Inhibition of nuclear factor-kappa B activation attenuates hydrogen peroxide-induced cytotoxicity in human lens epithelial cells

Time of day differences in the regulation of glutathione levels in the rat lens

Introduction

Evidence in non-ocular tissues indicate that the antioxidant glutathione (GSH) may be regulated in a circadian manner leading to the idea that GSH levels in the lens may also be controlled in a circadian manner to anticipate periods of oxidative stress.

Methods

Male rat Wistar lenses (6 weeks) were collected every 4 hours over a 24-hour period at 6am, 10am, 2pm, 6pm, 10pm and 2am and quantitative-PCR, western blotting and immunohistochemistry performed to examine the expression of core clock genes and proteins (BMAL1, CLOCK, CRY1-2, PER 1-3) and their subcellular localisation over a 24-hour period. Western blotting of lenses was also performed to examine the expression of NRF2, a transcription factor involved in regulating genes involved in GSH homeostasis and GSH related enzymes (GCLC, GS and GR) over the 24-hour period. Finally, HLPC was used to measure GSH levels in the aqueous humour and lenses every 4 hours over a 24-hour period.

Results

The rat lens contains the core molecular components of a circadian clock with the expression of core clock proteins, NRF2 and GSH related enzymes fluctuating over a 24-hour period. BMAL1 expression was highest during the day, with BMAL1 localised to the nuclei at 10am. NRF2 expression remained constant over the 24-hour period, although appeared to move in and out of the nuclei every 4 hours. GSH related enzyme expression tended to peak at the start of night which correlated with high levels of GSH in the lens and lower levels of GSH in the aqueous humour.

Conclusion

The lens contains the key components of a circadian clock, and time-of-day differences exist in the expression of GSH and GSH related enzymes involved in maintaining GSH homeostasis. GSH levels in the rat lens were highest at the start of night which represents the active phase of the rat when high GSH levels may be required to counteract oxidative stress induced by cellular metabolism. Future work to directly link the clock to regulation of GSH levels in the lens will be important in determining whether the clock can be used to help restore GSH levels in the lens.

Biliverdin/Bilirubin Redox Pair Protects Lens Epithelial Cells against Oxidative Stress in Age-Related Cataract by Regulating NF-κB/iNOS and Nrf2/HO-1 Pathways

Age-related cataract (ARC) is the leading cause of vision impairment globally. It has been widely accepted that excessive reactive oxygen species (ROS) accumulation in lens epithelial cells (LECs) is a critical risk factor for ARC formation. Biliverdin (BV)/bilirubin (BR) redox pair is the active by-product of heme degradation with robust antioxidative stress and antiapoptotic effects. Thus, we purpose that BV and BR may have a therapeutic effect on ARC. In the present study, we determine the expression levels of enzymes regulating BV and BR generation in human lens anterior capsule samples. The therapeutic effect of BV/BR redox pair on ARC was assessed in hydrogen peroxide (H₂O₂)-damaged mouse LECs in vitro. The NF-κB/inducible nitric oxide synthase (iNOS) and nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathways were evaluated to illustrate the molecular mechanism. The results revealed that the mRNA expressions of Nrf2, HO-1, and biliverdin reductase A (BVRA) were all decreased in human samples of age-related nuclear cataract. BV/BR redox pair pretreatment protected LECs against H₂O₂ damage by prohibiting NF-κB p65 nuclear trafficking, ameliorating iNOS expression, reducing intracellular and mitochondrial ROS levels, and restoring glutathione (GSH) and superoxide dismutase (SOD) levels. BV and BR pretreatment also regulated the expression of apoptotic molecules (Bax, Bcl-2, and cleaved caspase-3), thus decreasing the apoptosis of LECs. In addition, BV/BR pair promoted Nrf2 nuclear accumulation and HO-1 induction, whereas the knockdown of BVRA counteracted the effect of BV on activating Nrf2/HO-1 pathway and antiapoptosis. These findings implicated that BV/BR redox pair protects LECs against H₂O₂-induced apoptosis by regulating NF-κB/iNOS and Nrf2/HO-1 pathways. Moreover, BVRA is responsible for BV-mediated cytoprotection by reductive conversion of BV to BR. This trial is registered with ChiCTR2000036059.

