Neuregulin-1β Prevents Ca²⁺ Overloading and Apoptosis Through PI3K/Akt Activation in Cultured Dorsal Root Ganglion Neurons with Excitotoxicity Induced by Glutamate

Abstract

Neuregulin (NRG) plays an important role on the genesis and differentiation of neurons in the dorsal root ganglion (DRG). Whether NRG-1β regulates Ca²⁺ homeostasis and apoptosis of cultured DRG neurons with excitotoxicity induced by Glu remains unknown. In this study, primary cultured DRG neurons were used to determine the effects of NRG-1β on Ca²⁺ overload and apoptosis of DRG sensory neurons with excitotoxicity induced by Glu. The primary cultured DRG neurons at 48 h of culture age were then exposed to Glu (0.2 mmol/l), Glu (0.2 mmol/l) plus NRG-1β (20 nmol/l), or Glu (0.2 mmol/l) plus NRG-1β (20 nmol/l) and phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 (10 μmol/l) for additional 12 h. After that, intracellular Ca²⁺ concentration ([Ca²⁺]_i) in isolated DRG neurons using the fluorescent Ca²⁺ indicator fluo-3 was measured by confocal laser scanning microscope. Apoptotic neurons were monitored by Hoechst 33342 staining. Expression of caspase-3, procaspase-3, and pAkt was detected by Western blot assay. Administration of 0.2 mmol/l Glu evoked an increase in [Ca²⁺]_i, confirming the excitatory effect of Glu. Compared with the control group, apoptotic (condensed and fragmented nuclei) neurons were observed in Glu-treated cells after Hoechst 33342 staining. The increase caspase-3 of and decrease of procaspase-3 expression levels after administration of 0.2 mmol/l Glu suggested the apoptotic effects of Glu. These effects could be inhibited by the presence of NRG-1β. The effects of NRG-1β could be blocked by PI3K inhibitor LY294002. These results implicated that NRG-1β could prevents Ca²⁺ overload and apoptosis by activating PI3K/Akt pathway of primary cultured DRG neurons with excitotoxicity induced by Glu.