Antibody-mediated inhibition of tissue-type plasminogen activator binding to the low-density lipoprotein receptor-related protein 1 as a potential beneficial modulator for stroke therapy.

The acute ischemic stroke therapy of choice is the application of Alteplase, a drug containing the enzyme tissue-type plasminogen activator (tPa) which rapidly destabilizes blood clots. A central hallmark of stroke pathology is blood-brain barrier (BBB) breakdown associated with tight junction (TJ) protein degradation, which seems to be significantly more severe under therapeutic conditions. The exact mechanisms how tPa facilitates BBB breakdown are not entirely understood. There is evidence that an interaction with the lipoprotein receptor-related protein 1 (LRP1), allowing tPa transport across the BBB into the central nervous system, is necessary for this therapeutic side effect. Whether tPa-mediated disruption of BBB integrity is initiated directly on microvascular endothelial cells or other brain cell types is still elusive. In this study we could not observe any changes of barrier properties in microvascular endothelial cells after tPa incubation. However, we present evidence that tPa causes changes in microglial activation and BBB breakdown after LRP1-mediated transport across the BBB. Using a monoclonal antibody targeting the tPa binding sites of LRP1 decreased tPa transport across an endothelial barrier. Our results indicate that limiting tPa transport from the vascular system into the brain by coapplication of a LRP1-blocking monoclonal antibody might be a novel approach to minimize tPa-related BBB damage during acute stroke therapy.

Plasminogen Activators in Neurovascular and Neurodegenerative Disorders.

The neurovascular unit (NVU) is a dynamic structure assembled by endothelial cells surrounded by a basement membrane, pericytes, astrocytes, microglia and neurons. A carefully coordinated interplay between these cellular and non-cellular components is required to maintain normal neuronal function, and in line with these observations, a growing body of evidence has linked NVU dysfunction to neurodegeneration. Plasminogen activators catalyze the conversion of the zymogen plasminogen into the two-chain protease plasmin, which in turn triggers a plethora of physiological events including wound healing, angiogenesis, cell migration and inflammation. The last four decades of research have revealed that the two mammalian plasminogen activators, tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA), are pivotal regulators of NVU function during physiological and pathological conditions. Here, we will review the most relevant data on their expression and function in the NVU and their role in neurovascular and neurodegenerative disorders.

PAI-1 and tPA gene polymorphisms and susceptibility to chronic obstructive pulmonary disease in a sample of Turkish population.

OBJECTIVES: The aim of this study was to assess the influence of plasminogen activator inhibitor-1 (PAI-1) 4G/5G or tissue plasminogen activator (tPA) I/D polymorphisms in chronic obstructive pulmonary disease (COPD) cases in a sample of Turkish population. METHODS: PAI-1 4G/5G and tPA Alu-repeat I/D genetic polymorphisms in 153 COPD subjects and 160 controls were investigated using PCR-RFLP and PCR methods, respectively. RESULTS: 4G allele frequency was 0.62 and 0.39 for COPD and control groups, respectively. 4G allele had an estimated 2.56- fold [95% CI = 1.85-3.53] increased risk of COPD. tPA I allele frequency was 0.55 and 0.50, for COPD and control groups, respectively. I allele had an estimated 1.19-fold [95% CI = 0.87-1.62] increased risk of COPD. CONCLUSIONS: PAI-1 4G/4G and 4G/5G genotypes seemed to play a key role in the pathophysiology of COPD in Turkish individuals.

Production of human tissue-type plasminogen activator (htPA) using in vitro cultured transgenic pig mammary gland cells.

Tissue plasminogen activator (tPA) is a protein involved in the breakdown of blood clots. We have previously produced a human tPA (htPA)-overexpressing transgenic pig using a mammary gland-specific promoter. In this study, we have established a transgenic pig mammary gland cell line that produces recombinant htPA. The mammary gland cells grew well and retained their character over long periods of culture. There was no difference in the extent of apoptosis in transgenic cells compared to wild-type mammary gland cells. In addition, the transgenic mammary gland cells expressed and secreted htPA into the conditioned media at a concentration similar to that in milk. This transgenic cell line represents a simple and ethical method for recombinant htPA production.

