Mitochondria damage

Centrifuge the pH-adjusted suspension for 15 minutes at 26,000 X g. At least two distinct layers will be observed in the pellet. The top layer consists of loosely packed light mitochondria (damaged mitochondria). The bottom layer of the pellet is brown and consists of heavy mitochondria. 

Mitochondria damage Mitochondria membrane potential dyes (e.g., TMRM) [52]... 

As the power house of the cell, the mitochondrion is essential for energy metabolism. As the motor of cell death (1), this organelle is central to the initiation and regulation of apoptosis. In addition, mitochondria are critically involved in the modulation of intracellular calcium concentration and the mitochondrial respiratory chain is the major source of damaging reactive oxygen species. Mitochondria also play a crucial role in numerous catabolic and anabolic cellular pathways. 

Opening of leads to a local increase in the cytosolic Ca concentration from 10 M to 10 M. In this concentration region, the Ca transport systems mentioned above work very efficiently. However, if an increase in Ca concentration over lO M takes place, e.g., due to cell damage, a level critical for the cell is reached. In this case, Ca is pumped into the mitochondria with the help of Ca transport systems localized in the iimer membrane of the mitochondrion. 

It seems worthwhile to explore these ideas further. It would need the investigation of the pathway and rds for the reduction of 02 on some artificial membranes that simulate suspected reaction centers in the mitochondrion. A pan-electrochemical explanation of degenerative diseases would be to see them in terms of a slowdown of the bioelectrocatalysts of the 02 reduction. To that extent that age and accumulated fragments reduce the velocity of the enzymatic reduction of 02, is it likely that an excess 02 remains left over to form peroxy radicals and damage cells. 

As discussed previously, the mitochondrial theory of ageing rests on the observation that mitochondrial DNA is exposed to high levels of reactive oxygen species when the mitochondrion is performing its redox chemistry. These reactive oxygen species cause mutation. These mutations accumulate, gradually damaging the mitochondrion s ability to function. This happens in... 

Another consequence of the failure of electrons to move completely through the ETC is the increased release of reactive oxygen species (ROS) such as superoxide anion (02 ) in the mitochondrion. Such ROS are produced as oxygen molecules react with electrons at the CoQ or RC I stage. The superoxide and other ROS derived from it (H202 and OH ) cause damage to nearby proteins, membranes, and nucleic acids. 

Cultured human urinary bladder carcinoma cells treated with doxycycline and UVA showed mitochondrial damage. Cell membrane integrity was maintained for several hours after mitochondrial damage appeared, indicating that the mitochondrion is an earlier target of doxycycline than the cell membrane when irradiated with UVA. The authors of the study opine that the photochemical reaction involves singlet oxygen J1 A... 

The mitochondrial outer membrane is a physical barrier separating the metabolic processes of the cytoplasm from those of the mitochondrion. Integrity of the outer membrane of mitochondria can be determined using a cytochrome c accessibility assay (Douce et al. 1973). Since holocytochrome c cannot diffuse across intact outer membranes, the ratio of the initial rate of succinate icytochrome c oxidore-ductase activity by the mitochondria to that of the same mitochondria after deliberate lysis of their outer membranes is proportional to the extent of damage to the outer membranes incurred during mitochondrial isolation. 

Fio. 31. Distribution of the enzymes of heme biosyntbesis in the cell and hypothesis on the lesions in porphyria. If in acute porphyria S-AL-synthetase activity is enhanced as in chemical porphyria rather than that the Shemin cycle is blocked at (1) or the mitochondrion becomes permeable at (1) then i-AL will leak out, some will be converted to PBG, and both will be excreted. In congenital porphyria the PBG isomerase enzyme at (2) is decreased or damaged so UROGEN-I is formed and is in part transformed to COPROGEN-I, which are both excreted. 

The mitochondrion, as a primary source of ROS, is thus, itself, quite vulnerable to oxidative damage. Mn-SOD (sod2) is a mitochondrial form of the enzyme believed to play a key role in protecting the mitochondria from oxi tive injury. CuZnSOD (sodl). by far the more abundant form of SOD in... 

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