Induced LC degeneration in APP/PS1 transgenic mice accelerates early cerebral amyloidosis and cognitive deficits.

Degeneration of locus ceruleus neurons and subsequent reduction of norepinephrine concentration in locus ceruleus projection areas represent an early pathological indicator of Alzheimer's disease. In order to model the pathology of the human disease and to study the effects of norepinephrine-depletion on amyloid precursor protein processing, behaviour, and neuroinflammation, locus ceruleus degeneration was induced in mice coexpressing the swedish mutant of the amyloid precursor protein and the presenilin 1 DeltaExon 9 mutant (APP/PS1) using the neurotoxin N-(2-chloroethyl)-N-ethyl-bromo-benzylamine (dsp4) starting treatment at 3 months of age. Norepinephrine transporter immunolabelling demonstrated severe loss of locus ceruleus neurons and loss of cortical norepinephrine transporter starting as early as 4.5 months of age and aggravating over time. Of note, dsp4-treated transgenic mice showed elevated amyloid beta levels and impaired spatial memory performance at 6.5 months of age compared to control-treated APP/PS1 transgenic mice, indicating an accelerating effect on cerebral amyloidosis and cognitive deficits. Likewise, norepinephrine-depletion increased neuroinflammation compared to transgenic controls as verified by macrophage inflammatory protein-1alpha and -1beta gene expression analysis. Exploratory activity and memory retention was compromised by age in APP/PS1 transgenic mice and further aggravated by induced noradrenergic deficiency. In contrast, novel object recognition was not influenced by norepinephrine deficiency, but by the APP/PS1 transgene at 12 months. Overall, our data indicate that early loss of noradrenergic innervation promotes amyloid deposition and modulates the activation state of inflammatory cells. This in turn could have had impact on the acceleration of cognitive deficits observed over time.

Interplay of IGF-I and 17beta-estradiol at age-specific levels in human sebocytes and fibroblasts in vitro.

In order to obtain greater insights into the molecular mechanisms accompanying hormonal aging the effects of growth hormone (GH), insulin-like growth factor-I (IGF-I), 17beta-estradiol, progesterone and dehydroepiandrosterone were tested as single agents in concentrations corresponding to 20- and 60-year-old females on human SZ95 sebocytes and fibroblasts. Cell proliferation and viability were measured by 4-methylumbelliferyl heptanoate and lactate dehydrogenase microassays, respectively, whereas lipid accumulation was documented via nile red microassay and fluorescence microscopy. mRNA and protein expression were evaluated via real-time RT-PCR and Western blotting or ELISA, accordingly. Our results depict the importance of IGF-I for lipid synthesis in SZ95 sebocyte and demonstrate the lack of 17beta-estradiol, dehydroepiandrosterone and progesterone activity on lipid synthesis and SZ95 sebocyte proliferation suggesting that the action of these hormones in vivo may be implemented through indirect pathways. Fibroblast showed to be more susceptible to 17beta-estradiol treatment, while IGF-I could significantly stimulate fibroblast proliferation in a dose-dependent manner. Furthermore, an interplay between the 17beta-estradiol and IGF-I signaling pathway was documented in both cell types. In conclusion, IGF-I is a key regulator of human skin aging and declining IGF-I levels with age may play a significant role in the reduction of skin surface lipids and thickness.