Butylated hydroxyanisole inhibits tumor necrosis factor-induced cytotoxicity and arachidonic acid release

On the cytotoxicity and status of oxidative stress of two novel synthesized tri-aza macrocyclic diamides as studied in the V79 cell lines

Two tri-aza macrocycles as diamide derivatives of macrocyclic compounds possess a hydrophilic cavity surrounded by hydrophobic ring, which enables them to diffuse cell membrane and interfere with different living systems. In this study, we comparatively evaluated cytotoxicity effects of tri-aza dibenzo sulfoxide (TSD) and dibenzo sulfide (TTS) macrocyclic diamides in a range of doses (0.5-8mM) and the role of oxidative stress in V79 cell culture. We assessed the effects of these substances on ROS level, cellular viability, apoptosis events, activity of antioxidant enzymes including superoxide dismutase (SOD), glutathione peroxidase (GPX), catalase (CAT), and on some macromolecules' oxidative damage end-products: malondialdehyde (MDA), dityrosine, and 8-hydroxy-deoxyguanosine (8-OH-dG) that were assessed by spectrometry and HPLC methods. Both compounds revealed cytotoxicity effects on cell culture particularly at doses >1mM after 24-h incubation. They decreased cellular viability and significantly promoted ROS generation, increased enzyme activities, and enhanced oxidative damages in which TSD was more effective. Treatment of cells with each compound alone increased significantly the percent of apoptotic events at 2 and then 4mM. Co-treatment with alpha-tocopherol (alpha-TCP) drastically reduced these events. Cells' exposure with mixture of 30 microM alpha-tocopherol and 8mM of each compound exerted significant decrease in the levels of ROS, enzyme activities, and oxidative damage biomarkers. As conclusion, our study documented the oxidative radical forming ability of the studied compounds and further strengthened the documentation of their cytotoxicity effects through lipids, proteins and DNA oxidation damages.

Oxidative response of rat lung tissue after crown ethers exposure and the effects of alpha-tocopherol treatment

BACKGROUND

Ionophoric properties of crown ethers enable them ideally to transport across membranes and interfere with different living systems. We studied cytotoxicity effects of 18-crown-6 and 15-crown-5 and the role of oxidative stress in rat lung tissue culture.

METHODS

We assayed the effects of these crown ethers in a range of doses (0.1 to 2 mmol/l) on lipids and proteins oxidative damages end products; malondialdehyde (MDA) and dityrosine and on the activity of antioxidant enzymes; superoxide dismutase (SOD), glutathione peroxidase (GPX), catalase (CAT), in rat lung tissue culture by spectrometry and HPLC.

RESULTS

Both compounds significantly increased the levels of MDA, dityrosine and enzyme activities at doses >0.5 mmol/l after 48-h incubation in the lung tissue, representing promotion of ROS generation with respect to control. These effects were more considerable for 18-crown-6 than 15-crown-5. Treatment of lung tissue with 30 microm of alpha-tocopherol in addition to 2 mmol/l of crown ethers showed significant decrease on the levels of enzyme activities, MDA and dityrosine.

CONCLUSION

We showed the oxidative radicals forming ability of crown ethers as documented in their toxicity effects through lipid and proteins oxidation damages.

Closely related colon cancer cell lines display different sensitivity to polyunsaturated fatty acids, accumulate different lipid classes and downregulate sterol regulatory element-binding protein 1

