RagD gene expression and NRF2 mutations in lung squamous cell carcinomas

Novel long noncoding lncARF mediated hyperhomocysteinemia-induced atherosclerosis via autophagy inhibition in foam cells

INTRODUCTION

Homocysteine (Hcy) is well recognized to be an independent risk factor for atherosclerosis. Long non-coding RNAs (lncRNAs) are emerging regulators of pathophysiological processes including atherosclerosis, while the underlying mechanisms of its involvement in Hcy induced-atherosclerosis remain largely unknown.

OBJECTIVES

The primary aim of this study is to assess the role of lncARF (autophagy-related factor induced by Hcy) in Hcy induced-atherosclerosis and related mechanism.

METHODS

RNA sequencing of foam cells treated with Hcy revealed a novel specific long noncoding RNA called lncARF. Locked nucleic acid gapmeRs-mediated lncARF knockdown was used to explore the role of lncARF both in vivo and in vitro. Mass spectrometry, RNA pull-down and RNA immunoprecipitation (RIP) assays were employed to uncover a mechanistic role of lncARF. Mass array assay and chromatin immunoprecipitation (ChIP) were used to detect the transcriptional activation of lncARF mediated by transcription factor. Clinically, receiver operating characteristic (ROC) curve analysis was used to assess the diagnostic value of lncARF in atherosclerotic patients with hyperhomocysteinemia (HHcy).

RESULTS

We observed that the expression of lncARF was substantially upregulated in atherosclerotic plaques, and knockdown of lncARF decreased the formation of atherosclerotic lesions by promoting autophagy in foam cells. Mechanistically, lncARF physically binds to RRAGD and inhibits its ubiquitination, further activating the PI3K/Akt and MAPK signaling pathways. Moreover, in vitro experiments showed that transcription factor FosB inhibited the binding of DNMT1 at the lncARF promoter, leading to transcriptional activation through DNA hypomethylation. Clinically, lncARF expression was positively correlated with serum Hcy levels, and it could distinguish atherosclerotic patients with HHcy with a high area under the ROC curve, sensitivity and specificity.

CONCLUSIONS

Our study highlights the mechanisms of lncARF in protecting against the development of atherosclerosis involving the epigenetic modifications and RRAGD/PI3K/Akt and RRAGD/MAPK signaling pathways, which may provide novel diagnostic biomarkers to improve atherosclerosis treatment.

Acylated ghrelin suppresses doxorubicin-induced testicular damage and improves sperm parameters in rats via activation of Nrf2 and mammalian target of rapamycin

Background

Exogenous administration of acylated ghrelin (AG) afforded reproductive protective effect in several animal models but not in those treated with doxorubicin (DOX). This study evaluated the protective effect of AG against DOX-induced testicular damage and impairment in sperm parameters in rats and examined the potential mechanisms of action.

Materials and Methods

Adult male rats were divided into five groups (n = 8/each) as control, control + AG (40 nmol/kg/day; subcutaneous), DOX (10 mg/kg/day 1; intraperitoneal [i.p.]), DOX + AG, and DOX + AG + brusatol (an Nrf2 inhibitor) (2 mg/kg/every 3 days; i.p.). The treatment regimen continued for 65 days.

Results

AG prevented testicular damage and apoptosis; increased sperm count, motility, and viability; and reduced the number of abnormal sperms. It also increased their circulatory levels of AG, des-acylated ghrelin (DAG), and AG/DAG ratio and the testicular mRNA levels of ghrelin and growth hormone secretagogue receptor 1a Concomitantly, AG increased serum and testicular testosterone levels, reduced serum levels of the follicle-stimulating hormone and luteinizing hormone, and upregulated the testicular protein levels of the steroidogenic acute regulatory protein and 3β-hydroxysteroid dehydrogenase in DOX-treated rats. In the testes of the control and DOX-treated rats, AG increased the phosphorylation of mammalian target of rapamycin and stimulated the levels of glutathione and superoxide dismutase, as well as the nuclear activation of Nrf2. All these effects were completely prevented by co-treatment with brusatol.

Conclusion

AG replacement therapy could be a novel strategy to prevent reproductive toxicity in cancer patients.

