Oatp (Organic Anion Transporting Polypeptide)-Mediated Transport: A Mechanism for Atorvastatin Neuroprotection in Stroke

Beyond wrecking a wall: revisiting the concept of blood-brain barrier breakdown in ischemic stroke

The blood-brain barrier constitutes a dynamic and interactive boundary separating the central nervous system and the peripheral circulation. It tightly modulates the ion transport and nutrient influx, while restricting the entry of harmful factors, and selectively limiting the migration of immune cells, thereby maintaining brain homeostasis. Despite the well-established association between blood-brain barrier disruption and most neurodegenerative/neuroinflammatory diseases, much remains unknown about the factors influencing its physiology and the mechanisms underlying its breakdown. Moreover, the role of blood-brain barrier breakdown in the translational failure underlying therapies for brain disorders is just starting to be understood. This review aims to revisit this concept of "blood-brain barrier breakdown," delving into the most controversial aspects, prevalent challenges, and knowledge gaps concerning the lack of blood-brain barrier integrity. By moving beyond the oversimplistic dichotomy of an "open"/"bad" or a "closed"/"good" barrier, our objective is to provide a more comprehensive insight into blood-brain barrier dynamics, to identify novel targets and/or therapeutic approaches aimed at mitigating blood-brain barrier dysfunction. Furthermore, in this review, we advocate for considering the diverse time- and location-dependent alterations in the blood-brain barrier, which go beyond tight-junction disruption or brain endothelial cell breakdown, illustrated through the dynamics of ischemic stroke as a case study. Through this exploration, we seek to underscore the complexity of blood-brain barrier dysfunction and its implications for the pathogenesis and therapy of brain diseases.

Study on the uptake of Gastrodin in the liver

Background

Gastrodin is the active monomer of the Chinese herb Rhizoma Gastrodiae with the largest quantity of active components. Gastrodin is commonly used in the treatment of central nervous system disorders such as headaches and epilepsy due to its sedating and hypnotic properties. Its pharmacological mechanism and clinical application have been extensively explored due to its low toxicity.

Methods

To investigate the molecular mechanism of hepatic uptake of Gastrodin in rats, animals were randomly assigned to three groups: control group, rifampicin (RIF) group, and adrenalone (ADR) group. Blood samples were collected through the cardiac puncture 90, 180, and 300 min after injection, respectively. Rats were sacrificed 300 min after administration, and liver tissue was collected. Gastrodin concentration was determined by HPLC, and the Kp value was calculated.

Results

After administering the inhibitors of organic cation transporters (OCTs) and organic anion transporting polypeptides (OATPs), the KP values in the experimental groups were significantly lower compared to the blank control group (P < 0.05).

Conclusions

These findings imply that Gastrodin may be a substrate for both OCTs and OATPs.

Critical role of Slc22a8 in maintaining blood-brain barrier integrity after experimental cerebral ischemia-reperfusion

Blood-brain barrier (BBB) damage significantly affects the prognosis of ischemic stroke patients. This project employed multi-omics analysis to identify key factors regulating BBB disruption during cerebral ischemia-reperfusion. An integrated analysis of three transcriptome sequencing datasets from mouse middle cerebral artery occlusion/reperfusion (MCAO/R) models identified eight downregulated genes in endothelial cells. Additionally, transcriptome analysis of BBB (cortex) and non-BBB (lung) endothelium of E13.5 mice revealed 2,102 upregulated genes potentially associated with BBB integrity. The eight downregulated genes were intersected with the 2,102 BBB-related genes and mapped using single-cell RNA sequencing data, revealing that solute carrier family 22 member 8 (Slc22a8) is specifically expressed in endothelial cells and pericytes and significantly decreases after MCAO/R. This finding was validated in the mouse MCAO/R model at both protein and mRNA levels in this study. External overexpression of Slc22a8 using a lentivirus carrying Tie2 improved Slc22a8 and tight junction protein levels and reduced BBB leakage after MCAO/R, accompanied by Wnt/β-catenin signaling activation. In conclusion, this study suggested that MCAO/R-induced downregulation of Slc22a8 expression may be a crucial mechanism underlying BBB disruption. Interventions that promote Slc22a8 expression or enhance its function hold promise for improving the prognosis of patients with cerebral ischemia.