Hallmarks of lens aging and cataractogenesis

Lens homeostasis and transparency are dependent on the function and intercellular communication of its epithelia. While the lens epithelium is uniquely equipped with functional repair systems to withstand reactive oxygen species (ROS)-mediated oxidative insult, ROS are not necessarily detrimental to lens cells. Lens aging, and the onset of pathogenesis leading to cataract share an underlying theme; a progressive breakdown of oxidative stress repair systems driving a pro-oxidant shift in the intracellular environment, with cumulative ROS-induced damage to lens cell biomolecules leading to cellular dysfunction and pathology. Here we provide an overview of our current understanding of the sources and essential functions of lens ROS, antioxidative defenses, and changes in the major regulatory systems that serve to maintain the finely tuned balance of oxidative signaling vs. oxidative stress in lens cells. Age-related breakdown of these redox homeostasis systems in the lens leads to the onset of cataractogenesis. We propose eight candidate hallmarks that represent common denominators of aging and cataractogenesis in the mammalian lens: oxidative stress, altered cell signaling, loss of proteostasis, mitochondrial dysfunction, dysregulated ion homeostasis, cell senescence, genomic instability and intrinsic apoptotic cell death.

Long non-coding RNA nuclear paraspeckle assembly transcript 1 protects human lens epithelial cells against H2O2 stimuli through the nuclear factor kappa b/p65 and p38/mitogen-activated protein kinase axis

Background

Long non-coding RNA (lncRNA) nuclear paraspeckle assembly transcript 1 (NEAT1) plays a regulatory role in many biological processes; however, its role in cataracts has yet to be illuminated. This study aimed to investigate the protective role of NEAT1 in hydrogen peroxide (H₂O₂)-treated human lens epithelial cells (HLECs) and its underlying molecular mechanism.

Methods

HLECs (SRA01/04) were treated with 300 µM H₂O₂ to mimic cataract in vitro. Cell viability was detected by performing an MTT assay and EdU staining. Flow cytometry was carried out to detect apoptosis of HLECs. DNA damage was examined using γ-H2A histone family member X staining. and reactive oxygen species (ROS) production was measured using 2’,7’dichlorofluorescin diacetate staining. The expression levels of lncRNA and proteins were detected with quantitative real-time polymerase chain reaction and western blot, respectively.

Results

The expression of NEAT1 was observed to be increased in H₂O₂-treated HLECs and age-related cataract (ARC) tissues. Knockdown NEAT1 strongly protected against H₂O₂-induced cell death and also regulated the expression of cleaved caspase-3, B-cell lymphoma 2, and Bcl-2-associated X protein. Further, knockdown NEAT1 also significantly suppressed H₂O₂-induced intracellular ROS production and malondialdehyde (MDA) content, but elevated the glutathione (GSH) activity of H₂O₂-treated cells. Also, it is demonstrated that si-NEAT1 greatly inhibited H₂O₂-induced phosphorylation of NF-кB p65 and p38 MAPK.

Conclusions

This study confirmed that knockdown NEAT1 attenuated H₂O₂-induced damage in HLECs, and inhibited the oxidative stress and apoptosis of HLECs via regulating nuclear factor-kappa B (NF-κB) p65 and p38 MAPK signaling. It may provide a potential target for clinical treatment of cataracts.