The NRF2 antagonist ML385 inhibits PI3K-mTOR signaling and growth of lung squamous cell carcinoma cells

BACKGROUND

Lung squamous cell carcinoma (LUSC) currently has limited therapeutic options because of the relatively few validated targets and the lack of clinical drugs for some of these targets. Although NRF2/NFE2L2 pathway activation commonly occurs in LUSC, NRF2 has predominantly been studied in other cancer models. Here, we investigated the function of NRF2 in LUSC, including in organoid models, and we explored the activity of a small molecule NRF2 inhibitor ML385, which has not previously been investigated in LUSC.

METHODS

We first explored the role of NRF2 signaling in LUSC cancer cell line and organoid proliferation through NRF2 knockdown or ML385 treatment, both in vivo and in vitro. Next, we performed Western blot and immunofluorescence assays to determine the effect of NRF2 inhibition on PI3K-mTOR signaling. Finally, we used cell viability and clonogenic assays to explore whether ML385 could sensitize LUSC cancer cells to PI3K inhibitors.

RESULTS

We find that downregulation of NRF2 signaling inhibited proliferation of LUSC cancer cell lines and organoids, both in vivo and in vitro. We also demonstrate that inhibition of NRF2 reduces PI3K-mTOR signaling, with two potential mechanisms being involved. Although NRF2 promotes AKT phosphorylation, it also acts downstream of AKT to increase RagD protein expression and recruitment of mTOR to lysosomes after amino acid stimulation. We also find that ML385 potentiates LUSC growth inhibition by a pan-PI3K inhibitor, which correlates with stronger inhibition of PI3K-mTOR signaling.

CONCLUSIONS

Our data provide additional support for NRF2 promoting LUSC growth through PI3K-mTOR activation and support development of NRF2 inhibitors for the treatment of LUSC.

[Progress of NRF2 Signaling Pathway in Promoting Proliferation of Non-small Cell Lung Cancer]

The morbidity and mortality of lung cancer ranks among the top cancers in the world. Non-small cell lung cancer (NSCLC) is the main pathological type of lung cancer, with limited treatment options and poor prognosis. The nuclear factor E2-related factor 2 (NRF2) signaling pathway is highly mutated and activated in NSCLC, and promotes the malignant progression of lung cancer through various mechanisms. NRF2-targeted therapy will provide new treatment strategies for patients with NSCLC. This article will review the basic structure and response pathways of the NRF2 pathway, the mechanism of NRF2 regulating lung cancer cell proliferation, and the research and development progress of NRF2 inhibitors.
.

The Interaction of mTOR and Nrf2 in Neurogenesis and Its Implication in Neurodegenerative Diseases

Neurogenesis occurs in the brain during embryonic development and throughout adulthood. Neurogenesis occurs in the hippocampus and under normal conditions and persists in two regions of the brain—the subgranular zone (SGZ) in the dentate gyrus of the hippocampus and the subventricular zone (SVZ) of the lateral ventricles. As the critical role in neurogenesis, the neural stem cells have the capacity to differentiate into various cells and to self-renew. This process is controlled through different methods. The mammalian target of rapamycin (mTOR) controls cellular growth, cell proliferation, apoptosis, and autophagy. The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) is a major regulator of metabolism, protein quality control, and antioxidative defense, and is linked to neurogenesis. However, dysregulation in neurogenesis, mTOR, and Nrf2 activity have all been associated with neurodegenerative diseases such as Alzheimer’s, Huntington’s, and Parkinson’s. Understanding the role of these complexes in both neurogenesis and neurodegenerative disease could be necessary to develop future therapies. Here, we review both mTOR and Nrf2 complexes, their crosstalk and role in neurogenesis, and their implication in neurodegenerative diseases.

