Receptor-associated protein promotes t-PA expression, reduces PAI-1 expression and improves neurorecovery after acute ischemic stroke

Inducible miR-1224 silences cerebrovascular Serpine1 and restores blood flow to the stroke-affected site of the brain

The α-tocotrienol (TCT) form of natural vitamin E is more potent than the better known α-tocopherol against stroke. Angiographic studies of canine stroke have revealed beneficial cerebrovascular effects of TCT. This work seeks to understand the molecular basis of such effect. In mice, TCT supplementation improved perfusion at the stroke-affected site by inducing miR-1224. miRNA profiling of a laser-capture-microdissected stroke-affected brain site identified miR-1224 as the only vascular miR induced. Lentiviral knockdown of miR-1224 significantly blunted the otherwise beneficial effects of TCT on stroke outcomes. Studies on primary brain microvascular endothelial cells revealed direct angiogenic properties of miR-1224. In mice not treated with TCT, advance stereotaxic delivery of an miR-1224 mimic to the stroke site markedly improved stroke outcomes. Mechanistic studies identified Serpine1 as a target of miR-1224. Downregulation of Serpine1 augmented the angiogenic response of the miR-1224 mimic in the brain endothelial cells. The inhibition of Serpine1, by dietary TCT and pharmacologically, increased cerebrovascular blood flow at the stroke-affected site and protected against stroke. This work assigns Serpine1, otherwise known to be of critical significance in stroke, a cerebrovascular function that worsens stroke outcomes. miR-1224-dependent inhibition of Serpine1 can be achieved by dietary TCT as well as by the small-molecule inhibitor TM5441.

Elevated expression of cholesterol transporter LRP-1 is crucially implicated in the pathobiology of glioblastoma

Glioblastoma (GBM) is the most common primary malignant brain tumor with a grave prognosis. The present study evaluated the expression of Cholesterol transporter [importer -Lipoprotein Receptor-related Protein-1 (LRP-1) and exporter -ATP-binding cassette transporters-1 (ABCA-1)] in GBM and their implications in tumor-biology, clinical outcome and therapeutic potentials. The mRNA and protein expression was assessed by qRT-PCR and immunohistochemistry, respectively, in 85 GBMs. For comparison, 25 lower-grade astrocytomas (IDH-mutant, grade-2/3) [LGA] 16 cases of high-grade astrocytomas (IDH-mutant, grade-4) [HGA] were also evaluated. In-vitro analysis was performed on U87MG and LN229 glioma cell line. The expression of LRP-1 (mRNA and protein) was significantly higher in GBM than LGA, HGA and normal brain (NB) [p-values 0.007, 0.003 and <0.001 for mRNA; 0.024, <0.001 and <0.001 for immunohistochemistry]. Majority of the GBMs (82.4%) showed strong immunoreactivity for LRP-1, and all tumor cases were positive while the normal brain was negative. LRP-1 immunoreactivity positively correlated with the MIB-1 labeling index (p-value-0.013). LRP-1 knockdown in-vitro was associated with decreased cell survival, proliferation, migration, invasion, and increased apoptosis. Similar effect was also demonstrated by Receptor Associated Protein (RAP), a LRP-1 inhibitory drug. The silencing of LRP-1 was also associated with decreased cholesterol level. The ABCA-1 expression was higher in GBM than LGA and NB (p-value 0.011 and <0.001), however there was no significant association with other parameters. LRP-1 showed a positive correlation with ABCA-1 and associated with decreased expression with LRP-1 knock-down in-vitro. The expression of LRP-1 and ABCA-1 didn't correlate with overall survival in GBMs. Hence, LRP-1 is crucial for the tumor cells' survival and aggressive biological behavior which is maintain through the regulation of high intracellular cholesterol import. Its expression is significantly higher in GBMs and also implicated in the regulation of ABCA-1 expression. Considering its immune-positivity only in the neoplastic cell and strong positivity in GBM it may be a useful adjunct to the diagnosis. For the first time, the present study emphasized its role as a potential therapeutic target in the form of RAP which is presently being used in other neurological diseases under clinical trials.

Effects of MaiLiuPian on carotid thrombosis in rats and acute pulmonary embolism in mice and its antithrombotic mechanism

Mailiupian (MLP) is a new patent functional food that consists of Crataegi Fructus, Notoginseng Radix, and Ginkgo Folium, which was reported to be active in improving the microcirculation based on formulation screening. However, whether it is effective in inhibiting thrombus and its mechanism has not been evaluated. Therefore, in the present study, the models of arterial thrombosis induced by FeCl₃ and the models of APE by ADP were established to evaluate the antithrombosis effect of MLP. Results showed that MLP markedly reduced the weight and size of wet thrombosis in FeCl₃ -induced rats and decreased the recovery time from symptoms of APE mice. MLP was proved to prolong APTT, PT, TT and improve the levels of t-PA and 6-keto-PGF_1α significantly, meanwhile, PAI-1 and TXB₂ were reduced apparently. By comparing tail bleeding time, MLP showed antithrombotic effects, but without the risk of bleeding, taking aspirin as a control. PRACTICAL APPLICATIONS: Our experiments proved that MLP, a new patent health food, acted on both coagulation and fibrinolytic systems and the platelet aggregation to play antithrombosis roles, providing a theoretical basis for applications of MLP in preventing or curing thrombosis diseases.

