Serum deprivation-induced HepG2 cell death is potentiated by CYP2E1

Exploring the therapeutic potential: Apelin-13's neuroprotective effects foster sustained functional motor recovery in a rat model of Huntington's disease

Huntington's disease (HD) is a hereditary condition considered by the progressive degeneration of nerve cells in the brain, resultant in motor dysfunction and cognitive impairment. Despite current treatment modalities including pharmaceuticals and various therapies, a definitive cure remains elusive. Therefore, this study investigates the therapeutic potential effect of Apelin-13 in HD management. Thirty male Wistar rats were allocated into three groups: a control group, a group with HD, and a group with both HD and administered Apelin-13. Apelin-13 was administered continuously over a 28-day period at a dosage of around 30 mg/kg to mitigate inflammation in rats subjected to 3-NP injection within an experimental HD model. Behavioral tests, such as rotarod, electromyography (EMG), elevated plus maze, and open field assessments, demonstrated that Apelin-13 improved motor function and coordination in rats injected with 3-NP. Apelin-13 treatment significantly increased neuronal density and decreased glial cell counts compared to the control group. Immunohistochemistry analysis revealed reduced gliosis and expression of inflammatory factors in the treatment group. Moreover, Apelin-13 administration led to elevated levels of glutathione and reduced reactive oxygen species (ROS) level in the treated group. Apelin-13 demonstrates neuroprotective effects, leading to improved movement and reduced inflammatory and fibrotic factors in the HD model.

Anticancer effect of umbelliferone on MKN-45 and MIA PaCa-2 cell lines

In this study, the anticancer activity of umbelliferone (7-hydroxycoumarin-UMB) was investigated in MKN-45 human gastric cancer and MIA PaCa-2 human pancreatic cancer cells. The cytotoxic effect of UMB on MKN-45 and MIA PaCa-2 cells was determined by WST-8 cell viability assay; the effect on colony formation and migration potential by colony forming assay and wound healing/cell migration assay. Apoptotic effect of UMB was determined by measuring the change in mitochondrial membrane potentials, reactive oxygen species levels, and Caspase-3 activities in cells. Anticancer drugs cisplatin and gemcitabine were used as positive controls in experiments, and NIH/Swiss 3 T3 mouse embryonic fibroblast cells were used as a healthy cell group. The results of this study showed that umbelliferone had a significant cytotoxic effect in MKN-45 and MIA PaCa-2 cells, especially after 72 h treatment, while its cytotoxic effect in NIH/3 T3 cells was low. Furthermore, UMB reduces significantly the potential of cells to colonize and migrate; it has been determined that it causes apoptosis by decreasing the mitochondrial membrane potential, increasing intracellular ROS levels and Caspase-3 activity. UMB was found to have more anticancer effect on MIA PaCa-2 cells compared to MKN-45 cells. This showed that UMB has a cell-selective effect.

Differential Expression of ADP/ATP Carriers as a Biomarker of Metabolic Remodeling and Survival in Kidney Cancers

ADP/ATP carriers (AACs) are mitochondrial transport proteins playing a strategic role in maintaining the respiratory chain activity, fueling the cell with ATP, and also regulating mitochondrial apoptosis. To understand if AACs might represent a new molecular target for cancer treatment, we evaluated AAC expression levels in cancer/normal tissue pairs available on the Tissue Cancer Genome Atlas database (TCGA), observing that AACs are dysregulated in most of the available samples. It was observed that at least two AACs showed a significant differential expression in all the available kidney cancer/normal tissue pairs. Thus, we investigated AAC expression in the corresponding kidney non-cancer (HK2)/cancer (RCC-Shaw and CaKi-1) cell lines, grown in complete medium or serum starvation, for investigating how metabolic alteration induced by different growth conditions might influence AAC expression and resistance to mitochondrial apoptosis initiators, such as "staurosporine" or the AAC highly selective inhibitor "carboxyatractyloside". Our analyses showed that AAC2 and AAC3 transcripts are more expressed than AAC1 in all the investigated kidney cell lines grown in complete medium, whereas serum starvation causes an increase of at least two AAC transcripts in kidney cancer cell lines compared to non-cancer cells. However, the total AAC protein content is decreased in the investigated cancer cell lines, above all in the serum-free medium. The observed decrease in AAC protein content might be responsible for the decrease of OXPHOS activity and for the observed lowered sensitivity to mitochondrial apoptosis induced by staurosporine or carboxyatractyloside. Notably, the cumulative probability of the survival of kidney cancer patients seriously decreases with the decrease of AAC1 expression in KIRC and KIRP tissues making AAC1 a possible new biomarker of metabolic remodeling and survival in kidney cancers.

Mitochondrial connection to ginsenosides

Mitochondria play an essential role in energy synthesis and supply, thereby maintaining cellular function, survival, and energy homeostasis via mitochondria-mediated pathways, including apoptosis and mitophagy. Ginsenosides are responsible for most immunological and pharmacological activities of ginseng, a highly beneficial herb with antioxidant, anti-inflammatory, anti-apoptotic, and neuroprotective properties. Studies have shown that ginsenosides assist in regulating mitochondrial energy metabolism, oxidative stress, biosynthesis, apoptosis, mitophagy, and the status of membrane channels, establishing mitochondria as one of their most important targets. This article reviews the regulatory effects of ginsenosides on the mitochondria and highlights their beneficial role in treating mitochondrial diseases.

Flavokawain B and Doxorubicin Work Synergistically to Impede the Propagation of Gastric Cancer Cells via ROS-Mediated Apoptosis and Autophagy Pathways

Simple Summary

Among various kinds of treatment strategies for cancers, combination therapy has attracted significant attention due to its beneficial effects than the individual effects of the same compounds. Based on this idea, this study has investigated the synergistic effects of combination treatment of a natural anti-cancer agent flavokawain B (FKB) and a chemotherapeutic agent Doxorubicin on human gastric cancer cells and the underlying molecular mechanisms were deciphered through in vitro and in vivo approaches. Experimental data obtained in this study provided promising application prospects of FKB + Doxrubicin combination treatment in human gastric cancer cells.

Abstract

Chalcone flavokawain B (FKB) possesses a chemopreventive and anti-cancer activity. Doxorubicin is a chemotherapeutic DNA intercalating agent widely used in malignancy treatment. The present study investigated whether synergistic effects exist between the combination of FKB (1.25–5 µg/mL) and doxorubicin (0.5 µg/mL) on the apoptosis and autophagy in human gastric cancer (AGS) cells, and the possible in vitro and in vivo mechanisms. The MTT assay measured cell viability. Various apoptotic-, autophagy-associated protein expression was determined by the Western blot technique. FKB+doxorubicin synergy was estimated by the Chou-Talalay combination index (CI) method. In vivo studies were performed on BALB/c mice. Results showed that compared to FKB/doxorubicin treatments, low doses of FKB+doxorubicin suppressed AGS cell growth. FKB potentiated doxorubicin-induced DNA fragmentation, apoptotic cell death, and enhanced doxorubicin-mediated mitochondrial, death receptor pathways. FKB+doxorubicin activated increased LC3-II accumulation, p62/SQSTM1 expression, and AVO formation as compared to the FKB/doxorubicin alone treatments indicating autophagy in these cells. The death mechanism in FKB+doxorubicin-treated AGS cells is due to the activation of autophagy. FKB+doxorubicin-mediated dysregulated Bax/Bcl-2, Beclin-1/Bcl-2 ratios suggested apoptosis, autophagy induction in AGS cells. FKB+doxorubicin-induced LC3-II/AVOs downregulation was suppressed due to an apoptotic inhibitor Z-VAD-FMK. Whereas, 3-methyladenine/chloroquine weakened FKB+doxorubicin-induced apoptosis (decreased DNA fragmentation/caspase-3). Activation of ERK/JNK may be involved in FKB+doxorubicin-induced apoptosis and autophagy. FKB+doxorubicin-triggered ROS generation, but NAC attenuated FKB+doxorubicin-induced autophagic (LC3 accumulation) and apoptotic (caspase-3 activation and PARP cleavage) cell death. FKB+doxorubicin blocked gastric cancer cell xenografts in nude mice in vivo as compared to FKB/doxorubicin alone treatments. FKB and doxorubicin wielded synergistic anti-tumor effects in gastric cancer cells and is a promising therapeutic approach.

