Chronic mercury exposure at different concentrations produces opposed vascular responses in rat aorta

Mercury chloride exposure for 30 days decreases NO bioavailability and increases oxidative stress. However, the mechanisms underlying the effects of mercury on the cardiovascular system are not completely understood, and it is not known if they are dose‐dependent or if some concentrations have no harmful effects. Thus, we investigated the effects of chronic exposure to doses low (half) and high (2.5‐fold higher) than that needed to obtain 29 nmol/L of HgCl₂ on the vascular function. Three‐month‐old male Wistar rats received intramuscular (i.m.) HgCl₂ for 30 days and were divided in three groups: lower (Low Hg); higher (High Hg); and saline was used as the control. High Hg exposure increased the contractile response to phenylephrine (PHE) in aortic rings, but Low Hg reduced it. The hyporesponsiveness in the Low Hg rats was blunted by endothelial denudation and NOS inhibition with l ‐NAME (100 μmol/L). The phosphorylated‐eNOS/eNOS protein ratio increased in the aortas of Low Hg rats. In the High Hg group, endothelial denudation increased the PHE‐induced contractions, while l ‐NAME had no effects and indomethacin (10 μmol/L), losartan (10 μmol/L) and apocynin (30 μmol/L) reduced this response. In the High Hg group, protein levels of the NADPH oxidase subunit gp91phox and cyclooxygenase‐2 increased. Our results support previous suggestions that High Hg increases oxidative stress that might activate an inflammatory cascade and the renin‐angiotensin system. However, very low Hg concentrations below the level considered safe still reduced vascular reactivity, suggesting the need for special attention to continuous exposure as a putative cause of increased cardiovascular risk.     

Concomitant administration of sodium 2,3-dimercapto-1-propanesulphonate (DMPS) and diphenyl diselenide reduces effectiveness of DMPS in restoring damage induced by mercuric chloride in mice

The effect of combined therapy with diphenyl diselenide (PhSe)₂ and sodium 2,3-dimercapto-propane-1-sulphonate (DMPS) against alterations induced by mercury (Hg²⁺) was evaluated. Mice were exposed to mercuric chloride (HgCl₂) (1 mg/kg, subcutaneously) for two weeks. After that, mice received (PhSe)₂ (15.6 mg/kg), or DMPS (12.6 mg/kg), or a combination of both for one week. Thiobarbituric acid-reactive substances (TBARS), ascorbic acid and Hg²⁺ levels and glutathione S-transferase (GST) and catalase (CAT) activities were carried out in kidney. Hematological parameters, plasmatic billirubin, uric acid, urea and creatinine levels as well as lactate dehydrogenase (LDH) activity were determined. (PhSe)₂ or DMPS restored the increase in LDH activity and TBARS, bilirubin, uric acid, urea and creatinine levels caused by HgCl₂. The levels of erythrocytes, hemoglobin and hematocrit reduced by HgCl₂ exposure were restored by (PhSe)₂ or DMPS administration in mice. Leukocyte and platelet counts modified by HgCl₂ exposure were restored by (PhSe)₂ or DMPS therapy. DMPS restored the increase in Hg²⁺ levels induced by exposure to HgCl₂. Concomitant administration of (PhSe)₂ and DMPS reduced the effectiveness of DMPS in restoring damage induced by HgCl₂. Combined therapy with (PhSe)₂ and DMPS was less effective than isolated therapies in restoring the damage induced by HgCl₂ in mice.     

Diphenyl diselenide potentiates nephrotoxicity induced by mercuric chloride in mice

