The effects of lidocaine on superoxide production and p47 Phox translocation in opsonized zymosan-activated neutrophils

Lidocaine Prevents Oxidative Stress-Induced Endothelial Dysfunction of the Systemic Artery in Rats With Intermittent Periodontal Inflammation

BACKGROUND

Periodontal inflammation causes endothelial dysfunction of the systemic artery. However, it is unknown whether the use of local anesthetics during painful dental procedures alleviates periodontal inflammation and systemic endothelial function. This study was designed to examine whether the gingival or systemic injection of lidocaine prevents oxidative stress-induced endothelial dysfunction of the systemic artery in rats with intermittent periodontal inflammation caused by lipopolysaccharides (LPS).

METHODS

Some rats received 1500 µg LPS injections to the gingiva during a week interval from the age of 8 to 11 weeks (LPS group). Lidocaine (3 mg/kg), LPS + lidocaine (3 mg/kg), LPS + lidocaine (1.5 mg/kg), and LPS + lidocaine (3 mg/kg, IP) groups simultaneously received gingival 1.5 or 3 mg/kg or IP 3 mg/kg injection of lidocaine on the same schedule as the gingival LPS. Isolated aortas or mandibles were subjected to the evaluation of histopathologic change, isometric force recording, reactive oxygen species, and Western immunoblotting.

RESULTS

Mean blood pressure and heart rate did not differ among the control, LPS, LPS + lidocaine (3 mg/kg), and lidocaine (3 mg/kg) groups. LPS application reduced acetylcholine (ACh, 10 to 10 mol/L)-induced relaxation (29% difference at ACh 3 × 10 mol/L, P = .01), which was restored by catalase. Gingival lidocaine (1.5 and 3 mg/kg) dose dependently prevented the endothelial dysfunction caused by LPS application (24.5%-31.1% difference at ACh 3 × 10 mol/L, P = .006 or .001, respectively). Similar to the gingival application, the IP injection of lidocaine (3 mg/kg) restored the ACh-induced dilation of isolated aortas from rats with the LPS application (27.5% difference at ACh 3 × 10 mol/L, P < .001). Levels of reactive oxygen species were double in aortas from the LPS group (P < .001), whereas the increment was abolished by polyethylene glycol-catalase, gingival lidocaine (3 mg/kg), or the combination. The LPS induced a 4-fold increase in the protein expression of tumor necrosis factor-α in the periodontal tissue (P < .001), whereas the lidocaine (3 mg/kg) coadministration partly reduced the levels. Lidocaine application also decreased the protein expression of the nicotinamide adenine dinucleotide phosphate oxidase subunit p47phox, which was enhanced by the gingival LPS (5.6-fold increase; P < .001).

CONCLUSIONS

Lidocaine preserved the aortic endothelial function through a decrease in arterial reactive oxygen species produced by nicotinamide adenine dinucleotide phosphate oxidase and periodontal tumor necrosis factor-α levels in rats with periodontal inflammation. These results suggest the beneficial effect of the gingival application of local anesthetics on the treatment of periodontal diseases on endothelial function of systemic arteries.

Effects of local anesthetics on the respiratory burst of cord blood neutrophils in vitro

BACKGROUND

Whether local anesthetics exert anti-inflammatory effects in fetal and newborn systemic neutrophils is unclear. The aim of the present study was to assess the effects of bupivacaine and lidocaine on the respiratory burst of cord blood neutrophils in vitro compared with adult cells.

METHODS

Whole cord blood (n = 12) and control adult blood samples (n = 7) were incubated with bupivacaine (0.0005, 0.005, 0.05, 1 mmol/l) and lidocaine (0.002, 0.02, 0.2, 4 mmol/l) for 1 and 4 h. The production of reactive oxygen species (ROS) by unstimulated neutrophils and the phorbol myristate acetate-induced oxidative burst were assessed by flow cytometry. A subset of neutrophils showing high fluorescence intensity (rho+) was analyzed separately.

RESULTS

After 1 h incubation, local anesthetics decreased the respiratory burst in whole cord blood and adult neutrophils in a similar manner. At the clinically relevant concentration of 0.0005 mmol/l, bupivacaine was active, but its effect in cord blood cells could not be detected after 4 h. The cord blood rho+ cell subset was unresponsive to the inhibitory action of bupivacaine. In rho+ neutrophils, basal ROS production was stimulated by lidocaine at the lowest concentration tested.

CONCLUSION

Bupivacaine and lidocaine can decrease the respiratory burst in neutrophils of term newborns.

