Effects of the Cytoplasm and Mitochondrial Specific Hydroxyl Radical Scavengers TA293 and mitoTA293 in Bleomycin-Induced Pulmonary Fibrosis Model Mice.

Lung fibrosis is the primary pathology in idiopathic pulmonary fibrosis and is considered to result from an increase in reactive oxygen species (ROS) levels in alveolar epithelial cells. However, the exact mechanism underlying lung fibrosis remains unclear and there is no effective therapy. The hydroxyl radical (•OH) has the strongest oxidizing potential among ROS. Recently, •OH localized to the cytoplasm (cyto •OH) was reported to induce cellular senescence, while mitochondria-localized •OH (mt •OH) was reported to induce apoptosis. We developed the cyto •OH- and mt •OH-scavenging antioxidants TA293 and mitoTA293 to evaluate the effects of cyto •OH and mt •OH in a bleomycin (BLM)-induced pulmonary fibrosis model. Treatment of BLM-induced pulmonary fibrosis mice with TA293 suppressed the induction of cellular senescence and fibrosis, as well as inflammation in the lung, but mitoTA293 exacerbated these. Furthermore, in BLM-stimulated primary alveolar epithelial cells, TA293 suppressed the activation of the p-ATMser1981/p-p53ser15/p21, p-HRI/p-eIF2ser51/ATF4/p16, NLRP3 inflammasome/caspase-1/IL-1ß/IL1R/p-p38 MAPK/p16, and p21 pathways and the induction of cellular senescence. However, mitoTA293 suppressed the induction of mitophagy, enhanced the activation of the NLRP3 inflammasome/caspase-1/IL1ß/IL1R/p-p38 MAPK/p16 and p21 pathways, and exacerbated cellular senescence, inflammation, and fibrosis. Our findings may help develop new strategies to treat idiopathic pulmonary fibrosis.

Cytoplasmic OH scavenger TA293 attenuates cellular senescence and fibrosis by activating macrophages through oxidized phospholipids/TLR4.

AIMS: Elucidation of the biological roles of the mitochondrial and cytoplasmic hydroxyl radical (cyto OH) is hampered by the absence of site-specific OH scavengers. Earlier findings using cyto OH scavenger, TA293, indicated that cyto OH causes cellular senescence, and senescence-associated secretory phenotype (SASP) factors secreted from cells cause macrophage infiltration, inflammation, and apoptosis. However, we found that macrophage infiltration occurs before senescent cells appear. We therefore aimed to elucidate how cyto OH-induces macrophage activation and investigate the mechanism by which activated macrophages cause oxidative stress, inflammation, and apoptosis. MAIN METHODS: In vivo imaging of pyocyanin- and TA293-treated, macrophage-depleted Toll-like receptor 4-knockout (TLR4-/-) OKD48- and IDOL-Tg mouse models were used to visualize oxidative stress and inflammation. SA-ß-gal and TUNEL staining were used to detect cellular senescence and apoptosis. The mRNA expression of SASP factors were quantified by qRT-PCR. Activation mechanism of cyto OH-mediated macrophages was studied by an ex vivo analysis that created macrophage-activated oxidized phospholipids (OxPLs) using TLR4-/- mice. KEY FINDINGS: Cyto OH produced OxPLs that acted as TLR4 ligands, resulting in macrophage activation. Macrophages were not involved in oxidative stress in tissues or with oxidative damage caused by cyto OH, but significantly exacerbated cellular senescence, inflammation, apoptosis, and fibrosis. SIGNIFICANCE: We present a novel mechanism by which cyto OH-induced macrophage activation exacerbates cellular senescence, inflammation, apoptosis, and fibrosis independently from the known cyto OH-induced cellular senescence pathway. Notably, through suppression of this pathway, TA293 shows promise as a therapeutic agent to prevent fibrosis caused by cyto OH-induced oxidative stress.

Identification of novel selective P2Y6 receptor antagonists by high-throughput screening assay.

AIMS: The P2Y6 nucleotide receptor is widely involved in inflammatory responses, and is a promising molecular target for the treatment of inflammatory diseases. Although several P2Y6 receptor antagonists have been developed and evaluated thus far, none has successfully been developed into a therapeutic drug. In this study, we explored new promising compounds that inhibit the human P2Y6 receptor. MAIN METHODS: High-throughput screening (HTS) was used to study the effects of various compounds on human P2Y6 receptors expressed in 1321N1 human astrocytoma cells by monitoring intracellular Ca2+ concentration ([Ca2+]i) levels using an FDSS7000 real-time fluorescence detector. IL-8 concentration was measured by enzyme-linked immunosorbent assay. KEY FINDINGS: Among structurally diverse chemical libraries totalling 141,700 compounds, 43 compounds with an inhibitory activity against the P2Y6 receptor were identified. Further studies using a dose-response assay, receptor selectivity assay, and chemokine measurement assay revealed the selective P2Y6 receptor inhibitor TIM-38, which inhibited UDP-induced [Ca2+]i elevation in a dose-dependent manner. TIM-38 had an IC50 value of 4.3µM and inhibited P2Y6 without affecting the response induced by four other human P2Y or muscarinic receptors. In addition, TIM-38 inhibited UDP-induced interleukin-8 release in a dose-dependent manner without affecting releases caused by other stimulus such as interleukin-1ß or tumour necrosis factor-α. Analyses of TIM-38 derivatives revealed that the nitro moiety is vital to P2Y6 receptor inhibition. SIGNIFICANCE: TIM-38 acts as a novel structural antagonist of P2Y6 receptor and may be a good lead compound for developing a P2Y6 receptor-targeted anti-inflammatory drug.

