Redox-Activated Signal Transduction Pathways Mediating Cellular Functions in Inflammation, Differentiation, Degeneration, Transformation, and Death

An Enzyme-Encapsulated MOF@MOF Nanocomposite for Detecting H2O2 Derived From Superoxide Anion Released by Mitochondria of HeLa Cells

In this work, a horseradish peroxidase (HRP)-encapsulated metal organic framework (MOF)@MOF nanocomposite is developed for detecting H2O2 converted by dismutation of superoxide anions released from live HeLa mitochondria. Initially, an HRP-polyacrylic acid cluster is incorporated on a mesoporous, peroxidase-like Cu/Co-1,4-benzenedicarboxylate (BDC) MOF platform to avoid structural change and deactivation of HRP through its interactions with MOF metal ions. Additionally, a Cu/Co-BDC(HRP)@1,3,5-benzenetricarboxyate (BTC) core-shell MOF/MOF structure, also with peroxide-like properties, serves as a protective matrix for HRP. Then, ultrathin porous carbon shells (UPCS) are adopted to improve the electrical conductivity of the MOF@MOF. The Cu/Co-BDC(HRP)@BTC|UPCS sensing platform exhibits two linear ranges of 0.05-1 µM and 1-1000 µM with a sensitivity of 172 mA mM-1 cm-2 and 1.63 mA mM-1 cm-2, respectively. A limit of detection of 0.057 µM, good selectivity and stability over 35 days for H2O2 detection are also achieved. After treating the mitochondrial complex with specific inhibitors, amperometric results at the sensing platform confirmed complex I and III within mitochondria as the main electron leakage sites in the electron transfer chains. Therefore, this sensing platform provides a tool that may aid in predicting and even developing treatments for some oxidative stress diseases caused by mitochondrial abnormalities.

Research progress on the role of reactive oxygen species in the initiation, development and treatment of breast cancer

According to international cancer data, breast cancer (BC) is the leading type of cancer in women. Although significant progress has been made in treating BC, metastasis and drug resistance continue to be the primary causes of mortality for many patients. Reactive oxygen species (ROS) play a dual role in vivo: normal levels can maintain the body's normal physiological function; however, high levels of ROS below the toxicity threshold can lead to mtDNA damage, activation of proto-oncogenes, and inhibition of tumor suppressor genes, which are important causes of BC. Differences in the production and regulation of ROS in different BC subtypes have important implications for the development and treatment of BC. ROS can also serve as an important intracellular signal transduction factor by affecting the antioxidant system, activating MAPK and PI3K/AKT, and other signal pathways to regulate cell cycle and change the relationship between cells and the activity of metalloproteinases, which significantly impacts the metastasis of BC. Hypoxia in the BC microenvironment increases ROS production levels, thereby inducing the expression of hypoxia inducible factor-1α (HIF-1α) and forming "ROS- HIF-1α-ROS" cycle that exacerbates BC development. Many anti-BC therapies generate sufficient toxic ROS to promote cancer cell apoptosis, but because the basal level of ROS in BC cells exceeds that of normal cells, this leads to up-regulation of the antioxidant system, drug efflux, and apoptosis inhibition, rendering BC cells resistant to the drug. ROS crosstalks with tumor vessels and stromal cells in the microenvironment, increasing invasiveness and drug resistance in BC.

Antitumor efficacy of synthesized Ag-Au nanocomposite loaded with PEG and ascorbic acid in human lung cancer stem cells

