Antiarrhythmic agents. Scavengers of hydroxyl radicals and inhibitors of NADPH-dependent lipid peroxidation in bovine lung microsomes

The dose-response relationships of the direct scavenging activity of amide-based local anesthetics against multiple free radicals

This study aimed to illustrate the dose-response relationships of the direct scavenging activity of amide-based local anesthetics against multiple free radicals in vitro. We have demonstrated that amide-type local anesthetics selectively and directly scavenge some free radicals. Three kinds of free radicals were eliminated by all the four local anesthetics examined. Mepivacaine, lidocaine, bupivacaine, and dibucaine scavenged hydroxyl radicals in dose-dependent manners. Ascorbyl free radicals were also scavenged in dose-dependent manners, and lastly singlet oxygen was scavenged in dose-dependent manners. Three other free radicals were not scavenged by all of the four local anesthetics; tert-butoxyl radical was scavenged by all the anesthetics examined but dibucaine, nitric oxide by mepivacaine but not by the other three, and tyrosyl radical by mepivacaine and lidocaine but not by the other two. Some free radicals (superoxide anion, tert-butyl peroxyl radical, DPPH) were not scavenged by any of the four local anesthetics. The local anesthetics were also shown to inhibit lipid peroxidation by TBARS assay. These results suggest that local anesthetics have antioxidant properties through their free radical scavenging activities.

Effect of Intravenous Lidocaine on Inflammatory and Apoptotic Response of Ischemia-Reperfusion Injury in Pigs Undergoing Lung Resection Surgery

Background

Ischemia-reperfusion injury is one of the most critical phenomena in lung transplantation and causes primary graft failure. Its pathophysiology remains incompletely understood, although the inflammatory response and apoptosis play key roles. Lidocaine has anti-inflammatory properties. The aim of this research is to evaluate the effect of intravenous lidocaine on the inflammatory and apoptotic responses in lung ischemia-reperfusion injury.

Methods

We studied the histological and immunohistochemical changes in an experimental model of lung transplantation in pigs. Twelve pigs underwent left pneumonectomy, cranial lobectomy, caudal lobe reimplantation, and 60 minutes of graft reperfusion. Six of the pigs made up the control group, while six other pigs received 1.5 mg/kg of intravenous lidocaine after induction and a 1.5 mg/kg/h intravenous lidocaine infusion during surgery. In addition, six more pigs underwent simulated surgery. Lung biopsies were collected from the left caudal lobe 60 minutes after reperfusion. We conducted a double study on these biopsies and assessed the degree of inflammation, predominant cell type (monocyte-macrophage, lymphocytes, or polymorphous), the degree of congestion, and tissue edema by hematoxylin and eosin stain. We also conducted an immunohistochemical analysis with antibodies against CD68 antigens, monocyte chemoattractant protein-1 (MCP-1), Bcl-2, and caspase-9.

Results

The lungs subjected to ischemia-reperfusion injury exhibited a higher degree of inflammatory infiltration. The predominant cell type was monocyte-macrophage cells. Both findings were mitigated by intravenous lidocaine administration. Immunohistochemical detection of anti-CD68 and anti-MCP-1 showed higher infiltration in the lungs subjected to ischemia-reperfusion injury, while intravenous lidocaine decreased the expression. Ischemia-reperfusion induced apoptotic changes and decreased Bcl-2 expression. The group treated with lidocaine showed an increased number of Bcl-2-positive cells. No differences were observed in caspase-9 expression.

Conclusions

In our animal model, intravenous lidocaine was associated with an attenuation of the histological markers of lung damage in the early stages of reperfusion.

QSAR models for oxidation of organic micropollutants in water based on ozone and hydroxyl radical rate constants and their chemical classification

