DJ-1 is an indicator for endogenous reactive oxygen species elicited by endotoxin.

We previously found that DJ-1 protein of pI 5.8 (DJ-1/5.8) increased on 2D gels as DJ-1 of pI 6.2 (DJ-1/6.2) decreased, upon exposure of human cells to sublethal levels of oxidative stress, such as H2O2 and paraquat. Here, we show that the DJ-1/5.8 increases concomitantly with endogenous production of reactive oxygen species (ROS) under endotoxin-induced inflammatory conditions. Lipopolysaccharide (LPS) significantly increased the expression of DJ-1/5.8 in murine peritoneal macrophages (Mphi) and a murine macrophage cell line (J774). Diphenylene iodonium, a flavoenzyme inhibitor, blocked the effect of LPS on DJ-1/5.8 expression. Aminoguanidine (AG), a selective inhibitor of type II nitric oxide synthase, had no effect on the DJ-1/5.8 expression, but suppressed accumulation of nitrite in the culture medium after LPS treatment. We also examined the expression of DJ-1/5.8 in lung, since acute lung injury is seen in endotoxin shock. When female mice (6-weeks old) were intraperitoneally given LPS (10 mg/kg), myeloperoxidase (MPO) activity in lung, a marker of neutrophil infiltration, was transiently raised by 3.5 fold. The expression of DJ-1/5.8 in lung was enhanced and then reverted to the control level, in parallel with the MPO activity. These results, taken together, suggest that the DJ-1/5.8 might increase in response to endogenously produced ROS, probably due to activation of NADPH oxidase, and imply that DJ-1 may be useful as an endogenous indicator of oxidative stress status in vivo.     

Proteomic analysis of oxidative stress-responsive proteins in human pneumocytes: insight into the regulation of DJ-1 expression

Oxidative injury is believed to play an important role in the pathogenesis of lung diseases such as emphysema and lung cancer. We examined the effects of a classic reactive oxygen species, H 2O 2, on the hydrogen peroxide response proteins (HPRP) in human pneumocytes using comparative two-dimensional gel electrophoresis (2DE) and peptide mass fingerprinting. Four HPRP-associated proteins (DJ-1, peroxiredoxins [Prxs] I and IV and glyceraldehyde-3-phosphate dehydrogenase [GAPDH]) were changed upon exposure to H 2O 2 (1 mM for 24 h). H 2O 2 exposure increased the acid (oxidized) form and decreased the basic (reduced) form of DJ-1 (pI 5.8 and 6.2, respectively), Prx I and IV and GAPDH. Mechanistic studies on DJ-1 indicated that the slow recovery of the reduced form was blocked by cyclohexamide, suggesting that the recovery was due to new protein synthesis. Total DJ-1 expression was decreased by increasing concentrations of H 2O 2. In contrast, a more complex mix of oxidants in the form of cigarette smoke extract (CSE) dose-dependently increased DJ-1 expression and produced a novel DJ-1 isoform (p I 5.6). Moreover, DJ-1 expression was higher in the lungs of chronic cigarette smokers compared with nonsmokers, a result which resembled the effects of CSE in cultured cells. These data indicate that in human pneumocytes, DJ-1 functions as an antioxidant but that no enzymatic system converts the oxidized to the reduced form. Up-regulation of DJ-1 by cigarette smoke may be a compensatory mechanism that protects the lung from oxidative stress-related injury.     

Involvement of ERK1/2 signaling pathway in DJ-1-induced neuroprotection against oxidative stress

Parkinson’s disease (PD) is a progressive neurodegenerative disorder. Although the precise mechanism remains unclear, mounting evidence suggests that oxidative stress plays an important role in the pathogenesis of PD. DJ-1 gene is associated with oxidative stress and mutations in DJ-1 are involved in an autosomal recessive, early onset familial form of PD. The ERK1/2 signaling pathway contributes to neuroprotection during oxidative stress. However, the correlation between DJ-1 and the ERK1/2 signaling pathway remains unknown. To test for an association of DJ-1 with the ERK1/2 signaling pathway, we transfected wild-type and L166P mutated DJ-1 into COS-7 and MN9D cells. The results showed that over-expression of WT-DJ-1 dramatically enhanced the phosphorylation of ERK1/2 and its upstream kinase MEK1/2. Meanwhile, WT-DJ-1, but not L166P-DJ-1 inhibited the expression of protein phosphatase 2A (PP2A), an inhibitor of the ERK1/2 signaling pathway. Moreover, over-expression of WT-DJ-1 increased cell viability and decreased cell sensitivity to H₂O₂-induced neurotoxicity. Inhibition of the ERK1/2 signaling pathway with a MEK1/2 inhibitor reversed these changes. We conclude that DJ-1 does affect the ERK1/2 signaling pathway and change the susceptibility of cells to oxidative stress.     