Lung cancer is the leading cause of mortality worldwide of which non-small cell lung carcinoma constitutes majority of the cases. High mortality is attributed to early metastasis, late diagnosis, ineffective treatment and tumor relapse. Chemotherapy and radiotherapy form the mainstay of its treatment. However, their associated side effects involving kidneys, nervous system, gastrointestinal tract, and liver further adds to dismal outcome. These disadvantages of conventional treatment can be circumvented by use of engineered nanoparticles for improved effectiveness with minimal side effects. In this study we have synthesized silver gold nanocomposite (Ag-Au NC) using polyethylene glycol and l-ascorbic acid as surfactant and reducing agent respectively. Synthesized nanocomposite was characterized by ultraviolet-visible absorption, dynamic light scattering, scanning and transmission electron microscopy. Compositional analysis was carried out by energy dispersive X-ray analysis and average pore diameter was estimated using Barrett-Joyner-Halenda method. In-silico molecular docking analysis of the synthesized NC against active regions of epidermal growth factor receptor revealed good binding energy. Subsequently, we investigated the effect of NC on growth and stem cell attributes of A549 lung cancer cells. Results showed that NC was effective in inhibiting A549 cell proliferation, induced DNA damage, G2/M phase arrest and apoptosis. Further, tumor cell migration and spheroid formation were also negatively affected. NC also enhanced reactive oxygen species generation and mitochondrial depolarization. In addition, the effect of NC on putative cancer stem cells in A549 cells was evaluated. We found that Ag-Au NC at IC50 targeted CD44, CD24, CD166, CD133 and CD326 positive cancer stem cells and induced apoptosis. CD166 positive cells were relatively resistance to apoptosis. Together our results demonstrate the anticancer efficacy of Ag-Au NC mediated by a mechanism involving cell cycle arrest and mitochondrial derangement.

ERK2 Is a Promoter of Cancer Cell Growth and Migration in Colon Adenocarcinoma

ERK1/2 phosphorylation is frequently downregulated in the early phase of colon tumorigenesis with subsequent activation of ERK5. In the current work, we studied the advantages of ERK1/2 downregulation for tumor growth by dissecting the individual functions of ERK1 and ERK2. The patient sample data demonstrated decreased ERK1/2 phosphorylation in the early phase of tumorigenesis followed by increased phosphorylation in late-stage colon adenocarcinomas with intratumoral invasion or metastasis. In vitro results indicated that SOD3-mediated coordination of small GTPase RAS regulatory genes inhibited RAS-ERK1/2 signaling. In vitro and in vivo studies suggested that ERK2 has a more prominent role in chemotactic invasion, collective migration, and cell proliferation than ERK1. Of note, simultaneous ERK1 and ERK2 expression inhibited collective cell migration and proliferation but tended to promote invasion, suggesting that ERK1 controls ERK2 function. According to the present data, phosphorylated ERK1/2 at the early phase of colon adenocarcinoma limits tumor mass expansion, whereas reactivation of the kinases at the later phase of colon carcinogenesis is associated with the initiation of metastasis. Additionally, our results suggest that ERK1 is a regulatory kinase that coordinates ERK2-promoted chemotactic invasion, collective migration, and cell proliferation. Our findings indicate that ROS, especially H2O2, are associated with the regulation of ERK1/2 phosphorylation in colon cancer by either increasing or decreasing kinase activity. These data suggest that ERK2 has a growth-promoting role and ERK1 has a regulatory role in colon tumorigenesis, which could lead to new avenues in the development of cancer therapy.

Oral intake of titanium dioxide nanoparticles affect the course and prognosis of ulcerative colitis in mice: involvement of the ROS-TXNIP-NLRP3 inflammasome pathway

BACKGROUND

Titanium dioxide (TiO2), no matter in nanoscale or micron sizes, has been widely used in food industry as additives for decades. Given the potential impact of TiO2 on the gastrointestinal epithelial and parenchymal cells, including goblet cells, the public consumers may suffer the risk of diseases caused by its widespread dissemination in food products. We therefore set out to investigate the impact of TiO2 NPs on the course and prognosis of ulcerative colitis by oral gavaging TiO2 NPs at the doses levels of 0, 30, 100, and 300 mg/kg during the induction (7 days, from day 1 to day 7) and recovery (10 days, from day 8 to day 17) phases of colitis in mice.