Improving Telestroke Treatment Times in an Expanding Network of Hospitals.

BACKGROUND: Like all medical innovations, telestroke must demonstrate successful outcomes to achieve sustained growth and acceptance. Asserting that telemedicine is faster, employs the latest technology, or promotes a better use of limited resources is laudable but insufficient. An analysis of stroke treatment within a telemedicine network in 2013 showed that tissue-type plasminogen activator (tPA) could be safely and reliably administered within a practice-based model of telestroke care. Since then, hospital volume and tPA administration within this network have tripled. We hypothesize that a practice-based model of telestroke can maintain positive outcomes in the face of rapid growth. METHODS: Data on tPA treatment times and outcomes after thrombolysis were gathered for 165 patients treated with alteplase between November 2012 and November 2014. Comparisons were made to a previous published study of 54 patients seen between October 2010 and October 2012 in the same network. Primary outcome measures were average door-to-needle (DTN) time for TPA administration and average call-to-needle (CTN) time. RESULTS: Significant reductions were observed in median DTN (93 versus 75 minutes, P < .01) and median CTN (56 versus 41 minutes, P < .01). Quality outcome measures such as post-tPA symptomatic hemorrhage (2 [4%] versus 9 [5%], P = .23), length of stay (4 versus 4 days, P = .45), mortality (8 [15%] versus 16 [10%]; P = .32), and percentage of stroke patients treated remained stable. CONCLUSIONS: This study shows that a practice-based telemedicine system can produce meaningful improvement in markers of telestroke efficiency in the face of rapid growth of a telestroke network.

Association Between PAI-1 Activity Levels and t-PA Antigen with Glycemic Status in Prediabetic Population.

AIM: to evaluate an association between fibrinolysis defect and glycemic status in prediabetic population by assessing the levels of t-PA antigen and PAI-1 activity. METHODS: it was an observational study with cross-sectional approach. There were 72 subjects aged 30-50 years who had met the inclusion criteria. The diagnosis of diabetes mellitus (DM) and glycemic index were determined based on the American Diabetes Association (ADA) criteria. The PAI-1 and t-PA antigen levels were measured quantitatively using enzyme-linked immunosorbent assay (ELISA). Analysis between the levels of t-PA antigen and PAI-1 activity was performed using ANOVA. RESULTS: the t-PA antigen level was significantly higher in subjects with impaired glucose tolerance (IGT) and impaired fasting blood glucose (IFBG) as well as subject with impaired fasting blood glucose (IFBG) than those with normal glucose tolerance (NGT) (p=0.047). The PAI-1 activity was significantly higher in subjects with IGT, IFBG and subjects with IFBG than NGT (p=0.024). There was a significant association between glycemic status in prediabetic subjects and PAI-1 activity (p=0.04). CONCLUSION: the level of t-PA antigen and PAI-1 activity were significantly higher in prediabetic subjects than those with NGT; and there was a significant association between glycemic status in prediabetic subjects and PAI-1 activity.

LRP1 assembles unique co-receptor systems to initiate cell signaling in response to tissue-type plasminogen activator and myelin-associated glycoprotein.

