TSPO Ligands PK11195 and Midazolam Reduce NLRP3 Inflammasome Activation and Proinflammatory Cytokine Release in BV-2 Cells.

Baoyu Ma,Lina Sun,Yingxia Liang,Nannan Lan,Yongxin Liu,Hao Feng,Rui Zhang

doi:10.3389/fncel.2020.544431

Abstract

Neuroinflammation related to microglial activation plays an important role in neurodegenerative diseases. Translocator protein 18 kDa (TSPO), a biomarker of reactive gliosis, its ligands can reduce neuroinflammation and can be used to treat neurodegenerative diseases. Therefore, we explored whether TSPO ligands exert an anti-inflammatory effect by affecting the nucleotide-binding domain-like receptor protein 3 (NLRP3) inflammasome, thereby inhibiting the release of inflammatory cytokines in microglial cells. In the present study, BV-2 cells were exposed to lipopolysaccharide (LPS) for 6 h to induce an inflammatory response. We found that the levels of reactive oxygen species (ROS), NLRP3 inflammasome, interleukin-1β (IL-1β), and interleukin-18 (IL-18) were significantly increased. However, pretreatment with TSPO ligands inhibited BV-2 microglial and NLRP3 inflammasome activation and significantly reduced the levels of ROS, IL-1β, and IL-18. Furthermore, a combination of LPS and ATP was used to activate the NLRP3 inflammasome. Both pretreatment and post-treatment with TSPO ligand can downregulate the activation of NLRP3 inflammasome and IL-1β expression. Finally, we found that TSPO was involved in the regulation of NLRP3 inflammasome with TSPO ligands treatment in TSPO knockdown BV2 cells. Collectively, these results indicate that TSPO ligands are promising targets to control microglial reactivity and neuroinflammatory diseases.

Highlights

The incidence of neurodegenerative diseases increases with age, and the complications of neurodegenerative diseases seriously affect the quality of life and survival rate of the elderly (Karim et al, 2014)
The results indicated that PK11195 and midazolam inhibit the production of reactive oxygen species (ROS) in microglial cells (Figures 1A,B)
To further investigate whether the nucleotide-binding domain-like receptor protein 3 (NLRP3) inflammasome involved in the effect regulated by PK11195 and midazolam in microglia, the levels of NLRP3, a caspase recruitment domain (ASC), and caspase-1 were measured by western blot, RT-PCR, and immunocytochemistry

Summary

Introduction

The incidence of neurodegenerative diseases increases with age, and the complications of neurodegenerative diseases seriously affect the quality of life and survival rate of the elderly (Karim et al, 2014). Recent research suggests that the development of neuroinflammation is closely related to a variety of neurodegenerative diseases (Ransohoff, 2016). The NLRP3 inflammasome consists of NLRP3, an apoptosisassociated speck-like protein containing a caspase recruitment domain (ASC), and cysteinyl aspartate specific proteinase 1 (caspase-1). This inflammasome induces caspase-1 activation, which induces the maturation and secretion of proinflammatory cytokines, including IL-1β and interleukin-18 (IL-18; Li et al, 2017). Translocator protein 18 kDa (TSPO), which is a new name for a peripheral benzodiazepine receptor, has been studied as a biomarker of reactive gliosis and inflammation associated with a variety of neuropathological conditions (Chen and Guilarte, 2008). We examined the effects of PK11195 and midazolam pretreatment or post-treatment on neuroinflammation and determined that the NLRP3 inflammatory pathway is involved in these effects

Methods

Results

Conclusion