MST1-knockdown protects against impairment of working memory via regulating neural activity in depression-like mice

MST1 selective inhibitor Xmu-mp-1 ameliorates neuropathological changes in a rat model of sporadic Alzheimer's Disease by modulating Hippo-Wnt signaling crosstalk

Alzheimer's disease (AD), the most prevalent form of dementia, is characterized by progressive cognitive impairment accompanied by aberrant neuronal apoptosis. Reports suggest that the pro-apoptotic mammalian set20-like kinase 1/2 (MST1/2) instigates neuronal apoptosis via activating the Hippo signaling pathway under various stress conditions, including AD. However, whether inhibiting MST1/2 has any therapeutic benefits in AD remains unknown. Thus, we tested the therapeutic effects of intervening MST1/2 activation via the pharmacological inhibitor Xmu-mp-1 in a sporadic AD rat model. Sporadic AD was established in adult rats by intracerebroventricular streptozotocin (ICV-STZ) injection (3 mg/kg body weight). Xmu-mp-1 (0.5 mg/kg/body weight) was administered once every 48 h for two weeks, and Donepezil (5 mg/kg body weight) was used as a reference standard drug. The therapeutic effects of Xmu-mp-1 on ICV-STZ rats were determined through various behavioral, biochemical, histopathological, and molecular tests. At the behavioral level, Xmu-mp-1 improved cognitive deficits in sporadic AD rats. Further, Xmu-mp-1 treatment reduced STZ-associated tau phosphorylation, amyloid-beta deposition, oxidative stress, neurotoxicity, neuroinflammation, synaptic dysfunction, neuronal apoptosis, and neurodegeneration. Mechanistically, Xmu-mp-1 exerted these neuroprotective actions by inactivating the Hippo signaling while potentiating the Wnt/β-Catenin signaling in the AD rats. Together, the results of the present study provide compelling support that Xmu-mp-1 negated the neuronal dysregulation in the rat model of sporadic AD. Therefore, inhibiting MST/Hippo signaling and modulating its crosstalk with the Wnt/β-Catenin pathway can be a promising alternative treatment strategy against AD pathology. This is the first study providing novel mechanistic insights into the therapeutic use of Xmu-mp-1 in sporadic AD.

Altered gamma oscillations and beta-gamma coupling in drug-naive first-episode major depressive disorder: Association with sleep and cognitive disturbance

OBJECTIVE

Gamma oscillations contribute to the pathogenesis mechanisms of major depressive disorder (MDD) have been proposed, but gamma activity is not well characterized. This study is the first attempt to investigate the altered gamma oscillations in first-episode MDD, particularly the beta-gamma coupling, and to determine the potential symptomatic relationship with the identified gamma dysregulation.

METHODS

Resting electroencephalography was recorded for 43 drug-naive first-episode MDD and 57 healthy control (HC) subjects. Integrated analysis of relative spectral power, weighted phase lag index, and phase-amplitude coupling (PAC) were utilized to reveal the alterations of gamma activities. Pearson's correlation was implemented to identify the relationship between altered gamma activities and the clinical depressive symptoms, which were categorized into four factors: anxiety somatization, retardation, cognitive disturbance, and sleep disturbance.

RESULTS

Compared with HC subjects, MDD patients showed not only significantly decreased gamma powers in the left temporal and the bilateral occipital regions but also weakened gamma connectivity between the left hemisphere and the right frontal region. Furthermore, attenuated beta-gamma PAC of MDD patients was observed in the left temporal regions. Importantly, the suppression of left occipital mid- and high gamma oscillations were negatively correlated with sleep disturbance, while the deficits in left temporal beta-mid-gamma PAC and beta-high gamma PAC showed negative correlations with cognitive disturbance.

LIMITATIONS

Important limitations are the small sample size and the possible inclusion of bipolar depression in the MDD group.

CONCLUSIONS

Our findings provide the first evidence that in first-episode MDD, aberrant gamma powers and beta-gamma coupling are associated with sleep and cognitive impairments, respectively, deepening our understanding of the physiological mechanisms underlying sleep and cognitive symptoms in first-episode MDD. Altered gamma oscillations emerge as promising biomarkers for diagnosing MDD.