Following our long‐standing interest in the mechanisms involved in selenium toxicity, the aim of this work was to extend our previous studies to gain a better understanding of mercuric chloride (HgCl₂) + diphenyl diselenide (PhSe)₂ toxicity. Mice received one daily dose of HgCl₂ (4.6 mg kg^?1, subcutaneously) for three consecutive days. Thirty minutes after the last injection of HgCl₂, mice received a single dose of (PhSe)₂ (31.2 mg kg^?1, subcutaneously). Five hours after (PhSe)₂ administration, mice were euthanized and δ‐aminolevulinate dehydratase, catalase (CAT), glutathione S‐transferase (GST) and Na⁺, K⁺‐ATPase activities as well as thiobarbituric acid‐reactive substances (TBARS), ascorbic acid and mercury levels were determined in kidney and liver. Parameters in plasma (urea, creatinine, protein and erythropoietin), whole blood (hematocrit and hemoglobin) and urine (protein) were also investigated. HgCl₂ + (PhSe)₂ exposure caused a decrease in renal GST and Na⁺, K⁺‐ATPase activities and an increase in renal ascorbic acid and TBARS concentrations when compared with the HgCl₂ group. (PhSe)₂ potentiated the increase in plasma urea caused by HgCl₂. HgCl₂ + (PhSe)₂ exposure caused a reduction in plasma protein levels and an increase in hemoglobin and hematocrit contents when compared with the HgCl₂ group. There was a significant reduction in hepatic CAT activity and an increase in TBARS levels in mice exposed to HgCl₂ + (PhSe)₂ when compared with the HgCl₂ group. The results demonstrated that (PhSe)₂ did not modify mercury levels in mice. In conclusion, (PhSe)₂ potentiated damage caused by HgCl₂ affecting mainly the renal tissue. Copyright © 2011 John Wiley & Sons, Ltd.     

Arsenic trioxide induces growth inhibition and death in human pulmonary artery smooth muscle cells accompanied by mitochondrial increase and GSH depletion

Arsenic trioxide (ATO; As₂O₃) induces cell death in various cells via oxidative stress. Expose to chronic arsenic is involved in the development of vascular diseases. However, little is known about the cytotoxic effects of ATO on human normal vascular smooth muscle cells (VSMCs). Thus, in this study, we investigated the effects of ATO on cell growth and death in human pulmonary artery smooth muscle (HPASM) cells in relation to reactive oxygen species (ROS) and glutathione (GSH) levels. ATO treatment decreased the growth of HPASM cells with an IC₅₀ of ～30–50 μM at 24 h, and ATO induced HPASM cell death via apoptosis or necrosis dependent on the doses of it at this time. Treatment with 50 μM ATO did not increase ROS levels at the early time points, but it significantly increased mitochondrial levels at 24 h. ATO also induced GSH depletion in HPASM cells. N‐acetyl cysteine (NAC; a well‐known antioxidant) did not significantly affect apoptotic cell death, ROS levels, or GSH depletion in ATO‐treated HPASM cells. However, l ‐buthionine sulfoximine (BSO; an inhibitor of GSH synthesis) intensified mitochondrial levels in ATO‐treated HPASM cells, and significantly increased cell death and GSH depletion in these cells as well. In summary, we provided the first evidence that ATO inhibited the growth of HPASM cells, and induced apoptotic and/or necrotic cell death in these cells, accompanied by increases in mitochondrial level and GSH depletion.     

Biomarkers involved in energy metabolism and oxidative stress response in the liver of Goodea gracilis Hubbs and Turner, 1939 exposed to the microcystin‐producing Microcystis aeruginosa LB85 strain

Goodea gracilis is an endemic fish that only habitats in some water bodies of Central Mexico that are contaminated with cyanobacteria‐producing microcystins (MC); however, a lack of information on this topic prevails. With the aim to generate the first approximation about the physiological changes elicited by cyanobacterium that produce MC congeners in this fish species, specimens born in the laboratory was exposed for 96 h to cell densities of 572.5, 1145, 2290, 4580, and 9160 × 10⁶ cells of Microcystis aeruginosa strain LB85/L, and a set of novel endpoint related to hepatic gluconeogenesis (ADH/LDH) and pro‐oxidant forces ${\mathrm{O}}_2^{.}$, H₂O₂) in addition to biomarkers of oxidative damage and antioxidant response was evaluated in the liver. Results suggest that high inhibition of protein serine/threonine phosphatase (PP) may trigger many metabolic processes, such as those related to hepatic gluconeogenesis (ADH/LDH) and pro‐oxidant ${\mathrm{O}}_2^{?}$, H₂O₂, TBARS, ROOH, RC?O) as well as antioxidant (SOD, CAT, GPx) response to oxidative stress. Particularly, we observed that inhibition of LDH and PP, and H₂O₂ increase and TBARS production were the key damages induced by high densities of M. aeruginosa. However, changes between aerobic and anaerobic metabolism related with ROS metabolism and ADH/LDH balance are apparently an acclimation of this fish species to exposure to cyanobacteria or their MCs. Fish species living in environments potentially contaminated with cyanobacteria or their MCs possess mechanisms of acclimation that allow them to offset the damage induced, even in the case of fish that have never been exposed to MCs. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 1113–1124, 2015.     