Chinese medicine Tongxinluo capsule protects against blood-brain barrier disruption after ischemic stroke by inhibiting the low-density lipoprotein receptor-related protein 1 pathway in mice

BACKGROUND

Chinese medicine Tongxinluo capsule (TXL) has been extensively used to treat ischemic stroke in China, and one of its mechanisms is to protect against blood brain barrier (BBB) disruption after stroke. However, the underlying protective mechanisms are not fully illuminated. It is reported that the low-density lipoprotein receptor-related protein 1 (LRP-1) is involved in BBB disruption after brain ischemia. In this study, we explored whether TXL could downregulate LRP-1 expression and subsequently protect against BBB disruption after stroke using permanent middle cerebral artery occlusion (pMCAO) in mice.

METHODS

The animal model of ischemic stroke was induced by pMCAO in male adult C57BL/6J mice. The mice were orally administered TXL (3.0 g/kg) at 1, 3 and 21 h after pMCAO. Meanwhile, the LRP-1 antagonist receptor associated protein (RAP) was intracerebroventricularly injected at 1 and 21 h after stroke. We measured the following parameters at 6 and 24 h: LRP-1 protein level, BBB leakage, and the expression of tight junction (TJ) proteins including occludin, claudin-5 and zonula occludens-1 (ZO-1).

RESULTS

Our results showed that TXL downregulated LRP-1 level, upregulated these TJ proteins level, and reduced BBB leakage in peri-infarct regions after pMCAO. Further study found that the inhibitor RAP played the same role as did TXL in upregulating these TJ proteins level and reducing BBB leakage after stroke.

CONCLUSION

Our study demonstrates that TXL protects against BBB disruption after stroke via inhibiting the LRP-1 pathway.

LDL receptor blockade reduces mortality in a mouse model of ischaemic stroke without improving tissue-type plasminogen activator-induced brain haemorrhage: towards pre-clinical simulation of symptomatic ICH

Background

Symptomatic intracerebral haemorrhage (sICH) following tissue-type plasminogen activator (rt-PA) administration is the most feared and lethal complication of thrombolytic therapy for ischaemic stroke, creating a significant obstacle for a broader uptake of this beneficial treatment. rt-PA also undermines cerebral vasculature stability in a multimodal process which involves engagement with LDL receptor-related protein 1 (LRP-1), potentially underlying the development of sICH.

Aims and methods

We aimed to simulate rt-PA-induced haemorrhagic transformation (HT) in a mouse model of stroke and to assess if it drives symptomatic neurological deterioration and whether it is attenuated by LDL receptor blockade. rt-PA (10 mg/kg) or its vehicle, with or without the LDL receptor antagonist, receptor-associated protein (RAP; 2 mg/kg), were intravenously injected at reperfusion after 0.5 or 4 h of middle cerebral artery occlusion (MCAo). Albumin and haemoglobin content were measured in the perfused mouse brains 24 h post MCAo as indications of blood–brain barrier (BBB) compromise and HT, respectively.

Results

rt-PA did not elevate brain albumin and haemoglobin levels in sham mice or in mice subjected to 0.5 h MCAo. In contrast, administration of rt-PA after prolonged MCAo (4 h) caused a marked increase in HT (but similar changes in brain albumin) compared to vehicle, mimicking the clinical shift from a safe to detrimental intervention. Interestingly, this HT did not correlate with functional deficit severity at 24 h, suggesting that it does not play a symptomatic role in our mouse stroke model. Co-administration of RAP with or without rt-PA reduced mortality and neurological scores but did not effectively decrease brain albumin and haemoglobin levels.

Conclusion

Despite the proven causative relationship between severe HT and neurological deterioration in human stroke, rt-PA-triggered HT in mouse MCAo does not contribute to neurological deficit or simulate sICH. Model limitations, such as the long duration of occlusion required, the type of HT achieved and the timing of deficit assessment may account for this mismatch. Our results further suggest that blockade of LDL receptors improves stroke outcome irrespective of rt-PA, blood–brain barrier breakdown and HT.

Transporters as Drug Targets in Neurological Diseases

Membrane transport proteins have central physiological function in maintaining cerebral homeostasis. These transporters are expressed in almost all cerebral cells in which they regulate the movement of a wide range of solutes, including endogenous substrates, xenobiotic, and therapeutic drugs. Altered activity/expression of central nervous system (CNS) transporters has been implicated in the onset and progression of multiple neurological diseases. Neurological diseases are heterogeneous diseases that involve complex pathological alterations with only a few treatment options; therefore, there is a great need for the development of novel therapeutic treatments. To that end, transporters have emerged recently to be promising therapeutic targets to halt or slow the course of neurological diseases. The objective of this review is to discuss implications of transporters in neurological diseases and summarize available evidence for targeting transporters as decent therapeutic approach in the treatment of neurological diseases.