Tiron ameliorates acetic acid-induced colitis in rats: Role of TGF-β/EGFR/PI3K/NF-κB signaling pathway

BACKGROUND

Ulcerative colitis (UC), an ongoing inflammatory disorder of the colon, is marked by persistent mucosal surface irritation extending from the rectum to the near-proximal colon. Tiron is a synthetic analogue of vitamin E which is known to have antioxidant and anti-inflammatory effects in various animal models, so the goal of this study was to find out whether Tiron had any preventive impacts on UC inflicted by acetic acid (A.A) exposure in rats.

METHOD

Tiron (235 and 470 mg/kg) was administered intra-peritoneally for 2 weeks, and A.A (2 ml, 3 % v/v) was injected intra-rectally to cause colitis. Colon tissues and blood samples were then collected for measurement of various inflammatory and oxidative stress biomarkers.

RESULTS

Tiron administration significantly diminished lactate dehydrogenase (LDH), C-reactive protein (CRP), colon weight, and the weight/length ratio of the colon as compared to A.A-injected rats. Additionally, Tiron attenuated oxidative stress biomarkers. Tiron also enforced the levels of Glucagon-like peptide-1 (GLP-1) and trefoil factor-3 (TFF-3), while it greatly lowered the expression of nuclear factor kappa B (NF-κB), interleukin-6 (IL-6), interferon-γ (IFN-γ), and transforming growth factor-1(TGF-β1), phosphorylated epidermal growth factor receptor (P-EGFR), phosphatidylinositol-3-kinase (PI3K) and protein kinase B (AKT) expression in colonic cellular structures. Furthermore, colonichistopathologic damages, revealed by hematoxylin and eosin (H&E) and Alcian Blue stain, were significantly decreased upon Tiron administration.

CONCLUSION

Tiron prevented A.A-induced colitis in rats via modulating inflammatory pathway TGF-β1/P-EGFR/PI3K/AKT/NF-κB, alongside managing the oxidant/antioxidant equilibrium, and boosting the reliability of the intestinal barrier.

Adding of neurotensin to non-small cell lung cancer cells increases tyrosine phosphorylation of HER3

Neurotensin (NTS) receptor 1 regulates the growth non-small cell lung cancer (NSCLC) cells. NTS binds with high affinity to NTSR1, leading to increased tyrosine phosphorylation of the EGFR and HER2. Using Calu3, NCI-H358, or NCI-H441 cells, the effects of NTS on HER3 transactivation were investigated. HER3 tyrosine phosphorylation was increased by NTS or neuregulin (NRG1) addition to NSCLC cells. NCI-H358, NCI-H441, and Calu-3 cells have HER3, NTSR1 and neuregulin (NRG)1 protein. NTSR1 regulation of HER3 transactivation was impaired by SR48692 (NTSR1 antagonist) or monoclonal antibody (mAb)3481 (HER3 blocker). Immunoprecipitation experiments indicated that NTS addition to NCI-H441cells resulted in the formation of EGFR/HER3 and HER2/HER3 heterodimers. The ability of NTS to increase HER3 tyrosine phosphorylation was impaired by GM6001 (MMP inhibitor), PP2 (Src inhibitor), Tiron (superoxide scavenger), or N-acetylcysteine (antioxidant). Adding NTS to NSCLC cells increased phosphorylation of ERK, HER3, and AKT. NTS or NRG1 increased colony formation of NSCLC cells which was strongly inhibited by SR48692 and mAb3481. The results indicate that NTSR1 regulates HER3 transactivation in NSCLC cells leading to increased proliferation.

Tiron protects against nicotine-induced lung and liver injury through antioxidant and anti-inflammatory actions in rats in vivo

AIMS

Tobacco smoking is a major health problem associated with lung and liver damage. Lung and liver damage secondary to tobacco smoking is mediated through nicotine-induced oxidative stress. Therefore, we hypothesized that antioxidant treatment with tiron may improve nicotine-induced lung and liver damage.

MATERIALS AND METHODS

Rats were divided into six groups, a control, nicotine (10 mg/kg/day, i.p.; for 8 weeks) and tiron (100 or 200 mg/kg/day, i.p.; for 8 weeks) with or without nicotine administration.

KEY FINDINGS

Tiron improved survival rate and attenuated lung and liver damage as reflected by decreased total and differential cell counts, lactate dehydrogenase (LDH) activity in bronchoalveolar lavage fluid (BALF) and decreased alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) in serum; also histopathological examination confirmed the protective effect of tiron in lung and liver tissues of nicotine treated rats. Tiron attenuated dyslipidemia, which is associated with nicotine. These ameliorative effects of tiron may be mainly due to its antioxidant effect as proved by a significant decrease in malondialdehyde (MDA) content, reactive oxygen species (ROS) and total nitrite/nitrate (NOx) levels, and increase in reduced glutathione (GSH) level, catalase (CAT) and superoxide dismutase (SOD) activities. This is likely related to suppression of protein levels of NADPH oxidase enzyme (NOX1), inducible nitric oxide synthase (iNOS), nuclear factor kappa B (NF-κB) and tumor necrosis factor alpha (TNF-α); and up-regulation of protein levels of nuclear factor erythroid-2 (Nrf2).

SIGNIFICANCE

This makes tiron (synthetic analogue of vitamin E) good candidate for future use to minimize nicotine's hazards among smokers.

LAP-like non-canonical autophagy and evolution of endocytic vacuoles in pancreatic acinar cells

Activation of trypsinogen (formation of trypsin) inside the pancreas is an early pathological event in the development of acute pancreatitis. In our previous studies we identified the activation of trypsinogen within endocytic vacuoles (EVs), cellular organelles that appear in pancreatic acinar cells treated with the inducers of acute pancreatitis. EVs are formed as a result of aberrant compound exocytosis and subsequent internalization of post-exocytic structures. These organelles can be up to 12 μm in diameter and can be actinated (i.e. coated with F-actin). Notably, EVs can undergo intracellular rupture and fusion with the plasma membrane, providing trypsin with access to cytoplasmic and extracellular targets. Unraveling the mechanisms involved in cellular processing of EVs is an interesting cell biological challenge with potential benefits for understanding acute pancreatitis. In this study we have investigated autophagy of EVs and discovered that it involves a non-canonical LC3-conjugation mechanism, reminiscent in its properties to LC3-associated phagocytosis (LAP); in both processes LC3 was recruited to single, outer organellar membranes. Trypsinogen activation peptide was observed in approximately 55% of LC3-coated EVs indicating the relevance of the described process to the early cellular events of acute pancreatitis. We also investigated relationships between actination and non-canonical autophagy of EVs and concluded that these processes represent sequential steps in the evolution of EVs. Our study expands the known roles of LAP and indicates that, in addition to its well-established functions in phagocytosis and macropinocytosis, LAP is also involved in the processing of post-exocytic organelles in exocrine secretory cells.

ABBREVIATIONS

AP: acute pancreatitis; CCK: cholecystokinin; CLEM: correlative light and electron microscopy; DPI: diphenyleneiodonium; EV: endocytic vacuole; LAP: LC3-associate phagocytosis; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; PACs: pancreatic acinar cells; PFA: paraformaldehyde; PtdIns3K: phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol 3-phosphate; Res: resveratrol; TAP: trypsinogen activation peptide; TEM: transmission electron microscopy; TLC-S: taurolithocholic acid 3-sulfate; TRD: Dextran Texas Red 3000 MW Neutral; ZGs: zymogen granules.

Superoxide anions modulate the performance of apelin in the paraventricular nucleus on sympathetic activity and blood pressure in spontaneously hypertensive rats

The present study was designed to determine how apelin in paraventricular nucleus (PVN) modulates the renal sympathetic nerve activity (RSNA), arterial blood pressure (ABP), mean arterial pressure (MAP), and heart rate (HR), and whether superoxide anions regulate the performance of PVN apelin in spontaneously hypertensive rats (SHRs). Acute experiment was carried out with 13-week-old male Wistar-Kyoto rats (WKY) and SHRs under anaesthesia. RSNA, ABP, MAP and HR after PVN microinjection were measured. Apelin microinjection into PVN increased RSNA, ABP, MAP and HR in WKY rats and SHRs, more obviously in SHRs. APJ antagonist F13A decreased the RSNA, ABP, MAP and HR in SHRs, and inhibited the effects of apelin. Apelin and APJ mRNA levels were higher in the PVN in SHRs. PVN microinjection of superoxide anion scavengers tempol and tiron, or NAD(P)H oxidase inhibitor apocynin, decreased the RSNA, ABP, MAP and HR in SHRs, and inhibited the effects of apelin, but the superoxide dismutase (SOD) inhibitor diethyldithiocarbamic acid (DETC) potentiated the effects of apelin. NAD(P)H oxidase activity and superoxide anion levels in PVN were increased by apelin, but decreased by APJ antagonist F13A. The apelin-induced increases in NAD(P)H oxidase activity and superoxide anion level were abolished by pre-treatment with F13A. These results indicate that apelin in PVN increases the sympathetic outflow and blood pressure via activating APJ receptor. The enhanced activity of endogenous apelin and APJ receptor in PVN contributes to sympathetic activation in hypertension, and the superoxide anion is involved in these apelin-mediated processes in PVN.

Tiron ameliorates oxidative stress and inflammation in titanium dioxide nanoparticles induced nephrotoxicity of male rats

Although the widespread use of titanium dioxide nanoparticles (TiO₂ NPs), few studies were conducted on its hazard influence on human health. Tiron a synthetic vitamin E analog was proven to be a mitochondrial targeting antioxidant. The current investigation was performed to assess the efficacy of tiron against TiO₂ NPs induced nephrotoxicity. Eighty adult male rats divided into four different groups were used: group I was the control, group II received TiO2 NPs (100mg\Kg BW), group III received TiO2 NPs plus tiron (470mg\kg BW), and group IV received tiron alone. Urea, creatinine and total protein concentrations were measured in serum to assess the renal function. Antioxidant status was estimated by determining the activities of glutathione peroxidase, superoxide dismutase, malondialdehyde (MDA) level and glutathione concentration in renal tissue. As well as Renal fibrosis was evaluated though measuring of transforming growth factor-β1 (TGFβ1) and matrix metalloproteinase 9 (MMP9) expression levels and histopathological examination. TiO₂ NPs treated rats showed marked elevation of renal indices, depletion of renal antioxidant enzymes with marked increase in MDA concentration as well as significant up-regulation in fibrotic biomarkers TGFβ1 and MMP9. Oral administration of tiron to TiO₂ NPs treated rats significantly attenuate the renal dysfunction through decreasing of renal indices, increasing of antioxidant enzymes activities, down-regulate the expression of fibrotic genes and improving the histopathological picture for renal tissue. In conclusion, tiron was proved to attenuate the nephrotoxicity induced by TiO₂ NPs through its radical scavenging and metal chelating potency.

