Molecular mechanisms of hypertension-induced heart failure : Experimental studies with special emphasis on local renin-angiotensin system, cardiac metabolism and levosimendan

Hypertension is a major risk factor for stroke, ischaemic heart disease, and the development of heart failure. Hypertension-induced heart failure is usually preceded by the development of left ventricular hypertrophy (LVH), which represents an adaptive and compensatory response to the increased cardiac workload. Biomechanical stress and neurohumoral activation are the most important triggers of pathologic hypertrophy and the transition of cardiac hypertrophy to heart failure. Non-clinical and clinical studies have also revealed derangements of energy metabolism in hypertensive heart failure. The goal of this study was to investigate in experimental models the molecular mechanisms and signalling pathways involved in hypertension-induced heart failure with special emphasis on local renin-angiotensin-aldosterone system (RAAS), cardiac metabolism, and calcium sensitizers, a novel class of inotropic agents used currently in the treatment of acute decompensated heart failure. Two different animal models of hypertensive heart failure were used in the present study, i.e. hypertensive and salt-sensitive Dahl/Rapp rats on a high salt diet (a salt-sensitive model of hypertensive heart failure) and double transgenic rats (dTGR) harboring human renin and human angiotensinogen genes (a transgenic model of hypertensive heart failure with increased local RAAS activity). The influence of angiotensin II (Ang II) on cardiac substrate utilization and cardiac metabolomic profile was investigated by using gas chromatography coupled to time-of-flight mass spectrometry to detect 247 intermediary metabolites. It was found that Ang II could alter cardiac metabolomics both in normotensive and hypertensive rats in an Ang II receptor type 1 (AT1)-dependent manner. A distinct substrate use from fatty acid oxidation towards glycolysis was found in dTGR. Altered cardiac substrate utilization in dTGR was associated with mitochondrial dysfunction. Cardiac expression of the redox-sensitive metabolic sensor sirtuin1 (SIRT1) was increased in dTGR. Resveratrol supplementation prevented cardiovascular mortality and ameliorated Ang II-induced cardiac remodeling in dTGR via blood pressure-dependent pathways and mechanisms linked to increased mitochondrial biogenesis. Resveratrol dose-dependently increased SIRT1 activity in vitro. Oral levosimendan treatment was also found to improve survival and systolic function in dTGR via blood pressure-independent mechanisms, and ameliorate Ang II-induced coronary and cardiomyocyte damage. Finally, using Dahl/Rapp rats it was demonstrated that oral levosimendan as well as the AT1 receptor antagonist valsartan improved survival and prevented cardiac remodeling. The beneficial effects of levosimendan were associated with improved diastolic function without significantly improved systolic changes. These positive effects were potentiated when the drug combination was administered. In conclusion, the present study points to an important role for local RAAS in the pathophysiology of hypertension-induced heart failure as well as its involvement as a regulator of cardiac substrate utilization and mitochondrial function. Our findings suggest a therapeutic role for natural polyphenol resveratrol and calcium sensitizer, levosimendan, and the novel drug combination of valsartan and levosimendan, in prevention of hypertension-induced heart failure. The present study also provides a better understanding of the pathophysiology of hypertension-induced heart failure, and may help identify potential targets for novel therapeutic interventions.

On the charging state of atmospheric aerosols and ion-induced nucleation

Floating in the air that surrounds us is a number of small particles, invisible to the human eye. The mixture of air and particles, liquid or solid, is called an aerosol. Aerosols have significant effects on air quality, visibility and health, and on the Earth's climate. Their effect on the Earth's climate is the least understood of climatically relevant effects. They can scatter the incoming radiation from the Sun, or they can act as seeds onto which cloud droplets are formed. Aerosol particles are created directly, by human activity or natural reasons such as breaking ocean waves or sandstorms. They can also be created indirectly as vapors or very small particles are emitted into the atmosphere and they combine to form small particles that later grow to reach climatically or health relevant sizes. The mechanisms through which those particles are formed is still under scientific discussion, even though this knowledge is crucial to make air quality or climate predictions, or to understand how aerosols will influence and will be influenced by the climate's feedback loops. One of the proposed mechanisms responsible for new particle formation is ion-induced nucleation. This mechanism is based on the idea that newly formed particles were ultimately formed around an electric charge. The amount of available charges in the atmosphere varies depending on radon concentrations in the soil and in the air, as well as incoming ionizing radiation from outer space. In this thesis, ion-induced nucleation is investigated through long-term measurements in two different environments: in the background site of Hyytiälä and in the urban site that is Helsinki. The main conclusion of this thesis is that ion-induced nucleation generally plays a minor role in new particle formation. The fraction of particles formed varies from day to day and from place to place. The relative importance of ion-induced nucleation, i.e. the fraction of particles formed through ion-induced nucleation, is bigger in cleaner areas where the absolute number of particles formed is smaller. Moreover, ion-induced nucleation contributes to a bigger fraction of particles on warmer days, when the sulfuric acid and water vapor saturation ratios are lower. This analysis will help to understand the feedbacks associated with climate change.

