Tissue plasminogen activator inhibits NMDA-receptor-mediated increases in calcium levels in cultured hippocampal neurons

Tissue-type plasminogen activator induces conditioned receptive field plasticity in the mouse auditory cortex

Tissue-type plasminogen activator (tPA) is a serine protease that is expressed in various compartments in the brain. It is involved in neuronal plasticity, learning and memory, and addiction. We evaluated whether tPA, exogenously applied, could influence neuroplasticity within the mouse auditory cortex. We used a frequency-pairing paradigm to determine whether neuronal best frequencies shift following the pairing protocol. tPA administration significantly affected the best frequency after pairing, whereby this depended on the pairing frequency relative to the best frequency. When the pairing frequency was above the best frequency, tPA caused a best frequency shift away from the conditioned frequency. tPA significantly widened auditory tuning curves. Our data indicate that regional changes in proteolytic activity within the auditory cortex modulate the fine-tuning of auditory neurons, supporting the function of tPA as a modulator of neuronal plasticity.

Elevated levels of cortisol, brain-derived neurotropic factor and tissue plasminogen activator in male children with autism spectrum disorder

Several studies demonstrated biological effects of cortisol, brain-derived neurotrophic factor (BDNF) and tissue plasminogen activator (tPA) on human metabolism and central nervous system. Our study investigated the serum levels of tPA along with BDNF and cortisol in children with autism spectrum disorder (ASD). Thirty three male children with ASD ranging in age from 2 to 15 years were selected for the study group and 27 age-matched healthy male children were selected for the control group. The ASD severity was determined by the score on the Autism Behavior Checklist (ABC). The mean cortisol levels for the study group and the control group were 79.1 ± 30.2 ng/ml and 60.0 ± 25.1 ng/ml, respectively. The mean BDNF levels for the study group and the control group were 5.9 ± 2.8 ng/ml and 3.7 ± 1.8 ng/ml, respectively. The mean tPA levels for the study group and the control group were 32.9 ± 18.5 ng/ml and 25.5 ± 15.1 ng/ml, respectively. Cortisol, BDNF and tPA levels were significantly higher in the study group compared to the control group (p < 0.001). There was no statistically significant effect in terms of age, ABC total and subscale scores on serum cortisol, BDNF and tPA levels in the study group (p > 0.05). It may be suggested that elevations may indicate a role in the pathogenesis of ASD or it may be the case that ASD may alter the levels or pathways of these metabolic factors. LAY SUMMARY: The underlying mechanism or a specific metabolic target relevant to autism spectrum disorder (ASD) has not yet been identified. Cortisol, brain-derived neurotrophic factor (BDNF) and tissue plasminogen activator (tPA) have biological effects on neuroplasticity but little is known about the role of cortisol and tPA-BDNF pathway in ASD. In the present study focused on male children with ASD, we have found higher blood levels of cortisol, BDNF and tPA than their healthy peers. This is the first clinical study to evaluate the serum tPA levels along with BDNF and cortisol in ASD. The results suggest that several neurotrophic and other related markers should be born in mind while examining children with ASD.

Plasminogen Activator Inhibitor-1 Promotes the Recruitment and Polarization of Macrophages in Cancer

Plasminogen activator inhibitor-1 (PAI-1) has a pro-tumorigenic function via its pro-angiogenic and anti-apoptotic activities. Here, we demonstrate that PAI-1 promotes the recruitment and M2 polarization of monocytes/macrophages through different structural domains. Its LRP1 interacting domain regulated macrophage migration, while its C-terminal uPA interacting domain promoted M2 macrophage polarization through activation of p38MAPK and nuclear factor κB (NF-κB) and induction of an autocrine interleukin (IL)-6/STAT3 activation pathway. We then show in several experiments in mice that expression of PAI-1 is associated with increased tumorigenicity, increased presence of M2 macrophages, higher levels of IL-6, and increased STAT3 phosphorylation in macrophages. Strong positive correlations between PAI-1, IL-6, and CD163 (M2 marker) expression were also found by meta-analysis of transcriptome data in many human cancers. Altogether, these data provide evidence for a mechanism explaining the paradoxical pro-tumorigenic function of PAI-1 in cancer.

