Loss of AQP4 polarized localization with loss of β-dystroglycan immunoreactivity may induce brain edema following intracerebral hemorrhage.

The aquaporin-4 (AQP4) water channel contributes to brain water homeostasis in perivascular and subpial membrane domains of astrocytes where it is concentrated. These membranes form the interface between the neuropil and the extracellular liquid spaces. The brain-selective deletion of the dystroglycan (DG) gene causes a disorganization of AQP4 on the astroglial endfeet. First, we analyzed the expression of AQP4, β-DG in the brain following intracerebral hemorrhage (ICH) and correlated AQP4 expression with the expression pattern of the β-DG, which is a component of dystrophin-dystroglycan complex (DDC). Besides, the vessels ultrastructure and brain water content were investigated at different time points post-ICH (day 1, day 3, day 7). We found that AQP4 polarity was disturbed in parallel with the loss of β-DG in the perihematomal area post-ICH. At day 1 post-ICH, brain edema was obvious and the damage of vascular ultrastructure was the most severe. These results suggest a role for β-DG in targeting and stabilizing AQP4 channel in astrocytic cells, which may be critical for water homeostasis in brain.

Qiu GP ，Xu J ，Zhuo F ，Sun SQ ，Liu H ，Yang M ，Huang J ，Lu WT ，Huang SQ ... -  《-》

Edaravone Maintains AQP4 Polarity Via OS/MMP9/β-DG Pathway in an Experimental Intracerebral Hemorrhage Mouse Model.

Oxidative stress (OS) is the main cause of secondary damage following intracerebral hemorrhage (ICH). The polarity expression of aquaporin-4 (AQP4) has been shown to be important in maintaining the homeostasis of water transport and preventing post-injury brain edema in various neurological disorders. This study primarily aimed to investigate the effect of the oxygen free radical scavenger, edaravone, on AQP4 polarity expression in an ICH mouse model and determine whether it involves in AQP4 polarity expression via the OS/MMP9/β-dystroglycan (β-DG) pathway. The ICH mouse model was established by autologous blood injection into the basal nucleus. Edaravone or the specific inhibitor of matrix metalloproteinase 9 (MMP9), MMP9-IN-1, called MMP9-inh was administered 10 min after ICH via intraperitoneal injection. ELISA detection, neurobehavioral tests, dihydroethidium staining (DHE staining), intracisternal tracer infusion, hematoxylin and eosin (HE) staining, immunofluorescence staining, western blotting, Evans blue (EB) permeability assay, and brain water content test were performed. The results showed that OS was exacerbated, AQP4 polarity was lost, drainage function of brain fluids was damaged, brain injury was aggravated, expression of AQP4, MMP9, and GFAP increased, while the expression of β-DG decreased after ICH. Edaravone reduced OS, restored brain drainage function, reduced brain injury, and downregulated the expression of AQP4, MMP9. Both edaravone and MMP9-inh alleviated brain edema, maintained blood-brain barrier (BBB) integrity, mitigated the loss of AQP4 polarity, downregulated GFAP expression, and upregulated β-DG expression. The current study suggests that edaravone can maintain AQP4 polarity expression by inhibiting the OS /MMP9/β-DG pathway after ICH.

Wang Z ，Li Y ，Wang Z ，Liao Y ，Ye Q ，Tang S ，Wei T ，Xiao P ，Huang J ，Lu W ... -  《-》

Effects of Aquaporin-4 on edema formation following intracerebral hemorrhage.

Intracerebral hemorrhage (ICH) constitutes 10% to 15% of all strokes and is associated with high morbidity and mortality. To date, little is known about the role of AQP4 (Aquaporin-4), which is abundantly expressed in pericapillary astrocyte foot processes and in edema formation after intracerebral hemorrhage. The purpose of this study was to examine the role of AQP4 in edema formation after ICH by using AQP4(-/-) mice. ICH was induced by microinjecting 5microl autologous whole blood into the striatum of AQP4(+/+) and AQP4(-/-) mice. We compared neurological deficits, brain edema contents of whole hemorrhagic ipsilateral hemisphere, specific gravity of brain tissue surrounding hematoma, Evans blue leakage and ultrastructure of brain microvessels between AQP4(+/+) and AQP4(-/-) mice following ICH. Histological changes were also detected with Nissl's staining and TUNEL staining. Our experiments showed a significant increase of AQP4 expression following ICH in AQP4(+/+) mice. AQP4 deletion aggravated neurological deficits and brain edema contents of whole hemorrhagic ipsilateral hemisphere. Besides, it also reduced the specific gravity of brain tissue surrounding hematoma. Moreover, it enhanced Evans blue leakage and ultrastructure of brain microvessel damage. Histology also showed less Nissl's staining and more TUNEL staining in AQP4(-/-) mice following ICH. These results suggest that AQP4 deletion increases ICH damage, including edema formation, blood-brain barrier damage and neuronal death/TUNEL-positive cells. Further studies on the protective role of activated AQP4 expression following ICH may provide useful therapeutic target for ICH-induced brain injury.

Tang Y ，Wu P ，Su J ，Xiang J ，Cai D ，Dong Q ... -  《-》

Brain edema after intracerebral hemorrhage in rats: the role of iron overload and aquaporin 4.

Qing WG ，Dong YQ ，Ping TQ ，Lai LG ，Fang LD ，Min HW ，Xia L ，Heng PY ... -  《JOURNAL OF NEUROSURGERY》

Carvacrol alleviates cerebral edema by modulating AQP4 expression after intracerebral hemorrhage in mice.

Carvacrol is a natural compound extracted from many plants of the family Lamiaceae. Previous studies have demonstrated that carvacrol has potential neuroprotective effects in central nervous system diseases such as Alzheimer's disease and cerebral ischemia. In this study, we investigated the preclinical effect of carvacrol on cerebral edema after intracerebral hemorrhage (ICH) using a bacterial collagenase-induced ICH mouse model. Mice were randomly divided into sham (n=43), vehicle-treated (n=51), and carvacrol-treated groups (n=101). In carvacrol-treated group, carvacrol was administrated to mice at 0h, 1h, or 3h after ICH induction. Carvacrol was injected intraperitoneally with single doses of 10, 25, 50, or 100mg/kg. Neurologic dysfunctions, brain water content, aquaporins (AQPs) mRNAs level and AQP4 protein expression in the perihematomal area were evaluated post ICH. Our results showed that carvacrol administration improved neurological deficits after day 3 following ICH (p<0.05). Carvacrol reduced cerebral edema and Evans Blue leakage at day 3 (p<0.05). We also found that carvacrol treatment decreased AQP4 mRNA in a dose-dependent manner at 24h. Furthermore, AQP4 protein expression in the perihematomal area was reduced by carvacrol significantly at day 3 after ICH (p<0.05). Our findings suggest that carvacrol may exert its protective effect on ICH injury by ameliorating AQP4-mediated cerebral edema.

Zhong Z ，Wang B ，Dai M ，Sun Y ，Sun Q ，Yang G ，Bian L ... -  《-》