Stem cell-derived polarized hepatocytes.

Human stem cell-derived hepatocyte-like cells (HLCs) offer an attractive platform to study liver biology. Despite their numerous advantages, HLCs lack critical in vivo characteristics, including cell polarity. Here, we report a stem cell differentiation protocol that uses transwell filters to generate columnar polarized HLCs with clearly defined basolateral and apical membranes separated by tight junctions. We show that polarized HLCs secrete cargo directionally: Albumin, urea, and lipoproteins are secreted basolaterally, whereas bile acids are secreted apically. Further, we show that enterically transmitted hepatitis E virus (HEV) progeny particles are secreted basolaterally as quasi-enveloped particles and apically as naked virions, recapitulating essential steps of the natural infectious cycle in vivo. We also provide proof-of-concept that polarized HLCs can be used for pharmacokinetic and drug-drug interaction studies. This novel system provides a powerful tool to study hepatocyte biology, disease mechanisms, genetic variation, and drug metabolism in a more physiologically relevant setting.

Vitamin E reduces amyloidosis and improves cognitive function in Tg2576 mice following repetitive concussive brain injury.

Traumatic brain injury is a well-recognized environmental risk factor for developing Alzheimer's disease. Repetitive concussive brain injury (RCBI) exacerbates brain lipid peroxidation, accelerates amyloid (Abeta) formation and deposition, as well as cognitive impairments in Tg2576 mice. This study evaluated the effects of vitamin E on these four parameters in Tg2576 mice following RCBI. Eleven-month-old mice were randomized to receive either regular chow or chow-supplemented with vitamin E for 4 weeks, and subjected to RCBI (two injuries, 24 h apart) using a modified controlled cortical impact model of closed head injury. The same dietary regimens were maintained up to 8 weeks post-injury, when the animals were killed for biochemical and immunohistochemical analyses after behavioral evaluation. Vitamin E-treated animals showed a significant increase in brain vitamin E levels and a significant decrease in brain lipid peroxidation levels. After RBCI, compared with the group on regular chow, animals receiving vitamin E did not show the increase in Abeta peptides, and had a significant attenuation of learning deficits. This study suggests that the exacerbation of brain oxidative stress following RCBI plays a mechanistic role in accelerating Alphabeta accumulation and behavioral impairments in the Tg2576 mice.

12/15-lipoxygenase is increased in Alzheimer's disease: possible involvement in brain oxidative stress.

Alzheimer's disease (AD) is a chronic neurodegenerative disorder that impairs cognition and behavior. Although the initiating molecular events are not known, increasing evidence suggests that oxidative stress could play a functional role in its pathogenesis. Lipoxygenase (LOX) enzymes by oxidizing polyunsaturated fatty acids synthesize hydroperoxyacids, which are potent pro-oxidant mediators. Because circumstantial evidence suggests that 12/15-LOX is a major source of oxidative stress, we investigated the protein levels and activity of this enzyme in different brain regions of histopathologically confirmed AD and control cases. Using quantitative Western blot analysis we demonstrated that in affected frontal and temporal regions of AD brains the amount of 12/15-LOX was higher compared with controls, whereas no difference between the two groups was detected in the cerebellum. This observation was confirmed by immunohistochemical studies. Levels of 12/15-hydroxyeicosatetraenoic acids, metabolic products of 12/15-LOX, were also markedly elevated in AD brains compared to controls. This increase directly correlated with brain lipid peroxidation, and inversely with vitamin E levels. Finally, genetic deletion of this enzyme in vitro resulted in a reduction of the cellular oxidative stress response after incubation with H2O2 or amyloid beta. These data show that the 12/15-LOX metabolic pathway is increased and correlates with an oxidative imbalance in the AD brain, implying that this enzyme might contribute to the pathogenesis of this neurodegenerative disorder.

Early vitamin E supplementation in young but not aged mice reduces Abeta levels and amyloid deposition in a transgenic model of Alzheimer's disease.

Increased brain oxidative stress is a key feature of Alzheimer's disease (AD) and manifests predominantly as lipid peroxidation. However, clinical evidence that antioxidants can affect the clinical course of the disease is limited. In the present study, we investigated the effect of the antioxidant Vitamin E on the AD-like phenotype when given to a transgenic mouse model (Tg2576) of the disease before or after the amyloid plaques are deposited. One group of Tg2576 received Vitamin E starting at 5 months of age until they were 13 months old, the second group started at 14 months of age until they were 20 months old. Brain levels of 8,12-iso-iPF2alpha-VI, a specific marker of lipid peroxidation, were significantly reduced in both groups of mice receiving Vitamin E compared with placebo. Tg2576 administered with Vitamin E at a younger age showed a significant reduction in Abeta levels and amyloid deposition. By contrast, mice receiving the diet supplemented with Vitamin E at a later age did not show any significant difference in either marker when compared with placebo. These results support the hypothesis that oxidative stress is an important early event in AD pathogenesis, and antioxidant therapy may be beneficial only if given at this stage of the disease process.