In vitro and in vivo studies of cancer cell behavior under nutrient deprivation

Cancer cells are confronted with nutrient deprivation because of high proliferation rate, especially at the early stage of their development. There is a frequent assumption that nutrient deprivation decreases the basal activity of cancer cells. Contrarily, there are recent evidence suggesting that cancer cells are able to modulate signaling pathways to adapt with new condition and continue their survival. This property of cancer cells is believed to be one of the prerequisites for cancer progression and chemoresistance. Moreover, recent experiments show that serum starvation in vitro as a mimic situation of nutrient deprivation in vivo triggers different signaling pathways leading to changes in cancer cell behavior, which may interfere with experimental results. Considering these facts, a better understanding of the effect of nutrient deprivation on cancer cell behavior will help us to give more accurate conclusions regarding results of in vitro studies and also to develop new strategies to treat different cancers in vivo.

Albumin promotes proliferation of G1 arrested serum starved hepatocellular carcinoma cells

Albumin is the most abundant plasma protein and functions as a transport molecule that continuously interacts with various cell types. Because of these properties, albumin has been exploited by the pharmaceutical industry to improve drug delivery into target cells. The immediate effects of albumin on cells, however, require further understanding. The cell interacting properties and pharmaceutical applications of albumin incentivises continual research into the immediate effects of albumin on cells. The HepG2/C3A hepatocellular carcinoma cell line is used as a model for studying cancer pathology as well as liver biosynthesis and cellular responses to drugs. Here we investigated the direct effect of purified albumin on HepG2/C3A cell proliferation in the absence of serum, growth factors and other serum originating albumin bound molecules. We observed that the reduced cell counts in serum starved HepG2/C3A cultures were increased by the inclusion of albumin. Cell cycle analysis demonstrated that the percentage of cells in G1 phase during serum starvation was reduced from 86.4 ± 2.3% to 78.3 ± 3.2% by the inclusion of albumin whereas the percentage of cells in S phase was increased from 6.5 ± 1.5% to 14.3 ± 3.6%. A significant reduction in the cell cycle inhibitor protein, P21, accompanied the changes in the proportions of cell cycle phases upon treatment with albumin. We have also observed that the levels of dead cells determined by DNA fragmentation and membrane permeabilization caused by serum starvation (TUNEL: 16.6 ± 7.2%, ethidium bromide: 13.8 ± 4.8%) were not significantly altered by the inclusion of albumin (11.6 ± 10.2%, ethidium bromide: 16.9 ± 8.9%). Therefore, the increase in cell number was mainly caused by albumin promoting proliferation rather than protection against cell death. These primary findings demonstrate that albumin has immediate effects on HepG2/C3A hepatocellular carcinoma cells. These effects should be taken into consideration when studying the effects of albumin bound drugs or pathological ligands bound to albumin on HepG2/C3A cells.

SS31 attenuates oxidative stress and neuronal apoptosis in early brain injury following subarachnoid hemorrhage possibly by the mitochondrial pathway

BACKGROUND

SS31 has been shown to have neuroprotective effects in a number of neurological degenerative diseases. However, the mechanisms and its role of neuroprotection after subarachnoid hemorrhage (SAH) remain unexplored. The aim of the present study is to evaluate the neuroprotective effects of SS31 on early brain injury (EBI) induced by SAH in rats and the potential mechanisms of the protective effects of SS31.

METHODS

Sprague-Dawley rats were randomly divided into four groups: Sham, SAH, SAH + vehicle, and SAH + SS31 groups. The SAH-induced prechiasmatic cistern rat model was established in this study. Neurological scores were evaluated at 24 h and 72 h after SAH. The brain edema, blood-brain barrier (BBB) permeability, neuronal apoptosis, malondialdehyde (MDA), glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities, as well as the expression of mitochondrial and cytosolic cytochrome C (Cyt C), and Bax were analyzed at 24 h after SAH.

RESULTS

When compared with the vehicle-treated group, treatment with SS31 significantly reduced MDA levels and restored the activities of GPx and SOD in the temporal cortex following SAH when compared with the vehicle-treated group. In addition, the levels of mitochondrial Cyt C and Bax respectively increased and decreased by SS31 treatment. Moreover, SS31 treatment ameliorated brain edema and Evans blue dye extravasation, improved neurological deficits, and decreased neuronal apoptosis at 24 h after SAH.

CONCLUSION

Our data provides initial evidence that SS31 could alleviate EBI after SAH through its antioxidant property and ability in inhibiting neuronal apoptosis, likely by modulating the mitochondrial apoptotic pathway.

Anticancer activities of chalcone flavokawain B from Alpinia pricei Hayata in human lung adenocarcinoma (A549) cells via induction of reactive oxygen species-mediated apoptotic and autophagic cell death

Chalcones found in fruits and vegetables have promising cancer chemopreventive properties. This study attempts to identify the anticancer efficacies of chalcone flavokawain B (FKB) in the rhizomes of Alpinia pricei Hayata by examining key molecular events in non-small-cell lung cancer (A549) cells. Our results indicated that in human A549 cells, FKB (0-15 μg/ml) decreases cell viability and colony formation, dysregulates the Bax:B-cell lymphoma 2 ratio and increases apoptotic DNA fragmentation. Mitochondrial (caspase-9/-3 and poly ADP ribose polymerase [PARP]) signaling was found to be involved in FKB-induced apoptosis. In addition, FKB-induced reactive oxygen species (ROS) generation, and N-acetylcysteine attenuated FKB-induced apoptotic cell death. Moreover, FKB triggered autophagy, as evidenced by the improved acidic vesicular organelle formation, lipidated light chain 3 (microtubule-related light chain 3) accumulation, and ATG7 expression and the decreased mammalian target of rapamycin phosphorylation. Furthermore, FKB suppressed ROS-mediated ATG4B expression. Inhibiting autophagy using 3-methyladenine/chloroquine diminished FKB-induced cell death, indicating that autophagy is triggered as a death mechanism by FKB. In summary, FKB has a crucial role in the execution and propagation of ROS-mediated apoptotic and autophagic cell death of lung adenocarcinoma cells.

Oleanolic acid 3-acetate, a minor element of ginsenosides, induces apoptotic cell death in ovarian carcinoma and endometrial carcinoma cells via the involvement of a reactive oxygen species-independent mitochondrial pathway

Objectives

Oleanolic acid, a minor element of ginsenosides, and its derivatives have been shown to have cytotoxicity against some tumor cells. The impact of cytotoxic effect of oleanolic acid 3-acetate on ovarian cancer SKOV3 cells and endometrial cancer HEC-1A cells were examined both in vivo and in vitro to explore the underlying mechanisms.

Methods

Cytotoxic effects of oleanolic acid 3-acetate were assessed by cell viability, phosphatidylserine exposure on the cell surface, mitochondrial release of cytochrome C, nuclear translocation of apoptosis-inducing factor, depolarization of mitochondrial transmembrane potential (ΔΨ_m), and generation of reactive oxygen species (ROS). In vivo inhibition of tumor growth was also assessed with xenografts in immunocompromised mice.

Results

Oleanolic acid 3-acetate exhibited potent cytotoxicity toward SKOV3 and HEC-1A cells by decreasing cell viability in a concentration-dependent manner. Importantly, oleanolic acid 3-acetate effectively suppressed the growth of SKOV3 cell tumor xenografts in immunocompromised mice. Furthermore, oleanolic acid 3-acetate induced apoptotic cell death as revealed by loss of ΔΨ_m, release of cytochrome c, and nuclear translocation of apoptosis-inducing factor with a concomitant activation of many proapoptotic cellular components including poly(ADP-ribose) polymerase, Bcl-2, and caspases-8, caspase-3, and caspase-7. Oleanolic acid 3-acetate, however, caused a decrease in ROS production, suggesting the involvement of an ROS-independent pathway in oleanolic acid 3-acetate–induced apoptosis in SKOV3 and HEC-1A cells.

