Alveolar epithelial cell (AEC) senescence is considered to be a universal pathological feature of many chronic pulmonary diseases. Our previous study found that epoxyeicosatrienoic acids (EETs), produced from arachidonic acid (ARA) through the cytochrome P450 cyclooxygenase (CYP) pathway, have significant negative regulatory effects on cellular senescence in AECs. However, the exact mechanisms by which EETs alleviate the senescence of AECs still need to be further explored. In the present study, we observed that bleomycin (BLM) induced enhanced mitophagy accompanied by increased mitochondrial ROS (mito-ROS) content in the murine alveolar epithelial cell line MLE12. While EETs reduced BLM-induced mitophagy and mito-ROS content in MLE12 cells, and the mechanism was related to the regulation of NOX4/Nrf2-mediated redox imbalance. Furthermore, we found that inhibition of EETs degradation could significantly inhibit mitophagy and regulate NOX4/Nrf2 balance to exert anti-oxidant effects in D-galactose-induced premature aging mice. Collectively, these findings may provide new ideas for treating age-related pulmonary diseases by targeting EETs to improve mitochondrial dysfunction and reduce oxidative stress.
Pulmonary fibrosis (PF) is a disease characterized by diffusing alveolar inflammation and alveolar structural disorders that ultimately lead to pulmonary interstitial fibrosis. S-allylmercaptocysteine (SAMC) as a water-soluble organosulfur garlic derivative exhibits efficient anti-inflammatory and anti-oxidative activities. In this study, we attempted to explore the function of SAMC in inhibiting bleomycin (BLM)-induced pulmonary fibrosis in mice. 0.035 U/g of BLM was intraperitoneally injected into mice twice per week for 4 weeks to induce fibrosis. SAMC (25 and 50 mg/kg) and N-acetylcysteine (NAC, 600 mg/kg) were given to mice for 28 days. The results indicate that SAMC could significantly ameliorate the pathological structure, and decrease inflammatory cell infiltration and pro-inflammatory cytokines in bronchoalveolar lavage fluid (BALF) in BLM-induced pulmonary fibrosis mice. SAMC showed an anti-fibrosis effect by increasing anti-oxidants like HO-1, GSH and SOD as well as decreasing hydroxyproline (HYP) in BLM-induced mice. Mechanistic studies suggested that SAMC alleviated oxidative stress probably by impacting the Nox4/Nrf2 pathways, and played an anti-fibrosis role with decreasing the expression of α-SMA, collagen III, collagen I by suppressing the TGF-β1/Smad pathway. These findings indicate that SAMC may be partially responsible for the therapeutic effect on PF patients.
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