Inhibitor of DNA Binding Protein 3 (ID3) and Nuclear Respiratory Factor 1 (NRF1) Mediated Transcriptional Gene Signatures are Associated with the Severity of Cerebral Amyloid Angiopathy

Cerebral amyloid angiopathy (CAA) is a degenerative vasculopathy. We have previously shown that transcription regulating proteins- inhibitor of DNA binding protein 3 (ID3) and the nuclear respiratory factor 1 (NRF1) contribute to vascular dysregulation. In this study, we have identified sex specific ID3 and NRF1-mediated gene networks in CAA patients diagnosed with Alzheimer's Disease (AD). High expression of ID3 mRNA coupled with low NRF1 mRNA levels was observed in the temporal cortex of men and women CAA patients. Low NRF1 mRNA expression in the temporal cortex was found in men with severe CAA. High ID3 expression was found in women with the genetic risk factor APOE4. Low NRF1 expression was also associated with APOE4 in women with CAA. Genome wide transcriptional activity of both ID3 and NRF1 paralleled their mRNA expression levels. Sex specific differences in transcriptional gene signatures of both ID3 and NRF1 were observed. These findings were further corroborated by Bayesian machine learning and the GeNIe simulation models. Dynamic machine learning using a Monte Carlo Markov Chain (MCMC) gene ordering approach revealed that ID3 was associated with disease severity in women. NRF1 was associated with CAA and severity of this disease in men. These findings suggest that aberrant ID3 and NRF1 activity presumably plays a major role in the pathogenesis and severity of CAA. Further analyses of ID3- and NRF1-regulated molecular drivers of CAA may provide new targets for personalized medicine and/or prevention strategies against CAA.

The Regulatory Role of Nuclear Respiratory Factor 1 in Bladder Cancer Cells

BACKGROUND/AIM

Nuclear respiratory factor 1 (NRF1) is a key mediator of genes involved in mitochondrial biogenesis and the respiratory chain; however, its role in bladder cancer remains unknown. Transitional cell carcinoma, also known as urothelial cell carcinoma, is the most common type of bladder cancer resistant to chemotherapy. An established high-grade and invasive transitional cell carcinoma line from patients with urinary bladder cancer, known as T24, has been extensively used in cancer research. In this study, we aimed to investigate the mechanisms through which NRF1 regulates proliferation and cell migration of bladder cancer cells using the T24 cell line.

MATERIALS AND METHODS

Cells were transfected with plasmid cloning DNA for NRF1 to evaluate the effect of NRF1 overexpression on bladder cancer cells. Western blot was used to examine epithelial and mesenchymal markers (E-cadherin and α-smooth muscle actin), transcriptional regulators for epithelial-mesenchymal transition (snail family transcriptional repressors), components of transforming growth factor-β1/SMADs signaling, high-mobility group box 1 (HMGB1), and receptor for advanced glycation end-products (RAGE). The in situ expression of E-cadherin, α-smooth muscle actin and SMAD7 was determined using immunofluorescence staining. Cell migration capacity was assessed by wound-healing assay.

RESULTS

Transfection with NRF1 expression vector repressed the migration capacity of bladder cancer cells, diminishing HMGB1/RAGE expression and reducing transforming growth factor β-associated epithelial-mesenchymal transition in T24 cells.

CONCLUSION

Therapeutic avenues that increase NRF1 expression may serve as an adjunct to conventional treatments for bladder cancer.

Nuclear Respiratory Factor 1 Overexpression Inhibits Proliferation and Migration of PC3 Prostate Cancer Cells

BACKGROUND/AIM

The role of nuclear respiratory factor 1 (NRF1) on the prostate cancer progression is controversial. We aimed to investigate the effect of NRF1 overexpression on the metastasis potential of PC3 prostate cancer cells and the associated molecular mechanisms.

MATERIALS AND METHODS

Cell survival, migration capacity, mitochondrial biogenesis, the expression of TGF-β signaling and EMT markers were examined after overexpression and silencing of NRF1 in PC3 cells.