In addition to functioning as an activator of fibrinolysis, tissue-type plasminogen activator (tPA) interacts with neurons and regulates multiple aspects of neuronal cell physiology. In this study, we examined the mechanism by which tPA initiates cell signaling in PC12 and N2a neuron-like cells. We demonstrate that enzymatically active and inactive tPA (EI-tPA) activate ERK1/2 in a biphasic manner. Rapid ERK1/2 activation is dependent on LDL receptor-related protein-1 (LRP1). In the second phase, ERK1/2 is activated by tPA independently of LRP1. The length of the LRP1-dependent phase varied inversely with the tPA concentration. Rapid ERK1/2 activation in response to EI-tPA and activated α2-macroglobulin (α2M*) required the NMDA receptor and Trk receptors, which assemble with LRP1 into a single pathway. Assembly of this signaling system may have been facilitated by the bifunctional adapter protein, PSD-95, which associated with LRP1 selectively in cells treated with EI-tPA or α2M*. Myelin-associated glycoprotein binds to LRP1 with high affinity but failed to induce phosphorylation of TrkA or ERK1/2. Instead, myelin-associated glycoprotein recruited p75 neurotrophin receptor (p75NTR) into a complex with LRP1 and activated RhoA. p75NTR was not recruited by other LRP1 ligands, including EI-tPA and α2M*. Lactoferrin functioned as an LRP1 signaling antagonist, inhibiting Trk receptor phosphorylation and ERK1/2 activation in response to EI-tPA. These results demonstrate that LRP1-initiated cell signaling is ligand-dependent. Proteins that activate cell signaling by binding to LRP1 assemble different co-receptor systems. Ligand-specific co-receptor recruitment provides a mechanism by which one receptor, LRP1, may trigger different signaling responses.

Mechanisms of QiShenYiQi in Inhibiting Blood-Brain Barrier Damage Following Stroke: A Network Pharmacology and Experimental Study.

BACKGROUND AND PURPOSE: QiShenYiQi (QSYQ) has shown promise in the treatment of blood-brain barrier (BBB) damage following stroke. However, the identification of its bioactive components and the underlying molecular mechanisms of action remain unknown. This study aimed to investigate the active ingredients and mechanisms involved in the inhibitory effects of QSYQ on BBB damage after ischemic stroke based on network pharmacology and experimental verification. MATERIALS AND METHODS: The chemical composition and target information of QSYQ were obtained from the Traditional Chinese Medicine Systems Pharmacology and Analysis Platform. BBB injury-related targets were identified by screening databases, and the overlapping targets with QSYQ were collected. Cytoscape software was utilized to construct protein-protein interaction (PPI) networks. Molecular docking analysis was conducted using AutoDock software. Animal experiments were carried out to verify the protective effect of QSYQ on BBB and explore potential molecular mechanisms. RESULTS: A total of 131 active ingredients in QSYQ and 154 common targets related to QSYQ and BBB damage were identified. Analysis of the PPI network revealed key targets including ALB, INS, ACTB, TP53, and CASP3 against BBB injury. Molecular docking analysis indicated favorable binding interactions between dihydrotanshinlactone, tanshinone IIA, salviolone, and their respective target proteins, such as FOS, INS, CASP3, and JUN. In animal experiments, QSYQ demonstrated effective inhibition of BBB damage, and this effect may be attributed to the regulation of ALB, INS, TP53, and CASP3. CONCLUSION: This study provides intriguing insights into the mechanisms by which QSYQ protects against BBB injury following ischemic stroke. Key targets, including ALB, INS, TP53, and CASP3, could be potentially involved in the beneficial effects of QSYQ.

Fibrinolytic and Non-fibrinolytic Roles of Tissue-type Plasminogen Activator in the Ischemic Brain.

The neurovascular unit (NVU) is assembled by endothelial cells (ECs) and pericytes, and encased by a basement membrane (BM) surveilled by microglia and surrounded by perivascular astrocytes (PVA), which in turn are in contact with synapses. Cerebral ischemia induces the rapid release of the serine proteinase tissue-type plasminogen activator (tPA) from endothelial cells, perivascular astrocytes, microglia and neurons. Owning to its ability to catalyze the conversion of plasminogen into plasmin, in the intravascular space tPA functions as a fibrinolytic enzyme. In contrast, the release of astrocytic, microglial and neuronal tPA have a plethora of effects that not always require the generation of plasmin. In the ischemic brain tPA increases the permeability of the NVU, induces microglial activation, participates in the recycling of glutamate, and has various effects on neuronal survival. These effects are mediated by different receptors, notably subunits of the N-methyl-D-aspartate receptor (NMDAR) and the low-density lipoprotein receptor-related protein-1 (LRP-1). Here we review data on the role of tPA in the NVU under non-ischemic and ischemic conditions, and analyze how this knowledge may lead to the development of potential strategies for the treatment of acute ischemic stroke patients.

