Bax, a pro-apoptotic member of the Bcl-2 family of proteins has the ability to form transmembrane pores large enough to allow cytochrome c (Cyt c) release, as well as to activate the mitochondrial permeability transition pore (mPTP); however, no differential study has been conducted to clarify which one of these mechanisms predominates over the other in the same system. In the present study, we treated isolated mitochondria from MCF7 cells with recombinant protein Bax and tested the efficacy of the mPTP inhibitor cyclosporin A (CsA) and of the Bax channel blocker (Bcb) to inhibit cytochrome c release. We also, induced apoptosis in MCF7 cell cultures with TNF-α plus cycloheximide to determine the effect of such compounds in apoptosis induction via mPTP or Bax oligomerization. Cytochrome c release was totally prevented by CsA and partially by Bcb when apoptosis was induced with recombinant Bax in isolated mitochondria from MCF7 cells. CsA increased the number of living cells in cell culture, as compared with the effect of Bax channel blocker. These results indicate that mPTP activation is the predominant pathway for Bax-induced cytochrome c release from MCF7 mitochondria and for apoptosis induction in the whole cell.

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Titanium dioxide nanoparticles (TiO2 NPs) are widely used for industrial and commercial applications. Once inside the body, they translocate into the bloodstream and reach different areas of the cardiovascular system including the heart, increasing the risk of developing cardiovascular diseases; consequently, the investigation of their interaction with cardiac cells is required. We previously showed that TiO2 NPs are internalized by H9c2 rat cardiomyoblasts, and here, we examined the molecular mechanisms underlying this process. TiO2 NPs internalization was evaluated by transmission electron microscopy, time-lapse microscopy, and flow cytometry. Changes in the actin cytoskeleton were studied by phalloidin staining. Endocytic uptake mechanisms for nanoparticles were probed with chemical inhibitors, whereas clathrin and dynamin expression was measured by Western blot. Cellular uptake of TiO2 NPs occurred early after 30 min exposure, and large aggregates were observed after 1 h. Actin cytoskeleton reorganization included cell elongation plus lower density and stability of actin fibers. Cytochalasin-D inhibited TiO2 NPs uptake, indicating actin-mediated internalization. Dynamin and clathrin levels increased early after TiO2 NPs exposure, and their inhibition reduced nanoparticle uptake. Therefore, TiO2 NPs internalization by H9c2 rat cardiomyoblasts involves actin cytoskeleton reorganization and clathrin/dynamin-mediated endocytosis.

The exposure to low doses of ozone induces an oxidative stress state, which is involved in neurodegenerative diseases. Forkhead box O (FoxO) family of transcription factors are activated by oxidative signals and regulate cell proliferation and resistance to oxidative stress. Our aim was to study the effect of chronic exposure to ozone on the activation of FoxO 1a and FoxO 3a in the hippocampus of rats. Male Wistar rats were divided into six groups and exposed to 0.25 ppm of ozone for 0, 7, 15, 30, 60, and 90 days. After treatment, the groups were processed for western blotting and immunohistochemistry against FoxO 3a, Mn SOD, cyclin D2, FoxO 1a, and active caspase 3. We found that exposure to ozone increased the activation of FoxO 3a at 30 and 60 days and expression of Mn SOD at all treatment times. Additionally, increases in cyclin D2 from 7 to 90 days; FoxO 1a at 15, 30, and 60 days; and activate caspase 3 from 30 to 60 days of exposure were noted. The results indicate that ozone alters regulatory pathways related to both the antioxidant system and the cell cycle, inducing neuronal reentry into the cell cycle and apoptotic death.

Traumatic brain injury (TBI) is one of the major causes of disability in the USA. It occurs when external mechanical forces induce brain damage that causes deformation of brain tissue. TBI is also associated with alterations of the blood-brain barrier (BBB). Using primary rat brain microvascular endothelial cells as an in vitro BBB model, the effects of biaxial stretch were characterized at 5, 10, 15, 25, and 50% deformation using a commercially available system. The results were compared to the effects of mild and moderate TBI in vivo, induced by the weight-drop method in mice. In vitro, live/dead cells, lactate dehydrogenase (LDH) release, caspase 3/7 staining, and tight junction (TJ) protein expression were evaluated 24 h after a single stretch episode. In vivo, Evans blue extravasation, serum levels of S100β, and TJ protein expression were evaluated. Stretch induced a deformation-dependent increase in LDH release, cell death, and activation of caspase 3/7, suggesting the induction of apoptosis. Interestingly, low magnitudes of deformation increased the expression of TJ proteins, likely in an attempt to compensate for stretch damage. High magnitudes of deformation decreased the expression of TJ proteins, suggesting that the damage was too severe to counteract. In vivo, mild TBI did not affect BBB permeability or the expression of TJ proteins. However, moderate TBI significantly increased BBB permeability and decreased the expression of these proteins, similar to the results obtained with a high magnitude deformation. These data support the use biaxial stretch as valuable tool in the study of TBI in vitro.