Shikonin reduces oedema induced by phorbol ester by interfering with IκBα degradation thus inhibiting translocation of NF‐κB to the nucleus

Background and purpose:  In the present paper we studied the effect of shikonin on ear oedema induced by 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), and determined the mechanisms through which shikonin might exert its topical anti‐inflammatory action.

Experimental approach:  Acute ear oedema was induced in mice by topical application of TPA. The in vitro assays used macrophages RAW 264.7 cells stimulated with lipopolysaccharide. Cyclooxygenase‐2, inducible nitric oxide synthase, protein kinase Cα, extracellular signal‐regulated protein kinase (ERK), phosphorylated ERK (pERK), c‐Jun N‐terminal kinase (JNK), pJNK, p38, p‐p38, p65, p‐p65, inhibitor protein of nuclear factor‐κB (NF‐κB) (IκBα) and pIκBα were measured by Western blotting, activation and binding of NF‐κB to DNA was detected by reporter gene and electrophoretic mobility shift assay, respectively, and NF‐κB p65 localization was detected by immunocytochemistry.

Key results:  Shikonin reduced the oedema (inhibitory dose 50 = 1.0 mg per ear), the expression of cyclooxygenase‐2 (70%) and of inducible nitric oxide synthase (100%) in vivo. It significantly decreased TPA‐induced translocation of protein kinase Cα, the phosphorylation and activation of ERK, the nuclear translocation of NF‐κB and the TPA‐induced NF‐κB‐DNA‐binding activity in mouse skin. Moreover, in RAW 264.7 cells, shikonin significantly inhibited the binding of NF‐κB to DNA in a dose‐dependent manner and the nuclear translocation of p65.

Conclusions and implications:  Shikonin exerted its topical anti‐inflammatory action by interfering with the degradation of IκBα, thus inhibiting the activation of NF‐κB.

DOI: 10.1111/j.1476-5381.2010.00696.x

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