Anti-psoriatic effects of indigo naturalis on the proliferation and differentiation of keratinocytes with indirubin as the active component.

BACKGROUND: Indigo naturalis has shown efficacy in treating psoriasis in our previous clinical studies. OBJECTIVES: To investigate the potential effect of indigo naturalis on regulating keratinocyte proliferation and differentiation. METHODS: Skin samples from six patients were analyzed for proliferating cell nuclear antigen (PCNA) and involucrin expression by immunohistochemical staining. In addition, indigo naturalis extracts from 10 to 500 microg/ml were added to cultured keratinocytes and cell viability determined. Real-time RT-PCR, Western blotting analysis and indirect immunofluorescent labeling were used to investigate the messenger (m)RNA and protein expressions of PCNA and involucrin. Finally, high-performance liquid chromatography (HPLC) was used to identify major components of indigo naturalis and their in vitro effects compared. RESULTS: Immunohistochemical results demonstrated decreased PCNA and increased involucrin in psoriatic lesions after indigo naturalis treatment. Cultured keratinocytes decreased after indigo naturalis treatment, while G(0)/G(1) arrest was observed to dose-dependently increase. Staining revealed decreased PCNA-stained nuclei and increased cytosolic involucrin in treated keratinocytes. Decreased PCNA and increased involucrin at both the mRNA and protein levels were confirmed. Both major components, indirubin and indigo, could cause G(0)/G(1) phase arrest; however, only indirubin modulated the expressions of PCNA and involucrin similar to indigo naturalis. CONCLUSIONS: Together, these findings indicate that the anti-psoriatic effects of indigo naturalis are mediated, at least in part, by modulating the proliferation and differentiation of keratinocytes, with indirubin as the major active component.

Treatment of type 2 diabetes mellitus with agonists of the GLP-1 receptor or DPP-IV inhibitors.

Glucagon-like peptide-1 (GLP-1) is a peptide hormone from the gut that stimulates insulin secretion and protects beta-cells, inhibits glucagon secretion and gastric emptying, and reduces appetite and food intake. In agreement with these actions, it has been shown to be highly effective in the treatment of Type 2 diabetes, causing marked improvements in glycaemic profile, insulin sensitivity and beta-cell performance, as well as weight reduction. The hormone is metabolised rapidly by the enzyme dipeptidyl peptidase IV (DPP-IV) and, therefore, cannot be easily used clinically. Instead, resistant analogues of the hormone (or agonists of the GLP-1 receptor) are in development, along with DPP-IV inhibitors, which have been demonstrated to protect the endogenous hormone and enhance its activity. Agonists include both albumin-bound analogues of GLP-1 and exendin-4, a lizard peptide. Clinical studies with exendin have been carried out for > 6 months and have indicated efficacy in patients inadequately treated with oral antidiabetic agents. Orally active DPP-IV inhibitors, suitable for once-daily administration, have demonstrated similar efficacy. Diabetes therapy, based on GLP-1 receptor activation, therefore, appears very promising.

Effects of intracerebroventricular injection of glucagon like peptide-1 and its related peptides on serotonin metabolism and on levels of amino acids in the rat hypothalamus.

High concentrations of glucagon-like peptide-1 (7-36) amide (GLP-1) and its specific receptor (GLP-1R) have been found in the rat hypothalamus. In this study the actions of GLP-1 and its related peptides, exendin-4 (GLP-1R agonist), exendin (9-39) (GLP-1R antagonist) and GLP-1 (9-36) amide (the major GLP-1 metabolite) on levels of serotonin (5-HT), 5-hydroxyindolacetic acid (5-HIAA) and amino acids (Glu, Asp, Gln, Gly, Tyr, Trp, GABA) in the hypothalamus were investigated. Intracerebroventricular (ICV) injection of GLP-1 (4 nmol) produced a significant reduction in levels of 5-HT (54%) and all measured amino acids (34 to 56%) compared with saline injected controls, whereas exendin (9-39) (4 nmol) was ineffective. ICV injection of exendin-4 produced a significant reduction in the levels of 5-HT, 5-HIAA, Trp, Glu, and Tyr. ICV injection of GLP-1(9-36) amide showed a statistically significant increase in the level of 5-HT, 5-HIAA and all the amino acids tested in this study. Prior administration of exendin (9-39) or GLP-1 (9-36) amide blocked the effects of GLP-1 on the levels of 5-HT and the amino acids. These data are consistent with exendin-4 being a GLP-1R agonist and exendin (9-39) being a specific GLP-1R antagonist. GLP-1 (9-36) amide, a primary metabolite of GLP-1, appears to act as an endogenous antagonist at the GLP-1R.