N-6 polyunsaturated fatty acids (PUFAs) may be associated with increased risk of colon cancer, whereas n-3 PUFAs may have a protective effect. We examined the effects of docosahexaenoic acid (DHA), eicosapentaenoic acid and arachidonic acid on the colon carcinoma cell lines SW480 derived from a primary tumour, and SW620 derived from a metastasis of the same tumour. DHA had the strongest growth-inhibitory effect on both cell lines. SW620 was relatively more growth-inhibited than SW480, but SW620 also had the highest growth rate in the absence of PUFAs. Flow cytometry revealed an increase in the fraction of cells in the G2/M phase of the cell cycle, particularly for SW620 cells. Growth inhibition was apparently not caused by increased lipid peroxidation, reduced glutathione or low activity of glutathione peroxidase. Transmission electron microscopy revealed formation of cytoplasmic lipid droplets after DHA treatment. In SW620 cells an eightfold increase in total cholesteryl esters and a 190-fold increase in DHA-containing cholesteryl esters were observed after DHA treatment. In contrast, SW480 cells accumulated DHA-enriched triglycerides. Arachidonic acid accumulated in a similar manner, whereas the nontoxic oleic acid was mainly incorporated in triglycerides in both cell lines. Interestingly, nuclear sterol regulatory element-binding protein 1 (nSREBP1), recently associated with cell growth regulation, was downregulated after DHA treatment in both cell lines. Our results demonstrate cell-specific mechanisms for the processing and storage of cytotoxic PUFAs in closely related cell lines, and suggest downregulation of nSREBP1 as a possible contributor to the growth inhibitory effect of DHA.

An ortho dimer of butylated hydroxyanisole inhibits nuclear factor kappa B activation and gene expression of inflammatory cytokines in macrophages stimulated by Porphyromonas gingivalis fimbriae

Butylated hydroxyanisole, BHA, is widely used as a potent antioxidant, but its adverse effects such as carcinogenesis and proinflammatory activity have been reported, which are possibly due to the prooxidant property of this compound. We recently demonstrated that the dimer of 2-methoxyphenols exhibits cyclooxygenase-2 inhibition, because of lessening of its prooxidant property caused by the dimerization. In the present study, toward our goal of developing a chemopreventive agent for chronic periodontal diseases, we examined whether 2-BHA (2-tert-butyl-4-methoxyphenol) and its synthetic ortho dimer, bis-BHA (3,3'-di-tert-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diol) could inhibit the Porphyromonas gingivalis fimbria-stimulated inflammatory reaction. The fimbria-induced expression of interleukin-1beta and neutrophil chemoattractant KC genes in RAW264.7 murine macrophages was strongly inhibited by bis-BHA. In contrast, 2-BHA showed only slight inhibition. bis-BHA also significantly inhibited the fimbria-stimulated phosphorylation-dependent degradation of the alpha inhibitor of nuclear factor-kappaB and the transcriptional activity of this factor in the cells. These findings suggest that bis-BHA possesses anti-inflammatory activity against chronic periodontal diseases.

Cytotoxicity and the levels of oxidative stress parameters in WI38 cells following 2 macrocyclic crown ethers treatment

BACKGROUND

Crown ethers as macrocyclic polyethers possess a hydrophilic cavity surrounded by hydrophobic ring which enable them to diffuse cell membrane. We evaluated cytotoxicity effects of 15-crown-5 and 18-crown-6 and the role of oxidative stress in WI38 cells culture.

METHODS

The effect of these ethers in a range of doses (0.1 to 2 mmol/l) on the activity of antioxidant enzymes; superoxide dismutase (SOD), glutathione peroxidase (GPX), catalase (CAT), and on some macromolecules oxidative damages end products; malondialdehyde (MDA) and dityrosine were assessed by spectrometry and HPLC methods.

RESULTS

Both compounds markedly inhibited the viability of cells with respect to control particularly at doses >0.5 mmol/l after 24- or 48 h incubation. The survivals of cells were measured using MTT assay. They lowered cell's viability and significantly promoted ROS generation, increased enzyme activities and enhanced oxidative damages in which 18-crown-6 was more effective. Treating cells with 30 microm of alpha-tocopherol in addition to 2 mmol/l of crown ethers showed significant decrease on the levels of ROS, enzyme activities, MDA and dityrosine.

CONCLUSION

We document the oxidative radicals forming ability of the studied crown ethers and further strengthens the documentation of their cytotoxicity effects through lipid and proteins oxidation damages.

