The influence of beta-galactose specific lectins from prostate hyperplasic tissue mitochondria on the redox system

Author: Elene Davitashvili
Co-authors: E.Davitashvili
Keywords: lectins, prostate disease, mitochondria, redox system
Annotation:

In recent years, it has become clear that mitochondria also play a key role in the pathways to cell death. Mitochondrial dysfunction plays a central role in a wide range of age-related disorders and various forms of cancer. In addition, mitochondrial production of reactive oxygen species (ROS) also appears to play a role in carcinogenesis. The numbers of specific compounds, as cytoplasmic, as membrane components have been identified in transformed cells, which are not present in normal cells. Aberrations of membrane components especially are increased in the carbohydrate structures, which condition colonization and metastasis of the tumor cells. The protein-carbohydrate interactions play an important role in the many vital processes, such as cell-cell interactions, which manly realized by the membrane adhesion molecules with lectin nature. Lectins are biological active proteins, which characterized to bind specifically to the terminal carbohydrates Therefore, the goal of our experiments were the study the distribution of lectins in mitochondria subtractions’ (outer membrane, inner membrane, intermembrane space, matrix), their carbohydrate-specificity. Mitochondria isolated from prostate post-operative tissue with various diagnoses (normal, N, cytoprostatectomy, benign prostatic hyperplasia, BPH, intraepithelial neoplasia,PIN, atypical adenomatose hyperplasia, AAH). Mitochondrial fractions from human prostatic tissue (for lectin purification) as well as from bovine liver (for study of biochemical changes under the influence of human lectins) were obtained according to De-Robertis (1967) with differential centrifugation. Gal-lectins from mitochondria of prostate hyperplasic tissue with two different pathological forms were purified and their comparative effects on mitochondrial properties were investigated in vitro. Namely, changes in the: (i) amount of H2O2; (ii) redox state of Cu in cytochrome oxidase and (iii) redox state of hem in cyt a+a3 of cytochrome c oxidase complex were studied. Mitochondrial fraction was suspended in the following buffer: 300 mM sucrose, 5 mM Tris-HCl, 5 mM KH2PO4, 0,2 mM succinate, 0,2 mM EDTA and 0,1 % BSA, pH. 7,4. Changes in the redox state of copper in cytochrome c oxidase were measured simultaneously and continuously in the thermostat cell (t0=370C) with a two-channel dual-wavelength spectrophotometer (Specord, Germany). The change in the broad near-infrared band due to oxidized CuA was monitored at 830 nm, using the 722 and 900 nm wavepairs as refereneces, i.e. ΔCuA = ΔA830 nm –(ΔA722 nm + ΔA900 nm) / 2 [16]. Mitochondrial fraction was suspended in the buffer of the same composition as described above. Lectin activity was revealed in mitochondria outer membrane (with external and internal carbohydrate binding center), inner membrane and in matrix. Galactose-specific lectins, isolated from the mitochondrial fraction of prostate post-operational hyperplasic tissue of two diagnoses LGPIN and AAH had similar molecular weight and other properties. Effects of these lectins were investigated in vitro model experiments on bovine liver cells mitochondrial properties. Time-dependent changes: (i) in the amount of H2O2; (ii) redox state of Cu in cytochrome oxidase and (iii) redox state of hem in cytochrome a+a3 (cyt a+a3) of cytochrome c oxidase complex were studied. Lectins from both sources increase the amount of H2O2 and decrease the redox state of Cu in cytochrome oxidase and hem in cyt a+a3. However the Lectin from tissue with more severed transformation (AAH) expresses significantly more strong and long-lasting influence. These effects are mediated by galactose binding domain of the lectins as are completely abolished by the inclusion of galactose in reaction medium. Accumulation of H2O2 and long-lasting decrease in the redox state of key enzymes of mitochondrial respiration chain could induce defective functioning of these organelles and whole cells. Obtained data points to possible way, which enhances further transformation of prostate tissue by release of galactose-specific lectins from damaged mitochondria.