatory injury in EpH4-Ev cells by overexpressing the ACE2 gene as well as its silencing. The results showed that overexpression of the ACE2 gene significantly activated the interleukin-10/signal transducer and activator of transcription 3/suppressors-of-cytokine-signaling 3 (IL-10/STAT3/SOCS3) pathway, thereby inhibiting the nuclear factor-κB (NF-κB) as well as pyroptosis pathways. Furthermore, overexpression of the ACE2 gene reversed the downregulation of zonula occludens 1 (ZO-1), Occludin, Claudin-1, and Claudin-2 caused by S. uberis, suggesting that ACE2 could promote to repair the blood-milk barrier. However, siRNA silencing of the ACE2 gene produced the opposite effect. These results suggest that ACE2 ameliorates S. uberis-induced mammary epithelial cells injury. AVAILABILITY OF DATA: All data generated or analyzed during this study are included within the article and its additional information file.