Assessing potential desflurane-induced neurotoxicity using nonhuman primate neural stem cell models

Safety concerns about general anesthetics (GA), such as desflurane (a commonly used gaseous anesthetic agent), arose from studies documenting neural cell death and behavioral changes after early-life exposure to anesthetics and compounds with related modes of action. Neural stem cells (NSCs) can recapitulate most critical events during central nervous system (CNS) development <i>in vivo</i> and, therefore, represent a valuable <i>in vitro</i> model for evaluating potential desflurane-induced developmental neurotoxicity. In this study, NSCs harvested from the hippocampus of a gestational day 80 monkey brain were applied to explore the temporal relationships between desflurane exposures and neural stem cell health, proliferation, differentiation, and viability. At clinically relevant doses (5.7%), desflurane exposure did not result in significant changes in NSC viability [lactate dehydrogenase (LDH) release] and NSC proliferation profile/rate by Cell Cycle Assay, in both short term (3 h) and prolonged (24 h) exposure groups. However, when monkey NSCs were guided to differentiate into neural cells (including neurons, astrocytes, and oligodendrocytes), and then exposed to desflurane (5.7%), no significant changes were detected in LDH release after a 3-h exposure, but a significant elevation in LDH release into the culture medium was observed after a 24-h exposure. Desflurane (24 h)-induced neural damage was further supported by increased expression levels of multiple cytokines, e.g., G-CSF, IL-12, IL-9, IL-10, and TNF-α compared with the controls. Additionally, our immunocytochemistry and flow cytometry data demonstrated a remarkable attenuation of differentiated neurons as evidenced by significantly decreased numbers of polysialic acid neural cell adhesion molecule (PSA-NCAM)-positive cells in the desflurane-exposed (prolonged) cultures. Our data suggests that at the clinically relevant concentration, desflurane did not induce NSC damage/death, but impaired the differentiated neuronal cells after prolonged exposure. Collectively, PSA-NCAM could be essential for neuronal viability. Desflurane-induced neurotoxicity was primarily associated with the loss of differentiated neurons. Changes in the neuronal specific marker, PSA-NCAM, may help understand the underlying mechanisms associated with anesthetic-induced neuronal damage. These findings should be helpful/useful for the understanding of the diverse effects of desflurane exposure on the developing brain and could be used to optimize the usage of these agents in the pediatric setting.