Activity Of Membrane-bound Enzymes Research Articles

Cardioprotective Effect of Oleanolic Acid on Isoproterenol-Induced Myocardial Ischemia in Rats

This study was designed to investigate the protective effect of oleanolic acid (OA) against isoproterenol-induced myocardial ischemia in rat myocardium. Wistar strain rats were pretreated with OA (20, 40, and 60 mg/kg, s.c) for 7 days and then intoxicated with isoproterenol (ISO, 85 mg/kg, sc for 2 consecutive days). Heart were excised from the experimental animals and assessed for the activities of marker enzymes [alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and creatine phosphokinase (CPK)], the levels of lipid peroxide products [thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides (HP) and conjugated dienes (CD)], myeloperoxidase (MPO), lipid profiles [total cholesterol (TC), free cholesterol, ester cholesterol, triglycerides (TG), free fatty acids (FFA) and phospholipids (PL)], and membrane-bound ATPase enzymes (total ATPase, Na(+)K(+) ATPase, Ca(2 +) ATPase, and Mg(2 +) ATPase). Troponin T and I were estimated in plasma. Leakage of cardiac markers, elevated lipid peroxidation with increased lipid profiles and decreased activities of membrane-bound ATPase enzymes were confirmed the severe myocardial damage occurring as a consequence of isoproterenol-induced ischemia, and they also showed the significant improvement effected by oleanolic acid pretreatment. These findings provided evidence that oleanolic acid was found to be protecting rat myocardium against ischemic insult and the protective effect could attribute to its anti-oxidative, anti-hyperlipedemic, and anti-arrhythmic properties as well as its membrane-stabilizing action.

Protective Effect of Ursolic Acid Against Myocardial Ischemia Induced by Isoproterenol in Rats

ABSTRACTSustained high levels of circulating catecholamines may induce cardiotoxicity through oxidative mechanisms. Isoproterenol is a synthetic catecholamine with increasing attention owing to this application in cardiology. The aim of the present study was to investigate the cardioprotective effects of ursolic acid against isoproterenol-induced myocardial ischemia. Normal Wistar strain rats were pretreated with UA (20, 40, and 60 mg/kg, s.c.) for 7 days and then intoxicated with isoproterenol (ISO, 85 mg/kg, s.c. for 2 consecutive days). Hearts were excised from the experimental animals and assessed for the activities of cardiac markers [alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and creatine phosphokinase (CPK)], the levels of lipid peroxide products [thiobarbituric acid reactive substances (TBARS), lipid hydroperoxides (HPs), and conjugated dienes (CDs)], myeloperoxidase (MPO), lipid profiles [total cholesterol (TC), free cholesterol, ester cholesterol, triglycerides (TG), free fatty acids (FFAs), and phospholipids (PLs)], and membrane-bound enzymes (total ATPase, Na+K+ATPase, Ca2+ATPase, and Mg2+ATPase). In ISO-treated group, shrinkage of cardiac markers and elevated lipid peroxidation with compromised lipid profiles in the heart where accompanied by the decreased activities of membrane-bound enzymes. The prior administration of UA significantly (p < 0.05) prevented the isoproterenol-induced alterations and restored the enzymes to near normal. These findings indicate the cardioprotective activities of UA during isoproterenol-induced myocardial ischemia.

Alcohol ethoxylates mediate their bacteriostatic effect by altering the cell membrane of Escherichia coli NCTC 8196

The minimum inhibitory concentration (MIC) of a homologous series of alcohol ethoxylates with the same head group size (E6) but differing in the number of carbon atoms in their ‘tail group’ from 10 to 16 was determined for Staphylococcus aureus NCTC 4163 and Escherichia coli NCTC 8196 using a turbidimetric assay. All the surfactants tested demonstrated bacteriostatic activity against both organisms. A tetrazolium assay showed that C14E6 and C16E6 had little effect on the membrane-bound dehydrogenase enzyme activity of E. coli NCTC 8196 compared with C10E6 and C12E6. C10E6 caused leakage both of K + and nucleotides in a concentration-dependent manner above its MIC of 0.2 mM. C12E6 caused some leakage at concentrations below its MIC (0.12 mM).