Inorganic mercury exposure: toxicological effects,oxidative stress biomarkers and bioaccumulation in the tropical freshwater fish matrinxã, <Emphasis Type="Italic">Brycon amazonicus</Emphasis> (Spix and Agassiz, 1829)

Alterations in the antioxidant cellular system have often been proposed as biomarkers of pollutant-mediated toxicity. This study evaluated the effects of mercury on oxidative stress biomarkers and bioaccumulation in the liver, gills, white muscle and heart of the freshwater fish matrinxã, Brycon amazonicus, exposed to a nominal and sub-lethal concentration (~20% of 96 h-LC₅₀) of 0.15 mg L^?1 of mercury chloride (HgCl₂) for 96 h in a static system. Increases in superoxide dismutase, catalase, glutathione peroxidase (GPx), glutathione S-transferase (GST) and glutathione reductase (GR) were observed in all tissues after HgCl₂ exposure, except for white muscle GR activity and hepatic GPx. In the liver and gills, the exposure to HgCl₂ also induced significant increases in reduced glutathione (GSH). Conversely, exposure to HgCl₂ caused a significant decrease in the GSH levels and an increase in the oxidized glutathione (GSSG) content in the white muscle, while both GSH and GSSG levels increased significantly in the heart muscle. Metallothionein concentrations were significantly high after HgCl₂ exposure in the liver, gills and heart, but remained at control values in the white muscle. HgCl₂ exposure induced oxidative damage, increasing the lipid peroxidation and protein carbonyl content in all tissues. Mercury accumulated significantly in all the fish tissue. The pattern of accumulation follows the order gills > liver ? heart > white muscle. In conclusion, these data suggest that oxidative stress in response to inorganic mercury exposure could be the main pathway of toxicity induced by this metal in fish.     

Profiling of rutin‐mediated alleviation of cadmium‐induced oxidative stress in Zygophyllum fabago

Zygophyllum fabago grows in arid, saline soil, or disturbed sites, such as former industrial or mining areas. This species is able to grow in coarse mineral substrates contaminated with heavy metals. To investigate the effects of the flavonoid rutin (Rtn) on certain heavy metal stress responses such as antioxidant defense systems and water status, seedlings were subjected to 100 and 200 μM CdCl₂ treatment without or with 0.25 and 1 mM Rtn for 7 and 14 d (days). Cd stress decreased growth (RGR), water content (RWC), leaf osmotic potential (Ψ_Π), and chlorophyll fluorescence, all of which could be partly alleviated by addition of Rtn. Activities of superoxide dismutase, peroxidase (POX), ascorbate peroxidase, and glutathione reductase increased within the first 7 d after exposure to Cd. However, failure of antioxidant defense in the scavenging of reactive oxygen species (ROS) was evidenced by an abnormal rise in superoxide anion radical ( ${\mathrm{O}}_2^{??}$) and hydrogen peroxide contents and a decline in hydroxyl radical (OH^?) scavenging activity, resulting in enhancement of lipid peroxidation (TBARS) as a marker of Cd‐induced oxidative stress. However, exogenously applied Rtn considerably improved the stress tolerance of plants via a reduction in Cd accumulation, modulation of POX activity, increase of proline (Pro) content, decrease in TBARS and ROS content and consequent lowering of oxidative damage of membrane. Overall, 0.25 and 1 mM Rtn could protect Z. fabago from the harmful effects of 100 μM Cd‐induced oxidative stress throughout the experiment. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 816–835, 2015.     

