The protective effect of glutaredoxin 1/DJ-1/HSP70 signaling in renal tubular epithelial cells injury induced by ischemia

Effects of DJ‑1 on apoptosis and mitophagy of glomerular podocytes

By studying the effects of DJ-1 overexpression and silencing on the morphological structure and mitophagy of glomerular podocytes, the present study aimed to identify the effects of DJ-1 on glomerular podocyte apoptosis and mitophagy. MPC5 mouse glomerular podocytes were cultured in vitro and divided into four groups: Control, DJ-1 overexpression, empty vector and DJ-1 silencing. DJ-1 gene overexpression and silencing models were prepared, the morphological structures of podocytes and mitochondria in each group were observed, and podocyte apoptosis and DJ-1/PTEN expression were subsequently detected in each group. The experimental results showed reduced volume, retracted foot processes, loosened intercellular connections, presence of dead cells, increased apoptotic rate, increased expression of PTEN, and swollen mitochondria due to the number of vacuoles and autophagosomes in podocytes in the DJ-1 silencing group. The surface areas of podocytes in the DJ-1 overexpression group were greater than those in the control group. Moreover, the structure of the foot processes was more obvious, the number of cells was greater, the intercellular connections were closer, the apoptotic rate was reduced, the expression of PTEN was decreased, the mitochondrial structure was more obvious and the mitochondrial cristae were more whole. Notably, there were no differences between the empty vector and control groups. In conclusion, these results indicated that DJ-1 may regulate podocyte apoptosis and mitophagy through the DJ-1/PTEN pathway, and could maintain the stability of the normal morphology, structure and function of glomerular podocytes.

Oxidation of DJ-1 Cysteines in Retinal Pigment Epithelium Function

The retina and RPE cells are regularly exposed to chronic oxidative stress as a tissue with high metabolic demand and ROS generation. DJ-1 is a multifunctional protein in the retina and RPE that has been shown to protect cells from oxidative stress in several cell types robustly. Oxidation of DJ-1 cysteine (C) residues is important for its function under oxidative conditions. The present study was conducted to analyze the impact of DJ-1 expression changes and oxidation of its C residues on RPE function. Monolayers of the ARPE-19 cell line and primary human fetal RPE (hfRPE) cultures were infected with replication-deficient adenoviruses to investigate the effects of increased levels of DJ-1 in these monolayers. Adenoviruses carried the full-length human DJ-1 cDNA (hDJ) and mutant constructs of DJ-1, which had all or each of its three C residues individually mutated to serine (S). Alternatively, endogenous DJ-1 levels were decreased by transfection and transduction with shPARK7 lentivirus. These monolayers were then assayed under baseline and low oxidative stress conditions. The results were analyzed by immunofluorescence, Western blot, RT-PCR, mitochondrial membrane potential, and viability assays. We determined that decreased levels of endogenous DJ-1 levels resulted in increased levels of ROS. Furthermore, we observed morphological changes in the mitochondria structure of all the RPE monolayers transduced with all the DJ-1 constructs. The mitochondrial membrane potential of ARPE-19 monolayers overexpressing all DJ-1 constructs displayed a significant decrease, while hfRPE monolayers only displayed a significant decrease in their ΔΨm when overexpressing the C2S mutation. Viability significantly decreased in ARPE-19 cells transduced with the C53S construct. Our data suggest that the oxidation of C53 is crucial for regulating endogenous levels of ROS and viability in RPE cells.

Trehalose Attenuates Oxidative Stress and Endoplasmic Reticulum Stress-Mediated Apoptosis in IPEC-J2 Cells Subjected to Heat Stress