The Roles of Oxidative Stress in Regulating Autophagy in Methylmercury-induced Neurotoxicity

Methylmercury (MeHg) is a potential neurotoxin that is highly toxic to the human central nervous system. Although MeHg neurotoxicity has been widely studied, the mechanism of MeHg neurotoxicity has not yet been fully elucidated. Some research evidence suggests that oxidative stress and autophagy are important molecular mechanisms of MeHg-induced neurotoxicity. Researchers have widely accepted that oxidative stress regulates the autophagy pathway. The current study reviews the activation of Nuclear factor-erythroid-2-related factor (Nrf2)-related oxidative stress pathways and autophagy signaling pathways in the case of MeHg neurotoxicity. In addition, autophagy mainly plays a role in the neurotoxicity of MeHg through mTOR-dependent and mTOR-independent autophagy signaling pathways. Finally, the regulation of autophagy by reactive oxygen species (ROS) and Nrf2 in MeHg neurotoxicity was explored in this review, providing a new concept for the study of the neurotoxicity mechanism of MeHg.

Crosstalk between the mTOR and Nrf2/ARE signaling pathways as a target in the improvement of long-term potentiation

In recent years, a significant progress was made in understanding molecular mechanisms of long-term memory. Long-term memory formation requires strengthening of neuronal connections (LTP, long-term potentiation) associated with structural rearrangement of neurons. The key role in the synthesis of proteins essential for these rearrangements belong to mTOR (mammalian target of rapamycin) complexes and signaling pathways involved in mTOR regulation. Suppression of mTOR activity may impair synaptic plasticity and long-term memory, while mTOR activation inhibits autophagy, thereby potentiating amyloidosis and development of Alzheimer's disease (AD) accompanied by irreversible memory loss. Because of this, suppression/inhibition of mTOR might have unpredictable consequences on memory. The Nrf2/ARE signaling pathway affects almost all mitochondrial processes. The activation of this pathway improves memory and exhibits therapeutic effect in AD. In this review, we discuss the crosstalk between the Nrf2/ARE signaling and mTOR in the maintenance of synaptic plasticity. Nrf2 pathway can be activated by pharmacological agents and by changes in mitochondria functioning accompanying various neuronal dysfunctions.

Cancer Stem Cells: Emergent Nature of Tumor Emergency

A functional analysis of 167 genes overexpressed in Krebs-2 tumor initiating cells was performed. In the first part of the study, the genes were analyzed for their belonging to one or more of the three groups, which represent the three major phenotypic manifestation of malignancy of cancer cells, namely (1) proliferative self-sufficiency, (2) invasive growth and metastasis, and (3) multiple drug resistance. 96 genes out of 167 were identified as possible contributors to at least one of these fundamental properties. It was also found that substantial part of these genes are also known as genes responsible for formation and/or maintenance of the stemness of normal pluri-/multipotent stem cells. These results suggest that the malignancy is simply the ability to maintain the stem cell specific genes expression profile, and, as a consequence, the stemness itself regardless of the controlling effect of stem niches. In the second part of the study, three stress factors combined into the single concept of "generalized cellular stress," which are assumed to activate the expression of these genes, were defined. In addition, possible mechanisms for such activation were identified. The data obtained suggest the existence of a mechanism for the de novo formation of a pluripotent/stem phenotype in the subpopulation of "committed" tumor cells.

RagD regulates amino acid mediated-casein synthesis and cell proliferation via mTOR signalling in cow mammary epithelial cells

This research paper addresses the hypothesis that RagD is a key signalling factor that regulates amino acid (AA) mediated-casein synthesis and cell proliferation in cow mammary epithelial cells (CMECs). The expression of RagD was analysed at different times during pregnancy and lactation in bovine mammary tissue from dairy cows. We showed that expression of RagD at lactation period was higher (P < 0·05) than that at pregnancy period. When CMECs were treated with methionine (Met) or lysine (Lys), expression of RagD, β-casein (CSN2), mTOR and p-mTOR, and cell proliferation were increased. Further, when CMECs were treated to overexpress RagD, expression of CSN2, mTOR and p-mTOR, and cell proliferation were up-regulated. Furthermore, the increase in expression of CSN2, mTOR and p-mTOR, and cell proliferation in response to Met or Lys supply was inhibited by inhibiting RagD, and those effects were reversed in the overexpression model. When CMECs were treated with RagD overexpression together with mTOR inhibition or conversely with RagD inhibition together with mTOR overexpression, results showed that the increase in expression of CSN2 and cell proliferation in response to RagD overexpression was prevented by inhibiting mTOR, and those effects were reversed by overexpressing mTOR. The interaction of RagD with subunit proteins of mTORC1 was analysed, and the result showed that RagD interacted with Raptor. CMECs were treated with Raptor inhibition, and the result showed that the increase in expression of mTOR and p-mTOR in response to RagD overexpression was inhibited by inhibiting Raptor.

