Discovery of novel covalent inhibitors of DJ-1 through hybrid virtual screening.

Background: DJ-1 is a ubiquitously expressed protein with multiple functions. Its overexpression has been associated with the occurrence of several cancers, positioning DJ-1 as a promising therapeutic target for cancer treatment. Methods: To find novel inhibitors of DJ-1, we employed a hybrid virtual screening strategy that combines structure-based and ligand-based virtual screening on a comprehensive compound library. Results: In silico study identified six hit compounds as potential DJ-1 inhibitors that were assessed in vitro at the cellular level. Compound 797780-71-3 exhibited antiproliferation activity in ACHN cells with an IC50 value of 12.18 µM and was able to inhibit the Wnt signaling pathway. This study discovers a novel covalent inhibitor for DJ-1 and paves the way for further optimization.

Identifying chronic alcoholism drug disulfiram as a potent DJ-1 inhibitor for cancer therapeutics.

As a key regulator involved in tumor development and progression, DJ-1 has been proposed as a potential therapeutic target against cancer. Also, the development of DJ-1 inhibitors holds great interests in cancer treatment. In the current study, by utilizing a small molecule covalent compounds library screening, we found that disulfiram (DSF), an FDA-approved chronic alcoholism drug, is a potent DJ-1 inhibitor. Glyoxalase assay and microscale thermophoresis analysis suggested that DSF exhibits strong inhibitory activity and high affinity to DJ-1 protein. Additionally, DSF similarly inhibited the methylglyoxal detoxification function of DJ-1 protein at the intracellular level. Notably, we discovered that DSF could significantly enhance N-(4-hydroxyphenyl) retinamide-based proliferation inhibition and apoptosis induction in different types of cancer cell lines, but not in normal tissue lines. Thus, our data suggest DSF functions as a potential inhibitor targeting DJ-1, which may provide a potential synergistic treatment option for cancer therapy.

Bis-isatin derivatives: design, synthesis, and biological activity evaluation as potent dimeric DJ-1 inhibitors.

The PARK7 gene (encode DJ-1 protein) was first discovered as an oncogene and later found to be a causative gene for autosomal recessive early onset Parkinson's disease. DJ-1 has been proposed as a potential therapeutic anticancer target due to its pivotal role in tumorigenesis and cancer progression. Based on the homodimer structure of DJ-1, a series of bis-isatin derivatives with different length linkers were designed, synthesized, and evaluated as dimeric inhibitors targeting DJ-1 homodimer. Among them, DM10 with alkylene chain of C10 displayed the most potent inhibitory activity against DJ-1 deglycase. We further demonstrated that DM10 bound covalently to the homodimer of DJ-1. In human cancer cell lines H1299, MDA-MB-231, BEL7402, and 786-O, DM10 (2.5-20 µM) inhibited the cell growth in a concentration-dependent manner showing better anticancer effects compared with the positive control drug STK793590. In nude mice bearing H1299 cell xenograft, intratumor injection of DM10 (15 mg/kg) produced significantly potent tumor growth inhibition when compared with that caused by STK793590 (30 mg/kg). Moreover, we found that DM10 could significantly enhance N-(4-hydroxyphenyl)retinamide-based apoptosis and erastin-based ferroptosis in H1299 cells. In conclusion, DM10 is identified as a potent inhibitor targeting DJ-1 homodimer with the potential as sensitizing agent for other anticancer drugs, which might provide synergistical therapeutic option for cancer treatment.

Redox-active DJ-1 sustains brainstem cardiovascular regulation via maintenance of mitochondrial function during mevinphos intoxication.

DJ-1 (also known as PARK7) is a redox-active protein that protects against oxidative stress. This study evaluated the hypothesis that DJ-1 sustains brainstem cardiovascular regulation via maintaining mitochondrial function in the rostral ventrolateral medulla (RVLM), a brainstem site known to maintain blood pressure and sympathetic vasomotor tone, during cardiovascular depression elicited by the organophosphate insecticide mevinphos. In Sprague-Dawley rats, intravenous administration of mevinphos (640 µg kg-1) resulted in progressive hypotension, accompanied by an increase (Phase I) followed by a decrease (Phase II) of an experimental index for spontaneous baroreflex-mediated sympathetic vasomotor tone, alongside elevation in mitochondrial superoxide levels in the RVLM. There was concurrent activation of DJ-1 induced by oxidative stress in the RVLM, which was causally and temporally related to translocation of DJ-1 to mitochondria, reduction in mitochondrial membrane potential, increase in cytosolic apoptosis-inducing factor level, and apoptotic cell death in this brainstem site. Loss-of-function by immunoneutralization of DJ-1 in the RVLM significantly exacerbated those biochemical and cellular events, enhanced the progressive hypotension, diminished the increased and augmented the decreased spontaneous baroreflex-mediated sympathetic vasomotor tone respectively during Phases I and II, and heightened lethality during mevinphos intoxication. We conclude that DJ-1 in the RVLM sustains brainstem cardiovascular regulation induced by mevinphos via maintaining mitochondrial function.