Ozonation is an oxidation process for the removal of organic micropollutants (OMPs) from water and the chemical reaction is governed by second-order kinetics. An advanced oxidation process (AOP), wherein the hydroxyl radicals (OH radicals) are generated, is more effective in removing a wider range of OMPs from water than direct ozonation. Second-order rate constants (k(OH) and k(O3) are good indices to estimate the oxidation efficiency, where higher rate constants indicate more rapid oxidation. In this study, quantitative structure activity relationships (QSAR) models for O(3) and AOP processes were developed, and rate constants, k(OH) and [Formula: see text] , were predicted based on target compound properties. The k(O3) and k(OH) values ranged from 5 * 10(-4) to 10(5) M(-1)s(-1) and 0.04 to 18 * (10(9)) M(-1) s(-1), respectively. Several molecular descriptors which potentially influence O(3) and OH radical oxidation were identified and studied. The QSAR-defining descriptors were double bond equivalence (DBE), ionisation potential (IP), electron-affinity (EA) and weakly-polar component of solvent accessible surface area (WPSA), and the chemical and statistical significance of these descriptors was discussed. Multiple linear regression was used to build the QSAR models, resulting in high goodness-of-fit, r(2) (>0.75). The models were validated by internal and external validation along with residual plots.

Evaluation of the irritating influence of carane derivatives and their antioxidant properties in a deoxyribose degradation test

Previous studies of the propranolol monoterpene derivative (-)-4-[2-hydroxy-3-(N-isopropylamino)-propoxyimino]-cis-carane hydrochloride (KP-23) and its diastereoisomers, KP-23R and KP-23S, demonstrated different effects on the cyclic AMP generating system as well as anti-inflammatory, analgesic, antihistaminic and antioxidant activity. The present study examined the influence of KP-23 and its diastereoisomers KP-23R and KP-23S on the skin-irritating activity and the mucous membrane-irritating activity as well as their influence on a late-type contact allergy in the in vivo tests. The hydroxyl radical scavenging potential of the three analogues was evaluated using their ability to inhibit Fe(II)/H2O2-induced oxidative degradation of 2-deoxyribose (2-DR) in the in vitro tests. The results obtained indicated that the hydroxyamine carane derivative did not evoke irritative changes and did not induce a late-type contact allergy in the guinea-pig. Diastereoisomers of KP-23 exhibit antioxidant properties in a dose-dependent manner and protected against OH-radicals generated from the Fenton reaction.

Postoperative atrial fibrillation

Postoperative atrial fibrillation (POAF) is common among surgical patients and associated with a worse outcome. Pathophysiology of POAF is not fully disclosed, and several perioperative factors could be involved. Direct cardiac stimulation from perioperative use of catecholamines or increased sympathetic outflow from volume loss/anaemia/pain may play a role. Metabolic alterations, such as hypo-/hyperglycaemia and electrolyte disturbances, may also contribute to POAF. Moreover, inflammation, both systemic and local, may play a role in its pathogenesis. Strategies to prevent POAF aim at reducing its incidence and ameliorate global outcome of surgical patients. Nonpharmacological prophylaxis includes an adequate control of postoperative pain, the use of thoracic epidural analgesia, optimization of perioperative oxygen delivery, and, possibly, modulation of surgery-associated inflammatory response with immunonutrition and antioxidants. Perioperative potassium and magnesium depletion should be corrected. The impact of those interventions on patients outcome needs to be further investigated.

Scirpusin A, a hydroxystilbene dimer from Xinjiang wine grape, acts as an effective singlet oxygen quencher and DNA damage protector

BACKGROUND

Grapes and red wines are rich sources of phenolic compounds such as anthocyanins, catechins, flavonols and stilbenes, most of which are potent antioxidants showing cardioprotective properties. We first isolated scirpusin A, a hydroxystilbene dimer, from a wine grape of Xinjiang, and studied its antioxidant activity.

RESULTS

Reactive oxygen species scavenging effects and the protection against reactive singlet oxygen-induced DNA damage of scirpusin A have been investigated in our experiments. The concentration of scirpusin A required to inhibit 50% of (1)O(2) generation was 17 micromol L(-1), while addition of scirpusin A at 140 micromol L(-1) caused complete inhibition. Further kinetic study revealed that the reaction of Scirpusin A with singlet oxygen has an extremely high rate constant (k(a) = 4.68 x 10(9) L mol(-1) s(-1)). Scirpusin A (140 micromol L(-1)) exhibited significant inhibition effects on pBR322 DNA breakage. However, scavenging effects of scirpusin A on superoxide anion O(2) (*-) and hydroxyl radical .OH were not potent as the inhibitor rates at a concentration of 1400 micromol L(-1) were 28.83% and 19.5%, respectively.

CONCLUSION

The present study shows that scirpusin A is a selective quencher of singlet oxygen and a protector against reactive singlet oxygen-induced pBR322 DNA damage at very low concentrations.

