The level of intracellular glutathione is a key regulator for the induction of stress-activated signal transduction pathways including Jun N-terminal protein kinases and p38 kinase by alkylating agents

Biomimetic cytotoxicity control of select nitrogenous disinfection byproducts in water

Nitrogenous disinfection byproducts (N-DBPs) in water are carcinogenic, teratogenic, and mutagenic. In this work, we developed a biomimetic reduction approach based on the cysteine thiol that destructed the highly toxic, select nitrogenous haloacetamides (HAMs) and haloacetonitriles (HANs) while effectively controlling the cytotoxicity of the degradation products to serve as a basis for further technological applications (e.g. immobilized contact bed for terminal users). Mechanisms on toxicity control were elucidated. Results showed the degradation and cytotoxicity control of HAMs as more efficient than that of the HANs. The cytotoxicity of the chlorinated, brominated, and iodinated HAMs and HANs was reduced to 25 %- 0.25 % of the original after biomimetic reduction using a reasonable concentration ratio. Through a combination of thiol-specific reactivity, dehalogenation, and quantitative structure-activity relationship analyses, the major toxicity control mechanisms were found to be the reductive dehalogenation of the N-DBPs. The halogenated functional groups on the N-DBPs had a more pronounced effect than the amide and nitrile groups on the cytotoxicity and detoxification effect. Patterns of toxicity interaction variations with DBPs concentrations were identified to detect possible synergistic cytotoxicity interactions under various combinations of HAMs and HANs in the presence of the cysteine thiol. Results could benefit future N-DBPs control efforts.

The good Samaritan glutathione-S-transferase P1: An evolving relationship in nitric oxide metabolism mediated by the direct interactions between multiple effector molecules

Glutathione-S-transferases (GSTs) are phase II detoxification isozymes that conjugate glutathione (GSH) to xenobiotics and also suppress redox stress. It was suggested that GSTs have evolved not to enhance their GSH affinity, but to better interact with and metabolize cytotoxic nitric oxide (NO). The interactions between NO and GSTs involve their ability to bind and store NO as dinitrosyl-dithiol iron complexes (DNICs) within cells. Additionally, the association of GSTP1 with inducible nitric oxide synthase (iNOS) results in its inhibition. The function of NO in vasodilation together with studies associating GSTM1 or GSTT1 null genotypes with preeclampsia, additionally suggests an intriguing connection between NO and GSTs. Furthermore, suppression of c-Jun N-terminal kinase (JNK) activity occurs upon increased levels of GSTP1 or NO that decreases transcription of JNK target genes such as c-Jun and c-Fos, which inhibit apoptosis. This latter effect is mediated by the direct association of GSTs with MAPK proteins. GSTP1 can also inhibit nuclear factor kappa B (NF-κB) signaling through its interactions with IKKβ and Iκα, resulting in decreased iNOS expression and the stimulation of apoptosis. It can be suggested that the inhibitory activity of GSTP1 within the JNK and NF-κB pathways may be involved in crosstalk between survival and apoptosis pathways and modulating NO-mediated ROS generation. These studies highlight an innovative role of GSTs in NO metabolism through their interaction with multiple effector proteins, with GSTP1 functioning as a "good Samaritan" within each pathway to promote favorable cellular conditions and NO levels.

Influence of Asiatic acid on cell proliferation and DNA damage in vitro and in vivo systems

Asiatic acid (AA) is a triterpene with promising pharmacological activity. In the present study, in vitro and in vivo assays were conducted to understand the effect of AA on cell proliferation and genomic instability. AA was cytotoxic to human tumor cell lines (M059J, HeLa, and MCF-7), with IC₅₀ values ranging from 13.91 to 111.72 µM. In the case of M059J, AA exhibited selective cytotoxicity after 48 h of treatment (IC₅₀  = 24 µM), decreasing the percentage of cells in the G0/G1 phase, increasing the percentage of cells in the S phase, and inducing apoptosis. A significant increase in chromosomal damage was observed in V79 cell cultures treated with AA (40 µM), revealing genotoxic activity. In contrast, low concentrations (5, 10, and 20 µM) of AA significantly reduced the frequencies of micronuclei induced by the mutagens doxorubicin (DXR), methyl methanesulfonate, and hydrogen peroxide. A reduction of DXR-induced intracellular free radicals was found in V79 cells treated with AA (10 µM). The antigenotoxic effect of AA (30 mg/kg) was also observed against DXR-induced chromosomal damage in Swiss mice. Significant reductions in p53 levels were verified in the liver tissue of these animals. Taken together, the data indicate that AA exerted antiproliferative activity in M059J tumor cells, which is probably related to the induction of DNA damage, leading to cell cycle arrest and apoptosis. Additionally, low concentrations of AA exhibited antigenotoxic effects and its antioxidant activity may be responsible, at least in part, for chemoprevention.

In Situ Alkylation of Reconstructed Human Epidermis by Methyl Methanesulfonate: A Quantitative HRMAS NMR Chemical Reactivity Mapping

Allergic contact dermatitis (ACD) is a reaction of the immune system resulting from skin sensitization to an exogenous hazardous chemical and leading to the activation of antigen-specific T-lymphocytes. The adverse outcome pathway (AOP) for skin sensitization identified four key events (KEs) associated with the mechanisms of this pathology, the first one being the ability of skin chemical sensitizers to modify epidermal proteins to form antigenic structures that will further trigger the immune system. So far, these interactions have been studied in solution using model nucleophiles such as amino acids or peptides. As a part of our efforts to better understand chemistry taking place during the sensitization process, we have developed a method based on the use of high-resolution magic angle spinning (HRMAS) NMR to monitor in situ the reactions of ¹³C substituted chemical sensitizers with nucleophilic amino acids of epidermal proteins in reconstructed human epidermis. A quantitative approach, developed so far for liquid NMR applications, has not been developed to our knowledge in a context of a semisolid nonanisotropic environment like the epidermis. We now report a quantitative chemical reactivity mapping of methyl methanesulfonate (MMS), a sensitizing methylating agent, in reconstructed human epidermis by quantitative HRMAS (qHRMAS) NMR. First, the haptenation process appeared to be much faster in RHE than in solution with a maximum concentration of adducts reached between 4 and 8 h. Second, it was observed that the concentration of cysteine adducts did not significantly increase with the dose (2.07 nmol/mg at 0.4 M and 2.14 nmol/mg at 1 M) nor with the incubation time (maximum of 2.27 nmol/mg at 4 h) compared to other nucleophiles, indicating a fast reaction and a potential saturation of targets. Third, when increasing the exposure dose, we observed an increase of adducts up to 12.5 nmol/mg of RHE, excluding cysteine adducts, for 3112 μg/cm² (1 M solution) of (¹³C)MMS. This methodology applied to other skin sensitizers could allow for better understanding of the potential links between the amount of chemical modifications formed in the epidermis in relation to exposure and the sensitization potency.

Aurora A regulation by reversible cysteine oxidation reveals evolutionarily conserved redox control of Ser/Thr protein kinase activity

Reactive oxygen species (ROS) are physiological mediators of cellular signaling and play potentially damaging roles in human diseases. In this study, we found that the catalytic activity of the Ser/Thr kinase Aurora A was inhibited by the oxidation of a conserved cysteine residue (Cys290) that lies adjacent to Thr288, a critical phosphorylation site in the activation segment. Cys is present at the equivalent position in ~100 human Ser/Thr kinases, a residue that we found was important not only for the activity of human Aurora A but also for that of fission yeast MAPK-activated kinase (Srk1) and PKA (Pka1). Moreover, the presence of this conserved Cys predicted biochemical redox sensitivity among a cohort of human CAMK, AGC, and AGC-like kinases. Thus, we predict that redox modulation of the conserved Cys290 of Aurora A may be an underappreciated regulatory mechanism that is widespread in eukaryotic Ser/Thr kinases. Given the key biological roles of these enzymes, these findings have implications for understanding physiological and pathological responses to ROS and highlight the importance of protein kinase regulation through multivalent modification of the activation segment.