Thermotropic Lipid Phase Transition and the Behavior of Hydrolytic Enzymes in the Kidney Cortex Brush Border Membrane

Functional interactions of lipids and proteins were examined in brush-border membranes isolated from the kidney cortex by studying the temperature dependence of the hydrolytic enzyme activities. A close relationship was observed for the membrane proteins and the thermotropic lipid phase transitions. Three lines of evidences were provided for such dependence: a) Arrhenius relationship of the membrane-bound enzyme activities, and the effect of temperature in native and partially delipidated membranes, b) differential scanning calorimetric study of the membrane lipid phase transitions in the native and delipidated membranes, multilamellar vesicles prepared from the membrane extracted lipids, and in vesicles from dimyristoyl phosphatidylcholine, and c) the excimer (dimer)-formation studies of the membrane extrinsic fluorescent probe, pyrene, and the resultant membrane microviscosity. The brush-border membranes were partially delipidated with BuOH and 2,2,2-trifluoroethanol. The functional interactions of the delipidated membranes, which were greatly lost on lipid removal, were largely restored by the addition of exogenous lipids in the reconstitution process, which indicate the critical dependence of the membrane integral proteins on the neighboring lipid molecules in the bulk lipid phase.

Green tea impedes dyslipidemia, lipid peroxidation, protein glycation and ameliorates Ca 2+-ATPase and Na +/K +-ATPase activity in the heart of streptozotocin-diabetic rats

Diabetes-induced hyperlipidemia, oxidative stress and protein glycation impair cellular calcium and sodium homeostasis associated with abnormal membrane-bound enzyme activities resulting in cardiac dysfunction in diabetes. To explore the cardioprotective mechanism of green tea in diabetes, we measured the changes in the levels of calcium, sodium, potassium and the activities of Na +/K +-ATPase and Ca 2+-ATPase in green tea treated diabetic rat hearts. The effect of green tea on triglycerides, lipid peroxidation and protein glycation in diabetic heart were also measured to elucidate the underlying mechanisms. Diabetes was induced by streptozotocin (STZ, 60 mg/kg i.p.). Six weeks after the induction of diabetes, some of the diabetic rats were treated orally with green tea extract (GTE) (300 mg/kg/day) for 4 weeks. GTE produced reduction in blood glucose and lowered the levels of lipid peroxides, triglycerides and extent of protein glycation in the heart of diabetic rats. GTE blunted the rise in cardiac [Ca 2+] and [Na +] whereas increased the activities of Ca 2+-ATPase and Na +/K +-ATPase in diabetic rats. In conclusion, the data provide support to the therapeutic effect of GTE and suggest that a possible mechanism of action may be associated with the attenuation of the rise in [Ca 2+] and [Na +] by ameliorating Ca 2+-ATPase and Na +/K +-ATPase activities.

Decreased activity of brush border membrane-bound digestive enzymes in small intestines from pigs experimentally infected with porcine epidemic diarrhea virus

Brush border membrane-bound digestive enzymes such as disaccharidases (lactase, sucrase, and maltase), leucine aminopeptidase N, and alkaline phosphatase were measured in jejunum from pigs experimentally infected with porcine epidemic diarrhea virus (PEDV). Three piglets from the infected and control groups were euthanized by electrocution and subjected to necropsy at 24, 36, 48, 60, and 72 hours post-inoculation (hpi). The infection of PEDV to jejunum resulted in significant decreases in brush border membrane-bound digestive enzymes such as disaccharidases (lactase, sucrase, and maltase), leucine aminopeptidase N, and alkaline phosphatase. PEDV replication results in massive destruction of villous enterocytes leading to a marked reduction of intestinal epithelial surface and brush border membrane-bound digestive enzyme activity. Reduced enzymatic activity and villous atrophy in the small intestine is thought to result in a maldigestive and malabsorptive diarrhea.

