Intracellular GSH levels rather than ROS levels are tightly related to AMA-induced HeLa cell death

Precisely Inhibiting Excessive Intestinal Epithelial Cell Apoptosis to Efficiently Treat Inflammatory Bowel Disease with Oral Pifithrin-α Embedded Nanomedicine (OPEN)

The increased incidence of inflammatory bowel disease (IBD) has seriously affected the life quality of patients. IBD develops due to excessive intestinal epithelial cell (IEC) apoptosis, disrupting the gut barrier, colonizing harmful bacteria, and initiating persistent inflammation. The current therapeutic approaches that reduce inflammation are limited. Although IBD can be treated significantly by directly preventing IEC apoptosis, achieving this therapeutic approach remains challenging. Accordingly, the authors are the first to develop an oral pifithrin-α (PFTα, a highly specific p53 inhibitor) embedded nanomedicine (OPEN) to effectively treat IBD by inhibiting excessive IEC apoptosis. As a major hub for various stressors, p53 is a central determinant of cell fate, and its inhibition can effectively reduce excessive IEC apoptosis. The tailored OPEN can precisely inhibit the off-target and inactivation resulting from PFTα entry into the bloodstream. Subsequently, it persistently targets IBD lesions with high specificity to inhibit the pathological events caused by excessive IEC apoptosis. Eventually, OPEN exerts a significant curative effect compared with the clinical first-line drugs 5-aminosalicylic acid (5-ASA) and dexamethasone (DEX). Consequently, the OPEN therapeutic strategy provides new insights into comprehensive IBD therapy.

Effects of tumor necrosis factor-α-induced exosomes on the endothelial cellular behavior, metabolism and bioenergetics

OBJECTIVE

To investigate the effects of TNF-α-induced exosomes release on the biological behavior, metabolism, and bioenergetics of HUVECs.

METHODS

Exosomes were isolated from conditioned media of HUVECs by ultracentrifugation after treatment with or without TNF-α. HUVECs were treated with or without TNF-α, or different concentrations of exosomes isolated from conditioned media with or without TNF-α induction (T_Exo and C_Exo , respectively).

RESULTS

The results showed that TNF-α significantly inhibited migration, tube formation, and increased apoptosis rate of HUVECs compared with controls. Furthermore, TNF-α-induced exosomes (T_Exo ) rather than C_Exo , indicated similar effects to inhibit migration, tube formation and promote endothelial apoptosis. Although TNF-α treatment did not show a statistical difference, T_Exo significantly inhibited extracellular OCR compared with controls. T_Exo could significantly inhibited intracellular OCR in a hypoxia condition. TNF-α significantly increased L-ECA compared with control cells, and T_Exo showed similar stimulative effect on L-ECA.

CONCLUSIONS

TNF-α-induced exosomes could significantly (a) change migration, tube formation, and apoptosis; (b) inhibit endothelial extracellular OCR and intracellular OCR (hypoxia); (c) increase glycolysis rate of the endothelial cells. These data provide new evidence for exploring endothelial behavior regulation using exosomes and their effects on endothelial metabolism and bioenergetics.

Mechanisms underlying effect of the mycotoxin cytochalasin B on induction of cytotoxicity, modulation of cell cycle, Ca2+ homeostasis and ROS production in human breast cells

