The use of topical corneal anaesthetics for pain relief after cor

The use of topical corneal anaesthetics for pain relief after corneal abrasion also seems to have limited use [24]; Bisla and Tanelian examined epithelial regeneration in the presence of lidocaine 100–1000 µg/ml, and observed a dose-dependent impairment of epithelial wound healing with concentrations higher than 250 µg/ml, which would also demonstrate the negative

effect of LA [24]. All these studies demonstrated potential harm using local anaesthetics, but did not specify the exact impairment mechanism. Results from our study confirm other experimental findings, demonstrating that bupivacaine has a higher toxicity potential compared to lidocaine and ropivacaine [25,26]. In addition, it corroborates the results from Sturrock and Nunn, demonstrating compromised

cell survival in hamster lung fibroblasts with an effective dose (ED50) of 0·06% for bupivacaine compared to 0·09% for lidocaine [27]. The present study suggests that the learn more observed cell death is not BMS-777607 purchase due mainly to increased apoptosis rate, as activity of caspase-3 was correlated significantly with the amount of living cells. An exception was observed for the short stimulation period of 3 days for bupivacaine and ropivacaine. Caspase-independent mechanisms of cell death have been described in LA-induced cytotoxicity due to a change in intracellular Ca2+ homeostasis [28–33]. It is postulated in myocytes that LA induce Ca2+ release from the sarcoplasmic reticulum by interaction with ryanodine receptors [34,35]. Other studies have suggested an inhibition of Ca2+ reuptake into the sarcoplasmic reticulum, possibly regulated by Ca2+ ATPase activity [34,36]. Besides dysregulated intracellular Ca2+, the involvement

of ROS production is another possible mechanism of LA-induced cell death [37,38]. As described for cocaine, LA and/or its oxidative metabolites might trigger ROS release, which has a toxic effect on hepatocytes [37,38]. Other authors claimed a correlation between the dysregulation of mitochondrial Ca2+ and ROS production, therefore reflecting a possible combination of the two proposed insult pathways [39]. A trigger such as LA or, as O-methylated flavonoid described by Brookes et al., ischaemia/reperfusion, might lead to a mitochondrial Ca2+ overload, mitochondrial dysfunction and ROS production which exacerbates mitochondrial damage [39]. However, cytotoxic effects of LA have been described in several studies without elucidation of the underlying mechanism [10,40,41]. Park et al. have shown increased ROS concentration correlating with cell death of Schwann cells after incubation with bupivacaine [42]. The authors thereby suggested a ROS-triggered caspase-3-activated apoptosis in neuronal cells. These conclusions were supported by results from Perez-Castro, which showed caspase-3/-7 activation in human neuroblastoma cells after 10 min incubation with lidocaine, ropivacaine and bupivacaine [43].

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