Akt/mTOR Pathway Agonist SC79 Inhibits Autophagy and Apoptosis of Oligodendrocyte Precursor Cells Associated with Neonatal White Matter Dysplasia.

White matter dysplasia (WMD) in preterm infants due to intrauterine inflammation is caused by excessive apoptosis of oligodendrocyte precursor cells (OPCs). In recent years, studies have found that excessive autophagy and apoptosis are highly interconnected and important in infection and inflammatory diseases in general. Therefore, in this study, we aimed to confirm whether regulation of autophagy by using the Akt phosphorylation agonist SC79 can inhibit abnormal apoptosis of OPCs and promote myelin maturation and white matter development in neonatal rats with WMD. We investigated the effect of inflammation on oligodendrocyte development in P0 neonatal rats by intracerebellar injection of LPS, and collected brain tissue at P2 and P5. Immunohistochemical and immunofluorescence staining were used to evaluate white matter damage, while immunofluorescence staining, terminal deoxynucleotidyl transferase dUTP nick end labeling analysis (TUNEL), and western blotting were used to evaluate autophagy and apoptosis. First, we observed that white matter development was arrested and white matter fiber maturation was impaired in LPS-inflicted pups compared with those in the sham-operated group. Second, treatment with SC79 reduced the levels of LC3II, caspase 3, caspase 9, and Bax/Bcl-2 and increased the levels of p62, p-Akt, and p-mTOR in the brain tissue of neonatal rats. Finally, SC79 treatment inhibited OPC apoptosis by increasing the binding of Beclin 1 to Bcl-2, which promoted OPC differentiation and maturation. However, the opposite results were observed after rapamycin administration. Taken together, our results suggest that SC79 can inhibit the abnormal apoptosis of OPCs caused by excessive autophagy through the Akt/mTOR pathway and that SC79 is a potential therapeutic agent for WMD in preterm infants.

Rapamycin attenuates pyroptosis by suppressing mTOR phosphorylation and promoting autophagy in LPS-induced bronchopulmonary dysplasia.

PURPOSE/AIM: Bronchopulmonary dysplasia (BPD) is associated with poor survival in preterm infants. Intrauterine infection can aggravate the degree of obstruction of alveolar development in premature infants; however, the pathogenic mechanism remains unclear. In this study, we sought to determine whether pyroptosis could be inhibited by downregulating mammalian target of rapamycin (mTOR) activation and inducing autophagy in BPD-affected lung tissue. MATERIALS AND METHODS: We established a neonatal rat model of BPD induced by intrauterine infection via intraperitoneally injecting pregnant rats with lipopolysaccharide (LPS). Subsequently, mTOR levels and pyroptosis were evaluated using immunohistochemistry, immunofluorescence, TUNEL staining, and western blotting. The Shapiro-Wilk test was employed to assess the normality of the experimental data. Unpaired t-tests were used to compare the means between two groups, and comparisons between multiple groups were performed using analysis of variance. RESULTS: Pyroptosis of lung epithelial cells increased in BPD lung tissues. After administering an mTOR phosphorylation inhibitor (rapamycin) to neonatal rats with BPD, the level of autophagy increased, while the expression of autophagy cargo adaptors, LC3 and p62, did not differ. Following rapamycin treatment, NLRP3, Pro-caspase-1, caspase-1, pro-IL-1ß, IL-1ß, IL-18/Pro-IL-18, N-GSDMD/GSDMD, Pro-caspase-11, and caspase-11 were negatively regulated in BPD lung tissues. The opposite results were observed after treatment with the autophagy inhibitor MHY1485, showing an increase in pyroptosis and a significant decrease in the number of alveoli in BPD. CONCLUSIONS: Rapamycin reduces pyroptosis in neonatal rats with LPS-induced BPD by inhibiting mTOR phosphorylation and inducing autophagy; hence, it may represent a potential therapeutic for treating BPD.

Regulating NLRP3 Inflammasome-Induced Pyroptosis via Nrf2: TBHQ Limits Hyperoxia-Induced Lung Injury in a Mouse Model of Bronchopulmonary Dysplasia.

Nuclear factor e2-related factor 2 (Nrf2) plays a key role in cellular resistance to oxidative stress injury. Oxidative stress injury, caused by Nrf2 imbalance, results in increased pyroptosis, DNA damage, and inflammatory activation, which may lead to the arrest of alveolar development and bronchopulmonary dysplasia (BPD) in premature infants under hyperoxic conditions. We established a BPD mouse model to investigate the effects of tert-butylhydroquinone (TBHQ), an Nrf2 activator, on oxidative stress injury, pyroptosis, NLRP3 inflammasome activation, and alveolar development. TBHQ reduced abnormal cell death in the lung tissue of BPD mice and restored the number and normal structure of the alveoli. TBHQ administration activated the Nrf2/heme oxygenase-1 (HO-1) signaling pathway, resulting in the decrease in the following: reactive oxygen species (ROS), activation of the NOD-like receptor pyrin domain containing 3 (NLRP3) inflammasome, and IL-18 and IL-1ß expression and activation, as well as inhibition of pyroptosis. In contrast, after Nrf2 gene knockout in BPD mice, there was more severe oxidative stress injury and cell death in the lungs, there were TUNEL + and NLRP3 + co-positive cells in the alveoli, the pyroptosis was significantly increased, and the development of alveoli was significantly blocked. We demonstrated that TBHQ may promote alveolar development by enhancing Nrf2-induced antioxidation in the lung tissue of BPD mice and that the decrease in the NLRP3 inflammasome and pyroptosis caused by Nrf2 activation may be the underlying mechanism. These results suggest that TBHQ is a promising treatment for lung injury in premature infants with hyperoxia.