Conclusion

These findings support the notion that oleanolic acid 3-acetate could be used as a potent anticancer supplementary agent against ovarian and endometrial cancer. Oleanolic acid 3-acetate exerts its proapoptotic effects through a rather unique molecular mechanism that involves an unconventional ROS-independent but mitochondria-mediated pathway.

Melatonin protects hippocampal HT22 cells from the effects of serum deprivation specifically targeting mitochondria

Neurons contain a high number of mitochondria, these neuronal cells produce elevated levels of oxidative stress and live for a long time without proliferation; therefore, mitochondrial homeostasis is crucial to their health. Investigations have recently focused on mitochondrial dynamics revealing the ability of these organelles to change their distribution and morphology. It is known that mitochondrial fission is necessary for the transmission of mitochondria to daughter cells during mitosis and mitochondrial fragmentation has been used as an indicator of cell death and mitochondrial dysfunction. Oxidative stress is a trigger able to induce changes in the mitochondrial network. The aim of the present study was to determine the effects of melatonin on the mitochondrial network in HT22 serum-deprived cells. Our results showed that serum deprivation increased reactive oxygen species (ROS) content, promoted the activation of plasma membrane voltage-dependent anion channels (VDACs) and affected the expression of pDRP1 and DRP1 fission proteins. Moreover, parallel increases in apoptotic and autophagic features were found. Damaged and dysfunctional mitochondria are deleterious to the cell; hence, the degradation of such mitochondria through mitophagy is crucial to cell survival. Our results suggest that melatonin supplementation reduces cell death and restores mitochondrial function through the regulation of autophagy.

Vasoactive intestinal peptide induces proliferation of human hepatocytes

OBJECTIVES

Proliferation of hepatocytes in vitro can be stimulated by growth factors such as epidermal growth factor (EGF), but the role of vasoactive intestinal peptide (VIP) remains unclear. We have investigated the effect of VIP on maintenance and proliferation of human hepatocytes.

MATERIALS AND METHODS

Human hepatocytes were isolated from liver specimens obtained from patients undergoing liver surgery. Treatment with VIP or EGF was started 24 h after plating and continued for 3 or 5 d. DNA replication was investigated by Bromodeoxyuridine (BrdU) incorporation and cell viability detected by MTT assay. Cell lysate was analysed by western blotting and RT-PCR. Urea and albumin secretion into the culture supernatants were measured.

RESULTS

VIP increased DNA replication in hepatocytes in a dose-dependant manner, with a peak response at day 3 of treatment. VIP treatment was associated with an increase in mRNA expression of antigen identified by monoclonal antibody Ki-67 (MKI-67) and Histone Cluster 3 (H3) genes. Western blotting analysis showed that VIP can induce a PKA/B-Raf dependant phosphorylation of extracellular signal-regulated kinases (ERK). Although EGF can maintain hepatocyte functions up to day 5, no marked efffect was found with VIP.

CONCLUSIONS

VIP induces proliferation of human hepatocytes with little or no effect on hepatocyte differentiation. Further investigation of the role of VIP is required to determine if it may ultimately support therapeutic approaches of liver disease.

Ginsenoside Rg1 inhibits apoptosis by increasing autophagy via the AMPK/mTOR signaling in serum deprivation macrophages

Ginsenoside Rg1 (Rg1) has been widely used in a broad range of cardiovascular and cerebral-vascular diseases because of its unique therapeutic properties. However, the underlying mechanisms of Rg1 in the treatment of atherosclerosis have not been fully explored. This study sought to determine the precise molecular mechanisms on how Rg1 might be involved in regulating apoptosis in serum deprivation-induced Raw264.7 macrophages and primary bone marrow-derived macrophages. Results demonstrated that Rg1 treatment effectively suppressed apoptosis and the expression of phosphorylation level of mTOR induced by serum deprivation in Raw264.7 macrophages; the expressions of autophagic flux-related proteins including Atg5, Beclin1, microtubule-associated protein 1 light chain 3 (LC3), p62/SQSMT1, and the phosphorylation level of AMPK were concomitantly up-regulated. 3-Methyl-adennine (3-MA), the most widely used autophagy inhibitor, strongly up-regulated the expression of cleaved caspase-3, and blocked the anti-apoptosis function of Rg1 in macrophages. Importantly, autophagic flux was activated by Rg1, while Beclin1 knockdown partially abolished the anti-apoptosis of Rg1. Moreover, compound C, an AMPK inhibitor, partially decreased the expressions of phosphorylation of mTOR, Atg5, Beclin1, LC3, and p62/SQSMT1, which were increased by Rg1. AICAR, an AMPK inducer, promoted the protein expressions of phosphorylation of mTOR, Atg5, Beclin1, LC3, and p62/SQSMT1. In conclusion, Rg1 significantly suppressed apoptosis induced by serum deprivation in macrophages. Furthermore, Rg1 could effectively induce the autophagic flux by attenuating serum deprivation-induced apoptosis in Raw264.7 macrophages through activating the AMPK/mTOR signaling pathway.

A novel cytoprotective peptide protects mesenchymal stem cells against mitochondrial dysfunction and apoptosis induced by starvation via Nrf2/Sirt3/FoxO3a pathway

Background

Mesenchymal stem cell (MSC) has been widely explored in the past decade as a cell-based treatment for various diseases. However, poor survival of adaptively transferred MSCs limits their clinical therapeutic potentials, which is largely ascribed to the nutrient starvation. In this study, we determined whether a novel kidney protective peptide CHBP could protect MSCs against starvation and invested the underlying mechanisms.

Methods

MSCs were subjected to serum deprivation and CHBP of graded concentrations was administered. Cell viability and apoptosis were detected by CCK-8, Annexin V/PI assay and Hoechst staining. ROS generation, mitochondrial membrane potential indicated by JC-1 and mitochondrial mass were measured by flow cytometry. The location of cytochrome c within cells was observed under fluorescence microscopy. Expressions of Nrf2, Sirt3, and FoxO3a were analyzed by western blot. In addition, preconditioning MSCs with CHBP was applied to test the possible protection against starvation. Finally, the effect of CHBP on the differentiation and self-renewal capacity of MSCs was also examined.

Results

CHBP improved cell viability and suppressed apoptosis in a dose dependent manner. Starvation resulted in the mitochondrial dysfunction and treatment of CHBP could alleviate mitochondrial stress by diminishing oxidative injury of ROS, restoring mitochondrial membrane potential and maintaining mitochondrial membrane integrity. Importantly, Nrf2/Sirt3/FoxO3a pathway was activated by CHBP and Sirt3 knockdown partially abolished the protection of CHBP. Moreover, MSCs pretreated with CHBP were more resistant to starvation. Under normal condition, CHBP exerted little effects on the differential and self-renewal capacity of MSCs.

Conclusions

The present study demonstrated the efficient protection of CHBP upon MSCs against starvation-induced mitochondrial dysfunction and apoptosis and indicated possible involvement of Nrf2/Sirt3/FoxO3a pathway in the protective effect.

Overexpression of GRP78 enhances survival of CHO cells in response to serum deprivation and oxidative stress

Chinese hamster ovary (CHO) cells are regarded as one of the most commonly used mammalian hosts, which decreases the productivity due to loss in culture viability. Overexpressing antiapoptosis genes in CHO cells was developed as a means of limiting cell death upon exposure to environmental insults. Glucose-regulated protein 78 (GRP78) is traditionally regarded as a major ER chaperone that participates in protein folding and other cell processes. It is also a potent antiapoptotic protein and plays a critical role in cell survival, proliferation, and metastasis. In this study, the impact of GRP78 on CHO cells in response to environmental insults such as serum deprivation and oxidative stress was investigated. First, it was confirmed that CHO cells were very sensitive to environmental insults. Then, GRP78 overexpressing CHO cell line was established and exposed to serum deprivation and H₂O₂. Results showed that GRP78 engineering increased the viability and decreased the apoptosis of CHO cells. The survival advantage due to GRP78 engineering could be mediated by suppression of caspase-3 involved in cell death pathways in stressed cells. Besides, GRP78 engineering also enhanced yields of antibody against transferrin receptor in CHO cells. GRP78 should be a potential application in the biopharmaceutical industries.

