Role of autophagy in spinal cord in maintenance of post-herpetic neuralgia in mice / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the role of autophagy in the spinal cord in the maintenance of postherpetic neuralgia (PHN) in mice.Methods Forty-eight SPF Kunming mice,aged 6-8 weeks,weighing 18-22 g,were divided into 4 groups (n=12 each) using a random number tablenormal control group (group C),group PHN,PHN plus autophagy inducer rapamycin group (group PHN+R) and PHN plus autophagy inhibitor 3-methyladenine (3-MA) group (group PHN+3-MA).PHN model was established by intraperitoneal injection of resiniferotoxin 0.2 μg/g.In PHN+R and PHN+3-MA groups,rapamycin 1 μg/g and 3-MA 2 μg/g were intraperitoneally injected once a day for 14 consecutive days starting from 7 days after resiniferotoxin injection.The equal volume of normal saline was given instead in group PHN.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured on 1st,3rd,6th,9th,12th and 14th days of administration of autophagy regulator (before administration).The animals were sacrificed after the last measurement of pain threshold,and the spinal cord was removed for examination of the ultrastructure and for determination of the expression of microtubule-associated protein light chain 3 Ⅱ (LC3 Ⅱ),LC3 Ⅰ,Beclin-1 and P62 by Western blot.The ratio of LC3 Ⅱ to LC3 Ⅰ expression (LC3 Ⅱ /Ⅰ) was calculated.Results Compared with group C,the MWT was significantly decreased,TWL was prolonged,LC3 Ⅱ/Ⅰ was increased,Beelin-1 expression was up-regulated,P62 expression was down-regulated (P＜0.05),and the number of autophagosomes was increased under electron microscope in group PHN.Compared with group PHN,the MWT was significantly decreased,TWL,was prolonged,LC3 Ⅱ/Ⅰ was increased,Beclin-1 expression was up-regulated,P62 expression was down-regulated (P＜0.05),and the number of autophagosomes was increased under electron microscope in group PHN+R,and the MWT was significantly increased,TWL was shortened,LC3 Ⅱ/Ⅰ was decreased,Beclin-1 expression was down-regulated,P62 expression was up-regulated (P＜0.05),and the number of autophagosomes was decreased under electron microscope in group PHN+3-MA.Conclusion The maintenance mechanism of PHN may be related to the excessive activation of autophagy in the spinal cord of mice.