Antifibrillating effects of n-3 polyunsaturated fatty acids (PUFA) in aged hypertensive rats

PUFA have been shown in clinical trials to reduce the incidence of cardiovascular disease and sudden death, while experimental studies suggest their antiarrhythmic effects. Hypertension-related cardiomyopathy accompanied by myocardial remodelling deteriorates with age and increases a risk for malignant arrhythmias. The aim of the study was to investigate effect of PUFA on inducible ventricular fibrillation (VF) in aged spontaneously hypertensive rats (SHR). Male and female 14 moth-old SHR were fed with PUFA (20 mg/day for 2 months). Age-matched controls were used as well. Results showed that PUFA supplementation resulted in significant blood pressure reduction in both male and female SHR, while no change in body weight was observed. There was a decrease of heart rate and an increase of coronary flow in female PUFA-treated rats as measured in isolated heart preparation, while no significant changes in male rats. All untreated SHR were susceptible to electrically induced sustained VF. In contrast, inducible VF was significantly suppressed by 57% and 67% in PUFA-treated male and female SHR. Interestingly, PUFA supplementation led to clear antifibrillating effects despite myocardial remodelling, i.e. fibrosis and hypertrophy were not eliminated. However, histochemistry revealed increase of selected membrane-bound enzyme activities in the ventricles of PUFA treated rats. There were also alterations in immunolabeling of gap junction channel protein, connexin-43, which need further analysis.

Scaling of Na+,K+‐ATPase Molecular Activity and Membrane Fatty Acid Composition in Mammalian and Avian Hearts

We have examined Na(+),K(+)-ATPase molecular activity and membrane fatty acid composition in the heart of six mammalian and eight avian species ranging in size from 30 g in mice to 280 kg in cattle and 13 g in zebra finches to 35 kg in emus, respectively. Na(+),K(+)-ATPase activity scaled negatively with body mass in both mammals and birds. In small mammals, the elevated enzyme activity was related to allometric changes in both the concentration and molecular activity (turnover rate) of Na(+),K(+)-ATPase enzymes, while in small birds, higher Na(+),K(+)-ATPase activity appeared to result primarily from an increased molecular activity of individual enzymes. The unsaturation index of cardiac phospholipids scaled negatively with body mass in both groups, while a significant allometric increase in monounsaturate content was observed in the larger mammals and birds. In particular, the relative content of the highly polyunsaturated docosahexaenoic acid (22:6n-3) displayed the greatest variation, scaling negatively with body mass and varying greater than 40-fold in both mammals and birds. Membrane fatty acid profile was correlated with Na(+),K(+)-ATPase molecular activity in both mammals and birds, suggesting a potential association between membrane lipid composition and the activity of membrane-bound enzymes in the hearts of endotherms.

N-Acetylcysteine Ameliorates Carbofuraninduced Alterations in Lipid Composition and Activity of Membrane Bound Enzymes

The present work investigates the protective effects of N-acetylcysteine (NAC) on carbofuran-induced alterations in lipid composition and activity of membrane bound enzymes (Na+-K+-ATPase and Ca2+-ATPase) in the rat brain. Animals were exposed to carbofuran at a dose of 1 mg/kg body weight, orally, for a period of 28 days. A significant increase in lipid peroxidation in terms of TBARS was observed in brain after carbofuran exposure. NAC administration (200 mg/kg body weight) on the other hand lowered the carbofuran-induced lipid peroxidation to near normal. The increased lipid peroxidation following carbofuran exposure was accompanied by a significant decrease in the levels of total lipids, which is attributed to the reduction in phospholipid levels. Furthermore, NAC administration had a beneficial effect on carbofuran-induced alterations in lipid composition. The ratio of cholesterol to phospholipid, a major determinant of membrane fluidity, was increased in response to carbofuran exposure. This was associated with decreased activity of Na+-K+-ATPase and Ca2+-ATPase. NAC was observed to offer protection by restoring the cholesterol to phospholipid ratio along with the activity of Na+-K+-ATPase and Ca2+-ATPase. The results clearly suggest that carbofuran exerts its neurotoxic effects by increasing lipid peroxidation, altering lipid composition and activity of membrane bound enzymes. NAC administration ameliorated the effects of carbofuran suggesting its potential therapeutic effects in carbofuran neurotoxicity.

