Transcriptome profiling of brain edemas caused by influenza infection and lipopolysaccharide treatment

Area of Science:

• Neuroscience
• Virology
• Immunology

Background:

• Influenza A virus-associated encephalopathy (IAE) is a severe neurological complication of influenza infection, primarily affecting young children.
• The precise pathogenic mechanisms underlying IAE remain poorly understood, hindering effective treatment strategies.
• IAE is a significant cause of mortality and morbidity in pediatric populations during influenza outbreaks.

Purpose of the Study:

• To develop and characterize a novel mouse model that mimics key features of human Influenza A virus-associated encephalopathy.
• To investigate the molecular mechanisms, particularly concerning the blood-brain barrier (BBB), involved in the pathogenesis of IAE.
• To identify potential cellular and molecular pathways contributing to the severity of IAE.

Main Methods:

• Induction of an IAE-like model in mice through combined infection with Influenza A virus and administration of lipopolysaccharide (LPS).
• Assessment of brain edema severity using quantitative measurements.
• Analysis of cytokine levels in serum.
• Gene expression profiling of brain tissue using transcriptomic analysis.
• Gene ontology (GO) analysis to categorize upregulated genes and identify functional pathways.

Main Results:

• The developed mouse model exhibited significantly increased brain edema severity (nearly threefold) compared to control groups.
• Elevated levels of cytokines were detected in the sera of IAE model mice.
• Gene expression profiling revealed no significant upregulation of cytokine-related genes within the brain tissue.
• Conversely, genes associated with the disruption of the blood-brain barrier were found to be upregulated in the brain.
• Gene ontology analysis highlighted terms such as "ion channels," "calcium oscillation," and "membrane transporter activities" as significantly enriched functional groups.

Conclusions:

• The study successfully established a mouse model for Influenza A virus-associated encephalopathy, demonstrating increased brain edema and systemic cytokine elevation.
• Blood-brain barrier disruption in this IAE model appears to be driven by upregulated genes involved in cellular electrolyte imbalance and membrane transport, rather than a direct cytokine storm within the brain.
• These findings suggest that cellular electrolyte imbalance in neuronal tissue plays a crucial role in BBB disruption during IAE, offering new avenues for therapeutic intervention.