Role of nitric oxide in the antifibrotic and anticholestatic actions of interferon‐α2b

Interferons possess important antifibrotic properties. In addition, there is evidence that they induce the production of nitric oxide (NO) and that it downregulates the synthesis of extracellular matrix by certain cells. The aim of the present work was to evaluate if L ‐arginine, the NO synthase substrate, is able to increase the antifibrotic properties of interferon‐α_2b and if L ‐NAME, an NO synthesis inhibitor, can prevent them. Fibrosis was induced by bile duct ligation (BDL) for 5 weeks in rats and interferon‐α_2b (IFN; 100,000 IU rat, s.c., daily) and/or L ‐arginine (500 mg/kg, p.o., twice daily) or L ‐NAME (100 mg/kg, p.o., twice daily) were administered. Collagen content was determined by measuring hydroxyproline in liver samples. Malondialdehyde (MDA) was used to estimate lipid peroxidation levels. Glycogen was measured colorimetrically. Serum enzyme activities and bilirubins were determined by standard procedures. Fibrosis was increased 6‐fold by BDL. L ‐arginine or IFN partially prevented the increment in collagen. Furthermore, administration of both drugs simultaneously showed an additive effect (P < 0.05), while L ‐NAME abolished the protective effect of IFN. The same effect was observed on the other markers of liver function or damage studied herein. The additive effects of L ‐arginine and IFN could be due to a synergism of both compounds by increasing NO concentration, which can act as an antifibrotic agent but also as a cytoprotective compound. These results also suggest that the protective effects of IFN are mediated by NO, since L ‐NAME prevented them. Drug Dev. Res. 48:45–52, 1999. © 1999 Wiley‐Liss, Inc.     

Mangiferin,a dietary xanthone protects against mercury‐induced toxicity in HepG2 cells

Mercury is one of the noxious heavy metal environmental toxicants and is a cause of concern for human exposure. Mangiferin (MGN), a glucosylxanthone found in Mangifera indica, reported to have a wide range of pharmacological properties. The objective of this study was to evaluate the cytoprotective potential of MGN, against mercury chloride (HgCl₂) induced toxicity in HepG2 cell line. The cytoprotective effect of MGN on HgCl₂ induced toxicity was assessed by colony formation assay, while antiapoptotic effect by fluorescence microscopy, flow cytometric DNA analysis, and DNA fragmentation pattern assays. Further, the cytoprotective effect of MGN against HgCl₂ toxicity was assessed by using biochemical parameters like reduced glutathione (GSH), glutathione‐S‐transferase (GST), superoxide dismutase (SOD), catalase (CAT) by spectrophotometrically, mitochondrial membrane potential by flowcytometry and the changes in reactive oxygen species levels by DCFH‐DA spectrofluoremetric analysis. A significant increase in the surviving fraction was observed with 50 μM of MGN administered two hours prior to various concentrations of HgCl₂. Further, pretreatment of MGN significantly decreased the percentage of HgCl₂ induced apoptotic cells. Similarly, the levels of ROS generated by the HgCl₂ treatment were inhibited significantly (P < 0.01) by MGN. MGN also significantly (P < 0.01) inhibited the HgCl₂ induced decrease in GSH, GST, SOD, and CAT levels at all the post incubation intervals. Our study demonstrated the cytoprotective potential of MGN, which may be attributed to quenching of the ROS generated in the cells due to oxidative stress induced by HgCl₂, restoration of mitochondrial membrane potential and normalization of cellular antioxidant levels. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2012.     

Asymmetric dimethylarginine does not inhibit arginase activity and is pro‐proliferative in pulmonary endothelial cells

Asymmetric dimethylarginine (ADMA) is an endogenously produced nitric oxide synthase (NOS) inhibitor. l ‐Arginine can be metabolised by NOS and arginase, and arginase is the first step in polyamine production necessary for cellular proliferation. We tested the hypothesis that ADMA would inhibit NOS but not arginase activity and that this pattern of inhibition would result in greater l ‐arginine bioavailability to arginase, thereby increasing viable cell number. Bovine arginase was used in in vitro activity assays with various concentrations of substrate (l ‐arginine, ADMA, N^G‐monomethyl‐l ‐arginine (L‐NMMA) and N^G‐nitro‐l ‐arginine methyl ester (l ‐NAME)). Only l ‐arginine resulted in measurable urea production (K_m = 6.9 ± 0.8 mmol/L; V_max = 6.6 ± 0.3 μmol/mg protein per min). We then incubated bovine arginase with increasing concentrations of ADMA, l ‐NMMA and l ‐NAME in the presence of 1 mmol/L l ‐arginine and found no effect of any of the tested compounds on arginase activity. Using bovine pulmonary arterial endothelial cells (bPAEC) we determined the effects of ADMA on nitric oxide (NO) and urea production and found significantly lower NO production and greater urea production (P < 0.003) with ADMA, without changes in arginase protein levels. In addition, ADMA treatment resulted in an approximately 30% greater number of viable cells after 48 h than in control bPAEC. These results demonstrate that ADMA is neither a substrate nor an inhibitor of arginase activity and that in bPAEC ADMA inhibits NO production and enhances urea production, leading to more viable cells. These results may have pathophysiological implications in disorders associated with higher ADMA levels, such as pulmonary hypertension.     