Cell specific effects of polyunsaturated fatty acids on 5-aminolevulinic acid based photosensitization

The purpose of this study was to examine whether the dietary components n-6 and n-3 polyunsaturated fatty acids (PUFAs) may potentiate the effect of photodynamic therapy (PDT) in human cancer cell lines by enhancing the lipid peroxidation. The effects of the porphyrin precursor 5-aminolevulinic acid (5-ALA) and light (320 < lambda < 440 nm, 33 W m(-2)), with or without docosahexaenoic acid (DHA) or arachidonic acid (AA), were tested in the colon carcinoma cell lines SW480 and WiDr, the glioblastoma cell line A-172 and the lung adenocarcinoma cell line A-427. The production of endogenous protoporphyrin IX (PpIX) varied substantially between the cell lines and was approximately 4-fold higher in WiDr as compared with SW480. Cell killing by 5-ALA-PDT also varied between the cell lines, but without clear correlation with PpIX levels. Treatment with DHA or AA (10 or 70 microM, 48 or 72 h) in combination with 5-ALA-PDT (1 or 2 mM) enhanced the cytotoxic effect in A-172 and A-427 cells, but not in SW480 and WiDr cells. While 5-ALA-PDT alone increased the lipid peroxidation in A-172 and WiDr cells only, 5-ALA-PDT plus PUFAs increased the lipid peroxidation substantially in all four cell lines. Interestingly, alpha-tocopherol (50 microM, 48 h) strongly reduced lipid peroxidation after all treatments in all cell lines, while cytotoxicity was only reduced substantially in A-427 cells. This demonstrates that induction of lipid peroxidation is not a general mechanism responsible for the cytotoxicity of 5-ALA-PDT, although it may be important in cell lines with an inherent sensitivity to lipid peroxidation products. Thus, the mechanisms of cell growth inhibition/cell killing by PDT are complex and cell specific.

Oxidant mechanisms in response to ambient air particles

The toxic effects of air pollution are widely documented. In recent years, however, there has been an increasing interest in the study of the health effects of particulate matter (PM), a previously unexplored constituent of urban air pollution. Exposure to increased levels of PM of respirable size is strongly and consistently associated with increased cardiopulmonary morbidity and mortality. Conversely, improved air quality appears to correlate with decreased mortality. Particulate matter is a mixture of inorganic and organic components that vary in size, origin, and composition. The mechanisms of PM health effects are still poorly understood. However, studies in cellular and animal models suggest a variety of possible mechanisms including direct effects of particle components on the intracellular sources of reactive oxygen species (ROS), indirect effects due to pro-inflammatory mediators released from PM-stimulated macrophages, and neural stimulation after particle deposition in the lungs. The involvement of ROS in each one of these possible pathways is discussed.

Final report on the safety assessment of BHT(1)