Deferasirox protects against hydrogen peroxide-induced cell apoptosis by inhibiting ubiquitination and degradation of p21WAF1/CIP1

Deferasirox (DFX) is an iron chelator approved for the treatment of iron overload diseases. However, the role of DFX in oxidative stress-induced cell apoptosis and the exact molecular mechanisms underlying these processes remain poorly understood and require further investigation. In this study, we found that DFX rendered resistant to H₂O₂-induced apoptosis in HEK293T cells, reduced the intracellular levels of the labile iron pool (LIP) and oxidative stress induced by H₂O₂. Furthermore, DFX inhibited the ubiquitination and degradation of the cyclin-dependent kinase inhibitor p21^WAF1/CIP1 (p21) via modulation of the interaction of p21 with SCF-Skp2. DFX also showed the inhibition effect on the activation of c-Jun N-terminal kinase (JNK), pro-caspase-3 and related mitochondrial apoptosis pathway induced by H₂O₂. These results provide novel insights into the molecular mechanism underpinning iron-mediated oxidative stress and apoptosis, and they may represent a promising target for therapeutic interventions in related pathological conditions.

NF-κB/Cartilage Acidic Protein 1 Promotes Ultraviolet B Irradiation-Induced Apoptosis of Human Lens Epithelial Cells

The apoptosis of human lens epithelial cells (HLECs) is a characteristic change that occurs during the development of cataracts. Ultraviolet B (UVB) is known to induce the generation of reactive oxygen species (ROS) and apoptosis in HLECs, and thus cause cataracts. Previously, we reported the functions of cartilage acidic protein 1 (CRTAC1) in UVB-treated HLECs. However, the underlying mechanism was not known. In this study, we found that CRTAC1 expression and nuclear factor-kappa B (NF-κB) p65 nuclear translocation were elevated in capsule tissues of cataract patients in comparison with normal controls. The NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC), alleviated UVB-induced apoptosis in HLECs; while activation of NF-κB suppressed the effects of the ROS inhibitor, N-acetyl-L-cysteine (NAC), on UVB-treated HLECs. The expression and promoter activity of CRTAC1 was inhibited by PDTC and NAC. Moreover, the suppressed effects of CRTAC1 knockdown on UVB-induced ROS generation, cell apoptosis, nuclear translocation of NF-κB p65, and p38 phosphorylation were attenuated by a p38 agonist. In contrast, the p38 inhibitor abolished the promotional effects of CRTAC1 overexpression on HLECs. Taken together, our results for the first time show that NF-κB is a potential transcription factor for CRTAC1. The regulatory network involving NF-κB, CRTAC1, and p38 may therefore play an important role in cataract formation.

Inhibition of NLRP3 Protects Human Lens Epithelial Cells against Oxidative Stress-Induced Apoptosis by NF-κB Signaling

BACKGROUNDS/AIMS

To explore whether NLRP3 is involved in the development of cataract and to study the effect of NLRP3 on hydrogen peroxide (H2O2)-induced injury in human lens epithelial cells.

METHODS

Oxidative stress-induced apoptosis model was constructed by treating HLEB3 cells with 50 µM H2O2 at different times (6 h, 12 h) and was confirmed by flow cytometry and Western blot. HLEB3 were divided into NC, NC+H2O2, shNLRP3, and shNLRP3+H2O2 groups. Quantitative real-time polymerase chain reaction and Western blot were employed to detect mRNA and protein expressions, DCFH-DA to measure reactive oxygen species production, and Annexin V-FITC/PI staining to determine cell apoptosis.

RESULTS

NLRP3 expression significantly increased in H2O2-induced HLEB3 cells. shRNA interference of NLRP3 inflammasome protects HLEB3 cells against oxidative stress-induced apoptosis by decreasing the expression levels of caspase-3 and Bax and increasing Bcl-2 expression. shNLRP3 was able to effectively suppress H2O2-induced apoptosis via inhibition of NF-κB signaling.

CONCLUSION

NLRP3 might be involved in the apoptosis of lens epithelial cells. The inhibition of NLRP3 obviously attenuated H2O2-induced oxidative stress injury of human lens epithelial cells via NF-κB signaling.