Reprint of: Fibrinolytic and Non-fibrinolytic Roles of Tissue-type Plasminogen Activator in the Ischemic Brain.

The neurovascular unit (NVU) is assembled by endothelial cells (ECs) and pericytes, and encased by a basement membrane (BM) surveilled by microglia and surrounded by perivascular astrocytes (PVA), which in turn are in contact with synapses. Cerebral ischemia induces the rapid release of the serine proteinase tissue-type plasminogen activator (tPA) from endothelial cells, perivascular astrocytes, microglia and neurons. Owning to its ability to catalyze the conversion of plasminogen into plasmin, in the intravascular space tPA functions as a fibrinolytic enzyme. In contrast, the release of astrocytic, microglial and neuronal tPA have a plethora of effects that not always require the generation of plasmin. In the ischemic brain tPA increases the permeability of the NVU, induces microglial activation, participates in the recycling of glutamate, and has various effects on neuronal survival. These effects are mediated by different receptors, notably subunits of the N-methyl-D-aspartate receptor (NMDAR) and the low-density lipoprotein receptor-related protein-1 (LRP-1). Here we review data on the role of tPA in the NVU under non-ischemic and ischemic conditions, and analyze how this knowledge may lead to the development of potential strategies for the treatment of acute ischemic stroke patients.

New Wine in an Old Bottle: tPA for Ischemic Stroke Management.

As the only clinical thrombolytic drug approved by the FDA, tissue-type plasminogen activator (tPA) is the good standard acute treatment against ischemic stroke (IS) during the super-early stage. tPA forms the active principle of alteplase, a recombinant tissue-type plasminogen activator (rtPA), which is well known for its intravascular thrombolytic activity. However, the multifaceted functions of tPA in the central nervous system (CNS) hold untapped potential. Currently, increasing studies have explored the neuroprotective function of tPA in neurological diseases, particularly in acute ischemic stroke (AIS). A series of studies have indicated that tPA has anti-excitotoxic, neurotrophic, and anti-apoptotic effects on neurons; it is also involved in neuronal plasticity, axonal regeneration, and cerebral inflammatory processes, but how to deeply understand the underlying mechanism and take maximum advantage of tPA seems to be urgent. Therefore, more work is needed to illuminate how tPA performs with more diverse functions after stroke onset. In this comment, we focus on possible hypotheses about why and how tPA promotes ischemic neuronal survival in a comprehensive view. The text provides a holistic picture of the functions of tPA and enlists the considerations for the future, which might attract more attention toward the therapeutic potential of tPA in AIS.

Sodium aescinate significantly suppress postoperative peritoneal adhesion by inhibiting the RhoA/ROCK signaling pathway.

BACKGROUND: Although mechanical barriers and modern surgical techniques have been developed to prevent postoperative adhesion formation, high incidence of adhesions still represents an important challenge in abdominal surgery. So far, there has been no available therapeutic drug in clinical practice. PURPOSE: In this study, we explored the efficacy of sodium aescinate (AESS) treatment against postoperative peritoneal adhesions, the potential molecular mechanism was also investigated. STUDY DESIGN AND METHODS: Sixty male Sprague-Dawley rats were randomly divided into 6 groups for the study: the blank, vehicle, positive control and three AESS administration groups (0.5, 1 and 2 mg/kg/d, intravenous administration for 7 days). Adhesions were induced by discretely ligating peritoneal sidewall. An IL-1ß-induced HMrSV5 cell model was also performed to explore possible functional mechanism. RESULTS: The results indicated that the incidence and severity of peritoneal adhesions were significantly lower in the AESS-treated groups than that in the vehicle and positive control group. AESS-treated groups showed that the secretion, activity, and expression of tPA in rat peritoneum were notably increased. The FIB levels in rat plasma were decreased. The immunohistochemical staining analysis demonstrated that collagen I and α-SMA deposition were significantly attenuated in AESS-treated peritoneal tissues. Besides, we found that AESS treatment reduced the protein levels of p-MYPT1. To further explore the mechanisms of AESS, both activator and inhibitors of RhoA/ROCK pathway were employed in this study. It was found that AESS-induced up-regulation of tPA was reversed by activator of ROCK, but the effects of ROCK inhibitors were consistent with AESS. CONCLUSION: Taken together, the findings of in vivo and in vitro experiments proved that AESS could significantly suppress postoperative peritoneal adhesion formation through inhibiting the RhoA/ROCK signaling pathway. Our researches provide important pharmacological basis for AESS development as a potential therapeutic agent on peritoneal adhesions.

