Blood-Brain Barrier and Neurovascular Unit In Vitro Models for Studying Mitochondria-Driven Molecular Mechanisms of Neurodegeneration

Pathophysiology of chronic neurodegeneration is mainly based on complex mechanisms related to aberrant signal transduction, excitation/inhibition imbalance, excitotoxicity, synaptic dysfunction, oxidative stress, proteotoxicity and protein misfolding, local insulin resistance and metabolic dysfunction, excessive cell death, development of glia-supported neuroinflammation, and failure of neurogenesis. These mechanisms tightly associate with dramatic alterations in the structure and activity of the neurovascular unit (NVU) and the blood-brain barrier (BBB). NVU is an ensemble of brain cells (brain microvessel endothelial cells (BMECs), astrocytes, pericytes, neurons, and microglia) serving for the adjustment of cell-to-cell interactions, metabolic coupling, local microcirculation, and neuronal excitability to the actual needs of the brain. The part of the NVU known as a BBB controls selective access of endogenous and exogenous molecules to the brain tissue and efflux of metabolites to the blood, thereby providing maintenance of brain chemical homeostasis critical for efficient signal transduction and brain plasticity. In Alzheimer's disease, mitochondria are the target organelles for amyloid-induced neurodegeneration and alterations in NVU metabolic coupling or BBB breakdown. In this review we discuss understandings on mitochondria-driven NVU and BBB dysfunction, and how it might be studied in current and prospective NVU/BBB in vitro models for finding new approaches for the efficient pharmacotherapy of Alzheimer's disease.

Theranostic quantum dots for crossing blood-brain barrier in vitro and providing therapy of HIV-associated encephalopathy

The blood–brain barrier (BBB) is a complex physiological checkpoint that restricts the free diffusion of circulating molecules from the blood into the central nervous system. Delivering of drugs and other active agents across the BBB is one of the major technical challenges faced by scientists and medical practitioners. Therefore, development of novel methodologies to address this challenge holds the key for both the diagnosis and treatment of brain diseases, such as HIV-associated encephalopathy. Bioconjugated quantum dots (QDs) are excellent fluorescent probes and nano-vectors, being designed to transverse across the BBB and visualize drug delivery inside the brain. This paper discusses the use of functionalized QDs for crossing the blood–brain barrier and treating brain disease. We highlight the guidelines for using in vitro BBB models for brain disease studies. The theranostic QDs offers a strategy to significantly improve the effective dosages of drugs to transverse across the BBB and orientate to the targets inside the brain.