Isoflurane but Not Sevoflurane or Desflurane Aggravates Injury to Neurons In Vitro and In Vivo via p75NTR-NF-κB Activation

BACKGROUND: General anesthesia in patients with or at risk for neuronal injury remains challenging due to the controversial influence of volatile anesthetics on neuronal damage. We hypothesized that isoflurane, sevoflurane, and desflurane would exert variable degrees of neurotoxicity in vitro and in vivo via activation of the p75 neurotrophin receptor (p75(NTR)). METHODS: SH-SY5Y cells were exposed to oxygen glucose deprivation (OGD, 16 hours), preceded or followed by incubation with isoflurane, sevoflurane, or desflurane (1.2 minimal alveolar concentration, 2 hours). Neuronal cell death was analyzed by flow cytometry (mitochondrial membrane potential, Annexin V/propidium iodide [AV/Pi]) and quantification of lactate dehydrogenase release. We analyzed NF-kappa B activity by DNA-binding ELISA and luciferase assay. The role of p75(NTR) was studied using the p75(NTR)-blocking peptide TAT-pep5 and siRNA knockdown. The effect of isoflurane p75(NTR) inhibition on retinal ischennia-reperfusion injury (IRI) in adult Sprague-Dawley rats was assessed by analyzing retinal ganglion cell (RGC) density. RESULTS: Isoflurane but not sevoflurane or desflurane postexposure aggravated OGD-induced neuronal cell death (AV/Pi positive cells: OGD 41.1% [39.0/43.3] versus OGD + isoflurane 48.5% [46.4/63.4], P = 0.001). Isoflurane significantly increased NF-kappa B DNA-binding and transcriptional activity of NF-kappa B (relative Luminescence Units: OGD 500 [499/637] versus OGD + isoflurane 1478 [1363/1643], P = 0.001). Pharmacological inhibition or siRNA knockdown of p75(NTR) counteracted the aggravating effects of isoflurane. Isoflurane increased RGC damage in vivo (IRI 1479 RGC/mm(2) [1311/1697] versus IRI + isoflurane 1170 [1093/1211], P = 0.03), which was counteracted by p75(NTR)-inhibition via TAT-pep5 (P = 0.02). CONCLUSIONS: Isoflurane but not sevoflurane or desflurane postexposure aggravates neurotoxicity in preinjured neurons via activation of p75(NTR) and NE-kappa B. These findings may have implications for the choice of volatile anesthetic being used in patients with or at risk for neuronal injury, specifically in patients with a stroke or history of stroke and in surgical procedures in which neuronal injury is likely to occur, such as cardiac surgery and neurovascular interventions.