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Tumor suppressor phosphatase and tensin homolog (PTEN) is highly expressed in neurons and PTEN inhibition has been reported to be neuroprotective against ischemic stroke in experimental models. On the other hand, PTEN deletion has been shown to lead to cognitive impairment. In the current study, we examined the expression and functions of PTEN in an ischemic stroke rodent model. We found rapid S-nitrosylation and degradation of PTEN after cerebral ischemia/reperfusion injury. PTEN degradation leads to activation of Akt. PTEN partial deletion or PTEN inhibition increased the expression of GABAA receptor (GABAAR) γ2 subunit and enhanced GABAA receptor current. After cerebral ischemia, increased expression of GABAAR γ2 subunit was observed in the ischemia region and the penumbra area. We also observed PTEN loss in astrocytes after cerebral ischemia. Astrocytic PTEN partial knockout increased astrocyte activation and exacerbated ischemic damage. We speculated that ischemic stroke induced neuronal PTEN degradation, hence enhanced GABAA receptor-medicated neuronal activity inhibition which could attenuate excitotoxicity and provide neuroprotection during the acute phase after stroke, while inhibiting long-term functional recovery and contributing to vascular cognitive impairment after stroke. On the other hand, ischemic stroke induced astrocytic PTEN loss and enhanced ischemic damage and astrogliosis. Taken together, our study indicates that ischemic stroke induces rapid PTEN degradation in both neurons and astrocytes which play both protective and detrimental action in a spatiotemporal- and cell-type-dependent manner. Our study provides critical insight for targeting PTEN signaling pathway for stroke treatment., (Copyright © 2014 IBRO. Published by Elsevier Ltd. All rights reserved.)

The purpose of this study was to explore the mechanisms by which oxidative stress affects the aging process. The hypothesis that the rate of accumulation of oxidative damage to specific mitochondrial proteins is linked to the life expectancy of animals was tested in the housefly. The rate of oxygen consumption and life expectancy of the flies were experimentally altered by confining the flies in small jars, where they were unable to fly. Prevention of flight activity decreased the rate of oxygen utilization of flies and almost tripled their life span as compared to those permitted to fly. Rate of mitochondrial H(2)O(2) generation at various ages was lower in the low activity flies than in the high activity flies. Oxidative damage to mitochondrial proteins, adenine nucelotide translocase, and aconitase, detected as carbonyl modifications, was attenuated; and the loss in their functional activity occurring with age was retarded in the long-lived low activity flies as compared to the short-lived high activity flies. The two proteins were previously identified to be the only mitochondrial proteins exhibiting age-related increases in carbonylation. Results support the hypothesis that accrual of oxidative damage to specific protein targets and the consequent loss of their function may constitute a mechanism by which oxidative stress controls the aging process.

Cytochrome c is a component of the mitochondrial electron transport chain, where it transfers electrons from ubiquinol-cytochrome c reductase to cytochrome c oxidase. Autoxidation of some of the components of the electron transport chain is the main source of intracellular O(2)(-*)/H(2)O(2) production in aerobic organisms. Because cytochrome c is located on the outer surface of the inner mitochondrial membrane, it is likely to be constantly exposed to H(2)O(2), secreted by mitochondria into the cytosol. The specific objective of this study was to determine whether cytochrome c in the flight muscle mitochondria of the housefly is oxidatively damaged during aging and/or under severe oxidative stress induced by exposure of flies to 100% oxygen. Results of two independent methods, namely tritiated borohydride labeling for determining carbonylation and mass spectral analysis for the measurement of molecular mass, indicated that neither the carbonyl level nor the molecular mass of cytochrome c was affected by aging or hyperoxia. Thus, either cytochrome c is resistant to oxidative damage in vivo or the oxidized cytochrome c is promptly degraded. These findings also support the concept that protein oxidative damage during aging and under oxidative stress is selective.

The degree to which antioxidant loss occurs in human skin after UV irradiation is unknown, as is the cascade of events that might occur. We have, therefore, evaluated a tissue culture model of human skin for its usefulness for studying oxidative injury by UV-irradiation. Human skin equivalents, a tissue culture model, were irradiated using a full solar UV spectrum (UVA and UVB, 280-400 nm) (0 to 16.8 J/cm2, 0-12 minimal erythemal dose, MED), then incubated from 1 to 24 h. Ubiquinol was the most UV-light sensitive antioxidant and was depleted by 2.1 J/cm2 (1.5 MED, p < .004); ubiquinone decreased with 4.2 J/cm2 (3 MED, p < .0007). A linear decrease in alpha-tocopherol occurred--approximately 1.7 pmol tocopherol/cm2 surface were destroyed per J/cm2 UV-light. Urate was depleted by irradiation with 8.4 J/cm2 (6 MED), while ascorbate was depleted by 16.8 J/cm2 (12 MED). Cellular protein carbonyls and lactic dehydrogenase (LDH) leakage into the medium were only increased at 1 h incubation following exposure to 16.8 J/cm2 (12 MED). At 24 h incubation, PGE2 was increased in the medium of cells exposed to UV-irradiation at 0.35 J/cm2 (0.25 MED) compared with sham-exposed cells (p < .04); higher UV exposures lead to significant increases in both PGE2 (p < .001) and LDH (p < .001) in the medium. In conclusion, human skin equivalents respond to suberythemal levels of UV-irradiation by increasing production of PGE2; higher levels of UV-irradiation (at least 1 MED) were needed to deplete cellular antioxidants and induce immediately detectable oxidative damage.