Paeonol Suppresses Neuroinflammatory Responses in LPS-Activated Microglia Cells

In this work, we assessed the anti-inflammatory effects of paeonol (PAE) in LPS-activated N9 microglia cells, as well as its underlying molecular mechanisms. PAE had no adverse effect on the viability of murine microglia N9 cell line within a broad range (0.12∼75 μM). When N9 cell line was activated by LPS, PAE (0.6, 3, 15 μM) significantly suppressed the release of proinflammatory products, such as nitric oxide (NO), interleukin-1β (IL-1β), and prostaglandin E2 (PGE2), demonstrated by the ELISA assay. Moreover, the levels of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) were significantly reduced in PAE-treated N9 microglia cells. We also examined some proteins involved in immune signaling pathways and found that PAE treatment significantly decreased the expression of TLR4, MyD88, IRAK4, TNFR-associated factor 6 (TRAF6), p-IkB-α, and NF-kB p65, as well as the mitogen-activated protein kinase (MAPK) pathway molecules p-P38, p-JNK, and p-ERK, indicating that PAE might act on these signaling pathways to inhibit inflammatory responses. Overall, we found that PAE had anti-inflammatory effect on LPS-activated N9 microglia cells, possibly via inhibiting the TLR4 signaling pathway, and it could be a potential drug therapy for inflammation-associated neurodegenerative diseases.