Alzheimer's Disease-Related Phospho-Tau181 Signals Are Localized to Demyelinated Axons of Parvalbumin-Positive GABAergic Interneurons in an App Knock-In Mouse Model of Amyloid-ß Pathology.

BACKGROUND: The tau protein phosphorylated at Thr181 (p-tau181) in cerebrospinal fluid and blood is a sensitive biomarker for Alzheimer's disease (AD). Increased p-tau181 levels correlate well with amyloid-ß (Aß) pathology and precede neurofibrillary tangle formation in the early stage of AD; however, the relationship between p-tau181 and Aß-mediated pathology is less well understood. We recently reported that p-tau181 represents axonal abnormalities in mice with Aß pathology (AppNLGF). However, from which neuronal subtype(s) these p-tau181-positive axons originate remains elusive. OBJECTIVE: The main purpose of this study is to differentiate neuronal subtype(s) and elucidate damage associated with p-tau181-positive axons by immunohistochemical analysis of AppNLGF mice brains. METHODS: Colocalization between p-tau181 and (1) unmyelinated axons positive for vesicular acetylcholine transporter or norepinephrine transporter and (2) myelinated axons positive for vesicular glutamate transporter, vesicular GABA transporter, or parvalbumin in the brains of 24-month-old AppNLGF and control mice without Aß pathology were analyzed. The density of these axons was also compared. RESULTS: Unmyelinated axons of cholinergic or noradrenergic neurons did not overlap with p-tau181. By contrast, p-tau181 signals colocalized with myelinated axons of parvalbumin-positive GABAergic interneurons but not of glutamatergic neurons. Interestingly, the density of unmyelinated axons was significantly decreased in AppNLGF mice, whereas that of glutamatergic, GABAergic, or p-tau181-positive axons was less affected. Instead, myelin sheaths surrounding p-tau181-positive axons were significantly reduced in AppNLGF mice. CONCLUSION: This study demonstrates that p-tau181 signals colocalize with axons of parvalbumin-positive GABAergic interneurons with disrupted myelin sheaths in the brains of a mouse model of Aß pathology.

Drosophila Toll-9 is induced by aging and neurodegeneration to modulate stress signaling and its deficiency exacerbates tau-mediated neurodegeneration.

Drosophila Toll-9 is most closely related to mammalian Toll-like receptors; however, physiological functions of Toll-9 remain elusive. We examined the roles of Toll-9 in fly brains in aging and neurodegeneration. Toll-9 mRNA levels were increased in aged fly heads accompanied by activation of nuclear factor-kappa B (NF-kB) and stress-activated protein kinase (SAPK) signaling, and many of these changes were modulated by Toll-9 in glial cells. The loss of Toll-9 did not affect lifespan or brain integrity, whereas it exacerbated hydrogen peroxide-induced lethality. Toll-9 expression was also induced by nerve injury but did not affect acute stress response or glial engulfment activity, suggesting Toll-9 may modulate subsequent neurodegeneration. In a fly tauopathy model, Toll-9 deficiency enhanced neurodegeneration and disease-related tau phosphorylation with reduced SAPK activity, and blocking SAPK enhanced tau phosphorylation and neurodegeneration. In sum, Toll-9 is induced upon aging and nerve injury and affects neurodegeneration by modulating stress kinase signaling.

Bmi-1 regulates mucin levels and mucin O-glycosylation in the submandibular gland of mice.

Mucins, the major components of salivary mucus, are large glycoproteins abundantly modified with O-glycans. Mucins present on the surface of oral tissues contribute greatly to the maintenance of oral hygiene by selectively adhering to the surfaces of microbes via mucin O-glycans. However, due to the complex physicochemical properties of mucins, there have been relatively few detailed analyses of the mechanisms controlling the expression of mucin genes and the glycosyltransferase genes involved in glycosylation. Analysis performed using supported molecular matrix electrophoresis, a methodology developed for mucin analysis, and knockout mice without the polycomb group protein Bmi-1 revealed that Bmi-1 regulates mucin levels in the submandibular gland by suppressing the expression of the mucin Smgc gene, and that Bmi-1 also regulates mucin O-glycosylation via suppression of the glycosyltransferase Gcnt3 gene in the submandibular gland.

Alteration of mucins in the submandibular gland during aging in mice.

