Evaluation of antioxidant activities of local anesthetics by chemiluminescence

Some of the local anesthetics are known to impair leukocyte functions and inhibit lysosomal enzyme release. The ability of local anesthetics to inhibit reactive oxygen and nitrogen species generated by stimulated human leukocytes or cell-free systems either chemically or enzymatically was investigated by using luminol- and lucigenin-enhanced chemiluminescence (CL). Leukocytes were isolated from citrated human venous blood with dextran sedimentation and studied. A luminometer was used to assay free radical generation. The reaction mixture contained 106 cells mL"1, luminol plus the stimulant (Formyl-methionyl-leucyl-phenylalanine=FMLP, 2 uM) at 37°C. In cell-free experiments, hydrogen peroxide (H2O2), hypochlorous acid (HOC1), hydroxyl radical and peroxynitrite-induced luminol and/or lucigenin CL were produced by H202 (3.5 mM), sodium hypochloride (5 uM), FeSC«4 (40 nM), peroxynitrite (50 nM) and xanthine (0.1 mmol/L) with xanthine oxidase (0.2U/mL). The effects of local anesthetics were examined by adding it immediately prior to the administration of stimulant agent. Following peak CL measurement, the effects of local anesthetics were expressed as % change from the response to the stimulant alone.?56^ Lidocaine, prilocaine, bupivacaine and tetracaine inhibited FMLP induced-CL concentration dependently in isolated human leukocytes, whereas articaine activated at high concentrations. In cell free experiments, all of the studied local anesthetics markedly inhibited xanthine-xanthine oxidase induced- CL in a concentration dependent mannner. However, lidocaine, bupivacaine and tetracaine markedly activated hydrogen peroxide induced-CL while prilocaine inhibited. Additionally, prilocaine, articaine and tetracaine inhibited hydrogen peroxide induced lucigenin enhanced-CL. Only tetracaine inhibited ferrous iron- induced CL. All of the 5 local anesthetics inhibited hypochlorous acid induced CL. Other local anesthetics except prilocaine inhibited peroxynitrite induced luminol enhanced CL. The local anesthetics except prilocaine and bupivacaine inhibited peroxynitirite induced lucigenin enhanced CL. In conclusion, local anesthetics interacted with most of the free radicals and its metabolites, which could be considered to be responsible from the inhibition observed in isolated human neutrophils. Those results might contribute to the development of new molecules possessing antioxidant activities in accordance with the chemical structure of the local anesthetics.