gms | German Medical Science

Objective: Clinical studies suggests a neuroprotective impact of the L-type calcium channel blocker nimodipine after vestibular schwannoma and maxillofacialsurgeries. Cell culture experimental data demonstrated a cell type-independent neuroprotective effect under different stress conditions by 24-hour nimodipine pretreatment. But there exists only little information about the sufficient time of administration and the molecular mechanisms of treatment. Therefore, the present study should shed light on the molecular mode of action and the time of sufficient nimodipine pretreatment.

Methods: To analyze the required pretreatment time to achieve the neuroprotective effect immortalized cell lines from neurons (RN33B), astrocytes (C8-D1A) and Schwann cells (SW10) as well as primary astrocytes were pretreated with different concentrations of nimodipine for 4, 8, 12, 16 and 20 hours. Afterwards, cells were incubated under stress conditions like osmotic and oxidative stress for 24 h. Cytotoxicity was measured via fluorescence dye, which binds DNA in compromised cells. The fluorescence signal was normalized to total cell lysates. The nimodipine-dependent regulation of anti-apoptotic cell signaling pathways and endoplasmic reticulum stress-related genes or proteins was determined via quantitative PCR and Western blot analysis.

Results: Four hours nimodipine pretreatment showed no effect on cytotoxicity, whereas for 8-, 12-, 16-, and 20-hour pretreatment a reduced cell death was detected. Therefore, the studies determined that an 8-hour pretreatment period is sufficient to protect the cells against stress-dependent apoptosis and achieve a neuroprotective effect. Additionally, an induction of the anti-apoptotic Akt signaling pathway through nimodipine treatment was detected via higher levels of phosphorylated Akt protein on serine 473 during the different stress conditions. This was accompanied by regulation of further genes and protein involved in apoptosis.

Conclusion: Nimodipine treatment activate the anti-apoptotic Akt signaling pathway, thereby it protects neuronal and glial cells from stress-induced cell death after a pretreatment period of at least 8 hours.