OBJECTIVE: Mucins are large glycosylated glycoproteins that are produced in the salivary glands, and their changes may contribute to the development of xerostomia due to aging and the accompanying deterioration of oral hygiene. This study aimed to characterize the changes in the mucins produced in submandibular gland (SMG) during the aging process. METHODS: SMG mucins derived from mice of each age were separated using supported molecular matrix electrophoresis (SMME). Subsequently, the membranes were stained with Alcian blue (AB) or blotted with MAL-II lectin. The SMME membranes stained with AB were subjected to densitometric analysis and glycan analysis. The detailed structures of O-glycan were investigated by tandem mass spectrometry (MS/MS). RESULTS: The SMG of mice secreted three mucins with different glycan profiles: age-specific mucin, youth-specific mucin, and a mucin expressed throughout life, and the expression patterns of these mucins change during aging. Additionally, age-specific mucin began to be detected at about 12 months of age. A mucin expressed throughout life and age-specific mucin had the same mass of major glycans but different structures. Furthermore, the proportion of mucin glycan species expressed throughout life changed during the aging process, and aging tended to decrease the proportion of fucosylated glycans and increase the proportion of sialoglycans. CONCLUSION: There are three secretory mucins with different glycan profiles in the SMG of mice, and their expression patterns change according to the period of the aging process. The proportion of glycan species of mucin expressed throughout life also changes during the aging process.

Pyrophosphate-Induced Intramolecular Excimer Formation in Dinuclear Zinc(II) Complexes with Tetrakisquinoline Ligands.

Dinuclear Zn2+ complexes with HTQHPN ( N,N,N' ,N'-tetrakis(2-quinolylmethyl)-2-hydroxy-1,3-propanediamine) derivatives have been prepared, and their pyrophosphate (PPi, P2O74-) sensing properties were examined. The ligand library includes six HTQHPN derivatives with electron-donating/withdrawing substituents, an extended aromatic ring, and six-membered chelates upon zinc binding. Complexation of ligand with 2 equiv of Zn2+ promotes small to moderate fluorescence enhancement around 380 nm, but in the cases of HTQHPN, HT(6-FQ)HPN ( N,N,N' ,N'-tetrakis(6-fluoro-2-quinolylmethyl)-2-hydroxy-1,3-propanediamine), and HT(8Q)HPN ( N,N,N' ,N'-tetrakis(8-quinolylmethyl)-2-hydroxy-1,3-propanediamine), subsequent addition of PPi induced a significant fluorescence increase around 450 nm. This fluorescence enhancement in the long-wavelength region is attributed to the conformational change of the bis-(quinolylmethyl)amine moiety which promotes intramolecular excimer formation between adjacent quinolines upon binding with PPi. The structures of PPi- and phosphate-bound dizinc complexes were revealed by X-ray crystallography utilizing phenyl-substituted analogues. The zinc complex with HT(8Q)HPN exhibits the highest signal enhancement ( IPPi/ I0 = 12.5) and selectivity toward PPi sensing ( IATP/ IPPi = 20% and IADP/ IPPi = 25%). The fluorescence enhancement turned to decrease gradually after the addition of more than 1 equiv of PPi due to the removal of zinc ion from the ligand-zinc-PPi ternary complex, allowing the accurate determination of PPi concentrations at the fluorescence maximum composition. The practical application of the present method was demonstrated monitoring the enzymatic activity of pyrophosphatase.

Fluorescent Detection of Phosphate Ion via a Tetranuclear Zinc Complex Supported by a Tetrakisquinoline Ligand and µ4-PO4 Core.

The tetrakisquinoline ligand HT(6-MeO8Q)HPN (N,N,N',N'-tetrakis(6-methoxy-8-quinolylmethyl)-2-hydroxy-1,3-propanediamine) exhibited Zn2+-induced fluorescence enhancement with high specificity and sensitivity (IZn/I0 = 57 and ICd/IZn = 6% in the presence of 2 equiv of Zn2+; LOD (limit of detection) = 15 nM). This ligand also exhibited fluorescence enhancement specific to inorganic phosphate (PO43-) in DMF-HEPES buffer (50 mM HEPES, 100 mM KCl, pH = 7.5) (1:1) in the presence of 2 equiv of Zn2+. The structure of the unprecedented tetranuclear zinc complex with a µ4-PO4 bridge was elucidated by X-ray crystallography as the key species responsible for fluorescence enhancement.