Effect and mechanism of inhibition of PI3K/Akt/mTOR signal pathway on chronic neuropathic pain and spinal microglia in a rat model of chronic constriction injury

Abstract

// Jian-Rong Guo 1 , Huan Wang 1 , Xiao-Ju Jin 2 , Dong-Lin Jia 3 , Xun Zhou 1 and Qiang Tao 1 1 Department of Anesthesiology, Gongli Hospital, Second Military Medical University, Shanghai 200135, P.R. China 2 Department of Anesthesiology, Yijishan Hospital, Wannan Medical College, Wuhu 241001, P.R. China 3 Pain Department, Peking University Third Hospital, Beijing, 100191, P.R. China Correspondence to: Jian-Rong Guo, email: jr_guo@yeah.net Keywords: PI3K/Akt/mTOR signal pathway, chronic neuropathic pain, spinal microglia, chronic constriction injury, wortmannin Received: July 26, 2016     Accepted: January 03, 2017     Published: May 05, 2017 ABSTRACT Objective: To explore the effects of inhibition of PI3K/Akt/mTOR signal pathway on chronic neuropathic pain (CNP) and spinal microglia in a rat model of chronic constriction injury (CCI). Methods: Male SD rats were assigned into control, sham, CCI, wortmannin, dimethyl sulfoxide (DMSO) and wortmannin-positive control groups. Paw withdrawal mechanical threshold (PWMT) and thermal withdrawal latency (TWL) were recorded. qRT-PCR and Western blotting were used to detect PI3K, Akt and mTOR expressions and their phosphorylation. OX-4 expression was detected by immunohistochemistry and glial fibrillary acidic protein (GFAP) and nerve growth factor (NGF) expressions by immunofluorescence. Results: PWMT and TWL decreased in the CCI group than in the sham group on the 7 th and 14 th day after operation. Compared with the control and sham groups, the CCI group showed increased PI3K, Akt and mTOR mRNA expressions and elevated PI3K, p-Akt, p-mTOR and P70S6K protein expressions. More OX-42-positive cells and higher integrated optical density (IOD) of GFAP and NGF were found in the CCI group than the sham group at the 14 th day after operation. Compared with the DMSO group, the wortmannin group had higher PWMT and TWL, decreased PI3K, Akt and mTOR mRNA expressions and reduced PI3K, p-Akt, p-mTOR and P70S6K protein expressions. Less OX-42-positive cells and lower IOD of GFAP and NGF were found in the wortmannin group than the DMSO group 14 th day after operation. Conclusion: Inhibition of PI3K/Akt/mTOR signal pathway may alleviate CNP and reduce microglia and GFAP and NGF expressions in marrow in a rat model of CCI.