Modulation of Amyloid-ß1-40 Transport by ApoA1 and ApoJ Across an in vitro Model of the Blood-Brain Barrier.

Amyloid-ß (Aß) accumulation in Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA) is likely caused by the impairment of its brain clearance that partly occurs through the blood-brain barrier (BBB). In this context, an in vitro BBB model is a valuable tool for studying the molecular mechanisms that regulate this process. This study assessed brain Aß elimination across the BBB and its modulation by the natural chaperones Apolipoprotein A1 (ApoA1) and Apolipoprotein J/Clusterin (ApoJ). The model was based on primary cerebral endothelial cells that were cultured on Matrigel-coated Transwells and treated with fluorescently labeled-Aß1-40 to track its efflux across the BBB, which corresponds to trafficking from the basolateral (brain) to apical (blood) compartments. We observed that the transport of basolateral Aß1-40 was enhanced when it was complexed to rApoJ, whereas the complex formed with rApoA1 did not influence Aß1-40 efflux. However, the presence of rApoA1 in the apical compartment was able to mobilize Aß1-40 from the basolateral side. We also observed that both rApoA1 and rApoJ moderately crossed the monolayer (from blood to brain) through a mechanism involving the LDL receptor-related protein family. In contrast to the increased rApoJ efflux when complexed to Aß1-40, rApoA1 trafficking was restricted when it was bound to the Aß peptide. In summary, the present study highlights the role of ApoJ and ApoA1 in the in vitro modulation of Aß elimination across the BBB.

Identification of Plasma Biomarkers of Human Intracerebral Hemorrhage Subtypes through Microarray Technology.

BACKGROUND: Intracerebral hemorrhage (ICH) is a devastating form of stroke and depending on the underlying cause, primary ICH is mainly caused by hypertension (HTN-ICH) or cerebral amyloid angiopathy (CAA-ICH). Currently, neuroimaging markers are required to identify the pattern for each etiology. The discovery of new biomarkers to improve the management of this pathology is therefore needed. METHODS: A microarray analysis was carried out to analyze gene expression differences in blood samples from patients (>1.5 months since the last ICH event) who suffered a CAA-ICH and HTN-ICH, and controls. The results were replicated by quantitative polymerase chain reaction and the plasma protein level of the best candidate was measured with enzyme-linked immunosorbent assay. RESULTS: The microarray analysis and the validation study revealed an increase in Golgin A8 Family, Member A (GOLGA8A) mRNA and protein levels in ICH cases compared to controls (P < .01), although no differences were found between specific ICH etiologies. GOLGA8A plasma levels were also associated with the presence of multiple hemorrhages (P < .05). CONCLUSIONS: The GOLGA8A level was increased in the blood of patients who suffered a primary ICH. We did not, however, find any candidate biomarker that distinguished CAA-ICH from HTN-ICH. The role of GOLGA8A in this fatal disorder has yet to be determined.

ApoA1, ApoJ and ApoE Plasma Levels and Genotype Frequencies in Cerebral Amyloid Angiopathy.

The involvement of apolipoproteins, such as the ApoE4 isoform, in Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA) highlights the fact that certain lipid carriers may participate in soluble ß-amyloid (Aß) transport. Our general aim was to characterize the soluble levels of the apolipoproteins apoE, apoA1 and apoJ/clusterin and their genotype status in patients with CAA. We analyzed the genotypes frequency of APOA1 (rs5069, rs670), CLU (rs11136000, rs1532278, rs7012010, rs9331888) and APOE (rs429358, rs7412) in a cohort of patients with CAA-associated intracerebral hemorrhage (ICH) (n = 59) and compared the results with those from hypertension-associated ICH (n = 42), AD patients (n = 73) and controls (n = 88). In a subgroup of patients, we also determined the plasma concentrations of apoE, apoA1 and apoJ/clusterin. We found increased plasma apoJ/clusterin levels in CAA patients compared to AD patients or controls after adjusting for sex and age (CAA vs. controls, p = 0.033; CAA vs. AD, p = 0.013). ApoA1 levels were not altered between groups, although a strong correlation was observed between plasma Aß(1-40) and apoA1 among CAA patients (r = 0.583, p = 0.007). Regarding plasma apoE concentration, a robust association between circulating levels and genotype status was confirmed (p < 0.001). Whereas the APOE4 frequency was higher in AD (p < 0.001) and CAA (p = 0.013), the APOA1 and CLU genotypes were not different among groups. In the CAA cohort, the risk-linked CLU variant (C) rs11136000 was associated with white matter hyperintensities (p = 0.045) and the presence of lobar microbleeds (p = 0.023) on MRI. In summary, our findings suggest that apoA1 may act as a physiological transporter of Aß(1-40) and that apoJ/clusterin appears to be a chaperone related to distinctive lesions in CAA brains.

NURR1 involvement in recombinant tissue-type plasminogen activator treatment complications after ischemic stroke.

BACKGROUND AND PURPOSE: Despite the effectiveness of recombinant tissue-type plasminogen activator (r-tPA) during the acute phase of ischemic stroke, the therapy remains limited by a narrow time window and the occurrence of occasional vascular side effects, particularly symptomatic hemorrhages. Our aim was to investigate the mechanisms underlying the endothelial damage resulting from r-tPA treatment in ischemic-like conditions. METHODS: Microarray analyses were performed on cerebral endothelial cells submitted to r-tPA treatment during oxygen and glucose deprivation to identify novel biomarker candidates. Validation was then performed in vivo in a mouse model of thromboembolic stroke and culminated in an analysis in a clinical cohort of patients with ischemic stroke treated with thrombolysis. RESULTS: The transcription factor NURR1 (NR4A2) was identified as a downstream target induced by r-tPA during oxygen and glucose deprivation. Silencing NURR1 expression reversed the endothelial-toxicity induced by the combined stimuli, a protective effect attributable to reduced levels of proinflammatory mediators, such as nuclear factor-kappa-beta 2 (NF-κ-B2), interleukin 1 alpha (IL1α), intercellular adhesion molecule 1 (ICAM1), SMAD family member 3 (SMAD3), colony stimulating factor 2 (granulocyte-macrophage; CSF2). The detrimental effect of delayed thrombolysis, in conditions in which NURR1 gene expression was enhanced, was confirmed in the preclinical stroke model. Finally, we determined that patients with stroke who had a symptomatic hemorrhagic transformation after r-tPA treatment exhibited higher baseline serum NURR1 levels than did patients with an asymptomatic or absence of cerebral bleedings. CONCLUSIONS: Our results suggest that NURR1 upregulation by r-tPA during ischemic stroke is associated with endothelial dysfunction and inflammation and the enhancement of hemorrhagic complications associated to thrombolysis.

Mild hypothermia protects against oxygen glucose deprivation (OGD)-induced cell death in brain slices from adult mice.

Most of neuroprotective strategies in stroke have failed to move from bench to bedside. One explanation might be the use of excessive uniform and smooth experimental models. Therefore, we have employed a more stringent in vitro model based on cultured brain slices from adult mice submitted to OGD. Using this acute model, we have confirmed that mild hypothermia protects against OGD-induced cell death when cooling the tissue during and after OGD, but not when hypothermia is induced only during reoxygenation.