Amarogentin Displays Immunomodulatory Effects in Human Mast Cells and Keratinocytes

Keratinocytes express the bitter taste receptors TAS2R1 and TAS2R38. Amarogentin as an agonist for TAS2R1 and other TAS2Rs promotes keratinocyte differentiation. Similarly, mast cells are known to express bitter taste receptors. The aim of this study was to assess whether bitter compounds display immunomodulatory effects on these immunocompetent cells in the skin, so that they might be a target in chronic inflammatory diseases such as atopic dermatitis and psoriasis. Here, we investigated the impact of amarogentin on substance P-induced release of histamine and TNF-α from the human mast cell line LAD-2. Furthermore, the effect of amarogentin on HaCaT keratinocytes costimulated with TNF-α and histamine was investigated. Amarogentin inhibited in LAD-2 cells substance P-induced production of newly synthesized TNF-α, but the degranulation and release of stored histamine were not affected. In HaCaT keratinocytes histamine and TNF-α induced IL-8 and MMP-1 expression was reduced by amarogentin to a similar extent as with azelastine. In conclusion amarogentin displays immunomodulatory effects in the skin by interacting with mast cells and keratinocytes

Amarogentin Displays Immunomodulatory Effects in Human Mast Cells and Keratinocytes

Keratinocytes express the bitter taste receptors TAS2R1 and TAS2R38. Amarogentin as an agonist for TAS2R1 and other TAS2Rs promotes keratinocyte differentiation. Similarly, mast cells are known to express bitter taste receptors. The aim of this study was to assess whether bitter compounds display immunomodulatory effects on these immunocompetent cells in the skin, so that they might be a target in chronic inflammatory diseases such as atopic dermatitis and psoriasis. Here, we investigated the impact of amarogentin on substance P-induced release of histamine and TNF-α from the human mast cell line LAD-2. Furthermore, the effect of amarogentin on HaCaT keratinocytes costimulated with TNF-α and histamine was investigated. Amarogentin inhibited in LAD-2 cells substance P-induced production of newly synthesized TNF-α, but the degranulation and release of stored histamine were not affected. In HaCaT keratinocytes histamine and TNF-α induced IL-8 and MMP-1 expression was reduced by amarogentin to a similar extent as with azelastine. In conclusion amarogentin displays immunomodulatory effects in the skin by interacting with mast cells and keratinocytes

Expression and Functional Activity of the Human Bitter Taste Receptor TAS2R38 in Human Placental Tissues and JEG-3 Cells

Bitter taste receptors (TAS2Rs) are expressed in mucous epithelial cells of the tongue but also outside the gustatory system in epithelial cells of the colon, stomach and bladder, in the upper respiratory tract, in the cornified squamous epithelium of the skin as well as in airway smooth muscle cells, in the testis and in the brain. In the present work we addressed the question if bitter taste receptors might also be expressed in other epithelial tissues as well. By staining a tissue microarray with 45 tissue spots from healthy human donors with an antibody directed against the best characterized bitter taste receptor TAS2R38, we observed an unexpected strong TAS2R38 expression in the amniotic epithelium, syncytiotrophoblast and decidua cells of the human placenta. To analyze the functionality we first determined the TAS2R38 expression in the placental cell line JEG-3. Stimulation of these cells with diphenidol, a clinically used antiemetic agent that binds TAS2Rs including TAS2R38, demonstrated the functionality of the TAS2Rs by inducing calcium influx. Restriction enzyme based detection of the TAS2R38 gene allele identified JEG-3 cells as PTC (phenylthiocarbamide)-taster cell line. Calcium influx induced by PTC in JEG-3 cells could be inhibited with the recently described TAS2R38 inhibitor probenecid and proved the specificity of the TAS2R38 activation. The expression of TAS2R38 in human placental tissues points to further new functions and hitherto unknown endogenous ligands of TAS2Rs far beyond bitter tasting

The Herbal Bitter Drug Gentiana lutea Modulates Lipid Synthesis in Human Keratinocytes In Vitro and In Vivo

Gentiana lutea is a herbal bitter drug that is used to enhance gastrointestinal motility and secretion. Recently we have shown that amarogentin, a characteristic bitter compound of Gentiana lutea extract (GE), binds to the bitter taste receptors TAS2R1 and TAS2R38 in human keratinocytes, and stimulates the synthesis of epidermal barrier proteins. Here, we wondered if GE also modulates lipid synthesis in human keratinocytes. To address this issue, human primary keratinocytes were incubated for 6 days with GE. Nile Red labeling revealed that GE significantly increased lipid synthesis in keratinocytes. Similarly, gas chromatography with flame ionization detector indicated that GE increases the amount of triglycerides in keratinocytes. GE induced the expression of epidermal ceramide synthase 3, but not sphingomyelinase. Lipid synthesis, as well as ceramide synthase 3 expression, could be specifically blocked by inhibitors of the p38 MAPK and PPARγ signaling pathway. To assess if GE also modulates lipid synthesis in vivo, we performed a proof of concept half side comparison on the volar forearms of 33 volunteers. In comparison to placebo, GE significantly increased the lipid content of the treated skin areas, as measured with a sebumeter. Thus, GE enhances lipid synthesis in human keratinocytes that is essential for building an intact epidermal barrier. Therefore, GE might be used to improve skin disorders with an impaired epidermal barrier, e.g., very dry skin and atopic eczema

