Astrocytic mitochondrial frataxin-A promising target for ischemic brain injury

NOTCH3 Mutation Causes Glymphatic Impairment and Promotes Brain Senescence in CADASIL

AIMS

The aim of this study is to investigate the role of glymphatic function of cerebral autosomal dominant arteriopathy, subcortical infarcts, and leukoencephalopathy (CADASIL), the most common monogenic small vessel disease caused by NOTCH3 mutation, and to explore potential therapeutic strategies to improve glymphatic function.

METHODS

We assessed glymphatic influx and efflux function in CADASIL mouse models (Notch3R170C) and correlated these findings with brain atrophy in CADASIL patients. We also investigated the underlying mechanisms of glymphatic impairment, focusing the expression of AQP4 in astrocytic endfeet.

RESULTS

CADASIL mouse exhibited both impaired glymphatic influx and efflux, which impedes waste clearance and promotes brain senescence. In accordance, brain atrophy in CADASIL patients is associated with perivascular space enlargement, indicating that glymphatic impairment contributes to advanced brain senescence in CADASIL. The glymphatic malfunction in CADASIL is attributed to diminished AQP4 expression in astrocytic endfeet, which is the core mediator of glymphatic activity. Mechanistically, AQP4 expression is regulated by NOTCH3-RUNX1-CMYB signaling. Reinforcing AQP4 expression in astrocytes by AAV-based therapy resumes the glymphatic functions in CADASIL mice, which further prevents brain senescence.

CONCLUSION

We propose that to improve glymphatic function by reinforcing AQP4 expression is a promising therapeutic strategy in CADASIL.

Regulation of NAD+/NADH Redox Involves the Protective Effects of Ginsenoside Rb1 against Oxygen-Glucose Deprivation/Reoxygenation-Induced Astrocyte Lesions

The aim of this study was to investigate NAD+/NADH redox regulation in astrocytes by Ginsenoside Rb1 subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) and to reveal the neuroprotective mechanism of ginseng. Neonatal mouse brain was used to culture primary astrocytes. The third generation of the primary astrocytes was used for the experiments. OGD/R was introduced by culturing the cells in a glucose-free media under nitrogen for 6 h followed by a regular culture for 24 h. Ginsenoside Rb1 attenuated OGD/R-induced astrocyte injury in a dose-dependent manner. It improved the mitochondrial function of OGD/R astrocytes indicated by improving mitochondrial distribution, increasing mitochondrial membrane potential, and enhancing mitochondrial DNA copies and ATP production. Ginsenoside Rb1 significantly lifted intracellular NAD+/NADH, NADPH/NADP+, and GSH/GSSG in OGD/R astrocytes. It inhibited the protein expression of both PARP1 and CD38, while attenuating the SIRT1 drop in OGD/R cells. In line with its effects on PARP1, Ginsenoside Rb1 significantly reduced the expression of poly-ADP-ribosylation (PARylation) proteins in OGD/R cells. Ginsenoside Rb1 also significantly increased the expression of NAMPT and NMNAT2, both of which are key players in NAD/NADH synthesis. The results suggest that the regulation of NAD+/NADH redox involves the protective effects of ginsenoside Rb1 against OGD/R-induced astrocyte injury.