Vitamin D3 mediates autophagy to alleviate inflammatory responses in bovine endometrial epithelial cells and organoids via the PI3K/AKT/mTOR pathway

Abstract

As a natural anti-inflammatory agent, it remains unclear whether the anti-inflammatory effects of VD3 (1,25 dihydroxyvitamin D3) are related to autophagy. This study investigates the impact of VD3 on inflammatory injury, autophagy, oxidative stress, and apoptosis in bovine endometrial epithelial cells (BEECs) and bovine endometrial organoids (BEOs). BEECs and BEOs were treated with LPS (1 μg/ml) for 24 hours, followed by treatment with LPS+VD3 (50 ng/ml) for 6 hours. Cell viability was assessed using the CCK8 assay. The expression levels of inflammatory factors (IL-1β, IL-6, TLR4, NF-κB), autophagy markers (Beclin-1, ATG5, ATG7, p62), and components of the PI3K/AKT/mTOR pathway (PI3K, AKT, and mTOR) were quantified using qRT-PCR and Western blot analyses. LC3B expression was detected by immunofluorescence, and the apoptosis rate was assessed using Annexin V. The results demonstrated a significant decrease in the expression levels of IL-1β, IL-6, TLR4, and NF-κB, along with a notable increase in the activity of CAT and SOD2 in the LPS+VD3 group (P < 0.05). The expression of autophagy-related factors was significantly increased, whereas the expression of signaling pathway factors was decreased in the LPS+VD3 group (P < 0.05). Additionally, apoptosis was significantly alleviated in the LPS+VD3 group (P < 0.05). Collectively, these findings indicate that VD3 modulates autophagy, attenuates oxidative stress and inflammatory damage in BEECs and BEOs, and inhibits LPS-induced apoptosis via the PI3K/AKT/mTOR pathway.