Glutathione transferase P silencing promotes neuronal differentiation of retinal R28 cells

Glutathione transferases (GSTs) play an important role in retinal pathophysiology. Within this family, the GSTP isoform is known as an endogenous regulator of cell survival and proliferation pathways and of cellular responses to oxidative stress. In the present study we silenced GSTP in R28 cells, a retinal precursor cell line with markers of both glial and neuronal origin, and obtained stable clones which were viable and, unexpectedly, characterized by a more neuronal phenotype. The degree of neuronal differentiation was inversely correlated with GSTP residual expression levels. The clone with the lowest expression of GSTP showed metabolic reprogramming, a more favorable redox status and, despite its neuronal phenotype, a sensitivity to glutamate and 4-hydroxynonenal toxicity comparable to that of control cells. Altogether, our evidence shows that near full depletion of GSTP in retinal precursor cells, triggers neuronal differentiation and prosurvival metabolic changes.

1,4-Benzoquinone antimicrobial agents against Staphylococcus aureus and Mycobacterium tuberculosis derived from scorpion venom

Two 1,4-benzoquinone derivatives, found in the venom of the scorpion Diplocentrus melici following exposure to air, have been isolated, characterized, synthesized, and assessed for antimicrobial activities. Initially a white, viscous liquid, the extracted venom colors within minutes under ambient conditions. From this colored mixture, two compounds, one red, the other blue, were isolated and purified using chromatography. After a variety of NMR and mass spectrometry experiments, the red compound was determined to be 3,5- dimethoxy-2-(methylthio)cyclohexa-2,5-diene-1,4-dione, and the blue compound was determined to be 5-methoxy-2,3- bis(methylthio)cyclohexa-2,5-diene-1,4-dione. Because extremely small amounts of these compounds were isolated from the scorpion venom, we developed laboratory syntheses from commercially available precursors, allowing us to produce sufficient quantities for crystallization and biological assays. The red benzoquinone is effective against Staphylococcus aureus [minimum inhibitory concentration (MIC) = 4 µg/mL], while the blue benzoquinone is active against Mycobacterium tuberculosis (MIC = 4 µg/mL) and even against a multidrug-resistant (MDR) strain with nearly equal effectiveness. The bactericidal effects of both benzoquinones show comparable activity to commercially available antibiotics used against these pathogens and were cytotoxic to neoplastic cell lines, suggesting their potential as lead compounds for the development of novel antimicrobial and anticancer drugs. Importantly, the blue benzoquinone was also effective in vivo with mouse models of MDR tuberculosis infection. After treatment for 2 mo, four mice with late-stage active MDR tuberculosis had a significant decrease in pulmonary bacillary loads and tissue damage. Healthy mice served as negative controls and tolerated treatment well, without adverse side effects.

Dose-dependent thiol and immune responses to ovalbumin challenge in Brown Norway rats

Dose-dependent specific antibody production, antigen-dependent pulmonary inflammation, and thiol changes in the lung and associated lymph nodes were examined in a Brown Norway rat model of pulmonary sensitization. Cysteine (CYSH), glutathione (GSH), and markers of inflammation in bronchoalveolar lavage fluid (BALF) were measured following ovalbumin (OVA) inhalation challenge. Alveolar macrophages (AM) and pulmonary-associated lymph node cells (LNC) were isolated and intracellular CYSH and GSH assessed. OVA-specific IgE and IgG antibodies were quantified from sera. A dose-dependent biphasic response was noted with respect to OVA-specific IgE. OVA-specific IgG concentrations were maximal at 68 mg (OVA)/m3. OVA challenge to sensitized rats induced increases in BALF albumin, total protein, lactate dehydrogenase, CYSH and GSH that were independent of serum antibody concentrations. AM thiols were modestly elevated at low OVA challenge doses, but sharply reduced at the higher OVA challenge doses. In contrast, both thiols were dose dependently elevated in BALF. CYSH, but not GSH, was elevated in LNC of OVA challenged rats. In summary, antigen exposure caused a dose-dependent alteration of inflammatory, thiol and immune parameters in OVA sensitized and challenged rats. Changes in thiol levels did not correlate with antibody responses. While the results of the present study do not support a functional role for thiols in the immune response, it is important to note the dose-dependent dramatic alteration seen in thiols following sensitization and challenge.

Sublinear response in lacZ mutant frequency of Muta™ Mouse spermatogonial stem cells after low dose subchronic exposure to N-ethyl-N-nitrosourea

The transgenic rodent mutation assay was used to compare the dose-response relationship of lacZ mutant frequency (MF) in spermatogonial stem cells exposed acutely or subchronically to N-ethyl-N-nitrosourea (ENU). Muta(™) Mouse males were exposed orally to 0, 25, 50, or 100 mg/kg ENU for acute exposures and 0, 1, 2, or 5 mg/(kg day) for 28-day subchronic exposures. LacZ MF was measured in sperm collected 70 days post-exposure to target spermatogonial stem cells. Dose-response data were fit to linear, quadratic, exponential, or power models. Acute exposure resulted in a dose-dependent increase in MF that was significant (P < 0.05) at all doses tested and was best described by a quadratic dose-response model that was linear in the low dose range. In contrast, similar total doses fragmented over a 28-day subchronic exposure only resulted in a significant increase in lacZ MF at the highest dose tested. Therefore, the subchronic no observable genotoxic effect level (NOGEL) was 2 mg/(kg day) (or 56 mg/kg total dose). The subchronic dose-response was best described by the exponential and power models, which were sublinear in the low dose range. Benchmark dose lower confidence limits (BMDLs) for acute and subchronic exposure were 3.0 and 1.0 mg/(kg day) (or 27.4 mg/kg total dose), respectively. These findings are supportive of a saturable DNA repair mechanism as the mutagenic mode of action for ENU in spermatogonia and imply that sufficiently low exposures would not cause appreciable genotoxic effects over background. This may have important implications for the quantitative risk assessment of germ cell mutagens.

Ionizing radiation affects the expression of Toll-like receptors 2 and 4 in human monocytic cells through c-Jun N-terminal kinase activation

Pattern recognition receptors recognize pathogen-associated molecular patterns. Among these, Toll-like receptors (TLRs) have well-characterized roles in antibacterial and antiviral immunity. In the present study, the effects of ionizing radiation on the expression of TLRs and cellular responses to ligands were investigated in THP1 monocytes (human monocytic leukemia cells) and THP1-derived macrophage cells (macrophage-like cells), which are induced by culturing in the presence of phorbol 12-myristate 13-acetate. TLR2 and TLR4 expression was detected in THP1 and macrophage-like cells. X-irradiation caused increased expression of these TLRs in THP1 and decreased expression in macrophage-like cells. Responses to FSL-1 (TLR2 ligand) and lipopolysaccharide (LPS, TLR4 ligand) were estimated by determining the induction of tumor necrosis factor-α (TNF-α). After FSL-1 or LPS stimulation, TNF-α induction was greater in X-irradiated THP1 monocytes than in non-irradiated cells. However, although TNF-α expression was not affected by X-irradiation in macrophage-like cells, the expression of LPS-inducible interferon-β was lower following X-irradiation of macrophage-like cells. To clarify the mechanisms of TLR2 and TLR4 regulation by X-irradiation, expression of mitogen-activated protein kinase was investigated. These experiments showed that c-Jun N-terminal kinase (JNK) mediated increases in TLR expression in X-irradiated THP1 monocytes and decreases in TLR expression in X-irradiated macrophage-like cells. This study demonstrates that ionizing radiation modulates ligand-responsive TLR expression through the JNK pathway, depending on differentiation state.

