Propyl gallate is a superoxide dismutase mimic and protects cultured lens epithelial cells from H2O2 insult

Propyl gallate induces human pulmonary fibroblast cell death through the regulation of Bax and caspase-3

Propyl gallate (PG) has been found to exert an inhibitory effect on the growth of different cell types, including lung cancer cells. However, little is known about the cytotoxicological effects of PG specifically on normal primary lung cells. The current study examined the cellular effects and cell death resulting from PG treatment in human pulmonary fibroblast (HPF) cells. DNA flow cytometry results demonstrated that PG (100-1,600 μM) had a significant impact on the cell cycle, leading to G1 phase arrest. Notably, 1,600 μM PG slightly increased the number of sub-G1 cells. Additionally, PG (400-1,600 μM) resulted in the initiation of cell death, a process that coincided with a loss of mitochondrial membrane potential (MMP; ΔΨm). This loss of MMP (ΔΨm) was evaluated using a FACS cytometer. In PG-treated HPF cells, inhibitors targeting pan-caspase, caspase-3, caspase-8, and caspase-9 showed no significant impact on the quantity of annexin V-positive and MMP (ΔΨm) loss cells. The administration of siRNA targeting Bax or caspase-3 demonstrated a significant attenuation of PG-induced cell death in HPF cells. However, the use of siRNAs targeting p53, Bcl-2, or caspase-8 did not exhibit any notable effect on cell death. Furthermore, none of the tested MAPK inhibitors, including MEK, c-Jun N-terminal kinase (JNK), and p38, showed any impact on PG-induced cell death or the loss of MMP (ΔΨm) in HPF cells. In conclusion, PG induces G1 phase arrest of the cell cycle and cell death in HPF cells through apoptosis and/or necrosis. The observed HPF cell death is mediated by the modulation of Bax and caspase-3. These findings offer insights into the cytotoxic and molecular effects of PG on normal HPF cells.

Propyl gallate induces cell death in human pulmonary fibroblast through increasing reactive oxygen species levels and depleting glutathione

Propyl gallate (PG) exhibits an anti-growth effect on various cell types. The present study investigated the impact of PG on the levels of reactive oxygen species (ROS) and glutathione (GSH) in primary human pulmonary fibroblast (HPF) cells. Moreover, the effects of N-acetyl cysteine (NAC, an antioxidant), L-buthionine sulfoximine (BSO, a GSH synthesis inhibitor), and small interfering RNA (siRNAs) against various antioxidant genes on ROS and GSH levels and cell death were examined in PG-treated HPF cells. PG (100-800 μM) increased the levels of total ROS and O2·- at early time points of 30-180 min and 24 h, whereas PG (800-1600 μM) increased GSH-depleted cell number at 24 h and reduced GSH levels at 30-180 min. PG downregulated the activity of superoxide dismutase (SOD) and upregulated the activity of catalase in HPF cells. Treatment with 800 μM PG increased the number of apoptotic cells and cells that lost mitochondrial membrane potential (MMP; ΔΨm). NAC treatment attenuated HPF cell death and MMP (ΔΨm) loss induced by PG, accompanied by a decrease in GSH depletion, whereas BSO exacerbated the cell death and MMP (ΔΨm) loss without altering ROS and GSH depletion levels. Furthermore, siRNA against SOD1, SOD2, or catalase attenuated cell death in PG-treated HPF cells, whereas siRNA against GSH peroxidase enhanced cell death. In conclusion, PG induced cell death in HPF cells by increasing ROS levels and depleting GSH. NAC was found to decrease HPF cell death induced by PG, while BSO enhanced cell death. The findings shed light on how manipulating the antioxidant system influence the cytotoxic effects of PG in HPF cells.

Propyl gallate exposure affects the mouse 2-cell stage embryonic development through inducing oxidative stress and autophagy

Propyl gallate (PG), owing to its exceptional antioxidant properties, is extensively used in industries such as food processing. The potential harmful impacts of PG have sparked concern among people. It has been reported that exposure of PG has certain reproductive toxicity, which can affect the maturation of mouse oocytes and induce testicular dysfunction. However, its impact on early embryonic development is still unclear. In this study, we explored the toxic effects and potential mechanisms of PG on mouse 2-cell stage embryonic development. The results showed that exposure of PG can decrease the development of 2-cell stage embryos and repress the development of 4-cell stage embryos. Further study found that PG could induce intracellular oxidative stress and the accumulation of DNA damage in 2-cell stage embryos. Moreover, exposure of PG impaired the function of mitochondria and lysosomes in 2-cell stage embryos, thereby triggering the occurrence of autophagy. In addition, exposure of PG altered the epigenetic modification of 2-cell stage embryos, displaying a decreased level of DNA methylation and an increased level of H3K4me3. In summary, our results indicated that exposure of PG can damage the development of mouse 2-cell stage embryos by inducing oxidative stress, DNA damage, and autophagy, and altering epigenetic modification.

Transcriptome analysis reveals the effect of propyl gallate on kiwifruit callus formation

KEY MESSAGE

Exploring the potential action mechanisms of reactive oxygen species during the callus inducing, they can activate specific metabolic pathways in explants to regulate callus development. Reactive oxygen species (ROS) play an important role in the regulation of plant growth and development, but the mechanism of their action on plant callus formation remains to be elucidated. To address this question, kiwifruit was selected as the explant for callus induction, and the influence of ROS on callus formation was investigated by introducing propyl gallate (PG) as an antioxidant into the medium used for inducing callus. The results have unveiled that the inclusion of PG in the medium has disturbed the equilibrium of ROS during the formation of the kiwifruit callus. We selected the callus that was induced by the addition of 0.05 mmol/L PG to the MS medium. The callus exhibited a significant difference in the amount compared to the control medium without PG. The callus induced by the MS medium without PG was used as the control for comparison. KEGG enrichment indicated that PG exposure resulted in significant differences in gene expression in related pathways, such as phytohormone signaling and glutathione in kiwifruit callus. Weighted gene co-expression analysis indicated that the pertinent regulatory networks of both ROS and phytohormone signaling were critical for the establishment of callus in kiwifruit leaves. In addition, during the process of callus establishment, the ROS level of the explants was also closely related to the genes for transmembrane transport of substances, cell wall formation, and plant organ establishment. This investigation expands the theory of ROS-regulated callus formation and presents a new concept for the expeditious propagation of callus in kiwifruit.

Pharmacokinetic and toxicological overview of propyl gallate food additive

The progressive use of food additives in "ultra-processed" food has increased attention to them. Propyl gallate (PG) is an essential synthetic preservative that commonly used in food, cosmetics, and pharmacies as an antioxidant. This study aimed to outline the existing evidence on the toxicological studies of PG including its physicochemical properties, metabolism, and pharmacokinetics effects. The methods include updated searches for the relevant databases. The EFSA has evaluated the use of PG in food industry. It establishes an acceptable daily intake (ADI) of 0.5 mg/kg bw per day. Based on exposure assessment, it can be concluded that at the current level of use, PG is not of safety concern.

