The impact of experimental preconditioning using vascular endothelial growth factor in stroke and subarachnoid hemorrhage

Evaluation of Vascular Endothelial Growth Factor A and Selected Parameters of Coagulation and Fibrinolysis in a Group of Patients with Subarachnoid Haemorrhage

Introduction. Subarachnoid hemorrhage (SAH) is currently one of the most serious diseases of the central nervous system. To reduce the negative consequences of SAH and help clinicians to assess the patient's condition, there are attempts to search for new diagnostic markers, which quickly and accurately allow for the proper diagnosis. The aim of this research was the concentration and activity of Vascular Endothelial Growth Factor A (VEGF-A) and selected parameters of coagulation and fibrinolysis in the blood of patients with SAH. Serum levels of VEGF-A in patients diagnosed with SAH are measured to assess the correlation between VEGF-A and the clinical condition of patient. This may help with proper therapeutics and better prognosis. Methods. The study involved 85 patients with subarachnoid hemorrhage. The control group consisted of 45 healthy subjects, sex and age matched. The following parameters were determined: APTT (Activated Partial Thromboplastin Time), INR (International Normalized Ratio), D-dimers and fibrinogen concentration, and the concentration of VEGF-A by ELISA (R&D USA). Results. The average concentration of VEGF-A in the study group was significantly lower compared to the control group. The D-dimer concentration was higher in patients with SAH but the difference was not significant. Coagulation parameters such as INR, APTT, and fibrinogen did not show significant differences between investigated groups. Conclusions. VEGF-A cannot be an independent marker of SAH. Selected parameters of coagulation and fibrinolysis such as D-dimers, INR, APTT, and fibrinogen should not be used as markers of SAH.

HIF-1α Mediates Isoflurane-Induced Vascular Protection in Subarachnoid Hemorrhage

Objective

Outcome after aneurysmal subarachnoid hemorrhage (SAH) depends critically on delayed cerebral ischemia (DCI) – a process driven primarily by vascular events including cerebral vasospasm, microvessel thrombosis, and microvascular dysfunction. This study sought to determine the impact of postconditioning – the phenomenon whereby endogenous protection against severe injury is enhanced by subsequent exposure to a mild stressor – on SAH-induced DCI.

Methods

Adult male C57BL/6 mice were subjected to sham, SAH, or SAH plus isoflurane postconditioning. Neurological outcome was assessed daily via sensorimotor scoring. Contributors to DCI including cerebral vasospasm, microvessel thrombosis, and microvascular dysfunction were measured 3 days later. Isoflurane-induced changes in hypoxia-inducible factor 1alpha (HIF-1α)-dependent genes were assessed via quantitative polymerase chain reaction. HIF-1α was inhibited pharmacologically via 2-methoxyestradiol (2ME2) or genetically via endothelial cell HIF-1α-null mice (EC-HIF-1α-null). All experiments were performed in a randomized and blinded fashion.

Results

Isoflurane postconditioning initiated at clinically relevant time points after SAH significantly reduced cerebral vasospasm, microvessel thrombosis, microvascular dysfunction, and neurological deficits in wild-type (WT) mice. Isoflurane modulated HIF-1α-dependent genes – changes that were abolished in 2ME2-treated WT mice and EC-HIF-1α-null mice. Isoflurane-induced DCI protection was attenuated in 2ME2-treated WT mice and EC-HIF-1α-null mice.

Interpretation

Isoflurane postconditioning provides strong HIF-1α-mediated macro- and microvascular protection in SAH, leading to improved neurological outcome. These results implicate cerebral vessels as a key target for the brain protection afforded by isoflurane postconditioning, and HIF-1α as a critical mediator of this vascular protection. They also identify isoflurane postconditioning as a promising novel therapeutic for SAH.