Enhanced axon guidance and synaptic markers in rat brains using ferric-tannic nanoparticles.

Ferric-tannic nanoparticles (FTs) are now considered to be new pharmaceuticals appropriate for the prevention of brain aging and related diseases. We have previously shown that FTs could activate axon guidance pathways and cellular clearance functioning in neuronal cell lines. Herein, we further investigated whether FTs could activate the two coordinated neuronal functions of axon guidance and synaptic function in rat brains and neuronal cell lines. A single intravenous injection of a safe dose of FTs has been shown to activate a protein expression of axon attractant Netrin-1 and neurotransmitter receptor GABRA4 in the cerebral cortexes of male Wistar rats. According to RNA-seq with targeted analysis, axon guidance and synapses have been enriched and Ephrin membered genes have been identified as coordinating a network of genes for such processes. In vitro, as expected, FTs are also found to activate axon guidance markers and promote neuronal tubes in neuronal cell lines. At the same time, pre-synaptic markers (synaptophysin), post-synaptic markers (synapsin), and GABRA4 neurotransmitter receptors have been found to be activated by FTs. Interestingly, synaptophysin has been found to localize along the promoted neuronal tubes, suggesting that enhanced axon guidance is associated with the formation and transportation of pre-synaptic vesicles. Preliminarily, repeated injection of FTs into adult rats every 3 days for 10 times could enhance an expression of synaptophysin in the cerebral cortex, as compared to control rats. This work demonstrates that FTs can be used for activating brain function associated with axon guidance and synaptic function.

The role of labile iron on brain proteostasis; could it be an early event of neurodegenerative disease?

Iron deposits in the brain are a natural consequence of aging. Iron accumulation, especially in the form of labile iron, can trigger a cascade of adverse effects, eventually leading to neurodegeneration and cognitive decline. Aging also increases the dysfunction of cellular proteostasis. The question of whether iron alters proteostasis is now being pondered. Herein, we investigated the effect of ferric citrate, considered as labile iron, on various aspects of proteostasis of neuronal cell lines, and also established an animal model having a labile iron diet in order to evaluate proteostasis alteration in the brain along with behavioral effects. According to an in vitro study, labile iron was found to activate lysosome formation but inhibits lysosomal clearance function. Furthermore, the presence of labile iron can alter autophagic flux and can also induce the accumulation of protein aggregates. RNA-sequencing analysis further reveals the upregulation of various terms related to proteostasis along with neurodegenerative disease-related terms. According to an in vivo study, a labile iron-rich diet does not induce iron overload conditions and was not detrimental to the behavior of male Wistar rats. However, an iron-rich diet can promote iron accumulation in a region-dependent manner. By staining for autophagic markers and misfolding proteins in the cerebral cortex and hippocampus, an iron-rich diet was actually found to alter autophagy and induce an accumulation of misfolding proteins. These findings emphasize the importance of labile iron on brain cell proteostasis, which could be implicated in developing of neurological diseases.

TauSTED super-resolution imaging of labile iron in primary hippocampal neurons.

Iron dyshomeostasis is involved in many neurological disorders, particularly neurodegenerative diseases where iron accumulates in various brain regions. Identifying mechanisms of iron transport in the brain is crucial for understanding the role of iron in healthy and pathological states. In neurons, it has been suggested that iron can be transported by the axon to different brain regions in the form of labile iron; a pool of reactive and exchangeable intracellular iron. Here we report a novel approach to imaging labile ferrous iron, Fe(II), in live primary hippocampal neurons using confocal and TauSTED (stimulated emission depletion) microscopy. TauSTED is based on super-resolution STED nanoscopy, which combines high spatial resolution imaging (<40 nm) with fluorescence lifetime information, thus reducing background noise and improving image quality. We applied TauSTED imaging utilizing biotracker FerroFarRed Fe(II) and found that labile iron was present as submicrometric puncta in dendrites and axons. Some of these iron-rich structures are mobile and move along neuritic pathways, arguing for a labile iron transport mechanism in neurons. This super-resolution imaging approach offers a new perspective for studying the dynamic mechanisms of axonal and dendritic transport of iron at high spatial resolution in living neurons. In addition, this methodology could be transposed to the imaging of other fluorescent metal sensors.

Early Detection of Hepatocarcinogenicity in Rats Using MRI with Ferric-Tannic Nanoparticles.

Herein, we present molecular nanoparticles of ferric-tannic complexes (so called ferric-tannic nanoparticles, FT NPs) used to enhance the MRI signal in the early stage of hepatocarcinoma. FT NPs were found to accumulate in the hepatic parenchyma without tumor nodules of Wistar rats in which hepatocarcinogenicity had been induced using diethylnitrosamine (DEN). The MRI enhancement and accumulation of FT NPs were clearly observed in the early phase of hepatocarcinogenicity, which was possibly modulated by various solute carrier family members present in the entire hepatic parenchyma of the DEN-induced rats. These findings suggest that MRI with FT NPs is promising for the assessment of the early stage of hepatocarcinoma.

Molecular Nanoparticles of Ferric-Tannic Complexes Enhance Brain Magnetic Resonance Imaging and Activate Brain Clearance Pathways.

Iron-containing drugs can be considered beneficial for noninvasive magnetic resonance imaging (MRI) and induction of essential biochemical processes. Herein, we present a new type of iron-containing drug based on molecular nanoparticles of ferric-tannic complexes (FTs), which could be used to enhance noninvasive brain MRI and modulate brain clearance pathways. Once intravenously administered to healthy Wistar rats, the maximum enhancement of the T1-weighted MRI signal was observed at 0.5 h postinjection, corresponding to their maximum accumulation in the brain. After this time, FTs were rapidly cleared by the brain, which was possibly modulated by organic anion transporters present at the blood-brain barrier. This result describes the "come-and-run" concept of FTs, which could be utilized as a brain-targeting agent for various purposes. Although the "come-and-run" mechanism allows them to have a short half-life in the brain, they remain long enough to activate brain clearance pathways such as autophagy, lysosomal function, and cellular clearance. Therefore, FTs could be considered new clinically translatable pharmaceuticals for brain MRI and the prevention of brain aging and related diseases.