The Contribution of Fluoride to the Pathogenesis of Eye Diseases: Molecular Mechanisms and Implications for Public Health

This study provides diverse lines of evidence demonstrating that fluoride (F) exposure contributes to degenerative eye diseases by stimulating or inhibiting biological pathways associated with the pathogenesis of cataract, age-related macular degeneration and glaucoma. As elucidated in this study, F exerts this effect by inhibiting enolase, τ-crystallin, Hsp40, Na⁺, K⁺-ATPase, Nrf2, γ -GCS, HO-1 Bcl-2, FoxO1, SOD, PON-1 and glutathione activity, and upregulating NF-κB, IL-6, AGEs, HsP27 and Hsp70 expression. Moreover, F exposure leads to enhanced oxidative stress and impaired antioxidant activity. Based on the evidence presented in this study, it can be concluded that F exposure may be added to the list of identifiable risk factors associated with pathogenesis of degenerative eye diseases. The broader impact of these findings suggests that reducing F intake may lead to an overall reduction in the modifiable risk factors associated with degenerative eye diseases. Further studies are required to examine this association and determine differences in prevalence rates amongst fluoridated and non-fluoridated communities, taking into consideration other dietary sources of F such as tea. Finally, the findings of this study elucidate molecular pathways associated with F exposure that may suggest a possible association between F exposure and other inflammatory diseases. Further studies are also warranted to examine these associations.

Inhibition of histone deacetylase protects the damaged cataract via regulating the NF-κB pathway in cultured lens epithelial cells

Induction of oxidative damage by the activation of histone deacetylase (HDAC) is an integral event that causes major membrane damage of ocular tissues and leads to the pathogenesis of cataract. It is elucidated that nuclear factor-κB is a mediator in the process of cataract development. However, studies on the role played by epigenetic proteins in regulating cataract pathogenesis are limited. Hence, in the current investigation, ARPE-19 human retinal epithelial cells were used as an experimental model to elucidate the role of HDAC inhibition and its mechanism behind the cataract pathogenesis. ARPE-19 cells were exposed to H2O2, with and without Trichostatin A (TSA), a pan-HDAC inhibitor, and maintained along with control cells without any treatment. On exposure to H2O2, cells were susceptible to oxidative stress as it is evident from the reduced expression levels of superoxide dismutase (SOD), catalase, and GSH levels. Simultaneously, H2O2-exposed cells showed the nuclear translocation of NF-κB with the activation of inflammatory cytokines such as CXCL1 and IL-6. In addition, the mRNA expression analysis revealed that the GADD45α, COX-2, MCP-1, and ICAM-1 expressions were increased in H2O2 group. Moreover, the activity of HDAC was increased to 2-fold with a significant reduction in the histone acetyltransferase (HAT) activity in cells that were maintained under oxidative conditions. However, TSA was able to inhibit the critical cytokines’ expression with attenuated HDAC activity and limited NF-κB translocation. Furthermore, pre-treatment of TSA significantly suppressed the transcript levels of up-regulated inflammatory markers in cells. Together, these findings offer new insight into the role of HDACs in regulating cellular processes involved in the pathogenesis of cataract as well as the potential use of HDAC inhibitors as therapeutics for controlling the disease progression.

Hydrogen peroxide-induced apoptosis of human lens epithelial cells is inhibited by parthenolide

AIM

To explore the effect of parthenolide on hydrogen peroxide (H₂O₂)-induced apoptosis in human lens epithelial (HLE) cells.

METHODS

The morphology and number of apoptotic HLE cells were assessed using light microscopy and flow cytometry. Cell viability was tested by MTS assay. In addition, the expression of related proteins was measured by Western blot assay.

RESULTS

Apoptosis of HLE cells was induced by 200 µmol/L H₂O₂, and the viability of these cells was similar to the half maximal inhibitory concentration (IC50), as examined by MTS assay. In addition, cells were treated with either different concentrations (6.25, 12.5, 25 and 50 µmol/L) of parthenolide along with 200 µmol/L H₂O₂ or only 50 µmol/L parthenolide or 200 µmol/L H₂O₂ for 24h. Following treatment with higher concentrations of parthenolide (50 µmol/L), fewer HLE cells underwent H₂O₂-induced apoptosis, and cell viability was increased. Further, Western blot assay showed that the parthenolide treatment reduced the expression of caspase-3 and caspase-9, which are considered core apoptotic proteins, and decreased the levels of phosphorylated nuclear factor-κB (NF-κB), ERK1/2 [a member of the mitogen-activated protein kinase (MAPK) family], and Akt proteins in HLE cells.