Chronic mercury exposure impairs the sympathovagal control of the rat heart

Mercury is known to cause harmful neural effects affecting the cardiovascular system. Here, we evaluated the chronic effects of low‐dose mercury exposure on the autonomic control of the cardiovascular system. Wistar rats were treated for 30 days with HgCl₂ (1st dose 4.6 μg/kg followed by 0.07 μg/kg per day, intramuscular) or saline. The femoral artery and vein were then cannulated for evaluation of autonomic control of the hemodynamic function, which was evaluated in awake rats. The following tests were performed: baroreflex sensitivity, Von Bezold‐Jarisch reflex, heart rate variability (HRV) and pharmacological blockade with methylatropine and atenolol to test the autonomic tone of the heart. Exposure to HgCl₂ for 30 days slightly increased the mean arterial pressure and heart rate (HR). There was a significant reduction in the baroreflex gain of animals exposed to HgCl₂. Moreover, haemodynamic responses to the activation of the Von Bezold‐Jarisch reflex were also reduced. The changes in the spectral analysis of HRV suggested a shift in the sympathovagal balance toward a sympathetic predominance after mercury exposure, which was confirmed by autonomic pharmacological blockade in the HgCl₂ group. This group also exhibited reduced intrinsic HR after the double block suggesting that the pacemaker activity of the sinus node was also affected. These findings suggested that the autonomic modulation of the heart was significantly altered by chronic mercury exposure, thus reinforcing that even at low concentrations such exposure might be associated with increased cardiovascular risk.     

Detoxification and antioxidant effects of curcumin in rats experimentally exposed to mercury

Curcumin, a safe nutritional component and a highly promising natural antioxidant with a wide spectrum of biological functions, has been examined in several metal toxicity studies, but its role in protection against mercury toxicity has not been investigated. Therefore, the detoxification and antioxidant effects of curcumin were examined to determine its prophylactic/therapeutic role in rats experimentally exposed to mercury (in the from of mercuric chloride‐HgCl₂, 12 µmol kg^?1 b.w. single intraperitoneal injection). Curcumin treatment (80 mg kg^?1 b.w. daily for 3 days, orally) was found to have a protective effect on mercury‐induced oxidative stress parameters, namely, lipid peroxidation and glutathione levels and superoxide dismutase, glutathione peroxidase and catalase activities in the liver, kidney and brain. Curcumin treatment was also effective for reversing mercury‐induced serum biochemical changes, which are the markers of liver and kidney injury. Mercury concentration in the tissues was also decreased by the pre/post‐treatment with curcumin. However, histopathological alterations in the liver and kidney were not reversed by curcumin treatment. Mercury exposure resulted in the induction of metallothionein (MT) mRNA expressions in the liver and kidney. Metallothionein mRNA expression levels were found to decrease after the pre‐treatment with curcumin, whereas post‐treatment with curcumin further increased MT mRNA expression levels. Our findings suggest that curcumin pretreatment has a protective effect and that curcumin can be used as a therapeutic agent in mercury intoxication. The study indicates that curcumin, an effective antioxidant, may have a protective effect through its routine dietary intake against mercury exposure.     

Cinnabar is Different from Mercuric Chloride in Mercury Absorption and Influence on the Brain Serotonin Level