RESULTS

We found that NRF1-overexpressing cells exhibited a decreased cell viability and proliferation ability as well as a reduced migration capacity compared to control cells. Moreover, ectopic expression of NRF1 increased the mitochondrial biogenesis and inhibited the EMT characteristics, including a decrease in the mesenchymal marker, α-SMA and an increase in the epithelial cell marker, E-cadherin. We also demonstrated that overexpression of NRF1 suppressed the expression of TGF-β signaling in PC3 cells. As expected, silencing of NRF1 reversed the abovementioned effects.

CONCLUSION

This study demonstrated that upregulation of NRF1 holds the potential to inhibit the metastasis of prostate cancer, possibly through an elevation of mitochondrial biogenesis and the subsequent repression of TGF-β-associated EMT. Therapeutic avenues that increase NRF1 expression may serve as an adjunct to conventional treatments of prostate cancer.

Nuclear respiratory factor 1 transcriptomic signatures as prognostic indicators of recurring aggressive mesenchymal glioblastoma and resistance to therapy in White American females

PURPOSE

The mechanisms contributing to recurrence of glioblastoma (GBM), an aggressive neuroepithelial brain tumor, remain unknown. We have recently shown that nuclear respiratory factor 1 (NRF1) is an oncogenic transcription factor and its transcriptional activity is associated with the progression and prognosis of GBM. Herein, we extend our efforts to (1) identify influential NRF1-driven gene and microRNA (miRNA) expression for the aggressiveness of mesenchymal GBM; and (2) understand the molecular basis for its poor response to therapy.

METHODS

Clinical data and RNA-Seq from four independent GBM cohorts were analyzed by Bayesian Network Inference with Java Objects (BANJO) and Markov chain Monte Carlo (MCMC)-based gene order to identify molecular drivers of mesenchymal GBM as well as prognostic indicators of poor response to radiation and chemotherapy.

RESULTS

We are the first to report sex-specific NRF1 motif enriched gene signatures showing increased susceptibility to GBM. Risk estimates for GBM were increased by greater than 100-fold with the joint effect of NRF1-driven gene signatures-CDK4, DUSP6, MSH2, NRF1, and PARK7 in female GBM patients and CDK4, CASP2, H6PD, and NRF1 in male GBM patients. NRF1-driven causal Bayesian network genes were predictive of poor survival and resistance to chemoradiation in IDH1 wild-type mesenchymal GBM patients. NRF1-regulatable miRNAs were also associated with poor response to chemoradiation therapy in female IDH1 wild-type mesenchymal GBM. Stable overexpression of NRF1 reprogramed human astrocytes into neural stem cell-like cells expressing SOX2 and nestin. These cells differentiated into neurons and form tumorospheroids.

CONCLUSIONS

In summary, our novel discovery shows that NRF1-driven causal genes and miRNAs involved in cancer cell stemness and mesenchymal features contribute to cancer aggressiveness and recurrence of aggressive therapy-resistant glioblastoma.

Testosterone attenuates hypoxia-induced hypertension by affecting NRF1-mediated transcriptional regulation of ET-1 and ACE

Hypertension induced by hypoxia at high altitude is one of the typical symptoms of high-altitude reactions (HARs). Emerging evidence indicates that endothelial abnormalities, including increases in angiotensin-2 (Ang-2) and endothelin-1 (ET-1), are closely associated with hypertension. Thus, low blood oxygen-induced endothelial dysfunction through acceleration of Ang-2 and ET-1 synthesis may alleviate HARs. In this study, we investigated the effects of hypoxia on rat blood pressure (BP) and endothelial injury. We found that BP increased by 10 mmHg after treatment with 10% O₂ (~5500 m above sea level) for 24 h. Consistently, serum Ang-2 and ET-1 levels were increased along with decreases in NO levels. In endothelial cells, angiotensin-1-converting enzyme (ACE) and ET-1 expression levels were upregulated. Interestingly, nuclear respiratory factor 1 (NRF1) levels were also upregulated, consistent with the changes in ACE and ET-1 levels. We further demonstrated that NRF1 transcriptionally activated ACE and ET-1 by directly binding to their promoter regions, suggesting that the endothelial cell dysfunction induced by hypoxia was due to NRF1-dependent upregulation of ACE and ET-1. Surprisingly, testosterone supplementation showed significant protective effects on BP, while castration induced even higher BPs in rats exposed to hypoxia. We further showed that physiological testosterone repressed NRF1 expression in vivo and in vitro and thereby reduced Ang-2 and ET-1 levels, which was dependent on hypoxia. In summary, we have identified that physiological testosterone protects against hypoxia-induced hypertension through inhibition of NRF1, which transcriptionally regulates ACE and ET-1 expression.