MicroRNA-452 promotes tumorigenesis in hepatocellular carcinoma by targeting cyclin-dependent kinase inhibitor 1B

Rare genetic mutations in the DJ-1 and Parkin genes cause recessive Parkinsonism, however, the relationship between these two genes is not fully elucidated. Current emerging evidence suggests that these genes are involved in mitochondrial homeostasis, and that a deficiency in either of these two genes is associated with damages in mitochondrial function and morphology. In this study, we demonstrated that knockdown of DJ-1 expression or the overexpression of the DJ-1 L166P mutation results in a damaged phenotype in mitochondria and a hypersensitivity to H₂O₂-induced cell apoptosis. These phenotypes result from increased levels of endogenous oxidative stress. However, overexpression of wild-type Parkin rescued the phenotypes observed in the mitochondria of DJ-1 knockdown and DJ-1 L166P mutant cells. We also determined that there were differences between the two cell models. Furthermore, both H₂O₂ treatment and the DJ-1 L166P mutation weakened the interaction between DJ-1 and Parkin. Taken together, these findings suggested that DJ-1 and Parkin were linked through oxidative stress, and that overexpression of Parkin protects DJ-1 protein-deficient and DJ-1 L166P mutant-expressing cells via inhibition of oxidative stress.     

Lipid A fraction of LPS induces a discrete MAPK activation in acute lung injury

Lipopolysaccharide (LPS) induces acute lung injury (ALI) via Toll-like receptor 4 (TLR4)-mediated MAPK activation. The lipid A fraction of LPS is considered to be the active moiety, but whether the lipid A-TLR4 interaction accounts completely for ALI-associated MAPK activation in vivo has not been determined. The lipid A fraction of LPS induces a discrete MAPK activation pattern in murine ALI. Mice (C57BL/6J, C3H/HeJ) were treated with intratracheal instillations of purified lipid A or LPS (10, 30, and 100 microg per mouse) or vehicle. ALI was assessed by histology. Chromogenic myeloperoxidase (MPO) activity was measured in lung homogenates. MAPK expression was quantified by immunoblotting. In vitro ERK inhibitor studies using thioglycollate-elicited macrophages were also performed. MPO increased in a dose- and time-responsive fashion. Notably, MPO was 2.4-fold greater after lipid A compared with LPS and vehicle at 6 h after instillation (lipid A, 0.88 +/- 0.25 vs. LPS, 0.37 +/- 0.21 optical density units.min(-1).mg(-1); P < 0.05). However, ALI scores were comparable at 6 and 24 h between LPS and lipid A. MPO was also comparable in vehicle-treated or C3H/HeJ mice treated with LPS or lipid A at 6 and 24 h. Phospho-ERK activation was pronounced at 6 and 24 h after lipid A but not LPS treatment. In vitro studies confirmed the relationship between phospho-ERK activation and cytokine expression in macrophage stimulated with either LPS or lipid A. Compared with whole LPS, the lipid A fraction is associated with amplified whole lung MPO and ERK activation 6 h after intratracheal instillation in mice.     

