Phosphodiesterase 4 Inhibitor Roflumilast Protects Rat Hippocampal Neurons from Sevoflurane Induced Injury via Modulation of MEK/ERK Signaling Pathway

Background/Aims: Sevoflurane, a commonly used volatile anesthetic, recently has been found has neurotoxicity in the central nervous system of neonatal rodents. This study aimed to reveal whether phosphodiesterase 4 (PDE-4) inhibitor roflumilast has protective functions in sevoflurane-induced nerve damage. Methods: Hippocampal neurons were isolated from juvenile rats, and were exposed to sevoflurane with or without roflumilast treatment. Cell viability and apoptosis were respectively assessed by CCK-8 and flow cytometry. Western blot analysis was performed to detect the protein expressions of apoptosis-related factors, and core factors in MEK/ERK and mTOR signaling pathways. Results: Toxic effects of sevoflurane on hippocampal neurons were observed, as cell viability was reduced, apoptotic cell rate was increased, Bcl-2 was down-regulated, and Bax, cleaved caspase-3 and -9 were up-regulated after 1% sevoflurane exposure for 16 h. Sevoflurane exhibited a temporarily (less than 16 h) inhibitory effect on MEK/ERK pathway, but has no impact on mTOR pathway. Roflumilast promoted the release of cAMP and down-regulated the protein expression of PDE-4. Roflumilast (1 µM) alone has no impact on viability and apoptosis of hippocampal neurons. However, roflumilast increased cell viability and deceased apoptosis in sevoflurane-injured neurons. Besides, roflumilast could recover sevoflurane-induced deactivation of MEK/ERK pathway. Conclusion: To conclude, this study demonstrated a neuroprotective role of roflumilast in sevoflurane-induced nerve damage. Roflumilast promoted hippocampal neurons viability, and reduced apoptosis possibly via modulation of MEK/ERK signaling pathway.