Reproductive toxicity provoked by titanium dioxide nanoparticles and the ameliorative role of Tiron in adult male rats

Titanium dioxide nanoparticles (TDN) are widely used in paints, plastics, ceramics, cosmetics, printing ink, rubber and paper. Tiron is a water soluble metal chelator and antioxidant. This study was designed to investigate the reproductive toxicity of TDN in male albino rats and the ameliorative role of Tiron to minimize such toxic effects. Eighty adult male albino rats were assigned into 4 equal groups, group 1: control; group 2: received TDN at 100 mg/kg/day orally for 8 weeks; group 3: received Tiron at 470 mg/kg/day intraperitoneally for 2 weeks (the last 2 weeks of the experimental period); group 4: received both TDN and Tiron by the same previously mentioned dose, route and duration. The results revealed that TDN provoked reproductive toxicity which was proved by the deteriorated spermogram picture, high incidence of micronucleated RBCs, elevated oxidative stress parameters and up regulation of Testin gene. Whereas, Tiron co-treatment ameliorated most of these toxic alterations. Our findings highlighted the protective role of tiron against TDN intoxication.

Fusobacterium nucleatum-Induced Impairment of Autophagic Flux Enhances the Expression of Proinflammatory Cytokines via ROS in Caco-2 Cells

Fusobacterium nucleatum (F. nucleatum) plays a critical role in gastrointestinal inflammation. However, the exact mechanism by which F. nucleatum contributes to inflammation is unclear. In the present study, it was revealed that F. nucleatum could induce the production of proinflammatory cytokines (IL-8, IL-1β and TNF-α) and reactive oxygen species (ROS) in Caco-2 colorectal) adenocarcinoma cells. Furthermore, ROS scavengers (NAC or Tiron) could decrease the production of proinflammatory cytokines during F. nucleatum infection. In addition, we observed that autophagy is impaired in Caco-2 cells after F. nucleatum infection. The production of proinflammatory cytokines and ROS induced by F. nucleatum was enhanced with either autophagy pharmacologic inhibitors (3-methyladenine, bafilomycin A1) or RNA interference in essential autophagy genes (ATG5 or ATG12) in Caco-2 cells. Taken together, these results indicate that F. nucleatum-induced impairment of autophagic flux enhances the expression of proinflammatory cytokines via ROS in Caco-2 Cells.

Tiron Inhibits UVB-Induced AP-1 Binding Sites Transcriptional Activation on MMP-1 and MMP-3 Promoters by MAPK Signaling Pathway in Human Dermal Fibroblasts

Recent research found that Tiron was an effective antioxidant that could act as the intracellular reactive oxygen species (ROS) scavenger or alleviate the acute toxic metal overload in vivo. In this study, we investigated the inhibitory effect of Tiron on matrix metalloproteinase (MMP)-1 and MMP-3 expression in human dermal fibroblast cells. Western blot and ELISA analysis revealed that Tiron inhibited ultraviolet B (UVB)-induced protein expression of MMP-1 and MMP-3. Real-time quantitative PCR confirmed that Tiron could inhibit UVB-induced mRNA expression of MMP-1 and MMP-3. Furthermore, Tiron significantly blocked UVB-induced activation of the MAPK signaling pathway and activator protein (AP)-1 in the downstream of this transduction pathway in fibroblasts. Through the AP-1 binding site mutation, it was found that Tiron could inhibit AP-1-induced upregulation of MMP-1 and MMP-3 expression through blocking AP-1 binding to the AP-1 binding sites in the MMP-1 and MMP-3 promoter region. In conclusion, Tiron may be a novel antioxidant for preventing and treating skin photoaging UV-induced.

Photodynamic Therapy-Induced Apoptosis of Keloid Fibroblasts is Mediated by Radical Oxygen Species In Vitro

BACKGROUND

It has been demonstrated that photodynamic therapy (PDT) is a promising treatment approach for hyperplastic dermatosis and results in a beneficial outcome. In the present study, PDT involving hematoporphyrin monomethyl ether (HMME) was applied to keloid fibroblasts (KFB), and the effects and the mechanism of action were explored.

METHODS

Keloid fibroblastic cells were divided into four groups (PDT group, light alone group, HMME alone group, normal cultured group). Cell proliferation and apoptosis were observed. Radical oxygen species (ROS) were detected by means of dihydroethidium (DHE) and dihydrorhodamine (DHR123). ROS in the PDT group were also assessed after addition of tiron.

RESULTS

Cell proliferation was inhibited in the PDT group (p < 0.05), while the rate of apoptosis was also clearly increased (p < 0.05). The levels of ROS were significantly higher in the PDT group than was observed in the other three groups (p < 0.05). With the addition of tiron the damaging effects were reduced.

CONCLUSIONS

Our data indicated that HMME-mediated PDT could inhibit keloid fibroblast proliferation and could also induce apoptosis. This process was associated with the production of ROS.

Arterial levels of oxygen stimulate intimal hyperplasia in human saphenous veins via a ROS-dependent mechanism

Saphenous veins used as arterial grafts are exposed to arterial levels of oxygen partial pressure (pO₂), which are much greater than what they experience in their native environment. The object of this study is to determine the impact of exposing human saphenous veins to arterial pO₂. Saphenous veins and left internal mammary arteries from consenting patients undergoing coronary artery bypass grafting were cultured ex vivo for 2 weeks in the presence of arterial or venous pO₂ using an established organ culture model. Saphenous veins cultured with arterial pO₂ developed intimal hyperplasia as evidenced by 2.8-fold greater intimal area and 5.8-fold increase in cell proliferation compared to those freshly isolated. Saphenous veins cultured at venous pO₂ or internal mammary arteries cultured at arterial pO₂ did not develop intimal hyperplasia. Intimal hyperplasia was accompanied by two markers of elevated reactive oxygen species (ROS): increased dihydroethidium associated fluorescence (4-fold, p<0.05) and increased levels of the lipid peroxidation product, 4-hydroxynonenal (10-fold, p<0.05). A functional role of the increased ROS saphenous veins exposed to arterial pO₂ is suggested by the observation that chronic exposure to tiron, a ROS scavenger, during the two-week culture period, blocked intimal hyperplasia. Electron paramagnetic resonance based oximetry revealed that the pO₂ in the wall of the vessel tracked that of the atmosphere with a ~30 mmHg offset, thus the cells in the vessel wall were directly exposed to variations in pO₂. Monolayer cultures of smooth muscle cells isolated from saphenous veins exhibited increased proliferation when exposed to arterial pO₂ relative to those cultured at venous pO₂. This increased proliferation was blocked by tiron. Taken together, these data suggest that exposure of human SV to arterial pO₂ stimulates IH via a ROS-dependent pathway.

Reactive oxygen and nitrogen species in defense/stress responses activated by chitosan in sycamore cultured cells

Chitosan (CHT) is a non-toxic and inexpensive compound obtained by deacetylation of chitin, the main component of the exoskeleton of arthropods as well as of the cell walls of many fungi. In agriculture CHT is used to control numerous diseases on various horticultural commodities but, although different mechanisms have been proposed, the exact mode of action of CHT is still unknown. In sycamore (Acer pseudoplatanus L.) cultured cells, CHT induces a set of defense/stress responses that includes production of H2O2 and nitric oxide (NO). We investigated the possible signaling role of these reactive molecules in some CHT-induced responses by means of inhibitors of production and/or scavengers. The results show that both reactive nitrogen and oxygen species are not only a mere symptom of stress conditions but are involved in the responses induced by CHT in sycamore cells. In particular, NO appears to be involved in a cell death form induced by CHT that shows apoptotic features like DNA fragmentation, increase in caspase-3-like activity and release of cytochrome c from the mitochondrion. On the contrary, reactive oxygen species (ROS) appear involved in a cell death form induced by CHT that does not show these apoptotic features but presents increase in lipid peroxidation.

Acute restraint stress induces endothelial dysfunction: role of vasoconstrictor prostanoids and oxidative stress

We hypothesized that acute stress would induce endothelial dysfunction. Male Wistar rats were restrained for 2 h within wire mesh. Functional and biochemical analyses were conducted 24 h after the 2-h period of restraint. Stressed rats showed decreased exploration on the open arms of an elevated-plus maze (EPM) and increased plasma corticosterone concentration. Acute restraint stress did not alter systolic blood pressure, whereas it increased the in vitro contractile response to phenylephrine and serotonin in endothelium-intact rat aortas. NG-nitro-l-arginine methyl ester (l-NAME; nitric oxide synthase, NOS, inhibitor) did not alter the contraction induced by phenylephrine in aortic rings from stressed rats. Tiron, indomethacin and SQ29548 reversed the increase in the contractile response to phenylephrine induced by restraint stress. Increased systemic and vascular oxidative stress was evident in stressed rats. Restraint stress decreased plasma and vascular nitrate/nitrite (NOx) concentration and increased aortic expression of inducible (i) NOS, but not endothelial (e) NOS. Reduced expression of cyclooxygenase (COX)-1, but not COX-2, was observed in aortas from stressed rats. Restraint stress increased thromboxane (TX)B(2) (stable TXA(2) metabolite) concentration but did not affect prostaglandin (PG)F2α concentration in the aorta. Restraint reduced superoxide dismutase (SOD) activity, whereas concentrations of hydrogen peroxide (H(2)O(2)) and reduced glutathione (GSH) were not affected. The major new finding of our study is that restraint stress increases vascular contraction by an endothelium-dependent mechanism that involves increased oxidative stress and the generation of COX-derived vasoconstrictor prostanoids. Such stress-induced endothelial dysfunction could predispose to the development of cardiovascular diseases.

