High Glucose Enhances Isoflurane-Induced Neurotoxicity by Regulating TRPC-Dependent Calcium Influx

Isoflurane is a commonly used inhalational anesthetic that can induce neurotoxicity via elevating cytosolic calcium (Ca²⁺). High glucose regulates the expression of a family of non-selective cation channels termed transient receptor potential canonical (TRPC) channels that may contribute to Ca²⁺ influx. In the present study, we investigated whether high glucose enhances isoflurane-induced neurotoxicity by regulating TRPC-dependent Ca²⁺ influx. First, we evaluated toxic damage in mice primary cultured hippocampal neurons and human neuroblastoma cells (SH-SY5Y cells) after hyperglycemia and isoflurane exposure. Next, we investigated cytosolic Ca²⁺ concentrations, TRPC mRNA expression levels and tested the effect of the TRPC channel blocker SKF96365 on cytosolic Ca²⁺ levels in cells treated with high glucose or/and isoflurane. Finally, we employed knocked down TRPC6 to demonstrate the role of TRPC in high glucose-mediated enhancement of isoflurane-induced neurotoxicity. The results showed that high glucose could enhance isoflurane-induecd toxic damage in primary hippocampal neurons and SH-SY5Y cells. High glucose enhanced the isoflurane-induced increase of cytosolic Ca²⁺ in SH-SY5Y cells. High glucose elevated TRPC mRNA expression, especially that of TRPC6. SKF96365 and knock down of TRPC6 were able to inhibit the high glucose-induced increase of cytosolic Ca²⁺ and decrease isoflurane-induced neurotoxicity in SH-SY5Y cells cultured with high glucose. Our findings indicate that high glucose could elevate TRPC expression, thus increasing Ca²⁺ influx and enhancing isoflurane-induced neurotoxicity.