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Alzheimer’s disease (AD) is characterized by the deposition of amyloid β peptide (Aβ) in the brain. The neuropeptide somatostatin (SST) regulates Aβ catabolism by enhancing neprilysin (NEP)-catalyzed proteolytic degradation. However, the mechanism by which SST regulates NEP activity remains unclear. Here, we identified α-endosulfine (ENSA), an endogenous ligand of the ATP-sensitive potassium (KATP) channel, as a negative regulator of NEP downstream of SST signaling. The expression of ENSA is significantly increased in AD mouse models and in patients with AD. In addition, NEP directly contributes to the degradation of ENSA, suggesting a substrate-dependent feedback loop regulating NEP activity. We also discovered the specific KATP channel subtype that modulates NEP activity, resulting in the Aβ levels altered in the brain. Pharmacological intervention targeting the particular KATP channel attenuated Aβ deposition, with impaired memory function rescued via the NEP activation in our AD mouse model. Our findings provide a mechanism explaining the molecular link between KATP channel and NEP activation, and give new insights into alternative strategies to prevent AD.

We previously developed single App knock-in mouse models of Alzheimer’s disease (AD) that harbor the Swedish and Beyreuther/Iberian mutations with or without the Arctic mutation ( App NL-G-F and App NL-F mice). We have now generated App knock-in mice devoid of the Swedish mutations ( App G-F mice) and evaluated its characteristics. Amyloid β peptide (Aβ) pathology was exhibited by App G-F mice from 6 to 8 months of age and was accompanied by neuroinflammation. Aβ-secretase inhibitor, verubecestat, attenuated Aβ production in App G-F mice, but not in App NL-G-F mice, indicating that the App G-F mice are more suitable for preclinical studies of β-secretase inhibition given that most patients with AD do not carry the Swedish mutations. Comparison of isogenic App knock-in lines revealed that multiple factors, including elevated C-terminal fragment β (CTF-β) and humanization of Aβ might influence endosomal alterations in vivo. Thus, experimental comparisons between different isogenic App , knock-in mouse lines will provide previously unidentified insights into our understanding of the etiology of AD.

Amyloid-β and tau pathologies are important factors leading to neurodegeneration in Alzheimer’s disease (AD); however, the molecular mechanisms that link these pathologies remain unclear. Assuming that important though as yet unidentified factors inhibit/accelerate tau pathology and neuronal cell death under amyloid pathology, we sought to isolate and identify tau-interacting proteins from mouse brains with or without amyloid pathology. Among the proteins that were identified, we focused on protein arginine methyltransferase 8 (PRMT8), which interacts with tau specifically in the absence of amyloid pathology. To investigate the role of PRMT8 in the pathogenesis of AD, we conducted Prmt8 gene deletion and overexpression experiments in AppNL-G-F/MAPT double knock-in mice and analysed the resulting pathological alterations. PRMT8-knockout did not alter the AD pathology in double knock-in mice, whereas PRMT8-overexpression promoted tau phosphorylation, neuroinflammation and vacuole degeneration. To evaluate if such a PRMT8-induced vacuole degeneration depends on tau pathology, PRMT8 was overexpressed in tau-KO mice, which were consequently found to exhibit vacuole degeneration. In addition, proteomic analyses showed that PRMT8 overexpression facilitated the arginine methylation of vimentin. Abnormal protein methylation could be involved in PRMT8-induced brain pathologies. Taken together, PRMT8 may play an important role in the formation of tau pathology and vacuole degeneration.

SUMMARYWe previously developed single App knock-in mouse models of Alzheimer’s disease (AD) that harbor the Swedish and Beyreuther/Iberian mutations with or without the Arctic mutation (AppNL- G-F and AppNL-F mice). These models showed the development of amyloid β peptide (Aβ) pathology, neuroinflammation and cognitive impairment with aging. We have now generated App knock-in mice devoid of the Swedish mutations (AppG-F mice) and some additional mutants to address the following two questions: [1] Do the Swedish mutations influence the mode of β-secretase inhibitor action in vivo? [2] Does the quantity of C-terminal fragment of amyloid precursor protein (APP) generated by β-secretase (CTF-β) affect endosomal properties as previously reported as well as other pathological events? Aβ pathology was exhibited by AppG-F mice from 6 to 8 months of age, and was accompanied by microglial and astrocyte activation. We found that a β-secretase inhibitor, verubecestat, inhibited Aβ production in AppG-F mice, but not in AppNL-G-F mice, indicating that the AppG-F mice are more suitable for preclinical studies of β-secretase inhibition given that most AD patients do not carry Swedish mutations. We also found that the quantity of CTF-β generated by various App knock-in mutants failed to correlate with endosomal alterations or enlargement, implying that CTF-β, endosomal abnormalities, or both are unlikely to play a major role in AD pathogenesis. This is the first AD mouse model ever described that recapitulates amyloid pathology in the brain without the presence of Swedish mutations and without relying on the overexpression paradigm. Thus, experimental comparisons between different App knock-in mouse lines will potentially provide new insights into our understanding of the etiology of AD.

