Inhibition of cAMP/PKA Pathway Protects Optic Nerve Head Astrocytes against Oxidative Stress by Akt/Bax Phosphorylation-Mediated Mfn1/2 Oligomerization
Inhibition of cAMP/PKA Pathway Protects Optic Nerve Head Astrocytes against Oxidative Stress by Akt/Bax Phosphorylation-Mediated Mfn1/2 Oligomerization
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DOI：
10.1155/2019/8060962
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发表时间：
2019-11-06
影响因子：
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通讯作者：
Weinreb, Robert N.
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文献类型：
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作者：
Ju, Won-Kyu;Shim, Myoung Sup;Weinreb, Robert N.
青光眼的特征在于进行性视神经变性和视网膜神经节细胞丧失，但伴随的神经变性的潜在生物学基础尚不清楚。越来越多的证据表明，视神经乳头（ONH）内星形胶质细胞的结构和功能异常在青光眼性神经变性中起作用。在此，我们研究了环腺苷酸（cAMP）/蛋白激酶A（PKA）通路的激活对暴露于氧化应激的ONH星形胶质细胞的线粒体动力学的影响。ONH星形胶质细胞表现出显着的损失星形胶质细胞的过程中的胶质细胞层的胶质细胞瘤DBA/2 J小鼠，伴随着基底膜增厚和胶原蛋白沉积在血管和轴突变性。连续块面扫描电子显微镜数据分析表明，总的和分支的线粒体数量显着增加，而线粒体长度和体积密度显着减少。我们发现，过氧化氢-（H2 O2-）诱导的氧化应激不仅损害线粒体的生物能量学通过减少基础和最大呼吸，但也通过减少动力蛋白相关蛋白1（Drp 1）的蛋白表达在大鼠ONH星形胶质细胞的线粒体动力学的平衡。与此相反，二丁酰-cAMP（dbcAMP）或异丁基甲基黄嘌呤治疗的cAMP升高显着增加Drp 1蛋白在ONH星形胶质细胞的表达。升高的cAMP通过降低视神经萎缩1型（OPA 1）和线粒体融合蛋白（Mfn）1/2蛋白表达，加剧了ONH星形胶质细胞线粒体动力学的损伤和细胞活力对氧化应激的降低。在用H2 O2和dbcAMP联合处理后，PKA抑制通过增加线粒体长度和减少线粒体数量来恢复线粒体动力学，这促进了ONH星形胶质细胞的细胞活力。此外，PKA抑制显着促进Akt/Bax磷酸化和Mfn 1/2寡聚化在ONH星形胶质细胞。这些结果表明，cAMP/PKA信号通路的调制可能具有治疗潜力，通过激活Akt/Bax磷酸化和促进Mfn 1/2寡聚化的胶质瘤ONH星形胶质细胞。
Glaucoma is characterized by a progressive optic nerve degeneration and retinal ganglion cell loss, but the underlying biological basis for the accompanying neurodegeneration is not known. Accumulating evidence indicates that structural and functional abnormalities of astrocytes within the optic nerve head (ONH) have a role in glaucomatous neurodegeneration. Here, we investigate the impact of activation of cyclic adenosine 3 ',5 '-monophosphate (cAMP)/protein kinase A (PKA) pathway on mitochondrial dynamics of ONH astrocytes exposed to oxidative stress. ONH astrocytes showed a significant loss of astrocytic processes in the glial lamina of glaucomatous DBA/2J mice, accompanied by basement membrane thickening and collagen deposition in blood vessels and axonal degeneration. Serial block-face scanning electron microscopy data analysis demonstrated that numbers of total and branched mitochondria were significantly increased in ONH astrocytes, while mitochondrial length and volume density were significantly decreased. We found that hydrogen peroxide- (H2O2-) induced oxidative stress compromised not only mitochondrial bioenergetics by reducing the basal and maximal respiration but also balance of mitochondrial dynamics by decreasing dynamin-related protein 1 (Drp1) protein expression in rat ONH astrocytes. In contrast, elevated cAMP by dibutyryl-cAMP (dbcAMP) or isobutylmethylxanthine treatment significantly increased Drp1 protein expression in ONH astrocytes. Elevated cAMP exacerbated the impairment of mitochondrial dynamics and reduction of cell viability to oxidative stress in ONH astrocytes by decreasing optic atrophy type 1 (OPA1), and mitofusin (Mfn)1/2 protein expression. Following combined treatment with H2O2 and dbcAMP, PKA inhibition restored mitochondrial dynamics by increasing mitochondrial length and decreasing mitochondrial number, and this promoted cell viability in ONH astrocytes. Also, PKA inhibition significantly promoted Akt/Bax phosphorylation and Mfn1/2 oligomerization in ONH astrocytes. These results suggest that modulation of the cAMP/PKA signaling pathway may have therapeutic potential by activating Akt/Bax phosphorylation and promoting Mfn1/2 oligomerization in glaucomatous ONH astrocytes.