The toxicity of cinnabar, a naturally occurring mercury sulphide (HgS), has long been referred to soluble mercury chloride (HgCl₂). To investigate whether the speciation of mercury plays a role in its disposition and toxicity, we hereby investigated and compared cinnabar with soluble HgCl₂ and pure insoluble HgS in mice on mercury absorption, tissue distribution and in relation to the biological effects. The male C57BL/6J mice were treated by oral administration of various doses of cinnabar, with 0.01 g/kg of HgCl₂ for comparison, or the same dose of cinnabar or pure HgS (0.1 g/kg), once a day for 10 consecutive days. The total mercury contents in serum and tissue (brain, kidney, liver) were measured by atomic fluorescence spectrometer (AFS). The biological effects investigated involved monoamine neurotransmitters (serotonin, 5‐HT) in brain as an indicator of therapeutic function, and serum alanine transaminase (ALT) as a marker of hepatic damage, blood urea nitrogen (BUN) and serum creatinine as markers for renal function. The mercury absorption of cinnabar or HgS was much less than that of HgCl₂. The mercury levels in brains of the cinnabar group were only slightly changed and kept in a steady‐state with the dose elevated. Cinnabar or HgS suppressed brain 5‐HT levels. HgCl₂ could not cause any changes in brain 5‐HT although the mercury level increased considerably. The results revealed that cinnabar or HgS is markedly different from HgCl₂ in mercury absorption, tissue distribution and influence on brain 5‐HT levels, which suggests that the pharmacological and/or toxicological effects of cinnabar undertake other pathways from mercuric ions.     

Thymol,a monoterpene phenolic derivative of cymene,abrogates mercury‐induced oxidative stress resultant cytotoxicity and genotoxicity in hepatocarcinoma cells

Thymol (TOH) was investigated for its ability to protect against mercuric chloride (HgCl₂)‐induced cytotoxicity and genotoxicity using human hepatocarcinoma (HepG2) cell line. 3‐(4,5‐Dimethylthiazol‐2‐yl)?2,5‐diphenyl tetrazolium bromide assay confirmed the efficacy of TOH pretreatment in attenuating HgCl₂‐induced cytotoxicity. Pretreatment with TOH inhibited HgCl₂‐induced genotoxicity, depolarization of mitochondrial membrane, oxidative stress, and mitochondrial superoxide levels. Interestingly, TOH (100 µM) alone elevated the intracellular basal glutathione S‐transferase (GST) levels and TOH pretreatment abrogated the decrease in glutathione, GST, superoxide dismutase, and catalase levels even after HgCl₂ intoxication. Furthermore, TOH was also capable of inhibiting HgCl₂‐induced apoptotic as well as necrotic cell death analyzed by flowcytometric analysis of cells dual stained with Annexin‐FITC/propidium iodide. The present findings clearly indicate the cytoprotective potential of TOH against HgCl₂‐induced toxicity, which may be attributed to its free radical scavenging ability which facilitated in reducing oxidative stress and mitochondrial damage thereby inhibiting cell death. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 968–980, 2015.     

Evaluation of cytotoxicity of propofol and its related mechanism in glioblastoma cells and astrocytes

Propofol (2,6‐diisopropylphenol), one of the extensively and commonly used anesthetic agents, has been shown to affect the biological behavior of various models. Previous researches have shown that propofol‐induced cytotoxicity might cause anticancer effect in different cells. However, the mechanisms underlying the effect of propofol on cytotoxicity is still elusive in human glioblastoma cells. The aims of this study were to evaluate effects of propofol on cytotoxicity, cell cycle distribution and ROS production, and establish the relationship between oxidative stress and cytotoxicity in GBM 8401 human glioblastoma cells and DI TNC1 rat astrocytes. Propofol (20–30 μM) concentration‐dependently induced cytotoxicity, cell cycle arrest, and increased ROS production in GBM 8401 cells but not in DI TNC1 cells. In GBM 8401 cells, propofol induced G2/M phase cell arrest, which affected the CDK1, cyclin B1, p53, and p21 protein expression levels. Furthermore, propofol induced oxygen stresses by increasing and H₂O₂ levels but treatment with the antioxidant N‐acetylcysteine (NAC) partially reversed propofol‐regulated antioxidative enzyme levels (superoxide dismutase, catalase, and glutathione peroxidase). Most significantly, propofol induced apoptotic effects by decreasing Bcl‐2 but increasing Bax, cleaved caspase‐9/caspase‐3 levels, which were partially reversed by NAC. Moreover, the pancaspase inhibitor Z‐VAD‐FMK also partially prevented propofol‐induced apoptosis. Together, in GBM 8401 cells but not in DI TNC1 cells, propofol activated ROS‐associated apoptosis that involved cell cycle arrest and caspase activation. These findings indicate that propofol not only can be an anesthetic agent which reduces pain but also has the potential to be used for the treatment of human glioblastoma.     