[Hypoxia Accelerate β-Actin Expression through Transcriptional Activation of ACTB by Nuclear Respiratory Factor-1]

Cytoskeletal protein β-actin is abundant both in the cytoplasm and the nucleus, its mRNA is commonly utilized an internal control for gene expression analysis. Recent reports demostrated that hypoxia influences the levels of β-actin in a variety of cells. The mechanism underlying this change are not yet elucidated. In this work, we show that the changes in the levels of hypoxia-induced Nuclear respiratory factor-1 (NRF-1) lead to the change in expression of β-actin. We compared the protein levels of NRF-1 and β-actin in gastric cancer and adjacent tissues and found their significantly upregulation in cancer (33% patitents). When gastric cancer cells and normal gastric cells were treated with 1% O2 for 48 h, the trends in expression levels of NRF-1 and β-actin were similar. When NRF-1 expression was modified by its overexpressing or silencing, the levels of β-actin changed accordingly. In β-actin gene (ACTB), three binding sites for NRF-1 were found. These sites are conserved in human, mouse and rat genomes. In ChIP experiments, we showed that NRF-1 directly binds to human ACTB and mouse Actb coding regions. Its seems that the transcription of β-actin encoding gene is NRF-1 dependent.

Intermittent hypoxia preconditioning protects WRL68 cells against oxidative injury: Involvement of the PINK1/Parkin-mediated mitophagy regulated by nuclear respiratory factor 1

The protective effect of intermittent hypoxia (IH) preconditioning against oxidative injury in hepatic cells was investigated and the involvement of the PINK1/Parkin-mediated mitophagy regulated by nuclear respiratory factor 1 (NRF-1) was evaluated. The results showed that IH preconditioning protected HepG2 cells against oxygen and glucose deprivation/reperfusion (OGD/Rep)-induced injury and protected WRL68 cells against H₂O₂ or AMA-induced oxidative injury. IH preconditioning up-regulated the protein level of NRF-1, PINK1, Parkin, and LC3 II, promoted the recruitment of the cytosolic Parkin, indicating the initiation of the PINK1/Parkin-mediated mitophagy in WRL68 cells. When NRF-1 was down-regulated by NRF-1 specific shRNA, the protein level of PINK1 and Parkin as well as the mitophagy level were significantly decreased. After IH preconditioning, the protein level of PINK1 and the recruitment of Parkin in CCCP-treated group were significantly higher than that of the control group, indicating the increased mitophagy capacity. And the increased mitophagy capacity induced by IH preconditioning was also reduced by down-regulation of NRF-1. Furthermore, the protective effect of IH preconditioning against H₂O₂-induced oxidative injury in WRL68 cells was inhibited when NRF-1 or PINK1 was down-regulated by specific shRNA. Mitochondrial ROS generation may be responsible for the increased expression of NRF-1 induced by IH preconditioning. In conclusion, the PINK1/Parkin-mediated mitophagy regulated by NRF-1 was involved in IH preconditioning-induced protective effect against oxidative cellular injury in hepatic cells.