DNA photocleavage and anticancer activity of terpyridine copper(II) complexes having phenanthroline bases

Copper(II) complexes Cu(ph-tpy)(B)](ClO4) (1-3), where ph-tpy is (4'-phenyl)-2,2':6',2 `'-terpyridine and B is N,N-donor phenanthroline base, viz. 1,10-phenanthroline (phen, 1), dipyridoquinoxaline (dpq, 2), and dipyridophenazine (dppz, 3), were prepared and characterized from analytical and spectral data. Complex 1, characterized by X-ray crystallography, shows a distorted square-pyramidal (4 + 1) CuN5 coordination geometry having the tridentate ph-tpy ligand at the basal plane and bidentate phen bound to the axial-equatorial sites. The complexes display a d-d band near 650 nm in aqueous DMF. The complexes are avid binders to calf thymus DNA giving the binding order: 3 (dppz) > 2 (dpq) > 1 (phen). The dpq and dppz complexes show photo-induced DNA cleavage activity in red light via photo-redox pathway forming hydroxyl radicals. The cytotoxicity of the dppz complex 3 was studied by MTT assay in HeLa cancer cells. The IC50 values are 3.7 and 12.4 mu M in visible light of 400-700 nm and dark, respectively. (C) 2010 Elsevier Ltd. All rights reserved.

Photocytotoxicity and near-IR light DNA cleavage activity of oxovanadium(IV) Schiff base complexes having phenanthroline bases

Oxovanadium(IV) complexes VO(L)(B)] (1-3), where H2L is a Schiff base ligand 2-(2-hydroxybenzylideneamino) phenol and B is 1,10-phenanthroline (phen for 1), dipyrido3,2-d:2',3'-f]quinoxaline (dpq for 2) or dipyrido3,2-a:2',3'-c]phenazine (dppz for 3), have been prepared, characterized and their DNA binding property and photo-induced DNA cleavage activity studied. Complex 3 which is structurally characterized by X-ray crystallography shows the presence of an oxovanadium(IV) moiety in a six coordinate VO3N3 coordination geometry. The complexes show a d-d band within 800-850 nm in DMF. The complexes display an oxidative response near 0.7 V versus SCE for V(V)-V(IV) and a reductive response within -1.1 to -1.3 V due to V(IV)-V(III) couple in DMF-0.1 M TBAP. The complexes are avid binders to calf thymus DNA giving binding constant values of 4.2 x 10(4) to 1.2 x 10(5) M (1). The complexes do not show any ``chemical nuclease'' activity in dark. The dpq and dppz complexes are photocleavers of plasmid DNA in UV-A light of 365 nm via O-1(2) pathway and in near-IR light (752.5 to 799.3 nm IR optics) by HO* pathway. Complex 3 exhibits significant photocytotoxicity in visible light in HeLa cells giving IC50 value of 13 mu M, while it is less toxic in dark (IC50 = 97 mu M). (C) 2010 Elsevier B.V. All rights reserved.

Antipyretic and antibacterial activity of Chloranthus erectus (Buch.-Ham.) Verdcourt leaf extract: A popular folk medicine of Arunachal Pradesh