Characterization of the 5'-flanking region of the human TP53 gene and its response to the natural compound, Resveratrol

Tumour suppressor p53, which is encoded by theTP53gene, is widely known to play an important role in response to DNA damage and various stresses. It has recently been reported that p53 regulates glucose metabolism and that an increase in p53 protein level is induced after serum deprivation or treatments with a natural compound,trans-Resveratrol (Rsv). In this study, we constructed a Luciferase expression vector, pGL4-TP53-551, containing 551 bp of the 5'-upstream region of the humanTP53gene, which was then transfected into HeLa S3 cells. A Luciferase assay showed that Rsv treatment increased the promoter activity of theTP53gene in comparison to that ofPIF1 Detailed deletion and mutation analyses revealed that Nkx-2.5 and E2F-binding elements are required in addition to duplicated GGAA (TTCC), for the regulation ofTP53promoter activity. In this study, it is suggested that the transient induction ofTP53gene expression by Rsv treatment might be partly involved in its anti-aging effect through maintenance of chromosomal DNAs.

Hydrogen-rich saline protects against mitochondrial dysfunction and apoptosis in mice with obstructive jaundice

Previous studies have demonstrated that hydrogen-rich saline (HS) protects against bile duct ligation (BDL)-induced liver injury by suppressing oxidative stress and inflammation. Mitochondria, which are targets of excessive reactive oxygen species and central mediators of apoptosis, have a pivotal role in hepatic injury during obstructive jaundice (OJ); however, the implications of HS in the hepatic mitochondria of BDL mice remain unknown. The present study investigated the hypothesis that HS could reduce OJ‑induced liver injury through the protection of mitochondrial structure and function, as well as inhibition of the mitochondrial apoptotic pathway. Male C57BL/6 mice were randomly divided into three experimental groups: Sham operation group, BDL injury with normal saline (NS) treatment group, and BDL‑injury with HS treatment group. Mitochondrial damage and apoptotic parameters were determined 3 days post‑BDL injury and treatment. The results demonstrated that mitochondria isolated from the livers of NS-treated BDL mice exhibited increased mitochondrial swelling, cytochrome c release, and oxidative damage. In addition, liver samples from NS‑treated BDL mice exhibited significant increases in B‑cell lymphoma 2 (Bcl‑2)‑associated X protein expression, caspase activities, and hepatocyte apoptosis compared with livers from sham‑operated controls. Notably, treatment with HS reduced the levels of these markers and alleviated morphological defects in the mitochondria following injury. In addition, HS markedly increased the antioxidant potential of mitochondria, as evidenced by elevated adenosine triphosphate levels, mitochondrial respiratory function, and increased levels of active Bcl‑2. In conclusion, HS attenuates mitochondrial oxidative stress and dysfunction, and inhibits mitochondrial-mediated apoptosis in the livers of BDL mice.

Different Contribution of Redox-Sensitive Transient Receptor Potential Channels to Acetaminophen-Induced Death of Human Hepatoma Cell Line

Acetaminophen (APAP) is a safe analgesic antipyretic drug at prescribed doses. Its overdose, however, can cause life-threatening liver damage. Though, involvement of oxidative stress is widely acknowledged in APAP-induced hepatocellular death, the mechanism of this increased oxidative stress and the associated alterations in Ca²⁺ homeostasis are still unclear. Among members of transient receptor potential (TRP) channels activated in response to oxidative stress, we here identify that redox-sensitive TRPV1, TRPC1, TRPM2, and TRPM7 channels underlie Ca²⁺ entry and downstream cellular damages induced by APAP in human hepatoma (HepG2) cells. Our data indicate that APAP treatment of HepG2 cells resulted in increased reactive oxygen species (ROS) production, glutathione (GSH) depletion, and Ca²⁺ entry leading to increased apoptotic cell death. These responses were significantly suppressed by pretreatment with the ROS scavengers N-acetyl-L-cysteine (NAC) and 4,5-dihydroxy-1,3-benzene disulfonic acid disodium salt monohydrate (Tiron), and also by preincubation of cells with the glutathione inducer Dimethylfumarate (DMF). TRP subtype-targeted pharmacological blockers and siRNAs strategy revealed that suppression of either TRPV1, TRPC1, TRPM2, or TRPM7 reduced APAP-induced ROS formation, Ca²⁺ influx, and cell death; the effects of suppression of TRPV1 or TRPC1, known to be activated by oxidative cysteine modifications, were stronger than those of TRPM2 or TRPM7. Interestingly, TRPV1 and TRPC1 were labeled by the cysteine-selective modification reagent, 5,5′-dithiobis (2-nitrobenzoic acid)-2biotin (DTNB-2Bio), and this was attenuated by pretreatment with APAP, suggesting that APAP and/or its oxidized metabolites act directly on the modification target cysteine residues of TRPV1 and TRPC1 proteins. In human liver tissue, TRPV1, TRPC1, TRPM2, and TRPM7 channels transcripts were localized mainly to hepatocytes and Kupffer cells. Our findings strongly suggest that APAP-induced Ca²⁺ entry and subsequent hepatocellular death are regulated by multiple redox-activated cation channels, among which TRPV1 and TRPC1 play a prominent role.

AMPK activation by liquiritigenin inhibited oxidative hepatic injury and mitochondrial dysfunction induced by nutrition deprivation as mediated with induction of farnesoid X receptor

PURPOSE

Nutrition is indispensable for cell survival and proliferation. Thus, loss of nutrition caused by serum starvation in cells could induce formation of reactive oxygen species (ROS), resulting in cell death. Liquiritigenin (LQ) is an active flavonoid in licorice and plays a role in the liver as a hepatic protectant.

METHODS

This study investigated the effect of LQ, metformin [an activator of activated AMP-activated protein kinase (AMPK)] and GW4064 [a ligand of farnesoid X receptor (FXR)] on mitochondrial dysfunction and oxidative stress induced by serum deprivation as well as its molecular mechanism, as assessed by immunoblot and flow cytometer assays.

RESULTS

Serum deprivation in HepG2, H4IIE and AML12 cells successfully induced oxidative stress and apoptosis, as indicated by depletion of glutathione, formation of ROS, and altered expression of apoptosis-related proteins such as procaspase-3, poly(ADP-ribose) polymerase, and Bcl-2. However, LQ pretreatment significantly blocked these pathological changes and mitochondrial dysfunction caused by serum deprivation. Moreover, LQ activated AMPK in HepG2 cells and mice liver, as shown by phosphorylation of AMPK and ACC, and this activation was mediated by its upstream kinase (i.e., LKB1). Experiments using a chemical inhibitor of AMPK with LKB1-deficient Hela cells revealed the role of the LKB1-AMPK pathway in cellular protection conferred by LQ. LQ also induced protein and mRNA expression of both FXR as well as small heterodimer partner, which is important since treatment with FXR ligand GW4064 protected hepatocytes against cell death and mitochondrial damage induced by serum deprivation.

CONCLUSION

AMPK activators such as LQ can protect hepatocytes against oxidative hepatic injury and mitochondrial dysfunction induced by serum deprivation, and the beneficial effect might be mediated through the LKB1 pathway as well as FXR induction.

BMP9-Induced Survival Effect in Liver Tumor Cells Requires p38MAPK Activation

The study of bone morphogenetic proteins (BMPs) role in tumorigenic processes, and specifically in the liver, has gathered importance in the last few years. Previous studies have shown that BMP9 is overexpressed in about 40% of hepatocellular carcinoma (HCC) patients. In vitro data have also shown evidence that BMP9 has a pro-tumorigenic action, not only by inducing epithelial to mesenchymal transition (EMT) and migration, but also by promoting proliferation and survival in liver cancer cells. However, the precise mechanisms driving these effects have not yet been established. In the present work, we deepened our studies into the intracellular mechanisms implicated in the BMP9 proliferative and pro-survival effect on liver tumor cells. In HepG2 cells, BMP9 induces both Smad and non-Smad signaling cascades, specifically PI3K/AKT and p38MAPK. However, only the p38MAPK pathway contributes to the BMP9 growth-promoting effect on these cells. Using genetic and pharmacological approaches, we demonstrate that p38MAPK activation, although dispensable for the BMP9 proliferative activity, is required for the BMP9 protective effect on serum withdrawal-induced apoptosis. These findings contribute to a better understanding of the signaling pathways involved in the BMP9 pro-tumorigenic role in liver tumor cells.