Characterizing the role of tissue-type plasminogen activator in a mouse model of Group A streptococcal infection.

Plasmin(ogen) acquisition is critical for invasive disease initiation by Streptococcus pyogenes (GAS). Host urokinase plasminogen activator (uPA) plays a role in mediating plasminogen activation for GAS dissemination, however the contribution of tissue-type plasminogen activator (tPA) to GAS virulence is unknown. Using novel tPA-deficient ALBPLG1 mice, our study revealed no difference in mouse survival, bacterial dissemination or the pathology of GAS infection in the absence of tPA in AlbPLG1/tPA-/- mice compared to AlbPLG1 mice. This study suggests that tPA has a limited role in this humanized model of GAS infection, further highlighting the importance of its counterpart uPA in GAS disease.

Recognition of Plasminogen Activator Inhibitor Type 1 as the Primary Regulator of Fibrinolysis.

The fibrinolytic system consists of a balance between rates of plasminogen activation and fibrin degradation, both of which are finely regulated by spatio-temporal mechanisms. Three distinct inhibitors of the fibrinolytic system that differently regulate these two steps are plasminogen activator inhibitor type-1 (PAI-1), α2-antiplasmin, and thrombin activatable fibrinolysis inhibitor (TAFI). In this review, we focus on the mechanisms by which PAI-1 governs total fibrinolytic activity to provide its essential role in many hemostatic disorders, including fibrinolytic shutdown after trauma. PAI-1 is a member of the serine protease inhibitor (SERPIN) superfamily and inhibits the protease activities of plasminogen activators (PAs) by forming complexes with PAs, thereby regulating fibrinolysis. The major PA in the vasculature is tissue-type PA (tPA) which is secreted from vascular endothelial cells (VECs) as an active enzyme and is retained on the surface of VECs. PAI-1, existing in molar excess to tPA in plasma, regulates the amount of free active tPA in plasma and on the surface of VECs by forming a tPA-PAI-1 complex. Thus, high plasma levels of PAI-1 are directly related to attenuated fibrinolysis and increased risk for thrombosis. Since plasma PAI-1 levels are highly elevated under a variety of pathological conditions, including infection and inflammation, the fibrinolytic potential in plasma and on VECs is readily suppressed to induce fibrinolytic shutdown. A congenital deficiency of PAI-1 in humans, in turn, leads to life-threatening bleeding. These considerations support the contention that PAI-1 is the primary regulator of the initial step of fibrinolysis and governs total fibrinolytic activity.

Tissue-type plasminogen activator is a homeostatic regulator of synaptic function in the central nervous system.

Membrane depolarization induces the release of the serine proteinase tissue-type plasminogen activator (tPA) from the presynaptic terminal of cerebral cortical neurons. Once in the synaptic cleft this tPA promotes the exocytosis and subsequent endocytic retrieval of glutamate-containing synaptic vesicles, and regulates the postsynaptic response to the presynaptic release of glutamate. Indeed, tPA has a bidirectional effect on the composition of the postsynaptic density (PSD) that does not require plasmin generation or the presynaptic release of glutamate, but varies according to the baseline level of neuronal activity. Hence, in inactive neurons tPA induces phosphorylation and accumulation in the PSD of the Ca2+/calmodulin-dependent protein kinase IIα (pCaMKIIα), followed by pCaMKIIα-induced phosphorylation and synaptic recruitment of GluR1-containing α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. In contrast, in active neurons with increased levels of pCaMKIIα in the PSD tPA induces pCaMKIIα and pGluR1 dephosphorylation and their subsequent removal from the PSD. These effects require active synaptic N-methyl-D-aspartate (NMDA) receptors and cyclin-dependent kinase 5 (Cdk5)-induced phosphorylation of the protein phosphatase 1 (PP1) at T320. These data indicate that tPA is a homeostatic regulator of the postsynaptic response of cerebral cortical neurons to the presynaptic release of glutamate via bidirectional regulation of the pCaMKIIα /PP1 switch in the PSD.

