title: Prophylactic lithium alleviates splenectomy-induced cognitive dysfunction possibly by inhibiting hippocampal TLR4 activation in aged rats.
abstract: Though the pathogenesis of postoperative cognitive dysfunction (POCD) remains unclear, evidence is accumulating for a pivotal role of neuroinflammation in the disease process. Advanced age and severe surgical trauma are two main risk factors for POCD. Lithium, a neuroprotective agent, can alleviate peripheral surgery-induced memory impairment in aged rats. The results of in vivo and in vitro experiments also showed that toll like receptor 4 (TLR4) was associated with the occurrence and development of neuroinflammation and POCD. So we hypothesized that inhibition of TLR4 signaling in the hippocampus maybe involved in the protective effects of prophylactic lithium on the occurrence of inflammation and POCD. In the present study, we incubated BV-2 microglia with 1μg/ml lipopolysaccharide (LPS) to mimic neuroinflammation in vitro. We found that pretreatment with 10mM of lithium or 100nM of TLR4 siRNA could inhibit the tumor necrosis factor (TNF)-α and TLR4 mRNA expression induced by LPS in BV-2 microglia. Furthermore, combination of prophylactic lithium and TLR4 siRNA even decreased their mRNA expression to the baseline levels, which showed that TLR4 signaling may be vital in protective effects of prophylactic lithium on neuroinflammation. So we further undergone the in vivo experiment. Then, we firstly demonstrated that prophylactic 2mM/kg of lithium alleviated splenectomy-induced cognitive impairments, decreased splenectomy-associated systemic, central, and hippocampal TNF-α and interleukin (IL)-1β expression and reduced the increase of CD11b(+) area in hippocampal CA1 region caused by the surgery. Then, we also found that splenectomy merely increased hippocampal TLR2 and TLR4 mRNA levels in aged rats. At last, we confirmed that prophylactic lithium reduced the increased levels of hippocampal TLR4/NF-κB induced by splenectomy. Taken together, these results demonstrate that TLR4 signaling inactivation may contribute to the protective effects of prophylactic lithium on the occurrence of POCD by inhibiting systemic inflammation and especially neuroinflammation.
authors.affiliation: Department of Anesthesiology, 1st Affiliated Hospital, Nanjing Medical University, Nanjing, China.
authors.forename: Shun-Mei
authors.initials: SM
authors.lastname: Lu
authors.affiliation: Department of Anesthesiology, 1st Affiliated Hospital, Nanjing Medical University, Nanjing, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Gui
authors.affiliation: Department of Anesthesiology, 1st Affiliated Hospital, Nanjing Medical University, Nanjing, China.
authors.forename: Hong-Quan
authors.initials: HQ
authors.lastname: Dong
authors.affiliation: Department of Anesthesiology, 1st Affiliated Hospital, Nanjing Medical University, Nanjing, China.
authors.forename: Xiang
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Anesthesiology, 1st Affiliated Hospital, Nanjing Medical University, Nanjing, China.
authors.forename: Su-Su
authors.initials: SS
authors.lastname: Zhang
authors.affiliation: Department of Anesthesiology, 1st Affiliated Hospital, Nanjing Medical University, Nanjing, China.
authors.forename: Liu-Qing
authors.initials: LQ
authors.lastname: Hu
authors.affiliation: Department of Anesthesiology, Huai'an First People's Hospital, Nanjing Medical University, Huai'an, China.
authors.forename: Hai-Ling
authors.initials: HL
authors.lastname: Liu
authors.affiliation: Department of Anesthesiology, 1st Affiliated Hospital, Nanjing Medical University, Nanjing, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Sun
authors.affiliation: Department of Anesthesiology, 1st Affiliated Hospital, Nanjing Medical University, Nanjing, China. Electronic address: yanning_qian@aliyun.com.
authors.forename: Yian-Ning
authors.initials: YN
authors.lastname: Qian
mesh_terms: D000375:Aging / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D039481:CD11b Antigen / Q000378:metabolism; D002460:Cell Line; D003072:Cognition Disorders / Q000188:drug therapy* / Q000378:metabolism*; D004195:Disease Models, Animal; D053583:Interleukin-1beta / Q000378:metabolism; D008070:Lipopolysaccharides; D018021:Lithium Chloride / Q000008:administration & dosage*; D008297:Male; D051379:Mice; D017628:Microglia / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D015213:Neuroimmunomodulation / Q000187:drug effects / Q000502:physiology; D018697:Nootropic Agents / Q000008:administration & dosage*; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000008:administration & dosage; D011897:Random Allocation; D017207:Rats, Sprague-Dawley; D013156:Splenectomy; D051195:Toll-Like Receptor 2 / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D039481:CD11b Antigen; C000594089:IL1B protein, rat; D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D016328:NF-kappa B; D018697:Nootropic Agents; D012333:RNA, Messenger; D034741:RNA, Small Interfering; C495343:Tlr2 protein, rat; C495347:Tlr4 protein, rat; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D018021:Lithium Chloride
keywords: Lipopolysaccharide; Lithium chloride; Microglia; Postoperative cognitive dysfunction; Splenectomy; Toll-like receptor 4