Low Density Receptor-Related Protein 1 Interactions With the Extracellular Matrix: More Than Meets the Eye

The extracellular matrix (ECM) is a biological substrate composed of collagens, proteoglycans and glycoproteins that ensures proper cell migration and adhesion and keeps the cell architecture intact. The regulation of the ECM composition is a vital process strictly controlled by, among others, proteases, growth factors and adhesion receptors. As it appears, ECM remodeling is also essential for proper neuronal and glial development and the establishment of adequate synaptic signaling. Hence, disturbances in ECM functioning are often present in neurodegenerative diseases like Alzheimer’s disease. Moreover, mutations in ECM molecules are found in some forms of epilepsy and malfunctioning of ECM-related genes and pathways can be seen in, for example, cancer or ischemic injury. Low density lipoprotein receptor-related protein 1 (Lrp1) is a member of the low density lipoprotein receptor family. Lrp1 is involved not only in ligand uptake, receptor mediated endocytosis and lipoprotein transport—functions shared by low density lipoprotein receptor family members—but also regulates cell surface protease activity, controls cellular entry and binding of toxins and viruses, protects against atherosclerosis and acts on many cell signaling pathways. Given the plethora of functions, it is not surprising that Lrp1 also impacts the ECM and is involved in its remodeling. This review focuses on the role of Lrp1 and some of its major ligands on ECM function. Specifically, interactions with two Lrp1 ligands, integrins and tissue plasminogen activator are described in more detail.

Fibrinolysis: from blood to the brain

We all know about classical fibrinolysis, how plasminogen activation by either tissue-type plasminogen activator (t-PA) or urokinase-type plasminogen activator (u-PA) promotes fibrin breakdown, and how this process was harnessed for the therapeutic removal of blood clots. While this is still perfectly true and still applicable to thromboembolic conditions today, another dimension to this system came to light over two decades ago that implicated the plasminogen activating system in a context far removed from the dissolution of blood clots. This unsuspected area related to brain biology where t-PA was linked to a plethora of activities in the CNS, some of which do not necessarily require plasmin generation. Indeed, t-PA either directly or via plasmin, has been shown to not only have key roles in modulating astrocytes, neurons, microglia, and pericytes, but also to have profound effects in a number of CNS conditions, including ischaemic stroke, severe traumatic brain injury and also in neurodegenerative disorders. While compelling insights have been obtained from various animal models, the clinical relevance of aberrant expression of these components in the CNS, although strongly implied, are only just emerging. This review will cover these areas and will also discuss how the use of thrombolytic agents and anti-fibrinolytic drugs may potentially have impacts outside of their clinical intention, particularly in the CNS.

Is plasminogen activator inhibitor-1 a physiological bottleneck bridging major depressive disorder and cardiovascular disease?

Major depressive disorder (MDD) is estimated to affect one in twenty people worldwide. MDD is highly comorbid with cardiovascular disease (CVD), itself one of the single largest causes of mortality worldwide. A number of pathological changes observed in MDD are believed to contribute to the development of cardiovascular disease, although no single mechanism has been identified. There are also no biological markers capable of predicting the future risk of developing heart disease in depressed individuals. Plasminogen activator inhibitor-1 (PAI-1) is a prothrombotic plasma protein secreted by endothelial tissue and has long been implicated in CVD. An expanding body of literature has recently implicated it in the pathogenesis of major depressive disorder as well. In this study, we review candidate pathways implicating MDD in CVD and consider how PAI-1 might act as a mediator by which MDD induces CVD development: chiefly through sleep disruption, adiposity, brain-derived neurotrophic factor (BDNF) metabolism, systemic inflammation and hypothalamic-pituitary-adrenal (HPA)-axis dysregulation. As both MDD and CVD are more prevalent in women than in men, and incidence of either condition is dramatically increased during reproductive milestones, we also explore hormonal and sex-specific associations between MDD, PAI-1 and CVD. Of special interest is the role PAI-1 plays in perinatal depression and in cardiovascular complications of pregnancy. Finally, we propose a theoretical model whereby PAI-1 might serve as a useful biomarker for CVD risk in those with depression, and as a potential target for future treatments.

Neuroserpin Attenuates H2O2-Induced Oxidative Stress in Hippocampal Neurons via AKT and BCL-2 Signaling Pathways

Oxidative stress plays a critical role in neuronal injury and is associated with various neurological diseases. Here, we explored the potential protective effect of neuroserpin against oxidative stress in primary cultured hippocampal neurons. Our results show that neuroserpin inhibits H2O2-induced neurotoxicity in hippocampal cultures as measured by WST, LDH release, and TUNEL assays. We found that neuroserpin enhanced the activation of AKT in cultures subjected to oxidative stress and that the AKT inhibitor Ly294002 blocked this neuroprotective effect. Neuroserpin increased the expression of the anti-apoptotic protein BCL-2 and blocked the activation of caspase-3. Neuroserpin did not increase the level of neuroprotection over levels seen in neurons transduced with a BCL-2 expression vector, and an inhibitor of Trk receptors, K252a, did not block neuroserpin's effect. Taken together, our study demonstrates that neuroserpin protects against oxidative stress-induced dysfunction and death of primary cultured hippocampal neurons through the AKT-BCL-2 signaling pathway through a mechanism that does not involve the Trk receptors and leads to inhibition of caspase-3 activation.