Carnosol induces ROS-mediated beclin1-independent autophagy and apoptosis in triple negative breast cancer

Background

In this study we investigated the in vitro and in vivo anticancer effect of carnosol, a naturally occurring polyphenol, in triple negative breast cancer.

Results

We found that carnosol significantly inhibited the viability and colony growth induced G2 arrest in the triple negative MDA-MB-231. Blockade of the cell cycle was associated with increased p21/WAF1 expression and downregulation of p27. Interestingly, carnosol was found to induce beclin1-independent autophagy and apoptosis in MDA-MB-231 cells. The coexistence of both events, autophagy and apoptosis, was confirmed by electron micrography. Induction of autophagy was found to be an early event, detected within 3 h post-treatment, which subsequently led to apoptosis. Carnosol treatment also caused a dose-dependent increase in the levels of phosphorylated extracellular signal-regulated kinase 1 and 2 (pERK1/2). Moreover, we show that carnosol induced DNA damage, reduced the mitochondrial potential and triggered the activation of the intrinsic and extrinsic apoptotic pathway. Furthermore, we found that carnosol induced a dose-dependent generation of reactive oxygen species (ROS) and inhibition of ROS by tiron, a ROS scavenger, blocked the induction of autophagy and apoptosis and attenuated DNA damage. To our knowledge, this is the first report to identify the induction of autophagy by carnosol.

Conclusion

In conclusion our findings provide strong evidence that carnosol may be an alternative therapeutic candidate against the aggressive form of breast cancer and hence deserves more exploration.

NAC, tiron and trolox impair survival of cell cultures containing glioblastoma tumorigenic initiating cells by inhibition of cell cycle progression

Reactive oxygen species (ROS) are metabolism by-products that may act as signaling molecules to sustain tumor growth. Antioxidants have been used to impair cancer cell survival. Our goal was to determine the mechanisms involved in the response to antioxidants of a human cell culture (PT4) containing glioblastoma (GBM) tumorigenic initiating cells (TICs). ROS production in the absence or presence of N-acetyl-L-cysteine (NAC), tiron, and trolox was evaluated by flow cytometry (FCM). The effects of these antioxidants on cell survival and apoptosis were evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (MTT) and FCM. The biological processes modulated by these drugs were determined by oligonucleotide microarray gene expression profiling. Our results showed that NAC, tiron and trolox impaired PT4 cell survival, had minor effects on ROS levels and caused wide deregulation of cell cycle genes. Furthermore, tiron and trolox caused inhibition of cell survival in two additional cell cultures containing TICs, FO-1 and MM1, established from a melanoma and a mesothelioma patient, respectively. NAC, instead, impaired survival of the MM1 cells but not of the FO-1 cells. However, when used in combination, NAC enhanced the inhibitory effect of PLX4032 (BRAF V600E inhibitor) and Gefitinib (EGFR inhibitor), on FO-1 and PT4 cell survival. Collectively, NAC, tiron and trolox modulated gene expression and impaired the growth of cultures containing TICs primarily by inhibiting cell cycle progression.

Decrease of FGF receptor (FGFR) and interstitial fibrosis in the kidney of streptozotocin-induced diabetic rats

Fibrosis is the final disorder of end-stage renal disease. Activation of fibroblast growth factor (FGF) 23-klotho axis could suppress renal fibrosis in mice. Also, a marked decrease of klotho expression was observed in the kidney of streptozotocin-induced diabetic rats (STZ rats). However, relation of FGF in renal fibrosis remained unclear. This study was aimed to screen the effect of hyperglycemia on FGF receptor (FGFR) and fibrosis in kidney of rats with diabetic nephropathy and investigate this potential mechanism in cultured Madin-Darby Canine Kidney (MDCK) epithelial cells. STZ rats were used to treat with insulin or phloridzin at the dose sufficient to correct hyperglycemia for understanding the changes of renal dysfunction. The cultured MDCK cells were also used to treat with high glucose, hydrogen peroxide, or tiron in addition to transfection of siRNA to silence the klotho. Both insulin and phloridzin reversed fibrosis and FGFR expressions in kidney of STZ rats. It was confirmed in high glucose-exposed MDCK cells. However, klotho failed to modify the level of FGFR in MDCK cells. Meanwhile, FGFR was restored by tiron in MDCK cells and in diabetic rats without changing blood glucose. In conclusion, interstitial fibrosis and decreased FGFR expression are observed in the kidney of diabetic rats. This change is reversed by tiron without the correction of blood glucose. Also, klotho has no effect on expression of FGFR. Thus, decrease of oxidative stress is useful for the recovery of FGFR expression and improvement of renal fibrosis in type-1 like diabetic rats.

The role of RhoA and cytoskeleton in myofibroblast transformation in hyperoxic lung fibrosis

Myofibroblast transformation is a key process in the pathogenesis of lung fibrosis. We have previously reported that hyperoxia induces RhoA activation in HFL-1 lung fibroblasts and RhoA mediates collagen synthesis in hyperoxic lung fibrosis. In this study, we investigated the role of RhoA and actin cytoskeleton in hyperoxia-induced myofibroblast transformation. Exposure of HFL-1 lung fibroblasts to hyperoxia stimulated actin filament formation, shift of G-actin to F-actin, nuclear colocalization of myocardin-related transcription factor-A (MRTF-A), recruitment of MRTF-A to the α-smooth muscle actin (α-SMA) gene promoter, myofibroblast transformation, and collagen-I synthesis. Inhibition of RhoA by C3 transferase CT-04 or dominant-negative RhoA mutant T19N, and inhibition of ROCK by Y27632, prevented myofibroblast transformation and collagen-I synthesis. Moreover, inhibition of RhoA by CT-04 prevented hyperoxia-induced actin filament formation, shift of G-actin to F-actin, and nuclear colocalization of MRTF-A. In addition, disrupting actin filaments with cytochalasin D or scavenging reactive oxygen species (ROS) with tiron attenuated actin filament formation, nuclear colocalization of MRTF-A, myofibroblast transformation, and collagen-I synthesis. Furthermore, overexpression of constitutively active RhoA mutant Q63L or stabilization of actin filaments recapitulated the effects of hyperoxia on the actin cytoskeleton and nuclear colocalization of MRTF-A, myofibroblast transformation, and collagen-I synthesis. Interestingly, knocking down MRTF-A prevented hyperoxia-induced increase in the recruitment of MRTF-A to the serum response factor transcriptional complex on the α-SMA gene promoter, myofibroblast transformation, and collagen-I synthesis. Finally, Y27632 and tiron attenuated hyperoxia-induced increases in α-SMA and collagen-I in mouse lungs. Together, these results indicate that the actin cytoskeletal reorganization due to the ROS/RhoA-ROCK pathway mediates myofibroblast transformation and collagen synthesis in lung fibrosis of oxygen toxicity. MRTF-A contributes to the regulatory effect of the actin cytoskeleton on myofibroblast transformation during hyperoxia.

Tiron and trolox potentiate the autophagic cell death induced by magnolol analog Ery5 by activation of Bax in HL-60 cells

This study describes the mechanism of trolox and tiron induced potentiation of cytotoxicity caused by Ery5, an analog of magnolol, in human myeloid leukemia HL-60 cells. Ery5 induced cytotoxicity in HL-60 cells by involving activation of bax and cleavage of caspase 3, which contributed towards activation of both apoptotic and autophagic pathways. Trolox and tiron, even at non-toxic concentrations, contributed to the cytotoxicity of Ery5 by activation of autophagic proteins like ATG7, ATG12 and LC3-II. Z-VAD-fmk mediated reduction in the cytotoxicity and expression of autophagic proteins, further suggested that autophagy induced by Ery5 is largely dependent upon caspases. Interestingly, Ery5 induced autophagy was accompanied by the downregulation of PI3K/AKT pathway whereas, trolox and tiron strongly enhanced this effect. In addition to that treatment of cells with Ery5, trolox and tiron individually, displayed a marked upregulation of Bax. The involvement of Bax in trolox and tiron induced enhancement of the cytotoxicity of Ery5 was confirmed, when siRNA induced silencing of Bax led to increased viability of the cells and exerted a strong inhibitory effect on LC3-II accumulation and p62 degradation in case of cells treated by the combination of Ery5 with trolox or tiron. Additionally, an important role of PARP in Ery5 mediated cell death has been suggested by PARP silencing experiments, however, potentiation of autophagic cytotoxicity by trolox and tiron did not seem to be dependent on PARP-1. Therefore, Bax seems to play a vital role in trolox and tiron mediated potentiation of autophagic cell death by Ery5 in HL-60 cells.

NADPH oxidase 2-derived superoxide downregulates endothelial KCa3.1 in preeclampsia

Endothelial dysfunction is associated with KCa3.1 dysfunction and contributes to the development of hypertension in preeclampsia. However, evidence of endothelial KCa3.1 dysfunction in the vascular system from women with preeclampsia is still lacking. Therefore, we examined whether endothelial KCa3.1 dysfunction occurs in vessels from women with preeclampsia. We compared KCa3.1 and NADPH oxidase (NOX) expression in umbilical vessels and primary cultured human umbilical vein endothelial cells (HUVECs) from normal (NP; n=17) and preeclamptic pregnancy (PE; n=19) and examined the effects of plasma from NP or PE on KCa3.1 and NOX2 expression in primary cultured HUVECs from NP or human uterine microvascular endothelial cells. The endothelial KCa3.1 was downregulated, and NOX2 was upregulated, in umbilical vessels and HUVECs from PE, compared with those from NP. In addition, HUVECs from PE showed a significant decrease in KCa3.1 current. Plasma from PE induced KCa3.1 down regulation, NOX2 upregulation, phosphorylated-p38 mitogen-activated protein kinase downregulation, and superoxide generation, and these effects were prevented by antioxidants (tempol or tiron), NOX2 inhibition, or anti-lectin-like oxidized low-density lipoprotein (LDL) receptor 1 (LOX1) antibody. Oxidized LDL and the superoxide donor xanthine/xanthine oxidase mixture induced KCa3.1 downregulation. In contrast, plasma from PE did not generate hydrogen peroxide, and the hydrogen peroxide donor tert-butylhydroperoxide induced KCa3.1 upregulation. These results provide the first evidence that plasma from PE generates superoxide via a LOX1-NOX2-mediated pathway and downregulates endothelial KCa3.1, which may contribute to endothelial dysfunction and vasculopathy in preeclampsia. This suggests KCa3.1as a novel target for patients with preeclampsia.

