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

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.

Jujuboside A ameliorates high fat diet and streptozotocin induced diabetic nephropathy via suppressing oxidative stress, apoptosis, and enhancing autophagy.

Jujuboside A (JuA) is a triterpenoid saponins isolated from the seed of jujube (semen Ziziphi spinosae) with anti-oxidant, anti-inflammation and anti-apoptosis properties. The present study aimed to investigate the reno-protective effects of JuA on type II diabetes. JuA (20 mg/kg) and Metformin (Met, 300 mg/kg) were administrated to diabetic Sprague Dawley rat for 8 weeks daily. Our results showed that JuA reduced blood glucose and kidney function markers including 24 h urinary protein, urinary ß-NAG/urinary creatinine, serum urea nitrogen, serum uric acid and serum creatinine, and relieved renal pathological changes. In addition, JuA decreased O2- and H2O2 level, enhanced SOD, CAT and GPx activities, decreased NOX4 expression and improved mitochondrial respiratory chain function through regulating respiratory chain complex expression. Moreover, JuA downregulated the expressions of mitochondrial apoptosis proteins: Bax, CytC, Apaf-1 and caspase 9. Apoptosis mediated by ER stress also been inhibited by JuA via downregulating p-PERK, p-IRE1, XBP1s, ATF4, p-CHOP and caspase 12 expressions. JuA also enhanced autophagy and mitophagy via regulating CaMKK2-AMPK-p-mTOR and PINK1/Parkin pathways. Collectively, these results indicated that JuA protected against type II diabetic nephropathy through inhibiting oxidative stress and apoptosis mediated by mitochondria and ER stress. In addition, autophagy and mitophagy was enhanced by JuA.

Diosgenin Protects Against Kidney Injury and Mitochondrial Apoptosis Induced by 3-MCPD Through the Regulation of ER Stress, Ca2+ Homeostasis, and Bcl2 Expression.

SCOPE: Diosgenin (DIO) is a natural steroid sapogenin presented in various plants. It exerts anti-oxidant, anti-inflammatory and anti-diabetic nephropathy properties. The present study evaluates the intervention effect of DIO on nephrotoxicity induced by food contaminant 3-chloro-1, 2-propanediol (3-MCPD) in vivo and in vitro. METHODS AND RESULTS: Treatment with DIO (15 mg kg-1 d-1 ) in Sprague-Dawley rats for 4-week relieves kidney injury induced by 3-MCPD (30 mg kg-1 d-1 ). In vitro, DIO (2, 6, and 8 µM) alleviates cell injury and apoptosis effectively in human embryonic kidney (HEK293) cells. DIO realizes its protective function via the regulation of endoplasmic reticulum (ER) stress and mitochondrial apoptosis pathway. Blockage of ER stress by 4-phenylbutyric acid (4-PBA), a specific ER stress antagonist, inhibits mitochondrial apoptosis, suggesting a connection between mitochondrial apoptosis and ER stress. Furthermore, the study demonstrates that the maintenance of Ca2+ homeostasis and Bcl2 expression, two main targets of ER stress, contributes to the protection role of DIO on mitochondrial-dependent apoptosis. In addition, DIO relieves the impairment of oxidative phosphorylation. CONCLUSION: This study demonstrates that DIO exerts protective effect against kidney injury, mitochondrial dysfunction, and apoptosis through the inhibition of ER stress and the further maintenance of Ca2+ homeostasis and Bcl2 expression.

Involvement of NADPH oxidase in patulin-induced oxidative damage and cytotoxicity in HEK293 cells.