Tissue-type Plasminogen Activator (tPA) Modulates the Postsynaptic Response of Cerebral Cortical Neurons to the Presynaptic Release of Glutamate.

Tissue-type plasminogen activator (tPA) is a serine proteinase released by the presynaptic terminal of cerebral cortical neurons following membrane depolarization (Echeverry et al., 2010). Recent studies indicate that the release of tPA triggers the synaptic vesicle cycle and promotes the exocytosis (Wu et al., 2015) and endocytic retrieval (Yepes et al., 2016) of glutamate-containing synaptic vesicles. Here we used electron microscopy, proteomics, quantitative phosphoproteomics, biochemical analyses with extracts of the postsynaptic density (PSD), and an animal model of cerebral ischemia with mice overexpressing neuronal tPA to study whether the presynaptic release of tPA also has an effect on the postsynaptic terminal. We found that tPA has a bidirectional effect on the composition of the PSD of cerebral cortical neurons that is independent of the generation of plasmin and the presynaptic release of glutamate, but depends on the baseline level of neuronal activity and the extracellular concentrations of calcium (Ca2+). Accordingly, in neurons that are either inactive or incubated with low Ca2+ concentrations tPA induces phosphorylation and accumulation in the PSD of the Ca2+/calmodulin-dependent protein kinase IIα (pCaMKIIα), followed by pCaMKIIα-mediated phosphorylation and synaptic recruitment of GluR1-containing α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. In contrast, in neurons with previously increased baseline levels of pCaMKIIα in the PSD due to neuronal depolarization in vivo or incubation with high concentrations of either Ca2+ or glutamate in vitro, tPA induces pCaMKIIα and pGluR1 dephosphorylation and their subsequent removal from the PSD. We found that these effects of tPA are mediated by synaptic N-methyl-D-aspartate (NMDA) receptors and cyclin-dependent kinase 5 (Cdk5)-induced phosphorylation of the protein phosphatase 1 (PP1) at T320. Our data indicate that by regulating the pCaMKIIα/PP1 balance in the PSD tPA acts as a homeostatic regulator of the postsynaptic response of cerebral cortical neurons to the presynaptic release of glutamate.

Annexin A2 in primary afferents contributes to neuropathic pain associated with tissue type plasminogen activator.

Annexin A2 (ANX2) is a calcium (Ca(2+))-binding protein that binds to acidic phospholipids and is known to play a crucial role in many cellular regulatory processes. In particular, ANX2 has been described as a crucial receptor for thrombolysis by the tissue-type plasminogen activator (tPA) and plasmin system. In the nervous system, tPA is involved in processes of neuronal plasticity such as hippocampal long-term potentiation (LTP) and in the dorsal horn pain in several pain models. We investigated detailed changes in expression of ANX2 after nerve injury and evaluated the interaction with tPA using the rat spared nerve injury (SNI) model. SNI-induced the expression of ANX2 in L4/5 dorsal root ganglia (DRG) neurons. In the spinal cord, constitutive ANX2-immunoreactivity was expressed in laminae I-II. Peripheral nerve injury increased the ANX2 immunoreactive terminals mainly in laminae I-V of the dorsal horn on the side ipsilateral to the nerve injury. Double-labeling analysis revealed the co-localization of ANX2 with tPA in the axons of primary afferents in the dorsal horn. Experimental inhibition of ANX2 and tPA interaction by intrathecal administration of homocysteine significantly prevented and reversed SNI-induced mechanical allodynia. Thus, alterations of ANX2 may be involved in tPA-dependent plasticity after peripheral nerve injury and have an important role in neuropathic pain.