Differential effects of acute hypoxia on the activation of TRPV1 by capsaicin and acidic pH

Transient receptor potential vanilloid 1 (TRPV1) is a Ca(2+)-permeable cation channel activated by a variety of physicochemical stimuli. The effect of hypoxia (P(O(2)), 3%) on rat TRPV1 overexpressed in HEK293T has been studied. The basal TRPV1 current (I (TRPV1)) was partly activated by hypoxia, whereas capsaicin-induced TRPV1 (I (TRPV1,Cap)) was attenuated. Such changes were also suggested from hypoxia- and capsaicin-induced Ca(2+) signals in TRPV1-expressing cells. Regarding plausible changes of reactive oxygen species (ROS) under hypoxia, the effects of antioxidants, vitamin C and tiron, as membrane-impermeable and -permeable, respectively, were tested. Both I (TRPV1) and I (TRPV1,Cap) were increased by vitamin C, while only I (TRPV1) was slightly increased by tiron. The hypoxic inhibition of I (TRPV1,Cap) was still persistent under hypoxia/vitamin C. Interestingly, hypoxia/tiron strongly inhibited both I (TRPV1) and I (TRPV1,Cap). Also, with vitamin C applied through a pipette solution, hypoxia inhibited I (TRPV1) and I (TRPV1,Cap). In contrast, hypoxia and hypoxia/tiron had no effect on the I (TRPV1) induced by acid (pH 6.2, I (TRPV1,Acid)). Taken together, hypoxia partly activated TRPV1 while it decreased their sensitivity to capsaicin. Putative changes of ROS under hypoxia might underlie the side-specific effects of ROS on TRPV1: inhibitory at the extracellular and stimulatory at the intracellular side, respectively. The differential effects of hypoxia on I (TRPV1,Cap) and I (TRPV1,Acid) suggested that the intracellular ROS increase might attenuate the pharmacological potency of capsaicin.

Reactive oxygen species-dependent RhoA activation mediates collagen synthesis in hyperoxic lung fibrosis

Lung fibrosis is an ultimate consequence of pulmonary oxygen toxicity in human and animal models. Excessive production and deposition of extracellular matrix proteins, e.g., collagen-I, is the most important feature of pulmonary fibrosis in hyperoxia-induced lung injury. In this study, we investigated the roles of RhoA and reactive oxygen species (ROS) in collagen-I synthesis in hyperoxic lung fibroblasts and in a mouse model of oxygen toxicity. Exposure of human lung fibroblasts to hyperoxia resulted in RhoA activation and an increase in collagen-I synthesis and cell proliferation. Inhibition of RhoA by C3 transferase CT-04, dominant-negative RhoA mutant T19N, or RhoA siRNA prevented hyperoxia-induced collagen-I synthesis. The constitutively active RhoA mutant Q63L mimicked the effect of hyperoxia on collagen-I expression. Moreover, the Rho kinase inhibitor Y27632 inhibited collagen-I synthesis in hyperoxic lung fibroblasts and fibrosis in mouse lungs after oxygen toxicity. Furthermore, the ROS scavenger tiron attenuated hyperoxia-induced increases in RhoA activation and collagen-I synthesis in lung fibroblasts and mouse lungs after oxygen toxicity. More importantly, we found that hyperoxia induced separation of guanine nucleotide dissociation inhibitor (GDI) from RhoA in lung fibroblasts and mouse lungs. Further, tiron prevented the separation of GDI from RhoA in hyperoxic lung fibroblasts and mouse lungs with oxygen toxicity. Together, these results indicate that ROS-induced separation of GDI from RhoA leads to RhoA activation with oxygen toxicity. ROS-dependent RhoA activation is responsible for the increase in collagen-I synthesis in hyperoxic lung fibroblasts and mouse lungs.

Effects of antioxidants on drug absorption in in vivo intestinal ischemia/reperfusion

Ischemia/reperfusion (I/R) injury must be overcome in order to succeed in small intestinal transplantation. Reactive oxygen species (ROS) are generated by I/R, and they induce lipid peroxidation which is one of the causes of mucosal lesion. We previously reported the protection effects of antioxidants to I/R injury in the in vitro study. In the present study, we examined the inhibitive effect of antioxidants on intestinal I/R injury in the in vivo study. Intestinal ischemia was induced in Wistar/ST rats using the spring scale and the surgical suture for 1 h, followed by reperfusion for 1 h. We used 4,5-dihydroxy-1,3-benzene-disulfonic acid (Tiron), astaxanthin (ATX) and epigallocatechin gallate (EGCG) as antioxidants. The inhibitive effects on mucosal lesion, opening of TJ and decrease in protein expression level of P-gp by in vivo intestinal I/R were admitted by three kinds of antioxidant. Tiron and EGCG inhibited P-gp function but ATX did not. Therefore, for the use of P-gp substrate like immunosuppressants after the intestinal transplantation, ATX, which does not inhibit P-gp is considered to be effective for intestinal I/R injury.

Antioxidants protect keratinocytes against M. ulcerans mycolactone cytotoxicity

BACKGROUND

Mycobacterium ulcerans is the causative agent of necrotizing skin ulcerations in distinctive geographical areas. M. ulcerans produces a macrolide toxin, mycolactone, which has been identified as an important virulence factor in ulcer formation. Mycolactone is cytotoxic to fibroblasts and adipocytes in vitro and has modulating activity on immune cell functions. The effect of mycolactone on keratinocytes has not been reported previously and the mechanism of mycolactone toxicity is presently unknown. Many other macrolide substances have cytotoxic and immunosuppressive activities and mediate some of their effects via production of reactive oxygen species (ROS). We have studied the effect of mycolactone in vitro on human keratinocytes--key cells in wound healing--and tested the hypothesis that the cytotoxic effect of mycolactone is mediated by ROS.

METHODOLOGY/PRINCIPAL FINDINGS

The effect of mycolactone on primary skin keratinocyte growth and cell numbers was investigated in serum free growth medium in the presence of different antioxidants. A concentration and time dependent reduction in keratinocyte cell numbers was observed after exposure to mycolactone. Several different antioxidants inhibited this effect partly. The ROS inhibiting substance deferoxamine, which acts via chelation of Fe(2+), completely prevented mycolactone mediated cytotoxicity.

CONCLUSIONS/SIGNIFICANCE

This study demonstrates that mycolactone mediated cytotoxicity can be inhibited by deferoxamine, suggesting a role of iron and ROS in mycolactone induced cytotoxicity of keratinocytes. The data provide a basis for the understanding of Buruli ulcer pathology and the development of improved therapies for this disease.

Reversal of effects of intra peritoneally administered beryllium nitrate by tiron and CaNa3DTPA alone or in combination with alpha-tocopherol

To evaluate therapeutic efficacy of chelating agents tiron (Sodium-4,5-dihydroxy-1,3-benzene disulphonate) and CaNa3DTPA (Calcium trisodium diethylene triamine pentaacetic acid) in presence of alpha-tocopherol against beryllium induced toxicity, adult female albino rats were exposed to beryllium nitrate for 28 days followed by therapy with tiron (471 mg/kg, i.p.) and CaNa3DTPA (35 mg/kg, i.p.) alone and in combination with alpha-tocopherol (25 mg/kg, p.o.). Results revealed non-significant fall in haemoglobin and total serum protein content while significant fall in blood sugar level and activity of serum alkaline phosphatase. On the other hand, significant rise in the activity of serum transaminases and LDH was noticed after beryllium administration. Significant increase in total and esterified cholesterol was found in liver and kidney after toxicity. Significant increase in lipid peroxidation and decreased level of reduced glutathione in both the organs showed oxidative stress due to beryllium exposure. Histopathological and ultrastructural observations of liver and kidney revealed lesions due to beryllium toxicity followed by recovery due to combined therapy. CaNa3DTPA showed moderate therapeutic efficacy; however, its effectiveness was enhanced with alpha-tocopherol to some extent. Tiron in combination with alpha-tocopherol exerted statistically more beneficial effects in reversal of beryllium induced biochemical, histopathological and ultrastructural alterations.

Tiron, a ROS scavenger, protects human lung cancer Calu-6 cells against antimycin A-induced cell death

Antimycin A (AMA) inhibits the mitochondrial electron transport between cytochromes b and c. However, the relationship between AMA and lung cancer cells is poorly understood. In this study, we investigated the involvement of reactive oxygen species (ROS) and glutathione (GSH) in AMA-treated lung cancer Calu-6 cell death. Treatment with AMA reduced cell viability in a dose-dependent manner for 72 h. The intracellular ROS levels were decreased in Calu-6 cells treated with low doses of AMA (10, 25 or 50 microM) at 72 h. However, the levels increased in cells treated with a high dose of 100 microM AMA. Levels of O2.- were significantly increased in AMA-treated cells at 72 h. The increases in ROS levels including O2.- in AMA-treated cells were observed within 10 min. Treatment with AMA reduced the intracellular GSH content. SOD activity was up-regulated in AMA-treated Calu-6 cells at 72 h. However, catalase activity was down-regulated by AMA. Treatment with tiron, a ROS scavenger, reduced the intracellular ROS levels, which were associated with a partial reduction of apoptosis. Treatment with exogenous SOD and catalase significantly inhibited loss of the mitochondrial transmembrane potential (DeltaPsim) in AMA-treated Calu-6 cells. In conclusion, our results suggest that the changes of intracellular ROS and GSH affect apoptosis in AMA-treated Calu-6 cells.

