Thrombolysis by PLAT/tPA increases serum free IGF1 leading to a decrease of deleterious autophagy following brain ischemia

The Janus face of endogenous neuronal tPA: promoting self-protection and worsening the death of neighboring neurons

Recombinant tissue-type plasminogen activator (r-tPA/Actilyse) stands as the prevailing pharmacological solution for treating ischemic stroke patients, of whom because their endogenous circulating tPA alone is not sufficient to rescue reperfusion and to promote favorable outcome. Beyond the tPA contributed by circulating endothelial cells and hepatocytes, neurons also express tPA, sparking debates regarding its impact on neuronal fate ranging from pro-survival to neurotoxic properties. In order to investigate the role of neuronal tPA during brain injuries, we developed models leading to its conditional deletion in neurons, employing AAV9-pPlat-GFP and AAV9-pPlat-Cre-GFP along with tPA floxed mice. These models were subjected to N-methyl-D-aspartate (NMDA)-induced excitotoxicity or thromboembolic ischemic stroke in mice. Initially, we established that our AAV9 constructs selectively transduce neurons, bypassing other brain cell types. Subsequently, we demonstrated that tPA-expressing neurons exhibit greater resistance against NMDA-induced excitotoxicity compared to tPA negative neurons. The targeted removal of tPA in neurons heightened the susceptibility of these neurons to cell death and prevented a paracrine neurotoxic effect on tPA non-expressing neurons. Under ischemic conditions, the self-neuroprotective influence of tPA encompassed both excitatory (GFP+/Tbr1+) and inhibitory (GFP+/GABA+) neurons. Our data indicate that endogenous neuronal tPA is a protective or deleterious factor against neuronal death in an excitotoxic/ischemic context, depending on whether it acts as an autocrine or a paracrine mediator.

NanoSHP099-Targeted SHP2 Inhibition Boosts Ly6Clow Monocytes/Macrophages Differentiation to Accelerate Thrombolysis

Tumor-associated thrombus (TAT) accounts for a high proportion of venous thromboembolism. Traditional thrombolysis and anticoagulation methods are not effective due to various complications and contraindications, which can easily lead to patients dying from TAT rather than the tumor itself. These clinical issues demonstrate the need to research diverse pathways for adjuvant thrombolysis in antitumor therapy. Previously, the phenotypic and functional transformation of monocytes/macrophages is widely reported to be involved in intratribal collagen regulation. This study finds that myeloid deficiency of the oncogene SHP2 sensitizes Ly6Clow monocyte/macrophage differentiation and can alleviate thrombus organization by increasing thrombolytic Matrix metalloproteinase (MMP) 2/9 activities. Moreover, pharmacologic inhibition by SHP099, examined in mouse lung metastatic tumor models, reduces tumor and thrombi burden in tumor metastatic lung tissues. Furthermore, SHP099 increases intrathrombus Ly6Clow monocyte/macrophage infiltration and exhibits thrombolytic function at high concentrations. To improve the thrombolytic effect of SHP099, NanoSHP099 is constructed to achieve the specific delivery of SHP099. NanoSHP099 is identified to be simultaneously enriched in tumor and thrombus foci, exerting dual tumor-suppression and thrombolysis effects. NanoSHP099 presents a superior thrombus dissolution effect than that of the same dosage of SHP099 because of the higher Ly6Clow monocyte/macrophage proportion and MMP2/MMP9 collagenolytic activities in organized thrombi.

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.

The Multiple Roles of Autophagy in Neural Function and Diseases

Autophagy involves the sequestration and delivery of cytoplasmic materials to lysosomes, where proteins, lipids, and organelles are degraded and recycled. According to the way the cytoplasmic components are engulfed, autophagy can be divided into macroautophagy, microautophagy, and chaperone-mediated autophagy. Recently, many studies have found that autophagy plays an important role in neurological diseases, including Alzheimer's disease, Parkinson's disease, Huntington's disease, neuronal excitotoxicity, and cerebral ischemia. Autophagy maintains cell homeostasis in the nervous system via degradation of misfolded proteins, elimination of damaged organelles, and regulation of apoptosis and inflammation. AMPK-mTOR, Beclin 1, TP53, endoplasmic reticulum stress, and other signal pathways are involved in the regulation of autophagy and can be used as potential therapeutic targets for neurological diseases. Here, we discuss the role, functions, and signal pathways of autophagy in neurological diseases, which will shed light on the pathogenic mechanisms of neurological diseases and suggest novel targets for therapies.