This study was carried out to investigate the effects of trehalose (Tre) on antioxidant capacity, endoplasmic reticulum stress (ERS) response and apoptosis of heat-stressed intestinal porcine epithelial cells (IPEC-J2). IPEC-J2 cells were cultured at 37 °C until the end of the experiment (control, CON); exposed to heat stress for 2 h (43 °C, HS); or pretreated with 0.1, 1, 5, 10, and 15 mM trehalose at 37 °C for 4 h prior to heat stress exposure for 2 h. The optimum level of trehalose for protecting against HS-induced cell injuries was determined to be 10 mM, as evidenced by the highest cellular viability and lowest malondialdehyde (MDA) content and lactate dehydrogenase (LDH) activity. Based on these, IPEC-J2 cells were divided into three groups: the first group was cultured at 37 °C until the end of the experiment (control, CON); the second group was exposed to heat stress for 2 h (43 °C, HS); the third group was pretreated with 10 mM trehalose for 4 h at 37 °C prior to heat stress exposure for 2 h (Tre + HS). The reactive oxygen species (ROS) content, superoxide dismutase (SOD) activity, mitochondrial membrane potential (MMP) changes, and expressions of the manganese superoxide dismutase (SOD2), ERS and apoptosis-related proteins were determined. Compared to the CON group, HS significantly increased ROS generation (p < 0.01), decreased SOD activity (p < 0.05), and downregulated protein expression of SOD2 (p < 0.01). Compared to the HS group, Tre supplementation reduced ROS levels and increased SOD activity and SOD2 expression to the levels that were comparable to the control (p < 0.05). The HS-induced ERS response was evidenced by the increased protein expressions of glucose-regulated protein 78 (GRP78) (p < 0.01), eukaryotic translation initiation factor 2α (p-eif2α) (p < 0.01), transcription activator 4 (ATF4) (p < 0.01), and the protein expression of C/EBP homologous protein (CHOP) (p < 0.01), which were the four hallmarks of ERS. The Tre + HS group showed lower expressions of GRP78 (p < 0.01), p-eif2α (p < 0.01), ATF4 (p < 0.01), and CHOP (p < 0.01) than that of the HS group. Tre pretreatment attenuated HS-induced mitochondrial apoptosis in IPEC-J2 cells, demonstrated by the increased MMP and decreased proapoptotic proteins active caspase 3, Bax, and cytochrome c (Cyt c). Taken together, trehalose can protect against HS-induced oxidative damage and endoplasmic reticulum stress-mediated apoptosis in IPEC-J2 cells. These data may provide a nutritional strategy for alleviating heat stress in pig production.

PARK7 Protects Against Chronic Kidney Injury and Renal Fibrosis by Inducing SOD2 to Reduce Oxidative Stress

Renal fibrosis is the final common pathway to chronic kidney diseases regardless of etiology. Parkinson disease protein 7 (PARK7) is a multifunctional protein involved in various cellular processes, but its pathophysiological role in kidneys remain largely unknown. Here, we have determined the role of PARK7 in renal fibrosis and have further elucidated the underlying mechanisms by using the in vivo mouse model of unilateral ureteric obstruction (UUO) and the in vitro model of transforming growth factor-b (TGFB1) treatment of cultured kidney proximal tubular cells. PARK7 decreased markedly in atrophic kidney tubules in UUO mice, and Park7 deficiency aggravated UUO-induced renal fibrosis, tubular cell apoptosis, ROS production and inflammation. In vitro, TGFB1 treatment induced fibrotic changes in renal tubular cells, which was accompanied by alterations of PARK7. Park7 knockdown exacerbated TGFB1-induced fibrotic changes, cell apoptosis and ROS production, whereas Park7 overexpression or treatment with ND-13 (a PARK7-derived peptide) attenuated these TGFB1-induced changes. Mechanistically, PARK7 translocated into the nucleus of renal tubular cells following TGFB1 treatment or UUO, where it induced the expression of SOD2, an antioxidant enzyme. Taken together, these results indicate that PARK7 protects against chronic kidney injury and renal fibrosis by inducing SOD2 to reduce oxidative stress in tubular cells.

Glutaredoxin 1 protects neurons from oxygen-glucose deprivation/reoxygenation (OGD/R)-induced apoptosis and oxidative stress via the modulation of GSK-3β/Nrf2 signaling