Cytoprotective effect of short-term pretreatment with proanthocyanidin on human gingival fibroblasts exposed to harsh environmental conditions

Our previous study showed that exposing mouse fibroblasts to proanthocyanidin (PA) for only 1 min accelerated cell proliferation in a concentration-dependent manner. In this study, exposing human gingival fibroblasts (HGFs) to PA for 1 min similarly accelerated the proliferative response of the cells. Besides the accelerated proliferative response, PA showed a cytoprotective effect on HGFs exposed to harsh environmental conditions; short-term exposure of HGFs in the mitotic phase to pure water or physiological saline resulted in a lower recovery of viable cells. Pretreatment and concomitant treatment with PA improved the low recovery of cells exposed to pure water or physiological saline. In addition, HGFs exposed to PA for 1 min proliferated well even after being cultured in serum-free medium. In 100% confluent HGFs, being cultured in serum-free medium resulted in a high intracellular reactive oxygen species (ROS) level, but pretreatment with PA prevented the cells from increasing intracellular ROS. Thus, the results suggest that a short-term PA treatment exerts cytoprotective effects on HGFs exposed to harsh environmental conditions by improving the intracellular oxidative stress response.

Prooxidant properties of p66shc are mediated by mitochondria in human cells

p66shc is a protein product of an mRNA isoform of SHC1 gene that has a pro-oxidant and pro-apoptotic activity and is implicated in the aging process. Mitochondria were suggested as a major source of the p66shc-mediated production of reactive oxygen species (ROS), although the underlying mechanisms are poorly understood. We studied effects of p66shc on oxidative stress induced by hydrogen peroxide or by serum deprivation in human colon carcinoma cell line RKO and in diploid human dermal fibroblasts (HDFs). An shRNA-mediated knockdown of p66shc suppressed and an overexpression of a recombinant p66shc stimulated the production of ROS in the both models. This effect was not detected in the mitochondrial DNA-depleted ρ0-RKO cells that do not have the mitochondrial electron transport chain (ETC). The p66shc-dependent accumulation of mitochondrial ROS was detected with HyPer-mito, a mitochondria-targeted fluorescent protein sensor for hydrogen peroxide. The fragmentation of mitochondria induced by mitochondrial ROS was significantly reduced in the p66shc deficient RKO cells. Mitochondria-targeted antioxidants SkQ1 and SkQR1 also decreased the oxidative stress induced by hydrogen peroxide or by serum deprivation. Together the data indicate that the p66shc-dependant ROS production during oxidative stress has mitochondrial origin in human normal and cancer cells.

Endogenous signal transducer and activator of transcription 3 is required for the protection of hepatocytes against warm ischemia/reperfusion injury

Warm ischemia/reperfusion (I/R) is a common clinical problem during liver transplantation and liver resection. Warm ischemia also occurs during trauma and shock. However, there is still no safe and promising strategy for protecting the liver from I/R injury. Signal transducer and activator of transcription 3 (STAT3) is a major immediate response molecule for protecting cell survival. In this study, we first confirmed that a pharmacological STAT3 inhibitor, (E)-2-cyano-3-(3,4-dihydrophenyl)-N-(phenylmethyl)-2-propenamide (AG490), significantly reduced the survival of HepG2 cells, regardless of the serum condition. Furthermore, we created hepatocyte-specific STAT3-deficient mice with the cyclization recombination-locus of X-over P1 (Cre-LoxP) system to study the mechanisms of STAT3 in liver I/R injury. We found that the alanine aminotransferase level was significantly higher in hepatocyte-specific STAT3-deficient mice versus wild-type (WT) mice in a 70% liver I/R injury model. A histopathological examination showed that hepatocyte-specific STAT3-deficient mice suffered more severe damage than WT mice despite similar numbers of polymorphonuclear neutrophils in the 2 groups. These results indicate that endogenous STAT3 signaling in hepatocytes is required for protection of the liver in vitro and in vivo against warm I/R injury. In conclusion, endogenous STAT3 plays an important role in protecting the liver against I/R injury, and STAT3-targeting therapy could be a therapeutic approach to combating liver I/R injury.

Cellular trafficking of thymosin beta-4 in HEPG2 cells following serum starvation

Thymosin beta-4 (Tβ4) is an ubiquitous multi-functional regenerative peptide, related to many critical biological processes, with a dynamic and flexible conformation which may influence its functions and its subcellular distribution. For these reasons, the intracellular localization and trafficking of Tβ4 is still not completely defined and is still under investigation in in vivo as well as in vitro studies.

In the current study we used HepG2 cells, a human hepatoma cell line; cells growing in normal conditions with fetal bovine serum expressed high levels of Tβ4, restricted to the cytoplasm until 72 h. At 84 h, a diffuse Tβ4 cytoplasmic immunostaining shifted to a focal perinuclear and nuclear reactivity. In the absence of serum, nuclear reactivity was localized in small granules, evenly dispersed throughout the entire nuclear envelop, and was observed as earlier as at 48 h. Cytoplasmic immunostaining for Tβ4 in HepG2 cells under starvation appeared significantly lower at 48 h and decreased progressively at 72 and at 84 h. At these time points, the decrease in cytoplasmic staining was associated with a progressive increase in nuclear reactivity, suggesting a possible translocation of the peptide from the cytoplasm to the nuclear membrane. The normal immunocytochemical pattern was restored when culture cells submitted to starvation for 84 h received a new complete medium for 48 h.

Mass spectrometry analysis, performed on the nuclear and cytosolic fractions of HepG2 growing with and without serum, showed that Tβ4 was detectable only in the cytosolic and not in the intranuclear fraction. These data suggest that Tβ4 is able to translocate from different cytoplasmic domains to the nuclear membrane and back, based on different stress conditions within the cell.

The punctuate pattern of nuclear Tβ4 immunostaining associated with Tβ4 absence in the nucleoplasm suggest that this peptide might be localized in the nuclear pores, where it could regulate the pore permeability.

Regulation of Btg2(/TIS21/PC3) expression via reactive oxygen species-protein kinase C-ΝFκΒ pathway under stress conditions

Human B-cell translocation gene 2 (BTG2), an ortholog of mouse TIS21 (12-O-tetradecanoyl phorbol-13-acetate inducible sequence 21) and rat PC3 (Pheochromocytoma Cell 3), is a tumor suppressor gene that belongs to an antiproliferative gene family. Btg2 is involved in a variety of biological processes including cell growth, development, differentiation, senescence, and cell death and its expression is strongly regulated by p53. Recently, we have reported transient induction of Btg2 expression in response to oxidative damage; however, the regulatory mechanism was not explored. In the present study we revealed ΝFκΒ as the upstream mediator involved in Btg2 transcription in response to cell stress challenges such as serum deprivation and oxidative stress i.e. H2O2, TPA or doxorubicin treatments in several cell lines. We observed close interrelation between generation of reactive oxygen species (ROS), enhanced IκBα degradation, nuclear translocation of ΝFκΒ (p65/RelA) and the significant increase of Btg2 expression independent of p53 status. ChIP analysis revealed an enrichment of RelA (p65) bound to the κB response element on Btg2 promoter in response to the cell stress challenges. Employing various inhibitors led to cytoplasmic accumulation of IκBα, decreased p65 nuclear translocation along with significant reduction of Btg2 expression. Generation of ROS was the common event mediating ΝFκΒ activation and Btg2 transcription. Furthermore, PKC activation was also found to be a critical factor mediating ROS-mediated signals to NFκB pathway that culminate on Btg2 regulation, and specifically PKC-δ was responsible for this regulation under oxidative stress. However, serum deprivation-associated ROS generation bypassed PKC activation for induction of Btg2 expression via NFκB activation. The present data imply that oxidative stress upregulates Btg2 expression via ROS-PKC-ΝFκΒ cascade, independent of p53 status that in turn could be involved in mediating various biological phenotypes depending on the cellular context.

