Dietary lipophilic iron alters amyloidogenesis and microglial morphology in Alzheimer's disease knock-in APP mice.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized pathologically by amyloid beta (Aß) deposition, microgliosis, and iron dyshomeostasis. Increased labile iron due to homeostatic dysregulation is believed to facilitate amyloidogenesis. Free iron is incorporated into aggregating amyloid peptides during Aß plaque formation and increases potential for oxidative stress surrounding plaques. The goal of this work was to observe how brain iron levels temporally influence Aß plaque formation, plaque iron concentration, and microgliosis. We fed humanized APPNL-F and APPNL-G-F knock-in mice lipophilic iron compound 3,5,5-trimethylhexanoyl ferrocene (TMHF) and iron deficient diets for twelve months. TMHF elevated brain iron by 22% and iron deficiency decreased brain iron 21% relative to control diet. Increasing brain iron with TMHF accelerated plaque formation, increased Aß staining, and increased senile morphology of amyloid plaques. Increased brain iron was associated with increased plaque-iron loading and microglial iron inclusions. TMHF decreased IBA1+ microglia branch length while increasing roundness indicative of microglial activation. This body of work suggests that increasing mouse brain iron with TMHF potentiates a more human-like Alzheimer's disease phenotype with iron integration into Aß plaques and associated microgliosis.

Dietary lipophilic iron accelerates regional brain iron-load in C57BL6 mice.

Impaired brain iron homeostatic mechanisms, independent of pathological hallmarks, are harmful to the brain because excess free iron can cause DNA, protein, and lipid damage via oxidative stress. The goal of this study was to evaluate the longitudinal effect of chronic iron overload and deficiency in the vertebrate brain. Ten-week-old C57BL6 male mice were randomly assigned to one of four unique dietary regiments for 1 year: iron-deficient, normal iron, and two different concentrations of lipophilic iron diet containing 3,5,5-trimethylhexanoyl ferrocene (TMHF). Longitudinal MRI parametrics were used to assess the location and extent of ferric iron distribution. Tissue collected at 12 months was used to directly measure iron-load, protein alterations, and histological metrics. While the iron-deficient diet did not alter brain iron stores, 0.11% TMHF and early exposure with 0.5% TMHF elevated brain iron by roughly 40 and 100%, respectively. R 2 rate increased more in the TMHF groups within iron rich brain regions. Increased brain iron concentration was linearly correlated with an increase in L-ferritin expression, and TMHF diet was found to increase L-ferritin within the olfactory bulb, neocortex, pallidum, thalamus, corpus callosum, CA3 regions of the hippocampus, and substantia nigra. Moreover, gliosis and oxidative stress were detected in the TMHF groups in the regions associated with iron-load. Spatial memory impairment was evident in the iron-loaded mice. This work illustrates that lipophilic iron elevates brain iron in a regionally specific fashion and positions dietary TMHF administration as a model for brain iron overloading.

Rapid self-assembly of core-shell organosilicon microcapsules within a microfluidic device.

The preparation of hierarchically structured organosilicon microcapsules from commercially available starting materials is described. Using a microfluidic device, an emulsion of dichlorodiphenylsilane is formed in a continuous phase of aqueous glycerol. The silane droplets undergo hydrolysis, condensation, and crystallization within minutes to form self-assembled, core-shell microcapsules. The microparticles have been characterized with light and electron microscopy, nuclear magnetic resonance spectroscopy (NMR), diffusion-ordered NMR spectroscopy (DOSY), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and powder X-ray diffraction (XRD). The characterization data show that the microcapsule walls consist of amorphous, oligomeric poly(diphenylsiloxane) surrounded by a spiny layer of crystalline diphenylsilanediol. Glycerol is occluded within the wall material but is not covalently bound to the silicon components. Glycerol is a crucial element for producing low-dispersity microcapsules with well-ordered surface spines, as the use of methyl cellulose as viscomodifier yields amorphous surfaces.

Cytokine toxicity to oligodendrocyte precursors is mediated by iron.

Inflammatory processes play a key role in the pathogenesis of a number of common neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Abnormal iron accumulation is frequently noted in these diseases and compelling evidence exists that iron is involved in inflammatory reactions. Histochemical stains for iron repeatedly demonstrate that oligodendrocytes, under normal conditions, stain more prominently than any other cell type in the brain. Therefore, we examined the hypothesis that cytokine toxicity to oligodendrocytes is iron mediated. Oligodendrocytes in culture were exposed to interferon-gamma (IFN-gamma), interleukin-1beta (IL-1beta), and tumor necrosis factor-alpha (TNF-alpha). Toxicity was observed in a dose-dependent manner for IFN-gamma and TNF-alpha. IL-1beta was not toxic in the concentrations used in this study. The toxic concentration of IFN-gamma, and TNF-alpha was lower if the cells were iron loaded, but iron loading had no effect on the toxicity of IL-1beta. These data provide insight into the controversy regarding the toxicity of cytokines to oligodendrocytes by revealing that iron status of these cells will significantly impact the outcome of cytokine treatment. The exposure of oligodendrocytes to cytokines plus iron decreased mitochondrial membrane potential but activation of caspase 3 is limited. The antioxidant, TPPB, which targets mitochondria, protected the oligodendrocytes from the iron-mediated cytotoxicity, providing further support that mitochondrial dysfunction may underlie the iron-mediated cytokine toxicity. Therapeutic strategies involving anti-inflammatory agents have met with limited success in the treatment of demyelinating disorders. A better understanding of these agents and the contribution of cellular iron status to cytokine toxicity may help develop a more consistent intervention strategy.