Overexpression of DJ-1 enhances colorectal cancer cell proliferation through the cyclin-D1/MDM2-p53 signaling pathway.

Emerging evidence indicates that DJ-1 is highly expressed in different cancers. It modulates cancer progression, including cell proliferation, cell apoptosis, invasion, and metastasis. However, its role in colorectal cancer (CRC) remains poorly defined. The current study noted increased DJ-1 expression in CRC tumor tissue and found that its expression was closely related to clinical-pathological features. Similarly, DJ-1 increased in CRC cells (SW480, HT-29, Caco-2, LoVo, HCT116, and SW620), and especially in SW480 and HCT116 cells. Functional analyses indicated that overexpression of DJ-1 promoted CRC cell invasion, migration, and proliferation in vitro and in vivo. Mechanistic studies indicated that DJ-1 increased in CRC cell lines, activated specific protein cyclin-D1, and modulated the MDM2/p53 signaling pathway by regulating the levels of the downstream factors Bax, Caspase-3, and Bcl-2, which are related to the cell cycle and apoptosis. Conversely, knockdown of DJ-1 upregulated p53 expression by disrupting the interaction between p53 and MDM2 and inhibiting CRC cell proliferation, revealing the pro-oncogenic mechanism of DJ-1 in CRC. In conclusion, the current findings provide compelling evidence that DJ-1 might be a promoter of CRC cell invasion, proliferation, and migration via the cyclin-D1/MDM2-p53 signaling pathway. Findings also suggest its potential role as a postoperative adjuvant therapy for patients with CRC.

Rosmarinic acid exerts an anticancer effect on osteosarcoma cells by inhibiting DJ-1 via regulation of the PTEN-PI3K-Akt signaling pathway.

BACKGROUND: Osteosarcoma is the most common type of primary malignant bone tumor. This disease has exhibited a progressively lower survival rate over the past several decades, which has resulted in it becoming a main cause of death in humans. Rosmarinic acid (RA), a water-soluble polyphenolic phytochemical, exerts powerful anticancer effects against multiple types of cancer; however, its potential effects on osteosarcoma remain unknown. Hence, the present study investigated the efficacy of RA against osteosarcoma and aimed to clarify the mechanisms underlying this process. METHODS: The effects of RA on cell viability, apoptosis, cell cycle distribution, migration, invasion, and signaling molecules were analyzed by CCK-8 assay, flowcytometric analysis, wound healing assay, Transwell assay, proteomic analysis, and use of shRNAs. RESULTS: RA exerted anti-proliferation and pro-apoptotic effects on U2OS and MG63 osteosarcoma cells. Apoptosis was induced via extrinsic and intrinsic pathways by increasing the Bax/Bcl-2 ratio, triggering the intracellular production of reactive oxygen species (ROS), reducing the mitochondrial membrane potential (MMP), and upregulating the cleavage rates of caspase-8, caspase-9, and caspase-3. Additionally, RA suppressed the migration and invasion of osteosarcoma cells by inhibiting the expression levels of matrix metalloproteinase-2 and -9 (MMP-2 and -9), which are associated with a weakening of the epithelial-mesenchymal transition (EMT). Moreover, proteomic analyses identified DJ-1 as a potential target for RA. Several studies have indicated an oncogenic role for DJ-1 using knockdowns via the lentiviral-mediated transfection of shRNA, which caused the conspicuous suppression of cell proliferation, migration, and invasion as well as the arrest of cell cycle progression. At the molecular level, the expression levels of DJ-1, p-PI3K, and p-Akt were reduced, whereas the protein levels of phosphatase and tensin homologue (PTEN) were increased. CONCLUSION: In conjunction with the high levels of DJ-1 expression in osteosarcoma tissues and cell lines, the present results suggested that RA exhibited anticancer effects in osteosarcoma cells by inhibiting DJ-1 via regulation of the PTEN-PI3K-Akt signaling pathway. Therefore, DJ-1 might be a biological target for RA in osteosarcoma cells.