Energy adaptive response during parthanatos is enhanced by PD98059 and involves mitochondrial function but not autophagy induction

Parthanatos is a programmed necrotic demise characteristic of ATP (adenosine triphosphate) consumption due to NAD+ (nicotinamide adenine dinucleotide) depletion by poly(ADP-ribose) polymerase 1 (PARP1)-dependent poly(ADP-ribosyl)ation on target proteins. However, how the bioenergetics is adaptively regulated during parthanatos, especially under the condition of macroautophagy deficiency, remains poorly characterized. Here, we demonstrated that the parthanatic inducer N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) triggered ATP depletion followed by recovery in mouse embryonic fibroblasts (MEFs). Notably, Atg5-/- MEFs showed great susceptibility to MNNG with disabled ATP-producing capacity. Moreover, the differential energy-adaptive responses in wild-type (WT) and Atg5-/- MEFs were unequivocally worsened by inhibition ofAMP-activated protein kinase (AMPK), sirtuin 1 (SIRT1), and mitochondrial activity. Importantly, Atg5-/- MEFs disclosed diminished SIRT1 and mitochondrial activity essential to the energy restoration during parthanatos. Strikingly, however, parthanatos cannot be exasperated by bafilomycin A1 and MNNG neither provokes microtubule-associated protein 1A/1B-light chain 3 (LC3) lipidation and p62 elimination, suggesting that parthanatos does not induce autophagic flux. Intriguingly, we reported unexpectedly that PD98059, even at low concentration insufficient to inhibit MEK, can promote mitochondrial activity and facilitate energy-restoring process during parthanatos, without modulating DNA damage responses as evidenced by PARP1 activity, p53 expression, and gammaH2AX (H2A histone family, member X (H2AX), phosphorylated on Serine 139) induction. Therefore, we propose that Atg5 deficiency confers an infirmity to overcome the energy crisis during parthanatos and further underscore the deficits in mitochondrial quality control, but not incapability of autophagy induction, that explain the vulnerability in Atg5-deficient cells. Collectively, our results provide a comprehensive energy perspective for an improved treatment to alleviate parthanatos-related tissue necrosis and disease progression and also provide a future direction for drug development on the basis of PD98059 as an efficacious compound against parthanatos.

Assessment of the genotoxic effects of organophosphorus insecticides phorate and trichlorfon in human lymphocytes

In vitro genotoxic effects of organophosphorus insecticides Phorate (PHR) and Trichlorfon (TCF) were investigated using four genotoxicity endpoints. Different concentration ranges between 0.25-2.00 μg mL(-1) of PHR and 2.34-37.50 μg mL(-1) of TCF were applied to lymphocytes. PHR and TCF significantly increased the frequency of chromosomal aberrations (except 2.34 μg mL(-1) for TCF) and sister chromatid exchanges at all treatment times and concentrations. Most of the used concentrations induced a significant increase in the frequency of micronuclei. Furthermore, PHR and TCF significantly decreased the mitotic index at the higher concentrations after 24- and 48-h treatments. In the comet assay, PHR and TCF significantly increased the comet tail at all concentrations. However, the comet tail intensity was significantly increased at only the highest concentration of PHR and at all concentrations of TCF. According to these results, PHR and TCF possess clastogenic, mutagenic, and DNA damaging effects in human lymphocytes in vitro.

S-glutathionylation: relevance in diabetes and potential role as a biomarker

Glutathione is considered the main regulator of redox balance in the cellular milieu due to its capacity for detoxifying deleterious molecules. The oxidative stress induced as a result of a variety of stimuli promotes protein oxidation, usually at cysteine residues, leading to changes in their activity. Mild oxidative stress, which may take place in physiological conditions, induces the reversible oxidation of cysteines to sulfenic acid form, while pathological conditions are associated with higher rates of reactive oxygen species production, inducing the irreversible oxidation of cysteines. Among these, neurodegenerative disorders, cardiovascular diseases and diabetes have been proposed to be pathogenetically linked to this state. In diabetes-associated vascular complications, lower levels of glutathione and increased oxidative stress have been reported. S-glutathionylation has been proposed as a posttranslational modification able to protect proteins from over-oxidizing environments. S-glutathionylation has been identified in proteins involved in diabetic models both in vitro and in vivo. In all of them, S-glutathionylation represents a mechanism that regulates the response to diabetic conditions, and has been described to occur in erythrocytes and neutrophils from diabetic patients. However, additional studies are necessary to discern whether this modification represents a biomarker for the early onset of diabetic vascular complications.

Cellular stress response and innate immune signaling: integrating pathways in host defense and inflammation

Extensive research in the past decade has identified innate immune recognition receptors and intracellular signaling pathways that culminate in inflammatory responses. Besides its role in cytoprotection, the importance of cell stress in inflammation and host defense against pathogens is emerging. Recent studies have shown that proteins in cellular stress responses, including the heat shock response, ER stress response, and DNA damage response, interact with and regulate signaling intermediates involved in the activation of innate and adaptive immune responses. The effect of such regulation by cell stress proteins may dictate the inflammatory profile of the immune response during infection and disease. In this review, we describe the regulation of innate immune cell activation by cell stress pathways, present detailed descriptions of the types of stress response proteins and their crosstalk with immune signaling intermediates that are essential in host defense, and illustrate the relevance of these interactions in diseases characteristic of aberrant immune responses, such as chronic inflammatory diseases, autoimmune disorders, and cancer. Understanding the crosstalk between cellular stress proteins and immune signaling may have translational implications for designing more effective regimens to treat immune disorders.

Connexin43 hemichannel-mediated regulation of connexin43

Background

Many signaling molecules and pathways that regulate gap junctions (GJs) protein expression and function are, in fact, also controlled by GJs. We, therefore, speculated an existence of the GJ channel-mediated self-regulation of GJs. Using a cell culture model in which nonjunctional connexin43 (Cx43) hemichannels were activated by cadmium (Cd²⁺), we tested this hypothesis.

Principal Findings

Incubation of Cx43-transfected LLC-PK1 cells with Cd²⁺ led to an increased expression of Cx43. This effect of Cd²⁺ was tightly associated with JNK activation. Inhibition of JNK abolished the elevation of Cx43. Further analysis revealed that the changes of JNK and Cx43 were controlled by GSH. Supplement of a membrane-permeable GSH analogue GSH ethyl ester or GSH precursor N-acetyl-cystein abrogated the effects of Cd²⁺ on JNK activation and Cx43 expression. Indeed, Cd²⁺ induced extracellular release of GSH. Blockade of Cx43 hemichannels with heptanol or Cx43 mimetic peptide Gap26 to prevent the efflux of GSH significantly attenuated the Cx43-elevating effects of Cd²⁺.

Conclusions

Collectively, our results thus indicate that Cd²⁺-induced upregulation of Cx43 is through activation of nonjunctional Cx43 hemichannels. Our findings thus support the existence of a hemichannel-mediated self-regulation of Cx43 and provide novel insights into the molecular mechanisms of Cx43 expression and function.

The role of metal coordination complexes in cytosolic cellular defense

The metal coordination complexes are known to induce cytotoxic effects on various cell lines and shown to have great potential for therapeutic interventions. Their main mechanism of action is through the mediation of enzyme activities in signaling pathways essential for cellular functioning. The overall cellular responses are dose-dependent and require high exposure levels and duration to overcome cellular defense against external toxicants. However, their effect through signal transduction components is limited due to the conferred drug resistance associated with glutathione transferase (GST)-mediated mechanisms. The GST family of enzymes is not only related to anticancer drug resistance, but also associated with cancer development where they may also contribute kinase signaling events including non-receptor protein tyrosine kinase (PTK)-related pathways. In the current study, we evaluated the effect of symmetrical and mononuclear complexes of Pd(II), Pt(II), and Ni(II) with organic ligands on cytosolic targets involved in glutathione utilization, antioxidant defense, and kinase signaling by virtue of acellular in vitro analyses.