Cytochalasin B, a cell-permeable mycotoxin isolated from the fungus Phoma spp., shows a wide range of biological effects, among which its potent antitumor activity has raised great interests in different models. However, the cytotoxic activity of cytochalasin B and its underlying mechanisms have not been elucidated in breast cells. This study examined the effect of cytochalasin B on MCF 10A human breast epithelial cells and ZR-75-1 human breast cancer cells. Cytochalasin B (10-20μM) concentration-dependently induced cytotoxicity, cell cycle arrest, and [Ca²⁺]_i rises in ZR-75-1 cells but not in MCF 10A cells. In ZR-75-1 cells, cytochalasin B triggered G2/M phase arrest through the modulation of CDK1, cyclin B1, p53, p27 and p21 expressions. The Ca²⁺ signal response induced by cytochalasin B was reduced by removing extracellular Ca²⁺ and was inhibited by the store-operated Ca²⁺ channel blocker 2-APB and SKF96365. In Ca²⁺-free medium, cytochalasin B induced Ca²⁺ release through thapsigargin-sensitive endoplasmic reticulum stores. Moreover, cytochalasin B increased H₂O₂ levels but reduced GSH levels. The apoptotic effects evoked by cytochalasin B were partially inhibited by prechelating cytosolic Ca²⁺ with BAPTA-AM and the antioxidant NAC. Together, in ZR-75-1 cells but not in MCF 10A cells, cytochalasin B activated Ca²⁺-associated mitochondrial apoptotic pathways that involved G2/M phase arrest and ROS signaling. Furthermore, cytochalasin B induced [Ca²⁺]_i rises by releasing Ca²⁺ from the endoplasmic reticulum and causing Ca²⁺ influx through 2-APB or SKF96365-sensitive store-operated Ca²⁺ entry. Our findings provide new insights into the possible application of cytochalasin B in human breast cancer therapy.

The effect of oleuropein from olive leaf (Olea europaea) extract on Ca²⁺ homeostasis, cytotoxicity, cell cycle distribution and ROS signaling in HepG2 human hepatoma cells

Oleuropein, a phenolic compound found in the olive leaf (Olea europaea), has been shown to have biological activities in different models. However, the effects of oleuropein on Ca(2+) homeostasis, cytotoxicity, cell cycle distribution and ROS signaling in liver cells have not been analyzed. Oleuropein induced [Ca(2+)]i rises only in HepG2 cells but not in AML12, HA22T or HA59T cells due to the different status of 3-hydroxy-3-methylglutaryl-CoA reductase expression. In HepG2 cells, this Ca(2+) signaling response was reduced by removing extracellular Ca(2+), and was inhibited by the store-operated Ca(2+) channel blockers 2-APB and SKF96365. In Ca(2+)-free medium, pretreatment with the ER Ca(2+) pump inhibitor thapsigargin abolished oleuropein-induced [Ca(2+)]i rises. Oleuropein induced cell cycle arrest which was associated with the regulation of p53, p21, CDK1 and cyclin B1 levels. Furthermore, oleuropein elevated intracellular ROS levels but reduced GSH levels. Treatment with the intracellular Ca(2+) chelator BAPTA-AM or the antioxidant NAC partially reversed oleuropein-induced cytotoxicity. Together, in HepG2 cells, oleuropein induced [Ca(2+)]i rises by releasing Ca(2+) from the ER and causing Ca(2+) influx through store-operated Ca(2+) channels. Moreover, oleuropein induced Ca(2+)-associated cytotoxicity that involved ROS signaling and cell cycle arrest. This compound may offer a potential therapy for treatment of human hepatoma.

Value of phagocyte function screening for immunotoxicity of nanoparticles in vivo

Nanoparticles (NPs) present in the environment and in consumer products can cause immunotoxic effects. The immune system is very complex, and in vivo studies are the gold standard for evaluation. Due to the increased amount of NPs that are being developed, cellular screening assays to decrease the amount of NPs that have to be tested in vivo are highly needed. Effects on the unspecific immune system, such as effects on phagocytes, might be suitable for screening for immunotoxicity because these cells mediate unspecific and specific immune responses. They are present at epithelial barriers, in the blood, and in almost all organs. This review summarizes the effects of carbon, metal, and metal oxide NPs used in consumer and medical applications (gold, silver, titanium dioxide, silica dioxide, zinc oxide, and carbon nanotubes) and polystyrene NPs on the immune system. Effects in animal exposures through different routes are compared to the effects on isolated phagocytes. In addition, general problems in the testing of NPs, such as unknown exposure doses, as well as interference with assays are mentioned. NPs appear to induce a specific immunotoxic pattern consisting of the induction of inflammation in normal animals and aggravation of pathologies in disease models. The evaluation of particle action on several phagocyte functions in vitro may provide an indication on the potency of the particles to induce immunotoxicity in vivo. In combination with information on realistic exposure levels, in vitro studies on phagocytes may provide useful information on the health risks of NPs.

