Zanthoxylum zanthoxyoides root extract inhibits hemozoin-induced neuroinflammation in BV2 microglia

Zanthoxylum zanthoxyloides (Z. zanthoxyloides) is a plant used in West Africa to treat diseases such as stomach ache, toothache and malaria. Extract and bioactives from the rootbark of Z. zanthoxyloides have been suggested to have anti-inflammatory activity (1 and 2). In cerebral malaria, the accumulation of malaria pigment hemozoin induces inflammation leading to excessive production of pro-inflammatory cytokines which contributes to its pathology (3). However, whether Z. zanthoxyloides could suppress hemozoin-induced neuroinflammation remains unclear. In this study, we investigated the effect of Z. zanthoxyloides in hemozoin-induced BV2 microglia. Cultured BV2 microglia cells were treated with 4, 6 and 8 µg/ml of Z. zanthoxyloides 30 minutes before stimulation with hemozoin (400 µg/ml) for a further 24 hours. Levels of TNFα, IL-1β, IL-6, IL-10 released were measured using ELISA while PGE₂ production was measured by enzyme immunoassay. Nitric oxide (NO) production was determined using the Griess assay. Z. zanthoxyloides (4, 6 and 8 µg/ml) significantly (p < 0.05) reduced the production of TNF α (40 ± 5%), IL-1β (40 ± 2%), IL-6 (50 ± 2%), NO (40 ± 3%) and PGE₂ (40 ± 2%). Western blot experiments showed that Z. zanthoxyloides reduced levels of iNOS (45 ± 5%), COX-2 (50 ± 5%), phospho-p65 (50 ± 5%) and phospho-IκBα (40 ± 5%) in comparision with hemozoin control. These results suggest that Zanthoxylum zanthoxyloides might be inhibiting neuroinflammation in hemozoin induced microglia cells by targeting NF-kB signalling. These results have significant implications in cerebral malaria.

[1] Prempeh, A.B.A. and Mensah-Attipoe, J, 2009. Ghana Medical Journal 43.

[2] Oriowo MA. (1982) Planta Medica 44: 54 – 56

[3] Sultan, S. and Irfan, S.M, 2015. Blood Research, 50, 72 – 72.