Ghrelin alleviates early brain injury after subarachnoid hemorrhage via the PI3K/Akt signaling pathway.

Early brain injury (EBI) plays a key role in the pathogenesis of subarachnoid hemorrhage (SAH). Although the neuroprotective effects of ghrelin have been demonstrated in several studies, whether ghrelin reduces EBI after SAH remains unknown. In this study, we hypothesized that treatment with ghrelin would attenuate EBI after SAH, and that this protection would be mediated, at least in part, by activation of the PI3K/Akt signaling pathway. Adult male Sprague-Dawley rats (n=100) were randomly divided into the following groups: control group (n=20), SAH group (n=20), SAH+vehicle group (n=20), SAH+ghrelin group (n=20) and SAH+ghrelin+LY294002 group (n=20). The rats were injected with autologous blood (0.3mL) into the prechiasmatic cistern to induce SAH. Ghrelin (80μg/kg, IP), or an equal volume of vehicle, was administered immediately after surgery. The PI3K inhibitor, LY294002, was applied to manipulate the proposed pathway. Mortality, neurological scores, brain edema, cell apoptosis, and the expression of p-Akt, and cleaved caspase-3 proteins were assayed after 24h SAH. Ghrelin significantly improved neurological function and reduced neuronal apoptosis and brain edema at 24h after SAH. The level of p-Akt, expressed mainly in neurons, was markedly up-regulated. Additionally, the level of cleaved caspase-3 was decreased by ghrelin treatment. The beneficial effects of ghrelin in SAH rats were partially suppressed by LY294002. These results demonstrate that ghrelin may reduce EBI after SAH, via a mechanism involving the PI3K/Akt signaling pathway.

Hao XK ，Wu W ，Wang CX ，Xie GB ，Li T ，Wu HM ，Huang LT ，Zhou ML ，Hang CH ，Shi JX ... -  《-》

Neuroprotective effect of hydrogen-rich saline against neurologic damage and apoptosis in early brain injury following subarachnoid hemorrhage: possible role of the Akt/GSK3β signaling pathway.

Hong Y ，Shao A ，Wang J ，Chen S ，Wu H ，McBride DW ，Wu Q ，Sun X ，Zhang J ... -  《PLoS One》

Exendin-4 attenuates neuronal death via GLP-1R/PI3K/Akt pathway in early brain injury after subarachnoid hemorrhage in rats.

Neuronal apoptosis is considered to be a crucial therapeutic target against early brain injury (EBI) after subarachnoid hemorrhage (SAH). Emerging evidence indicates that Exendin-4 (Ex-4), a glucagon-like peptide 1 receptor (GLP-1R) agonist, plays a neuroprotective role in cerebrovascular disease. This study was conducted in order to verify the neuroprotective role of EX-4 in EBI after SAH in rats. The endovascular perforation model of SAH was performed in Sprague-Dawley rats (n = 153). Ex-4 was intraperitoneally injected 1 h after SAH induction in the rats (SAH + Ex-4). To elucidate the underlying molecular mechanism, small interfering ribonucleic acid (siRNA) for GLP-1R and a specific inhibitor of PI3K, LY294002, were injected intracerebroventricularly into SAH + Ex-4 rats before induction of SAH (n = 6 per group). SAH grading evaluation, immunohistochemistry, Western blots, neurobehavioral assessment, and Fluoro-Jade C (FJC) staining experiments were performed. Expression of GLP-1R was significantly increased and mainly expressed in neurons at 24 h after SAH induction. Administration of Ex-4 significantly improved both short- and long-term neurobehavior in SAH + Ex-4 group compared to SAH + Vehicle group after SAH. Ex-4 treatment significantly increased the expression of GLP-1R, PI3K, p-Akt, Bcl-xl, and Bcl-2, while at the same time was found to decrease expression of Bax in the brain. Effects of Ex-4 were reversed by the intervention of GLP-1R siRNA and LY294002 in SAH + Ex-4+GLP-1R siRNA and SAH + Ex-4+LY294002 groups, respectively. In conclusion, the neuroprotective effect of Ex-4 in EBI after SAH was mediated by attenuation of neuronal apoptosis via GLP-1R/PI3K/Akt signaling pathway, therefore EX-4 should be further investigated as a potential therapeutic agent in stroke patients.

