Extract of Laurus nobilis attenuates inflammation and epithelial ulcerations in an experimental model of inflammatory bowel disease

Inflammatory bowel diseases (IBD), including Crohn's disease and ulcerative colitis, are classified as chronic inflammatory disorders and typically require anti-inflammatory drug therapies, such as glucocorticoid regimens, non-steroidal anti-inflammatory drugs, and biologics, aimed at reducing inflammation in the bowel wall. However, each of these therapies is accompanied by a list of possible serious side effects. Because of this, there remains an urgent need to identify new pharmacologic options to reduce or prevent the pro-inflammatory events of IBD while minimizing adverse side effects and making available more cost-effective treatment modalities. We have previously identified several herbal extracts that demonstrate the potent bio-inhibitory activity of the innate immune response. In particular, Laurus nobilis (LN), or more commonly called bay laurel, demonstrated significant anti-inflammatory function by inhibiting nuclear factor-κB activation. Based upon our original in vitro findings, we have now examined the effects of this herbal extract on a murine dextran sodium sulfate (DSS) model of IBD. Hematoxylin and eosin-stained paraffin sections prepared from DSS-treated animals show clear epithelial damage, including ulcerations, extensive neutrophil infiltration into the mucosal layer, and granuloma formation. Tissue from DSS-treated animals that also received LN extract showed improved tissue morphology more closely resembling that from control animals. In addition, DSS-treated mice with co-administration of LN extract showed a significant reduction in CD4+ antibody staining within the mucosal layer in colonic sections indicating reduced lymphocyte infiltration. Based on these findings, we believe that the administration of LN extracts may be effective in reducing the intestinal epithelial damage seen in human IBD and warrants further investigation through clinical trials. Lay Summary: Inflammatory bowel diseases (IBD), such as Crohn's disease (CD) and ulcerative colitis (UC), manifest as chronic inflammation and ulceration of tissues lining the digestive tract. CD involves inflammation of the deeper layers of the digestive tract, including both the small and large intestines, and less commonly, the upper digestive tract. UC involves inflammation along the lining of the colon and rectum. Steroid or biological treatments for IBD are common, however, they are limited due to significant side effects and/or prohibitive costs. In the present study, we provide evidence for use of the natural product, Laurus nobilis (bay leaf), as a safe and effective anti-inflammatory therapy for IBD.