Dexmedetomidine Attenuates Glutamate-Induced Cytotoxicity by Inhibiting the Mitochondrial-Mediated Apoptotic Pathway

Abstract

BACKGROUND Glutamate (GLU) is the most excitatory amino acid in the central nervous system and plays an important role in maintaining the normal function of the nervous system. During cerebral ischemia, massive release of GLU leads to neuronal necrosis and apoptosis. It has been reported that dexmedetomidine (DEX) possesses anti-oxidant and anti-apoptotic properties. The objective of this study was to investigate the effects of DEX on GLU-induced neurotoxicity in PC12 cells. MATERIAL AND METHODS PC12 cells were treated with 20 mM GLU to establish an ischemia-induced injury model. Cell viability was accessed by MTT assay. MDA content and SOD activity were analyzed by assay kits. Apoptosis rate, ROS production, intracellular Ca²⁺ concentration, and MMP were evaluated by flow cytometry. Western blot analysis was performed to analyze expressions of caspase-3, caspase-9, cyt-c, bax, and bcl-2. RESULTS PC12 cells treated with GLU exhibited reduced cell viability and increased apoptosis rates, which were ameliorated by pretreatment with DEX. DEX significantly increased SOD activity, reduced content of MDA, and decreased production of ROS in PC12 cells. In addition, DEX clearly reduced the level of intracellular Ca²⁺ and attenuated the decline of MMP. Moreover, DEX notably reduced expressions of caspase-3, caspase-9, cyt-c, and bax and increased expression of bcl-2. CONCLUSIONS Our findings suggest that DEX can protect PC12 cells against GLU-induced cytotoxicity, which may be attributed to its anti-oxidative property and reduction of intracellular calcium overload, as well as its ability to inhibit the mitochondria-mediated apoptotic pathway.

Figure 1

Effect of DEX on cell viability rate (A) and apoptosis rate (B) in GLU-injured PC12 cells. The data are represented as mean±SE. n=6. * p<0.05 vs. Con group, ^# p<0.05 vs. GLU group.

Figure 2

Effect of DEX on MDA content (A), SOD activity (B), and ROS level (C) in GLU-exposed PC12 cells. The data are represented as mean±SE. n=6. * p<0.05 vs. Con group; ^# p<0.05 vs. GLU group

Figure 3

Effect of DEX on level of intracellular ca2+ by MFI of Fluo8 in GLU-induced PC12 cells. The data are represented as mean±SE of 3 independent experiments. * p<0.05 vs. Con group, ^# p<0.05 vs. GLU group.

Figure 4

Effect of DEX on mitochondrial membrane potential (MMP) by ratio of MFI of J-aggregates to JC-1 in GLU-induced PC12 cells. The data are represented as mean±SE, n=6. * p<0.05 vs. Con group, ^# p<0.05 vs. GLU group.

Figure 5

Effect of DEX on the protein expression of caspase-3 (A), caspase-9 (B), cyt-c (C), bax (D), and bcl-2 (E) in GLU-injured PC12 cells. The data are represented as mean±SE of 3 independent experiments. * p<0.05 vs. Con group, ^# p<0.05 vs. GLU group.