Pien-Tze-Huang, a Chinese patent formula, attenuates NLRP3 inflammasome-related neuroinflammation by enhancing autophagy via the AMPK/mTOR/ULK1 signaling pathway

Abstract NLRP3 inflammasome is a key mediator in ischemic stroke-induced neuroinflammation and subsequent brain injury. Our previous study demonstrated the potent activity of Pien-Tze-Huang (PTH), a well-known Chinese patent formula, in reducing mitochondria-mediated neuronal apoptosis in cerebral ischemia/reperfusion impaired rats. This study aims to elucidate the mechanistic action of PTH related to neuroinflammation in LPS-induced BV2 microglial cells and cerebral ischemia/reperfusion impaired rats. BV2 cells were stimulated with LPS for 12 h and treated with PTH with various concentrations. Modulation by PTH of relevant genes (IL-6, IL-1β, IL-18, TNF-α, COX-2 and iNOS mRNA) and proteins (NLRP3 inflammasome, autophagy and AMPK/mTOR/ULK signaling) was analyzed by real-time PCR and western blot, respectively. Similar analyses were conducted in middle cerebral artery occlusion rat model including neurological deficit, infarct volume, microglial activation, and key genes and proteins in modulating autophagy and NLRP3. Our results showed that PTH significantly inhibited the production of key proinflammatory mediators and protein expressions of NLRP3 and caspase-1 p20 in LPS induced BV2 cells. It also enhanced the autophagy response by modulating the key autophagy proteins via AMPK/mTOR/ULK related pathway. The reduced inflammatory responses and NLRP3 expressions by PTH were partially blocked by the autophagy inhibitor (3-MA) and AMPK blocker (compound C). In rats, PTH significantly reduced infarct size, suppressed microglial activation, and improved neuron deficit. It also promoted autophagy and reduced NLRP3 activity. Our study demonstrated that PTH inhibited NLRP3 inflammasome-mediated neuroinflammation, which was associated with enhanced autophagy via AMPK/mTOR/ULK1 pathway in vitro and in vivo.