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

作者：Wang, Wei; Gu, Li; Verkhratsky, Alexei; Peng, Liang^*

来源：Neurochemical Research, 2017, 42(3): 762-776.

DOI：10.1007/s11064-016-2004-z

• Astrocyte
• Hepatic encephalopathy
• Ammonium
• Cav-1
• PTEN
• PI3K/AKT
• GSK-3 beta

Hyperammonemia occurring following acute liver failure is the primary cause of hepatic encephalopathy. In the brain, ammonium is catabolised by glutamine synthetase expressed exclusively in astroglia; ammonium overload impairs astroglial homeostatic systems. Previously, we had reported that chronic treatment with 3 mM ammonia increased expression of transient receptor potential canonic 1 (TRPC1) channels and Ca2+ release from intracellular Ca2+ stores (Liang et al. in Neurochem Res 39: 2127-2135, 2014). Glycogen synthase kinase 3 beta(GSK-3 beta) has a key role in several astroglial signalling pathways and is known to be affected in various CNS diseases. We have studied the involvement of Cav-1/ PTEN/ AKT/ GSK-3 beta signalling system in regulation of TRPC1 gene expression by ammonium. Effects of chronic (1-5 days) treatment with ammonium chloride (ammonium), at pathologically relevant concentrations of 1-5 mM were investigated on primary cultures of mouse cerebral astrocytes. We quantified expression of caveolin-1 (Cav-1), membrane content of phosphatase and tensin homologue (PTEN), phosphorylation of AKT and GSK-3 beta, and expression of TRPC1 channels. Ammonium significantly increased expression of Cav-1 mRNA and protein, mRNA of TRPC1 as well as membrane content of PTEN; conversely phosphorylation of AKT and GSK-3 beta were significantly decreased. These changes were abolished following astrocytes treatment with siRNA specific to Cav-1, indicating the involvement of Cav-1/ PTEN/ PI3K/ AKT pathway. Similar results were found in the brains of adult mice subjected to intraperitoneal injection of urease (a model for hyperammoniemia) for 1-5 days. In transgenic mice tagged with an astrocyte-specific or neurone-specific markers (used for fluores-cence-activated cell sorting of astrocytes vs. neurones) and treated with intraperitoneal injections of urease for 3 days, the Cav-1 gene mRNA expression was up-regulated in astrocytes, but not in neurones. The up-regulation of TRPC1 gene expression by ammonium was suppressed by GSK-3 beta inhibitors, lithium salt and AR-A014418, suggesting that increase of GSK-3 beta activity may play a role in ammonium-related pathologies.

• 出版日期2017-3
• 单位中国医科大学