Protein-thiol oxidation and cell death: regulatory role of glutaredoxins

SIGNIFICANCE

Glutaredoxin (Grx) is the primary enzyme responsible for catalysis of deglutathionylation of protein-mixed disulfides with glutathione (GSH) (protein-SSG). This reversible post-translational modification alters the activity and function of many proteins important in regulation of critical cellular processes. Aberrant regulation of protein glutathionylation/deglutathionylation reactions due to changes in Grx activity can disrupt both apoptotic and survival signaling pathways.

RECENT ADVANCES

Grx is known to regulate the activity of many proteins through reversible glutathionylation, such as Ras, Fas, ASK1, NFκB, and procaspase-3, all of which play important roles in control of apoptosis. Reactive oxygen species and/or reactive nitrogen species mediate oxidative modifications of critical Cys residues on these apoptotic mediators, facilitating protein-SSG formation and thereby altering protein function and apoptotic signaling.

CRITICAL ISSUES

Much of what is known about the regulation of apoptotic mediators by Grx and reversible glutathionylation has been gleaned from in vitro studies of discrete apoptotic pathways. To relate these results to events in vivo it is important to examine changes in protein-SSG status in situ under natural cellular conditions, maintaining relevant GSH:GSSG ratios and using appropriate inducers of apoptosis.

FUTURE DIRECTIONS

Apoptosis is a highly complex, tightly regulated process involving many different checks and balances. The influence of Grx activity on the interconnectivity among these various pathways remains unknown. Knowledge of the effects of Grx is essential for developing novel therapeutic approaches for treating diseases involving dysregulated apoptosis, such as cancer, heart disease, diabetes, and neurodegenerative diseases, where alterations in redox homeostasis are hallmarks for pathogenesis.

Mitochondrial HSP70 cognate-mediated differential expression of JNK1/2 in the pollution stressed grey mullets, Mugil cephalus

Cells have evolved different networks of cellular stress responses to adapt during environmental changes and survive combating wide variety of stress. Mitochondrial heat shock protein 70 (mtHSP70) are essential for maintaining cellular homeostasis. c-Jun-N terminal kinase (JNK), a subfamily of MAPK, plays a key role in the transmission of extracellular signal for survival and death. In the present investigation, the differential expression of phosphorylated JNK1/2 with corresponding increases in heat shock transcription factor-1 (HSF-1) under high levels of B-cell lymphoma 2 (Bcl-2), HSP70 transcripts (twofold) and mtHSP70 has been correlated with fish survival in polluted Ennore estuary. This study suggests that in Ennore sample, the amplification in HSP70 transcripts along with corresponding mtHSP70 overexpression might be due to activation of JNK1/2 and HSF-1. This would influence the expression of Bcl-2 protein involved in mitochondrial survival under pollution-stressed condition.

Comparative genomics of duplicate γ-glutamyl transferase genes in teleosts: medaka (Oryzias latipes), stickleback (Gasterosteus aculeatus), green spotted pufferfish (Tetraodon nigroviridis), fugu (Takifugu rubripes), and zebrafish (Danio rerio)

The availability of multiple teleost (bony fish) genomes is providing unprecedented opportunities to understand the diversity and function of gene duplication events using comparative genomics. Here we examine multiple paralogous genes of γ-glutamyl transferase (GGT) in several distantly related teleost species including medaka, stickleback, green spotted pufferfish, fugu, and zebrafish. Through mining genome databases, we have identified multiple GGT orthologs. Duplicate (paralogous) GGT sequences for GGT1 (GGT1 a and b), GGTL1 (GGTL1 a and b), and GGTL3 (GGTL3 a and b) were identified for each species. Phylogenetic analysis suggests that GGTs are ancient proteins conserved across most metazoan phyla and those paralogous GGTs in teleosts likely arose from the serial 3R genome duplication events. A third GGTL1 gene (GGTL1c) was found in green spotted pufferfish; however, this gene is not present in medaka, stickleback, or fugu. Similarly, one or both paralogs of GGTL3 appear to have been lost in green spotted pufferfish, fugu, and zebrafish. Syntenic relationships were highly maintained between duplicated teleost chromosomes, among teleosts and across ray-finned (Actinopterygii) and lobe-finned (Sarcopterygii) species. To assess subfunction partitioning, six medaka GGT genes were cloned and assessed for developmental and tissue-specific expression. On the basis of these data, we propose a modification of the "duplication-degeneration-complementation" model of subfunction partitioning where quantitative differences rather than absolute differences in gene expression are observed between gene paralogs. Our results demonstrate that multiple GGT genes have been retained within teleost genomes. Questions remain, however, regarding the functional roles of multiple GGTs in these species.

Immunomodulatory and immunotoxic effects of bilirubin: molecular mechanisms

The immunomodulatory and immunotoxic effects of purified UCB have not been evaluated previously at clinically relevant UCB concentrations and UCB:BSA ratios. To delineate the molecular mechanism of UCB-induced immunomodulation, immune cells were exposed to clinically relevant concentrations of UCB. It inhibited LPS-induced B cell proliferation and cytokine production from splenic macrophages. UCB (≥25 μM) was toxic to unfractionated splenocytes, splenic T cells, B cells, macrophages, LPS-stimulated CD19(+) B cells, human PBMCs, and RBCs. Purified UCB also was found to be toxic to splenocytes and human PBMCs. UCB induced necrosis and apoptosis in splenocytes. UCB activated the extrinsic and intrinsic pathways of apoptosis, as reflected by the markers, such as CD95, caspase-8, Bax, MMP, cytoplasmic Ca(+2), caspase-3, and DNA fragmentation. UCB depleted GSH and activated p38MAPK. NAC, caspase inhibitors, and p38MAPK inhibitor attenuated the UCB-induced apoptosis. In vivo administration of ≥25 mg/kbw UCB induced atrophy of spleen, depletion of bone marrow cells, and leukopenia and decreased lymphocyte count and the T and B cell response to mitogens. UCB administration to mice led to induction of oxidative stress, activation of p38MAPK, and cell death in splenocytes. These parameters were attenuated by the injection of NAC and the p38MAPK inhibitor. Our results demonstrate for the first time that clinically relevant concentrations of UCB induce apoptosis and necrosis in immune cells by depleting cellular GSH. These findings should prove useful in understanding the immunosuppression associated with hyperbilirubinemia.

Fibroblasts from long-lived bird species are resistant to multiple forms of stress

Evolutionary senescence theory postulates that aging results from the declining force of natural selection with increasing chronological age. A goal of comparative studies in the biology of aging is to identify genetic and biochemical mechanism(s) driving species-specific differences in the aging process that are the end product of life history trade-offs. We hypothesized that cells from long-lived bird species are more resistant to stress agents than are cells from short-lived species, and that cells from birds are more resistant to stress than are cells from relatively short-lived mammals of similar size. We tested primary fibroblast cultures from 35 species of free-living birds for their resistance to multiple forms of cellular stress and found that cell lines from longer-lived species were resistant to death caused by cadmium (R(2)=0.27, P=0.002), paraquat (R(2)=0.13, P=0.03), hydrogen peroxide (R(2)=0.09, P=0.07) and methyl methanesulfonate (R(2)=0.13, P=0.03), as well as to the metabolic inhibition seen in low-glucose medium (R(2)=0.37, P<0.01). They did not differ in their resistance to UV radiation, or to thapsigargin or tunicamycin, inducers of the unfolded protein response. These results were largely consistent even after accounting for the influence of body mass and phylogeny. Cell lines from longer-lived bird species also proliferate more rapidly than cells from short-lived birds, although there was no relationship between proliferation and stress resistance. Finally, avian fibroblasts were significantly more resistant than rodent fibroblasts to each of the tested stressors. These results support the idea that cellular resistance to injury may be an important contributor to the evolution of slow aging and long lifespan among bird species, and may contribute to the relatively long lifespan of birds compared with rodents of the same body size.

