F. Sánchez de la Cuesta

Effects of silymarin MZ-80 on oxidative stress in patients with alcoholic cirrhosis

BACKGROUND The role of silymarin in the treatment of liver cirrhosis is controversial. AIM Clinical outcome,biochemical profile and the antiperoxidative effects of silymarin MZ-80 during 6 months treatment were investigated in patients with alcoholic liver cirrhosis. METHODS Sixty consecutive patients with alcoholic liver cirrhosis were randomized to receive either silymarin MZ-80 (S) (150 mg t.i.d. per day) or placebo (P) for periods of 6 months. Erythrocyte total glutathione (GSH) content, platelet malondialdehyde (MDA) and serum amino-terminal propeptide of procollagen Type III (PIIINP) were determined at baseline and at the end of treatment. RESULTS Forty-nine patients completed the study (24 S and 25 P). The 2 groups were well-matched for demographic as well as baseline clinical and laboratory parameters. Silymarin increased total GSH at 6 months (4.5 +/- 3.4 to 5.8 +/- 4.0 micromol/g Hb) whereas, in the placebo group, GSH remained unchanged (4.1 +/- 3.9 to 4.4 +/- 4.1 micromol/gHb) (p < 0.001), and platelet-derived non-induced MDA decreased by 33% (p < 0.015). A parallel decrease in PIIINP values was seen with silymarin (1.82 1.03 to 1.36 +/- 0.5 U/ml, p < 0.033) but not with placebo (1.31 +/- 0.4 to 1.27 +/- 0.6 U/ml). There were no concurrent changes on laboratory indices of the pathology. CONCLUSIONS Silymarin is well-tolerated and produces a small increase in glutathione and a decrease in lipid peroxidation in peripheral blood cells in patients with alcoholic liver cirrhosis. Despite these effects no changes in routine liver tests were observed during the course of therapy.

Characterization of muscarinic receptor subtypes in human tissues

The affinities of selective, pirenzepine and AF-DX 116, and classical, N-methylscopolamine and atropine, muscarinic cholinergic receptor antagonists were investigated in displacement binding experiments with [3H]Pirenzepine and [3H]N-methylscopolamine in membranes from human autoptic tissues (forebrain, cerebellum, atria, ventricle and submaxillary salivary glands). Affinity estimates of N-methylscopolamine and atropine indicated a non-selective profile. Pirenzepine showed differentiation between the M1 neuronal receptor of the forebrain and the receptors in other tissues while AF-DX 116 clearly discriminated between muscarinic receptors of heart and glands. The results in human tissues confirm the previously described selectivity profiles of pirenzepine and AF-DX 116 in rat tissues. These findings thus reveal the presence also in man of three distinct muscarinic receptor subtypes: the neuronal M1, the cardiac M2 and the glandular M3.

Inhibition of ferrous-induced lipid peroxidation by pyrimido-pyrimidine derivatives in human liver membranes

The effects of pyrimido-pyrimidine derivatives (dipyridamole, RA-642, and RA-233) on lipid peroxidation, using d-α-tocopherol as standard, were studied in enriched membrane fractions from human and rat hepatocytes. Equimolar concentrations of ferrous sulfate and ascorbic acid were used to induce lipid peroxidation. The amount of peroxidized lipids observed in membrane fractions from human liver was smaller than in those from rat liver. In both species, however, pyrimido-pyrimidine derivatives, except for RA-233 in rat liver, inhibited lipid peroxidation dose-dependently in the following sequence: RA-642 > dipyridamole > d-α-tocopherol RA-233.

Lipid peroxidation and glutathione system in hyperlipemic rabbits: influence of olive oil administration

We studied the effect of supplementation (10% w/w) of a hyperlipemic diet (1% cholesterol) with olive oil (OLIV) for 6 weeks in four groups of 10 rabbits each. At the end of this period, we determined lipid peroxidation, glutathione content, and glutathione peroxidase, reductase and transferase activities in liver, brain, heart, aorta and platelets. The atherogenic diet increased tissue lipid peroxidation and decreased the protective antioxidant effect of glutathione. Dietary supplementation with olive oil reduced tissue lipid peroxidation by 71.6% in liver, 20.3% in brain, 84.5% in heart, 63.6% in aorta, 72% in platelets. The ratios total/oxidized glutathione were increased in all tissues (49% in liver, 48% in brain, 45% in heart, 83% in aorta, 70% in platelets). Olive oil increased glutathione peroxidase and transferase activities in all tissues. We conclude that in rabbits made hyperlipemic with a diet rich in saturated fatty acids, olive oil decreased tissue oxidative stress.

