Anti-inflammatory potential of ursolic acid in Mycobacterium tuberculosis-sensitized and concanavalin A-stimulated cells.

Ursolic acid (3-ß-3-hydroxy-urs-12-ene-28-oic-acid; UA) is a triterpenoid carboxylic acid with various pharmaceutical properties. It is commonly found in apples, basil, berries, rosemary, peppermint, lavender, oregano, thyme, hawthorn and prunes. In the present study, the activities of UA against the Mycobacterium tuberculosis H37Rv­induced release of a panel of inflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin (IL)-1ß and IL-6 from RAW 264.7 murine macrophages, A549 alveolar epithelial cells and in concanavalin A (Con A)-stimulated rat splenocytes were investigated. In addition, the present study examined the ability of UA to reduce the expression levels of the inflammatory mediators, cyclooxygenase­2 (COX­2) and inducible nitric oxide synthase (iNOS) in the stimulated cells. The reduction of nitric oxide (NO) release by UA was also examined in the stimulated cells. UA significantly inhibited the mRNA expression levels of TNF­α, IL­1ß and IL­6 in the stimulated cells. The expression levels of COX­2 and iNOS were also suppressed by UA, as was the release of NO at a significant level. The data indicated the potency of UA on different cell types, which may assist in the development of anti­inflammatory drugs. In the case of adjunct host­directed immune therapy for tuberculosis, UA may be used, in addition to established antibiotic therapies, to improve treatment efficacy and outcome due to their anti­inflammatory potential. Further detailed investigations are required to establish its use as an anti-inflammatory.

Ursolic Acid Reduces Mycobacterium tuberculosis-Induced Nitric Oxide Release in Human Alveolar A549 cells.

Alveolar epithelial cells have been functionally implicated in Mycobacterium tuberculosis infection. This study investigated the role of ursolic acid (UA)-a triterpenoid carboxylic acid with potent antioxidant, anti-tumor, anti-inflammatory, and anti-tuberculosis properties in mycobacterial infection of alveolar epithelial A549 cells. We observed that M. tuberculosis successfully entered A549 cells. Cytotoxi-city was mediated by nitric oxide (NO). A549 toxicity peaked along with NO generation 72 h after infection. The NO generated by mycobacterial infection in A549 cells was insufficient to kill mycobacteria, as made evident by the mycobacteria growth indicator tube time to detect (MGIT TTD) and viable cell count assays. Treatment of mycobacteria-infected cells with UA reduced the expression of inducible nitric oxide synthase, NO generation, and eventually improved cell viability. Moreover, UA was found to quench the translocation of the transcription factor, nuclear factor kappa B (NF-κB), from the cytosol to the nucleus in mycobacteria-infected cells. This study is the first to demonstrate the cytotoxic role of NO in the eradication of mycobacteria and the role of UA in reducing this cytotoxicity in A549 cells.

In vitro effect of ursolic acid on the inhibition of Mycobacterium tuberculosis and its cell wall mycolic acid.

Mycobacterium tuberculosis is a dangerous intracellular pathogen. In order to protect against mycobacterium infection, novel agents with anti-mycobacterial activity should be given emergency priority for evaluation. Ursolic acid (UA), a plant triterpenoid, shows promising bioactivities, including anti-mycobacterial potency. In this study, the action of UA against Mycobacterium tuberculosis H37Ra was evaluated, and the inhibitory concentration was found to range between 10 and 20 µg/ml in a resazurin assay and MGIT 960 instrument. The total mycolic acid in UA-treated H37Ra was detected and compared with INH-treated and non-treated bacterium by LC-MS/MS. Quantitative LC-MS/MS data confirmed that both UA and INH decreased mycolic acid biosynthesis in a dose-dependent manner. Thin-layer chromatogram (TLC) analysis showed that all mycolic acid subtypes were affected by UA treatment in the wild type but not in strains resistant to UA. Electron microscopy images also confirmed that UA treatment affected both H37Ra cell and intracellular content of H37Ra. Altogether, these data confirmed the promise of the inhibitory action of UA in mycolic acid, which might further delineate the mechanistic pathway of mycobacterial inhibition by UA.

Extracellular signal-regulated kinase pathway play distinct role in acetochlor-mediated toxicity and intrinsic apoptosis in A549 cells.

Acetochlor (ACETO), a member of the chloroacetanilide family of herbicides, is widely used globally and is very frequently detected in watersheds of agricultural lands and fresh water streams. The human health consequences of environmental exposure to ACETO are unknown. This study was designed to elucidate the effect and molecular mechanisms of ACETO on human alveolar A549 cells. Established assays of cell viability and cytotoxicity were performed to detect the potential effects of ACETO on A549 cells. ACETO generated reactive oxygen species, which may have been crucial to apoptosis-mediated cytotoxicity. ACETO-treatment showed a concentration dependent up-regulation of pro-apoptotic proteins including Bax, Bak, BID and Bad, but a differential level of expression of anti-apoptotic proteins were observed, leading to the release of cytochrome c from mitochondria to the cytoplasm as well as activation of caspase-3, and cleavage of caspase-9 and PARP. ACETO also induced activation of extracellular signal-regulated kinase (ERK). Inhibition of the expression of ERK by PD98059 partially reversed ACETO-induced cytotoxicity, apoptosis and the expression of caspase-3, -9 and PARP in A549 cells. Comparative evaluation of the results indicates that the principal mechanism underlying ACETO-mediated cytotoxicity is likely to be through ERK-mediated intrinsic pathway of apoptosis.