Sensitive DsRed fluorescence-based reporter cell systems for genotoxicity and oxidative stress assessment

Various in vitro test systems have been developed for genotoxic risk assessment in early drug development. However, these genotoxicity tests often show limited specificity, and provide limited insights into the mode of toxicity of the tested compounds. To identify genes that could serve as specific biomarkers for genotoxicity or oxidative stress, we exposed mouse embryonic stem (ES) cells to various genotoxic and oxidative stress-inducing compounds and performed genome-wide expression profiling. Differentially expressed genes were classified based on the fold-change of expression and their specificity for either genotoxic or oxidative stress. Promoter regions of four selected genes (Ephx1, Btg2, Cbr3 and Perp) were fused to a DsRed fluorescent reporter gene and stably integrated in mouse ES cells. Established stable reporter cell lines displayed significant induction of DsRed expression upon exposure to different classes of genotoxic and oxidative stress-inducing compounds. In contrast, exposure to non-genotoxic carcinogenic compounds did not induce DsRed expression even at cytotoxic doses. Expression of the Cbr3-DsRed reporter was more responsive to compounds that induce oxidative stress while the other three DsRed reporters reacted more specific to direct-acting genotoxic agents. Therefore, the differential response of the Btg2- and Cbr3-DsRed reporters can serve as indicator for the main action mechanism of genotoxic and oxidative stress-inducing compounds. In addition, we provide evidence that inhibition of DNA replication results in preferential activation of the Btg2-DsRed genotoxicity reporter. In conclusion, we have generated sensitive mouse ES cell reporter systems that allow detection of genotoxic and oxidative stress-inducing properties of chemical compounds and can be used in high-throughput assays.

Late activation of stress-activated protein kinases/c-Jun N-terminal kinases triggered by cisplatin-induced DNA damage in repair-defective cells

Although stress-activated protein kinases/c-Jun N-terminal kinases (SAPK/JNK) are rapidly activated by genotoxins, the role of DNA damage in this response is not well defined. Here we show that the SEK1/MKK4-mediated dual phosphorylation of SAPK/JNK (Thr-183/Tyr-185) correlates with the level of cisplatin-DNA adducts at late times (16-24 h) after drug treatment in both human and mouse cells. Transfection of platinated plasmid DNA also caused SAPK/JNK activation. A defect in transcription-coupled nucleotide excision repair resting on a mutation in Cockayne syndrome group B protein promoted the late SAPK/JNK activation following cisplatin exposure. Signaling to SAPK/JNK was accompanied by activation of Ataxia telangiectasia mutated- and Rad3-related kinase, replication protein A, and checkpoint kinases as well as by the formation of DNA double strand breaks (DSBs). Ionizing radiation-induced DSBs did not provoke SAPK/JNK activation, and inhibition of transcription also failed to provoke this response. Late activation of SAPK/JNK stimulated by cisplatin-induced DNA lesions was reduced in the absence of specific DNA repair proteins, such as xeroderma pigmentosum protein C, pointing to an essential function of individual repair factors in DNA damage signaling to SAPK/JNK. Collectively, the data indicate that late SAPK/JNK activation is triggered by non-repaired cisplatin adducts in transcribed genes and involves replication-associated events, DSBs, tyrosine kinases, Rho GTPases, and specific repair factors.

Methylguanidine cytotoxicity on HK-2 cells and protective effect of antioxidants against MG-induced apoptosis in renal proximal tubular cells in vitro

Methylguanidine (MG), a small molecule among guanidine compounds, is a product of protein catabolism. The concentration of MG in the serum of uremic patients is nearly 80 times of that in the serum of normal people. The present study was designed to explore the toxic effect of MG on renal proximal tubular cells as well as the protective effect of antioxidants PGE1 and probucol against MG-induced apoptosis in renal proximal tubular cells. HK-2 cells were used as the subject. The cell viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. N-Acetyl-3-D-glucosaminidase (NAG) activity, malondialdehyde (MDA) content, and superoxide dismutase (SOD) activity were determined. Cell apoptosis was determined by flow cytometry (light scatter and propidium iodide/annexin V-FTC fluorescence) and by nuclear staining with Hoechst 33258. Cells were exposed to MG (0.25, 0.5, or 1 mmol/L), MG (0.5 mmol/L) + PGE1 (2 microg/L), and MG (0.5 mmol/L) + probucol (20 micromol/L) respectively for 24 h. MG induced a significant dose-dependent loss of cell viability. Both PGE1 and probucol improved the viability of MG-treated HK-2 cells. Cells showed apoptotic morphology (deepened stain, karyopyknosis, and apoptotic body) when exposed to 0.5 mmol/L MG for 24 h, and the apoptosis ratio was increased compared with the control. The presence of PGE1 or probucol significantly lowered the apoptotic ratio. Moreover, PGE1 or probucol notably decreased the MDA content and increased the SOD activity compared with when the cells were treated with MG only. The results of the present study clearly demonstrate that MG could promote apoptosis of renal proximal tubular cells in vitro. Both PGE1 and probucol could protect renal proximal tubular cells from MG-induced apoptosis.

Kaempferol suppresses cisplatin-induced apoptosis via inductions of heme oxygenase-1 and glutamate-cysteine ligase catalytic subunit in HEI-OC1 cell

PURPOSE

The present study was undertaken to elucidate the chemoprotective mechanism of kaempferol, which possesses anti-oxidative and anti-apoptotic properties.

METHODS

House Ear Institute-Organ of Corti 1 (HEI-OC1) cells were treated with kaempferol in the presence or absence of cisplatin. Cisplatin-induced oxidative stress was assessed by analysis of Comet assay, DNA-laddering assay and activation of caspases. Heme oxygenase-1 (HO-1), mitogen-activated protein kinase (MAPK) pathway and nuclear factor-E2-related factor 2 (Nrf2) were measured by Western blot analysis. Transfection of small interfering RNAs (siRNA), glutathione (GSH) assay and RT-PCR were performed in this study.

RESULTS

Kaempferol protected cells against cisplatin-induced apoptosis in a dose-dependent manner in HEI-OC1 cells. Kaempferol-induced HO-1 expression protected against cell death though the c-Jun N-terminal kinase (JNK) pathway and by the aid of Nrf2 translocation. Kaempferol increased the cellular level of GSH and the expression of GCLC time-dependently. siRNA GCLC blocked the increase of GSH level by kaempferol and the protective effect of kaempferol against cisplatin-induced cell death.

CONCLUSION

The expression of HO-1 by kaempferol inhibits cisplatin-induced apoptosis in HEI-OC1 cells, and the mechanism of protective effect is also associated with its inductive effect of GCLC expression.

Solar radiation induced skin damage: review of protective and preventive options

PURPOSE

Solar energy has a number of short- and long-term detrimental effects on skin that can result in several skin disorders. The aim of this review is to summarise current knowledge on endogenous systems within the skin for protection from solar radiation and present research findings to date, on the exogenous options for such skin photoprotection.

RESULTS

Endogenous systems for protection from solar radiation include melanin synthesis, epidermal thickening and an antioxidant network. Existing lesions are eliminated via repair mechanisms. Cells with irreparable damage undergo apoptosis. Excessive and chronic sun exposure however can overwhelm these mechanisms leading to photoaging and the development of cutaneous malignancies. Therefore exogenous means are a necessity. Exogenous protection includes sun avoidance, use of photoprotective clothing and sufficient application of broad-spectrum sunscreens as presently the best way to protect the skin. However other strategies that may enhance currently used means of protection are being investigated. These are often based on the endogenous protective response to solar light such as compounds that stimulate pigmentation, antioxidant enzymes, DNA repair enzymes, non-enzymatic antioxidants.