In conclusion, our study showed that RagD is an important activation factor of mTORC1 in CMECs, activating AA-mediated casein synthesis and cell proliferation, potentially acting via Raptor.

Milk's Role as an Epigenetic Regulator in Health and Disease

It is the intention of this review to characterize milk's role as an epigenetic regulator in health and disease. Based on translational research, we identify milk as a major epigenetic modulator of gene expression of the milk recipient. Milk is presented as an epigenetic "doping system" of mammalian development. Milk exosome-derived micro-ribonucleic acids (miRNAs) that target DNA methyltransferases are implicated to play the key role in the upregulation of developmental genes such as FTO, INS, and IGF1. In contrast to miRNA-deficient infant formula, breastfeeding via physiological miRNA transfer provides the appropriate signals for adequate epigenetic programming of the newborn infant. Whereas breastfeeding is restricted to the lactation period, continued consumption of cow's milk results in persistent epigenetic upregulation of genes critically involved in the development of diseases of civilization such as diabesity, neurodegeneration, and cancer. We hypothesize that the same miRNAs that epigenetically increase lactation, upregulate gene expression of the milk recipient via milk-derived miRNAs. It is of critical concern that persistent consumption of pasteurized cow's milk contaminates the human food chain with bovine miRNAs, that are identical to their human analogs. Commercial interest to enhance dairy lactation performance may further increase the epigenetic miRNA burden for the milk consumer.

Nrf2 Transcription Factor Can Directly Regulate mTOR: LINKING CYTOPROTECTIVE GENE EXPRESSION TO A MAJOR METABOLIC REGULATOR THAT GENERATES REDOX ACTIVITY

Nrf2 is a master transcription factor that regulates a wide variety of cellular proteins by recognizing and binding to antioxidant response elements (AREs) in their gene promoter regions. In this study we show that increasing cellular Nrf2 results in transcriptional activation of the gene for mTOR, which is central to the PI3K signaling pathway. This is the case in cells with normal physiological PI3K. However, in cells with abnormally active PI3K increased cellular Nrf2 levels have no effect on mTOR. ChIP assays results show that increased Nrf2 binding is associated with decreased p65 binding and H3-K27me3 signal (marker of gene repression) as well as increased H3-K4me3 signal (marker of gene activation). However, in cells with PI3K activation, no effect of cellular Nrf2 increase on mTOR transcription was observed. In these cells, increasing Nrf2 levels increases Nrf2 promoter binding marginally, whereas p65 binding and H3-K27me3 mark were significantly increased, and H3-K4me3 signal is reduced. Together, these data show for the first time that Nrf2 directly regulates mTOR transcription when the PI3K pathway is intact, whereas this function is lost when PI3K is activated. We have identified a link between the Nrf2 system of sensing environmental stress and mTOR, which is a key cellular protein in metabolism. Studies in cells with activating mutations in the PI3K pathway suggest that Nrf2 transcriptional regulation of mTOR is related to promoter binding of p65 and of methylation of histone residues permissive of transcription.

Functional polymorphisms in Nrf2: implications for human disease

Nuclear factor (erythroid derived)-2 like 2 (NFE2L2), also known as nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2), is a ubiquitous transcription factor essential for protecting cells and tissues from oxidative stress-induced injury. Positional cloning and studies with Nrf2 knockout mice have identified important roles for this transcription factor in disease phenotypes for many organ systems. Studies have also characterized the means through which human Nrf2 is regulated and the mechanisms of interaction with antioxidant response elements (ARE) in promoters of effector genes. Moreover, single nucleotide polymorphisms (SNPs) in Nrf2 have been identified and evaluated for effects on gene expression and function, and translational investigations have sought to determine whether loss of function SNPs associate with disease progression. In this review, we present 1) an overview of the human Nrf2 gene and protein domain, 2) identification of genetic mutations in Nrf2 and associations of the mutations with multiple diseases, and 3) the role of somatic mutations in Nrf2 in diseases, primarily various cancers.