Objective : The main objective of this work was to study the antipyretic and antibacterial activity of C. erectus (Buch.-Ham.) Verdcourt leaf extract in an experimental albino rat model. Materials and Methods : The methanol extract of C. erectus leaf (MECEL) was evaluated for its antipyretic potential on normal body temperature and Brewers yeast-induced pyrexia in albino rats model. While the antibacterial activity of MECEL against five Gram (-) and three Gram () bacterial strains and antimycotic activity was investigated against four fungi using agar disk diffusion and microdilution methods. Result : Yeast suspension (10 mL/kg b.w.) elevated rectal temperature after 19 h of subcutaneous injection. Oral administration of MECEL at 100 and 200 mg/kg b.w. showed significant reduction of normal rectal body temperature and yeast-provoked elevated temperature (38.8 0.2 and 37.6 0.4, respectively, at 2-3 h) in a dose-dependent manner, and the effect was comparable to that of the standard antipyretic drug-paracetamol (150 mg/kg b.w.). MECEL at 2 mg/disk showed broad spectrum of growth inhibition activity against both groups of bacteria. However, MECEL was not effective against the yeast strains tested in this study. Conclusion : This study revealed that the methanol extract of C. erectus exhibited significant antipyretic activity in the tested models and antibacterial activity as well, and may provide the scientific rationale for its popular use as antipyretic agent in Khamptiss folk medicines.

Glycodelin A suppresses the cytolytic activity of CD8(+) T lymphocytes

Maternal tolerance to the semi-allogenic fetus is brought about by several mechanisms in humans Glycodelin A (GdA) secreted by the uterine mucosa and decidua is induced to high levels by progesterone between 12 and 16 weeks of pregnancy The glycoprotein an immunomodulator has been shown to be inhibitory to the survival and functions of almost all the immune cells CD8(+) T cells which predominate the T lymphocyte population in the decidua are relatively less studied We attempted to find out the possible mechanism if any of regulation of the cytolytic function of CD8(+) T cells during pregnancy Alloactivated CD8(+) T cells harbouring specific cytolytic activity against target cells exhibited compromised activity upon treatment with high concentrations of GdA Interestingly unlike the CD4(+) T cells CD8(+) T cells were resistant to GdA-induced apoptosis The inhibition of cytotoxic T lymphocyte activity was brought about by the downregulation of transcription of the cytolytic effector molecules granzyme B and perform and the degranulation of cytolytic vesicles These results suggest a protective role played by GdA during pregnancy by regulating the cytolytic activity of CD8(+) T cells (C) 2010 Elsevier Ltd All rights reserved

Signaling different pathways of cell death: Abrin induced programmed necrosis in U266B1 cells

Abrin is a type II ribosome-inactivating protein comprising of two subunits, A and B. Of the two, the A-subunit harbours the RNA-N-glycosidase activity and the B subunit is a galactose specific lectin that enables the entry of the protein inside the cell. Abrin inhibits protein synthesis and has been reported to induce apoptosis in several cell types. Based on these observations abrin is considered to have potential for the construction of immunotoxin in cell targeted therapy. Preliminary data from our laboratory however showed that although abrin inhibited the protein synthesis in all cell types, the mode of cell death varied. The aim of the present study was therefore to understand different death pathways induced by abrin in different cells. We used the human B cell line, U266B1 and compared it with the earlier studied T cell line Jurkat, for abrin-mediated inhibition of protein translation as well as cell death. While abrin triggered programmed apoptosis in Jurkat cells in a caspase-dependent manner, it induced programmed necrosis in U266B1 cells in a caspase-independent manner, even when there was reactive oxygen species production and loss of mitochondrial membrane potential. The data revealed that abrin-mediated necrosis involves lysosomal membrane permeabilization and release of cathepsins from the lysosomes. Importantly, the choice of abrin-mediated death pathway in the cells appears to depend on which of the two events occurs first: lysosomal membrane permeabilization or loss of mitochondrial membrane potential that decides cell death by necrosis or apoptosis. (C) 2010 Elsevier Ltd. All rights reserved.

Stereochemistry of 2'-5' linked nucleic acids: crystal and molecular structure of ammonium adenylyl-2',5'-adenosine tetrahydrate: a core fragment of 2'-5' oligo A's produced by interferon induced adenylate synthetase

