Retinal macroglia changes in a triple transgenic mouse model of Alzheimer's disease.

The retinas of Alzheimer's disease (AD) patients and transgenic AD animal models display amyloid beta deposits and degeneration of ganglion cells. Little is known, however, about the glial changes in the AD retina. The present study used a triple transgenic mouse model (3xTG-AD), which carries mutated human amyloid precursor protein, tau, and presenilin 1 genes and closely mimics the human brain pathology, to investigate retinal glial changes in AD. AD cognitive symptoms are known to begin in the 3xTG-AD mice at four months of age but plaques and tangles are not seen until six to twelve months. Müller cells in 3xTG-AD animals were GFAP-positive, indicating activation, at the earliest time point investigated, nine months. Astrocyte activation was also suggested in the 3xTG-AD mice by an apparent increase in size and process number. Another glial marker, S100, was expressed by astrocytes in both the non-transgenic (NTG) controls and 3xTG-AD retinas. Labeling was predominantly nuclear in nine month non-transgenic (NTG) control mice but was also seen in the cytoplasm and processes at 18 months of age. Interestingly, the nuclear localization was not as prominent in the 3xTG-AD retina even at nine months with labeling observed in astrocyte processes. The diffusion of S100 suggests the possible secretion of this protein, as is seen in the brain, with age and, more profoundly, associated with AD. Several dense, abnormally shaped, opaque structures were noted in all 3xTG-AD mice investigated. These structures, which were enveloped by GFAP and S100-positive astrocytes and Müller cells, were positive for amyloid beta, suggesting that they are amyloid plaques. Staining control retinas with amyloid showed similar structures in 30% of NTG animals but these were fewer in number and not associated with glial activation. The results herein indicate retinal glia activation in the 3xTG-AD mouse retina.

Cognitive recovery and restoration of cell proliferation in the dentate gyrus in the 5XFAD transgenic mice model of Alzheimer's disease following 2-hydroxy-DHA treatment.

Alzheimer's disease (AD) is the most common neurodegenerative disorder in the elderly. In the last years, abnormalities of lipid metabolism and in particular of docosahexaenoic acid (DHA) have been recently linked with the development of the disease. According to the recent studies showing how hydroxylation of fatty acids enhances their biological activity, here we show that chronic treatment with a hydroxylated derivative of DHA, the 2-hydroxy-DHA (2OHDHA) in the 5XFAD transgenic mice model of AD improves performance in the radial arm maze test and restores cell proliferation in the dentate gyrus, with no changes in the presence of beta amyloid (Aß) plaques. These results suggest that 2OHDHA induced restoration of cell proliferation can be regarded as a major component in memory recovery that is independent of Aß load thus, setting the starting point for the development of a new drug for the treatment of AD.

Synechococcus elongatus PCC 7942 as a Platform for Bioproduction of Omega-3 Fatty Acids.

Alpha-linolenic acid and stearidonic acid are precursors of omega-3 polyunsaturated fatty acids, essential nutrients in the human diet. The ability of cyanobacteria to directly convert atmospheric carbon dioxide into bio-based compounds makes them promising microbial chassis to sustainably produce omega-3 fatty acids. However, their potential in this area remains unexploited, mainly due to important gaps in our knowledge of fatty acid synthesis pathways. To gain insight into the cyanobacterial fatty acid biosynthesis pathways, we analyzed two enzymes involved in the elongation cycle, FabG and FabZ, in Synechococcus elongatus PCC 7942. Overexpression of these two enzymes led to an increase in C18 fatty acids, key intermediates in omega-3 fatty acid production. Nevertheless, coexpression of these enzymes with desaturases DesA and DesB from Synechococcus sp. PCC 7002 did not improve alpha-linolenic acid production, possibly due to their limited role in fatty acid synthesis. In any case, efficient production of stearidonic acid was not achieved by cloning DesD from Synechocystis sp. PCC 6803 in combination with the aforementioned DesA and DesB, reaching maximum production at 48 h post induction. According to current knowledge, this is the first report demonstrating that S. elongatus PCC 7942 can be used as an autotrophic chassis to produce stearidonic acid.

ß-Catenin Role in the Vulnerability/Resilience to Stress-Related Disorders Is Associated to Changes in the Serotonergic System.

We previously reported that the inactivation (cKO) or the stabilization (cST) of ß-catenin in cells expressing the astrocyte-specific glutamate aspartate transporter (GLAST) is associated with the vulnerability or resilience to exhibit anxious/depressive-like behaviors, respectively, and to changes in hippocampal proliferation. Here, we used these cKO and cST ß-catenin mice to study the serotonergic system functionality associated with their behavioral/molecular phenotype. The activity of 5-HT1A receptors was assessed by (+)-8-OH-DPAT-induced hypothermia and [35S]GTPγS binding autoradiography. The animals' response to acute stress and the levels of extracellular serotonin (5-HT) in the medial prefrontal cortex (mPFC) were also assessed. cKO mice presented higher 5-HT1A autoreceptor functionality, lower 5-HT1A heteroreceptor functionality, and a decrease in extracellular 5-HT levels in the mPFC. These neurochemical changes were accompanied with a blunted physiological response to stress-induced hyperthermia. In contrast, cST mice showed a reduced 5-HT1A autoreceptor functionality and higher extracellular 5-HT levels in the mPFC after fluoxetine administration. Moreover, cST mice subjected to chronic corticosterone administration did not show a blunted response to fluoxetine. Our findings suggest the existence of a link between ß-catenin levels and 5-HT1A receptor functionality, which may be relevant to understand the neurobiological bases underlying the vulnerability or resilience to stress-related disorders.

Notch activates cell cycle reentry and progression in quiescent cardiomyocytes.

The inability of heart muscle to regenerate by replication of existing cardiomyocytes has engendered considerable interest in identifying developmental or other stimuli capable of sustaining the proliferative capacity of immature cardiomyocytes or stimulating division of postmitotic cardiomyocytes. Here, we demonstrate that reactivation of Notch signaling causes embryonic stem cell-derived and neonatal ventricular cardiomyocytes to enter the cell cycle. The proliferative response of neonatal ventricular cardiomyocytes declines as they mature, such that late activation of Notch triggers the DNA damage checkpoint and G2/M interphase arrest. Notch induces recombination signal-binding protein 1 for Jkappa (RBP-Jkappa)-dependent expression of cyclin D1 but, unlike other inducers, also shifts its subcellular distribution from the cytosol to the nucleus. Nuclear localization of cyclin D1 is independent of RBP-Jkappa. Thus, the influence of Notch on nucleocytoplasmic localization of cyclin D1 is an unanticipated property of the Notch intracellular domain that is likely to regulate the cell cycle in multiple contexts, including tumorigenesis as well as cardiogenesis.