High-dose synthetic phenolic antioxidant propyl gallate impairs mouse oocyte meiotic maturation through inducing mitochondrial dysfunction and DNA damage

Propyl gallate (PG) is one of the most widely used antioxidants in food products, cosmetics and pharmaceutical industries. Increased research has suggested that exposure to PG influences reproductive health in humans and animals. However, until now, it has not yet been confirmed whether PG would impact oocyte quality. In this study, the hazardous effects of PG on oocyte meiotic maturation were investigated in mice. The findings showed that PG exposure compromises oocyte meiosis by inducing mitochondrial stress which activates apoptosis to trigger oocyte demise. Moreover, DNA damage was significantly induced in PG-treated oocytes, which might be another cause of oocyte developmental arrest and degeneration. Besides, the level of histone methylation (H3K27me2 and H3K27me3) in oocyte was also significantly increased by PG exposure. Furthermore, PG-induced oxidative stress was validated by the increased level of reactive oxygen species (ROS), which might be the underlying reason for these abnormities. In conclusion, the foregoing findings suggested that PG exposure impaired oocyte meiotic maturation by yielding mitochondrial stress to activate apoptosis, inducing DNA damage and oxidative stress, and altering histone methylation level.

A spectroscopic and quantum chemical calculation method for the characterisation of metal ions complexed with propyl gallate and procyanidins

The deprotonation mechanism for the phenolic hydroxyl and the complexing of metal ions with a commonly used food additive, propyl gallate (PG) were studied theoretically and experimentally. The interaction of procyanidins [PC, epicatechin₁₆ (4 → 8) catechin], and its basic monomeric unit catechin (CA) with metal ions was studied by the fluorescence quenching spectra. The results showed that the 9-OH quinoid PG was formed at higher pH (10.9) by the oxidization of phenolic hydroxyl. The binding affinities (K_a) and stoichiometry of these metal ions with PG were determined. The Al³⁺ in PG-Al complex [Al(PG)(H₂O)₂Cl₂]^- was coordinated at the 8,9-OH doubly deprotonated catechol site with double chloride ions (Cl^-) and double water molecules (H₂O). The fluorescence quenching titration with Sn²⁺, Zn²⁺, Cu²⁺, Al³⁺ and Fe³⁺ revealed that the stoichiometries of metal-bound PC were 1:1, 2:3, 2:3, 2:3 and 1:1, respectively. The presence of bovine serum albumin (BSA) could enhance the complexing strength of PC with metal ions.

A novel approach for the prevention of ionizing radiation-induced bone loss using a designer multifunctional cerium oxide nanozyme

The disability, mortality and costs due to ionizing radiation (IR)-induced osteoporotic bone fractures are substantial and no effective therapy exists. Ionizing radiation increases cellular oxidative damage, causing an imbalance in bone turnover that is primarily driven via heightened activity of the bone-resorbing osteoclast. We demonstrate that rats exposed to sublethal levels of IR develop fragile, osteoporotic bone. At reactive surface sites, cerium ions have the ability to easily undergo redox cycling: drastically adjusting their electronic configurations and versatile catalytic activities. These properties make cerium oxide nanomaterials fascinating. We show that an engineered artificial nanozyme composed of cerium oxide, and designed to possess a higher fraction of trivalent (Ce³⁺) surface sites, mitigates the IR-induced loss in bone area, bone architecture, and strength. These investigations also demonstrate that our nanozyme furnishes several mechanistic avenues of protection and selectively targets highly damaging reactive oxygen species, protecting the rats against IR-induced DNA damage, cellular senescence, and elevated osteoclastic activity in vitro and in vivo. Further, we reveal that our nanozyme is a previously unreported key regulator of osteoclast formation derived from macrophages while also directly targeting bone progenitor cells, favoring new bone formation despite its exposure to harmful levels of IR in vitro. These findings open a new approach for the specific prevention of IR-induced bone loss using synthesis-mediated designer multifunctional nanomaterials.

The Anti-Apoptotic Effects of Caspase Inhibitors in Propyl Gallate-Treated Lung Cancer Cells Are Related to Changes in Reactive Oxygen Species and Glutathione Levels

Propyl gallate [3,4,5-trihydroxybenzoic acid propyl ester; PG] exhibits an anti-growth effect in various cells. In this study, the anti-apoptotic effects of various caspase inhibitors were evaluated in PG-treated Calu-6 and A549 lung cancer cells in relation to reactive oxygen species (ROS) and glutathione (GSH) levels. Treatment with 800 μM PG inhibited the proliferation and induced the cell death of both Calu-6 and A549 cells at 24 h. Each inhibitor of pan-caspase, caspase-3, caspase-8, and caspase-9 reduced the number of dead and sub-G1 cells in both PG-treated cells at 24 h. PG increased ROS levels, including O₂^∙−, in both lung cancer cell lines at 24 h. Generally, caspase inhibitors appeared to decrease ROS levels in PG-treated lung cancer cells at 24 h and somewhat reduced O₂^∙− levels. PG augmented the number of GSH-depleted Calu-6 and A549 cells at 24 h. Caspase inhibitors did not affect the level of GSH depletion in PG-treated A549 cells but differently and partially altered the depletion level in PG-treated Calu-6 cells. In conclusion, PG exhibits an anti-proliferative effect in Calu-6 and A549 lung cancer cells and induced their cell death. PG-induced lung cancer death was accompanied by increases in ROS levels and GSH depletion. Therefore, the anti-apoptotic effects of caspase inhibitors were, at least in part, related to changes in ROS and GSH levels.

Investigation of the Antioxidant Properties of the Quaternized Chitosan Modified with a Gallic Acid Residue Using Peroxidase that Produces Reactive Oxygen Species

Chitosan modified with a (2-hydroxy-3-trimethylammonium) propyl group and gallic acid residue, or quaternized chitosan with gallic acid (QCG), was synthesized. Antioxidant properties of the produced QCG have been investigated. Peroxidase in combination with NADH and salicyl hydroxamate (SHAM) caused consumption of oxygen and production of H2O2 in aqueous solution as a result of O2 reduction in the peroxidase-oxidase reactions. The rates of O2 consumption and H2O2 generation were reduced in the presence of QCG. The antioxidant propyl gallate (PG) and superoxide dismutase (SOD) had the same effect, but not the quaternized chitosan (QC) without gallic acid. The effect of chitosan derivatives on the production of reactive oxygen species (ROS) in the cells of pea leaf epidermis and on the cell death detected by the destruction of cell nuclei, was investigated. QCG, QC, and SOD had no effect, while PG decreased the rate of ROS generation in the cells of the epidermis, which was induced by NADH with SHAM or by menadione. QCG and QC prevented destruction of the guard cell nuclei in the pea leaf epidermis that was caused by NADH with SHAM or by KCN. SOD had no effect on the destruction of nuclei, while the effect of PG depended on the inducer of the cell death. Suppression of the destruction of guard cell nuclei by chitosan derivatives was associated not with their antioxidant effect, but with the disruption of the plasma membrane of the cells. The results obtained have shown that QCG exhibits antioxidant properties in solutions, but does not prevent generation of ROS in the plant cells. The mechanism of antioxidant effect of QCG is similar to that of PG and SOD.

