Research on ketamine in mediating autophagy and inhibiting apoptosis of astrocytes in cerebral cortex of rats through NF-κB pathway

J. Yang, X. Li, C. Yang, X.-X. Bu, J. Shen, T. Hong

Department of Anesthesiology, First People’s Hospital of Changzhou & Third Affiliated Hospital of Suzhou University, Changzhou, Jiangsu, China. TaoHonghj@163.com

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• Pharmacology

OBJECTIVE: To investigate the effects of ketamine on autophagy and apoptosis of astrocytes in the cerebral cortex of rats, and determine whether nuclear factor-κB (NF-κB) pathway is involved in the regulation of autophagy and apoptosis of astrocytes.

MATERIALS AND METHODS: A total of 36 male Sprague-Dawley (SD) rats were randomly divided into 3 groups: control group (Group C: intraperitoneal injection of equal amount of normal saline), glutamic acid group (Group G: intraperitoneal injection of 1 mg/kg glutamic acid) and glutamic acid + ketamine group (Group GK: intraperitoneal injection of 1 mg/kg glutamic acid and then injection of 5 mg/kg ketamine after 30 min). The cerebral cortex of rats in each group was taken after successive administration for 5 d. The number of glial fibrillary acidic protein (GFAP)-positive cells in the cerebral cortex of rats in each group was detected via immunofluorescence. The number of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells (apoptotic cells) in the cerebral cortex was detected via TUNEL staining. The levels of inflammatory factors were detected using the enzyme-linked immunosorbent assay (ELISA) kit. Moreover, the expressions of autophagy-related proteins and apoptosis-related proteins in the cerebral cortex were detected via Western blotting, and the expressions of IκB-a and NF-κBp65 were also detected.

RESULTS: The results of immunofluorescence showed that the number of GFAP-positive cells in the cerebral cortex of rats in Group G was significantly increased compared with that in Group C (p<0.01), and it was significantly decreased in Group GK compared with that in Group G (p<0.01). The results of TUNEL staining revealed that the number of TUNEL-positive cells in the cerebral cortex in Group G was significantly larger than that in Group C, and it was significantly smaller in Group GK than that in Group G (p<0.01). Results of ELISA demonstrated that compared with those in Group C, the contents of interleukin-6 (IL-6) and tumor necrosis factor-a (TNF-a) in Group G were significantly increased (p<0.01), but the content of IL-10 was significantly decreased (p<0.01). Compared with those in Group G, the contents of IL-6 and TNF-a in Group GK were significantly decreased (p<0.01), but the level of IL-10 was statistically elevated (p<0.01). Compared with those in Group C, the levels of LC3 II/I and cleaved caspase-3 in the cerebral cortex in Group G were significantly increased (p<0.01), but the p62 level and B-cell lymphoma-2/Bcl-2 associated X protein (Bcl-2/Bax) ratio were significantly decreased (p<0.01). In Group GK, the levels of LC3 II/I and cleaved caspase-3 were reduced, but the p62 level and Bcl-2/Bax ratio were increased. The expressions of IκB-α and NF-κBp65 in Group G were significantly decreased compared with those in Group C (p<0.01), and they were significantly higher in Group GK than those in Group G (p<0.01).

CONCLUSIONS: Ketamine can reduce the glutamic acid-induced activation of astrocytes in the cerebral cortex, inhibit the autophagy and alleviate the apoptosis of astrocytes, the process of which is mediated by the NF-κB pathway, which provides the new molecular basis of ketamine in protecting astrocytes.

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