CONCLUSION

Parthenolide may suppress H₂O₂-induced apoptosis in HLE cells by interfering with NF-κB, MAPKs, and Akt signaling.

Carbon monoxide (CO) inhibits hydrogen peroxide (H2O2)-induced oxidative stress and the activation of NF-κB signaling in lens epithelial cells

Lens epithelial cells (LECs) play a critical role in the maintenance of clear crystalline lens. Previously, we reported that heme oxygenase-1 can protect LECs from hydrogen peroxide (H₂O₂)-induced apoptosis and oxidative stress; however, to the best of our knowledge, these protection mechanisms have not yet been explained. As carbon monoxide (CO) is an active by-product of heme degradation, we investigated its cytoprotective mechanism in both H₂O₂-treated human LECs (SRA 01/04) and primary rabbit LECs. CO-releasing molecule-3 was used as a CO releasing vehicle. The nuclear translocation of nuclear factor kappa B (NF-κB) p65 was monitored by Western blot and immunofluorescence staining. In addition, the levels of intracellular reactive oxygen species (ROS), antioxidants, and apoptotic molecules (Bax, Bcl-2, and caspase-3) were measured. Furthermore, cell apoptosis rate was quantified by flow cytometry. Our results disclosed that low concentrations of CO released from CO-releasing molecule-3 can attenuate NF-κB p65 nuclear translocation, reduce ROS generation, and enhance intracellular glutathione and superoxide dismutase levels. Moreover, low concentrations of CO inhibited H₂O₂-induced apoptotic molecules, thereby decreasing the apoptosis of LECs. These findings suggest that low concentrations of CO protect LECs from H₂O₂-induced oxidative damage by attenuating NF-κB p65 nuclear translocation, reducing the generation of ROS and apoptotic molecules, and restoring antioxidant enzyme levels, thereby inhibiting LECs apoptosis.

Relationship of cytokines and AGE products in diabetic and non-diabetic patients with cataract

OBJECTIVES

Cytokines are important mediators of inflammatory and immune responses. The aim of this study was to investigate the changes in cytokines concentration (IL-6, IL-8 and TNF-α) and serum advanced glycation end products (sAGEs) in senile diabetics with or without cataract and non-diabetic patients with cataract.

METHODOLOGY

The study included 124 subjects (sixty or over sixty years age), distributed as four groups thirty senile diabetic patients with cataract (Group I) (16 female and 14 male), thirty senile non-diabetic patients with cataract (Group II) (15 female and 15 male), thirty three senile diabetic patients without any complication (Group III) (16 female and 17 male), thirty one apparently normal healthy individuals (Group IV) (16 female and 15 male), age, sex and weight matched with senile control subjects were investigated. Patients were selected on clinical grounds from Eye Ward Jinnah Postgraduate Medical Centre.

RESULTS

Interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor-α (TNF-α) levels were significantly increased (P < 0.001) in Group I and III as compared to Group II and IV. Fasting blood glucose, glycosylated hemoglobin, serum fructosamine, malondialdehyde (MDA), sAGEs, IL-6, IL-8 and TNF-α levels were significantly increased (P < 0.001) in Group I as compared to Group II and the levels were almost same in Group II and IV. There was a significant decrease in serum vitamin E and total antioxidant status (p< 0.001) in Group I and Group III as compared to Group II and Group IV.

CONCLUSION

The results of the present study thus demonstrated that levels increased in both condition but are more severe in diabetic patients with cataract that may be a predictor for cataractogenesis and the levels were almost same in Group II and IV.

Transcriptional regulation of crystallin, redox, and apoptotic genes by C-Phycocyanin in the selenite-induced cataractogenic rat model

PURPOSE

This study was designed to examine the constrictive potential of C-Phycocyanin (C-PC) in regulating changes imposed on gene expression in the selenite-induced cataract model.