Analysis, occurrence, toxicity and environmental health risks of synthetic phenolic antioxidants: A review

The continuous improvement of living standards is related to higher requirements for the freshness and taste of food. For example, synthetic phenolic antioxidants (SPAs) are added to fats and fried foods as food additives to minimize the oxidative rancidity of oils and fats. Hence, the global use of SPAs is increasing year by year. Dibutyl hydroxytoluene is one of the widely used SPAs, often in combination with butyl hydroxyanisole or gallate SPAs. The extensive use of these compounds makes them and their transformation products to be widespread in various environmental matrices, including indoor dust, wastewater, river water, sewage sludge, and sediment, as well as human samples, such as nails and urine, at concentrations varying from nanogram per gram (ng/g) to microgram per gram (μg/g). Animal experiments have shown that high-dose SPA exposure is toxic, which may lead to DNA damage and mismatches and the development of cancerous tumors. Since the biosphere shares the same set of genetic codes, humans and animals have many identical or similar feedback mechanisms and information pathways. Therefore, the damage of SPAs to animals may also threaten human health. This review discusses the properties, occurrence, analysis, and environmental health risks of typical SPAs, including butyl hydroxyanisole, dibutyl hydroxytoluene, tert-butylhydroquinone, propyl gallate, octyl gallate, and lauryl gallate, used as food additives. In addition, AO2246, which is used in food packaging bags, is also considered. Future research directions on SPAs and their transformation products (TPs) are identified and discussed.

Propyl gallate decreases the proliferation of Calu-6 and A549 lung cancer cells via affecting reactive oxygen species and glutathione levels

Propyl gallate (3,4,5-trihydroxybenzoic acid propyl ester, PG) has an anti-proliferative effect in various cells. In this study, Calu-6 and A549 lung cancer cells were used to examine the anti-proliferative effect of PG in relation to reactive oxygen species (ROS) and glutathione (GSH) levels. PG (100-1,600 μM) dose-dependently inhibited the proliferation of Calu-6 and A549 cells at 24 h, and PG at 800-1,600 μM strongly induced cell death in both cell lines. PG (800-1,600 μM) increased cellular metabolism in Calu-6 but not A549 cells at 4 h. PG either increased or decreased ROS levels, including O₂ ˙^- and ˙OH, depending on the incubation doses and times of 1 or 24 h. Even these effects differed between Calu-6 and A549 cell types. PG reduced the activity of superoxide dismutase (SOD) in Calu-6 cells, and it augmented the activity of catalase in A549 cells. PG dose-dependently increased the number of GSH depleted cells in both Calu-6 and A549 cells at 24 h. In addition, PG decreased GSH levels in both lung cancer cells at 1 h. Furthermore, diethyldithiocarbamate (DDC; an inhibitor of SOD) and 3-amino-1,2,4-triazole (AT; an inhibitor of catalase) differently affected cellular metabolism, ROS and GSH levels in PG-treated and PG-untreated Calu-6 and A549 cells at 1 h. In conclusion, PG dose-dependently decreased the proliferation of Calu-6 and A549 lung cancer cells, which was related to changes in ROS levels and the depletion of GSH.

Effects of Superoxide Dismutase Inhibitors and Glucose on Cell Death and Generation of Reactive Oxygen Species in Pea Leaves

The effects of superoxide dismutase (SOD) inhibitors, diethyldithiocarbamate (DDC), triethylenetetramine (trien), and their combination with glucose on cells of the epidermis from pea leaves of different age (rapidly growing young leaves and slowly growing old leaves) was investigated. DDC and trien caused death of the guard cells as determined by destruction of their nuclei. Glucose did not affect destruction of the nuclei induced by SOD inhibitors in the cells from old leaves, but intensified it in the cells from young leaves. 2-Deoxyglucose, an inhibitor of glycolysis, and propyl gallate, SOD-mimic and antioxidant, suppressed destruction of the nuclei that was caused by SOD inhibitors and glucose in cells of the epidermis from the young, but not from the old leaves. Glucose and trien stimulated, and propyl gallate reduced generation of reactive oxygen species (ROS) in the pea epidermis as determined by the fluorescence of 2',7'-dichlorofluorescein (DCF). Carbonyl cyanide m-chlorophenylhydrazone (CCCP), a protonophoric uncoupler of oxidative and photosynthetic phosphorylation, suppressed the DCF fluorescence in the guard cells. Treatment of the cells with CCCP followed by its removal with washing increased destruction of the nuclei caused by SOD inhibitors and glucose. In young leaves, CCCP was less effective than in old ones. The findings demonstrate the effects of SOD inhibitors and glucose on the cell death and generation of ROS and could indicate glycolysis-dependent ROS production.

Enhanced cell death effects of MAP kinase inhibitors in propyl gallate-treated lung cancer cells are related to increased ROS levels and GSH depletion

Propyl gallate (PG) has an anti-growth effect in lung cancer cells. The present study investigated the effects of mitogen-activated protein kinase (MAPK; MEK, JNK, and p38) inhibitors on PG-treated Calu-6 and A549 lung cancer cells in relation to cell death as well as reactive oxygen species (ROS) and glutathione (GSH) levels. PG induced cell death in both Calu-6 and A549 lung cancer cells at 24 h, which was accompanied by loss of mitochondrial membrane potential (MMP; ΔΨ_m). All of the tested MAPK inhibitors increased cell death in both PG-treated lung cancer cell lines. In particular, MEK inhibitor strongly enhanced cell death and MMP (ΔΨ_m) loss in PG-treated Calu-6 cells and p38 inhibitor had the same effects in A549 cells as well. PG increased ROS levels and caused GSH depletion in both cell lines at 24 h. MAPK inhibitors increased O₂^•- levels and GSH depletion in PG-treated Calu-6 cells, and JNK and p38 inhibitors increased ROS levels and GSH depletion in PG-treated A549 cells. In conclusion, MAPK inhibitors increased cell death in PG-treated Calu-6 and A549 lung cancer cells. Enhanced cell death and GSH depletion in Calu-6 cells caused by the MEK inhibitor were related to increased O₂^•- levels, and the effects of the p38 inhibitor in A549 cells were correlated with increased general ROS levels.