Use of vitamins C and E as a prophylactic therapy to prevent postoperative atrial fibrillation

Oxidative stress has been strongly involved in the underlying mechanism of atrial fibrillation, particularly in the arrhythmia occurring in patients undergoing cardiac surgery with extracorporeal circulation (postoperative atrial fibrillation). The ischemia/reperfusion injury thus occurring in the myocardial tissue contributes to the development of tissue remodeling, thought to be responsible for the functional heart impairment. Consequently, structural changes due to the cardiac tissue biomolecules attack by reactive oxygen and/or nitrogen species could account for functional changes in ion channels, transporters, membrane conductance, cytosolic transduction signals, and other events, all associated with the occurrence of arrhythmic consequences. The lack of success and significant side effects of anti-arrhythmic drugs have given rise to attempts aimed to develop alternative novel pharmacologic treatments. On this line, the biological properties of the antioxidant vitamins C and E suggest that they could decrease the vulnerability of the heart to the oxidative damage. Nevertheless, very few studies to assess their anti-arrhythmic effects have been reported in humans. The clinical and experimental evidence supporting the view that the pharmacological use of antioxidant vitamins could contribute to prevent postoperative atrial fibrillation is presented.

Targeting Cancer Cells by Novel Engineered Modular Transporters

A major problem in the treatment of cancer is the specific targeting of drugs to these abnormal cells. Ideally, such a drug should act over short distances to minimize damage to healthy cells and target subcellular compartments that have the highest sensitivity to the drug. We describe the novel approach of using modular recombinant transporters to target photosensitizers to the nucleus, where their action is most pronounced, of cancer cells overexpressing ErbB1 receptors. We have produced a new generation of the transporters consisting of (a) epidermal growth factor as the internalizable ligand module to ErbB1 receptors, (b) the optimized nuclear localization sequence of SV40 large T-antigen, (c) a translocation domain of diphtheria toxin as an endosomolytic module, and (d) the Escherichia coli hemoglobin-like protein HMP as a carrier module. The modules retained their functions within the transporter chimera: they showed high-affinity interactions with ErbB1 receptors and alpha/beta-importin dimers and formed holes in lipid bilayers at endosomal pH. A photosensitizer conjugated with the transporter produced singlet oxygen and (*)OH radicals similar to the free photosensitizer. Photosensitizers-transporter conjugates have >3,000 times greater efficacy than free photosensitizers for target cells and were not photocytotoxic at these concentrations for cells expressing a few ErbB1 receptors per cell, in contrast to free photosensitizers. The different modules of the transporters, which are highly expressed and easily purified to retain full activity of each of the modules, are interchangeable, meaning that they can be tailored for particular applications.

Redox-cycling of anthracyclines by thioredoxin system: increased superoxide generation and DNA damage

Anthracyclines such as doxorubicin and daunomycin undergo bioreductive activation by redox-cycling, and this is associated with generation of reactive oxygen species. Toxicity of anthracyclines is attributed to DNA intercalation by an anthracycline semiquinone radical that is generated via redox-cycling. Flavoprotein enzymes catalyze the bioreductive activation of anthracyclines. Thioredoxin reductase (TR), which is also a flavoprotein enzyme, participates in bioreductive activation of anthracyclines. In the present study we showed that addition of E. coli thioredoxin (Trx) enhances the rate of superoxide production by E. coli TR in the presence of anthracyclines. The superoxide generated in this redox-cycling process induced DNA damage as determined by an in vitro plasmid DNA damage assay. In addition, Trx-SH enhanced the activity of cyto-chrome P450 reductase and the redox-cycling of anthracyclines independently of NADPH. Furthermore,when A549 cells were incubated with E. coli Trx followed by doxorubicin treatment, increased levels of ROS generation were observed. Taken together, these results show a novel property of the Trx system in bioreductive activation of anthracyclines.

Lidocaine has better antioxidant potential than ropivacaine and bupivacaine: in vitro comparison in a model of human erythrocytes submitted to an oxidative stress

BACKGROUND

Local anesthetic agents may exert antioxidant properties in various models. The aim of this work was to compare the antioxidant properties of lidocaine, bupivacaine and ropivacaine using an in vitro model of human erythrocytes submitted to an oxidative stress.