Melatonin Protects Against Mercury(II)‐Induced Oxidative Tissue Damage in Rats

Abstract: Mercury exerts a variety of toxic effects in the body. Lipid peroxidation, DNA damage and depletion of reduced glutathione by Hg(II) suggest an oxidative stress‐like mechanism for Hg(II) toxicity. Melatonin, the main secretory product of the pineal gland, was recently found to be a potent free radical scavenger and antioxidant. N‐Acetylcysteine, a precursor of reduced glutathione and an antioxidant, is used in the therapy of acute heavy metal poisoning. In this study the protective effects of melatonin in comparison to that of N‐acetylcysteine against Hg‐induced oxidative damage in the kidney, liver, lung and brain tissues were investigated. Wistar albino rats of either sex (200–250 g) were divided into six groups, each consisting of 8 animals. Rats were intraperitoneally injected with 1) 0.9% NaCl, control (C) group; 2) a single dose of 5 mg/kg mercuric chloride (HgCl₂), Hg group; 3) melatonin in a dose of 10 mg/kg, 1 hr after HgCl₂ injection, Hg‐melatonin group; 4) melatonin in a dose of 10 mg/kg one day before and 1 hr after HgCl₂ injection, melatonin‐Hg‐melatonin group; 5) N‐acetylcysteine in a dose of 150 mg/kg, 1 hr after HgCl₂ injection, Hg‐N‐acetylcysteine group, and 6) N‐acetylcysteine in a dose of 150 mg/kg one day before and 1 hr after HgCl₂ injection, N‐acetylcysteine‐Hg‐N‐acetylcysteine group. Animals were killed by decapitation 24 hr after the injection of HgCl₂. Tissue samples were taken for determination of malondialdehyde, an end‐product of lipid peroxidation; glutathione (GSH), a key antioxidant, and myeloperoxidase activity, an index of neutrophil infiltration. The results revealed that HgCl₂ induced oxidative tissue damage, as evidenced by increases in malondialdehyde levels. Myeloperoxidase activity was also increased, and GSH levels were decreased in the liver, kidney and the lungs. All of these effects were reversed by melatonin or N‐acetylcysteine treatment. Since melatonin or N‐acetylcysteine administration reversed these responses, it seems likely that melatonin or N‐acetylcysteine can protect all these tissues against HgCl₂‐induced oxidative damage.     

Vascular responses to β‐adrenoceptor subtype‐selective agonists with and without endothelium in rat common carotid arteries

1 Using the cannula inserting method, vasodilator responses to β‐adrenoceptor agonists (isoprenaline, denopamine and procaterol) were investigated in isolated and perfused rat common carotid arteries. 2 Each β‐adrenoceptor agonist induced a vasodilation in preparations preconstricted by phenylephrine in a dose‐related manner. The potencies were in the order of isoprenaline > procaterol >> denopamine. 3 Denopamine‐induced dilations were significantly inhibited by 1 nmol betaxolol (a selective β₁‐adrenoceptor antagonist), but it was not influenced by 1 nmol ICI 118,551 (a selective β₂‐adrenoceptor antagonist). On the other hand, procaterol‐induced vasodilations were significantly inhibited by 1 nmol ICI 118,551 but not modified by 10 nmol betaxolol. 4 ACh‐induced vasodilations disappeared after intraluminal saponin injection to remove endothelium, but procaterol‐ and denopamine‐induced dilations were not modified by removal of the endothelium. 5 Pretreatment with L ‐N^G‐nitroarginine methyl ester (L ‐NAME) readily inhibited ACh‐induced vasodilations. However, neither procaterol‐ or denopamine‐induced vasodilation was modified by L ‐NAME treatment. 6 From these results, it is concluded that in the rat common carotid arteries (1) there are abundant β₂‐ and a few β₁‐adrenoceptors, and (2) there is no participation of the endothelium‐dependent mechanism in β‐adrenoceptor mediated vasodilations.     