METHODS

Wistar rat pups were divided into three groups of eight each. On P10, Group I received an intraperitoneal injection of normal saline. Groups II and III received a subcutaneous injection of sodium selenite (19 μmol/kg bodyweight); Group III also received an intraperitoneal injection of C-PC (200 mg/kg bodyweight) on P9-14. Total RNA was isolated on P16, and the relative abundance of mRNA of the crystallin structural genes, redox components, and apoptotic cascade were ascertained with real-time PCR with reference to the internal control β-actin.

RESULTS

Real-time PCR analysis showed the crystallin genes (αA-, βB1-, γD-) and redox cycle components (Cat, SOD-1, Gpx) were downregulated, the apoptotic components were upregulated, and antiapoptotic Bcl-2 was downregulated in Group II. Treatment with 200 mg/kg bodyweight C-PC (Group III) transcriptionally regulated the instability of the expression of these genes, thus ensuring C-PC is a prospective anticataractogenic agent that probably delays the onset and progression of cataractogenesis induced by sodium selenite.

CONCLUSIONS

C-PC treatment possibly prevented cataractogenesis triggered by sodium selenite, by regulating the lens crystallin, redox genes, and apoptotic cascade mRNA expression and thus maintains lens transparency. C-PC may be developed as a potential antioxidant compound applied in the future to prevent and treat age-related cataract.

Lipid peroxidation: pathophysiological and pharmacological implications in the eye

Oxygen-derived free radicals such as hydroxyl and hydroperoxyl species have been shown to oxidize phospholipids and other membrane lipid components leading to lipid peroxidation. In the eye, lipid peroxidation has been reported to play an important role in degenerative ocular diseases (age-related macular degeneration, cataract, glaucoma, diabetic retinopathy). Indeed, ocular tissues are prone to damage from reactive oxygen species due to stress from constant exposure of the eye to sunlight, atmospheric oxygen and environmental chemicals. Furthermore, free radical catalyzed peroxidation of long chain polyunsaturated acids (LCPUFAs) such as arachidonic acid and docosahexaenoic acid leads to generation of LCPUFA metabolites including isoprostanes and neuroprostanes that may further exert pharmacological/toxicological actions in ocular tissues. Evidence from literature supports the presence of endogenous defense mechanisms against reactive oxygen species in the eye, thereby presenting new avenues for the prevention and treatment of ocular degeneration. Hydrogen peroxide (H2O2) and synthetic peroxides can exert pharmacological and toxicological effects on tissues of the anterior uvea of several mammalian species. There is evidence suggesting that the retina, especially retinal ganglion cells can exhibit unique characteristics of antioxidant defense mechanisms. In the posterior segment of the eye, H2O2 and synthetic peroxides produce an inhibitory action on glutamate release (using [(3)H]-D-aspartate as a marker), in vitro and on the endogenous glutamate and glycine concentrations in vivo. In addition to peroxides, isoprostanes can elicit both excitatory and inhibitory effects on norepinephrine (NE) release from sympathetic nerves in isolated mammalian iris ciliary bodies. Whereas isoprostanes attenuate dopamine release from mammalian neural retina, in vitro, these novel arachidonic acid metabolites exhibit a biphasic regulatory effect on glutamate release from retina and can regulate amino acid neurotransmitter metabolism without inducing cell death in the retina. Furthermore, there appears to be an inhibitory role for neuroprostanes in the release of excitatory amino acid neurotransmitters in mammalian retina. The ability of peroxides and metabolites of LCPUFA to alter the integrity of neurotransmitter pools provides new potential target sites and pathways for the treatment of degenerative ocular diseases.

