The effect of nigellone and thymoquinone on inhibiting trachea contraction and mucociliary clearance.

NIGELLA SATIVA L. has many effects including those on the gastrointestinal tract and trachea and is, therefore, used in the Mediteranean area and in India/Pakistan. Our aim was to investigate the effect of two main constituents, nigellone and thymoquinone, on trachea (antispasmodic effect) and their influence on respiratory clearance. The effects on Ba (2+)-, carbachol- and leukotriene-induced trachea contractions and the transport of the fluorescence dye rhodamin B concerning ciliary action in the tracheal area were investigated using a microdialysis technique. Nigellone and high concentrations of thymoquinone had a concentration-dependent inhibitory effect on the trachea when being contracted by the depolarizing effect of Ba (2+). The trachea contractions induced by leukotriene-d (4) were inhibited by nigellone and by thymoquinone. The cholinergic system (stimulation by carbachol) was hardly involved. The rate of ciliary clearance (mucociliary transport) was slightly modified by a high thymoquinone concentration (153.0 vs. 505.0 sec/12 mm distance, respectively), and was highly increased by nigellone (217.5 vs. 505.0 sec/12 mm distance). In conclusion, this study provides evidence for an antispasmodic effect and an increase in mucociliary clearance for nigellone but not for thymoquinone. Altogether the data indicate that nigellone but not thymoquinone may be useful in treatment of different respiratory diseases.

The effect of thyme extract on beta2-receptors and mucociliary clearance.

UNLABELLED: Thyme is a broncholytic und secretomotoric agent. Thus, our aim was to investigate the influence of a thyme extract on beta (2)-receptors in competition binding experiments and relaxation experiments on rat uteri and trachea. Furthermore, the influence of the extract on respiratory clearance was of interest. Binding experiments were performed using purified rat lung membranes with the beta(2)-receptor ligand [(125)I]-CYP {[(125)I]-(+/-)-Iodocyanopindolol}. The transport of the fluorescence dye rhodamin 123 concerning ciliary action in the tracheal area of a mouse was investigated using a microdialysis technique. The thyme extract reduces only slightly [(125)I]-CYP binding and amplifies the displacement of [(125)I]-CYP by propranolol (non-specific beta-receptor antagonist): the displacement curve in the concentration range representing beta (2)-receptors (nM) is shifted to the left. Thyme extract had relaxing effects on organs possessing beta (2)-receptors (uterus and trachea). The propranolol-induced antagonism to isoprenaline is reverted concentration-dependently by the extract. A duplication of the rate of ciliary clearance by the extract was observed. IN CONCLUSION: 1) There is evidence for an influence of a thyme extract on beta (2)-receptors by both binding studies and biological effects: As can be derived from the shift of the propranolol displacement curve (nM), ingredients of the thyme extract slightly interact with beta (2)-receptors in rat lung tissue. This effect is indirect since no full range competition curve was reached. 2) An at least indirect interaction with beta (2)-receptors in rat uteri and trachea is revealed by a decreased antagonism of propranolol on the relaxing effect of isoprenaline by the plant extract. 3) An additional mechanism is presumed because at high extract concentrations isoprenaline-induced relaxation is complete, whereas the displacement of propranolol at beta (2)-receptors is only weak. 4) Thyme extract has an indirect (modulatory) effect on the beta (2)-receptor system. 5) Mucociliary clearance is improved in vivo. Its mechanism has still to be elucidated.

Hypoglycaemic constituents of Stachytarpheta cayennensis leaf.

The aqueous infusion (tea) of Stachytarpheta cayennensis leaves is used ethnomedically in Peru, Nigeria and other tropical countries for the management of diabetes. Oral administration (p. o.) of aqueous (125 mg/kg) and methanolic (2000 mg/kg) extracts of the leaves to alloxan-diabetic rats showed significant blood glucose reductions by 43 and 53%, respectively, at the end of a 4 hour period similar to the strong effect of glibenclamide (5 mg/kg, P. O.). The methanolic extract was successively partitioned into ethyl acetate, butanol and water fractions, and the same test showed that the butanol fraction (2000 mg/kg) had the highest (50%) hypoglycaemic activity at 4 hours after oral administration. It was also the most active fraction when tested in vitro [insulin release from an insulin secreting cell line (INS-1)] and was also active in normal rats and rats made hyperglycaemic by a glucose load. Its activity was comparable to that of glibenclamide (positive control) in these models. This active butanol fraction was subjected to chromatographic subfractionation; some subfractions reduced hyperglycaemia in alloxan-diabetic rats to 60 and 78% and induced insulin release from the INS-1 cells; other subfractions, however, gave hyperglycaemic activities IN VIVO and inhibition of insulin release from the INS-1 cells. Three major compounds of the butanol fraction were isolated and characterised as 6beta-hydroxyipolamide, ipolamide and isoverbascoside; they increased insulin secretion from INS-1 cells to 125, 128 and 127%, respectively, whereas glibenclamide increased insulin secretion to 157%. The results justify the ethnomedical use of the plant in the management of diabetes and suggest that the butanol fraction and some of its isolated constituents mediate their actions primarily by stimulating insulin release directly.

Cardiac hypertrophy and impaired relaxation in transgenic mice overexpressing triadin 1.

Triadin 1 is a major transmembrane protein in cardiac junctional sarcoplasmic reticulum (SR), which forms a quaternary complex with the ryanodine receptor (Ca(2+) release channel), junctin, and calsequestrin. To better understand the role of triadin 1 in excitation-contraction coupling in the heart, we generated transgenic mice with targeted overexpression of triadin 1 to mouse atrium and ventricle, employing the alpha-myosin heavy chain promoter to drive protein expression. The protein was overexpressed 5-fold in mouse ventricles, and overexpression was accompanied by cardiac hypertrophy. The levels of two other junctional SR proteins, the ryanodine receptor and junctin, were reduced by 55% and 73%, respectively, in association with triadin 1 overexpression, whereas the levels of calsequestrin, the Ca(2+)-binding protein of junctional SR, and of phospholamban and SERCA2a, Ca(2+)-handling proteins of the free SR, were unchanged. Cardiac myocytes from triadin 1-overexpressing mice exhibited depressed contractility; Ca(2+) transients decayed at a slower rate, and cell shortening and relengthening were diminished. The extent of depression of cell shortening of triadin 1-overexpressing cardiomyocytes was rate-dependent, being more depressed under low stimulation frequencies (0.5 Hz), but reaching comparable levels at higher frequencies of stimulation (5 Hz). Spontaneously beating, isolated work-performing heart preparations overexpressing triadin 1 also relaxed at a slower rate than control hearts, and failed to adapt to increased afterload appropriately. The fast time inactivation constant, tau(1), of the l-type Ca(2+) channel was prolonged in transgenic cardiomyocytes. Our results provide evidence for the coordinated regulation of junctional SR protein expression in heart independent of free SR protein expression, and furthermore suggest an important role for triadin 1 in regulating the contractile properties of the heart during excitation-contraction coupling.