Effects And Mechanism Of Calcineurin On Neuronal Apoptosis Induced By Pro-inflammatory Factors

[OBJECTIVE]: The purpose of this study is to investigate whether calcineurin mediate the injury introduced by the interleukin-1βand tumor necrosis factorαby culturing the primary cortical neurons and astrocytes. [METHODS] : The authors employed the MTT assay , LDH releasing rate and immunofluorescence staining assay to determine the cellular viability and injury degree, western blot assay to detect the expression of p-JNK and p-ERK1/2, which induced by the IL-1βand TNFα. RESULTS: In the group injured by IL-1βand TNFα, cell viability and cell count decreased comparing to the control(p<0.05). For the cell treated with cyclosporine A, a specific calcineurin inhibitor, cell viability and cell count increased comparing to the group injured by IL-1βand TNFα(p<0.05). In cooperation group of IL-1βand TNFα, cell viability increase significantly, while there were not significant change in TNFαand CsA group (P>0.05). The results of western blot assay showed that the expression of p-ERK1/2 protein increased in IL-1βand CsA group in primary cortical neuron. The expression of p-ERK1/2 protein was higher than the control group in IL-1βand TNFαinjured group respectively; while the p-ERK1/2 expression was significantly higher than cytokine-injured group, and also higher in IL-1βand CsA co-treated group. However, there was no significant change in the expression of p-JNK in groups. In astrocytes, the expression of p-ERK1/2 decreased in IL-1βand CsA co-treated group. The expression of p-JNK protein increased in TNFαtreated group. But in astrocytes, cytokine, especially TNFα, induced neuron injury via increasing the expression of p-JNK protein. In contrary to the IL-1βinjured group, the expression of p-ERK1/2 protein decreased in the group co-treated by both IL-1βand CsA . The higher expression of NF-κΒp65 was induced by IL-1βor NMDA, which were coincident with the damage of neurons. The calcineurin inhibitor cyclosporine A (CsA) inhibited the higher expression of NF-κΒp65 and neuron damage which induced by IL-1β(p<0.05) but not the NMDA(p>0.05). Annexin V and PI immunofluorescence shown that IL-1βmainly induced the neuron apoptosis, otherwise the NMDA induced the neuron necrosis. [CONCLUSION]: The cortical neurons injured by IL-1βunderwent its apoptosis through inhibiting p-ERK1/2 phosphorylation and decreasing its activity, but not through enhancing the activity of p-JNK. Calcineurin mediated it in neuron. On the other hand, TNFαinduced cell injury via other pathways, not via calcineurin pathway. Moreover, cell injury induced by IL-1βand mediated by calcineurin was via inhibiting the p-ERK1/2 phosphorylation and decreasing its activity in neurons and astrocytes. The calcineurin...