Preliminary study on XAGE-1b gene and its mechanism for promoting tumor cell growth

The XAGE-1b gene has been identified in numerous malignancies in the human body. However, little is known regarding its mechanism for promoting tumorigenesis in adenoid cystic carcinoma. The aim of this study was to explore the correlation between tumor cell growth and the XAGE-1b gene. The constructed PCMV-Myc plasmid vector containing the XAGE-1b gene and transfected adenoid cystic carcinoma (ACC)-2 cells was applied to study cell cycle alterations and anti-apoptotic effects. These were assessed by flow cytometry with PI staining and the measurement of cell content at its Sub-G₁ phase, respectively. The fluorescence intensity representing the regulation of XAGE-1b on the transcription factors located downstream of the signaling pathway using the Mercury pathway profiling system was also detected. XAGE-1b over expression promoted cell growth by shortening G₀-G₁ and prolonging the G₂-M phase. Additionally, XAGE-1b overexpression enhanced the anti-apoptotic effects induced by tumor necrosis factor-α (TNF-α) and serum deprivation in ACC-2 cells. The results of the present study suggested that XAGE-1b gene is crucial in the tumorigenesis of ACC, and its mechanism should be further investigated.

Effect of dicycloplatin, a novel platinum chemotherapeutical drug, on inhibiting cell growth and inducing cell apoptosis

Dicycloplatin, a new supramolecular platinum-based antitumor drug, has been approved by the State Food and Administration (SFDA) of China. In this study, we investigated the anticancer activity of dicycloplatin in cancer cells and signaling pathways involved in dicycloplatin-induced apoptosis. Dicycloplatin inhibited the proliferation of cancer cells and increased the percentage of apoptosis in a concentration-dependent manner. Besides, some apoptosis related events were observed after treatment with dicycloplatin, including increase of reactive oxygen species (ROS), collapse of mitochondrial membrane potential (Δψm), release of cytochrome c from the mitochondria to the cytosol, upregulation of p53, which were accompanied by activation of caspase-9, caspase-3, caspase-8, and poly (ADP-ribose) polymerase cleavage in a concentration-dependent manner. The role of apoptosis in dicycloplatin-mediated cell death was further confirmed by the concomitant treatment with caspase-8 or caspase-9 inhibitors, which inhibited apoptosis and PARP cleavage. Intracellular glutathione (GSH) was also found to inhibit the cytotoxic effect of dicycloplatin. In conclusion, these findings suggest that dicycloplatin induces apoptosis through ROS stress-mediated death receptor pathway and mitochondrial pathway which is similar to carboplatin.

Downregulation of galectin-3 by EGF mediates the apoptosis of HepG2 cells

Epidermal growth factor (EGF) in high concentrations induces apoptosis of the tumor cells which express high levels of epidermal growth factor receptor. However, the precise mechanism for this induction is not clear. Galectin-3 is the most probable candidate for mediating this effect, as it is known to induce anti-apoptotic activity in a variety of tumor cells exposed to diverse apoptotic stimuli. In this study, we determined whether galectin-3 plays a role in high concentrations of EGF-induced apoptosis of HepG2 cells. We found that EGF in high concentrations led to the growth inhibition of HepG2 cells, which were associated with promotion of cell death. High concentrations of EGF suppressed cytoplasmic expression of galectin-3. Moreover, we demonstrated overexpression of galectin-3 could reduce EGF-induced apoptosis in HepG2 cells. Our study demonstrated for the first time that downregulation of cytoplasmic galectin-3 was essential for high concentrations of EGF-induced apoptosis in HepG2 cells.

Hypoxia improves expansion potential of human cord blood-derived hematopoietic stem cells and marrow repopulation efficiency

OBJECTIVES

In bone marrow, hematopoietic stem cells (HSCs) reside in the most hypoxic endosteum niche, whereas the proliferating progenitors are located near the relatively oxygen-rich vascular region. High oxygen tension is potentially detrimental to HSCs. The objective of this investigation was to compare cellular, functional, and molecular responses of human umbilical cord blood (UCB)-derived hematopoietic stem and progenitor cells in culture under hypoxic and normoxic conditions.

METHODS

CD133-enriched UCB cells were cultured in growth factor containing serum-free and serum-supplemented medium under 5% O(2) (hypoxia) or 21% O(2) (normoxia) for 10 d. The phenotypes of expanded cells were analyzed by flow cytometry and the engraftability by SCID-repopulation assay. The expression of hypoxia-inducible factor (HIF)-1α and some of its target genes was analyzed by real-time RT-PCR.

RESULTS

In hypoxic culture, CD34(+) CD38(-) cells were expanded about 27-fold, which was significantly (P < 0.01) higher than that obtained in normoxic culture. Serum-free culture did not support the growth of cells in the presence of 21% O(2) . Myeloid colony-forming potential of cells was significantly (P < 0.05) increased in 5% O(2) compared with 21% O(2) culture. SCID-repopulation efficiency seems to be better preserved in the cells cultured under hypoxic conditions. Hypoxia significantly (P < 0.05) induced the expression of HIF-1α, vascular endothelial growth factor (VEGF), and ABCG2 genes and also upregulated CXCR4 receptor expression.

CONCLUSIONS

Low oxygen tension enhanced the proliferation of UCB-derived HSC/progenitor cells and maintenance of SCID-repopulating cells than normoxia. These expanded cells are expected to be beneficial in the patients who lack human leukocyte antigen (HLA)-matched donors.

Regulation of reactive oxygen species generation in cell signaling

Reactive oxygen species (ROS) including superoxide anion and hydrogen peroxide (H(2)O(2)) are thought to be byproducts of aerobic respiration with damaging effects on DNA, protein, and lipid. A growing body of evidence indicates, however, that ROS are involved in the maintenance of redox homeostasis and various cellular signaling pathways. ROS are generated from diverse sources including mitochondrial respiratory chain, enzymatic activation of cytochrome p450, and NADPH oxidases further suggesting involvement in a complex array of cellular processes. This review summarizes the production and function of ROS. In particular, how cytosolic and membrane proteins regulate ROS generation for intracellular redox signaling will be detailed.

Glutaredoxin 2a, a mitochondrial isoform, plays a protective role in a human cell line under serum deprivation

The roles of mitochondrial glutaredoxin (Grx2a) under serum deprivation were assessed using the human stable HepG2 cell lines overexpressing or down-regulating Grx2a. The Grx2a-overexpressing stable cells displayed enhanced proliferation, decreased reactive oxygen species (ROS) and caspase-3 activity levels, and increased total GSH level, compared to the vector control cells. These characteristics of the overexpressing stable cells were reversed by down-regulating Grx2a in the same cell line. In the limited serum conditions, the Grx2a-overexpressing stable pcDNA3.0/HA-Grx2a cells exhibited higher cellular viabilities and total GSH level, and showed much lower enhancement in ROS and caspase-3 activity levels than the vector control pcDNA3.0/HA cells. However, the Grx2a-down-regulating stable cells gave rise to diminished cellular viabilities and further decreased total GSH level, and contained significantly higher ROS and caspase-3 activity levels, under serum deprivation than the vector control cells. These results suggest that Grx2a plays proliferative and anti-apoptotic roles under serum deprivation.

