HO-1 enhances autophagy to alleviate oxidative damage in BMECs via Keap1/Nrf2 and AMPK/mTOR signaling

Heme oxygenase-1 (HO-1) plays an important role in maintaining Nrf2-mediated redox homeostasis. Lipopolysaccharide (LPS), a major pathogenic factor in Bacterial mastitis, induces oxidative stress and inflammation in bovine mammary epithelial cells (BMECs). HO-1-induced Autophagy has been shown to mitigate oxidative damage across various tissues in previous studies. Therefore, we hypothesized that HO-1 may alleviate oxidative stress in BMECs by promoting Autophagy via the Keap1/Nrf2 and AMPK/mTOR signaling pathways. We examined the effects of HO-1 on oxidative stress, including antioxidant enzyme production and inflammatory response, as well as Autophagy in LPS-stimulated BMECs. In this study, overexpression and knockout of HO-1 or Nrf2 were performed in BMECs to verify the involvement of HO-1 in the Keap1/Nrf2 pathway. In addition, Autophagy inhibitors and mTOR Inhibitor were used to determine whether the antioxidant effects of HO-1 were mediated by Autophagy via the AMPK/mTOR signaling pathway. We found that HO-1 alleviated LPS-induced inflammation response and improved the resistance of BMECs to oxidative stress. Furthermore, HO-1 activated the Keap1/Nrf2 signaling pathway, thereby enhancing antioxidant capacity, which was further confirmed by in vitro overexpression and knockout experiments targeting Nrf2 or HO-1. Meanwhile, HO-1 also upregulated the expression of autophagy-related genes, whereas treatment with an Autophagy inhibitor attenuated the antioxidant effects of HO-1. In addition, administration of an mTOR Inhibitor further indicated that HO-1-mediated Autophagy was regulated via the AMPK/mTOR signaling pathway. In conclusion, HO-1 alleviates oxidative damage in BMECs by promoting Autophagy through the Keap1/Nrf2 and AMPK/mTOR signaling pathways. These findings identify HO-1 as a potential therapeutic target for reducing tissue damage in Bacterial mastitis.