The reversible low-temperature instability of human DJ-1 oxidative states

DJ-1 is a homodimeric protein that is centrally involved in various human diseases including Parkinson disease (PD). DJ-1 protects against oxidative damage and mitochondrial dysfunction through a homeostatic control of reactive oxygen species (ROS). DJ-1 pathology results from a loss of function, where ROS readily oxidizes a highly conserved and functionally essential cysteine (C106). The over-oxidation of DJ-1 C106 leads to a dynamically destabilized and biologically inactivated protein. An analysis of the structural stability of DJ-1 as a function of oxidative state and temperature may provide further insights into the role the protein plays in PD progression. NMR spectroscopy, circular dichroism, analytical ultracentrifugation sedimentation equilibrium, and molecular dynamics simulations were utilized to investigate the structure and dynamics of the reduced, oxidized (C106-SO₂⁻), and over-oxidized (C106-SO₃⁻) forms of DJ-1 for temperatures ranging from 5°C to 37°C. The three oxidative states of DJ-1 exhibited distinct temperature-dependent structural changes. A cold-induced aggregation occurred for the three DJ-1 oxidative states by 5°C, where the over-oxidized state aggregated at significantly higher temperatures than both the oxidized and reduced forms. Only the oxidized and over-oxidized forms of DJ-1 exhibited a mix state containing both folded and partially denatured protein that likely preserved secondary structure content. The relative amount of this denatured form of DJ-1 increased as the temperature was lowered, consistent with a cold-denaturation. Notably, the cold-induced aggregation and denaturation for the DJ-1 oxidative states were completely reversible. The dramatic changes in the structural stability of DJ-1 as a function of oxidative state and temperature are relevant to its role in PD and its functional response to oxidative stress.     

Blocking of tripartite motif 8 protects against lipopolysaccharide (LPS)-induced acute lung injury by regulating AMPKα activity

Acute lung injury (ALI) and its more serious form, respiratory distress syndrome (ARDS), are considered as an acute and severe inflammatory process existing in lungs, and still remain high mortality rates. Tripartite motif 8 (TRIM8) contains an N-terminal RING finger, which is followed by two B-boxes and a coiled-coil domain, belonging to the TRIM/RBCC family and playing significant role in meditating inflammation, oxidative stress and apoptosis. In the study, we investigated the role of TRIM8 in ALI induced by lipopolysaccharide (LPS) and the underlying molecular mechanisms. The in vitro results indicated that LPS time-dependently enhanced TRIM8 expression in lung epithelial cells. Suppressing TRIM8 markedly ameliorated LPS-elicited inflammatory response, as evidenced by the down-regulated mRNA levels of interleukin-1β (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α) in cells mainly through inactivating nuclear factor-kappa B (NF-κB) signaling pathway; however, over-expressing TRIM8 markedly promoted inflammation in LPS-challenged cells. In addition, LPS-induced oxidative stress was accelerated by TRIM8 over-expression, while being alleviated by TRIM8 knockdown by regulating Nrf2 signaling. Importantly, TRIM8 could negatively meditate AMP-activated protein kinase-α (AMPKα) activation to modulate LPS-triggered inflammatory response and ROS generation in vitro. Additionally, our in vivo findings suggested that TRIM8 knockdown effectively attenuated LPS-induced lung injury nu decrease of lung wet/dry (W/T) ratio, protein concentrations, neutrophil infiltration, myeloperoxidase (MPO) activity, reactive oxygen species (ROS) production and superoxide dismutase (SOD) depletion. Meanwhile, the loss of TRIM8 markedly lessened IL-1β, IL-6 and TNF-α expression in lung tissues of LPS-challenged mice, and reduced NF-κB phosphorylation. Furthermore, TRIM8 knockdown evidently improved nuclear factor-erythroid 2 related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) expressions in lung of LPS-treated mice. The anti-inflammation and anti-oxidant role of TRIM8-silence might be associated with AMPKα phosphorylation. Together, our study firstly provided a support that TRIM8 knockdown effectively protected LPS-induced ALI against inflammation and oxidative stress largely dependent on the promotion of AMPKα pathway.     

α-Synuclein and neuronal cell death

Mutations in the DJ-1 gene have been linked to autosomal recessive familial Parkinson's disease. To understand the function of DJ-1, we determined the DJ-1 expression in both zebrafish and post mortem human brains. We found that DJ-1 was expressed early during zebrafish development and throughout adulthood. Knock down (KD) of DJ-1 by injection of morpholino did not cause dramatic morphologic alterations during development, and no loss of dopaminergic neurons was observed in embryos lacking DJ-1. However, DJ-1 KD embryos were more susceptible to programmed cell death. While a slight reduction in staining for islet-1 positive neurons was observed in both DJ-1 KD and H₂O₂ treated embryos, the number of apoptotic cells was significantly increased in both KD and H₂O₂ treated embryos. Interestingly, DJ-1 expression was increased in brains of zebrafish under conditions of oxidative stress, indicating that DJ-1 is a part of stress-responsive machinery. Since oxidative stress is one of the major contributors to the development of Alzheimer's disease (AD), we also examined DJ-1 expression in AD brains. Using DJ-1 specific antibodies, we failed to detect a robust staining of DJ-1 in brain tissues from control subjects. However, DJ-1 immunoreactivity was detected in hippocampal pyramidal neurons and astrocytes of AD brains. Therefore, our results strongly suggest that DJ-1 expression is not necessary during zebrafish development but can be induced in zebrafish exposed to oxidative stress and is present in human AD brains.     