Flavokawain B inhibits growth of human squamous carcinoma cells: Involvement of apoptosis and cell cycle dysregulation in vitro and in vivo

Flavokawain B is a natural chalcone isolated from the rhizomes of Alpenia pricei Hayata. In the present study, we have investigated the antiproliferative and apoptotic effect of flavokawain B (5-20 μg/ml; 17.6-70.4 μM) against human squamous carcinoma (KB) cells. Exposure of KB cells with flavokawain B resulted in apoptosis, evidenced by loss of cell viability, profound morphological changes, genomic DNA fragmentation and sub-G1 phase accumulation. Apoptosis induced by flavokawain B results in activation of caspase-9, -3 and -8, cleavage of poly ADP ribose polymerase (PARP) and Bid in KB cells. Flavokawain B also down-regulate Bcl-2 with concomitant increase in Bax level, which resulted in release of cytochrome c. Taken together, the induction of apoptosis by flavokawain B involved in both death receptor and mitochondrial pathway. We also observed that flavokawain B caused the G2/M phase arrest that was mediated through reductions in the levels of cyclin A, cyclin B1, Cdc2 and Cdc25C and increases in p21/WAF1, Wee1 and p53 levels. Moreover, flavokawain B significantly inhibits matrix metalloproteinase-9 and urokinase plasminogen activator expression, whereas tissue inhibitor of matrix metalloproteinase-1 and plasminogen activator inhibitor-1 were increased, which are playing critical role in tumor metastasis. In addition, flavokawain B treatment significantly inhibited in vivo growth of human KB cell-derived tumor xenografts in nude mice, which is evidenced by augmentation of apoptotic DNA fragmentation, as detected by in situ terminal deoxynucleotidyl transferase-meditated dUTP nick end-labeling staining. The induction of cell cycle arrest and apoptosis by flavokawain B may provide a pivotal mechanism for its cancer chemopreventive action.

Dissection of mitogenic and neurodegenerative actions of cystine and glutamate in malignant gliomas

Malignant glioma represents one of the most aggressive and lethal human neoplasias. A hallmark of gliomas is their rapid proliferation and destruction of vital brain tissue, a process in which excessive glutamate release by glioma cells takes center stage. Pharmacologic antagonism with glutamate signaling through ionotropic glutamate receptors attenuates glioma progression in vivo, indicating that glutamate release by glioma cells is a prerequisite for rapid glioma growth. Glutamate has been suggested to promote glioma cell proliferation in an autocrine or paracrine manner, in particular by activation of the (RS)-α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid hydrate (AMPA) subtype of glutamate receptors. Here, we dissect the effects of glutamate secretion on glioma progression. Glioma cells release glutamate through the amino-acid antiporter system X(c)(-), a process that is mechanistically linked with cystine incorporation. We show that disrupting glutamate secretion by interfering with the system X(c)(-) activity attenuates glioma cell proliferation solely cystine dependently, whereas glutamate itself does not augment glioma cell growth in vitro. Neither AMPA receptor agonism nor antagonism affects glioma growth in vitro. On a molecular level, AMPA insensitivity is concordant with a pronounced transcriptional downregulation of AMPA receptor subunits or overexpression of the fully edited GluR2 subunit, both of which block receptor activity. Strikingly, AMPA receptor inhibition in tumor-implanted brain slices resulted in markedly reduced tumor progression associated with alleviated neuronal cell death, suggesting that the ability of glutamate to promote glioma progression strictly requires the tumor microenvironment. Concerning a potential pharmacotherapy, targeting system X(c)(-) activity disrupts two major pathophysiological properties of glioma cells, that is, the induction of excitotoxic neuronal cell death and incorporation of cystine required for rapid proliferation.

Export of microRNAs and microRNA-protective protein by mammalian cells

The discovery of microRNAs (miRNAs) as a new class of regulators of gene expression has triggered an explosion of research activities, but has left many unanswered questions about how this regulation functions and how it is integrated with other regulatory mechanisms. A number of miRNAs have been found to be present in plasma and other body fluids of humans and mice in surprisingly high concentrations. This observation was unexpected in two respects: first, the fact that these molecules are present at all outside the cell at significant concentrations and second, that these molecules appear to be stable outside of the cell. In light of this it has been suggested that the biological function of miRNAs may also extend outside of the cell and mediate cell–cell communication. We report here that after serum deprivation several human cell lines tested promptly export a substantial amount of miRNAs into the culture medium and the export process is largely energy dependent. The exported miRNAs are found both within and outside of the 16.5 and 120 K centrifugation pellets which contain most of the known cell-derived vesicles, the microvesicles and exosomes. We have identified some candidate proteins involved in this system, and one of these proteins may also play a role in protecting extracellular miRNAs from degradation. Our results point to a hitherto unrecognized and uncharacterized miRNA trafficking system in mammalian cells that is consistent with the cell–cell communication hypothesis.

Neuroprotective effect of the endogenous neural peptide apelin in cultured mouse cortical neurons

The adipocytokine apelin and its G protein-coupled APJ receptor were initially isolated from a bovine stomach and have been detected in the brain and cardiovascular system. Recent studies suggest that apelin can protect cardiomyocytes from ischemic injury. Here, we investigated the effect of apelin on apoptosis in mouse primary cultures of cortical neurons. Exposure of the cortical cultures to a serum-free medium for 24 h induced nuclear fragmentation and apoptotic death; apelin-13 (1.0-5.0 nM) markedly prevented the neuronal apoptosis. Apelin neuroprotective effects were mediated by multiple mechanisms. Apelin-13 reduced serum deprivation (SD)-induced ROS generation, mitochondria depolarization, cytochrome c release and activation of caspase-3. Apelin-13 prevented SD-induced changes in phosphorylation status of Akt and ERK1/2. In addition, apelin-13 attenuated NMDA-induced intracellular Ca(2+) accumulation. These results indicate that apelin is an endogenous neuroprotective adipocytokine that may block apoptosis and excitotoxic death via cellular and molecular mechanisms. It is suggested that apelins may be further explored as a potential neuroprotective reagent for ischemia-induced brain damage.

Parathyroid hormone suppresses osteoblast apoptosis by augmenting DNA repair

Daily injection of parathyroid hormone (PTH) is a clinically approved treatment for osteoporosis. It suppresses apoptosis of bone-forming osteoblasts although its exact anti-apoptotic mechanism(s) is incompletely understood. In this study, PTH treatment of cultured osteoblasts blocked the pro-apoptotic effects of serum withdrawal and nutrient deprivation; hydrogen peroxide induced oxidative stress, and UV irradiation. We hypothesized that PTH might suppress osteoblast apoptosis by enhancing DNA repair. Evidence is provided showing that post-confluent, non-proliferating osteoblasts treated with PTH exhibited a protein kinase A-mediated activation of two proteins that regulate DNA repair processes (proliferating cell nuclear antigen and forkhead box transcription factor 3a) as well as a suppression of the pro-apoptotic growth arrest and DNA damage protein 153. Additional proof of a connection between DNA damage and osteoblast apoptosis came from an unexpected finding whereby a majority of fixed PTH-treated osteoblasts scored weakly positive for Terminal Deoxynucleotidyl dUTP Nick-End Labeling (TUNEL), even though similar cultures were determined to be viable via a trypsin replating strategy. TUNEL identifies DNA excision repair, not just apoptotic DNA fragmentation, and the most likely explanation of these TUNEL results is that PTH's activation of DNA repair processes would permit nucleotide incorporation as a result of enhanced excision repair. This explanation was confirmed by an enhanced incorporation of bromodeoxyuridine in PTH-treated cells even though a majority of the cell population was determined to be non-replicating. An augmentation of DNA repair by PTH is an unreported finding, and provides an additional explanation for its anti-apoptotic mechanism(s).

Acetyl derivate of quercetin increases the sensitivity of human leukemia cells toward apoptosis

The hydroxyl groups of flavonoids are important for their bioactive functions and also prone to oxidation to quinones. To block the potential oxidation of quercetin, and generate a stronger bioactive compound, we synthesized acetyl and methyl derivatives of quercetin, 3,7,3',4'-O-tetraacetylquercetin (4Ac-Q) and 3,7,3',4'-O-tetramethylquercetin (4Me-Q), which substituted the hydroxyl groups of quercetin with acetyl or methyl groups at the 3,7,3',4' positions of quercetin, and then evaluated the ability to cause cell proliferation inhibition and apoptosis in HL-60 cells. The results revealed that 4Ac-Q and quercetin, but not 4Me-Q, significantly inhibit cell proliferation by caspase-mediated apoptosis when characterized by DNA fragmentation, activation of caspase-3 and PARP cleavage while 4Me-Q lost this ability. Interestingly, 4Ac-Q revealed stronger apoptotic activity than parent quercetin via a ROS-independent pathway. These findings provide a valuable strategy to increase the sensitivity of human leukemia HL-60 cells toward apoptosis by modifying quercetin structure.

