Bovine endometritis is a common reproductive system disease in dairy cows that leads to decreased milk production and reproductive performance, causing significant economic losses for farmers. Research has shown that microRNAs (miRNAs) play a significant role in regulating the expression of biological genes and are closely related to the occurrence of inflammation, including bta-miR-22-3p. However, the specific molecular mechanisms by which miRNAs regulate bovine endometritis remain unclear. To investigate the regulatory mechanism of bta-miR-22-3p in yak endometritis, uterine tissues were collected from three healthy bos grunniens and three bos grunniens with endometritis, approximately 21 days postpartum. Various methods were employed, including real-time quantitative polymerase chain reaction (RT-qPCR), Western blot (WB), enzyme-linked immunosorbent assay (ELISA), and immunofluorescence (IF). The results demonstrated that overexpression of bta-miR-22-3p led to a significant decrease (P < 0.05) in factors related to the mitogen-activated protein kinase (MAPK) signaling pathway and associated inflammatory factors, such as extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (P38), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β). Furthermore, dual-luciferase assays confirmed that the kinase suppressor of the Ras 2 (KSR2) gene is a downstream target of bta-miR-22-3p. Overexpression of bta-miR-22-3p inhibited the expression of KSR2. When KSR2 was inhibited, the levels of MAPK signaling pathway-related factors and inflammation also significantly decreased (P < 0.05). Thus, bta-miR-22-3p suppresses the activation of the MAPK signaling pathway through the inhibition of KSR2, resulting in a reduction of inflammatory factors. In conclusion, this study demonstrated that bta-miR-22-3p targets the KSR2 gene to alleviate LPS (Lipopolysaccharide)-induced inflammatory damage.