Repression of TXNIP–NLRP3 axis restores intestinal barrier function via inhibition of myeloperoxidase activity and oxidative stress in nonalcoholic steatohepatitis

Dysfunction of the intestinal barrier function occurs in hepatic injury, but the specific mechanisms responsible are largely unknown. Recently, NOD-like receptor 3 (NLRP3) inflammasome functions in impairing endothelial barrier function. In this study, we test the hypothesis that TXNIP–NLRP3 axis repression prevents against intestinal barrier function disruption in nonalcoholic steatohepatitis (NASH). First, lipopolysaccharide (LPS)-induced alterations in expression of ZO-1 and occludin, myeloperoxidase (MPO) activity, reactive oxygen species (ROS) level, and transepithelial electric resistance (TEER) in intestinal epithelial cells (IECs) isolated from C57BL/6 wild-type (WT) and TXNIP^−/− mice were evaluated. The underlying regulatory mechanisms of TXNIP knockout in vivo were investigated with the detection of expressions of TXNIP, NLRP3 and ZO-1, and occludin, the interaction of TXNIP–NLRP3, MPO activity, ROS level, permeability of intestinal mucosa, levels of inflammatory factors in serum, and LPS concentration. We identified that TXNIP knockout promoted ZO-1 and occludin expression, yet reduced MPO activity, ROS level, and cell permeability in IECs, indicating restored the intestinal barrier function. However, LPS upregulated TXNIP and NLRP3 expression, as well as contributed to the interaction between TXNIP and NLRP3 in vitro. Furthermore, TXNIP was significantly upregulated in the intestinal mucosa of NASH mice and its knockout repaired the intestinal barrier disrupt, inhibited expression of inflammatory factors, and reduced LPS concentration as well as hepatic injury in vivo. Taken together, our findings demonstrated that inhibited the activation of the TXNIP–NLRP3 axis reduced MPO activity and oxidative stress and thus restoring the intestinal barrier function in NASH. TXNIP–NLRP3 axis may be a promising therapeutic strategy for the NASH treatment.     

Sitagliptin activates the p62–Keap1–Nrf2 signalling pathway to alleviate oxidative stress and excessive autophagy in severe acute pancreatitis-related acute lung injury

Acute lung injury (ALI) is a complication of severe acute pancreatitis (SAP). Sitagliptin (SIT) is a DPP4 inhibitor that exerts anti-inflammatory and antioxidant effects; however, its mechanism of action in SAP-ALI remains unclear. In this study, we investigated the effects of SIT on SAP-ALI and the specific pathways involved in SAP-induced lung inflammation, including oxidative stress, autophagy, and p62–Kelch-like ECH-associated protein 1 (Keap1)–NF-E2-related factor 2 (Nrf2) signalling pathways. Nrf2 knockout (Nrf2^−/−) and wild-type (WT) mice were pre-treated with SIT (100 mg/kg), followed by caerulein and lipopolysaccharide (LPS) administration to induce pancreatic and lung injury. BEAS-2B cells were transfected with siRNA-Nrf2 and treated with LPS, and the changes in inflammation, reactive oxygen species (ROS) levels, and autophagy were measured. SIT reduced histological damage, oedema, and myeloperoxidase activity in the lung, decreased the expression of pro-inflammatory cytokines, and inhibited excessive autophagy and ROS production via the activation of the p62–Keap1–Nrf2 signalling pathway and promotion of the nuclear translocation of Nrf2. In Nrf2-knockout mice, the anti-inflammatory effect of SIT was reduced, resulting in ROS accumulation and excessive autophagy. In BEAS-2B cells, LPS induced ROS production and activated autophagy, further enhanced by Nrf2 knockdown. This study demonstrates that SIT reduces SAP-ALI-associated oxidative stress and excessive autophagy through the p62–Keap1–Nrf2 signalling pathway and nuclear translocation of Nrf2, suggesting its therapeutic potential in SAP-ALI.Subject terms: Macroautophagy, Acute pancreatitis     