Insulin withdrawal induces apoptosis via a free radical-mediated mechanism

Diabetes is characterized by chronic hyperglycemia as well as insulin deficiency or resistance. However, the majority of research has focused on the consequences of hyperglycemia in development of diabetic complications, whereas the effects of insulin deficiency or resistance, independent of hyperglycemia, have received little attention. Since insulin is a well known cytoprotective factor, we hypothesized that its removal could significantly impact cell survival. To examine this possibility, cultured neonatal cardiomyocytes were subjected to insulin withdrawal and examined for apoptosis. Insulin deficient cells succumbed to apoptosis, an effect associated with impaired PI3-kinase/Akt signaling and reduction in the Bcl-2 to Bax ratio. Perhaps more importantly, superoxide generation was altered in cells subjected to insulin withdrawal. Removal of insulin caused a significant increase in reactive oxygen species production and resulted in oxidative mitochondrial DNA damage the latter effect is associated with impaired expression of mitochondrially encoded proteins that make up the electron transport chain. Significantly, the effects of insulin withdrawal could be mitigated by treatment with the antioxidant, Tiron. Collectively, these data demonstrate that insulin deficiency leads to apoptosis and suggest a role for oxidative mitochondrial DNA damage in this cascade.

IGF-I plus E2 induces proliferation via activation of ROS-dependent ERKs and JNKs in human breast carcinoma cells

Induction of 17beta-estradiol (E2) and insulin-like growth factor-I (IGF-I) has been detected in breast carcinoma, however the interaction between E2 and IGF-I in the proliferation of breast carcinoma cells is still unclear. In the present study, we found that IGF-I enhances the E2-induced proliferation in MCF-7 human breast carcinoma cells in accordance with stimulation of colony formation via a soft agar assay. Activation of insulin receptor substrate-1 (IRS-1) protein and extracellular signal-related kinases (ERKs) and c-Jun N-terminal kinases (JNKs), but not p38 mitogen-activated protein kinase (MAPK), via phosphorylation induction was detected in MCF-7 cells treated with IGF-I plus E2 (E2/IGF-I). E2/IGF-I-induced proliferation was blocked by chemical inhibitors of ERKs (PD98059) and JNKs (SP600125). An increase in the expression of c-Jun protein was detected in E2/IGF-I-treated MCF-7 cells, and this was inhibited by PD98059 and SP600125. Transfection of the dominant negative MEKK and JNK plasmids significantly reduced E2/IGF-I-induced proliferation with suppression of c-Jun protein expression. An increase in peroxide production was detected in E2/IGF-I-treated cells, and N-acetyl-L-cysteine (NAC) and Tiron (TIR) addition significantly inhibited E2/IGF-I-induced cell proliferation with blocking of the phosphorylation of ERKs and JNKs, and the expression of c-Jun protein. Additionally, 3-OH flavone, baicalein, and quercetin showed effective inhibitory activities against E2/IGF-I-induced proliferation through suppressing proliferative events such as phosphorylation of IRS-1, ERKs, and JNKs proteins, and induction of c-Jun protein and colony formation. These results indicate that IGF-I interacts with E2 to promote the proliferation of breast carcinoma cells via ROS-dependent MAPK activation and c-Jun protein expression. The structure-related inhibition of E2/IGF-I-induced proliferative events by flavonoids is elucidated.

NADPH oxidase mediates angiotensin II-induced endothelin-1 expression in vascular adventitial fibroblasts

OBJECTIVE

We have recently reported that adventitial fibroblasts are able to express endothelin-1 (ET-1) in response to angiotensin II (Ang II) stimulation. However, the mechanism by which this occurs in the adventitia remains unclear. As Ang II has been reported to increase oxidant production by NADPH oxidase, we examined the role of this complex in Ang II stimulated ET-1 expression in vascular adventitial fibroblasts.

METHODS AND RESULTS

Adventitial fibroblasts were isolated and cultured from mouse aorta. Cells were treated with Ang II (100 nmol/L) in the presence or absence of NADPH oxidase inhibitors, apocynin (100 micromol/L) and diphenyleneiodonium (10 micromol/L), superoxide scavengers, SOD (350 units/mL), tempol (100 micromol/L), tiron (100 micromol/L), and ET-receptor antagonists (10 microM), BQ123 (for ET(A)-) and BQ788 (for ET(B)-). PreproET-1 mRNA and ET-1 level were determined by relative RT-PCR and ELISA, respectively. Type I procollagen-alpha-I (collagen) level was detected by Western blot. Superoxide anion (superoxide) production was determined by coelenterazine or lucigenin chemiluminescence. Ang II-induced collagen expression was inhibited by BQ123, suggesting that adventitial ET-1 plays a significant role in regulating the extracellular matrix. NADPH oxidase inhibitors and superoxide scavengers significantly decreased Ang II-induced ET-1 mRNA and peptide expression, superoxide production as well as collagen expression. Furthermore, deletion of gp91(phox) (a key subunit of NADPH oxidase) and overexpression of SOD1 attenuated Ang II-induced responses.

CONCLUSION

Ang II-evoked expression of ET-1 in adventitial fibroblasts appears to be mediated, at least in part, by NADPH oxidase. Functionally, this mechanism stimulates collagen expression thereby implicating the adventitia as a potential contributor to the vascular pathophysiology associated with oxidative stress and vascular remodeling.

Effect of mitochondria poisoning by FCCP on Ca2+ signaling in mouse skeletal muscle fibers

We have studied the effects of mitochondria poisoning by carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP) on Ca(2+) signaling in enzymatically dissociated mouse flexor digitorum brevis (FDB) muscle fibers. We used Fura-2AM to measure resting [Ca(2+)](i) and MagFluo-4AM to measure Ca(2+) transients. Exposure to FCCP (2 microM, 2 min) caused a continuous increase in [Ca(2+)](i) at a rate of 0.60 nM/s and a drastic reduction of electrically elicited Ca(2+) transients without much effect on their decay phase. Half of the maximal effect occurred at [Ca(2+)](i) = 220 nM. This effect was partially reversible after long recuperation and was not diminished by Tiron, a reactive oxygen species (ROS) scavenger. FCCP had no effects on fiber excitability as shown by the generation of action potentials. 4CmC, an agonist of ryanodine receptors, induced a massive Ca(2+) release. FCCP diminished the rate but not the amount of Ca(2+) released, indicating that depletion of Ca(2+) stores did not cause the decrease in Ca(2+) transient amplitude. Ca(2+) transient amplitude could also be diminished, but to a lesser degree, by increases in [Ca(2+)](i) induced by repetitive stimulation of fibers treated with ciclopiazonic acid. This suggests an important role for Ca(2+) in the FCCP effect on transient amplitude.

The role of nitric oxide synthase-derived reactive oxygen species in the altered relaxation of pulmonary arteries from lambs with increased pulmonary blood flow

Congenital cardiac defects associated with increased pulmonary blood flow (Q(p)) produce pulmonary hypertension. We have previously reported attenuated endothelium-dependent relaxations in pulmonary arteries (PA) isolated from lambs with increased Q(p) and pulmonary hypertension. To better characterize the vascular alterations in the nitric oxide-superoxide system, 12 fetal lambs underwent in utero placement of an aortopulmonary vascular graft (shunt). Twin lambs served as controls. PA were isolated from these lambs at 4-6 wk of age. Electron paramagnetic resonance spectroscopy on fourth-generation PA showed significantly increased superoxide anion generation in shunt PA that were decreased to control levels following inhibition of nitric oxide synthase (NOS) with 2-ethyl-2-thiopseudourea. Preconstricted fifth-generation PA rings were relaxed with a NOS agonist (A-23187), a nitric oxide donor [S-nitrosyl amino penicillamine (SNAP)], polyethylene glycol-conjugated superoxide dismutase (PEG-SOD), or H(2)O(2). A-23187-, PEG-SOD-, and H(2)O(2)-mediated relaxations were impaired in shunt PA compared with controls. Pretreatment with PEG-SOD significantly enhanced the relaxation response to A-23187 and SNAP in shunt but not control PA. Inhibition of NOS with nitro-L-arginine or scavenging superoxide anions with tiron enhanced relaxation to SNAP and inhibited relaxation to PEG-SOD in shunt PA. Pretreatment with catalase inhibited relaxation of shunt PA to A-23187, SOD, and H(2)O(2). We conclude that NOS catalyzes the production of superoxide anions in shunt PA. PEG-SOD relaxes shunt PA by converting these anions to H(2)O(2), a pulmonary vasodilator. The redox environment, influenced by the balance between production and scavenging of ROS, may have important consequences on pulmonary vascular reactivity in the setting of increased Q(p).

Antioxidants tiron and N-acetyl-L-cysteine differentially mediate apoptosis in melanoma cells via a reactive oxygen species-independent NF-kappaB pathway

Tiron and N-acetyl-L-cysteine (NAC) have been recognized as potential antioxidants capable of inhibiting apoptosis induced by reactive oxygen species (ROS). Although the ROS-scavenging function of tiron and NAC is clear, the mechanism for their regulation of apoptosis is still elusive. Here we demonstrate that tiron increases nuclear factor-kappaB (NF-kappaB)/DNA binding and as a result enhances NF-kappaB transcriptional activity. In contrast, NAC inhibits NF-kappaB activation by reducing inhibitor of kappaB kinase (IKK) activity. Moreover, the expression of an NF-kappaB target gene, the chemokine CXCL1, is promoted by tiron and suppressed by NAC. Finally, tiron confers an antiapoptotic function, while NAC imparts a proapoptotic function in melanoma cells. These functions correlate with the alteration of mitochondrial membrane potential but not ROS production or induction of activating protein-1 (AP-1). This study underscores the potential benefits of regulating NF-kappaB activity in melanoma cells as a therapeutic approach.

