New Strategies for Endovascular Recanalization of Acute Ischemic Stroke

Pro‑angiogenic activity of salvianolate and its potential therapeutic effect against acute cerebral ischemia

Salvianolate (Sal) is a medicinal composition that is widely used in China for the treatment of coronary heart disease and angina pectoris. The aim of the present study was to investigate the potential macrophage-mediated pro-angiogenic effects of Sal in vitro. In addition, another aim was to explore the effects of Sal in a rat model of transient middle cerebral artery occlusion (tMCAO) along with the potential mechanism by which it promotes angiogenesis. In this study, human umbilical vein endothelial cells (HUVECs) and Raw264.7 macrophages in vitro, and a rat tMCAO model in vivo were used to detect the pro-angiogenic effect and mechanism of Sal. The results of in vitro experiments showed that the viability, migration and tube formation of HUVECs were promoted by the supernatant of Sal-treated Raw264.7 macrophages (s-Sal) but not by Sal alone. s-Sal also increased the levels of phosphorylated (p-)VEGFR-2, p-AKT and p-p38 MAPK in HUVECs while Sal alone did not. In vivo, treatment with Sal significantly reduced the cerebral infarction volume and neurological deficit scores in the rat tMCAO model. Similar to the mechanism observed in the in vitro experiments, Sal treatment upregulated the protein expression of VEGF and VEGFR-2, in addition to the phosphorylation of VEGFR-2, AKT and p38, in the brain tissues of the tMCAO model rats. In summary, the results of the present study suggest that the mechanism of Sal-mediated angiogenesis is associated with stimulation of the VEGF/VEGFR-2 signaling pathway by macrophages. This suggests the potential of Sal as a therapeutic option for the treatment of acute cerebral ischemic injury, which may act via the promotion of angiogenesis.

Multi-pathway neuroprotective effects of a novel salidroside derivative SHPL-49 against acute cerebral ischemic injury

SHPL-49 ((2R,3S,4S,5R,6R)-2-(hydroxymethyl)-6-(4-(4-methoxyphenyl) butoxy) tetrahydro-2H-pyran-3,4,5-triol) is a novel glycoside derivative obtained from structural modification of salidroside, which is isolated from the medicinal plant Rhodiola rosea L. SHPL-49 was administered to rats with permanent middle cerebral artery occlusion (pMCAO) for 5 days, and it was found that SHPL-49 could alleviate the cerebral infarct volume and reduce the neurological deficit score. Moreover, the effective time window of SHPL-49 in the pMCAO model was from 0.5 to 8 h after embolization. In addition, the result of immunohistochemistry showed that SHPL-49 could increase the number of neurons in the brain tissue and reduce the occurrence of apoptosis. Morris water maze and Rota-rod experiments showed that SHPL-49 could improve neurological deficits, repair neurocognitive and motor dysfunction, and enhance learning and memory ability in the pMCAO model after 14 days of SHPL-49 treatment. Further in vitro experiments showed that SHPL-49 significantly reduced the calcium overload of PC-12 cells and the production of reactive oxygen species (ROS) induced by oxygen and glucose deprivation (OGD), and increased the levels of antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), decreased the production of malondialdehyde (MDA). Furthermore, SHPL-49 could reduce cell apoptosis by increasing protein expression ratio of anti-apoptotic factor Bcl-2 to pro-apoptotic factor Bax in vitro. SHPL-49 also regulated the expression of Bcl-2 and Bax in ischemic brain tissue, and even inhibited the caspase cascade of pro-apoptotic proteins Cleaved-caspase 9 and Cleaved-caspase 3. Taken together, SHPL-49 exhibited neuroprotective effects against cerebral ischemic injury through multiple pathways, such as alleviating calcium overload, reducing oxidative stress damage, and inhibiting apoptosis.

HMGB1 as a Key Mediator of Immune Mechanisms in Ischemic Stroke

SIGNIFICANCE

Stroke is the leading cause of morbidity and mortality worldwide. Inflammatory cascades have a major impact on outcome and regeneration after ischemic stroke. High-mobility group box 1 (HMGB1) has come into the focus of experimental and clinical stroke research because it is released from necrotic brain tissue and its differential redox forms attract and activate immune cells after ischemic brain injury. HMGB1 is a potent inducer of inflammatory cascades, and thereby, secondary deterioration of neurological outcome.

RECENT ADVANCES

The role of HMGB1 in sterile inflammation is well established. Emerging evidence suggests that HMGB1 modulates neuroinflammation after experimental brain ischemia and that it may be a useful prognostic biomarker for stroke patients.

CRITICAL ISSUES

HMGB1 is instantly released from necrotic cells in the ischemic core and activates an early inflammatory response. In addition, brain-released HMGB1 can be redox modified in the circulation and activate peripheral immune cells. HMGB1 concentrations correlate with disease severity and outcome after brain injury. This is the first review depicting the crucial role of HMGB1 in the initiation and perpetuation of secondary immune alterations after experimental and clinical stroke.

FUTURE DIRECTIONS

HMGB1-dependent signaling pathways are on the verge and have the potential to become a central topic in experimental stroke research. Current and upcoming projects in this field will be paving the way for future translational approaches targeting the center of poststroke inflammation to improve stroke recovery and long-term outcome.