DJ-1 Contributes to Self-renewal of Stem Cells in the U87-MG Glioblastoma Cell Line.

BACKGROUND/AIM: DJ-1, an oncogenic molecule, helps to maintain somatic stem cells by reducing the intracellular level of reactive oxygen species (ROS). This study investigated the role of DJ-1 in glioma stem cells (GSCs). MATERIALS AND METHODS: U87-MG (U87) and U251-MG (U251) glioblastoma cell lines that express wild-type and mutant p53, respectively, were used. These were cultured with DJ-1-targeting siRNA and subjected to a variety of in vitro experiments or intracranial transplantation into nude mice. RESULTS: Knockdown of DJ-1 reduced clonogenicity only in U87 cells, which was rescued by p53 depletion. ROS accumulated in DJ-1-depleted cells, although treatment with N-acetyl cysteine, which quenches ROS, did not affect exhaustion of CSCs among U87 cells by DJ-1 knockdown. In a serial transplantation study, DJ-1 knockdown prolonged the survival of mice in secondary transplantation. CONCLUSION: DJ-1 plays a pivotal role in maintenance of stem cell self-renewal in the U87 cell line.

DJ-1 overexpression confers the multidrug resistance phenotype to SGC7901 cells by upregulating P-gp and Bcl-2.

Gastric cancer (GC) is one of the most malignant tumors with high incidence and mortality worldwide, and the multidrug resistance (MDR) often results in chemotherapy failure in GC. DJ-1 has been well indicated to be associated with drug resistance in multiple cancers. However, the role of DJ-1 in the MDR of gastric cancer cells and its possible mechanism remain to be elucidated. Therefore, the current study was investigated whether DJ-1 expression is differential in parental gastric cancer cell SGC7901 and vincristine (VCR)-induced gastric cancer MDR cell SGC7901/VCR, and whether DJ-1 plays a significant role in development of MDR in gastric cancer. The results showed that DJ-1 expression in SGC7901/VCR cells was significantly higher than its sensitive parental SGC7901 cells. Furthermore, DJ-1 overexpressed gastric cancer cell line SGC7901/LV-DJ-1 led to the increase of cell survival rate, the IC50 of chemotherapeutic drugs and number of cell clones as well as decrease of cell cycle G0/G1 phase ratio compared with its parental cells under the treatment of VCR, adriamycin (ADR), 5-Fluorouracil (5-FU) and cisplatin (DDP). However, the DJ-1 knockdown stable cell line SGC7901/VCR/shDJ-1 reversed the above mentioned series of MDR. Moreover, it was found that upregulation of DJ-1 protein expression promoted the pumping rate of GC cells to ADR and reduced the apoptotic index of GC cells treated with chemotherapeutic drugs by upregulating P-gp and Bcl-2. Similarly, knocking down DJ-1, P-gp or Bcl-2 displayed a converse effect. In conclusion, the current study demonstrated that DJ-1 overexpression confers the MDR phenotype to SGC7901 cells and this process is related to DJ-1 promoting active efflux of drugs and enhancing the anti-apoptotic ability of MDR GC cells by upregulating P-gp and Bcl-2.

Discovery and Optimization of Inhibitors of the Parkinson's Disease Associated Protein DJ-1.

DJ-1 is a Parkinson's disease associated protein endowed with enzymatic, redox sensing, regulatory, chaperoning, and neuroprotective activities. Although DJ-1 has been vigorously studied for the past decade and a half, its exact role in the progression of the disease remains uncertain. In addition, little is known about the spatiotemporal regulation of DJ-1, or the biochemical basis explaining its numerous biological functions. Progress has been hampered by the lack of inhibitors with precisely known mechanisms of action. Herein, we have employed biophysical methodologies and X-ray crystallography to identify and to optimize a family of compounds inactivating the critical Cys106 residue of human DJ-1. We demonstrate these compounds are potent inhibitors of various activities of DJ-1 in vitro and in cell-based assays. This study reports a new family of DJ-1 inhibitors with a defined mechanism of action, and contributes toward the understanding of the biological function of DJ-1.

Insulin signaling pathway protects neuronal cell lines by Sirt3 mediated IRS2 activation.

