Okanin, effective constituent of the flower tea Coreopsis tinctoria, attenuates LPS-induced microglial activation through inhibition of the TLR4/NF-?B signaling pathways.

Scientific reports

PubMedID: 28367982

Hou Y, Li G, Wang J, Pan Y, Jiao K, Du J, Chen R, Wang B, Li N. Okanin, effective constituent of the flower tea Coreopsis tinctoria, attenuates LPS-induced microglial activation through inhibition of the TLR4/NF-?B signaling pathways. Sci Rep. 2017;745705.
The EtOAc extract of Coreopsis tinctoria Nutt. significantly inhibited LPS-induced nitric oxide (NO) production, as judged by the Griess reaction, and attenuated the LPS-induced elevation in iNOS, COX-2, IL-1ß, IL-6 and TNF-a mRNA levels, as determined by quantitative real-time PCR, when incubated with BV-2 microglial cells. Immunohistochemical results showed that the EtOAc extract significantly decreased the number of Iba-1-positive cells in the hippocampal region of LPS-treated mouse brains. The major effective constituent of the EtOAc extract, okanin, was further investigated. Okanin significantly suppressed LPS-induced iNOS expression and also inhibited IL-6 and TNF-a production and mRNA expression in LPS-stimulated BV-2 cells. Western blot analysis indicated that okanin suppressed LPS-induced activation of the NF-?B signaling pathway by inhibiting the phosphorylation of I?Ba and decreasing the level of nuclear NF-?B p65 after LPS treatment. Immunofluorescence staining results showed that okanin inhibited the translocation of the NF-?B p65 subunit from the cytosol to the nucleus. Moreover, okanin significantly inhibited LPS-induced TLR4 expression in BV-2 cells. In summary, okanin attenuates LPS-induced activation of microglia. This effect may be associated with its capacity to inhibit the TLR4/NF-?B signaling pathways. These results suggest that okanin may have potential as a nutritional preventive strategy for neurodegenerative disorders.