Propyl gallate inhibits hepatocellular carcinoma cell growth through the induction of ROS and the activation of autophagy

The poor prognosis of hepatocellular carcinoma (HCC) has been attributed to a high frequency of tumor metastasis and recurrence even after successful surgical resection. With less than 30% of patients benefiting from curative treatment, alternative treatment regimens for patients with advanced HCC are needed. Propyl gallate (PG), a synthetic antioxidant used in preserving food and medicinal preparations, has been shown to induce cancer cell death, but the anticancer effects of PG in HCC are unclear. In the present study, we demonstrated that PG inhibited HCC cell proliferation in vitro and in zebrafish models in vivo in a dose- and time-dependent manner. PG also induced cell apoptosis and increased the number of necrotic cells in a time- and dose-dependent manner as determined using a high-content analysis system. We found that PG also increased the intracellular levels of superoxide and reactive oxidative stress as well as the formation of autophagosomes and lysosomes. Regarding the molecular mechanism, PG did not alter the levels of autophagy-related 5 (ATG5), ATG5/12 or Beclin-1 but increased the rate of the LC3-I to LC3-II conversion, suggesting autophagy induction. PG exposure increased the levels of the pro-apoptotic proteins cleaved caspase-3, cleaved PARP, Bax, and Bad and a decreased level of the anti-apoptotic protein Bcl-2. In conclusion, we demonstrate that PG inhibits HCC cell proliferation through enhanced ROS production and autophagy activation. Finally, PG-treated cells induced cell apoptosis and may be a new candidate for HCC therapy.

The induction of salt stress tolerance by propyl gallate treatment in green microalga Dunaliella bardawil, through enhancing ascorbate pool and antioxidant enzymes activity

The effect of propyl gallate (PG), a synthetic antioxidant, on antioxidant responses and salinity tolerance was investigated in the cells of the green microalga, Dunaliella bardawil. Algal suspensions grown at three salinity levels of 1, 2, and 3 M NaCl were incubated with 1 mM of PG. The number of cells was significantly lower in all PG-treated cells compared to untreated controls. Despite PG-induced cell death, the fresh weight of all PG-treated cells was considerably higher than controls. PG-treated cells had enhanced antioxidant capacity because of increased levels of Chlorophyll a, β-carotene, reduced ascorbate, protein, and enzymatic activities, but accumulated lower levels of malonyldialdehyde and hydrogen peroxide compared to untreated cells. The results suggest that PG acts as a signal molecule both directly by reducing of free radical oxidants and indirectly by augmenting ascorbate pool levels, β-carotene production, and antioxidant enzymes activity to boost the capacity of antioxidant systems and radical oxygen species scavenging. Therefore, induction of salt stress tolerance by PG in D. bardawil is associated with metabolic adjustments through activation or synthesis of both enzymatic and non-enzymatic molecules involved in antioxidant systems.

An iron hydroxyl phosphate microoctahedron catalyst as an efficient peroxidase mimic for sensitive and colorimetric quantification of H2O2 and glucose

An iron hydroxyl phosphate that possesses high peroxidase activity is synthesized via a one-step hydrothermal method and used for colorimetric glucose detection in human serum.

ROS induced distribution of mitochondria to filopodia by Myo19 depends on a class specific tryptophan in the motor domain

The role of the actin cytoskeleton in relation to mitochondria function and dynamics is only recently beginning to be recognized. Myo19 is an actin-based motor that is bound to the outer mitochondrial membrane and promotes the localization of mitochondria to filopodia in response to glucose starvation. However, how glucose starvation induces mitochondria localization to filopodia, what are the dynamics of this process and which enzymatic adaptation allows the translocation of mitochondria to filopodia are not known. Here we show that reactive oxygen species (ROS) mimic and mediate the glucose starvation induced phenotype. In addition, time-lapse fluorescent microscopy reveals that ROS-induced Myo19 motility is a highly dynamic process which is coupled to filopodia elongation and retraction. Interestingly, Myo19 motility is inhibited by back-to-consensus-mutation of a unique residue of class XIX myosins in the motor domain. Kinetic analysis of the purified mutant Myo19 motor domain reveals that the duty ratio (time spent strongly bound to actin) is highly compromised in comparison to that of the WT motor domain, indicating that Myo19 unique motor properties are necessary to propel mitochondria to filopodia tips. In summary, our study demonstrates the contribution of actin-based motility to the mitochondrial localization to filopodia by specific cellular cues.

Immunofluorescence evaluation of 4-hydroxynonenal and 8-hydroxy-2-deoxyguanosine activation in zebrafish (Daino rerio) larvae brain exposed (microinjected) to propyl gallate

Propyl gallate (PG) is a chemical compound obtained by esterification of propanol with gallic acid. Due to its antioxidative properties, it is widely used in cosmetics and pharmaceutical industries as well as to protect the oils in foods such as butter, milk-based desserts, chewing gum, mayonnaise, meat, soups, cereals, spices and seasonings from rancidity. This study has been designed to assessment 8-OHdG and 4-HNE activity, and histopathological changes in the brain tissues of zebrafish larvae, which is a lecithotrophic organism, after 96 h of PG exposure via microinjecting to yolk sac of embryo. To this end, approximately 5 nL of various concentrations of PG (1, 10, and 50 ppm) has been injected into yolk sac of fertilized embryo (final exposure concentrations are 5, 50, 250 pg/egg) with micro manipulator system. After 96 h exposure time, propyl gallate caused immunofluorescence positivity of 8-OHdG and 4-HNE in the brain tissues of zebrafish larvae. PG was not effect brain tissue histopathological in low concentrations (1 and 10 ppm) but highest concentration (50 ppm) caused degenerative changes in brain. These results suggests that PG treatment could lead oxidative DNA damage by causing an increase 8-OHdG and 4-HNE activities. This strategy will enable us to better understand the mechanisms of propyl gallate in brain tissues of zebrafish larvae.

Identification of Rosmarinic Acid-Adducted Sites in Meat Proteins in a Gel Model under Oxidative Stress by Triple TOF MS/MS

Triple TOF MS/MS was used to identify adducts between rosmarinic acid (RosA)-derived quinones and meat proteins in a gel model under oxidative stress. Seventy-five RosA-modified peptides responded to 67 proteins with adduction of RosA. RosA conjugated with different amino acids in proteins, and His, Arg, and Lys adducts with RosA were identified for the first time in meat. A total of 8 peptides containing Cys, 14 peptides containing His, 48 peptides containing Arg, 64 peptides containing Lys, and 5 peptides containing N-termini that which participated in adduction reaction with RosA were identified, respectively. Seventy-seven adduction sites were subdivided into all adducted proteins including 2 N-terminal adduction sites, 3 Cys adduction sites, 4 His adduction sites, 29 Arg adduction sites, and 39 Lys adduction sites. Site occupancy analyses showed that approximately 80.597% of the proteins carried a single RosA-modified site, 14.925% retained two sites, 1.492% contained three sites, and the rest 2.985% had four or more sites. Large-scale triple TOF MS/MS mapping of RosA-adducted sites reveals the adduction regulations of quinone and different amino acids as well as the adduction ratios, which clarify phenol-protein adductions and pave the way for industrial meat processing and preservation.

