Ammonium Increases TRPC1 Expression Via Cav-1/PTEN/AKT/GSK3β Pathway

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Hyperammonemia, a consequence of acute liver failure, is the primary driver of hepatic encephalopathy.
• Ammonium overload disrupts astroglial homeostatic systems, crucial for brain function.
• Previous research indicated ammonia increases Transient Receptor Potential Canonic 1 (TRPC1) channel expression and calcium release.

Purpose of the Study:

• To investigate the role of the caveolin-1 (Cav-1)/phosphatase and tensin homologue (PTEN)/AKT/glycogen synthase kinase 3β (GSK-3β) signaling pathway in ammonium-induced TRPC1 gene expression.
• To elucidate the specific cellular localization and pathway involvement in hyperammonemia-induced changes.

Main Methods:

• Primary mouse cerebral astrocyte cultures were treated with ammonium chloride (1-5 mM) for 1-5 days.
• Gene and protein expression of Cav-1, PTEN, AKT, GSK-3β, and TRPC1 were quantified.
• In vivo studies utilized urease injections in adult mice and transgenic mice with astrocyte- or neuron-specific markers.

Main Results:

• Ammonium significantly upregulated Cav-1 and TRPC1 mRNA and protein expression, alongside increased membrane PTEN.
• Phosphorylation of AKT and GSK-3β was significantly decreased by ammonium.
• Cav-1 knockdown abolished ammonium-induced changes, implicating the Cav-1/PTEN/PI3K/AKT pathway.
• In vivo studies confirmed Cav-1 upregulation in astrocytes, not neurons, following hyperammonemia.

Conclusions:

• The Cav-1/PTEN/PI3K/AKT pathway is critically involved in regulating ammonium-induced TRPC1 gene expression in astrocytes.
• Increased GSK-3β activity may contribute to ammonium-related pathologies, suggesting potential therapeutic targets.