Effects of elevated physiological temperatures on sarcoplasmic reticulum function in mechanically skinned muscle fibers of the rat

Properties of the sarcoplasmic reticulum (SR) with respect to Ca(2+) loading and release were measured in mechanically skinned fiber preparations from isolated extensor digitorum longus (EDL) muscles of the rat that were either kept at room temperature (23 degrees C) or exposed to temperatures in the upper physiological range for mammalian skeletal muscle (30 min at 40 or 43 degrees C). The ability of the SR to accumulate Ca(2+) was significantly reduced by a factor of 1.9-2.1 after the temperature treatments due to a marked increase in SR Ca(2+) leak, which persisted for at least 3 h after treatment. Results with blockers of Ca(2+) release channels (ruthenium red) and SR Ca(2+) pumps [2,5-di(tert-butyl)-1,4-hydroquinone] indicate that the increased Ca(2+) leak was not through the SR Ca(2+) release channel or the SR Ca(2+) pump, although it is possible that the leak pathway was via oligomerized Ca(2+) pump molecules. No significant change in the maximum SR Ca(2+)-ATPase activity was observed after the temperature treatment, although there was a tendency for a decrease in the SR Ca(2+)-ATPase. The observed changes in SR properties were fully prevented by the superoxide (O(2)(*-)) scavenger Tiron (20 mM), indicating that the production of O(2)(*-) at elevated temperatures is responsible for the increase in SR Ca(2+) leak. Results show that physiologically relevant elevated temperatures 1) induce lasting changes in SR properties with respect to Ca(2+) handling that contribute to a marked increase in the SR Ca(2+) leak and, consequently, to the reduction in the average coupling ratio between Ca(2+) transport and SR Ca(2+)-ATPase and muscle performance, and 2) that these changes are mediated by temperature-induced O(2)(*-) production.

Real-time measurement of nitric oxide in single mature mouse skeletal muscle fibres during contractions

Nitric oxide (NO) is thought to play multiple roles in skeletal muscle including regulation of some adaptations to contractile activity, but appropriate methods for the analysis of intracellular NO activity are lacking. In this study we have examined the intracellular generation of NO in isolated single mature mouse skeletal muscle fibres at rest and following a period of contractile activity. Muscle fibres were isolated from the flexor digitorum brevis muscle of mice and intracellular NO production was visualized in real-time using the fluorescent NO probe 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM DA). Some leakage of DAF-FM was apparent from fibres loaded with the probe, but they retained sufficient probe to respond to changes in intracellular NO following addition of the NO donor 3-(2-hydroxy-1-methyl-2-nitrosohydrazino)-N-methyl-1-propanamine (NOC-7) up to 30 min after loading. Electrically stimulated contractions in isolated fibres increased the rate of change in DAF-FM fluorescence by approximately 48% compared to non-stimulated fibres (P < 0.05) and the rate of change in DAF-FM fluorescence in the stimulated fibres returned to control values by 5 min after contractions. Treatment of isolated fibres with the NO synthase inhibitors NG-nitro-L-arginine methyl ester hydrochloride (L-NAME) or NG-monomethyl-L-arginine (L-NMMA) reduced the increase in DAF-FM fluorescence observed in response to contractions of untreated fibres. Treatment of fibres with the cell-permeable superoxide scavenger 4,5-dihydroxy-1,3-benzenedisulphonic acid (Tiron) also reduced the increase in fluorescence observed during contractions suggesting that superoxide, or more probably peroxynitrite, contributes to the fluorescence observed. Thus this technique can be used to examine NO generation in quiescent and contracting skeletal muscle fibres in real time, although peroxynitrite and other reactive nitrogen species may potentially contribute to the fluorescence values observed.

An approach to elucidate potential mechanism of renal toxicity of arsenic trioxide

OBJECTIVE

To investigate arsenic trioxide's renal toxicity, we analyzed the gene-expression patterns of primary renal and human kidney cells (HEK293 cell line) following exposure to arsenic trioxide. Moreover, we examined a potential renal toxic mechanism(s) of arsenic trioxide by using a toxicity-related gene and investigated potential treatments to reduce the renal toxicity of arsenic trioxide.

MATERIALS AND METHODS

Arsenic trioxide was exposed to primary renal and HEK293 cells, and the gene-expression analysis was conducted using DNA microarray. Then, reactive oxygen species inhibitors or alpha-lipoic acid were added to HEK293 cells exposed arsenic trioxide and cell viability was determined.

RESULTS

Expression of HMOX1 mRNA increased in a time- and dose-dependent manner, and translation of heme oxygenase 1 protein was also induced. Arsenic trioxide-induced cytotoxicity was inhibited by reactive oxygen species inhibitors. Moreover, superoxide anion was detected in arsenic trioxide-treated HEK293 cells. alpha-Lipoic acid ameliorated arsenic trioxide-induced cytotoxicity and reduced superoxide anion production in HEK293 cells, whereas it had no effect in promyelocytic leukemia cells (HL-60 cells and NB4 cells) and myeloma cells (KMS12BM cells and U266 cells).

CONCLUSIONS

Arsenic trioxide-induced renal toxicity is strongly associated with the increased expression of HMOX1, and the cytotoxic mechanisms of arsenic trioxide involves reactive oxygen species production as well as another pathway. These preliminary results suggest that alpha-lipoic acid may be a suitable agent for prevention or treatment of arsenic trioxide-induced renal toxicity.

Role of combined administration of Tiron and glutathione against aluminum-induced oxidative stress in rat brain

The current study was carried out to investigate the potential role of 4,5 dihydroxy benzene 1,3 disulfonic acid di sodium salt (Tiron) and glutathione (GSH) either individually or in combination against aluminum (Al)-induced toxicity in Wistar rats. Animals were exposed to aluminum chloride at a dose of 172.5mg/kg/d orally for 10 weeks. Tiron and GSH were administered at a dose of 471-mg/kg/d i.p. and 100mg/kg/d orally, respectively, for 7 consecutive days. Tiron is a diphenolic chelating compound which forms water soluble complexes with a large number of metal ions. Induction of oxidative stress was recorded in brain and serum after Al exposure. Significant decrease was recorded in reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GP(x)), catalase (CAT), superoxide dismutase (SOD), acetyl cholinesterase (AChE) and an increase was observed in thiobarbituric acid reacting substance (TBARS) and glutathione-S-transferase (GST) in brain and serum. Most of the above parameters responded positively to individual therapy with Tiron, but more pronounced beneficial effects on the above-described parameters were observed when Tiron was administered in combination with GSH. Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) studies also showed significantly high concentration of Al in brain and blood. Tiron was slightly more effective then GSH in reducing the concentration of Al from the brain and blood, however, no further improvement was recorded when Tiron was administered in combination with GSH in reducing the concentration of Al.

EFFECT OF TIRON AND ITS COMBINATION WITH NUTRITIONAL SUPPLEMENTS AGAINST VANADIUM INTOXICATION IN FEMALE ALBINO RATS

In the present study an attempt has been made to evaluate the effect of Tiron along with Zinc, Selenium and Vitamin E against vanadium intoxication in female albino rats. Toxicant caused significant increase in the activities of serum transaminases, serum alkaline phosphatase and lactate dehydrogenase. Significant decrease was observed in blood sugar, serum albumin and triglyceride levels whereas serum proteins, cholesterol and urea levels increased significantly during toxicity (p </= 0.001). Hepatic lipid peroxidation increased significantly, whereas significant depletion was observed in reduced glutathione after vanadium administration. The activity of glucose-6-phosphatase in the liver was also inhibited significantly after vanadium administration. A significant rise was observed in glycogen content of liver and kidney after toxicant exposure. Activities of alkaline phosphatase, adenosine triphosphatase and succinic dehydrogenase were inhibited significantly on the contrary activity of acid phosphatase elevated in kidney. Histopathological examination of the liver and kidney using light and ultramicroscopic study also substantiated the above findings. It was found that therapy with Tiron was effective but significant recovery in all the parameters was found with Tiron + Se followed by Tiron+ VitE and Tiron +Zn.

Highly sensitive determination of transient generation of biophotons during hypersensitive response to cucumber mosaic virus in cowpea

The hypersensitive response (HR) is one mechanism of the resistance of plants to pathogen infection. It involves the generation of reactive oxygen species (ROS) which have crucial roles in signal transduction or as toxic agents leading to cell death. Often, ROS generation is accompanied by an ultraweak photon emission resulting from radical reactions that are initiated by ROS through the oxidation of living materials such as lipids, proteins, and DNA. This photon emission, referred to as 'biophotons', is extremely weak, but, based on the technique of photon counting imaging, a system has been developed to analyse the spatiotemporal properties of photon emission. Using this system, the dynamics of photon emission which might be associated with the oxidative burst, which promotes the HR, have been determined. Here, the transient generation of biophotons is demonstrated during the HR process in cowpea elicited by cucumber mosaic virus. The distinctive dynamics in spatiotemporal properties of biophoton emission during the HR expression on macroscopic and microscopic levels are also described. This study reveals the involvement of ROS generation in biophoton emission in the process of HR through the determination of the inhibitory effect of an antioxidant (Tiron) on biophoton emission.

NAD(P)H oxidase activity of Nox4 in chondrocytes is both inducible and involved in collagenase expression

Reactive oxygen species (ROS) are regulators of redox-sensitive cell signaling pathways. In osteoarthritis, human interleukin-1beta is implicated in cartilage destruction through an ROS-dependent matrix metalloproteinase production. To determine the molecular source of ROS production in the human IL-1beta (hIL-1beta)-sensitive chondrocyte immortalized cell line C-20/A4, transfected cells were constructed that overexpress NAD(P)H oxidases. First, RT-PCR analysis showed that the C-20/A4 cell line expressed Nox2, Nox4, p22( phox ), and p67( phox ), but not p47( phox ). It was found that ROS production by C-20/A4 chondrocytes does not depend on PMA and ionomycin activation. This indicates that Nox2 was not involved in the production of ROS. In C- 20/A4 cells that overexpress Nox4, hIL-1beta stimulated ROS production three times more than the normal production of C-20/A4 cells. Moreover, there was a fourfold increase in the production of collagenase (MMP-1) by chondrocytes that overexpress Nox4. Interestingly, MMP-1 production in cells that overexpress Nox2 was not sensitive to hIL-1beta. These data suggest that under hIL-1beta stimulation, C-20/A4 chondrocytes produce MMP-1 through a Nox4-mediated, ROS-dependent pathway.