The preponderance of 3'-5' phosphodiester links in nucleic acids is well known. Albeit less prevalent, the 2'-5' links are specifically utilised in the formation of 'lariat' in group II introns and in the msDNA-RNA junction in myxobacterium. As a sequel to our earlier study on cytidylyl-2',5'-adenosine we have now obtained the crystal structure of adenylyl-2',5'-adenosine (A2'p5'A) at atomic resolution. This dinucleoside monophosphate crystallizes in the orthorhombic space group P2(1)2(1)2(1) with a = 7.956(3) A, b = 12.212(3) A and c = 36.654(3) A. CuK alpha intensity data were collected on a diffractometer. The structure was sloved by direct methods and refined by full matrix least squares methods to R = 10.8%. The 2' terminal adenine is in the commonly observed anti (chi 2 = 161 degrees) conformation and the 5' terminal base has a syn (chi 1 = 55 degrees) conformation more often seen in purine nucleotides. A noteworthy feature of A2'p5'A is the intranucleotide hydrogen bond between N3 and O5' atoms of the 5' adenine base. The two furanose rings in A2'p5'A show different conformations - C2' endo, C3' endo puckering for the 5' and 2' ends respectively. In this structure too there is a stacking of the purine base on the ribose O4' just as in other 2'-5' dinucleoside structures, a feature characteristically seen in the left handed Z DNA. In having syn, anti conformation about the glycosyl bonds, C2' endo, C3' endo mixed sugar puckering and N3-O5' intramolecular hydrogen bond A2'p5'A resembles its 3'-5' analogue and several other 2'-5' dinucleoside monophosphate structures solved so far. Striking similarities between the 2'-5' dinucleoside monophosphate structures suggest that the conformation of the 5'-end nucleoside dictates the conformation of the 2' end nucleoside. Also, the 2'-5' dimers do not favour formation of miniature classical double helical structures like the 3'-5' dimers. It is conceivable, 2-5(A) could be using the stereochemical features of A2'p5'A which accounts for its higher activity.

Distinct Allostery Induced in the Cyclic GMP-binding, Cyclic GMP-specific Phosphodiesterase (PDE5) by Cyclic GMP, Sildenafil, and Metal Ions

The activity of many proteins orchestrating different biological processes is regulated by allostery, where ligand binding at one site alters the function of another site. Allosteric changes can be brought about by either a change in the dynamics of a protein, or alteration in its mean structure. We have investigated the mechanisms of allostery induced by chemically distinct ligands in the cGMP-binding, cGMP-specific phosphodiesterase, PDE5. PDE5 is the target for catalytic site inhibitors, such as sildenafil, that are used for the treatment of erectile dysfunction and pulmonary hypertension. PDE5 is a multidomain protein and contains two N-terminal cGMP-specific phosphodiesterase, bacterial adenylyl cyclase, FhLA transcriptional regulator (GAF) domains, and a C-terminal catalytic domain. Cyclic GMP binding to the GAFa domain and sildenafil binding to the catalytic domain result in conformational changes, which to date have been studied either with individual domains or with purified enzyme. Employing intramolecular bioluminescence resonance energy transfer, which can monitor conformational changes both in vitro and in intact cells, we show that binding of cGMP and sildenafil to PDE5 results in distinct conformations of the protein. Metal ions bound to the catalytic site also allosterically modulated cGMP- and sildenafil-induced conformational changes. The sildenafil-induced conformational change was temperature-sensitive, whereas cGMP-induced conformational change was independent of temperature. This indicates that different allosteric ligands can regulate the conformation of a multidomain protein by distinct mechanisms. Importantly, this novel PDE5 sensor has general physiological and clinical relevance because it allows the identification of regulators that can modulate PDE5 conformation in vivo.

Role of lattice defects and crystallite morphology in the UV and visible-light-induced photo-catalytic properties of combustion-prepared TiO2

The physico-chemical, photo-physical and micro-structural properties responsible for the strikingly different photocatalytic behavior of combustion-prepared TiO2 (c.TiO2) and Degussa P25 (d.TiO2) samples are elucidated in this study. Electron microscopy and selected area electron diffraction micrographs revealed that the two samples exhibited different morphologies. The grains of c.TiO2 were spherical and comprised of 5-6 nm size primary particle. On the other hand, d.TiO2 consisted of large (0.5-3.0 mu m) size and irregular shape aggregates having primary particles of 15-40 nm cross-sectional diameter. The ESR study revealed that the presence of certain defect states in c.TiO2 helped in stabilization of O-. and Ti3+-OH type species during room-temperature UV-irradiation. No such paramagnetic species were however formed over d.TiO2 under similar conditions. C1s and Ti 2p XPS spectra provide evidence for the presence of some lattice vacancies in c.TiO2 and also for the bulk Ti4+ -> Ti3+ conversion during its UV-irradiation. Compared to d.TiO2, c.TiO2 displayed considerably higher activity for discoloration of methyl orange but very poor activity for splitting of water, both under UV and visible light radiations. This is attributed to enhanced surface adsorption of dye molecules over c.TiO2, because of its textural features and also the presence of photo-active ion-radicals. On the other hand, the poor activity of c.TiO2 for water splitting is related to certain defect-induced inter-band charge trapping states in the close vicinity of valence and conduction bands of c.TiO2, as revealed by thermoluminescence spectroscopy. Further, the dispersion of nanosize gold particles gave rise to augmented activity of both the catalysts, particularly for water splitting. This is explained by the promotional role of Au-0 or Au-0/TiO2 interfacial sites in the adsorption and charge-adsorbate interaction processes. (C) 2011 Elsevier B.V. All rights reserved.

