Abstract
Ketamine is a widely used anesthetic in pediatric clinical practice. Previous studies have demonstrated that ketamine induces neurotoxicity and has a modulatory effect on the cells of the immune system. Here, we evaluated the potential protective effect and underlying mechanisms of natural phenolic compound curcumin against ketamine-induced toxicity in rat thymocytes. Rat thymocytes were exposed to 100 µM ketamine alone or combined with increasing concentrations of curcumin (0.3, 1, and 3 μM) for 24 hours. Cell viability was analyzed with CCK-8 assay kit. Apoptosis was analyzed using flow cytometry and propidium iodide as well as Z-VAD-FMK and Z-LEHD-FMK inhibitors. Reactive oxygen species (ROS) production and mitochondrial membrane potential [MMP] were measured by flow cytometry. Colorimetric assay with DEVD-pNA substrate was used for assessing caspase-3 activity. Involvement of phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway was tested with Wortmannin inhibitor. Ketamine induced toxicity in cells, increased the number of hypodiploid cells, caspase-3 activity and ROS production, and inhibited the MMP. Co-incubation of higher concentrations of curcumin (1 and 3 μM) with ketamine markedly decreased cytotoxicity, apoptosis rate, caspase-3 activity, and ROS production in rat thymocytes, and increased the MMP. Application of Z-VAD-FMK (a pan caspase inhibitor) or Z-LEHD-FMK (caspase-9 inhibitor) with ketamine effectively attenuated the ketamine-induced apoptosis in rat thymocytes. Administration of Wortmannin (a PI3K inhibitor) with curcumin and ketamine significantly decreased the protective effect of curcumin on rat thymocytes. Our results indicate that ketamine-induced toxicity in rat thymocytes mainly occurs through the mitochondria-mediated apoptotic pathway and that the PI3K/Akt signaling pathway is involved in the anti-apoptotic effect of curcumin.
Highlights
Ketamine, a noncompetitive N-methyl-D-aspartic acid (NMDA) receptor antagonist, is a widely used intravenous anesthetic in pediatric anesthesia, for sedation and/or analgesia of children during painful procedures
We found that the co-incubation of thymocytes with 1 or 3 μM curcumin and 100 μM ketamine resulted in markedly decreased ketamine-induced toxicity and apoptosis rate
Our results showed that the inhibitory effect of curcumin on caspase-3 activity was significantly suppressed by the phosphoinositide 3-kinase (PI3K)/Akt inhibitor Wortmannin, suggesting that the PI3K/Akt pathway is required for the anti-apoptotic effects of curcumin in ketamine-induced rat thymocytes
Summary
A noncompetitive N-methyl-D-aspartic acid (NMDA) receptor antagonist, is a widely used intravenous anesthetic in pediatric anesthesia, for sedation and/or analgesia of children during painful procedures. Submitted: 30 October 2017/Accepted: 08 December 2017 use in anesthesia, different in vivo studies showed the ability of ketamine to induce neurotoxic effects in the immature brain of primates and rodents [2,3]. The toxic effect of ketamine was confirmed in in vitro studies, demonstrating the pro-apoptotic potential of ketamine in neurons [4,5] and cells of the immune system [6]. These findings raised the concern whether similar toxicity occurs in the human brain or other developing organs. The precise mechanism of ketamine toxicity still remains unclear, even though most of the studies suggested apoptosis as a common mechanism involved in ketamine-induced toxicity [7]
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