RESULTS

The ulcerative colitis (UC) disease model was established by administrating of 2.5% dextran sulfate sodium (DSS) solution. Our results show that TiO2 NPs significantly enhanced the severity of DSS-induced colitis, decreased the body weight, increased the disease activity index (DAI) and colonic mucosa damage index (CMDI) scores, shortened the colonic length, increased the inflammatory infiltration in the colon. The most significant changes occurred in the low dose (30 mg/kg) group of TiO2 NPs exposure during the development phase of UC and the high dose (300 mg/kg) group of TiO2 NPs during UC self-healing phase. Increased reactive oxygen species (ROS) level and upregulation of anti-oxidant enzymes including total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-PX) and catalase (CAT), demonstrate that the TiO2 NP exposure has triggered oxidative stress in mice. Moreover, the upregulation of caspase-1 mRNA and increased expression of thioredoxin interacting protein (TXNIP) further demonstrate the involvement of the ROS-TXNIP-NLR family pyrin domain containing 3 (NLRP3) inflammasome pathway in aggravating the development of UC.

CONCLUSION

Oral intake of TiO2 NPs could affect the course of acute colitis in exacerbating the development of UC, prolonging the UC course and inhibiting UC recovery.

TXNIP shuttling - a key molecular link in regulating inflammation and mitochondrial dysfunction in freeze tolerant wood frogs

Amphibians such as the wood frogs,Rana sylvatica, are a primary example of a freeze-tolerant vertebrate that undergoes whole body freezing. Multiple adaptations including sequestering 65-70% of total body water as extracellular/extra organ ice and producing massive amounts of glucose as a cryoprotectant support this. Interestingly, the high glucose levels induced in response to freezing can amplify oxidative stress's effects (reactive oxygen species, ROS) and induce inflammation and mitochondrial dysfunction. Since both freezing and dehydration stress (independent of freezing) can render wood frogs hyperglycemic, this study focussed on these two stresses to elucidate the role of a scaffold protein thioredoxin interacting protein (TXNIP), which localizes in multiple compartments inside the cell under hyperglycemic conditions and mediate diverse stress responses. The results from this study suggest a stress-specific response of TXNIP in inducing the cell-damaging pathway of inflammasome activation via its cytoplasmic localization during freezing. Interestingly, mitochondrial localization of TXNIP did not leads to increase in its binding to thioredoxin 2 (TRX-2) and activating the dysfunction of this organelle by releasing a mitochondrial protein cytochrome c (Cyt c) in cytoplasm under both freezing and dehydration stresses. Post-translational modifications of TXNIP hinted on changes in the regulating proteins involved in the inflammasome and mitochondrial dysfunction pathways, whereas sequential differences (cytosine residues) of amphibian TXNIP (compared to mammalian) assessed via 3D-modeling attributed to its weak binding to TRX-2. Overall, this study summarizes differential role of proteins activated under freeze and dehydration induced hyperglycemic response in freeze tolerant wood frogs.

N-Acetyl-L-cysteine facilitates tendon repair and promotes the tenogenic differentiation of tendon stem/progenitor cells by enhancing the integrin α5/β1/PI3K/AKT signaling

BACKGROUND

Tendon injury is associated with oxidative stress, leading to reactive oxygen species (ROS) production and inflammation. N-acetyl-L-cysteine (NAC) is a potent antioxidant. However, how NAC affects the biological functions of tendon stem/progenitor cells (TSPCs) and tendon repair has not been clarified.  METHOD: The impacts of NAC on the viability, ROS production, and differentiation of TSPCs were determined with the cell counting kit-8, fluorescence staining, Western blotting, and immunofluorescence. The effect of NAC on gene transcription in TSPCs was analyzed by transcriptomes and bioinformatics and validated by Western blotting. The potential therapeutic effect of NAC on tendon repair was tested in a rat model of Achilles tendon injury.