Dioscin, a natural steroid saponin, induces apoptosis and DNA damage through reactive oxygen species: a potential new drug for treatment of glioblastoma multiforme

Dioscin, a natural product obtained from medicinal plants shows lipid-lowering, anti-cancer and hepatoprotective effects. However, the effect of it on glioblastoma is unclear. In this study, dioscin significantly inhibited proliferation of C6 glioma cells and caused reactive oxygen species (ROS) generation and Ca²⁺ release. ROS accumulation affected levels of malondialdehyde, nitric oxide, glutathione disulfide and glutathione, and caused cell apoptosis. In addition, ROS generation caused mitochondrial damage including structural changes, increased mitochondrial permeability transition and decreased mitochondria membrane potential, which led to the release of cytochrome C, nuclear translation of programmed cell death-5 and increased activities of caspase-3,9. Simultaneously, dioscin down-regulated protein expression of Bcl-2, Bcl-xl, up-regulated expression of Bak, Bax, Bid and cleaved poly (ADP-ribose) polymerase. Also, oxygen stress induced S-phase arrest of cancer cells by way of regulating expression of DNA Topo I, p53, CDK2 and Cyclin A and caused DNA damage. In a rat allograft model, dioscin significantly inhibited tumor size and extended the life cycle of the rats. In conclusion, dioscin shows noteworthy anti-cancer activity on glioblastoma cells by promoting ROS accumulation, inducing DNA damage and activating mitochondrial signal pathways. Ultimately, we believe dioscin has promise as a new therapy for the treatment of glioblastoma.

Magnolol protects osteoblastic MC3T3-E1 cells against antimycin A-induced cytotoxicity through activation of mitochondrial function

Antimycin A treatment of cells blocks the mitochondrial electron transport chain and leads to elevated ROS generation. In the present study, we investigated the protective effects of magnolol, a hydroxylated biphenyl compound isolated from Magnolia officinalis, on antimycin A-induced toxicity in osteoblastic MC3T3-E1 cells. Osteoblastic MC3T3-E1 cells were pre-incubated with magnolol before treatment with antimycin A. Cell viability and mineralization of osteoblasts were assessed by MTT assay and Alizarin Red staining, respectively. Mitochondrial dysfunction in cells was measured by mitochondrial membrane potential (MMP), complex IV activity, and ATP level. The cellular antioxidant effect of magnolol in osteoblastic MC3T3-E1 cells was assessed by measuring cardiolipin oxidation, mitochondrial superoxide levels, and nitrotyrosine content. Phosphorylated cAMP-response element-binding protein (CREB ) was evaluated using ELISA assay. Pretreatment with magnolol prior to antimycin A exposure significantly reduced antimycin A-induced osteoblast dysfunction by preventing MMP dissipation, ATP loss, and CREB inactivation. Magnolol also reduced cardiolipin peroxidation, mitochondrial superoxide, and nitrotyrosine production induced by antimycin A. These results suggest that magnolol has a protective effect against antimycin A-induced cell damage by its antioxidant effects and the attenuation of mitochondrial dysfunction. All these data indicate that magnolol may reduce or prevent osteoblast degeneration in osteoporosis or other degenerative disorders.

Abrogation of nimesulide induced oxidative stress and mitochondria mediated apoptosis by Fumaria parviflora Lam. extract

ETHNOPHARMACOLOGICAL RELEVANCE

[corrected] Fumaria parviflora Lam. is used for treating aches and pains, diarrhea, fever, influenza and other complications. The herb mixed with honey is taken to prevent vomiting as per Ayurvedic text.

