PKA信号通路参与高糖介导的THP-1细胞G6PD活性改变及呼吸爆发功能障碍

目的观察高糖环境下THP-1细胞葡萄糖-6-磷酸脱氢酶(G6PD)活性及呼吸爆发功能改变及其可能信号通路。方法利用蛋白激酶A(PKA)特异性抑制剂PKI和PKA激动剂Forskolin预处理不同浓度葡萄糖培养的THP-1细胞,检测不同处理组的G6PD活性、腺苷酸环化酶(cAMP)含量、ROS产量及磷酸化p47phox的表达变化。结果与正常对照组相比,高糖组及PKA激动组的G6PD活性、ROS产量及磷酸化p47phox的表达减少,cAMP含量明显增加(P<0.01)。PKA抑制组的G6PD活性、cAMP含量及磷酸化p47phox的表达未见明显变化,与正常对照组相比无明显差异(P>0.01)。结论高糖通过激活cAMP-PKA信号通路来抑制G6PD活性,从而影响THP-1细胞的NADPH氧化酶(NOX)的激活,引起呼吸爆发功能障碍,为糖尿病患者白细胞功能低下,抗感染能力降低的可能机制之一。

Protein kinase A signaling pathway participates in high glucose-induced inhibition of G6PD activity and respiratory burst dysfunction in THP-1 cells

Objective To observe the changes in glucose 6-phosphate dehydrogenase(G6PD) activity,cAMP and respiratory burst function in THP-1 cells exposed to high glucose and identify the possible signaling pathways to mediate these changes.Methods THP-1 cells were treated with high glucose,high glucose plus the PKA inhibitor(PKI),or normal glucose plus Forskolin.The changes in the G6PD activity and cAMP in the exposed cells were assayed using the spectrophotometric method,and the reactive oxygen species(ROS) content in the cell culture was determined using the fluorescent probe DCFH-DA.Western blotting was employed to examine the expression of phosphorylated p47 phox in the cells.Results Compared with the normal control cells,the cells exposed to high glucose and to normal glucose and Forskolin showed a significantly lowered G6PD activity,ROS content and expression of phosphorylated p47 phox,but with a increased cAMP content(P<0.01).High glucose exposure in the presence of PKI caused no significant changes in G6PD activity,ROS level,phosphorylated p47 phox or cAMP compared to those in the normal control cells(P>0.01).Conclusion High glucose causes inhibition of G6PD activity in THP-1 cells via activation of PKA and thus leads to respiratory burst dysfunction,which is the probable mechanism underlying the lowered leucocyte function and susceptibility to infections in diabetic patients.