Leukocyte-mediated inactivation of alpha 1-proteinase inhibitor is inhibited by amino analogues of alpha-tocopherol

Lipid peroxidation and decomposition--conflicting roles in plaque vulnerability and stability

The low density lipoprotein (LDL) oxidation hypothesis has generated considerable interest in oxidative stress and how it might affect atherosclerosis. However, the failure of antioxidants, particularly vitamin E, to affect the progression of the disease in humans has convinced even staunch supporters of the hypothesis to take a step backwards and reconsider alternatives. Preponderant evidence for the hypothesis came from animal antioxidant intervention studies. In this review we point out basic differences between animal and human atherosclerosis development and suggest that human disease starts where animal studies end. While initial oxidative steps in the generation of early fatty streak lesions might be common, the differences might be in the steps involved in the decomposition of peroxidized lipids into aldehydes and their further oxidation into carboxylic acids. We suggest that these steps may not be amenable to attenuation by antioxidants and antioxidants might actually counter the stabilization of plaque by preventing the formation of carboxylic acids which are anti-inflammatory in nature. The formation of such dicarboxylic acids may also be conducive to plaque stabilization by trapping calcium. We suggest that agents that would prevent the decomposition of lipid peroxides and promote the formation and removal of lipid hydroxides, such as paraoxonase (PON 1) or apo A1/high density lipoprotein (HDL) might be more conducive to plaque regression.

Antioxidant and antiradical activities of L-carnitine

L-carnitine plays an important regulatory role in the mitochondrial transport of long-chain free fatty acids. In this study, the antioxidant activity of L-carnitine was investigated as in vitro. The antioxidant properties of the L-carnitine were evaluated by using different antioxidant assays such as 1, 1-diphenyl-2-picryl-hydrazyl free radical (DPPH.) scavenging, total antioxidant activity, reducing power, superoxide anion radical scavenging, hydrogen peroxide scavenging and metal chelating activities. Total antioxidant activity was measured according to ferric thiocyanate method. alpha-tocopherol and trolox, a water-soluble analogue of tocopherol, were used as the reference antioxidant compounds. At the concentrations of 15, 30 and 45 microg/mL, l-carnitine showed 94.6%, 95.4% and 97.1% inhibition on lipid peroxidation of linoleic acid emulsion, respectively. On the other hand, 45 microg/mL of standard antioxidant such as alpha-tocopherol and trolox indicated an inhibition of 88.8% and 86.2% on peroxidation of linoleic acid emulsion, respectively. In addition, L-carnitine had an effective DPPH. scavenging, superoxide anion radical scavenging, hydrogen peroxide scavenging, total reducing power and metal chelating on ferrous ions activities. Also, those various antioxidant activities were compared to alpha-tocopherol and trolox as references antioxidants.

Antiradical and antioxidant activity of total anthocyanins from Perilla pankinensis decne

The purpose of this work comprise the assessment of the antioxidant activity of total anthocyanins from Perilla pankinensis samples (TAPP) by different analytical methods: 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging, total antioxidant activity, total reducing activity, superoxide anion radical scavenging, hydrogen peroxide scavenging and metal chelating activities. Total antioxidant activity was measured according to ferric thiocyanate method. alpha-Tocopherol and trolox, which water-soluble analogue of tocopherol were used as references antioxidant compounds. At the concentrations of 30 and 45 microg/mL, TAPP showed 91.9 and 96.4% inhibition on lipid peroxidation of linoleic acid emulsion, respectively. In comparison, 45 microg/mL of standard antioxidant such as alpha-tocopherol and trolox exhibited 88.8 and 86.2% inhibition on peroxidation of linoleic acid emulsion, respectively. In addition, TAPP have found effective on DPPH scavenging, superoxide anion radical and hydrogen peroxide scavenging, total reducing power and metal chelating on ferrous ions activities. Also, these various antioxidant effects were compared to alpha-tocopherol and trolox.

