Dexmedetomidine Pretreatment of Neuronal Cells Has Protective Effect Against Cell Death During Oxygen-glucose Deprivation/Reoxygenation, Based on IGF-1 Production.

Abstract

Objective: Insulin-like growth factor 1 (IGF-1) protects neuronal-cell damage by ischemia. Although neuronal cells have been reported to produce IGF-1, the molecular mechanisms remains obscure. Dexmedetomidine (DEX) protects neuronal cells from ischemic damage. We investigated the involvement of IGF-1 in the effect of DEX pretreatment on neuronal ischemic damage using an in vitro mouse hippocampal neuron model.

Materials: We used Dexmedetomidine and cryopreserved passaged mouse hippocampal neuronal HT22. Other reagents in this study were analytical grade.

Methods: Ischemia-reperfusion was modeled using the in vitro oxygen-glucose deprivation/reoxygenation (OGD/R). The effect of DEX was examined by incubating cells in DEX-containing medium for 1 hour prior to OGD/R. The cell damages were evaluated by lactate dehydrogenase (LDH) release. The amount of released IGF-1 were evaluated quantitatively by ELISA. The degree of Akt phosphorylation was evaluated by western blotting.

Results: OGD/R loading promoted LDH release from neuronal cells, while DEX pretreatment suppressed the LDH release. IGF-1 release from them was primed by DEX pretreatment under OGD/R condition, but not under normal conditions. Akt was activated in DEX-pretreated cells following OGD/R loading. IGF-1 neutralizing antibody (αIGF-1) eliminated the above effects of DEX pretreatment. However, IGF-1 receptor expression in neuronal cells was not affected by DEX pretreatment prior to OGD/R loading.

Conclusions: Our results demonstrate that neuronal cells primed with DEX under OGD/R conditions could release IGF-1 and potentially protect themselves via the IGF-1/Akt pathway. Consequently, it appears that neuronal cells activated by DEX have the capacity to self-protect from ischemic damage.