CONCLUSION

More research is needed to confirm the effectiveness of new alternatives to photoprotection such as use of DNA repair and antioxidant enzymes and plant polyphenols and to find an efficient way for their delivery to the skin. New approaches to the prevention of skin damage are important especially for specific groups of people such as (young) children, photosensitive people and patients on immunosuppressive therapy. Changes in public awareness on the subject too must be made.

Curcuminoids activate p38 MAP kinases and promote UVB-dependent signalling in keratinocytes

Curcuminoids exhibit anti-proliferative properties in many cell lines by modulating signalling pathways to inhibit cell growth. However, the specific effects of curcuminoids on human keratinocytes are not well defined, and this situation impairs mechanistic thinking regarding potential therapeutic uses. We hypothesized that curcuminoids would modulate key growth regulatory pathways in keratinocytes to inhibit cell proliferation. To test this hypothesis, the effects of curcumin and tetrahydrocurcumin (THC) on mitogen-activated protein (MAP) kinase signalling in keratinoctyes were determined. Primary human keratinocytes treated with curcumin or THC demonstrated decreased activation of p44/42 MAP kinases but increased levels of activated p38 MAP kinases. These data suggest that curcuminoids specifically activate stress-induced MAP kinases while inhibiting mitogen-induced MAP kinases. Curcuminoids also promote the phosphorylation of p53 on serine 15 in a dose-dependent and p38-dependent manner, suggesting that these compounds may activate p53. The effects of curcuminoids on keratinocytes mirrored some aspects of UVB and could be inhibited by N-acetylcysteine, suggesting that these compounds activate p38 through a mechanism that involves glutathione depletion. Both curcuminoids induced G2/M block and inhibited keratinocyte growth, and THC increased cellular levels of p21, a known p53 transcriptional target. These data demonstrate that curcuminoids can differentially regulate MAP kinases to inhibit keratinocyte growth while inducing p21. Curcuminoids also synergize with UVB to enhance p53 phosphorylation. The findings provide a rationale for testing curcuminoids in disorders associated with impaired p53 function or in which UVB-treatment is efficacious.

IL-8 production by macrophages is synergistically enhanced when cigarette smoke is combined with TNF-alpha

Macrophages are key inflammatory cells in chronic obstructive pulmonary disease (COPD). The pathophysiology of cigarette smoke-induced lung emphysema is complex but there is a clear role for reactive oxygen species (ROS, such as peroxynitrite), tumor necrosis factor (TNF-alpha) and interleukin (IL)-8. We investigated whether TNF-alpha or cigarette smoke medium (CSM) alone or in combination induces the production of IL-8 by human macrophages or monocyte lymphoma U937. CSM and TNF-alpha induce a dose- and time-dependent increase in IL-8 production. Interestingly, when sub-threshold concentrations of CSM and TNF-alpha were co-incubated, a 1500% increase in IL-8 production was observed compared to either of the compounds alone. Similar results were obtained with TNF-alpha and the peroxynitrite donor SIN-1. Moreover, the overproduction of IL-8 was associated with an enhanced increase in the translocation of NF-kappaB and an enhanced decrease in glutathione levels. Preincubation of the cells with antioxidants, such as N-acetyl-L-cysteine (NAC), prevented the overproduction of IL-8 and activation of NF-kappaB. In conclusion, CSM exposure of macrophages up-regulates the expression and the production of IL-8 via reactive oxygen species and NF-kappaB activation. Moreover, CSM dramatically enhances the production of IL-8 in combination with TNF-alpha. Based upon the strong synergistic action, a combination therapy directed against ROS and TNF-alpha could be a new approach to stop the progression in lung damage during emphysema.

Prunella vulgaris extract and rosmarinic acid suppress lipopolysaccharide-induced alteration in human gingival fibroblasts

Periodontitis is a chronic disease associated with inflammation of the tooth-supporting tissues. The inflammation is initiated by a group of gram-negative anaerobic bacteria. These express a number of irritating factors including a lipopolysaccharide (LPS), which plays a key role in periodontal disease development. Plant extracts with anti-inflammatory and anti-microbial properties have been shown to inhibit bacterial plaque formation and thus prevent chronic gingivitis. In this study we tested effects of Prunella vulgaris L. extract (PVE; 5, 10, 25microg/ml) and its component rosmarinic acid (RA; 1microg/ml) on LPS-induced oxidative damage and inflammation in human gingival fibroblasts. PVE and RA reduced reactive oxygen species (ROS) production, intracellular glutathione (GSH) depletion as well as lipid peroxidation in LPS-treated cells. Treatment with PVE and RA also inhibited LPS-induced up-regulation of interleukin 1beta (IL-1beta), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and suppressed expression of inducible nitric oxide synthase (iNOS). The results indicate that PVE and RA are able to suppress LPS-induced biological changes in gingival fibroblasts. The effects of PVE and RA are presumably linked to their anti-inflammatory activities and thus use of PVE and RA may be relevant in modulating the inflammation process, including periodontal disease.

Comparison of gene expression profiles in HepG2 cells exposed to arsenic, cadmium, nickel, and three model carcinogens for investigating the mechanisms of metal carcinogenesis

Carcinogenesis is an important chronic toxicity of metals and metalloids, although their mechanisms of action are still unclear. Comparison of gene expression patterns induced by carcinogenic metals, metalloids, and model carcinogens would give an insight into understanding of their carcinogenic mechanisms. In this study, we examined the gene expression alteration in human hepatoma cell line, HepG2, after exposing to two metals (cadmium and nickel), a metalloid (arsenic), and three model carcinogenic chemicals N-dimethylnitrosoamine (DMN), 12-O-tetradecanoylphorbol-13-acetate (TPA), and tetrachloroethylene (TCE) using DNA microarrays with 8,795 human genes. Of the genes altered by As, Cd, and Ni exposures, 31-55% were overlapped with those altered by three model carcinogenic chemical exposures in our experiments. In particular, the metals and metalloid shared certain characteristics with TPA and TCE in remarkable upregulations of the genes associated with progression of cell cycle, which might play a central role in As, Cd, and Ni carcinogenesis. This characteristic of gene expression alteration was partially counteracted by intracellular accumulation of vitamin C in As-exposed cells, whereas the number of cell-cycle associated genes was increased in Cd- and Ni-exposed cells. In our experimental conditions, ROS might have an accelerative effect on the cell proliferation mechanisms of As, but have an inhibitory effect on those of other two heavy metals. Furthermore, based on the results of Q-PCR, the oncogene PTTG1, which was upregulated by all carcinogenic chemical exposures in the array experiments, might be a useful biomarker for evaluation of the carcinogenesis of inorganic carcinogens.

DNA replication arrest in response to genotoxic stress provokes early activation of stress-activated protein kinases (SAPK/JNK)

The impact of DNA damage-induced replication blockage for early activation of stress kinases [stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK)] is largely unknown. Here, we show that induction of dual phosphorylation of SAPK/JNK by the DNA polymerase inhibitor aphidicolin was not ameliorated by additional exposure to ultraviolet (UV) light, indicating that overlapping mechanisms participate in signaling to SAPK/JNK triggered by both agents. UV-induced DNA replication blockage, cyclobutane pyrimidine dimer formation and DNA strand break induction coincided with SAPK/JNK phosphorylation at early (< or =30 min) but not late (> or =2 h) time points after exposure. Genotoxin-stimulated SAPK/JNK activation was attenuated in nonproliferating cells, indicating that S phase-dependent mechanisms are involved in signaling to SAPK/JNK. Correspondingly, UV-induced phosphorylation of SAPK/JNK was higher in S-phase cells as compared with G(1)-phase cells. Activation of SAPK/JNK by genotoxins was below detection limit in nonproliferating human peripheral blood lymphocytes, whereas peripheral blood lymphocytes stimulated to proliferation displayed clear SAPK/JNK activation. UV-induced phosphorylation of SAPK/JNK was attenuated in XPC-defective cells, ameliorated in BRCA2 mutated cells and not changed in cells lacking ATM, DNA-PK, CSB, XPA, p53, ERCC1 or PARP as compared with the corresponding wild types. Based on these data, we suggest that DNA replication blockage caused by genotoxin-induced DNA damage contributes to early activation of SAPK/JNK.

