Madecassoside protects BV2 microglial cells from oxygen-glucose deprivation/reperfusion-induced injury via inhibition of the toll-like receptor 4 signaling pathway.

In a previous study, the authors reported that madecassoside (MA) exerted a potent neuroprotective effect against cerebral ischemia-reperfusion (I/R) injury in rats, mediated by anti-oxidative, anti-inflammatory, and anti-apoptotic mechanisms. However, the cellular and molecular bases for its neuroprotective effects have not been fully elucidated. In this study, an in vitro ischemic model of oxygen-glucose deprivation followed by reperfusion (OGD/R) was used to investigate the role of the toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)/nuclear factor-kappa B (NF-κB) pathway in the neuroprotective and anti-inflammatory effects of MA. BV2 microglia viability after OGD/R, treated with or without MA, was measured using the MTT assay. Messenger RNA and protein expression of pro-inflammatory cytokines (tumor necrosis factor α [TNF-α], interleukin-1β [IL-1β], interleukin-6 [IL-6]) were measured using real-time polymerase chain reaction (RT-PCR) and ELISA after OGD/R or lipopolysaccharide treatment. Expression of TLR4/MyD88 and NF-κB p65 were measured using RT-PCR, Western blotting, and immunofluorescence analysis. MA significantly rescued OGD/R-induced cytotoxicity in BV2 microglia. Meanwhile, MA suppressed the secretion of pro-inflammatory mediators, including TNF-α, IL-1β, and IL-6, induced by OGD/R or lipopolysaccharide in BV2 microglia. The mechanism of its neuroprotection and anti-inflammation from OGD/R may involve the inhibition of activation of TLR4 and MyD88 in BV2 microglia, and the blockage of NF-κB p65 nuclear translocation. MA exhibited a significant neuroprotective effect against I/R injury in both in vivo and in vitro experiments by attenuating microglia-mediated neuroinflammation via inhibition of the TLR4/MyD88/NF-κB signaling pathway.

Luo Y ，Wang C ，Li WH ，Liu J ，He HH ，Long JH ，Yang J ，Sui X ，Wang S ，You Z ，Wang YA ... -  《-》

Toll-like receptor 4 signaling is involved in PACAP-induced neuroprotection in BV2 microglial cells under OGD/reoxygenation.

Qin X ，Sun ZQ ，Dai XJ ，Mao SS ，Zhang JL ，Jia MX ，Zhang YM ... -  《-》

TLR4 signaling is involved in the protective effect of propofol in BV2 microglia against OGD/reoxygenation.

Qin X ，Sun ZQ ，Zhang XW ，Dai XJ ，Mao SS ，Zhang YM ... -  《-》

Ginkgolides and bilobalide protect BV2 microglia cells against OGD/reoxygenation injury by inhibiting TLR2/4 signaling pathways.

Zhou JM ，Gu SS ，Mei WH ，Zhou J ，Wang ZZ ，Xiao W ... -  《-》

Uric acid inhibits HMGB1-TLR4-NF-κB signaling to alleviate oxygen-glucose deprivation/reoxygenation injury of microglia.

Mounting evidence has implicated inflammation in ischemia-reperfusion injury following acute ischemic stroke (AIS). Microglia remain the primary initiator and participant of brain inflammation. Emerging evidence has indicated that uric acid has promise for the treatment of AIS, but its explicit mechanisms remain elusive. Here, we observed that uric acid reduced the severity of cerebral infarction and attenuated the activation of microglia in the cerebral cortex in a mouse middle cerebral-artery occlusion/reperfusion model. Thus, we speculated that uric acid may play a role by directly interfering with the inflammatory response of microglia. First, we investigated whether the HMGB1-TLR4-NF-κB signaling plays a role in oxygen glucose deprivation and reperfusion (OGD/R) injury of BV2 cells. Inhibition of the signaling significantly reduced the release of the proinflammatory cytokines tumor necrosis factor α (TNF-α), interleukin 1β (IL1β), and IL6 caused by OGD/R in BV2 cells. Second, uric acid weakened the decreased cell viability and lactate dehydrogenase release induced by OGD/R in BV2 cells. Finally, uric acid reduced the release of the proinflammatory cytokines TNF-α, IL1β, and IL6 caused by OGD/R in BV2 cells by dampening HMGB1-TLR4-NF-κB signaling, which was reversed by probenecid treatment, an inhibitor of the uric acid channel. Hence, uric acid halted the release of inflammatory factors and the decreased cell viability induced by ODG/R via inhibiting the microglia HMGB1-TLR4-NF-κB signaling, thereby alleviating the damage to microglia. This may be part of the molecular mechanisms by which uric acid protects mice against the brain damage of middle cerebral-artery occlusion/reperfusion.

Wang Q ，Zhao H ，Gao Y ，Lu J ，Xie D ，Yu W ，He F ，Liu W ，Hisatome I ，Yamamoto T ，Wang W ，Cheng J ... -  《-》