Anomalous oxidation of MDL 73,404 by horseradish peroxidase

3,4-Dihydro-6-hydroxy-N,N,N-2,5,7,8-heptamethyl-2H-1-benzopyran-2-ethanaminium-4-methylbenzene sulfonate (MDL 73,404) is a cardioselective water-soluble quaternary ammonium analogue of Vitamin E which is synthesized to augment the antioxidant defence in situations of free radical injury such as myocardial infarction/reperfusion. Its oxidation by any peroxidative enzyme has not been studied kinetically. This paper describes its enzymatic oxidation by horseradish peroxidase (HRP). The activity was followed spectrophotometrically at 255nm, and the experimental results were simulated using the program "KINETIC 3.1" for Windows 3.x. The MDL 73,404 was oxidized by horseradish peroxidase in the presence of H2O2 to its corresponding MDL 73,404 quinone. During this oxidation, the horseradish peroxidase showed an unexpectedly slow kinetic response with time, which contrast with the linear product accumulation curve measured with 2,2'-azino-bis-(3-estilbenzotiazol-6-sulfonic acid) (ABTS). This response was dependent on the respective concentrations of enzyme, MDL 73,404 and H2O2. However, when the enzyme was incubated with H2O2, the slow kinetic response disappeared and a lag period was observed. Furthermore, when p-coumaric acid (PCA) was added, the activity increased and the slow kinetic response became a straight line. In order to explain this anomalous behaviour, a kinetic model has been proposed and its differential equations simulated. From the correlation between experimental and simulated results it is concluded that MDL 73,404 can act as a slow response substrate for peroxidase, probably due to the presence of a quaternary ammonium side chain that confers on it a slow capacity to convert compound III into ferriperoxidase.

Fumonisin B1-induced DNA damage in rat liver and spleen: effects of pretreatment with coenzyme Q10, L-carnitine, alpha-tocopherol and selenium

Active oxygen radical species are reported to cause organ damage. This study was designed to determine whether oxidative stress contributed to the initiation or progression of hepatic and splenic cell DNA damage induced by fumonisin B1 (FB1) in rats. Another aim was to investigate the protective effects of the antioxidants coenzyme Q10 (CoQ10), L-carnitine, vitamin E (alpha-tocopherol) and selenium against DNA damage in the liver and spleen of rats treated with FB1. Fasted rats were injected intravenously with a single dose of fumonisin B1 at 1.55 mg kg-1 body wt. into the tail vein. Treatment with FB1 led to splenic and hepatic DNA fragmentation in 85% of the test animals. DNA fragmentation was investigated as a critical event in toxic cell death by testing total Ca2+ in liver. FB1 administration caused total Ca2+ in liver to increase within 4 h (204% of control). Measurement of liver enzyme activities showed an increase in aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT). FB1 also markedly decreased splenic and hepatic glutathione (GSH) levels. Pretreatment with CoQ10 (30 mg CoQ10 kg-1 diet) together with L-carnitine (2.8 mg carnitine kg-1 diet), alpha-tocopherol (30 IU vitamin E kg-1 diet) and selenium (1 mg selenium as sodium selenite kg-1 diet), decreased DNA damage and the activities of Ca2+, ASAT and ALAT in the liver. On the other hand, the level of GSH was slightly increased. The CoQ10 alone did not significantly protect against toxic cell death and glutathione depletion caused by FB1. Oxidative damage caused by FB1 may be one of the underlining mechanisms of FB1-induced cell injury and DNA damage.

Serpin=serine protease-like complexes within neurofilament conglomerates of motoneurons in amyotrophic lateral sclerosis

Neurofilamentous conglomerates (NfCg), as axonal spheroids or conglomerates in motoneurons, are the histopathologic hallmarks for early stages of amyotrophic lateral sclerosis (ALS). We hypothesize that NfCg may be formed by post-translational modifications of altered Nf proteins that include: (1) hyperphosphorylation, (2) glycosylation (or glycoxidation), (3) nitration, (4) ubiquitination and/or (5) crosslinking by the Ca++-dependent transglutaminase (TGase). These, as well as other changes, are predicted to be initiated or accentuated by oxidative damage. The damaged Nf proteins then activate cascades of intracellular protein degradation which include ATP-dependent ubiquitin/proteasome proteolysis. Other proteolytic systems, either Ca++-dependent or independent, may also be activated, such as serine and cysteine protease systems. These enzymes, either lysosomal or non-lysosomal may also participate in the degradation of damaged Nf proteins being balanced by their cognate inhibitors. Protein complexes formed by these protease=inhibitor systems, along with damaged Nf proteins, may accumulate within the cell bodies as neuronal inclusions, since a number of intracellular inclusions are found in motor neurons in ALS. In the current study, we investigated the involvement of serine proteases and their serpins in NfCg formation. Pairs of three serine proteases (trypsin, chymotrypsin and thrombin) and their cognate serpins (alpha1-anti-trypsin, alpha1-anti-chymotrypsin, and protease nexin I) were probed in motoneurons with their antibodies for both NfCg and inclusions. Positive immunoreactivities for all serine proteases and their cognate serpins support the contention that the imbalance of serine proteases and internalized serpins may have a role in formation of NfCg and inclusions, and hence, the pathogenesis of ALS.

