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High-mobility group box-1 (HMGB-1) acts as a pro-inflammatory cytokine contributing to the occurrence of many central inflammatory and infectious disorders. Brain mast cells (MCs) are the first responders to peripheral inflammatory stimulation because of their rapid response to external stimuli coupled with their release of preformed and newly synthesized reactive chemicals. Little is known about the involvement of brain MCs in the pro-inflammatory effects of HMGB-1 on the central nervous system (CNS). Thus, we investigated the activation process of MCs by HMGB-1 and explored whether this process is involved in the pro-inflammatory effects of HMGB-1 on the CNS. In this study, we used P815 cells to study the activating role of HMGB-1 on MCs and to explore its potential mechanism in vitro. In an in vivo study, adult male Sprague-Dawley rats received i.c.v. injection of sterile saline or cromoglycate (stabilizer of MCs) 30 min prior to i.p. injection of HMGB-1. Increased levels of tumor necrosis factor and IL-1β were observed in the P815 cells, as well as in the rats' brains, after HMGB-1 treatment. Pretreatment with the receptor of advanced glycation endproducts (RAGE)-siRNA inhibited the HMGB-1-induced inflammatory process in the P815 cells. Activation of the RAGE/nuclear factor-κB (NF-κB) pathway was observed in both the P815 cells and rats' brains. In addition, HMGB-1 induced the accumulation of brain MCs in the hippocampal CA1 region, and the blood-brain barrier was disrupted. Pretreatment with cromoglycate, a stabilizer of MCs, mitigated these HMGB-1-induced pro-inflammatory processes in rats. These findings indicate that brain MCs are involved in the pro-inflammatory effect of HMGB-1 on the CNS, probably via activating the RAGE/NF-κB pathway., (© 2019 International Society for Neurochemistry.)

Background : The pathophysiological mechanisms underlying postoperative cognitive dysfunction (POCD) remain unclear over the years. Neuroinflammation caused by surgery has been recognized as an important element in the development of POCD. Many studies also suggest that the vagus nerve plays an important role in transmitting peripheral injury signals to the central nervous system (CNS) and the resultant neuroinflammation. Previously, we have demonstrated that brain mast cells (BMCs), as the "first responders", play a vital role in neuroinflammation and POCD. However, how the vagus nerve communicates with BMCs in POCD has not yet been clarified. Methods : In the current study, we highlighted the role of the vagus nerve as a conduction highway in surgery-induced neuroinflammation for the first time. In our model, we tested if mice underwent unilateral cervical vagotomy (VGX) had less neuroinflammation compared to the shams after laparotomy (LP) at an early stage. To further investigate the roles of mast cells and glutamate in the process, we employed KitW-sh mice and primary bone marrow-derived MCs to verify the glutamate-NR2B axis on MCs once again. Results : Our results demonstrated that there were higher levels of glutamate and BMCs activation as early as 4 h after LP. Meanwhile, vagotomy could partially block the increases and reduce neuroinflammation caused by peripheral inflammation during the acute phase. Excitingly, inhibition of NR2B receptor and knockout of mast cells can attenuateneuroinflammation induced by glutamate. Conclusion : Taken together, our findings indicate that the vagus is a high-speed pathway in the transmission of peripheral inflammation to the CNS. Activation of BMCs triggered a neuroinflammatory cascade. Inhibition of NR2B receptor on BMCs can reduce glutamate-induced BMCs activation, neuroinflammation, and memory impairment, suggesting a novel treatment strategy for POCD. [ABSTRACT FROM AUTHOR]