BHT is the recognized name in the cosmetics industry for butylated hydroxytoluene. BHT is used in a wide range of cosmetic formulations as an antioxidant at concentrations from 0.0002% to 0.5%. BHT does penetrate the skin, but the relatively low amount absorbed remains primarily in the skin. Oral studies demonstrate that BHT is metabolized. The major metabolites appear as the carboxylic acid of BHT and its glucuronide in urine. At acute doses of 0.5 to 1.0 g/kg, some renal and hepatic damage was seen in male rats. Short-term repeated exposure to comparable doses produced hepatic toxic effects in male and female rats. Subchronic feeding and intraperitoneal studies in rats with BHT at lower doses produced increased liver weight, and decreased activity of several hepatic enzymes. In addition to liver and kidney effects, BHT applied to the skin was associated with toxic effects in lung tissue. BHT was not a reproductive or developmental toxin in animals. BHT has been found to enhance and to inhibit the humoral immune response in animals. BHT itself was not generally considered genotoxic, although it did modify the genotoxicity of other agents. BHT has been associated with hepatocellular and pulmonary adenomas in animals, but was not considered carcinogenic and actually was associated with a decreased incidence of neoplasms. BHT has been shown to have tumor promotion effects, to be anticarcinogenic, and to have no effect on other carcinogenic agents, depending on the target organ, exposure parameters, the carcinogen, and the animal tested. Various mechanism studies suggested that BHT toxicity is related to an electrophillic metabolite. In a predictive clinical test, 100% BHT was a mild irritant and a moderate sensitizer. In provocative skin tests, BHT (in the 1% to 2% concentration range) produced positive reactions in a small number of patients. Clinical testing did not find any depigmentation associated with dermal exposure to BHT, although a few case reports of depigmentation were found. The Cosmetic Ingredient Review Expert Panel recognized that oral exposure to BHT was associated with toxic effects in some studies and was negative in others. BHT applied to the skin, however, appears to remain in the skin or pass through only slowly and does not produce systemic exposures to BHT or its metabolites seen with oral exposures. Although there were only limited studies that evaluated the effect of BHT on the skin, the available studies, along with the case literature, demonstrate no significant irritation, sensitization, or photosensitization. Recognizing the low concentration at which this ingredient is currently used in cosmetic formulations, it was concluded that BHT is safe as used in cosmetic formulations.

5-aminolevulinic acid induced lipid peroxidation after light exposure on human colon carcinoma cells and effects of alpha-tocopherol treatment

This work relates to studies on modes of phototoxicity by protoporphyrin (PpIX) after incubation of 5-aminolevulinic acid (5-ALA) on cultured cells. Lipid peroxidation in the 5-ALA incubated primary adenocarcinoma cells from the rectosigmoid colon (WiDr cells) was determined by measurement of protein-associated thiobarbituric acid reactive substances (TBARS). TBARS were increased 2-fold in cells treated with 2 mM 5-ALA for 3.5 h in serum enriched medium. After illumination of 5-ALA incubated cells, TBARS were formed in a light dose dependent manner. TBARS analysis were compared with high-performance liquid chromatography (HPLC) analysis of malondialdehyde, and results indicate that 90% of the thiobarbituric reactive substances were due to malondialdehyde. Pretreating WiDr cells with alpha-tocopherol for 48 h inhibits the cytotoxic effect of 5-ALA and increases 5-fold the light dose needed to kill 50% of the cells. Pretreatment with alpha-tocopherol shows a considerable decrease (about 80%) on TBARS formation after illumination. The cellular content of alpha-tocopherol was determined by HPLC and found to be 15.3 pmol/10(6) cells.

Sensitization to death receptor cytotoxicity by inhibition of fas-associated death domain protein (FADD)/caspase signaling. Requirement of cell cycle progression

Upon binding of their ligands, death receptors belonging to the tumor necrosis factor (TNF) receptor family initiate a signaling pathway leading to the activation of caspases and ultimately apoptosis. TNF, however, in parallel elicits survival signals, protecting many cell types from cell death that can only be induced by combined treatment with TNF and inhibitors of protein synthesis. Here, we report that in NIH3T3 cells, apoptosis in response TNF and cycloheximide is not inhibited by the broad spectrum caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVAD. fmk). Moreover, treatment with zVAD.fmk sensitizes the cells to the cytotoxic action of TNF. Sensitization was also achieved by overexpression of a dominant-negative mutant of Fas-associated death domain protein and, to a lesser extent, by specific inhibition of caspase-8. A similar, but weaker sensitization of zVAD.fmk to treatment with the TNF-related apoptosis-inducing ligand (TRAIL) or anti-CD95 antibody was demonstrated. The unexpected cell death in response to TNF and caspase inhibition occurs despite the activation of nuclear factor kappaB and c-Jun N-terminal kinases. The mode of cell death shows several signs of apoptosis including DNA fragmentation, although activation of caspase-3 was excluded. TNF/zVAD.fmk-induced cell death is preceded by an accumulation of cells in the G(2)/M phase of the cell cycle, indicating an important role of cell cycle progression. This hypothesis is further strengthened by the observation that arresting the cells in the G(1) phase of the cell cycle inhibited TNF/zVAD.fmk-induced cell death, whereas blocking them in the G(2)/M phase augmented it.