Alzheimer's disease (AD) is characterized by the deposition of amyloid β peptide (Aβ) in the brain. The neuropeptide somatostatin (SST) regulates Aβ catabolism by enhancing neprilysin (NEP)-catalyzed proteolytic degradation. However, the mechanism by which SST regulates NEP activity remains unclear. Here, we identified α-endosulfine (ENSA), an endogenous ligand of the ATP-sensitive potassium (K

The neuropeptide somatostatin (SST) regulates amyloid β peptide (Aβ) catabolism by enhancing neprilysin (NEP)-catalyzed proteolytic degradation. However, the mechanism by which SST regulates NEP activity remains unclear. Here we report the identification by differential proteomics of α-endosulfine (ENSA), an endogenous ligand of the ATP-sensitive potassium (KATP) channel, as a negative regulator of NEP activity downstream of SST signaling. Genetic deficiency of ENSA resulted in enhanced NEP activity and decreased Aβ deposition in the brains of wild-type and Alzheimer’s disease (AD) model mice. Pharmacological intervention to increase the probability of KATP channel opening reduced Aβ deposition in AD model mice. Our findings provide new insights into possible mechanisms to prevent AD.

Endoplasmic reticulum (ER) stress is believed to play an important role in the etiology of Alzheimer's disease (AD). The accumulation of misfolded proteins and perturbation of intracellular calcium homeostasis are thought to underlie the induction of ER stress, resulting in neuronal dysfunction and cell death. Several reports have shown an increased ER stress response in amyloid precursor protein (APP) and presenilin1 (PS1) double-transgenic (Tg) AD mouse models. However, whether the ER stress observed in these mouse models is actually caused by AD pathology remains unclear. APP and PS1 contain one and nine transmembrane domains, respectively, for which it has been postulated that overexpressed membrane proteins can become wedged in a misfolded configuration in ER membranes, thereby inducing nonspecific ER stress. Here, we used an App-knockin (KI) AD mouse model that accumulates amyloid-β (Aβ) peptide without overexpressing APP to investigate whether the ER stress response is heightened because of Aβ pathology. Thorough examinations indicated that no ER stress responses arose in App-KI or single APP-Tg mice. These results suggest that PS1 overexpression or mutation induced a nonspecific ER stress response that was independent of Aβ pathology in the double-Tg mice. Moreover, we observed no ER stress in a mouse model of tauopathy (P301S-Tau-Tg mice) at various ages, suggesting that ER stress is also not essential in tau pathology–induced neurodegeneration. We conclude that the role of ER stress in AD pathogenesis needs to be carefully addressed in future studies.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

To understand the molecular processes that link Aβ amyloidosis, tauopathy and neurodegeneration, we screened for tau-interacting proteins by immunoprecipitation/LC-MS. We identified the carboxy-terminal PDZ ligand of nNOS (CAPON) as a novel tau-binding protein. CAPON is an adaptor protein of neuronal nitric oxide synthase (nNOS), and activated by the N-methyl-D-aspartate receptor. We observed accumulation of CAPON in the hippocampal pyramidal cell layer in the AppNL-G-F -knock-in (KI) brain. To investigate the effect of CAPON accumulation on Alzheimer’s disease (AD) pathogenesis, CAPON was overexpressed in the brain of AppNL-G-F mice crossbred with MAPT (human tau)-KI mice. This produced significant hippocampal atrophy and caspase3-dependent neuronal cell death in the CAPON-expressing hippocampus, suggesting that CAPON accumulation increases neurodegeneration. CAPON expression also induced significantly higher levels of phosphorylated, oligomerized and insoluble tau. In contrast, CAPON deficiency ameliorated the AD-related pathological phenotypes in tauopathy model. These findings suggest that CAPON could be a druggable AD target., To understand the molecular processes that link Aβ amyloidosis, tauopathy and neurodegeneration, the authors screened for tau-interacting proteins. They demonstrated that a novel tau binding protein CAPON accelerates tau pathology and neuronal cell death in an Alzheimer’s disease mouse model.