AIM OF THE STUDY

In vivo studies were conducted to explore the hepatoprotective potential of Fumaria parviflora Lam. Fp extract against nimesulide induced oxidative stress and regulation of critical events in mitochondria mediated apoptosis.

MATERIALS AND METHODS

Group of Wistar rats were fed with nimesulide for 5 days (80 mg/kg/day, po), another group was pre-treated with Fp extract/silymarin (200mg/kg/day, po) for 5 days followed by nimesulide exposure. Liver serum biomarkers and histopathology were done to assess hepatotoxicity caused by nimesulide. Antioxidant enzymes (SOD, LPO, GPx, GR) were assessed using biochemical assays as well as gene expression by RT-PCR. GSH content and ROS generation was also evaluated using flow cytometry. Key apoptotic markers like phosphatidyl serine externalization, Bax, Bcl-2 translocation, mitochondrial membrane potential, cytochrome c release, caspases (9/3) activation and DNA damage were also observed in all the groups to confirm involvement of mitochondrial pathway.

RESULTS

Pre-treatment with Fp extract for 5 days significantly reduced the impact of nimesulide induced toxicity as evident from the serum biomarkers of liver damage and histopathology. It also modulated antioxidant enzymes mRNA expression as well as activity (SOD, glutathione peroxidase, glutathione reductase) and reduced lipid peroxidation during nimesulide toxicity. Nimesulide exposure decreased GSH content (92.9%) and increased reactive oxygen species (9.29 fold) which was attenuated in Fp treated rats. Fp pre-treatment significantly altered key apoptotic events like Bcl2 and Bax translocation, inhibited mitochondrial depolarization, prevented cytochrome c release, caspase-9/caspase-3 activation and DNA damage.

CONCLUSION

Our in vivo findings regarding protection accorded by Fp extract against nimesulide toxicity suggest that Fp not only reduced hepatotoxicity but attenuated critical control points of apoptotic cell death.

Effect of gold nanoparticles on glutathione depletion-induced hydrogen peroxide generation and apoptosis in HL7702 cells

Gold nanoparticles (AuNPs) have shown promising biological and military applications due to their unique electronic and optical properties. However, little is known about their cytotoxicity when they come into contact with a biological system. The primary objective of this study is to determine the sequence of apoptotic signaling events that occur after modulation of the cellular redox state in HL7702 cells (human liver cell line), with emphasis on the role of the interaction of AuNPs with glutathione (GSH). After incubation with 8nm AuNPs at 50nM, there was an early decline in cytosolic GSH, which initiated mitochondrial transmembrane potential (ΔΨm) depolarization and apoptosis. Mitochondrial GSH depletion was observed at approximately 48h, after which mitochondrial hydrogen peroxide (H(2)O(2)) production increased significantly and apoptosis was further exacerbated. Bax translocation, cytochrome c release and downstream caspase 3 were first detected at 24h, notably after 48h, corresponding with increasing H(2)O(2) level. These data suggest that HL7702 cells are depleted of intracellular GSH as a result that 8nm AuNPs possess strong Au-S bonding interactions with GSH. A decrease in GSH alone can act as a potent early activator of apoptotic signaling. Increased H(2)O(2) production following mitochondrial GSH depletion represents a crucial event, which commits HL7702 cells to apoptosis through mitochondrial pathway.

Firefly luciferase and RLuc8 exhibit differential sensitivity to oxidative stress in apoptotic cells

Over the past decade, firefly Luciferase (fLuc) has been used in a wide range of biological assays, providing insight into gene regulation, protein-protein interactions, cell proliferation, and cell migration. However, it has also been well established that fLuc activity can be highly sensitive to its surrounding environment. In this study, we found that when various cancer cell lines (HeLa, MCF-7, and 293T) stably expressing fLuc were treated with staurosporine (STS), there was a rapid loss in bioluminescence. In contrast, a stable variant of Renilla luciferase (RLuc), RLuc8, exhibited significantly prolonged functionality under the same conditions. To identify the specific underlying mechanism(s) responsible for the disparate sensitivity of RLuc8 and fLuc to cellular stress, we conducted a series of inhibition studies that targeted known intracellular protein degradation/modification pathways associated with cell death. Interestingly, these studies suggested that reactive oxygen species, particularly hydrogen peroxide (H(2)O(2)), was responsible for the diminution of fLuc activity. Consistent with these findings, the direct application of H(2)O(2) to HeLa cells also led to a reduction in fLuc bioluminescence, while H(2)O(2) scavengers stabilized fLuc activity. Comparatively, RLuc8 was far less sensitive to ROS. These observations suggest that fLuc activity can be substantially altered in studies where ROS levels become elevated and can potentially lead to ambiguous or misleading findings.