Effects of formaldehyde on mitochondrial dysfunction and apoptosis in SK-N-SH neuroblastoma cells.

Methanol ingestion is neurotoxic in humans due to its metabolites, formaldehyde and formic acid. Here, we compared the cytotoxicity of methanol and its metabolites on different types of cells. While methanol and formic acid did not affect the viability of the cells, formaldehyde (200-800 µg/mL) was strongly cytotoxic in all cell types tested. We investigated the effects of formaldehyde on oxidative stress, mitochondrial respiratory functions, and apoptosis on the sensitive neuronal SK-N-SH cells. Oxidative stress was induced after 2 h of formaldehyde exposure. Formaldehyde at a concentration of 400 µg/mL for 12 h of treatment greatly reduced cellular adenosine triphosphate (ATP) levels. Confocal microscopy indicated that the mitochondrial membrane potential (MMP) was dose-dependently reduced by formaldehyde. A marked and dose-dependent inhibition of mitochondrial respiratory enzymes, viz., NADH dehydrogenase (complex I), cytochrome c oxidase (complex IV), and oxidative stress-sensitive aconitase was also detected following treatment with formaldehyde. Furthermore, formaldehyde caused a concentration-dependent increase in nuclear fragmentation and in the activities of the apoptosis-initiator caspase-9 and apoptosis-effector caspase-3/-7, indicating apoptosis progression. Our data suggests that formaldehyde exerts strong cytotoxicity, at least in part, by inducing oxidative stress, mitochondrial dysfunction, and eventually apoptosis. Changes in mitochondrial respiratory function and oxidative stress by formaldehyde may therefore be critical in methanol-induced toxicity.

Cytotoxicity and gene expression profiling of polyhexamethylene guanidine hydrochloride in human alveolar A549 cells.

In Korea, lung disease of children and pregnant women associated with humidifier disinfectant use has become a major concern. A common sterilizer is polyhexamethylene guanidine (PHMG), a member of the guanidine family of antiseptics. This study was done to elucidate the putative cytotoxic effect of PHMG and the PHMG-mediated altered gene expression in human alveolar epithelial A549 cells in vitro. Cell viability analyses revealed the potent cytotoxicity of PHMG, with cell death evident at as low as 5 µg/mL. Death was dose- and time-dependent, and was associated with formation of intracellular reactive oxygen species, and apoptosis significantly, at even 2 µg/mL concentration. The gene expression profile in A549 cells following 24 h exposure to 5 µg/mL of PHMG was investigated using DNA microarray analysis. Changes in gene expression relevant to the progression of cell death included induction of genes related to apoptosis, autophagy, fibrosis, and cell cycle. However, the expressions of genes encoding antioxidant and detoxifying enzymes were down-regulated or not affected. The altered expression of selected genes was confirmed by quantitative reverse transcription-polymerase chain reaction and Western blot analyses. The collective data suggest that PHMG confers cellular toxicity through the generation of intracellular reactive oxygen species and alteration of gene expression.

Antioxidant action of ellagic acid ameliorates paraquat-induced A549 cytotoxicity.

Ellagic acid (EA) is a natural dietary polyphenol whose benefits in a variety of diseases shown in epidemiological and experimental studies involve anti-inflammation, anti-proliferation, anti-angiogenesis, anti-carcinogenesis and anti-oxidation properties. This study aimed to evaluate the effect of EA against paraquat (PQ)-induced oxidative stress. PQ decreased the viability of A549 cells in dose- and time-dependent manners, which was associated with the massive generation of reactive oxygen species (ROS). However, cell viability was significantly recovered by the treatment of EA, from 47.01±1.59% to 66.04±2.84%. The release of lactate dehydrogenase (LDH) was also decreased with the treatment of EA in PQ-treated A549 cells. EA induced the level of expression and activation of nuclear factor-erythroid 2-related factor (Nrf2) and its target cytoprotective and antioxidant genes, heme oxygenase-1 (HO-1) and quinone oxidoreductase 1 (NQO1). The antioxidant potential of EA might be directly correlated with the increased expression of HO-1 and NQO1, whose expression may have surmounted the oxidative stress generated by PQ. Notably, EA treatment significantly reduced the levels of biochemical markers as lipid peroxidation, reduced the intracellular ROS level, and surmounted total glutathione level in A549 cells. Data indicate that the antioxidant and cytoprotective properties of EA reduce PQ-induced cytotoxicity in human alveolar A549 cells.

Protein profiling of paraquat-exposed rat lungs following treatment with Acai (Euterpe oleracea Mart.) berry extract.