Propyl gallate inhibits adipogenesis by stimulating extracellular signal-related kinases in human adipose tissue-derived mesenchymal stem cells

Propyl gallate (PG) used as an additive in various foods has antioxidant and anti-inflammatory effects. Although the functional roles of PG in various cell types are well characterized, it is unknown whether PG has effect on stem cell differentiation. In this study, we demonstrated that PG could inhibit adipogenic differentiation in human adipose tissue-derived mesenchymal stem cells (hAMSCs) by decreasing the accumulation of intracellular lipid droplets. In addition, PG significantly reduced the expression of adipocyte-specific markers including peroxisome proliferator-activated receptor-γ (PPAR-γ), CCAAT enhancer binding protein-α (C/EBP-α), lipoprotein lipase (LPL), and adipocyte fatty acid-binding protein 2 (aP2). PG inhibited adipogenesis in hAMSCs through extracellular regulated kinase (ERK) pathway. Decreased adipogenesis following PG treatment was recovered in response to ERK blocking. Taken together, these results suggest a novel effect of PG on adipocyte differentiation in hAMSCs, supporting a negative role of ERK1/2 pathway in adipogenic differentiation.

Simple biological systems for assessing the activity of superoxide dismutase mimics

SIGNIFICANCE

Half a century of research provided unambiguous proof that superoxide and species derived from it-reactive oxygen species (ROS)-play a central role in many diseases and degenerative processes. This stimulated the search for pharmaceutical agents that are capable of preventing oxidative damage, and methods of assessing their therapeutic potential.

RECENT ADVANCES

The limitations of superoxide dismutase (SOD) as a therapeutic tool directed attention to small molecules, SOD mimics, that are capable of catalytically scavenging superoxide. Several groups of compounds, based on either metal complexes, including metalloporphyrins, metallocorroles, Mn(II) cyclic polyamines, and Mn(III) salen derivatives, or non-metal based compounds, such as fullerenes, nitrones, and nitroxides, have been developed and studied in vitro and in vivo. Very few entered clinical trials.

CRITICAL ISSUES AND FUTURE DIRECTIONS

Development of SOD mimics requires in-depth understanding of their mechanisms of biological action. Elucidation of both molecular features, essential for efficient ROS-scavenging in vivo, and factors limiting the potential side effects requires biologically relevant and, at the same time, relatively simple testing systems. This review discuses the advantages and limitations of genetically engineered SOD-deficient unicellular organisms, Escherichia coli and Saccharomyces cerevisiae as tools for investigating the efficacy and mechanisms of biological actions of SOD mimics. These simple systems allow the scrutiny of the minimal requirements for a functional SOD mimic: the association of a high catalytic activity for superoxide dismutation, low toxicity, and an efficient cellular uptake/biodistribution.

The effect of MAPK inhibitors and ROS modulators on cell growth and death of H₂O₂-treated HeLa cells

Reactive oxygen species (ROS) influence the signaling of mitogen‑activated protein kinases (MAPKs) involved in cell survival and death. In the present study, the toxicological effect of hydrogen peroxide (H2O2) on HeLa cervical cancer cells was evaluated following treatment with MAPK inhibitors [MAP kinase or ERK kinase (MEK), c‑Jun N‑terminal kinase (JNK) or p38], N‑acetyl cysteine (NAC) and propyl gallate (PG) (well‑known antioxidants), or L‑buthionine sulfoximine [BSO; an inhibitor of glutathione (GSH) synthesis]. Treatment with 100 µM H2O2 inhibited the growth of HeLa cells and induced cell death, which was accompanied by loss of the mitochondrial membrane potential (MMP; ΔΨm). H2O2 did not induce any specific phase arrests of the cell cycle. ROS levels increased, while GSH levels decreased in H2O2‑treated HeLa cells after 1 and 24 h of treatment. The MAPK inhibitors enhanced H2O2‑induced HeLa cell death, while only p38 inhibitor increased ROS levels. Both NAC and PG attenuated H2O2‑induced HeLa cell growth inhibition and death together with the suppression of ROS levels. BSO increased ROS levels in H2O2‑treated HeLa cells without increasing cell death. The levels of MMP (ΔΨm) loss and GSH depletion were not closely associated with the levels of apoptosis in HeLa cells treated with the MAPK inhibitors, NAC, PG or BSO, in the presence of H2O2. In conclusion, H2O2 induced HeLa cell growth inhibition and death. MAPK inhibitors generally enhanced H2O2‑induced HeLa cell death. In particular, p38 inhibitor increased ROS levels in H2O2‑treated HeLa cells, while NAC and PG attenuated H2O2‑induced HeLa cell death by suppressing ROS levels.

Effects of antioxidants and MAPK inhibitors on cell death and reactive oxygen species levels in H2O2-treated human pulmonary fibroblasts

H₂O₂-induced cytotoxicity in normal human pulmonary fibroblasts (HPFs) is of interest in toxicological research since HPFs are involved in lung inflammation, fibrosis and cancer. The present study investigated the cytotoxic effects of H₂O₂ on normal HPFs in relation to reactive oxygen species (ROS) and mitogen-activated protein kinases (MAPKs) using the well-known antioxidants N-acetyl cysteine (NAC) and propyl gallate (PG), as well as MAPK inhibitors. Treatment with 50 μM H₂O₂ inhibited the growth of the HPFs by ∼45% in 24 h. H₂O₂ induced cell death via apoptosis and triggered the loss of mitochondrial membrane potential (MMP; Δψ_m) in the HPFs. H₂O₂ also increased the ROS levels, including O₂^•−, in the HPFs and induced glutathione (GSH) depletion. NAC and PG attenuated the death of the HPFs and the loss of MMP (Δψ_m) through the use of H₂O₂. NAC decreased the ROS levels in the H₂O₂-treated HPFs and PG markedly prevented an increase in O₂^•− levels in these cells. However, PG alone induced cell death in the HPF control cells and increased the ROS levels in these cells. None of the MAPK (MEK, JNK and p38) inhibitors affected cell growth inhibition or cell death by H₂O₂. In addition, these inhibitors did not significantly affect the ROS levels and GSH depletion in the H₂O₂-treated HPFs. In conclusion, H₂O₂ induced growth inhibition and cell death in the HPFs via GSH depletion. NAC and PG attenuated H₂O₂-induced HPF cell death but each regulated the ROS levels in a different manner. Treatment with MAPK inhibitors did not affect cell death or the ROS levels in the H₂O₂-treated HPFs.

Improvement of aminolevulinic acid (ALA)-mediated photodynamic diagnosis using n-propyl gallate

BACKGROUND

Photodynamic diagnosis (PDD) using aminolevulinic acid (ALA) is widely used in clinical fields. In PDD, protoporphyrin IX (PpIX) is generated from ALA in tumors, allowing the detection of the tumors by PpIX fluorescence. However, it is well known that PpIX is bleached by light irradiation (photobleaching) resulting in reduced PDD efficiency. In this study, n-propyl gallate (NPG) was investigated as an enhancer of PDD efficiency.

METHODS

Tumor cells were incubated with NPG after treatment with ALA, and reactive oxygen species and PpIX fluorescence were measured.

RESULTS

The antioxidant NPG suppressed the production of reactive oxygen species from light-irradiated porphyrins and ameliorated photobleaching of PpIX generated from ALA in vitro and in vivo.