3-Bromopyruvate induces necrotic cell death in sensitive melanoma cell lines

Clinicians successfully utilize high uptake of radiolabeled glucose via PET scanning to localize metastases in melanoma patients. To take advantage of this altered metabolome, 3-bromopyruvate (BrPA) was used to overcome the notorious resistance of melanoma to cell death. Using four melanoma cell lines, BrPA triggered caspase independent necrosis in two lines, whilst the other two lines were resistant to killing. Mechanistically, sensitive cells differed from resistant cells by; constitutively lower levels of glutathione, reduction of glutathione by BrPA only in sensitive cells; increased superoxide anion reactive oxygen species, loss of outer mitochondrial membrane permeability, and rapid ATP depletion. Sensitive cell killing was blocked by N-acetylcysteine or glutathione. When glutathione levels were reduced in resistant cell lines, they became sensitive to killing by BrPA. Taken together, these results identify a metabolic-based Achilles' heel in melanoma cells to be exploited by use of BrPA. Future pre-clinical and clinical trials are warranted to translate these results into improved patient care for individuals suffering from metastatic melanoma.

Proliferative and anti-proliferative effects of thymosin alpha1 on cells are associated with manipulation of cellular ROS levels

Reactive oxygen species (ROS) are constantly generated and eliminated in the biological system and play important roles in a variety of physiological and pathological processes. Previous studies indicate that modulation of cellular ROS affects cell proliferation. Thymosin alpha 1 (Talpha1) is a naturally occurring thymic peptide and has previously been shown to be a potential therapy for some immunodeficiencies, malignancies, and infections. However, few reports have focused on manipulation of cellular ROS level effects of Talpha1. In this study, the Talpha1-treated leukomonocytes, which were isolated from mice spleens, exhibited a higher ROS level and a lower reduced glutathione (GSH) level; however, HepG2 cells treated with Talpha1 exhibited lower ROS level and higher GSH level. In addition, after treatment with Talpha1, the population of leukomonocytes in the G(2) phase increased, resulting in a slight increase in viability. However, in Talpha1-treated HepG2 cells, the cell cycle was delayed in the G(1) phase, thereby inhibiting tumor cell proliferation; in addition, dephosphorylation of the serine/threonine kinase Akt was detected. In conclusion, we show that Talpha1 has potent anti-proliferative activity against malignant human hepatoma cells and proliferative activity against leukomonocytes associated with manipulation of oxidative stress levels which indicates the potential of Talpha1 as an antitumor drug.

Glutathione and apoptosis

Apoptosis or programmed cell death represents a physiologically conserved mechanism of cell death that is pivotal in normal development and tissue homeostasis in all organisms. As a key modulator of cell functions, the most abundant non-protein thiol, glutathione (GSH), has important roles in cellular defense against oxidant aggression, redox regulation of proteins thiols and maintaining redox homeostasis that is critical for proper function of cellular processes, including apoptosis. Thus, a shift in the cellular GSH-to-GSSG redox balance in favour of the oxidized species, GSSG, constitutes an important signal that could decide the fate of a cell. The current review will focus on three main areas: (1) general description of cellular apoptotic pathways, (2) cellular compartmentation of GSH and the contribution of mitochondrial GSH and redox proteins to apoptotic signalling and (3) role of redox mechanisms in the initiation and execution phases of apoptosis.