Humic acid induces G1 phase arrest and apoptosis in cultured vascular smooth muscle cells

Humic acid (HA) in well water used by the inhabitants for drinking is one of the possible etiological factors for Blackfoot disease (BFD). In this study, the ability of HA to inhibit cell cycle progression and induce apoptosis in cultured smooth muscle cells (SMCs; A7r5) was investigated. Treatment of the SMCs at various HA concentrations (25-200 microg/mL) resulted in sequences of events marked by apoptosis, as shown by loss of cell viability, morphology change, and internucleosomal DNA fragmentation. HA-induced apoptotic cell death that is associated with loss of mitochondrial membrane potential (Delta Psi m), cytochrome c translocation, caspase-3, -8, and -9 activation, poly ADP-ribose polymerase (PARP) degradation, dysregulation of Bcl-2 and Bax, and upregulation of p53 and phospholyrated p53 (p-p53) in SMCs. Flow cytometry analysis demonstrated that HA blocked cell cycle progress in the G1 phase in SMCs. This blockade of cell cycle was associated with reduced amounts of cyclin D1, CDK4, cyclin E, CDK2, and hyperphosphorylated retinoblastoma protein (pRb) in a time-dependent manner. Apparent DNA strand breaks (DNA damage) were also detected in a dose-dependent manner using Single-cell gel electrophoresis assay (comet assay). Furthermore, HA induced dose-dependent elevation of reactive oxygen species (ROS) level in SMCs, and antioxidant vitamin C and Trolox effectively suppressed HA-induced DNA damage and dysregulation of Bcl-2/Bax. Our findings suggest that HA-induced DNA damage, cell cycle arrest, and apoptosis in SMCs may be an underlying mechanisms for the atherosclerosis and thrombosis observed in the BFD endemic region.

Inhibition of the mitochondrial permeability transition by cyclosporin A prevents pyrazole plus lipopolysaccharide-induced liver injury in mice

Previous results showed that pyrazole potentiates lipopolysaccharide (LPS)-induced liver injury in mice. Mechanisms involved the overexpression of cytochrome P450 2E1 (CYP2E1), oxidative stress, and activation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). The current study was carried out to test the hypothesis that the mitochondria permeability transition (MPT) plays a role in this pyrazole plus LPS toxicity. Mice were injected intraperitoneally with pyrazole for 2 days, followed by a challenge with LPS with or without treatment with cyclosporin A (CsA), an inhibitor of the MPT. Serum alanine aminotransferase and aspartate aminotransferase were increased by pyrazole plus LPS treatment, and CsA treatment could attenuate these increases. CsA also prevented pyrazole plus LPS-induced hepatocyte necrosis. Formation of 4-hydroxynonenal protein adducts and 3-nitrotyrosine protein adducts in liver tissue was increased by the pyrazole plus LPS treatment, and CsA treatment blunted these increases. Swelling, cytochrome c release from mitochondria to the cytosol, and lipid peroxidation were increased in mitochondria isolated from the pyrazole plus LPS-treated mice, and CsA treatment prevented these changes. CsA did not prevent the increased levels of inducible nitric oxide synthase (iNOS), tumor necrosis factor-alpha (TNF-alpha), pp38 MAPK, and p-JNK2. In conclusion, although CsA does not prevent elevations in upstream mediators of the pyrazole plus LPS toxicity (iNOS, TNF-alpha, CYP2E1, MAPK), it does protect mice from the pyrazole plus LPS-induced liver toxicity by preventing the MPT and release of cytochrome c and decreasing mitochondrial oxidative stress. These results indicate that mitochondria are the critical targets of pyrazole plus LPS in mediating liver injury.

Overexpression of CYP2E1 induces HepG2 cells death by the AMP kinase activator 5'-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR)

5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK) is a phylogenetically conserved serine/threonine protein kinase. AMPK may inhibit cell growth and proliferation and also regulates apoptosis. 5'-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) is a cell-permeable AMPK activator. Activation of AMPK with AICAR has been shown to induce apoptosis of the rat hepatoma cell line FTO2B cells and almost completely inhibited HepG2 cells growth. In this study, a HepG2 cell line, which was transfected with a vector containing human CYP2E1 cDNA (E47 cells), was treated with AICAR. Cell proliferation was blocked, and apoptosis and necrosis were elevated as assessed by cellular morphology, DNA content assay, and lactate dehydrogenase leakage. AICAR treatment significantly increases CYP2E1 activity (20-fold) and expression (5.5-fold) in E47 cells. Iodotubericidin, which inhibits the conversion of AICAR to its activated form AICAR monophosphate, the antioxidants trolox and MnTMPyP, and 4-methylpyrazole, an inhibitor of CYP2E1, all can protect the E47 cells from AICAR-induced necrosis. Production of intracellular reactive oxygen species was increased by AICAR treatment in E47 cells. The cytotoxicity mechanism of AICAR in E47 cells is suggested to include AMPK activation, p53 phosphorylation, p21 expression, overexpression of CYP2E1, and intracellular ROS accumulation.

Farnesoid X receptor protects liver cells from apoptosis induced by serum deprivation in vitro and fasting in vivo

The farnesoid X receptor (FXR) is a key metabolic regulator in the liver by maintaining the homeostasis of liver metabolites. Recent findings suggest that FXR may have a much broader function in liver physiology and pathology. In the present work, we identify a novel role of FXR in protecting liver cell from apoptosis induced by nutritional withdrawal including serum deprivation in vitro or starvation in vivo. Two FXR ligands, chenodeoxycholic acid (CDCA) and GW4064, rescued HepG2 cells from serum deprivation-induced apoptosis in a dose-dependent manner. This effect of FXR on apoptotic suppression was compromised when FXR was knocked down by short interfering RNA. Similarly, the effects of both CDCA and GW4064 were abolished after inhibition of the MAPK pathway by a specific inhibitor of MAPK kinase 1/2. Immunoblotting results indicated that FXR activation by CDCA and GW4064 induced ERK1/2 phosphorylation, which was attenuated by serum deprivation. In vivo, FXR(-/-) mice exhibited an exacerbated liver apoptosis and lower levels of phosphorylated-ERK1/2 compared to wild-type mice after starvation. In conclusion, our results suggest a novel role of FXR in modulating liver cell apoptosis.

A decrease in S-adenosyl-L-methionine potentiates arachidonic acid cytotoxicity in primary rat hepatocytes enriched in CYP2E1

Previous studies show that treatment with a polyunsaturated fatty acid, arachidonic acid (AA), or high concentrations of cycloleucine, an inhibitor of methionine adenosyltransferase (MAT), which lowers levels of S-adenosyl-L-methionine (SAM), increased toxicity in hepatocytes from pyrazole-treated rats which expressed high levels of cytochrome P450 2E1 (CYP2E1). In this study, I used concentrations of cycloleucine or AA, which by themselves do not produce any toxicity, to evaluate whether a decrease in SAM sensitizes hepatocytes to AA toxicity, especially in hepatocytes enriched in CYP2E1. Levels of SAM were lower by 50% in hepatocytes from pyrazole- compared to saline-treated rats. Cycloleucine treatment caused a 50% decline in SAM levels with both hepatocyte preparations and SAM levels were lowest in the pyrazole-treated hepatocytes. The combination of cycloleucine plus AA produced some toxicity and apoptosis in hepatocytes from saline-treated rats but increased toxicity and apoptosis was found in the hepatocytes from pyrazole-treated rats. Cytotoxicity could be prevented by incubation with SAM, the antioxidant trolox, and the mitochondrial permeability transition inhibitor trifluoperazine. The enhanced cytotoxicity could also be protected by treating rats with chlormethiazole, a specific inhibitor of CYP2E1, thus validating the role of CYP2E1. Cycloleucine plus AA treatment elevated production of reactive oxygen species (ROS) and lipid peroxidation to greater extents with the hepatocytes from pyrazole-treated rats than that from the saline-treated rats. I hypothesize that increased production of ROS by hepatocytes enriched in CYP2E1 potentiates AA-induced lipid peroxidation and toxicity when hepatoprotective levels of SAM are lowered. Such interactions, e.g. induction of CYP2E1, decline in SAM and polyunsaturated fatty acid-induced lipid peroxidation, may contribute to alcohol-induced liver injury.