Role of the MAPK pathway in human lung epithelial-like A549 cells apoptosis induced by paraquat.

This study aims to investigate the value of mitogen-activated protein kinases (MAPKs) for paraquat (PQ)-induced apoptosis in human lung epithelial-like A549 cells and the specific mechanism. A549 cell apoptosis were induced by PQ. These cells were divided into six groups: control group (cells were cultured in RPMI-1640 medium); SP600125 group (cells were preconditioned with SP600125); SB203580 group (cells were preconditioned with SB203580); PQ group (cells were treated with PQ); SP600125+PQ group (cells were preconditioned with SP600125 following PQ); SB203580+PQ group (cells were preconditioned with SB203580 following PQ). The cell survival rate, apoptosis rate, and activities of caspase-3 and -9 were detected. When compared with the control group, both SP600125 and SB203580 groups had no significant difference in the detected indicators. When compared with PQ group, the cells in both SP600125+PQ group and SB203580+PQ group had significantly increased viability and level of anti-apoptotic protein Bcl-2; and had decreased apoptotic rates, decreased levels of caspase-3 and -9, and decreased level of pro-apoptotic protein Bax. The ratio of p-JNK/JNK protein expression in the SP600125+PQ group significantly decreased, while the ratio of the p-P38/P38 protein expression in the SB203580+PQ group decreased. PQ induced A549 cell apoptosis through the MAPKs pathway.

Effect of endoplasmic reticulum calcium on paraquat­induced apoptosis of human lung type II alveolar epithelial A549 cells.

The present study aimed to explore the role of endoplasmic reticulum calcium (ER Ca2+) in the apoptosis of human lung type II alveolar epithelial A549 cells induced by paraquat (PQ) in vitro. PQ significantly elevated the intracellular Ca2+ concentration. Treatment with the Ca2+­ATPase inhibitor thapsigargin significantly increased PQ­induced cytotoxicity, elevated the intracellular level of Ca2+, and increased the apoptosis rate, the protein expression of glucose­regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP), and the activities of caspase­7 and caspase­12 in PQ­treated cells. By contrast, treatment with heparin, an inositol 1,4,5­triphosphate receptor inhibitor, remarkably attenuated cytotoxicity and decreased the intracellular level of Ca2+, the apoptosis rate and the expression levels of GRP78, CHOP and Caspases. In conclusion, PQ impaired the regulating function of ER Ca2+ and resulted in an excessive increase of intracellular Ca2+. Therefore, influencing the Ca2+ signaling in the ER influenced the apoptosis of A549 cells via the ER stress pathway.

Involvement of PINK1/Parkin-mediated mitophagy in paraquat- induced apoptosis in human lung epithelial-like A549 cells.

Paraquat (PQ) is one of the most popular herbicides and has been widely used all over the world over the past several decades. However, PQ exposure can cause multiple organ failure, especially acute lung injury in humans as well as in rodent animals. Mitochondrial dysfunction plays a crucial role in PQ-induced lung cell damage. Mitophagy, defined as the selective autophagic elimination process of mitochondria, is a significant mechanism controlling mitochondrial quality. In this study, we investigated PINK1/Parkin-mediated mitophagy activated in the process of the PQ-induced cell apoptosis by using human lung epithelial-like A549 cells. We showed that PQ inhibited cell viability and induced mitochondrial damage as well as cell apoptosis in A549 cells. During this process, PQ induced PINK1/Parkin-mediated mitophagy. Knocking down the expression of Parkin gene by the transient transfection of Parkin small interfering RNA mitigated PQ-induced mitophagy and worsened A549 cell apoptosis. On the contrary, overexpression of Parkin attenuated PQ-induced cell injury by promoting mitophagy. These results indicated PINK1/Parkin-mediated mitophagy played a protective role in PQ-induced A549 cell damage and provided a potential therapeutic strategy for enhancing mitophagy against PQ poisoning.

Eukaryotic translation initiation factor 2 subunit α (eIF2α) inhibitor salubrinal attenuates paraquat-induced human lung epithelial-like A549 cell apoptosis by regulating the PERK-eIF2α signaling pathway.

Paraquat (PQ), as one of the most widely used herbicides in the world, can cause severe lung damage in humans and animals. This study investigated the underlying molecular mechanism of PQ-induced lung cell damage and the protective role of salubrinal. Human lung epithelial-like A549 cells were treated with PQ for 24h and were pre-incubated with salubrinal for 2h, followed by 500µM of PQ treatment. Silencing eIF2α gene of the A549 cells with siRNA interference method was conducted. Cell morphology, cell viability, apoptosis and caspase-3 activity were assessed by different assays accordingly thereafter. The expression of PERK, p-PERK, ATF6, c-ATF6, IRE1α, p-IRE1α, CHOP, GRP78, p-eIF2α and ß-actin was assayed by western blot. The data showed that PQ significantly reduced A549 cell viability, changed cell morphology, induced cell apoptosis and significantly upregulated the levels of GRP78, CHOP, p-PERK, c-ATF6 and p-IRE1α. However, 30µM salubrinal could attenuate the effects of PQ on damages to A549 cells through upregulating p-eIF2α. In contrast, knocking down eIF2α gene inhabited the effects of salubrinal. These results suggest that PQ-induced A549 cell apoptosis involved endoplasmic reticulum (ER) stress, specially the PERK-eIF2α pathway. Salubrinal attenuated A549 cells from PQ-induced damages through regulation of the PERK-eIF2α signaling.