Role of the aryl hydrocarbon receptor signaling pathway in promoting mitochondrial biogenesis against oxidative damage in human melanocytes

BACKGROUND

Reactive oxygen species (ROS)-induced mitochondrial damage aggravates oxidative stress and activates mitochondrial apoptosis pathway to mediate melanocyte death. However, the repair mechanisms underlying damaged mitochondria of melanocytes remain unclear. Accumulative evidence has revealed that the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor, plays a vital role in maintaining mitochondrial homeostasis.

OBJECTIVE

To investigate whether the AHR signaling pathway could protect human melanocytes from oxidative damage through controlling mitochondrial quality.

METHODS

We constructed an oxidative stress model of melanocytes with hydrogen peroxide (H₂O₂) in the human normal melanocyte PIG1 cell line, and detected ROS level, apoptosis, mitochondrial ROS level, mitochondrial membrane potential, ATP production, mitochondrial DNA and mitochondrial modulators after co-treatment with AHR ligand or antagonist and H₂O₂ in the PIG1 cells.

RESULTS

In the present study, we found that H₂O₂-induced oxidative stress directly activated the AHR signaling pathway in melanocytes, whereas abnormal activation of AHR signaling pathway enhanced oxidative damage to mitochondria and melanocytes. Further studies showed that the AHR signaling pathway promoted mitochondrial DNA synthesis and ATP production probably by regulating the expression of nuclear respiratory factor 1 (NRF1) and its downstream targets.

CONCLUSION

Our findings reveal that the AHR signaling pathway might have a major role in protecting melanocytes against oxidative damage via inducing mitochondrial biogenesis, while impaired AHR activation could cause defective repair of mitochondria and exacerbate oxidative damage-induced apoptosis in melanocytes. Our data suggest that the AHR signaling pathway might be a novel mechanism of mitochondrial biogenesis involved in protecting melanocytes from oxidative stress.

Evaluating the role of NRF-1 in the regulation of the goldfish COX4-1 gene in response to temperature

Cold acclimation in fish typically increases muscle mitochondrial enzymes. In mammals, stressors that increase mitochondrial content are mediated though transcriptional regulators, including nuclear respiratory factor-1 (NRF-1). Focusing on the goldfish gene for cytochrome c oxidase (COX) subunit 4-1, we analysed the regulatory regions in various contexts to identify a mechanistic link between NRF-1 and cold-induced mitochondrial proliferation. Promoter analysis implicated two putative NRF-1 sites: one in the proximal promoter and a second in exon 1, which encodes the 5' untranslated region (5'-UTR). Transfection into mouse myoblasts showed that deletion of a region that included the proximal NRF-1 site reduced promoter activity by 30%; however, mutagenesis of the specific sequence had no effect. Thermal sensitivity analyses performed in rainbow trout gonadal fibroblasts (RTG-2) showed no effect of temperature (4 vs 19°C) on reporter gene expression. Likewise, reporters injected into muscle of thermally acclimated goldfish (4 vs 26°C) showed no elevation in expression. There was no difference in thermal responses of COX4-1 promoter reporters constructed from homologous regions of eurythermal goldfish and stenothermal zebrafish genes. NRF-1 chromatin immunoprecipitation of thermally acclimated goldfish muscle showed no temperature effect on NRF-1 binding to either the proximal promoter or 5'-UTR. It remains possible that the cold-induced upregulation of COX4-1 expression is a result of NRF-1 binding to distal regulatory regions or through indirect effects on other transcription factors. However, the proximal promoter does not appear to play a role in mediating the thermal response of the COX4-1 gene in fish.

Recombinant human augmenter of liver regeneration protects hepatocyte mitochondrial DNA in rats with obstructive jaundice

BACKGROUND

Hepatocyte mitochondrial DNA (mtDNA) damage is an important cause of mitochondrial and hepatic function impairment in obstructive jaundice (OJ). This study investigated the protective effect of recombinant human augmenter of liver regeneration (rhALR) on hepatocyte mtDNA in rats with OJ.

