Biotoxicity of paraquat to lung cells mediated by endoplasmic reticulum-mitochondria interaction

The high lethality caused by paraquat (PQ) poisoning has attracted much attention in public and human health due to its high toxicity and lethality. However, the understanding of the mechanism of PQ-induced apoptosis from the perspective of organelles, especially inter-organelle interactions, is still scarce. Exploring the linkage of multiple organelles during PQ poisoning and the molecular mechanisms of PQ poisoning under its mediation will help to gain insight into the mode of PQ poisoning at the organelle level. In this study, we observed that a certain dose of PQ gavage induced oxidative stress, mitochondrial dysfunction and endoplasmic reticulum stress in rat lung tissue cells. PQ toxicity led to the occurrence of Ca²⁺ overload in the endoplasmic reticulum, and the activated BIP and CHOP pathways directly/indirectly led to the expression of apoptogenic factors Caspase family factors. In addition, PQ promoted Ca²⁺ release from the endoplasmic reticulum and Ca²⁺ uptake by mitochondria, which induced the disruption of Bax/Bcl-2 channel proteins in response to the IP₃R/RyR/VDAC1&2/MCU Ca²⁺ axis thereby leading to the release of CytoC, which ultimately induced endoplasmic reticulum stress and apoptotic cell death. In addition, 10 differential proteins were screened and validated by proteomics that may act as upstream and downstream active factors of mitochondria-endoplasmic reticulum interaction-mediated biotoxicity. Our findings provide new perspectives for researchers to explore the toxicity mechanisms of PQ to reduce their adverse effects.