Genetic and epigenetic inactivation of T-cadherin in human hepatocellular carcinoma cells

T-cadherin is an atypical cadherin and growing evidence has indicated that T-cadherin exerts tumor-suppressive effects on cancers of epithelial cell type and also causes positive effects on tumor angiogenesis. Human hepatocellular carcinoma (HCC) is a hypervascular tumor and T-cadherin has been shown to be overexpressed in intratumoral endothelial cells of HCCs. However, the expression status and functions of T-cadherin in hepatocytes or HCC cells remain unclear. Here, we demonstrated that T-cadherin was underexpressed in HCC cells (26.5%, 13/49 cases), but was frequently (77.6%, 38/49) overexpressed in intratumoral endothelial cells immunohistochemically. Semiquantitative RT-PCR analysis also showed that the T-cadherin gene was underexpressed in 7 of 11 HCC cell lines. Loss of heterozygosity analysis revealed that 32-38% of the 42 human HCC samples had allelic losses at this locus. Upon pharmacological treatment with demethylating agent 5-aza-2'-deoxycytidine or histone deacetylase inhibitor trichostatin A, T-cadherin promoter hypermethylation and/or histone deacetylation was frequently observed in HCC samples and cell lines. Functionally, enforced expression of T-cadherin induced G(2)/M cell cycle arrest, reduced cell proliferation in low serum medium, suppressed anchorage-independent growth in soft agar and increased sensitivity to TNFalpha-mediated apoptosis in HCC cells. Intriguingly, we found that T-cadherin significantly suppressed the activity of c-Jun, a crucial oncoprotein constitutively activated in HCC cells. To conclude, T-cadherin was differentially expressed in human HCCs. The underexpression of T-cadherin in HCC cells suggests it may be another critical event in addition to T-cadherin-mediated angiogenesis during HCC development.

A systems approach to delineate functions of paralogous transcription factors: role of the Yap family in the DNA damage response

Duplication of genes encoding transcription factors plays an essential role in driving phenotypic variation. Because regulation can occur at multiple levels, it is often difficult to discern how each duplicated factor achieves its regulatory specificity. In these cases, a "systems approach" may distinguish the role of each factor by integrating complementary large-scale measurements of the regulatory network. To explore such an approach, we integrate growth phenotypes, promoter binding profiles, and gene expression patterns to model the DNA damage response network controlled by the Yeast-specific AP-1 (YAP) family of transcription factors. This analysis reveals that YAP regulatory specificity is achieved by at least three mechanisms: (i) divergence of DNA-binding sequences into two subfamilies; (ii) condition-specific combinatorial regulation by multiple Yap factors; and (iii) interactions of Yap 1, 4, and 6 with chromatin remodeling proteins. Additional microarray experiments establish that Yap 4 and 6 regulate gene expression through interactions with the histone deacetylase, Hda1. The data further highlight differences among Yap paralogs in terms of their regulatory mode of action (activation vs. repression). This study suggests how other large TF families might be disentangled in the future.

Bilberry extract reduces UVA-induced oxidative stress in HaCaT keratinocytes: a pilot study

Exposure to UVA radiation is known to cause many adverse biological effects by inducing the stricken cells to produce reactive oxygen species (ROS). In recent years the use of botanicals has received considerable interest in the skin protection. Bilberry (Vaccinium myrtillus L.) fruit contains several polyphenols with strong antioxidant and anti-inflammatory properties. In this study we evaluated potential UVA preventive effect of V. myrtillus fruit extract (VME; anthocyanins, 25% w/w) in HaCaT keratinocytes. Pre-treatment (1 h) or post-treatment (4 h) of HaCaT with VME resulted in attenuation of UVA-caused damage. Application of the extract significantly reduced UVA-stimulated ROS formation in keratinocytes. VME also prevented/reduced UVA-caused peroxidation of membrane lipids and depletion of intracellular GSH. The observed cytoprotective effect may be linked to the antioxidant activity of the plant constituents, namely anthocyanins.

Regulation of heme oxygenase-1 mRNA deadenylation and turnover in NIH3T3 cells by nitrosative or alkylation stress

Background

Heme oxygenase-1 (HO-1) catalizes heme degradation, and is considered one of the most sensitive indicators of cellular stress. Previous work in human fibroblasts has shown that HO-1 expression is induced by NO, and that transcriptional induction is only partially responsible; instead, the HO-1 mRNA half-life is substantially increased in response to NO. The mechanism of this stabilization remains unknown.

Results

In NIH3T3 murine fibroblasts, NO exposure increased the half-life of the HO-1 transcript from ~1.6 h to 11 h, while treatments with CdCl₂, NaAsO₂ or H₂O₂ increased the half-life only up to 5 h. Although poly(A) tail shortening can be rate-limiting in mRNA degradation, the HO-1 mRNA deadenylation rate in NO-treated cells was ~65% of that in untreated controls. In untreated cells, HO-1 poly(A) removal proceeded until 30–50 nt remained, followed by rapid mRNA decay. In NO-treated cells, HO-1 deadenylation stopped with the mRNA retaining poly(A) tails 30–50 nt long. We hypothesize that NO treatment stops poly(A) tail shortening at the critical 30- to 50-nt length. This is not a general mechanism for the post-transcriptional regulation of HO-1 mRNA. Methyl methane sulfonate also stabilized HO-1 mRNA, but that was associated with an 8-fold decrease in the deadenylation rate compared to that of untreated cells. Another HO-1 inducer, CdCl₂, caused a strong increase in the mRNA level without affecting the HO-1 mRNA half-life.

Conclusion

The regulation of HO-1 mRNA levels in response to cellular stress can be induced by transcriptional and different post-transcriptional events that act independently, and vary depending on the stress inducer. While NO appears to stabilize HO-1 mRNA by preventing the final steps of deadenylation, methyl methane sulfonate achieves stabilization through the regulation of earlier stages of deadenylation.

Glutathione depletion activates mitogen-activated protein kinase (MAPK) pathways that display organ-specific responses and brain protection in mice

Because mitogen-activated protein kinases (MAPK) are downstream effectors of antioxidant responses, changes in GSH levels in an organism might induce organ-specific responses. To test our hypothesis, mice were treated intraperitoneally with L-buthionine-S-R-sulfoximine (BSO) to inhibit GSH synthesis. A time-related GSH depletion in the liver and kidney correlated with p38(MAPK) phosphorylation and induction of thioredoxin 1 (Tx-1) transcription. This positive regulation was associated with nuclear translocation of NF-kappaB and ATF-2 and c-Jun phosphorylation in the liver, but only c-Jun phosphorylation in the kidney. Increased levels of GSH were observed in the brain together with extracellular regulated kinase 2 (ERK2) activation, Nrf2 nuclear accumulation, and increases in transcription of Nrf2, xCT, gamma-glutamylcysteine synthetase (gammaGCSr), and Tx-1. Pretreatment with MAPK inhibitors SB203580 and U0126, or addition of the exogenous thiol N-acetylcysteine, abrogated both p38(MAPK) and ERK2 activation as well as downstream effects on gene expression. No effect on gammaGCSr was observed. These results indicate that in mice, GSH depletion is associated with p38(MAPK) phosphorylation in the liver and kidney and with ERK2 activation in the brain, in what could be considered part of the brain's protective response to thiol depletion.