BHA diet enhances the survival of mice exposed to phosgene: the effect of BHA on glutathione levels in the lung

Phosgene-induced pulmonary edema formation has been under investigation for many years. One mechanism of protection may involve the use of antioxidants. Previously, it has been shown that butylated hydroxyanisole (BHA) treatment can enhance glutathione (GSH) levels. The present study focused on dietary supplementation in mice using BHA, a phenolic compound used in food preservation. Three groups of male CD-1 mice were studied: group 1, control animals fed with Purina rodent chow 5002; group 2, fed 0.75% BHA (w/w) in 5002; and group 3, fed 1.5% BHA (w/w) in 5002. Mice were fed for 22 days. On day 23 mice were exposed to 32 mg/m(3) phosgene for 20 min in a whole-body exposure chamber. Survival rate (SR) and odds ratio (OR) were determined at 12 and 24 h. In mice that died within 12 h, the lungs were removed immediately and lung wet weights (WW), dry weights (DW), lung wet weight/body weight ratio (LWW/BW), and lung tissue total glutathione (GSH) were assessed. For 12-h data, 6 mice from the 1.5% BHA group were sacrificed for lung tissue measurements. The SR for 0.75% BHA was 80% at 12 h and 55% at 24 h, compared with 36% and 23%, respectively, for controls. For 1.5% BHA, the 12- and 24-h SR were 100% and 92%, respectively. Odds ratios of 6.9 for 0.75% BHA and 46.6 for 1.5% BHA at 12 h and 4.0 and 42 for 0. 75% and 1.5% BHA, respectively, at 24 h were significantly (chi2) higher than control diet phosgene-exposed mice. Dietary pretreatment with 0.75% and 1.5% BHA significantly enhanced lung tissue GSH, 1.8-fold (p < or =.01) and 5.8-fold (p < or =.01), respectively, compared with phosgene-exposed control diet. Both BHA-supplemented diets significantly reduced WW. Only 1.5% BHA reduced DW, a measure of lung hyperaggregation. and LWW/BW compared with control diet. In air-exposed controls, BHA induced a dose-responsive decrease in WW, DW, LWW/BW ratio, and GSH. In conclusion, dietary pretreatment with BHA at the two dose levels reduced lung edema and lethality by enhancing lung tissue GSH in mice exposed to phosgene.

How does superoxide dismutase protect against tumor necrosis factor: a hypothesis informed by effect of superoxide on "free" iron

The manganese-containing mitochondrial superoxide dismutase (MnSOD) is induced by TNF and protects against the necrotic effect of this cytokine. Yet TNF does not increase production of O2- in mitochondria. How is this to be reconciled? TNF is known to increase production of arachidonate, by activation of phospholipase A2 (PLA2). Arachidonate will be converted to the corresponding alkyl hydroperoxide by lipoxygenase. O2- increases "free" iron by oxidizing [4Fe-4S] clusters of dehydratases, such as aconitase. Ferrous iron in turn reacts with alkyl hydroperoxides, in an analogue of the Fenton reaction, to produce alkoxyl radicals: which can initiate the oxidation of polyunsaturated lipids by a free radical chain reaction. MnSOD protects against TNF by decreasing O2- attack on [4Fe-4S] clusters and thus lowering free iron. Inhibitors of PLA2 and of lipoxygenase should also protect by decreasing fatty acyl hydroperoxides and they are known to do so. Cells having little mitochondrial MnSOD, or cells unable to induce that defensive enzyme in response to TNF, will consequently have relatively high levels of "free" iron in that organelle; leading to enhanced lipid peroxidation. Such cells will be preferentially killed by this cytokine.