Antioxidant status and alpha1-antiproteinase activity in subarachnoid hemorrhage patients

The antiproteasic activity of alpha1-antitrypsin (alpha1-AT) is reduced in cases of subarachnoid hemorrhage from ruptured intracranial aneurysm and particularly in patients currently smoking; alpha1-AT is very sensitive to oxidant agents. About 50% of physiological anti-oxidant systemic capacity is represented by Vitamin A, E and C. Plasmatic amounts of alpha1-AT, alpha1-AT Collagenase Inhibitory Capacity (CIC) and levels of vitamin A, vitamin E and vitamin C were analyzed in 39 patients, 26 women and 13 men, operated for intracranial aneurysm; 11 patients with unruptured intracranial aneurysm were considered as controls while 28 patients were included within 12 hours from subarachnoid hemorrhage (SAH). Plasmatic levels of vitamin A and vitamin E were significantly lower (p=0.038 and p=0.0158) in patients suffering SAH than in controls, while no statistically significant differences were found in mean plasmatic vitamin C levels. Level of alpha1-AT was not statistically different in controls and in patients with SAH; however, the activity of alpha1-AT, evaluated as CIC, is significantly reduced in patients with SAH (p=0.019). We have observed that systemic plasmatic levels of vitamins did not significantly differ in relation to smoking habit. Vitamin A and E represent an important defensive system against free radicals reactions. Particularly, vitamin E acts as an antioxidant by scavenging free-radicals. A reduced anti-oxidant status might be related to the higher sensibility of alpha1-AT to oxidative reactions and the activity of alpha1-AT is dependent on the antioxidant capacity of liposoluble vitamins. We can speculate that an acute systemic oxidative stress condition might influence the rupture of intracranial aneurysms.

Inactivation of alpha1-antiproteinase (alpha1-AT) and changes in antioxidants' plasma levels in subarachnoid hemorrhage

Recent studies have suggested that a quantitative or a qualitative imbalance between the activity of proteases and its inhibitors hypothetically might be involved in intracranial aneurysm rupture. In the present study we test the hypothesis that the systemic reduction of alpha1-antitrypsin activity might be related to the elevated oxidative potential exerted by cigarette smoking and/or to a systemic low antioxidant capacity. We studied, in a series of 57 patients bearing intracranial aneurysms, the relationship between alpha1-antitrypsin activity, cigarette smoking and the following variables measured in plasma: vitamin A, vitamin E, thiol groups, urate and lipid peroxide levels. Serum levels of alpha1-antitrypsin are higher in patients with subarachnoid hemorrhage than in cases of unruptured aneurysms, while the levels of vitamin A and vitamin E are significantly lower in patients that suffered subarachnoid hemorrhage than in controls. Both vitamin A and E levels are related to the occurrence of rupture of the aneurysm, as elicited by logistic regression analysis (P=0.017 and P=0.014, respectively), with a protective effect of higher levels of the variables, as shown by their odds ratio (0.028 and 0.84, respectively). No significant changes in the strength of the association could be appreciated when controlling for smoking habit. None of the other tested variables could be related to the occurrence of the aneurysm rupture. Both alpha1-antitrypsin serum level and the level of vitamin A appeared to be independently related to alpha1-antitrypsin collagenase inhibitory capacity percentage (P=0.03 and P=0.025), with no independent influence of the type of aneurysm and the smoking habit. The results of the present study show that the qualitative pattern of alpha1-antitrypsin is significantly related to the serum level of liposoluble vitamin A, while the type of aneurysm and the smoking habit have no independent influence. This suggests that in a situation in which systemic levels of vitamin A are reduced, the risk of a reduced activity of alpha1-antitrypsin as controller of proteases is elevated, with the consequent increased risk of aneurysm bleeding.

Amphiphilic alpha-tocopherol analogues as inhibitors of brain lipid peroxidation

Neurological disorders, such as stroke, trauma, tardive dyskinesia, Alzheimer's and Parkinson's diseases, may be partially attributed to excessive exposition of the nervous tissue to oxygen-derived radicals. A novel water-soluble alpha-tocopherol analogue, 2,3-dihydro-2,2,4,6,7-pentamethyl-3-(4-methylpiperazino) methyl-1-benzofuran-5-ol dihydrochloride (MDL), is a potent radical scavenger. Following subcutaneous administration to mice, MDL inhibited the lipid peroxidation induced in the 100-fold diluted brain homogenates, with an ID50 of 8 mg/kg. Rapid brain penetration, within 30-60 min postadministration, and even distribution into different brain areas were observed. MDL was also detected after oral administration. In brain homogenate undergoing lipid peroxidation, MDL prevented the consumption of an equal amount of alpha-tocopherol, while inhibiting the concomitant malondialdehyde formation. The radical scavenging capacity of MDL was superior to that of alpha-tocopherol, although the peak and half-peak potentials were not significantly different. However, MDL was much less lipophilic, the partition coefficient (log P) at the octanol/water interface being 1.91. Although it is yet unknown, whether the applied criteria sufficiently predict its usefulness, beneficial effects of MDL may be expected in the above mentioned disorders.

