MicroRNA-155 negatively affects blood-brain barrier function during neuroinflammation

Area of Science:

• Neuroscience
• Molecular Biology
• Immunology

Background:

• Blood-brain barrier (BBB) dysfunction is central to neurological diseases like multiple sclerosis (MS) and stroke.
• Molecular mechanisms driving BBB breakdown and neurovascular dysfunction are not fully understood.
• MicroRNAs (miRNAs) are emerging as key regulators, but their role in CNS microvascular disorders is largely unexplored.

Purpose of the Study:

• To investigate the role of microRNAs, specifically miR-155, in regulating neuroinflammation and BBB function.
• To identify miR-155 as a critical factor in BBB breakdown during central nervous system (CNS) inflammatory conditions.

Main Methods:

• Expression analysis of miR-155 in brain vasculature of MS patients and EAE mouse models.
• Functional studies in mice lacking miR-155, assessing BBB permeability using tracer extravasation.
• In vitro experiments using cultured human brain endothelial cells exposed to inflammatory cytokines.

Main Results:

• miR-155 is expressed in the neurovascular unit of MS patients and EAE mice.
• Loss of miR-155 significantly reduced BBB permeability in mouse models of neuroinflammation and systemic inflammation.
• miR-155 mimics cytokine-induced BBB dysfunction in vitro and its inhibition partially restores barrier integrity.
• miR-155 targets key molecules involved in cell-cell junctions and focal adhesion.

Conclusions:

• Brain endothelial miR-155 acts as a negative regulator of BBB integrity.
• miR-155 is a potential therapeutic target for mitigating BBB dysfunction in CNS neuroinflammatory disorders.