Could shikonin, a drug used in traditional Chinese medicine, be effective in ulcerative colitis?

I Andújar, A Martí, JL Ríos, MC Recio. Universitat de Val è ncia, Farmacologia 46100, Spain

Introduction. It is generally accepted that bowel macrophages and CD4+ T cells play a key role in the inflammatory process, which is directed by cytokines and which leads to inflammatory bowel disease (IBD). Current treatments are symptomatic, they do not stop the progression of the disease, nor are they free of adverse effects. (Triantafillidis et al., 2011). The identification of substances that promote resolution of inflammation in a homeostatic and effective way is essential. Traditional medicine, based on the use of medicinal plants and their products, has provided first-line drugs for millions of people around the world. Indeed, many patients with ulcerative colitis (UC) do not adhere to the conventional treatment and seek alternative medicine remedies in the form of medicinal plants and dietary supplements (Ahimi et al., 2009). Medicinal plant extracts are also an important source of potential therapeutic agents for the pharmaceutical industry (Recio et al., 2012). One example of this is shikonin, a naphthoquinone present in Lithospermum erythrorhizon roots, which has demonstrated anti-inflammatory properties (Andújar et al., 2010). In the present work, we undertake the study of the anti-inflammatory activity of shikonin against an experimental model of intestinal inflammation that reproduces some of the main characteristics of UC.

Experimental approach. UC was induced in female Balb/C mice (18-20g) by administering dextran sulfate sodium (DSS) in drinking water for 7 days. The disease activity index (DAI) was evaluated and a histological study was carried out. Myeloperoxidase activity was measured and expression of cyclooxygenase (COX)-2, activation of nuclear factor (NF)-κB and signal transducer and activator of transcription (STAT)-3 were determined by Western Blot in the colon homogenates. Cytokine levels were measured by ELISA both in colon homogenates and in peritoneal macrophages treated with shikonin (0.5-1.0 μM) for 1h and stimulated with LPS (1 μg/mL) for 24h. A complementary study on the effect of shikonin (0.1-0.5 μM) on cytokine production of TPA/ionomycin-activated human lymphocytes from healthy volunteers was also carried out.

Key results and discussion. Shikonin (25 mg kg-1, p.o., twice) prevents the development of experimental UC induced by oral administration of DSS: it prevents the shortening of the colorectum and decreases weight loss by 5% while improving the appearance of faeces and preventing bloody stools. It also inhibits MPO activity (44%, p<0.05), COX-2 expression (90%, p<0.01), and colonic production of IL-6 (p<0.05), IL-1β (p<0.05), TNFα (p<0.05), and IFNγ (p<0.05). The inhibition of the expression and release of these cytokines has been confirmed in primary cultures of mouse peritoneal macrophages and human lymphocytes. The observed results can be justified, in part, by the inhibition of the transcription factors NF-κB (57%, p<0.01) and STAT3 (55%, p<0.01). Statistical analysis was carried out by ANOVA followed by Dunnett’s t-test.

References: Ahimi et al. Dig Dis Sci. 2009;54:471−80. Andújar et al. Br J Pharmacol. 2010;160: 376−88. Recio et al. Curr Med Chem. 2012;19:2088-103. Triantafillidis et al. Drug Des Develop Ther. 2011;5:185-210. Acknowledgements: This study was supported by Spanish Government, MICIIN (SAF 2009-13059-C03-01). I.A. was recipient of a fellowship from GVA (BFPI/2008/040).