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The Protective Effect of Liquiritin in Hypoxia/Reoxygenation-Induced Disruption on Blood Brain Barrier.

ABSTRACT: Background: Stroke is the second leading cause of death in human life health, but current treatment strategies are limited to thrombolytic therapy, and because of the tight time window, many contraindications, and only a very small number of people can benefit from it, new therapeutic strategies are needed to solve this problem. As a physical barrier between the central nervous system and blood, the blood-brain barrier (BBB) maintains the homeostasis of the central nervous system. Maintaining the integrity of the BBB may emerge as a new therapeutic strategy. Liquiritin (LQ) is a flavonoid isolated from the medicinal plant Glycyrrhiza uralensis Fisch. ex DC. (Fabaceae), and this study aims to investigate the protective effects of LQ on brain microvascular endothelial cells (BMECs), to provide a new therapeutic strategy for stroke treatment, and also to provide research ideas for the development of traditional Chinese medicine (TCM). Methods: The protective effects of LQ on HBMECs under the treatment of hypoxia reoxygenation (H/R) were investigated from different aspects by establishing a model of H/R injury to mimic ischemia-reperfusion in vivo while administrating different concentrations of LQ, which includes: cell proliferation, migration, angiogenesis, mitochondrial membrane potential as well as apoptosis. Meanwhile, the mechanism of LQ to protect the integrity of BBB by antioxidation and inhibiting endoplasmic reticulum (ER) stress was also investigated. Finally, to search for possible targets of LQ, a proteomic analysis approach was employed. Results: LQ can promote cell proliferation, migration as well as angiogenesis and reduce mitochondrial membrane potential damage and apoptosis. Meanwhile, LQ can also reduce the expression of related adhesion molecules, and decrease the production of reactive oxygen species. In terms of mechanism study, we demonstrated that LQ could activate Keap1/Nrf2 antioxidant pathway, inhibit ER stress, and maintain the integrity of BBB. Through differential protein analysis, 5 disease associated proteins were found. Conclusions: Studies have shown that LQ can promote cell proliferation, migration as well as angiogenesis, and reduce cell apoptosis, which may be related to its inhibition of oxidative and ER stress, and then maintain the integrity of BBB. Given that five differential proteins were found by protein analysis, future studies will revolve around the five differential proteins.

SUBMITTER: Li M

PROVIDER: S-EPMC8290897 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:We recently demonstrated that when mice are exposed to chronic mild hypoxia (CMH, 8% O2), blood vessels in the spinal cord show transient vascular leak that is associated with clustering and activation of microglia around disrupted vessels. Importantly, microglial depletion profoundly increased hypoxia-induced vascular leak, implying that microglia play a critical role maintaining vascular integrity in the hypoxic spinal cord. The goal of the current study was to examine if microglia play a similar vasculo-protective function in the brain. Employing extravascular fibrinogen leak as an index of blood-brain barrier (BBB) disruption, we found that CMH provoked transient vascular leak in cerebral blood vessels that was associated with activation and aggregation of Mac-1-positive microglia around leaky vessels. Interestingly, CMH-induced vascular leak showed regional selectivity, being much more prevalent in the brainstem and olfactory bulb than the cerebral cortex and cerebellum. Pharmacological depletion of microglia with the colony stimulating factor-1 receptor inhibitor PLX5622, had no effect under normoxic conditions, but markedly increased hypoxia-induced cerebrovascular leak in all regions examined. As in the spinal cord, this was associated with endothelial induction of MECA-32, a marker of leaky CNS endothelium, and greater loss of endothelial tight junction proteins. Brain regions displaying the highest levels of hypoxic-induced vascular leak also showed the greatest levels of angiogenic remodeling, suggesting that transient BBB disruption may be an unwanted side-effect of hypoxic-induced angiogenic remodeling. As hypoxia is common to a multitude of human diseases including obstructive sleep apnea, lung disease, and age-related pulmonary, cardiac and cerebrovascular dysfunction, our findings have important translational implications. First, they point to a potential pathogenic role of chronic hypoxia in triggering BBB disruption and subsequent neurological dysfunction, and second, they demonstrate an important protective role for microglia in maintaining vascular integrity in the hypoxic brain.

Project description:BackgroundAfter cerebral injury blood-brain barrier disruption significantly impairs brain homeostasis. Volatile anesthetics have been shown to be protective in ischemia-reperfusion injury scenarios. Their impact on brain endothelial cells after hypoxia-reoxygenation (H/R) has not yet been studied in detail.MethodsRat brain endothelial cells (RBE4) were exposed to severe hypoxia and reoxygenated in air in the presence or absence of sevoflurane. Changes in dextran permeability and architecture of the cellular junctional proteins ZO-1 and ?-catenin were measured. To determine necrosis and apoptosis rate DNA content, LDH release and caspase activity were quantified. The role of vascular endothelial growth factor (VEGF) as an inflammatory mediator increasing vascular permeability was assessed. At the same time, it was evaluated if sevoflurane effects are mediated through VEGF. Results were analyzed by unpaired t-tests or one way-analysis of variance followed by Bonferroni's correction.ResultsH/R led to a 172% increase in permeability (p<0.001), cell swelling and qualitatively but not quantitatively modified expression of ZO-1, ?-catenin and F-actin. In the presence of sevoflurane during reoxygenation, barrier function improved by 96% (p = 0.042) in parallel to a decrease of the cell size and less re-arranged junction proteins and F-actin. Sevoflurane-induced improvement of the barrier function could not be explained on the level of necrosis or apoptosis as they remained unchanged independent of the presence or absence of the volatile anesthetic. Increased expression of VEGF after H/R was attenuated by sevoflurane by 34% (p = 0.004). Barrier protection provided by sevoflurane was similar to the application of a blocking VEGF-antibody. Furthermore, the protective effect of sevoflurane was abolished in the presence of recombinant VEGF.ConclusionsIn H/R-induced rat brain endothelial cell injury sevoflurane maintains endothelial barrier function through downregulation of VEGF, which is a key player not only in mediating injury, but also with regard to the protective effect of sevoflurane.

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The Protective Effect of Liquiritin in Hypoxia/Reoxygenation-Induced Disruption on Blood Brain Barrier.

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