Small Ubiquitin-related Modifier Ligase Activity of Mms21 Is Required for Maintenance of Chromosome Integrity during the Unperturbed Mitotic Cell Division Cycle in Saccharomyces cerevisiae

The SUMO ligase activity of Mms21/Nse2, a conserved member of the Smc5/6 complex, is required for resisting extrinsically induced genotoxic stress. We report that the Mms21 SUMO ligase activity is also required during the unchallenged mitotic cell cycle in Saccharomyces cerevisiae. SUMO ligase-defective cells were slow growing and spontaneously incurred DNA damage. These cells required caffeine-sensitive Mec1 kinase-dependent checkpoint signaling for survival even in the absence of extrinsically induced genotoxic stress. SUMO ligase-defective cells were sensitive to replication stress and displayed synthetic growth defects with DNA damage checkpoint-defective mutants such as mec1, rad9, and rad24. MMS21 SUMO ligase and mediator of replication checkpoint 1 gene (MRC1) were epistatic with respect to hydroxyurea-induced replication stress or methyl methanesulfonate-induced DNA damage sensitivity. Subjecting Mms21 SUMO ligase-deficient cells to transient replication stress resulted in enhancement of cell cycle progression defects such as mitotic delay and accumulation of hyperploid cells. Consistent with the spontaneous activation of the DNA damage checkpoint pathway observed in the Mms21-mediated sumoylation-deficient cells, enhanced frequency of chromosome breakage and loss was detected in these mutant cells. A mutation in the conserved cysteine 221 that is engaged in coordination of the zinc ion in Loop 2 of the Mms21 SPL-RING E3 ligase catalytic domain resulted in strong replication stress sensitivity and also conferred slow growth and Mec1 dependence to unchallenged mitotically dividing cells. Our findings establish Mms21-mediated sumoylation as a determinant of cell cycle progression and maintenance of chromosome integrity during the unperturbed mitotic cell division cycle in budding yeast.

Glutathione peroxidase3 of Saccharomyces cerevisiae protects phospholipids during cadmium-induced oxidative stress

The present study was undertaken to determine the role of glutathione peroxidase3 (gpx3) in phospholipid protection in cells. Wild-type (WT) cells showed an overall increase in phospholipids upon 50 mu M cadmium (Cd)-treatment, whereas an untreated gpx3 Delta strain showed a drastic reduction in overall phospholipids which was further reduced with 50 mu M Cd. In WT cells, Cd-exposure increased the short chain fatty acids and decreased the unsaturated fatty acids and the magnitude was high in Cd-treated gpx3 Delta cells. Purified recombinant gpx3p showed higher activity with phospholipid hydroperoxides than shorter hydroperoxides. An increase in gpx activity was observed in Cd-treated WT cells and no such alteration was observed in gpx3 Delta. WT cells treated with Cd showed an increase in MDA over untreated, while untreated gpx3 Delta cells themselves showed a higher level of MDA which was further enhanced with Cd-treatment. Iron, zinc and calcium levels were significantly altered in WT and gpx3 Delta cells during Cd-treatment.

Evidence for follicle-stimulating hormone mediation in the hemiorchidectomy-induced compensatory increase in the function of the remaining testis of the adult male bonnet monkey (Macaca radiata)