The Effect of Herbal Medicinal Products on Psoriasis-Like Keratinocytes

Psoriasis is a chronic inflammatory skin disease characterized by hyperproliferation of keratinocytes and expression of pro-inflammatory cytokines in the epidermis. New biological drugs were developed for the systemic treatment of moderate to severe psoriasis. However, products for the topical treatment of mild psoriasis are still required. Here, we examined the effect of natural compounds on psoriasis-like keratinocytes in vitro and ex vivo. Psoriasis-like keratinocytes were generated by treating human primary keratinocytes with the psoriasis-associated cytokines IL-17A, TNF-α and IL-22. Initially, 10 botanical extracts from Ayurvedic Medicine, Traditional Chinese Medicine, Northern American traditional medicine and Occidental Monastic Medicine were investigated using BrdU assays and IL-6 and IL-8 ELISAs. Curcuma amada, Humulus lupulus and Hypericum perforatum turned out to be the most effective plant extracts. In vitro, the plant extracts inhibited the expression of anti-microbial peptides (β-defensin 2), the hyperproliferation marker keratin 17, the glucose transporter 1 and downregulated the nuclear translocation of NF-κB and pSTAT3. In an ex vivo psoriasis model, Humulus lupulus displayed the most prominent anti-proliferative and anti-inflammatory effect. In conclusion, among the plant extracts investigated, Humulus lupulus showed the most promising anti-psoriatic effect. It is an interesting candidate for topical psoriasis treatment that should be further studied in clinical trials

Anti-Inflammatory Effects of Agrimoniin-Enriched Fractions of Potentilla erecta

Potentilla erecta (PE) is a small herbaceous plant with four yellow petals belonging to the Rosaceae family. The rhizome of PE has traditionally been used as an antidiarrheal, hemostatic and antihemorrhoidal remedy. PE contains up to 20% tannins and 5% ellagitannins, mainly agrimoniin. Agrimoniin is a hydrolyzable tannin that is a potent radical scavenger. In this study we tested the anti-inflammatory effect of four PE fractions with increasing amounts of agrimoniin obtained by Sephadex column separation. First, we analyzed in HaCaT keratinocytes the expression of cyclooxygenase-2 (COX-2) induced by ultraviolet-B (UVB) irradiation. As COX-2 catalyzes the metabolism of arachidonic acid to prostanoids such as PGE2, we also measured the PGE2 concentration in cell culture supernatants. PE inhibited UVB-induced COX-2 expression in HaCaT cells and dose-dependently reduced PGE2. The PE fraction with the highest agrimoniin amount (PE4) was the most effective in this experiment, whereas fraction PE1 containing mainly sugars had no effect. PE4 also dose dependently inhibited the phosphorylation of the epidermal growth factor receptor (EGFR) which plays a crucial role in UVB-mediated COX-2 upregulation. A placebo-controlled UV-erythema study with increasing concentrations of PE4 demonstrated a dose dependent inhibition of UVB-induced inflammation in vivo. Similarly, PE4 significantly reduced UVB-induced PGE2 production in suction blister fluid in vivo. In summary, PE fractions with a high agrimoniin content display anti-inflammatory effects in vitro and in vivo in models of UVB-induced inflammation

Hop Extract Acts as an Antioxidant with Antimicrobial Effects against Propionibacterium Acnes and Staphylococcus Aureus

Acne is associated with hyperkeratosis, elevated levels of skin sebum and growth of Propionibacterium acnes (P. acnes) and Staphylococcus aureus (S. aureus). Furthermore, P. acnes promotes inflammation by inducing IL-6 production and oxidative stress. The aim of this study was to assess the antioxidant, anti-inflammatory and antibacterial potential of a hop-CO2-extract with 50% humulone and lupulone. The susceptibility of P. acnes and S. aureus to the hop extract was tested by using the broth microdilution technique. The minimal inhibitory concentrations (MIC) for P. acnes and S. aureus were 3.1 and 9.4 µg/mL, respectively. In addition, the hop extract showed an antioxidative effect with a half maximal inhibitory concentration (IC50) of 29.43 µg/mL as well as additional anti-inflammatory effects by reducing the IL-6 expression (IC50: 0.8 µg/mL). In addition, a gel formulation with 0.3% hop extract (w/w) had antibacterial activity against P. acnes and S. aureus (inhibition zone value: 5.5 mm and 3 mm, respectively) which was significantly superior to the placebo gel. The positive control (a gel with the antibiotic clindamycin) showed an inhibition zone of 9 mm. Due to its antioxidant, anti-inflammatory and antibacterial effects hop extract might be a treatment option for acne-prone skin

The Anti-Inflammatory Effect of Humulus lupulus Extract In Vivo Depends on the Galenic System of the Topical Formulation

We demonstrated the anti-inflammatory and anti-oxidative effects of Humulus lupulus (HL) extract on solar simulator-irradiated primary human keratinocytes (PHKs) by analyzing ERK and p38 MAPK phosphorylation and production of IL-6 and IL-8. The anti-inflammatory effect of topically applied HL was further tested in vivo on human skin. To this end, we developed an oil-in-water (O/W) and a water-in-oil (W/O) cream with a lipid content of 40%. The anti-inflammatory effect of 1% HL extract incorporated in these two vehicles was assessed in a randomized, prospective, placebo controlled, double-blind UVB erythema study with 40 healthy volunteers. Hydrocortisone acetate (HCA) in the corresponding vehicle served as positive control. Surprisingly, both HL and HCA were only effective in the O/W system but not in the W/O formulation. Release studies using vertical diffusion cells (Franz cells) revealed that HCA was released in much higher amounts from the O/W cream compared to the W/O formulation. In summary, we have shown that 1% HL extract exerts anti-inflammatory effects comparable to 1% HCA, but only when incorporated in our O/W cream. Our findings confirm the critical role of the vehicle in topical anti-inflammatory systems