Immunomodulatory drug discovery from herbal medicines: Insights from organ-specific activity and xenobiotic defenses.

Traditional herbal medicines, which emphasize a holistic, patient-centric view of disease treatment, provide an exciting starting point for discovery of new immunomodulatory drugs. Progress on identification of herbal molecules with proven single agent activity has been slow, in part because of insufficient consideration of pharmacology fundamentals. Many molecules derived from medicinal plants exhibit low oral bioavailability and rapid clearance, leading to low systemic exposure. Recent research suggests that such molecules can act locally in the gut or liver to activate xenobiotic defense pathways that trigger beneficial systemic effects on the immune system. We discuss this hypothesis in the context of four plant-derived molecules with immunomodulatory activity: indigo, polysaccharides, colchicine, and ginsenosides. We end by proposing research strategies for identification of novel immunomodulatory drugs from herbal medicine sources that are informed by the possibility of local action in the gut or liver, leading to generation of systemic immune mediators.

Indigo Naturalis Ameliorates Dextran Sulfate Sodium-Induced Colitis in Mice by Modulating the Intestinal Microbiota Community.

Indigo naturalis (IN) is a traditional Chinese medicine, named Qing-Dai, which is extracted from indigo plants and has been used to treat patients with inflammatory bowel disease (IBD) in China and Japan. Though there are notable effects of IN on colitis, the mechanisms remain elusive. Regarding the significance of alterations of intestinal flora related to IBD and the poor water solubility of the blue IN powder, we predicted that the protective action of IN on colitis may occur through modifying gut microbiota. To investigate the relationships of IN, colitis, and gut microbiomes, a dextran sulfate sodium (DSS)-induced mice colitis model was tested to explore the protective effects of IN on macroscopic colitis symptoms, the histopathological structure, inflammation cytokines, and gut microbiota, and their potential functions. Sulfasalazine (SASP) was used as the positive control. Firstly, because it was a mixture, the main chemical compositions of indigo and indirubin in IN were detected by ultra-performance liquid chromatography (UPLC). The clinical activity score (CAS), hematoxylin and eosin (H&E) staining results, and enzyme-linked immunosorbent assay (ELISA) results in this study showed that IN greatly improved the health conditions of the tested colitis mice, ameliorated the histopathological structure of the colon tissue, down-regulated pro-inflammatory cytokines, and up-regulated anti-inflammatory cytokines. The results of 16S rDNA sequences analysis with the Illumina MiSeq platform showed that IN could modulate the balance of gut microbiota, especially by down-regulating the relative quantity of Turicibacter and up-regulating the relative quantity of Peptococcus. The therapeutic effect of IN may be closely related to the anaerobic gram-positive bacteria of Turicibacter and Peptococcus. The inferred metagenomes from 16S data using PICRUSt demonstrated that decreased metabolic genes, such as through biosynthesis of siderophore group nonribosomal peptides, non-homologous end-joining, and glycosphingolipid biosynthesis of lacto and neolacto series, may maintain microbiota homeostasis during inflammation from IN treatment in DSS-induced colitis.

Aryl hydrocarbon receptor agonist indigo protects against obesity-related insulin resistance through modulation of intestinal and metabolic tissue immunity.

BACKGROUND/OBJECTIVES: Low-grade chronic inflammation in visceral adipose tissue and the intestines are important drivers of obesity associated insulin resistance. Bioactive compounds derived from plants are an important source of potential novel therapies for the treatment of chronic diseases. In search for new immune based treatments of obesity associated insulin resistance, we screened for tissue relevant anti-inflammatory properties in 20 plant-based extracts. METHODS: We screened 20 plant-based extracts to assess for preferential production of IL-10 compared to TNFα, specifically targetting metabolic tissues, including the visceral adipose tissue. We assessed the therapeutic potential of the strongest anti-inflammatory compound, indigo, in the C57BL/6J diet-induced obesity mouse model with supplementation for up to 16 weeks by measuring changes in body weight, glucose and insulin tolerance, and gut barrier function. We also utilized flow cytometry, quantitative PCR, enzyme-linked immunosorbent assay (ELISA), and histology to measure changes to immune cells populations and cytokine profiles in the intestine, visceral adipose tissue (VAT), and liver. 16SrRNA sequencing was performed to examine gut microbial differences induced by indigo supplementation. RESULTS: We identifed indigo, an aryl hydrocarbon receptor (AhR) ligand agonist, as a potent inducer of IL-10 and IL-22, which protects against high-fat diet (HFD)-induced insulin resistance and fatty liver disease in the diet-induced obesity model. Therapeutic actions were mechanistically linked to decreased inflammatory immune cell tone in the intestine, VAT and liver. Specifically, indigo increased Lactobacillus bacteria and elicited IL-22 production in the gut, which improved intestinal barrier permeability and reduced endotoxemia. These changes were associated with increased IL-10 production by immune cells residing in liver and VAT. CONCLUSIONS: Indigo is a naturally occurring AhR ligand with anti-inflammatory properties that effectively protects against HFD-induced glucose dysregulation. Compounds derived from indigo or those with similar properties could represent novel therapies for diseases associated with obesity-related metabolic tissue inflammation.

