Changes in tissue factor and the effects of tissue factor pathway inhibitor on transient focal cerebral ischemia in rats

rTFPI Protects Cardiomyocytes from Hypoxia/Reoxygenation Injury through Inhibiting Autophagy and the Class III PI3K/Beclin-1 Pathway

Autophagy plays various roles at different stages of ischemia reperfusion (I/R) injury in cardiomyocytes. It has been reported that tissue factor pathway inhibitor (TFPI) has a protective effect on I/R injury. This study aimed to determine the roles of TFPI in autophagy during the I/R injury process in cardiomyocytes and the possible mechanisms. An isolated hypoxia/reoxygenation (H/R) pattern of cardiomyocytes was established by the MIC101 system. The cell viability and oxidative stress of cardiomyocytes were detected by an MTT assay and ROS assay, respectively. The autophagy level was measured by Ad-mCherry-GFP-LC3B and MDC. We detected the expression levels of autophagy-related proteins by western blotting. After 2 h of hypoxia and 12 h of reoxygenation, the cardiomyocyte viability in the H/R group was significantly lower than that in the control group (p < 0.05) than in the H/R group. According to intracellular ROS production, the fluorescence intensity in the H/R group was enhanced compared with that in the negative control group, and it was weaker in the H/R + rTFPI group compared with the H/R group. The level of autophagy and the expression levels of autophagy-related proteins (LC3-II/LC3-I, Beclin-1 and PI3K) were markedly increased in the H/R group compared to the control group (p < 0.05) whereas the levels were markedly decreased in the H/R + rTFPI group compared to the H/R group (p < 0.05). TFPI could relieve cardiomyocyte injury by inhibiting the Class III PI3K/Beclin-1 pathway and oxidative stress; thus, TFPI decreased autophagy and protected cardiomyocytes induced by H/R injury. In conclusion, TFPI may be a new direction for the prevention of myocardial I/R injury.

Platelets as drivers of ischemia/reperfusion injury after stroke

Ischemic stroke is a leading cause of morbidity and mortality worldwide and, despite reperfusion either via thrombolysis or thrombectomy, stroke patients often suffer from lifelong disabilities. These persistent neurological deficits may be improved by treating the ischemia/reperfusion (I/R) injury that occurs following ischemic stroke. There are currently no approved therapies to treat I/R injury, and thus it is imperative to find new targets to decrease the burden of ischemic stroke and related diseases. Platelets, cell fragments from megakaryocytes, are primarily known for their role in hemostasis. More recently, investigators have studied the nonhemostatic role of platelets in inflammatory pathologies, such as I/R injury after ischemic stroke. In this review, we seek to provide an overview of how I/R can lead to platelet activation and how activated platelets, in turn, can exacerbate I/R injury after stroke. We will also discuss potential mechanisms by which platelets may ameliorate I/R injury.

Subarachnoid hemorrhage - Induced block of cerebrospinal fluid flow: Role of brain coagulation factor III (tissue factor)

Subarachnoid hemorrhage (SAH) in 95% of cases results in long-term disabilities due to brain damage, pathogenesis of which remains uncertain. Hindrance of cerebrospinal fluid (CSF) circulation along glymphatic pathways is a possible mechanism interrupting drainage of damaging substances from subarachnoid space and parenchyma. We explored changes in CSF circulation at different time following SAH and possible role of brain tissue factor (TF). Fluorescent solute and fluorescent microspheres injected into cisterna magna were used to track CSF flow in mice. SAH induced by perforation of circle of Willis interrupted CSF flow for up to 30 days. Block of CSF flow did not correlate with the size of hemorrhage. Following SAH, fibrin deposits were observed on the brain surface including areas without visible blood. Block of astroglia-associated TF by intracerebroventricular administration of specific antibodies increased size of hemorrhage, decreased fibrin deposition and facilitated spread of fluorophores in sham/naïve animals. We conclude that brain TF plays an important role in localization of hemorrhage and also regulates CSF flow under normal conditions. Targeting of the TF system will allow developing of new therapeutic approaches to the treatment of SAH and pathologies related to CSF flow such as hydrocephalus.

Hemostasis and alterations of the central nervous system

Modulation of coagulation has been successfully applied to ischemic disorders of the central nervous system (CNS). Some components of the coagulation system have been identified in the CNS, yet with limited exception their functions have not been clearly defined. Little is known about how events within the cerebral tissues affect hemostasis. Nonetheless, the interaction between cerebral cells and vascular hemostasis and the possibility that endogenous coagulation factors can participate in functions within the neurovascular unit provide intriguing possibilities for deeper insight into CNS functions and the potential for treatment of CNS injuries. Here, we consider the expression of coagulation factors in the CNS, the coagulopathy associated with focal cerebral ischemia (and its relationship to hemorrhagic transformation), the use of recombinant tissue plasminogen activator (rt-PA) in ischemic stroke and its study in animal models, the impact of rt-PA on neuron and CNS structure and function, and matrix protease generation and matrix degradation and hemostasis. Interwoven among these topics is evidence for interactions of coagulation factors with and within the CNS. How activation of hemostasis occurs in the cerebral tissues and how the brain responds are difficult questions that offer many research possibilities.