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A metabolic shift from oxidative phosphorylation to glycolysis (i.e. the Warburg effect) occurs in Alzheimer's disease accompanied by an increase of both activity and level of HK-I. The findings reported here demonstrate that in the early phase of apoptosis VDAC1 activity, but not its protein level, progressively decreases, in concomitance with the physical interaction of HK-I with VDAC1. In the late phase of apoptosis, glucose-6-phosphate accumulation in the cell causes the dissociation of the two proteins, the re-opening of the channel and the recovery of VDAC1 function, resulting in a reawakening of the mitochondrial function, thus inevitably leading to cell death., (Copyright © 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.)

To find out whether and how the adenine nucleotide translocator-1 (ANT-1) inhibition due to NH2htau and Aβ1-42 is due to an interplay between these two Alzheimer's peptides, ROS and ANT-1 thiols, use was made of mersalyl, a reversible alkylating agent of thiol groups that are oriented toward the external hydrophilic phase, to selectively block and protect, in a reversible manner, the -SH groups of ANT-1. The rate of ATP appearance outside mitochondria was measured as the increase in NADPH absorbance which occurs, following external addition of ADP, when ATP is produced by oxidative phosphorylation and exported from mitochondria in the presence of glucose, hexokinase and glucose-6-phosphate dehydrogenase. We found that the mitochondrial superoxide anions, whose production is induced at the level of Complex I by externally added Aβ1-42 and whose release from mitochondria is significantly reduced by the addition of the VDAC inhibitor DIDS, modify the thiol group/s present at the active site of mitochondrial ANT-1, impair ANT-1 in a mersalyl-prevented manner and abrogate the toxic effect of NH2htau on ANT-1 when Aβ1-42 is already present. A molecular mechanism is proposed in which the pathological Aβ-NH2htau interplay on ANT-1 in Alzheimer's neurons involves the thiol redox state of ANT-1 and the Aβ1-42-induced ROS increase. This result represents an important innovation because it suggests the possibility of using various strategies to protect cells at the mitochondrial level, by stabilizing or restoring mitochondrial function or by interfering with the energy metabolism providing a promising tool for treating or preventing AD., (Copyright © 2013 Elsevier B.V. All rights reserved.)

In order to find out whether and how proteasomes participate in the processes leading cerebellar granule cells to death either in necrosis, due to glutamate neurotoxicity, or in apoptosis, due to K(+) shift, we measured the three proteasome activities by using specific fluorescent probes and investigated the effect of several proteasome inhibitors, including MG132, on the cytochrome c release taking place in the early phase of both apoptosis and necrosis. We show that differently from apoptosis, the early phase of necrosis does not require proteasome activation. Inhibition of proteasome activity can prevent cytochrome c release in cerebellar granule cells undergoing apoptosis, thus improving cell survival, but not necrosis. These findings show that proteasomes play an important role in the early phase of apoptosis but not that of necrosis, and that these two types of cell death differ from each other in their mechanism of cytochrome c release.

Isolated hepatocytes were irradiated with Helium-Neon laser (fluence: 0.24 Joules x cm-2, fluence rate: 12 mW x cm-2) and changes of both cytosolic free Ca2+ concentration and cell membrane potential were checked by measuring fura-2 and bis-oxonol fluorescence respectively. Irradiation resulted in an enhancement in cytosolic free Ca2+ concentration that requires the presence of Ca2+ in the phase outside hepatocytes; consistently an increase in cell membrane potential was measured correlated with it. Interestingly, the rate of increase of both cytosolic free Ca2+ concentration and cell membrane potential shows special time dependent features similar to those peculiar of oscillatory processes.

In order to gain a degree of insight into the mitochondrial component/s responsible of the mitochondria-red light interaction, isolated rat liver mitochondria were irradiated with a Helium-Neon laser (energy dose 2 Joules/cm2, light power 10 mW) and measurements made of the activity of cytochrome c oxidase. A low, but statistically significant increase in the oxygen uptake was found, as polarographically measured, in the presence of rotenone and antimycin A, with ascorbate and TMPD used as substrate pair. Measurements were also made both of the electron transfer and of proton pumping activity: as a result of a major stimulation in the proton pumping activity, about 55% increase of <--H+/e- ratio was found in irradiated mitochondria.

The effect of hyper- and hypothyroidism on lipid peroxidation has been studied in rat liver microsomes under three different experimental conditions. Under none of these conditions was the formation of TBA-reactive substances affected by either of these two pathological states. On the contrary, with NADPH as the only peroxidation inducer, hydroperoxide concentration increased some three fold in microsomes from hyperthyroid rats, while a small decrease was measured in those from hypothyroid animals. Similarly, the activity of NADPH-cytochrome P-450 reductase was found to be 45.1% higher in hyperthyroid and 40.3% lower in hypothyroid microsomes. The possibility discussed here is that two distinct peroxidative mechanisms (of which one, NADPH-cytochrome P-450 reductase-dependent, is influenced by the thyroid hormone) can compete with each other for the substrate polyunsaturated fatty acids.