Inhibition of ER stress attenuates kidney injury and apoptosis induced by 3-MCPD via regulating mitochondrial fission/fusion and Ca2+ homeostasis

Abstract

3-Chloro-1, 2-propanediol (3-MCPD) is a food-borne toxic substance well-known for more than 40 years that is mainly associated with nephrotoxicity. A better understanding of 3-MCPD nephrotoxicity is required to devise efficacious strategies to counteract its toxicity. In the present work, the role of endoplasmic reticulum (ER) stress along with its underlying regulatory mechanism in 3-MCPD-mediated renal cytotoxicity was investigated in vivo and in vitro. Our data indicated that 3-MCPD-stimulated ER stress response evidenced by sustained activation of PERK-ATF4-p-CHOP and IRE1 branches in Sprague Dawley (SD) rats and human embryonic kidney (HEK293) cells. Moreover, ER stress-associated specific apoptotic initiator, caspase 12, was over-expressed. Blocking ER stress with its antagonist, 4-phenylbutyric acid (4-PBA), improved the morphology and function of kidney effectively. 4-PBA also increased cell viability, relieved mitochondrial vacuolation, and inhibited cell apoptosis through regulating caspase-dependent intrinsic apoptosis pathways. Furthermore, the enhanced expressions of two mitochondrial fission proteins, DRP1/p-DRP1 and FIS1, and the relocation of DRP1 on mitochondria subjected to 3-MPCD were reversed by 4-PBA, while the expression of the fusion protein, MFN2, was restored. Moreover, cellular Ca²⁺ overload, the over-expression of CaMKK2, and the loss of mitochondria-associated membranes (MAM) were also relieved after 4-PBA co-treatment. Collectively, our data emphasized that ER stress plays critical role in 3-MCPD-mediated mitochondrial dysfunction and subsequent apoptosis as well as blockage of ER stress ameliorated kidney injury through improving mitochondrial fission/fusion and Ca²⁺ homeostasis. These findings provide a novel insight into the regulatory role of ER stress in 3-MCPD-associated nephropathy and a potential therapeutic strategy. Graphical Headlights 1. 4-PBA inhibits ER stress mainly through regulating PERK-ATF4-CHOP and IRE1-XBP1s branches. 2. Inhibition of ER stress by 4-PBA mitigates ER associated and mitochondrial apoptosis 3. Inhibition of ER stress by 4-PBA helps maintaining calcium homeostasis and mitochondrial dynamic.

Keywords: 3-MCPD; 4-PBA; Apoptosis; Endoplasmic reticulum stress; Kidney; Mitochondrion.