MATERIALS AND METHODS

Wistar rats were randomly divided into three groups as follows: sham-operation, biliary obstruction and recanalization with rhALR treatment (BDO-RBF-rhALR), and BDO-RBF-Vehicle (n = 48 per group). After biliary obstruction, rats were intraperitoneally injected with 40 μg/kg rhALR in BDO-RBF-rhALR group and same volume of normal saline in other two groups once every 12 h, until sacrifice. Mitochondrial transcription factor A (mtTFA) and nuclear respiratory factor-1 (NRF-1) expression in hepatocytes were detected by real-time reverse transcription-polymerase chain reaction and Western blot. Hepatocyte mtDNA damage was evaluated by real-time-polymerase chain reaction. Mitochondrial and hepatic functions were also assessed.

RESULTS

After biliary obstruction, hepatic function was clearly impaired, as shown by the increases in serum alanine aminotransferase, aspartate aminotransferase, and total bilirubin levels, and the decrease in albumin level. Mitochondrial respiratory control ratio, phosphorus oxygen ratio, and ATP levels (all indicators of mitochondrial function) were decreased. The relative amount of total mtDNA, mtTFA, and NRF-1 expression in rat liver tissues were decreased, whereas the relative amount of deleted mtDNA was increased. However, the damage was significantly improved in the BDO-RBF-rhALR group. After recanalization, these changes were gradually restored, but the recovery was faster in the BDO-RBF-rhALR group than in BDO-RBF-Vehicle group.

CONCLUSIONS

rhALR may protect and improve mitochondrial and hepatic functions in rats with OJ by promoting the expression of mtTFA and NRF-1 and by protecting and repairing damaged mtDNA.

Neuroprotective effect of p-coumaric acid in rat model of embolic cerebral ischemia

OBJECTIVES

Stroke poses a crucial risk for mortality and morbidity. Our study aimed to investigate the effect of p-coumaric acid on focal cerebral ischemia in rats.

MATERIAL AND METHODS

Rats were randomly divided into four groups, namely Group I (control rats), Group II (ischemia rats), Group III (6 hr ischemia + p-coumaric acid rats) and Group IV (24 hr ischemia + p-coumaric acid rats). Cerebral ischemia was induced via intraluminal monofilament occlusion model. In all groups, the brain was removed after the procedure and rats were sacrificed. Malondialdehyde, superoxide dismutase and nuclear respiratory factor-1 were measured in the ischemic hemisphere. The histopathological changes were observed in the right hemisphere within the samples. Functional assessment was performed for neurological deficit scores.

RESULTS

Following the treatment, biochemical factors changed significantly. Histopathologically, it was shown that p-coumaric acid decreased the oxidative damage. The neurological deficit scores of p-coumaric acid-treated rats were significantly improved after cerebral ischemia.

CONCLUSION

Our results showed that p-coumaric acid is a neuroprotective agent on account of its strong anti-oxidant and anti-apoptotic features. Moreover, p-coumaric acid decreased the focal ischemia. Extra effort should be made to introduce p-coumaric acid as a promising therapeutic agent to be utilized for treatment of human cerebral ischemia in the future.

Glycogen synthase kinase-3 (GSK3) controls deoxyglucose-induced mitochondrial biogenesis in human neuroblastoma SH-SY5Y cells

Mitochondrial biogenesis, a mitochondrial growth and division process, is crucial for adaptation to metabolic stress. The present study demonstrated that treatment with a specific inhibitor of GSK3, SB216763, attenuated induction of mitochondrial biogenesis by a glycolysis inhibitor, 2-deoxyglucose (2-DG), without affecting this biogenesis at basal condition. Additionally, overexpression of WT-GSK3β promoted whereas GSK3β-KD attenuated 2-DG-induced mitochondrial protein expression. The mitochondrial biogenesis attenuation by GSK3 inhibitor was not due to inhibition of protein degradation. Furthermore, GSK3 inhibition further reduced transcription of mitochondrial (COXII), but not nuclear (VDAC) gene by 2-DG suggesting its participation in 2-DG-induced mitochondrial transcription. Together, our results show that GSK3 regulates mitochondrial biogenesis induced by glycolysis inhibition.