Alkylating agent methyl methanesulfonate (MMS) induces a wave of global protein hyperacetylation: implications in cancer cell death

Protein acetylation modification has been implicated in many cellular processes but the direct evidence for the involvement of protein acetylation in signal transduction is very limited. In the present study, we found that an alkylating agent methyl methanesulfonate (MMS) induces a robust and reversible hyperacetylation of both cytoplasmic and nuclear proteins during the early phase of the cellular response to MMS. Notably, the acetylation level upon MMS treatment was strongly correlated with the susceptibility of cancer cells, and the enhancement of MMS-induced acetylation by histone deacetylase (HDAC) inhibitors was shown to increase the cellular susceptibility. These results suggest protein acetylation is important for the cell death signal transduction pathway and indicate that the use of HDAC inhibitors for the treatment of cancer is relevant.

CD40-40L Signaling in Vascular Inflammation

Ligation of CD40 in circulating cells or in the vessel wall may promote mononuclear cell recruitment, participate in the weakening of the plaque, and contribute to thrombosis. This process appears to be redox-sensitive, but the precise signaling mechanism by which the interaction between CD40L and its receptor CD40 mediates inflammatory secretion is unclear. Our previous studies have shown that the CD40-CD40L interaction modulates release of reactive oxygen species (ROS) and the current findings demonstrate that in endothelial cells CD40L dose dependently induces intracellular CD40L and MCP1 release in a redox sensitive manner. Pharmacological inhibition of phosphatidylinositol 3-kinase and p38 MAPK as well as adenovirus-mediated inactivation of Akt and p38 MAPK inhibited CD40L effects on endothelial cells. Akt, in particular, appeared to mediate CD40L-induced CD40L synthesis and MCP1 release by endothelial cells in a redox sensitive manner via NFkappaB activation. In addition, using confocal microscopy, exogenous addition of recombinant CD40L or adenoviral mediated CD40L overexpression was found to stimulate nuclear translocation of NFkappaB, which was further augmented by Akt overexpression and inhibited by Akt inactivation. These data support a mechanism whereby redox-sensitive CD40-CD40L interactions induce activation of Akt and p38 MAPK, leading to stimulation of NFkappaB and enhanced synthesis of CD40L and MCP1. Increased CD40L and MCP1 may contribute to the adherence of CD40-positive cells, such as platelets and monocytes, to the vessel wall modulating atherothrombosis.

Glutathione regulation of redox-sensitive signals in tumor necrosis factor-α-induced vascular endothelial dysfunction

We investigated the regulatory role of glutathione in tumor necrosis factor-alpha (TNF-alpha)-induced vascular endothelial dysfunction as evaluated by using vascular endothelial adhesion molecule expression and monocyte-endothelial monolayer binding. Since TNF-alpha induces various biological effects on vascular cells, TNF-alpha dosage could be a determinant factor directing vascular cells into different biological fates. Based on the adhesion molecule expression patterns responding to different TNF-alpha concentrations, we adopted the lower TNF-alpha (0.2 ng/ml) to rule out the possible involvement of other TNF-alpha-induced biological effects. Inhibition of glutathione synthesis by l-buthionine-(S,R)-sulfoximine (BSO) resulted in down-regulations of the TNF-alpha-induced adhesion molecule expression and monocyte-endothelial monolayer binding. BSO attenuated the TNF-alpha-induced nuclear factor-kappaB (NF-kappaB) activation, however, with no detectable effect on AP-1 and its related mitogen-activated protein kinases (MAPKs). Deletion of an AP-1 binding site in intercellular adhesion molecule-1 (ICAM-1) promoter totally abolished its constitutive promoter activity and its responsiveness to TNF-alpha. Inhibition of ERK, JNK, or NF-kappaB attenuates TNF-alpha-induced ICAM-1 promoter activation and monocyte-endothelial monolayer binding. Our study indicates that TNF-alpha induces adhesion molecule expression and monocyte-endothelial monolayer binding mainly via activation of NF-kappaB in a glutathione-sensitive manner. We also demonstrated that intracellular glutathione does not modulate the activation of MAPKs and/or their downstream AP-1 induced by lower TNF-alpha. Although AP-1 activation by the lower TNF-alpha was not detected in our systems, we could not rule out the possible involvement of transiently activated MAPKs/AP-1 in the regulation of TNF-alpha-induced adhesion molecule expression.

Melphalan reduces the severity of experimental colitis in mice by blocking tumor necrosis factor-alpha signaling pathway

Melphalan is an alkylating agent, which is commonly used as an antineoplastic drug. Its cytostatic effect can be realized in humans in the dose range of 0.6-1.4 mg/kg body weight. However, previously it was shown that in the case of gradual dose decrease, the number of targets for alkylation was also reduced and the drug lost its cytostatic properties switching to cell growth modifier. It has been postulated that application of alkylating agents in such ultra-low concentrations (50- to 100-fold lower than cytostatic ones) may result in a beneficial effect in the therapy of diseases associated with mucosa inflammation. The aim of the article was to investigate the effect of ultra-low doses of melphalan in the murine experimental colitis induced by the replacement of drinking water with 5% solution of dextran sulphate sodium (DSS). Daily administration of melphalan (25 microg/kg body weight) markedly reduced the severity of DSS-colitis as determined by clinical and quantitative histological criteria. Both systemic and local anti-inflammatory effects of melphalan have been observed. The possible mechanisms of the beneficial effect of the drug have been discussed.

Resveratrol modulates mRNA transcripts of genes related to redox metabolism and cell proliferation in non-small-cell lung carcinoma cells

Resveratrol is a polyphenolic chemopreventive agent that has been shown to influence cellular redox reactions. As a systematic approach to elucidating the complex effects of resveratrol on eukaryotic cells, we studied its dose-dependent effects on the transcript levels of genes and activities of enzymes related to redox metabolism, cell cycle regulation, and apoptotic cascades in the cancer cell line A549. Glutathione peroxidase (GPx)1 mRNA levels, as well as GPx and thioredoxin reductase (TrxR) activities, were significantly increased after resveratrol treatment, whereas total glutathione concentrations decreased. Increased transcript levels were also detected for selenophosphate synthetase 2 and superoxide dismutase 2. However, mRNA levels of thioredoxin, TrxR, glutathione reductase, glutathione S-transferase, superoxide dismutase 1, and catalase were not altered. Among the 12 genes studied that are related to the cell cycle, differentiation and apoptosis, mRNA levels of six genes, including P53, FAS, and BCL2, were upregulated, while the mRNA level of survivin was reduced. The results suggest that GPx and other selenoproteins are important targets of resveratrol. Furthermore, genes supporting cell survival and differentiation, as well as genes involved in proliferation inhibition and apoptosis, are induced by resveratrol, resulting in a delicate balance that is likely to contribute to the chemopreventive effects of resveratrol.

Incinerator fly ash provokes alteration of redox equilibrium and liberation of arachidonic acid in vitro

Numerous epidemiological studies have associated exposure to ambient particulate matter (PM) with pulmonary and cardiovascular health effects. Macrophages as a part of the primary pulmonary defence system play a crucial role by generating pro- and anti-inflammatory mediators. The aim of the present study was to examine the effect of incinerator fly ash (MAF02) as a model of environmental particulate matter on the formation of reactive oxygen species (ROS) and their ability to induce oxidative stress in RAW264.7 macrophages. Furthermore, the liberation of arachidonic acid (AA) was observed. The interaction of MAF02 with macrophages caused increased mobilisation of AA, accompanied by enhanced expression of cyclooxygenase-2 (COX-2). The MAF02-induced AA liberation was found to depend on an increased intracellular calcium concentration. In addition, MAF02-induced liberation of AA was selectively blocked by an ERK1/2 pathway-specific inhibitor, while inhibition of the p38 MAPK activity had no effect. Fly ash was also observed to induce an increase in cellular glutathione (GSH) content and antioxidative enzyme haem oxygenase-1 (HO-1). In correlation, experiments with dichlorofluorescein demonstrated increased formation of ROS upon treatment with fly ash. In summary, incinerator fly ash induces oxidative stress to a certain extent, resulting in the onset of important mechanisms related to inflammation.