Identification of reference genes for qRT-PCR in human lung squamous-cell carcinoma by RNA-Seq

Although the accuracy of quantitative real-time polymerase chain reaction (qRT-PCR) is highly dependent on the reliable reference genes, many commonly used reference genes are not stably expressed and as such are not suitable for quantification and normalization of qRT-PCR data. The aim of this study was to identify novel reliable reference genes in lung squamous-cell carcinoma. We used RNA sequencing (RNA-Seq) to survey the whole genome expression in 5 lung normal samples and 44 lung squamous-cell carcinoma samples. We evaluated the expression profiles of 15 commonly used reference genes and identified five additional candidate reference genes. To validate the RNA-Seq dataset, we used qRT-PCR to verify the expression levels of these 20 genes in a separate set of 100 pairs of normal lung tissue and lung squamous-cell carcinoma samples, and then analyzed these results using geNorm and NormFinder. With respect to 14 of the 15 common reference genes (B2M, GAPDH, GUSB, HMBS, HPRT1, IPO8, PGK1, POLR2A, PPIA, RPLP0, TBP, TFRC, UBC, and YWHAZ), the expression levels were either too low to be easily detected, or exhibited a high degree of variability either between lung normal and squamous-cell carcinoma samples, or even among samples of the same tissue type. In contrast, 1 of the 15 common reference genes (ACTB) and the 5 additional candidate reference genes (EEF1A1, FAU, RPS9, RPS11, and RPS14) were stably and constitutively expressed at high levels in all the samples tested. ACTB, EEF1A1, FAU, RPS9, RPS11, and RPS14 are ideal reference genes for qRT-PCR analysis of lung squamous-cell carcinoma, while 14 commonly used qRT-PCR reference genes are less appropriate in this context.

Oncogenic potential of Nrf2 and its principal target protein heme oxygenase-1

Nuclear factor erythroid 2-related factor 2 (Nrf2) is an essential component of cellular defense against a vast variety of endogenous and exogenous insults, including oxidative stress. Nrf2 acts as a master switch in the circuits upregulating the expression of various stress-response proteins, especially heme oxygenase-1 (HO-1). Paradoxically, however, recent studies have demonstrated oncogenic functions of Nrf2 and its major target protein HO-1. Levels of Nrf2 and HO-1 are elevated in many different types of human malignancies, which may facilitate the remodeling of the tumor microenvironment making it advantageous for the autonomic growth of cancer cells, metastasis, angiogenesis, and tolerance to chemotherapeutic agents and radiation and photodynamic therapy. In this context, the cellular stress response or cytoprotective signaling mediated via the Nrf2-HO-1 axis is hijacked by cancer cells for their growth advantage and survival of anticancer treatment. Therefore, Nrf2 and HO-1 may represent potential therapeutic targets in the management of cancer. This review highlights the roles of Nrf2 and HO-1 in proliferation of cancer cells, their tolerance/resistance to anticancer treatments, and metastasis or angiogenesis in tumor progression.

Genomic structure and variation of nuclear factor (erythroid-derived 2)-like 2

High-density mapping of mammalian genomes has enabled a wide range of genetic investigations including the mapping of polygenic traits, determination of quantitative trait loci, and phylogenetic comparison. Genome sequencing analysis of inbred mouse strains has identified high-density single nucleotide polymorphisms (SNPs) for investigation of complex traits, which has become a useful tool for biomedical research of human disease to alleviate ethical and practical problems of experimentation in humans. Nuclear factor (erythroid-derived 2)-like 2 (NRF2) encodes a key host defense transcription factor. This review describes genetic characteristics of human NRF2 and its homologs in other vertebrate species. NRF2 is evolutionally conserved and shares sequence homology among species. Compilation of publically available SNPs and other genetic mutations shows that human NRF2 is highly polymorphic with a mutagenic frequency of 1 per every 72 bp. Functional at-risk alleles and haplotypes have been demonstrated in various human disorders. In addition, other pathogenic alterations including somatic mutations and misregulated epigenetic processes in NRF2 have led to oncogenic cell survival. Comprehensive information from the current review addresses association of NRF2 variation and disease phenotypes and supports the new insights into therapeutic strategies.