RESULTS

Compared with the untreated control, treatment with 500 µM NAC greatly promoted the proliferation of TSPCs and significantly mitigated hydrogen peroxide-induced ROS production and cytotoxicity in vitro. NAC treatment significantly increased the relative protein expression of collagen type 1 alpha 1 (COL1A1), tenascin C (TNC), scleraxis (SCX), and tenomodulin (TNMD) in TPSCs. Bioinformatics analyses revealed that NAC modulated transcriptomes, particularly in the integrin-related phosphoinositide 3-kinase (PI3K)/AKT signaling, and Western blotting revealed that NAC enhanced integrin α5β1 expression and PI3K/AKT activation in TSPCs. Finally, NAC treatment mitigated the tendon injury, but enhanced the protein expression of SCX, TNC, TNMD, and COLIA1 in the injured tissue regions of the rats.

CONCLUSION

NAC treatment promoted the survival and differentiation of TSPCs to facilitate tendon repair after tendon injury in rats. Thus, NAC may be valuable for the treatment of tendon injury.

Protective Effects of Antioxidant Chlorophyllin in Chemically Induced Breast Cancer Model In vivo

Glutathione-related enzymes belong to the protection mechanism of the cells against harmful oxidative damage and chemicals. Glutathione S-transferase (GST) is frequently over-expressed in various cancer cells and is involved in drug resistance. Chlorophyllin is an antioxidant molecule interfering with the GST P1-1 activity. The purpose of this study is to evaluate the short- and long-term protective effects of chlorophyllin as an antioxidant molecule on DNA damage, antioxidant enzyme activities, trace elements, and minerals in chemically induced breast cancer model in vivo. In our study, N-methyl-N-nitrosourea (MNU) was used for inducing breast carcinogenesis in female Sprague-Dawley rats. A total of 36 rats were divided into groups as short term and long term. Each group was divided into four sub-groups as control group received physiological saline solution (n = 3), Chl group (n = 5) received chlorophyllin, MNU group (n = 5) was administered MNU, and Chl + MNU group (n = 5) was treated with both chlorophyllin and MNU. Results illustrated that chlorophyllin had a significant anti-genotoxic effect in the short term, and glutathione-related enzyme activities were protected by chlorophyllin treatment in MNU-induced breast cancer model. Additionally, MNU administration impaired mineral and trace element levels including Na, Mg, K, Fe, Zn, and Co in the liver, kidney, spleen, heart, and tumor tissues; however, adverse effects of MNU were recovered upon chlorophyllin treatment in the indicated tissues of the rats. In conclusion, chlorophyllin can be used as an antioxidant molecule to ameliorate adverse effects of MNU by enhancing antioxidant enzyme activities and regulating trace element and mineral balance in several organs and tumor tissue in the breast cancer model.

MNS16A VNTR polymorphism of human telomerase gene: Elucidation of a gender specific potential allele associated with type 2 diabetes in Bangladeshi population

BACKGROUND

Type 2 diabetes (T2D) is a multifactorial disorder that affects multi-organ and can alter telomerase (encoded by hTERT gene) activity and thus, may affect telomere length. The variable number of tandem repeats MNS16A in hTERT gene facilitates extension of telomeres by regulating telomerase. In the present study, genetic analysis of MNS16A tandem repeats in hTERT gene was performed with the aim of finding out any association of allelic and genotypic variations with the risk of T2D in Bangladeshi population.

METHODS

A total of unrelated 395 individuals with T2D and 247 healthy individuals were included in the study. The genotypic and allelic frequencies were determined using allele specific polymerase chain reaction. The association of allelic and genotypic frequencies with risk of T2D was analyzed using logistic regression analysis on the basis of odds ratio at 95% confidence interval. Hardy-Weinberg equilibrium (HWE) test was performed to evaluate the uniformity of the genotypic frequencies and deviation from the HWE was tested using Chi-square test.