Determination of MDL 74,405, a synthetic analogue of alpha-tocopherol, in dog plasma and heart tissue by high-performance liquid chromatography with electrochemical detection

A high-performance liquid chromatographic (HPLC) procedure with electrochemical detection was developed to analyze MDL 74,405 (I), the (-)-(S)-enantiomer of an alpha-tocopherol analogue, in dog plasma and heart tissue after infusion (0.3 mg/kg/h). The sample preparation involved the addition of an internal standard to either the dog plasma and heart tissue prior to protein precipitation. After centrifugation, the resulting supernatant was directly analyzed by HPLC with a Zorbax Rx C8 column and a mobile phase of acetonitrile-0.04 M potassium phosphate, pH 7.0 (70:30, v/v). The concentration of I found was ca. 100 ng/ml in plasma and ca. 3 micrograms/g in heart tissue. A chiral separation with an Ultron ES-OVM column and a mobile phase of methanol-0.025 M potassium phosphate, pH 6.5 (17:83, v/v) was also used to investigate the enantiomeric conversion of I. Preliminary results of a probe study indicated that I is not inverted to the (+)-(R)-enantiomer in vivo.

Structural changes of high-density-lipoprotein apolipoproteins following incubation with human polymorphonuclear cells

Based on the analogy in mechanisms and events between the pathogenesis of atherosclerosis and the inflammatory reaction, we investigated the impact of human polymorphonuclear leukocyte (PMN) degranulation and oxidative process on high-density-lipoprotein (HDL) structure. HDL were incubated (37 degrees C) with PMN at a physiological ratio (370 nmol cholesterol-HDL/ml with 2 x 10(6) PMN/ml) for 15, 30 and 60 min with or without stimulating agent. PMN activation was assessed by measurement of superoxide anion generation and elastase production, which both reached peak concentration at 15 min. HDL apolipoproteins (apo) analysed by immunoblotting after SDS/PAGE and electrofocusing evidenced the following modifications: (a) a slow hydrolysis of apo AII and apo Cs; (b) a rapid hydrolysis of apo E; (c) a change in apo AI isoform distribution with an increase in the most acidic isoform (AI-2) at the expense of a less acidic form (AI-1); (d) a shift of the major apo AII isoform into two more basic forms. In contrast, no quantifiable lipid modification nor lipid oxidation, assessed by thiobarbituric-acid-reactive substances (TBARS) were noted. Despite a lack of variation of TBARS, a decrease in HDL vitamin E content by 80% was observed. Since this decrease was prevented by addition of superoxide dismutase in the medium, we concluded the occurrence of an oxidative process affecting HDL. Experiments with proteolytic inhibitors showed that elastase caused the proteolytic cleavage of apolipoprotein E, AII and Cs. In contrast, apo AI modification might involve both oxidative and proteolytic processes.

Protection of infarcted, chronically reperfused hearts by an alpha-tocopherol analogue

Free radicals may cause part of the irreversible injury which occurs during myocardial infarction and reperfusion. In the present study MDL 73404, a hydrophilic, cardioselective, free radical scavenger analogue of alpha-tocopherol, was evaluated for its effects on infarct size as well as on indicators of reperfusion injury. A pentobarbitone-anaesthetised rat model of coronary artery ligation (60 min; followed by 8 days of reperfusion) was used. Intravenous infusion of MDL 73404 (3 mg/kg per h) began 10 min before occlusion until 30 min after the onset of reperfusion. MDL 73404 reduced (P < 0.02) the elevated serum levels of thiobarbituric acid reactive substances and plasma levels of creatine phosphokinase (P < 0.01). An increase in cardiac output and heart rate together with a decrease (P < 0.01) in infarct size was evident in rats that had received MDL 73404, 8 days previously. Isolated infarcted hearts obtained from rats after 8 days of reperfusion had greater (P < 0.01) + dP/dt max, -dP/dt max, left ventricular systolic pressure and coronary flow after MDL 73404 compared to saline-treated controls. Infusion of [14C]MDL 73404, during the time of occlusion resulted in a concentration of 14.5 +/- 2.2 mg eq/g in the non-ischaemic ventricular tissue and a concentration of 3.0 +/- 0.4 mg eq/g in the area at risk. After infusion for the 30 min of reperfusion, 6.4 +/- 0.2 mg eq/g was detected in the non-ischaemic ventricular tissue but only 3.1 +/- 0.5 mg eq/g in the area at risk.(ABSTRACT TRUNCATED AT 250 WORDS)