CONCLUSION

Incubation with NPG decreased the production of reactive oxygen species from PpIX and suppressed PpIX photobleaching. These results indicate that the antioxidant NPG may significantly improve PDD efficiency.

Anti-inflammatory activity of n-propyl gallate through down-regulation of NF-κB and JNK pathways

The present study aimed to assess anti-inflammatory activity and underlying mechanism of n-propyl gallate, the n-propyl ester of gallic acid. n-Propyl gallate was shown to contain anti-inflammatory activity using two experimental animal models, acetic acid-induced permeability model in mice, and air pouch model in rats. It suppressed production of nitric oxide and induction of inducible nitric oxide synthase and cyclooxygenase-2 in the lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. It was able to diminish reactive oxygen species level elevated in the LPS-stimulated RAW264.7 macrophage cells. It also suppressed gelatinolytic activity of matrix metalloproteinase-9 enhanced in the LPS-stimulated RAW264.7 macrophage cells. It inhibited inhibitory κB-α degradation and enhanced NF-κB promoter activity in the stimulated macrophage cells. It was able to suppress phosphorylation of c-Jun NH(2)-terminal kinase 1/2 (JNK1/2) and activation of c-Jun promoter activity in the stimulated macrophage cells. In brief, n-propyl gallate possesses anti-inflammatory activity via down-regulation of NF-κB and JNK pathways.

The enhancement of propyl gallate-induced HeLa cell death by MAPK inhibitors is accompanied by increasing ROS levels

Propyl gallate (PG) as a synthetic antioxidant exerts a variety of effects on tissue and cell functions. Here, we investigated the effects of MAPK (MEK, JNK and p38) inhibitors on PG-treated HeLa cells in relation to cell death, ROS and GSH levels. PG induced cell growth inhibition and apoptosis in HeLa cells, which was accompanied by the loss of mitochondrial membrane potential (MMP; ΔΨm). ROS levels were increased or decreased in PG-treated HeLa cells depending on the incubation times. PG also increased GSH depleted cell numbers in HeLa cells. All the MAPK inhibitors slightly enhanced cell growth inhibition, death and MMP (ΔΨm) loss, and increased ROS levels in PG-treated HeLa cells. However, MAPK inhibitors did not significantly affect GSH depletion in PG-treated cells. In conclusion, the enhanced effect of MAPK inhibitors on PG-induced HeLa cell death was accompanied by increasing ROS levels but the effect was not related to changes of GSH level.

Metabolic stress-induced programmed cell death in Xanthomonas

Xanthomonas campestris pv. glycines (Xcg), an etiological agent of the bacterial pustule disease of soybean, displayed nutritionally regulated caspase-dependent programmed cell death (PCD). Experiments showed that Xcg was under metabolic stress during PCD, as evident from the intracellular accumulation of NADH and ATP. Further, the accumulation of reactive oxygen species (ROS), as confirmed by 2',7'-dichlorofluorescein diacetate labeling, electron spin resonance spectroscopy, and scopoletin assay, was also observed along with the activation of caspase-3. ROS scavengers such as dimethylsulfoxide, glutathione, n-propyl gallate, and catalase significantly inhibited caspase biosynthesis as well as its activity, eventually leading to the inhibition of PCD. The presence of a sublethal concentration of an electron transport chain uncoupler, 2,4-dinitrophenol, was found to reduce the ROS generation and the increase in the cell survival. These results indicated that Xcg cells grown in a protein-rich medium experienced metabolic stress due to electron leakage from the electron transport chain, leading to the generation of ROS and the expression as well as the activation of caspase-3, and resulting in PCD. A bacterial DNA gyrase inhibitor, nalidixic acid, was also found to inhibit PCD. Gyrase, which regulates DNA superhelicity, and consequently DNA replication and cell multiplication, appears to be involved in the process.

Modeling of the in vivo kinetics of antioxidants delineates suitable parameters for selecting potential antioxidant adjuvants for cancer therapy

To find in vivo behaviors of an antioxidant when used as an adjuvant cancer therapy, a more detailed integrated pharmacokinetic scheme is needed. Major reaction parameters associated with the sequential routes from ingestion to decay of an antioxidant were used in mathematical analysis, which included absorption rate coefficient k(a), quenching rate coefficient of the antioxidant k(q1) and tissue quenching rate coefficient k(r). The model was then treated with computer simulation using cited decay rate coefficients and some assumed parameters. When intestinal absorption rate coefficient k(a) becomes larger, retention time of antioxidant in plasma would be prolonged. moreover, k(a) had no effect on either quenching ability of antioxidants or tissue recovering capability. in quenching plasma ROS, the larger the quenching coefficient k(q1), the shorter peak- and the life-times would be for the secondary free radicals that are formed in primary quenching. Conclusively, it is suggestive to prescribe an antioxidant therapy with an appropriate values of k(a) and larger values of k(q1).

Propyl gallate inhibits the growth of calf pulmonary arterial endothelial cells via glutathione depletion

Propyl gallate (PG) as a synthetic antioxidant exerts a variety of effects on tissue and cell functions. Here, we evaluated the effects of PG on the growth and death of endothelial cells (ECs), especially calf pulmonary artery endothelial cells (CPAEC) in relation to reactive oxygen species (ROS) and glutathione (GSH). PG dose-dependently inhibited the growth of CPAEC and human umbilical vein endothelial cells (HUVEC) at 24h. PG induced cell death in CPAEC, which was accompanied by the loss of mitochondrial membrane potential (MMP; DeltaPsi(m)). PG generally increased ROS level in CPAEC but not in HUVEC. PG also dose-dependently increased GSH depleted cells in both ECs. The treatment with antioxidant of N-acetyl-cysteine (NAC) or ascorbate acid (AA) prevented CPAEC growth inhibition and death by PG, which was accompanied by the attenuation of GSH depletion but not by the reduction of ROS level. In conclusion, PG induced growth inhibition and death of ECs, especially CPAEC via GSH depletion.

Effects of propyl gallate on adhesion of polymorphonuclear leukocytes to human endothelial cells induced by tumor necrosis factor alpha

OBJECTIVE

To investigate the effects of Propyl Gallate (PrG) on cellular adhesion between human To investigate the effects of Propyl Gallate (PrG) on cellular adhesion between human umbilical vein endothelial cells (HUVEC) and polymorphonuclear leukocytes (PMN) as well as the expression umbilical vein endothelial cells (HUVEC) and polymorphonuclear leukocytes (PMN) as well as the expression of intercellular adhesion molecule-1 (ICAM-1, CD54) and E-selectin (CD62E) on the VEC surface. of intercellular adhesion molecule-1 (ICAM-1, CD54) and E-selectin (CD62E) on the VEC surface.