Activin A alleviates neuronal injury through inhibiting cGAS-STING-mediated autophagy in mice with ischemic stroke

Activin A plays an essential role in ischemic stroke as a well-known neuroprotective factor. We previously reported that Activin A could promote white matter remyelination. However, the exact molecular mechanism of Activin A in neuronal protection post-stroke is still unclear. In this study, the middle cerebral artery occlusion/reperfusion (MCAO/R)-induced ischemic stroke mouse model and oxygen-glucose deprivation/reoxygenation (OGD/R)-treated primary neurons were used to explore the molecular mechanism of Activin A-mediated neuroprotection against ischemic injuries. We found that Activin A significantly inhibits cGAS-STING-mediated excessive autophagy through the PI3K-PKB pathway, but not mTOR-dependent autophagy. Consequently, Activin A protected neurons against OGD/R-induced ischemic injury and improved cell survival in a dose-dependent manner. In addition, Activin A improved neurological functions and reduced infarct size of mice with MCAO/R-induced ischemic stroke by inhibiting autophagy. Furthermore, Activin A depended on ACVR1C receptor to exert neuroprotective effects in 1 h MCAO/R treated mice. Our findings showed that Activin A alleviated neuronal ischemic injury through inhibiting cGAS-STING-mediated excessive autophagy in mice with ischemic stroke, which may suggest a potential therapeutic target for ischemic stroke.

GluA1 Degradation by Autophagy Contributes to Circadian Rhythm Effects on Cerebral Ischemia Injury

The mechanisms of many diseases, including central nervous system disorders, are regulated by circadian rhythms. The development of brain disorders such as depression, autism, and stroke is strongly associated with circadian cycles. Previous studies have shown that cerebral infarct volume is smaller at night (active phase) than during the day (inactive phase) in ischemic stroke rodent models. However, the underlying mechanisms remain unclear. Increasing evidence suggests that glutamate systems and autophagy play important roles in the pathogenesis of stroke. Here, we report that GluA1 expression was decreased and autophagic activity was increased in active-phase male mouse models of stroke compared with the inactive-phase models. In the active-phase model, induction of autophagy decreased the infarct volume, whereas inhibition of autophagy increased the infarct volume. Meanwhile, GluA1 expression was decreased following activation of autophagy and increased following inhibition of autophagy. We used Tat-GluA1 to uncouple p62, an autophagic adapter, from GluA1 and found that this blocked the degradation of GluA1, an effect similar to that of inhibition of autophagy in the active-phase model. We also demonstrated that knock-out of the circadian rhythm gene Per1 abolished the circadian rhythmicity of the volume of infarction and also abolished GluA1 expression and autophagic activity in wild-type (WT) mice. Our results suggest an underlying mechanism by which the circadian rhythm participates in the autophagy-dependent regulation of GluA1 expression, which influences the volume of infarction in stroke.SIGNIFICANCE STATEMENT Circadian rhythms affect the pathophysiological mechanisms of disease. Previous studies suggested that circadian rhythms affect the infarct volume in stroke, but the underlying mechanisms remain largely unknown. Here, we demonstrate that the smaller infarct volume after middle cerebral artery occlusion/reperfusion (MCAO/R) during the active phase is related to lower GluA1 expression and activation of autophagy. The decrease in GluA1 expression during the active phase is mediated by the p62-GluA1 interaction, followed by direct autophagic degradation. In short, GluA1 is the substrate of autophagic degradation, which mainly occurs after MCAO/R during the active phase but not the inactive phase.

Stromal Interaction Molecule 1-Mediated Store-Operated Calcium Entry Promotes Autophagy Through AKT/Mammalian Target of Rapamycin Pathway in Hippocampal Neurons After Ischemic Stroke

The pathophysiological process of neuronal injury due to cerebral ischemia is complex among which disturbance of calcium homeostasis and autophagy are two major pathogenesis. However, it remains ambiguous whether the two factors are independent. Stromal interaction molecule 1 (STIM1) is the most important Ca²⁺ sensor mediating the store-operated Ca²⁺ entry (SOCE) through interacting with Orai1 and has recently been proven to participate in autophagy in multiple cells. In this study, we aimed to investigate the potential role of STIM1-induced SOCE on autophagy and whether its regulator function contributes to neuronal injury under hypoxic conditions using in vivo transient middle cerebral artery occlusion (tMCAO) model and in vitro oxygen and glucose deprivation (OGD) primary cultured neuron model respectively. The present data indicated that STIM1 induces autophagic flux impairment in neurons through promoting SOCE and inhibiting AKT/mTOR signaling pathway. Pharmacological inhibition of SOCE or downregulation of STIM1 with siRNA suppressed the autophagic activity in neurons. Moreover, stim1 knockdown attenuated neurological deficits and brain damage after tMCAO, which could be reversed by AKT/mTOR pathway inhibitor AZD5363. Together, the modulation of STIM1 on autophagic activation indicated the potential link between Ca²⁺ homeostasis and autophagy which provided evidence that STIM1 could be a promising therapeutic target for ischemic stroke.