Effect of bacoside A on membrane‐bound ATPases in the brain of rats exposed to cigarette smoke

Membrane-bound enzymes play a vital role in neuronal function through maintenance of membrane potential and impulse propagation. We have evaluated the harmful effects of chronic cigarette smoking on membrane-bound ATPases and the protective effect of Bacoside A in rat brain. Adult male albino rats were exposed to cigarette smoke for a period of 12 weeks and simultaneously administered with Bacoside A (the active principle isolated from Bacopa monniera) at a dosage of 10 mg/kg b.w/day, p.o. The levels of lipid peroxides as marker for evaluating the extent of membrane damage, the activities of Na+/K+-ATPase, Ca2+-ATPase and Mg2+-ATPase, and associated cations sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+) were investigated in the brain. Neuronal membrane damage was evident from the elevated levels of lipid peroxides and decreased activities of membrane-bound enzymes. Disturbances in the electrolyte balance with accumulation of Na+ and Ca2+ and depletion of K+ and Mg2+ were also observed. Administration of Bacoside A inhibited lipid peroxidation, improved the activities of ATPases, and maintained the ionic equilibrium. The results of our study indicate that Bacoside A protects the brain from cigarette smoking induced membrane damage.

Protective effects of exogenous fatty acids on root tonoplast function against salt stress in barley seedlings

Salinity stress is one of the most serous factors limiting the productivity of agricultural crops. Previous studies have shown that exogenous fatty acids (EFAs) enhanced plant performance in saline environment. However, the mechanisms remained unclear. This study aimed to investigate whether EFAs (palmitic and linoleic acids) had ameliorating effects on salt injury in NaCl-treated barley ( Hordeum vulgare L.) seedlings, and to explore the possible mechanisms by determining tonoplast composition and function. The results showed that linoleic acid at 1 mmol l −1 in culture solution possessed protective effects on root tonoplast function against salt stress in the barley seedlings; this was accompanied with a significant suppression of the degradation of phospholipids and PAs in tonoplast vesicles. Moreover, these salt-ameliorating effects of linoleic acid on tonoplast function were also indicated by the increase in H +-ATPase and H +-PPase activities. In response to the changes in membrane bound enzyme activities, an augmentation in the activity of a vacuolar Na +/H + antiport was occurred by the application of linoleic acid under saline conditions. These findings suggested that the application of linoleic acid exhibited protective effects on tonoplast function in the barley seedlings under salt stress, perhaps due partly to suppress the degradation of phospholipids and PAs in tonoplast vesicles, thus leading partial restorations in the activities of vacuolar H +-ATPase, H +-PPase and Na +/H + antiport.

Omega-3 fatty acids in colorectal cancer prevention.

Omega-3 fatty acids in colorectal cancer prevention.

Drug targeting of estrogen receptor signaling in the cardiovascular system: preclinical and clinical studies.

Atherosclerosis and associated coronary heart disease events have lower prevalence in women than in men, especially during young adult years. Although multiple lines of evidence suggest that estrogens contribute to this difference, the efficacy of hormone replacement therapy for the prevention of cardiovascular disease in postmenopausal women is controversial. The protective action of estrogen in the cardiovascular system appears to be mediated indirectly by an effect on serum lipoprotein and triglyceride profiles and on the expression of coagulant and fibrinolytic proteins, and by a direct effect on the vessel wall itself. Estrogen has both rapid effects involving alteration of membrane ionic permeability and activation of membrane-bound enzymes and increases in endothelial cell nitric oxide synthase activity, as well as longer-term effects on gene expression that are mediated, at least in part, by the ligand-activated transcription factors, estrogen receptor alpha and beta. Compounds with pure antiestrogenic activity and selective estrogen receptor modulators that regulate estrogen receptor function in a tissue-specific manner have been developed in an attempt to achieve the cardioprotective effects of estrogens while minimizing the undesirable risks associated with hormone replacement therapy (e.g., endometrial and breast cancer). In this review, we will discuss recent developments on the mechanisms of estrogen action in the cardiovascular system. The results of clinical trials testing the long-term efficacy of hormone replacement therapy for the treatment of cardiovascular disease will also be discussed.