The role of oxidative stress in blood-brain barrier disruption during ischemic stroke: Antioxidants in clinical trials

Ischemic stroke is one of the leading causes of death and disability. Occlusion and reperfusion of cerebral blood vessels (i.e., ischemia/reperfusion (I/R) injury) generates reactive oxygen species (ROS) that contribute to brain cell death and dysfunction of the blood-brain barrier (BBB) via oxidative stress. BBB disruption influences the pathogenesis of ischemic stroke by contributing to cerebral edema, hemorrhagic transformation, and extravasation of circulating neurotoxic proteins. An improved understanding of mechanisms for ROS-associated alterations in BBB function during ischemia/reperfusion (I/R) injury can lead to improved treatment paradigms for ischemic stroke. Unfortunately, progress in developing ROS targeted therapeutics that are effective for stroke treatment has been slow. Here, we review how ROS are produced in response to I/R injury, their effects on BBB integrity (i.e., tight junction protein complexes, transporters), and the utilization of antioxidant treatments in ischemic stroke clinical trials. Overall, knowledge in this area provides a strong translational framework for discovery of novel drugs for stroke and/or improved strategies to mitigate I/R injury in stroke patients.

CNS Drug Delivery in Stroke: Improving Therapeutic Translation From the Bench to the Bedside

Drug development for ischemic stroke is challenging as evidenced by the paucity of therapeutics that have advanced beyond a phase III trial. There are many reasons for this lack of clinical translation including factors related to the experimental design of preclinical studies. Often overlooked in therapeutic development for ischemic stroke is the requirement of effective drug delivery to the brain, which is critical for neuroprotective efficacy of several small and large molecule drugs. Advancing central nervous system drug delivery technologies implies a need for detailed comprehension of the blood-brain barrier (BBB) and neurovascular unit. Such knowledge will permit the innate biology of the BBB/neurovascular unit to be leveraged for improved bench-to-bedside translation of novel stroke therapeutics. In this review, we will highlight key aspects of BBB/neurovascular unit pathophysiology and describe state-of-the-art approaches for optimization of central nervous system drug delivery (ie, passive diffusion, mechanical opening of the BBB, liposomes/nanoparticles, transcytosis, intranasal drug administration). Additionally, we will discuss how endogenous BBB transporters represent the next frontier of drug delivery strategies for stroke. Overall, this review will provide cutting edge perspective on how central nervous system drug delivery must be considered for the advancement of new stroke drugs toward human trials.

Blood-brain barrier transporters: a translational consideration for CNS delivery of neurotherapeutics

INTRODUCTION

Successful neuropharmacology requires optimization of CNS drug delivery and, by extension, free drug concentrations at brain molecular targets. Detailed assessment of blood-brain barrier (BBB) physiological characteristics is necessary to achieve this goal. The 'next frontier' in CNS drug delivery is targeting BBB uptake transporters, an approach that requires evaluation of brain endothelial cell transport processes so that effective drug accumulation and improved therapeutic efficacy can occur.

AREAS COVERED

BBB permeability of drugs is governed by tight junction protein complexes (i.e., physical barrier) and transporters/enzymes (i.e., biochemical barrier). For most therapeutics, a component of blood-to-brain transport involves passive transcellular diffusion. Small molecule drugs that do not possess acceptable physicochemical characteristics for passive permeability may utilize putative membrane transporters for CNS uptake. While both uptake and efflux transport mechanisms are expressed at the brain microvascular endothelium, uptake transporters can be targeted for optimization of brain drug delivery and improved treatment of neurological disease states.

EXPERT OPINION

Uptake transporters represent a unique opportunity to optimize brain drug delivery by leveraging the endogenous biology of the BBB. A rigorous understanding of these transporters is required to improve translation from the bench to clinical trials and stimulate the development of new treatment paradigms for neurological diseases.