METHODS

A human VEC inflammation model was induced by tumor necrosis factor alpha (TNF-alpha). VECs were pre- A human VEC inflammation model was induced by tumor necrosis factor alpha (TNF-alpha). VECs were preincubated with varying concentrations of PrG (0.001-5 mmol/L) or 1 per thousand DMSO (v:v) or 10 mmol/L acetylsalicylic incubated with varying concentrations of PrG (0.001-5 mmol/L) or 1 per thousand DMSO (v:v) or 10 mmol/L acetylsalicylic acid (ASA) for 1 h, and then were stimulated with 10 ng/mL TNF-alpha for 6 h. Rose bengal vital staining method acid (ASA) for 1 h, and then were stimulated with 10 ng/mL TNF-alpha for 6 h. Rose bengal vital staining method was used to measure the adherence rate of PMN to VEC, while flow cytometry was used to determine the was used to measure the adherence rate of PMN to VEC, while flow cytometry was used to determine the expression of CD54 and CD62E on the VEC surface. expression of CD54 and CD62E on the VEC surface.

RESULTS

After 6 h of incubation with TNF-alpha, the adherence After 6 h of incubation with TNF-alpha, the adherence of PMN to HUVECs as well as the percentage of fluorescence-positive cells and mean fluorescence intensity of PMN to HUVECs as well as the percentage of fluorescence-positive cells and mean fluorescence intensity (MFI) of surface CD54 and CD62E in HUVECs increased significantly ( (MFI) of surface CD54 and CD62E in HUVECs increased significantly (P<0.01). Pre-treatment of HUVECs with <0.01). Pre-treatment of HUVECs with PrG (0.1-5 mmol/L) significantly suppressed the adherence of PMN to VECs induced by TNF-alpha (PrG (0.1-5 mmol/L) significantly suppressed the adherence of PMN to VECs induced by TNF-alpha (P<0.05). PrG <0.05). PrG (1-5 mmol/L) inhibited the VEC surface expression of CD62E and CD54 in a dose-dependent way ( (1-5 mmol/L) inhibited the VEC surface expression of CD62E and CD54 in a dose-dependent way (P<0.05). PrG <0.05). PrG at lower concentrations (0.001-0.1 mmol/L) showed no effect on CD54 expression, while it showed a slightly at lower concentrations (0.001-0.1 mmol/L) showed no effect on CD54 expression, while it showed a slightly increasing trend in CD62E expression (increasing trend in CD62E expression (P>0.05). ASA at 10 mmol/L had no obvious effect on the positive rate of >0.05). ASA at 10 mmol/L had no obvious effect on the positive rate of CD62E and CD54. CD62E and CD54.

CONCLUSIONS

High concentrations of PrG (0.1-5 mmol/L) exert its inhibitory effect on cellular High concentrations of PrG (0.1-5 mmol/L) exert its inhibitory effect on cellular adherence of PMN to HUVECs, and its mechanism may be related to inhibiting surface expression of CD54 and adherence of PMN to HUVECs, and its mechanism may be related to inhibiting surface expression of CD54 and CD62E in HUVECs. Its action concentration was lower than that of ASA. CD62E in HUVECs. Its action concentration was lower than that of ASA.

Compounds that confer thermal stress resistance and extended lifespan

The observation that long-lived and relatively healthy animals can be obtained by simple genetic manipulation prompts the search for chemical compounds that have similar effects. Since aging is the most important risk factor for many socially and economically important diseases, the discovery of a wide range of chemical modulators of aging in model organisms could prompt new strategies for attacking age-related disease such as diabetes, cancer and neurodegenerative disorders [Collins, J.J., Evason, K., Kornfeld, K., 2006. Pharmacology of delayed aging and extended lifespan of Caenorhabditis elegans. Exp. Gerontol.; Floyd, R.A., 2006. Nitrones as therapeutics in age-related diseases. Aging Cell 5, 51-57; Gill, M.S., 2006. Endocrine targets for pharmacological intervention in aging in Caenorhabditis elegans. Aging Cell 5, 23-30; Hefti, F.F., Bales, R., 2006. Regulatory issues in aging pharmacology. Aging Cell 5, 3-8]. Resistance to multiple types of stress is a common trait in long-lived genetic variants of a number of species; therefore, we have tested compounds that act as stress response mimetics. We have focused on compounds with antioxidant properties and identified those that confer thermal stress resistance in the nematode Caenorhabditis elegans. Some of these compounds (lipoic acid, propyl gallate, trolox and taxifolin) also extend the normal lifespan of this simple invertebrate, consistent with the general model that enhanced stress resistance slows aging.

BRCA1-mediated ubiquitination inhibits topoisomerase II alpha activity in response to oxidative stress

Topoisomerase IIalpha is known to be critically involved in both cell proliferation and cell death. The mechanisms responsible for stress-dependent topoisomerase IIalpha alterations, however, remain unclear. This study focused on the behavior of topoisomerase IIalpha in response to oxidative stress induced by hydrogen peroxide (H(2)O(2)). The catalytic activity of topoisomerase IIalpha in MOLT-4 cells treated with H(2)O(2) decreased in parallel with the alteration of topoisomerase IIalpha expression. The ubiquitination of topoisomerase IIalpha was dependent on oxidative stress. BRCA1, a tumor-suppressor gene, appeared to be involved in these alterations in topoisomerase IIalpha. Furthermore, the retinoblastoma protein (pRb) was required for the ubiquitination of topoisomerase IIalpha by BRCA1. We conclude that the functions of topoisomerase IIalpha are regulated by ubiquitination on exposure to oxidative stress.

n-Propyl gallate activates hypoxia-inducible factor 1 by modulating intracellular oxygen-sensing systems

HIF-1 (hypoxia-inducible factor 1) is a master regulator of cellular adaptive responses to hypoxia. The expression and transcriptional activity of the HIF-1alpha subunit is stringently controlled by intracellular oxygen tension through the action of prolyl and asparaginyl hydroxylases. In the present study we demonstrate that PG (n-propyl gallate) activates HIF-1 and expression of its downstream target genes under normoxic conditions in cultured cells and in mice. The stability and transcriptional activity of HIF-1alpha are increased by PG. PG treatment inhibits the interaction between HIF-1alpha and VHL (von Hippel-Lindau protein) and promotes the interaction between HIF-1alpha and p300, indicating that PG inhibits the activity of both prolyl and asparaginyl HIF-1alpha hydroxylases. We conclude that PG activates HIF-1 and enhances the resultant gene expression by directly affecting the intracellular oxygen sensing system in vitro and in vivo and that PG represents a lead compound for the development of a non-toxic activator of HIF-1.

Protective effects of pretreatment with Radix Paeoniae Rubra on acute lung injury induced by intestinal ischemia/reperfusion in rats

OBJECTIVE

To investigate the effect of pretreatment with Radix Paeoniae Rubra (RPR) on acute lung injury induced by intestinal ischemia/reperfusion in rats and its protective mechanism.

METHODS

Thirty-two Wistar rats were randomly divided into four groups: Sham-operation group, ischemia/reperfusion group (I/R group), RPR-pretreatment group and hemin group. The model of intestinal ischemia/reperfusion was established by clamping the superior mesenteric artery for 1 hour followed by 2-hour reperfusion. The effect of RPR on the expression of heme oxygenase-1 (HO-1) in lung tissues was detected by immunohistochemistry and morphometry computer image analysis. Arterial blood gas analysis, lung permeability index, malondialdehyde (MDA) and superoxide dismutase (SOD) contents in lungs were measured. The histological changes of lung tissue were observed under light microscope.