Hemiorchidectomy (HO) in the adult male bonnet monkey results in a selective increase in circulating concentrations of FSH and testosterone, and this is accompanied by compensatory increase in sperm production by the remaining testis. We investigated the possible role of increased FSH concentration that occurs after HO in the compensatory increase in the activity of the remaining testis. Of eight adult male bonnet monkeys that underwent HO, four received i.v. injections every other day for 30 days of a well-characterized ovine FSH antiserum (a/s) that cross-reacts with monkey FSH. The remaining four males received normal monkey serum (NMS) as control treatment in a protocol similar to that employed for ais-treated males. Blood samples were collected between 2100 and 2200 h before and 1/2, 1, 3, 5, 7, 14, 22, and 29 days after HO. Testicular weight, number of 3 beta-hydroxy steroid dehydrogenase-positive (3 beta-HSD+) cells, and DNA flow cytometric analysis of germ cell populations were obtained for testes collected before and at the termination of NMS or ais treatment. In NMS-treated males, circulating serum FSH concentrations progressively increased to reach a maximal level by Day 7 after HO (1.95 +/- 0.3 vs. 5.6 +/- 0.7 ng/ml on Days -1 and 7, respectively). Within 30 min of ais injection, FSH antibodies were detected in circulation, and the antibody level was maintained at a constant level between Day 7 and end of treatment (exhibiting 50-60% binding to I-125-hFSH). Although circulating mean nocturnal serum testosterone concentration showed an initial decrease, it rose gradually to pre-HO concentrations by Day 7 in NMS-treated males. In contrast, nocturnal mat serum testosterone concentrations in a/s-treated males remained lower than in NMS-treated controls (p < 0.05) up to Day 22 and thereafter only marginally increased. Testicular weights increased (p < 0.05) over the pre-HO weight in NMS- but not in ais-treated males. After HO, the number of 3 beta-HSD+ cells (Leydig cells) was markedly increased but was significantly (p < 0.05) higher in NMS-treated males compared to a/s-treated males. A significant (p < 0.05) reduction in the primary spermatocyte population of germ cells was observed in ais-treated compared to NMS-treated males. These results suggest that the increased FSH occurring after HO could be intimately involved in increasing the compensatory functional activity of the remaining testis in the male bonnet monkey.

The effect of malathion, an organophosphate, on the plasma FSH, 17 beta-estradiol and progesterone concentrations and acetylcholinesterase activity and conception in dairy cattle

The effect of malathion on jugular plasma concentrations of follicle-stimulating hormone (FSH), estradiol (E2), progesterone (P4) and acetylcholinesterase (AchE) on conception in dairy cattle during a cloprostenol (prostaglandin F2-alpha analogue, PG)-induced estrus was studied. Malathion (1 mg/kg, intraruminally) given at the onset of estrus (48 h after PG) did not alter the plasma FSH or E2 concentrations but significantly (P < 0.05) inhibited plasma P4 concentration. The mean P4 concentration in the malathion-treated group on days 8 and 12 were 0.8 +/- 0.4 and 1.0 +/- 0.5 ng/ml, as compared to 2.6 +/- 0.0 and 2.4 +/- 0.3 ng/ml in the control group. There was a nonsignificant (P > 0.05) inhibition of plasma AchE activity in malathion-treated cattle. Conception was 16.6% in malathion-treated cows and 50% in controls. Inhibition of progesterone secretion and poor conception occurred after the single intraruminal dose of malathion at the onset of estrus.

Antioxidant and antihepatotoxic effect of Spirulina laxissima against carbon tetrachloride induced hepatotoxicity in rats

The vast biodiversity of nature provides bioactive compounds that may be useful in the fight against chronic diseases. This study was designed to investigate the protective effects of the ethanol extract of Spirulina laxissima West (Pseudanabaenaceae) (EESL) against carbon tetrachloride (CCl4) induced hepatotoxicities in rats. Male albino rats of Sprague-Dawley strain were treated orally with the ethanol extract of S. laxissima (50, 100 mg kg(-1) body wt.) 1 h before each CCl4 administration. The ethanol extract of S. laxissima showed the maximum antioxidant property in vitro. There were statistically significant losses in the activities of antioxidant enzymes and an increase in TBARS and liver function marker enzymes in the serum of the CCl4-treated group compared with the control group. However, all the tested groups were able to counteract these effects. The antioxidant activity of the extracts might be attributable to its proton-donating ability, as evidenced by DPPH. In the present study, the decline in the level of antioxidant observed in CCl4-treated rats is a clear manifestation of excessive formation of radicals and activation of the lipid peroxidation system resulting in tissue damage. The significant increases in the concentration of antioxidant enzymes in tissues of animals treated with CCl4 + EESL indicate the antioxidant effect of EESL. This study suggests that EESL can protect the liver against CCl4-induced oxidative damage in rats, and the hepatoprotective effect might be correlated with its antioxidant and radical-scavenging effects.