Effect of propofol on oxidative stress in an in vitro model of anoxia-reoxygenation in the rat brain

Propofol, an intravenous anaesthetic, is similar in chemical structure to the active nucleus of antioxidant substances such as alpha-tocopherol (vitamin E). The present study was designed to test whether propofol had antioxidant effects in an in vitro model of anoxia-reoxygenation in slices of rat brain. We used seven experimental groups: (1) control oxygenated tissue; (2) tissue subjected to anoxia for 20 min and reoxygenation for 3 h; and tissues processed as described and incubated with (3) Intralipid (commercial solvent for propofol), or propofol at a concentration of (4) 10 micromol/l, (5) 50 micromol/l, (6) 150 micromol/l or (7) 300 micromol/l. The production of lipid peroxides was quantified as thiobarbituric acid reactive substances (TBARS); tissular glutathione production and the activities of glutathione peroxidase (GSHpx), glutathione reductase (GSSGrd) and glutathione transferase (GSHtf) were also measured. Reoxygenation led to tissular oxidative stress, which was curtailed by propofol. The anaesthetic led to a 47% reduction in TBARS, a 165% increase in the reperfusion-inhibiting glutathione content, a 47% decrease in GSHpx activity, and an 87% increase in GSHtf activity. Intralipid had no effect on any of the parameters studied here. We conclude that propofol has a clear antioxidant effect in rat brain tissue subjected to anoxia-reoxygenation.

Clonidine decreases intraoperative bleeding in middle ear microsurgery

Background: The antihypertensive drug clonidine is a centrally acting α2 agonist useful as a premedicant because of its sedative, anxiolytic, and analgesic properties. We examined the effect of clonidine given as an oral preanesthetic medication in producing a bloodless surgical field in patients undergoing middle ear microsurgery. We also evaluated whether the administration of clonidine would alter the reflex cardiovascular response to laryngoscopy and endotracheal intubation, anesthetic requirement, postoperative pain intensity and consumption of analgesics, and pre‐ and postoperative sedation and anxiety.

The In vitro Effects of Propofol on Tissular Oxidative Stress in the Rat

This study was designed to evaluate the in vitro effects of propofol on lipid peroxide formation and the glutathione antioxidant system in some tissues of Wistar rats (n = 8-10 per experiment). We measured thiobarbituric acid reactive substances (TBARS), and the activities of glutathione peroxidase (GSHpx), reductase (GSSGrd), and transferase (GSHtf). Propofol inhibited TBARS formation in a concentration-dependent manner. Etomidate and thiopental sodium 10-6 to 10-3 M had no effect. The effect of propofol was apparent immediately and was observed for up to 15-20 min after the start of TBARS formation. Propofol inhibited GSHpx activity by a maximum of 75.1% +/- 8.4%, increased GSSGrd activity by a maximum of 188% +/- 12.6%, and increased GSHtf activity by a maximum of 230% +/- 20%. The solvent intralipid had no significant effect on any of the enzyme activities or on lipid peroxidation. We conclude that propofol not only inhibits lipid peroxidation, but also enhances the cellular antioxidant defense system. Propofol is thus able to prepare tissues against oxidative attack by boosting stores of reduced glutathione. Implications: This study demonstrates that the anesthetic propofol increases one of the most important mechanisms against cellular damage, the glutathione system. The study was performed in several tissues of healthy rats. This could be applied as a possible protection in surgical patients suffering from an ischemic process (cerebrovascular disease, coronary ischemia, etc.). (Anesth Analg 1998;87:1141-6)

The effect of propofol on oxidative stress in platelets from surgical patients.