Cellular stress like ER and oxidative stress are the principle causative agents of various proteinopathies. Multifunctional protein PARK7/DJ-1 provides protection against cellular stress. Recently, insulin/IGF also has emerged as a neuro-protective molecule. However, it is not known whether DJ-1 and insulin/IGF complement each other for cellular protection in response to stress. In this study, we show for the first time, that in human and mouse neuronal cell lines, down regulation of DJ-1 for 48 h leads to compensatory upregulation of insulin/IGF signaling (IIS) pathway genes, namely, insulin receptor, insulin receptor substrate, and Akt under normal physiological conditions as well as in cellular stress conditions. Moreover, upon exogenous supply of insulin there is a marked increase in the IIS components both at gene and protein levels leading to down regulation and inactivation of GSK3ß. By immunoprecipitation, it was observed that Sirt3 mediated deacetylation and activation of FoxO3a could not occur under DJ-1 downregulation. Transient DJ-1 downregulation also led to Akt mediated increased phosphorylation and nuclear exclusion of FoxO3a. When DJ-1 was downregulated increased interaction of Sirt3 with IRS2 was observed leading to its activation resulting in IIS upregulation. Thus, transient downregulation of DJ-1 leads to stimulation of IIS pathway by Sirt3 mediated IRS2 activation. Consequently, antiapoptotic program is triggered in neuronal cells via Akt-GSK3ß-FoxO3a axis. © 2018 BioFactors, 44(3):224-236, 2018.

microRNAs in Parkinson's Disease: From Pathogenesis to Novel Diagnostic and Therapeutic Approaches.

Parkinson's disease (PD) is the most prevalent central nervous system (CNS) movement disorder and the second most common neurodegenerative disease overall. PD is characterized by the progressive loss of dopaminergic (DAergic) neurons in the substantia nigra pars compacta (SNpc) within the midbrain, accumulation of alpha-synuclein (α-SYN) in Lewy bodies and neurites and excessive neuroinflammation. The neurodegenerative processes typically begin decades before the appearance of clinical symptoms. Therefore, the diagnosis is achievable only when the majority of the relevant DAergic neurons have already died and for that reason available treatments are only palliative at best. The causes and mechanism(s) of this devastating disease are ill-defined but complex interactions between genetic susceptibility and environmental factors are considered major contributors to the etiology of PD. In addition to the role of classical gene mutations in PD, the importance of regulatory elements modulating gene expression has been increasingly recognized. One example is the critical role played by microRNAs (miRNAs) in the development and homeostasis of distinct populations of neurons within the CNS and, in particular, in the context of PD. Recent reports demonstrate how distinct miRNAs are involved in the regulation of PD genes, whereas profiling approaches are unveiling variations in the abundance of certain miRNAs possibly relevant either to the onset or to the progression of the disease. In this review, we provide an overview of the miRNAs recently found to be implicated in PD etiology, with particular focus on their potential relevance as PD biomarkers, as well as their possible use in PD targeted therapy.

DJ-1 as a Therapeutic Target Against Cancer.

DJ-1 is a gene involved in various cellular processes, including transcriptional regulation, oxidative stress response, fertilization, mitochondrial regulation, inflammatory and fibrogenic niche formation, and glycation damage prevention. Although a disease-associated genetic study within the past decade has demonstrated that the mutation of DJ-1 is associated with autosomal early-onset Parkinson's disease, increasing evidence suggests that DJ-1 also plays a critical role in tumor development and progression. In this review, we provide an overview of current knowledge concerning the role and the mechanism of DJ-1 in cancer and also discuss the possibility of DJ-1 as a therapeutic target against cancer.

Free radicals impair the anti-oxidative stress activity of DJ-1 through the formation of SDS-resistant dimer.

DJ-1 is a causative gene for familial Parkinson's disease (PD). Loss-of-function of DJ-1 protein is suggested to contribute to the onset of PD, but the causes of DJ-1 dysfunction remain insufficiently elucidated. In this study, we found that the SDS-resistant irreversible dimer of DJ-1 protein was formed in human dopaminergic neuroblastoma SH-SY5Y cells when the cells were exposed to massive superoxide inducers such as paraquat and diquat. The dimer was also formed in vitro by superoxide in PQ redox cycling system and hydroxyl radical produced in Fenton reaction. We, thus, found a novel phenomenon that free radicals directly affect DJ-1 to form SDS-resistant dimers. Moreover, the formation of the SDS-resistant dimer impaired anti-oxidative stress activity of DJ-1 both in cell viability assay and H2O2-elimination assay in vitro. Similar SDS-resistant dimers were steadily formed with several mutants of DJ-1 found in familial PD patients. These findings suggest that DJ-1 is impaired due to the formation of SDS-resistant dimer when the protein is directly attacked by free radicals yielded by external and internal stresses and that the DJ-1 impairment is one of the causes of sporadic PD.