Plasma VAP-1/SSAO activity predicts intracranial hemorrhages and adverse neurological outcome after tissue plasminogen activator treatment in stroke

Evolving role of biomarkers in acute cerebrovascular disease

The development of a clinically validated biomarker of acute cerebral ischemia would have the potential to facilitate the use of time-sensitive reperfusion strategies, allow for individualization of patient care by predicting relative risk of hemorrhage and volume of penumbral tissue, and add valuable prognostic information for patients presenting with acute stroke. Additionally, a stroke biomarker might benefit early stage clinical research by serving as a surrogate measure of ischemic injury. Although at present there are no clinically validated biomarkers of acute stroke, previous studies have focused on markers associated with different components of the ischemic cascade, including microglial activation, inflammation, oxidative stress, neuronal injury, hemostasis, and endothelial dysfunction. Evolving technologies have provided high throughput approaches to investigate potential gene and protein signatures, and methods to measure newly discovered markers of cell death and immune responses. Prior to defining the clinical utility of stroke biomarkers, it is critical to understand the inherent limitations of a biomarker-based approach and define its potential value for providing adjunctive diagnostic and prognostic information. The identification and validation of a clinically relevant biomarker, or panel of markers, of stroke will ultimately require incorporation of both stringent research design and assessment in the clinical context in which the marker will be used.

Vascular cell lines expressing SSAO/VAP-1: a new experimental tool to study its involvement in vascular diseases

BACKGROUND INFORMATION

PrAO (primary amine oxidase), also known as SSAO (semicarbazide-sensitive amine oxidase)/VAP-1 (vascular adhesion protein-1), is an enzyme (EC 1.4.3.21) that is highly expressed in blood vessels and participates in many cell processes, including glucose handling or inflammatory leucocyte recruitment. High activity levels of this enzyme are associated with diabetes, atherosclerosis, AD (Alzheimer's disease) or stroke, among others, thus meaning that studies concerning SSAO as a therapeutic target are becoming more frequent. However, the study of this enzyme is difficult, owing to its loss of expression in cell cultures.

RESULTS

We have developed an endothelial cell line that stably expresses the human SSAO/VAP-1 to be used as endothelial cell model for the study of this enzyme. The transfected protein is mainly expressed as a dimer in the membrane of these cells, and we demonstrate its specific localization in the lipid rafts of endothelial cells. The protein shows levels of enzymatic activity and kinetic parameters comparable with those observed in vivo by the same cell type. The transfected SSAO/VAP-1 is also able to mediate the adhesion of leucocytes to the endothelium, a known function of this protein under inflammatory conditions. This distinctive function is not exerted by the SSAO/VAP-1 transfected protein in a smooth muscle cell line that expresses 3-fold higher protein levels. These differences have been widely reported to exist in vivo. Furthermore, using this endothelial cell model, we describe for the first time the involvement of the leucocyte-adhesion activity of SSAO/VAP-1 in the Aβ (amyloid β-peptide)-mediated pro-inflammatory effect.

CONCLUSIONS

The characterization of this new cell line shows the correct behaviour of the transfected protein and endorses the use of these cellular models for the in-depth study of the currently poorly understood functions of SSAO/VAP-1 and its involvement in the above-mentioned pathologies. This cellular model will be also useful for the evaluation of potential compounds that could modulate its activity for therapeutic purposes.

VAP-1/SSAO plasma activity and brain expression in human hemorrhagic stroke

BACKGROUND

Vascular adhesion protein-1 (VAP-1) is a cell surface and circulating enzyme that belongs to the semicarbazide-sensitive amine oxidase (SSAO) family, which oxidatively deaminates primary amines and is implicated in leukocyte extravasation. Our aim was to investigate the alteration of soluble VAP-1/SSAO activity in plasma samples after acute intracerebral hemorrhage (ICH) and its presence in human ICH brain tissue.

METHODS

VAP-1/SSAO activity was determined in plasma of 66 ICH patients and 58 healthy controls. In addition, we assessed the expression of VAP-1/SSAO in postmortem brain tissue from hemorrhagic stroke patients by Western blot and immunohistochemistry.

RESULTS

We observed significantly higher levels of plasma VAP-1/SSAO activity in patients with ICH compared to matched elderly controls (p = 0.001). Plasma VAP-1/SSAO activity <2.7 pmol/min·mg and baseline ICH volume <17 ml were independent predictors of neurological improvement after 48 h (OR 6.8, 95% CI 1.14-41.67, p = 0.035, and OR 10.64, 95% CI 1.1-100, p = 0.041, respectively), after adjustment for baseline stroke severity. We also found that membrane-bound VAP-1/SSAO levels were lower in the perihematoma region than in the corresponding contralateral brain areas of patients deceased due to ICH (p = 0.024).

CONCLUSIONS

Our data demonstrate that plasma VAP-1/SSAO activity is increased in ICH and predicts neurological outcome, suggesting a possible contribution of the soluble protein in secondary brain damage. Furthermore, anti-VAP-1/SSAO strategies might be a promising approach to prevent neurological worsening following ICH.

Impact of tissue plasminogen activator on the neurovascular unit: from clinical data to experimental evidence

About 15 million strokes occur each year worldwide. As the number one cause of morbidity and acquired disability, stroke is a major drain on public health-care funding, due to long hospital stays followed by ongoing support in the community or nursing-home care. Although during the last 10 years we have witnessed a remarkable progress in the understanding of the pathophysiology of ischemic stroke, reperfusion induced by recombinant tissue-type plasminogen activator (tPA-Actilyse) remains the only approved acute treatment by the health authorities. The objective of the present review is to provide an overview of our present knowledge about the impact of tPA on the neurovascular unit during acute ischemic stroke.

Update on the Serum Biomarkers and Genetic Factors Associated with Safety and Efficacy of rt-PA Treatment in Acute Stroke Patients

An accurate understanding of the mechanisms underlying an individual's response to rt-PA treatment is critical to improve stroke patients' management. We thus reviewed the literature in order to identify biochemical and genetic factors that have been associated with safety and efficacy of rt-PA administration after stroke.