RESULTS

The expression of HO-1 in RPR-pretreatment group and hemin group was obviously higher than that in sham-operation group and I/R group (P < 0.01). The level of MDA and lung permeability index in RPR-pretreatment and hemin group were significantly lower than those in I/R group (P < 0.01 or P < 0.05), while the activity of SOD in RPR-pretreatment and hemin group was obviously higher than that in I/R group (P < 0.01). Under light microscope, the pathologic changes induced by I/R were significantly attenuated by RPR.

CONCLUSION

Intestinal ischemia/reperfusion may result in acute lung injury and pretreatment with RPR injection can attenuate the injury. The protective effect of RPR on the acute lung injury is related to its property of inducing HO-1 expression and inhibiting lipid peroxidation.

In vitro studies on the binding, antioxidant, and cytotoxic actions of punicalagin

The protective bioactivity of punicalagin, a high molecular weight polyphenol isolated from pomegranate fruit pith and carpellary membrane, against oxidative damages to lipids, amino acids constituting the proteins, and guanosine as a model for DNA has been investigated. The ABTS*-, guanosine, and tryptophan radical generated pulse radiolytically were repaired by punicalagin, k = (0.9-15) x 10(7) dm3 mol-1 s-1. The results are rationalized on the basis of the scavenging activity of punicalagin against various one-electron oxidizing radicals, namely, .OH, N3., and NO2. . The formation of the transient species in these reactions and the rate constants of the scavenging reactions have been probed using a time-resolved kinetic spectrophotometric technique. The antioxidant action of punicalagin is expressed not only through its scavenging reactions but also by its ability to form metal chelates. Binding of punicalagin with bovine serum albumin and metal ions such as iron and copper revealed different binding affinities, whereas its binding with DNA was very weak and nonspecific. In vitro cytotoxic studies against three cell lines, namely, Vero (normal African green monkey kidney cell line), Hep-2 (human larynx epithelial cancer cell line), and A-549 (human small cell lung carcinoma cell line) showed that this polyphenol is toxic only at higher concentration.

Radical scavenging and catalytic activity of metal-phenolic complexes

A series of metal-ligand complexes were prepared by the reaction of various metal ions, namely, Cu(II), Mn(II), or Fe(II) with phenolic derivatives of [catechol, chlorogenic acid (CGA), n-propyl gallate (nPG), 3-hydroxy anthranilic acid, resveratrol, and rutin] and characterized by UV-vis spectroscopy. The metal/ligand complexing ratio and complexation constants have been determined. The complexes were probed for their reactivity toward various free radicals (e aq-, CO2*-, and O2*-). Pulse radiolysis studies showed that the one-electron reduction of metal/phenol complexes by CO2*- radicals was metal-centered, and this was confirmed by the formation of an initial adduct with CO2*- radicals. Rate constants for the scavenging of superoxide anions with metal complexes ranged between 10(7)-10(9) dm3 mol(-1) s(-1) and those for the reaction of e aq- with the metal complexes were in the range of (1-5) x 10(9) dm3 mol(-1) s(-1), depending on the pH of the solution. Cyclic and differential pulse voltammetric studies showed that the reduction potential of the complexes are found to range between -0.022 to 0.45 V vs normal hydrogen electrode.

Thiol reducing compounds prevent human amylin-evoked cytotoxicity

Human amylin (hA) is a small fibrillogenic protein that is the major constituent of pancreatic islet amyloid, which occurs in most subjects with type-2 diabetes mellitus (T2Dm). There is growing evidence that hA toxicity towards islet beta-cells is responsible for their gradual loss of function in T2Dm. Preventing hA-mediated cytotoxicity has been proposed as a route to halt the progression of this disease, although this has not yet been demonstrated in vivo. The aim of our studies, in which we show that a small number of hA-treated cells exhibit intracellular accumulation of reactive oxygen species (ROS), was to evaluate the role of oxidative stress in the mechanism of hA-mediated cytotoxicity. Here we report that catalase and n-propyl gallate, antioxidants that are thought to act mainly as free radical scavengers, afford RINm5F cells only limited protection against hA-mediated toxicity. By contrast, the thiol antioxidants, N-acetyl-L-cysteine (NAC), GSH and dithiothreitol, which not only react with ROS, but also modulate the cellular redox potential by increasing intracellular levels of GSH and/or by acting as thiol reducing agents, afford almost complete protection and inhibit the progression of hA-evoked apoptosis. We also show that hA treatment is not associated with changes in intracellular GSH levels and that inhibition of GSH biosynthesis has no effect on either hA-mediated cytotoxicity or NAC-mediated protection. These results indicate that, in addition to the induction of oxidative stress, hA appears to mediate cytotoxicity through signalling pathways that are sensitive to the actions of thiol antioxidants.

Effects of propyl gallate on interaction between TNF-alpha and sTNFR-I using an affinity biosensor

AIM

To study the effects of propyl gallate on the interaction of tumor necrosis factor-alpha (TNF-alpha) with its soluble receptor, sTNFR-I.

METHODS

Interactions between TNF-alpha and sTNFR-I were analyzed using an IAsys biosensor. sTNFR-I was immobilized on the carboxymethyl dextran (CMD) surface of the IAsys biosensor cuvettes, and TNF-alpha preincubated with different concentrations of propyl gallate was added to the cuvettes. The resonant angle shift caused by the binding between TNF-alpha and sTNFR-I was then recorded.

RESULTS

sTNFR-I was immobilized on the CMD surface at a density of 2.76 ng/mm(2). TNF-alpha then bound the immobilized sTNFR-I specifically, and propyl gallate was able to enhance the binding between TNF-alpha and sTNFR-I in a dose-dependent manner.

CONCLUSION

The binding between TNF-alpha and sTNFR-I is one of the targets that propyl gallate can act on in vivo. The IAsys biosensor offers a new clue as to the study on the mechanisms of action of propyl gallate.

Cataract formation and prevention

Cataract, a leading cause of blindness worldwide, is a multifactorial eye disease. In developing countries the incidence of cataract among young generations is not uncommon due to malnutrition, excess exposure to ultraviolet radiation and so on. In developed countries, age-related cataract affecting the population over 65 years of age is a major concern. Oxidative stress was suggested to inflict damage to the lens and induce opacification, and a variety of antioxidant nutrients were tested for the prevention or delay of cataract development. Although promising results were obtained in animal studies of various antioxidants, epidemiological studies on human populations do not seem to support their protective effects unequivocally. It is unlikely that age-related cataract in man, similar to the ageing process itself, will be prevented or delayed by therapeutic drugs in the foreseeable future. At present, keeping a health-conscious life style (i.e., no smoking) may be the most effective and least expensive strategy to prevent the onset of age-related cataract.