Inhibition of voltage-gated proton channels by local anaesthetics in GMI-R1 rat microglia

Voltage-gated proton channels play crucial roles during the respiratory burst in phagocytes, such as microglia. As local anaesthetics have a variety of anti-inflammatory properties, including inhibition of phagocytosis, they may act on the proton channels. Most local anaesthetics are tertiary amines and may affect proton channels through modification of pH(i) as weak bases. To test these hypotheses, the effects of lidocaine and bupivacaine on proton channels were examined in a rat microglial cell line (GMI-R1) as a function of pH(o) and pH(i). Both lidocaine and bupivacaine reversibly decreased the current, with IC(50) values of ∼1.2 and ∼0.5 mM, respectively, at pH(o)/pH(i) 7.3/5.5. The inhibition was enhanced with either pH(o) increase or pH(i) decrease, suggesting that the protonation of the base forms inside the cell contributed to the inhibitory effects. Both local anaesthetics shifted the reversal potentials to more positive voltages, indicating increases in pH(i). The potencies of inhibition were correlated well with the degree of increase in pH(i). The lidocaine-induced inhibition was eliminated when the pH(i) increases were cancelled by co-application of a weak acid, butyrate. The cytosolic alkalizations by lidocaine and bupivacaine were confirmed using a pH-sensitive fluorescent dye, BCECF, in non-voltage-clamped cells. Furthermore, chemiluminescence measurement proved that both anaesthetics inhibited production of reactive oxygen species by the cells. In conclusion, lidocaine and bupivacaine inhibit proton channels primarily by the weak base mechanism via an increase in pH(i). This is a novel mechanism underlying actions of local anaesthtics.

Study of monocyte membrane proteome perturbation during lipopolysaccharide-induced tolerance using iTRAQ-based quantitative proteomic approach

Human monocytes' exposure to low-level lipopolysaccharide (LPS) induces temporary monocytic insensitivity to subsequent LPS challenge. The underlying mechanism of this phenomenon could have important clinical utilities in preventing and/or treating severe infections. In this study, we used an iTRAQ-based quantitative proteomic approach to comprehensively characterize the membrane proteomes of monocytes before and after LPS exposure. We identified a total of 1651 proteins, of which 53.6% were membrane proteins. Ninety-four percent of the proteins were quantified and 255 proteins were shown to be tightly regulated by LPS. Subcellular location analysis revealed organelle-specific response to LPS exposure: more than 90% of identified mitochondrial membrane proteins were significant downregulated, whereas the majority of proteins from other organelles such as ER, Golgi and ribosome were upregulated. Moreover, we found that the expression of most receptors potentially involved in LPS signal pathway (CD14, toll-like receptor 4, CD11/CD18 complex) were substantially decreased, while the expression of molecules involved in LPS neutralization were enhanced after LPS challenge. Together, these findings could be of significance in understanding the mechanism of LPS tolerance and provide values for designing new approaches for regulating monocytic responses in sepsis patients.

Effects of Edaravone on Singlet Oxygen Released From Activated Human Neutrophils

The effects of edaravone, a curative agent for acute brain infarction, on singlet oxygen ((1)O2) released from activated human neutrophils were examined, and the effects were compared to those of histidine, a (1)O2 singlet oxygen scavenger. The neutrophils, stimulated with opsonized zymosan, released (1)O2 that was detected by chemiluminescence using a (1)O2 specific probe, trans-1-(2'-methoxyvinyl)pyrene. Edaravone dose-dependently suppressed the (1)O2 release with an IC(50) of approximately 0.3 microM, while the IC(50) of histidine was approximately 1 mM. This (1)O2 scavenging activity of edaravone might be involved in its curative effects on acute brain infarction.

Anti-inflammatory properties of local anesthetics and their present and potential clinical implications

Development of new local anesthetic agents has been focused on the potency of their nerve-blocking effects, duration of action and safety and has resulted in a substantial number of agents in clinical use. It is well established and well documented that the nerve blocking effects of local anesthetics are secondary to their interaction with the Na+ channels thereby blocking nerve membrane excitability and the generation of action potentials. Accumulating data suggest however that local anesthetics also possess a wide range of anti-inflammatory actions through their effects on cells of the immune system, as well as on other cells, e.g. microorganisms, thrombocytes and erythrocytes. The potent anti-inflammatory properties of local anesthetics, superior in several aspects to traditional anti-inflammatory agents of the NSAID and steroid groups and with fewer side-effects, has prompted clinicians to introduce them in the treatment of various inflammation-related conditions and diseases. They have proved successful in the treatment of burn injuries, interstitial cystitis, ulcerative proctitis, arthritis and herpes simplex infections. The detailed mechanisms of action are not fully understood but seem to involve a reversible interaction with membrane proteins and lipids thus regulating cell metabolic activity, migration, exocytosis and phagocytosis.