Pyrrolidine dithiocarbamate augments Hg(2+)-mediated induction of macrophage cell death via oxidative stress-induced apoptosis and necrosis signaling pathways

Exposure to mercury can lead to several injuries in mammals, including immune system dysfunction, and pyrrolidine dithiocarbamate (PDTC), as a metal chelator and antioxidant, has been indicated to increase the cytotoxic effects of toxic metals. However, the toxicological effects and possible mechanisms of mercury in combination with PDTC are mostly unclear. In this study, we showed that PDTC dramatically increase the cytotoxic effect of HgCl(2) on cultured murine macrophages (RAW 264.7 cells). PDTC augmented HgCl(2)-induced cytotoxic effects by facilitating the entry of mercury into the cells. The Hg(2+)/PDTC complex significantly and rapidly increased the formation of reactive oxygen species (ROS) and decreased intracellular glutathione (GSH) levels in these cells. Flow cytometry analysis showed that the numbers of sub-G1 hypodiploid cells and annexin V-FITC binding cells increased after Hg(2+)/PDTC complex exposure, and several features of mitochondria-dependent apoptosis were also induced, including mitochondrial membrane depolarization, cytosolic cytochrome c release, poly(ADP-ribose) polymerase (PARP) and caspase 3/7 activation, and DNA fragmentation. Moreover, both apoptotic and necrotic cells were detected using acridine orange/ethidium bromide dual staining. Meanwhile, depleted intracellular ATP levels and increased lactate dehydrogenase (LDH) release were observed, suggesting the induction of necrotic cell death processes. These Hg(2+)/PDTC complex-induced cytotoxicity-related signals could be reversed by pretreatment with the antioxidant N-acetylcysteine. In conclusion, these results suggest that Hg(2+)/PDTC complex-induced oxidative stress causes macrophage cell death via both apoptosis and necrosis. These findings imply for the first time that PDTC dramatically increases the uptake and toxicological effects of Hg(2+) instead of detoxification.

ROS-induced ZNF580 expression: a key role for H2O2/NF-κB signaling pathway in vascular endothelial inflammation

ZNF580, a newly found C2H2 zinc finger transcription factor, was first described by Zhang (GenBank ID: AF184939). Emerging evidence has suggested that reactive oxygen species (ROS) play an important role in redox-sensitive signal transduction, and the vascular endothelium plays a critical role in the vascular inflammatory response. In this communication, we present evidence for the potential role of ZNF580 in hydrogen peroxide (H2O2)-regulated inflammation-related signaling pathways. In a human endothelial cell hybridoma line (EA.hy926), ZNF580 levels were markedly upregulated with H2O2 stimulation in different concentrations (0-400 μM) and at different time-points (0-6 h). H2O2 promoted the rapid translocation of p65 from the cytoplasm into the nucleus according to immunocytochemistry staining. In subsequent research, inhibition of NF-κB by pyrrolidine dithiocarbamate (PDTC, a selective chemical inhibitor of NF-κB) was shown to block the upregulated expression of ZNF580 that was induced by H2O2. Furthermore, transient transfection of ZNF580 resulted in an increase of the pro-inflammatory cytokine interleukin-8 (IL-8) 3.01±0.05 folds according to real-time RT-PCR and ELISA assays, which also showed significantly enhanced motility of human acute monocytic leukemia cells (THP-1). These results suggest that H2O2 upregulates the expression of ZNF580 via the NF-κB signaling pathway, and overexpression of ZNF580 plays a critical role in augmenting the release of pro-inflammatory cytokine IL-8.

Grape seed proanthocyanidin extract protects human lens epithelial cells from oxidative stress via reducing NF-кB and MAPK protein expression

PURPOSE

Oxidative damage induced by H₂O₂ treatment can irreversibly damage the lens epithelium, resulting in cell death and cataract. Grape seed extract (GSE) is a widely consumed dietary supplement that has the capability to scavenge oxidants and free radicals. GSE contain 70%-95% standardized proanthocyanidins. The study described herein investigated the protective effect of Grape seed proanthocyanidin extract (GSPE) on H₂O₂-induced oxidative stress in human lens epithelial B-3 (HLEB-3) cells and the possible molecular mechanism involved.