METHODS

Blood was obtained from healthy volunteers. After separation, erythrocytes were suspended in phosphate buffer. Oxidative stress was induced by incubation with 2,2'-azobis (2-amidinopropane) hydrochloride (AAPH). (1) Effects of four different concentrations (50, 100, 300 and 600 microg ml(-1)) of lidocaine, bupivacaine and ropivacaine were studied in absence or presence of AAPH (20 mM). Potassium efflux was assessed by flame photometry. (2) Effects of 50 and 600 microg ml(-1) of lidocaine, bupivacaine and ropivacaine on AAPH (50 mM) induced hemolysis were also studied. (3) The oxygen radical absorbing capacity of lidocaine, bupivacaine and ropivacaine at the four concentrations was evaluated by the analysis of the allophycocyanin fluorescence.

RESULTS

In absence of AAPH, neither extracellular potassium nor hemolysis was noted. AAPH (20 mM) induced a significant increase in extracellular potassium that was reduced by all local anesthetic agents, with greater effects for lidocaine. AAPH-induced hemolysis was significantly decreased by all the local anesthetic agents at higher concentration, but only by lidocaine at 50 microg ml(-1). Finally, none of the local anesthetic agents modified the allophycocyanin fluorescence.

CONCLUSION

In this model, lidocaine was proved more effective than bupivacaine and ropivacaine in protecting human erythrocytes submitted to an oxidative challenge. This was not due to a free radical scavenging effect.

Curcumin (diferuloylmethane), a singlet oxygen ((1)O(2)) quencher

Curcumin (diferuloylmethane) is a major component of food flavoring turmeric (Curcuma longa), and has been reported to be anticarcinogenic and anti-inflammatory. Although curcumin was shown to have antioxidant properties, its exact antioxidant nature has not been fully investigated. In this report we have investigated the possible antioxidant properties of curcumin using EPR spectroscopic techniques. Curcumin was found to inhibit the (1)O(2)-dependent 2,2,6,6-tetramethylpiperidine N-oxyl (TEMPO) formation in a dose-dependent manner. (1)O(2) was produced in a photosensitizing system using rose bengal as sensitizer, and was detected as TEMP-(1)O(2) adducts by electron paramagnetic resonance (EPR) spectroscopic techniques using TEMP as a spin-trap. Curcumin at 2.75 microM caused 50% inhibition of TEMP-(1)O(2) adduct formation. However, curcumin only marginally inhibited (24% maximum at 80 microM) reduction of ferricytochrome c in a xanthine-xanthine oxidase system demonstrating that it is not an effective superoxide radical scavenger. Additionally, there was minor inhibition of DMPO-OH adduct formation by curcumin (solubilized in ethanol) when an ethanol control was included in the EPR spin-trapping study, suggesting that curcumin may not be an effective hydroxyl radical scavenger. Together these data demonstrate that curcumin is able only to effectively quench singlet oxygen at very low concentration in aqueous systems.

Scavenger effect of experimental and clinically used cardiovascular drugs

Oxygen free radicals play an important role in several physiologic and pathophysiologic processes. In pathophysiologic circumstances they can modify and damage biologic systems. Their functional properties (exposed to high oxygen tension) place red blood cells among the most susceptible cells to the harmful effect of free radicals. Because oxygen free radicals are involved in a wide range of diseases, scavenging these radicals should be an important therapeutic approach. In this study the antioxidant capacities of experimental and clinically used cardiovascular drugs were investigated. Phenazine methosulfate was used to generate free radicals and thus harden red blood cells. Filtration technique and potassium leaking were used to detect the scavenging effect of the examined drugs. The experimental drug H-2545 provided 43% protection against phenazine methosulfate-induced changes in red blood cell filterability (p < 0.001). Although some of the examined, clinically used cardiovascular drugs (carvedilol, metoprolol, verapamil, trimetazidine) also showed significant (p < 0.05) antioxidant effect, they were less efficient than H-2545. The scavenger effect of this novel drug exceeded the antioxidant properties of vitamin E. Modification of mexiletine with a pyrroline ring significantly improved its antioxidant capacity, suggesting that this molecular segment is responsible for the antioxidant effect.