Endoplasmic reticulum (ER) stress is believed to play an important role in the etiology of Alzheimer's disease (AD). The accumulation of misfolded proteins and perturbation of intracellular calcium homeostasis are thought to underlie the induction of ER stress, resulting in neuronal dysfunction and cell death. Several reports have shown an increased ER stress response in amyloid precursor protein (APP) and presenilin1 (PS1) double-transgenic (Tg) AD mouse models. However, whether the ER stress observed in these mouse models is actually caused by AD pathology remains unclear. APP and PS1 contain one and nine transmembrane domains, respectively, for which it has been postulated that overexpressed membrane proteins can become wedged in a misfolded configuration in ER membranes, thereby inducing nonspecific ER stress. Here, we used an App-knockin (KI) AD mouse model that accumulates amyloid-β (Aβ) peptide without overexpressing APP to investigate whether the ER stress response is heightened because of Aβ pathology. Thorough examinations indicated that no ER stress responses arose in App-KI or single APP-Tg mice. These results suggest that PS1 overexpression or mutation induced a nonspecific ER stress response that was independent of Aβ pathology in the double-Tg mice. Moreover, we observed no ER stress in a mouse model of tauopathy (P301S-Tau-Tg mice) at various ages, suggesting that ER stress is also not essential in tau pathology–induced neurodegeneration. We conclude that the role of ER stress in AD pathogenesis needs to be carefully addressed in future studies.

症例は74歳の女性で, 腹膜膨満, 上腹部痛を主訴に受診, 腹部CTにて腹水貯留を認めるも, 血液検査所見にては, 腫瘍マーカーCA15-3, CA125の異常高値を認めるのみであった. 試験開腹術を施行した. 腹膜播種と部分的に肥厚した大網を認めるも, 原発巣不明の癌性腹膜炎の状態で, 術中迅速病理検査では卵巣癌と類似した組織像であった.Omental cake状の大網を可及的に切除し, 腹腔内にCDDPを散布して閉腹した. 術後の病理組織学的検査で腹膜原発漿液性乳頭状腺癌と診断され, CDDPを用いた化学療法を続けた. 8か月後に再開腹したところ, 腹膜播種巣は消失しており, 遺残した大網にわずかな腫瘍遺残を認めるのみであった.初回手術より24か月後の現在, 再発徴候もなく健在である. 腹膜原発漿液性乳頭状腺癌はまれな疾患であるが, 原発巣不明の癌性腹膜炎の鑑別診断として銘記すべき疾患と考えられた.

胃悪性リンパ腫の術後に敗血症性ショックを発症し, 急激な経過で死亡した1例を経験した. 症例は74歳の女性. 胃悪性リンパ腫に対し, 胃全摘術を施行した. 手術当日から, 高熱, 低血圧, 呼吸不全を呈し, 翌日には, 腹壁周囲に皮下出血斑が出現し, その後数時間で広範な壊死性筋膜炎となった.腹壁切開創, 腹水, 血液の塗抹グラム染色でグラム陰性桿菌(後日Aeromonas hydrophila; 以下, AHと同定)が多数認められた. 壊死創部を切開ドレナージして, 広範囲スペクトルの抗生物質への変更を行ったが, 手術後50時間で死亡した. AHは免疫能の低下した病態では重症化することが報告されているが, AHによる術後の重篤な敗血症と壊死性筋膜炎の報告は, 本例が第1例目である. 免疫能低下症例の手術時には, 本症を合併する可能性を念頭におき, Bacterial translocationのリスクを最小限にして手術を施行する必要があると考えられた.

PURPOSE: In North America and other high-risk areas, there has been a proximal shift in the subsite distribution of colorectal cancer. We wanted to determine whether any similar change has occurred in Japan, and where the incidence of this disease has increased sharply. METHODS: Data from the Reports of the Japanese Society for Cancer of the Colon and Rectum were used to analyze the time trend of colorectal cancer in Japan between 1974 and 1994 according to the patients' age at diagnosis and sex, and the site of the tumor within the colon or rectum. RESULTS: The percentage of patients over the age of 70, especially females, increased. The increase in the percentage of right-sided colon cancer in colorectal cancer cases was accompanied by a continuous decline in the percentage of rectal cancer in both sexes at all ages. In general, the percentage of right-sided colon cancer in colon cancer cases was stable in men, but increased in women. The rate among patients older than 70 years increased in men, but predominated and remained stable in women. No proximal shift in colon cancer was found in either sex under the age of 69. CONCLUSION: These findings indicated that a proximal shift in the subsite distribution of colorectal cancer has occurred in Japan. This rightward shift of colorectal cancer is due to the decreasing proportion of rectal cancer. Furthermore, the increasing proportion of older patients, especially females, may be another major determinant of the changing colon cancer subsite distribution.