Docosahexaenoic acid in the diet: its importance in maintenance and restoration of neural membrane function

The central nervous system has the second highest concentration of lipids after adipose tissue. Long chain fatty acids, particularly arachidonic acid and docosahexaenoic acid, are integral components of neural membrane phospholipids. Alterations in neural membrane phospholipid components cannot only influence crucial intracellular and intercellular signaling but also alter many membrane physical properties such as fluidity, phase transition temperature, bilayer thickness, and lateral domains. A deficiency of docosahexaenoic acid markedly affects neurotransmission, membrane-bound enzyme and ion channel activities, gene expression, intensity of inflammation, and immunity and synaptic plasticity. Docosahexaenoic acid deficiency is associated with normal aging, Alzheimer disease, hyperactivity, schizophrenia, and peroxisomal disorders. Although the molecular mechanism of docosahexaenoic acid involvement in the disorders remains unknown, the supplementation of docosahexaenoic acid in the diet restores gene expression and modulates neurotransmission. Also, improvements are seen in signal transduction processes associated with behavioral deficits, learning activity, peroxisomal disorders, and psychotic changes in schizophrenia, depression, hyperactivity, stroke, and Alzheimer disease.

Polymer-enzyme inhibitor conjugates: influence of the molecular mass on the inhibition of membrane-bound aminopeptidase N activity

Conjugates of mucoadhesive polymers and protease inhibitors have been developed to protect incorporated (poly)peptides from enzymatic attack by luminally secreted or membrane-bound proteases. Within the present study, the influence of the molecular mass of such polymer conjugates on the inhibition of membrane-bound enzyme activity was evaluated. The aminopeptidase N inhibitor bacitracin (Bac) was covalently immobilised on the mucoadhesive polymer model poly(acrylic acid) with a molecular mass of 2 kDa (PAA 2 ) and 3000 kDa (polycarbophil, PCP). The resulting conjugates PAA 2 -Bac and PCP-Bac exhibited comparable amounts of bacitracin (24.4 and 25.3% (m/m), respectively) and were used to perform inhibition studies on isolated and membrane-bound aminopeptidase N. The conjugates showed no differences in the inhibition of isolated aminopeptidase N, whereas PAA 2 -Bac exhibited a significantly higher inhibitory activity versus membrane-bound aminopeptidase than PCP-Bac. Due to its lower molecular mass, PAA 2 -Bac could more easily diffuse into the mucus layer to get in contact with the enzyme. Obtained results should provide helpful basic knowledge for the development of multifunctional polymers as auxiliary agents for the oral administration of peptide drugs.

Calcium signaling in plant cells in altered gravity

Changes in the intracellular Ca 2+ concentration in altered gravity (microgravity and clinostating) evidence that Ca 2+ signaling can play a fundamental role in biological effects of microgravity. Calcium as a second messenger is known to play a crucial role in stimulus - response coupling for many plant cellular signaling pathways. Its messenger functions are realized by transient changes in the cytosolic ion concentration induced by a variety of internal and external stimuli such as light, hormones, temperature, anoxia, salinity, and gravity. Although the first data on the changes in the calcium balance in plant cells under the influence of altered gravity have appeared in 80 th, a review highlighting the performed research and the possible significance of such Ca 2+ changes in the structural and metabolic rearrangements of plant cells in altered gravity is still lacking. In this paper, an attempt was made to summarize the available experimental results and to consider some hypotheses in this field of research. It is proposed to distinguish between cell gravisensing and cell graviperception; the former is related to cell structure and metabolism stability in the gravitational field and their changes in microgravity (cells not specialized to gravity perception), the latter is related to active use of a gravitational stimulus by cells presumebly specialized to gravity perception for realization of normal space orientation, growth, and vital activity (gravitropism, gravitaxis) in plants. The main experimental data concerning both redistribution of free Ca 2+ ions in plant cell organelles and the cell wall, and an increase in the intracellular Ca 2+ concentration under the influence of altered gravity are presented. Based on the gravitational decompensation hypothesis, the consequence of events occurring in gravisensing cells not specialized to gravity perception under altered gravity are considered in the following order: changes in the cytoplasmic membrane surface tension → alterations in the physicochemical properties of the membrane → changes in membrane permeability, ion transport, membrane-bound enzyme activity, etc. → metabolism rearrangements → physiological responses. An analysis of data available on biological effects of altered gravity at the cellular level allows one to conclude that microgravity environment appears to affect cytoskeleton, carbohydrate and lipid metabolism, cell wall biogenesis via changes in enzyme activity and protein expression, with involvement of regulatory Ca 2+ messenger system. Changes in Ca 2+ influx/efflux and possible pathways of Ca 2+ signaling in plant cell biochemical regulation in altered gravity are discussed.