Effects of hydroquinone-type and phenolic antioxidants on calcium signals and degranulation of RBL-2H3 cells

We previously reported that a hydroquinone-type antioxidant, 2,5-di(tert-butyl)-1,4-hydroquinone (DTBHQ), increases intracellular free Ca2+ concentration ([Ca2+]i), causes degranulation together with a protein kinase C activator, phorbol 12-myristate 13-acetate (TPA), and increases antigen-induced degranulation in rat basophilic leukemia (RBL-2H3) cells. In this study, the effects of five-hydroquinone-type and phenolic antioxidants (2,5-di(tert-amyl)-1,4-hydroquinone [DTAHQ], 2-tert-butyl-1,4-hydroquinone [MTBHQ], 3,5-di(tert-butyl)-4-hydroxytoluene [BHT], 3,5-di(tert-butyl)-4-hydroxyanisole [DTBHA], and 3-tert-butyl-4-hydroxyanisole [MTBHA]) on [ca2+]i and degranulation (beta-hexosaminidase release) were examined and compared with that of DTBHQ. DTAHQ (> or = 3 microM) showed effects similar to those of DTBHQ (10 microM) on [Ca2+]i elevation, induction of degranulation with TPA, and increase of antigen-induced degranulation. BHT (50 microM) and DTBHA (50 microM) caused [Ca2+]i elevation and increased degranulation in the presence of TPA or antigen, but their effects were less than those of DTBHQ and DTAHQ. MTBHQ and MTBHA had no effect on [Ca2+]i and degranulation, even at 50 microM. The degree of Ca2+ response caused by the compounds correlated well with the increase in degranulation, but not with their antioxidant activity estimated with the first oxidation potential. From these results, it is suggested that the increasing effects of six antioxidants on degranulation in the presence of TPA or antigen were dependent on [Ca2+]i increase caused by the compounds, probably through their ability to inhibit endoplasmic reticulum Ca2+-ATPase.

The antioxidant, U74389, ameliorates the depression of vascular reactivity caused by lipopolysaccharide

There is growing evidence that an oxidant stress contributes to the deleterious effects of bacterial lipopolysaccharide (LPS). The present study evaluated the ability of the antioxidant, U74389, to prevent the depression of vascular reactivity caused by LPS. Aortic rings taken from rats given LPS showed a depression of maximum force in response to phenylephrine that was reversed by an inhibitor of nitric oxide synthase. Pretreatment of animals with U74389 attenuated this depression of vascular reactivity. U74389 did not limit the increase in serum tumor necrosis factor levels caused by LPS. These results show that U74389 can ameliorate the depression of vascular reactivity caused by LPS possibly by interfering with the induction of nitric oxide synthase.

Redox regulation of programmed cell death in lymphocytes

A redox imbalance caused by an over-production of prooxidants or a decrease in antioxidants seems to play a role in the programmed cell death that occurs in various developmental programs. Such a physiological function for oxidative stress is particularly applicable to the immune system, wherein individual lymphocytes undergo continuous scrutiny to determine if they should be preserved or programmed to die. Following activation, lymphocytes produced increased levels of reactive oxygen species (ROS) which may serve as intracellular signaling molecules. The ultimate outcome of this increased ROS formation, i.e., lymphocyte proliferation versus programmed cell death, may be dictated by macrophage-derived costimulatory molecules that bolster or diminish lymphocyte antioxidant defenses. HIV-1-infected individuals display multiple symptoms of redox imbalance consistent with their being in oxidative stress, and lymphocytes from such individuals are more prone to undergo apoptosis in vitro. It is suggested that oxidative stress, and lymphocytes from such individuals are more prone to undergo apoptosis in vitro. It is suggested that oxidative stress is a physiological mediator of programmed cell death in lymphoid cells, and that HIV disease represents an extreme case of what can happen when regulatory safeguards are compromised.