|M.Sc Thesis||Department of Medicine|
|Supervisors:||Prof. Gavish Moshe|
|Assoc. Prof. Bomzon Arieh|
|Full Thesis text - in Hebrew|
Introduction: Teucrium polium is a deciduous plant, which widely distributed in the hills and deserts of Mediterranean countries and has been used for over 2000 years in traditional medicine to treat various liver diseases. Glutathione is an important intracellular antioxidant which exists in two forms: GSH - reduced form and GSSG - oxidized form.Glutathione is found almost exclusively in its reduced form and the ratio of reduced to oxidized glutathione is ~ 500/1. This ratio is maintained by an intracellular glutathione cycle in which the enzyme glutathione peroxidase converts reduced glutathione to its oxidized form, and the enzyme glutathione reductase reduces the oxidized form resulting in restoration of reduced glutathione. Aqueous and alcoholic extracts of T. polium possess antioxidant activity, with several studies showing that it can suppress Fe²+- induced lipid peroxidation. In chronic liver diseases, such as cholestastis and cirrhosis, intrahepatic glutathione levels are depleted. Moreover, there are no laboratory data on the effect of aqueous extract of T. polium on intracellular glutathione levels and its intracellular homeostasis.
Hypothesis: Aqueous extracts of T. polium possesses antioxidant activity by virtue of its ability to enhance the total and reduced intracellular glutathione levels by augmenting glutathione peroxidase and glutathione reductase activity.
Methods: The effects of various concentrations (0.01 - 1 mg/mL) of aqueous extract of T. polium was assessed in cultured HepG2 cells following 24 hours incubation on (1) cell integrity using (a) trypan blue exclusion assay, (b) di-methylthiazol-2yl]-2,5-diphenyl-tetrazoliumbromide (MTT) assay, (c) lactate dehydrogenase (LDH) assay; (2) glutathione redox state; and (3) glutathione peroxidase and glutathione reductase activities.
Results: low concentrations 0.01 - 0.25 mg/mL of T. polium extract had no effect on cell integrity. At higher concentrations 0.75 - 1 mg/mL, the extract was toxic to cells because it inhibited mitochondrial respiration and increased cellular LDH efflux. At concentrations of 0.375 mg/mL and 0.5 mg/mL, the extract significantly increased the intracellular levels of total and reduced glutathione and had no effect on intracellular amounts of oxidized glutathione. Because the extract increased the reduced glutathione levels without affecting oxidized glutathione levels, the GSH/GSSG ratio increased. The three concentrations of the extract did not alter the activities of glutathione peroxidase and glutathione reductase.
Discussion: These data indicate that the mechanism of the hepatoprotective properties of aqueous extracts of T. polium may be, in part, due to enhancement of intracellular glutathione levels.