TNF-alpha increases human melanoma cell invasion and migration in vitro: the role of proteolytic enzymes.

Inflammatory mediators have been reported to promote malignant cell growth, invasion and metastatic potential. More specifically, we have recently reported that tumour necrosis factor alpha (TNF-α) increases melanoma cell attachment to extracellular matrix (ECM) substrates and invasion through fibronectin. In this study, we extend these investigations asking specifically whether the TNF-α effect on cell invasion and migration involves activation of proteolytic enzymes. We examined the effect of TNF-α on melanoma expression/activation of type IV gelatinases matrix metalloproteinases 2 and 9 (MMPs -2 and -9) and general proteolytic enzymes. Stimulation with TNF-α significantly increased both melanoma cell migration at 24 h (+21%) and invasion through fibronectin (+35%) but did not upregulate/activate the expression of latent MMP-2 constitutively produced by these cells and did not upregulate their general protease activity. However, the increased cell migration and invasion through fibronectin observed following stimulation with TNF-α were inhibited by the general protease inhibitor α2 macroglobulin. These findings suggest that the promigratory and proinvasive effect of TNF-α on this melanoma cell line may be mediated to some extent by induction of localised cell membrane-bound degradative enzyme activity, which is not readily detected in biochemical assays.

Effects of estrogen on the vascular system.

The cardiovascular protective actions of estrogen are partially mediated by a direct effect on the vessel wall. Estrogen is active both on vascular smooth muscle and endothelial cells where functionally competent estrogen receptors have been identified. Estrogen administration promotes vasodilation in humans and in experimental animals, in part by stimulating prostacyclin and nitric oxide synthesis, as well as by decreasing the production of vasoconstrictor agents such as cyclooxygenase-derived products, reactive oxygen species, angiotensin II, and endothelin-1. In vitro, estrogen exerts a direct inhibitory effect on smooth muscle by activating potassium efflux and by inhibiting calcium influx. In addition, estrogen inhibits vascular smooth muscle cell proliferation. In vivo, 17beta-estradiol prevents neointimal thickening after balloon injury and also ameliorates the lesions occurring in atherosclerotic conditions. As is the case for other steroids, the effect of estrogen on the vessel wall has a rapid non-genomic component involving membrane phenomena, such as alteration of membrane ionic permeability and activation of membrane-bound enzymes, as well as the classical genomic effect involving estrogen receptor activation and gene expression.

Effect of Polyamines on Mesangial Cell Ecto-5′-Nucleotidase and Ecto-ATPase Activity

Polyamines were found to modulate the activity of several membrane-bound enzymes, participating in cell growth and differentiation. We have studied the effect of polyamines (spermidine, spermine and putrescine) on rat mesangial cell ectoenzymes: 5′-nucleotidase, Mg²⁺-ATPase and Ca²⁺-ATPase. Ecto-5′-nucleotidase activity was significantly increased after 48 h treatment with spermine and spermidine. Mg²⁺-ATPase was increased only after treatment with spermidine; however, Ca²⁺-ATPase was significantly increased after both spermine and spermidine treatment of mesangial cells. Culture of mesangial cells with putrescine did not change the activity of these ectoenzymes. Increased expression of mesangial cell ecto-ATPase and ecto-5′-nucleotidase after spermine and spermidine treatment could result in an increased production of adenosine, a powerful autacoid interesting with respect to a role of mesangial cells in inflammatory processes.

Supernatant Protein Relevant to the Activity of Membrane-Bound Enzymes: Studies on Lathosterol 5-Desaturase

Supernatant Protein Relevant to the Activity of Membrane-Bound Enzymes: Studies on Lathosterol 5-Desaturase