ABSTRACT
The indolo[2,1- b]quinazoline alkaloid tryptanthrin has previously been identified as the cyclooxygenase-2 (COX-2) inhibitory principle in the extract ZE550 prepared from the medicinal plant Isatis tinctoria (Brassicaceae). We here investigated the potential inhibitory activity of tryptanthrin and ZE550 on COX-2, COX-1 in cellular and cell-free systems. A certain degree of selectivity towards COX-2 was observed when COX-1-dependent formation of thromboxane B(2) (TxB(2)) in HEL cells and COX-2-dependent formation of 6-ketoprostaglandin F(1alpha) (6-keto-PGF(1alpha)) in Mono Mac 6 and RAW 264.7 cells were compared. Preferential inhibition of COX-2 by two orders of magnitude was found in phorbol myristate acetate (PMA) activated bovine aortic coronary endothelial cells (BAECs). Assays with purified COX isoenzymes from sheep confirmed the high selectivity towards COX-2. The leukotriene B(4) (LTB(4)) release from calcium ionophore-stimulated human granulocytes (neutrophils) was used as a model to determine 5-lipoxygenase (5-LOX) activity. Tryptanthrin and the extract ZE550 inhibited LTB(4) release in a dose dependent manner and with a potency comparable to that of the clinically used 5-LOX inhibitor zileuton.
Subject(s)
Brassicaceae , Cyclooxygenase Inhibitors/pharmacology , Leukotriene B4/biosynthesis , Phytotherapy , Prostaglandins/biosynthesis , Quinazolines/pharmacology , Animals , Cells, Cultured/drug effects , Cyclooxygenase 1 , Cyclooxygenase 2 , Cyclooxygenase 2 Inhibitors , Cyclooxygenase Inhibitors/administration & dosage , Dose-Response Relationship, Drug , Humans , Isoenzymes , Membrane Proteins , Neutrophils/drug effects , Plant Extracts/administration & dosage , Plant Extracts/pharmacology , Prostaglandin-Endoperoxide Synthases , Quinazolines/administration & dosage , SheepABSTRACT
Previous studies have suggested that histamine and leukotrienes (LTs) play an important pathobiological role in IgE-mediated allergic diseases. In vitro studies suggested that an extract of Petasites hybridus (Ze339) blocks LT synthesis in monocytes and granulocytes. Petasins are considered to be the pharmacologically active fraction within Ze339. Patients suffering from allergic rhinitis received three times a day two tablets of Ze339 standardized to 8 mg petasins within a time period of 1 week. After 5 days of treatment, Ze339 significantly improved primary end points, which were day- and nighttime nasal symptoms. Nasal resistance, which was measured by rhinomanometry, gradually decreased as a consequence of Ze339 treatment reaching normal levels after 5 days (rhinomanometry: from 403.5+/-62.0 to 844.8+/-38.8 ml). Levels of inflammatory mediators in nasal fluids and serum were measured 90 min after drug administration every day in the morning. After 5 days of treatment, a significant reduction of histamine (from 153.7+/-32.1 to 53.0+/-8.4 pg/ml) and LT levels (LTB4: from 313.1+/-46.5 to 180.6+/-32.2 pg/ml; cysteinyl-LT: from 137.0+/-42.2 to 70.1+/-16.5 pg/ml) could be observed. Moreover, quality-of-life scores significantly improved. The drug had no effect on the distribution of lymphocyte subpopulations in the blood as well as on the capacity of blood leukocytes to generate cytokines and lipid mediators. These results suggest that Ze339 is effective in treating allergic rhinitis patients by decreasing levels of nasal inflammatory mediators.
