Clearance of β-amyloid mediated by autophagy is enhanced by MTORC1 inhibition but not AMPK activation in APP/PSEN1 astrocytes

Artemisiae Iwayomogii Herba mitigates excessive neuroinflammation and Aβ accumulation by regulating the pro-inflammatory response and autophagy-lysosomal pathway in microglia in 5xFAD mouse model of Alzheimer's disease

Alzheimer's disease (AD) presents a growing societal challenge, driven by an aging population. It is characterized by neurodegeneration linked to β-amyloid (Aβ) and tau protein aggregation. Reactive glial cell-mediated neuroinflammation exacerbates disease progression by facilitating the accumulation of Aβ and impairing its clearance, thus highlighting potential therapeutic targets. Aerial parts of Artemisia iwayomogi (AIH), a kind of mugwort, has been consumed as a medicinal herb in East Asia for relieving inflammation-related diseases. Previously, AIH was found to exert potent inhibitory effects on neuroinflammation. This study aimed to examine whether AIH mitigates AD pathogenesis by regulating neuroinflammation and reducing Aβ deposition. AIH treatment to primary mixed glial cultures attenuated the pro-inflammatory responses evoked by Aβ stimulation. When treated to 5 × familial AD (5xFAD) mice, AIH improved learning and cognitive ability and reduced Aβ burden in the brain. AIH suppressed glial overactivation, as well as inhibited the expressions of pro-inflammatory mediators in the brain. Moreover, AIH regulated AKT signaling and elevated the expression of autophagy-lysosomal mediators in vitro. It was confirmed that lysosome-associated membrane protein 1 (LAMP1) was increased in the Aβ-associated microglia in the mouse hippocampus. Finally, it was observed that tau phosphorylation was alleviated, and synaptic protein expression was increased in AIH-treated 5xFAD mice. Overall, this study demonstrated that AIH ameliorated excessive neuroinflammation and Aβ accumulation by regulating microglial activation and autophagy-lysosomal pathway, thereby suggesting AIH as a promising therapeutic candidate for AD treatment.

USP9X-mediated deubiquitination of Raptor contributes to autophagy impairment and memory deficits in P301S mice

BACKGROUND

Tauopathies, including Alzheimer's disease, are characterized by the pathological aggregation of tau protein, which is strongly linked to dysregulation of the autophagy-lysosomal degradation pathway. However, therapeutic strategies targeting this pathway remain limited.

METHODS

We used both in vitro and in vivo models to investigate the role of Raptor in tau pathology. Knockdown of Raptor was performed to assess its impact on mTORC1 activation, autophagy, and tau accumulation. The relationship between USP9X and Raptor was also examined. Pharmacological inhibition of USP9X with WP1130 was employed to further confirm the involvement of the USP9X-Raptor-mTORC1 axis in tau degradation.

RESULTS

Elevated Raptor levels in the hippocampus of P301S mice led to hyperactivation of mTORC1, impairing autophagy flux. Knockdown of Raptor effectively suppressed mTORC1 activation, promoted autophagy, and mitigated the accumulation of tau and its phosphorylated isoforms. This reduction in tau pathology was accompanied by decreased neuronal loss in the hippocampus, amelioration of synaptic damage, and improvement in cognitive function. The increased Raptor protein observed in the hippocampus of P301S mice was likely attributable to elevated USP9X content, which enhanced Raptor deubiquitination and protected it from proteasomal degradation. Pharmacological inhibition of USP9X with WP1130 in vitro effectively suppressed Raptor, promoted autophagy, and accelerated the degradation of tau and phosphorylated tau.

CONCLUSIONS

Our findings highlight Raptor and USP9X as promising molecular targets for therapeutic intervention in tauopathies. Targeting the USP9X-Raptor-mTORC1 axis may provide a novel strategy for promoting autophagy and mitigating tau pathology in Alzheimer's disease and other tauopathies.

Metformin Lysosomal Targeting: A Novel Aspect to Be Investigated for Metformin Repurposing in Neurodegenerative Diseases?

Metformin is a widely employed drug in type 2 diabetes. In addition to warranting good short- and long-term glycemic control, metformin displays many intriguing properties as protection against cardiovascular and neurodegenerative diseases, anti-tumorigenic and longevity promotion. In addition to being a low-cost drug, metformin is generally well tolerated. However, despite the enthusiastic drive to aliment these novel studies, many contradictory results suggest the importance of better elucidating the complexity of metformin action in different tissues/cells to establish its possible employment in neurodegenerative diseases. This review summarises recent data identifying lysosomal-dependent processes and lysosomal targets, such as endosomal Na+/H+ exchangers, presenilin enhancer 2 (PEN2), the lysosomal pathway leading to AMP-activated protein kinase (AMPK) activation, and the transcription factor EB (TFEB), modulated by metformin. Lysosomal dysfunctions resulting in autophagic and lysosomal acidification and biogenesis impairment appear to be hallmarks of many inherited and acquired neurodegenerative diseases. Lysosomes are not yet seen as a sort of cellular dump but are crucial in determining key signalling paths and processes involved in the clearance of aggregated proteins. Thus, the possibility of pharmacologically modulating them deserves great interest. Despite the potentiality of metformin in this context, many additional important issues, such as dosing, should be addressed in the future.

View on Metformin: Antidiabetic and Pleiotropic Effects, Pharmacokinetics, Side Effects, and Sex-Related Differences

Metformin is a synthetic biguanide used as an antidiabetic drug in type 2 diabetes mellitus, achieved by studying the bioactive metabolites of Galega officinalis L. It is also used off-label for various other diseases, such as subclinical diabetes, obesity, polycystic ovary syndrome, etc. In addition, metformin is proposed as an add-on therapy for several conditions, including autoimmune diseases, neurodegenerative diseases, and cancer. Although metformin has been used for many decades, it is still the subject of many pharmacodynamic and pharmacokinetic studies in light of its extensive use. Metformin acts at the mitochondrial level by inhibiting the respiratory chain, thus increasing the AMP/ATP ratio and, subsequently, activating the AMP-activated protein kinase. However, several other mechanisms have been proposed, including binding to presenilin enhancer 2, increasing GLP1 release, and modification of microRNA expression. Regarding its pharmacokinetics, after oral administration, metformin is absorbed, distributed, and eliminated, mainly through the renal route, using transporters for cationic solutes, since it exists as an ionic molecule at physiological pH. In this review, particular consideration has been paid to literature data from the last 10 years, deepening the study of clinical trials inherent to new uses of metformin, the differences in effectiveness and safety observed between the sexes, and the unwanted side effects. For this last objective, metformin safety was also evaluated using both VigiBase and EudraVigilance, respectively, the WHO and European databases of the reported adverse drug reactions, to assess the extent of metformin side effects in real-life use.