Anti-inflammatory activity of Anchusa italica Retz. in LPS-stimulated RAW264.7 cells mediated by the Nrf2/HO-1, MAPK and NF-κB signaling pathways

Abstract

Ethnopharmacological relevanceAnchusa italica Retz. (Boraginaceae) is an important medicinal plant for the treatment of meningitis and pneumonia in traditional Uygur medicines. Aim of the studyTo clarify the anti-inflammatory activity of A. italica, to reveal its molecular mechanisms, and to discover the anti-inflammatory active ingredients. Materials and methodsDried and crushed aerial parts of A. italica were extracted with 75% ethanol to yield crude extract (AICE) and AICE was fractionated to obtain petroleum ether extract (AIPE), dichloromethane extract (AIDE), ethyl acetate extract (AIEE), n-butanol extract (AIBE) and residues (AIW). By measuring the effects of AIPE, AIDE, AIEE, AIBE and AIW on cell viability and nitric oxide (NO) in Lipopolysaccharide (LPS) stimulated RAW264.7 cell lines, AIDE with the lowest cytotoxicity and NO contents was finally selected for further chemical and anti-inflammatory investigations. LC-MS/MS experiment was applied to analyze the chemical composition of AIDE. MTT and Griess methods were used to detect the cell viability and to quantify the nitrite levels in culture supernatants, respectively. Prostaglandin E2 (PGE2), interleukin-6 (IL-6), interleukin-1β (IL-1β) and tumor necrosis factor α (TNF-α) production was examined by ELISA assays. Real-time quantitative PCR was used to detect the expression of hemeoxygenase-1 (HO-1), Nrf2-mediated quinone oxidoreductase 1 (NQO-1), glutathione S-transferase A 1 (GSTA1) and glutathione S-transferase M 1 (GSTM1) mRNA. Western blot analysis was employed to examine the protein expression and enzymatic activities. ResultsIn preliminary anti-inflammatory screening, AIDE showed the lowest cytotoxicity and the most significant inhibitory effect on the production of NO (the inhibitory is 89%) induced by LPS among the tested five extracts. Thirty-three compounds including twenty-five triterpenoids were identified by LC-MS/MS analysis. AIDE could inhibit LPS-induced the over-expression of NO, IL-6, PGE2, IL-1β and TNF-α and down-regulate the levels of extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase (JNK), P38-MAPK (P38) and nuclear transcription factors κB-P65 (P65) phosphorylation. It promoted the mRNA expression level of HO-1, NQO-1, GSTA1 and GSTM1 and the protein expression level of nuclear factor erythroid 2-related factor 2 (Nrf2) and HO-1. After the treatment of AIDE, P65 nuclear translocation was inhibited and Nrf2 nuclear translocation was increased. In addition, the protein expression of pyrolytic relevant protein nod-like receptor family pyrin domain-containing 3 (NLRP3) and IL-1β were decreased after the AIDE treatment. ConclusionsAnchusa italica Retz. exerted its anti-inflammatory activity by inhibiting the mitogen-activated protein kinase (MAPK), nuclear transcription factors κB (NF-κB) and pyrolytic relevant proteins, down-regulating inflammatory factor levels, and activating the Nrf2/HO-1 pathway. Triterpenoids might be its major active anti-inflammatory ingredients.