Tissue-type plasminogen activator is a neuroprotectant in the central nervous system.

Tissue-type plasminogen activator (tPA) is a serine proteinase found not only in the intravascular space but also in a well-defined sub-set of neurons in the brain. tPA is rapidly released from neurons after either exposure to hypoxia or hypoglycemia in vitro, or the induction of cerebral ischemia in vivo. It has been proposed that tPA has a neurotoxic effect in the ischemic brain. However, recent evidence indicate that once released into the synaptic cleft tPA activates specific cell signaling pathways that promote the detection and adaptation to metabolic stress. More specifically, the non-proteolytic interaction of tPA with N-methyl-D-aspartate receptors (NMDARs) and a member of the low-density lipoprotein receptor (LDLR) family in dendritic spines activates the mammalian target of rapamycin (mTOR) pathway that adapts cellular processes to the availability of energy and metabolic resources. TPA-induced mTOR activation in neurons leads to hypoxia-inducible factor 1α (HIF-1α) accumulation, HIF-1α-induced expression and membrane recruitment of the neuronal transporter of glucose GLUT3, and GLUT3-mediated uptake of glucose. These and other data discussed in this Review suggest that the postulated neurotoxic effect of tPA needs to be reconsidered and instead indicate the emergence of a new paradigm: that tPA is an endogenous neuroprotectant in the central nervous system (CNS).

Small molecules inhibitors of plasminogen activator inhibitor-1 - an overview.

PAI-1, a glycoprotein from the serpin family and the main inhibitor of tPA and uPA, plays an essential role in the regulation of intra and extravascular fibrinolysis by inhibiting the formation of plasmin from plasminogen. PAI-1 is also involved in pathological processes such as thromboembolic diseases, atherosclerosis, fibrosis and cancer. The inhibition of PAI-1 activity by small organic molecules has been observed in vitro and with some in vivo models. Based on these findings, PAI-1 appears as a potential therapeutic target for several pathological conditions. Over the past decades, many efforts have therefore been devoted to developing PAI-1 inhibitors. This article provides an overview of the publishing activity on small organic molecules used as PAI-1 inhibitors. The chemical synthesis of the most potent inhibitors as well as their biological and biochemical evaluations is also presented.

Tissue-type plasminogen activator mediates neuroglial coupling in the central nervous system.

The interaction between neurons, astrocytes and endothelial cells plays a central role coupling energy supply with changes in neuronal activity. For a long time it was believed that glucose was the only source of energy for neurons. However, a growing body of experimental evidence indicates that lactic acid, generated by aerobic glycolysis in perivascular astrocytes, is also a source of energy for neuronal activity, particularly when the supply of glucose from the intravascular space is interrupted. Adenosine monophosphate-activated protein kinase (AMPK) is an evolutionary conserved kinase that couples cellular activity with energy consumption via induction of the uptake of glucose and activation of the glycolytic pathway. The uptake of glucose by the blood-brain barrier is mediated by glucose transporter-1 (GLUT1), which is abundantly expressed in endothelial cells and astrocytic end-feet processes. Tissue-type plasminogen activator (tPA) is a serine proteinase that is found in endothelial cells, astrocytes and neurons. Genetic overexpression of neuronal tPA or treatment with recombinant tPA protects neurons from the deleterious effects of metabolic stress or excitotoxicity, via a mechanism independent of tPA's ability to cleave plasminogen into plasmin. The work presented here shows that exposure to metabolic stress induces the rapid release of tPA from murine neurons but not from astrocytes. This tPA induces AMPK activation, membrane recruitment of GLUT1, and GLUT1-mediated glucose uptake in astrocytes and endothelial cells. Our data indicate that this is followed by the synthesis and release of lactic acid from astrocytes, and that the uptake of this lactic acid via the monocarboxylate transporter-2 promotes survival in neurons exposed to metabolic stress.