Mitochondria play an important role in the cell aging process. Changes in calcium homeostasis and/or increased reactive oxygen species (ROS) production lead to the opening of mitochondrial permeability transition pore (MPTP), depolarization of the inner mitochondrial membrane, and decrease of ATP production. Our work aimed to monitor age-related changes in the Ca2+ ion effect on MPTP and the ability of isolated rat liver mitochondria to accumulate calcium. The mitochondrial calcium retention capacity (CRC) was found to be significantly affected by the age of rats. Measurement of CRC values of the rat liver mitochondria showed two periods when 3 to 17-week old rats were tested. 3-week and 17-week old rats showed lower CRC values than 7-week old animals. Similar changes were observed while testing calcium-induced swelling of rat liver mitochondria. These findings indicate that the mitochondrial energy production system is more resistant to calcium-induced MPTP opening accompanied by the damaging effect of ROS in adult rats than in young and aged animals.
Literature data support that green tea and its major component epigallocatechin gallate (EGCG) have powerful antioxidant effects. Contrary, hepatotoxicity can be induced by high-dose EGCG. The timing of exposure to green tea in relation to administration of hepatotoxic agent plays an import role too. The aim of our work was a verification of antioxidative effect of EGCG on D-galactosamine-induced injury in primary culture of rat hepatocytes. Hepatocytes were incubated with EGCG at concentrations of 1.25-10 μM and toxic D-galactosamine (GalN) for 24 hrs. Alternatively, hepatocytes were pretreated with EGCG for 24 hrs, and then incubated with EGCG and GalN for further 24 hrs. Cytotoxicity was analysed by lactate dehydrogenase activity, functional capacity by albumin production. Oxidative stress was evaluated from a production of malondialdehyde and glutathione content in the cells. EGCG protected hepatocytes against GalN-induced cytotoxicity but preventive treatment of intact hepatocytes with EGCG was required to diminish the development of hepatocyte injury. Oxidative stress induced in our study seems to overcome the ability of hepatocytes to improve GSH depletion and albumin production. Prolongation of the pretreatment with EGCG could be a promising strategy leading to amelioration of its hepatoprotective effect. and Alena Moravcová, Zuzana Červinková, Otto Kučera, Vojtěch Mezera, Halka Lotková
Values of the calcium retention capacity (CRC) of rat liver mitochondria are highly dependent on the experimental conditions used. When increasing amounts of added calcium chloride are used (1.25-10 nmol), the values of the CRC increase 3-fold. When calcium is added in 75 s intervals, the CRC values increase by 30 % compared with 150 s interval additions. CRC values are not dependent on the calcium/protein ratio in the measured sample in our experimental design. We also show that a more detailed evaluation of the fluorescence curves can provide new information about mitochondrial permeability transition pore opening after calcium is added.
Odpřahující protein 2 (UCP2, uncoupling protein 2) objevený v roce 1997 je homologem rozpřahujícího proteinu 1 (UCP1), který byl objeven v mitochondriích hnědé tukové tkáně novorozených savců a dospělých hibernantů jako součást mechanismu netřesové termogeneze. Zatímco UCP1 byl prokázán pouze v hnědé tukové tkáni, UCP2 je exprimován v kosterním svalu, bílé tukové tkáni, plicích a v dalších buněčných populacích. Odpřahující proteiny fungují jako iontové kanály. Jejich otevření snižuje mitochondriální membránový potenciál, tím se snižuje účinnost energetické přeměny – snižuje se tvorba ATP a zvyšuje se uvolnění energie ve formě tepla. UCP proteiny tím, že odpřahují procesy oxidace od tvorby ATP, zvyšují oxidaci substrátů, snižují podíl redukovaných komponent respiračního řetězce a tím redukují produkci reaktivních kyslíkových radikálů mitochondriemi. V tomto článku jsou popsány možné funkce UCP2., Uncoupling protein 2 (UCP2), discovered in 1997, is the fi rst homologue of uncoupling protein 1 (UCP1) that was discovered in mitochondria of brown adipose tissue of newborn mammals and adult hibernators as the part of mechanism in non-shivering thermogenesis. While UCP1 was presented only in brown adipose tissue, UCP2 is expressed in skeletal muscle, white adipose tissue, lungs and in other cell populations. Uncoupling proteins work as ion channels. Opening of these channels decrease the mitochondrial membrane potential thereby the effi ciency of energy conversion is decreased – it is decreased production of ATP and is increased dissipation of energy in the form of heat. Uncoupling proteins uncouple the process of oxidation from the ATP formation, increase the substrate oxidation and decrease the part of reduced components of respiratory chain thereby reducing the production of reactive oxygen species in mitochondria. In this review possible functions of UCP2 are also described., Bolehovská R., Červinková Z., Pospíšilová M., Lotková H., Plíšková L., Palička V., and Lit.: 24