UNLABELLED We investigated the changes in oxidative stress in platelets from surgical patients anesthetized with propofol. We studied 60 surgical patients (ASA physical status I and II) and 12 healthy volunteers. The patients were divided into three groups: anesthesia induced with an IV bolus dose of 4 mg/kg thiopental; anesthesia induced with an IV bolus dose of 2 mg/kg propofol; and total IV anesthesia (induction with propofol 2 mg/kg, infusion with propofol 10 mg/kg during the first 10 min, then 8 mg/kg for 10 min, and 6 mg/kg during the rest of the operation). Healthy volunteers were given an IV bolus dose of 10% fat emulsion (Intralipid). We measured the following variables in platelets: thiobarbituric acid reactive substances content, glutathione content, and glutathione peroxidase, reductase, and transferase activities. Thiopental did not modify any of the variables. Propofol decreased thiobarbituric acid reactive substances production by 25.7% and increased total glutathione content by 24.6%. The percentage of glutathione in oxidized form was 29.5% smaller in patients anesthetized with propofol. Glutathione peroxidase activity was 28.3% less, glutathione transferase was 44.5% more, and glutathione reductase was not significantly different. Intralipid had no effect on any of the variables. After infusion of propofol for 1 h, the effects were, in qualitative terms, the same as those seen after an initial bolus dose. In conclusion, our findings show that propofol has an antioxidant effect in humans. This effect may be beneficial in patients who have diseases in which free radicals play an important role. IMPLICATIONS This study demonstrates that propofol inhibits cellular oxidative damage, measured in platelets from surgical patients. Neither thiopental nor the fat emulsion (Intralipid) showed any effect. Moreover, propofol increased the antioxidant defense of glutathione. This could be applied in the protection of tissues from ischemic damage.

Propofol inhibits in vitro platelet aggregation in human whole blood

To help clarify the mechanism of propofol-induced vasodilation, we investigated whether propofol, at concentrations ranging from 10-6 to 10-3 M, inhibited platelet aggregation in human whole blood. Propofol inhibited platelet aggregation induced by adenosine diphosphate, collagen, or arachidonic acid in a concentration-dependent manner, with a 50% inhibited concentration (micro mol/L) of 136 +/- 9.8 for adenosine diphosphate, 77.8 +/- 6.6 for collagen, and 71.8 +/- 5.4 for arachidonic acid. In platelet-rich plasma, propofol had no significant antiaggregant effect except when arachidonic acid was used as the aggregant (50% inhibited concentration 105 +/- 9.9 micro mol/L). The antiaggregant effect of propofol in platelet-rich plasma was increased in the presence of red blood cells or leukocytes in a cell number-dependent manner. We conclude that propofol reduces the platelet activity in human whole blood in vitro. (Anesth Analg 1997;84:919-21)

Antioxidant effect of acetylsalicylic and salicylic acid in rat brain slices subjected to hypoxia

Acetylsalicylic acid (ASA) reduces the incidence of ischemic stroke mainly through its antithrombotic action; however, it also has a direct neuroprotective effect. The present study was designed to evaluate the effect of ASA on oxidative stress and the activity of nitric oxide synthase (NOS) in an in vitro model of hypoxia in rat brain slices. Rat brain slices were perfused with nitrogen (hypoxia) for a maximum of 120 min, after which we measured lipid peroxidation, glutathione levels, glutathione‐related enzyme activities, and constitutive nitric oxide synthase (cNOS) and inducible nitric oxide synthase (iNOS) activities. In brain tissue subjected to hypoxia, ASA reduced oxidative stress and iNOS activity (all increased by hypoxia), but only when used at higher concentrations. The effects of salicylic acid (SA) were similar but more intense than were those of ASA. After oral administration, the effect of SA was much greater than that of ASA, and the decrease in cell death with SA was seen much more clearly. In view of the greater effect of SA compared to ASA on changes in oxidative stress parameters in a model of hypoxia, and higher brain concentrations of SA when it is administered alone than when ASA is given (undetectable levels), we conclude that SA plays an important role in the cytoprotective effect in brain tissue after ASA administration.