Abstract: Objective To investigate the effect of TLR2 in mediating the pathological activation of microglia and neuronal injury in vascular dementia ( VaD) rat model and its molecularmechanisms. Methods In vitro experiments were carried out by using LPS-induced activation of human microglia cell line HMC3 cells. The proliferation ability of HMC3 cells was determined by CCK- 8 assay. Systemic TLR2 knockdown was performed by using Adv-TLR2 shRNA or Adv-shRNA NT. The VaD rat model was established by permanent bilateral common carotid artery occlusion (2VO) . The expression levels of TLR2, NF-κB, Iba-1, Claudin-5 and ZO-1 in HMC3 cells and rats’white matter tissues were determined by Western blotting. The levels of inflammatory cytokines IL-6, IL-1β and TNF-α, and the ferroptosis-related indicators of Fe2 + , malondialdehyde (MDA) and glutathione (GSH) in rats’white matter tissues were determined by ELISA. Morris water maze (MWM) test was used to determine rats’brain neuronal injury. Results The expression levels ofTLR2, NF-κB and Iba-1 in the LPS group were enhanced when compared with those in the Controlgroup (P< 0. 05). The expression levels of the above proteins in the Adv-TLR2 shRNA group were decreases when compared with those in the LPS groups ( P < 0. 05). The expression levels ofTLR2 / NF-κB and Iba-1 were up-regulated, and those of Claudin-5 and ZO-1 were down-regulatedin the white matter tissues of Model group rats, when compared with those of the Sham group, (P<0. 05). In addition, the levels of inflammatory cytokines IL-6, IL-1β and TNF-α were up-regulated(P< 0. 05), the Fe2 + and MDA levels were increased, and the GSH levels were decreased (P <0. 05). TLR2 knockdown had reversed the values of above indicators in the Model + Adv-TLR2 shRNA group when compared with those in the Model group (P< 0. 05). Morris water maze test showedthat rats in the Model group and Model + Adv-TLR2 shRNA group took longer time to find the targetquadrant (upper left quadrant) ( P < 0. 05), stayed shorter time in the target quadrant ( P <0. 05) when compared with those in the Sham group, the swimming routes of rats in the four quadrants of MWM were evenly distributed. Compared with Model group, the Model + Adv-TLR2 shRNAgroup showed a reversion in the values of above indicators and had a denser distribution of swimroutes in the target quadrant. Conclusion Knock-down of TLR2 could inhibit the activation of microglia and its mediated tight junction protein degradation and cerebrovascular barrier network leakage, and reduce nerve damage in the vascular dementia rat model.

Key words: vascular dementia, inflammation, Toll-like receptor 2, microglia, ferroptosis