Xie Z ，Enkhjargal B ，Wu L ，Zhou K ，Sun C ，Hu X ，Gospodarev V ，Tang J ，You C ，Zhang JH ... -  《-》

Propofol Reduces Inflammatory Brain Injury after Subarachnoid Hemorrhage: Involvement of PI3K/Akt Pathway.

Our previous study showed that propofol, one of the widely used anesthetic agents, can attenuate subarachnoid hemorrhage (SAH)-induced early brain injury (EBI) via inhibiting inflammatory and oxidative reaction. However, it is perplexing whether propofol attenuates inflammatory and oxidative reaction through modulating PI3K/Akt pathway. The present study investigated whether PI3K/Akt pathway is involved in propofol's anti-inflammation, antioxidation, and neuroprotection against SAH-induced EBI. Adult Sprague-Dawley rats underwent SAH and received treatment with propofol or vehicle after 2 and 12 hours of SAH. LY294002 was injected intracerebroventricularly to selectively inhibit PI3K/Akt signaling. Mortality, SAH grading, neurological scores, brain water content, evans blue extravasation, myeloperoxidase, malondialdehyde, superoxide dismutase, and glutathione peroxidase were measured 24 hours after SAH. Immunoreactivity of p-Akt, t-Akt, nuclear factor- kappa B (NF-κB) p65, nuclear factor erythroid-related factor 2 (Nrf2), NAD(P)H:quinone oxidoreductase (NQO1), and cyclooxygenase-2 (COX-2) in rat brain was determined by western blot. Tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in rat brain were examined by ELISA. Propofol significantly reduces neurological dysfunction, BBB permeability, brain edema, inflammation, and oxidative stress, all of which were reversed by LY294002. Propofol significantly upregulates the immunoreactivity of p-Akt, Nrf2, and NQO1, all of which were abolished by LY294002. Propofol significantly downregulates the overexpression of NF-κB p65, COX-2, TNF-α, and IL-1β, all of which were inhibited by LY294002. These results suggest that propofol attenuates SAH-induced EBI by inhibiting inflammatory reaction and oxidative stress, which might be associated with the activation of PI3K/Akt signaling pathway.

Zhang HB ，Tu XK ，Chen Q ，Shi SS ... -  《-》

Standardized Ginkgo biloba extract EGb 761® attenuates early brain injury following subarachnoid hemorrhage via suppressing neuronal apoptosis through the activation of Akt signaling.

Early brain injury (EBI) plays a critical role in determining the outcome of subarachnoid hemorrhage (SAH). The present study was designed to investigate the role of EGb 761, a standardized extract of Ginkgo biloba, in SAH-induced EBI and to explore its potential mechanism of action. A rat SAH model was established by the endovascular perforation process. Doses of 10, 50 and 100 mg/kg EGb 761 were injected intraperitoneally 2 h after SAH was induced. Mortality, SAH grade, neurological score and brain water content were measured 24 h after SAH was induced. A Western blot assay was performed to assess the expression of the apoptosis-related proteins Bax, Bcl-2, cleaved caspase-3, Akt and phosphorylated Akt (p-Akt). Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and neuronal nuclei (NeuN) double immunofluorescence staining were used to detect apoptotic neurons. Animals suffered from serious neurological deficits and increased brain water content after induction of SAH. Rats treated with EGb 761 experienced dose-dependent attenuation of neurological dysfunction and decreased brain water content. In addition, EGb 761 significantly activated Akt signaling accompanied by increased Bcl-2 levels and decreased expression of Bax and cleaved caspase-3. Moreover, EGb 761 decreased the number of TUNEL/NeuN-positive cells in a dose-dependent manner. However, all the beneficial effects of EGb 761 for SAH were abolished by the Akt inhibitor MK2206. Our results indicated that EGb 761 could ameliorate SAH-induced EBI and that the neuroprotective effects of EGb 761 against SAH were exerted via suppression of neuronal apoptosis through activation of the Akt pathway.

Yu T ，Fan Y ，Xu Y ，Xu L ，Xu G ，Cao F ，Jiang H ... -  《-》