The novel antioxidant TA293 reveals the role of cytoplasmic hydroxyl radicals in oxidative stress-induced senescence and inflammation.

The hydroxyl radical (OH) possesses the strongest oxidation potential among reactive oxygen species (ROS). Hydroxyl radicals react nonpreferentially with proteins, lipids, and nucleic acids. Additionally, mitochondrial localization of OH causes dysfunction in the mitochondria. The cytoplasmic targets of OH-induced oxidation are unknown. No cytoplasm-specific OH scavenger is available; thus, elucidating the cytoplasmic targets of OH-induced oxidation has proven difficult. Accordingly, we developed a cytoplasm-specific OH-targeted scavenger, TA293, and a mitochondrion-specific scavenger, mitoTA293. Both TA293 and mitoTA293 scavenged OH but not O2- or H2O2. We then examined the intracellular localization of both scavengers in vitro and in vivo. TA293 scavenged pyocyanin-induced cytoplasmic OH but not antimycin A-induced mitochondrial oxidation. mitoTA293 scavenged antimycin A-induced mitochondrial OH but not cytoplasmic OH. TA293 but not mitoTA293 suppressed pyocyanin-induced oxidative damage in the lungs and kidneys of mice. Additionally, TA293 suppressed the expression of inflammatory signaling pathway components and mediators and suppressed OH-induced cellular senescence and apoptosis. These data suggested that TA293 could be used as a novel tool for studying the effects of hydroxyl radical damage within the cytoplasm.

Study on action mode of sphingosine 1-phosphate in rat hepatocytes.

Sphingosine-1-phosphate (S1P) acts on a set of G protein-coupled receptors in the plasma membrane and also as a second messenger in certain cell types. There are two possible pathways to mobilize intracellular Ca(2+) concentration by S1P. One is through phospholipase C, and the other is through intracellular Ca(2+) channels operated by S1P. The Mn(2+) quenching method was applied to elucidate the action mode of S1P-induced Ca(2+) mobilization in rat hepatocytes. In permeabilized hepatocytes, inositol trisphosphate induced Mn(2+) quenching, and it was blocked by heparin. However, S1P did not induce Mn(2+) quenching. Results suggest that S1P did not mobilize Ca(2+) through intracellular Ca(2+) channels.

Differential change of Ins-P3-Ca2+ signaling during culture of rat hepatocytes.

Decrease of alpha-adrenergic responses during primary culture of rat hepatocytes was studied. Activation of glycogen phosphorylase by phenylephrine was decreased in the early stage of the culture (within 6 h), however, Ins-P3 production was almost intact until 12 h of the culture and then declined. alpha-Adrenoceptor-mediated Ca2+-mobilization and Ins-P3-induced Ca2+ release from microsomal fractions were decreased in the early stage of the culture, similar to the above change of phosphorylase activation. We found that decrease of Ins-P3-binding sites in the early stage of the culture was the cause of differential change of Ins-P3-Ca2+ signaling during the culture of hepatocytes. Similar changes described above were also observed in vasopressin-induced responses. However, the changes of Ins-P3-Ca2+ signaling did not occur in a high-cell density culture of rat hepatocytes. In conclusion, the loss of phenylephrine- and vasopressin-induced responses in cultured liver cells appear to be due to change of Ins-P3-binding sites as well as decreased Ins-P3 production due to reduction of receptor numbers.

TA-270 [4-hydroxy-1-methyl-3-octyloxy-7-sinapinoylamino-2(1H)-quinolinone], an anti-asthmatic agent, inhibits leukotriene production induced by IgE receptor stimulation in RBL-2H3 cells.