Loss of DJ-1 does not affect mitochondrial respiration but increases ROS production and mitochondrial permeability transition pore opening

Background

Loss of function mutations in the DJ-1 gene have been linked to recessively inherited forms of Parkinsonism. Mitochondrial dysfunction and increased oxidative stress are thought to be key events in the pathogenesis of Parkinson’s disease. Although it has been reported that DJ-1 serves as scavenger for reactive oxidative species (ROS) by oxidation on its cysteine residues, how loss of DJ-1 affects mitochondrial function is less clear.

Methodology/Principal Findings

Using primary mouse embryonic fibroblasts (MEFs) or brains from DJ-1−/− mice, we found that loss of DJ-1 does not affect mitochondrial respiration. Specifically, endogenous respiratory activity as well as basal and maximal respiration are normal in intact DJ-1−/− MEFs, and substrate-specific state 3 and state 4 mitochondrial respiration are also unaffected in permeabilized DJ-1−/− MEFs and in isolated mitochondria from the cerebral cortex of DJ-1−/− mice at 3 months or 2 years of age. Expression levels and activities of all individual complexes composing the electron transport system are unchanged, but ATP production is reduced in DJ-1−/− MEFs. Mitochondrial transmembrane potential is decreased in the absence of DJ-1. Furthermore, mitochondrial permeability transition pore opening is increased, whereas mitochondrial calcium levels are unchanged in DJ-1−/− cells. Consistent with earlier reports, production of reactive oxygen species (ROS) is increased, though levels of antioxidative enzymes are unaltered. Interestingly, the decreased mitochondrial transmembrane potential and the increased mitochondrial permeability transition pore opening in DJ-1−/− MEFs can be restored by antioxidant treatment, whereas oxidative stress inducers have the opposite effects on mitochondrial transmembrane potential and mitochondrial permeability transition pore opening.

Conclusions/Significance

Our study shows that loss of DJ-1 does not affect mitochondrial respiration or mitochondrial calcium levels but increases ROS production, leading to elevated mitochondrial permeability transition pore opening and reduced mitochondrial transmembrane potential.     

Isovitexin Exerts Anti-Inflammatory and Anti-Oxidant Activities on Lipopolysaccharide-Induced Acute Lung Injury by Inhibiting MAPK and NF-κB and Activating HO-1/Nrf2 Pathways

Oxidative damage and inflammation are closely associated with the pathogenesis of acute lung injury (ALI). Thus, we explored the protective effect of isovitexin (IV), a glycosylflavonoid, in the context of ALI. To accomplish this, we created in vitro and in vivo models by respectively exposing macrophages to lipopolysaccharide (LPS) and using LPS to induce ALI in mice. In vitro, our results showed that IV treatment reduced LPS-induced pro-inflammatory cytokine secretion, iNOS and COX-2 expression and decreased the generation of ROS. Consistent findings were obtained in vivo. Additionally, IV inhibited H₂O₂-induced cytotoxicity and apoptosis. However, these effects were partially reversed following the use of an HO-1 inhibitor in vitro. Further studies revealed that IV significantly inhibited MAPK phosphorylation, reduced NF-κB nuclear translocation, and upregulated nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) expression in RAW 264.7 cells. In vivo, pretreatment with IV attenuated histopathological changes, infiltration of polymorphonuclear granulocytes and endothelial activation, decreased the expression of ICAM-1 and VCAM-1, reduced the levels of MPO and MDA, and increased the content of GSH and SOD in ALI. Furthermore, IV treatment effectively increased Nrf2 and HO-1 expression in lung tissues. Therefore, IV may offer a protective role against LPS-induced ALI by inhibiting MAPK and NF-κB and activating HO-1/Nrf2 pathways.     

