TSPO ligand etifoxine attenuates LPS-induced cognitive dysfunction in mice.

The translocator protein (TSPO), once known as peripheral-type benzodiazepine receptor, was reported to be related with several physiological functions. Etifoxine is a clinically available anxiolytic drug, and has recently shown neuroprotective effects as a TSPO ligand. The aim of the present study was to investigate the influence of etifoxine on LPS-induced neuroinflammation and cognitive dysfunction. C57/BL6 male mice were injected with etifoxine (50 mg/kg, i.p.) three days before lipopolysaccharide (LPS, 500 µg/kg, i.p.) administration. Etifoxine pretreatment alleviated hippocampal inflammation, increased brain levels of progesterone, allopregnanolone and attenuated cognitive dysfunction in LPS-injected mice. While LPS increased expression of caspase-3 and decreased p-Akt/Akt, etifoxine returned caspase-3 and p-Akt/Akt to control levels. Finasteride, a 5α-reductase inhibitor that blocked allopregnanolone production, partially reversed the effects of etifoxine. We concluded that etifoxine exerted neuroprotective effects in LPS-induced neuroinflammation and the neuroprotection may be related with increase of neurosteroids synthesis and decrease of apoptosis.

TSPO ligand PK11195 alleviates neuroinflammation and beta-amyloid generation induced by systemic LPS administration.

Translocator protein 18 kDa (TSPO) is now an attractive drug target for controlling neuroinflammation. Studies applying TSPO ligands to neurodegenerative diseases, especially Alzheimer's disease (AD), were rare. Our study was aimed to evaluate the effect of PK11195, a specific TSPO ligand, in an animal model of neuroinflammation caused by systemic LPS administration. C57/BL6 mice were treated with lipopolysaccharide (LPS, 500 µg/kg, i.p.) three days after PK11195 administration (3mg/kg, i.p.). The drugs were not discontinued until the mice were sacrificed. Cognitive function was assessed by Morris water maze (MWM) seven days after LPS injection. Chronic LPS-injection in mice was characterized by cognitive dysfunction, increased expression of cyclooxygenase (COX)-2 and TSPO, elevated Aß content with increased expression of ß-site APP cleaving enzyme-1 (BACE-1) and insulin-degrading enzyme (IDE) as well as decreased brain progesterone and brain-derived neurophic factor (BDNF) level. PK11195 pretreatment protected cognitive function in LPS-injected animals and normalized the inflammatory proteins. Moreover, PK11195 pre-administration decreased elevated hippocampal Aßx-42 levels and increased brain levels of progesterone, allopregnanolone. However, LPS-induced BDNF decrease was not reversed by PK11195 administration. Our data demonstrated that PK11195 could protect cognitive deficits induced by chronic LPS administration. The underling mechanism may involve alleviated neuroinflammation, increased synthesis of neurosteroid and decreased Aß accumulation accompanied by down-regulation of BACE-1.