Paraquat (1,1'-dimethyl-4,4'-bipyridinium chloride, PQ) is a non-selective herbicide, and PQ poisoning by accidental or intentional ingestion is a cause of numerous fatalities around the world every year. Although a great deal of research has been conducted into the development of an acceptable treatment for PQ poisoning, no effective guidelines for patients have been developed thus far. Acai berry extract and juice have been highlighted in this regard, due to their observed antioxidant effects in various diseases. Furthermore, the acai berry has been used in dietary supplements, as it contains a variety of nutrients, including proteins, lipids, vitamins A, C and E and polyphenols. In this study, we conducted proteomic analysis of PQ-poisoned rat lungs to evaluate the changes in protein expression induced by PQ and to identify any protective effects of acai berry on the PQ poisoning. Our data revealed that the expression of the calcium signaling-related proteins calcium binding protein 1 (CaBP1), FK506 binding protein 4 (FKBP4), S100A6 and secreted protein acidic and rich in cysteine (Sparc, also known as osteonectin) were induced by PQ treatment and downregulated by acai berry treatment. However, the levels of protein kinase C substrate 80K-H were shown to be downregulated as the result of PQ treatment. Our results indicated that these proteins may function as biomarkers for acute poisoning by PQ exposure. Further studies may be necessary to understand their clinical relevance with regard to PQ poisoning.

Quercetin reduces oxidative damage induced by paraquat via modulating expression of antioxidant genes in A549 cells.

Oxidative injury can occur in the lung through the generation of reactive oxygen species (ROS) via redox cycling owing to intentional or accidental ingestion of paraquat (PQ), a common herbicide. A wide array of phytochemicals has been shown to reduce cellular oxidative damage by modulating cytoprotective genes. Quercetin, a well-known flavonoid, has been reported to display cytoprotective effects by up-regulating certain cytoprotective genes. In this context, we investigated the effect of quercetin on PQ-induced cytotoxicity in alveolar A549 cells, modulation of antioxidant genes, activation of transcription factor-Nrf2 and its target HO-1 expression. Quercetin reduced PQ-induced cytotoxicity in A549 cells that was evaluated by both 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays. Modulation of antioxidant genes was compared when cells were treated with PQ, quercetin and both using qRT-PCR. Activation of transcription factor-Nrf2 and induction of its target gene, HO-1 was demonstrated by western blot analysis. A remarkable reduction in the ROS level as well as an increase in the total cellular glutathione (GSH) level occurred when PQ-exposed cells were treated with quercetin. Our findings suggest that quercetin may be used to mitigate or minimize oxidative stress via reducing the generation of ROS.

Antioxidant effect of silymarin on paraquat-induced human lung adenocarcinoma A549 cell line.

Paraquat (PQ) is not only widely used as a potent herbicide but also causes severe fatality to humans around the world due to accidental or intentional ingestion. Silymarin is a well-known phytochemical whose multi-functional effects in humans include anti-oxidant, anti-inflammatory and anti-cancer activities. The efficacy of silymarin in protecting against PQ-induced cytotoxicity is unknown. This study investigated the potential role of silymarin against PQ-induced oxidative stress on human A549 adenocarcinoma cell line. Colorimetric-based viability assay, determination of reactive oxygen species, cell damage assay based on lactate dehydrogense retention, anti-oxidant enzyme assay, Western blot and quantitative reverse transcription-polymerase chain reaction analyses were done. Our data revealed that silymarin could dramatically prevent cell toxicity, and reduce the LDH retention induced by PQ on A549 cell line. Silymarin acted as a potent cytoprotective effector through the effective induction of anti-oxidant related genes, including Nrf2, NQO1 and HO-1, in the presence of PQ. The induction of the Nrf2, HO-1 and NQO1 genes was first evident after 3h. The data indicate the potential of silymarin in alleviating PQ intoxication.

Protective effect of methylprednisolone on paraquat-induced A549 cell cytotoxicity via induction of efflux transporter, P-glycoprotein expression.

Paraquat (PQ) is the third most extensively used herbicide in the world, causing thousands of deaths due to accidental or intentional self-poisoning in developing countries. Although many therapeutic treatments for PQ-induced poisonings have been proposed and developed, the efficacy of these treatments is still poor and requires further investigation. Methylprednisolone (trade name Solumedrol, hereinafter MP) is a widely used steroid for the treatment of various diseases but the function of MP has not yet been studied in the context of PQ-induced intoxication. The aim of this study was to determine if MP can ameliorate PQ-induced toxicity in an alveolar A549 cell line by inducing ATP-dependent transporter P-glycoprotein (P-gp) expression. P-gp expression and activity in the PQ-treated A549 cell line were enhanced by MP treatment and cytotoxicity by PQ was dramatically decreased. We also found that MP per se or together with PQ induced P-gp expression by both Western blot and qRT-PCR analyses. In addition, induced P-gp transporter was shown to improve the efflux effect on PQ-treated A549 cell lines as was demonstrated using the Calcein-AM fluorescence accumulation assay. In summary, MP induces the transmembrane ATP-dependent transporter P-gp expression, which greatly improves PQ-treated A549 cell viability, reduces accumulation of intracellular PQ and prevents PQ induced cytotoxicity but it should be further evaluated in in vivo studies.