Indigo Naturalis Ameliorates Oxazolone-Induced Dermatitis but Aggravates Colitis by Changing the Composition of Gut Microflora.

BACKGROUND: Indigo naturalis (IND) is an herbal medicine that has been used as an anti-inflammatory agent to treat diseases including dermatitis and inflammatory bowel disease in China. However, the mechanism by which IND exerts its immunomodulatory effect is not well understood. METHODS: A murine model of dermatitis and inflammatory bowel disease, both induced by oxazolone (OXA), was treated with IND. The severity of dermatitis was evaluated based on ear thickness measurements and histological scoring. The severity of colitis was evaluated by measuring body weight, histological scoring, and endoscopic scoring. The expression of inflammatory cytokines in ear and colon tissue was evaluated using real-time PCR. 16S rRNA DNA sequencing of feces from OXA-induced colitis mice was performed before and after IND treatment. The effects of IND on OXA-induced colitis were also evaluated after depleting the gut flora with antibiotics to test whether alteration of the gut flora by IND influenced the course of intestinal inflammation in this model. RESULTS: IND treatment ameliorated OXA dermatitis with a reduction in IL-4 and eosinophil recruitment. However, OXA colitis was significantly aggravated in spite of a reduction in intestinal IL-13, a pivotal cytokine in the induction of the colitis. It was found that IND dramatically altered the gut flora and IND no longer exacerbated colitis when colitis was induced after gut flora depletion. CONCLUSIONS: Our data suggest that IND could modify the inflammatory immune response in multiple ways, either directly (i.e., modification of the allergic immune cell activity) or indirectly (i.e., alteration of commensal compositions).

Indigo Naturalis ameliorates murine dextran sodium sulfate-induced colitis via aryl hydrocarbon receptor activation.

BACKGROUND: Indigo Naturalis (IN) is used as a traditional herbal medicine for ulcerative colitis (UC). However, the mechanisms of action of IN have not been clarified. We aimed to evaluate the efficacy of IN for ameliorating colonic inflammation. We further investigated the mechanisms of action of IN. METHODS: Colitis severity was assessed in dextran sodium sulfate-induced colitis and trinitrobenzene sulfonic acid-induced colitis models with or without the oral administration of IN or indigo, which is a known major component of IN. Colonic lamina propria (LP) mononuclear cells isolated from IN-treated mice were analyzed with quantitative reverse transcription polymerase chain reaction (qRT-PCR) and flow cytometry. LP and splenic mononuclear cells cultured in vitro with IN or indigo were also analyzed. The role of the candidate receptor for indigo, the aryl hydrocarbon receptor (AhR), was analyzed using Ahr-deficient mice. RESULTS: Colitis severity was significantly ameliorated in the IN and indigo treatment groups compared with the control group. The mRNA expression levels of interleukin (Il)-10 and Il-22 in the LP lymphocytes were increased by IN treatment. The treatment of splenocytes with IN or indigo increased the expression of anti-inflammatory cytokines and resulted in the expansion of IL-10-producing CD4+ T cells and IL-22-producing CD3-RORγt+ cells, but not CD4+Foxp3+ regulatory T cells. The amelioration of colitis by IN or indigo was abrogated in Ahr-deficient mice, in association with diminished regulatory cytokine production. CONCLUSIONS: IN and indigo ameliorated murine colitis through AhR signaling activation, suggesting that AhR could be a promising therapeutic target for UC.

Modern industrial and pharmacological applications of indigo dye and its derivatives--a review.

Plant sources, chemical properties, bioactivities, as well as the synthesis of indigo dye and its derivatives, are reviewed in this paper. These compounds were chosen because of their significant benefits and scope of application as both coloring agents in the textile industry and as pharmacologically active natural products. Their use in traditional chinese medicine (TCM) has directed the attention of European researchers and medical doctors alike. The preparation of indigoferous plants--Indigo naturalis is currently about to be introduced into the European Pharmacopoeia.

Hysterosalpingography contrast media and chromotubation dye inhibit peritoneal lymphocyte and macrophage function in vitro: a potential mechanism for fertility enhancement.

OBJECTIVE: To determine the effects of hysterosalpingography (HSG) contrast media (CM) and chromotubation dye on peritoneal lymphocyte proliferation and macrophage phagocytosis in vitro. DESIGN: Peritoneal fluid (PF) lymphocytes and macrophages were isolated from 40 subfertile women undergoing diagnostic laparoscopy and 12 fertile women having laparoscopic tubal ligation. Dilutions of renografin, ethiodol, methylene blue, and indigo carmine were added to peritoneal lymphocyte and macrophage cultures. Tissue culture media alone served as control. Lymphocyte proliferation was assessed by hemocytometer counts and 3H-thymidine incorporation. Macrophage function was determined by phagocytosis of fluorescent microspheres. RESULTS: Peritoneal lymphocyte proliferation and macrophage phagocytosis were significantly inhibited by renografin, ethiodol, methylene blue, and indigo carmine in a dose-dependent manner. CONCLUSION: Inhibition of PF immune cell function by HSG CM and chromotubation dye may provide a potential mechanism for fertility enhancement after these diagnostic procedures.