RESULTS

Logistic regression analyses revealed significant association of short allele containing 243 bp (OR: 1.37 and p = 0.03) with T2D, when the long alleles (commonly found) were considered as reference. The heterozygous genotype 272/302 was significantly associated with the decreased risk of T2D (OR: 0.33, p = 0.001). The combined results of genotypes indicated that the MNS16A polymorphism was significantly associated with the increased risk of T2D under the dominant model (LL vs SL + SS; OR: 2.62, p < 0.0001). Interestingly, short allele 243 was associated with the risk of disease only in male population (OR: 1.62, p = 0.02). The genotype 272/302 was also found to be associated with the decreased risk of T2D when respective data for male was analyzed individually.

CONCLUSIONS

We have identified four variable number of tandem repeats with varying patterns of association with T2D in Bangladeshi population and to extend our knowledge of understanding regarding these VNTRs, further large-scale studies are warranted.

Protective Effects of a Lutein Ester Prodrug, Lutein Diglutaric Acid, against H2O2-Induced Oxidative Stress in Human Retinal Pigment Epithelial Cells

Oxidative stress-induced cell damage and death of the retinal pigmented epithelium (RPE), a polarized monolayer that maintains retinal health and homeostasis, lead to the development of age-related macular degeneration (AMD). Several studies show that the naturally occurring antioxidant Lutein (Lut) can protect RPE cells from oxidative stress. However, the poor solubility and low oral bioavailability limit the potential of Lut as a therapeutic agent. In this study, lutein diglutaric acid (Lut-DG), a prodrug of Lut, was synthesized and its ability to protect human ARPE-19 cells from oxidative stress was tested compared to Lut. Both Lut and Lut-DG significantly decreased H₂O₂-induced reactive oxygen species (ROS) production and protected RPE cells from oxidative stress-induced death. Moreover, the immunoblotting analysis indicated that both drugs exerted their protective effects by modulating phosphorylated MAPKs (p38, ERK1/2 and SAPK/JNK) and downstream molecules Bax, Bcl-2 and Cytochrome c. In addition, the enzymatic antioxidants glutathione peroxidase (GPx) and catalase (CAT) and non-enzymatic antioxidant glutathione (GSH) were enhanced in cells treated with Lut and Lut-DG. In all cases, Lut-DG was more effective than its parent drug against oxidative stress-induced damage to RPE cells. These findings highlight Lut-DG as a more potent compound than Lut with the protective effects against oxidative stress in RPE cells through the modulation of key MAPKs, apoptotic and antioxidant molecular pathways.

Possible Beneficial Effects of N-Acetylcysteine for Treatment of Triple-Negative Breast Cancer

N-acetylcysteine (NAC) is a widely used antioxidant with therapeutic potential. However, the cancer-promoting effect of NAC observed in some preclinical studies has raised concerns regarding its clinical use. Reactive oxygen species (ROS) can mediate signaling that results in both cancer-promoting and cancer-suppressing effects. The beneficial effect of NAC may depend on whether the type of cancer relies on ROS signaling for its survival and metastasis. Triple-negative breast cancer (TNBC) has aggressive phenotypes and is currently treated with standard chemotherapy as the main systemic treatment option. Particularly, basal-like TNBC cells characterized by inactivated BRCA1 and mutated TP53 produce high ROS levels and rely on ROS signaling for their survival and malignant progression. In addition, the high ROS levels in TNBC cells can mediate the interplay between cancer cells and the tissue microenvironment (TME) to trigger the recruitment and conversion of stromal cells and induce hypoxic responses, thus leading to the creation of cancer-supportive TMEs and increased cancer aggressiveness. However, NAC treatment effectively reduces the ROS production and ROS-mediated signaling that contribute to cell survival, metastasis, and drug resistance in TNBC cells. Therefore, the inclusion of NAC in standard chemotherapy could probably provide additional benefits for TNBC patients.

