Yongwei Wang1, Luying Lai1, Wenjing Guo1, Shenghui Peng2, Ruimeng Liu3, Pu Hong1, Guanshan Wei1, Fengxian Li1, Shan Jiang1, Pei Wang1, Ji Li1, Hongyi Lei1, Wei Zhao4, Shiyuan Xu5. 1. Department of Anesthesiology, Zhujiang Hospital, Southern Medical University, No. 253 Middle Gongye Street, Guangzhou, Guangdong Province, 510282, China. 2. Department of Rehabilitation, Zhujiang Hospital, Southern Medical University, No. 253 Middle Gongye Street, Guangzhou, Guangdong Province, 510282, China. 3. Department of Anesthesiology, Shenzhen Hospital, Southern Medical University, No. 1333, Xinhu Road, Baoan District, Shenzhen, Guangdong Province, 518110, China. 4. Department of Anesthesiology, Zhujiang Hospital, Southern Medical University, No. 253 Middle Gongye Street, Guangzhou, Guangdong Province, 510282, China. Electronic address: zw618812@smu.edu.cn. 5. Department of Anesthesiology, Zhujiang Hospital, Southern Medical University, No. 253 Middle Gongye Street, Guangzhou, Guangdong Province, 510282, China. Electronic address: xsy998@smu.edu.cn.
Abstract
BACKGROUND: Bupivacaine (BP) is commonly used as a local anaesthetic(LA) in the clinic, but it can also cause neurotoxicity, especially in patients with diabetes. Previous studies have found that high-glucose environments can aggravate BP-induced DNA damage in nerve cells. Ku70 is subunit of the DNA damage repair enzyme DNA-PK. This study was designed to determine whether high-glucose conditions enhance BP neurotoxicity and DNA damage by inhibiting Ku70 expression. METHODS: We examined the effect of BP on apoptosis and DNA damage in murine dorsal root ganglion (DRG) neurons under hyperglycaemic conditions. Untreated DRG cells and DRG cells pretreated with NU7441, a DNA-PK inhibitor, were cultured for 3 days under normal culture conditions or with 50 mM glucose, and the cells were then treated with BP for 3 h. DNA damage was investigated via comet assays, the ratio of early to late apoptotic cells was assessed by Annexin V-FITC/PI staining, and cell viability was measured by CCK-8 assays. The protein expression levels of DNA-PK, Ku70, Bax, Bcl-2 and γH2ax were measured by immunofluorescence or Western blotting. RESULTS: Compared to its effect under normal culture conditions, BP treatment led to decreased cell viability and increased DNA damage in DRG cells grown under high-glucose conditions. The rate of DRG cell apoptosis and the expression of γH2ax, the ratio of Bax to Bcl-2 also increased under the high-glucose conditions. Furthermore, Ku70 expression was inhibited. The DNA-PK inhibitor, NU7441, could significantly inhibit DNA-PK and Ku70 expression, simultaneously further aggravating BP-induced apoptosis and DNA damage under high-glucose conditions. CONCLUSION: These data indicate that hyperglycaemia may enhance BP-induced neurotoxicity and DNA damage by inhibiting the DNA repair protein Ku70.
BACKGROUND:Bupivacaine (BP) is commonly used as a local anaesthetic(LA) in the clinic, but it can also cause neurotoxicity, especially in patients with diabetes. Previous studies have found that high-glucose environments can aggravate BP-induced DNA damage in nerve cells. Ku70 is subunit of the DNA damage repair enzyme DNA-PK. This study was designed to determine whether high-glucose conditions enhance BPneurotoxicity and DNA damage by inhibiting Ku70 expression. METHODS: We examined the effect of BP on apoptosis and DNA damage in murine dorsal root ganglion (DRG) neurons under hyperglycaemic conditions. Untreated DRG cells and DRG cells pretreated with NU7441, a DNA-PK inhibitor, were cultured for 3 days under normal culture conditions or with 50 mM glucose, and the cells were then treated with BP for 3 h. DNA damage was investigated via comet assays, the ratio of early to late apoptotic cells was assessed by Annexin V-FITC/PI staining, and cell viability was measured by CCK-8 assays. The protein expression levels of DNA-PK, Ku70, Bax, Bcl-2 and γH2ax were measured by immunofluorescence or Western blotting. RESULTS: Compared to its effect under normal culture conditions, BP treatment led to decreased cell viability and increased DNA damage in DRG cells grown under high-glucose conditions. The rate of DRG cell apoptosis and the expression of γH2ax, the ratio of Bax to Bcl-2 also increased under the high-glucose conditions. Furthermore, Ku70 expression was inhibited. The DNA-PK inhibitor, NU7441, could significantly inhibit DNA-PK and Ku70 expression, simultaneously further aggravating BP-induced apoptosis and DNA damage under high-glucose conditions. CONCLUSION: These data indicate that hyperglycaemia may enhance BP-induced neurotoxicity and DNA damage by inhibiting the DNA repair protein Ku70.