Natural Shikonin Potentially Alters Intestinal Flora to Alleviate Acute Inflammation

Shikonin, derived from the herb Lithospermum erythrorhizon (Purple Cromwell), is extensively utilized in traditional Chinese medicine as an anti-inflammatory agent; however, its effect on the intestinal flora is not yet known. Herein, we demonstrate that, compared to a blank control group, the intragastric administration of shikonin suppressed the swelling rate of ears in a mouse model of acute inflammation in a dose-dependent manner via animal experiments; furthermore, the 20 mg/kg shikonin treatment exhibited the highest inhibitory effect. In formal animal experimentation, we discovered that the inhibitory effect of shikonin with 20 mg/kg on inflammation was closely linked to the intestinal flora, whereby the microbiota phylum was altered in feces through a 16S rDNA sequencing analysis, implying that shikonin improves gut microbiota structures and compositions to counteract inflammation. Notably, using a real-time quantitative polymerase chain reaction (RT-qPCR), a Western blotting assay, and an immunohistochemistry (IHC) assay, we found that inflammatory cytokines such as TNF-α, IL-6, and IL-1β reduced in both the shikonin-administration group and the positive control group than those in the blank control group, as expected. To the best of our knowledge, this is the first study to outline the underlying mechanism through which shikonin acts on gut microbes to alleviate acute inflammation, providing an alternative mechanism for shikonin to become a preventive agent in countering inflammation.