A novel quinolinone derivative, TA-270 [4-hydroxy-1-methyl-3-octyloxy-7-sinapinoylamino-2(1H)-quinolinone], has been shown to inhibit antigen-induced asthmatic responses including the early-phase bronchoconstriction in actively sensitized guinea pigs. Here we characterized the action mechanisms of TA-270 in cellular level in vitro. In RBL-2H3 mast cells sensitized with dinitrophenol (DNP)-specific IgE, the antigen exhibited several mast cell functions, including hexosaminidase release as a marker of degranulation, production of tumor necrosis factor-alpha, and production of immunologically detective leukotrienes. These antigen-induced actions were associated with the activation of several early signaling events, including inositol phosphate production reflecting phospholipase C activation and extracellular signal-regulated kinase activation. When the cells were treated with TA-270, the antigen-induced leukotriene production was almost completely suppressed, but other antigen-induced actions listed above were hardly affected. This drug also failed to affect the antigen-induced phospholipase A2 activation as evaluated by the total release of arachidonic acid and its metabolites from the cells prelabeled with radioactive arachidonic acid. However, TA-270 clearly changed the arachidonic acid metabolic pathway. It suppressed the accumulation of 5-lipoxygenase products, including leukotrienes, but hardly affected the accumulation of cyclooxygenase products. The inhibitory action of TA-270 on leukotriene production was also observed in human neutrophils and eosinophils. We conclude that TA-270 inhibits 5-lipoxygenase activity and, thereby, suppresses the antigen-induced leukotriene production.

Absorption and metabolism of glycosidic sweeteners of stevia mixture and their aglycone, steviol, in rats and humans.

Stevia mixture, sweeteners extracted from the leaves of Stevia rebaudiana Bertoni, consists mainly of the glycosides of the diterpene derivative steviol. The aims of this study were to investigate the absorption (in rats) and the hepatic metabolism (in rats and humans) of both stevia mixture and steviol. Absorption was investigated both in vivo and ex vivo. In ex vivo experiments using the rat everted sac method, no absorption of stevia mixture was observed, but significant absorption of steviol was noted (equivalent to approximately 70% of the absorption reference- salicylic acid- value). In the in vivo experiment, rats received a single oral administration of either steviol or stevia mixture; a peak steviol concentration in plasma was observed 15 min after its oral administration, demonstrating rapid absorption. However, after oral administration of stevia mixture, the steviol concentration in plasma increased steadily over 8 h, suggesting that stevia mixture components are first degraded and then absorbed as steviol in the rat intestine. Steviol metabolism in humans and rats was examined by incubating steviol with liver microsomes from the two species. Oxidative (monohydroxy and dihydroxy) metabolites of steviol were observed by LC-ESI/MS after incubation with both human and rat liver microsomes. The intrinsic clearance of steviol in human liver microsomes was 4-times lower than that found in rat liver microsomes. In conclusion, this study suggests that there are no major species differences in steviol hepatic metabolism between rats and humans. Absorption from the human intestine can be predicted to occur in an analogous manner to that from the rat intestine.

Activation of the human innate immune system by Spirulina: augmentation of interferon production and NK cytotoxicity by oral administration of hot water extract of Spirulina platensis.

Spirulina platensis is a cyanobacterial species that is surmised to potentiate the immune system leading to suppression of cancer development and viral infection. Here, we identified the molecular mechanism of the human immune potentiating capacity of Spirulina by analyzing blood cells of volunteers with pre and post oral administration of hot water extract of Spirulina. NK functions represented by IFN gamma production and cytolysis were enhanced after administration of Spirulina in >50% subjects. IFN gamma was produced in an IL-12/IL-18-dependent fashion. In vitro stimulation of blood cells with BCG cell wall skeleton (CWS) allowed more potent IL-12 p40 production in cells from volunteers given Spirulina than in cells without pre-exposure to Spirulina. As BCG-CWS serves as a ligand for Toll-like receptor (TLR) 2 and 4 to raise the maturation stage of monocytes/macrophages, Spirulina may be involved in the signaling responses through Toll in blood cells even when orally administered. These observations indicated that in humans Spirulina acts directly on myeloid lineages and either directly or indirectly on NK cells. The presence of co-operative IL-12 and IL-18 is critically important for NK-mediated IFN gamma production.

High levels of RAE-1 isoforms on mouse tumor cell lines assessed by anti-"pan" RAE-1 antibody confer tumor susceptibility to NK cells.

Two sublines of the benzpyrene-induced mouse hepatoma cell line, G-1 and G-5, showed low and high metastatic ability, respectively, to the lung. We produced a polyclonal antibody (pAb) against RAE-1alpha. Five isoforms of RAE-1 have been identified to date, and this pAb recognized all isoforms and was named anti-"pan" RAE-1 pAb. The level of RAE-1 was approximately 5-fold higher in G-5 than in G-1, which was almost RAE-1-negative, as determined using anti-pan RAE-1 pAb. Expression levels of other markers including MHC class I (MHC-I) and Qa-1b were very low and indistinguishable in these sublines. NK-mediated cytotoxicity was determined with these sublines; G-5 was highly susceptible to NK-mediated cytolysis, while G-1 was relatively resistant. The NK-mediated G-5 > G-1 killing profile was diminished if the G-5 cells were pretreated with F(ab)(2)(') of anti-pan RAE-1 pAb. G-1, when transfected with Rae-1alpha cDNA, acquired NK-responsiveness similar to that of G-5. These and additional data using mouse cell lines with low MHC-I levels and various RAE-1 levels also demonstrated that RAE-1 level is critically associated with NK-susceptibility in tumor cells.