Integrative network pharmacology and in silico analyses identify the anti-omicron SARS-CoV-2 potential of eugenol

Eugenol as a natural product is the source of isoniazid, and purified eugenol is extensively used in the cosmetics industry and the productive processes of edible spices. Accumulating evidence suggested that eugenol exerted potent anti-microorganism and anti-inflammation effects. Application of eugenol effectively reduced the risk of atherosclerosis, arterial embolism, and Type 2 diabetes. A previous study confirmed that treatment with eugenol attenuated lung inflammation and improved heart functions in SARS-CoV-2 spike S1-intoxicated mice. In addition to the study, based on a series of public datasets, computational analyses were conducted to characterize the acting targets of eugenol and the functional roles of these targets in COVID-19. The binding capacities of eugenol to conservative sites of SARS-CoV-2 like RNA-dependent RNA polymerase (RdRp) and mutable site as spike (S) protein, were calculated by using molecular docking following the molecular dynamics simulation with RMSD, RMSF, and MM-GBSA methods. The results of network pharmacology indicated that six targets, including PLAT, HMOX1, NUP88, CTSL, ITGB1 andTMPRSS2 were eugenol-SARS-CoV-2 interacting proteins. The omics results of in-silico study further implicated that eugenol increased the expression of SCARB1, HMOX1 and GDF15, especially HMOX1, which were confirmed the potential interacting targets between eugenol and SARS-CoV-2 antigens. Enrichment analyses indicated that eugenol exerted extensive biological effects such as regulating immune infiltration of macrophage, lipid localization, monooxyenase activity, iron ion binding and PPAR signaling. The results of the integrated analysis of eugenol targets and immunotranscription profile of COVID-19 cases shows that eugenol also plays an important role in strengthen of immunologic functions and regulating cytokine signaling. As a complement to the integrated analysis, the results of molecular docking indicated the potential binding interactions between eugenol and four proteins relating to cytokine production/release and the function of T type lymphocytes, including human TLR-4, TCR, NF-κB, JNK and AP-1. Furthermore, results of molecular docking and molecular dynamics (100ns) simulations implicated that stimulated modification of eugenol to the SARS-CoV-2 Omicron Spike-ACE2 complex, especially for human ACE2, and the molecular interaction of eugenol to SARS-CoV-2 RdRp, were no less favorable than two positive controls, molnupiravir and nilotinib. Dynamics (200ns) simulations indicated that the binding capacities and stabilities of eugenol to finger subdomain of RdRp is no less than molnupiravir. However, the simulated binding capacity of eugenol to SARS-CoV-2 wild type RBD and Omicron mutant RBD were less than nilotinib. Eugenol was predicted to have more favor LD50 value and lower cytotoxicity than two positive controls, and eugenol can pass through the blood-brain barrier (BBB). In a brief, eugenol is helpful for attenuating systemic inflammation induced by SARS-CoV-2 infection, due to the direct interaction of eugenol to SARS-CoV-2 proteins and extensive bio-manipulation of pro-inflammatory factors. This study carefully suggests eugenol is a candidate compound of developing drugs and supplement agents against SARS-CoV-2 and its Omicron variants.

Dysregulation of mTOR Signaling after Brain Ischemia

In this review, we provide recent data on the role of mTOR kinase in the brain under physiological conditions and after damage, with a particular focus on cerebral ischemia. We cover the upstream and downstream pathways that regulate the activation state of mTOR complexes. Furthermore, we summarize recent advances in our understanding of mTORC1 and mTORC2 status in ischemia–hypoxia at tissue and cellular levels and analyze the existing evidence related to two types of neural cells, namely glia and neurons. Finally, we discuss the potential use of mTORC1 and mTORC2 as therapeutic targets after stroke.

Two-Chains Tissue Plasminogen Activator Unifies Met and NMDA Receptor Signalling to Control Neuronal Survival

Tissue-type plasminogen activator (tPA) plays roles in the development and the plasticity of the nervous system. Here, we demonstrate in neurons, that by opposition to the single chain form (sc-tPA), the two-chains form of tPA (tc-tPA) activates the MET receptor, leading to the recruitment of N-Methyl-d-Aspartate receptors (NMDARs) and to the endocytosis and proteasome-dependent degradation of NMDARs containing the GluN2B subunit. Accordingly, tc-tPA down-regulated GluN2B-NMDAR-driven signalling, a process prevented by blockers of HGFR/MET and mimicked by its agonists, leading to a modulation of neuronal death. Thus, our present study unmasks a new mechanism of action of tPA, with its two-chains form mediating a crosstalk between MET and the GluN2B subunit of NMDARs to control neuronal survival.