Tanshinone IIA suppresses lipopolysaccharide-induced neuroinflammatory responses through NF-κB/MAPKs signaling pathways in human U87 astrocytoma cells

Tanshinone IIA (tan IIA), a key component of Salvia miltiorrhiza Bunge (Danshen), has been proven to play a significant role in suppressing inflammation. However, the molecular mechanisms underlying the anti-inflammatory properties of tan IIA against lipopolysaccharide (LPS)-induced neuroinflammation and neurotoxicity in human U87 astrocytoma cells have not been well justified. Therefore, in this study, U87 cells were pretreated with tan IIA (1, 5 and 10 μM) for 30 min, followed by stimulation with LPS for 24 h. Immunofluorescence, reverse transcription-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), and western blotting were performed to investigate the effects of tan IIA on neuroinflammatory responses. The findings demonstrated that tan IIA prevented LPS-induced cell viability decrease, inhibited U87 cells activation, and suppressed the expression of glial fibrillary acidic protein (GFAP). Furthermore, tan IIA significantly reduced the mRNA expression of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in LPS-stimulated U87 cells. Meanwhile, the increased protein levels of IL-1β, TNF-α, and IL-6 in cell culture supernatants were also markedly inhibited by tan IIA. Moreover, tan IIA significantly alleviated the phosphorylation of IκBα, nuclear factor-kappa B (NF-κB), p38, and JNK induced by LPS. Additionally, tan IIA suppressed the upstream signaling adaptor molecules toll-like receptor 4 (TLR4), myeloid differentiation primary response protein 88 (MyD88), and tumor necrosis factor receptor-associated factor 6 (TRAF6). Blockade of NF-κB, p38, and JNK obviously attenuated IL-1β, TNF-α, and IL-6 in U87 cells. In conclusion, the present results suggested that tan IIA can attenuate LPS-induced neurotoxicity and neuroinflammation partly by inhibiting TLR4/NF-κB/MAPKs signaling pathways in U87 cells.

Keywords: Lipopolysaccharide; Mitogen-activated protein kinases; Nuclear factor-kappa B; Pro-inflammatory cytokines; Tanshinone IIA.