Differentiation by in vitro treatment of lidocaine-epinephrine and prilocaine-felypressine in neutrophils

Neutrophils are often the first cells of the immune system to encounter an invader, such as bacteria and fungi. Lidocaine-epinephrine induced transient potentiation of the production of superoxide anion, while prilocaine-felypressine induced persistent inhibition of the production in neutrophils. Moreover, lidocaine-epinephrine inhibited the production of hydrogen peroxide in spite that it potentiated the production of superoxide anion, while prilocaine-felypressine inhibited the production of hydrogen peroxide as well as superoxide anion. By contrast, lidocaine-epinephrine and prilocaine-felypressine are both effective in significantly inhibiting adhesion and phagocytosis. Using flow cytometric analysis, both local anesthetics were found to be effective in inhibiting the expression of Mac-1 (CD11b/CD18) in neutrophils. These results suggest that lidocaine-epinephrine and prilocaine-felypressine differentially modulate the production of superoxide anion, and could similarly inhibit adhesion, phagocytosis, and the production of hydrogen peroxide by neutrophils.

Comparison of the effect of lidocaine-epinephrine and prilocaine-felypressine to alter macrophage functions

In vitro treatment of macrophages with lidocaine-epinephrine or prilocaine-felypressine resulted in inhibition of their adhesion, chemotaxis and phagocytosis. However, prilocaine-felypressine was a much more potent inhibitor of adhesion and phagocytosis than lidocaine-epinephrine. On the other hand, lidocaine-epinephrine induced transient potentiation of superoxide anion production by macrophages, while prilocaine-felypressine consistently inhibited this. Moreover, lidocaine-epinephrine and prilocaine-felypressine both inhibited the production of hydrogen peroxide. In contrast, epinephrine strongly potentiated superoxide anion production, while markedly inhibiting hydrogen peroxide production. This potentiation by epinephrine was not prevented by adrenergic antagonists. In addition, superoxide dismutase potentiated the production of hydrogen peroxide, which was in part prevented by epinephrine. These results suggest that lidocaine-epinephrine and prilocaine-felypressine inhibit adhesion, chemotaxis, phagocytosis, and the production of hydrogen peroxide by macrophages. In addition, lidocaine-epinephrine evidently differs from prilocaine-felypressine regarding the molecular mechanisms underlying the modulation of superoxide anion production by macrophages.

Thioredoxin, a singlet oxygen quencher and hydroxyl radical scavenger: redox independent functions

Thioredoxin is a ubiquitous small protein known to protect cells and tissues against oxidative stress. However, its exact antioxidant nature has not been elucidated. In this report, we present evidence that human thioredoxin is a powerful singlet oxygen quencher and hydroxyl radical scavenger. Human thioredoxin at 3 microM caused 50% inhibition of TEMP-(1)O(2) (TEMPO) adduct formation in a photolysis EPR study. In contrast, Escherichia coli thioredoxin caused 50% inhibition of TEMPO formation at 80 microM. Both E. coli thioredoxin and human thioredoxin inhibited (*)OH dependent DMPO-OH formation as demonstrated by EPR spectrometry. The quenching of (1)O(2) or scavenging of (*)OH was not dependent upon the redox state of thioredoxin. Using a human thioredoxin in which the structural cysteines were mutated to alanine, Trx-C3A, we show that structural cysteines that do not take part in the catalytic functions of the protein are also important for its reactive oxygen scavenging properties. In addition, using a quadruple mutant Trx-C4A, where one of the catalytic cysteines, C35 was mutated to alanine in addition to the mutated structural cysteines, we demonstrated that catalytic cysteines are also required for the scavenging action of thioredoxin. Identification of thioredoxin as a (1)O(2) quencher and (*)OH scavenger may be of significant importance in explaining various redox-related antioxidant functions of thioredoxin.

In vitro study on antioxidant potential of various drugs used in the perioperative period

BACKGROUND

Since surgical trauma not only intensifies the oxidative stress by generating reactive oxygen species (ROS), but also weakens the biological defense system against ROS attack, the antioxidant activity of drugs used during the perioperative period, which possibly normalizes the impaired redox state in the patient, is of fundamental importance and great clinical interest.

METHODS

We have applied the phycoerythrin fluorescence-based assay, in which 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH)-generated peroxyl radical attacks B-phycoerythrin (B-PE) to lead to a sensitive decrease in its fluorescence intensity linearly, to evaluate the antioxidant activity of major drugs in anesthetic practice.