Effect of orchiectomy on renal function in control and diabetic rats with chronic inhibition of nitric oxide

• 1 Male gender is associated with higher blood pressure (BP) and more rapid loss of renal function in a spectrum of clinical and experimental renal diseases, including diabetic nephropathy. Consequently, modulation of testosterone levels could exert beneficial effects in the diabetic kidney.
• 2 The aim of the present study was to determine whether testosterone deficiency (orchiectomy) could influence BP and renal function in streptozotocin‐diabetic rats, with or without accelerated endothelial dysfunction achieved by chronic inhibition of nitric oxide (NO) synthesis using N^G‐nitro‐l‐ arginine methyl ester (l ‐NAME; 40–100 mg / L in the drinking water for 2 weeks), as well as in age‐matched non‐diabetic rats subjected to the same interventions.
• 3 Orchiectomy did not affect l ‐NAME‐induced increases in BP in non‐diabetic or diabetic rats. In non‐diabetic rats, orchiectomy prevented l ‐NAME‐induced increases in proteinuria. These effects on proteinuria were not observed in diabetic rats. In non‐diabetic rats, orchiectomy had no effect on renal haemodynamics in animals receiving vehicle and did not affect l ‐NAME‐induced changes in renal haemodynamics, characterized by reductions in renal plasma flow (RPF) and higher filtration fractions (FF). In intact diabetic rats, l ‐NAME treatment resulted in lower RPF. This difference was not observed in diabetic rats subjected to orchiectomy, although l ‐NAME‐treated diabetic orchiectomized rats had lower RPF and higher FF compared with vehicle‐treated intact diabetic rats.
• 4 In conclusion, we report modest beneficial effects of orchiectomy on proteinuria in normal, but not in diabetic, rats with inhibition of NO production. This suggests that testosterone reduction does not attenuate the deleterious impact of the diabetic metabolic milieu in the kidney.

     

Inhibition of hepatic δ-aminolevulinate dehydratase activity induced by mercuric chloride is potentiated by N-acetylcysteine in vitro

Mercuric chloride (HgCl)₂ is a toxic metal that causes oxidative damage in several tissues. N-acetylcysteine (NAC) is a sulfhydryl compound with antioxidant activity. In the present study, we investigated the in vitro effects of the association between HgCl₂ and NAC in tissues of mice. For this purpose, we evaluated the in vitro effect of HgCl₂ + NAC association on δ-aminolevulinate dehydratase (δ-ALA-D) activity and on thiobarbituric acid reactive substances (TBARS) levels in liver and kidney of mice. The results demonstrate that HgCl₂ inhibited δ-ALA-D activity in both tissues. Hepatic δ-ALA-D activity inhibited by HgCl₂ was potentiated by the highest concentration of NAC. The inhibition of hepatic δ-ALA-D activity seems to be related to sulfhydryl groups oxidation of the enzyme. We observed also that HgCl₂ increased TBARS levels in kidney and liver. Hepatic TBARS levels were reduced by NAC, at higher concentration. In contrast, NAC, at higher concentration, increased renal TBARS levels. In conclusion, the inhibition of hepatic δ-aminolevulinate dehydratase activity induced by HgCl₂ is potentiated by NAC in vitro, and this effect is not related to hepatic lipid peroxidation.     

Oxidative stress biomarkers in Cyprinus carpio exposed to commercial herbicide bispyribac‐sodium

Cyprinus carpio were exposed under field conditions to 20.87 µg l^?1 of commercial herbicide bispyribac‐sodium (Nominee®, SC), during 7, 21 and 72 days. Enzymatic parameters such as catalase (CAT), glutathione S‐transferase (GST) and acetylcholinesterase (AChE) activities, as well as thiobarbituric acid‐reactive substances (TBARS) and protein carbonyl contents were studied in different tissues. After 7 days of exposure, GST activity decreased. At the same period, brain AChE activity increased, but a reduction of activity was observed in muscle tissue. Brain TBARS levels increased at 7 days. After 21 days of exposure liver CAT levels and muscle AChE activities decreased. In the same period, liver protein carbonyl and muscle TBARS increased. After 72 days of exposure in the field, AChE activity was reduced in both brain and muscle. Protein carbonyl contents in liver and brain TBARS levels increased. Muscle AChE activity, TBARS and protein carbonyl can be used as biomarkers of exposure to the herbicide bispyribac‐sodium. This study demonstrates effects of exposure to bispyribac‐sodium under rice field conditions on oxidative stress parameters in tissues of Cyprinus carpio. Copyright © 2010 John Wiley & Sons, Ltd.