NRF2 level is negatively correlated with TGF-β1-induced lung cancer motility and migration via NOX4-ROS signaling

Transforming growth factor-β1 (TGF-β1) is a multifaceted factor in cancer biology that regulates cell proliferation and migration. Overactivation of nuclear factor erythroid 2-like 2 (NFE2L2; NRF2) in cancers has been associated with facilitated tumor growth and therapy resistance; however, role in cancer migration has not been clearly explained yet. In this study, we investigated the role of NRF2 on TGF-β1-induced cell motility/migration. In NRF2-silenced lung cancer A549 cells, both basal and TGF-β1-inducible cell motility/migration increased compared to those in A549. SMAD transcription activity and phosphorylated SMAD2/3 levels were higher in TGF-β1-treated NRF2-low A549 cells than those in A549. Notably, the levels of reactive oxygen species (ROS) that were elevated by TGF-β1 treatment were higher in the NRF2-low A549 than those in control cells, and treatment with ROS scavenger blocked TGF-β1-induced cell motility. As an underlying molecular link, NADPH oxidase 4 (NOX4) was associated with higher ROS elevation and cell motility of NRF2-low A549. NOX4 and TGF-β1-inducible NOX4 levels were higher in NRF2-low A549 cells than those in A549. Moreover, the pharmacological inhibition of NOX4 blocked the TGF-β1-induced motility of NRF2-low A549 cells. Collectively, these results indicate that TGF-β1-induced cell motility/migration is facilitated in NRF2-inhibited lung cancer cells and that high levels of NOX4/ROS are associated with enhanced motility/migration.

Stressing the (Epi)Genome: Dealing with Reactive Oxygen Species in Cancer

SIGNIFICANCE

Growing evidence indicates cross-talk between reactive oxygen species (ROS) and several key epigenetic processes such as DNA methylation, histone modifications, and miRNAs in normal physiology and human pathologies including cancer. This review focuses on how ROS-induced oxidative stress, metabolic intermediates, and epigenetic processes influence each other in various cancers. Recent Advances: ROS alter chromatin structure and metabolism that impact the epigenetic landscape in cancer cells. Several site-specific DNA methylation changes have been identified in different cancers and are discussed in the review. We also discuss the interplay of epigenetic enzymes and miRNAs in influencing malignant transformation in an ROS-dependent manner.

CRITICAL ISSUES

Loss of ROS-mediated signaling mostly by epigenetic regulation may promote tumorigenesis. In contrast, augmented oxidative stress because of high ROS levels may precipitate epigenetic alterations to effect various phases of carcinogenesis. We address both aspects in the review.

FUTURE DIRECTIONS

Several drugs targeting ROS are under various stages of clinical development. Recent analysis of human cancers has revealed pervasive deregulation of the epigenetic machinery. Thus, a better understanding of the cross-talk between ROS and epigenetic alterations in cancer could lead to the identification of new drug targets and more effective treatment modalities.

Pulse frequency dependency of photobiomodulation on the bioenergetic functions of human dental pulp stem cells

Photobiomodulation (PBM) therapy contributes to pain relief, wound healing, and tissue regeneration. The pulsed wave (PW) mode has been reported to be more effective than the continuous wave (CW) mode when applying PBM to many biological systems. However, the reason for the higher effectiveness of PW-PBM is poorly understood. Herein, we suggest using delayed luminescence (DL) as a reporter of mitochondrial activity after PBM treatment. DL originates mainly from mitochondrial electron transport chain systems, which produce reactive oxygen species (ROS) and adenosine triphosphate (ATP). The decay time of DL depends on the pulse frequencies of applied light, which correlate with the biological responses of human dental pulp stem cells (hDPSCs). Using a low-power light whose wavelength is 810 nm and energy density is 38 mJ/cm², we find that a 300-Hz pulse frequency prolonged the DL pattern and enhanced alkaline phosphatase activity. In addition, we analyze mitochondrial morphological changes and their volume density and find evidence supporting mitochondrial physiological changes from PBM treatment. Our data suggest a new methodology for determining the effectiveness of PBM and the specific pulse frequency dependency of PBM in the differentiation of hDPSCs.