Serotype-specific invasiveness and colonization prevalence in Streptococcus pneumoniae correlate with the lag phase during in vitro growth

Serotypes of Streptococcus pneumoniae differ in colonization prevalence and the likelihood of causing disease. In vitro growth in brain heart infusion broth with or without 5% fetal calf serum (FCS) was compared for 47 clinical isolates representing 15 pneumococcal serotypes. Serotype-specific colonization prevalence and odds ratios for the invasive potential were obtained from an international and a local epidemiological study. The duration of the lag phase increased with the invasiveness and was inversely associated with the colonization prevalence of a serotype. Supplementation with FCS shortened the lag phase preferentially in serotypes associated with invasive disease (P=0.007). Reduction of oxidative stress by addition of manganese (Mn(2+)), Tiron, mannitol or catalase did not influence the duration of the lag phase significantly. Serotype specific invasiveness and colonization prevalence of S. pneumoniae are associated with the length of the lag phase during in vitro growth. This may correlate with serotype specific selection in vivo.

Modulation by homocysteine of the iberiotoxin-sensitive, Ca2+ -activated K+ channels of porcine coronary artery smooth muscle cells

We evaluated the acute effect of homocysteine on the iberiotoxin-sensitive, Ca(2+)-activated K(+) (BK(Ca)) channels of the porcine coronary artery smooth muscle cells. NS 1619 (1 to 30 microM) caused a concentration-dependent enhancement of the BK(Ca) amplitude (recorded using the whole-cell, membrane-rupture configuration) only with an elevated [Ca(2+)](i) of approximately 444 nM, but not with [Ca(2+)](i) of approximately 100 nM. Homocysteine (30 microM) caused a small inhibition ( approximately 16%) of the BK(Ca) amplitude ([Ca(2+)](i)= approximately 444 nM), and a greater inhibition ( approximately 77%) was observed with 100 microM NADH present in the pipette solution. The inhibition persisted after washing. With NADPH (100 microM), a smaller magnitude of inhibition ( approximately 34%) of the BK(Ca) amplitude was recorded. The NS 1619-mediated enhancement of the BK(Ca) amplitude (with elevated [Ca(2+)](i) plus NADH in the pipette) was attenuated by homocysteine. The homocysteine-mediated inhibition of the BK(Ca) amplitude was suppressed by Tiron (10 mM) or diphenylene iodonium (30 nM), applied alone, but not by superoxide dismutase (500 U/ml) and catalase (500 U/ml). Generation of superoxide (O(2)(-)) of the smooth muscle cells (with NADH presence), measured using the lucigenin-enhanced chemiluminescence, was markedly increased by angiotensin II (100 nM) and homocysteine (30 microM). The chemiluminescence signal was sensitive to apocynin (300 microM) or Tiron, applied alone, but not to superoxide dismutase and catalase. In conclusion, our results demonstrate that acute homocysteine application inhibits the iberiotoxin-sensitive BK(Ca) channels (with elevated [Ca(2+)](i) and NADH present) which is probably caused by the NADH oxidase activation and the concomitant generation of intracellular superoxide.

Internal mammary artery smooth muscle cells resist migration and possess high antioxidant capacity

OBJECTIVE

This study investigated whether differences exist in atherogen-induced migratory behaviors and basal antioxidant enzyme capacity of vascular smooth muscle cells (VSMC) from human coronary (CA) and internal mammary (IMA) arteries.

METHODS

Migration experiments were performed using the Dunn chemotaxis chamber. The prooxidant [NAD(P)H oxidase] and antioxidant [NOS, superoxide dismutase, catalase and glutathione peroxidase] enzyme activities were determined by specific assays.

RESULTS

Chemotaxis experiments revealed that while both sets of VSMC migrated towards platelet-derived growth factor-BB (1-50 ng/ml) and angiotensin II (1-50 nM), neither oxidized-LDL (ox-LDL, 25-100 microg/ml) nor native LDL (100 microg/ml) affected chemotaxis in IMA VSMC. However, high dose ox-LDL produced significant chemotaxis in CA VSMC that was inhibited by pravastatin (100 nM), mevastatin (10 nM), losartan (10 nM), enalapril (1 microM), and MnTBAP (a free radical scavenger, 50 microM). Microinjection experiments with isoprenoids i.e. geranylgeranylpyrophosphate (GGPP) and farnesylpyrophosphate (FPP) showed distinct involvement of small GTPases in atherogen-induced VSMC migration. Significant increases in antioxidant enzyme activities and nitrite production along with marked decreases in NAD(P)H oxidase activity and O2- levels were determined in IMA versus CA VSMC.

CONCLUSIONS

Enhanced intrinsic antioxidant capacity may confer on IMA VSMC resistance to migration against atherogenic agents. Drugs that regulate ox-LDL or angiotensin II levels also exert antimigratory effects.

Production of superoxide and dissipation of mitochondrial transmembrane potential by vitamin K2 trigger apoptosis in human ovarian cancer TYK-nu cells

We reported previously that vitamin K(2) selectively induces apoptosis in human ovary cancer cells (TYK-nu cells) and pancreatic cancer cells (MIA PaCa-2 cells) through a mitochondrion-dependent pathway. In the present study, we examined the details of the mechanism of vitamin K(2)-induced apoptosis in TYK-nu cells. We found that superoxide (O(2)(*-)) was produced by TYK-nu cells between 2 and 3 days after the start of treatment with vitamin K(2), whereas it was produced within 30 min after the start of treatment with geranylgeraniol. The vitamin K(2)-induced apoptosis was inhibited by anti-oxidants, such as alpha-tocopherol, Tiron and N-acetyl-L-cysteine (NAC). Furthermore, both the production of superoxide and the induction of apoptosis by vitamin K(2) were inhibited almost completely by cycloheximide, an inhibitor of protein synthesis, suggesting that the synthesis of enzymes for the production of superoxide might be required for these processes. In parallel with the production of superoxide, the mitochondrial transmembrane potential, as measured by staining with Mitotracker Red CMXRos, dissipated during treatment of TYK-nu cells with vitamin K(2) for 3 days. The vitamin K(2)-induced depolarization of mitochondrial membranes was completely inhibited by alpha-tocopherol and, to a lesser extent, by Tiron and NAC. Since alpha-tocopherol reacts with oxygen radicals, such as superoxide, within the hydrophobic environment of the mitochondrial membrane, we postulate that vitamin K(2)-induced oxidative stress in mitochondria might damage mitochondrial membranes, with subsequent release of cytochrome c, the activation of procaspase 3 and, eventually, apoptosis.

NAD(P)H oxidase-stimulating activity of serum from type 2 diabetic patients with retinopathy mediates enhanced endothelial expression of E-selectin

Endothelial expression of E-selectin is enhanced in diabetic patients with retinopathy, however, the underlying mechanisms are unclear. Therefore, this study was aimed to determine if endothelial expression of E-selectin is stimulated with serum from type 2 diabetic patients with retinopathy, and whether this process is related to NAD(P)H oxidase-derived oxidative stress. Serum was obtained from type 2 diabetic patients with (T2DR) or without (T2DM) retinopathy, and age-matched non-diabetic healthy person (Control). Serum was added to in vitro-grown human coronary artery endothelial cells (HCAEC), after which E-selectin expression, reactive oxygen species (ROS) production, and NAD(P)H oxidase activity were measured. Serum from T2DR induced a significantly higher expression of E-selectin than serum from T2DM and control in association with an enhanced production of ROS in HCAEC. T2DR serum enhanced E-selectin expression in a ROS-dependent manner since this process was significantly attenuated not only by tiron (1 mM), a superoxide scavenger, but also by DPI (10 micromol/L) and apocynin (100 micromol/L), inhibitors of NAD(P)H oxidase. Furthermore, the activity of NADH oxidase was markedly increased by T2DR serum, and this was accompanied by the enhanced membrane translocation of p47phox, a cytosolic subunit of NAD(P)H oxidase. These findings suggest that serum from T2DR induced up-regulation of E-selectin expression in HCAEC, and this process might be dependent on activation of endothelial NADH oxidase via an enhanced membrane translocation of p47phox.

Aluminum-induced maternal and developmental toxicity and oxidative stress in rat brain: Response to combined administration of Tiron and glutathione

The current study was performed to assess the potential of 4,5-dihydroxy 1,3-benzene disulfonic acid di sodium salt (Tiron) and glutathione (GSH) either individually or in combination against aluminum (Al)-induced developmental toxicity in fetuses and sucklings of Wistar rats. Female rats were exposed to aluminum chloride at a dose of 345 mg/(kg day) oral from days 0 to 16 of gestation and 0 to 16 of post-partum (P.P.). Tiron and GSH were administered at a dose of 471 mg/(kg day) i.p. and 100 mg/(kg day) oral, respectively, on days 5, 7, 9, 11, 13, 15 and 17 of gestation and post-partum. Al caused reduction in number of corpora lutea, number of implantation sites, placental and fetal weight and stunted growth. Skeletal malformations were also observed in fetuses. Maternal toxicity was demonstrated by reduction in body weight gain. Induction of oxidative stress was also recorded in the brain of mother as well as in fetuses and sucklings after Al exposure. Significant decrease was recorded in reduced glutathione, glutathione reductase (GR), glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), acetyl cholinesterase (AChE) and increase was observed in TBARS and glutathione-S-transferase (GST) in brain of pregnant mothers, fetuses and sucklings. Most of the above parameters responded positively with individual therapy with Tiron, but more pronounced beneficial effects on the above-described parameters were observed when Tiron was administered in combination with GSH. Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) studies also showed significantly high concentration of Al in suckling's brain and maternal blood, brain, placenta and fetal brain. Treatment with Tiron individually or in combination with glutathione, reduced the accumulation of the Al in almost all the organs studied. It is concluded that chelating agents reduced the Al-induced toxicity and Tiron was more effective in reducing blood Al concentration than glutathione when given individually.

Tempol in the dorsomedial hypothalamus attenuates the hypertensive response to stress in rabbits

BACKGROUND

We have recently shown that microinjection of the superoxide dismutase mimetic tempol into the pressor region of the rostral ventrolateral medulla attenuates the cardiovascular response to mental (air-jet) stress in rabbits. In the present study, we examined the influence of tempol on the blood pressure (BP) and heart rate (HR) responses to stress in the key region of the hypothalamic defense area, the dorsomedial hypothalamus (DMH).