RESULTS

By the protective effect on B-PE fluorescence decay, the antioxidant activities of the drugs were classified into three groups: Group I drugs, which only slowed B-PE fluorescence decay (nicardipine, verapamil, diltiazem, ephedrine, aminophylline, vecuronium, lidocaine, mepivacaine, midazolam, thiamylal, droperidol, ketamine, hydroxyzine, butorphanol, prednisolone, hydrocortisone, betamethasone, dexamethasone, methylprednisolone, and furosemide); Group II drugs, which protected B-PE oxidation completely and stopped fluorescence decay in a certain duration (dopamine, epinephrine, norepinephrine, dobutamine, isoproterenol, and buprenorphine); and Group III drugs, which had no protective effect on B-PE oxidation (nitroglycerin, prostaglandin E1, neostigmine, pancuronium, suxamethonium, atropine, bupivacaine, pentazocine, and heparin).

CONCLUSION

These results indicate that Group I and II drugs exert some antioxidant activity in vitro, as measured by their protection of fluorescence decay of B-PE. Careful consideration of these properties might, then, serve to facilitate more efficient drug application.

Nonsteroidal antiinflammatory drugs interact with horseradish peroxidase in an in vitro assay system for hydrogen peroxide scavenging

The established horseradish peroxidase/guaiacol in an in vitro assay system was used for investigation of the reactivity of nonsteroidal antiinflammatory drugs with hydrogen peroxide. Although the drugs rapidly seemed to react in the selected conditions, difficulties were encountered in attempts to quantify the reaction and an interaction with horseradish peroxidase was suspected. A more specific assay system based on the absolute specificity of the enzyme glutathione peroxidase for glutathione was subsequently used which demonstrated that none of the investigated nonsteroidal antiinflammatory drugs was able to scavenge hydrogen peroxide. An original procedure to further evidence the interaction was developed thereafter, based on the reaction of 5-aminosalicylic acid with similar hemoproteins. This led to the demonstration that nonsteroidal antiinflammatory drugs were substrates for horseradish peroxidase and explained their reactivity in the horseradish peroxidase/guaiacol assay system. The compound 5-aminosalicylic acid showed an unusual behaviour that was attributed to its ability to both scavenge hydrogen peroxide and interact with horseradish peroxidase. It was concluded that the lack of specificity of horseradish peroxidase for its donor substrate may lead to erroneous results in assays for hydrogen peroxide scavenging of some drugs. An alternative method is however available and a simple spectroscopic assay can evidence the interaction with horseradish peroxidase.

Impairment of raw 264.7 macrophage function by antiarrhythmic drugs

The effect of the antiarrhythmic drugs lidocaine, quinidine and procainamide on macrophage function was investigated in RAW 264.7 mouse monocytic macrophage cell. Cells stimulated by either zymosan or phorbol ester were found to generate both superoxide (O2-) and H2O2. The production of O2 was detected as superoxide dismutase inhibitable ferricytochrome c reduction. H2O2 production was monitored in both chemical and flow cytometric fluorescent assays. Although all three drugs inhibited both O2 and H2O2 release in a dose-dependent manner, only quinidine was found to have significant inhibitory effects. The amounts of quinidine required to cause a 50% inhibition in O2 production in zymosan and phorbol ester stimulated cells were found to be 250 microM and 300 microM, respectively and the amounts required to cause one-half optimum levels of H2O2 production in these cells were found to be 50 microM and 100 microM, respectively. The effect of these drugs on O2 producing NADPH oxidase was investigated and only procainamide was found to have a significant effect (p < 0.001) in inhibiting the oxidase activity. Lidocaine and quinidine had no significant effect on the activation of the respiratory burst oxidase. A sensitive and convenient 'differential phagocytosis' assay was devised on the basis of number of particles engulfed by individual phagocytes using flow cytometric techniques. It appears to be remarkably free of interference and was applied to investigate the role of antiarrhythmic drugs on the phagocytosis of fluorescent latex beads. All three antiarrhythmic drugs inhibited phagocytosis of latex beads in a dose dependent manner irrespective of the number of particles phagocitized by the cells. The results of these studies do not conclusively establish a mechanism of action of these drugs on the generation of O2 and H2O2 by stimulated macrophages; nevertheless, it is interesting that all three drugs inhibited the phagocytic activity.