Patulin (PAT) is a kind of mycotoxins that commonly found in decayed fruits and their products. Our previous studies have shown that PAT induced cell apoptosis and the overproduction of reactive oxygen species (ROS) in human embryonic kidney (HEK293) cells. The present study aimed to further investigate the functional role of NADPH oxidase, one of the main cellular sources of ROS, in PAT-induced apoptosis and oxidative damage in HEK293 cells. We demonstrated that the protein and mRNA expression levels of NADPH oxidase catalytic subunit NOX2 and regulatory subunit p47phox were up-regulated under PAT stress. Inhibiting of NADPH oxidase with the specific antagonist diphenyleneiodonium (DPI) suppressed cytotoxicity and apoptosis induced by PAT as evidenced by the increase of cell viability, the decrease of LDH release and the inhibition of caspase activities. Furthermore, DPI re-established mitochondrial membrane potential (MMP) and enhanced cellular ATP content. Importantly, DPI supplementation elevated endogenous GSH contents as well as the ratio of GSH/GSSG. Meanwhile, the antioxidant-enzyme activities of GPx, GR, CAT and SOD were significantly promoted. Collectively, our results suggested that NADPH oxidase played a critical role in PAT-induced nephrotoxicity, and inhibition of NADPH oxidase by DPI attenuated cell injury and apoptosis via regulation of oxidative damage.

Drp1-mediated mitochondrial fission induced autophagy attenuates cell apoptosis caused by 3-chlorpropane-1,2-diol in HEK293 cells.

3-chlorpropane-1,2-diol (3-MCPD) is a heat-induced food process contaminant that threatens human health. As the primary target organ, the morphological and functional impairment of kidney and the related mechanism such as apoptosis and mitochondrial dysfunction were observed. However, the precise molecular mechanism remains largely unclear. This study aimed to explore the important role of mitochondrial fission and autophagy in the 3-MCPD-caused apoptosis of human embryonic kidney 293 (HEK293) cells. The results showed that blockage of dynamin-related protein-1 (Drp1) by mitochondrial division inhibitor 1 (Mdivi-1, 15 µM) apparently restored 3-MCPD-induced mitochondrial dysfunction, accompanied by prevented the collapse of mitochondrial membrane potential and ATP depletion, and suppressed the occurrence of autophagy. Induction of autophagy occurred following 2.5-10 mM 3-MCPD treatment for 24 h via AMPK mediated mTOR signaling pathway. Meanwhile, enhancement of autophagy by pretreatment with rapamycin (1 nM) alleviated the loss of cell viability and apoptosis induced by 3-MCPD whereas suppression of autophagy by 3-methyladenine (1 mM) further accelerated apoptosis, which was modulated through the mitochondria-dependent apoptotic pathway. Taking together, this study provides novel insights into the 3-MCPD-induced apoptosis in HEK293 cells and reveals that autophagy has potential as an effective intervention strategy for the treatment of 3-MCPD-induced nephrotoxicity.

The renoprotective effect of diosgenin on aristolochic acid I-induced renal injury in rats: impact on apoptosis, mitochondrial dynamics and autophagy.

Aristolochic acid I (AA-I) remains a leading cause of aristolochic acid nephropathy (AAN), however few prevention and treatment strategies exist. In this work, the nephroprotective effect of diosgenin, a steroidal saponin distributed abundantly in several plants, on AA-I-induced renal injury and its underlying mechanism were investigated. Sprague-Dawley rats were intragastrically administered with 30 mg kg-1 d-1 diosgenin two hours before exposure to 10 mg kg-1 d-1 AA-I for consecutive four weeks, and the histological change, the renal and liver function, apoptosis, autophagy and the involved pathways were investigated. The results showed that diosgenin relieved AA-I-induced renal histological damage, including mild edematous disorder of renal tubular arrangement and widening of renal tubular lumen. No obvious changes in the hepatic tissue structure were observed in all treatment groups. Moreover, diosgenin up-regulated the expression of Bcl-2 and down-regulated Bax, and subsequently inhibited AIF expression and the cleaved form of Caspase-3, thereby alleviating apoptosis triggered by AA-I. Diosgenin also mitigated AA-I-induced renal mitochondrial dynamics disorder by increasing the expression of mitochondrial dynamics-related proteins including DRP1 and MFN2. Diosgenin inhibited AA-I-evoked autophagy via ULK1-mediated inhibition of the mTOR pathway. Overall, these results suggest that diosgenin has a protective effect against AA-I-induced renal damage and it may be a potential agent for preventing AA-I-induced AAN.