METHODS

New Zealand White rabbits were implanted with guide cannulae for microinjection into the DMH. After 2 weeks of recovery, the cardiovascular response to air-jet stress was evaluated before and after bilateral injections of equimolar doses (20 nmol) of the superoxide scavengers tempol, tiron, or 3-carbamoyl proxyl (3-CP).

RESULTS

Microinjection of superoxide scavengers into the DMH did not alter resting BP or HR. Air-jet stress evoked a sustained increase in BP (+16 +/- 2 mm Hg) and HR (+48 +/- 5 beats/min). Tempol attenuated the pressor and tachycardic responses to air-jet stress by 39% +/- 10% and 37% +/- 8%, respectively (P < .05), without altering stress-induced tachypnea. Similarly, tiron selectively decreased the BP and HR responses to stress by 33% +/- 8% and 53% +/- 13%, respectively (P < .05). Conversely, 3-CP, which is structurally close to tempol but has a lower superoxide scavenging activity, did not alter the cardiovascular stress response, and neither did vehicle. Microinjection of tempol or tiron just outside the DMH had little effect on stress responses.

CONCLUSIONS

This study provides first published evidence that superoxide in the DMH is important in the regulation of acute hypertensive and tachycardic responses to mental stress.

Effects of Tiron, 4,5-dihydroxy-1,3-benzene disulfonic acid, on human promyelotic HL-60 leukemia cell differentiation and death

Tiron, 4,5-dihydroxy-1,3-benzene disulfonic acid, has been known to be a widely used antioxidant to rescue ROS-evoked cell death and a non-toxic chelator to alleviate an acute metal overload. In this study, we showed that Tiron is a potent inducer of cell differentiation and apoptotic cell death in human promyelotic HL-60 leukemia cell. At a low level of concentration (<0.5mM), Tiron caused HL-60 cells to induce differentiation-related alterations such as the increase of CD11b and CD14 expression or chromatin condensation. Hypoxia inducible factor-1alpha (HIF-1alpha) was also increased at mRNA and protein level, and thus the CCAAT/enhancer-binding protein alpha, which is a downstream target of HIF-1alpha and acts as a critical factor for granulocytic differentiation was increased. High dose of Tiron (>0.5mM) induced severe DNA damage in HL-60 cells, as measured by the cytokinesis-block micronucleus test and the comet assay. Consequently, high dose of Tiron led to apoptotic cell death, which showed the DNA fragmentation, the caspase activation and the unbalance between antiapoptotic (Bcl-2) and proapoptotic proteins (Bax). However, an exogenous supplement of iron (FeCl(3)) reversed all of these effects, the cell differentiation and the apoptotic cell death. Therefore, these results suggest that Tiron-mediated differentiation and cell death result from the disturbance of iron metabolism.

Effects of acute ethanol administration on LPS-induced expression of cyclooxygenase-2 and inducible nitric oxide synthase in rat alveolar macrophages

BACKGROUND

Activation of alveolar macrophages acts as a primary defense mechanism of lung with immunologic and inflammatory processes. Incidence of respiratory distress syndrome (ARDS) has been reported to be higher in alcoholics than that in nonalcoholics. Both cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) are induced by inflammatory stimuli such as LPS and cytokines and are involved in host defense. COX-2 and iNOS have been reported to play important roles in pathophysiology of ARDS. The aim of the present study was to elucidate whether acute ethanol administration to rats affects on COX-2 and iNOS expression in isolated alveolar macrophages.

METHODS

Ethanol (4.5 g per kg body weight as a 20% solution) was intraperitoneally injected to male Wistar rats. At 2.5 hrs after the injection, alveolar macrophages were collected from rats by bronchoalveolar lavage and were stimulated with lipopolysaccharide (LPS, 1 mug/ml). Expression of COX-2 and iNOS and activation of MAPKs was evaluated by Western blotting.

RESULTS

In alveolar macrophages isolated from ethanol-treated rats, LPS-stimulated production of both prostaglandin E2 and nitrite was significantly lower than that in macrophages isolated from vehicle-treated control rats. LPS-induced expression of both COX-2 and iNOS was significantly lower in macrophages from ethanol-treated rats than that in macrophages from the control rats, while expression of beta-actin was not different in these groups. LPS increased phosphorylation of both extracellular signal-regulated protein kinase (ERK) and p38 mitogen-activated protein kinase (MAPK). The levels of phosphorylated ERK and p38 were significantly lower in macrophages from ethanol-treated rats compared with those from the control rats. Treatment of macrophages with ethanol (100 - 400 mM) in vitro significantly inhibited expression of COX-2 in a concentration-dependent manner, while only a high concentration (400 mM) of ethanol significantly inhibited expression of iNOS. Ethanol also inhibited COX-2 expression in the presence of Tiron. Expression of COX-2 and iNOS was significantly inhibited by U0126 but not by SB203580.

CONCLUSION

In rat alveolar macrophages, LPS-induced expression of COX-2 and iNOS is mediated by ERK MAPK but not by p38 MAPK. Acute ethanol administration to rats attenuates induction of both COX-2 and iNOS in alveolar macrophages by inhibiting phosphorylation of ERK.

Homocysteine-induced changes in vascular reactivity of guinea-pig pulmonary arteries: role of the oxidative stress and poly (ADP-ribose) polymerase activation

This study was aimed to examine the effects of homocysteine (Hcy) on vascular responsiveness of guinea-pig isolated pulmonary arteries and to investigate possible underlying mechanisms. In order to evaluate vascular reactivity, isometric tension studies were performed in response to potassium chloride (KCl), phenylephrine (Phe), acetylcholine (ACh), and sodium nitroprusside (SNP). Incubation of pulmonary artery rings with Hcy (10(-3)M, 180min) resulted in significant inhibition of response to ACh (an endothelium-dependent vasodilator)(E(max): 55.3+/-6.7 vs. 13.1+/-2.0(*), P<0.05) while SNP (an endothelium-independent vasodilator)-induced relaxation was not changed significantly. Furthermore, Hcy enhanced KCl- and Phe-induced contraction of pulmonary artery rings (E(max): 1568+/-81 vs. 2101+/-145(*)mg for KCl and 1081+/-101 vs. 1544+/-117(*)mg for Phe, P<0.05). Pulmonary artery ring contractions induced by stepwise addition to Ca(2+) to high KCl solution with no Ca(2+) were also significantly augmented by Hcy incubation (E(max): 1750+/-121 vs. 2295+/-134(*)mg, P<0.05). To investigate mechanisms of Hcy action, additional sets of experiments involving rings incubation with Hcy alone or with addition of Tiron (an intracellular superoxide anion scavenger, 10(-2)M), PJ34 (an inhibitor of polyADP-ribose polymerase, 3x10(-6)M), and combination of two antioxidant enzymes superoxide dismutase (SOD, 100U/ml) and catalase (CAT, 120U/ml) for 180min. The findings of our study clearly show that all these co-treatments significantly prevented the development of endothelial dysfunction induced by Hcy. Furthermore, the effect of Hcy on KCl- and Phe-induced contraction was significantly inhibited by the concomitant incubation with either SOD plus CAT, Tiron or PJ34. This study demonstrates that Hcy causes a significant alteration in vascular reactivity of pulmonary arteries, and this alteration seems to be via oxidative stress in pulmonary artery endothelium with subsequent DNA damage and activation of poly(ADP-ribose) polymerase (PARP) pathway.

In vivo fragmentation of the large subunit of ribulose-1,5-bisphosphate carboxylase by reactive oxygen species in an intact leaf of cucumber under chilling-light conditions

Previous studies have demonstrated that the large subunit (LSU) of ribulose-1,5-bisphosphate carboxylase (Rubisco) is site-specifically cleaved by a hydroxyl radical (*OH) generated in the illuminated chloroplast lysates or by an artificial *OH-generating system. However, it is not known whether such cleavage of the LSU by reactive oxygen species (ROS) actually occurs in an intact leaf. When leaf discs of chilling-sensitive cucumber (Cucumis sativus L.) were illuminated at 4 degrees C, five major fragments of the LSU were observed. This fragmentation was completely inhibited by ROS scavengers, such as n-propyl gallate (for *OH) and 1,2-dihydroxybenzene-3,5-disulfonic acid (Tiron) (for superoxide). FeSO4 stimulated this fragmentation, whereas an iron-specific chelator, deferoxamine, suppressed it. Furthermore, such fragments were identical to those generated from the purified Rubisco by an *OH-generating system in vitro on two-dimensional PAGE. These results indicate that the direct fragmentation of the LSU by reactive oxygen species also occurs in an intact leaf.

Ischemia/Reperfusion Injury in the Monolayers of Human Intestinal Epithelial Cell Line Caco-2 and Its Recovery by Antioxidants

We previously established a in vitro system for assessing early ischemia/reperfusion injury using monolayers of human intestinal epithelial cell line Caco-2, in which lipid peroxidation caused by tertiary-butylhydroperoxide (t-BuOOH), a lipid peroxidation inducer, acts as a trigger of the injury. By now, we have shown that superoxide anion participates in the opening of tight junctions (TJ) induced by reoxygenation following the induction of lipid peroxidation by t-BuOOH at a low concentration. The present objectives are to elucidate the dysfunction of P-glycoprotein (P-gp) in addition to the opening of TJ by t-BuOOH at a high concentration condition using rhodamine123 (Rho123) as a P-gp substrate and cyclosporine A (CyA) as a P-gp inhibitor. Also, we compared the inhibition effect of lutein and other compounds such as biliverdin as a radical scavenger on the opening of TJ and the dysfunction of P-gp. t-BuOOH at a high concentration increased the permeability of Rho123 in the apical to basal direction and decreased basal to apical direction when compared with control conditions. t-BuOOH at a high concentration showed no significant difference between directional transport of Rho123 and no inhibition was observed in the permeability of both directions by CyA. The staining intensity of Western blot was decreased by t-BuOOH at a high concentration. Although lutein and the other compounds had recovery effects on the opening of TJ and P-gp dysfunction induced by t-BuOOH, lutein is more advantageous than other compounds since it has effective effects at the lower concentration. In conclusion, the barrier dysfunction such as the inhibition of P-gp in addition to the opening of TJ was induced by t-BuOOH at a high concentration condition. The above two barrier dysfunctions was ameliorated by antioxidant such as lutein and biliverdin.