The regulatory role of mitochondrial pora and the possibility of its pharmacological modulation

The review is devoted to the role of mitochondrial Ca2+-dependent pore (mPTP) in the regulation of metabolic processes in cells under physiological and pathological conditions. The mechanisms of reperfusion injury in the postischemic period involving mPTP are discussed in the paper. The possibilities of pharmacological regulation of metabolic and functional processes in cells by target action on mPTP work are assessed. This approach allows to regulate key cell functions, stimulating either mechanisms of adaptation and survival in extreme conditions or apoptosis. Pharmacological modulators of the mitochondrial pore as drugs have promising value for treatment of ischemic diseases as well as tumor therapy.

Spreading Depression and Related Events Are Significant Sources of Neuronal Zn2+ Release and Accumulation

Spreading depression (SD) involves coordinated depolarizations of neurons and glia that propagate through the brain tissue. Repetitive SD-like events are common following human ischemic strokes, and are believed to contribute to the enlargement of infarct volume. Accumulation of Zn2+ is also implicated in ischemic neuronal injury. Synaptic glutamate release contributes to SD propagation, and because Zn2+ is costored with glutamate in some synaptic vesicles, we examined whether Zn2+ is released by SD and may therefore provide a significant source of Zn2+ in the postischemic period. Spreading depression-like events were generated in acutely prepared murine hippocampal slices by deprivation of oxygen and glucose (OGD), and Zn2+ release was detected extracellularly by a Zn2+-selective indicator FluoZin-3. Deprivation of oxygen and glucose-SD produced large FluoZin-3 increases that propagated with the event, and signals were abolished in tissues from ZnT3 knockout animals lacking synaptic Zn2+. Synaptic Zn2+ release was also maintained with repetitive SDs generated by microinjections of KCl under normoxic conditions. Intracellular Zn2+ accumulation in CA1 neurons, assessed using microinjection of FluoZin-3, showed significant increases following SD that was attributed to synaptic Zn2+ release. These results suggest that Zn2+ is released during SDs and could provide a significant source of Zn2+ that contributes to neurodegeneration in the postischemic period.

Extracellular Diffusion Parameters in the Rat Somatosensory Cortex during Recovery from Transient Global Ischemia/Hypoxia

Changes in the extracellular space diffusion parameters during ischemia are well known, but information about changes during the postischemic period is lacking. Extracellular volume fraction (α) and tortuosity (Λ) were determined in the rat somatosensory cortex using the real-time iontophoretic method; diffusion-weighted magnetic resonance imaging was used to determine the apparent diffusion coefficient of water. Transient ischemia was induced by bilateral common carotid artery clamping for 10 or 15 mins and concomitant ventilation with 6% O2 in N2. In both ischemia groups, a negative DC shift accompanied by increased potassium levels occurred after 1 to 2 mins of ischemia and recovered to preischemic values within 3 to 5 mins of reperfusion. During ischemia of 10 mins duration, α typically decreased to 0.07 ± 0.01, whereas Λ increased to 1.80 ± 0.02. In this group, normal values of α = 0.20 ± 0.01 and Λ = 1.55 ± 0.01 were registered within 5 to 10 mins of reperfusion. After 15 mins of ischemia, α increased within 40 to 50 mins of reperfusion to 0.29 ± 0.03 and remained at this level. Tortuosity (Λ) increased to 1.81 ± 0.02 during ischemia, recovered within 5 to 10 mins of reperfusion, and was increased to 1.62 ± 0.01 at the end of the experiment. The observed changes can affect the diffusion of ions, neurotransmitters, metabolic substances, and drugs in the nervous system.

Heat pretreatment differentially affects cardiac fatty acid accumulation during ischemia and postischemic reperfusion

We investigated whether the cardioprotection induced by heat stress (HS) pretreatment is associated with mitigation of phospholipid degradation during the ischemic and/or postischemic period. The hearts, isolated from control rats and from heat-pretreated rats (42°C for 15 min) either 30 min (HS0.5-h) or 24 h (HS24-h) earlier, were subjected to 45 min of no-flow ischemia, followed by 45 min of reperfusion. Unesterified arachidonic acid (AA) accumulation was taken as a measure for phospholipid degradation. Significantly improved postischemic ventricular functional recovery was only found in the HS24-h group. During ischemia, AA accumulated comparably in control and both HS groups. During reperfusion in control and HS0.5-h hearts, AA further accumulated (control hearts from 82 ± 33 to 109 ± 51 nmol/g dry wt, not significant; HS-0.5h hearts from 52 ± 22 to 120 ± 53 nmol/g dry wt; P < 0.05). In contrast, AA was lower at the end of the reperfusion phase in HS24-h hearts than at the end of the preceding ischemic period (74 ± 18 vs. 46 ± 23 nmol/g dry wt; P < 0.05). Thus accelerated reperfusion-induced degradation of phospholipids in control hearts is completely absent in HS24-h hearts. Furthermore, the lack of functional improvement in HS0.5-h hearts is also associated with a lack of beneficial effect on lipid homeostasis. Therefore, it is proposed that enhanced membrane stability during reperfusion is a key mediator in the heat-induced cardioprotection.