PM2.5 induces autophagy-dependent ferroptosis by endoplasmic reticulum stress in SH-SY5Y cells.

Fine particulate matter (PM2.5 ) has been a global environmental problem threatening public health in recent years. PM2.5 exposure was associated with an increased risk of neurodegenerative diseases related to neuronal apoptosis. Ferroptosis is a nonapoptotic form of programmed the cell death, characterized by excess iron-dependent lipid peroxidation products. Whether PM2.5 could induce ferroptosis in cells and thus be involved in its neurotoxicity is unknown. In this study, we found that PM2.5 induced endoplasmic reticulum stress, apoptosis, autophagy, and ferroptosis in neuroblastoma human neuroblastoma cells (SH-SY5Y). Interestingly, ferroptosis was the predominant form of mortality in the presence of high doses of PM2.5 exposure. In addition, the endoplasmic reticulum stress inhibitor 4-phenylbutyric acid (4-PBA) inhibited PM2.5 -induced cellular autophagy, apoptosis, and ferroptosis. Autophagy inhibitors chloroquine (CQ) alleviated PM2.5 -induced ferroptosis but did not reverse apoptosis. We also found that inhibition of both endoplasmic reticulum stress and autophagy reversed the PM2.5 -induced increase in the expression level of cytophagy nuclear receptor coactivator 4 (NCOA4). Our results suggested that PM2.5 -induced ferroptosis in SH-SY5Y cells was autophagy-dependent ferroptosis due to endoplasmic reticulum stress, which might be associated with the elevation of iron content caused by NCOA4-mediated ferritin autophagy.

Effect of scrubbing by NaClO backwashing on membrane fouling in anammox MBR.

NaClO based chemically enhanced backwash (CEB) is often administered to maintain membrane permeability during the operation of MBR. However, the effect and working mechanism of NaClO concentrations in CEB were rarely investigated. The current investigation examined the changes in membrane resistance, permeate production and membrane morphology with or without CEB in an anammox MBR to reveal the scrubbing effect of different NaClO concentrations (0-596 mg/L). Good cleaning effect indicated by membrane fouling rate of 1.98-2.26 kPa/day and membrane permeate production of 80-88 L was observed when NaClO concentration of 149-596 mg/L was used. The best cleaning effect was observed when 298 mg/L of NaClO was used. To explore the mechanism of CEB action, backwashing foulants were also analyzed. Insoluble EPS transformed into soluble forms like S-EPS or SMP after the sludge was exposed to NaClO. The NaClO based CEB removed 112-675 mg of polysaccharide (PS)/m2 in foulants at NaClO concentration of 149-596 mg/L, which was significantly higher than the value obtained by pure water (35 mg PS/m2). The possible mechanisms behind the detachment of soluble PS seemed as oxidation and sterilization by NaClO. The current investigation provides useful guidelines on NaClO concentrations applied during CEB for anammox MBR.