Increasing evidence has indicated that glutaredoxin 1 (GRX1) is a potent antioxidant protein that promotes cell survival under conditions of oxidative stress. Oxidative stress-induced neuronal injury contributes to cerebral ischemia/reperfusion injury. However, the role of GRX1-mediated antioxidant defense against neuronal damage during cerebral ischemia/reperfusion injury has not been thoroughly investigated. Thus, the objective of this study was to evaluate whether GRX1 protects neurons against oxygen-glucose deprivation/reoxygenation (OGD/R)-evoked oxidative stress injury in an in vitro model of cerebral ischemia/reperfusion injury. Our data revealed that GRX1 was induced by OGD/R treatment in neurons. Functional assays indicated that loss of GRX1 exacerbated OGD/R-induced apoptosis and the generation of reactive oxygen species (ROS), while GRX1 up-regulation protected against OGD/R-evoked neuronal injury. Further investigation revealed that GRX1 promoted the nuclear expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and enhanced transcription of the Nrf2/antioxidant response element (ARE) in GOD/R-exposed neurons. Furthermore, GRX1 promoted the activation of Nrf2/ARE associated with the modulation of glycogen synthase kinase-3β (GSK-3β). GSK-3β inhibition blocked GRX1 knockdown-mediated suppression of Nrf2 activation. Notably, the suppression of Nrf2 partially reversed GRX1-mediated anti-oxidative stress injury in OGD/R-exposed neurons. In summary, these findings indicate that GRX1 protects neurons against OGD/R-induced oxidative stress injury by enhancing Nrf2 activation via the modulation of GSK-3β. Our study suggests that GRX1 is a potential neuroprotective protein that protects against cerebral ischemia/reperfusion injury.

Deficiency in the anti-apoptotic protein DJ-1 promotes intestinal epithelial cell apoptosis and aggravates inflammatory bowel disease via p53

Parkinson disease autosomal recessive, early onset 7 (PARK7 or DJ-1) is involved in multiple physiological processes and exerts anti-apoptotic effects on multiple cell types. Increased intestinal epithelial cell (IEC) apoptosis and excessive activation of the p53 signaling pathway is a hallmark of inflammatory bowel disease (IBD), which includes ulcerative colitis (UC) and Crohn's disease (CD). However, whether DJ-1 plays a role in colitis is unclear. To determine whether DJ-1 deficiency is involved in the p53 activation that results in IEC apoptosis in colitis, here we performed immunostaining, real-time PCR, and immunoblotting analyses to assess DJ-1 expression in human UC and CD samples. In the inflamed intestines of individuals with IBD, DJ-1 expression was decreased and negatively correlated with p53 expression. DJ-1 deficiency significantly aggravated colitis, evidenced by increased intestinal inflammation and exacerbated IEC apoptosis. Moreover, DJ-1 directly interacted with p53, and reduced DJ-1 levels increased p53 levels both in vivo and in vitro and were associated with decreased p53 degradation via the lysosomal pathway. We also induced experimental colitis with dextran sulfate sodium in mice and found that compared with DJ-1-/- mice, DJ-1-/-p53-/- mice have reduced apoptosis and inflammation and increased epithelial barrier integrity. Furthermore, pharmacological inhibition of p53 relieved inflammation in the DJ-1-/- mice. In conclusion, reduced DJ-1 expression promotes inflammation and IEC apoptosis via p53 in colitis, suggesting that the modulation of DJ-1 expression may be a potential therapeutic strategy for managing colitis.

Analysis of Spatiotemporal Urine Protein Dynamics to Identify New Biomarkers for Sepsis-Induced Acute Kidney Injury

Acute kidney injury (AKI) is a frequent complication of sepsis and contributes to increased mortality. Discovery of reliable biomarkers could enable identification of individuals with high AKI risk as well as early AKI detection and AKI progression monitoring. However, the current methods are insensitive and non-specific. This study aimed to identify new biomarkers through label-free mass spectrometry (MS) analysis of a sepsis model induced by cecal ligation and puncture (CLP). Urine samples were collected from septic rats at 0, 3, 6, 12, 24, and 48 h. Protein isolated from urine was subjected to MS. Immunoregulatory biological processes, including immunoglobin production and wounding and defense responses, were upregulated at early time points. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses identified 77 significantly changed pathways. We further examined the consistently differentially expressed proteins to seek biomarkers that can be used for early diagnosis. Notably, the expression of PARK7 and CDH16 were changed in a continuous manner and related to the level of Scr in urine from patients. Therefore, PARK7 and CDH16 were confirmed to be novel biomarkers after validation in sepsis human patients. In summary, our study analyzed the proteomics of AKI at multiple time points, elucidated the related biological processes, and identified novel biomarkers for early diagnosis of sepsis-induced AKI, and our findings provide a theoretical basis for further research on the molecular mechanisms.