alpha-Synuclein protects SH-SY5Y cells from dopamine toxicity

Dopaminergic human neuroblastoma SH-SY5Y cells were stably transformed to increase expression of alpha-synuclein, a Parkinson's disease-related protein. Transformed cells were more resistant to oxidative insults, showing a cytoprotective role of alpha-synuclein. The expression of redox chaperonins (DJ-1, HSP70, and 14-3-3) was evaluated by Western blotting. Expression of alpha-synuclein reduced HSP70 levels even in the presence of dopamine, with a twofold increase of DJ-1 in the absence of oxidants. DJ-1 is significantly reduced by dopamine, and even more by dopamine and Cu(II). Increased alpha-synuclein expression did not affect 14-3-3, although dopamine increased its level by 60% in wild-type cells. alpha-Synuclein not only upregulated DJ-1, but also shifted all DJ-1 forms to a single spot at pI=5.7 not observed in wild-type cells. Dopamine gradually restored the distribution of DJ-1 forms to a situation similar to wild-type cells, with the form at pI=6.1 progressively enriched under oxidative conditions.     

Oxidized forms of peroxiredoxins and DJ-1 on two-dimensional gels increased in response to sublethal levels of paraquat

We previously found hydroperoxide-responsive proteins (HPRPs), which are comprised of peroxiredoxin I(Prx I), Prx II, Prx III, Prx VI, HSP27, G3PDH and two unidentified proteins (HPRP-2' and HPRP-5'), in human umbilical vein endothelial cells. It was demonstrated by two-dimensional polyacrylamide gel electrophoresis (2D PAGE) that most HPRPs are converted into variants with lower pI upon exposure to hydroperoxides. In this study, we examined the HPRP response on 2D gels upon exposure of human endothelial cells (ECV304) to paraquat (PQ²⁺), which generates reactive oxygen species (ROS) within cells. PQ²⁺ exerted cytotoxic effects in a dose- (10μM-10mM) and time- (24-168h) dependent manner. Two-dimensional PAGE analysis revealed that HPRP-2', and oxidized forms of Prx I, Prx II and Prx III were clearly increased upon exposure of cells to sublethal levels of PQ²⁺. Microsequence analysis revealed that both HPRP-2 and -2' were identical with human DJ-1. Moreover immunoblot analysis confirmed the increase of oxidized forms of Prx II, Prx III and DJ-1 in response to sublethal levels of PQ²⁺. PQ²⁺ treatment failed to increase fluorescence intensity derived from DCF, which is believed to be an indicator for intracellular levels of hydroperoxide. Although pentachlorophenol (PCP), an uncoupler of the mitochondrial respiratory chain, clearly elevated the fluorescence, PCP had no effect on HPRP response. These observations indicated that DCF-derived fluorescence is not correlated with HPRP response. We consider that the response of Prxs and DJ-1 on 2D gels could reflect endogenous production of ROS in PQ²⁺-treated cells, and might be a sensitive indicator of oxidative stress status.     

Protection of Pancreatic β-Cells from Various Stress Conditions Is Mediated by DJ-1

Pancreatic β-cells are vulnerable to multiple stresses, leading to dysfunction and apoptotic death. Deterioration in β-cells function and mass is associated with type 2 diabetes. Comparative two-dimensional gel electrophoresis from pancreatic MIN6 cells that were maintained at varying glucose concentrations was carried out. An induced expression of a protein spot, detected in MIN6 cells experiencing high glucose concentration, was identified by mass spectrometry as the oxidized form of DJ-1. DJ-1 (park7) is a multifunctional protein implicated in familial Parkinsonism and neuroprotection in response to oxidative damage. The DJ-1 protein and its oxidized form were also induced following exposure to oxidative and endoplasmic reticulum stress in MIN6 and βTC-6 cells and also in mouse pancreatic islets. Suppression of DJ-1 levels by small interfering RNA led to an accelerated cell death, whereas an increase in DJ-1 levels by adenovirus-based infection attenuated cell death induced by H₂O₂ and thapsigargin in β-cell lines and mouse pancreatic islets. Furthermore, DJ-1 improved regulated insulin secretion under basal as well as oxidative and endoplasmic reticulum stress conditions in a dose-dependent manner. We identified TFII-I (Gtf2i) as DJ-1 partner in the cytosol, whereas the binding of TFII-I to DJ-1 prevented TFII-I translocation to the nucleus. The outcome was attenuation of the stress response. Our results suggest that DJ-1 together with TFII-I operate in concert to cope with various insults and to sustain pancreatic β-cell function.