METHODS

HLE-B3 cells exposed to different doses of H₂O₂ were cultured with various concentrations of GSPE and subsequently monitored for cell viability by the 4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT) assay. The apoptosis rate and ROS generation were detected by flow cytometric analysis. Expression of NF-кB/P65 and mitogen activated protein kinase (MAPK) proteins were measured by western blot.

RESULTS

GSPE clearly reduced H₂O₂ induced cell apoptosis and reactive oxygen species (ROS) generation and protected HLEB-3 cells from H₂O₂ induced oxidative damage. GSPE depressed H₂O₂-induced activation and translocation of NF-кB/p65. GSPE also depressed H₂O₂-induced phosphorylation of the p38 and c-Jun N-terminal kinase (JNK) proteins of the MAPK family at various time points studied.

CONCLUSIONS

GSPE could be useful in attenuation of H₂O₂-induced oxidative stress and the activation of NF-кB and MAPK signaling in HLE-B3 cells, which suggests that GSPE has a potential protective effect against cataractogenesis.

Inhibitory activity of nuclear factor-kappaB potentiates cisplatin-induced apoptosis in A549 cells

Whether inhibiting the activity of nuclear factor (NF)-kappaB potentiates cisplatin-induced apoptosis in non-small cell lung cell line A549 cells was investigated. The recombinant plasmid pcDNA3.1 (+)/IkappaBalpha expressing IkappaBalpha was constructed. The in vitro cultured A549 cells were transfected with pcDNA3.1 (+)/IkappaBalpha alone, or pcDNA3.1 (+)/IkappaBalpha combined with cisplatin. The mitochondrial membrane potential (Deltapsim) was determined by rhodamine 123, the activity of caspase-3 was tested by colorimetric assay, and cell apoptosis was detected by flow cytometry with the annexin V /propidium iodide assay. The results showed that the activity of NF-kappaB in A549 cells was inhibited by transfecting pcDNA3.1(+)/IkappaBalpha. Transfection of pcDNA3.1(+)/IkappaBalpha alone did not promote apoptosis. Treatment of cisplatin alone had a little effect on cell apoptosis. Transfection of pcDNA3.1(+)/IkappaBalpha combined with cisplatin treatment significantly induced apoptosis of A549 cells. It was concluded that inhibiting the activity of NF-B potentiated cisplatin-induced apoptosis of A549 cells.

Antioxidant effects of green tea and its polyphenols on bladder cells

Genitourinary tract inflammation/ailments affect the quality of life and health of a large segment of society. In recent years, studies have demonstrated strong antioxidant effects of green tea and its associated polyphenols in inflammatory states. This in vitro study examined the antioxidant capabilities (and putative mechanisms of action) of green tea extract (GTE), polyphenon-60 (PP-60, 60% pure polyphenols), (-)-epicatechin-3-gallate (ECG) and (-)-epigallocatechin-3-gallate (EGCG) in normal/malignant human bladder cells following catechin treatment+/-1 mM H2O2 (oxidative agent). Cell viability, apoptosis and reactive oxygen species (ROS) formation were evaluated. Our results showed that H2O2 exposure significantly reduced normal (UROtsa) and high-grade (TCCSUP, T24) bladder cancer (BlCa) cell viability compared with control-treated cells (p<0.001). No affect on low-grade RT4 and SW780 BlCa cell viability was observed with exposure to H2O2. Compared to H2O2-treated UROtsa, treatment with PP-60, ECG and EGCG in the presence of H2O2 significantly improved UROtsa viability (p<0.01), with strongest effects evoked by ECG. Additionally, though not as effective as in UROtsa cells, viability of both high-grade TCCSUP and T24 BlCa cells, in comparison to H2O2-treated cells, was significantly improved (p<0.01) by treatment with PP-60, ECG, and EGCG in the presence of H2O2. Overall, our findings demonstrate that urothelium cell death via H2O2-induced oxidative stress is mediated, in part, through superoxide (O2-.;), and potentially, direct H2O2 mechanisms, suggesting that green tea polyphenols can protect against oxidative stress/damage and bladder cell death.